HomeMy WebLinkAbout04.29.26 Board Correspondence - FW_ Lake Oroville Community Update - April 29, 2026.ATTENTION: This message originated from outside Butte County. Please exercise judgment before opening
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From:Clerk of the Board
To:Clerk of the Board; Connelly, Bill; Cook, Holly; Cook, Robin; Durfee, Peter; Jessee, Meegan; Kimmelshue, Tod;
Kitts, Melissa; Krater, Sharleen; Lee, Lewis; Little, Melissa; Pickett, Andy; Ritter, Tami; Stephens, Brad J.;
Sweeney, Kathleen; Teeter, Doug; Zepeda, Elizabeth
Cc:Loeser, Kamie; Cannon, Jamie
Subject:Board Correspondence - FW: Lake Oroville Community Update - April 29, 2026
Date:Wednesday, April 29, 2026 3:58:17 PM
Attachments:image001.png
Please see Board Correspondence -
Lewis LeeAdministrative Technician - ConfidentialButte County Administration25 County Center Drive, Suite 200 • Oroville, CA 95965T: 530.552.3326www.buttecounty.ca.gov | lelee@buttecounty.ca.gov
From: California Natural Resources Agency <CNRA@public.govdelivery.com>
Sent: Wednesday, April 29, 2026 10:01 AM
To: Clerk of the Board <clerkoftheboard@buttecounty.ca.gov>
Subject: Lake Oroville Community Update - April 29, 2026
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Lake Oroville Community Update
April 29, 2026
DWR Modifies its Invasive Mussel Inspection Program at
Oroville
The California Department of Water Resources (DWR) is modifying its inspection program
for invasive mussels at Lake Oroville, the Thermalito Forebay, and the Thermalito
Afterbay. Effective today, April 29, watercraft inspections, decontamination services, and
seal checking at the Oroville facilities are no longer required. Blue Oroville seals are no
longer required to launch watercraft and owners have permission to remove seals
themselves, as inspectors will no longer be stationed at launch ramps. DWR will also
reopen facilities that were closed to trailered launching including those at the Thermalito
Forebay and Thermalito Afterbay. At locations requiring the removal of physical barriers,
additional time will be required for crews to fully reopen facilities. Launching access at
Lake Oroville will once again be available 24 hours a day, every day.
The decision to implement an invasive mussel boat inspection program at DWR’s Oroville
facilities in May 2025 was based on available information about how best to protect DWR
infrastructure from golden mussel establishment. While DWR does not control many of the
lakes and reservoirs upstream of Lake Oroville, it quickly established a program to reduce
the potential risk of invasive mussel introduction through recreational boating. Additional
analyses of golden mussel biology and habitat requirements, as well as an assessment
of DWR’s Oroville infrastructure, have shown a lower risk of golden mussel establishment
than was originally anticipated.
During the last year, DWR performed a vulnerability review of Lake Oroville, the Upper
Feather River Lakes, the Feather River Fish Hatchery, and Oroville-Thermalito Complex
infrastructure to golden mussel colonization. The seasonal water temperature conditions
at Lake Oroville and the Upper Feather River Lakes were evaluated based on a 2017
study in which researchers assessed the conditions golden mussels need to survive and
reproduce.
For golden mussel maturation and reproduction to occur, water temperatures greater
than 61.7°F for about 150 days are necessary for successful spawning and the formation
of veligers, the larval stage of mussels. For veligers to complete their development and
settle into a hard-shell mussel, water temperatures must be nearly 70°F for
approximately 70 days.
Temperature thresholds for golden mussel maturation exist within the top 60 feet of Lake
Oroville, meaning that sustained mussel populations would be confined to specific areas
of the reservoir, such as floating infrastructure, and boats that remain on the water for
lengthy periods. Mussels could survive in shallow shoreline locations until lake levels drop,
at which point they would dry out and die. Extended cold water temperatures in the Upper
Feather River lakes, the depth of Lake Oroville, and the continuous cold water releases
from Oroville Dam to support salmon habitat are limiting factors for golden mussel
spawning and larval development. Any veligers that are transported through the dam at
lower lake elevation temperatures would be unlikely to survive, would have a difficult time
growing, and would not have a significant impact on the Feather River Fish Hatchery and
Oroville-Thermalito Complex powerplants.
Given this analysis of potential impacts to State Water Project infrastructure, DWR is no
longer requiring watercraft inspections at Oroville. Ongoing water testing and visual
inspections of infrastructure for invasive mussels will continue. Golden mussels have not
been detected at DWR’s Oroville facilities or the Upper Feather River lakes. Program
changes are being coordinated with local recreation partners at the California Department
of Parks and Recreation and the California Department of Fish and Wildlife.
DWR continues to partner with federal, State, and local agencies to mitigate golden
mussel colonization throughout California’s water systems. This includes coordinating with
partners on a statewide reporting system for watercraft, continued public education
campaigns about golden mussels and how they spread, ongoing studies about effective
treatment options, and implementing a variety of mitigation and maintenance actions to
maintain State Water Project operations that are currently affected by the presence of
golden mussels.
When recreating on California’s waterways, always remember to:
Clean aquatic plants and animal material from your boat, trailer, and equipment
before leaving the ramp or parking lot.
Drain ballast, bilge, live-wells, and other water-containing devices, and never
drain back into the waterway.
Dry equipment, including bilge, ballast tanks, and live well, before launching into
another body of water.
More details about DWR’s invasive mussel inspection program are available
at water.ca.gov/mussels.
California Department of Water Resources
715 P Street
Sacramento, CA 95814
Call our general information line at 916-820-8142
or email us at oroville@water.ca.gov
Contact Us
Stay Connected with the California Department of Water Resources
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