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r <br /> Mr. Paul Supple <br /> Arco Station No. 6100 <br /> 25775 Patterson Pass Road <br /> Page 2 of 2 <br /> In the 15 October 2002 work plan (WP), Delta proposes to advance four soil borings to <br /> approximately 150 feet bsg utilizing mud-rotary drilling to obtain continuous soil core <br /> samples to identify Sand 2 and augment the geological model. Monitoring wells will be <br /> installed in borings advanced by hollow stem auger drilling adjacent to the exploratory <br /> borings. The monitoring wells will be completed in Sand 2, advancing approximately 10 <br /> feet into the underlying silt unit. The purpose for the monitoring wells is to delineate and <br /> characterize free product and/or impacted ground water toward the southeast. <br /> The WP also proposes to destroy vapor well VW-15, as the well is obstructed, by <br /> overdrilling to its total depth and backfilling to surface grade with neat cement. Free <br /> produce removal from MW-1 will continue on a weekly basis. A work plan to complete <br /> the soil vapor extraction system and initiate operation is in preparation. <br /> EHD approves the proposed work as necessary and adequate to continue corrective <br /> action for the site. Please submit all necessary access agreements, encroachment <br /> permits and well permit application forms with required fees to EHD. A well permit <br /> application form and $89 fee are required for each parcel and a well permit application <br /> form with a $60 fee are required for the well destruction permit. Contact EHD a minimum <br /> of 48 hours prior to initiation of field work and submit a report of findings within 60 days <br /> of completion of field work. <br /> In addition to the approved work, EHD requests that all monitoring and vapor wells that <br /> are not routinely sampled, but that contain measurable water be sampled once for <br /> laboratory analysis over the next two quarterly monitoring events. This is not anticipated <br /> to be part of the normal monitoring regimen at the site, but may be useful to <br /> conceptualize the distribution and migration pathways for the contaminants in the <br /> subsurface. During the next monitoring event, all such wells should be purged; those <br /> that recharge sufficiently to be sampled should be sampled during that event, the more <br /> slowly recharging wells can be sampled during the following monitoring event without <br /> prior purging. The samples should be analyzed for the same suite of analytes as the <br /> more routinely acquired samples. <br /> Questions or comments may be directed to Nuel Henderson by telephone at <br /> (209)468-3436, by e-mail at nhenderson@sjcehd.com, or by mail (address on letter <br /> head). <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Nuel C. Henderson, Jr., R.G. <br /> Unit IV- Site Mitigation <br /> cc: James L. L. Barton — CVRWQCB <br /> Steven Carter- Stratus <br />