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Gas station sets stormwater quality precedent.

Design engineers find that stormwater quantity is no longer the only variable to consider when recommending a drainage system. Quality is the new buzzword in the stormwater game.

The development engineer for Lombard, Ill., a suburban Chicago village (population 43,000), recently approved a stormwater system proposal at the reconstructed site of an old gas station only after there was a mechanism in place to ensure the runoff was cleaned before it entered the municipal storm sewer system. The revised design includes an oil/water separator unit.

Project engineer Tim Reber with Chicago-based Terra Engineering will now change the way he submits stormwater management plans to match the one he eventually proposed to the Village of Lombard.

"For smaller sites--like this one at the Cove Mart Cafe--a system like this is ideal," said Reber. "We're 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/convenience mart I do from now on."

Reber chose a Storm Water Quality (SWQ) unit manufactured by Hancor, Findlay, Ohio. It's designed to reduce the velocity of water flow, thus allowing the grit, sediment, and other solids, toxins, and heavy oils common to gas stations, car washes, parking lots, and roadways, to settle and remain in the unit while the clean effluent is discharged.

The high-density polyethylene (HDPE) unit is capable of reducing floating and suspended solids as well as hydrocarbons via the patent-pending Baffle 55 device. The unit is also 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.

A SWQ unit was installed as part of the release structure for a detention basin designed to store 0.271 acre-feet. The allowable release rate from the detention pond of 0.1 cubic feet per second (CFS) is well within the 2.4 CFS operating range of the SWQ unit. Hancor recommends cleanout twice per year.


"What's happening in this industry now is the gradual setting of precedents," said Dave Gorman, P.E., Village of Lombard's development engineer. "The EPA's NPDES Phase II requirements are changing how we look at new developments. Precedents like the one we set at the Cove Mart Cafe create policy that becomes simply a cost of development."

Gorman's village, like many in expanding metro areas, has neighboring suburbs on every border. He said that the EPA's new regulations must be applied evenly across municipal boundaries in order to be fair to developers and avoid creating an advantage for a less restrictive community. That's one reason he and the area's other municipal engineers hold monthly meetings to discuss their stormwater ordinance requirements.



Controlling stormwater has evolved from an afterthought to a design requirement. One of the six minimum control measures of the stormwater program under Phase II NPDES is the elimination of illicit discharges.


The essence of the regulations are that small municipal separate storm sewer systems (MS4s) must have a program to reduce pollutant discharge, protect water quality, and satisfy other Clean Water Act requirements. Pollutants include sediment, petroleum products, heavy metals, toxic chemicals, and other contaminants. Implementing Best Management Practices (BMPs) will be instrumental in allowing MS4 communities like the Village of Lombard to meet the EPA rule.

EPA considers a BMP as a technique, measure, or structural control that is used for a given set of conditions to manage quantity and 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.


The theory behind product offerings like Hancor's 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, 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 communicating ways they can manage the quantity and quality of its 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."

By Daniel J. Figola, P.E.

--Figola is a former land development consultant and now serves as the Western Great Lakes Area Engineer for Hancor Inc.
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Title Annotation:Products Solving Problems
Author:Figola, Daniel J.
Publication:Public Works
Date:May 15, 2004
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