SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

i 4648 Waterloo Road Page 2 IT Until it can be demonstrated that vapor extraction is the most efficient remedial alternative for soil cleanup, PHSIEHD cannot concur with the recommendation to perform vapor extraction that was presented within the revised CAP. The revised CAP indicated that costs of excavation,treatment and disposal and backfilling would range between $80 to$120 per cubic yard. If the excavation is extended to 30 feet bgs more than 50%of the contamination soil would be remediated based on the petroleum mass distribution. Excavation of a volume of soil with the dimensions of 30 feet deep,20 feet wide and 20 feet long would remove approximately 445 cubic yards of soil for an estimated cost of$44,500. Since the average concentration of the remaining contaminatioriI before remediation is 1.1 ppm TPH-gas, it is unlikely that vapor extraction would be considered effective to remediate the remaining mass of petroleum hydrocarbons. If additional remediation is necessary following.excavation,natural attenuation and the assoicated costs for additional soil sampling to monitor remediation rates,"may appear more feasible. The revised CAP indicated that if air sparge is selected as a groundwater remedial activity than a vapor extraction system must be installed as well. An alternative methodology for the introduction of oxygen into the groundwater is biosparging. Biosparging does not require the operation of a vapor extraction system because the introduction rate is much lower and rather than stripping the contaminated groundwater as with airsparging, biosparging enhances the natural biodegradation rate that is occurring at the site. In either case it is important that Iron 11 concentrations be ascertained because the introduction of oxygen causes the oxidation of Iron I1 to Iron III which is insoluble and forms a precipitate that interferes with the migration of oxygen from the sparging:'well. Since air sparging was.the selected alternative and critical information was not available for PHS/EHD to determine its cost and technical feasibility, PHS/EHD cannot concur with the recommendation to perform air sparging. Please perform the necessary analysis to evaluate the site's potential to undergo groundwaterremediation using sparging technology. Please submit the additional information which has been requested for compliance with the corrective action requirements of the Underground Storage Tank Regulations. If you have an questions or comments, lease contact me at 209 468-03"7. Y any P � ) 3 Donna Heran, RENS, Director Environmental Health Division i; ! F Mary Meays, Senior REHS Margare agorio, REHS Site Mitigation Unit Supervisor;', 'I cc: Elizabeth Thayer, Central Valley Regional Water Quality Control!Board;. cc: Ismael Jacabo, State Water Resources Control Board,Cleanup Fund Unit �r cc: Tim Cuellar,Advanced GeoEnvironmental d j ' J j e