FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

5.2.2 Procedure--Observation log 10/25/95 Following a conversation with Linda Turkatte, San Joaquin County Environmental Health Specialist, the excavation was centered over the original borehole where contamination was detected in 1993. As the pea gravel was now completely stabilized and casing was not required, a larger soil auger was used. The soil auger diameter was six feet. 1. The drill rig was placed over the east end of the excavation. Due to the size of the auger the span traversed the full width of the opening from North to South. The stabilized pea gravel and CDF sat at a slope, sloping from the east wall toward the center of the hole. 2. Augering began and removed pea gravel and CDF. At a depth of approximately twelve feet hydrocarbon odor was noted. 3. At sixteen feet the hydrocarbon odor was strong. Side samples were taken from the North, South, and East sides of the hole. 4. Augering was continued. The sampling equipment was not suitable to take side samples at depths greater than sixteen feet. The auger was halted at eighteen to nineteen feet for evaluation with the OVM. 5. Augering was resumed and stopped again at twenty eight feet. We attempted to secure a discrete bottom sample. At this point hydrocarbon odor from hole and soil pile was making it difficult to take readings with the OVM. Because of the tight working space soil cuttings were falling back into the hole when unloading the soil auger. We decided to over-excavate and try for a clean bottom. 6. Excavation continued to thirty six feet. We stopped at several points and checked samples from the soil auger with the OVM. At this depth we were beyond the reach of any of our soil sampling equipment. We scraped cleaned the soil auger. Along the leading edge we scraped and wire-brushed the tips of cutting edge. 7. We introduced the cleaned auger into the hole and drove the cutting edge below any slough into the native soil. The soil at this depth being stiff and clayey adhered to the cutting edge. We used the brass sample tube to scoop the soil from the cutting edge. OVM confirmation showed that some background hydrocarbon may have been present. Individual samples of soil were hand screened, (broken open and smelled), and discrete soil agglomerates showed no discernible hydrocarbons. Margaret Lagorio, San Joaquin County Lead Senior Registered Environmental Health Specialist was on-site. She concurred with our decision to stop drilling, we all felt we had over-excavated past the contamination. Lab analysis confirmed non-detect. 8. The drill rig was removed and the excavation was filled with control density fill. Page 6