Coquitlam Dam Seismic Upgrade Project ... - BC Hydro

More documents

Recommendations

Info

Figure 2. Aerial view of the Coquitlam Dam. As a result of these findings the maximum operating level of El. 154.86 m was reduced to El. 149 m in December 2000 as an interim measure. Since that time, studies have concentrated on identifying conceptual remediation options and obtaining engineering properties of the dam fills and foundation materials for design of structural improvements. Various options, including two structural remedial options (upstream and downstream embankments), decommissioning, and operational options, were investigated in 2002/03. Construction of a downstream embankment has been determined as the preferred structural remediation option. Higher cost, greater environmental impacts, engineering/construction difficulties, and operational constraints on both BC Hydro and the GVWD are the significant factors that have lead to the internal discounting of the alternative options. 1.3. PROJECT DESCRIPTION The proposed downstream embankment option provides a cost effective solution to enhance the seismic withstand of the existing dam. This option involves construction of a rockfill embankment on the downstream toe of the existing dam (Figure 3), which requires relocation of the existing GVWD water supply pipeline and the valve house. The embankment will have a footprint of approximately 20,000 m 2 . The crest elevation will remain the same as the existing dam (161 m) with a maximum crest height of 31 m. A draft plan view and section of the embankment are provided in Appendix 1. The GVWD drinking water pipeline currently runs immediately downstream of the existing dam but would be within the footprint of the embankment. Relocation of this facility is necessary to keep the pipeline outside the footprint of the proposed embankment. The proposed relocated Coquitlam Dam Seismic Rehabilitation Page 3 Environmental Management Plan – Version 4 June 15, 2004
pipeline will run north along the existing spillway channel on the west side of the Coquitlam River for about 100 m and then turn to the west and follow the downstream toe of the new embankment. Geotechnical investigations to determine the actual alignment are currently underway (as of May 15, 2004). An estimated 250,000 m 3 of materials (impervious till and rock fills) will be required for construction of the embankment. Approximately 130,000 m 3 of rock will be mined from a rock quarry located on the east side of the Coquitlam Reservoir about 1 km north of the dam (Figure 3). Geotechnical investigation to determine the impervious fill borrow sites have started. Geotechnical investigations have been undertaken at two locations on the west side of the reservoir. Additional locations east of the reservoir will also be examined to determine the best location to extract the fills. Granular earthfill materials will likely be obtained from outside sources. As a referral agency for the Land and Water BC permitting process, the GVRD has stated that off-drainage sources for impervious fill material are preferred and should be pursued by BC Hydro. Grant’s Tomb fish habitat will be dewatered and fish will be relocated in the early stages of the project, August, 2004 . This will allow for expansion of this fish habitat to compensate for the loss of habitat impacted by the downstream toe of the embankment and the relocated GVWD pipeline. The pond will be rewatered, but will be isolated from fish access until the pipeline and valve house work has been completed and the remaining embankment construction activities can be isolated from the pond (currently scheduled for January 2006). This will reduce the risk of construction related impacts to fish, as the pond is in close proximity to the active construction area. This will also allow for use of the pond as a temporary settling basin for silt and sediment before January 2006. A proposed compensation plan has been discussed with DFO and is provided in Appendix 2. Final details of the compensation plan will require Fisheries and Oceans Canada approval. The existing Coquitlam Dam spillway and low level outlet structures will not be impacted by the proposed project. Flow releases into Coquitlam River will also not be impacted. Fish flow and Water Use Plan agreements between BC Hydro and the regulatory agencies will be upheld during construction. Embankment and GVRD pipeline construction is expected to take 20 months starting in the summer of 2004. It has been estimated that the project will employ approximately 30 people for its duration. This work will require significant environmental controls at the dam site as well as the haul roads and working areas within the watershed. The reservoir will continue to supply drinking Coquitlam Dam Seismic Rehabilitation Page 4 Environmental Management Plan – Version 4 June 15, 2004
Page 1 and 2: Coquitlam Dam Seismic Rehabilitatio
Page 3 and 4: LIST OF FIGURES Figure 1. Location
Page 5: indicate that the hydraulic fill co
Page 9 and 10: will plan work to avoid impacts on
Page 11 and 12: Municipal Local municipal bylaws sh
Page 13 and 14: observed (Decker, 1999b). Mean annu
Page 15 and 16: 2.5. RECREATION/VISUAL As the Coqui
Page 17 and 18: technical opportunities and risks,
Page 19 and 20: • Spill response plan including l
Page 21 and 22: water over a larger portion of the
Page 23 and 24: • All machinery employed will be
Page 25 and 26: water and any blasts near fish bear
Page 27 and 28: • the areas will be covered with
Page 29 and 30: 6.0 ORGANIZATION AND AGENCY CONTACT
Page 34: APPENDIX 2 - Fish Habitat Compensat
Page 37 and 38: Watershed Regulations OF THE GREATE
Page 39 and 40: 1.0 SANITARY REGULATIONS 1.1 Unless
Page 41 and 42: 2.0 POLLUTION CONTROL REGULATIONS 2
Page 43 and 44: 2.8 All waste petroleum products, f
Page 45 and 46: 4.0 GENERAL REGULATIONS 4.1 There s
Page 47 and 48: APPENDIX 4 - Procedures to Import F
Page 49 and 50: Table of Contents Introduction.....
Page 51 and 52: Part 1 - Definitions & References D
Page 53 and 54: DRAFT FINAL (APRIL 2004) Part 2 - M
Page 55 and 56: Part 3 - Materials Testing 3.1 INTR
Page 57 and 58:
DRAFT FINAL (APRIL 2004) Part 3 - M
Page 59 and 60:
DRAFT FINAL (APRIL 2004) Part 3 - M
Page 61 and 62:
Part 4 - Reporting DRAFT FINAL (APR
Page 63 and 64:
Table 1 Key Information DRAFT FINAL
Page 65 and 66:
DRAFT FINAL (APRIL 2004) Part 5 - T
Page 67 and 68:
Table 5 Parameters for Determinatio
Page 69 and 70:
APPENDIX 6 - Instream Work, Pump Ar
Page 71 and 72:
INCIDENT APPENDIX 7 COQUITLAM DAM S
Page 73 and 74:
SORBENT SUPPLIERS Spill containment
show all

Coquitlam Dam Seismic Upgrade Project ... - BC Hydro

Create successful ePaper yourself

Delete template?

Save as template?