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

Bonita Springs, FL

United States of America

City of Bonita Springs

Completion Date:
September 2014





  • To address the impacts of stormwater from land development, the U.S. Environmental Protection Agency considered several regulatory options and is currently analyzing costs, environmental effects, and benefits of several options. These analyses include modeling water-related impacts to quantify water quality improvements, reduction in flood damages, and changes in other physical processes, such as in-stream erosion and sedimentation, introduced by the application of green infrastructure for stormwater management.

    In support of the new stormwater rule that EPA will release for public comment in late 2012, Atkins is conducting a nationwide study to estimate flood losses avoided as a result of the rule’s application. Atkins developed a modeling methodology to arrive at an estimate using publicly available national datasets and a set of sample watersheds. The results indicate that the rule can result in flood losses avoided, ranging between $40 and $300 per acre of urban area across the lower 48 states.

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  • To reduce the risk of flash flooding in downtown Las Vegas, Atkins provided engineering design services for a 5-mile storm drain system serving the city’s central regions. The system starts at the intersection of Sahara Avenue and Decatur Boulevard, about 5 miles northwest of the famous Las Vegas Strip, ending at the Oakey Meadows detention basin near Springs Preserve. Atkins designed 15,000 feet of storm drain conveyance, an additional 5,000 feet of storm drain collection facilities and 1,600 feet of concrete open channel, capable of conveying up to 4,772 cubic feet per second (cfs) to the basin.

    The storm drain will provide enhanced flood protection for buildings and street intersections along the system’s route, in particular the flood-prone intersections along Decatur Boulevard. The system is one of about 20 flood control projects being developed by the Clark County Regional Flood Control District, including channels, underground diversion tunnels, and detention basins.

    Due to the magnitude of construction, the project was split into four phases to divide the construction up into manageable sections. The project includes reinforced concrete box culverts ranging in size from 12 by 5 feet to 23 by 8 feet; rectangular reinforced concrete channel up to 45 feet wide and 10 feet deep; reinforced concrete pipes; storm drain drop inlets; junction manholes; transition structures; pavement renewal and replacement along the storm drain corridor, and a confluence structure for the Alta Channel and Oakey Meadows storm drain.

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  • Installing BMPs can be both time consuming and expensive, often requiring the use of a professional engineer or architect. To create a more cost-effective approach, we helped the Tahoe Regional Planning Agency (TRPA) develop a website that allows Lake Tahoe homeowners to easily design stormwater best management practices that can be installed on their property.

    The free website, called BMP Designer, leads users through a step-by-step process of building the BMP site design. Property owners enter basic property information and general site conditions. Then, in an aerial view on the website, users can outline the property’s rooftops, driveways, decks, and other areas that can potentially drain stormwater too quickly. After the BMP Designer provides a selection of BMPs for each area, including average costs for installation and maintenance, the property owner then selects the BMPs and submits the preferred site design to TRPA for review. Once TRPA approves the site design, the property owner can install the chosen BMPs, request a site inspection through the tool, and complete the BMP certification process.

    Atkins used its expertise in developing step-by-step tools, called “wizards”, to help users understand complex regulatory, permitting, design, and decision-making processes as they relate to future-proofing in a cost effective manner. The BMP Designer makes the process of correctly planning and installing BMPs a much simpler and cost effective one for Lake Tahoe area residents.

    Atkins continues to advise TRPA on concepts that expand the tool set to accommodate additional future proofing requirements to further the benefits already realized.

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