Coquitlam Dam Seismic Upgrade Project ... - BC Hydro

Note: To ensure the protection of aquatic life and their habitats, BC Hydro and its
contractors will ensure that water exiting the construction areas and entering a
drainage course will meet the following criteria:
Total Suspended Solids: 1) 25 mg/l above background during dry weather
2) 75 mg/l above background during design storm event
There will be no sediment laden water permitted to enter the reservoir.
Efforts will be made to control silt-laden runoff from the working and stockpile areas. This will
involve utilizing a combination of several techniques on a site-specific basis as described below:
• Installation of upslope drainage interception to remove clean uncontaminated water and
reduce amount of water flowing through the site.
• Minimize the exposed area for excavation at any one time. Once excavation is completed
within an area it will be immediately restored to finish grade, layered with a compost
medium and re-vegetated. Additional erosion control measures such as wattle fences,
fascines and live pole drains may also be required in some areas.
• Installation of cross-slope swales to enhance drainage and to prevent erosion of excavated
materials.
• Installation of silt fence material on the downslope side between working areas or stockpile
areas and any drainages or wetlands; these will be set up prior to the initiation of any
excavation work; the geotextile fence fabric shall be Terrafix 370 RF, AMOCO 2125 or an
approved equivalent.
• Isolation of any identified sensitive sites with fencing, ribbon or rope to exclude accidental
intrusion.
• Filter cloth and clean gravel will be readily available on-site should they be required; these
materials provide a reasonably effective, on the spot filtration device in field situations and
may be placed in any small ditches etc. to filter water laden with silt or sediments.
• Ditches and culverts will be used to maintain adequate drainage over the newly excavated
site.
• Natural drainage patterns will be retained wherever possible.
• Soil excavation stockpiles will either be completely contained by berms and silt fences or
covered with polyethylene to prevent erosion.
• Settling ponds will be constructed to clarify turbid water prior to release from the site.
Construction of settling ponds will be completed in accordance with the ‘Land Development
Guidelines for the Protection of Aquatic Habitat’.
• Should site discharge water not meet the legislated criteria, the Contractor will be requested
to implement other techniques to ensure the water entering watercourses meets authorized
levels. These methods can include, but will not be limited to, trucking of water, dispersion of
Coquitlam Dam Seismic Rehabilitation Page 17
Environmental Management Plan – Version 4
June 15, 2004