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Model for evaluating the effectiveness and life cycle costs of stormwater best management practices




Olson, Christopher C., author
Roesner, Larry, advisor
Grigg, P. E., committee member
Stednick, John, committee member

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Structural best management practices (BMPs) are devices designed and implemented for the purpose of reducing or eliminating the effects of urbanization on receiving waters. Structural BMPs each have their own unique effectiveness and costs, however BMPs are rarely evaluated or selected for their long-term cost effectiveness because most of the information required to do so is not readily available to the decision maker. The purpose of this model is to integrate the best available information on BMP costs and effectiveness into a tool that decision makers can use when selecting what type of BMP to implement under certain circumstances. A spreadsheet model was developed using relatively few required inputs to describe the watershed and BMPs to be implemented. The model computes the number and size of BMPs required for the watershed, the annual pollutant load reduction and runoff volume reduction expected from implementing the BMPs and the net present value of the life cycle costs of the BMPs. These outputs can be used to determine BMP cost effectiveness, computed as cost per pound of pollutant removed or cost per volume of runoff reduced. The model was applied to two theoretical stormwater management planning scenarios. The first application seeks to determine the unit cost of land at which it is less costly to use underground hydrodynamic separators instead of an extended detention basin in a highly urbanized watershed, assuming that both BMPs meet a minimum water quality requirement. The results show that hydrodynamic separators are less expensive when land costs exceed approximately $1.5 million per acre, however the cost effectiveness ($ per lb of pollutant removed) was not evaluated under this scenario. In the second application four different BMPs were evaluated to determine the most cost effective at removing 60% of the total suspended solids (TSS) generated from a highly developed watershed. The four BMPs evaluated (hydrodynamic separator, porous landscape detention, sand filter vault and inlet inserts) were chosen because they can be retrofitted into an existing development more easily than many other BMPs. Using an iterative procedure, the BMPs were applied to a certain percentage of the watershed until the annual TSS load discharged to the receiving waters was reduced to approximately 60%. The results suggest that porous landscape detention is the most cost effective BMP at approximately $4.20 per lb of TSS removed annually. Inlet inserts were the second most expensive at $6.00 per lb of TSS removed annually, despite having the lowest initial capital costs. The latter result shows the importance of including long-term operations and maintenance costs when selecting BMPs.


2010 Spring.
Includes bibliographic references (pages 8-1-8-4).
Covers not scanned.
Print version deaccessioned 2022.

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Urban runoff -- Management
Watershed management


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