Structural best management practices
Catching pollutants has never seemed so easy and so complicated as structural best management practices (BMPs), including stormwater treatment devices, become more advanced and more precise to meet increasing municipal, state, and federal water-quality regulations. Arguably, emerging innovations in structural BMPs may be the best protection for our nation’s small waterways since the Clean Water Act.
Whether the sites mentioned below are located in crowded, urban settings, or wooded, pastoral venues, they share the common goal of improving water-quality through stormwater treatment.
Retrofitting in Milwaukee
At the Northwood Industrial Park on the northwest side of Milwaukee, WI, a mix of warehouse manufacturing companies and large corporations needed a stormwater plan that suited the site’s challenges.
“They have a lot of hard surface area and a lot of truck traffic,” says R. C. Tally, P.E., a civil engineer for the city of Milwaukee, explaining why he selected Kenilworth, NJ-based Hydroworks’ Hydroguard separator for use at the site. “You have a great deal of stormwater runoff and TSS [total suspended solids]. These Hydroguard systems are designed to reduce that.”
|Photo: Imbrium Systems
Stormceptor unit installation
|Photo: Imbrium Systems
Imbrium Systems' Stormceptor slows incoming stormwater and traps TSS, heavy metals, nutrients, and free oils in its stormwater treatment system.
Retrofitting any existing city site can be challenging when working to improve water quality, but a 15-acre industrial site can be especially so. At the industrial park, a large amount of runoff travels to a center point at the site. City workers have tried several types of stormwater protection devices in the past.
“The Hydroguard gave us the opportunity to address the problems we had with other systems already in place—not just the visible results, but after you do the testing, you’re actually getting the best bang for the buck,” says Tally, who adds that he’s comfortable using the unit, which he likened to an open grill. “We typically use these in areas where you have larger diameter.”
Oils, grime, and salt can wash from vehicles on the 15-acre site into the storm system, he explains. “They have detention ponds. The idea is to remove as much of the solids and debris so they don’t wash into the sewers,” says Tally, who likes the product’s baffle in particular. “[There] you can clearly see the floatables inside, and the large oil deposits that are restricted from moving out of it.”
Although the BMPs selected had to be economically feasible and easy to maintain, contractors also had to meet select criteria established at the site during the bidding process.
“We work with the designers to make sure that the product will work,” says Tally, who says that in addition to the Hydroguard, Rinker Materials’ Stormceptor is also used at the site. “That’s decided in the bidding process.”
Utility location posed the greatest problem during the retrofit.
“The biggest challenge is the conflict with the existing utilities. It’s more a matter of moving your stormwater treatment unit instead moving the utilities; it’s more prudent,” says Tally, adding that this process can “blow the budget out of the water. A lot of times a different engineering body handles the construction. I simply do the design.”
The retrofitted elements will remain a permanent stormwater solution at the site.
“The idea now is to check the water quality in the downstream portion,” says Tally, adding the units will be checked on an annual basis. “Where we’ve used these, water quality has improved.
“We’ve seen some good results from Hydroguard. Our success is based on our regulatory [city, state, and federal] requirements. It’s one of many elements we’re using to meet those
Capturing Pollutants at MCAS Miramar
The Miramar Marine Corps Air Station (MCAS Miramar) in San Diego, CA, where the movie Top Gun was filmed, is currently working to protect water quality, just as its residents work to protect our country.
Brown and Caldwell Engineering, with offices spanning the United States including an office in San Diego, was hired to complete the basis of a design study to “select stormwater treatment sites at selected outfalls on the base,” explains Herb Baylon, environmental division director at MCAS Miramar.
“We’re bisected by Rose Canyon, and that’s where our stormwater discharges to. One of the criteria was to find the most cost-effective systems that would also reduce pollutants from stormwater—something that’s static, doesn’t need any pumps, and something that could be maintained very easily,” he says. “I didn’t want to get involved with filters. I’ve dealt with other water separators that are high maintenance. I don’t run the maintenance side. I’m trying to make it easier for them.”
As a result, Brown and Caldwell suggested a combination solution—Rinker Materials’ Stormceptor treatment and separation device and Contech Stormwater Solutions’ Vortechs system—to treat stormwater runoff at the site.
The Stormceptor, which is manufactured with precast concrete components, can remove free oil (TPH) and TSS from stormwater runoff. The water-quality treatment device’s fiberglass disc insert meets AASHTO and ASTM standards.
Similar to the Stormceptor, the Vortechs system is designed to remove sediment, grease, oil, and debris in high-flow areas. “Water enters the swirl chamber at a tangent, inducing a gentle swirling flow pattern and enhancing gravitational separation,” according Contech. Heavier pollutants remain in the chamber, and floatables are stopped by the baffle wall. Eighty percent of runoff that travels through the system will be controlled by the low-flow control itself, the company states, reducing turbulence and inflow velocity.
“In the design, Stormceptor has a small footprint, but it goes deep,” explains Baylon. “Vortechs has a bigger footprint, but it’s shallower. We’re installing this before the outfall.”
Utilities crisscross the entire site, creating a challenge for installation, but the stormwater plan was designed with them in mind.
“If there’s an area where there’s a lot of utilities going on and it’s shallower, we go with Stormceptor. We’re putting something in an existing area. We try to use one that will require the least digging or moving of utilities,” says Baylon. “I’m doing this also to anticipate future regulations. I’m thinking ahead of the game.”
In general, San Diego has an arid climate, but when it rains, the downfalls quickly add up. For example, the area typically gets 10 inches of rain annually, but in the month of January 2010, it received 6 inches of rainfall. Part of the appeal of this stormwater treatment plan is the capacity of the system.
“They range, in total capacity, from 952 gallons to 7,420 gallons; it’s much simpler,” says Baylon. “You drop a hose, suck any sediment out, then fill it back up with water, depending on the manufacturer recommendations.”
Of course, any military base is threatened by more than natural disasters. “If I were to have a spill of some sort, this will hold it before it gets out to the canyon, and then we could just pump out the stormwater treatment system.”
Baylon notes that the base is required to follow the regulations of the California State Water Resources Board.
“I’m required by the state to take samples, to come up with a stormwater treatment plan,” he says, adding that he is pleased with the results of the system that’s in place, especially the reduction of copper and zinc in the runoff.
Road Expansion in Ontario
In a vastly different climate, McCormick Rankin, a Toronto, ON, firm, used Toronto-based Imbrium Systems’ Stormceptor last year to protect water quality at a road expansion project in Oakville, ON. Conservation authorities required water-quality controls to be implemented on the road-widening project in an effort to protect a nearby creek, explains Peter Lim, a project manager at McCormick Rankin. Monitoring the site, however, will be done based on the individual town policy.
|Photo: Storm Water Systems
The Bandalong Litter Trap is helping filter water from city canals before it enters Georgia's Satilla River.
“In Ontario, any new development would require water-quality treatment,” says Lim. “Every site requires some kind of treatment.”
Imbrium Systems’ Stormceptor slows incoming stormwater and traps TSS, heavy metals, nutrients, and free oils in its stormwater treatment system. The debris and free oils rise in the device, while sediment settles. The system removes finer particles 20 microns and greater while preventing resuspension and pollutant loss during large rain events. Stormceptor can also be tailored to capture a specific particle size distribution.
Imbrium Systems makes available PCSWMM for Stormceptor; this advanced continuous simulation modeling software, based on US EPA’s SWMM, allows users to access current local National Oceanic and Atmospheric Administration rainfall data gathered at hundreds of North American stations with various particle sizes. This information can then be used to determine the Stormceptor system that would work best at a given site.
Ken Cheney of Ainley Group, based in Barrie, ON, has used the system on a variety of sites.
“In general, I can tell you when I look at options for stormwater management for smaller sites, I consider Stormceptor units because of its versatility—multiple configurations and various sizes—in addition to competitive pricing,” says Cheney. “In various retrofit urban and residential situations, when I have run into restrictions due to multiple existing utilities, I consider the Stormceptor because of its compact size and ability to integrate with existing infrastructure. The PCSWMM for Stormceptor sizing tool also comes in very handy when I need a rough estimates for unit sizing.”
Cleaning Up the Satilla River
Stretching through the southeast Georgia wetlands, the Satilla River empties into the Atlantic Ocean at Cumberland Sound. Beloved by area residents and vital to the forests it snakes through, the river has nevertheless suffered from water-quality problems. One city has taken on role to protect the waterway. A spring 2010 instillation of Storm Water Systems Inc.’s Bandalong Litter Trap will help filter water rushing from several city canals at a point just before the water will enter the Satilla River in Waycross, GA.
“That’s where the main city drainage is. Any trash conveyed will ultimately get to that point,” says Frank Baugh, P.E., the city engineer for Waycross. He notes that a newly extended 350-foot service road to the streambank, which will also be lined with riprap, will provide easy access for city workers from the nearby wastewater treatment plant to service the system as required. “The stream is about a half mile up from the river. It was the logical place to put the project.”
While the trap, which was designed in Australia and has been in use internationally for 12 years, will be located near the local wastewater treatment plant, it isn’t part of the wastewater treatment process. The project emerged from years of planning.
“Over the years, there had been a lot of concern on the part of the Satilla Riverkeeper. One of the top priorities was trash,” says Baugh, noting that not all of the debris was generated by city residents. “We have a very good standing with the EPD [Environmental Protection Department]. There was a concern about a large rash of trash seen by people who would fish or use the river. We work pretty closely with the Riverkeeper, partner with him
on water-quality issues.”
Urban settings are not the only types of sites that wrestle with nutrients and pollutants found in stormwater runoff.
The Satilla Riverkeeper, based in Waynesville, GA, is part of the grassroots Waterkeeper Alliance that oversees more than 140 regional waterkeepers. An area’s waterkeeper or riverkeeper is expected to patrol and defend the waterway against polluters. Current Satilla Riverkeeper Bill Miller began his term earlier this year, after former and the first-ever Satilla Riverkeeper Gordon Rogers, who began his term in 2004, resigned from the post to tackle a new position as Flint Riverkeeper.
|Photo: Storm Water Systems
The Bandalong Litter Trap is constructed of booms made of HDPE and aluminum baskets to collect debris.
Baugh explains that the city pursued a state grant to improve water quality more than four years ago, but it was not approved.
“The stream is an impaired stream, but not because of trash. It was nonpoint-source pollution, too,” says Baugh. “There was no legal obligation to the city, but we want to be stewards of the environment.”
When the stimulus bill passed, however, a portion of it set aside money for the Green Infrastructure Pact. A subset of the Department of Natural Resources’ Georgia Environmental Protection Division is the Georgia Environmental Facilities Authority (GEFA), which typically finances water, sewer, and environmental-quality projects for municipalities. For example, Baugh says, municipalities can apply for loans to cover the cost of repairing old sewer pipes. The increased funding brought hope to those hoping to protect the Satilla River.
“We submitted this as a candidate project. We went through all the steps to get it approved. In November 2009 it was approved for funding,” says Baugh. “GEFA will finance the total project cost, then they will forgive 60% of the loan. We pay 40% of the cost over 10 years. Sixty percent is an outright grant.”
The total cost of the project is $124,000.
“At the time we were applying for this project, we heard about Storm Water Systems’ Bandalong. The Riverkeeper made us aware of this litter trap that was available.”
“The Bandalong Litter Trap is constructed of booms made of high-density polyethylene [HDPE], which provide the flotation, and aluminum and stainless steel hardware, braces, and maintenance platform,” says Kari Morris of Storm Water Systems. “The Waycross trap will include removable aluminum baskets, which can be lifted with the aid of a truck-mounted boom crane to empty the trash into a receptacle for proper disposal or recycling.”
Pairing the right system with this site was no easy task.
The location is in a fairly heavily wooded area, a flood plain. “It had to be below the last confluence point,” says Baugh. “The area doesn’t lend itself to any bar screen, a fixed infrastructure type thing.” This is why the Bandalong seemed an ideal solution, he says. “It anchors above the flood line, collects any floating trash, and channels it to a basket that’s extended into the channel. The nice thing about that is it doesn’t have to be anchored within the stream itself. You can anchor it above the water line. It minimizes the amount of disturbance to the stream buffer.”
Extending the service road was part of the project. Baugh expects that the Bandalong, which is manufactured in Storm Water Systems’ Cleveland, GA, facility, “should intercept the vast amount of trash” without the need to clear any streambank area.
“It’s relatively nonintrusive in terms of disrupting the stream,” says Baugh. “It allowed us to have an easy way to get to it to service it.”
Because there are city workers in close proximity, the site will be monitored frequently, particularly after all rain events. Baugh says that it will be serviced as needed.
The water level of the stream that the canals flow into, where the trap is located, fluctuates. During a period of low flow, as is typical during the summer months, it is approximately 1 to
2 feet deep.
“It doesn’t run with enough velocity to convey anything like trash,” says Baugh. However, during periods of high flow, which occur in the late winter and early spring, the stream can reach depths of 10 to 12 feet deep.
“As the water level changes, [the trap] moves with the water level,” says Baugh. “It should work at different flow conditions.”
Floatables enter the tributaries in a wide variety of ways and at different locales. Litter from four-lane highways and runoff from a development make their way into the canals. Business traffic visiting large commercial stores in the area also plays a role in generating the trash that enters this system.
“It’s probably the biggest concentration of retail shopping in a 50-mile radius. The canal system starts out as natural channels; upstream they become part of the infrastructure of the city. That canal system converges downstream,” says Baugh, noting that this is where the litter trap was placed “so we can intercept it before it gets into the river.”
He says the project has generated interest among the city commissioners.
“Our elected officials were very happy to support the project. Everybody is very happy with the prospect of getting this project underway. We hope to build goodwill [because of] the fact that we made the effort to go the extra mile instead of just doing what’s required.”
Through this project, the city of Waycross is addressing future compliance issues today.
“Waycross does not yet come under state MS4 [municipal separate storm sewer system] permit coverage, but we’re still subject to NPDES [National Pollutant Discharge Elimination System] erosion and sediment control regulations, which continue to evolve,” says Baugh. “Stormwater management regulations seem to be trending toward implementation of more measures to reduce pollutant loadings in stormwater runoff, and this project should help posture Waycross for compliance if it eventually falls under MS4 permitting that is currently limited to larger municipalities. The extent to which this type of litter trap might become widespread will depend on the proven efficacy of the system and direction EPD goes with stormwater management regulation.”
Ultimately, the most effective stormwater management plans will have successfully determined and implemented the best stormwater structural BMP or treatment train for each specific site.
Author's Bio: Based in Morgantown, PA, Tara Beecham writes frequently for Forester publications.
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