Inlet Expertise

Photo: KCI Environmental

Whether during construction or post-construction, erosion control contractors are turning to the latest technologies to help site clients manage erosion and stormwater in a way that is cost effective yet comprehensive enough to meet regulatory requirements.

An 85-acre athletic field complex being constructed at James Madison University in Harrisonburg, VA, calls for careful erosion control methods. Site runoff flows into a local stream, and the site is in the Chesapeake Bay watershed, meaning construction activities are highly monitored.

To that end, Partners Excavating Co. in Harrisonburg is using ACF Environmental’s Grate Pyramid to protect inlet structures. The reusable inlet protection device designed to protect inlet structures from sediment and debris during construction. Grate Pyramid attaches to the inlet grate with hooks.

The heavy-duty frame forms a barricade over most drop inlets. The high-flow geotextile filter skirt stops sediment and debris while allowing the filtered water to leave the site. Built-in overflow prevents ponding during major wet weather events.

The athletic field site entails elevation differences from one side to the other. “There are a lot of slopes and a lot of terracing of various fields; therefore, we have a lot of inlet protection, primary drop inlets,” notes Rich Kauffman, project manager for Partners Excavating. If more traditional types of inlet protection were used, it would be “very difficult” to access them for cleaning after the project’s completion, he says.

“That inlet protection needs to stay in place until everything is stabilized upstream,” Kauffman says.

Partners Excavating had never used Grate Pyramid prior to this project. Robert Connelly, CPESC, of ACF Environmental had met with company officials to discuss the use of the product.

“It’s a device that one man can take and place on the DI [drop inlet] top, and it secures in place with a fastener on the grate,” Kauffman says. “At the end of the project, when it needs to come off, one man can walk in with a wrench, take it off, and carry it away.”

A challenge in accessing the slopes was that they are heavily landscaped and, in some cases, Partners Excavating was not permitted to drive on the sidewalks with rubber-tired equipment that would leave marks, so installation of the Grate Pyramids by hand worked well.

The Grate Pyramids are being used in conjunction with silt fence that lines the site perimeter.

“There are various sediment control basins and a large underground detention facility that all the water from these areas flows into,” says Kauffman. “One of the reasons we have an interest, other than just silt leaving the site, is that any silt that gets into this underground system would need to be cleaned out at the end of the job with vacuum trucks in a confined-space environment. It’s in our best interest to keep everything as clean as possible, and these devices are doing a great job of that.”

Kauffman’s company also is mindful of the extensive site monitoring due to the sensitivity of the watershed area.

“We are heavily monitored here by the Virginia Department of Conservation and Recreation, and while the EPA has not made any visits to the site, it would also fall under their jurisdiction. James Madison University has its own Environmental Management System personnel, and they do regular site inspections as we do our own as well,” he notes.

Partners Excavating Co. monitors the influent, measuring the success of the Grate Pyramid by ascertaining whether silt is getting into the underground detention facility.

“As long as we are getting relatively sediment-free water in there, they are working as designed,” Kauffman says.

“There are new products coming out that are aiding us and controlling the amount of silt that leaves a site, which is the ultimate goal,” he adds. “Anytime a new product comes out that helps us attain those goals, it’s something we take a close look at. We took at look at the Grate Pyramid, and we liked what we saw as far as the way it was made, but we also liked the fact that it was very easy to apply and to remove at the end of the job.”

Expanding Stormwater Services
A partnership between AbTech Industries and Waste Management means AbTech’s SmartSponge technology will now be deployed to provide stormwater services.

The initial rollout of the program is in pilot markets in California, eastern Canada, Florida, Georgia, and other parts of the Southeast, including the Carolinas.

The stormwater services will broaden what Waste Management already provides in terms of solid waste collection, transfer, recycling, and disposal to include being the exclusive waste and environmental services company distributor of SmartSponge in North America. SmartSponge is a spongelike material with polymers to filter, absorb, and solidify petroleum hydrocarbons and other pollutants from stormwater runoff.

“This represents the first time a Fortune 500 company has moved into the stormwater space in this capacity,” notes Bjornulf White, executive vice president of corporate strategy and business development for AbTech Industries.

In deploying the technology for municipalities, AbTech and Waste Management assess the cities’ needs, then conduct a full design and consultation to provide a set of solutions.

“Regulations are always changing,” White points out. “Testing protocol are always updated. This is something that we’re finding is very useful to cities.”

The Waste Management/AbTech team also offers continued inspection and maintenance services. “It’s a full solution set that the cities can obtain through one master contract with Waste Management,” says White. “They have a private entity that’s essentially going to make sure that efficiencies are driven into the process.”

SmartSponge was originally invented to deal with oil spills, but evolved to be deployed for stormwater management as well. “It removes contaminants from flowing water without impeding the flow of water and then permanently locks those contaminants into its molecular structure,” White explains. “Once it’s trapped and incorporated the contaminants into its structure, it’s still not classified as a hazardous material because those contaminants can never leach out of that material under any amount of pressure. It’s not just a sponge or a filter that’s mechanically trapping contaminants, but it’s actually attracting them and locking them up.”

The technology does not require any electricity or moving parts. “You just engineer a setting that allows you to take advantage of either gravity or the force of the water, and then the water gets cleaned as it flows through,” White says.

SmartSponge Plus is includes an antimicrobial agent that has been permanently bound to the SmartSponge core filter material. “It was approved by the EPA in 2010 for reduction of fecal coliform in stormwater, wastewater-both municipal and industrial-and other industrial water treatment,” White says.

He explains that as the water column containing pathogens flows through the material, the bacteria are rendered inactivated because they can no longer pose any hazard or replicate. “It does this by rupturing their cell wall as they pass through,” he adds. “Because the antimicrobial agent is permanently bound to the material itself, you don’t worry about any downstream toxicity, which is one of the big breakthroughs this technology has created.”

Traditionally, there have always been downstream concerns, White points out. “You might use chlorine or some other type of material that can kill the pathogens, but now you have another problem to deal with,” he says. “This allows you to deploy the technology in a decentralized way without electricity or moving parts.”

A popular deployment of the SmartSponge is as an end-of-pipe treatment system.

“Right now, stormwater essentially enters the storm drain, goes through pipes, and goes right out into the ocean, lakes, and rivers completely untreated,” White says. “The cost of redoing the infrastructure so that it flows into a centralized treatment facility would be astronomical.

“That’s how we handle our wastewater and our drinking water, but stormwater is even more dispersed and decentralized,” he adds. “It would be too much for municipalities. We”˜ve developed a system where very cost-effectively you retrofit a concrete vault at the end of the pipe so it’s minimal infrastructure disruption.”

The SmartSponge or SmartSponge Plus is deployed inside the vault. As the water flows through the pipe and is about to be discharged, it flows through the underground concrete vault retrofitted into the pipe and flows through the treatment material.

“This works well regardless of what contaminants you’re treating for,” White says. “The antimicrobial version is especially useful in beach scenarios where beach closures are most frequently caused by discharging stormwater that has bacteria in it.” The technology is currently deployed in a treatment vault in the Outer Banks of North Carolina for that reason, White says.

Maintenance depends on local conditions. “Depending on the situation, you might see an inspection and maintenance cycle from six months to every year or two,” White says. “In terms of replacement of the media, the antimicrobial technology itself would last forever. It doesn’t get used up. What actually causes you to eventually have to replace the media is either that it’s trapped a large amount of sediment-which is good to trap anyway-but also it absorbs hydrocarbons. We have seen everywhere from one to five years in replacement needs, with three to five years being typical.” At an airport or industrial port where there is a greater amount of fuel present, it would likely be replaced more often, he says.

SmartSponge also gives municipal solid waste (MSW) operations the ability to harvest the hydrocarbons collected in the material as a fuel in a waste-to-energy facility. About 320 pounds of SmartSponge is estimated to create a megawatt of power, creating an opportunity to generate revenue from stormwater runoff.

The next step after the pilot markets are up and running is to do a continental-wide rollout, White says. California was the first market in which the product was rolled out for municipal use and is where the company has the most experience.

AbTech has a laboratory in Phoenix, where the company continues to develop new technologies in the advanced materials sector and in engineered solutions.

More Reusable Materials
The Syman Co. in Nampa, ID, provides erosion control and excavation services, with current projects including three residential subdivisions. Most of the company’s work is related to transportation or commercial projects, including utility pipelines.

The company designs and installs a wide range of erosion control best management practices (BMPs) and handles stormwater pollution prevention plans and other work related to SWPPP management. Among the products the company distributes and uses is Gator Guard.

“We use whatever works best, and we use Gator Guard when it works best,” says Adam Lyman, the company’s engineering manager. “We use other types of wattles for inlet protection when we need to.”

Gator Guard is a UV-resistant geotextile tube filled with recycled foam material. The reusable sediment control wattle can be used in place of silt fence or straw wattles and has a five-year lifespan.

When installed, Gator Guard is cut to fit, connected end to end with a pin apron located every 3 feet. One inch of dirt is placed upon the apron. Five-inch cap nails are included with the Gator Guard. Cuts can be repaired with caulk.

A recent project illustrates what Lyman favors about Gator Guard, which his company selected to protect an inlet after the job was finished until the vegetation was established.

“We had to get in and out of the site a few times,” he says. “We used Gator Guard at the site and ran it over three or four times getting in there and getting back out when maintaining the BMPs.”

Lyman likes the fact that that he can reuse Gator Guard. “We can pull it out, take it to the next job,” he says. “It’s tough. We know if we need to run it over, it’s easier than putting straw wattle down and then having to move it out of the way when we come back to the site.”

He adds, “It retains the stormwater at the end of the site longer than most wattles we use,” noting that there are a few impaired waterways on the 303(d) list in Idaho.

Sometimes Lyman’s company uses Gator Guard in combination with other erosion control methods, such as blankets, matting, or hydroseeding. “We’ll leave it there until the vegetation has grown and we’ll pull it out,” he says.

The ability to recycle it makes it attractive to clients with tight budgets, Lyman says. “It lasts a long time. We’ve had it in several places for six months to a year and then taken it to another job. Most of our clients like it for that reason. They can use it around stockpiles or a staging area for six months, then they can roll it back up and store it for another while and take it to the next job.”

Lyman says he has “no complaints” about maintenance of Gator Guard.

“It’s easy to patch if it gets torn,” he says. “We had some that got hooked on equipment and had to be reinstalled. Our experience is we’re able to reinstall and repair it quickly.”

Lucinda Dustin’s company, Mud Hen Environmental in Sacramento, CA, is working on the Doyle Drive Project in San Francisco, CA. Doyle Drive is a major artery that feeds and empties the Golden Gate Bridge. A structurally and seismically deficient section is being removed and replaced with a new, safer, up-to-date structure. It is being re-envisioned as the Presidio Parkway, running through the natural contours of the Presidio of San Francisco and the Golden Gate National Recreation Area.

Mud Hen Environmental has deployed several types of ERTEC inlet protection on the project, which is being constructed by R&L Brosamer. In fact, Dustin has been using ERTEC products for many years.

“They came out several years ago with ERTEC invented inlet devices that we placed primarily the changed the standard way the industry was protecting inlets. An example is the device that protects what I call combo inlets, where you have a grate, a curb, and a standard storm drain inlet,” she says.

“One of the biggest problems I’ve seen over the 18 years I’ve been doing this was the fact that we’d insert drain insert bags into the drains, and if you don’t have a good maintenance schedule, the bags get full underground and under the grate. They’re heavy and it’s not always easy to work with them.”

Dustin tried the new inlet protection products at the recommendation of ERTEC.

“Their products provide surface protection, which means the devices are installed aboveground,” Dustin says. “They have curb inlet guards for curb openings only. They’ve got combo guards for curb and grate combos, and the one I’m absolutely sold on and have been ever since they came up with it is GR8 Guard for hardscape drains. The best thing about it is that there’s no inlet bag. They’re easy to install, inspect, maintain, clean, and remove.”

Made from recyclable HDPE, GR8 Guard is a four-layer system designed to reduce sedimentation into grated storm drain inlets in paved areas as part of a BMP for site sediment control. The integrated filter is designed for concentrated flows. The outer berm allows water to rise to nearly 1 inch before reaching the filter, causing heavier particles to settle. The system filters stormwater above the ground for ease of visual inspection and maintenance.

Dustin says the GR8 Guard device attaches to the surface of the grate with ratchet-style cable ties. “Instead of having to pull up the grate, take out the bag, clean the bag, and put it back, you just clean this device that’s attached to the top of the grate,” she says. “It’s large enough and has special fabric so that when it gets wet, it adheres itself to the surface of the pavement. You’re covering the grate but you’re also sealing outside of the grate area so that sediment isn’t entering underneath it.”

Dustin says one of the obstacles her company encountered in the past was that street sweepers destroyed some of the inlet protection devices. “They were black,” Dustin says. “The sweeper operators ran over the top of them. We were making frequent trips to fix them.” She suggested to ERTEC that if the guards were more visible, the street sweepers would most likely avoid them. In response, ERTEC produced “international orange” devices.

“That seems to have resolved my issue.  I’ve had one on there for five months and I have had no damage to it at all,” Dustin says. “They go around it.”

Dustin says installers like the guards because they are easy to work with. “We attach them to the grate cover with plastic ties-that seems to be working well,” she says. “I’m not having issues with losing any of those devices. For me, it’s time saving, which means it’s cost saving. When we’re finished, if they’re still usable, we just take them and put them someplace else. It’s just become a much easier and cleaner way to deal with the inlet issues.”

To maintain the guards, Dustin’s crew checks them every day. “They can see from the surface, so it cuts their time down,” she says. “You don’t have to worry about getting bags that are too full. This turns out to be an excellent way to manage the inlet systems.”

She appreciates that benefit during the rainy season. “It’s windy, and we’ve got all kinds of issues going on and it’s worked out for us because our time is cut down,” she says. “Instead of having six guys on the site, I can work with three guys. They can get this done immediately. If I’m going through a storm, I can manage these very quickly and easily because we can see immediately what has to happen.”

Dustin’s company monitors the influent and effluent if it’s required, such as a job in which her company is currently involved.

“We have a discharge to a marsh,” she says of the project. “There is a team that does that. There are guidelines on when that happens. I’m usually here during the storms. If I monitor it, I let them know if samples need to be pulled. We have to watch the site pretty closely. We’re inside a national park.”

Roadway Construction
In San Luis Obispo, CA, KCI Environmental is providing erosion control services for an extension of Willow Road. “It’s a new intersection on Highway 101 south of us by the town of Nipomo,” explains Jim Gorter, vice president and manager of the erosion control division for KCI Environmental. “A large bridge is being built on the highway, and Willow Road is going to pass underneath it. The highway will appear the same, but traffic will be going across two bridges-one for the northbound and one for the southbound-and they’re going to extend Willow Road to a connecting road to try to alleviate some of the traffic problems they have in the area.”

The job is a joint administrative effort between Caltrans and San Louis Obispo County, with a third-party firm retained to oversee the installation and maintenance portion of the 2.5-year project, which began in March 2011.

KCI will be using $100,000 worth of jute-covered rice straw wattles from KriStar for sediment control on the project. After the hard structure is put in, the company will do landscaping and irrigation on the interchange portion of the project.

“This area is primarily a loose sand material, and once it’s reworked, it’s like a sand dune, so the erosion control was a big issue,” says Gorter. “We’re putting the fiber rolls everywhere. The slopes get shredded with any kind of water that goes across if they are not stabilized.”

The contract called for a temporary fiber roll and a permanent fiber roll, with the temporary going in during the construction phase and then removed and replaced with the permanent rolls.

“As most jobs go, the temporary was pretty much deleted and they decided to get the permanent in as soon as the slopes are built,” says Gorter. “Then we only have to do half of the quantities, which is still a pretty good amount. It will probably be six or seven truck and trailer loads of fiber rolls.”

The primary concern is to keep the soil from coming down from the construction, getting onto the roadway, and going down into the storm drains, Gorter says.

“They’re also using biofiltration swale technology, where the runoff from the roadway is going through a biofilter that is a compost blanket overlaid with a heavy coir netting and then seeded with plants that tend to absorb or assimilate the pollutants that are coming off of the roadway before it goes down into the ditches,” he adds.

KCI has done a few projects to date with the biofiltration swales. “So far, they seem like they are pretty effective,” Gorter says. “They’ve been used extensively on the East Coast for mitigating the hydrocarbons coming off of the roadway before it goes into the waterways.”

On the Willow Road project, 400-gram coir netting is being applied in several locations where the roadway is being built so the water drains off to the side. Application of coir netting will be followed by hydroseeding, planting, and irrigation.

“Rather than it going down an inlet right off the road, they’re going to have it go across these filtering areas. The hydrocarbons in the water will be assimilated by the plants that are growing in the filter strip,” Gorter says.

As for the maintenance of the fiber rolls, Gorter notes that a few wet-weather events have occurred during the project, and although his company isn’t responsible for maintenance, employees are keeping an eye on them.

“There are a few places where so much sediment came over the top of them that they had to be cleaned out and repositioned, but that’s been pretty minor,” he says. “The sand is great in that a lot of the water will flow right down in and perk right into the soil, and it stays put.”

KCI has made a few minor changes on the job, such as using compost instead of wood chip mulch over to compost. “So far, it looks like it’s doing a better job controlling surface erosion until we can get the hydroseeding down and established, so we’re happy with the job so far,” Gorter says.

Sewering a City
The Weiler Engineering Group in Punta Gorda, FL, is a small engineering company with a number of large public and private clients. For one client-the city of Marathon in the Florida Keys-the Weiler Engineering Group serves as the engineer of record. The company is nearing completion of a $27 million sewer, stormwater, and road-paving project, which has involved sewering the entire city, providing stormwater treatment to all city rights of way, and overlaying every city street. In that project, the Snout-an oil and debris separator from Best Management Products-was used in some 940 inlet structures.

“One of the biggest challenges in the Keys is the high groundwater table,” notes Michael Giardullo, P.E., LEED AP, director of civil engineering for Weiler. “The other is the discharge right into the ocean. It’s a national marine sanctuary. There are a lot of rules about direct discharge or even discharge after detention.”

Marathon has a population of 10,000 residents-with more visiting during the tourist season-who inhabit a 13-mile-long collection of islands composing the 9.6-square-mile land area in the center of the Florida Keys.

The city was incorporated in 1999, and eventually the need arose for a retrofitted stormwater system for more than 500 acres of rights of way and public and private land that had been developed but had no previous stormwater treatment. The city began planning for the project at its incorporation in 1999. After funding was lined up, design and construction began in 2006.

Marathon’s National Pollutant Discharge Elimination System (NPDES) permit mandated the provision of advanced wastewater treatment. The city chose a vacuum sewer collection system to provide central sewer service to all properties.

In areas with little or no shoulder between the edge of the pavement and the edge of the right of way, the city developed creative ways to capture and treat stormwater. In these areas, stormwater had previously flowed untreated into environmentally sensitive wetlands and both the Gulf of Mexico and the Atlantic Ocean.

Now, a swale intercepts stormwater and provides dry retention pretreatment and exfiltration treatment. In that narrow landmass, Marathon has installed curbing to prevent runoff from discharging directly into the surface waters and instead route it into a stormwater inlet structure containing a Snout and underground exfiltration treatment.

The Snouts trap floatable and settleable contaminants in the catch basins, which are routinely vacuum-cleaned by maintenance staff, rather than allowing them to the exfiltration piping. The Snouts capture of 50% of fine solids, 95% of floatables, and 50% of hydrocarbons.

Some 159,000 linear feet of dry retention treatment swales were constructed. The system treats approximately 85,000 cubic feet of stormwater, in excess of what is required by state rules. Ten direct outfalls into surface waters were eliminated.

“One of the challenges we see with these exfiltration trenches is their lifespan can be lowered when you get a lot of debris from tree leaves, gravel driveways, and that sort of thing,” says Giardullo. “One of the biggest things the Snout does is that it will essentially clog up before all of that sediment and debris gets into the stormwater system. Cleaning those exfiltration trenches is a lot more challenging than a normal pipe and culvert stormwater system.”

The city is in the process of purchasing a vacuum truck, which will be used to maintain the system as needed, Giardullo says. Reducing the inflow of particles into the exfiltration piping, which can impede the ability to filter and percolate stormwater, will extend the life of the system.

Through GPS mapping of the stormwater system components, the city has developed a detailed asset management system to aid in maintenance.

The project aimed to create a master stormwater system to reduce pollutant loading into the near-shore waters, where contamination has led to the degradation of the world’s third-largest coral reef system.

Although the sewer and stormwater systems are independent, Marathon chose to use the trenches that were dug for the sewer mains as stormwater exfiltration trenches. Because the caprock commonly found inches from the road surface is extremely difficult to trench, by putting stormwater pipe in the trenches already created for the sewer, Marathon reduced the time and effort needed and the amount of clean backfill, ballast rock, and road base that would have been required for separate systems.

The total project cost was nearly $27 million dollars, funded by $3.3 million in grants secured through the American Recovery and Reinvestment Act, Local Agency Program (LAP), and the South Florida Water Management District. Some $10.3 million was secured through a state revolving fund loan. The remainder of the project was paid for through a special taxing district.

One of the objectives of the system was to address standing water after rain events, Giardullo says. “In a lot of those locations, we were able to take the water very quickly during the rain event. Even in some low areas, we might not have been able to take it instantly, but it dissipated much, much faster than it did before. Sometimes it stood for days.”

The use of sewer trenches as exfiltration trenches has received several honors, including recognition by the USEPA with its 2008 PISCES award for innovative use of state revolving funds. The project received a 2011 Florida Stormwater Association Excellence Award for Stormwater Programs and Projects.

Public outreach was a key fac

Comments

Leave a Reply

Enter Your Log In Credentials
×