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RULE §21.40Underground Utilities

(a) General.

  (1) Encasement.

Attached Graphic

    (A) Underground utility facilities crossing the highway shall be encased as shown in Figure §21.40(a)(1). The encasement must be a single structure with no open seams. If used, polyvinyl chloride (PVC) and high-density polyethylene (HDPE) pipe shall be glued with an appropriate adhesive, bonded, or mechanically fastened. Steel pipe shall be welded or bolted.

    (B) The encasement may be of metallic or non-metallic material, depending on the type of utility facility. If the encasement is not schedule 40 polyvinyl chloride (PVC) pipe, high-density polyethylene (HDPE), or made of steel, the utility must demonstrate that the encasement is adequate for the expected loads and stresses.

    (C) The length of any encasement shall extend, as applicable, to within five feet of the right of way, two feet of a connecting longitudinal line, or five feet beyond the face of the curb, whichever is greatest. These lengths of encasement include areas under center medians and outer separations. At a district's discretion, the district may waive the encasement requirement under center medians or under outer separations that are more than 76 feet wide. At a district's discretion and after considering traffic volume, condition of highway, maintenance responsibility, and district practice, the district may waive the encasement requirement under side road entrances.

    (D) Unless waived by the district, an encasement is required for installation under other department structures, such as retaining walls, headwalls, and sound walls.

  (2) Depth.

    (A) Underground utility facilities shall be installed at the applicable minimum depth of cover shown in Figure §21.40(a)(2)(A) unless the district requires or authorizes a different depth under this paragraph.

Attached Graphic

    (B) The district may require a greater depth at specific areas due to site conditions including areas such as culvert crossings, drainage areas, and future project considerations.

    (C) The district may require a greater depth based on distance from edge of pavement.

    (D) Where placements at the depths in this section are impractical or where unusual conditions exist, the department may allow installations at a lesser depth, but will require other means of protection, including encasement or the placement of a reinforced concrete slab. Reinforced concrete slabs or caps shall meet the following standards:

      (i) width -- five feet, or three times the diameter of the pipe, whichever is greater;

      (ii) thickness -- a minimum of six inches;

      (iii) reinforcement -- #4 bars at 12 inch centers each way or equivalent reinforcement; and

      (iv) cover -- no less than six inches of sand or equivalent cushion between the bottom of the slab/cap and the top of the pipe.

  (3) Manholes.

    (A) Manholes may not be installed unless necessary for installation and maintenance of underground lines. In no case shall a manhole be placed or permitted to remain in the pavement or shoulder of a highway. However, on noncontrolled access highways in urban areas, the district may, in its discretion, allow existing lines to remain in place under existing or proposed highways. In these cases, manholes may remain in place or be installed under traffic lanes of low volume highways in municipalities only if measures are taken to minimize the installations and to avoid locating them at intersections or in wheel paths.

    (B) To conserve space, a manhole's dimensions must be the minimum acceptable by appropriate engineering and safety standards. The only equipment that may be installed in manholes located on the right of way is equipment that is essential to the normal flow of the utility facility, such as circuit reclosers, cable splices, relays, valves, and regulators. Other equipment, such as substation equipment, large transformers, and pumps, shall be located outside the right of way.

    (C) Inline manholes are the only type permitted within the right of way. The width dimensions may not be larger than necessary to hold equipment involved and to meet safety standards for maintenance personnel. Outside width, the dimension of the manhole perpendicular to the highway, may not exceed ten feet, with the length to be held to a reasonable minimum. The outside diameter of the manhole chimney at the ground level may not exceed 36 inches, except that if the utility demonstrates necessity, the district may, at its discretion, allow an outside diameter of up to 52 inches. The top of the roof of the manhole must be five feet or more below ground level.

    (D) All manhole covers shall be installed flush with the ground or pavement structure. In order to minimize vandalism, manhole covers must weigh at least 175 pounds. Manhole rings and covers must be designed for HS-20 loading.

    (E) Manholes shall be straight, inline installations with a minimum overall width necessary to operate and maintain the enclosed equipment. The utility is responsible for any adjustment of the manhole rim that may be needed to meet grade changes.

  (4) Installation.

    (A) A department permit is required for all installation of utility facilities in the department's right of way.

    (B) If the installation of the utility facility deviates from the approved location, the district, at its sole discretion, may require the adjustment of the utility facility to the approved location.

    (C) Utility facilities placed beneath any existing highway shall be installed by boring or tunneling. Jacking may not be used unless approved in writing by the district. The use of explosives is prohibited. Pipe bursting or fluid/mist jetting may not be used unless approved in writing by the department. Longitudinal installation of a utility facility across driveways and intersecting roadways shall be bored. Open trench construction through intersecting roadways and driveways may not be used unless approved in writing by the district engineer.

    (D) To preserve and protect trees, shrubbery, and other aesthetic features within the department's right of way, the district may specify the extent and methods of tree removal, tree trimming, or the replacement of the aesthetic features. Landscape areas in the department's right of way that are associated with residences shall be bored, unless the district approves another method. The district may require boring on steep slopes where vegetation may be damaged.

    (E) For rural, uncurbed highway crossings, all borings shall extend beneath all travel lanes. Unless precluded by right of way limitations, the following clearances are required for rural highway crossings:

      (i) 30 feet from all freeway mainlanes and other high-speed (exceeding 40 mph) highways except as indicated in clauses (ii) - (iv) of this subparagraph;

      (ii) 16 feet for high-speed highways with current average daily traffic volumes of 750 vehicles per day or fewer;

      (iii) 16 feet for ramps; or

      (iv) ten feet for low-speed (40 mph or less) highways.

    (F) The reamed bore size may not exceed 40 percent of the outside diameter of the encasement, and a reamer that allows the natural wet grout to remain shall be used. Alternately, annular voids greater than one inch between the bore hole and the carrier line or encasement], if used, shall be filled with a slurry grout or other flowable fill acceptable to the department to prevent settlement of the highway facility.

    (G) Unless an open-trench installation is approved by the district in locations where adequate space is not available, all borings for curbed highway crossings shall extend beneath travel and parking lanes and beyond the back of curb and sidewalk, plus:

      (i) 30 feet from facilities with speed limits of 40 mph or greater; or

      (ii) five feet from highway facilities with speed limits of less than 40 mph or less.

    (H) Where circumstances necessitate the excavation of a bore pit or the presence of directional boring equipment closer than 30 feet from the edge of pavement, approved protective devices shall be installed for protection of the traveling public in accordance with §21.38 of this subchapter (relating to Construction and Maintenance). Bore pits shall be located and constructed in such a manner as not to interfere with the highway structure or traffic operations. Shoring shall be utilized for the protection of the highway facility, and its use and design must be approved by the district.

    (I) All traffic control devices, including signs, markings, or barricades used to warn motorists and pedestrians of the construction activity must conform to the TMUTCD.


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