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Wright Environmental Services, Inc. Construction ♦ Engineering ♦ Remediation April 20,1998 Mr. John Best City of Tracy 520 Tracy Boulevard Tracy,Ca 95376 Re. Work Plan for Environmental Site Investigation,Boyd Service Center,Bldg.C Wright Project 4529-D PHS EHD Site Code 1421 Dear Mr.Best, Wright Environmental Services, Inc. (Wright) is pleased to provide you with this workplan for environmental investigation at the above referenced site located at 520 Tracy Blvd.,shown on Figure 1. The purpose of this work is to ascertain the depth to groundwater,identify suspected petroleum contaminants in soil and groundwater,and define the extent of contamination in soil and ground water around the existing underground storage tank area as required by San Joaquin County Public Health Services Environmental Health Division is their letter Dated January 26, 1998. Scope of Work F%ploratorY Borings and Monitoring Well Installation Six exploratory borings will be drilled at the locations shown on Figure 2. Drilling and well installation permits will be secured prior to doing the field work. Dyeg boreholes will be converted to groundwater monitoring wells. The boreholes will be drilled with truck mounted hollowstem auger and/or direct push drilling equipment. All drilling equipment and sampling tools will be cleaned prior to arriving, and before leaving the site. The augers will be advanced to the desired sampling depth interval,and a drive split spoon sampler will be driven ahead of the drill bit. The sampler will then be retrieved--aa-d dissembled and the soil tilled brass liner will be sealed with Teflon® paper and plastic endcaps, labeled, logged onto chain-of-custody forms and place in a chilled ice chest. The boreholdes will be logged using the Unified Soil Classification System under the supervision of a registered geologist using the attached Geoscience protocols Wright has developed for drilling, sealing, well construction and sampling. Additionai lithologic information will be collected to describe the subsurface geology. The samples will be collected at five-foot intervals, at intervals of obvious contamination and at stratigraphic features of interest. Upon completion of the borehole drilling and collection of information, the boreholes not converted to monitoring wells will be backfilled with grout,placed from the bottom to top of the borehole. one monitoring well may be installed using the attached protocols as an option. The well be cased with Sch. 40 PVC casing,threaded together,glues will not be used. The slotted interval will be a 0.020 inch slot and the annular space around the slots will be backfilled with a 2/12 size sand. Previous experience has shown this to be a reliable well design m fine grained and stratified despositional environments. Final well design will be modified to the site specific conditions encountered in the borehole during drilling. Once the aquifer strata has been defined,the casing will be lowered to the bottom of the borehole, leaving a slotted interval above the occurrence of groundwater to observe for floating product. The sand pack will be placed to a point about two feet above the slots. A bentonite seal will be placed atop the sand pack,and a cement grout seal placed atop the bentonite using a tremie line, filling from the bottom to top of the borehole. A traffic rated well head access box and security device will complete the well. 4220 Commercial Dr., Suite 5 . Tracy,CA 95376 209.833.0758 . Fax 209.832.5152 is wright@inreach.com Lic.#651501 A-B HazMat