BMP Economics and Sizing

Abstract

Stormwater quality management is a mandated practice in the United States by the Clean Water Act of 1972 and the interpretation of this law by the U.S. Environmental Protection Agency (USEPA) through its Municipal Separ-ate Stormwater Sewer System (MS4) permit program. This MS4 program is driving the use of best management practices (BMPs) for the management of stormwater runoff, including a subset of these called low impact development (LID practices). In attempting to comply, various states and local govern-ments (jointly referred as communities) instituted programs requiring a range of stormwater treatment and disposal facilities, namely BMPs, including the use of LID installations. Often, these requirements were imposed without considering the long term effectiveness and economics of the decision. The latter is crucial for communities to know since by law they are required to ensure that the BMPs they approve for installation will continue to function as designed in perpetuity, or until replaced by new facilities. Few analytical tools exist to help communities assess which BMPs are most effective under their site conditions and what will be the long term budgetary implication of these selections. For example, the USEPA's SUS-TAIN model (Shoemaker, et.al., 2009) incorporates sophisticated algorithms for evaluating BMP effectiveness, but its default cost functions are limited only to construction costs and its use requires a relatively high level of tech-nical expertise. The Water Environment Research Foundation's Performance and Whole Life Costs of BMPs and SUDS spreadsheet tools (Lampe et al., 2005) can be used to estimate the whole life costs of a single BMP at a time; however, they lack BMP effectiveness algorithms. Neither of these explicitly account for the inflation of maintenance, operation and administrative costs.