SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Section 1.2.6.2, Pages 1-9 and 1-10 First Bullet Item, Paragraph 2 Though the "sand" unit may be more transmissive, the interpretation by Ms. Bice that the aquifer is 1 to 3 feet thick, is incorrect. The aquifer in this area is not an isolated sand lens sandwiched between two less permeable layers, rather, the aquifer exists within a soil horizon which has interbedded sands, silts, and clays. The interpretation that the sand is a confined aquifer overlooks the description of the materials beneath the site which have been presented in several of the boring logs. Whether the silty sand lenses are shown in the boring logs as discrete layers, or interbedded with silts and clays, the soils beneath the site are interbedded, the aquifer water table is approximately 10 feet below grade, and is not constrained within the "sand" unit as described by Ms. Bice. First Bullet Item, Paragraph 3 The calculation of drawdown presented assumes the aquifer is confined. The aquifer may have lenses which are confined, but the aquifer as a whole is unconfined. If unconfined corrections are made to the calculations, drawdown values will again be within those observed in the field. First Bullet Item, Paragraph 4 The aquifer thickness used by Alton Geoscience is the amount of aquifer that the wells are screened through. Field observations made during installation of the monitoring wells do not suggest that water is confined within a 1 foot to 3 feet thick "sand" lens. The aquifer is not the lower sand unit. First, there is more than one "sand" lens that is described in the boring logs, second, the sand is described as a silty sand, and third, as discussed above, the aquifer is more likely interbedded sand, silts, and clays, and not an isolated sand layer 1 foot to 3 feet thick, 14 to 18 fbg, as shown in typical boring logs. Section 1.2.7.1., Page 1-10 The areal extent of the excavation was defined, to the north and west, not by property boundaries, but to the north by Grantline Road, and to the west by public utilities. Once again, it must be noted here that the Alton Geoscience work plan for Subsurface Investigation and Soil Remediation was approved by the SJC PHSIEHD. Extensive time, effort, and expense have been invested by Mobil Oil Corporation to investigate the possibility for offsite migration, the results of which suggest that soil and ground water contamination has not crossed, and has a low potential to cross, Grantline Road in the downgradient direction. Geomatrix states that "there is no documentation of the areal extent of contamination, and no documentation that all of the high concentrations of hydrocarbons were removed. " Alton 8