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Mr.Ron Rowe
<br /> November 24, 1997
<br /> Page 4
<br /> benzene,and xylene concentrations observed in borehole MW-7 are included in Table 1. MTBE and DIPE were
<br /> observed at concentrations of 52 and 7 ppb at depths of 34.5 and 79 feet, respectively. Concentrations of
<br /> methanol,ethanol,TBA,ETBE,and TAME were not detected above the laboratory reporting limits in two soil
<br /> samples.
<br /> Groundwater chemical results are presented on Table 1. Maximum concentrations of TPHg and benzene were
<br /> observed in the grab groundwater sample,MW-713 which was collected at 41-44 feet bgs. The concentrations
<br /> of TPHg and benzene in the two grab groundwater samples were 340 and 400 ppm and 22,000 and 28,000 ppb,
<br /> respectively. Toluene,ethylbenzene,and xylene concentrations observed in the two grab groundwater samples
<br /> are included in Table 1. MTBE concentrations of 3,200 and 3,000 ppb were reported in grab groundwater
<br /> samples, MW-7A and MW-7B, respectively. Concentrations of methanol, ethanol, TBA, DIPE, ETBE, and
<br /> TAME were not detected above the laboratory reporting limits in the grab groundwater samples.
<br /> A ten-fold decrease in TPHg and benzene concentrations was observed between well samples MW7-S and MW-
<br /> 7-1), from 100 to 10 ppm and 19,000 to 1,300 ppb, respectively. Toluene, ethylbenzene, and xylene
<br /> concentrations observed in the two samples are included in Table 1. A MTBE concentration of 120 ppb was
<br /> observed in sample MW-7-S. Concentrations of methanol,ethanol,TBA,DIPE,ETBE,and TAME were not
<br /> detected above the laboratory reporting limits in the two groundwater samples.
<br /> Four soil samples were analyzed for porosity,bulk density,moisture content,and fraction organic carbon. The
<br /> results of the porosity analysis ranged from 26.8 to 48.1 percent of total volume and the results of the bulk
<br /> density analysis ranged from 89.7 to 123.3 pounds per cubic foot. The results of the moisture content analysis
<br /> ranged from 9.6 to 30.7 percent of total weight and the results of the fraction organic carbon analysis ranged from
<br /> 0.5 to 2.6 percent of total weight. In general,the analytical results of porosity, moisture content,and fraction
<br /> organic carbon decreased with depth at which the soil sample was collected and bulk density increased with depth.
<br /> The results of the physical analyses are included in Table 2 and the laboratory analytical reports and chain-of-
<br /> custody records are included in Attachment A.
<br /> PROPOSED CPT SURVEY
<br /> Objective and Technical Approach
<br /> The results of prior Site investigations suggests that petroleum hydrocarbon-affected soil and groundwater are
<br /> present beneath the Site to a minimum depth of 8.5 feet bgs. Given the current depth to groundwater and physical
<br /> characteristics of petroleum fuel products(less dense than water),the presence of relatively high concentrations
<br /> of dissolved phase petroleum hydrocarbon at 85 feet bgs suggests that significant fluctuations in the depth to
<br /> groundwater have likely occurred in the past.
<br /> The objective of the proposed CPT survey is to assess the vertical and lateral extent of petroleum hydrocarbon-
<br /> affected soil and groundwater underlying the Site. To meet this objective, SECOR proposes to use a cone
<br /> penetrometer testing(CPT)rig to hydraulically advance small-diameter CPT boreholes. A CPT rig provides a
<br /> rapid, reliable and economical means of determining soil stratigraphy, relative density, strength, and
<br /> hydrogeologic characteristics such as hydrostatic head and relative permeability without generating waste
<br /> cuttings. Furthermore,multiple depth discrete soil and groundwater samples can be collected using a CPT rig.
<br /> Chemical analysis of groundwater samples will be performed on an overnight(15-hour)rush basis,thus allowing
<br /> for decisions to be made in the field regarding the placement of additional CPT locations and sampling depths.
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<br /> H ASHMSTOCKTONMKPI RPT
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