ARCHIVED REPORTS XR0010941 - Laserfiche WebLink

Home Browse Search

is an analysis for total recoverable metals. STLC (Soluble Threshold Limit Concentration) extraction is an extraction for soluble metals. It usually gives a number 10 times lower than the TTLC value. None of the samples analyzed for Ni and Cr exceeded the TTLC Criteria for these elements and Ni and Cr were reported below detection limits in the STLC extraction run on Sample D-5-10. 1 6.0 Site Assessment Conclusions Based on the assessment results, a interpretation of the extent of contamination was developed. The maximum limits of significantly impacted soils is depicted on Exhibit 3, whereas, the vertical dimension of the plume is best shown on the Cross Section, Exhibit 5. Only Boring D-1 , drilled at the suspected point of origin of the diesel release at the north end of the present excavation, encountered impacted soils. Hydrocarbons were evident from 13 feet to a depth of 33 feet, although staining was present in the wall of the excavation 5 feet from the surface. The highest concentration of 4100 ppm TPH(diesel) occurred at 23 feet, which also appeared to be the most impacted horizon based on field observations. The sample at 33 feet was found to contain 410 ppm i TPH(diesel). No hydrocarbons were evident below that depth. No benzene was detected by the laboratory and the other aromatics were present at low concentrations (below 7.9 ppm) No hydrocarbons were detected in the three borings drilled to define the lateral margins of the plume. These were drilled 15 to 25 feet from the north edge of the excavation. Assuming the migration of the diesel fuel occurred uniformly from the spill point, the radial dimension of the plume from the stained area at the north end of the excavation is estimated to be 10 to 15 feet. As interpreted on Exhibit 3, an area estimated between 300 to 550 sq. ft is impacted. The maximum vertical extent of detectable hydrocarbons is approximately 35 feet. Regarding the former waste oil tank site, there is no evidence of hydrocarbons, PCBs or heavy metal concentrations in excess of regulatory limits. The concentration of Ni and Cr in this area were found to be well below the TTLC and STLC concentrations necessary to create a hazardous waste. The primary focus of regulatory concern in matters involving hydrocarbon releases into the environment is protection of groundwater resources. To evaluate risks to groundwater, the Leaking Underground Fuel Tank (LUFT) Manual, which provides regulatory agencies and consultants guidelines for the conduct of site investigations and evaluation of risks, particularly to groundwater, was consulted. A Leaching Potential for Gasoline and Diesel Using Total Petroleum Hydrocarbons (TPH) is presented in this document. It uses information on the site's characteristics (soils, 10