Runoff Reduction & Bioremediation Through Design of a Swale

1. Runoff Reduction & Bioremediation Through Design of a Swale Service Learning Project Andrew Weiss, Todd Cridge & Dr. T. Endreny. FEG 340 Engineering Hydrology & Hydraulics Course, SUNY College of Environmental Science and Forestry, Syracuse, NY 13210 Where are we working? What is being replaced? Safety factors in design The catchment area is located between Fabius St. and Corcoran Ct. Syracuse, NY • Non residential area • No formal runoff considerations • Room for Swale between Fabius St. and bordering lot • The calculations for this particular area were done assuming all runoff surfaces initially will not infiltrate (C=1). • In this specific catchment there is a great deal of permeable surfaces along with many impermeable. • With permeability throughout the catchment accounted for (C ~=.51) the peak runoff flows into the Swale are almost half. • In this case the Swale will be engineered such that during normal storm activity it will accommodate the runoff very effectively. Positive aspects of a Swale What is the problem? • Promote sediment deposition • Bio-filtration and remediation of pollutants • Reduces creek flow and the sediment/contaminant load contained in it • Replenish ground water in the local area • Aesthetically pleasing • Typically cheaper and easier to install then storm water piping and more effective including added environmental benefits. • Local storm events generate large amounts of runoff. • The runoff is often polluted and sediment loaded. • There is no time for infiltration due to the majority of surfaces being paved. • Nearby Onondaga Creek is overloaded with a discharge of sediments and pollutants. Calculated peak runoff flows • Runoff Area: 1.7 Hectares • 24 Hour Storm events How do we solve the problem? • Infiltration basin • Storage facilities • Redesigning the creek • Decrease paved surfaces • SWALE Example of success using Swales • SEATTLE PILOT PROJECT REDUCES RUNOFF BY 98 PERCENT! • "Our objective is to now engineer our streets in a new way. We are mimicking nature's functions," said Denise Andrews, an adviser for Seattle Public Utilities' drainage and wastewater programs • Andrew’s said the use of a natural drainage system costs about the same as a typical curb-and-gutter design. This is before the environmental benefits. What is a Swale? Runoff area & flow data • Engineered depression which catches and controls the local area runoff. • Lined with vegetation and dense moisture tolerating plants. (ex: grasses) • Long like a channel but not designed for rapid flow. • Promotes bio-filtration and runoff infiltration. • Water stands but for only a short period of time while infiltrating. • Calculations done with a 25 year, 24-hour storm duration • Rational Method for overland flow Conclusion • The swale provides many benefits and great functionality. It is an ideal method for reducing runoff and reducing contamination and sediment loading of Onondaga Creek. • In conjunction with the Swale, localized ways of reducing runoff can be implemented. • Small scale individual Swales called “rain gardens” can be used. • Use pervious surfaces wherever possible, like open face pavers for parking instead of impervious blacktop. • Additional Swale projects would also be necessary to see the true beneficial effect. Swale design dimensions • Initially Bermuda Grass or equivalent. • Local species will eventually reclaim the swale area. • For speed and ease of construction pre-seeded matting can be used for instantaneous structure and greater seeding success. References Location for this Swale • Chin, David A. Water-Resources Engineering. New Jersey: Upper Saddle River, 2000. • FEG 340 – Engineering Hydrology & Hydraulics, Professor T. Endreny. • Various online reference sources. • Swale should extend from Onondaga Creek West along Fabius St. 100 year storm considerations • In the event of a 100 year storm damage could occur to the swale. • A check dam/weir can be placed at the creek end of the swale. • In the event of sever flooding of the swale the water would overtop the dam and freely discharge into the creek. • As the storm subsides the water level will drop and once at a safe level the dam will retain the remaining water to be infiltrated.