What Do Stormwater Design Engineers and Water Feature Designers have in Common?

Published on November 6, 2007

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Question: What do Stormwater Design Engineers and Water Feature Designers have in Common?

“Engineerspeak” is a foreign language spoken mainly by design engineers. Learn this language and you could be on your way toward business expansion and knowledge in a way that will utilize, challenge and refine your pond and wetland building skills.

“Stormwater” designers are very good at math, they are usually no-nonsense and generally not the most artistically inclined folks. Water feature designers and installers are often land artisans and not necessarily the best mathematicians.

Let’s explore how these are two radically different groups that can realize real benefits by teaming up!

Since 1972, the EPA's enforcement of the Clean Water Act has prohibited the discharge of any pollutant into waters of the United States unless each discharge is authorized by a National Pollutant Discharge Elimination System (NPDES) permit. Since its introduction, the NPDES permit program is responsible for on-going improvement of our Nation's overall water quality. State and municipal regulatory requirements for stormwater are based upon the federal regulations with additional provisions to address specific the needs and conditions of watersheds within their regions.

Bioretention Basins

Stormwater management structures may take many forms. Bioretention areas are shallow stormwater basins that utilize special soils and vegetation to capture and treat stormwater runoff. They are utilized to capture stormwater runoff from relatively small areas of impermeable surface (< 5 acres). Bioretention areas typically consist of a ponding or infiltration area covered by an organic or mulch layer, surrounded with native herbaceous and woody plants installed in an engineered planting soil bed. Water flows from the contributing drainage area through a grassed, stone or a recycled materials infiltration strip to the ponding or infiltration area.

Individual residential bioretention areas, known as rain gardens, may be constructed by excavating a small depression designed to hold and infiltrate runoff water from downspouts, driveways or other impervious surfaces. Bioretention areas most often have deep-rooted native grasses and sedges to prevent erosion and increase the water detention time to maximum water infiltration.

Retention and Detention Basins

Stormwater retention basins or “wet” ponds hold water for the longest periods of time and are sized to meet watershed and regulatory requirements. Often these ponds slowly seep the water back into local aquifers through their native soil linings or better yet, through engineered filtration beds that mechanically and biologically clean the water going into the ground.

Detention basins or ponds are containment areas in which excess stormwater is stored or held temporarily. Detention ponds slowly drain their waters into receiving channel as they recede. In essence, the water in a detention basin is temporarily detained until additional room becomes available in the receiving channel. Soil lined detention basins are used extensively throughout the United States. Detention basins are essentially “dry ponds” and pose the designers the challenge of finding plant materials that withstand submersion in water, wet and dry cycles while controlling day-to-day erosion. Soil lined detention basins serve as a valuable flood control measure in most parts of the U.S.

Meeting the Regulations Case Study

Regulatory requirements for projects of this nature vary from state to state, municipalities and they also vary between storm water and wastewater wetlands. For the constructed wetland, businesses often to modify their storm water management plans to reflect the addition of a wetland or water feature. For example, in August 2005, the Indiana Department of Environmental Management announced a new regulation to monitor groundwater contamination that will be enforced beginning in August 2006. This regulation will requires industrial dischargers to collect quarterly water samples and send them to a lab for analysis. Rose Acre Farms, an egg producer chose to construct a series of constructed wetlands that processed both stormwater and industrial wastewater overseen by the Indiana Department of Environmental Management and the Indiana Department of Health.

Constructed Wetlands

In general terms, a subsurface flow wetland consists of a basin, sometimes called a “cell,” that is lined with a barrier to prevent seepage. The basin is then filled with gravel to support the root structure of aqueous vegetation, which is planted directly into the gravel. The plants then translocate oxygen down to the roots through the plant. This oxygen forms aerobic areas that sustain bacteria and other microorganisms that live in the gravel and root zone. The bacteria do all the work of removing the pollutants in the water. Moreover, the sun is the only energy source used to treat the water. During winter months when plants move into a dormant phase, the roots remain active and the oxygen transfer remains steady. Therefore, these systems perform even in sustained cold temperatures.

There is an incredible amount of biological activity happening in a relatively small space in a properly constructed wetland. For the typical pond to accomplish the same thing as a one-acre wetland, it would have to cover at least three to four acres. Because there’s no standing water in a subsurface flow wetland, there is almost no likelihood of producing mosquitoes, and odor is not a factor either. Constructed wetlands are an environmentally responsible, economical and low maintenance water treatment option.

Under the planting bed of a constructed wetland, gravel and perforated pipe underdrain carry water away that has filtered through the bed. High percolation rate soils may not require this under-drain system. Where groundwater protection is required, liners such as Firestone PondGard EPDM are used to contain or direct the stormwater to holding basins.

Stormwater treatment wetlands are one of the most effective best management practices for removal of pollutants from stormwater. These wetlands have been found to be highly effective at removing total suspended solids (TSS), biochemical oxygen demand (BOD), heavy metals, and plant nutrients such as phosphorus and nitrogen.

Stormwater treatment wetlands typically consist of several features designed to retain and filter water. First, the water flows into a forebay that removes the coarse sediments. This forebay is checked and cleaned as needed. It prevents sediment from clogging the main filtration basin, particularly during construction. The water then flows into a broad primary treatment basin through a long circuitous channel in order to maximize exposure to the wetland filtration processes. Finally, the water level and rate of discharge are controlled by an outfall structure. An assortment of shallow and deepwater emergent vegetation is then utilized throughout the main treatment basin to create the effective filtration environment. The basin may be lined with a geomembrane to prevent “short circuiting” and contain the pollutants during the water’s remediation.

America’s best run companies pride themselves on their commitment to environmental stewardship. Good business stays ahead of environmental regulations, they are good neighbors, who leave things cleaner than they found them and in the process they stay ahead of their competition. When local development in your area addresses storm water runoff and even types of wastewater treatment, business directs its attention to unique, environmentally responsible methods of treatment such as retention/detention ponds, biofiltration areas and constructed wetlands. Treatment via municipal or package treatment plants is expensive. Environmentally responsible stormwater systems have been widely tested and used worldwide since the 1960.

A Whole New Paradigm

Constructed wetlands, retention/detention ponds and biofiltration areas offer numerous benefits, from the economical, operational and environmental perspectives. There is no downside when the land is available. These systems provide a simple, low-cost, natural treatment alternative to conventional water treatment options driven by the sun. These systems use no mechanical apparatus, whereas conventional water treatment options are mechanically intensive. Constructed wetlands and biofiltration basins use the plants and sunlight to accomplish their purposes. No harvesting or special maintenance of plants is necessary (except occasional mowing of biofiltration basins) in order to maintain the proper levels of biological activity.

The absence of pumps and motors means that these systems have no utility bills and no need for special training of staff. Constructed wetlands, ponds and biofiltration basins handle variables much better than traditional, operationally intensive forms of water treatment. If there’s a power outage, there’s no concern that the system will shut down. If there’s a torrential rain, there’s no concern the treatment plant will become overwhelmed.

Practice and learn the Engineerspeak, seek out local engineers who are designing stormwater and light industrial wastewater facilities. Study local and state stormwater regulations and you can grow your business while improving the look and function of your local stormwater and certain wastewater treatment facilities. Offer your services and suggestions. Embrace this new paradigm.

For more information, contact Firestone Specialty Products, Bill Johnson, Field Sales Engineer, 310 East 96th Street, Indianapolis, IN 46240, (800) 428-4442, (317) 575-7252 or email: johnsonbill@firestonesp.com.

About the Author

William A. Johnson CGCS instructs geomembrane and porous paving installers in the installation techniques for use with Firestone geomembranes and porous paving products. He works with decorative and golf course water feature engineers, designers and installers. He also consults with engineers and other designers on geomembrane and porous paving applications such as constructed wetlands, wastewater containment, stormwater management and specialty adhered applications. Mr. Johnson is a member of the D35 Geosynthetics committee of the American Society for Testing Materials and a member of the Golf Course Builders Association.

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