Extreme water flows produced by Hurricane Irene caused severe erosion to the earthen emergency spillways at the 40-year-old Maplecrest, Nauvoo and Mitchell Hollow Dams serving the Batavia Kill (River) Watershed District in Windham, N.Y. The Tensar VMax P550 turf reinforcement mat (TRM), a permanent and economical erosion control solution, was chosen to permanently protect and revegetate the site.
The challenge
The timing of the repairs was critical, since vegetation needed to be established in advance of the rainy season and snow. Also, the spillways were surrounded by farmland, so the district preferred a more natural, reinforced, vegetated solution. Cool weather, a short timeline and heavy, compacted clay soils posed additional challenges for the site.
A competitive TRM product was considered, but extensive engineering test reports on the performance of the VMax P550 TRM and its proven track record of establishing vegetation was the determining factor in its use on the spillway site.
The solution
The VMax P550 TRM, part of the RollMax Systems family of rolled erosion control products, combines a UV-stabilized three-dimensional matting with a 100% polypropylene fiber matrix to offer one of the line’s most rigorous erosion protection, vegetation establishment and reinforcement properties. One of the benefits of the VMax P550 TRM is its ability to quickly establish vegetation through the mat, providing both an anchor for vegetation and the ability to filter fines during inclement weather.
Fastracs crews completed the four installations of VMax P550 TRM over a five-week period (interrupted by periods of cold weather) in fall 2012. Altogether, 35,000 sq yd of product, covering nearly seven acres of graded surface with a 3-in. layer of native topsoil, were placed. Jerry Paschal, Fastracs project manager, scheduled 12- to 16-man crews for the installation. Paschal said that the rolls of TRM were easy to handle and unroll; however, due to the compacted clay soil, the crew devised its own stapling tool to overcome the surface resistance of the hard, cold soils.
Prior to installation, the sites were seeded with a three-variety blend of fescue. Both early winter and spring frosts delayed some germination, but “In areas where seeding took hold over late summer and early fall, it’s looking great,” said Thomas Hoyt, the Town of Windham’s highway and water superintendent and contract officer for the watershed district. Despite more inclement weather—including a 50-year rain event in September 2012—Hoyt said that the TRMs are performing to expectations.
