Water & Sediment Control Basin
(WASCOB)Mike Cox
State Conservation Engineer
Contractor Certification
Training
March 2008
Purpose: 1) Reduce gully erosion 2) Trap Sediment 3) Reduce and manage downstream runoff
Water & Sediment Control Basin (638)
WASCOBs are typically used when drainage
areas are smaller.
WASCOB Spacing is to reduce slope length and accommodate equipment width
Farmed - WASCOB
• Slopes are flatter (5:1 to 10:1)• More yardage must be used during construction• Harder to fit into steep areas
Grassed - WASCOB
• Slopes are steeper (3:1 to 5:1)• Less yardage used during construction• Fits better into steep areas• Slopes steeper than 5:1 must be grassed
Compaction of Earth Fill
• Use 6-9” Lifts• Dozer or Loaded Pan on Each Lift – 2 passes• Sheepsfoot Roller – 1 pass
Borrow Areas
• Don’t get borrow at the channel– Unless plans call for the channel to be excavated
• Borrow should come from field above• Remember to stockpile topsoil
Outlets for WASCOBs
• Underground Outlet (620)• Outlet tile is sized per orifice diameter• Orifice plates must be installed
Risers
• Must be minimum of 2.5’ in height
Installation Report http://www.in.nrcs.usda.gov/technical/engineering/engineering.html
Look Under Contractor Certification Section
Landowner:WASCoB Number:TBM # and description:TBM Elev: TBM reading: HI:
Orifice diameter: Orifice elev.: Outlet tile diam:Riser diameter: Riser height: Outlet tile elev at riser:
Channel RidgeRod Rod Description
I certify that I have constructed the WASCoB in accordance with this report and the NRCS plans and specifications.Contractor: Signature: Date:
(print name)
ElevationStation Elevation
PROFILE
WASCoB CONSTRUCTION CHECKOUT SHEET
Construction Tolerances-WASCOB
Orifice Elevation: +0.1 foot
Levee Width: Planned width or wider
Top of Levee: Grade or above
Side Slopes: Planned slope or flatter
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