For more information on the
Isabella Dam Safety Modification Study,
please contact us at the following:
U.S. Army Corps of Engineers,
Isabella Dam Safety Modification Study
1325 J Street, Room 1513
Sacramento, CA 95814
Construction is tentatively scheduled to begin in 2017. We are still in the Pre-Construction Engineering and Design phase.
Isabella Reservoir is located forty miles northeast of Bakersfield, Kern County, California, and consists of an earthfill main dam and auxiliary dam across Kern River and Hot Springs Valley, respectively. The dam was authorized under the Flood Control Act of 1944 and construction was completed in 1953. The reservoir provides flood-risk management, irrigation and recreational benefits. With more than 300,000 people living and working below the dams, primarily in the town of Lake Isabella and the city of Bakersfield, the U.S. Army Corps of Engineers (USACE) began a dam safety modification study (DSMS) in 2006 to address seismic, hydrologic (potential overtopping during an extreme flood event) and seepage issues at the dams.
An operating restriction is currently in place, limiting the lake’s normal storage capacity, to reduce the risk of the seepage and seismic concerns while a permanent solution is investigated. USACE has implemented increased surveillance and monitoring; stockpiling of emergency materials; warning sirens in the town of Lake Isabella; installation of additional instrumentation for monitoring; and continued public outreach with Kern County and the local public.
In 2013, following the signing of the Record of Decision in December 2012, the Corps entered the Pre-Construction Engineering and Design phase of the project. A number of procedural tasks must still be completed in preparation of physical construction, which is scheduled to begin in 2017.
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Given the multiple purposes of this dam facility and the long-term benefits it provides, we require thorough analysis of any modification to assure public safety and benefits are not compromised by modification to the dam.
Dam analysis and designs are complex technical efforts. Risk assessments must be performed to understand the extent of a problem and to evaluate options to fix the dams. In this case the dam has multiple deficiencies that require correction which increases the time required to understand and to start the fixes.
We also take great effort to comply with the National Environmental Protection Act and the Endangered Species Act which does require significant time to assure that all requirements are met.
The Auxiliary Dam Recreation Area is planned to primarily be a temporary staging area that would be returned for recreation use after the project is complete. It will also serve as a secondary on-site borrow source for filter sand on the main and auxiliary dams should the excavation of the emergency spillway not be able to provide sufficient quantities.
Other camping areas around the lake are not scheduled to be affected by the project, and the U.S. Forest Service would continue to be the managing agency for these areas.
We recognize and appreciate the value of the public lands here, so a recreation plan is anticipated for 2013 to further explore and identify options for mitigation to offset adverse effects on recreation. Public participation will be solicited to address concerns over the negative impacts of the project.
Not under the current dam safety modification study. Increasing of the storage capacity would require separate authorization and would require a different study.
We understand the concern regarding the duration of construction and are doing everything possible to shorten completion dates. Currently, we are finalizing our costs and schedule for design and construction, and will have a more accurate reflection once that is complete. There are always unknowns associated with construction, but we are committed to minimizing any impacts that may arise. We will continue to refine the schedule to ensure efficiency in construction.
There are no guarantees in regards to funding. However with the continued support of the community and the “high risk” ranking of the dam, we will continue to express the need for timely funding to keep the project on schedule.
Investigations have shown that obtaining borrow materials from the lake bottom are not cost effective for filter and drain materials and would introduce other environmental concerns, such as water quality effects associated with lake lowering, and increased fugitive dust concerns.
We are working with the U.S. Forest Service and local community groups to further minimize the impacts to local events on the lake, campgrounds, boat launches, etc. The majority of the time the lake would remain under its current operation with the pool restriction, and recreation will still be permitted on the lake during construction.
We are committed to working with the community, and one of the concerns we are hearing is about reducing the amount of time the lake elevation would be reduced. As a result, under the preferred alternative, the lowered pool elevation for construction has been limited to a single four-to-six month window between October 2020 and March 2021.
This takes advantage of the natural low reservoir elevations during the fall and winter months when it is already being drawn down for flood control operation, minimizing impacts to recreation, water quality, fisheries, and socioeconomics, and further reduces the impacts over the entire construction period. A more detailed Recreation Plan resulting from this process will be presented in 2013.
Under the preferred plan, the construction pool elevation has been limited to a single four-to-six month window between October 2020 and March 2021 in order to take advantage of the natural low reservoir elevations during the fall and winter months when it is being drawn down for flood control operation. This reduces the potential for dust impacts described in the draft environmental impact statement from lake lowering.
For the majority of the construction period, the lake will remain under its current operation with the pool restriction. Potential impacts from windblown dust can be effectively reduced to less than significant levels through the use of best management practices, which will be required. These practices are described in Section 3.3.3 of this final environmental impact statement and Section 3.5.4 of the draft EIS.
Information about the preferred plan can be viewed here.
A downstream replacement dam at the auxiliary dam site was evaluated, but not selected based on increased cost, larger demand for materials, a longer construction schedule and increased air quality concerns based on the additional earthwork. This project won’t come cheap, but our duty is to modernize the dams by getting the most value for every taxpayer dollar, and that’s what we believe our identified plan does.
The Record of Decision
allows for the official start of the next phase of the project and was signed at the Corps’ headquarters in Washington, D.C., by James Dalton, Chief of Engineering and Construction on Dec. 18. The ROD is a document that states what the decision is; identifies the alternatives considered, including the environmentally preferred alternative; and discusses mitigation plans, including any enforcement and monitoring commitments. Read more about the ROD here
The estimated project cost is: $400 - $600 million.
The storage and release of flood water in Isabella Lake is under the control of our Water Management Section; however, we have no influence over the operation of the reservoir outside of flood operations. During construction, the release of water will continue to be dependent on inflow, irrigation needs and downstream storage capacity.
We’re doing everything we can to minimize the impact to the public, with as little disruption as possible. We plan to put together a Recreation Plan in 2013 to further explore and identify options for mitigation to offset adverse effects on recreation including the needs for recreational flows in the lower Kern River.
As a side note, rafting companies that operate above the reservoir would continue operations as normal and be unaffected by the dam safety modification project.
We are still in the Pre-Construction Engineering and Design phase. Once complete, construction would begin. Our current schedule shows construction beginning in 2017.
It could range from 4 years to 8 years depending on final recommendations, designs and availability of funds. We have a current construction schedule lasting from 2017 to 2022.
In 2013, we entered the Pre-Construction Engineering and Design phase of our project. We still have a number of procedural tasks to complete in preparation for physical construction of the selected alternative. The highway relocations would begin in 2014. The major components of construction would begin in 2017.
The South Fork Delta sand borrow area has been eliminated as a sand source for the preferred plan. Sand will now be manufactured at the dam site utilizing waste materials generated from the emergency spillway excavation. This refinement has eliminated the largest contributor to short-term construction-related traffic and circulation impacts along Highway 178 within the Kern River Valley. The majority of the truck traffic is planned to occur onsite for excavation, processing, and fill placement to reduce impacts. Deliveries to the site are planned to be limited to weekdays only.
Highway trucks will still be required to meet all standards; therefore there should be no impacts to roads except for the everyday wear and tear that they are designed for.
We anticipate some increased traffic along both highways during roadway realignments, but the increase would not exceed roadway and intersection limits.
The potential impacts from the highway realignments will be analyzed and further addressed in a follow-on tiered National Environmental Policy Act action, and we will continue to work with Caltrans up to and during construction for additional opportunities to minimize short-term traffic and circulation impacts.
Potential real estate actions are outlined in the draft EIS but not analyzed in detail. The Corps will initiate a detailed NEPA analysis with an anticipated completion in late 2013. Until the detailed NEPA is complete and the design phase is nearly complete, there is not enough specific information to initiate real estate consultation with impacted residents. We expect that level of detail to be available in early 2015. At that point, impacted residents will be contacted by a Corps real estate specialist. Until officially contacted or notified by a Corps real estate specialist, property owners are encouraged not to change, plan, or do anything in anticipation of being contacted.
It’s important that we go into this with realistic expectations. There are still many requirements and milestones, including project approval and funding, before we can begin to provide more details on property acquisition requirements and schedule.
At that point, we can begin to discuss options to assist affected individuals in applying for relocation benefits. However, until we have an approved project and funding, we cannot acquire or discuss offers with potentially affected land owners.
The workforce will vary depending on the phase of construction; however, the rough estimate of a typical work crew would likely be between 100-150 workers. We will hire a prime contractor on a national level to complete the work, and the contractor will be responsible for hiring any work force to complete the job.
The refinements we’ve made to the preferred plan would reduce many of the anticipated construction-related impacts, but negative short-term impacts on property values may occur during construction.
Our assessment of potential project impacts to the local economy found both short- and long-term benefits associated with construction-related spending in the Kern River Valley and unrestricted reservoir operations upon completion of the project.
Long-term economic improvement resulting from recreation, higher lake levels, employment opportunities, and lower safety risk would likely result in improved property values. These project benefits may serve to provide the Kern River Valley with greater long-term economic stability, which is a major factor in determining regional property values.
The Freedom of Information Act (FOIA) process is the best way to obtain documents that are not released for public review at a minimal cost (if any).
The current low water (summer 2013) is due to lower than average rainfall and snowmelt. The Corps is only responsible for directing releases during the winter months (Nov. 1 - Feb. 1) to maintain storage space for the rainy season and anticipated snowmelt. Downstream water users control the outflow based on irrigation demand the rest of the year. The Corps plays no role in those decisions.
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The Isabella reservoir offers fishing, boating, water sports, camping, and picnicking. Close proximity to Los Angeles and Bakersfield makes this lake a popular yearround vacation spot for southern Californians. The lake is one of the state’s most popular windsurfing areas; reliable afternoon winds, from 35-50 miles an hour, create ideal conditions for intermediate to advanced windsurfers. Enjoy shoreline camping and day use activities at Auxiliary Dam, Old Isabella Road, or South Fork Recreation Area with the purchase of a Southern Sierra Pass or other Interagency Pass. South Fork Wildlife Area, one of the most extensive riparian woodlands remaining in California, provides fishing, hunting, canoeing, and hiking opportunities; no developed recreation facilities are located here. When operating on the lake, every boat, personal watercraft, and sailboard must display a permit from Kern County. These permits may be obtained at any lake marina or at various locations throughout the Kern River Valley. Be sure to check for required safety equipment.
For more information on Annual, Senior, Access, Volunteer, and the Southern Sierra Passes including Fee-Free Days in 2013 can be viewed here: http://1.usa.gov/14x1ukz.
Information is also available for Campfire Permits, River Permits, and Wilderness Permits at the same website. For more information, please contact the U.S. Forest Service at (760) 376-3781.
Weather information, including current temperature, wind speed, rainfall and humidity, as well as live weather webcams around Lake Isabella can be viewed here: http://bit.ly/17qAuui
Information on developed campgrounds at Lake Isabella, managed by the U.S. Forest Service, can be viewed here: http://1.usa.gov/12t0MKA
Water safety tips from the Kern County sheriff's office can be viewed here.