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Botanical Gardens North Watershed
Richard HollanderArturo Huesca
Noah Posthuma
April 20, 2011
Unique Characteristics and Challenges of Catchment
• Long but narrow catchment area, with steeply sloped channel width, constrains size of treatment cells
– requires treatment train of pocket wetlands
• Allow for future residential and/or commercial development
• Handle pollutant loading from existing commercial and residential areas
• Provide amenity for residential areas in addition to a stormwater engineering solution
– design with high aesthetic values
• Manage for mosquitos, algal blooms and safety, given proximity to residential areas
Watershed Exploration
Dominos Farms Corporate Headquarters: Parking Lot Runoff
Dominos Farms Corporate Headquarters: Infiltration Pond
Stump sprouted deciduous forest
growing American Elms
Artificial pond surrounded by Scots Pine
Natural Riverine Forest (Poplars and Elms)
Across Plymouth Road
Across Plymouth Road – Permanent Water Flow
Pasture Land
Development at the lower end of the catchment
Catchment outlet pipe across Dixboro Road
Catchment Soil Hydrology
Catchment Land Use
TR-55 Inputs• Stormwater pocket wetland sized for 2-yr storm, 2.26 inches rainfall
• Channel Details• Total channel length of 7,547 feet• Manning coefficient ranging from top of catchment grassy
area of 0.41 to channel end of 0.022• Slope ranging from top of catchment of 0.001 to 0.043
through forested open areas to 0.016 through channels
• Total catchment area is 264 acres• Residential of 72 acres (density of 0.25 acre lot sizes)• Commercial (Domino’s corporate HQ buildings, parking lots,
private school) of 24 acres• Roads and Streets (including Plymouth Road and Dixboro
Road) of 19 acres• Open Space (primarily wooded forests) of 149 acres
TR-55 Results
•Total runoff of 0.453 inches
•Time of Concentration of 1.764 hours
•WQv of 10.01 acre-feet
• Pocket wetland system substantially dewatered within 48 hours, using 8 inch diameter pipe for outlet
HydrographHydrograph for 4-cell constructed stormwater pocket wetland, with 8 inch
diameter pipe for the outlet to allow for dewatering in 48 hours
Contaminant EstimatesLOADING
Land Use AcresPhosphoru
s Loading Nitrogen Loading TSS Loading
pounds per acre per year per land use
pounds per acre per year per land use
tons per acre per
year
pounds per year
pounds per year
tons per year
Residential 0.5 units/acre 0.8 6.2 0.09 1 units/acre 0.8 6.7 0.11 2 units/acre 0.9 7.7 0.14
10 units/acre** 72.144 1.5 108.216 12.1 872.942 0.27 19.479
Commercial 23.84 0.7 16.69 7.1 169.264 0.08 1.907
Industrial 0.7 9.5 0.15 Roads 19.17 0.8 15.336 7 134.19 0.14 2.684 Ag/Pasture 0.7 12.4 0.15
Forest 148.846 0.2 29.769 5.5 818.653 0.05 7.4423
Total 264.0 170.0 1,995.1 31.5
Sources for loading calculations: Claytor and Schueler (1996), Steuer et al. (1997), Bannerman 1993), Caraco (2001), Camp et al. (2004), Marsh (2010).** Note we estimate lot sizes for residential units as 0.25 acres/unit; thus, assuming 10 units/acre or 0.10 acre lot sizes is conservative (ie, overestimates contaminant loading for purposes of designing phytoremediating plant schedule).
Contaminant Estimates cont’d
REMOVAL
Phosphorus Nitrogen TSS
pounds per acre per yearpounds per acre per
year Tons per acre per year
96.9 877.8 18.0
(based upon Table 14.3 from Randolph (2004))
Constructed Wetland Placement
Unique Characteristics and Challenges of Catchment
Unique Characteristics and Challenges of Catchment
Pocket Wetland 1
Pocket Wetland 2
Pocket Wetland 3
Pocket Wetland 4
Plant Selection Criteria
• Enhance the use of native plants of Michigan to create an aesthetic riverine ecosystem
• Our catchment is in a rural environment
and constructed wetlands should provide food and cover for wildlife (waterfowl, pollinators, birds)
• Control of phosphorous – in our opinion, an excess of P in runoff is currently being discharged into ponds in the area, increasing the presence of algae and water eutrophication
Other design considerations
• For all forebay and micropools, use slope of no greater than 3:1
• Safety bench around all pools• Plant emergent vegetation on safety
bench to further deter people from entering pools
High Marsh (0-6 in)
Food and cover for wildlife
Peltandra virginicaSun/ShadeRhizomatous
Decodon verticillatusShallow waterGood for waterfowl
Eupatorium perfoliatumNative perennial, full sun
Iris versicolor
Aesthetic value
Low Marsh (6-18 in) and Micropool (>18 in)
Water Column AerationElodea canadensis
Phosphorous control to prevent eutrophication/Food and cover for wildlife
Nuphar lutea Lemna minor
Recommendations
• For control of algal bloom, plant floating water lilies which reduce sunlight for algae, as well as submerged oxygenating plants like Elodea which outcompete algae for nutrients, in addition to introducing tadpoles
• Vacuum decomposed algae from pond pools
• Implement city ordinances limiting or banning inorganic lawn fertilizer use, or institute impact fees, for residential units in catchment
• For mosquito control, introduce mosquito-eating Gambosia affinis fish to forebays and micropools; live well in Michigan
Recommendations cont’d
• Engage Huron River Watershed Council and City of Ann Arbor to coordinate volunteer teams to remove invasive plants (buckthorn, honeysuckle, phragmites)
• Remove sediment from forebays at least annually, disposing in landfill as needed