ML20210T307

Draft Completion Review Rept for Remedial Action at Rifle,Co U Mill Tailings Site

ML20210T307
Person / Time
Issue date:	08/29/1997
From:	NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:
Shared Package
ML20210T303	List: ML20210T297 ML20210T307
References
REF-WM-62 NUDOCS 9709150050
Download: ML20210T307 (38)

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i DRAFT  :

COMPLETION REVIEW REPORT I

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REMEDIAL ACTION i

AT THE ,

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. URANIUM MILL TAILINGS SITE AUGUST 1997 i

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TABLE OF CONTENTS Pace SECTION INTR 000CTION..................................................................

I I

1.0 BACKGROUND

1.1 UMTRCA........................................................ I 1.2 CONCURRENCE PROCESS FOR THE SELECTION OF DOE'S REMEDIAL ACTIONS....................................................... I 1.3 CONCURRENCE PROCESS FOR THE PERFORMANCE OF DOE'S REMEDIAL

............... 2 ACTIONS.....................................

1,4 RIFLE SITE.................................................... 2 1.5 COMPLETION REVIEW REPORT (CRR) ORGANIZATION................... 6 ANALYSIS OF DOE REMEDIAL ACTION PERFORMANCE....................... 6 2.0 2.1 PREVIOUS ACT10NS.............................................. 6 2.2 REVIEW 0F REMEDIAL ACTION PERFORMANCE......................... 6 2.2.1 Geotechnical Engineering Review Results................. 7 2.2.2 Surface Water Hydrology and Erosion Protection Review Results.......................................... 8 2.2.3 Radiation Cleanup and Control Review Results. . . . . . . . . . . . 9 2.2.4 Groundwater Protection Review Results................... 21 3.0

SUMMARY

........................................................... 22 24

4.0 REFERENCES

APPENDIX A . NRC SITE VISITS TO THE RIFLE UMTRA PROJECT SITE.................. A-1 APPENDIX B . UMTRCA. THE EPA STANDARDS. AND THE PHASED UMTRA PROJECT.......... B-1 APPENDIX C . OPEN ISSUES ..................................................... C-1 1

1 LIST OF FIGURES Fiaure EfLqe 1.1 Location of the Rifle Site and Estes Gulch 4 1.2- -Old Rifle Processing Site- 4 1.3 New Tailings Processing Site- 5

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• l RIFLE, COLORADO DRAFT COMPLETION REVIEW REPORT j l

I INTRODUCTION The Rifle site is one of the 24 abandoned uranium mill tailings sites to be remediated by the U.S. Department of Energy (DOE) under the Uranium Mill Tailings Radiation Control Act of 1978 (UMIRCA). UMTRCA requires, pursuant to Section 104(f)(1). that the U.S. Nuclear Regulatory Commission concur with the DOE's determination that the remedial action has been proper'y completed.

This Completion Review Report (CRR) documents the NRC staff', basis for its concurrence decision with respect to DOE's Certification " mary for the completion of the Rifle site.

1.0 BACKGROUND

1.1 UMTRCA Title I of UM!RCA provides for remedial action at abandoned uranium mill tailings sites and associated vicinity pro)erties. The purpose of this legislation is to protect the public healta and safety and the environment from radiological and non-radiologica; hazards associated with the process related materials at these sites.

UMTRCA directs DOE to select and perform remedial actions at 24 abandoned .

uranium mill tailings sites to ensure compliance with the general environmental standards promulgated by the Environmental Protection Agency (EPA) under Section 275(a) of the Atomic Energy Act of 1954. as amended by UMTRCA. UMIRCA also requires DOE to obtain NRC's concurrence with DOE's selection and performance of the remedial actions. Following completion of the remedial actions. UMTRCA authorizes NRC to license the long-term custody, maintenance, and monitoring of the disposal sites to ensure continued protection of the public health and safety and the environment. Appendix B includes a more detailed discussion of this legislation. ,

1.2 CONCURRENCE PROCESS FOR THE SELECTION OF DOE'S REMEDIAL ACTIONS To document its selection of tae remedial action to be implemented at a 3 articular site. DOE develops and issues a Remedial Action Plan (RAP). The LAP describes the series of activities and presents the design proposed by DOE to provide for the long term protection of the public and the environment.

Usually this involves cleanup of the processing site, adjacent windblown areas, and vicinity properties in addition to stabilization of the residual radioactive materials. In addition. DOE issues a Remedial Action Inspection Plan (RAIP) which establishes the quality control program of testing and ins)ection that will be employed for the remedial action. In accordance with UMilCA Section 108(a)(1), the NRC staff reviews and concurs with the RAP and the RAIP, and any subsequent modifications. By its concurrence in the remedial action selection, the NRC staff concludes that the )lanned remedial actions will comply with EPA's applicable standards in 40 CFR 192. Subparts A.

B. and C. The basis for the concurrence in DOE's selection of remedial action is documented in a Technical Evaluation Report (TER).

I

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.. 1.3 CONCURRENCE PROCESS FOR THE PERFORMANCE Of DOE'S REMEDIAt ACTIONS

, The remedial action work is performed by DOE contractors under Federai  ;

procurement regulations. During construction. 00E inspects and documents activities in accordance with the UMTRA Project Quality Assurance Plan, the i Remedial Action Inspection Plan (RA!P). and the RAP. In addition, the NRC staff conducts independent inspections during construction, as determined i necessary.

1 Upon completion of the remedial action, DOE compiles construction records and prepares a completion report to document that remedial actions were performed in accordance with the RAP or RAP modifications, and the RAIP. Based on this information. DOE certifies that all provisions of the RAP have been satisfied and therefore, that the remedial actions comply with the applicable EPA standards in 40 CFR 192. ,

i .

Based on its review of DOE's documentation, and on its site visits and '

observations. NRC makes a concurrence decision with regard to DOE's remedial action completion determination for each site. and then documents the basis i for this concurrence decision in the Completion Review Report (CRR). By its  !

concurrence in the remedial action performance, the NRC staff concludes that l

. the remedial action has been com)leted in accordance with the NRC approved design. NRC's concurrence with 20E's completion determination fulfills the Commission's responsibility under UMTRCA Section 104(f)(1).

1.4 RIFLE SITE k The Rifle uranium mill tailings sites are two separate tailings sites adjacent to the city of Rifle in Garfield Couaty. Colorado, as shown in figure 1.1.

figure 1.2 shovs that the eastern size known as Old Rifle. and the western site, known as New Rifle, are located 0.3 miles southeast and 2 miles souths, ;t cs pectively, of the center of the city of Rifle. Both are north of the Cclorado River.

i l The Old Ri le site covers 22 acres. It included the 13-acre tailings pile and the 9-oc,e mill area with ore storage and milling facilities. Prior to remediation, the assay building was the only building still standing, and the f foundations of other mill structures were exposed or buried at the east end of the mill area. The contaminated materials at the site were orig-;cially

, estimated to be approximately 333.000 cubic yards (cy) of tailings. 168.000 cy of subpile contaminants, and 160.000 cy of windblown and mill area contaminants.

i The New Rifle site covers 142 acres, i t included 33 acres of tailings, a mill facility, water retention pond, and two ore storage ponds. The estimated contamination at the New Rifle site consisted of approximately 2.415.000 cy of tailings. 375.000 cy of subaile contaminants and 442.000 cy of windblown and

. mill area contaminants. Otler contaminated materials include an estimated ,

203.000 cy of vicinity property materials and 34.000 cy of demolition debris from the processing site.

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. The designated disposal site. Estes Gulch, is located approximately 6 miles ['

north of the city. 7 miles north of the Old Rifle tailings site and 9 miles north of the New Rifle talings area. Figures 1.1 and 1.2 show the location of )

the Estes Gulch disposal site. i 1

The remedial action performed by 00E consisted of the following major  ;

activities: ,

1. All tailings and contaminated materials from the Old Rifle and New Rifle processing sites were relocated, consolidated, and stabilized into the Estes Gulch / Rifle disposal cell. The disposal cell covers approximately 95 acros and contains approximately 4.100.000 cy of contaminated material.

2. The stabilized embankment was constructed partially below the existing ground surface. The excavation for the below grade portion of the embankment extends to within a few feet of the bedrock and/or may extend 2 to 3 feet into the highly weathered bedrock of the Wasatch formation.

3. A 1.5 foot-thick radon / infiltration barrier consisting of compacted silty and sandy clay with the upper .12 inches mixed with 4% bentonite was placed  ;

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4. A frost barrier ranging in thickness from 6.8 fbet to 18.6 feet and '

averaging 11.4 feet in thickness, was placed over the radon / infiltration barrier. A 6-inch thick drain layer of relatively coarse material was constructed between the main frost barrier and another 6 12 inch layer of ,

frost barrier material that was applied directly to the surface of the radon / infiltration barrier. The drain is intended to prevent the build up of hydraulic head over the radon / infiltration barrier. and the drain layer gradation will prevent migration into the drain of the finer materials from ,

the frost and radon barriers, lhe additional layer of frost barrier material '

was added to the design through Project Interface Document (P10) 40 as a means of protecting the moisture content of the radon barrier during construction of '

the disposal cell.

5. The erosion protection for the topslope of the embankment consists of a 12- '

i inch-thick iayer of lype A riprap. with a 0 50 minimum of 3.5 inches and a 0100 maximum of 6 Inches. The erosion protection for the emb.nkment sideslopes including the tcc ditch and berms cans 3ts of a 12-inch thick layer of Type B riprap with a D-50 minimum of 5.7 inches and a 0-100 maximum of 10 inches. The  :

entire riprap layer is underlain by a 6 inch thick drain leyer to facilitate .

drainage of any-surface runoff that may percolate down into it.

figure 1.3 shows the as-built Estes Gulch disposal site.

The NRC was not involved with the actual remedial action activities which were performed by the DOE cont. actors. However. 00E obtained NRC concurrence with the site construction and design and a few significant modifications thereof as PIDs. NRC also performed on site construction reviews to-monitor the progress of the construction activity (see Appendix A).

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. 'l.b COMPLETION REVIEW REPORT ORGANIZATION lhe purpose of this Completion Review Report (CRR) is to document the NRC staff review of DOE's Rifle Completion Report (CR). Section 2 of this report pesents the analysis of remedial action construction. Th1; section is organized by technical discipline and addresses engineering and radiation protection aspects of the remedial action. Ap>endix A provides a listing of NRC staff visits to the Rifle site. A)pendix 3 provides a detailed description of the requirements of UMT?.CA and the resulting phased arocess of the UMTRA project. Appendix C presents the open technical issues w1ich have resulted from NRC's review and for which DOE needs to provide response.

2.0 ANALYSIS OF DOE REMEDIAL ACTION PERFORMANCE 2.1 PREVIOUS ACTIONS NRC staff, based on its review of the RAP (DOE. 1992a. b, c. and d), and the RAIP (DOE. 1991) concurred that the remedial action, as designed, would meet the applicable EPA standards. This concurrence was based on technical findings that there is reasonable assurance that the selection of the remedial action would meet the standards for long-term stability, radon attenuation, water resources protection, and cleanup of contaminated land and buildings.

Staff resiews included assessments in the areas of geology. geotechnical engineering. surface water hydrology, and health >hysics. The NRC concuired on the final RAP and the RAlP in May. 1992. The ) asis for the NRC staff's concurrence in DOE's selection of remedial action at the Rifle site is documented in a Technical Evaluation Report (1rR) issued in May, 1992 (NRC, 1992).

2.2 BLylEW OF REMEDIAL ACTION PERFORMANCE NRC staff's primary objective in reviewing DOE's certification of remedial action completion is to determine whether the remedial actions have been performed in a manner consistent with specifications provided in the RAP. RAP modifications or PIDs, and the RAIP. and if not. that deviations to these specifications still result in compliance with the EPA standards. In support of this action, the NRC staff participated in site reviews (See Appendix A).

field observctions. #ssments of o,esite data and records, and revicw ;f DOE Site Audit Reports. During remedial ac'4on construction activities, there were conditions encountered which required modifications of the original remedial action plan. These conditions and the associated design changes were submitted by DOE as eight Class 1 PIDs. i.e. those related to meeting the EPA standards, and were concurred in by the NRC staff. These PID1s are listed M Section 1 of Volume 1 of the CR. summarized in Section 11 of Volume I, and are reflected in the as-built _ conditions presented in the CR.

The following sections present the results of the review of remedial action performance by individual technical discipline. Note that for the Rifle remedial action completion review, the pertinent technical disciplines are; l) geotechnical engineering. 2) surface water hydrology and erosion protection. 3) radiation cleanup and control protection, and 4) groundwater resources protection.

6

-. 2.2.1 Geotechnical Engineering Review Results The NRC staff reviewed the Rifle. Colorado, final Completion Report. (DOE.

1997) to determine whether the geotechnical engineering aspects of the remedial action were completed in accordance with: (1) the applicable construction specifications in the RAP: (2) all RAP modifications: (3) the RAIP: and (4) the final design. Items reviewed included descriptions of construction operations, as built drawings. laboratory and field testing data, and Remedial Action Contractor (RAC) inspection reports In addition. the review was based on staff observations and review of records during on site-inspection (.

i During its review, the NRC staf f noted the following:

1. Appropriate tests (gradation and Atterberg limits) and inspections were performed by DOE or its agents to ensure that- the proper material type was

-placed in each phase of construction. Placement and compaction of construction materials were routinely inspected by DOE or its agents to ensure that the moisture and density requirements were met and that the soil moisture was uniform throughout the_ compacted lifts. The-loose thickness of the lifts was verified periodically by DOE or its agents to-ensure compliance with the specification requirements for each particular type of material.

2. Laboratory and field testing by DOE or its agents was conducted in accordance with acceptable test procedures and by trained and qualified personnel. Records indicating acce) table calibration of measuring and testing ?quipment are provided in t le DOE CR.

3. The CR shows that frequencies of material testing and inspection comply with the frequencies specified in the RAIP and in the NRC Staff Technical Position on Testing and inspection plans (NRC, 1989).

4. Continuous inspections by DOE or its agents confirmed that the volume of organics included in the construction materials was limited to the range specified in the RAP.

5. The radon barrier layer was continually inspected by DOE or its agents to ensure that the spec,fied lift thickhasses and compaction levels were achievei 6, The material type, placement, and compaction methods specified for the radon barrier layer resulted in the desired permeability and density of the barrier.

7. As-built drawings adequately document that the completed remedial action is consistent with the NRC approved design;

8. Final slope, elevation and compaction operations of the foundation soil and capillary break were adequately inspected to ensure that the final conditions were consistent with those stated in the RAP and final design.

7

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. Based on the above observations, and on the results of on-site ins >ections (see Appendix A) performed by NRC staff during construction, the N1C staff ,

concludes that the geotechnical engineering aspects of construction were

)erformed in accordance with the specifications identified in the RAP and  !

MIP.  !

2.2.2 Surface Water Hydrology and Erosion Protection Review Results-NRC staff reviewed 1;1e surface water hydrology and erosion protection aspects of remedial' actions at Rifle to ensure that they were constructed in accordance with the applicable construction specifications as stipulated in i the RAP. RAP modifications. RAIP, and the final design. Areas of review included construction operations, and laboratory and field testing. In addition. the review was also based on NRC observations of the remedial actions' and review of records and testing during several NRC i onsite inspections.

The remedial action design included crosion protection in several s)ecific areas including: (1) riprapped top and side slopes and drainage clannels:-

and (2) riprapped toes. The top and side slopes and drainage channels of the cell were designed to prevent long-term erosion and gullying of the cell -!

cover. The buried ripra j gullies toward the cell.p toes were placed to prevent erosion and migration of The NRC staff reviewed each of these features and determined that testino, placement, and configuration complied with specifications in the RAP. RAP modifications, and the RAIP The review was partially based on NRC staff observations and review of onsite records during the remedial actions, as well as assessment of the verification results presented in the DOE Completion Report, in addition, the NRC staff reviewed records of the placement of riprap on the top and side slopes of the cell.

During the review the NRC staff noted the following: ,

1. Tests (gradation and durability) and inspections were performed by DOE or its agents to ensure that erosion protection materials were properly i selected. The review of the documentation indicated that placement of materials was routinely inspected by DOE or its agents to ensure that the rock site and gradation spect fications were met likewise, the thickness of the rock layers were verifled periodically by DOE or its agents to ensure com material. pliance with the specifications for the particular type of

2. :1.aboratory and field testing was conducted by DOE or its agents in

. accordance with specified test procedures.

3. Testing and inspection frequencies for materials used at the site for erosion prM ection were documented by DOE as complying with the frequencie 9ecified in the RAIP.

Based on NRC h / observations and review of-onsite records during remedial actions, as-well as assessment-of the verification results presented in the CR 0

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0 v the NRC staff concludes that the required duribility gradation.--and layer i

- thickness testing was performed during the remedial action.-- Based ori these :

tests 3 the ri) rap-1s of adequate size und quality. and has= been acceptably placed; 'The 1RC staff concurs that the remedial action has been adequately r completed at the Rifle, with respect:to crosion protection.

2.2.3 Radiation Cleanup and Control Review Results I

The NRC staf f reviewed radioactivity cleanup aspects of remedidl actions at the Rifle sites to ensure that residual radioactive materials were cleaned up 1 in accordance with specifications in the RAP and the final design. Areas of radioactivity cleanup review Included contara4nated material enavation, cleanup verification procedures and data. ano application of supplemental standards, In addition. NRC reviewed the radioactivity control aspects of the remedial action. Construction data and the as-built details of the disposal cell cover were reviewed to ensure compliance with the RAP design for limiting radon releases (see Section 2.2.1), and the final raden attenuation calculation was reviewed to ensure compliance with the RAP design for limiting radon releases and with the long-term racon flux standard in 4J CFR 192.024 The review wts based primarily on the staff's assessment of information presented in the Rifle CR.

The criteria for site clean"o and radon attenuation were established in the RAP and concurred in by NRL staff in the TER as providing assurance that the

, 3rocessing sites and disposal cell would meet the EPA requirements of 40 CFR 3 art 192. The criterion for radium (Ra 226) remediation in soil requires cleanup at the )rocessing sites and on adjacent lands to levels complying with the applicable EPA standards (40 CFR 192.12).

concentrations above background in each 100 aream,such that (grid) do notthe average radium exceed i either 5 pC1/g in the top.15 cm of soil or 15 pC1/g in any underlying 15-cm j layer.

~

The RAP indicated that the buildings and structures at both R1fle processing sitet had been demolished and the resulting debris and nonhazardous materials wert to be buried in the Estes Gulch disposal cell. Therefore, cleanup

- cr cria were not specified in the RAP and verification of buildings and structures was not required. -

A su]plemental cleanup standard for thorium (Th-230) in soil was proposed in the 1AP for cases where significant concentrations of uranium or Th<230 would remain in the soil af ter the planned excavation and cleanup of the Ra 226.

The DOE would impose supplemental standards under criterion (h) of the- -

standards of 40 CFR 192.21. For thorium buried within eight feet of the final grade, the extent of thorium excavation would be based on 1000-year Ra 226-concentrations meeting the Ra-226 cleanup limits of 40 CFR 192. Thus, the Th-230 cleanup standard could vary, based on residual Ra-226 concentration.

for lh 230 buried deeper than eight feet below grade, the concentration of Th-230 that could remain would be based on the calculated concentration of radon progeny that might exist in a slab on grade house built over the area containing the contaminated material, These supplemental standards

applications for Th-230 were the only planned applications of supalemental standards at-the Rifle sites that were specified in the RAP and TER.

y 9 .

. For verification of land cleanup, a number of criteria were approved for the Rifle sites. The RAP indicated that the final radiological verification survey would be based on 100 m2 areas. Verification for Ra-226 in soil would use the standard verification method. composite soil samples analyzed by gamma spectrometry. Other methods could be used if approved. Of particular relevance to topics discussed later in this review the RAP (Appendix C.

section C 3.4) provided a performance criterion for operation of the gamma s)ectrometry system used for the Ra-226 analyses: "At the concentrations of t'le standards. the Ra-226 verification must be performed such that the analytical results are within plus or minus 30 percent of true concentrations, at the 95 percent confidence level."

Because the soils underneath the New Rifle site included areas of cobbles, the RAP also discussed criteria to be used in the verification of cleanup when the subsoil consists of a percentage of cobbles sufficient to affect the measurement of the total radionuclide concentration, In that case, excavation control and verification were to be based on bulk radionuclide concentrations calculated from measurements on the finer soil fraction. The TEd noted that

-NR" staff had concurred with a generic procedure for correcting for radionuclides in cobbles, but a site-specific procedure was to be presented as a RAP modification.

The TER also provided criteria to be used in determining the frequency of Th-230 analyses for soil verification samples. Where Th-230 contamination (here Th-230 contamination means Th-230 in excess of Ra-226 contamination) was neither known nor expected. 4% of all verification samples collected from the arocessing sites were to be analyzed for Th-230 (in addition to the usual Ra-226 analysis). In areas of known Th-230 contamination. 10% of the verification grids were to be analyzed for Th-230. If significant Th-230 levels were found, further remedial action was to be considered. And, where excavation was required because of the Th-230 contamination, all verification grids were to be analyzed for Th-230.

The radon attenuation design provided in the RAP was revised, with the most recent revision based on PID-38. The most recent design calculation (in sup) ort of PID-38) was submitted by DOE in June 1996 (Arp 1996) and approved by 4RC in July 1996 (Holonich 1996). The design calculation, number 06-570-14 02 (an enclosure to Arp 1996T. was revision 2 of the calculation.

The final design included a radon barrier of Enree layers: (1) a g Jt layer of radon barrier material, followed by (2) a 1-ft layer of radon barrier material amended with 4% bentonite. all covered by (3) a layer of frost barrier material. For the radon attenuation calculations. the frost barrier was modeled as two layers, with the two described similarly, except that the uppermost layer was assumed to be degraded by frost penetration. Tlle transmittal letters of the submittal (Arp 1996) and approval (Holonich 1996) both indicated that the frost barrier would have a minimum thickness of 7.5 ft though the design calculations were based on a minimum thickress of 7 ft.

10

t

- During the review of the CR. with respect to the above criteria and commitments, NRC staff noted the following: ,

l '. Site Cleanup: ,

a) Adequacy of the extent of excavation: It appears that excavation and verification of cleanup have generally been performed in the contaminated areas within the boundaries of the >

designated processing sites as described in the RAP, b) Cleanup of buildings: Section IV (page 8. section 2.0 of section D) of the CR indicates that all buildings located on the two processing j sites were demolished and placed in the disposal cell. -

c)- Routine application of supplemental standards for Th-230 contamination:. A)pendix J (pages 2-3, st:ction 1.1.3) of the CR indicates that tie application of supplemental standards to areas of Th-230 contaminut. ion near the surface (within eight ft. of the final grade) was consistent with the method described in the RAP.

(Two areas existed where Th-230 contamination was more than 8 ft below the final grade. The application of supplemental standards for these areas of deep Th-230 contamination is discussed under item number 3 in this section under "Nonroutine Application of Supplemental Standards".)

2. Soil Cleanup Verification:

a) Verification method: Approved procedures were used by DOE for soil cleanup verification measurements for essentially all of the sampling locations at both the Old Rifle and New Rifle sites. The 4- CR () age 7 of Appendix J) indicated that seven grid locations on the New Rifle site did not have the final, equilibrated sample analysis performed on the Opposed Crystal gamma spectrometry system (OCS), a departure from the routine processing of the samples. Of these seven. five locations had samples that were sent to an offsite laboratory for quality assurance Ra-226 analyses, and the two remaining locations did have initfal counts on the OCS. At all seven locations the backfill depth was at least 15 cm, so the applicaola EPA cleanu) stand ed was 15 pCi/g above background. The NRC staff concludes tlat the available information for these -

locations indicates a high degree of confidence that the EPA-standard has been met, be Areal extent of verification: Tables J.4 and J.6 of Appendix J of the CR. contain verification results that indicate that DOE cleaned up each of the contaminated areas within the designated boundaries of each of the Rifle sites.

c) Results of verification measurements: Appendix J of the CR discusses the soil verification measurements and results. The Ra-226 concentrations and 1000-year Ra-226 concentrations that were 11

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- __ - -_- - - - . _ - - ~ . . . - . . - - . - - - ~ _ _ - . -

s

e -

. . provided for each of the samples were nominal. Thus, the verification measurements seem to show that the EPA standards were met for soil cleanup of Ra 226-and for routine application of supplemental standards.of Th 230 contamination. However. NRC-has-concerns regarding quality control and quality assurance measurements as discussed in the following comments -.2d and 2e, d) Quality assurance measurements by outside laboratory: The operating procedure for verification soll sampling, procedure OP-003-1.

indicated that 4% of all verification samples would be sent to an

- outside vendor laboratory _ for quality assurance (0A) analysis 'of the Ra-226 concentration. For the Rifle site, the outside laboratory used was Barringer. Results-of comparisons of the onsite OCS i measurements to the Barringer measurements of Ra-266 are briefly 4

described in Ap)endix J (page-10) of the CR.- The CR indicates that

- Barringer made la-226 measurements on about 5% of all OCS samples collected at the Rifle sites for Ra-226 verification. For these samples. the over age OCS (site measurements) result was 2.3 pCi/g and the average OA (Barringer) result was 2.5 pC1/g. The CR did not describe any statistical comparisons of these two averages and the individual data were not provided, so it is unclear whether the difference in means is signif1 cant. The difference may be an Indication of an underbias in analyses made by the OCS (the OCS average is about 8% less than the Barringer average). Such an

- underbias would be consistent with results of the OCS quality

. control measurements, discussed in "e" below.

If the DOE intends to use the Barringer 0A analyses of Ra-226 to support the quality of the verification results for the Rifle sites, j

statistical analyses of the OA data should be performed and provided

in the CR.

I e) Quality control measurements for the OCS: As indicated previously, the RAP included a performance criterion for operation of the gamma spectrometry system (the OCS) used for Ra-226 verification rneasurements: "At the concentrations of the standards, the Ra-226 verification must be performed such that the analytical results are within plus or minus 30 percent of true concentrations, at the 95

percent confidence level." It appears from the informati-..i oros ided

. in the draft CR that this performance criterion was not met for OCS instrument #6 at the Rifle site.

Appendix J of the CR briefly describes the measurements made and the results used to show compliance with this criterion. It was indicated (page 2 of Appendix J) that the error limits were -

empirically determined, using a National Institute of Standards and Technology traceable reference material. having a Ra-226 concentration of 5.12 pCi/g. that was routinely analyzed during the

- verification process. The soil verification procedure. 0P-003-1. '

does not describe the way these measurements were to be taken and used, and the RAC procedure-for o)eration of the OCS was not included in the CR. But, it i_s t1e understanding of the NRC staff ,

12

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. _- . _ _ _ _ _ _ _ _ - . .. . _ . ~ _ _ . .

. based on conversations with DOE staff and the Contractor that these-measurements were performed multiple times per day. and the results were to be plotted in quality control charts and used to continuously evaluate the performance of the OCS. As such, these were quality control measurements.

A summary of these OCS quality control (OC) measurements was provided in Table J.1 of Appendix J of the CR. and those data are repeated below in Table 1. As described on page 9 of Appendix J.

the lower bound of the 95% confidence interval (as expressed by the mean minus 2 standard deviations) for OCS 6 fell outside the required bounds of the true mean plus or minus 30%. thus indicating that DCS 6 was not operating properly. The true concentration of the standard used for the OC checks was 5.12 pCi/g. Thus, a range of this value plus or minus 30% would be a range of 3.58-6.66 pCi/g.

For OCS 6. the nean measurement was 4.3 pCi/g. and the 95%

confidence interval was the range 3.4-5.2 pCi/g.

Table I. Summary of Rifle Site OCS OC Measurements Average OCS number result 2s

• Number of checks 1 5.2 0.8 2121 2 5.2 0.8 757 3 5.1 0.8 726

, 4 4.6 0.9 3429 5 4.6 0.9 3701 6 4.3 2 0.9 1301 Here 25 means plus or minus 2 standard deviations (though the CR used the term sigma). Note that the true concentration of the stcr.dard used for the OC checks was 5.12 pCi/g.

The NRC staff believes that if the 30% performance criterion was intended for quality control pur3oses and was not met it appears that DCS ' was not operating witlin acceptable bou'ds. This would mean that the results from DCS 6 are suspect and may not be valid.

The NRC staff also notes that in stction 1.1.2 of Appendix J (page

2) of the CR. the text indicates tnat the 30% performance criterion was achieved with the 0(.S. which contradicts the c- information on page 9 of Appendix J. The DOE should correct this statement or address the inconsis':ency.

The CR fncludes additional discus; ion intended to indicate that the measurements made with OCS 6 still showed that the EPA standards had been met. First, the CR described results of the offsite vendor QA analyses of Ra-226: "However. the Barringer Ra-226 0C samales for DCS 6 indicated that the instrurent was counting within t1e 30%

13

range. The average of the 20-day Ra-226 concentration for OCS 6 0C samples was 2.4 pCi/g. as compared to the Barringer average of-2.3 pCi/g."' The NRC staf f does not see the relevance of the comparison of mean concentrations from the OCS measurements and the Barringer 0A measurements. The i 30% performance criterion seems to focus on the acceptable precision (the variability) in the measurements,-not the acceptable accuracy (bias in the mean). The comparison of mean

- concentrations does not provide any information about the variability in the OCS measurements, and thus this comparison does not. in contradiction to the CR statement, indicate that the instrument was within the 1 30% performance criterion. The DOE should remove the discussion of the Barringer 0A results, or revise i the discussion to provide relevant conclusions.

The second additional discussion in the CR on this issue focuses on providing a correction to the Ra-226 results from OCS 6. to account for the apparent low bias in results from this OCS. This discussion (page 10 of Appendix J of the CR) indicates that OCS 6 measurements were biased low by 16%: the measured average was 4.3 pCi/g and the known average was 5.12 pC1/g. The maximum measured values from OCS -

6 were given as 4.4 pCi/g for the top 15 cm of soil, and 13.4 pCi/g for soil in layers deeper than 15 cm. With application of a correction factor (presumably this would be a factor of 5.12/4.3).

corrected values were given as maxima of 5.2 3C1/g for the surface soils and 16.0 pCi/g for deeper soils. The C1 concluded that the corrected values indicate that the EPA standards for Ra-226 had been met for those samples measured with OCS 6.

The NRC staff concludes that if the results from OCS 6 were biased low and there were no problems in the operations of the OCS. then the application of this correction factor is reasonable, and the

- results would indicate that there is a good degree of confidence that the EPA standards had been met. However, the evidence presented in the CR has not convinced the NRC staff that there were not problems in the operation of OCS 6. As mentioned before, the NRC staf f believes that if the quality control criterion was not met. it appears that OCS 6 may not have been operating within acceptable bounds, and so the results from OCS 6 are suspect.

The DOE should provide additi aal relevant evidence to indicate that OCS 6 was operating properly and that it is therefore reasonable to apply a constant correction factor to all analys_is results from OCS 6. One additional piece of evidence may be the results of an investigation that was ]erformed by the RAC to examine the performance of this OCS as noted ]y the RAC in a conversation with NRC staff (Andrews and Arp 1997).

From the data shown in Table'J.1 of the CR (see Table I above). the-NRC staff also evaluated the significance of the differences between the mean OC measurements for OC$s 4 and 5 and the true mean concentration of the reference material. Using a Student's t test.

14

-,,a,-, y ,, , - y , e.evs --

- the mean concentrations measured by these two OCSs are significantly different from the true mean concentration (p<0.05), Since the measurements were a)parently performed as quality control measurements, the NRC staff concludes-that the performances of OCSs 4~and 5 may not have been within reasonable bounds and so the results from these OCSs are suspect. The CR has not provided any analysis of these means of the OC measurements and has not provided any analysis of potential corrections that could be performed to account for the apparent low bias in OCSs 4 and 5 (perhaps similar to what was done for-0CS 6 results). The DOE should provide analyses and discussion of the apparent low bias in results from OCSs 4 and 5 and, if appropriate, should discuss potential corrections to data from these OCSs.

Overall, the NRC staff concludes that based on the quality control measurement results for OCSs 4, 5, and 6. these instruments may not have been o>erating properly, so the verification results are suspect. T1e DOE should revise and expand the discussions in the CR regarding the performance of these OCSs, as described above, to support the validity of the soil cleanup verification results.

f) Corrections for cobbles in soil: As described earlier, verification measurements for ccbbly soils were to be based on bulk radionuclide concentrations, and the TER indicated that a site-s)ecific procedure was to be submitted as a RAP modification. Althougi a document entitled " Analysis of Cobbly Soils for Cobbles to Fines Corrections to Radionuclide Concentrations at the New Rifle Colorado Processing Site" was submitted by DOE to NRC for information by letter dated May 19. 1994, apparently there was not a formal modification to the RAP to incorporate a site-specific procedure for verification of cobbly soils. NRC staff raised several concerns with the protocol

that was set out in that document and submitted comments to that effect to DOE by letter dated August 26, 1994. NRC still has concerns u.th the procedures for measuring radionuclides in the cobbly soils at Rifle.

The measurement data for the radionuclide concentrations in the cobble fraction and for the mass ratios of cobbles to fines from the test pits are grovided in Table J.7 of Appendix J of the CR. The test pit locations are shown in Figures J l. J.2. and J.3 of Appendix J. The same figures also show the locations of the 64 grids where verification used the cobbles to fines correction. Of

, these verification grids, 4 grids were in subpile areas and 60 were in what was called the "non-contact ponds area."

For measurement of the radionuclide (Ra-226 and Th-230) concentrations in the cobbles, there were 10 test pits located offpile and 11 test pits located in subpile areas. The average radionuclide concentrations to be used were taken as the average

from all 21 test pits. The NRC staff agrees that this approach was reasonable, since the radionuclide concentrations appeared 15

1 l

', relatively similar for the two different. areas, and the concentrations were in the same range as background concentrations (the means were 1.1 pC1/g for Ra-226 and 0.8 pCi/g for Th-230).

For measurements of the mass ratios of cobbles to fines. there were 5 test pits in the sub)ile area and five test pits in the non-

, contact ponds area. Tle locations of the five test pits in the subpile area generally encompassed the subpile verification grids for which the cobbles to fines correction was used. Since there were only four verification grids in the subpile area for which the cobbles to-fines correction was used, five test pits may be adecuate. The locations of the five test pits in the non-contact poncs area also generally encom)assed the verification grids in the non-contact ponds area for whic1 the cobbles to fines correction was used. However, in this case there were 60 verification grids for

! which the cobbles to fines correction was used. Procedure OP-003-4 Indicates that usually 30 test pits would be used for an entire 4

site. Tus, five test pits may not have been a sufficient number -

for develoaing the statistical value of the mass ratio of cobbles to fines in t11s area.

For the test pits to be representative of the cobbly areas of the verification grids (to which the cobbles to fines correction is applied), the test pit depths should be similar to the depths of the verification samples. However, the depths of the test pits and the verification grids were not provided in the CR so NRC staff cannot confirm their representativeness.

The NRC staf f concludas that the representativeness of the test pit samples for mass ratios of cobbles to fines has not been sufficiently justified. The DOE should provide additional information to establish the representativeness of the test pits for the verification samples, including the depths of samples and the suf ficiency of the 10 test pits used to develop the statistical values of the mass ratio of cobbles to fines.

g) - Frequency of Th-230 measurements: Section 1.1.3 of Appendix J (pages 2 and 3) of the CR describes when Th-230 verification analyses were performed at the Rifle sites. This section stated. In part:

" Verification measurements for Th-230 were conducted on more than 4% of the off-pile grids at the New Rifle site, and on more than 5% of all the grids at the Old Rifle Site. Additionally, 10% of the soil verification samples collected in sub-pile areas at the -

New Rifle Site were analyzed for Th-230. When a verification sample indicated elevated Th-230. a minimum of four of the '

adjacent grid samples were then analyzed for Th-230."

From this description in the CR the NRC staff cannot determine whether the frequency requirements outlined in the TER have been met. The DOE should revise the text or provide additional 16 4

,v-,,-, , - , , , , ,

)

' - -discussion to indicate whether the approved Th 230 analysis frequencies'were followed.

3; Nonroutine Application of Supplemental Standards:

The nonroutine application of su)plemental standards.for soil cleanup is l described:in Appendix K of the CR (MK-F 1997-).

cover three categories or' areas of the Rifle processing The nonroutine app)lications sites: (1 part of the g

river dike at the New Rifle site (described in-section A of Appendix K), (2) a road berm at-the Old Rifle site (section B of Aapendix K), and (3) locations of elevated Th-230, at concentrations greater t1an addressed in the routine Th-230 verification, at the New Rifle site (section C of Appendix K).

a) Supplemental standards for New Rifle river dike: A)pendix K of the l CR indicates that about 600 ft of the river dike, w11ch is roughly l 10 ft in height. located on the east side of the New Rifle site, is contaminated with residual radioactive material. It was estimated that about 400 yd' of contaminated material remained in the dise (page 16 of Appendix K). Table A.2 of section A of Appendix K-provides a summary of soil samples taken in 37 boreholes in the dike. The Ra-226 concentrations in these samples ranged up to 115 pCi/g.

The CR includes a recommendation that supplemental standards be

applied for the dike based on Criterion (a) of 40 CFR 192.21, but the only support in section A of Appendix K was the following statement (pages 17 and 18)

"The additional construction hazards

' associated with remedial action of the river dike, due to dike failure, outweigh the radiation risks associated with exposure to the contaminated materials contained in the d1ke construction." No details were provided about precisely what the risks of injury were

or about why reasonable measures could not be employed to mitigate the risks. The CR actually provides, under discussion of alternatives. a brief description of what work would have to be done to perform complete remediation of the dike (no sup)lemental standards), and this discussion includes some possiale mitigating measures. For complete remediation DOE indicates that excavation-would have to ba conducted when the Colorado River was at its steasonal low flow, to reduce floodtag potential, and that pumping would likely be needed to keep water seepage into excavated areas at a minimum (page 14 of Appendix K). These actions may be Jotentially reasonable measures to mitigate the risk of injury-to worcers. The CR does not provide any justification for why such measures would not be reasonable, i The CR focuses more on the minimal health benefits that would be achieved from cleanup of the dike. However, the health benefits -or lack thereof do not directly relate to the applicability of criterion (a) of 40 CFR 192.21. Thus, the NRC staff concludes that the applicability of criterion (a) has not been sufficiently justi fled. If supplemental standards are to be applied to the river dike, and are believed to=be warranted under criterion (a), the DOE must provide additional information to justify the applicability of criterion (a).

17

l L

l b) Supplemental standards for Old R1fle road berm: Section B of-Appendix K of the draft CR indicates that about 1600 ft of the road berm for State Highway 6 and 24, along the north side of the Old Rifle site, contains mill tailings contaminated material _ buried under clean fill. This area is proposed for application of i supplemental standards for soil cleanup. It was estimated that about. 24.000 yd of contaminated material remained in the road berm 3

(page 37 of Appendix K). Table B.2 of section B of Appendix K

.provides a summary of soil sam)les taken in 18 traverses of the exposed (after excavation to t1e extent performed) contaminated material in the berm. The Ra-226 concentrations in these samples ranged up to 1320 pCi/g.

Section B.1 of Appendix K (page 31) indicates that the applicable criterion from 40 CFR 192.21. for application of supalemental d

standards, is also Criterion (a) (see above). The CR includes a recommendatioa that supplemental standards be applied, but the main support in section B of Appendix K is the following statement (page 41): "The additional construction hazards associated with remedial action of the road berm outweigh the risk from e..posure to contaminated materials contained in the road berm construction."

Earlier in section B of Appendix K (page 32) DOE indicates that excavation ".,was stopped as close to the edge of the road as possible without endangering workers by de-stabilizing the slope."

Thus, there is an indication that the concern for possible injuries to workers stems from the potential for slope failure. However, no details are provided about precisely what tie risks of injury were or about why reasonable measures could not be employed to mitigate the risks. In fact, the CR provides a brief description of what work would have to be done to perform complete remediation of the road berm (no supplemental standards), and this discussion included some possible mitigating measures. For complete remediation. DOE states that temporary support features would be required to avoid excessive ground movement and failure of the excavated face (page 37 of Appendix K). This action may be a potentially rea;onable measure 4 to mitigate the risk of injury to workers. The CR does not provide any justification for why such a measure would not be reasonable.

Just as it does for the New Rifle river dike area, for th a Old Rifle road berm, the CR seems to focus more on the (indicated) minimal health benefits that would be achieved with cleanup of the road berm. However, the health benefits or lack thereof do not directly relate to the applicability of criterion (a) of 40 CFR _192.21.

Thus, the NRC staff concludes'that the applicability of criterion (a) has not been sufficiently justified. If supplemental standards are to be applied to the road berm, and are believed to be warranted under criterion (a), the DOE must provide additional information to justify the applicability of criterion (a).

18 i

!~

c) Supplemental standards for nonroutine areas of elevated Th 230:- 2 Section C of Appendix K of the CR indicates that for two 100-m verification grids, nonroutine application of supplemental standards was made due to elevated Th 230 (elevated such that the 1000-year Ra-226' concentration would exceed the EPA standard of 15 pCi/g above

- background). Based on the criterion of 40 CFR 192.21(h),

application of supplemental standards- for these areas is required because the primary contamination is other than radium, and concentrations were (before cleanu)) sufficient to cause a  :

potentially significant radiation lazard. The two affected verification grids-are close together in the excavated area under the non contact ponds.

The RAP and TER provided a criterion that would be used to judge the acceptability of leaving concentrations of Th-230 in soil at concentrations greater than that which would lead to a 1000-year ,

i Ra-226= concentration in excess of.15 pC1/g. For contamination that would be buried (with clean backfill) dee)er than 8 f t, residual levels of Th-230 would be acceptable if t1e expected radon progeny concentration in a slab-on grade house built over the contamination would be no greater than 0.01 WL. DOE used an NRC approved method for estimating radon progeny as set out in a generic protocol for Th-230 concentrations (Chernoff. 1993).

The 1000-year Ra-226 concentrations for the two grids were 18 and

16.4 pCi/g, and the contamination was to be backfilled with a total of 9 ft of uncontaminated material (page 78 of Appendix K). Since the Ra-226 concentrations are only slightly higher than the EPA l standard of 16.2 aCi/g for the Rifle sites (15 pCi/g abcve background) and t1e contamination is deep, it is expected that the analysis would show acceptable radon progeny concentrations. In fact, the calculated radon 3rogeny concentration was 0.01 WL for both of the grids. Thus, t1e NRC staff concludes that the methods used for the calculations of radon progeny concentrations for the two grids and the results of the calculations (if they do not change-see below) are acceptable.

However, the NRC staff has concerns about some of the )arameter values usad in the calcuiati os. The description of tie parameter values used for the RAECOM code (page 75 of Appendix K) indicates that for the topsoil material, values were typically taken from the reference values given in the NRC's Regulatory Guide 3.64 (NRC 1989) 4 and values for the cobbly contaminated material and cobbly fill material were taken from a report described as: " Measurements of Radon Gas Diffusion in Cobbly Soils" (RAE-8944/3-1. September 1991).

(The complete reference citation. including author, was not provided.) There was no justification provided for the use of values from this latter report for the cobbly material, and it-appears that the report included data only from the Gunnison UMTRA Project site.

19

~. . _ - . __ _ _ _ . _ - - _ _ _ _ . . _ _ _ __ _ _

- The parameter values may be reasonable. but-without justification this can not be verified. In-particular, the NRC staff nctes that site-specific values should be available for the radon emanation

-fraction (see the section of the CR dealing with the radon barrier calculation) and aerhaps for other parameters. If site-specific values are availaale, they are preferred to more generic values from

-the literature.

The NRC staff concludes that the parameter values used in the calculation of the radon-flux have not been sufficiently justified.

The DOE should provide additional justification for use of literature values for these parameters, and should consider the use of site-specific values when appropriate and available. *

4. Radon Attenuation: The CR (MX-F 1997) includes the most recent calculation for the radon barrier design. This calculation is

, number 06-570-14-04. and is a further revision (revision 4) to the

calculation suomitted in support of PID-38. A comparison of the two calculations has shown only one change that affects the radon

. ' attenuation calculation. This change is in the layer thicknesses of the two parts of the frost barrier (the total frost barrier thickness was unchanged). In the PID-38 calculation. the unaffected layer of frost barrier was modeled with thickness 4.0 ft and the degraded layer was modeled with thickness 3.0 ft. In the CR caIculation, the depth of f.ost penetration was increased-(see page 11-4 of calculation 06-570-14-04 in MK-F 1997) to 5.7 ft, of which 4.5 ft was the uppermost part of the frost barrier layer. The thickness of the unaffected part of the frost barrier was correspordingly decreased to 2.5 ft.

The calculations to support the CR were performed for a baseline case, which used nominal values of parameters, and for a worst case, which used the nominal values adjusted by plus or minus the standard error of the value, where the adjustment was always in the direction to produce higher exit flux. According to the calculation in the CR. the result of the changes in thickness of the frost barrier layers is that the calculated radon flux from the surface of the frost barrier ~ layer of the disposal cell (the exit flux) increased about 11% (the revised results are summarized on page II-; of calculation 06-570-14-04 in MK-F 1997). The results were a Daseline exit flux of 3.48 pCi/m's and-worst case exit flux of 6,55 pCi/m's.

Because the change to the previously app oved design was very limited, the NRC staff spot-checked the revised calculation by-repeating the model calculation. The spot-check results were -

acceptably close to the values provided in the CR.

The NRC staff also notes that the thicknesses of the radon barrier

and frost barrier layers assumed for the radon flux calculations (MK-F 1997) are less than the average. as-built thicknesses of these layers. The as-built- thicknesses are described in a " Disposal layer Thickness" table in-Section II - Critical Review Summary, of Volume 1 of the CR. In particular, the average.-as-built thickness of the 20

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. - frost barrier layers was 11.4' ft, significantly_ greater than the 7.0 ft used in the radon flux calculations. Because the as-built thicknesses of layers that provide radon attenuation are greater than used in the flux calculations, the calculations should-overestimate the actual long-term average radon flux from the disposal cell.

Based on this review. the NRC staff concludes that there is adequate assurance that the long-term radon flux standard of 20 pCi/m2 s will be met.

The open issues identified above, and requests for clarification of Jortions of the CR are noted for DOE response in Appendix C of this report. 3ased on the above statements, the NRC staff concludes that additional information is needed in order to complete its assessment of the completion status of the Rifle site in the areas of radiation cleanup and control.

2.2.4 Groundwater Protection Review Results The NRC staff has reviewed the groundwater hydrology and the groundwater

! resources protection aspects of the remedial actions taken by DOE at the Rifle site and as documented in the CR to ensure that they were in compliance with EPA's groundwater 3rotection standards in 40 CFR Part 192. Subparts A-C. and are consistent wit 1 the commitments made in the RAP. Areas of review included water resources protection standards for disposal _ performance assessment, closure performance standards, and groundwater monitoring and corrective action program.

DOE concluded, and NRC concurred in the TER, that the proposed remedial action would comply with the EPA standards because the tailings contaminants will not migrate to the Point of Com)liance (POC) in 1000 years. DOE estimated the vertical travel time from t7e bottom of the disposal cell to the uppermost aquifer to be over 1000 years. The estimated vertical travel time from the base of the disposal cell to a point just below the deepest exploratory borehole at the Estes Gulch site (544 feet) is in excess of the 200 year minimum design criterion established in UMTRCA. Consequently. DOE concluded that the proposed remedial action plan is in compliance with EPA's groundwater arotection standards. The great denth and high degree of hydraulic isolation 3etween the uppermca aquifer and the disposal cell make amb:ent groundwater quality characterization. Point of Compliance monitoring. and proposed corrective actico plans inappropriate for demonstrating groundwater resource protection.

In the Rifle RAP. DOE committed to several water resources protection activities. These commitments included:

1. Construction of an impermeable geomembrane on the downslope side wall of the Estes Gulch disposal cell subgrade.

2. Construction of a sand blanket, finger drains and 3 dewatering wells

/ within the disposal cell at the low point of the bottom subgrade.

21

- _ _ _ _ _ _ _- _ =

. 3. Actively pumping the dewatering wells if water levels approach the top of the installed geomembrane.

4. Installing piezometers in any paleochannel downslope of the disposal cell, which had been truncated by the disposal cell excavation.

5. Plugging and abandoning certain monitoring wells used for characterization at the Old and New Rifle former processing sites.

and the Estes Gulch disposal site.

During the review, the NRC staff noted that the DOE provided confirmation of completion of the following commitments:

1. Geomembrane construction as evidenced by Drawing RFL-DS-10-0718

2. Sand blanket finger drains and dewatering wells as shown in Drawings RFL-DS-10-0721; RFL-DS-10-0722: RFL-DS-10-0731: and RFL-DS-10-0732

3. Pump if water approaches the top of the geomembrane as set out in Calculation 06-579-05-00

4. Piezometer in Paleochannel: N0 INFORMATION PROVIDED

5. Well Abandonment: NO INFORMATION PROVIDED The CR for Rifle should document which monitoring wells DOE has abandoned both at the former arocessing sites and the disposal site. Additionally, locations of any wells tlat have not been abandoned, including any piezometers at the disposal site, should be included on the as-built drawings that are part of the CR. The need for this additional information is noted in Appendix C of this report.

DOE has elected to postpone the groundwater remedial action activities at the two processing sites to a separate phase of the project. so related issues are not addressed in the CR.

Based on the review of the water resources protection information in the Rifle CR. the NRC staff concludes that additional information is needed regarding the status of monito ing wells and t:1e piezometer in the paleochannel in order to complete its ass %sment of the compktion status of the Rifle site.

3.0

SUMMARY

NRC staff reviewed geotechnical engineering surface water hydrology and erosion protection, and radiation protection aspects of the remedial action performed at the Rifle uranium mill tailings site. The purpose of this review was to determine whether DOE had performed remedial actions at the site in accordance with specifications in the RAP. RAP modifications, and other supporting project documents, and thus.with the EPA standards in 40 CFR Part 192. Subparts A-C. Based on its review of the CR and on observations made during periodic on-site construction visits, the NRC staff concludes that with 22

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. the. exception of the:open-issues as noted in Appendix C.- 00E appears to have performed remedial action at the Rifle site in accordance with the EPA standards. Since open issues remain at this time. NRC cannot concur that. DOE- t has completed the remedial-actions specified for this site. However, NRC-is prepared to-concur in completion after the outstanding issues are resolved.

This-Draft CRR will-be finalized in the future when 00E has resolved the open '

issues.

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4.0' REFERENCES Arp S.J. 1996. -Letter to D. Gillen. U.S. Nuclear Regulatory Commission, dated June 10,1996. U.S. Department of Energy. Albuquerque Operations Office, Albuquerque. New Mexico.

Andrcws D and S. Arp. 1997. Teleconference with J. Lambert and D. Schmidt.

U.S. Nuclear Regulatory Commission. on June 26. 1997. MK-Ferguson Company and U.S. Department of Energy. Albuquerque. New Mexico. ,

Chernoff A. 1993. Letter to J.J. Surmeier. U.S. Nuclear Regulatory Commission. dated December 22. 1993, with attached report: " Generic Protocol for Thorium 230 Cleanup / Verification at UMTRA Project Sites." U.S. Department of Energy Uranium Mill Tailings Remedial Action Project Office. Albuquerque.

New Mexico.

DOE (U.S Departmen of Energy) Remedial Action Inspection Plan, Revision C.

Uranium Hill Tailings Remedial Action Project. Rifle, Colorado. December.

1991.

DOE. Remedial Action Plan and Site Design for StabiliZJtion of the inaClive Uranium Mill Tallings Sites at Rifle. Colorado. Final Report. dated FebruEry 1992.

DOE (U.S. Department of Energy) " Final Audit Report of Remedial Action Construction at the UMTRA Project Rifle, Colorado, Site." January 1997 Holonich J.3. 1996. Final NRC Concurrence on Project Interface Document (PID) No. 06-5-38 for the R1fle. Colorado Uranium Mi11 Remedial Action Project Site. Letter to R. Sena. U.S. Department of Energy dated July 23, 1996.

U.S. Nuclear Regulatory Commission. Washington. DC.

MK-F (MK-Ferguson Company) Rifle. Colorado. NRC Copy. Final Completion Report. Draft Report, dated April 1997.

U.S. Nuclear Regulatory Commission (NRC) " Final Technical Evaluation Report for the Propsed Remedial Action of the Rifle, Colorado Uranium Hill Tailings Site," May 1992.

NRC 1989. Calculation of Radon Flux Attenuation by Earthen Uranium Mill Tailings Covers. Regulatory Guide 3.64. NRC Office of Nuclear Regulatory Research. Washington, DC.

24

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I l

APPENDIX A j NRC SITE VISITS TO THE

. RIFLE UMTRA PROJECT SITE

. i APPENDIX A NRC SITE VISITS TO THE RIFLE UMTRA PROJECT SITE DbAIE STAFF / DISC 1PLINE PURPOSE 9/84 T. Johnson / surface hydrology Site evaluation review D. Gillen/geotech. engineer R. Pennefill/ project manager 2

D. Martin / manager 8/3/88 J. Grimni/ geologist Pre-RAP review visit L. Derring/ hydrologist S. Wastler/ project manager 6/14/89 T. Johnson / surface hydrologist Site visit / evaluation of rock M. Weber /geo-hydrologist D. Gillen/geotech. engineer ,

M. Fliegel/ manager 9/6 7/89 J. Grimm / geologist Pre-construction review M. Dunkelman 5/3/90 T. Johnson / surface hydrologist Pre-RAP review visit D. Gillen/geotech. engineer A. Fan /hydrolop c 10/6/92 D. Rom /geotech/ engineering On-site construction review M. Layton/ hydrologist 11/16-17/92 D. Rom /geotech/ engineering Observe excavated disposal cell / on-site construction rev 8/5/93 D. Rom /geotech/ engineering On-site construction review T. Johnson / surface hydrologist 9/11/95 D. Rom /geotech. engineering Observe radon barrier J. Lambert / project manager placement A-1

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4 APPENDIX B UMTRCA, THE EPA-STANDARDS, AND THE PHASED UMTRA PROJECT

l APPENDIX B UMTRCA THE EPA STANDARDS, AND THE PHASED UMTRA PROJECT Title 1 of UMTRCA defines the catutory authority and roles of the DOE, the NRC, and the EPA with regard J the remedial action program for inact4"e uranium mill tailings sites.

The Standards UMTRCA charced the EPA with the responsibility for promulgating remedial action stancards for inactive uranium mill sites. The pur)ose of these standards is to protect the public health and safety and t1e environment from radiological and non-radiological hazards associated with radioactive -

materials at the sites. UMTRCA required that EPA promulgate these standards by.no later than October 1, 1982. After October 1, 1982, if the EPA had not promulgated standards in final form. DOE was to comply with the standards ,

proposed by EPA under Title 1 of UMTRCA until such time as the EPA had promulgated its standards in final form.

The final EPA standards were promulgated with an effective date of March 7, 1983 (48 fB 602: January 5, 1983); see 40 CFR Part 192 - Standards for Remedial Actions at inactive Uranium Processing Sites Subparts A, B, and C.

These regulations may be summarized as follows:

1. The disposal site shall be designed to control the tailings and other residual radioactive materials for up to 1000 years, to the extent reasonably achievable, and, in any case, for at least 200 years [40 CFR 192.02(a)].

2. Provide reasonable assurance that the disposal site design shall prevent radon-222 from residual radioactive material to the atmosphere from exceeding an average release rate of 20 picocuries per square meter per second, or from increasing the annual average concentration of radon-222 in air, at or above any location outside the disposal site, by more than one half picocurie per liter [40 CFR 192,02(b)].

3. The remedial action shall be conducted so as to provide reasonable assurance that, as a result of residual radioactive materials from any designated processing site, the concentrations of radium-226 in land averaged e over any area of 100 square meters shall not exceed the background level by more than 5 picocuries/ gram averaged over the first 15 centimeters of soil below the surface and 15 picocuries/ gram averaged over 15 centimeter thick layers of soil more than 15 centimeters below the surface [40 CFR 192.12(a)].

4. The objective of remedial action involving buildings shall be, and reasonable effort shall be made to achieve, an annual average (or equivalent) radon decay product concentration (including b6ckground) not to exceed 0.02 WL and the level of gamma radiation shall not exceed the background level by more than 20-microroentgens pr.r hour [40 CFR 192.12(b)].

B1

w 4 The portion of the EPA standards dealing with groundwater requirements, I 4

40 CFR 192.2.0(a)(2)-(3) were_ remanded-by the Tenth Circuit Court of Appeals on ,

September.3. 1985. Based on this court decision. EPA was directed to y

promulgate new groundwater standards. EPA proposed these standards in the- >

form of revisions to Subparts A-C of. 40.CFR Part 192 in Seatember 1987. and i now is in the process of completing action to promulgate t1e final _ groundwater standards.

As mandated by Section 108(a)(3) of UMTRCA, however, the remedial action at

! the inactive uranium processing sites. is to comply with EPA's proposed standards until such time as the final standards are promulgated. DOE-t continues to perform remedial action at the inactive processing sites in accordance with NRC's concurrence with the remedial action approach based on the proposed EPA groundwater standards (52 8 36000: September 24. 1987L Delaying implementation of the remedial action 3rogram would be inconsistent with Congress' intent of timely completion of tie program. Modifications of

. disposal sites after completion of the_ remedial action to comply with EPA's final groundwater protection standards may be unnecessarily complicated and expensive and may not yield commensurate benefita in terms of human and i

environmental protection. Therefore. the Commission believes that sites where remedial action has been essentially completed prior to EPA's promulgation of final groundwater standards will not be impacted by the final groundwater standards. Although additional _ effort may be appropriate-to assess and clean

- up contaminated groundwater at these sites. the existing designs of the dispnsal sites should be considered suf ficient to provide long-term protection against future groundwater contamination. NRC does not view UMTRCA as requiring tne reopening of those sites that have been substantially completed when NRC concurred with the selection of remedial action in accordance with applicable EPA standards, proposed or otherwise in place at the time such NRC L concurrence was given.

DQf Selection (Desinn) Phase l For each site. UMTRCA requires that DOE select a plan of remedial action that

will satisfy the EPA standards and-other applicable laws and regulations. and with which the NRC will-concur. For each site, this phase includes preparation by 00E of an Environmental Assessment or an Environmental Impact Statement. and a Remedial Action Plan (RAP). The RAP is structured to. provide a comprehensive und rstanding of the remedial actions propos'd at that site and contains s)ecific design and construction raquirements, To complete the first phase. NRC and the ap3ropriate State or in@n tribe will review the RAP and then concur that the RArwill meet the EPA standards.

4 The Performance (Construction) Phase-t l :In-this phase the actual remedial action '(which includes decontamination, decommissioning, and reclamation) at the site is done in accordance with the-RAP. The NRC and the State / Indian tribe, as applicable, must concur in any

- changes to the concurred-in plan that arise during construction. At the completion of remedial action activities at the' site. NRC concurs in DOE's

determination that the activities at the site have been completed in accordance with the approved plan. Prior to-licensing (the next phase), title-B-2 a

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to the disposed tailings and contaminated materials must be transferred to the United States and the land upon which they are disposed of must be in Federal custody to provide for long-term Federal control. Disposal sites on Indian land will remain in the beneficial _ ownership of the Indian tribe.

NRC concurrence in the DOE determination that remedial action at a processing site has been accomplished in accordance with the approved plan may be accomplishiJ in two steps where residual radioactive material is not being moved from the processing site to a dif ferent disposal site. The Uranium Mill lailings Remedial Action Amendments Act of 1988 allows for a two-step approach for Title I disposal sites. The Amendments Act will allow DOE to do all remedial actions. Other than groundwater restoration, for the first step of closure and licensing. The second step, which can go on for many years, will deal with existing groundwater restoration. When groundwater restoration is completed, the Long-Term Surveillance Plan required under the licensing phase will be appropriately amended. For sites that are being moved, licensing will occur in one step. There is no groundwater restoration at the disposal site and the processing site will not be licensed after completion of remedial action.

The ! itensinq Phase Title I of UMTRCA further requires that, upon completion of the remedial action program by DOE. the permanent disposal sites be cared for by the DOE or other Federal agency designated by the President, under a license issued by the Commission. DOE will receive a general license under 10 CFR Part 40.27 following: (1) NRC concurrence in the DOE determination that the disposal site has been properly reclaimed, and (2) the formal receipt by NRC of an acceptable Long-lerm Surveillance Plan (LTSP). NRC concurrence with DOE's performance of the remedial action indicates that DOE has demonstrated that the remedial action complies with the provisions of the EPA standards in 40 CFR part 192. Subparts A. B. and C. This NRC concurrence may be completed in two steps as discussed above. There is no termination date for the general license.

Public involvement has been and will continue to be provided through DOE's overall-remedial action program for Title I sites. The local public will have an opportunity to comment on the remedial action or closure plans proposed and implemented by DOE a J to raise conc 2rns regarding final staailization a..d the degree of protection acnieved. NRC ful'v endorses State / Indian tribe ano public input in all stages of the program. At the time the LTSP is submitted, the NRC will consider the need for a public meeting in response to requests and public concerns.

The Surveillance and Monitorina Phase in this phase. DOE and NRC periodically inspect the disposal site to ensure its integrity. The LTSP will require the DOE to make repairs, if needed.

One of the requirements in the EPA standards is that control of the tailir.gs should be designed to be ef fective for up to 1000 years without active maintenance. Although the design of the stabilized pile is such that reliance B-3

V

• on active maintenance should be minimized or eliminated the NRC license will

. require emergency repairs as necessary. In the event that significant repairs are necessary, a determination will be made on a site specific basis regarding the need for additional National Environmental Policy Act actions, and health and safety considerations based on 10 CFR Parts 19, 20, and 21.

4 B-4 i

.c .

4 APPENDIX C OPEN ISSUES FOR DOE RESOLUTION

o o

7 .

- OPEN ISSUES RADIATION CLEANUP AND CONTROL

1. Soil Cleanup Verification A) If the DOE intends to use the Barringer 0A analyses of Ra-226 to support the quality of the verification results for the Rifle sites.

statistical analyses of the OA data should be performed and provided in the CR. (see discussion /coment in 2(d) of main document p.10)

B) The NRC staff concludes that based on the quality control measurement results for OCSS 4. 5 and 6. these instruments may not have been oaerating properly so the verification results are suspect. 11e DOE should revise and expand the discussions in the CR regarding the performance of these OCSs. as described below and as elaborated on in discussion / comment 2(e) of main document, in order to support the validity of the soil cleanup verification results.

(1) The NRC staff notes that in section 1.1.2 of Appendix J (page 2) of the CR, the text indicates that the 30% 3erformance criterion was achieved with the OCS, which contradicts t7e information on page 9 of Appendix J. The DOE should correct this statement or address the inconsistency. (see discussion / comment in 2(e) of main document, p.

11)

(2) The NRC staf f does not see the relevance of the ccmparison of mean concentrations from the OCS measurements and the Barringer QA measurements. The 30% performance criterion seems to focus on the acceptable precision (the variability) in the measurements, not the acceptable accuracy (bias in the mean). The comparison of mean concentrations does not provide any information about the variability in the OCS measurements, and thus this comparison does not, in contradiction to the CR statement indicate that the instrument was within the 30% performance criterion. The DOE should remove the discussion of the Barringer 0A results, or revise the discussion to provide relevant conclusions. (see u ncussion/ comment in 2(e) of main document, p. 12)

(3) It appears that OCS 6 was not operating within acceptable bounds, and so the results from OCS 6 are suspect. The DOE should provide additional, relevant evidence to indicate that OCS 6 was operating properly and that it is therefore reasonable to apply a constant correction factor to all analysis results from OCS 6. (see discussion / comment in 2(e) of main document. p. 12)

(4) The performances of OCSs 4 and 5 may not have been within reasonable bounds and so the results from these OCSs are suspect. The draft CR has not provided any analysis of the means of the OC measurements and has not provided any analysis of potential corrections that C-1

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. could be performed to account for the apparent low bias in OCSs 4 and 5 (perhaps similar to what was done for OCS 6 results). The DOE should provide analyses and discussion of the apparent low bias in results from OCSS 4 and 5. and, if appropriate, should discuss potential corrections to data from taese OCSs.

C) The representativeness of test pit samples for mass ratios of cobbles to fines has not been suf ficiently justifled. The DOE should provide additional information in the CR to establish the representativeness of the test pits for the verification samples, including the depths of samples and the sufficiency of the 10 test pits used to develop the statistical values of the mass ratio of cobbles to fines. (see discussion / comment in 2(f) of main document,

p. 15.)

D) From the description in the CR. the NRC staff cannot determine whether the frequency requirements outlined in the RAP and TER for the frequency of verification of Th-230 measurements have been met.

The DOE should revise the text or provide additional discussion to indicate whether the approved Th-230 analysis frequencies were followed. (see discussion / comment in 2(g) of the main document. p.

15.

2. Nonroutine Applicatior, of Supplemental Standards a) Supplemental standards for New Rifle river dike:

The CR included a recommendation that supplemental standards be a3 plied for the dike based on Cr1terion (a) of 40 CFR 192.21. but t1e only support iri section A of Appendix K was the following statement (pages 17 and 18): "The additional construction hazards associated with remedial action of the river dike. due to dike failure, outweigh tne radiation risks associated with exposure to the contaminated materials contained in the dike construction." No details were provided about precisely what the risks of injury were or about why reasonable measures could not be employed to mitigate the risks. If supplemental standards are to be applied to the river dike, and are believed to be warranted under criterion (a). the DOE must provide adoitional inf o,mation to justify the app'icability of criterion (a). (see discussion in 3a of the main document p. 16) b) Supplemental standards for Old Rifle road berm:

The CR included a recommendation that sup]lemental standards be applied, but the main support in section 3 of Appendix K was the fodowing statement (page 41): "The additional construction hazards associated with remedial action of the road berm outweigh the risk from exposure to contaminated materials contained in the road berm construction." Earlier in section B of Appendix K (page 32) it was indicated that excavation "..was stopped as close to the edge of the road as slope." possible without Thus, there is anendangering workers indication that by de-stabilizing the concern for possiblethe C-2

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, injuries to workers stems from the potential for slope failure.

However. no details were provided about precisely what the risks of injury were or about why reasonable measures could not be employed to mitigate the risks. The NRC staff concludes that the applicability of criterion (a) has not been sufficiently justified.

If supplemental standards are to be applied to the road berm. and are believed to be warranted under criterion (a). the DOE must provide additional information to justify the ap)licability of criterion (a). (See discussion in 2.3.3(b) of t,e main document) c) Supplemental standards for nonroutine areas of elevated Th-230:

The parameter values s. sed to calculate radon progeny concentrations may )e reasonable, but without justification this can not be verified. In particular, site-specific values should be available for the radon emanation fraction (see the section of the CR dealing with the radon barrier calculation) and perhaps for other parameters. If 3ite-specific values are available, they are preferred to more generic values from the literature.

The ]arameter values used in the calculation of the radon flux have not seen suf ficiently justified. The DOE should provide additional Justification for use of literature values for these paramaters, and should consider the use of site-specific values when appropriate and aVallable. ($ee discussion in 2.2.3.(c) of the main document.)

GROUNDWATER RESOURCE PROTECTION

3. Based on the review of the water resources protection information in the Rifle CR. the NRC staff concludes that additional information is needed regarding the status of monitoring wells and the piezometer in the paleochannel in order to complete its assessment of the completion status of the Rifle site. The CR for Rifle should document which monitoring wells DOE has abandoned both at the former processing sites and the disposal site. Additionally, locations of any wells that have not been abandoned, including any piezometers at the disposal site. should be included on the as-built drawings that are part of the CR. (See discussion in 2.2.4 of the main document.)

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