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June 12, 2001 528221 Michael Infurna, Senior REHS San Joaquin County Public Health Services Environmental Health Division Page 2 Six of the monitoring wells (MW-1 through MW-6)were installed with total depths ranging from 22-feet to 41-feet below ground surface (bgs) in non-impacted soil (HLA, 1999) and were therefore destroyed by pressure grouting in accordance with the following procedures A state-licensed C57 well driller destroyed the wells under the direction of a Harding ESE geologist or engineer All Site wells were sounded to check for obstructions that could interfere with filling or sealing The wells were then pressure grouted with a tremae pipe from the bottom up,to a depth of approximately three feet bgs The grout consisted of neat cement mix of less that 6 gallons of clean water per sack of cement, and less than five percent powdered bentonite The top of the 2-inch diameter well casing was drilled out with a 2l-inch diameter solid flight auger to a depth of approximately 3 feet bgs Cuttings were removed from the bottom of the resulting hole, and additional grout was added to fill the settled grout in the casing, and the bottom foot of the over-bored hole The remaining portion of the hole was backfilled with native soil cuttings The wells that were located in paved areas were completed to match the surrounding surface Monitoring well MW-7 was installed within impacted soil, which was first encountered at a depth of 12 5 feet bgs just beneath the former UST excavation Non-impacted soil is present above this depth within the former UST excavation The presence of impacted soil below 12 5 feet bgs required that MW-7 be over-drilled to beyond the total depth of 41 5 feet bgs Non-impacted cuttings from above 12 5 feet bgs were distributed around the bare ground surface of the well Impacted cuttings were drummed and stored on-site for later disposal The resulting borehole was tremae grouted to three feet bgs and the top 3 feet was filled with clean cuttings Because the potential for contact between the impacted soil and non-impacted groundwater, the PHS/EHD required the water displaced by the grout to be collected and containerized for off-site disposal The well destruction activities were performed by Woodward Drilling Company of Rio Vista, California a C- 57 licensed(710079)well driller Contamerized soil cuttings and groundwater from the destruction of MW-7,three drums of spent granule activated carbon used in a former groundwater remediation system, as well as several drums of previously generated investigation derived waste were removed from the Site on May 21, 2001 A total of 1 I drums were disposed of at the Forward Landfill in Manteca, California on May 21, 2001 A copy of the non- hazardous waste manifest and the weigh ticket are attached In accordance with previous communications with the PHS/EHD, Harding ESE, on behalf of TVG, request that a No Further Action letter be issued for the Site Harding ESE A MACTEC COMPANY