Bonita Springs Best Management Practices (BMP) Assessment Tool

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Cities across the country are grappling with the dual challenge of meeting their stormwater quality goals, while remaining fiscally responsible and encouraging economic growth. For the city of Bonita Springs, regulations stipulate the total maximum daily load (TMDL) goals for stormwater pollutant levels, and also require that control structures be designed using a method specified by the Florida Department of Environmental Protection. Constraints to improving the stormwater system, such as a limited city-owned land and competing objectives for improving city recreation and economic growth, add complexity to this challenge.

The primary tools for controlling and treating stormwater are referred to as stormwater best management practices (BMPs). BMPs include features such as detention ponds, rain gardens, and swales, which slow and treat stormwater as it moves through the system, helping to reduce flood risk during storms and also improve water quality.

To help the city decide where BMPs should be placed for the best results, Atkins worked with Bonita Springs to develop the BMP Assessment Tool (BAT). The tool allows the city to simulate various scenarios for placing BMPs throughout the stormwater drainage system. Using a rainfall/runoff algorithm, the tool estimates pollutant loads across the network for each scenario, supporting informed decision-making on which BMPs to implement and where to place them.

A challenge in evaluating pollutant levels is estimating the amount of directly connected impervious areas (DCIA) in a community. These areas include buildings, driveways, parking lots, and roads that contribute to high concentrations of pollution. Traditionally, the way to accurately estimate DCIA is to use aerial imagery—an expensive and labor-intensive process many communities cannot afford. The BAT uses a new process of “virtualizing” DCIA by interpreting available road and parcel databases to simulate its likely location, producing a more accurate (and less costly) estimate of DCIA than traditional land use-based methods.

By creating what-if scenarios, based on existing conditions and proposed BMP plans, the city was able to reach consensus on their citywide BMP plan. The plan includes a new multi-million dollar park project, which will improve recreation while helping the city reach, their total nitrogen TMDL goals.

Key facts

Location:
Bonita Springs, FL

Country/Region:
United States of America

Client:
City of Bonita Springs

Completion Date:
September 2014

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