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their proximity to the corporation yard. The aerial photograph search should be done using the City records as available, and aerial photographs as available from 1960 forward. Site -investigations performed on adjacent sites will be reviewed using records available at PHS EHD. This data will be used to position boring(s)to ascertain whether off-site contaminants may be coming on-site from the former railroad source. Exploratory Borings and Monitoring Well lnstallatign Up to six exploratory borings will be drilled at the site (Figure 4). The borings should be positioned to ascertain distribution of the contaminants in soil and groundwater under the site. Drilling and well installation permits will be secured from the PHS EHD, and all utilities will be cleared prior to doing the field work. 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 and dissembled, and the soil filled brass liners, it retained for chemical analysis, will be sealed with Teflon® paper and plastic endeaps, labeled,logged onto chain-of-custody forms and place in a chilled ice chest. The boreholes will be logged using the Unified Soil Classification System under the supervision of a registered geologist following the Tri-Regional guidelines. Additional lithologic information will be collected as needed to describe the subsurface geology. The samples will be collected at minimum five-foot intervals, at intervals of obvious contamination and at siratigraphic features of interest. Upon completion of the, borehole drilling and collection of information,the boreholes will be backfifled with grout,placed from the bottom to top of the borehole. Three monitoring wells will be installed using the six exploratory boreholes data to locate the wells for long term plume monitoring. The wells will 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 in fine grained and stratified depositional environments. Final well design should 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 tremic line, filling from the bottom to top of the borehole.' A traffic rated well head access box and security device will complete the well. Monitoring Well Sampling and Developrugnt All monitoring wells will be developed to remove the drilling muck,grade the sand pack and provide a more complete hydraulic connection to the aquifer. A well development log will be kept of the well volumes .removed until the water becomes clear and the amount of sand pumped is minimal. The well will be allowed to recover for at least 72 hours prior to sampling. The elevation of the casing will be surveyed to a know datum to accurately measure groundwater elevation contours. Groundwgter Sampling Each exploratory boring and the monitoring well will be sampled. The ground water samples collected from the boreholes will be used for a more rapid assessment of the site groundwater contamination and to locate the permanent wells. A brief summary of these procedures follows: Each borehole will be advanced into the aquifer and temporarily cased. The water entering the borehole will be sampled using a clean bailer, and carefully poured into the appropriate laboratory prepared container with minimum cavitation. Upon completion of the borehole sampling, the.borehole will be sealed and placed in a chilled ice chest. Each monitoring well will be purged using calculated well volumes based upon the depth to water in each casing. Depth to groundwater measurements will be made to the nearest one-one hundredth of one foot, and also checked for the presence of separate phase product. As each purge volume is removed, measurements of pH, electrical conductivity, dissolved oxygen and temperature will be taken until these parameters Page 2 J