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[SWMU B-8]

TO0019 Work Plan Addendum, SWMU B-8

December 2003

Site Description and History

SWMU B-8 is a former burn area that contains a trench suspected to have been used for waste disposal, including fire bricks and ammunition. The site is nearly flat and comprises approximately 0.5 acres (Figure B8-2). An overhead utility line trending northeast-southwest and an abandoned underground 4 inch diameter pipe are located just south of the site.

Summary of Previous Investigation Results

Geophysical Survey

An EM geophysical survey was conducted in 1995 at SWMU B-8. Two anomalies were identified during the survey. One of these anomalies was associated with the underground pipe; however, the second anomaly was thought to be related to subsurface metallic debris. This anomaly is presented in Figure B8-2.

A second EM geophysical survey was performed in 2003 because of surficial ordnance items (37mm projectile, a 60mm projectile, another 37mm projectile, and a fuze) found during a soil sampling event in May 2003. The intent of this survey was to determine whether any buried UXO might be present in the area surrounding B-8. A significant number of anomalies were present, with the majority concentrated in the northern and especially northeastern portions of the site. Several of the anomalies occupied a relatively extensive area, as shown in Figure B8-1.

Unexploded Ordnance Survey and Excavation

The possible presence of UXO at SWMU B-8 has been the subject of two excavation events. In 1997, excavation of the unknown geophysical anomaly identified at SWMU B-8 during the 1995 geophysical survey required the presence of UXO specialists to inspect the excavated materials for UXO and scrap metal. No UXO was found during the excavation. Concrete slabs containing rebar were found in the location of the second anomaly determined by the 1995 geophysical survey. These were stockpiled on-site along with the excavated material. This stockpile, which is approximately 2 ft high and 66 ft in diameter, contains an estimated 250 CY of soil.

After ordnance items were identified on the ground surface in the area outside the original B-8 boundary, another geophysical survey was conducted at the site in 2003. Based on the results of the 2003 EM survey, several anomalies were selected for intrusive investigation based on either their size or location. Trained UXO technicians conducted an intrusive investigation using a backhoe in July 2003. Some of the excavated anomalies contained ordnance-related scrap, but the majority were nails and wire. The waste was encountered at depths ranging from 0 to 18 inches. No evidence of waste trenches was discovered.

Soil Stockpile Sampling

Three sifted samples were collected from the stockpiled material. VOCs and an explosive compound were detected in the only sample analyzed for VOCs and explosives (B8-SIFT01). Copper and lead concentration in all three sift samples well exceeded RRS1 closure standards. Barium and zinc levels were also above RRS1 standards in B8-SIFT02 and B8-SIFT03.

Soil Borings

Three borings were advanced in March of 2000 at SWMU B-8. Three samples were collected from the top, middle, and terminus of each boring and analyzed for metals, explosives, VOCs, and SVOCs. These borings were drilled around the location of the concrete pad excavated in 1997.

For the soil samples, metals were detected above RRS1 closure standards. The highest concentrations were detected in the duplicate sample collected at SB02, where barium (10,814 [milligrams per kilograms] mg/kg), copper (110,240 mg/kg), lead (156,640 mg/kg), and zinc (40,638 mg/kg) all greatly exceeded RRS1 closure standards. The lowest metals concentrations were detected at SB03, where only barium (224.4 mg/kg), copper (112.1 mg/kg), and lead (443 mg/kg) exceeded RRS1 standards.

At SB02, zinc concentrations exceeded RRS1 closure standards for both subsurface bedrock samples, and barium, copper, and lead were detected above RRS1 in the middle sample. Barium slightly exceeded background for both subsurface samples at SB03. The deepest sample also contained zinc and chromium in concentrations above RRS1 standards.

In March of 2003, twelve soil samples were collected to define the extent of metals contamination at SWMU B-8. However, significant concentrations of metals were reported for these samples. Because these samples did not adequately define the extent of contamination, an additional 19 soil samples were collected in May 2003. These samples were analyzed for lead using a Palintestâ field test kit because lead concentrations were high in the previous samples and therefore provide a good indication of the lateral extent of contamination. Eight of these 19 samples contained lead at concentrations above RRS1 closure standards. These eight samples were located primarily in the north and the west of the site. Figure B8-2 shows the approximate boundary of surface soils containing above-background metals concentrations.

Planned Work

The recent geophysical survey and intrusive UXO results indicate that the site may have the potential for containing UXO items, mostly in the northern half of the site, where past waste management activities are known to have occurred. Although some of the anomalies have already been investigated, and no waste trenches were encountered, further investigation of the cause of these anomalies by UXO specialists will be conducted. Results of the additional excavations will be amended to the RCRA Facility Investigation (RFI) Report Addendum for SWMU B-8.

Further, metals concentrations in soils at the site are in excess of RRS1 closure standards. In order to ultimately achieve RRS1 closure, further investigations into the site will be required.

Summary Of Planned Work

  1. Identify coordinates of remaining anomalies using the CSSA geographical information system (GIS).

  2. Reacquire locations of anomalies in the field using global positioning system (GPS) and hand-held Schonstedt magnetometer.

  3. Excavate anomalies to determine if any UXO or additional ordnance-related items may be present at the site.

  4. Backfill excavated soil and re-grade.

  5. Prepare addendum to SWMU B-8 RFI Report to document results of additional excavations.