A Thursday night town hall meeting on the Big Creek watershed posed several questions to the Forsyth County community on development, property rights and environmental regulations.
For the meeting, the county planning department invited speakers to present the issue of the impervious surface coverage limitations placed on the watershed, said Jerry Oberholtzer, long-range planner.
“Georgia state law currently places restrictions on the amount of impervious surface coverage allowable in a small supply watershed such as Big Creek,” Oberholtzer said. “There has been much discussion about this requirement, its effectiveness and possible alternatives.”
Only 25 percent of the watershed can be covered by impervious surfaces, according to the state Environmental Protection Division.
The Forsyth County unified development code also calls for the 25-percent rule on impervious surface areas, which are defined as "a manmade structure or surface which prevents the infiltration of storm-water into the ground below the structure or surface."
The limitation on the coverage area is intended to stop too much runoff water from getting into the streams, said presenter John Moll, of Crystal Stream Technologies.
“When you cover ground with impervious surface, you stop groundwater infiltration,” Moll said.
Too much runoff can cause degradation of streams, which Moll said cannot be renewed and must be protected.
He said in his presentation that Forsyth’s requirements for developers adhere to the Georgia Stormwater Management Manual, known as the “bluebook,” which sets tougher water quality standards.
“I think your rules, which are being enforced by the engineering department and planning,” Moll said, “are giving you better water quality than just throwing a 25-percent rule at the problem.”
In his presentation, he said the number for the 25-percent rule was decided arbitrarily at a meeting in 1989, while the manual passed in 2001 when better technologies and more data were available.
Whether 25 percent is the proportion the community desires is up for debate. But the number was rooted in science, even before the rule was passed, said Bob Slaughter, who presented for Smart Growth Forsyth County.
Citing a 1983 study by the U.S. Geological Survey, Slaughter said streams and habitats become “severely impacted” at 25 percent impervious surface coverage.
“Smart Growth is here to make sure that … if a decision is made about removing the 25-percent impervious surface limitation,” he said, “that’s it’s taken with a full array of information available to the public and the county commissioners.”
He recommended considering developer standards, protective measures and compensation for land marked “unbuildable” due to those restrictions in addressing development in the Big Creek watershed.
Slaughter posed a number of questions the public and the county need to address before reconsidering the 25-percent rule.
“What makes sense for us? What’s a good number?” Slaughter said, calling for more studies to be done on the health of the watershed and a review over time to determine the best criteria.
Forsyth is estimated to have covered about 14 percent of the watershed. That number grows to about 20 percent if projects approved but not yet built are included.
The 25-percent rule, however, hasn’t been followed across the board, he said.
The Big Creek watershed spans several cities and counties, with southwestern Forsyth containing the most of its area.
Roswell, which has a water intake at the watershed’s southern end, and Cumming have well exceeded the percentage of impervious coverage, he said.
While Forsyth County’s unified development code and other jurisdictions consider accepting alternative criteria for equal or better watershed protection, it must be approved by EPD, Slaughter said.
The EPD rule states that the 25 percent coverage area will be the standard unless all local governments agree to different criteria.
Forsyth commissioners have not stated any intent to take action on the regulations.
The commission did call for the town hall in December as a condition to approving the comprehensive master plan, which serves as a guide for decisions involving future growth and land use through 2032.
Commissioners decided not to include any language addressing the Big Creek watershed in the plan.