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r � ANDY EGGIMAN 1112 E. Harding Way. Page 2 of 3 generally higher concentrations of the analytes of concern were encountered during the April 2002 ground water monitoring event according to preliminary results faxed or verbally communicated to EHD. To date, MTBE has been detected at concentrations as high as 170 micrograms per liter (µg/1), TPH-g at 3,400 µg/I, benzene at 17 µg/1, and 1,2-DCA at 99 pg/I. To complete delineation of the vertical extent of impacted ground water, ATC proposes advancing a CPT boring through the first significant clay unit into the underlying coarse-grained unit and obtaining a grab ground water sample from the coarse-grained unit utilizing a geoprobe sampling rig. ATC anticipates the boring will be advanced to 100 feet bsg, but will go deeper if a significant clay unit has not been encountered by that depth. To complete the lateral delineation of impacted ground water and further refine the impacted soil model, -ATC proposes to advance 5 outlying soil borings utilizing hollow-stem auger drilling to collect soil samples at 5-foot intervals and to utilize a geoprobe to collect grab ground water samples from total depth (approximately 55 feet bsg). At least one soil boring, unspecified as to which, is proposed for completion as a ground water monitoring well, with other borings also converted to ground water monitoring wells if petroleum hydrocarbons have obviously impacted the sampled media. Pending procurement of an access agreement, ATC will sample the water well at the northeast corner of the state hospital, approximately 800 feet west of the subject site, for laboratory analysis as previously requested by EHD. Ground water samples and selected soil samples will be analyzed for TPH-g, BTEX and fuel oxygenates. EHD approves the work plan with the following comments: • Due to the reported geoprobe refusals on the site at depths ranging from 16 to 30 feet bsg, the technology employed to advance the proposed borings (CPT, hollow-stem augers) should also be utilized to collect ground water samples. • One of the proposed borings north of MW-2 would appear to be the most favorable to convert to a monitoring well if the boring is located in the most down-gradient position relative to MW-2. If a proposed boring is relocated to be in the most down-gradient location, the adjoining proposed boring locations should be adjusted to maintain the coverage spread shown in the work plan. • All sample analyses should include 1,2-DCA and ethylene dibromide (EDB). Please report and quantify all peaks encountered during laboratory analysis. r