Erosion Control March/April 2017 : Page 28

creek so that it dropped off steeply. The sand bags would have had to be hand-laid, and the workers couldn’t reach high enough to lay the sand bags prop-erly. The cofferdam was a much better solution for work in this creek. “In rain events it gets 9 or 10 feet high because of runoff from hundreds of acres of surrounding farmland,” explains Powell. “We had several pretty hard rain events, but aside from that, weather was not a factor. We lost a couple of [work] days to hard rain.” He adds, “Several times we were within inches of the top of the cof-ferdam. It was a blessing. It saved us thousands of dollars. Without it we would have been flooded out four or five times.” Powell says that if the project site had been flooded after the formwork and rebar were already in place, “the flood would have filled the site full of dirt and rocks. We would have had to clear all that out. We’d lose days of work, thousands of dollars in man-power. The bridge replacement was [already] on a pretty aggressive sched-ule to have it operating by the end of the year,” so major delays would have cost Deblin a great deal of money. The cofferdam, made by Porta Dam of Williamstown, NJ, was 10 feet tall. It measured 220 feet in length. Powell says of the Portdam, “It’s a very good system. We’ve used it three or four times on other jobs.” It took the crew three days each time they set up the Portadam, but only two days when they removed it. The dam was set up and removed three differ-ent times for the separate phases of the work, thus saving the expense of buying a new one each time. Deblin’s contract with PennDOT required the company to have the new two-lane bridge ready for use by the end of 2016, in time for winter travel. By running a 50-hour workweek, the crew finished the job in November, well ahead of schedule. During the last part of the project the approaches to both sides of the bridge will be paved. “We’ll do permanent seeding and mulching then,” says Powell. “And For related articles: within 50 feet of waterways you have to use erosion control matting.” South Shore Keys Aer-Flo’s Tough Guy turbidity curtains were used on a dredging project at the entryway to the South Shore Keys in South Lake Tahoe, CA. The project was done by Tahoe Marine and Excavating of Tahoe City, CA. “We used about 500 feet of Aer-Flo turbidity curtains,” says Matt Daniels, owner of Tahoe Marine and Excavat-ing, adding that he has used Aer-Flo curtains on various other projects. Completed in late 2015, the project lasted about five weeks. The dredging took place in open water, about 1,000 feet out on the lake. The wind in the open area made the work challenging. Aer-Flo’s Tough Guy turbidity curtains were supplied by the Geosyn-thetics Division of Reed and Graham, a family-owned asphalt and erosion con-trol supply company in business since 1928. The Geosynthetics Division of the firm is located in Sacramento, CA. The turbidity curtains are manufactured by Aer-Flo Inc. of Bradenton, FL, at that location and at another factory in Anniston, AL. Tough Guy turbidity curtains, also knows as turbidity barriers, are available in three types, each meeting DOT specifications. Type 1 is for areas with light winds and current velocities of less than 1 foot per second. Type 2 can handle rougher conditions, with current velocities of up to 5 feet per second. Type 3 is a special adaption of the Type 2 barrier. Approximately 20% of the area of the barrier skirt fabric is replaced with a polypropylene filter fabric. As these four projects show, cofferdams and turbidity curtains play an essential role in controlling erosion and maintaining water quality. With environmental regulation—on both federal and state levels—not only here to stay, but likely to increase, cofferdams and turbidity curtains will continue to be useful tools. EC Author Margaret Buranen writes on the environment and business. WWW.EROSIONCONTROL.COM SURFACE DRAINS FOR SEDIMENT BASINS t t t t t PVC skimmer floats on the surface, releasing the cleanest water Drains from the basin’s SURFACE instead of the bottom Improves basin performance Simple, automatic, gravity operation Works in basins with risers or sediment traps with spillway t t t t Replaces perforated risers and stone outlets as the basin’s drain Convenient for use in a detention basin as a temporary sediment basin during construction 8 sizes available Inlet orifice easily adjusted for drawdown requirements Patent # 5,820,751 Sizes, flow rates, prices, illustrations and instructions are available at JW Faircloth & Son Inc. Hillsborough, NC 27278 | 919.732.1244 | 919.732.1266 fax 28 EROSION CONTROL

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