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ROM Fi]e No. 070.2 19 December 1991 Page 13 and disposal of the carbonicarbon filters (maintenanee of the system). However, this treatment alternative could be viable for relatively small 1 remediation projects, such as the Rainbo Bakery. i 5.2.4 Groundwater Extraction and Physical Treatment - Vapor Phase Carbon Adsoption This groundwater treatment alternative first requires the extraction of the contaminated groundwater from the aquifer via a groundwater extraction system. 'fie contaminants are Cher- transferred to the vapor phase (transferred from a liquid medium to a vapor medium) by running air currents though the contaminated groundwater. The treated groundwater is then discharged. The air, now hosting the contaminants, is then either 1) released directly to the atmosphere, or 2) passed through activated carbon filters where the contaminants adsorb to the carbon. If carbon j filters are utilized, disposal of the spent carbon filters would be necessary, as with the previously discussed treatment alternative. Limits on the direct release of contaminated air to the atmosphere are enforced by local Air Pollution Control Districts. Obtaining a permit to release the contaminated air directly to the atmosphere may be difficult (Proceedings of Petroleum Hydrocarbon and Organic Chemicals in Ground Water: Prevention, Detection and Restoration, 1988). Even utilizing activated carbon filters with this treatment alternative still results in the release of some air emissions to the atmosphere. Since this method ultimately produces air emissions, it is subject to restrictions and permitting processes of the local Air Pollution Control District. Due to this constraint, we do not recommend this treatment alternative for the Rain bo Bakery site. 5.3 Disposal of Treated Groundwater Following treatment of the contaminated groundwater via one of the above-described treatment alternatives, the groundwater is then discarded. Tile easiest and least costly method of discarding the treated groundwater would be to directly discharge it to the sanitary sewer system or the storm drain system. During our investigation, we researched the possibility of direct disposal of the treated groundwater to both the sanitary sewer system and the storm drain system. As of June 1991, the Stockton Municipal Utilities District no longer would allow discharge of groundwater, whether treated or not, to the Stockton sanitary sewer system. We contacted the Regional Water Quality Control Board concerning their restrictions for discharge to the storm drain system. The RWQCB indicated that a waste disposal permit must be obtained prior to discharge. Each site is assessed on an individual basis as to whether a Waste Disposal permit will be issued. According to the RWQCB, evaluation of Lhe permit is usually a lengthy and potentially costly process. Additionally, upon assessment, the RWQCB may chose to deny the permit. ANDERSON CONSULTING GROUP F