12.20A.080 Specific requirements—Underground utilities.
A. Underground Utilities—Location and Alignment.
(1) For all crossings the angles of crossing should be as near a right angle to the road centerline as practicable, however, lesser angles may be permitted based upon economic considerations of practical alternatives.
(2) Crossings should avoid deep cuts, footings of bridges and retaining walls, wet or rocky terrain or locations where highway drainage would be affected.
(3) Where irregular shaped portions of the right-of-way extend beyond the normal right-of-way limits, variances in the location of the utility lines will be allowed as necessary to maintain a reasonable uniform alignment.
B. Underground Utilities—Cover.
(1) The minimum cover of underground utilities as measured from the actual surface point of the installation within the road right-of-way shall be as follows:
a. Thirty-six (36) inches within the roadway prism which may be reduced to twenty-four (24) inches with approved casing or protective concrete slab or to twelve (12) inches in solid rock when backfilled with CDF.
b. Thirty (30) inches outside the roadway prism which may be reduced to twenty-four (24) inches with approved casing or protective concrete slab or to twelve (12) inches in solid rock when backfilled with CDF.
c. Secondary electrical service lines and all communication, cable television and other low-voltage lines may be placed within the roadway prism at a depth of eighteen (18) inches if backfilled with CDF.
The requirement for CDF backfill shall not apply when the underground utility is constructed by means of pushing, boring or bore-pulling as specified in subsection (F)(1) of this section.
(2) Where less than the minimum cover is made necessary to avoid obstacles, the utility shall either be rerouted or protected with a casing, concrete slab or other method acceptable to the county.
(3) Cover for utilities carrying transmittants that are flammable, corrosive, expansive, energized, or unstable shall not be reduced below the safety limits specified in the appropriate industry standards and specifications.
C. Underground Utilities—Encasement.
(1) Casings shall be required for roadway crossings where casing is required by appropriate industry code, where local features, embankment materials, construction methods or other conditions indicate any possible damage to the protective coating during installation, or where the county determines the installation of casings will reduce or eliminate damage to the county right-of-way.
(2) Casings may be required for the following conditions:
a. As an expediency in the insertion, removal, replacement or maintenance of a carrier line crossing or other locations where it is necessary in order to avoid open trench construction.
b. As protection for carrier lines from external loads or shock either during or after construction of a road.
c. As a means of conveying leaking fluids or gases away from the area directly beneath the traveled way to a point of venting or drainage.
d. Jacked or bored installations of coated carrier lines will be contained within a casing unless assurance is provided to the county that there will be no damage to the protective coating.
(3) Casing pipes shall extend a minimum of six (6) feet beyond the toe of fill slopes, back of roadway ditch or outside of curb.
(4) Other than for necessary vents and/or drains, casing pipes shall be sealed at both ends.
(5) Casing pipes shall be designed to support the load of the road and superimposed loads thereon and, as a minimum, shall equal the structural requirements for road drainage facilities. Casings shall be composed of materials of sufficient durability to withstand any conditions to which they may normally be exposed.
D. Underground Utilities—Uncased Carriers.
(1) The carrier pipe shall conform to the material and design requirements of the appropriate utility industry and governmental codes and specifications.
(2) The carrier pipe shall be designed to support the load of the road plus superimposed loads thereon when the pipe is operated under all ranges of pressure from maximum internal to zero pressure.
(3) Suitable bridging, concrete slabs or other appropriate measures as approved by the county shall be used to protect existing carriers which by reason of shallow bury or location makes them vulnerable to damage from road construction or maintenance operations.
(4) Existing carriers may remain in place without further protective measures if they are of adequate depth and do not conflict with road construction or maintenance and provided that the utility and the county mutually agree that the lines are, and will remain, structurally sound and operationally safe.
E. Underground Utilities—Appurtenances.
(1) Vents shall be required for casings, tunnels and galleries enclosing carriers of fuel where required by federal safety standards. Vent standpipes as well as air release valves, locator stations, pressure cleanouts and other appurtenances projecting above the ground and/or requiring periodic examination or maintenance should be located and constructed so as neither to interfere with maintenance of the road nor to be concealed by vegetation; preferably they should stand by a fence or on the right-of-way line.
(2) Drains shall be required for casings, tunnels or galleries enclosing carriers of liquid, liquefied air or heavy gas. Drains for carriers of hazardous materials shall be directed to natural or artificial holding areas that will prevent the potential for surface or groundwater contamination. Drains for which only water or other nonhazardous liquids may discharge may be directed into the roadway ditch or other natural watercourse at locations approved by the county. The drain outfall shall not be used as a wasteway for routine purging of the carrier unless specifically authorized by the county.
(3) Surface markings of underground utilities shall be in accordance with applicable state and federal standards.
(4) Automatic shutoff valves shall be installed in line at or near ends of structures and near unusual hazards unless other sectionalization devices within a reasonable distance can isolate the hazardous segments.
(5) Unless otherwise approved by the county, all aboveground appurtenances to underground installations proposed for location within the county right-of-way that may constitute a roadside obstacle for traffic using the road shall be located as close as possible to the right-of-way line. If, due to narrow right-of-way or other conditions as may be determined by the county, an adjacent to the right-of-way appurtenance location still constitutes an unacceptable roadside obstacle, said obstacle must be (a) relocated to another place within the right-of-way,
(b) converted to a breakaway design, (c) crash-protected, or (d) relocated to another location off the road right-of-way. Actions (a), (b) and (c) of this subsection must be approved by the county as a condition of permit approval.
(6) All installations of nonmetallic materials that may contain hazardous or environmentally objectionable liquids or gases under pressure must have a metal locating wire or equivalent placed alongside the nonmetallic conduit. All subsurface installations, both active and inactive, must be locatable unless otherwise exempted.
F. Underground Utilities Installation. All utility installations shall ensure safety of traffic and preservation of the roadway structure.
Untrenched construction (i.e., pushing, boring, or bore-pulling) will be required for all utilities two (2) inch diameter and smaller crossing roads paved with asphaltic concrete or cement concrete and for roads paved with a bituminous surface treatment except when another method is approved for a specific location.
Trenched installations shall provide for restoration of the pavement, paved shoulders, curbs and gutters in accordance with Section 12.20A.120 of this chapter and the following controls:
(1) Trenched Construction and Backfill.
a. Where the pavement must be removed, it first shall be cut in vertical (or undercut) continuous straight lines using appropriate sawing machinery. On urban arterials and rural collectors, the pavement will be removed and replaced on the entire surface of any traffic lane that is disturbed by a longitudinal trench except in those instances where the entire roadway is required to be overlaid. On all roads where four (4) feet or less of pavement remains between the outside of a longitudinal trench and the edge of pavement or the curb, the pavement shall be removed and the restoration shall be from the cut nearest the roadway center line to the curb or edge of pavement. When any construction damages the edge of an existing pavement, a minimum of a three (3) foot wide section of pavement will be removed and replaced for the full length of the damaged section unless other arrangements are approved by the county.
b. Where soil and depth conditions permit, trenches shall be cut to have vertical faces, with a maximum width of outside diameter of pipe plus two (2) feet for pipes eight (8) inch diameter and larger and with a maximum width of outside diameter of pipe plus one (1) foot for pipes six (6) inch diameter and smaller. Narrower trench widths are permitted as long as the pipe, conduit or cable can be properly bedded and compaction of the backfill can be achieved. Where compaction can not be readily achieved, CDF shall be used as backfill. All pavements shall be cut parallel one (1) foot beyond the top of the excavation to ensure that the remaining pavement is not undermined. Shoring shall comply with the Department of Labor and Industries Safety Code.
c. The pipe or carrier shall be installed and the trench backfilled in a manner assuring no deformation of the pipe likely to cause leakage and provide restoration of the structural integrity of the roadway structure. This shall include providing bedding to a depth of six (6) inches or half the diameter of the pipe, whichever is least plus additional pipe bedding to cover the pipe to a depth of one (1) foot maximum. Pipe bedding shall be granular material meeting Sections 9-03.9(3), 9-03.15, or 9-03.16 of the Standard Specifications and be approved by the county. It shall be graded to a firm but yielding surface without abrupt change in bearing value. Unstable soils and rock ledges shall be subexcavated from the bedding zone and replaced with suitable material.
d. Gravel base backfill shall be placed on top of the pipe bedding up to no more than one (1) foot below the former grade surface exclusive of the pavement thickness. Backfill shall be imported or native material meeting or exceeding Section 9-03.14(1) of the Standard Specifications. The use of native material must be approved by the county prior to construction. All backfilling within the trench zone shall be by Method C as set forth in Section 2-03.3(14)C of the Standard Specifications. Consolidation by saturation or ponding is not permitted. See Appendix B of the ordinance codified in this chapter—a copy of which is available in the office of the department of public works—if controlled density fill (CDF) is required.
e. A minimum depth of 0.8 feet of crushed surfacing base course (CSBC) and a minimum depth of 0.2 feet of crushed surfacing top course (CSTC) meeting the requirements of Section 9-03.9(3) of the Standard Specifications shall be placed above the trench zone backfill. The layers shall be compacted to a ninety-five percent (95%) maximum density as determined by AASHTO Method T-99 and the top surface shall be finished flush with the bottom of the existing adjoining pavement. In lieu of CSBC and CSTC, asphalt treated base may be used and placed in accordance with Section 4-06 of the Standard Specifications.
f. Compaction testing of backfill shall be required to be performed by an independent testing laboratory or company, and the results to be furnished to the county. Utilities which have their own employees who are certified for compaction testing may use such employees to perform the required testing provided a copy of the certification is provided to the county in advance. Unless otherwise approved by the county, a minimum set of compaction tests consisting of one test at fifty percent (50%) of the trench depth and at the surface for each trench or excavation two hundred fifty (250) feet in length or less. For trenches exceeding two hundred fifty (250) feet in length, one additional set of tests will be required for each additional two hundred fifty (250) foot length (or increment thereof).
Alternative methods of achieving and certifying the required compaction may be submitted to the county in advance and are subject to approval by the county prior to proceeding with the excavation.
g. Utility installation requirements shall meet Standard Specifications Sections 7-08.3(1)A and 7-08.3(3), trenching and backfilling, respectively except as noted above.
h. Asphalt concrete pavement (ACP) for restoration shall include placing Class B ACP a minimum of 0.35 feet thick or the thickness of the existing pavement on urban arterials and rural collectors whichever is greater. Placement and placement conditions shall be as specified in Section 5-04 of the Standard Specifications.
i. Portland Cement Concrete (PCC) roadway shall be restored in kind and in full panels unless otherwise approved by the county. All patches in PCC pavements will require installation of dowel bars and tie bars as set forth in the Standard Specifications and in accordance with the WSDOT Standard Plan for Cement Concrete Pavement Joints.
j. When controlled density fill is used for backfill, the county may approve a trench of a lesser width than that specified in subsection (F)(1)(b) of this section.
k. Where roadway surfaces are windowed and potholed, controlled density fill will be used for backfilling the void; provided, however, if the resultant void depth is greater than three (3) feet, only the top three (3) feet shall require CDF.
l. Where urban arterials or rural collectors must be transversely trenched because obstructions preclude untrenched construction, the county will require controlled density fill to be used as the top three (3) feet of the backfill. Controlled density fill will also be required as backfill for transverse cuts on all paved roads that have been reconstructed or resurfaced within five (5) years. In all other cases, including all unpaved roads and streets, granular backfill as approved by the county must be used.
m. When trenching is approved on paved roads, the pavement shall be restored with either asphalt concrete or cement concrete depending on the roadway surface or as required by the county. See Section 12.20A.120 for further guidance.
(2) Untrenched Construction.
a. The length of untrenched construction shall extend a minimum of four (4) feet from edge of pavement or greater if specified by the engineer, except that a two (2) foot minimum may be permitted by the county engineer for service connections where conditions warrant.
b. Pipelines installed under a road without disturbing the surface shall be made using a technique approved by the county but in no case shall the size of the opening exceed the pipe diameter by more than five percent (5%) or one (1) inch, whichever is greater, unless bentonite or an equivalent nonshrinking material is injected into the void. If, during the process of pushing, boring or bore-pulling, the roadway or shoulder of the road is damaged or distorted in any manner, the utility must make immediate repairs to the satisfaction of the county.
c. Overbreaks, unused holes or abandoned casings shall be backfilled as directed by the county.
d. Jetting under roadways will not be permitted. This does not prohibit the use of boring or driving techniques which use water to only remove cuttings and does not permit the water to remove material outside the designed bore dimensions. In all cases where water is used, the discharge shall be captured and disposed of or otherwise controlled such as not to violate the county’s water quality regulations.
(3) Plowing of communication, electrical and all other lines on or adjacent to existing roads by means of a vibratory or static plow will be permitted under the following conditions:
a. Plowing will not be permitted when conditions are such that surface water will enter the area disturbed by the plow. Surface water may be streams, ponds or other standing water as well as precipitation runoff.
b. Plowing will normally be restricted to those areas outside the roadway prism unless there is insufficient right-of-way or topographic features that make the use of plows not feasible. The preferred location of all plowing is between the back of ditch and the right-of-way line in cut sections and at the base of the fill slope in fill sections.
c. Plowing within the roadway prism shall be performed as far from the traveled way as practical irrespective of the road surfacing. In no case shall plowing be permitted within the paved portion of any paved road. If the wheels or tracks of the plow damage any of the paved portion of the road, repairs must be made in accordance with the provisions of subsection (F)(1)(a) of this section.
d. In all cases, the utility or its contractor shall immediately apply suitable compactive effort to the area disturbed by the plow to seal the disturbed area and prevent surface water from penetration.
G. Underground Utilities—Adjustment.
(1) Existing underground utilities on county road right-of-way shall be either removed or relocated when roadwork authorized by the county would cause the existing underground utility to violate either county or industry standards. All such removal or relocation shall be at the sole expense of the owning utility and all work must be accomplished by the same permitting process as for new installations.
(2) Notwithstanding reinforcement or protection otherwise provided, a permittee shall be responsible for the security of each existing pipeline and utility within a road construction zone. Where there are unusual utility hazards or where heavy construction equipment will be used the permittee shall provide adequate temporary protection. In replacing the roadway, the design should give due consideration to the protection of previously existing utilities in the roadway section without sacrificing the geometrics of roadway design. (Sec. 1 of Ord. 1999-11-15)