A Low Cost Method to Enhance Stormwater Basins and Reduce Maintenance Costs ...
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Nacaa springdale basin

Published on: Mar 3, 2016
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  • 1. A Low Cost Method to Enhance Stormwater Basins and Reduce Maintenance Costs Mike Haberland 1, Craig McGee 2, Chasity Williams 2 1Rutgers Cooperative Extension of Burlington & Camden Counties, NJ, 2Camden County Soil Conservation District, NJ. VegetationAbstract Native switchgrass was hand seeded in the basin bottom (Fig. 4).Stormwater detention basins are primarily designed for flood control but can be “retrofitted” Native herbaceous vegetation, or wild flower mix can also be used. Thisby increasing native vegetation, altering flow through structures and minimizing mowing to is done by either: removing the sod layer and replanting with seed; byprovide increased infiltration and increased wildlife habitat. Rutgers Cooperative “drilling” seed through the existing grass; or by planting plugs of newExtension Agents are working with the Camden Soil Conservation District and Cherry Hill, herbaceous plants into the existing bottom. If shrubs are to be used,NJ, municipal officials to retrofit existing basins. Retrofitting, or “naturalizing” basins can they should be clumped in “islands” and not spread out through theprovide a benefit to the surrounding ecosystem by providing sufficient time and area for basin. This will help keep the shrubs from being mowed down during thestormwater to infiltrate on site, while incorporating native vegetation for pocket suburban annual maintenance.habitats. Naturalizing a basin can also provide valuable environmental educationopportunities.Current Project Fig. 1 Concrete low flow channel in basinIn this project we retrofitted several existing detention basins in Cherry Hill, NJ. These retrofits should provideimproved water quality treatment, reducing sediment and nutrient loadings to the stream, increase infiltration(Guo, 2009) and be cost effective. Basin retrofits are also designed to provide detention of stormwater over agreater surface area allowing for infiltration and pollutant removal of the smaller, more frequent storm events(less than 1.25 inches), and reducing or delaying the peak discharge to the receiving waterbody.The identification of a good basin to retrofit would include finding onethat has: short turf-type vegetation from regular mowing; a low flowconcrete channel (Fig. 1); a discharge orifice greater than 3 inches; Fig. 2 Removing concrete low flow channel Fig.3 Leveling ponding areaand is not used for other purposes when dry. It is also important to Maintenanceconsider the depth to groundwater so that the potential infiltration is Instead of weekly or bi-weekly mowing, retrofitted basinsmaximized. need only be mowed once a year, preferably in late fallOne of the main goals with retrofitting a basin is to increase the after the first frost. By not mowing during the growingsurface area that stormwater covers thereby increasing the volume season, the mature vegetation can improve wildlife habitatof stormwater that can be filtered through the vegetation and and provide ecological benefit. If possible, mowing wheninfiltrated into the soil. This typically involves modifying the low flow the ground is frozen will prevent or greatly reducechannel by either: 1) removing the concrete low flow channel and compaction and rutting in the basin bottom. In addition,replacing it with vegetation or stone; 2) placing a structure across annually remove woody or unwanted vegetation before itthe channel to deflect the stormwater out into the basin, modifying gets out of control.the outlet structure (Emerson, et. al., 2005). Results Fig. 4 Hand seeding switchgrassStormwater detention basins are primarily designed for flood control The desired result of a successful detention basin retrofit is to provide runoff from the smallerbut can be “retrofitted” by increasing native vegetation, altering flow storms with the time and space (storage) to infiltrate to groundwater, while providing thethrough structures and minimizing mowing to provide increased necessary flood protection at all times. Beautiful native vegetation can become a site ofinfiltration and increased wildlife habitat. Retrofitting, or environmental education while providing the local community with increased ecosystem“naturalizing” basins can provide a benefit to the surrounding diversity.ecosystem by providing sufficient time and area for stormwater to An additional benefit of the basin retrofits is the potential maintenance cost savings due toinfiltrate on site, while incorporating native vegetation for pocket reduced mowing schedules and reduced consumption of resources for mowing (Blaine &suburban habitats. Naturalizing a basin can also provide valuable Smith, 2006). Since retrofitting five basins, the Director of Public Works for the Township ofenvironmental education opportunities. This project was designed Cherry Hill, NJ, estimates saving up to $20,000 annually in maintenance costs. Thisto implement and report on the efficiency of a cost effective provides a window into the potential benefit that changing the manicuring methods ofstormwater basin retrofit option using native switchgrass. The stormwater management that have become entrenched in towns across the country couldcurrent basin retrofit and renovations took advantage of the existing have on our future.basin conditions, including soil conditions and topography toimprove the basins effectiveness in reducing peak rates of runoff Referencesand treating stormwater for nutrients, bacteria and total suspended Blanie, T. W. & Smith, T. (2006). From Water Quality to Riparian Corridors: Assessing Willingness to Paysolids. The low flow channel was removed (Fig. 2) and the slope of for Conservation Easements Using the Contingent Valuation Method. Journal of Extension [On-line],the basin bottom was flattened to 0% to increase the ponding area 44(2) Article 2FEA7. Available at: http://www.joe.org/joe/2006april/a7.php(Fig.3). Emerson, C., C. Welty, & R. Traver. (2005). Watershed-Scale Evaluation of a System of Storm Water Detention Basins. Journal Hydrologic Engineering. Volume 10, Issue 3, pp. 237-242 Guo, J. (2009). Retrofitting Detention Basin with Water Quality Control Pool. Journal of Irrigation and Drainage Engineering, Vol. 135, No. 5, pp. 671-675