WORK PLANS - Laserfiche WebLink

Home Browse Search

Supplemental Information Report Of Waste Discharge 8200 N. Highway 99,Stockton, CA Page 2 of 6 6. The treatment system will be monitored pursuant to Monitoring and Reporting Program for Order No. R5-2003-0044, General Order for Land Disposal of Groundwater and Surface Water from Cleanup of Petroleum Fuel Pollution, which includes monthly influent and effluent sampling for constituents listed in the General Order (attached). In addition, samples will be collected from the treatment system influent, effluent, and between GAC units on a weekly basis during the first four weeks of operation to monitor the potential for contaminant break through between GAC units. The samples will be analyzed by a State- certified analytical laboratory on a 48-hour turnaround. Samples will be analyzed for TPHg, BTEX, and oxygenated gasoline additives, including MTBE, using appropriate methods. 7. A data table showing historical results of all site monitoring wells, including the proposed extraction well MWI, are attached. The most recent sample collected from the well MWI in June 2003 was analyzed for TPHg by EPA method 801513, BTEX by EPA method 802113, and for oxygenated gasoline additives, including MTBE, EDB, and 1,2-DCA, by EPA method 8260B. The well contained elevated levels of gasoline constituents, including 230,000 ppb TPHg, 13,000 ppb benzene, and 28,000 ppb MTBE. B. Site Hydrogeology 1. The depth to shallow groundwater beneath the site, as measured in well MWI, has ranged from 56.33 feet below the top of the well casing (btoc) in June 2000 to 67.38 feet btoc in September 2003. A copy of a table summarizing historical water level information in site monitoring wells is attached. 2. Groundwater in the shallow aquifer beneath the site generally flows to the northeast, but has varied from the east to the north. The most recent gradient (September 10, 2003) was calculated at 0.0027, or approximately 14 feet per mile, flowing N48°E. The two most recent gradient maps (June 2003 and September 2003) are presented on Figures 5 and 6. 3. Site maps showing the extent of MTBE in shallow groundwater beneath the site during June 2003 September 2003 are presented on Figures 7 and 8. Only one deeper monitoring well has been installed (MW9B) approximately 120 feet northeast of the former USTs. Additional deep wells are proposed east of the former USTs, between the former water supply well and the new water supply well. 4. The proposed point of discharge is located outside of the plume area. Since the discharge will be free of contaminants (ND) and located outside the area of the plume, the discharge should have no impact on the groundwater plume. If anything, the discharge may act to hinder groundwater flow toward the east. 5. Since the point of extraction (MWI) is located at the heart of the plume, the extraction system will have an immediate impact on the plume by creating a cone of depression around the extraction well. The actual radius of influence will be calculated after startup, once groundwater measurements can be collected from site wells, and additional extraction wells may be proposed as necessary. G:IGROUN DZEITULEBtl ltG\ReportshvorkplanlW DRSupplemcntal.doc