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Mr. Joel Weiss <br /> August 25, 1994 <br /> Page 2 <br /> The purpose of this letter is to serve as an addendum to the workplan submitted to the <br /> Regional Board on December 17, 1993. The following Items 1 through 4 address changes <br /> and additions to the workplan which will be implemented as part of the original workplan <br /> (Items 3 and 4 have previously been addressed and agreed upon by SPTCo and the Regional <br /> Board in IC's letter dated March 16, 1994 (letter entitled: Responses to Comments on <br /> Workplan for Further Site Characterization): <br /> Item 1 SPTCo will include 9 surface soil samples for analyses of <br /> barium, cadmium, copper, mercury and zinc, using the Waste <br /> Extraction Test (WET), as defined in Title 22 of the California <br /> Code of Regulations. As described in the December 17, 1993 <br /> workplan, SPTCo will execute the WET test using deionized <br /> water as the mobilizing medium provided the soil pH is 6.0 or <br /> above, and will follow the sampling protocol outlined in the <br /> workplan. The attached Figure 2 has been revised to show the <br /> 9 surface soil sampling locations. <br /> Item 2 Based on discussions during the meeting on July 27, 1994 <br /> between yourself and Mr. Jim Tjosvold (DTSC), soil lead <br /> cleanup levels protective of human health have not been <br /> finalized. Soil lead levels protective of ground water, however, <br /> have been accepted by your office, at a level of 500 mg/kg. In <br /> an effort to expedite site remediation, SPTCo proposes to <br /> proceed with soil excavation at the site, so that the remaining <br /> mean soil lead concentration does not exceed 500 mg/kg. <br /> SPTCo proposes using the mean soil concentration, since <br /> individual soil sample results can misrepresent the true <br /> characteristics of soils surrounding the sampling location. On <br /> the other hand, a gross calculation of mean soil concentration <br /> can overlook localized "hot spots" of soil lead levels. To <br /> correct for gross mean calculations, SPTCo proposes to <br /> calculate the mean soil concentration based upon three adjacent <br /> confirmation soil sample locations from the same sampling depth <br /> range. The mean concentration from any three adjacent <br /> excavation confirmation samples shall not exceed 500 mg/kg. <br /> tracy274.I V/08-25-94/u/cwilWtracy/letters <br />