When preparing a proposal, there are a number of technical considerations that should be kept in mind. A number of these are outlined below. Please note that this is not intended to be a comprehensive list of requirements, but aims to serve as a guideline to prepare a proposal. Reviews for each proposal are conducted individually by Hydro One and may require several weeks or months to complete depending on the complexity of the proposal.
Transmission conductors (wires) are dynamic in nature. They can sag lower to the ground depending on parameters such as ambient temperature and operating conditions. Minimum vertical clearances must be maintained from the maximum design sag levels of the conductors (worst-case scenario). Hydro One will review these clearances as they are case-specific and not immediately apparent by observation alone.
ACCESS TO STRUCTURES
An unhindered, minimum 6-metre wide access path to facilities on the corridor must be provided for maintenance vehicles. A 15-metre clear working radius around transmission structures is required in order to maintain access for vehicles carrying out routine maintenance. A 3-metre radius around each tower footing must be left unpaved for access to the footing.
Hydro One crews use heavy equipment to perform maintenance work on a 500 kV transmission tower.
GRADING, DRAINAGE AND STORMWATER MANAGEMENT
Grading changes must not impact vertical clearance requirements or result in standing water anywhere along the corridor.
No fill material may be placed on the ROW without written approval from Hydro One.
Catch basins that are not positioned within a paved roadway are not permitted.
Stormwater management (SWM) ponds placed under 115 and 230 kV transmission lines cannot exceed two-thirds of the corridor width.
SWM ponds under 500 kV transmission lines cannot exceed one-third of the corridor width.
SWM ponds must be designed to withstand the effects of 100-year storm conditions.
ROADS AND PARKING
Roads crossing the ROW should be perpendicular to the hydro corridor. Curb cuts or access gates should be provided for Hydro One maintenance vehicles. Parking facilities on 115 kV and 230 kV ROWs should be restricted to passenger vehicles only. Large truck and trailer parking is not permitted. Parking facilities are not permitted under 500 kV ROWs. Transmission towers near roads and parking areas must be protected by standard highway barriers.
PIPELINES AND UNDERGROUND FACILITIES
All underground facilities must be designed to withstand the loading conditions created by heavy maintenance vehicles that may be used by Hydro One. The ROW must be restored to pre-construction condition once the project is completed. Excavation using heavy machinery is prohibited within 10 metres of tower footings to protect foundations. Within 10 metres, excavation must be carried out by hand or by use of a VAC system. Pipelines on ROWs must adhere to the provisions of CSA Standard C22.3 No. 6.
Plantings which grow to a maturity height over 4 metres are not permitted on the ROW. These low-growing shrubs are permitted to be planted on ROWs, including: Gray Dogwood, Red Oiser Dogwood, Alternate Leaf Dogwood, Cornus racemosa, Cornus sericea, Cornus alternifolia, Elderberry, Sambucus Canadensis, Forsythia, Forsythia ovate, Honeysuckle, High Bush Cranberry, Lonicera spp., Viburnum trilobum, Mugo Pine and Pinus mugo mugo.
These shrubs should be planted in such a way as to not impede access to the transmission towers. An area of 15 metres around transmission towers should be kept clear of shrubs to permit Hydro One access to towers.
All plantings must be consistent with the Hydro One-approved species list and the overall plan is subject to Hydro One’s approval. Visit
Vegetation Management for more details.
Buildings and permanent structures are not permitted on ROWs.
Flammable or hazardous materials may not be stored on ROWs.
Consideration should be given to minimizing the use of conductive (metallic) material where alternatives exist (e.g. fences).
The proponent is responsible for all costs of modifying, relocating, or monitoring Hydro One assets as a result of its proposal.
Requirements for performing work in the vicinity of international powerlines: