Options to trap sediment
By Jennifer Pinkley
Ensuring that debris and pollutants don’t enter inlets and storm drains has become an important issue since the National Pollutant Discharge Elimination System (NPDES) Phase II went into effect in 2003. Protecting inlets and storm drains is only part of an overall erosion and sediment control plan, but a very important part. Inlets and drains are the last point at which sediment and pollutants can be captured before escaping a job site or entering rivers and streams. Therefore, many contractors, developers, and city inspectors recognize the importance of integrating effective inlet and storm drain protection into the overall erosion and sediment control plan.
Paul Bucich of the City of Federal Way, WA, notes that inlet and storm drain protection is just one part of the erosion control puzzle. “Erosion and sediment control is like making a good Dagwood sandwich,” says Bucich. “You have to have all the pieces to make it truly effective.”
The Design, Planning, and Implementation Phase
Coming up with effective erosion control plans always includes integrating inlet and storm drain protection before construction even begins. Bucich ensures that inlet and storm drain protection is addressed from the beginning of every proposed project in his city. “At the time of application, the developers and their engineers are required to put together an erosion and sediment control plan that is submitted for review and approval,” he says. “Typically, the plan includes inlet devices such as catch basin inserts, or they have the standard silt fence wrapped around the structure itself to make sure nothing gets into it.” Bucich says that his city has had a few contractors who want to use catch basin inserts or other inlet filtration devices as their primary erosion and sediment control method, but his city won’t let them do that. Inlet protection devices must always be used in conjunction with other erosion control devices appropriate for the particular site to achieve maximum sediment control.
Mike Bandos of FISCO (Federal Industrial Sales Corp.) in Columbus, IN, often evaluates sites in Indiana before construction starts to figure out how to best utilize Inlet Filter devices onsite. “The Inlet Filter is the last part before the water and the sediment slips away out of your control, because we’re providing filtration right at the inlet,” Bandos says. “If there aren’t silt fences, coir logs, or some other type of wattle out there holding back seriously open ground,” inlet filters alone will not be effective, he notes.
Bandos also points out that there’s a certain balancing act when choosing the correct inlet protection device—especially in the applications his company focuses on, specifically new construction and subdivisions. “Even with associated materials that are out there, such as silt fences, there will always be an additional need to prevent more material from going into the storm drains,” Bandos says.
The Inlet Filters, from Blocksom & Co. in Michigan City, IN, consist of fibrous mats with varying densities that are placed on top of inlet grates and then tied down. The density each job requireswill vary depending on the terrain. “Some places are more susceptible to gully washers with heavy rains,” Bando explains. “In those instances, since you have such an onslaught of water and mud all of a sudden, it has greater requirements for filtration than other areas that might tend to have more moderate rainfalls.”
Lee Llewellyn of Pine Knoll Construction in Winchester, VA, uses a variety of devices on his projects, based on requirements from the engineer who draws up the design plans. “The engineers tell us which devices are to be used where based on erosion control standards for Virginia,” Llewellyn explains. For storm drain protection he often uses trash racks on top of stormwater management pond outlet structures to control stormwater runoff. “That’s just in case water gets out, to control sticks and debris and clogging the pipe up,” he says.
King Lloyd of the City of Glenwood Springs, CO, is involved mostly with private developments and making sure contractor proposals meet the city’s criteria. When first talking with developers and engineers about a new project and the type of inlet and storm drain protection devices to use onsite, “we don’t necessarily tell them a specific make or manufactured item,” Lloyd explains. “We tell them what the criteria are, and based on their ideas or their budgets, they propose the different systems they want to use.”
Lloyd says that sometimes the engineers will not take an aggressive enough approach to inlet and storm drain protection. He says that some think they can just “throw a couple straw bales out there around the inlets and call it good.” Lloyd says that although that method may “sometimes work on roadside projects, you can’t put those out of a curb and gutter of a city street.”
There’s another problem with only using straw bales to protect inlets and storm drains, according to Lloyd. “Once they’re out there and staked down, they’re kind of forgotten and not maintained appropriately.” Lloyd and his staff encourage developers to come up with more aggressive inlet protection and filtration. Of further concern in his area is that many projects are adjacent to a river or a body of water, so effective inlet filtration devices provide the last chance contractors get to make sure sediments and pollutants won’t cause problems in rivers and streams.
The City of Federal Way also gets involved at the very beginning of projects to ensure inlet and storm drain protection devices work in conjunction with other erosion and sediment control methods. “We’ve set up a program that before the contractors are allowed to disturb the site, they have to have a pre-construction meeting with our inspector onsite so they can talk about what erosion control practices they have to have in place at a minimum,” says Bucich. He explains that if the work is in a subdivision or a plat that’s been approved, the roads are in place, and the site’s been cleared, to stabilize it, “we’re talking about having to have silt fences and a construction entrance, and a lot of times a contractor will want to put in catch basin inserts. We encourage them to do that—to install them correctly, maintain them correctly, and remove them when they’re done.”
Even though erosion control professionals recognize the need to integrate effective inlet and storm drain practices, Bandos observes that “everyone’s trying to do more with less since the stiffer regulations went into effect.” Andy Smith of EcoTurf in Raleigh, NC, agrees. He notes that many of his customers consider cost an important aspect of deciding on the type of inlet and storm drain devices to use. “There are a lot of good products out there,” Smith says. “But it helps when the price is good and the product performs well.”
Bandos says that there are a number of products on the market that do an effective job, but no one product does everything in all instances. “We use our products to complement some of the other products that are out there,” Bandos says. “Many contractors these days will do their work and try to apply sod as quickly as possible to get the dirt covered up and sealed away,” says Bandos. “If we went out and it’s all open and plowed ground, it would be a difficult task to keep it under control just with Inlet Filters.”
Dustin Hicks of Indydust Construction Services says he uses a variety of products to tackle inlet and storm drain protection in central Indiana, but the devices he considers the most effective are IPP Inlet Filter’s drop baskets. Although the devices cost more than other devices he often uses (such as coir fiber mats), Hicks says that if developers would budget drop baskets in at the beginning of a project, maintenance burdens would be very minimal. He considers drop baskets very long lasting, easily serviceable, reusable in different locations, and durable. For some materials, like a coir fiber mat, the initial cost is much less and it’s easy to change them out every couple of weeks with new ones. “But I’d rather install the product that will work the best in the field and work the best for the customer,” says Hicks. “Everybody wants to try something that will save them money. But that’s not always the most effective route.” However, he says many people in his area are starting to realize the benefit of reduced maintenance even with a higher initial cost, especially since options like drop baskets usually pay for themselves over time. Considering these types of issues is an important part of not only designing an economic inlet and storm drain protection plan but also ensuring that all of the different erosion control devices in use complement each other to achieve the best results.
Inspection
Most erosion control professionals regularly monitor inlet and storm drain protection devices to make sure they’re working properly. Sometimes, firms that install the devices perform regular inspections. Andy Smith pays close attention to any new product EcoTurf installs in the field. If the product is new to his company, he will also monitor the influent and effluent to see how much difference the devices are making. “But once we get comfortable with them,” Smith says, “we just check for maintenance at that point.”
In Federal Way, inspections of inlet devices are part of an integrated inspection program to ensure the devices are properly cleaned and maintained on schedule. Bucich explains that if there’s a problem with any device, the responsible party gets a written letter stating what needs to be corrected within a certain time frame. “If they don’t take care of it,” Bucich says, “we try to work with the contractor to make sure the problems get fixed.” On the rare occasions the problems aren’t corrected, Bucich’s department issues a stop-work order until the devices are working as they should.
Bucich’s department also sends two inspectors out to inspect over 600 private and commercial facilities in Federal Way each year. “They walk the site, look in every single catch basin, inspect the control structures, inspect any ponds and water-quality facilities, and then they develop a list of items that need to be done,” Bucich explains. The property owner receives information in the mail about what needs to be corrected. Property owners are usually given 30 days to fix any problems, which is usually more than enough time. “Sometimes we come across some old ones that have never been inspected,” he says. “We work with those property owners to phase work in over months or even years to correct the problems.”
Inspectors in Glenwood Springs inspect sites at least weekly and especially after a weather event. “Sometimes we go out on a daily basis,” Lloyd says. “We’re in the mountains, so sometimes a pretty good downfall can cause immediate impact to a construction site,” he explains.
When construction is no longer active, Lloyd’s staff will check any devices that the city maintains, but the staff members don’t typically go onto private property. However, if inspectors notice a problem out in the street, Lloyd says his staff tries to backtrack and figure out if someone isn’t properly maintaining his devices.
Bandos says that FISCO monitors its filters “especially on the front end before the customer gets a firm footing on how the material works. We’ll do spot checks on job sites and frequently go around with contractors to make sure things are working as they should.” Inspections last for the duration of the job.
Maintenance
Another aspect of these types of devices is maintaining and cleaning them. Many contractors have a regular schedule for both cleaning and maintenance, often relying on the firm that installed the devices to provide these services.
Andy Smith says that his company inspects about 75% of the curb inlet filters and other devices it installs. “Most of our clients do NPDES inspections,” Smith says, so EcoTurf inspects sites once every seven days or within 24 hours of over 0.5 inch of rain. “For the sites we don’t inspect,” says Smith, “the developer or project manager will call to schedule maintenance on devices.”
Smith says the price for maintaining different devices can be hourly, a per-unit price, or included in the installation cost. Smith charges on an hourly basis for silt fence maintenance and cleaning. For bags that go into inlets, the company has a per-unit price. For fiber-mat inlet filters, Smith includes maintenance and cleaning with the installation cost because maintenance is so easy. “You just basically brush it off,” Smith explains.
Ease of maintenance also factors into bottom-line decisions when finalizing an overall erosion and sediment control plan. Even if devices are less expensive initially, sometimes additional maintenance can cause overall costs to creep up. Hicks says that devices such as drop baskets are simple to maintain. One benefit is since they are located inside grates instead of on the surface, they’re less prone to damage. Maintenance usually means simply removing debris from the baskets. To empty them, Hicks says, he just pulls the grate and then pulls the basket out of the casting. “I’ll empty baskets into skid-steer buckets and then replace the baskets,” Hicks says. “We’ll take the debris and unload it in a concrete washout area so the debris is contained and disposed of appropriately.” Maintenance crews can also replace basket liners without having to replace the basket framework. Maintenance is obviously weather dependent but usually occurs less frequently than for some other types of devices.
One maintenance issue to consider in some parts of the country is snow removal, which Hicks says is a problem with top-of-grate inlet protection devices. Snowplows clean them off, but it’s hard for snowplows to properly clear streets without damaging top-of-grate devices. For these types of devices, the overall plan needs to take additional maintenance into consideration. Hicks considers drop baskets, which are located under grates, a better solution in areas susceptible to heavy snow. They aren’t damaged by snowplows and therefore don’t require any additional maintenance.
Unusual Approaches
Several professionals have implemented some approaches to inlet and storm drain protection. King Lloyd describes a unique project he worked on in Glenwood Springs. “Six years ago, several of the communities that are adjacent to the Roaring Fork River decided to hire a consultant to come in and evaluate existing stormwater techniques and identify problems for several of the communities that border the Roaring Fork River. We’re the last one in line just before the Roaring Fork runs into the Colorado River.”
Lloyd says the consultant started with Glenwood Springs because the city is closest to the river and then went upstream to three other communities. “The result was they gave us a report card, so to speak, as to how our existing systems worked and where improvement might be needed to maintain water quality in the Roaring Fork River.”
The consultant identified some areas that could be improved, including installing a settling basin at the outfall of an existing storm system. Lloyd started to investigate ways to solve the problem. “I stumbled upon Snouts on the Internet,” Lloyd says, referring to the devices manufactured by Best Management Products Inc. of Lyme, CT. Where the study had identified a need to install an open settling basin, it looked to Lloyd like using the Snout—an outlet cover that separates grit, debris, and oil—would be better. “Rather than digging or excavating a large pond that might create mosquito or maintenance problems down the road, I came up with a design where the Snouts could skim off the pollutants—the oils that wash out of the streets and into the system, as well as trash and sediment,” Lloyd says. “They’d be trapped in this chamber where everything would be collected in one location.”
The way this design removes pollutants from stormwater is by first running stormwater through a series of Snout skimmers that fit over the outflow pipes. The Snouts prevent a variety of pollutants and debris, such as hydrocarbons or heavy solids, from escaping the vault installed in line of the existing outflow to the river. This system also incorporates a secondary means of removing sedimentation and debris from stormwater. The first flush of stormwater is diverted through a 10-inch outflow pipe with a skimmer at a lower elevation than the primary 3-foot-diameter outflow pipe that goes to the Roaring Fork River. Lloyd says it is the first half-inch, or first flush, of stormwater runoff that transports most of the pollutants.
After the water is skimmed, or effectively cleaned, the clean water washes out into an open, grassy area. Lloyd says it creates “irrigation of land that didn’t get irrigated before.” By running the cleaned water out over an open space instead of a pond, Lloyd was able to use native grasses to do even more cleanup of the water. “The grasses filter out the suspended solids that didn’t get trapped in the basin,” explains Lloyd.
The larger of the two pipes takes care of any overflow should the smaller pipe reach its capacity. Due to the skimming effect at each outflow within the vault, even at maximum flow, no trash, hydrocarbons, or heavy solids can escape the vault. The vault has a sump with a capacity of 180 cubic feet, making for a very effective stormwater control system.
Another method for improving inlet and stormwater protection, as well as other issues related to NPDES Phase II, is working well in Washington state. There, a group of stormwater inspectors from jurisdictions across the state meet quarterly to share ideas and methods. Bucich says that this has been a great way “for inspectors across the state to figure out what everyone’s doing across the board, to learn from each other, and to teach.” He says that many jurisdictions have implemented ideas that they learned about at these meetings, resulting in improved overall practices.
Chris Van Hoof of the City of Kent, WA, says the group has been a great way to network. The group started in 2000 shortly after the NPDES Phase II regulations were published. “We started talking to other cities just starting programs, and it was just a way to collaborate, network, and talk about what other cities were going through,” says Van Hoof. “Some had codes and enforcements, and others didn’t. Larger cities could help the smaller cities. We even got some Phase I cities, like Seattle, involved.” Sixteen cities, five counties, and the Department of Ecology for the state of Washington all participate in the group.
According to Van Hoff, before his city started thinking about NPDES, it had mainly focused on cleaning public catch basin inserts. “In Kent, when we started, nobody cared about the system until it flooded,” Van Hoff says. “Some catch basins hadn’t been cleaned in years.”
The collaborative group has allowed professionals to share information about effective techniques to improve inlet and storm drain protection practices, as well as other erosion control methods. “Participants range from professionals in Seattle, our largest city, down to Milton, a city of about 7,000,” Van Hoff says. Seattle has numerous people involved in implementing NPDES Phase II programs, while many smaller cities only have one person involved. “Members range from young people right out of college to guys who have been doing it forever,” he says. “When we first started, everybody had topics and questions.” Van Hoff says the group has worked so well and all of the members now have good systems up and running that meetings will likely be reduced to twice a year.
Van Hoff says the group invites manufacturers to come to meetings to describe new products out on the market or products that members might not be familiar with. It’s a good way to learn how to install, operate, inspect, and maintain different devices. Members also introduce topics they’d like to discuss during the two-hour meetings.
The collaborative effort has provided Washington inspectors with a great way to make sure the state has comprehensive inlet and storm drain protection practices, as well as well-designed overall erosion and sediment control plans and procedures. After all, the ultimate goal of inlet and storm drain protection for professionals all across the country is reducing sedimentation and pollution as much as possible. As Van Hoof says, “In an ideal world, the only things you want getting in storm drains and inlets is rain.”
Jennifer Pinkley is a writer based near Huntsville, AL.
EC - November/December 2007
|
|
