Stormwater Best Management Practices in an Ultra-Urban Setting: Selection and Monitoring
5. Selected BMP Monitoring Studies
Monitoring evaluations of BMPs provide a wealth of information on their performance, both in terms of verification of design criteria and evaluation of site-specific performance. Monitoring studies throughout the United States, Canada, and Europe were identified as part of the literature search process. Ultra-urban monitoring studies were selected based on the criteria presented in Chapter 2. They focused on an array of BMP technologies, physical locations, and monitoring program protocols. To illustrate the wide variety of studies accumulated as part of the literature search process, a number of these studies were chosen to amplify and illustrate the information presented in the previous chapters, focusing on ultra-urban characteristics, BMP design criteria, and effective monitoring techniques.
The BMP monitoring studies included here were chosen to illustrate the variety of BMP evaluations being conducted. As mentioned in Chapter 4, BMP monitoring programs can be used to achieve a number of objectives. These objectives can be focused on:
- Evaluating a specific BMP to refine established design criteria.
- Verifying performance under specific site conditions.
- Determining the operation and maintenance requirements of the BMP.
- Evaluating potential impacts on surrounding site conditions (e.g., impacts to groundwater).
- Evaluating modifications to improve BMP performance and constituent removal effectiveness.
The studies selected for presentation in this chapter were chosen because they illustrate one or more of these objectives and provide excellent examples of the type of information that can be gained from a BMP monitoring program. Case studies on a cross-section of the ultra-urban BMP technologies addressed in Chapter 3 have been included in this chapter. The technologies include:
- Infiltration trench.
- Detention pond.
- Underground sand filters.
- Vegetated swale.
- Vegetated rock filter.
Each of these evaluations provides a unique opportunity to present an array of monitoring and data evaluation techniques, to provide critical information on effective monitoring protocols that achieved the specified goals, and to illustrate how monitoring programs must be adaptable to changing conditions and evaluation results. Depending of the outcome of the study, areas for additional evaluation may be identified by the study.
Following are nine detailed summaries of different BMP monitoring studies. The summaries of these comprehensive monitoring reports include citations within each case study presentation. The reader should refer to the original BMP monitoring study for additional information and discussion on the monitoring program and specific BMP evaluation. A brief description of each of the case studies is presented below.
Two Exfiltration Trenches Located near Miami International Airport in Dade County, Florida - this study evaluated the effects of stormwater recharge on the water quality of the Biscayne Aquifer, a shallow aquifer in Dade County, Florida. Two exfiltration trenches located at two small commercial sites were investigated, with monitoring performed using wells at two different horizontal distances and vertical depths.
Modified Dry Pond BMP and Grassed Swale BMP, Charlottesville, Virginia - a dry detention pond was monitored before and after modification of the outlet structure to increase detention, and a grassed swale was monitored to evaluate its pollutant removal effectiveness. Modifications were made to the swale to improve the accuracy of the mass balance removal estimates.
Delaware Sand Filter BMPs at AirPark, Alexandria, Virginia - an evaluation of two modified Delaware sand filters was performed to determine their pollutant removal effectiveness in the Northern Virginia area. In addition, other sand filter design factors were evaluated.
Modified Delaware Sand Filter BMPs at Alaska Marine Lines, Seattle, Washington - this study evaluated the pollutant removal effectiveness of a sand filter during typical storm conditions. In addition, core samples of the filter medium were taken to determine the operational condition of the medium and predict potential maintenance requirements for the filter.
Compost Stormwater Treatment System, Hillsboro, Oregon - a prototype leaf compost stormwater treatment facility was evaluated to determine its pollutant removal effectiveness.
Vertical Volume Recovery Structure (VVRS), Orlando, Florida - an evaluation of a VVRS was performed to determine the efficiency of the sump, the effectiveness of the VVRS overall, and the backwash requirements for the system.
Vegetated Water Quality Buffer Strips, Austin, Texas - four different vegetation compositions were evaluated to determine whether a relationship exists between vegetation cover and infiltration capacity, pollutant removal effectiveness, and buffer width.
Streetsweeping BMP Evaluation, Port of Seattle, Washington - a stormwater quality computer model was calibrated using pollutant accumulation data from several sites in different activity areas of a container storage yard. The model was then used to evaluate the pollutant removal effectiveness of high-efficiency pavement sweepers in conjunction with conventional catch basins, and compared to the pollutant removal effectiveness of wet vaults.
Packed Bed Filter BMP near Lake Beardall, Orlando, Florida - a packed bed filter system, consisting of 10 separate cells, was evaluated. Two different media were used, and four different types of vegetation were evaluated. The beds were evaluated separately, and as a system, at three different flow rates.