SITE INFORMATION AND CORRESPONDENCE

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Delta Truck Sales -2- 11 October 1989 establish locations for verification sampling beneath the former impoundments. d. Document sampling locations in the excavation and the soil stockpiles. A baseline should be established in the field from which future sampling locations can easily be located. 2. A quality assurance plan should be implemented which includes collection and analysis of duplicate samples. 3. A physical description of samples should be included in the final report. This should note the apparent degree of contamination with oily waste, grain size distribution of the sample (from field observations) , color, and other pertinent information. 4. The work plan should describe how samples with significant amounts of gravels or cobbles will be prepared for analysis. SUGGESTIONS FOR DETERMINING EXTENT OF FURTHER EXCAVATION We feel additional tasks should be considered for implementation at this time in order to guide further excavation of impacted soils at the site. 1 . Verification sampling of excavated areas should be conducted to determine if the vertical extent of excavation is sufficient. 2. Sidewalls determined to be at the location of the filled impoundment should be sampled to determine the extent of excavation on either side and below the former impoundment. Samples should be analyzed for total petroleum hydrocarbons. 3. The fill material which was a potential pathway for the contaminants should be sampled to determine if further lateral excavation is needed. 4. As stated above, the boundaries of the surface impoundment as determined from aerial photographs should be located in the field using land surveying techniques. Verification sampling should be conducted beneath the former impoundments located with this technique. NATURE OF FILL MATERIAL ADJACENT TO THE FORMER SURFACE IMPOUNDMENT During excavation of the backfilled surface impoundment debris was uncovered in adjacent areas of the subsurface. This debris was apparently waste generated by former owners of the site. Besides providing a pathway for contaminants, there is a possibility that the material itself poses a threat to water quality. In order to determine whether chemical characterization of the debris is needed we reqest you submit a description of the source of the debris, and the history of waste disposal to the areas adjacent to the surface impoundment.