MICHELLE GERRITSEROSION & SEDIMENT CONTROL SPECIALIST
WISDOT608-264-8417
Dewatering Technical Standard
http://dnr.wi.gov/runoff/stormwater/techstds.htm
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
What do you need to know before dewatering?
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
What are your dewatering options?
Geotextile BagsType I & Type II
Sized by soil particle size, pumping rate & 50% clogging factor
Gravity based settling >Portable Sediment Tank>Sediment Trap or Basin >Wet Detention Basin
Rely on gravity settling as primary method, require quiescent conditions
Passive filtration >Manufactured Filters>Portable Filter Tank>Filter Basin>Vegetative Filter
Relies on filtration as primary method
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.
FLOW CHART
SOIL TEXTURE
DEWATERING MATRIX
How do you chose the right BMP for your situation?
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
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
Key issues to remember when dewatering