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Dewatering Technical Standard

Dewatering Technical Standard

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Dewatering Technical Standard

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  1. Dewatering Technical Standard Michelle gerrits Erosion & sediment control specialist Wisdot 608-264-8417 http://dnr.wi.gov/runoff/stormwater/techstds.htm

  2. What do you need to know before dewatering? Sanitary and storm sewer locations Potential contamination Soil texture Depth to ground water Karst features Discharge outfall locations Topography & ground cover condition Distance & conveyance to receiving waters

  3. What are your dewatering options? Reuse as dust control Onsite infiltration Transport to sanitary /treatment facility Geotextile bags Gravity based settling systems Passive filtration systems Pressurize filtration systems Polymer addition

  4. Geotextile BagsType I & Type II Sized by soil particle size, pumping rate & 50% clogging factor

  5. Gravity based settling >Portable Sediment Tank>Sediment Trap or Basin >Wet Detention Basin Rely on gravity settling as primary method, require quiescent conditions

  6. Passive filtration >Manufactured Filters>Portable Filter Tank>Filter Basin>Vegetative Filter Relies on filtration as primary method

  7. Pressurized filtration>Portable Sand Filter>Wound Cartridge Units>Membranes and Micro-filtration Pressurized systems force water through a media designed to handle higher flow rates and typically have automatic backwash systems. Most efficient at removing fine sediment.

  8. How do you chose the right BMP for your situation? Flow chart Soil texture Dewatering matrix

  9. Need to know 3 Basic Soil Textures Clayey - Fine to very fine particles >Snake Silty - Medium to fine particles >Binds Sandy - Coarse to medium particle >Falls apart

  10. Key issues to remember when dewatering Use a floating suction hose Prevent erosion at the outfall Infiltrate when practical Polymer use increases efficiency Remove accumulated sediment Combination of practices may be needed