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Rc401 construction jennings e&s

Rc401 construction jennings e&s






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    Rc401 construction jennings e&s Rc401 construction jennings e&s Presentation Transcript

    • Erosion & Sediment Control for Stream Restoration Projects
      Greg Jennings, PhD, PE
      Professor & Extension Specialist
      Biological & Agricultural Engineering
      North Carolina State University
      Thanks to Wyatt Brown, LSS, CPESC
      NC Ecosystem Enhancement Program
    • NC Sediment Pollution Control Act, 1973
      15A NCAC 04B .0105
      Persons conducting land‑disturbing activity shall take all reasonable measures to protect all public and private property from damage caused by such activities.
      History Note: Authority G.S. 113A‑54(b); 113A‑54(d)(2);
      Eff. February 1, 1976;
      Amended Eff. August 1, 1988; November 1, 1984.
    • Construction Practices
      Site Preparation
      Site Stabilization
    • 1. Site Preparation
      • Construction entrance
      • Silt fence
      • Staging & stockpile
      • Temporary crossings
      • Stream flow diversion
    • Silt Fence
      Metal Posts 8 feet apart
      Reinforcing wire backing (14 ga. w/ 6-inch mesh)
      Bury fence 8 inches deep
    • Silt Fence Problems
    • Silt Fence Problems
    • Staging and Stockpile
    • Stockpile AreaSilt fence & seeding
    • Problems?
    • Temporary Stream Crossing
      Rock ford
      Portable log mat
    • Problems?
    • Prevent erosion around culvert
    • Problems?
    • Stream Flow Diversion
      Open channel
      Pump around
      Work in wet
    • Open channel
      Must dissipate energy at end
    • Problems?
    • Pipe
    • Pipe Undersized
    • Pump Around: Match pump to 2 x base flow
    • Check dam to retain base flow
      Quiet pump in residential area
    • Pump discharge downstream
    • Problem?
    • Special Stilling Basin: Filter Bag
    • Problem?
    • Problem?
    • 2. Grading
      Stage project to limit exposed areas
      Use temporary ground cover
      Use track equipment if possible
      Keep stormwater runoff away from site
    • Clearing & Grubbing
      Followed by Survey Stakeout
    • Problem?
    • Problem?
    • 3. Structures
      Build according to design
      Check elevations (twice)
      Footer boulders and backer logs
      Seal structures to prevent piping
      • “Chink” rock structures
      • Filter fabric for all structures
    • Boulder Cross Vane
      20-30 degree angles
      2-5 % arm slopes
      20-30 degrees
      2-5 % arm slopes
    • Laser Level for Grade Check
    • Log Vane (with root wad)
      Backer Log
    • Woven filter fabric nailed to top log
    • Geotextilenailed to top log
    • Overhanging top log for fish cover
    • Why do structures fail?
      • Rocks or logs not placed properly
      • Piping under or through rocks or logs
      • Lack of geotextile, improperly placed
      • Excess scour
      • Poor vegetation & bank stability
    • Structure Problems
      • Wrong Location
      • Too Steep
      • Not Keyed Into Bank
      • Poor Vegetation Establishment
      • Not Sealed
    • Poor placement and not keyed in
    • Drop too great
    • Easy to spot during high flows…
    • Also easy to spot…after the flows have receded
    • Too steep
    • Too steep
      How about this one?...
      Keep log wet…even at normal daily flow
    • Structural collapse
    • Root Wads Too High
      Too Few & Washed Out Behind
    • Problem?
    • Problem?
    • Problem?
    • 4. Site Stabilization
      Temporary ground cover (mulch & matting)
      Permanent ground cover (vegetation)
      Prepare for rain!
    • Straw Mulch: 75% cover (2 tons/acre)
    • Hydroseeder (mulch, seed, fertilizer)
    • Matting
      Biodegradable (coir, jute, excelsior, straw)
      Seed and straw UNDER matting
      Keep matting relaxed
      Stakes: wood or biodegradable plastic
    • No Plastic!
    • Each Day:
      Seed, straw, matting
    • Erosion control every day
    • Large stakes at toe of slope
    • Problem?
    • Irrigation
    • Overland Flow
    • Straw Wattle used as Berm
    • Straw Wattle used as Berm
    • Site Inspection
    • Note: Channel stabilized before floodplain
    • Successful Project:
      Good design considering hydraulic & sediment transport processes
      Communication between designer & contractor
      Flexibility to make field changes
      Understanding of environmental regulations
      Prepare for flooding!
    • Use Common Sense
    • Thanks to:Wyatt Brown, NC EEPDan Clinton, CaryDarrell Westmoreland, North State EnvironmentalJan Patterson, Cary, NC