A Dominion Energy solar farm in Powhatan County. Courtesy of Dominion Energy.

A Virginia Tech-led research team plans to spend six years studying how large solar farms affect soil erosion and stormwater runoff, going beyond modeling based on assumptions and instead focusing on collecting real-world data at a level perhaps not seen before.

Backed by a $3.4 million grant from the Virginia Department of Environmental Quality, researchers plan to identify six large solar farm sites in a variety of locations and states of development. Then, they’ll install instruments at those sites to measure water quality, runoff from solar panels and more.

While Virginia’s clean energy goals call for more new solar energy sources in the decades to come, DEQ is concerned about utility-scale solar farms potentially increasing stormwater runoff and furthering the loss of sediment and nutrients on site — not just during the facilities’ initial setup, but also after they’re operational and even further down the road when they’re decommissioned.

“DEQ staff have noticed a number of stormwater and erosion issues related to the current design standards for solar projects and have determined that the state of the science has not kept up with the needs of this industry in Virginia,” DEQ spokesperson Irina Calos said in an email.

But the agency says it is not aware of any studies that use actual site-specific measurements that reflect runoff from such facilities under conditions typically found in Virginia. That’s where the research team comes in.

“The ability to collect these field data at this scale is a great, unique opportunity,” said Ryan Stewart, associate professor in Virginia Tech’s School of Plant and Environmental Sciences and the project lead.

The research team, which also includes experts from Virginia State University, hopes the six solar farm sites will reflect a variety of geographic areas within Virginia as well as a variety of stages of development, with some sites still under construction and others fully established.

“Every site’s going to be a little bit unique in how the actual instrumentation is put in because the drainages are different, the conveyances, all of that looks a little different,” Stewart said. “We’re still in the process of figuring out exactly what recipe goes for each site, and what those sites are.”

With data in hand, researchers will be able to look at how closely their measurements match up with the models used to develop the solar farms’ site plans — for example, how much runoff was a site predicted to generate, versus how much runoff actually occurs. 

“If it’s not doing a good job of matching up, can we adjust certain things within those models to get a more accurate estimate for future installations of these solar sites?” Stewart said, explaining a potential application of the research.

Lee Daniels, the T.B. Hutcheson Jr. Professor Emeritus in Virginia Tech’s School of Plant and Environmental Sciences and a fellow investigator on the project, said he is especially interested in studying what happens to the sites during the process of clearing the land and installing solar panels.

“What happens at many of them, not all, but many of them is that what was there as a preexisting natural soil or landscape gets considerably cut and filled and moved around,” Daniels said.

That, along with how much vegetation a site has and how much vegetation is replanted after construction work is done, are among the factors that can affect runoff and the loss of sediment, he said.

Solar farms are a growing part of Virginia’s energy portfolio. For example, Dominion Energy, the state’s largest electric utility, today has just over 1,500 megawatts of solar energy in operation — enough to power 375,000 homes — and just under 6,500 megawatts in various stages of development, said spokesperson Aaron Ruby. 

“We’re moving full steam ahead on building out solar in communities across Virginia,” Ruby said. 

[Disclosure: Dominion is one of our donors, but donors have no say in news decisions; see our policy.]

But building solar farms is not without controversy. Utilities have fielded complaints from neighboring landowners about the impacts on their properties and in some cases paid thousands of dollars in fines.

In March, Energix US, which operates seven solar farms across Southwest and central Virginia, agreed to pay $97,651 and fix problems related to violations of erosion and sediment control regulations, according to The Roanoke Times.

In Louisa County, neighbors of Dominion’s Belcher solar project told the Richmond-based station WTVR in 2021 that excess runoff from the solar facility was eroding their land; one county supervisor called it “pretty catastrophic.” Dominion told the TV station that heavy storms the previous year had hampered its ability to properly stabilize the construction site.

Recently, some localities, including Culpeper, Henry, Mecklenburg and Surry counties, have adopted ordinances limiting the amount of solar farm development that can be approved there. It’s a result of local governments trying to balance a growing demand for energy with residents’ desire to preserve agricultural land.

Ruby said that since Dominion started building solar farms 10 years ago, the utility has learned lessons about mitigating their impact on the environment.

Buffers, silt fences, sediment basins and vegetation have all been used to keep stormwater runoff out of streams and rivers, Ruby said. But today, for example, the utility might install double rows of silt fencing instead of single rows to better reduce soil erosion, or it might replant grass at a solar farm site sooner than it would have in years past.

Dominion is among industry partners supporting the research. Virginia’s largest utility has offered the team access to its solar facilities and has offered a $250,000 grant toward the project, said Amelia Boschen, manager of environmental services for Dominion.

“If their data can provide information about whether what’s being done is effective, or what types of things might be more effective, that’s a benefit,” Boschen said, “because ultimately our intention now, and the way that we’re developing solar now, is with the goal of both being mindful to our neighbors and ensuring that we’re not impacting our neighbors, Virginia’s waterways and ultimately are minimizing any nutrient or sediment loss from the site.”

Appalachian Power, the largest electric utility operating in Southwest Virginia, is not involved in the project, likely because it only owns one solar farm; most of its solar power is purchased from elsewhere, said spokesperson Teresa Hamilton Hall.

Regulations around solar farms continue to evolve. Just last year, Gov. Glenn Youngkin’s administration introduced a number of new rules related to stormwater management and development, including classifying solar panels as impervious surfaces unable to absorb runoff.

“Research findings could help DEQ, Virginia localities, and the solar industry to better understand the impacts of [utility scale solar] facilities on surface waters and determine what best practices are needed to minimize such impacts to land and water,” Calos said.

Although the project has a six-year timeline, some of the information it yields could come out earlier. Graduate students will use the work in their theses, while Stewart aims to submit the project’s findings to peer-reviewed publications.

For now, the next steps include identifying the six sites and gathering the necessary measuring instruments.

“This study and how it’s set up in combination where we’re doing this site-specific work and gathering these data sets and the actual runoff amounts and the water quality — I’m not aware of anything being done like it on solar sites anywhere,” Daniels said. “And even related work in urban environments, most of that kind of work is decades old. … This one is much larger in scope and time.”

Matt Busse is the business reporter for Cardinal News. Matt spent nearly 19 years at The News & Advance,...