Construction projects around water have inherent challenges in ensuring that sediment and debris from the disturbed ground don’t enter the water. To that end, turbidity curtains and cofferdams offer a measure of “insurance.”
Turbidity curtains are barriers placed in the water-usually attached to floats at the top and anchored or weighted at the bottom-to provide containment for the work area. Constructed of permeable material, the curtains stop sediment particles while allowing water to flow through.
Cofferdams are temporary dams set up to divert water from a work area. Often, two are used, and the water that is diverted in between is pumped out.
Lake Beauclair
“NPDES [the National Pollutant Discharge Elimination System] Phase II requires construction sites of 1 acre or more, or construction sites that are smaller tracts of land that total 1 acre or more, have BMPs to contain the eroded sediment and soil in the water,” points out Bill Henning, president of Aer-Flo, manufacturer of floating and staked turbidity barriers. “That means any construction site that is near or on a waterway in the United States-lakes, rivers, streams, ponds, coastal areas.”
Aer-Flo makes three types of Tough Guy, a floating yellow turbidity barrier that relies on a heavy galvanized steel chain sealed into a hem along the entire bottom of the curtain to provide ballast to keep the curtain vertical in the water.
End hems are sealed around a rope and grommeted to allow attachment to each barrier with rope or bolts, nuts, and washers. The turbidity barriers come in sizes from 2 feet deep to more than 100 feet deep and in lengths from 25 feet through 125 feet.
As the product is manufactured and distributed in the United States through environmental and construction supply distributors, Aer-Flo can provide onsite assistance as needed.
“We deliver very quickly because many construction companies don’t exactly order their BMPs or their barriers on time, and many times we have to rush the product to their job site,” says Henning.
The company’s turbidity barriers were recently used at Lake Beauclair in Lake County, FL, during an aquatic restoration project. Just under 1.5 million cubic yards of organic sediments are being dredged from the lake and hydraulically transported 8.5 miles to a disposal area through a pumping system using a series of booster pumps and a dredge.
The 600-acre site-owned by the Lake County Water Authority-was former farmlands that were mitigated back to wetlands by the St. Johns River Water Management District.
To work in the area, Jahna Dredging fashioned a floating discharge ring 100 feet in diameter out of HDPE pipe. The ring surrounds the company’s equipment. At the company’s request, Aer-Flo constructed 350 feet of Type II turbidity barriers to hang from the floating ring.
The barriers were manufactured in sections measuring 2 feet by 50 feet with no floats, with a quarter-inch galvanized chain at the bottom, and with grommets 2 feet along the top to attach to the ring and four down each side to connect the barriers together.
Jahna Dredging also ordered 500 feet of Aer-Flo’s standard 3- by 50-foot Type II floating turbidity barriers with floats.
“It’s only a 4-foot-deep pond, and these curtains are holding that material in place,” says Ron Mincey, project manager. “There’s a 1-foot-thick deposit across the bottom of these ponds. The ultimate goal is to remove nutrient-rich sediments from Lake Beauclair to clean the lake up and reduce its nutrient loading, to propagate cleaner water, and at the same time to put a barrier on some contaminated soils on the bottom of these ponds,” he adds.
The soils were contaminated during the farming process with fertilizers and pesticides over the last several decades, Mincey notes.
Jahna Dredging came up with the approach based on previous designs that had been successful, he says.
One of the challenges has been settling the material after it’s slurrified, pumping it for 8.5 miles, and holding it inside the settling ring, then also moving the ring at the proper time to get a uniform deposit on the bottom of the lake Jahna Dredging is trying to mitigate, Mincey says.
“Our design works very well, and with the proper management of the disposal area, we’ve been able to succeed in our attempts,” Mincey says.
The project commenced in August 2011, and in September 2012 the work was more than half completed.
Naval Station Newport
On a busy roadway at the Naval Station Newport in Rhode Island, East Coast Construction installed 725 linear feet of a rock sea wall as a coastal revetment. Steve Bakios, an estimator for East Coast Construction, says the roadway was being eroded by the waters of Narragansett Bay. The shoulders of the road were starting to be lost to erosion.
“We filled areas and built out areas that had been eroded,” he says. “We protected the entire length of roadway that was along the coastline with the stone revetment.”
East Coast Construction used turbidity curtains from Spilldam Environmental on the job, which lasted from May to October 2012.
“We surrounded the work with a turbidity curtain because we had machines working on the beach during periods of low tide. We wanted to contain the sediment and everything we were introducing into the water and disturbing,” says Bakios
Bakios says one of the challenges on the job was that the area was “not particularly calm or well protected. Working with Tim Prevost at Spilldam, we were able to select the right product to work with the conditions and get the right anchoring procedure down based on the tides and the field conditions we were working in,” notes Bakios.
“Tim helped us figure out what type of turbidity curtain and what type of anchorings we would need, and the intervals the anchors needed to be spaced,” he adds.
Bakios says the job went smoothly once his company had the right product and it was properly installed.
“Recently, our focus has shifted more to remediation projects than construction,” says Prevost, president of Spilldam Environmental. “We’ve worked on some pretty high-profile cases, including the Hudson River and the Fox River, on remediation of old contaminated brownfield sites that are being cleaned up for reuse.”
Siltdam turbidity barriers are designed to accommodate a variety of wind, sea, and current conditions. They can also contain debris and oil at the waterline with the use of 22-ounce PVC oil boom fabric around the floatation compartment.
The floatation compartment is heat-sealed to be completely watertight and prevent the floats from shifting. A skirt section is installed at the desired depth and is constructed of either permeable, woven polypropylene geotextile fabrics or impermeable polypropylene and PVC fabrics. The barriers are ballasted continually along the bottom using galvanized steel chain.
The turbidity curtains can be custom-manufactured for a specific job.
“In the Northeast, the waters tend to be wide and varied,” Prevost points out.
Northside Park
In 2010, E.P. Doyle & Son in Wheaton, IL, was called upon for a dewatering job for a mitigation and renovation project at Northside Park.
Over the years, a lake at the park had silted up. “The ultimate goal of the project was to restore the park to the original condition when it was built back in the 1930s,” says Russell Wennerstrom, senior project manager for E.P. Doyle & Son. “It was a restoration of the existing lake, and there were added amenities, including bridges, natural vegetation, fishing docks, and water-control structures.”
The company used Dam-It Dams for the project.
“We had to do lake excavation to improve the water quality at the lake, and the dams allowed us to separate different sections of the lake, allowing us to isolate specific areas to do the excavation work to construct bridge abutments, retaining walls, and the new water level control weir structure,” says Wennerstrom.
“We had various existing water level depths, and it fluctuated quite a bit based on rainfall,” he adds. “Dam-It Dams helped us select the right size dams for each application. We purchased about eight dams over the course of the project in various sizes and lengths.”
Because of a large tributary area and low base flow, the lake water fluctuated frequently, says Wennerstrom. “This complicated an already challenging project. We also faced varying sediment depths and varying bank conditions.”
Wennerstrom credits the Dam-It Dam staff with being helpful in selecting dam that could be used multiple times in different locations. “The company’s onsite assistance was especially helpful in training our personnel in proper deployment and recovery techniques,” he says. “Not to say the project went without difficulties, but we are sure that we would have learned many more lessons the hard way without this assistance.
“When we did have washouts, it was either due to a significant storm event with resultant cofferdam overtopping or unanticipated excess sediment depth. When these factors were accurately factored in, the dams worked very well.”
Dam-It Dams staff helped after washouts when a dam repair or new dams were needed, sending new dams within days and an employee to provide onsite assistance, Wennerstrom says.
“We were pleased with how the dams performed,” he adds. “They provided training on the initial dam placement so we could learn the proper techniques to deploy them as well as to retrieve them. That helped a great deal. They had a man onsite for us.”
As an alternative to sand bags and earthen fill, Dam-It Dams Portable Dams Cofferdam Systems are reusable water-filled cofferdams that offer the ability to use onsite water. The company offers a training course to end users to help them save costs.
Company owner Jack Nichols says the cofferdam installation jobs can usually be done in a day. End users often choose the system when seeking an environmentally friendly product, he adds.
Like other manufacturers, Nichols notes that many jobs utilizing his company’s products are for remediation work. Such was the case in September 2010 when 10 Dam-It Dams measuring 4 feet high and 150 feet long were applied in water depths of 2 to 3 feet in Marshall, MI, during a cleanup efforts after an oil spill following a pipeline rupture in a tributary of the Kalamazoo River. The product was placed beyond the contaminated area, allowing workers to remediate the problems without dragging the product further downstream. That saved a significant amount of time and money, Nichols points out.
“We do a lot for the gas-line companies,” Nichols says. “After you remove the dam, everything pretty much springs back in a month or so. You can’t tell that the dam was even there.”
Westlock County Treatment Plant
For the past two years, Gabriel Construction has been involved in a project in Alberta, Canada, that will help supply water to the Westlock County treatment plants. In 2011, the company built two large reservoirs and in 2012 worked on a raw water intake in the Pembina River.
To help minimize the environmental impact of the construction project, Gabriel Construction has used Portadam cofferdams. The Portadam system creates temporary, portable cofferdams for use in construction and aboveground impoundments for water storage and retention, such as property flood protection, flood barriers, and inspection projects in rivers, streams, lakes, reservoirs, and other retaining areas, as well as in natural gas fracking job sites.
“We had to take over about 45% of the river in a horseshoe shape to block the river so we could walk in there and do our well water intakes,” says Randy Pelletier, site superintendent of the Pembina River job.
Two cofferdams totaling 860 linear feet were used on the project: one on the upstream side at the site of the raw water intake for Westlock, and the other about 500 yards downstream of the intake area, where a fish habitat is being constructed.
“When working in sensitive water bodies, sometimes when you’re taking something away, you have to put something in place in order to give fish place to spawn,” says Jerry Mann of Portadam. The habitat will consist of a series of rock vanes, with deeper water in between to give fish a protected space with less water movement. Excavation is taking place between the vanes on a downstream angle.
Although using the Portadam system meant having to do more dewatering than with other systems, Pelletier says he finds the system to be “cleaner” than other options. “Our eco plan is fairly extensive,” he says. “We can’t introduce any turbid water into the system. The environmental impact of Portadam is minimal compared to other systems.”
Mann says the Portadam system doesn’t require prep work to be installed, but instead sits on the bottom of the water body with the weight of the water keeping it stable and in position with “zero” potential for turbidity.
Cleanup in the Gulf
Post-oil-spill work continues in the Gulf of Mexico.
In October 2012, workers gathered in Pensacola, FL, in to begin the first Florida project funded under the Natural Resource Damage Assessment Early Restoration Projects. Funding for this and future projects are part of a $1 billion agreement struck between the Deepwater Horizon Natural Resource Trustees and BP Oil Company in response to the Deepwater Horizon oil spill that occurred in April 2010.
The project’s goal is restore the dunes along the gulf side of Pensacola Beach. The dunes were damaged by previous cleanup activities explains Jimmy McDaniel, who serves as foreman for this project.
The implementation of early restoration projects is the first step by the BP Oil Co. in fulfilling its obligation to fund the complete restoration of natural resources affected by the spill.
The Florida Department of Environmental Protection gave Escambia County officials the green light to proceed on the project, expected to cost $644,487. It entails natural plantings and a sand fence. The overall dune planting zone consists of 8.1 miles of existing primary dune line along the Gulf of Mexico shoreline at Pensacola Beach.
McDaniel is field operations director for Aquatic Plants of Florida. His team was tasked with the installation of 475,000 plants. The overall planting consists of 75% sea oats and 20% panic grass, with the remaining 5% being other diverse species. The width of the planting zone varies from 15 to 60 feet.
A sand fence of 28,000 feet will be installed seaward of the planting zone along the project’s length. The sand fence will consist of 2-foot by 2-foot planks strung together with wire, McDaniel says. The fence will direct sand blown onshore into designated spots to rebuild the dunes and will also prevent the sand from getting blown into nearby areas such as parking lots.
McDaniel expected the weather to present a challenge in executing the project. On the first day of the project, the team encountered winds in excess of 30 miles an hour and 3- to 5-foot seas. Long-term, the project is expected to protect the beach, McDaniel points out.
“They want to keep what they have here,” he says. “They don’t want to lose any more beach.”