Laserfiche WebLink
L <br /> Section 4 <br /> L Preliminary Site Assessment <br /> L <br /> 4.1 Technical Approach <br /> i <br /> I <br /> L <br /> Based on the tank removal sample results, Tetra Tech conducted a preliminary subsurface <br /> � assessment around the removed UST. The primary purpose of this site assessment was to <br /> � <br /> ' collect samples beneath the former UST to evaluate the extent of subsurface contamination <br /> identified during tank removal operations. Since local groundwater had been documented at <br /> shallow depths, groundwater quality was evaluated by hydropunching and collecting water <br /> samples at the former tank cavity. In addition to subsurface sampling, the stockpiled soil from <br /> the UST removal excavation was re-sampled to evaluate the presence of petroleum <br /> hydrocarbons. The results of this program have been used as criteria to determine if further <br /> 1 <br /> L action at the site is required. This site assessment was completed in accordance with criteria <br /> established by SJPHS and the Regional Board. <br /> Tetra Tech initially submitted a technical work plan, dated September 9, 1994, outlining a <br /> L proposed soil boring program. Following discussions with SJPHS representative Mr. Steve <br /> Sasson, the scope of work was amended to reflect anticipated groundwater conditions. The <br /> amended workplan was submitted on January 9, 1995. Formal regulatory approval was issued <br /> Lby SJPHS on January 30, 1995 to proceed with the proposed scope of work. Drilling permits <br /> were also filed with SJPHS prior to field activities. Copies of all regulatory correspondence <br /> and permits are presented in Appendix B. <br /> IM <br /> L4.2 Boring Locations <br /> The investigation consisted of drilling two soil borings at the former location of the UST. One <br /> L boring (HP-1) was completed at the midpoint of the former tank cavity to evaluate <br /> groundwater quality directly at the suspected point source. A second boring (HP-2) was <br /> Lplaced approximately 15 feet down-gradient (in the east direction) from the UST to determine <br /> if down-gradient migration of hydrocarbons had potentially occurred. All boring locations are <br /> Lpresented in Figure 3. Both borings were drilled to a depth of approximately 9 feet bgs to <br /> I collect a soil sample and a grab groundwater sample directly beneath the former UST. <br /> L Maw, <br /> TETRA TECH:Castle Rock Forest Fire Station,Preliminary Site Assessment Report Page 8 <br /> L <br />