United States Solid Waste and EPA530-R-93-017 Environmental Protection Emergency Response November 1993 Agency (5305) www.epa.gov/osw 

# Solid Waste Disposal Facility Criteria
Technical Manual

### DISCLAIMER

The information in this document has been funded wholly or in part by the United State s E nvironmental Protect

ion Agency under Contract Number 68-WO-0025. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.



### NOTICE T he policies set out in this manual are not final Agency action, but are intended solely as guidance. T hey are not intended, nor can theybe relied upon, to create any rights enforceable by any party in l itigation with the United States . EPA officials may decide to follow the guidance provided in this memora ndum, or to act at variance with the guidance, based on an analysis of specific sit e circumstances. The Agency also reserves the right to change this guidance at any time withou t public notice.i Revised April 13, 1998 TABLE OF CONTENTS INTRODUCTION

......................................................... iv CHAPTER 1. SUBPART A

.................................................. 1 1.1 INTRODUCTION

................................................ 3 1.2 PURPOSE, SCOPE, AND APPLICABILITY 40 CFR §258.1 (a)(b)

.......... 4 1.3 PURPOSE, SCOPE, AND APPLICABILITY (cont.) 40 CFR §258.1 (c)-(e)

.... 5 1.4 SMALL LANDFILL EXEMPTIONS 40 CFR §258.1 (f)

................... 7 1.5 APPLICABILITY 40 CFR §258.1 (g)-(j)

............................... 9 1.6 DEFINITIONS 40 CFR §258.2

..................................... 10 1.7 CONSIDERATION OF OTHER FEDERAL LAWS 40 CFR §258.3

......... 14 CHAPTER 2. SUBPART B

................................................. 15 2.1 INTRODUCTION

............................................... . 18 2.2 AIRPORT SAFETY 40 CFR §258.10

................................ . 19 2.3 FLOODPLAINS 40 CFR §258.11

................................... . 24 2.4 WETLANDS 40 CFR §258.12

...................................... . 28 2.5 FAULT AREAS 40 CFR §258.13

................................... . 37 2.6 SEISMIC IMPACT ZONES 40 CFR §258.14

.......................... . 41 2.7 UNSTABLE AREAS 40 CFR §258.15

............................... . 45 2 .8 CLOSURE OF EXISTING MUNICIPAL SOLID WASTE LANDFILL UNITS 40 CFR §258.16

.............................................. . 61 2.9 FURTHER INFORMATION

....................................... . 63 CHAPTER 3. SUBPART C

................................................. 73 3.1 INTRODUCTION

............................................. . 76 3.2 PROC EDURES FOR EXCLUDING THE RECEIPT OF HAZARDOU S WASTE 40 CFR §258.20

....................................... . 77 3.3 COVER MATERIAL REQUIREMENTS 40 CFR §258.21

.............. . 84 3.4 DISEASE VECTOR CONTROL 40 CFR §258.22

.................... . 85 3.5 EXPLOSIVE GASES CONTROL 40 CFR §258.23

................... . 87 3.6 AIR CRITERIA 40 CFR §258.24

................................ . 101 3.7 ACCESS REQUIREMENT 40 CFR §258.25

....................... . 103 3.8 RUN-ON/RUN-OFF CONTROL SYSTEMS 40 CFR §258.26

.......... . 104 3.9 SURFACE WATER REQUIREMENTS 40 CFR §258.27

.............. . 105 3.10 LIQUIDS RESTRICTIONS 40 CFR §258.28

....................... . 107 3.11 RECORDKEEPING REQUIREMENTS 40 CFR §258.29

.............. . 110 3.12 FURTHER INFORMATION

.................................... . 114Revised April 13, 1998 ii CHAPTER 4. SUBPART D

................................................ 117 4.1 INTRODUCTION

............................................ 121 4.2 PERFORMANCE-BASED DESIGN 40 CFR §258.40

................ 122 4.3 COMPOSITE LINER AND LEACHATE COLLECTION SYSTEM 40 CFR §258.40

.................................................... 149 4.4 RELEVANT POINT OF COMPLIANCE 40 CFR §258.40(d)

.......... 188 4.5 PETITION PROCESS 40 CFR §258.40(e)

......................... 191 4.6 FURTHER INFORMATION

.................................... 193 CHAPTER 5. SUBPART E

................................................ 205 5.1 INTRODUCTION

............................................ 211 5.2 APPLICABILITY 40 CFR §258.50 (a) & (b)

....................... 211 5.3 COMPLIANCE SCHEDULE 40 CFR § 258.50 (c)

................... 214 5.4 ALTERNATIVE C OMPLIANCE SCHEDULES 40 CFR 258.50 (d)(e) & (g)

.......................................................... 215 5.5 QUALIFICATIONS 40 CFR 258.50 (f)

........................... 217 5.6 G ROUND-WATER MONITORING SYSTEMS 40 CFR §258.51 (a)(b)(d)

.......................................................... 219 5.7 GR OUND-WATERMONITORING WELL DESIGN AN D CONSTRUCTION 40 CFR §258.51 (c)

........................... 241 5.8 G ROUND-WATER SAMPLING AND ANALYSIS REQUIREMENTS 40 CFR §258.53

................................................ 253 5.9 STATISTICAL ANALYSIS 40 CFR §258.53 (g)-(I)

................. 268 5.10 DETECTION MONITORING PROGRAM 40 CFR §258.54

........... 274 5.11 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(a)-(f)

..... 281 5.12 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(g)

....... 286 5.13 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(h)-(j)

..... 289 5.14 ASSESSMENT OF CORRECTIVE MEASURES 40 CFR §258.56

...... 291 5.15 SELECTION OF REMEDY 40 CFR §258.57 (a)-(b)

................. 298 5.16 SELECTION OF REMEDY 40 CFR §258.57 (c)

.................... 299 5.17 SELECTION OF REMEDY 40 CFR §258.57 (d)

.................... 303 5.18 SELECTION OF REMEDY 40 CFR §258.57 (e)-(f)

.................. 305 5.19 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 4 0 CFR §258.58 (a)

............................................. . 307 5.20 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 4 0 CFR §258.58 (b)-(d)

.......................................... . 309 5.21 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 4 0 CFR §258.58 (e)-(g)

.......................................... . 311 5.22 FURTHER INFORMATION

.................................... . 313iii Revised April 13, 1998

CHAPTER 6. SUBPART F

................................................ 319 6.1 INTRODUCTION

............................................. 322 6.2 FINAL COVER DESIGN 40 CFR §258.60(a)

........................ 322 6.3 ALTERNATIVE FINAL COVER DESIGN 40 CFR §258.60(b)

......... 332 6.4 CLOSURE PLAN 40 CFR §258.60(c)-(d)

........................... 338 6.5 CLOSURE CRITERIA 40 CFR §258.60(e)-(j)

....................... 339 6.6 POST-CLOSURE CARE REQUIREMENTS 40 CFR §258.61

........... 342 6.7 POST-CLOSURE PLAN 40 CFR §258.61(c)-(e)

..................... 345 6.8 FURTHER INFORMATION

..................................... 348

APPENDICES CHAPTER 2 APPENDIX I FAA Order 5200.5A

............................................ 69 CHAPTER 3 APPENDIX I - SPECIAL WASTE ACCEPTANCE AGREEMENT

................. 115The Agency originally intended to extend to Indian Tribes the same opportunity to apply for permit program 1 approval as is available to States, but a court decision blocked this approach. See the Tribal Process section below for complete details. EPA finalized several revisions to 40 CFR Part 258 on October 1, 1993 (58 FR 51536) and issued a correction 2 notice on October 14, 1993 (58 FR 53136). Questions regarding the final rule and requests for copies of the Federal Register notices should be made to the RCRA/Superfund Hotline at 800 424-9346. Revised April 13, 1998 iv Ex ample of Technical and Performanc e Standards in 40 CFR Part 258: Liners Technical standard: MSWLF s must be built with a composit e liner consisting of a 30 mil flexible mem

brane liner over 2 feet compacted soil with a hydraulic conductivity of no more than 1 x 10 - cm/sec. 7 Performance standard: MSWLFs must be b uilt in accordance with a desig n approved by the Director of a n appr ovedState or as specified in 40 CF R § 25 8.40(e) for unapproved States. Th e de sign must ensure that the concentratio n values listed in Table 1 of 40 CFR § 258.40 will not be exceeded in the uppermost aquifer at

the relevant point of compliance, a s sp ecifiedby the Director of an approve d State under paragraph 40 CFR § 258.40(d). INTRODUCTION
T his m anual was originally published in November, 1993 as a companion to the Criteria for M unicipal Solid Waste Landfills (MSWLF Criteria) that were promulgated on October 9, 1991 as 40 CFR Part 258. Since that time the MSWLF Criteria have been modified several times due t o s tatutory revisions and court decisions that are discussed below. Most of the modifications delayed the effective d ates but all provisions are now effective. All changes to the rule are included in the text of the m anual. The technical content of the manual did not require revision and onl y typographical errors were corrected.
T he manual is now available in electronic forma t and can be accessed on the Environmental Protection Agency’s (EPA) web site <www.epa.gov/osw>

. Purpose of This Manual This technical manual has been developed to assist owners/operators of MSWLFs in achievin g compliance with the revised MSWLF Criteria. This manual is not a regulatory document, and does no t pro vide mandatory technical guidance, but doe s provide assistance for coming into compliance with the technical aspects of the revised landfill Criteria. Implementation of the Landfill Criteria The EPA f ully intends that States and Tribes maintain the lead role in imple menting and enforcing the revised Cr iteria. States will achieve this through approvedState permit programs. Due to recen t decisi ons by the courts, Tribes will do so using a case-by- case review process. Whether in a State or 1 in Indian Country, landfill owners/operators mus t comply with the revised MSWLF Criteria. 2 State Process
T he Agency’s role in the regulation of MSWLFs is to establish national minimum standards that the states are to incorporate into their MSWLF permitting programs. EPA evaluates stat eIntroduction

v Revised April 13, 1998 M SWLF permitting programs under the procedures set out in 40 CFR Part 239, “Requirements for S tate Permit Program Determination of Adequacy,” proposed on January 26, 1996 (61 FR 2584), t o determine whether programs are adequ ate to ensure that MSWLF owners/operators comply with the federal standards. As of early 1998, 40 States and Territories had received full approval an d another seven had received partial approval.
I f their permitting programs have been approved by EPA, States can allow the use of flexible p erformance standards established in 40 CFR Part 258 in addition to the self-implementing technical standa rds for many of the Criteria. Approved States can provide owners/operators flexibility i n sati sfying the location restrictions, operating criteria, and requirements for liner design, ground

wa ter monitoring, corrective action, closure and post-closure care, and financial assurance. Thi s flexibilit y allows for the consideration of site-specific conditions in designing and operating a M SWLF at the lowest cost possible while ensuring protection of hum an health and the environment. In unapproved states, owners/operators must follow the self-implementing technical standards.
E PA continues to work with States toward approval of their programs and recommends that o wners/operators stay informed of the approval status of the programs in their State. States may be in various stages of the program approval process. The majority of states have received ful l p rogram approval and others hav e received “partial” program approval (i.e., only some portions of the State program are approved while the remainder of the program is pending approval)

. Regardl ess of a State’s program approval status, landfill owners/operators must comply with th e C riteria. States can grant flexibility to owners/operators o nly in the areas of their program that have be en approved. For example, a state in which only the ground-water monitoring area of th e permi tting program has been approved by EPA cannot grant owners/operators flexibility to us e alternative liner designs. S tates are free to enact landfill regulations that are m ore stringent than the MSWLF Criteria. C ertain areas of fl exibility provided by the Criteria (e.g., the small landfill exemption) may not be reflected i n a State program. In such instances, the owner/operator must comply with the mor e stringent provisions (e.g., no exemption). These regulations would be enforced by the Stat e i ndependently from

the Criteria. NOTE: The program requirements for approved States may differ from those described in this manual, which are based specifically on the Federa l C riteria. Therefore, owners/operators are urged to work closely with their approved State in order to ensure that they are fully in compliance with all applicable requirements. State regulatory personnel will find this document helpful when reviewing permi t applications for landfills. This manual presents technical information to be used in siting, designing, operating, and closing landfills, but does not present a mandatory approach for demonstratin g c ompliance with the

Criteria. This manual also outlines the types of information relevant to make the demonstrations required by the Criteria, including demonstrations for restricted locations and performance-based designs in approved States. Tribal Process
F rom the beginning of EPA’s development of the permitting program approval process, the A gency planned to offer permitting p rogram approval to tribes as well as to states. In a 1996 courtIntroduction

Backcountry Against Dumps v. EPA , 100 F.3d 147 (D.C. Cir. 1996). 3 This manual uses the term “Indian Country” as defined in 40 CFR § 258.2. 4 In the original 40 CFR Part 258 rulemaking, promulgated October 9, 1991, the Agency provided an 5 exemption from ground-water monitoring for small MSWLF units located in dry or remote locations. In 1993, the U.S. Court of Appeals for the District of Columbia set aside this ground-water monitoring exemption. Sierra Club v. EPA , 992 F.2d 337 (D.C. Cir. 1993). Revised April 13, 1998 vi dec ision , however, the court ruled that EPA cannot approve tribal permitting programs. Th e

3 A gency has th erefore developed a site-specific rulemaking process to meet its goal of quickly and eff iciently providing owners/operators in Indian Country the same flexibility that is available t o 4 l andfill owners/operators in states with EPA-approved MSWLF permitting programs. The process is described in Site-Specific Flexibility Requests for Municipal Solid Waste Landfills in India n Country—Draft Guidance (EPA530-R-97-016). Under this process, an owner or operator can request to use certain alternative approaches at a specific MSWLF site to meet the 40 CFR Part 258 performance standards. Unless the tribal g overnment is the owner/operator, the tribal government should review the request for consistency with tribal l aw and policy and forward it to EPA with a recommendation. If EPA approves a request , it will issue a site-specific rule allowing the use of the requested alternative approaches

. Owners/o perators in Indian Country should therefore understand that when this manual refers t o areas of flexibility that can be granted by a “State Director,” they would instead seek such flexibility i n the form of a site-specificrulemaking from EPA after tribal government review of their petition f or rulemaking. Although tribes will not issue permits as EPA-approved permitting entities under the Criteria, they are free to enact separate tribal landfill regulations that are more stringent than the Criteria. Tribal regulations are enforced by the tribe independently of the Criteria. The site-specific process encourages active dialogue among tribes, MSWL F owners/ope rators, EPA, and the public. The guidance is designed so that the Agency works i n p artnership with tribes. Because EPA recognizes tribal sovereignty , EPA will respect tribal findings concerning consistency of proposed approaches with tribal law and policy. Revisions to Part 258 Some important changes have been made to Part 258 since its original promulgation. I n addition, other regulations that affect solid waste management have been implemented. Gro und-Water

Monitoring Exemption for Small, Dry, and Remote Landfills (40 CF R § 258.1(f)(1)) T he La nd Disposal Program Flexibility Act (LDPFA) of 1996 reestablished an exemption f or ground-water monitoring for owners/operators of certain small MSWLFs. EPA revised 40 CFR § 258.1(f)(1) on September 25, 1996 (61 FR50409) to codifythe LDPFA ground-water monitoring e xemption. To qualify for an exemptio n, owners/operators must accept less than 20 tons per day of MSW (based on an annual average), have no evidence of ground-water contamination, and b e located in either a dry or remote location. This exemption eases the burden on certain smal l MSWLFs without compromising ground-water quality. 5Introduction

vii Revised April 13, 1998 New Flexibility for Small Landfills (40 CFR §§ 258.21, 258.23, 258.60)
In addition to reestablishing the ground-water exemption for small, dry, and remot e M SWLFs, the LDPFA provided additional flexibility to approved states for any small landfill that r ecei ves 20 tons or less of MSW per day. EPA revised 40 CFR Part 258 to allow approved states to gran t the use of alternative frequencies of daily cover, alternative frequencies of methan e m onitoring, and alternative infiltration layers for final cover (62 FR 40707 (July 29, 1997)). The LDPFA also authorized flexibility to establish alternative means for demonstrating financia l assurance, and this flexibility was granted in another action. The additional flexibility will allow o wners and operators of small MSWLFs the opportunity to reduce their costs of MSWLF operation while still protecting human health and the environment. Added Financial Assurance Options (40 CFR § 258.74) A revision to 40 CFR Part 258, published November 27, 1996 (61 FR 60328), provide d additional options to the menu of financial assurance instruments that MSWLF owners/operators can use to demonstrate that adequate funds will be readily available for the costs of closure , post-closure care, and corrective action for known releases associated with their facilities. Th e existi ng regulations specify several mechanisms that owners and operators may use to make that d emonstration, such as trust funds and surety bonds. The additional mechanisms are a financial test f or use by local government owners and operators, and a provision for local governments that wish t o guarantee the cl osure, post-closure, and corrective action costs for an owner or operator. These f inancial assurance options allow local governments to use their fin ancial strength to avoid incurring the expenses associated with the use of third-party financial instruments. This action granted the fl exibility to all owners and operators (including owners and operators of small facilities) t o establish alternative means for demonstrating financial assurance as envisioned in the LDPFA. A dditionally, EPA promulgated a regulation allowing corporate financial tests and corporate g uarantees as fi nancial assurance mechanisms that private owners and operators of MSWLFs may u se to demonstrate financial assurance (63 FR 17706 (April 10, 1998)). This test extends to private o wners and

operators the regulatory flexibility already provided to municipal owners or operators o f MSWLFs. These regulations allow firms to demonstrate financial assurance b y passing a financial t est. For firms that qualify for the financial test, this mechanism will be less costly than the use of a third party financial instrument such as a trust fund or a surety bond. How to Use This Manual
T his document is subdivided into six chapters arranged to follow the order of the Criteria. The first chapter addresses the general applicability of the Part 258 Criteria; the second cover s location restrictions; the third explains the operating requirements; the fourth discusses desig n standards; the fifth covers ground-water monitoring and corrective action; and the sixth chapter a ddresses closure and post-closure care. Each chapter contains an introduction to that section of the Crite ria. This document does not include a section on the financial responsibility requirements ;Introduction

Revised April 13, 1998 viii q uestions regarding these requirements may be addressed to EPA’s RCR A/Superfund Hotline at 800 424-9346. Within each chapter, the Criteria have been subdivided into smaller segments. Th e S tatement of Regulation section provides a verbatim recital of the regulatory language. The second sect ion, entitled Applicability , provides a general explanation of the regulations and who mus t c omply with them. Finally, for each se gment of the regulation, a Technical Considerations section i dentifies key technical issues that may need to be addressed to ensure compliance with a particular re quirement. Each chapter ends with a section entitled Further Information , which provide s references, addresses, organizations, and other information that may be of use to the reader. Limitations of This Manual
T he ability of this document to provide current guidance is l imited by the technical literature that was available at the time of preparation. Technology and product development are advancing r apidly, especi ally in the areas of geosynthetic materials and design concepts. As experience with n ew waste management techniques expands in the engineering and science community, an increase i n published literature, research, and technical information will follow. The owners and operators o f MSWLFs are encouraged to keep abreast of innovation through technical journals, professional o rganizations, and technical information developed byEPA. Many of the Criteria contained in Part 258 are p erformance-based. Future innovative technology may provide additional means fo r owners/operators to meet performance standards that previously could not be met by a particular facility due to site-specific conditions. Deadlines and Effective Dates The original effective date for the Criteria, October 9, 1993, was revised for severa l c ategories of landfills, in response toconcerns that a variety of circumstances was hampering some c ommunities' abilitie s to comply by that date. Therefore, the Agency provided additional time for c ertain landfills to come into compliance, especially small units and those that accepted waste from the 1993 Midwest floods. As the accompanying table indicates, th e extended general effective dates for all MSWLF categories have passed, and all units should now be in compliance.SUMMARY OF CHANGES TO THE EFFECTIVE DATES OF THE MSWLF CRITERIA

MSWLF Units MSWLF Units Accepting MSWLF Units That MSWLF Units Accepting Greater 100 TPD or Less; Are Not Meet the Small Receiving Floodthan 100 TPD on the NPL; and Are Landfill Exemption in Related Waste Located in a State That 40 CFR §258.1(f) Has Submitted an Application for Approval by 10/9/93, or on Indian Lands or Indian Country General effective date. October 9, 1993 April 9, 1994 October 9, 1997; exempt Up to October 9, 1994 1,2,3 This is the effective date for location, requirementsoperation, design, and closure/postclosure. from the design as determined by State

Date by which to install final cover October 9, 1994 October 9, 1994 October 9, 1998 Within one year of date if cease receipt of waste by the determined by State; no general effective date. later than October 9, 2,3 1995 Effective date of ground-water Prior to receipt of waste October 9, 1993 for new Exempt from the October 9, 1993 for monitoring and corrective action. for new units; October units; October 9, 1994 ground-water new units; October 9, 2,3 9, 1994 through October through October 9, 1996 for monitoring 1994 through October 9, 1996 for existing existing units and lateral requirements. 9, 1996 for existing units and lateral expansions units and lateral expansions expansions 5

Effective date of financial April 9, 1997 April 9, 1997 October 9, 1997 April 9, 1997 assurance requirements. 3,4 If a MSWLF unit receives waste after this date, the unit must comply with all of Part 258. 1 See the final rule and preamble published on October 1, 1993 (58 FR 51536) for a full discussion of all changes and related conditions. 2 See the final rule and preamble published on October 6, 1995 (60 FR 52337) for a full discussion of all changes and related conditions. 3 See the final rule and preamble published on April 7, 1995 (60 FR 17649) for a discussion of this delay. 4 See the final rule and preamble published on September 25, 1990 (61 FR 50409) for a discussion of the ground-water monitoring exemption. 51 

# CHAPTER 1 SUBPART A GENERAL2 CHAPTER 1 SUBPART A TABLE OF CONTENTS

1.1 INTRODUCTION

.................................................... 3 1.2 PURPOSE, SCOPE, AND APPLICABILITY 40 CFR §258.1 (a)(b)

.............. 4 1.2.1 Statement of Regulation

........................................... 4 1.2.2 Applicability

.................................................... 4 1.2.3 Technical Considerations

.......................................... 4 1.3 PURPOSE, SCOPE, AND APPLICABILITY (cont.) 40 CFR §258.1 (c)-(e)

........ 5 1.3.1 Statement of Regulation

........................................... 5 1.3.2 Applicability

.................................................... 5 1.3.3 Technical Considerations

.......................................... 7 1.4 SMALL LANDFILL EXEMPTIONS 40 CFR §258.1 (f)

....................... 7 1.4.1 Statement of Regulation

........................................... 7 1.4.2 Applicability

.................................................... 8 1.4.3 Technical Considerations

.......................................... 8 1.5 APPLICABILITY 40 CFR §258.1 (g)-(j)

................................... 9 1.5.1 Statement of Regulation

........................................... 9 1.5.2 Applicability

................................................... 10 1.5.3 Technical Considerations

......................................... 10 1.6 DEFINITIONS 40 CFR §258.2

......................................... 10 1.6.1 Statement of Regulation

.......................................... 10 1.6.2 Applicability

................................................... 13 1.6.3 Technical Considerations

......................................... 13 1.7 CONSIDERATION OF OTHER FEDERAL LAWS 40 CFR §258.3

............. 14 1.7.1 Statement of Regulation

.......................................... 14 1.7.2 Applicability

................................................... 14 1.7.3 Technical Considerations

......................................... 143 

### CHAPTER 1 SUBPART A GENERAL

1.1 INTRODUCTION Under the authority of both th e Resource Conservation and Recovery Act (RCRA), as amended by the Hazardous and Solid Waste Amendments (HSWA) of 1984, and Section 405 of the Clean Water Act, the EPA issued "Solid Waste Disposal Facility Criteria" (40 CFR Part 258) on October 9, 1991. These regulations revise the "Criteria for Classification of Solid Waste Disposal Facilities an d Practices," found in 40 CFR Part 257. Part 258 was established to provide minimum nationa l criteria for all solid waste landfills that are not regulated under Subtitle C of RCRA, and that:

! Receive municipal solid waste; or
! Co-dispose sewage sludge with municipal solid waste; or
! Accept nonhazardous municipal waste combustion ash. Part 257 remains in effect for all other non-hazardous solid waste facilities and practices. Subpart A of the regulations defines the purpose, scope, and applicability of Part 258 and provides de finitions necessary for proper interpretation of the requirements. In summary, the applicability of the Criteria is dependent on the operational status of the MSWLF unit relative to the date o f publication of Part 258 and the effective date of the ru le (October 9, 1993). An exemption from the design requirements is provided for small MSWLF units if specific operating, environmental, and location conditions are present. [The final rule as promulgated on October 9, 1991 exempted the owner/operators of small landfill units from both Subparts D and E. O n May 7, 1993 the U.S. Court of Appeals for the District of Columbia Circuit issued an opinion that EPA did not have th e authority to exempt these small landfills from the ground-water monitoring requirements (Subpart E), therefore, t

hese small landfills can not be exempted from Subpart E. EPA is delaying the date of com pliance for these units until October 9, 1995 (58 FR51536). In addition, the Agency i s investigating alternative ground-water monitoring procedures for these units.] Owners or operators of MSWLF units that do not meet the Part 258 Criteria will be considered to be engaging in the practice of "open dumping" in violation of Section 4005 of RCRA. Similarly, owners and operators of MSWLF units that receive sewage sludge and do not comply with these Criteria will also be in violation of applicable sections of the Clean Water Act.Subpart A

4 1.2 PURPOSE, SCOPE, AND 1.2.3 Technical Considerations APPLICABILITY 40 CFR §258.1 (a)(b) Criteria that define a solid waste disposa l 1.2.1 Statement of Regulation RC RA (Criteria for Classification of Soli d (a) Th e purpose of this part is t o Definitions pertaining to the r evised Criteria establish minimum national criteri a are included in the de finition section of Part und er the Resource Conservation an d 258. A MSWLF unit is defined as a discrete Recovery Act (RCRA or the Act), a s are a of land or excavation that receive s ame nded, for all municipal solid wast e househ old waste, and that is not considered landfill (MSWLF) units and under th e a l and application unit, surfac e Cle an Water Act, as amended, fo r impoundment, injection well, or waste pile mu nicipal solid waste landfills that ar e as those terms are defined under § 257.2. An used to dispose of sewage sludge. Thes e ex isting unit is a solid waste disposal uni t minimum national criteria ensure th e that is receiving solid wast e as of October 9, protection of human health and th e 1993. A lateral expansion is a horizonta l environment. exp ansion of the waste boundaries of a n (b) These Criteria apply to owner s MSWLF unit that has not received wast e and operators of new MSWLF units , before October 9, 1993. exi sting MSWLF units, and latera l expansions, except as otherwis e In addition to household waste, a MSWL F specifically provided in this part; al l unit may receive commercial waste, non

other solid waste disposal facilities an d hazardous solid waste from industria l prac tices that are not regulated unde r facilities including non-hazardous sludges , Su btitle C of RCRA are subject to th e and sewage sludge from wastewate r criteria contained in Part 257. treatment plants. The terms commercia l 1.2.2 Applicability waste are defined in §258.2 (Definitions). Owners and operat ors of MSWLF units that The types of landfills regulated under Par t receive municipal solid waste or that receive 257 include those facilities that receive: municipal waste combust ion ash and are not curr ently regulated under Subtitle C o f ! Construction and demolition debri s RCR A must comply with the Criteria

. only; Furthermore, MSWLF units that r eceive and co-dispose sewage sludge must comply with ! Tires only; and Part 258 to be in compliance with Sections 309 and 405(e) of the Clean Water Act. ! Non-hazardous industrial waste only. faci lity are contained within Part 257 o f Waste Disposal Facilities and Practices)

.

existing MSWLF unit. A new unit is a

solidwaste, industrial waste and householdGeneral

5 MSWLF units are not intended, no r rec eiving waste before October 9, 199 3 allowed, to receive regulated quantities o f are exempt from all the requirements o f haz ardous wastes. Should a MSWL F Part258, except the final cove r ow ner/operator discover that a shipmen t requirement s pecified in Section 258.60(a). contains regulated quantities of hazardou s The final cover must be installed within six wast e while still in the possession of th e months of last receipt of wastes. Owners or transporter, the owner/operator shoul d operators of MSWLF units described i n refu se to accept the waste from th e thi s paragraph that fail to complete cove r tran sporter. If regulated quantities o f ins tallation within this six month perio d hazardous wastes are discovered afte r wil l be subject to all the requirements o f accepting the waste from the tra nsporter, the Part 258, unless otherwise specified. owner/opera tor must return the shipment or mana ge the wastes in accordance wit h (e) All MSWLF units that receiv e RCRA Subtitle C requirements. waste on or after October 9, 1993 mus t S u btitle C of RCRA establishes procedures unless otherwise specified. fo r making a hazardous wast e de termination. These procedures ar e 1.3.2 Applicability summarized in Chapter 3 and Appendi x B of this document. The applicability of Par t 258, in its entirety or

1.3 PURPOSE, SCOPE, MSWLF unit relative to the date o f AND APPLICABILITY (cont.) public ation, October 9, 1991, or the effective 40 CFR §258.1 (c)-(e) date of the rule, October 9, 1993 (see Figur e 1.3.1 Statement of Regulation * exist: *[NOTE: EPA finalize d several revisions (1) The MSWLF unit received i ts last to 4 0 CFR Part 258 on October 1, 199 3 load of waste prior to October 9, 1991. These (58 FR 51536) and issued a correctio n facilitie s are exempt from all requirements of notice on October 14, 1993 (58 F R 53136). the Criteria. Th ese revisions delay the effective dat e for some categories of landfills. Mor e (2) The last load of waste wa s deta il on the content of the revisions i s rec eivedafter October 9, 1991, but befor e included in the introduction.] Oct ober 9, 1993. The owners and operator s (c) These Criteria do not apply t o requirements of §258.60( a). If the final cover municipal so lid waste landfill units that do is not installed within six (6) months of th e not receive waste after October 9, 1991. las treceipt of wastes, the owners an d (d) MSWLF units tha t receive waste requirements of Part 258. after October 9, 1991 but sto p co mply with all requirements of Part 25 8

with exemptions to specific requirements, i s based upon the operational status of th e

1-1 ). Three possible operational scenario s

must comply only with the final cove r

operators will be required to comply with allSubpart A

6 Figure 1-1 Applicability Flow ChartGeneral

7 (3) The MSWLF unit continues t o 1.4 SMALL LANDFILL receive waste after October 9, 1993. Th e owners or operators must comply with al l req uirements of Part 258, except wher e specified otherwise. 1.3.3 Technical Considerations MS WLF units that receive the last load o f waste between October 9, 1991 and October 9, 1993, must complete closure within si x months of the last receipt of waste. Closure requirements are specified in Subpart F ; howe ver, these MSWLF units will b e su bject only to the closure requirements o f §25 8.60(a) unless they fail to complet e cl osure within the six-month period. Th e alternative cover design is not an option for MSWLF units in unapproved States. The f inal cover system must be designed to minimize infiltration a nd erosion. The final cover must have a permeability that is les s than or equal to the permeability of th e botto m liner system or the natural subsoil s pr esent, or a permeability no greater than 1 x 10 cm/sec, whichever is less. The system -5 must be composed of an erosion layer tha t cons ists of at least six inches of an earthe n material capable of sustaining native plan t gr owth and an infiltration layer that i s composed of at least 18 inches of an earthen ma terial. However, if a MSWLF unit i s cons tructed with a synthetic membrane i n the liner system, it is anticipated that th e fina l cover also will require a syntheti c liner. Currently, it is not possible t o co nstruct an earthen liner with a permeability less than or equal to a synthetic membrane. Detailed technica l con siderations for the cover requirement s under §258.60(a) are p rovided in Chapter 6. EXEMPTIONS 40 CFR §258.1 (f) 1.4.1 Statement of Regulation (f)(1) Ow ners or operators of ne w MS WLF units, existing MSWLF units , and lateral expansions tha t dispose of less tha n twenty (20) tons of municipal soli d waste daily, based on an annual average, are exempt from subparts D [and E] o f * this Part, so long as there is no evidenc e of existing ground-water contaminatio n fro m the MSWLF unit and the MSWL F unit serves: (i) A community that experiences an annual interruption of at leas t th ree consecutive months of surfac e transportation that prevents a ccess to a regional waste managemen t facility, or (ii) A community that has n o practicable wa ste managemen t alternative and the la ndfill unit is located in an area that annually recei ves less than or equal to 25 inches of precipitation. (2) Ow ners or operators of ne w MS WLF units, existing MSWLF units , and lateral expansions that meet th e criteria in (f)(1)(i) or (f)(1)(ii) must place in the operating record informatio n demonstrating this. (3) If the owner or operator of a new MSWLF unit, existing MSWLF unit, or lateral expansion has knowledge o f ground-water contamination resultin g from the unit that has asserted th e exemption in (f)(1)( i) or (ii), the owner or operator must notify the Stat eSubpart A

8 Average Daily Waste Calculation 4 days/week x 52 weeks/year = 208 days/year; and 25 tons/day x 208 days/year = 5200 tons/year; then 5200 tons/year ÷ 365 days/year = 14.25 tons/day. The facility would meet the criteria for receiving less than 20 tons per day. Di rector of such contamination and , and corrective action requirements. Th e therea fter, comply with Subparts D [ and E ]* of this Part. [Note: On May 7, 1993 the U.S. Court o f * Appeals for the District of Columbia Circuit issued an opinio n that EPA did not have the aut hority to exempt these small landfill s from the ground-water monitorin g req uirements (Subpart E), therefore, thes e sm all landfills can not be exempted fro m Subpart E. EPA is delaying the date o f compliance for these units until October 9 , 1995 (58 FR 51536; October 1, 1993).] 1.4.2 Applicability The exemption from Subpart D (Design) is appl icable only to owners or operators o f landfill units that receive, on an annua l average, less than 20 tons of solid waste per day. The exemption is allowed so long a s the re is no evidence of existing ground

water contamination fromthe MSWLF unit. In addition, the MSWLF unit must serve a co mmunity that meets one of the following two conditions:

! For at least three conse cutive months of the year, the community's municipa l so lid waste cannot be transported b y rail , truck, or ship to a regional wast e management facility; or

! There is no practicable alternative fo r ma naging wastes, and the landfill uni t is lo cated in an area that receives les s than 25 inches of annual precipitation. If either of th e above two conditions is met, and there is no evi dence of existing groundwater contamination, th e landfill unit owner or o perator is eligible for the exemptio n from the design, ground-water monitoring, ow ner or operator must place informatio n documenting eligibility for th e exemption in th e facility's operating record. Once a n ow ner or operator can no longer demon

strate compliance with any of the conditions of the exemption, the MSWLF facility must be in compliance with Subpart D. 1.4.3 Technical Considerations The we ight criterion of 20 tons does no t have to be based on actual weigh t me asurements but may be based on weigh t or volume estimates. If the daily wast e receipt records, which include load weights, are not available for the facility, wast e vol umes can be estimated by usin g co nversion factors of 1 ton = two to thre e cubic yards per ton depending o n the type of co mpaction used at the MSWLF unit

. Wast e weights may be determined b y co unting the number of trucks an d estimating an average weight for each. To d etermine the daily waste received, a n aver age may be used. If the facility is no t open on a daily basis, the average numbe r should reflect that fact. For example, if a facil ity is open four days per week (20 8 days/ year) and accepts 25 tons each day , then the average daily amount of wast e received can be calculated as follows:General

9 Compliance with the 20 tons per da y consideration of technical, economic, an d criterion should be based on all wast e received, including household waste an d agricultural or industrial was tes. As defined in the regulations, hou sehold waste includes any solid waste (including garbage, trash , and sanitary waste in septic tanks) derive d from households (including single an d multiple residences, hotels and motels , bun khouses, ranger stations, crew quarters, cam pgrounds, picnic grounds, and day-us e recreation areas). The exemption from Subpart D requires that ther e be "no evidence of existing ground

wat er contamination" as a condition fo r eligibility . Evidence of contamination may include detected or known contamination of ne arby drinking water wells, or physica l evidence such as stressed vegetation that is attributable to the landfill. One of two other condition s must be present for the exemption to apply. The first o f these conditions is an annual interruption in tran sportation for at least three consecutive months. For example, some rural v illages in Alaska may be restricted from transporting wastes to a regional facility due to extreme win ter climatic conditions. These village s would find it i mpossible to transport wastes to a regi onal waste facility for at least three months out of the year due to snow and ice accumulation. Th e second condition is composed of tw o requ irements: (1) the lack of a practicabl e waste management alternative; and (2) a loc ation that receives little rainfall. Th e exemption applies only to those areas tha t meet both requirements. Th e determination of a "practicable wast e management alternative" include s soci al factors. For example, some smal l rural communities, espec ially in the western part of the United States, are located grea t distances from alternative wast e management units (other MSWLF units , co mposting facilities, municipal wast e co mbustors, transfer stations, etc.) makin g re gionalization of waste managemen t difficult. Furthermore, many rural communities ar e locate d in arid areas that receive 25 inche s or less of precipitation annually, whic h re duces the likelihood of ground-wate r contam ination because of lessened leachate generation and contaminant migration

. Rainfall information can be obtained fro m the National Weather Service, the National Oceanographic a nd Atmospheri c Administration (NOAA), and the Unite d Sta tes Geological Survey (USGS) Wate r Atlases.

1.5 APPLICABILITY 40 CFR §258.1 (g)-(j) 1.5.1 Statement of Regulation (g) Municipal solid waste landfil l units failing to satisfy these criteria ar e con sidered open dumps for purposes o f State solid waste management plannin g under RCRA. (h) Municipal solid waste landfil l unit s failing to satisfy these criteri a constitute open dumps, which ar e prohibi ted under Section 4005 of RCRA. (i) Municipal s olid waste landfill units con taining sewage sludge and failin gSubpart A

10 to satisfy these Criteria violate section s criminal actions enforcedunder Section 309 309 and 405(e) of the Clean Water Act. of the Clean Water Act. (j) The effective date of this part i s Oc tober 9, 1993, unless otherwis e 1.6 DEFINITIONS specified.* 40 CFR §258.2 *[NOTE: EPA finalize d several revisions 1.6.1 Statement of Regulation to 4 0 CFR Part 258 on October 1, 199 3 (58 FR 51536) and issued a correctio n Unless otherwise noted, all term s notice on October 14, 1993 (58 F R 53136). contained in this part are defin ed by their Th ese revisions delay the effective dat e pla in meaning. This section contain s for some categories of landfills. Mor e de finitions for terms that appea r deta il on the content of the revisions i s throughout this Part; additiona l included in the introduction.] definitions appear in the specific sections 1.5.2 Applicability All MSWLF facilities that receive waste on or after the effe ctive date must comply with all of Part 258 except where otherwis e noted. MSWLF facilities that fai l to comply wi th the Part 258 Criteria will be i n violation of Section 4005 of RCRA and with Sections 309 a nd 405(e) of the Clean Water Act if the facility receives sewage sludge. 1.5.3 Technical Considerations Failure to comply with the Part 258 Criteria will result in a MSWLF unit bein g catego rized as an open dump under Section 4005 of RCRA. The practice of operatin g an open dump is prohibited. If a MSWLF unit co-disposes sewag e sludge wit h municipal solid waste and fails t o comp ly with Part 258, it also will be i n vi olation of Section 405(e) of the Clea n Wate r Act (CWA), which requires tha t sewage sludge be disposed of in accordance with regulations established for suc h disposal. If found to be in violation, owners or operators may be li able for both civil and to which they apply. Active life means the period of operation begi nning with the initial receipt of solid waste and ending at completion of closure act ivities in accordance with §258.60 o f this Part. Ac tive portion means that part of a facility or unit that has received or i s receiving wastes and that has not bee n clos ed in accordance with §258.60 of this Part. Aquifer means a geological formation , group of formations, or portion of a for mation capable of yielding significant quan tities of ground water to wells o r springs. Comm ercial solid waste means all type s of solid waste generated by stores, offices, restaurants, warehouses, and other non manufacturing activities, excludin g residential and industrial wastes.General

11 D i rector of an approved State means the products; inorganic chemicals; iron an d ch ief administrative officer of the Stat e ag ency responsible for implementing the St ate municipal solid waste permi t program or other system of prio r app roval that is deemed to be adequat e by EPA under regulations publishe d pursuant to section 4005 of RCRA. Ex isting MSWLF unit means an y municipal solid waste landfill unit that is receiving solid waste as of the effectiv e date of this Part. Waste placement i n existing units must be consistent wit h past operating practices or modifie d practices to ensure good management. Faci lity means all contiguous land an d st ructures, other appurtenances, an d improvements on the land used for th e disposal of solid waste. Grou nd water means water below th e land surface in a zone of saturation. Hou sehold waste means any solid wast e (i ncluding garbage, trash, and sanitar y waste in septic tanks) derived fro m households (including sin gle and multiple re sidences, hotels and motels , bunkhouses, ranger stations, cre w quarters, campgrounds, picnic grounds , and day-use recreation areas). In dustrial solid waste means solid wast e generated by manufacturing orindustrial proce sses that is not a hazardous wast e re gulated under Subtitle C of RCRA . Such waste may include, but is not limited to, waste resulting from the following manufacturing processes : Electric power generation; fertilizer/agricultura l chemicals; f

ood and related products/bys t eel manufacturing; leather and leather products; nonferrous metals manufac turing/foundries; organic chemicals ; pl astics and resins manufacturing; pul p an d paper industry; rubber and miscel laneous plastic products; stone, glass , cla y, and concrete products; textil e manufacturing; transportatio n equipment; and water treatment. Thi s term does not incl ude mining waste or oil and gas waste. Lat eral expansion means a horizonta l expansion of the waste boundaries of a n existing MSWLF unit. Le achate means a liquid that has passe d through or emerged f

rom solid waste and co ntains soluble, suspended, or miscibl e materials removed from such waste. Municipal solid w aste landfill unit means a dis crete area of land or an excavatio n that receives house hold waste, and that is not a land application unit, surfac e impoundment, injection well, or wast e pile, as those terms are defined unde r §257.2. A MSWLF unit also may receive other types of RCRA Subtitle D wastes , su ch as commercial solid waste , nonhazardous sludge, conditionall y ex empt small quantity generator waste , and industrial solid waste. Such alandfill may be publicly or privately owned. A MSW LF unit may be a new MSWL F unit, an existing MSWLF unit or a lateral expansion. Ne w MSWLF unit means any municipa l solid waste landfill unit that has no t received waste prior to the effective date of this Part.Subpart A

12 Open burning means the combustion o f Solid waste means any garbage, or refuse, solid waste without: sl udge from a wastewater treatmen t (1) Co ntrol of combustion air t o air pollution control facility and othe r maintain adequate temperature fo r discarded material, including solid , efficient combustion, liq uid, semi-solid, or contained gaseou s (2) Containment of th e commercial, mining, and agricultura l combustion reaction in an enclos ed device operations, and from communit y to provide sufficient residence time an d act ivities, but does not include solid o r mixing for complete combustion, and di ssolved materials in domestic sewage , (3) Control of the emission of the irr igation return flows or industria l combustion products. dis charges that are point sources subject Operatormeans the person(s) responsible so urce, special nuclear, or by-produc t for the overall operation of a facility o r material as defined by the Atomic Energy part of a facility. Act of 1954, as amended (68 Stat. 923). Owner means the person(s) who owns a State means any of the several States, the facility or part of a facility. District of Columbia, the Commonwealth Run-off means any rainwater, leachate , American Samoa, and the Common or other liquid that drains ove r land from w e alth of the Northern Mariana Islands. any part of a facility. Run-on means any rainwater, leachat e, or administrative off icer of the State agency other liquid that drains over land ont o responsible for implementing the Stat e any part of a facility. municipal soli d waste permit program or Satu rated zone means that part of th e earth's crust in which all voids are filled Up permost aquifer means the geologi c with water. formation nearest the natural groun d Sludge means any solid, semi-solid, o r aq uifers that are hydraulicall y liquid waste ge nerated from a municipal, in terconnected with this aquifer withi n co mmercial, or industrial wastewate r the facility's property boundary. treatment plant, water supply treatment pla nt, or air pollution control facilit y Waste management unit bou ndary means exc lusive of the treated effluent from a a ve rtical surface located at th e wastewater treatment plant. hydraulically downgradient limit of th e pla nt, water supply treatment plant, o r

ma terial resulting from industrial ,

or solid or dissolved materials i n

to p ermit under 33 U.S.C. 1342, o r

of Puerto Rico, the Virgin I slands, Guam,

Sta te Director means the chie f

other system of prior approval.

surface that is an aquifer, as well as lower

un it. This vertical surface extends dow n into the uppermost aquifer.General

13 1.6.2 Applicability must yield enough water for ground-wate r The definitions are applicable to all new , ex isting, and lateral expansions of existin g MS WLF units regulated under 40 CF R §25 8. Additional definitions are provide d wi thin the body of the regulatory languag e and will apply to those particular sections

. Definitions in Subpart A apply to al l Sections of Part 258. 1.6.3 Technical Considerations Selected defini tions will be discussed in the following brief narratives. Approved State: Section 4005(c) of RCRA requires that each State adopt an d imp lement a State permit program. EPA is required to determine whether the State has developed an adequate program. State s ha ve primary responsibility for implemen

tation and enforcement of th e Criteria. EPA has the authority to enforce the Criteria i n State s where EPA has deemed the permi t program to be inadequate. The Agenc y intended to extend to Indian T ribes the same op portunity to apply for permit progra m approval as is av ailable to States. A federal court ruled, however, in Backcountr y Against Dump s v. EPA , 100 F.3d 147 (D.C. Cir. 1 996), that EPA cannot do so. Th e Ag ency therefore developed a site-specifi c rulemaking process to provide warrante d flexibility to owners and operators o f MSWLF s in Indian Country. Obtain th e draft guidance document Site-Specifi c Fl exibility Requests for Municipal Soli d Wa ste Landfills in Indian Country ( EP A 530-R-97-016 ) for further information. Aquifer: An aquifer is a formation o r group of formations capable of yielding a significant amo unt of ground water to wells or spr ings. To be an aquifer, a formatio n monitoring samples. An un confined aquifer is one where the water table is exposed t o the atmosphere through openings in th e overlyi ng geologic formations. A confined aquifer is isolated from the atmosphere a t the discharge point by impermeabl e ge ological units. A confined aquifer ha s rel atively impermeable beds above an d below. Existing unit: Any MSWLF unit that i s receiving household waste as of October 9, 1993 must continue to oper ate the facility in a manner that is consistent with both pas t op erating practices and modified practice s that continue or improve good wast e management. Changes in operatin g pr actices intended to circumvent th e purpose, intent, or applicability of an y portions of Part 258 will not be considered in conformance w ith the Criteria. Facilities spread ing a thin layer of waste over unused new areas will not be exempt from th e de sign requirements for new units. Th e por tion of a facility that is considered to be an ex isting unit will include the wast e management area that has received wast e prior to the effective date of Part 258

. Existing units may expand vertically

. However, vertical placement of waste over a clo sed unit would cause the unit to b e considered a new unit andwould subject the unit to the design requirements in Part 258. Note: Not all units that have a valid Stat e permit are considered existing units. To be an existing unit, the land surface must b e covered by waste by October 9, 1993. Lateral expansion: Any horizonta l expansion of the waste boundary of a unit is a la teral expansion. This means that ne wSubpart A

14 land surface would be covered by wast e 1.7 CONSIDERATION OF after October 9, 1993. Expansions to th e OTHER FEDERAL LAWS existing unit

have to be consistent with past 40 CFR §258.3 operati ng procedures or operating practices to ensure good management. 1.7.1 Statement of Regulation Spr eading wastes over a large area t o The owner or operator of a mun icipal increase the size o f an existing unit, prior to solid waste landfill unit must comply with th e effective date would not be consisten t an y other applicable Federal rules, laws, with good management practices. If a new regulations, or other requirements. land surface adjacent to an ex isting unit first receives waste after October 9, 1993, tha t 1.7.2 Applicability area is classified as a lateral expansion and therefore, is subject to the new desig n Owners and operators of MSWLF unit s stan dards. However, Part 258 regulation s must comply with Federal reg ulations, laws, provide the flexibility for appro ved States to rules or requirements that ar e in effect at the determine what would constitute a latera l time of publication of Part 258 or that may expansion. become effective at a later date. Municipal solid waste landfill unit : 1.7.3 Technical Considerations Municipal solid waste landfill un its are units that receive household waste, such as tha t Spe cific sections of Part 258 referenc e from single and multiple residences, hotels maj or Federal regulations that also may b e and motels, bunkhouses, ranger stations , applicable to MSWLF units regulated under crew quarters, campgrounds , picnic grounds Part 258. These regulations include th e and day-use recreation areas. Other Subtitle Clean Water Act (wetlands, sludge dis

D w astes, such as commercial solid waste , posa l, point and non-point source dis

nonhazardous sludge, and industrial soli d charge s), the Clean Air Act, other parts o f waste , may be disposed of in a municipa l RCR A (Subtitle C if the MSWLF uni t solid waste landfill. inadvertently receives regulated hazardou s New municipal solid waste landfill unit : Furthermore, additio nal Federal rules, laws, A new MSWLF unit is any unit that has not or re gulations may need to be considered

. rece ived waste prior to October 9, 1993

. The owner or operator of the MSWLF unit Lateral expansions are considered ne w is responsible for deter-mining th e MSW LF units for the purpose of locatio n con ditions present at the facility that ma y re strictions and design standards. Ne w require consid eration of other Federal Acts, MSWL F units are subject to al l rules, requireme nts, or regulations. Careful requirements of Part 258. review of the Part 258 Criteria will help t o waste), and the Endangered Species Act

.

identify most of the major Federal laws that ma y be applicable to a particular MSWL F unit.15 

# CHAPTER 2 SUBPART B LOCATION CRITERIA16 CHAPTER 2 SUBPART B TABLE OF CONTENTS

2.1 INTRODUCTION

..................................................... 18 2.2 AIRPORT SAFETY 40 CFR §258.10

...................................... 19 2.2.1 Statement of Regulation

.......................................... 19 2.2.2 Applicability

.................................................. 20 2.2.3 Technical Considerations

......................................... 20 2.3 FLOODPLAINS 40 CFR §258.11

......................................... 24 2.3.1 Statement of Regulation

.......................................... 24 2.3.2 Applicability

.................................................. 24 2.3.3 Technical Considerations

......................................... 25 Floodplain Identification

........................................ 25 Engineering Considerations

...................................... 27 2.4 WETLANDS 40 CFR §258.12

............................................ 28 2.4.1 Statement of Regulation

.......................................... 28 2.4.2 Applicability

.................................................. 30 2.4.3 Technical Considerations

......................................... 31 2.5 FAULT AREAS 40 CFR §258.13

......................................... 37 2.5.1 Statement of Regulation

.......................................... 37 2.5.2 Applicability

.................................................. 37 2.5.3 Technical Considerations

......................................... 38 2.6 SEISMIC IMPACT ZONES 40 CFR §258.14

................................ 41 2.6.1 Statement of Regulation

.......................................... 41 2.6.2 Applicability

.................................................. 41 2.6.3 Technical Considerations

......................................... 42 Background on Seismic Activity

.................................. 42 Information Sources on Seismic Activity

............................ 42 Landfill Planning and Engineering in Areas of Seismic Activity

.......... 4217

2.7 UNSTABLE AREAS 40 CFR §258.15

..................................... 45 2.7.1 Statement of Regulation

.......................................... 45 2.7.2 Applicability

.................................................. 46 2.7.3 Technical Considerations

......................................... 47 Types of Failures

.............................................. 49 Subsurface Exploration Programs

................................. 54 Methods of Slope Stability Analysis

................................ 54 Design for Slope Stabilization

.................................... 56 Monitoring

................................................... 60 Engineering Considerations for Karst Terrain

........................ 60 2.8 CLOSURE OF EXISTING MUNICIPAL SOLID WASTE LANDFILL UNITS 4 0 CFR §258.16

....................................................... 61 2.8.1 Statement of Regulation

.......................................... 61 2.8.2 Applicability

.................................................. 62 2.8.3 Technical Considerations

......................................... 62 2.9 FURTHER INFORMATION

............................................. 63 2.9.1 References

.................................................... 63 2.9.2 Organizations

.................................................. 65 2.9.3 Models

....................................................... 68 APPENDIX I - FAA Order 5200.5A

..................................... 6918 

### CHAPTER 2 SUBPART B LOCATION RESTRICTIONS

2.1 INTRODUCTION Part 258 includes location restrictions to address both the potential effects that a municipal soli d w aste landfill (MSWLF) unit may have on the surrounding environment, and the effects that natural a nd human-made conditions may have on the performance of the landfill unit. These criteria pertain t o new and existin g MSWLF units and lateral expansions of existing MSWLF units. The location criteria of Subpart B cover the following:

! Airport safety;

! Floodplains;

! Wetlands;

! Fault areas;

! Seismic impact zones; and

! Unstable areas. Floodplain, fault area, seismic impact zone, and unstable area restrictions address conditions that m ay have adverse ef

fects on landfill performance that could lead to releases to the environment or d isruptions of natur al functions (e.g., floodplain flow restrictions). Airport safety, floodplain, and w etlands criteria are intended to restrict MSWLF units in areas where sen sitive natural environments and/or the public may be adversely affected. O wners or operators must demonstrate t hat the location criteria have been met when Part 258 takes effect. Components of such demonstrations are identified in this section. The owner or operator of the landfill unit must also comply with all other applicable Federal and State regulations, such a s State wellhead protection programs, that are not specifically identified in the Criteria. Owners o r operators should note that many States are now developing Comprehensive State Ground Water Protection Programs. These programs are designed to coordinate and implement ground-wate r programs in the States; they may include additional requirements. Owners or operators shoul d c heck with State environmental agencies concerning Comprehensi ve State Ground Water Protection P rogram requirements. Table 2-1 provides a quick reference to the location standards required by the Criteria.Location Criteria

19 Table 2-1 Location Criteria Standards

Restricted Applies to New Units Approved State" Location Existing Units and Lateral OR Applies to "Director of an
Expansions Retain

Make Demonstration to

Demonstration in Operating Record Existing

Units Must Close ifDemonstration Cannot be Made
Airport Yes Yes Operating Record Yes Floodplains Yes Yes Operating Record Yes Wetlands No Yes Director N/A Fault Areas No Yes Director N/A Seismic Impact No Yes Director N/A Zones Unstable Areas Yes Yes Operating Record Yes

2.2 AIRPORT SAFETY (b) Owners or operators proposing to 40 CFR §258.10 si te new MSWLF units and latera l 2.2.1 Statement of Regulation airport runway end used by turbojet (a) Owners or operators of ne w affected airport and the Federal Aviatio n M SWLF units, existing MSWLFunits, and Administration (FAA). la teral expansions that are located withi n 10,000 feet (3,048 meters) of any airpor t (c) The owner or operator must place runway end used by turbojet aircraft o r the demonstration in paragraph (a) in the withi n 5,000 feet (1,524 meters) of an y operating record and notify the Stat e airport runway end used by only piston - Di rectorthat it has been placed in th e ty pe aircraft must demonstrate that th e operating record. u nits are designed an d operated so that the MSWLF unit does not pose a bird hazar d (d) For purposes of this section: to aircraft. expansions within a f ive-mile radius of any

orpiston-type aircraft must notify th eSubpart B

20 (1) Airport

means public-use airpor t pose bird hazards to aircraft. The regulation o pen to the public without prior p ermission a nd without restrictions within the physical capacities of available facilities. (2) Bird hazard means an increase in the likelihood of bird/aircraft collision s that m ay cause damage to the aircraft o r injury to its occupants. 2.2.2 Applicability O wner s and operators of new MSWLF units, e xisting MSWLF units, and lateral expansions of existing units that are located near a n airp ort, who cannot demonstrate that th e MS WLF unit does not pose a bird hazard , must close their units. Thi s requirement applies to owners an d operators of MSWLF units located withi n 1 0,000 feet of any airport ru nway end used by turbojet aircraft or within 5,000 feet of an y airpo rtrunway end used only by piston-typ e airc raft. This applies to airports open to th e publi c without prior permission for use, an d where use of available facilities is no t r estricted. If the above condi tions are present, the o wner or operator must demonstrate tha t the MSWLF unit does not pose a bird hazard to aircraft and notify the State Director tha t the demonstration has been placed in th e operating record. If the demonstration is not made , existing units must be closed i n accordance with §258.16. Th e regulation, based on Federal Aviatio n Administration (FAA) Order 5200.5 A ( Appendix I), prohib its the disposal of solid wast e within the specified distances unles s the owner or operator is able to make th e req uired demonstration showing that th e l andfill is designed and opera ted so as not to defi nes a "danger zone" within whic h particular care must be taken to ensure that no bird hazard arises. Owners or operators proposing to site ne w units or lateral units within five miles of any airp ortrunway end must notify both th e affected airport and the FAA. Thi s requi rement

is based on the FAA's positio n that MS WLF units located within a five mile radius of any airport runway end, and which at tract or sustain hazardous bird movement s across aircraft flight paths and runways, will be considered inconsistent with safe fligh t ope rations. Notification by the MSWL F owner/operator to the appropriate regiona l FAA office will allow FAA review of th e proposal. 2.2.3 Technical Considerations A demonstration that a MSWLF unit does not pose a bird haz ard to aircraft within specified dis tances of an airport runway end shoul d addre ss at least three elements of th e regulation:

! Is the airport facilit

y within the regulated distance?;

! Is the runway part of a public-us e airport?; and

! Doe s or will the existence of the landfill inc rease the likelihood of bird/aircraf t col lisions that may cause damage to th e aircraft or injury to its occupants? The first element can be addressed usin g exi sting maps showing the relationship o f existing runways at the airport to th e existing or proposed new unit or latera lLocation Criteria

21 ex pansion. Topographic maps (USGS 15

- • Shredding, milling, or baling th e minu te series) or State, regional, or loca l waste-containing food sources; and g overnment agency maps prov iding similar or b etter accuracy would allow direct scaling, or • Eliminating the acceptance of wastes m easurement, of th e closest distance from the at the landfill unit that represent a end of a runway to the nearest MSWLF unit. food source for birds (by alternativ e The measurement can be made by drawing a waste management tec hniques such as cir cle of appropriate radius (i.e., 5,000 ft. , sou rce separation and composting o r 1 0,000 ft, or 5 miles, depen ding on the airport waste minimization). t ype) from the centerline of each runway end. The measurement only should be mad e Freq uent covering of wastes that represent a b etween the end of the runway a nd the nearest foo dsource for the birds effectively reduce s MS WLF unit perimeter, not between an y the availability of the food supply. Depending other boundaries. on s ite conditions such as volume and type s T o deter mine whether the runway is part of a of the working face, cover may need to b e public use airport and to determine whethe r applied several times a day to keep th e all applicable public airports have bee n inact ive portion of the working face smal l identified, the MSWLF unit owner/operato r relativ e to the area accessible to birds. B y sh ouldcontact the airport administration o r maintaining a small working face, spreading the regional FAA office. This rule does no t and compaction equipment are concentrate d apply to private airfields. in a small area that further disrupt s The MSWLF unit design features an d op erational practices can have a significan t Milling or shredding municipal solid wast e ef fect on the likelihood of increase d bre aks up food waste into smaller particl e b ird/aircraft collisions. Birds maybe attracted sizes and distributes the particles throughout to MSW LF units to satisfy a need for water , non-food wastes, thereby dilu ting food wastes foo d, nesting, or roosting. Scavenger bird s to a level that frequently makes the mixtur e s uch as starlin gs, crows, blackbirds, and gulls no longer attractive as a food supply for birds. are most commonly associated with activ e Similarly, baling municipal solid wast e landfill units. Where bird/aircraft collision s reduces the surface area of waste that may be o ccur, these types of birds are often involved available to scavenging birds. due to their flocking, feeding, roosting, an d flight behaviors. Waste managemen t The use of varying bird control technique s techniques to reduce the supply of food t o may prevent the birds from adjusting to a these birds include: single method. Methods such as visua l

• Frequent

covering of wastes tha t mixed success in an attempt to discourag e provide a source of food; bir ds from food scavenging. Visua l o f wastes, waste delivery schedules, and size

scavenging by the birds.

dete rrents or sound have been used wit h

deterrents include realistic models (still o r an imated) of the bird's natural predator sSubpart B

22 ( e.g., humans, owl s, hawks, falcons). Sounds approach to addres sing this part of the airport that have had limited success as deterrent s incl ude cannons, distress calls of th e scavenger birds, and sounds of its natura l preda tors. Use of physical barriers such a s fine wires strung across or near the workin g fac e have also been successfully used (se e Fig ure 2-1). Labor intensive efforts hav e included falconry and firearms. Many o f thes e methods have limited long-term effects on controlling bird populations at landfil l un its/facilities, as the birds adapt to th e environment in which they find food. Pro per design and operation also can reduc e the attraction of birds to the landfill uni t thr ough eliminating scavenger bird habitat

. For ex ample, the use of the landfill unit as a so urce of water can be controlled b y enc ouraging surface drainage and b y preventing the ponding of water. Birds also may be attracted to a landfill unit as a nesti ng area. Use of the landfill site as a roosting or nesting area is usually limited to g round-roos ting birds (e.g., gulls). Operational lan dfillunits that do not operate continuously of ten provide a unique roosting habitat due to elevated ground temperatures (as a result o f wast e decomposition within the landfill) an d freedom from disturbance. Nesting can b e minimized, however, by examining the nesting patterns and requirements of undesirable bird s and designing controls accordingly. Fo r exa mple, nesting by certain species can b e controlled through the mowing an d maintenance schedules at the landfill. In addition to design features an d operational procedures to control bir d po pulations, the demonstration shoul d address the likelihood tha t the MSWLF unit may increase bird/aircraft collisions. On e safety criterio n is to evaluate the attraction of birds to the MSWLF unit and determin e whe ther this increased population would b e expec ted to result in a discernible increase in bir d/aircraft

collisions. The evaluation o f bi rd attraction can be based on fiel d obs ervations at existing facilities wher e sim ilar geographic location, design features , and operational procedures are present. All observations, measurements, data , calculations and analyses, and evaluation s should be documented and included in th e dem onstration. The demonstration must b e pla cedin the operating record and the Stat e Dire ctor must be notified that it has bee n plac edin the operating record (see Sectio n 3.11 in Chapter 3). If an owner or operator of an existin g MSWLF unit cannot successfully de monstrate comp liance with §258.10(a), then the uni t must be closed in accordance with §258.6 0 and post-closure activities must be conducted in accordance with §258.61 (see §258.16)

. Closure must

occur by October 9, 1996. The Director of an approved State can extend the perio d up to 2 years if it is demonstrated that no available alternative disposal capacity exist s and the unit poses no immediate threat to human health and the environment (se e Section 2.8). In accordance with FAA guidance, if a n owner or operator is proposing to locate a new un it or lateral expansion of an existin g MSWL F unit within 5 miles of the end of a public-use airport runway, the affected airport and the re gional FAA office must be notified to provide an opportunity to review an d comment on t

he site. Identification of public airports in a given area can beLocation Criteria

23 

### Figure 2-1. Bird Control DeviceSubpart B

24 r eq uested from the FAA. Topographic maps (3) Washout means the

carrying away (e. g., USGS 15-minute series) or othe r of solid waste by waters of the base flood. similarly accurate maps showing th e relationship of the airport runway and th e 2.3.2 Applicability MSWLFunit should provide a suitable basis for determining whether the FAA should b e Own ers/operators of new MSWLF units , notified. exi sting MSWLF units, and latera l

2.3 FLOODPLAINS dem onstrate that the units will not restric t 40 CFR §258.11 the flow of a 100-year flood nor reduce the 2.3.1 Statement of Regulation in a wash-out of solidwaste, must close the (a) Owners or operators of ne w and temporary storage capacity of a M SWLF units, existing MSWLFunits, and floodplain. Highe r flood levels and greater lat eral expansions located in 100-yea r flood damage both upstream an d f loodplains must demonstrate that the unit downstream can be cre ated and could cause wil l not restrict the flow of the 100-yea r a potential hazard to human health an d f loo d, reduce the temporary water storage saf ety. The rule does not prohibit locating cap acity of the floodplain, or result i n a MSWLF unit in a 100-year floodpl ain; for wash outof solid waste so as to pose a ex ample, the owner or operator is allowe d hazard to human health and th e to d emonstrate that the unit will compl y e nvironment. The ow ner or operator must wit h the flow restriction, temporar y place the demonstration in the operatin g storage, and washout provisions of th e r ecord and not

ify the State Director that it regulation. If a dem onstration can be made has been placed in the operating record. that the landfill unit will not pose threats , (b) For purposes of this section: operating record, and the State Directo r (1) Floodplain

means the lowland and mad e and placed in the record. If th e re latively flat areas adjoining inland an d demonstration cannot be made for a n c oastal waters, including flood-prone areas exi sting MSWLF unit, then the MSWL F of offshore islands, that are inundated b y unit must be closed in 5 years in accordance the 100-year flood. with §258.60, and the owner or operato r (2) 100-year flood means a flood that accordance with §258.61 (see §258.16)

. has a 1-percent or greater chance o f Th e closure deadline may be extended fo r recurring in any given year or a flood of a up to two years by the Director of a n m agnitude equaled or exceed ed once in 100 approved State if th e owner or operator can years on the average over a significantl y de monstrate that no available alternativ e long period. dis posal capacity exists and ther e expan sions of existing units located in a 100-year river floodplain who canno t

wat er storage capacity, and will not resul t unit(s). A MSWLF unit can affect the flow

the demonstration must be placed in th e must be notified that the demonstration was

mu st conduct post-closure activities i nLocation Criteria

25 is n o immediate threat to human health an d Guida nce on using FIRMs is provided i n the environment (see Section 2.8). "How to Read a Flood Insurance Rate Map " 2.3.3 Technical Considerations "The National Flood Insurance Progra m Compliance with the floodplain criterio n communities that may not be involved in the beg ins with a determination of whether th e National Flo od Insurance Program but which MSW LF unit is located in the 100-year have FIRMs or Floodway maps published

. fl oodplain. If the MSWLF unit is located i n Maps and other FEMA publications may b e th e 100-year floodplain, then the owner o r obtained from t he FEMA Distribution Center oper ator must demonstrate that the unit wil l (see Section 2.9.2 for the address). Areas not not pose a hazard to human health and th e coveredby the FIRMs or Floodway map s environment due to: may be included in floodplain maps available

! Restricting the base flood flow; the U.S. Geological Survey, the U.S. Soi l

! Reducing the temporary water storage ; Ma nagement, the Tennessee Valle y and Au thority, and State, Tribal, and loca l

! Resulting in the washout of solid waste. Guidance for identifying floodplains an d maps may have undergone modification fo r d emonstrating facilitycompliance is provided hydropower or flood control projects and , below. th erefore, the floodplain boundarie s Floodplain Identification re presentative. It may be necessary t o River floodplains are readily identifiable a s air photographs to identify current rive r the fl at areas adjacent to the river's norma l channel modifications and land us e channel. One hundred-year floodplain s watersheds that could affect floodplai n r epresent th e sedimentary deposits formed by designations. If floodplain maps are no t flo ods that have a one percent chance o f av ailable, and the facility is located within a occu rrence in any given year and that ar e flo odplain, then a field study to delineate the ident ifiedin the flood insurance rate map s 100-year floodplain may be required. A (F IRMs) and flood boundary and floodwa y floodplain delineation program can be based ma ps published by the Federal Emergenc y pri marily on meteorological records an d Management Agency (FEMA) (see Figur e physiographic information such as existin g 2-2). Areas classified as "A" zones ar e an dplanned watershed land use , subject to the floodplain location restriction

. top ography, soils and geologic mapping , Areas classified as "B" or "C" zones are no t andair photo interpretation o f s ubject to the restriction, although care should geomorphologic (land form) features. Th e be taken to design facilities capable o f Uni tedStates Water Resource Counci l withstanding some potential flooding. (1977) provides information for determining pu blishedby FEMA. FEMA also publishe s Com munity Status Book" that list s

through the U.S. Army Corps of Engineers , Conservation Service, the Bureau of Lan d
agencies. Many of the river channels covered by these

representedmay not be accurate o r compare the floodplain map series to recen t26 

### Figure 2-2 Example Section of Flood Plain MapLocation Criteria

27 the pote ntial for floods in a given location by impinging river waters. Depending on th e s tream gauge records. Estimation of the peak amou nt of inundation, the landfill unit ma y dis charge also allows an estimation of th e act as a channel side slope or bank or it may probability of exceeding the 100-year flood. be iso lated as an island within the overban k Engineering Considerations the r iver velocity would be part of a prope r If the MSWLF unit is within the 100-year flo odplain, it must be located so that th e Th e assessment of flood water velocity MSWLFunit does not significantly restric t req uires that the channel cross section b e th e base flood flow or significantly reduc e know n above, at, and below the landfill unit. t emp orary storage capacity of the floodplain. Frict ion factors on the overbank are deter

T he MSWLF unit must be designed to prevent m i ned from the surface conditions and vegethe washout of solid waste during th e tation prese nt. River hydrologic models may expect edflood event. The rule requires tha t be us ed to simulate flow levels and estimat e flo odplain storage capacity, and flo w velocities through these river cross sections. restrictions that occur as the result of th e M SWLF uni t, do not pose a hazard to human Th e Army Corps of Engineers (COE, 1982 ) health and the environment. has developed several numerical models t o The demonstration that these consideration s flow parameters, t he effect of obstructions on ar e met relies on estimates of the flo w flow levels, the simulation of flood contro l ve locity and volume of floodplain storage i n structures, and sediment transport. Thes e th e vicinity of the MSWLF unit during th e methods may or may not be appropriate for a bas e flood. The assessment should conside r site ; however, the following models provid e the floodplain storage capacity and floodwater well-tested analytical approaches: v elocities that would likely exist in absence of the MSWLF unit. The volume occupied by a HEC-1 Flood Hydrograph Packag e MSWLF unit in a floodplain ma y (watershedmodel that simulates th e theoretically alter (reduce) the storag e surface run-off response of a river basin capac ity and restrict flow. Raising the bas e to precipitation); flood l evel by more than one foot can be a n indic ation that the MSWLF unit may reduc e HEC- 2 Water Surface Profiles (compute s and restrict storage capacity flow. water surface profiles due t o T he location of the M SWLF unit relative to encroachment potential); t he velocity distrib ution of floodwaters will gr eatly influence the susceptibility t o HEC-5 Simulation of Flood Control an d washout. This type of assessment wil l Co nservation Systems (simulates th e require a con servative estimate of the shear sequential operation of a reservoi r s tress on the landfill components caused by cha nnel system with a branche d the depth, velocity, and duration o f net work configuration; used to desig n river channel. In both cases an estimate o f
assessment.

aidin the prediction of flood hydrographs ,

obstructions; evaluates floodwa ySubpart B

28 routing that will minimize downstrea m 2.4 WETLANDS flooding); and 40 CFR §258.12 HEC-6 Scour and Deposition in River s 2.4.1 Statement of Regulation andReservoirs (calculates water surface and sediment bed surface profiles). (a) New MSWLF units and latera l The HEC-2 model is not appropriate fo r unless the owner o r operator can make the sim ulation of sediment-laden braided strea m following demonstrations to th e Director of sy stems or other intermittent/dry strea m an approved State: s ystems that are subject to flash flood events. Standard run-off and peak flood hydrograp h (1) Where applicable under section 404 methods would be more appropriate for such of the Clean Wate r Act or applicable State conditions to predict the effects of sever e we tlands laws, the presumption that a flooding. pra cticable alternative to the propose d There are many possible cost-effectiv e wetlands is clearly rebutted; methods to protect the MSWLF unit fro m f lood damage including embankment designs (2) The construction and operation of with rip-rap, geotextiles, or other materials

. the MSWLF unit will not: G uideline s for designing with these materials may be found in Maynard (1978) and SC S (i) Cause or contribute to violations of (1983 ). Embankment design will require a n any applicable State water qualit y e stimate of river flow velocities, flow profiles standard, (depth), and wave activity. Figure 2- 3 pr ovides a design example for dik e (ii) Violate any applicable toxi c construction and protection of the landfil l effluentstandard or prohibition unde r s urface from flood water. It addresses height Section 307 of the Clean Water Act, req uirements to control the effects of wav e a c tivity. The use of alternate erosion control (iii) Jeopardize the contin ued existence methods such as gabions (cubic-shaped wir e of endangered or threatened species o r structures filled with stone), paving bricks , re sultin the destruction or advers e and mats may be considered. It should b e modification of a critical h abitat, protected n oted, however, that th e dike design in Figure under the Endangered Spe cies Act of 1973, 2-3 may further decrease the water storag e and and flow capacities. expansions shall not be located i n wetlands,

landfil l is available which does not involve

(iv) Violate any requiremen t under the Marine Protection, Research, and Sanctuaries Act of 1972 for the protection of a marine sanctuary;29 

### Figure 2-3. Example Floodplain Protection Dike DesignSubpart B

30 (3) The MSWL F unit will not cause or una voidable impacts to the maximu m con tribute to significant degradation o f extent practicable, and finally offsettin g wetla nds. The owner or operator mus t remaining unavoidable wetland impact s demo nstrate the integrity of the MSWL F through all appropriate and practicabl e unit and its ability to protect ecologica l compensatory mitigation actions (e.g. , res ources by addressing the followin g restoration of existing degraded wetland s factors: or creation of man-made wetlands); and (i ) Erosion, stability, and migratio n (5) Suff icient information is available p otential of n ative wetland soils, muds and to make a reasonable determination wit h d eposits used to support the MSWLF unit; respect to these demonstrations. (ii ) Erosion, stability, and migratio n (b) For purposes of this section , p otential of dredged an d fill materials used "wet lands" means those areas that ar e to support the MSWLF unit; defined in 40 CFR §232.2(r). (iii) The volume and chemical nature 2.4.2 Applicability o f the waste mana ged in the MSWLF unit; (iv) Impacts on fish, wildlife, an d wet lands are prohibited, except in approve d oth eraquatic resources and their habita t Stat es. The wetland restrictions allo w from release of the solid waste; existing MSWLF units located in wetlands to (v) The potential effects o f wi th the other requirements of Part 258 ca n c atastrophic release of waste to the wetland be maintained. and the resulting impacts on th e environment; and In addition to the regulatio ns listed in 40 CFR (vi) Any additional factors, a s may be applica ble in siting a MSWLF unit in nec essary, to demonstrate that ecologica l a wetland. These include: reso urces in the wetland are sufficientl y protected. ! Sections 401 , 402, and 404 of the CWA; (4 ) To the extent required unde r ! National Environmental Policy Act; Section 404 of the Clean Water Act o r ! Migratory Bird Conservation Act; applicable St ate wetland laws, steps have ! Fish and Wildlife Coordination Act; been t aken to attempt to achieve no ne t ! Coastal Zone Management Act; los s of wetlands (as defined by acreag e ! Wild and Scenic Rivers Act; and the a nd function) by first avoi ding impacts to ! National Historic Preservation Act. wet lands to the maximum exten t pr acticable as required by paragrap h As authorized by the EPA, the use o f (a)(1) of this section, then minimizin g wetlands for location of a MSWLF facility New MSWLF

units and lateral expansions in

cont inue operations as long as complianc e

§258.12(a)(2), other Federal requirement s

! Rivers and Harbors Act of 1989;

may require a permit from the U.S. Arm yLocation Criteria

31 Corps of Engineers (COE). The types o f proposedin the Federal Register on Augus t w etlands present ( e.g., headwater, isolated, or adj acent), the extent of the wetland impact , an dthe type of impact proposed wil l determine the applicable category of CO E permit (individual or general) and the permit app lication procedures. The COE Distric t Engineer should be contacted prior to permit ap plication to determine the availabl e categories of permits for a particular site

. Wetland permitting or permit review an d comment can include additional agencies at the federal, state, regional, and local level

. T he requirements for wetland permits should be reviewed by the owner/operator to ensur e compliance with all applicable regulations. When proposing to locate a new facility o r later al expansion in a wetland, owners o r ope rators must be able to demonstrate that a lternative sites are not available and that the impact to wetlands is unavoidable. If it is demonstrated that impacts to th e wetlandare unavoidable, then all practicable efforts must be made to minimize and, when nec essary, compensate for the impacts. Th e i mpacts must be compensated for by restoring degraded wetlands, enhancing or preservin g existing wetlands, or creating new wetlands

. It is an EPA objective that mitigatio n activi ties result in the achievement of no ne t loss of wetlands. 2.4.3 Technical Considerations
T he term wetlands, referenced in §258.12(b), i s defined in §2 32.2(r). The EPA currently is studying the issues involved in defining an d del ineating wetlands. Proposed changes t o the "Federal Manual for Identifying an d Delineating Jurisdictional Wetlands," 1989 , are still being reviewed. [ These changes were 14, 1991 (56 FR 40446) and on De cember 19, 1991 (56 FR65964).] Therefore, as o f January 1993, the method used for delineating a wetland is based on a previously existin g doc ument, "Army Corps of Engineer s Wetlands Delineation Manual," 1987. A Me morandumof Understanding betwee n EPA and the Department of the Army, Corps of Engineers, was amended on January 4 , 1993, to state that both agencies would no w use the COE 1987 manual as guidance fo r delineating wetlands. The methodolog y applied by an owner/operator to define an d deline ate wetlands should be in keeping with the federal guidance in place at th e time of the delineation. Because of the uni que nature of wetlands, the owner/operator is required to demo nstrate that the landfill unit will not ca use or contribute to sig nificant

degradation of wetlands. Th e de monstration must be reviewed an d approved by the Director of an approved State and placed in the facility operating record

. Th is provision effectively bans the siting o f ne w MSWLF units or lateral expansions i n wetlands in unapproved States. There are several key issues that need to b e addr essed if an owner or operator proposes to loc ate a lateral expansion or a new MSWLF uni t in a wetland. These issues include: (1 ) rev iewof practicable alternatives, (2 ) evaluation of

wetland acreage and function, (3) evaluation of impacts of MSWLF units o n wetlands, and (4) offsetting impacts. Although EPA has an objective of no net loss of wetlands in terms of acreage and function, it recognize s that regions of the country exist where pr oportionallylarge areas are dominated b y wetlands. In these regions, sufficientSubpart B

32 acreage and a suitable type of upland may not • Cause or contribute to violation o f be p resent to allow construction of a ne w any requirement for the protection of MS WLF unit or lateral expansion withou t a marine sanctuary; and wet landimpacts. Wetlands evaluations ma y become an integral part of the siting, design, • Jeopa rdize the continued existence of permitting, and environmental monitorin g endangeredor threatened species o r a spects of a landfill unit/faci lity (see Figure 2- critical habitats. 4). Practicable Alternatives to significant degradation of wetlands

. E PA believes that locating new MSWLF units or lateral expansions in wetlands should b e • Ensu re the integrity of the MSWL F done only where there are no less damagin g unit, including consideration of th e alte rnatives available. Due to the extent o f er osion, stability, and migration o f wetl ands that may be present in certai n native wetland soils and dredged/fil l r egions, the banning of new MSWLF units or materials; la teral expansions in wetlands could caus e s er ious capacity problems. The flexibility of • Minimize impacts on fish, wildlife , the rule allows owners or operators t o and other aquatic resources and thei r demonstrate that there are no practicabl e hab itat from the release of soli d a lternativ es to locating or laterally expanding waste; MSWLF units in wetlands. As part of the evaluation of practicabl e release of wastes o n the wetlands; and alternatives, the owner/operator shoul d con sider the compliance of the location with • Assure that ecological res ources in the o ther reg ulations and the potential impacts of we tlands are sufficiently protected , the MSWLF unit on wetlands and relate d including consider ation of the volume re sources. Locating or laterally expandin g and chemical nature of wast e MSWLFunits in wetlands require s managed in the MSWLF unit. compliance with other environmenta l regulations. The owner or operator mus t The se factors were partially derived fro m s how that the operation or construction of the Section 404(b)(1) of the Clean Water Act

. landfill unit will not: These guidelines addres s the protection of the

• Vio late any applicable State wate r quality standards; Af ter consideration of these factors, if n o

• C ause or contribute to the violation of in w etlands is available, compensatory step s a ny a pplicable toxic effluent standard must b e taken to achieve no net loss o f or prohibition; wetlands as defined by acreage and The M SWLF unit cannot cause or contribute Therefore, the owner/operator must:

• Evaluate the effects of catastrophi c

ecological resources of the wetland.
practi cable alternative to locating the landfill33 Figure 2-4 Wetlands Decision Tree for Owners/Operators

in Approved StatesSubpart B

34 function. The owner/operator must try t o a specific ca se. Typical criteria may include: av oidand/or minimize impacts to th e wetlands to the greatest extent possible

. • Di stance from waste generatio n W here avoidance and minimi zation still result sources; in wetland impacts, mitigation to offse t • Minimum landfill facility siz e i mpacts is required. Mitigation plans must be requirements; approved by the appropriate regulatory • Soil conditions; agencies and must achieve an agreed-upo n • Proximity to ground-water users; me asure of success. Examples of mitigatio n • Proximity of significant aquifers; include restoration of degraded wetlands o r • Exclusions from protected natura l creation of wetland acreage from existin g areas; uplands. • Degree of difficulty to remediat e P art 258 presumes that practicable alternatives • Setbacks from roadways an d are available to locating landfill units i n residences. we tlands because landfilling is not a water

d ependent activity. In an approved State, the Wetland Evaluations owner or operator can rebut the presumption that a practicable alternative to the propose d The term "wetlands" includes swamps , landfill unit or lateral expansion is available. ma rshes, bogs, and any areas that ar e The term "practicable" pertains to th e inund atedor saturated by ground water o r e conomic and social feasibility of alternatives surfac e water at a frequency and duration t o (e .g., collection of waste at transfer station s support, and that under normal circumstances a nd trucking to an existing landfill facility or do s upport, a prevalence of vegetatio n oth er possible landfill sites). The feasibility adaptedfor life in saturated soil conditions

. evaluation may entail financial, economic , As defined under current g uidelines, wetlands ad ministrative, and public acceptability are identified ba sed on the presence of hydric analyses as well as engineerin g soils, hydrophytic vegetatio n, and the wetland c onsid erations. Furthermore, the evaluations hyd rology. These characteristics also affec t gen erally will require generation an d the functional value of a wetland in terms of a ssessment of land use, geologic, hydrologic, its role in: supporting fish and wildlif e ge ographic, demographic, zoning, traffi c hab itats; providing aesthetic, scenic, an d maps, and other related information. recreational value; accommodating floo d
T o rebut the presump tion that an alternative re lationships to surrounding natural area s p racticable si te exists generally will require through nutrient retention and productivity t h at a site search for an alternative location ex portation (e.g., releasing nutrients t o be c onducted. There are no standar d do wnstreamareas, providing transportabl e methods for co nducting site searches due to food sources). the variability of the number and hierarchy of screening criteria that may be applied in Often , a wetland assessment will need to b e features; and

sto rage; sustaining aquatic diversity; and it s

conducted by a qualified and experiencedLocation Criteria

35 multi-disciplinary team. The assessmen t of wetland that triggers State agenc y s ho uld identify: (1) the limits of the wetland boundary based on hydrology, soil types and plant types; (2) the type and relativ e abundance o f vegetation, including trees; and (3) rare, endangered, or otherwise protecte d species and their habitats (if any). The current methods used to delineat e wetl ands are presented in "COE Wetland s D elineation Manual," 1987. In January 1993, E PA and COE agreed to u se the 1987 Manual for purposes of delineation. The Federa l Manual for Identifying and Delineatin g J urisdictional Wetlands (COE, 1989) contains an extensive reference list of availabl e wetlandliterature. For example, lists o f references for the identification of plan t species characteristic of wetlands throughout the Unite d States, hydric soils classifications, andrelated wetland topics are presented

. US GS topographic maps, National Wetlan d In ventory (NWI) maps, Soil Conservatio n Se rvice (SCS) soil maps, wetland inventory m aps, and aerial photogra

phs prepared locally also may provide useful information. Aft er completion of a wetland study, th e impact of the MSWLF unit on wetlands an d its r elationship to adjacent wetlands can b e assessedmore effectively. During th e permitting process, local, State, and federa l agencies with jurisdiction over wetlands will need t o be contacted to schedule a site visit

. I t is usuall y advantageous to encourage this c ollabora tion as early as possible in the site evaluation process, especially if the Stat e program office that is responsible fo r wetl and protection is different from th e solid waste management office

. Reg ulations will vary significantly fro m S tate to State with regard to the size and type invol vement. In general, the COE wil l require notification and/or consultation o n any proposed impact on any wetlan d regardless of the actual degree of the impact. Other agencies such as the Fish and Wildlife Servi ce and the SCS may need to b e contacted in some States. Eva luation of ecological resource protectio n ma y include assessment of the value of th e affected wetland. Various techniques ar e avai lable for this type of evaluation, and th e most ap propriate technique for a specific site should be selected in conjunction with ap plicable regulatory agencies. Availabl e methods include analysis of functional value, the Wetland Evaluation Technique (WET) , and the Habi tat Evaluation Procedure (HEP). The 1987 Manual does not address functional value in the detail provided by the 198 9 manual. The methodology for conducting a functional value assessment should b e re viewedby the applicable regulatory agencies. It is important to note tha t func tional value criteria may become a standard part of wetland delineati on following revi sion of the federal guidance manual(s)

. The owner

or operator should remain current with the accepted practices at the time of the delineation/assessment. The functional value of a given wetland i s depe ndent

on its soil, plant, and hydrologi c characteristics, particularly the diversity , pr evalence, and extent of wetland plan t spe cies. The relationship between th e wetland and surroun ding areas (nutrient sinks and sources) and the ability of the wetland to support animal habitats, or r are or endangered sp ecies, contributes to the evaluation o f functional value.Subpart B

36 Other wetland and related assessmen t wetlands are formed in response to perche d m ethodologies include WET and HEP. WET water tables over geologic material of lo w a llows comparison of the value s and functions hydraulic conductivity and, therefore , o f wetlands be fore and after construction of a significant drawdown impacts may not occur. fac ility, thereby projecting the impact a facil ity may have on a wetland. WET wa s It is possible t hat the landfill unit/facility will dev elopedby the Federal Highwa y not directly displace wetlands, but tha t Administration and revised by the CO E adverse effects may be caused by leachate or (Ada mus et al ., 1987). HEP was develope d run-off. Engineered containment systems for b y the Fish and Wildlife Service to determine both leachate and run-off should mitigate the the quality and quantity of available habita t potential for discharge to wetlands. for selected species. HEP and WET may b e u sed in conjunction with each oth er to provide Ad ditional actions and consideration s an integrated assessment. relevant to mitigating impacts of fil l Impact Evaluation appropriate for MSWLF facilities ar e If the new unit or lateral expansion is to b e Adv erse Effects) of 40 CFR §23 0 loc atedin a wetland, the owner or operato r (G uidelines for Specification of Disposa l must demonstrate that the unit will not cause Sites for Dredged or Fill Materials). o r contributeto significant degradation of the wet land. Erosion potential and stability o f Wetland Offset w etland soi ls and any dredged or fill material used to support the MSWLF unit should b e Al l unavoidable impacts must be "offset" o r iden tifiedas part of the wetlands evaluation

. compensated for to ensure th at the facility has A ny adverse stability or ero sion problems that not caused, to the extent practicable, any net co uldaffect the MSWLF or contaminan t loss of wetland acreage. This compensatory effec ts that could be caused by the MSWL F mi tigation may take the form of upgradin g unit should be resolved. ex isting marginal or lower-quality wetland s Al l practicable steps are to be taken t o studies require review and development on a minimize potential impacts of the MSWLF site-specific basis. unit to wetlands. A number of measure s that can aid in minimization of impacts are To id entify potential sites that may b e available. Appropriate measures are site

- prop osed for upgrade of existing wetland s s pecific and sho uld be incorporated into the or cr eation of new wetlands, a cursory des ign and operation of the MSWLF unit

. assessment of surrounding wetlands an d For example, placement of ground wate r uplands should be conducted. Th e b arriers may be required if soil and shallow assessment may include a study to defin e gr ound-water conditions would caus e the functional characteristics and inter

dewat ering of the wetland due to th e rel ationships of these potential wetlan d existence of underdrain pipe systems at the mitigation areas. An u pgrade of an existing faci lity. In many instances, however , we tland may consist of transplantin g material in wetlands that may b e provided in Subpart H (Actions to Minimize

or c reating new wetlands. Wetland offse tLocation Criteria

37 ap propriate vegetation and importing low

- alte rnative setback distance of less tha n permeability soil materials that would b e 200 feet (60 meters) will pr event damage to co nducive to forming saturated soi l the structural integrity of the M SWLF unit conditions. Excavation to form open wate r and will be protective of h uman health and bodi es or gradual restoration of salt wate r the environment. m arshes by culvert expansions to promote sea water influx are other examples o f (b) For the purposes of this section: compensatory mitigation. Indiv idual States may have offset ratios t o fractures in any material along whic h de termine how much acreage of a give n strata on one side have bee n displaced with functional value is required to replace th e respect to that on the other side. wetlands that were lost or impacted

. Pr eservation of lands, such as throug h (2 ) Displacementmeans the relativ e perpetual conservation easements, may b e movement of any two sides of a faul t cons ideredas a viable offset option. Stat e measured in any direction. offset ratios may require that for wetlands of an equivalent functional value, a large r (3) Holocene means the most recen t acreage be created than was displaced. epoch of the Quate rnary period, extending
D ue tothe experimental nature of creating or the present. e nhancing wetla

nds, a monitoring program to eval uate the progress of the effort should b e 2.5.2 Applicability considered and may be required as a wetland permitcondition. The purpose of th e Except in approved States, the reg ulation bans monit oring program is to verify that th e all new MSWLF units or lateral exp ansions of cr eated/upgradedwetland is successfull y exist ing units within 200 feet (60 meters) o f establishedand that the intended function o f the outermost boundary of a fault that ha s the wetland becomes self-sustaining ove r experienced displacement during th e time. Holo cene Epoch (within the last 10,000 t o

2.5 FAULT AREAS are located in fault areas. 40 CFR §258.13 2.5.1 Statement of Regulation provi ded if the owner or operator ca n (a) New MSWLF units and latera l State that a shorter distance will preven t expansions shall not be located within 200 damag e to the structural integrity of th e fe et(60 meters) of a fault that has ha d MS WLF unit and will be protective o f dis placementin Holocene time unless th e hu man health and the environment. Th e owne ror operator demonstrates to th e de monstration for a new MSWLF unit o r Direc torof an approved State that a n la teral expansion requires review an d (1) Fault means a fracture or a z one of

fr om the end of the Pleistocene Epoch t o

12,00 0 years). Existing MSWLF units ar e neither required toclose nor to retrofit if they

A variance to the 200-foot setback i s demon strate to the Director of an approvedSubpart B

38 approval by the Director of an ap proved State. used. A series of maps known as th e If the demonstration is approved, it must b e "Preliminary Young Fault Maps , placed in the facility's operating record. The Miscellan eous Field Investigation (MF) 916" o p tion to have a setback of less than 200 feet was p ublished by the USGS in 1978

. from a Holocene fault is not available i n Information about these maps can be obtained unapproved States. from the USGS by calling 1-800-USA

2.5.3 Technical Considerations Center in Reston, V irginia, or by calling 303- Lo cating a landfill in the vicinity of an are a Sales Center in Denver, Colorado. that has experienced faulting in recent tim e h as inherent dangers. Fault ing occurs in areas For locations where a fault zone has bee n w here the geologi c stresses exceed a geologic subject to movement since the USGS map s mat erial's ability to withstand those stresses

. wer e published in 1978, a geologi c Such areas also tend to be subject t o rec onnaissance of the site and surroundin g ear thquakes and ground failures (e.g. , areas may be req uired to map fault traces and lan dslides, soil liquefaction) associated with to determine the faults along whic h seismic activity. A more detailed discussio n movement has occurred in Holocene time

. o f seismic activity is presented in Section 2.6. This reconnaissanc e also may be necessary to
Pr oximity to a fault can cause damag e than 200 feet. Additional requirements ma y through: needto be met before a new unit or latera l

• Mo vement

along the fault which ca n cause di splacement of facility structures, A site fault characterization is necessary to

• Seismic activity associated with faulting a fa ult that has had movement during th e which can cause damage to facility Hol ocene epoch. An investigation woul d structures through vibratory action (se e include obtaining information on an y Figure 2-5), and lin eaments (linear features) that suggest th e

• Earth shaking which can cause groun d of t he site. The information could be base d failures such as slope failures. on: C onsequently, appropriate setbacks from fault • A review of available maps, logs , area s are required to minimize the potentia l reports, s cientific literature, or insurance for damage. claim reports; To de termine if a proposed landfill unit i s • An aerial reconnaissance of the are a loca tedin a Holocene fault area, U.S

. within a five-mile radius of the site , Geological Survey (USGS) mapping can be including aerial photo analysis; or MAPS , which reaches the USGS Nationa l 236- 7477, which reaches the USGS Map

support a demonstration for a setback of less
expansion may be approved.

determine whet

her a site is within 200 feet of

presence of faults within a 3,000-foot radiu sLocation Criteria

39 Figure 2-5 Potential Seismic Effects

A schematic diagram of a landfill showing potential deformation of the leachate collection and removal system by seismic stresses. Source: US EPA, 1992Subpart B

40 • A field reconnaissance that include s Based on this information as well a s walking portions of th e area within 3,000 sup porting maps and analyses, a qualifie d feet of the unit. professional should prepare a report tha t I f thesite fault characterization indicates that fault(s) and the associated 200-foot setback. a fault or a set of faults is situated withi n 3 ,000 feet of the pro posed unit, investigations If requesting an alternate setback, a shouldbe conducted to determine th e demonstration must be made to show that no presence or absence of any faults within 20 0 dam age to the landfill's structural integrity fee tof the site that have experience d wil l result. Examples of engineerin g m ovement durin g the Holocene period. Such consideration s and modifications that may be investigations can include: included in such demonstrations are a s

• Subsurface exploration, includi ng drilling and trenching, to locate fault zones an d • For zones with high probabilities of high evidence of faulting. accelerations (horizontal) within th e

• T renching perpendicular to any faults or designs should be developed. lineaments within 200 feet of the unit.

• Det ermination of the age of an y slopes should be performed to guid e displacements, for example b y examining sel ection of materials and gradients fo r displacement of surfi cial deposits such as slopes. gla cial or older deposits (if Holocen e deposits are absent). • Where in-situ and laboratory test s

• Examination of seismic epicente r susceptible to liquefaction, groun d information to look for indications o f improvement measures like grouting , recent movement or activity alon g dewatering, heavy tamping, an d structures in a given area. excavation should be implemented.

• Rev iew of high altitude, high resolutio n • Engineering options include: aerial photographs with stereo-visio n coverage. The photogr aphs are produced

— Flexible pipes, by the National Aerial Photographi c Program(NAPP) and the National High

— Ground improvement measure s Alti tude Program (NHAP). Information (grouting, dewatering, heav y on these photos can be obtained from the tamping, and excavation), and/or USGS EROS Data Center in Sioux Falls, South Dakota at (605) 594-61 5

— Redundant precautionar y delineates the location of the Holocen e

follows:

moderate range of 0.1g to 0.75g, seismic

• Se ismic stability analysis of landfil l

indicate that a potential landfill site i s

measures (secondary containment system).Location Criteria

41 I n addi tion, use of such measures needs to be accel eration will not be exceeded in 25 0 d emonstrated to be protective of h uman health years, or the maximum expected horizontal andthe environment. The types o f acceleration based on a site-specific seismic engineering controls described above ar e risk assessment. similar to those that would be employed i n are as that are likely to experienc e (3) Lithified earth material means al l earthquakes. rock, including all n aturally occurring and

2.6 SEISMIC IMPACT ZONES that formed by crystallization of magma or 40 CFR §258.14 by i nduration of loose sediments. Thi s 2.6.1 Statement of Regulation such as fill, concrete, and asphalt, o r (a) New MSWLF units and latera l rego lith lying at or near the earth surface. expa nsions shall not be located in seismi c i mpact zones, unles s the owner or operator 2.6.2 Applicability demonstrates to the Director of a n approved State that all containmen t New MSWLF units and lateral expansions in structures, including liners, leachat e seismic impact zones are prohibited, except in col lection systems, and surface wate r approved States. A se ismic impact zone is an cont rol systems, are designed to resist th e area that has a ten percent or greate r maximum horizontal acceleration i n pro bability that the maximum expecte d lithi fied earth material for the site. Th e horizontal acceleration in lithified earth owneror operator must place th e ma terial, expressed as a percentage of th e d emonstration i n the operating record and ear th's gravitational pull (g), will excee d no tify the State Director that it has bee n 0.10g in 250 years. placed in the operating record. (b) For the purposes of this section: lateral expansions in a seismic impact zon e (1) Seismic impact

zone means an area that the structural components of the uni t wi th a ten percent or greater probabilit y (e.g., liners, leac hate collection systems, final t ha t the maximum horizontal acceleration cover, and surface water control systems) are in l ithified earth material, expressed as a de signedto resist the maximum horizonta l p ercentage of t

he earth's gravitational pull accel eration in lithified earth material at th e (g), will exceed 0.10g in 250 years. sit e. Existing units are not required to b e (2) Maximum horizontal acceleratio n or lateral expan sions must notify the Director in lithified earth material means th e of an approved State and place th e m aximum expected horiz ontal acceleration dem onstration of compliance with th e depict ed on a seismic hazard map, with a co nditions of the restriction in the operatin g 90 percent or greater probability that th e record. natu rally formed aggregates or masses o f minerals or small particles of older roc k

term does not include man-made mate rials, unconsolidated earth materials, soil, o r

The regulation prohibits locating new units or unless the owner or operator can demonstrate

retrofitted. O wners or operators of new unitsSubpart B

42 2.6.3 Technical Considerations for t he United States and Puerto Rico " Background on Seismic Activity T o understand seismicactivity, it is helpful to know its origin. A brief introduction to th e geologic underpinnings of seismic activity is presented below. Th e earth's crust is not a static system. I t consists of an assemblage of earthen masse s that are in slow motion. As new crust i s g ener ated from within the earth, old edges of cru st collide with one another, thereb y causing stress. The weaker edge is forced to m ove benea

th the stronger edge back into the earth. The dynamic conditions of the earth's crus t c an be manifested as shaking ground (seismic ac tivity), fracturing (faulting), and volcani c eruptions. Seismic activity also can result in t ypes of gro und failure. Landslides and mass m ovements (e.g., slope failures) are common on slopes; soil compaction or groun d subsidence tends to occur in unconsolidate d valley sediments; and liquefaction of soil s tends to happen in areas where sandy or silty s oils that are sat

urated and loosely compacted become in effect, liquefied (like quicksand ) due t o the motion. The latter types o f phe nomenaare addressed in Section 2.7 , Unstable Areas. Information Sources on Seismic Activity To determine the maximum horizonta l acce leration of the lithified earth materia l fo r the site (see Figure 2-6), owners o r operators of MSWLF units should revie w the s eismic 250-year interval maps in U.S

. Geological Survey Miscellaneous Fiel d S tudy Map MF-2120, entit led "Probabilistic E arthquake Acceleration and Velocity Maps (A lgermissen et al., 1991). To view th e original of the m ap that is shown in Figure 2- 6 (reduced in size), contact the USGS offic e in yo ur area. The original map (Horizonta l Acceleration - Base modified from U.S.G.S. Na tional Atlas, 1970, Miscellaneous Fiel d Studi es, Map MF 2120) shows county line s within each State. For areas not covered b y the aforementioned ma

p, USGS State seismic maps may be used to estimate the maximum horizontal acceleration. The Nationa l Earthquake Information Ce nter, located at the Colorado School of Mines in Golden , Colorado, can

provide seismic maps of all 50 states. The Center also maintains a database of known earthquakes and fault zones. Information on the location of earthquak e epicenters and intensities may be available through State Geologic Surveys or th e Earthquake Information Center. Fo r infor mation concerning potentia l earthquakes in specific areas, the Geologic Ri skAssessment Branch of USGS may b e of a ssistance. Other organizations tha t stu dy the effects of earthquakes o n engineered structures include the Nationa l Information Service for Earthquak e Eng ineering, the Building Seismic Safet y Cou ncil, the National Institute of Scienc e and Technology, and the A merican Institute of Architects. Landfill Planning and Engineering i n Areas of Seismic Activity Studies indicate that during earthquakes , superf icial (shallow) slides and differential disp lacement tend to be produced, rathe r than massive slope failures (U.S. Nav y 1983). Stresses created by superficia l failures can affect the liner and final cover

### Figure 2-6. Seismic Impact Zones

(Areas with a 10% or greater probability that the maximum horizontal acceleration will exceed .10g in 250 years)Subpart B

44 sys tems as well as the leachate and ga s pr ecautionary measures should be designe d collection and removal systems. Tensiona l and built into the various landfill systems. stress es within the liner system can result i n fracturing of the soil liner and/or tearing o f For th ose units located in an area with a n the f lexible membrane liner. Thus, whe n estimatedmaximum horizontal acceleratio n selecting suitable sites from many potentia l gre ater than 0.1g, an evaluation of seismi c sites during the siting process, th e ef fects should consider both foundation soi l o wner/operator should try to av oid a site with: stability and waste stability under seismi c

• Holocene fault zones, fo rthe evaluation include the constructio n
• Sites with potential ground motion, and phase (maximum open excavation depth o f

• Sites with liquefaction potential. new cell adjacent to an existing unit), closure If on e of the above types of sites is selected , waste and subsoil), and post-closure car e th e owner/operator must consider the cost s (after final consolidation of both waste an d associated with the development of the site. fou ndation soil). If the maximum horizontal
I f, due to a

lack of suitable alternatives, a site the design of the unit will not have t o is chosen that is located in a seismic impac t inc orporate an evaluation of seismic effect s zone, a demonstration must be made to th e unless th e facility will be situated in an area Director of an approved State that the design wit h low strength foundation soils or soil s of the unit's structural components (e.g. , with potential for liquefaction. The facility l iners, leachate collection, fin al covers, run-on should be assessed for the effects of seismi c a nd run-off sys tems) will resist the maximum activity even if the horizontal acceleration is h orizontal acceleration in lithified materials at expected to be less than 0.1g. the s ite. As part of the demonstration , owner/operators must: In determining the potentia l effects of seismic

• Det ermine the expected peak groun d acc eleration from a maximum strength earthquake that could occur in the area,

• De termine the site-specific seismi c hazards such as soil settlement, and

• Design the facility to withstand th e expected peak ground acceleration. Th e design of the slopes, leachate collectio n system, and other structural component s sho uldhave built-in conservative desig n factors. Additionally, redundan t loadi ng. Conditions that may be considere d

activitie s (prior to final consolidation of both

acceleration is les s than or equal to 0.1g, then

ac tivity on a structure, an engineerin g evaluation shoul d examine soil behavior with re spect to earthquake intensity. Whe n e v aluating soil characteristics, it is necessary to kno w the soil strength as well as th e magnitude or intensity of the earthquake i n term s of peak acceleration. Other soi l ch aracteristics, including degree o f compaction, sorting (organization of the soil particles), and deg ree of saturation, may need to be considered because of their potentia l inf luence on site conditions. For example , de posits of loose granular soils may b e compactedby the ground vibrations induced by an earthquake. Such volume reduction s could result in large uniform or differentia lLocation Criteria

45 s ettlements of the ground s urface (Winterkorn well-es tablished analytical methods. Several and Fang, 1975). Well-compactedcohesionless embankment s or reasonably flat slopes in insensitive cla y are less likely to fail under moderate seismic shocks (up to 0.15g and 0.20g acceleration)

. Embankments made of insensitive cohesiv e soils founded on cohesive soils or rock ma y with standeven greater seismic shocks. Fo r earthen embankments in seismic regions , desi gns with internal drainage and cor e m aterial most resistant

to fracturing should be cons idered. Slope materials vulnerable t o earthquake shocks are described below (U.S. Navy, 1983):

• Very steep slopes of weak, fractured and bri ttle rocks or unsaturated loess ar e vulnerable to transient shocks caused by tensional faulting;

• Loess and saturated sand may b e liq uefiedby seismic shocks causing th e sudd en collapse of structures and flo w slides;

• Similareffects are possible in sensitiv e cohesive soils when natural moistur e exceeds the soil's liquid limit; and

• Dry cohesionless material on a slope at an angle of repose will respond t o seismic shock by shallow sloughing and slight flattening of the slope. In general, loess, deltaic soils, floodplai n soils, and loose fills are highly susceptible to liquefaction under saturated condition s (USEPA, 1992). Geotechnical stability investigation s fre quently incorporate the use of compute r models to reduce the computational time of computer software packages are available that app roximate the anticipated dynamic force s of the design earthquake by resolving th e force s into a static analysis of loading o n de sign cross sections. A conservativ e approach would in corporate both vertical and horizontal forces caused by bedroc k acceleration if it can be shown that the types of mat erial of interest are susceptible to th e vertical force component. Typically, th e hor izontal force caused by bedroc k ac celeration is the major force to b e considered in the seismic stability analysis

. Exa mples of computer models include PC

Slope by Geoslope

Programming (1986), and FLUSH by the University of California. Design modifications to accommodate a n earthquake may include shallower wast e sideslopes, more co nservative design of dikes an drun-off controls, and additiona l contingencies for leachate collection shoul d primary systems be disrupted. Strengths o f th e landfill components should be able t o withstand these additional forces with a n accep table factor of safety. The use o f professio nals experienced in seismic analysis is s trongly recommended for design o f facilities located in

areas of high seismic risk.

2.7 UNSTABLE AREAS 40 CFR §258.15 2.7.1 Statement of Regulation (a) Owners or operators of ne w MSWLF units, existing MSWLF units , and lateral expansions located in a n unstable area must demonstrate tha t engineering measures have bee n inc orporated into the MSWLF unit' sSubpart B

46 design to ensure that the integrity of th e indicate that a natural or man-induce d s tructural componentsof the MSWLF unit will not be disrupted. The owner o r operator must place the demonstration i n the operating record and notify the Stat e Directorthat it has been placed in th e operating record. The owner or operato r mu st consider the following factors, at a minimum, when determining whether a n area is unstable: (1) On-site

or local soil conditions that may result in significant differentia l settling; (2 ) On-site or local geologic o r geomorphologic features; and (3) On-site or local human-mad e fe atures or events (both surface an d subsurface). (b) For purposes of this section: (1) Unstable area

means a location that i s susceptible to natural or human-induced events or forces capable of impairing th e integrity of some or all of the landfil l st ructural components responsible fo r pr eventing releases from a landfill . U nstable areas can include poor fo undation co nditions, areas susceptible to mas s movements, and Karst terrains. (2 ) Structural components mean s liners, leachate collection systems, fina l covers, run-on/run-off systems, and an y other component used in the constructio n and operation of the MSWLF that i s necessary for protection of human healt h and the environment. (3) Poor foundation conditions means thos e areas where features exist whic h event may re sult in inadequate foundation support for the structural components of a MSWLF unit. (4) Areas susceptible to mas s movementmeans those areas of influenc e (i .e., areas characterized as having a n active or substantial possibility of mas s move ment) where the movement of eart h mate rial at, beneath, or adjacent to th e MSWLF unit, because of natural or manindu ced events, results in the downslop e tran sportof soil and rock material b y means of gr avitational influence. Areas of mass movement include, but are no t li mited to, landslides, avalanches, debri s slides and fl ows, solifluction, block sliding, and rock fall. (5) Karst terrains means areas where kar st topography, with its characteristi c sur face and subterranean features, i s developed as the result of dissolution o f limesto ne, dolomite, or other soluble rock. Characteristic physiographic feature s pr esent in karst terrains include, but ar e not limited to, sinkholes, sinking streams , caves, large springs, and blind valleys. 2.7.2 Applicability Own ers/operators of new MSWLF units , exi sting MSWLF units, and latera l exp ansions of units that are located i n un stable areas must demonstrate th e structural integrity of the unit. Existin g units for which a successful demonstration cannot be made must be closed. Th e regulation applies to new units, existin g units, and lateral expansions that are located on sites classified as unstable areas

. Unst able areas are areas susceptible t oLocation Criteria

47 na tural or human-induced events or force s (e.g. , heavy rain) or man-made event s that are capable of impairing o r destroying the (e.g., explosions). int egrity of some or all of the structura l components. Structural components consis t

— E xpansive soils usually are clayof liners, leachate collection systems, fina l rich soils that, because of thei r cov er systems, run-on and run-off contro l molecular struct ure, tend to swell systems, and any other component necessary andshrink by taking up an d for protection of human health and th e rel easing water and thus ar e environment. sensitive to a variable hydrologic MSWL F units can be located in unstabl e smectite (montmorillonite group) areas, but the owner or operator mus t and vermiculite clays; bentonit e d emonstrate that the structural integrity of the is a smectite-rich clay. I n MSW LF unit will not be disrupted. Th e ad dition, soils rich in "whit e demonstration must show that engineerin g alkali" (sodium sulfate) , measures have been incorporated into th e anhydrite (calcium sulfate), o r d esign of the unit to ensure the integrity of the pyrite (iron sulfide) also ma y structural components. Existing MSWL F exhib it swelling as water content u nits that do not meet the demonstration must increases. Such soils tend to b e be c losed within 5 years in accordance with found in the arid western states. §25 8.60, and owners and operators mus t undertake post-closure activities i n — Soils that are subject to rapi d a ccordance with

§258.61. The Director of an settlement (subsidence) includ e approved State can grant a 2-y ear extension to lo ess, unconsolidated clays, an d the closure requirement under two conditions: wet landsoils. Loess, which i s ( 1) no disposal alternative is a vailable, and (2) fou ndin the central states, is a n o immediate threat is posed to human health wind-depositedsilt that i s and the environment. mo isture-deficient and tends t o 2.7.3 Technical Considerations Unco nsolidated clays, which can Ag ain, for the purposes of this discussion , states, can undergo considerabl e n atural unstabl e areas include those areas that com paction when fluids such a s have poor soils for foundations, ar e wat er or oil are removed

. susceptible to mass movement, or have kars t Similarly, wetland soils, whic h features. by their nature a re water-bearing,

• Are as with soils that make poo r subsidence when water i s fo undations have soils that ar e withdrawn. expa nsive or settle suddenly. Suc h areas may lose their ability to support a • Anot her type of unstable area is a n foundation when subjected to natura l ar ea that is subject to mas s re gime. Such soils include :

compact upon wetting

. be found in the southwestern

al so tend to be subject t o

movement . Suc h areas can be situatedSubpart B

48 o n steep or gradual s lopes. They tend to have • A closed landfill as the foundation for a rock or soil conditions that are conducive t o new landfill ("piggy-backing") may b e downslope movement of soil, rock, and/o r unstable unless the closed landfill ha s debri s (either alone or mixed with water ) un dergone complete settlement of th e under the influence of gravity. Examples o f underlying wastes. mass movements include avalanches , landslides, debris slides and flows, and roc k As part of their demonstration to site a slides. landfil l in an unstable area, owners/operators

• Kar st

terrains tend to be subject t o to serve as a foundation as well as the ability extreme incidents of differentia l of the site embankments and slopes t o settlement, namely complete groun d maint ain a stable condition. Once thes e collapse. Karst is a term used to describe fa ctors have been evaluated, a MSWL F ar eas that are underlain by solubl e design should be developed that will address bedrock, such as limestone, wher e these types of concerns and prevent possibl e solution of the rock by water create s as sociateddamage to MSWLF structura l sub terranean drainage systems that ma y components. include areas of rock collapse. Thes e area s tend to be characterized by larg e In designing a new unit or lateral expansio n su bterranean and surficial voids (e.g. , or re-evaluating an existing MSWLF unit, a caverns and sinkh oles) and unpredictable stability assessment should be conducted in sur face and ground-water flow (e.g. , order to avoid or prevent a d estabilizing event sinking streams and large spr ings). Other from impairing the structural integrity of the ro cks such as dolomite or gypsum als o landfill component systems. A stability may be subject to solution effects. assessment involves essentially thre e Ex amples of human-induced unstable area s conditions, an analysis of slope stability, and are described below: an examination of related design needs. A n

• The presence of cut and/or fill slope s during construction of the MSWLF uni t • Assessing the stability of foundatio n may cause slippage of existing soil o r soils, adjacent em bankments, and slopes; rock.

• Exc essive drawdown of ground wate r geological characteristics of the site t o increases the effective overburden on the est ablishsoil strengths and othe r foundation so ils underneath the MSWLF en gineering properties by performin g unit, which may cause excessiv e sta ndardpenetration tests, field van e settlement or bearing capacity failure on shear tests, and laboratory tests; and the foundation soils. must assess the ability of the soils and/or rock

components: an evaluation of subsurfac e

eva luation of subsurface conditions requires:

• In vestigating the geotechnical an dLocation Criteria

49 • Testing the soil properties such as water In formation on natural features can b e content, shear strength, plasticity, an d obtained from: grain size distribution. A stability assessment should conside r en titled"Engineering Aspects o f (USEPA, 1988): Karst," published in 1984;

• Th e adequacy of the subsurfac e • Regional or local soil maps; exploration program;

• The liquefaction potential of th e karst areas); and embankment, slopes, and foundatio n soils; • Site-specific investigations.

• The expected behavior of th e To examine an area for possible sources of embankment, slopes, and foundati on soils human-induced ground instability, the sit e wh en they are subjected to seismi c and surrounding area should be examine d activity; fo r activities related to extensiv e

• Th e potential for seepage-induce d subsurface units as well as construction o r failure; and other operations that may result in groun d

• The potential for differential settlement.
In addition, a qualified professional mus t a ssess, at a minimum, natura l conditions (e.g., Fail ures occur when the driving force s soil , geology, geomorphology) as well a s impo sed on the soils or engineere d hu man-made features or events (both structure s exceed the resisting forces of the sub surface and surface) that could caus e material . The ratio of the resisting force to differential settlement of ground. Natura l the driving force is considered the factor of cond itions can be highly unpredictable an d safety (FS). At an FS value less than 1.0 , d estructive, especiallyif amplified by human- failure will occur by definition. There is a i nduced changes to the environment. Specific high probability that, due to natura l ex amples of natural or human-induce d vari ability and the degree of accuracy i n phenomena include: debris flows resultin g me asurements, interpreted soil condition s from heavy rainfall in a small watershed; the will not be precisely representative of th e rapid formation of a sinkhole as a result o f act ual soil conditions. Therefore, failur e exce ssive local or regional ground wate r ma y not occur exactly at the calculate d wit hdrawal in a limestone region; earth val ue, so factors of safety greater than 1. 0 dis placement

by faulting activity; an d are required for the design. For plastic soils rockfalls along a cliff face caused b y su ch as clay, movement or deformatio n vib rations resulting from the detonation o f (cre ep) may occur at a higher factor o f explosives or sonic booms. safety prior to catastrophic failure

. • The USGS National Atlas map

• Aerial photographs (especially i n

wit hdrawal of oil, gas, or water fro m
motion (e.g., blasting). Types of FailuresSubpart B

50 Princi pal modes of failure in soil or roc k settle ment, which can be used to aid i n include: estimating differential settlement.

• Rot ation (change of orientation) of a n Allowable settlement is typicall y earthen mass on a curved slip surfac e ex pressedas a function of tota l approximated by a circular arc; settlement because differential settlement

• Tra nslation (change of position) of a n di fferential settlement is a more seriou s eart hen mass on a planar surface whos e thre at to the integrity of the structur e length is large compared to depth below than total settlement. Differentia l ground; se ttlement also is discussed in Sectio n

• Di splacement

of a wedge-shaped mas s along one or more planes of weakness; • Loss of bearing strength is a failur e

• Earth and mud flows in loose clayey and have soils that tend to expand, rapidl y silty soils; and settle, o r liquefy, thereby causing failure

• Debris flows in coarse-grained soils. MSWLF compone nts. Another example Fo rthe purposes of this discussion, thre e failures that have occurred at operatin g types of failures can occur at a landfill unit : sit es where excavations for landfil l se ttlement, loss of bearing strength, an d expa nsions adjacent to the filled area s sinkhole collapse. reduce d the mass of the soil at the toe of

• If not properly engineered, a landfill i n st rength (resisting force) of th e an unstable area may undergo extrem e foundation soil. settlement , which ca

n result in structural failure. Differential settlement is a • Catastrophic collapse in the form o f particular mode of failure that generall y sin kholes is a type of failure that occurs oc curs beneath a landfill in response t o in k arst regions. As water, especiall y co nsolidation and dewatering of th e ac idic water, percolates throug h fo undation soils during and followin g limestone (calcium carbonate), th e waste loading. so luble carbonate material dissolves , Se ttlement

beneath a landfill unit, both overlying caverns can collapse suddenly, total and differential, should be assessed result ing in sinkhole features that can be andcompared to the elongation strength 100 feet or more in depth and 300 feet or and flexure properties of the liner an d more in width. lea chate collection pipe system. Eve n small amounts of settlement ca n Table s 2-2 and 2-3 provide examples o f se riously damage leachate collectio n analytical considerations for mode of failur e pi ping and sumps. The analysis wil l assessments in both natural and human-made pro vide an estimate of maximu m slopes. is mo re difficult to predict. However ,

6.3 of Chapter 6.

mode that tends to occur in areas that

orreducing performance of overlyin g of loss of bearing strength involve s

the slope, thereby reducing the overal l

forming cavities and caverns. Lan dLocation Criteria

51 1. Slope in Coarse-Grained Soil with

Some Cohesion Low Groundwater High Groundwater Failure of thin Failure at relatively wedge, position shallow toe circles influenced by tension cracks • With low groundwater, failure occurs on shallow, straight, or slightly curved surface. Presence of a tension crack at the top of the slope influences failure location. With high groundwater, failure occurs on the relatively shallow toe circle whose position is determined primarily by ground elevation.

• Analyze with effective stress using strengths C' and Ø' from CD tests. Pore pressure is governed by seepage condition. Internal pore pressures and external water pressures must be included.

2. Slope in Coarse-Grained, Soil Cohesion Low Groundwater High Groundwater Stable slope angle Stable slope angle = effective friction = 1⁄2 effective angle friction angle • Stability depends primarily on groundwater conditions. With low groundwater, failures occur as surface sloughing until slope angle flattens to friction angle. With high groundwater, stable slope is approximately 1/2 friction angle.

• Analyze with effective stress using strengths C' and Ø' from CD tests. Slight cohesion appearing in test envelope is ignored. Special consideration must be given to possible flow slides in loose, saturated fine sands.

3. Slope in Normally Consolidated or Slightly Preconsolidated Clay Location of failure depends on variation of shear strength with depth. • Failure occurs on circular arcs whose position is governed by theory. Position of groundwater table does not influence stability unless its fluctuation changes strength of the clay or acts in tension cracks.

• Analyze with total stresses, zoning cross section for different values of shear strengths. Determine shear strength from unconfined compression test, unconsolidated undrained triaxial test or vane shear.

Source: Soil Mechanics, NAVFAC Design Manual 7.01

Table 2-2. Analysis of Stability of Natural SlopesSubpart B

52 4. Slope in Stratified Soil Profile Location of failure depends on relative Failure surface is combination of active and strength and orientation of layers. • Location of failure plane is controlled by relative strength and orientation of strata. passive wedges with central sliding block chosen to conform to stratification.

• Analyze with effective stress using strengths C' and Ø' for fine-grained strata and Ø' for cohesionless material.

5. Depth Creep Movements in Old Slide Mass Bowl-shaped area of low slope (9 to 11%) bounded at top by old scarp. • Strength of old slide mass decreases with magnitude of movement that has occurred previously. Most dangerous situation is in stiff, over-consolidated clay which is softened, fractured, or slickensided in the failure zone.

Source: Soil Mechanics, NAVFAC Design Manual 7.01

Table 2-2. Analysis of Stability of Natural Slopes (Continued)Location Criteria

53 1. Failure of Fill on Soft Cohesive Foundation with Sand Drains

Location of failure depends on geometry and

strength of cross section. • Usually, minimum stability occurs during placing of fill. If rate of construction is controlled, allow for gain in strength with consolidation from drainage.

• Analyze with effective stress using strengths C' and Ø' from CU tests with pore pressure measurement. Apply estimated pore pressures or piezometric pressures. Analyze with total stress for rapid construction without observation of pore pressures, use shear strength from unconfined compression or unconsolidated undrained triaxial. 2. Failure of Stiff Compacted Fill on Soft Cohesive Foundation

Failure surface may be rotation on circular arc or translation with active and passive wedges. • Usually, minimum stability obtained at end of construction. Failure may be in the form of rotation or translation, and both should be considered.

• For rapid construction ignore consolidation from drainage and utilize shear strengths determined from U or UU tests or vane shear in total stress analysis. If failure strain of fill and foundation materials differ greatly, safety factor should exceed one, ignoring shear strength of fill. Analyze long-term stability using C and Ø from CU tests with effective stress analysis, applying pore pressures of 3. Failure Following Cut in Stiff Fissured Clay

Failure surface depends on pattern of fissures or depth of softening. • Release of horizontal stresses by excavation causes expansion of clay and opening of fissures, resulting in loss of cohesive strength.

• Analyze for short-term stability using C' and Ø'with total stress analysis. Analyze for longterm stability with C' and Ø' based on r m residual strength measured in consolidated drained tests.

Source: Soil Mechanics, NAVFAC Design Manual 7.01

Table 2-3. Analysis of Stability of Cut and Fill Slopes,

Conditions Varying With TimeSubpart B

54 Subsurface Exploration Programs Methods of Slope Stability Analysis
F oundation soil s tability assessments for non- Slo pe stability analyses are performed fo r c atastrophic failure require field i nvestigations both excavated side slopes and abovegroun d to determine soil strengths and other soi l embankments. The analyses are performed as prope rties. In situ field vane shear test s appropriate to verify the struct ural integrity of com monly are conducted in addition t o a cut slope or dike. The design configuration coll ection of piston samples for laboratory is evaluated for its stabi lity under all potential te sting of undrained shear strengths (biaxia l hy draulic and loading conditions, includin g and triaxial). Field vanes taken at depth conditions that may exist during construction provide a profile of soil strength. Th e of an expansion (e.g., excavation). Analyses r equired field vane depth intervals vary, based typ ically performed are slope stability , on soi l strength and type, and the number o f settlement, an d liquefaction. Factor of safety b orings required d epends on the variability of rationale and selection for different conditions the soils, the site size, and landfill uni t are described by Huang (1983) and Terzaghi dim ensions. Borings and field vane testin g andPeck (1967). Table 2-4 list s shou ldconsider the anticipated design t o rec ommendedminimum factor of safet y i dentify segments of the f

acility where critical values for slopes. Many States may provid e cro ss sections are likely to occur. Critica l thei rown minimum factor of safety sections are where factors of safety ar e requirements. anticipated to be lowest. O t her tests that are conducted to characterize available for performing slope stabilit y a soil include determination of water content, analy ses. Method selection should be base d Atterberg limits, grain size distribution , on t he soil properties and the anticipate d co nsolidation, effective porosity, an d mo de of failure. Rationale for selecting a saturated hydraulic conductivity. The sit e specific method should be provided. hydrogeologic conditions should be assesse d to d etermine if soils are saturated o r The majority of these methods may b e unsaturated. cate gorized as "limit equilibrium" methods Catastrophic failures, such as sinkhol e det ermined and compared. The basi c c ollapse in karst terrain s or fault displacement assumption of the limit equilibriu m durin g an earthquake, are more difficult t o approach is that the failure criterion i s p redict. Subsurface kar st structures may have satisfied along an assumed failure surface

. surface topographic expressions such a s This surface may be a straight line, circular ci rcular depressions over subsiding solutio n arc, logarithmic spiral, or other irregula r cav erns. Subsurface borings or geophysica l pl ane. A free body diagram of the drivin g tech niques may provide reliable means o f force s acting on the slope is constructe d i dentif ying the occurrence, depth, and size of usin g assumed or known values of th e sol ution cavities that have the potential fo r forces. Next, the soil's shear resistance as it catastrophic collapse. pe rtains to establishing equilibrium i s Th ere are numerous methods currentl y

in w hich driving and resisting forces ar e

calculated. This calculated shear resistanceLocation Criteria

55 

### Table 2-4 Recommended Minimum Values of Factor of Safety

for Slope Stability Analyses

Uncertainty of Strength Measurements Consequences of Slope Failure Small Large 1 2 No imminent danger to human life or 1.25 1.5 major environmental impact if slope (1.2)* (1.3) fails Imminent danger to human life or 1.5 2.0 or greater major environmental impact if slope (1.3) (1.7 or greater) fails The uncertainty of the strength measurements is smallest when the soil 1 conditions are uniform and high quality strength test data provide a consistent, complete, and logical picture of the strength characteristics. The uncertainty of the strength measurements is greatest when the soil 2 conditions are complex and when available strength data do not provide a consistent, complete, and logical picture of the strength characteristics.

* Numbers without parentheses apply for static conditions and those within parentheses apply to seismic conditions.

Source: EPA Guide to Technical Resources for the Design of Land Disposal

Facilities.Subpart B

56 then is compared to t

he estimated or available excavating a bench in the upper part o f s hear strength of the soil to give an indication o f thefactor of safety (Winterkorn and Fang, 1975). Methods that consider only the whole fre e bo dy as a single unit include the Culman n methodand the friction circle method

. Anoth er approach is to divide the free bod y into vertical slices and to consider th e e quilibrium of each s lice. Several versions of the slice method are avail able; the best known are the Swedish Circle method and the Bishop method. Discussions of these and othe r methods may be found in Winterkorn an d Fang (1975), Lambe and Whitman (1969) , and U.S. Navy (1986). A comp uter program that is widely used fo r slope stability analysis is PC STABL, a twodimensional model that computes th e min imumcritical factors of safety betwee n l ayer interfaces. This model uses the method of vertical slices to analyze the slope an d c alculate the factor of

safety. PC STABL can account for heterogeneous soil systems , ani sotropic soil strength properties, exces s p ore water pressure due to shear, static ground wat er and surface water, pseudostati c earthquake loading, surcharge boundary l oading, and ti eback loading. The program is w ritten in F ORTRAN IV and can be run on a P C. Figure 2-7 presents a typical output from the model. Design for Slope Stabilization Methods for slope stabilization are presented in Table 2-5 and are summarized below.

• Th e first illustration shows that stability can be increased by changing the slop e geometry through reduction of the slope height, flattening the slope angle, or the slope.

• The second illustration shows ho w co mpactedearth or rock fill can b e placed in the form of a berm at an d bey ondthe slope's toe to buttress th e slope

. To prevent the development o f undesirable water pressure behind th e ber m, a drainage system may be place d behind the berm at the base of the slope.

• Th e third illustration presents severa l typ es of retaining structures. Thes e structures generally involve drillin g and/or excavation followed b y constructing cast-in-place concrete piles and/or slabs.

— Th e T-shaped cantilever wal l des ign enables some of th e reta inedsoil to contribute to th e stability of the structure and i s ad visable for use on slopes that have vertical cuts.

— Closely-spacedvertical pile s placedalong the top of the slope area provide reinforcemen t aga inst slope failure through a soil arching effect that is created between the piles. This type o f re taining system is advisable fo r use on steeply cut slopes.

— Ve rtical piles also may b e de signedwith a tie bac k component at an angle to th e vertical to develop a hig h resistance to lateral forces. Thi s type of wall is recommended for use in areasLocation Criteria

57 Figure 2-7 Sample Output from PC STABL Model

Œ Subgrade: Internal friction angle = 32 degrees œ Refuse: Internal friction angle of waste = 25 degrees – Refuse: Internal friction angle of waste = 25 degreesScheme Applicable Methods Comments

1. Changing Geometry 1. Reduce slope height by 1. Area has to be accessible excavation at top of slope to construction 2. Flatten the slope angle. needed for excavated soil. 3. Excavate a bench in incorporated in this upper part of slope. method. equipment. Disposal site Drainage sometimes

2. Earth Berm Fill 1. Compacted earth or rock 1. Sufficient width and berm placed at end thickness of berm beyond the toe. Drainage required so failure will may be provided behind not occur below or the berm. through the berm. 3. Retaining Structures 1. Retaining wall: crib or 1. Usually expensive. cantilever type. Cantilever walls might 2. Drilled, cast-in-place vertical piles and/or slabs 2. Spacing should be such founded well below that soil can arch between bottom slide plane. piles. Grade beam can be Generally 18 to 36 inches used to tie piles together. in diameter and 4- to 8- Very large diameter (6 foot spacing. Larger feet±) piles have been diameter piles at closer used for deep slide. spacing may be required in some cases with mitigate failures of cuts in highly fissured clays. have to be tied back.

Source: Soil Mechanics, NAVFAC Design Manual 7.01

Table 2-5 Methods of Stabilizing Excavation SlopesScheme Applicable Methods Comments
3. Drilled, cast-in-place 3. Space close enough so vertical piles tied back soil will arch between with battered piles or a piles. Piles can be tied deadman. Piles founded together with grade beam. well below slide plane. Generally, 12 to 30 inches in diameter and at least 4- to 8-foot spacing.

4. Earth and rock anchors 4. Can be used for high and rock bolts. slopes, and in very

5. Reinforced earth. 5. Usually expensive restricted areas. Conservative design should be used, especially for permanent support. Use may be essential for slopes in rocks where joints dip toward excavation, and such joints daylight in the slope.

4. Other methods See TABLE 7, NAVFAC DM7.2, Chapter 1
Source: Soil Mechanics, NAVFAC Design Manual 7.01

Table 2-5 (continued) Methods of Stabilizing Excavation SlopesSubpart B

60 with steeply cut slopes where soi l Monitoring arch ing can be developed between th e piles. During construction activities, it may b e

— The last retaining wall show n because of the additional stresses placed on uses a cantilever setup alon g natural and engineered soil systems (e.g. , wit h soil that has bee n slo pes, foundations, dikes) as a result o f reinforced with geosyntheti c ex cavation and filling activities. Post

material to provide a syst em that clo sure slope monitoring usually is no t is highly resistant to ve rtical and necessary. la teral motion. This type o f sy stem is best suited for use i n Im portant monitoring parameters ma y situations where vertically cu t include settlement, lateral movement, an d sl opes must have latera l por e water pressure. Monitoring for por e movement strictly controlled. water pressure is usually accomplished with Oth er potential procedures for stabilizin g Lateral movements of structures may b e n atura l and human-made slopes include the detected on the surface by surveyin g us e of geotextiles and geogrids to provid e ho rizontal and vertical movements

. a d ditional strength, the installation of wick Subsu rface movements may be detected by and t oe drains to relieve excess por e use of slope incli nometers. Settlement may pr essures, grouting, and vacuum an d be m onitored by surveying ground surfac e wel lpoint pumping to lower ground-wate r el evations (on several occasions over a l evels. In addition, surfa ce drainage may be per iodof time) and comparing them with controlled to decrease infiltration, thereb y areas that are not likely to experienc e redu cing the potential for mud and debri s changes in elevations (e.g., USGS surve y s lides in some areas. Lowering the ground- monuments). wa ter table also may have stabilizin g effects. Walls or large-diameter piling can Engineering Considerations for Kars t b e used to stabilize slides of relatively small Terrains dimen sion or to retain steep toe slopes s o t hat failure will not extend back in to a larger The principal concern with karst terrains is m ass (U.S. Navy , 1986). For more detailed progressive and/or catastrophic failure o f information regarding slope stabilizatio n subsurface conditions due to the presence of desi gn, refer to Winterkorn and Fan g si nkholes, solution cavities, an d (19 75), U.S. Navy (1986), and Sower s subterranean caverns. The unpredictabl e ( 1979). Richardson and Koerner (1987) and and catastrophic nature of subsidence i n Koerner (1986) provide design guidance for these area s makes them difficult to develop geosynthetics in both landfill and genera l as landfill sites. Before s ituating a MSWLF applications. in a karst region, the subject site should be appropriate to monitor slope stabilit y

piezometers screene d in the sensitive strata.

characterized thoroughly.Location Criteria

61 The f irst stage of demonstration is t o heavily compacted to achieve the neede d ch aracterize the subsurface. Subsurfac e stability. Similarly, in areas where the karst d rilling, sinkhole monitoring , and geophysical voi ds are relatively small and limited i n testing are direct means that can be used t o ext ent, infilling of the void with slurr y cha racterize a site. Geophysical technique s ceme nt grout or other material may be a n include tests using electromagneti c option. conductivity, seismic refraction, ground

penetrating radar, gravity, and electrica l In general, due to the unpredictable an d r esistivity. Interpretation and applicability of catastrophic nature of ground failure in suc h differentgeophysical techniques should b e area s, engineering solutions that try t o reviewed by a qualified geophysicist. Ofte n compensate for the weak geologic structures m ore than o ne technique should be employed by constructing manmade ground support s to c onfirm and correlate findings an d tend to b e complex and costly. For example, an omalies. Subsurface drilling i s rein forced raft (or mat) foundations could be r ecommended

highly for verifying the results usedto compensate for lack of groun d of geophysical investigations. strength in some karst areas. Raft foundations Ad ditional information on karst condition s of a concrete footing that extends over a very can come from remote sensing techniques , l a rge area. Such foundations are used where su chas aerial photograph interpretation

. soils have a low bearing capacity or wher e S urface map ping of karst features can help to soil conditions are variable and erratic; these pr ovide an understanding of structura l foundations are able to reduce and distribute patterns and relationships in karst terrains

. loads. However, it should be noted that, i n A n u nderstanding of local carbonate geology some instances, raft foundations may no t and s tratigraphy can aid in the interpretatio n necessarily be able to prevent the extrem e of both remote sensing and geophysica l type of collapse an d settlement that can occur techniques. in karst areas. In addition, the construction of A demons tration that engineering measures on the size of the area. h ave been incorporated into a un it located in a k arst terrain may include both initia l design and site modifications. A relatively 2.8 CLOSURE OF EXISTING s imple engineering m odification that can be MUNICIPAL SOLID WASTE use d to mitigate karst terrain problems i s LANDFILL UNITS g round-water a nd surface water control and 40 CFR §258.16 c onveyance. Such water co ntrol measures are u sed to minimize the rate of dissolution within 2.8.1 Statement of Regulation k nown ne ar-surface limestone. This means o f controlling karst developme nt may not be (a) Existing MSWLF units tha t appl icable to all karst situations. In area s cannotmake the demonstration specifie d where development of karst topograph y in §§258.10(a), pertaining to airports , t e nds to be minor, loose soils overlying the 258.11(a), pertaining to floodplains, an d lim estone may be excavated o r 258.15(a), pertaining to unstable areas , are a type of "floating foundatio n" that consist

raft foundations can be very costl y, dependingSubpart B

62 must close by October 9, 1996, i n 2.8.3 Technical Considerations accordance with §258.60 of this part an d conduct post-closure activities i n The engineering considerati ons that should be accordance with §258.61 of this part. addressedfor airport safety, 100-year (b) The deadline for closure require d are discussed in Sections 2.2, 2.3, and 2.7 of by p aragraph (a) of this section may b e this chapter. Information and evaluation s exten ded up to two years if the owner o r necessary for these demonstrations also ar e o perator demonstrates to the Director of an presented in these sections. If applicabl e approved State that: demonstrations are not made by the owners or (1) There is no available alternativ e acco rding to the requirements of sectio n disposal capacity; §258.60 by October 9, 1996. (2) T here is no immediate threat t o For MSWLF units located in ap proved States, human health and the environment. this de adline may be extended if there is n o 2.8.2 Applicability environment and no waste disposa l alternative These requirements are applicable to al l disposal alternative should consider all waste MSWLF units that receive waste afte r ma nagement facilities, including landfills , Octobe r9, 1993 and cannot meet the airport municipal waste combustors, and recyclin g sa fety, floodplain, or unstable are a facilities. The demonstration for the two-year requirements. The owner or operator i s extension should consider the impacts o n req uiredto demonstrate that the facility: (1 ) huma n health and the environment as the y will not pose a bird hazard to aircraft unde r r e late to airport safety, 100-year floodplains, § 258.10(a); (2) is designed to preve nt washout or unstable areas. of s olid waste, will not restrict floodplai n s to rage capacity, or increase floodwater flow §§258.17-258.19 [Reserved]. in a 100-year floodplain under §258.11(a) ; and 3) can withstand damage to landfil l structural component systems (e.g., liners , leachate collection, and other engineere d str uctures) as a result of unstable condition s unde r§258.15(a). If any of thes e dem onstrations cannot be made, the landfil l must close by October 9, 1996. In approved States, the closure deadline may be extended up to two additional years if it can be show n tha talternative disposal capacity is no t ava ilable and that the MSWLF unit does no t p ose an immediate threat

to human health and the environment. floodplain encroachment, and unstable area s

oper ators, the landfill unit(s) must be close d

im mediate threat to human health and th e is available. The demonstration of n oLocation Criteria

63 2.9 FURTHER INFORMATION 2.9.1 References General Linsley and Franzini, (1972). "Water Resources Engineering"; McGraw-Hill; pp. 179-184. U.S. EPA, (1988). "Guide to Technical Resources for the Design of Land Disposal Facilities"; EPA/62 5/6-88/018; USEPA; Risk Reduction Engineering Laboratory and Center fo r En vironmental Research Information; Office of Research and Development; Cincinnati , Ohio 45268. USGS. Books and Open File Section, Branch Distribution, Box 25046, Federal Center, Denver, CO 80225. Floodplains COE, (1982). HEC-1, HEC-2, HEC-5, HEC-6 Computer Programs; Hydrologic Engineerin g Center (HEC); U.S. Army Corps of Engineers; Hydrologic Engineering Center; Davi s California. Federal Emergency Management Agency, (1980). "How to Read a Flood Insurance Rate Map"; April 1980. Available from FEMA Regional Offices. Maynard, S .T., (1978). "Practical Riprap Design"; Hydraulics Laboratory Miscellaneous Paper H -78-7; U.S. Army Engineers Waterways Experiment Station; Vi cksburg, Mississippi. SCS, (1983). "Maryl andStandards and Specifications for Soil Erosion and Sediment Control"; U.S. Soi l Conservation Service; College Park, Maryland. U.S. W ater Resources Council, (1977). "Guidelines for Determining Flood Flow Frequency" ; Bulletin #17A of the Hydrology Committee; revised June 1977. Wetlands COE, (19 87). "Corps of Engineers Wetlands Delineation Manual," Technical Report (Y-87-1), Waterways Experiment Station, Jan. 1987.Subpart B

64 COE, (1989). "Federal Manual for Identifying and Delineating Jurisdictional Wetlands, " F ederal Interagency Committee for Wetland Delineation; U.S. Army Corp s of Engineers, U .S. Environmenta l Protection Agency, U.S. Fish and Wildlife Service, and U.S.D.A., S oil Conservation Service; Washington, D.C., Cooperative Techni cal Publication. 1989. Fault Areas, (1992). "Aspects of Landfill Design for Stability in Seismic Zones," Hilary I. Inyang, Ph.D. Seismic Impact Zones Algermissen, S.T., et al., (1991). "Probabilistic Earthquake Acceleration and Velocity Maps for th e United States and Puerto Rico," USGS Miscellaneous Field Study Map MF

2120. Al germissen, S.T., et al., (1976). "Probabilistic Estimates of Maximum Acceleration an d Velocity in Rock in the Contiguous United States"; Open File Report 82-1033; U.S

. Geological Survey; Washington, D.C. U.S

. EPA, (1992). "Aspects of Landfill Design for Stability in Seismic Zones", Hilary I

. Inyang. Ph.D. U. S. Navy, (1983). "Design Manual-Soil Dynamics, Deep Stabilization, and Specia l G eotechnical Constructi on," NAVFAC DM-7.3; Department of the Navy; Washington, D.C.; April, 1983. Win terkorn, H.F. and Fang, H.Y., (1975). "Foundation Engineering Handbook." Va n Nostrand Reinhold. 1975. Unstable Areas Geoslope Programming Ltd., (1986). PC-SLOPE, Version 2.0 (May); Calgary, Alberta , Canada. Huang, U.H., (1983). "Stability Analysis of Earth Sl opes"; Van Nostrand Reinhold Co.; New York. Koerne r, R.M., (1986). "Designing with Geosynthetics"; Prentice-Hall Publishing Co. ; Englewood Cliffs, New Jersey. Lambe, W.T. and R.V. Whitman, (1969). "Soil Mecha nics"; John Wiley and Sons, Inc.; New York.Location Criteria

65 Richard son, G.N. and R.M. Koerner, (1987). "Geosynthetic Design Guidance for Hazardou s W aste Landfill Cells and Surf ace Impoundments"; Hazardous Waste Engineering Research L aboratory; USEPA, Office of Research and Development; Cincinnati, Ohio; Contract No. 68-07-3338. Sowers, G .F., (1979). "Soil Mechanics and Foundations: Geotechnical Engineering," Th e MacMillan Company, New York. Terzaghi, K. and R.B. Peck, (1967). "Soil Mechanics in Engin eering Practice", 2nd Edition; John Wiley and Sons, Inc.; New York. U.S. N avy, (1986). "Design Manual-Soil Mechanics, Foundations and Earth Structures, " NAVFAC DM-7; Department of the Navy; Washington, D.C.; September 1986. Winterhorn, H.F. and Fang, H.Y., (1975). "Foundation Engineering Handbook," Van Nostrand Reinhold, 1975. 2.9.2 Organizations American Institute of Architects Washington, D.C. (202) 626-7300 Aviation Safety Institute (ASI) Box 304 Worthington, OH 43085 (614) 885-4242 American Society of Civil Engineers 345 East 47th St. New York, NY 10017-2398 (212) 705-7496 Building Seismic Safety Council 201 L Street, Northwest Suite 400 Washington, D.C. 20005 (202) 289-7800 Bureau of Land Management 1849 C St. N.W. Washington, D.C. 20240 (202) 343-7220 (Locator) (202) 343-5717 (Information)Subpart B

66 Federal Emergency Management Agency Flood Map Distribution Center 6930 (A-F) San Thomas Road Baltimore, Maryland 21227-6227 1-800-358-9616 Federal Emergency Management Agency (800) 638-6620 Continental U.S. only, except Maryland (800) 492-6605 Maryland only (800) 638-6831 Continental U.S., Hawaii, Alaska, Puerto Rico, Guam, and the Virgin Islands Note: T he toll free numbers maybe used to obtain any of the numerous FEMA publications such as "The National Flood Insurance Program Community Status Book," which is publishe d bimonthly. To obtain Flood Insurance Rate Maps and other flood maps, the FEMA Flood Map Distribution Center should be contacted at 1-800-358-9616. Federal Highway Administration 400 7th St. S.W. Washington, D.C. 20590 (202) 366-4000 (Locator) (202) 366-0660 (Information) Hydrologic Engineering Center (HEC Models) U.S. Army Corps of Engineers 609 Second St. Davis, CA 95616 (916) 756-1104 National Information Service for Earthquake Engineering (NISEE) University of California, Berkeley 404A Davis Hall Berkeley, CA 94720 (415) 642-5113 (415) 643-5246 (FAX) National Oceanic and Atmospheric Administration Office of Legislative Affairs 1825 Connecticut Avenue Northwest Room 627 Washington, DC 20235 (202) 208-5717Location Criteria

67 Tennessee Valley Authority 412 First Street Southeast, 3rd Floor Washington, DC 20444 (202) 479-4412 U.S. Department of Agriculture Soil Conservation Service P.O. Box 2890 Washington, DC 20013-2890 (Physical Location: 14th and Independence Ave. N.W.) (202) 447-5157 U.S. Department of the Army U.S. Army Corps of Engineers Washington, DC 20314-1000 (202) 272-0660 U.S. Department of the Interior Fish and Wildlife Service 1849 C Street Northwest Washington, DC 20240 (202) 208-5634 U.S. Department of Transportation Federal Aviation Administration 800 Independence Ave., S.W. Washington, D.C. 20591 (202) 267-3085 U.S. Geological Survey 12201 Sunrise Valley Drive Reston, Virginia 22092 (800) USA-MAPS U.S. Geological Survey Branch of Geologic Risk Assessment Stop 966 Box 25046 Denver, Colorado 80225 (303) 236-1629 U.S. Geological Survey EROS Data Center Sioux Falls, South Dakota 57198 (605) 594-6151Subpart B

68 U.S. Geological Survey National Earthquake Information Center Stop 967 Box 25046 Denver Federal Center Denver, Colorado 80225 (303) 236-1500

2.9.3 Models Adam us, P.R., et al., (1987). "Wetland Evaluation Technique (WET); Volume II : M ethodology"; Operational Draft Technical Report Y-87; U.S. Army Engineer Waterways Experiment Station; Vicksburg, MS. COE, (1982). HEC-1, HEC-2, HEC-5, HEC-6 Computer Programs; Hydrologic Engineerin g Center (HEC); U.S. Army Corps of Engineers; Hydrologic Engineering Center; Davi s California. Geoslope Programming Ltd., (1986). PC-SLOPE , Version 2.0 (May); Calgary, Alberta, Canada. Lysemer, John, et al., (1979). "FLUSH: A Computer Program for Approximate 3-D Analysis"; U niversity of C alifornia at Berkeley; March 1979. (May be obtained through the National I nformation Service for Earthquake Engin eering at the address provided in subsection 2.9.2 of this document.) Purdue University, Civil Engineering Dept., (1988). PC STABL, West Lafayette, IN 47907. Unit edStates Fish and Wildlife Service, (1980). "Habitat Evaluation Procedures". ESM 102 ; U.S. Fish and Wildlife Service; Division of Ecological Services; Washington, D.C.69 APPENDIX I

FAA Order 5200.5A70 U.S. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION
5200.5A l/31/90
SUBJ: WASTE DISPOSAL SITES ON OR NEAR AIRPORTS
1

. P URPOSE. This order provides guidance concerning the est ablishment, elimination or monitoring of landfills, open dumps, waste disposal sites or similarly titled facilities on or in the vicinity of airports.
2. D I STRIBUTION. This order is distributed to the division level in the Offices of Airport Planning and Programming Airport Safety and Standards, Air Traffic Evaluations and Analysis Aviation Safety Oversight, Air Traffic Operations Service, and Flight Standards Service; to th e division level in the regional Airports, Air Traffic, and Flight Standards Divisions; to the director level at the Aeronautical Center and the F A A Technical Center, and a limited distribution to all Airport District Offices, Flight Standards Field Offices, and Air Traffic Facilities.
3. C ANCELLATION. Order 5200.5, FAA Guidance Concerning Sanitary Landfill s On Or Near Airports, dated October 16, 1974, is canceled.
4. B ACKGROUND. Landfills, garbage dumps, sewer or fi sh waste outfalls and other similarly licensed or titled facilities used for operations t o process, bury, store or otherwise dispose of waste, trash and refuse will attract rodents and birds. Where the dump is ignited and produces smoke, an addit ional attractant is created. All of the above are undesirable and potential hazards to aviation since they erode the safety of the airpo r t environ ment. The FM neither approves nor disapproves locations of the facilities above. Such action is the responsibility of the Environment a l Protection Agency and/or the appropriate state and local agencies. The role of the FAA is to ensure that airport owners and operators meet the i r contractual obliga tions to the United States government regarding compatible land uses in the vicinity of the airport. While the chance of a n u nforeseeable, random bird strik e in flight will always exist, it is nevertheless possible to define conditions within fairly narrow limits where the risk i s increased. Those high-risk condi tions exist in the approach and departure patterns and landing areas on and in the vicinity of airports. The number o f bird strikes reported on aircraft is a matter of continuing concer n to the FM and to airport management. Various observations support the conclusion that waste disposal site s are artificial attractants to birds. Accordingly, disposal sites located in the vicinity of an airport are potentially incompatible w ith saf e flight operations. Those sites that are not compatible need to be eliminated. Airport owners need guidance in making those decisions and the FM must be in a posi tion to assist. Some airports are not under the jurisdiction of the community or local governing body having control of land u sage in the vicinity of the airport. In these areas , the airport owner should use its resources and exert its best efforts to close or control waste disposal operations within the general vicinity of the airport.
5. EXPLANATION OF CHANGES. The following list outlines the major changes to Order 5200.5:

a . Recent developments and new tec hniques of waste disposal warranted updating and clarification of what constitutes a sanitary landfill. This listing of new titles for waste disposal was outlined in paragraph 4.
b . Due to a reorganization which placed the Animal Damage Control Branch of the U.S. Department of Interior Fish and Wildlife Service under the jurisdiction of the U.S. Department of Agriculture an address addition was necessary c. A zone of notification was added to the criteria which should provide the appropriate FM Airports office an opportunity to comment on the proposed disposal site during the selection process.
6. ACTION.

a. Waste disposal sites located or proposed to be located within the areas established for an airport by the guidelines set forth in paragraphs 7 a b, and c of this order should not be allowed to operate. If a waste disposal site is incompatible with an airport in accordance with guidelines o f p aragr aph 7 and cannot be closed within a reasonable time, it should be operated in accordance with the criteria and instructions issued by Federal a gencies such as the Environmental Protection Agency an d the Department of Health and Human Services, and other such regulatory bodies that may have applicable requirements. The appropriate FM airports office should advise airport owners, operators and waste disposal proponents again s t locating, permitting or concurring in the location of a landfill or similar facility on or in the vicinity of airports.71 ( 1) Additionally, any operator proposing a new or expanded waste disposal site within 5 miles of a runway end should notify the airport a nd the appropriate FM Airports office soas to provide an opportunity to review and comment on the site in accordance with the guidance contained i n this order. FM field offices may wish to contact the appro priate State director of the United States Department of Agriculture to assist in this review. A lso, any Air Traffic cont

rol tower manager or Flight Standards District Office manager and their staffs that become aware of a proposal to develop or expand a disposal site should notify the appropriate FM Airports office.

b . The operation of a disposal si te located beyond the areas described in paragraph 7 must be properly supervised to ensure compatibility with the airport.

c . If at any time the disp osal site, by virtue of its location or operation, presents a potential hazard to aircraft operations the owner should t ake action to correct the situation or terminate operation of the facility. If the owner of the airport also owns or controls the disposal facility and is s ubject to Federal obligations to protect compatibility of land uses around the airport, failure to take corrective action could place the airport owner i n noncompliance with its commitments to the Federal gover nment. The appropriate FM office should immediately evaluate the situation to determine complianc e with federal agreements and take such action as may be warranted under the guidelines as prescribed in Order 5190.6, Airport s Compliance Requirements, current edition.

(1) Airport owners should be encouraged to make periodic inspections of current operations of existing disposal sites near a federally obligated airport where potential bird hazard problems have been reported.

d

. This order is not intended to resolve all related problems but is specifically directed toward eliminating waste disposal sites, landfills and similarly titled facilities in the proximity of airports, thus providing a safer environment for aircraft operations.

e . At airports certified under Federal Aviation Regulations, part 139, the airport certification manual/specifications should require disposal s ite inspections at appropriate intervals for thos e operations meeting the criteria of paragraph 7 that cannot be closed. These inspections are necessary t o assure t hat bird populations are not increasing and that appropriate control procedures are being established and followed. The appropriate FAA airportoffices should develop working relationships with state aviation agencies and state agencies that have authority over waste disposal an d landfills to stay abreast of proposed developments and expansions and apprise them of the hazards to aviation that these present.

f

. When proposing a disposal site, operators should make their plans available to the appropriate state regulatory agencies. Many states have criteria concerning siting requirements specific to their jurisdictions.

g. Additional information on waste disposal, bird hazard and related problems may be obtained from the following agencies:

U.S. Department of Interior Fish and Wildlife Service 18th and C Streets, NW Washington, DC 20240 U.S. Department of Agriculture Animal Plant Health Inspection Service P.O. Box 96464 Animal Damage Control Program Room 1624 South Agriculture Building Washington, DC 20090-6464 U.S. Environmental Protection Agency 401 M Street, SW Washington, DC 20460 U.S. Department of Health and Human Services 200 Independence Avenue, SW Washington, DC 20201
7. CRITERIA. Disposal sites will be considered as incompatible if located within areas established for the airport through the application of the following criteria: a. Waste disposal sites located within 10,000 feet of any runway end used or planned to be used by turbine powered aircraft b. Waste disposal sites located within 5,000 feet of any runway end used only by piston powered aircraft.72 c . Any waste disposal site located within a 5-mil e radius of a runway end that attracts or sustains hazardous bird movements from feeding, water or roosting areas into, or across the runway and/or approach and departure patterns of aircraft.
Leonard E. Mudd Director, Office of Airport Safety and Standards

# CHAPTER 3 SUBPART C OPERATING CRITERIA74 CHAPTER 3 SUBPART C TABLE OF CONTENTS

3.1 INTRODUCTION

........................................................... 76 3.2 P ROCEDURES FOR EXCLUDING T HE RECEIPT OF HAZARDOUS WASTE 40 CFR §258.20

................................................................. 77 3.2.1 Statement of Regulation

............................................... 77 3.2.2 Applicability

........................................................ 77 3.2.3 Technical Considerations

.............................................. 77 Inspections

........................................................ 78 Alternative Methods for Detection and Prevention

.......................... 81 Recordkeeping

..................................................... 82 Training

.......................................................... 82 Notification to Authorities and Proper Management of Wastes

................. 82 3.3 COVER MATERIAL REQUIREMENTS 40 CFR §258.21

......................... 84 3.3.1 Statement of Regulation

............................................... 84 3.3.2 Applicability

........................................................ 84 3.3.3 Technical Considerations

.............................................. 84 3.4 DISEASE VECTOR CONTROL 40 CFR §258.22

................................ 86 3.4.1 Statement of Regulation

............................................... 86 3.4.2 Applicability

........................................................ 86 3.4.3 Technical Considerations

.............................................. 87 3.5 EXPLOSIVE GASES CONTROL 40 CFR §258.23

............................... 87 3.5.1 Statement of Regulation

............................................... 87 3.5.2 Applicability

........................................................ 88 3.5.3 Technical Considerations

.............................................. 89 Gas Monitoring

.................................................... 90 Landfill Gas Control Systems

.......................................... 94 Passive Systems

.................................................... 96 Active Systems

..................................................... 96 3.6 AIR CRITERIA 40 CFR §258.24

............................................. 101 3.6.1 Statement of Regulation

............................................... 101 3.6.2 Applicability

........................................................ 101 3.6.3 Technical Considerations

.............................................. 10175

3.7 ACCESS REQUIREMENT 40 CFR §258.25

.................................... 103 3.7.1 Statement of Regulation

............................................... 103 3.7.2 Applicability

........................................................ 103 3.7.3 Technical Considerations

.............................................. 103 3.8 RUN-ON/RUN-OFF CONTROL SYSTEMS 40 CFR §258.26

....................... 104 3.8.1 Statement of Regulation

............................................... 104 3.8.2 Applicability

........................................................ 104 3.8.3 Technical Considerations

.............................................. 104 3.9 SURFACE WATER REQUIREMENTS 40 CFR §258.27

.......................... 105 3.9.1 Statement of Regulation

............................................... 105 3.9.2 Applicability

........................................................ 106 3.9.3 Technical Considerations

.............................................. 106 3.10 LIQUIDS RESTRICTIONS 40 CFR §258.28

.................................... 107 3.10.1 Statement of Regulation

.............................................. 107 3.10.2 Applicability

....................................................... 107 3.10.3 Technical Considerations

............................................. 108 3.11 RECORDKEEPING REQUIREMENTS 40 CFR §258.29

.......................... 110 3.11.1 Statement of Regulation

.............................................. 110 3.11.2 Applicability

....................................................... 110 3.11.3 Technical Considerations

............................................. 111 3.12 FURTHER INFORMATION

.................................................. 114 3.12.1 References

......................................................... 114 3.12.2 Addresses

......................................................... 114

APPENDIX I - SPECIAL WASTE ACCEPTANCE AGREEMENT

............ Following Page 11476 

### CHAPTER 3 SUBPART C OPERATING CRITERIA

3.1 INTRODUCTION
T he Solid Waste Disposal

Facility Criteria contain a series of operating requirements pertaining to rou tine operation, management, and environmental monitoring at municipal solid waste landfil l u nits (MSWLF units). The operating requirements per tain to new MSWLF units, existing MSWLF units, and lateral expansions of existing MSWLF units.
T he operating requirements have been developed to ensure the safe d aily operation and management at MSWLF units. The operating requirements include:

! The exclusion of hazardous waste; ! Facility access;
! Cover material; ! Run-on/run-off control systems;
! Disease vector control; ! Surface water requirements;
! Explosive gases control; ! Liquid restrictions; and
! Air monitoring; ! Recordkeeping requirements. A ny owner or operator of a MSWLF unit must c omply with the operating requirements by October 9, 1993.
In specific cases, the operating requirements require compliance with other Federal laws. Fo r example, surface water discharges from a MSWLF unit into the waters of the United States must be in conformance with applicable sections of the Clean Water Act. In addition, burning o f municipal solid waste (MSW) is regulated under applicable sections of the Clean Air Act.Operating Criteria

77 3.2 PROCEDURES FOR EXCLUDING 3.2.2 Applicability THE RECEIPT OF HAZARDOUS WASTE 40 CFR §258.20 This regulation applies to all MSWLF unit s 3.2.1 Statement of Regulation 1993. (a) Owners or operators of all MSWLF The owner or operator must develop a unit s must implement a program at th e program to detect and prevent disposal o f faci lity for detecting and preventing th e r eg ulated hazardous wastes or PCB wastes at disp osal of regulated hazardous wastes a s the MSWLF facility. Hazardous wastes may define d in Part 261 of this title an d be gases, liquids, solids, or sludges that ar e p olychlorinated biphenyls (PCB) wastes as list edor exhibit the characteristics describe d de fined in Part 761 of this title. Thi s in 4 0 CFR Part 261. Household hazardou s program must include, at a minimum: wastes are excluded from Subtitle C (1 ) Random inspections of incomin g conditionally exempt small quantity loads unless the owner or operator take s ge nerators (CESQGs) are not considere d othersteps to ensure that incoming load s re gulatedhazardous wastes for purposes o f d o not contain regulated hazardous wastes complying with §258.20; therefore, thes e or PCB wastes; wastes may be accepted for disposal at a (2) Records of any inspections; (3) Training of facility personnel t o progr amshould be capable of detecting an d recognize regulated hazardous waste an d prev enting disposal of PCB wastes. PC B PCB wastes; and w astes may be li quids or non-liquids (sludges (4) Notification of State Director o f 761.60. PCB wastes do not include smal l au thorized States under Subtitle C o f capacitors found in fluorescent light ballast , R CRA or the EPA Region al Administrator white goods (e.g., washers, dryers , if in an unauthorized State if a regulate d refrigerators) or other consumer electrica l hazardous waste or PCB waste i s products (e.g., radio and television units). discovered at the facility. (b) For purposes of this section , in tendedto identify whether regulate d regulated hazardous waste means a soli d hazardous waste or PCB waste was receive d w aste that isa hazardous waste, as defined at th e MSWLF unit or facility prior to th e i n 40 CFR 2 61.3, that is not excluded from effective date of the Criteria. re gulation as a hazardous waste under 4 0 CFR 261.4(b) or was not generated by a 3.2.3 Technical Considerations conditionally exempt small quantit y generator as defined in §261.5 of this title. A solid waste is a regulated hazardous wast e that receive wastes on or after October 9 ,

regulation, and wastes generated b y

MSWLF unit. Th e MSWLF hazardous waste exclusio n

orsolids) and are defined at 40 CFR Sectio n

T he hazardous waste exclusion program is not

if it: (1) is listed in Subpart D of 40 CFRSubpart C

78 P art 261 (termed a "listed" waste); (2) exhibits T hese sources are not regulated under 40 CFR a characteristic of a hazardous waste a s Part 76 1 and, therefore, are not part of th e definedin Subpart C of 40 CFR Part 261; or de tection program required by §258.20

. (3) is a mixture of a listed hazardous wast e Co mmercial or industrial sources of PC B and a non-hazardous solid waste

. wa stes that should be addressed by th e C haracteristics of hazardous wastes as defined program include: in Subp art C of 40 CFR Part 261 includ e ignitability, corrosivity, reactivity, an d ! Min eral oil and dielectric fluid s toxicity. The toxicity characteristic leaching containing PCBs; pr ocedure (TCLP) is the test method used t o determine the mobility of organic an d ! Co ntaminatedsoil, dredged material , i norgani c compounds present in liquid, solid, sew age sludge, rags, and other debri s an dmultiphase wastes. The TCLP i s from a release of PCBs; presented in Appendix II of Part 261.
T he MSWLF Criteria exclude CESQG waste eq uipment containing dielectric fluids ; (as de fined in 40 CFR §261.5) from th e and de finition of "regulated hazardous wastes. " CES QGwaste includes listed hazardou s ! Hydraulic machines. wa stes or wastes that exhibit a characteristi c of a hazardous waste that are generated i n The owner or operator is required t o quantities no greater than 100 kg/month, o r implement a program to detect and exclud e for acute hazardous waste, 1 kg/month

. re gulatedhazardous wastes and PCBs fro m U nder 40 CFR §261.5(f)(3)(iv) an d (g)(3)(iv), d is posal in the landfill unit(s). This program c onditionally exempt smal l quantity generator must include elements for: h azardous wastes may be disp osed at facilities p ermitted, licensed, or

registered by a State to ! R andom inspections of incom ing loads or manage municipal or industrial solid waste. other prevention methods; Oth er solid wastes are excluded fro m ! Maintenance of inspection records; regul ation as a hazardous waste under 4 0 CFR §261.4(b) and may be accepted fo r ! Facility personnel training; and disposal at a MSWLF unit. Refer t o §261.4(b) for a listing of these wastes. ! Not ification to appropriate authorities i f PCB s are regulated under the Toxi c detected. Subs tances Control Act (TSCA), but PCB

co ntaining wastes are considered hazardou s Ea chof these program elements is discusse d w astes in some States. PC Bs typically are not separately on the following pages. foun din consumer wastes except fo r fl uorescent

ballast and small capacitors i n Inspections white goods and electrical appliances. A n inspection is typically a visual observation ! Tr ansformers and other electrica l

ha zardous wastes or PCB wastes ar e

of the incoming waste loads byOperating Criteria

79 an in dividual who is trained to identif y Ins pection priority also can be given t o r egulated hazardous or PCB wastes t hat would haulers with unknown service areas, to loads n ot be acc eptable for disposal at the MSWLF b rought to the facility in vehi cles not typically u nit. An inspe ction is considered satisfactory us edfor disposal of municipal solid waste , if the inspector knows the nature of al l a nd to loads transported by pre vious would-be materia ls received in the load and is able t o o ffenders. For wastes of unidentifiable nature discern whether the materials are potentiall y received from sources other than household s regulated hazardous wastes or PCB wastes. (e.g., industrial or commercia l Ideally, all loads should be screened ; the transporter about the source/compositio n however, it is generally not practical t o of the materials. i nspect i n detail all incoming loads. Random i nspectio ns, therefore, can be used to provide Load s should be inspected prior to actua l a reasonable means to adequately control the disp osal of the waste at the working face o f receipt of inappropriate wastes. Rando m the landfill unit to provide the facility owner in spections are simply inspections made o n o r operator the opportunit y to refuse or accept less than every load. the wastes. Inspections can be conducted on
T he frequ ency of random inspections may be transfer of the waste to the disposal facility

. based on the type and quantity of waste s I nspections also may occur at the tipping floor received daily, and the accuracy an d l ocated near the facility scale h ouse, inside the c onfidence desired in conc lusions drawn from site entrance, or near, or adjacent to, th e inspection observations. Because statistica l worki ng face of the landfill unit. A n p arameters are no t provided in the regulation, inspe ction flow chart to identify, accept, o r a reasoned, knowledge-based approach ma y refuse solid waste is provided as Figure 3-1. b e taken. A random inspection program may tak e many forms such as inspecting every I nspections of materials may be accomplished i ncoming lo ad one day out of every month or by discharging the vehicle load in an are a inspecting one or more loads fro m designed to contain potentially hazardou s transporters of waste s of unidentifiable nature wastes that may arrive at the facility. Th e each day. If these inspections indicate that waste should be carefully spread fo r unauthorized wastes are being brought to the observation using a front end loader or other MSWLFsite, then the random inspectio n pi ece of equipment. Personnel should b e prog ramshould be modified to increase th e trai nedto identify suspicious wastes. Som e frequency of inspections. indications of suspicious wastes are:
I nspection frequencyalso can vary depending • Hazardous placards or marking; on the nature of the waste. For example , wa stes received predominantly fro m • Liquids; c ommercialor industrial sources may require more frequent inspections than waste s • Powders or dusts; predominantly from households. e stablishments), the i nspector should question

a tipp ing floor of a transfer station befor e

### Figure 3-1 Hazardous Waste Inspection Decision Tree Inspection Prior to Working Face

80Operating Criteria

81 • Sludges; it is disposed of properly. Most facilitie s

• Bright or unusual colors;

• Drums or commercial size containers; or Ch aracteristic Leaching Procedure (TCLP )

• Chemical odors. w astes in cluding corrosivity, ignitability, and Th e owner or operator should develo p hazar dous should be handled and stored as a spec ific procedures to be followed whe n hazardous waste until a determination i s sus picious wastes are discovered. Th e made. procedure should include the followin g points: I f the wastes temporarily stored at the site are

• Segregate the wastes; o perator is responsible for the management of

• Question the driver; f rom the facility, the waste mus t be: (1) stored

• Review the manifest (if applicable); r equirements of a hazardous waste generator,

• Contact possible source; tr ansporter, and (4) sent to a permitte d

• Ca ll the appropriate State or Federa l facility for disposal. These requirements are agencies; discussed further in this section.

• Use appropriate protective equipment; Alternative Methods for Detection an d

• Contact laboratory support if required; and

• Notify a response agency if necessary. insp ections as an acceptable means o f Conta iners with contents that are not easil y was tes, preventing the disposal of thes e ide ntifiable, such as unmarked 55-gallo n wa stes may be accomplished through othe r dru ms, should be opened only by properl y me thods. These methods may includ e trained personnel. Because these drums could receiving only household wastes an d cont ain hazardous waste, they should b e p rocess ed (shredded or baled) wastes that are ref usedwhenever possible. Upon verifyin g scree nedfor the presence of the exclude d that th e solid waste is acceptable, it may then w astes pr ior to processing. A pre-acceptance be tr ansferred to the working face fo r a greement between th e owner or operator and disposal. the waste hauler is another alterna tive method. Some facilities may consider it reasonable to presentedas Appendix I. The owner o r test unidentified waste, store it, and see that operator should would not consider this reasonable.
T esting typ ically would include The Toxicity

a nd other tests for characteri stics of hazardous

r eactivity. Wastes that are suspected of being

de terminedto be hazardous, the owner o r
the waste. If the wastes are to be transported
at th e MSWLF facility in accordance with (2) manifested, (3) transported by a license d
Tr eatment, Storage, or Disposal (TSD )

Prevention Wh ile the regulations explicitly refer t o d etecting regulated hazardous waste s and PCB

A n example of

a pre-acceptance agreement isSubpart C

82 ke ep any such agreements concerning thes e T raining also sh ould address hazardous waste alternatives in the operating record. han dling procedures, safety precautions, an d Recordkeeping information is provided in training course s A reco rd should be kept of each inspectio n S afety and Health Act (OS HA) under 29 CFR that is performed. These records should b e §1910.120. Information covered in thes e in cludedand maintained in the facility courses includes regulatory requirement s oper ating record. Larger facilities that tak e u nder 40 CFR Parts 260 through 270, 29 CFR la rge amounts of industrial and commercia l Pa rt1910, and related guidance document s w astes may use more detailed procedures than that discus s such topics as: general hazardous sm aller facilities that accept househol d wa ste management; identification o f wast es. Inspection records may include th e h azardous wastes; trans portation of hazardous following information: wastes; standards for hazardous wast e

! The date and time wastes were received for hazardous waste worker health and safety inspection; training and monitoring requirements.

! Source of the wastes; Not ification to Authorities and Prope r

! Vehicle and driver identification; and

! All observations made by the inspector. Th e Director of an approved State ma y establish alternative recordkeeping location s and requirements. Training Owners or operators must ensure tha t personnel are trained to identify potentia l reg ulatedhazardous waste and PCB wastes

. These personnel could include supervisors , de signatedinspectors, equipment operators , and weigh station attendants who ma y e ncou nter hazardous wastes. Documentation of tr aining should be placed in the operatin g re cordfor the facility in accordance with §258.29. The training program should emphasiz e met hods to identify containers and label s typical of hazardous waste and PCB waste

. re cordkeeping requirements. Thi s des ignedto comply with the Occupationa l

treatment; storage and disposal facilities; and

Management of Wastes
I f regulate d quantities of hazardous wastes or PCB wastes are found at the landfill facility , the owner or operator must notify the proper autho rities. Proper authorities are either th e Dir ector of a State authorized to implemen t the hazardous waste program under Subtitle C of RCRA, or the EPA Regiona l Administrator, in an unauthorized State. If the owner or operator discovers regulate d quan tities of hazardous waste or PCB wast e while it is still in the possession of th e transporter, the owner or operator can refus e to a ccept the waste at the MSWLF facility , a nd the waste will remain the responsibility of the transporter. If the owner or operator i s u nable to identify the tran sporter who brought th e hazardous waste, the owner or operato r must ensure that the waste is managed i n accordanceOperating Criteria

83 with all applicable Federal and Stat e analogous State/Tribal requirements. Th e regulations. owner or operator is required to: Operators of MSWLF facilities should b e ! Obtain an EPA identification numbe r preparedto handle hazardous wastes that are (E PA form 8700-12 may be used t o i nadvertently received at the MSWLF facility. ap ply for an EPA identification number; Thi s may include having containers such a s State or Regional personnel may be able 55- gallon drums available on-site an d to provide a provisional identificatio n retaining a list of names and telephon e number over the telephone); numbers of the nearest haulers licensed t o transport hazardous waste. ! Pac kage the waste in accordance with Hazardous waste may be stored at th e r egulations under 49 CFR Parts 173, 178, MSWLFfacility for 90 days, provided tha t and179 (The container must be labeled, the following p rocedures required by 40 CFR mar ked, and display a placard i n § 262.34, or applicable S tate requirements, are ac cordance with DOT regulations o n followed: ha zardous wastes under 49 CFR Part

! The waste

is placed in tanks or containers;

! The d ate of receipt of the waste is clearl y marked and visible on each container;

! The container or tank is marked clearl y with the words "Hazardous Waste";

! An employee is designated as th e emergen cy coordinator who is responsible fo rcoordinating all emergency respons e measures; and

! The name and telephone number of th e e mergency coordinator and the number of the fire department is posted next to th e facility phone.
E xtension s to store the waste beyond 90 days m ay be approved p ursuant to 40 CFR 262.34.
I f the owner or operator transports the wastes off- site, the owner or operator must compl y with 40 CFR Part 262 or the Department of Transportation (DOT )

172); and

! Properly manifest the waste designatin g a per mitted facility to treat, store, o r dispose of the hazardous waste.
I f the owner or opera

tor decides to treat, store (formore than 90 days), or dispose of th e haza rdous waste on-site, he or she mus t comply with the applicable State or Federa l req uirements for hazardous waste treatment , stor age, and disposal facilities. This ma y require a permit. PCB wastes detected at a MSWLF facility must be stored and disposed of according t o 40 CFR Part 761. The owner or operator i s required to:

! Obt ain an EPA PCB identificatio n number;

! Properly store the PCB waste;

! M ark containers or items with the words "Caution: contains PCBs"; andSubpart C

84 ! Manifest

the PCB waste for shipment to a 3.3.2 Applicability permittedincinerator, chemical wast e lan dfill, or high efficiency boile r The regulation applies to all MSWLF unit s (de pending on the nature of the PC B receiving waste after October 9, 1993. Th e waste) for disposal. r e gulation requires MSWLF unit owners and

3.3 COVER MATERIAL ope rating day. More frequent application o f REQUIREMENTS s oil may be required if the soil cover does not 40 CFR §258.21 control: 3.3.1 Statement of Regulation ! Dis ease vectors (e.g., birds, flies an d (a) Except as provided in paragraph (b) of this section, the owners or operators o f ! Fires; a ll MSWLF units must cover dispo sed solid w aste with six inches of e arthen material at ! Odors; the end of each operating day, or at mor e fr equentintervals if necessary, to contro l ! Blowing litter; and d isease vectors, fires, odors, blowing litter, and scavenging. ! Scavenging. (b ) Alternative materials of a n T he Direc tor of an approved State may allow a lternative thickness (other than at least six an owner or operator to use alternative cover inches of earthen material) may b e m aterialof an alternative thickness or grant a app roved by the Director of an approve d te mporary waiver of this requirement. A n St ate if the owner or operato r alternative material must not present a threa t d emon strates that the alternative material to human health and the environment, an d a nd thickness control disease vectors, fires, m ust continue to control diseas e vectors, fires, odors, blowing litter, and scavengin g odo rs, blowing litter, and scavenging. Th e without presenting a threat to huma n only basis for a temporary waiver from th e health and the environment. req uirement to cover at the end of eac h (c) The Director of an approved Stat e s easonal climatic conditions make compliance may grant a temporary waiver from th e impractical. requi rementof paragraph (a) and (b) o f this section if the owner or operato r 3.3.3 Technical Considerations dem onstrates that there are extrem e seasonal climatic conditions that mak e O wner s and operators of new MSWLF units, meeting such requirements impractical. e xisting MSWLF units, and lateral expansions operators to cover wastes with a 6-inch layer of earthen material at the end of eac h

other insects, rodents);

oper ating day would be where extrem e

are required to c over solid waste at the end of e ach op erating day with six inches of earthen material. This coverOperating Criteria

85 m aterial requirement is not related to the final 1) Si de by side (six inches of earthe n cover required under §258.60. m aterials and alternativ e cover) test pads;
T he placement of

six inches of cover controls 2) Full-scale demonstration; and d isease vectors (birds, insects, or rodents that represent the principal transmission pathwa y 3) Short-term full-scale tests. of a human disease) by preventing egres s from the waste and by preventing access t o A lternative daily cover materials may include breeding environments or food sources

. in digenous materials or commercially

Covering also reduces exposure o f a vailabl e materials. Indigenous materials are c ombustib le materials to ignition sources and those materials that would be disposed a s may reduce the spread of fire if the dispose d wast e; therefore, using these materials is a n wa ste burns. Odors and blowing litter ar e effici ent use of landfill space. Examples o f reduced by eliminating the direct contact o f i ndigenous materials i nclude (USEPA, 1992): win dand disposed waste. Similarly , s cavengingis reduced by removing the waste • Ashfrom municipal wast e fro mobservation. Should these unwante d combustors and utility companies; e ffects of inadequate cover persist, the owner or op erator may increase the amount of soi l • Compost-based material; used or apply it more frequently. Any soi l type can meet the requirements of th e • Fo undry sand from th e regulation when placed in a six-inch layer. m anufacturing process of discarding Ap provedStates may allow demon-stration s o f alter native daily cover materials. The rule • Ya rd waste such as lawn clippings , does not specify the time frame for th e leaves, and tree branches; demonstration; usually the State decides. A p eriod of six months should be ample time for • Sludge-basedmaterials (i.e., sludg e the owner or operato r to make the demonstra- treated with lime an d mixed with ash tion. There are no numerical require-ment s or soil); for the alternative cover; rather, th e a lternative cover must cont rol disease vectors, • Co nstruction and demolition debri s fires, odors, blowing litter, and scavengin g ( which h as been processed to form a with out presenting a threat to human health slurry); and the environment.
D emonstrations c an be conducted in a variety of ways. Some suggested methods fo r • Discarded carpets; and demonstrating alternative covers are: used dies;

• Shredded automobile tires;

• Gr itfrom municipal wastewate r treatment plants.Subpart C

86 Commercially developed alternatives hav e ! Spreading and compacting the soil t o been on the market since the mid-1980s

. achieve the required functions. S ome of the c ommercial alternative materials re quire specially designed applicatio n Extremely cold conditions may prevent th e eq uipment, while others use equipmen t e fficie nt excavation of soil from a borrow pit g enerally available at most landfills. Some of o r the spreading and compaction of the soil on th e types of commercially available dail y the waste. Extremely wet conditions (e.g. , cover materials include (USEPA, 1992): prolongedrainfall, flooding) may preven t

• Foam that usually is sprayed on th e andmay make it impractical to excavate o r working face at the end of the day; s pread and compact . The duration of waivers

• Geos ynthetic products such as a tarp or storm s, or as long as several months fo r fabric panelthat is applied at the end of extreme seasonal climatic conditions. the working day and removed at th e be ginning of the following workin g day; and 3.4 DISEASE VECTOR CONTROL

• Sl urry products (e.g., fibers fro m recyclednewspaper and wood chi p 3.4.1 Statement of Regulation slurry, clay slurry). Ot her criteria to consider when selecting a n M SWLF units mu st prevent or control onalt ernative daily cover material includ e site populations of disease vectors usin g ava ilability and suitability of the material , techniques appropriate for the protectio n equipment requirements, and cost. of human health and the environment. The temporary climatic waiver of the cove r (b) For purposes of this section , requi rement

is available only to owners o r di sease vectors means any rodents, flies , opera tors in approved States. The Stat e mo squitoes, or other animals, includin g Directo rmay grant a waiver if the owner o r insects, capable of transmitting disease t o operator demonstrates that meeting th e humans. requirements would be impractical due t o extreme seasonal climatic conditions

. 3.4.2 Applicability Activities that may be affected by extrem e seasonal climatic conditions include: The regulation applies to existing MSWL F

! Obtaining cover soil from a borrow pit; uni ts. The owner or operator is required t o

! Tr ansporting cover soil to the workin g popu lations of rodents, flies, mosquitoes, o r face; or oth er animals, including other insects. Th e trans porting cover soil to the working fac e

may b e as short as one day for unusual rai n

40 CFR §258.22

(a) Owners or operators of al l

uni ts, lateral expansions, and new MSWL F
pr event or control on-site disease vecto r
techniques that may be used in fulfilling thi s requirement must be appropriate for th eOperating Criteria

87 prot ection of human health and th e Vectors may reach the landfill facility no t environment. only from areas adjacent to the landfill, bu t 3.4.3 Technical Considerations a nd breedin g of disease vectors. Such modes Di sease vectors such as rodents, birds, flies , co llection vehicles and transfer stations

. and mosquitoes typically are attracted b y Th ese transport modes and areas also shoul d putrescent

waste and standing water, whic h be included in the disease vector contro l act as a food source and breeding ground

. pr ogramif disease vectors at the landfil l Putre scent

waste is solid waste that contain s fac ility become a problem. Keeping th e o rganic matter (such as food waste) capable of col lection vehicles and transfer station s be ing decomposed by micro-organisms. A c overed; emptying and clea ning the collection MSWLFfacility typically accepts putrescent v ehicles and transfer stations; usi ng repellents, wastes. i nsecticides, or rodent icides; and reproductive Applic ation of cover at the end of eac h disease vectors in these areas. o perating day generally is su fficient to control d isease vectors; howev er, other vector control alt ernatives may be required. Thes e 3.5 EXPLOSIVE GASES CONTROL alternatives could include: reducing the siz e 40 CFR §258.23 of the working face; other operationa l mo difications (e.g., increasing cove r 3.5.1 Statement of Regulation thickness, changing cover type, density , p lacement frequency, and grading); repellents, ( a) Owners or operators of allMSWLF insecticides or rodenticides; composting o r units must ensure that: p rocessing of organic wastes prior to disposal; an dpredatory or reproductive control o f (1) The concentration of methane ga s ins ect, bird, and animal populations

. g enerated by the facility does not exceed 25 Additional methods to control birds ar e pe rcentof the lower explosive limit fo r discussed in Chapter 2 (Airport Safety). met hane in facility structures (excludin g Mosquitoes, for example, are attracted b y components); and s tanding water found at MSWLFs, which can p rovide a potential breedin g ground after only (2) The concentration of methane ga s three days. Water generally collects i n d oes not exceed the LEL for methane at the s urface depressions, open containers, exposed facility property boundary. tir es, ponds resulting from soil excavation , leachate storage ponds, and siltation basins

. ( b) Owners or operators of all MS WLF Landfill operations that minimize standin g unit s must implement a routine methan e water and that use an insecticide sprayin g moni toring program to ensure that th e p rogram ordinarily are effect ive in controlling sta ndards of paragraph (a) of this sectio n mosquitoes. are met. through other modes conducive to harborage

m ay include reside ntial and commercial route

co ntrol are all measures available to reduc e

ga s control or recovery syste mSubpart C

88 (1) The type and frequency o f (4) The Director of an approved State moni toring must be determined based o n may establish alternative schedules fo r the following factors: d emonstrating compliance with paragr aphs (i) Soil conditions; (ii) The hydrogeologic condition s explosive limit(LEL) means the lowes t surrounding the facility; p ercent by volume of a mixture of explosive (i ii) The hydraulic condition s 25 C and atmospheric pressure. surrounding the facility; and (iv) The location of facilit y structures an d propert y The regulation applies to existing MSWL F boundaries. uni ts, lateral expansions, and new MSWL F (2) The minimum frequency o f MSWLFstructures can potentially result i n monitoring shall be quarterly. fir e and explosions that can endange r (c) If methane gas levels exceeding th e occu pants of nearby structures, or caus e limits specified in paragraph (a) of thi s dam age to landfill containment structures

. s ection are detecte d, the owner or operator The se hazards are preventable throug h must: mon itoring and through corrective actio n (1) Imm ediately take all necessary steps l imits in the facility structures (excluding gas to en sure protection of human health an d c ontrol or recovery syste m components), or at notify the State Director; th e facility property boundary. MSWL F (2) Within seven daysof detection, place with the following requirements: in t he operating record the methane ga s le vels detected and a description of th e ! Monitor at least quarterly; steps taken to protect human health; and (3) Within 60 days of detection , h ealt h in the event of methane gas levels implement a remediation plan for th e exc eeding 25% of the lower explosiv e metha ne gas releases, place a copy of th e l imit (LEL) in facility structures, such as p lan in the operating record, and notify the evacuating the building; Stat e Director that the plan has bee n im plemented. The plan shall describe th e ! Notify the State Director if methan e nat ure and extent of the problem and th e l evel s exceed 25% of the LEL in facility proposed remedy. struc tures or exceed the LEL at th e (2) and (3). (d) For purposes of this section, lower

gases in air that will propagate a flame a t
o 3.5.2 Applicability

units. The accumulation of methane i n

em ployees, users of the disposal site, an d

sho uldmethane gas levels exceed specifie d

faci lity owners and operators must compl y

! Take immediate steps to protect huma n

facility property boundary;Operating Criteria

89 ! Wit hin 7 days of detection, place in th e readily identified by its "rotten egg" smell at op erating record documentation tha t methane gas concentrations exceeded th e criteria, along with a description o f immediate actions taken to protect human health; and

! Wit hin 60 days of detection, implement a remediation plan for the methane ga s rel eases, notify the State Director, an d place a copy of

the remediation plan in the operating record.
T h e compliance schedule for monitoring and responding to methane levels that exceed the crit eriaof this regulation can be changed b y the Director of an approved State. 3.5.3 Technical Considerations
T o implement an approp riate routine methane mo nitoring program to demonstrat e co mpliance with allowable methan e con centrations, the characteristics of landfil l g a s production and migration at a site should b e understood. Landfill gases are the result of microbial decomposition of solid waste

. Gases produced include methane (CH ) , 4 car bon dioxide (CO ), and lesser amounts o f 2 other gases (e.g., hydrogen, volatile organi c c ompounds, and hydrogen sulfide). Methane g as, the principal compon ent of natural gas, is gene rally the primary concern in evaluatin g land fill gas generation because it is odorles s a nd highly combus tible. Typically, hydrogen g as is present at much lower concentra-tions. H ydrogen forms as decomposition progresses fromthe acid production phase to th e methanogenic phase. While hydrogen i s explosive and is occasionally detected i n l andf ill gas, it readily reacts to form methane or hydrogen sulfide. Hydrogen sulfide i s toxic and is a threshold concentration near 5 ppb. Lan dfill gas production rates vary spatiall y within a landfill unit as a result of pockets of e le vated microbial activity but, due to partial pre ssure gradients, differences in ga s composition are reduced as the gase s commingle within and outside the landfil l u nit. Although methane

gas is lighter than air a nd carbon di oxide is heavier, these gases are concurrently produced at the microbial leve l and will not separate by their individua l dens ity. The gases will remain mixed an d w ill migrate according to the dens ity gradients bet ween the landfill gas and the surroundin g gases (i.e., a mixture of methane and carbo n d ioxide in a landfill unit or in s urrounding soil wi ll not separate by rising and sinkin g res pectively, but will migrate as a mass i n acc ordance with the density of the mixtur e and other gradients such as temperature an d partial pressure). When undergoing vigorous microbia l p roductio n, gas pressures on the order of 1 to 3 inches of water relative to atmospheri c p ressure are common at landfill faci lities, with m uch higher pressures occasionally reported. A baro metric pressure change of 2 inches o f m ercury is equivalent to 27.2 inches of water. Relative gauge pressures at a particular landfill unit or portion of a landfill unit, th e ab ility of site conditions to contain landfil l gas, barometric pressure variations, and th e microbial gas production rate contro l pr essure-inducedlandfill gas migration

. Ne gative gas pressures are commonl y o bserved an d are believed to occur as a result of the delayed response within a landfill unit to the passage of a high pressure syste m outside the landfill unit. Barometric high s wi ll tend to introduce atmospheric oxyge n into surface soils inSubpart C

90 shallow portions of the landfill unit, whic h Stressedvegetation may indicate ga s may alter microbial activity, particularl y migration. Landfill gas present in the soi l methane production and gas composition. atmosphere tends to make the soil anaerobi c Migration of landfill gas is caused b y asph yxiating the roots of plants. Generally , concentration gradients, pressure gradients , th e higher the concentration of combustibl e a nd density gradients . The direction in which gas and/or carbon dioxide and the lower th e landfi ll gas will migrate is controlled by th e amou nt of oxygen, the greater the extent o f driving gradients and gas permeability of the damage to vegetation (Flowers, et. al, 1982). p orous material through which it is migrating. Ge nerally, landfill gas will migrate throug h Gas Monitoring the path of least resistance. Coar se, porous soils such as sand and grave l uni t/facility must implement a routin e will allow greater lateral migration o r m ethan e monitoring program to comply with transport of gases than finer-grained soils

. the lower explo sive limit (LEL) requirements Ge nerally, resistance to landfill gas flo w for methane. Methane is explosive whe n inc reases as moisture content increases and , pre sent in the range of 5 to 15 percent b y therefore, an effective barrier to gas flow can volume in air. When present in air a t be created under saturated conditions. Thus, con centrations greater than 15 percent, th e r eadily drained soil conditions, such as sands mixtu re will not explode. This 15 percen t and g ravels above the water table, ma y thr esholdis the Upper Explosive Limi t p rovide a preferred flowpath, but unless finer- (UEL). The UEL is the maximu m g rained soils are ful ly saturated, landfill gases con centration of a gas or vapor above whic h als o can migrate in a "semi-saturated" zone

. the substance will not explode when exposed Figure 3-2 illustrates the potential effects o f t o a source of ignition. The explosive hazard surrounding geology on gas migration. r ange is between the LEL and the UEL . Note, While geomembranes may not eliminat e the UEL remain a significant concern; fir e l andfill g as migration, landfill gas in a closed andasphyxiation can still occur at thes e MSWLFunit will tend to migrate laterally if levels

. In addition, even a minor dilution o f the final cover contains a geo membrane and if the methane by increased ventilation can bring the si de slopes of the landfill do not contai n the mixture back into the explosive range. a n effective gas barrier. Lateral gas migration is mo re common in older facilities that lac k To demonstrate compliance, th e appropriate gas control systems. The degree own er/operator would sample air withi n o f lateral migration in older faci lities also may f ac ility structures where gas may accumulate depen don the type of natural soil s and in soil at the property boundary. Othe r surrounding the facility. mo nitoring methods may include: (1 ) by displacing the oxygen, thereb y

The owner or operator of a MSWL F

however, that methane concentrations abov e

s ampling gases from probes within the landfill unit or from within the leachate collectio n system; or (2) sampling gases

### Figure 3-2 Potential Effects of Surrounding Geology on Gas Migration

91Subpart C

92 from monitoring probes installed in soi l s tructures, and changes in landscaping or land betwe en the landfill unit and either th e use practices. The rate of landfill ga s pr operty boundary or structures where ga s migration as a result of these anticipate d migrati on may pose a danger. A typical ga s ch anges and the site-specific condition s monitoring probe installation is depicted i n p rovides the basis for establishing monitoring Figure 3-3. frequency. Monitoring is to be conducted a t Alth ough not required by the regulations , c ol lection of data such as water presence and T he number and location of gas probes is also le vel, gas probe pressure, ambien t site-specific and highly dependent o n tem perature, barometric pressure, and th e subsurface conditions, land use, and location occ urrence of precipitation during sampling , and design of facility structures. Monitoring pr ovides useful information in assessin g for gas migration should be within the mor e monitoring results. For example, fallin g permeable strata. Multiple or nested probe s barometric pressure may cause increase d are useful in defining the vertica l s ubsurfac e (gas) pressures and corresponding co nfiguration of the migration pathway

. i ncreased methane content as gas more readily S tructures with basements or crawl spaces are migr ates from the landfill. Gas prob e mor e susceptible to landfill gas infiltration

. pressure can be measured using a portabl e Elevated structures are typically not at risk. g auge capable of me asuring both vacuum and p ressure in the range of zero to five inches of Mea surements are usually made in the fiel d wat er pressure (or other suitable ranges fo r w ith a p ortable methane meter, explosimeter, pr essure conditions); this pressure should b e ororganic vapor analyzer. Gas samples also measuredprior to methane measurement o r may be collected in glass or metal containers sa mple collection in the gas probe. A fo rlaboratory analysis. Instruments with re presentative sample of formatio n s cales o f measure in "percent of LEL" can be (s ubsurface) gases can be collected directl y calibratedand used to detect the presence o f from the probe. Purging typically is no t meth ane. Instruments of the hot-wir e necess ary due to the small volume of th e Wh eatstone bridge type (i.e., catalyti c prob e. A water trap is recommended t o combustion) directly measure combustibility protect instrumentation that is connecte d o f the gas mixture withdrawn from the probe. d irectly to the gas probe. A fter measurements The thermal conductivity type meter i s are obtained, the gas probe should be capped susceptible to interference as the relative gas t o reduce the effects of venting or barometric composition and, therefore, the therma l p ress ure variations on gas composition in the conductivity, changes. Field instrument s vicinity of the probe. should be calibrated prior to measurement s Th e frequency of monitoring should b e monitoring activity. su fficientto detect landfill gas migratio n b ased on subsurface conditions and changing l andfill conditio ns such as partial or complete capping, landfill expansion, gas migratio n control system operation or failure , construction of new or replacement least quarterly.

and should be rechecked after each day' sOperating Criteria

93 

### Figure 3-3 Typical Gas Monitoring ProbeSubpart C

94 L aboratory mea surements with organic vapor soil w ithin the area of concern. Th e a nalyzers or gas chro matographs may be used i nves tigation should consider possible causes to confirm the identity and concentrations of of the increase in gas concentrations such a s gas. la ndfill operational procedures, gas contro l
In addition to measuring gas composition , closur e activity. Based on the extent an d othe rindications of gas migration may b e nature of the excessive methane migration, a observed. These include odor (generall y remedial action should be described, if th e descri bedas either a "sweet" or a rotten eg g exc eedance is persistent, that can b e (H S) odor), vegetation damage, septic soil , implementedwithin the prescribed schedule. 2 and audible or visual venting of gases , The sixty-day schedule does not address th e esp ecially in standing water. Exposure t o prot ection of human health and th e some gases can cause headaches and nausea. env ironment. The owner or operator stil l
I f meth ane concentrations are in excess of 25 p rotection of hu man health, including interim percent of the LEL in facility structures o r measures. e xceed the LEL

at the property boundary, the d an ger of explosion is imminent. Immediate Landfill Gas Control Systems a c tion must be taken to protect human health fr ompotentially explosive conditions. Al l Landf ill gas may vent naturally or b e personnel should be evacuated from the are a purposely vented to the atmosphere b y i mmedi ately. Venting the building upon exit vertical and/or lateral migration controls

. (e.g., leaving the door open) is desirable bu t Systems used to control or prevent ga s should not replace evacuation procedures. m igratio n are categorized as either passive or Own ers and operators in unapproved State s pref erential flowpaths by means of natura l hav e 60 days after exceeding the methan e p ressure, concentration, and density gradients. l evel to prepare and implement a remediation Pa ssive systems are primarily effective i n pla n. The remediation plan should describ e c o ntrolling convective flow and have limited the nature and extent of the methane problem success controlling diffusive flow. Activ e as well as a proposed remedy. s ystems are effective in controlling both types To c omply with this 60-day schedule, a n equipment to direct or control landfill gas by i nvestigation of sub surface conditions may be pr oviding negative or positive pressur e n eeded in the vicinity of the monitoring probe g radients. Suitability of the systems is based wh ere the criterion was exceeded. Th e o n the desi gn and age of the landfill unit, and objec tives of this investigation should be t o on the soil, hydrogeologic, and hydrauli c d escribe the frequency an d lateral and vertical con ditions of the facility and surroundin g extent of excessive methane migration (that e nvironment. Because of these varia bles, both whi chexceeds the criterion). Such a n s ystems ha ve had varying degrees of success. investigation also may yield additiona l characterization of unsaturated Passi ve systems may be used in conjunctio n s ystem failure or upset, climati c conditions, or

must take all steps necessary to ensur e

ac tive systems. Passive systems provid e

of flow. Active systems use mechanica l

with active systems. An example of thisOperating Criteria

95 m ay be the use of a low-permeability passive 150 m egagrams per year (167 tons per year ) s ystem for the closed portion of a landfill unit o r greater. Allowable cont rol systems include ( for remedial purpose s) and the installation of op en and enclosed flares, and on-site or off

an active system in the active portion of th e sit e facilities that process the gas fo r landfill unit (for future use). su bsequent sale or use. EPA believes that , Selection of construction materials for either syst ems may be more cost-effective tha n t ype of gas control system sh ould consider the pass ive systems in ensuring that the syste m elevated temperature conditions within a effectively captures the gas that is generate d l andfill unit as compa

red to the ambient air or with in the landfill unit. The provisions fo r soil conditions in which gas control syste m new landfill units are self-implementing an d co mponents are constructed. Becaus e will be effective upon promulgation of th e a mbient conditions a

re typically cooler, water rule. c ontaining cor

rosive and possibly toxic waste constituents may be expected to condense

. I n addition to the emiss ions standards for new This condensate should be considered i n muni cipal solid waste landfill units, th e selecting construction materials. Provision s regulations proposed on May 30, 199 1 for managing this condensate should b e esta blishguidelines for State programs fo r incorporated to prevent accumulation an d re ducing NMOC emissions from certai n p ossible failure of the collection system. The exi sting municipal landfill units. Thes e c ondensate can be returned to the landfill unit provi sions apply to landfill units for whic h if t he landfill is designed with a composit e c onstruction was commenced before May 30, line rand leachate collection system pe r 1991, and that have accepted waste sinc e § 258.40(a)(2). See C hapter 4 for information Novem ber 8, 1987 or that have remainin g regarding design. See Section 3.10 of thi s capac ity. Essentially, the State must requir e Chap ter for information regarding liquids i n th e same kinds of collection and contro l landfills. system s for landfill units that meet the siz e Add itional provisions (under the Clean Ai r fornew landfill units. The requirements fo r A ct) w ere proposed on May 30, 1991 (56 FR exi sting facilities will be effective after th e 2446 8), that would require the owners / Stat e revises its State Implementation Pla n o perators of certain landfill facilities to install and receives approval from EPA. gas collection and control systems to reduc e the emissions of nonmethane organi c The rule is scheduled to be promulgated i n compounds (NMOCs). The proposed rul e l ate 1993; t he cutoff numbers for landfill size am ends 40 CFR Parts 51, 52, and 60. Fo r and e mission quantity may be revised in th e n ew municipal solid waste landfill u nits (those fi nal rule. EPA expects that the ne w forwhich construction was begun after Ma y re gulations will affect less than 9% of th e 30, 199 1), and for those units that have a municipal landfill facilities in the U.S. de sign capacity greater than 111,000 tons, a gas collection and control system must b e i nstalled if emissions evaluations indicate that the NMOC emissions rate is d epending on landfill design , active collection

criteria and emissions levels outlined abov eSubpart C

96 Passive Systems Some problems have been associated with Passi ve gas control systems rely on natura l m ay accumulate in vent pipes, preventing gas pr essure and convection mechanisms to ven t from venting. Vent pipes landf ill gas to the atmosphere. Passiv e at the surface are susceptible to clogging b y systems typically use "high-permeability" o r v andalism. Biologica l clogging of the system "low-permeability" techniques, eithe r is also more common in passive systems. singularly or in combination at a site. High

per meability systems use conduits such a s Active Systems ditches, trenches, vent wells, or perforate d vent pipes surrounded by coarse soil to ven t Acti ve gas control systems use mechanica l l andfill gas to the sur

face and the atmosphere. me ans to remove landfill gas and consist o f Low-permeability systems block latera l eit her positive pressure (air injection) o r migr ation through barriers such as syntheti c ne gative pressure (extraction) systems

. membranes and high moisture-containin g Positive pressure systems induce a pressur e fine-grained soils. g reater than the pressure of the migrating gas Passive systems may be incorporated into a the landfill unit in a controlled manner

. l andfill design or maybe used for remedial or N ega tive pressure systems extract gas from a corrective purposes at both closed and active lan dfill by using a blower to pull gas out o f landfills. They may be installed within a the landfill. Negative pressure systems ar e la ndfill unit along the perimeter, or betwee n more commonly used because they are mor e th e landfill and the disposal facility property effective and offer more flexibility i n boundary. A detailed discussion of passiv e con trolling gas migration. The gas may b e systems for remedial or corrective purpose s recoveredfor energy conversion, treated, o r may be found in U.S. EPA (1985). combu stedin a flare system. Typica l A passive system may be incorporated int o Figu re 3-5. Negative pressure systems ma y the f inal cover system of a landfill closur e be used as either perimeter gas contro l desi gn and may consist of perforated ga s systems or interior gas collection/recovery co llection pipes, high permeability soils, o r sys tems. For more information regardin g h igh tran smissivity geosynthetics located just n egative pressure gas cont rol systems, refer to b elow the low-permeab ility gas and hydraulic U.S. EPA (1985). barrieror infiltration layer in the cove r system. These systems may be connected t o An active gas extraction well is depicted i n vent pipes that vent gas through the cove r Figure 3-6. Gas extraction wells may b e system or that are connected to header pipe s in stalledwithin the landfill waste or, a s locatedalong the perimeter of the landfil l depi ctedin Figure 3-7A and Figure 3-7B , unit. Figure 3-4 illustrates a passive system

. perimeter extraction trenches could be used

. T he landfill gas collection s ystem also may be One possible configuration of an interior gas c onnected with t

he leachate collection system collection/recovery system is illustrated in to ve nt gases in the headspace of leachat e collection pipes. p assive systems. For example, snow and dirt

a nd drive the gas out of the soil and/or back to

co mponents of a flare system are shown i nOperating Criteria

97 

### Figure 3-4 Passive Gas Control System (Venting to Atmosphere)Subpart C

98 

### Figure 3-5. Example Schematic Diagram of a Ground-based Landfill Gas Flare

### Figure 3-6 Example of a Gas Extraction Well

99

### Figure 3-7A. Perimeter Extraction Trench System

Figure 3-7B. Perimeter Extraction Trench System
100Operating Criteria

101 Figur e 3-8. The performance of activ e 3.6 AIR CRITERIA syst ems is not as sensitive to freezing o r 40 CFR §258.24 saturation of cover soils as that of passiv e systems. Although active gas systems ar e 3.6.1 Statement of Regulation mor e effective in withdrawing gas from th e la ndfill, capital, operation, and maintenanc e (a) Owners or operators of al l c osts of such systems will be higher and these M SWLFs must ensure that the units do not c o sts can be expected to continue throughout violate any applicable requirement s the post-closure period. At some future time, developed under a State Implementatio n own ers and operators may wish to convert P lan (SIP) approved or promulgated by the a ctive gas controls into passive systems when Administratorpursuant to section 110 o f gas production diminishes. The conversio n the Clean Air Act, as amended. op tion and its environmental effect (i.e., ga s release causing odors and health and safety ( b) Open burning of solid waste , except c oncerns) should be addressed in the original fo rthe infrequent burning of agricultura l design. wastes, silvicultural wastes, land-clearin g T here are many benefits to recovering landfill em ergency clean-up operations, i s g as. Landfill gas recovery syste ms can reduce prohibited at all MSWLF units. landfill gas odor and migration, can reduc e the danger of explosion and fire, and may be 3.6.2 Applicability used as a source of revenue that may help t o r educe the cost of closure. Landfi ll gas can be The regulation applies to existing MSWL F use dwith a minimal amount of treatment o r units, lateral expansions to existing MSWLF can be upgraded to pipeline standard s units, and new MSWLF units. Routine open (SWANA , 1992). An upgraded gas is on e burn ing of municipal solid waste i s which has had the carbon dioxide and othe r p rohibited. Infrequent burning of agricultural noncombustible constituents removed. an dsilvicultural wastes, diseased trees, o r Raw landfill gas may be used for heatin g u p op erations is allowed when in compliance smal l facilities and water, and may requir e with any applicable requirements develope d r emoval of only water and parti culates for this under a State Implementation Plan (SIP) o f applic ation. A slightly upgraded gas can b e the Clean Air Act. Agricultural waste doe s u sed for bo th water and space heating as well not include empty pesticide containers o r as lighting, electrical generation , waste pesticides. cogeneration, and as a fuel for industria l boile rs-burners. Landfill gas also may b e 3.6.3 Technical Considerations pro cessedto pipeline quality to be sold t o utili ty companies and may even be used t o Airpollution control requirements ar e fue l conventional vehicles. The amount o f d eveloped under a SIP, which is developed by u pgrading and use of lan dfill gas is dependent the S tate and approved by the EP A on the landfill size. Administrator. The owner or operator of a debris, diseased trees, or debris fro m

d ebris from land clearing or emergency clean-

### Figure 3-8 Example of an Interior Gas Collection/Recovery System

102Operating Criteria

103 M SWLF unit should consult the State or local [ Note : The Agency plans to issue regulations a gency responsible fo r air pollution control to u nder the Clean Air Act to control landfill gas a s certain that the burning of wastes complies emissions from large MSWLF units in 1993. w ith applicable requirement s developed under The se regulations are found at 40 CFR Part s the SIP. The SIP may include variances , 51, 52, and 60.] pe rmits, or exemptions for burnin g a gricultural was tes, silvicultural wastes, landc learing deb ris, diseased trees, or debris from 3.7 ACCESS REQUIREMENT em ergency clean-up operations. Routin e 40 CFR §258.25 bur ning of wastes is banned in all cases, an d the SI P may limit burning of waste such a s 3.7.1 Statement of Regulation a gricultural wastes to certain hours of the day; days of the year; designated burn areas ; Ow ners or operators of all MSWLF unit s specific types of incinerators; atmospheri c mus tcontrol public access and preven t co nditions; and distance from working face , un authorized vehicular traffic and illega l public thoroughfares, buildings, an d dumping of wastes by using artificia l residences. barriers, natural barriers, or both, a s R equirements under the SIP also may include the environment. notifying applicable State or local agencie s whos e permits may: (1) restrict times whe n 3.7.2 Applicability lim itedburning of waste may occur; (2 ) s pecify periods when suffic ient fire protection The regulation applies to existing MSWL F i s deemed to be available ; or (3) limit burning uni ts, lateral expansions, and new MSWL F to certain areas. uni ts. The owner or operator is required t o Open burning is defined under §258.2 as th e ex cept under controlled conditions durin g com bustion of solid waste: (1) withou t hours when wastes are being received. control of combustion air to maintai n adequate temperature for efficien t 3.7.3 Technical Considerations combustion; (2) without containment of th e c o mbustion reaction in an enclosed device to provide sufficient residence time and mixing f or complete combustion; and (3) without the cont rol of the emission of the combustio n products. Trench or pit burners, and ai r curtain destructors are considered ope n bu rning units because the particulat e e mission s are similar to particulate emissions from open burning, a nd these devices do not control the emission of combustion products. app ropriate to protect human health an d

pre vent public access to the landfill facility ,

Owners and operators are required to control publ ic access to prevent illegal dumping , p ublic exposures to hazards at MSWLF units, an dunauthorized vehicular traffic

. Frequently, unauthorized persons ar e unfamiliar with the hazards associated with lan dfill facilities, and consequences o f uncontrolled access may include injury an d even death. Potential hazards are related t o in ability of equipment operators to se e unauthorizedindividuals during operation of e quipment and haul vehicles; direct exposure to waste (e.g., sharp objects and pathogens) ;Subpart C

104 inad vertent

or deliberate fires; and earth

- 3.8.2 Applicability moving activities. Ac ceptable measures used to limit access o f un authorizedpersons to the disposal facility i nclude gates and fences, trees, hedges, berms, ditc hes, and embankments. Chain link , ba rbedwire added to chain link, and ope n farm-type fencing are examples of fencin g that may be used. Access to facilities should b e controlled through ga

tes that can be locked when the site is unsupervised. Gates may be the only ad ditional measure needed at remote facilities.

3.8 RUN-ON/RUN-OFF CONTROL SYSTEMS 40 CFR §258.26 3.8.1 Statement of Regulation (a) Owners or operators of all MSWLF u nits must design, construct, a nd maintain: (1) A run-on control system to preven t flow onto the active portion of the landfil l duri ng the peak discharge from a 25-yea r storm; (2 ) A run-off control system from th e active portion of the landfill to collect and c ontr ol at least the water volume resulting from a 24-hour, 25-year storm. (b) Run-off from the active portion o f the l andfill unit must be handled i n accordance with §258.27(a) of this Part. The regulation applies to existing MSWL F uni ts, lateral expansions, and new MSWL F uni ts. The owner or operator is required t o prevent run-on onto the active portion of th e l andfill units and to collect and c ontrol run-off f rom the active porti on for a 24-hour, 25-year storm. Management of run-off must comply w ith the point and n on-point source discharge requirements of the Clean Water Act. 3.8.3 Technical Considerations If s tormwater enters the landfill unit an d cont acts waste (including water within dail y c o ver), the stormwater becomes leachate and m ust be managed as leach ate. The purpose of a run -on control system is to collect an d redi rect surface waters to minimize th e amount of surface water entering the landfill u nit. Run-on c ontrol can be accomplished by co nstructing berms and swales above th e fil ling area that will collect and redirect th e water to stormwater control structures. As s tated above, stormwater that does ente r the l andfill unit should be managed a s leachate. Run-off control systems ar e de signedto collect and control this run-of f fromthe active portion of the landfill , incl uding run-off from areas that hav e receiveddaily cover, which may hav e cont actedwaste materials. Run-off contro l can be accomplished through stormwate r con veyance structures that divert this run

off/leachate to the leachate storage device. After a landfill unit has been closed with a f inal cover , stormwater run-off from this unit can be managed as stormwater and no t leach ate. Therefore, waters running off th e final cover system of closed areas may no tOperating Criteria

105 require treatment and generally can b e T he Soil Conservati on Service (SCS) Method combined with run-on waters. For landfill s and/or the Rational Method are generall y with steep side slopes, a bench system may ad equate for estimating storm flows fo r prov ide the best solution for run-off control

. des igning run-on and/or run-off contro l A bench creates a break in the s lope where the systems. The SCS method estimates run-of f v elocity of the stormwater run-off is expected vo lume from accumulated rainfall and the n t o become erosive. The bench converts sheet app lies the run-off volume to a simplifie d flo w run-off into channel flow. Benche s triangular uni t hydrograph for peak discharge t ypically are spaced 30 to 50 feet apart up the estimation and total run-off hydrograph. A slope. An alternative to benches is a syste m d iscussion o f the development and use of this of downchutes whereby stormwater i s methodis available from the U. S

. collec tedoff the top of the landfill an d D epartment of Agricult ure, Soil Conservation conveyeddown the slope through a pipe o r Service (1986). channel. Caution should be taken not t o con struct downchutes with heavy materia l The Rational Method approximates th e be cause of possible subsidence. Corrugate d maj ority of surface water discharge supplie d metal pipes or plastic-lined channels ar e by the watershed upstream from the facility

. e xamples of

lightweight materials that can be The Rational Method generally is used fo r used for downchute construction. areas of less than 200 acres. A discussion of Run- on and run-off must be managed i n EPA (1988). a ccordance with the requirements of the Clean Wa ter Act including, but not limited to, th e Ru n-on/run-off control structures, both National Pollutant Discharge Eliminatio n temporary and permanent, may b e Syste m(NPDES). [See Section 3.9 of thi s incor poratedinto the system design. Othe r c hapter for further inform ation on compliance structures (not mentioned above) mos t with the Clean Water Act.] f requently used for run-on/run-off control are Ru n-on and run-off control systems must b e an dsedimentation basins. U.S. EPA (1985 ) de signedbased on a 24-hour, 25-year storm

. provides an in-depth discussion for each o f I nformation on the 24-hour , 25-year recurring these structures. storm can be obtained from Technical Pape r 40 "Rainfall Frequency Atlas of the Unite d States for Durations from 30 Minutes to 2 4 3.9 SURFACE WATER Hours and Return Periods from 1 to 10 0 REQUIREMENTS Ye ars", prepared by the Weather Bureau 40 CFR §258.27 und er the Department of Commerce

. Al ternatively, local meteorological data ca n 3.9.1 Statement of Regulation be an alyzed to estimate the criterion storm

. To estimate run-on, the local watershe d MSWLF units shall not: should be identified and evaluated t o document the basis for run-on design flows. ( a) Cause a discharge of poll utants into the Rational Method may be found in U.S

.

waterways, seepage ditches, seepage basins ,

wat ers of the United States, includin gSubpart C

106 w etlands, that violate s any requirements of A MSW LF unit(s) that has a point sourc e the Clean Water Act, including, but no t d isch arge must have a NPDES permit. Point l imited to, the National Pollutant Discharge s ource discharges for landf ills include, but are Elimination System (NPDES ) no tlimited to: (1) the release of leachat e requirements, pursuant to section 402. f rom a leachate collection

or on-site treatment (b) Cause the discharge of a nonpoin t (2) disposal of solid waste into waters of th e s o urce of pollution to waters of the United UnitedStates; or (3) release of surface water States, including wetlands, that violates (s tormwater) run-off which is directed by a a nyrequirement of an area-wide or State- run-off control system into the waters of th e wide water quality management plan that Un itedStates. Leachate that is piped o r ha s been approved under section 208 o r truc kedoff-site to a treatment facility is no t 319 of the Clean Water Act, as amended. regarded as a point source discharge. 3.9.2 Applicability The Clean Water Act (CWA) provide s The regulation applies to existing MSWL F wat ers of the United States, pollutants, an d uni ts, lateral expansions, and new MSWL F discharge of pollutants. uni ts. The owner or operator is required t o compl y with the Clean Water Act for an y Owners/operators also should be aware that discharges to surface water or wetlands. there are reg ulations promulgated pursuant to 3.9.3 Technical Considerations from landfill facilities. These regulation s The ow ner or operator of a MSWLF facility applications to be submitted by certai n sho ulddetermine if the facility is i n l andfills that accept or have accepted specific c onformance

with applicable requirements of t ypes of industrial waste. See 4 0 CFR Section w ater quality plans developed under Sections 122.26(a)-(c), which originally appeared i n 208 and 319 of the Clean Water Act, and the the Federal Register on November 16, 199 0 National Pollutant Discharge Eliminatio n (55 FR47990). S ystem (NPDES) requirements under Section 402 of the Clean Water Act. The EPA an d In addition, EPA codified several provision s approvedStates have jurisdiction ove r pur suant to the Intermodal Surfac e d ischarge of pollutants (other than dredge and T ransportation Efficiency Act of 199 1 into the fi ll materials) in waters of the United State s NPDES regulations. These regulations onl y in cluding wetlands. MSWLF unit s aff ect the deadlines for submitting permi t discharging pollutants or disposing of fil l applications for stormwater discharges, an d ma terial into waters of the United State s they apply to both uncontrolled and controlled requ ire a Section 402 (NPDES) permit

. san itary landfills. "Uncontrolled sanitary Dis charge of dredge and fill material int o landf ills" are defined as landfills or ope n waters of the United States is under th e du mps that do notmeet the requirements fo r jur isdiction of the U.S. Army Corps o f ru n-on or run-off controls that are found i n Engineers. the sy steminto the waters of the United States ;

clarifications of terms such as point source ,

the CWA regarding stormwater discharge s require stormwater discharge permi tOperating Criteria

107 MSWLFCriteria, Section 258.25

. this part. The owner or operator mus t "Co ntrolledsanitary landfills" are those that place the demonstration in the operatin g d omeet th e run-on and run-off requirements. r ecord and not ify the State Director that it Th e NPDES regulations specify tha t has been placed in the operating record. un controlled sanitary landfills owned o r ope ratedby municipalities of less tha n (b) Containers holding liquid wast e 100,000 (population) must submit a NPDE S may not be placed in a MSWLF uni t per mitapplication for their stormwate r unless: discharge or obtain coverage under a general pe rmit. For controlled sanitary landfill s (1) The container is a small containe r owned or operated by a municipality with a simila rin size to that normally found i n popul ation less than 100,000, there is n o household waste; r equirement to submit

a stormwater discharge permit application (before October 1, 1992 ) (2) The container is designed to hol d unl ess a permit is required under Sectio n liquids for use other than storage; or 402(p) (2)(A) or (E) of the Clean Water Act

. O ther deadlines are set for municipalities with (3) The waste is household waste. a pop ulation less than 250,000 that own o r oper ate a municipal landfill. For furthe r (c) For purposes of this section: in formation contact the Stormwater Hotlin e (703) 821-4823. See the April 2, 199 2 (1) Liquid waste means any wast e Federal Register (57 FR11394), 40 CF R mat erial that is determined to contai n 122.26. "fr ee liquids" as defined by Method 909 5

3.10 LIQUIDS RESTRICTIONS W astes, Physical/Chemical Metho ds" (EPA 40 CFR §258.28 Pub. No. SW-846). 3.10.1 Statement of Regulation (2) Gas condensate means the liqui d (a) Bulk or noncontainerized liqui d process(es) at the MSWLF unit. waste may not be placed in MSWLF units unless: 3.10.2 Applicability (1) The waste is household waste othe r T he regulat ion applies to new MSWLF units, than septic waste; or e xisting MSWLF units, and lateral expansions (2) The waste is leachate or ga s oper ator is prohibited from placing bulk o r c ondensate d erived from the MSWLF unit no n-containerizedliquid waste, o r and the MSWLF unit, whether it is a n cont ainerizedliquid waste into the MSWL F exi sting or new unit, is designed with a unit. Liquids from households are exempt

. com posite liner and leachate collectio n Tank trucks of wastes are not exempt. system as described in §258.40 (a)(2) of ( Paint Filter Liquids Test), as described in "Test Methods for Evaluating Soli d

gene rated as a result of gas recover y

of exi sting MSWLF units. The owner o rSubpart C

108 3.10.3 Technical Considerations s pecial management requirements for sewage Th e restriction of bulk or containerize d li quids is intended to control a source o f Owners and operators of MSWLF units ma y l iquids that m ay become a source of leachate. L iquid waste ref

ers to any waste material that is determined to contain free liquids a s d efined by SW-846 (U.S. EPA, 1987 ) Method 9095 - Paint Filter Liquids Test. The pain t filter test is performed by placing a 10 0 mi lliliter sample of waste in a conical, 40 0 m icron paint filter. The waste is considered a liq uidwaste if any liquid from the wast e passes through the filter within five minutes. The apparatus used for performing the pain t filter test is illustrated in Figure 3-9. If the waste is considered a liquid waste , absorbent materials may be added to render a

" solid" material (i.e., waste/absorbent mixture that no longer fails the paint filter liquid s tes t). One common waste stream that ma y co ntain a significant quantity of liquid i s sludge

. Sludge is a mixture of water an d sol ids that has been concentrated from, an d pro ducedduring, water and wastewate r trea tment. Sludges may be produced as a resu ltof providing municipal services (e.g. , p otable water supply, sewage tre atment, storm drain maintenance) or commercial o r industrial operations. Sewage sludge is a mixture of organic and inorganic solids an d water, removed from wastewater containin g domestic sewage. Sludge disposal i s acce ptable provided the sludge passes th e paint filter test. [NOTE: Additional Federal regulation s res tricting the use and disposal of sewag e sludge were published on February 19, 199 3 in the Federal Register

(58 FR9248). These regulations, however, do not establis h ad ditional treatment standards or othe r sludge that is codisposed with solid waste.]

r eturn leachate and gas condensate generated from a gas recovery process to the MSWLF , p rovided th e MSWLF unit has been designed and constructed with a composite liner an d l eachate collection sy stem in compliance with 4 0 CFR §258.40(a)(2 ). Approved States may al low leachate and landfill gas condensat e r ecirculation in MSWLF units with alternative designs. Rec irculating leachate or landfill ga s concentrate may require demonstrating tha t the added volume of liquid will not increas e the depth of leachate on t

he liner to more than 30 cm. Returning gas condensate to the landfill uni t m ay represent a reasonable lo ng-term solution for relatively small volumes of condensate

. Gas condensate recirculation can b e accomplishedby pumping the condensat e th rough pump stations at the gas recovery s ystem and into d edicated drain fields (buried p ipe) atop the

landfill, or into other discharge points (e.g., wells). Because gas condensate may be odorous , spray systems for recirculation are not use d un less combined with leachate recirculatio n systems. Leachate recirculation to a MSWLF unit ha s b een used as a measure for managing leachate or a s a means of controlling and managin g li quidand solid waste decomposition

. L eachate recirculation can b e accomplished in the same manner as recirculation of landfil l gas c ondensate. Because of the large r volu me, however, discharge points may no t be as effective as drainfields. In some cases, discharge pointsOperating Criteria

109 

### Figure 3-9. Paint Filter Test ApparatusSubpart C

110 have been a source of odor. In addition, a ( 6) Closure and post-clos ure care plans d ischarge point may not allow for dissipation an d any monitoring, testing, or analytica l of the leachate. (For additional informatio n d ata as required by §§258.60 and 258.61 of rega rding the effectiveness of using leachat e this Part; and rec irculation to enhance the rate of organi c degradation, see (Reinhart and Carson , (7) Any cost estimates and financia l 1993).) assurance documentation required b y

3.11 RECORDKEEPING (8) Any information demonstratin g REQUIREMENTS co mpliance with small communit y 40 CFR §258.29 exemption as required by §258.1(f)(2). 3.11.1 Statement of Regulation (b) Th e owner/operator must notif y (a) The owner or operator of a fr om paragraph (a) of this section hav e M SWLF un it must record and retain near been placed or added to the operatin g t he facility in a n operating record, or in an reco rd, and all information contained i n alternative location approved by th e the operating record must be furnishe d D irector of an approved state, the following upon request to the State Director or b e information as it becomes available: made available at all reasonable times fo r (1) Any location restrictio n demonstration required under Subpart B (c) T he Directo r of an approved State of this part; ca n set alternative schedules fo r (2) Inspection records, trainin g r equirements as specified in p aragraphs (a) procedures, and notification procedure s and (b), except for the notificatio n required in §258.20 of this Part; re quirements in §258.10(b) an d (3) Gas monitoring results fro m monitoring and any remediation plan s 3.11.2 Applicability required by §258.23 of this Part; (4) Any MSWLF unit desig n d ocumentation for placement of leachate or gas condensate in a MSWLF unit a s r equir ed under §258.28 (a)(2) of this Part; (5) Any demonstration, certification , finding, monitoring, testing, or analytica l data required by Subpart E of this Part; Subpart G of this Part.

th e State Director when the document s

inspection by the State Director.

recordkeepi ng and notificatio n

§258.55(g)(1)(iii).

The regulation applies to existing MSWL F units, lateral expansions of existing MSWLF units , and new MSWLF units. Th e r ecordkeeping requirements are i ntended to be s elf-implementing so that owners/ o perators in una pprovedStates can comply without Stat e o r E PA involvement. The owner or operator is required to maintain records o f demonstrations, inspections, monitorin g results, design documents, plans, operationalOperating Criteria

111 procedures, notices, cost estimates, an d • Date and time wastes were received durin g financial assurance documentation. the inspection; 3.11.3 Technical Considerations • Names of the transporter and the driver;
T he operating record should be maintained in • Source of the wastes; a single location. The location may be at the fac ility, at corporate headquarters, or at city • Vehicle identification numbers; and h a ll, but should be near the facility. Records shouldbe maintained throughout the life o f • All observations made by the inspector. th e facility, including the post-closure car e perio d. Upon placement of each require d Training records should include procedure s docu ment in the operating record, the Stat e used to train personnel on hazardous wast e Director should be notified. The Director of and on PCB waste recognition. Notificatio n an approved State may establish alternativ e to EPA, State, and local agencies should b e re quirements for recordkeeping, includin g documented. u sin g the State permit file for recordkeeping. Recordkeeping at the landfill facility shoul d remed iation plans : If gas levels exceed 2 5 include the following: p ercent of the LEL for methan e in any facility (a) L o cation restriction demonstrations : the facility boundary, the owner or operato r D emonstrations are required for any location mu st place in the operating record, withi n res trictions under Subpart B. The locatio n se ven days, the methane gas levels detected , restrictions apply to: a nd a des cription of the steps taken to protect

• Airports; the ow ner or operator must place a copy o f

• Floodplains; the operating record.

• Wetla (d) MSWLF unit desig n

• Fault areas; g as condensate in a MSWLF unit : If leachate

• Seismic impact zones; and MSWLF unit, documentation of a composite

• Unstable areas. of maintaining a maximum of 30 cm o f (b) Inspection records, trainin g placed in the operating record. procedures, and notification procedures : Inspection records should include: (c) Gas monitoring results and an y

str uctures or exceed the LEL for methane a t

human health. Within 60 days of detection , the remediation plan used for gas releases i n

do cumentation for placement of leachate o r

a nd/or gas condensate are recirculated into the l iner and a leachate collection system capable lea chate head in the MSWLF unit must b eSubpart C

112 (e) Demonstration, certification , • A notice identifying the Part 25 8 monitoring, testing, or analytical findin g Appendix II constituents that hav e requiredby the ground-water criteria : exceeded the ground-water protection standard ; Documents to be placed in the operatin g record include: • A c ertification by a qualified ground

-

• Do cumentation of design, installation , the MSWLF unit caused th e development, and decommission of an y co ntamination or an error in sampling , mon itoring wells, piezometers, and othe r a nalys is, statistical evaluation, or natural measurement, sampling, and analytica l ground-water variation caused a devices; st atistically significant increase (fals e

• Certification by a qualified ground-wate r constituents (if applicable); sc ientist of the number, spacing, an d depths of the monitoring systems; • The remedies selected to remediat e

• Documentation of sampling and analysi s programs and statistical procedures; • C ertification of remediation completion.

• Noti ce of finding a statistically significant (f) Closure and post-closure plans an d increase over background for one or more an y monitoring, testing, or analytical dat a of the constituents listed in Appendix I of associated with these plans : The landfil l Par t258 (or alternative list in approve d f acility own er or operator is required to place States) at any monitoring well at the waste a copy of the closure plan, post-closure plan, ma nagement

unit boundary (States with and a notice of intent to close the facility i n inadequate program) or the relevant poin t the operating record. Monitoring, testing, or of compliance (approved States); anal ytical data associated with closure an d

• Certification by a qualified ground-wate r ground-water and landfill gas monitorin g scientist that an error in s ampling, analysis, must be placed in the operating record. A statistical evaluation, or natural variation in copy of the notation on the deed to th e gr oundwater caused an increase (fals e MSWLF facility property, as require d po sitive) of Appendix I constituents, o r f ollowing closure, along with certification and tha ta source other than the MSWLF uni t ve rification that closure and post-closur e caused the contamination (if appropriate); a ctiv ities have been completed in accordance

• A notice identif

ying any Appendix II (Part placed in the operating record. 25 8) constituents that have been detecte d in ground water and their concentrations; (g) Estimates and financial assuranc e water scientist that a source other tha n

positive) in Appendix II (Part 258 )

ground-water contamination; and

post-closure information generated fro m

with their respective plans, also must b e

documentation required : The followin g documents must be placed in the operatin g record:Operating Criteria

113 • An estimate of the cost of hiring a thir d part y to close the largest area of al l MSWLF units that will re quire final cover;

• Justification for the reduction of th e closure cost estimate and the amount o f financial assurance (if appropriate);

• A cost estimate of hiring a third party t o conduct post-closure care;

• The justification for the reduction of th e post-closure cost estimate and financia l assurance (if appropriate);

• An estimate and financia l assurance for the cost of a third party to conduct correctiv e action, if necessary; and

• A copy of the financial assuranc e mechanisms.Subpart C

114 3.12 FURTHER INFORMATION 3.12.1 References
F lower, et al., (1982). "Vegetation Kills in Landfill Environs"; Franklin B. Flower, Ida A. Leone, Edward F. Gilman and John J. Arthur; Cook Co llege, Rutgers University; New Brunswick, New Jersey 08903. Reinhart, D.R., and D. Carson, (1993). "Experiences with Full-Scale Application of Landfill Biorea ctor

Technology," Thirty-First Annual Solid Waste Exposition of the Solid Wast e Association of North America, August 2-5, 1993. SW ANA, (1992). "A Compilation of Landfill Gas Field Practices and Procedures"; Landfill Ga s Division of the Solid Waste Association of North America (SWANA); March 1992. U.S. Department of Agriculture Soil Conservation Service, (1986). "Urban Hydrology for Small Watersheds"; PB87-101580. U .S. Department of Commerce, Weather Bureau, "Rainfall Frequ ency Atlas of the United States for Durations from 30 Minutes to 24 Hours and Return Periods from 1 to 100 Years." U.S. EP A, (1985). "Handbook - Remedial Action at Waste Disposal Sites"; EPA/625/6-85/006 ; U.S. EPA, Office of Research and Development; Cincinnati, Ohio 45268. U.S. EPA, (1986). "Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods" ; Third Edition as amended by Updates I and II. U.S. EPA SW-846; Office of Solid Waste and Emergency Response; Washington, D.C. U. S. EPA, (1988). "Guide to Technical Resources for the Design of Land Disposal Facilities" ; EPA/625/6-88/018; U.S. EPA; Risk Reduction Engineering Laboratory and Center fo r Environmental Research Information; Cincinnati, Ohio 45268. U.S. EPA, (1992). "Alternative Daily Cover Materials for Municipal Solid Waste Landfills;" U.S. EPA Region IX; San Francisco, California 94105.

3.12.2 Addresses Solid Waste Association of North America (SWANA/GRCDA) P.O. Box 7219 Silver Spring, MD 20910 (301) 585-2898115 

### APPENDIX I
Special Waste Acceptance Agreement

### Appendix I. Example Special Waste Acceptance Agreement

116

# CHAPTER 4 SUBPART D DESIGN CRITERIA118 CHAPTER 4 SUBPART D TABLE OF CONTENTS 4.1 INTRODUCTION

........................................................ 121 4.2 PERFORMANCE-BASED DESIGN 40 CFR §258.40

.......................................................... 122 4.2.1 Statement of Regulation

............................................... 122 4.2.2 Applicability

.................................................. 123 4.2.3 Technical Considerations

.............................................. 123 Demonstration Requirements

.......................................... 123 Leachate Characterization

............................................. 124 Assessment of Leakage Through Liners

.................................. 125 Leachate Migration in the Subsurface

.................................... 126 Physical Processes Controlling Contaminant Transport in the Subsurface

. . 126 C hemical Proc esses Controlling Contaminant Transport in the Subsurface

.................................................... 128 B iological Processes Controll ing Contaminant Transport in the Subsurface

.................................................... 129 Leachate Migration Models

........................................... 130 Overview of the Modeling Process

...................................... 130 Model Selection

.................................................... 135 Analytical Versus Numerical Models

.............................. 135 Spatial Characteristics of the System

.............................. 136 Steady-State Versus Transient Models

............................. 136 Boundary and Initial Conditions

................................. 137 Homogeneous Versus Heterogeneous Aquifer/Soil Properties

........... 137 Availability of Data

........................................... 138 Summary of Available Models

......................................... 138 The EPA Multimedia Exposure Assessment Model (MULTIMED)

............. 139 Overview of the Model

........................................ 147 Application of MULTIMED to MSWLF Units

............................. 147119

4.3 COMPOSITE LINER AND LEACHATE COLLECTION SYSTEM 40 CFR §258.40

.......................................................... 149 4.3.1 Statement of Regulation

............................................... 149 4.3.2 Applicability

........................................................ 150 4.3.3 Technical Considerations

............................................... 150 Standard Composite Liner Systems

..................................... 150 Soil Liner

......................................................... 151 Thickness

................................................... 151 Lift Thickness

............................................... 151 Bonding Between Lifts

........................................ 152 Placement of Soil Liners on Slopes

............................... 152 Hydraulic Conductivity

........................................ 152 Soil Properties

............................................... 153 Amended Soils

.............................................. 154 Testing

..................................................... 154 Soil Liner Construction

........................................ 159 Geomembranes

..................................................... 160 Material Types and Thicknesses

.................................. 160 Chemical and Physical Stress Resistance

........................... 160 Installation

.................................................. 162 Leachate Collection Systems

.......................................... 165 Grading of Low-Permeability Base

............................... 166 High-Permeability Drainage Layer

................................ 167 Soil Drainage Layers

.......................................... 167 Geosynthetic Drainage Nets

..................................... 168 Leachate Collection Pipes

............................................. 171 Protection of Leachate Collection Pipes

............................ 173 Protection of the High-Permeability Drainage Layer

.................. 178 Soil Filter Layers

............................................. 178 Geotextile Filter Layers

........................................ 179 Leachate Removal System

............................................ 181 Other Design Considerations

.................................... 182 Construction Quality Assurance and Quality Control

........................ 182 CQA/CQC Objectives

......................................... 182 Soil Liner Quality Assurance/Quality Control

............................. 183 Soil Liner Pilot Construction (Test Fill)

.................................. 185 Geomembrane Quality Assurance/Quality Control Testing

.................... 185 Destructive Testing

........................................... 185 Non-Destructive Testing

....................................... 186 Geomembrane Construction Quality Assurance Activities

.................... 186 Leachate Collection System Construction Quality Assurance

.................. 187120

4.4 RELEVANT POINT OF COMPLIANCE 40 CFR §258.40(d)

....................... 188 4.4.1 Statement of Regulation

............................................... 188 4.4.2 Applicability

........................................................ 189 4.4.3 Technical Considerations

.............................................. 189 Site Hydrogeology

.................................................. 189 Leachate Volume and Physical Characteristics

............................. 189 Quality, Quantity and Direction of Ground-Water Flow

...................... 189 Ground-Water Receptors

............................................. 190 Alternative Drinking Water Supplies

.................................... 190 Existing Ground-Water Quality

........................................ 190 Public Health, Welfare, Safety

......................................... 190 Practicable Capability of the Owner or Operator

............................ 191 4.5 PETITION PROCESS 40 CFR §258.40(e)

...................................... 191 4.5.1 Statement of Regulation

................................................ 191 4.5.2 Applicability

........................................................ 191 4.6 FURTHER INFORMATION

................................................ 193 4.6. 1 REFERENCES (Specific to Performance-Based Design Assessment and Solut e Transport Modeling)

................................................. 193 4.6.2 REFERENCES (Specific to Design Criteria )

................................ 199 4.6.3 Models

............................................................ 202121 

### CHAPTER 4 SUBPART D DESIGN CRITERIA

4.1 INTRODUCTION New MSWLF facilities and lateral expansions of existing units must comply with either a design s tandard or a performance standard for landfill design. The Federal Criteria do not require existing u nits to be retrofitted with lin ers. The design standard requires a composite liner composed of two feet of soil with a hydraulic conductivity of no more than 1 x 10 cm/sec, overlain by a flexibl e -7 membran e liner (FML) and a leachate collection system. A performance-based design mus t d emonstrate the capability of maintaining contaminant concent rations below maximum contaminant levels (M CLs) at the unit's relevant point of compliance. The performance standard has bee n e stablished to allow design innovation and consideration of site-specific conditions; approved States m ay have adopted alternative design stan dards. Owners/operators are advised to work closely with State permitting agencies to determine the applicable design standard. Owners/operators i n unapprov edStates may use the petition process (§258.40(c)) to allow for use of a performance

based design. This process is discussed in Section 4.5.
T he technical considerations discussed in this chapter are intended to ident ify the key design features andsystem components for the composite liner and leachate collection system standards, and for th e performance standard. The technical considerations include 1) design concepts, 2) desig n calculations, 3) physical properties, and 4) construction methods for the following: 1) Designs Based on the Performance Standard

! Leachate characterization and leakage assessment;

! Leachate migration in the subsurface;

! Leachate migration models; and

! Relevant point of compliance assessment. 2) Composite Liners and Leachate Collection Systems

! So il liner component (soil properties lab testing, design, construction, and quality assurance/quality control testing);

! Flex ible membrane liners (FML properties, design installation, and quality assurance/quality control testing);

! Leachate collection systems (strength and compatibility, grading and drainage, clogging potential, and filtration);Subpart D

122 ! Leachate removal systems (pumps, sumps, and standpipes); and

! Inspections (field observations and field and laboratory testing). Desig ns based on the performance standard are described in Section 4.2. Requirements fo r composi te liners are discussed in Section 4.3. These sections address the minimum regulatory r equirements th at should be considered during the design, construction, and operation of MSWLF units to en sure that they perform in a manner protective of human health and the environment

. A dditional features or procedures m ay be used to demonstrate conformance with the regulations or to control leachate release and subsequent effects. For example, during construction of a ne w MS WLF unit, or a lateral expansion of an existing MSWLF unit, quality control and quality assurance procedures and documentation may be used to ensure that material properties an d c onstruction methods meet the de sign specifications that are intended to achieve the expected level o f performance. Section 4.4 presents methods to assess ground-water quality at the relevant point o f compliance for performance-based designs. Section 4.5 des cribes the applicability of the petition process for States wishing to petition to use the performance standard.

4.2 PERFORMANCE-BASED DESIG N the regulatory language for requirement s 40 CFR §258.40(a)(1) 4.2.1 Statement of Regulation (a) New MSWLF units and latera l expansions shall be constructed: (1) In accordance with a desig n app roved by the Director of an approve d Sta te or as specified in §258.40(e) fo r u napproved States. The design mu st ensure th atthe concentration values listed i n Tab le 1 will not be exceeded in th e u ppe rmost aquifer at the relevant point of co mpliance as specified by the Director o f a n a pproved State under paragraph (d) of this section, or (2) (See Statement of Regulation i n Sect ion 4.3.1 of this guidance document fo r the regulatory language for composite line r requirements). (b) (See Statement of Regulation i n Sect ion 4.3.1 of this guidance document fo r per taining to composite liner and leachate collection systems). (c ) When approving a design tha t com plies with paragraph (a)(1) of thi s se ction, the Director of an approved Stat e s hall consider at least the following factors: ( 1) The hydrogeologic characteristics of the facility and surrounding land; (2 ) The climatic factors of the area ; and (3) The volume and physical an d chemical characteristics of the leachate. (d) (See Statement of Regulation i n S ection 4.4 .1 of this guidance document for a d iscussion of the determinati on of the relevant point of compliance.)Design Criteria

123 TABLE 1 (40 CFR 258.40; 56 FR 51022; October 9, 1991) Chemical MCL(mg/l) Arsenic 0.05 Barium 1.0 Benzene 0.005 Cadmium 0.01 Carbon tetrachloride 0.005 Chromium (hexavalent) 0.05 2,4-Dichlorophenoxy acetic acid 0.1 1,4-Dichlorobenzene 0.075 1,2-Dichloroethane 0.005 1,1-Dichloroethylene 0.007 Endrin 0.0002 Fluoride 4.0 Lindane 0.004 Lead 0.05 Mercury 0.002 Methoxychlor 0.1 Nitrate 10.0 Selenium 0.01 Silver 0.05 Toxaphene 0.005 1,1,1-Trichloroethane 0.2 Trichloroethylene 0.005 2,4,5-Trichlorophenoxy acetic acid 0.01 Vinyl Chloride 0.002 4.2.2 Applicability Th e Director of an approved State ma y approve a performance-based design for new MSWLFunits and lateral expansions o f exis ting units (see Section 4.3.2), if it meet s the requirements specified in 40 CF R 2 58.40(a)(1). A performance-based design is an alternative to the design standar d (composite liner with a leachate collectio n s ystem). Th e composite design is required in u napproved Sta

tes; however, if EPA does not promulgate procedures for State approval by October 9, 1993, the performance-base d des ign may be available through the petitio n process (see Section 4.5). 4.2.3 Technical Considerations Demonstration Requirements Forapproval of landfill designs no t c onforming to th e uniform design standard of a composite liner system and a leachat e c ollection system (40 CFR §258. 40(a)(2)), the owner or operator of the proposed MSWL F unit m ust demonstrate to the Director of a n approvedState that the design will not allow the compounds listed in Ta ble 1 of §258.40 to exc eedthe MCLs in ground water at th e rel evant point of compliance. Th e d emonstr ation should consider an assessment of l eachate quality and quantity, leachat e le akage to the subsurface, and subsurfac e transp ort to the relevant point of compliance. Thes e factors are governed by sit e hydrogeology, waste characteristics, an d climatic conditions. T he nature of the demonstration is essentially an assessment of the potential for leachat e pr oduction and leakage from the landfill t o gro undwater, and the anticipated fate an d trans portof constituents listed in Table 1 t o the proposed relevant point of compliance at the facility. Inherent in this approach is th e needto evaluate whether contaminants i n grou ndwater at the relevant point o f compliance will exceed the concentratio n v alues listed in Tab le 1. If so, then the owner or operator needs to obtain sufficient site

specific data to adequately characterize th e existing ground-Subpart D

124 wate rquality and the existing ground-wate r As suming leachate is produced, th e flow regime (e.g., flow direction, horizonta l demonstration should evaluate whethe r a nd vertical gradients, hydraulic conductivity, c onstitue nts listed in Table 1 can be expected stratigraphy, and aquifer thickness). t o be present at concentrations gre ater than the An assessment should be made of the effec t m ust address the hydrogeologic cha racteristics MSWLF facility construction will have o n of the facility and the surrounding land t o site hydrogeology. The assessment shoul d com ply with §258.40(d). The followin g fo cus on the reduced infiltration over th e sections describe the various parts of a l andfill area

and altered surface water run-off demonstration in greater detail. p atterns. Reduction of ground-water recharge and changes in surface water pattern s Leachate Characterization r esulting from landfill constru ction may affect gr ound-water

gradients in some cases an d Le achate characterization should include a n ma y result in changes in lateral flo w a ssessment and demonstration of the quantity directions. One example of a hypothetica l a nd composition of leachate anticipated at the performance-based demonstration follows. proposedfacility. Discussion of thi s I t is possible that a MSWLF unit located in an arid climatic zone would not produce leachate Esti mates of volumetric production rates o f fr omsources of water (e.g., precipitation ) le achate are important in evaluating the fat e o ther than that existing w ithin the waste at the andtransport of the constituents listed i n t ime of disposal. In such an environment, an T able 1. Leachate production rates depend on owner or operator may demonstrate tha t rainfall, run-on, run-off, evapotranspiration , s ignificant quantities of

leachate would not be w ater table eleva tion relative to the bottom of pr oduced. The demonstration should b e the landfill unit, in-place moisture content of s upported b y evaluating historic precipitation w aste, and the preventi on of liquid disposal at an devaporation data and the likelihood tha t the site. Run-on, run-off, and water tabl e the unit could be flooded as the result o f factors can be managed traditionally through hea vy rains, surface run-off, or high wate r d esign and operational controls. Th e MSWLF table s. It may be possible, throug h Criteria prohibit bulk or containerized liqui d o peratio nal controls, to avoid exposing waste dis posal. Incident precipitation an d to precipitation or infiltration of wate r evapotranspiration can be evaluated usin g through overlying materials. If significan t mode ls (e.g., HELP) or other methods o f leac hate production would not be expected , es timating site-specific leachate productio n the regulatory authority, when reviewing th e (e.g., local historical meteorologic data). demonstration, should consider th e hydrogeologic characteristics of the facility If leachate composition data that ar e andthe surrounding area, in addition to th e r epresentati ve of the proposed facility are not expectedvolume of leachate and climati c avail able, then leachate data with a similar factors. expectedcomposition should be presented

. M CLs. If such a demonstration is possible, it

assessment follows.

Landfill leachate composition is influence d by:Design Criteria

125 (1) The annual infiltration of precipitatio n I n lieu of the existence or availability of such and rate of leaching; information, conservative analytica l (2) Th e type and relative amounts o f anticipated leakage rates. materials in the waste stream; and (3) The age and the biological maturity o f th rough geomembranes differs in principl e the landfill unit, which may affect th e fro mtransport through soil liner materials

. type s of organic and inorganic acid s The dominant mode of leachate transport g enerated, oxidation/redu ction potential through liner components is flow throug h (Eh), and pH conditions. holes and penetrations of the geomembrane , An existing landfill unit in the same region , T ransport through geomembranes where tears, w ith similar waste strea

m characteristics, may p unctures, imper fections, or seam failures are p rovide information

that will allow the owner no tinvolved is dominated by molecular o r operator to ant

icipate leachate composition diffu sion. Diffusion occurs in response to a of t he proposed landfill unit. A review o f con centration gradient and is governed b y exis ting literature also may be required t o Fick's first law. Diffusion rates throug h assess anticipated leachate composition i f g eomembranes are very low in comparison to act ual data are unavailable (see U.S. EPA , hydra ulic flow rates in soil liners, includin g 19 87b). A wide range of leachat e co mpactedclays. For synthetic liners, th e concentrations are reported in the literatur e mos tsignificant factor influencing line r wit h higher concentrations of specifi c performance is penetration of the liner , con stituents typically reported for the initia l i ncluding imperfect seams or pinholes caused l eachate from laboratory or field experimental by c onstruction defects in the geomembran e test fills or test cells. These "batch" one-day (U.S. EPA, 1989). l andfill tes ts do not account for the long-term climatic and meteorological influences on a A relatively new product now being used i n f ull-scale landfil l operation. Such high initial line rsystems is the geosynthetic clay line r concentrations are not typical of full-scal e (GCL). GCLs consist of a layer of pur e opera tions (which are subject to the dilutio n bento nite clay backed by one or tw o ef fects of incidental rainfall on unuse d geotextiles. GCLs exhibit properties of both portions of the unit). soil liners and geomembranes, and hav e Assessment of Leakage Through Liners c omponent in compo site liner designs. GCLs An assessment of leakage (the volumetri c through diffusion according to their lo w release of leachate from the propose d h yd raulic conductivities (i.e., 1 x 10 cm/sec performance-based design) should be base d r eported by m anufacturers). Applications for on analytical approaches supported b y G CLs are discussed further in the sections that e mpirical data from ot

her existing operational follow. facilities of similar design, particularly those that have leak detection monitoring system s Sev eral researchers have studied the flow o f (see U.S. EPA, 1990b). fluids through imperfections in singl e assumptions may be used to estimat e

T he transport of fluids and waste constituents

and Darcian flow through soil components

.

successfully substituted for the soi l

ar e believed to transport fluids primaril y

-9Subpart D

126 ge omembrane and composite liner systems

. degradation of contaminants. The degree o f Furtherdiscussion of liner leakage rates ca n be found in Section 4.3.3 below. Fo r em pirical data and analytical methods th e reader is referred to Jayawickrama et al

. (1988), Kastman (1984), Haxo (1983), Haxo et a l. (1984), Radian (1987), Giroud an d Bonaparte (1989, Parts I and II), and Girou d et al. (1989). Leakage assessments also may b e conducted with the use o f the HELP model (U.S. EPA, 1988). Version 3.0 of the model i s under revision and will include an updated methodto assess leakage that is based o n recent research and data compiled by Giroud and Bonaparte. Leachate Migration in the Subsurface L eachate that escapes from a landfill unit may migr ate through the unsaturated zone an d eventually reach the uppermost aquifer. I n s ome instances, how ever, the water table may b e located above the base of the landfill unit, s o that only saturated flow and transport from the landfill unit need to be considered. Once l eachate reaches the water

table, contaminants m ay be transported through t he saturated zone to a point of discharge (i.e., a pumping well , a stream, a lake, etc.). The migration of leachate in the subsurfac e depends on factors such as the volume of the liquid component of the waste, the chemica l and physical properties of the leachat e c onstituents, the loading rate, climate, and the chem ical and physical properties of th e s ubsurface (saturated and unsaturated zones). A number of physical, chemical, an d bi ological processes also may influenc e mi gration. Complex interactions betwee n th ese processes may result in specifi c contaminants being transported through th e subs urface at different rates. Certai n processes result in the attenuation an d attenu ation is dependent on the time that th e c onta minant is in contact with the subsurface material, the physical and chemica l c haracteristics of the subsurface material, the dist ance that the contaminant has traveled , and the volume and characteristics of th e l eachate. Some of the ke y processes affecting l eachate migration are discussed briefly here. Th e information is based on a summary i n Travers and Sharp-Hansen (1991), who i n turn r elied largely on Aller et al. (1987) , K eely (1987) , Keely (1989), Lu et al. (1985), and U.S. EPA (1988a). Physical Processes Controlling Contaminant Transport in the Subsurface
P hysical processes that control the transport of co ntaminants in the subsurface includ e ad vection, mixing and dilution as a result o f dispersion and diffusion, mechanica l f iltration, phys ical sorption, multi-phase fluid flo w, and fracture flow. These processes, i n turn, are affected by hydrogeologi c c haracteristics, such as hydraulic conductivity and porosity, and by chemical processes. Ad vection is the process by which solut e con taminants are transported by the overal l motio n of flowing ground water. A non

r eactive solute wi ll be transported at the same r ate and in the same direc tion as ground water flo w (Freeze and Cherry, 1979). Advectiv e transport is chiefly a function of th e s ubsurface hydraulic conductivity di stribution, porosity, and hydraulic gradients. Hydrodynamic dispersion is a non-steady , ir reversible mixing process by which a c ontaminant plume spreads a s it is transported through the subsurface. Dispersion result s from the effects of twoDesign Criteria

127 components operating at the microscopi c and alter its flow direction to conform to th e level: mechanical dispersion and molecular d iffusion. Mechanical di spersion results from v ariations in pore velocities within the soil or aqu iferand may be more significant tha n mo lecular

diffusion in environments wher e the flow rates are moderate to high

. Molecular

diffusion occurs as a result o f contaminant

concentration gradients ; che micals move from high concentrations t o low concentrations. At very slow ground

water velocities, as occur in clays and silts , dif fusion can be an important transport mechanism. Mec hanical filtration removes from groun d wat er contaminants that are larger than th e pore spaces of the soil. Thus, the effects o f m echanical filtration

increase with decreasing p o re size within a medium. Filtration occurs ov er a wide range of particle sizes. Th e rete ntion of larger particles may effectivel y r educe the permeability of the soil or aquifer. Ph ysical sorption is a function of Van de r Wa als forces, and the hydrodynamic an d electrokinetic properties of soil particles

. S orption is the process by which contaminants are r emoved from solution in ground wate r and adh ere or cling to a solid surface. Th e distribution of a contaminant between th e solu tion and the solid phase is calle d partitioning. Multiphase fluid flow occurs because man y s olvents and oils are

highly insoluble in water and may migrate in the subsurface as a sep arate liquid phase. If the viscosity an d d ensity of a fluid differ from th at of water, the f luid may flow at a different rate and direction than the ground water. If the fluid is mor e den se than water it may reach the bottom o f the aquifer (top of an aquitard) shape and slope of the aquitard surface. Hydraulic conductivity is a measure of th e abili ty of geologic media to transmit fluid s ( USGS, 1987). It is a f

unction of the size and arrangement of water-transmitting opening s (p ores and fractures) in the media and of th e c haracteristics of the fluids (d ensity, viscosity, etc.). Spatial variations in hydrauli c c onductivity are referred to as heterogeneities. A variation in hydrau lic conductivity with the dire ction of measurement is referred to a s anisotropy. Va riable hydraulic conductivity of th e geologic formation may cause ground-wate r f low velocities to vary spatially. Variations in the rate of advection may result in non

uni formplume spreading. The changes i n aquifer properties that lead to this variability in hydraulic conductivity may be three

dimen sional. If the geologic medium i s relatively homogeneous, it may b e appropriate, in some instances, to assume that the aquifer properties also are homogeneous. S econdary porosity in rock may be caused by the d issolution of rock or by regiona l f racturing; in soils, secondary p orosity may be ca usedby desiccation cracks or fissures

. Fr actures or macropores respond quickly t o rainfall events and other fluid inputs and can transmit water rapidly along unexpecte d pat hways. Secondary porosity can result i n l ocalized high concentrations of contaminants at significant distances from the facility. The rel ative importance of secondary porosity t o hydraulic conductivity of the subsurfac e dep ends on the ratio of fracture hydrauli c conductivity to intergranular hydrauli c condu ctivity (Kincaid et al., 1984a). Fo r s cenario s in which fracture flow is dominant, the relationshipsSubpart D

128 used to describe porous flow (Darcy's Law ) gen erally occurs at a relatively rapid rat e do not apply. compared to precipitation reactions. Chemical Processes Controlling T he dominant mec hanism of organic sorption Contaminant Transport in the Subsurface is the hydrophobic attraction between a Chem ical processes that are important i n i n some aquifers. Th e organic carbon content controlling subsurface transport includ e of the porous medium, and the solubility o f precipitation/dissolution, chemical sorption , the contaminant, are im portant factors for this r edox reactions, hydrolysis, io n exchange, and type of sorption. com plexation. In general, these processes , exc ept for hydrolysis, are reversible. Th e There is a direct relationship between th e reversible processes tend to retard transport , quant ity of a substance sorbed on a particl e b ut do not permanently remove a contaminant surface and the quantity of the substanc e fr omthe system. Sorption and precipitatio n sus pendedin solution. Predictions about th e are generally the dominant mechanism s sorption of contaminants often make use o f re tarding contaminant transport in th e s orption isotherms, which relate the amount of saturated zone. con taminant in solution to the amoun t P recipitation/dissolution reactions can control contaminants, these isotherms are usuall y co ntaminant

concentration levels. Th e assume dto be linear and the reaction i s solu bility of a solid controls the equilibriu m assumedto be instantaneous and reversible

. stat e of a chemical. When the solubl e The linear equilibrium approach to sorptio n concentration of a contaminant in leachate is may not be adequate for all situations. hi gher than that of the equilibrium state , precipitation occurs. When the solubl e Oxi dation and reduction (redox) reaction s concentration is lower than the equilibriu m invol ve the transfer of electrons and occu r v alue, the contaminant ex ists in solution. The whe n the redox potential in leachate i s p recipitat ion of a dissolved substance may be differ ent from that of the soil or aquife r i nitiated by changes in pressure, temperature, environment. Redox reactions are important p H, concentration, or red ox potential (Aller et processes for inorganic compounds an d al. , 1987). Precipitation of contaminants i n metallic elements. Together with pH, redo x the pore space of an aquifer can decreas e rea ctions affect the solubility, complexin g a quifer porosity. Precipitation and dissolution cap acity, and sorptive behavior o f rea ctions are especially important processe s c onstituents, and thus control the presence and for trace metal migration in soils. mo bility of many substances in water

. Ch emical adsorption/desorptionis the mos t proportion of redox reactions that occur i n common mechanism affecting contaminan t groundwater. The redox state of an aquifer, migr ation in soils. Solutes become attache d an dthe identity and quantity of redox-activ e to the solid phase by means of adsorption

. reactants, are difficult to determine. Like precipitation/dissolution , a ds orption/desorption is a reversible process. However, adsorption/desorption c hemical and natural organic matter that exists

adsorbed to the solids. For organi c

Micr oorganisms are responsible for a larg eDesign Criteria

129 Hyd rolysis is the chemical breakdown o f Therefore, these processes are usuall y carbon bonds in organic substances by water grouped together as one mechanism. a nd it s ionic species H and OH . Hydrolysis +
- is de pendent on pH and Eh and is mos t Biological Processes Controlling s ignifi cant at high temperatures, low pH, and Contaminant Transport in the Subsurface l ow redox potential. For many biodegradable c ontaminants, hy drolysis is slow compared to Bio degradation of contaminants may resul t biodegradation. f rom the enzyme-catalyzed transformation of Ion exchange originates primarily fro m Con taminants can be degraded to harmles s exch ange sites on layered silicate clays an d byproducts or to more mobile and/or toxi c o rganic matter that have a p ermanent negative prod ucts through one or more of severa l cha rge. Cation exchange balances negativ e biological processes. Biodegradation of a charges in order to maintain neutrality. Th e c o mpound depends on environmental factors c apacity of

soils to exchange cations is called such as redox potential, dissolved oxyge n the cation exchange capacity (CEC). CEC is concentration, pH, temperature, presence o f affect edby the type and quantity of cla y o ther compounds and nutrients, salinity, depth m ineral present, the

amount of organic matter below land surface, competition amon g p resent, and the pH of the soil. Major cations di fferenttypes of organisms, an d i n leachate (Ca , Mg, K, Na) usually dominate c oncentrations of compounds and organisms. the CEC sites, res ulting in little attenuation in T he transformations that occur in a subsurface soils of trace metals in the leachate. sys temare difficult to predict because of th e A s maller ion exchange effect for anions i s rea ctions that may occur. Quantitativ e ass ociatedwith hydrous oxides. Soil s p redictions of the fate of biologically reactive typi cally have more negatively charged cla y substances are subject to a high degree o f particles than positively charged hydrou s u ncertainty, in part , because little information oxides. Therefore, the transport of cations is is available on biodegradation rates in soi l attenuated more than the transport of anions. sy stems or ground water. First-order deca y C omplexation

involves reactions of

metal ions w ith inorganic anions or organic ligands. The Th e operation of Subtitle D facilities ca n metal a nd the ligand bind together to form a introduce bacteria and viruses into th e new soluble species called a complex

. s ubsurface. The fate and transport of bacteria Co mplexation can either increase th e and viruses in the subsurface is an importan t conce ntration of a constituent in solution b y con sideration in the evaluation of the effect s f orming solubl e complex ions or decrease the of MSWLF units on human health and th e concentration by forming a soluble io n environment. A large number of biological , comp lex with a solid. It is often difficult t o c hemical, and physical processes are known to di stinguishamong sorption, solid-liqui d in fluence virus and bacterial survival an d complexation, and ion exchange. tr ansport in the subsurface. Unfortunately , organic compounds by microbes

.

complexity of the chemical and biologica l

constants are often used instead.

know ledge of the processes and the available data are insufficient to develop models tha t canSubpart D

130 simulate a wide variety of site-specifi c evaluatedby qualified investigators, shoul d conditions. adequately simulate the significant processes Leachate Migration Models consistent with the complexity of the stud y After reviewing the hydrogeologi c of the study. chara cteristics of the site, the nature of line r lea kage, and the leachate characteristics, i t First, an evaluation of the need for modeling may b e appropriate to use a mathematica l s hould be made (Figure 4-1). When selecting mo del to simulate the expected fate an d a model to evaluate the potential for soil and transport of the constituents listed in Table 1 g round- water contamination (Boutwell et al., to t he relevant point of compliance. Solut e 19 86), three basic determinations must b e transport and ground-water modeling effort s m ade (Figure 4-2). Not all studies require the shou ldbe conducted by a qualified ground

- use of a mathematical model. This decisio n water scientist (see Section 5.5). It i s s hould be made at the beginning of the study, nece ssary to consider several factors whe n since modeling may require a substantia l sele cting and applying a model to a site

. amoun tof resources and effort. Next, th e Tra vers and Sharp-Hansen (1991) provide a level of model complexity required for a thoro ugh review of these issues. The tex t spec ific study should be determined (Figur e p rovided below i s a summary of their review. 4-3). Boutwell et al. (1986) classify model s Overview of the Modeling Process ( complex/numerical) models. A flowchart for A number of factors can influence leachat e r equired is shown in Figure 4-3. Finally, the migration from MSWLF units. Thes e model capabilities necessary to represent a incl ude, but are not limited to, climati c pa rticular system should be considere d effects, the hydrogeologic setting, and th e ( Figure 4-4 ). Several models may be equally n ature o f the disposed waste. Each facility is s uitable for a par ticular study. In some cases, diff erent, and no one generic model will b e it may be necessary to link or couple two o r app ropriate in all situations. To develop a m ore computer models to accur ately represent mode l for a site, the modeling needs and th e the pro cesses at the site. In the section that objectives of the study should be determined foll ows, specific issues that should b e f irst. Next, it will b e necessary to collect data cons ideredwhen developing a scenario an d to characterize the hydrological, geological , selecting a model are described. chem ical, and biological conditions of th e syste m. These data are used to assist in th e Models are a simplified representation of the de velopment

of a conceptual model of th e real system, and as such, cannot full y system, including spatial and tempora l re produce or predict all site characteristics

. c haracteris tics and boundary conditions. The Err ors are introduced as a result of: 1 ) conceptual model and data are then used t o s implifyingassumptions; 2) a lack of data; 3) select a mathematical model that accuratel y unc ertainty in existing data; 4) a poo r represents the conceptual model. The model u nderstanding of the processes influencing the selected should have been tested an d fate and transport of contaminants; and present in the actual system, and should b e

area, amount of available data, and objectives

as Level I (simple/analytical) and Level I I det ermining the level of model complexity131 

### Figure 4-1 Three Basic Decisions in Model Selection

(Boutwell et. al., 1986)132 

### Figure 4-2 Flow Chart to Determine if Modeling is Required

(Boutwell et. al., 1986)133 

### Figure 4-3 Flow Chart to Determine the Level of Modeling Required for

Soil and Groundwater Systems (Boutwell et. al., 1986)134 

### Figure 4-4 Flow Chart for Required Model Capabilities for Soil and Groundwater Systems (Boutwell et. al., 1986)Design Criteria

135 5) limitations of the model itself. Therefore, Model Selection mo del results should be interpreted a s est imates of ground-water flow an d con taminant

transport. Bond and Hwan g (1988) recommend that models be used fo r comparing various scenarios, since al l sc enarios would be subject to the sam e limitations and simplifications. The quality of model results can depend to a l arge extent on the experience and judgement o f themodeler, and on the quality of the data u se d to develop model input. The process of appl ying the model may highlight dat a deficiencies that may require additional dat a col lection. The model results should b e c alibrated to obtain the best fi t to the observed data

. The accuracy of the results obtaine d from modeling efforts should then b e validated. Model validation, which is th e comparison of model results with e xper imental data or environmental data, is a crit ical aspect of model application, and i s particularly important for site-specifi c evaluations. Sev eral recent reports present detaile d discussions of the issues associated with model selection, application, and validation

. Do nigian and Rao (1990) address each o f th ese issues, and present several options fo r d eveloping a framework for model validation. EPA's Exposure Assessment Group ha s developedsuggested recommendations an d guidance on model validation (Versar Inc. , 1987). A recent report by the Nationa l R es earch Council (1990) discusses the issues rel atedto model application and validation , a nd provides rec ommendations for the proper use of ground-water models. Weaver et al

. l imited data available in most field situations ( 19 89) discuss options for selection and field validation of mathematical models. Gr ound-water flow and solute transport mod els range from simple, analytica l calculations to sophisticated compute r p rograms that use numerical solut ions to solve mathematical equations describing flow an d transport. A sophisticated model may no t y ield an exact estimate of water quality at the r elevant point of compliance f or a given set of sit e conditions, but it may allow an estimat e of the effects of complex physical an d ch emical processes. Depending on th e com plexity of site conditions and th e appropriateness of the simplifyin g a ss umptions, a fairly sophisticated numerical m od el may provide useful estimates of water quality at the relevant point of compliance. The following considerations should b e addressed when selecting a model. Analytical Versus Numerical Models Mat hematical models use either analytical , semi-analytical, or numerical solutions fo r ground-water

flow and transport equations

. Eac h technique has advantages an d dis advantages. Analytical solutions ar e c omputationally more efficient tha n numerical simulations and are more conducive t o un certainty analysis (i.e., Monte Carl o te chniques). Typically, input data fo r an alytical models are simple and do no t r equire detailed familiarity with the computer mod el or extensive modeling experience

. An alytical solutions are typically used whe n d ata necessary for characterization of the site are sparse and simplifying assumptions ar e appropriate (Javandel et al., 1984). Th e

m ay not justify the use of a det ailed numerical model; in some cases, results from simpl e analytical models may be appropriat eSubpart D

136 (Huyakorn et al., 1986). Analytical model s " screening level" model to define the range of require simplifying assumptions about th e p ossible values, an d to use a numerical model system. Therefore, complex interaction s when there are sufficient data. i nvolving several fate and transport processes can not be addressed in detail. Analytica l A highly complex hydrogeologic syste m m odels gen erally require a limited number of cann ot be accurately represented with a param eters that are often assumed to b e simp le analytical model. Heterogeneous o r const ant in space and time (van der Heijd e anisotropic aquifer properties, multipl e and Beljin, 1988). aq uifers, and complicated boundary S emi-analytical mode ls approximate complex m o dels. In addition, sophisticated numerical an alytical solutions using numerica l mo dels are available that can simulat e t echniques (van

der Heijde and Beljin, 1988). p rocesses such as fracture flow . Because each Semi-analytical methods allow for mor e site is unique, the modeler should determin e c omplex site conditions than those that can be w hich conditio ns and processes are important simu latedwith a purely analytical solution

. at a specific site, and then select a suitabl e S emi-analytical solution methods ca n consider model. multiple sources or recharging an d d ischarging wells. However, they still require Spatial Characteristics of the System si mplifying assumptions about th e dim ensionality and homogeneity of th e Al though actual landfill units an d system. h ydrogeologic systems are three-dimensional, Num erical models are able to evaluate mor e dimensions simulated in a mathematica l c omplex s ite conditions than either analytical mode l to one or two. Two- and three

o r semi-analytical models . Numerical models di mensional models are generally mor e prov ide the user with a large amount o f c omplexand computationally expensive than fl exibility; irregular boundaries and spatia l one-dimensional models, and therefor e and temporal variations in the system can b e require more data. In some instances, a oneco nsidered. Numerical models requir e d imensi onal model may adequately represent significantly more data than analytica l the system; the available data m ay not warrant models, and are typically mor e the use of a multi-dimensional model

. computationally intensive. Use of a H owever, modelin g a truly three-dimensional nu merical model requires an experience d system using a two-dimensional model ma y mod eler, and can involve a larger amount o f produce results without adequate spatia l computer time than simulations using a n detail. The choice of the number o f analytical or semi-analytical method. dim ensions in the model should be made fo r To select an appropriate model, th e site and the availability of data. co mplexity of the site hydrology and th e av ailability of data should be considered. I f Steady-State Versus Transient Models dataare insufficient, a highly sophisticate d and c omplex model should not be used. I n Mo dels can simulate either steady-state o r some s ituations, it is beneficial to use a n analytical or semi-analytical model as a cond itions can be simulated using numerica l

itis often desirable to reduce the number o f

a specific site, based on the complexity of the

transient flow conditions. It may beDesign Criteria

137 appropriate to assume that so me ground-water On e of the most significant boundary flow systems have reached approximat e "steady-state" conditions, which implies tha t the system has reached equilibrium and n o significant

changes are occurring over time

. Th e assumption of steady-state condition s generally simplifies the mathematica l e quations used to describe flow p rocesses, and reduces the amount of input data required.
H owever, assuming s teady-state conditions in a sys tem that exhibits transient behavior may prod uce inaccurate results. For example , c limati c variables, such as precipitation, vary ove rtime and may have strong seasona l c omponents. In suc h settings, the assumption of constant recharge of the ground-wate r system would be incorrect. Steady-stat e models also may not be appropriate fo r evaluating the transport of chemicals whic h s orb or transform significantly (Mulkey et al., 1 989) . The choice of simulating steady-state o r transient condi tions should be based on the degree of temporal variability in the system. Boundary and Initial Conditions The solution of differential equation s describing flow and transport processe s req uires that initial and boundary condition s be specified. The initial conditions describ e the c onditions present in the system at th e b eginning of the simulation. I n many groundwat er flow and transport models, thes e condi tions are related to the initial hydrauli c co nditions in the aquifer and the initia l co ncentration of contaminants. Boundary c onditions define the conditions pre sent on the borders of the system, which may be steadystat e or temporally variable. The initial an d b oundary conditions chosen to represent a site can s ignificantly affect the results of th e simulation. cond itions in solute transport models is th e int roduction of a contaminant to the system

. A source of ground-water contaminatio n shouldbe described in terms of its spatial , c hemical, and physical characteristics, and its t emporal behavior. Spatially, a s ource may be cl assifiedas a point source, line source, a di stributedsource of limited areal or three

dimensional extent, or as a non-point sourc e of unl imited extent (van der Hjeide et al. , 1 988). Typically, temporal descript ions of the sou rce term boundary conditions for model s w ith analytical solutions are const ant, constant pu lse, and/or exponential decay (Mulkey e t a l., 1989). Numerical models typi cally handle a much wider range of source boundary condi tions, allowing for a wide range o f contaminant loading scenarios. Homogeneous Versus Heterogeneou s Aquifer/Soil Properties The extent of the spatial variability of th e pr operties of each aquifer will significantl y a f fect the selection of a mathematical model. Ma ny models assume uniform aquife r properties, which simplifies the governin g equations and improves computationa l efficiency. For example, a constant value of hydraulic conductivity may be assumed at ev ery point in the aquifer. However, thi s as sumption may ignore the heterogeneity i n the hydrogeologic system. Bond and Hwang (1988) present guidelines for determinin g whether the assumption of uniform aquife r pro perties is justified at a particular site

. T hey state that the error associated with using an average value versus a spatial distribution is site-specific and extremely difficult t o determine. When site-specific data are limited, it i s com mon to assume homogeneous an dSubpart D

138 isotropic aquifer properties, and to develop a U ncertainty in model predictions results from "r easonable worst-case" scenario fo r the inability to characterize a site in terms of contaminant

migration in the subsurface

. the boundary conditions or the key parameters H owe ver, as Auerbach (1984) points out, the des cribing the significant flow and transport ass umption of homogeneous and isotropi c p rocesses (Nati onal Research Council, 1990). a quifers ofte n will not provide a "worst-case" T he applica tion of a mathematical model to a scenario. For example, a continuous zone of s ite typically requires a large amount of data. h igher hydr aulic conductivity in the direction I nexperienced mode lers may attempt to apply of g round-water flow can result in muc h a model with insufficient data and, as a result, hi gher rates of contaminant movement tha n produce model results that are inconclusive. woul dbe predicted in a completel y homo geneous aquifer. To develop a tru e To obtain accurate model results, it i s "worst-case" model, information on th e essent ial to use data that are appropriate fo r probable heterogeneity and anisotropy of the the particular site being modeled. Models that site should be collected. i nclude ge neric parameters, based on average
T h e number of aquifers in the hydrogeologic i nitial guidance and general i nformation about system also will affect the selection of a th e behavior of a system, but it i s mathematical model. Some systems includ e i nappropriate to apply generic parameters to a o nly a single unconfined or confined aquifer, s p ecific hydrogeologic system. An excellent wh ich is hydraulically isolated from th e summa ry of the data required to mode l sur rounding layers. Some mathematica l s aturate d and unsaturated flow, surface water m odels, and in particular t

hose with analytical flow, and solute transport is presented i n s olut ions, can simulate only single layers. In Mer cer et al. (1983). This report provide s ot her cases, the upper aquifer may b e def initions and possible ranges of values fo r hydraulically connected to underlyin g sou rce terms, dependent variables, boundary aq uifers. The MSWLF Criteria specify tha t conditions, and initial conditions. M CLs not be exceeded at the rel evant point of com pliance within the uppermost aquifer

. Summary of Available Models The u ppermost aquifer includes not only th e a quifer that is nearest the ground surface, but Several detailed reviews of ground-wate r also all lower aquifers that are hydraulicall y mod els are available in the literature. A c onnected to the uppermost aquifer within the number of ground-water models, includin g vicinity of the facility. s aturated flow, solute transport, h eat transport, Availability of Data are su mmarized in van der Heijde et al

. Although computer models can be used t o (19 88) provides detailed descriptions of 6 4 make predictions about leachate generatio n ground-water flow and solute transport an dmigration, these predictions are highl y mo dels that were selected for use i n dependent on the quantity and quality of th e dete rmining wellhead protection areas. A avail able data. One of the most commo n review of ground-water flow and limitations to modeling is insufficient data

. v alues for similar sites, can be used to provide

frac ture flow, and multiphase flow models , ( 1988). A report by van der Heijd e and BeljinDesign Criteria

139 trans portmodels for the unsaturated zone i s contaminant source terms and the releases of p resented in Oster (1 982). A large number of contaminants to the subsurface. Flow an d gro und-water

flow and transport models ar e tra nsport models simulate the transport o f summarizedby Bond and Hwang (1988)

. contaminants released from the source to the Fin ally, Travers and Sharp-Hansen (1991 ) unsaturated and saturated zones

. summarize models that may be applicable t o Geochemical models are available tha t p roblems of leachate generation and migration con sider chemical processes that may b e from MSWLF units. (See Reference s acti ve in the subsurface such as adsorption , supplied in Section 4.6.) precipitation, oxidation/reduction, aqueou s Table 4-1 (adapted from Travers and Sharp

Hansen (1991)) provides information o n C omplex flow models have been developed to select leachate generation models. Tables 4- simulate the effects of nearby pumping an d 1 a, b, and c list some of the available models d ischarging wells, f racture flow, conduit flow that can be used to predict contaminan t i n karst terrane, and multiphase flo w for fluids tra nsport. The factors used to select thes e that are less dense or more dense than water. models include availability, documentation , However, the use of the more comple x uniqueness, and the size of the use r models requires additional data based on a c ommunity. These models are categorized by thorough investigation of the subsurfac e the t echniques used to solve flow an d c haracteristic s at a site as well as well-trained transport equations. Table 4-1a list s users to apply the model correctly. analytical and semi-analytical models, an d Tables 4-1b and 4-1c list numerical model s Most of the ground-water flow and solut e that are solved by the finite-difference and the transp ort models are deterministic. However, finite-element method, respectively. the us e of stochastic models, which allow for Th e types of models that are available fo r v ariability in systems, is increasing. A few of application to the evaluation of MSWL F the models include a Monte Carlo capability de signs include leachate generation model s for addressing the uncertainty inherent in the and saturated and unsaturated zone flow an d input parameters. transpor t models. The level of sophistication of each of these types of models is based o n The EPA Multimedia Exposure the complexity of the processes bein g Assessment Model (MULTIMED) mode led. The majority of the model s consider flow and transport based o n EPA has developed a modeling package t o advection dispersion equations. Mor e meet the needs of a large percentage o f complex models consider physical an d MSWLF unit owners and operators who will chemical transformation processes, fractur e r equire f ate and transport modeling as part of flow, and multiphase fluid flow. the performan ce-based design demonstration. Leachate generation models predict th e Assessment Model (MULTIMED), i s q uantity and characteristics of leachate that is inten dedfor use at sites where certai n r eleased f rom the bottom of a landfill. These si mplifying assumptions can be made

. models are used to estimate MULTIMED can be used in speciation, and kinetics.

cha racterization of spatial and tempora l

Th is model, the Multimedia Exposur e

### Table 4-1. Models for Application to Leachate Generation Problems (adapted from Travers and Sharp-Hansen, 1991)

### Table 4-1a. Analytical and Semi-Analytical Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991)

### Table 4-1a. Analytical and Semi-Analytical Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991) (continued)

### Table 4-1b. Finite-Difference Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991)

### Table 4-1b. Finite-Difference Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991) (continued)

### Table 4-1c. Finite-Element Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991)

### Table 4-1c. Finite-Element Models for Application to Leachate Migration Problems (adapted from Travers and Sharp-Hansen, 1991) (continued)Design Criteria

147 co njunction with a separate leachate sourc e beca use the effects of lateral or vertica l m odel, such as HELP (Schroeder et al ., 1984). d ispers ion may significantly affect the model Output from HELP is then used i n results. MULTIMED to demonstrate that either a lan dfill design or the specific hydrogeologi c T herefore, reducing the dimensions to one in conditions present at a site will preven t this module would prod uce inaccurate results. co ntaminant

concentrations in ground wate r The saturated zone transport module als o from exceeding the concentrations listed i n c onsiders li near adsorption, first-order decay, T able 1 of §258.40. (Re fer to pp. 4-53 and 6- anddilution as a result of ground-wate r 8 for further discussion of HELP.) A rec harge. In addition, MULTIMED has th e des cription of MULTIMED follows with capability to assess the impact of uncertainty gu idance for determining if its use i s in the model inputs on the model outpu t appropriate for a given site. (c ontaminant concentration at a specifie d [ NOTE: Version 3.0 of the HELP model will technique. be available during the fall of 1993. T o obtain a copy, call EPA's Office of Research The simplifying assumptions required t o an dDevelopment (ORD) in Cincinnati at obta in the analytical solutions limit th e (513) 569-7871.] co mplexity of the systems that can b e Overview of the Model n ot account for site- specific spatial variability T he MULTIMED model consists of modules la nddisposal facility, site-specific boundary that estimate contaminant releases to air, soil, c onditi ons, or multiple aquifers and pumping grou ndwater, or surface water. Genera l wells. Nor can MULTIMED simulat e i nform ation about the model and its theory is processes, such as flow in fractures an d provided in Salhotra et al. (1990)

. c hemical reactions between contam inants, that Additionally, information about th e may have a significant effect on th e application of

MULTIMED to MSWLF units conce ntration of contaminants at a site. I n ( devel oped by Sharp-Hansen et al. [1990]) is m ore complex systems, it may be be neficial to s ummarized here. In MULTIMED, a steady- u se MULTIMED as a "screening le vel" model state, one-dimensional, semi-analytica l t o allow the user to obtain an understanding of module simulates flow in the unsaturate d the system. A more complex model coul d z one. The output from this module, which is then be used if there are sufficient data. w ater saturation as a function of depth, is used as i nput to the unsaturated zone transport Application of MULTIMED to MSWLF modu le. The latter simulates transient, one

- Units di mensional (vertical) transport in th e unsaturatedzone and includes the effects o f Procedures have been developed for th e dispersion, linear adsorption, and first-orde r appl ication of MULTIMED to the design o f decay

. Output from the unsaturated zon e M SWLF units . They are explained in Sharpm odules is used as input to the semi-analytical Hansen et al. (1990) and are briefl y sa turatedzone transport module. The latte r summarized here. The procedures are: considers three-dimensional flow point), using the Monte Carlo simulatio n

e valuated with MULTIMED. The model does ( e.g., aquifer heterogeneities), the shape of theSubpart D

148 ! C ollect site-specifichydrogeologic data, 4 -2. A "no" answer to any of the questions in i n cluding amount of leachate generated Table 4-2 may indicate that MULTIMED i s (see Section 4.3.3); not the most appropriate model to use. A s

! Ide ntify the contaminant(s) to b e an dsemi-analytical solution techniques t o simulated and the point of compliance; so lve the mathematical equations describin g

! P ropose

a landfill design and determine the corresponding infiltration rate; then

! Ru n MULTIMED and calculate th e dilution attenuation factor (DAF) (i.e. , the factor by which the concentration is exp ectedto decrease between th e lan dfill unit and the point o f compliance); and

! Multiply the initial contaminan t c onc entration by the DAF and compare the resultin g concentration to the MCLs to determine if the design will meet the standard. A t this time, only contaminant transport in the uns aturatedand/or saturated zones can b e modeled, because the other options (i.e. , sur face water, air) have not yet bee n tho roughly tested. In addition, only steady

state transport simulations are allowed. N o decay of the contaminant source term i s permitted; the concentration of contaminants entering the aquifer system is assumed to b e constant over time. The receptor (e.g., a drinking water well) is located directl y d owngradient of the facili ty and intercepts the contaminant plume; also, the contaminan t con centration is calculated at the top of th e aquifer. The user should bear in mind tha t MUL TIMED may not be an appropriat e m odel for some sites. Some of the issues that s hould be considered before modeling efforts proceed are summarized in Table s tated ab ove, MULTIMED utilizes analytical

flo w and transport. As a result, th e re presentation of a system simulated by th e model is simple, and little or no spatial o r temporal variability is allowed for th e param eters in the system. Thus, a highl y complex hydrogeologic system cannot b e accurately represented with MULTIMED. The spatial characteristics assumed i n MU LTIMED should be considered whe n applying MULTIMED to a site. Th e assumption of vertical, one-dimensiona l unsaturatedflow may be valid for facilitie s that receive uniform areal recharge

. However, this assumption may not be vali d for facilities where surface soils (covers o r dail y backfill) or surface slopes result in a n incr ease of run-off in certain areas of th e facility, and ponding of precipitation i n oth ers. In addition, the simulation of one

dimensional, horizontal flow in the saturated zone requires several simplifyin g a ssumptions. The saturated zone is treated as a single, horizontal aquifer with unifor m p roperties (e.g. , hydraulic conductivity). The e ffects of pumping or discharging we lls on the ground-water

flow system cannot b e addressed with the MULTIMED model. T he MULTIMED model assumes steady-state flow in all applications. Some ground-water flow systems are in an approximate "steady

s tate ," in which the amount of water entering the fl ow system equals the amount of wate r le aving the system. However, assumin g ste ady-state conditions in a system tha t exhibits transient behavior may produc e inaccurate results.Design Criteria

149 TABLE 4-2 ISSUES TO BE CONSIDERED BEFORE APPLYING MULTIMED (from Sharp-Hansen et al., 1990)

________________________________ Objectives of the Study

! Is a "screening level" approach appropriate?
! Is modeling a "worst-case scenario" acceptable? Significant Processes Affecting Contaminant Transport

! Does MULTIMED simulate all the significant processes occurring at the site?
! Is the contaminant soluble in water and of the same density as water? Accuracy and Availability of the Data

! Have sufficient data been collected to obtain reliable results?
! What is the level of uncertainty associated with the data?
! Would a Monte Carlo simulation be useful? If so, are the cumulative probability distributions for the parameters with uncertain values known? Complexity of the Hydrogeologic System

! Are the hydrogeologic properties of the system uniform?
! Is the flow in the aquifer uniform and steady?
! Is the site geometry regular?
! Does the source boundary condition require a transient or steady-state solution? MUL TIMED may be run in either a determ inistic or a Monte Carlo mode. Th e Mo nte Carlo method provides a means o f estimating the uncertainty in the results of a m odel, if the uncertainty of the input variables is known or can be estimated. However, i t may be difficult to determine the cumulative p robability distributi on for a given parameter. A ssuming a parameter probabi lity distribution when the distribution is unknown does no t help reduce uncertainty. Furthermore, t o obtain a valid estimate of the uncertainty i n the ou tput, the model must be run numerou s t imes (typically several hundre d times), which c an be time-consuming. These issues should be considered before utilizing the Mont e Carlo technique.

4.3 COMPOSITE LINER AND LEACHATE COLLECTION SYSTEM 40 CFR §258.40 4.3.1 Statement of Regulation (a) New MSWLF units and latera l expansions shall be constructed: (1) See Statement of Regulation i n Sect ion 4.2.1 of this guidance document fo r performance-based design requirements. ( 2) With a co mposite liner, as defined in par agraph (b) of this section and a le achate collection system that is designe d a nd constructed to mai ntain less than a 30- cm depth of leachate over the liner, (b) For purposes of this section , composite linermeans a system consistin g of two components; the upper componen t mustconsist of a minimum 30-mil flexibleSubpart D

150 memb rane liner (FML), and the lowe r Standard Composite Liner Systems componentmust consist of at least a two foo tlayer of compacted soil with a h ydraulic conduct

ivity of no more than 1 x 10 cm/sec. FML componen ts consisting of -7 h igh de nsity polyethylene (HDPE) shall be a t least 60-mil thick . The FML component must be installed in direct and unifor m con tactwith the compacted soi l component. 4.3.2 Applicability New MSWLF units and expansions o f existing MSWLF units in States withou t approved programs must be constructed with a composite liner and a leachate collectio n sys tem(LCS) that is designed to maintain a depth of leachate less than 30 cm (12 in. ) above the liner. A co mposite liner consists of a flexible me mbrane liner (FML) installed on t op of, and in direct and uni form contact with, t wo feet of compacted soil. The FML must be at least 30-mil thick unless the FML is made of HDPE, which must be 60-mil thick. Th e c ompac ted soil liner must be at least two feet thi ck and must have a hydraulic conductivity of no more than 1 x 10 cm/sec. -7
Owners and operators of MSWLF unit s l ocated in approved States have the option of proposing a performance-based desig n providedthat certain criteria can be met (se e Section 4.2.2). 4.3.3 Technical Considerations This section provides information on th e com ponents of composite liner system s including soils, geomembranes, and leachat e collection systems. The composite liner system is an effectiv e hydraulic barrier because it combines th e com plementary properties of two differen t m aterials into one system: 1) compacted soil with a low hydraulic conductivity; and 2) a F ML (FMLs are also referred to a s g eomembranes). Geomembranes ma y contain defects including tears, improperly bonde d sea ms, and pinholes. In the absence of a n underlying low-permeability soil liner, flo w through a defect in a geomembrane i s essentially unrestrained. The presence of a l ow-permeability soil liner beneath a defect in the geomembrane reduces leakage by limiting the flow rate through the defect. Flow through the soil component of the liner is cont rolled by the size of the defect in th e g eomembrane, the available air s pace between the two liners into which leachate can flow , the hydraulic conductivity of the soi l comp onent, and the hydraulic head. Flui d flow through soil liners is calculated b y Da rcy's Law, where discharge (Q) i s proportional to the head loss through the soil (dh/ dl) for a given cross-sectional flow are a (A) and hydraulic conductivity (K) where: Q = KA(dh/dl) Leakage through a geomembrane withou t d efects is controlled byFick's first law, which describes the process of liquid diffusio n through the membrane liner. The diffusio n p rocess is similar to flow gov erned by Darcy's law fo r soil liners except that diffusion i s driven by concentration gradients and not by hydra ulic head. Although diffusion rates i n geomembranes are several orders o f mag nitude lower than comparable hydrauli c flow rates in low-permeability soil liners , co nstruction of a completely impermeabl e geomembrane isDesign Criteria

151 di fficult. The factor that most strongl y Soil Liner influences geomembrane performance is th e p resence of imperfections such as improperly The following subsections discuss soil line r bon dedseams, punctures and pinholes. A construction practices including thicknes s detailed discussion of leakage throug h r equirements, lift placement, bonding of lifts, geom embranes and composite liners can b e test methods, prerequisite soil properties , foundin Giroud and Bonaparte (1989 (Part I qu ality control, and quality assuranc e a nd Part II)). A geomembrane installed with activities. excel lent control over defects may yield th e e qu ivalent of a one-centimeter-diameter hole Thickness per acre of liner installed (Giroud an d Bon aparte, 1989 (Part I and Part II)). If th e Two feet of soil is generally considered th e geo membrane were to be placed over sand , m inimum thickness needed to obtain adequate this size imperfection under one foot o f c ompaction to meet the hydraulic co nductivity c o nstant hydraulic head could be expected to re quirement. This thickness is considere d acco unt for as much as 3,300 gal/acre/da y necessary to minimize the number of crack s ( 31,000 liters/hectare/

day) of leakage. Based orimperfections through the entire line r u pon measurements of

actual leakage through thickness that coul d allow leachate migration. liners at facilities that have been built unde r Bothlateral and vertical imperfections ma y r igorous contro l, Bonaparte and Gross (1990) exis tin a compacted soil. The two-foo t have estimated an actual leakage rate, unde r m inimum thickness is believed to be sufficient one foot of constant head, of 20 0 to i nhibit hydraulic short-circuiting of th e l iters/hectare/day or about

21 gallons/acre/day entire layer. for landfill units. The uniformity of the contact between th e geo membrane and the soil liner is extremel y S oil liners should be c onstructed in a series of imp ortantin controlling the effective flo w c ompacted lifts. Determination of appropriate area of leachate through t

he soil liner. Porous lift thickness is dependent on the soi l mat erial, such as drainage sand, filter fabric , characteristics, compaction equipment , or ot her geofabric, should not be place d firmness of the foundation materials, and the be tween the geomembrane and the lo w ant icipatedcompactive effort needed t o p ermeabil ity soil liner. Porous materials will ach ieve the required soil hydrauli c create a layer of higher hydrauli c co nductivity. Soil liner lifts should be thi n c on ductivity, which will increase the amount e nough to allow adequate compactiv e effort to of leakage below an imperfection in th e reach t he lower portions of the lift. Thinne r g eomembrane. C onstruction practices during li fts also provide greater assurance that the installation of the soil and th e sufficient compaction can be achieved t o geom embrane affect the uniformity of th e p rovide good, homogeneous bonding between ge omembrane/soil interface, and strongl y s ubsequent lifts . Adequate compaction of lift in fluence the performance of the composit e thic kness between five and ten inches i s liner system. pos sible if appropriate equipment is use d Lift Thickness

(U SEPA, 1988). Nine-inch loose lif t thicknesses that will yield a 6-Subpart D

152 inch soil layer also have been recommende d i ncludes scarifying (roughening) , and possibly prior to compaction (USEPA, 1990a). we tting, the top inch or so of the last lif t So il liners usually are designed to be o f equipment before placing the next lift. u niform thickness with smooth slopes over the entire facility. Thicker areas may b e Placement of Soil Liners on Slopes considered wherever recessed areas fo r leachate collection pipes or collection sumps T he method used to place the soil li ner on side ar e located. Extra thickness and compactiv e s lopes depe nds on the angle and length of the ef forts near edges of the side slopes may slope. Gradual inclines from the toe of th e e nhance b onding between the side slopes and s lope enable continuous placement of the lifts the bottom liner. In smaller facilities, a soi l up the slopes and provide better continuity l iner may be designed for

installation over the between the bottom and sidewalls of the soi l entir e area, but in larger or multi-cel l liner. When steep slopes are encountered , f acilities, liners maybe designed in segments. however, lifts may need to be placed an d If this is the case, the design should addres s c ompacted hor izontally due to the difficulties how the old and new liner segments will b e o f operati ng heavy compaction equipment on bonded together (U.S. EPA, 1988). steeper slopes. Bonding Between Lifts When sidewalls are compacted horizontally , It is not possible to construct soil liner s bottom of the soil liner to reduce th e w ithout some microscopic and/or mac roscopic p robability of seepage planes ( USEPA, 1988). zo nes of higher and lower hydrauli c A significant amount of additional soil line r co nductivity. Within individual lifts, thes e mater ial will be required to construct th e preferential pathways for fluid migration ar e h orizontallifts since the width of the lifts has tru ncatedby the bonded zone between th e to be wide enough to accommodate th e l ifts. I f good bonding between the lifts is not c ompaction eq uipment. After the soil liner is achieved during construction, the vertica l constructed on the side slopes using thi s pat hways may become connected b y metho d, it can be trimmed back to th e horizontal pathways at the lift interface , requi redthickness. The trimmed surface o f ther eby diminishing the performance of th e the soi l liner should be sealed by a smooth

hydraulic barrier. drum roller. The trimmed excess material s Two methods may be used to ensure prope r specified moisture-density requirements. b onding bet

ween lifts. Kneading or blending a th inner, new lift with the previousl y Hydraulic Conductivity co mpactedlift may be achieved by using a foo tedroller with long feet that can full y A chieving the hydraulic conduc tivity standard p enetrate a loose lif

t of soil. If the protruding depends on the degree of compaction , rods or feet of a sheepsfoot roller ar e com paction method, type of clay, soi l s ufficient in length to penetrate th e top lift and moisture content, and density of the soi l knead the pre vious lift, good bonding may be during liner construction. Hydraulic achieved. Another method placed with a disc harrow or other similar

it is important to tie in the edges with th e

can be reused provided that they meet th eDesign Criteria

153 c onductivity is the key design pa rameter when characterize proposed liner soils shoul d e valuating the acceptab ility of the constructed inc lude grain size distribution (ASTM D

s oil liner. The hydraulic conducti vity of a soil 422 ), Atterberg limits (ASTM D-4318), an d d epends, in part, on the viscosity and density compaction curves depicting moisture an d of t he fluid flowing through it. While wate r density relationships using the standard o r and l eachate can cause different test results , m odified Proctor (ASTM D-6 98 or ASTM Dwate ris an acceptable fluid for testing th e 1557), whichever is appropriate for th e co mpactedsoil liner and source materials

. c ompaction equipment u sed and the degree of T he effective poros ity of the soil is a function firmness of the foundation materials. of si ze, shape, and area of the conduit s th rough which the liquid flows. Th e Liner soils usually have at least 30 percen t h ydraulic conduc tivity of a partially saturated fi nes (fine silt- and clay-sized particles)

. soil is less than the hydraulic conductivity of Some soils with less than 30 percent fine s the same soil when saturated. Becaus e may be worked to obtain hydrauli c invading water only flows through water

- conductivities below 1 x 10 cm/sec, but use fi lledvoids (and not air-filled voids), th e of these soils requires greater control o f d ryn ess of a soil tends to lower permeability. construction practices and conditions. Hydraulic conductivity testing should b e c ondu cted on samples that are fully saturated The s oil plasticity index (PI), which i s to attempt to measure the highest possibl e d etermined from the Atterberg limits (defined hydraulic conductivity. by the liquid limit minus the plastic limit) , EPA has published Method 9100 i n However, soils with very high PI, (greate r publication SW-846 ( Test Methods fo r tha n 30 percent), are cohesive and sticky and Evaluating Solid Waste ) to measure th e become difficult to work with in the field

. h ydraulic conductiv ity of soil samples. Other Wh en high PI soils are too dry durin g meth ods appear in the U.S. Army Corps o f pl acement, they tend to form hard clump s En gineers Engineering Manual 1110-2-190 6 ( clods) that are diff icult to break down during (COE , 1970) and the newly publishe d compaction. Preferential flow paths may b e "Measurement

of Hydraulic Conductivity o f c reated around the clods allowing leachate to Satu ratedPorous Materials Using a Flexibl e migrate at a relatively high rate. Wall Permeameter" (ASTM D-5084). T o v erify fullsaturation of the sample, this latter So il particles or rock fragments also ca n m ethod may be perfor

med with back pressure create preferential flow paths. For thi s sat uration and electronic pore pressur e r eason, soil particles or rock fragments should measurement. be less than 3 inches in diameter so as not to Soil Properties the soil liner (USEPA, 1989). Soil s typically possess a range of physica l The maximum density of a soil will b e ch aracteristics, including particle size , ac hievedat the optimum water content, bu t grad ation, and plasticity, that affect thei r this point generally does not correspond to the ability to achieve a hydraulic conductivity of point at which minimum hydraulic 1 x 10 cm/sec. Testing methods used t o

-7 -7

sho uldgenerally be greater than 10 percent

.

af fect the overall hydraulic performance o fSubpart D

154 c onductivity is achieved . Wet soils, however, i s difficult and may lead to incons istent results h ave low shear strengt

h and high potential for with respect to complying with the hydraulic desiccation cracking. Care should be take n conductivity criterion. not to compromise other engineerin g pro perties such as shear strengths of the soi l The most common additive used to amen d lin er by excessively wetting the soil liner

. so ils is sodium bentonite. The disadvantag e D epending on the spec ific soil characteristics, of u sing sodium bentonite includes it s c ompaction equipment and compactive effort, vul nerability to degradation as a result o f th e hydraulic conductivity criterion may b e contact with chemicals and waste leachate s achievedat moisture values of 1 to 7 percent (U.S. EPA, 1989). above the optimum moisture content. Al though the soil may possess the require d than sodium bentonite, also is used as a soi l properties for successful liner construction , amendment. Approximately twice as muc h the soil liner may not meet the hydrauli c cal ciumbentonite typically is needed t o conductivity criterion if the constructio n achieve a hydraulic conductivity comparable prac tices used to install the liner are no t to that of sodium bentonite. ap propriate and carefully controlled

. Co nstruction quality control and quality So il/bentonite mixtures generally requir e a ssu rance will be discussed in a later section. central plant mixing by means of a pugmill , Amended Soils w here water ca n be added during the process. If lo cally available soils do not posses s d istribution must be controlled during mixing prop erties to achieve the specified hydrauli c and placement. Spreading of th e c onducti vity, soil additives can be used. Soil soil/bentonite mixture may be accomplishe d addit ives, such as bentonite or other cla y i n the same manner as the spreadin g of natural ma terials, can decrease the hydrauli c soil liners, by using scrapers, graders , cond uctivity of the native soil (USEPA , bull dozers, or a continuous asphalt pavin g 1988b). machine (U.S. EPA, 1988). B entonite may be obtained in a dry, powdered M aterials other than bentonite, i ncluding lime, formthat is relatively easy to blend with on- cement, and other clay minerals such a s site soils. Bentonite is a clay minera l atapulgite, may be used as soil additives (U.S. ( sodium-mo ntmorillonite) that expands when EP A, 1989). For more informatio n itcomes into contact with water (hydration) , co ncerning soil admixtures, the reader i s by absorbing the water within the minera l r eferred to the technical resource document on m atrix. This property allows relatively small the design and construction of clay liner s am ounts of bentonite (5 to 10 percent) to b e (U.S. EPA, 1988). a dded to a noncohesive soil (sand) to make it m ore cohesive (U.S. EPA, 1988b). Thorough Testing mixing of additives to cohesive soils (clay) C alcium bentonite, although more permeable

cem ent mixer, or other mixing equipmen t Water, bentonite content, and particle siz e

Prior to construction of a soil liner, th e re lationship between water content, density ,Design Criteria

155 a nd hydraulic conductivity for a pa rticular soil c onstruction contractor during soil placement. shouldbe established in the laboratory

. Figu re 4-6 presents compaction data as a Fi gure 4-5 shows the influence of moldin g f unction of dry unit weight and molding water water content (moisture content of the soil at conte nt for the construction of clay liners

. the time of compaction) on hydrauli c The amount of soil testing required t o c onductivity of the soil. Th e lower half of the det ermine these construction parameters i s d iagram is a

compaction curve and shows the d ependent on th e degree of natural variability relat ionship between dry unit weight, or dry of the source material. density of the soil, and water content of th e soil. The optimum moisture content of th e Quality assurance and quality control of soi l soil is related to a peak value of dry density lin er materials involve both laboratory an d know n as maximum dry density. Maximu m field testing. Quality control tests ar e dry density is achieved at the optimu m pe rformedto ascertain compactio n moisture content. re quirements and the moisture content o f The lowest hydraulic conductivity o f quality assurance provide an opportunity t o c ompacted claysoil is achieved when the soil chec k representative areas of the liner fo r is compacted at a moisture content slightl y co nformance to compaction specifications , high er than the optimum moisture content , including density and moisture content

. generally in the range of 1 to 7 percent (U.S. Q uality assurance laboratory testing is usually EPA, 1989). When compacting clay, wate r c onducted on field samples for determination cont ent and compactive effort are the tw o o f hydraulic conductivity of the in-place liner. fact ors that should be controlled to meet th e L aboratory testing allows full saturation of the maximum hydraulic conductivity criterion. s oil samples and sim ulates the effects of large It i s impractical to specify and construct a done conveniently in the field (U.S. EPA , c lay liner to a specific moisture content and a 1989). spe cific compaction (e.g., 5 percent wet o f optimum and 95 percent modified Procto r Dif ferences between laboratory and fiel d d ensity). Moisture content can be difficult to con ditions (e.g., uniformity of material , cont rol in the field during construction ; control of water content, compactive effort , therefore, it may be more appropriate t o c ompaction eq uipment) may make it unlikely specify a range of moisture contents an d that minimum hydraulic conductivity value s corresponding soil densities (percen t m easured in the laboratory on remolded, prec ompaction) that are considered app ropriate to construction borrow source samples are th e achieve the required hydraulic conductivity

. same as the values achieved during actua l B enson and Daniel (U.S. EPA, 1990) propose li ner construction. Laboratory testing o n wa ter content and density criteria for th e r emolded soil sp ecimens does not account for con struction of clay liners in which th e ope rational problems that may result i n moisture-density criteria ranges ar e desi ccation, cracking, poor bonding of lifts , established based on hydraulic conductivity an dinconsistent degree of compaction o n tes tresults. This type of approach i s si dewalls (U.S. EPA, 1988b). Th e re commendedbecause of the flexibility an d relationship between field and laboratory guidance it provides to the hydraulic conductivity testing has bee n materi al delivered to the site. Field tests fo r

o verburden stress on the soi l, which cannot be

investigated by the U.S. Environmental156 

### Figure 4-5 Hydraulic Conductivity and Dry Unit Weight as a Function of Molding Water ContentFigure 4-6. Compaction Data for Silty Clay 157Subpart D

158 Protection Agency using field case studie s susceptible to the effects of temperatur e (U.S. EPA, 1990c). v aria tion; as the water temperature increases, I n situ , or field, hydrau lic conductivity testing the system contracts. This situation coul d operates on the assumption that by testin g l ead to erroneous measureme nts when the rate larger masses of soil in the field, one ca n of flow is small. o btain more realistic results. Four types of in s ituhydraul ic conductivity tests generally are The sealed double-ring infiltrometer ha s us ed: borehole tests, porous probes , proven to be the most successful method and infil trometer

tests, and underdrain tests. A is the one currently used. The outer rin g borehole test is conducted by drilling a hole , forces infiltration from the inner ring to b e then filling the hole with water, an d more or less one-dimensional. Covering th e measuring the rate at which water percolate s i nner ring with w ater insulates it substantially i nto the borehole. In the borehole test, water from temperature variation. a lso can percolate through th e sidewalls of the b orehole. As a result , the measured hydraulic U nderdrains, the fourth type of in situ test, are cond uctivity is usually higher than tha t the most accurate in situ permeability testing mea suredby other one-dimensional fiel d device because they measure exactly what testings. mig rates from the bottom of the liner

. The s econd type of test involves driving o r data for low permeability liners, because o f pushi ng a porous probe into the soil an d the length of time required to accumulat e p ouring water through the probe into the soil. measurable flow. Also, underdrains must be W ith this method, however, the advantage of in stalledduring construction, so fewe r t esting directly in

the field is somewhat offset under drains are used than other kinds o f by t he limitations of testing such a smal l testing devices. volume of soil. A th ird method of testing involves a devic e usually performed on the completed line r calle dan infiltrometer. This device i s be cause the tests may take several weeks t o embed dedinto the surface of the soil line r c omplete (during whi ch time the liner may be such that the rate of flow of a liquid into th e damagedby desiccation or freezin g line rcan be measured. The two types o f temperatures) and because large penetrations i nfilt rometers most widely used are open and must b e made into the liner. If fiel d s ealed. Open rings are less desirable because, co nductivity tests are performed, they ar e with a hydraulic conductivity of 10 cm/sec, u sually cond ucted on a test pad. The test pad -7 itis difficult to detect a 0.002 inch per da y s hould be con structed using the materials and drop in water level of the pond fro m me thods to be used for the actual soil liner

. evaporation and other losses. T he width of a test pad is usually the width of W it h sealed rings, very low rates of flow can length is one to two times the width

. be measured. However, single-rin g Thick ness is usually two to three feet. Tes t inf iltrometers allow lateral flow beneath th e p ads can be used as a me ans for verifying that ring, which can complicate the interpretation the proposed of t est results. Single rings are als o the entire system expands. As it cools down,

How ever, under-drains are slow to generat e

Fieldhydraulic conductivity tests are no t

three to four construction vehicles, and th eDesign Criteria

159 materials and construction procedures wil l ! Soil water content; and meet performance objectives. If a test pad is constructed, if tests verify that performanc e object ives have been met, and if the actua l s oil liner is constructed to standards that equal or e xceed those used in building the test pa d (a s verified through quality assurance), the n the ac tual soil liner should meet or excee d performance objectives. Other than the four types of field hydrauli c c onductivit

y tests described earlier, ASTM D 293 7 "Standard Test Method for Density o f Soil in Place by the Drive-Cylinder Method" may be used to obtain in-place hydrauli c co nductivity of the soil liner. This tes t m ethod uses a U.S . Army Corps of Engineers su rface soil sampler to drive a thin-walle d cylinder (typically 3-inch by 3-inch) into a comple tedlift of the soil liner to obtai n r el atively undisturbed samples for laboratory density and hydraulic conductivity testings

. This test can provide useful correlation t o oth er field and quality assurance testin g res ults (e.g, Atterberg limits, gradation, in

p lace moisture and densi ty of the soil liner) to e valuate the in-place hydraulic con ductivity of the soil liner. Soil Liner Construction Standard compaction procedures are usuall y e mplo yed when constructing soil liners. The fo llowing factors influence the degree an d quality of compaction:

! Lift thickness;

! Full scale or segmented lift placement;

! Number of equipment passes;

! Scarification between lifts; ! The type of equipment and compactiv e effort. The method used to compact the soil liner i s an important factor in achieving the required mi nimumhydraulic conductivity. Highe r degr ees of compactive effort increase soi l den sity and lower the soil hydrauli c cond uctivity for a given water content. Th e res ults of laboratory compaction tests do no t n ecessarily cor

relate directly with the amount of compaction that can be achieved durin g construction. Heavy compaction equipment (greater tha n 25,0 00 lbs or 11,300 kg) is typically use d wh en building the soil liner to maximiz e com pactive effort (U.S. EPA, 1989). Th e preferredfield compaction equipment is a sheep sfoot

roller with long feet that full y pen etrates loose lifts of soil and provide s higher compaction while kneading the cla y p articles together. The sha pe and depth of the f e et are important; narrow, rod-like feet with a m inimum length of about seven inche s p rovide the best results. A progres sive change from t he rod-like feet to a broader foot ma y be necessary in some soils after initia l c ompaction, to allow the roller to walk out of the compacted soil. The sheepsfoot feet also aidin breaking up dry clods (see Soi l Pro perties in this section). Mechanical roa d reclaimers, which are typically used to stri p and re-pave asphalt, can be extremel y effect ive in reducing soil clod size prior t o compaction and in scarifying soil surface s b etween l ifts. Other equipment that has been usedto compact soil includes discs an d rototillers. To a chieve adequate compaction, the lif t thickness (usuallyfive to nine inches) may be decreased or the number of passes overSubpart D

160 th e lift may be increased. Generally , fi llers, plasticizers, processing aids , com paction equipment should pass over th e crosslinking chemicals, anti-degradants, an d soil liner five to twenty times to attain th e b i ocides. The polymers used to manufacture co mpaction needed to comply with th e geom embranes include a wide range o f minimumhydraulic conductivity criterio n plas tics and rubbers differing in propertie s (U.S. EPA, 1989). suc h as chemical resistance and basi c Efforts made to reduce clod size durin g 1988e). The polymeric materials may b e excavation and placement of the soil for th e categorized as follows: liner should improve the chances fo r achieving low hydraulic conductivity i n ! Thermoplastics such as polyviny l several ways. Keeping clods in the soil liner chloride (PVC); mate rial small will facilitate a more uniform wate rcontent. Macropores between clo d r emnants can result in un acceptably high field hydraulic conductivity. O pinions differ on acceptable clod sizes in the u ncompacted soil. Some suggest a maximum o f one to three inches in diameter , or no larger than one-half the lift thickness. The mai n obj ective is to remold all clods in th e compaction process to keep hydrauli c c onductivi ty values consistent throughout the soil liner (U.S. EPA, 1988). Geomembranes Geomembranes are relatively thin sheets o f f lexible thermoplast

ic or thermoset polymeric ma terials that are manufactured an d prefabricatedat a factory and transported t o the site. Because of their inheren t impermeability, use of geomembranes i n landfill unit construction has increased. Th e desi gn of the side slope, specifically th e friction between natural soils an d ge osynthetics, is critical and requires carefu l review. Material Types and Thicknesses Geo membranes are made of one or mor e poly mers along with a variety of othe r ing redients such as carbon black, pigments , c omposition (U.S. EPA, 1983 and U.S. EPA,

! Cr ystalline thermoplastics such as hig h d ensity polyethylene (HDPE), very low density polyethylene (VLDPE), an d linear low density polyethylen e (LLDPE); and

! Th ermoplastic elastomers such a s chlorinatedpolyethylene (CPE) an d chlorosulfonated polyethylene (CSPE). T he polymeric materials used most frequently as g eomembranes are HDPE, PVC, CSPE , a nd CPE. The thicknesses of geomembranes r ange from 20 to 120 mil(1 mil = 0.001 inch) ( U.S. EPA, 1983 and U.S. EPA, 1988e). The recommendedminimum thickness for al l geomembranes is 30 mil, with the exceptio n of HDPE, which must be at least 60 mil t o allow for proper seam welding. Som e geomembranes can be manufactured by a c alendering process with fabric rei nforcement, calledscrim, to provide additional tensil e strength and dimensional stability. Chemical and Physical Stress Resistance T he design of the landfill u nit should consider str esses imposed on the liner by the desig n conf iguration. These stresses include th e following:Design Criteria

161 ! Differential settlement in foundatio n of th e original material every thirty days. A soils; sof tware system entitled Flexible Line r

! S train requirements at the anc hor trench; in t he hazardous waste permitting process , and m ay aid in interpreting EPA Met hod 9090 test

! S train requirements over long, steep side of bo th Method 9090 and FLEX is availabl e slopes. from EPA. An extensive body of literature has bee n Itis imperative that a geomembrane line r d eveloped by manufacturers and independent mai ntain its integrity during exposure t o re searchers on the physical properties o f s hort-term and long-ter m mechanical stresses. liners. Geosynthetic design equations ar e Short-term mechanical stresses includ e presentedin several publications includin g equi pment traffic during the installation of a Kas tman (1984), Koerner (1990), and U.S

. l iner system, as well as therm al expansion and EPA (1988e). shr inkage of the geomembrane during th e T he chemical resist ance of a geomembrane to unit. Long-term mechanical stresses resul t leac hate has traditionally been considered a from the placement of waste on top of th e c ritical issue

for Subtitle C (hazardous waste) l iner system and from subsequent differential facilities where highly concentrated solvent s s ettlement of the subgrade (U.S. EPA, 1988a). may be encountered. Chemical resistanc e t esting of geomembra

nes may not be required Long-term success of the liner require s for MSWLF units containing only municipal adequate friction between the components of solid waste; EPA's data base has shown that a liner system, particularly the soil subgrad e l eachate from MSWLF units is not aggressive and the geomembrane, and betwee n to t hese types of materials. Testing fo r geosynthetic components, so that slippage or che mical resistance may be warrante d s loughing does not occur on the slopes of the considering the waste type, volumes , unit. Specifically, the foundation slopes and c haracteristics, an d amounts of small quantity th e subgrade materials must be considered in generator waste or other industrial wast e design equations to evaluate: prese nt in the waste stream. The followin g g uidance is pro vided in the event such testing • Th e ability of a geomembrane t o is of interest to the owner or operator. suppo rtits own weight on the sid e EPA's Method 9090 in SW-846 is th e esta blishedtest procedure used to evaluat e • Th e ability of a geomembrane t o d egr adation of geomembranes when exposed wi thstanddown-dragging during an d to hazardous waste leachate. In th e after waste placement; proc edure, the geomembrane is immersed i n the site-specific chemical environment for a t • T he best anchorage configurati on for the leas t120 days at two different temperatures

. geomembrane; Phys ical and mechanical properties of th e tested material are then compared to those E valuation Expert (FLEX), designed to assist

d ata (U.S. EPA, 1989) . A detailed discussion

construction and operation of the MSWL F

slopes;Subpart D

162 • The stability of a soil cover on top of a Manufactured Sheet Specifications geomembrane; and

• The stability of other geosyntheti c c omponents such as geo textile or geonet on top of a geomembrane. The se requirements may affect the choice o f geomembrane material, including polyme r type, fabric reinforcement, thickness, an d te xture (e.g., smooth or textured for HDPE ) ( U.S. EPA, 1988 ). PVC also can be obtained in a r oughened or file finish to increase th e friction angle. D esign specificatio ns should indicate the type o f raw poly mer and manufactured sheet to be use das well as the requirements for th e d elivery, storage, installation, and sampling of the geomembrane. Material properties can be ob tainedfrom the manufacturer-supplie d average physical property values, which ar e p ublished in the Geotechnical Fabr ics Report's S pe cifier's Guide and updated annually. The minimumtensile properties of th e g eomembrane must be suffi cient to satisfy the stre sses anticipated during the service life o f the geomembran e. Specific raw polymer and manufacturedsheet specifications and tes t pr ocedures include (U.S. EPA, 1988e, an d Koerner, 1990): Raw Polymer Specifications

! Density (ASTM D-1505);

! Melt index (ASTM D-1238);

! Carbon black (ASTM D-1603); and

! Thermogravimetric analysis (TGA ) or differential scanning calorimetry (DSC). ! Thickness (ASTM D-1593);

! Tensile properties (ASTM D-638);

! Tear resistance (ASTM D-1004);

! Car bon black content (ASTM D

1603);

! Carbon black dispersion (ASTM D

3015);

! Dimensional stability (ASTM D

1204); and

! St ress crack resistance (ASTM D

1693). Geomembranes may have different physica l characteristics, depending on the type o f p olymer and

the manufacturing process used, that can affect the design of a liner system

. When reviewing manufacturers' literature, i t is i mportant to remember that eac h m anufacturer may use more than one polymer o r resin type for each grade of geomembrane and that the material specifications may b e generalizedto represent several grades o f material. Installation In stallation specifications should addres s installation procedures specific to th e prope rties of the liner installed. Th e coefficient of thermal expansion of th e g eo membrane sheet can affect its installation and its service performance. Th e geomembrane should lie flat on th e underlying soil. However, shrinkage an d expansion of the sheeting, due to changes i n t empera ture during installation, may result in exce ssive wrinkling or tension in th eDesign Criteria

163 ge omembrane. Wrinkles on th e in an EPA guidance document (USEPA , geomembrane surface will affect th e u niformity of the soil-geomembrane interface and may result in leakage throug h imperfections. Excessive tautness of th e ge omembrane may affect its ability to resis t rupt ure from localized stresses on the seam s o r at the toe of slopes wh ere bridging over the subgrade may occur during installation. I n a ddition to thermal e xpansion and contraction of t he geomembrane, residual stresses fro m m anufacturing remain in some g eomembranes and can cause non-uniform expansion an d co ntraction during construction. Som e flexi bility is needed in the specifications fo r geo membrane selection to allow fo r anticipateddimensional changes resultin g f rom thermal expansion and contraction (U.S. EPA, 1988). Te chnical specifications for geomembrane s also should include: information fo r prot ection of the material during shipping , st orage and handling; quality contro l c ertifications provided b y the manufacturer or fabricator (if panels are constructed); an d qual ity control testing by the contractor , ins taller, or a construction quality assuranc e (CQA) agent. Installation procedure s add ressedby the technical specification s include a geomembrane layout plan , deployment of the geomembrane at th e co nstruction site, seam preparation, seamin g methods, seaming temperature constraints , det ailedprocedures for repairing an d d ocumenting construction def ects, and sealing of the geomembrane to appurtenances, both ad joining and penetrating the liner. Th e p erformance of inspection activitie s, including bo th non-destructive and destructive quality cont rol field testing of the sheets and seam s during installation of the geomembrane , shou ldbe addressed in the technica l s pecifications. Construction quality assurance is addressed 1992). T he geomembrane sheeti ng is shipped in rolls o r panels from the supplier, manufacturer, or fabricator to the construction site. Each rol l or panel may be labeled according to it s posit ion on the geomembrane layout plan t o facilitate installation. Upon delivery, th e g eomembrane sheeting s hould be inspected to ch eck for damage that may have occurre d during shipping. (U.S. EPA, 1992). Prop er storage of the rolls or panels prior t o in stallation is essential to the fina l performance of the geomembrane. Som e geomembrane materials are sensitive t o u lt raviolet exposure and should not be stored i n direct sunlight prior

to installation. Others, such as CSPE and CPE, are sensitive t o moisture and heat and can partially crosslink or block (stick together) under imprope r storage conditions. Adhesives or weldin g mat erials, which are used to joi n geomembrane panels, also should be store d appropriately (U.S. EPA, 1992). Visu al inspection and acceptance of the soi l line rsubgrade should be conducted prior t o ins talling the geomembrane. The surface o f the subgrade should meet desig n specifications with regard to lack o f protruding objects, grades, and thickness

. Once these inspections are conducted an d c omplete , the geomembrane may be installed on top of the soil liner. If necessary, othe r means should be employed to protect th e subgrade from precipitation and erosion, and to prevent desiccation, moisture loss, an d erosi on from the soil liner prior t o g eomembrane placement. Such methods may inc lude placing a plastic tarp on top o f completed portions of the soil linerSubpart D

164 ( USEP A, 1992). In addition, scheduling soil tested non-destructively (U.S. EPA, 1988)

. li ner construction slightly ahead of th e Destructive testing should be done at regular geomembrane and drainage layer placemen t intervals along the seam (see page 4-66). c an reduce the exposure of t he soil liner to the elements. C onsistent quality in fabricat ing field seams is Deployment, or placement, of th e that m ay affect seaming should be monitored geom embrane panels or rolls should b e and controlled during installation. A n de scribedin the geomembrane layout plan

. i nspection should b e conducted in accordance Roll s of sheeting, such as HDPE, generall y with a construction quality assurance plan t o can be deployed by placing a shaft throug h d ocument the integrity of field sea ms. Factors the cor e of the roll, which is supported an d af fecting the seaming process include (U.S

. d eployed using a

front-end loader or a winch. EPA, 1988): Panels composed of extremely flexible line r mater ial such as PVC are usually folded o n ! A mbient temperature at which th e seams p allets, requiring workers to manually unfold are made; an dplace the geomembrane. Placement o f the geomembrane go es hand-in-hand with the ! Relative humidity; s eaming proce ss; no more than the amount of sheeting that can be seamed during a shift or ! Control of panel lift-up by wind; w ork day sho uld be deployed at any one time (USE PA, 1988). Panels should be weighte d ! The effect of clouds on th e w ith sand bags if wind uplift of the membrane geomembrane temperature; or excessive movement from therma l expa nsion is a potential problem. Prope r ! W ater content of the subsurface beneath stormwater

control measurements should b e the geomembrane; employedduring construction to preven t erosi on of the soil liner underneath th e ! The supporting surface on which th e ge omembrane and the washing away of th e seaming is bonded; geomembrane. Once deployment of a section of th e ge omembrane is complete and each sectio n ! Q uality and co nsistency of the chemical h as be en visually inspected for imperfections or welding material; and te sted to ensure that it is the specifie d thickness, seaming of the geomembrane may ! Properpreparation of the liner surfaces be gin. Quality control/quality assuranc e to be joined; monitoring of the seaming process should be implementedto detect inferior seams

. ! Moisture on the seam interface; and Seam ing can be conducted either in th e factory or in the field. Factory seams ar e ! Cl eanliness of the seam interface (e.g. , made in a controlled environment and ar e th e amount of airborne dust and debri s g enerally of high quality, but the entire seam present). length (100 percent) still should be crit ical to liner performance, and condition s

! The skill of the seaming crew;Design Criteria

165 Depending on the type of geomembrane , de sign plans and specifications (USEPA , s e veral bonding systems are available for the 1988). construction of both factory and field seams. B onding methods includ e solvents, heat seals, Geomembranes that are subject to damag e hea tguns, dielectric seaming, extrusio n f rom expo sure to weather and work activities weld ing, and hot wedge techniques. T o s hould be covere d with a layer of soil as soon ensu re the integrity of the seams, a as possible after quality assurance activitie s geom embrane should be seamed using th e as sociatedwith geomembrane testing ar e bonding system recommended by th e com pleted. Soil should be placed withou t manufacturer (U.S. EPA, 1988). EPA ha s driving construction vehicles directly on th e dev elopeda field seaming manual for al l geo membrane. Light ground pressur e types of geomembranes (U.S. EPA, 1991a). bu lldozers may be used to push material ou t The rmal methods of seaming requir e n ot attempt to push a large pile of soil forward cle anliness of the bonding surfaces, heat , in a continuous manner over the membrane

. pres sure, and dwell time to produce hig h S uch methods can c ause localized wrinkles to q uality seams. The requ irements for adhesive develop and overturn in the direction o f systems are the same as those for therma l m ovement. Overturned wrinkles create sharp systems, except that the adhesive takes th e crea ses and localized stresses in th e plac e of the heat. Sealing the geomembran e geomembrane that could lead to prematur e to appurtenances and penetrating structure s fai lure. Instead, the operator shoul d shou ldbe performed in accordance with co ntinually place smaller amounts of soil o r d etailed drawings included in the design plans dra inage material working outward over th e and approved specifications. toe of the previously placed material

. An anc hor trench along the perimeter of th e p lace soil over the geomembrane tha t can later cel l generally is used to secure th e be spread with a bulldozer or similar g eomembrane during c onstruction (to prevent equipment. Although such methods ma y slou ghing or slipping down the interior sid e soun dtedious and slow, in the long run the y s lopes). Run out calculation s (Koerner, 1990) will be faster and more cost-effective tha n areavailable to determine the depth of burial p lacing too much mater ial too fast and having at a trench necessary to hold a spec ified length to remobilize the liner installer to repai r of m embrane, or combination of membran e damagedsections of the geomembrane. The an dgeofabric or geotextile. If forces large r QA activities conducted during constructio n than the tensile strength of the membrane are also should include monitoring th e inadvertently developed, then the membran e contractor's activities on top of the liner t o c ould tear. For thi s reason, the geomembrane avoiddamage to installed and accepte d s hould be allowed toslip or give in the trench geomembranes. afte rconstruction to prevent such tearing

. However, during construction, th e Leachate Collection Systems geomembrane should be anchored accordin g to the detailed drawings provided in the Lea chate refers to liquid that has passe d in fron t over the liner, but the operator mus t

Al ternatively, large backhoes can be used t o

through or emerged from solid waste an d c ont ains dissolved, suspended, or immiscibleSubpart D

166 mater ials removed from the solid waste. A t layer to collect leachate and carry i t MSW LF units, leachate is typically aqueou s rapi dly to a sump or collection heade r with limited, if any, immiscible fluids o r pipe; dissolvedsolvents. The primary function o f the leachate collection system is to collect and ! A protective filter layer over the hig h c onvey leacha

te out of the landfill unit and to permeability drainage material, i f control the depth of the leachate above th e necessary, to prevent physical clogging lin er. The leachate collection system (LCS ) o f the material b y fine-grained material; sh ouldbe designed to meet the regulatory and p erformance standard of maint aining less than 30 c m (12 inches) depth of leachate, o r ! Le achate collection sumps or heade r "head," above the liner. The 30-cm hea d pipe system where leachate can b e a llowance is a design standard and t he Agency removed. recognizes that this design standard may b e excee dedfor relatively short periods of tim e T he design, construction , and operation of the dur ing the active life of the unit. Flow o f leac hate through imperfections in the line r system increases with an increase in leachate head above the liner. Maintaining a lo w l eachate level above the liner help s to improve the performance of the composite liner. Le achate is generally collected from th e landfill through sand drainage layers , synt hetic drainage nets, or granular drainag e l ayers with perforated pl astic collection pipes, a nd is then removed throu gh sumps or gravity dra in carrier pipes. LCS's should consist o f the follo wing components (U.S. EPA, 1988):

! A low-permeability base (in this case a composite liner);

! A high-permeability drainage layer , constructed of either natural granular m aterials (sand and gravel) or synthetic dr ainage material (e.g., geonet) place d directly on the FML, or on a protective be dding layer (e.g., geofabric) directl y overlying the liner;

! Perforated leachate collection pipe s within the high-permeability drainag e LCS should maintain a maximum height o f le achate above the composite liner of 30 c m (12 in ). Design guidance for calculating th e maxim umleachate depth over a liner fo r granular drainage systems materials i s pr ovidedin the reference U.S. EPA (1989)

. T he leachate head

in the layer is a function of the liquid impingement rate, bottom slope , pipe spacing, and drainage layer hydrauli c co nductivity. The impingement rate i s estimatedusing a complex liquid routin g procedure. If the maximum leachate depth exce eds 30 cm for the system, except fo r short-termoccurrences, the design should be modified to improve its efficiency b y increasing grade, decreasing pipe spacing, or increasing the hydraulic conductivity (tra nsmissivity) of the drainage layer (U.S

. EPA, 1988). Grading of Low-Permeability Base The typical bottom liner slope is a minimum o f two percent after

allowances for settlement at all points in each system. A slope i s nec essary for effective gravity drainag e th rough the entire operating and post-closure pe riod. Settlement estimates of th e foundation soils should set this two-Design Criteria

167 perc ent grade as a post-settlement desig n f ric tion angle between the geomembrane and objective (U.S. EPA, 1991b). soil, and if possible, supported by laboratory High-Permeability Drainage Layer Th e high-permeability drainage layer i s d esignation of GW or GP on the Unified Soils p laced directly over the liner or its protective Class ification Chart can be expected to hav e b edding layer at a slope of at le ast two percent a hydraulic conductivity of greater than 0.0 1 (the same slope necessary for the composit e cm/ sec, while sands identified as SW or S P liner). Often the selection of a drainag e can be expected to have a coefficient o f m aterial is base d on the on-site availability of permeability greater than 0.001 cm/sec. The n atural granular materials. I n some regions of sand or gravel drains leachate that enters th e the country, hauling costs may be very hig h dra inage layer to prevent 30 cm (12 in) o r for sand and gravel, or appropriate material s m oreaccumulation on top of the liner during may be unavailable; therefore, the designe r the act ive life of the MSWLF unit LCS. The may elect to use geosynthetic drainage net s des ign of a LCS frequently uses a drainag e ( geonets) or synthetic drainag e materials as an material with a hydraulic conductivity of 1 x alternative. Frequently, geonets ar e 10 cm/sec or higher. Drainage material s sub stitutedfor granular materials on stee p with hydraulic conductivities in this order of si dewalls because maintaining sand on th e m agnitu de should be evaluated for biological s lope during construction and operation of the and particulate clogging (USEPA, 1988)

. la ndfill unit is more difficult (U.S. EPA , A lternatively, if a geonet is used, the design is 1988). based on the transmissivity of the geonet. Soil Drainage Layers If a filter layer (soil or geosynthetic) i s I f the drainage layer of the leachate collection protect it from clogging, and the LCS i s sys temis constructed of granular soi l designed and operated to avoid drasti c ma terials (e.g., sand and gravel), then i t c hanges in the oxidation reduction potential of sh ouldbe demonstrated that this granular the leachate (thereby avoiding formation o f d rai nage layer has sufficient bearing strength p recipitates within the LCS), then there is no to support expected loads. Thi s conceptual basis to anticipate tha t d emonstrat

ion will be similar to that required c o nductivity will decrease over time. Where forthe foundations and soil liner (U.S. EPA, conductivity is expected to decrease ove r 1988). time, the change in impingement rate als o I f the landfill unit is desig ned on moderate-to- bec ause the reduced impingement rate an d stee p (15 percent) grades, the landfill desig n h ydra ulic conductivity may still comply with s hould include calculations demo nstrating that the 30 cm criterion. the selected granular drainage materials wil l be stable on the most critical slopes (e.g. , Unl ess alternative provisions are made t o u sually th e steepest slope) in the design. The calculations and assumptions should b e shown, especially the and/or field testing (USEPA, 1988). Generally, gravel soil with a grou p

-2

constr uctedon top of a drainage layer t o

s hould be evaluated over the same time period

control incident precipitation and resultin g surface run-off, the impingement rate during the operating period of the MSWLF unit i sSubpart D

168 u sually at least an order of magnitude greater G ranular materials are generally placed using than t he impingement rate after final closure. The critical design condition for meeting the 30 cm (12 in) criterion can therefore b e expe ctedduring the operating life. Th e desig ner may evaluate the sensitivity of a de sign to meet the 30 cm (12 in) criterion a s a res ult of changes in impingement rates , hydraulic conductivity, pipe spacing, an d g rades. Such sensitivity analy sis may indicate whi chelement of the design should b e emphasized during construction quality monit oring or whether the design can b e altered to comply with the 30 cm (12 in ) criterion in a more cost-effective manner. The s oil material used for the drainage laye r s hould be investigated at the borrow pit prior to us e at the landfill. Typical borrow pi t ch aracterization testing would includ e laboratory hydraulic conductivity and grai n si ze distribution. If grain size distributio n in formation from the borrow pi t c haracteri zation program can be correlated to the hydraulic conductivit

y data, then the grain size test, which can be conducted in a short t ime in the field, may be a useful construction quality control parameter. Compliance with th is parameter would then be indicative tha t the hydraulic conductivity design criterio n was achieved in the constructed drainag e l ayer. This information coul d be incorporated i nto construction documents after the borrow pi thas been characterized. If a correlatio n cannot be made between hydrauli c conductivity and grain size distribution, then cons truction documents may rely on direc t fieldor laboratory measurements t o demonstrate that the hydraulic conductivity d esign criterion was met in t he drainage layer. conventional earthmoving equipment , inc luding trucks, scrapers, bulldozers, an d front-endloaders. Vehicles should not b e driven directly over the geosyntheti c membr ane when it is being covered. (U.S

. EPA, 1988a). Co arse granular drainage materials, unlik e l ow-permeabil ity soils, can be placed dry and do not need to be heavily compacted

. Com pacting granular soils tends to grind th e so il particles together, which increases th e fine material and reduces hydrauli c con ductivity. To minimize settlemen t fol lowing material placement, the granular ma terial may be compacted with a vibratory roller. The final thickness of the drainag e layer should be checked by optical surve y me asurements or by direct test pi t measurements (U.S. EPA, 1988). Geosynthetic Drainage Nets Geosynthetic drainage nets (geonets) may be s ubstituted for the granular layers of the LCRs on the bottom and sidewalls of the landfil l cells

. Geonets require less space tha n pe rforatedpipe or gravel and also promot e ra pidtransmission of liquids. They do , h owever, require geotextil e filters above them and can experience problems with creep an d intrusion. Long-term operating an d p erf ormance experience of geonets is limited be cause the material and its application ar e relatively new (U.S. EPA, 1989). If a geonet is used in place of a granular d rainage layer, it must provide the same level of performance (maintaining less than 30 cm of leachate head above the liner). A n e xplanation of the calculation used to compute the capacity of a geo net may be found in U.S. EPA (1987a). TheDesign Criteria

169 trans missivity of a geonet can be reduce d critical specification is the ability to transmit significantly by intrusion of the soil or a flu ids under load. The specifications als o geotextile. A protective geotextile betwee n sho uldinclude a minimum transmissivity the soil and geonet will help alleviate thi s under expected landfill operating (dynamic ) c oncern. If labora

tory transmissivity tests are or completion (static) loads. Th e performed, they should be done unde r spe cifications for thickness and types o f conditions, loads, and configurations tha t m aterial should be identified on the drawings c losely replicate the actual field conditions. It or in the materials section of th e i s important that the transmissivity value used spe cifications, and should be consistent with in the leachate collection system desig n the design calculations (U.S. EPA, 1988). ca lculations be selected based upon thos e l oaded conditions (U.S. EPA, 1988). It is also Geon ets are often used on the sidewalls o f i mportant to ensure that

appropriate factors of landfills because of their ease of installation. safety are used (Koerner, 1990). They should be placed with the top ends in a The flow rate or transmissivity of geonet s l ongitudinal length extending down the slope. may be evaluated by ASTM D-4716. Thi s T he geonets need not b e seamed to each other f low rate may then be compared to design-by- o n the slopes, only tied at the e dges, butted, or fu nction equations presented in U.S. EP A o verlapped. They s hould be placed in a loose (19 89). In the ASTM D-4716 flow test, th e condi tion, not stretched or placed in a prop osedcollector cross section should b e conf iguration where they are bearing thei r modeled as closely as possible to actual field own weight in tension. The constructio n conditions (U.S. EPA, 1989). specifications should contain appropriat e F igure 4-7 shows the flow rate "signatures" of orthe requirements of the geone t a geonet between two geomembranes (uppe r ma nufacturer. All geonets need to b e curves) and the same geonet between a layer prote ctedby a filter layer or geotextile t o of clay soil and a geomembrane (lowe r prevent clogging (U.S. EPA, 1988). c urves). The differences between the two sets of c urves represent intrusion of th e Th e friction factors against sliding fo r geotextile/clay into the apertures of th e g eotextiles, geonets, an d geomembranes often g e onet. The curves are used to obtain a flow can be estimated using manufacturers dat a ra te for the particular geonet being designe d because these materials do not exhibit th e ( U.S. EPA, 1989). Equati ons to determine the range of characteristics as seen in soi l de sign flow rate or transmissivity are als o mate rials. However, it is important that th e p resented in U.S. EPA (1989), Giroud (1982), desi gner perform the actual tests using sit e Carroll (1987), Koerner (1990), and FHW A ma terials and that the sliding stability (1987). ca lculations accurately represent the actua l G enerally, geonets perform well and result in specifiedmaterial characteristics (U.S. EPA , high factors of safety or performance desig n 1988). r atios, unless creep (elongati on under constant st ress) becomes a problem or adjacen t mate rials intrude into apertures (U.S. EPA , 1989). For geonets, the most se cure anchor trench with the stronges t

in stallation requirements as described abov e

d e sign configuration, site conditions, and theFigure 4-7. Flow Rate Curves for Geonets in Two Composite Liner Configurations 170h max ' L c 2 [ tan 2 " c % 1

& tan " c tan 2 " % c ] Design Criteria

171 Leachate Collection Pipes ! The required flow using know n All components of the leachate collectio n sys tem must have sufficient strength t o support the weight of the overlying waste , c over system, and post-closure loadings, as well as the stresses from operatin g equipment. The component that is mos t vulnerable to compressive stre ngth failure is the drainage layer piping. Leachat e collection system piping can fail b y exc essive deflection, which may lead t o b u ckling or collapse (USEPA, 1988). Pipe st rength calculations should includ e resistance to wall crushing, pipe deflection, and critical buckling pressure. Desig n equa tions and information for most pip e types can be obtained from the major pip e man ufacturers. For more informatio n regarding pipe structural strength, refer t o U.S. EPA (1988). P erforated drainage pipes can provide good lon g-term performance. These pipes hav e b een shown to transmit fluids rapidly and to mainta in good service lives. The depth o f t he drainage layer around th e pipe should be dee per than the diameter of the pipe. Th e pipes can be placed in trenches to provid e the extra depth. In addition, the trenc h serv es as a sump (low point) for leachat e coll ection. Pipes can be susceptible t o particulate and biological clogging simila r to the drainage layer material. Furthermore, pipes also can be susceptible to deflection

. Pr oper maintenance and design of pip e systems can mitigate these effects an d pro vide systems that function properly

. Ac ceptable pipe deflections should b e evaluated for the pipe material to be use d (USEPA, 1989). The design of perforated collection pipe s should consider the following factors: p erco lation impingement rates and pipe spacing;

! Pipe size using required flow an d maximum slope; and

! The structural strength of the pipe. The pipe spacing may be determined by th e Mo undModel. In the Mound Model (se e Fi gure 4-8), the maximum height of flui d bet ween two parallel perforated drainag e pipes is equal to (U.S. EPA, 1989):

where c = q/k k = permeability q = inflow rate " = slope. The two unknowns in the equation are: L = distance between the pipes; and c = amount of leachate. U sing a maximum al lowable head, h , of 30 max cm (12 in), the equation is usually solved for "L" (U.S. EPA, 1989). T he amount of leacha

te, "c", can be estimated in a variety of ways including the Wate r Balance Method (U.S. EPA, 1989) and th e com puter model Hydrologic Evaluation o f Landfill Performance (HELP). The HEL P M odel is a qu asi-two-dimensional hydrologic mod el of water movement across, into , through, and out of landfills. The model uses c limatologic, soil, and landf ill design data and incorporates a solution technique tha t acco unts for the effects of surface storage , r un-off, infiltration, percolation, soil-moistureSubpart D

172 

### Figure 4-8. Definition of Terms for Mound Model

Flow Rate CalculationsDesign Criteria

173 st orage, evapotranspiration, and latera l ! Diameter and wall thickness; drai nage. The program estimates run-of f dra inage and leachate that are expected t o ! Size and distribution of slots an d result from a wide variety of landfil l perforations; c onditions, including open, partial ly open, and closedlandfill cells. The model also may be ! Typ e of coatings (if any) used in th e use dto estimate the depth of leachate abov e pipe manufacturing; and the bottom liner of the landfill unit. Th e results may be used to compare designs or to ! Type of pipe bedding material an d aid in the design of leachate collectio n r equired compactio n used to support the systems (U.S. EPA, 1988). pipes. Once the percolation and pipe spacing ar e T he con struction drawings and specifications known, the design flow rate can be obtaine d s hould c learly indicate the type of bedding to u singthe curve in Figure 4-9. The amount of b e used under the pipes a nd the dimensions of leachate percolation at the particular site i s any trenches. The specifications shoul d located on the x-axis. i ndicate how the pipe lengths are joined. The The r equired flow rate is the point at whic h pla cedwith respect to the perforations. T o this value intersects with the pipe spacin g maintain the lowest possible leachate head , value determined from the Mound Model

. there should be perforations near the pip e Using this value of flow rate and the botto m i nvert, but not dire ctly at the invert. The pipe s lope of the site, the required diameter for the invert itself should be solid to allow fo r pi pe can be determined (see Figure 4-10)

. e fficient pipe flow at low volumes (U.S. EPA, Finally, the graphs in Figures 4-11 and 4-1 2 1988). show two ways to determine whether th e s trength of the pipe is adequa te for the landfill W hen drainage pipe systems are embedded in design. In Figure 4-11, the vertical soi l f ilter and drainage layers, no unplugged ends p ressure is loca

ted on the y-axis. The density shou ldbe allowed. The filter materials i n o f the b ackfill material around the pipe is not c ontact with the pipes sh ould be appropriately g overned bystrength, so it will deform under s ized to prevent migrat ion of the material into p ressure rather t

han break. Ten percent is the the pipe. The filter media, drai nage layer, and abs olute limiting deflection value for plasti c p ipe network should be compatible an d should p ipe. Using Figure 4-11, the applied pressure represent an integrated design. o n the pipe

is located and traced to the trench geometry, and then the pipe deflection valu e Protection of Leachate Collection Pipes i s checked for its adequacy(U.S. EPA, 1989). The LCS specifications should include (U.S. dep ends on the design used to protect pipe s EPA, 1988): f rom physical clogging (sedime ntation) by the

! Type of piping material; material around the pipes is most effective if draw ings should show how the pipes ar e

The long-term performance of the LC S

g ranular drainage materials. Use of a graded

acco mpaniedby proper sizing of pip e perforations. The Army Corps ofSubpart D

174 

### Figure 4-9. Required Capacity of Leachate Collection Pipe

### Figure 4-10. Leachate Collection Pipe Sizing ChartSubpart D

176 

### Figure 4-11. Vertical Ring Deflection Versus Vertical Soil Pressure for 18-inch Corrugated Polyethylene in High Pressure Soil CellDesign Criteria

177 

### Figure 4-12. Example of the Effect of Trench Geometry

and Pipe Sizing on Ring DeflectionSubpart D

178 Engineers (GCA Corporation, 1983) ha s e stablished design c riteria using graded filters to prevent physical clogging of leachat e drain age layers and piping by soil sedimen t dep osits. When installing graded filters , c aution should be taken to prevent segregation of the material (USEPA, 1991a). Clo gging of the pipes and drainage layers o f the leachate collection system can occu r through several other mechanisms, including ch emical and biological fouling (USEPA , 1988 ). The LCS should be designed with a cl eanout access capable of reaching all part s of t he collection system with standard pip e cleaning equipment. C hemicalclogging can occur when dissolved spe cies in the leachate precipitate in th e piping. Clogging can be minimized b y periodically flushing pipes or by providing a s ufficiently steep slope in the system to allow forhigh flow velocities for self-cleansing

. The se velocities are dependent on th e diameter of the precipitate particles and o n their specific gravity. AS CE (1969) discusses these relationships. General ly, flow velocities shouldbe in the range of one or two feet per secon dto allow for self-cleansing of th e piping (U.S. EPA, 1988). B iological clogging du e to algae and bacterial growth can be a serious problem in MSWLF There are three parts to an analysis of a sand units. There are no universally effectiv e filterthat is placed above drainage material

. methods of preventing such biologica l The first determines whether or not the filter gr owth. Since organic materials will b e allows adequate flow of liquids. The second prese nt in the landfill unit, there will be a eval uates whether the void spaces are smal l p otential for bio logical clogging. The system e nough to prevent solid s from being lost from des ign should include features that allow fo r the upstream materials. The third estimate s pipe system cleanings. The components o f the long-term clogging behavior of the filte r the cleaning system should include (U.S

. (U.S. EPA, 1989). EPA, 1991b):

! A minimum of six-inch diameter pipe s to facilitate cleaning; ! Ac cess located at major pip e intersections or bends to allow fo r inspections and cleaning; and

! V alves, po rts, or other appurtenances to in troduce biocides and/or cleanin g solutions. I n it s discussion of drainage layer protection, the following section includes furthe r information concerning protection of pipe s using filter layers. Protection of the High-Permeability Drainage Layer The openings in drainage materials, whethe r h oles in pipes, voids in gravel, or apertures in geon ets, must be protected against cloggin g b y accumulation

of fine (silt-sized) materials. An intermediate material that has smalle r openings than those of the drainage materia l can be used as a filter between the waste and drainage layer. Sand may be used as filte r mat erial, but has the disadvantage of takin g u p vertical space (USEPA, 1989). G eotextiles do not use up air space and can be used a s filter materials. Soil Filter Layers

Th e particle-size distribution of the drainag e s ystem and the particle-size distribution of the invading (or upstream) soils are requiredDesign Criteria

179 in th e design of granular soil (sand filter ) s pecifications should indicate the extent of the m a terials. The filter material should have its envelope. The construction quality contro l larg e and small size particles intermediat e prog ramshould document that the envelop e be tween the two extremes. Equations fo r was installed according to the plans an d adequate flow and retention are: specifications (U.S. EPA, 1988).

! Adequate Flow: A granular filter layer is generally place d d > (3 to 5)d u sing the same e arthmoving equipment as the 85 15 f d.s.

! Adequate Retention: should be checked by optical survey or b y d < (3 to 5)d d irect test pit measurement (U.S. EPA, 1988). 15 85 f w.f. Where f = required filter soil; This filter layer is the uppermost layer in the d.s. = drainage stone; and leachate collection system. A landfill design w.f. = water fines. o ption includes a buf fer layer, 12 inches thick There are no quantitative methods to asses s dr ainage layer from damage due to traffic

. so il filter clogging, although empirica l T his final layer can be general fill, as long as gu idelines are found in geotechnica l it is no finer than the soil used in the filte r engineering references. layer (U.S. EPA, 1988). However, if th e The specifications for granular filter layer s leachate recirculation attempts. that surround perforated pipe s and that protect the drainage layer fro m clogging are based on Geotextile Filter Layers a w ell-defined particle size distribution. The or ientation and configuration of filter layer s relat ive to other LCS components should b e shown on all drawings and should b e d escribed, with ranges of particle sizes, in the ma terials section of the specifications (U.S

. EPA, 1988a). T hickness is an im

portant placement criterion fo rgranular filter material. Generally, th e g ranular filter mater

ials will be placed around perforatedpipes by hand, forming a n "envelope." The dimensions of the envelope s hould be cl early stated on the drawings or in the s pecifications. This envelope can b e pla cedat the same time as the granular drain age layer, but it is important that th e fi lter envelope protect all areas of the pip e w here the clogging potential exist s. The plans and gra nular drainage layer. The final thicknes s

( 30 cm) or more, to protect th e filter layer and

laye rhas a low permeability, it will affec t

Geotextile filter fabrics are often used. Th e open spaces in the fabric allow liquid flo w while simultaneously preventing upstrea m fin e particles from fouling the drain

. Geot extiles save vertical space, are easy t o install, and have the added advantage o f r emaining stationary under load. Geotextiles al so can be used as cushioning material s above geomembranes (USEPA, 1989)

. Because geotextile filters are susceptible t o bio logical clogging, their use in area s inu ndatedby leachate (e.g., sumps, aroun d l eachate collection pipes, and t renches) should be avoided. Geotextile filter design parallels sand filte r design with some modifications (U.S. EPA , 198 9). Adequate flow is assessed b ySubpart D

180 co mparing the material (allowable ) t o the inside so that the glass b eads used in the permittivity to the design impose d tes tcannot escape around the edges of th e p ermittivity. Permittivity is measured by the g eotextile filter. The par ticle-size distribution ASTM D-4491 test method. The desig n of retained glass beads is compared to th e pe rmittivity utilizes an adapted form o f allow able value using any of a number o f D arcy's law. The resulting comparison yields existing formulas (U.S. EPA, 1989). a desi gn ratio, or factor of safety, that is th e focus of the design (U.S. EPA, 1989): T he third considerat ion in geotextile design is DR = ø /ø probl emthat may be adopted by ASTM i s

allow reqd called the Gradient Ratio Test. In this test , where: the hydraulic gradient of 1 inch of soil plu s ø = permittivity from ASTM the underlying geotextile is compa red with the allow D-4491 hydr aulic gradient of 2 inches of soil. Th e ø = (q/a) (1/h ) h ig her the gradient ratio, the more likely that reqd max q/a = inflow rate per unit area a clo g will occur. The final ASTM gradien t h = 12 inches ratio test will include failure criteria. A n

max T he second par

t of the geotextile filter design flow test that also is performed in a i s determining the opening size necessary for labo ratory. The test models a soil-to-fabri c retai ning the upstream soil or particulates i n system at the anticipated hydraulic gradient

. the leachate . It is well established that the 95 The flow rate through the system i s percent opening size is related to particles t o moni tored. A long-term flow rate wil l be re tained in the following type o f gra dually decrease until it stops altogethe r relationship: (U.S. EPA, 1989). O < fct. (d , CU, DR) Th e primary function of a geotextile is t o 95 50 where: leach ate pipes while allowing the passage o f O = 95% opening size of leachate. The most important specification s 95 geotextile; are those for hydraulic conductivity an d d = 50% size of upstream particles; reten tion. The hydraulic conductivity of th e 50 CU = Uniformity of the upstream geote xtile generally should be at least te n particle size; and t imes the soil it is retaining. An evaluation of DR = Relative density of the the retention ability f or loose soils is based on upstream particles. the a verage particle size of the soil and th e The O size of a geotextile in the equation is The maximum apparent opening size ,

95 the opening size at which 5 percent of a given sometimes called equivalent opening size, i s val ue should be less than the particle siz e d eterm ined by the size of the soil that will be cha racteristics of the invading materials. I n retained; a geotextile is then selected to meet the t est for the O size of the geotextile, a that specification. The material specifications 95 s ieve with a very coarse me sh in the bottom is s hould contain a range of AOS values for the u sed as a support. The

geotextile is placed on geotextile, and top of the mesh and is bonded lo ng-termclogging. A test method for thi s

alternative to this test method is a long-term

prevent the migration of fines into th e

apparent opening size (AOS) of the g eotextile.Design Criteria

181 these AOS v alues should match those used in o perati onal problems. Because they may run the design calculations (U.S. EPA, 1988). One o f the advantages of geotextiles is thei r li ght weight and ease of placement. Th e geo textiles are brought to the site, unrolled , an dheld down with sandbags until they ar e coveredwith a protective layer. They ar e u suallyoverlapped, not seamed; however, on s lopes or in other co nfigurations, they may be sewn (U.S. EPA, 1988). As wi th granular filter layers, it is importan t that the design drawings be clear in thei r d esignation of geotext

ile placement so that no potential route of pipe or drainage laye r c logging is left unprotecte d. If geotextiles are u se d on a slope, they should be secured in an an chor trench similar to those fo r g eomemb ranes or geonets (U.S. EPA, 1988). Leachate Removal System S umps, l ocated in a recess at the low point(s) within the leachate collection drainage layer, prov ide one method for leachate remova l from the MSWLF unit. In the past, lo w volume sumps have been constructe d s uccessfully from reinforced concrete pipe on a concrete footing, and supported above th e geomem brane on a steel plate to protect th e geomembrane from puncture. Recently , however, prefabricated polyethylen e structures have become available. Thes e stru ctures may be suitable for replacing th e concr ete components of the sump and hav e the advantage of being lighter in weight. These sumps typically house a submersibl e pu mp, which is positioned close to the sump floor to pump the leachate and to maintain a 30 cm (12 in) maximum leachate depth

. Low -volume sumps, however, can presen t dry frequently, there is an increase d p robability of the submersible pumps burning out. For this reason, some landfill operator s p refer to have sumps placed at dep ths between 1.0 an d 1.5 meters. While head levels of 3 0 cm or less are to be maintained on the liner , higher levels are acceptable in sumps

. A lternatively, the sump may be designed with level controls and with a backup pump t o c ontrol initia

tion and shut-off of the pumping seq uence and to have the capability o f alte rnating between the two pumps. Th e s econd pump also may be

used in conjunction w ith the primary pump during periods of high flow (e.g., following storm events) and as a b ackupif the primary pump fails to function. A visible alarm warning light to indicat e pump failure to the operator also may b e installed. Pumps used to remove leachate from th e sump s should be sized to ensure removal o f leachate at the maximum rate of generation

. Thes e pumps also should have a sufficien t operat ing head to lift the leachate to th e req uiredheight from the sump to the acces s port. Portable vacuum pumps can be used if the required lift height is within the limit o f the pump. They can be moved in sequenc e f rom one leachate sump to another. The type of p ump specified and the leachate sump a ccess pipes shou ld be compatible and should co nsider performance needs under operatin g and closure conditions (U.S. EPA, 1988). Alternative methods of leachate remova l include internal standpipes and pip e penetrations through the geomembrane, both of w hich allow leachate removal by gravity flow to either a leachate pond or exterio r p ump station. If a leacha

te removal standpipe is u sed, it should be extended through th e entire landfill from liner toSubpart D

182 cover an d then through the cover itself. If a sl iding material to tear the geomembran e gravity drainage pipe that require s geom embrane penetration is used, a hig h d egree of care shoul d be exercised in both the design and construction of the penetration

. The penetration should be designed an d cons tructedin a manner that allow s nondestructive quality control testing of 10 0 percent of the seal between the pipe and th e geomembrane. If not properly constructe d a nd fabricated, geomembrane penetr ations can be come a source of leakage through th e geomembrane. Other Design Considerations Th e stability of the individual leachat e collection system components placed o n geomembrane-coveredslopes should b e co nsidered. A method for calculating th e factor of safety (FS) against sliding for soil s placedon a sloped geomembrane surface i s provided in Koerner (1990). This metho d considers the factors affecting the system , including the slope length, the slope angle , and the friction angle between th e ge omembrane and its cover soil. Generally , th e slope angle is known and is specified o n the design drawings. A minimum FS is then selected. From the slope angle and the FS, a mi nimumallowable friction angle i s dete rmined, and the various components o f the li ner system are selected based on thi s minimum friction angle. If the desig n e valuation results in an unacceptably low FS, then either the sidewall slope or the materials shou ldbe changed to produce an adequat e d esign (U.S. EPA, 1988). For short slopes in a landfill unit, the FS can be as low as 1.1 to 1.2 if the slope will be unsupported (i.e., n o w aste will be fill ed against it) for only a short time, and if any failures that do occur can be repai redfairly easily. Longer slopes ma y require higher factors of safety due to th e potential of along the slope or near the toe of the slope. Construction Quality Assurance and Quality Control T he foll owing section is excerpted from U.S. EPA (1992). This section discusses quality assurance and quality control (QA/QC ) o bjectives. For a more detailed discussion on QA/ QC and specific considerations, refer t o U.S. EPA (1992). CQA/CQC Objectives Construction quality assurance (CQA ) consists of a planned series of observation s a nd tests to ensure that the fi nal product meets pro ject specifications. CQA plans , s pecifications, observations, and tests are used to provide quantitative criteria with which to accept the final product. On routine construction projects, CQA i s normal ly the concern of the owner and i s ob tainedusing an independent third-party te sting firm. The independence of the third

p arty inspection firm is important, particularly w hen the owner is a corpora tion or other legal e ntity that has under its corporate "umbrella" the c apacity to perform the CQA activities

. Although "in-house" CQA personnel may be r egistered professional engineers, a perception o f misrepresentation may exist if CQA is not performed by an independent third party. The CQA officer should fully disclose an y activities or relationships with the owne r that may impact his impartiality o r objectivity. If such activities o r relationships exist, the CQA officer should descr ibe actions that have been or can b e taken to avoid, mitigate, or neutralize th e po ssibility they might affect the CQ ADesign Criteria

183 officer's objectivity. Regulator y project plans and specifications , re presentatives can then evaluate whethe r the reby allowing the contractor t o t hese mechanisms are sufficient to ensure an correct the construction process if the acceptable CQA product. qua lity of the product is not meetin g Construction quality control (CQC) is a n on- going process of measuring an d • Construction Quality Assuranc e c ontrolling the characteristi cs of the product (CQ A) Testing by the Owne r in or der to meet manufacturer's or projec t ( Acceptance Inspe ction) performed by specifications. CQC is a production too l the owner usually through the third

that is employed by the manufacturer o f p arty testing firm, provides a measure m aterials and by the contractor ins talling the of the final product quality and it s m aterials a t the site. CQA, by contrast, is a conformance with project plans an d veri fication tool employed by the facilit y sp ecifications. Due to the size an d owner or regulatory agency to ensure tha t costs of a typical MSWLF uni t the materials and installations meet project co nstruction project, rejection of th e specifications. CQC is performe d project at completion would be costly inde pendently of the CQA Plan. Fo r t o al l parties. Acceptance Inspections example, while a geomembrane line r as p ortions of the project becom e ins taller will perform CQC testing of fiel d co mplete allow deficiencies to b e seams, the CQA program will requir e found and corrected before the y in dependent CQA testing of those sam e become too large and costly. seams by a third-party inspector. The CQA/CQC plans are implemente d pe rformed by a regulatory agency t o thr ough inspection activities that includ e e nsure tha t the final product conforms visual observations, field testing an d wit h all applicable codes an d measurements, laboratory testing, an d re gulations. In some cases, th e ev aluation of the test data. Inspectio n reg ulatory agency will use CQ A activities typically are concerned with four documentation and the as-built plan s separate functions: or "record drawings" to confir m

• Qua lity Control (QC) Inspection b y the Manufacturer provides an in

- Soil Liner Quality Assurance/Quality p rocess measure of t he product quality Control and its conformance with the projec t pla ns and specifications. Typically , Quality control testing performed o n the manufacturer will QC test result s m aterials used in construct ion of the landfill to certify that the product conforms to u nit includes source testing and construction project plans and specifications. tes ting. Source testing defines materia l

• Construction Quality Control (CQC ) S ource testing co mmonly includes moisture I n spection by the Contractor provides c ontent, soil dens ity, Atterberg limits, grain a n i n-process measure of construction s ize, and la boratory hydraulic conductivity. qua lity and conformance with th e Co nstruction testing ensures that landfil l the specifications and plans.

• Regulatory Inspection often i s

compliance with the regulations.

pro perties that govern material placement

.Subpart D

184 con struction has been performed i n Quality assurance testing for soil liner s accordance with the plans and technica l includes the same testing requirements a s sp ecifications. Construction testin g spe cified above for control testing

. generally includes tests of soil moistur e Gen erally, the tests are performed les s content, density, lift thickness, an d frequently and are performed by a n hydraulic conductivity. ind ividual or an entity independent of th e T he method of determining complia nce with qua lity assurance (CQA) officer ar e the maximum hydraulic conductivit y essential to document quality o f criterion should be specified in the QA/QC con struction. The CQA officer' s plan. Some methods have included the use responsibilities and those of the CQ A of th e criterion as a maximum value tha t officer's staff members may include: never should be exceeded, while othe r methods have used statistical techniques to ! Communicating with the contractor; esti mate the true mean. The sampl e co llection program should be designed t o ! Interpreting and clarifying projec t work with the method of complianc e dr awings and specifications with th e determination. Selection of sampl e designer, owner, and contractor; coll ection points should be made on a random basis. ! Recommending acceptance o r T hin wall sampling tube s generally are used wo rk completed by the constructio n to collect compacted clay samples fo r contractor; l aboratory hydraulic conducti vity testing. It i s im portant to minimize disturbance of the ! Submitting blind samples (e.g. , sample being collected. Tubes pushed into duplicates and blanks) for analysis by the soil by a backhoe may yield disturbe d the contractor's testing staff or one o r s amples. A recom mended procedure (when mo re independent laboratories, a s a backhoe is available during sampl e applicable; c ollection) is to use the backhoe bucket as a s tationary support and push t he tube into the c lay with a jack positio ned between the clay and the tube. The sample hole should b e filled with bentonite or a bentonite cla y mixture, and compacted using short lifts of material. If geophysical methods are used fo r moisture and density measurements, it i s recommended that alternative methods b e used less frequently to verify the accurac y of the faster geophysical methods

. Ad ditional information on testin g pro cedures can be found in U.S. EP A (1988b) and U.S. EPA (1990a). co ntractor. Activities of the constructio n

rejection by the owner/operator o f

! Notifying owner or operator o f construction quality problems no t resolved on-site in a timely manner;

! Ob serving the testing equipment , p ersonnel , and procedures used by the construction contractor to check fo r d etrimentally significant changes over time;

! Reviewing the c onstructio n c ont ractor's quality control recording, main tenance, summary, an d int erpretations of test data fo r accuracy and appropriateness; andDesign Criteria

185 ! Rep orting to the owner/operator o n b etween lifts or between placements in monitoring results. Soil Liner Pilot Construction (Test Fill) A pilot construction or test fill is a small

s cale test pad that can be used to verify that th e soil, equipment, and constructio n p rocedures can produce a liner that performs a c cording to the construction drawings and specifications. An owner or operator ma y want to consider the option of constructing a test fill prior to the construction of th e liner. A test pad is useful not only i n teaching people how to build a soil liner, it al so can function as a construction qualit y a ssurance tool. If the variables us ed to build a test pad that achieves a 1x10 cm/se c -7 hydraulic conductivity are f ollowed exactly, then the completed full-size liner shoul d me et the regulatory requirements (U.S

. EPA, 1989). A test fill may be a cost

effective method for the contractor t o evaluate the construction methods an d b orrow s ource. Specific factors that can be ex amined/tested during construction of a test fill include (U.S. EPA, 1988b):

! Pr eparation and compaction o f fo undation material to the require d bearing strength;

! Methods of controlling uniformity o f the soil material;

! Compactive effort (e.g., type o f equipment, number of passes) t o achieve required soil density an d hydraulic conductivity;

! Lift thickness and placemen t pro cedures to achieve uniformity o f den sity throughout a lift and th e absence of apparent boundary effect s the same lift;

! Pr ocedures for protecting agains t d esiccatio n cracking or other site- and s eason-specific failure me chanisms for t he finishe d liner or intermediate lifts;

! Measuring the hydraulic conductivit y on the test fill in the field an d c ollectin g samples of field-compacted soil for laboratory testing;

! Test procedures for controlling th e quality of construction;

! Abili ty of different types of soil t o me et hydraulic conductivit y requirements in the field; and

! Sk ill and competence of th e construction team, includin g equipment operators and qualit y control specialists. Geomembrane Quality Assurance/ Quality Control Testing As with the construction of soil liners , installation of geomembrane liners shoul d be in conformance with a qualit y as surance/quality control plan. Test s performed to evaluate the integrity o f ge omembrane seams are generall y con sidered to be either "destructive" o r "non-destructive." Destructive Testing Quality control testing of geomembrane s g ene rally includes peel and shear testing of scra p test weld sections prior t o commencing seaming activities and a t periodic intervals throughout the day

. Add itionally, destructive peel and shea r fieldSubpart D

186 te sts are performed on samples from th e se am or reseaming the affected area (U.S

. installed seams. E P A, 1988). In situations where the seams Quality assuranc e testing generally requires may have to be retrained. t hat an independent l aboratory perform peel and s hear tests of samples from installe d Non-Destructive Testing seams . The samples may be collecte d ra ndomly or in areas of suspect quality

. N on-destructive t est methods are conducted HDPE seams are generally tested a t in the field on an in-place geomembrane

. i ntervals equivalent to one sample per every These test methods determine the integrit y 300 to 400 feet of installed seam fo r of t he geomembrane field seams. Non

extr usion welds, and every 500 feet fo r dest ructive test methods include the prob e fusi on-welded seams. Extrusion seams o n test, air lance, vacuum box, ultrasoni c HD PE require grinding prior to welding , met hods (pulse echo, shadow an d which can greatly diminish parent material impedance plane), electrical spark test , strengths if excessive grinding occurs

. p ressurized dual seam, electrical resistivity, D etailed discussion of polyet hylene welding a nd hydrostatic tests. Detailed discussion of p rotocol can be fou nd in U.S. EPA (1991a). th ese test methods may be found in U.S

. For dual hot wedge seams in HDPE, bot h EPA (1991a). Seam sections that fai l the in ner and outer seam may be subjecte d ap propriate, non-destructive tests must b e to destruc tive shear tests at the independent carefully delineated, patched or reseamed , l aboratory. Destructive s amples of installed and retested. Large patches or reseame d seam welds are generally cut into severa l a reas should be subjected to destructive test pieces and distributed to: pro cedures for quality assurance purposes

.

! The installer to perform constructio n the degree to which non-destructive an d quality control field testing; dest ructive test methods will be used i n

! The owner/operator to retain an d appropriately catalog or archive; and

! An independent laboratory for pee l and shear testing. If the test results for a seam sample do no t pa ss the acceptance/rejection criteria, the n s amples are cut from the sa me field seam on both sides of the rejected sample location

. Sampl es are collected and tested until th e areal limits of the low quality seam ar e de fined. Corrective measures should b e u ndertaken t o repair the length of seam that has not passed the acceptance/rejectio n cri teria. In many cases, this involve s s eaming a cap over the length of th e rejected continually fail testing, the seaming crew s

The specifications should clearly describ e

e valuating failed portions of non -destructive seam tests. Geomembrane Construction Quality Assurance Activities Th e responsibilities of the constructio n qual ity assurance (CQA) personnel for th e installation of the geomembrane ar e g enerally the same as the respo nsibilities for the c onstruction of a soil liner with th e following additions:

! Observation of liner storage area an d line rs in storage, and handling of th e l iner as the panels are pos itioned in the cell;Design Criteria

187 ! Observation of seam overlap, seam they meet the construction plans an d preparation prior to seaming, an d specifications. These include (U.S. EPA , material underlying the liner; 1988):

! Observation of destructive testin g ! Geonets; c ond ucted on scrap test welds prior to seaming; ! Geotextiles;

! Observation of destructive sea m ! P i pe size, materials, and perforations; sam pling, submission of the sample s to an independent testing laboratory , ! Gr anular material gradation an d a nd revie w of results for conformance prefabricated structures (sumps , to specifications; manholes, etc.);

! Obs ervation of all seams and panel s ! M echanical, electrical , and monitoring fo r defects due to manufacturin g equipment; and and/or handling and placement;

! Obs ervation of all pipe penetratio n boots and welds in the liner; Th e leachate collection system foundatio n

! Preparation of reports indicatin g li ner) should be inspected and surveye d sampling conducted and samplin g up on its completion to ensure that it ha s results, locations of destructiv e pro per grading and is free of debris an d samples, locations of patches , liquids (U.S. EPA, 1988). locations of seams constructed, an d any problems encountered; and, During construction, the followin g

! Preparation of record drawings of th e obs erved and documented (U.S. EPA , liner installation, in some cases. 1988): T he last responsibility is frequentl y assigned ! Pi pe bedding placement includin g to the contractor, the owner's representative, q uality, thi ckness, and areal coverage; or the engineer. Leachate Collection System including material quality an d Construction Quality Assurance thickness; The purpose of leachate collection syste m CQ A is to document that the syste m cons truction is in accordance with th e d esign specifications. Prior to construction, a ll materials sh ould be inspected to confirm that ! Concrete forms and reinforcement.
(geomembrane or low permeability soi l

activities, as appropriate, should b e

! Granular filter layer placemen t

! Pipe installation including location , co nfiguration, grades, joints, filte r layer placement, and final flushing;

! Gr anular drainage layer placemen t in cluding protection of underlyin g liners, thickness, overlap with filterSubpart D

188 fabrics and geonets if applicable, an d 4.4 RELEVANT POINT OF weather conditions; COMPLIANCE

! Geonet placement including layout , o verlap, and protection from clogging 4.4.1 Statement of Regulation by granular material carried by win d or run-off during construction; (a) (See Statement of Regulation i n

! G eotextile/geofabric placemen t th e regulatory language for performance

including coverage and overlap; based design requirements.)

! Sumps and structure installation; and (b) (See Statement of Regulation i n

! Me chanical and electrical equipmen t installation including testing. I n addition to field observations , actual field a nd lab oratory testing may be performed to d ocument that the ma terials meet the design specifications. These activities should b e do cumented and should include th e following (U.S. EPA, 1988):

! Geo net and geotextile sampling an d testing;

! Gra nular drainage and filter laye r sa mpling and testing for grain siz e distribution; and

! Tes ting of pipes for leaks , obstructions, and alignments. Up on completion of construction, eac h comp onent should be inspected to identif y any damage that may have occurred during its installation, or during construction o f another component (e.g., pipe crushin g du ring placement of granular drainag e l ayer). Any damage that does occur should be repaired, and these corrective measure s should be documented in the CQA record s (U.S. EPA, 1988). 40 CFR §258.40(d)

Section 4. 2.1 of this guidance document for

Section 4. 3.1 of this guidance document for the regulatory language for requirement s pertaining to composite liner and leachat e collection systems.) (c ) (See Statement of Regulation i n Section 4. 2.1 of this guidance document for th e regulatory language for performance

based design requirements.) ( d) The relevant point o f compliance specified by the Director of an approved Sta te shall be no more than 150 meter s fro m the waste management uni t boundary and shall be located on land o wned by th e owner of the MSWLF unit. In d etermining the relevant point o f compliance, the State Director shal l consider at least the following factors: ( 1 ) The hydrogeologi c characteristics of the facility an d surrounding land; (2) The volume and physical an d chemical characteristics of the leachate; (3) The quantity, quality, an d direction of flow of ground water; (4) The proximity and withdrawa l rate of the ground-water users;Design Criteria

189 (5) The availability of alternativ e drinking water supplies; (6 ) The existing quality of th e g round water, including other sources of contamination and their cumulativ e i mpacts on the ground water and w hether the ground water is currently used o r reas onably expected to be used fo r drinking water; ( 7) Public health, safety, and welfare effects; and (8 ) Practicable capability of th e owner or operator. 4.4.2 Applicability In States with approved permit programs , o wners/op erators may have the opportunity to employ an alte rnative liner design, as per §258.40(a)(1). In these situations, som e flexibility is allowed in terms o f e stablishing a relevant point of compliance. The relevant point of compliance may b e l oc ated a maximum of 150 meters from the w aste management unit b oundary; however, the location must be on property owned by the MSWLF unit owner or operator. In u napproved States the relevant point o f compliance is set at the waste management u nit boundary. Th e waste management unit bound ary is defined as the vertical surfac e loc ated at the hydraulically downgradien t limit of the unit. This vertical surfac e ex tends down into and through the entir e thickness of the uppermost aquifer. 4.4.3 Technical Considerations At least eight factors should be considere d in establishing the relevant point of compliance for any design under §258.40

. The factors provide information needed t o determine if the alternative boundary i s s uff iciently protective of human health and t he environme nt and if the relevant point of co mpliance is adequate to measure th e performance of the disposal unit. Site Hydrogeology Th e first factor to be considered whe n de termining the relevant point o f compliance is site hydrogeology. Sit e hy drogeologic characteristics should b e us ed to identify additional informatio n required to set the relevant point o f compliance. The site data should b e su fficient to determine the lateral well

sp acing required to detect contaminan t releases to the uppermost aquifer

. Hydrogeologic information requ ired to fully cha racterize a site is presented in greate r detail in Section 5.6.3. Leachate Volume and Physical Characteristics Data on leachate volume and quality ar e need ed to make a determination of th e "det ectability" of leakage from the facilit y a t the relevant point of co mpliance. The net conc entration at any given point resultin g f rom the transport o f contaminants from the landfill is a function of contaminant type , initial contaminant concentration, an d leak age rate. Assessment of leachat e v olume is discussed in Sections 4.2 and 4.3. The assessment of contaminant fate an d transport was discussed in Section 4.3. Qua lity, Quantity and Direction o f Ground-Water Flow Th e hydrogeologic data collected shoul d provide information to assess the ground

water flow rate, ground-water flo wSubpart D

190 dir ection, and the volume of ground-wate r un it, should be determined prior t o flow. Background ground-water qualit y establishing the relevant point o f dat a should be used to establish baselin e compliance (see Section 5.6.3). Th e co ncentrations of the monitorin g performance standard for landfill desig n cons tituents. This information will b e req uires that landfill units be designed s o required as input to determine i f t hat the concentrations listed in Table 1 are con taminants from the landfill unit hav e not exceeded at a relevant point o f been released and have migrated to th e compliance. Issues for approved States t o relevant point of compliance. co nsider are whether the ground water i s Ground-Water Receptors be used as a drinking water source whe n The goal of establishing the relevant poin t th e ground water is not currently o r o f compliance is to ensure ea rly detection of r easonably expe cted to be used for drinking con tamination of the uppermost aquifer

. water, the State may allow the relevan t The distance to the relevant point o f point of compliance to be set near the 150- c ompliance shou ld allow sufficient time for meter limit. c orrective measures to be implemen ted prior to the migration of contaminants to private Public Health, Welfare, Safety or public water supply wells. E xisting users of

ground water immediately potential overall effect on public health , down gradient from the facility should b e w elfare, and safet y of the proposed relevant identi fied on a map. Users located at a po int of compliance. Issues that should b e downgradient point where contaminant s considered include: migh t be expected to migrate during th e active life and post-closure care period o f the facility should be identified. Alternative Drinking Water Supplies Con sideration should be given to th e availability of alternate drinking wate r supplies in the event of a ground-wate r con tamination problem. If the uppermos t aqu ifer is the sole water supply sourc e available, all reasonable efforts should b e mad e to locate the relevant point o f c ompliance as close as pos sible to the actual waste management unit boundary. Existing Ground-Water Quality Th e existing ground-water quality, bot h up gradient and downgradient of th e MSWLF currently used or is reasonably expected t o setting a relevant point of compliance. I f

Con sideration should be given to th e

! Distance to the nearest ground-wate r user or potentially affected surfac e water;

! The response time (based on th e distance to the propo sed relevant point of compliance) required to identif y and remediate or otherwise contai n ground water that may becom e impacted and potentially affec t downgradient water supplies; and

! T he risk that detection moni toring data may n ot be representative of a wors t c ase release of contam inants to ground water.Design Criteria

191 Practicable Capability of the Owner or 4.5 PETITION PROCESS Operator 40 CFR §258.40(e) I f the relevant point of

compliance is placed 4.5.1 Statement of Regulation far ther from the waste management uni t boundary, the volume of water requirin g (a) - (d) (See Statement of Regulation t reatm ent, should the ground water become in S ections 4.2.1, 4.3.1, and 4.4.1 of thi s c ontaminated, will increase. One o r more of gu idance document for regulator y the following conditions could affect th e language.) owner's or operator's practicable capability (technical and financial) to remediat e (e ) If EPA does not promulgate a contaminant releases: rul e establishing the procedures an d

! Area of impact, remedial costs, scope R CRA Sec tion 4005(c)(1)(B) by October of remedial investigation, and sit e 9, 1993, owners and operators i n characterization; unapproved States may utilize a desig n

! I n creased response time due to higher §2 58.40(a)(1) if the following condition s c ost s and increased technical scope of are met: selected remedial method;

! A reduction of the removal efficiency meets the performance standard i n of treatment technologies; and §258.40(a)(1);

! Increased difficulty in ground-wate r (2 ) The State petitions EPA t o extraction or containment if thes e review its determination; and technologies are chosen. T he Director may require some indica tion of d etermination or do es not disapprove the f inancial capability of the owner or operator determination within 30 days. to maintain a longer and more costl y remedial program due to the longe r [Note to Subpart D: 40 CFR Part 239 i s det ection time frame associated with a reserved to establish the procedures and relevant point of compliance located at a re quirements for State compliance wit h g reater distance from the waste management RCRA Section 4005(c)(1)(B).] uni t boundary. Additional information o n rem edial actions for ground water i s 4.5.2 Applicability provided in this document in Chapter 5. re quirements for State compliance wit h

mee ting the performance standard i n

(1) The State determines the design

(3 ) EPA approves the Stat e

I f EPA does not p romulgate procedures and requirements for state approval by October 9, 19 93, owners and operators of MSWL F units located in unapproved States may b e abl e to use an alternative design (i n compliance with §258.40(a)(1)) unde r certain circumstances.Subpart D

192 Owners or operators of MSWLF unit s sh ould contact the municipal solid wast e regulatory department in their State t o deter mine if their State has been approve d by the U.S. EPA.Design Criteria

193 4.6 FURTHER INFORMATION

4.6.1 REFERENCES (Specific to Performance-Based Design Assessment and Solute Transport Modeling) Abriola, L.M., and G.F. Pinder, (1985a). A Multiphase Approach to the Modeling of Porous M edia Contamination by Organic Compounds 1. Equation D evelopment. Water Resources Research 21(1):11-18. Abriola, L.M., and G.F. Pinder, (1985b). A Multiphase Approach to the Modeling of Porous M edia Contamination by Organic Comp ounds 2. Numerical Simulation. Water Resources Research 21(1):19-26. A ller, L., T. Bennett, J.H. Lehr, R.J. Petty, and G. H ackett, (1987). DRASTIC: A Standardized S ystem for Evaluation Ground Water Pollution Potential Using Hydrogeologic Settings. EPA-60 0/2-87-035, Kerr Environmental Research Lab, U.S. Environmental Protectio n Agency, Ada, Oklahoma. 455 pp. Auerbach, S.I., C. Andrews, D. Eyman, D.D. Huff, P.A. Palmer, and W.R. Uhte, (1984)

. Report of the Panel on Land Disposal. In: Disposal of Industrial and Domestic Wastes: La nd and Sea Alternatives. National Research Council. National Academy Press

. Washington, DC. pp. 73-100. Belj in, M.S., (1985). A Program Package of Analytical Models for Solute Transport i n G roundwater "SOLUTE". BAS15, International Groundwate r Modeling Center, Holcomb Research Institute, Butler University, Indianapolis, Indiana. 163 pp. B ond, F., and S. Hwang, (1988). Selection Criteria fo r Mathematical Models Used in Exposure A ssessments: Groun dwater Models. EPA/600/8-88/075, U.S. Environmental Protection Agency, Washington, DC. Boutwell, S .H., S.M. Brown, B.R. Roberts, and D.F. Atwood, (1986). Modeling Remedia l A ctions at Uncontrolled Hazardous Wa ste Sites. EPA/540/2-85/001, U.S. Environmental Protection Agency, Athens, Georgia. Cederber g, G.A., R.L. Street, and J.O. Leckie, (1985). A Groundwater Mass Transport an d E quilibrium Chemistry Model for Multicomponent Systems. Water Resources Research, 21(8):1095-1104. D ean, J.D., P.S. Huyakorn, A.S. Donigian, Jr., K.S. Voos, R.W. Schanz, Y.J.Meeks, and R.F. C arsel, (1989). Risk of Unsaturated/Saturate d Transport and Transformation of Chemical Concentrations (RUSTIC). EPA/600/3-89/048a, U.S. EPA, Athens, Georgia.Subpart D

194 de Marsily, G., (1986). Quantitative Hydrogeology: Groundwater Hydrology for Engineers. Academic Press, San Diego, California. 440 pp. Dillon, R.T. , R.M. Cranwell, R.B. Lantz, S.B. Pahwa, and D.S. Ward, (1978). Ris k Methodology for Geologic Disposal of Radioactive Waste: The Sandia Waste Isolation F low and Transport (SWIFT) model. Sand 78-1267/NUREG-CR-0424, Sandia national Laboratories, Albuquerque, New Mexico. Domeni co, P.A., and V.V. Palciauskas, (1982). Alternative Boundaries in Solid Wast e Management. Ground Water, 20(3):303-311. D omenico, P.A., and G.A. Robbi ns, (1985). A New Method for Contaminant Plume Analysis. Ground Water, 23(4):476-485. Donigian, A.S., and P.S.C. Rao, (1990). Selection, Application, and Validation o f E nvironmental Models. In : Proceedings of the International Symposium on Water Quality Mo deling of Agricultural Non-Point Sources, Part 2. D.G. DeCoursey (ed.). ARS-81 , U.S. Department of Agriculture Agricultural Research Services. pp. 577-600. Erdogen, H., and R.D. Heufeld, (1983). Modeling Leachates at Landfill Boundaries. Journal of Environmental Engineering, 109(5):1181-1194. F aust, C.R., J.H. G uswa, and J.W. Mercer, (1989). Simulation of Three-Dimensional Flow of I mmisci ble Fluids Within and Below the Unsaturated Zone. Water Resources Research, 25(12):2449-2464. F reeze, R.A., and J.A . Cherry, (1979). Ground Water. Prentice-Hall, Englewood Cliffs, New Jersey. 604 pp. GeoTrans , Inc., (1985). SWANFLOW: Simultaneous Water, Air and Non-Aqueous Phas e Flow, Version 1.0-Code Documentation. Herndon, Virginia. 97 pp. Grove, D.B., and K.G. Stollenwerk, (1987). Chemical Reactions Simulated by Groundwater Quality Models. Water Resources Bulletin, 23(4):601-615. G upta, S.K., C.R. Cole, C.T. Kin caid, and F.E. Kaszeta, (1982). Description and Applications o f the FE3 DGW and CFEST Three-dimensional Finite Element Models, Battelle Pacific NW Laboratories, Richland, Washington. Gupta, S .K., C.T. Kincaid, P. Meyer, C. Newbill, and C.R. Cole, (1982). CFEST : Multidi mensional Finite Element Code for the Analysis of Coupled Fluid, Energy an d S olut e Transport. PNL-4260, Battelle Pacific NW Laboratories, Richland, Washington.Design Criteria

195 Gureghian, A. B., D.S. Ward, and R.W. Cleary, (1980). A Finite Element Model for th e Mi gration of Leachate from a Sanitary Landfill in Long Island, New York - Part I : Theory. Water Resources Bulletin, 16(5):900-906. Guvan asen, V., (1984). Development of A Finite Element Code and Its Application t o G eoscience Rese arch. Proceedings 17th Information Meeting of the Nuclear Fuel Waste Manag ement Program, Atomic Energy of Canada, Ltd. Technical Record TR-199. pp

. 554-566. Haji-Dj afari, S., (1983). User's Manual GEOFLOW Groundwater Flow and Mass Transpor t Computer Program. D'Appolonia, Pittsburgh, Pennsylvania. Huyakor n, P.S. et al., (1984). Testing and Validation of Models for Simulating Solut e Tra nsport in Groundwater: Development, Evaluation and Comparison of Benchmar k Techniques. GWMI 84-13, International Groundwater Modeling Center, Holcom b Research Institute, Indianapolis, Indiana. Huyako rn, P.S., M.J. Ungs, L.A. Mulkey, and E.A. Sudicky, (1987). A Three-Dimensiona l Analytical Method for Predicting Leachate Migration. Ground Water, 25(5):588-598. Huyakorn, P.S., H.O. White, Jr., V.M. Guvanasen, and B.H. Lester, (1986). TRAFRAP: A Tw o-dimensional Finite Element Code for Simulating Fluid Flow and Transport o f R adionuclides in Fractured Porous M edia. FOS-33, International Groundwater Modeling Center, Holcomb Research Institute, Butler University, Indianapolis, Indiana. Javandel, I., C. Doughty, and C.F. Tsang, (1984). Groundwater Transport: Handbook o f Math ematical Models. Water Resources Monogram 10, American Geophysical Union , Washington, DC 228 pp. K eely, J.F., (1987). The Use of Models in Managing Gro und-Water Protection Programs. U.S. Environmental Protection Agency. EPA/600/8-87/003, Ada, Oklahoma. 72 pp. K e ely, J.F., (1989). Performance Evaluations of Pump-and-Treat Remediations. EPA/540/4- 89/005, U.S. Environmental Protection Agency, Ada, Oklahoma. 19 pp. Kin caid, C.T., J.R. Morrey, and J.E. Rogers, (1984a). Geohydrochemical Models for Solut e Migra tion- Volume 1: Process Description and Computer Code Selection. EA-3417 , Electric Power Research Institute, Palo Alto, California. Kinca id, C.T., J.R. Morrey, S.B. Yabusaki, A.R. Felmy, and J.E. Rogers, (1984b)

. Geo hydrochemical Models for Solute Migration- Volume 2: Preliminary Evaluation o f Se lected Computer Codes. EA-3417, Electric Power Research Institute, Palo Alto , California.Subpart D

196 K ipp, K.L., Jr., (1987). HST3D: A Computer Code for Simulation of Heat and Solute Transport in Th ree-Dimensional Groundwater Flow Systems. WRI 86-4095, U.S. Geologica l Survey, Lakewood, Colorado. Konikow , L.F., and J.D. Bredehoeft, (1985). Method-of-Characteristics Model for Solut e Transport (1985 revision). U.S. Geological Survey. Lindst rom, F.T., and L. Boersma, (1989). Analytical Solutions for Convective-Dispersiv e Transport in Confined Aquifers with Different Initial and Boundary Conditions. Wate r Resources Research, 25(2):241-256. Lu , J.C.S., B. Eichenberger, and R.J. Stearns, (1985). Leachate Migration from Municipa l Landfills. Pollution Technology Review No. 19. Noyes Publications, Park Ridge, New Jersey. 453 pp. Mercer, J.W., S.D. Thomas, and B. Ross, (1983). Parameters and Variables Appearing i n Repository Siting Models. NUREG/CR-3066. Prepared for U.S. Nuclear Regulator y Commission, Washington, DC. 244 pp. Mulkey, L.A., A.S. Donigian, Jr., T.L. Allison, and C.S. Raju, (1989). Evaluation of Source Term Initi al Conditions for Modeling Leachate Migration from Landfills. U.S. EPA , Athens, Georgia. N arasimhan, T.N., A.F. White, and T. To kunaga. 1986. Groundwater Contamination From an I nactive Uranium Mill Tailin gs Pile 2. Application of a Dynamic Mixing Model. Water Resources Research, 22(13):1820-1834. Nationa l Research Council, (1990). Ground Water Models: Scientific and Regulator y Applications. National Academy Press, Washington, DC. 320 pp. N e lson, R.W., and J.A. Schur, (1980). PATHS Groundwater Hydrologic Model. PNL-3162, Battelle Pacific NW Laboratories, Richland, Washington. Osborne, M., and J. Sykes, (1986). Numerical Modeling of Immiscible Organic Transport at the Hyde Park Landfill. Water Resources Research, 22(1):25-33. O stendor f, D.W., R.R. Noss, and D.O. Lederer, (1984). Landfill Leachate Migration through Shallow Unconfined Aquifers, Water Resources Research, 20(2):291-296. Oster, P. A. Review of Ground-Water Flow and Transport Models in the Unsaturated Zone , (19 82). NUREG/CR-2917, PNL-4427. Pacific Northwest Laboratory, Richland , Washington. P rakash, A., (1984). Groundwater C ontamination Due to Transient Sources of Pollution. J. of Hydraulic Engineering, 110(11):1642-1658.Design Criteria

197 P rickett , T.A., T.G. Naymik, and C.G. Lonnquist, (1981). A Random-Walk Solute Transport Model for Selected Groundwater Quality Evaluations. Bulletin 65, Illinois State Wate r Survey, Champaign, Illinois. R unchal, A.K. , (1985). PORFLOW: A General Purpose Model for Fluid Flow, Heat Transfer and Mass Transport in Anisotropic, Inhomogeneous, Equivalent Porous Media, Volume I: Theory, Volume II: User's Manual. ACRI/TN-O11. Analytic and Computationa l Research, Inc. West Los Angeles, California. Runchal, A.K., (1985). Theory and Application of the PORFLOW Model for Analysis o f Coupled Flow, Heat and Radionuclide Transport in Porous Media. Proceedings , international Symposium on Coupled Processes Affecting the Performance of a Nuclear Waste Repository, Berkeley, California. Salhotra, A.M., P. Mineart, S. Sharp-Hansen, and T. Allison, (1990). Multimedia Exposur e Asses sment Model (MULTIMED) for Evaluating the Land Disposal of Wastes--Mode l The ory. Prepared for U.S. Environmental Protection Agency, Environmental Researc h Laboratory, Athens, Georgia. Schroe der, A.C., A.C. Gibson, and M.D. Smolen, (1984). The Hydrologic Evaluation o f Lan dfill Performance (HELP) Model, Volumes I and II. EPA/530/SW-009 an d EPA/530/SW-010, U.S. Environmental Protection Agency, Cincinnati, Ohio. Sharp-H ansen, S., C. Travers, P. Hummel, and T. Allison, (1990). A Subtitle D Landfil l Ap plication Manual for the Multimedia Exposure Assessment Model (MULTIMED)

. Prepared for the U.S. EPA, Environmental Research Laboratory, Athens, Georgia. Sum mers, K.V., S.A. Gherini, M.M. Lang, M.J. Ungs, and K.J. Wilkinson, (1989). MYGR T Code Versi on 2.0: An IBM Code for Simulating Migration of Organic and Inorgani c Ch emicals in Groundwater. EN-6531. Electric Power Research Institute, Palo Alto , California. Temple, Barker and Sloane, Inc., (1988). Draft Regulatory Impact Analysis of Propose d Revisions to Subtitle D Criteria for Muni cipal Solid Waste Landfills. Prepared for Office of Solid Waste, U.S. Environmental Protection Agency. Thei s, T.L., D.J. Kirkner and A.A. Jennings, (1982). Multi-Solute Subsurface Transpor t M odeling for Energy S olid Wastes. Technical Progress Report for the Period September 1, 1981-August 31, 1982, COO-10253-3, Prepared for Ecological Research Division , Office of Health and Environmental Research, U.S. Department of Energy. T ravers, C.L., and S. Sharp-Hansen, (1991). Leachate Generation and Migration at Subtitle D F acilities: A Summary and Review of Processes and Mathematical Models. Prepared for U.S. EPA, Environmental Research Laboratory, Athens, Georgia.Subpart D

198 Travis , B., (1984). TRACR3D: A Model of Flow and Transport in Porous/Fractured Media

. LA-9667-MS. Los Alamos National Laboratory, Los Alamos, New Mexico. U nge, M.J. , K.V. Summers, and S.A. Gherini, (1986). MYGRT: An IBM Personal Computer Code for Simulation Solute Migration in Groundwater, User's Manual. EA-4545-CCM. Electric Power Research Institute, Palo Alto, California. U .S. EPA, (1988). Superfund Exposure Assessme nt Manual. EPA/540/1-88/001, Washington, DC. NTIS No. PB89-135859. 157 pp. U .S. EPA, (1993). Compilation of G round-Water Models; PB93-209401; U.S. EPA; Office of Solid Waste; Washington, D.C.

van der Heijde, P.K., Y. Bachmat, J. Bredehoeft, B. Andrews, D. Holtz, and S. Sebastian , (1985). Groundwater Management: The Use of Numerical Models. America n Geophysical Union, Washington, D.C.

v an der Heijde, P.K., and M.S. Beljin, (1988a). Model Assessment for Delineating Wellhead Protection Areas. EPA-440/6-88-002, U.S. EPA, Washington, DC.

v an der H eijde, P.K., El-Kadi, A.I., and S.A. Williams, (1988b). Groundwater Modeling: An Overview and Status Report. EPA/600/2-89/028, U.S. EPA, Ada, Oklahoma.

v an Genu chten, M.T., (1978). Simulation Models and Their Application to Landfill Disposal S iting; A Review of Curre nt Technology. In Land Disposal of Hazardous Wastes. EPA660/9-78-016, U.S. EPA, Cincinnati, Ohio.

van Genuchten, M.T., and W.J. Alves, (1982). Analytical Solutions of the One-Dimensional C onvective-Dispersive Solute Transp ort Equation. USDA, Technique Bulletin No. 1661. U.S. Department of Agriculture, Washington, DC. V ersar, Inc., (1987). Current and Suggested Practices in the Validatio n of Exposure Assessment Models, Draft Report. Prepared for U.S. EPA Office of Health and Environmenta l Assessme nt, Exposure Assessment Group, Washington, DC. EPA Contract No. 69-02

- 4254, Work Assignment No. 55. Voss, C .I., (1984). SUTRA: A Finite Element Simulation Model for Saturated-Unsaturate d Fluid Density-Dependent Groundwater Flow with Energy Transport or Chemicall y Reactive Single Species Solute Tran sport. Water Resources Investigations 84-4369, U.S. Geological Survey. W alton, W.C., (1984). 35 Basic Groundwater Model Programs for Desktop Microcomputers. G WMI 84-06/4, International Groundwater Modeling Center, Hol comb Research Institute, Butler University, Indianapolis, Indiana.Design Criteria

199 W eaver, J., C.G . Enfield, S. Yates, D. Kreamer, and D. White, (1989). Predicting Subsurface C ontaminant Transport and Transformation: Considerations for Model S election and Field Validation. U.S. EPA, Ada, Oklahoma. Yeh, G.T., (1981). AT123D: Analytical, Transient, One-, Two-, Three-Dimensiona l S imulation of Was te Transport in the Aquifer System. Publication No. 1439. Oak Ridge National Laboratory, Oak Ridge, Tennessee. Y eh, G.T., (1990). Use rs' Manual of a Three-Dimensional Hybrid Lagrangian-Eulerian Finite E lement Model of WASTE Transport through Saturated-Unsaturated Media. Pennsylvania State University, University Park, PA. Y eh, G.T., and D.S. Ward, (1981). FEMWASTE: A Finite-Elem ent Model of Waste Transport through Saturated-Unsaturated Porous Media. ORNL-5601. Oak Ridge Nationa l Laboratory, Oak Ridge, Tennessee. Yeh, G.T ., and D.S. Ward, (1987). FEMWATER: A Finite-Element Model of Water Flo w throu gh Saturated-Unsaturated Porous Media. ORNL-5567/R1. Oak Ridge Nationa l Laboratory, Oak Ridge, Tennessee.

4.6.2 REFERENCES (Specific to Design Criteria) ASCE, (1969). "Design and Construction of Sanitary and Storm Sewers"; ASCE Manual o n Engineering Practice; No. 37. Bear , Jacob and Arnold Veruijt, (1987). "Modeling Groundwater Flow and Pollution"; D

. Reidel Publishing Company; Dordracht, Holland. B enson, Craig H. and David E. Daniel, (199 0). "Influence of Clods on Hydraulic Conductivity o f C ompacted Clay"; Journal of Geotechnical Engineering; Volume 116, No. 8; August, 1990. Bonaparte, R. and Gross, B.A., (1990). "Field Behavior of Double-Liner Systems. In Waste Containment Systems: Construction, Regulation, and Performance, Edited by R

. Bonaparte. Geotechnical Pub 1.26, ASCE. Carroll, Jr., R.G., (1987). "Hydraulic Properties of Geotextiles." Geotextile Testing and the D esign Engineers, ASTEM 952, American Society for Testing and Materials, Philadelphia, PA, pp 7-20. C OE, (1970). "Laboratory Soils Testing"; EM1110-2-1906; Headquarters, Department of the Army; Office of the Chief of Engineers; Washington, DC 20314.Subpart D

200 FHWA, (1985). "FHWA Geotextile Engineering Manual." Contract No.l DTF H61-83-C

00150. FH WA, (1990). "Geotextile Design & Construction Guidelines. Contract No. FHW A DTFH61-86-C-00102. GCA Corporation, (1983). "Draft Permit Writers' Guidance Manual for Hazardous Wast e Treatment, Storage, and Disposal Facility"; 1983. G iroud, J.P., (1982). "Filter Criteria for Geotextiles ," Proceeding 2nd International Conference on Geotextiles, Las Vegas, Nevada. Giroud, J .P. and R. Bonaparte, (1989). "Leakage Through Liners Constructed wit h Ge omembranes - Part I: Geomembrane Liners"; Geotextiles and Geomembranes 8(2) ; 0266-1144/89; pp. 27-67; Elsevier Science Publishers Ltd., England, Great Britain. Giroud, J .P. and R. Bonaparte, (1989). "Leakage Through Liners Constructed wit h G eomembranes - Part II: Composite Liners" ; Geotextiles and Geomembranes 8(2); 0266- 1144/89; pp. 71-111; Elsevier Science Publishers Ltd., England, Great Britain. G iroud, J.P., A. Khatami and K. Badu-Tweneboah, (1989). "Te chnical Note - Evaluation of the Rate of Leakage Through Composite Liners"; Geotextiles and Geomembranes 8; 0266

- 1144/89; pp. 337-340; Elsevier Science Publishers Ltd., England, Great Britain. Haxo, H.E., Jr., (1983). "Analysis and Fingerprinting of Unexposed and Exposed Polymeric M embrane Line rs"; Proceedings of Ninth Annual Research Symposium: Land Disposal, Incine ration, and Treatment of Hazardous Waste; EPA/600/9-83/018; U.S. EPA ; Cincinnati, Ohio. H axo, H.E., Jr., J.A. Miedema and H.A. Nelson, (1984). "Permeabili ty of Polymeric Membrane Li ning Materials"; Matrecon, Inc.; Oakland, California; International Conference o n Geomembranes; Denver, Colorado. Industri al Fabrics Association International (1990). "1991 Specifiers Guide;" Geotechnica l Fabrics Report, Volume 8, No. 7, 1990. Jav endale, I., C. Doughty and C.F. Tsang, (1984). "Groundwater Transport; Handbook o f Mathematical Models"; American Geophysical Union; Washington, DC 20009. Jayawickra ma, P.W., K.W. Brown, J.C. Thomas and R.L. Lytton, (1988). "Leakage Rate s Through Flaws in Membrane Liners"; Journal of Environmental Engineering; Vol. 114, No. 6; December, 1988.Design Criteria

201 K astman, Kenneth A., (1984). "Hazardous Waste Landfill Geomembrane: Design, Installation and Monitoring"; Woodward-Clyde Consultants, Chicago, Illinois; Internationa l Conference on Geomembranes; Denver, Colorado. Koe rner, Robert M., (1990). "Designing with Geosynthetics"; 2nd Edition; Prentice Hall ; Englewood-Cliffs, New Jersey 07632.

R adian Corporation, (1987). "T echnical Data Summary: Hydraulic Performance of Minimum Technology Double Liner Systems"; Radian Corporation; Austin, Texas 78766 for U.S. EPA; Contract No. 68-01-7310; Task 7-4. U.S. EPA, (1982). "Landfill and Surface Impoundment Performance Evaluation"; SW-869 ; Charles A. Moore; U.S. EPA. NTIS PB-81-166357. U.S. EPA, (1983). "Lining of Waste Impoundment and Disposal Facilities"; SW-870; U.S

. E PA; Office of Solid Waste and Emergency Response; Washington, D C 20460. NTIS PB81-166365 Revised: PB-86-192796. U.S. EPA, (1987a). "Background Document on Bottom Liner Performance in Double-Lined L andfills and Surface Impoundments"; EPA/530/SW-87/013; U.S. EPA; Washington, DC. NTIS PB-87-182291. U.S. EPA , (1987b) " Characterization of MWC Ashes and Leachates from MSW Landfills , M onofills and Co-Disposal Site s: Volume VI of VII ; Characterization of Leachates from Mun icipal Solid Waste Disposal Sites and Co-Disposal Sites"; EPA/530/SW-87/028F , Washington, D.C. NTIS PB-88-127998. U .S. EPA, (1988). "Guide to Technic al Resources for the Design of Land Disposal Facilities"; EPA/625/6-88/018; U.S. EPA; Risk Reduction Engineering Laboratory; Center fo r Environmental Research Information; Cincinnati, Ohio 45268. U .S. EPA, (1988a). Superfund Exposure Assessment Manual. EPA/540/1- 88/001, Washington, D.C., NTIS No. PB89-135.859, 157 pp. U.S. EP A, (1988b). "Design, Construction and Evaluation of Clay Liners for Wast e Management Facilities; EPA/530/SW-86/007F; U.S. EPA; Office of Solid Waste an d Emergency Response; Washington, DC 20460. NTIS PB-86-184496. U.S. EPA, (1988c). "Groundwater Modeling: An Overview and Status Report"; EPA/ 600/2-89/028; U.S. EPA; Environmental Research Laboratory; Ada, Oklahom a 74820. NTIS PB-89-224497.Subpart D

202 U.S. EPA, (1988d). "Multimedia Exposure Assessment Model for Evaluating the Lan d D isposal of Hazardous Wastes, Volume I."; Woodward-Clyde Consultants, Oakland, CA 9 4607 -4014 for U.S. EPA; Environmental Research Laboratory; Office of Research and Development; Athens, Georgia 30613. U.S. EP A, (1988e). "Lining of Waste Containment and Other Impoundment Facilities" ; E PA/600/2-88/052; U.S. EPA; Risk Reduction Engineering Laborato ries; Cincinnati, Ohio 45268. NTIS PB-89-129670. U .S. EPA, (1989). "Seminar Publication - Requiremen ts for Hazardous Waste Landfill Design, Constru ction and Closure"; EPA/625/4-89/022; U.S. EPA; Center for Environmenta l Research Information; Office of Research and Development; Cincinnati, Ohio 45268. U .S. E PA, (1990a). "Seminars - Design and Construction of RCRA/CERCLA Final Covers", CERI 90-50; U.S. EPA; Office of Research and Development; Washington, DC 20460. U .S. EPA, (1990b). "Draft - LDCRS Flow Data from Operating Units - Technical Support for Proposed Liner/Leak Detection System Rule"; Geoservices, Inc. Consulting Engineers ; Norcross, Georgia 30093. U.S. EP A, (1990c). "Relationship of Laboratory- and Field-Determined Hydrauli c C onductivit y in Compacted Clay Layer"; EPA/600/2-90/025; U.S. EPA; Risk Reduction Engineering Laboratory; Cincinnati, Ohio 45268. NTIS PB-90-257775. U .S. EPA, (1991a). "Technical Guidance Document: Inspection Techniques for the Fabrication of Geomembrane Field Seams"; EPA 530/SW-91/051, May 1991, Cincinnati, Ohio. U.S. EPA, (1991b). "Landfill Leachate Clogging of Geotextiles (and Soil) Filters"; EPA/600/2-91/025, August 1991; Risk Reduction Engineering Laboratory; Cincinnati, Ohio, 45268. NTIS PB-91-213660. U.S. EPA, (1992). "Technical Guidance Document: Construction Quality Management for R emedial Action and Remedial Design Waste Containmen t Systems"; EPA/540/R-92/073, October 1992; Risk Reduction Engineering Laboratory, Cincinnati, Ohio 45268 an d Technology Innovation Office, Washington, D.C. 20460. 4.6.3 Models List of Contacts for Obtaining Leachate Generation and Leachate Migration Models Center for Exposure Assessment Modeling (CEAM), U.S. EPA, Office of Research and Development, Environmental Research Laboratory, Athens, Georgia 30605-2720, Model Distribution Coordinator (706) 546-3549, Electronic Bulletin Board System (706) 546-3402: MULTIMED, PRZM, FEMWATER/FEMWASTE, LEWASTE/3DLEWASTEDesign Criteria

203 Electric Power Research Institute, Palo Alto, California, (214) 655-8883: MYGRT, FASTCHEM Geo-Trans Inc., 46050 Manekin Plaza, Suite 100, Sterling, VA 20166, (703) 444-7000: SWANFLOW, SWIFT, SWIFT II, SWIFT III, SWIFT/386. Geraghty & Miller, Inc., Modeling Group, 10700 Parkridge Boulevard, Suite 600 Reston, VA 22091: MODFLOW , MODPATH , MOC , SUTRA , Quickflow, 386 386 386 386 International Groundwater Modeling Center, Colorado School of Mines, Golden, Colorado (303) 273-3103: SOLUTE, Walton35, SEFTRAN, TRAFRAP, National Technical Information Services (NTIS), 5285 Port Royal Road, Springfield, VA 22161, (703) 487-4650: HELP Dr. Zubair Saleem, U.S. EPA, 401 M Street SW, Washington, DC, 20460, (202) 260-4767: EPACML, VHS Scientific Software Group, P.O. Box 23041, Washington, DC 20026-3041 (703) 620-9214: HST3D, MODFLOW, MOC, SUTRA, AQUA, SWIMEV.

# CHAPTER 5 SUBPART E GROUND-WATER MONITORING AND CORRECTIVE ACTION206 CHAPTER 5 SUBPART E TABLE OF CONTENTS 5.1 INTRODUCTION

................................................... 211 5.2 APPLICABILITY 40 CFR §258.50 (a) & (b)

.............................. 211 5.2.1 Statement of Regulation

.......................................... 211 5.2.2 Applicability

.................................................. 212 5.2.3 Technical Considerations

......................................... 212 5.3 COMPLIANCE SCHEDULE 40 CFR § 258.50 (c)

.......................... 214 5.3.1 Statement of Regulation

.......................................... 214 5.3.2 Applicability

.................................................. 214 5.3.3 Technical Considerations

......................................... 214 5.4 ALTERNATIVE COMPLIANCE SCHEDULES 40 CFR 258.50 (d)(e) & (g)

..... 215 5.4.1 Statement of Regulation

.......................................... 215 5.4.2 Applicability

.................................................. 216 5.4.3 Technical Considerations

......................................... 217 5.5 QUALIFICATIONS 40 CFR 258.50 (f)

.................................. 217 5.5.1 Statement of Regulation

.......................................... 217 5.5.2 Applicability

.................................................. 218 5.5.3 Technical Considerations

......................................... 218 5.6 GROUND-WATER MONITORING SYSTEMS 40 CFR §258.51 (a)(b)(d)

....... 219 5.6.1 Statement of Regulation

.......................................... 219 5.6.2 Applicability

.................................................. 220 5.6.3 Technical Considerations

......................................... 221 Uppermost Aquifer

............................................ 221 Determination of Background Ground-Water Quality

.................. 221 Multi-Unit Monitoring Systems

................................... 222 Hydrogeological Characterization

................................. 224 Characterizing Site Geology

...................................... 225 Monitoring Well Placement

...................................... 235207

5.7 G ROUND-WATER MONITORING WELL DESIGN AND CONSTRUCTION 40 CFR §258.51 (c)

.................................................... 241 5.7.1 Statement of Regulation

.......................................... 241 5.7.2 Applicability

.................................................. 241 5.7.3 Technical Considerations

......................................... 241 Monitoring Well Design

......................................... 244 Well Casing

............................................ 244 Filter Pack Design

....................................... 248 Surface Completion

...................................... 250 5.8 GROUND-WATER SAMPLING AND ANALYSIS REQUIREMENTS 40 CFR §258.53

.................................................... 253 5.8.1 Statement of Regulation

.......................................... 253 5.8.2 Applicability

.................................................. 254 5.8.3 Technical Considerations

......................................... 255 Sample Collection

............................................. 255 Frequency

.............................................. 255 Water Level Measurements

................................ 256 Well Purging

........................................... 256 Field Analyses

.......................................... 258 Sample Withdrawal and Collection

........................... 258 Sample Preservation and Handling

................................. 260 Sample Containers

....................................... 262 Sample Preservation

...................................... 262 Sample Storage and Shipment

.............................. 262 Chain-of-Custody Record

........................................ 263 Sample Labels

.......................................... 263 Sample Custody Seal

..................................... 264 Field Logbook

.......................................... 264 Sample Analysis Request Sheet

............................. 265 Laboratory Records

...................................... 265 Analytical Procedures

.......................................... 265 Quality Assurance/Quality Control

................................. 266 Field Quality Assurance/Quality Control

...................... 266 Validation

.............................................. 267 Documentation

................................................ 268208

5.9 STATISTICAL ANALYSIS 40 CFR §258.53 (g)-(i)

........................ 268 5.9.1 Statement of Regulation

.......................................... 268 5.9.2 Applicability

.................................................. 270 5.9.3 Technical Considerations

........................................ 271 Multiple Well Comparisons

...................................... 272 Tolerance and Prediction Intervals

................................. 273 Individual Well Comparisons

..................................... 274 Intra-Well Comparisons

......................................... 274 Treatment of Non-Detects

....................................... 274 5.10 DETECTION MONITORING PROGRAM 40 CFR §258.54

.................. 274 5.10.1 Statement of Regulation

......................................... 274 5.10.2 Applicability

................................................. 276 5.10.3 Technical Considerations

........................................ 277 Independent Sampling for Background

............................. 277 Alternative List/Removal of Parameters

............................. 279 Alternative Frequency

.......................................... 279 Notification

.................................................. 280 Demonstrations of Other Reasons For Statistical Increase

............... 280 Demonstrations of Other Sources of Error

........................... 281 5.11 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(a)-(f)

............ 281 5.11.1 Statement of Regulation

......................................... 281 5.11.2 Applicability

................................................. 283 5.11.3 Technical Considerations

........................................ 285 Alternative List

............................................... 285 Alternative Frequency

.......................................... 285 5.12 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(g)

.............. 286 5.12.1 Statement of Regulation

......................................... 286 5.12.2 Applicability

................................................. 287 5.12.3 Technical Considerations

........................................ 287 Release Investigation

........................................... 288 Property Boundary Monitoring Well

............................... 288 Notification of Adjoining Residents and Property Owners

.............. 288 Demonstrations of Other Sources of Error

........................... 288 Return to Detection Monitoring

................................... 289 5.13 ASSESSMENT MONITORING PROGRAM 40 CFR §258.55(h)-(j)

............ 289 5.13.1 Statement of Regulation

......................................... 289 5.13.2 Applicability

................................................. 290 5.13.3 Technical Considerations

........................................ 290209

5.14 ASSESSMENT OF CORRECTIVE MEASURES 40 CFR §258.56

............. 291 5.14.1 Statement of Regulation

......................................... 291 5.14.2 Applicability

................................................. 291 5.14.3 Technical Considerations

........................................ 291 Source Evaluation

............................................. 292 Plume Delineation

....................................... 292 Ground-Water Assessment

....................................... 294 Corrective Measures Assessment

.................................. 295 Active Restoration

............................................. 296 Plume Containment

............................................ 297 Source Control

................................................ 298 Public Participation

............................................ 298 5.15 SELECTION OF REMEDY 40 CFR §258.57 (a)-(b)

........................ 298 5.15.1 Statement of Regulation

......................................... 298 5.15.2 Applicability

................................................. 299 5.15.3 Technical Considerations

........................................ 299 5.16 SELECTION OF REMEDY 40 CFR §258.57 (c)

........................... 299 5.16.1 Statement of Regulation

......................................... 299 5.16.2 Applicability

................................................. 300 5.16.3 Technical Considerations

........................................ 301 Effectiveness of Corrective Action

................................. 301 Effectiveness of Source Reduction

................................. 302 Implementation of Remedial Action

................................ 302 Practical Capability

...................................... 302 Community Concerns

........................................... 303 5.17 SELECTION OF REMEDY 40 CFR §258.57 (d)

........................... 303 5.17.1 Statement of Regulation

......................................... 303 5.17.2 Applicability

................................................. 304 5.17.3 Technical Considerations

........................................ 304 5.18 SELECTION OF REMEDY 40 CFR §258.57 (e)-(f)

......................... 305 5.18.1 Statement of Regulation

......................................... 305 5.18.2 Applicability

................................................. 306 5.18.3 Technical Considerations

........................................ 306210

5.19 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 40 CFR §258.58 (a)

.................................................. 307 5.19.1 Statement of Regulation

......................................... 307 5.19.2 Applicability

................................................. 308 5.19.3 Technical Considerations

........................................ 308 Monitoring Activities

........................................... 308 Interim Measures

.............................................. 308 5.20 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 40 CFR §258.58 (b)-(d)

............................................... 309 5.20.1 Statement of Regulation

......................................... 309 5.20.2 Applicability

................................................. 309 5.20.3 Technical Considerations

........................................ 310 5.21 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 40 CFR §258.58 (e)-(g)

............................................... 311 5.21.1 Statement of Regulation

......................................... 311 5.21.2 Applicability

................................................. 311 5.21.3 Technical Considerations

........................................ 312 5.22 FURTHER INFORMATION

............................................ 313 5.22.1 References

................................................... 313211 

### CHAPTER 5 SUBPART E GROUND-WATER MONITORING AND CORRECTIVE ACTION

5.1 INTRODUCTION
T he Criteria e stablish ground-water monitoring and corrective action requirements for all existing and new MSW LF units and lateral expansions of existing units except where the Director of a n approve dState suspends the requirements because there is no potential for migration of leachat e constituents from the unit to the uppermost aquifer. The Criteria include requirements for th e l ocation, design, and installation of groun d-water monitoring systems and set standards for groundw ater sampling and analysis. They also provide specific statistical methods and decision criteria for identifying a significant change in ground-water quality. If a significant change in ground-water q uality occurs, the Criteria require an assessment of the nature a nd extent of contamination followed by an evaluation and implementation of remedial measures. Porti ons of this chapter are based on a draft technical document developed for EPA's hazardou s waste program. This document, "RCRA Ground-Water Monitoring: Draft Technical Guidance" (EPA/530-R-93-001), is undergoing internal review, and may change. EPA chose to incorporate the information from the draft document into this chapter because the draft contained the mos t recent information available. 5.2 APPLICABILITY act ive life of the unit and the post-closur e 40 CFR §258.50 (a) & (b) care period. This demonstration must b e 5.2.1 Statement of Regulation scientist and approved by the Director o f ( a) The requirements in this Part apply to upon: MSW LF units, except as provided i n paragraph (b) of this section. (1) Site-specific field collecte d (b) Ground-water monitorin g physical, chemical, and biologic al processes requirements under §258.51 throug h aff ecting contaminant fate and transport , §258.55 of this Part may be suspended b y and the Director of an approved State for a M SWLF u nit if the owner or operator can (2) Contaminant fate and transpor t demon strate that there is no potential fo r pr edictions that maximize contaminan t mi gration of hazardous constituents fro m migration and consider impacts on human th atMSWLF unit to the uppermos t health and environment. aquifer (as defined in §258.2) during the ce rtified by a qualified ground-wate r

an approved State, and must be base d

me asurements, sampling, and analysis o fSubpart E

212 5.2.2 Applicability §258 .51 through §258.55 if the owner o r Th e ground-water monitoring requirement s app ly to all existing MSWLF units, latera l expa nsions of existing units, and ne w MSWLF units that receive waste afte r Octo ber 9, 1993. The requirements fo r g round-water monitoring may be suspended if the Director of an approved State finds that no pote ntial exists for migration of hazardou s constituents from the MSWLF unit to th e u ppermost aquifer during t he active life of the un it, including closure or post-closure car e periods. The "no potential for migration" demonstra

t ion must be based upon site-sp ecific informati on relevant to the fate and transport of an y hazardous constituents that may be expecte d t o b e released from the unit. The predictions of f ate and transport must identify the max

imumanticipated concentrations of constitu

en ts migrating to the uppermost aquifer s o tha ta protective assessment of the potentia l effects to human health and the environmen t can b e made. A successful demonstratio n co uldexempt the MSWLF unit fro m re quirements of §§258.51 through 258.55 , which include installation of ground-wate r monitoring systems, and sampling an d an alysis for both detection and assessmen t mo nitoring constituents. Preparing No

Migration Demonstrations for Municipa l Solid Waste Disposal Facilities-Screenin g To ol is a guidance document describing a process owners/ operators can use to prepare a no-migration demonstration (NMD ) requesting suspension of the ground-wate r monitoring requirements. 5.2.3 Technical Considerations A ll MSWLF units that receive waste after the eff ective date of Part 258 must comply with the ground-water monitoring requirements. Th e Director of an approved State ma y ex empt an owner/operator from the ground

water monitoring requirements at op erator demonstrates that there is n o potenti al for hazardous constituent migration to the uppermost aquifer throughout th e operating, closure, and post-closure car e perio ds of the unit. Owners and operators of MSWLFs not

located in approved States will no tbe eligible for this waiver and will b e requiredto comply with all ground-wate r monitoring requirements. The "no- migration" demonstration must be certifie d by a qualified gro und-water

scientist and approved by th e Direc torof an approved State. It must b e based on site-specific field measurements and sa mpling and analyses to determine th e physical, chemical, and biological processe s aff ecting the fate and transport of hazardou s constituents. The demonstration must b e supported by site-specific data and predictions of the maximum contaminant migration

. Sit e-specific information must include, at a minimum, the information necessary t o eval uate or interpret the effects of th e fo llowing properties or processes o n contaminant fate and transport: Physical Properties or Processes:

! Aquifer

Characteristics , includin g hydraulic conductivity, hyd raulic gradient, ef fective porosity, aquifer thickness, de

gree of saturation, stratigraphy, degree of frac turing and secondary porosity of soils and bedrock, aquifer heterogeneity , ground-water discharge, a

nd ground-water recharge areas;

! Waste Ch aracteristics , including quantity, typ e, and origin (e.g., commercial , industrial, or small quantity generators of unregulated hazardous wastes);Ground-Water Monitoring and Corrective Action

213 ! Climatic Conditions , including annua l transport should be biased toward over

precipitation, leachate generatio n estimating transport and the anticipate d estimates, and effects on leachat e concentrations. Assumptions and sit e quality; spec ific data that are used in the fate an d

! Leachate Characteristics , includin g transport principles and processes , l eachate composition, solu bility, density, in cluding adherence to mass-balance an d t he presence of immiscible constituents, chemical equilibria limitations. Withi n Eh, and pH; and these physicochemical limitations ,

! En gineered Controls , including liners , objective of assessing the maximu m c over systems, and aquifer controls (e.g., potential impact on human health and th e l owerin g the water table). These should env ironment. The evaluation of site

be evaluated under design and failur e specific data and assumptions may includ e co nditions to estimate their long-ter m some of the following approaches: residual performance. Chemical Properties or Processes: par ameters and conditions that wil l

! Attenuation of contaminants in th e hydraulic conductivity, effectiv e subsurface, including adsorption / porosity, horizontal and vertica l de sorption reactions, ion exchange , gradients), rather than average values organic content of soil, soil water pH , an d consideration of possible reaction s ! Use of the lower r ange of known aquifer causing chemical transformation o r con ditions and parameters that tend t o chelation. attenuate or retard con taminant transport Biological Processes: cation exchange capacities, organi c

! M icrobiological Degradation , w hich may conditions), rather than average values attenuate target compounds or caus e transformations of compounds , ! Consideration of the cumulative impacts p otentially forming more toxic chemical on water quality, in cluding both existing species. water quality data and cumulative health The alternative design section of Chapte r likely to migrate from the MSWLF unit 5 .0 di scusses these and other processes that and other potential or known sources. a ffect contaminant fate and solute transport. When owners or operators prepare a no

- for evaluating contaminant or solut e mig ration demonstration, they must us e transport is provided in Chapter 5. pred ictions that are based on maximu m contaminant migration both from the uni t and through the subsurface media

. As sumptions about variables affectin g tr ansport predictions should conform wit h

ass umptions should be biased toward th e

! Use of the upper bound of known aquifer

ma ximize contaminant transport (e.g. ,

(e .g., dispersivities, decay coefficients ,
ca rbon contents, and recharg e

risks posed by hazardous constituent s

A discussion of mathematical approache sSubpart E

214 5.3 COMPLIANCE SCHEDULE (4) New MSWLF units must be i n 40 CFR § 258.50 (c) co mpliance with the ground-wate r 5.3.1 Statement of Regulation * §§2 58.51 - 258.55 before waste can b e

* [NOTE: EPA finalized several revisions to 4 0 CFR Part 258 on October 1, 199 3 5.3.2 Applicability (5 8 FR 51536), and these revisions dela y the e ffective date for some categories o f The rule establishes a self-implementin g land fills. More detail on the content o f schedule for owners or operators in State s th e revisions is included in th e with programs that are deemed inadequat e introduction.] or not yet approved. As indicated in th e (c ) Owners and operators of MSWL F depends on the distance of the MSWLF unit u nits must comply with th e ground-water from drinking water sources. Approve d mo nitoring requirements of this par t St ates may specify an alternative schedul e a ccording to the following schedul e unless un der §258.50 (d), which is discussed i n a n alternative sc hedule is specified under Section 5.4. paragraph (d): (1) Existing MSWLF units and latera l than one mile from a drinking water intake expan sions less than one mile from a mus t be in compliance with the ground

drinking water intake (surface o r water monitoring requirements by October subsurface) must be in compliance wit h 9, 1994 . If the units are greater than on e the ground-water monitorin g mile but less than two miles fr om a drinking requirements specified in §§258.51 - water intake, they must be in compliance by 258.55 by October 9, 1994; October 9 , 1995. Those units located more (2) Existing MSWLF units and latera l mu st be in compliance by October 9, 199 6 expansions gre ater than one mile but less (see Table 5-1). than two miles from a drinking wate r i ntake (surf

ace or subsurface) must be in New MSWLF units, defined as units tha t compliance with the ground-wate r have not received waste prior to October 9, mo nitoring requirements specified i n 19 93, must be in compliance with thes e §§258.51 - 258.55 by October 9, 1995; requirements before receiving wast e (3) Existing MSWLF units and latera l supply intake. expansions greater than two miles from a drinking water intake (surface o r 5.3.3 Technical Considerations subsurface) must be in compliance wit h the ground-water monitorin g F o r most facilities, these requirements will requirements specified in §§258.51 - become applicable 3 to 5 years after th e 258.55 by October 9, 1996; promulgation date of the rule. This period monitoring requirements specified i n placed in the unit.

Statement of Regulation, this schedul e

Ex isting units and lateral expansions les s

than two miles from a dr inking water intake

re gardless of the proximity to a wate rGround-Water Monitoring and Corrective Action

215 Table 5-1. Compliance Schedule for Existing Units and Lateral Expansions

in States with Unapproved Programs
Distance From Water Supply Intake Time to Comply From October 9, 1991 One mile or less 3 Years More than one mile but less than two 4 Years miles More than two miles 5 Years

s hould provide sufficient time for the owner compliance by October 9, 1996. I n o r operator to conduct site investigation and characterization studies to comply with the re quirements of 40 CFR §258.51 throug h §258.55. For those facilities closest t o drinking water intakes, the period provides 2to 3 ye ars to assess seasonal variability in gr ound-water quality. A drinking wate r inta ke includes water supplied to a use r f rom either a sur face water or ground-water source. 5.4 ALTERNATIVE COMPLIANCE SCHEDULES 40 CFR 258.50 (d)(e) & (g) 5.4.1 Statement of Regulation (d) The Director of an approved Stat e may specify an alternative schedule fo r the owners or operators of existin g MSW LF units and lateral expansions t o comply with the ground-wate r mo nitoring requirements specified i n §§2 58.51 - 258.55. This schedule mus t en sure that 50 percent of all existin g MS WLF units are in compliance b y O ctober 9, 1994 and all existing MSWLF units are in setting the compliance schedule, th e Dir ector of an approved State mus t consider potential r isks posed by the unit to h uman health and the environment . The following factors should b e considered in dete rmining potential risk: (1) Proximity of human an d environmental receptors; (2) Design of the MSWLF unit; (3) Age of the MSWLF unit; (4) The size of the MSWLF unit; (5) Types and quantities of waste s disposed, including sewage sludge; and (6) Re source value of the underlyin g aquifer, including: (i) Current and future uses; (ii) Proximity and withdrawal rate of users; and (iii) Ground-water quality an d quantity.Subpart E

216 (e) Onc e established at a MSWL F 5.4.2 Applicability unit, ground-water monitoring shall b e c ond ucted throughout the active life and Th e Director of an approved State ma y p ost- closure care period of that MSWLF establish an alternative schedule fo r unit as specified in §258.61. requiring owners/opera tors of existing units (f) (Se e Section 5.5 for technica l ground-water monitoring requirements

. guidance on qualifications of a ground
- The altern ative schedule is to ensure that at water scientist.) least fifty percent of all existing MSWL F (g) The Director of an approved Stat e by October 9, 1994 and that all units are in ma y establish alternative schedules fo r compliance by October 9, 1996. demonstrating compliance wit h §258.51(d)(2), pertaining to notificatio n In establi shing the alternative schedule, the o f placement o f certification in operating Director of an approved State may use siterecord; § 258.54(c)(1), pertaining t o specific information to assess the relativ e no tification that statistically significan t risks p osed by different waste management increase (SSI) notice is in operatin g units and will allow priorities to b e record; § 258.5 4(c)(2) and (3), pertaining develo pedat the State level. This site

to an assessment monitoring program ; spe cific information (e.g., proximity t o § 258.55(b), pertaining to sampling an d receptors, proxi mity and withdrawal rate of analyzing Appendix II constituents ; ground-water users, waste quantity, type , § 258.55(d)(1), pertaining to placement of cont ainment design and age) should enable n otice (Appendix II constituents d etected) th e Director to assess potential risk to th e in record and notification of notice i n uppermost aquifer. The resource value o f rec ord; § 258.55(d)(2), pertaining t o the aquifer to be monitored (e.g., ground

sampling for Appendix I and II ; water quality and quantity, present an d § 2 58.55(g), pertaining to notificatio n future uses , and withdrawal rate of ground- ( and placement of notice in reco rd) of SSI water users) also may be considered. above ground-water prote ction standard; § 2 58.55(g)(1)(iv) and § 258.56(a) , Once ground-water monitoring has bee n pe rtaining to assessment of correctiv e ini tiated, it must continue throughout th e measures; § 258.57(a), pertaining t o ac tive life, closure, and post-closure car e selection of remedy and notification o f peri ods. The post-closure period may las t placement in record; § 258.58(c)(4) , up to 30 years or more after the MSWL F p ertaining to noti fication of placement in unit has received a final cover. record (alternative corrective actio n m easures ); and § 258.58(f), pertaining to In addition to establishing alternativ e no tification of placement in recor d schedules for compliance with ground

- (certification of remedy completed). water monitoring requirements, the Director and lateral expansions to comply with th e

units within a given State are in compliance

of an approved State may establis h alternative schedules for certainGround-Water Monitoring and Corrective Action

217 sampling and analysis requirements o f at existing MSWLF units, the Di rector of an §§258.54 and 258.55, as well as correctiv e ap proved State may consider informatio n act ion requirements of §§258.56, 258.57 , in cluding the age and design of existin g and 2 58.58. See Table 5-2 for a summar y facilities. Using this type of information, in of notification requirements for whic h conjunction with a knowledge of the wastes app roved States may establish alternativ e disposed, the Director should be able t o schedules. qualitatively assess or rank facilities based 5.4.3 Technical Considerations resources. The rule allows approved States flexibilit y in establishing alternate ground-wate r 5.5 QUALIFICATIONS mon itoring compliance schedules. I n 40 CFR 258.50 (f) sett ing an alternative schedule, the Stat e wil l consider potential impacts to huma n 5.5.1 Statement of Regulation he alth and the environment. Approve d Sta tes have the option to address MSWL F (f) Fo r the purposes of this Subpart, a units that have environmental problem s qua lified ground-water scientist is a immediately. In establishing alternativ e scientist or engineer who has received a sc hedules for installing ground-wate r baccalaureate or post-graduate degree in monitoring systems on their risk to local ground-wate r

Table 5-2. Summary of Notification Requirements

Section Description §258.51(d)(2) 14 day notification period after well installation

certification by a qualified ground-water scientist (GWS) §258.54(c)(1) 14 day notification period after finding a statistical increase

over background for detection parameter(s) §258.55(d)(1) 14 day notification period after detection of Appendix II

constituents §258.57(a) 14 day notification period after selection of corrective

measures §258.58(c)(4) 14 day notification period prior to implementing alternative

measures §258.58(f) 14 day notification period after remedy has been completed

and certified by GWSSubpart E

218 the natural sciences or engineering an d 5.5.3 Technical Considerations has sufficient training and experience i n ground-water hydrology and relate d A qualified ground-water scientist mus t fie lds as may be demonstrated by Stat e ce rtify work performed pursuant to th e registration, professional certifications , fol lowing provisions of the ground-wate r or completion of accredited universit y monitoring and corrective actio n programs that enable that individual t o requirements: make sound professional judgement s regarding ground-water monitoring , ! No potential for migratio n con taminant fate and transport, an d demonstration (§258.50(b)) corrective action. 5.5.2 Applicability spacin g, and depths of monitoring wells The qualifications of a ground-wate r scientist are defined to ensure tha t ! Determination that contamination wa s pro fessionals of appropriate capability an d caused by another source or that a ju dgement are consulted when required b y statisti cally significant increase resulted the Criteria. The ground-water scientis t fr om an error in sampling, analysis, o r m ust possess the fundamen tal education and ev aluation (§§258.54 (c)(3) and 258.5 5 exp erience necessary to evaluate ground

- (g)(2)) water flow, ground-water monitorin g systems, and ground-water monitorin g ! Determination that compliance with a tec hniques and methods. A ground-wate r remedy requirement is not technicall y sc ientist must understand and be able t o practicable (§258.58(c)(1)) apply methods to solve solute transpor t problems and evaluate ground-wate r ! Completion of remedy (§258.58(f)). remedial technologies. Hi s or her education ma y include undergraduate or graduat e T h e owner or operator must determine that st udies in hydrogeology, ground-wate r the professional qualifications of th e hydrology, engineering hydrology, wate r gro und-water specialist are in accordanc e resource engineering, geotechnica l with the regulatory def inition. In general, a engineering, geology, ground-wate r ce rtification is a signed document tha t m odeling/ground-water compute r modeling, tr ansmits some finding (e.g., tha t and other aspects of the natural sciences

. mon itoring wells were installed accordin g The qualified ground-water scientist mus t to acceptable practices and standards a t have a college degree but need not hav e locations and depths ap propriate for a given p rofessional certific ation, unless required at facility). The certification must be place d the State or Tribal level. Som e in the operating record of the facility, an d States/Tribes may have certificatio n the State Director must be notified that the pr ograms for ground-water scientists ; certification has been made. Specifi c however, there are no recognized Federa l details of these certifications will b e certification programs. ! Specifications concerning the number , (§258.51(d))Ground-Water Monitoring and Corrective Action

219 addressed in the order in which they appear represe ntative than that provided by the in this guidance document. upgradient wells; and Many State environmental regulator y (2) Represent the quality of groun d agencies have ground-water scientists o n wate r passing the relevant point o f staff. The owner or operator of a MSWL F compliance specified by the Director o f u nit or facility i s not necessarily required to an approved State under §258.40(d) or at obtain certification from an independen t t h e waste management unit boundary in ( e.g., consulting) ground-w ater scientist and un approved States. The downgradien t may , if agreed to by the Director in a n moni toring system must be installed a t ap proved State, obtain approval by th e the relevant point of complianc e specified Director in lieu of certification by a n by the Director of an approved Stat e outside individual. under §258.40(d) or at the wast e

5.6 GROUND-WATER of ground-water contamination in th e MONITORING SYSTEMS upp ermost aquifer. When physica l 40 CFR §258.51 (a)(b)(d) obstacles preclude installa tion of ground5.6.1 Statement of Regulation point o f compliance at existing units, the (a) A ground-water monitoring syste m installed at the closest practicabl e must be installed that consists of a distance hydraulically down-gradien t sufficient number of wells, installed a t from the relevant point of compliance or appropriate locations and dep ths, to yield specified by the Director of an approved gr ound-water samples from the upper - State under §258.40 that ensure s most aquifer (as defined in §258.2) that: detection of ground-wa ter contamination (1) R epresent the quality o f background ground water that has not been affecte d (b) The Director of an approved Stat e b y leakage from a unit. A determination may approve a multi-unit ground-wate r of background quality may includ e mon itoring system instead of separat e sa mpling of wells that are no t gr ound-water monitoring systems fo r hy draulically upgradient of the wast e each MSWLF unit when the facility ha s management area where: sev eral units, provided the multi-uni t (i) Hydrogeologic conditions do no t the requirement of §258.5 1(a) and will be allow the owner or operator to determine as pr otective of human health and th e what we lls are hydraulically upgradient; environmentas individual monitorin g or s y stems for each MSWLF unit, based on (ii) Sampling at other wells will provide an indication of background ground - (1) Number, sp acing, and orientation of w ate r quality that is as representative or the MSWLF units; more ma nagement unit boundary i n unapproved States thatensures detection

water monitoring wells at the relevan t down-gradient monitoring system may be

in the uppermost aquifer.

ground-water monitoring system meet s

the following factors:Subpart E

220 (2) Hydrogeologic setting; 5.6.2 Applicability (3) Site history; The requirements for establishing a ground- (4) Engineering design of the MSWL F §25 8.51 apply to all new units, existin g units; and units, and lateral expansions of existin g (5 ) Type of waste accepted at th e in 4 0 CFR §258.50. A ground-wate r MSWLF units. monitoring system consists of bot h (c) (Se e Section 5.7 for technica l point of compliance or waste managemen t guidance on monitoring well design an d unit boundary (i.e., downgradient wells)

. construction.) The ground-water monitori ng network must (d) T he number, spacing, and depths of MSW LF unit. A sufficient number o f monitoring systems shall be: mon itoring wells must be locate d ( 1) Determined based upon site-specific intervals in th e uppermost aquifer to ensure tec hnical information that must includ e contaminant detection. Generally , thorough characterization of: up gradient wells are used to determin e (i) Aquifer thickness, ground-wate r flow rate, ground-water flow directio n The downgradient wells must be located at in cluding seasonal and tempora l the relevant point of compliance specifie d fluctuations in ground-water flow; and by t he Director of an approved State, or a t (ii) S aturated and unsaturate d States that are not in compliance wit h g eologic units and fil l materials overlying regulations. If existing physical structures the uppermost aquifer, material s obstruct well placement, the downgradien t comprising the uppermost aquifer, an d monitoring system should be placedas close mat erials comprising the confining uni t to the relevant point of compliance a s defining the lower boundary of th e possible. Wells located at the relevant point up permost aquifer; including, but no t of complianc e must be capable of detecting limited to: thicknesses, stratigraphy , contaminant releases fro m the MSWLF unit lithology, hydraulic conductivities , to the uppermost aquifer. As discusse d porosities and effective porosities. ear lier in the section pertaining to th e (2) Certified by a qualified ground - compliance (Section 4.4), the point o f wa ter scientist or approved by th e compliance must be no greater than 15 0 D irector of an approved Sta te. Within 14 meters from the unit boundary. days of this certification, the owner o r op erator must notify the State Directo r Th e Director of an approved State ma y tha t the certification has been placed i n al low the use of a multi-unit ground-wate r the operating record. monitoring system. MSWLF units in water monitoring system pursuant t o

uni ts according to the schedules identifie d
backg round wells and wells located at th e

be ca pable of detecting a release from th e downgradient of the unit and be screened at

background ground-water quality.

the waste management unit boundary i n

designation of a relevant point o fGround-Water Monitoring and Corrective Action

221 Sta tes that are deemed not in complianc e aquifer is defined in §258.2 a s "the geologic w ith the regulations mus t have a monitoring system for each unit. A qualified ground-water scientist mus t c ertify that the number, spacing, and depths of the monitoring wells are appropriate fo r t he MSWLF unit. This certificati on must be pl aced in the operating records. The Stat e Dire ctor must be notified within 14 day s that the certification was placed in th e operating record. 5.6.3 Technical Considerations
T he objective of a gr ound-water monitoring s ystem i s to intercept ground water that has be en contaminated by leachate from th e M SWLF uni t. Early contaminant detection is important to allow sufficient time fo r cor rective measures to be developed an d implemented before sensitive receptors are sig nificantly affected. To accomplish thi s obje ctive, the monitoring wells should b e locat ed to sample ground water from th e uppermost aquifer at the closest practicable dis tance from the waste management uni t bound ary. An alternative distance that i s pro tective of human health and th e environment may be granted by the Director o f an appro ved State. Since the monitoring pr ogram is intended to operate through th e pos t-closure period, the location, design , and installation of monitoring wells should address both existing conditions an d a ntic ipated facility development, as well as expected changes in ground-water flow. Uppermost Aquifer M onitoring wel ls must be placed to provide representative ground-water samples fro m th e uppermost aquifer. The uppermos t formation nearest to the natural groun d sur face that is an aquifer, as well as lowe r aquifers that are hydraulicall y interconnected with this aquifer within th e fa cility property boundary." These lowe r aqui fers may be separated physically fro m the uppermost aquifer by less permeabl e strata (having a lower hydrauli c con ductivity) that are often terme d aqu itards. An aquitard is a less permeabl e geol ogic unit or series of closely layere d units (e.g., silt, clay, or shale) that in itself will not yield signific ant quantities of water but will transmit water through it s th ickness. Aquitards may include thicke r stratigraphic sequences of clays, shales, and dense, unfractured c rystalline rocks (Freeze and Cherry, 1979). To be considered part of the uppermos t aquifer, a lower zone of saturation must be hy draulically connected to the uppermos t aquifer within the facility propert y bo undary. Generally, the degree o f co mmunication between aquifers i s ev aluated by ground-water pumping tests

. Methods have been devised for use i n analyz ing aquifer test data. A summary i s pr esented in Handbook: Ground Water , Vol. II (USEPA, 1991). The followin g discussions under this section (5.6.3) should ass ist the owner or operator i n ch aracterizing the uppermost aquifer an d the hydrogeology of the site.Determination of Background GroundWater Quality The goal of monitoring-well p lacement is to dete ct changes in the quality of groun d wat er resulting from a release from th e MSWLF unit. The natural chemica l composition of ground water is controlle dSubpart E

222 p rimarily by the mineral composition of the ! The facility is located near productio n geolo gic unit comprising the aquifer. A s wells that influence the direction o f g round water move s from one geologic unit ground-water flow. to another, its chemical composition ma y chang e. To reduce the probability o f ! Upgradient ground-water quality i s d etecti ng naturally occurring differences in af fectedby a source of contaminatio n gr ound-water quality between backgroun d other than the MSWLF unit. and downgradient locations, only ground

water samples collected from the sam e ! The proposed or existing landfil l geologic unit should be compared. ov erlies a ground-water divide or loca l Gr ound-water quality in areas where th e geolo gy is complex can be difficult t o ! Geologic units present at downgradien t c haracterize. As a result, t he rule allows the lo cations are absent at upgradien t o wner or operator flexibility in determining locations. where t o locate wells that will be used t o establish background water quality. ! Karst terrain or fault zones modify flow. I f the facili ty is new, ground-water samples ! Nearby surface water in fluences groundcollected from both upgradient an d water flow directions. do wngradient locations prior to wast e disposal can be used to establish ba ckground ! Wa ste management areas are locate d wa ter quality. The sampling should b e cl ose to a property boundary that i s c o nducted to account for both seasonal and upgradient of the facility. spatial variability in ground-water quality

. Determining background ground-wate r quali ty by sampling wells that are no t A multi-unit ground-water monitorin g hyd raulically upgradient may be necessar y syst em does not have wells at individua l wh ere hydrogeologic conditions do no t MSW LF unit boundaries. Instead, a n allow the owner or operator to determin e imaginary line is drawn around all of th e which wells are hydraulically upgradient

. units a t the facility. (See Figure 5-1 for a Additionally, background ground-wate r comparison of single unit and multi-uni t qua lity may be determined by samplin g systems. ) This line constitutes the relevant w ells t hat provide ground-water samples as point of compliance. The option t o rep resentative or more representative tha n establish a multi-unit monitoring system is those provided by upgradient wells. These restricted to facilities located in approve d conditions include the following: Stat es. A multi-unit system must b e

! The facility is located above an aquife r Sta te after consideration has been given t o in which ground-water flow direction s the: change seasonally. source of recharge.

Multi-Unit Monitoring Systems

app roved by the Director of an approve d

! Number, spacing, and orientation of the MSWLF units

### Figure 5-1. Comparison of Single Unit and Multi-Unit Monitoring System

223Subpart E

224 ! Hydrogeologic setting ! The geology at the owner's/operator' s

! Site history structural setting)

! E ngineering desi gn of the MSWLF units ! The chemical properties of th e

! Type of wastes accepted at the facility. lay ers relative to local ground-wate r Th e purpose of a multi-unit system is t o facility reduce the number of monitoring wells that can provide the same information. Th e ! Ground-water flow, including: conceptual design of the multi-unit syste m s hould consi der the use and management of

- Th e vertical and horizontal direction s th e facility with respect to anticipated uni t o f ground-water f low in the uppermost l ocations. In some cas es, it may be possible aquifer to justify a reducti on in the number of wells if t he waste management units are aligne d

- Th e vertical and horizonta l alo ng the same flow path in the ground

- com ponents of the hydraulic gradien t water system. i n the uppermost and a ny hydraulically Th e multi-unit monitoring system mus t pr ovide a level of protection to huma n - The hydraulic conductivities of th e health and the environment that i s m aterials that compri se the upper-most comparable to monitoring individual units. aquifer and its confining units/layers The multi-unit system should allo w adequate time after detection o f - T h e average linear horizontal velocity contamination to develop and implemen t o f ground-water f low in the uppermost corrective measures before sensitiv e aquifer. receptors are adversely affected. Hydrogeological Characterization the h ydrogeology of a site are discusse d Adequate monitoring-well placemen t a ddressed in more detail in "RCRA Groundde pends on collecting and evaluatin g Wat er Monitoring: Draft Technica l hydrogeological information that can b e Guidance" (USEPA, 1992a). u sed to form a c onceptual model of the site. T he goal of a h ydrogeological investigation Pri orto initiating a field investigation, th e is to acquire site-specific data concerning: owner or operator should perform a

! The lateral and vertical extent of th e investigation will involve reviewing al l uppermost aquifer available information about the site, which

! The lateral and vertical extent of th e upper and lower confining units/layers f acilit y (e.g, stratigraphy, lithology, and

uppermost aquifer and its confinin g ch emistry and wastes managed at th e

connected aquifer

The elements of a program to characteriz e briefly in the sections that follow and ar e

p relimina ry investigation. The preliminary
may consist of:Ground-Water Monitoring and Corrective Action

225 ! Information on the waste managemen t Characterizing Site Geology history of the site, including:

- A chronological history of the site , com plete, the owner/operator will hav e including descriptions of waste s i nformation that he/sh e can use to develop a managed on-site plan to characterize site hydrogeolog y

- A summary of documented releases

- Details on the structural integrity o f inc lude a subsurface boring program. A t he MSWLF unit an d physical controls bo ring program is necessary to define sit e on waste migration hydrogeology and the small-scale geolog y

! A literature review, including: usua lly requires more than one iteration

.

- Rep orts of research performed in th e re fine the conceptual model of the sit e area of the site d erive d from the preliminary investigation.

- Journal articles The subsurface boring program should b e

- St udies and reports available fro m l oca l, regional, and State offices (e.g., ! T he initial number of boreh oles and their geo logic surveys, water boards, an d spac ing is based on the informatio n environmental agencies) ob tained during the preliminar y

- S tudies availabl e from Federal offices, such as USGS or USEPA ! A dditional boreholes should be installed

! In formation from file searches , about the site. including:

- Reports of previous investigations a t borin gs at changes in lithology. Fo r the site bo reholes that will be completed a s

- Geological and environmenta l s hould be collected from th e interval that a ssessment data from State and Federal w ill be the screened interval. Boreholes reports. t hat will not be completed as monitoring T he documenta tion itemized above is by no means a complete listing of informatio n G eophysical techniques, cone penetrometer available for a preliminary investigation

. s urveys, m apping programs, and laboratory Many other sources of hydrogeologica l a nalyses of borehol e samples can be used to information may be available for revie w plan and supplement the subsurface borin g during the preliminary investigation. p rogram. Downhole geophysical t echniques After the preliminary investigation i s

further. Ne arly all hydrogeological investigation s

of the area beneath the site. The progra m The objective of the initial boreholes is t o

designed as follows:

investigation.

as n eeded to provide more informatio n

! Samples should be collected from th e

mo nitoring wells, at least one sampl e

w ells must be prope rly decommissioned.Subpart E

226 i nclude electri c, sonic, and nuclear logging. ! Seasonal/temporal, natural, an d Surface geophysical techniques includ e artificially induced (e.g., off-sit e s eismic reflection and refraction, as well as p roducti on well-pumping, agricultural electromagnetic induction and resistivity. use) short-term and long-ter m The data obtained from the subsurfac e and flow patterns b oring program should enable the owner or operator to identify: ! The hydraulic conductivities of th e

! Lithology, soil types, and stratigraphy ve rtical hydraulic conductivity of th e

! Zones of potentially high hydrauli c conductivity Determining Ground-Water Flo w

! T he presen ce of confining formations or layers I nstalling monitoring wells that will provide

! Unp redicted geologic features, such a s do wngradient water samples requires a f ault zones , cross-cutting structures, and th orough understanding of how groun d pinch-out zones w ater flows beneath a site. Devel oping such

! C ontinuity of petrographic features, such information regarding both ground-wate r as sorting, grain size distribution, an d flo w direction(s) and hydraulic gradient

. cementation G round-water flow direc tion can be thought

! The potentiometric surface or wate r foll ows as it passes through the subsurface. table. H ydraulic gradient (i) is the change in static Characterizing Ground-Water Flo w direction. The static head is defined as the Beneath the Site h eight above a standard datum of the surface In addition to characterizing site geology , can be supported by the static pressure at a the owner/operator should characterize th e gi ven point (i.e., the sum of the elevatio n hydrology of the uppermost aquifer and its head and pressure head). c onfining l ayer(s) at the site. The owner or operator should install wells and/o r T o de termine ground-water flow directions pie zometers to assist in characterizing sit e and hydraulic gradient, owners an d hyd rology. The owner/operator shoul d operators should develop and implement a determine and assess: wat er level-monitoring program. Thi s

! T he direction( s) and rate(s) of ground- pre cise water level measurements in a wa ter flow (including both horizonta l s ufficient number of piez ometers or wells at and vertical components of flow) a sufficient frequency to gauge bot h variations in ground-water elevation s

s tratigraphic units at the site, including confining layer(s).
Direction and Hydraulic Gradient

repr esentative background an d

an understanding requires obtainin g

of as the idealized path that ground-wate r

head p er unit of distance in a give n

of a co lumn of water (or other liquid) tha t

prog ram should be structured to provid e

seasonal average flow directions an dGround-Water Monitoring and Corrective Action

227 tempor al fluctuations in ground-water flow the w aste types managed at the facility) i n direct ions. Ground-water flow direction(s) the subsurface at the facility, both th e sh ould be determined from water level s depth(s) to the immiscible layer(s) and th e measured in wells screened in the sam e thickness(es) of the immiscible layer(s) i n hydro-stratigraphic position. I n the well should be recorded. he terogeneous geologic settings (i.e. , se ttings in which the hydrauli c For t he purpose of measuring total head , con ductivities of the subsurface material s piezometers and wells should have as short va ry with location in the subsurface), lon g a s creened interval as possible

. we ll screens can intercept stratigraphi c Specifically, the screens in piezometers o r horizons with different (e.g., contrasting ) wel ls that are used to measure head shoul d gr ound-water flow directions and differen t genera lly be less than 10 feet long. I n h ea ds. In this situation, the resulting water c ircumstances incl uding the following, well lev els will not provide the depth-discret e sc reens longer than 10 feet may b e he ad measurements required for accurat e warranted: det ermination of the ground-water flo w direction. ! Na tural water level fluctuation s In addition to evaluating the component o f ground-water flow in the horizonta l ! Th e interval monitored is slightl y dire ction, a program should be undertake n greater than the appropriate scree n to assess the vertical component of ground- length (e.g., the interval monitored i s wa ter flow. Vertical ground-water flo w 12 feet thick). i nformation should be based, at least in part, on field data from wells and piezometers , ! T he aquifer monitored is homogeneous suc h as multi-level wells, piezomete r a nd extremely thick (e.g., greater than cl usters, or multi-level sampling devices , 3 00 feet) ; thus, a longer screen (e.g., a where appropriate. The following sections 20-foot screen) represents a fairl y provide acceptable methods for assessin g discrete interval. the vertical and horizontal components o f flow at a site. The hea d measured in a well with a lon g Ground-Water Level Measurements d ifferen t heads over the entire length of the T o de termine ground-water flow directions whe n interpreting water levels collecte d a nd ground-water flow rates, accurate water f rom wells that have lon g screened intervals l evel measurements (measured to the nearest (e.g., greater than 10 feet). 0. 01 foot) should be obtained. Section 5. 8 de lineates procedures for obtaining wate r T he water-level mon itoring program should l evel measurements. At facilit ies where it is b e st ructured to provide precise water level kno wn or plausible that immiscibl e me asurements in a sufficient number o f co ntaminants (i.e., non-aqueous phas e piez ometers or wells at a sufficien t liquids (NAPLs)) occur (or are determine d frequency to gauge both seasonal averag e to be potentially present after considerin g f low directions andtemporal fluctuations in necessitate a longer screen length.

screene d interval is a function of all of th e screened interval. Care should be take nSubpart E

228 ground-water flow directions. Th e USEP A (1989c) and Freeze and Cherr y o wner/operator should determine and assess (1979). Methods for calculating hydrauli c se asonal/temporal, natural, and artificiall y gra dient are provided by Heath (1982) an d in duced (e.g., off-site production well

- USEPA (1989c). pumping, agricultural use) short-term an d long-term variations in ground-wate r A potentiometric surface or water table map e levations, ground-water flow patterns, and will give an approximate idea of genera l ground-water quality. g round-wat er flow directions. However, to Establishing Horizontal Flow Directio n water flow direction(s) and hydrauli c and the Horizontal Component o f g radient(s) should be est ablished in both the Hydraulic Gradient hori zontal and vertical directions and ove r A fter the w ater level data and measurement period at 3-month intervals). pr ocedures are reviewed to determine tha t they are accurate, the data should be use d E stablishing Vertical Flow Direction and to: the Vertical Component of Hydrauli c

! C onstruct pot entiometric surface maps and water table maps based on th e To make an adequate determination of th e dis tribution of total head. The dat a gro und-water flow directions, the vertica l use d to develop water table map s c ompone nt of ground-water flow should be should be from piezometers or well s evaluated directly. This generally requires scree ned across the water table. Th e th e installation of multiple piezometers o r da ta used to develop potentiometri c w ells i n clusters or nests, or the installation su rface maps should be fro m o f multi-level well s or sampling devices. A pi ezometers or wells screened a t piezo meter or well nest is a closely space d app roximately the same elevation i n group of piezometers or wells screened a t the same hydrostratigraphic unit; d ifferent de pths, whereas a multi-level well

! De termine the horizontal direction(s ) nests and multi-level wells allow for th e o f ground-w ater flow by drawing flow measurement of vertical variations i n l ines on the potentiometric sur face map hydraulic head. or water table map (i.e., construct a flow net); Whe n reviewing data obtained fro m

! Cal culate value(s) for the horizonta l i n single boreholes, the construction details an d vertical components of hydrauli c of the well should be carefully evaluated

. gradient. Not only is it extremely difficult to sea l Me thods for constructing potentiometri c with in a single borehole, but sealan t surf ace and water table maps, constructin g materials may migrate from the seal of one flow nets, and determining the direction(s ) piezometer/well to the screened interval o f of ground-water flow are provided b y ano ther piezometer/well. Therefore, th e lo cate monitoring wells properly, ground

t ime at regu lar intervals (e.g., over a 1-year

Gradient

is a single device. Both piezometer/wel l

m ulti ple placement of piezometers or wells

s everal piezome ters/wells at discrete depthsGround-Water Monitoring and Corrective Action

229 desi gn of a piezometer/well nest should b e Furt her information can be obtained fro m considered carefully. Placement o f Freeze and Cherry (1979). piezometers/wells in closely space d boreholes, where piezometers/wells hav e Determining Hydraulic Conductivity be en screened at different, discrete dept h i ntervals, is likel y to produce more accurate Hydra ulic conductivity is a measure of a i nformation. The primary conc erns with the material's ability to transmit water

. installation of piezometers/wells in closel y Gene rally, poorly sorted silty or claye y spac ed, separate boreholes are: 1) th e m aterials have low hydrauli c conductivities, di sturbance of geologic and soil material s w hereas wel l-sorted sands and gravels have t hat occurs when one piezo meter is installed high hydraulic conductivities. An aquife r may be reflected in the data obtained fro m m ay be cla ssified as either homogeneous or another piezometer located nearby, and 2 ) heterogeneous and either isotropic o r th e analysis of water levels measured i n anisotropic according to the way it s piezometers that are closely spaced, bu t hydraulic conductivity varies in space. An separated horizontally, may produc e aqu ifer is homogeneous if the hydrauli c i mprecise information regar ding the vertical con ductivity is independent of locatio n co mponent of ground-water flow. Th e within the aquifer; it is heterogeneous i f li mitations of installing multipl e hy draulic conductivities are dependent o n pi ezometers either in single or separat e l ocation within the aquifer. If the hydraulic bor eholes may be overcome by th e c onductivity is independent of the direction i nstallation of sing le multi-level monitoring of me asurement at a point in a geologi c wel ls or sampling devices in singl e formati on, the formation is isotropic at that boreholes. The advantages an d poi nt. If the hydraulic conductivity varie s disadvantages of these types of devices are with the direction of measurement at a discussed by USEPA (1989f). po int, the formation is anisotropic at tha t T he owner or operator should determine the vertical direction(s) of ground-water flo w Determining Hydraulic Conductivit y us ing the water levels measured in multi

- Using Field Methods le vel wells or piezometer/well nests t o c onstruct flow nets. Flow nets shou ld depict Sufficient aquifer testing (i.e., fiel d t he piezom eter/well depth and length of the meth ods) should be performed to provid e s creened inter val. It is important to portray re presentative estimates of hydrauli c t he screened interval accurately on the flow conductivity. Acceptable field method s net to ensure that the piezometer/well i s i nclude cond ucting aquifer tests with single actually monitoring the desire d w ells, conducting aquifer tests with multiple wa ter-bearing unit. A flow net should b e we lls, and using flowmeters. This sectio n developed from information obtained from provides brief overviews of these methods, pie zometer/well clusters or nests screene d including two methods for obtainin g at different, discrete depths. Detaile d ve rtically discrete measurements o f g uidance for the construction an d evaluation hyd raulic conductivity. The identifie d of flow nets in cross section (vertical flo w re ferences provide detailed descriptions o f nets) is provided by USEPA (1989c)

. the methods summarized in this section. point.Subpart E

230 A c ommonly used test for determinin g to provide hydraulic conductivity data fo r hor izontal hydraulic conductivity with a t hat zone. Multiple-well tests for hydraulic single well is the slug test. A slug test i s conductivity characterize a greate r performed by suddenly adding, removing , prop ortion of the subsurface than single

o r displacing a known volume of w ater from w ell t ests and, thus, provide average values a wel l and observing the time that it take s of hydraulic conductivity. Multiple-wel l fo r the water level to recover to its original tests require measurement of parameter s le vel (Freeze and Cherry, 1979). Simila r sim ilar to those required for single-wel l results can be achieved by pressurizing th e te sts (e.g., time, drawdown). When usin g w ell casin g, depressing the water level, and aq uifertest data to determine aquife r suddenly releasing the pressure to simulate p ar ameters, it is important that the solution t he removal of water from th e well. In most assu mptions can be applied to sit e cases, EPA recommends that water not b e cond itions. Aquifer test solutions ar e i ntroduced into wells during aquifer tests to available for a wide variety o f av oid altering ground-water chemistry

. h ydrogeologic settings, but are oft en applied S ing le-well tests are limited in scope to the in correctly by inexperienced persons

. area directly adjacent to the well screen

. Incorrect assumptions rega rdin g The vertical extent of the well scree n hydrogeology (e.g., aquifer boundaries , generally defines the part of the geologi c aqu ifer lithology, and aquifer thickness ) formation that is being tested. ma y translate into incorrect estimations o f A modified version of the slug test, known w ater scientist w ith experience in designing as the multilevel slug test, is capable o f and interpreting aquifer tests should b e providing depth-discrete measurements o f c onsulted to ensure that a quifer test solution hydr aulic conductivity. The drawback o f methods fit the hydrogeologic setting

. t he mul tilevel slug test is that the test relies Kru semanand deRidder (1989) provide a o n the abilit y of the investigator to isolate a comprehensive discussion of aquifer tests. porti on of the aquifer using a packer

. Ne vertheless, multilevel slug tests, whe n Mu ltiple-well tests conducted with well s performed properly, can produce reliabl e sc reened in different water-bearing zone s measurements of hydraulic conductivity. furnish information concerning hydrauli c Mu ltiple-well tests involve withdrawin g levels in these zones should be monitore d wat er from, or injecting water into, on e d uring the aquifer test to determine the type well, and obtaining water leve l of aquifer system (e.g., confined , measurements over time in observatio n unconfined, semi-confined, or semi

wel ls. Multiple-well tests are ofte n un confined) beneath the site, and thei r p e rformed as pumping tests in which water lea kance (coefficient of leakage) an d is p umped from one well and drawdown i s dr ainage factors (Kruseman and deRidder , o bserved in nearby wells. A ste p-drawdown 1989). A multiple-well aquifer test should test should precede most pumping tests t o be cons idered at every site as a method t o det ermine an appropriate discharge rate

. esta blish the vertical extent of th e A quifer tests conduct ed with wells screened u ppermost aquifer and t o evaluate hydraulic i n the s ame water-bearing zone can be used connection between aquifers. hydraulic conductivity. A qua lified groundco mmunication among the zones. Wate rGround-Water Monitoring and Corrective Action

231 Cer tain aquifer tests are inappropriate fo r ! In designing aquifer tests an d us e in karst terrains characterized by a in terpreting aquifer test data , well-developed conduit flow system, an d owners/operators should account an d t h ey also may be inappropriate in fractured cor rect for seasonal, temporal, an d bedro ck. When a well located in a kars t anthropogenic effects on th e conduit or a large fracture is pumped, th e potentiometric surface or water table

. water level in the conduit is lowered. This Thi s is usually done by installin g lowering produces a drawdown that is no t pi ezometers outside the influence o f radial (as in a granular aquifer) but i s the stressed aquifer. Thes e ins tead a trough-like depression parallel t o pi ezometers should be continuousl y t he pumped conduit or fracture. R adial flow monitored during the aquifer test. equa tions do not apply to drawdown dat a coll ected during such a pump test. Thi s ! O wners and op erators should be aware mea ns that a conventional semi-log plot o f that, in a very high hydrauli c dra wdown versus time is inappropriate fo r conductivity aquifer, the screen siz e the purpose of determining the aquifer' s and/or filter pack used in the test well t ransmissivity and storativity. Aquifer tests can aff ect an aquifer test. If a ver y in kar st aquifers can be useful, but vali d s mal l screen size is used, and the pack de terminations of hydraulic conductivity , is improperly graded, the test ma y storativity, and transmissivity may b e reflect the characteristics of the filte r impos sible. However, an aquifer test ca n pack, rather than the aquifer. provide information on the presence o f conduits, on storage characteristics, and on ! EPA r ecommends the use of a step

the percentage of Darcian flow. McGle w drawdown test to provide a basis fo r a nd Thomas (1984) provide a more detailed sel ecting discharge rates prior t o discu ssion of the appropriate use of aquifer co nducting a full-scale pumping test

. tests in fractured bedrock and on th e This will ensure that the pumping rate suita ble interpretation of test data. Dy e ch osen for the subsequent pumpin g t racing also is used to determine the rate and test(s) can be sustained withou t dir ection of ground-water flow in kars t exceeding the available drawdown o f settings (Section 5.2.4). t he pumped wells. In addition , this test Se veral additional factors should b e in the observation wells. considered when planning an aquifer test:

! Ow ners and operators should provid e fo r the proper storage and disposal o f p otentially co ntaminated ground water pumped from the well system.

! O wne rs and operators should consider th e potential effects of pumping o n ex isting plumes of contaminate d ground water. wil l produce a measurable drawdow n

Ce rtain flowmeters recently have bee n recognized for their ability to provid e accurate and vertically discret e me asurements of hydraulic conductivity

. On e of these, the impeller flowmeter, i s ava ilable commercially. More sensitiv e type s of flowmeters (i.e., the heat-puls e flowmeter and electromagnetic flowmeter ) should be available in the near future. Use of the impeller flowmeter requires runnin gSubpart E

232 a caliper log to measure the uniformity o f h ydraul ic properties of the tested material). t he diameter of the well screen. The well is Spe cial attention should be given to th e t hen pumped with a small pump operated at s election of the appropriate test method and a constant flow rate. The flowmeter i s test conditions and to quality control o f l owered into the well, and t he discharge rate l aboratory results. McWhorter and Sunada is measured every few feet by raising th e (19 77), Freeze and Cherry (1979), an d fl owmeter in the well. Hydrauli c S evee (1991) discu ss determining hydraulic conductivity values can be calculated fro m conductivity in the laboratory. Laborator y the recorded data using the Cooper-Jaco b test s may provide the best estimates o f (19 46) formula for horizontal flow to a hydraulic conductivity for materials in th e well. Use of the impeller flowmeter i s unsa turated zone, but they are likely to b e limite d at sites where the presence of lo w les s accurate than field methods fo r permeability materials does not allo w mate rials in the saturated zone (Cantor e t pumping of the wells at rates sufficient t o al., 1987). opera te the flowmeter. The application o f flowmeters in the measure of hydrauli c Determining Ground-Water Flow Rate co nductivity is described by Molz et al

. (1990) and Molz et al. (1989). T he calculation of the averag e ground-water Determining Hydraulic Conductivit y water flow), or seepage velocity, i s Using Laboratory Methods discussed in detail in USEPA (1989c), i n It m ay be beneficial to use laborator y and deRidder (1989). The average linea r me asurements of hydraulic conductivity t o vel ocity of ground-water flow ( v  ̄ ) is a a

ugment the results of f ield tests. However, fu nction of hydraulic conductivity (K) , field methods provide the best estimates of h ydraulic gradient (i), and effe ctive porosity hydraulic conductivity in most cases

. ( n ): Beca use of the limited sample size , lab oratory tests can fail to account fo r v  ̄ = - Ki sec ondary porosity features, such a s n fractures and joints, and hence, can greatly underestimate overall aquifer hydrauli c M ethods for determi ning hydraulic gradient conductivities. Laboratory tests ma y and hydraulic conductivity have bee n pro vide valuable information about th e pr esented previously. Effective porosity , ve rtical component of hydrauli c t he percentage of the total volume o f a given c onductivity of aquifer materials. However, ma ss of soil, unconsolidated material, o r la boratory test results always should b e roc k that consists of interconnected pore s co nfirmed by field measurements, whic h thro ugh which water can flow, should b e s ample a much larger p ortion of the aquifer. est imatedfrom laboratory tests or fro m In addition, laboratory test results can b e v alues cited in th e literature. (Fetter (1980) pro foundly affected by the test metho d pro vides a good discussion of effectiv e select ed and by the manner in which th e p orosity. Barari and Hedg es (1985) provide tests are carried out (e.g., the extent t o default values for effective porosity. ) which sample collection and preparatio n USEPA (1989c) provides methods for have changed the in situ f low rate (average linear velocit y of groundF

reeze and Cherry (19 79), and in Kruseman

e

eGround-Water Monitoring and Corrective Action

233 de termining flow rates in heterogeneou s p rel iminary investigation to verify the and/or anisotropic systems and should b e collected information. consulted prior to calculating flow rates. Interpreting and Presenting Data fie ld data corroborate and ar e The following sections offer guidance o n porosity, hydraulic conductivity , in terpreting and presenting hydrogeologi c lateral and vertical stratigraphi c da ta collected during the sit e relationships, and ground-water flo w characterization process. Graphica l directions and rates. rep resentations of data, such as cros s se ctions and maps, are typically extremel y A fter the hydrogeologic data are int erpreted, h elpful both when evaluat ing data and when the findings should be reviewed to: presenting data to interested individuals. Interpreting Hydrogeologic Data Once the site characterization data hav e additional data or reassessment o f bee n collected, the following tasks shoul d exist ing data is required to fill in th e be undertaken to support and develop th e gaps interpretation of these data:

! Re view borehole and well logs t o like ly to affect the ability to design a identify major rock, unconsolidate d RCRA monitoring system. material, and soil types and establis h t heir horizontal and vertical extent and Generally, lithologic data should correlat e distribution. w ith hyd raulic properties (e.g., clean, well-

! From borehole and well log (an d hig h hydraulic conductivity). Additiona l outcrop, where available) data , boreholes should be drilled and additiona l c onstruct representative cross-sections s a mples should be collected to describe the for each MSWLF unit, one in th e hydrogeology of the site if the investigato r direction of ground-water flo w and one is unable to 1) correlate stratigraphic unit s orthogonal to ground-water flow. between borings, 2) identify zones o f

! Identify zones of suspected hig h the thickness and lateral extent of thes e hy draulic conductivity, or structure s zon es, or 3) identify confinin g li kely to influence contaminan t formations/layers and the thickness an d migr ation through the unsaturated and lateral extent of these formation layers. saturated zones.

! Compare findings with other studie s t hat will be used to m onitor ground water in and information collected during the hy drogeologic settings characterized b y ! Determine whether laboratory an d

s ufficient to define petrol ogy, effective

! Identify information gaps

! Determine whether the collection o f

! Identify how information gaps ar e

s orted, unc onsolidated sands should exhibit

p otent ially high hydraulic conductivity and

When establishing the locations of well s

grou nd-water flow in porous media, th e following should be documented:Subpart E

234 ! The ground-water flow rate should b e Geologic and soil maps should be based on bas ed on accurate measurements o f rock, unconsolidated material, and soi l hydraulic conductivity and hydrauli c identifications gathered from borings an d g radient and accura te measurements or out crops. The maps should use colors o r estimates of effective porosity symbols to represent each soil ,

! Th e horizontal and vertica l outc rops on the surface. The maps als o components of flow should b e shou ld show the locations of outcrops an d acc urately depicted in flow nets an d all borings placed during the sit e based on valid data characterization. Geologic and soil map s

! A ny seasonal or temporal variations in i nformation describing how sit e geology fits the water table or potentiometri c i nto the local and regional geologic setting. surface, and in vertical flo w components, should be determined. Structure contour maps and isopach map s Once an understanding of horizontal an d zone that comprises the uppermost aquife r vertical ground-water flow has bee n and for each significant confining layer , e st ablished, it is possible to estimate where e specially the one underl ying the uppermost monitoring wells will most likely intercep t aquif er. A structure contour map depict s contaminant flow. th e configuration (i.e., elevations) of th e Presenting Hydrogeologic Data particular geologic or soil formation, unit , Sub sequent to the generation an d e specially important in understanding dense i nterpretation o f site-specific geologic data, no n-aqueous phase liquid (DNAPL ) th e data should be presented in geologi c movement because DNAPLs (e.g. , cross-sections, topographic maps, geologic tet rachloroethylene) may migrate in th e m aps, a nd soil maps. The Agency suggests di rection of the dip of lower permeability t hat owners/ operators obtain or prepare and units. Separate structure contour map s review topographic, geolog ic, and soil maps should be constructed for the upper an d o f the facility, in addition to si te maps of the l ower surfaces (or contacts) of each zone of facility and MSWLF units. In cases where int erest. Isopach maps should depic t s uitable maps are not available, or where the contours that indicate the thickness of each i n formation contained on available maps is zone. These maps are generated fro m n ot complete or accurate, detailed mapping bori ngs and geologic logs and fro m o f the site should be performed by qualified g eop hysical measurements. In conjunction and experienced individuals. An aeria l with cross-sections, isopach maps may b e pho tograph and a topographic map of th e us ed to help determine monitoring wel l si te should be included as part of th e l ocations, depths, and screen lengths during presentation of hydrogeologic data. Th e th e design of the detection monitorin g topographic map should be constructe d system. un der the supervision of a qualifie d surveyor and should provide contours at a maximum of 2-foot intervals. u ncon solidated material, and rock type that

are important because they can provid e

should be prepared for each water-bearin g

upper or lower surface or boundary of a

or zone. Structure contour maps ar eGround-Water Monitoring and Corrective Action

235 A potentiometric surface map or water table a c onceptual model. This model is th e map s hould be prepared for each water

- in tegrated picture of the hydrogeologi c bearing zone that comprises the uppermos t system and the waste management setting

. aquifer. Potentiometric surface and wate r The final conceptual model must be a site

table maps should show both the directio n s pecific description of the unsaturated zone, and r ate of ground-water flow and th e th e uppermost aquifer, and its confinin g locat ions of all piezometers and wells o n units. The model should contain all of th e which they are based. The water leve l info rmation necessary to design a ground

measurements fo r all piezometers and wells water monitoring system. o n which the potentiometric surface map or water table map is based should be show n Monitoring Well Placement o n the potentiometric surface or water table ma p. If seasonal or temporal variations i n T his section s eparately addresses the lateral gr ound-water flow occur at the site, a pl acement and the vertical samplin g s ufficient n umber of potentiometric surface intervals of point of compliance wells

. or wa ter table maps should be prepared t o Ho wever, these two aspects of wel l sh ow these variations. Potentiometri c placement should be evaluated together i n surf ace and water table maps can b e the design of the monitoring system. Site

c ombined with s tructure contour maps for a s pecific hydrogeologic data obtained during particular formation or unit. An adequat e th e site characterization should be used t o number of cross sections sho uld be prepared d etermine the lateral placement of detection to depict significant stratigraphic an d monitoring wells and to select the lengt h s tructu ral trends and to reflect stratigraphic and vertical position of monitoring wel l and structural features in relation to loca l i ntakes. Potential pathways fo r contaminant and regional ground-water flow. migration are t hree-dimensional

. Hydrogeological Report mo nitoring network that intercepts thes e T he hyd rogeological report should contain, three-dimensional approach. at a minimum:

! A description of field activities Compliance Monitoring Wells

! Drilling and/or well construction logs Po int of compliance monitoring well s

! Analytical data the edge of the MSWLF unit(s) and should

! A di scussion and interpretation of th e m ay act as co ntaminant transport pathways. data The lateral placement of monitoring well s

! Recommendations to address data gaps. distribution of potential contaminan t T he fin al output of the site characterization thicknesses of stratigraphic horizons tha t pha se of the hydrogeological investigatio n can serve as contaminant migratio n is pathways. Consequently, the design of a detectio n potential pathways requires a

Lat eral Placement of Point o f

should be as close as physically possible to be screened in all transmissive zones tha t

sh ould be based on the number and spatia l mi gration pathways and on the depths an dSubpart E

236 Po int of compliance monitoring well s In some settings, the ground-water flo w sho uld be placed laterally along th e d irection may reverse seasonally (depending downg radient edge of the MSWLF unit t o o n precipi tation), change as a result of tidal intercept potential pathways fo r in fluences or river and lake stag e contaminant migration. The local ground

- fluc tuations, or change temporally as a water flow direction and gradient are th e r esult of well-pumping or c hanging land use major factors in determining the latera l patt erns. In other settings, ground wate r p lacement of point of compliance wells. In m ay flow away from the waste management a homogeneous, isotropic hydrogeologi c area in all directions. In such cases, EP A setting, well placement can be based o n recommends that monitoring wells b e ge neral aquifer characteristics (e.g. , in stalled on all sides (or in a circula r direction and rate of ground-water flow) , p attern) around the waste management area a nd potential contaminan t fate and transport t o allow f or the detection of contamination. c haracterist ics (e.g., advection, dispersion). In these cases, certain wells may b e More commonly, however, geology i s d owngradient only part of the t ime, but such v ariable and preferential p athways exist that a configuration should ensure that release s control the migration of contaminants

. from the unit will be detected. Th ese types of heterogeneous, anisotropi c geo logic settings can have numerous , The lateral placement of monitoring well s discrete zones within which contaminant s also should be based on the physical / may migrate. c hemical characteristics of the contaminants P otential mi gration pathways include zones in MSWLFs may limit the introduction o f of relatively high intrinsic (matrix ) hazardous constituents into landfills, it i s hydraulic conductivities, fractured/faulte d i mportant to con sider the physical/chemical zones, and subsurface material that ma y characteristics of contaminants whe n increase in hydraulic conductivity if th e designing the well system. Thes e material is exposed to waste(s) managed at characteristics include solubility, Henry' s the site (e.g., a limestone layer tha t L aw constant, partition coefficien ts, specific underlies an acidic waste). In addition t o g ravity, contaminant reaction or d egradation na tural hydrogeologic features, human

- p roducts, and the poten tial for contaminants mad e features may influence the ground

- to degrade confining layers. For example , water flow direction and, thus, the latera l c ontaminants w ith low solubilities and high pl acement of point of compliance wells

. specific gravities that occur as DNAPL s S uch human -made features include ditches, m ay migrate in the subsurface in directions areas where fill material has been placed , d ifferent from the directio n of ground-water b uried piping, buildin gs, leachate collection flow

. Therefore, in situations where th e sys tems, and adjacent disposal units. Th e r eleas e of DNAPLs is a concern, the lateral lat eral placement of monitoring well s placement of compliance point ground

sh ould be based on the number and spatia l wat er monitoring wells should no t distribution of potential contaminan t n ecessarily only be along the downgradient mi gration pathways and on the depths an d e dge of the MSWLF unit. Considering both thicknesses of stratigraphic horizons tha t conta minant characteristics an d can serve as contaminant migratio n h ydrogeologic pr operties is important when pathways. o f conc ern. While the restriction of liquidsGround-Water Monitoring and Corrective Action

237 determining the lateral placement o f the boring program, and from sample s monitoring wells. c ollected while drilling th e monitoring well. Vertical Placement and Screen Lengths geophysical data, available regional/loca l Pr oper selection of the vertical samplin g p rovide the vertical distribution of hydraulic in terval is necessary to ensure that th e c onductivity. The vertical sampl ing interval m onitorin g system is capable of detecting a i s n ot necessarily synonymous with aquifer release from the MSWL F unit. The vertical th ickness. Monitoring wells are ofte n pos ition and lengths of well intakes ar e s creened at intervals that represent a portion f unctions of (1) hydro-geologic factors that of the thickness of the aquifer. Whe n det ermine the distribution of, an d monitoring an unconfined aquifer, the well f luid/vapor phase transp ort within, potential s creen typically should be positioned so that pa thways of contaminant migration to an d a port ion of the well screen is in th e with in the uppermost aquifer, and (2) th e satu rated zone and a portion of the wel l che mical and physical characteristics o f screen is in the unsaturated zone (i.e., th e c ontaminants that control their transport and wel l screen straddles the water table)

. di stribution in the subsurface. Well intak e W hile the restr iction of liquids in MSWLFs length also is determined by the need t o may limit the introduction of hazardou s ob tain vertically discrete ground-wate r c onstitu ents into landfills, it is important to samp les. Owners and operators shoul d consider the physical/chemica l determine the probable location, size, an d characteristics of contaminants whe n geo metry of potential contaminant plume s designing the well system. when selecting well intake positions an d lengths. Th e vertical positions and lengths o f Si te-specific hydrogeologic data obtaine d th e same physical/chemical characteristic s dur ing the site characterization should b e of the contaminants of concern tha t used to select the length and vertica l influence the lateral placement o f position of monitoring well intakes. Th e mon itoring wells. Considering bot h v ertical positio ns and lengths of monitoring contaminant characteristics an d w ell intake s should be based on the number h ydrogeologic pr operties is important when and spatial distribution of potentia l c hoosing the vertical position and length of c ontaminant mig ration pathways and on the the w ell intake. Some contaminants ma y depths and thicknesses of stratigraphi c migr ate within very narrow zones. O f hor izons that can serve as contaminan t c ourse, for well placement at a n ew site, it is migr ation pathways. Figure 5-2 illustrate s unlikely that the owner or operator will b e exa mples of complex stratigraphy tha t able to assess contaminant characteristics. would require multiple vertical monitoring intervals. Different transport processes contro l The depth and thickness of a potentia l whether the contaminant dissolves or i s contaminant migration pathway can b e immiscible in water. Immiscible determined from soil, unconsolidate d m aterial, and rock samples collected during D irect physical data can be suppl emented by hydrogeological data, and other data tha t

m onitori ng well intakes should be based on

contaminant migration depending o nSubpart E

238 

### Figure 5-2 Upgradient and Downgradient Designations for Idealized MSWLFGround-Water Monitoring and Corrective Action

239 cont aminants may occur as light no n ! "Down-the-dip" of lower hydrauli c aqueous phase liquids (LN APLs), which are c onductivity units that act as confining l ighter t han water, and DNAPLs, which are layers, both upgradient an d denser than water. LNAPLs migrate in the downgradient of the wast e cap illary zone just above the water table

. management area. Wells installed to monitor LNAPLs should b e screened at the water ta ble/capillary zone B ecause of the nature of DNAPL migration interface, and the screened interval shoul d ( i.e., along struc tural, rather than hydraulic, i ntercept the water tab le at its minimum and gradients), wells installed to monito r m aximum elevation. LNAPLs may become DNAP Ls may need to be installed bot h t rapp ed in residual form in the vadose zone upg radient and downgradient of the wast e and become periodically remobilized an d manag ement area. It may be useful t o c ontribute fu rther to aquifer contamination, const ruct a structure contour map of lowe r eith er as free phase or dissolved phas e per meability strata and identify lowe r cont aminants, as the water table fluctuate s pe rmeability lenses upgradient an d and precipitation infiltrates the subsurface. downgradient of the unit along whic h DNAPLs may migrate. The wells can then Th e migration of free-phase DNAPLs ma y be located accordingly. be influenced primarily by the geology , rathe r than the hydrogeology, of the site

. The l engths of well screens used i n That is, DNAPLs migrate downwar d gr ound-water monitoring wells ca n throu gh the saturated zone due to densit y s ignif icantly affect their ability to intercept and then migrate by gravity along les s rel eases of contaminants. The complexit y p erme able geologic units (e.g., the slope of o f the hydrogeology of a site i s an important confi ning units, the slope of clay lenses i n c onsi deration when selecting the lengths of mor e permeable strata, bedrock troughs) , well screens. Most hydrogeologic setting s even in aquifers with primarily horizonta l ar e complex (heterogeneous an d g round-water flow. Consequen tly, if wastes anisotropic) to a certain degree. Highl y disp osed at the site are anticipated to exis t he terogeneous formations require shorte r i n the subsurface as a DNAPL, the potential well screens to allow sampling of discret e DNAPL should be monitored: port ions of the formation that can serve a s

! A t the base of the aquifer (immediately screens that span more than a singl e above the confining layer) sat urated zone or a single contaminan t

! I n structural depres sions (e.g., bedrock c ontamination of transmissive units, thereby tr oughs) in lower hydrauli c increasing the extent of contamination

. conductivity geologic units that act as Well intakes should be installed in a single confining layers s aturatedzone. Well intakes (e.g., screens)

! Along lower hydraulic conductivit y i nterconnect, or promote the inter connection lenses and units within units of higher of, zones that are separated by a confinin g hydraulic conductivity layer. con taminant migration pathways. Wel l
mig ration pathway may cause cross

and filter pack materials should no tSubpart E

240 Ev en in hydrologically simple formations , w oul d represent a fairly discrete interval in or within a single potential pathway fo r a very thick formation. Formations wit h contaminant migration, the use of shorte r v e ry low hydraulic conductivities also may well screens may be necessary to detec t re quire the use of longer well screens t o contaminants concentrated at particula r a llow sufficient amounts of formation water d epths. A contaminant may be concentrated to enter the well for sampling. Th e at a particular depth because of it s importance of accurately identifying suc h p hysical/chemical propert ies and/or because conditions highlights the need for a of hydrogeologic properties. I n complete hydrogeologic site investigatio n h omogeneous formations, a long wel l screen prior to the design and placement o f can permit excessive amounts o f detection wells. unc ontaminated formation water to dilut e t he contami nated ground water entering the Multiple monitoring wells (well clusters or well

. At best, dilution can mak e mu ltilevel sampling devices) should b e contaminant detection difficult; at worst , in stalled at a single location when (1) a co ntaminant detection is impossible if th e s ingl e well cannot adequately intercept and con centrations of contaminants are dilute d monitor the vertical extent of a potentia l to levels below the detection limits for th e pat hway of contaminant migration, or (2 ) pres cribed analytical methods. The use o f t here is more than one potential pathway of s horter wel l screens allows for contaminant co ntaminant migration in the subsurface a t detection by reducing excessive dilution

. a s ingle location, or (3) there is a thic k Whe n placed at depths of predicte d s aturated zone and immisc ible contaminants pref erential flow, shorter well screens ar e are present, or are determined to b e effective in monitoring the aquifer or th e potentially present after considering wast e portion of the aquifer of concern. t ypes managed at the facility. Conversely, at G enerally, screen le ngths should not exceed con taminatedby a single contaminant , 10 feet. However, certain hydrogeologi c where there is a thin saturated zone, an d sett ings may warrant or necessitate the us e where the site is hydrogeologicall y of longer well screens for adequat e h omogeneous, the need for mu ltiple wells at d etecti on monitoring. Unconfined aquifers eachsampling location is reduced. Th e with widely fluctuating water tables ma y number of wells that should be installed a t require longer scree ns to intercept the water eac h sampling location increases with sit e table surface at both its maximum an d complexity. mi nimum elevations and to provid e m onitoring for the presence o f contaminants The following sources provided additiona l tha t are less dense than water. Saturate d i nfo rmation on monitoring well placement: zone s that are slightly greater in thicknes s USEPA (1992a), USEPA (1990), USEP A than the appropriate screen length (e.g., 12 (1991), and USEPA (1986a). fee t thick) may warrant monitoring wit h longer screen lengths. Extremely thic k ho mogeneous aquifers (e.g., greater tha n 300 feet) may be monitored with a longe r scre en (e.g., a 20-foot screen) because a slightly longer screen sit es where ground water may b eGround-Water Monitoring and Corrective Action

241 5.7 GROUND-WATER dec ommissioning of any monitoring wel l MONITORING WELL DESIGN m ust be documented i n the operating record AND CONSTRUCTION of the facility and certified by a qualifie d 40 CFR §258.51 (c) ground-water scientist. Documentation i s 5.7.1 Statement of Regulation devices, and water level measuremen t (c) Monitoring wells must be cased in a man ner that maintains the integrity o f Th e monitoring wells must be cased t o the monitoring well bore hole. Thi s protec t the integrity of the borehole. Th e casi ng must be screened or perforate d d esign a nd construction of the well directly and packed with gravel or sand, wher e a ffects the quality and representativeness of n ecessary, to enabl e collection of ground- the samples collected. The wel l casing must water samples. The annular space (i.e. , hav e a screened or perforated interval t o the space between the bore hole and well allow the entrance of water into the wel l c asing) above the sampling de pth must be c asing. The annula r space between the well se aled to prevent contamination o f screen and the formation wall must b e samples and the ground water. packed with material to inhibit th e (1) Th e owner or operator must notif y well. The well screen must have opening s the State Director that the design , sized according to the packing materia l installation, development, an d used. The annular space above the filte r decommission of any monitoring wells , pa ck must be sealed to provide a discret e piezometers and other measurement , sampling interval. sa mpling, and analytical device s doc umentation has been placed in th e All monitoring wells, piezometers, an d operating record; and samp ling and analytical devices must b e (2) Th e monitoring wells, piezometers , c ontin ued performance according to design an d other measurement, sampling, an d s pecifications over the life of the monitoring anal ytical devices must be operated an d program. m aintained so that they perform to d esign sp ecifications throughout the life of th e 5.7.3 Technical Considerations monitoring program. §258.52 [Reserved]. m onitoring wells w ill affect the consistency 5.7.2 Applicability design must be based on site-specifi c The requirements for monitoring wel l (lithology and grain size distribution) wil l design, installation, and maintenance ar e determine the selection of proper packin g app licable to all wells installed at existin g and sealant materials, and the stratigraph y unit s, lateral expansions of units, and ne w will determine the screen length for th e M SWLF units. The design, insta llation, and interval to be monitored. Installation re quired for wells, piezometers, samplin g i nstruments used in the monitoring program.

mi gration of formation material into th e

ma intained in a manner that ensures thei r

T he design, installation, a nd maintenance of and accuracy of samples collected. Th e in formation. The formation materia lSubpart E

242 pr actices should be specified and oversee n ! Rela tive ease of well completion an d to ensure that the monitoring well i s dev elopment, including the ability t o insta lled as designed and will perform a s in stall the well in the give n intended. This section will discuss th e hydrogeologic setting. factors that must be considered whe n d esigning monitoring wells. Each well must I n addition to these factors, USEPA (1989f) be t ailored to suit the hydrogeologica l inclu des matrices to assist in selecting a n setting, the contaminants to be monitored , a ppropriate drilling method. Th ese matrices and other site-specific factors. Figure 5- 3 li st the most commonly used drillin g de picts the components of a typica l t echnique s for monitoring well installation, monitoring well installation. taking into consideration hydrogeologi c The following sections provide a brie f program. ove rview of monitoring well design an d co nstruction. More comprehensiv e T he following basic p erformance objectives discussions are provided in USEPA (1989f) shouldguide the selection of drillin g and USEPA (1992a). procedures for installing monitoring wells: Selection of Drilling Method ! Dril ling should be performed in a T he method chosen for drilling a m onitoring p rop erties of the subsurface materials. well depends largely on the followin g factors (USEPA, 1989f): ! Contamination and/or cross

-

! Versatility of the drilling method a quifer materials during drill ing should

! Relative drilling cost

! S ample rel iability (ground-water, soil, the collection of representativ e unconsolidated material, or roc k samples of rock, unconsolidate d samples) materials, and soil.

! Availability of drilling equipment ! The drilling method should allow th e

! Accessibility of the drilling site appropriate location for the screene d

! Re lative time required for wel l installation and development ! The drilling method should allow fo r

! Ability of the drilling technology t o a nnular s ealants. The borehole should preserve natural conditions be at least 4 inches larger in diamete r

! Ability to install a well of desire d casing and screen to allow adequate diameter and depth s ettings and the objectives of the monitoring

ma nner that preserves the natura l

co ntamination of ground water an d be avoided.

! The drilling method should allow fo r

o wn er/operator to determine when the interval has been encountered.

p roper placement of

the filter pack and

than the nominal diameter of the wel l

### Figure 5.3. Example of a Monitoring Well Design-Single Cased Well

243Subpart E

244 space for placement of the filter pac k Monitoring Well Design and annular sealants.

! The drilling method should allow fo r t he collection of representative ground- Well Casing and Screen Materials water samples. Drilling fluid s (including air) should be used onl y A casi ng and well screen are installed in a whe n minimal impact to th e ground-water monitoring well for severa l su rrounding formation and groun d r easons: to provide access from the surface water can be ensured. of the ground to some point in th e T he following guidelines a pply to the use of and to prevent hydraulic communicatio n drilling fluids, drilling fluid additives, an d betw een zones within the subsurface. I n lu bricants when drilling ground-wate r some cases, State or local regulations ma y monitoring wells: specify the casing and material that th e

! D rilling fluids, drilling fluid additives, comprehensive discussion of well casin g o r lubric ants that affect the analysis of a nd s creen materials is provided in USEPA h azardous constituents in gr ound-water (1989f) and in USEPA (1992a). Th e samples should not be used. following discussion briefly summarize s

! The owner/operator shoul d dem onstrate the inertness of drillin g M onitoring well casing and screen materials fluids, drilling fluid additives, an d ma y be constructed of any of several type s lubricants by performing analytica l o f m aterials, but should meet the following testing of drilling fluids, drilling fluid performance specifications: additives, and lubricants and/or b y providing information regarding th e ! Mon itoring well casing and scree n c ompo sition of drilling fluids, drilling ma terials should maintain thei r fl uid additives, or lubricants obtaine d structural integrity and durability i n from the manufacturer. t he environment in which the y are used

! The owner/operator should conside r th e potential impact of drilling fluids , ! Mon itoring well casings and screen s drilling fluid additives, and lubricants shou ld be resistant to chemical an d on the physical and chemica l microbiological corrosion an d c haracteristics of the subsu rface and on de gradation in contaminated an d ground-water quality. uncontaminated waters.

! The volume of drilling fluids, drilling ! Mon itoring well casings and screen s fluid additives, and lubricants use d sho uld be able to withstand th e d uring the drilling of a monit oring well ph ysical forces acting upon the m should be recorded. d uri ng and following their installation Well Casing

subsurface, to prevent borehole collapse ,

owne r or operator should use. A

information contained in these references.

over their operating life.

a nd during their use - - including forcesGround-Water Monitoring and Corrective Action

245 due to suspension in the borehole , background wells and downgradien t grouting, development, purging , wells and including: pumping, and sampling and force s ex erted on them by the surroundin g - Natural ground-water geochemistry geologic materials.

! Mon itoring well casing and scree n contaminants mat erials should not chemically alte r g round-wa ter samples, especially with

- C oncentration of suspec ted or known respect t o the analytes of concern, as a contaminants res ult of their sorbing, desorbing, o r lea ching analytes. For example, i f ! Design life of the monitoring well. c hromium is an analyte of interest, the well casing or screen should no t C asing materials w idely available for use in inc rease or decrease the amount o f gr ound-water monitoring wells can b e ch romium in the ground water. An y divided into three categories: mate rial leaching from the casing o r sc reen should not be an analyte o f 1) Fluoropolymer materials , includin g inter est or interfere in the analysis o f polytetrafluoroeth ylene (PTFE) , an analyte of interest. t etra fluoroethylene (TFE), fluorinated ethylene propylene (FEP) , In a ddition, monitoring well casing an d perfluoroalk oxy (PFA), an d s creen materials should be relatively easy to polyvinylidene fluoride (PVDF) i nstall into the bor ehole during construction of the monitoring well. 2) Metallic materials , including carbo n The selection of the most suitable wel l s teel, a nd stainless steel (304 and 316) c asing and scre en materials should consider site-specific factors, including: 3) Thermoplastic materials , includin g

! Dep th to the water-bearing zone(s) t o a crylo nitrile butadiene styrene (ABS). be monitored and the anticipated wel l depth In addition to these three categories o f

! Geologic environment (FRP) has been used for monitorin g

! Geochemistry of soil, unconsolidate d use d in general application across th e material, and rock over the entir e country, very little data are available on its i nterval in which the well is to be cased characteristics and performance. All wel l

! Geoc hemistry of the ground water a t s trength-related characteristics and chemical the site, as determined through a n resistance/chemical interferenc e ini tial analysis of samples from bot h characteristics that influence thei r - Nature of suspected or know n

steel, low-carbon steel, galvanize d

po lyvinyl chloride (PVC) an d

materials, fiberglass-reinforced plasti c

a pplications. Becaus e FRP has not yet been

constructio n materials posses s

performance in site-specific hydrogeologicSubpart E

246 and contaminant-related monitorin g selecting monitoring well materials

. situations. Me tallic casing materials are more subjec t The casing must be made of a materia l materials are more susceptible to chemica l s trong enough to last fo r the life of the well. degr adation. The geochemistry of th e T ens ile strength is needed primarily during for mation water influences the degree t o w ell installati on when the casing is lowered whi ch these processes occur. If ground

into the hole. The joint strength wil l wat er chemistry affects the structura l d etermin e the maximum length of a section integrity of the casing, then the sample s t hat can be suspended from the surface in an collec tedfrom the well are likely to b e air-filled borehole. affected. Co llapse strength is the capability of a Materials used for monitoring well casin g casi ng to resist collapse by any externa l m ust not exhibi t a tendency to sorb or leach load s to which it is subjected both durin g chemical constituents from, or into, wate r and after installation. A casing is mos t s ampled fromthe well. If a casing material susceptible to collapse during installatio n s orbs constituen ts from ground water, those before placement of the filter pack o r constituents may either not be detecte d annular seal materials around the casing

. d uring mo nitoring or be detected at a lower Once a casing is installed and supported , concentration. Chemical constituents als o c ollapse is seldom a concern. Several steps c an be leached from the casing materials by that can be taken to avoid casing collaps e agg ressive aqueous solutions. Thes e are: constituents may be detected in sample s 1) Drilling a straight, clean borehole ind icate contamination that is due to th e 2) Uniformly distributing filter pac k C asing materi als must be selected with care materials at a slow, even rate to avoid degradation of the well and t o 3) Avoiding use of quick-setting (hig h temperature) cements for ther moplastic I n certain situati ons it may be advantageous casings installation. to design a well using more than on e Compr essive strength of the casing is a where stainless steel or fluoropolyme r measure of the greatest compressive stres s mate rials are preferred in a specifi c t hat a casing can bear without deformation. chem ical environment, costs may be save d C asing failure due to a compr essive strength b y using PVC in non-c ritical portions of the limitation generally is not an importan t well

. These savings may be considerable , f actor in a properly installed well . This type es pecially in deep wells where only th e of failure results from soil friction o n lower portion of the well is in a critica l unsupported casing. che mical environment and where tens o f Chemical resistance/interferenc e upper portion of the well. In a composit e characteristics must be evaluated befor e well design, dissimilar metallic to corrosion, while thermoplastic casin g

collected from the well. The results ma y casi ng rather than the formation water

.
avoid erroneous results.

m aterial for well components. For example,

feet o f lower-cost PVC may be used in th eGround-Water Monitoring and Corrective Action

247 components should not be used unless a n thr eaded joints should be used o n e lec trically isolating design is incorporated ( i.e., a dielect ric coupling) (USEPA, 1986). Coupling Procedures for Joining Casing Only a limited number of methods ar e av ailable for joining lengths of casing o r casin g and screen together. The joinin g meth od depends on the type of casing an d type of casing joint. The re are generally two options availabl e for joining metallic well casings: weldin g vi a application of heat, or threaded joints

. Threaded joints provide inexpensive, fast , an d convenient connections and greatl y re duce potential problems with chemica l resistance or int erference (due to corrosion) a nd explosion potential. Wr apping the male th reads with fluoropolymer tape prior t o j oining sections improves the watertightness of the joint. One disadvantage to usin g t hreaded joints i s that the tensile strength of th e casing string is reduced t o approximately 70 percent of the casin g strength. This reduction in strength doe s n ot usually pose a pro blem because strength requirements for sma ll diameter wells (such as ty pical monitoring wells) are not a s critical and because metallic casing has a high initial tensile strength. Joints should create a uniform inner an d ou ter casing diameter in monitoring wel l ins tallations. Solvent cementing o f thermoplastic pipe should never be used i n t he construction of ground-water mo nitoring w ells. The cements used in solvent welding, whic h are organic chemicals, have bee n sho wn to adversely affect the integrity o f g round-water samples fo r more than 2 yearsafter well installation; only factorythermoplastic well material. Well Casing Diameter Alth ough the diameter of the casing for a monitoring well depends on the purpose of t he well, the casing size is general ly selected to accommodate downhole equipment

. A dditional casing diameter se lection criteria include the 1) drilling or well installatio n metho d used, 2) anticipated depth of th e well and associated strength requirements , 3 ) anticipate d method of well development, 4) v olume of water required to be purge d p rior to sam pling, 5) rate of recovery of the we ll after purging, and 6) anticipate d aquifer testing. Casing Cleaning Requirements Well casing and screen materials should be cleaned prior to installation to remove an y c oatings or manufacturing residues . Prior to us e, all casing and screen materials shoul d be w ashed with a mild, non-phosphate , d eter gent/potable water solution and rinsed w i th potable water. Hot pressurized water, s uch as in steam cle aning, should be used to remov e organic solvents, oils, or lubricants fro m casing and screens composed o f m ater ials other than plastic. At sites where volatile organic contaminants may b e moni tored, the cleaning of well casing an d s creen materials sh ould include a final rinse with deionized water or potable water tha t ha s not been chlorinated. Once cleaned , casings and screens should be stored in a n ar ea that is free of potential contaminants

. Pl astic sheeting can generally be used t o cove r the ground in the decontaminatio n area to provide protection fro m con tamination. USEPA (1989f) describe s the proceduresSubpart E

248 that should be used to clean casing an d because the owner/operator will need t o screen materials. Well Intake Design The owner/operator should design an d c onstruct t he intakes of monitoring wells to (1 ) accurately sample the aquifer zone tha t t he well is intended t o sample, (2) minimize the passage of formation material s (tu rbidity) into the well, and (3) ensur e s uffi cient structural integrity to prevent the c ollapse of the intake st ructure. The goal of a properly completed monitoring well is to provide low turbidity water that i s representative of ground-water quality i n the vicinity of the well. Close attention t o proper selection of packing materials an d well development procedures for well s installed in fine-grained formations (e.g. , clay s and silty glacial tills) is important t o minimize sample turbidity from suspende d and c olloidal solids. There may b e i nstances where wells completed in rock do n ot require screens or filter packs; the State regulatory agency sh ould be consulted prior to completion of unscreened wells. The selection of screen length usuall y depends on the objective of the well

. P iezometers and wells whe re only a discrete flow path is monitored (such as thin gravel interbedded with clays) are generall y completed using short screens (2 feet o r less)

. To avoid dilution, the well screen s shou ld be kept to the minimum lengt h app ropriate for intercepting a contaminan t p lume, especially in a high- yielding aquifer. The screen length should generally no t excee d 10 feet. If construction of a wate r table well is the objective, either fo r defining gradient or detecting floatin g phases, then a longer screen is acceptable provi de a margin of safety that wil l guara ntee that at least a portion of th e screen always contacts the water tabl e rega rdless of its seasonal fluctuations. The own er or operator should not employ wel l intake designs that cut across hydraulically separated geologic units. Well screen slot size should be selected t o retain from 90 percent to 100 percent of the fil ter pack material (discussed below) i n a rtificially filter packed we lls. Well screens should be factory-slotted. Manual slottin g of screens in the field should not b e performed under any circumstances. Filter Pack Design T he primary filter pack material should be a c hemically ine rt material and well rounded, with a high coefficient of uniformity. Th e best filter pack materials are made fro m i ndustrial grade glass (quartz) san d or beads. The u se of other materials, such as local , na turally occurring clean sand, i s dis couraged unless it can be shown that the material is inert (e.g., low cation exchang e capacity), coarse-grained, permeable, an d u niform in grain size. The filter pack should exten d at least 2 feet above the screene d interval in the well. Although design techniques for selectin g fi lter pack size vary, all use the filter pac k ratio to establish size differential betwee n formation materials and filter pac k ma terials. Generally, this ratio refers t o eith er the average (50 percent retained ) g rain size of the formation ma terial or to the 70 percent retained size of the formatio n ma terial. Barcelona et al. (1985b ) rec ommend using a uniform filter pac k g rain s ize that is three to five times the sizeGround-Water Monitoring and Corrective Action

249 of t he 50 percent retained size of th e op erators should remember that the entir e formation material (USEPA, 1990). l ength of th e annular space filled with filter Filter pack material should be installed in a mon itored zone. Moreover, if the filte r m anner that prevents bridging and particle- pa ck/sand extends from the screened zon e size segregation. Filter pack materia l into an overlying zone, a conduit fo r inst alled below the water table shoul d h ydraulic connec tion is created between the g enerally be t remied into the annular space. two zones. All owing filter pack material to fall b y grav ity (free fall) into the annular space i s Annular Sealants onl y appropriate when wells are relativel y s hallow , when the filter pack has a uniform P roper sealing of th e annular space between g rain size, and when the filter pack material the w ell casing and the borehole wall i s ca n be poured continuously into the wel l required to prevent contamination o f without stopping. sam ples and the ground water. Adequat e At least 2 inches of filter pack materia l w ithin the well annulus. The materials used s houl d be installed between the well screen for annular sealants should be chemicall y an d the borehole wall. The filter pac k inert with the highest anticipate d s hould extend at least 2 feet abov e the top of concentration of chemical constituent s the w ell screen. In deep wells, the filte r e xpected in the ground water at the facility. pac k may not compress when initiall y In general, the permeability of the sealin g installed. Consequently, when the annula r mat erial should be one to two orders o f and su rface seals are placed on the filte r magn itude lower than the least permeabl e p ack, the filter pack c ompresses sufficiently partof the formation in contact with th e to al low grout into, or very close to, th e well. The precise volume of annula r s creen. Consequently, filter packs may need sealants required should be calculated an d to be i nstalled as high as 5 feet above th e recorded before placement, and the actua l scre ened interval in monitoring wells tha t volume used should be determined an d are de ep (i.e., greater than 200 feet). Th e rec orded during well construction. An y pre cise volume of filter pack materia l significant discrepancy between th e required should be calculated and recorded ca lculated volume and the actual volum e bef ore placement, and the actual volum e should be explained. used should be determined and recorde d duri ng well construction. Any significan t When the screened interval is within th e discrep ancy between the calculated volume a nd the actual volume should be explained. Prior to installing the annular seal, a 1- t o 2-foo t layer of chemically inert fine san d m ay be placed over the filter pack t o prevent the intrusion of annular or surface sealant s in to the filter pack. When designin g monitoring wells, owners and pack material or sand is effectively th e

se aling will prevent hydraulic connectio n

satura ted zone, a minimum of 2 feet o f seal ant material, such as raw (>10 percen t sol ids) bentonite, should be place d im mediately over the protective sand laye r ove rlying the filter pack. Granula r ben tonite, bentonite pellets, and bentonit e chi ps may be placed around the casing b y mean s of a tremie pipe in deep well s (gr eater than approximately 30 feet deep) ,Subpart E

250 or by dropping them directly down th e When the annular sealant must be installed annu lus in shallow wells (less tha n in th e unsaturated zone, neat cement o r a pprox imately 30 feet deep). Dropping the shrinkage-compensated neat cemen t b entonite pellets down the annulus presents mixtures should be used for the annula r a potential for bridging (from prematur e sea lant. Bentonite is not recommended a s hydra tion of the bentonite), leading to gaps an annular sealant in the unsaturated zon e in the seal below the bridge. In shallo w because the moisture available i s moni toring wells, a tamping device shoul d insufficient to fully hydrate bentonite. b e used to preve nt bridging from occurring. A neat cement or shrinkage-compensate d nea t cement grout seal should be installe d Mo nitoring wells are commonly eithe r on top of the bentonite seal and exten d above-ground completions or flush-to

v er tically up the annular space between the gro und completions. The design of bot h w e ll casing and the borehole wall to within types must consider the prevention o f a few feet of land s urface. Annular sealants in filtration of surface runoff into the wel l i n slurry form (e.g., ce ment grout, bentonite annu lus and the possibility of accidenta l s lurry) should be placed by the tremie/pump dam age or vandalism. Completing a (from the bottom up) method. The botto m monitoring well involves installing th e of the placement pipe should be equippe d following components: with a side discharge deflector to preven t the slurry from jetting a hole through th e ! Surface seal protective sand layer, filter pack, o r b entonite seal. The benton ite seal should be ! Protective casing allowed to completely hydrate, set, or cur e in conformance with the manufacturer' s ! Ventilation hole sp ecifications prior to installing the grou t s eal in the annular space. The time required ! Drain hole f or the bentonite seal to completely hydrate, set, or cure will differ with the material s ! Cap and lock used and the specific condition s encountered, b ut is generally a minimum of ! Guardposts when wells are complete d 4 to 24 hours. Allowing the bentonite sea l above grade. to hydrate, set, or cure pre vents the invasion of t he more viscous and more chemicall y A su rface seal, installed on top of the grout reactive grout seal into the screened area. seal, extends vertically up the well annulus W hen using bentoni te as an annular sealant, h eave, t he seal should extend at least 1 foot the appropriate clay should be selected o n b elow the frost line. The compos ition of the t he basis of the environment in which it is to surface seal should be neat cement o r b e u sed, such as the ion-exchange potential co ncrete. In an above-ground completion , of the sediments, sediment permeability , t he surface seal should format least a 2-foot and compatibility with expecte d wide, 4-inch thick apron. contaminants. Sodium bentonite is usually acceptable. Surface Completion

to the land su rface. To protect against frostGround-Water Monitoring and Corrective Action

251 A locking protective casing should b e unavoidable, such as in active roadways, a in stalled around the well casing to preven t pro tective structure, such as a utility vaul t dama ge or unauthorized entry. Th e o r meter box, should b e installed around the p rotective casi ng should be anchored below well casing. In addition, measures shoul d the frost line (where applicable) into th e be taken to prevent the accumulation o f su rface seal and extend at least 18 inche s s urface water in the protective structure and a

bove the surface of the g round. A 1/4-inch arou nd the well intake. These measure s v ent hole pi pe is recommended to allow the shouldinclude outfitting the protectiv e escape of any potentially explosive gase s stru cture with a steel lid or manhole cove r th at may accumulate within the well. I n t hat has a rubber seal or gasket and ensuring additi on, a drain hole should be installed in that the bond between the cement surfac e t h e protective casing to prevent water from seal and the protective structure i s accumulating and, in freezing climates , watertight. f reezi ng around the well casing. The space between the protective casing and the wel l Well Surveying c asing may be filled with gravel to allow the retrieval of tools and to prevent smal l T he location of all wells should be surveyed a

nimal/insect entranc e through the drain. A by a licensed professional surveyor (o r s uitable ca p should be placed on the well to equ ivalent) to determine their X-an d-Y prev ent tampering or the entry of an y coo rdinates as well as their distances fro m forei gn materials. A lock should b e the units being monitored and thei r i nstalled on the cap to provide security. To distan ces from each other. A State Plan e p revent cor rosion or jamming of the lock, a Coordinate System, Universal Transvers e prote ctive cover should be used. Car e Mercator System, or Latitude/Longitud e s hould be taken when using such lubricants s hould be used, as approved by the Regional as g raphite or petroleum-based sprays t o A dministrator. The survey should also note lubr icate the lock, as lubricants ma y the coordinates of any temporar y in troduce a potential for sampl e ben chmarks. A surveyed reference mar k contamination. sho uld be placed on the top of the wel l To guard against accidental damage to th e well apron, for use as a measuring poin t w ell from facility traffic, the owne r/operator because the well casing is more stable than should install concrete or steel bumpe r t he protective casing or we ll apron (both the guards around the edge of the concret e protective casing and the well apron ar e a

pron . These should be located within 3 or mo re susceptible to frost heave an d 4 fe et of the well and should be painte d spalling). The height of the referenc e o range or fitted with refl ectors to reduce the survey datum, permanently marked on to p possibility of vehicular damage

. of the inner well casing, should b e The use of flush-to-ground surfac e m ean sea level, which in turn is determined c ompletions sh ould be avoided because this by reference to an established Nationa l de sign increases the potential for surfac e Ge odetic Vertical Datum. The referenc e water infiltration into the well. In case s marked on top of inner well casings should where flush-to-ground completions ar e be re surveyed at least once every 5 years , casing, not on the protective casing or th e

determined within ±0.01 foot in relation toSubpart E

252 unless changes in ground-water flo w W hen development is initiated, a wide range patterns/direction, or damage caused b y of g rain sizes of the natural material i s freeze/thaw or desiccation processes, ar e dr awn into the well, and the well typicall y note d. In such cases, the Regiona l pr oduces very turbid water. However, a s A dministrator may re quire that well casings de velopment continues and the natura l be resurveyed on a more frequent basis. mater ials are drawn into the filter pack, a n Well Development pro cess. Inducing movement of groun d A ll monitoring wells should be d eveloped to g enerally results in bridging of the particles. creat e an effective filter pack around th e A m eans of inducing flow reversal i s we ll screen, to rectify damage to th e ne cessary to break down bridges an d f ormation caused by drilling , to remove fine produce a stable filter. particles from the formation near th e bo rehole, and to assist in restoring th e The commonly accepted methods fo r natu ral water quality of the aquifer in th e deve loping wells are described in USEP A vici nity of the well. Development stresse s (1989f) and Driscoll (1986) and include: the formation around the screen, as well as th e filter pack, so that mobile fines, silts , ! Pumping and overpumping an d clays are pulled into the well an d removed. The process of developing a well ! Surging with a surge block c re ates a graded filter pack around the well s creen. Development is also u sed to remove ! Bailing. a ny foreign mat erials (drilling water, muds, etc.) that may have been introduced into the USEPA (1989f) provides a detaile d well borehole during drilling and wel l over view of well development and shoul d inst allation and to aid in the equilibratio n be consulted when evaluating wel l t hat will oc cur between the filter pack, well development methods. casing, and the formation water. The d evelopment of a well is extremel y Construction, and Development important to ensuring the collection o f representative ground-w ater samples. If the I nformation on the design, cons truction, and well has been properly completed, the n deve lopment of each well should b e adeq uate development should remove fines c ompiled. Such inf ormation should include t hat may enter the wel l either from the filter ( 1) a boring log that documents well drilling pac k or the formation. This improves th e and associated formation sampling and (2 ) yi eld, but more importantly it creates a a well construction log and wel l mo nitoring well capable of producin g construction diagram ("as built"). s amples of acceptably low turb idity. Turbid s amples from an improperly constr ucted and dev eloped well may interfere wit h subsequent analyses. effective filter will form through a sortin g
wat er into the well (i.e., in one direction )

Documentation of Well Design ,Ground-Water Monitoring and Corrective Action

253 Decommissioning Ground-Wate r In some States, similar regulations ma y Monitoring Wells and Boreholes a pply to the decommissioning of monitoring G round-water conta mination resulting from in volved regulatory agencies, as well a s improperly decommissioned wells an d experienced geologists, geotechnica l boreholes is a serious concern. An y e nginee rs, and drillers, should be consulted bor ehole that will not be completed as a p rior to decommissioning a wel l or borehole mon itoring well should be properl y to ensure that decommissioning i s de commissioned. The USEPA (1975) an d performed properly and to ensur e the American Water Works Associatio n complian ce with State law. If a well to b e (1 985) provide the following reasons , decommissioned is contaminated, the saf e summarized by USEPA (1989f), as to wh y remo val and proper disposal of the wel l improperly constructed or unused well s ma terials should be ensured by th e should be properly decommissioned: owner/operator. Appropriate measure s

! To eliminate physical hazards s afety of individuals when decommi ssioning

! To prevent ground-wate r contamination

! To conserve aquifer yield an d AND ANALYSIS hydrostatic head REQUIREMENTS

! To prevent intermixing of subsurfac e water. 5.8.1 Statement of Regulation Shoul d an owner or operator have a (a) The ground-water monitorin g borehole or an improperly constructed o r program must include consisten t u nused well at his or her facility, the well or sampling and analysis procedures tha t bor ehole should be decommissioned i n a re designed to ensur e monitoring results ac cordance with specific guidelines

. tha t provide an accurate representatio n US EPA (1989f) provides comprehensiv e of ground-water quality at th e guidance on performing wel l background and downgradient well s dec ommissioning that can be applied t o i nstalled in compliance wit h §258.51(a) of bore holes. In addition, any State/Triba l th is Part. The owner or operator mus t regulatory guidance should be consulte d notify the State Director that th e p rior to decommission ing monitoring wells, sampling and analysis progra m pi ezometers, or boreholes. Lamb an d doc umentation has been placed in th e K in ney (1989) also provide information on ope rating record and the program mus t d ecommiss ioning ground-water monitoring include procedures and techniques for: wells. M any States require that specif ic procedures be followed and certain paperwork be filed (2) Sample preservation and shipment; w hen decomm issioning water supply wells. wel ls and boreholes. The EPA and othe r

shoul d be taken to protect the health an d a well or borehole.

5.8 GROUND-WATER SAMPLING
40 CFR §258.53

(1) Sample collection;Subpart E

254 (3) Analytical procedures; §258.55(a) of this Part. Backgroun d (4) Chain of custody control; and a t wells that are not loca ted hydraulically (5) Qu ality assurance and qualit y meets the requirements of §258.51(a)(1). control. (b) The ground-water monitorin g e stablish ground-waterquality data must program must include sampling an d be consistent with the appropriat e ana lytical methods that are appropriat e statistical procedures determine d for ground-water sampling and tha t p ursuant to paragr aph (g) of this section. accurately measure hazar dou s The sampling procedures shall be thos e co nstituents and other monitorin g sp ecified under §258.54(b) for detectio n parameters in ground-water samples . monitoring, §258.55(b) and (d) fo r G round-wate r samples shall not be field- a ssessment monitoring, and §258.56(b) of filtered prior to laboratory analysis. corrective action. (c) The sampling procedures an d 5.8.2 Applicability frequency must be protective of huma n health and the environment. T he requirements for sampling and analysis (d) Gr ound-water elevations must b e ground-water monitoring throughout th e m easured in each well immediately prior a ctive life, closure, and post-closure periods to purging, each time ground water i s o f operation. Quality assurance and quality samp led. The owner or operator mus t control measures for both field an d determine the rate and direction o f lab oratory activities must be implemented

. ground-water flow each time groun d The methods and procedures constitutin g wa ter is sampled. Ground-wate r t he program must be pl aced in the operating el evations in wells which monitor th e record of the facility. sam e waste management area must b e mea sured within a period of time shor t F or the sampling and analysis program to be enough to avoid temporal variations i n t echn ically sound, the sampling procedures g roun d-water flow which could preclude a nd analytical methods used should provide accurate determination of ground-water a dequate a ccuracy, precision, and detection flow rate and direction. l imits for the analyte determinations. Prior (e) The owner or operator mus t e levation s in the wells must be measured to establish background ground-wate r allo w determination of the direction o f qual ity in a hydraulically upgradient o r gr ound-water flow and estimates of rate o f bac kground well(s) for each of th e fl ow. The time interval betwee n monitoring parameters or constituent s mea surements at different wells must b e re quired in the particular ground-wate r min imized so that temporal changes i n mo nitoring program that applies to th e ground-water elevations do not cause an MSW LF unit, as determined unde r §258.54(a), or g round-water quality may be established
up gradient from the MSWLF unit if i t
(f) The number of samples collected t o

apply to all facilities required to conduc t

to sampling, the static ground-wate rGround-Water Monitoring and Corrective Action

255 incorrect determination of ground-wate r ! Chain of custody control flow direction. Background ground-water quality must b e e st ablished at all upgradient or background T he ground-water monitoring program must we lls. The background water quality ma y be documented in the operating record o f be determined from wells that are no t the facility. upg radient of the MSWLF unit, provide d th at the wells yield representative ground

- The objectives of the monitoring progra m water samples. s hould cle arly define the quality of the data T he sampling program must be designed in g round-water chemistry due to th e operation consideration of the anticipated statistica l of the solid waste disposal facility. Thes e meth od applied by the owner or operator

. data quality objectives should address: The data objectives of the monitorin g p rogram, in terms of the number of samples ! A ccuracy and precision of methods used col lected and the frequency of collection , in t he analysis of samples, includin g sho uld be appropriate for the statistica l field measurements method selected for data comparison. 5.8.3 Technical Considerations p rocedures use d to ensure the validity of The purpose of a ground-water samplin g record keeping, and data validation) and analysis program is to establish a p rotocol that can be followed thro ughout the ! Number of samples required to obtain a mo nitoring period of the site (operating , certain degree of statistical confidence closure, and post-closure). The protocol is neces sary so that data acquired can b e ! Lo cation and number of monitorin g com pared over time and accuratel y wells required. re present ground-water quality. Sampl e c oll ection, preservation, shipment, storage, Sample Collection a nd analyses should a lways be performed in a co nsistent manner, even as monitorin g Frequency staff change during the monitoring period. The owner's/operator's ground-wate r det ection monitoring should be evaluate d monitoring program must include a for each site according to hydrogeologi c d escription of p rocedures for the following: c onditions and landfill design. In States, the

! Sample collection semiannual. The backgroun d

! Sample preservation and shipment independent samples at each monitorin g

! Analytical procedures (i.e ., during the first 6 months o f ! Quality assurance and quality control.

requ ired to detect significant changes i n

! Qu ality control and quality assuranc e the results (e.g., use of blank samples ,

The frequency of sample collection unde r

mi nimum sampling frequency should b e characterization should include fou r location during the first semi-annual even tSubpart E

256 mo nitoring). (See the discussion unde r Me asurements of the static water level an d Section 5.10.3 on collecting independen t the depth to the well bottom can be mad e sam ples to determine background.) Mor e with a wetted steel tape. Electronic wate r fre quent sampling may be selected. Fo r level measuring devices may also be used

. exa mple, quarterly sampling may b e A ccepted standard operating p rocedures call con ducted to evaluate seasonal effects o n for the static water level to be accuratel y ground-water quality. mea sured to within 0.01 foot (USEPA , The frequency of sample collection durin g be made at all monitoring wells and wel l assessment monitoring activities wil l c lusters in a time frame that avoids changes depend on site-specific hydrogeologi c that may occur as a result of barometri c c onditions and contami nant properties. The pressure changes, significant infiltratio n f requency of sampling is intended to obtain ev ents, or aquifer pumping. To preven t a data set th at is statistically independent of p ossible cross contaminatio n of wells, water the previous set. Guidance to estimate this lev el measurement devices must b e mi nimum time to obtain independen t decontaminated prior to use at each well. s ample s is provided in "Statistical Analysis o f Ground-water Monitoring Data at RCRA The ground-water monitoring progra m Fa cilities - Interim Final Guidance " sho uld include provisions for detectin g (USEPA, 1989). imm iscible fluids (i.e., LNAPLs o r Water Level Measurements immiscible liquids that are less dense tha n T he ground-water monitoring program must s urface. DNAPLs a re relatively immiscible in clude provisions for measuring stati c l iqui ds that are more dense than the ground wa ter level elevations in each well prior t o wate r and tend to migrate verticall y purging the well for sampling

. downward in aquifers. The detection of an Measurements of ground-water elevation s immiscible layer may require specialize d are used for determining horizontal an d equipment and should be performed before vertical hydraulic gradients for estimatio n the well is evacuated for conventiona l of flow rates and direction. sam pling. The ground-water monitorin g Field measurements may include th e LNAP Ls will be detected. The progra m following: also should include a contingency pla n

! D epth to standing water from a surveyed an alyzing these liquids. Guidance fo r d atu m on the top of the well riser (static d etec ting the presence of immiscible layers water level) can be found in USEPA (1992a).

! Total depth of well from the top of th e Well Purging riser (to verify condition of well)

! Thickness of immiscible layers, i f present. 1992a). Water level measurements shoul d

DN APLs). LNAPLs are relativel y

w ater and that spread across the water table

pr ogram should specify how DNAPLs an d
describing procedures for sampling an d

B ecause the water standing in a well prior to sa mpling may not represent in-sit u g round-water quality, st agnant water shouldGround-Water Monitoring and Corrective Action

257 b e purged from the well and filter pack prior ensure that purging does not caus e to sampling. The QAPjP should includ e de tailed, step-by-step procedures fo r p urging wells, includin g the parameters that will be monitored during purging and th e equipment that will be used for wel l purging. Purging should be accomplished b y removing ground water from t he well at low f low rates usin g a pump. The use of bailers to purge monitoring wells generally should be avoided. Research has shown that th e "pl unger" effect created by continuall y r aising and lowe ring the bailer into the well ca n result in continual development o r o verdevelopment of the well. Moreov er, the ve locities at which ground water enters a bailer can actually correspond t o un acceptably high purging rates (Puls an d Powell, 1992; Barcelona et al., 1990). The rate at which ground water is removed f rom the well dur ing purging ideally should be approximately 0.2 to 0.3 L/min or les s (Puls and Powell, 1992; Puls et al., 1991 ; Puls and Barcelona, 1989a; Barcelona, e t al., 1990). Wells should be purged at rates below those used to develop the well t o p r event further development of the well, to prevent damage to the well, and to avoi d di sturbing accumulated corrosion o r reacti on products in the well (Kearl et al. , 1 992; Puls et al., 1990; Puls and Barcelona, 198 9a; Puls and Barcelona, 1989b ; Barcelona, 1985b). Wells also should b e purged at or below their recovery rate s o that migration of water in the formatio n a bove the well screen does not occur . A low p urge rate also will r educe the possibility of stripping VOCs from the water, and wil l reduce the likeliho od of mobilizing colloids in the subsurface that are immobile unde r n atural flow conditions. The owner/operator should fo rmation water to cascade down the side s o f the well screen. At n o time should a well be purged to dryness if recharge causes the fo rmation water to cascade down the side s of the screen, as this will cause a n accelerated loss of volatiles. This problem sho uld be anticipated; water should b e purged from the well at a rate that does not caus e recharge water to be excessivel y ag itated. Laboratory experiments hav e s hown that unless cascading is prev ented, up to 70 percent of the volatiles present coul d be lost before sampling. To eli minate the need to dispose of larg e volumes of purge water, and to reduce th e amount of time required for purging, wells may b e purged with the pump intake jus t above or just within the screened interval

. T his procedure eli minates the need to purge t he colu mn of stagnant water located above the well screen (Barcelona et al., 1985b ; Robin and Gillham, 1987; Barcelona , 1 985b; Kearl et al., 1992) . Purging the well at th e top of the well screen should ensur e that fresh water from the aquifer move s through the well screen and upward withi n t he screened i nterval. Pumping rates below the recharge capability of the aquifer mus t b e maintained if purging is performed with the pum p placed at the top of the wel l screen, below the stagnant water colum n above the top of the well screen (Kearl e t al. , 1992). The Agency suggests that a p acker be placed above the screene d interval to ensure that "stagnant" casing water is not d rawn into the pump. The packer should be kept inflated in the well until after groundwater samples are collected. In certain situations, purging must b e performed with the pump placed at, o r i mm ediately below, the air/water interface.Subpart E

258 If a bailer must be used to sample the well, decontaminated prior to use. If the purge d the well should be purged by placing th e pu mp intake immediately below th e a ir/water interface. This will ensure that all of the water in the casing and filter pack i s p urge d, and it will minimize the possibility of mixing and/or sampling stagnant wate r when the bailer is lowered down into th e w ell and subsequently retrieve d (Keeley and Boateng, 1987). Similarly, purging should be performed at the air/water interface i f s ampling is not performed immediate ly after the well is purged without removing th e pump. Pumping at the air/water interfac e will prevent the mixing of stagnant an d fres h water when the pump used to purg e the well is removed and then lowered bac k down into the well for the purpose o f sampling. I n cases where an LNAPL has b een detected in t he monitoring well, special procedure s shoul d be used to purge the well. Thes e pr ocedures are described in USEP A (1992a). Fo r most wells, the Agency recommend s t hat purging continue unti l measurements of tur bidity, redox potential, and dissolve d oxy gen in in-line or downhole analyses o f gro und water have stabilized withi n app roximately 10% over at least tw o measurements ( Puls and Powell, 1992; Puls and Eychaner, 1990; Puls et al., 1990; Puls and Barcelona, 1989a; Puls and Barcelona, 198 9b; USEPA, 1991; Barcelona et al. , 1988b). If a well is purged to dryness or is purged such that full recovery exceeds two h ours, the well should be sampled as soon as a sufficient volume of ground water ha s en tered the well to enable the collection o f the necessary ground-water samples. A ll purging eq uipment that has been or will be in contact with ground water should be wa ter or the decontamination water i s contaminated (e.g., based on analytica l re sults), the water should be stored i n appropriate containers until analytica l resul ts are available, at which time prope r arrangements for disposal or treatmen t sh ould be made (i.e., contaminated purg e water may be a hazardous waste). Field Analyses Several constituents or parameters tha t owners or operators may choose to include i n a ground -water monitoring program may be p hysically or chemically unstable an d sho uld be tested after well purging an d be fore the collection of samples fo r labo ratory analysis. Examples of unstabl e par ameters include pH, redox (oxidation

re duction) potential, dissolved oxygen , temperature, and specific conductance. Field analyses should not be performed o n s a mples designated for laboratory analysis. An y field monitoring equipment or field

te st kits should be calibrated at th e be ginning of each use, according to th e m anufacturers' specif

ications and consistent w ith me thods in SW-846 (USEPA, 1986b). Sample Withdrawal and Collection T h e equipment used to withdraw a groundwater sample from a well must be selecte d b ased on consideration of the parameters to be ana lyzed in the sample. To ensure th e s amp le is representative of ground water in the formation, it is important to kee p ph ysical or chemical alterations of th e sa mple to a minimum. USEPA (1992a ) p rovides an overv iew of the issues involved in selecting ground-water samplin g eq uipment, and a summary of th eGround-Water Monitoring and Corrective Action

259 application and limitations of variou s Bladder pumps are generally recognized as s ampli ng mechanisms. Sampling materials the best overall sampling device for both and equipment should be selected t o o rganic and inorganic constitu ents, although pre serve sample integrity. Samplin g other types of pumps (e.g., low-rat e equipment should be constructed of iner t s ubmersible centrifugal pump s, helical rotor mat erial. Sample collection equipmen t electric submersible pumps) have bee n sh ould not alter analyte concentrations , fou nd suitable in some applications

. c ause loss o f analytes via sorption, or cause B ailers, althou gh inexpensive and simple to g ain of analytes via desorption , degradation, u se, have been found to cause volatilization or corrosion. Sampling equipment shoul d of samples, mobilization of particulates i n be designed such that Viton®, Tygon® , wel ls and imprecise results (USEPA , sil icone, or neoprene components do no t 1992a). come into contact with the ground-wate r sa mple. These materials have bee n The following recommendations apply t o demonstrated to cause sorptive losses o f the use and operation of ground-wate r co ntaminants (Barcelona et al., 1983 ; sampling equipment: Barce lona et al., 1985b; Barcelona et al. , 198 8b; Barcelona et al., 1990). Barcelon a ! Che ck valves should be designed an d (1988b) suggests that sorption of volatil e ins pected to ensure that foulin g or ganic compounds on silicone , problems do not reduce deliver y p olyethylene, and P VC tubing may result in ca pabilities or result in aeration o f gr oss errors when determinin g samples.concentrations of trace organics in groundwa ter samples. Barcelona (1985b ) ! Sampling equipment should never b e discourages the use of PVC samplin g dropped into the well, as this wil l eq uipment when sampling for organi c cau se degassing of the water upo n con taminants. Fluorocarbon resin (e.g. , impact. T eflon®) or stainless steel sampling devices which can be easily disassembled fo r ! C ontents of the sampling devi ce should t hor ough decontamination are widely used. be transferred to sample containers i n Dedicating sampling equipment to eac h a controlled manner that will minimize mon itoring well will help prevent cross

- sample agitation and aeration. contamination problems that could aris e f rom improper decontamina tion procedures. ! Decontaminatedsampling equipmen t Sampling equipment should cause minimal con tact with the ground or othe r sample agitation and should be selected t o co ntaminated surfaces prior t o reduce/eliminate sample contact with th e insertion into the well. atmosphere during sample transfer

. Sa mpling equipment should not allo w ! Ground-water samples should b e vol atilization or aeration of samples to th e extent that analyte concentrations ar e altered. sho uld not be allowed to come int o

collected as soon as possible after th e wel l is purged. Water that ha s rem ained in the well casing for mor e than about 2 hours has had th eSubpart E

260 o pportunity to exchan ge gases with the Once appropriate sampling equipment ha s atmosphere and to interact with th e been selected and operating procedure s w ell casin g material (USEPA, 1991b). e stablished, samples should be collected and

! The rate at which a well is sample d volatilization sensitivity of the parameter

. s hould not exceed the rate at which the The preferred collection order for some o f w ell was pu rged. Low sampling rates, the mo re common ground-water analytes is approximately 0.1 L/min, ar e depicted on the flow chart shown in Figure suggested. Low sampling rates wil l 5-4. he lp to ensure that particulates , immobile in the subsurface unde r The ground-water monitoring progra m am bient conditions, are not entraine d documentation should include explici t in the sample and that volatil e procedures for disassembly an d compounds are not stripped from th e decontamination of sampling equipmen t sample (Puls and Barcelona, 1989b ; before each use. Improperl y Barc elona, et al., 1990; Puls et al. , de contaminated equipment can affec t 1991; Kearl et al., 1992; USEPA , sampl es in several ways. For example , 199 1b). Pumps should be operated a t residual contamination from the previou s rat es less than 0.1 L/min whe n w ell may remain on equipm ent, or improper c ollecting samples for volat ile organics decontamination may not remove all of the analysis. de tergents or solvents used durin g

! Pump lines should be cleared at a rate regarding decontamination of the sampling of 0. 1 L/min or less before collectin g e quipment is available (USEPA 1992 a). To samples for volatiles analysis so tha t kee p sample cross-contamination to a t he samples collected will not be from min imum, sampling should proceed fro m t he p eriod of time when the pump was upgradient or background locations t o operating more rapidly. downgradient locations that would contai n

! Pum ps should be operated in a c o ntinuous manner so that they do not Sample Preservation and Handling p roduce samples t hat are aerated in the return tube or upon discharge. T he procedures fo r preserving and handling

! Whe n sampling wells that contai n t he integrity of the samples as the collection LN APLs, a stilling tube should b e device itself. Detailed procedures fo r ins erted in the well. Ground-wate r s ample preservation must b e provided in the samples should be collected from th e Qu ality Assurance Project Plan (QAPjP ) s creened interv al of the well below the that is included in the s ampling and analysis base of the tube. program description.

! Ground-water samples collected fo r ana lysis for organic constituents o r p arameters should not be filtered in the field. cont ainerized in the order of th e

decontamination. Specific guidanc e

higher concentrations of contaminants.

s amples are nearly as importan t for ensuring

### Figure 5-4 Generalized Flow Diagram of Ground-Water Sampling Steps

261Subpart E

262 Sample Containers maintains sample quality. Samples shoul d To a void altering sample quality, th e t hey are collecte d. These conditions should samples should be transferred from th e b e maintained until the sampl es are received s ampling equipment directl y into a prepared at the laboratory. Sample container s co ntainer. Proper sample containers fo r gene rally are packed in picnic coolers o r e ach constituent or group of constituents are special containers for shipment. ide ntified in SW-846 (USEPA, 1986b)

. Sa mples should never be composited in a P olystyrene foam, vermiculite, and "bubble common container in the field and the n pack" are frequently used to pack sampl e s p lit. Sample containers should be cleaned containers to prevent breakage. Ice i s in a manner that is appropriate for th e pl aced in sealed plastic bags and added t o con stituents to be analyzed. Cleanin g the cooler. All related paperwork is sealed procedures are provided by USEP A i n a plastic bag and taped to the in side top of ( 1986 b). Sample containers that have been the co oler. The cooler top is then tape d cleaned according to these procedures ca n s hut. Custody seals should be placed across be procured commercially. the hinges and latches on the outside of the M ost vendors w ill provide a certification of cleanliness. Transportation arrangements shoul d Sample Preservation provide for effective sample pickup an d Du ring ground-water sampling, ever y s hould be coordinated with the laboratory so attempt should be made to minimiz e that appropriate sample receipt, storage , c hanges in the chemistry of th e samples. To anal ysis, and custody arrangements can b e assist in maintaining the natural chemistr y provided. of the samples, it is necessary to preserv e the sample. The owner or operator shoul d Mos t analyses must be performed within a re fer to SW-846 (USEPA, 1986b) for th e s pecified period (holding t ime) from sample spe cific preservation method and holdin g c ollection. Holding time refers to the period time s for each constituent to be analyzed

. that begins when the sample is collecte d Methods of sample preservation ar e f rom the well and ends with its extraction or relatively limited and are intended to retard ana lysis. Data from samples not analyze d che mical reactions, such as oxidation , wit hin the recommended holding time s retard, biodegradation, and to reduce th e should be considered suspect. Som e effects of sorption. Preservation method s ho lding times for Appendix I constituent s are generally limited to pH control , are as short as 7 days. To provide th e refrigeration, and protection from light. laboratory with operational flexibility i n Sample Storage and Shipment usually are shipped via overnight courier

. The storage and transport of ground-wate r i nfluence sampling schedules. Coordination s amples must be performed in a manner that with laboratory staff during be co oled to 4 E C as soon as possible afte r

cooler.

maintain proper storage conditions an d delivery to the laboratory. Sampling plans

mee ting these holding times, sample s L aboratory capacity or operating hours mayGround-Water Monitoring and Corrective Action

263 pl anning and sampling activities i s ! In ternal temperature of shippin g imp ortant in maintaining sample an d c ontainer when samples were sealed into analysis quality. the container for shipping The documentation that accompanie s ! In ternal temperature of container whe n samp les during shipment to the laborator y opened at the laboratory u sually includes chain-of-custody (i ncluding a listing of all sample c ontainers), requested ! A ny remarks regardi ng potential hazards a nalyses, and full identification of the origin or other information the laboratory may o f samples (inclu ding contact names, phone need. numb ers, and addresses). Copies of al l d ocuments shippe d with the samples should An adequate chain-of-custody progra m be retained by the sampler. allows for tracing the possession an d Chain-of-Custody Record time of collection through completion o f To document sample possession from th e program should include: t ime of collection, a chain-of-custo dy record sh ould be filled out to accompany ever y ! Sample labels to pre ven t samp le shipment. The record shoul d misidentification of samples c onta in the following types of information:

! Sample number in tegrity of the samples from the tim e

! Signature of collector in the laboratory

! Date and time of collection ! Fie ld notes to record information abou t

! Media sampled (e.g., ground water) water monitoring program

! Sample type (e.g., grab) ! Ch ain-of-custody record to documen t

! Identification of sampling location/well

! Number of containers ! L aboratory st orage and analysis records,

! Parameters requested for analysis and which record pertinent informatio n

! Sig natures of persons involved in th e chain of possession Sample Labels

! Incl usive dates of possession with tim e Ea ch sample's identification should b e in 24-hour notation mar ked clearly in waterproof ink on th e ha ndling of individual samples from th e la boratory analysis. A chain-of-custod y

! Samp le custody seals to preserve th e they are collected until they are opene d

e ach sample collected during the groundsam ple possession from the time o f collection to analysis

whic h are maintained at the laborator y about the sample.

sample container. To aid in labeling, th eSubpart E

264 inf ormation should be written on eac h ! Well depth c ontainer prior to filling with a sample. The la bels should be sufficiently durable t o ! Sta tic water level depth an d remai n legible even when wet and shoul d measurement technique contain the following information:

! Sample identification number layers and the detection method

! Name and signature of the sampler ! Well yield (high or low) and wel l

! Date and time of collection

! Sample location

! Analyses requested. Sample Custody Seal Sam ple custody seals should be placed o n layers th e shipping container and/or individua l s ample bottle in a manner that wi ll break the ! Sample withdrawal procedure an d se al if the container or sample is tampere d equipment with. Field Logbook To p rovide an account of all activitie s i n volved in sample collection, all sampling ! Well sampling sequence activities, measurements, and observation s should be noted in a field log. Th e ! Typ es of sample bottles used an d information should include visua l sample identification numbers a ppearance (e.g., color, turbidit y, degassing, surface film), odor (type, strength), an d ! Preservatives used field measurements and calibration results

. Ambient conditions (tempe rature, humidity, ! Parameters requested for analysis wind, precipitation) and well purging an d s a mpling activities should also be recorded ! Field observations of sampling event as an aid in evaluating sample analysi s results. ! Name of collector The field logbook should document th e ! We ather conditions, including ai r following: temperature

! Well identification ! Pr esence and thickness of immiscibl e

recovery after purging (slow, fast)

! W ell purging procedure an d equipment

! Purge volume and pumping rate

! Time well purged

! Co llection method for immiscibl e

! Date and time of sample collection

! Results of field analysisGround-Water Monitoring and Corrective Action

265 ! In ternal temperature of field an d gro und-water samples analyzed. Th e shipping containers. Sample Analysis Request Sheet A sample analysis request sheet shoul d accompany the sample(s) to the laborator y and clearly identify which sampl e cont ainers have been designated for eac h requested parameter and the preservatio n metho ds used. The record should includ e the following types of information:

! Name of person receiving the sample

! Lab oratory sample number (if differen t from field number)

! Date of sample receipt

! Analyses to be performed (includin g desired analytical method)

! In formation that may be useful to th e labo ratory (e.g., type and quantity o f p reservatives added, unusual co nditions). Laboratory Records Once the sample has been received in th e laboratory, the sample custodian and/o r laboratory personnel should clearl y document the processing steps that ar e ap plied to the sample. All sampl e preparation (e.g., extraction) an d de terminative steps should be identified i n the laboratory records. Deviations fro m established methods or standard operatin g proce dures (SOPs), such as the use o f sp ecific reagents (e.g., solvents, acids) , temperatures, reaction times, an d instrument s ettings, should be not ed. The results of the analyses of all quality control sample s shou ld be identified for each batch o f l aboratory logboo k should include the time, d ate, and name of the person who p erformed each processing step. Analytical Procedures The requirements of 40 CFR Part 25 8 include detection and assessmen t monitoring activities. Under detectio n mo nitoring, the constituents listed in 4 0 CFR Part 258, Appendix I are to b e analy zed for. This list includes volatil e organic compounds (VOCs) and selecte d inorganic constituents. No specifi c anal ytical methods are cited in th e regu lations, but there is a requirement (4 0 CFR §258.53(h)(5)) that any practica l quantitation limit (PQL) used in subsequent sta tistical analysis "be the lowes t co ncentration level that can be reliabl y achieved within specified limi ts of precision an d accuracy during routine laborator y o perating conditions that are av ailable to the f acil ity." Suggested test methods are listed i n Appendix II of Part 258 fo r informational purposes only. Method 8240 (ga s c hromatog raphy with packed column; mass sp ectrometry) and Method 8260 (ga s ch romatography with capillary column ; mas s spectrometry) are typical method s used f or all Appendix I VOCs. Th e inor ganic analyses can be performed usin g i nductively coupled plasma a tomic emission spe ctroscopy (ICP) Method 6010. Thes e methods, as well as other method s a ppropr iate to these analyses, are presented in T ests Methods for Evaluating Soli d Waste, Physical/Chemical Methods , SW-846 (USEPA, 1986), and are routinely performed by numerous analytical testin g la boratories. These methods typicall y pr ovide PQLs in the 1 to 50 μg/L range

. The ground-water monitoring plan mus t specify the analytical method to be used.Subpart E

266 E valuation an d documentation of analytical laboratory of choice is exercising a n performance requires that quality contro l appropriate QA/QC program. samp les be collected and analyzed alon g w ith the ground-water monitoring samples. The owner or operator should provide fo r Chapter One of SW-846 (Qualit y the use of standards, laboratory blanks , Ass urance) describes the types of qualit y du plicates, and spiked samples fo r co ntrol samples necessary, as well as th e cal ibration and identification of potentia l frequency at which they must be collecte d mat rix interferences, especially for meta l and a nalyzed. In general, these qualit y de terminants. Refer to Chapter One o f co ntrol samples may include trip blanks , SW-8 46 for guidance. The owner o r e quipment rinsate samples, field duplicates, operator should use adequate statistica l method blanks, matrix spikes an d p rocedures (e .g., QC charts) to monitor and duplicates, and laboratory control samples. d ocument performance an d to implement an Other mechanisms, including sampl e problems (e.g., instrument maintenance , hol ding times, surrogate constituents, an d operator training). Data from QC sample s s tandard additions, are also used to control (e .g., blanks, spiked samples) should b e an d document data quality. Th e us ed as a measure of performance or as a n spec ification of and adherence to sampl e indicator of potential sources of cross

hol ding times minimizes the sampl e cont amination, but should not be used b y deg radation that occurs over time

. the laboratory to alter or correct analytica l Eva luating the recovery of surrogat e da ta. All laboratory QC data should b e constituents spiked into organic sample s s ubmitted with the ground-water monitoring allows the analyst and data user to monitor sample results. the efficiency of sample extraction an d a nalysis. The method of standard additions Field Quality Assurance/Quality Control is used to eliminate the effects of matri x interferences in inorganic analyses. To verify the precision of field samplin g Quality Assurance/Quality Control bla nks, equipment blanks, and duplicates , One of the fundamental responsibilities o f sample also should be collected fo r th e owner or operator is to establish a laboratory QC samples. c ontinuing pro gram to ensure the reliability and validity of field and analytica l All field QC samples should be prepare d labo ratory data gathered as part of th e overall ground-water monitoring program

. The owner or operator must explicitl y describe the QA/QC program that will b e us ed in the laboratory. Most owners o r operators will use commercial laboratorie s to conduct analyses of ground-wate r samp les. In these cases, the owner o r o perator is responsible for ensuring that the eff ective program to resolve testin g

procedures, field QC samples, such as tri p

s hould be coll ected. Additional volumes of

exa ctly as regular investigation sample s with regard to sample volume, containers , a nd preservation. The concentra tions of any c ontaminants found in blank s amples should not be used to correct the ground-wate r data

. The contaminant concentrations i n blan ks should be documented, and if th e conc entrations are more than an order o f magnitude greater than the field sampl eGround-Water Monitoring and Corrective Action

267 results, the ow ner/operator should resample Equi pment rinsate samples are used t o th e ground water. The owner/operato r assess the efficacy of sampling equipmen t shou ld prepare the QC samples a s decontamination procedures. The dat a re commended in Chapter One of SW-84 6 valid ation process uses the results from al l and at the frequency recommended b y of these QC samples to determine if th e C hapter One of SW-84 6 and should analyze r eported analytical data accurately describe the m for all of the required monitorin g the samples. All reported data must b e par ameters. Other QA/QC practices, suc h e valuated -- a reported value of "non-detect" as sampling equipment calibration , i s a quanti tative report just like a numerical e quipment decontamination procedures, and value and must be validated. chain-of-custody procedures, are discussed in other sections of this chapter and should The data validation process must als o b e described in the owner/opera tor's QAPjP. co nsider the presence and quality of othe r Validation ( e.g., calibrat ion frequency and descriptors, The analytical data report provided by th e c riter ia for data quality are described in the l aboratory will pre sent all data measured by qual ity assurance project plan (QAPjP) o r t he labora tory but will not adjust those data sampl ing and analysis plan (SAP). Thes e for field or laboratory quality contro l d ocuments may reference criteria fro m some ind icators. This means that just becaus e other source, (e.g., the USEPA Contrac t dat a have been reported, they are no t La boratory Program). The performanc e n ecessarily an accurate re presentation of the c riteria must be correctly spec ified and must quality of the ground water. For example , be used for data validation. It is a waste of acetone and methylene chloride are ofte n tim e and money to evaluate data agains t used in laboratories as cleaning an d standards other than those used to generate extraction solvents and, consequently, ar e them

. Several documents are available t o often laboratory contaminants, transmitte d assist the reviewer in validation of data b y th rough the ambient air into samples

. diff erent criteria (i.e., Chapter One of Tes t M eth od blanks are analyzed to evaluate the Methods for Evaluating Solid Waste , ex tent of laboratory contamination

. Physical/Chemical Methods, USEPA CL P Constituents found as contaminants in th e Functional Guidelines for Evaluatin g met hod blanks are "flagged" in the sampl e O rganics Analyses, USEPA CLP Funct ional data. The sample data are not, however , G u idelines for Evaluating Pesticides/PCBs adjusted f

or the contaminant concentration. Analyses, etc.). Other kinds of samples are analyzed t o In addition to specific data that describ e assess other data quality indicators. Tri p data quality, the validator may conside r bla nks are used to assess contamination b y oth er information that may have an impac t v o latile organic constituents during sample on the end-use of the data, such a s shipment and storage. Matrix spike/matrix background concentrations of th e spike duplicate sample pairs are used t o constituent in the environment. In an y evaluate analytical bias and precision. ev ent, the QAPjP or SAP also shoul d kind s of data used to ensure data qualit y

m atrix spec ific detection limits). All of the

d esc ribe the validation procedures that will be used. The result ofSubpart E

268 this validation should be the classificatio n ! S tatistical methods to be us ed to evaluate o f data as acceptable or una cceptable for the ground-water monitoring data and p urposes of the proje ct . In some cases, data demonstrate compliance with th e may be further qualified, based either o n performance standard; ins ufficient data or marginal performanc e (i.e., qualitative uses only, estimate d ! A pproved demonstration that monitoring concentration, etc.). requirements are suspended (i f Documentation The ground-water monitoring progra m required b y §258.50 through §258.55 relies ! Piezometer and well construction log s on documentation to demonstrat e for the ground-wa ter monitoring system. compl iance. The operating record of th e MS WLF should include a complet e de scription of the program as well a s 5. 9 STATISTICAL ANALYSIS periodic implementation reports. 40 CFR §258.53 (g)-(i) At a mini mum, the following aspects of the 5.9.1 Statement of Regulation g round-water monitoring program s hould be des cribed or included in the operatin g (g ) The owner or operator must specify record: in t he operating record one of th e

! The Sampling and Analysis plan tha t details sample parameters, samplin g frequency, sample collection , pr eservation, and analytical methods t o b e used, shipping procedures, and chainof-custody procedures;

! The Quality Assurance Project Pla n (QA PjP) and Data Quality Objective s (DQOs);

! The locations of monitoring wells;

! The design, installation, development , and decommission of monitoring wells , pi ezometers, and other measurement , sampling, and analytical devices;

! Site hydrogeology; applicable);

! Boring logs;

f ollowing statistical methods to be used in e valuating ground-water monit oring data for each hazardous constituent. Th e statistical test chosen shall be conducte d s eparately for each hazardous constituent in each well.

(1 ) A parametric analysis of varianc e (A NOVA) followed by multipl e co mparisons procedures to identif y st atistically significant evidence o f c ontamination. The method mus t include es timation and testing of the contrast s b etween each compliance well's mean and the background mean levels for eac h constituent.

(2 ) An analysis of variance (ANOVA ) based on ranks followed by multipl e co mparisons procedures to identif y st atistically significant evidence o f c ontamination. The method mus t includeGround-Water Monitoring and Corrective Action

269 es timation and testing of the contrast s (2) If an individual well compariso n bet ween each compliance well's media n proc edure is used to compare a n and the background median levels fo r individual compliance well constituen t each constituent. concentration with backgroun d (3) A t olerance or prediction interva l water protection standard, the test shal l procedure in which an interval for eac h be done at a Type I error level of no les s co nstituent is established from th e than 0 .01 for each testing period. If a d istribution of the background data, and multiple comparisons procedure is used, the level of each constituent in eac h t he Type I exper iment wise error rate for c ompliance well is compar ed to the upper each testing period shall be no less tha n tolerance or prediction limit. 0 .05; however , the Type I error of no less (4) A control chart approach that gives mu st be maintained. This performanc e control limits for each constituent . stan dard does not apply to toleranc e i ntervals, prediction intervals, or control (5) Ano ther statistical test method tha t charts. meets the performance standards o f § 258. 53(h). The owner or operator must (3) I f a control chart approach is used to p lace a justification for this alternative in ev aluate ground-water monitoring data , the operati ng record and notify the State the specific type of control chart and it s D irector of the use of thi s alternative test. associated parameter values shall b e The justification must demonstrate tha t pr otective of human health and th e the alternative method meets th e environment. The parameters shall b e pe rformance standards of §258.53(h) . d etermined after con sidering the number of samples in the background data base , (h) A ny statistica l method chosen under t he data distribution, and the range of the §258.53(g) shall comply with th e c oncentration va lues for each constituent following performance standards, a s of concern. appropriate: (1) The statistical method used t o pre dictional interval is used to evaluat e evaluate ground-water monitoring dat a g round-water mo nitoring data, the levels sha ll be appropriate for the distributio n o f confidence and, for toler ance intervals, of chemical parameters or hazardou s t he perce ntage of the population that the cons tituents. If the distribution of th e i nterval mus t contain, shall be protective chemical parameters or hazardou s of h uman health and the environment . constituents is shown by the owner o r These parameters shall be determine d o perator to be inappropriate for a normal afterconsidering the number of samples th eory test, then the data should b e in th e background data base, the dat a t ransformed or a distr ibution-free theory distribution, and the range of th e test should be used. If the distribution s c oncentration va lues for each constituent f or the constituent s differ, more than one of concern. statistical method may be needed. constituent concentrations or a ground than 0.01 for individual well comparisons

(4) If a tolerance interval or aSubpart E

270 (5) T he statistical method shall account significant increase over background a t f or data be low the limit of detection with one or more statistical procedures tha t ar e protective of human health and th e e nvironment. Any p ractical quantitation limit (PQL) that is used in the statistical m ethod s hall be the lowest concentration l evel that can be reliably achieved within s pecified limits of precision and accuracy during routine laboratory operatin g co nditions that are available to th e facility. (6) If necessary, the statistical metho d shall include procedures to control o r correct for seasonal and spatia l v ariability as well as temporal correlation in the data. (i) The owner or operator mus t determine whether or not there is a st atistically significant increase ove r b ackground values for eac h parameter or constituent required in the particula r gr ound-water monitoring program tha t appl ies to the MSWLF unit, a s determined under §§258.54(a) o r 258.55(a) of this part. (1) In determining whether a statistically significant increase ha s occurred, the owner or operator mus t compare the ground-water quality o f eac h parameter or constituent at eac h mon itoring well designated pursuant t o § 258.5 1(a)(2) to the background value of that constituent, according to th e st atistical procedures and performanc e s tandards specified under paragraphs (g) and (h) of this section. (2) Within a reasonable period of tim e aft er completing sampling and analysis , the owner or operator must determin e whether there has been a statistically each monitoring well. 5.9.2 Applicability The statistical analysis requirements ar e appli cable to all existing units, new units , and lateral expansions of existing units fo r w hich ground-water monitoring is required. T he use of stati stical procedures to evaluate monitoring data shall be used for th e duration of the monitoring program , including the post-closure care period. The owner or operator must indicate in th e operating record the statistical method tha t w ill be used in t he analysis of ground-water mo nitoring results. The data objectives o f th e monitoring, in terms of the number o f sa mples collected and the frequency o f col lection, must be consistent with th e statistical method selected. S everal options for analysis of g round-water data are provided in the criteria. Othe r methods may be used if they can be show n to meet the performance standards. Th e app roved methods include both parametri c a nd nonparametric procedures, which differ prim arily in constraints placed by th e stati stical distribution of the data. Contro l ch art, tolerance interval, and predictio n interval approaches also may be applied. The owner or operator must conduct th e statistical comparisons between upgradient a nd downgradie nt wells after completion of e ach sampling event and receipt of validated data

. The statistical procedure mus t co nform to the performance standard of a Type I e rror level of no less than 0.01 fo r int er-well comparisons. Control chart , tolerance interval, and prediction interva l a pproaches must incorporate decisi on valuesGround-Water Monitoring and Corrective Action

271 that are protective of human health and the us eful for selecting other methods (Dixo n env ironment. Generally, this is meant t o in clude a significance level of a least 0.05

. Procedures to treat data below analytica l met hod detection levels and seasonalit y effec ts must be part of the statistica l analysis. 5.9.3 Technical Considerations Th e MSWLF rule requires facilities t o evaluate ground-water monitoring dat a us ing a statistical method provided i n §258.53(g) that meets the performanc e standard of §258.53(h). Section 258.53(g ) c ontains a provision allowing for the use of an al ternative statistical method as long a s t he performance standards of §2 58.53(h) are met. T he requirements of §258.5 3(g) specify that on e of five possible statistical methods b e used for evaluating ground-wate r moni toring data. One method should b e spe cified for each constituent. Althoug h different methods may be selected for each c onstituent at new facilities, use of a method m ust be substantiat ed by demonstrating that the distribution of data obtained on tha t cons tituent is appropriate for that metho d (§2 58.53(h)). Selection of a specifi c method is described in Statistical Analysi s o f Ground-Water Monitoring Data at RCRA Fac ilities - Interim Final Guidance " (US EPA, 1989) and in Statistical Analysi s o f Ground-Water Monitoring Data at RCRA Fa cilities - Addendum to Interim Fina l Gui dance (USEPA, 1992b). EPA als o offers software, entitled Use r Do cumentation of the Ground-Wate r I nformation Tracking Syst em (GRITS) with S tatistical A nalysis Capability, GRITSTAT Ve rsion 4.2. In addition to the statistica l guid ance provided by EPA, the followin g references may be an d Massey, 1969; Gibbons, 1976 ; Aitchison and Brown, 1969; and Gilbert , 1987). The statistical methods that may be u sed in evaluating gro und-water monitoring data include the following:

! Parametric analysis of varianc e (ANOVA) with multiple comparisons

! Rank-based (nonparametric) ANOV A with multiple comparisons

! T olera nce interval or prediction interval

! Control chart

! An alternative statistical method (e.g. , CABF t-test or confidence intervals). If an alternative method is used, then th e St ate Director must be notified, and a j ustification for its use mus t be placed in the operating record. T he statistical analysis methods ch osen must meet performance standa rds specified under §258.53(h), which include the following: 1) The method must be appropriate for the observed distribution of the data 2) Individual well comparisons t o ba ckground ground-water quality or a ground-water protection standard shal l b e done at a Type I error level of no less t han 0.01 or, if th e multiple comparisons pr ocedure is used, the experiment-wis e error rate for eac h testing period shall be no less than 0.05 3) If a control chart is used, the type o f cha rt and associated parameter value sSubpart E

272 shall be protective of human health an d Multiple Well Comparisons the environment 4) The level of confidence and percentag e d owngradient combined) are screened in the o f the population contained in an interval s ame stratigraphic unit, then the appropriate shall be protective of human health an d statistical comparison method is a multiple the environment well comparison using the ANOV A 5) T he method must acco unt for data below pr ocedure assumes that the data from eac h t he limit of detection (less than the PQL) well group come from the same type (e.g. , in a manner that is protective of huma n Normal) of distribution with possibl y health and the environment di fferent mean concentrations. Th e 6) Th e method must account for seasona l there are multiple background wells, on e and spatial variability and tempora l should consider the possibility of trying t o correlation of the data, if necessary. p ool these background data into one group. These statistical analysis methods shall b e for more accurate statistical comparisons , us ed to determine whether a significan t primarily because better information i s increase over background values ha s k nown about the backgroun d concentrations occ urred. Monitoring data must b e a s a whole. Downgradient wells should not s tat istically analyzed after validated results be po oled, as stated in the regulations

. fr om each sampling and analysis event ar e Ground-water monitoring data tend t o received. follow a log normal distribution (USEPA , The statistical performance standard s prior to applying a parametric ANOV A provi de a means to limit the possibility o f procedure. By conducting a lo g making false conclusions from th e transformation, ground-water monitorin g monitoring data. The specified error leve l d ata will generally be converted to a normal o f 0. 01 for individual well comparisons for di stribution. By applying a Shapiro-Wil k proba bility of Type I error (indication o f test, probability plots, or other normalit y c ontamination when it is not present or false tests on the residuals (errors) from th e p ositive) esse ntially means that the analysis ANOVA procedure, the normality of th e is predicting with 99-percent confidenc e tr ansformed data can be determined. I n th at no significant increase in contaminan t addition, data variance for each well in th e l evels is evident when in fact no increase is comparison must be approximatel y p resen t. Non-detect results must be treated eq uivalent; this condition can be checke d in an appropriate manner or their influence u sing Levene's or Bartle tt's test. These tests o n the sta tistical method may invalidate the are provided in USEPA (1992b) an d statistical conclusion. Non-detect result s USEPA (1989). are discussed in greater detail later in thi s section. If t he transformed data do not conform t o If more than two wells (background an d

pro cedure. The parametric ANOV A

ANOV A tests for a difference in means. If

S uch an increase in sample si ze often allows

1989), and usually need to be transforme d

the normality assumption, a nonparametri c ANOV A procedure may be used. Th eGround-Water Monitoring and Corrective Action

273 n o nparametric statistical procedures do not d esigned to co ntain a designated proportion depend as much on the mathematica l of the population (e.g., 95 percent of al l properties of a specified distribution. Th e possible sample measurements). Becaus e n o nparametric equivalent to the parametric t he interval is constructed fr om sample data, ANO VA is the Kruskal-Wallis test, whic h i t also is a random i nterval. And because of a n alyzes variability of the average ranks of sam pling fluctuations, a tolerance interva l the data instead of the measurement s can contain the specified proportion of th e themselves. population only with a certain confidenc e If

t he data display seasonality (regular , per iodic, and time-dependent increases o r Tol erance intervals are very useful fo r decreases in parameter values), a two-wa y g round-water data analy sis because in many ANOV A procedure should be used. If th e s ituations one wants to ensure that at most a seasonality can be corrected, a one-wa y small fraction of the compliance wel l ANOVA procedure may still be a ppropriate. sa mple measurements exceed a specifi c M ethods to treat seasonality are described in c oncentration l evel (chosen to be protective USEPA (1989)

. of human health and the environment). ANO VA procedures attempt to determin e Prediction intervals are constructed t o whe ther different wells have significantl y contain the next sample value(s) from a different average concentrations o f popu lation or distribution with a specifie d c onstituents. If a difference is indicated, the probability. That is, after sampling a ANO VA test is followed by a multipl e background well for some time an d c omparisons procedur e to investigate which measuring the concentration of an analyte, specific wells are different among thos e t he data can be used to construct an interval tested. The overall experiment-wis e t ha t will contain the next analyte sample or significance level of the ANOVA must b e samples (assuming the distribution has no t kept to a minimum of 0.05, while th e ch anged). Therefore, a prediction interva l minimum significance level of eac h will c ontain a future value or values wit h ind ividual comparison must be set at 0.01

. specified probability. Prediction interval s USEPA (1992b) provides alternativ e can also be constructed to contain th e methods that can be used when the number average of several future observations. of in dividual contrasts to be tested is ver y high. I n summary, a tolerance interval contains a Tolerance and Prediction Intervals prediction interval contains one or mor e Two types of statistical intervals are ofte n statement or "confidence coefficient " co nstructed from data: tolerance interval s assoc iated with it. It should be noted tha t and prediction intervals. A comprehensive these intervals assume that the sample data discu ssion of these intervals is provided i n u sed to construct the intervals are normally U SEPA 1992b. Though of ten confused, the distributed. interpretations and uses of these interval s are quite distinct. A tolerance interval i s level.

prop ortion of the population, and a f uture obs ervations. Each has a probabilitySubpart E

274 Individual Well Comparisons m onitoring data. Such data m ay be adjusted When only two wells (e.g., a singl e degr ee of change over time. Guidance fo r bac kground and a single compliance poin t and limitations of intra-well compariso n well ) are being compared, owners o r te chniques are provided in USEPA (1989 ) o perators should not per form the parametric and USEPA (1992b). or nonparametric ANOVA. Instead, a parametric t-test, such as Cochran' s Treatment of Non-Detects Approximation to the Behrens-Fishe r Stu dents' t-test, or a nonparametric tes t The t reatment of data below the detectio n shoul d be performed. When a singl e l imit of th e analytical method (non-detects) c ompliance well group is bei ng compared to used depends on the number or percentag e b ackground data and a nonparametric test is of non-detects and the statistical metho d n eeded, the Wilcoxi n Rank-Sum test should emplo yed. Guidance on how to treat non

be performed. These tests are discussed i n detects is provided in USEPA (1992b). m ore detail in standar d statistical references and in USEPA (1992b). 5.10 DETECTION MONITORING Intra-Well Comparisons 40 CFR §258.54 In tra-well comparisons, where data of on e 5.10.1 Statement of Regulation well are evaluated over time, are useful i n e valuating trends in indiv idual wells and for (a) D etec tion monitoring is required at i dentifying seasonal effec ts in the data. The MSWLF units at all ground-wate r intra-well comparison methods do no t monitoring wells defined unde r com pare background data to complianc e § §258.51(a) (1) and (a)(2) of this part. At data. Where some existing facilities ma y a m inimum, a detection monitorin g not have valid background data, however , p rogram must include t he monitoring for int ra-well comparisons may represent th e the constituents listed in Appendix I o f only valid comparison available. In th e this part. absen ce of a true background well, severa l monitoring events may be required t o 1) Th e Director of an approved Stat e determine trends and seasonal fluctuation s may delete any of the Appendix I in ground-water quality. m onitorin g parameters for a MSWLF Control charts may be used for intra-wel l removed constituents are no t co mparisons but are only appropriate fo r reas onably expected to be in o r uncontaminated wells. If a well i s derived from the waste contained i n inter cepting a release, then it is already i n the unit. a n "out-of-contro l" state, which violates the principal assumption underlying contro l 2) Th e Director of an approved Stat e c hart procedures. Tim e series analysis (i.e., plotting concentrations over time) i s extremely useful for identifying trends i n for seasonal effects to aid in assessing th e

PROGRAM

unit if it can be shown that th e

may establish an alternative list o f inorganic indicator parameters for a MSWLF unit, in lieu of some or all ofGround-Water Monitoring and Corrective Action

275 t h e heavy metals (constituents 1-15 in must be collected and analyzed durin g Appendix I), if the alternativ e pa rameters provide a reliabl e ind ication of inorganic releases fro m the MSWLF unit to the ground water. I n determining alternativ e parameters, the Director shal l consider the following factors: (i) Th e types, quantities, an d concentrations of constituents i n wastes managed at the MSWLF unit; (ii) The mobility, stability, an d persistence of waste constituents o r th eir reaction products in th e unsaturated zone beneath th e MSWLF unit; (iii) The detectability of indicato r p a rameters, waste constituents, and reaction products in the groun d water; and (iv) Th e concentration or values an d coefficients of variation o f monitoring parame ters o r constituents in the backgroun d ground-water. (b) Th e monitoring frequency for al l co nstituents listed in Appendix I, or th e alternative list approved in accordanc e wit h paragraph (a)(2), shall be at leas t semiannual during the active life of th e faci lity (including closure) and the post cl osure period. A minimum of fou r ind ependent samples from each wel l ( background an d downgradient) must be collected and analyzed for the Appendi x I co nstituents, or the alternative lis t ap proved in accordance with paragrap h (a)(2), during the first semiannua l s ampling event. At least one sample from e ach well(background and downg radient) subsequent semiannual sampling events. The D irector of an approved State ma y sp ecify an appropriate alternativ e frequency for repeated sampling an d ana lysis for Appendix I constituents, o r the alternative list approved i n a ccordance with paragraph (a) (2), during the active life (including closure) and the p ost-closure care period. The alternative fr equency during the active lif e (including closure) shall be no less tha n annual. The alternative frequency shal l b e based on consideration of the fol lowing factors: 1) Lit hology of the aquifer an d unsaturated zone; 2) Hydraulic conductivity of the aquifer and unsaturated zone; 3) Ground-water flow rates; 4) Minimum distance betwe e n upg radient edge of the MSWLF uni t an d downgradient monitoring wel l screen (minimum distance of travel) ; and 5) Resource value of the aquifer. (c) I f the owner or ope rator determines, purs uant to §258.53(g) of this part, tha t there is a sta tistically significant increase over background for one or more of th e cons tituents listed in Appendix I or th e alternative list approved in accordanc e with paragraph (a)(2), at any monitoring well at the boundary specified unde r §258.51(a)(2), the owner or operator: (1) M ust, wit hin 14 days of this finding, plac e a notice in the operating recor d i ndicating which constit uents have shown statistically significant changes fromSubpart E

276 background levels, and notify the Stat e lis t has been established by the Director o f D irector that this notice was placed in the an approved State. operating record; and (2) Must establish an assessmen t e vent, the owner or operator must collect at monitoring program meeting th e le ast four independent ground-wate r requirements of §258.55 of this par t samp les from each well and analyze th e within 90 days, except as provided for in s amples for all const ituents in the Appendix paragraph (3) below. I or alternative list. Each subsequen t (3) The owner/operator ma y m inimum, the collection and analysis of one demonstrate that a source other than a samp le from all wells. The monitorin g MSWLF unit caused the contaminatio n r equirement continues thr oughout the active or that the statistically significan t l ife o f the landfill and the post-closure care i ncrease resulted from error in sampling, period. a nalysis, statistica l evaluation, or natural variation in ground-water quality. A If an owner or operator determines that a report documenting this demonstratio n statistically significant increase ove r must be certified by a qualified ground - background has occurred for one or mor e wa ter scientist or approved by th e A pp endix I constituents (or constituents on Di rector of an approved State and b e an alternative list), a notice must be placed place d in the operating record. If a i n the facility operating record (see Table 5- suc cessful demonstration is made an d 2). The owner or operator must notify th e documented, the owner or operator may S tate Director within 14 d ays of the finding. continue detection monitoring a s W ithin 90 da ys, the owner or operator must s pecifi ed in this section. If after 90 days, e stablish an assessment m onitoring program a successful demonstration is not made , c onforming to the requirements of §258.55. the o wner or operator must initiate a n assessment monitoring program a s If evidence exists that a statisticall y required in §258.55. sig nificant increase is due to factor s 5.10.2 Applicability may make a demonstration to this effect t o E xcept for the small landfill exemption and ce rtifieddemonstration in the operatin g the no migration demonstration, detectio n reco rd. The potential reasons for a n monitoring is required at existing MSWL F apparent statistical increase may include: unit s, lateral expansions of units, and ne w MSWLF units. Monitoring must occur a t ! A contaminant source other than th e l east semiannually at both background wells landfill unit and downgradient well locations. Th e Dir ector of an approved State may specif y ! A natural variation in ground-wate r an alternative sampling frequency

. quality Monitoring parameters must include al l Appendix I constituents unless a n ! An analytical error alternative During the first semiannual monitorin g

semiannual event must include, at a

unrelated to the unit, the owner or operator
t he Director of an approved State or place aGround-Water Monitoring and Corrective Action

277 ! A statistical error Independent Sampling for Background

! A sampling error. T he groun d-water monitoring requirements T he demonstration th at one of these reasons collected from each well to establis h i s responsible for the stat istically significant ba ckground during the first semiannua l i n crease over background must be certified m onitoring event. This is because a lmost all by a qualified ground-water scientist o r stat istical procedures are based on th e ap proved by the Director of an approve d a ssumption that samples are independent of S tate. If a successful demons tration is made eac h other. In other words, independen t a nd documented, the owne r or operator may samples more accurately reflect the tru e continue detection monitoring. rang e of natural variability in the groun d If a successful demonstration is not mad e independent samples are more accurate

. within 90 days, the owner or operator must Replicate samples, whether field replicate s i n itiate an assessment monitoring program. or lab splits, are not statisticall y A flow chart for a detection monitorin g independent measurements. prog ram in a State whose program has no t b een approved by EPA is provided in Figure It may be necessary to gather th e 5-5. independent samples over a range of tim e 5.10.3 Technical Considerations d i fferences. If seasonal differences are not I f there is a statistically significant increase positives increases (monitoring result s over background during detectio n ind icate a release, when a release has no t moni toring for one or more constituent s occ urred). The sampling interval chose n list ed in Appendix I of Part 258 (or a n m us t ensure that sampling is being done on a lternative list of par ameters in an approved different volumes of ground water. T o State), the owner or operator is required t o determine the appropriate interval between be gin assessment monitoring. Th e sample collection events that will ensur e requirement to conduct assessmen t independence, the owner or operator ca n monitoring will not change, even if th e de termine the site's effective porosity , Director of an approved State allows th e hydraulic conductivity, and hydrauli c mo nitoring of geochemical parameters i n grad ient and use this information t o lieu of some or all of the metals listed i n calculate ground-water velocity (USEPA , Appen dix I. If an owner or operato r 1 989). Kn owing the velocity of the ground sus pects that a statistically significan t wate r should enable an owner/operator t o inc rease in a geochemical parameter i s establish an interval that ensures the fou r c aused by natur al variation in ground-water samp les are being collected from fou r quality or a source other than a MSWL F different volumes of water. For additiona l unit, a demonstration to this effect must be information on establishing samplin g d ocumented i n a report to avoid proceeding in terval, see Statistical Analysis o f to assessment monitoring. Groundwater Monitoring Data at RCRA specify that four independent samples b e

water, and statistical analyses based o n

sufficient to account for seasona l take n into account, the chance for fals e

### Figure 5-5. Detection Monitoring Program
278Ground-Water Monitoring and Corrective Action

279 Fac ilities - Interim Final Guidance , co nstituents from Appendix I may b e (USEPA, 1989). a cceptable. Usually, a waste would have to Alternative List/Removal of Parameters d et ermination. The owner or operator may An alternative list of Appendix I pre sence or absence of certain constituent s c onstituents may be all owed by the Director in th e waste. The owner or operator als o of an approved State. The alternative lis t w ould have to demon strate that constituents may use geochemical parameters, such a s propo sed for deletion from Appendix I ar e pH a nd specific conductance, in place o f not degradation or reaction products o f some o r all of the metals (Parameters 1 c onstituents potentially pres ent in the waste. through 15) in Appendix I. Thes e alternative parameters must provide a Alternative Frequency reliable indication of inorganic release s f rom the MSWLF unit to ground water. The In approved States, 40 CFR §258.54(b ) option of establishing an alternative lis t a llows the Direct or to specify an alternative app lies only to Parameters 1 through 15 o f fr equency for ground-water monitoring

. Appen dix I. The list of ground-wate r Th e alternative frequency is applicabl e monitoring parameters must include all o f d ur ing the active life, including the closure the volatile organic compounds (Appendi x and the post-closure periods. Th e I, Parameters 16 through 62). al ternative frequency can be no less tha n A p otential problem in substitutin g geoc hemical parameters for metals on th e T he need to vary monitoring frequen cy must alternative list is that many of th e be ev aluated on a site-specific basis. Fo r geochemical parameters are naturall y e xample, for MS WLF units located in areas o ccurring. However , these parameters have w ith low ground-water flow rates, it may be b een used to indicate release s from MSWLF acceptable to monitor ground water les s uni ts. Using alternative geochemica l f requently. The samp ling frequency chosen parameters is reasonable in cases wher e must be sufficient to protect human healt h na tural background levels are not hig h and the environment. Depending on th e eno ugh to mask the detection of a releas e gr ound-water flow rate and the resourc e fro m a MSWLF unit. The decision to us e val ue of the aquifer, less frequen t a lte rnative parameters also should consider monitoring may be allowable or mor e nat ural spatial and temporal variability i n f req uent monitoring may be necessary. An the geochemical parameters. approved State may specify an alternativ e T he types, qu antities, and concentrations of a nalysis of Appendix I constituent s based on w astes managed at the M SWLF unit play an the following factors: important role in determining whethe r removal of parameters from Appendix I i s 1) Li thology of the aquifer and th e appr opriate. If an owner or operator ha s unsaturated zone definite knowledge of the nature of waste s acc epted at the facility, then removal o f be ho mogeneous to allow for this kind o f submit a demonstration that documents the

annual.

fr equency for repeated sampling an dSubpart E

280 2) Hyd raulic conductivity of the aquife r 2) A comprehensive audit of sampling , and the unsaturated zone 3) Ground-water flow rates 4) Minimum distance between th e upgradient edg e of the MSWLF unit and the downgradient well screen 5) The resource value of the aquifer. Approved States also can set alternativ e f requenc ies for monitoring during the postcl osure care period based on the sam e factors. Notification T he notific ation requirement under 40 CFR § 258.54(c) requi res an owner or operator to 1 ) place a notice in the o perating record that indicates which constituents have show n statistically significant increases and 2 ) n otify the St ate Director that the notice was plac ed in the operating record. Th e constituents can be from either Appendix I or from an alternative list. Demonstrations of Other Reasons For Statistical Increase An ow ner or operator is allowed 90 days to d emonstrate t hat the statistically significant inc rease of a contaminant/constituent wa s c aused by statistical, sa mpling, or analytical errors or by a source other than the landfill uni t. The demonstration allowed i n §258.54(c)(3) may include: 1) A demonstration that the increas e re sulted from another contaminan t source laboratory, and data evaluatio n procedures 3) Res ampling and analysis to verify th e presence and concentration of th e constituents for which the increase wa s reported. A de monstration that the increase i n constituent concentration is the result of a so urce other than the MSWLF unit shoul d document that:

! An alternative source exists.

! H ydraulic co nnection exists between the alternative source and the well with th e significant increase.

! C onstituent(s) (or precursor c onstituents) ar e present at the alternative source o r along the flow path from the alternative s ource prior to possible release from the MSWLF unit.

! Th e relative concentration an d distribution of constituents in the zone of co ntamination are more strongly linke d to the alternative source than to th e M SWLF unit when the fate a nd transport characteristics of the constituents ar e considered.

! The concentration observed in groun d wate r could not have resulted from th e MSWLF unit given the wast e constituents and concentrations in th e MS WLF unit leachate and wastes, an d site hydrogeologic conditions.

! Th e data supporting conclusion s regarding the alternative source ar e historically consistent wit h hydrogeologicGround-Water Monitoring and Corrective Action

281 co nditions and findings of th e 5.11 ASSESSMENT MONITORIN G monitoring program. PROGRAM Th e demonstration must be documented , certified by a qualified ground-wate r 5.11.1 Statement of Regulation s cientist, an d placed in the operating record of the facility. (a) Assessment monitoring is require d Demonstrations of Other Sources of increase over background has bee n Error det ected for one or more of th e A s uccessful demonstration that th e alternate list approved in accordanc e statistically significant change is the resul t with § 258.54(a)(2). of an error in sampling, analysis, or dat a evaluation may include the following: (b) Wit hin 90 days of triggering a n

! Clear indication of a transcription o r an nually thereafter, the owner o r calculation error ope rator must sample and analyze th e

! Clear indication of a systematic error in identified in Appendix II of this part. A analysis or data reduction mini mum of one sample from eac h

! Resampling, analysis, and evaluation of analyzed during each sampling event . results For a ny new constituent detected in th e

! Cor rective measures to prevent th e recurrence of the err or and incorporation o f these measures into the ground-water monitoring program. If r esampling is necessary, the sample(s ) take n must be independent of the previou s sa mple. More than one sample may b e req uired to substantiate the contention tha t the original sample was not representativ e of the ground-water quality in the affecte d well(s). 40 CFR §258.55(a)-(f)

whenever a statistically significan t

c onstituents listed in A ppendix I or in the

assessment monitoring program, an d
ground water for all constituent s

d owngra dient well must be collected and

down gradient wells as a result of th e co mplete Appendix II analysis, a min imum of four independent sample s from each well (background an d dow ngradient) must be collected an d a nalyzed to establish background for the new constituents. The Director of a n app roved State may specify a n appropriate subset o f wells to be sampled and analyzed for Appendix I I constituents during assessmen t m onitoring. The Director o f an approved Sta te may delete any of the Appendix I I monitoring parameters for a MSWL F unit i f it can be shown that the remove d c on stituents are not reasonably expected to be contained in or derived from th e waste contained in the unit.Subpart E

282 (c) The Director of an approved Stat e I to t his Part or in the alternative lis t may specify an appropriate alternat e approved in accordance wit h frequency for repeated sampling an d §258.54(a)(2), and for those constituent s analysis for the full set of Appendix I I in Appendix II that are detected i n constituents required by §258.55(b) o f r esponse to paragraph (b) of this section, this part, during the active life (including and record their concentrations in th e closure) a nd post-closure care of the unit facility operating record. At least on e considering the following factors: sa mple from each well (background an d (1) Lithology of the aquifer an d analyzed during these sampling events . unsaturated zone; The D irector of an approved State ma y (2) Hy draulic conductivity of th e fr equency during the active lif e aquifer and unsaturated zone; (inc luding closure) and the post closur e (3) Ground-water flow rates; thi s paragraph. The alternativ e (4) Minimum distance betwee n t he alterna te list approved in accordance u pgradient edge of the MSWLF unit and with §258.54(a)(2) during the active lif e downgradient monitoring well scree n (including closure) shall be no less tha n (minimum distance of travel); annual. The alternative frequency shal l (5) Resource value of the aquifer; and s pecified i n paragraph (c) of this section; (6) Nat ure (fate and transport) of an y (3) E stablish background concentration s con stituents detected in response to thi s f or any constit uents detected pursuant to section. pa ragraphs (b) or (d)(2) of this section ; (d) After obtaining the results from the ini tial or subsequent sampling event s (4) Establish ground-water protectio n required in p aragraph (b) of this section, sta ndards for all constituents detecte d the owner or operator must: pursu ant to paragraph (b) or (d)(2) o f (1) W ithin 14 days, place a notice in the p rotect ion standards shall be established operating record identifying th e in accordance with paragraphs (h) or (i ) Appendix II constituents that have bee n of this section. detected and notify the State Directo r that this notice has been placed in th e (e) I f the concentrations o f all Appendix operating record; II constituents are shown to be at o r (2) Within 90 days, and on at least a statistical procedures in §258.53(g), for s emiannual bas is thereafter, resample all tw o consecutive sampling events, th e we lls specified by § 258.51(a), conduc t own er or operator must notify the Stat e a na lyses for all constituents in Appendix dow ngradient) must be collected an d
specify an alternative monitorin g

p e riod for the constituents referred to in f requency for Appendix I constituents or

be based on consideration of the factor s

and

this section. The ground-wate r

bel ow background values, using th eGround-Water Monitoring and Corrective Action

283 D irector of this finding and may re turn to may specify an appropriate subset of well s detection monitoring. t o be included in the assessment monitoring (f) If the concentrations of an y also may specify an alternative frequenc y Appendix II constituents are abov e for repeated sampling and analysis o f b ackground values, but all concentr ations App endix II constituents. This frequenc y are below the ground-water protectio n may be decreased or increased based upo n standard established under paragraph s co nsideration of the factors i n (h) or (i) of this section, using th e §25 8.55(c)(1)-(6). These options fo r st atistical procedures in §258.53(g), th e as sessment monitoring programs ar e owner or operator must continu e av ailable only with the approval of th e as sessment monitoring in accordanc e Director of an approved State. with this section. 5.11.2 Applicability the initial sampling for Appendix I I As sessment monitoring is required at al l t he owner or oper ator must place the results existing units, lateral expansions, and ne w in the operating record and notify the State fac ilities whenever any of the constituent s Director that this notice has been placed i n listed in Appendix I are detected at a the operating record. co ncentration that is a statisticall y s ignificant increase over backg round values. Within 90 days of receiving these initia l Figure 5-6 presents a flow chart pertainin g r esults, the owner or operator must resample to applicability requirements. all wells for all Appendix I and detecte d Within 90 days of beginning assessmen t l ist of constituents must be sampled at least moni toring, the owner or operator mus t s emiannually thereafter, an d the list must be res ample all downgradient wells an d upd ated annually to include any newl y anal yze the samples for all Appendix I I detected Appendix II constituents. const ituents. If any new constituents ar e identified in this process, four independent With in the 90-day period, the owner o r samp les must be collected from al l op erator must establish background value s upgradient and downgradient wells an d and ground-water protection standard s analyzed for those new constituents t o (GWPSs) for all Appendix II constituent s est ablish background concentrations. Th e d etected. The requirem ents for determining comp lete list of Appendix II constituent s GW PSs are provided in §258.55(h). If th e m ust be monitored in each well annually for concentrations of all Appendix I I the duration of the assessment monitorin g c onstituents are at or below the background p rogram. In an approved Sta te, the Director values after two independent, consecutiv e ma y reduce the number of Appendix I I s ampling events, th e owner or operator may co nstituents to be analyzed if it can b e ret urn to detection monitoring afte r reasonably shown that those co nstituents are notification has been made to the Stat e not present in or derived from the wastes

. Director. If, after these two The Director of an approved State p rogram. The Director of an ap proved State

Withi n 14 days of receiving the results o f constituents under assessment monitoring ,

Ap pendix II constituents. This combine d

### Figure 5-6 ASSESSMENT MONITORING

284Ground-Water Monitoring and Corrective Action

285 sa mpling events, any detected Appendix I I the owner or operator must collect at leas t c onstituent is statistically above background one sample from each downgradient wel l but below the GWPSs, the assessmen t a nd analyze the samples for the Appendix II monitoring program must be continued. pa rameters. If a downgradient well ha s 5.11.3 Technical Considerations c onstitu ent, four independent samples must T he purp ose of assessment monitoring is to d owngradient wells t o establish background eval uate the nature and extent o f for the new constituent(s). The date, wel l c ontaminat ion. The assessment monitoring locations, parameters detected, and thei r p rogram is phase d. The first phase assesses concentrations must be documented in th e th e presence of additional assessmen t operating record of the facility, and th e monitoring constituents (Appendix II or a State Director must be notified within 1 4 revised list designated by an approv ed State) days of the initial detection of Appendix II in all downgradient wells or in a subset o f parameters. On a semiannual basi s g round-water monito ring wells specified by thereafter, both background an d th e Director of an approved State. I f d owngradient w ells must be sampled for all concentrations of all Appendix I I Appendix II constituents. constituents are at or below backgroun d values using the statistical procedures i n Alternative List §25 8.53(g) for two consecutive samplin g periods, then the owner or operator ca n In a n approved State, the Director ma y return to detection monitoring. de lete Appendix II parameters that th e Fol lowing notification of a statisticall y not be anticipated at the facility. A significant increase of any Appendix I demo nstration would be based on a c onstituent above background, the owner or characterization of the wastes contained i n operator has 90 days to develop an d th e unit and an assessment of the leachat e implement the assessment monitorin g c onstituents. Add itional information on the pro gram. Implementation of the progra m alte rnative list can be found in Sectio n i nvolves sampling downgradie nt monitoring 5.10.3. w ell s for ground water passing the relevant point of compliance for the unit (i.e., th e Alternative Frequency wa ste management unit boundary o r alternative boundary specified by th e The Director of an approved State ma y Di rector of an approved State)

. s pecify a n alternate sampling frequency for Downgradient wells are identified i n th e entire Appendix II list for both th e §25 8.51(a)(2). Initiation of assessmen t ac tive and post-closure periods of th e mo nitoring does not stop the detectio n facility. The decision to change th e m o nitoring program. Section 258.55(d)(2) monitoring frequency must consider: s pecifies tha t analyses must continue for all Ap pendix I constituents on at least a 1) L ithology o f the aquifer and unsaturated s emiannual basis. Within the 90-day period, zone; detectable quantities of a new Appendix I I be collected from all background an d

owne r or operator can demonstrate woul dSubpart E

286 2) Hyd raulic conductivity of the aquife r 5.12 ASSESSMENT MONITORIN G and unsaturated zone; 3) Ground-water flow rates; 4) M inimum distance of travel ( between the MSWLF unit edge to downgradien t monitoring wells); and 5) Nat ure (fate and transport) of th e detected constituents. T he Director of an approved State also may all ow an alternate frequency, other tha n s emiannual, for the monit oring of Appendix I and detected Appendix II constituents. The monitoring frequency must b e su fficient to allow detection of ground

water contamination. If contamination i s detected early, the volume of ground water contaminated will be smaller and th e required remedial response will be les s b urdensome. Additiona l information on the a lternate frequency can be found in Section 5.10.3. In a n approved State, the Director ma y spec ify a subset of wells that can b e monitored for Appendix II constituents t o confirm a release and track the plume o f contamin ation during assessmen t monitoring. The owner or operator shoul d w ork closely with the State in developing a monitoring plan that targets the specifi c ar eas of concern, if possible. This ma y rep resent a substantial cost savings , especially at large facilities for which onl y a very small percentage of wells showe d e xceedances abov e background. The use of a subset of wells l ikely will be feasible only i n cases where the directio n and rate of flow are relatively constant. PROGRAM 40 CFR §258.55(g) 5.12.1 Statement of Regulation (g) If o ne or more Appendix I I con stituents are detected at statisticall y s ignificant leve ls above the ground-water protection standard established unde r p aragraphs (h) or (i) of this se ction in any sam pling event, the owner or operato r m ust, within 14 days of this finding, place a no tice in the operating recor d id entifying the Appendix II constituent s that have exceeded the ground-wate r p rotection standard and , notify the State Director and all appropriate loca l gov ernment officials that the notice ha s b een placed in th e operating record. The owner or operator also: ( 1) (i) Mu st characterize the nature and ext ent of the release by installin g a dditional monitor ing wells as necessary; (ii) Must install at least one additiona l mon itoring well at the facility boundar y i n the direction of contamin ant migration and sample this well in accordance wit h §258.55(d)(2); (ii i) Must notify all persons who ow n the land or reside on the land tha t d irectly overlies any part of the plume of contamination if contaminants hav e m igrated off-site if in dicated by sampling o f wells in acc ordance with §258.55(g)(i); and (i v) Must initiate an assessment o f cor rective measures as required b y §255.56 of this part within 90 days; orGround-Water Monitoring and Corrective Action

287 (2) May demonstrate that a sourc e installing and sampling an appropriat e othe r than a MSWLF unit caused th e number of additional monitoring wells co ntamination, or that the statisticall y s ignificant increase resulted from error in 2) Install at least one additiona l s ampling, analysis, statistical evaluation, do wngradient well at the facilit y or natural variation in ground-wate r prop erty boundary in the direction o f qu ality. A report documenting thi s m igrat ion of the contaminant plume and demonstration must be certified by a sample that well for all Appendix I I qu alified ground-water scientist o r com pounds initially and thereafter, i n approved by t he Director of an approved co nformance with the assessmen t S tate and p laced in the operating record. monitoring program If a successfu l demonstration is made the owner or operator must continu e 3) Notify all property owners whose lan d mo nitoring in accordance with th e ov erlies the suspected plume, if th e a ssessment monitoring program p ursuant sa mpling of any property boundary to § 258.55, and may return to detectio n w ell( s) indicates that contaminants have mo nitoring if the Appendix I I migrated offsite con stituents are below background a s s pecified in §258.55( e). Until a successful 4) Initiate an assessment of correctiv e dem onstration is made, the owner o r m easures, as required by § 258.56, within ope rator must comply with §258.55(g ) 90 days. inc luding initiating an assessment o f corrective measures. In assessment monitoring, the owner o r 5.12.2 Applicability other than the MSWLF unit caused th e Th is requirement applies to facilities i n sig nificant increase was the result of a n assessment monitoring and is applicabl e er ror in sampling, analysis, statistica l during the active life, closure, and post

- eval uation, or natural variation in ground

closure care periods. wate r quality. The demonstration must b e 5.12.3 Technical Considerations scientist or approved by the Director of a n If an Appendix II constituent(s) exceeds a de monstration is made, the owner o r G WPS in any sampling event, the owner or operator must comply with §258.55(g) and oper ator must notify the State Directo r ini tiate assessment of corrective measures

. with in 14 days and place a notice of thes e I f the demonstration is successful, the owner fin dings in the operating record of th e or operator must return to assessmen t M SWLF facility. In addition, the owner or monitoring and may return to the detection operator must: prog ram provided that all Appendix I I 1) Ch aracterize the lateral and vertica l two consecutive sampling periods. extent of the release or plume b y ope rator may demonstrate that a sourc e

co ntamination or that the statisticall y

certified by a qualified ground-wate r ap proved State. Until a successfu l

c onstituen ts are at or below background forSubpart E

288 Release Investigation s emian nually or at an alternative frequency I f the GWPS is exceeded, a series of actions State. The initial sample must be analyzed m

ust be taken. These actions are described for all Appendix II constituents. in th e next several paragraphs. The owne r or operator must investigate the extent o f Notification of Adjoining Residents and the release by installing additiona l Property Owners mo nitoring wells and obtaining additiona l ground-water samples. The investigatio n If ground-water monitoring indicates tha t sho uld identify plume geometry, bot h contamination has migrated offsite, th e la terally and vertically. Prior to such fiel d owner or operator must notify propert y ac tivities, records of site operation an d ow ners or residents whose land surfac e maintenance activities should be reviewe d o verlies any part of the c ontaminant release. to identif y possible release locations within A lthough the requirement does not describe th e landfill and whether such releases ar e t he contents of the no tice, it is expected that expec ted to be transient (e.g., one tim e the notice could include the followin g rele ase due to repaired liner) or long-term

. items: Due to the presence of dissolved ioni c co nstituents, such as iron, magnesium , ! Date of detected release ca lcium, sodium, potassium, chloride , sulfate, and carbonate, typically associate d ! Chemical composition of release with MSWLF unit leachates, geophysica l technique s, including resistivity and terrain ! R eference to the constituent(s), reported conductivity, may be useful in defining the concentration(s), and the GWPS plume. Characterizing the nature of th e re lease should include a description of th e ! Representatives of the MSWLF facilit y r ate and dire ction of contaminant migration wi th whom to discuss the finding , and the chemical and physica l including their telephone numbers characteristics of the contaminants. Property Boundary Monitoring Well At least one monitoring well must b e protect human health and th e installed at the facility boundary in th e environment. direction of contaminant migration

. Ad ditional wells may be required t o Demonstrations of Other Sources of del ineate the plume. Monitoring wells a t Error the facility boundary should be screened to m onitor all stratigraphic units that could be T he owner or operator may demonstrate that preferential pathways for contaminan t th e source of contamination was not th e mi gration in the uppermost aquifer. I n MSWL F unit. This demonstration i s s om e cases, this may require installation of discussed in Section 5.10.3. n ested we lls or individual wells screened at s everal discrete intervals. The w ell installed at the facility boundary must be sample d det ermined by the Director of an approve d

! Plans and schedules for future activities

! I nterim recommen dations or remedies toGround-Water Monitoring and Corrective Action

289 Return to Detection Monitoring (3) For constituents for which th e A facility conducting assessment mo nitoring i denti fied under subparagraph (1) above ma y return to detection monitoring if th e or health based levels identified unde r concentrations of all Appendix I I §258.5 5(i)(1), the backgroun d constituents are at or below backgroun d concentration. l evels for two cons ecutive sampling periods us ing the statistical procedures i n (i) The Director of an approved Stat e §258.53(g). The requirement tha t may establish an alternative ground background concentrations must b e water protection standard fo r mai ntained for two consecutive samplin g constituents for which MCLs have no t events will reduce the possibility that th e bee n established. These ground-wate r owne r or operator will fail to detec t p rotection standards shall be appropriate con tamination or an increase in a he alth based levels that satisfy th e con centration of a hazardous constituen t following criteria: wh en one actually exists. The Director o f an approved State can establish a n (1) The level is derived in a manne r alternative time period (§258.54(b). consistent with Agency guidelines fo r

5.13 ASSESSMENT MONITORIN G 34006, 34014, 34028); PROGRAM 40 CFR §258.55(h)-(j) (2) The level is based on scientificall y 5.13.1 Statement of Regulation with the Toxic Substances Control Ac t (h) The owner or operator mus t CFR Part 792) or equivalent; establish a ground-water protectio n sta ndard for each Appendix I I (3) F or carcinogens, t he level represents c onstituent dete cted in the ground water. a concentration associated with an excess Th e ground-water protection standar d lifetime cancer risk level (due t o shall be: cont inuous lifetime exposure) with the 1 (1) For constituents for which a maximum contaminant level (MCL) ha s (4) For systemic toxicants, the leve l been promulgated under Section 1412 of rep resents a concentration to which th e the Safe Drinking Water Act (codified ) human population (including sensitiv e u nder 40 CFR Part 141, the MCL for that s ubgroups) could be exposed to on a daily constituent; bas is that is likely to be withou t (2) For constituents for which MCL s during a lifetime. For purposes of thi s have not been promulgated, th e subpart, systemic toxicants include toxic background concentration for th e ch emicals that cause effects other tha n constituent established from wells i n cancer or mutation. accordance with §258.51(a)(1); or b ackground level is h igher than the MCL

assessing the health risks o f env ironmental pollutants (51 FR 33992 ,

val id studies conducted in accordanc e G ood Laborato ry Practice Standards (40

x 10 to 1 x 10 range; and -4 -6

appreciable risk of deleterious effect sSubpart E

290 (j) In establishing ground-wate r 5.13.3 Technical Considerations pr otection standards under paragrap h ( i), the Director of an approved S tate may For each Appendix II constituent detected , consider the following: a GWPS must be established . The GWPS is (1) M ultiple contaminants in th e ground Where the background concentration i s water; higher than the MCL, then the GWPS i s (2) Exposure threats to sensitiv e environmental receptors; and D irectors of approved States have the option (3) Ot her site-specific exposure o r c onstituents without MCLs. This alt ernative potential exposure to ground water. G WPS must b e an appropriate health-based 5.13.2 Applicability levels must: The criteria for establishing GWPSs ar e ! Be consistent with EPA health ris k applicable to all facilities conductin g assessment guidelines a ssessment monitoring w here any Appendix II co nstituents have been detected. Th e ! Be based on scientifically valid studies owner or operator must establish a GWP S for each Appendix II constituent detected. ! B e within a risk range of 1x10 to 1x10 If the constituent has a promulgate d max imum contaminant level (MCL), the n ! Fo r systemic toxicants (causing effect s t he GWPS is the MCL. If no MCL has been oth er than cancer or mutations), be a published for a given Appendix I I concentration to which the huma n c onstituent, the background concentr ation of population could be exposed on a dail y the constituent becomes the GWPS. I n bas is without appreciable risk o f c ases where the background conce ntration is deleterious effects during a lifetime. higher than a promulga ted MCL, the GWPS is set at the background level. T he health-based GWPS ma y be established In approved States, the Director ma y constituent, exposure to sensitiv e establish an alternative GWPS fo r en vironmental receptors, and other site

c onstituents for which MCLs have not been spe cific exposure to ground water. Ris k e stablished. Any alternative GWPS must be ass essments to establish the GWPS mus t h ealth-based levels that satisfy the criteria in consider cumulative effects of multipl e § 258.55(i). The Dir ector may also consider pathways to receptors and cumulativ e any of the criteria identified in §258.55(j)

. effects on exposure risk of multipl e In cases where the backgroun d c ontaminants. Guidance and procedures for concentration is higher than the health

- establishing a health-based risk assessment based levels, the GWPS is set at th e may be found in Guidance on Remedia l background level. Actions for to b e set at either the MCL or background

. established at background.

of establishing an alternative GWPS fo r
level, based on specific criteria. Thes e

-4 -6 for carcinogens

cons idering the presence of more than on eGround-Water Monitoring and Corrective Action

291 Co ntaminated

Groundwater at Superfun d (3) T he costs of remedy implementat ion; Sites, (USEPA, 1988). and

5.14 ASSESSMENT OF as S tate or local permit requirements o r CORRECTIVE MEASURES oth er environmental or public healt h 40 CFR §258.56 requirements that may substantiall y 5.14.1 Statement of Regulation (a) W ithin 90 days of finding t hat any of the results of the corrective measure s the constituents listed in Appendix I I ass essment, prior to the selection o f have been detected at a statisticall y rem edy, in a public meeting wit h significant level exceeding the ground - interested and affected parties. w ater protection standards de fined under § 258.5 5(h) and (i) of this part, the owner 5.14.2 Applicability o r operator must initiate an ass essment of c orr ective measures. Such an assessment A n asse ssment of corrective measures must must be completed within a reasonabl e be c onducted whenever any Appendix I I period of time. co nstituents are detected at statisticall y (b) The owner or operator mus t ass essment of corrective measures must b e continue to monitor in accordance wit h initi ated within 90 days of the finding

. the assessment monitoring program a s Duri ng the initiation of an assessment o f specified in §258.55. c orrective measures, assessment monitoring (c) The assessment shall include a n corrective measures must conside r an alysis of the effectiveness of potentia l performance (including potential impacts) , corrective measures in meeting all of the ti me, and cost aspects of the remedies. I f req uirements and objectives of th e i mplement ation requires additional State or remedy as described under §258.57 , local permits, such requirements should b e addressing at least the following: id entified. Finally, the results of th e (1) T he performan ce, reliability, ease of discussed in a public meeting wit h i mplementation, and potential impacts of interested and affected parties. appropriate potential remedie s, including s afety imp acts, cross-media impacts, and 5.14.3 Technical Considerations co ntrol of exposure to any residua l contamination; An assessment of corrective measures i s (2) Th e time required to begin an d depending on the design and age of th e complete the remedy; faci lity, the completeness of the facility' s (4) T h e institutional requirements such

affect implementation of the remedy(s). (d) T he owner or operator must discuss

s ignificant levels exceeding the GWP S. The

must be continued. The assessment o f

corrective measures assessment must b e

site-specific and will vary significantl y

hi storical records, the nature an d concentration of the contaminants found inSubpart E

292 t he ground wat er, the complexity of the site ( e.g., unlin ed leachate storage ponds, failed hy drogeology, and the facility's proximit y c over system, leaky leachate transp ort pipes, to sensiti ve receptors. Corrective measures pa st conditions of contaminated storm are generally approached from tw o overflow), such information should b e directions: 1) identify and remediate th e consi dered as part of the assessment o f s ource of contam ination and 2) identify and corrective measures. remediate the known contamination

. Because each case will be site-specific, the Exi sting site geology and hydrogeolog y owner or operator should be prepared t o information, ground-water monitorin g docum ent that, to the best of his or he r results, and topographic and cultura l te chnical and financial abilities, a diligen t i nformation must be documented clear ly and eff ort has been made to complete th e ac curately. This information may includ e assessment in the shortest time practicable. s oil boring logs, test pit and mo nitoring well The factors listed in §258.56(c)(1) must be d ata, and other informat ion collected during c onsidered in assessing corre ctive measures. fa cility design or operation. Th e T hese general factors are discu ssed below in information should be expressed in a te rms of source evaluation, plum e manner that will aid interpretation of data

. delineation, ground-water assessment, an d S u ch data may include isopach maps of the corrective measures assessment. t hickness of the upper aquif er and important Source Evaluation c ontaminants, flow ne ts, cross-sections, and As part of the assessment of correctiv e i nterpretation that m ay be useful in a source measures, the owner or operator w ill need to ev aluation is presented in RCRA Facilit y identify the nature of the source of th e Investigation Guidance: Volume I

- release. The first step in this identification Development of an RFI Work Plan an d is a review of all available site information General Considerations for RCRA Facilit y re garding facility design, wastes received , Investigations, (USEPA 1989a), RCR A an d onsite management practices. Fo r Facility Investigation Guidance: Volume IV new er facilities, this may be a relativel y - C ase Study Examples, (USEPA 1989d) , simple task. However, at some olde r and Practical Guide For Assessing an d facilities, detailed records of the facility' s Remediating Contaminated Sites (USEP A hist ory may not be as well documented , 1989e). making source definition more difficult

. Design, climatological, and waste-typ e Plume Delineation information should be used to evaluate th e dur ation of the release, potential seasona l To effectively assess corrective measures , eff ects due to precipitation (increase d infiltration and leachate generation), an d possible constituent concentrations. I f sour ce evaluation is able to identify a repaira ble engineering condition that likely con tributed to the cause of contaminatio n l ogs, geophysical data, wat er level elevation

strata, isoconcentration maps o f

c ontour maps. Additional guidance on data

the lateral and vertical extent o f con tamination must be known. When it i s d etermined that a GWPS i s exceeded during t he assessment monitoring program, it may be n ecessary to install additional wells t o cha racterize the contaminant plume(s). A tGround-Water Monitoring and Corrective Action

293 least one additional well must be added a t a nd effective por osity) should be developed the p roperty boundary in the direction o f for modeling contaminant transport i f con taminant migration to allow timel y s ufficient data are not available. Anisotropy n otification to p otentially affected parties if and heterogeneity of the aquifer must b e contamination migrates offsite. evaluated, as well as magnitude an d Th e following circumstances may requir e present and predicted plume configuration. additional monitoring wells:

! Faci lities that have not determined th e gr ound-water contamination at MSWL F hor izontal and vertical extent of th e units involve pump and treat or in-sit u contaminant plume biological technologies (bio-remediation)

.

! Locations where the subsurface i s on the size of the plume, the pumpin g heterogeneous or where ground-wate r characteristics of the aquifer, and th e flow patterns are difficult to establish che mical transport phenomena. Sourc e

! Mounding associated with MSWL F measures to reduce the rate of contaminant units. m igration should be included in the costs of Bec ause the requirements for additiona l water modeling of the plume may b e mo nitoring are site-specific, the regulatio n initiated to establish the following: do es not specifically establish cases wher e ad ditional wells are necessary or establis h ! Th e locations and pumping rates o f t he number of additional wells that must be withdrawal and/or injection wells installed. During the plume delineation process, th e concentrations at exposure points owne r or operator is not relieved fro m co ntinuing the assessment monitorin g ! L ocations of addition al monitoring wells program. T he rate of plum e migration and the change may have on ground-water remediation in contaminant concentrations with tim e m

ust be monitored to allow predicti on of the ! T he effects of advection and dispersion, extent and timing of impact to sensitiv e retardation, adsorption, and othe r receptor s. The receptors may include users attenuation processes on the plum e of b oth ground-water and surface wate r dimensi ons and contaminan t bodies where contaminated ground wate r concentrations. m ay be discharged. In some cases, transfer o f volatile compounds from ground water to Any modeling effort must consider tha t th e soil and to the air may provide a n simulations of remedial response measure s addition al migration pathway. Information and contaminant transport are based o n regarding the aquifer characteristics (e.g. , many necessary simplifying assumptions, hydraulic conductivity, storage coefficients, dura tion of source inputs, to help explai n

Cu rrently, most treatment options fo r

T he co st and duration of treatment depends

control and ground-water flow contro l

a

ny r emedial activity undertaken. Ground-

! Predictions of contaminan t

! The effect that source control option sSubpart E

294 whi ch affect the accuracy of the model

. ! S trat igraphy and hydraulic properties of These assumptions include boundar y the aquifer c onditions, the degree and spa tial variability of anisotropy, dispersivity, effectiv e ! Treatment concentration goals an d po rosity, stratigraphy, and the algorithm s objectives. used to solve contaminant transpor t eq uations. Model selection should b e The owner or operator should conside r a ppropriate for the amount of data available, w hether immediate measures to li mit further an d the technical uncertainty of the mode l p lume migration (e.g., con tainment options) results mus t be documented by a sensitivity or measures to minimize furthe r analysis on the input parameters. A introduction of contaminants to groun d sen sitivity analysis is generally done afte r water are necessary. model calibration by varying one inpu t param eter at a time over a realistic rang e The process by which a remedial action i s and then evaluating changes in mode l undertaken will generally include th e outp ut. For additional information o n following activities: mod eling, refer to the Further Informatio n Section of Chapter 5.0 and the RCR A ! H ydrogeologic inves tigation, which may F acility Investigat ion Guidance: Volume II in clude additional well installations ,

- Soil, Groundwater and Subsurface Ga s de tailed vertical and lateral sampling t o Releases (USEPA, 1989b). characterize the plume, and cor e Ground-Water Assessment sor ption of constituents on the geologi c To assess the potential effectiveness o f corrective measures for ground-wate r ! R isk assessment, to determ ine the impact c ontamination, th e following information is on sensitive receptors, which ma y needed: inc lude identification of the need t o

! Plume definition (includes the types , GWPSs c oncentration, a nd spatial distribution of the contaminants) ! Literature and technical review o f

! The amenability of the contaminants t o further study or implementation specific treatment and potential fo r contaminants to interfere wit h ! E valuation of costs of differe nt treatment treatability options

! Fate of the contaminants (whethe r ! Estimation of the time required fo r chemical transformations have, are, o r com pletion of remediation under th e may be occurring, and the degree t o different treatment options which the species are sorbed to th e geologic matrix) sa mpling to determine the degree o f matrix

develop treatment goals other tha n

treatment technologies considered fo rGround-Water Monitoring and Corrective Action

295 ! Bench-scale treatability studie s ! The anticipated cost of the remediation, conducted to assess potentia l effectiveness of options

! Selection of technology(ies) an d pro posal preparation for regulatory an d public review and comment

! Full-scale pilot study for verification of tr eatability and optimization of th e selected technology

! In itiation of full-scale treatmen t technology with adjustments, a s necessary

! Co ntinuation of remedial action unti l treatment goals are achieved. Corrective Measures Assessment To compare different treatment options , s ubstantial amounts of technical i nformation mus t be assembled and assessed. Th e o bjective of this information-gathering task is to identify the following items for eac h treatment technology:

! T he e xpected performance of individual approaches

! Th e time frame when individua l approaches can realistically b e implemented

! Th e technical feasibility of th e re mediation, including new an d innovative technologies, performance , rel iability and ease of implementation , safety and cross media impacts

! The anticipated time frame whe n remediation should be complete including capital expenditures, design , o n going engineering, and monitoring of results

! T echnical a nd financial capability of the ow ner or operator to successfull y complete the remediation

! Disposal requirements for treatmen t residuals

! Other regulatory or institutiona l requirements, including State and loca l pe rmits, prohibitions, or environmenta l restrictions that may affect th e i mplementation of the propos ed remedial activity. The performance objectives of th e c orrective measures shou ld be considered in terms of source reduction, cleanup goals , and cleanup time frame. Source reductio n woul d include measures to reduce or sto p fu rther releases and may include the repai r of existing facility components (line r s ystems, leachate storage pond line rs, piping sy stems, cover systems), upgrading o f com ponents (liners and cover systems), o r prem ature closure in extreme cases. Th e technology proposed as a cleanup measur e shou ld be the best available technology , g iven the practicable capability o f the owner or operator. The technologies identified should b e reliable, based on their previou s performance; however, new innovativ e technologies are not discouraged if they can be shown, with a reasonable degree o f confidence, to be reliable. B ecause most treatment processes, i ncluding biorestoration, potentially produc e byproducts or release contaminants t oSubpart E

296 different media (e.g., air stripping o f of a qualified professional and wil l volatile compounds), the impacts of suc h potential releases must be evaluated

. Re leases to air may constitute a worke r he alth and safety concern and must b e addressed as part of the alternative s as sessment process. Other cross medi a i mpacts, i ncluding transfer of contaminants f rom soils to ground water, surfac e water, or a ir, shoul d be assessed and addressed in the a ssessment of corrective actions. Guidance fo r addressing air and soil transport an d con tamination is provided in USEP A (1989b) and USEPA (1989c). Analyses should be conducted on treatment o ptions to determine whether or not they are pro tective of human health and th e environment. Envir onmental monitoring of ex posure routes (air and water) ma y n eces sitate health monitoring for personnel inv olved in treatment activities i f un acceptable levels of exposure ar e possible. On a case-by-case basis , imp lementation plans may require bot h forms of monitoring. The development and screening o f in dividual corrective measures requires a n understanding of the physio-chemica l rela tionships and interferences between the cons tituents and the sequence of treatmen t measures that must be imple mented. Proper s equencing of treatment met hods to produce a fe asible remedial program must b e e valuated t o avoid interference between the presence of some constituents and th e e ffective removal of the targe ted compound. I n addition, screening and design pa rameters of potential treatment options should b e eva luated in the early stages of conceptua l development and planning to eliminat e te chnically unsuitable treatment methods

. In general, selection of an appropriat e tre atment method will require th e experience necessitate a literature review of the bes t available treatment technologies. Numerous case studies and publ ished papers fr om scientific and engineering technica l jour nals exist on treatability of specifi c compounds and groups of relate d compounds. Development of ne w technologies and refinements o f technologies have been rapid. A co mpendium of available literature tha t i ncludes treatment technologies for organic and inorganic contaminants, technolog y selection, and other sources of information (e.g., literature search data bases pertinen t to ground-water extraction, treatment, an d re sponses) is included in Practical Guid e for Assessing and Remediatin g Contaminated Sites (USEPA, 1989e). The general approach to remediatio n t ypic ally includes active restoration, plume containment, and source control a s disc ussed below. The selection of a pa rticular approach or combination o f a pproac hes must be based on the corrective action objectives. These genera l approaches are out lined in Table 5-3. It should b e emphasized that the obje ctive of a treatment pro gram should be to restore ground wate r to pre-existing conditi ons or to levels below applicable ground-water protectio n standards while simultaneously restrictin g further releases of contaminants to groun d water
. Once treatment objectives are met , the chance of further contamination should be mitigated to the extent practicable. Active Restoration Ac tive restoration generally include s g round-water extractio n, followed by onsite or o ffsite wastewater treatment. Offsit eGround-Water Monitoring and Corrective Action

297 was tewater treatment may include sendin g pi lot field studies to determine th e the c ontaminated water to a local publicl y feas ibility and the reliability of full-scal e own ed treatment works (POTW) or to a t reatment. It must be demonstrated that the f

acility designed to treat the cont aminants of tre atment techniques will not caus e co ncern. Treated ground water may be re

- degradation of a target chemical to another in

jected, sent to a local POTW, o r c ompound that has unacceptable h ealth risks discharged to a local body of surface water, and that is subject to further degradation

. depe nding on local, State, and Federa l Alternative in-situ methods may also b e requirements. Typical treatment practice s de signed to increase the effectiveness o f that may be implemented includ e d esorption or removal of c ontaminants from coagulation and precipitation of metals , the aquifer matrix. Such methodologie s che mical oxidation of a number of organi c may include steam stripping, soil flushing , c ompounds, air st ripping to remove volatile vapor extraction, thermal desorption, and organic compounds, and biologica l s olvent washing, and e xtraction for removal degradation of other organics

. of strongly sorbed organic compounds

. The rate of contaminant removal fro m un saturated zones where residua l grou nd water will depend on the rate o f c ontaminants may be sorbed to the geologic g round-w ater removal, the cation exchange mat rix during periodic fluctuations of th e capa city of the soil, and partitio n w ater table. De tails of in-situ methods may c oefficients of the consti tuents sorbed to the b e found in several sources: USEPA (1988); so il (USEPA, 1988). As the concentratio n USEPA (1985); and Eckenfelder (1989). of contaminants in the ground water i s red uced, the rate at which constituent s Plume Containment be come partitioned from the soil to th e aque ous phase may also be reduced. Th e Th e purpose of plume containment is t o amo unt of flushing of the aquifer materia l limit the spread of the contaminants

. required to remove the contaminants to a n Met hods to contain plume movemen t acceptable level will generally determin e in clude passive hydraulic barriers, such a s t he time frame required for restoration. This grout curtains and slurry walls, and activ e tim e frame is site-specific and may las t g radient control systems involving pumping indefinitely. wells and french drains. The types o f In -situ methods may be appropriate fo r containment include: some sites, particularly where pump an d tr eat technologies create serious advers e ! Water naturally unsuited for huma n effe cts or where it may be financiall y consumption pro hibitive. In-situ methods may includ e b iologi cal restoration requiring pH control, ! Contaminants present in lo w addition of specific micro-organis ms, and/or concentration with low mobility add ition of nutrients and substrate t o augment and encourage degradation b y ! Low potential for exposure t o indigenous microbial populations

. con taminants and low risk associate d Bioremediation requires laborator y with exposure treatability studies and Th ese methods also may be used i n

aqu ifer characteristics that favor plum eSubpart E

298 ! Low transmissivity and low future use r ! Preventing additional leachat e demand. g ene ration that may reach a liner failure O ften, it may be advantageous fo r the owner she lter during operations or cappin g or operator to consider implementin g landfill areas that contribute to leachat e gr ound-water controls to inhibit furthe r m ig rating from identified failure areas). contamination or the spread o f c ontamination. I f ground-water pumping is In extreme cases, excavation of deposite d c onsidered for capturing the leading edge of w ast es for treatment and/or offsite disposal the contaminant plume, the contaminate d may be considered. wate r must be managed in conformanc e wi th all applicable Federal and Stat e Public Participation requirements. Under most conditions, it i s nec essary to consult with the regulator y T h e owner or operator is required to hold a agencies prior to initiating an interi m pub lic meeting to discuss the results of th e remedial action. c orrective act ion assessment and to identify Source Control contacting local public agencies, tow n Source control measures should b e po sting a notice in prominent loca l eva luated to limit the migration of th e ne wspapers, and making radi o plu me. The regulation does not limit th e ann ouncements are effective. The publi c defi nition of source control to exclude an y meeting should provide a detaile d specific type of remediation. Remedie s d iscussion of how the ow ner or operator has must control the source to reduce o r addressed the factors at §258.56(c)(1)-(4). e liminate further releases b y identifying and locating the cause of the release (e.g., tor n geo membrane, excessive head due t o 5.15 SELECTION OF REMEDY b locked leachate collection system, leaking 40 CFR §258.57 (a)-(b) leachate collection well or pipe). Sourc e c ontrol measures may include the f ollowing: 5.15.1 Statement of Regulation

! Mo difying the operational procedure s (a) B ased on the results of t he corrective (e.g., banning specific wastes o r measure assessment conducted unde r lowe ring the head over the leachat e §258.56, the owner or operator mus t c ollection sys tem through more frequent selec ta remedy that, at a minimum , leachate removal) me ets the standards listed in paragrap h

! Undertaking more extensive an d no tify the State Director, within 14 day s effective maintenance activities (e.g. , of selecting a remedy, that a repor t e xcavate waste to repai r a liner failure or des cribing the selected remedy has bee n a clogged leachate collection system) p laced in the operatin g record and how it ( e .g., using a portable or temporary rain

proposed remedies. Notifications, such a s g overnments, and State/Tribal governments,

(b ) below. The owner or operator mus t

mee ts the standards in paragraph (b) o f this section.Ground-Water Monitoring and Corrective Action

299 (b) Remedies must: and comply with waste managemen t (1) Be protective of human health an d the environment; 5.15.3 Technical Considerations (2) Attain the ground-water protectio n The final method selected fo r standard as specified pursuant t o impl ementation must satisfy the criteria i n §§258.55(h) or (i); § 258.57(b)(1)-(4). The report documenting (3) C ontrol the source(s) of releases so as m eet these fo ur criteria should include such to reduce or eliminate, to the maximu m information as: ext ent practicable, further releases o f Appendix II constituents into th e ! Theoretical calculations envir onment that may pose a threat t o human health or the environment; and ! Com parison to existing studies an d (4) Comply with standards fo r histories management of wastes as specified i n §258.58(d). ! Be nch-scale or pilot-scale treatabilit y 5.15.2 Applicability These provisions apply to facilities tha t have been required to perform correctiv e The demonstration presented in the repor t measures. The selection of a remedy i s mu st document the alternative optio n c losely related to the assessment pr ocess and selection process. c annot be accomplished unless a s ufficiently t horough evaluation of alt ernatives has been c ompleted. The process of documenting the 5.16 SELECTION OF REMEDY rationale for selecting a remedy require s 40 CFR §258.57 (c) that a report be placed in the facilit y operating record that clearly defines th e 5.16.1 Statement of Regulation co rrective action objectives an d dem onstrates why the selected remedy i s (c) I n se lecting a remedy that meets the ant icipated to meet those objectives. Th e standards of §258.57(b), the owner o r State Director must be notified within 1 4 operator shall consider the followin g days of the placement of the report in th e evaluation factors: o perating records of the facility. The study mus t identify how the remedy will b e (1) The long- and short-ter m pro tective of human health and th e eff ectiveness and protectiveness of th e environment, attain the GWPS (eithe r potential remedy(s), along with th e b ac kground, MCLs, or, in approved States, de gree of certainty that the remedy wil l h ealth-based standards, i f applicable), attain prove successful based on consideratio n source control objectives, of the following: standards.

the capability of the selected method t o

re sults of similar treatment cas e

test results

! Waste management practices.Subpart E

300 (i) Ma gnitude of reduction of existin g (ii) The extent to which treatmen t risks; technologies may be used. (ii) Mag nitude of residual risks i n (3) The ease or difficulty o f t erms of likelihood of further re leases due i mplementing a potential remedy(s) b ased to waste remaining followin g o n consideration of the following types of implementation of a remedy; factors: (iii) The type and degree of long-ter m (i) De gree of difficulty associated wit h management required, includin g constructing the technology; m onitoring, operati on, and maintenance; (iv) Sh ort-term risks that might b e the technologies; posed to the community, workers, or the environment during implementation o f (iii) N eed to coordinate with and o btain suc h a remedy, including potentia l ne cessary approvals and permits fro m thre ats to human health and th e other agencies; environment associated with excavation, transportation, and redisposal o r (iv) Availabilit y of necessar y containment; equipment and specialists; and (v) Time until full protection i s (v) Available capacity and location o f achieved; needed treatment, storage, and disposa l (vi) Potential for exposure of human s an d environmental receptors t o (4) Practicable capability of the owne r re maining wastes, considering th e o r op erator, including a consideration of p otential threat to human health and the the technical and economic capability. environment associated with excavation, transportation, redisposal, o r (5) Th e degree to which communit y containment; concerns are addressed by a potentia l (vii) Long-term reliability of th e engineering and institutional controls ; 5.16.2 Applicability and (viii) Potential need for replacement o f se lecting a remedy for corrective action

. the remedy. The rule presents the considerations an d (2) The effectiveness of the remedy i n evaluate when selecting the appropriat e cont rolling the source to reduce furthe r corrective measure. rele ases based on consideration of th e following factors: (i) The extent to which containmen t practices will reduce further releases; (ii) E xpected operational reliability of

services.

remedy(s).

T he se provisions apply to facilities that are

fa ctors that the owner or operator mus tGround-Water Monitoring and Corrective Action

301 5.16.3 Technical Considerations r eleases of contaminants to the envi ronment, Th e owner or operator must conside r r emedy to mee t or exceed the GWPSs. The specific topics to satisfy the performanc e ow ner or operator must make a reasonabl e criteria under selection of the fina l effort to estimate and quantify risks, base d co rrective measure. These topics must b e on exposure pathways and estimates o f add ressed in the report documenting th e ex posure levels and durations. Thes e sel ection of a particular corrective action

. es timates include risks for both ground

Th e general topic areas that must b e water and cross-media contamination. considered include the following:

! The anticipated long- and short-ter m implemented, including excavation , effectiveness of the corrective action transporta tion, re-disposal, an d

! The anticipated effectiveness of sourc e respect to potential exposure and risk t o reduction efforts human health and the environment. Th e

! The ease or difficulty of implementin g as an integral component of the overal l the corrective measure cor rective action. Health consideration s

! Th e technical and economic practicabl e and the general public and provid e capability of the owner or operator contingency plans should an unanticipate d

! T he degree to which the selected remedy consider both long- and short-term case s will address concerns raised by th e b efore, d uring, and after implementation of community. corrective actions. Effectiveness of Corrective Action The t ime to complete the remedial activit y In selecting the remedial action, th e di rect financial impacts on the projec t anticipated long-term and short-ter m m a nagement needs and financial capability effectiveness should be evaluated. Long

- of the owner or operator to meet th e term effectiveness focuses on the risk s r emedial objectives. Th e long-term costs of re maining after corrective measures hav e the remedial alternatives and the long-term be en taken. Short-term effectivenes s f inancial conditio n of the owner or operator addresses the risks during construction and shou ld be reviewed carefully. Th e implementation of the corrective measure

. implementation schedule should indicat e Review of case studies where simila r quality control measures to assess th e tech nologies have been applied provide the progress of the corrective measure. best measures to judge technica l u ncertain ty, especially when relatively new T he ope rational reliability of the corrective te chnologies are applied. The long-term , m easures should be considered. In addition, post-cleanup effectiveness may be judge d the institutional controls and managemen t on the ability of the proposed remedy t o p ra ctices developed to assess the reliability mitigate further should be identified. a s well as on the feasibility of the proposed

The s ource control measures that will b e

con tainment, should be evaluated wit h

sour ce control measures should be viewe d

mu st address monitoring risks to worker s

exposure occur. Potential exposure should

must be estimated, because it will hav eSubpart E

302 Effectiveness of Source Reduction Technical considerations, including p H So urce control measures identified i n o r the ability to inject nutrien ts, may need to prev ious sections should be discussed i n be considered, depending on the propose d ter ms of their expected effectiveness. I f trea tment method. Potential impacts, suc h source control consists of the removal an d as potential cross-media contamination , re-disposal of wastes, the r esidual materials, need t o be reviewed as part of the overal l such as contaminated soils above the water feasibility of the project. table, should be quantified and thei r potential to cause further contaminatio n The schedule of remedial activities shoul d e valuated. Engineering co ntrols intended to identi fy the start and end points of th e up grade or repair deficient conditions i n following periods: l andfill component systems, i ncluding cover systems, should be quantified in terms o f ! Permitting phase anticipated effectiveness according t o current and future conditions. Thi s ! Co nstruction and startup period, durin g a ssessment m ay indicate to what extent it is wh ich initial implementation succes s tec hnically and financially practicable t o wil l be evaluated, including time t o make use of existing technologies. Th e correct any unexpected problems decision against using a certain technology may be based on health considerations an d ! Tim e when full-scale treatment will b e t he potential for unacceptable ex posure(s) to i nitiated and duration of trea tment period both workers and the public. Implementation of Remedial Action source control measures, including th e The ease of implementing the propose d associated remedial acti on will affect the schedule and w ith interim management and dis posal of s tar tup success of the remedial action. The waste materials or treatment residuals. following key factors need to be assessed:

! The availability of technical expertise ide ntified early in the process and thos e

! Co nstruction of equipment o r implementation occurs in the shortes t technology practicable period.

! The ability to properly manage an d Practical Capability dis pose of wastes generated b y treatment The owner or operator must be technicall y

! Th e likelihood of obtaining loca l chosen remedial alternative and ensurin g permits and public support for th e p roject completion, includ ing provisions for proposed project. future changes to the remedial plan afte r c ontrol, ground-wate r extraction feasibility,

! Implementation and completion o f timeframe for solving problem s

I tems that requir e long lead times should be
t asks should be in itiated early to ensure that

a

nd financially capable of implementing the

progress is reviewed. If either technical or fin ancial capability is inadequate for aGround-Water Monitoring and Corrective Action

303 p articular alternative, then ot her alternatives (3) A vailability o f treatment or disposal w ith simi lar levels of protectiveness should ca pacity for wastes managed durin g be considered for implementation. implementation of the remedy; Community Concerns (4) D esirabi lity of utilizing technologies T he public meetings hel d during assessment which may offer significant advantage s o f alternative measures are i ntended to elicit over already available technologies i n publ ic comment and response. The owne r terms of effectiveness, reliability, safety , or operator must, by means of meetin g o r a bility to achieve remedial objectives; minutes and a record of written comments, id entify which public concerns have bee n (5) P ot ential risks to human health and expressed and addressed by correctiv e the environment from exposure t o measure options. In reality, the fina l c ontaminat ion prior to completion of the rem edy selected and implemented will b e remedy; one that the State regulatory agency, th e public, and the owner or operator agree to. (6) Resource value of the aquife r

5.17 SELECTION OF REMEDY (i) Current and future uses; 40 CFR §258.57 (d) 5.17.1 Statement of Regulation users; (d) The owner or operator shall specif y (iii) Ground-water quantity an d as part of the selected remedy a quality; s che dule(s) for initiating and completing remedial activities. Such a schedule must (iv) Th e potential damage to wildlife , re quire the initiation of remedia l c rops, vegetation, and ph ysical structures act ivities within a reasonable period o f c aus ed by exposure to waste constituent; time taking into consi deration the factors set forth in paragraphs (d) (1-8). Th e (v) The hydrogeologic characteristic o f owner or operator must consider th e the facility and surrounding land; following factors in determining th e schedule of remedial activities: (vi) Ground-water removal an d (1) E xtent and nature of c ontamination; (2) Practical capabilities of remedia l alternative water supplies. t echnologies in achieving complia nce with ground-water protection standard s (7) Practicable capability of the owne r e s tablished under §§258.55(g) or (h) and or operator. other objectives of the remedy; that are not currently available, bu t

including:

(ii) Proximity and withdrawal rate o f

treatment costs; and (vii) The cost and availability o f

(8) Other relevant factors.Subpart E

304 5.17.2 Applicability a ffects the ultimate treatment rate. The size The requirements of §258.57(d) apply t o ow ners or operators of all new units , existing units, and laterally expanded units at all facilities required to implemen t cor rective actions. The requirements mus t be complied with prior to implementin g c orrective me asures. The owner or operator mu st specify the schedule for remedia l activities based on the followin g considerations:

! The size and nature of the contaminated a rea at the time the corrective measure is to be implemented

! The practicable capabilities of th e remedial technology selected

! Av ailable treatment and disposa l capacity

! Potential use of alternative innovativ e technologies not currently available

! Pote ntial risks to human health and th e environment existing prior to completion of the remedy

! Resource value of the aquifer

! Th e practicable capability of th e owner/operator

! Other relevant factors. 5.17.3 Technical Considerations Th e time schedule for implementing an d completing the remedial activity i s influenced by many factors that should b e co nsidered by the owner or operator. Th e most critical factor is the nature and extent of the contamination, which significantl y of the treatment facility and the ground

w ater extract ion and injection rates must be ba lanced for system optimization, capita l resources, and remedial timefram e o bjectives. The nature of the contamination wi ll influence the degree to which th e aquifer must be f

lushed to remove adsorbed s pecies. These fa ctors, which in part define the practicable capability of the alternative (t reatment efficiency, treatment rate, an d replenishment of contaminants by natura l pro cesses), should be considered whe n selecting the remedy. I n addition, the rate at which treatment may occur may be restricted by the availabilit y o r capacity to handle treatment residues and the normal flow of wastes durin g r e mediation. Alternative residue treatment or disposal capacity must be identified a s part of the implementation plan schedule. I f contaminant mi gration is slow due to low transport properties of the aquifer , additional time may be a vailable to evaluate the value of emerging and promisin g inno vative technologies. The use of suc h technologies is not excluded as part of th e requirement to im plement a remedial action as soon as practicable. Delayin g imp lementation to increase the availabilit y of new technologies must be evaluated i n terms of achievable cleanup levels, ultimate cos t, additional environmental impact, an d pote ntial for increased risk to sensitiv e recept ors. If a new technology clearly i s su perior to existing options in attainin g remediation objectives, it may b e ap propriate to delay implementation. Thi s m ay require that existi ng risks be controlled through interim measures.Ground-Water Monitoring and Corrective Action

305 I n setting the implementation schedule, the 5.18 SELECTION OF REMEDY owne r or operator should assess the risk t o 40 CFR §258.57 (e)-(f) huma n health and the environment withi n the timeframe of reaching treatmen t 5.18.1 Statement of Regulation objectives. If the risk is unacceptable , co nsidering health-based assessments o f (e) The Director of an approved Stat e exposure paths and exposure limits, th e may determine that remediation of a imp lementation time schedule must b e rel ease of an Appendix II constituen t accelerated or the selected re medy altered to from a MSWLF unit is not necessary i f provide an acceptable risk level in a timely th e owner or operator demonstrates t o manner. the satisfaction of the Director of a n Establishment of the schedule also ma y include consideration of the resource value (1) The ground water is additionall y of th e aquifer, as it pertains to current an d contaminated by substances that hav e futur e use, proximity to users, quality an d origi nated from a source other than a quantity of grou nd water, agricultural value MSWLF unit and those substances ar e and uses (irrigation water source or impact pre sent in concentrations such tha t on adjacent agricultural lands), and th e cleanup of the release from the MSWL F availability of alternative supplies of water unit would provide no significan t of sim ilar quantity and quality. Based o n reduc tion in risk to actual or potentia l the se factors, a relative assessment of th e receptors; or aqui fer's resource value to the loca l community can be established. Impacts t o (2) Th e constituent(s) is present i n the resource and the degree of financial o r ground water that: he alth-related distress by users should b e c onsidered. The implementation timeframe (i) Is not currently or reasonabl y s hould attempt to minimize t he loss of value expec ted to be a potential source o f o f the resource to users. The possibility that drinking water; and alternative water supplies will have to b e developed as part of the remedial activities ( ii ) Is not hydraulically connected with may need to be considered. wat ers to which the hazardou s Be cause owners or operators may not b e migrate in a concentration(s) that would knowledgeable in remediation activities , ex ceed the ground-water protectio n reliance on the owner or operator to devise st andards established under §258.55(h ) the schedule for remediation may b e or (i); or i mpractic able. In these instances, use of an ou tside firm to coordinate remediatio n (3) Re mediation of the release(s) i s scheduling may be necessary. Similarly , technically impracticable; or dev elopment of a schedule for which th e ow ner or operator cannot finance, whe n (4) R emediation r esults in unacceptable ot her options exist that do allow for owne r cross-media impacts. o r op erator financing, should be prevented. approved State that:

c onstituents are migrating o r are likely toSubpart E

306 (f) A determination by the Director o f fr om implementing some or all of th e a n approved State pursuant to paragraph corrective measure requirements. Th e ( e) above shall not affect the authority of owner or operator must demonstrate that the State to require the owner or op erator clea nup of a release from its MSWLF uni t to undertake source control measures or wo uld provide no significant reduction i n other measures that may be necessary to ris k to receptors due to concentrations o f eliminat e or minimize further releases to constituents from the other source. the ground water, to prevent exposure to the ground water, or to remediate th e A waiver from corrective measures al so may ground water to concentrations that ar e b e granted if the contamina ted ground water technically practicable and significantl y is not a current or reasonably expecte d re duce threats to human health or th e potential future drinking water source, an d environment. i t is unlikely that the hazardous constituents 5.18.2 Applicability exceedance of GWPS. The owner o r T he criteria under §258.57(e) and (f) apply uppermost aquifer is not hydraulicall y i n approved States only. Remedia tion of the c onnected wi th a lower aquifer. The owner release of an Appendix II constituent ma y o r operat or may seek an exemption if it can n ot be necessary if 1) a source ot her than the be demonstrated that attenuation , MSWLF unit is partly responsible for th e advection/dispersion or other natura l g round-water contamination, 2) th e resource pro cesses can remove the threat t o v alue of the aquifer is extremely limited, 3) inte rconnectedaquifers. The owner o r remediation is not technic ally feasible, or 4) oper ator may seek the latter exemption i f re mediation will result in unacceptabl e the contaminated zone is not a drinkin g cr oss-media impacts. The Director ma y water resource. d etermine that while total re mediation is not required, so urce control measures or partial The Director of an approved State ma y remediation of ground water t o wa ive cleanup requirements if remediatio n concentrations that are technicall y is not technically feasible. In addition, the p ractic able and significantly reduce risks is Director may wave requirements i f required. rem ediation results in unacceptable cross

5.18.3 Technical Considerations that remediation is not technically feasibl e T here are four situation s where an approved to this demonstration. Technica l S tate may not require cleanup of hazardous impr acticabilities may be related to th e co nstituents released to ground water fro m acc essibility of the ground water t o a MSWLF unit. If sufficient evid ence exists treatm ent, as well as the treatability of th e to document that the ground water i s gro und water using practicable treatmen t co ntaminated by a source other than th e tec hnologies. If the owner or operator ca n MSWLF unit, the Director of an approve d demonstrate that unacceptable cross-medi a State may grant a waiver imp acts are uncontrollable under a give n would migrate to waters causing a n op erator must demonstrate that th e

media impacts. A s uccessful demonstration

mu st document specific facts that attribut e

remedial optionGround-Water Monitoring and Corrective Action

307 (e .g., movement in response to ground

- (iii) Demonstrates compliance wit h wat er pumping or release of volatil e ground-water protection standar d o r ganics to the atmosphere) and that the no p ursuant to para graph (e) of this section. action option is a le ss risky alternative, then the Director of an approved State ma y (2) Implement the corrective actio n d etermine that remedia tion is not necessary. remedy selected under §258.57; and A wai ver of remedial obligation does no t (3) Take any interim measures necessar y necessarily release the owner or operato r t o ensure the protection of human health f rom the responsibility of con ducting source and the environment. Interim measure s co ntrol measures or minimal ground-wate r s hould, to the great est extent practicable, remediation. The State may require tha t be consistent with the objectives of an d sour ce control be implemented to th e co ntribute to the performance of an y ma ximum extent practicable to minimiz e r emedy that may be requir ed pursuant to fut ure risk of releases of contaminants t o §258. 57. The following factors must b e g round water or that ground water b e treated consi dered by an owner or operator i n to the extent technically feasible. determining whether interim measure s

5.19 IMPLEMENTATION OF THE (i) Time required to develop an d CORRECTIVE ACTION implement a final remedy; PROGRAM 40 CFR §258.58 (a) (ii) Ac tual or potential exposure o f 5.19.1 Statement of Regulation receptors to hazardous constituents; (a) Based on the schedule establishe d (iii) A c tual or potential contamination und er §258.57(d) for initiation an d of drinking water supplies or sensitiv e com pletion of remedial activities th e ecosystems; owner/operator must: (1) E stablish and implement a correcti ve w ater that may occur if remedia l action is a ction ground-water monitoring program not initiated expeditiously; that: (i) At a minimum, meets th e ha zardous constituents to migrate or b e requirements of an assessmen t released; monitoring program under §258.55; (ii) Ind icates the effectiveness of th e potential for exposure to hazardou s corrective action remedy; and constituents as a result of an accident o r are necessary:

nearby populations or environmenta l

(iv) F urther degradation of the ground

(v) We ather conditions that may caus e

(vi) Ri sks of fire or explosion, o r

f ailure of a container or handling system; andSubpart E

308 (vii ) Other situations that may pos e groun d water degradation or the spread o f thre ats to human health and th e the contaminant plume, replacement of th e environment. system with an alternative measure may be 5.19.2 Applicability condition of the aquifer must be monitored T he se provisions apply to facilities that are may be necessary to install additiona l requi red to initiate and complete corrective mo nitoring wells to more clearly evaluat e actions. remediation progress. Also, if it become s The owner or operator is required t o achievable technically, in a realistic time

co ntinue to implement its ground wate r frame, the performance objectives of th e a ssessme nt monitoring program to evaluate corrective measure must be reviewed an d t he eff ectiveness of remedial actions and to amended as necessary. dem onstrate that the remedial objective s have been attained at the completion o f Interim Measures remedial activities. Ad ditionally, the owner or operator mus t h ealth andthe environment exist prior to or ta ke any interim actions to protect huma n during implementation of the correctiv e he alth and the environment. The interi m action, the owner or operator is required to mea sures must serve to mitigate actua l take interim measures to protect receptors

. th reats and prevent potential threats fro m T hese interim measures are typically shortbeing realized while a long-ter m te rm solutions to address immediat e c omprehensive response is bei ng developed. con cerns and do not necessarily addres s 5.19.3 Technical Considerations measures may include activities such a s Im plementation of the corrective measure s h igh-volume withdraw al of ground water or encompass all activities n ecessary to initiate resp onse to equipment failures that occu r and continue remediation. The owner o r d uring remedia tion (e.g., leaking drums). If operator must continue assessmen t contamination migrates offsite, interi m mo nitoring to anticipate whether interi m mea sures may include providing a n me asures are necessary, and to determin e al ternative water supply for human , wh ether the corrective action is meetin g live stock, or irrigation needs. Interi m stated objectives. measures also pertain to source contro l Monitoring Activities of the overall corrective action. This ma y D uring the implementation period, ground- sourc e material or in-situ treatment of th e water monitoring must be conducted t o contaminated source. Interim measure s demonstrate the effectiveness of th e sho uld be developed with consideratio n corrective action remedy. If the remedia l giv en to maintaining conformity with th e acti on is not effectively curtailing furthe r objectives of the final corrective action. warra nted. The improvement rate of th e and compared to the cleanup objectives. It

ap parent that the GWPS will not b e

If unacceptable potential risks to huma n

lo ng-term remediation objectives. Interi m

co ntrol of ground-water migration throug h

activities that may be implemented as par t include activities such as excavation of th eGround-Water Monitoring and Corrective Action

309 5.20 IMPLEMENTATION OF THE equ ipment, units, devices, or structure s CORRECTIVE ACTION that are: PROGRAM 40 CFR §258.58 (b)-(d) (i) Technically practicable; and 5.20.1 Statement of Regulation (ii) Consistent with the overal l (b) An owner or operator ma y determine, based on informatio n (4) Noti fy the State Director within 1 4 dev eloped after implementation of th e days that a report justifying th e re medy has begun or other information , alternative measures prior t o that compliance with requirements o f implementing the alternative measure s §258.57(b) are not being achieve d has been placed in the operating record. through the remedy selected. In suc h cas es, the owner or operator mus t (d) All solid wastes that are manage d implement other methods or technique s pur suant to a remedy required unde r that could practicably achieve compl iance §258.57, or an interim measure required with the requirements, unless the owne r u nder §258 .58(a)(3), shall be managed in or operator makes the determinatio n a manner: under §258.58(c). (c) I f th e owner or operator determines and the environment; and that compliance with requi rements under § 258.57(b) cannot be pra ctically achieved (2) That complies with applicable RCR A with any currently available methods, the requirements. owner or operator must: (1) Ob tain certification of a qualifie d ground-water specialist or approval b y The requirements of the alternativ e the Director of an approved State tha t measures are applicable when it become s compliance with requirements unde r ap parent that the remedy selected will no t § 258.57(b) cannot be pra ctically achieved achieve the GWPSs or other significan t with any currently available methods; objectives of the remedial program (e.g. , (2) Im plement alternate measures t o de termining that the selected correctiv e co ntrol exposure of humans or th e ac tion approach will not achieve desire d environment to residual contamination , results, the owner or operator mus t a s necessary to protec t human health and implement alternate corrective measures to the environment; and achieve the GWPSs. If it becomes eviden t (3) Implement alternate measures fo r obtainable by existing practicabl e control of the sources of contamination , technology, the owner or operator mus t or f or removal or decontamination o f im plement actions to control exposure o f objective of the remedy.

(1) That is protective of human healt h

5.20.2 Applicability

pr otection of sensitive receptors). I n

that the cleanup goals are not technicall y

huma ns or the environment from residua lSubpart E

310 c ontami nation and to control the sources of ! Inappropriately applied technology co ntamination. Prior to implementin g a lternat ive measures, the owner or operator mus t notify the Director of an approve d S tate wi thin 14 days that a report justifying t h e alternative measures has been placed in the operating record. A ll wastes that are manage d by the MSWLF uni t during corrective action, includin g inte rim and alternative measures, must b e managed according to applicable RCR A requirements in a manner that is protective of human health and the environment. 5.20.3 Technical Considerations An owner or operator is required to continue the assessment monitoring program durin g the remedial action. Through monitoring , the short and long term success of th e remedial action can be gauged agains t expe cted progress. During the remedia l ac tion, it may be necessary to instal l additional ground-water monitori ng wells or pu mping or injection wells to adjust t o c onditions that vary from initia l assessments of the ground-water flow system. A s remediation progresses and data ar e compiled, it may become evident that th e remediation activities will not protec t hum an health and the environment, mee t GWPSs, control sources of contamination , or comply with waste managemen t standards. The reasons for unsatisfactor y results may include:

! Re fractory compounds that are no t ame nable to removal or destructio n (detoxification)

! Th e presence of compounds tha t interfere with treatment method s identified for target compounds ! Fai lure of source control measures t o achieve desired results

! F ailur e of ground-water control systems to achieve adequate containment o r removal of contaminated ground water

! Residual concentrations above GWPS s t hat cannot be effectively reduc ed further because treatment efficiencies are to o low

! Transformation or degradation of target com pounds to different forms that ar e not amenable to further treatment b y present or alternative technologies. Th e owner or operator should compar e treatment assumptions with existin g co nditions to determine if assumption s adequately depict site conditions. I f imp lementation occurred as designed, th e o wner or operato r should attempt to modify or upgrade existing remedial technology to opt imize performance and to improv e trea tment effectiveness. If the existin g technology is found to be unable to mee t remediation objectives, alternativ e approaches must be evaluated that coul d meet these objectives while the presen t reme diation is continued. During this re

evaluation period, the owner or operato r m ay susp end treatment only if continuation of remedial activities clearly increases th e t hreat to human health and the environment.Ground-Water Monitoring and Corrective Action

311 5.21 IMPLEMENTATION OF THE (iii) Accuracy of monitoring o r CORRECTIVE ACTION modeling techniques, including an y PROGRAM se asonal, meteorological, or othe r 40 CFR §258.58 (e)-(g) environmental variabilities that ma y 5.21.1 Statement of Regulation (e) Remedies selected pursuant t o water. §258.57 shall be considered complet e when: (3) A l l actions required to complete the (1) T he owner or operator complies with the ground-water protection standard s (f) U po n completion of the remedy, the e stablished under §§ 258.55(h) or (i) at all own eror operator must notify the Stat e p oints within the plum e of contamination Dire ctor within 14 days that a that lie beyond the ground-wate r certification that the remedy has bee n m onitoring well system established under co mpleted in compliance with th e §258.51(a). re quirements of §258.58(e) has bee n (2) Compliance with the ground-wate r c ertification mustbe signed by the owner protection standards established unde r or op erator and by a qualified ground - §§2 58.55(h) or (i) has been achieved b y wate r specialist or approved by th e demonstrating that concentrations o f Director of an approved State. Ap pendix II constituents have no t exceeded the ground-water protectio n (g) When, upon completion of th e standard(s) for a period of thre e cer tification, the owner or operato r consecutive years using the statistica l determines that the corrective actio n p rocedures and performance standard s in r emedy has been completed in accorda nce §258.5 3(g) and (h). The Director of a n wit h the requirements under paragrap h app roved State may specify a n (e) of this section, the owner or operator alternative length of time during whic h sha ll be released from the requirement s the o wner or operator must demonstrate for financial assurance for correctiv e that concentrations of Appendix I I action under §258.73. co nstituents have not exceeded th e ground-water protection standard(s ) §258.59 [Reserved]. taking into consideration: (i) Ex tent and concentration of th e release(s); T hese crite ria apply to facilities conducting (ii) Be havior characteristics of th e c omplete when, afte r 3 consecutive years of hazardous constituents in the groun d m onitoring (o r an alternative length of time water; as id entified by the Director), the result s affect the accuracy; and (iv) Characteristics of the groun d

remedy have been satisfied.

place d in the operating record. Th e

5.21.2 Applicability

c orrective a ction. Remedies are considered

sh ow significant statistical evidence tha tSubpart E

312 Appendix II constituent concentrations ar e St ate. Upon completion of the remedia l b elow t he GWPSs. Upon completion of all act ion, in accordance with §258.58(e), th e re medial actions, the owner or operato r owner or operator is released from th e must c ertify to such, at which point th e f inancial as surance requirements pertaining o wner or operator is released from financial to corrective actions. assurance requirements. 5.21.3 Technical Considerations require an alternate time period (other than The regulatory period of compliance is 3 d etermining an alterna te period the Director consecutive years at all points within th e must consider the following: con taminant plume that lie beyond th e g round -water monitoring system unless the ! The extent and concentration of th e Direc tor of an approved State specifies a n release(s) al ternative length of time. Compliance i s ac hieved when the concentrations o f ! The behavior characteristics (fate an d Appendix II constituents do not exceed the transport) of the hazardous constituent s G WPSs for a predetermined length of time. in the ground water (e.g., mobility , St atistical procedures in §258.53 must b e persistence, toxicity, etc.) us ed to demonstrate compliance with th e GWPSs. ! Ac curacy of monitoring or modelin g The preferred statistical method fo r meteorological or other environmenta l comp arison is to construct a 99 percen t variabilities that may affect accuracy confidence interval around the mean of the las t 3 years of data and compare the uppe r ! Th e characteristics of the ground wate r limit of the confidence interval to th e (e.g., flow rate, pH, etc.). G WPS. An upper lim it less than the GWPS is c onsidered significant evidence that th e C onsideration of these factors may result in standard is no longer being exceeded. Th e an ex tension or shortening of the tim e confidence interval must be based on th e re quired to show compliance wit h appropriate model describing th e remediation objectives. distribution of the data. Upon completion of the remedy, includin g mee ting the GWPS at all points within th e contaminant plume, the owner or operato r must notify the State Director withi n four teen days that a certification that th e remedy has been comple ted has been placed in th e operating record. The certificatio n m ust be signed by the owner or operator and a qualified ground-water scientist o r ap proved by the Director of an approve d The Director of an approved State ma y 3 years) to demonstrate compliance. I n

techniques, including any seasonal ,Ground-Water Monitoring and Corrective Action

313 5.22 FURTHER INFORMATION

5.22.1 References Aitchison, J., and J.A.C. Brown (1969) . "The Lognormal Distribution"; Cambridge University Press; Cambridge. American Water Works Association (1984). "Abandonment of Test Holes, Partially Completed Wells and Completed Wells." Appendix I. American Water Works Association Standard for Water Wells, American Water Works Association, Denver, CO, pp 45-47. B arari, A., and L.S. Hedg es (1985). "Movement of Water in Glacial Till." Proceedings of the 17th International Congress of International Association of Hydrogeologists. Barcelona, M.J., J.A. Helfrich and E.E. Garske, (1985). "Sampling Tube Effects o n Groundwater Samples"; Analytical Chemistry 47(2): 460-464. Barcelona, M.J., J.P. Gibb, J.A. Helfrich, and E.E. Garske, (1985b). "Practical Guide fo r Ground-Water Sampling," USEPA, Cooperative Agreement #CR-809966-01, EPA/600/2

- 85/104, 169 pp. Barcelona , M.J., et al. 1990. Contamination of Ground Water: Prevention, Assessment , Restoration . Pollution Technolog y Review No. 184, Noyes Data Corporation, Park Ridge, NJ, 213 pp. C antor, L.W., R.C. Knox, and D.M. Fairchild (1987). Grou nd-Water Quality Protection . Lewis Publishers, Inc., Chelsea, MI. Cooper, H.H. , Jr., and C.E. Jacob (1946). "A Generalized Graphical Method for Evaluatin g F ormation Constants and Summarizing Well-Field History." A merican Geophys. Union Trans., V. 27, No. 4. D aniel, D.E., H.M. Liljestrand, G.P. Broderick, and J.J. Bounders, Jr. (1988). "Interaction of Earthen Linear Materials with Industrial Waste Leachate in Hazardous Waste and Hazardous Materials," Vol. 5, No. 2. Dixon, W.J. and F.J. Massey, Jr. (1969). "Introduction to Statistical Analysis"; 3rd Edition ; McGraw-Hill Book Co.; New York, New York. D riscoll , F.G., (1986). "Groundwater and Wells"; Johnson and Johnson; St. Paul, Minnesota. E ckenfelder, W.W., Jr., (1989). Industrial Water Pollution Control . McG raw-Hill, Inc., Second Edition.Subpart E

314 F etter, C.W., Jr. (1980). Applied Hyd rogeology . Charles E. Merrill Publishing Co., Columbus, OH. Freeze, R .A. and J.A. Cherry, (1979). Groundwater ; Prentice-Hall, Inc.; Englewood Cliffs , New Jersey. Gibbons, J.D., (1976). "Nonparametric Methods for Quantitative Ana lysis"; Holt, Rinehart, and Winston Publishing Co.; New York, New York. Gilber t, R.O., (1987). Statistical Methods for Environmental Pollution Monitoring ; Va n Nostrand Reinhold Co.; New York, New York. Heath, R.C. (1982). Basic Ground-Water Hydrology . U.S. Geological Survey Water Suppl y Paper 2220, 84 pp. Hsieh, P .A., and S.P. Neuman (1985). "Field Determination of the Three - Dimensiona l Hydraulic Cond uctivity Teasor of Anisotropic Media." Water Resources Research, V. 21, No. 11. Kearl, P.M., N.E. Korte, and T.A. Cronk. 1992. "Suggested Modifications to Ground Water Sampli ng Procedures Based on Observations from the Colloidal Borescope." Ground-Wate r Monitoring Review, Spring, pp. 155-160. K ruseman, G.P., and N.A. de Ridder (1 989). "Analysis and Evaluation of Pumping Test Data," International Institute for Land Reclamation and Improvement/ILRI, Bulletin II, 4 Edition. th
Lamb , B. and T. Kinney (1989). "Decommissioning Wells - Techniques and Pitfalls. " Proceedings of the Third National Outdoor Action Conferen ce on Aquifer Restoration, GroundWater Monitoring and Geophysical Methods, NWWA, May 22-25, 1989, pp 217-228. McGlew, P.J. and J.E. Thomas (1984). "Determining Contaminant Migration Pathways i n Fractu red Bedrock." Proceedings of the Fifth National Conference on Management o f Uncontrolled Hazardous Waste Sites. M cWhorter , D.B., and D.K. Sunada (1977). Ground-Water Hydrology and Hydraulics . Water Resources Publications, Fort Collins, CO. M iller, J.C. and J.N. Miller, (1986). Statistics for Analytical Chemistry ; John Wiley and Sons; New York, New York. Molz, F.J., O. Guven and J.G. Melville (1990). "A New Approach and Methodologies fo r Character izing the Hydrogeologic Properties of Aquifers." EPA Project Summary. EP A 600/52-90/002.Ground-Water Monitoring and Corrective Action

315 M olz, F.J., R.H. Norin, A.E. Hess, J.G. Melville, an d O. Guven (1989) "The Impeller Meter for Measuring Aquifer Permeability Variations: Evaluation and Comparison with Other Tests. " Water Resources Research, V 25, No. 7, pp 1677-1683. Puls, R .W. and R.M. Powell. 1992. "Acquisition of Representative Ground Water Qualit y Samples for Metals." Ground-Water Monitoring Review, Summer, pp. 167-176. Puls, R.W., R.M. Powell, D.A. Clark, and C.J. Paul. 1991. "Facilitated Transport of Inorganic Contaminants in Ground Water: Part II." Colloidal Transport, EPA/600/M-91/040, 12 pp. Puls, R.W ., and M.J. Barcelona. 1989a. "Filtration of Ground Water Samples for Metal s Analysis." Hazardous Waste and Hazardous Materials, v. 6, No. 4. Puls, R.W., and M.J. Barcelona. 1989b. "Ground Water Sampling for Metals Analysis. " USEPA Superfund Ground Water Issue, EPA/504/4-89/001, 6 pp. S evee, J. (1991). "Methods and Procedures fo r Defining Aquifer Parameters," in D.M. Nielsen, ed., Practical Handbook of Ground-Water Monitoring . Lewis Publishers, Chelsea, MI. U SEPA (1975). Manual of Water Well Construction Practices . USEPA Office of Water Supply, Report No. EPA-570/9-75-001, 156 pp. U SEPA, (1985). "Handbook: Remedial Action at Waste Disposal Sites"; EPA/540/G-88/003; U.S. EPA; Office of Emergency and Remedial Response; Washington, D.C. USEPA, (1986a). "RCRA Groundwater Monitoring Technical Enforcement Guidanc e Document"; Office of Solid Waste and Emergency Response - 9950.1. USEPA, (1986b). "Test Methods for Evaluating Solid Waste - Physical/Chemical Methods"; EPA SW- 846, 3rd edition; PB88-239-233; U.S. EPA; Office of Solid Waste and Emergenc y Response; Washington, D.C. USEPA, (1986c). "Superfund Public Health Evaluation Manual"; PB87-183-125; U.S. EPA; Office of Emergency and Remedial Response; Washington, D.C. 20460. U SEPA, ( 1986d). "Superfund Risk Assessment Information Directory"; PB87-188-918; U.S. EPA; Office of Emergency and Remedial Response; Washington, D.C. 20460. U SEPA, (1988). "Guidance on Remedial Action s for Contaminated Groundwater at Superfund S ites"; PB89-184-618; U.S. EPA; Office of Emergency and Remedial Response; Washington, D.C. 20460.Subpart E

316 USEPA, (19 89). "Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities

I nterim Final Guidance"; EPA/530-SW-89-026; U.S. EP A; Office of Solid Waste; Washington, D.C. USEPA, (1989a). "RCRA Facility Investigation (RFI) Guidance; Interim Final; Vol. I Develop ment of an RFI Work Plan and General Considerations for RCRA Facilit y Investigations"; PB89-200-299; U.S. EPA; Office of Solid Waste; Washington, D.C. U SEPA, (1989b). "RCRA Faci lity Investigation (RFI) Guidance; Interim Final; Vol. II - Soil, G round Water and Subsurface Gas Releases"; PB89-200-299; U.S. EPA; Offi ce of Solid Waste; Washington, D.C. USEPA , (1989c). "Criteria for Identifying Areas of Vulnerable Hydrogeology Under th e Resource Conservation and Recovery Act, Interim Final. Appendix B -Ground-Water Flo w Net/Flow Line Construction and Analysis." USEPA, (19 89d). "RCRA Facility Investigation (RFI) Guidance; Vol IV: Case Stud y Examples;" PB89-200-299; U.S. EPA; Office of Solid Waste; Washington, D.C. U SEPA, (1989e). "Practical Guide for Assessing and Remediating Contaminated Sites - Draft"; U. S. EPA; Waste Management Division, Office of Solid Waste, 401 M Street, S.W. ; Washington, D.C. May 1989. U SEPA, (1989f). "Handbook of Suggested Practices for the De sign and Installation of GroundWater Monitoring Wells"; PB90-159-807; U.S EPA; Office of Research and Development ; Washington, D.C. U SEPA, (1990). "Handbook: Groundwater Vol I;" EPA/625/6-90/016a; U.S. EPA; Office of Research and Development; Cincinnati, Ohio. U SEPA, (1991). "Handbook: Groundwat er Vol II"; EPA/625/6-90/016b; U.S. EPA; Office of Research and Development; Cincinnati, Ohio. U SEPA, (1992a). "RCRA Ground-Water Monitoring: Draft Technical G uidance"; EPA/530-R93-001; U.S. EPA; Office of Solid Waste; Washington, D.C. PB93-139-350. U SEPA, (1992b). "Statistical Training Course for Ground-Water Monitoring Data Analysis", EPA/530-R-93-003; U.S. EPA; Office of Solid Waste; Washington, D.C. USEPA, (1992c). "User Documentation of the Ground-Water Information Tracking Syste m ( GRITS) wi th Statistical Analysis Capability, GRITSTAT Version 4.2;" EPA/625/11-91/002; USEPA Office of Research and Development, Center for Environmental Research, OR D Publications.Ground-Water Monitoring and Corrective Action

317 US GS, (1989). "Chapter C2, Computer Model of Two-Dimensional Solute Transport an d Dis persion in Groundwater"; L.F. Konikow and J.D. Bredehoeft; Book 7; U.S. Geologica l Survey; U.S. Department of Interior. Way, S.C., and C.R. McKee (1982). "In-Situ Determination of Three-Dimensional Aquife r Permeabilities." Ground Water, V. 20, No. 5.Subpart E

318

# CHAPTER 6 SUBPART F CLOSURE AND POST-CLOSURE320 CHAPTER 6 SUBPART F TABLE OF CONTENTS 6.1 INTRODUCTION

...................................................... 322 6.2 FINAL COVER DESIGN 40 CFR §258.60(a)

............................. 322 6.2.1 Statement of Regulation

......................................... 322 6.2.2 Applicability

................................................... 323 6.2.3 Technical Considerations

........................................ 323 Infiltration Layer

.............................................. 324 Geomembranes

.......................................... 329 Erosion Layer

................................................. 330 6.3 ALTERNATIVE FINAL COVER DESIGN 40 CFR §258.60(b)

.............. 332

6.3.1 Statement of Regulation

................................... 332 6.3.2 Applicability

............................................. 332 6.3.3 Technical Considerations

.................................. 333 Other Considerations

........................................... 333 Drainage Layer

.......................................... 333 Gas Vent Layer

.......................................... 335 Biotic Layer

............................................. 336 Settlement and Subsidence

....................................... 336 Sliding Instability

.............................................. 337 6.4 CLOSURE PLAN 40 CFR §258.60(c)-(d)

................................ 338 6.4.1 Statement of Regulation

......................................... 338 6.4.2 Applicability

................................................... 338 6.4.3 Technical Considerations

........................................ 338 6.5 CLOSURE CRITERIA 40 CFR §258.60(e)-(j)

............................ 339 6.5.1 Statement of Regulation

......................................... 339 6.5.2 Applicability

................................................... 340 6.5.3 Technical Considerations

........................................ 341 6.6 POST-CLOSURE CARE REQUIREMENTS 40 CFR §258.61

............... 342 6.6.1 Statement of Regulation

......................................... 342 6.6.2 Applicability

................................................... 343 6.6.3 Technical Considerations

........................................ 343321 6.7 POST-CLOSURE PLAN 40 CFR §258.61(c)-(e)

......................... . 345 6.7.1 Statement of Regulation

........................................ . 345 6.7.2 Applicability

.................................................. . 346 6.7.3 Technical Considerations

....................................... . 346 6.8 FURTHER INFORMATION

............................................ . 348 6.8.1 References

.................................................... . 348 6.8.2 Organizations

................................................. . 349 6.8.3 Models

....................................................... . 349 6.8.4 Databases

.................................................... . 349322 

### CHAPTER 6 SUBPART F CLOSURE AND POST-CLOSURE

6.1 INTRODUCTION The cr iteria for landfill closure focus on two central themes: (1) the need to establish low

maintenance c over systems and (2) the need to design a final cover that minimizes th e i nfiltration of precipitation into the waste. Landfill closure technology, d esign, and maintenance p rocedures continue to evolve as new ge osynthetic materials become available, as performance requirements become m ore specific, and as limited performance history becomes available for the relatively small number of landfills that have been closed using current procedures an d materials. Critical technical issues that must be faced by the designer include the:

! Degree and rate of

post-closure settlement and stresses imposed on soil liner components;
! Long-term durability and survivability of cover system;
! Long-term waste decomposition and management of landfill leachate and gases; and
! Environmental performance of the combined bottom liner and final cover system.
Full closu re and post-closure care requirements apply to all MSWLF units that receive wastes on or after October 9, 1993. For MSWLF units that stop receiving wastes prior to October 9, 1993, only the final cover requirements of §258.60(a) apply. *[NOTE: EPA finalized several revisions to 40 CFR Part 258 on October 1, 1993 (58 F R 5 1536) and issued a correction notice on October 14, 1993 (58 FR53136). Questions regarding th e final rule and requests for copies of the Federal Register notices should be made to th e RCRA/Superfund Hotline at (800) 424-9346. Thes e revisions delay the effective date for some categories of landfills. More detail on the content of the revisions is included in th e introduction.

6.2 FINAL COVER DESIGN (1) Have permeability less than or 40 CFR §258.60(a) equa l to the permeability of any botto m 6.2.1 Statement of Regulation o r a permeability no great er than 1 x 10 (a) Own ers or operators of al l MSWLF units must install a final cove r (2) Minimi ze infiltration through system that is designed to minimiz e the closed MSWLF unit by the use of a n infiltration and erosion. The final cover infiltration layer that contains a s ystem must be de signed and constructed minimum of 18-inches of an earthe n to: material, and li ner system or natural subsoils present , -5 cm/sec, whichever is less, andClosure and Post-Closure

323 (3) Minimize erosion of the fina l In approved States, an alternate cove r cover by the use of an erosion layer tha t con tains a minimum 6-inches of earthe n mat erial that is capable of sustainin g native plant growth. 6.2.2 Applicability These final cover requirements apply to all MSWLF units required to close i n ac cordance with Part 258, includin g MSWL F units that received wastes afte r Octo ber 9, 1991 but stopped receivin g wast es prior to October 9, 1993. Unit s cl osing during this two-year period ar e required to install a final cover. The final cover system required to close a M SWLF unit, whether the unit is an existing u nit, a new unit, or a lateral expansion of an exist ing unit, must be composed of a n infiltration layer that is a minimum of 1 8 in ches thick, overlain by an erosion laye r that is a minimum of 6 inches thick. The final cover should minimize, over th e l ong term , liquid infiltration into the waste. The final cover must have a hydrauli c condu ctivity less than or equal to an y bot tom liner system or natural subsoil s p resen t to prevent a "bathtub" effect. In no cas e can the final cover have a hydrauli c co nductivity greater than 1 x 10 cm/se c -5 regardless of the perm eability of underlying li ners or natural subsoils. If a syntheti c membrane is in t he bottom liner, there must be a flexible membrane liner (FML) in th e f inal c over to achieve a permeability that is l ess tha n or equal to the permeability of the b ottom liner. Currentl y, it is not possible to co nstruct an earthen liner with a p ermeability less than or equal to a synthetic membrane. system may be approved by the Directo r (see Section 6.3). 6.2.3 Technical Considerations Desig n criteria for a final cover syste m should be selected to:

! Minimize infiltration of precipitatio n into the waste;

! Promote good surface drainage;

! Resist erosion;

! Control landfill gas migration and/o r enhance recovery;

! Separate waste from vectors (e.g. , animals and insects);

! Improve aesthetics;

! Minimize long-term maintenance;

! Pro tect human health and th e environment; and

! Consider final use. The first three points are directly related to the regulatory requirements. The othe r p oints typic ally are considered in designing cover systems for landfills. Reductio n of infiltration in a well-designed f inal cover system is a chieved through good su rface drainage and run-off with minima l eros ion, transpiration of water by plants i n th e vegetative cover and root zone, an d restriction of percolation through earthe n mater ial. The cover system should b e des igned to provide the desired level o fSubpart F

324 long-term performance with minima l Figure 6-3a. Figure 6-3b shows a fina l m aintena nce. Surface water run-off should co ver system for a MSWLF unit that ha s b e properly controlled to prevent excessive both a double FML and double leachat e eros ion and soil loss. Establishment of a collection system. h ealthy vegetativ e layer is key to protecting the cover from erosion. However , T he earthen material used for the infiltration co nsideration also must be given t o l aye r should be free of rocks, clods, debris, se lecting plant species that are not deepl y cob bles, rubbish, and roots that ma y rooted because they could damage th e increase the hydraulic conductivity b y un derlying infiltration layer. In addition , promoting preferential flow paths. T o the cover system should be geotechnicall y f acilitate ru n-off while minimizing erosion, stable to prevent failure, such as sliding , the s urface of the compacted soil shoul d that may occur between the erosion an d have a minimum slope of 3 percent and a infiltration layers, within these layers, o r m aximum slope of 5 percent afte r allowance within the waste. Figure 6-1 illustrates the for settlement. I t is critical that side slopes, minimum requirements for the final cove r w hich are freque ntly greater than 5 percent, system. be evaluated for erosion potential. Infiltration Layer M embrane and c lay layers should be placed The infiltration layer must be at least 1 8 penetration to avoid freeze-thaw effect s i nches thick and consist of earthen material (U.S. EPA, 1989b). Freeze-thaw effect s that has a hydraulic conductivit y m ay include dev elopment of microfractures (co efficient of permeability) less than o r or r ealignment of interstitial fines, whic h equal to the hydraulic conductivity of an y can increase the hydraulic conductivity o f bottom liner system or natural subsoils

. clays by more than an order of magnitud e MSW LF units with poor or non-existen t (U.S. EPA, 1990). Infiltration layers ma y bo ttom liners possessing hydrauli c be s ubject to desiccation, depending o n conductivities greater than 1 x 10 cm/se c climate and soil water retention in th e -5 m ust have an infiltration layer that meets the erosion layer. Fracturing and volumetri c 1 x 10 cm/sec minimum requirement

. shrinking of the clay due to water loss may

-5 Figure 6-2 presents an example of a fina l in crease the hydraulic conductivity of th e cover with a hydraulic conductivity les s infi ltration layer. Figure 6-4 shows th e than or equal to the hydraulic conductivit y r egional average depth of frost penetration; of the bottom liner system. h owever, these v alues should not be used to F or uni ts that have a composite liner with a for a particular area of concern at a FML, or natur ally occurring soils with very particular site. Information regarding th e l ow permeabil ity (e.g., 1 x 10 cm/sec), the maxi mumdepth of frost penetration for a -8 A gency anticipates that th e infiltration layer p articular area can be obtained f rom the Soil in the final cover will include a syntheti c Co nservation Service, local utilities , membrane as part of the final c over. A final construction companies, and loca l cover system for a MSWLF unit with a universities. FML combined with a soil liner an d le achate collection system is presented i n be low the maximum depth of fros t

f ind the maximum depth of frost penetrationClosure and Post-Closure

325 

### Figure 6-1 Example of Minimum Final Cover RequirementsSubpart F

326 

### Figure 6-2 Example of Final Cover With Hydraulic Conductivity(K) < K of Liner

### Figure 6-3a

Example of Final Cover Design for a MSWLF Unit With a FML

and Leachate Collection System

Figure 6-3b Example of Final Cover Design for a MSWLF Unit With a Double FML and Leachate Collection System

327Subpart F

328 

### Figure 6-4 Regional Depth of Frost Penetration in InchesClosure and Post-Closure

329 Th e infiltration layer is designed an d avai lable but should be verified a s c onstructed in a manner similar to that used reasonable for the site modeled. Output s fo r soil liners (U.S. EPA, 1988), with th e fr om the model include precipitation, run

following differences: off, percolation through the base of eac h

! Beca use the cover is generally no t a nd lateral drainage from each profile. The sub ject to large overburden loads, th e m odel also calculates the maximum head on iss ue of compressive stresses is les s t he b arrier soil layer of each subprofile and critical unless post-closure la nd use will the maximum and minimum soil moistur e entail co nstruction of objects that exert c ontent of the evaporative zone. Data from large amounts of stress. the model are presented in a tabular repor t

! Th e soil cover is subject to loading s used and a summary of the simulatio n from settlement of underlyin g resul ts. Results are presented in severa l mate rials. The extent of settlemen t tab les of daily, monthly, and annual total s an ticipated should be evaluated and a for each year specified. A summary of th e closure and post-closure maintenanc e o utputs also is produced, including average plan s hould be designed to compensate mont hly totals, average annual totals, an d for the effects of settlement. pea k daily values for several simulatio n

! Direct shear tests performed o n construction materials should b e The HE LP model may be used to estimat e con ducted at lower shear stresses tha n the hydraulic performance of the cove r those used for liner system designs. s ystem designed for a MS WLF unit. Useful Th e design of a final cover is site-specifi c includes surface run-off, duration an d a nd the relative performance of cove r design q uantity of wa ter storage within the erosion o pt ions may be compared and evaluated by l ayer, and net infiltration through the cover the HELP (Hydrologic Evaluation o f system to evaluate whether leachate wil l Landfill Performance) model. The HEL P accum ulate within the landfill. For th e model was developed by the U.S. Arm y m odel to be used properly, the HELP Model C orps of E ngineers for the U.S. EPA and is Us er's Guide and documentation should b e wi dely used for evaluating expecte d consulted. hydraulic performance of landfil l cover/liner systems (U.S. EPA, 1988). Geomembranes The HELP program calculates daily , If a geomembrane is used as an infiltratio n av erage, and peak estimates of wate r layer , the geomembrane should be at leas t movement across, into, through, and out of 20 mils (0.5 mm) in thickness, althoug h landfills. The input parameters for th e so me geomembrane materials may need t o m od el include soil properties, precipitation be a greater thickness (e.g., a minimu m an d other climatological data, vegetatio n thi ckness of 60 mils is recommended fo r typ e, and landfill design information

. H DPE because of the difficulties in making Defa ult climatologic and soil data ar e consistent field seams in thinner material)

. cover layer subprofile, evapotranspiration ,

format and include the input parameter s

variables (U.S. EPA, 1988).

information provided by the HELP mode lSubpart F

330 Increased thickness and tensile strength s X = RKLSCP may be necessary to prevent failure unde r stresses caused by construction and wast e where X = Soil loss (tons/acre/year) settlement during the post-closure car e R = Rainfall erosion index period. The strength, resistance to sliding , K = Soil erodibility index hydraulic performance, and actual thickness L = Slope length factor of geomembranes should be carefull y S = Slope gradient factor e va luated. The quality and performance of C = Crop management factor some textured sheets may be difficult t o P = Erosion control practice. evalu ate due to the variability of th e textured surface. V alues for the Universal Soil Loss Equation Erosion Layer Soi l Conservation Service (SCS) technica l The thickness of the erosion layer i s Rai nfall Erosion Losses, Guidebook 537 " i nfluenced by depth of frost penetration and (1 978), available at local SCS office s erosion po tential. This layer is also used to l ocated th roughout the United States. State supp ort vegetation. The influence of fros t or lo cal SCS offices can provide factors t o penetration was discussed previously o n be used in the soil loss equation that ar e page 6-3. appropriate to a given area of the country

. Erosion can adversely affect th e rat io due to the slope of the site as used i n p erformance of the final co ver of a MSWLF the U niversal Soil Loss Equation. Los s unit by causing rills that requir e f rom wind erosion can be determined by the ma intenance and repair. As previousl y following equation (U.S. EPA, 1989a): s tated, a healthy vegetative l ayer can protect the cover from erosion; conversely, sever e X' = I'K'C'L'V' eros ion can affect the vegetative growth

. E xtreme erosion may lead to the expo sure of where X' = Annual wind erosion t he infiltration layer, initiate o r contribute to I' = Field roughness factor sl iding failures, or expose the waste

. K' = Soil erodibility index Anti cipated erosion due to surface wate r C' = Climate factor run- off for given design criteria may b e L' = Field length factor approximated using the USDA Universa l V' = Vegetative cover factor. S oil Lo ss Equation (U.S. EPA, 1989a). By evalu ating erosion loss, the design may b e A vegetative cover not only improves th e optimized to reduce maintenance throug h ap pearance of the site, but it also control s s election of t he best available soil materials e rosion of the final cover; a vegetated cover o r by initially ad ding excess soil to increase may require only minimal maintenance

. the time required before maintenance i s The vegetation component of the erosio n n eeded. Pa rameters in the equation include layer should have the following the following: parameters may be obtained from the U. S. guidance document entitled "Predictin g

Figu re 6-5 can be used to find the soil los sClosure and Post-Closure

331 

### Figure 6-5 Soil Erosion Due to SlopeSubpart F

332 sp ecifications and characteristics (U.S

. S election of the soil for th e vegetative cover EPA, 1989b): ( erosion layer) should include consideration

! Loc ally adapted perennial plants tha t s pecies of the vegetation selected, mulching, are resistant to drought and temperature and seeding time. Loamy soils with a extremes; sufficient organic content generally ar e

! Roo ts that will not disrupt the low

- s and in loamy soils provides an en vironment permeability layer; conducive to seed germination and roo t

! The ability to thrive in lo w-nutrient soil with minimum nutrient addition; T he Director of an approved State can allow

! Su fficient plant density to minimiz e p roblems (e.g., the use of pavement or other cover soil erosion; ma terial) in areas that are not capable o f

! The ability to survive a nd function with litt le or no maintenance (i.e., self

supportive); and 6.3 ALTERNATIVE FINAL COVER

! Sufficient variety of plant species t o 40 CFR §258.60(b) continue to achieve these chara cteristics and specifications over time. 6.3.1 Statement of Regulation The us e of deep-rooted shrubs and trees i s (b) Th e Director of an approve d generally inappropriate because the roo t Stat e may approve an alternative fina l s ystems may penetrate the infiltration layer cover design that includes: and create preferential pathways o f perc olation. Plant species with fibrous o r (1) An infiltration layer tha t b ranchin g root systems are suited for use at achieves an equivalent reduction i n landfills, and can include a large variety of infiltration as the infiltration laye r grasses, herbs (i.e., legumes), and shallow- sp ecified in paragraphs (a)(1) and (a)(2 ) rooted plants. The suitable species in a of this section, and region will vary, dependent on climate and site -specific factors such as soil type an d (2) An erosion layer that provides slop e gradient and aspect. The timing o f equivalent protection from wind an d see ding (spring or fall in most climates) i s water erosion as the erosion laye r cr itical to successful germination an d specified in (a)(3) of this section. e sta blishment of the vegetative cover (U.S. EPA, 1989b). Temporary winter cover s 6.3.2 Applicability m ay be grown from fast -growing seed stock such as winter rye. The Director of an approved State ma y o f soil type, nutrient and pH levels, climate,

preferred. The balance of clay, silt, an d
growth (USEPA, 1988).

alt ernate designs to address vegetativ e
sustaining plant growth.

DESIGN

a pprove alte rnative final cover systems that can achieve equivalent performance asClosure and Post-Closure

333 the minimum design specified i n T he erosion layer may be made o f asphalt or § 258.60(a). This provides an opportunity to concrete. These materials promote run-off incorporate different technologies o r wi th negligible erosion. However, asphal t imp rovements into cover designs, and t o an d concrete deteriorate due to therma l address site-specific conditions. e xpansion and due to deformati on caused by 6.3.3 Technical Considerations over the landfill cover in areas wher e An alternative material and/ or an alternative rain, or temperature extremes commonl y thi ckness may be used for an infiltratio n cause deterioration of vegetative cover s laye r as long as the infiltration laye r (U.S. EPA, 1989b). requirements specified in §258.60(a)(1) and (a)(2) are met. Other Considerations For example, an armored surface (e.g., one Additional Cover System Components compo sed of cobble-rich soils or soils ric h i n weathered r ock fragments) could be used To reduce the generation of post-closur e as an alternative to the six-inch erosio n lea chate to the greatest extent possible , l ayer. An armored surface, or har dened cap, owners and operators can install a i s general ly used in arid regions or on steep co mposite cover made of a geomembran e slopes where the establishment an d and a soil component with low hydrauli c m aintenance of vegetation may be hindered conductivity. The hydraulic properties o f by lack of soil or excessive run-off. the se components are discussed in Chapte r The materials used for an armored surfac e typically are (U.S. EPA, 1989b): Other components that may be used in th e

! Ca pable of protecting the underlyin g a gas vent layer, and a biotic barrier layer

. infiltration layer during extrem e Th ese components are discussed in th e weath er events of rainfall and/or wind; fol lowing sections and are shown in Figure

! Ca pable of accommodating settlemen t of the underlying material withou t Drainage Layer compromising the component;

! Designed with a surface slope that i s s oil or geosynthetic drainage material, may approximately the same as th e be c onstructed between the erosion laye r und erlying soil (at least 2 percen t and t he underlying infiltration layer. Th e slope); and dr ainage layer in a final cover syste m

! Capa ble of controlling the rate of soi l infiltrated through the erosion layer afte r erosion. su rface run-off and evapotranspiratio n subs idence. Crushed rock may be sprea d

we ather conditions such as wind, heav y

4 (Subpart D).

f inal cover system include a drainage layer,

6-6.

A pe rmeable drainage layer, constructed of

removes percolating water that ha s

los ses. By removing water in contact wit h t he low-permeability layer, the potential for

### Figure 6-6 Example of an Alternative Final Cover DesignClosure and Post-Closure

335 l eac hate generation is diminished. Caution evaluate the relative expected performance s hould be taken when using a drainage layer beca use this layer may prematurely dra w mois ture from the erosion layer that i s needed to sustain vegetation. If a drainage layer is used, owners o r operators should consider methods t o minimize physical clogging of the drainage layer by root systems or soil particles. A filt er layer, composed of either a lo w nu trient soil or geosynthetic material, ma y be p laced between the drainage layer an d the cover soil to help minimize clogging. If g ranular drainage layer material is used , th e filter layer should be at least 12 in. (3 0 cm) thick with a hydraulic conductivity i n the range of 1 x 10 cm/sec to 1 x 10 -2 -3 c m/sec. The layer should be sloped at least 3 percent at the bottom of the l ayer. Greater thickness and/or slope may be necessary to pr ovide sufficient drainage flow a s d et ermined by site-specific modeling (U.S. EPA , 1989b). Granular drainage materia l w i ll vary from site to site depending on the t ype of material th at is locally available and economical to use. Typically, the materia l shoul d be no coarser than 3/8 inch (0.9 5 cm) , classified according to the Universa l Soil Classification System (USCS) as typ e S P, sm ooth and rounded, and free of debris that could damage an underlyin g geomembrane (U.S. EPA, 1989b). Crushed stone generally is not appropriat e b ecause of the sharpness of the particles. If the available drainage material is of poo r quality, it may be necessary to increase the t hickness and/or slope of the drainage layer to maintain adequate drainage. The HEL P model c an be used as an analytical tool t o of alternative final cover designs. If geosynthetic materials are used as a d r ainage layer, the fully saturated effective tr ansmissivity should be the equivalent o f 12 inches of soil (30 cm) with a hydrauli c c onductivity range of 1 x 10 cm/sec to 1 x -2 10 cm/sec. Transmissivity can b e -3 calculated as the hydraulic conductivit y multiplied by the drainage layer thickness

. A f ilter layer (preferably a non-wove n n eedle punch fabric) should be placed above th e geosynthetic material to minimiz e intrusion and clogging by roots or by soi l material from the top layer. Gas Vent Layer Land fill gas collection systems serve t o inhi bit gas migration. The gas collectio n systems typically are installed directl y b eneath the infiltration layer. The function o f a ga s vent layer is to collect combustible gases (methane) and other potentiall y h armful ga ses (hydrogen sulfide) generated b y micro-organisms during b iological decay o f organic wastes, and to divert these gases via a pipe system through the infiltratio n laye r. A more detailed discussio n c oncerning landfill ga s, including the use of ac tive and passive collection systems, i s provided in Chapter 3 (Subpart C). T he gas vent layer is usually 12 in. (30 cm) thick and should be located between th e infiltration layer and the waste layer

. Mater ials used in construction of the ga s vent layer should be medium to coarse

g rained porou s materials such as those used in the drainage layer. Geosyntheti c materials may be substituted for granula r materials in the vent layer if equivalen t p erformance ca n be demonstrated. VentingSubpart F

336 to an exterior collection point can b e Biotic Layer p rovided b y means such as horizontal pipes patt erned laterally throughout the gas ven t De ep plant roots or burrowing animal s l ayer, which channel gases to vertical risers (collectively called biointruders) ma y o r lateral headers. If vertical ri sers are used, disru pt the drainage and the low hydrauli c their number should be minimized (as they c onductivity layers, thereb y interfering with ar e frequently vandalized) and located a t t he draina ge capability of the layers. A 30- h i gh points in the cross-section (U.S. EPA, cm (12-inch) biotic barrier of cobble s 1989 b). Condensates will form within th e directly beneath the erosion layer may stop gas collection pipes; therefore, the desig n th e penetration of some deep-rooted plant s shou ld address drainage of condensate t o an d the invasion of burrowing animals

. p revent blockage by its ac cumulation in low Most research on biotic barriers has bee n points. done in, and is applicable to arid areas

. Th e most obvious potential problem wit h t ime-released herbicide into the ma trix or on ga s collection systems is the possibility o f t he surface of the polymer also may be used g as vent pipe penetrations through the cover t o retard plant roots. The longevity of these system. Settlement within the landfill may products requires evaluation if the cove r cause concentrated stresses at th e syst em is to serve for longer than 30 to 5 0 penetrations, which could result i n years (USEPA, 1991). infilt ration layer or pipe failure. If a geom embrane is used in the infiltratio n Settlement and Subsidence l ayer, p ipe sleeves, adequate flexibility and slackmaterial should be provided at thes e E xcessive settlement and subsidenc e, caused connec tions when appropriate

. by decomposition and consolidation of th e Alte rnatively, if an active gas contro l wastes, can impair the integrity of the final sys tem is planned, penetrations may b e cove r system. Specifically, settlement ca n carrie d out through the sides of the cove r contribute to: dir ectly above the liner anchor trenche s wh ere effects of settlement are les s ! Ponding of surface water on the cap; p ronounced. The gas col lection system also m ay be conn ected to the leachate collection ! Di sruption of gas collection pip e sys tem, both to vent gases that may for m systems; insid e the leachate collection pipes and t o remove gas condensates that form w ithin the ! Fracturing of low permeabilit y g as collection pipes. This method generally infiltration layers; and is no t preferred because if the leachat e c ollection pipe is full, gas will not be able to ! Failure of geomembranes. move through the system. Landfill ga s systems are also discussed in Chapter 3 T he deg ree and rate of waste settlement are (Subpart C). difficult to estimate. Good record s Geosynthetic products that incorporate a

regarding the type, qu antity, and location of was te materials disposed will improve th e estimate. Settlement due to consolidatio nClosure and Post-Closure

337 m ay be minimized by compacting the waste c orr ected during post-closure maintenance. d uring daily operat ion of the landfill unit or b y landfilling baled waste. Organic wastes wi ll continue to degrade and deteriorat e after closure of the landfill unit. Se veral models have been developed t o an alyze the process of differentia l s ettlement. Most models equate the layered co ver to a beam or column undergoin g d eflection due to various loading conditions. Wh ile these models are useful to designer s i n understanding the qua litative relationship between the various land disposal uni t characteristics and in identifying th e co nstraining factors, accurate quantitativ e a nalytical methods have not been developed (U.S. EPA, 1988). If the amount of total settlement can b e est imated, either from an analytica l approach or from empirical relationship s f rom data collected during the operating life of the facility, the designer should attemp t to estimate the potential strain imposed o n the cover system components. Due to th e uncertainties inherent in the settlemen t analysis, a biaxial strain calculation should be sufficient to estimate the stresses tha t may be imposed on the cover system. Th e am ount of strain that a liner is capable o f enduring may be as low as several percent; f or geomembranes, it may be 5 to 12 percent (U.S. EPA, 1990). Geomembrane testin g may be included as part of the desig n pro cess to estimate safety factors agains t cover system failure. The cover system may be designed with a g reater thickness and/or slope to co mpensate f or settlement after closure. However, even i f sett lement and subsidence are considered in the design of the final cover, pondin g may still occur after closure and can be The cost estimate for post-closur e maintenance should include earthwor k required to regrade the final cover due t o total and differential settlements. Based on the estimates of total and differentia l se ttlements from the modeling method s described earlier, it may be appropriate t o a ssume that a cer tain percentage of the total area needs regrading and then incorporat e the costs into the overall post-closur e maintenance cost estimate. Sliding Instability T he slope angle, slope lengt h, and overlying soil load limit the stability of componen t interfaces (geomembrane with soil , geo textile, and geotextile/soil). Soil wate r por e pressures developed along interface s a lso can dramatically reduce stab ility. If the design slope is steeper than the effectiv e f riction angles betwe en the material, sliding instability generally will occur. Sudde n slid ing has the potential to cause tears i n g eomembr anes, which require considerable t ime and expense to repair. Unstable slopes may require remedial measures to improv e stability as a means of offsetting potentia l long-term maintenance costs. The friction angles between various medi a are best determined by laboratory direc t s hear test s that represent the design loading co nditions. Methods to improve stabilit y inc lude using designs with flatter slopes , us ing textured material, constructin g b en ches in the cover system, or reinforcing the cover soil above the membrane wit h ge ogrid or geotextile to minimize th e driv ing force on the interface of concern

. Methods for applying these design features c an be found in (U.S. EPA 1989), (U.S.EPA 1 991), and (Ri chardson and Koerner 1987).Subpart F

338 6.4 CLOSURE PLAN 1 993, must prepar e a closure plan and place 40 CFR §258.60(c)-(d) the plan in the operating record. The pla n 6.4.1 Statement of Regulation t hat will be followedto close the unit at any (c) The owner or operator mus t time it reaches its waste disposal capacity. prepare a written closure plan tha t descr ibes the steps necessary to close al l The cl osure plan must include at least th e MSWL F units at any point during thei r following information: activ e life in accordance with the cove r d esign req uirements in §258.60(a) or (b), ! A description of the final cover and the as applicable. The closure plan, at a methods and procedures to be used t o min imum, must include the followin g install the cover; information: (1) A description of the fina l have to be co vered (typically this is the cover, designed in accordance wit h ar ea that will exist when the final ful l §2 58.60(a) and the methods an d capacity is attained); and p rocedures to be used to ins tall the cover; (2) An estimate of the largest are a o f the MSWLF unit ever requ iring a final The area requiring cover should b e c over as required under §258.6 0(a) at any estimatedfor the operating period fro m time during the active life; initial receipt of waste through closure. (3) An estimate of the maximu m Th e closure plan must be prepared an d inventory of wastes ever on-site over th e pla ced in the operating record befor e active life of the landfill facility; and Octob er 9, 1993 or by the initial receipt o f (4) A schedule for completing al l oper ator must notify the State Directo r ac tivities necessary to satisfy the closur e when the plan has been completed an d criteria in §258.60. placed in the operating record. (d) The owner or operator mus t 6.4.3 Technical Considerations notify the State Director that a closur e p lan has been prep ared and placed in the T he closure plan is a critical document that operating record no later than th e d escribes the steps that an own er or operator effective date of this part, or by the initial will take to ensure that all units will b e receipt of waste, whichever is later. clos ed in a manner that is protective o f 6.4.2 Applicability pl ans provide the basis for cost estimate s An own er or operator of any MSWLF uni t responsibility that must be demonstrated. that r eceives wastes on or after October 9 , mus t describe specific steps and activitie s
t ime after it first receives waste through the

! An estimate of the largest area that will

! A schedule for completing closure.

waste, whichever is later. The owner o r

human health and the enviro nment. Closure
t hat in turn establish the a mount of financialClosure and Post-Closure

339 The closure plan must describe all areas o f ! Preparing construction contrac t t he MSWLF unit that are subje ct to Part 258 documents and securing a contractor; regu lations and that are not closed i n acco rdance with §258.60. Portions of th e landfill unit that have not received a fina l c over must be included in the estimate. The area to be covered at any point during th e active life of the operating unit can b e de termined by examining design an d planned operation procedures and b y c omparing the procedu res with construction re cords, operation records, and fiel d o bservations. Un its are operated frequently in ph ases, with some phases conducted o n top of previously deposited waste. If th e owner or operator routinely closes landfil l cells as they are filled, the plan shoul d i ndicate the greatest n umber of cells open at one time. T he estimate must account for the maximum a mount of waste on-sit e that may need to be disposed in the MSWLF unit ov er the life of the facility (this includes any waste on-site y et to be disposed). The maximum volume o f waste e ver on-site can be estimated from t he maximum capacity of each unit and any op erational procedures that may involv e tra nsfer of wastes to off-site facilities

. W here insufficient design, co nstruction, and ope rational records are found, areas an d v olumes may be estimated from to pographic maps and/or aerial photographs. Steps that may be included in the closur e plan are as follows:

! Noti fying State Director of intent t o initiate closure §258.60(e);

! Dete rmining the area to receive fina l cover;

! Developing the closure schedule; ! Hiring an independent registere d professional engineer to observ e closure activities and provid e certification;

! Securing borrow material;

! Constructing the cover system;

! Obtaining signed certificate and placing it in operating record;

! Notifying State Di rector that certificate was placed in operating record; and

! Rec ording notation in deed to land o r other similar instrument. Th e closure plan should include a d escription of the final cove r system and the methods and proced ures that will be used to install the cover. The description of th e methods, procedures, and processes ma y include design documents; constructio n specifications for the final cover system , i ncludin g erosion control measures; quality control testing procedures for th e construction materials; and qualit y as surance procedures for construction. A general discussion of the methods an d procedures for cover installation i s presented in Section 6.3.3.

6.5 CLOSURE CRITERIA 40 CFR §258.60(e)-(j) 6.5.1 Statement of Regulation (e) Pri or to beginning closure o f each MSWLF unit as specified i nSubpart F

340 §258.60(f), an owner or operator mus t noti fy the State Director that a not ify the State Director that a notice o f ce rtification, signed by an independen t the intent to close the unit has bee n re gistered professional engineer o r placed in the operating record. approved by Director of an approve d (f) The owner or operator mus t c ompleted in accor dance with the closure begin closure activities of each MSWL F pl an, has been placed in the operatin g unit no later than 30 days after the dat e record. on which the MSWLF unit receives th e known final receipt of wastes or, if th e (i)(1) Following closure of al l M SWLF unit has remaining capacity and MSWLF units, the owner or operato r ther e is a reasonable likelihood that th e m ust record a nota tion on the deed to the MSWLF unit will receive additiona l landfill facility property, or some othe r wastes, no later than one year after th e in strument that is normally examine d m ost rec ent receipt of wastes. Extensions during title search, and notify the Stat e be yond the one-year deadline fo r Director that the notation has bee n b egin ning closure may be granted by the recorded and a copy has been placed i n Direc tor of an approved State if th e the operating record. o wner or operator demonstrates that the MSWLF unit has the capacity to receiv e (2) The notation on the deed must ad ditional wastes and the owner o r in perpetuity notify any potentia l op erator has taken and will continue t o purchaser of the property that: t ake all steps necessary t o prevent threats to human health and the environmen t (i) The land has been used as a from the unclosed MSWLF unit. landfill facility; and (g) T he owner or operator of al l (ii) Its use is restricted unde r MS WLF units must complete closur e §258.61(c)(3). ac tivities of each MSWLF unit i n acco rdance with the closure plan withi n (j) The owner or operator ma y 180 days following the beginning o f request permission from the Director o f cl osure as specified in paragraph (f) . a n approved State to rem ove the notation Exten sions of the closure period may b e from t he deed if all wastes are remove d granted by the Director of an approve d from the facility. St ate if the owner or operato r demonstrates that closure will, o f 6.5.2 Applicability ne cessity, take longer than 180 days an d h e has take n and will continue to take all T hese closure requirements are app licable to steps to prevent threats to human health all MSWLF units that receive wastes on o r and the environment from the unclose d after October 9, 1993. The owner o r MSWLF unit. operator is required to: ( h) Following closure of each MSWLF ! Not ify the State Director of the inten t unit, the owner or operator must to close; St ate, verifying that closure has bee nClosure and Post-Closure

341 ! B egi n closure within 30 days of the last receipt of waste (or 1 year if there i s remaining capacity and it is likely that it will be used);

! Complete closure within 180 day s foll owing the beginning of closure (i n ap proved States, the period of time t o begin or complete closure may b e extended by the Director);

! O btain a certification, by an i ndependent re gistered professional engineer, tha t cl osure was completed in accordanc e with the closure plan;

! Plac e the certificate in the operatin g record and notify the S tate Director; and

! No te on a deed (or some othe r inst rument) that the land was used as a landfill and that its use is restricted

. Shoul d all wastes be removed from th e unit in an approved State, the owner o r ope rator may request permission fro m the Director to remove the note on th e deed. 6.5.3 Technical Considerations C losure activities must begin within 30 days of th e last receipt of waste and must b e c ompleted within 1 80 days. Some MSWLF units , such as those in seasonal populatio n a reas, may have remain ing capacity but will not rec eive the next load of waste for a lengthy period of time. These MSWL F u nits m ust receive waste within one year or they must close. Extensions to both th e 1 -year and the 180-day requirement s may be a vailable to owners or op erators of MSWLF u nits in approved St ates. An extension may be granted if the owner or oper ator can demonstrate that there i s remaining capacity or that additional time is ne eded to complete closure. Thes e extensions could be granted to allo w leachate recirculation or to allow fo r se ttlement. The owner or operator mus t take, and continue to take, all step s n ecessary to prevent threats to human health and the environment from the unclose d MSWLF unit. In general, this requirement sh ould be established for a unit i n compliance with the requirements of Par t 258. The owner or operator may need t o d emonstrate how access to t he unclosed unit w ill be controlled prior to closure or receipt o f waste and how the vari ous environmental co ntrol and monitoring systems (e.g. , surface run-off, surface run-on, leachat e c oll ection, gas control system, and groundwater and gas monitoring) will be operated and maintained while the unit remain s unclosed. F ollowing closure of each M SWLF unit, the o wner or operator m ust have a certification, signed by an independent registere d p rofessional engin eer, verifying closure. In app roved States, the Director can approv e the certification. The certificate shoul d verify that closure was completed i n accor dance with the closure plan. Thi s c ertifi cation should be based on knowledge of the closure plan, observations mad e during closure, and documentation o f closure activities provided by the owner or opera tor. The signed certification must b e p laced in the operating record and the State Dir ector must be notified that th e certification was completed and placed i n the record. After closure of all units at a MSWL F faci lity, the owner or operator must recor d a no tation in the deed, or in record sSubpart F

342 t ypically examined during a title search, that care must be conducted for 30 years , t he property was used as a M SWLF unit and ex ceptas provided under paragraph (b ) that its use is restricted under 40 CF R of this part, and consist of at least th e § 258.61(c)( 3). Section 258.61(c)(3) states: following: "... Post-closure use of the property shal l (1) Main taining the integrity and not disturb the integrity of the final cover , e ffectiveness of a ny final cover, including lin er(s), or any other components of th e making repairs to the cover as necessary con tainment systems or the function of th e to correct the effects of settlement , mo nitoring systems unless necessary t o subsidence, erosion, or other events, and comply with the requirements of Par t pr eventing run-on and run-off fro m 258...and... The Director of an approve d ero ding or otherwise damaging the fina l State may approve any other disturbance if cover; the owner or operator demonstrates tha t disturbance of the final cover, liner, or other (2) Maintaining and operating the component of the containment system , lea chate collection system in accordanc e inclu ding any removal of waste, will no t wi th the requirements in §258.40, i f i ncrease the potential threa t to human health a pplica ble. The Director of an approved or the environment." S tate may allow the owner or operator to The se restrictions are described further i n ope rator demonstrates that leachate n o Sec tion 6.7 (Post-Closure Plan) of thi s longe r poses a threat to human healt h document. and the environment; The owner or operator may reques t (3) Mo nitoring the ground wate r p ermission from the Director of an a pproved in a ccordance with the requirements o f S tate to remo ve the notation to a deed. The Sub partE and maintaining the ground request should document that all waste s wa ter monitoring system, if applicable ; h ave been removed from the facility. Such and documentation may include photographs , gro und-water and soil testing in the are a (4) Maintaining and operating the w here wastes were deposi ted, and reports of g as monitoring system in accorda nce with waste removal activity. the requirements of §258.23.

6.6 POST-CLOSURE CARE care period may be: REQUIREMENTS 40 CFR §258.61 (1) De creased by the Director o f 6.6.1 Statement of Regulation operator demonstrates that the reduce d (a) Following closure of each MSWLF health and the environment and thi s u nit, the owner or operator must conduct demonstration is approved by th e post-closure care. Post-closur e Director of an approved State; or stop managing leachate if the owner o r

(b) The length of the post-closure

an approved State if the owner o r pe riod is sufficient to protect huma nClosure and Post-Closure

343 (2) Increased by the Director of a n doe s not pose a threat to human health an d appro ved State if the Director of a n the environment. approved State determines that th e l engthe ned period is necessary to protect 6.6.3 Technical Considerations human health and the environment. 6.6.2 Applicability and maintenance may be necessary to keep Post-closure care requirements apply t o Maintenance may include inspection , MSWLF units that stop receiving wast e te sting, and cleaning of leachate collectio n after October 9, 1993. They also apply t o and removal system pipes, repairs of fina l units that stop receiving waste betwee n cover, and repairs of gas and ground-water October 9, 1991, and October 9, 1993, an d monitoring networks. fa il to complete closure within six month s of the final receipt of waste. Inspections should be made on a routin e Post-closure care requirements are focused check that routine inspections ar e on o perating and maintaining the prope r c ompleted. Records of inspect ions detailing fun ctions of four systems that prevent o r o bservations should be kept in a log book so monitor releases from the MSWLF unit: t hat changes in any of the MSWLFunits can

! Cover system; kept detailing changes in post-closure car e

! Leachate collection system; w ill no t affect post-closure care due to lack

! Ground-water monitoring system; and act ivities and frequency of inspections ar e

! Gas monitoring system. a re monitored and m aintained for as long as O wners or operators must comply with these environment. requ irements for a period of 30 year s following closure. In approved States, th e Inspection of the final cover may b e p ost-closure care period may b e shortened if p erformed on the ground and through aerial the o wner or operator demonstrates to th e photography. Inspections should b e sat isfaction of the Director that huma n cond ucted at appropriate intervals and th e he alth and the environment are protected

. c ondit ion of the facility should be recorded C onversely, the Director may dete rmine that with notes, maps, and photographs. Th e a period longer than 30 years is necessary

. ins pector should take notice of erode d T he requirement to operate and maintain the ban ks, patches of dead vegetation, anima l leachate collection system may b e burrows, subsidence, and cracks along th e elimi nated by the Director of an approve d cover. The inspector also should note th e S tate if the owner or operator demonstrates condition of concrete structures (e.g. , that leachate m anholes ), leachate collection and removal When the final cover is installed, repair s th e cover in good working order

.

basis. A schedule should be developed t o

b e monitored; in addition, records should be
p ersonnel to ensure that changing personnel of knowledge of routine activities. Th e subject to State review to ensure that unit s i s necessary to protect human health and theSubpart F

344 pipes, gas monitoring systems, an d E rosion may lead to increas ed infiltration of monitoring wells. surface water into the landfill. Area s For larger facilities, annual aeria l phot ography may be a useful way t o C ertain types of veget ative cover (e.g., turfd ocument the extent of veg etative stress and type grasses) may require mowing at leas t sett lement if either of these has bee n two ti mes a year. Mowing can aid i n observed during routine inspections. It i s s uppre ssion of weed and brush growth, and im portant to coordinate the photograph y ca n increase the vigor of certain gras s wi th the site "walkover" to verif y species. Alternatively, certain cover type s interpretations made from aeria l (e.g., native prairie grasses) require les s ph otographs. Aerial photography shoul d frequent mowing (once every three years ) n ot be used in place of a site walk over but in a nd may be suitable fo r certain climates and co njunction with the site walkover. A n facilities where a low-maintenance regim e EPA document (U.S. EPA 1987) provide s is preferable. For certain cover types , fu rther information on using aeria l fertilization schedules may be necessary t o pho tography for inspecting a landfil l sustain desirable vegetative growth

. faci lity. (See the Reference section at th e Fe rtilization schedules should be based o n end of this chapter.) the cover type present. Annual or biennia l Topographic surveys of the landfill unit(s ) grasses, while legumes and nativ e may be used to determine whethe r v egetation m ay require little or no fertilizer settl ement has occurred. These should b e o nc e established. Insecticides may be used re peated every few years until settlemen t to eliminate insect populations that ar e b ehavior is esta blished. If settlement plates detrimental to vegetation. Insecticide s are used, they should be permanent an d sho uld be carefully selected and applie d pr otected from vandalism and accidenta l wi th consideration for potential effects o n disturbance (U.S. EPA , 1987). Depressions surface water quality. ca used by settlement may lead to pondin g and should be filled with soil. Excessiv e So me leachate collection and remova l settlement may warrant reconstructing o r syst ems have been designed to allow fo r ad ding to portions of the infiltration layer

. inspec tions in an effort to ensure that the y Da mage caused by settlement such a s are working properly. Leachate collectio n tens ion cracks and tears in the syntheti c and removal pipes may be flushed an d membrane should be repaired. p ressure-cleaned on a regular sc hedule (e.g., Co ver systems that have areas where th e sed iment and precipitation and to preven t slope is greater than 5 percent may b e biological fouling. s usceptible to erosion. L arge and small rills (crevices) may form along the cover where S imi larly, gas collection systems should be water has eroded the cover. This may lead inspe cted to ensure that they are workin g to exposure of the synthetic geomembran e pr operly. Vents should be checked t o a nd, in severe cases, depen ding on the cover ensure they are not clogged by foreig n sy stem installed, exposure of the waste

. matter such as rocks. If not workin g s howing signs of erosion should be repaired.

fer tilization may be necessary for certai n

ann ually) to reduce the accumulation o fClosure and Post-Closure

345 properly, the gas collection systems should 6.7 POST-CLOSURE PLAN be flushed and pressure-cleaned. 40 CFR §258.61(c)-(e) At some landfill facilities, leachat e c onc entrations eventually may become low enou gh so as not to pose a threat to huma n health or the environment. In an approve d St ate, the Director may allow an owner o r ope rator to cease managing leachate if th e owner or operator can demonstrate that the leach ate no longer poses a threat to huma n heal th and the environment. Th e demonstration should address direc t exp osures of leachate releases to groun d water , surface water, or seeps. Indirec t effects, such as accumulated leachat e adv ersely affecting the chemical, physical , and structural containment systems tha t prevent leachate release, also should b e addressed in the demonstration. The threat posed by direct exposures t o l eachate released to ground wate r, to surface wate rs, or through seeps may be assesse d using health-based criteria. These criteri a and methods are available through th e Integrated Risk Information System (IRIS) (a database maintained by U.S. EPA), th e RCRA Facility Investigation Guidanc e (U.S

. EPA, 1989c), the Risk Assessmen t G uidance for Superfund (U.S. EP A, 1989d), a nd certain U.S. EPA regulations, including MC Ls established under the Safe Drinkin g Wat er Act and the ambient water qualit y criteria under the Clean Water Act. Thes e criteria and assessment procedures ar e descr ibed in Chapter 5 (Subpart E) of thi s document. Concentrations at the points o f exposure, rather than concentrations in th e leachate in the collection system, may b e used when assessing threats. 6.7.1 Statement of Regulation (c) The owner or operator of al l MSWLF units must prepare a writte n pos t-closure plan that includes, at a minimum, the following information: (1) A description of th e mo nitoring and maintenance activitie s required in §258.61(a) for each MSWLF un it, and the frequency at which thes e activities will be performed; (2) Name, a ddress, and telephone n umber of t he person or office to contact about the f

acility during the post-closure period; and (3) A description of the planne d use s of the property during the post clo sure period. Post-closure use of th e p roperty shall not distu rb the integrity of the final cover, liner(s), or any othe r components of the containment system , o r the function of the monitoring systems unless necessary to comply with th e req uirements in Part 258. The Directo r of a n approved State may approve an y ot her disturbance if the owner o r op erator demonstrates that disturbanc e of th e final cover, liner or othe r component of the containment system , including any removal of waste, will no t in crease the potential threat to huma n health or the environment. (d) The owner or operator mus t notify the State Director that a post clos ure plan has been prepared an d placed in the operating record no laterSubpart F

346 than the effective date of this part , ! The procedure for verifying that post

October 9, 1993, or by the initial receip t clo sure care was provided i n of waste, whichever is later. accordance with the plan. (e) Following completion of th e In approved States only, the owner o r po st-closure care period for eac h operator may request the Director t o MSWLF unit, the owner or operato r approv e a use that disturbs the final cove r must notify the State Director that a ba sed on a demonstration that the use wil l ce rtification, signed by an independen t not increase the potential threat to huma n re gistered professional engineer o r health and the environment. approved by t he Director of an approved S tate, verifying that post -closure care has 6.7.3 Technical Considerations bee n completed in accordance with th e post-closure plan, has been placed in the The State Director must be notified that a operating record. post-closure plan, describing th e 6.7.2 Applicability MSW LF unit, has been placed in th e O wners and operators o f existing units, new shouldprovide a schedule for routin e units, and lateral expansions of existin g ma intenance of the MSWLF unit systems

. MSWLF units that stop receiving wast e These systems include the final cove r after October 9, 1993 are required t o s ystem, the leachate collection and removal p rovide a post-closure plan. MSWLF units sy stem, and the landfill gas and ground

that received the final waste shipmen t water monitoring systems. between October 9, 1991 and October 9 , 1 993 but failed to complete installation of a The plan must include the name, address , f inal cover system within six months of the and telephone number of the person o r final receipt of waste also are required t o office to contact regarding the facilit y provide a post-closure plan. th roughout the post-closure period

. The post-closure plan describes th e p roperty during the post-closure per iod must m onitoring ac tivities that will be conducted b e provided in the plan. These uses may not throughout the 30-year period. The pla n dist urb the integrity of the final cove r also establishes: sys tem, the liner system, and any othe r

! The schedule or frequency at whic h mo nitoring systems unless necessary t o these activities are conducted; com ply with the requirements of Part 258

.

! N ame, address, and telephone number of MSWLF components must be approved b y a person to contact about the facility; the Director of an approved State. A n

! A descriptio n of a planned use that does include remedial action necessary t o not disturb the final cover; and m inimize the threat to human health and the mai ntenance activities required for eac h
op erating record. The post-closure pla n

Additionally, the planned uses of th e

com ponents of the containment o r

An y other disturbances to any of th e
example of an acceptable disturbance ma y

environment.Closure and Post-Closure

347 Fo llowing completion of the post-closur e car e period, the State Director must b e no tified that an independent registere d professional engineer has verified an d certified that post-closure care has bee n completed in accordance with the post

clo sure plan and that this certification ha s been placed in the operating record

. Alt ernatively, the Director of an approve d St ate may approve the certification

. C ertifi cation of post-closure care should be submitted for each MSWLF unit.Subpart F

348 6.8 FURTHER INFORMATION 6.8.1 References G iroud, J.P., Bonaparte, R., Bee ch, J.F., and Gross, B.A., "Design of Soil Layer -Geosynthetic Systems Overlying Voids". Journal of Geotextiles and Geomembranes, Vol. 9, No. 1, 1990, pp. 11-50. Richardson, G.N. and R.M. Koerner, (1987). "Geosynthetic Design Guidance for Hazardous Waste Landfill Cells and Surface Impoundments "; Hazardous Waste Engineering Research Laboratory; USEPA, Office of Research and De velopment; Cincinnati, Ohio; Contract No. 68-07-3338. U.S. EPA, (1987). "Design, Construction and Maintenance of Cover Systems for Hazardous Wa ste: An Engineering Guidance Document"; PB87-19156; EPA/600/2-87/039; U.S

. Department of Commerce, National Technical Information Service; U.S. A rmy Engineering Waterways Experiment Station; Vicksburg, Mississippi. U .S. EPA, (1988). "Guide to Technic al Resources for the Design of Land Disposal Facilities"; EPA/6 25/6-88/018; U.S. EPA; Risk Reduction Engineering Laboratory and Center fo r Environmental Research Information; Office of Research and Development; Cincinnati , Ohio 45268. U.S. EPA, (1989a). "Seminar Publication - Requirements for Hazardous Waste Landfil l Design, Construction and Closure"; EPA/625/4-89/022; U.S. EPA; Center fo r Environmental Research Information; Office of Research and Development; Cincinnati , Ohio 45268. U.S. EPA, (1989b). "Technical Guidance Document: Final Covers on Hazardous Wast e Landfills and Surface Impoundments"; EPA/530-SW-89-047; U.S. EPA; Office of Solid Waste and Emergency Response; Washington, D.C. 20460. U.S. EPA, (1989c). "Interim Final: RCRA Facility Investigation (RFI) Guidance"; EP A 530/SW-89 -031; U.S. EPA; Waste Management Division; Office of Solid Waste; U.S

. Environmental Protection Agency; Volumes I-IV; May 1989. U .S. EPA, (1989d). "Interim Final: Ris k Assessment Guidance For Superfund; Human Health Evaluatio n Manual Part A"; OS-230; U.S. EPA; Office of Solid Waste and Emergenc y Response; July 1989. U .S. EPA, (1991). "Seminar Publications - Design and Construction of RCRA/CERCLA Final Covers"; EPA/625/4-91/025; U.S. EPA, Office of Research and D evelopment; Washington, D.C. 20460.Closure and Post-Closure

349 6.8.2 Organizations U.S. Department of Agriculture Soil Conservation Service (SCS) P.O. Box 2890 Washington, D.C. 20013-2890 (Physical Location: 14th St. and Independence Ave. NW.) (202) 447-5157 Note: This is the address of th e SCS headquarters. To obtain the SCS technical guidance

document concerning the Universal Soil Loss Equation (entitled "Pre dicting Rainfall Erosion Loss, Guidebook 537," 1978), contact SCS regional offices locate d throughout the United States. 6.8.3 Models Schroeder, et al., (1988). "The Hydrologic Evaluation of Landfill Performance (HELP ) Mode l"; U.S.EPA; U.S. Army Engineer Waterways Experiment Station; Vicksburg, M S 39181-0631; October 1988. S chroeder, P.R., A.C. Gibson, J.M. Morgan, T.M. Walski, (19 84). "The Hydrologic Evaluation of Landfill Performance (HE LP) Model, Volume I - Users Guide for Version I (EPA/530- SW-84- 009), and Volume II - Documentation for Version I (EPA/530-SW-84-010); U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, June 1984. 6.8.4 Databases I ntegrated Risk Information System (IRIS), U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, Ohio.