Cathodic Protection Operation and Maintenance Requirements
 
All regulated underground storage tanks system (USTs) must have cathodic protection.
 
State and federal rules require corrosion protection for UST systems because unprotected steel UST systems corrode and release product through corrosion holes. You already meet the requirements for corrosion protection if your UST system matches one of the following performance standards for new USTs:
 
  • Tank and piping completely made of noncorrodible material, such as fiberglass. Corrosion protection is also provided if tank and piping are completely isolated from contact with the surrounding soil by being enclosed in noncorrodible material (sometimes called "jacketed" with noncorrodible material).
 
  • Tank and piping made of steel having a corrosion-resistant coating AND having cathodic protection (such as an sti-P3® tank with appropriate piping). A corrosion-resistant coating electrically isolates the coated metal from the surrounding environment to help protect against corrosion. Asphaltic coating does not qualify as a corrosion-resistant coating.
 
  • Tank made of steel clad with a thick layer of noncorrodible material (such as an ACT-100® tank). This option does not apply to piping. Galvanized steel is not a noncorrodible material.
 
 
Impressed current system. An impressed current system uses a rectifier to convert alternating current to direct current (see the picture). This current is sent through an insulated wire to the "anodes," which are special metal bars buried in the soil near the UST. The current then flows through the soil to the UST system, and returns to the rectifier through an insulated wire attached to the UST. The UST system is protected because the current going to the UST system overcomes the corrosion-causing current normally flowing away from it. Impressed Current System
 
 
Sacrificial anode system. Another type of cathodic protection (see the picture) is called a sacrificial anode or galvanic system. Although sacrificial anode systems work with new USTs (sti-P3® tanks single or double wall), corrosion protection experts generally agree that sacrificial anodes do not work effectively or economicall with most existing steel USTs. Only a qualified cathodic protection expert candetermine what kind of cathodic protection will work at your UST site. Sacrificail Anode

 

Operation and maintenance requirements

A qualified cathodic protection tester must test the system within six months after installation and every three years thereafter. A negative potential of –850 millivolts or –0.85 volts should be obtained between the UST system and a reference electrode touching the soil above the tank. Results of the last two inspections performed by a qualified cathodic protection tester must be kept. In addition, an impressed current system must be checked by the owners or operators every 60 days to ensure that the system is operating properly. A log must be kept for the last three check ups to show that the impressed current system is operating properly. The records may be kept at a central office rather than the facility itself.

 

If you have any further questions, please contact
Doug Miller, Nayyer Syed, Terry Florentz or Justin Allen in Pierre at (605) 773-3296,
or Scott Bickler in Sioux Falls at (605) 362-3500
or Mike Tietz in Rapid City at (605) 394-2229 or E-mail.