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Soil and Groundwater Investigation Report <br /> Mountain House Development Site#6 July 2008 <br /> by Condor Earth Technologies,Inc. (Condor,2001). During the current site investigation,depth to <br /> groundwater was observed between 4.9 and 12 feet bgs. <br /> 2.4 EXISTING AND PLANNED DEVELOPMENT <br /> Byron Road is currently a two-lane thoroughfare serving southwest San Joaquin and eastern Contra Costa <br /> counties between Tracy and the Sacramento River Delta. The site is located among agricultural areas in <br /> the community of Mountain House, California. Nearby development of the area consists of agricultural <br /> and light-industrial facilities. Mountain House is a master-planned development where single-family <br /> homes are under construction in areas west of the site. <br /> 2.5 PREVIOUS ENVIRONMENTAL ACTIVITIES <br /> Condor's 2001 Chevron Pipeline Easement Assessment Report documented affected soil at the site in <br /> borings GP-152, GP-156 through GP-158, GP-160, and GP-161 at depths ranging from 4.5 to 20 feet bgs. <br /> Soil samples were collected at boring locations and submitted to a laboratory for analytical testing. <br /> Laboratory analytical results indicated detectable TPH quantified as crude oil(TPHc)at concentrations <br /> ranging from 880 milligrams per kilogram(mg/kg) in boring GP-152 at 15.5 feet bgs to 29,000 mg/kg in <br /> GP-156 at 12 feet bgs. <br /> Grab groundwater samples were also collected at boring locations and submitted to a laboratory for <br /> analytical testing. TPH quantified as diesel(TPHd)were detected at concentrations ranging from <br /> 2,200 micrograms/liter(gg/L) in GP-152 to 260,000 gg/L in GP-161. TPH quantified as gasoline(TPHg) <br /> were also detected at concentrations ranging from 8,500 gg/L in GP-156 to 9,900 gg/L in GP-161. <br /> Soils encountered in the borings were predominantly clays, silts, and sands. Borings advanced on the <br /> shoulder of Byron Road encountered clay and gravel fill in the upper 1 to 3 feet that appeared to be road <br /> sub-base. Groundwater was observed at the site at depths ranging from 7 to 17 feet bgs. <br /> See Appendix B for additional documentation regarding the soil analytical results of the 2001 Condor <br /> investigation. <br /> 3. OBJECTIVE AND SCOPE <br /> SAIC implemented the work plan as described in sections 3.1 to 3.4. <br /> 3.1 PERMITTING,ACCESS,AND SITE SAFETY <br /> To maintain regulatory and legal compliance,protect the health of all involved persons, and prevent <br /> accidents, SAIC implemented the following: <br /> • Determined the ownership of and obtain access to private properties coincident with the scope of <br /> work described herein; <br /> • Obtained boring permits from the San Joaquin County Environmental Health Department <br /> (SJCEHD) for advancement of the soil borings; <br /> • Obtained an encroachment permit from the Mountain House Community Services District <br /> (MHCSD) for borings located in the Byron Road ROW; <br /> • Obtained an approved traffic-control plan; <br /> • Prepared a site-specific Health and Safety Plan; <br /> • Prepared a site-specific Journey Management Plan; <br /> • Conducted a site visit to mark boring locations for Underground Service Alert(USA),notified <br /> USA at least 48 hours in advance of field activities, and requested USA to mark underground <br /> facilities in adjacent public ROWS; and <br /> 3 <br /> From Science to Solutions <br />