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Former Lexington School STS Project #95192-XF Table I Summary of Soil Sample Analysis Parameter Units . Target Detection Limit S-I* Benzene Toluene Ethylbenzene Xylenes mg/kg mg/kg mg/kg mg/kg 0.06 0.11 0.05 0.28 < 0.06 < 0.11 < 0.05 < 0.28 Total hydrocarbons as fuel oil mg/kg 1.4 < 1.4 HNU reading HNU Units o mg/kg = parts per million = ppm * 2 feet below middle of tank Site Reconstruction Backfilling commenced upon completion of soil excavation. Backfill material was a mixture of on-site clayey materials and imported sand material. Backfill was mechanically com- pacted as it was placed in the excavation. Field density tests were performed on the backfill material to assure that compaction, as specified in the project specifications. was met. Some areas did not meet the specified compaction upon initial testing. These areas were re-excavated and re-compacted to meet specifications. Nuclear density and sand cone tests were conducted to confirm compaction of the backfill material. Nuclear density tests were performed with a Troxler Model 3411-B nuclear density gauge. The nuclear density gauge is an electronic device containing a small amount of radioactive material used to measure the density and moisture content of soils. Density measurements are related to the number of gamma rays that are detected after being trans- mitted through the test material. The higher the number of detected rays in a fixed period of time. the less dense is the material being tested. Moisture content is determined by the number of neutrons that are deflected by collisions with hydrogen (water). The higher - 5 -