Forsyth County could be doing a more effective job of protecting its watershed while allowing responsible development, according to engineers who addressed commissioners Tuesday.

John Moll, CEO of Lawrenceville-based CrystalStream Technologies, was invited to talk about alternate criteria for development in the Big Creek watershed.

The Georgia Environmental Protection Division requires that the impervious surface area coverage, such as pavement, of the entire watershed be limited to 25 percent.

Forsyth has adopted this rule in its unified development code, in addition to other criteria to protect the environmentally sensitive water supply watershed.

“You are doing more today than was envisioned by the 25 percent rule,” said Moll, an engineer who specializes in water protection. “It’s been a tough road for developers and financial interests to have rules as tough as yours … but you guys have stayed course and protected your stream.”

He added that the law allows local governments to adopt alternate criteria to protect the watershed, which Moll said Forsyth has been considering.

Moll and Brian King, an engineer from his company, discussed reusing water on site, harvesting rainwater and other low-impact development techniques.

Construction, Moll said, can put 30 times more sediment into a stream than an existing structure. The sediment can be a surrogate for other pollutants.

“Just controlling the impervious surface … by not developing 75 percent of the land is certainly not going to control that,” he said.

King added that many lots in the county cannot be developed due to the 25-percent requirement.

He emphasized that protecting the floodplain first is more important for stream health.

In sum, Moll said Forsyth’s plan, which institutes larger stream buffers and other measures, does a better job of protecting the watershed, and alternate criteria could be considered.

At the start of his presentation, Moll said he was asked to share some of his findings, but would not discuss what his business does unless asked

At a previous meeting, and after a vote on the comprehensive master plan update, Commissioner Patrick Bell had requested Moll’s attendance.

Bell said after Tuesday’s meeting that he’d met the engineers at a previous function and they discussed the 25-percent rule, which they said is not supported by scientific data.

“My concern is that we have an arbitrary limit,” Bell said. “It’s a ticking time bomb on that area, because we don’t know [when we’re going to reach that].”

After Moll’s presentation, commissioners set a town hall meeting for March 20 to discuss alternate criteria for the watershed.

Bob Slaughter, founder of Smart Growth Forsyth County, has been following the issue with some concerns.

He suggested the commission hear from a different set of engineers prior to the town hall for another perspective. Commissioners agreed.

“I think it’s a little bit simplified to equate a 25-percent impervious surface limitation with not developing 75 percent,” said Slaughter, adding that he will request the engineers attend a February work session.