Electrical · E-JFSEM

Underground Conduit Trench Configuration and Spacing Details

Materials

Elements

Walls Retaining Walls Roof / Floor Openings

About this detail

Underground electrical conduit installations require one inch of earth bedding at the bottom of the trench to prevent damage from rocks, sags, and pockets. Secondary conduit configurations are limited to a two wide by five deep or five wide by two deep arrangement utilizing spacers and a one-sack concrete slurry backfill, ensuring no single conduit is completely surrounded on all four sides by other conduits. Conduits may alternatively be installed side by side directly on the trench bottom without spacers or concrete slurry for a maximum of four conduits. Primary and secondary conduits terminate flush with the top of the pad or at least three inches above the bottom of the handhole where required. Transition areas near ninety-degree bends use spacers to allow straight entry into the pad opening.

INSTALLATION: 1 INCH EARTH IN THE BOTTOM OF TRENCH IS REQUIRED TO PREVENT DAMAGE FROM ROCKS, SAGS AND POCKETS. PLACE ALL SECONDARY CONDUITS WITHIN THE PAD OR HANDHOLE OPENING AS SHOWN ON PAGES 3426.1 OR 3426.2. TERMINATE PRIMARY OR SECONDARY CONDUITS FLUSH WITH THE TOP OF THE PAD. WHEN A HANDHOLE IS REQUIRED FOR SECONDARY CONDUITS, TERMINATE THEM NOT LESS THAN 3 INCHES ABOVE BOTTOM OF HANDHOLE. DO NOT CUT INTO THE CURVED PORTION OF THE ELBOWS. RADIUS OF CURVATURE IS 36 INCHES MINIMUM FOR 3 INCH, 4 INCH AND 5 INCH CONDUITS. THE CONDUIT CONFIGURATION REQUIREMENT BETWEEN TERMINATING POINTS LIMITS THE SECONDARY CONDUIT CONFIGURATION TO 2 WIDE X 5 DEEP OR 5 WIDE X 2 DEEP (NO ONE CONDUIT IS TO BE COMPLETELY SURROUNDED ON ALL FOUR SIDES BY OTHER CONDUITS), USING SPACERS AND ONE SACK CONCRETE SLURRY BACKFILL. CONDUITS MAY ALSO BE INSTALLED SIDE BY SIDE ON THE BOTTOM OF THE TRENCH WITHOUT SPACERS OR CONCRETE SLURRY (4 CONDUITS MAX.). IN THE TRANSITION AREA WHERE THE CONDUITS FROM THE BOTTOM OF THE TRENCH START TOWARD THE SURFACE (THE STRAIGHT PORTION BY THE 90° BEND), SPACERS MAY BE REQUIRED TO ALLOW THE 90° BENDS TO ENTER STRAIGHT INTO THE PAD OPENING. AT THE SURFACE POINT, THE CONDUITS MAY BE BUNDLED TOGETHER. USE SDG&E APPROVED BASE, SHADING AND BACKFILL. A B C 2 WIDE X 5 DEEP 5 WIDE X 2 DEEP 1-SACK CONCRETE SLURRY BACKFILL MAXIMUM OF 4 CONDUITS WITHOUT SPACERS OR CONCRETE SLURRY SHADING A EARTH D THE TOP AND INTERMEDIATE 3314 HANDHOLE SECTIONS MAY BE ELIMINATED WHEN INSTALLATION SERVES ONLY ONE CUSTOMER ULTIMATELY AND CONDUIT REQUIREMENTS DO NOT EXCEED PAGE 3426.1 OR AS SPECIFIED IN NOTE "F". IF MORE THAN FIVE 5 INCH CONDUITS ARE USED (REGARDLESS OF THE NUMBER OF CUSTOMERS), ONE TOP SECTION AND TWO INTERMEDIATE SECTIONS ARE REQUIRED. FOR SECONDARY INSTALLATION WITHOUT A HANDHOLE (ULTIMATELY ONE CUSTOMER ONLY), ANY COMBINATION OF 3 INCH, 4 INCH OR 5 INCH SECONDARY CONDUITS MAY BE USED PROVIDED THEY DO NOT EXCEED A TOTAL OF SIX OR THE TOTAL OF EACH SIZE CONDUIT SHOWN ON PAGE 3426.1. TWO EXTRA 1 INCH OR TWO EXTRA 2 INCH CONDUITS MAY BE ADDED TO SERVE STREET LIGHT, RECREATION BUILDINGS, ETC. FOR SECONDARY IN INSTALLATIONS WITH A HANDHOLE, ANY COMBINATION OF 3 INCH, 4 INCH, OR 5 INCH SECONDARY CONDUITS MAY BE USED, PROVIDED THEY DO NOT EXCEED THE TOTAL OF 9 OR THE MAXIMUM OF EACH SIZE CONDUIT (9-3", 9-4" OR 6-5"). TWO EXTRA 1 INCH OR TWO EXTRA 2 INCH CONDUITS MAY BE ADDED TO SERVE STREET LIGHT, RECREATION BUILDINGS, ETC. WHEN THE NUMBER OF REQUIRED CONDUITS IS LESS THAN THE TOTAL SHOWN ON THE SKETCHES, INSTALL THE CONDUITS IN NUMBERED SEQUENCE AS SHOWN. IF THE INSTALLATION IS FOR A 12KV TO 4KV TRANSFORMER (HPR TYPE), DO NOT USE HANDHOLE AND TERMINATE CONDUITS FLUSH WITH TOP OF PAD. INSTALL HANDHOLE 36" X 72" (STANDARD 3314), ONE TOP SECTION (STOCK NUMBER 336210), TWO INTERMEDIATE SECTIONS (STOCK NUMBER 336212) AND ONE PARKWAY COVER (WITH LIP STOCK NUMBER 286843). IN SOFT SOILS A CONCRETE BACKFILL (1-SACK MIX.) IS REQUIRED UNDER THE PAD, 12 INCHES BEYOND THE SIDE EDGES OF PAD AND 12 INCHES DEEP. F G H I J K REFERENCE: P. SEE STANDARD 3211 FOR PAD IDENTIFICATION. Q. SEE STANDARD 3370 OR 3371 FOR TRENCH, UTILITY POSITIONING, SHADING AND BACKFILL REQUIREMENTS. R. SEE STANDARD 3376 FOR CONCRETE SLURRY, SHADING AND TYPE OF CONDUIT. S. SEE STANDARD 3481 FOR TRANSFORMER BARRIER PROTECTION. T. SEE STANDARD 3483 FOR MINIMUM OPERATING AND CLEARANCE REQUIREMENTS (PAD PLACEMENT). U. SEE STANDARD 3484 FOR PAD INSTALLATION OF PAD-MOUNTED EQUIPMENT. V. SEE STANDARD 3486 FOR RETAINING WALL REQUIREMENTS AND CLEARANCES FROM REVERSE SUBGRADE RETAINING WALLS. W. SEE STANDARD 3487 FOR RETAINING WALLS. X. SEE STANDARD 3751 FOR TRANSFORMER INSTALLATION. Y. SEE STANDARD 4512 FOR EQUIPMENT GROUNDING. Z. SEE STANDARD 4514 FOR GROUNDING TELCO CONDUCTOR IN PAD-MOUNTED EQUIPMENT.

Members view this detail in full resolution, download the CAD files (SVG, PDF), and can adapt it in the built-in CAD editor — export DXF, DWG, or PDF.

Start membership

Similar details