SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Mr. Ken Gillies Gillies Trucking 3931 Newton Road, Stockton Page 2 of 3 the west, nearly perpendicular to the inferred channel axis. The plume of dissolved TPH-d is delineated toward the southwest. Dissolved TPH-d was detected in all three groundwater samples collected from wells screened in this interval at concentrations ranging from 56 to 390 µg/I, groundwater flow was inferred to be toward the south, nearly perpendicular to the inferred axis of the channel. The plume of dissolved TPH-d is not delineated, but GT-14B with 56 µg/I TPH-d appears to be located near the down-gradient extent. Soil impacted by TPH-g at concentrations suggestive of vadose zone leaching was encountered at depths as great as 90 feet below surface grade (bsg), and more certainly to depths of 71 feet bsg (GT-11). Locally, hydrocarbon odor with low to non-detectable TPH-d concentrations were interpreted as being due to sorbtion of dissolved petroleum hydrocarbons. Based on these results, UEC recommended: • Moving the location proposed for GT-19 approximately 100 feet northward to increase the potential to delineate the extent of impacted groundwater west of MW-13; • Adding a clustered well in the 3`d Riverbank aquifer near GT-12 or GT-16 to delineate impacted groundwater toward the northeast; • Installing monitoring wells GT-16 through GT-21 in one phase of work rather than the two phases previously proposed and approved; • EHD should request new confirmation borings to collect data needed to prepare a contaminant mass estimate; and • Delaying preparation of a dissolved contaminant mass estimate until all new monitoring wells have been installed. EHD approves the new proposed location for GT-19 and adding the cluster well in the 3`d Riverbank aquifer near GT-12 or GT-16. EHD also approves installation of GT-16 through GT-19 in one phase of work. Delaying preparation of the mass estimate for dissolved contaminants until all the wells have been installed would be appropriate and is approved. EHD has requested an estimate of the sorbed contaminant mass for your use in preparing the fate and transport model. If UEC requires additional soil data to complete this directive, UEC should propose the borings needed to acquire adequate data for the mass estimate. At a meeting with you and your consultant on 15 August 2001 you had agreed to provide construction details or a video log of G-1 and to destroy the domestic well (G-1) and replace it with a well designed pursuant to current standards. This