Twitchell Island Revegetation
Sacramento County, CA
Reclamation District No. 1601
Spring 2000
Hanford ARC constructed this levee setback revegetation project, located in Sacramento County, Ca., in February and March of 2000. Prior to the project, 2,400 linear feet of new levee on the San Joaquin River had been constructed with a 100-foot setback from the old levee, which remains in place as a breakwater and revegetation planting zone. The project included the installation of nearly 24,000 herbaceous plants, 1,660 woody plants, and a temporary irrigation system. Hanford ARC is currently implementing an extensive three-year monitoring program, including weekly site visits and preparation of regular monitoring reports.
Our work was administered by Reclamation District No. 1601 (Twitchell Island) through Kjeldsen, Sinnock and Neudeck, Inc. of Stockton, Ca., also the designers. The levee setback and revegetation project is critical for the State Department of Water Resources (the funding agency), as it is the first of its kind in the delta, and the success may determine the extent of future funding by CALFED for similar projects. Hanford ARC and the project are under observation by numerous federal and state agencies.
A 3-year maintenance period was part of the contract. This was recently extended to four years, ending in April of 2004. This includes hand weeding, mechanical weeding, spraying, and operation of irrigation system. The irrigation system installed was designed by Hanford ARC and is wildland drip and spray head, operated by a 6” diesel pump. Plant protection was installed due to beaver damage. The protection included cones and weed mats initially. This was met with limited success. Continuing beaver damage required installation of wire cages on affected plants. This method has been very effective, allowing the plants to establish. Specifically affected by the beaver were the willows and cottonwoods. Also a part of the maintenance operations is continuing removal of invasive plant species including water hyacinth and cattails.
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