Presentation on theme: "Stormwater Overview of Construction BMPs Scott Taylor, P.E., CISEC."— Presentation transcript:
Stormwater Overview of Construction BMPs Scott Taylor, P.E., CISEC
Stormwater Construction BMP Review Erosion controls Sediment controls Tracking controls Material and waste storage 2
Stormwater When Should BMPs be Implemented? Perimeter controls should be installed before breaking ground In preparation for a rain event In all areas that have been inactive for >14 days At all times – ‘appropriate’. This means if there is a discharge, there is no excuse Permit does not have a ‘rainy season’ 3
Stormwater Erosion Controls Erosion controls provide 80% of sediment management Sediment controls provide 20% of sediment management Protect surface from rain drop impact Help retain moisture in the soil Minimize the down-slope transport of soil particles They will degrade over time 4
Stormwater Erosion Controls: Soil Binder Generally temporary and may require reapplication Soil type dictates kind of soil binder to use Must be environmentally benign Typically last months Polyacrylamide (PAM) is an effective, low cost option 5
Stormwater Erosion Controls: Mulches Hydraulic Mulch/Bonded Fiber Matrix Most types need 24 hours to dry before rainfall occurs Hydraulic mulch generally good for 3 – 6 months Bonded Fiber Matrix may last several wet seasons Mixture of mulch and binder Maximum slope about 4:1 Place over previously seeded area, or add seeds to the mixture 6 V
Stormwater Erosion Controls: Rolled Erosion Control Products Used when disturbed soil may be difficult to stabilize or drying time an issue Blankets and mats may need to be removed and disposed of prior to application of permanent soil stabilization Install perpendicular to contours 7
Stormwater 8 V
Erosion Control Cost/Performance CategoryMaterialCost/acre Sediment Reduction (%) Longevity Binders Guar$ Short Starch$ Short Acrylic polymers$1, Short Polyacrylamide$ Short Mulches Straw$2, Medium Cellulose Fiber$ Short Recycled Paper$ Short Bonded Fiber Matrix$5, Medium Rolled Erosion Control Products Woven Jute Mesh$6, Medium Excelsior$10, Long Straw Blanket$9, Long Coir (coconut shells)$13, Long Plastic Mesh Woven$2, Long 9
Stormwater Spray-on Erosion Control VideoControl Erosion control = turbidity control
Stormwater RECP Video Installation is critical for RECPs!
Stormwater Sediment Controls: Fiber Rolls Locate on level contours Use at top and on face of slopes Good for perimeter control Use recommended spacing in 2009 CGP Must be installed correctly: trenched and staked 12
Sediment Controls: Silt Fence Located level on contours, not perpendicular Not for concentrated flow areas Must be keyed in (bottom six inches must be buried) 16
Stormwater Sediment Control: Inlet Protection Protect active inlets year-round Use where ponding won’t encroach into traffic Maintain/clean out after every storm 17
Stormwater Sediment Control: Sediment Ponds Capture and de-silt sediment laden runoff Use for large drainages and steep slopes where erosion control is not feasible Maintain/clean out on an as needed basis 18 Video
Stormwater Tracking Controls A VERY visible indicator of compliance effort (or lack of) Minimize number of access points Use coarse aggregate over filter fabric Year-round requirement In high traffic areas, street sweepers may be needed 19
Stormwater Sediment Control Summary BMPApplicationFlow TypeCostLongevity Silt FencePerimeter ProtectionSheet flow$ $9/foot12-36 mo Reinforced S.F.Sediment TrapShallow conc.high end of SF12-36 mo Fiber RollPerimeter, inletSheet flow$1/foot (plus installation)12-36 mo Sed. BasinOnline/offlineConcentrated$2000/drainage acreIndefinite Inlet FilterInlet ProtectionConcentrated$200/inlet12-24 mo Rock EntranceTracking ControlsN/a$1200-$ rain events Rumble PlateTracking ControlsN/a$1200-$4800Indefinite 20
Stormwater Material Storage Cover and contain Keeps site clean / good housekeeping Avoids potential sampling for non-visible pollutants 21
Stormwater Waste Management Debris discharge from site is a permit violation! Cover trash containers Provide water-tight concrete washouts 22
Stormwater EXAMPLE PHOTOS
Stormwater 24 Soil Stabilization Potential Violation: Inactive area with no erosion control
Stormwater 25 Soil Stabilization Better Practice: Inactive area with erosion control BMPs
Stormwater 40 Silt Fence Better Practice Proper installation Maintained
Stormwater 41 Streets and Sidewalks Clean regularly – dry sweep or vacuum No water unless runoff directed away from drain inlets to pervious areas Potential Violation
Stormwater 42 Streets and Sidewalks Better Practice Well maintained
Stormwater 43 Construction Material Storage No protection of soil Potential Violations
Stormwater 44 Cover, berm, and contain Better Practice Construction Material Storage
Stormwater 45 Washout Pits Potential Violation Not using washout at all Leaking / ineffective washout
Stormwater 46 Washout Pits Better Practice Contractors must use a designated concrete washout Do not overfill Washout must be water tight
Stormwater 47 Leaking Equipment Potential Violations Leaks onto ground & no clean up Damaged drip pans Flat oil trays Plastic does not prevent runoff
Stormwater 48 Leaking Equipment Better Practice
Stormwater 49 Construction Waste Potential Violations Good housekeeping is critical
Stormwater 50 Cover trash cans/bins when storm is predicted Empty at least every week Construction Waste Better Practice
Stormwater 51 Sawcutting Potential Violation Better Practice Vacuum saw cut slurry Away from concentrated flow paths Discharge to gutter/storm drain
Stormwater 52 Secondary Containment Potential Violations Storage of fuel/oils Improper storage No containment
Stormwater 53 Secondary Containment Better Practice Do not store fuel on site Use proper secondary containment
Stormwater 54 Portable Toilets Avoid placement in street gutter / flow areas Potential Violation
Stormwater 55 Portable Toilets Better Practice Placed out of gutters and flow paths
Stormwater 56 Good or Bad?
Stormwater 57 Good or Bad?
Stormwater 58 Good or Bad?
Stormwater 59 Good or Bad?
Stormwater 60 Good or Bad?
Stormwater 61 Good or Bad?
Stormwater 62 Good or Bad?
Stormwater 63 Good or Bad?
Stormwater 64 Good or Bad?
Stormwater 65 Good or Bad?
Stormwater 66 Good or Bad?
Stormwater Solutions for Traditional Problem Areas Site construction roadways, and undercut roadway sections Slopes Concentrated Drainage Areas near inlets (high energy) Final stabilization
Stormwater Roadways Lignosulfonate naturally occurring, glue-like polymer found in wood binds surface particles together Completely insoluble and water resistant provides dust control to PM10 standards Provides erosion control in low velocity applications
Stormwater Roadways - Application Scarify to the depth of cementation desired. Introduce Lignin and blade mix subgrade to optimum moisture content is reached. The lignin is applied during the mixing process just as water would be to hydrate/condition the soil Compact with vibratory roller. Spray rolled surface once more with lignin as a topical application and let dry (24 hrs). Apply asphaltic emulsion like PASS QB (water based emulsion) so as to be dry to the touch within 24 hrs. Apply Type 2 slurry as the final layer
Stormwater Roadways - Application
Stormwater Slopes Slopes require good cover supplemented by a sediment control BMP A BFM or similar type of product is generally required on slopes to eliminate rilling Straw wattles are difficult to install correctly, and tend to deteriorate in less than one season – An alternative is compost socks.
Stormwater Slope Treatments
Stormwater Concentrated Drainage Concentrated drainage on a construction site must be managed. Ultimate conveyances are preferred Temporary conveyances that use material for later construction stages is next best option New rules will necessitate temporary concrete ditches and rock ditches.
Stormwater Concentrated Flow Solutions
Stormwater Areas Near Inlets Areas at inlets are high-energy locations Last line of defense A good practice is staged reduction in flow velocity prior to reaching the inlet pool Options: Shotcrete lining and compost socks or rock over filter fabric and gravel bags
Stormwater Areas Near Inlets
Stormwater Final Stabilization May require irrigation to establish vegetation Include compost in hydroseed mix to help with water retention/germination Mulch is a good final cover for slopes Use fast-germinating seed mixes appropriate for the season (warm or cool) Blankets and BFM may be an option