Closure Report for Building 650 Leachfield Corrective Action Unit 94: Nevada Test Site, Nevada - REVISION:0 - October 1998

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Closure Report for Corrective Action Unit 94: Nevada Test Site, Nevada Controlled Copy Number: !Ff\CO...S. Distribution A ·Approved for public release; further dissemination unlimited. U.S. Department of Energy Nevada Operations Office

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Available to the public from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Available electronically at http://W\YW.doe.gov/bridge. Av~lable to U.S. Department of Energy and its contractors in paper from: U.S. Department of Energy Office of Scientific and Technical Information Reference herein to any specific commercial product, process, or service by trade name, \ trademark, manufacturer, or otherw'ise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof or its contractors or

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CLOSURE REPORT FOR CORRECTIVE ACTION UNIT 94: NEVADA TEST SITE, NEVADA Prepared for the U.S. Department of Energy Nevada Operations Office Work Performed Under Contract No. DE-AC08-96NV11718

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CLOSURE REPORT FOR CORRECTIVE ACTION UNIT 94: NEVADA TEST SITE, NEVADA Industrial Sites Subproject Nevada Environmental Restoration Project ·

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TABLE OF CONTENTS ACRONYMS AND ABBREVIATIONS ......................................... viii 1.3 CLOSURE REPORT CONTENTS ...................................... 6 2.1 DESCRIPTION OF CORRECTIVE ACTION ACTIVITIES .................. 7 2.1.1 Preplanning and Site Preparation ................................. 7 2.1.2 Removal of the Distribution Box ................................. 8 2.1.3 Excavation of Discharge Piping and Soil Upgradient of the 2.1.4. Sampling and Grouting of the Discharge Piping .................... 10 2.1.5 Removal of the Soil below the Distribution Box .................... 11 2.1.6 Excavation of the Northeast Corner of the Leachfield ................ 11 2.1. 7 Excavation of the Leachfield Piping ............................. 12 2.1.8 Collection of Soil Samples .................................... 14 2.1.9 Backfilling the Excavated Areas ................................. 15 2.2 DEVIATIONS FROM CLOSURE PLAN AS APPROVED .................. 16 2.3 CORRECTIVE ACTION SCHEDULE AS COMPLETED .................. 17 4.0 CLOSURE VERIFICATION RESULTS ....................................... 21 4.1 UPGRADIENTEXCAVATION AND DISCHARGE PIPELINE ............. 21 4.1.2 Radiological Soil Samples ..................................... 23 4.1.3 Radiological Swipe Samples ................................... 23

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TABLE OF CONTENTS (Continued) 4.2 DISTRIBUTION BOX EXCAVATION ................................. 23 4.2.1 VOC Soil Samples ........................................... 23 4.2.2 Radiological Soil Samples ..................................... 27 4.3 'NORTHEAST CORNER OF LEACHFIELD EXCAVATION ................ 27 4.3.1 VOC Soil Samples ........................................... 27 4.3.2 Radiological Soil Samples ..................................... 27 4.3.3 Radiological Swipe Samples ................................... 29 4.4 LEACHFIELD PIPELINE EXCAVATION .............................. 29 4.4.1 VOC Soil Samples ........................................... 29 4.4.1.1 East Inner Pipeline ................................... 29 4.4.1.2 East Outer Pipeline .....................•............. 32 4.4.1.3 West Inner Pipeline ................................... 32 4.4.1.4 West Outer Pipeline .................................. 37 4.4.2 Radiological Soil Samples ..................................... 38 4.4.3 Radiological Instrument Readings and Swipe Samples ............... 38 4.5 QUALITY CONTROL SAMPLES ..................................... 38 Appendix A: Closure Certification Appendix B: Waste Manifests Appendix C: Test Results Appendix D: Photographs of Closure Activities

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TABLE OF CONTENTS (Continued) Figure 1 - CAU 94- Building 650 Leachfield Location ................................. 2 Figure.2 - Location of Building 650 Leachfield and Previously Identified Impacted Areas ..... 3 Figure 3 - Building 650 Leachfield Site Layout for Closure Activities .................... 9 Figure 4 - Building 650 Leachfield Borehole and Trench Sample Locations ............... 13 Table 1 - Building 650 Leachfield Closure·Schedule as Completed ...................... 18 Table 2 - Sample Results from the Upgradient Excavation and Discharge Line ............. 22 Table 3 - Sample Results from the Distribution Box Excavation ........................ 24 Table 4 - Sample Results from the Northeast Comer ofLeachfield Excavation ............. 28 Table 5 - Residue and Swipe Sample Results from the Leachfield Piping ................. 30 Table 6 - Sample Results from the East Inner Leachfield Pipeline ....................... 31 Table 7 - Sample Results from the East Outer Leachfield Pipeline ....................... 33 Table 8 - Sample Results from the West Inner Leachfield Pipeline ...................... 35 Table 9 - Sample Results from the West Outer Leachfield Pipeline ...................... 39 Table I 0 - Results of Quality Control Samples ...................................... 41

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ACRONYMS AND ABBREVIATIONS AST Aboveground Storage Tank BGS Below Ground Surface CAS Corrective Action Site CAU Corrective Action Unit CFR Code of Federal Regulations CMP Corrugated Metal Piping DOE U.S. Department of Energy DOE/NV U.S. Department of Energy. Nevada Operations Office dpm disintegrations per minute EPA Environmental Protection Agency FFACO Federal Facility Agreement and Consent Order IT International Technology Corporation μglkg microgram per kilogram Section: ACR & ABB

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Section: ACR & ABB ACRONYMS AND ABBREVIATIONS (Continued) MDL method detection limit NA not analyzed ND not detected above the method detection limit NDEP Nevada Division of Environmental Protection NEPA National Environmental Policy Act NTS Nevada Test Site NTSWAC Nevada Test Site Waste Acceptance Criteria OD outer diameter pCi/g picocuries per gram PEER Pollution, Environment, Energy, and Resources Consultants SDG sample delivery group RCRA Resource Conservation·and Recovery Act REE Co Reynolds Electrical and Engineering Co., Inc. RWAP Radioactive Waste Acceptance Program VCP vitrified clay pipe voe Volatile Organic Compound

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Closure Report - CAU No. 94 Building 650 currently houses the Radiochemistry Laboratory used for bioassay and environ;mental sample analysis in support of the Nevada Test Site (NTS) radiological environmental monitoring and other programs. Historically, laboratory effluent was discharged to the leachfield through two clay pipelines that converged into a distribution box. The Distribution Box was connected to four infiltration leachfield pipelines spaced across a 9-meter (m) (30-foot [ft]) wide field. The length of the pipelines varied between 10 m and 15 m (33 ft and 50 ft). These pipes provided for the distribution of effluent over a large area so that liquid could slowly percolate through the gravel into the underlying soil of the leachfield. Characterization results showed that the Distribution Box, soil below the Distribution Box, leachfield piping, and soil had been impacted with radiological and hazardous constituents. Closure activities at the Building 650 Leachfield began on June 15, 1998. Excavation and sampling was completed in multiple phases. Phase I included the excavation and sampling of all areas reported to be impacted during site characterization. These areas included the Distribution Box, the northeast comer of the leachfield, and the up gradient pipeline. During Phase I, the upgradient pipeline was also grouted closed. Phase II included the excavation and sampling of the leachfield pipeline. Phase III included overexcavation, both laterally and vertically as required, of the leachfield area after the Phase II sampling revealed detectable levels of constituents of concern. After overexcavation and when sample results indicated that the soil met established clean-up criteria, the excavations were backfilled, the site was graded, and all fencing was removed. Closure activities were completed on September 17, 1998, with the shipment and disposal of the 89 B-25 boxes of mixed waste generated during closure. The closure was completed in accordance with the approved Closure Plan (DOE, 1998c) and subsequent agreements between DOE and the NDEP (DOE, l 998a) as a Clean Closure under Section V.A.l of the Resource Conservation and Recovery Act (RCRA) Operational Permit (NDEP, 1995). Under the conditions of 40 Code of Federal Regulations (CFR) §270.l(c)(5) and (6) for a closure by removal equivalency, this Closure Report demonstrates that the closure meets or exceeds the requirements of 40 CFR §264.280(e). Impacted soils and materials have been removed from the site and verification samples provide lateral and vertical confirmation of the removal. All RCRA-hazardous waste has been transferred to the NTS Area 5 Waste Storage Unit to await final disposal at an off-site treatment, storage, and disposal facility. All mixed waste generated at the site has been disposed in Pit 3 at the NTS Area 5 Radioactive Waste· Management Site. All non-hazardous debris has been disposed of in the Area 9 1OC Landfill. Therefore, the Department of Energy, Nevada Operations, requests that a Notice of Completion be issued by the Nevada Department of Environmental Protection and the Building 650 Leachfield, Corrective Action Unit 94, be moved from Appendix III to Appendix IV of the Federal Facilities Agreement and Consent Order "Closed Corrective Action Units." Under 40 CFR §270.l(c)(5) and (6), Post-Closure Monitoring is not required at this site.

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Closure Report - CAU No. 94 This report describes the remediation activities performed and the results of confirmatory sampling conducted at the Building 650 Leachfield. The Building 650 Leachfield was a historic laboratory disposal unit located southeast of Building 650 in Mercury, Nevada, Area 23 of the Nevada Test Site (NTS) (Figure 1). The Federal Facility Agreement and Consent Order (FF ACO, 1996) lists the Building 650 LeacJ:ifield as Corrective Action Unit (CAU) 94 and Corrective Action Site (CAS) 23-05-01. Remediation of the Building 650 Leachfield was required under the Resource Conservation and Recovery Act (RCRA) Operational Permit, which Environmental Protection [NDEP], 1995), and the FFACO (1996). The Building 650 Leachfield is listed in Part V of the RCRA Operational Permit. · The purpose of this report is to provide documentation of the completed corrective action and provide data supporting the completion of the action. Building 650 currently houses the Radiochemistry Laboratory used for bioassay and environmental sample analysis in support of the NTS radiological environmenta,l monitoring and other programs. Historically, laboratory effluent was discharged to the leachfield through two clay pipelines, one originating at the north end of Building 650 and extending south along the east side of the building and the other originating at the south end of Building 650 and extending east along the south side of the building. The pipeline along the south side of Building 650. originated as a drain from an · emergency shower. The shower was never used and it was disconnected and grouted in November 1992 (REECo, 1993). These two pipelines converged into a single pipeline off the southeast comer of Building 650 (Figure 2). The pipelines terminated at a Distribution Box measuring 0.9 x 0.9 x 2 m (3 x 3 x 7 ft). The pipeline was grouted from the Distribution Box back 0.6 m (2 ft) during the operational closure (Reynolds Electrical and Engineering Co., Inc. The Distribution Box was connected to four infiltration leachfield pipelines spaced across a 9-m- (30-ft-) wide field. The length of the pipelines varied between 10 m and 15 m (33 ft and 50 ft). The leachlines consisted of small sections of solid clay pipe. Each section of piping is approximately 0.3 m (1 ft) long with 5 cm (2 in) spacing between each section. The pipes were located approximately 2 m to 2.5 m (6 ft to 8 ft) below the ground surface and rested on 0.3 m to 0.6 m (1 ft to 2 ft) of gravel packing. These pipes provided for the distribution of effluent over a large area so that liquid could slowly percolate through the gravel into the underlying soil of the leachfield. Characterization results showed that the Distribution Box and soil below the Distribution Box and northeast comer of the leachfield had been impacted with radiological and

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Closure Report - CAU No. 94 CAU 94 - BUILDING 650 LEACHFIELD LOCATION

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Closure Report - CAU No. 94 Chain Link Fence VCP Vitrified Clay Pipe LOCATION OF BUILDING 650 LEACHFIELD AND PREVIOUSLY IDENTIFIED IMPACTED AREAS

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Closure Report • CAU No. 94 hazardous waste (U.S. Department of Energy [DOE], 1998b). Verification sampling was conducted on the lower leachfield pipelines concurrent with site closure activities. The leachfield was used as a land disposal unit from 1965 to October 1993, with an estimated annual discharge rate ofless than 984 liters (L) (260 gallons [gal]) (REECo, 1993). Hazardous waste discharged to the leachfield included hydrochloric acid, nitric acid, toluene, xylene, acetone, detergents, and other chemicals used to perform radionuclide separations. Radionuclides found in the discharge included tritium, Americium-241, Cobalt-60, Cesium-137, Discharge of radioactive waste was discontinued in 1979. Discharge ofRCRA-regulated materials to the leachfield ended in 1987. Discharge ofnon-RCRA regulated materials (water) continued until the discharge piping leading to the Distribution Box was sealed in 1994 (REECo~ 1994). Previous characterization activities at the Building 650 Leachfield have involved excavating and sampling a series of trenches {REECo, 1993; International Technology Corporation [IT], 1995), collecting soil samples during closure of the discharge line (REECo, 1994), a geophysical evaluation (IT, 1996), and subsurface sampling of the Distribution Box (Erner, 1995). The results of these previous site characterization studies are summarized in the Building 650 Leachfield Characterization Plan (DOE, 1997a). The most recent site characterization report (DOE, 1998b) suggested that waste was limited in extent. Constituents of concern exceeding background levels were found in the following • Radioactive constituents Plutonium-238 and Plutonium-239/240 were detected in the Distribution Box and the soil below the Distribution Box to a depth of 6. 7 m (22 ft) at • Acetone, a listed hazardous waste, was detected at low-level 3.4 m (11 ft) below ground During site characterization, other constituents were also detected in the northeast comer of the leachfield; however, the concentrations were less than regulatorily established clean-up levels. These consisted of the following: · These constituents were found at sample location LCHB-2 (Figure 2). The area where these constituents were detected was also excavated and disposed of as a mixed waste because of the proximity to the other areas requiring remediation.

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Oosure Report - CAU No. 94 In addition to the constituents of concern identified during site characterization, additional constituents of concern were identified in closure verification samples from the leachfield. These included 2-Butanone, methylene chloride, toluene, and tetrachloroethylene (PCE), The scope of work for this project consists of the following activities: • Preplanning and site preparation, including the preparation of all plans and permits, utility clearance, and mobilization of equipment to the site. • Removal of the Distribution Box using a backhoe. • Removal of the grouted section of the discharge piping leading into the Distribution Box and collection of swipe samples from within the ungrouted section. • Excavation of discharge piping and surrounding soil approximately 30 m (100 ft) north • Grouting the entire discharge pipeline from the north excavation location. • Removal of the soil within a 4.9-m (16-ft) diametei: of the Distribution Box, to a depth of } m (10 ft), using a backhoe and emplacement of a 3.7-m- (12-ft-) diameter corrugated pipe for surface casing. • Removal of the soil below the box to a depth of7.6 m (25 ft) using a 2.6-m- (8.5-ft-) diameter auger drill rig. • Excavation of the piping and the soil below the piping to 3.7 m (12 ft) in the northeast comer of the leachfield using a backhoe. • Excavation of the remaining piping and impacted soil in the leachfield using a backhoe. • Collection of verification soil samples. • Backfilling the excavated areas and returning the site to unrestricted use. • Disposal of excavated materials following applicable federal, state, and DOE • Certification of Closure by an independent, Professional Engineer.

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Closure Report - CAU No. 94 Site characterization revealed that the only constituents of concern were acetone and Plutonium; however, sampling during closure revealed additional volatile organic compounds (VOCs) and radioisotopes. The following remediation levels were used to verify clean closure: • Background levels for radioactive constituents have been established in the Offsite Radiation Exposure Review Project, Phase IT Soils Programs report (DOE, 1989). The level established in this report for Plutonium-238/239/240 is 0.5 picocuries per gram detected in verification samples. Because it is a daughter product, Americium-241 has the same background level of0.5 pCi/g as Plutonium. The background level for Cobalt60 has been established …