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Site Characterization Report ABF Freight System,Inc. Manteca California Pae 5 • MW2 and MW3 were drilled through asphalt Both the concrete and asphalt were in fair condition before drilling commenced 3 12 Sampling Locations and Rationale A soil and groundwater sampling and analyses program was implemented to evaluate soil and groundwater conditions in the vicinity of the former UST and dispensing island The locations of the monitoring wells drilled during the investigation are shown on Figure 4 The soil boring and sampling program consisted of drilling three monitoring wells The monitoring well locations included one well drilled through the former 10,000 gallon UST excavation pit (MW1), and two wells drilled hydraulically down gradient from the excavation site (MW2 &MW3) Drilling permits to install the monitoring wells were obtained from the San Joaquin PHS/EHD prior to drilling (Appendix 4) The purpose of the soil borings and monitoring well installations was to evaluate the vertical and lateral extent of petroleum hydrocarbon in the vicinity of the former 10,000 gallon UST Soil samples were collected from the borings at 5-foot intervals in order to delineate vertical distribution of petroleum hydrocarbons Grab groundwater samples were collected from the monitoring wells after installation and development 3 13 Soil Sampling Methodologies Monitoring wells MW1 through MW3 were drilled by Bay Area Explorations of Suisan California, using a CME 45 drill rig equipped with an 8 inch diameter hollow-stem augers Soil samples were collected from each monitoring well borehole Soils samples were collected from the target sample depths using an 18-inch long California modified split-spoon sampler (CMSS) attached to a winch-driven 140-pound slide hammer The CMSS was lined with three 6-inch long by 2-inch diameter brass sample tubes The CMSS was advanced through the hollow-stem augers into undisturbed soil ahead of the auger drill bit with the winch driven 140-pound slide hammer, and undisturbed soil was retrieved in the three brass sample tubes The middle sample tube was capped and placed in a chest cooled with ice, the bottom sample was screened for odors and screened with a photolonization detector (PID), which measures concentrations of volatile organic compounds (VOCs) relative to an isobutylene standard, and used for lithologic description purposes 3 1 4 Monitonng Well Construction and Developing MW1 through MW3 were constructed of 2-inch diameter PVC well casings All three wells were screened with 0 010-inch slotted well screen from approximately 5 feet below ground surface to the total depth of the well at 25 feet A filter pack of#2 sand extended from the total depth of the well to 4 feet bsg Bentonite seal was placed from 4 feet bsg to 3 feet bsg and grout fill was used from 3 feet bsg to the top of casing • The top of casing elevation for the monitoring wells were surveyed by Moroe Surveying of West Sacramento, California The top of casing elevations for all three monitoring wells were 11SERVERIIC-DRIVEIPROJECTS\32721Plans and ReportslABF Freight Site Characterization Closure Report doc 11/17/98