Severe channel aggradation combined with high stream flow velocities resulted in accelerated streambank erosion and channel migration within Buckeye Creek, which is an intermittent tributary to the Sacramento River.  The Buckeye Creek watershed is located within the western Sacramento Valley region of Northern California, and drains an area of approximately 100 km2, primarily rangeland.  The largest land uses in the basin are primarily dryland ranching and irrigated almond orchards.  The region receives approximately 750 mm of precipitation annually, typically between November and June.  Buckeye Creek along this project reach is primarily a “dry” riparian area, and the most abundant xeric species include chamise, toyon and buckeye.  There are a few cottonwood trees on-site.  The highly eroded outer banks are generally devoid of vegetation and the toe of the vertical banks are composed of consolidated gravely clay loam and poorly consolidated gravely alluvium.  The few places along the banks where cottonwoods or the random almond tree have established show reduced streambank recession.

Between 1940 and 1976 Yolo County owned and operated a waste disposal site adjacent to Buckeye Creek, approximately 5 miles NW of Dunnigan.  During this period the 2 ha dump received primarily household waste that was periodically burned and buried to consolidate the landfill.  The Dunnigan Burn Dump is typical of many abandoned landfills throughout the State and these burn dumps require remediation when erosion exposes the waste and burn ash.  Burn ash is toxic and must be handled carefully, usually by in-situ burying, to ensure the ash does not become airborne.  The California Integrated Waste Management Board (CIWMB) has an AB 2136 Solid Waste Disposal and Codisposal Site Cleanup Program to assists with remediation of burn dumps.  The CIWMB can provide cost-share funding, project design and project administration to qualifying applicants.
In recent years, streambank erosion exposed the waste and burn ash at the Dunnigan Bun Dump.  In one winter alone, 1997/98, the accelerated erosion resulted in approximately 7 to 10 meters (20-30 feet) of lateral bank erosion which allowed the toxic waste to be washed into Buckeye Creek.  The Yolo County Public Works Department requested the assistance of the CIWMB to manage the cleanup and remediation of the site.  Subsequently, CIWMB engineers developed plans and specifications for the remediation.  The remediation plans involved:  (1) the removal of exposed waste from the landfill, streambank, and creek channel; (2) regrading the streambanks to the desired slope; (3) capping the areas of exposes waste; (4) constructing deflectors to divert flow away from the bank; and (5) install biotechnical erosion control along the streambank.

The CIWMB hired John McCullah, Salix Applied Earthcare, to provide design and specifications for the erosion control aspects of this project.  The erosion control consultant enlisted the services of David Derrick, River Research and Design, to provide more detailed designs for the Bendway Weirs and Longitudinal Peaked Stone Toe Protection.  All non-Mississippi River Bendway Weir projects in the U.S. (25 projects at this time) were designed or co-designed by Mr. Derrick.  Doug Hanford, Hanford and Company provided designs and implementation for post-construction soil bioengineering elements.

The goals for this project was to prevent the exposed waste, car bodies, glass and burn ash from further contaminating the area.  The waste would be pulled back from the streambank, re-consolidated, and capped with topsoil.  The long-term goals would be achieved with effective erosion control.  The topsoil cover would be protected from future erosion with appropriate native grass species while the streambank erosion and lateral migration would be arrested with a combination of structural and vegetative methods.

Both gabions and rock riprap were initially considered for this project.  The large rock for riprap and angular stone for the gabions was not locally available and would have to be delivered great distances.  The gabions and rock riprap were ultimately rejected for several reasons:  In sand and gravel streambeds, the anticipated or calculated scour on the streamside of a gabion structure, even with a good foundation, can result in stability problems, undermining and failure.  Pullback and stabilization with rock riprap would be expensive because significant quantities of large rock would be required.  There was no guarantee that rock riprap would solve the problems of streambank scour and erosion, and the use of riprap alone was rejected for this project.  Additionally, some state resource agencies had recently voiced concerns over long-term loss of habitat from the use of gabions and riprap along streambanks in California.  It was determined that the construction of rock weirs to deflect flows away from the eroding outer bank would require less rock material.