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i FROM = Ground Zero Analysis PHONE NO. = 209 S38 9883 Feb. 15 2000 04:59PM P3 i Mr.Hadin Knoll � Febniary 15,2004 Page 2 of 4 w occurred. Sail boring locations are shown on Fi re Analytical results are summarized in Table 1. One '10,000-gallon UST for storage of diesel fuel and two 1t1,E�f} gallon USTs for the.storage of ;j gasoline and associated piping were removed under p it from PHSlEHD on January 21, 1999. 1 Analytical results of sidewall soil samples andgroundwater grab sample collected from beneath the USTs indicated that elevated levels of petroleum ydrocarbons were present in the moil and groundwater. Sample locations are shown on Figure 2. Analytical results are summarized in Table 2. 2.2 Soil Boring Investigation In xuly 1994, five direct push sail boring were advanced along the perimeter of the former UST location to investigate the vertical and lateral extent of soil and groundwater contamimkrr, and. four band augered sail borings were advanced to in estigate the lateral extent of shallow soil contaminatt*n_ Soil boring locations are shown on Figure 2.. Analytical results are summarized in Tables 3 and 4_ The results of this investigatiDn were submitted to PH SIEHD in a report dated October 19, 1999. Based upon the localized contamination and its current accessibility, Ground Zem recommends the � implementation of remedial actions consisting ofexca ation and limited groundwater extrad#ion, as well as the installation,of groundwater monitoring;well to further define the extent of groundwater contamination. This workplan addcndurn addresse proposed interim soil and groundwater remedial actions. The installation of groundwater monitoring wells will be scheduled upon completion of o=vation and balling activities and have been addressed under separate cover. !` 2.3 Hydrageological Setting � The site is located in Thornton, California, approximately 5,100 feet southwest of the Mokelurnne River, the nearest body of surf ce water. Surface elevation at the site is i approximately eight feet above sea leveL Based on, historical information provided by Son aaGquin County Flood Control and Water i Conservation District and groundwater information I rorn a nearby site, groundwater beneath the site is expected to flaw in a. southwesterly direction Groundwater was first encountered at a depth of 6 to 7 feet in the borings drilled on the propt rty. 3.0 NAT =AND EXTENT OF CONTAMIN TIEON 3A Soil Contamination The data kom.the sail boring investigation combined with data previously obtained have largely .defined the exted of soil contamination Soil cot tarnination appears to be limited to depths between approximately 6 and 1.3 feet bgs and is gener,My :found in the area immediately adjacent to i G.WW,%GR0Vk4DZHWANSL LkWnecrztiMerimwp.&C; �i.