Case Study: Big Sky Channel

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Case Study Overview

Project: Big Sky Channel
Location: Big Sky, MT, United States
Project Type: Shoreline Reinforcement
Application: Reinforced Channel
ProductS Used: PYRAMAT®

Photo showing Big Sky channel construction.

Problem

In February 2006, Shea Homes was in the process of constructing Big Sky, a high-end canyon residential development adjacent to a meandering channel that had significant scour potential. Because Shea Homes could not close escrow on several of the lots until the channel improvements were completed, the installation of an erosion control solution was required to occur as quickly as possible. Concrete and rip-rap and turf reinforcement mats were considered. VTN West, the site civil engineer, is no stranger to southern California residential development projects involving challenging flood control constraints. Additionally, Dr. Howard Chang, a world-renowned sediment transport consulting engineer, was intimately involved with the channel design. Dr. Chang has been retained by the Ventura County Watershed Protection District on several occasions to work on Ventura County's challenging flood control issues.

Solution

The design prepared by VTN West and Dr. Chang included the Pyramat high performance turf reinforcement mat (HPTRM), vegetation for aesthetic and habitat creation purposes, and 14 ft deep cut-off walls at the upstream end, downstream end, and incrementally spaced throughout the project. A grouted rip-rap combination design was used at locations designated to have high scour potential. The tan colored Pyramat was chosen for this canyon channel application to match the intended future native vegetation. The Pyramat® high performance turf reinforcement mat (HPTRM) was selected because of the aesthetic, cost-saving, water quality benefits and performance over the other alternatives. Pyramat® outperforms other turf reinforcement mat products because of its long-term design life through superior tensile strength, UV protection, flexibility, woven technology and X3® fiber technology, which allows for faster vegetation growth.

Photo showing PYRAMAT HPTRM installation in conjunction with 14 ft deep cut-off walls.
Photo showing vegetation established within approximately one year due in part to PYRAMAT's X3 fiber technology.

Performance

Gallion Erosion Control began the Pyramat® installation in February 2006 during a rain event. The Pyramat® performed very well despite the rain that ocurred during the installation. Native vegetation was planted during the summer and fall of 2006. Shea Homes has been very pleased with the performance and benefits of the Pyramat® for this project and would use it again for future applications.


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