California Water Well Standards, DWR Bulletin 74 ... - County of Glenn

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 inAugust 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.Oil-producingcoastal region from San Diego to Santa Barbara,.San Francisco Bay Area.areas of the southern San Joaquin Valley and the Central Coast, and,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 rangefrom 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 installationexceeding 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 "anodeinterval."(3) Backfilling the anode interval around the anodes with an electrically conductive material, such asgranular coke.(4) Installing a small-diameter vent pipe that extends from the top of the anode interval to land surface, orabove. The purpose of the vent pipe is to release generated gases. Medium to large-diameter pipe orcasing used in water wells to maintain the well bore and house pumping equipment is not normally usedfor cathodic protection wells.(5) Backfilling the annulus between the vent pipe and borehole wall with an electrically non-conductive fillmaterial 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 tostabilize the walls of the borehole.In the past this material was sometimes used to fill the annulus between the vent pipe and the boreholewall from the top of the anode interval to land surface. These standards require specific interval(s) ofthe 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-conductiveannular 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-