Underground electrical equipment

A qualified utility employee of EPCOR must be present on site when working within 5 m of transmission voltages of greater than or equal to 72 kV. It is the obligation of the contractor to contact EPCOR in this situation.

The depth and alignment of the cables must be confirmed before mechanical excavation equipment is allowed to move any soil. All cables in the proposed excavation area must be exposed to sight by hand digging and/or hydro excavation [Source: Alberta's OHS Code 2009, Sections 448(2) and 448(1)].

All workers must be equipped with and be wearing the following Personal Protective Equipment while exposing buried EPCOR facilities:

• Protective head wear: CSA Standard CAN/CSA-Z94.1-05 / ANSI Standard Z89.1-2003.
• Protective eye wear: CSA Standard Z94.3-07.
• Protective footwear: CSA Standard Z195-02 / ASTM Standard F2413-05.
• Arc rated clothing (minimum protection rating of 8 cal/cm2 ): ASTM Standard F1506, ASTM Standard F2302, Canadian General Standards Board (CGSB) Standard CAN/CGSB 155.20, and CSA Standard Z96.
• Any additional equipment as required by Alberta Occupational Health and Safety Code Part 18, Personal Protective Equipment.

Never probe for buried facilities with pointed tools such as pick axes or pointed bars. A shovel with a dry, nonconductive handle must be used to remove materials away from cables.

• Do not use full body weight on the shovel when digging.
• Use a prying (rather than striking) motion to loosen hard dirt.
• Dig on an angle and from the side.
• Excessive prying, pulling, or bending when moving cables must be avoided.

Hydrovac operating specifications:

• The water pressure and temperature settings must not exceed 1,500 psi and 38°C. Any hydrovacing over these maximums can only be done on de-energized cables.
• The wand tip must be equipped with a high pressure nozzle single jet oscillating head.
• The end of the water wand and vacuum hose must have a urethane or equivalent cover to prevent mechanical damage.
• Signs indicating 'Danger' must be a minimum of 1.2 m from the job site.

The following safe work methods must be followed when hydrovacing:

• The water wand must be in a constant circular motion, avoid moving the wand parallel to the buried facility (jabbing motions are to be avoided).
• The water wand must never be left unattended with the pressure on and water flowing.
• The excavation should begin beside the locate mark(s) and go to a depth below the expected depth of the buried facility. At that point, soil covering the buried facility can be removed.
• Once the buried facility has been exposed, a distance of at least 175 mm (7 in.) should be maintained between it and the oscillating head of the water wand.

Under faulted conditions, the water, wand, and vacuum may become energized.

"Spotting" or "pilot" holes must be large enough and suitably spaced to confirm the depth and alignment of the cables: cable depth is consistent = 3 m intervals, and if cable depth varies or is unclear = 1.5 m intervals.

In situations where large volumes of soil need to be hydro excavated, additional slot trenches must be cut once the expected buried facilities have been exposed. This will help confirm that no unmarked buried facilities are present. The slot trenches must:

• Be at right angles from the exposed facilities.
• Go outwards from the exposed buried facilities to the full width of the excavation.
• Be cut down to the full depth of the exposed facilities / proposed excavation / depth. determined through on-site assessment of conditions by a competent worker.

Once the cables are visible through the "spotting" or "pilot " holes, the soil in the hand exposed zone can be removed using mechanical excavation equipment. An undisturbed layer of soil immediately above the cables at least 150 mm to 300 mm thick (6 in to 12 in.) must remain. This layer of soil must be removed by hand digging, and checked with a probe to confirm the location of all buried facilities.

When removing soil with a bucket, the bucket must not scrape more than 2 m of soil horizontally at a time along the cable route.

If a green tape splice is located while excavating, all excavation work must stop within 1 m of the splice location and EPCOR must be contacted. Moving an energized splice must only be done by a qualified EPCOR tradesperson.

If a power cable or facility is damaged or severed during the digging process, all digging must stop immediately and all work activities must be shut down. The employee-in-charge must notify EPCOR at 780-412-4500 to have the power shut off. Digging can only resume once the cable is inspected, assessed, and deemed safe by EPCOR. Repairs may be required before work can resume.

The employee-in-charge must ensure that the excavation is properly shored or cut back. Before the crew leaves the excavation at the end of the work day, the employee-in-charge must ensure that the excavation is appropriately secured with signage, barriers, barricades, etc.

Duct banks and conduit

For any excavation that results in a duct bank or conduit to be exposed more than 2 m in length, the contractor must contact EPCOR's Electricity Safety Codes Officer at safetycodes@epcor.com or call 780-412-4500 to request a Safety Codes Consult.

DO NOT ATTEMPT TO HANDLE POWER CABLES.

Concrete encased duct banks must be supported as determined by a civil engineer.

The work site must not be left unattended at any time unless all open excavations on the work site have been properly secured:

• Place plywood over the cables, and sec​ure by placing soil bags on the plywood (minimum 1 ft. cover of sand/soil).
• Where excavations are too large to cover, the excavation must be secured with barricades (at least one must have a contact phone number), snow fence, and barrier tape.

In situations where an excavated site will be left overnight with energized cables and it is not practical to secure the cables, site security personnel will be retained by the contractor to ensure public safety.

Notify EPCOR's Electricity Safety Codes Officer during business hours at 780-412-4450 prior to any backfilling.

All excavations must be backfilled with sand (free of stones and items with sharp edges), and be placed in uniform lifts not exceeding 300 mm and compacted to the City of Edmonton Design and Construction Standards, Volume 2 (epcor.com / edmonton.ca) – Roadways. Soil with high thermal resistivity that contains large amounts of organics, peat, black loam, sod, hardened clay, stones, straw, snow, or frozen material is not acceptable.

All excavations around transmission cables must be backfilled using thermal backfill for the full length of cable that was uncovered during excavation. Place the thermal backfill around cable in the following quantities:

• 0.4 m below cable.
• 0.5 m on each side of cable.
  
• 1.3 m above cable.

If you require specific instruction from EPCOR for backfill requirements, contact EPCOR's Underground Transmission Foreman at 780-412-7819.