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