BC H YDRO – S TAVE F ALLS S PILLWAY G ATES R EPLACEMENT P ROJECT E XHIBIT B-2 CD B C h y d ro F O R G E f\lE IO N S Jo a n n a S o fie ld C h ie f R e g u la to ry O ffice r P h o n e : (6 0 4 ) 6 2 3 -4 0 4 6 F a x: (6 0 4 ) 6 2 3 -4 4 0 7 b ch yd ro re g u la to ryg ro u p @ b ch yd ro .co m Ja n u a ry 1 9 , 2 0 1 0 M s. E rica M . H a m ilto n C o m m issio n S e cre ta ry B ritish C o lu m b ia U tilitie s C o m m issio n S ixth F lo o r - 9 0 0 H o w e S tre e t V a n co u ve r, B C V 6 Z 2 N 3 D e a r M s. H a m ilto n : R E : P ro je ct N o . 3 6 9 8 5 8 8 B ritish C o lu m b ia U tilitie s C o m m issio n (B C U C ) B ritish C o lu m b ia H yd ro a n d P o w e r A u th o rity (B C H yd ro ) S ta ve F a lls S p illw a y G a te s R e p la ce m e n t P ro je ct A tta ch e d a s E xh ib it B -2 is B C H yd ro 's p re se n ta tio n fro m th e S ta ve F a lls S p illw a y G a te s P ro je ct W o rksh o p h e ld o n Ja n u a ry 1 8 , 2 0 1 0 . F o r fu rth e r in fo rm a tio n , p le a se co n ta ct L yle M cC le lla n d a t 6 0 4 6 2 3 -4 3 0 6 . Y o u rs sin ce re ly, Jo a n n a S o fie ld C h ie f R e g u la to ry O ffice r E n clo su re c.· B C U C P ro je ct N o . 3 6 9 8 5 8 8 S ta ve F a lls S p illw a y G a te s P ro je ct' R e g iste re d In te rve n o r D istrib u tio n L ist. B ritish C o 1 u m b ia H yd ro a n d P o w e r A u th o rity, 3 3 3 D u n sm u ir S tre e t, V a n co u ve r B C V 6 B 5 R 3 w w w .b ch yd ro .co m
Stave Falls Spillway Gates Replacement Project Workshop January 18, 2010
Introduction • BCUC Order • Introduction to Spillway Gate Systems • Spillway Gates Program • Facility Description • Need for the Project • Project Description • Alternatives Considered • Project Costs • Project Schedule • Project Effects (Rate Impact, Environmental & Social) • Project Risks • Project Consultation • Conclusions 2
BCUC Order • 44.2 (3)(a) of the Utilities Commission Act (the UCA ) • BCUC acceptance that the expenditures for Stave Falls Spillway Gates Replacement Project are in the public interest • Considerations: > the Government’s energy objectives; > BC Hydro’s most recent Long-Term Resource Plan; > whether the expenditure schedule is consistent with sections 64.01 and 64.02 of the UCA in respect of electricity self sufficiency and clean and renewable resources; and > the interests of present and future ratepayers. • Project Costs: > Expected Cost: $61.5M > Authorized Cost: $70.6M BCUC Order 3
Functions of a Gate Water barrier Flood discharge • Part of the dam • Open on demand • Don’t open without • Close on demand demand Introduction to Spillway Gate Systems 4
Spillway Gate Operations Operated to ensure: • safe release of excess flows or floods to prevent overtopping • essential to ensure safe dam operation Other Operations : • proper regulation of water flow downstream • rapid release of water for emergency or precautionary reservoir drawdown • post catastrophe operational requirement Introduction to Spillway Gate Systems 5
Emergency Reservoir Drawdown Zipingpu Dam, China, 2005 • Concrete Face Rockfill Dam • Damage to upstream concrete face slabs • Reservoir was immediately lowered • Declared structurally stable and safe Introduction to Spillway Gate Systems 6
Precautionary Reservoir Drawdown Introduction to Spillway Gate Systems W.A.C. Bennett Dam, 1996
Post-Catastrophe Operational Requirement Sayano Hydroelectric Plant, Russia, August 17, 2009 •6400 MW Facility •Unreliable backup power •Overtopping potential in 2 days •Just made it in time…. Introduction to Spillway Gate Systems 8
Examples of Spillway Gate Failures Structural Failures: Folsom Dam, California • Commissioned in 1956 • Failed, July 1995 • Trunnion friction not included in design; not checked Introduction to Spillway Gate Systems 9
Examples of Spillway Gate Failures Operational Failures: Manatee Dam, Florida • Spillway Gate jammed in half-open position in July 2003 • 600 homes evacuated • Workers managed to open Gate before dam overtopped Introduction to Spillway Gate Systems 10
Examples of Spillway Gate Failures Tirlyan Dam, Russia • August, 1994 • Spillway Gate jammed in half-open position Introduction to Spillway Gate Systems 11
Examples of Spillway Gate Failures Catastrophic Embankment failure Introduction to Spillway Gate Systems 12
Examples of Spillway Gate Failures • caused about 20 deaths • significant property destruction Introduction to Spillway Gate Systems 13
Spillway Gates Program In 2005, BC Hydro began an initiative to improve equipment and procedures to ensure reliable operation of spillway gate systems • Equipment • Power supplies • Control systems • Testing and Maintenance, Management 2005 Condition evaluated against a set of design and operation principles Spillway Gates Program 14
Reliability Principles and ALARP • Formalized and adopted in 2006, based on work by external consultant on spillway gate systems • New concept to hydroelectric industry, but common practice in other high-hazard industries • System should operate on demand with less than a 1 in 1000 chance of failure • Reduce risk to A s L ow A s R easonably P racticable Spillway Gates Program 15
Prioritization of Sites All 22 sites with spillways were evaluated and prioritized based upon: • Current physical condition of equipment • Availability of alternative ways to control water • Frequency of use • Current reliability • Possibility of interim risk management methods • Consequences of failure Spillway Gates Program 16
Summary Spillway Gate Systems are: • Critical Infrastructure for Public Safety • Cannot be taken for granted Spillway Gates Program 17
Stave Falls Facility Stave Falls Facility Stave Falls Facility is located about 16 kilometres northwest of the town of Mission, on the Stave River. Facility Description 18
Stave Falls Facility Facility Description 19
Stave Falls Facility • Originally constructed between 1910 and 1927 • Facility includes Stave Reservoir, Stave Falls Generating Station, main dam, two intake structures and the Blind Slough Dam (provides flood discharge control) • Part of the Alouette-Stave Falls Hydroelectric System which consists of three facilities: Alouette (upstream), Stave Falls, and Ruskin (downstream) • Operation of Stave Falls and Ruskin facilities closely coordinated in order to maximize use of water and ensure water licence compliance Facility Description 20
Stave Falls Facility (Blind Slough Dam) • Blind Slough Dam constructed to impound Stave Reservoir and to provide controlled release of water during flood conditions • Passing of water to the spillway is controlled via 4 radial gates and 10 vertical gates • When all 14 gates are fully open, they allow safe passage of the most severe inflow flood • The four radial gates provide about 45% of the overall discharge capacity and are the preferred means of passing water through Blind Slough because they allow BC Hydro to more precisely control water releases Facility Description 21
Stave Falls Facility (Blind Slough Dam) Longitudinal view of Blind Slough Dam Spillway Gates Facility Description 22
Stave Falls Facility (Blind Slough Dam) Radial Gate Vertical Gate (Side Profile) (Side Profile) Facility Description 23
Operating History • The Blind Slough Dam’s radial gates were originally installed around 1923 • BC Hydro refurbished the radial gates in 1997/1998 in order to extend their life by about 15 years; refurbishment consisted of replacing corroded components and repainting of the gates • New radial gates are scheduled be installed in 2011 & 2012; about 14 years after the 1997/1998 refurbishment • Radial Gate ropes replaced in 2007 as a result of rope failure Facility Description 24
Key Concerns 1. Installed in the 1920s, the four radial gates and hoists are at end-of-life and do not meet current seismic criteria. 2. Existing design deficiencies could lead to a common cause failure which could result in all spillway gates becoming inoperable. Consequently, the Spillway Gate System cannot currently be relied upon to operate effectively during flood conditions Need for the Project 25
Key Concerns Hoist System Portion of Radial Gate Need for the Project 26
Consequences of Failure Dam Overtopping • If the spillway gates become inoperable during flood conditions, the Stave Falls Dam and Blind Slough Dam could be overtopped by 1 to 2 metres depth of water flow • This level of overtopping would result in a catastrophic dam failure at both the Stave Falls facility and the downstream Ruskin facility • Catastrophic dam failures have the potential to result in loss of life and significant financial and environmental damage Need for the Project 27
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