(a) Pipe-to-soil electrical potential tests or other acceptable electrical tests shall be conducted over each pipeline 100 feet (30.5 meters), or longer that is under cathodic protection at least once each calendar year, but with intervals not exceeding 15 months, to determine whether the cathodic protection meets the requirements of section 255.463 of this Part. These should also be conducted for pipelines shorter than 100 feet (30.5 meters). However, if tests at those intervals are impractical for separately protected short sections of mains or transmission lines, not in excess of 100 feet (30.5 meters), or separately protected service lines, these pipelines may be surveyed on a sampling basis. At least 10 percent of these protected structures, distributed over the entire system must be surveyed each calendar year, with a different 10 percent checked each subsequent year, so that the entire system is tested in each 10-year period.

(b) Each cathodic protection rectifier or other impressed current power source must be inspected six times each calendar year, but at intervals not exceeding 2½ months, to ensure that it is operating.

(c) Each reverse current switch, each diode, and each interference bond whose failure would jeopardize structure protection must be electrically checked for proper performance six times each calendar year, but at intervals not exceeding 2½ months. Each other interference bond must be checked at least once each calendar year, but at intervals not exceeding 15 months.

(d) Each operator shall take prompt remedial action to correct any deficiencies indicated by the monitoring.

(e) After the initial evaluation required by sections 255.455(b)-(c) and 255.457(b) of this Part, each operator must, not less than every three years, at intervals not exceeding 39 months, reevaluate its unprotected pipelines and cathodically protect them in accordance with this Part in areas in which active corrosion is found. The operator must determine the areas of active corrosion by electrical survey. However, on distribution lines and where an electrical survey is impractical on transmission lines, areas of active corrosion may be determined by other means that include review and analysis of leak repair and inspection records, corrosion monitoring records, exposed pipe inspection records, and the pipeline environment.

(f) The operator shall determine the areas of active corrosion by electrical survey, or where electrical survey is impractical, by using the required leakage survey (see section 255.723[b] of this Part) in conjunction with an analysis of the corrosion and leak history records, or by other approved means.