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Many cathodic protection wells have been constructed to protect pipelines that transport natural gas or other "hazardous" materials. The Natural Gas Pipeline Safety Act, Public Law 90-481 adopted by Congress in August 1968, provides requirements for cathodic protection of certain pipelines. Most cathodic protection wells in California are located in areas where underground pipelines or"conveyance" systems are numerous and must be protected. These areas include: • South coastal region from San Diego to Santa Barbara, • Oil-producing areas of the southern San Joaquin Valley and the Central Coast, and, • San Francisco Bay Area. Few cathodic protection wells exist in California north of Sacramento. Many cathodic protection wells, as illustrated in Figure 6, have been constructed by: (1) Drilling a 6-to 12-inch diameter borehole to a desired depth. Cathodic protection wells normally range from 100 to 500 feet in total depth. A few wells have been constructed to depths of 800 feet. California Water Code Section 13711 defines a "cathodic protection well" as an anode installation exceeding 50 feet in depth. Installations less than 50 feet deep are"legally"considered"shallow anodes," not cathodic protection wells. Shallow anode installations are not specifically covered by these standards. (2) Placing a string of anodes in the borehole within a designated interval,usually referred to as the"anode interval." (3) Backfilling the anode interval around the anodes with an electrically conductive material, such as granular coke. ' (4) Installing a small-diameter vent pipe that extends from the top of the anode interval to land surface,or above. The purpose of the vent pipe is to release generated gases. Medium to large-diameter pipe or casing used in water wells to maintain the well bore and house pumping equipment is not normally used for cathodic protection wells. (5) Backfilling the annulus between the vent pipe and borehole wall with an electrically non-conductive fill material to a specific height above the anode interval. Such fill material usually consists of uniform, small-diameter gravel. Its purpose is to provide a permeable medium for migration of gases and to stabilize the walls of the borehole. In the past this material was sometimes used to fill the annulus between the vent pipe and the borehole wall from the top of the anode interval to land surface. These standards require specific interval(s) of the upper annular space of a cathodic protection well be filled with sealing materials instead of gravel, to protect ground water quality. (6) Sealing the annulus between the vent pipe and the borehole wall, from the top of the non-conductive annular fill to land surface,with sealing material. (7) Installing a permanent cover over the well at ground surface. (8) Connecting the anode leads to the facility to be protected, possibly through an electrical current source. Individual designs of cathodic protection wells vary. -60-