SITE INFORMATION AND CORRESPONDENCE

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Mr. Joel Weiss February 15, 1996 Page 4 a minimum of 95 percent of the treated soil is below the soluble threshold limit concentration for lead of 5 mg/L. * Place and compact the treated soil in the bottom portion of the excavated areas on the site. Some portion or all of the waste concrete presently piled on site may be crushed and mixed with the treated soil during backfilling. Backfill will be placed in maximum 12 to 18 inch uncompacted lifts. Water will be added, if necessary, to achieve approximate optimum moisture content. Compaction will consist of a minimum of three passes with a sheepsfoot roller or other appropriate compaction device. No compaction testing will be performed, however, it is anticipated that the compactive effort planned will be sufficient to achieve a dry density of the compacted soil that is at least 90 percent of its maximum dry density. The compaction technique may be modified based on observations by a Terranext field representative if compactive effort is deemed unsuitable. * Import suitable clean backfill to place in the upper portion of all excavated areas on site. Imported backfill will be free of expansive clays, debris or other geotechnically unsuitable material. Analytical test results will be requested to document that the fill material is not impacted with hydrocarbons and that metals, especially lead, are within normal background ranges for the region. Given the amount of impacted soil shipped offsite, it is estimated that approximately 1 foot of compacted clean backfill will overlay treated soil in all of the excavated areas. The imported backfill will be placed and compacted as described above. To assist in your evaluation of this modified remedial program, Table 1 (attached) lists analytical results for soluble lead (WET with deionized water leach) for composite samples taken from the sidewalls and floors of excavated areas and composite samples taken from the remaining sidewall areas with lead-impacted soil (total lead greater than 220 mg/kg). Analytical results from the excavated areas show residual soluble lead concentrations ranging from nondetect (less than 0.0050 mg/L) to 0.2 mg/L. The arithmetic average of all samples from excavated areas is 0.027 mg/L. The standard deviation of these data is 0.039 mg/L. Analytical results from the remaining sidewalls with lead-impacted soil show soluble lead concentrations ranging from nondetect to 0.89 mg/L. The arithmetic average of the seven sidewall samples is 0.20 mg/L. The standard deviation of these data is 0.31 mg/L. 469-022.Itr/02-15-96/u/kevdata/oldtracy/letters TerraNext