Coquitlam Dam Seismic Upgrade Project ... - BC Hydro

3.8. CONCRETE AND GROUTING
All concrete work must be completed in a manner that ensures water quality standards are
maintained. Runoff from uncured concrete or concrete wash water may be high in pH. Levels
over 9.0 pH units are considered harmful to fish and aquatic life.
Note: BC Hydro and its contractors will ensure that water exiting the construction site and
entering a drainage course will meet the following criteria:
pH units Maximum 9.0, Minimum 6.0
Turbidity Maximum 25 NTU
Uncured concrete will be covered with polyethylene sheets or tarps during rain events to ensure
high pH runoff is not generated. Wash water from the concrete trucks will be contained and
removed from the site by the concrete supplier. The Contractor must ensure that water with
elevated pH greater than 9.0 pH units does not leave the site. Elevated pH levels will be reduced
with a CO2 bubbler system if required.
The vast majority of the concrete and grouting work will occur downstream of the dam and will
be off reservoir drainage. However, there is a possibility that some minor concrete and/or
grouting work may be required on the crest of the dam or on the upstream face of the dam. All
concrete or grouting work in these areas will be completely contained to ensure that no runoff
enters the reservoir or adjacent drainages.
3.9. ACID ROCK DRAINAGE
Some rocks in British Columbia have significant concentrations of reactive iron-bearing sulphide
minerals. Weathering may cause the sulphide minerals to oxidize, forming weak acids which
may leach toxic concentrations of heavy metals such as zinc into waterways. Tests to determine
the potential for generation of acid leachates as a result of quarrying and tunneling activities as
well as the placement of rock for fish habitat will be conducted. If this potential is identified,
site management plans will be developed to place reactive waste rock in a confined area or basin
where it can be covered with compacted soil to reduce weathering and infiltration of
precipitation and groundwater. Acid generating rock will not be placed in streams or
watercourses.
3.10. EXPLOSIVES AND BLASTING
Explosives will be used at the rock quarry and for tunnel and bedrock excavation for the GVRD
pipeline alignment. Any blasting near water will be carried out following the “Guidelines for the
use of Explosives in or Near Canadian Fisheries Waters”. Explosives will not be used in the
Coquitlam Dam Seismic Rehabilitation Page 21
Environmental Management Plan – Version 4
June 15, 2004