DT-SS-C-1005_Rev_11_Concrete_Transformer_Pad_Rev_11.pdf
PDF 265 KB Posted
- Attached to
- Purchase and Delivery of Assorted Precast Underground Concrete Vaults, Pads and lids for a 5 year period
- Solicitation number
- RFQ194877
- Issued by
- Santa Clara County, California
About this file
This is an engineering standard document for a Concrete Transformer Pad from the City of Palo Alto, California, detailing precise specifications for transformer pad construction and installation. The standard drawing (DT-SS-C-1005) provides comprehensive technical details for both poured-in-place and precast transformer pads, including dimensional requirements for different transformer sizes ranging from 25 to 2500 kVA. The document specifies critical installation parameters such as conduit placement, ground rod positioning, reinforcing bar specifications, and concrete composition requirements.
The technical specifications include detailed requirements for pad construction, such as using concrete designed to achieve 3000 PSI strength in 28 days, proper compaction of disturbed earth, slurry placement, and specific curing procedures. Additional critical instructions cover conduit installation (including termination with end bells or ground bushings), minimum clearance requirements (3 feet radial clearance from other structures, 8 feet in front of the pad), and guidelines for guard post installation. The document also provides notes on rebar specifications, ground rod placement, and requirements for transformer anchoring, with references to additional City of Palo Alto standard drawings for related infrastructure components.
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Text version
USE REMOVABLE GUARD POSTS WHEN INSTALLED LESS THAN 8 FEET IN FRONT OF EQUIPMENT DOORS
OR WHERE PERMANENT POSTS WOULD OBSTRUCT ACCESS FOR INSTALLATION OR MAINTENANCE.
GUARD POST INSTALLATION MUST BE COORDINATED WITH CONDUIT INSTALLATION TO AVOID
CONFLICTS.
CONTACT CPAU ENGINEERING OR UNDERGROUND INSPECTOR FOR GUARD POST PLACEMENT
LOCATIONS DETAIL.
NOTES
1. DISTURBED EARTH UNDER THE PAD SHALL BE REPLACED BY SAND OR OTHER SUITABLE MATERIAL COMPACTED TO 95% OF MAXIMUM DRY DENSITY (ASTM D-1557). COMPACTION TEST RESULTS SHALL BE
PROVIDED TO THE CPAU INSPECTOR.
2. PLACE 6” DEPTH ONE SACK, PER CUBIC YARD, SLURRY IMMEDIATELY BELOW THE PAD.
3. CONCRETE IS REQUIRED BETWEEN ALL CONDUITS, LEVEL TO TOP OF THE PAD.
4. CONCRETE SHALL BE DESIGNED TO ATTAIN A STRENGTH OF 3000 PSI IN 28 DAYS.
5. AFTER PLACING, MOIST CURE CONCRETE FOR 7 DAYS BEFORE PLACING EQUIPMENT.
6. WOOD FLOAT FINISH TOP OF SLAB. ALL EDGES AND CORNERS ARE TO BE FINISHED SMOOTH.
7. EXPOSED HORIZONTAL SURFACES ARE TO BE SLOPED SLIGHTLY FOR DRAINAGE.
8. A MINIMUM OF 6 FEET SHALL BE MAINTAINED BETWEEN GROUND RODS.
9. CAP ALL CONDUITS.
10. CONTACT CPAU FOR APPROVED PRE-CAST TRANSFORMER PADS.
11. PADS NOT SECURED IN PLACE BY CONCRETE OR ASPHALT SHALL HAVE A 2’ WIDE BY 6” DEEP STRIP OF 90%
COMPACTED GRAVEL ALONG ALL EDGES.
12. A MINIMUM OF 3 FEET OF RADIAL CLEARANCE BETWEEN THE TRANSFORMER PAD AND ANY OTHER
STRUCTURE SHALL BE PROVIDED (SEE NOTE 21).
13. IF THE TRANSFORMER IS TO BE LOCATED IN AN AREA SUBJECTED TO VEHICULAR TRAFFIC, BARRIERS SHALL BE PROVIDED IN ACCORDANCE WITH DETAIL 1 OR 2 ON SHEET 3. CONTACT CPAU ENGINEERING OR UG
INSPECTOR FOR THE TYPE, NUMBER REQUIRED, AND LOCATION OF BARRIERS.
14. PLASTIC CONDUITS SHALL BE TERMINATED WITH END BELLS. GALVANIZED STEEL CONDUITS SHALL BE TERMINATED WITH GROUND BUSHINGS. ALL CONDUITS AND ENDS WILL BE TO THE FINAL GRADE OF THE PAD.
15. CONDUIT RISER BENDS SHALL HAVE A MINIMUM RADIUS OF 36”.
16. PRIMARY CONDUITS SHALL BE LOCATED IN THE LEFT HALF OF THE CONDUIT OPENING. SECONDARY
CONDUITS SHALL OCCUPY THE RIGHT HALF. (SEE SHEET 1)
17. CLEARANCE AROUND THE TRANSFORMER PAD SHALL BE PER CPAU STANDARD DWG. DT-CL-U-1031.
18. ALL REBAR SHALL BE #4 A-615 GRADE 40. REBAR JOINTS SHALL BE FIRMLY AND SECURELY HELD IN POSITION
BY WIRING AT INTERSECTIONS WITH NO. 16 GAUGE WIRE.
19. THE MAXIMUM NUMBER OF CONDUITS ENTERING THE SECONDARY SLOT SHALL BE FOUR. CONTACT THE ELECTRIC UTILITY PROJECT ENGINEER FOR DESIGNS REQUIRING MORE THAN FOUR SECONDARY CONDUITS.
20. GROUND ROD AND CLAMP, 5/8” X 8’. SEE CPAU STANDARD DWG. # DT-SS-U-1001 FOR MATERIALS
INFORMATION.
21. TRANSFORMER ANCHORS SHALL BE INSTALLED BY CPAU ACCORDING TO MANUFACTURER’S INSTRUCTIONS.
EXPANSION BOLT SHALL BE “PARABOLT” BY MOLY OR APPROVED EQUIVALENT. MINIMUM EMBEDMENT LENGTH
AND EDGE DISTANCE SHALL MEET THE MANUFACTURER’S REQUIREMENTS.
22. A MINIMUM OF 8 FEET CLEARANCE SHALL BE MAINTAINED FROM THE FRONT OF THE PAD FOR OPERATIONAL
NEEDS. A MINIMUM OF 3 FEET SHALL BE MAINTAINED ON UNOPERABLE SIDES AND BACK. ALL
MEASUREMENTS ARE TAKEN FROM THE EDGE OF THE PAD. SEE CPAU ENGINEERING STANDARD DT-CL-U-1031.
23. UNLESS OTHERWISE APPROVED BY CPAU, A BOX SHALL BE INSTALLED NEXT TO THE TRANSFORMER PAD.
PRIMARY CONDUITS ENTERING THE PAD WILL FIRST GO TO THIS BOX. REFER TO APPLICABLE LAYOUT DRAWING FOR LOCATION AND SIZE. SEE CPAU STANDARD DWG. # DT-SS-U-1002 FOR BOX INSTALLATION
DETAILS.
| 1005 - DT-SS-C-1005 - rev 11 Sheet 1 (1) |
| 1005 - DT-SS-C-1005 - rev 11 Sheet 2 (1) |
| 1005 - DT-SS-C-1005 - rev 11 Sheet 3 (1) |
| 1005 - DT-SS-C-1005 - rev 11 Sheet 4 (1) |
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