When new developments pop up, so does additional stormwater runoff.

Soil and vegetation naturally absorb precipitation. When concrete is slapped on top, this reduces the natural percolation of water and increases runoff being redirected to drains. On its way out, stormwater collects sediment, oil, pesticides, heavy metals and other harmful substances from developments and carries it into lakes, streams and rivers.

For years, Bowling Green developers building on an acre-plus of land or covering 10,000 square feet have had to construct and maintain systems to treat stormwater.

Now, the city thinks there’s a better option to foster growth without compromising water quality.

The city would like to collect fees from developers, pool the funds together and create larger treatment mechanisms the city would maintain, according to Matt Powell, Bowling Green’s environmental manager.

“The primary reason I’m looking at this is economy of scale,” Powell said.

On a one-acre lot, an individual water treatment structure might cost $30,000 to $35,000 to come into compliance. Then it might cost an additional $1,500 to $5,000 each year after to maintain a structure that’s treating a small volume of water, according to Powell.

With the new program, the city would construct a single treatment mechanism for a dozen or more projects downstream in the watershed.

“We’d be building something larger for the same kind of money,” Powell said. “We can build larger, more passive style treatment systems.”

To treat stormwater, there are various technologies used to achieve compliance, such as cyclonic separation or membrane filters. Basically, a “passive” system collects water in a single bowl, and gravity helps pull sediment and other debris down.

It requires a lot of space, but it’s less expensive than some alternatives and produces great results, according to Powell.

“Much like most stormwater systems, there isn’t a golden bullet that solves everyone’s problems,” Powell said. “It’s not intended to be a cure-all for every situation.”

The developer’s advantage is that they don’t have to install or maintain the systems – nor would they have to submit reports regularly to the city. They would pass the responsibility to the city staff, who would gain the advantage of treating more water and conducting fewer inspections. The downside is that staff will have to conduct the maintenance – but the fee is designed to offset the cost.

The initial feedback has been positive, but questions remain. To pay the fees, developers might be offered the choice of buying themselves out of dealing with post-construction stormwater maintenance entirely, or paying a smaller, upfront fee with additional fees to offset the city’s maintenance work.

But the actual dollar amount hasn’t been decided.

“That’s going to be the most complex and controversial part of the project,” Powell said. “It has to be high enough that taxpayers aren’t subsidizing development, and low enough that (the city) is going to be able to achieve the same goals as developers would be with smaller projects.”

The city hired Louisville-based consultants Land Design and Development to prepare a plan.

“Generally, the idea is that a larger, regional-based approach would be more effective than a lot of smaller, scattered sites,” said Mike Hill, the senior land planner at Land Design and Development. “One collective effort by the city would have a greater net effect than small randomly placed projects.”

Powell estimates the final proposal will be ready in the next six weeks.

“We’re intending to have the program ready for review this fiscal year,” Powell said.