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Jerry Ule Page 3 March 3, 2005 5) Add SV-6 under the building in location of SV-9 on Figure 2 of the July 14, 2004 HRA. Follow DTSC guidance of stepping out if refusal of hand auger is encountered. 6) Add SW in the vicinity of SV-4 and SV-7 on Figure 2 of the July 14,2004 HRA, g. Collect samples not only from 5 ft, but also at or just above the capillary fringe for SV-2, SV-6, and SV-7. h. Collect soil geotechnical parameters for use in indoor air modeling from all samples. Analyze samples from SV-2, SV-4, SV-5,and SV-6. Hold samples from SV-3 and SV-5; analyze if SV-2 results are not consistent with results from SV-12 in the July 14, 2004 HRA. i. Include all sample boring logs In the baseline report. 3. Undeveloped area of L& M OU a_ The vapor barrier Installed Is not sufficient to prevent future building vapor intrusion (DTSC, 2004). Some examples follow. 1) The impermeable barrier installed above the SVE system horizontal wells is 30 milliliters thick high density polyethylene (HDPE), whereas DTSC guidance (DTSC.2004)calls for 60 mil HDPE). 2) At feast two Inches of protective layering (sand and/or geotextile)above and below the membrane are needed (DTSC,2004). 3) Leak testing with smoke is required (DTSC, 2004). b. Many data gaps exist,some of which may have been filled by confirmation sampling during excavation and SVE installation prior to backfilling. Evaluation of these data and deciphering remaining data gaps is not feasible within the time frame allotted for reviewing this work plan prior to SVE start up, c. HERD recommends addressing the L&M OU as two areas of concern(ADCs),to expedite risk evaluations In the apartments'area. One AOC being the Delta View Apartments (the apartments'area)and the second AOC being the undeveloped area. d. VOC sampling at the perimeters of the barriers and above and below the barriers from areas of high pre-or post-excavation VOC concentrations Is recommended for monitoring the SVE system. 0503D=,doc