4 minute read
Green infrastructure the answer for Frog Hollow residents
After years of flooding, constructed wetlands offer relief for neighborhood, savings for city
Jennifer Whitson
Marketing/Proposal Specialist Bernardin, Lochmueller & Associates, Inc. Indianapolis, Indiana
or decades, the City of
Indianapolis struggled with how to help the residents of Frog Hollow, a small neighborhood on the near southside. The neighborhood is made up of a cluster of about 150 modest homes surrounded by industrial and commercial buildings.
Every time the city received as little as one inch of rain, Frog Hollow’s streets would flood and become unpassable. When the storms were heavier, people moved everything of value up to the higher shelves in their homes. When storms were downright relentless, there was no stopping the flooding.
Frog Hollow Neighborhood Association President Gary Gaskin said many in the neighborhood started giving up. “With flood damage all the time, people stopped trying to fix up their homes,” he said. “Why bother, when it would just get damaged again.”
When Mayor Greg Ballard took office in 2008, he heard from Frog Hollow residents and sent a clear message to the Department of Public Works (DPW): Find a solution.
The Indianapolis Department of Public Works included a constructed wetlands in a stormwater drainage improvement project to slow down runoff and improve water quality. State regulators also counted the effort towards wetland mitigation goals for an unrelated construction project.
But there wasn’t a simple answer. Frog Hollow sits on lowland that drains into the White River, which is west of the houses. Highland Creek, which has a peak rate of 400,000 gallons per minute, winds through the neighborhood and it routinely floods. Germania Creek, which has a peak rate of 300,000 gallons per minute, is north of the neighborhood and bypasses the residences. When heavy rains hit, the White River rises and both creeks experience backward flow.
DPW and engineering consultants reviewed several solutions, which included everything from cost estimates for buying all the houses to installing additional storm sewers. DPW settled on a project that would cost roughly $5 million and would reroute flow from Highland Creek into Germania Creek via new storm sewers.
It wasn’t the ideal solution— Germania Creek is a smaller creek and it was already at capacity. Also, the path chosen would require the City to dig trenches for pipes along Bluff Road, through the busy intersection with Troy Avenue, potentially causing traffic to snarl and requiring very costly relocation of utility poles or natural gas lines.
In October 2008, Mayor Ballard founded the Office of Sustainability and called on all City departments
The diversion structure that allows low to medium flow to continue on Highland Creek (left) while redirecting a portion of higher flows to a constructed wetland (right).
to incorporate sustainable solutions into projects. As a result, DPW asked Bernardin, Lochmueller & Associates, Inc. (BLA) to review the Frog Hollow project.
BLA drainage designer Don Wilson, P.E., LEED AP, started by broadly scanning the terrain surrounding Highland Creek, searching for two things—a way to buffer the load of stormwater going into Germania Creek and a different path that wouldn’t require utility relocations. What he found offered even more.
Wilson noticed that one plot of land near both Highland and Germania Creeks had a pond bordered by nearly 40 acres of vacant land. What if, he thought, we could have no utility relocations, buffer the load on Germania Creek, and treat the stormwater runoff to make it cleaner?
To do that, Wilson wanted to divert medium flow from Highland Creek into a newly built and planted wetland next to the pond. The water would be directed through the plants and swales of the wetland before reaching the pond, which would have its level slightly lowered. Thus both the wetland and pond could hold and slow down the runoff during a storm.
This solution would also avoid construction along Bluff Road, meaning construction costs would be $200,000 less than the former proposal. During a 10-year, onehour storm event, 85 percent of the water that used to flood Frog Hollow would be diverted and cleaned through the system.
Wilson pitched the idea to DPW and city leaders jumped at the idea. “This was a very unique solution,” said Craig Cordi, CPM, DPW’s Project Manager for Construction for the Frog Hollow project. “Most of us on the construction or maintenance side would have thought of conventional storm sewers first.”
The bonus of using a wetland and routing the water through the pond, Cordi said, was that it not only slows the water during a rain event, it improves water quality. “You just let nature take its course,” he said.
Plus DPW could count the project towards meeting state wetland mitigation requirements.
Since the project, there have been several low- to medium-volume rains and the streets of Frog Hollow have been drier. And Gaskin, with the neighborhood association, said that’s kindled new hope in the area. “People have been cleaning up in the neighborhood and around their houses,” he said. “There’s more of a sense of pride.”
Jennifer Whitson can be reached at (317) 222-3878 or JWhitson@blainc. com.
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