Biofilter at Prairie Elementary School

Rettler says something is wrong with the biofilter at Prairie Elementary School.

Waunakee Community School District has decided to investigate a problem at one of its schools. This week, it hired an outside firm to find out exactly what is going on.

School-board president Joan Ensign said it’s time to solve the issue.

“This has been ongoing for three to four years,” Ensign said. “We hired this firm to analyze, and they have found things that could’ve been done better…That’s why we hired them. So we don’t know the outcome. We don’t know if it’s going to make it better. But I hope it does.”

The school board has hired Rettler Corporation to take a closer look at Prairie Elementary School and figure out why neighbors have experienced increased sump-pump activity the past few years.

“I feel really bad that these neighbors have (had to deal with this),” Ensign said. “And I think we have a responsibility to take care of our own water-management issues. I think every homeowner has that responsibility.”

The problem began after additions were made to the school in 2015.

Four classrooms were added onto the west wing, along with a large playground to the southwest. Asphalt was chosen for the playground surface, in part, to meet ADA requirements.

A bio-filtration system needed to be installed to filter rainwater that would run off the blacktop.

“A biofilter was constructed on the south side of the school building approximately 580 feet west of Madison Street and 20 feet north of the school’s south property line as part of the project to address regulatory stormwater requirements,” said civil engineer Chase Rettler in a recent report.

Since its installation, neighbors to the south have reported increased sump-pump activity in their homes. Several have attributed it to some kind of problem with the filtration system.

Pam Whalen said it’s tough to imagine that heavy rains are to blame.

“Literally overnight,” Whalen said, “the pump started running 24 hours a day – all day, for three years straight. So it’s hard to believe that rain would make this happen overnight. There are more residents along the south side that are affected by this, and some across the street as well.”

Earlier this year, the school board began to explore possible causes.

Rettler Corporation was brought in to take a look at the improvements that were made in 2015, and compare the site’s current storm-water management to that of previous years.

The company confirmed the filtration system was underperforming.

“Stormwater runoff tributary to the biofilter did not infiltrate into the biofilter engineered soil at a rate consistent with industry standards,” Rettler said. “It also appeared the storm sewer inlet to which the biofilter underdrain system is routed was not accepting stormwater from the biofilter.”

Rettler said slow infiltration and drainage rates are evidence that the bio-filtration system has not performed as it was originally intended, and that something is wrong with the system.

“The combination of slower than anticipated infiltration of runoff into the biofilter and minimal discharge from the biofilter underdrain indicates the biofilter is not performing as designed,” Rettler stated, “resulting in a longer drawdown period for storm events and ponding.”

A civil engineer of 17 years, another neighbor of the school, Jennifer Hurlebaus, said she agrees with the finding.

“Originally,” Hurlebaus said, “there was a culvert that went underneath the sidewalk that would get the drainage over to that (southeast detention) basin. That is where that water would be slowed down before it would be discharged into the storm sewer.”

Hurlebaus said that culvert was removed during the 2015 improvement project, which resulted in water flow being restricted long before it reached the detention basin.

“With the removal of that culvert and replacing it with a biofilter,” Hurlebaus said, “you have basically eliminated that drainage way that existed. And I believe that is why they are seeing that flooding.”

Others have questioned Rettler’s findings, though, and the idea of replacing the system.

Waunakee resident Robert McPherson cited the fact that groundwater levels are at an all-time high, and that many homeowners in the area have faced similar issues.

“The water table is much higher than it’s ever been in Dane County,” McPherson said. “And there are a lot of houses that are dealing with wet basements. Mine is one of them. I had to install a sump pump last year.”

He said investing in a project just to alleviate concerns of the school’s neighbors would be unfair to other homeowners in the district – many of whom have dealt with such problems themselves.

“It’s concerning that there are taxpayer funds that might be going into a repair of the biofilter,” McPherson said, “considering the fact that we as homeowners within the village are responsible for maintaining our own properties and dealing with our own flooding issues.”

School-board member Mike Brandt agreed.

“I’m really sympathetic to the folks who have had issues with their sump pumps running,” Brandt said. “I have neighbors who have had sump pumps running for the last four years, too. And the difference is that I live in Westport.”

Brandt echoed McPherson’s point about an elevated water table, and wondered whether the excess water was a result of that rather than a faulty filtration system at the school.

“If you look at the precipitation tables for the last five years,” Brandt said, “it’s been above average at every point in the last five years…So are we doing this just to be good neighbors, or because we actually need to fix something?”

Waunakee resident Ann Lewandowski voiced similar thoughts.

“I commend the district on its efforts to be good neighbors,” Lewandowski said. “But I believe you have a duty to all of the taxpayers within the community to ensure we will be fixing an issue caused by the district, and not simply trying to address the larger issue of higher water tables.”

The school board’s vice president, Dave Boetcher acknowledged that the water table has risen. However, he said the district would still do its part to address the issue at Prairie Elementary.

Beyond that, though, the homeowners would be on their own.

“The water table has gone up,” Boetcher said. “Dane County admits it, and we know it. But we’re going to fix that biofilter if it’s a problem. And that’s the most we can do. We can’t pump water out of our property from all the residential areas around us.”

The board voted to have Rettler investigate what work, exactly, needs to be done on the biofilter. Rettler could be bringing its findings back to board members as early as this month.

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