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Permeable concrete block system reduces contaminants in stormwater runoff to Lake Michigan

City of Cudahy

Cudahy, WI

The City of Cudahy needed a green infrastructure solution to remove suspended solids and phosphorous from stormwater runoff entering Lake Michigan and the Kinnikinic River. Using a permeable articulating concrete block (P-ACB) system, the city was able to filter and remove contaminants from its stormwater.

Topics Covered

Stormwater Management
Ecosystem Degradation

Cost

Initial: 90 Thousand USD

Funding

General Fund/Existing Public Funds

Project Status

Operational since 2018

Problem Addressed

Cudahy, WI needed an effective green infrastructure technology to reduce contaminated stormwater runoff per new compliance standards.

The City of Cudahy, Wisconsin sits in a unique position as part of the city is in a Municipal Separate Storm Sewer System (MS4) and part of it is not. The city is also part of the Milwaukee River Basin TMDL which has its own regulations to meet water quality standards under the Clean Water Act.

Cudahy was ordered to reduce Total Suspended Solids (TSS) and Total Phosphorus (TP) in its stormwater runoff by 80% and 88%, respectively. The compliance change was intended to be a big step in helping restore local waterways, like the Kinnickinnic River, that were not meeting water quality standards under the Clean Water Act.

The city needed to find a way to meet these compliance goals and began evaluating various green infrastructure products to incorporate into its stormwater management program. The ideal green infrastructure solution would reduce runoff draining into Lake Michigan and the Kinnickinnic River, reduce the levels of contaminants in the stormwater, and be easily incorporated in the MS4 areas of the city as well as the non-MS4 areas.

However, the stormwater capture and infiltration capabilities of the products tested were disappointing, and complicated maintenance further deterred officials from large-scale implementation. The city needed to find a green infrastructure technology that was effective in capturing and infiltrating stormwater, and that could be easily implemented in the MS4 areas of the city as well as the non-MS4 areas.

Solutions Used

The city installed a permeable articulating block system (P-ACB) to remove contaminants from stormwater runoff and meet compliance standards

Wanting to use a green infrastructure solution, Cudahy found PaveDrain and planned to install its P-ACB systems in both an alleyway and a parking lot to infiltrate stormwater and prevent runoff. Although the system seemed effective, the city worried that the largely clay soils would significantly impede stormwater infiltration.

The city redesigned the parking lot and alley by placing P-ACB pavements atop an aggregate layer of blast furnace slag. The pavements capture stormwater before it can be washed away and allow it to slowly infiltrate through the aggregate. The aggregate filters out the suspended solids and phosphorus in the stormwater so that the contaminants no longer impact the aquatic health of Lake Michigan and the Kinnikinic River.

It was clear after installation that the system was successful in infiltrating stormwater despite the clay soils, reducing the volume of runoff that reached Lake Michigan and the Kinnikinic River. The system could also be easily implemented in both MS4 and non-MS4 areas, meeting the unique needs of the city. Based on the successful implementation of the work done, Cudahy made PavedDrain the primary permeable surface for future projects as part of its new Green Alley program. Additionally, Cudahy has now taken the steps to begin documenting how much stormwater the PaveDrain system is infiltrating.

Outcomes

1

The city successfully achieved compliance by implementing permeable concrete block systems in both the MS4 and non-MS4 areas

2

The health of the city’s waterways was prioritized by reducing runoff and filtering out contaminants that negatively affect aquatic health.

3

The P-ACB system is very easy to maintain, only requiring dedicated maintenance using existing city sewer-vac trucks after three years of operation

4

City officials have a reliable method to further reduce stormwater runoff as part of future Green Alley projects.

Lessons Learned

1

The infiltration behavior of the P-ACB system after several storms was different than what stormwater models had predicted and led the city to investigate the accuracy of its modeling.

Something Unique

The City of Cudahy, WI was introduced to PaveDrain and its permeable articulating block (P-ACB) system by Todd Weik of Virginia engineering firm KBJW Group which had successfully installed PaveDrain on several projects in the past.

Who Should Consider

Cities wanting to use green infrastructure solutions to achieve MS4 compliance

Last Updated

Apr 18th, 2022
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