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0 <br /> 1 . UNDERGROUND TANKS <br /> a. Cathodically Protected Steel . <br /> (1 ) Must be coated steel which is cathodically protected and UL <br /> listed and designed in accordance with UL Standard 58. <br /> (2) Corrosion Protection. <br /> (a) Via sacrificial galvanic anodes for anodes energized by <br /> impressed direct current. Use of galvanized steel for cathodic protection is <br /> unacceptable for any size tank. <br /> (b) Regularly monitored to track effectiveness of cathodic <br /> protection system which must maintain a -.85 volt potential tank-to-soil as <br /> measured by a copper-coppper sulfate reference half-call . <br /> 1 . Galvanic: tank-to-soil potential measurements are to <br /> be monitored a minimum of twice a year. Automatic system for continuous or <br /> Intermittent monitoring is recommended. <br /> 2. Impressed current - monitored a minimum of monthly for <br /> electrical continuity. Rectifier output should be measured with a voltage or <br /> current indicator. Tank-to-soil potential measurements must be measured a <br /> minimum of once a year. <br /> (c) Designed by qualified corrosion engineer. <br /> (3) Coatings. <br /> (a) Factory-applied to entire exterior surface as passive <br /> protection to supplement active cathodic protection. <br /> (b) If interior of tank is not coated, internal cathodic <br /> protection in the form of sacrificial zinc anodes recommended. <br /> (c) Finished coating inspected by fabricator to insure proper <br /> thickness on all surfaces and edges. <br /> (d) Minimum exterior coating thicknesses: <br /> 1 . 13 mils wet (10 mils dry) . <br /> 2. On tank head and within 48' of shell-mounted anodes 22 <br /> mils wet (15 mils dry) . <br /> (e) Coated tank should be carefully handled during all phases <br /> of installation to minimize damage to coating. Any repairs to coating must <br /> be in strict accordance with manufacturer's recommendations. <br /> 1 <br />