HomeMy WebLinkAboutLake Oroville Community Update - Lake Oroville Spillways Construction Updates Menchaca, Clarissa
From: DDR Oroville Spillways <orovill,e@water.ca.gov>
Sent: Wednesday, April 18, 2018 1:09 PM
To: Menchaca, Clarissa
Subject: Lake Oroville Spillways Construction Updates
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Lake
Oroville
April 1 , 2018
Lake rovil a Spillways Construction Updates
Today the Department of Water Resources (D +'R) provided an update on construction-related
activities for the Lake Oroville Spillways Emergency Recovery Project.:
Update to the 2018 Operations Plan
DWR has updated the 20118 Lake Oroville Aerations Plan to begin construction as soon as
possible this spring and maximize the 20�18 construction window to ensure the main spillway
is fully reconstructed before next winter. The plan; was submitted yesterday to the federal
Energy Regulatory Commission (FERC) and the California Division of Safety of Dams (D SOD)
for approval.
With inflows into Lake Oroville expected to be low this summer due to below-average
snowpack and snow water content in the Northern Sierra, the updated plan targets a lake
level of approximately 830 feet before triggering more aggressive outflows. The plan provides
flexibility to manage dynamic weather in real time.
The current lake level is 808 feet„ and the main pilllways are at elevation 813 feet. Cance the
lake level surpasses 813 feet, DWR anticipates some water will pass through the gates onto
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the main spillway. Minimal amounts of water have passed through the main spillway gates
since original construction, and the gate seals were replaced in 2014 and 2015.
Lake levels will fluctuate through the year as DWR manages the lake to meet multiple uses
and benefits, including flood protection, environmental releases, recreation, salinity control
and flow requirements in the Delta, and contractual water deliveries to senior water users
locally and to State Water Project water users.
Construction on the Main Spillway
* DWR has requested approval from FERC and DSOD to close the main spillway gates
on May 8 to allow construction to resume for the remainder of the construction season.
* Prep work to resurface, or mill, the top layer of the roller-compacted concrete (RCC)
middle chute is targeted to begin on April 25, which will create a uniform surface to
prepare for placement of steel-reinforced structural concrete slabs. Crews will remove
up to five inches of the surface of the RCC section of the chute.
* Overall plans for Phase Two construction on the main spillway include:
* Demolition of the original 730 feet of the upper chute leading to the radial gates
and reconstruction with steel-reinforced structural concrete slabs and walls.
* Placement of three-foot, steel-reinforced structural concrete slabs over the RCC
middle chute, and placement of a drainage system.
Removal of the RCC walls in the middle chute and replacement with structural
concrete walls, with a permanent drainage systern,
o hydro-blasting and resurfacing of the energy dissipaters at the base of the main
spillway.
Construction at the Emergency Spillway
DWR has requested approval frorn FERC and DOD to begin removal of the
remaining surface layer of the grouted rip rap on the emergency spillway hillside on
April 25. This is the rip rap that was placed as part of the February 2017 emergency
response,
Crews are Currently placing a concrete cap, or grade beam, on the recently completed
underground secant pile cutoff wall. The cap will reinforce the structural concrete piles
and secure the wall to the RCC spl,ashpad. The secant pile wall is 1,450 feet long and
located 750 feet downhill of the emergency spillway with concrete piles, at depths of 35
to 65 feet.
Crews continue to construct the RCC splashpad, which will cover the hillside between
the emergency spillway and secant pile wall. The splashpad, in conjunction with the
secant pile wall, will armor the existing hillside to significantly reduce the type of uphill
erosion that occurred during the February 2017 incident.
Later this year, an RCC buttress will be constructed at the base of the emergency
spillway structure to provide further reinforcement.
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Additional Updates
• Over the next four to six weeks, DWR will be conducting routine maintenance on three
of the six turbines (turbines four, five, and six) at Hyatt Powerplant.
• This maintenance will ensure the performance of Hyatt Powerplant throughout the
construction season when the main spillway will be unavailable.
• DWR had planned to begin this maintenance at the beginning of April but delayed the
work to provide full outflow capacity from Hyatt Powerplant to safely manage lake
levels during recent storms.
• Turbine one is undergoing an extensive upgrade and has been offline since 2015.
Work on turbine one is targeted for completion by the end of this year.
• With two turbines active, Hyatt Powerplant has an outflow capacity of 5,000 cubic-feet
per second.
• As reported in Jlanua[y, DWR's Design, Team has been in consultation with the
Independent Board of Consultants (BOC) regarding a section of structural concrete
wall placed last year that is 1 percent out of alignment. Memo #16 from the BOC, which
was posted this week, concurs with the Design Team's recommendation to leave the
wall in place, saying it is "'in the best interest of the project not to demolish and
reconstruct the walls."
• DWR will meet with the BOC for the 17th time on April 23 and A.
To view photos, and video of the Lake Oroville Spillways construction, visit DWR's Oroville
Spillway photo gallery and YouTube channel.
For r-nore information, follow us on Twitter or Facebook, read out,news releases or visit our
Oroville, Spillway Incident webpag .
Connect With Us!
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