BC Hydro is asking for permission to leave 45 structures at the bottom of the Peace River once the multibillion-dollar Site C reservoir begins filling.
In a request to the B.C. Environmental Assessment Office, BC Hydro claims the structures would be more detrimental to the local fish species and habitat if removed than if allowed to stay in place once filling begins sometime in the next year.
The original Environmental Assessment Certificate issued to the Site C project had many conditions designed to minimize the environmental impact of the massive construction project.
Condition #4 of Schedule B required BC Hydro “manage harmful project effects on fish and fish habitat during the construction and operation phases by implementing mitigation measures.”
This condition stated any temporary structures used in construction needed to be removed as soon as they were no longer required to be used.
BC Hydro is asking for this condition to be amended to allow structures to stay if they provide a benefit or removal will result in harm.
“Any structures that will be retained in the reservoir will be assessed by a qualified environmental professional to confirm they won’t pose a risk to the environment,” BC Hydro states.
If the removal of a structure affected the area in a way that was equal to its retention, BC Hydro stated it would like to leave it behind.
Items are generally considered more hazardous to fish populations if the work required to remove them would be more invasive than if they were submerged when the reservoir fills sometime in 2023 or 2024, according to the request.
“Steel, concrete and aggregate are the primary materials used to build infrastructure in waterways all across the province as they are inert building materials – leaving these materials in place is common construction practice,” said BC Hydro.
“The Site C project’s earthfill dam, powerhouse and spillways are made up of similar materials like concrete, steel and aggregate and these components will also be under water for the next 100 years.”
An example of how structural removal could be more detrimental is the temporary reservoir causeways, primarily made of gravel and riprap.
Removing these structures could increase “the risk of sedimentation and fuel spills from having equipment working in the river,” reads the request.
“In addition, if a temporary structure is large and more than one-third buried in the stream substrates (e.g., steel piles for the Moberly Debris Facility), its removal may result in a large amount of sediment being suspended and may result in undesirable changes to in-channel habitats.”
The 45 structures include concrete abutments and riprap from temporary construction bridges, portions of causeways to access gravel material in the reservoir, and diversion channels for realignment of Highway 29 made from riprap and rock-filled gabions, among others.
BC Hydro emphasized the practice is commonplace and would not result in anything untoward being left behind.
“It’s necessary to clarify that we are not leaving behind debris, or garbage, as some have characterized it, when the reservoir fills. We’ve proposed this amendment based on advice we have received by environmental experts who say leaving the structures in place is in the best interest of the fish and their habitat,” BC Hydro said, adding most of the temporary structures were actually made from gravel and riprap sourced from the Peace River and Portage Mountain Quarry and that none of the proposed structures contain leachates.
In a report attached to BC Hydro’s written request, senior biologist for WSP Canada Inc. Katie Frye, found 37 of the 45 proposed structures would cause more harm to fish if they were removed. The other eight had an equal rating, meaning retention and removal would have similar effects.
The three structures found to bring the most risk if removed were all abutments and causeways. Frye writes the structures had a high risk “due to the requirement for reactivation of access, which would include four stream crossings for access as well as heavy equipment use for structure removal.”
BC Hydro said the project is currently 75 per cent complete and “on-track to have all six generating units in-service by fall 2025.
“Provided work continues to advance as scheduled in the months ahead, reservoir filling could occur as early as this fall.”