Wrestling with Runoff: Storm-water control efforts

Each new project built in the city is required to adhere to guidelines for how naturally occurring water – such as rainwater or melted snow – will leave the site, whether the project is a single building or a multistructure development.

New developments create impervious surfaces, such as buildings and parking lots, that don’t absorb water. Left unchecked, the additional water runoff can contaminate streams with pollutants that range from fertilizers to petroleum products.

Detention basins, concrete drainage ditches and box culverts throughout the city are visible signs of efforts to minimize the impact of new development on the area’s watersheds and delicate karst topography.

Controlling the amount

The city handles a lot of storm water, though the exact amount varies depending on the weather.

Todd Wagner, the city’s principal storm-water engineer, said that one major rainfall in spring 2000 dumped as much water on the city as the Southwest Waste Water Treatment Plant cleans in a year – an amount that Wagner said is in the “billions of gallons.”

Potential for that volume is part of the reason why developers must create detention basins or drainage systems for new developments – to keep water runoff levels at pre-development levels.

The thought process behind dealing with storm water has changed over the years.

“It used to be that we tried to get the water off the site as quickly and efficiently as possible, and sometimes that speeds up the water so much that it causes problems downstream,” said Milton Dickensheet, project manager with Scott Consulting Engineers.

“Now we’re trying to get back more to traditional natural channels,” he added.

At Chestnut Crossing, the 36-acre development at Chestnut Expressway and West Bypass, Scott Consulting worked with developer Paul Larino to address storm-water detention.

Larino said the two-acre detention area on the site was specially designed.

“A lot of detentions are constructed where there’s a big ugly hill out there,” Larino said, noting that his project’s inclusion in the Northwest Community Improvement District provided money to create a larger, flatter basin that blends more with the natural surroundings.

“We also put some special grasses in that would help feed the birds and create seeds at different times of the year,” he added.

A standard detention basin collects water and discharges it, through a pipe or channel system, into the city’s storm-water system, which controls the rate at which the water flows into streams to prevent flooding.

Loring Bullard, executive director of the Watershed Committee of the Ozarks, said many developers also are working to reduce the amount of water that ultimately leaves their developments.

“The trend is toward more low-impact development, where we don’t create runoff in the first place,” Bullard said, pointing to techniques such as natural filters, plants and grasses, and pervious concrete that allows water to percolate back into the ground.

Quality control

Controlling the amount of water leaving development sites, however, is only part of the storm-water equation. The other issue is the quality of the water coming off of developed properties.

Dickensheet said both Springfield and Greene County incorporate water quality controls into development requirements.

“If you have a big paved area that has had activity on it and then it rains, a lot of contaminants will wash off that (area) into the streams,” Dickensheet said. “What the city and county require are designs that will help settle the first flush and not wash (it) off into the stream and degrade the stream.”

There are numerous ways to improve the quality of runoff water.

Most projects incorporate some kind of filtration system into the detention area, ranging from rocks that catch pollutants to filters that discharge water at a predetermined rate.

The Watershed Committee’s Bullard said there are natural alternatives as well, including rain gardens, vegetative barriers and biofilters.

Reaping benefits

Aside from the environmental benefits, runoff prevention and quality control have economic potential.

“Once the water leaves the site, it has to be dealt with somewhere downstream,” Bullard said.

“When you create a system of piping runoff away, you’re assured that you have to have a bigger pipe the farther you go. That’s more money. If you can use vegetation instead of concrete, or reduce the amount or runoff, cities can save billions of dollars in maintenance on concrete drains,” he added.

The main issue, though, is protecting the environment from excess runoff water and from what that water may contain.

“Any time you can get pollutants out of the water before it goes back into the stream, that’s better for fish, wildlife, and for the quality of that water that we use,” said Paula Brookshire, professional engineer with Great River Engineering. [[In-content Ad]]