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@4428/1999 11:08 20983281.52 WRIGHT ENVIRONMENTAL PAGE 05 it is Wright's opinion that a limited cleanup and continued monitoring are the pres`erred Approach to this project. The sources will be excavated and diseased of to remov the continuing groundwater source. While the excavation is open, groundwater collecting m the pit will be pumped out to remove the mobilized ccmtaxz aims in the immediate tank v cinrty and immediately north of the site under the street. It is anticipated that the existing monitoring well near the curb, MW-1 will be destroyed ;y the excavation process. However, a replacement well will be installed across the street, as definition work has supported that location as the downgrad=t extent of the plum a (see Figure 1). In this way, the site monitoring can continue and is anticipated to document a declining trend of residual contaminants. Field Activities-Excavation and So$and Water Treatment 1 Two field pleases are planned for the site; excavation and disposal of sort and water rerYoved j from the former subsurface tank location and pump island, and drilling one exploratorw soil I boring to install the new groundwater monitoring well(see Figure 1). Soil will be excavated from the immediate area of the foiLmex tank location and pump ishand as defined by soil chemical assessment data. Overburden soil .winch apparently.has no+'been impacted with petroleum hydrocarbons will.be stockpiled separately from the underlying contaminated soil. Excavation will continue in;the former.tank vicinity to a depth of aboui'10 feet below existing grade (roughly 1.5- to 2.0 fleet into groundwater). "This will it glude removing obvious (by held observation) areas of vadose soil contamination. 'Exc;Oation perimeter soil samples will be collected for chemical analysis for residual contamvnants. Any contaminated soil removed will be-done under approved permits of the San Joaquin Valley Unified Air Pollution control District. i. The excavated and stockpiled soil will be characterized for reuse and disposal by collectu:g soil stockpile samples for analysis by a certified analytical laboratory. Soil samples will be coilected by pressing a clean brass liner into the soil to a depth of about one foot completely fiU ig the Inner. The liner will be removed, sealed, labeled, logged onto a chain-of-custody foras and packed in.a chilled ice chest for transport to GaoAnalytical laboratory. Characterizati,an for i disposal will include testing for total Lead TFHQ, TPHD, and SMX. Once soils are teste cl and shown to not contain hazardous materials, the scii will,be properly disposed off-t11te at , Forward Landfill in San Joaquin County. The excavation pit recharge water (since the Fit will be advanced below groundwater) will be properly treated and disposed. The water.r;41.be pumped by a licensed hazardous waste hauler and taken directly to a treatment facility. The pit will be pumped out one time(one pit volume) prior to site restoration. Excavation backfill will be imported from Teichard Aggregates of Tracy, CA,and will consist of pea gravel and Class Ll base rock. Pea gravel will be placed from the.base of the excavation up to approximately 4 feet beiew existing ground surface(bgs). Uncontanrunated clean.overburdens previously removed will be placed from 4 feet bp'to 15; feet bgs. - j