US Army Corps of Engineers BUILDING STRONG ® Boise River Feasibility Study Ellen Berggren, PMP...
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Transcript of US Army Corps of Engineers BUILDING STRONG ® Boise River Feasibility Study Ellen Berggren, PMP...
US Army Corps of Engineers
BUILDING STRONG®
Boise River Feasibility Study
Ellen Berggren, PMPOutreach Coordinator/ Project Manager
Idaho Governor’s Roadless Commission BriefingJune 10, 2015
BUILDING STRONG®
Study Authority
Water Resources Development Act (WRDA) of 1999, Section 41
- Flood control authority
WRDA 2007, Section 4038
- Added ecosystem restoration & water supply authority
- Pre-agreement credit to Sponsor for $500K
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BUILDING STRONG®
Non-Federal Sponsor
Idaho Water Resources Board (IWRB) Established by Idaho Constitution Appointed by Governor Develops and implements State Water Plans Idaho Department of Water Resources provides
project support and coordination Pays 50 percent of feasibility study costs
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BUILDING STRONG®
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Boise River WatershedAvg. Annual Runoff = 1,940 KAFSystem Storage = 950 KAF
Arrowrock DamReclamationCompleted in 1915Storage = 286 KAF
Anderson Ranch DamReclamationCompleted in 1945Storage = 418 KAF
Lucky Peak DamUSACECompleted in 1954Storage = 264 KAF
BUILDING STRONG®
Flood Risk Problems Extensive floodplain development
$10 billion of property at risk
Repeated minor floodingProtection to ~ 3% event from existing system
Largest population center in ID 40% of ID residents live in the Boise River Watershed
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BUILDING STRONG®
Boise Rr Flood Hydrology
1943 – Flood in Eagle, ID
Annual Peak Spring Discharge Flood Frequencies
FrequencyUnregulated Flow
at Lucky Peak Dam(cfs)
Regulated Flowat Glenwood
(cfs)
10% (1 in 10 chance) 25,200 7,500
5% (1 in 20 chance) 32,300 7,900
2% (1 in 50 chance) 38,000 11,000
1% (1 in 100 chance) 44,100 16,600
0.2% (1 in 500 chance) 59,800 35,000
• Bankfull flow = 6,500 cfs (at Glenwood)• Flood stage = 7,000 cfs (at Glenwood)
BUILDING STRONG®
3% chance flood -
8,000 cfs
0.2% chance flood -
35,000 cfs
1% chance flood –
16,600 cfs
0.2% chance flood - Infrastructure at riskover $10 billion*
1% chance flood -Infrastructure at riskover $1 billion*
Source: Ada and Canyon County Hazard Mitigation Plans, 2011 and 2013
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BUILDING STRONG®
Water Supply Problems
Semi-Arid: 8-12” of precip. per year High Population Growth:
- 4.5% 1990 to 2000- 3.3% between 2000-2010- 4th fastest growing state population
98% of existing DCMI water is from groundwater
Prohibitions on development of additional groundwater sources
Curtailment of junior water rights
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BUILDING STRONG®
Water Supply Problems
Projected increase in water demand for the 50-year study period (estimated future needs additional 83,000 – 170,000 acre-feet)
Constrained storage system
Climate variability
Interconnected surface and ground water
Uncertain reliability of current and future water supply
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BUILDING STRONG®
Study Objectives
1) Reduce flood damage and life safety risk
2) Increase operational flexibility and resiliency
3) Increase conveyance
4) Reduce the potential for severe erosion and/or sudden channel migration
5) Increase water supply to meet current and future water demands
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BUILDING STRONG®
Alternatives
MEASURESALTERNATIVES
A B C DNo
ActionArrowrock Dam Raise X X X Managed Aquifer Recharge X Upgrade Irrigation Headgates X X X Replace Push-Up Dams X X Upgrade Bridges X Controlled Flooding of Pits/Ponds X Temporary Conveyance of Water In Floodplain X X X Flow Split Structure X Enhanced Water ConservationNon-Structural Measures X X
BUILDING STRONG®
Arrowrock Dam Raise
Multi-purpose Storage• Flood risk management • Water supply
Potential Maximum Raise • Dam raise up to 74 feet • Up to 270,000 acre-feet increased storage• About 6.5 miles of river inundated
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Maximum Potential Raise • Dam raise - 74 ft. • Reservoir elevation increase - about 70 ft. • Approx 270, 000 acre-feet additional storage.• Approx. 6.5 additional river miles inundated
BUILDING STRONG®
Timeline
January 2016 Tentatively Selected Plan Milestone*
February 2016 Draft Feasibility Report / Environmental Impact Statement released for public review
May 2016 Agency Decision Milestone*
December 2016 Final Feasibility Report / Environmental Impact Statement
March 2017 Civil Works Review Board*
June 2017 Chief’s Report*
BUILDING STRONG®
Questions?
Lucky Peak Project, 1954