ARCHIVED REPORTS_XR0012452 - Laserfiche WebLink

Home Browse Search

lie 16 January 2003 AGE-NC Project No. 98-0450 ' Page 5 of 8 ' 3.1. ANALYTICAL RESULTS OF CONFIRMATION SOIL SAMPLES Petroleum hydrocarbons were detected only in confirmation soil samples collected from boring CB 1, ' in the former UST area. TPH-g was detected in one soil sample(CB1-35) at a concentration of 580 milligrams per kilogram (mg/kg). TPH-d was detected in three soil samples at a maximum concentration of 800 mg/kg(CB 1-35). TBA was detected in two soil samples,CBI-25 and CBI-30, ' at concentrations of 260 microgram per kilogram (pg/kg) and 590 µg/kg, respectively. No other target analytes were detected in the samples analyzed.Confirmation soil sample analytical ' results are summarized in Table 2.The laboratory report(MAI Lab ID 0210505), quality assurance and quality control (QA/QC) and chain-of-custody are included in Appendix B. ' 3.2. RELATIVE GROUND WATER ELEVATION AND GRADIENT The depths to ground water from the tops of the monitoring well casings were measured at 49.53 to 50.60 feet bsg. The ground water elevations ranged from 4.85 feet below mean sea level (MSL) in well MW-5 to 4.43 feet below MSL in MW-4(Table 1); ground water elevation had increased an ' average of 3 feet at the site since the previous quarterly monitoring event. The ground water flow direction was inferred to be southwest to south-southwest at a hydraulic gradient of approximately ' 0.003 ft/ft (Figure 3). Table 1 lists the screen intervals for monitoring wells BMW-1 through BMW-5 and MW-5 and the ' assumed screen intervals for monitoring wells BMW-1 and BMW-2. With the exception of MW-5, the wells were screened across the ground water table; laboratory analytical results obtained from these wells should be representative of the dissolved hydrocarbon concentrations in the shallow ' ground water. ' 3.3. LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-g and TPH-d were detected in two ground water samples collected at the site,at concentrations ' of 1,300 micrograms per liter(µg/1)and 3,500 ptg/l,respectively,in sample MW-4 at the former UST area and 170µg11 and 130µg11,respectively,in sample MW-5 at the down-gradient edge of the site. Benzene was not-detected in the samples analyzed; the other BTEX compounds were detected at --- various concentrations with the highest concentrations'occurring in BMW-4 (17 µg/l of toluene). MTBE was detected in samples BMW-2 and MW-5 by EPA method 8260 Modified at concentrations of 5.7 gg/1 and 45 µg/l,respectively. In addition,TBA was detected in sample MW-5 ' at a concentration of 11 gg/l. Advanced GeoEnvironmental,Inc. 1