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GETTLER-RYAN INC May 26, 2000 Mr. Michael Schafer City of Lodi Public Works Department v S. Ham Lane C- 1331 Lodi, CA 95242 Subject: Proposed Sampling Schedule for Discharge of Treated Groundwater to the Irdlust�7L- Waste Line at Former Chevron Station #9-5775, 301 West Kettleman Lane, Lodi, Mr. Schafer: During our telephone conversation on May 24, 2000, you requested information regarding the estimated time for breakthrough for the proposed treatment system. You also requested a proposed sampling schedule. Modeling of the activated carbon usage was performed by Chevron's carbon supplier, USFilter Westates. Based on influent concentrations of 51,000 ppb of TPHg, 39,000 ppb of benzene, 720,000 ppb of MTBE, 18,000 ppb of DIPE and an flow rate of 1 gpm, the calculated life of the carbon in the initial vessel ranges from 30 to 50 days. Extracted groundwater will be pumped through a particulate filter then through three 2,000 pound liquid phase carbon vessels plumbed in series prior to discharge to the industrial waste line. A schematic representation of the treatment system is attached. Gettler-Ryan Inc. proposes to collect treatment system samples at startup, then weekly thereafter, to verify the accuracy of the model. Samples will be collected from the influent stream, between the first and second vessels, between the second and third vessels, and from the effluent line (after the third vessel). Samples will be analyzed on a 24-hour basis for TPI -Ig and BTEX by EPA Method 8015 Modified, and for the fuel oxygenates MTBE, DIPE, TAME, ETBE and TBA by EPA Method 8260. Reports containing the analytical data and flow meter reading will be prepared and submitted to you on a monthly basis. After two months of system operation and sampling, the weekly analytical data will be evaluated. If these data support a reduction in the sampling frequency, a proposal to alter the sampling schedule will be submitted to the City of Lodi. The sampling frequency will not be changed until receipt of written approval from the City of Lodi. Carbon changeout will be triggered when gasoline hydrocarbons or fuel oxygenates are detected in the sample collected between the first and second vessels. When this occurs the carbon will be replaced in the first vessel by USFilter Westates. The second carbon vessel will then become the first vessel, the third carbon vessel will then become the second, and the first vessel with the new carbon will then become the third vessel. This procedure will be implemented each time carbon is changed in the first vessel. 346408.07 6747 Sierra Court, Suite J Dublin, California 94568 • ( 9 2 5 ) 551 -7555