N.M. Admin. Code § 17.4.2.14

Current through Register Vol. 36, No. 1, January 14, 2025

Section 17.4.2.14 - DEFINITIVE DESIGN REQUIREMENTS

A. Pipeline installations; location and alignment: From the highway viewpoint, there are sound reasons for requiring pipeline crossings at right angles to the roadway alignment. Oblique angle highway crossing pipeline installations have many detrimental characteristics as they increase the interference with traffic during construction, are more liable to conflict with highway drainage and structures, upset distribution of live loads to the subgrade and across pavement joints, are considerably harder to control as to line and grade when boring or jacking the pipeline beneath the highway, and they usually create more damage to the pavement structure and subgrade on open cut installations. Diagonal crossings usually require more maintenance and repairs; therefore, all pipeline crossings shall be at or near ninety (900) degrees. Minor variations will only be considered on a case by case basis, upon justification submitted to the Department by the utility. Conditions which are generally unsuitable for pipeline crossings should be avoided, such as locations in deep cuts, across cuts and fills on steep slopes, near the footings of bridge piers, abutments, retaining walls and other structures, across interSections at grade or entrance and exit ramp terminals, at cross drains (transverse drop inlets) where flow may be obstructed, or in locations requiring extensive rock excavations to provide the minimum bury.

B. Pipeline casings; encasement: A carrier pipe is said to be cased (or encased) if it is installed freely inside in a larger diameter pipe. Encasement may also be complete or partial, designed to protect the carrier pipe, lighten its burden, facilitate its insertion and withdrawal and guarantee the integrity of the roadway structure or prism. Common types of casements are those carriers cased or sleeved inside a larger pipe, cradled by a continuous concrete seat fitting the pipe (cradling), walled by a continuous concrete sidefill (walling), boxed or jacketed by concrete completely surrounding the pipe (boxing), capped by a continuous concrete topping or slab (capping)), coated or wrapped by a substantial girdling cover (wrapping), grouted by mortar filling borehole annulus and overbreak (grouting), or tunneled by installation in a utility subway.

(1) Of these methods, only the casing, tunnel, utility subway or gallery provide the complete independence of the carrier pipe from the surrounding roadway structure, and adequate protection to the roadway from leakage of the pipeline. These methods also provide means for insertion and replacement of carriers without access or disturbance to through-traffic roadways.

(2) The following encasement methods do not provide all of the above benefits, but may be utilized subject to individual approvals, on substantiation submitted by the utility: Concrete cradling enhances the load supporting capability of rigid pipes, but accomplishes little else. Walling does the same for semi-rigid and flexible pipes. Capping strengthens both rigid and flexible pipes, and somewhat protects from highway operations penetrating the overfill. When applied to weak or brittle pipes, concrete boxing or jacketing provides protection to the pipe from earth loads, leakage, corrosion or abrasion to some degree. Adequate coating or wrapping prevents contact with corrosive water, soil or vapors. Grouting aids in restoring the continuity and integrity of the earth supporting the pavement structure.

C. Uncased carriers: An uncased carrier crossing a highway becomes an integral part of the embankment supporting the pavement structure. Just as for a culvert, the Department must be assured of adequate structural design. All uncased carriers shall be designed to withstand all combinations of earth and live load, internal pressure, earth and live load plus internal pressure, and earth and live load plus alterations to full and zero internal pressure. Rigid carriers will generally be satisfactory, if they meet culvert design criteria and withstand the internal pressure. Semi-rigid and flexible carrier pipes shall be cased within a rigid pipe encasement.

D. Hazardous transmittants: Transmittants which are flammable, corrosive, expansive, unstable, at high pressure, and/or possibly hazardous to the traveling public or the roadway itself, shall be encased on all highway crossings of carrier pipes over 2 inches in diameter. Uncased crossings of welded steel pipelines may be permitted, provided additional protective measures are taken in lieu of encasement. Such measures may include higher safety factors in design, materials and construction, coating, and wrapping of carriers in accordance with industry standards, and cathodic protection, subject to the approval of the Engineer, District Engineer or his/her representative. Requirements for uncased carriers: Uncased hazardous or corrosive product pipeline crossings on state highways will be allowed provided they are:

(1) welded steel pipelines;

(2) cathodically protected;

(3) coated in accordance with industry standards;

(4) meet requirements of the pipeline safety regulations -- 49 Code of Federal Regulations, Parts 191 and 192, or Parts 191 and 195 with respect to wall thickness;

(5) designed for operating stress levels in accordance with federal pipeline safety regulations;

(6) appropriately marked with permanent signs at each right-of-way line indicating ownership, type of facility, and an emergency telephone number; and

(7) owner provides an official signed written statement certifying that the facility complies with the conditions and provisions required in this Section, Paragraph 14.4.1 [now Subsection D of 17.4.2.14 NMAC].

(8) It should be noted that each request for waiver of casing will be considered on an individual bases. The ultimate decision to approve or reject a waiver will not be subject to pipeline owner criteria, but will be based on the following casing considerations:

(a) as an expediency in the insertion, removal, replacement, or maintenance of carrier pipe crossings of freeways, expressways, and other controlled access highways and at other locations where it is necessary to avoid trenched construction;

(b) as protection for carrier pipe from external loads or shock, either during or after construction of the highway;

(c) as a means of conveying leaking fluids or gases away from the area directly beneath the traveled way to a point of drainage in the highway ditch or a natural drainage way; and

(d) traffic safety considerations and maintaining the structural integrity of the roadway.

E. Restriction against varied use: Subject to the safety requirements of the various regulatory bodies, the following precautionary measures are required for pipeline crossings:

(1) Pipeline crossing utility accommodation permit applications shall specify the class of transmittants, the maximum working or test pressure, and the design standards for the carrier pipe.

(2) Prior approval shall be obtained from the Department before the utility is allowed to change the type of transmittant or raise the working or potential pressures beyond those provided for in the design and the utility accommodation permit. Non-compliance by the utility with any of the provisions of this regulation shall be grounds for rejection of the utility accommodation permit or the revocation of an existing permit.

F. Trenched construction and backfill: In trenched construction, bedding is the subgrade soil and its surface, as prepared to support a pipe. Backfill is the material that refills the rest of the trench, consisting of sidefill up to the level of top of facility, and of overfill above that level. The latter specifically includes restoration of the pavement structure and the road surface. From the Department's viewpoint, the pavement structure which is broken, disturbed, cut or otherwise damaged in any way, shall be removed and replaced to a design equal to or greater than the surrounding undisturbed pavement structure, as determined by the Department.. Open cut trenched construction on State roads shall be limited to areas where the pavement structure is deteriorated and in generally poor condition and only when justified in writing by the utility and subsequently approved by the District Traffic Engineer or his/her representative.

(1) In cases where the utility owner is allowed an open cut installation, the utility shall be responsible for the restoration and maintenance of the pavement structure, until such time that the Section of roadway is improved by resurfacing as approved by the Department.

(2) Where the utility or other party making the installation is not equipped to or fails to properly repair the damage to the pavement structure, the Department shall repair the damage and will bill the utility owner the actual costs incurred, including any administrative costs.

(3) open trench installations crossing the highway: From the Department's viewpoint, the essential features of open trench construction are detailed as follows:

(a) Restoration of the structural integrity of the roadbed.

(b) Security of the pipe against deformation and leakage.

(c) Assurance that the trench does not become a drainage channel, and that the backfill does not block road drainage.

(d) Open-cut trenched installations shall not be permitted unless it is not feasible to bore, push or jack under the roadway. All trenched or other utility installations shall conform to the applicable provisions of the current construction requirements of the Department, i.e., The New Mexico State Highway and Transportation Department Standard Specifications for Road and Bridge Construction, and any supplemental provisions thereto.

(e) Trenches shall be cut to have vertical faces with a maximum width of .61 m (2 feet), or the outside diameter of the pipe plus .46 m (1.5 feet) on each side, or as approved by the Engineer or his representative. The trench shall be shored where necessary to prevent cave-ins or sloughing, and shall meet OSHA requirements.

(f) Bedding should be provided to a depth of half the diameter of the pipe. Bedding shall consist of granular material, free from rocks, lumps, clods, cobbles, or frozen materials and shall be graded to a firm surface without abrupt change in bearing value. Unstable soils and rock ledges shall be sub-excavated from beneath the bedding zone and replaced with suitable granular material.

(g) Backfill shall be placed in 150.6 mm (6 inch) layers of granular materials, and each layer shall be consolidated (compacted) by mechanical tamping equipment and with a controlled addition of moisture, to a density of 95% maximum dry density (modified proctor method "C," T-99 or equivalent) determined by a standard compaction test. Consolidation by super-saturation, ponding or flooding will not be permitted in any circumstance. Materials and methods of compaction shall be adapted to achieve rapid restoration of traffic service. There shall be additional cutback of base and surfacing courses to minimize later development of sag in the replaced pavement over the trench.

(h) Pavement replacement may be performed by either the utility, or a contractor engaged by the utility, (constructed to a specification approved by the state) or by Department forces at the expense of the utility. The utility shall be liable from the date of completion of the pavement replacement, for the cost of repairs if the backfill subsides or the patched pavement fails, until such time that the roadway cut is resurfaced as approved by the Department..

G. Untrenched construction and grout: Methods for installing a utility under a highway or roadway without disturbing the pavement surface are as follows:

(1) A pipe with a pilot shoe may be driven through compressible soil by steady thrust, hammering or vibration. Driven pipe must be smooth and uncoated, thus a casing or corrosion resistant carrier pipe should be used. Line and grade are difficult to control on long drives.

(2) Coring -- A casing without a pilot shoe can be drilled into more difficult soil, which enters the casing as it advances. The core is removed during and after the drilling. Control of line and grade is fairly easy.

(3) Boring -- A pipe can be jacked through a slightly oversized bore carved progressively ahead of the leading edge of the advancing pipe as the spoil is mucked back through the pipe. Line and grade control is excellent, but annular voids and overbreaks may be large and must be backfilled.

(4) Wet Boring -- A hole is sluiced by a jet of slurry and kept full of pressurized slurry to avoid collapse. The pipe is pushed through the slurry evacuating the excess. Soils may soften, expand or disintegrate from saturation by slurry moisture. This method is absolutely forbidden on all highways and roads under the jurisdiction of the Department.

(5) Untrenched installations (boring, coring or driving) will be required for all pipeline crossings of access controlled and other major highways. Open trench installations on other highways and roads will be permitted only where bad soil conditions or extremely difficult rocky conditions preclude untrenched construction, or where older pavement is severely deteriorated. All untrenched pipeline installations should extend under and across the entire roadway prism to a point 1.22 m (4 feet) beyond the toes of the foreslopes or borrow ditch bottom or across the access control lines, or as otherwise required by the Engineer or his/her representative.

(6) The oversize of boring operations is restricted to the minimum size necessary for the pipeline installation. The boring hole shall not exceed the pipe installation diameter by more than five percent (5%) oversize. The oversize excavation shall be backfilled to the satisfaction of the Engineer or his/her representative.

(7) All overbreaks, unused holes or larger diameter abandoned casings or pipes shall be backfilled with grout. The composition of the grout shall be cement mortar, a slurry of fine sand, or other fine granular materials, as local conditions dictate, and subject to the approval of the Engineer or his/her representative.

H. Relocation of existing pipelines: Highway design and construction requirements generally preclude compromise of proposed highway alignment or grade for new construction projects in order to avoid conflict with the line and grade of an existing pipeline. The feasibility of minor adjustments in the highway design to avoid extensive conflicts with existing utility facilities will be investigated, but in most instances a utility relocation or added pipeline protection will be required. Specific case factors are so varying as to make each such crossing unique. Therefore, standardized solutions are not uniformly applicable, but the following items will be considered:

(1) An existing pipeline should be relocated in alignment and/or grade, where the angle of the crossing is too acute, the top of the pipe is too close to the designed highway gradient, or its bedding will be depressed by static and dynamic highway loadings.

(2) An existing or relocated pipeline shall be encased or otherwise protected as would normally be required for a future pipeline installation, built under the same conditions.

(3) An existing pipeline, inadequate to support highway loadings, shall be sheltered by an adequately designed casing or reinforced by a jacket, cap, or replaced with heavier weight pipe.

(4) An existing pipeline which would lack adequate cover for protection from vehicular loads or highway construction operations, may be protected by a floating slab in lieu of encasement.

(5) Notwithstanding utility facility protection, the highway construction contractor shall be warned of, and made responsible for the security of utility facilities located within the construction limits of a project. Where there are unusual utility hazards, or where heavy construction equipment will cross a facility, the highway contractor shall provide a temporary earth cover, or other such protection as may be required.

(6) Further clarification of the responsibility of highway contractors to protect utilities and for the relocation of utilities concurrently with highway construction and other utility/highway contractor relationships, are defined as to the joint responsibilities required, in the New Mexico State Highway and Transportation Department Standard Specification for Highway and Bridge Construction, and any modifying provisions or rule changes applicable thereto.

I. Other design requirements:

(1) Overhead Power and Communication Lines: The type of utility construction, vertical clearances, the lateral location of poles and down guys and related ground mounted utility facilities along the roadside are factors of major importance in preserving a safe traffic environment, the appearance of the highway, and the efficiency and economy of highway construction and maintenance. As such, the physical location of aerial utility facilities shall be as close to the right-of-way line as possible, normally .3048 m (1 foot) inside the right-of-way line.

(2) Aerial utility lines to be installed longitudinally on highway rights of way will usually be limited to single pole construction. Joint-use single pole construction is encouraged at locations where more than one utility or type of facility are involved. Except in very unusual circumstances and for short distances only, duplication of utility facility aerial pole-line installations on the same side of the highway will not be permitted.

(3) The vertical clearance for overhead power and communication lines above the highway, and the lateral and vertical clearances from structures shall conform to the National Electrical Safety Code as a minimum, except where greater clearances are required by the utility, or where required by other industry or governmental codes or regulations.

(4) On and along conventional highways in rural areas, poles and related facilities shall be located at or as near to the right-of-way line as possible, normally within .3048 m (1 foot) thereof. Down guys, anchors or other components shall not project into cut and fill slopes, nor shall such surface mounted obstacles intrude into the clear roadside area for the segment of the highway involved.

(5) In keeping with the nature and extent of roadside development along conventional highways in urban areas, aerial or buried utility facilities shall be located at, or as near as possible to the right-of-way line. On curbed Sections, the utilities shall be located as far as possible behind the face of the outer curbs, and preferably behind the sidewalks. Utilities located within sidewalks shall not be permitted unless no other viable alternative can be identified; however, under no circumstances shall their location compromise ADA requirements. Utilities must be protected in accordance with the AASHTO guide insofar as possible. Variations must be fully justified to the Engineer or his/her representative. The Department may require certain details of the method and manner of relocation in order to accommodate aesthetic, environmental, ecological and historical considerations (i.e. commitments contained in EIS or other documents) or in order to obtain consistency with local zoning, codes or ordinances.

(6) Locations of aerial utility facilities on highways with exceptionally narrow rights-of-way, or on urban streets with abutting improvements are special cases that must be resolved in a manner consistent with prevailing limitations and conditions. Locations behind sidewalks are required where feasible. Before a utility requests Department approval of a location other than near the right-of-way line, consideration shall be given to designs utilizing self-supporting armless single pole construction, with vertical alignment of wires and cables, or other techniques permitted by the utility, industry or governmental standards or codes that are also conducive to a safe traffic environment. Exceptions to these clearances may be made where poles and guys may be placed behind existing barriers, guardrails, beyond deep drainage ditches, the toe or top of steep slopes, retaining walls and other similar protected locations, or when poles are of a breakaway type manufacture.

(7) Where irregularly shaped portions of the right-of-way lines extend beyond the normal right-of-way limits, individual consideration will be given to requests for variations to maintain a reasonably uniform alignment for longitudinal, aerial or underground utility facility installations.

(8) Longitudinal installations of utility facilities shall not be permitted in the highway median. In rare instances, aerial components of utility crossings may be permitted in a highway median in excess of 24.38 m (80 feet) in width, if the highway is not access controlled.

N.M. Admin. Code § 17.4.2.14

3/10/71, 11/15/96; Recompiled 12/31/01