Sturdy BMPs for Sediment Control
Reusable and recyclable are keys to contractors’ choices.
The King Coal Highway is an unusual stretch of roadway being built through the mountains of southern West Virginia, part of a new corridor highway system across the bottom of the state.
“The King Coal is an unusual highway project in that it’s kind of a partnership between the coal mining industry and our highway department,” explains Jamie Bailey of the West Virginia office of ACF Environmental. “They’re using a mountaintop removal site and running this highway on a portion of coal mining property. That’s why it’s called King Coal—different segments of the road run along reclaimed surface mines. It’s a new four-lane highway that is a combined West Virginia DOT [Department of Transportation] and federal highway project, in conjunction with coal mining interests.”
During the highway construction process, Grate Pyramids from ACF were used as inlet protection devices. This reusable product attaches to the inlet grate and comes with a high-flow geotextile filter skirt to stop sediment and other debris, while permitting the filtered water to leave the site.
| Photos: WOLF CONSTRUCTION
|Recycled wood chips served as filter material in the FilterSoxx at this site.
“The base of the Pyramid is a big square base that fits down over the grate,” says Bailey. “Then the pyramid part comes in, rising off that base, and there are built-in overflows. In some places, we put a light on top, like a solar-powered lawn light, a landscaping light. That way, if somebody’s out at night they won’t run into it. We put reflective elements on it, and it’s a highly reflective orange, so it has high visibility. If someone is in an area where they could drive into it or hit it, they’ll be able to see it.”
There are currently about 200 of these Grate Pyramids being used on the project. They come in varying sizes, depending on the size of the grate. A typical unit is approximately 2.5 feet tall.
“Some of the Pyramids are in the median, and some are on the side of the highway,” says Bailey. “They are put down during construction, and at different phases of the construction process when it’s really rough, they can really get under siege with a lot of sediment. Then when [work crews] get the final grade, they leave them in place, and everything gets vegetated in.
“Typically, I’ve seen them on the highways even after the highway is open. They’ll leave them out there for quite some time.”
Bailey explains why the Grate Pyramid was selected as the primary inlet protection device for the project. “The alternatives typically have been using 2x4 frames and silt fence fabric, and some of them don’t perform that well, and they’re hard to maintain.
“The Grate Pyramids are performing real well, with high visibility. They’re easy to maintain, and they’re reusable. As the highway construction workers complete a phase, they can move them down to the next phase, once they’ve vegetated the area. When the highway department deems it to be sufficiently complete to safely take off the inlet protection, they can be reused.
“We wanted to go with something that would be more functional and have a better overflow system than some of the other above-the-grate inlet protection devices we’ve used in the past. In the event of a major rain event, we don’t want any ponding; we want a better system for the water to get offsite.”
The Grate Pyramid does require occasional maintenance. “There is no self-cleaning inlet protection device,” Bailey explains. “They definitely need to be maintenanced. You can easily clean out around it, remove it from the grate, clean it up, then reinstall it. How frequently this is required depends on the rain event. If you can see that sediment is way up on it and it’s going to hurt performance, then it’s time to maintenance it.”
In addition, this project used Erosion Eels, 9.5 inches in diameter and 10 feet long, as ditch checks in lieu of rock check dams, to help control sediment on the side of the highway.
“The Erosion Eel is a geosynthetic textile tube filled with recycled tire chips,” Bailey says. “They conform to the ditch geometry real well. You can install them without having to use a piece of equipment. They are used with the same design principles you would use for any ditch check.
“They are fairly heavy, approximately 10 to 14 pounds per linear foot, and they are reusable, unless they are damaged by a piece of equipment, for example. Once you have vegetated the area and remove the Erosion Eel from the site, you have a very minimal disturbed area, as opposed to a big pile of rocks that you have to remove with equipment. [When using rocks] you’re left with a raw area with no vegetation; no grass can grow under those rocks.”
Bailey explained that if the Erosion Eel will encounter significant water velocity, it needs to be anchored in. “You can use metal T-posts in behind it, with straps on it for the posts. Two guys in a pickup truck can go right down and install it,” he notes.
“The Erosion Eels have been performing really well, and again, they’re easy to maintenance. If you get a big sediment buildup behind them, you just move them out of the way and replace them once you’ve cleaned up the ditch, if needed.”
Recycling at an Electrical Substation
Manhattan, KS, nicknamed “The Little Apple” as a play on New York City’s “Big Apple,” is best known for being the home of Kansas State University. Located in the northeastern part of Kansas, Manhattan is an anomaly in a stagnant nationwide economy. Over the past several years its population and economic base have continued to grow and prosper.
Westar Energy, Kansas’ largest electric utility, services this vibrant and growing metropolitan area. In 2010, Westar acquired the property for the design and development of a new electrical substation. The substation site is situated on the side of a rocky hillside with natural slopes exceeding 1:2. Maintaining erosion control measures during and following the construction of the site work represented a significant challenge to Wolf Construction, a Topeka, KS, industrial/manufacturing general contractor.
It was important to both Westar Energy and Wolf Construction, however, that the project proceed in an environmentally sensitive manner. To this end, the design of the substation exceeded normal erosion control requirements, and both companies strongly emphasized the use of recycling technology. The development of the project stormwater pollution prevention plan (SWPPP) and the selected BMPs reflected this concern.
For example, shrubs and trees that had to be cut down on the 9.5-acre site were shredded, with the resulting wood chips being used onsite rather than being dumped in a landfill. These recycled wood chips were incorporated in a number of elements within the project:
- To create berms in high-risk areas to minimize erosion
- For mulching around the landscaping surrounding the substation pad
- As filter material within the FilterSoxx used as erosion and sediment control devices
John Harsch, a partner in Sustainable Environmental Consultants, says his company used these wood chips in the 8-inch and 12-inch FilterSoxx for the project.
General foreman/superintendent Bill Ledeboer of Wolf Construction explains why the FilterSoxx were chosen for sediment control on this job: “With the typical old-fashioned black silt fence, particularly in this area with the rock close to the surface, it would have been really difficult to get in, if not impossible. Plus, you have such a maintenance issue with the fence, with it tearing and falling down. Our maintenance issues with the Soxx are pretty much nil. Then, of course, installing them is not an issue with the rock; you just lay it on the ground for the most part, and you’re done.”
He adds that it’s important to anchor the FilterSoxx correctly. “We’re experimenting a little here. We anchored just the ends, because when you poke a hole in them, of course, that’s where they’re going to start tearing on you. So to minimize that, we anchored just on the ends, and then put the other stakes on the downhill side, not through the sock, but just beside it. That seemed to work pretty well for us.”
Ledeboer is impressed with the performance of the Filtrexx material, and he increased their effectiveness by modifying the spacing called for in the project plans. “I doubled what the engineer designed, as far as spacing,” he says. “I went every 6 feet in elevation change for my sock placement, whereas they had us at every 12 feet. That would have been inadequate, with my field experience, even with a silt fence. You would have been constantly fixing it and tearing it out.”
According to Ledeboer, approximately 120,000 yards of dirt and rock were moved, necessitating the use of just over 2 miles of FilterSoxx. A benefit of this material is that it naturally degrades, so that removal and disposal may not be necessary. “On this site, I’m able to just leave them. It’s just pasture, so I’m going to let them degrade on their own, and they’ll just go away with time.” Five months after the material was put in place, he found that it was just starting to deteriorate.
“It was a hot, dry summer, and I think that might have contributed to that,” he adds. “Foliage didn’t get up high enough to shade them a lot. I’m pretty confident that, come next spring, grass is going to pick up, assuming it starts raining again. We haven’t had a decent rainfall in months. But when it starts raining again next spring, I think we’ll be looking real good. I don’t think there will be any need to put new Soxx in. We’ve got the vegetation; they just need to get a drink.”
Ledeboer explains that there are various types of Filtrexx FilterSoxx. “They do have long-term Soxx; they also have ones in a sock that is 100% cotton that’s real short-term. I think this one is designed to last about a year. Typically, if I’m doing my job right on seeding, and if I’ve got a normal year with rainfall, the Soxx that last about 12 months would be adequate. That’s all I’ve used to date.
“It’s a bit more pricey up front, but I haven’t had anyone up here doing maintenance, because I don’t need it. So you make up for the higher price in the long term, and it doesn’t look crappy. If you didn’t know what you were looking for, you wouldn’t even notice them now with the grass grown up.”
|Photos: SILVER LEAF SWPPP
|Reusable GatorGuard lasted through several phases of work at this Utah clinic.
Salt Lake Clinic Upgrade
Silver Leaf SWPPP was asked to handle sediment control on a recent project at the busy Salt Lake Clinic in Salt Lake City, UT. Owner Mike Christofferson explains, “They’ve got an existing clinic, and they were outgrowing it and it was getting old. They phased [the work] into three different projects. Phase 1 included a parking garage that went underground, phase 2 included the new building, and phase 3 will be the demolition of the existing building and repaving the site.”
Christofferson had to decide what product would work best on a potentially challenging project. “It’s a high-profile job in a high-traffic area,” he notes. “It’s in a very, very busy corner of town. What we didn’t want to have happen was to have a pedestrian walking down the street and kicking holes in the side of a silt fence—problems like that.
“On other projects, we had been using a lot of straw wattle, but the problem we were having with the straw wattle was that in certain situations in high-traffic areas, the wattle wouldn’t last very long.
“I thought this was a perfect project to try out GatorGuard, which I had been referred to. So we put that in and instantly the owner was really happy with it, the general contractor was happy, and I was happy because we end up spending a lot of time on maintenance if our BMPs don’t hold up, and that reflects back on us. We want to use a good product and we want to do it right.”
Even though the work was done in phases, he says, “we ended up having to install the BMPs upfront on all phases, because portions of each phase had had work done on them and earth was disturbed.” As work progresses, he notes, “we’ve just had to go in and either remove the BMPs because they weren’t needed any longer, or move them to a new spot within that phase.
He notes that the GatorGuard has held up well through heat and traffic. “One of its benefits is that it can be reused. The general contractor for this particular project started another project up on the campus of the University of Utah, which is just a mile up the road. He’s using the same dirt guy, and he called and asked if they can reuse some of this GatorGuard. They were able to pull out some of those BMPs as [phase 1 of this project] came to a certain point. They had about 400 feet they wanted to reuse, so we took it on up and reinstalled it on the second project, and it looks almost as new as the day we installed it the first time.”
Christofferson says that, at least so far, he has not had to clean out his GatorGuard product. “In this case, it didn’t need to be cleaned, because it wasn’t in an area where it got a lot of sediment that sat there and gunked up the material. I would guess that if it was dirty, you’d want to clean it out, but we were able to pick it up and put it back down and rebury it.
“That doesn’t mean we don’t still use straw wattle,” he adds. “There are still applications for straw wattle, but we’re finding that there are a lot of plans that call for silt fence and, really, it would be very difficult to get in there and put in silt fence. So we’ve gone in and reengineered it to put in GatorGuard, and everybody has been very pleased with how it has held up, how it looks, and how it functions.
“We rarely have problems with it. We’ll get guys that drive over it or people that walk on it, and it’s never a problem. In fact, we were working recently at Hogle Zoo, which is the main zoo in Salt Lake City. Due to the design of the project, we had to put straw wattle on one side of a pedestrian pathway, and on the other side we had to do the GatorGuard. We put the GatorGuard there because we knew it was going to get stepped on. We put it down, turned around, and we’d have little kids walking on it, but it didn’t do anything to it. We have confidence it will hold up.
“More important from my point of view is how the BMP works. I put the reputation of my company on our installs; that’s how we get repeat business. We do a good job and use good products. We’re always trying to find the best products that work the best.”
Twenty-nine Acres at Michigan State
On the campus of Michigan State University (MSU) sat 29 acres of old 1950s-era married housing dormitories. They had long since outlived their usefulness, having been built with a 20-year lifespan in mind. Demolition began in July 2011.
“We’re going to need to rebuild with something in the future, but right now, nothing’s been confirmed. We’ve covered most of the 29 acres with erosion control fence from SiltShield,” explains Dennis Hansen, senior landscape architect for MSU and an employee of the university for 38 years. The SiltShield fence comes in a semi-rigid structure designed to last longer and filter sediment better than traditional silt fence.
“The reason I used SiltShield was that I hated the other stuff we used,” he says. “Wood pulp is a plastic; fabric melts in the summer and sags. When you tear it out of the ground, you have this big, wide ditch of disturbed soil, so then you have to reseed it. Then after using it once, usually you have to throw it away, because nobody wants to recycle it since it’s a mix of materials, wood, and plastic.
“We’re big on recycling on campus, and with this new product, you can power wash it and use it over again. Plus, it is recyclable because it’s not a mixed material. When you tear it out of the ground, it’s just an inch wide. We install it with a power root saw—put a couple blades on with an inch-wide slot. When you pull it out of the ground, you don’t need to do any reseeding.
“You can hold on to the SiltShield and use it on the next project. So we save money on the installation cost since we don’t have to buy it again. We stockpile it; we buy a lot of material that we sell to the contractor at cost.”
It makes sense for the school to keep a lot of product in inventory. The MSU campus is very large, with nearly 50,000 students and 5,200 acres of land. “I think we’re the biggest university in the country for one chunk of land,” Hansen says. “Some other agriculture schools have more academic or more farm land, but they usually have farms out in the country. Our president back in the 1950s bought all the land he could get hold of. So we’re now 2.5 miles wide and 5 miles long.”
Hansen explained that the demolished married housing project is actually composed of two nearby sections.
“We have two segments split by a highway, our campus road. There are about 15 acres in one segment and 14 acres on the other. We don’t have fence around the whole 29 acres, because some of the site is lower than the surrounding ground, so we don’t need to put fence there to prevent water from flowing offsite, but we’ve got a good share covered with fence.”
Hansen notes that he had experimented with SiltShield before using it on this 29-acre project. “On some other installations, we used a small amount of SiltShield just to test it out. A contractor was also using some other products, some other kinds of recyclable filter and non-recyclable product. With that woven fabric, it can wilt in the summer, but the SiltShield doesn’t.
“We also had it on another erosion site that was just tenaciously awful, and it held up real well. At one point, the storms got so bad, it just collapsed the SiltShield, but that wasn’t the product’s fault. We didn’t put enough pegs in; we had something like 3 inches of rain in an hour. There’s nothing that will stop that.”
Hansen says he appreciates that the product has avoided becoming a headache for him. “It’s like construction fence—you’ve got to have it, but you don’t want it to become an issue on the project. You want it to be a feature of the project that doesn’t cause any problems. You don’t want facilities and materials that are required by regulations to become a nightmare. You want the contractor to spend time doing his job, building or tearing down, not maintaining regulatory features. This is what the SiltShield product allows.”
In addition to the SiltShield, a number of other BMPs were used on the site. “We’re using silt bags to go in a catch basin, and we’re using some wattles, the woven fabric with rubber chips on the inside,” Hansen says. “They weigh about 200 pounds apiece for a 10-foot section. We use those across the pavement, where we have to still get access in and out, until we close up the road and power down. We like those because they don’t float in heavy rain. Those work really well. We had to retain some dense liquid and they stopped it all. We brought in a power washer, washed them down, and used them again. They’re not cheap, but you can use them over and over again, and they’re good for emergencies; we inventory them, and have about 20 or 30 of them.
As for what will replace the married housing on those 29 acres, Hansen offers a couple possibilities.
“I don’t know what we’re going to do yet,” he says. “It could be housing, it could be condos for retired faculty. It’s right near our athletic complex, so we might be putting our new ice arena and volleyball combination in this site. We might take the site where our current ice arena is and turn into intramural fields, because we need more intramural fields for the students. We have a big intramural program—the students play each other until 2:00 or 3:00 or 4:00 in the morning.”
Below the Grate in North Dakota
A new residential development was being built in West Fargo, ND. George Sholy, owner of S&S Landscaping, explains, “In the initial part of the project, storm sewers were installed, and we put in inlet protection devices around the storm sewer. Some of this included silt fence around the pipe.
“Then after they got the curb and gutter in, we switched over to Dandy Curb Sacks. There have been other inlet protection devices that we’ve used, but the good thing about the Dandy Sack is that the bulk of it sits below the grate. The contractor said he really liked them because sometimes if they have dirt in the street, they can go along with the skid steer and clean up the curb. This Dandy Curb Sack was below the grate, but some of the inlet protections they had been using stood on top of the grate. When the skid steer came by, if they hit the inlet protection, it would have to be replaced.”
The site also included a pond to collect runoff. “We put in native plugs at the water line, then for the next layer we put in a straw coconut blanket, and we used native seed there. There was one more layer above that, which was a straw blanket that also had native seed.”
Sholy notes that Dandy Curb Sacks can often be reused. “It depends upon how rough the project is. Sometimes they only last one project, but sometimes you can use them a few times.”
The only challenge Sholy faced, he says, was the speed with which his crew had to work. “Once they got the storm sewer in, we had to be there. They called, and we were there the same day, putting in the temporary silt fence. Once they got the curb and the gutter in, we were there the next day putting in the Dandy Curb Sack. It had to be quick.”
Steve Goldberg writes on issues related to erosion control and the environment.