Site investigations and groundwater monitoring have been conducted by the Army, U.S. Army Environmental Hygiene Agency (USAEHA), U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), and US Geological Survey (USGS) in various areas throughout the installation since 1974. The primary contaminates of concern are explosives (2,4,6-Trinitrotoluene (TNT), 1,3,5-Trinitro-1,3,5-Triazacychlohexane (RDX), nitrate/nitrite) and Unexploded Ordnance (UXO).

     Prior to the transfer of HWAAP to the Department of Army, the USGS conducted a study in three phases under the direction of the Department of Navy to assess the possibility of groundwater contamination in the vicinity of disposal pits at facilities 103-41 (HWAAP B-29) and 103-16 (HWAAP B-27a). The disposal pits were constructed to receive explosive waste from the demilitarization operation. The explosive waste included composition D (ammonium picrate), amatol (TNT plus ammonium nitrate) and RDX.

     In Phase I & III, November 1974 - November 1977, the USGS installed a total of 26 exploratory wells in immediate proximity and northwest of the disposal area adjacent to demilitarization facility 103-41 (HWAAP B-29). Analysis of water samples taken from the wells showed levels of nitrate/nitrite above background, and several of the wells were found to contain TNT. The highest concentration of TNT (300 ppb and 430 ppb) was detected in two separate sampling events in one of the wells. The compound dinitrotoluene (DNT) was also detected in one of the wells. A study indicated that a narrow plume of TNT contamination existed in a northwesterly direction.

     In Phase II, June 1976 - November 1977, the USGS installed eight exploratory wells in the vicinity of disposal pits adjacent to the demilitarization facility 103-16 (HWAAP B-27a). Chemical analysis of the groundwater samples revealed nitrate/nitrite levels to be above background in most cases and one sample from one of the wells showed TNT at a trace level.

     After the transfer of HWAAP in 1977 to the Department of Army, the U.S. Army Armament Material Readiness Command (ARRCOM) requested USATHAMA, then known as Project Manager for Chemical Demilitarization and Installation Restoration (PMCDIR), to conduct assessments of HWAAP to determine if there was any contamination resulting from past waste disposal practices.

     An installation assessment was conducted between 1977 and 1981 by USATHAMA. Over 25 pits were identified to have received explosive wastes from loading and demilitarization operations in the production areas: 101, 102, 103, 104/49, and 108. The assessment concluded that TNT contamination in groundwater had migrated in a narrow plume a distance of between 1,200 and 3,200 feet down gradient from the building 103-41 disposal pits. The migration rate of TNT was slower than the groundwater flow rate. The assessment also concluded that nitrogen compounds, primarily nitrate, were migrating in two plumes toward Walker Lake. A study was performed showing no impact from HWAD operations to Walker Lake.

     A disposal area for mustard and phosgene chemical munitions (HWAAP A-05) was located during the assessment. The area was first used during World War II and it was last used in 1946 to decontaminate and bury an unspecified quantity of mustard munitions and their toxic agent contents. In 1991 an attempt was made to locate the munitions and to determine if any mustard agent remained either in the soil or in the munitions. Several pits were located and excavated. M-15 chemical detectors gave positive readings for mustard at only one munition; however, laboratory analysis of samples taken from the munitions were negative. Testing of vapors from the pits were negative. Since the analyses were inconclusive, the area could still have chemical agent munitions buried beneath the surface.

     Several test ranges were also identified in the assessment. Of particular concern is the range near Walker Lake where extensive munition testing was conducted from World War II to the early seventies. Most of the rounds impacted in the lake and many/do remain there as UXO. Live rounds are frequently found on the receding shoreline of Walker Lake.

     Another area of concern is west of Walker Lake which was used for training. It was reported by Explosive Ordnance Division (EOD) personnel to be one of the most heavily UXO contaminated areas at HWAD.

     The Rocket Test Area located near the southern boundary of HWAD also contains UXO in the impact area. Adjacent to the Rocket Test Area is also a site that was used for fuze and ordnance disposal from World War II through the Korean War. It was reported that demolition charges used to destroy the munitions were so large that live munitions were found as far as one mile from the detonation pit. The area is considered extremely hazardous and is fenced to discourage trespassing.

     An evaluation of Solid Waste Management Units (SWMUs) was performed by USAEHA between May 1987 and August 1988. At that time 82 SWMUs were identified. Site screening inspections were conducted from July 1992 through December 1992 to verify the SWMUs and data were gathered for the US EPA to revise the Hazard Ranking System (HRS). As a result of the site screening inspections, a total of 119 SWMUs were identified.

     Under the Installation Restoration Program (IRP) remedial investigation of Group A (33 SWMUs), Group B (55 SWMUs), Old Bomb disposal sites and UXO and explosive disposal/burned sites (12 SWMUs), 7 underground storage tank (UST) sites, and one above ground storage tank site have been conducted.

     Group A SWMUs consist of 29 catchment pits/ponds/impoundments sites, two disposal pit sites, one disposal pile site and one landfill. Work performed included surface geophysical surveys, near surface soil and subsurface soil sampling and analyses, and groundwater sampling at three existing wells. Baseline risk assessments for the 29 sites have been completed. And groundwater sampling is included in the long term groundwater monitoring plan.

     Group B SWMUs consist of 23 landfills, 15 catchment/pits/impoundments, two deactivation furnace areas, seven disposal pits/ditches/trenches, two open burn pits, five discharge/spill areas, and one mustard/phosgene chemical munitions disposal area. Work performed included aerial photography, GPS surveying, an airborne geophysical survey, surface geophysical surveys, subsurface screening for utilities and UXO, soil gas surveys, soil sampling and analyses, and groundwater measurements. Groundwater sampling at some of these sites are part of the base wide groundwater monitoring program. Baseline risk assessments for most of the sites will be included in the RI/FS.

     A pilot study for windrow composting was performed during the summer of 1997. In this study, 2,500 cubic yards of soil containing TNT, HMX and DNT were treated at SWMUs B-20, B-32 and I-15. Remediation was completed at these sites and they are currently going through the closure process. As part of the pilot study, regulatory requirements for the composting process as well as operating conditions were established.

     The NDEP did determined that the remediation process did not require a containment building or a solid surface pad. In addition, using treated wooden ammunition boxes as a wood source was deemed acceptable. The original study was expanded to include 300 cubic yards of ammonium picrate contaminated soil. Results indicated that this treatment process will successfully remediate soil contaminated with ammonium picrate for which, prior to this pilot study, there was no accepted treatment methodology.

     The Old Bomb disposal sites consists of six landfills, four open burn burial pits and two popping furnaces. These sites were used for disposal of ordnance. An airborne ground penetration radar (AGPR) survey was conducted to evaluate these sites. As a result of the survey and previous geophysical surveys, test pits are proposed to characterize geophysical anomalies and soil sampling is proposed to determine if the release of hazardous constituents has occurred.

     Seven UST sites were located at Building 13, 103-6, 101-25, 94, Camp Jumbo, Building 106-10, and 20-21. The tanks were removed between 1991 and 1993. Soil sampling results showed evidence of elevated levels of total petroleum hydrocarbons (TPH) ranging from about 6,000 mg/kg to 73,000 mg/kg at depths ranging from 5 to 19 feet. Three sites (Camp Jumbo, Building 106-10, and Building 20-21) have signed decision documents for no further action. A pilot study bioventing system at Building 13 has been turned over to the installation for long term monitoring. Installation of bioventing systems at Building 103-6 and 101-25 is complete.

     An above ground storage tank (AST) Site, HWAAP J-03 (Building 70 Diesel Leak), consists of two 100,000 gallon ASTs that were installed in the 1940s and had been leaking diesel fuel over a period of time. In 1991 the contaminated soils were removed by HWAD creating a large excavation pit. Remedial investigation conducted in 1994 indicated that soil contamination of TPH was at an elevated level of over 40,000 mg/kg in the excavation pit, and TPH in ground water was at 11 mg/I. The two AST tanks were removed in February 1997. A bioventing pilot study was completed at this site. Stockpiled soils contaminated with petroleum hydrocarbons from twelve sites were collected at HWAAP J-03. This soil was used to fill the excavation pit. The enhanced bioventing test results indicate that bioventing may be able to remediate the site within eight years.

     Large-scale windrow composting of contaminated soils within the 101 production area is underway. The soils contaminated with explosives are mixed with, hay, wood chips, manure and potatoes. The composting is performed outside, on the bare ground.

     As new remediation activities are undertaken at the HWAD, they will be discussed on this website.

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