Solar Mounting System

Stormwater controls for ground-mount solar projects



Stormwater controls for ground-mount solar projects

Stormwater controls for ground-mount solar projects
April 19, 2024

Installing solar at a large scale requires increasingly bigger plots of land to host acres and even miles of PV arrays on a single tract. Accompanying that growing scale of project scope is the responsibility to implement proper stormwater runoff measures to protect the environments and communities the projects are built in.

In any construction project requiring civil work, excavated land that isn’t seeded or is missing topsoil has higher risk for erosion. Stormwater runoff, like rainfall or melted snow, can take substances like pollutants and debris that are detrimental to local waterways and carry them into neighboring land and municipal sewer systems.

The National Pollutant Discharge Elimination System (NPDES) is a federally mandated permit program with measures for stormwater runoff remediation at construction sites. This permit is issued either directly by the Environmental Protection Agency or through an authorized state, which most are qualified as. From there, states can have their own requirements for stormwater runoff remediation at worksites.

Any construction project with land disturbance exceeding one acre is generally required to have an NPDES permit. It describes design parameters for building proper stormwater runoff management at a construction site and how to close the permit once a project is complete.

“The biggest challenge is managing stormwater to prevent any impacts off site that could impact sensitive habitat,” said Christina Hebb, stormwater pollution prevention plan and vegetation senior manager at McCarthy Building Companies. “The permit language states that we have to do everything in our power during planning designs to really minimize the release of sediment off site.”

There are many preventative measures that can be taken to curb stormwater runoff on solar projects. Hebb oversees solar project site preparations for McCarthy, a national construction company with a utility-scale solar installation arm. She said the most important part of preparing solar sites is establishing vegetation on the land before construction begins.

“Until you really get vegetation established, you’re not going to have a fully stabilized site,” Hebb said. “Any type of seeding we can do ahead of pile installation is going to significantly reduce your costs, it reduces your risk and it will increase production during construction because you’re not going to work on muddy soil conditions.”

Rooted plants stabilize topsoil — the first several of inches of dirt starting from the ground surface. As precipitation and runoff percolate and pass over that soil, the roots of plants prevent it from washing away. It’s nutrient-rich and the ideal place to sow native seed crop.

While ground-mount racking and solar tracker systems have become more adaptable to undulating topographies, there’s still the possibility that some grading at a solar project site will be necessary to install the array. If the land must be graded, Hebb implores contractors to save the topsoil they remove, because it can be replaced later.

Failing to establish initial seeded topsoil can require additional ground amendments, soil compaction and possibly reseeding multiple times after construction to grow vegetation.


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