Guidelines for Solar Array Projects Located in the FEMA 100-year Floodplain.

Solar array project sites often encompass large portions of land; therefore, it is economically desirable to minimize land costs. As a result, many sites that meet these two criteria are within flood prone areas.

When considering a site for a potential solar project, contact the Monterey County Water Resources Agency to learn of known floodplains including flooding areas that impact the project site.  If recent floodplain studies accepted by the District are not available, a floodplain study will be required.  Certain mapped FEMA zones require more detailed study prior to project design. 

A project site with FEMA approximate 1-foot mapping  

It’s usually not necessary to avoid flood prone areas, however certain design considerations are necessary within flood prone areas. The design requirements should be discussed with the project team, and the methods to meet these requirements need to be shown on the site construction plans. 

Basic design requirements include:

1. Determination of all regulatory floodplains or shallow flooding areas impacting the project site.

2. Elevation of the lowest edge of all photovoltaic panels at or above the 100-year water surface elevation when at full-tilt.

3. The following must be elevated at least 1 foot above the 100-year water surface elevation: a. electrical service equipment; b. inverter skid platforms; and c. permanent structures.

4. A setback of 200 feet from the top of the bank of a river and 50 feet from the top of the bank of a watercourse shall be established, unless the encroachment is certified by a registered civil engineer to 1) not significantly reduce the capacity of the watercourse, or adversely affect other properties, and 2) will be safe from flow related erosion and will not cause flow related erosion hazards.

5. Fencing to provide for flow-through of 100year flood waters.

6. Grading along site boundaries shall be compatible with the upstream and downstream conditions. For most projects, a floodplain review fee will be required. 

A solar array installation located in the FEMA 100-year floodplain (Salinas River, unincorporated Monterey County)