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Soil and Groundwater Investigation Report
<br /> Vernalis Offsite June 2008
<br /> First Semi-Annual 2008 Groundwater Monitoring and Sampling Report(SAIL,2008). SAIC
<br /> conducted groundwater monitoring and sampling of monitoring wells MW-2,MW-3, MW-5, MW-6 and
<br /> MW-7 in January 2008. Well MW-6 and MW-7 are located on the Bogetti property and sampled
<br /> quarterly. The COCs were at non-detect concentrations in off-site MW-6 and MW-7 with the exception
<br /> of TPHd detected in MW-7 at a concentration of 390 pg/L.
<br /> Arcos Property
<br /> ' Report of Soil and Groundwater Investigations(Geomatrix,20041. Geomatrix conducted a
<br /> preliminary soil and groundwater investigation in October 2003 at the Arcos property, which had not been
<br /> investigated previously. The preliminary site investigation included a review of public records, historical
<br /> ' maps, and aerial photographs; a geophysical survey; an evaluation of current property conditions; and a
<br /> subsurface investigation. Gregg Drilling,under the supervision of Geomatrix,advanced soil borings
<br /> ASB-1 through ASB-12 on and around the Arcos property between October 20 and 28, 2003.
<br /> TPHc were detected in borings ASB-1,ASB-2, and ASB-4, with a maximum concentration of 17,000
<br /> mg/kg in ASB-2 at 29 feet bgs. TPHc were not detected in any other borings. Low concentrations of
<br /> BTEX and PAHs were sporadically detected in several soil samples; however,no concentration exceeded
<br /> a PRG,except benzene in ASB-2 at 29 feet bgs and naphthalene in ASB-4 at 10.5 feet bgs.
<br /> Geomatrix collected grab groundwater samples from soil borings ASB-1, ASB-5 through ASB-8,
<br /> ASB-10, ASB-11, and ASB-12. TPHd were detected in the groundwater samples collected from borings
<br /> ASB-1,ASB-5,ASB-6,ASB-7, and ASB-11, with a maximum concentration of 2,900 µg/L in ASB-1.
<br /> BTEX were not detected in any sample. The only PAH detected was acenapthene in ASB-1 at 36.5 to 45
<br /> feet bgs; however,the concentration was well below the WQO.
<br /> ' Soil and Groundwater Investigation Report(SAIC,2006). SAIC submitted a site investigation report
<br /> in August 2006 for the Vernalis Pump Station, which summarized the findings of the May 2005
<br /> investigation and well installation and concluded the following:
<br /> ' • Affected soil and groundwater are delineated vertically to a maximum depth of approximately
<br /> 80 feet bgs. The RWQCB accepted these delineation results in a letter dated March 19, 2004.
<br /> • In the immediate vicinity of the boiler house and the pump house,the lateral extent of affected
<br /> soil was defined by several borings located near monitoring well MW-1.
<br /> • In addition to a small area of affected groundwater at MW-1,two areas of affected groundwater
<br /> were present: one on the Arcos property, which encompasses Geomatrix borings ASB-1,ASB-4,
<br /> ASB-5,ASB-6,ASB-7, and ASB-11; and one on the Bellini and Bogetti properties, which
<br /> includes borings SB-15, SB-16, SB-18, SB-19, SB-20, SB-23 (MW-6), SB-24, SB-25, and
<br /> monitoring well MW-7 (Figure 3).
<br /> • The extent of affected groundwater is delineated up gradient at the following locations,from
<br /> north to south: soil boring SB-30; monitoring wells MW-3 and MW-4; and soil borings ASB-2,
<br /> ASB-3, and ASB-9.
<br /> • The extent of affected groundwater is undefined at boring SB-25 and at monitoring well MW-7,
<br /> and further off-site investigation is necessary down gradient on the Bogetti property.
<br /> • The extent of affected groundwater on the Arcos property is undefined, and investigation is
<br /> necessary down gradient on the San Joaquin Valley Hay Growers Association(SJVHGA;
<br /> Stanislaus County APN 016-002-006) property, or in the Highway 33 ROW.
<br /> To define the extent of affected groundwater down gradient and off-site(east of Highway 33), SAIC
<br /> proposed the following:
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