Inlets: Collect Water, Nothing Else

May 1, 2011

In a perfect world, all your jobs would go smoothly. None of your crew would get sick, no equipment would break down, and all needed supplies would arrive on time, in good condition. Most importantly, the weather would cooperate; there wouldn’t be a drop of rain until all earthmoving was finished and your vegetation had been seeded.

Then there’d be a gentle rain to give your seeds just enough moisture to germinate, grow, and hold onto the soil.

But it’s an imperfect world, and nothing, especially the weather, fully cooperates. That’s why there are so many best management practices (BMPs) available to trap or block sediment from getting into stormwater systems. Inlets and drains are of crucial importance; because they’re designed to collect water, everything else that can get into water, such as litter, ends up being collected as well.

Grab It at the Grate
After you’ve taken care to avoid erosion, curb and yard inlets are the “last line of defense.” Many devices have been invented to capture sediment and trash before they get into storm drain systems. Environmental manager Rebecca Hersey of Chesapeake, VA’s Vico Construction Corp. works in an area dotted with natural wetlands that must be protected; she uses a variety of BMPs to accomplish her goals.

“Vico does a combination of every kind of project-residential, commercial, city, and capital improvement projects,” she says. “We do grading, and we install underground utilities like storm pipes and gas lines. Often, we’ll also do roadwork, sidewalks, and aprons; we’re on some projects from the beginning almost to the end. As we work, we’re trying to protect wetlands in our region. We’re very conscious of anything that could get into creeks and other natural waterways. No matter where drainage water goes, it passes through a series of filtrations.”

Digging a temporary basin is often a first step. “These can later be turned into BMPs or lakes. Sometimes they’re really temporary; we’ll fill them in and make them appear like a natural area. It all depends on what state the project is in. Once everything is complete and we’re seeding the site, we might put down straw mats or erosion control blankets. These mats are to prevent the erosion from occurring, while also keeping moisture in to get vegetation growing.”

Permanent sediment basins often have yard drains in the center. “We’ll put a silt fence around those and also cover them with GrateGators,” she explains. “The inlet protection stays in place until the site’s final stabilization.”

GrateGator, from ACF Environmental of Richmond, VA, is an “above-the-grate” filter designed to prevent sediment and debris from entering the stormwater system. GrateGator easily slides over grate edges, creating a filter that won’t move, as the grate’s weight holds it in place. Also available in custom sizes, the low-profile GrateGator can be cleaned and reused over the life of a project.

“We use GrateGators all over, on D-1s or yard drains,” Hersey says. “They don’t break, they’re easy to clean and maintain, and, because they’re bright yellow, they’re easy to see, so we can avoid driving over them. They stay in place until I have vegetation behind my curb. They stop sediment from getting in, although water easily filters through.”

Because they’re reusable, the GrateGators have to be cleaned from time to time. “You do have to maintain them, clean them,” she goes on. “But they’ve been designed for easy cleaning. They contain four screens. One side of the GrateGator is sewn; the other three sides are Velcroed, so we can open them up, spray them out, and make sure they’re clean. Sometimes you can open them and pop back the sediment behind the curb. With any product, you have to maintain it, but because GrateGator has elastic on the bottom, we don’t have to mess with a drawstring closure, and crews don’t have to take them all the way off to make sure they’re working properly.”

On a typical job, Hersey uses a variety of sediment controls: silt fence, straw matting, and the GrateGators. “I’ve also started using ACF’s GutterEel, a long gutter pan. The ACF guys will custom-size GrateGators-although 30 inches by 30 inches is standard, they’ve made me 24- and 18-inch-square models. And although the bright yellow is the standard color, on a government job I once did, I couldn’t use yellow, so ACF produced GrateGators with silver over-bags.”

Maintenance is key to any successful project, she emphasizes. “You have to understand how the catch basin’s been installed. Look at the specs; see how it has to be installed.”

Her firm also does dewatering operations. “When dewatering ponds to work on them, we use sediment bags. We’ll build a 10-foot-by-10-foot basin, build a berm around it, place sediment bags into it, then pump the water into the bags, so they’ll catch the sediment. We’ll also have a rock check dam on one wall, so the water is actually filtered twice. How long this will take us depends on how much sediment is in the pond. Does the sediment basin cover the whole lake? Well, you’d want to prevent anything going in, in the first place-that’s why we take so many precautions.”

During such a process, sediment, influent, and effluent are monitored. “After any substantial rainfall, you have to make sure your sediment bags, pumps, and so on are working properly. You can’t leave something and not pay attention to it. You can end up with a mess.”

Hersey tracks storms in her area. “I actually track the storms on my laptop. By doing this, I know which job sites I have to go to first, to see what impact the rain is having. If it’s a light rain, I can see the BMPs working; I then know that with X amount of rain, things are working well. As weather can vary from area to area, if I see a job site that received a heavier rainfall, I know I need to get a crew in there to make sure nothing bad is happening. Every month Vico has a safety meeting; that’s my chance to update the crews. For example: “˜We had a lot of rain, here’s what we’re looking for’-and then, they’re looking, too. I tell them, “˜If you see something, call me; we’ll correct it.’ To do this job right, you have to have everyone working together. People can’t think, “˜That’s not my job.”

Her work as an environmental manager has an impact on her entire life. “I just happened to fall into his field by chance, but, with my love of the outdoors, it’s a natural fit for me. Also, my dad had been in construction for years; I have to give him a lot of credit for the common-sense way I approach things. The job I do is dear to my heart because I like to fish. We have to take care of the water, to take care of the fish. The Chesapeake Bay area is very concerned about its blue crabs; most municipalities have educated the public about proper use of fertilizers, and about not putting stuff into storm drains. I used to work for one of the cities, so I do see the other side of the fence.

“The rules of the game are changing, because people are more concerned with environment,” she continues. “As far as technology goes, that’s changing too, and for the better-we can now do so much more about keeping water clear. Vico Construction does all it can do to accomplish this. We’re trying to put our best foot forward out in the community. But my job is that of a leader-everyone on the crew must work together to reach these goals. Environmental education has to start with the guy with the shovel in his hand.”

Filter Out Debris, and Cost Savings Filter In
Debris in stormwater causes more than pollution; collect enough sediment, fast-food containers, and various trash in an inlet or pipe, and a blockage can occur. Then, there’s usually only one solution: It has to be cleaned out, by hand.

“In the past, our site had just grates,” says Larry Wallace, vice president and manager of production for Oklahoma City, OK’s Capitol Steel and Iron. “Once a month, we’d have to clean the inlets out-send men down there to clean them, because they’d get stopped up. There had to be a better, cheaper way of dealing with that. In March 2010, Rebecca Dallen, of the city’s Storm Water Quality Management Department, brought me a sample of Blocksom’s Inlet Filter, which sits on top of a grated drain. We installed it and watched what happened with it.”

Blocksom & Co. of Michigan City, IN, manufactures the filter, which is often attached to storm sewer inlets during a site’s construction phase. However, Wallace found the product worked well on an established site, too. “Capitol Steel has been here 100 years,” he points out.

“The filter was placed on a drain that experiences a lot of traffic from forklifts and cars; it traps all the debris, and it’s still out there working. We checked it after the first big rain event, noted how much debris collected, and then checked again after it was cleaned. I thought the product would fail in a high-traffic area, but it has not. It’s a simple process to clean it: We sweep up the debris with a push broom, then materials are collected and properly disposed.

“We had a flash flood-11 inches of rain-in summer 2010, and the Blocksom filter trapped everything that washed down there. About all that gets through is water, and maybe a little sand. If we get a rain over half an inch, we sample and visually inspect the collected water. Before we installed the filter, the water contained a lot of dirt; you couldn’t see through it. Now the water is almost like drinking water. Everything is based on visual inspection; we don’t take water samples to be lab tested. But every five years we do have to test a sample for everything from heavy metals on down. However, we don’t have a lot of oil coming off this property, other than that dripped from vehicles.”

Capitol Steel installed six Blocksom Inlet Filters, “one on each inlet,” Wallace says. “Their sizes vary, although normally, a square inlet is two-and-a-half by two-and-a-half feet. These drain into a stormwater system and collection area. We don’t have a retention pond on site. Actually, this is a natural watershed area and the sandy soil is very porous; water filters through it quickly. A nearby waterway, the North Canadian River, feeds into one of the many drinking water lakes around Oklahoma City, so we certainly want to keep that clean.”

Although his company is using no other stormwater products, Wallace is going to add some soil-binding vegetation to the site. “In spring we will plant some Buffalo grass, which does well in Oklahoma, around our fenced-off areas, to hold more moisture and debris. For other ideas, we’ve been working closely with Rebecca [Dallen]; she believes in her job-and so do we. That’s why I entered in this inlet filter test with her.”

So far, so good. “The Blocksom Inlet Filter is made from 100% natural materials, except the tie-down system, which is made of plastic. I don’t know the lifetime of these things, but they’re still in good condition and lasting longer than I thought they would. We clean them out after every rain-it takes about eight to 10 minutes per inlet. That’s certainly a lot faster, and cheaper, than the old way of mucking out an inlet once a month!”

Move Over, Wattles
During construction, some firms use straw wattles on the soil side of the curb, to keep sediment out of the gutter. However, when soaked with water and soil, the wattles can be extremely heavy, and nearly impossible to move. Therefore, they’re often left where they lie, becoming unsightly as they slowly decompose. In addition, if the wattles can’t be moved, contractors must purchase more and more of them for each project.

“We’ve been using Gator Guard in place of straw wattle or fiber rolls,” says Todd Hudson, project engineer for SWIMS [Storm Water Inspection and Maintenance Services] Inc. in Discovery Bay, CA. “I had seen it at trade shows, but I first used it in quantity at the Enclave in Fairfield-a William Lyons Homes residential project-in October 2010.” Manufactured by Gator Guard Environmental Products Inc. of Boise, ID, Gator Guards are filled with recycled scrap foam housed in a fabric sleeve.

“We placed the Gator Guard behind sidewalks, curbs, and gutters as a sediment protection for the 100 existing graded lots. These are fairly flat lots, which have already been graded, and the streets are in. There is a total of 300 lots in this development; they’re starting in the first 100. There had been old straw wattles on the Enclave site, and we replaced those with Gator Guard-6,000 linear feet of Gator Guard went in. When this section is done, in a year or two, we will pull these Gator Guards up and move them to the next job site.” The Gator Guard is one of the few sediment control BMPs on site. “Only in the catch basins themselves did we use gravel bags, but that was pretty much it.”

Why did SWIMS Inc. decide to use Gator Guard? “I first gave William Lyons Homes a proposal with straw wattles. They had 1,000 feet of a Gator Guard competitor’s brand on hand, and said they might want to use it. I searched for more of that material, and couldn’t find it-but I found Gator Guard. I got a price from them, which was better than what Lyons Homes had paid for the other product. Gator Guard was easier to install, and it’s a nicer, cleaner-looking unit. The customer was very pleased with the product.”

SWIMS Inc. performs stormwater BMP maintenance and related activities. “We’re a full-service erosion control company, a qualified SWPPP practitioner. We do installation and maintenance, as well as dewatering, and street sweeping for clients before streets are finished and turned over to the city,” Hudson says. “We’re also an area leader in post-construction maintenance-once stormwater goes into the drain. For example, the CDS units that filter stormwater and take out all the trash and sediment-we clean those out. Here in California, construction projects must have a post-construction unit onsite; all the detritus onsite washes down into drainage pond. The ponds contain filters, which catch oil, sediment, heavy metals, and so on, and we go in there and clean them out.”

For future projects, Hudson will use Gator Guard where it “fits.” “I like Gator Guard because it can be reused, but it’s still something new,” he says. “I think it’s a good product, but it’s not mainstream yet, and often I don’t get the choice of what to put in. The city or state specifies or approves what goes in. We do lot of commercial work; those crews are in and out and done, and an office building doesn’t really have a large footprint. Construction crews for those jobs don’t want to be storing items, so they’d probably be hesitant to use a reusable item like Gator Guard. On the other hand, residential developments are sprawling, with more square footage or acreage-you’ll likely use 1,000 feet of wattle, on two sides of the street-and crews are there for a longer time, building one section, then another. Builders usually have multiple projects going, and know where their next three projects will be built. I think Gator Guard is good fit for this type of building. Since the clients get to keep Gator Guards, ultimately that will save them money. Wattles last about 18 months and are very heavy, hard to move, and they degrade. Gator Guards will last for years.”

Inlet Protection That Adds Beauty-and Shade
Trees beautify a neighborhood. They also need plenty of water to flourish. Some stormwater products can furnish trees with the moisture they need, while also keeping streets clear of excess rainwater. Using such products, the city of College Park, GA, came up with an ingenious plan to revitalize a blighted neighborhood, while it also contained-and recycled-its stormwater.

College Park’s 16-block corridor west of the busy Hartsfield-Jackson Atlanta International airport was mostly vacant. Before the 1980s, the area had been residential; however, due to the airport’s expansion, an FAA noise-abatement plan bought out the homeowners, and most of the buildings had been leveled. Ironically, the land parcel now has great potential as a commercial district because of its proximity to the airport, an interstate highway, the Georgia International Convention Center, two hotels, an office park, and a golf course. Yet it had drawbacks; although some infrastructure was in place (gas, water, and sanitary sewer), the parcel contained no stormwater drainage system, and the road surfaces were bad.

In early 2009, the Obama administration proposed funding infrastructure-related projects to stimulate the economy. “The Georgia Environmental Protection Division [EPD] requested a list from municipalities, outlining what “˜shovel-ready’ projects they had, which would allow Georgia to get its share of stimulus dollars,” explains College Park city engineer Jackson Myers. “We submitted a two-phase proposal: first, to install a stormwater system into the neighborhood, which would be piped to two new sedimentation ponds. These ponds would not only eliminate the need for builders to make their own ponds, saving them money, but the ponds would also be part of an irrigation system that would offer lower-cost water for the eventual landscaping.

“The second phase involved the adjacent Gordon Morris Memorial Golf Course, where stormwater runoff drains to the golf course pond, a former stone quarry. We proposed piping from the pond to irrigate not only the golf course, but also the grounds of the Georgia International Convention Center, again saving money and natural resources. In September 2009, the project was approved by the Georgia Environmental Facilities Authority, which was a part of the American Reinvestment and Recovery Act, and Georgia EPD. We were funded $5,000,000: a $3,000,000 grant and a 30-year, 2% interest loan of $2,000,000.”

Work began. “With some of the money we got, we excavated 30,000 cubic yards of sediment out of the golf course lake. We also ran a mile of irrigation to the Georgia International Convention Center. Anyone building along that water main line can tap into the line to irrigate plants, rather than use city water. Then, to replenish our supply, the stormwater infrastructure carries water back to the golf course lake. This irrigation water can be sold much more cheaply-about one dollar per 1,000 gallons-than can tap water. Eventually, the golf course lake will have a walking trail around it, and they will stock the lake with fish, for kids’ fishing. Someday there will also be a botanical garden near the lake.”

Problems arose. “The USEPA said it didn’t want stormwater detention ponds,” Myers explains. “I looked at bioretention facilities; Virginia was the first to put them in, and universities had studied them. We decided we wanted something environmentally friendly, not a bunch of holes. We decided upon, and installed, 82 bioretention facilities-KriStar’s Treepod Biofilters-throughout the 16-block area.”

Manufactured by KriStar Enterprises Inc. of Santa Rosa, CA, Treepods use trees to filter out ultrafine and dissolved pollutants. They also include a prefiltration chamber to trap gross pollutants. “We had a list of Georgia species to include in the Treepods, such as holly and cypress. All oil, street debris, and so on get filtered out before the stormwater reaches the streams and pond,” Myers explains.

The topography posed challenges; there’s a downstream hill to the golf course pond, and an upstream hill to the convention center. “The irrigation water component has two pump stations to get the water moving,” he says.

The golf course pond work and stormwater/irrigation lines were completed in December 2010. “We had some money left over for the project, but we couldn’t have open trenches in the streets during the winter, so we got a project extension to March 2011 for the installation of additional stormwater-related facilities.” Because the 16-block area was empty, the project was able to move fairly quickly. “There was nothing there but pavement. We had little disturbance of soil. Sidewalks were put in. Otherwise, kudzu and strawberries-from gardens left over from when homeowners were there-were all we had to contend with.

“The Treepods allow us to have not just inlets, but something pretty-innovative ways to get storm sewers, while also removing debris and pollutants from streams and the pond. The trees are installed. As for projected maintenance, there’s a one-year warranty on the Treepods once we close out the project. I assume maintenance will be the same as for any other inlet; we’ll have to pick up any leaves, rocks, and sticks that float in. As for removing sediment, I can’t answer that yet. This is the first time this type of bioretention facility has been used in the southeastern part of the US.” Late in 2010, Myers received word from the EPA that his project will likely be studied as a good example of a low-impact development effort.

College Park’s innovative use of stormwater is an idea whose time has come-especially with southern states squabbling over water rights. “Lake Lanier, which was built by US Army Corps of Engineers, is the main fresh water source for the area,” Myers notes. “Florida says Atlanta is taking too much water from the lake, robbing the state’s freshwater mussels of the water they need. Alabama and Tennessee are also complaining about lack of water. In July 2009, a judge ruled that Atlanta had three years to find its water someplace else. At least College Park will be making the most of the stormwater it has!”

Saving Stormwater by Separation
Oil and water don’t mix-and, for that matter, water doesn’t care for much debris, either. Is costly filtering or treatment the only way to remove these contaminants? Perhaps not: By changing the shape of your inlets, these items’ physical characteristics will make them remove themselves.

“I’ve installed and actively maintain many Snouts,” says Theodore E. Scott, P.E., CPESC, LEED-AP, of Hunt Valley, MD’s T.E. Scott & Associates Inc. and Stormwater Maintenance LLC. “Snouts are high-impact plastic oil-water-debris separators, which are installed into new construction inlets.” Snouts, available in four different sizes and shapes for different structures, are a product of Middle River, MD’s Best Management Products. Fitted to the exit pipe, a Snout extends down into the standing stormwater; because oil, and many trash items, float, they cannot get down to the Snout’s intake level, and are trapped in the inlet.

“I’ve spec’d them for a project,” Scott says. “They offer simplicity of operation and effectiveness for getting sinkables and floatables as close to the source as possible. These are specified with a deeper manhole structure. We prefer to see them distributed throughout a site; that’s more effective. A Snout advantage is that you don’t have higher flows going through, and the system is easier to maintain with smaller pipes. Sometimes Snouts are the only treatment my projects require. However, manholes or inlets that contain Snouts are designed to have pooled water in them; if you don’t have permanent pools of water in the inlet, the Snouts don’t work right.”

How do Snouts stand up to 10- or 100-year storms? “Because they’re concave, they’re very strong. Water forces hitting the curve flow back to the concrete structure. Significant debris or ice flows might hurt them, however,” Scott says.

Due to the required structure depth and amount of water needed, the vast majority of Snouts installed are in new construction. “Snouts are put into new projects 90 to 95% of the time; you can’t just slap these into existing manholes,” he explains. “The Snout model used will depend upon the total dimensions of the inlet, which will depend on the size of the pipe, the storm drain system, and its size. It’s difficult to come up with an answer to “˜how many per acre.” Different designers might call for twice the amount of inlets that another does. We see Snouts more in industrial sites, less in residential.”

Scott follows a defined maintenance program. “There are two levels of maintenance. The most important is inspection, a level one. This is done twice a year, in no specific season. If we have a client who wants only one inspection a year, we prefer to do it in the spring, to gather debris from the fall and winter. During inspection, if there are floatables present, they’re removed with a device like a pool skimmer. If there’s a presence of sediments at the bottom, we’ll use a Sludge Judge, or something like that-something you can lower into the water.”

The sediment’s depth determines further action. “If the sediment is significant, 25% to 50% of storage volume, then you have to do level-two maintenance, which takes out heavy oils and piles of sediments. That task is done by a vac truck. Any water that needs to be removed can be pumped out through geotextile bags, which catch any sediments that might be suspended. Then you can release the water. The sediment goes to a landfill, unless there’s a lot of oil in it. Significant oil, like a spill, is handled differently; the oil is taken to an oil-recycling facility. This, too, is removed by using a vac truck. Manholes or inlets are usually 4 feet deep; if you find between 2 inches and 1 foot of oil, you have to soak it up. Hypothetically, unusual pollutants in certain areas, like the trash problems in Baltimore, might require quarterly inspections and cleanouts. We do have some clients that we inspect monthly; it all depends upon their goals, or on the local codes. Regulatory drivers vary among individual municipalities. Cities adjacent to natural waterways are usually more stringent with stormwater treatment.”

About the Author

Janis Keating

Janis Keating is a frequent contributor to Forester Media, Inc. publications.