Village News Reporter
The Metropolitan Water District of Southern California has added upgrading the Red Mountain Control Structure to MWD’s two-year Capital Investment Plan.
The MWD board vote June 13 amends the Fiscal Years 2022-23 and 2023‑24 CIP to add upgrades to the Red Mountain Control Structure and the Auld Valley Control Structure in Temecula, replacing chemical storage tanks at the Robert A. Skinner Water Treatment Plant in Temecula, and column panel replacement at the Jensen Administration Building in Granada Hills.
The board action also awarded a construction contract for the Jensen Administration Building panels while the addition to the CIP will allow design activities for the control structure upgrades and the Skinner storage tanks.
Six MWD pipelines carry water along the San Diego Aqueduct from the Skinner treatment plant. Pipelines 1, 2 and 4 convey treated water while Pipelines 3, 5 and 6 deliver untreated supply. (Pipeline 6 currently carries untreated water for seven miles from Lake Skinner to Anza Road and De Portola Road; the southern portion which would serve San Diego County is not expected to be needed in the near future so that part of the project has been deferred.)
Flows to Pipeline 3 are regulated at the Auld Valley Control Structure and flows to Pipeline 5 are regulated at the Red Mountain Control Structure. Each control structure includes two 66-inch diameter pipes each fitted with two 42-inch diameter throttling sleeve valves. The valves are used to regulate flows within the pipelines. The Auld Valley Control Structure was built in 1975 and the Red Mountain Control Structure was constructed in 1981.
Inspections of the control structures conducted after the initial CIP was approved found that the sleeve valves have extensive wear and tear and require rehabilitation. One of the valves on the Red Mountain Control Structure was discovered to be structurally compromised. MWD staff attempted to repair that valve, but the deterioration was beyond repair.
Isolation bulkheads were utilized in the interim to resume operation of the Red Mountain Control Structure at reduced flows. The other sleeve valve at the Red Mountain Control Structure was refurbished under the Minor Capital Program in 2022.
The original design of the control structures did not include isolation valves so Pipelines 3 and 5 cannot be operated without the sleeve valves in service. A complete shutdown of the pipelines is required if one of the sleeve valves must be removed for maintenance. MWD staff recommended installation of eight new butterfly valves upstream and downstream of the sleeve valves at the Auld Valley and Red Mountain control structures to allow for isolation to allow the pipelines to remain in service during maintenance of the sleeve valves and recommended that work to rehabilitate the remaining three sleeve valves begin at the earliest possible time.
The planned work will include replacing a sleeve valve at the Red Mountain Control Structure, refurbishing or replacing two sleeve valves on the Auld Valley Control Structure and installing eight 42-inch diameter isolation butterfly valves (four at each control structure).
The planned design activities for the control structure upgrades include preparation of procurement documents for one sleeve valve for the Red Mountain Control Structure, performing alternative evaluations for refurbishing or replacing sleeve valves for the Auld Valley Control Structure, field investigations, topographic survey and mapping, geotechnical analysis and site layouts for the installation of the isolation valves at both control structures.
The change to the 2023-24 budget adds $550,000 for the control structure upgrades, which will cover $420,000 for the design activities, $80,000 for project management and project controls and $50,000 for contingency. The total estimated cost to complete the project, including future procurement and construction, ranges from $13 million to $15 million. MWD staff will return to the board to request the award of a construction contract after the design is complete.
Including the Auld Valley and Red Mountain control structure rehabilitation in the CIP will allow for completion of the project in early 2025. Complete field investigations and sleeve valve alternative analysis of the control structures are expected by May 2024.