New Article Featuring John McCullah of Salix in the Jan/Feb issue of Land and Water Magazine.
Environmentally Sensitive Streambank Stabilization
“Are there any habitat-enhancing alternatives to rip rap that
the highway engineer can choose?”
The above question was asked by highway engineers from various State DOTs across the nation. The Highway Engineer is finding it increasingly difficult to get their stream-corridor highway or bridge project permitted. Rip rap has been increasingly used for decades and as a California Department of Fish and Game permit requirement noted “the continuing use of rip rap and gabions are resulting in long-term, cumulative habitat problems”. Biotechnical Streambank Stabilization Research the problem statement was posted by the Transportation Research Board and in 2002 funded for research by the National Cooperative Highway Research Project
(NCHRP). Salix Applied Earthcare won the 3-year research project. John McCullah, CPESC/ Geomorphologist; Dr. Donald Gray, Geotechnical Engineering Professor Emeritus of University of Michigan; and Dr. F. Douglas Shields, Hydrologist at the USDA-ARS National Sedimentation
Laboratory were the principle researchers. Published in 2005, NCHRP Report 544 Environmentally-Sensitive Channel and Bank Protection Measures (also referred to as Environmentally-Sensitive Streambank Stabilization (E-SenSS)), was developed to answer the need for specifications and
guidance regarding environmentally-sensitive channel and bank protection measures. This CD manual includes typical design drawings, construction and installation specifications, and an extensive photo gallery of project examples, all based on extensive research and experience.
Alberta Infrastructure and Transportation (AIT) has been employing these habitat-enhancing stabilization techniques starting in 2005, which has resulted in very successful environmental compliance and therefore easier permitting and consents. The AIT has now sponsored 3 highway/
streambank projects demonstrating the application of these techniques. The first two projects, referred to as Hinton I and II took place on the Pembina River in the Canadian Rockies. This article will highlight the third project, which took place at Willow Creek in the plains area of Southern
Alberta. All of these projects have included 3-day hands-on training courses, intended for design engineers, agency regulators, and contractors. AIT, Salix, and Blink Works produced videos that show and describe the implementation processes - on the ground and during construction. With these Dirt Time videos “you are really there, tasting the dust and smelling the diesel!” Demonstration Project !e Willow Creek project was proposed by AIT to protect Highway 2, a major north to south highway running from Edmonton through Calgary and south to the US-Canadian border. !e Willow Creek project site is about 1.5 hours south of Calgary near Fort MacLeod. At this site, Willow Creek has historically been impinging on the highway corridor. While not directly eroding the highway, the stream has been undercutting the
toe of a geotechnically unstable slope between the creek and highway. The constant undercutting has exacerbated the block failures occurring to the extent that only 60 feet exist between the highway ROW and edge of slope. The purpose of the project is to protect the toe of the slope from further erosion by Willow Creek, anchor the top of the slope with pneumatically-inserted slope pins and then treat the slope for erosion. Additionally, a 125 ft long drainage gully would be repaired. The secondary purpose of this project was to once again demonstrate the use of these techniques and hold a Biotechnical Erosion Control Field-training course. This demonstration has proven to be very important because there is much resistance to using anything but rip rap for the channel banks, even though the research shows techniques like longitudinal peaked stone toe protection (LPSTP) and redirective techniques, such as rock vanes or bendway weirs, have been used successfully for decades under many hydrologic conditions.
!ere is also reluctance in the West to use well-graded, poorly sorted, and subsequently self-adjusting, stone. Selfadjusting or self-launching stone better facilitates the incorporation of bioengineering techniques, such as pole planting, live siltation and/or brushlayering into the rock
structures. Most importantly, the use of self-launching stone can preclude the need for constructing scour or key trenches. This measure alone, again widely used and documented for decades, can eliminate the need to excavate into live channels. This approach can replace the need for turbidity barriers or other costly isolation techniques. The Pembina River projects were
intensively monitored for turbidity and sedimentation during construction and showed no increase in either. Construction In Willow Creek, John McCullah provided the design and AMEC did the project engineering, geotechnical analysis and wrote the tender (contract) documents and environmental clearances. !e contracts were “tendered” and the project began in
October of 2008. The first order of work was to build access roads and grade the slope. Simultaneously, three rows of 30’ long slope nails were installed with a Soil Nail Launcher to ensure stability of the upper slope edge. Work then began on the lower channel bank.
Nine Rock Vanes, projecting out approximately 30 feet into the stream were used to “re-direct” the high velocities away from the bank for the almost 3000’ feet of streambank protection. Additionally, the design would employ a Longitudinal Peaked Stone Toe Protection (LPSTP) to
protect the bank from erosion between the vanes. !e use of redirective techniques, combined with LPSTP, built to an elevation equal to annual high water or bankfull discharge, can often replace the rip rap-type “resistive” techniques so often employed to a much higher elevation up the bank. This philosophy is not operative when the stream or river is channelized or incised, of course, because some of the redirected flood flows may need “access” to the inner
bend and point bar. LPSTP provides a perfect opportunity to incorporated willows in the Live Siltation array. However, modified construction techniques are required for successful installation. After constructing a section of LPSTP one must be careful not to back fill behind the peaked stone. Then place the pre-soaked and properly handled willow branches with their basal ends as deep as possible into the bank with their tips sticking out toward the stream. !en the area can be back filled around the branches. It is best to “water in” the back fill. Woody perennial vegetation is not generally seen below the elevation of annual high water or bankfull discharge; so determining this elevation is a critical design element. If the LPSTP is built to roughly the elevation of bankfull discharge, then the Live Siltation branches, protruding above are likely to
successfully establish. It was also decided to employ and demonstrate Brushlayering with Soil Wrap (aka, Vegetated Mechanically Stabilized Earth (VMSE)) at the bottom section of a spoil slope. !e branches, the rocks, the geogrids, and the roots growing into the bank all provide mutual reinforcement. In biotechnical erosion control, the “whole is much stronger that any of the pieces alone”. The Training Course !e coordination of the training course and the video production with the actual construction was a major challenge. Fortunately the design team had some experience under their belt with the previous Pembina/Hinton projects. C-TEP (Centre
for Transportation Engineering and Planning) handled all course administration and AMEC provided the actual coordination with the contractor. The course was held on November 4,5, and 6, 2008, with over 50+ professionals attending. The first day was classroom instruction and the last two days were in the field actually building the biotechnical structures and implementing the new erosion control techniques. Field Course, Erosion Control and Slope Stabilization With the top and toe of the slope stablized, erosion control techniques were needed to be employed to the slope itself and treat the gully.This is when the education goals really came into play. AIT wanted Salix to design and demonstrate as many new and appropriate technologies as was feasible. This was also a great opportunity to get the course attendees involved, it was very cold and they did need to keep moving! The slope, which averaged 1.5:1, was prepared with Trackwalking where ever possible. Laboratory studies for Caltrans at San Diego State University (SDSU) document that this soil roughening technique reduces erosion by 52%. Fiber Rolls, while
quite common in California, had never been installed in the Province. Two installation
techniques were demonstrated, 1.) the trench and stake method and 2.) the stake and rope method - the latter doesn’t require a key trench. Soil surface stabilization techniques
were demonstrated, including Straw Mulching, Compost Blankets, and Hydromulching with Flexterra. Again the Caltrans/ SDSU studies show these techniques are all 90%+ effective for raindrop erosion. The gully was graded uniformly by shaping and widening the bottom. Instead of the ubiquitous check dam, not really the most sustainable or environmentally friendly technique, the bottom of the gully was lined with TRMs to protect the channel from erosion. Scour Stop mats were placed where high velocities were anticipated. The original plan was to install the Green Armor System but the wrong TRM Geotextile was provided. A lesson here is that one must be careful when purchasing products, as equivalency does not always exist, even though materials providers will cite the opposite. Summary Redirective bank protection techniques, e.g., Rock Vanes, Bendway Weirs, are environmentally-sensitive as they provide substrate complexity and direct high velocities of the bank. The use of stone which is well-graded and sized to self launching can eliminate the need to excavate and destroy the channel bottom. The heavy equipment work can then proceed from the bank such that turbidity and sedimentation levels
will not signifi cantly increase. Redirection of erosive flows allows the incorporation of more vegetative materials that provide additional geotechnical strength, shade, cover, organic
matter, and roughness. These “biotechnical techniques” are usually combined with structural materials, e.g., rock, gabion baskets, geogrids, stakes etc, in a mutually reinforcing manner. Biotechnical techniques are generally stable immediately and then get stronger with time. Thank goodness that Alberta Infrastructure and Transportation has been willing to accept some risk in employing these relatively unknown approaches. Because of their willingness and dedication to
education and awareness, several hundred professionals have had the opportunity to
increase their knowledge base and increase the contents of their streambank protection. This next January John McCullah will be traveling to Auckland, New Zealand to help design and build (restore) an urbanized stream for the North Shore City Council. !ey have seen the Alberta experiences and want to use these E-SenSS techniques. James and John are hoping to produce a new Dirt Time episode in Kiwiland… More later! L&W by John McCullah, Watershed Geologist, CPESC For more information contact John Mc- Cullah or James Swirsky at www.watchyourdirt. com. John McCullah can also be reached at Salix Applied Earthcare, 2455 Athens Ave, Redding, CA 96001, www.salixaec. com or john@salixaec.com.
