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CLEARW_ '�:W' TER G R O L P I \ C E n i r roe ut en tiff S,r in 2.0 SCOPE OF WORK 21 Purpose In accordance with the EHD letter dated August 20, 1998, this workplan proposes a subsurface investigation to fully delineate the lateral extent of petroleum hydrocarbons that may have been released from USTs formerly located at the site Three monitoring wells will be installed, and soil and groundwater samples will be chemically analyzed for fuel constituents Prior to implementation of this workplan, a Site-specific Health and Safety Plan will be prepared 2 2 Installation of Monitoring Wells Three soil borings will be drilled and converted to 2-inch-diameter monitoring wells in the locations shown on Figure 2 Prior to installing the monitoring wells, permits will be obtained from the San Joaquin County EHD by a California C-57 licensed driller Drilling will be conducted using a truck- mounted hollow-stem auger rig equipped with 8-inch-diameter augers Down-hole drilling and sampling equipment will be steam-cleaned prior to arriving onsite and between drilling at each boring location All drilling and sampling methods will be consistent with ASTM Method D-1452-80 and local, state, and federal regulations, as well as Clearwater's attached protocols Soil Sampling Discrete soil samples will be collected at five-foot intervals or at stratigraphic changes The soil • samples will be obtained by advancing a California-modified split spoon sampler lined with three 6- inch-long brass sampling tubes The sampler will be driven 18 inches past the lead auger by a dropping a 140-pound hammer from a height of approximately 30 inches The number of blows necessary to drive the sampler and the amount of soil recovered will be recorded on the boring log All soil sampling equipment will be decontaminated between samples to avoid cross-contamination Soil samples will be used for sedimentologic description (in accordance with the Unified Soil Classification System) and to screen the soil for organic vapors The field screening equipment used will be a photoionization detector (PID) Results of the field screening for organic vapors will be recorded on the field log Two samples from each boring (one from the capillary fringe and the sample indicated to be most highly contaminated during field screening) will be selected for laboratory analysis One sample tube from each selected interval will be sealed at both ends with Teflon sheets and plastic end caps The sample tubes will be labeled, documented on a chain-of-custody form, and placed in a cooler for transport to a state-certified analytical laboratory MonitorMg Well Construction Depth to groundwater has varied from 6 to 12 feet below top of casing during the course of the investigation The monitoring wells will be constructed with 15 feet of screen so that the screen extends from 4 to 19 feet bgs Wells will be constructed of 2-inch-diameter Schedule 40 PVC casing and 0 02- inch slotted screen A sand filter pack consisting of#2/12 sand will be placed in the well annulus from total depth to six-inches above the top of the screened interval A bentonite seal one foot thick will be placed over the filter pack (the seal will be made by hydrating bentonite pellets) The remainder of the well annulus will be filled with grout consisting of neat cement or cement/bentonite grout with no more than 3% bentonite Traffic-rated well boxes w.11 be mounted (flush to grade) over the monitoring wells, and locking well caps will be placed in the top of the well casings 0-178 WP 2 November 18, 1998