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Margaret Lagorio September 16,2008 CONESTOGA-ROVERS &ASSOCIATES A typical well..construction diagram is presented as Figure 3. Actual well installation details will be based on drilling conditions encountered during drilling. Soil Sample Analysis Soil samples from the borings will be submitted for chemical analysis based on photo-ionization detector readings, visual and olfactory observations, and-at the soil water interface in each boring. At a minimum soil samples will be submitted for chemical analysis at 10 foot intervals. Well MW-8 Screen Interval The proposed screen interval for well MW-8 was based on the,screen.interval for onsite deep well MW-7. CRA agrees with SJCEHD staff that well MW-8 should be-screened in permeable material if present and if it provides groundwater data from a deeper water bearing zone. Well MW-8 will be located near existing well MW-S. As shown on the-boring log presented in Attachment A, well MW-5 is screened from 60 to 75 feet below grade (fbg). Sand (SM and SP) was observed in this boring from approximately 67.5 to 75 fbg. It is unknown what depth the sand layer in this area extends to: The soil types observed in boring'MW-7 (Figure 4 and Attachment A) show that a sand layer extends from approximately 67.5 to 87.5 fbg in the northern corner of the site. As shown on Figures 4 and 5, the sand layer does not appear to be continuous beneath the site. -However,this sand interval does appear to be at least partially present in boring MW-5. If similar soil types are observed in boring MW-8 as in MW-5 and MW-7 and if the screen is set at the bottom of this sand layer in boring N4W-8, the well may be monitoring the same water bearing zone as shallow zone well MW-5 which may not serve the intended purpose of a deeper zone well in this area. However, as 1,2-dichloroethane (1 2-DCA) is a constituent of concern in well MW-5, and 1,2-DCA is a "sinker," a deeper screened well in the sand layer may be appropriate. Until soil types in soil boring MW-8 are confirmed, the actual screen interval in proposed well MW-8 cannot be determined. CRA will determine the screen interval based on soil types observedduring_ drilling. CRA will discuss the proposed screen interval with,and will obtain SJCEHD staff approval,prior to constructing Well MW-8. Waste Disposal Soil generated during drilling will be stored in 55-gallon drums or on, and covered with,plastic sheeting. Water generated during drilling will be stored in 55-gallon drums. Soil and groundwater will be profiled for disposal according to disposal facility requirements. Upon approval, the waste material(s) will be transported to the selected disposal facility. 1359 2 Worldwide Engineering, Environmental,Construction,and IT Services - I