2004-03-02_REVISION - M1978056 - Laserfiche WebLink

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Soil Remediation Report and Treatment Plan Vaasa Companies, Inc. Durham Pit 117 Greeley, Colorado Sample Analysis February 12, 2004 Page 3 of 8 Soil samples were submitted to Technology Laboratories, Inc. (Techlab) of Fort Collins, Colorado for analysis to determine concentrations of benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA method 8260B and total petroleum hydrocazbon diesel range organics (TPH-DRO) by EPA method 8015B. Soil laboratory analysis data is summazized in Table 1 and depicted on Figwe 3. Laboratory Analysis reports and chain-of- custody documentation is provided in Attachment B. Review of Table 1 shows hydrocazbon concentration ranges in the sidewall soil samples included benzene at <0.002 to 0.017 mg/Kg, toluene at 0.0096 to 0.0886 mg/Kg, ethylbenzene at <0.002 to 0.0328, xylenes at 0.0051 to 0.112 mg/Kg and TPH-DRO at <10 to 98.8 mg/Kg. No BTEX concentrations were detected in the excavation bottom samples and TPH-DRO was only detected in one soil sample, sample B-2 at 15.1 mg/Kg.. Review of the stockpile soil analytical data shows TPH-DRO concentrations ranging from ],854 to 6,667 mg/Kg. The sample exhibiting the highest TPH-DRO concentration (SP-1) was also analyzed for BTEX. Concentrations reported included benzene at 0.005 mg/Kg, toluene at 0.021 mg/Kg, no detectable ethylbenzene and xylenes at 2.51 mg/Kg. Data Evaluation: Hydrocarbon concentrations in the confnmation soil samples were compared to the OPS Guidance Document Tier 1 Risk Based Screening Levels (RBSLs). Based on the site chazacteristics, subsurface soil leachate to groundwater ingestion exposure pathway is considered the most significant potential exposwe threat. Tier 1 RBSL target cleanup levels for this exposure pathway aze the most stringent and include concentrations of benzene at 0.26 mg/Kg, toluene at 170 mg/Kg, ethylbenzene at 200 mg/Kg and xylenes at 1,900 mg/Kg. The tazget cleanup level for total petroleum hydrocarbons (TPH) is a threshold value of 500 mg/Kg. Review of the confirmation soil sample analytical data documents that soil excavation activities effectively removed the petroleum hydrocazbon impacted soil to concentrations below the tazget cleanup levels and the vertical and horizontal extent of petroleum hydrocazbons has been defined to concentrations below the Tier I RBSLs and 500 mg/Kg TPH threshold value. Groundwater was not encountered in the excavation and no BTEX compounds were present in the samples obtained from the bottom of the excavation. TPH-DRO was detected in one of the three bottom samples at 15.1 mglKg, which is well below the 500 mg/Kg tazget cleanup level. As such, soil analytical data indicate groundwater was not affected by the release. Petroleum Contaminated Soil Treatment Plan: The corrective acfion plan proposed for the petroleum contaminated soil excavated from the fuel depot is on- cite rnmT~t inrem Pdiatinn ieatment S.p rp ifir,atinnc ~'nr ihr nn-c+tr trratmrnt nl•rn are ac fnllnwc• ,_ _ • A bioremediation treatment cell will be constructed in an inactive location within the Varra facility with dimensions of approximately 100-ft x 100-ft. The cell azea will be excavated to a depth of approximately 12-inches. Polyethylene sheeting will be placed across the base of the azea to prevent leaching to the underlying soil and covered with approximately 12-inches of compacted fill. A 12 to 18-inch containment berm will be constructed azound the perimeter of the cell to prevent precipitation runoff. • Soil to be treated will be blended with a 25% to 30% by volume mixtwe of cow manure and compost. Blending of the material will be performed using available on-site earth moving and soil processing equipment. The blended soil will be transported to the treatment cell and thin spread in 12 to 18-inch lifts. • Soil in the treatment cell will be tilled on a weekly to bi-weekly bases. During treatment water will be applied as needed to maintain moisture content above 10%. Soil pH will be monitored periodically. To