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Mr James Barton ' July 30, 2004 Page 4 ' Soil Borings and Sampling On July 6 and July 7, 2004, a geologist from ENSR observed Cascade Drilling, Inc of Rancho ' Cordova, California advance soil borings MW-28 through MW-30 to approximate depths of 70 feet bgs The borings were advanced using a truck mounted drill rig using 8 114-inch diameter hollow stem augers The soil borings were completed as groundwater monitoring wells MW-28 through MW-30 The locations of the monitoring wells are shown on Figure 2 Soil samples were collected from MW-28 using a continuous core sampler to the total depth of the boring Soil samples were collected from MW-29 and MW-30 at a minimum of 5-foot ' intervals and at changes in lithology to the total depth of each boring The soil samples from each boring were logged using Unified Soil Classification System (USCS) ' visual and manual methods Soil samples collected were field screened for the presence of volatile organic compounds using a photolonization detector (PID) Soil boring logs containing PID readings, USCS descriptions, and other pertinent drilling information are included in Attachment C Soil Sample Analytical Results Selected soil samples collected from each boring at depths between 40 and 41 feet bgs were submitted to California Laboratory Services (CLS) in Rancho Cordova, California under chain- of-custody protocol Sall samples were analyzed for benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Method 8021, total petroleum hydrocarbons as gasoline (TPHg) by EPA Method 8015 Modified and methyl tertiary butyl ether (MtBE) using EPA Method 8260B Soil samples were collected using procedures described in Attachment D Concentrations of BTEX, TPHg and MtBE were not reported at or above the laboratory reporting limits in soil samples collected during this investigation ' Soil sample analytical results are summarized in Table 1 and copies of the laboratory analytical reports are included in Attachment E ' Monitoring Well Installation Groundwater monitoring wells MW-28 through MW-30 were constructed using 2 inch diameter, flush threaded, Schedule 40 polyvinyl chloride (PVC) casing installed to a total depth of approximately 70 feet bgs The wells are screened from approximately 50 to 70 feet bgs with a 0 02 inch machine slotted casing No 3 Monterey sand filter pack was placed from the base of ' the borings to approximately 4 to 8 feet above the top of the well screen A 2-feet thick bentonite seal was emplaced above each filter pack, and the remaining annular space was filled with cement grout containing approximately five percent bentonite to approximately 1-foot bgs The top of each well was completed with a flush grade traffic rated vault box set In concrete Well completion diagrams for wells MW-28 through MW-30 are presented In Attachment C J 1Proiects106940W98-2931FinaAReports15098 Well Results Report doc M ' 01 p 3( Vea- Cn"nr1Pl C`'f11 EMIHN7117enlal Seine