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Title: POST CLOSURE INSPECTION AND MONITORING REPORT FOR CORRECTIVE ACTION UNIT 417: CENTRAL NEVADA TEST AREA - SURFACE, HOT CREEK VALLEY, NEVADA; FOR CALENDAR YEAR 2005

Abstract

Corrective Action Unit (CAU) 417, Central Nevada Test Area - Surface, is located in Hot Creek Valley in northern Nye County, Nevada, and consists of three areas commonly referred to as UC-1, UC-3, and UC-4. CAU 417 consists of 34 Corrective Action Sites (CASs) which were closed in 2000 (U. S. Department of Energy, National Nuclear Security Administration Nevada Operations Office, 2001). Three CASs at UC-1 were closed in place with administrative controls. At CAS 58-09-01, Central Mud Pit (CMP), a vegetated soil cover was constructed over the mud pit. At the remaining two sites CAS 58-09-02, Mud Pit and 58-09-05, Mud Pits (3), aboveground monuments and warning signs were installed to mark the CAS boundaries. Three CASs at UC-3 were closed in place with administrative controls. Aboveground monuments and warning signs were installed to mark the site boundaries at CAS 58-09-06, Mud Pits (5), CAS 58-25-01, Spill and CAS 58-10-01, Shaker Pad Area. Two CASs that consist of five sites at UC-4 were closed in place with administrative controls. At CAS 58-09-03, Mud Pits 9, an engineered soil cover was constructed over Mud Pit C. At the remaining three sites in CAS 58-09-03 and at CAS 58-10-05, Shaker Padmore » Area, aboveground monuments and warning signs were installed to mark the site boundaries. The remaining 26 CASs at CAU 417 were either clean-closed or closed by taking no further action. Quarterly post-closure inspections are performed at the CASs that were closed in place at UC-I, UC-3, and UC-4. During calendar year 2005, site inspections were performed on March 15, June 16, September 22, and December 7. The inspections conducted at the UC-1 CMP documented that the site was in good condition and continued to show integrity of the cover unit. No new cracks or fractures were observed until the December inspection. A crack on the west portion of the cover showed evidence of lateral expansion; however, it is not at an actionable level. The crack will be sealed by filling with bentonite during the first quarter of 2006 and monitored during subsequent inspections. The cover vegetation was healthy and well established. No issues were identified with the CMP fence, gate, or subsidence monuments. No issues were identified with the warning signs and monuments at the other two UC-1 locations. The inspections at UC-3 indicated that the sites are in excellent condition. All monuments and signs showed no displacement, damage, or removal. A small erosion gully from spring rain runoff was observed during the June inspection, but it did not grow to an actionable level during 2005. No other issues or concerns were identified. Inspections performed at UC-4 Mud Pit C cover revealed that erosion rills were formed during March and September exposing the geosynthetic clay liner. Both erosion rills were repaired within 90 days of reporting. Sparse vegetation is present on the cover. The overall condition of the monuments, fence, and gate are in good condition. No issues were identified with the warning signs and monuments at the other four UC-4 locations. Subsidence surveys were conducted at UC-1 CMP and UC-4 Mud Pit C in March and September of 2005. The results of the subsidence surveys indicate that the covers are performing as expected, and no unusual subsidence was observed. The June vegetation survey of the UC-1 CMP cover and adjacent areas indicated that the revegetation has been very successful. The vegetation should continue to be monitored to document any changes in the plant community and identify conditions that could potentially require remedial action in order to maintain a viable vegetative cover on the site. Vegetation surveys should be conducted only as required. Precipitation during 2005 was above average, with an annual rainfall total of 21.79 centimeters (8.58 inches). Soil moisture content data show that the UC-1 CMP cover is performing as designed, with evapotranspiration effectively removing water from the cover. It is recommended to continue quarterly site inspections and the collection of soil moisture data for the UC-1 CMP cover.« less

Publication Date:
Research Org.:
DOE/NNSA NEVADA SITE OFFICE
Sponsoring Org.:
USDOE
OSTI Identifier:
901908
Report Number(s):
DOE/NV-1122
TRN: US200717%%105
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; BENTONITE; CLAYS; CLOSURES; FRACTURES; MOISTURE; MONITORING; PLANTS; PRECIPITATION; RAIN; REMEDIAL ACTION; REMOVAL; REVEGETATION; RUNOFF; SECURITY; SOILS; STREAMS; WATER

Citation Formats

NONE. POST CLOSURE INSPECTION AND MONITORING REPORT FOR CORRECTIVE ACTION UNIT 417: CENTRAL NEVADA TEST AREA - SURFACE, HOT CREEK VALLEY, NEVADA; FOR CALENDAR YEAR 2005. United States: N. p., 2006. Web. doi:10.2172/901908.
NONE. POST CLOSURE INSPECTION AND MONITORING REPORT FOR CORRECTIVE ACTION UNIT 417: CENTRAL NEVADA TEST AREA - SURFACE, HOT CREEK VALLEY, NEVADA; FOR CALENDAR YEAR 2005. United States. doi:10.2172/901908.
NONE. Sat . "POST CLOSURE INSPECTION AND MONITORING REPORT FOR CORRECTIVE ACTION UNIT 417: CENTRAL NEVADA TEST AREA - SURFACE, HOT CREEK VALLEY, NEVADA; FOR CALENDAR YEAR 2005". United States. doi:10.2172/901908. https://www.osti.gov/servlets/purl/901908.
@article{osti_901908,
title = {POST CLOSURE INSPECTION AND MONITORING REPORT FOR CORRECTIVE ACTION UNIT 417: CENTRAL NEVADA TEST AREA - SURFACE, HOT CREEK VALLEY, NEVADA; FOR CALENDAR YEAR 2005},
author = {NONE},
abstractNote = {Corrective Action Unit (CAU) 417, Central Nevada Test Area - Surface, is located in Hot Creek Valley in northern Nye County, Nevada, and consists of three areas commonly referred to as UC-1, UC-3, and UC-4. CAU 417 consists of 34 Corrective Action Sites (CASs) which were closed in 2000 (U. S. Department of Energy, National Nuclear Security Administration Nevada Operations Office, 2001). Three CASs at UC-1 were closed in place with administrative controls. At CAS 58-09-01, Central Mud Pit (CMP), a vegetated soil cover was constructed over the mud pit. At the remaining two sites CAS 58-09-02, Mud Pit and 58-09-05, Mud Pits (3), aboveground monuments and warning signs were installed to mark the CAS boundaries. Three CASs at UC-3 were closed in place with administrative controls. Aboveground monuments and warning signs were installed to mark the site boundaries at CAS 58-09-06, Mud Pits (5), CAS 58-25-01, Spill and CAS 58-10-01, Shaker Pad Area. Two CASs that consist of five sites at UC-4 were closed in place with administrative controls. At CAS 58-09-03, Mud Pits 9, an engineered soil cover was constructed over Mud Pit C. At the remaining three sites in CAS 58-09-03 and at CAS 58-10-05, Shaker Pad Area, aboveground monuments and warning signs were installed to mark the site boundaries. The remaining 26 CASs at CAU 417 were either clean-closed or closed by taking no further action. Quarterly post-closure inspections are performed at the CASs that were closed in place at UC-I, UC-3, and UC-4. During calendar year 2005, site inspections were performed on March 15, June 16, September 22, and December 7. The inspections conducted at the UC-1 CMP documented that the site was in good condition and continued to show integrity of the cover unit. No new cracks or fractures were observed until the December inspection. A crack on the west portion of the cover showed evidence of lateral expansion; however, it is not at an actionable level. The crack will be sealed by filling with bentonite during the first quarter of 2006 and monitored during subsequent inspections. The cover vegetation was healthy and well established. No issues were identified with the CMP fence, gate, or subsidence monuments. No issues were identified with the warning signs and monuments at the other two UC-1 locations. The inspections at UC-3 indicated that the sites are in excellent condition. All monuments and signs showed no displacement, damage, or removal. A small erosion gully from spring rain runoff was observed during the June inspection, but it did not grow to an actionable level during 2005. No other issues or concerns were identified. Inspections performed at UC-4 Mud Pit C cover revealed that erosion rills were formed during March and September exposing the geosynthetic clay liner. Both erosion rills were repaired within 90 days of reporting. Sparse vegetation is present on the cover. The overall condition of the monuments, fence, and gate are in good condition. No issues were identified with the warning signs and monuments at the other four UC-4 locations. Subsidence surveys were conducted at UC-1 CMP and UC-4 Mud Pit C in March and September of 2005. The results of the subsidence surveys indicate that the covers are performing as expected, and no unusual subsidence was observed. The June vegetation survey of the UC-1 CMP cover and adjacent areas indicated that the revegetation has been very successful. The vegetation should continue to be monitored to document any changes in the plant community and identify conditions that could potentially require remedial action in order to maintain a viable vegetative cover on the site. Vegetation surveys should be conducted only as required. Precipitation during 2005 was above average, with an annual rainfall total of 21.79 centimeters (8.58 inches). Soil moisture content data show that the UC-1 CMP cover is performing as designed, with evapotranspiration effectively removing water from the cover. It is recommended to continue quarterly site inspections and the collection of soil moisture data for the UC-1 CMP cover.},
doi = {10.2172/901908},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}

Technical Report:

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  • This post-closure inspection and monitoring report has been prepared according to the stipulations laid out in the Closure Report (CR) for Corrective Action Unit (CAU) 417, Central Nevada Test Area (CNTA)--Surface (U.S. Department of Energy, National Nuclear Security Administration Nevada Operations Office [NNSA/NV], 2001), and the Federal Facility Agreement and Consent Order (FFACO, 1996). This report provides an analysis and summary of site inspections, subsidence surveys, meteorological information, and soil moisture monitoring data for CAU 417, which is located in Hot Creek Valley, Nye County, Nevada. This report covers Calendar Year 2004. Inspections at CAU 417 are conducted quarterly tomore » document the physical condition of the UC-1, UC-3, and UC-4 soil covers, monuments, signs, fencing, and use restricted areas. The physical condition of fencing, monuments, and signs is noted, and any unusual conditions that could impact the integrity of the covers are reported. The objective of the soil moisture monitoring program is to monitor the stability of soil moisture conditions within the upper 1.2 meters (m) (4 feet [ft]) of the UC-1 Central Mud Pit (CMP) cover and detect changes that may be indicative of moisture movement exceeding the cover design performance expectations.« less
  • This report presents data collected during the annual post-closure site inspection conducted at the Central Nevada Test Area Surface Corrective Action Unit (CAU) 417 in May 2007. The annual post-closure site inspection included inspections of the UC-1, UC-3, and UC-4 sites in accordance with the Post-Closure Monitoring Plan provided in the CAU 417 Closure Report (NNSA/NV 2001). The annual inspection conducted at the UC-1 Central Mud Pit (CMP) indicated the site and soil cover were in good condition. No new cracks or fractures were observed in the soil cover during the annual inspection. A crack on the west portion ofmore » the cover was observed during the last quarterly inspection in December 2006. This crack was filled with bentonite as part of the maintenance activities conducted in February 2007 and will be monitored during subsequent annual inspections. The vegetation on the soil cover was adequate but showing signs of the area's ongoing drought. No issues were identified with the CMP fence, gate, or subsidence monuments. New DOE Office of Legacy Management signs with updated emergency phone numbers were installed as part of this annual inspection, no issues were identified with the warning signs and monuments at the other two UC-1 locations. The annual subsidence survey was conducted at UC-1 CMP and UC-4 Mud Pit C as part of the maintenance activities conducted in February 2007. The results of the subsidence surveys indicate that the covers are performing as expected, and no unusual subsidence was observed. A vegetation survey of the UC-1 CMP cover and adjacent areas was conducted as part of the annual inspection in May 2007. The vegetation survey indicated that revegetation continues to be successful, although stressed due to the area's prevailing drought conditions. The vegetation should continue to be monitored to document any changes in the plant community and to identify conditions that could potentially require remedial action to maintain a viable vegetation cover on the site. It is suggested that future vegetation surveys be conducted once every 2 years or as needed to help monitor the health of the vegetation.« less
  • Corrective Action Unit (CAU) 417, Central Nevada Test Area - Surface, is located in Hot Creek Valley in northern Nye County, Nevada, and consists of three areas commonly referred to as UC-1, UC-3, and UC-4. CAU 417 consists of 34 Corrective Action Sites (CASs) which were closed in 2000 (U.S. Department of Energy, National Nuclear Security Administration Nevada Operations Office, 2001). Three CASs at UC-1 were closed in place with administrative controls. At CAS 58-09-01, Central Mud Pit (CMP), a vegetated soil cover was constructed over the mud pit. At the remaining two sites, CAS 58-09-02, Mud Pit, and CASmore » 58-09-05, Mud Pits (3), aboveground monuments and warning signs were installed to mark the CAS boundaries. Three CASs at UC-3 were closed in place with administrative controls. Aboveground monuments and warning signs were installed to mark the site boundaries at CAS 58-09-06, Mud Pits (5), CAS 58-25-01, Spill, and CAS 58-10-01, Shaker Pad Area. Two CASs that consist of five sites at UC-4 were closed in place with administrative controls. At CAS 58-09-03, Mud Pits (5), an engineered soil cover was constructed over Mud Pit C. At the remaining three sites in CAS 58-09-03 and at CAS 58-10-05, Shaker Pad Area, aboveground monuments and warning signs were installed to mark the site boundaries. The remaining 26 CASs at CAU 417 were either clean-closed or closed by taking no further action.« less
  • This report presents results of data collected during the annual post-closure site inspections conducted at the Central Nevada Test Area surface Corrective Action Unit (CAU) 417 in May 2011 and July 2012. The annual post-closure site inspections included inspections of the UC-1, UC-3, and UC-4 sites in accordance with the Post-Closure Monitoring Plan provided in the CAU 417 Closure Report (NNSA/NV 2001). The annual inspections conducted at the UC-1 Central Mud Pit (CMP) indicated that the site and soil cover were in good condition. No new fractures or extension of existing fractures were observed and no issues with the fencemore » or gate were identified. The vegetation on the cover continues to look healthy, but the biennial vegetation survey conducted during the 2012 inspection indicated that the total foliar cover was slightly higher in 2009 than in 2012. This may be indicative of a decrease in precipitation observed during the 2-year monitoring period. The precipitation totaled 9.9 inches from July 1, 2010, through June 30, 2011, and 5 inches from July 1, 2011, through June 30, 2012. This decrease in precipitation is also evident in the soil moisture data obtained from the time domain reflectometry sensors. Soil moisture content data show that the UC-1 cover is performing as designed, and evapotranspiration is effectively removing water from the cover.« less
  • This report presents results of data collected during the annual post-closure site inspection conducted at the Central Nevada Test Area, surface Corrective Action Unit (CAU) 417 in June 2009. The annual post-closure site inspection included inspections of the UC-1, UC-3, and UC-4 sites in accordance with the Post-Closure Monitoring Plan provided in the CAU 417 Closure Report (NNSA/NV 2001). The annual inspection conducted at the UC-1 Central Mud Pit (CMP) indicated that the site and soil cover were in good condition. Three new fractures were identified in the soil cover and were filled with bentonite chips during the inspection. Themore » vegetation on the soil cover was adequate but showed signs of the area's ongoing drought. No issues were identified with the CMP fence, gate, or subsidence monuments. No issues were identified with the warning signs and monuments at the other two UC-1 locations« less