SECTION 709: RIGID ELECTRICAL CONDUIT
709.1 Description
This Work consists of providing and installing rigid electrical conduit.
709.2 Materials
709.2.1 Nonmetallic Conduit
Nonmetallic conduit shall be hi gh-impact PVC. Schedule 40 cond uit and elbows are manufactured to NMEA TC-2 UL 651 Specifications. Conduit and fittings shall comply with requirements of UL Stand ards (Publication UL 651) and carry respective UL listings and labels.
709.2.2 Metallic Conduit
The Contractor shall provide gal vanized rigid conduit in accord ance with UL 6, ANSI C80 and Federal Specification WW-C-581E , or intermediate metallic c onduit (IMC) in accordance with UL 1242 and Federal Specification WW-C-581E. The Contractor shall hot-dip galvanize IMC. The Contractor sha ll provide watertight fittings of the same Material as the conduit. The Contractor shall provide approved watertight, expansion cou plings for metallic conduit, as recommended by the m anufacturer and designed to com pensate for linear thermal expansion of a run of metallic conduit.
709.2.3 Liquid-Tight Flexible Conduit
The Contractor shall provide li quid-tight flexible conduit cons isting of an extruded polyvinyl jacket over a flexibl e hot-dipped galvanized core (Ty pe UAG), UL listed, and in accordance with the NEC®.
709.3 Construction Requirements
709.3.1 General
The Contractor shall run electrical cable and wire in conduit, except inside poles, unless otherwise specified in the Contract. Where wire is not installed, a tr acer wire must be installed fo r line locating. When trenching, the Contractor s hall place caution tape one (1) foot above the conduit. The Contractor shall use nonmetallic conduit for underground in stallations. The Contractor shall use metallic conduit for Bridge decks and rail ings. The Contractor may encase conduit in c oncrete bases. The Contractor shall use metallic conduit for above ground inst allations. The Contractor may use larger size conduit than specified in th e Contract, at no additional cost to the Department, provided the larger size is used for the entire run from outlet to outlet. The Department will not allow reducing couplings. When using existing underground metallic conduit in a new syste m, the Contractor shall clean with a mandrel and blow out with compressed air. The Con tractor shall blow out existing nonmetallic conduit with compress ed air. If the existing condu it contains excessive amounts of Deleterious Material, the C ontractor shall flush conduit wit h water and blow with compressed air, as directed by the Project Manager. The Contractor shall provide pull boxes at the locations specif ied in the Contract.
709.3.1 1 Conduit Routings
The Project Manager may change c onduit run routings specified i n the Contract to avoid underground obstructions. The Contractor shall keep accurate r ecords of any change from conduit locations specified in the Contract on as-built drawing s, and submit the details to the Project Manager before the Depart ment’s final Acceptance of the Project.
709.3.1 2 Excavation and Backfill
The Contractor shall plan the trenching and conduit placement o peration to minimize overnight open trenches and exposed conduit. The Contractor shall excavate (trench) and backfill conduit tre nch in accordance with Section 705.2.2, “Backfill Materials,” and Section 705.3.2, “Ex cavation and Backfill.”
709.3.1 3 Conduit Placement Depth
The Contractor shall lay conduit at least 30 inches below the f ollowing: 1. Finished surface in Street and driveway areas; 2. Top of curb in Sidewalk areas; and 3. Natural ground line in unpaved areas. If approved by the Pr oject Manager, the Contractor may place the conduit from 18 inch to 30 inch deep i n the following areas: a. Unpaved Median; b. Open (natural ground) where the Department Plans no future d evelopment; and c. Where underground utility conflicts occur at the 30 inch dep th.
709.3.1 4 Conduit Terminations
The Contractor shall terminate, stub, and cap empty conduit. T he Contractor shall thread metallic conduit ends and cap with standard conduit caps until wire placement begins. The Contractor shall provide insulated metal ground bushings for th readed ends when caps are removed and electrically connect them in accordance with the NE C®. The Contractor shall cap nonmetallic conduit ends until wiring begins. The Contractor shall extend condui t terminating in poles, cabin ets, or pedestal bases from two (2) inches to four (4) inches vertically above the bas es. The Contractor shall terminate conduit that enters a pull box f rom one (1) inch to three
3.inch inside the box wall and from two (2) inch to three (3) inch above the top of gravel sump and slope it to facilitate convenient pulling of wires or cables. To ensure pull boxes are uncluttered, the Contractor shall run conduit into the pull box Section 709: Rigid Electrical Conduit Page 824 bottom at the nearest wall. The Contractor shall allow for exp ansion and contraction of the conduit. The Contractor shall install conduit terminations with bushings to prevent wire insulation damage during installation.
709.3.1 5 Conduit Bends
The Contractor shall make conduit bends, except factory bends, with a radius of at least six (6) times the inside diameter of the conduit. The Contract or shall ensure bending radii and the number of bends in accordance with the NEC® and local codes . The Contractor shall use factory-made bends or bend conduit wit hout crimping or flattening, using the l ongest radius practical. The Contractor shall use metallic bends for difficult or long c onduit runs.
709.3.2 Nonmetallic Conduit
The Contractor shall straigh t cut nonmetallic conduit; square a nd trim ends after cutting to remove rough edges. The Contractor shall use solvent weld conn ections in accordance with the conduit manufacturer's rec ommendations. If connecting nonm etallic conduit to metallic conduit, the Contractor shall use threaded couplings. The Contractor shall run a solid, bare No. 8 or larger, AWG cop per conductor continuously in nonmetallic c onduit, except in conduit containi ng only communication cables. The Contractor shall install expansion couplings according to t he manufacturer’s diagrams and instructions.
709.3.2 1 HDPE Conduit Extruded over Conductors
If allowed by local electrical codes for lighting and service r un conduit, the Contractor may use HDPE conduit that is continually extruded over the wire or cable specified in the Contract. The Contractor shall prevent adhesion between the wi re or cable and the conduit. The Contractor shall obtain approval for this method from the e lectrical inspecting authority and provide proof to the Project Manager before insta llation.
709.3.2 2 Bending of Nonmetallic Conduit
The Contractor shall bend nonmetallic conduit using one (1) of the following methods: 1. Apply an even heat, not to exceed 300 °F, to a portion of th e conduit wrapped in aluminum foil, until attaining the desired flexibility. Minimi ze charring of the conduit; and 2. Use of a thermobender, suitable for bending nonmetallic cond uit.
709.3.3 Installation Under Existing Pavement
The Contractor shall install metallic conduit under existing pa vement by approved jacking or boring methods. If using drilling mud, the Contractor may install nonmetallic c onduit by machine pulling through a directionally bored hole. The Contractor shall not m achine pull nonmetallic conduit Section 709: Rigid Electrical Conduit Page 825 through dry holes (made by hole hog or other dry-expansion meth ods). The Contractor shall place jacking or boring pits a t least two (2) ft from the edge of any type of pavement, measured from the side of the pit nearest to the pavement. The Contractor shall only use metallic conduit, if jacking conduit. The Department will not allow the excessive use of water in the installation of conduit under existing pavement. The Project Manager may approve r elocation of conduit runs or p avement cutting where insufficient room exists for ja cking or boring pits, or if unde rground obstacles are encountered. The Contractor shall repair existing pavement, Sidewalks, drive ways and landscaped areas to original or better c ondition at no additional cost to the Department.
709.3.4 Conduit for Structures and Foundations
The Contractor shall cap conduit stubbed out for future use fro m Structures or foundations. The Contractor shall rust-protect metallic conduit to a minimum of six (6) inches inside concrete Structures or foundations. The Department will not re quire rust protection for nonmetallic conduit. The Contractor shall seal conduits running to soffits, walls, o r light fixtures below the elevation of the pull box with an approved sealing compound. A lso, the Contractor shall seal light fixtures located below t he elevation of the pull box.
709.3.4 1 Bridge Structures
The Contractor shall use metallic conduit embedded in concrete for abutments, piers, or Bridge decks. The Contractor shall securely attach conduit to the reinforcing steel (by approved methods) at intervals not to exceed four (4) ft. The Contractor shall use galvani zed malleable iron clamps (or o ther approved methods) to secure conduit runs on Struct ure surfaces spaced no more tha n five (5) ft apart.
709.3.4 1.1 Expansion Fittings
The Contractor shall install expansion fittings where conduit c rosses a Structure joint, using tubing the same size as the conduit. The Contractor shal l provide expansion fittings with a bonding jumper of No. 6 AWG flexible wire or approved equival ent. If use of expansion fittings or flexible tubing is not feasible, as determined by t he Project Manager, the Contractor shall install the conduit in a watertight metal sleeve. The Co ntractor shall ensure a clearance between the outside of the conduit and the inside of the metal sleeve of from 1/2 inch to one
1.inch.
709.3.4 1.2 Liquid-Tight Flexible Conduit
The Contractor may use liquid-tight flexible conduit between St ructure sections to accommodate movement, if specified in the Contract. The Contra ctor may use liquid-tight flexible conduit within a concre te pour, if approved by the Pro ject Manager.
709.4 Method of Measurement
Section 709: Rigid Electrical Conduit Page 826 The Department will measure Rigi d Electrical Conduit parallel t o the centerline of the installed conduit.
709.5 Basis of Payment
Pay Item Pay Unit Rigid Electrical Conduit ____inch Dia. Foot
709.5.1 Work Included in Payment
The following Work and items will be considered as included in the payment for the main items and will not be measured or paid for separately: 1. Hardware for conduit installation, 2. Excavation, backfill, bor ing, jacking and compaction, 3. Protective coatings; 4. Bare No. 8 AWG copper conducto r for nonmetallic conduit inst allation, 5. Caution tape; and 6. Cutting of pavement and replacement of surfacing. Section 710: Pull Boxes and Splice Cabinets Page 827
Source: New Mexico Standard Specifications for Highway and Bridge Construction, 2019 Edition. Pages 0–0 of 974.