For further information, please contact Geoff Higgins at or by at

Transcription

1 B-1-3 Tom A. Loski Chief Regulatory Officer Phone: Fax: November 30, 2015 Ms. Erica Hamilton Commission Secretary British Columbia Utilities Commission Sixth Floor 900 Howe Street Vancouver, BC V6Z 2N3 Dear Ms. Hamilton: RE: British Columbia Utilities Commission (BCUC or Commission) British Columbia Hydro and Power Authority (BC Hydro) W.A.C. Bennett Riprap Upgrade Project (the Application) Supporting Evidence Exhibit B-1-3 BC Hydro writes to provide supporting evidence to its statement at page 2-13 of the Application, lines 7 through 9 where BC Hydro said: BC Hydro believes that the advice from an expert engineering panel that the riprap condition is a serious deficiency that should be remedied as soon as possible confirms that timing for the Project is appropriate. In support of this statement, BC Hydro provides as Attachment 1 the following excerpts from a report titled BC Hydro WAC Bennett Dam Expert Engineering Panel Report Volume 1 dated August ,, authored by Kaare Hoeg, Robin Fell, and Rodney Bridle. BC Hydro is not providing the entire Report as it is much broader in scope than just the condition of the riprap, and is therefore beyond the scope of this Application. Included in the excerpts are the Reports cover page, the authors signature page, the relevant paragraphs from sections 3.7 and BC Hydro confirms these two sections are the only sections in the report that directly discuss the riprap erosion. For further information, please contact Geoff Higgins at or by at bchydroregulatorygroup@bchydro.com. Yours sincerely, Original signed Tom Loski Chief Regulatory Officer gh/ma 2/ British Columbia Hydro and Power Authority, 333 Dunsmuir Street, Vancouver BC V6B 5R3

2 November 30, 2015 Ms. Erica Hamilton Commission Secretary British Columbia Utilities Commission W.A.C. Bennett Riprap Upgrade Project (the Application) Supporting Evidence Exhibit B-1-3 Page 2 of 2 Copy to: BCUC Project No (F2012 to F2014 Revenue Requirements Application) Registered Intervener Distribution List. Fort Nelson First Nation jennifer.coupe@fnnation.ca Prophet River First Nation chief.ltsakoza@prophetriverfn.ca bev_stager@yahoo.ca councillor.jenreno@prophetriverfn.ca brian_wolf2@msn.com lands.bwolf@prophetriverfn.ca lands.rtsakoza@prophetriverfn.ca Blueberry River First Nations lhotte@blueberryfn.ca chiefyahey@blueberryfn.ca myahey@blueberryfn.ca npyle@blueberryfn.ca sdominic@blueberryfn.ca wyahey@blueberryfn.ca execassist@blueberryfn.ca lblue@blueberryfn.ca Halfway River First Nation dhunter@hrfn.ca ametecheah@hrfn.ca cachla@hrfn.ca rnotseta@hrfn.ca Saulteau First Nations CMarshall@saulteau.com nowens@saulteau.com Doig River First Nation ndavis@doigriverfn.com sacko@doigriver.com sreiter@doigriverfn.com jcalvert@doigriver.com Mpoucecoupe@doigriverfn.c om snelson@doigriverfn.com tthielen@doigriverfn.com Mcleod Lake Indian Band dorr@mlib.ca jkeutzer@mlib.ca cdavis@mlib.ca espence@mlib.ca adchingee@mlib.ca iroreception@mlib.ca ChiefandCouncil@mlib.ca West Moberly First Nations rwillson@westmo.org cwillson@westmo.org dokkiefamily@westmo.org laurawebb@westmo.org forestry@westmo.org Bruce.Muir@erm.com wmfndirector@westmo.org jlewis@westmo.org lureception@westmo.org patricia.brown@westmo.org landusemanager@westmo.or g caleb.behn@gmail.com

3 BC HYDRO WAC BENNETT DAM EXPERT ENGINEERING PANEL REPORT - VOLUME 1 Kaare Hoeg Robin Fell Rodney Bridle 13 W.A.C. Bennett Riprap Upgrade Project Page 1 of 6

4 BC HYDRO WAC BENNETT DAM EXPERT ENGINEERING PANEL REPORT - VOLUME 1 AUGUST 2012 Dr Kaare Hoeg Norwegian Geotechnical Institute PO Box 3930 Ullevaal Stadion NO-0806 Oslo, Norway Emeritus Professor Robin Fell UNSW Global Consulting Pty Ltd University of New South Wales Sydney Australia 2052 Rodney Bridle Dam Safety Ltd Amersham HP7 0DT United Kingdom W.A.C. Bennett Riprap Upgrade Project Page 2 of 6

5 BC HYDRO WAC BENNETT DAM EXPERT ENGINEERING PANEL REPORT - VOLUME 1 AUGUST 2012 Prepared by: Dr Kaare Hoeg Norwegian Geotechnical Institute PO Box 3930 Ullevaal Stadion NO-0806 Oslo, Norway Prepared by: Emeritus Professor Robin Fell UNSW Global Consulting Pty Ltd University of New South Wales Sydney Australia 2052 Prepared by: Rodney Bridle Dam Safety Ltd Amersham HP7 0DT United Kingdom W.A.C. Bennett Riprap Upgrade Project Page 3 of 6

6 BC Hydro WAC Bennett Dam: Expert Engineering Panel Report Volume 1 - Page REDACTED 3.7 DAMAGE TO UPSTREAM SLOPE AND REQUIRED REPAIR TO TOP PART OF DAM Wind generated waves have eroded Zone 5 material through gaps in the damaged riprap. The erosion has been severe between Stations and The damage to the riprap and the erosion of gravel in Zone 5 have seriously undercut the upper part of the upstream slope as shallow sliding has occurred, and Zone 5 is now exposed in the slide head scarps. Continued wave action, floods and relatively minor earthquake loads may trigger deeper sliding that could endanger the integrity of the crest and even cause overtopping and eventual breaching of the dam. If instability of the upstream slope were to occur it would remove support for the core, longitudinal cracking of the remaining core would be likely, and transverse cracks in the core might occur, forming a potential pathway for concentrated leak erosion under high reservoir levels. The Panel considers this to be a serious deficiency that should be remedied as soon as possible. The Panel is pleased to learn that a Riprap Upgrade Project is scheduled to start in 2012 and is planned to W.A.C. Bennett Riprap Upgrade Project Page 4 of 6

7 BC Hydro WAC Bennett Dam: Expert Engineering Panel Report Volume 1 - Page be completed within 3 years. It should not be delayed. If an earthquake were to happen before the upstream slope and the top of the dam are repaired, serious damage may occur. REDACTED W.A.C. Bennett Riprap Upgrade Project Page 5 of 6

8 BC Hydro WAC Bennett Dam: Expert Engineering Panel Report Volume 1 - Page REDACTED Repairs of rip-rap and reduction in the likelihood of upstream slope instability The EEP understands that BC Hydro is progressing with the investigations and design of the repairs to the erosion and shallow slope instability which has occurred on the upstream slope by wave action. This work is important not only from the viewpoint of controlling damage to the upstream slope and crest of the dam, but also from the viewpoint of mitigating the risks from internal erosion. If instability of the upstream slope were to occur it would remove support for the Core and longitudinal cracking of the remaining Core would be likely. Furthermore, transverse cracks in the core might occur, forming a potential pathway for concentrated leak erosion under high reservoir levels. REDACTED W.A.C. Bennett Riprap Upgrade Project Page 6 of 6