Date of Award

8-2004

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Steve Kahl

Second Committee Member

Chet Rock

Third Committee Member

John Jemison

Abstract

This study examined the perfomance of a dry swale designed to meet the provisions of Maine stormwater regulations. A dry swale is classified as an open channel best management practice (BMP). The dry swale incorporates design elements of detention and filtration, and is intended to reduce peak flows, and nutrient, sediment and metal concentrations in stormwater from developed areas. The dry swale was monitored for thirteen storm events over a two-year period. The system reduced sediment, nutrients, and metals at higher input concentrations, and reduce peak flows for smaller (less than 2.5 cm) storm events. There were threshold concentrations of all analytes above which reduction in concentrations occurred. Maximum concentration reductions obtained were: TSS, 85%; total phosphorus, 51%; bioavailable phosphorus, 71%; total nitrogen, 42%; nitrate, 38%; copper, 33%; lead, 40%; and zinc, 90%. The reults do not conclusively show that this dry swale BMP effectively reduces nutrients, sediment and metals in stormwater. Further investigation of the performance of the dry swale as a stormwater BMP is needed, with amended sampling strategies and design changes. Monitoring before the swale site completely stablized probably reduced the documented efficiency of the system. The sampling approach used in this study changed the performance ot the dry swale, and may have masked the ture capabilities fo the system. Changing the dry swale from an on-line to an off-line BMP by installing a flow splitter and drecting only the first flush of runoff to the system may also increase performance.

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