5704.1 The piping that routinely contains regulated substances and is in contact with earthen materials shall be properly designed, constructed, and protected from corrosion in accordance with a code of practice developed by a nationally recognized association or independent testing laboratory, as specified by the Director.

5704.2 Except as provided in § 5704.7, underground storage tank system piping shall be constructed of:

1. (a) Fiberglass-reinforced plastic;
2. (b) Steel and shall be cathodically protected in accordance with the requirements of § 5901; or
3. (c) Other materials approved by the Director in accordance with § 5704.8.

5704.3 Steel UST piping shall be cathodically protected by being coated with a suitable dielectric material, and, in addition:

1. (a) Field-installed cathodic protection systems shall be designed by a corrosion expert; and
2. (b) Impressed current cathodic protection systems shall be designed to allow determination of current operating status as required by § 5901.6.

5704.4 Each cathodic protection system shall be operated and maintained in accordance with § 5901.

5704.5 Except as provided in § 5704.7, underground piping for hazardous substance USTs, and pressurized underground piping and non-safe suction piping for all petroleum USTs, shall be equipped with secondary containment features that are designed and constructed in compliance with the requirements of § 5701.4 of this chapter.

1. (a) Suction piping that does not comply with the requirements of § 6004.8 (a) through (e), shall be considered non-safe suction piping.

5704.6 For the purposes of this section, "pressurized underground piping" includes pressurized supply lines, return lines, and remote fill lines.

5704.7 Secondary containment shall not be required for vent pipes, Stage II vapor recovery pipes, vertical fill pipes, or piping for hazardous substance USTs used for industrial use.

5704.8 Other materials and construction techniques may be used for UST piping if the piping construction and corrosion protection are determined by the Director to be designed to prevent the release or threatened release of any stored regulated substance in a manner that is no less protective of human health and the environment than the other provisions of this section.

SOURCE: Final Rulemaking published at 40 DCR 7835, 7857 (November 12, 1993); as amended by Final Rulemaking published at 46 DCR 7699 (October 1, 1999); as amended by Final Rulemaking published at 56 DCR 6678 (August 21, 2009).