Rain Gardens

 

Colerain Township,the largest Township in the State of Ohio, oversees eleven park and seven public buildings and facilities.  The Township has partnered in the past with the Mill Creek Watershed in the installation of signs at stream crossings in the Mill Creek and Great Miami watershed.  Heritage Park on East Miami River Road was designed to include a rain garden component.

Colerain Township continued its partnership with the Mill Creek Watershed Council to further our compliance with Phase II EPA regulations to enhance water quality in our jurisdiction.  To that end, Colerain Township sought opportunities for a rain garden as a retrofit to an existing township structure as part of a Hamilton County Storm Water District (HSCWD) mini grant project.  The rain garden site at Colerain Park serves as a demonstration and educational site for the Mill Creek Watershed Council of Communities for other municipalities and for local schools to visit.

The rain garden at Colerain Park was completed with funds from the mini grant from HSCWD and donations of materials from our generous sponsors; Alvis Landscape and Golf Course Materials Inc. for donating compost and topsoil, and White Oak Garden Center for donating plants.

Location

The rain garden is located in the valley between shelter 3 and the large main parking lot at Colerain Park.  This site was chosen because it receives water from two drain pipes at the west end of the garden and has an overflow exit pipe at the east end of the garden.

The rain garden collects storm water from 3 main areas: the roof top of the Parks Department garage; the surface area of the Parks Department parking and storage area; and the entry drive leading into Colerain Park (from Springdale Road down to the rain garden).

Prior to the rain garden, the park was designed so that the stormwater would flow through this valley directly to the existing storm water drain system.  The rain garden will now capture much of this water and any pollutants from the runoff and allow the water to filter through the ground and be cleansed of pollutants before passing into the groundwater.

Rain Garden Specifications

The rain garden is approximately 53 ft long by 25 ft wide at its widest point.  We designed the shape of the rain garden based on the water flow from the two entry pipes to the overflow exit pipe.  The site was excavated to a depth of two feet.  We then amended the soil with approximately three inches of compost which we rotor tilled approximately a foot into the soil.  We added another three inches of compost on top of the amended soil and then added another three inches of a topsoil blend (1/3 topsoil, 1/3 compost and 1/3 sand).  The soil amendments were done to break up the clay in the soil and to enrich the soil for the plants.

The rain garden depth was chosen to hold as much water as possible and still allow all of the captured water to drain in 24 – 48 hours, which is important to prevent mosquitoes from breeding.

Plant Selection

We chose as many native plants as possible to inhabit the rain garden for two reasons: native plants grow well in the soils we have in the area and native plants have deep root systems, some as much as three feet deep.  As these plants mature, their deep roots will decrease the time to filter the water captured in the rain garden.  Plants were chosen based on the following criteria: soil moisture, sun, plant height, bloom time and color.

Below is a list of plants used in the rain garden:

Common Name Moisture Sun Bloom Color Height
Joe Pye Weed wet – med Full July-Sept Mauve 4′ – 5′
Great Blue Lobelia wet – med F-p shade July-Sept Blue 2′ – 3′
Virginia Sweetspire wet – med F-p shade May-June White 3′-4′
Blue Flag Iris wet Full May-June Blue 2′ – 2.5′
Astilbe moist – not dry Shade-p June-July Red 1.5′ – 2′
Spiderwort moist – not dry Shade-p May-July Blue 2′-2.5′
Spiderwort wet – med F-p shade May-Aug Purple 1′
Beard Tongue med -well drained F -p May-June White 2 ‘- 3’
Blue False Indigo med – well drained F-p shade May-June Blue 3′ – 4′
Butterfly Bush med – not wet Full Jun-Sept Black 4′ – 5′