Erosion Control June 2012 : Page 47
widespread use to optimize system op-eration and ensure that the system fail-safes are working as designed to prevent unnecessary flooding,” Roman says. Battling Erosion in Maine With 3,478 miles of coastline, Maine’s ex-posure to sea level changes and increased storm activity creates significant erosion issues. On April 16, 2007, the Patriot’s Day storm brought high tidal flooding dur-ing the late morning hours, putting it on the books as the seventh biggest tide on record for Portland at 13.28 feet. Waves 30 feet high ripped at buoys and dam-aged personal property at such locations as Chabeague Island in Casco Bay off the coast of Portland. Seven residential property owners on the island with exposure to the north and west hired Baker Design Consultants to engineer a solution to resulting erosion. The area also includes a town right of way to the beach. Baker Design Consultants is a civil engi-neering consulting firm in Yarmouth, ME, specializing in waterfront projects such as piers, docks, bulkheads, boat ramps, coast-al walkways, and coastal erosion solutions. The firm had 750 feet of the shoreline surveyed and calculated the erosion that’s occurred over the last 100 years. Some of the property markers that once used to be at the top of the bank are now on the beach. Barney Baker, P.E., says his firm de-termined a loss of some 40 feet of beach frontage in a span of 100 years. The soil formation at the site created a soft clay, with water coming through the bank, creating what Baker calls “a real nightmare in terms of embankment stabilization.” The site presented challenges prompt-ing Baker Design Consultants to consider several options. “It’s an island that has no quarries, no rock supply,” Baker says. “Everything— even loam—has to come from the main-land. We looked at using a natural stone, which meant a riprap solution. We looked at a sheet pile wall.” Ultimately, Baker’s firm chose Tensar’s Triton Marine Mattresses, designed to be uniform, porous, and flexible, and to con-form to uneven topography. “We even-tually came to these mattresses because they have the unique ability to reinforce the slope and be planted, so you have a green solution when you’re finished,” Baker says. “They also are used in areas of unstable slopes because they’re anchored at the top—they are essentially hung onto the slope—so we felt they would be resilient to continued wave attack, but also allow the bank to recover from and support water.” Baker also used several types of rolled erosion control products, such as Tensar/ North American Green P550 and SC250 turf reinforcement mats (TRMs). P550 is a permanent TRM designed to provide long-term, prevegetated erosion protection and permanent turf reinforcement in severe applications including steep slopes and ex-treme, high-flow channels and shorelines. The Vmax 3 SC250 TRM is constructed of a permanent, high-strength, three-di-mensional matting incorporating a straw/ coconut fiber matrix to enhance the mat-ting’s initial mulching and erosion control performance for up to 24 months. Because there had been a lot of water coming through the bank, Baker’s firm designed a natural surface drain and added other drains as well. “The mattresses seem to be very JUNE 2012 EROSION CONTROL 47