Analyzing Surface Water Issues During Solar Site Evaluations

Analyzing surface water issues when evaluating a solar site for development can play a pivotal role in successfully entitling, permitting and operating a project. The following outlines three key considerations.

Thorough Hydrology and Hydraulics Due Diligence. Hydrology and hydraulics analysis during site evaluation should go beyond a simple FEMA flood plain review. A thorough fatal flaw analysis should include the presence of jurisdictional boundaries, typical storm intensity and duration, upstream physical conditions that may contribute flow to the site, downstream physical conditions that could be impacted, soil characteristics for erosive potential, and regional water quality issues should all be considered in the analysis.

Local jurisdictional requirements should be analyzed. Requirements vary significantly among cities, counties and regional boards, and sometimes vary within each jurisdiction. Understanding local issues you may encounter will help inform decisions throughout the project’s life.

Understanding Link Between Technology Impact and Mitigation Costs. Knowing how your solar technology will affect a site can help you mold the site plan to minimize impacts to local drainage and reduce mitigation costs.

Sample questions to review with your engineers include:

  • Are fixed array or trackers used?
  • Can the technology accommodate a variety of topographic conditions, or is significant site leveling needed?
  • What are construction-related impacts to local drainage?
  • What considerations in the hydraulic analysis need to be made for construction staging areas, access roads, and soil stockpile areas?

An often overlooked consideration for solar projects is how a specific system sheds stormwater. While a high-level overview of a site may indicate minimal impacts (limited grading, no or minimal impervious surfaces, etc.) a closer look may indicate that the individual system can impact systems hydraulics by concentrating flow in a local area. This flow concentration may require additional hydromodification measures be considered.

Pre-Plan Mitigation Measures. Once site impacts have been quantified, your engineers can help select, analyze and design the appropriate mitigation measures. These may include infiltration trenches around proposed structures, retention/detentions basins, types of dissipation systems for areas of concentrated flows, natural versus engineered erosion control systems, and water quality improvement best management practices.

The planning and design stage should take into account which mitigation measures will be the most efficient and cost-effective for the site’s owner to construct, operate and maintain in the near and long-term.