WORK PLANS - Laserfiche WebLink

Home Browse Search

• TREADWELL & ROLLO applications, however, were documented and were judged to have the potential to affect the groundwater underlying the site. On 15 August 1990, Treadwell & Rollo drilled 1 boring (Figure 2) to obtain a "grab" sample of the groundwater from within the open borehole. The boring was drilled to a depth of 35 feet using hollow-stem auger drilling equipment. The sample was analyzed for the presence of petroleum hydrocarbons, hydrocarbon oil & grease, chlorinated herbicides, carbamates, benzene, toluene, ethylbenzene, and xylenes, organophosphorus and organochlorine pesticides, PCBs, and VOCs and Title 26 metals. No chemical constituents were detected above laboratory method reporting limits with the exception of several trace metals which were within concentration ranges considered to be "background" levels in the western United States. 4.0 FIELD INVESTIGATION The investigation consisted of drilling three borings and converting those borings to monitor wells and subsequently developing and sampling the wells. The wells were installed under permit from the San Joaquin County Public Health Services Department (Appendix A) from 21 to 22 August 1991. The wells were developed and sampled on 23 August 1991 and a confirming round of groundwater sampling was conducted on 17 September 1991. The well installation and sampling procedures are discussed in the following sections. 4.1 Drilling and Sampling Three borings (MW-1, MW-2, and MW-3) were drilled to depths of 37, 36.5, and 38 feet using a truck-mounted drill equipped with 9-inch-diameter hollow-stem augers. The boring locations are shown on Figure 2. All down-hole equipment was steam cleaned prior to drilling and between borings to minimize the potential for cross contamination. Soil samples were collected from Borings MW-1 and MW-2 at depths of 20 and 23.5 3 1107A201.CRJ 5 November 1991