Ecological issues: Erosion
The Peace River area consists of glaciolacustrine sediments (e.g. shale consisting of Montmorillite clay) and fine silt,"...that are particularly susceptible to creep, slumping and sliding." (http://www.em.gov.bc.ca/Mining/geolsurv/surficial/landslid/ls3.htm) This shale is very weak, quickly turning back to mud when near the surface and/or exposed to water.
One need only to take a boat ride through the proposed Site C floodzone to see hundreds of active slides and recent sloughs. For example, on May 23, 1973 the Attachie Slide completely blocked off the Peace River for approximately 10 hours with over 24 million cubic metres of sediment. (See an arial view of this slide after the river was able to flow again: Thurber Consultants' photo of Attachie Slide.)
Peace River area slides became much more common after the WAC Bennett and Peace Canyon dam projects were built. Fortunately, both dam faces were located on stronger bedrock - but the proposed Site C dam face is not. A few kilometers downstream from the proposed Site C dam face is the Taylor bridge. In a report on the 1957 collapse of this bridge, the Peace River Branch of the Professional Engineers and Geoscientists of BC conclude that, "Valley slopes in the Peace River region are susceptible to landslides because of the nature of the rocks and sediments that are found in the area. Building in the valleys can make this situation worse." (www.apeg.bc.ca/services/branches/documents/pr/Peace_River_Bridge_Collapse.pdf). To read more on this catastrophe, once hailed one of Canada's most costly landslides, download the attached 3 page report, "Peace River Bridge Collapse" (PDF 114KB).
The Site C Heritage Resource Inventory and Assessment completed by Brian Spurling (1980) for BC Hydro compares the impacts of erosion and slope stability with and without the construction of the Site C project. The report's discussion and conclusions rely heavily upon the work of Thurber Consultants Ltd., which was also contracted by BC Hydro during the planning stages of the original Site C proposal. This work is primarily found in Thurber Consultants' (1978a) report, Peace River Site C Hydroelectric Development, Physical Environment Impact Assessment.
Spurling states that, "...it cannot be predicted were slides will take place..." (p.63) and so appears to accept Thurber Consultants' established 'flood safeline' (FSL). This FSL would be imposed on all privately owned land on the north side of the river. According to the Thurber report,
"For the 130km (81 miles) of low banks, the average setback based upon studies of private property would be 65m (215 feet) for the FSL. The residential safeline location for high banks would fall 150 to 180m (500 to 600 feet) back from the top of the present slope for the entire 120km (73 miles) of shoreline. The safeline for high bank areas under present conditions is identical to that after flooding. In low bank areas, the present safeline lies close to the river bank" (p.19).
Who wants such a safety hazard in their backyard?
How do these private landowners feel about losing valuable riverfront property and related recreational opportunities?
Hasn't BC Hydro ruined enough Peace River banks?
One need only to take a boat ride through the proposed Site C floodzone to see hundreds of active slides and recent sloughs. For example, on May 23, 1973 the Attachie Slide completely blocked off the Peace River for approximately 10 hours with over 24 million cubic metres of sediment. (See an arial view of this slide after the river was able to flow again: Thurber Consultants' photo of Attachie Slide.)
Peace River area slides became much more common after the WAC Bennett and Peace Canyon dam projects were built. Fortunately, both dam faces were located on stronger bedrock - but the proposed Site C dam face is not. A few kilometers downstream from the proposed Site C dam face is the Taylor bridge. In a report on the 1957 collapse of this bridge, the Peace River Branch of the Professional Engineers and Geoscientists of BC conclude that, "Valley slopes in the Peace River region are susceptible to landslides because of the nature of the rocks and sediments that are found in the area. Building in the valleys can make this situation worse." (www.apeg.bc.ca/services/branches/documents/pr/Peace_River_Bridge_Collapse.pdf). To read more on this catastrophe, once hailed one of Canada's most costly landslides, download the attached 3 page report, "Peace River Bridge Collapse" (PDF 114KB).
The Site C Heritage Resource Inventory and Assessment completed by Brian Spurling (1980) for BC Hydro compares the impacts of erosion and slope stability with and without the construction of the Site C project. The report's discussion and conclusions rely heavily upon the work of Thurber Consultants Ltd., which was also contracted by BC Hydro during the planning stages of the original Site C proposal. This work is primarily found in Thurber Consultants' (1978a) report, Peace River Site C Hydroelectric Development, Physical Environment Impact Assessment.
Spurling states that, "...it cannot be predicted were slides will take place..." (p.63) and so appears to accept Thurber Consultants' established 'flood safeline' (FSL). This FSL would be imposed on all privately owned land on the north side of the river. According to the Thurber report,
"For the 130km (81 miles) of low banks, the average setback based upon studies of private property would be 65m (215 feet) for the FSL. The residential safeline location for high banks would fall 150 to 180m (500 to 600 feet) back from the top of the present slope for the entire 120km (73 miles) of shoreline. The safeline for high bank areas under present conditions is identical to that after flooding. In low bank areas, the present safeline lies close to the river bank" (p.19).
Who wants such a safety hazard in their backyard?
How do these private landowners feel about losing valuable riverfront property and related recreational opportunities?
Hasn't BC Hydro ruined enough Peace River banks?