Water Quality Subsurface Gravel Wetland: Green Tree Basin (MKE)

Purpose

To arrest the negative impacts of nonpoint source pollution, the Milwaukee Metropolitan Sewerage District seeks to innovate a subsurface gravel wetland that holds rainwater where it falls, infiltrates and filters it, absorbs it through plant root systems, and evapotranspires it to the atmosphere. Through this project, the Sewerage District will implement this innovative infrastructure measure in the Green Tree Basin on Lincoln Creek, a tributary of the Milwaukee River, to address six beneficial use impairments in the Milwaukee Estuary Area of Concern.

Objective

Address key features: Subsurface gravel wetlands have been demonstrated to reduce fecal coliform, total suspended solids and phosphorus (among other pollutant levels) in other parts of the country but have not yet been innovated in clay soils of the Greater Milwaukee Watersheds to MMSDÂ’s knowledge. Preexisting MMSD ownership and control of the property eliminates otherwise time-consuming site acquisition and permission issues. Historical pre-construction in-stream Lincoln Creek monitoring at a point downstream from the proposed project provides a ready-made site at which to also monitor and compare post-construction conditions. This innovative environmental approach has been proven elsewhere to work in cold climates even in wintertime, and therefore may provide greater year-round benefits than other innovative environmental approaches.

Outcome

The expected results of the proposed project include providing region-specific recommendations for the implementation of a subsurface gravel wetland based on the measured water quality enhancements, improvement of habitat, and regional cooperation to benefit the Milwaukee Estuary AOC and Lake Michigan

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Great Lakes Restoration Initiative
Nearshore Health and NPS
GLRI_37714856
2010
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To arrest the negative impacts of nonpoint source pollution, the Milwaukee Metropolitan Sewerage District seeks to innovate a subsurface gravel wetland that holds rainwater where it falls, infiltrates and filters it, absorbs it through plant root systems, and evapotranspires it to the atmosphere. Through this project, the Sewerage District will implement this innovative infrastructure measure in the Green Tree Basin on Lincoln Creek, a tributary of the Milwaukee River, to address six beneficial use impairments in the Milwaukee Estuary Area of Concern.
 
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