Determining Urban Stormwater Best Management Practice (BMP) Removal Efficiencies: Final Data Exploration and Evaluation Report

Strecker, E., Quigley, M.M., Howell, J.M.

The purpose of this cooperative agreement between EPA and the American Society of Civil Engineers (ASCE) is to develop a more useful set of data on the performance and effectiveness of individual best management practices (BMPs). BMP monitoring data should not only be useful for a particular site, but should also be useful for comparing data collected in studies of both similar and different types of BMPs in other locations and with different design attributes. Most past BMP monitoring studies have provided very limited data that is useful for comparing BMP design and selection. The initial data set and the Database on which it resides, are work products of Phases I and II of the cooperative agreement. During Phase I, protocols for the collection and storage of BMP information were established as part of a conceptual design for the Database. Phase I also included the compilation of an annotated bibliography for the identification of existing urban stormwater BMP monitoring documents. Phase II, Task 1 included the creation of the Database structure and software front end. Task 2 addressed the collection and review of BMP monitoring studies identified in the Phase I bibliography. The Task 2 collection of documents yielded ~500 references that were subsequently reviewed for inclusion in the database. This multileveled review of the collected documents produced ~71 BMPs that contained event based water quality data suitable for inclusion in the database. The extent of the design information for a number of the documents did not meet the detailed protocol for submission of design information to the Database. Primarily due to this shortfall, the evaluation of the relationship between design and efficiency will be limited until a significantly larger data set is compiled. Some of the data collected and stored in the initial data set were not comparable and were not explored utilizing the rigorous statistical methods described in this document. This report describes the results of exploration and evaluation (Task 3 of Phase II) of the initial data set (Version 1.0) of the National Stormwater Best Management Practices Database. The primary goals of the data exploration and evaluation are to: · Evaluate the efficiency and effluent quality the BMPs stored in the Database using a uniform statistical approach to the event based water quality data to obtain comparable estimates of efficiency and effluent concentrations, as appropriate. · Utilize the results of the statistical evaluation of efficiency and mean effluent quality to quantitatively elucidate the relationships between efficiency and static and state variables (i.e., design, environmental, and climatic). This document is broken down into five primary sections: description of the methodology used, an overview of the results of efficiency calculations by BMP type and parameter, exploration of the relationship between design, climatic, and environmental parameters and their influence on efficiency, a summary of conclusions, and recommendations.