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30 May 2000 AGE-NC Project No. 97-0372 Page 7 of 17 preparation activities are not currently known to AGE, but may have included cutting and etching of materials. Potential contaminants of concern would include metals and corrosive pH disposed down the drain. 2.4.5. Miscellaneous and Tank Storage Areas The asphalt-paved area east of the building was utilized for above-ground tank storage of treated waste water. A release of untreated, or contaminated water from a polyvinyl tank in the driveway near the building resulted in excavation of soil. An oval area approximately 8 feet wide and 42 feet long was excavated, as shown on Figure 2. There is a shallow pit or open boring in the area that was a shallow sump for the release valve on the poly tank. The shallow pit is also shown on Figure 2. 2.5. PREVIOUS INVESTIGATIONS On 25 September 1997, at the request of Mr. John Hinkel, AGE advanced eight soil boring on the site to assess soil samples for pH, chromium, copper and zinc. Four borings were advanced in the eastern portion of the plating bath area and four borings were advanced in the treatment/chemical storage area, as shown on Figure 2. Soil samples were collected from depths of 2 feet and 5 feet below surface grade(bsg) in each of the eight borings. The borings were reentered on 24 May 1999 to collect additional soil samples at approximately 6 feet bsg for analysis for lead. The borings were advanced by hand-augering through holes cut in the concrete-flooring. The samples were collected utilizing a hammer-driven metric soil sampler loaded with pre-cleaned brass sleeves. The samples were properly preserved and shipped to a California Department of Health Services (DHS)-certified analytical laboratory under chain-of-custody. The results of the analysis are presented in Table 1. The pH of the soil samples ranged from 6.7 to 9.0 except for two samples from boring B7, which had pH values of 4.5 and 3.6 at 2 feet bsg and 5 feet bsg, respectively. Chromium concentrations ranged from 18 milligrams per kilogram (mg/kg) to 69 mg/kg. Copper concentrations ranged from 27 mg/kg to 60 mg/kg, except for the samples from boring B7 with 780 mg/kg copper at 2 feet bsg and 380 mg/kg at 5 feet bsg. Zinc concentrations ranged from 40 mg/kg to 485 mg/kg. Lead concentrations for soil samples collected at approximately 6 feet bsg ranged from 6.9 mg/kg to 9.6 mg/kg, except for the 6-foot sample from B7, which contained 110 mg/kg (samples from 2 feet bsg and 5 feet bsg were not analyzed for lead). The data is suggestive of an impact to the subsurface soil in the area of boring B7, which was advanced next to a small, circular, cement-filled sump in the eastern plating area. Samples from B7 had lowered pH and elevated concentrations of copper and lead. The pH levels of 6.7 and 6.8 in the 2-foot bsg samples from B6 and B8 may be within the normal range of soil pH for the area, but may Advanced GcoEnvlronmental,Inc