NUREG-1724

Standard Review Plan 

for the Review of 

DOE Plans for 

Achieving Regulatory 

Compliance at Sites With 

Contaminated Ground Water 

Under Title I of the 

Uranium Mill Tailings 

Radiation Control Act 

Draft Report for Comment 

U.S. Nuclear Regulatory Commission 

Office of Nuclear Material Safety and Safeguards 

Washington, DC 20555-0001
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NUREG-1724 

Standard Review Plan 

for the Review of 

DOE Plans for 

Achieving Regulatory 

Compliance at Sites With 

Contaminated Ground Water 

Under Title I of the 

Uranium Mill Tailings 

Radiation Control Act 

Draft Report for Comment 

Manuscript Completed: May 2000 

Date Published: June 2000 

Division of Waste Management 

Office of Nuclear Material Safety and Safeguards 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001
COMMENTS ON DRAFT REPORT

Any interested party may submit comments on this report for consideration by the NRC staff. 

Comments may be accompanied by additional relevant information or supporting data. Please 

specify the report number draft NUREG- 1724, in your comments, and send them by month, day, 

year to: 

Chief, Rules Review and Directives Branch 

U.S. Nuclear Regulatory Commission 

Mail Stop T6-D59 

Washington, DC 20555-0001 

You may also provide comments at the NRC Web site, http://www.nrc.gov. See the link under 

"Technical Reports in the NUREG Series" on the 'Reference Library" page. Instructions for 

sending comments electronically are included with the document, NUREG- 1724, draft, at the web 

site. 

For any questions about the material in this report, please contact: 

William Ford 

Mail Stop: T-7 J8 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 

Phone: 301-415-6630 

E-maiI:WHF
NUREG-1724 has been reproduced from 

the best available copy.

I II
ABSTRACT

The Department of Energy postponed implementation of ground-water corrective action plans at most 

Title I sites until completion of surface remediation, because Environmental Protection Agency 

ground-water standards were not finalized until 1995. Consistent with this approach, 10 CFR 40.27, allows 

for licensing of disposal sites that require ground-water restoration in two steps. The first step, surface 

restoration, is conducted by the DOE under the Uranium Mill Tailings Remedial Action Surface Project. 

After completion of surface restoration, the site is placed under a general license through Nuclear 

Regulatory Commission acceptance of a Long-Term Surveillance Plan that may leave ground-water 

restoration issues open. Ground-water corrective action, the second step, is conducted under the Uranium 

Mill Tailings Remedial Action Ground-Water Project. 

This Standard Review Plan is prepared for the guidance of staff reviewers in the Office of Nuclear Material 

Safety and Safeguards in performing safety and environmental reviews of corrective action plans and 

revised long-term surveillance plans of ground-water quality compliance activities for uranium recovery 

sites covered by Title I of the Uranium Mill Tailings Radiation Control Act. The purpose of this Standard 

Review Plan is to ensure the quality and uniformity of Nuclear Regulatory Commission staff reviews of 

site-specific documents describing Department of Energy plans for achieving regulatory compliance at sites 

with contaminated ground water. 

This standard review plan is written to cover a variety of site conditions and plans. Each section provides 

a description of the areas of review, review procedures, acceptance criteria, an evaluation of findings, and 

a list of references.

°o° NUREG-1724
CONTENTS 

ABSTRACT .......................................................... iii 

LIST OF ABBREVIATIONS ............................................... Vi 

INTRODUCTION ...................................................... 1 

1.0 SITE CHARACTERIZATION .......................................... 1-1 

1.1 Areas of Review ............................................ 1-1 

1.2 Review Procedures .......................................... 1-2 

1.3 Acceptance Criteria ......................................... 1-2 

1.4 Evaluation Findings ........................................ 1-11 

1.5 References .............................................. 1-13 

2.0 GROUND-WATER PROTECTION STANDARDS ............................ 2-1 

2.1 Areas of Review ............................................ 2-1 

2.2 Review Procedures .......................................... 2-1 

2.3 Acceptance Criteria ......................................... 2-2 

2.4 Evaluation Findings ......................................... 2-4 

2.5 References ............................................... 2-4

3.0 HAZARD 

3.1 

3.2 

3.3 

3.4 

3.5

ASSESSMENT FOR ALTERNATE CONCENTRA 

Areas of Review ....................... 

Review Procedures ..................... 

Acceptance Criteria .................... 

Evaluation Findings .................... 

References ..........................

tTION LIMITS 

S. ... . . . . . . 

S. ... . . . . . . 

. . . . . . . . . . 

. . . . . . . . . .

4.0 GROUND-WATER CORRECTIVE ACTION AND 

COMPLIANCE MONITORING PLANS .... 

4.1 Areas of Review ................ 

4.2 Review Procedures .............. 

4.3 Acceptance Criteria ............. 

4.4 Evaluation Findings ............. 

4.5 References ................... 

5.0 LONG-TERM SURVEILLANCE PLAN ....... 

5.1 Areas of Review ................ 

5.2 Review Procedures .............. 

5.3 Acceptance Criteria ............. 

5.4 Evaluation Findings ............. 

5.5 References ...................

NUIREG-1724

i

3-1 

3-1 

3-1 

3-2 

3-9 

3-9

4-1 

4-1 

4-1 

4-2 

4-9 

4-9

... 5-1 

... 5-1 

... 5-1 

... 5-1 

... 5-2 

... 5-2

V
CONTENTS (cont'd)

APPENDICES 

A GUIDANCE TO THE NRC STAFF ON THE USE OF STANDARD 

STATISTICAL HYPOTHESIS TESTING AS APPLIED TO 

GROUND-WATER QUALITY ...................................... A-1 

FIGURE 

Figure 4.1 Ground-water compliance strategy selection ............................. 4-3 

TABLE 

Table 1.1 Common Uranium Mill Chemical Constituents ............................ 1-7

NUREG-1724 vi

1 1
LIST OF ABBREVIATIONS 

ACL alternate concentration limit 

ANOVA analysis of variance 

ASTM American Society for Testing and Materials 

CAP corrective action program 

CFR Code of Federal Regulations 

DOE Department of Energy 

EAP emergency action plan 

EPA Environmental Protection Agency 

LTSP long-term surveillance plan 

MCL maximum concentration limit 

NRC Nuclear Regulatory Commission 

POC point of compliance 

POE point of exposure 

SRP standard review plan 

UMTRCA Uranium Mill Tailings Radiation Control Act of 1978 as amended 

UR uranium recovery

vii NUREG-1724
INTRODUCTION

Protection of water resources at Title I sites is a process that encompasses two distinct strategies. 

The first strategy is to contain the spread of contaminants to ground water, surface water, and surrounding 

lands. The second strategy is to mitigate the threat to public health from contaminants that have already 

been mobilized-particularly through ground-water pathways. The Nuclear Regulatory Commission (NRC) 

reviews the cleanup of contaminated ground water by the Department of Energy (DOE) at Title I sites to 

determine if the cleanup complies with applicable sections of the Environmental Protection Agency's 

standards in 40 CFR Part 192, titled "Health and Environmental Protection Standards for Uranium and 

Thorium Mill Tailings". The DOE has postponed implementation of ground-water corrective action plans 

at most Title I sites until completion of surface remediation, because Environmental Protection Agency 

(EPA) ground-water standards were not finalized until 1995. Consistent with this approach, 10 CFR 40.27, 

allows for licensing of disposal sites that require ground-water restoration in two steps. The first step, 

surface restoration, is conducted by the DOE under the Uranium Mill Tailings Remedial Action Surface 

Project. After completion of surface restoration, the site is placed under a general license through Nuclear 

Regulatory Commission (NRC) acceptance of a Long-Term Surveillance Plan (LTSP) that may leave 

ground-water restoration issues open. Ground-water corrective action, the second step, is conducted under 

the Uranium Mill Tailings Remedial Action (UMTRA)Ground-Water Project. The purpose of this Standard 

Review Plan (SRP) is to aid NRC staff in reviewing site-specific documents describing DOE plans for 

achieving regulatory compliance at sites with contaminated ground water. 

Restoration of contaminated ground water has been postponed, in most cases, until completion of 

surface reclamation. With the completion of most surface reclamation, and the 1995 publication of final 

U.S. Environmental Protection Agency (EPA) ground-water standards (60 FR 2854), the DOE has begun 

to implement the Uranium Mill Tailings Remedial Action Ground-Water Project. Barring the identification 

of any new Title I sites, the only remedial action plans yet to be reviewed by the NRC for Title I sites 

should deal solely with implementation of the UMTRA Ground-Water Project. Reviewers of Uranium Mill 

Tailings Remedial Action Ground-Water Project Remedial Action Plans (sometimes called Ground-Water 

Compliance Action Plans)shall verify that all of the areas of review outlined in this chapter have been 

addressed, either through an earlier UMTRA Surface Project Remedial Action Plans (RAPs), or in the 

Ground-Water Project RAP under review. Reviewers shall also be familiar with the long term surveillance 

plan (if one exists) for the site under review, and be mindful of how ground-water restoration processes 

might affect provisions of the long term surveillance plan. 

The DOE implementation strategy for ground-water cleanup has been termed the Observational 

Approach. Implementation of the Observational Approach is discussed in the DOE 1993 "Technical 

Approach to Groundwater Restoration" (U.S. Department of Energy, 1993) and the DOE 1996 "Final 

Programmatic Environmental Impact Statement for the UMTRA Ground Water Project". This decision 

framework is implemented by the DOE through one or more site observational work plans that are 

provided for NRC review and comment on whether the stated approach appears viable for achieving 

compliance. The purposes of site observational work plans are to select a preliminary restoration strategy 

based on existing data, and to identify additional data collection needs. As data collection needs are met 

through further site characterization and model refinement, either the preliminary restoration strategy is 

supported, or a new strategy is selected. Once it is determined that remaining uncertainties can be managed 

as reasonable deviations, the final restoration strategy is presented in a Ground-Water Corrective Action 

Plan, which is submitted for NRC concurrence.

I NUREG-1724
The purpose of this standard SRP is to aid NRC staff in the review of the following UMTRA 

Ground-Water Project documents that may be submitted by the DOE for NRC review: 

(1) Site observation work plans 

(2) Remedial action plans 

(3) Ground-Water Corrective Action Plans 

(4) Updates to long term surveillance plans. 

Site observation work plans are precursors to corrective action plans. The DOE uses site 

observation work plans to summarize what is known about a site, identify needs for additional data, and 

document the decision process for selecting a specified restoration strategy. A first-draft site observation 

work plan for a Title I site will likely contain a summary of what is known about the site, a working 

strategy for restoration based on existing data, and identification of additional data needs. Successive 

iterations of site observation work plans will be more complete, with fewer needs for additional data, and 

will more closely approach a remedial action plan. 

A complete corrective action plan provides detailed information on (1) preparing a hydrologic site 

conceptual model, (2) defining ground-water protection standards, (3) Identifying a restoration strategy 

selection, and (4) preparing a corrective action plan. 

Completion of ground-water corrective actions may necessitate updates to the long term 

surveillance plan. Because ground-water restoration and ground-water compliance monitoring may not have 

been fully examined during review of the original long term surveillance plan.

NUREG-1724 2

I II
1.0 SITE CHARACTERIZATION

1.1 Areas of Review 

The staff shall review the characterization information, given the circumstances and life cycle of 

a particular site, and the nature of the document under review. The staff shall also evaluate regional and 

site-specific hydrologic information related to both the former processing site and the proposed disposal 

site if they are different. The hydrologic information shall include both surface-water and ground-water 

systems, along with any interrelations among those systems. Complete site characterization should include 

or reference the following: 

(1) Site background data that include descriptions of: 

(a) The site history of mining and/or milling operations; 

(b) Surrounding land and water uses; and 

(c) Site meteorological data. 

(2) Ground-water and surface-water hydrology data, including: 

(a) Descriptions of hydrogeology and ground-water conditions; 

(b) Estimation of hydraulic and transport properties for each hydrogeologic unit; 

(c) Descriptions of surface-water hydrology and estimations of ground-water and 

surface-water interactions; and 

(d) Assessment of potential for flooding and erosion. 

(3) Information concerning geochemical conditions and water quality, including: 

(a) Identification of constituents of concern; 

(b) Determination of background ground-water quality; 

(c) Confirmation of proper statistical analysis; 

(d) Delineation of the nature and extent of contamination; 

(e) Identification of contaminant source terms; 

(f) Characterization of subsurface geochemical properties; and 

(g) Identification of attenuation mechanisms and estimation of attenuation rates.

1-1 NUREG-1724
(4) Human health and environmental risk evaluations.

1.2 Review Procedures 

The level of effort necessary to adequately characterize a particular site depends on site-specific 

circumstances. For example, if a particular site has no ground-water contamination and tailings are 

disposed of off-site, there will be very little need for detailed site characterization in support of water 

resources protection. Conversely, at a site with an existing source of ground-water contamination, the site 

characterization must be sufficient to support selection of restoration strategies and to determine the level 

of risk to human health and the environment. 

Because the appropriate level of site characterization is specific to the methods of tailings disposal and ground-water corrective action selected for a particular site, there is not a single acceptable approach 

to conducting a site characterization. As such, the reviewer shall: 

(1) Thoroughly evaluate the characterization information using the acceptance criteria in SRP, but 

reserve final judgment until all sections of the application have been reviewed; and; 

(2) Assess whether the level of detail and technical merit of the characterization are sufficient to 

support the proposals, assumptions, and assertions in the application that are used to demonstrate 

regulatory compliance. 

1.3 Acceptance Criteria 

Knowledge of the site is needed to evaluate the existing and potential contamination. This 

characterization information shall include a description of activities and physical properties that may affect 

water resources at the mill site, The site characterization will be acceptable if it meets the following 

criteria: 

(1) It contains a description of the site that is sufficient to assess the environmental impact the former 

mill site may have on the surrounding area; the populations that may be affected by such impacts; and meteorological conditions that may act to transport contaminants offsite. An acceptable site 

description will contain the following specific information: 

(a) A site history that includes: 

(i) A list of the known leaching solutions and chemicals used in the milling process 

and their relative quantities in mill wastes. The list should also identify any constituent listed in 40 CFR Part 192, Appendix I that may have been disposed 

of in the tailings pile. 

(ii) A description of the wastes generated at the site during milling operations, waste 

discharge locations, types of retaining structures used (e.g.-; tailings piles, ponds, 

landfills), quantities of waste generated, and a chronology of waste management 

practices. 

NUREG-1724 1-2

I II
(iii) A summary of the known impacts of the site activities on the hydrologic system 

and background water quality. 

(iv) If applicable, descriptions of any human activities or natural processes unrelated 

to the milling operation that may have altered the hydrogeologic system. Such 

human activities include ground-water use, crop irrigation, mine dewatering, ore 

storage, municipal waste land filling, oil and gas development, or exploratory 

drilling. Natural processes include geothermal springs, natural concentration of 

soluble salts by evaporation, erosion processes, and ground-water/surface-water 

interactions. 

(b) Information pertaining to surrounding land and water uses that includes: 

(i) A general overview of water uses, locations, quantities of water available, and the 

potential uses to which quality of water is suited; 

(ii) Definitions of the class-of-use category for each water source (e.g., drinking 

water, agricultural, livestock, limited use); 

(iii) Identification of potential receptors of present or future ground-water or 

surface-water contamination; and 

(iv) Descriptions of non-mill-related human activities or natural processes that may 

affect water quality or water uses (e.g., oil and gas development, municipal waste 

landfills, crop irrigation, drought, erosion, etc.). 

Human water consumption is not the only water use that must be considered in the 

review. Any use that may bring someone into contact with the contaminated water 

must be considered when evaluating health hazards. For example, nonpotable, 

radon-contaminated water piped to a public lavatory could pose a substantial health 

hazard. 

(c) Sufficient meteorologic data for the region, including rainfall and evaporation data in 

sufficient detail to assess projected water infiltration through the disposal cell. 

Monthly averages are an acceptable means of presenting general meteorological 

conditions; however, the reviewer shall ensure that extreme weather conditions are 

adequately described. 

(2) The ground-water and surface-water hydrology is described adequately to support predictions of 

likely contaminant migration paths; selection of monitor well locations; and, when ground-water 

contamination exists, selection of a restoration strategy. The following specific information is 

provided to support these objectives: 

(a) A description of hydrogeologic units that may affect transport of contaminants away from 

the site via ground-water pathways.

1-3 NUREG-1724
(i) Hydrostratigraphic cross-sections'and maps are included to delineate the geometry, 

lateral extent, thickness, and rock or sediment type of all potentially affected 

aquifers and confining zones beneath the processing and disposal sites. Data used 

to construct such maps are referenced and of adequate quality and quantity to 

support a technically defensible interpretation. 

(ii) The hydrogeologic units that constitute the uppermost aquifer (where regulatory 

compliance will be evaluated) are identified. The uppermost aquifer is the geologic 

formation nearest the natural ground surface that is an aquifer, as well as lower 

aquifers that are hydraulically interconnected with this aquifer within the facility's 

property boundary. 

(iii) If local perched aquifers are found at the site, their presence is noted. These 

formations may cause contaminated water to be diverted around monitoring 

systems, or may be improperly interpreted as the uppermost aquifer. Any 

saturated zone created by uranium or thorium recovery operations would not be 

considered an aquifer unless the zone is or potentially is: (1) hydraulically 

interconnected to a natural aquifer; (2) capable of discharge to surface water; or 

(3) reasonably accessible because of migration beyond the vertical projection of 

the boundary, of the land by the government. 

(iv) Unsaturated zones, through which contaminants may be conveyed to the water

bearing units, are described. This information is adequate to support the 

assumptions used in estimating the source term for contaminant transport 

pathways. This information includes identification of potential preferential flow 

pathways that are either natural (e.g., buried stream channels), or man-made (e.g., 

abandoned wells or mine shafts). 

(v) Information on geologic characteristics that may affect ground-water flow beneath 

the former mill site is provided. Examples of pertinent geologic characteristics 

include identification of significant faulting in the area, fracture and joint 

orientation and spacing for the underlying bedrock, and geomorphology of soil 

and sedimentary deposits (e.g., fluvial, glacial, or volcanic deposits). 

(iv) Hydraulic-head contour maps, of both local and regional scale, for the uppermost 

aquifer and any units connected hydraulically beneath the site are sufficient to 

determine hydraulic gradients, ground-water flow direction, and proximity to 

offsite ground-water users. These maps are based on static water level 

observations at onsite and regional wells. Several measurements are taken at each 

observation well (American Society of Testing and Materials Standards D4750, 

D5092, D5521, D5787, and D5978). These measurements are sufficiently spaced 

in time to capture water level fluctuations caused by seasonal changes or local 

pumping of ground water. Enough observation wells are sampled to produce an 

adequate water elevation contour map. The appropriate number of wells is 

dependent on the size of the site and the choice of contour interval. However, as 

a rough estimate, there is at least one observation well for each contour line on the 

map. A more detailed contour map (small contour interval) is produced for the site 

NUREG-1724 1-4

I II
and surrounding properties. The level of detail used for the regional contour map 

may be limited by the number of observation wells available offsite. The reviewer 

shall bear in mind that calculations of hydraulic gradients from hydraulic head 

contour maps is only rigorously valid for horizontal flow in aquifers. 

(b) Estimations of hydraulic and transport properties of the underlying aquifer. 

Hydrogeologic parameters used to support the choice of a ground-water restoration 

strategy or to demonstrate compliance include hydraulic conductivity, saturated thickness 

of hydrogeologic units, hydraulic gradient, effective porosity, storage coefficient, and 

dispersivity. The reviewer shall consider the influence of each of these parameters on 

evaluating compliance with standards established pursuant to Part 40, Appendix A, and 

determine whether estimates for each parameter are reasonably conservative, based on the 

data provided. 

(i) Hydraulic conductivity and storage coefficients are determined by conducting 

aquifer pump tests on several wells at the site. Pump test methods that are 

consistent with American Society of Testing and Materials standards for the 

measurement of geotechnical properties and for aquifer hydraulic tests are 

considered acceptable by the NRC. These American Society of Testing and 

Materials standards include D4044, D4050, D4104, D4105, D4106, D4630, 

D5269, D5270, D5472, D 5473, D5737, D5785, D5786, D5850, D5855, D5881, 

and D5912. Any other peer-reviewed method or commonly accepted practice for 

aquifer parameter estimation may be used. When curve fitting is used to analyze 

pump test data, deviations of observation data from ideal curves are explained in 

terms of likely causes (e.g., impermeable or recharge boundaries, leaky aquitards, 

or heterogeneities). When average hydraulic parameters are reported, the reviewer 

shall consider that many hydrogeologic parameters, including hydraulic 

conductivity, typically exhibit a log-normal distribution. Consequently, the 

geometric mean may be more representative of the overall conditions within a unit 

than the arithmetic mean. 

(ii) Horizontal components of hydraulic gradient are estimated by measurement of the 

distance between contour intervals on hydraulic head contour maps. Vertical 

components of hydraulic gradient are estimated from head measurements in 

different aquifers or at different depths in the same aquifer. 

(iii) Generally, analyses considering steady state conditions are acceptable unless site 

conditions indicate otherwise. If transient conditions are modeled, storage 

coefficients estimated from standard tests indicated in (i) above are used. 

(iv) If contaminant transport is modeled, then longitudinal and transverse dispersivity 

values are either obtained from a tracer test or conservative values based on 

published literature are used. Because dispersivities depend on the size of the 

modeled region, the reviewer shall carefully compare the values for dispersivity 

used in the DOE's transport modeling with those values cited in survey studies

1-5 NUREG-1724
such as Gelhar et al. (1992), and verify that they represent conservative estimates 

for the site. 

(c) Estimation of ground-water/ surface-water interactions at sites with nearby streams, 

rivers, or lakes. 

The location of surface-water bodies that are connected to the site ground-water flow 

system are identified. Surface-water elevations shall be used to help describe the site 

ground-water flow system if a stream or other surface-water body discharges into or drains 

the site ground-water flow system. Another acceptable approach is to evaluate hydraulic 

head contour based on data from monitor wells in the vicinity of streams. 

(3) Geochemical conditions and water quality are characterized sufficiently to: 

(a) Identify the constituents of concern. 

Any chemical constituent that meets both of the following criteria must be listed as a 

constituent of concern: 

(i) The constituent is reasonably expected to be in or derived from the tailings. 

(ii) The constituent is listed in either 40 CFR Part 192, Appendix I or 

40 CFR Part 192, Subpart A, Table I. 

Table 1.1 provides a list of constituents commonly associated with uranium mill 

tailings (Smith, 1987). This list is based on a chemical survey performed by staff 

at 17 Title 11 sites. 

Most of the constituents in 40 CFR Part 192, Appendix 1 are organic compounds 

that are not normally associated with uranium milling processes. The expected 

presence of organic compounds is assessed from knowledge of the chemicals used 

during the milling process or other materials that may have been disposed of in the 

tailings. If there is no record of organic compounds used in the process, screening 

tests for volatile and semivolatile organics are performed to confirm the absence 

of organic compounds in the tailings and ground water. 

(b) Provide a determination of background (baseline) water quality. 

Background water quality is defined as the chemical quality of water that would be 

expected at a site if contamination had not occurred from the uranium milling operation. 

When adequate site-specific baseline data cannot be obtained for identified constituents of 

concern, samples of adjacent, and up-gradient, uncontaminated, water are taken as proxies 

to onsite baseline samples.

NUREG-1724 1-6
Table 1.1 Common Uranium Mill Chemical Constituents

Inorganic Constituents J Organc Constituents 

Arsenic Carbon Disulfide 

Barium Chloroform 

Beryllium Diethyl Phthalate 

Cadmium 2-Butanone 

Chromium 1,2-Dichloroethane 

Cyanide Naphthalene

Lead 

Mercury 

Molybdenum 

Net Gross Alpha 

Nickel 

Radium-226 and -228

Selenium

Silver

Thorium-230

Uranium I

To determine acceptability of background water quality determination, the following 

information is provided: 

(i) Maps are of sufficient detail and legibility to show the background monitoring 

locations. 

(ii) Descriptions of sampling methods, monitoring devices, and quality assurance 

practices are provided. Examples of acceptable methods include those that are 

consistent with American Society of Testing and Materials Standards D 4448, 

D 4696, and D 4840. Other methods, if used, are properly referenced and 

justified. 

(iii) When they exist, zones of differing background water quality are delineated. A 

discussion of the possible causes of these differing water quality zones is included 

(e.g., changes from geochemically oxidizing to reducing zones in the aquifer; 

changes in rock type across a fault boundary). 

(iv) A table for each zone of distinct water quality, listing summary statistics (i.e., 

mean, standard deviation, and number of samples) for baseline water quality 

sampling for each constituent of concern, is provided.

1-7 NUREG-1724
(c) Confirm the proper use of statistical techniques for assessing water quality. 

Statistical hypothesis testing methods used for: (i) establishing background water quality; 

(ii) establishing ground-water protection standards for compliance monitoring; 

(iii) determining the extent of ground-water contamination; and (iv) establishing the 

ground-water cleanup goals, are described in Appendix A and American Society of Testing 

and Materials Standard D6312. 

(d) Define the extent of contamination. 

A hazardous constituent is defined as a constituent that meets all three of the following 

tests: 

(i) The constituent is reasonably expected to be in or derived from the byproduct 

material in the disposal area; 

(ii) The constituent has been detected in the ground water in the uppermost aquifer; 

and 

(iii) The constituent is listed in 40 CFR Part 192, Appendix I or 40 CFR Part 192, 

Subpart A, Table 1. 

For each hazardous constituent the DOE determines the extent of contamination in ground 

water at the site. Ground-water contamination at uranium mill sites is usually limited to 

the uppermost aquifer. Maps showing the locations of sampling wells should be included, 

along with a discussion of sampling practices. The most useful way to present this 

information is on a map showing concentration contours for each hazardous constituent 

and water surface elevation contours. In this manner, the size, shape, source, and direction 

of movement can be readily examined by the reviewer. 

The extent of contamination is delineated in three dimensions. This typically involves 

drilling a number of characterization wells and determining whether the water quality in 

each of these wells meets background water quality (i.e., null hypothesis) or whether the 

ground water is contaminated (i.e., alternative hypothesis). It may not be necessary to 

sample all hazardous constituents, to delineate the extent of contamination. Two or three 

indicator parameters (e.g., total dissolved solids, and chloride) might be selected. These 

indicators should be conservative-meaning that they are neither reactive, nor are they 

easily sorbed to soil-so that they provide a good indication of the maximum extent of 

contamination. 

The transition from contaminated to uncontaminated ground water is often gradual. Thus, 

difficulty arises in determining where the contaminated water ends and the background 

water begins. The background data provide the easiest means for comparison of 

characterization well measurements to background measurements for the indicator 

parameters. The easiest method is to use the tolerance limit method to determine the upper limit for the range of background concentrations; characterization wells with

NUREG-1724 1-8
concentrations above this limit can be assumed to have been affected by ground-water 

contamination. 

Complications in delineating the extent of contamination arise at sites that have zones of 

differing water quality, or where on-site background water quality is not properly 

determined before discovery of ground-water contamination. Where zones of differing 

water quality are present, the reviewer shall verify that characterization wells are 

compared with the background sample from the appropriate water quality zone. Where 

on-site background water quality has not been properly determined, then up gradient or 

offsite samples are obtained. 

The reviewer shall verify that the DOE has provided the following information to support 

determining the extent of contamination. 

(i) A map or maps showing the distribution of surface wastes and contaminated 

materials at and near the site. 

(ii) A map or maps showing the approximate shape and extent of ground-water 

contamination (e.g., concentration contour maps for indicator parameters in 

ground water). 

(iii) Identification of any off-site sources of water contamination or other factors that 

may have a bearing on observed water quality. 

(iv) Properly estimate the source term. 

Existing sources of ground-water contamination are defined in terms of location 

and rate of entry into the subsurface. At some sites, the contaminant sources have 

been effectively eliminated through stabilization or removal of tailings piles. 

However, residual sources may still exist in contaminated subsurface soils at the 

site. For ground-water contamination that originates from an onsite tailings pile, 

the source term is determined based on the chemical properties of the leachate and 

the rate at which leachate is released from the disposal area. The level of review 

given to source term calculations is commensurate with the overall importance of 

source term estimations to the selection of the restoration strategy. 

Source terms are reasonably correlated to the history of ore processing. All 

facilities from which leakage can occur are identified. Leaking constituents are 

identified based on the nature of the processing fluids. The volume of leakage is 

estimated in a realistic yet conservative manner. This can be done using water 

balance calculations, infiltration modeling, or seepage monitoring approaches. 

When geochemical models are used to predict the fate and transport of existing 

contamination where the original source has been eliminated, the distribution of 

each hazardous constituent in place is taken as the source term. 

(f) Characterize the subsurface geochemical properties.

1-9 NUREG-1724
To effectively model the fate and transport of contaminants in ground water, it is important 

to characterize the geochemical properties of the natural waters and the aquifer 

mineralogy. Characterization of the underlying lithologies includes measurements of 

buffering capacity, total organic carbon, cation exchange capacity, and identification of 

the clay mineralogy. The general chemical characteristics of fluids within the lithologies 

are described by measurements of pH, temperature, dissolved oxygen, redox potential 

(Eh), buffering capacity, and the concentrations of major ions and trace metals. 

(i) Aquifer geochemistry data are adequate to model the attenuation of contaminants. 

The values of the geochemical parameters used in transport models are justified. 

Acceptable parameter estimation methods include, direct measurement, use of a 

conservative bounding estimate, reference to literature values for similar aquifer 

conditions, and laboratory studies of aquifer materials. 

(g) Identify contaminant attenuation mechanisms. 

The major attenuation mechanisms that work to mitigate the effects of ground-water 

contamination are dilution in surrounding ground water, sorption of contaminants to the 

soil matrix, and immobilization of contaminants from geochemical and biochemical 

reactions. 

Claims that contamination is reduced by dilution are supported by a sufficient technical 

basis. There are two mechanisms for dilution of a contaminant plume in ground water: 

dispersion and mixing. Dispersion is a process whereby contaminant plumes tend to spread 

out and become less concentrated as they are advected away from the source. Mixing is 

the result of uncontaminated water being added to the ground-water system through 

natural recharge, injection, or upward movement of water from underlying aquifers, 

which reduces the concentration of contaminants. Estimation of surface recharge or 

upward flow through leaky aquitards is either established from field measurements or 

conservative assumptions are used. 

(i) The values of sorption coefficients are based on the nature of the constituent and 

site-specific geochemical conditions. The degree of sorption of contaminants to the 

soil matrix depends on the affinity of each constituent for the soil in a particular 

aquifer. Constituents that carry a positive charge, as do most trace metals in 

solution, are good candidates for cation exchange adsorption to clay and oxide 

surfaces. However, because surface charges of clays and oxides decrease with 

decreasing pH, the reviewer shall carefully examine claims of attenuation from 

cation exchange under low pH conditions. Organic contaminants tend to be 

hydrophobic and are strongly attenuated in soils that have high organic carbon 

content. Most contaminant fate and transport models quantify the affinity of 

contaminants for soil by use of a distribution coefficient or KD. Batch or column 

equilibria experiments, using representative leachate and soil samples, are 

performed to support estimations of KD for each hazardous constituent. 

(b) Estimations of attenuation from geochemical or biochemical equilibrium 

reactions are accomplished by use of acceptable modeling software 

NUREG-1724 1-10

I I I
packages such as MINTEQA2 (Allison, et al., 1991) and PHREEQE 

(Parkhurst, et al., 1980). However, these packages are limited in that they 

do not consider transport of contaminants. Thus, results are only valid for 

reactions within a confined space (e.g., within the disposal cell). The 

reviewer shall determine that all model input parameters have sufficient 

technical bases and represent reasonably conservative estimations. 

Additionally, conclusions drawn from such models are supported by field 

observation; that is, they are consistent with site characterization data. 

(ii) At sites where the contamination source has been effectively eliminated, 

monitoring data are used to assess attenuation of contaminants. If the contaminant 

source has been eliminated by surface reclamation, changes in the nature and 

extent of contamination over time are monitored. In such situations the center of 

mass of the contaminant plume moves along the direction of ground-water flow. 

The effects of dispersion are also observable over time as a decrease in peak 

concentrations near the center of the contaminant plume and a lateral spreading of 

the plume. If significant precipitation or adsorption is occurring, it is reflected in 

a decrease in the mass of contaminants in the aqueous phase. 

1.4 Evaluation Findings 

If the staff's review, as described in standard review plan results in the acceptance of the site 

characterization, the following conclusions may be presented in the technical evaluation report. 

NRC has completed its review of the site characterization at the uranium 

milling facility. 

The DOE has provided an acceptable history of the site, including: (1) a description of leaching 

solutions and other chemicals used in the process and their relative quantities; (2) a description of the 

wastes generated at the site during the milling process, and the waste handling facilities; (3) a summary 

of the known impact of site activities on the hydrologic system and water quality; and (4) a description of 

non-milling-related activities that may have altered the hydrologic system. 

The DOE has provided acceptable information pertaining to the surrounding land and water use 

including: (1) an overview of water uses, quantity available, and potential uses to which the water is suited; 

(2) definitions of the class-of-use category of each water source; (3) identification of potential receptors 

of ground-water or surface-water contamination; (4) assessment of variations in dilution effects of stream 

flow on contaminants; and (5) assessments of the effects of meteorological conditions on erosion, 

infiltration, and water-table elevation. 

The DOE has provided acceptable meteorologic data, including : (1) wind speed and direction; (2) 

rainfall; and (3) evaporation data, to allow an evaluation of potential impacts of the meteorologic conditions 

on disposal cell performance. 

The ground-water and surface-water hydrology is acceptably described, including: (1) geometry, 

lateral extent, and thickness of potentially affected aquifers and confining units; (2) a determination of

1-11 NUREG-1724
which aquifers constitute the uppermost aquifer where regulatory compliance will be evaluated; 

(3) descriptions of the unsaturated units that convey hazardous constituents to the water-bearing units; (4) 

maps of acceptable detail showing the relative dimensions and locations of hydrogeologic units that have 

been impacted by milling activities; (5) information on geologic characteristics that may affect 

ground-water flow beneath the site; and (6) hydraulic head contour maps of both local and regional scale 

for the uppermost aquifer beneath the site. 

The estimation of hydraulic and transport properties is acceptable and includes: (1) hydraulic 

conductivity and storage coefficients determined by conducting aquifer pump tests on several wells; 

(2) determination of hydraulic gradients using hydraulic head contour maps; (3) calculations of storage 

coefficients, as applicable; and (4) longitudinal and transverse dispersivities, as appropriate. The evaluation 

of ground-water/ surface-water interactions with nearby streams, rivers, or lakes is acceptable. 

Geochemical conditions and water quality are acceptably analyzed, including identification of constituents 

of concern that are reasonably expected to be derived from the tailings. Each constituent of concern is 

found in 40 CFR Part 192, Appendix I or 40 CFR Part 192, Subpart A, Table 1. The DOE has made an 

acceptable determination of baseline water quality, including: (1) maps of appropriate scale and legibility; 

(2) descriptions of sampling methods, monitoring devices, and quality assurance practices; (3) where 

applicable, delineation of zones of differing water quality and their possible origin; and (4) a table of 

summary statistics for each zone of differing quality. The applicant has provided an acceptable delineation 

of the extent of contamination supported by appropriate samples, maps of surface wastes and contaminated 

materials, maps of the approximate shape and extent of ground-water contamination, and identification 

of any offsite sources of water contamination. The description of the source term is acceptable and includes 

not only mill tailings constituents but those contaminants that might mobilize by contact with tailings 

leachate. 

The characterization of the subsurface geochemical properties is acceptable. Attenuation 

mechanisms have been described including the technical bases for determining that contamination will be 

reduced by dilution, sorption on the soil matrix, or geochemical or biochemical reactions. The DOE has 

provided direct measurements in support of attenuation of contaminants where the source has been 

eliminated by surface reclamation. 

On the basis of the information provided in the application and the detailed review conducted of 

the site characterization for the uranium milling facility, the NRC staff has concluded 

that the information is acceptable and is in compliance with 40 CFR 192.02 (c), which requires the NRC 

to establish a list of hazardous constituents, concentration limits, a point of compliance, and a compliance 

period; 40 CFR Part 192, Subpart A, Table 1, which provides a table of concentration limits for certain 

constituents when they are present in ground water above background concentrations. 

NUREG-1724 1-12

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1.5 References

American Society for Testing and Materials Standards 

D4044 Standard Test Method for (Field Procedure) for Instantaneous Change in Head (Slug) Tests 

for Determining Hydraulic Properties of Aquifiers. 

D4050 Standard Test Method (Field Procedure) for Withdrawal and Injection Well Tests for 

Determining Hydraulic Properties of Aquifer Systems. 

D4104 Standard Test Method (Analytical Procedure) for Determining Transmissivity of Nonleaky 

Confined Aquifers by Overdamped Well Response to Instantaneous Change in Head (Slug 

Tests). 

D4105 Standard Test Method (Analytical Procedure) for Determining Transmissivity and Storage 

Coefficient of Nonleaky Confined Aquifers by the Modified Theis Nonequilibrium Method. 

D4106 Standard Test Method (Analytical Procedure) for Determining Transmissivity and Storage 

Coefficient of Nonleaky Confined Aquifers by the Theis Nonequilibrium Method. 

D4448 Standard Guide for Sampling Groundwater Monitoring Wells. 

D4630 Standard Test Method for Determining Transmissivity and Storage Coefficient of 

Low-Permeability Rocks by In Situ Measurements Using the Constant Head Injection Test. 

D4696 Standard Guide for Pore-Liquid Sampling from the Vadose Zone. 

D4750 Standard Test Method for Determining Subsurface Liquid Levels in a Borehole or 

Monitoring Well (Observation Well). 

D4840 Standard Guide for Sampling Chain-of-Custody Procedures. 

D5092 Standard Practice for Design and Installation of Ground Water Monitoring Wells in 

Aquifers. 

D5269 Standard Test Method for Determining Transmissivity of Nonleaky ConfinedAquifers by 

the Theis Recovery Method D5270-96 Standard Test Method for Determining Transmissivity and 

Storage Coefficient of Bounded, Nonleaky, Confined Aquifers. 

D5472 Standard Test Method for Determining Specific Capacity and Estimating Transmissivity 

at the Control Well. 

D5473 Standard Test Method for (Analytical Procedure for) Analyzing the Effects of Partial 

Penetration of Control Well and Determining the Horizontal and Vertical Hydraulic Conductivity 

in a Nonleaky Confined.

1-13 NUREG-1724
D5521 Standard Guide for Development of Ground-Water Monitoring Wells in Granular Aquifers. 

D5737 Standard Guide for Methods for Measuring Well Discharge. 

D5785 Standard Test Method for (Analytical Procedure) for Determining Transmissivity of 

Confined Nonleaky Aquifers by Underdamped Well Response to Instantaneous Change in Head 

(Slug Test). 

D5786 Standard Practice for (Field Procedure) for Constant Drawdown Tests in Flowing Wells 

for Determining Hydraulic Properties of Aquifer Systems. 

D5787 Standard Practice for Monitoring Well Protection. 

D5850 Standard Test Method for (Analytical Procedure) Determining Transmissivity, Storage 

Coefficient, and Anisotropy Ratio from a Network of Partially Penetrating Wells. 

D5855 Standard Test Method for (Analytical Procedure) for Determining Transmissivity and 

Storage Coefficient of a Confined Nonleaky or Leaky Aquifer by Constant Drawdown Method in 

a Flowing Well. 

D5881 Standard Test Method for (Analytical Procedure) Determining Transmissivity of Confined 

Nonleaky Aquifers by Critically Damped Well Response to Instantaneous Change in Head (Slug). 

D5912 Standard Test Method for (Analytical Procedure) Determining HydraulicConductivity of 

an Unconfimed Aquifer by Overdamped Well Response to Instantaneous Change in Head (Slug). 

D5978 Standard Guide for Maintenance and Rehabilitation of Ground-Water Monitoring Wells. 

D6312-98 Standard Guide for Developing Appropriate Statistical Approaches for Ground-Water 

Detection Monitoring Programs. 

Allison, J.D., D.S. Brown, and K.J. Novo-Gradac, 1991, MINTEQA2/PRODEFA2, A Geochemical 

Assessment Model for Environmental Systems: Version 3.0 User's Manual. Environmental 

Protection Agency Publication EPA/600/3-91/021, 1991. 

Environmental Protection Agency, 40 CFR Part 192, Health and Environmental Protection Standards for 

Uranium and Thorium Mill Tailings. 

Gelhar, L.W., C. Welty, and K.R. Rehfeldt, 1992, A critical review of data on field-scale dispersion in 

aquifers. Water Resources Research 28(7), 1992. 

NRC, 1996, Staff Technical Position; Alternate Concentration Limits for Title II Uranium Mills, 

January 1996. 

Parkhurst, D.L., Thorstensen, and L.N. Plummer, 1980, PHREEQE-A Computer Program for 

Geochemical Calculations. U.S. Geological Survey, Water Resources Investigation 80-96, 1980. 

NUREG-1724 1-14

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Smith R.D. 1987, Nuclear Regulatory Commission, "Sampling of Uranium Mill Tailings 

Impoundments for Hazardous Constituents", Memorandum, February 9, 1987, Division of Waste 

Management, Nuclear Regulatory Commission.

1-15 NUREG-1724
2.0 GROUND-WATER PROTECTION STANDARDS 

2.1 Areas of Review 

Ground-water protection standards are established for each hazardous constituent. The staff will 

review the technical basis that the DOE has presented for the following elements of acceptable 

ground-water protection standards: 

(1) The list of hazardous constituents; 

(2) A description of the point of compliance; 

(3) Ground-water Protection Standards for hazardous constituents may be either: 

(a) Background concentration limit 

As defined in 40 CFR 192.02 (c)(3)(i)(A) the background concentration limit is the 

background concentration. 

(b) Maximum concentration limit. 

Maximum concentration limits are identified in 40 CFR Part 192, Subpart A, Table 1. 

(c) Alternate concentration limit 

Alternate concentrations limits are established as described in 40 CFR 192.02(c)(3)(ii). 

(d) Supplemental Standards 

Supplemental standards are established as described in 40 CFR Parts 192.21 and 192.22. 

2.2 Review Procedures 

The reviewer shall examine the ground-water protection standards to verify that they have been 

defined consistent with the acceptance criteria. Specifically, the reviewer shall: 

(1) Verify that the DOE has identified all constituents of concern that are present in the tailings 

leachate. 

(2) Verify that the point of compliance has been properly delineated. 

(3) Evaluate whether the proposed concentration limits for each ground-water Protection Standard are 

within a range that is reasonably expected to represent background concentrations; or, if any 

alternate concentration limits or supplemental standards are proposed, verify that the appropriate 

evaluations have been presented in accordance with 40 CFR Parts 192.02 and 192.21 and 192.22.

2-1 NUREG-1724
2.3 Acceptance Criteria

Ground-water protection standards establish a concentration limit for each hazardous constituent, 

at the point of compliance. The development of ground-water protection standards will be acceptable if 

it meets the following criteria: 

(1) Hazardous constituents are identified. 

(2)A point of compliance is established in accordance with 40 CFR 192.02(c)(4). 

The point of compliance is the location where the ground water is monitored to determine 

compliance with the ground-water protection standards. The objective in selecting the point of 

compliance is to provide the earliest practicable warning that the impoundment is releasing hazardous constituents to the ground water. The point of compliance must be selected to provide 

prompt indication of ground-water contamination on the hydraulically downgradient edge of the 

disposal area. The point of compliance is defined as the intersection of a vertical plane with the 

uppermost aquifer at the hydraulically downgradient limit of the waste management area. 

When tailings are disposed of on site, the NRC generally interprets the downgradient limit of the 

waste management area to be the edge of the reclaimed tailings side slopes. However, it is not 

recommended that DOEs be required to compromise the cover integrity to install monitoring wells 

at the actual edge of the reclaimed tailings. 

(3) A concentration limit is specified for each of the hazardous constituents. 

(a) Background concentration limit 

Proper statistical methods, as discussed in Appendix A, are used to determine the expected 

range of naturally occurring background (baseline) concentrations for each hazardous 

constituent. 

(b) Maximum Concentration Limits 

Maximum concentration limits may be established for each hazardous constituent identified 

in 40 CFR Part 192, Subpart A, Table 1 and at the concentrations given in the table, if 

the background level of the constituent is below the value given in the table. 

Alternate Concentration Limits 

Within 40 CFR 192.02(c)(3)(ii), the option for ACLs is established. ACLs are established on a 

site-specific basis after considering remedial or corrective actions to achieve MCLs or background, 

provided it is demonstrated that the constituents will not pose a substantial present or potential 

hazard to human health or the environment, as long as the ACLs are not exceeded. Factors are 

outlined in 40 CFR 192.02(c)(3)(ii)(B)(1 and 2). The criteria for the hazard assessment for ACLs 

is outlined in Section 3.0 of this SRP. 

NUREG-1724 2-2

IlIl
Supplemental Standards

Criteria for applying supplemental standards is detailed in 40 CFR 192.21 and 192.22. 

Supplemental standards may be applied when it is determined that the following circumstances 

exist: 

(a) Remedial actions required under 40 CFR Part 192 Subpart A or B would pose a clear and 

present risk of injury to workers or to members of the public, notwithstanding reasonable 

measures to avoid or reduce risk. 

(b) Remedial actions to satisfy the cleanup standards for land and ground water directly 

produce harm that is clearly excessive compared to the health and environmental benefits, 

now or in the future. A clear excess of health and environmental harm, is harm that is 

long term, manifest, and grossly disproportionate to health and the environmental benefits 

that may reasonably be anticipated. 

(c) The estimated cost of remedial action is unreasonably high relative to the long-term 

benefits, and the residual radioactive materials do not pose a clear present or future 

hazard. 

(d) The cost of a remedial action for cleanup of a building is clearly unreasonably high relative 

to the benefits. 

(e) There is no known remedial action. 

(f) The restoration of ground water is technically impracticable from an engineering 

perspective. 

(g) The ground water meets the definition of limited use groundwater per 40 CFR 192.1 (e). 

The definition of a limited use groundwater, per 40 CFR 192.1 (e), is defined as: "groundwater that is not a current or potential source of drinking water because (1) the 

concentration of total dissolved solids is in excess of 10,000 mg/l, or (2) widespread, 

ambient contamination not due to activities involving residual radioactive materials from 

a designated processing site exists that cannot be cleaned up using treatment methods 

reasonably employed in public water systems, or (3) the quantity of water reasonably 

available for sustained continuous use is less than 150 gallons per day". 

(h) Radionuclides other than radium 226 and its decay products are present in sufficient 

quantity and concentration to constitute a significant radiation hazard from residual 

radioactive materials 

When one or more of the criteria applies, the remedial alternative that comes as close to meeting the 

applicable standard under 40 CFR 192.02 (c)(3) as is reasonably achievable should be implemented.

2-3 NUREG-1724
2.4 Evaluation Findings

If the staff's review results in the acceptance of the site ground-water protection standards, the following 

conclusions may be presented in the technical evaluation report. 

NRC has completed its review of the ground-water protection standards at the 

uranium milling facility. 

The DOE has acceptably identified the hazardous constituents and has established acceptable concentration 

limits and cleanup standards. Established background levels are acceptable. Acceptable statistical methods 

have been used to establish the concentration limits. If alternate concentration limits have been requested, 

the DOE has acceptably supported the request with appropriate data and calculations. The DOE has 

established an acceptable point of compliance at the edge of the tailings impoundment on the down-gradient 

direction of hydraulic flow. 

On the basis of the information provided in the application and the detailed review conducted of the 

ground-water protection standards for the uranium milling facility, the staff has 

concluded that the information is acceptable and is in compliance with 40 CFR 192.02, which requires the 

NRC to establish a list of hazardous constituents, concentration limits, a point of compliance, and a 

compliance period; 40 CFR Parts 192.02, 192.21, 192.22 and 40 CFR 192, Subpart A, Table 1, which 

allows use of maximum concentration limits, alternate concentration limits, and supplemental standards. 

2.5 References 

Environmental Protection Agency, 40 CFR Part 192, Health and Environmental Protection Standards for 

Uranium and Thorium Mill Tailings.

NUREG-1724 2-4

I I
3.0 HAZARD ASSESSMENT FOR ALTERNATE CONCENTRATION LIMITS 

3.1 Areas of Review 

Alternate concentration limits must be protective of human health and the environment at the point 

of exposure. Alternate concentration limits which "are not protective of human health and the 

environment" will not satisfy the alternate concentration limit framework. 

The staff shall review the following elements of alternate concentration limit assessments: 

(1) Identification of a point of exposure; 

(2) Characterization of the hazardous constituent source term and the extent of ground-water 

contamination; 

(3) Assessment of hazardous constituent transport in the ground water and hydraulically connected 

surface waters, and their adverse effects on water quality, including present and potential health 

and environmental hazards; 

(4) Assessment of human and environmental exposure to hazardous constituents, including the cancer 

risk and other health and environmental hazards; and 

(5) A demonstration that hazardous constituent concentrations will not pose substantial present nor 

potential hazards to human health and the environment at the point of exposure. 

(6) Assessment of potential remedial alternatives. 

3.2 Review Procedures 

The reviewer shall examine the information and assessments provided for establishing alternate 

concentration limits to make the following determination. 

(1) The hazardous constituent source term has: (a) been characterized; (b) is sufficient to provide a 

defensible estimate of the types, characteristics, and release rates of hazardous constituents that 

have been or are anticipated to be released from the source term; and (c) the extent of 

ground-water contamination at the site has been defined. 

(2) The rates and directions of hazardous constituent migration and transport in the ground water and 

hydraulically connected surface waters have been adequately determined. 

(3) The pathways for human and environmental exposure to hazardous constituents have been 

identified, and exposure magnitudes and effects, including the cancer risk, have been acceptably 

evaluated. 

(4) The alternate concentration limits proposed at the point of compliance are at a level that will allow 

the consituent concentrations to be protective of human health and the environment at the point of

3-1 NLJREG-1724
exposure, considering the attenuation capacity of the aquifer between the point of compliance and 

the point of exposure, there will be no adverse effects on the ground water or on surface-water 

quality that would cause substantial health or environmental hazards at or beyond the point of 

exposure location(s). 

(6) Remedial alternatives have been adequately evaluated and factors such as the length of time to 

reach the standard, applicability to the site conditions, and cost comparisons have been assessed. 

3.3 Acceptance Criteria 

The hazard assessments for alternate concentration limits will be acceptable if they meet the 

following criteria: 

(1) A hazard assessment is performed, that is in accordance with 40 CFR 192.02. The assessment 

addresses the present and potential health and environmental hazards, including the cancer risk 

caused by human exposure to radioactive constituents and other health hazards that may be caused 

by the chemical toxicity of constituents. 

The acceptability of the proposed alternate concentration limit values is based on a finding that the 

constituent will not pose a substantial present nor potential hazard to human health and the 

environment as long as the alternate concentration limit is not exceeded. The use of previously 

established and documented health-based constituent concentration limits in the hazard assessment 

is used as a basis for establishing alternate concentration limit values at specific sites, or such 

values are determined for constituents for which health-based concentration limits have not been 

established. 

(2) The point of exposure is identified. 

The point of exposure is defined as the location(s) at which people, wildlife, or other species could 

reasonably be exposed to hazardous constituents from the ground water. For example, the point 

of exposure may be represented by the location where one or more domestic wells could be 

constructed and might withdraw contaminated ground water, or it may be represented by springs, 

rivers, streams, or lakes into which contaminated ground-water might discharge. In most cases, 

the point of exposure is located at the downgradient edge of land that will be held by either the 

Federal Government or the State for long-term institutional control. The concept of a point of 

exposure is used to assess the potential hazard to human health and the environment. Alternate 

concentration limits for hazardous constituents are established at the point of compliance. The 

point of exposure may be situated at some distance from the point of compliance, allowing the 

hazardous constituent concentrations to diminish through dispersion, attenuation, or sorption within 

the aquifer. As a result, an alternate concentration limit may be set at a concentration that is higher 

than a limit that would be protective of human health and environment at the point of compliance 

location, as long as the hazardous constituent concentration at the point of exposure protects human 

health and environment. 

A distant-point of exposure could be justified, on the basis that land ownership by DOE would 

ensure that ground water from the contaminated aquifers between the disposal site and the point 

NUREG-1724 3-2

I I I
of exposure would not be used. In some rare instances, a distant-point of exposure may be 

established without invoking land ownership or long-term custody. Land ownership or long-term 

custody will not be an issue for establishing a distant point of exposure, if the possibility of human 

exposuer is effectively impossible. When ground water is inaccessible or unsuitable for use, 

human exposure is considered effectively impossible. 

(3) The hazardous constituent source term and the extent of ground-water contamination 

are characterized. 

Characterization of the contaminant source(s) and their extent provides the source term for 

contaminant transport assessments. The source characterization provides reliable estimates of the 

release rates of hazardous constituents as well as constituent distributions. 

The source term characterization provides relevant information about the facility, including: (a) 

the uranium recovery processes used; (b) types and quantities of the reagents used in milling; (c) 

milled-ore compositions; and (d) historical and current waste management practices. This 

information is considered, in conjunction with the physical and chemical composition of the waste 

and the type and distribution of existing contaminants, to characterize the source term and evaluate 

future hazardous constituent release into the ground water (e.g., location of waste discharges, 

retaining structures for wastes, and waste constituents). 

Depending on the hazardous constituents present, additional information on them and their 

properties is provided including: (a) density, solubility, valence state, vapor pressure, viscosity, 

and octanol-water partitioning coefficient; (b) presence and effect of complexing ligands and 

chelating agents, to the extent that constituent mobility may be enhanced; (c) potential for 

constituents to degrade because of biological, chemical, and physical processes; and (d) constituent 

attenuation properties, considering such processes as ion exchange, adsorption, absorption, 

precipitation, dissolution, and ultrafiltration. 

At sites with well-defined contaminant plumes, the spatial distribution of the various hazardous 

constituents is specified. This information calibrates contaminant transport models and supports 

evaluations of whether humans and environmental populations are being exposed to elevated 

concentrations of hazardous constituents. Characterization of the contamination extent includes: 

(a) the type and distribution of hazardous constituents in the ground water and contamination 

sources; (b) the monitoring program used to delineate and characterize hazardous constituent 

distribution; and (c) documentation of the sampling, analysis and quality assurance programs 

followed in the implementation of the site monitoring programs. Such information is used to assess 

present human and environmental population exposure to elevated concentrations of hazardous 

constituents, calibrate contaminant transport models, and evaluate projected future exposures. 

(4) The hazardous constituent transport in ground water and hydraulically connected surface water 

and the adverse effects on water quality, including the present and potential health and 

environmental hazards, are assessed. 

The hydrogeologic and contaminant transport assessment provides and documents estimates of 

projected contaminant distribution, including contaminant transport and degradation and attenuation 

mechanisms between the point of compliance and the point of exposure. The assessment generally

3-3 NUREG-1724
characterizes and provides information on: (a) site hydrogeologic characteristics, including 

ground-water flow direction and rates; (b) background water quality; and (c) estimated transport 

rates, geochemical attenuation, and concentrations of hazardous constituents in the ground water 

and hydraulically connected surface water. 

All likely and significant pathways of hazardous transport in ground water and surface water 

should be identified and assessed. Estimated hazardous constituent concentrations and projected 

distributions are either best estimates or reasonably conservative representations of the rate, 

extent, and direction of constituent transport. 

Projections should be calibrated based on site-specific information. When there is great uncertainty 

in the attenuation-rate estimate, the DOE may rely on measurements of constituent concentrations 

at the point of compliance and the point of exposure over a sufficient time period, before alternate 

concentration limits are established, to verify the projected attenuation rate. 

When projecting (modeling) the concentrations of hazardous constituents at the POE, the staff has 

found it acceptable to project impacts at the POE over at least a 1,000 year time frame. This is 

consistent with the design standard of 40 CFR 192.02 which states that "control of residual 

radioactive materials and their listed constituents shall be designed to be effective for up to one 

thousand years, to the extent reasonably achievable, and in any case, for a least 200 years." 

(5) An assessment of human or environmental exposures to hazardous constituents, including cancer 

risk and other health and environmental hazards, is provided. 

The exposure assessment identifies the maximum levels permissible at the point of compliance that 

are protective of human health and the environment at the point of exposure by evaluating human 

and environmental exposure to hazardous constituents and then demonstrating that the proposed 

alternate concentration limits do not pose substantial present nor potential hazards to human health 

or the environment. 

The exposure assessment at specific sites evaluates health and environmental hazards using water 

classification and water use standards, and existing and anticipated water uses. Agricultural, 

industrial, domestic, municipal, environmental, and recreational water uses, as they pertain to the 

site, are considered. The assessment identifies and evaluates hazardous constituent exposure 

pathways and makes projections of human and environmental population response based on the 

projected constituent concentrations, dose levels, and available information on the radiological and 

chemical toxicity effects of hazardous constituents. The assessment addresses the underlying 

assumptions and variability of the projected health and environmental effects. 

The human exposure assessment is evaluated primarily on the basis of the extent to which people 

are using, and are likely to use, contaminated water from the site. Site-specific water uses are 

determined on the basis of the following considerations: (a) ground-water quality in the site area 

and present water uses; (b) statutory or legal constraints and institutional controls on water use in 

the site area; (c) Federal, State, or other ground-water classification criteria and guidelines; 

(d) applicable water use criteria, standards, and guidelines; and (e) availability and characteristics 

of alternative water supplies. 

NUREG-1724 3-4

I I I
The human exposure assessment considers two potential exposure pathways: (a) ingestion of 

contaminated water and (b) ingestion of contaminated foods. The assessments distinguish between 

health effects associated with threshold and nonthreshold constituents. Mutagenic, teratogenic, and 

synergistic effects are considered in the analysis, if applicable, based on toxicological testing, 

structure-activity relationships, or epidemiological studies. Other pathways that may impact human 

health, such as dermal contact and inhalation, are also to be considered, but need not always be 

assessed, unless it is determined that these exposures could result in significant hazards to human 

health or the environment. 

The assessment of adverse effects associated with present and potential human exposure to 

hazardous constituents should be based on the exposure pathways characterization. The human 

exposure assessment includes: (a) classification of affected water resources; (b) assessment of 

existing and potential water uses; (c) evaluation of the likelihood that people will be exposed to 

hazardous constituents; and (4) evaluation of adverse effects associated with exposure to hazardous 

constituents, including assessment of the permanence and persistence of adverse effects. 

Assessments of the probability of human exposure are often difficult to establish quantitatively. 

Consequently, defensible qualitative estimates are often necessary, and can be characterized as 

either: 

(a) Reasonably likely - when exposure has or could have occurred in the past, or available 

information indicates that exposure to contamination may reasonably occur during the 

contamination period, or 

(b) Reasonably unlikely - when exposure could have occurred in the past, but will probably 

not occur in the future, either because initial incentives for water use have been removed, 

or because available information indicates that no incentives for water use are currently 

identifiable, based on foreseeable technological developments. 

Information in support of the exposure assessment should be supplied, or relevant information and 

studies; such as those available from the International Commission on Radiological Protection and 

the National Council on Radiation Protection and Measurement, for the effects of radioactivity, 

and EPA's Integrated Risk Information System, for chemical-toxicity effects, should be referenced. 

Alternatively site-specific information provided in previous reports, such as the license application 

or the environmental report, can be referenced. A technical basis to establish a reasonable 

assurance that the proposed alternate concentration limits do not pose a hazard to human health or 

the environment should be provided for each constituent for which an alternate concentration limit 

may be established. 

Exposure determinations should consider existing and potential water uses. Potential uses include 

those uses that are reasonably sure to occur (i.e., anticipated use) and uses that are compatible with 

the untreated background water quality (i.e., possible use). Past uses may be included as existing 

or potential uses. 

Water resource classification of existing and potential water use should include: (a) domestic and 

municipal drinking-water use; (b) fish and wildlife propagation; (c) special ecological communities; 

and (d) industrial, agricultural, and recreational uses. The classification of existing and potential

3-5 NUREG-1724
uses of water at the facility should be consistent with Federal, State, and local water-use 

inventories. 

Water yields, costs for development of alternate water supply sources, and legal, statutory, or other 

administrative constraints on the use and development of the water resources should be verified. 

The cancer risk should be evaluated for individual constituents, including radioactive and 

carcinogenic chemicals, and compared with the maximum permitted risk level. The health effects 

of non-radioactive and non-carcinogenic constituents that are chemically toxic will be evaluated 

considering their risk-specific dose levels, and for some chemicals that have threshold effects, it 

will be necessary to calculate a Hazard Index using the reference doses. The Hazard Index is the 

ratio of calculated intake to the risk-reference dose, and an acceptable Hazard Index must be less 

than unity. 

Reasonably conservative or best estimates of potential health effects caused by human exposure 

to hazardous constituents should include an assessment of potential health hazards for each 

constituent for which an alternate concentration limit is proposed, based on comparisons of existing 

and projected constituent concentrations with appropriate exposure limits and dose-response 

relationships from available literature. This assessment of potential health hazards should include 

the maximum concentration limits, risk-reference doses, or risk-specific doses. Risk-reference 

doses are the amounts of toxic constituents to which humans can be daily exposed without suffering 

any adverse effect. Risk-specific doses are the amounts of proven or suspected carcinogenic 

constituents to which humans can be daily exposed, without increasing their risk of contracting 

cancer, above a specified risk level. 

Maximum concentration limits, risk-reference doses, and risk-specific doses for most hazardous 

constituents in uranium mill tailings can be obtained from EPA. The risk-reference dose and risk

specific dose assessment assume a human mass of 70 kg (154 pounds) and consumption of 2 liters 

of water per day (0.53 gallon/day). More stringent criteria may apply if sensitive populations are 

exposed to hazardous constituents. Maximum concentration limits, Risk-reference doses, and/or 

risk-specific doses, can be used to show compliance with the risk level and Hazard Indices. In 

the absence of applicable maximum concentration limits, risk-reference doses, or risk-specific 

doses, a technical basis for the risk assessment can base dose-response relationships on literature 

searches or toxicological research. The exposure analysis should distinguish between threshold 

(toxic) and non-threshold (carcinogenic) effects associated with human exposure, as well as 

teratogenic, fetotoxic, mutagenic, and synergistic effects. 

The cumulative effects of human exposure to hazardous constituents for which alternate 

concentration limits are proposed and other constituents present in contaminated ground water 

will be maintained at a level adequate to protect public health. The combined effects from both 

radiological and non-radiological constituents should be considered. 

Proposed human exposure levels should be reasonably conservative, defensible, and sufficiently 

protective of human health to avoid a substantial present or potential hazard to people for the 

estimated duration of the contamination. When considering the potential for health risks from 

human exposure to known or suspected carcinogens, it is acceptable if alternate concentration 

NUREG-1724 3-6

I I1
limits are established at concentration levels which represent an excess lifetime risk, at a point of 

exposure, to an average individual no greater than between 10' and 106. 

Potential responses of environmental or nonhuman populations to the various hazardous 

constituents are assessed if such populations can realistically be exposed to contaminated ground 

water or hydraulically connected surface water. Terrestrial and aquatic wildlife, plants, livestock, 

and crops are included in the assessment. In the absence of available information that readily may 

be used to demonstrate that there will be no substantial environmental impacts caused by 

ground-water contamination from the site, the exposure assessment provides: (a) inventories of 

potentially exposed environmental populations; (b) recommended tolerance or exposure limits; 

(c) contaminant interactions and their cumulative effects on exposed populations; (d) projected 

responses of environmental populations that result from exposure to hazardous constituents; and 

(e) anticipated changes in populations, independent of the hazardous constituent's exposure. 

Alternatively, DOE demonstrates that environmental hazards are not anticipated, because exposure 

will not occur. 

The potential for adverse effects, such as: (a) contamination-induced biotic changes, (b) loss or 

reduction of unique or critical habitats, and (c) jeopardizing endangered species should be 

described. Aquatic wildlife effects are evaluated by comparing estimated constituent 

concentrations with Federal and State water-quality criteria. Consultation with the U.S. Fish and 

Wildlife Service is required under the Endangered Species Act, if an endangered or threatened 

species is found on the site, or is believed to inhabit the site. 

Terrestrial wildlife exposure to constituents through direct exposure and food-web interactions 

should be considered. 

Agricultural effects from both direct and indirect exposure pathways, crop impacts, reduced 

productivity, and bioaccumulation of constituents should be considered. Reasonably conservative 

estimates of constituent concentrations are compared with Federal and State water-quality criteria 

to estimate agricultural effects associated with constituent exposure. Additionally, crop exposures 

through contaminated soil, shallow ground-water uptake, and irrigation, along with livestock 

exposure through direct ingestion of contaminated water and indirect exposure through grazing, 

should be assessed. 

When appropriate, the hazard assessment considers potential damage to physical structures (e.g., 

from corrosiveness), that may result from exposure to the hazardous constituents in ground water 

and hydraulically connected surface water. Alternatively, DOE demonstrates that damage to 

physical structures is not anticipated, because the exposure will not occur. 

For physical structures, such as foundations, underground pipes, and roads, the reviewer ensures 

that estimated constituent concentrations will not result in any significant degradation or loss of 

function as a result of contamination exposure. 

(6) An adequate assessment of alternative remedial actions has been provided. 

In compliance with 40 CFR 192.02(c)(3)(ii)(A) remedial or corrective actions to achieve must be 

considered to achieve the either background concentration levels or the concentrations in 40 CFR

3-7 NUREG-1724
Part 192, Subpart A, Table 1. Remedial or corrective actions must be alternatives that could 

realistically be applied at the site. The evaluation of alternatives should include the time to reach 

the appropriate concentration levels, applicability of the remedial technology to the site conditions, 

and cost. 

The costs and benefits of each of the corrective action alternative should be considered. It may 

not be necessary in some cases to select and adopt the most stringent alternative if it can be 

demonstrated that the cost of implementing such an alternative is too high compared with the 

expected benefits. The ground-water corrective-action alternative assessments should ensure that: 

(a) a complete range of reasonable alternative corrective actions have been identified; (b) the 

identified corrective actions are feasible and appropriate to reduce constituent concentrations at the 

site; (c) the corrective actions have been designed to optimize their effectiveness; and (d) an 

objective comparison of the costs and benefits associated with the corrective actions is complete. 

Corrective-action alternatives should be based on cleanup goals that are at or below the 

concentration limit determined by the hazard assessment to be protective of human health and the 

environment. A reasonable range of alternative goals should be evaluated (usually at least three). 

The goals should be (a) meaningfully different, (b) reasonably attainable by practicable corrective 

action, and (c) at or below the level identified in the hazard assessment. 

Different corrective actions are currently in operation at uranium mill sites and Title I sites. These 

corrective actions, their results, and their application at other sites can serve as the basis for DOEs 

selection of a corrective-action program. Projections of hazardous, constituent concentrations at 

specific corrective-action measures could be based on present experience and data obtained from 

the implementation of such measures at other sites. 

The corrective actions should be selected and designed to optimize the effectiveness in reducing 

hazardous constituent concentrations. This may be demonstrated with backup calculations that 

provide approximations of the effects of the proposed actions on the ground-water quality under 

the site-specific hydrogeologic conditions. 

The direct and indirect benefits of implementing each of the identified corrective actions should 

be compared with the costs of performing (or not performing) such measures. The cost estimates 

include consideration of costs for design, operation, maintenance and decommissioning. The 

reviewer verifies estimates of the current and projected value of pre-contaminated water resources, 

based on water rights, availability of alternative water supplies, and projected water-use demands. 

The reviewer generally considers the value of potentially contaminated water resources as equal 

to either the cost of domestic or municipal drinking-water supplies, or the cost of supplied water 

to replace the contaminated resources. The absence of alternative water supplies increases the 

relative value of potentially contaminated water resources. The adequacy of the benefits 

assessment is similarly evaluated, considering the avoidance of adverse health effects, value of pre

contaminated ground-water resources, prevention of land-value depreciation, and benefits accrued 

from performing the corrective action. 

NUREG-1724 3-8

I I II
3.4 Evaluation Findings

If the staff's review, as described in this standard review plan, results in the acceptance of the site 

hazard for alternate concentration limit evaluations, the following conclusions may be presented in the 

TER. 

The NRC has completed its review of the site hazard assessment for alternate concentration limit 

evaluations at the uranium milling facility. 

The DOE has performed an acceptable hazard assessment by considering present and potential health and 

environmental hazards, including cancer risk by human exposure to radioactive constituents and other 

health hazards resulting from the chemical toxicity of the constituents. The point of exposure has been 

identified and is acceptably sited at the downgradient edge of the affected land. When a distant point of 

exposure is used, written assurance has been secured, either by the DOE or NRC, that the appropriate 

Federal or State agency will accept the transfer of the specific property, including land in excess of that 

needed for tailings disposal. The hazardous constituent source term and the extent of ground-water 

contamination have been acceptably characterized. The transport of the hazardous constituent in ground 

water and surface water has been defined and any adverse effects on water quality, including present and 

future, have been assessed. The cancer risk and other health and environmental hazards from human or 

environmental exposures to hazardous constituents have been evaluated acceptably including: (a) 

identification of maximum levels permissible at the point of compliance; (b) evaluation of health and 

environmental hazards using water classification and use standards and existing and anticipated water uses; 

(c) appropriate consideration of impact, based on site-specific water uses; (d) consideration of ingestion 

of contaminated water and food; (e) consideration of response of environmental and nonhuman populations 

to the various hazardous constituents including terrestrial and aquatic wildlife, plants, livestock, and crops; 

and (f) consideration of potential damage to physical structures. 

On the basis of the information provided in the application and the detailed review conducted of 

the site hazard assessment for alternate concentration limit evaluations for the uranium 

milling facility, the staff has concluded that the information is acceptable and is in compliance with 

40 CFR 192.02. 

3.5 References 

Environmental Protection Agency, 40 CFR Part 192, Health and Environmental Protection Standards for 

Uranium and Thorium Mill Tailings.

3-9 NUREG-1724
4.0 GROUND-WATER CORRECTIVE ACTION AND 

COMPLIANCE MONITORING PLANS 

4.1 Areas of Review 

The staff shall review any ground-water Corrective Action Plan. For review of some information, the 

reviewer may use review procedures in other chapters of this standard review plan. The following are 

specific portions of a Corrective Action Plan to be reviewed. 

(1) Selection of a ground-water compliance strategy, 

(2) The remedial action design and implementation plan, 

(3) Waste management practices, 

(4) Institutional controls, and 

(5) Ground-water monitoring plans. 

4.2 Review Procedures 

The ground-water compliance strategy shall be examined by the reviewer considering the previously 

reviewed hydrologic and geochemical site characterizations and ground-water protection standards. 

Requirements of 40 CFR 192.03 include that corrective action must be implemented as soon as is 

practicable, and result in conformance with the established concentration limits. 40 CFR Part 192.12 allows 

the DOE to choose between active remediation and natural flushing alternatives, and requires that a 

program be put in place to monitor compliance with restoration goals. Regulations do not provide any 

specific requirement for the design and operation of the ground-water remedial action program. In fact, 

40 CFR 192.20 states that protection of water should be considered on a case-specific basis, drawing on 

hydrological and geochemical surveys, and other relevant data 

The reviewer shall examine corrective action plans and compliance monitoring plan information to verify 

the following: 

(1) The selected ground-water compliance strategy is likely to result in timely compliance with 

established standards. 

(2) The DOE specifies a timetable for meeting minimum performance goals as an indication that the 

remedial action is working. 

(3) The corrective action design and the implementation plan are appropriate for the site 

characteristics, and clearly defined restoration cleanup standards have been defined. 

(4) Waste management practices are in compliance with environmental protection regulations.

4-1 NUREG-1724
(5) Institutional controls during the restoration period are sufficient to prevent significant hazards to 

human health and the environment. 

(6) The ground-water monitoring system is sufficient to verify the performance of the selected 

restoration strategy, and to monitor the long-term performance of any onsite tailings disposal cells. 

4.3 Acceptance Criteria 

Regulation 40 CFR 192.04 requires that if the ground-water protection standards are found or projected 

to be exceeded, a corrective action program shall be placed into operation as soon as is practicable, and 

in no event later than 18 months after a finding of exceedance. Unless otherwise directed by the 

Commission, before putting the program into operation, the DOE shall submit the supporting rationale for 

the proposed corrective action program. The objective of the program is to return hazardous constituent 

concentration levels in ground water to the concentration limits set as standards. 

The corrective action should result in conformance with the established concentration limits, address either 

removing the hazardous constituents or treating them in place, and include a program to monitor 

compliance with cleanup standards. Regulations do not require any specific designs or methods to be used 

for the ground-water corrective action program. Because of the nearly limitless possibilities for designing 

and implementing ground-water corrective actions, staff reviewers shall focus on the technical feasibility 

from an engineering perspective and evaluate whether the proposed design is likely to result in timely 

compliance with established concentration limits and whether the monitoring program is adequate to verify 

the effectiveness of the design. A ground-water corrective action program or a compliance monitoring 

program will be acceptable if it meets the following criteria: 

(1) The selection of a restoration strategy conforms to the decision tree in figure 4-1 which was 

developed by the DOE (1993) and has been found acceptable by the NRC. 

NRC has found the strategies to be acceptable for achieving compliance with ground-water 

protection standards: 

(a) No remediation-This is an acceptable strategy at sites where ground-water contamination 

related to uranium processing activities is not present, or where contamination does not 

exceed either background levels, maximum concentration limits, alternate concentration 

limits, or supplemental standards, depending on the applicable regulatory requirements. 

(b) Natural Flushing-Natural flushing is acceptable in accordance with 40 CFR 192.12(c)(2) 

.and may be used in lieu of active remediation if the three following conditions are met: 

(i) either background concentrations, maximum concentration limits, or alternate 

concentration limits can be achieved within 100 yr; (ii) enforceable institutional controls 

will protect health and environment and satisfy beneficial uses of ground water during the 

natural flushing period; and (iii) the ground water is not now, nor is it projected to be, 

used as a source of public drinking water. 

NUREG-1724 4-2

I I 1 1
B-n Ixeso aimma~nr 

UmCharacfterzePurrnd Flydrologi

Will Nakiral Hushing Resultin Ca n Ins i tu torsi Controls be 

Compliance with Nb)dnum Ye s YP Mi n1a ined Duri ng the Flushi ng Peri, W Yes 

Conce nta don U rri is, Baclkgrou nc a rdis Na Ural Rus hi rig Protective ol 

Levels, or AJ ter na le Come nta doi i Hj rrB n He al th a nd the Erwironrre nt ? 

Units within 100 Yrs? 

BOX 13 Noj ýb Box 141 

Ca n Ins I tu torsi Controls be Will Na Ural Rus hi ng a nd Ac Ive hbi n1a ined Duri ng the Flushi ng Peri, )d Grou nd Wa ter Re media Ion Resul [iny, andis NaUral Rushingand Active Corrplia nDe W th kbxi rru m GroundWafer I'lernedialon Prolacbe- Yes 

Come nVa ton U rri tr,, Backgrou nd of Hu rm n Heal th a nd the Environrre nt? Levels. or A] ter na te Concentation 

Unit; Within 100 Yrs ? No 

BOX 1 

Will Acive Ground Water Yes 

Rernadiallon Wthods Pesultin 

Con-plia noe W th Backgrou nd Leve s. PJaximurnConoentation Urriis, 

orAlternate ConoentationUrrits? 

Nc4 

Box I I 

Apply Supple rrental Standards Based 

on Tech nioal I rrprac icabili V a nd 

A;Vy Irks I bu Iona[ Controls Where Nee 

Figure 4-1 Ground-water compliance strategy selection.

4-3 NUREG-1724

KEY 

Conplia nce

4-3
Evaluation of natural flushing relies extensively on hydrogeologic data collected during the site 

characterization. The effectiveness of natural flushing in achieving cleanup standards is 

demonstrated using flow and transport models. The DOE identifies the model used to simulate the 

natural flushing process. Model development is described in terms of how model dimensions, grid 

spacing, and input parameters relate to the site conceptual model. Model inputs are summarized 

in tabular form, and an appendix containing model input and output files is included and 

referenced. Ideally, modeling results are presented as a series of contour plots that illustrate 

changes in the extent of contamination over time for each hazardous constituent. When practical, 

the DOE overlays contour plots on a site map--or provides points of reference-to show proximity 

of contaminants to local features. If the DOE demonstrates the efficacy of natural flushing by 

including the dilution effect of ground-water discharge to a surface water body, the reviewer shall 

ensure that assumptions regarding average flows are conservative. For example, stream dilution 

is estimated for an extended period of low discharge. 

(c) Active remediation-Active remediation methods are employed at contaminated sites where 

contamination exceeds either background levels, maximum concentration limits, alternate 

concentration limits, or supplemental standards and natural flushing is not an acceptable 

alternative. 

(e) A combination of active remediation and natural flushing-This option is appropriate for 

sites where contamination is of a limited aerial extent. Active remediation is employed at 

certain sections within the site while allowing the remainder of the site to flush naturally. 

This option is also appropriate for a scenario in which active remediation is used initially 

to reduce contamination to the point where natural flushing can then be used to meet 

restoration standards within 100 yr. 

(2) The remedial action design and implementation is adequate. 

When active remediation is necessary, a timetable for ground-water cleanup is established. This 

timetable can be based on model predictions of a design's likely restoration performance. When 

models are used to predict performance, a sensitivity analysis is performed to evaluate a variety 

of scenarios and their effect on the expected system performance. All modeling input parameters 

are based on site characterization data or on technically justified assumptions. 

There are as many potential active remediation designs as there are contaminated sites. As such, 

it is beyond the scope of this standard review plan, and would be unnecessarily restrictive, to 

attempt to provide specific acceptance criteria for every possible active remediation scenario. In 

general, however, if active remediation methods are to be employed, a discussion of the type of 

active remediation is provided along with engineering specifications and an analysis 

of effectiveness. 

Engineering specifications include design details such as pumping/injection rates, treatment 

methods, equipment and maintenance requirements, plans and schedules for construction, and maps 

showing locations of equipment. 

An analysis is conducted to determine the expected effectiveness of the remediation system. 

Analyses are conducted to demonstrate that: 

NUREG-1724 4-4

I I I
(a) The chosen active remediation technology is appropriate for the hydrogeologic and 

geochemical conditions at the site. 

(b) Design pumping rates are sustainable and sufficient to control the migration of 

contaminants away from the site. 

(c) The effects of natural aquifer heterogeneity are properly and conservatively accounted for 

in the remediation strategy. 

(3) Adequate waste management practices are defined. 

The disposition of effluent generated during active remediation is addressed in the corrective action 

plan. When retention systems such as evaporation ponds are used, design considerations from 

erosion protection and stability along with construction plans reviewed by a qualified engineer are 

included. Ideally the ponds should have leak detection systems capable of reliably detecting a leak 

from the pond into the ground water and should be located where they will not impede the timely 

surface reclamation of the tailings impoundment. 

If water is to be treated and reinjected, either into the upper aquifer or into a deep-disposal well, 

the injection program is approved by the appropriate State or Federal authority. If effluent is to be 

discharged to a surface-water body, DOE obtains a National Pollutant Discharge Elimination 

System permit for discharge to surface water. 

(4) Appropriate site access control is provided by the DOE. 

Site access control should be provided by the DOE until site closure to protect human health and 

the environment from potential harm. Site access control is accomplished by limiting access to the 

site with a fence and by conducting periodic inspections of the site. 

(5) Effective corrective action and compliance monitoring programs are provided. 

The DOE's monitoring programs are adequate to evaluate the effectiveness of ground-water 

restoration and control activities, and to monitor compliance with ground-water cleanup standards. 

The description of the monitoring program includes or references the following information: 

(a) Quality assurance procedures used for collecting, handling, and analyzing ground-water 

samples; 

(b) The number of monitor wells and their locations; 

(c) A list of constituents that are sampled and the monitoring frequency for each monitored 

constituent; 

(d) Action levels that trigger implementation of enhanced monitoring or revisions to cleanup 

activities (i.e., timeliness and effectiveness of the corrective action). 

Corrective action monitoring

4-5 NUREG-1724
The same wells used to determine the nature and extent of contamination may be used to 

monitor the progress of ground-water corrective action activities. An appropriate well 

configuration should be designed once the plume has been delineated and the rate and 

direction of ground-water flow has been established. The monitoring well configuration 

must be able to adequately evaluate performance of the remedial action and monitor 

compliance. 

DOE chooses a monitoring interval that is appropriate for monitoring corrective action 

progress. Not all hazardous constituents need to be monitored at each interval. It is 

generally acceptable for DOE to choose a list of more easily measured constituents that 

serve as good indicators of performance. These indicators include conservative constituents 

that are less likely to be attenuated such as chloride, total dissolved solids, and alkalinity. 

However, if a hazardous constituent is causing a demonstrated risk to human health or the 

environment, that constituent must be monitored during the corrective action. 

Termination of corrective action 

The corrective action program may be terminated after the corrective action monitoring 

demonstrates that all hazardous constituents are at or below the licensed limits. An 

observation period, after active corrective action measures cease, is necessary to assure 

that hazardous constituents will remain at or below compliance limits and not begin to rise 

before the corrective action program is terminated. The length of this observation period 

is determined on a site-specific basis, with a minimum period of 1 year. 

Compliance monitoring 

After a corrective action program has been terminated, compliance monitoring at the point 

of compliance will resume as defined in the long term surveillance plan. 

(6) Design of Surface Impoundments 

The reviewer shall determine that any lined impoundment built as part of the corrective action 

program to contain wastes is acceptably designed, constructed, and installed. The design, 

installation, and operation of these surface impoundments must meet relevant guidance provided 

in Regulatory Guide 3.11, Section 1. Materials used to construct the liner shall be reviewed to 

determine that they have acceptable chemical properties and sufficient strength for the design 

application. The reviewer shall determine that the liner will not be overtopped. The reviewer shall 

determine that a proper quality control program is in place. 

If the waste water retention impoundments are located below grade, the reviewer shall determine 

that the surface impoundments have an acceptable liner to ensure protection of ground water. The 

location of a surface impoundment below grade will eliminate the likelihood of embankment failure 

that could result in any release of waste water. The reviewer shall determine that the design of 

associated dikes is such that they will not experience massive failure. 

The design of a clay or synthetic liner and its component parts should be presented in the 

application or related amendment applications for a uranium recovery operation. At a minimum, 

NUREG-1724 4-6

I I I ll
design details, drawings, and pertinent analyses should be provided. Expected construction 

methods, testing criteria, and quality assurance programs should be presented. Planned modes of 

operation, inspection, and maintenance should be discussed in the application. Deviation from 

these plans should be submitted to the staff for approval before implementation. 

The liner for a surface impoundment used to manage uranium and thorium byproduct material must 

be designed, constructed, and installed to prevent any migration of wastes out of the impoundment 

to the subsurface soil, ground water, or surface water at any time during the active life of the 

surface impoundment. The liner may be constructed of materials that allow wastes to migrate into 

the liner provided that the impoundment decommissioning includes removal or decontamination 

of all waste residues, contaminated containment system components, contaminated subsoils, and 

structures and equipment contaminated with waste and leachate. 

The liner must be constructed of materials that have appropriate chemical properties and sufficient 

strength and thickness to prevent failure caused by pressure gradients, physical contact with the 

waste or leachate, climatic conditions, and the stresses of installation and daily operation. The 

subgrade must be sufficient to prevent failure of the liner caused by settlement, compression, or 

uplift. Liners must be installed to cover all surrounding earth that is likely to be in contact with 

the wastes or leachate. 

Tests should show conclusively that the liner will not deteriorate when subjected to the waste 

products and expected atmospheric and temperature conditions at the site. Applicant test data and 

all available manufacturers' test data should be submitted with the application. For clay liners, 

tests, at a minimum, should consist of falling head permeameter tests performed on columns of 

liner material obtained during and after liner installation. The expected reaction of the 

impoundment liner to any combination of solutions or atmospheric conditions should be known 

before the liner is exposed to them. Field seams of synthetic liners should be tested along the 

entire length of the seam. Representative sampling may be used for factory seams. The testing 

should use state-of-the-art test methods recommended by the liner manufacturer. Compatibility 

tests that document the compatibility of the field seam material with the waste products and 

expected weather conditions should be submitted for staff review and approval. If it is necessary 

to repair the liner, representatives of the liner manufacturer should be called on to supervise the 

repairs. 

Proper preparation of the subgrade and slopes of an impoundment is very important to the success 

of the surface impoundment. The strength of the liner is heavily dependent on the stability of the 

slopes of the subgrade. The subgrade should be treated with a soil sterilant. The subgrade surface 

for a synthetic liner should be graded to a surface tolerance of less than 2.54 cm (1 in) across a 

30.3-cm (1-ft ) straightedge. NRC Regulatory Guide 3.11, Section 2 (NRC, 1977) outlines 

acceptable methods for slope stability and settlement analyses, and should be used for design. If 

a surface impoundment with a synthetic liner is located in an area in which the water table could 

rise above the bottom of the liner, underdrains may be required. The impoundment will be 

inspected in accordance with Regulatory Guide 3.11.1 (NRC, 1980). 

To prevent damage to liners, some form of protection should be provided, such as (a) soil covers; 

(b) venting systems; (c) diversion ditches; (d) side slope protection; and (e) game-proof fences.

4-7 NUIREG-1724
A program for maintenance of the liner features should be developed, and repair techniques should 

be planned in advance. 

The surface impoundment must have sufficient capacity and must be designed, constructed, 

maintained, and operated to prevent overtopping resulting from (a) normal or abnormal operations, 

overfilling, wind and wave actions, rainfall, or run-on; (b) malfunctions of level controllers, 

alarms, and other equipment; and (c) human error. If dikes are used to form the surface 

impoundment, they must be designed, constructed and maintained with sufficient structural 

integrity to prevent their massive failure. In ensuring structural integrity, the applicant must not 

assume that the liner system will function without leakage during the active life of the 

impoundment. 

Controls should be established over access to the impoundment, including access during routine 

maintenance. A procedure should be provided that ensures that unnecessary traffic is not directed 

to the impoundment area. 

In addition, the reviewer shall evaluate the proposed surface impoundment to determine if it meets 

the definition of a dam as given in Regulatory Guide 3.11 (NRC, 1977). If this is the case, the 

surface impoundment should be included in the NRC dam safety program, and be subject to 

Section 215, National Dam Safety Program of the Water Resources Development Act of 1996. 

If the reviewer finds that the impoundment conforms to the definition of a dam, an evaluation of 

the dam ranking (low or high hazard) shall be made. If the dam is considered a high hazard, an 

emergency action plan is needed consistent with Federal Emergency Management Agency 

requirements. For low-hazard dams, no EAP is required. For either ranking of a dam, the 

reviewer shall also determine that the licensee has an acceptable inspection program in place to 

ensure that the dikes are routinely checked, and that performance is properly maintained. 

A quality control program should be established for the following factors (a) clearing, grubbing, 

and stripping; (b) excavation and backfill; (c) rolling; (d) compaction and moisture control; 

(e) finishing; (f) subgrade sterilization; and (g) liner subdrainage and gas venting. 

(7) Appropriate institutional control is provided for the site. 

The primary purpose of institutional controls is to protect human health and the environment from 

potential harm while the site is being brought into compliance. Institutional controls are typically 

either government controls or property controls. Government controls include zoning restrictions, 

permit programs, well-drilling restrictions, and other restrictions that are traditionally established 

under the authority of governments. Property controls are legal devices, such as deed restrictions, 

easements, and restrictive covenants, that are based on state property law and are used to restrict 

the private use of a site. Care must be taken to assure that an institutional control is durable and 

enforceable. Successful implementation of institutional controls under long-term care, requires 

that difficulties such as keeping track of property ownership, enforcement of the controls, and 

variations in State property laws, are resolved during the review period. For the use of 

institutional controls on third party sites, staff should consult with NRC Office of General Council. 

NUREG-1724 4-8

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4.4 Evaluation Findings

If the staff review, results in the acceptance of the ground-water corrective action plan and compliance 

monitoring plans, the following conclusions may be presented in the technical evaluation report. 

NRC has completed its review of the ground-water corrective action and compliance monitoring plans at 

the uranium milling facility. The ground-water corrective action program should 

achieve the goal of returning hazardous constituent concentration levels in ground water to the 

concentration limits set as standards. The monitoring program will provide reasonable assurance that at 

the end of corrective actions the ground-water protection standard will not be exceeded. 

The DOE has established a ground-water compliance strategy, that is acceptable for the site, which consists 

either of no remediation or active remediation, when contaminants are present at concentrations above 

background levels, maximum concentration limits, alternate concentration limits, or supplemental 

standards. When active remediation is necessary, the remedial action design and implementation are 

acceptable. The DOE has acceptably presented pumping/injection rates, treatment methods, equipment and 

maintenance requirements, and plans and schedules for construction, and has produced maps showing 

locations of remediation equipment. An analysis has been conducted that demonstrates: (1) the chosen 

active remediation system technology is appropriate for the site conditions; (2) design pumping rates are 

sustainable and will control migration of contaminants away from the site; and (3) the natural heterogeneity 

of the system has been acceptably accounted for in a conservative remediation strategy. The DOE has 

identified acceptable waste management practices. Institutional controls are appropriate for the site, 

including: (1) controlling access to the site; (2) conducting periodic inspections; and (3) periodically 

monitoring restoration performance. The monitoring program includes: (1) a description of quality 

assurance procedures; (2) the number of monitoring wells and their locations; (3) a list of constituents that 

will be sampled, along with the sampling frequency for each monitored constituent; and (4) action levels 

for triggering enhanced monitoring or revisions to cleanup activities. The DOE has described an acceptable 

scheme for restoration and compliance monitoring. The DOE will sample ground water at the point of 

compliance for all hazardous constituents of concern. 

On the basis of the information provided in the application and the detailed review conducted of the 

ground-water corrective action and compliance monitoring plans for the uranium milling 

facility, the staff has concluded that the plans are acceptable and are in compliance with 40 CFR Part 192. 

If surface impoundments are to be used at the facility to manage byproduct material, their design has been 

found to be acceptable. If the surface impoundment meets the definition of a dam, it will be inspected and 

evaluated as part of the NRC's dam safety program. 

4.5 References 

DOE, 1993, "Technical Approach to Groundwater Restoration", DOE/AL62350-20F, November. 

Environmental Protection Agency, 40 CFR Part 192, Health and Environmental Protection Standards for 

Uranium and Thorium Mill Tailings.

4-9 NUREG-1724
5.0 LONG-TERM SURVEILLANCE PLAN

5.1 Areas of Review 

The staff shall review the following information in the long-term surveillance plan: 

(5) (1) Description of the land ownership arrangements and the disposal area; 

(6) (2) The location of background, points of compliance and if applicable points of exposure as 

to surface placement and aquifer completions 

(3) Stipulations regarding inspection frequency, the frequency of reporting to the Commission, ground

water monitoring requirements, record keeping requirements, and quality assurance procedures; 

(4)Criteria for initiating maintenance or emergency procedures. In 40 CFR 192.04 it is stated that "if the 

groundwater concentration limits established for disposal sites under the provisions of § 192.02(c) are 

found or projected to be exceeded a corrective action program shall be placed into operation as soon as 

is practicable, and in no event later than eighteen (18) months after a finding of exceedance". 

5.2 Review Procedures 

The reviewer shall examine ground-water standards to verify that they have been defined consistent with 

the acceptance criteria in this standard review plan. The staff will reference previously submitted 

descriptions of the geology, hydrology, geochemistry, and the ground-water corrective action strategy. 

5.3 Acceptance Criteria 

The long term surveillance plan will be acceptable with respect to water resources protection if it 

meets the following criteria: 

(1) Background, points of compliance, and, if applicable, points of exposure have been located as 

described in the existing license. Wells should be correctly located as to surface locations and 

aquifer completions. Well locations should be surveyed in and should be located on site scale 

maps. 

(2) If there has been no leakage from the impoundment into the ground water, appropriate 

ground-water parameters should be monitored and detection concentrations established that will 

provide early warning of leakage. Appropriate parameters should be indicative of the tailings 

material and not significantly affected by retardation reactions. For acid tailings appropriate 

detection parameters might include total dissolved solids, chloride or sulfate. 

(3) The sampling frequency is sufficient to protect the public and environment at the point of exposure 

and sufficient to ensure that the ground-water downgradient of the point of compliance will not be 

degraded to any great extent before contamination is detected. This will require a knowledge of 

potential contaminant plume velocities. It is anticipated that the calculation of potential 

contaminant plume velocities will be based on advective calculations (ASTM Standards D5447,

5-1 NUREG-1724
D5490, D5609, D5610, D5611, D5718, E978 and Anderson, 1992 ). However, more complex 

calculations that include such processes as dispersion and retardation should be performed if site 

conditions warrant them. For sites with alternate concentrations limits, the sampling frequency 

should be sufficient to detect a potential contaminant plume, well before ground water at the point 

of exposure is degraded. 

(4) It is anticipated for most sites that routine monitoring of once every three years will be acceptable 

unless site-specific conditions warrant an increased or decreased frequency of monitoring. If 

more frequent monitoring is required; the reviewer shall also need to identify the increase in the 

long-term care payment that must be made to support the more frequent monitoring. This increase 

will need to be included in the existing surety as well as the long-term care payment made at the 

time of license termination. 

(5) Water quality sampling and analysis procedures use appropriate American Society of Testing and 

Materials or equivalent standards. Wells should be constructed to prevent surface-water 

contamination and capped and secured to prevent tampering by the populace (ASTM standard 

D5787). 

(6) Any potential needs for future well maintenance or replacement are identified. If periodic well 

replacement is projected, an increase in the long-term care payment must be included (ASTM 

standard D5978). 

(7) Actions that the long-term custodian would take should ground-water protection standards be 

exceeded are described. 

5.4 Evaluation Findings 

If the staff review results in acceptance of the long-term surveillance plan, the staff may conclude that DOE 

will conduct a Long Term Surveillance Plan that will confirm that constituents of concern will remain 

below the relevant standards in 40 CFR Part 192. 

5.5 References 

Anderson, M.P., and Woessner, W.W., 1992, Applied Groundwater Modeling: Simulation of Flow and 

Transport. Academic Academic Press, NY. 

American Society for Testing and Materials (ASTM) Standards 

D5447 Standard Guide for Application of a Ground-Water Flow Model to a Site-Specific Problem 

D5490 Standard Guide for Comparing Ground-Water Flow Model Simulations to Site-Specific 

Information 

D5609 Standard Guide for Defining Boundary Conditions in Ground-Water Flow Modeling 

D5610 Standard Guide for Defining Initial Conditions in Ground-Water Flow Modeling 

NUREG-1724 5-2

I I 1 1
D5611 Standard Guide for Conducting a Sensitivity Analysis for a Ground-Water Flow Model 

Application 

D5718 Standard Guide for Documenting Ground-Water Flow Model Application. 

D5787 Standard Practice for Monitoring Well Protection. 

D5978 Standard Guide for Maintenance and Rehabilitation of Ground-Water Monitoring Wells. 

E978 Standard Practice for Evaluating Mathematical Models for the Environmental Fate of 

Chemicals. 

Environmental Protection Agency, 40 CFR Part 192, Health and Environmental Protection Standards for 

Uranium and Thorium Mill Tailings.

5-3 NUREG-1724
APPENDIX A 

GUIDANCE TO THE NRC STAFF 

ON THE USE 

OF STANDARD STATISTICAL HYPOTHESIS TESTING 

AS APPLIED TO 

GROUND-WATER QUALITY
APPENDIX A 

GUIDANCE TO THE NRC STAFF 

ON THE USE 

OF STANDARD STATISTICAL HYPOTHESIS TESTING 

Hypothesis Testing 

Statistical hypothesis testing methods used for: (1) establishing background water quality; 

(2) establishing groundwater protection standards for compliance monitoring; (3) determining the extent 

of groundwater contamination; and (4) establishing the groundwater cleanup goals, are described in this 

appendix. 

The following discussion on the use of standard statistical hypothesis testing is adapted from Environmental 

Protection Agency (EPA) guidance 1989a, b; 1993) and statistics texts (Haan, 1977; Gibbons, 1994; 

Abramson et al. 1988). The information presented here is referenced in other chapters of this SRP. 

Statistical hypothesis testing methods are used for: (1) establishing background water quality; 

(2) establishing groundwater protection standards for compliance monitoring; (3) determining the extent 

of groundwater contamination; and (4) establishing cleanup standards. 

A statistical test of a hypothesis is a rule used for deciding whether a statement (i.e., null hypothesis) 

should be rejected in favor of an alternative statement (i.e., alternative hypothesis). The null hypothesis 

can be expressed as: "There is no difference between background and onsite water quality." The 

alternative hypothesis can be expressed as: "Onsite contaminant concentrations are above background." 

Because the concern lies only with concentrations of contaminants that are above background, this 

expression of the alternative hypothesis implies a one-tailed test of significance. Presumably, concentrations 

of any constituent in concentrations below background water quality pose no excess risk. 

Two types of error are possible in hypothesis testing: the null hypothesis may be rejected when it is true 

(Type I error or false positive) or it may be accepted when it is false (Type II error or false negative). An 

example of Type I error in the context of this discussion would be to conclude that ground-water has been 

contaminated from mill tailings when, in fact, it has not. Thus, Type I error could result in unnecessary 

remediation. Conversely, Type II error could result in contaminated water being left untreated. In 

customary notations, a (alpha) denotes the probability of the hypothesis test leading to a Type I error, and 

P3 (beta) denotes the probability of Type II error. Most statistical comparisons refer to the value 100oa (in 

percent) as the level of significance. For example, if a = 0.01, there is a 1 percent chance of concluding 

that concentrations of contaminants are higher than background when they actually are not. 

Before any groundwater monitoring criteria are determined, the implications of each type of error are 

considered. Clearly, if a Type I error is made, the error tends to favor protection of human health and the 

environment, but will result in unnecessary expenditure of capital. Thus, a higher value of a is more 

conservative when considering risk to human health and the environment; however, values that are too high 

could result in unrealistic restoration goals with little or no reduction in risk.

A-1 NUREG-1724
In testing hypotheses, the value for a is usually specified a priori. The value of 1P, however, is not known 

unless the true parameter values being tested (e.g., the true background contaminant levels) are already 

known; this, of course, is rarely the case, as the parameter values are only estimated on the basis of a 

limited number of samples. In general, as the value of a decreases, the value of P increases. The value of 

P can also be reduced by ensuring that an adequate number of samples are obtained. Because an accurate 

assessment of background water quality is crucial to all subsequent monitoring efforts, the number of 

background samples collected should be sufficient to accept or reject the null hypothesis with a specified 

Generally, the likelihood of Type II error can be sufficiently limited with a sample size that includes a 

minimum of six randomly distributed monitor well locations to capture spatial variations, and four sample 

periods to capture temporal variations. The Nuclear Regulatory Commission finds it acceptable to space 

sampling at least 2 weeks apart to capture temporal variations. Licensees are expected to take samples at 

greater intervals if seasonal variations are expected to be significant. The term "sample" is used to refer 

to the set of concentration measurements for each sampled constituent. 

Thus, a single sample will contain at least 24 concentration measurements for each water quality parameter 

(constituent) of concern. 

Ideally, background water quality is determined at a uranium mill site before the commencement of any 

milling operations. Background samples are collected both onsite and offsite. In the event that a mill site 

may have conducted operations before the determination of background water quality, then background 

may have to be determined using only offsite, upgradient samples. Once the background sample has been 

collected, some statistical analysis is required. The statistical analysis process can be divided into five major 

steps, and these steps are common to any data that are being analyzed. These steps will be referred to 

extensively in later sections. They include the following: 

(1) Checking for the validity of statistical assumptions 

(2) Handling nondetects 

(3) Analysis of variance (ANOVA) test 

(4 Analysis for statistical intervals 

(5) Strategies for multiple comparisons 

From the regulatory viewpoint, EPA recommends (Environmental Protection Agency, 1993) that a specific 

statistical analysis should be performed to meet the groundwater protection standards. The following table, 

Table B. 1. summarizes the use of statistical methods. 

NUREG-1724 A-2

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Table B.1. Summary of Statistical Methods 

Compound Type of Comparison Recommended Method 

Any compound in background Background versus compliance well ANOVA 

Tolerance limits 

Prediction intervals 

Intra-well Control charts 

ACLIMCL specific* Fixed standard Confidence intervals 

Tolerance limits 

Synthetic Many nondetects in data set Cohen's adjustment 

Aitchison's adjustment 

*ACL-Alternate Concentration Limits; MCL --Maximum Concentration Limits. 

Checking for the Validity of Statistical Assumptions 

The inherent assumption with all parametric statistical methods described in Table B. 1 is that the data being 

analyzed are normally distributed or can be transformed into a normal distribution. This assumption should 

be verified by testing the normality of data. If the measured data are not normally distributed, the log of 

measured data should be tested for lognormal distribution. In environmental compliance, measured 

concentration data will be most likely to be lognormally distributed. If the background sample exhibits 

variability in constituent concentrations over several orders of magnitude and a high positive skew, then 

log-transformation of the sample data may be necessary to obtain a distribution that more closely 

approximates normal. If the background sample exhibits a bimodal distribution due to zones of distinct 

water quality, it may be necessary to split the sample to obtain two normally distributed samples-one for 

each zone of water quality. When a sample is split, it may be necessary to obtain additional measurements 

from new sample locations, to obtain the minimum of six measurements for each distinct water quality 

zone. If bimodal distributions are encountered because of temporal variations, it is acceptable to evaluate 

the measurements collected during each sample period separately; this would result in four background 

samples, each containing a minimum of six measurements for each constituent. Whenever a bimodal 

distribution is encountered, the reviewer shall 

verify that it is caused by changes in natural variations in water quality, and not caused by the presence 

of contamination. 

Summary statistics are calculated for the background sample. The two most important statistics for 

hypothesis testing are the mean and standard deviation. For normal distributions, the mean represents the 

arithmetic mean; for log-normal distributions, the mean represents the geometric mean of the sample data. 

The various methods that can be used for testing the normality or lognormality of data are: Probability 

Plots, Coefficient of Skewness, Shapiro-Wilk test, Shapiro-Francia test, and Probability Plot Correlation 

Coefficient (Environmental Protection Agency, 1993). If the assumption of lognormality is valid, further 

statistical analyses should be performed. However, if the data are neither normal nor lognormal, a non

parametric technique should be used. 

Handling Nondetects

A-3 NUREG-1724
If fewer than 15 percent of all samples are nondetect, replace each nondetect by half its detection or 

quantitation limit. Care should be taken in choosing between the method detection limit (MDL) and the 

physical quantitation limit (PQL) (Environmental Protection Agency, 1993). The nondetects are reported 

as "undetected" or "detected but not quantified" and with or without an estimated concentration. If an 

estimated concentration value is given, the value should be used for statistical analysis. Otherwise, 

nondetects should be substituted by one-half of PQL since PQL is a better representative of actual 

laboratory conditions than MDL. After this correction, the data can be analyzed by any parametric 

approach, (e.g., ANOVA or statistical interval). 

If more than 15 percent but fewer than 50 percent of all samples are nondetects, either Cohen's adjustment 

or Aitchison's (Environmental Protection Agency, 1993) adjustment should be applied. If more than 50 

percent but fewer than 90 percent of the samples are nondetects, nonparametric statistical intervals, for 

example, Poisson Prediction Limit (Environmental Protection Agency, 1993), should be used. 

Analysis of Variance (ANOVA) Test 

The ANOVA test is used to compare concentration data from several compliance wells with concentration 

data with background wells. This method is used to test for the statistically significant evidence of higher 

mean concentration in compliance wells than the background concentration as provided by background 

wells. ANOVA is best used for comparisons between wells that are hydraulically upgradient of a site and 

those that are downgradient from the site. The parametric ANOVA technique makes two key assumptions: 

(1) that the data residual are normally distributed and (2) that the group variances are approximately equal. 

If any of these assumptions are not valid, it is recommended that a nonparametric approach, such as the 

Kruskal-Wallis test or the Wilcoxon Rank-Sum test (also known as the Mann-Whitney U test) ( 

Environmental Protection Agency, 1993), is used in analyzing the data. The Kruskal-Wallis test is used 

when three or more well groups are compared; however, for comparing one compliance well with one 

background well, the Wilcoxon Rank-Sum test should be used. A non-parametric ANOVA based on 

ranks, followed by multiple comparison procedures can be used to identify statistically significant evidence 

of contamination. The method 

includes estimation and testing of the contrasts between each compliance well median and the background 

median levels for each constituent. 

Analysis for Statistical Intervals 

There are three types of statistical intervals that are most commonly constructed from the data: confidence 

intervals, tolerance intervals, and prediction intervals. The interpretation and use of each of these intervals 

is quite distinct. A confidence interval is a random interval that is designed to contain the specified 

population parameter with a designated level of confidence or probability, denoted as 1- Ca. A confidence 

interval should be used only in two situations for groundwater data analysis: 

(1) when directly specified by permit or (2) in compliance monitoring, when downgradient samples are 

being compared with a fixed groundwater protection standard, (e.g., Part 40 or ACLs). In other cases, 

it is usually desirable to use either tolerance or prediction intervals. 

A tolerance interval, also random interval, is designed to contain a designated proportion of population 

with a certain confidence level. Two coefficients are associated with any tolerance interval: coverage and 

tolerance coefficients. Coverage is the proportion of the population that the interval is supposed to contain 

NUREG-1724 A-4

I I V
and the tolerance coefficient is the degree of confidence with which the interval reaches the specified 

coverage. A tolerance interval with coverage of 99 percent and a tolerance coefficient of 99 percent are 

constructed to contain, on average, 99 percent of the distribution with a probability of 99 percent. Since 

a tolerance interval is designed to cover all but a small percentage of the population's measurements, 

observations should rarely exceed the upper tolerance limit when testing small sample size. The tolerance 

intervals can be used in detection monitoring when comparing compliance data with background values. 

They can be used in compliance monitoring when comparing compliance data with certain fixed standards, 

(e.g., Part 40 or ACLs). 

A one-sided test of significance is used to determine the upper limit of the range of background 

concentrations. This is also known as the tolerance limit method. This limit is given by 

U=x+t S (4.1) 

where x is the mean value determined for the background sample; s. is the standard deviation of the 

background sample; t., v is the t-statistic for y = (1- c); and v = (n- 1) of degrees of freedom, where n is 

the number of background measurements for each constituent. Values for t-statistics are obtained from 

t-tables that can be found in most basic statistics textbooks. The value of U for each constituent is 

interpreted as the maximum concentration of that constituent that may be present in any single monitor well 

without concluding that the constituent concentration is above the range of reasonable background 

concentrations. 

Equation (4.1) is used for determining whether constituent concentrations meet the background criterion 

in any single well. However, it is often the case that a licensee wishes to demonstrate compliance with the 

background criterion by using well field average concentrations for each constituent. That is, while a 

concentration in one or more wells may exceed background, the water quality of the aquifer, on average, 

meets the background criterion. NRC finds this approach to be acceptable; however, it necessitates a 

change to Eq. (4.1). Rather than the standard deviation of the single background sample ( sx ), the standard 

deviation of the sample average ( sx ) must be used. Normally, this would require that at least six 

background samples be collected, the mean of each sample be determined, and a calculation be made of 

the standard deviation for these background sample means. However, it is rarely the case that enough 

background samples are collected to calculate s

directly. For these purposes, s can be approximated by the equation 

S $ 

s- = (4.2) 

A prediction interval is a statistical interval calculated to include one or more future observations from the 

same population with a specified confidence. In groundwater monitoring, a prediction interval approach 

can be used in two ways: (1) to compare compliance well data with background well data and (2) to make 

intrawell comparisons for an uncontaminated well. If future observations are found to be in the prediction 

interval, then there is no contamination. However, if the measured concentration is above the prediction 

interval's upper limit, it is statistically significant evidence of contamination.

A-5 NUREG-1724
Another commonly used technique for intrawell comparison is control charts (Environmental Protection 

Agency, 1993). The control chart method is recommended for uncontaminated wells only. This is an 

effective technique to monitor contamination over time. The control charts should be constructed with data 

that are free from seasonal variability. It is important to note that the control charts should not be used for 

wells that show evidence of contamination or an increasing trend. 

Strategies for Multiple Comparisons 

When more than one statistical test is performed during any monitoring period, the problem of multiple 

comparisons needs to be addressed. These comparisons can arise from the fact that multiple compliance 

wells were tested against multiple background wells for several contaminants. Usually the same statistical 

test is performed in every comparison, each test having a fixed level of confidence (1- a), and a 

corresponding false positive rate, a. 

The selection of an a value is not arbitrary: the consequences that would result from Type I error must be 

considered. In most cases, Type I error favors protection of human health and the environment, but results 

in unnecessary expenditure of capital for restoration. Thus, a higher value of a is more conservative when 

considering risk to human health and the environment; however, values that are too high could result in 

unrealistic cleanup standards, with little or no reduction in risk. EPA recommends an a-value of 0.05 

(Environmental Protection Agency, 1989a). The number of contaminants present at a site should also be 

considered when selecting a value for a. For example, the EPA-recommended a-value of 0.05 translates 

to a 1-in-20 chance of Type I error. However, if 20 constituents are being evaluated for cleanup standards, 

and each has a 1-in-20 chance of Type I error, the result is a 64 percent chance that at least one Type I 

error will occur. In such cases, using an a-value of 0.05 is likely to result in unnecessary restoration. 

However, a-values lower than 0.01 should not be used at sites where public water supplies or sensitive 

environmental areas may be threatened by contamination. 

Once a background sample has been properly collected and analyzed for each constituent of concern, it is 

then possible to conduct hypothesis testing for establishing cleanup standards and groundwater protection 

standards, and for determining the extent of any existing contamination. The review should confirm that 

the statistical method used complies with the following, as appropriate: 

(1) The statistical method used to evaluate groundwater monitoring data is appropriate for the 

distribution of chemical parameters or hazardous constituents. If the distribution of the 

chemical parameters or hazardous constituents is shown by the owner or operator to be 

inappropriate for a normal theory test, then the data are transformed or a distribution-free 

theory test is used. If the distributions for the constituents differ, more than one statistical 

'method is needed. 

(2) If an individual well comparison procedure is used to compare an individual compliance 

well constituent concentration with background constituent concentrations or a 

groundwater protection standard, the test is done at a Type I error level no less than 0.01 

for each testing period. If a multiple, comparisons procedure is used, the Type I error rate 

for each testing period is no less than 0.05; however, the Type I error of no less than 0.01 

for individual well comparisons is maintained. This does not apply to tolerance intervals, 

prediction intervals, or control charts. 

NUREG-1724 A-6

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(3) If a control chart approach is used to evaluate groundwater monitoring data, the specific 

type of control chart and its associated parameter values are proposed by the licensee. 

(4) If a tolerance interval or a prediction interval is used to evaluate groundwater monitoring 

data, the levels of confidence and, for tolerance intervals, the percentage of the population 

that the interval must contain, are proposed by the licensee. These parameters are 

determined after considering the number of samples in the background database, the data 

distribution, and the range of the concentration values for each constituent of concern. 

(5) The statistical method accounts for data below the limit of detection with one or more 

statistical procedures that are protective of human health and the environment. The limit 

of detection that is used in the statistical method is the lowest concentration level that can 

be reliably achieved, within specified limits of precision and accuracy, during routine 

laboratory operating conditions that are available to the facility. 

(6) If necessary, the statistical method includes procedures to control or correct for seasonal 

and spatial variability as well as temporal correlation in the data. 

References 

Abramson, L.R., et al., 1988, "Statistical Methods for Nuclear Material Management," Nuclear 

Regulatory Commission, NUREG/CR-4604, 1988. 

Gibbons, R.D., 1994, Statistical Methods for Groundwater Monitoring. New York, NY: John Wiley & 

Sons, Inc., 1994. 

Haan, C.T., 1977, Statistical Methods in Hydrology, Ames, IA: Iowa State University Press, 1977. 

Environmental Protection Agency, 1989a, Statistical Analysis of Ground-Water Monitoring Data atRCRA 

Facilities, Interim Final Guidance, EPA/530/SW-89/026, 1989. 

Environmental Protection Agency, 1989b, Risk Assessment Guidance for Superfund," Vol. I, Human 

Health Evaluation Manual (Interim Final 9/29/89), OSWER Directive 9285.7-01a, 1989. 

Environmental Protection Agency, 1993, Statistical Training Course for Groundwater Monitoring Data 

Analysis, EPA/530-R-93-003, 1993.

A-7 NUREG-1724
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER 

9-19) 11(Assigned by NRC, Add Vol., Supp., Rev., 

ROM 102,and Addendum Numbers, If any.) 3201, 322 BIBLIOGRAPHIC DATA SHEET 

(See instrutons on the reverse) 

2. TITLE AND SUBTITLE NUREG-1724 

Standard Review Plan for the Review of DOE Plans for Achieving Regulatory Compliance at 

Sites with Contaminated Ground Water under Title I of the Uranium Mill Tailings Radiation 3. DATE REPORT PUBLISHED 

Control Act MONTH - YEAR 

Draft Report for Comment June 2000 

4. FIN OR GRANT NUMBER 

5. AUTHOR(S) 6. TYPE OF REPORT 

Fuel Cycle Ucensing Branch 

Division of Fuel Cycle Safety and Safeguards Draft 

U.S. Nuclear Regulatory Commission 7. PERIOD COVERED (inclusive Dates) 

Washington, DC 20555-0001 

8. PERFORMING ORGANIZATION -NAME AND ADDRESS (If NRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address; if contractor, 

provide name and mailing address.) 

Division of Fuel Cycle Safety and Safeguards 

Office of Nuclear Material Safety and Safeguards 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC, type 'Same as above'; if contractor, provide NRC Division, Office or Region, U.S. Nuclear Regulatory Commission, 

and mailing address.)

Same as above

10. SUPPLEMENTARY NOTES

11. ABSTRACT (200 words or less) 

The Department of Energy postponed implementation of ground-water corrective action plans at most Title I sites until 

completion of surface remediation, because Environmental Protection Agency ground-water standards were not finalized until 1995. Consistent with this approach, 10 CFR 40.27, allows for licensing of disposal sites that require ground-water restoration 

in two steps. The first step, surface restoration, is conducted by the DOE under the Uranium Mill Tailings Remedial Action 

Surface Project. After completion of surface restoration, the site is placed under a general license through Nuclear Regulatory Commission acceptance of a Long-Term Surveillance Plan that may leave ground-water restoration issues open. Ground-water corrective action, the second step, is conducted under the Uranium Mill Tailings Remedial Action Ground-Water 

Project. 

This Standard Review Plan is prepared for the guidance of staff reviewers in the Office of Nuclear Material Safety and 

Safeguards in performing safety and environmental reviews of corrective action plans and revised long-term surveillance plans of ground-water quality compliance activities for uranium recovery sites covered by Title I of the Uranium Mill Tailings Radiation Control Act. The purpose of this Standard Review Plan is to ensure the quality and uniformity of Nuclear Regulatory Commission staff reviews of site-specific documents describing Department of Energy plans for achieving regulatory compliance at sites with contaminated ground water. 

This standard review plan is written to cover a variety of site conditions and plans. Each section provides a description of the 

areas of review, review procedures, acceptance criteria, an evaluation of findings, and a list of references.

12. KEY WORDS/DESCRIPTORS (List words orphrases that wil assist researchers in locating the report.) 13. AVAILABILITY STATEMENT 

Title I, ground water, groundwater, draft, standard review plan, corrective action, long term unlimited 

surveillance, restoration, uranium recovery, mill tailings, radiation control act, 14. SECURITY CLASSIFICATION 

(This Pape) 

unclassified 

(This Report) 

unclassified 

15. NUMBER OF PAGES 

16. PRICE

NRK IFUOM 335•28 9Z)J
Federal Recycling Program
NUREG-1724 

DRAFT

STANDARD REVIEW PLAN FOR THE REVIEW OF DOE PLANS FOR ACHIEVING REGULATORY COMPLIANCE AT 

SITES WITH CONTAMINATED GROUND WATER UNDER TITLE I OF THE URANIUM MILL TAILINGS RADIATION CONTROL ACT

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

WASHINGTON, D.C. 20555-0001

years

JUNE 2000