Sedimentation Ponds and Retention Basins

Background Statement
Sediment basins, sediment traps, diversions or similar required measures shall be installed well in advance of any clearing or grading and maintained by the permit-issuing authority. The design of such structures should account for abating potential mosquito problems.*

1. Sedimentation ponds and retention basins may be any shape but should not have small coves or irregularities around their perimeters.

2. Ponds/basins should be designed to be emptied by gravity or pumping for cleaning or drying and have graded bottoms so all water can be removed.

3. Side slopes of excavations and levees should be as steep as possible, consistent with soil characteristics and risk factors of slope failure.

4. Ponds/basins should be kept dry during the period between April 1 and November 1. This serves to prevent mosquito production and substantially reduce the efforts required to keep the vegetation under control.

5. Where steep side slopes cannot be economically achieved, the slopes should be adequately constructed to support maintenance vehicular traffic.

6. The top width of embankments should be a minimum of 12 feet and should be adequately constructed to support vehicular traffic.

7. An access ramp should be provided on an inside slope for launching a small boat for mosquito control.

8. Ponds designed for long term storage should have a minimum storage depth of 4 feet.

9. A maintenance program for weed and erosion control along inner slopes is essential.

10. All accumulation of dead algae, vegetation and debris should be routinely removed from the impounded water surface and properly disposed.

Water Conveyance Facilities
1. Ditches must be maintained free of emergent, marginal and floating vegetation.

2. Ditches should be sized and graded for adequate flow and must not be used for water storage.

3. Unpressurized and low pressure pipelines, commonly used in irrigation distribution systems, should be designed to be emptied when not in use and should not be used for water storage because of the mosquito breeding potential in the partially filled pipes.

* This ordinance became effective on January 25, 1980 and is binding on all grading and vegetative removal activities in the county. It is Erosion Control Ordinance 1087 and is contained in Chapter 31 of the Solano County Code, Article III, Section 31-300.

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.