Shallow landscaped depression that treats stormwater runoff. Designed to merge two important goals: aesthetics and water quality Can be blended into the landscape and made to look natural. Water is directed into them by pipes, swales, or curb openings. Designed to intercept, treat, and infiltrate stormwater at the source before it becomes runoff Helps prevent flooding by redirecting the flow of stormwater Provides very high pollutant removal efficiencies Site for Future Rain Garden in Thompson Park USDA Rain Garden Video www.csrees.usda.gov/newsroom/partners/ fluid_planet.html 1
Types of Plants http://plants.usda.gov Obligate Wetland (OBL), Facultative Wetland (FACW) Facultative Upland (FACU), Upland (UPL) Lowest Zone/ Ponding Area Highest Zone/ Upland Area Facultative Wetland (FACW), Facultative (FAC), Facultative Upland (FACU) Middle Zone/ Depression Area 90% of rainfall events are less than 1.25 New Jersey has approx. 44 of rain per year The rain garden will treat and recharge: 0.9 x 44 = 40 /year = 3.3 ft/year The rain garden receives runoff from 1,000 sq.ft. Total volume treated and recharged by the rain garden is 1,000 sq. ft. x 3.3 ft. = 3,300 cubic feet, which is 25,000 gallons per year Build 40 of these and we have treated and recharged 1,000,000 gallons of water per year! 0 Hours 12 ponding depth 6 Hours 9 ponding depth 3 infiltration 12 Hours 6 ponding depth 6 infiltration After 24 hours there should be no ponding How To Build A Rain Garden The rain garden should be at least 10 feet from the house so infiltrating water doesn t seep into the foundation. Do not place the rain garden directly over a septic system. Do not put rain garden in places where the water already ponds. Place in full or partial sunlight. Select a flat part of the yard for easier digging. Call hotline before you dig to get mark out of utilities: 1-800-272-1000 http://clean-water.uwex.edu/pubs/pdf/home.rgmanual.pdf 2
Is the rain garden able to handle the drainage area? If not, consider multiple rain gardens http://clean-water.uwex.edu/pubs/pdf/home.rgmanual.pdf http://clean-water.uwex.edu/pubs/raingarden/rgmanual.pdf Planning Steps Site Visit Percolation Test Steps: 1. Dig a hole 12 inches deep by 6 inches in diameter. 2. Fill hole with water and let stand until all the water has drained into the ground. 3. Refill the empty hole with water again. Measure the depth of water with a ruler. 4. Check the depth of water with a ruler every hour for 4 hours. 5. Calculate how many inches of water drained per hour. ~1 inch of water draining per hour is good Percolation Test 12 34 st nd rd th Hour Ruler Water should be completely drained within 24 hours. Soil Test Sample the soil and send to the Rutgers Soil Testing Lab for: Nutrient analysis/ recommendations ph analysis/ recommendations Percent sand/ silt/ clay Soil Texture Test Roll soil into a ball in hand and see how it forms Hard ball Clay/Silt soil Soft ball Loamy soil No ball Sandy soil Problem: How big does a rain garden need to be to treat the stormwater runoff from my driveway? But, don tworry clay/silt and sandy soils can be amended to get the preferred loamy soil texture 3
How much water can be captured and treated? Drainage Area = 1,000 square feet 1.25 inches of rain = 0.1 feet of rain 1,000 sq. ft. x 0.1 ft. = 100 cubic feet of water for the design storm The depth of your rain garden depends upon the slope of your lawn. Most rain gardens are between 4 and 8 deep Slope Rain Garden Depth < 4% 3 5 5% 7% 6 7 8% 12% 8 > 12% Consider Another Location Slope = _H_ W x 100 = _6 _ 10 _0.5 _ 10 x 100 = 5% slope Exception: Sites with poor percolation or high percentage of clay soils will be shallower with a larger surface area since they percolate slowly (see Tips for Rain Gardens in Clay Soils worksheet) Rain Garden Sizing Table for NJ s Water Quality Design Storm Area of Impervious Surface to be Treated (ft 2 ) Size of 6 deep Rain Garden (ft 2 ) or [w x d] Size of 12 deep Rain Garden (ft 2 ) or [w x d] 500 100 or 10 x10 50 or 10 x5 750 150 or 15 x10 75 or 10 x7½ 1,000 200 or 20 x10 100 or 10 x10 Call hotline before you dig to get mark out of utilities: 1-800-272-1000 Between 3% and 8% slope lawn: Before Digging After Digging Digging the Garden 1,500 300 or 30 x10 150 or 15 x10 http://clean-water.uwex.edu/pubs/pdf/home.rgmanual.pdf 2,000 400 or 20 x20 200 or 20 x10 4
Remove Existing Grass Q: What to I do with my existing grass before starting the rain garden? A: Two options: (1) Kill the grass with herbicide beforehand, or (2) Remove the turf as sod pieces. You can reuse it on your berm or another area of your yard. Excavate to the Desired Elevation and Grade Add Soil Amendments such as sand or compost to the planting bed Leonard Park, Morris County Prepare the Berm Prepare the Overflow Overflow Leonard Park, Morris County Leonard Park, Morris County 5
Level the Lowest Zone/ Ponding Area so it is consistent Plant the Native Plants Cut the Root Ball Ulster County, New York Wheaton Arts and Cultural Center, Cumberland County Plant the Native Plants Apply the Mulch about 3 depth Planting Hole Same Depth as Root Ball Protect Small Plants when Mulching Ulster County, Ulster County, New York Hockman Farm, Winchester, Virginia New York Triple shredded hardwood mulch. NO dye preferred Newark, NJ Maintaining Your Rain Garden Water the Native Plants Types of Maintenance Measures: 1. Inspections: Invasives 2. Soil Testing: ~3 yrs 3. Weeding: watch for over aggresive plants 4. Pruning 5. Mowing 6. Revegetating as necessary 7. Sediment removal as necessary 8. Cleaning of gutters Hockman Farm, Winchester, Virginia 6
Rain Garden Plant Selection NJ Native Plants Plants native to New Jersey are planted in the rain garden Native plants do not require fertilization or other chemicals Native plants are water-loving as well as drought tolerant You can purchase native plants at most garden centers. Check first with the garden center to see if they sell the native plant you are looking for. Mary Vaux Walcott Illustrations, http://www.swsbm.com/images/walcott.html Photo taken from http://www.swsbm.com/images/walcott.html Blue Flag Iris Iris versicolor May-June FACU Depression Photo by David Graper Obedient Plant Physostegia virginiana June-Sept FAC Depression NJ Native Plants NJ Native Plants Photo taken from http://www.swsbm.com/images/walcott.html Blackhaw Viburnum Viburnum prunifolium August-Nov. FACU Depression or grass buffer Photo by Thomas G. Barnes Tall Ironweed Vernonia altissima August- October FAC Depression Photo taken from http://www.swsbm.com/images/walcott.html Cardinal Flower Lobelia cardinalis July-Sept FACW Ponding Area/Depression Rose Mallow Photo by Erv Evans Hibiscus palustris July-Sept FACW Ponding Area/Depression NJ Native Plants Cost of A Rain Garden Construction Element 100 sq. ft. Rain Garden 400 sq. ft. Rain Garden Unit Cost Total Unit Cost Total Rototiller Rental Price/Day $38.00 Price/Day $38.00 River Rock (covering 12 sq. ft. at 2 depth) $3.75/bag (covers 3.0 sq. ft. at a 2 depth) $15.00 $3.75/bag (covers 3.0 sq. ft. at a 2 depth) $15.00 Photo by Larry Allain Soft Rush Juncus effusus FACW Ponding Area Photo by Ear J.S. Rook Sensitive Fern Onoclea sensibilis FACW Ponding Area Hardwood Mulch (hauling included in price) Vegetation $28/yard (4 depth) $33.60 $28/yard (4 depth) $137.20 $0.47/2 herbaceous plug + $35/gallon sized shrub + $1.79/4 pot perennial (48 plugs, 3 shrubs, 5 perenials) $136.51 $0.47/2 herbaceous plug + $35/gallon sized shrub + $1.79/4 pot perennial (96 plugs, 6 shrubs, 10 perenials) $273.02 Total per sq. ft. $223.11 / 100 sq. ft. $463.22 / 400 sq. ft. 7
To learn more about rain gardens: www.water.rutgers.edu Click on Rain Gardens 8