Stormwater | From the Trenches

By Brant Keller

Recently the City of Griffin's Stormwater Utility was awarded $700,000 from the Georgia Department of Transportation (GDOT) under a TEA-21 grant. The purpose of the grant is to evaluate the effectiveness of stormwater management practices or best management practices (BMPs) in the removal of pollutants from a state highway corridor. The city's cost is $140,000, and recently the city's new partner, the NSF International and EPA's Environmental Technology Verification group, agreed to contribute a share of $180,000 for additional evaluation efforts, bringing the total to a little more than $1 million. All to answer a simple question: Does it work?

Griffin is heavily involved in ensuring clean stormwater runoff from its jurisdiction. We have a regional detention pond with constructed wetlands and associated natural wetlands; we are conducting detailed watershed assessments within the city's jurisdiction; we have in place for the downtown area a detention and wetland facility; and currently under construction is a retrofit of an existing detention pond in an urban area to include gravity filter systems and "first flush" storage.

And now we are participating in this TEA-21—funded project. What a great place to research BMPs, especially when some of the city's water-quality problems are associated with urbanized highway runoff. The project setting is the Georgia Highway 16 corridor bisecting the city in half, north and south. Highway runoff flows to the north as headwaters of Potato Creek, a major tributary to the Flint River. Potato Creek is listed as partially supporting its fishing designated use, with habitat and fecal coliform the major issues. The city's assessment efforts, however, have revealed other water-quality issues in the headwaters that don't show up in far downstream areas. The City of Griffin and GDOT have formed a partnership to determine "Does it work?" with regard to mitigating urban highway runoff. GDOT needs to know what devices to specify in the future to meet water-quality needs, and it requires objective and consistent data to make those decisions. This project makes sense because it will set the record straight.

For the record, several companies' devices will be evaluated. Abtech Industries, Aquashield, BaySaver, CDS Technologies, CSR Stormceptor, Practical Best Management, Stormwater Management Inc., and Vortechnics are all participating. Currently others are being reviewed as the project gets underway. Each company will be required to have its engineers involved from the beginning, particularly for onsite inspection, to certify that the product is delivered and installed correctly according to the company's specifications. Once the BMPs are in place, sampling of storm events will begin. Baseline sampling has already been completed and will provide the benchmark for evaluating a BMP's effectiveness.

Clearly GDOT would like to have more than a brochure and a guess at what might work. All parties will be attentive to this accountability. Strict compliance with specified protocol will be maintained so that an objective set of criteria can be developed to assess the effectiveness of a particular product.

In the end, GDOT will have a working set of reports to refer to in the specification of products that can be used in highway runoff management. These reports will also have associated cost-benefit analyses and operation and maintenance costs. As a bonus, the devices will be listed in the Atlanta Regional Commission's Stormwater Design Manual for the State of Georgia. The results of this project will be available in late 2002.

What's next? The City of Griffin is experimenting with such measures as composted filter berms and socks in lieu of silt fence on construction sites. Another stormwater management practice the city is monitoring is streambank restoration and its effect on water quality. How much is required to improve the water quality–25 ft., 50 ft., 100 ft.? Results of field testing and monitoring will be made available. Still another stormwater structure is the reconstruction of an existing detention pond retrofitted with a filter system and vegetated with wetlands plant materials and outlet valves.

Achieving water-quality goals and meeting total maximum daily loads will depend heavily on mechanical and manufactured devices as well as natural attributes improvements and restorations. We, as professionals in the field, must rely on scientific procedure and ensure that our reporting is accurate and detailed to determine how our stormwater management practices and BMPs really do work.

Brant Keller is director of public works and stormwater utilities for the City of Griffin, GA.

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