GROUND WATER RULE CORRECTIVE ACTIONS 

GUIDANCE MANUAL 

November 2008 

EPA 815-R-08-011 
Office of Water (4606) EPA 815-R-08-011 www.epa.gov/safewater November 2008 
DISCLAIMER 

This manual provides guidance in meeting corrective action requirements under the 

Ground Water Rule (GWR). Corrective actions are an important part of helping public water 

systems protect public health. 

The statutory provisions and U.S. Environmental Protection Agency (EPA) regulations 

described in this document contain legally binding requirements. This guidance is not a 

substitute for applicable legal requirements, nor is it a regulation itself. Thus, it does not impose 

legally-binding requirements on any party, including EPA, States, or the regulated community. 

While EPA has made every effort to ensure the accuracy of the discussion in this guidance, the 

obligations of the regulated community are determined by statutes, regulations, or other legally 

binding requirements. In the event of a conflict between the discussion in this document and any 

statute or regulation, the statute or regulation, not this document, would be controlling. 

Interested parties are free to raise questions or objections to the guidance and the 

appropriateness of using it in a particular situation. 

Although this manual describes suggestions for complying with GWR requirements, the 

guidance presented here may not be appropriate for all situations, and alternative approaches 

may provide satisfactory performance. 

Mention of trade names or commercial products does not constitute an EPA endorsement 

or recommendation for use. 

Questions regarding this document should be addressed to: 

Michael Finn 

U.S. EPA Office of Ground Water and Drinking Water 

1200 Pennsylvania Avenue, N.W. 4607M 

Washington, DC 20460 

Finn.Michael@epa.gov 

Phone: 202-564-5261 Fax: 202-564-3767 

ACKNOWLEDGMENT OF PEER REVIEWERS 

Association of State Drinking Water Administrators (ASDWA) 

Association of Metropolitan Water Agencies (AMWA)

American Water Works Association (AWWA)

Gregory Eager, P.E., Drinking Water Program, Idaho Department of Environmental Quality; 

Eugene H Leung, P.E., Drinking Water Field Operations, California Department of Health 

Services; 

Bob Moore, Southwest District Office, Ohio Environmental Protection Agency; 

Richard L. Overmyer, Noncommunity Drinking Water Unit, Water Bureau, Michigan 

Department of Environmental Quality; 

Eva Tor, P.E., Massachusetts Department of Environmental Protection reviewed early drafts of 

the Corrective Action Guidances Manual for the Ground Water Rule. 

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Corrective Actions Guidance Manual
CONTENTS 

Exhibits ........................................................................................................................................ viii 

Acronyms....................................................................................................................................... ix 

1. Introduction to the Ground Water Rule Corrective Actions Guidance Document........ 1-1 

1.1 The Ground Water Rule (GWR).......................................................................... 1-1 

1.2 Overview of the Corrective Action Process under the GWR .............................. 1-2 

1.3 Requirements for States and PWSs Related to Corrective Actions in Response to

Significant Deficiencies and Fecal Indicator Positives........................................ 1-4 

1.3.1 State Requirements ........................................................................................ 1-4 

1.3.2 PWS Requirements ........................................................................................ 1-4 

1.4 Goal and Organization of the Guidance Manual ................................................. 1-5 

2. Correcting Significant Deficiencies ..................................................................................... 2-1 

2.1 Identifying Significant Deficiencies .................................................................... 2-2 

2.1.1 Sanitary Surveys ............................................................................................ 2-2 

2.1.2 Other Ways of Identifying Significant Deficiencies ...................................... 2-3 

2.2 Source Deficiencies ............................................................................................. 2-3 

2.2.1 Examples of Significant Deficiencies ............................................................ 2-3 

2.2.2 Identifying Corrective Actions ...................................................................... 2-3 

2.2.3 Additional Information and Resources .......................................................... 2-4 

2.3 Treatment Deficiencies ........................................................................................ 2-4 

2.3.1 Examples of Significant Deficiencies ............................................................ 2-4 

2.3.2 Identifying Corrective Actions ...................................................................... 2-5 

2.3.3 Additional Information and Resources .......................................................... 2-5 

2.4 Distribution System Deficiencies ........................................................................ 2-5 

2.4.1 Biofilm Control .............................................................................................. 2-6 

2.4.2 Cross-Connection Control ............................................................................. 2-7 

2.4.2.1 Existing Requirements ....................................................................... 2-8 

2.4.2.2 Choosing a Backflow Preventer......................................................... 2-8 

2.4.2.3 Installing and Testing Backflow Preventers ...................................... 2-9 

2.4.2.4 Cross-Connection Control and Backflow Prevention Programs ..... 2-10 

2.4.3 Examples of Significant Deficiencies .......................................................... 2-10 

2.4.4 Identifying Corrective Actions .................................................................... 2-11 

2.4.5 Additional Information and Resources ........................................................ 2-11 

2.5 Finished Water Storage ...................................................................................... 2-11 

2.5.1 Correcting Defective Vents .......................................................................... 2-13 

2.5.2 Correcting Inadequate Access Hatches ........................................................ 2-14 

2.5.3 Correcting Insufficient Overflows ............................................................... 2-14 

2.5.4 Hydropneumatic Tanks ................................................................................ 2-14 

2.5.5 Examples of Significant Deficiencies .......................................................... 2-16 

2.5.6 Identifying Corrective Actions .................................................................... 2-16 

2.5.7 Additional Information and Resources ........................................................ 2-16 

2.6 Pumps................................................................................................................. 2-17 

2.6.1 Examples of Significant Deficiencies .......................................................... 2-17 

2.6.2 Identifying Corrective Actions .................................................................... 2-17 

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2.6.3 Additional Information and Resources ........................................................ 2-17 

2.7 Monitoring, Reporting and Data Verification .................................................... 2-18 

2.7.1 Examples of Significant Deficiencies .......................................................... 2-18 

2.7.2 Identifying Corrective Actions .................................................................... 2-18 

2.7.3 Additional Information and Resources ........................................................ 2-18 

2.8 System Management and Operations................................................................. 2-19 

2.8.1 Identifying Financial Resources .................................................................. 2-19 

2.8.2 Security Measures ........................................................................................ 2-20 

2.8.3 Examples of Significant Deficiencies .......................................................... 2-21 

2.8.4 Identifying Corrective Actions .................................................................... 2-21 

2.8.5 Additional Information and Resources ........................................................ 2-21 

2.9 Operator Compliance with Certification Requirements .................................... 2-22 

2.9.1 Examples of Significant Deficiencies .......................................................... 2-23 

2.9.2 Identifying Corrective Actions .................................................................... 2-23 

2.9.3 Additional Information and Resources ........................................................ 2-23 

3. Eliminating Sources of Contamination ............................................................................... 3-1 

3.1 Source Water Rehabilitation ................................................................................ 3-1 

3.1.1 Identifying Contamination Causes ................................................................. 3-1 

3.1.2 Preventing Contamination from an Abandoned Well .................................... 3-3 

3.1.3 Remediating an Existing Well ....................................................................... 3-4 

3.1.3.1 Correcting Drainage Problems........................................................... 3-8 

3.1.3.2 Replacing a Sanitary Well Seal .......................................................... 3-9 

3.1.3.3 Eliminating a Well Pit / Buried Well ............................................... 3-10 

3.1.3.4 Temporary Disinfection of Wells by Applying Shock 

Chlorination .................................................................................................... 3-11 

3.1.4 Minimizing Contamination after a Flood .................................................... 3-14 

4. Providing an Alternative Source of Drinking Water ......................................................... 4-1 

4.1 Providing Bottled Water (Short Term) ................................................................ 4-1 

4.2 Consolidating/Purchasing Water from Another Utility ....................................... 4-2 

4.3 Installing a New Well .......................................................................................... 4-2 

4.3.1 Critical Factors in Well Construction ............................................................ 4-3 

4.3.2 Types of Wells ............................................................................................... 4-4 

4.3.2.1 Bored Wells ....................................................................................... 4-6 

4.3.2.2 Driven Wells ...................................................................................... 4-6 

4.3.2.3 Jetted Wells ........................................................................................ 4-6 

4.3.2.4 Drilled Wells ...................................................................................... 4-7 

4.3.3 Characteristics of Wells ............................................................................... 4-10 

4.3.3.1 Yields of Different Types of Wells .................................................. 4-10 

4.3.3.2 Sanitary Construction of Wells ........................................................ 4-10 

4.3.3.3 Grouting Requirements .................................................................... 4-11 

4.3.3.4 Well Screens .................................................................................... 4-12 

4.3.3.5 Well Development ........................................................................... 4-13 

4.3.3.6 Testing Wells for Yield and Drawdown .......................................... 4-14 

4.3.4 Disinfection of Newly Constructed Wells ................................................... 4-15 

4.4 Switching to a Surface Water Source ................................................................ 4-16 

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5. Installing Treatment ............................................................................................................. 5-1 

5.1 Chemical Disinfection ......................................................................................... 5-3 

5.1.1 Temporary Hypochlorination ......................................................................... 5-5 

5.1.2 Chlorine Gas .................................................................................................. 5-6 

5.1.2.1 Background........................................................................................ 5-6 

5.1.2.2 System Design ................................................................................... 5-6 

5.1.2.3 Operation and Maintenance ............................................................... 5-7 

5.1.2.4 Advantages and Disadvantages .......................................................... 5-7 

5.1.3 Hypochlorite .................................................................................................. 5-8 

5.1.3.1 Background........................................................................................ 5-8 

5.1.3.2 System Design ................................................................................... 5-9 

5.1.3.3 Operation and Maintenance ............................................................... 5-9 

5.1.3.4 Advantages and Disadvantages ........................................................ 5-10 

5.1.4 Chlorine Dioxide (ClO2) Disinfection ......................................................... 5-11 

5.1.4.1 Background...................................................................................... 5-11 

5.1.4.2 System Design ................................................................................. 5-11 

5.1.4.3 Operation and Maintenance ............................................................. 5-12 

5.1.4.4 Advantages and Disadvantages ........................................................ 5-12 

5.1.5 Ozone (O3) Disinfection .............................................................................. 5-13 

5.1.5.1 Background...................................................................................... 5-13 

5.1.5.2 Operation and Maintenance ............................................................. 5-14 

5.1.5.3 Advantages and Disadvantages ........................................................ 5-14 

5.2 UV Radiation Disinfection ................................................................................ 5-15 

5.2.1 Background.................................................................................................. 5-15 

5.2.2 Inactivation Mechanism and Effectiveness ................................................. 5-16 

5.2.3 System Design ............................................................................................. 5-16 

5.2.4 Operation and Maintenance ......................................................................... 5-17 

5.2.5 Advantages and Disadvantages .................................................................... 5-18 

5.3 Membrane Filtration Technologies.................................................................... 5-18 

5.3.1 Background.................................................................................................. 5-20 

5.3.2 System Design ............................................................................................. 5-20 

5.3.3 Operation and Maintenance ......................................................................... 5-21 

5.3.4 Advantages and Disadvantages .................................................................... 5-22 

5.4 Additional Resources............................................................................................... 5-23 

6. References.......................................................................................................................... 6-1 

Appendix A: Applications of Various Backflow Prevention Assemblies or Methods ...... A-1 

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EXHIBITS 

Exhibit 1.1 Overview of Corrective Action Process ................................................................... 1-3 

Exhibit 2.1 Typical Ground Storage Tank ................................................................................ 2-12 

Exhibit 2.2 Raised Sill Appropriate for a Hatch ....................................................................... 2-14 

Exhibit 2.3 Types of Pressure Tanks ........................................................................................ 2-15 

Exhibit 3.1 Sealed Well that is Not Housed ............................................................................... 3-5

Exhibit 3.2 Pump House and Well Appurtenances ..................................................................... 3-6 

Exhibit 3.3 Submersible Pump with Pitless Adapter .................................................................. 3-7 

Exhibit 3.4 Example of Correcting Drainage Problems ............................................................. 3-9 

Exhibit 3.5 Sanitary Well Seal with Expandable Gasket .......................................................... 3-10 

Exhibit 3.6 Overlapping Exterior Well Seal ............................................................................. 3-10 

Exhibit 3.7 Quantities of Calcium Hypochlorite, 70% to Provide a Chlorine Dosage of at Least 

100 mg/L ................................................................................................................ 3-12 

Exhibit 3.8 Liquid Chlorine Bleach* (5.25%) to Provide a Chlorine Dosage of at Least 100 

mg/L....................................................................................................................... 3-13 

Exhibit 4.1 Well Construction and Condition............................................................................. 4-3 

Exhibit 4.2 Ten State Standards (2007) Recommendations for Casing...................................... 4-4 

Exhibit 4.3 Suitability of Well Construction Methods with Different Geological Conditions .. 4-5 

Exhibit 4.4 Drilled Well with Submersible Pump ...................................................................... 4-8 

Exhibit 4.5 Typical Wellhead Design for Submersible Pumps .................................................. 4-9 

Exhibit 5.1 CT Values for Inactivation of Viruses by Free Chlorine (mg-min/L) ..................... 5-4

Exhibit 5.2 CT Values (mg-min/L) for Inactivation of Viruses1 by Chlorine Dioxide for 

pH 6 to 9................................................................................................................. 5-11

Exhibit 5.3 CT Values (mg of O3-min/L) for Virus Inactivation by Ozone ............................. 5-13 

Exhibit 5.4 UV Dose Requirements for Virus Inactivation (mJ/cm2) ...................................... 5-15 

Exhibit 5.5 Particle Size Removal for Various Membrane Technologies ................................ 5-19 

Exhibit 5.6 Schematic of a Typical RO/NF Treatment System ................................................ 5-21 

November 2008 Ground Water Rule viii

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ACRONYMS 

μg/L micrograms per liter 

2D Twice the Diameter 

AG Air Gap 

AOC Assimilable Organic Carbon 

AVB Atmospheric Vacuum Breaker 

AWWA American Water Works Association 

AwwaRF American Water Works Association Research Foundation 

BAT Best Available Technology 

BL Barometric Loop 

BMP Best Management Practice 

CCR Consumer Confidence Reports 

CFR Code of Federal Regulations 

CT Concentration of Residual Disinfectant (in mg/L) multiplied by Time of Water 

Contact (Detention Time) (in minutes) 

CWS Community Water System 

DBP Disinfection Byproduct 

D/DBPR Disinfectants/Disinfection Byproducts Rule 

DCDC Double Check Detector Check 

DCIAV Double Check Valve with Intermediate Atmospheric Vent 

DCV Double Check Valve 

DEP Department of Environmental Protection 

DNA Deoxyribonucleic Acid 

EPA United States Environmental Protection Agency 

EPS Extracellular Polysaccharides 

FDA United States Food and Drug Administration 

GWR Ground Water Rule 

GWS Public Water Systems that are subject to the requirements of the Ground 

Water Rule (includes PWSs that also deliver surface water and/or GWUDI) 

GWUDI Ground Water Under the Direct Influence of Surface Water 

HAA Haloacetic Acid 

HB Hose Bib Vacuum Breaker 

HPC Heterotrophic Plate Count 

HSA Hydrogeologic Sensitivity Assessment 

HTH High-test Hypochlorite 

IBWA International Bottled Water Association 

ICR Information Collection Rule 

IESWTR Interim Enhanced Surface Water Treatment Rule 

LT1 Long Term 1 Enhanced Surface Water Treatment Rule 

LT2 Long Term 2 Enhanced Surface Water Treatment Rule 

MCL Maximum Contaminant Level 

November 2008 Ground Water Rule ix 

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MF Microfiltration 

mg/L milligrams per liter 

MWCO Molecular Weight Cut Off 

NCWS Non-community Water Systems 

NDPES National Pollutant Discharge Elimination System 

NF Nanofiltration 

NOM Natural Organic Matter 

NPDW National Primary Drinking Water 

O&M Operation and Maintenance 

PVB Pressure Vacuum Breaker 

PVC Polyvinyl Chloride 

PWS Public Water System 

RCRA Resource Conservation and Recovery Act 

RDC Residential Dual Check 

RO Reverse Osmosis 

RPBA Reduced Pressure Principle Blackflow Prevention Assembly 

SDWIS Safe Drinking Water Information System – Federal Version 

SMCL Secondary Maximum Contaminant Level 

SRF State Revolving Fund 

SWTR Surface Water Treatment Rule 

TCR Total Coliform Rule 

THM Trihalomethane 

TOC Total Organic Carbon 

TOX Total Organic Halogen 

UF Ultrafiltration 

UFTREEO University of Florida Training, Research, and Education for Environmental 

Occupations 

UIC Underground Injection Control 

USGS United States Geological Survey 

UV Ultraviolet 

UVT UV Transmittance 

November 2008 Ground Water Rule x 

Corrective Actions Guidance Manual 
1. Introduction to the Ground Water Rule Corrective Actions Guidance 

Document 

The purpose of this guidance manual is to assist States and Public Water Systems 

(PWSs)1 to select and implement corrective actions in response to significant deficiencies 

identified during sanitary surveys or in response to fecal contamination of source water as 

required under the Ground Water Rule (GWR). Other important aspects of the GWR related to 

corrective actions are discussed more fully in other guidance manuals, such as: 

• The Consecutive Systems Guidance Manual for the Ground Water Rule (USEPA 

2007b) 

• The Source Water Monitoring Guidance Manual (USEPA 2007c) 

• The Ground Water Rule Sanitary Survey Guidance Manual (to be published) 

This introduction provides an overview of the portions of the GWR that relate 

specifically to corrective actions. 

1.1 The Ground Water Rule (GWR) 

The GWR was signed by the United States Environmental Protection Agency (EPA) 

Administrator on October 11, 2006 and was published in the Federal Register on November 8, 

2006 (71 FR 65574). The primary purpose of the GWR is to provide for increased protection 

against microbial pathogens in PWSs that use ground water as their source. 

PWSs that are subject to the requirements of the GWR include systems that use only 

ground water sources, “mixed systems” that use both ground and surface water sources, and 

wholesale and consecutive systems that serve ground water2. 

The GWR does not apply to “subpart H” systems that combine all of their ground water 

with surface water prior to treatment and those systems identified as ground water under the 

direct influence of surface water (GWUDI). The GWR may apply to all types of PWSs: 

community water systems (CWSs), non-transient non-community water systems (NCWSs), and 

transient NCWSs. 

EPA has estimated that approximately 147,330 PWSs in the United States, serving over 

114 million people, are subject to the requirements of the GWR based on data from the Safe 

Drinking Water Information System – Federal Version (SDWIS) (USEPA, 2006). 

1 PWSs are systems that have at least 15 service connections, or regularly serve at least 25 individuals daily at least 

60 days out of the year. 

2 These systems are referred to as Ground Water Systems (GWSs) throughout this guidance document. 

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Corrective Actions Guidance Manual 
The GWR established a risk-targeting approach to identify Ground Water Systems 

(GWSs) subject to the rule that may pose a risk of exposure to microbial pathogens to customers. 

The key provisions of the risk-targeting approach of the GWR are: 

• Periodic sanitary surveys of Ground Water Systems (GWSs) focusing on eight critical 

elements to identify any significant deficiencies that must be addressed through 

corrective action. States must complete the first of these periodic sanitary surveys by 

December 31, 2012 for most CWSs and by December 31, 2014 for CWSs with a 

history of outstanding performance and for all non-community water systems 

(NCWSs) (40 CFR 141.401). 

• Triggered source water monitoring of GWSs that have a total coliform positive of a 

routine sample in the distribution system under the Total Coliform Rule (TCR) if that 

GWS does not currently provide treatment that achieves at least 99.99 percent (4-log) 

inactivation or removal of viruses. Triggered source water monitoring tests for the 

presence of a microbial pathogen indicator (E. coli, enterococci, or coliphage) as 

required by the State. A GWS that has microbial pathogen indicator positive 

identified in the source water may be required by the State to take immediate 

corrective action or, if not so required, must take five additional source water samples 

and undertake corrective action if any of those additional samples are positive (40 

CFR 141.402(a)). 

• Assessment source water monitoring may also be required by a State as a 

complement to triggered monitoring. A State has the option to require systems, at any 

time, to conduct source water assessment monitoring for fecal indicators to help 

identify high risk systems. Hydrogeologic sensitivity assessments (HSAs) can be 

used as an optional tool to identify those high risk systems for assessment source 

water monitoring (40 CFR 141.402(b)). 

• Compliance monitoring for GWSs that currently disinfect to ensure that the treatment 

technology installed reliably achieves at least 99.99 percent (4-log) inactivation or 

removal of viruses (40 CFR 141.403(b)). 

1.2 Overview of the Corrective Action Process under the GWR 

Under §141.403(a) the GWR, systems must implement a corrective action if one or more 

significant deficiencies are identified by the State, or if a fecal indicator positive result is 

detected in a source water sample collected under §141.402(a)(3) or if directed by the State 

based on results of monitoring under §141.402(a)(1) or §141.402(b). 

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Corrective Actions Guidance Manual 
Exhibit 1.1 Overview of Corrective Action Process 

Fecal 

Indicator 

Positive 

Sample 

State Requires 

Corrective Action 

Fecal Indicator 

Positive Sample (from 

1 of 5 additional 

samples) System 

Required to 

Take 

Corrective 

Action 

State Identifies 

Significant Deficiency 

Source 

Water 

Monitoring1 

Other State 

Oversight 

Path 3 

Sanitary 

Survey 

Path 2 

Path 1 

1

Source water monitoring is triggered by a total coliform-positive sample in the distribution 

system. See 40 CFR 141.402(a). 

Corrective actions performed under the GWR include one or more of the following 

alternatives: 

• Correct all significant deficiencies; 

• Eliminate the source of contamination; 

• Provide an alternate source of water; and 

• Provide treatment which reliably achieves 99.99 percent (4-log) inactivation or 

removal of viruses. 

The following briefly summarizes the requirements related to corrective actions that 

States and PWSs must take in response to the identification of significant deficiencies or fecal 

indicator positives. 

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Corrective Actions Guidance Manual 
1.3 Requirements for States and PWSs Related to Corrective Actions in Response 

to Significant Deficiencies and Fecal Indicator Positives 

1.3.1 State Requirements 

The GWR requires States to provide written notice to the PWS describing all significant 

deficiencies (i.e., those that require corrective action) identified. The notice may be provided onsite at the time the significant deficiency is identified or it may be sent to the PWS within 30 

days of identifying the significant deficiency. 

In the cases of either the identification of significant deficiencies or the determination of 

a fecal indicator positive in source water monitoring, the State may specify the corrective actions 

and deadlines to the affected GWS, or it may work with the affected GWS to determine an 

appropriate corrective action plan. The State must approve the corrective action plan and 

schedule (and must also approve any subsequent modifications to it). The State must also verify 

that corrective actions have been completed through written confirmation or a site visit within 30 

days after the PWS has reported to the State that the corrective action has been completed. 

1.3.2 PWS Requirements 

Within 30 days of receiving written notice from the State of a significant deficiency or 

written notice from a laboratory of a fecal-indicator positive, the GWS must consult with the 

State regarding the appropriate corrective action. In some cases, the system may be directed by 

the State to implement a specific corrective action. 

If the State does not specify a corrective action to be taken by the GWS, then within 120 

days (or earlier if directed by the State) of receiving written notice from the State of a significant 

deficiency or written notice from a laboratory of a fecal indicator positive, the GWS must either 

have completed the appropriate corrective action or be in compliance with a State-approved 

corrective action plan and schedule. 

The GWS must notify the State that a required corrective action has been completed 

within 30 days of completion. 

Also, in addition to other public notification requirements under the GWR, community 

GWSs must provide a special notice to the public of any significant deficiencies uncorrected at 

the time of the Consumer Confidence Report (CCR) or any fecal indicator positives, and 

continue to inform the public annually until the significant deficiency or the fecal contamination 

has been corrected in accordance with the State approved corrective action plan. 

CCRs apply only to community GWSs. Non-community GWSs must provide notice to 

the public regarding any significant deficiency that has not been corrected within 12 months. 

Non-community GWSs must repeat notification annually until the significant deficiency is 

corrected. 

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Corrective Actions Guidance Manual 
1.4 Goal and Organization of the Guidance Manual 

The next four chapters of this guidance document provide detailed information on the 

four different general categories of corrective actions that may be required under the GWR for 

systems for which States have identified a significant deficiency. 

• Chapter 2 - Correcting Significant Deficiencies 

• Chapter 3 - Eliminating Sources of Contamination 

• Chapter 4 - Providing an Alternate Source of Drinking Water 

• Chapter 5 - Installing Treatment 

The final chapter, Chapter 6, contains a list of references cited within the guidance 

manual. 

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Corrective Actions Guidance Manual 
2. Correcting Significant Deficiencies 

The GWR requires States to conduct periodic sanitary surveys at all GWSs, and to 

identify significant deficiencies during those surveys. Sanitary surveys include reviewing PWS 

records and monitoring data as well as an onsite evaluation to identify both minor and significant 

deficiencies. The GWR requires that significant deficiencies identified during sanitary surveys, 

or during other State field visits or reviews, must be addressed through corrective action. 

Significant deficiencies are not explicitly defined or specified in the final GWR. 

However, 40 CFR 142.16 of the GWR indicates that significant deficiencies would include, 

though are not limited to, defects in design, operation, or maintenance, or a failure or 

malfunction of the sources, treatment, storage, or distribution system that the State determines to 

be causing, or has the potential for causing, the introduction of contamination into the water 

delivered to consumers. States are required to define and describe in their primacy package at 

least one specific significant deficiency in each of the eight elements (listed below) that 40 CFR 

142.16 specifies must be included in sanitary surveys conducted under the GWR: 

1. Source, 

2. Treatment, 

3. Distribution system, 

4. Finished water storage, 

5. Pumps, pump facilities, and controls, 

6. Monitoring, reporting, and data verification, 

7. System management and operation, and 

8. Operator compliance with State requirements. 

This chapter discusses the eight different elements of a sanitary survey and provides 

examples of significant deficiencies for each element in the respective sections that follow. It 

also addresses what States and PWSs should do when a significant deficiency is identified. 

Correcting significant deficiencies can involve a wide range of technical or managerial changes 

in the PWS, with a wide range of resource requirements. 

The corrective actions that are proposed in this manual vary from actions that can easily 

be completed to those that will require a significant amount of time and effort on the part of the 

water system and the State. In order to ensure public health protection while also allowing for 

the time needed to design and implement the optimal long-term solution, the State should 

consider creating a two-phased corrective action if the GWS needs an extended period of time 

(such as six months) to complete the corrective action. The first phase of the corrective action 

would be designed for the short-term to protect public health while providing the system with the 

time to implement a permanent solution that finally completes the corrective action. Throughout 

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Corrective Actions Guidance Manual 
this manual, you will see short-term and temporary solutions (e.g., providing bottled water, 

interim disinfection, etc.) as well as long term solutions (e.g., constructing a new well). 

EPA expects State drinking water programs to draw on their extensive experience to 

develop specific criteria for determining which deficiencies are significant and how to correct 

them in particular cases. This may include the State specifying the corrective action to the PWS 

or working with the PWS to determine how to correct a particular significant deficiency 

identified in its sanitary survey. Either way, it is critical that the GWS consult with the State to 

identify an appropriate corrective action. 

2.1 Identifying Significant Deficiencies 

As part of a State’s primacy package under the GWR, the State must describe the 

approach it will use to determine if a deficiency is significant. Based on this approach, States 

will decide on a case-by-case basis whether an identified deficiency is a significant deficiency. 

There is a wide range of risks associated with significant deficiencies, ranging from those with a 

small, but not insignificant likelihood of introducing microbial contamination to the finished 

water, to those where the continued unaltered operation of the system poses a serious imminent 

health threat to the population. The GWR requires all deficiencies identified by the State as 

“significant” to be corrected by the water system. Inspectors should be familiar with the 

approach the State will use to determine if a deficiency is significant. 

2.1.1 Sanitary Surveys 

Sanitary surveys have been conducted by staff or authorized agents of State drinking 

water programs for decades. Sanitary surveys provide an opportunity for State drinking water 

officials, or approved third party inspectors, to visit the water system and educate operators 

about proper monitoring and sampling procedures, provide technical assistance, and inform them 

of any changes in regulations. At the same time, sanitary surveys are driven by compliance with 

existing regulations and by efforts to provide public health protection. EPA believes that 

periodic sanitary surveys, along with appropriate corrective measures, are indispensable for 

assuring the long-term safety and quality of drinking water. Currently, all States, except for one, 

conduct sanitary surveys. 

A sound sanitary survey program is an essential element of an effective State drinking 

water program for PWSs. As required by the GWR, systems must provide all necessary 

information and assistance requested from States for conducting sanitary surveys. The GWR 

requires States to conduct sanitary surveys of ground water CWSs every three years (every five 

years for CWSs that meet performance criteria) and of ground water NCWSs every five years. 

States are required to complete the initial sanitary survey cycle by December 31, 2012 for CWSs, 

except those that meet performance criteria (e.g., 4-log treatment or outstanding performance and 

no TCR violations), and December 31, 2014 for all NCWSs and CWSs that meet performance 

criteria. States may conduct more frequent sanitary survey cycles for any GWS as appropriate. 

The EPA Guidance Manual for Conducting Sanitary Surveys of PWSs Served Solely by 

Ground Water Sources (to be published) contains information on how to perform an onsite 

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Corrective Actions Guidance Manual 
inspection and sanitary survey and can be referenced for guidance on the specifics on conducting 

sanitary surveys under the GWR. 

2.1.2 Other Ways of Identifying Significant Deficiencies 

While significant deficiencies are often identified during sanitary surveys, other 

situations may also bring them to the attention of regulators. If a water system reports higher 

levels of contaminants than normal, even if there has not been a violation, the regulator may take 

the preventative step of visiting the system to try and identify the source of the contamination. 

When customers complain to regulators of low water pressure or colored water at their water 

system, the regulator may follow up with a visit to the system to help identify or investigate the 

problem. Complaints of illness that may be attributable to waterborne pathogens can also prompt 

a visit by regulators. It is not unusual for deficiencies to be found during such site visits. 

Sometimes it's a coincidence that a significant deficiency is found; a regulator may be at the 

water system for another purpose and notice a significant deficiency during his or her visit. 

2.2 Source Deficiencies 

A water supply’s ground water source can contain contaminants, pathogens, and 

particles. Preventing source water contamination is an effective way to prevent contaminants 

from reaching consumers. Source water protection also helps prevent additional, potentially 

more costly treatment from being necessary for the removal of contaminants. During a sanitary 

survey, the major components of the well or spring are reviewed to determine reliability, quality, 

quantity, and vulnerability. The potential for degradation of source water quality is also 

evaluated. 

2.2.1 Examples of Significant Deficiencies 

• Well does not meet State-specified setback distances from hazards. 

• Well is improperly constructed. 

• Well does not have a sanitary seal. 

• Spring box is poorly constructed and/or subject to flooding. 

2.2.2 Identifying Corrective Actions 

• Remove hazards to well or relocate well. 

• Address components of well that are not properly constructed (e.g., height of casing 

above ground, screened vent, grouting). 

• Replace or supplement existing well cover with cap that provides a sanitary seal. 

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2.2.3 Additional Information and Resources1 

Bloetscher, F., A. Muniz, J. Largey. 2007. Siting, Drilling, and Construction of Water Supply 

Wells. AWWA. Denver, CO. 

Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statesstandards.com/waterstandards.html 

2.3 Treatment Deficiencies 

Water treatment facilities are the primary means of preventing unacceptable drinking 

water quality from being delivered for public consumption. The treatment facilities and 

processes should be capable of removing, sequestering, or inactivating physical, chemical, and 

biological impurities in the source water. Water treatment plants should be designed, operated, 

maintained, and managed in a way that minimizes existing or potential sanitary risks. 

During a sanitary survey, the treatment facilities and processes are evaluated to determine 

their ability to meet regulatory requirements and to provide an adequate supply of safe drinking 

water at all times, including periods of high water demand. The distinct parts of the treatment 

process, including but not limited to disinfection, chemical feed systems, hydraulics, and 

controls, are inspected. Features of the water treatment process that may pose a sanitary risk, 

such as inadequate treatment, monitoring, or maintenance, lack of reliability, and cross 

connections are also identified. 

2.3.1 Examples of Significant Deficiencies 

• Inadequate application of treatment chemicals and/or no provisions to notify of 

chemical feed failure. 

• Inadequate disinfection contact time. 

• No provision to prevent chemical overfeed and/or no provisions to notify of chemical 

feed failure. 

• System delivered untreated or inadequately treated drinking water to customers, when 

its permit was based on meeting specific treatment requirements. 

1 Many States have well standards that need to be met for newly installed wells. Water systems should make sure 

any actions they take to remediate or install wells are consistent with their State’s requirements. 

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2.3.2 Identifying Corrective Actions 

• Written operations and maintenance procedures for water treatment. 

• Supplement disinfectant contact time (e.g., additional storage, slower flows, baffling). 

• Add controls to notify of chemical feed failure and/or eliminate the possibility of 

chemical overfeeds (e.g., check valves, day tanks). 

• Install and monitor valves or other control measures that allow treatment units to be 

bypassed; do not serve water to public when bypassing results in inadequately treated 

water (e.g., does not comply with SDWA requirements). 

2.3.3 Additional Information and Resources 

AWWA. 2006. Water Chlorination and Chloramination Practices and Principles (M20), Second 

Edition. Denver, CO. 

MWH. 2005. Water Treatment: Principles and Design, Second Edition. John Wiley & Sons. 

Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statesstandards.com/waterstandards.html 

EPA. 2006. Ultraviolet Disinfection Guidance Manual for the Long Term 2 Enhanced Surface 

Water Treatment Rule. Office of Water. EPA 815-R-06-007. 

EPA. 2005. Membrane Filtration Guidance Manual. Office of Water. EPA 815-R-06-009. 

2.4 Distribution System Deficiencies 

A well maintained and operated distribution system is an important barrier in protecting 

water quality. During a sanitary survey, the surveyor evaluates the condition (to the extent 

possible) and maintenance of the distribution system, and one of the eight elements included in 

the GWR sanitary survey requirements. 

All types of ground water systems face the challenge of the introduction of contaminants 

into finished water in the distribution system. Seasonal ground water systems, in particular, can 

be at risk. These systems shut down their distribution systems for extended periods of time 

before starting them up for the next season. During this period of shutdown, the pressure in the 

pipe can be lower than the pressure outside the pipe (making the distribution system subject to 

intrusion or structural failure); suspended particulates in the stagnant water settle into pipe 

sediments, and biofilm can rapidly develop. When the system starts back up, sudden flow 

increases can cause accumulated biofilm, sediment, and tubercles to be released into the water 

column. Seasonal systems should work with their State to determine operating procedures for 

system shut down and start up that minimize the potential for contamination. This could be a 

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combination of disinfecting, flushing the system, and minimizing the magnitude of pressure 

transients by slowing the rate of opening and closing valves (USEPA, 2006d). 

2.4.1 Biofilm Control 

Biofilm is a general term used to describe the combination of microorganisms, extracellular polymer, organic compounds, and inorganic compounds found on the inside of pipe 

walls and other surfaces in contact with water. Any microorganism in the bulk water can attach 

or become enmeshed in biofilm. Organisms of concern for drinking water include coliforms, 

nitrifying microorganisms (in chloraminated systems), and opportunistic pathogens. Coliform 

growth in biofilms can lead to detection and possible violations under the Total Coliform Rule. 

Nitrifying bacteria can reduce chloramine residual concentration and lead to elevated nitrate and 

nitrite levels. The EPA distribution system issue paper on biofilms (USEPA 2002, see 

http://www.epa.gov/OGWDW/disinfection/tcr/pdfs/whitepaper_tcr_biofilms.pdf for full 

reference) includes a list of opportunistic pathogens identified in biofilm, some of which have 

been associated with waterborne disease outbreaks. Biofilm growth can result in corrosion of 

metal pipe by suppressing the pH at locations along the pipe wall. This can lead to loss of pipe 

integrity and aesthetic problems (e.g., red water). For these reasons, it is important to control 

biofilm growth in wells and distribution systems in order to maintain a potable water supply. 

Factors that generally favor biofilm growth include: 

• Presence of corroded metal pipe (in particular iron pipe), which provides a protected 

environment for microorganisms to grow. 

• Elevated temperatures (microorganisms generally grow faster at warmer temperatures 

compared to colder temperatures). 

• Low or no disinfectant residual. 

• Available nutrients such as carbon, nitrogen, phosphorus (often, assimilable organic 

carbon is the limiting nutrient with respect to biofilim growth). 

In their Total Coliform Rule Distribution System White Paper (2002), EPA lists the 

following strategies for controlling biofilm growth, citing corrosion control as possibly the most 

important factor: 

• Nutrient control, 

• Control of contamination from materials and equipment, 

• Control and mitigation of system hydraulic problems, 

• Cross-connection control and backflow prevention, 

• Disinfectant residuals, 

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• Corrosion control, 

• Infrastructure replacement and repair, 

• Security, and 

• Storage vessel management and alteration. 

The authors caution that biofilm control often requires the use of a variety of tools, rather than a 

single “best” tool, and the relative effectiveness of a control practice may be site specific. See 

http://www.epa.gov/OGWDW/disinfection/tcr/pdfs/whitepaper_tcr_biofilms.pdf for additional 

information. 

2.4.2 Cross-Connection Control 

Another public health threat that can arise in the distribution system is contamination 

introduced through cross-connections. A cross-connection is “any unprotected actual or potential 

connection or structural arrangement between a public or a consumer’s potable water system and 

any other source or system through which it is possible to introduce into any part of the potable 

system any used water, industrial fluids, gas, or substance other than the intended potable water 

with which the system is supplied” (AWWA, 1990a). Backflow prevention devices are 

appropriate on connections between a PWS distribution system and irrigation wells, other 

irrigation water supplies, or private wells. 

Backflow refers to a reverse flow condition created by a difference in water pressures 

that causes water to flow back into the distribution pipes of a potable water supply from any 

source or sources other than an intended source (USEPA, 2000). Backflow can occur under two 

different conditions. The first condition called backpressure exists when a potable system is 

connected to a non-potable supply operating under a higher pressure by means of a pump, boiler, 

elevation difference, air or steam pressure, or other means (AWWA, 1990a). The second 

condition that causes backflow occurs when there is negative or reduced pressure in the supply 

piping (i.e., the distribution system’s pressure is lower than atmospheric pressure) and is known 

as backsiphonage (AWWA, 1990a). 

Distribution systems can lose pressure and even experience a partial vacuum when water 

is withdrawn at a very high rate, such as during fire fighting or when booster pumps are used. 

Systems also lose pressure during events like main repairs and line breaks. If the system pressure 

drops sufficiently, the direction of flow within portions of the system will reverse; if there are 

cross-connections, contaminants can be siphoned into the distribution system (AWWA, 1990a). 

For example, fecal contamination can be introduced into the distribution system anytime during 

a backpressure or backsiphonage event, if the PWS has a cross-connection with a source 

containing fecal contamination. 

This section provides an overview of cross-connection control requirements, equipment, 

and program elements. Detailed information on cross-connection control is available from the 

following resources: 

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• The EPA Distribution System Issue Paper: Potential Contamination Due to CrossConnections and Backflow and the Associated Health, available online at 

http://www.epa.gov/OGWDW/disinfection/tcr/regulation_revisions.html 

• The EPA Cross-Connection Control Manual (2006), available online at 

http://www.epa.gov/OGWDW/pdfs/crossconnection/crossconnection.pdf 

• The University of Southern California Foundation for Cross Connection Control and 

Hydraulic Research and associated publications http://www.usc.edu/dept/fccchr/ 

• The American Water Works Association Recommended Practice for Backflow 

Prevention and Cross-Connection Control (M14), Third Edition (2004). 

2.4.2.1 Existing Requirements 

All 50 States require cross-connection control through various means such as plumbing 

codes, health codes or environmental protection codes. The majority of States require systems or 

individual localities to implement cross-connection control programs that uphold State 

regulations; however, other States require individual customers to comply with State regulations 

that are enforced by a public water supplier. 

There are two methods commonly used to control or eliminate backflow hazards due to 

cross-connections - physically eliminating the cross-connection or installing a backflow 

preventer. Several States require systems to physically separate the cross-connections rather than 

install a backflow prevention assembly (Florida DEP, 1996). Some States only allow installation 

of a backflow prevention assembly when a physical separation is not possible. Systems that 

physically separate the cross-connection should do so in a manner that the cross-connection 

cannot be re-established. Additionally, systems should always check State requirements before 

considering a backflow prevention assembly. 

If a cross-connection is implicated as the significant deficiency or source of fecal 

contamination entering the distribution system, a backflow preventer can be used to eliminate 

further contamination from entering the distribution system. Backflow prevention used in 

response to a contamination event can be an effective means of eliminating a source of 

contamination. 

Some jurisdictions regard a cross-connection as a significant deficiency with backflow 

prevention as the proper corrective action. If the cross-connection is viewed as a significant 

deficiency, the system is required to correct the significant deficiency as part of the GWR 

sanitary survey requirements. 

2.4.2.2 Choosing a Backflow Preventer 

Several types of backflow preventers exist; however, not all types are applicable for all 

situations. Below is a list of the basic types of backflow preventers (USEPA, 1989). 

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• Air gap (AG), 

• Atmospheric vacuum breaker (AVB), 

• Pressure vacuum breaker (PVB), 

• Double check valve (DCV), 

• Reduced pressure principle backflow prevention assembly (RPBA), and 

• Double check valve with intermediate atmospheric vent (DCIAV). 

Mechanical backflow preventers should be capable of being tested to determine 

effectiveness. Several factors should be considered when choosing the right type of backflow 

prevention assembly. These considerations include the following: 

• The degree of hazard protection needed; 

• The likelihood that backpressure may result; and 

• If the system wants to provide protection inside the customer’s premises (isolation) or 

at the service connection (containment). 

Appendix A presents the applications of various backflow prevention 

assemblies/methods. Systems deciding to provide backflow prevention against health hazards 

should use only air gaps, PVBs, AVBs, or RPBAs. Among these, only air gaps and RPBAs 

should be used to protect against high hazards. Although all backflow prevention assemblies 

protect against backsiphonage, only AGs, DCVs, and RPBAs should be used to protect against 

backpressure. 

When choosing a backflow preventer, systems should keep in mind that isolation 

provides protection within premises and containment devices prevent a contaminant from 

leaving the premises. Backflow preventers that provide isolation are typically more expensive 

than containment devices since multiple assemblies may be required for a single customer 

(USEPA, 2003). Because isolation occurs within a customer’s premises, devices can be easily 

bypassed, eliminating the benefit of the backflow prevention assembly. Alternatively, 

containment remains under the control of the system, and therefore, bypassing is less of a 

concern. 

2.4.2.3 Installing and Testing Backflow Preventers 

Backflow prevention assemblies should only be installed by certified backflow 

prevention assembly installers and only tested by backflow prevention assembly testers. There 

are many organizations that provide training for backflow prevention assembly installers and 

testers such as the following: 

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• University of Florida Center for Training, Research & Education for Environmental 

Occupations (UFTREEO); 

• American Water Works Association (AWWA); and 

• USC Foundation for Cross-Connection Control and Hydraulic Research. 

A number of organizations including the UFTREEO Center, USC, and the American 

Society of Sanitary Engineers (www.asse-plumbing.org) provide certification of backflow 

prevention assembly installers and/or testers. 

2.4.2.4 Cross-Connection Control and Backflow Prevention Programs 

Cross-connection control and backflow prevention programs are commonly used as a 

Best Management Practice (BMP) in many systems to prevent contamination from entering the 

distribution system. Many States have requirements for cross-connection control and backflow 

prevention programs for some or all systems or facilities. When a system intends to implement a 

cross-connection control and backflow prevention program, it is essential to check the specific 

State regulations to determine what elements may be required in a program. 

According to industry experts, a program is considered comprehensive if it contains these 

five elements (USEPA, 2001) 

• Authority to implement the program (e.g., city ordinance); 

• Certification of backflow assembly testers; 

• Reporting and record keeping; 

• Public notification of backflow events; and 

• Authority to enforce the program. 

Other potential elements could include approval of specific devices, specific testing 

requirements, what types of premises are required to have protection, and public education. 

2.4.3 Examples of Significant Deficiencies 

• Negative pressures due to an incident outside of normal operating ranges that could 

result in the entrance of contaminants. 

• Unprotected cross-connections. 

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2.4.4 Identifying Corrective Actions 

• Corrective action for cross-connections and/or cross-connection control program. 

• Installation of a backflow protection device to prevent future backflow events. 

2.4.5 Additional Information and Resources 

Asset Management: A Handbook for Small Water Systems Publication Number EPA 816-R-03-

016 

American Water Works Association 

(800)-926-6142 

www.awwa.org 

AWWA (American Water Works Association). 1995d. Water Transmission and Distribution. 

Second edition. Denver, Colo.: 

AWWA. Recommended Practice for Backflow Prevention and Cross Connection Control, 

Manual of Water Supply Practice M14, (AWWA 2004) 

Backflow Prevention Theory and Practice. University of Florida, Division of Continuing 

Education, Center for Training Research and Education for Environmental Occupations. 

Ritland, Robin L. 1990Kendall/ Hunt Publishing Company, Dubuque, Iowa. 

Cross Connection Control Manual (USEPA, 2003b) 

Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statesstandards.com/waterstandards.html 

Sacramento State University-Office of Water Programs 

(916) 278-6142 

http://www.owp.csus.edu/training/onlinecourses.php 

University of Florida, Division of Continuing Education, Center for Training Research and 

Education for Environmental Occupations(TREEO Center) 

(352)-392-9570 

http://www.treeo.ufl.edu/ 

2.5 Finished Water Storage 

Finished water storage facilities should be maintained and regularly inspected to ensure 

that distributed water quality is maintained. During a sanitary survey, the surveyor evaluates the 

condition and maintenance of finished water storage facilities, one of the eight elements included 

in the GWR sanitary survey requirements. Storage facilities are designed to protect the quality of 

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the finished water while allowing air to enter and escape as the water level changes. They are 

also designed to allow overflow to occur. There are often penetrations in the tanks to allow 

access for cleaning and for water level gauging devices. It is important that storage tank integrity 

be maintained to keep contaminants from entering. Exhibit 2.1 shows a typical ground storage 

tank. Deficiencies related to a system’s water storage facilities may cause water quality and 

health-related problems for PWSs (NETA, 1998). Such deficiencies can be due to a lack of 

maintenance on the part of the PWS. 

Exhibit 2.1 Typical Ground Storage Tank 

Source: (NETA, 1998) 

Storage facilities and the grounds surrounding them should be routinely surveyed to 

prevent water quality problems. It is recommended that water utilities have comprehensive 

inspections of the structural condition of their storage facilities every 3 to 5 years, including 

areas of the facility that are not normally accessible from the ground (Kirmeyer, 1999). A 

comprehensive inspection should include a close evaluation of the condition of interior and 

exterior coatings, foundation, ladder, vent, hatch, overflow pipe, screens, cathodic protection 

system, and the depth of the interior sediment. 

There are no Federal regulatory requirements for storage tank maintenance or cleaning 

procedures. Many States recommend adhering to AWWA Standards, NSF Standard 61, and 

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Recommended Standards for Water Works (2007). AWWA Standards and guidance that apply to 

finished water storage facilities include: 

• C652 Disinfection of Water Storage Facilities; 

• D100 Welded Steel Tanks for Water Storage; 

• D102 Coating Steel Water-Storage Tanks; 

• D103 Factory-Coated Bolted Steel Tanks for Water Storage; 

• D120 Thermosetting Fiberglass-Reinforced Plastic Tanks; 

• G200 Distribution Systems Operation and Management; and 

• AWWA Manual M42 Steel Water Storage Tanks. 

When cleaning and maintaining their storage tanks, systems should be aware if their State 

has environmental regulations that govern discharge of chlorinated water from storage facilities. 

Dechlorination of the water may be required prior to disposal. 

As stated earlier, deficiencies found at storage tanks are frequently associated with 

insufficient maintenance. Vent screens and flexible sealing materials deteriorate over time and 

steel eventually corrodes even when properly coated. Each of these problems can cause openings 

for microbial contaminants to enter the finished water. Often when these defects are found they 

have progressed to the point where they cannot be quickly and easily corrected in a permanent 

manner. In these cases, temporary measures should be put in place to minimize public health 

risk. For example, silicone caulking can sometimes be used to temporarily seal small holes in 

steel. Noncorrodible screens can be obtained and held in place with stainless steel hose clamps. 

To accomplish permanent corrective measures, it is advisable to obtain up-to-date construction 

standards from the primacy agency and bring the storage facility into compliance with those 

standards. This will often require the use of a licensed professional engineer and submission of 

plans and specifications for State review and approval. 

2.5.1 Correcting Defective Vents 

Defective vents should be repaired or replaced according to the Ten States Standards 

(2007) or State design criteria to prevent the entrance of surface water and rainwater and exclude 

birds, animals, and, as much as possible, insects and dust. Ground level tanks should be 

corrected so that vents terminate in an inverted U fashion (see Exhibit 2.1) with the opening 24 - 

36 inches above the roof or sod cover with a noncorrodible screen installed within the pipe at a 

location least susceptible to vandalism. The vent should also be protected from ice formation. 

Vents should not be replaced by overflows because a storage tank should have both a vent and 

an overflow pipe; an overflow pipe is not a reliable way to ventilate a tank because the overflow 

pipe might be in use at the same time that ventilation is needed. (Ten States Standards, 2007). 

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2.5.2 Correcting Inadequate Access Hatches 

In some cases, the State may find defective access hatches that allow insects and dust to 

enter the storage tank or allow the storage tank to be vandalized. Exhibit 2.2 shows a finished 

water storage area with an access hatch designed to allow entry for cleaning and maintenance. 

Systems should refer to State design criteria or other accepted engineering standards for details. 

Exhibit 2.2 Raised Sill Appropriate for a Hatch 

2.5.3 Correcting Insufficient Overflows 

Insufficient overflows may also pose a problem for PWSs. PWSs should ensure that all 

finished water storage facilities have an overflow that is brought down to an elevation between 

12 and 24 inches above the ground surface and discharges over a drainage structure or splash 

pad. The PWSs should make sure that the discharge point is visible and cannot be connected to 

any waste water structure. The discharge pipe should also be screened with 24-mesh 

noncorrodible screen (Ten States Standards, 2007). There are also additional standards available 

for reference (e.g., AWWA standards). 

2.5.4 Hydropneumatic Tanks 

Hydropneumatic pressure tanks are commonly used by smaller systems or to serve small 

pressure zones. The main purpose of hydropneumatic tanks is to prevent excessive cycling of 

pumps. They contain a fixed volume of air that becomes compressed as water enters the tank. 

Once the pressure in the tank has reached a predetermined level (i.e., the cut-out pressure) the 

pump stops and the compressed air starts to expand while it pushes the water into the distribution 

system. As the water leaves the tank, the pressure in the tank decreases until it reaches a point 

where the pump will be triggered to start again (i.e., the pump-on level) and the cycle is 

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repeated. The cycle rate is the number of times the pump starts and stops in one hour (typically 

10 to 15 cycles per hour). 

Hydropneumatic tank systems can use any of several types of pressure storage tanks. 

Exhibit 2.3 depicts the various types of pressure tanks available. Most small ground water 

systems use vertical tanks like the two on the right side of the exhibit. 

Exhibit 2.3 Types of Pressure Tanks 

Source: ©Arasmith Consulting Resources 

Suggested minimum design components for hydropneumatic tanks include: 

• Tank is located completely above ground. 

• Tank meets American Society of Mechanical Engineers (ASME) standards with an 

ASME name plate attached. 

• Access port is available for periodic inspections. 

• Tank is fitted with a pressure relief device with a pressure gauge. 

• There is a control system to maintain proper air/water ratio for the air/interface. 

• Air injection lines are equipped with filters to remove contaminants from the air line. 

• Sight glass can provide a visual determination of the water level for proper air/water 

ratio. 

• Tank should have slow closing valves and time delay pump controls to prevent water 

hammer. 

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2.5.5 Examples of Significant Deficiencies 

• Inspection and cleaning of storage tanks not included in system operation and 

maintenance (O&M) plan or failure to inspect and clean storage tanks. 

• Lack of screening of overflow pipes, drains or vents. 

• Storage tanks roofs or covers need repairs (e.g., holes, hatch damage or improper 

construction, failing floating cover). 

2.5.6 Identifying Corrective Actions 

• Corrective action plan for cleaning and maintenance. 

• Corrective action schedule for repairs. 

• Repair screens. 

2.5.7 Additional Information and Resources 

Asset Management: A Handbook for Small Water Systems Publication Number EPA 816-R-03-

016 

American Water Works Association 

(800)-926-6142 

www.awwa.org 

AWWA (American Water Works Association). 1987b. AWWA Standard for Factory-Coated 

Bolted Steel Tanks for Water Storage. AWWA D103-87. Denver, Colo.: AWWA. 

AWWA (American Water Works Association). 1995a. AWWA Standard for Circular 

Prestressed Concrete Water Tanks with Circumferential Tendons, AWWA D115-95. 

Denver,Colo: AWWA. 

AWWA (American Water Works Association). 1995b. AWWA Standard for Wire- and StrandWound Circular Prestressed-Concrete Water Tanks. AWWA D110-95. Denver, Colo: 

AWWA. 

AWWA (American Water Works Association). 1996a. AWWA Standard for Flexible-Membrane 

Lining and Floating-Cover Materials for Potable-Water Storage. AWWA D130. Denver, 

Colo.:AWWA. 

AWWA (American Water Works Association). 1996. AWWA Standard for Welded Steel Tanks 

for Water Storage. AWWA D100-96. Denver, Colo.: AWWA. 

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AWWA (American Water Works Association). 1998. AWWA Manual M42—Steel WaterStorage Tanks. Denver, Colo.: AWWA. 

Kirmeyer, G.J., L. Kirby, B.M. Murphy, P.F. Noran, K.D. Martel, T.W. Lund, J.L. Anderson, 

and R. Medhurst. 1999. Maintaining and Operating Finished Water Storage Facilities. 

Denver, Colo.: AWWA and AWWARF. 

Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statesstandards.com/waterstandards.html 

2.6 Pumps 

For many public water systems, pumps are a critical component of the distribution 

system. During a sanitary survey, the conditions of pumps/pump facilities and controls should be 

reviewed. The surveyor should evaluate the operation and maintenance as well as safety 

practices to determine that water supply pumping facilities are reliable. 

2.6.1 Examples of Significant Deficiencies 

• Lack of adequate pumping capacity or emergency power at critical facilities. 

• Cross connections to auxiliary supplies or cooling water. 

• Pump inspection and maintenance not included in system O&M plan; system does 

not comply with plan. 

2.6.2 Identifying Corrective Actions 

• Corrective action plan for installation of required pumping capacity or emergency 

power. 

• Remove cross connection or install backflow protection. 

• Include pump inspection and maintenance in O&M plan; perform as required. 

2.6.3 Additional Information and Resources 

Asset Management: A Handbook for Small Water Systems 

Publication Number EPA 816-R-03-016 

American Water Works Association 

(800)-926-6142 

www.awwa.org 

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Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statesstandards.com/waterstandards.html 

2.7 Monitoring, Reporting and Data Verification 

All PWSs are required to perform water quality monitoring to determine compliance with 

drinking water standards. The constituents monitored and the monitoring frequency vary with 

system size and source. Compliance with National Primary Drinking Water (NPDW) standards 

is based on self-monitoring and reporting and the sanitary survey provides an opportunity to 

review these procedures. 

2.7.1 Examples of Significant Deficiencies 

• Failure to monitor water quality or treatment. 

• Failure to monitor water quality in accordance with required monitoring plans. 

• Failure to report water quality monitoring. 

• Operators are using improper procedures and/or methods when collecting samples or 

conducting onsite analyses. 

• Falsification of sampling records, laboratory, or other data. 

2.7.2 Identifying Corrective Actions 

• Monitoring plans or revisions to monitoring plans. 

• Training plan for system staff. 

• Contracts with certified laboratories. 

2.7.3 Additional Information and Resources 

The Standardized Monitoring Framework: A Quick Reference Guide, Publication Number EPA 

816-F-04-010. www.epa.gov/safewwater/regs.html 

Lead and Copper Rule: A Quick Reference Guide, Publication Number EPA 816-F-04-009. 

www.epa.gov/safewwater/regs.html 

Analytical Methods for Drinking Water 

http://www.epa.gov/safewater/methods/methods.html 

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EPA’s Interactive Sampling Guide for Drinking Water System Operators, Publication Number 

EPA 816-C-06-001. http://yosemite.epa.gov/water/owrccatalog.nsf/ 

A Small System Guide to the Total Coliform Rule, Publication Number EPA 816-R01-017A. 

http://yosemite.epa.gov/water/owrccatalog.nsf/ 

2.8 System Management and Operations 

PWSs need access to technical managerial and financial resources to provide a reliable 

supply of drinking water meeting State and Federal standards and to maintain public health 

protection. Smaller systems, many of which are groundwater systems, face unique challenges in 

providing drinking that meets standards and in operating and maintaining treatment and 

distribution systems. 

2.8.1 Identifying Financial Resources 

Small communities may be unable to maintain even low-cost ground water technologies 

without adequate management and revenues. Fee structures should take into account operating 

funds and revenues for capital improvements. In some communities, insufficient funding is the 

result of a small population and very low average per capita income. Unfortunately, without 

adequate funding, small systems have difficulty hiring skilled managers who could increase 

revenues and ensure effective business planning. 

State and local governments, as well as Technical Assistance Centers, Environmental 

Finance Centers, Rural Water Associations, Rural Community Assistance Partnerships, and other 

technical assistance providers, may be available to assist small systems with identifying and 

overcoming these deficiencies. Some States have performance appraisal programs that require 

each regulated water system to assess its short-and long-term ability to: 

• Provide adequate quantities of water; 

• Meet water quality standards; and 

• Operate and maintain the plant. 

States can also require PWSs to achieve levels of performance prior to issuing operating 

permits. The performance appraisal by either the State or PWS may include evaluating the 

following: 

• The system’s record of responses to previous significant deficiencies, orders, or 

outbreaks. 

• Compliance with water quality standards, including monitoring requirements. 

Regulators historically have considered waterborne disease outbreaks, compliance with 

drinking water standards, operator certification, and sanitary surveys when evaluating small 

systems. According to the National Research Council (1997), an area that has been overlooked is 

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comprehensive short-term (less than 5 years) and long-term financial planning (20 years). PWSs 

should engage local governments to provide information on future trends in the service area, 

population, land use policies, and water demands to evaluate the need for system improvements. 

Costs for future improvements can be compared to current and future budgets enabling the GWS 

to project the future rates that would be needed to sustain these budgets. 

If funding problems affecting a system’s future fiscal viability are discovered, the system 

should restructure on its own or involve outside entities such as regional water authorities, local 

government, or private water systems to plan for and solve the problems. Financial restructuring 

fits one of four categories (National Academy Press, 1997): 

• Direct ownership where the PWS agrees with another authority to take over system 

ownership or to join with another system to form a regional water authority or 

agency. 

• A regulatory takeover where the State takes responsibility for transferring 

management of a failing utility to another entity, or where the owner does not 

voluntarily relinquish control of the PWS. 

• Contract service where O&M, monitoring, emergency assistance, and routine 

administration are handled by a contractor. 

• Support from another utility in the form of training, or purchasing supplies or water 

to receive high volume discounts. 

Each of these options should be designed to control consumer costs by consolidating one 

or more PWS responsibility within a larger agency or system while improving operations, 

reliability, quantity, or quality as needed. The unwillingness of an entity to take over a PWS with 

problems because of the potential for financial burdens for system improvements, or the fear of 

liability for water quality standards violations can become a barrier to financial restructuring. 

States should develop incentives for consolidation or restructuring where appropriate, and limit 

the use of State Revolving Funds (SRFs) to circumstances where all other possibilities have been 

exhausted (as determined from State performance appraisals). American Water Works 

Association Research Foundation (AwwaRF) project #4075 (expected to be finalized in 2008) 

and AwwaRF Report 91146 should present benefits of system consolidation and other regional 

solutions to water services, including case studies. 

2.8.2 Security Measures 

Systems have areas that are potentially susceptible to security breaches such as at a 

system’s wells, storage facilities, and pumping stations. During a sanitary survey, the surveyor 

should assess the site security of the water system to determine the potential for intruder access. 

If the water system is permitted, there may be provisions related to security in the permit that 

will be checked. Vulnerable areas include un-manned or temporarily un-manned areas with 

finished water. If a system is notified of potential areas for vandalism, it should install 

appropriate security measures. Helpful references, such as Guidelines for Physical Security of 

Water Utilities (AWWA, 2006), should be used for guidance. Any potable water storage tank 

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should be enclosed by an intruder-resistant fence with a lockable access gate. Systems should 

also ensure that all buildings such as well houses and pump stations are locked with secure 

locking systems. Facility staff should remove ladders to storage facilities and/or lock the ladder 

access opening. Systems should padlock access hatches, ensure that vents are secure, and include 

an internal or in-line check valve for design overflows to prevent the introduction of 

contaminants. In the rare cases where vandalism is a real problem and presents a significant risk, 

the system may need to provide a security staff. 

2.8.3 Examples of Significant Deficiencies 

• Failure to meet water supply demands/interruptions in service. 

• Inadequate technical, managerial and financial resources to continue to reliably 

operate the system. 

• Inadequate resources for emergency response or lack of emergency response plan. 

• Inadequate staffing to ensure proper operation and system control. 

2.8.4 Identifying Corrective Actions 

• Additional source of supply, new service limits, interconnections or cooperative 

agreements with nearby systems. 

• TMF capacity development improvement plan. 

• Asset management plan, operations plan, and/or business plan. 

• Emergency response plans, cooperative agreements. 

2.8.5 Additional Information and Resources 

AWWA 

Effective Utility Management Primer for Water and Wastewater Utilities: 

http://www.awwa.org/files/Resources/EffectiveUtilityManagement4color.pdf 

Regional Solutions to Water Supply Provision. AwwaRF Report 91146. 

http://www.awwarf.org/ 

EPA 

Technical: http://www.epa.gov/safewater/smallsystems/technical_help.html 

Managerial: http://www.epa.gov/safewater/smallsystems/managementhelp.html 

Financial: http://www.epa.gov/safewater/smallsystems/financialhelp.html 

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Compliance: http://www.epa.gov/safewater/smallsystems/compliancehelp.html 

Emergency/Response Planning: http://cfpub.epa.gov/safewater/watersecurity 

Sources of Technical and Financial Assistance for Small Drinking Water Systems, Publication 

number EPA 816-K-02-005 

Asset Management: A Handbook for Small Water Systems, Publication Number EPA 816-R-03-

016 

Strategic Planning; A Handbook for Small Water Systems, Publication Number EPA 816-R-03-

015 

Drinking Water State Revolving Fund-http://www.epa.gov/safewater/dwsrf/ 

2.9 Operator Compliance with Certification Requirements 

Operator certification programs establish minimum professional standards for the 

operation and maintenance of public water systems. In 1999, EPA issued operator certification 

program guidelines specifying minimum standards for certification and recertification of the 

operators of community and nontransient noncommunity public water systems. While the 

specific requirements vary from State to State, operator certification programs generally set 

minimum certification requirements based on criteria such as system size and the type of 

treatment provided. 

All States have operator training programs for PWS operators through workshops, 

informal instruction, equipment vendors, and technical schools and universities. Management 

and administration of the system are essential to system sustainability, but many training 

programs do not address these areas, even though many operators of small systems are 

responsible for them (National Academy Press, 1997). Recommended training areas for running 

a small water system include the following: 

• Metering, 

• Customer service, 

• Financing, 

• Administration, 

• Budget management (unless another entity is responsible for it), 

• Water treatment, 

• Water distribution, and 

• Public health. 

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Several types of training should be part of an on-going and coordinated effort to meet the needs 

of small systems. A PWS design may be very advanced even in a small system. Therefore it is 

recommended that small system operators receive system-specific training from either the 

equipment manufacturer or other sources on how to operate their treatment processes to ensure 

that they are thoroughly educated. 

2.9.1 Examples of Significant Deficiencies 

• No certified operator where one is required by the State. 

• Operator is not certified at the level required by the State. 

2.9.2 Identifying Corrective Actions 

• Corrective action plan or compliance plan/agreement for certification. 

• Assistance from other PWSs. 

• Contracts or other formal arrangement for certified operator support. 

2.9.3 Additional Information and Resources 

Association of Boards of Certification (ABC) http://www.abccert.org/certificationrecip.html 

EPA Operator Certification Information www.epa.gov/safewater/operatorcertification/index.html 

AWWA Operator Certification Information 

(800)-926-6142 

http://www.awwa.org 

University of Florida TREEO Center 

(352) 392-9570 

http://www.treeo.ufl.edu/ 

Sacramento State University-Office of Water Programs 

(916) 278-6142 

http://www.owp.csus.edu/ 

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3. Eliminating Sources of Contamination 

This chapter presents some of the corrective actions a PWS can employ to eliminate, 

remove, or remediate causes and sources of contamination. The purpose of these corrective 

actions is to eliminate existing potential sources of microbial contamination within water supply 

sources, distribution systems, and storage tanks; to minimize the impact of flooding; and to 

eliminate cross-connections that can contaminate a PWS. This chapter will discuss the following 

corrective actions: 

• Source Water Rehabilitation 

- Identifying contamination causes, 

- Preventing contamination from an abandoned well, 

- Rehabilitating an existing well, and 

- Minimizing contamination after a flood. 

3.1 Source Water Rehabilitation 

3.1.1 Identifying Contamination Causes 

Salvato (1998) identified five probable causes of fecal contamination of ground water 

used as a source for drinking water: 

1. Lack of proper disinfection of a well following repair or construction; 

2. Failure or lack of a sanitary seal at the place where the pump line goes through the 

casing; 

3. Failure to seal the annular space between the drilled hole and the outside of the 

casing; and 

4. Contamination by surface water or wastewater from the surrounding soil or the 

aquifer. 

5. Cracked or separated well casing that allows ground water from the surface or a 

contaminated strata to enter. 

For situations where the appropriate corrective action is not obvious, or where the 

sanitary survey does not provide enough information, the State should work with the system to 

fill in the information gaps as necessary to identify effective actions that can be taken quickly 

and at a low cost. Where needed, extra time may be required to determine the direction of ground 

water flow under static and pumping conditions. Federal and State records should be reviewed to 

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determine potential underground sources of contamination. County or local health department 

records may also have to be reviewed and local land and business owners interviewed to identify 

all possible underground sources of contamination. 

Additionally, multiple contamination sources may complicate identification or 

elimination of the contaminant sources. Even if a source of contamination is eliminated, there 

may be a period of time that a well will continue to be contaminated. Therefore, systems should 

decontaminate any contaminated wells and verify results of corrective actions with further source 

water microbial monitoring. 

Additional detail about item one (the lack of proper disinfection) is provided in Section 

3.1.3.4; the remaining items are discussed in more detail in this section. 

Failure or lack of a sanitary seal at the place where the pump line goes through the casing 

If the suspected cause of contamination is an underground leak where a pump line goes 

through the casing, a dye or salt solution can be poured around the casing, and samples taken for 

visual or chemical analysis. The seal can also be excavated to visually inspect for damage. If 

contamination is through holes in the casing or if there are channels leading to the casing from a 

source of contamination, dyes can be used to trace the flow path. A light source or mirror can be 

lowered into the casing to see if light coming through cracks in the casing is visible outside the 

casing (Salvato, 1998). 

Failure to seal the annular space between the drilled hole and the outside of the casing 

Depending on the results of dye tests and other investigation, some sources can be 

remediated with simple repairs. Other deficiencies, such as an unsealed annular space, are more 

difficult to correct. An experienced well-driller should be contacted to investigate the possibility 

of grouting the annular space and installing a new casing or inner casing in rock or other tight 

sealing material (Salvato, 1998). If the casing is not a problem, then pollutants are most likely 

flowing to the well through the aquifer. In some cases, although this is costly, the well casing 

could be sealed at some depth to seal off the polluted stratum, or drilled deeper to a new waterbearing layer. Unless the polluted layer of water-bearing material is effectively sealed off, future 

contamination cannot be prevented. 

Contamination by surface water or wastewater from surrounding soil or the aquifer 

Shallow wells and wells near a surface water body in an aquifer that is loosely 

consolidated can experience contamination from surface water. If a ground water source is 

experiencing contamination from surface water, then it should be evaluated to determine if it is 

GWUDI. If classified as GWUDI, the system would be considered a subpart H system and must 

provide treatment and meet the other requirements of the SWTRs. If not classified as GWUDI or 

an underground aquifer is contaminated by leaking septic tanks or other contamination sources 

and the source of contamination cannot be eliminated, the system may need to replace, 

rehabilitate, or abandon the well. 

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Systems replacing or abandoning a well should check with their State to determine the 

State-specific closure requirements to ensure that the well is properly disconnected and filled. 

Wells that are not properly abandoned can create pathways that allow contamination to enter an 

otherwise protected aquifer. An abandoned well should be sealed in a manner that restores 

geological conditions that existed before the well was installed (Recommended Standards for 

Water Works. 2007). The well should be filled, preferably with cement grout or concrete, and 

sealed to prevent any water from passing into the aquifer (or in accordance with State or local 

requirements). 

Cracked or separated casing of a well that allows ground water from the surface or a 

contaminated strata to enter. 

If a well casing becomes cracked or separated it may allow ground water from the surface 

or a contaminated strata to enter into the well. This and other problems occurring below grade 

may be diagnosed by completing a video inspection of the interior of the well. If a crack or 

separation is identified during the inspection, the system may need to rehabilitate, replace, or 

properly abandon the well. 

3.1.2 Preventing Contamination from an Abandoned Well 

Abandoned wells can offer a near-perfect conduit for contaminants from the surface (i.e., 

runoff water, waste disposal) or below-grade (i.e., septic systems, Class 5 shallow injection 

wells, overlaying contaminated aquifers) to migrate into underground sources of drinking water. 

Some abandoned wells have had the casing removed leaving the entire bore hole open for 

passage of fluids. Larger, open wells also pose safety hazards for small children and animals. 

Often these abandoned wells are old and poorly constructed with no grout seal around the casing 

and/or no cap on the casing. This allows water and contaminants to move down the casing 

through the annular opening or casing and contaminate the aquifer that supplies drinking water to 

the nearby PWS. 

When a system has concluded that an abandoned well is the source of contamination it 

should contact the State primacy agency to obtain information on the correct procedures for 

proper abandonment. Currently, the majority of States have detailed construction standards for 

well abandonment that are crafted to keep water and contaminants from migrating up or down 

the bore hole. In most cases, when a well is to be permanently abandoned, the State will require 

it to be completely filled in such a manner that vertical movement of water within the well bore, 

including vertical movement of water within the annular space surrounding the well casing, is 

effectively and permanently blocked. All fluids within the well should be confined to the specific 

strata that they were originally encountered in and the controlling geologic conditions restored to 

those of pre-well construction. 

Artesian wells, free-flowing artesian wells, and gravel pack wells can present special 

abandonment problems. Often States have specific standards for abandoning these kinds of 

wells. If the State does not have such standards, the system should seek advice from an engineer, 

well driller, hydrologist, or other professional. 

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When installing a new well, or rehabilitating a current well, it is important to comply 

with State standards and requirements. Many States may also have certification or other approval 

requirements for contractors working on well installation or maintenance. 

3.1.3 Remediating an Existing Well 

A well’s structure should be in good operational condition to ensure a dependable supply 

of high quality source water is available at all times. Good operational condition means the 

piping is not leaking or corroded, the valves and controls are operable, and the electrical system 

is protected from the elements and is not corroded. In some cases, the transport of 

microorganisms occurs due to improper well seals or casings that can result in conduits for fecal 

contamination to pass into the water supply. This is particularly true of small systems and older 

systems that were not originally constructed in accordance with their respective State’s design 

and construction standards (Linsley et al., 1992). Prior to making significant investments in well 

remediation, systems should consider hiring a qualified contractor to assess the well integrity and 

condition. Remediating an existing well that is at the end of its useful life may not be costeffective. 

If a system must remediate a well, it may need to repair or replace the well screen, well 

casing, well seal, or even the well pump. The system should consult with applicable State or 

local standards when repairing or replacing well components. Systems should also carefully 

adhere to any applicable standards required during the well’s reparation (e.g., NSF/ANSI 

Standard 61 for drinking water system components) and for disinfecting and flushing after the 

well has been serviced (e.g., ANSI/AWWA Standard C654-03 for disinfection of wells). 

Surface runoff can migrate down the annular space along the outside of the well casing 

and contaminate the aquifer. Therefore, all sources of leakage should be plugged to prevent 

contamination. The most visible point of leakage is the encasement at the surface. The 

construction of the well above the surface should prevent leakage down the outside of the well 

casing as well as through the casing cap located on top of the casing. By extending the casing at 

least 18 inches above the well slab, surface runoff should not be able to enter the casing. The 

well slab should be concrete and sloped away from the casing. The well site should be graded to 

prevent ponding of surface water and to direct drainage away from the wellhead. The well casing 

cap should be a watertight sanitary seal to prevent water from entering through it. In addition, the 

casing vent through the cap should extend above flood level to preclude surface runoff from 

entering the well directly, and the end of the vent should be terminated with a downward turned 

gooseneck and screen to prevent rain and bugs from entering. 

Valves and meters should be fully functional and well maintained to keep out 

contamination. Personnel should have sufficient access to these valves for cleaning. The 

electrical system should be protected from lightning since the sudden electrical surge caused by 

lightning striking the wellhead or nearby may cause the electrical components to burn out. 

Ground fault protection is important to protect the operator. 

Wells with submersible pumps should be capped and the cap should be sealed so no 

water or contamination can enter the well. Seals should fit properly to accommodate all well 

appurtenances. If the well is not housed, the well cap should be locked and lightning protection 

should be provided. Exhibit 3.1 provides an example of a properly sealed well that is not housed. 

Wells with a lineshaft turbine pump mounted on top of the casing should have a metal support 

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plate on which a rubber gasket is mounted to provide a sanitary seal. The motor, along with an 

attached column and discharge head, is mounted on top of the gasket and support plate. The 

rubber gasket should be checked periodically to ensure it is in good condition and providing a 

sanitary seal. 

Exhibit 3.1 Sealed Well that is Not Housed 

Well casings should be vented to the atmosphere. For wells with submersible pumps, the 

vent should terminate in a downward “U” position, and should be located at or above the top of 

the casing. The vent’s opening should be screened with a 24 mesh corrosion resistant screen. 

Wells with turbine pumps mounted on top of the casing frequently are vented to the side of the 

casing. These vents should be located high enough to prevent water from entering them and 

should also be properly screened (Recommended Standards for Water Works, 2007). 

The discharge from the well should have a sample tap with a smooth nozzle to allow for 

sampling before the addition of any chemicals or disinfectants and before any treatment step. A 

sample of the raw water will allow the water system to test for contaminants that might be 

present or any changes in source water quality. 

Wells that are housed should be located in a properly constructed and maintained 

building. Exhibit 3.2 shows an example of a properly constructed pump house and its 

appurtenances. The discharge piping of housed wells and wells in the open is often located below 

ground. In such cases, the well is usually fitted with a pitless unit or pitless adaptor. Water 

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systems should check with their States to see if there are restrictions on the use of pitless 

adaptors. Exhibit 3.3 shows an example of a submersible pump with pitless adapter. 

The pump room floor should be watertight, preferably made of concrete and should slope 

away from the well casing in all directions (Ten States Standards, 2007). It is unnecessary to use 

an underground discharge connection if an insulated, heated pump house is provided. If the 

pump room is not continuously manned, it is not necessary to maintain the temperature at typical 

room conditions, only warm enough to prevent freezing. For individual installations in rural 

areas, a thermostatically controlled electric heater will generally provide adequate protection for 

the equipment when the pump house is properly insulated. 

Exhibit 3.2 Pump House and Well Appurtenances 

Source: USEPA, 2003 

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Exhibit 3.3 Submersible Pump with Pitless Adapter 

Source: USEPA, 2003 

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In some cases, the transport of microorganisms occurs due to improper well seals or 

casings that can result in large, open conduits for fecal contamination to pass unimpeded into the 

water supply. This is particularly true of small systems and older systems that were not originally 

constructed in accordance with their respective State’s design and construction standards 

(Linsley et al., 1992). 

If a system must remediate a well, it may need to repair or replace the well screen, well 

casing, well seal, or even the well pump. The well casing should extend above ground, and the 

system should grade the ground surface at the well site to drain away from the well. If a new well 

casing is needed, the system should consult with applicable State or local standards, or where no 

regulations exist, consult with other national criteria such as the AWWA Standards (1997) or the 

Ten States Standards (2007) (Chapter 3.2). 

The following subsections contain information regarding well rehabilitation, including 

correcting drainage problems, replacing a sanitary well seal, eliminating a well pit, and 

disinfecting wells and applying shock chlorination. 

3.1.3.1 Correcting Drainage Problems 

Wells should be located in areas with good drainage to prevent surface water runoff from 

entering the well casing where it may find its way into the ground water via the annular opening 

around the casing. Drilling in an area of low elevation allows the driller to penetrate the aquifer 

at a shallower depth from ground surface and reduces drilling costs. Unfortunately, it can also 

make the well subject to contamination from surface runoff. 

Exhibit 3.4 depicts how a drainage problem can be corrected by placing fill material 

around the well casing, compacting the fill, and grading it away from the casing. In some cases 

the well casing may need to be extended to ensure that it terminates a minimum of 18 inches 

above the final ground surface (Ten States Standard, 2007). EPA recommends that systems pour 

a concrete pad around the casing to ensure drainage away from the well. 

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Exhibit 3.4 Example of Correcting Drainage Problems 

Drainage toward well 

Ground Surface 

Sanitary Well Seal 

18" 

(b) Well casing exetended and fill placed (a)Well with drainage toward casing to direct water away from well. 

3.1.3.2 Replacing a Sanitary Well Seal 

Well seals are used to cover the top of a well casing pipe to prevent surface runoff from 

entering the casing (Purdue, 1997). In some cases sanitary well seals must be replaced to prevent 

additional contamination from entering the well through the top of the casing. 

Well seals are provided with vents to allow air movement in and out of the casing as the 

water level fluctuates with pumping. The vents are screened to exclude insects and have 

openings turned downward in order to keep out dust. Systems should check seals and vents 

regularly, however, because insects and mice may enter in the event that a power cable opening 

is unprotected, a vent is unscreened, or a well cap overlaps with, but does not completely seal, 

the well casing. 

The sanitary well seal pictured in Exhibit 3.4 is designed for use on wells that are 

terminated within well houses. As the bolts are tightened, the two plates are pulled together, 

expanding the gasket material located between the plates. This seals the openings around the 

casing, the pump drop pipe, the inverted U-type screened vent, and the electrical conduit. 

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Exhibit 3.5 Sanitary Well Seal with Expandable Gasket 

The well seal shown in Exhibit 3.5 is more commonly used in outdoor applications with 

submersible pumps and pitless adapter units. This seal has no openings on its top and is sloped so 

that rainwater will run off. The vents are located on the underside of the lip surrounding the 

casing, and gasket material seals all openings around the casing and conduit. 

Exhibit 3.6 Overlapping Exterior Well Seal 

The replacement well seal must be of the proper size and type to fit the casing and 

accommodate other well appurtenances. Systems should coordinate with the State to make sure 

that the type of replacement well seal chosen is approved by the State. 

3.1.3.3 Eliminating a Well Pit / Buried Well 

In the northern parts of the United States, many older wells were terminated within pits in 

order to keep them from freezing during colder months. Such pits are dangerous to enter because 

of confined space safety issues, and are subject to flooding that can cause loss of service and 

contamination of the aquifer. Well pits are not considered a method of sanitary construction. 

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To eliminate the well pit, the system should extend the casing so that it will terminate at 

least 18 inches above the finished grade or 12 inches above the pump house slab (Ten States 

Standards, 2007). The pit then should be backfilled with suitable material and compacted. 

Bentonite or other grout material should be placed around the casing as backfilling occurs in 

order to keep water from moving down the casing. A pump house should be constructed around 

the well if the original pit well was constructed to keep the top of the well below the frost line. 

3.1.3.4 Temporary Disinfection of Wells by Applying Shock Chlorination 

If a system is found to have a serious deficiency or fecal contamination, it may take time 

for the system to design and install a corrective action. In the meantime, the system cannot serve 

the contaminated water to its customers. The primacy agency may require the system, as part of 

its corrective action, to apply chlorination until the contamination is eliminated or a corrective 

action is put in place. Hypochlorination will generally be used because it is easier to install and 

operate than gaseous chlorination or other disinfection methods and is the least costly of the 

treatment methods. 

It is important to note that temporary disinfection is meant to deal with a single 

contamination event, such as a flood, or maintenance on a well. Shock chlorination is not 

intended to deal with a chronic problem, such as a cracked casing or a well next to a failed septic 

system. 

Shock chlorination can be effectively used to treat iron- and sulfate-reducing bacteria in 

PWSs and to treat PWSs contaminated with high levels of heterotrophic plate counts (HPC) or 

coliform bacteria (Alberta, 1999). Disinfection should occur promptly in order to reduce the 

possibility of growth of undesirable biofilms within the well and reduce the potential for 

migration of the microbial contaminants. 

It is essential to make sure that the disinfecting agent comes in contact with all portions 

of the well, pumping equipment, and plumbing during shock chlorination. To be effective, shock 

chlorination must disinfect the following (Alberta, 1999): 

• The entire well depth; 

• The formation around the bottom of the well; 

• The pressure system; 

• Some water treatment equipment; and 

• The distribution system, if needed. 

Disinfection with Calcium Hypochlorite 

Calcium hypochlorite solution (approximately 65 percent available chlorine by weight) is 

an effective and widely used method of disinfecting wells (USEPA, 1982). Calcium hypochlorite 

is available in tablet and powder form. Exhibit 3.7 shows quantities of calcium hypochlorite to 

be used in treating wells of different diameters and water depths. 

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When disinfecting newly constructed wells or disinfecting wells after maintenance, 

calcium hypochlorite is added to provide a dosage of at least 100 milligrams per liter (mg/L) of 

available chlorine in the well water. For wells with chronic biofouling problems, much higher 

concentrations of chlorine and repeated applications may be necessary. Additional chemicals and 

treatment techniques may be needed if biological growth has caused encrustation of the well (see 

Borch, et al., 1993 for details). While preparing a stock solution of calcium hypochlorite, the 

percent available of chlorine by weight must be taken into account during the weighing of the 

chemicals. It is useful to prepare a stock solution first (e.g., mixing 2 ounces of hypochlorite with 

2 quarts of water). 

Exhibit 3.7 Quantities of Calcium Hypochlorite, 70% to Provide a Chlorine

Dosage of at Least 100 mg/L 

Well 

Diam.Inches 2 3 4 5 6 8 10 12 16 20 24 28 32 42 48 

Depth(feet) 

5 1T 1T 1T 1T 1T 1T 2T 3T 5T 6T 3 oz. 4 oz 5 oz 7 oz 9 oz 

10 1T 1T 1T 1T 1T 2T 3T 5T 8 T 4 oz 6 oz 8 oz 10 13 oz 1.5 lb 

15 1T 1T 1T 1T 2T 3T 5T 8 T 4 oz 6 oz 9 oz 12 oz 1 lb. 1.5 lb. 1.5 lb 

20 1T 1T 1T 2T 3 T 4 T 6 T 3 oz 5 oz 8 oz 

30 1T 1T 2T 3T 4 T 6 T 3 oz 4 oz 8 oz 12 oz 

40 1T 1T 2T 4 T 6T 8 T 4 oz 6 oz 10 oz 1 lb 

60 1T 2T 3 T 5T 8 T 4 oz 6 oz 9 oz 

80 1T 3 T 4 T 7 T 9 T 5 oz 8 oz 12 oz 

100 2T 3 T 5 T 8 T 4 oz 7 oz 10 oz 1 lb 

150 3T 5 T 8 T 4 oz 6 oz 10 oz 1 lb 1.5 lb 

Source: (USEPA, 1982) 

Notes: Quantities are T = tablespoons; oz = ounces (by weight); lb = pounds. 

Values corresponding are solid calcium chloride required. 

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Exhibit 3.8 Liquid Chlorine Bleach* (5.25%) to Provide a Chlorine Dosage of at 

Least 100 mg/L 

Well 

Diam.Inches 2 3 4 5 6 8 10 12 16 20 24 28 32 42 48 

Depth(feet) 

5 1C 1C 1C 1C 1C 1C 1C 1C 2C 4C 1 Q 2 Q 3 Q 3Q 3 Q 

10 1C 1C 1C 1C 1C 1C 2C 2 C 1 Q 2 Q 3 Q 4 Q 4 Q 6 Q 8 Q 

15 1C 1C 1C 1C 1C 2C 3C 4 C 2 C 2.5 Q 4 Q 5 Q 6 Q 2 G 3 G 

20 1C 1C 1C 1C 1C 2 C 4C 1 Q 2.5 Q 3.5 Q 

30 1C 1C 1C 1C 2C 4C 1.5 Q 2 Q 4 Q 5 Q 

40 1C 1C 1C 2C 2 C 1 Q 2 Q 2.5 Q 4.5 Q 7 Q 

60 1C 1C 2 C 3C 4 C 2 Q 3 Q 4 Q 

80 1C 1C 2C 4 C 1 Q 2 Q 3.5 Q 5 Q 

100 1C 2C 3 C 1 Q 1.5 Q 2.5 Q 4 Q 6 Q 

150 2C 2C 4 C 2Q 2.5 Q 4 Q 6 Q 2.5 G 

* That meets NSF Standard 60. 

Notes: Quantities are C = cups; Q = quarts; G = gallons. 

Values corresponding are amounts of liquid household bleach. 

Operators of systems using calcium hypochlorite should be cautious when handling and 

storing the chemical and should always carefully read and follow all safety and storage 

instructions. Calcium hypochlorite should always be added to water (i.e., water should never be 

added to calcium hypochlorite). Calcium hypochlorite will release chlorine gas on contact with 

acids and should be stored separately. Also, since the chemical exhibits caustic and corrosive 

properties, operators should wear goggles, gloves, and respirators when working with calcium 

hypochlorite, and should only work in areas with suitable ventilation. 

Protocols for disinfecting new or recently repaired wells can be found in American Water 

Works Association (AWWA) C654-03. A simpler procedure that can be used for smaller wells is 

as follows (USEPA, 1982): 

• Determine the volume of water in the well based on the casing diameter, static water 

level, and depth of casing. Calculate the amount of chlorine solution or granular 

chlorine necessary to bring that volume of water, and the water in the plumbing, to 

the required concentration (see Exhibit 3.7 and 3.8). Before disinfection, the well 

must be purged of any accumulated sediment and debris and be free of turbidity for 

disinfection to be effective. 

• Add the correct amount of chlorine to 5 - 10 gallons of fresh water and pour the water 

down the casing. Try to make sure the chlorinated water contacts the inside of the 

casing and outside of the drop pipe as it enters the well so it can clean and disinfect 

those surfaces. 

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• Operate the pump until the odor of chlorine can be detected or use a DPD test kit (a 

kit which uses test reagents and color charts) to measure the chlorine residual in 

addition to detecting chlorine odor. 

• Shut off the pump and allow the chlorinated water to remain in the well and plumbing 

for 24 hours. 

• After 24 hours, turn on the pump and flush the chlorinated water from the well and 

plumbing equipment. Make sure the chlorinated water is not discharged to surface 

water or to any other area where the chlorine could cause damage or violations of the 

Clean Water Act. Continue flushing for at least one hour after the odor of chlorine has 

dissipated. 

• Collect one coliform sample at the well head for three consecutive days. If any of the 

three samples are coliform positive, repeat the process. 

Once the source water is tested free of chlorine residual, the operator should collect a few 

samples of water for water quality analysis from a clean non-leaking tap. Water should be 

flushed from the tap for a few minutes before sampling. The number of bacteriological samples 

collected depends on State guidelines; samples are sent to a State-approved laboratory for 

analysis. 

Make sure to contact the laboratory for the proper sample collection and storage 

procedures. Analyses can be run on several chemical, physical, and biological parameters such as 

nitrogen, lead, manganese and other metals, sulfates, cyanide, pH, and/or coliforms. Most States 

designate the specific parameters required for analyses. 

One of the concerns with disinfecting a newly developed or rehabilitated well is the 

potential risk of discharging chlorinated waters directly into surface water bodies. Since high 

levels of chlorine (prior to discharge) can be harmful to aquatic life, chlorinated waters may need 

to be dechlorinated to reduce the chlorine in the water to acceptable levels. Dechlorination can be 

achieved by applying dechlorination chemicals such as thiosulfate or ascorbic acid. If the amount 

of water to be dechlorinated is small, passive techniques such as discharge through hay bales or 

other natural structures and detention in holding ponds can be used (Tikkanen et al., 2001). 

These approaches may also be used to treat superchlorinated water pumped from a well. 

In some cases, the discharge may be regulated by a National Pollutant Discharge 

Elimination System (NPDES) or a State permit. PWSs should contact their primacy agency for 

more information about applying for an NPDES or a State permit. Some utilities may be allowed 

to inject the chlorinated water and other waste streams into the ground by underground injection 

wells. The underground injection control (UIC) program regulates the discharge of such units 

and ensures that the water is discharged below the lowest level of any aquifer serving as a source 

of potable water and that the migration of the injectate into pristine ground waters is avoided. 

3.1.4 Minimizing Contamination after a Flood 

After a flood, PWSs should inspect, clean, and pump wells, and then disinfect wells that 

have been flooded and test the water prior to use. Flood precautions issued by the State and local 

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health department should be followed in addition to EPA guidelines (USEPA, 2005a). 

Additionally, a PWS should address why the flooding occurred and determine whether the cause 

of flooding can be eliminated, mitigated, and/or minimized. A system is much better off 

preventing the contamination by managing the risk of flooding rather than responding to 

contamination from a flood after the fact. 

Floods may cause some wells to collapse; therefore, conditions at the wellhead should be 

checked. Swiftly moving flood water can carry large debris that could loosen well hardware, 

dislodge well construction materials, or distort casing. Coarse sediment in flood waters could 

erode pump components. If the well is not tightly capped, sediment and flood water could enter 

the well and contaminate it. 

Electrical systems should not be turned on until after flood waters have receded and the 

pump and electrical system have dried. The wiring system should be checked by a qualified 

electrician, well contractor, or pump contractor. If the pump’s control box was submerged during 

the flood, all electrical components must be dry before electrical service can be restored. Pumps 

and their electrical components can be damaged by sediment and floodwater. The pump, 

including the valves and gears, should be cleaned of silt and sand. 

To avoid damage to drilled, driven, or bored wells, remove mud, silt and other debris 

from around the top of the well. If excessive mud, silt or sediment has entered the well, the pump 

may need to be removed or bailers used to remove mud and silt from the bottom of the well. It is 

not recommended to attempt to disinfect or use a dug well after it has been flooded. 

To minimize contamination after a flood, pump the well until the water runs clear to rid 

the well of flood water. Depending on the size and depth of the well and extent of contamination, 

pumping times will vary. If the water does not run clear, further investigation into the cause of 

the problem is necessary before attempting to disinfect. 

Emergency disinfection after a flood should be performed according to the shock 

chlorination procedures described in Section 3.1.3.4. Wells can remain contaminated even after 

disinfection procedures are followed, so sampling and testing the water may be necessary to 

ensure safe drinking water. In extensive flood areas, the speed and direction of ground water 

flow can cause wells to remain contaminated for months. Septic systems should not be used 

immediately after floods because drain fields will only work once the ground is no longer 

saturated. Additionally, water systems should avoid pumping of a septic tank when the soil is 

saturated to prevent the tank from collapsing due to a static pressure differential. In such cases, 

long range precautions such as testing should be used to protect drinking water. 

Since well disinfection does not provide protection from pesticides, metals, or other types 

of non-biological contamination, further cleanup and analyses may be necessary when such 

contamination is suspected. Also, if drums or barrels are moved by the flood within the wellhead 

protection area, special treatment may be required. For specific questions on various 

contaminants, the EPA Safe Drinking Water Hotline (1-800-426-4791) or the Superfund Hotline 

(1-800-424-9346) can be contacted. 

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4. Providing an Alternative Source of Drinking Water 

If remediating an existing source of drinking water is not an option, the next step is to 

consider alternative sources of drinking water. If a well is contaminated, abandoning the well 

and connecting to another public water supply, or consolidating with another utility are options 

for providing safe drinking water. In some cases bottled water can be used as a short-term

solution. Another choice is to install a new well that is properly constructed, cased, and sealed to 

prevent ground water contamination. This chapter provides detailed descriptions of the types of 

new wells and well characteristics to consider when installing a new well. The alternative source 

options addressed in this chapter are: 

• Providing bottled water (Section 4.1); 

• Consolidating/purchasing water from another utility (Section 4.2);

• Installing a new well (Section 4.3); and 

• Switching to a surface water source (Section 4.4). 

4.1 Providing Bottled Water (Short Term) 

One option for a utility to ensure safe drinking water to its customers is to provide them

with bottled water. The use of bottled water in lieu of piped water for direct consumption and 

cooking purposes is used only as a short-term solution to a contamination problem while other 

permanent solutions are being implemented for the following reasons (40 CFR 141.101): 

• Relative expense of bottled water; 

• Demanding logistics of distribution; and 

• Does not provide safe water for other household uses. 

Bottled water is regulated by the United States Food and Drug Administration (FDA) 

under the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 301 et seq.) if sold in interstate 

commerce and by some States when it is sold in those States. Water systems that are distributing 

bottled water to their users should be sure the bottled water they are distributing meets all 

applicable State and Federal standards. Systems may elect to require bottled water vendors to 

conduct or arrange for testing of the bottled water provided to assure consumers of its quality. 

If a water system provides its users with bottled water, it should issue a “do not use” or 

“do not drink” public notice, as appropriate, so the tap water is not consumed. The system should 

work closely with its drinking water regulators to ensure proper notification is made. The water 

being provided should be made as readily available as possible to all of the system’s usual users, 

and special consideration should be given to housebound and immobile people. Systems may 

consider preparing a brief fact sheet about details of the short-term situation, the bottled water 

being used, and how it can be obtained. Alternatively, the water system could include such 
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information in its public notice if the State agrees and the system is required to make public 

notice. Community water systems may consider providing a phone number consumers can call 

for additional information. 

4.2 Consolidating/Purchasing Water from Another Utility 

Consolidating with another public water utility may be the only option for a utility with 

extremely limited financial and technical resources. Such utilities may not be able to invest in 

new infrastructure for providing their customers with an alternate source of drinking water. 

Consolidating with a utility that has greater resources at its disposal can help ensure a safe and 

alternative drinking water supply source to customers. 

Purchasing water from another PWS may be a sound economical solution to providing an 

alternate source of safe drinking water. There are many benefits to purchasing water from a 

nearby utility including a reduction in the regulatory burden (i.e., monitoring and reporting) that 

comes from eliminating the source(s) as well as more simplified operations and maintenance. 

However, the purchasing utility may have to disinfect the water before bringing the purchased 

water into the distribution system. Deciding to disinfect depends on whether the purchased water 

has an adequate disinfectant residual to control microbial re-growth in the distribution system

and whether disinfection is necessary at all. If disinfection is needed, the purchasing utility may 

need to install or modify existing contactor and/or clearwell capacity to post-disinfect the water. 

Whether the purchasing utility adds a chemical disinfectant or the wholesale system adds a 

chemical disinfectant, the purchasing water system will have to comply with the Disinfection 

and Disinfection Byproducts Rules (Stage 1 and/or Stage 2) and should work with the State in 

doing so. 

4.3 Installing a New Well 

In many cases, the primacy agency and ground water system may find the best corrective 

action for a contaminated well or significantly deficient well is to install a new well. There are 

many types of wells –bored, driven, jetted, drilled – which are discussed in this section. In 

addition, there are basic construction components to wells, such as the well casing (typically 

steel, plastic, or PVC), grout (typically cement, concrete, or clay), surface seal, and screens. Well 

siting factors should be considered for the proposed location, including any contamination 

sources nearby. The proposed well’s location in relation to other wells and surface water bodies, 

its relative size and draw down influences, as well as accessibility to the well site and power 

sources should also be considered. This section provides an overview of some of the issues that 

the primacy agency and system should discuss when considering installing a new well as part of 

a corrective action. The specific standards for design, testing, and installation vary from State to 

State. When considering installation of a new well, the system should ensure that all relevant 

issues (e.g., siting, hydraulics, costs, financing, security, etc.) are considered. 
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4.3.1 Critical Factors in Well Construction 

If a decision has been made to install a new well, the availability of adequate quantity 

and quality of water is the first critical factor. Other critical factors controlling well suitability 

include well casing and grouting, surface seals, and the potential for flooding (Jorgenson, et al., 

1998). These assumptions regarding what constitutes an acceptable well are shown in Exhibit 

4.1. Section 4.3.3 provides additional information on sanitary construction of wells. 

Exhibit 4.1 Well Construction and Condition 

Acceptable Unacceptable 

The well is cased and grouted to the confining layer 

or production zone 

The casing, grouting, or surface seal is damaged or 

leaking 

The casing is steel, plastic, PVC, or other nonporous material The well is subject to periodic flooding 

The well has a surface seal Shallow well or well under the direct influence of 

surface water 

Well should be of adequate depth and distance from 

a body of surface water and in an appropriate 

geology to prevent it from being classified as a 

GWUDI 

Source: Jorgenson, et al./USEPA, 1998 

Casing 

All wells should be cased and grouted or otherwise sealed. The casing should extend 

from the surface through a confining layer (if there is one) or to the production zone in the 

aquifer. The casing should be composed of a nonporous material such as steel or plastic (Ten 

States Standards, 2007). 

All wells should be constructed in accordance with State and local requirements; 

common State standards are shown in Exhibit 4.2. 
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Exhibit 4.2 Ten State Standards (2007) Recommendations for Casing 

Steel Casing Nonferrous Casing 

• Temporary steel casing used for construction 

must be capable of withstanding the structural 

load imposed during its installation and 

removal. 

• Permanent steel casing pipe should: 

o Be a new single steel casing pipe meeting 

AWWA Standard A-100, ASTM, or API 

specifications for water well construction; 

o Have specified minimum weights and 

thickness; 

o Have additional thickness and weight if 

minimum thickness is not considered 

sufficient to assure reasonable life 

expectancy of a well; 

o Be capable of withstanding forces to which 

it is subjected; 

o Be equipped with a drive shoe when driven; 

and 

o Have full circumferential welds or threaded 

coupling joints. 

• The following guidelines are for nonferrous 

casing materials: 

o Approval of any nonferrous well-casing 

material is subject to special determination 

by the reviewing authority before 

submissions of plans and specifications; and

o Nonferrous well-casing material must be 

resistant to: 

- Water corrosivity, 

- Stresses of installation, and 

- Grouting and operation. 

Surface Seal 

The surface seal should be installed around the well to protect it from contamination that 

could enter between the casing and the borehole wall. The seal should fill the space between the 

casing and borehole wall and extend to a depth at least below the frost line. In some cases, the 

cement grout can be extended to the surface to form the surface seal (Massachusetts DEP, 2004). 

Protection from Flooding 

The well should be protected from flooding. A well located in a periodic floodplain or in 

a topographic depression that collects surface runoff can become contaminated by either direct 

flow or seepage around the seal. To prevent flooding, the casing can be extended to a height 

above the expected flood level and surface seals and grout can be used to seal it (Ten States 

Standards, 2007). 

4.3.2 Types of Wells 

This section describes different types of wells and how each is constructed. Most wells 

constructed today are drilled wells. However, bored wells may also be installed or constructed. 
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According to Ten State Standards (2007), drilling fluids and additives should not impart any 

toxic substances to the water or promote bacterial contamination. Minimum protected depths of 

drilled wells provide watertight construction to such depths as may be required by the State to 

exclude contamination and seal off formations that are or may be contaminated. The system's 

State may require minimum protected depths for drilled wells in order to exclude contamination 

and seal off surficial aquifers that may be contaminated. Exhibit 4.3 describes general soil 

characteristics suitable to different types of wells. Systems installing new wells should be careful 

to adhere to State well standards. 

Exhibit 4.3 Suitability of Well Construction Methods with Different Geological 

Conditions 

Characteristics Bored Driven Jetted 

Range of practical depths 0-100 ft 0-50 ft 0-100 ft 

Diameter 2-30 inches 1.25-2 inches 2-12 inches 

Type of geologic formation 

 Clay Yes Yes Yes 

 Silt Yes Yes Yes 

 Sand Yes Yes Yes 

 Gravel Yes Fine 1⁄4” pea gravel 

 Cemented gravel No No No 

 Boulders Yes, if less than 

well diameter 

No No 

 Sandstone Yes, if soft and/or 

fractured 

Thin layers No 

 Limestone Yes, if soft and/or 

fractured 

No No 

 Dense igneous and 

 metamorphic rock 

No No No 

Characteristics Drilled 

Percussion Rotary Hydraulic Rotary Air 

Range of practical depths 0-1,000 ft 0-1,000 ft 0-750 ft 

Diameter 4-18 inches 4-24 inches 4-10 inches 

Type of geologic 

formation 

 Clay Yes Yes No 

 Silt Yes Yes No 

 Sand Yes Yes No 

 Gravel Yes Yes No 

 Cemented gravel Yes Yes No 

 Boulders Yes, when in firm 

bedding 

Difficult No 

 Sandstone Yes Yes Yes 

 Limestone Yes Yes Yes 

 Dense igneous and 

 metamorphic rock 

Yes Yes Yes 

Source: Grundfos, 2007
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4.3.2.1 Bored Wells 

Bored wells are usually constructed with earth augers turned by hand or power 

equipment (USEPA, 1973). These wells can be constructed to a depth of up to 100 feet if the 

water requirement is low and the overlying material contains few large boulders and has noncaving properties (Purdue Research Foundation, 2001). Because the bore holes for these wells 

must remain open until the casing is installed, the construction of bored wells is most successful 

in fine-textured soils (Purdue, 1997). 

Once the well is bored, casing should be inserted into the hole. Bored wells are cased 

with vitrified tile, concrete pipe, standard wrought iron pipe, steel casing, or other suitable 

materials capable of sustaining imposed loads (Purdue Research Foundation, 2001). The well is 

usually completed by installing well screens or perforated casing in the water bearing strata. A 

gravel layer (approximately 4 inches) is placed around the casing from 10 feet below the land 

surface to the well bottom. Cement grouting up to adequate depth is necessary to protect the well 

from surface drainage. The upper 10 feet of the well should be protected from surface 

contamination by approved construction methods (Purdue, 1997). 

4.3.2.2 Driven Wells 

The simplest and often least expensive method of well construction is to drive a drivewell point that is fitted to the end of a series of pipe sections (USEPA, 2006a). Drive-well points 

come in a variety of designs and materials. Drive points are usually 1.25 inches or 2 inches in 

diameter and are driven with the aid of a maul, or a special drive weight. For deeper wells, the 

well points are sometimes driven into the water bearing strata from the bottom of a bored well 

(Kansas Geological Survey, 2004). If they can be driven to an appreciable depth below the water 

table, they are no more likely than bored wells to be seriously affected by water table 

fluctuations. The most suitable locations for driven wells are areas containing alluvial deposits of 

high permeability. 

When driving a well, it is common practice to use a hand auger slightly larger than the 

well point to prepare a pilot hole that extends to the maximum practical depth. The assembled 

point and pipe are then lowered into the hole. The pipe is driven by directly striking the drive cap 

that is threaded to the top of the protruding section of the pipe. A maul, a sledge, or a “special 

driver” may be used to hand drive the pipe. The “special driver” may consist of a weight and 

sleeve arrangement that slides over the drive cap as the weight is lifted and dropped in the 

driving process (Department of the Army, 1994) 

4.3.2.3 Jetted Wells 

The jetted well technique is a rapid and efficient method of sinking well points (USEPA, 

1973). A source of water and a pressure pump are needed to use this technique. 

Water is first forced under pressure down the riser and comes out of a special washing 

point. The well point and pipe are then lowered as material is loosened by the impact of the 

water jet. Often the riser pipe is used as the suction pipe for the pump. In such cases, surface 
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water may be drawn into the well if the pipe develops holes. An outside protective casing may 

have to be installed to an adequate depth to ensure protection from the possible entry of 

contaminated surface water run-off. The space between the casings is also filled with cement 

grout. It is recommended that the system install the protective casing as an auger hole and to 

drive the point inside it. 

4.3.2.4 Drilled Wells 

Exhibit 4.4 shows the layout of a drilled well with a submersible pump. Exhibit 4.5 

shows a typical wellhead design for submersible pumps. Construction of drilled wells is 

accomplished by either percussion or rotary drilling. 

Percussion (Cable-tool) Method: This method is accomplished by raising and dropping a 

heavy drill bit and stem. The impact of the bit crushes and dislodges pieces of the formation. The 

reciprocating motion of the drill tools mixes the drill cuttings with water into a slurry at the 

bottom of the hole. This is periodically brought to the surface with a bailer (a 10-20 foot long 

pipe equipped with a valve at the lower end). Caving is prevented as drilling progresses by 

driving or sinking a casing slightly larger in diameter than the bit. When good drilling practices 

are followed, water-bearing beds are readily detected in cable holes because the slurry does not 

tend to seal off the water bearing formation. A rise or fall in the water level in the hole during 

drilling or increased recovery water during bailing indicates that the well has entered a 

permeable bed. 
Exhibit 4.4 Drilled Well with Submersible Pump 

Source: USEPA, 2003b 

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Exhibit 4.5 Typical Wellhead Design for Submersible Pumps 

Source: USEPA, 2003a 

Hydraulic Rotary Drilling Method 

The hydraulic rotary drilling may be used in almost all formations. The drilling 

equipment consists of the following: 

• Derrick, 

• Hoist, 

• Revolving table through which the drill pipe passes, 

• Series of drill pipe sections, 

• Cutting bit at the lower end of the drill pipe, and 

• Pump for circulating the drilling fluid and a power source. 

The bit breaks up the material as it rotates and advances while the drilling fluid (mud) 

that is pumped down the drill pipe picks up the drill cuttings and carries them up the space 

between the rotating pipe and the wall of the hole. The mixture of mud and cuttings is discharged 

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to a settling pit where the cuttings decant to the bottom and the mud is recirculated to the drill 

pipe. Once the hole is completed the drill pipe is withdrawn and the casing is placed. The drilling 

mud is usually left in place and pumped out after the casing and screen are positioned. The space 

between the hole wall and the casing is generally filled with cement grout in non-water bearing 

sections, but may be enlarged and filled with gravel at the level of the water-bearing strata 

(NGWA, 2007). 

Air Rotary Drilling Method 

The air rotary drilling method uses similar equipment to that used for the hydraulic rotary 

drilling method. The major difference between the two methods is that the air rotary method uses 

air and the hydraulic rotary drilling method uses mud and water. 

The air rotary method is well adapted to rapid penetration of consolidated formations and 

is especially popular in regions with limestone aquifers. Penetration rates of 20-30 feet per hour 

are usually achieved in very hard rock formations. To remove cuttings, upward velocities of at 

least 3000 feet per minute are required. The air rotary method usually is not suitable for 

unconsolidated formations where careful sampling of rock materials is required for well-screen 

installation. 

4.3.3 Characteristics of Wells 

4.3.3.1 Yields of Different Types of Wells 

Driven wells can be sunk to 30 feet or more below the static water level. Because of their 

small diameters (2 to 12 inches) they can have relatively small yields. Combining several driven 

wells can offset the small yield of a single well. Deeper wells with large available drawdowns 

tend to have higher yields. Drilled and jetted wells can usually be sunk to such depths that the 

available drawdown can be hundreds of feet (Purdue Research Foundation, 2001). 

Exhibit 4.3 provides details about penetrating various types of geological formations 

using different well drilling methods. 

4.3.3.2 Sanitary Construction of Wells 

When a well penetrates a water-bearing formation, it provides a direct route for potential 

contamination at the source. To prevent contamination from reaching the ground water, the 

following basic sanitary guidelines should always be followed during the construction of wells 

(USEPA, 1992). 

• Fill the open space outside the casing with a watertight cement grout from a point just 

below the frost line (or deepest level of excavation near the well) to as deep as 

necessary to prevent entry of surface water. See Section 4.3.3.3 for a detailed 

description of grouting requirements. 
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• For artesian basins, seal the casing into the overlying impermeable formations to 

retain artesian pressure. 

• When a water-bearing formation containing poor quality water is penetrated, seal off 

the formation to prevent infiltration of water into the well and aquifer. 

• Install a sanitary well seal with an approved vent at the top of the well casing to 

prevent the entrance of contaminated water or other objectionable material. 

• It is difficult to provide a sanitary seal for large diameter wells. Therefore, a 

reinforced concrete slab should be installed that overlaps the casing and seals to it 

with a flexible sealant or rubber gasket. 

4.3.3.3 Grouting Requirements 

According to Ten State Standards (2007), all permanent well casing, except driven 

Schedule 40 steel casing with the approval of the reviewing authority, shall be surrounded by a 

minimum of 1.5 inches of grout to a depth required by the reviewing authority. Temporary 

construction casings should be removed. If it is not possible or practicable to remove the 

temporary construction casing, it should be withdrawn by at least 5 feet to ensure grout contact 

with the native formation. 

The following types of grout mixes are recommended by Ten State Standards (2007): 

• Neat cement grout 

- Consists of cement (conforming to ASTM standard C150) and water. 

- No more than six gallons of water per sack of cement are to be added. 

- Additives may be used to increase the fluidity of the grout, subject to approval by 

the reviewing authority. 

- Can be used for only 1.5 inch openings and not for larger openings. 

• Concrete grout 

- Equal parts of cement (conforming to AWWA A100 Section 7) and sand with no 

more than six gallons of water per sack of cement may be used for openings 

larger than 1.5 inches. 

- When an annular opening larger than four inches is available, gravel not larger 

than 0.5 inch in size may be added. 
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• Clay seal 

- Where an annular opening of greater than six inches is available, a clay seal of 

local clay mixed with at least 10 percent swelling bentonite may be used when 

approved by the reviewing authority. 

Ten State Standards (2007) also stipulates that the following requirements should be met 

prior to or during the application of the grout mix: 

• Sufficient annular space should be provided to permit a minimum of 1.5 inches of 

grout around permanent casings. 

• Bentonite or similar materials may be added to the annular opening prior to grouting 

through fractured geological formations. 

• Grout should be installed under pressure using a grout pump. When the annular 

opening is less than four inches, the annular opening should be filled in one 

continuous operation. 

• Gravity placement can be performed using a grout pipe installed at the bottom of the 

annular opening, in one continuous operation when: 

- The annular opening is four or more inches and less than 100 feet deep, and 

- Concrete grout mix is being used. 

• A clay seal placed by gravity may be employed when the annular opening is greater 

than six inches and less than 100 feet deep. 

• Work on the well should be discontinued until the cement or concrete grout sets 

properly with no air pockets. 

4.3.3.4 Well Screens 

Screens (slotted casings) are installed in wells to permit sand-free water flow into wells 

and to prevent unstable formations from caving in. The slot size for screens is based on a sieve 

analysis of carefully selected samples of the water bearing formation. If the slots are too large, 

the well may pump significant quantities of sand. If the slots are too small, they become easily 

plugged with fines, which results in reduced yield. In a drilled well, the screens are normally 

placed after the casing has been installed. However, in a driven well, the screen is a part of the 

drive assembly and is sunk to its final position as the well is driven. 

Well screen manufacturers provide tables of capacities and other information to aid in 

selecting the most economical screen size. According to the Ten State Standards, the following 

minimum standards are applicable to well screens: 
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• They should be constructed of materials that are resistant to damage by the chemical 

action of ground water or those of cleaning operations. 

• Their installation should ensure that the pumping water level remains under the 

screen for all operating conditions. 

• Where applicable, they should be designed and installed to allow easy removal and 

replacement without adversely impacting water-tight construction of the well. 

• They should be provided with a bottom plate or washdown bottom fitting of the same

materials as the screen. 

4.3.3.5 Well Development 

Before a well becomes operational, it is essential to remove all the silt and fine sand next 

to the well screen by employing a process called “well development.” Development unplugs the 

formation and produces a natural filter of coarser and more uniform particles of high 

permeability surrounding the well screen (Purdue Research Foundation, 2001). After 

development is completed, a well-graded, stabilized layer of coarse material will enclose the 

entire well screen and facilitate the flow of water into the well. Surging and high-velocity 

hydraulic jetting are two common methods for conducting well development and are described 

below. 

Surging 

This process agitates the silt and sand grains by a series of rapid reversals in the direction 

of water flow, which cause the silt and sand grains to be drawn toward the screen through larger 

pore openings. One method of surging a well is to move a plunger up and down the well, 

resulting in water moving in and out of the formation alternately. When water containing the 

fines flows into the well the particles settle into the bottom of the screen and are then removed 

by pumping or bailing. (Purdue Research Foundation, 2001) 

High-Velocity Hydraulic Jetting 

Water under high pressure is ejected through the slot openings and violently agitates the 

aquifer material. Sand grains finer than the slots move through the screen and either settle at the 

bottom or are washed out to the top. Water pressures in the vicinity of 150 psi are required. 

High-velocity jetting is most useful for screens having continuous horizontal slot design. It is 

also effective in washing out drilling mud and crevice cuttings in hard-rock wells. However, it is 

less useful for slotted or perforated pipes. 
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4.3.3.6 Testing Wells for Yield and Drawdown

A pumping test should be performed on a developed well to determine its yield and 

drawdown. The results of a pumping test can help select what type of pumping equipment should 

be used. The pumping test should include the following (Purdue Research Foundation, 2001): 

• Volume of water pumped per minute or hour; 

• Depth to the pumping level as determined over a period of time at one or more 

constant rates of pumping; 

• Recovery of water level after pumping is stopped; and 

• Length of time the well is pumped at each rate during the test procedure. 

According to Ten State Standards (2007), yield and drawdown tests need to be performed 

on every production well after construction and prior to the placement of the permanent pump. 

Test methods should be clearly indicated in the project specifications. The test pump capacity at 

maximum anticipated drawdown should be at least 1.5 times the quantity anticipated. The yield 

and drawdown tests should provide for continuous pumping for at least 24 hours at the design 

pumping rate or until stabilized drawdown has continued for at least six hours when pumped at 

1.5 times the design pumping rate. There may also be State requirements for testing and 

stabilization. Ten State Standards (2007) recommends that the following data be provided by any 

yield/drawdown test: 

• Test pump capacity-head characteristics; 

• Static water level; 

• Depth of test pump setting; 

• Start and end time of each test cycle; and 

• Zone of influence of the well. 

The test should also provide hourly readings of the following parameters: 

• Pumping rate, 

• Pumping water level, 

• Drawdown, and 

• Water recovery rate and levels. 

When testing a well for yield and drawdown, it is best to test it near the end of the dry 

season. When this cannot be done it is important to estimate the additional seasonal decline in 

water levels from wells tapping the same formations. This additional drawdown should be added 
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to the drawdown determined by the pumping test in order to arrive at the maximum pumping 

water level. Additional information regarding testing wells for yield and drawdown can be 

obtained from the United States Geological Survey (USGS), the State health department, and 

manufacturers of well screens and pumping equipment. 

4.3.4 Disinfection of Newly Constructed Wells 

All newly constructed wells should promptly be disinfected to destroy disease-causing 

microorganisms that may have been introduced into the well during construction, hookup, 

maintenance, or as a result of faulty well construction. The system should follow all applicable 

State requirements and can also consult AWWA standard C-654-03 for well disinfection. 

All elements of the well should be disinfected including the gravel pack, casing, and 

pump. Disinfection can be performed using liquid chlorine, sodium hypochlorite, or calcium

hypochlorite. If liquid chlorine is used, it should conform to ANSI/AWWA standard B301. If 

hypochlorite is used, it should conform to ANSI/AWWA standard B300. 

Similar to the shock chlorination procedures discussed in Chapter 3 (section 3.1.3.4), the 

following procedures for disinfecting newly constructed wells (AWWA 2003) can be followed 

to disinfect the well and its components. Individual States may have standards which deviate 

from these and should be consulted prior to performing any disinfection. 

To disinfect the gravel pack, one quarter to one half a pound of calcium hypochlorite 

tablets can be mixed per ton of gravel prior to the gravel being placed. Care should be taken to 

ensure that the gravel is free from organic material. Alternatively, chlorinated water can be 

added to the well after the gravel is in place and the drilling mud has been displaced. Chlorinated 

water should be added until the concentration is 50 mg/L or greater throughout the entire volume 

of the well. 

Equipment such as pumps, meters, and valves should be disinfected just prior to 

installation by spraying with a solution containing at least 200 mg/L of chlorine. 

The procedure to disinfect the well after all the components have been installed is as 

follows (AWWA, 2003): 

• Add chlorine until the water throughout the well volume is 50 mg/L or greater. If 

calcium hypochlorite is used, it can be dribbled down the casing vent. Sodium

hypochlorite should be pumped using a tube down the casing vent to the bottom of 

the well. 

• Surge the well at least 3 times to provide mixing. 

• Leave the chlorine solution in contact with the well for 12 to 24 hours. 

• Establish at least a 2 inch pressure tight connection from the pump discharge piping 

to the casing vent. 
• Operate the pump against a throttled discharge valve to return several hundred 

gallons per minute flow to the casing vent, not to exceed one half the well’s capacity, 

while the rest is discharged to waste. Be sure the throttle is not so extensive as to 

cause damage to the well or piping. 

• Continue the discharge until no chlorine residual is detected for at least 15 minutes. 

• After there is no detectable residual, the well should be tested for coliform bacteria. If 

coliform bacteria are detected, the well should be pumped for another 15 minutes and 

re-sampled. If still positive for bacteria, it must be re-disinfected or undergo 

corrective action to correct the contamination source. 

The discharge of chlorinated water is a potential problem and is discussed in Section 

3.1.3.4. 

4.4 Switching to a Surface Water Source 

It may become necessary for a utility to switch to a surface water source if alternate 

reliable and safe ground water sources are not available. Surface waters are generally more 

susceptible to chemical and microbial contamination and are therefore usually treated more 

extensively than ground water sources before serving the public. Ground water systems 

switching to a surface water source often require large investments to modify their treatment 

trains and set up additional unit processes (along with the necessary instrumentation, controls, 

and monitoring systems). In addition to surface water systems having more extensive treatment 

requirements, they also have more elaborate reporting requirements and usually require more 

highly trained operators. 

Systems switching to surface water sources are often required to obtain a permit from the 

State for drawing water from the surface water body. This may be a more challenging prospect in 

areas where water rights are an important factor, especially in areas of the country threatened by 

drought. 

Surface water intakes on streams or rivers should be located upstream of sewer outlets 

and other sources of contamination. If a lake or reservoir is used, the intake should be set away 

from discharges with the potential to contaminate the source water being drawn and used. 

Systems should check with their States to see what intake setback distance requirements may 

apply. Utilities should also be aware of the nature and locations of any activities in the watershed 

that may introduce contamination. 

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5. Installing Treatment 

Ground water systems that choose to install treatment to correct significant deficiencies 

or fecal contamination must provide at least 99.99 percent (4-log) inactivation (disinfection) or 

removal (filtration) of viruses. EPA has determined that the treatment technologies or 

combination of technologies that have demonstrated the ability to achieve 4-log inactivation of 

viruses are chlorine (chlorine gas or hypochlorite), chlorine dioxide, ozone, ultraviolet (UV) 

radiation, anodic oxidation, reverse osmosis (RO), and nanofiltration (NF). Though these last 

two, RO and NF, are filtration methods that have demonstrated the ability to remove 4-log of 

viruses (AWWA, 1990b; USEPA, 2006b; USEPA, 2006c), these technologies will have different 

impacts on cost, operation, maintenance, and reporting requirements for systems. Selecting the 

most appropriate treatment technology (or combination of technologies) to achieve 4-log 

treatment is a site-specific decision best left to utility personnel and State agencies. 

Americans expect tap water to be available at reasonable costs, with minimal to no 

associated health risks. In some cases, however, those served by small systems may face 

significantly higher per capita costs both to install and operate new treatment and to employ 

qualified operators needed to ensure compliance with drinking water standards than the per 

capita costs for those served by larger systems. 

Small systems should exhaust all possible options (including switching to higher quality 

source water such as another ground water well) before installing new technologies. Purchasing 

water from another system is another potentially lower cost option for small systems. If full 

water treatment is necessary, a package treatment plant may be a lower-cost option. While 

disinfection technology designs are readily available without need for pilot studies prior to 

installation systems may find pilot studies useful in minimizing DBP formation and in lowering 

costs to meet pathogen inactivation requirements. The effectiveness of disinfection systems is 

based on laboratory results that are applicable to all systems. 

This chapter describes the types of treatment that can be used to achieve 4-log 

inactivation or removal of viruses. It is organized in three main sections: 

• Chemical disinfection (Section 5.1); 

• UV light disinfection (Section 5.2); and 

• Membrane technologies-filtration (Section 5.3). 

This chapter provides an overview discussion of each treatment technology along with 

advantages and disadvantages of each to help systems and States with the selection process. In 

addition, Section 5.4 provides a list of additional references where systems and States can find 

more detailed information. 

GWSs that install disinfection or filtration treatment must demonstrate (through 

compliance monitoring as specified in 40 CFR 141.403(b) of the GWR), that their treatment 

reliably and effectively achieves 4-log virus inactivation, removal, or a State-approved 

combination of inactivation and removal before or at the first customer. Existing GWSs that 

provide such 4-log treatment and want to avoid triggered source water monitoring must notify 

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the State in writing of their treatment status by December 1, 2009, and include engineering, 

operational, or other information requested by the State to evaluate the submission. GWSs with a 

new ground water source going into service after November 30, 2009, that provide 4-log 

treatment must also notify the State in writing to that effect (and also include engineering, 

operational, or other information requested by the State to evaluate the submission). GWSs with 

new ground water sources that are disinfected must initiate compliance monitoring within 30 

days of placing the source in service. 

The requirements for systems choosing to conduct compliance monitoring or required to 

conduct compliance monitoring vary depending on the type of treatment provided and, for those 

systems using chemical disinfection, the size of the system. In addition, the exact treatment 

technique standards (e.g., disinfectant concentration level) will be defined by each State and may 

differ significantly from State to State. 

GWSs using chemical disinfection must maintain the State-determined residual 

disinfectant concentration every day the system serves water from the ground water source to the 

public. Disinfectant residual monitoring must be conducted in accordance with 40 CFR 141.74 

(a)(2): 

• GWSs serving more than 3,300 people and using chemical disinfection must monitor 

the residual disinfectant concentration continuously at a location approved by the 

State. Systems doing continuous monitoring must record the lowest residual 

disinfectant concentration each day. If there is a failure in the continuous monitoring 

equipment, the system must conduct grab sampling every four hours until the 

equipment is returned to service. Continuous monitoring must resume within 14 days. 

• GWSs serving 3,300 or fewer people and using chemical disinfection must either take 

a daily grab sample during the hour of peak flow (or at another time specified by the 

State) or monitor the residual disinfectant concentration continuously. For systems 

taking grab samples, if a daily grab sample is below the State-determined residual 

disinfectant concentration, the system must take follow-up samples every four hours 

until the residual disinfectant concentration is restored to the State-determined level. 

A GWS that uses membrane filtration to achieve 4-log virus removal must monitor and 

operate the membrane process in accordance with all State-specified requirements. The system is 

in compliance if: 

1. The membrane has an absolute molecular weight cut-off (MWCO) (or an alternate 

parameter describing the membrane’s exclusion characteristics) that can reliably 

achieve 4-log removal of viruses; 

2. The membrane process is operated in accordance with State-Specified compliance 

requirements; and 

3. The integrity of the membrane is intact. 

A GWS that uses an alternative State-approved treatment (i.e., other than chemical 

disinfection or membrane filtration) must monitor and operate the alternative treatment in 

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accordance with State-specified requirements that the State determines are necessary to achieve 

at least 4-log virus inactivation, removal, or a combination of inactivation and removal before or 

at the first customer. 

5.1 Chemical Disinfection 

Chemical disinfection of viruses involves maintaining a certain disinfectant concentration for 

a period of time. Desirable properties for a chemical disinfectant include: 

• Inactivates pathogens of concern, 

• Stability, 

• Solubility, 

• Low toxicity to humans and other animals that are exposed during normal operation 

(or ability to control exposure), 

• Dependability, 

• Residual effect, 

• Ease of use and measurement, 

• Availability, and 

• Low cost. 

In general, the level of inactivation depends on site-specific water quality parameters such as 

temperature, pH, and TOC. 

The CT value is the residual disinfectant concentration (in milligrams per liter (mg/L)) 

multiplied by the contact time (the time in minutes it takes the water to move between the point 

of disinfectant application and a point downstream before or at the first customer during peak 

hourly flow) (USEPA 1991). The system compares the CT value achieved to the published CT 

value for a given level of treatment to determine the level of treatment attained. As long as the 

CT value achieved by the system meets or exceeds the CT value needed for 4-log inactivation or 

removal of viruses, the system meets the treatment technique requirement of the GWR. Exhibit 

5.1 presents the required CT values identified by the SWTR that achieve 2-, 3-, and 4-log 

inactivation of viruses with chlorine. Note that much higher CTs are required to achieve 4-log 

inactivation at pH 10 than at pH 6 to 9. The contact time (the “T” in “CT”) is affected by baffling 

factors; in addition not all processes receive credit for the full “time” that it can take for water to 

go through the process. 

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Exhibit 5.1 CT Values for Inactivation of Viruses by Free Chlorine (mg-min/L) 

Temperature 

(

o

C) 

Log Inactivation1 

2.0 3.0 4.0 

pH 6-9 pH 10 pH 6-9 pH 10 pH 6-9 pH 10 

0.5 6 45 9 66 12 90 

5 4 30 6 44 8 60 

10 3 22 4 33 6 45 

15 2 15 3 22 4 30 

20 1 11 2 16 3 22 

25 1 7 1 11 2 15 

Source: EPA, 1991 

1. Presents data for inactivation of Hepatitis A virus (HAV) at pH = 6 - 9, and 10 and temperature = 0.5, 5, 10, 15, 20, 

and 25 degrees centigrade (o

C). CT values include a safety factor of 3. To adjust for other temperatures, simply 

double the CT value for each 10o

C drop in temperature. 

The Guidance Manual for Compliance with the Filtration and Disinfection Requirements 

for Public Water Systems Using Surface Water Sources (EPA 1991) presents a detailed 

description of the application of the CT concepts to disinfection practices. 

Contact time, contact tank design, and baffling are all interrelated in the area of 

disinfection treatment of the finished water supply. All of these areas of scenario design are 

important in ensuring that the disinfectant is allowed adequate contact time with the 

contaminated water in order to inactivate viruses and other microorganisms. When a disinfectant 

like chlorine is added to the water supply, it reacts with other chemicals in the water (e.g., iron, 

manganese, hydrogen sulfide, and ammonia) and is not fully available for disinfection. The 

amount of disinfectant that reacts with the other chemicals plus the amount required to achieve 

disinfection represents the disinfectant demand of the water. Disinfectant demand may change 

with dosage, time, temperature, pH, and nature and amount of the impurities in the water. 

For instance, chlorine is the most commonly used chemical disinfectant. The chlorine 

dose (in mg/L) is the amount of chlorine added to satisfy the chlorine demand and provide a free 

chlorine residual up to the end of the contact period: 

Chlorine dose = chlorine demand + free available residual chlorine (the “C” in “CT”) 

Within the distribution system, free chlorine residuals range from 0.2 mg/L to as high as 3-3.5 

mg/L in some systems. Most US systems maintain a chlorine residual above 0.2 mg/L in the 

distribution system (AWWA, 1990b). EPA has established maximum residual disinfectant levels 

(MRDLs) that cannot be exceeded without incurring a violation. Systems experiencing high 

levels of disinfection byproducts (DBPs) in their distribution systems should work with the State 

or their engineer to identify compliance options. See the Simultaneous Compliance Guidance 

Manual (USEPA, 2007a) for more information. 

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In addition to inactivation of viruses and harmful microbes, chemical disinfection serves 

other useful purposes in water treatment including: 

• Taste and odor control; 

• Prevention of algal growths; 

• Maintenance of clean filter media; 

• Removal of iron and manganese; 

• Destruction of hydrogen sulfide; 

• Bleaching of certain organic colors; 

• Maintenance of distribution system water quality; 

• Restoration and preservation of pipeline capacity; and 

• Restoration of well capacity, water main sterilization. 

Some of the above list apply more generally to surface water systems, while others apply 

to all systems. Chemical disinfection technologies discussed in this chapter include chlorine 

(applied in the form of chlorine gas or hypochlorite solution), chlorine dioxide, and ozone. The 

most commonly used disinfectants in small systems are chlorine gas or hypochlorite solution. 

Chloramines are not addressed, as they are ineffective for virus inactivation, but they may be 

used as a secondary disinfectant. 

5.1.1 Temporary Hypochlorination 

If a system is found to have a significant deficiency or fecal contamination, it may take 

time for the system to design and install a corrective action. In the meantime, the system should 

not serve the contaminated water to its customers. The Primacy Agency may require the system 

to apply 4-log virus disinfection until the contamination is eliminated or a corrective action is put 

in place. For most applications, hypochlorination should be used because it is easier to install and 

operate than gaseous chlorination or other disinfection methods and is the least costly of the 

treatment methods. Although hypochlorination may be a viable temporary solution, systems 

should remember that there is an ongoing cost of operation, maintenance, and reporting for water 

that remains unsafe, so eliminating contamination or completing a corrective action as soon as 

possible is recommended. 

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5.1.2 Chlorine Gas 

5.1.2.1 Background 

Disinfection using chlorine gas is less common at water utilities than in the past, but is 

still widely used. This process involves the addition of elemental chlorine (Cl2) to the water 

supply at one or more locations within the treatment train. Elemental chlorine is typically 

supplied as a liquefied gas. It comes in high-pressure containers that typically weigh between 

100-2000 lbs. 

Although it is extensively used for many purposes, there are some safety and security 

issues associated with the use of chlorine gas. Facilities storing more than 1,500 pounds of 

chlorine are subject to the Process Safety Management standards regulated by the Occupational 

Safety and Health Administration under 29 CFR 1910 and the Risk Management Program Rule 

administered by EPA under Section 112(r) of the Clean Air Act. All of these regulations (as well 

as local and State codes and regulations) should be considered during the design and operation of 

chlorination facilities at a water treatment plant. Systems should develop appropriate safety and 

security plans when installing chlorine gas. Systems should also have their own safety equipment 

and operators should take the following precautions when using or handling chlorine gas: 

• Chlorine gas is poisonous and corrosive; therefore, adequate exhaust and ventilation 

should be used when applying chlorine for water treatment. The ventilation should be 

positive at the floor level because chlorine gas is heavier than air. Operators should 

wear proper personal protective equipment including goggles, gloves, and respirators. 

Each operator should also have access to a self-contained breathing apparatus. 

• Liquid and gaseous chlorine should be delivered using rubber lined or polyvinyl 

chloride (PVC) piping with hard rubber (using rubber lined or PVC piping will 

increase the life of the piping system and decrease maintenance costs). 

• Cylinders should be placed on platform scales that are flush with the floor and 

continuously monitored for leaks. Loss of weight of the cylinders should be directly 

recorded as chlorine dosage. 

5.1.2.2 System Design 

The design criteria for chlorine disinfection usually encompass a variety of factors to 

ensure proper chlorine dose application. Some of these factors are chlorine gas application (gas 

delivery), contact time, contact tank design, contact tank baffling, and residual effluent water 

concentrations. 

The chlorinator is a supply-metering device for chlorine gas controlled by regulated 

pressure and/or variable orifices. The chlorine feed rate can be manually or automatically 

regulated. It is also convenient to use an electronic or mechanical scale to measure the chlorine 

gas usage. A scale will allow the system to determine a cylinder's content level. Scales are 

intended for use in chlorination and other gas feeding applications and can be used to measure 

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liquefied chlorine, sulfur dioxide, ammonia, hydrogen chloride, or carbon dioxide packaged in 

cylinders. Small systems may choose to use manual chlorination to control chlorine dosage. 

Contact time, contact tank design, and baffling are all interrelated in the area of chlorine 

gas treatment of the finished water supply. All of these areas of scenario design are important in 

ensuring that the chlorine gas is allowed adequate contact time with the contaminated water in 

order to inactivate viruses and other microorganisms. When chlorine is added to the water 

supply, it reacts with other chemicals in the water (e.g., iron, manganese, hydrogen sulfide, and 

ammonia) and is not fully available for disinfection. The amount of chlorine that reacts with the 

other chemicals plus the amount required to achieve disinfection represents the chlorine demand 

of the water. Since chlorine is hazardous and corrosive, systems should store chlorination 

equipment away from other treatment facilities and chemicals. Chlorine can also react with 

natural organic matter in drinking water and form harmful byproducts. Systems experiencing 

high levels of disinfection byproducts (DBPs) in their distribution systems should work with the 

State or their engineer to identify compliance options. See the Simultaneous Compliance 

Guidance Manual (USEPA, 2007a) for more information. 

5.1.2.3 Operation and Maintenance 

Normal operation of gas chlorination includes both routine observation and preventive 

maintenance. On a daily basis the operator should: 

• Read the chlorination rotameter; 

• Record the reading time, date, and initial entries; 

• Read flow meters and record the number of gallons of water pumped; 

• Check the chlorine residual and increase or decrease the chemical feed rate of the 

chlorine gas mixture based on the residual concentration; and 

• Calculate and record the chlorine usage. 

On a weekly basis the operator should: 

• Clean all of the equipment and the chlorine storage and housing area; and 

• Perform any necessary preventive maintenance on the application equipment and 

piping. 

Individual States may have additional or more stringent requirements for routine observations 

and preventative maintenance. Systems should consult the State for specific requirements. 

5.1.2.4 Advantages and Disadvantages 

Chlorine has many attractive features that contribute to its wide use in the industry. The 

use of chlorine gas is highly advantageous because it is readily available. There is an abundance 

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of chlorine gas for continuous plant operation without any significant chemical mixing, which 

makes the process much easier to apply. Chlorine leaves a residual that is easily measured and 

controlled. Chlorine is also economical and has an excellent track record of successful use in 

improving water treatment operations. 

There are also disadvantages in using chlorine as a disinfectant. The use of chlorine 

promotes the formation of chlorinated organic compounds, such as trihalomethanes (THMs), 

which are potentially harmful to humans. CWSs and non-transient non-community water 

systems (NTNCWSs) must comply with DBP MCLs and monitoring requirements if chlorine or 

other disinfectants are used. In addition, high chlorine doses can cause taste and odor problems. 

Chlorine gas has specific hazards associated with its use or misuse and requires special 

handling and response programs. Chlorine gas combines with the mucous membranes in the nose 

and throat, as well as the fluids in the eyes and lungs, irritating and inflaming those areas. 

Therefore, a very small percentage of chlorine gas in the air can irritate the lungs and cause 

severe coughing; heavy exposure can be fatal (White, 1999). Systems should ensure that safety 

equipment (e.g., eye wash, shower, chlorine gas detectors) is routinely available, routinely check 

for leaks in the chlorine cylinders, and routinely clean interior parts of the gas chlorination 

system. For emergency purposes, self-contained breathing apparatuses should be available 

outside the chlorine gas cylinder storage area. 

5.1.3 Hypochlorite 

5.1.3.1 Background 

Many properties of hypochlorite are similar to those of chlorine gas as far as oxidizing 

principles and corrosiveness of the substance; however, since storage of hypochlorite is generally 

safer than storage of chlorine gas, many small systems choose to use hypochlorination instead of 

gaseous chlorination to treat their drinking water. Hypochlorite compounds are non-flammable; 

however, they can cause fires when they come in contact with certain organic compounds or 

easily oxidizable substances. If a spill occurs, then it should be washed with a large amount of 

water and cleaned up immediately. Skin contact with hypochlorite can burn the skin and may 

cause damage to the eyes. 

Systems typically use either sodium hypochlorite (NaHOCl) or calcium hypochlorite 

(CaHOCl). Sodium hypochlorite, which is produced when chlorine gas is dissolved in a sodium 

hydroxide solution, is most commonly used in aqueous form. Calcium hypochlorite, which is 

formed from the precipitate that results from dissolving chlorine gas in a solution of calcium 

oxide (lime) and sodium hydroxide, is more commonly used in dry solid form (White, 1999). 

Sodium hypochlorite is available in concentrations of 5 to 15 percent, and typically 

contains 12.5 percent available chlorine (White, 1999). One gallon of 12.5 percent sodium 

hypochlorite solution typically contains the equivalent of one pound of chlorine. Sodium 

hypochlorite (commonly referred to as liquid bleach or Javelle water) can be purchased in bulk 

quantities ranging from 55-gallon drums to 4,500-gallon truckloads. Bulk loads can be stored in 

fiberglass or plastic tanks. The stability of the sodium hypochlorite solution depends on 

hypochlorite concentration, storage temperature and duration, impurities of the solution, and 

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exposure to light. Decomposition of hypochlorite over time can affect the feed rate and dosage, 

as well as produce undesirable byproducts such as chlorite ions or chlorate (Gordon et al., 1995). 

Because of these storage problems and high transport cost, many systems are investigating onsite 

generation of hypochlorite instead of purchasing it from a manufacturer or vendor (USEPA, 

1998). 

Calcium hypochlorite has a high oxidizing potential and typically comes in the powdered 

form of high-test hypochlorite (HTH). Calcium hypochlorite also comes in tabular and granular 

forms containing at least 65 percent available chlorine and dissolves easily in water (USEPA, 

1991). This means that 1.5 pounds of calcium hypochlorite contains the equivalent of one pound 

of chlorine. Similar to sodium hypochlorite solution, the addition of calcium hypochlorite to 

water yields hydroxyl ions that will increase the pH of the water. One option for continuous 

chlorination is the use of HTH tablet erosion feeders. These are devices containing HTH tablets. 

As water feeds through the device, the HTH erodes and dissolves it into solution, which is then 

reintroduced to the raw water. 

Calcium hypochlorite is stable under proper storage and is therefore favored for most 

hypochlorite disinfection schemes. Calcium hypochlorite should be stored in a cool dry location 

in corrosion-resistant containers away from heat sources or organic materials such as wood, 

cloth, and petroleum products (USEPA, 1998). 

5.1.3.2 System Design 

The application of hypochlorite in potable water achieves the same result as chlorine gas. 

Therefore, similar contact times and concentrations are used in design (White, 1999). Systems 

apply hypochlorite by injecting a stock solution into the water supply using chemical metering 

pumps (hypochlorinators). Systems should ensure that mixing occurs to have adequate 

disinfection. Typically, positive displacement meters and pumps are employed as feed 

mechanisms for hypochlorite. These types of hypochlorinators are designed to pump an aqueous 

chlorine solution into the water being pumped and treated and are usually available at a modest 

price. These pumps are typically designed to operate against pressures up to 100 psi but can also 

be used to inject chlorine on the suction side of the pump. These pumps are quite accurate and 

have been found to maintain a constant dose as long as the water flow is relatively constant. If 

this is not the case, a metering device is placed on the pump to vary the dosage in conjunction 

with the flow rate of the water being treated. 

5.1.3.3 Operation and Maintenance 

In general, hypochlorination facilities are easier to operate than gas chlorination facilities. 

Operation and maintenance (O&M) costs include daily, weekly, and monthly operations, 

preventive maintenance, and personnel training and certification. Activities regularly conducted 

at hypochlorination facilities are listed below. 

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On a daily basis the operator should: 

• Read and record the level of the solution tank at approximately the same time 

everyday; 

• Read meters and record the amount of water pumped; 

• Check the free chlorine residual and adjust as necessary; and 

• Observe chemical pump operation by reading the dial that indicates chlorine feed 

rate. The pump should be operated in the upper ranges of the dial for optimum 

performance. Also, frequency of piston or diaphragm strokes should be such that 

hypochlorite is constantly being supplied to the water that is being treated. 

On a weekly basis the operator should: 

• Clean the building and all application equipment; and 

• Replace chemicals and wash all chemical storage equipment. 

On a monthly basis the operator should: 

• Check the operation of all delivery equipment and examine all safety devices such as 

check valves and backup power devices; and 

• Perform all preventive maintenance on system, and check for leaks and corrosion. 

Small system hypochlorinators typically have a limited number of repairable parts. 

Therefore, it is often advisable to replace all essential parts at the time of any single part failure. 

Minor maintenance, such as oil changes and lubrication of all moving parts, can significantly 

increase the life span of small system hypochlorinators. 

5.1.3.4 Advantages and Disadvantages 

Hypochlorite has many of the same advantages and disadvantages of gaseous chlorine as 

described in Section 5.1.2.4, including DBP compliance requirements for CWSs and NTNCWSs. 

However, hypochlorite may be more advantageous than chlorine for small systems because spills 

and leaks of hypochlorite can be more easily managed and contained than chlorine gas leaks. 

Additional advantages and disadvantages associated with the use of hypochlorite are discussed 

below. 

Sodium hypochlorite is easier to handle than chlorine gas or calcium hypochlorite, 

however, it is very corrosive and should be stored with care and kept away from equipment that 

can be damaged by corrosion. It also should be stored in a cool, dark, and dry area and cannot be 

stored longer than one month. 

Calcium hypochlorite is very stable when properly packaged and can be stored up to a 

one year. Since it is a corrosive material with a strong odor, it should be properly handled and 

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stored. Reactions with organic material can generate enough heat to cause an explosion. Since it 

readily absorbs moisture, forming chlorine gas, shipping containers should be emptied 

completely or carefully resealed. Also, using calcium hypochlorite in dust form requires dust 

control practices to guard against breathing the dust and minimizing skin exposure. 

5.1.4 Chlorine Dioxide (ClO2) Disinfection 

5.1.4.1 Background 

Chlorine dioxide is one of the most powerful oxidizing agents used for water treatment. It 

is also used to control taste and odor, iron, manganese, hydrogen sulfide, and phenolic 

compounds. The SWTR Guidance Manual (AWWA, 1991) provides CT values for inactivation 

of viruses as shown in Exhibit 5.2. 

Exhibit 5.2 CT Values (mg-min/L) for Inactivation of Viruses1

 by Chlorine Dioxide 

for pH 6 to 9 

Inactivation Temperature 

< 1oC 5oC 10oC 15oC 20oC 25oC 

2-Log 8.4 5.6 4.2 2.8 2.1 1.4 

3-Log 25.6 17.1 12.8 8.6 6.4 4.3 

4-Log 50.1 33.4 25.1 16.7 12.5 8.4 

Source: EPA, 1991 

1. Studies pertain to the Hepatitis A virus. 

Chlorine dioxide is a highly unstable material and is typically generated onsite for the 

disinfection of water. Chlorine dioxide gas is yellow/red, has a noticeable odor, and is more 

explosive than in the liquid form. 

It exists in solution without the need for hydrolysis and disinfects by oxidation, not by 

chlorination. Since free chlorine species are not the reactants, the production of THMs in the 

distribution system are highly unlikely; however, total organic halogen (TOX) may be produced. 

Waters with high alkalinity reduce the yield and effectiveness of chlorine dioxide by reducing 

the oxidation-reduction potential and give rise to potentially harmful byproducts. 

5.1.4.2 System Design 

Chlorine dioxide is most frequently generated using aqueous sodium chlorite solution 

(White 1999). Sodium chlorite is used in the liquid or solid form along with a high level acid 

mixture to create chlorine dioxide that is used to treat the influent water. The formation reaction 

for chlorine dioxide is more effective at a lower pH. 

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If mixed properly, the production of chlorine dioxide will generate a 95 percent yield 

with no more than 5 percent excess chlorine in the effluent. If this is the case, there is minimal 

potential for THM and haloacetic acid (HAA) formation in the effluent plant flow. 

5.1.4.3 Operation and Maintenance 

O&M of a chlorine dioxide generation system requires significant knowledge of the 

system. Therefore, it is important to have highly trained personnel operating and maintaining 

sodium chlorite storage and feed systems and chlorine dioxide generator and feed equipment. 

Compared to other disinfectants, chlorine dioxide has a low MRDL; exceeding the MRDL is 

considered an acute health risk and requires immediate response. Chlorine dioxide generation 

requires constant monitoring and tweaking of the chlorine dioxide production amount, based on 

any changes in the original amount of water being treated and the flow rate of the water being 

treated. Also, the volatility of the chlorine dioxide generation process, which can create a risk of 

explosion, must be taken into account when working with chlorine dioxide generation. 

On a daily basis, operators should adjust flow meters and rotameters that control all gas 

flow within the plant. Also, constant monitoring of all delivery equipment should take place to 

ensure the highest amount of chlorine dioxide yield efficiency. For example, operators should 

take measures to prevent crystallization (that can go through the pipes and plug valves and 

generator equipment) or stratification (i.e., more dense material shifts to the bottom of the bulk 

(storage) tank causing an inappropriate level of feed) of sodium chlorite. Operators should be 

trained in the areas of equipment calibration as well as start-up and shut-down procedures for the 

plant in the event of an emergency. Proper calibration of all application equipment keeps the cost 

of operation down as well. 

5.1.4.4 Advantages and Disadvantages 

Systems have found that there are many advantages to using chlorine dioxide to disinfect 

water supplies. Chlorine dioxide is more effective than chlorine for inactivation of Giardia and 

Cryptosporidium. Also, it does not react with ammonia or nitrogen to form unpleasant tastes and 

odors or react with any oxidizable materials that aid in the formation of THMs and HAAs. In 

fact, chlorine dioxide destroys as much as 30 percent of all DBP precursors allowing free 

residual chlorination to be used without the production of unwanted THMs and HAAs within the 

distribution system (Lagerquist et al., 2004). Chlorine dioxide is also advantageous because its 

biocidal properties are not affected by the pH at levels from 6 to 9. Chlorine dioxide is also 

superior to chlorine in the oxidation of iron and manganese from water, and it provides a 

residual, although the residual is limited with high levels of total organic carbon (TOC). 

There are several disadvantages to chlorine dioxide use. Chlorine dioxide is not as costeffective as chlorination since the chemical cost of chlorine dioxide is several times that of 

chlorine (White, 1999). It is generally less effective than chlorine for inactivation of viruses. 

Chlorine dioxide also forms chlorite, a regulated DBP. The MCL for chlorite was set at 1.0 mg/L 

and the MRDL was set at 0.8 mg/L by the Stage 1 Disinfection/Disinfectants Byproducts Rule 

(D/DBPR). All systems (including transient systems) using chlorine dioxide must comply with 

an intensive compliance monitoring schedule that includes monitoring daily at the entrance to the 

distribution system for both chlorine dioxide and chlorite. If either exceeds the federal standard, 

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the system must collect 3 follow-up samples the next day in the distribution system. They must 

also collect 3 chlorite samples per month in the distribution system. As much as 70 percent of the 

chlorine dioxide added to water can break down to form chlorite. This limits the dose of chlorine 

dioxide that can be used and therefore the amount of inactivation that can be achieved. 

Due to its high volatility and explosive nature, chlorine dioxide should be generated onsite and cannot be transported. There are also high costs associated with containing the 

compound and proper operator and maintenance training. Storage of the compound should be 

monitored very carefully since chlorine dioxide decomposes in sunlight. 

Additional information on advantages and disadvantages of chlorine dioxide are available 

in the Simultaneous Compliance Guidance Manual (USEPA 2007a) and the Alternative 

Disinfectants Guidance Manual (USEPA 1999b). 

5.1.5 Ozone (O3) Disinfection 

5.1.5.1 Background 

Ozone is used to inactivate bacteria and viruses and oxidize organic compounds in water 

treatment plants. Ozone treatment is known to reduce problems with taste, odor, and color in 

drinking water. Ozone is injected into the flow of the water being treated by mechanical mixing 

devices, counter-current and co-current flow columns, porous diffusers, or jet injectors. Typical 

ozone dosages range from 3–10 mg/L (AWWA, 1990b). 

Ozone forms highly reactive and highly potent free radicals such as OH-, which are very 

strong oxidizing species. These act quickly to inactivate bacteria and viruses. Because of its 

quick germicidal action, ozone needs relatively short contact time to disinfect most waters, 

provided the initial turbidity of the water being treated is low at the time of ozone addition (as is 

generally the case with ground waters). Exhibit 5.3 provides CT values for virus inactivation by 

ozone. 

Exhibit 5.3 CT Values (mg of O3-min/L) for Virus Inactivation by Ozone 

Inactivation Temperature 

< 1oC 5oC 10oC 15oC 20oC 25oC 

2-Log 0.9 0.6 0.5 0.3 0.25 0.15 

3-Log 1.4 0.9 0.8 0.5 0.4 0.25 

4-Log 1.8 1.2 1.0 0.6 0.5 0.3 

Source: EPA, 1991 

Ozone is a powerful oxidant of organic materials, breaking them into smaller chain 

organic molecules. These smaller chain particles, sometimes measured as AOC are an easily 

degradable food source for microorganisms in the distribution system. While biological filtration 

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following ozonation can effectively remove these materials to create biologically stable finished 

water and reduce the occurrence of microbial growth in the distribution system, it may not be 

necessary for ground waters with low TOC (USEPA 2007a). 

5.1.5.2 Operation and Maintenance 

The general O&M needs for an ozonation facility are labor, energy, and materials. The 

three O&M cost categories are daily operation, preventive maintenance, and personnel training. 

The time spent on operation activities varies by the size of the facility. Although ozone 

generators are complex, they use complete automation and require modest amounts of time for 

routine maintenance. Technicians require training in preventive maintenance and repair to 

operate the ozone generator. This includes checking the generator and keeping system parts 

clean. Ozone is a strong oxidizer; therefore, the system parts require cleaning to prevent 

corrosion. Parts requiring occasional cleaning are the ozone contacting unit and the ozone 

exhaust gas destruction unit. Other parts for the dehumidifying process also require cleaning and 

maintenance. In addition, users should clean the air preparation or oxygen feed and dehumidify 

the saturated desiccant. 

Ozone leaks in and around the ozone generation facility may create a health hazard to 

operators of the treatment plant and may destroy or enhance the wear of other equipment 

materials. Therefore, facilities should apply strict safety measures, install an ozone gas detector, 

and periodically check alarms. 

The materials needed to ensure the equipment functions adequately comprise the final 

O&M component of the ozonation facility. Materials include cleaning chemicals, replacement 

parts, and additional necessary supplies for periodic maintenance, system cleaning, and 

unanticipated breakdowns. 

5.1.5.3 Advantages and Disadvantages 

Ozone has powerful disinfection capabilities. Its high diffusion characteristics make it 

one of the most efficient chemical disinfectants, with its contact time of only a few minutes. 

Ozone inactivates microbes without forming chlorinated DBPs. Ozone also oxidizes iron and 

manganese and improves the taste, odor, and color of raw water. It enhances the biodegradability 

of natural and synthetic organic compounds and destroys many organic compounds. Due to its 

relatively short half-life and safety issues, ozone requires on-site production. Due to the 

difficulty in determining an adequate dose, ozone is most beneficial to systems with a constant 

demand or little demand fluctuation, such as ground water systems. 

Disadvantages of ozone include its relatively high cost and complexity in its use 

(AWWA, 1990b). Relative to other treatment technologies, ozone also requires more highly 

skilled operators. Ozone decomposes quickly in water with high pH levels (about 8-9) and 

therefore does not provide an adequate residual to protect against recontamination in distribution 

or water storage systems (USEPA, 1999b). Therefore, secondary disinfection may be required. If 

the source water has a high bromide concentration, ozone can react with bromide to form 

bromate, a regulated DBP. CWSs and NTNCWs using ozone are required to comply with a 10 

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microgram per liter (μg/L) MCL for bromate. Ozonation in conjunction with chlorination could 

result in high concentrations of brominated DBPs. 

Water containing large amounts of organic matter and bromide may increase ozone 

demand and the potential for byproduct formation. However, high natural organic matter (NOM) 

content in raw waters is generally not an issue for most ground water systems. 

5.2 UV Radiation Disinfection 

5.2.1 Background 

UV disinfection continues to grow in popularity as a microbial treatment strategy. UV 

light is generated artificially through a wide variety of arcs and incandescent lamps. Low 

pressure mercury-vapor lamps produce UV light as a result of an electron flow between the 

electrodes in an ionized mercury vapor. The principle behind inactivating microorganisms is 

based on photochemical reactions that result in nucleic acid and pyrimidine and/or thymine 

dimerization, disrupting the reproductive system. UV light has proven to be effective in the 

inactivation of several waterborne organisms such as Giardia, E.coli, some viruses, and most 

recently, Cryptosporidium (USEPA, 2006b). 

Unlike chemical disinfection, UV leaves no residual that can be monitored to determine 

UV dose and inactivation credit. The UV dose depends on the UV intensity (measured by UV 

sensors), the flow rate, and the UV transmittance (UVT). As described further in Section 5.2.5, 

the very high dose requirements for 3- and 4-log virus inactivation present challenges for 

validation testing of UV reactors (USEPA, 2006b). Exhibit 5.4 presents UV dose requirements 

for virus inactivation. 

Exhibit 5.4 UV Dose Requirements for Virus Inactivation (mJ/cm2) 

Log Inactivation 

1.0 2.0 3.0 4.0 

UV Dose 58 100 143 186 

Source: 40 CFR 141.720 (d)(1) 

The doses in Exhibit 5.4 are based on the inactivation of adenoviruses, which are 

particularly resistant to UV light. EPA is concerned that fecally-contaminated ground water may 

contain adenoviruses and/or other UV resistant viruses that present a human health risk. The UV 

doses in Exhibit 5.4 are significantly higher than those considered for the proposed GWR 

(USEPA, 2000). When developing the proposed rule, EPA considered only the UV inactivation 

of Hepatitis A virus (HAV), which is much less resistant to UV light than adenovirus. Based on 

HAV inactivation alone, EPA included UV light in the GWR proposal regulatory text as a standalone treatment technology that could provide 4-log virus inactivation. However, data published 

subsequent to the GWR proposal indicated that some viruses, particularly adenoviruses, are 

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much more resistant to UV light than HAV. EPA believes that the UV doses in Exhibit 5.4 are 

sufficient to achieve the designated level of inactivation of all waterborne pathogenic viruses that 

have been studied. 

5.2.2 Inactivation Mechanism and Effectiveness 

Proteins and nucleic acids absorb invisible shortwave UV light. The photochemical 

changes induced by molecular absorption are very harmful to living cells. The most effective 

spectral region corresponding to maximum absorption by nucleic acids is around 254 nm 

(USEPA, 2006b). UV affects the cell replication process by promoting the dimerization reaction 

of pyrimidine nucleotides. Inhibition of replication results in inactivation and the death of cells. 

5.2.3 System Design 

Detailed guidance on UV system design can be found in Ultraviolet Disinfection 

Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule (EPA 

815-R-06-007) (USEPA, 2006b). The guidance manual is available on line at 

http://www.epa.gov/safewater/disinfection/lt2/compliance.html. The design should include a UV 

reactor with accessible banks of lamps so that maintenance of the lamps can be accomplished. 

This maintenance includes cleaning of quartz sleeves and replacement of sensors and ballasts. 

Access to the critical parts of the UV reactor minimizes off-line operation of the UV disinfection 

portion of the treatment scheme. Also, the design of a UV disinfection system should always 

include redundancy to ensure continuous microbial inactivation. 

UV lamps emit UV light that passes through the quartz sleeve and into the water to be 

treated. The microorganisms are inactivated by the UV light that transmits through the water, 

into the cell, and is partially absorbed by the microorganism’s DNA. As a result, the water’s 

turbidity, turbulence and the presence of UV absorbing substances are the principle factors that 

affect the UV transmittance through the water. 

For design purposes, it is important that turbulence occurs (to allow all elements of fluid 

to come sufficiently close to the lamp surfaces), but short circuiting should be minimized. In 

some cases, within the chamber, there are baffles that force the flowing water being treated to 

travel tangentially through the chamber in a spinning motion around the quartz sleeves. This 

increases the light versus water contact time and therefore increases the level of disinfection 

achieved. 

UV has been employed in a variety of physical configurations. Lamp placement may be 

horizontal (perpendicular to the flow) or vertical (parallel to the flow). 

Important considerations in evaluating UV as a treatment strategy include: 

• Existing and emergency power supply–A reliable power supply and emergency 

power with adequate capacity (and fuel supply) to support the demand of the UV 

system and provide continuous disinfection. 

• UV equipment availability–What is available for the system size and configuration? 

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• UV doses needed-Is it feasible to provide the necessary UV doses to the water being 

treated, or does the current system configuration or operation require other 

consideration of other disinfection or removal strategies? 

• Cost–Are total suspended solids, color, and turbidity a problem in the supply? These 

factors may require additional treatment processes and increase capital and/or 

operating costs. 

5.2.4 Operation and Maintenance 

Accumulation of solids onto the surface of UV sleeves can reduce the applied UV 

intensity and, consequently, disinfection efficacy (USEPA, 1999b). If the water being treated 

contains biofilms and/or buildup of inorganics, the lamps are susceptible to scaling. In addition, 

the quartz sleeves can be fouled by organic and inorganic debris in the water. Scaling and fouling 

reduce the amount of UV light reaching the water. Therefore, it is important to minimize 

inorganic and dissolved organics upstream, preventing scaling and increasing UV efficacy. 

The lamps should be maintained by cleaning the quartz sleeves to prevent fouling. If the 

source water is fairly clean, the lamps need not be cleaned as often, and vice versa. Approaches 

for cleaning include on-line mechanical cleaning, on-line mechanical/chemical cleaning, and offline chemical cleaning. On-line systems usually use wipers to remove scale from the sleeves. For 

off-line systems, the reactor is shut down, drained, and flushed with a cleaning solution (USEPA, 

2006b). 

One of the main operational concerns involving UV disinfection is the need for a constant 

and reliable power source to power the ballasts. It is imperative that an alternate, dependable 

power source be supplied to provide continuous disinfection of the water supply. 

The life expectancy of a typical UV lamp varies in the range of 4,000 to 12,000 hours 

(USEPA, 2006b). Because lamp output decays over time, UV lamps should be replaced 

regularly. The replacement schedule should be based on lamp decay characteristics and the 

guaranteed lamp life (USEPA, 2006b). Because lamps contain mercury, they are often 

considered a hazardous waste under Subtitle C of the Resource Conservation and Recovery Act 

(RCRA) and should be disposed of accordingly. 

UV reactors should undergo validation testing to determine the operating conditions 

under which the reactor delivers the UV dose required for the necessary virus inactivation level. 

In general, the operating conditions determined in validation testing should include flow rate, 

UV intensity as measured by a UV sensor, and UV lamp status. These operating conditions, as 

well as any State-specified monitoring or operating conditions, would be both a part of State 

approval of an alternative treatment process that meets the requirement of the GWR and part of 

compliance monitoring for an alternative treatment process for GWR compliance. The 

Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water 

Treatment Rule (EPA 815-R-06-007) (USEPA, 2006b) provides additional information on UV 

disinfection, planning and design of UV facilities, validation of UV reactors, and start-up and 

operation of UV facilities. 

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5.2.5 Advantages and Disadvantages 

UV has many advantages for primary disinfection. Since there is no chemical 

consumption, there is no need for large-scale storage facilities, transportation, or chemical 

handling. UV requires low contact time to inactivate most microorganisms, and forms no known 

harmful byproducts. UV disinfection is not dependent upon temperature or pH. Finally, low 

doses of UV are effective against Giardia and Cryptosporidium. 

There are, however, disadvantages to using UV light for ground water disinfection. A UV 

treatment system can lose power in the event of a power interruption, voltage fluctuation, or 

power quality anomaly. Source water quality can reduce UV transmittance and cleaning costs 

can be significantly increased with poor source water quality. Since UV light does not provide a 

residual disinfectant in the distribution system, a secondary disinfectant may be required. Also, 

very high UV doses are needed for 4-log inactivation of viruses. 

At present, EPA is unaware of available testing protocols that can validate the 

performance of UV reactors at the dose of 186 mJ/cm2 needed for a 4-log virus inactivation 

credit. However, UV reactors validated at lower doses can be used in a series configuration or in 

combination with other inactivation or removal technologies to provide a total 4-log treatment of 

viruses to meet GWR requirements. The GWR allows States to approve and set compliance 

monitoring and performance parameters for any alternative treatment, including UV light or UV 

light in combination with another treatment technology, which will ensure that systems 

continuously meet the 4-log virus treatment requirements. Further, a UV reactor validation 

protocol for 4-log inactivation of viruses may be developed in the future. 

The UV dose requirements shown in Exhibit 5.4 were derived exclusively from studies 

with low pressure (LP) UV lamps. UV dose is well defined and can be determined accurately for 

this type of lamp. However, a recent bench scale study has observed that medium pressure (MP) 

and pulsed UV (PUV) lamps may inactivate viruses, particularly adenovirus, at lower UV doses 

than LP UV lamps (Linden et al., 2007). A recent full scale study also found that MP UV lamps 

may inactivate adenovirus at lower doses than LP UV lamps (Linden et al., 2008). MP and PUV 

lamps emit UV light at many wavelengths (polychromatic), while LP UV lamps primarily emit 

light at a single wavelength. 

If future studies support the finding that MP and PUV lamps inactivate adenoviruses at 

lower UV doses than LP lamps, then the identification of alternative UV doses for virus 

inactivation credit with MP and PUV lamps may be warranted. Such development of UV dose 

requirements for specific polychromatic lamp types would potentially also require the use of 

specialized validation and monitoring approaches to account fully for the effects of different 

light wavelengths. 

5.3 Membrane Filtration Technologies 

Generally, only ultrafiltration, nanofiltration, and reverse osmosis membranes provide 

virus removal. While microfiltration has been shown to achieve partial virus removal in some 

cases, removal is typically attributable to the formation of a time-dependant cake layer on the 

membrane surface, thus microfiltration is generally considered to be unreliable for high levels of 

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virus removal, such as those required by the GWR (USEPA, 2005). Also, bag and cartridge 

filters have not been shown to achieve the necessary virus removal. 

All membrane filtration technologies employ similar filtration mechanisms (including 

sieving, repulsion due to like charges at the membrane/liquid interface, etc.), similar materials, 

and similar module configurations. Their difference lies in their ability to separate particles and 

ions of different sizes and molecular weights. Exhibit 5.5 illustrates the ability of each type of 

membrane process to remove various drinking water contaminants based on size. 

The factors affecting membrane performance include pore size, molecular weight cutoff 

(MWCO), material and geometry, removal of targeted materials, and the quantity (and quality) 

of the treated water. Membrane pore sizes vary with differing technologies; RO systems have a 

smaller pore size than that of NF systems. Membrane performance is measured by recovery. 

Recovery represents the percentage of feed converted to product: 

feed rate - brine rate Recovery Rate = feed rate x 100

Exhibit 5.5 Particle Size Removal for Various Membrane Technologies 

Source: USEPA, 2005 

Generally, the higher the recovery rate, the greater the product water yield from the feed 

water. Factors that determine the recovery rate are water quality and the saturation percentage of 

critical membrane foulants such as calcium and barium sulfates in the concentrate. 

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A number of different types of membrane materials, modules, and systems are used by 

different classes of membrane filtration systems. In general, MF and UF systems use hollowfiber membranes, while NF and RO systems use spiral-wound membranes (USEPA, 2005). A 

spiral wound membrane consists of two flat sheets of membrane separated by a porous support. 

5.3.1 Background 

In drinking water applications, RO is usually employed by systems to reduce the salinity 

of brackish ground water. However, it is also very effective in removing organic and dissolved 

solids, bacteria, and viruses. 

In RO, the water to be treated is forced by high pressure through the membrane (usually 

cellulose acetate or aromatic polyamide) into the product water. Operation pressures vary 

between 300 and 1500 psi, with a typical range of 600-800 psi (Viessman, 1998). 

NF units operate under pressures between 70-150 psi and use thin film 

membranes to filter particles of sizes greater than 1 nm. Typical NF systems employ an MWCO 

of approximately 200 to 800 daltons, but NF membranes used for potable water applications use 

MWCOs of 200 to 400 daltons (USEPA, 2005). NF systems are typically used for water 

softening and removal of NOM. Because of its very small pore size, NF can remove 

exceptionally high levels of microorganisms, including viruses. 

Under the GWR, membrane technologies used to provide 4-log removal of viruses to 

meet GWR requirements must have an absolute molecular weight cut off (MWCO), or an 

alternate parameter that describes the exclusion characteristics of the membrane, which reliably 

achieves at least 4-log removal of viruses. 

Manufacturers of membrane technologies may have performed challenge or 

demonstration studies according to State or other protocols to demonstrate virus removal 

performance. Manufacturers may have also participated in treatment device certification 

programs such as the National Sanitation Foundation (NSF) (http://www.nsf.org) or EPA’s 

Environmental Technology Verification (ETV) Program (http://www.epa.gov/etv). 

5.3.2 System Design 

The key components of an RO or NF plant include: 

• Chemical feed system for pretreatment and pH adjustment; 

• Cartridge filter to remove large particles (greater than 1 micron) that could potentially 

foul the membrane; 

• Medium to high pressure booster pumps for the feed-water; 

• Membrane vessels; and 

• Disposal system for concentrate. 

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Exhibit 5.6 shows a schematic for a typical RO/NF treatment system. 

Exhibit 5.6 Schematic of a Typical RO/NF Treatment System 

Source: USEPA, 2005 

5.3.3 Operation and Maintenance 

The feed-water supply should be checked routinely for changes in water quality (e.g., 

increased concentration of chemical ions like calcium that can cause scaling). Water quality 

parameters, both chemical and biological, should be monitored and the trends charted. Silt and 

iron oxides are common ground water contaminants. The acid injection system consisting of bulk 

storage tanks, chemical feeders, ratio controllers, and injection lines should be routinely checked 

for maintenance and safety related conditions. Acid quality should be verified on the shipments 

and certified analyses reviewed. Operators should routinely calibrate and check pH controllers 

and clean pH probes weekly. 

Cartridge filter vessel drains should be flushed daily, and the pressure drop across the 

filters should be checked and recorded. Upon filter changeout, proper seating of the cartridges 

should be ensured (USEPA, 2005). Residual particulate matter inside the cartridge filter vessel 

should not be allowed to enter downstream piping during filter cartridge changeout. Maximum 

flow rates per individual cartridge should not be exceeded. Membrane block feed-water, brine 

and product conductivity, flows, pH, and pressure should be logged daily. Any unusual changes 

in preset membrane block operating conditions may require adjustment to the system. Highpressure pumps and motors require routine maintenance as recommended by the manufacturer. 

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All instrument systems associated with fail-safe or shutdown conditions should be kept 

operational. Minimum spare parts inventory recommended by the manufacturer should be kept at 

hand. The degasifier packed tower or tray aeration system should be inspected and cleaned 

periodically. Slime buildups occur in degasifiers and require cleaning. Degasifier blowers and 

motors require routine maintenance. 

The GWR also requires that membrane technologies used to provide 4-log removal of 

viruses to meet GWR requirement be operated in accordance with State-specified performance 

requirements and show that the integrity of the membrane is intact. The most accurate method of 

demonstrating membrane integrity currently available is direct integrity testing. The most 

commonly applied direct integrity test is the pressure decay test, but other tests such as the 

vacuum decay test are used in some applications. Three important attributes of a direct integrity 

test are defined in the Membrane Filtration Guidance Manual (USEPA, 2005): sensitivity, 

resolution, and frequency. Available direct integrity tests are capable of demonstrating integrity 

capable of achieving 4-log removal, however, site-specific conditions may result in direct 

integrity test sensitivity lower than 4-log removal. Thus it is important to demonstrate the 

sensitivity of a direct integrity test in each application of the technology. States may choose to 

limit the virus removal credit awarded to a membrane process based on the demonstrated 

sensitivity of the direct integrity test. 

Operation of a membrane treatment system requires disinfecting and cleaning the 

membranes to prevent fouling. Depending on the influent water quality, systems should clean the 

membrane every few days to every few months. Membrane concentrates are usually discharged 

to: 

• Surface waters such as lakes, rivers, or oceans (requiring a NPDES permit); 

• Injection wells (under the UIC program); 

• Sanitary sewers (possibly requiring State or Local Permits); or 

• Evaporation ponds. 

Federal, State, and local authorities, regulations, and permitting requirements regulate 

disposal methods. 

5.3.4 Advantages and Disadvantages 

RO and NF systems are advantageous because they are extremely efficient in removing 

viruses, bacteria, and DBP precursors. 

There are several disadvantages associated with the use of RO and NF, including the high 

cost of the process. Both processes are highly energy-intensive and require a large amount of 

power to sustain proper removal levels of viruses and bacteria. They also require highly skilled 

personnel to operate and maintain the filters and to ensure that proper cleaning of the filters is 

conducted. RO and NF do not provide any residual to control microbial regrowth in the 

distribution system. A disadvantage of RO is that the feedwater may be wasted as brine when the 

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goal is to lower ion concentrations by reducing the permeate recovery. This is especially 

significant in areas with limited water supplies. 

As described previously, the most accurate method of demonstrating membrane integrity 

currently available is direct integrity testing. Resolution is the smallest integrity breach that 

contributes to the response from a direct integrity test. EPA is not aware of any commonly used, 

pressure-based direct integrity test that can achieve a resolution consistent with the size of a virus 

particle. The required test pressure is beyond the pressure tolerances of most membrane 

technologies in use today and pressure-based direct integrity tests applied at lower pressures may 

not detect small integrity breaches that could pass viruses and thus compromise the log-removal 

capability of the system. Appendix E of the Membrane Filtration Guidance Manual (USEPA, 

2005) provides additional information on the application of direct integrity tests to membrane 

processes used for virus removal. 

Continuous indirect integrity monitoring, using turbidity, particle counts or other 

surrogate water quality parameters, may be used to assess membrane integrity on a continuous 

basis and establish performance criteria. Some methods of indirect integrity monitoring may not 

have sufficient accuracy to serve as more than gross measures of membrane integrity for virus 

removal (USEPA, 2005). For most ground water sources, turbidity and particles are not likely to 

be present at levels high enough to set performance criteria or use in continuous monitoring, and 

States may need to use other water quality parameters (e.g., TDS, conductivity) or operating 

parameters (e.g., transmembrane pressure, flux rate) as performance indicators. Monitoring of 

some parameters may require laboratory analysis or additional monitoring equipment. It is 

important to note that the continuous indirect integrity monitoring techniques discussed here are 

significantly less sensitive than direct integrity tests, and do not provide verification that 

membrane integrity is sufficient to meet virus log removal requirements. Rather, continuous 

indirect integrity monitoring is used to monitor for major integrity problems, such as a failed seal 

or end-cap. 

As with other treatment technologies, membranes may be combined with another 

treatment technology to provide a total of 4-log treatment of viruses. The combination of a 

membrane technology with chlorine disinfection, which easily inactivates viruses at low doses, 

would provide multiple virus barriers with a level of redundancy. 

5.4 Additional Resources 

More detailed guidelines can be found in other publications, including but not limited to: 

• Alternative Disinfectants Guidance Manual (USEPA, 1999b) 

• Handbook of Chlorination and Alternative Disinfectants (White, 1999) 

• Ultraviolet Disinfection Guidance Manual for the Long Term 2 Enhanced Surface 

Water Treatment Rule (USEPA, 2006b) 

• Water Quality and Treatment (AWWA, 1990b) 

November 2008 Ground Water Rule 5-23 

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• Membrane Filtration Guidance Manual (USEPA, 2005) 

• Simultaneous Compliance Guidance Manual (USEPA 2007a) 

November 2008 Ground Water Rule 5-24 

Corrective Actions Guidance Manual
6. References 

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Iron Bacteria. Adapted from Agdex FS716 (D12). Available at: 

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AWWA (American Water Works Association). 1987b. AWWA Standard for Factory-Coated 

Bolted Steel Tanks for Water Storage. AWWA D103-87. Denver, Colo.: AWWA. 

AWWA. 1990a. Recommended Practice for Backflow Prevention and Cross Connection 

Control. AWWA Manual M14. Denver: AWWA. 

AWWA. 1990b. Water Quality and Treatment. F.W. Pontius (editor). AWWA. New York: 

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AWWA. 1995a. AWWA Standard for Circular Prestressed Concrete Water Tanks with 

Circumferential Tendons, AWWA D115-95. Denver,Colo: AWWA. 

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Water Tanks. AWWA D110-95. Denver, Colo: AWWA. 

AWWA. 1995d. Water Transmission and Distribution. Second edition. Denver, CO 

AWWA. 1996. AWWA Standard for Welded Steel Tanks for Water Storage. AWWA D100-96. 

Denver, Colo.: AWWA. 

AWWA. 1996a. AWWA Standard for Flexible-Membrane Lining and Floating-Cover Materials 

for Potable-Water Storage. AWWA D130. Denver, Colo.:AWWA. 

AWWA (American Water Works Association). 1998. AWWA Manual M42—Steel WaterStorage Tanks. Denver, Colo.: AWWA. 

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AwwaRF. 2007. Regional Solutions to Water Supply Provision. AwwaRF Report 91146. 

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Backflow Prevention Theory and Practice. University of Florida, Division of Continuing 

Education, Center for Training Research and Education for Environmental Occupations. 

Ritland, Robin L. 1990Kendall/ Hunt Publishing Company, Dubuque, Iowa. 

Bloetscher, F., A. Muniz, J. Largey. 2007. Siting, Drilling, and Construction of Water Supply 

Wells. AWWA. Denver, CO. 

Borch, M.A., S.A. Smith, and L.N. Noble. 1993. Evaluation and Restoration of Water Supply 

Wells. Denver: AWWA/AwwaRF. 

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Florida Department of Environmental Protection (DEP). 1996. The State of Florida’s Evaluation 

of Cross-Connection Control Rules/Regulations in the 50 States. Tallahassee: Florida DEP. 

Department of the Army. 1994. “Chapter 9: Alternative Well Construction.” Multiservice 

Procedures for Well-Drilling Operations. Field Manual 5-484. Available at 

GlobalSecurity.org.: http://www.globalsecurity.org/military/library/policy/army/fm/5-

484/Ch9.htm. 

Gordon, G., L. Adam, and B. Bubnis. 1995. Minimizing Chlorate Ion Formation in Drinking 

Water when Hypochlorite Ion is the Chlorinating Agent. Denver: AWWA/AwwaRF. 

Great Lakes-Upper Mississippi River Board of State and Provincial Public Health and 

Environmental Managers.Recommended Standards for Water Works. 2007. 

Grundfos Engineering Manual Water Systems Engineering Manual for Groundwater Supply and 

Special Applications. Available at: 

http://www.burdickandburdick.com/Grundfos%20Manuals/L-SP-TL-500.pdf. 

IBWA. 2005. Bottled Water Code of Practice. Available at: 

http://www.bottledwater.org/public/pdf/IBWA05ModelCode_Mar2.pdf 

Jorgenson, D., M. Wireman and D. Olsen. Spring 1998. USEPA Update: Assessing the 

Vulnerability of Public Water Supply Wells to Microbial Contamination. GWMR. 

Kansas Geological Survey. 2004. “Ground Water: Recovery.” Marshall County Geohydrology. 

Available at: http://www.kgs.ku.edu/General/Geology/Marshall/05_gw3.html. 

Kirmeyer, G.J., L. Kirby, B.M. Murphy, P.F. Noran, K.D. Martel, T.W. Lund, J.L. Anderson, 

and R. Medhurst. 1999. Maintaining and Operating Finished Water Storage Facilities. 

Denver,Colo.: AWWA and AWWARF. 

Lagerquist, J.M., and R.S. Summers. 2004. Disinfection Byproduct Control with Chlorine 

Dioxide and Other Alternative Oxidant Strategies. Presented at the 2005 AWWA WQTC 

conference. 

Linden, K.G., J. Thurston, R. Schaefer, J.P. Malley. 2007. Enhanced UV Inactivation of 

Adenovirus under Polychromatic UV Lamps. Applied and Environmental Microbiology. 

73(23):7571-7574. 

Linden, K.G., G.Shin, J.Lee, K. Scheible, C.Shen, P. Posy. 2008. Demonstrating 4-log 

Adenovirus Inactivation in a MP UV Reactor. Presented at the American Water Works 

Association Annual Conference and Exposition, Atlanta, GA, June 8-12. 

Linsley, R.K., J.B. Franzini, D.L. Freyburg, and G. Tchobanoglous. 1992. Water-Resources 

Engineering. Fourth Edition. Boston: Irwin McGraw-Hill. 

National Academy Press. 1997. Safe Water from Every Tap. National Academy of Sciences. 

Washington, DC. Available at: http://www.epa.gov/safewater/mdbp/word/alter/app_b.doc. 

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National Environmental Training Association. 1998. Learner’s Guide: How to Conduct a 

Sanitary Survey of Small Water Systems. Phoenix: NETA. 

National Groundwater Association. 2007. Water Well Basics: Types of Wells. Available at: 

http://www.wellowner.org/awaterwellbasics/typesofwells.html. 

 National Research Council (NRC). 1997. Safe Water from Every Tap, Improving Water Service 

to Small Communities. Washington, DC: National Academy Press. 

Purdue Research Foundation (Purdue). 2001. Well Drilling Methods. Available at: 

http://abe.www.ecn.purdue.edu/~epados/farmstead/private/src/drill.htm#bored. 

Purdue University. 1997. Well Water Location and Condition Tutorial. Information gathered 

from the Farmstead Assessment Program, a cooperative project of the University of 

Wisconsin-Extension, Minnesota Extension Service, and the United States Environmental 

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http://abe.www.ecn.purdue.edu/~epados/farmstead/well/src/title.htm. 

Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of 

State and Provincial Public Health and Environmental Managers. 

http://10statestandards.com/waterstandards.html 

Salvato, J. 1998. Environmental Engineering and Sanitation. Fourth Edition. John Wiley and 

Sons, Inc. 

Ten States Standards. 2003. Recommended Standards for Water Works (Ten States Standards). 

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Managers. Available from: Health Education Services, PO Box 7126, Albany, NY 12224. 

Available at: www.hes.org. 

Ten States Standards. 2007. Recommended Standards for Water Works (Ten States Standards). 

Great Lakes Upper Mississippi River Board of State Public Health and Environmental 

Managers. Available from: Health Education Services, PO Box 7126, Albany, NY 12224. 

Available at: www.hes.org. 

Tikkanen, M., J.H. Schroeter, L.Y.C. Leong, and R. Ganesh. 2001. Guidance Manual for 

Disposal of Chlorinated Water. Denver: AWWA/AwwaRF. 

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85016-4412, Phone: 602-956-6099. 

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Washington, DC. 

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USEPA. 1989. Cross Connection Control Manual. USEPA 570-9-89-007. Washington, DC. 

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Systems. USEPA 625-R-92-001. Washington, DC. 

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Requirements for Public Water Systems Using Surface Water Sources. Available from: 

AWWA, 6666 West Quincy Avenue, Denver, CO 80235. 

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Malcolm Pirnie, Inc for USEPA, Office of Ground Water and Drinking Water, PB93-

162998. Washington, DC. 

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Treatment Rule: Turbidity Provisions. EPA 815-R-99-010 . USEPA. Washington DC. 

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014.USEPA. Washington DC. 

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Associated Health. Office of Water (4601M) Office of Ground Water and Drinking Water 

Distribution System Issue Paper. 

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816-R01-017A. http://yosemite.epa.gov/water/owrccatalog.nsf/. 

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Publication number EPA 816-K-02-005 

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DC. Available at: http://www.epa.gov/safewater/crossconnection.html. 

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Sanitary Survey of a Small Ground Water System. EPA 816-R-03-023. Washington, DC. 

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EPA 816-R-03-015 

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Water Treatment Rule – Turbidity Provisions. USEPA. EPA 816-F-02-001. Washington, 

DC. 

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Publication Number EPA 816-F-04-010. www.epa.gov/safewwater/regs.html 

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816-F-04-009. www.epa.gov/safewwater/regs.html 

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Washington, DC. 

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Surface Water Treatment Rule. Office of Water. USEPA. EPA 815-R-06-007. Washington 

DC. 

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Publication Number EPA 816-C-06-001. http://yosemite.epa.gov/water/owrccatalog.nsf/ 

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DBP Rules. Office of Water. EPA 815-R-07-017. 

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Water. EPA 815-R-07-020. 

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019. 

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Viessman Jr., W., and M.J. Hammer. 1998. Water Supply and Pollution Control. Sixth Edition. 

Menlo Park: Addison-Wesley. 

White, G.C. 1999. Handbook of Chlorination and Alternative Disinfectants. New York: Van 

Nostrand Reinhold. 

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Appendix A 

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Appendix A. Applications of Various Backflow Prevention Assemblies or Metho

Description Advantages/Disadvantages

Protects 

Against

Backpressure

Protects 

Against

Backsiphonage

Hazard 

Type 

Air Gap

- A physical separation between the free flowing outlet of a potable water pipe and an unpressurized receptacle(USCFCCCHR, 1993). - Physical separation should be at least twice the diameter (2D) of the outlet pipeand no less than one inch (USEPA, 2003). - The only means of absolute separation between plumbing systems, and shouldbe used whenever possible and not bypassed (USPHS, 1966).- Well-designed and properly maintainedair gaps are AWWA’s recommended method of protection against backflow for extremely hazardous installations (AWWA, 1990a). - Mainly used at the end of a service line (USEPA, 2003), an air gap is the recommended protection for sewage pumps and ejectors, sewer pipe connections, trap primers, and swimmingpools. 

Advantages

-Non-mechanical -Highly effective and easy to integrate into a current system-Provides maximum protection Disadvantages

- Pressure loss can lead to the need for secondary pumping requirements in continuous piping systems (USEPA, 1989). - Frequent inspection is needed to maintain 2D physical separation and prevent backsplash (USEPA, 2003). - Water exposure to the surrounding atmosphere can lead to contamination byairborne contaminants and can allowdisinfectant residuals to escape (USEPA, 1989). 

Yes Yes Health 

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Description Advantages/Disadvantages

Protects 

Against

Backpressure

Protects 

Against

Backsiphonage

Hazard 

Type 

Pressure Type Vacuum Breaker

- Under normal flow conditions, the inlet water pressure opens the check valve allowing flow to continue, while pushing the PVB’s air inlet valve against the air inlet canopy preventing air from entering. However, when normal flow is interrupted due to at least a partial vacuum, the check valve closes preventing backflow. If the check valve is fouled and does not close, the air inlet valve acts as a second check and opens, allowing air to enter the system (AWWA, 1990a). - Must be installed only in a vertical position, above grade with a minimum of 12 inches of vertical clearance above the highest point in the downstream piping, and must be accessible for testing and repair (BMI, 1996). - PVBs are available for piping ranging from one-half to 10 inches in diameter and are widely used in agricultural and industrial applications (USEPA, 1989). 

Advantages

- Can be used under constant pressure and can be tested in line (USEPA, 2003). - Available in sizes ranging from one-half to ten inches (USEPA, 2003) Disadvantages

- Some manufacturers may have pressure or temperature limitations placed on their assemblies (BMI, 1996). 

No Yes Health/Non

Health 

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Description Advantages/Disadvantages

Protects 

Against

Backpressure

Protects 

Against

Backsiphonage

Hazard 

Type 

Double check valve 

- Consists of two check valves in one body located between two tightly closing gate valves. The check valves are springloaded and require approximately one pound of pressure to open (USEPA, 2003). - Under normal flow conditions in excess of one pound of pressure, the water pressure will hold the check valves openallowing water to flow through the assembly. When backflow conditions occur, the check valves close and prevent backflow.Modified DCVs

- Double check detector check (DCDC), is commonly used for fireline installations. DCDC differs from the DCV in that it has a metered bypass line for low flowsituations (USEPA, 1989). - Residential dual check (RDC) that differs from the DCV in that it has no test cocks or gate valves. RDCs were designed to provide inexpensive protection against backpressure and backsiphonage from household hazards (USEPA, 1989). They are available insizes ranging from one-half to one inch (USEPA, 1989).

Advantages

- Can be installed in pits or vaults, and, in some cases can be installed vertically(BMI, 1996). - The internal loading or weighting allowsthe check valve to seal even in the presence of small debris (USEPA, 2003).-Ability to be used under constant pressure(USEPA, 2003)Disadvantages

-should only be used for low to medium hazard situations 

Yes Yes Non-health 

October 2008 Ground Water Rule A-5
Corrective Actions Guidance Manual 

Description Advantages/Disadvantages

Protects 

Against

Backpressure

Protects 

Against

Backsiphonage

Hazard 

Type 

Reduced pressure principle backflow prevention device

- Consist of two independent check valves - one is a differential relief valve between the two check valves and the other is located below the first check valve (AWWA, 1990a). Both valves are equipped with gate valves and test cocks. - Under normal flow conditions, water pressure forces both check valves open. When the water passes through the first check valve a slight predetermined pressure drop results (USEPA, 1989). The space between the first and second check valves is normally maintained at two psi lower than the inlet pressure. The second check valve is lightly loaded to allow the water pressure to hold it open and results in a pressure drop of one psi. When reduced pressure from the inlet, or increased pressure downstream occurs, the check valves close and the pressuredifferential between the inlet and the space between the two check valves forces the flow out of the differential relief valve (USEPA, 1989). - RPBAs are available for service lines ranging from three-fourths to 10 inches and can be installed in pits or vaults. 

Advantages

- Provides maximum protection (USEPA, 2003). - Discharge of flow out of the differential relief valve also acts as an indication of a backflow event. - The differential relief valve also provides backflow protection in the event that the second check valve becomes fouled. Disadvantages

- Some models can only be installed horizontally and have temperature and pressure limitations (BMI, 1996). - More expensive than the other backflowpreventers. 

Yes Yes Health 

October 2008 Ground Water Rule A-6
Description Advantages/Disadvantages 

Protects 

Against 

Backpressure 

Protects 

Against 

Backsiphonage 

Hazard 

Type 

Double check valve with intermediate atmospheric vent 

- Similar in construction and function to a DCV in that it has double check valves within a single body. However, it also has an atmospheric vent located between the two check valves, which adds extra protection (USEPA, 2003). 

Advantages - Compact with protection for moderate hazards -Can be used under constant pressure - Available in sizes ranging from one-half to three-fourths of an inch (USEPA,2003). 

Yes Yes Non-health 

1 A high hazard is when a cross connection endangers human health. Low hazards may result in contamination but generally not affect hum

October 2008 Ground Water Rule A-7Corrective Actions Guidance Manual