Try as they might, it’s impossible for contractors to build sound structures on solid ground without soil disturbance. Byproducts of the creative process, the particulates that can cause erosion onsite and can threaten water quality travel by way of dry soil meeting the air, vehicle tires, foot traffic, and water. As the EPA prepares to reissue its effluent limitation guidelines for construction sites, it’s a good time to consider the impact a project will create well before putting pen to paper during the planning stages.
Just as sediment control practices vary with the needs of each construction site, budget, and region, so, too, do they have the same purpose: protection. Learning from the strategies of others who have overcome onsite challenges can broaden our common understanding of the steps and stages of protecting the environment.
New Hope in the Southwest
An 11-story, $300 million expansion at the Phoenix Children’s Hospital, targeted for completion this summer, needed a durable method of construction-site sediment control, particularly at the points of entry to the site.
“The project began in mid-2007 with site demolition activities and utility relocations, followed immediately by an early construction of one of the two parking garages for dedicated PCH staff and employee use, while concurrently constructing the new Central Plant facility,” explains Mike Milewski, a senior project manger with Phoenix-based Kitchell Contractors, which was the general contractor and construction manager for the site. “The new facility will provide 248 patient beds and will include a new kitchen and dining, servery, outpatient, and surgical suites.”
Meeting regulations at the very public site was taken seriously from the outset of the project. According to Mike Zarley, field manager for Kitchell Environmental Services, “Strict regulations and restrictions in the Arizona marketplace are in full effect, and contractors, especially Kitchell, take these seriously, as the fines can be large and expensive. In fact, Maricopa County has one of the most stringent dust-control regulatory structures anywhere in the country.”
With the intent of making sure the project was in compliance with the county regulations, Kitchell Environmental Services was brought in and made a part of the stormwater pollution prevention plan (SWPPP), the county dust control rulings, and the construction waste and recycling program, explains Milewski.
“One of the largest challenges as it related to site logistics was the amount of truck traffic to deliver materials to, and then exit from, the site,” he says. “Site layout was structured such that deliveries would route inboard through one gate, offload, and exit through a dedicated egress gate onto a public thoroughfare. Just prior to this exit gate, Kitchell installed Rumble Grate/Grizzly devices to limit the amount of trackout debris when construction vehicles exited.” The devices are manufactured by Tempe, AZ-based Trackout Control.
“These Rumble Grate devices have been found to eliminate well over 80% of construction-site debris being tracked offsite,” he says, noting that that was the project’s goal. “Kitchell was one of the leading pioneers in the use of the Rumble Grate/Grizzly devices throughout the southwestern US and continues to use them on the majority of its projects. At the peak of construction, there were four or five devices in use at various entry and exit points on the PCH project.”
In addition to helping control particulate matter on the site, the Grizzly devices also serve to slow traffic, and they can be easily transported or removed. They prevent debris overflow from reaching the city streets, notes Milewski. This is important because regulations are not only strict but also strictly enforced.
“County enforcement in the metropolitan Phoenix area operates 24/7, and inspections are random and unannounced,” says Milewski. “Having the Rumble Grate/Grizzly products approved and installed is a basic component of the dust control and trackout permitting and management process in Maricopa County.”
In southwest Pima County, AZ, four 8-foot-by-10-foot Grizzly trackout devices were used at the entrances to multiple construction sites on a federal civil construction project completed in September 2010, explains Andrew Kingry, project engineer at Tucson-based Granite Construction Co.
“It was a road and dirt work project. The devices were used to keep dust and mud from construction traffic off of a state highway,” he says. “The entrance roads in which they were used were very narrow, and the Grizzly devices required much less effort and space to install than typical stone trackouts.”
These particular features were appealing for a project that was begun and completed in less than nine months.
“The challenges faced were minimal in terms of soil conditions, but as with any construction project, we were faced with a difficult timetable. The Grizzly was mobile, quick to install, and easily visible,” says Kingry. “Another challenge that was overcome was its ability to handle all types of vehicular traffic. During its use, the product had everything from pickup trucks to fully loaded concrete trucks pass over it. This was important, because this trackout product required minimal upkeep and proved to have great durability. It also proved to have a “˜one-size-fits-all’ quality to it. There was no need to have multiple types of trackout devices to serve the different types of vehicular traffic.
“Space was the only restriction” at the site, he notes. “The Trackout Control product was great because it was smaller than most trackout pads that are typically created with stone.”
In the Midwest and Southeast
Disturbance in urban construction sites can take many forms.
In Oklahoma City, OK, relocating utilities caused the largest part of the ground disturbance at an industrial facility construction site that includes expanding shipping and receiving capacity.
“They are building a new building,” explains Joshua Rasp, owner of Tall Grass Environmental Solutions based in Luther, OK, just northeast of Oklahoma City. The project began in January 2011. “The client called for silt fence and wanted to use it as a perimeter control around a utility area and a parking lot. There was an extremely compacted gravel lot.” He notes that although Tall Grass has a machine for installing silt fence, “we could not even get the plow in the ground.”
Instead, he says, “We were able to talk the client into using Triangular Silt Dikes. There were a lot of private utilities running through this area; it was going to be a very high-traffic area. One of the great benefits of the Silt Dike is that vehicles can drive over it, within reason, and not tear it up.”
Tall Grass Environmental Solutions was subcontracted to work on the site and complete compliance inspections for a local developer. Rasp notes that developers have found having one person in charge of documenting everything regarding compliance issues to be helpful.
“The city inspector will come out once to make sure everything is in place. For the most part at this site, there’s not much ongoing inspection. It’s up to basically whoever’s name is on the discharge permit to make sure they’re doing all their inspections. That would be the general contractor in this instance. They just hired us for the initial consultations.”
Gravel bags were initially to be used as barriers, but Rasp says they, too, were replaced by the Triangular Silt Dikes onsite.
“The Silt Dikes are more resilient than the gravel bags,” he notes, adding that gravel bags can often be rendered useless if a truck drives over them once or twice. “They’re so easy to install that in my mind there is really no challenging side. We actually installed the silt dikes two different ways.” One is the traditional method, in which the apron on either side of the reusable dike is inserted into a shallow trench and stapled down. “We were able to do that through the gravel parking lot area,” Rasp says. The areas that were originally slated for the gravel bags, however, were a combination of concrete and asphalt, and trenching wasn’t possible. “We used the silt dikes and glued them to the concrete and asphalt,” Rasp explains. “We’ve used liquid nails in the past, an asphalt glue.”
Similar dikes were used on a construction project at a commercial shopping center project in Cary, NC, begun in August 2010. The job started during hurricane season, according to Mike Sciortino, a project manager with Raleigh, NC-based S.T. Wooten, when battling the elements often becomes a race against time.
Other challenges included “steep slopes, a lot of shot rock, and a lot of retaining walls needed to be installed,” Sciortino says. Richmond, VA-based ACF Environmental products that were used to fight these trials included coir baffles, polymer floc logs, super silt fence, and Triangular Silt Dike. “We couldn’t log the whole site until Wake County took over the site-that delayed construction for up for 30 days,” he notes. “This holdup pushed the installation of the retaining walls back.”
Revegetation was an important part of the project. Sciortino explains that portions of the site were seeded with ACF’s Earthshield seed mix, which is designed for quick plant establishment.
Mid-Atlantic Barriers
Another popular construction-site sediment control tool is the compost filter sock, which traps sediment as water passes through it.
Compost filter socks are being used in some areas of Pennsylvania where new technology is helping access and extract natural gas. Jonathan Hunt, owner of Hunt Ventures in Gettysburg, provides some background on this process.
“Marcellus Shale is a black, gas-bearing shale found in a region that extends from the southern part of West Virginia to southern New York. A large portion of it is in Pennsylvania. Geologists have known about it for decades, but they didn’t have the technology to extract the gas.” Now, he explains, “they’ll drill down several thousand feet then turn and drill horizontally for about a thousand feet. They will blast holes through the well casing, then inject water, sand, and other chemicals into the hole under high pressure. The whole purpose of it is to fracture the shale, so that instead of a hard rock you have more of a porous sponge you can extract the gas from. Then they have to pump the fracturing fluid back out for treatment.”
This fracturing process is known as fracking, and the water in this process is called frackwater. This practice is becoming increasingly widespread in Pennsylvania, where the black “gas shale” ranges from 50 to nearly 300 feet thick.
“They can extract gas from approximately a 2,500-foot radius,” he notes. “In some places, you can see wells every half-mile dotting the countryside. There’s a lot of drilling going on. There are more than 4,000 permits already, and that’s just in the past couple years,” says Hunt, who represents Filtrexx International in the region. “There’s a lot of construction activity, project after project, many of them in the Allegheny region of the Appalachian Mountains. Filtrexx FilterSoxx are used a lot on these projects.”
Gas companies in the region are expected to self-inspect each site and ensure they are in compliance with all regulations, he explains.
“If they think something is not quite right, they fix it,” says Hunt. “A cease-work order could cost them hundreds of thousands of dollars.”
Performance, he says, is the reason regulators like Filtrexx compost filter socks.
“There’s virtually no disturbance to install them. They’re recyclable, because they are made of a recyclable wood, so they degrade,” he explains.
Keith Weaver, owner of KW Site Services, based in Milton, PA, just north of Harrisburg, describes how the socks were used on a particularly challenging Marcellus Shale site near Towanda, PA, in the first half of 2010. The woodland area was being cleared for Marcellus shale drilling.
“It’s along the woods. It is a remote site. They were still constructing an access road.” The lower boundary of the site, says Weaver, is adjacent to some wetlands, “and we had to protect that wetland.”
With an approximately 4:1 slope on site, the company used a bulldozer with a winch to back down over the steep embankment so the tandem-axle truck wouldn’t “get away from us. We were worried about the brakes not holding,” he explains. The team had to secure the disturbed area quickly and completed the work in three days.
“Filtrexx [compost] socks were used in a sediment trap configuration at the toe of the fill slope on the well pad. It’s a 400-foot-by-400-foot square where they set the drill,” explains Weaver, noting that the area has to be level. “Socks had been an engineering requirement by the state DEP. They have been asking for compost filter socks on everything. The gas companies are extremely conscious of environmental regulations. They want to do everything they can to be in compliance.”
He says the costs for erosion control measures were “$17 per foot to install the sediment track configuration” for the approximately 500 feet of sediment trap on the site. Revegetation efforts at the site, including seeding, will be handled by the contractor that built the site, says Weaver. More compost filtration socks were added after the well had been drilled, and the long-term goal is to reclaim the site. About 80% of the KW Site Services work involving Marcellus Shale sites is located in the northeastern border of Pennsylvania, particularly in Susquehanna, Tioga, Bradford, Sullivan, and Potter counties. At these sites, the Pennsylvania Department of Environmental Protection sets out the regulations.
“That’s all handled between the gas company, the engineer, and the DEP. Maintenance is normally handled by the contractor that built the site,” says Weaver, who adds that his company might typically be hired to come in and do future repair if any is needed. “The gas company also does environmental inspections as a third-party audit over and above what DEP does to ensure everything has been installed.” The DEP is involved, explains Weaver, to consolidate all operations in the state under a single regulator.
Measuring Nephelometric Turbidity Units
Maintenance was required after each rain event at a 50-acre commercial office construction site begun in early 2010 and located in Jessup, MD, part of Anne Arundel County. The site is located on the outskirts of the Baltimore metropolitan area, and site runoff would eventually reach the Chesapeake Bay. Dewatering was an integral part of the maintenance requirements after each rain event. American Infrastructure was the general construction firm for the project, although earthwork on the site was subcontracted.
“There were multitiered sediment ponds designed to hold water, allowing controlled discharge. The water wasn’t clean enough to meet local requirements,” explains Matt Burns of StormKlear, the company that, along with Hanes Geo Components, set up the semipassive treatment system used at the site. Construction was still active onsite when the treatment system installation was started. The mass grading work was complete, but building construction and installation of stormwater infrastructure were still under way.
Anne Arundel County regulations, as well as those established by the Maryland Department of Environment’s NPDES requirements, were stringent and had to be met on a daily basis-including during prolonged rain events or when the existing stormwater ponds reached capacity and needed to be discharged to allow for additional storage.
“The end goal for this project was an approximate 35-acre impervious area, with 15 acres of pervious site management techniques such as landscaping features and permanent stormwater ponds,” according to a case study written by Jennifer Hildebrand, CPSWQ, a compliance officer with WSB and Associates in Minnesota. She was interested in viewing the project because of the new, advanced technology system used on this site. As suggested by state and county inspectors during a routine review, StormKlear’s dual biopolymer treatment system was employed on the site. Hildebrand notes that during the original plan review and approval process, it was not specified whether active, semipassive, or passive treatment was required.
The system included a “two-chamber semipassive PVC routing pipe [that] was built and secured to a flat wooden surface. A trash pump and 4-inch line were then connected to the PVC routing system. One sock of DBP2100 BioPolymer flocculent was installed in the first PVC chamber. A second GelFloc sock was installed within the second PVC chamber,” states Hildebrand. “After the initial exposure to the dual PVC chamber the “˜treated’ water was then routed to a traditional geotextile bag for entrapment of flocculated materials, thereby allowing the nonturbid water to be controllably discharged into the designed spillway system.”
Rock riprap with geotextile liner was used to control scour at the system outfall. “The first temporary sediment trap that was initially dewatered was approximately 40 feet wide and 80 feet long. The depth of water was variable; however, approximately 12 to 18 inches of water was in need of treatment prior to discharge. The initial turbidity of the water column was also variable; however, grab sampling techniques indicated a mean turbidity measurement of 625 NTUs [nephelometric turbidity units],” according to Hildebrand. “After the initial exposure to the two-part system, the discharge NTU rate of water was approximately 25 to 28 NTUs. After additional settling time, an average of 15 NTUs was achieved consistently over a 24- to 48-hour period. The allowable discharge limits of turbidity were not written into regulatory law; however, local similar project requirements were consistently required to meet a 50-NTU monthly average. This treated NTU result was well below the historical average requirement of 50 NTUs. There were several temporary and permanent sediment ponds on this project, and continuous site dewatering occurred for approximately 78 days, with no compromise of NTU discharge values.”
More treatment options may be added post-construction if the pond systems are in need of prolonged treatment, explains Burns, noting that “the ponds are designed appropriate to site capacity requirements.” Straw was being blown into areas of the site prior to the onset of winter conditions to bolster revegetation efforts and protect soils.
Construction of the Beaver Creek housing development near Harbeson, DE. inland of vacation destination Rehoboth Beach, began in 2005. Forty lots have already been prepped for sale, and 154 homes are ultimately planned for the site.
“The challenge on that property is that it is particularly flat. There was enough of a silty factor to the sediment that the water wants to stay cloudy,” explains Jessica Watson, program manager for the sediment and stormwater program of the Sussex Conservation District. She notes that the challenging soil is combined with a slightly high water table.
George Adams, co-owner with Alphie Adams of Adams Construction, says that in addition to using erosion control blankets at the outfalls beneath riprap, his company installed Grate Gators from ACF Environmental at the site.
“It’s a 20-foot, paved street,” he says. “There is not a lot of difference between the grade of the manholes and the catch basins. We needed something to get rid of the water a lot quicker.”
Not having used the product on a site like this in the past, he called the company and was told to try using the Grate Gator at the worst spot on the site for water drainage.
“Within 48 hours we had 3 inches of rain, and the street was underwater completely except where I used the Grate Gator,” says Adams. “If you need to get rid of stormwater in a basin quickly, they are the ticket.” He explains that a cover fits around the inlet and the fabric of the Grate Gator is Velcroed to the cover. “If you get a lot of water quick, there is actually a raised hole in the center of Grate Gator. All you have to do after a major rain event is take the top piece off and wash off all the sediment, which is minimal, then refasten the Velcro and it’s ready to go for the next rain. I was surprised.”
Adams discussed the results with the local conservation district and ordered 10 more Grate Gators for the site. He notes that the conservation department was pleased with the Grate Gator performance.
“Inlet protection is a challenge, especially when you have a community where people are living permanently” while construction continues, says Watson. “It’s difficult to have a happy medium.” The goal is to avoid having standing water onsite and also to avoid sediment in the water.
She describes a typical site inspection process in the area. “We’re required to inspect it from the very beginning. We discuss the sediment and stormwater plan to make sure [the contractor] is in compliance. We go over it with them preconstruction to make sure they understand what’s required in that plan. Then the district will inspect it until it’s fully built out,” she says, adding that inspections can take place as often as once a week, depending upon what stage of construction a project is in. “Early on, where there is more disturbance, there will be more inspection.
“It is our job to inform the contractor, keep them on track if they have issues, giving guidance on a plan of action. We don’t want sediment discharges. It’s in everybody’s best interest to educate and look for solutions, from a water-quality standpoint.”
With restrictions, come responsibilities. Contractors can only benefit from making the most of a visit with regulators and, if possible, site inspectors, at a project’s outset.
“In general, knowing of upcoming weather and rain events is mostly the responsibility of the contractor,” notes Burns. “Inspectors will periodically stop in and look at the SWPPP and make sure BMPs are in place. They can make recommendations for repair. They’ll make recommendations for additional measures, and they can write citations. They can do a lot.”
Often, the answer to meeting state and local requirements most effectively can be summed up in one word: anticipation. Good planning at a project’s outset can help adapt to the challenges imposed by a region’s weather events and topography.