Date of Award

Spring 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

First Advisor

McDonald, Walter M.

Second Advisor

Parolari, Anthony J.

Third Advisor

Mayer, Brooke K.

Abstract

Milwaukee, like many other aging cities, struggles with combined sewer overflows, basement backups, and urban stream syndrome. It is increasingly looking to green stormwater infrastructure as a way to alleviate stormwater concerns by treating, retaining, and slowly releasing stormwater near the locations where it falls. However, green stormwater infrastructure varies in its performance, and few studies have been performed in Southeast Wisconsin. Therefore, two bioswales and a pervious pavement installation were monitored for water quantity, total nitrogen, total phosphorus, and total suspended solids. The bioswales were also monitored for dissolved phosphorus. The north bioswale reduced total phosphorus concentrations by a median of 71% and the south bioswale reduced total nitrogen, total phosphorus, and dissolved phosphorus concentrations by a median of 46%, 69%, and 80%, respectively. Significant exfiltration of water in the bioswales resulted in significant load reductions of 99-100% across all pollutants except total suspended solids from the south bioswale. Both bioswales effectively reduced total flow volumes and peakflows. The green alley reduced total suspended solids and total phosphorus concentrations by 97% and 61%, respectively. It is likely that a lack of infiltration in the system produced lower load reductions in total suspended solids and total phosphorus of 54% and 29%, respectively. However, at the green alley there was little change to total nitrogen concentrations or loads. Overall, this study shows that green stormwater infrastructure can effectively manage stormwater and provides additional guidance for the Milwaukee Metropolitan Sewerage District as they continue to expand their green infrastructure practices. Furthermore, this study can help guide state agencies such as the Wisconsin Department of Natural Resources develop more accurate stormwater crediting systems.

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