(1) Casings shall not be required for the following conditions:

(a) Pipelines conveying natural or other gas which meet the design, installation and cathodic protection provisions of the Minimum Federal Safety Standards, 49 C.F.R. part 192 and chapter 480-93 WAC Gas companies—Safety.

(b) Local service lines and connections conveying natural or other gas which meet the design, installation and cathodic protection provisions of the Minimum Federal Safety Standards, 49 C.F.R. part 192 and chapter 480-93 WAC Gas companies—Safety.

(2) Casings shall be required for the following conditions:

(a) Pipeline crossings where casing is required by appropriate industry practice or special conditions.

(b) Pressurized carrier pipes and carriers of transmittants other than natural gas which are flammable, corrosive, expansive, energized, or unstable.

(c) Pipeline installations where local features, embankment materials, construction methods or other conditions indicate probability of damage to the pipeline that will render it unusable.

(3) Casings may be required as protection for carrier pipe from external loads or shock during existing highway improvement projects or new highway construction.

(4) Casing pipes shall extend a minimum of six feet beyond the toe of fill slopes, or back of ditch line, or outside curb unless limited by restrictive local conditions. The casing pipe need not be continuous on freeways with or without frontage roads; however, maintenance in the median shall not be required on a routine basis.

(5) Casing pipes shall be sealed at the ends.

(6) Casing pipes shall be designed to support the load of the highway and superimposed loads thereon and, as a minimum, shall equal the structural requirements for highway drainage facilities. Casings shall be composed of materials of sufficient durability to withstand any conditions to which they may be exposed.