FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

C3eologicafTkhnicr Znc. Page 7 Hunter Container Report-Soil and Groundwater Investigation i Project No.397.2 October 25, 1996 'i 2.0 DISCUSSION The three boreholes and one groundwater monitoring well was installed as planned and the f following information was gathered. J 2.1 Geology and Hydrogeology of the Site The dominant soil type in the upper 40 feet of subsurface geologic soils investigated is dominated by fine grain sediments. Even in the sandy horizons, a silt or clay matrix is present. A summary of the geology is given below. Total depth of the three boreholes wash-1 30 feet and total depth of the monitoring well was 40 feet. • Silt - sandy and clayey, occasional pebble and root tubes, slightly plastic, 0 -18.5 feet ti • Gravel - some clast size > 2", broken pieces in split spoon, sand matrix, 18.5 - 23.5 feet Silt- sandy and clayey,fine grained sand lenses, slightly plastic,23.5 -28 feet t ' AD Clay- blue green, grading to sandy gravel at 30 feet, 28 - 30 feet • Sand and Gravel - course grained sand to fine grained gravel, fine grained matrix, blue`; _ green, 30 -40 feet „•� Groundwater was encountered at about '30 feet and that is the depth that water is in the monitoring well. The capillary fringe appeared to extend up to 26 feet, with decreasing moisture content upward from the saturated zone. 2.2 Chemical Distribution lA data table enclosed in front of Appendix A summarizes the analytical data collected in this portion of the property. Lab test results corroborate well with field observations and are l discussed below. Chemical Distribution in the Soil The preliminary investigation work performed by ERM in 1995 showed low concentrations i of Trichloroethene (TCE) and low to moderate levels of Ethylbenzene in the upper 10 feet of soil. They collected samples at two feet intervals starting at four feet and continuing down to 10 feet and tested there for volatile organic compounds. TCE decreases with increase.in vertical depth while Ethylbenzene increases with depth. Benzene, Toluene, and Xylene were l found towards the bottom of borehole HB-4. I This distribution pattern is constant with what we observed in our work, in that the gasoline 1 and the BTEX compounds were present in these boreholes in the deeper soils. With HB-4 picking up BTEX compounds at 8 to 10 feet, this suggests that these were related to the gasoline we found at increasingly higher concentrations from 6 to 10 feet down to groundwater at 30 feet. Field observation show that there is a distinct upper boundary of dark"oil" stained soil which starts at 11.5 feet in MW-1 and at 5 feet in SB-2, and extends down to groundwater. Lab data corroborates with the field observations and show a high concentration of diesel and motor oil in this soil zone.