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1995 Technical Memorandum on Soil Boring Investigation

Section 5 - SWMU Burn Area 3 (B-3)

Five soil borings were drilled and sampled at this former landfill area primarily used for garbage disposal and burning trash (Figure 5.1).

5.1 - Geology and Hydrogeology

The cap and fill material associated with the trenches was dark brown, reddish brown, and black clay with limestone fragments and trace to little silt. Limestone fragments were also encountered, which made drilling appear to be hard enough to air core. Once the fragment was penetrated, the core would drop quickly through the waste material and fill, resulting in poor to no recovery.

Limestone bedrock was encountered from exposed at ground surface (B3-SB1) to a maximum of 18 ft bgl (B3-SB5). The bedrock geology at the site is very similar to the other sites. Highly weathered, pale yellow, marly limestone interbedded with hard, massive, white limestone. The limestone changes to a light gray color between 16 to 18 ft bgl. Intervals of vugs, some with calcite crystal growths, bedding, bioturbation, and fracturing were observed in B3-SB1.

Fossiliferous intervals of foraminifera with a few pelcypods were noted in B3-SB2, B3-SB5, B3-SB6, and B3-SB7 at depths ranging from 18 to 30 ft bgl. In addition, gastropods steinkerns and echinoid spines were observed in B3-SB6.

Perched groundwater accumulated in only one soil boring (B3-SB1). Water was observed on the B3-SB1 core barrel at 19.5 ft bgl. Another perched water zone was observed in the same boring at a depth of 23 to 24 ft bgl. Groundwater was measured in B3-SB1 at a depth of 21.9 ft bgl.

5.2 - Observed Waste Material in the Borings

Materials recovered from the cores include: metal debris, coal, black and white plastic, clear plastic with parallel fibers, fibrous cloth, a gray putty-like substance, charred material such as paper and cardboard, and what appeared to be old batteries. A solvent-like odor was detected in B3-SB3 from 11 to 13 ft bgl.

5.3 - Soil/Rock Analytical Results

Twenty-two soil/rock samples were collected for analysis (Table B3-1). Chloroform was detected at a depth of 2 to 4 feet in SB4 and m,p-xylene was detected in SB3 from 11 to 13 ft. Cis-1,2-dichloroethene (DCE) was detected in one sample each from four borings. Sample depths ranged from 2 to 19 ft. Trans-1,2-DCE was detected at the same depths as cis-1,2-DCE in borings SB4 and SB5. Tetrachloroethene (PCE) was detected in three samples from two borings at depths ranging from 5 to 28 ft. Trichloroethene (TCE) was detected in six samples collected from four borings at depths of 1 to 19 feet. Di-n-butylphthalate, a common laboratory contaminant, was detected in thirteen samples. Copper and iron were detected in the twenty-two samples collected. Chromium and lead were detected in seventeen samples and nickel was detected in twenty-one. Due to high concentrations of iron creating false positive cadmium concentrations, all cadmium concentrations were qualified as nondetect.

5.4 - Groundwater Analytical Results

One groundwater sample was collected from B3-SB1 (Table B3-2). No SVOCs were detected in the sample. Cis- and trans-1,2-DCE, PCE, TCE, and vinyl chloride were detected. Site B-3 contains the same chemicals detected in well 16 and therefore is a potential source of groundwater contamination.

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

Concentrations of TCE detected in soil borings B3-SB4, B3-SB5, and B3-SB6 were greater than the MSC (0.5 mg/kg). PCE, chloroform, cis- and trans-1,2-DCE, and an additional concentration of TCE were below MSC. Two samples exceeded MSCs for metals. Sample B3-SB3 (4-5 ft) exceeded the MSC for chromium. MSCs were exceeded for chromium, lead, and nickel in B3-SB4 (2-4 ft). The locations and concentrations of the samples that exceeded MSCs are shown in Figure 5.2.

The groundwater sample collected from B3-SB1 exceeds TNRCC criteria for PCE, TCE, cis-1,2-DCE, and vinyl chloride. The concentration of trans-1,2-DCE did not exceed TNRCC criteria (Figure 5.2).

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