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04/08/2008 15:82 FAX 209 9480`8" � 11008 Page 2 of 3 Del Monte 1003-69V-0115 Longitudinal Encroachment Exception The Longitudinal Encroachment Exception is submitted for your review and consideration for approval. It involves a request from Kleinfelder, Inc. to install four ozone sparging wells on the northern shoulder of the eastbound on-ramp to State Highway 4 (Crosstown Freeway in Stockton). The depth of the wells will be approximately 140 feet with sparge points at 90, 60, and 30 feet below groundwater. The sparging wells will be connected by a 2" High Density Polyethylene (HDPE) plumbed line that will be drilled Horizontal Directional Drilling (NIDD) under the on-ramp (to miniinisurface disturbance). The ozone conveyed to the four sparging wells will be located north of the wells (outside Caltrans right of way), it will be conveyed through 2"HDPE plumbed piping under State Highway 4(HDD)to the respective wells. The source area (former underground fuel storage tanks) for the contamination lies north of the ozone sparging wells and the freeway, at a former gasoline station. Concentradous of TPH-g, benzene, toluene, ethylbenzene, xylene (BTE3 ), MTBE, and 1,2-DCA are currently being monitored in the surrounding area(including the northern shoulder on-ramp). The groundwater flow is to the south, with the leading edge of the plume located near the State Highway 4 on- ramp. The installation of the sparging wells will be conducted on the eastbound on-ramp to State I-Tighway 4(Filbert Street) in Stockton in San Joaquin County. The limits for the project begin at the west end of the on-ramp and and approximately 350 feet to the east towards State Highway 4. This portion of the project is expected to cost approximately $50,000. (of which none of the finding is expected to be government-derived). There are 5 projects listed in the District 10 Status of Projects. This encroachment will not impact these projects. An exception is being requested based upon the requirements by Caltrans due to the project falling within the longitudinal encroachment of the access control of State Highway 4. The locations for the ozone sperging wells and the existing groundwater monitoring wells were chosen based primarily upon the location of the groundwater gradiem,and the concentrations of contaminants in the area It is Kleinfelder's opinion that the location chosen for the ozone sparging wells will have the greatest impact on mitigating the southern edge of the plume. Alternative locations for the wells were not chosen based upon the location of the trace levels of comamirmts, and access. Kleinfelder will maintain the ozone sparging wells on a monthly basis (pressumlleak checks); traffic control procedures outlined by Caltrans will be utilized. The esgmated costs of this portion of the project are associated with driller fees in boring the wells, and setting the sparge points at 30, 60, and 90 fiat Slliug the well with bentonite and grout, plumbing each well together, and setting traffic-rated vaults. Kleinfelder will be taking water samples 4 times per year for approximately 3 years. It is anticipated that the contaminants will be remedied by that time. It is not practical and feasible to acquire temporary access/easement from the private property located along the eastbound on ramp. The predominant benefit of this project, which is overseen by the Regional Water Quality Control Board and the San Joaquin County Department of Environmental Health, is to prevent the finther migration of contaminant in the groundwater. If an exception is denied, then the affected groundwater will continue to migrate south of Route 4,unchecked. Wca&CM improves mobft aaass Coafbr='