Modified and Phased Bay-Delta Conveyance Option with Tunnel Components Supporting Dual Conveyance
Overview of the Alternative Phasing - (3 Phases)
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PHASE ONE
- The Phase One system involves a 65 mile pressurized 37 foot inside diameter tunnel system from North of Sacramento to the Clifton Court fore bay. The system is designed on a phased basis to allow deliveries to build over time as experience is gained in operating the system.
- This alternative moves the initial location for the conveyance system intakes up the Sacramento River to the area above the City of Sacramento west of the International Airport to take advantage of better quality water, to remove the intakes from the tidal effect5, and to a river location that works better hydraulically. Concurrently the Colusa Drain would be permanently diverted down the Yolo By-Pass further improving water quality down river and providing a year around water source for portions of the By-Pass.
- Phase 1 would involve a gravity flow basis of roughly 3,000 to 4,000 cfs, with an ability to deliver annually about 1.5 to 2.1 MAF of flows assuming 260 days per year of operation with a shutdown of 100 days per year to accommodate fish migrations.
- The tunnel from the Sacramento River intake would cross the Sacramento River and then pass under the Yolo By-Pass to the vicinity of the Rio Vista ai8rport, continue to the North side of the Sacramento River under the Montezuma Hi8lls, cross the Sacramento River west of Decker Island, and then run parallel with the transmission lines crossing Sherman island, the San Joaquin River and Jersey Island before continuing to Clifton Island, the San Joaquin River and Jersey Island before continuing to Clifton Court. this tunnel is planned to provide connections to the North Bay Aqueduct, Contra Cost Canal, East Bay MUD system and the North Delta users at their option.
- A Second tunnel would be constructed from the Montezuma Hills to Jersey Island and would daylight on both Sherman and Jersey Islands. The setback levies would protect the utilities and tunnel as they cross the tow islands and provide a stable, elevated roadway on which to relocate Highway 160. The further benefit of these levies w2ould be the protection of the "Central Pool" from salt intrusion from the rising sea levels and during periods of internal levy failure.
- The North side of the Sacramento River was chosen for the river crossings because of the availability of materials from the Montezuma Hills and the need to build a platform for a pump station and conveyance crossing of the Sacramento and San Joaquin Rivers in Phase Three. The site also has the advantage of the close proximity to the high voltage electrical power.
Benefits of Phase One of this modified western alignment option include:
- Connects major users of the Delta (North Bay, Northern Delta cities and agencies, South Bay, Contra Costa, EBMUD along with the State and Federal Projects) to connect to the system and provides better quality water for all who chose to connect.
- Phase One facilities would be delivered by gravity at a much lower volume that the 15,000 cfs facility being evaluated and would allow the reduction of the south Delta pumping to more historic amounts.
- The Colusa Drain would be tied into the Yolo Bypass to provide better quality Sacramento River water to all downstream users and to provide water for environmental and bio-attenuation purposes within the Yolo By-Pass.
- Would remove the current proposed intake area from below a major sewer that over time would likely cause significant downstream user treatment.
PHASE TWO
- Adds pumps at the Phase ONE Sacramento River intake to increase the carrying capacity of the system. It may be necessary to add more intakes off the Sacramento River. With a relatively low lift, the carrying capacity of the system from gravity to a pumped condition could increase the system delivery capacity to about 7,000 cfs (3.6 MAF if operated 260 days per year).
- An interconnection and an increase in the size of Los Vaqueros Reservoir would be constructed and transmission facilities connecting it to the pumps at Clifton Court and the newly constructed tunnel system. Water introduced to Los Vacqueros will improve reliability and quality of the Contra Costa system, add flexibility to pump and store water during periods of high flows, and provide water supply to users during periods that the intake system is shut down.
- An in delta storage facility allows reduced pumping during fish migrations while maintaining flow and qualityh requirements for water agencies.
- Pumping in the South Delta would be further reduced but would continue at rates that insure a "fresh" central delta.
PHASE THREE
- A pump station and lower Sacramento River intake would be constructed on the North side of the Sacramento River intake would be constructed on the North side of the Sacramento River opposite Decker Island to allow high quality water to be accessed during periods of high Delta outflows. This second intake would be connected to the second tunnel crossing Sherman island and Jersey Islands which would be extended to connect to both Bethany Reservoir and Clifton Court.
- This second system could provide up to an additional 7,500 dfs of supply during periods of high flow and good water quality.
FINANCING PRINCIPLES
Phase One: would be financed on a subscription basis up to the reliable supply provided by this gravity facility.
Over subscription would be reduced on a prorated basis.
- All Delta users and exporters can elect to opt in and participate in the effort or can elect to rely as they do today on the prospects of the system having a decreasing reliability and not be forced to pay for any of the improvements. Those who elect not to participate or who can not get as much capacity as they believe they need can elect to purchase an option allowing Hto have a priority to participate in the Phase Two facilities.
- The agencies that opt in to Phase One would receive the benefits out of the system in the form of a higher reliability of the water able to be supplied from the system when supplies are curtailed. Higher priority rights holders will be respected to the extent that they would have received water without the new facilities.
- Total cost of the proposed system when and if completed will be higher than that currently contemplated but with the financing spaced out over the 15-20 years to complete the system water rates should not experience large spikes. The value of the added reliability will be considerable. Even if only Phase One is completed the system will enhance overall reliability.
- The facilities will provide the operators with much greater flexibility in operations and deliver higher quality water to existing facilities frequently without significant added use of electrical power.
