stormcon 2014
TRANSCRIPT
Todd WacomeWynwood Associates
Andover, MA.
Using Standard and Retrofit Catch Basins for Rainwater Harvesting & Non-Blinding Groundwater Recharge
Why I’m Here‣ Developed a MASTEP reviewed technology.‣ First technology in a new category. ‣ MaDEP approves of for meeting treatment
and recharge standards.‣ Commission members are asking for more,
looking for more.‣ The SiltPrison can solve problems - yours,
theirs, and DPW’s
‣ Custom homebuilder, designer, and developer of small projects.
‣ Involved in a broad range of activities related to land development
‣ Concerned with orders of conditions, site monitoring through the life cycle of developing a subdivision.
‣ Curious about the lack of focus catch basins
Background
An appreciation for clean & safe water
‣ Inlet protection now required but in the way after construction.
‣ Inserts can’t handle large flows‣ Deep sumps help, but don’t do
enough.‣ Most of the problem is with fine
particles in the built environment.
Inlet grates and catch basins are ignored
A Typical catch basin in section view
A Typical catch basin in section view
A Typical catch basin in section view
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A Typical catch basin in section view
A Typical catch basin in section view
Catch basins need to handle high flows
Started experiments with cone shaped filters
‣ Open top and open bottom
‣ Cone shaped so inner side of fabric is “upside down”
‣ Graduated flow rates using different fabrics
‣ Utilize full volume of catch basin
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What’s Actually Happening?
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Preliminary Testing
Looking down through an inverted cone filter from street level between scoops during a cleanout process
Inverted cone filtration has shown remarkable performance
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What Are They Testing For?‣ Testing requirements
have become extremely strict. Now Lab testing is very expensive.
‣ To determine three main characteristics:• Hydraulic Capacity,• Removal Efficiency• Re-entrainment
What Was Determined?‣ Sediment testing utilized the New
Jersey Corporation for Advanced Technology (NJCAT) specified protocol sediment, with a PSD of 1 to 1000 microns and a specific gravity of 2.65.
‣ Hydraulic testing was performed on the unit for flows ranging from 25 to 857 gpm. The maximum flow capacity of the 25-micron skirt was approximately 400 gpm (11.25 gpm/ft2).
‣ The maximum treatment flow prior to bypass was approximately 675 gpm (15 gpm/ft2). The unit did not surcharge at maximum flow.
What Was Determined?‣ Re-entrainment
tests were performed at flows ranging from 0 to 475 gpm, with an initial sediment loading of 100% of the stated unit’s capacity using the NJCAT sediment PSD of 50-1000 microns.
‣ The sediment bed was prepared with a flat profile.
‣ The maximum average sediment concentration, adjusted for background, was 4.0 mg/L at 350-gpm.
What Was Determined?
‣ The average removal efficiencies ranged from 41.6% to 72.3% for the mass balance methodology and 48.2% to 78.6% for the sampling methodology, with combined averages ranging from 44.9% to 75.9%.
‣ The average treatment removals were 83.1% through the 25-micron skirt and 73.4% through the 212-micron skirt. An average removal of 60.9% was measured in bypass.
‣ Testing of a partially-blinded skirt at 10 gpm flow resulted in removal efficiencies ranging from 95.1% to 74.9%, with an average removal of 81.5% for the entire test.
Recharging Filtered Water:
‣ Water through blue region has been filtered <20 microns.
‣ Add a “Separator skirt” to isolate it from water escaping through the upper 2 regions which will discharge through the “grey pipe”.
‣ Add a port to the casting(lower) to reroute this filtered water as recharge.
‣ Infiltration trench will not blind
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