Effective July 1, 2003, the United States Environmental Protection Agency issued revised rules dealing with the National Pollutant Discharge Elimination System (NPDES) regulations explicitly for construction sites. Along with some specific additions and deletions to the permit areas covered—changes from the five-year construction general permits EPA issued in 1998—the new general permit has been broadened to cover sites as small as 1 ac., which was also a provision of NPDES Phase II. Construction sites smaller than 1 ac. also must obtain coverage if they’re part of a larger common plan of development or sale that totals at least 1 ac.; for example, if a developer improves a 20-ac. lot with roads, piping, and electricity with the intention of constructing homes, that site would be considered a “larger common plan of development or sale.” If for some reason the land is parceled off or sold and construction by separate, independent builders occurs on plots smaller than 1 ac., stormwater permits still would be required if these plots were included on the original site plan. Full text of the final NPDES general permit for stormwater discharges from construction activities is available online at www.epa.gov/fedreg/EPA-WATER/2003/July/Day-01/w16575.htm.
Wet basin with skimmerPerhaps on a smaller scale, the best management practices (BMPs) required for stormwater pollution prevention plans (SWPPPs) on plots smaller than 5 ac. are no different than those required for larger sites. Stabilization practices—the covering or maintaining of an existing cover over soil—still entail temporary or permanent seeding, mulching, sod stabilizing, installing vegetative buffer strips, contouring sensitive areas, and preserving existing trees. Structural practices—installing devices to divert, store, or limit runoff—include earth dikes or level spreaders, silt fences, drainage swales, sediment traps, check dams, subsurface and pipe slope drains, temporary storm drain diversions, storm drain inlet protection, and rock outlet protection. Did the Change Cause a Change?
“It’s creating more work,” says Russ Foster, vice president of Total Site Maintenance in Sacramento, CA. “More sites are coming under the regulations because of reduction in size from 5 to 1 acres. Mainly commercial jobs have now come under that umbrella; now they need SWPPPs. Maybe two to three years ago, those clients didn’t have to worry because [sites] were under 5 acres.”Foster’s clients have to meet state guidelines as well. “California follows EPA’s lead. Other jurisdictions—some counties and towns—run with the ball a bit more. Of course, many SWPPP regulations are site-specific too; if the site is on a creek, the regulations are stricter. In other places, you just make sure to keep sediment out of storm drains.”Stricter guidelines mean more inspections. “We’re definitely inspected more, both at the local government level—where they’ve hired more inspectors and are paying more attention, especially to target sites—and at the state and federal levels,” Foster says, adding that not all SWPPPs are created equal. “Each site is required to do one and to file a Notice of Intent, stating that they will abide by the rules. Some SWPPPs are extremely detailed—‘so many wattles here, blankets there, et cetera.’ However, others are basically a couple of paragraphs: ‘To be determined, as needed.'”The skimmer allows for drainage of the cleanest runoff first, allotting more time for sediments to settle.But even the most detailed SWPPP might require revision while the project is in the works. “A site under construction is like a living thing. The SWPPP needs to change as your site does,” Foster explains. “Inspectors look for that a lot. They’ll ask, ‘Did you make changes?’ We don’t have to make a new report, but inspectors will look for the plan in the site trailer to see if we’ve noted the changes. Most adaptations have to do with evolutions of the site. What you planned on paper might look good, but when you look at the geography of the site, you might have to change it.”For many of its projects, Total Site Maintenance uses Earth Saver wattles. “As a BMP, it’s the best product of its type,” Foster says. “We use them on slopes, on the back of walkways, on hillsides, and around drain inlets, manhole covers, and storm drains—usually at that time before you put the streets in. We’ll put crushed gravel around it. The wattles keep the gravel in place and out of the storm drains.”He adds, “Ninety percent of what we do is with straw wattles. We typically don’t use PAM [polyacrylamide], although sometimes on slopes we’ll broadcast straw, and maybe put some PAM in with the straw.”Total Site Maintenance has been using wattles for about six years. Before then, “we used nothing,” Foster says. “We didn’t have a need for them before that. We used rock bags around storm drains, but they did little to stop erosion elsewhere, except around the drains. The enforcement of stormwater programs has given us a need for wattles.”Although his firm might move them around on the site, they typically don’t move wattles from one site to another. “Usually by the time the job’s complete, the wattle has seen its life. Afterwards, we’ll compost the wattles; sometimes they’re broken up and landscaped over.”Brian Tillman, manager of Livermore, CA’s East Bay Environmental, also has seen increased activity since July 2003. “I’ve been doing more erosion control work—straw tack or hydroseeding—around home building sites. I think the smaller sites are being inspected more. Even on the bigger sites, the superintendents are checking their sites more often, filling out paperwork.”Automated stormwater testing stationEast Bay Environmental, a subsidiary of a large landscape company, furnishes erosion control services to a variety of customers. Tillman often is the first contractor who sees the site’s SWPPP. “All the developers I work with give their plans to me before I bid on the project. Some customers hire EC consultants who sometimes make the SWPPPs. If I disagree, I bring it to their attention, but most of the time they are right on. I have some customers who make their own SWPPPs. In those cases, I will go out and make recommendations based on my experience.” In terms of the BMPs the plans call for, Tillman comments, “Everything’s pretty common up here; along with wattles, we use bonded fiber matrixes on steeper slopes, and so far so good—everything’s holding up.”Tillman also uses Earth Saver wattles on most of his projects. “We put them behind walks or curbs and place them every 20 feet on hillsides, then hydroseed over them. We also use wattles as actual barriers—along creeks, for example. Those wattles behind sidewalks and other structures are taken away sooner or later; if they can be reused, we’ll stockpile them.”Although the wattles perform well for most of Tillman’s needs, there are times when he adds other products to the mix. “I use product combinations depending on site conditions. Sometimes I straw tack the site. Depending on the site, we also shoot bonded fiber matrix with our Finn HydroSeeder. It all depends on the site. Some of these BMPs might be not enough; some might be overkill, wasting customers’ money. I want to make my services the most cost-efficient for my customers.”Keeping Dirt Away From Water
No matter what size the site is, the main objective is to keep soils out of the site runoff and away from storm drains, rivers, and streams. Jim Gorter, erosion control division manager with KCI Environmental Inc. in San Luis Obispo, CA, has seen an increase in smaller jobs. “We’re often hydroseeding on smaller scales,” he says, adding that “the threat of being fined $50,000 is why they call us. Even those who were usually more conscientious—builders of one to three homes, for example—want us to come out to make sure they have enough silt fences. It’s better to be safe than sorry. After we go out a few times, they get the hang of it.”KCI Environmental consults with clients on erosion control procedures and often does the work on a site. “Normally an engineering firm comes up with the SWPPPs, which are approved by the county. The plans usually already are done by the time we’re called in. We just instruct them with implementation.” He says he selects BMPs according to “whatever specifications work for the site and whatever’s the cheapest.” He has, however, some favorite BMPs.“Blankets offer a greater degree of protection, due to their structure; hydroseeding alone is not sufficient. Erosion control blankets offer protection while the grasses grow through it. For example, in a water channel, once the water comes through, your hydroseeding will be washed away. A blanket keeps the seed there. Polyethylene and plastic blankets are often used in channel linings—they’re usually sold as ‘turf reinforcement’ or ‘channel lining’—the vegetation grows up through them.”Gorter explains his company’s procedures. “After hydroseeding, the blankets—we use Greenfix America and North American Green—are fastened down with U-shaped pins and wires 8 to 9 inches long. The biodegradable ones are left in place. We often use PAM in conjunction with the hydroseeding, but once it dissolves, it’s gone—that’s why you have the blanket.“Where you place your blankets depends on how the project is graded. On most slopes now, they’ll grade a ‘bench’—a flat area between slopes, which collects debris. When water collects there, you get a scouring situation; that’s where the blanket becomes a critical item. In some places you don’t need much protection, but sometimes a blanket is necessary. It depends on the site: How much rainfall does it get? What’s its soil type? Is it irrigated naturally or by a sprinkler? Caltrans [the California Department of Transportation] uses blankets and hydroseeding, and we do a lot of work for them. They’re always looking at the budget; is the blanket needed, and what’s the cost?“Every day it seems like more and more products are on the market,” Gorter concludes. “They’re all good if they’re used in a particular situation, but none of them is a cure-all for every situation. Even a blanket won’t fix it every time.”Flocculent pellets in wire baskets can be placed inside the drainage pipe to trap clay soils.Sediment Stays, Water Goes
Drainage is essential for any plot of land, but to minimize both erosion on-site and water pollution off-site, one has to make sure the water drains away and the soil stays. Erosion control instructor and technical consultant Eddie Snell of R.H. Moore & Associates in Tampa, FL, has used PAM for sediment control since the late 1990s when he was working at Walt Disney World in Orlando. “Disney was building a new timeshare resort on the site,” Snell explains. “We ended up having to dewater the site into an existing canal that empties into Village Lake, which is one of the park’s major amenities. Manmade Village Lake is used for sport fishing, and it’s also crossed several times daily by water taxis. During construction, we hit tough colloidal clay soil that wouldn’t work with the water at all. We certainly couldn’t let that mud go into the lake.“Along with a jute particle curtain, we used PAM during the [dewatering] pumping operation, and the turbidity of the water went from several hundred NTUs [nephelometric turbidity units] down to 15—and we only had to get it lower than 25 to put it into the lake!”Ensuring high water quality wasn’t the only benefit. “Using a particle curtain and PAM also helped us get ahead of our construction schedule because it allowed us to work even if we had rain.”Snell since has used PAM from Applied Polymer Systems (APS) of Woodstock, GA, on a variety of applications. “After my experience with it at Disney World, I tested PAM for another 18 months with the Florida Department of Transportation. I’ve used it for slope stabilization as a turbidity treatment and for demucking operations—PAM will dry the muck out, giving it a wet-sand consistency.”PAM is available in three basic forms: dry powder, concentrated liquid, or gel-block semisolid. “You use a different formula for different kinds of soil,” Snell says. “APS will batch the blend for what kind of soil you have. Their polymer is a combination of different materials, which creates a ‘molecule magnet’ for soils and sediment. The powder form is put directly on soil, or you can apply it to water.”According to Snell, not all PAM is created equal. “Other companies use the generic version that the US [Department of Agriculture] originally developed to save soil on farms, to hold down topsoil. However, on some applications, either this doesn’t work if you have the ‘wrong’ soil or you have to use 10 times more. We only use the amount we need for this temporary measure; with APS products, which are ‘food-grade’ materials, we use 5 to 10 pounds per acre to hold things in place until construction is done and permanent erosion controls are put in place. The PAM is then broken down by native soil bacteria and sunlight—and in sunny Florida this is a faster process—and the PAM is often taken up by plants.”Snell finds PAM easy to use. “You can apply it with almost any equipment; for the sugar-fine powder, we use spreader/seeder equipment. We have also put it in a leaf blower by duct-taping a funnel onto the blower and adding the PAM. This gives us a 50- to 100-foot spread. When we use PAM with mulch, the PAM will hold particles in place during fairly high runoff flows. In addition to properly installed BMPs, PAM offers a very powerful tool to get in and get the job done within the footprint of the project. You can keep your dirt on your site.”Keeping Water Away From Dirt
When working around a stream or a river, sometimes it’s easier—or necessary—to contain the water rather than the soil. “We’re getting ready to put riprap in the Chickahominy River. We have a T-wall to put in and have to put in riprap to hold it back,” explains Thomas Talley of English Construction in Richmond, VA. “We use Portadams as sediment containment; they keep debris from getting into the river, but they also keep the water away from us as we work on the site. We’re able to get our equipment behind it.”For some applications, one might use a turbidity curtain to hold back debris. Talley, however, who’s been using Portadams since 1985, believes the product does a much better job. “It attaches to the bottom of the river—you seal it to the river. In the past we had to use sheeting, but we couldn’t get it into the ground or the riverbed. The Portadam we’re using now is 270 feet long and about 25 feet wide, and we set it right in the middle of the riverbed where the water, on average, is about 6.5 feet deep.”When the riprap is completed, English Construction will remove the Portadam and return it to the manufacturer. Further runoff will be routed through 6-in. pumps into a filtration box and then run through straw bales so when it goes back into the river, the water is clean. With all these checks in place, Talley says, “we don’t have anything getting in the river.” Putting More “B” in BMP
Fine clay is the most difficult type of sediment to control. Not only does clay have much smaller particles than silt, sand, or loam soil does, but colloidal clays also have an electromagnetic (EM) charge, which makes them adhere to water, surfaces, workers’ boots, and so on. When left in a sediment basin, other soils settle to the bottom in a short period of time, but colloidal clays can take weeks or even months to settle out, meaning that the runoff, although it might meet regulations, still often looks more like gravy than water.Ray Smalling, P.E., CPESC, with Archer Engineers in Lee’s Summit, MO, often runs up against this clay problem. “Missouri’s Department of Natural Resources [MDNR] says you’re allowed to discharge 2.5 milliliters per liter per hour of settleable solids,” he explains. “If you have more sediment than that, you must modify, improve, or change your SWPPP.”Smalling explains the testing procedure: “Using a 1-liter sampling jar, you take a grab sample from drainage on-site and send it to the lab. The sample may look like gravy—the suspended-solids EPA test 160.2 is not regulated by MDNR—but you let it sit there an hour to let it settle. You can’t have more than 2.5 milliliters, or 2,500 parts per million, of total settlable solids. If you’re upstream from a significant natural resource, such as a cold, running stream—like a trout stream—the limit is lowered to 0.5 milliliter per liter per hour.”EPA’s 160.2 method is actually designed for coarse silt and larger particles, Smalling says. Silt tends to stay in suspension. MDNR uses an Emhoff cone test to determine the total sediment; the Emhoff cone is a clear, cone-shaped jar with markings to indicate the amount of sediment present. “MDNR doesn’t regulate clays and fine silts since they will not settle out in the one-hour test,” Smalling goes on. “So you can have this chocolate milk–looking water going downstream, and you can still pass your test. However, that doesn’t mean that just because you’re meeting the guidelines, you’re entirely in the clear; developers who are doing testing are doing so to have a defense from a lake community downstream, which typically [can be] very litigious. I have clients who are on both sides of this fence—developers and lake communities—so I am well aware of everyone’s concerns.”MDNR requires installation of sediment basins for projects disturbing more than 10 ac. “That may be a common practice in the greater Kansas City area, but the common dewatering method is to outlet temporary runoff to a perforated standpipe—a corrugated metal pipe that has holes punched in it every 6 inches—which is surrounded by gravel, much like a French drain. When you put in a sediment basin, the best practice is to place this sediment basin at the same place where you will make the permanent detention basin. The common practice is to impound 3,600 cubic feet of volume per tributary acre running to it—a figure determined by capturing 1 inch of runoff per acre.”Smalling maintains, however, that the perforated standpipe isn’t the ideal method for dewatering a sediment basin during construction and might not allow a developer to meet MDNR’s requirements. “Like a bucket with holes in it, the hole on the bottom will have the most discharge. And since gravity pulls the sediment to the bottom, the pipe is discharging the dirtiest water first. Yet this procedure can remove up to 85% of sediment coming to this basin,” he says. “With clays, though, that remaining 15% is a visual problem. So what’s the better mousetrap?” He often recommends a skimmer to ensure that the cleanest water—that on the top—is discharged first. “My current favorite is the JW Faircloth Skimmer, a PVC ring with a crossbar, which has holes in it, and a vent.”The skimmer floats on the surface of the sediment basin and should be sized to dewater a full basin in seven days, via a flexible pipe. This allows seven days for sediment to settle to the bottom. Studies at Penn State (Millen et al., 1996) found that a skimmer can remove up to 95% of sediment—”a marked improvement,” notes Smalling. “You’re really doing the best job, discharging the cleanest water first, and [doing it] over seven days—rather than using a standpipe, which does this in two to three days.”Albert R. Jarrett, P.E., PLS, a professor of agricultural engineering at Penn State, gives more details. “We’ve used the Faircloth Skimmer in about a half dozen studies here. Joe Millen, then a grad student, did initial studies in 1996. We then heard from Warren Faircloth, the skimmer’s inventor. He’d seen Millen’s study and asked if we would do further research to determine the skimmer’s effectiveness. We already had data on perforated risers, which are a standard of the industry; risers capture about 80% of sediment in a one-day dewatering time—by the end of 24 hours the water will be emptied. Using the same parameters as that study, with Faircloth’s skimmer we got 90% sediment capture. This was such a considerable improvement that Pennsylvania has adopted the skimmer technology as a BMP.”Jarrett still is experimenting with the device. “We’ve done other things with it, such as adding a gadget to the skimmer, which delays the releasing pipe. With this solar-driven electromagnetic valve, we have pushed sediment capture up to 92 to 98%. Even as it stands now, without the EM valve, the skimmer is a pretty reliable, useful technology.”This lush landscape is a sediment basin.Warren Faircloth invented his device to solve problems he faced during 18 years in erosion control in Orange County, NC. “Small basins are the nature of the development—I’d been experimenting with ways to improve how they work well. Because outlet structures usually aren’t designed to let the sediment settle out, I thought maybe draining from the top could solve that problem. I would make skimmers of various designs, then convince contractors to install them so I’d learn what works. I had to make sure the skimmers were practical devices, to make sure contractors would use them. I read an article by one of Jarrett’s students who was trying to design something similar. I’d received a research grant from North Carolina to test my device, so I contacted Penn State and asked if Jarrett and his students would test it.”Faircloth, who calls himself “both CEO and custodian” of his one-man operation, constructs his skimmers himself. “Originally I planned to sell only the designs, but now I’m making them myself. I didn’t want to take the chance that people would make one and cut corners, then be mad when the device didn’t work.”He cautions, “The basin has to be properly sized and shaped to work, and it only makes common sense to drain from the top where the cleaner water is. This is the better way to build a sediment basin; however, it doesn’t work well with clay soils because they don’t settle out as fast as other soils.”Second Steps to Solve Problems With Clay Soil
Smalling knew the skimmer’s limitations; however, working in a state of clay soils, he was determined to do something about it. “Stokes’s Law quantifies the settling velocity of small particles accelerated by gravity but slowed by the drag force of water. Particles greater than 0.0012 millimeter [1.2 microns] in diameter can be settled out of a 10-foot-high water column over the seven-day design dewatering time per Stokes’s Law. Finer particles lower in the water column can also be settled out. To compare, a grain of sand is 1 millimeter, and since there are a thousand microns in a millimeter, you’re talking about a difference between, say, a yardstick and the period at the end of a sentence. But this still leaves the colloid fine clays, which have an EM charge. The particles repel each other like a balloon charged with static electricity that sticks to the wall rather than falls to the power of gravity. Now, using the skimmer, you can meet MDNR’s 2.5-milliliter-per-liter-per-hour release rate, but you still have ‘chocolate milk’ for discharge to whatever recipient, due to colloidal action.” That means that while the developer or contractor might have met MDNR’s guidelines to the letter, downstream neighbors seeing the muddy-looking water might still object—possibly, as happens more and more frequently, with a lawsuit. Cf505 sediment control tablets in basket inside pipeTo trap the clay sediments and improve the appearance of the discharge, another step is needed. “That’s where PAMs come into play,” Smalling explains. Several types are available from companies, including Atlanta, GA–based Applied Polymer Systems, which makes Floc Log; Construction Fabrics & Materials (CFM) in Cottage Grove, WI; and Redmond, WA–based Natural Site Solutions, which sells chitosan. “Any of these products has a dosing rate,” Smalling notes. “With stormwater, how do you properly dose the flow? It rains; you get runoff, which peaks and falls off. It’s hard to dose stormwater unless you meter it in some way. “If you use a skimmer, you can quantify how much water is being discharged,” Smalling goes on. “For example, the 6-inch skimmer discharges 0.6 cubic feet per second, which is equal to about 260 gallons per minute. Now we have a device dewatering the cleanest water off of the top, and we have a constant flow; we can properly size our flocculent and can dose the flow to clean it up. We can ask our PAM supplier, ‘I have 260 [gallons per minute]; how much product do I need?’ In the past, at a higher rate I would use hundreds of pounds of PAM; the water rate would be overdosed when the water was lower than its peak. But if I dose flocculent at the output of the skimmer, I know the flow rate—now less than 1 cubic foot per second.”“Turn Gravy Into Chardonnay”
Smalling places flocculents where the skimmer empties into a discharge pipe. “I can affix flocculent to a 15-inch-diameter [high-density polyethylene] pipe and attach that to the skimmer pipe. This can be accomplished about three different ways. CFM will send you wire-mesh minnow or crawfish traps in which you’ll place CFM’s CF 500 PAM product, sold in 2-inch-diameter pellets. You can also use Floc Logs or chitosan. You’ll need to figure how many mesh traps or logs to put into or connect with the pipes.”In addition to being dosed correctly, a flocculent requires movement to allow it to mix, and then the water must be allowed to settle, such as in another sediment basin. Another option, says Smalling, is to use ground-up wood from the site to create windrows about 5 ft. high and 12 ft. wide at the base. “These are not really pretty but useful. Why burn those scrap trees when it’s cheaper to mulch and use them?”The flocculent, with its positive electromagnetic charge, attracts the negatively charged particles of silt and clay. “We can turn gravy into Chardonnay,” says Smalling. Not just any PAM will do, however. He recommends anionic PAM, rather than cationic PAM, which is commonly used in wastewater treatment plants. “Cationic PAM is harmful to fish and others if you don’t use it properly; that’s why wastewater treatment plants need to have several extra processes later to remove it before final discharge. Anionic PAM is safe for the environment. Once it attaches to soil, it drops to the bottom of sediment traps. It’s safe to have full-body contact with water flow downstream, but you need to work with the manufacturer’s rep to get the correct dosing rates.”Smalling, who has been using this process since July 2002, believes he is the only engineer in the Kansas City area currently doing so. “I seem to be the pioneer in the area for using PAM and reusable skimmers.”What about other sediment controls? “I will use sediment fence at the bottom of a hill, but only with 100 feet of flow. I use skimmers in all sediment basins for up to 100-acre areas disturbed at one time. You get the best rate and performance from contractors by allowing them to work in large areas since they don’t want to be bound by miles and miles of sediment fence. How can they work in that environment? To illustrate, sediment fence works like a coffee filter. How well does that filter keep coffee from being black? It doesn’t. In the same way, sediment fence lets some sediment through.”
“It’s creating more work,” says Russ Foster, vice president of Total Site Maintenance in Sacramento, CA. “More sites are coming under the regulations because of reduction in size from 5 to 1 acres. Mainly commercial jobs have now come under that umbrella; now they need SWPPPs. Maybe two to three years ago, those clients didn’t have to worry because [sites] were under 5 acres.”Foster’s clients have to meet state guidelines as well. “California follows EPA’s lead. Other jurisdictions—some counties and towns—run with the ball a bit more. Of course, many SWPPP regulations are site-specific too; if the site is on a creek, the regulations are stricter. In other places, you just make sure to keep sediment out of storm drains.”Stricter guidelines mean more inspections. “We’re definitely inspected more, both at the local government level—where they’ve hired more inspectors and are paying more attention, especially to target sites—and at the state and federal levels,” Foster says, adding that not all SWPPPs are created equal. “Each site is required to do one and to file a Notice of Intent, stating that they will abide by the rules. Some SWPPPs are extremely detailed—‘so many wattles here, blankets there, et cetera.’ However, others are basically a couple of paragraphs: ‘To be determined, as needed.'”The skimmer allows for drainage of the cleanest runoff first, allotting more time for sediments to settle.But even the most detailed SWPPP might require revision while the project is in the works. “A site under construction is like a living thing. The SWPPP needs to change as your site does,” Foster explains. “Inspectors look for that a lot. They’ll ask, ‘Did you make changes?’ We don’t have to make a new report, but inspectors will look for the plan in the site trailer to see if we’ve noted the changes. Most adaptations have to do with evolutions of the site. What you planned on paper might look good, but when you look at the geography of the site, you might have to change it.”For many of its projects, Total Site Maintenance uses Earth Saver wattles. “As a BMP, it’s the best product of its type,” Foster says. “We use them on slopes, on the back of walkways, on hillsides, and around drain inlets, manhole covers, and storm drains—usually at that time before you put the streets in. We’ll put crushed gravel around it. The wattles keep the gravel in place and out of the storm drains.”He adds, “Ninety percent of what we do is with straw wattles. We typically don’t use PAM [polyacrylamide], although sometimes on slopes we’ll broadcast straw, and maybe put some PAM in with the straw.”Total Site Maintenance has been using wattles for about six years. Before then, “we used nothing,” Foster says. “We didn’t have a need for them before that. We used rock bags around storm drains, but they did little to stop erosion elsewhere, except around the drains. The enforcement of stormwater programs has given us a need for wattles.”Although his firm might move them around on the site, they typically don’t move wattles from one site to another. “Usually by the time the job’s complete, the wattle has seen its life. Afterwards, we’ll compost the wattles; sometimes they’re broken up and landscaped over.”Brian Tillman, manager of Livermore, CA’s East Bay Environmental, also has seen increased activity since July 2003. “I’ve been doing more erosion control work—straw tack or hydroseeding—around home building sites. I think the smaller sites are being inspected more. Even on the bigger sites, the superintendents are checking their sites more often, filling out paperwork.”Automated stormwater testing stationEast Bay Environmental, a subsidiary of a large landscape company, furnishes erosion control services to a variety of customers. Tillman often is the first contractor who sees the site’s SWPPP. “All the developers I work with give their plans to me before I bid on the project. Some customers hire EC consultants who sometimes make the SWPPPs. If I disagree, I bring it to their attention, but most of the time they are right on. I have some customers who make their own SWPPPs. In those cases, I will go out and make recommendations based on my experience.” In terms of the BMPs the plans call for, Tillman comments, “Everything’s pretty common up here; along with wattles, we use bonded fiber matrixes on steeper slopes, and so far so good—everything’s holding up.”Tillman also uses Earth Saver wattles on most of his projects. “We put them behind walks or curbs and place them every 20 feet on hillsides, then hydroseed over them. We also use wattles as actual barriers—along creeks, for example. Those wattles behind sidewalks and other structures are taken away sooner or later; if they can be reused, we’ll stockpile them.”Although the wattles perform well for most of Tillman’s needs, there are times when he adds other products to the mix. “I use product combinations depending on site conditions. Sometimes I straw tack the site. Depending on the site, we also shoot bonded fiber matrix with our Finn HydroSeeder. It all depends on the site. Some of these BMPs might be not enough; some might be overkill, wasting customers’ money. I want to make my services the most cost-efficient for my customers.”Keeping Dirt Away From Water
No matter what size the site is, the main objective is to keep soils out of the site runoff and away from storm drains, rivers, and streams. Jim Gorter, erosion control division manager with KCI Environmental Inc. in San Luis Obispo, CA, has seen an increase in smaller jobs. “We’re often hydroseeding on smaller scales,” he says, adding that “the threat of being fined $50,000 is why they call us. Even those who were usually more conscientious—builders of one to three homes, for example—want us to come out to make sure they have enough silt fences. It’s better to be safe than sorry. After we go out a few times, they get the hang of it.”KCI Environmental consults with clients on erosion control procedures and often does the work on a site. “Normally an engineering firm comes up with the SWPPPs, which are approved by the county. The plans usually already are done by the time we’re called in. We just instruct them with implementation.” He says he selects BMPs according to “whatever specifications work for the site and whatever’s the cheapest.” He has, however, some favorite BMPs.“Blankets offer a greater degree of protection, due to their structure; hydroseeding alone is not sufficient. Erosion control blankets offer protection while the grasses grow through it. For example, in a water channel, once the water comes through, your hydroseeding will be washed away. A blanket keeps the seed there. Polyethylene and plastic blankets are often used in channel linings—they’re usually sold as ‘turf reinforcement’ or ‘channel lining’—the vegetation grows up through them.”Gorter explains his company’s procedures. “After hydroseeding, the blankets—we use Greenfix America and North American Green—are fastened down with U-shaped pins and wires 8 to 9 inches long. The biodegradable ones are left in place. We often use PAM in conjunction with the hydroseeding, but once it dissolves, it’s gone—that’s why you have the blanket.“Where you place your blankets depends on how the project is graded. On most slopes now, they’ll grade a ‘bench’—a flat area between slopes, which collects debris. When water collects there, you get a scouring situation; that’s where the blanket becomes a critical item. In some places you don’t need much protection, but sometimes a blanket is necessary. It depends on the site: How much rainfall does it get? What’s its soil type? Is it irrigated naturally or by a sprinkler? Caltrans [the California Department of Transportation] uses blankets and hydroseeding, and we do a lot of work for them. They’re always looking at the budget; is the blanket needed, and what’s the cost?“Every day it seems like more and more products are on the market,” Gorter concludes. “They’re all good if they’re used in a particular situation, but none of them is a cure-all for every situation. Even a blanket won’t fix it every time.”Flocculent pellets in wire baskets can be placed inside the drainage pipe to trap clay soils.Sediment Stays, Water Goes
Drainage is essential for any plot of land, but to minimize both erosion on-site and water pollution off-site, one has to make sure the water drains away and the soil stays. Erosion control instructor and technical consultant Eddie Snell of R.H. Moore & Associates in Tampa, FL, has used PAM for sediment control since the late 1990s when he was working at Walt Disney World in Orlando. “Disney was building a new timeshare resort on the site,” Snell explains. “We ended up having to dewater the site into an existing canal that empties into Village Lake, which is one of the park’s major amenities. Manmade Village Lake is used for sport fishing, and it’s also crossed several times daily by water taxis. During construction, we hit tough colloidal clay soil that wouldn’t work with the water at all. We certainly couldn’t let that mud go into the lake.“Along with a jute particle curtain, we used PAM during the [dewatering] pumping operation, and the turbidity of the water went from several hundred NTUs [nephelometric turbidity units] down to 15—and we only had to get it lower than 25 to put it into the lake!”Ensuring high water quality wasn’t the only benefit. “Using a particle curtain and PAM also helped us get ahead of our construction schedule because it allowed us to work even if we had rain.”Snell since has used PAM from Applied Polymer Systems (APS) of Woodstock, GA, on a variety of applications. “After my experience with it at Disney World, I tested PAM for another 18 months with the Florida Department of Transportation. I’ve used it for slope stabilization as a turbidity treatment and for demucking operations—PAM will dry the muck out, giving it a wet-sand consistency.”PAM is available in three basic forms: dry powder, concentrated liquid, or gel-block semisolid. “You use a different formula for different kinds of soil,” Snell says. “APS will batch the blend for what kind of soil you have. Their polymer is a combination of different materials, which creates a ‘molecule magnet’ for soils and sediment. The powder form is put directly on soil, or you can apply it to water.”According to Snell, not all PAM is created equal. “Other companies use the generic version that the US [Department of Agriculture] originally developed to save soil on farms, to hold down topsoil. However, on some applications, either this doesn’t work if you have the ‘wrong’ soil or you have to use 10 times more. We only use the amount we need for this temporary measure; with APS products, which are ‘food-grade’ materials, we use 5 to 10 pounds per acre to hold things in place until construction is done and permanent erosion controls are put in place. The PAM is then broken down by native soil bacteria and sunlight—and in sunny Florida this is a faster process—and the PAM is often taken up by plants.”Snell finds PAM easy to use. “You can apply it with almost any equipment; for the sugar-fine powder, we use spreader/seeder equipment. We have also put it in a leaf blower by duct-taping a funnel onto the blower and adding the PAM. This gives us a 50- to 100-foot spread. When we use PAM with mulch, the PAM will hold particles in place during fairly high runoff flows. In addition to properly installed BMPs, PAM offers a very powerful tool to get in and get the job done within the footprint of the project. You can keep your dirt on your site.”Keeping Water Away From Dirt
When working around a stream or a river, sometimes it’s easier—or necessary—to contain the water rather than the soil. “We’re getting ready to put riprap in the Chickahominy River. We have a T-wall to put in and have to put in riprap to hold it back,” explains Thomas Talley of English Construction in Richmond, VA. “We use Portadams as sediment containment; they keep debris from getting into the river, but they also keep the water away from us as we work on the site. We’re able to get our equipment behind it.”For some applications, one might use a turbidity curtain to hold back debris. Talley, however, who’s been using Portadams since 1985, believes the product does a much better job. “It attaches to the bottom of the river—you seal it to the river. In the past we had to use sheeting, but we couldn’t get it into the ground or the riverbed. The Portadam we’re using now is 270 feet long and about 25 feet wide, and we set it right in the middle of the riverbed where the water, on average, is about 6.5 feet deep.”When the riprap is completed, English Construction will remove the Portadam and return it to the manufacturer. Further runoff will be routed through 6-in. pumps into a filtration box and then run through straw bales so when it goes back into the river, the water is clean. With all these checks in place, Talley says, “we don’t have anything getting in the river.” Putting More “B” in BMP
Fine clay is the most difficult type of sediment to control. Not only does clay have much smaller particles than silt, sand, or loam soil does, but colloidal clays also have an electromagnetic (EM) charge, which makes them adhere to water, surfaces, workers’ boots, and so on. When left in a sediment basin, other soils settle to the bottom in a short period of time, but colloidal clays can take weeks or even months to settle out, meaning that the runoff, although it might meet regulations, still often looks more like gravy than water.Ray Smalling, P.E., CPESC, with Archer Engineers in Lee’s Summit, MO, often runs up against this clay problem. “Missouri’s Department of Natural Resources [MDNR] says you’re allowed to discharge 2.5 milliliters per liter per hour of settleable solids,” he explains. “If you have more sediment than that, you must modify, improve, or change your SWPPP.”Smalling explains the testing procedure: “Using a 1-liter sampling jar, you take a grab sample from drainage on-site and send it to the lab. The sample may look like gravy—the suspended-solids EPA test 160.2 is not regulated by MDNR—but you let it sit there an hour to let it settle. You can’t have more than 2.5 milliliters, or 2,500 parts per million, of total settlable solids. If you’re upstream from a significant natural resource, such as a cold, running stream—like a trout stream—the limit is lowered to 0.5 milliliter per liter per hour.”EPA’s 160.2 method is actually designed for coarse silt and larger particles, Smalling says. Silt tends to stay in suspension. MDNR uses an Emhoff cone test to determine the total sediment; the Emhoff cone is a clear, cone-shaped jar with markings to indicate the amount of sediment present. “MDNR doesn’t regulate clays and fine silts since they will not settle out in the one-hour test,” Smalling goes on. “So you can have this chocolate milk–looking water going downstream, and you can still pass your test. However, that doesn’t mean that just because you’re meeting the guidelines, you’re entirely in the clear; developers who are doing testing are doing so to have a defense from a lake community downstream, which typically [can be] very litigious. I have clients who are on both sides of this fence—developers and lake communities—so I am well aware of everyone’s concerns.”MDNR requires installation of sediment basins for projects disturbing more than 10 ac. “That may be a common practice in the greater Kansas City area, but the common dewatering method is to outlet temporary runoff to a perforated standpipe—a corrugated metal pipe that has holes punched in it every 6 inches—which is surrounded by gravel, much like a French drain. When you put in a sediment basin, the best practice is to place this sediment basin at the same place where you will make the permanent detention basin. The common practice is to impound 3,600 cubic feet of volume per tributary acre running to it—a figure determined by capturing 1 inch of runoff per acre.”Smalling maintains, however, that the perforated standpipe isn’t the ideal method for dewatering a sediment basin during construction and might not allow a developer to meet MDNR’s requirements. “Like a bucket with holes in it, the hole on the bottom will have the most discharge. And since gravity pulls the sediment to the bottom, the pipe is discharging the dirtiest water first. Yet this procedure can remove up to 85% of sediment coming to this basin,” he says. “With clays, though, that remaining 15% is a visual problem. So what’s the better mousetrap?” He often recommends a skimmer to ensure that the cleanest water—that on the top—is discharged first. “My current favorite is the JW Faircloth Skimmer, a PVC ring with a crossbar, which has holes in it, and a vent.”The skimmer floats on the surface of the sediment basin and should be sized to dewater a full basin in seven days, via a flexible pipe. This allows seven days for sediment to settle to the bottom. Studies at Penn State (Millen et al., 1996) found that a skimmer can remove up to 95% of sediment—”a marked improvement,” notes Smalling. “You’re really doing the best job, discharging the cleanest water first, and [doing it] over seven days—rather than using a standpipe, which does this in two to three days.”Albert R. Jarrett, P.E., PLS, a professor of agricultural engineering at Penn State, gives more details. “We’ve used the Faircloth Skimmer in about a half dozen studies here. Joe Millen, then a grad student, did initial studies in 1996. We then heard from Warren Faircloth, the skimmer’s inventor. He’d seen Millen’s study and asked if we would do further research to determine the skimmer’s effectiveness. We already had data on perforated risers, which are a standard of the industry; risers capture about 80% of sediment in a one-day dewatering time—by the end of 24 hours the water will be emptied. Using the same parameters as that study, with Faircloth’s skimmer we got 90% sediment capture. This was such a considerable improvement that Pennsylvania has adopted the skimmer technology as a BMP.”Jarrett still is experimenting with the device. “We’ve done other things with it, such as adding a gadget to the skimmer, which delays the releasing pipe. With this solar-driven electromagnetic valve, we have pushed sediment capture up to 92 to 98%. Even as it stands now, without the EM valve, the skimmer is a pretty reliable, useful technology.”This lush landscape is a sediment basin.Warren Faircloth invented his device to solve problems he faced during 18 years in erosion control in Orange County, NC. “Small basins are the nature of the development—I’d been experimenting with ways to improve how they work well. Because outlet structures usually aren’t designed to let the sediment settle out, I thought maybe draining from the top could solve that problem. I would make skimmers of various designs, then convince contractors to install them so I’d learn what works. I had to make sure the skimmers were practical devices, to make sure contractors would use them. I read an article by one of Jarrett’s students who was trying to design something similar. I’d received a research grant from North Carolina to test my device, so I contacted Penn State and asked if Jarrett and his students would test it.”Faircloth, who calls himself “both CEO and custodian” of his one-man operation, constructs his skimmers himself. “Originally I planned to sell only the designs, but now I’m making them myself. I didn’t want to take the chance that people would make one and cut corners, then be mad when the device didn’t work.”He cautions, “The basin has to be properly sized and shaped to work, and it only makes common sense to drain from the top where the cleaner water is. This is the better way to build a sediment basin; however, it doesn’t work well with clay soils because they don’t settle out as fast as other soils.”Second Steps to Solve Problems With Clay Soil
Smalling knew the skimmer’s limitations; however, working in a state of clay soils, he was determined to do something about it. “Stokes’s Law quantifies the settling velocity of small particles accelerated by gravity but slowed by the drag force of water. Particles greater than 0.0012 millimeter [1.2 microns] in diameter can be settled out of a 10-foot-high water column over the seven-day design dewatering time per Stokes’s Law. Finer particles lower in the water column can also be settled out. To compare, a grain of sand is 1 millimeter, and since there are a thousand microns in a millimeter, you’re talking about a difference between, say, a yardstick and the period at the end of a sentence. But this still leaves the colloid fine clays, which have an EM charge. The particles repel each other like a balloon charged with static electricity that sticks to the wall rather than falls to the power of gravity. Now, using the skimmer, you can meet MDNR’s 2.5-milliliter-per-liter-per-hour release rate, but you still have ‘chocolate milk’ for discharge to whatever recipient, due to colloidal action.” That means that while the developer or contractor might have met MDNR’s guidelines to the letter, downstream neighbors seeing the muddy-looking water might still object—possibly, as happens more and more frequently, with a lawsuit. Cf505 sediment control tablets in basket inside pipeTo trap the clay sediments and improve the appearance of the discharge, another step is needed. “That’s where PAMs come into play,” Smalling explains. Several types are available from companies, including Atlanta, GA–based Applied Polymer Systems, which makes Floc Log; Construction Fabrics & Materials (CFM) in Cottage Grove, WI; and Redmond, WA–based Natural Site Solutions, which sells chitosan. “Any of these products has a dosing rate,” Smalling notes. “With stormwater, how do you properly dose the flow? It rains; you get runoff, which peaks and falls off. It’s hard to dose stormwater unless you meter it in some way. “If you use a skimmer, you can quantify how much water is being discharged,” Smalling goes on. “For example, the 6-inch skimmer discharges 0.6 cubic feet per second, which is equal to about 260 gallons per minute. Now we have a device dewatering the cleanest water off of the top, and we have a constant flow; we can properly size our flocculent and can dose the flow to clean it up. We can ask our PAM supplier, ‘I have 260 [gallons per minute]; how much product do I need?’ In the past, at a higher rate I would use hundreds of pounds of PAM; the water rate would be overdosed when the water was lower than its peak. But if I dose flocculent at the output of the skimmer, I know the flow rate—now less than 1 cubic foot per second.”“Turn Gravy Into Chardonnay”
Smalling places flocculents where the skimmer empties into a discharge pipe. “I can affix flocculent to a 15-inch-diameter [high-density polyethylene] pipe and attach that to the skimmer pipe. This can be accomplished about three different ways. CFM will send you wire-mesh minnow or crawfish traps in which you’ll place CFM’s CF 500 PAM product, sold in 2-inch-diameter pellets. You can also use Floc Logs or chitosan. You’ll need to figure how many mesh traps or logs to put into or connect with the pipes.”In addition to being dosed correctly, a flocculent requires movement to allow it to mix, and then the water must be allowed to settle, such as in another sediment basin. Another option, says Smalling, is to use ground-up wood from the site to create windrows about 5 ft. high and 12 ft. wide at the base. “These are not really pretty but useful. Why burn those scrap trees when it’s cheaper to mulch and use them?”The flocculent, with its positive electromagnetic charge, attracts the negatively charged particles of silt and clay. “We can turn gravy into Chardonnay,” says Smalling. Not just any PAM will do, however. He recommends anionic PAM, rather than cationic PAM, which is commonly used in wastewater treatment plants. “Cationic PAM is harmful to fish and others if you don’t use it properly; that’s why wastewater treatment plants need to have several extra processes later to remove it before final discharge. Anionic PAM is safe for the environment. Once it attaches to soil, it drops to the bottom of sediment traps. It’s safe to have full-body contact with water flow downstream, but you need to work with the manufacturer’s rep to get the correct dosing rates.”Smalling, who has been using this process since July 2002, believes he is the only engineer in the Kansas City area currently doing so. “I seem to be the pioneer in the area for using PAM and reusable skimmers.”What about other sediment controls? “I will use sediment fence at the bottom of a hill, but only with 100 feet of flow. I use skimmers in all sediment basins for up to 100-acre areas disturbed at one time. You get the best rate and performance from contractors by allowing them to work in large areas since they don’t want to be bound by miles and miles of sediment fence. How can they work in that environment? To illustrate, sediment fence works like a coffee filter. How well does that filter keep coffee from being black? It doesn’t. In the same way, sediment fence lets some sediment through.”
He notes that for about the same cost as 1,250 ft. of silt fence, a contractor can purchase the materials to use in a sediment basin. The reusable skimmers can range from about $500 to $1,600. “Say you’ll u
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Andrea Weissenbuehler
