Constructed wetlands provide a great way to capture and treat stormwater municipal run-off. Depending on the need and the available area, they can save significant construction and operation costs over mechanical treatment, as well as address flooding issues. Wetlands can also provide habitat for animals and birds or walking trails.

• 
  Cost-Saving Contructed Wetlands for Stormwater
  and Combined Sewer Overflows
• Constructed Wetlands for CSO Treatment, Washington, Indiana

  • Client: The City of Washington

    When Washington, Indiana, needed to consider innovative alternatives to address its CSOs, it decided to revise its LTCP to include constructed wetlands and UV disinfection. The city's collection system is unique in that several of the main interceptors are actually creeks that had been enclosed in large pipes. During wet weather, the pipes not only convey sewage and run-off from the city proper, but also from watersheds beyond the city limits. The estimated cost to separate the sewers was more than $60 million, well beyond the means of this town of 12,000. Using a constructed wetland to treat the CSOs reduced construction costs to $26.4 million as well as saving $1.6 million in annual operation costs! The system, the largest of its type to date, captures the first flush flow in a 4-mg storage tank, pumping this to a wastewater treatment plant. Overflow from the tank-up to a 10-year, 1-hour storm event will travel via two 84-inch pipes to a 21-mg, 27-acre constructed wetland for treatment. The system is operated via a SCADA system that can control detention time in the wetland. Additionally, the system can be fed with groundwater produced from a groundwater control system. Due to the depth of the basin and the underlying soil, strata groundwater will be available for the wetland system even during drought events.

• Highland Creek Stormwater Redesign, Indianapolis, Indiana

  • Client: City of Indianapolis, Department of Public Works

    The city of Indianapolis Clean Stream Team chose BLA to design a diversion of Highland Creek to prevent flooding and address septic issues in a nearby residential neighborhood named Frog Hollow. BLA reviewed the city's previously prepared scoping report that analyzed several options and recommended building a concrete culvert to divert flow from Highland Creek to the smaller, nearby Germania Creek. This solution: 1) did not address water quality; 2) would have included substantial utility impacts; and 3) did not account for the additional flow impacts on Germania Creek. BLA's design includes a decorative diversion structure, with a fish passage to maintain Highland Creek's ecology during normal dry weather flows. During storm events, the diversion structure directs stormwater runoff to the bio-swale and 1-acre constructed wetland. From there, stormwater flows into a nearby stormwater detention basin. Modifications to this basin and the addition of the constructed wetland allow the city to increase stormwater retention capacity and improve water quality. The bio-swale is planted with trees and vegetation. The solution will route 80% of water away from the neighborhood during the majority of rain events, protecting the residential neighborhood from flooding.

•