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petroleum hydrocarbon constituents. Petroleum hydrocarbons were detected in groundwater samples collected from MWl through MW4. From November 10 to 12 and 15 to 17, 2004, an ATC geologist supervised the installation of monitoring wells MW5 through MW12. Soil samples were collected from the boreholes of MW5 , MW6, MW7, MW8, MW9, MW10, MWl1 , and MW12 for purposes of logging soil type, and selected soil samples were submitted for laboratory analyses . Each well was constructed with 2-inch diameter PVC casing, with MW8, MW9, MW10, and MWl I extending to a depth of 65 feet bgs in the shallow groundwater bearing zone, MW5 , MW6, and MW12 extending to a depth of 90 feet bgs in the intermediate groundwater bearing zone, and MW7 extending to a depth of 121 feet bgs in the deep groundwater bearing zone. Monitoring wells MW5, MW6, MW8 , MW9, MW10, and MW12 were developed on December 22 and 23 , 2004. An obstruction encountered in MW7 at approximately 64 to 65 feet bgs prevented development of this well. MWll was purged dry after removing 0.5 gallons of water. Efforts to develop this well using a bailer revealed the presence of grout inside the well and the total depth of the well was measured to be approximately 58 feet. On December 22 and 23 , 2004, monitoring wells MW 1 through MW12 were surveyed relative to NAD 83 and NGVD29 for position and elevation and groundwater samples were collected from MWl through MW6, MW8, MW9, MW10 , and MW12. Petroleum hydrocarbon constituents were detected in soil samples collected from the boreholes of MW5 through MW9 and MW12. Groundwater samples were not collected from MW7 and MWll due to an obstruction in MW7 and grout infiltration in MW11 . Petroleum hydrocarbons were detected in the groundwater samples collected from MWl through MW6, MW8 through MW 10, and MW12. The results of the subsurface investigation activities are presented in ATC ' s Subsurface Investigation Report, dated July 25, 2005 , On April 7, 2005, an ATC geologist supervised the destruction of MWll and the installation of replacement monitoring well MW11R to a depth of approximately 65 feet bgs using 2-inch diameter schedule 40 PVC casing. Refer to ATC ' s First and Second Quarter 2005 Monitoring Report, dated October 10, 2005, for additional information. SCOPE OF WORK Planning ATC will schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform other necessary field preparation and job start-up activities . A private utility locating service will also be used to locate underground utilities that may be present in the work areas. A drilling permit application will be completed and submitted to the San Joaquin County Environmental Health Department (SJCEHD) prior to initiation of drilling activities. ATC will attempt to obtain off-site access for the proposed off-site drilling location. ATC will require authorization from off-site property owner prior to conducting drilling activities. S:\Envh on=nta]\28349\wkp.doc 2 ATC Associates Inc.