FIELD DOCUMENTS_CASE 2 - Laserfiche WebLink

Home Browse Search

6eolo icd Tecknid Inc. e 7 Pa g g r. City of Escalon(Escalon) Project No.: 1114.2 4 September 29,2003 13. Residual Contamination Contaminate mass estimate calculations were performed to determine the possible volume of MtBE (Table 5) and diesel (Table 6) present on this site. These calculations suggest that approximately 18 gallons of diesel and 1.4 gallons of MtBE are present in the soil. Depth to groundwater is approximately 43 feet below the lowest detected contamination at the site. The calculations were prepared as follows: Diesel I. Two different soil plumes are identified at this site and are designated'primary and secondary plumes (Figure 14). Both soil plumes were assumed to resemble elliptical cylinders, which is consistent with observed conditions. 2. Contamination was detected in the primary plume between 9 and 12 feet bgs. To be conservative a seven-foot thick plume was assumed for the primary plume. 3. When the USTs were removed, the stockpiled soil was aerated at the surface for no less than four months prior to being backfilled into the excavated tank pits. However, the higher concentration level detected during the removal of the tanks is used to provide a conservative estimate. 4. The primary plume is divided into four sections, each decrease an order of magnitude from the center. • The four sections of the plume were generated using Surfer® software program. The highest contamination concentrations were used to define the Core. • Areas A, B and C were calculated using the highest concentrations determined by the software program to ensure a conservative estimate. 5. Three soil samples were analyzed from the area of the south bay hoist and the average diesel contamination was 1,830 mg/Kg. However, 3,000 mg/Kg was used in the calculations to ensure a conservative estimate. 6. The soil type for both areas resembles silts and clays. 7. It was assumed degradation of the contaminant, even with aerated stockpiled soil, does not occur. 8. The conversion factor of 1 gallon of diesel equals 6.96 pounds was used. 9. Groundwater was not impacted with diesel contamination. Depth to groundwater at the site is approximately 57 feet bgs and it is unlikely the any contamination, originating at. rthis site, will reach groundwater. MtBE 1. MtBE was detected in three soil samples collected at the site. Primarily from samples collected near the former gasoline UST known as Tank 1. -2. No MtBE was detected in the 50-foot soil borings (EZ 2-1, EZ 2-2 and EZ 2-3) or the 25-foot soil borings (B-13, B-14 and B-15). 3. The contour snap (Figure 11) was generated using the Surfer® software program. r Concentrations decrease in orders of magnitude from the center.