Finding the best fit for the job
BMPs in stormwater pollution prevention are all designed for specific applications, each with strengths and weaknesses.
DuraWattle has many strengths and can be a great innovative solution.
To better understand its possible benefits, it’s helpful to see it in context with other traditional stormwater BMPs.
BMP Design Comparison
(nonwoven/woven or wire-backed)
(incl. Straw Wattle)
|Weight||5lb/12ft section||41-52lb/100ft (without stakes)||30-60lb/section (dry)||8-200lb/ft. (depending on length and diameter)|
|Height||5.5in||3-4ft||9-20in (diameter)||5-32in (diameter)|
|AOS||40 US Sieve||20-30 US Sieve||n/a||<6 US Sieve (3-10mm)|
|Sediment retention rate||96.6%||60-90% (lower if prefab silt fence)||47-60%||50-78%|
|Turbidity reduction rate||58%||52%||28.6-42%||63%|
|Clean flow through rate||100 gpm/ft2||1-18 gpm/ft2||7.5-8 gpm/ft2||4.5-35 gpm/ft2 (*Flow rate varies based on diameter of sock)|
|UV resistance||1000 hrs: 90%||500 hrs: 80%||500 hrs: n/a||1000 hrs: 23-90%|
|Tensile strength||320x290lb||100x100lb – 125x125lb||n/a||26-200psi|
|How does it filter?||The outer layer of fabric filters the sediment-laden water as it passes through the base of the wattle above the “tail section”. Clean flow-through rate of approx. 100gpm/ft^2. It does not filter hydrocarbons or dissolved metals.||The fabric ponds sediment-laden water causing sediment to be retained as it settles. Clean water flow-through rate of approx 1-13gpm/ft^2. It does not typically filter hydrocarbons or dissolved metals.||When properly trenched and secured, a fiber roll will slow the velocity of sheet flow runoff, filtering sediment-laden water through the roll and ponding excess runoff behind the barrier allowing the sediment to settle. Clean water flow through rate of approx. 7-8gpm/ft^2. It does not typically filter hydrocarbons or dissolved metals.||A compost filter sock will dewater sites while retaining sediment, absorbing pollutants, and ponding excess runoff allowing additional sediment to settle. Clean water flow through rate of approx. 4.5-35 gpm/ft^2. Compost filter socks may be designed to absorb hydrocarbons or dissolved metals.|
|What applications is it designed for?||Perimeter control, stockpile management, drain inlet protection, and site access points. It is most effective when installed where heavy concentrated flow is expected and dewatering is a priority.||Stockpile management and Perimeter control. It is most effective when installed at the toe of slopes where heavy sheet flow is expected.||Perimeter control, check dam, drain inlet protection or erosion control. Most effective when installed on slopes perpendicular to sheet flow to pond water and prevent erosion.||Stockpile management, perimeter control, or drain inlet protection. Most effective when installed downslope perpendicular to sheet flow or low concentrated flow.|
|How is it installed?||Soil and curb applications
trenched six inches, nailed every foot, and backfilled. Hard surface applications: tail section is folded over itself, piece of cold rolled steel is placed ontop of folded tail section, and concrete fasteners are used to secure the product to the surface
|Trenched into the soil using either static slicing or traditional trenching, surrounding backfill is compacted, wood or steel support posts are driven 2ft into the soil, and filter fabric is secured to support posts (wire backing is optionally attached).||Before installation, slopes must be prepared by smoothing any gullies. The wattle is trenched into the soil, excess soil is backfilled behind the upstream side of the wattle, pilot holes are driven into the wattle using a steel bar, and stakes are driven every 3-4ft.||The compost sock is set in place and then filled using a mechanical compost spreader. Stakes are driven into the sock every 10ft for sheet flow and every 5ft for concentrated flow. Edges of the socks should be turned upslope to prevent failure.|
|How long does it typically last?||3-5 years
(unless heavy equipment is maneuvering/working on top of the installed product rather than directly driving over it to enter a site)
(unless driven over or improperly installed)
|6 months – 2 years
(unless driven over or they reach their sediment retention capacity)
|9 months – 3.5 years
(unless driven over or they reach their sediment retention capacity)
|Is it reusable?||Yes
Approx 70-90% of DuraWattle can be removed and reused at different jobsites.
The filter fabric and damaged wooden posts are often transported to a landfill while the steel posts (and wirebacking) may be reused.
After a fiber roll has reached its sediment retention capacity it cannot be reused with the same effectiveness.
Typically a compost sock is left onsite to help stabilize and promote vegetation.
|Is it effective on hard surfaces?||Yes
DuraWattle is designed to be secured to hard surfaces without a change in filtering surface area (installation described above).
Silt fence cannot be installed on hard surfaces without trenching of some kind.
Without being trenched or properly weighted, there is not enough contact with the ground to filter sediment laden water effectively.
If properly weighted, a compost filter sock can be used on hard surfaces with concrete blocks or gravel bags behind the sock to help stabilize during rain events.
- United States Department of Agriculture – Natural Resources Conservation Service. (January 2011) “Agronomy Technical Note No. 4 – Utilization of Compost Filter Socks”
- Oregon Department of Environmental Quality. (April 2015) “Erosion and Sediment Control Manual”
- California Stormwater Quality Association. (2003) “California Stormwater BMP Handbook – Construction”
- United States Environmental Protection Agency. (April 2012) “Stormwater Best Management Practice – Silt Fences: Design, installation, maintenance, inspection”
- California Department of Parks and Recreation – Off-Highway Motor Vehicle Recreation Division. (November 2007) “OHV BMP Manual for Erosion and Sediment Control”
- Dean A. Moulis, EIT & Raymond D. Morgan, PE PLS – Arizona Department of Environmental Quality. (2010) “Good and Bad uses of BMPs”
- Michigan Department of Environmental Quality. (December 2012) “MDEQ Nonpoint Source Best Management Practices Manual”
- Bugg, R.A.; Donald, W.; Zech, W.; Perez, M. Performance Evaluations of Three Silt Fence Practices Using a Full-Scale Testing Apparatus. Water 2017, 9, 502.
- La Crosse County Land Conservation Department. (March 2006) “Erosion Control – Urban Programs”
- Idaho Department of Environmental Quality – Water Quality Division. (September 2005) “Catalog of Stormwater Best Management Practices for Idaho Cities and Counties”
- Filtrexx Sustainable Technologies. “Design Manual – Section 1: Construction Filtrexx Sediment/Perimeter Control (Siltsoxx)”
- American Excelsior Company – Earth Science Division. (April 2017) “Design Values for Curlex Sediment Log and AEC Premier Straw Wattles”
- Sprague, Joel Sr. Engineer – TRI Environmental, Inc. & Geohay, LLC. (September 2008) “Bench-scale Sediment Retention Device Testing ASTM D 5141”