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SWMU Demo Dud Area (DD) Area

TO 0019 Work Plan Addendum, December 2003

Site Description and History

SWMU Demo Dud (DD) Area consists of approximately 1.71 undeveloped acres in the southern inner cantonment area of CSSA (Figure DD-2).  The site area is approximately 450 ft long by 250 ft wide.  Prior uses of the site are unknown; however, the area was posted with “Demolition Dud Area” warning signs.  These signs were removed in 1997 during UXO removal activities described below.  The site is mostly level and covered with sparse vegetation and a thin soil profile.

Summary of Previous Investigation Results

UXO Clearance/Excavation Activities

UXO identification and removal activities were conducted between February 4 and May 30, 1997.  UXO specialists from UXB International in Chantilly, Virginia conducted the UXO identification and removal, with oversight from Parsons.  Investigation of the site commenced with a sweep for surface UXO.  During the surface sweep, a 250-foot long disposal trench was identified.  The trench was situated adjacent to the paved road to the north and was approximately 250 ft long and eight ft wide.  Several potentially live ordnance items were identified during the sweep and use of Schonstedt magnetometers indicated subsurface metal was present at the site.

Due to the presence of subsurface metal at the site, sifting was identified as a cost-effective method for removing any buried UXO or other subsurface metal debris.  The sifting operation commenced on May 20 and continued until May 30, 1997.  The trench was found to be up to five ft deep.

UXO specialists examined all waste as it was excavated from the trench, as it was loaded into the hopper, and as it was discharged from the sifter.  Most UXO was identified during excavation activities.  Sifted material included metal scrap, limestone cobbles, clumps of hard clay, and UXO.  The sifted material was spread out on the ground surface.  Metal scrap and UXO were either removed by a trailer-mounted electromagnet or hand-picked.  A final inspection of the remaining material was conducted to ensure that it was UXO-free.  The trench was excavated until no additional waste material was encountered on the bottom or in each of the walls of the trench.

As material was sifted, a total of approximately 300 CY of soil was stockpiled on site.  All metal scrap found at the site was placed into roll-off containers and later transported to Newell Recycling in San Antonio, Texas.  All UXO found at the site was segregated and later detonated at SWMU B-20.  The trench was regraded with native soil at the conclusion of the UXO removal activities.  The UXO removal actions resulted in the removal of 240 UXO items and approximately 10,040 pounds of metal scrap.

Surface Soil Samples and Soil Borings

To characterize the subsurface soils near the excavated trench, three soils borings were advanced at SWMU DD Area on March 31, 2000.  Borings SB01, SB02, and SB03 were advanced to depths of 10, 13, and 11 ft bgs, respectively (Figure DD-2).  Samples were collected at the surface, from 5.0-5.5 ft bgs, and the total depth of each boring.  Samples were analyzed for VOCs, explosives, and metals (arsenic, cadmium, lead, mercury, barium, chromium, copper, nickel, and zinc).  At the time of sampling, no discernable evidence of contamination was noted in the core samples.

Surface soil sample results indicate that metals and VOCs are present above RRS1.  The metal constituents detected above background (RRS1) concentrations include copper, lead, mercury, and zinc.  Copper was detected above the background concentration (23.2 mg/kg) in samples SB02 (38.17 mg/kg), SB03 (61.15 mg/kg), and SB03 FD1 (63.28 mg/kg).  Lead was detected above the background concentration (84.5 mg/kg) in samples SB01 (162.36 mg/kg), SB02 (749.06 mg/kg), SB03 (445.63 mg/kg), and SB03 FD1 (427.04 mg/kg).  Mercury was detected above the background concentration (0.77 mg/kg) in samples SB03 (2.80 mg/kg) and SB03 FD1 (2.54 mg/kg).  Finally, zinc was detected above the background concentration (73.2 mg/kg) in samples SB03 (111.09 mg/kg) and SB03 FD1 (122.29 mg/kg).

VOCs detected above RLs (RRS1) in surface soil samples were toluene and methylene chloride.  Toluene was detected slightly above the RL (0.005 mg/kg) in samples SB01 (0.0205 mg/kg), SB02 (0.0100 mg/kg), SB03 (0.0213 mg/kg), and the field duplicate sample SB03 FD1 (0.0055 mg/kg).  Methylene chloride was detected above the RL (0.005 mg/kg) in sample SB01 (0.0063 mg/kg).  Methylene chloride is a common laboratory contaminant and was detected in the laboratory blank sample.  Therefore, the presence of methylene chloride is believed to be a laboratory artifact and not representative of soil conditions at the site.

Analytical results from the subsurface soil samples indicate analyte concentrations below RRS1 with the exception of cadmium and methylene chloride.  Cadmium was detected above the background concentration (0.1 mg/kg) in the 4.5-5.0 ft deep sample in boring SB03 (0.20 mg/kg).  Methylene chloride was detected slightly above the RL (0.005 mg/kg) in the 9.5-10.0 ft deep sample in boring SB01 (0.0054 mg/kg).  The presence of methylene chloride in this sample is believed to be a laboratory artifact and not representative of soil conditions at the site.

Soil Stockpile Sampling

Three soil samples were collected from the soil stockpile in August 1997.  Due to questionable activities by the analytical laboratory, the EPA deemed these data unsuitable for site closure.  In April 2000, three additional soil samples were collected from the soil stockpile.  The samples were analyzed for VOCs, SVOCs, metals, and explosives.  Sample results showed SVOC and metals concentrations above RRS1.

Copper was detected above the background concentration (RRS1) of 23.2 mg/kg in samples SIFT04 (300.05 mg./kg), SIFT05 (75.85 mg/kg), SIFT06 (112.31 mg/kg), and SIFT06 FD1 (9,849.4 mg/kg).  Lead was detected above the background concentration (84.5 mg/kg) in samples SIFT04 (1212.67 mg/kg), SIFT05 (514.72 mg/kg), SIFT06 (416.43 mg/kg), and SIFT06 FD1 (484.0 mg/kg).  Mercury was detected above the background concentration (0.77 mg/kg) in samples SIFT04 (7.58 mg/kg), SIFT05 (1.26 mg/kg), SIFT06 (3.41 mg/kg), and SIFT06 FD1 (5.78 mg/kg).  Zinc was detected above the background concentration (73.2 mg/kg) in samples SIFT04 (175.62 mg/kg), SIFT05 (162.33 mg/kg), SIFT06 (132.29 mg/kg), and SIFT06 FD1 (185.13 mg/kg).

Results of the SVOC analysis indicate the presence of several constituents above their respective RLs (RRS1) in SIFT04.  These analytes include benzo(a)anthracene (1.7 mg/kg), benzo(a)pyrene (1.5 mg/kg), benzo(b)fluoranthene (2.0 mg/kg), benzo(g,h,i)perylene (0.92 mg/kg), chrysene (1.6 mg/kg), fluoranthene (3.6 mg/kg), indeno(1,2,3-cd)pyrene (0.89 mg/kg), naphthalene (1.0 mg/kg), phenanthrene (3.4 mg/kg), and pyrene (2.9 mg/kg).  The RL for each of these compounds is 0.7 mg/kg.

Several additional VOCs and SVOCs were detected in the samples at concentrations above the laboratory method detection limit but below the RLs, including methylene chloride, toluene, TCE, bis(2-ethylhexyl)phthalate, 4-chloroaniline, dibenz(a,h)anthracene, dibenzofuran, fluorene, and 2-methylnaphthalene.  All explosives results were below the method detection limits.

In addition, several samples were collected from the stockpiles to provide information regarding the leachability of contaminants.  The TCLP results for a composite sample from the DD stockpile indicated the soil meets Class 1 nonhazardous criteria. 

Closure Plan and Sampling Recommendations

Closure of SWMU DD under RRS1 requires removal of waste and waste residue at the site.  Stockpiled soil at the site, as well as surface soil in the vicinity of DD-SB01, DD-SB02, and DD-SB03.  All waste encountered must be removed from CSSA for off-post disposal to pursue RRS1 closure with respect to the soil unit at SWMU DD.  Groundwater and competent bedrock will be addressed as part of the groundwater operable unit.  The soil excavation will extend to the depth that waste or waste residue is encountered or to bedrock, whichever comes first.

The estimated volume of waste material and waste residue present at SWMU DD is 600 CY.  Confirmation samples should be collected following removal/remediation to verify that no contamination remains.  Analysis should include copper and zinc (SW-6010B), lead (SW-7421), mercury (SW-7471), toluene (SW-8260), and SVOCs (SW-8270C), based on sample results from 2000.  Samples will be collected at a frequency of one per 100 linear ft of sidewall, with a minimum of one sample per sidewall.  If the bottom of the excavation is bedrock, bottom samples will be collected at a frequency of one per 20,000 ft2 of bottom surface area, with a minimum of two samples per excavation area.  If the bottom of the excavation is soil, bottom samples will be collected at a frequency of one per 100 ft (100-ft grids).

Following excavation of waste and waste residue, any resulting trenches will be backfilled with clean fill and the site restored.

Summary Of Planned Work

  1. Amend CSSA’s Waste Profile using DD RFI data.  RFI data indicates that the material at this site meets nonhazardous Class 2 criteria.

  2. Excavate contaminated soils, which includes the soil stockpile and surrounding surface soil.  It is estimated that 600 CY of contaminated soil will be removed from the site.

  3. Remove all contaminated soil for disposal.  Dispose of any waste encountered and soils exceeding CSSA background levels at Covel Gardens Landfill under waste profile CG-25591 C-3.

  4. Collect samples of the excavation sidewalls and bottom.  Samples will be analyzed for copper, lead, mercury, zinc, toluene, and SVOCs, based on the results of samples collected at the site in 2000. 

  5. Continue excavation until RRS1 soil criteria or competent bedrock, whichever comes first, is reached.

  6. Re-grade the site with clean fill and reseed.

  7. Validate data and prepare Closure Report for SWMU DD.