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Mr Michael Infurna April 30,2004 Page 2 AES to install the wells using a truck-mounted hollow-stem auger rig The wells were installed inside 8-inch diameter boreholes The air sparge and vapor extraction wells were completed approximately ten feet deeper than originally estimated in the Remedial Action Plan Between the submittal and approval of the Remedial Action Plan and installation of the remediation system wells, the site water levels decreased approximately 3 to 4 feet The lowered water table required that the total depth of the sparge and vent wells be increased by approximately 10 feet Also, an additional air sparge well had to be installed to replace the existing pilot test air sparge well because the screened section did not fully penetrate the water table AES submitted a letter describing these changes to the San Joaquin County EHD on April 2, 2004 The San Joaquin County EHD indicated in a follow- up letter dated April 13, 2004, that the changes were adequate and necessary A copy of the San Joaquin EHD letter is attached Borings for the air sparge wells were completed to approximately 70 feet below ground surface (bgs) The air sparge wells were constructed of 2-inch diameter Schedule 40 PVC casing and screen (0 010 slot size) The screen sections were set at approximately 65 to 70 feet bgs The top of the screen section extended about seven feet below the top of the water table A sand pack was emplaced in the annular space from the bottom of the borehole to approximately two feet above the top of the screen section A two foot hydrated bentonite chip seal was placed on top of the sand pack and the remaining annular space was sealed with a Portland cement grout mix i Borings for the vapor extraction wells were completed to approximately 40 or 50 feet below ground surface (bgs) The vapor extraction wells were constructed of 2-inch diameter Schedule 40 PVC casing and screen (0 010 slot size) The top of the screen sections were set at approximately 10 feet bgs A sand pack was emplaced in the annular space from the bottom of the borehole to approximately two feet above the top of the screen section A two-foot hydrated bentonite chip seal was placed on top of the sand pack and the remaining annular space was sealed with a Portland cement grout mix Each well was completed inside a steel 18-inch diameter flush-mount well vault set in a 3-ft x 3- ft concrete pad Well completion logs showing typical air sparge and vapor extraction well construction details are included as Figure 3 Meryl Component Installation The remediation system components were installed during the period from March 8 through 23, 2004 The system installation was completed under the supervision of a Registered Geologist in the State of California AES subcontracted WRS Infrastructure and Environment, Inc to install the remediation system components •