These lands were originally tidal marshes, vegetated areas subject to daily tidal action. They were reclaimed for agricultural and other uses by the construction of levees and the installation of one or more water control structures to control the inflow and outflow of water. The Suisun Marsh Protection Plan recommends the restoration of former tidal marshes to tidal action where and when possible.
Salt marsh restoration projects on former exterior areas generally have a great potential for producing large numbers of mosquitoes. At least one mosquito species produced in these types of areas is an aggressive pest of man and is capable of flying in excess of 20 miles. Mosquito control in California has its origin in the San Francisco Bay Area where efforts were undertaken to control this pest by ditching to enhance drainage and water circulation.
Removing or breaching the levee will subject the sites to tidal flow. The extent of tidal flow depends, of course, on the relative elevation of the site to tide. Tidal flushing itself does not create mosquito problems. Mosquito problems arise from the residual tidal and flood waters remaining in depressions and cracked ground.
The following District Practices should be considered prior to removal or breaching of any levee or water control structure.
Policies for Management of Salt Marsh Restoration of Exterior Levee Lands
1. Develop a management program for the control of mosquitoes. Such a plan should be developed in coordination with the Solano County Mosquito Abatement District (SCMAD).
2. If necessary, obtain an engineering survey to locate depressions that would retain tidal water, and to determine the location of ditches for water circulation and drainage.
3. Establish a water recirculation system by interconnecting depressions with ditches that will enhance water movement and provide access for predator fish.
4. Disk or harrow all cracked ground caused by shrinkage and subsidence.
5. Plan and fund a long-term maintenance program on the marsh. The maintenance should include:
- Dredging and cleaning of sloughs, spreader ditches and main ditches to provide.
- Disking of cracked ground as needed.
- Maintenance and repair of water control structures.
The preceding mosquito prevention criteria are intended only to offer guidance when considering the development of design options during the planning process for projects. Be advised that these practices have been found to be effective, however, once the project has been completed it is essential that conscientious maintenance and management practices be followed to help ensure the successful prevention of mosquito production.
Be further advised that under the California Health and Safety Code (Sections 2274 et. seq.) the responsibility for the cost of mosquito control may fall on the property owner.