BUILDING YOUR RAIN GARDEN

Garden Location Where does water flow from? Where does water travel or collect? Observe your yard during a rainfall event

“Pinch Point”

Garden Location Place your garden between runoff source and destination We want to intercept water before it reaches surface waters or low spots!

Garden Location SITING GUIDELINES: >10 feet from house foundation or wellhead >10 feet from house foundation or wellhead > 25 ft from septic system drain field > 25 ft from septic system drain field Away from utility lines Away from utility lines In full to partial sun if possible In full to partial sun if possible

Garden Location

Garden Timing Add garden after other construction is finished Add garden after other construction is finished Planting best Planting best done between November and April

Soil Evaluation

Soils and Drainage Signs of an impermeable soil Signs of an impermeable soil Ponding water Ponding water Wetland soils – grey Wetland soils – grey with areas of brown color Water remains after Water remains after two days of no rainfall Design as a Backyard Wetland!

Wetland Soils

Backyard Wetland What is it? An area where the soil is saturated or covered with water for 2-3 weeks during the growing season An area where the soil is saturated or covered with water for 2-3 weeks during the growing season Located in spots where water collects much faster than it drains. Located in spots where water collects much faster than it drains.

Backyard Wetland Install in an area where there is a naturally occurring wet spot or drainage way. Install in an area where there is a naturally occurring wet spot or drainage way. Can be as simple as installing wetland plants in the wet area Can be as simple as installing wetland plants in the wet area

Backyard Wetland

Sizing your Rain Garden How much runoff is coming from impervious areas?

Sizing Rain Gardens Roof Area Roof Area Driveway Area Driveway Area Total Impermeable Drainage Area Total Impermeable Drainage Area Depth  Dimensions Depth  Dimensions Ponding depth 6” – Divide Impermeable area by 20 Ponding depth 6” – Divide Impermeable area by 20 Ponding Depth 3” – Divide impermeable area by 10 Ponding Depth 3” – Divide impermeable area by 10 Use chart: Sizing Your Rain Garden Use chart: Sizing Your Rain Garden

Sizing Chart Impermeable Surface Area Required Size of Rain Garden (6” deep) Potential Rain Garden Dimensions (ftXft) Required Size of Rain Garden (3” deep) Potential Rain Garden Dimensions (ftXft) 800 ft 2 40 ft 2 4X10, 5X8, 6X7 80 ft 2 7X12, 8X10, 9X ft 2 50 ft 2 5X10, 6X8100 ft 2 7x15, 10X ft 2 60 ft 2 4X15, 5X12, 6X10, 8X8 120 ft 2 10X12, 8X ft 2 70 ft 2 5X14, 7X10140 ft 2 10X14, 7X ft 2 80 ft 2 7X12, 8X10, 9X9 160 ft 2 8X20, 10X ft 2 90 ft 2 6X15, 7X13, 8X12, 9X ft 2 9X20,10X18, 12X15

Sizing Example EXAMPLE: A house is 60 feet by 60 feet. by 60 feet. Based on owner estimation: 25% of the roof area 25% of the roof area is draining to the downspout. The driveway area draining The driveway area draining to the rain garden is 500 square feet. For a desired 6 inch ponding depth, what size should the rain garden be?

Sizing Example Roof area: 60 X 60 = 3600 sq. ft. Roof area: 60 X 60 = 3600 sq. ft. ¼ of the flow to ¼ of the flow to downspouts: (3600 sq.ft) X 25% = 900 sq.ft Roof area plus driveway: = 1400 sq. ft Roof area plus driveway: = 1400 sq. ft Divide square footage by 20: 1400/20 = 70 sq. ft. Divide square footage by 20: 1400/20 = 70 sq. ft. ANSWER: The water garden should be at least 70 square feet. A 5 x 14 or 7 x 10 foot garden design A 5 x 14 or 7 x 10 foot garden design would be sufficient

Rain Gardens can be Small

Depth of 3 – 8 inches Depth of 3 – 8 inches Larger for clay soils, smaller for sandy ones Larger for clay soils, smaller for sandy ones Work with the area you have! Work with the area you have! Size is flexible

Rain Garden Construction

Potential Site

Define the boundary by using string or spray paint Before digging, lay out the area

Digging Your Rain Garden Dig garden 4-6 inches, with a slight depression in the center

Digging Your Rain Garden On sloped sites:  Use dug out soil to create a berm along one side of garden  This will serve to retain water during a storm

Planting and Mulching Berm Cover the berm with grass or mulch to prevent erosion

Planting and Mulching

Mulch with 2-3 inches of hardwood mulch

Avoid Pine Straw and Lighter Mulches – They Will Float!

Mulching  Removes Pollutants  Maintains Soil Moisture  Prevents Erosion