•	Benefits
•	Limitations
•	History
•	Benefit/Cost Research
•	Project Cost Information
•	Tools and References
•	Details and Specifications
•	Funding Information
•	Native Plants, Supplies, & Materials
•	Project Showcase
•	Soil Amendments

For more information on Soil Bioengineering, contact:
Mark Maurer
maurerm@wsdot.wa.gov
Phone: 360 705-7242
Fax: 360 705-6815
or
Sandy Salisbury
salisbs@wsdot.wa.gov
Phone:360 705-7245
Fax: 360 705-6815

•	Access
•	Utilities, Railroad and Agreements
•	CAE Support Team
•	Design Policy, Standards, and Safety Research
•	Hydraulics
•	Project Development
•	Right of Way Plans
•	Roadside and Site Development
•	Standard Plans
•	Value Engineering
•	WSDOT Design Office

Soil Bioengineering

Soil bioengineering (SB) uses live plant materials to provide erosion control, slope and stream bank stabilization, landscape restoration, and wildlife habitat. These techniques are used alone or in conjunction with conventional engineering techniques.

Soil bioengineering employs a partnership of the professions of soil science, landscape architecture, civil, hydrological, and geotechnical engineering, and horticulture.

Soil bioengineering is an excellent tool for stabilizing soil erosion. These methods shouldnot, however, be viewed as the only solution to erosion problems.

Benefits

• Projects usually require less heavy equipment excavation. As a result, there is less cost and less impact. In addition, limiting crews to one entrance and exit route will cause less soil disturbance to the site and adjoining areas.
• Erosion areas often begin small and eventually expand to a size requiring costly traditional engineering solutions. Installing soil bioengineered systems while the site problem is small will provide economic savings and minimize potential impacts to the road and adjoining resources.
• Use of native plant materials and seed may provide additional savings. Costs are limited to labor for harvesting, handling, and transport to the project site. Indigenous plant species are usually readily available and well adapted to local climate and soil conditions.
• Soil bioengineering projects may be installed during the dormant season of late fall, winter, and early spring. This is often when other construction work is slow.
• Soil bioengineering is often useful on sensitive or steep sites where use of heavy machinery is not feasible.
• Soil bioengineering systems are strong initially and grow stronger as vegetation becomes established. Even if plants die, roots and surface organic litter continues to play an important role during reestablishment of other plants.
• Once plants are established, root systems reinforce the soil mantel and remove excess moisture from the soil profile. This is often the key to long-term soil stability.
• Soil bioengineering provides improved landscape and habitat values.

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Limitations

• Soil bioengineering has unique requirements and is not appropriate for all sites and situations. On certain surface erosion areas, for example, distribution of grass and forb seed mixes, hydromulching, or spreading of a protective layer of weed-free straw may be satisfactory and less costly than more extensive bioengineering treatments.
• On areas of potential or existing mass wasting, it may be best to use a geotechnically-engineered system alone or in combination with soil bioengineering.
• Project areas require periodic monitoring. On highly erosive sites, maintenance will be needed until plants are established.
• Established vegetation can be vulnerable to drought, soil nutrient and sunlight deficiencies, road maintenance sidecast debris, grazing, or trampling, and may require special management measures to ensure long-term project success.

Reference - Soil Bioengineering - An Alternative to Roadside Management by Lisa Lewis

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Typical Costs
Cost information is in 2000-2001dollars.

• Typical cost estimates
  Generic cost estimates for some typical soil bioengineering treatments.
• Chelan Project
  Actual costs for terracing, biosolids treatment, and planting a 2,400 sq ft slope near Lake Chelan, WA.
• Forks Project
  Actual costs for gully repair, terracing, and planting an 8,660 sq ft project near Forks, WA.
• Raymond Project
  Actual costs for installing a cribwall, terracing, and planting a 28,075 sq ft project near Raymond, WA.
• Eastern Region Project
  Estimated costs for gully repair, terracing, and planting a 2,000 sq ft project near Rosalia, WA.
• North Central Region Project
  Estimated costs for gully repair, terracing, and planting a 4,500 sq ft project on SR 2.
• Northwest Region Project
  Estimated costs for gully repair, terracing, and planting a 4,500 sq ft project on SR 2.
• Olympic Region Project
  Estimated costs for gully repair, terracing, live staking, and planting a 600 sq ft project in Olympia, WA.
• Southwest Region Project
  Estimated costs for gully repair, terracing, live staking, and planting a 600 sq ft project near Vancouver, WA.

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Tools and References

• Soil Bioengineering References organized by author (pdf)
  Soil Bioengineering References organized by title (pdf)
  Soil bioengineering, biotechnical stabilization, native plant, erosion control, and other topics are covered in this list of 200+ scientific papers, journal articles, books, and other published materials.
• Designer's Cheat Sheet (pdf)
  A simple guide for choosing among several soil bioengineering options, based on erosion conditions.
• Soil Bioengineering Video On-Line Order Form
  A soil bioengineering instructional video is available from WSDOT Engineering Publications for $20. See soil bioengineering techniques as they are implemented. Video clips of live staking, live gully repair, brushlayering, live fascines, and willow walls with a brushlayer base.
• Biotechnical Stabilization of Steepened Slopes (pdf)
  By Donald H. Gray and Robbin B. Sotir, this scientific paper describes the basic principles of biotechnical stabilization. Guidelines are presented for analyzing the surficial, internal, and global stability of brushlayer reinforced fills. A case study is reviewed of live, brushlayer inclusions used to stablize steep slopes along a roadway.
• Guidelines for Developing and Managing Ecological Restoration Projects
  This document, from the Society for Ecological Restoration International, covers pre-planning, prelimiinary tasks, and post-installation tasks.
• Soil Bioengineering An Alternative to Roadside Management (pdf)
  A practical guide by Lisa Lewis, US Forest Service. This guide covers basic soil bioengineering concepts. It includes a site evaluation and design, planning, and implementation checklist. It covers twelve different upland techniques.
• WSDOT Roadside Manual Chapter 740 - Soil Bioengineering (pdf)
  This practical guide covers definitions, planning, design, implementation, site evaluation, and eleven upland soil bioengineering techniques. This guide is similar to the USFS guide, but gives WSDOT-specific information.
• Soil Bioengineering for Upland Slope Stabilization - WSDOT Research Report (pdf)
  This report covers three soil bioengineering projects near the City of Raymond, Lake Chelan, and the City of Forks.
• Toward Quality Biosolids Management; A Trainer's Manual (pdf)
  By Dan M. Sullivan, Professor of Crop and Soil Science, Oregon State University. This is a resource for those who oversee and conduct biosolids training programs.
• Engineering Field Handbook, Chapter 16 - Streambank and Shoreline Protection (pdf) This is a large file and may take several minutes to download.
  By the USDA Natural Resources Conservation Service. This guide focuses on riparian protection and includes a planning and selecting measures section, separate streambank and shoreline sections, and useful appendices. (This download may be lengthy.)
• Engineering Field Handbook, Chapter 18 - Soil Bioengineering for Upland Slope Protection and Erosion Reduction (pdf) This is a large file and may take several minutes to download.
  By the USDA Natural Resources Conservation Service. This guide focuses on upland work and includes sections on integrated planning and design, soil bioengineering combined with geotechnical engineering, and nine different soil bioengineering techniques. (This download may be lengthy.)

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Details and Specifications

Specifications

Examples of Special Provisions written to amend the Standard Specifications for Soil Bioengineering projects. These are for review and guidance only... they need to be altered to fit the circumstances of each project.

Example 1 - used with WSDOT Standard Specs, includes planting, live stakes and fascines.

Example 2 - used with FHWA Standard Specs, covers planting, seeding, compost, live staking, log timber cribwall, and more.

Details

Details are not WSDOT Standard Details, and are available for educational and demonstration purposes only. It is necessasary to tailor details to each specific project.

WSDOT is not responsible for accuracy or completeness of these details, or the outcome of any project employing them.

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Funding Information

The following is not an exhaustive list of potential funding sources. We are in search of other quality sources. Please e-mail the WSDOT Roadside and Site Development Unit, with details of additional sources for review.

Please note that we are not offering funding nor are we a resource for those wishing to apply for the funding opportunities below. Please contact the agencies for information about their offerings.

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Native Plant Suppliers

Supplies, materials and equipment for erosion control and soil bioengineering use can be very specialized, and therefore, difficult to find. The following are some sources of: native plant supplies, erosion control products and services, and WSDOT approved products (WSDOT Qualified Products List).

Many of these products and services have not been tested or approved in any way by WSDOT. WSDOT does not endorse any particular products or service providers over others, whether they are included or not. This is not an exhaustive list, please contact the organizations below to add your product.

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Soil Amendments

Soil conditions are the key to a successful revegetation or restoration project. Many times, soil properties must be changed by adding soil amendments. Information on some of these is listed below.

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