Controlling stormwater has evolved from an afterthought to a design requirement, and management on small, urban sites increasingly is focused on effluent quality, as well as on quantity. Elimination of illicit discharges is one of the six, minimum control measures of the stormwater program under Phase II of the National Pollutant Discharge Elimination System (NPDES).
The essence of the regulations is that small, municipal separate storm sewer systems (MS4s) must have a program to reduce pollutant discharges, to protect water quality, and to satisfy other Clean Water Act requirements. Pollutants include sediment, petroleum products, heavy metals, and toxic chemicals.
The EPA’s NPDES Phase II requirements are changing how we look at new developments,” said Dave Gorman, P.E., development engineer for the Village of Lombard, Ill., a growing suburb of Chicago with a population of 43,000. What’s happening in this industry now is the gradual setting of precedents.”
Recently, Gorman approved a stormwater system proposal for the Cove Mart Cafe, a convenience store being built on the site of an old gas station. He required a mechanism in place to ensure that the runoff from the site was cleaned before it entered the municipal storm sewer system. The design includes an oil/water separator unit. This is the first such unit installed in Lombard.
Implementing Best Management Practices (BMPs) to control the quality of site runoff will be instrumental in allowing MS4 communities, such as the Village of Lombard, to meet the U.S.
Environmental Protection Agency’s (EPA) rule. The EPA considers a BMP as a technique, measure, or structural control that is used for a given set of conditions to manage quantity and to improve the quality of stormwater runoff in the most cost-effective manner. The decisions of exactly how BMPs will be used to solve local problems are developed at the local level, where the problem, the solution, and the financial situation are best understood.
There is general acceptance that BMPs will improve the local stormwater problems, even though the criteria necessary to quantify precisely how much of an improvement to expect may be available only for a limited set of conditions,” said Bill Vanhoose, applications engineering manager for Findlay, Ohio-based Hancor, a supplier of stormwater management systems.
Cove Mart Cafe Project Engineer Tim Reber, E.I.T., with the Chicago-based consulting firm Terra
Engineering, Ltd., now will change the way he submits stormwater management plans to match the one he eventually proposed to the Village of Lombard. For that project, Reber chose a Storm Water Quality (SWQ) Unit manufactured by Hancor. It is designed to reduce the velocity of water flow, allowing grit, sediment, and other solids, toxins, and heavy oils common to gas stations, car wash parking lots, and roadways to settle and remain in the unit while the clean effluent is discharged.
Clean effluent from the Storm Water Quality Unit will be discharged into a small pond. The unit also can be combined with an underground retention/detention system.
For smaller sites – like this one at the Cove Mart Cafe – a system such as this is ideal,” Reber said. We [were] designing on less than an acre. So a compact system that also cleans the water is something I’ll probably look at for every gas station and convenience mart I do from now on.”
The high-density polyethylene unit is capable of reducing floating and suspended solid substances, as well as hydrocarbons, with a patent-pending baffle device. The unit also is designed to simplify installation and maintenance. The SWQ Unit improves the quality of the runoff from a localized area before discharging to a storm sewer or receiving body of water.
At the Cove Mart site, the system was installed as part of the release structure for a detention basin designed to store 0.271 acre-feet of water. The allowable release rate from the detention pond of 0.1 cubic feet per second is well within the 2.4-cubic-feet-per-second operating range of the SWQ Unit. Hancor recommends cleanout twice per year.
A baffle device in the high-density polyethylene stormwater unit is capable of reducing floating and suspended solids as well as hydrocarbons, according to Hancor.
The theory behind product offerings such as the SWQ unit, catch basin filters, and retention/ detention systems is that dealing with the equipment side of the NPDES regulations is an investment in the future of our environment. Why go through the effort to comply if the same issues will surface in a few years?” said Rich Gottwald, P.E., president of the Plastics Pipe Institute. Our member manufacturers are thinking long-term. They want to provide the market with products that are going to meet these regulations long into the future.”
That long-term approach applies to the public participation/education/outreach aspect of NPDES – another of the six, minimum requirements. Communities are charged with conveying ways they can manage the quantity and quality of stormwater.
This is really about the long process of educating people and changing behaviors, too,” said Wendy Bell, stormwater program team leader for the EPA. We have to look at our pollution and how it can be prevented. We have to start to do things differently.”A cost of development
Precedents like the one we set at the Cove Mart Cafe create policy that becomes simply a cost of development,” said Gorman. Lombard, like many municipalities in expanding metropolitan areas, has neighboring suburbs on every border. Gorman said that the EPA’s new regulations must be applied evenly across municipal boundaries in order to be fair to developers and to avoid creating an advantage for a less restrictive community. That’s one reason why he and the area’s other municipal engineers hold monthly meetings to discuss their stormwater ordinance requirements.
Another important consideration is maintenance,” Gorman added. We have a regular inspection program to ensure that property owners maintain their stormwater management systems. Such inspections are crucial when properties change hands, in order to educate the new owners about required maintenance.”Daniel J. Figola, P.E., is a former land development consultant and now serves as engineer for Findlay, Ohio-based Hancor’s Western Great Lakes Area. He can be reached at 630-692-1272; e-mail: email@example.com.