Erosion and Sediment Control
Product Case Study
The Skeleton Keys of Turf Reinforcement
The stretch of SH23 between Hamilton and Raglan was identified as a high-risk rural road by the Safe Roads and Roadside program by the New Zealand Transportation Authority (NZTA). The project required a 25 m high and 60 m long cut face to cut back a corner to improve sight lines.
The Katikati project in the Bay of Plenty had a similar sight line issue and had an embankment that had become unstable. To add an interesting twist, the top of the slope that required improvements was a cemetery. This presented a unique challenge as to how to perform the work without disturbing any of the graves while creating a natural look.
The engineers had to take into account a number of factors when designing both projects. How far back do we need to cut the slope back to provide better sight lines? How much space do we have to work with? What kind of equipment will we be limited to? How steep will the slope be? How will we get vegetation to establish? Will we need temporary, permanent or a mix to stabilize the slope?
Broadspectrum was selected as the contractor to do the work for SH23. Broadspectrum knew Cirtex (a distributor for East Coast Erosion Control) had been a part of numerous other Safe Roads and Roadside projects so they reached out to see if they had any recommendations. Due to the geometry of the embankment, it was decided that a double net with a polypropylene fiber matrix coupled with 300 mm HD steel pins would be used to stabilize the new slope.
EcoTec BOP was selected for the Katikati project. Since the work zone was limited and it was already unstable, a high performance turf reinforcement mat (HPTRM) was recommended along with percussion driven earth anchors to secure the embankment. After the grade changes were made, the contractor was able to install the HPTRM without using heavy equipment to preserve the grave sites at the top of the slope. The UV stabilized, permanent turf reinforcement mat provided an aesthetically pleasing finish and met the environmental needs for the project.
The end result was a safer, aesthetically pleasing landscape for both projects. SH 23 was much safer and taken off the “high risk” list. Visitors to the cemetery in Katikati are content to see a lovely final resting place for their loved ones. Broadspectrum and EcoTec BOP were satisfied at how quickly the turf reinforcement mats on their respective projects were installed and vegetated.