EWI Cattail Remediation Plan for Retail Chain Sees Results in Second Year

Left unchecked, cattails can take over shallow ponds and wreak havoc on aquatic ecosystems. They can “dominate plant communities, reducing plant diversity and habitat for other organisms, and they can impede water flow through irrigation or drainage channels,” according to the website of the Noble Research Institute, “an independent nonprofit agricultural research organization dedicated to delivering solutions to great agricultural challenges.” It was this cattail remediation challenge that Environmental Works, Inc. (EWI), was faced with.

A major retail client was having outfall drainage issues at 50 of its store locations in Kansas and Nebraska. The client anticipated that the stormwater ponds at many of the stores would need to be cleaned and dredged, and then completely reconstructed with new soil and new clean outs. Upon investigating, EWI offered a much more cost efficient and eco-friendly solution.

“We said, ‘Hold on. First, let’s identify why the ponds aren’t draining,” Operations Manager Willie Vance said.

Led by Project Manager David Lewis and Vance, EWI performed site walks and inspections on the store sites. Field crews from EWI conducted camera surveys on the clogged outfalls and removed excess sediment. Lewis and Vance learned that the soil in the ponds was permeable and therefore well-draining. They also noticed that many on-site ponds were overwhelmed with cattails (Typha latifolia, T. glauca, and T. angustifolia), a native “obligate wetland” species that thrives in aquatic ecosystems of less that 2.5 feet of standing freshwater.

Cattails “have a tendency to grow in thick, nearly impenetrable stands, blocking the view of open water and raising concern that they will take over and cover a pond,” according to Cornell Cooperative Extension’s website. “As long as the water is not too deep, the cattails feast off the open sunshine and abundant water, storing a large amount of food in the root system. In fact, cattails at the edge of ponds can grow faster than fertilized corn in a field. The dense foliage and debris from old growth makes it very difficult for competing plant species to grow.”

Lewis and Vance consulted with others at EWI, as well as outside contractors, and came up with a phased cattail remediation plan. The first phase, carried out in early spring 2019, called for the cattails to be sprayed with Alligare IMOX, an aquatically safe herbicide that uses ammonium salt of imaxamox to stunt the growth of the plants when they are 12-24 inches in height.

EWI field crews revisited the store sites in fall 2019 and cut and raked the cattails out of the ponds. When Vance once again visited the sites this spring, he was pleased to see that the cattail remediation plan was ahead of schedule.

“We started out spraying 50 acres of cattail last year; now we’re down to 30 acres (across 50 stores),” said Vance. “We’ve reduced cattail coverage by 50% in one year.”

EWI’s cattail remediation plan is saving these freshwater ecosystems, as well as money and maintenance for the client.

“They wanted to do a very expensive system-wide repair,” said Vance. “We came back with a plan to do the repairs at a number well below.”

The plan will also add significant service life to the man-made ponds.

“We’re saving their ponds years of service,” said Vance. “If you look at a pond that lets cattail build up happen, after about three years it’s going to require major repairs. So, you have a three-year window if you let your nuisance vegetation grow up. With our plan, these ponds will last at least 5-7 years before a sediment removal or repair is necessary.”

EWI plans to do a second spray of the cattails this year “right in the heat of summer,” said Vance, adding that in the third year of the plan they anticipate having to spray even less.

“We can really maintenance these sites better with the current herbicide plan we have in place,” he said.