Can wetlands fix Water Works' nitrate problems?
It's little more than an acre patch of plowed earth right now, with a few cattails and bulrushes starting to poke through the soggy dirt.
But Des Moines Water Works hopes that very soon this newly created wetland may prove itself to be part of the solution to the utility's thorny water quality problems.
Water Works is creating a wetland test site for a unique nitrate-removal process that could expand to 80 acres of land at Water Works Park.
The pilot project, part of the utility's $80 million effort to update its nitrate removal system, utilizes a wetland that has been designed to naturally siphon nitrates from the contaminated source water feeding the public utility.
The pre-treatment method would be a first of its kind in Iowa, where nutrient reduction has become a hotly debated issue amid a Water Works lawsuit targeting three northern Iowa counties.
“This is something that we would hope to see adopted by people upstream,” said Bill Stowe, CEO of Des Moines Water Works. “Wetlands are an important conservation practice that we don’t see enough of in Iowa.”
The Iowa Nutrient Reduction Strategy encourages the use of wetlands and some of these natural low-lying areas have been preserved across Iowa. They can improve water quality as edge-of-field measures to filter contaminants from farm runoff.
Water Works plans to put a new spin on the practice by creating wetlands in a controlled environment that doesn't rely on rainfall and the natural movement of water.
"We’re going to pump from the Raccoon River into the wetland," Stowe said. "We’re not just relying on a gravity connection, as an example, from farm fields."
Workers at the public utility, which provides drinking water to about half a million Iowans, have already dug out two dirt cells on a one-acre plot in the northeast end of Water Works Park. It's near the Raccoon River and the Fleur Drive water treatment plant.
About 10,000 cattails and 10,000 bulrushes planted last month are sprouting through the wet soil.
In the months ahead, they'll get covered several inches with a steady flow of water from the Raccoon River and monitored closely while nature runs its denitrifying course.
"The cattails and bulrushes actually use some of those nutrients, but they also create an environment where microorganisms do the real work of removing the nitrate," said Ted Corrigan, Des Moines Water Works chief operating officer.
For the pilot, one of the half-acre cells will serve as a control wetland that will simply be monitored once the water covers the plants.
Staff workers plan to experiment with the second cell by testing extraordinary conditions such as flooding or extreme nitrate spikes to gauge the potential of the wetland denitrification process.
If successful over the course of one to two years, Water Works plans to create an 80-acre wetland in an open space that is occasionally used for events in the southwestern side of Water Works Park.