(a) When any cast iron pipe, eight inches or less in nominal diameter, has been or will be exposed and undermined by an excavation 36 inches (914 millimeters) or greater in width, the purpose of which is for work other than normal gas operation and maintenance work being performed on the exposed cast iron main, one of the following actions must be taken in the listed order of preference:
(1) the cast iron main is to be replaced prior to the third-party construction activity occurring; or
(2) the cast iron main is to be surveilled for leakage daily until the contractor allows access to the excavation area for replacement. After access is allowed, the operator is to immediately replace the affected cast iron main or maintain daily surveillance with an open vent hole and replace the cast iron main as soon as practical.
(b) For right angle crossings of cast iron mains, the length replaced shall be equal to at least the width of the excavation plus twice the distance from the top of the main to the bottom of the trench.
(c) For crossings of cast iron mains at other than right angles, the length of the replacement shall be increased so that all cast iron pipe will be removed from within the trench settlement area under the gas main, assuming an angle of repose of 45 degrees from the bottom of the trench.
(d) Where replacement of cast iron main is required it shall extend approximately equally on both sides of said excavations.