1. (a) Method of protection.

   1. (1) Encasement. In general, underground utility line crossings shall be encased in the interest of safety, protection of the utility, protection of the highway, and for access to the utility. Encasement shall be as specified for each type of line discussed herein. Casing shall consist of a pipe or other separate structure around and outside the carrier line and shall be designed to support the load of the highway and superimposed loads thereon, including that of construction machinery. The strength of the casing shall equal or exceed structural requirements for drainage culverts and it shall be composed of materials of satisfactory durability under conditions to which it may be subjected.

   2. (2) Optional for gas or liquid petroleum pipelines. Welded steel pipeline crossings may be installed without encasement provided such pipelines conform with 49 Code of Federal Regulations, Part 192, Transportation of Natural and Other Gas By Pipeline or Part 195, Transportation of Liquids By Pipeline as applicable. In accordance thereof such pipelines shall provide:

      1. (A) increased wall thickness and/or higher strength steel;
      2. (B) greater depth of cover; and
      3. (C) adequate markings as specified for each type of line discussed herein. Such pipelines shall also be designed to withstand internal design pressures and the superimposed loads of the roadway and traffic, including that of construction machinery.
2. (b) Manholes. Manholes serving this type of utility should be straight on line installations with a minimum overall width necessary to operate and maintain the enclosed equipment.
3. (c) Depth of underground lines. The depth of underground lines shall be as specified herein for each type of utility. Where placements at such depths are impractical or where unusual conditions exist, the department shall specify other protection as may be appropriate in lieu of the depth of bury required for the particular utility line.

4. (d) Methods of installation.

   1. (1) Lines placed under any existing roadway shall be installed by boring or tunneling in accordance with appropriate specifications. Jacking may be used only when approved by the district engineer. When installed by jacking or boring, encasement of the line may be required.

   2. (2) For rural (uncurbed) highway cross sections, all borings shall extend beneath all travel lanes plus:

      1. (A) 30 feet from all freeway main lanes and other high-speed (exceeding 40 mph) highways except as indicated in subparagraph (B) of this paragraph;
      2. (B) 16 feet for high-speed highways with current average daily traffic volumes of 750 vehicles per day or less;
      3. (C) 16 feet for ramps; and
      4. (D) 10 feet for low-speed (40 mph or less) highways.

   3. (3) For urban (curbed) highway cross sections, all borings shall extend beneath travel and parking lanes and extend beyond the back of curb plus:

      1. (A) 30 feet from high-speed (greater than 40 mph) facilities; and
      2. (B) three feet from low-speed (40 mph or less) facilities, plus any additional width to clear an existing sidewalk.
   4. (4) All traffic control devices (signs, markings, barricades, etc.) used to warn motorists of the construction activity must conform to the TMUTCD.
   5. (5) Where circumstances necessitate the excavation of a bore pit closer to the edge of pavement than set forth in paragraph (1) of this subsection, a guard fence or other approved protective devices will be installed for protection of the traveling public in accordance with current departmental standards. Bore pits shall be located and constructed in such a manner as not to interfere with highway structural footings, safe roadside clearance, or traffic operations. If necessary, shoring shall be utilized.
   6. (6) The use of explosives for any excavations on the right-of-way incident to utility line installation shall be permitted only when the department has adequate assurance that no damage or hazard will be caused thereby. Such assurance should normally include detailed plans and procedures approved by a person who is qualified and experienced in the use of demolitions.
   7. (7) Where longitudinal trenching on the right-of-way is permitted, backfill shall be compacted to densities equal to that of the surrounding soil. Trenching across jointed concrete pavement should not be permitted, and in no instance shall trenching across continuously reinforced concrete pavement be permitted. Exceptions may be made to permit trenching across low volume roadways or urban noncontrolled access roadways where conditions justify. Where trenching across other type pavements is justified, the department shall specify detailed methods for removal and replacement of embankment, base, and surfacing.
5. (e) Unsuitable conditions. Conditions which are generally unsuitable or undesirable for pipeline crossings should be avoided. These include locations such as deep cuts; near footings or bridges and retaining walls; across intersections at-grade or ramp terminals; at cross-drains where flow of water, drift, or stream bedload may be obstructed; within basins or an underpass drained by a pump if pipeline carries a liquid or liquefied gas; and in wet or rocky terrain where minimum depth of cover would be difficult to attain.
6. (f) Clearances. Vertical and horizontal clearances between a pipeline and a structure or other highway or utility facilities should be sufficient to permit maintenance of the pipeline and the other facilities.
7. (g) Drainage easements. Where it is necessary for pipelines to cross drainage easements, outside of the right-of-way, the same minimum depth of cover shall be maintained as required for crossing ditches inside of the right-of-way. In cases where soil conditions are such that erosion might occur or where it is not feasible to obtain specified depth, it shall be the responsibility of the utility owner to install retards, encasement, concrete slabs over the pipe, or take such other measures as needed for safety and to protect the highway and the pipeline. Where grades on the pipelines must be maintained, such as gravity flow sewer lines, each case will be worked on an individual basis, keeping in mind that the main purpose of the channel is to carry drainage water and that this flow must not be obstructed.

Source Note:The provisions of this §21.42 adopted to be effective January 1, 1976; amended to be effective May 29, 1989, 14 TexReg 2366.