Changes to reduce mega Delta project impact
22 Aug 2013
Shani Wallis, TunnelTalk
- Major project changes, including shortening the length of the tunnels and reducing the size of an intermediate forebay, are to be incorporated by the California Department of Water Resources (DWR) to shrink by 50% the total permanent footprint of the proposed water conveyance system in the Sacramento-San Joaquin Delta and otherwise substantially reduce the effects of the project on Delta residents.
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Fig 1. Major design changes will reduce project impact
- DWR is making the changes to the Bay Delta Conservation Plan (BDCP) to overcome major objections voiced by local landowners and advocates against the mega-project effort by Federal and State agencies and other stakeholders to stabilize water deliveries from the Delta and protect and enhance the Delta's ecosystem. Changes will shift more than 400 acres of permanent and temporary construction impacts from private to public lands and avoid direct confrontation with local private property owners.
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In detail, the changes, announced on Thursday last week, 15 August 2013, include:
• Shrinking the new intermediate forebay from
750 acres to 40 surface acres and shifting its
location away from the towns of Hood and
Courtland and closer to Interstate 5;
• Realigning a segment of the proposed twin
tunnels several miles to the east to lands
owned by a private non-profit group and
away from the Pearson District, Brannan
Island, and Walnut Grove;
• Shortening the main tunnels from 35 miles
each to 30 miles each;
• Using DWR-owned properties south of Hood
as a construction staging area and
DWR-owned properties near Interstate 5 as
a re-usable tunnel material storage area;
• Decreasing from 151 to 81 the number of
structures affected by the project;
• Reducing from 60ft to 30ft the height of the intake pumping plants along the Sacramento River by relying on a
mobile crane rather than a permanent gantry crane inside each building;
• Reducing from seven to five the number of tunnel excavation launch/retrieval access shaft locations;
• Eliminating borrow pit areas north of Hood and reducing the staging area from 400 acres to 200 acres;
• Working with landowners and stakeholders to use excavated material to improve and preserve wildlife habitat
on Zacharias Ranch, on Glanville Tract, and on the Delta's Staten Island;
• Modifying and strengthening the existing Clifton Court Forebay for improved operations of north and south Delta
conveyance.
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Owner is committed to "minimizing disruption to local residents"
- In all, the recent project refinements would shrink the permanent water conveyance project footprint from 3,654 acres to 1,851 acres (not including several sites where tunnel material would be stored temporarily). The amount of privately-owned land affected either temporarily or permanently would decrease from 5,965 acres to 5,557 acres. Use of public lands for the conveyance project would more than double, from 240 acres to 657 acres.
- "We take seriously the effects our proposal would have on the property and daily lives of Delta residents," said DWR Director Mark Cowin in a published statement. "We have worked hard to find ways to eliminate or modify some of the construction activity and permanent infrastructure in ways that minimize disruption to local residents. We will keep working to reduce impacts wherever possible, and we are committed to mitigating those that are unavoidable."
- The project seeks to obtain a 50-year permit to cover the Delta pumping of the State Water Project that is operated by DWR in coordination with the Central Valley Project owned by the US Bureau of Reclamation and to comply with the US Endangered Species Act and the California Natural Community Conservation Planning Act.
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Project will feed water to interstate canal system
- The administrative draft plan that proposes construction of three new intakes on a stretch of the Sacramento River near Hood and twin 37 mile long x 33ft i.d. (60km x 10m) TBM bored tunnels directly under the Delta to convey water to the existing pumping plants in the south Delta near Tracy and reduce reliance on the existing pumps in the south Delta that cause disruption to the population of fish species in the area. Other environmental measures include protection or restoration of 145,000 acres of Delta habitat over 50 years.
- The draft BDCP and a corresponding environmental analysis consider different ways to convey water from the Delta (Fig 1). No final decisions have been made on which alternative will be selected by Federal and State agencies. A public review draft of both the plan and environmental documents will be released in October. From the pumping plants in the south Delta, water is lifted into canals that supply consumers in Southern California, the Santa Clara Valley, and the San Joaquin Valley.
- The proposed project analyzed in the documents has changed significantly in the last two years in response to concerns from State and Federal wildlife agencies. The capacity of the proposed north Delta intakes has been downsized from a maximum of 15,000 cubic feet per second (cfs) to 9,000 cfs. The number of intakes along the Sacramento River has dropped from five to three, and the proposal has been modified to flow by gravity from the intermediate forebay to the main forebay, rather than by pumping. This change would greatly reduce energy costs and emissions and eliminate the need for some power lines and an intermediary pumping plant.
- The additional changes, announced last Thursday (15 August), are said to be, in part, the result of discussions with landowners and residents in response to local concerns and the result of the optimization process by which "engineers and planners refine projects to achieve better effectiveness and higher efficiency".
- To help Delta citizens and community members obtain additional information or offer input on the project plans, DWR is to hold information sessions at local libraries during the month of September. Details will be posted on the project's website.
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Governor supports mega water tunnels project - TunnelTalk, July 2012
Mega water tunnel plan for California - TunnelTalk, February 2010
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