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Blackstone 'P O. Box 1689 <br /> Group 'Danville, California 94526 <br /> 510 736-0783 <br /> 510736-0788-Fax <br /> July 21, 1998 <br /> JUL <br /> City of Lodi <br /> r <br /> 221 West Pine Street <br /> Lodi, CA 95241-1910 <br /> Attention: Mr. Mark Lindseth <br /> Reference: Cathodic Protection System Inspection <br /> 2 Locations With Underground Storage Tanks <br /> City of Lodi, Lodi California <br /> Dear Mr. Lindseth: <br /> On July 17, 1998, Blackstone Group, Ltd., installed shunt boards and completed final <br /> system inspection and testing. This work was based on our initial inspection and <br /> subsequent current requirement testing. During our June 26, 1998 survey it was <br /> determined that the existing magnesium anodes could be used to provide proper levels of <br /> cathodic protection (CP) to the tanks. <br /> The existing anodes were connected to the shunt boards. Each board had a to 0.01 ohm <br /> shunt for each anode to enabled current measurements to be monitored as well as provide <br /> a fixed connection point for future testing. Negative connections for both the drain and <br /> test wires were made using a electrical pipe clamp attached to the fill pipe of each tank. <br /> CRITERIA FOR CATHODIC PROTECTION <br /> The testing of the cathodic protection systems were performed in accordance with EPA <br /> and NACE International guidelines. The National Association of Corrosion Engineers <br /> (MACE) recommended practice RP-02-85 lists five criteria for cathodic protection of <br /> underground metallic tank systems. Listed below is one criterion used to evaluate the <br /> existing cathodic protection systems: <br /> A negative (cathodic) voltage of at least 0.85 Volt as measured between the <br /> structure surface and a saturated copper/copper sulfate reference electrode <br /> contacting the electrolyte. Determination of this voltage is to be made with the <br /> protective current applied. Consideration should be given to voltage (IR) drop. <br />