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1995 Technical Memorandum on Soil Boring Investigation

Section 6 - SWMU Burn Area 4 (B-4)

Six soil borings were drilled at this former classified burn area, which was used for burning classified documents and trash (Figure 6.1).

6.1 - Geology and Hydrogeology

Logging of soil and rock samples indicated between 5 and 12 ft of fill material overlying highly weathered marly limestone interbedded with massive hard limestone. This clay seams were also noted. The fill material consisted of clay with limestone fragments and some silt mixed with waste material. A high angle fracture approximately 4 inches long with staining on the sides was observed in B4-SB2 from 10 to 15 ft bgl. Solution cavities were observed in B4-SB4 between 18 and 21 ft bgl.

The total depth of SWMU B-4 was not determined during drilling, because borings were drilled near the perimeter. The fill material was the thickest (12.3 ft) at B4-SB1A. This boring was not drilled to a TD of 30 ft because a white fibrous material was encountered. For health and safety concerns, drilling was halted and the material was sampled for asbestos.

Cretaceous-age foraminifera and pelecypods of the Glen Rose Formation were the predominant fossils identified in the borings. A crinoid stem was also observed in B4-SB4 from 21 to 24 ft. Fossiliferous zones were observed in B4-SB4 from 21 to 30 ft and in B4-SB3 from 33 to 34 ft and in B4-SB5 from 22 to 30 ft bgl.

Shallow groundwater was observed in one boring (B4-SB5). Two water-bearing zones were noted in B4-SB5, one at 16 ft and one at 26 to 27 ft bgl. Groundwater was measured in B4-SB5 at a depth of 12.5 ft bgl.

6.2 - Observed Waste Material in the Borings

Waste material found in the borings included: coal, fibrous material, nails, piece of non-oxidized metal, rusted hinges, wire, screen, and charred material.

6.3 - Soil/Rock Analytical Results

Eighteen soil/rock samples were collected for chemical analysis. SVOCs and VOCs were not detected in the samples. Iron, lead, and nickel were detected in all seventeen samples collected. Chromium was detected in fourteen samples and copper in eleven. Cadmium concentrations were qualified as nondetect for all samples, except B4-SB1A (11.2-12.3 ft). Table B4-1 presents the analytical results.

One sample was collected from B4-SB1A and analyzed for asbestos. None was detected.

6.4 - Groundwater Analytical Results

Shallow groundwater accumulated in one soil boring (B4-SB5). One groundwater sample was collected from B4-SB5 (Table B4-2). No VOCs or SVOCs were detected. Chromium and nickel were detected in the groundwater sample.

6.5 - Statistical Comparison with Background Metals and Risk-Based Closure Criteria

Two samples contained metals that exceeded comparison criteria. B4-SB1 (6-9 ft) exceeded levels for chromium, lead, and nickel. Sample B4-SB1A (11.2-12.3) exceeded the levels for cadmium and nickel. Sample locations and concentrations are shown in Figure 6.2.

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