ARCHIVED REPORTS_XR0004042 - Laserfiche WebLink

Home Browse Search

Clutogkof Teekn"t". Page 10 Sinclair Trucking Project No.: 1030.2 August 11,2005 2.8.3 Soil Sample Results Below is a summary of the findings for MW-1R installed and sampled on March 11, 2005: • 7 ft: Non-detect above laboratory reporting limits for all analyzed constituents. ' • 10 ft: Trace levels of benzene were detected. The sample from this depth was non- detect above laboratory reporting limits for all other analyzed constituents. ' • 12 ft: Low levels of ethylbenzene, total xylenes and TPH-G were detected. The sample from this depth was non-detect above laboratory reporting limits for all other analyzed constituents. ' 2.8.4 Monitoring Well Survey On June 23, 2005, GTI and Thompson-Hysell Engineering (Licensed Land Surveyor #6953) ' personnel arrived on-site to survey the new monitoring well (MW-1R) as required under and in accordance with the guidelines outlined in AB-2886. The surveyors report is attached as Appendix E. ' The location (xy) data and elevation (z) data were submitted to GeoTracker on August 4, 2005. Confirmation numbers are 5363050699 and 2905349552, respectively. ' 3.0 CONTAMINANT MASS ESTIMATE CALCULATIONS Original mass balance calculations, discussed in GTI's: Initial Site Conceptual Model dated June 18, 2003, indicated as much as 3,400 pounds of TPH-G is bound to the soil at the ' Sinclair site. Mass estimate calculations generated after the soil excavation activities suggest there is approximately 748 pounds of TPH-G remaining in the soil. The calculations suggest that the excavation activities removed approximately 80% of the soil contamination. The ' mass balance calculations are summarized in Table 4 of Appendix A. The following summarizes the data and assumptions used in the mass balance estimates: ' • Figure 5 shows contours of TPH-G concentrations generated using soil data gathered from sidewall soil samples and new well installation soil samples. The contours were generated by importing analytical results from the sidewall and well installation soil ' samples into Surfer 7.00 contour generating software. Bold lines indicate the separation of the two selected zones; the core and the ring. • The heaviest contamination is found in an area of approximately 300-ft2 near the former ' UST. This 300-ft2 area is called the core and an average concentration of 1,250 mg/Kg was used to calculate the mass in the core. • The area between the non-detect and the 800 mg/Kg contours is approximately 3,000-ft2 and is called the ring. The largest portion of the ring lies between the.non-detect and the Z g000— 200 mg/Kg contour lines. To be conservative'250�g/Kg was used to calculate the mass in the ring. • The thickness of the TPH-G contamination is assumed to be 7-feet, primarily occupying the depths between 7 and 14 feet bgs. Groundwater depth at the time of this work was 1