Project overview
The concept of pretreatment of stormwater as the first stage of a pond treatment system is emphasized in many manuals, such as the Minnesota Stormwater Manual, but the actual design rationale is limited and not supported by data. Additionally, there is little data collected on pretreatment systems such that we cannot start to design systems according to metrics of pollution removal or cost.
We believe that data needs to be collected specifically on existing pond forebay elements to understand how these have functioned. During maintenance cleanout of material, we propose having careful documentation of excavation quantities from the forebay as well as the rest of the system. Additionally, we propose to track the labor and equipment hours needed to perform these actions. This data collection would occur by shadowing and data sharing other scheduled maintenance work and sharing data collected by partner cities. These data are a critical piece that will allow for the modeling of the system and refinement of design procedures that will allow future designers to size forebay systems based on metrics of cost and pollutant removal. Additionally, we possess some data on pretreatment using sumps, catch basins, and other inlets that would allow for a greater comparison of pond forebay cost and treatment effectiveness compared to other treatment options.
Pond forebay sizing will be modeled through software and will consider various pollutant removal, including sediments, nutrients, and metals as well as impacts to maintenance frequency and possible P release that may incur due to maintenance activity.
Research questions
- Can a better design methodology be developed for pretreatment and pond forebay sizing that is optimized for treatment and maintenance economics?
- Can we make economic comparisons between stormwater control measure pretreatment systems by collecting new data on time and materials needed for maintenance?
- Can a better understanding of BMP pretreatment of coarse organic matter (COM) reduce overall costs of COM management?
Key innovations/contributions
This study will document pond forebay pollution removal effectiveness as well as maintenance costs so that future pond design decisions can be data-based.
What does this mean for Minnesota?
This project will result in a table-based decision tool that can be used to give specific guidance on forebay design to achieve desired reductions in sediment and soluble-P along with maintenance cost information. Additionally, this project will provide new information on the cost effectiveness of various stormwater treatment options for removing sediment and soluble-P prior to stormwater entering ponds, including the cost effectiveness of pond forebays. This data will help cities and stormwater professionals make informed decisions on best practices based on their desired pollutant capture rates and budget.