Key Facts / FAQs
What type of dam construction makes up the Crane Valley Dam?
Crane Valley Dam consists of two distinct dams separated by a rock knoll. The Main Dam is location in the main channel of the creek, and has earth fill on the upstream side of the core wall and rock fill on the downstream side. The West Dam is located adjacent to the main dam in a smaller side channel west of the creek, and has earth fill on both sides of the core wall. The spillway is located on a saddle about 500 feet to the east of the dam.
What are the seismic improvements being made to the Crane Valley Dam?
In summary, the seismic retrofit project will include the following measures:
- Installation of rockfill buttresses on the sections of the dam that have hydraulic fill on both the upstream and downstream sides of the concrete core wall
- Tying back the top of the concrete core wall in the section of the dam where the downstream shell consists of a massive rockfill embankment
- Raising and re-grading the crest to elevation 3387, about 7 feet above present minimum crest elevation, to provide more freeboard
Will parts of the lake be closed off during the retrofit construction?
During parts of construction it is expected that an area by the dam will be closed. However, this work is scheduled to be completed during normal drawdown of the reservoir and should not have an impact to recreation in the summer months.
Will local roads be closed during the seismic retrofit construction?
In order to safely and efficiently transport material and equipment to and from the construction site, a traffic control plan will be developed in accordance with conditions required by the Madera County Road Department and other resource agencies. Road safety signs will be installed and flag persons will be used in accordance with traffic control best management practices (BMP). Along with public warning signs, temporary chain link fencing with gates will be installed at both ends of the dam.
What government agencies regulate Dam safety?
The California Department of Water Resources, Division of Safety of Dams (DSOD) reviews the stability of dams. In recent years, DSOD has worked with Dam owners to meet new standards based on improved design approaches as well as new findings and requirements regarding earthquake hazards and hydrologic estimates in California. FERC is also a regulatory agency for PG&E and they also support the retrofit work.
If seismic issues were reviewed in 2002, why is the retrofit project starting now?
DSOD asked PG&E to review the seismic stability of the Crane Valley Dam in 2002. The technical investigation and study of the dam’s stability required time to complete. The analysis from the study indicated a retrofit project was needed. PG&E has since worked with DSOD and FERC as well as other governmental agencies to determine the engineering design and extent of the retrofit needed to achieve the stability requirements. PG&E is working as quickly as possible to secure all needed permits and approvals to begin and complete the retrofit project.
Bass Lake is being required to maintain a water level reduction to 10 feet below maximum water level for safety of downstream residents. Will this restriction be year round or just in the summer months?
As an operating reservoir, Bass Lake water level fluctuates throughout the year and during the winter months is often lower than the level 10 feet below maximum lake level restriction. Hydro generation will continue throughout the construction project and the 10 foot reduction restriction is specific to summer months.
How long will the Bass Lake water level reduction be in place?
The reservoir restriction will remain in place until completion of the dam seismic retrofit estimated to be 2011.
Will homeowners be allowed to move or extend docks to reach the lower water level? What is the approval process for homeowners?
PG&E will work with homeowners to allow extensions and replacement of boat docks where it is safe and feasible. Please contact Dan Clark, Land Planner at 559-263-7385 to coordinate approval process.
Will resort owners be allowed to move or extend docks to reach the lower water level? What is the approval process for resort owners?
PG&E will work with resort owners to allow re-adjustments of facilities where it is safe and feasible. Please contact Dan Clark, Land Planner at 559-263-7385 to coordinate approval process.
Will PG&E reimburse businesses that may be impacted from the lower lake level?
The seismic retrofit of the Crane Valley Dam is essential to the long term stability of the dam as well as safety for the downstream residents. Even with the lower lake level, Bass Lake will remain open for recreation throughout the construction of the project. Bass Lake is an operating reservoir and levels do fluctuate during drought years, dependent on the State’s energy needs, etc. PG&E is not responsible for private businesses along the shorelines. However, PG&E work cooperatively with the local community and through our FERC License to manage recreation as one of the beneficial values of the reservoir.
