ARCHIVED REPORTS_XR0004007 - Laserfiche WebLink

Home Browse Search

Geological Technics InO Page 3 Sinclair Trucking t Report-Subsurface Investigation Project No,320.2 September 27,1995 observation noting sediment type, especially grain size and clay content; moisture content; visible evidence of contamination, i.e., color change due to reduction of iron or discoloration from hydrocarbons and other pollutants, and the readings above background on a organic vapor meter (OVM). The OVM is a field portable photo ' ionization detector that uses a 10.0 eV lamp to detect compounds with ionization potential below 10.0 eV (hydrocarbon range). The OVM is calibrated daily using a 100 part per million concentration isobutylene gas standard. 2.0 SITE GEOLOGY ' Based on sediments recovered in the split spoon sampler the soil profile of the site was observed to generally consist of a sandy silt and/or a clayey silt with varying amounts of very fine grained sand. A fine to coarse sand unit which exhibited flowing properties was observed to be present between ±12-16 ft. Below 16 feet a dense clayey silt was observed. ' The sediments containing clay fines exhibited varying degrees of plasticity from non plastic and even friable to very plastic. The soil below a depth of ten feet was observed to be saturated (the water table stabilized at approximately 9.5 feet after well development). The boring logs for the borings are attached in Appendix B. 3.0 SITE HYDROLOGY ' On June 23, 1995 the three monitoring wells were measured for depth to � g p ' groundwater by Del-Tech Geotechnical Support personnel. The average depth to water was measured to be 9.56 feet from the top of casing measuring point. The groundwater gradient and bearing of flow were calculated to be 0.00433 ft/ft ' flowing north 60°east respectively (Figure 3-Gradient Map). This hydrologic behavior is consistent with what would be expected based on surface topography (Figure 1- Vicinity Map). 4.0 CONCLUSIONS AND RECOMMENDATIONS ' The recent subsurface investigation was conducted with the intention of cost effectively obtaining as much geologic, hydrogeologic, and chemical information as possible while operating under the Underground Storage Tank Cleanup Fund -- Program's (USTCFP) deductible amount. This preliminary investigation was successful in that the site now has site specific hydrologic monitoring capability, we have evidence which suggests that the plume has been defined in the southwest and southeast direction, and we now have enough information to consider methods for cost effectively defining the extent of hydrocarbon impact at this site.