2008-2010 Capital Improvements

The Cachuma Project provides approximately 80% of the potable water delivered by Goleta Water District, City of Santa Barbara, Montecito, and Carpinteria Valley Water District. No redundant supply or pipeline exists to convey Cachuma Project water or State Project water to the the Goleta Reach if the South Coast Conduit is out of service, due to scheduled and/or unexpected repairs.

The purpose of the project is to increase the operational flexibility, reliability, and capacity of the Conduit, between the South Portal of the Tecolote Tunnel and the Corona Del Mar Water Treatment Plan. The increase in operational flexibility, reliability, and capacity are intended to accommodate peak demand levels and to allow maintenance of the pipeline.

In 2005, Cachuma Operation and Maintenance Board retained Boyle Engineering Corporation to perform a Phase II Reliability Study for the South Coast Conduit Upper Reach - Tecolote Tunnel to the Corona Del Mar Water Treatment Plant and Lower Reach - the Conduit Booster Pump Station to Ortega Reservoir.

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No redundant pipeline exists for conveyance of water supply in the South Coast Conduit when a section of the pipeline needs to be isolated for emergencies or repair. In addition, dewatering this section of the Conduit is a lengthy process, greatly reducing its operational flexibility and reliability. Due to the age and the material from which it is constructed, the pipe is inherently difficult to repair or modify.

Two of four Conduit Reaches have been studied and a program has been defined to make the necessary modifications/additions or improvements to those Reaches. This project component is to do similar studies for the remaining two Reaches.

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As part of the Phase 2 Reliability Study for the South Coast Conduit conducted in 2006, seven creek crossings, identified as areas of concern in the 2005 Reliability and Alternatives Study, were evaluated.

In the 1970s, the Conduit was damaged by "rock impact" during high flow in the Mission Creek, exposing the creek to undermining. The Conduit underwent emergency repairs. The Cachuma Operation and Maintenance Board desires to replace the Conduit at Mission Creek and the proposed stream channel improvements in one project. Six additional Conduit Creek crossings require investigation and probable repairs.

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Prior to 2004, there was only one isolation valve along the South Coast Conduit Carpinteria Reach. No redundant pipeline exists for conveyance of water supply in the Conduit when a section of the pipeline needs to be isolated for emergencies or repair. Three isolation valves have been installed since 2005. It will be beneficial to install additional in-line isolation valves at three more locations.

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In the Phase II Reliability Study recommendations for the Conduit between the Conduit Booster Pump Station to Ortega Reservoir reach were made for design engineering tasks.

Those tasks were intended to increase the flow in the Conduit from 18 to 24 million gallons a day, as originally designed by the U.S. Bureau of Reclamation. The proposed vent structure improvements at Barker Pass Sheffield Tunnel and Lauro Reservoir are intended to accommodate the refined hydraulic capacity, and surge suppression.

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Corrosion protection for the interior of the South Coast Conduit is cement mortar, except for the outlets on the Upper Reach of the Conduit, which are unlined.

Inspections of the Upper Reach confirmed that the unlined outlets are badly corroded, with a high failure risk. Repair, consisting of removal of the tuberculation (rust products), welding new pipe sleeves, and then lining each outlet with cement mortar, is necessary to maintain the reliability of the Goleta Reach of the Conduit.

Also, within the Carpinteria Reach of the Conduit, most of the turnout valves are considered inoperable, and the meters at the turnouts need maintenance.

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Airbinding was identified as the possible source of excessive head loss measured between the Sheffield Flow Control Station and the eastern portal of the Sheffield Tunnel. That recommendation was confirmed in a 2005 report titled "Reliability and Alternatives Study for the South Coast Conduit Carpinteria Reach Cater Booster Pump Station to the Ortega Reservoir".

Subsequent analysis has confirmed that the head loss is likely due to airbinding in a short down-sloping segment of pipe between the Flow Control Station and the adjacent dry creek. Addition of piping to the existing manway will include a combination air- and vacuum- release valve and positive vault drainage.

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The Tecolote Tunnel and the South Coast Conduit were originally designed and built for conveyance of approximately 65 million gallons per day of unfiltered surface water. Due to a combination of issues, among them the original design assumptions, limitations and age of original equipment, significant system modifications, and increased demands, the Bureau of Reclamation design flow rates cannot be achieved.

One of the limitations is the weir placed in the Glen Anne Turnout to maintain adequate hydraulic head for the Goleta West Conduit. Reconstruction and reconfiguration of the weir to increase its length will improve reliability, reduce undesirable head loss, and facilitate maintenance of the turnout.

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Installation of system modifications to the South Coast Conduit, including the Glen Anne and Corona Del Mar turnouts, have resulted in significantly different operation of the pipeline from original design assumptions.

Engineering analyses of the hydraulic repercussions of these modifications indicate that the system reliability can be increased, and flow downstream can be increased with modifications to the piping at Ortega, Sheffield, and Lauro flow control facilities. These modifications will include removal of redundant valves and piping, as well as installation of hydraulically efficient meters and automated control valves.

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The Glen Annie Turnout structure was constructed concurrent with the South Coast Conduit. In 1962 a weir was constructed in the structure to serve the Goleta West Conduit.

Deliveries to the Goleta West Conduit are metered, utilizing a high-flow venturi meter and a low-flow venturi meter. Currently, the high-flow venturi meter is utilized to measure the flow to keep head loss low, but it barely reads the 3 million gallons per day average rate. A better approach is needed that also minimizes the head loss. Replacement of the two venturi meters with a single sonic-type meter will increase the system reliability, increase the accuracy of flow measurement and reduce head loss.

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In previous studies it was noted that encroachment into the South Coast Conduit pipeline easement is widespread. This program will implement the recommendations of those reports, with the intent to make the buried facility "open and notorious."

Action required to maintain the reliability of the Conduit include identifying, locating and labeling the pipeline, and surveying and formatting for GIS; notifying encroaching landowners that COMB has the right to maintain the government's pipeline; clearing the alignment where the pipeline is within U.S. Government fee property; and other steps.

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The Tecolote Tunnel connects the Lake Cachuma north portal to the South Coast Conduit. The tunnel was dewatered and inspected in 1978, 1981, 1987, 1993, 1999, and 2005. Most of the interior is in good condition. However, observed deterioration of the lining in limited areas has progressed to such an extent that repairs may be necessary to maintain the reliability of the South Coast Conduit.

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The Lake Cachuma north portal of the Tecolote Tunnel is supplied from the intake tower in Lake Cachuma. The intake tower was constructed in 1953 with multiple gates.

Minimal maintenance activities have been allocated to this structure. The operation of the lower gates has become difficult. Because of submergence, the exact nature of the gate operability has not yet been ascertained, but could be the result of trapped debris or corrosion. The decision to repair, rehabilitate or replace the gates will require engineering analyses and conceptual design to determine the extent of the program.

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The Lake Cachuma north portal of the Tecolote Tunnel is supplied from the intake tower in the Lake. About 850 feet from the intake tower, in the tunnel, is a jet flow valve that regulates the flow in the tunnel.

Water infiltration into the elevator shaft has become problematic. Action required to maintain the reliability of the South Coast Conduit is to determine the cause of the water infiltration, and determine the most appropriate means of remediating the infiltration.

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Based upon the state of knowledge gained in the 57 years since the intake tower was first designed, the tower may be at-risk during a major earthquake.

Action required to maintain the reliability of the South Coast Conduit is to structurally inspect and analyze the tower using modern codes and computer analyses. That will allow assessment of the level of risk, and preparation of a conceptual design, if necessary.

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Previous studies identified flow limitations in the South Coast Conduit system, some of which were due to the pressure class of pipe in the Sheffield Tunnel. Analyses determined that most of the tunnel pipeline is not designed for any overstress due to increased flows or unanticipated surge events in the pipeline.

The replacement of the pipe within the Sheffield Tunnel will require engineering analyses and conceptual design to determine the extent of the program.

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