Rain Gardens

Rain garden constructed by Clean Annapolis River Project (www.annapolisriver.ca)

Rain gardens are small, landscaped areas that capture, filter and infiltrate rainwater.  Rain gardens can create an attractive detention area where runoff can slowly soak into the ground, be taken up by plants and return to the atmosphere through evapotranspiration. Planted with water-tolerant native plants, rain gardens can become a beautiful and functional feature on your property.

Rain gardens allow at least 30% more water to infiltrate into the ground, compared to a conventional lawn (source). They can help recharge groundwater resources, reduce stormwater volumes and create habitat. Rain gardens are relatively easy and inexpensive to design and build. Just keep in mind a few important considerations when deciding where and how to install a rain garden on your property:

-Observe how stormwater naturally runs in your yard. Place the rain garden at a low point or elsewhere along the natural flow path.

- Maintain at least a 1% slope from the impervious surface to the garden. 

- Rain gardens should be located approximately 3 m away from a building to avoid drainage problems on your property.

-Clay soils don’t allow for proper drainage, therefore look for a place with soil that is sandy, gravelly, loam or a mix. If your soil has a high clay percentage, you can add sand, fine gravel and/or organic matter to improve permeability.

- The surface area of a rain garden should be 20-30% of the roof/parking lot area it drains.

- A general guideline for rain garden depth is 7.5 cm in soils with relatively low infiltration rates (i.e., loam) and up to 15 cm in soils with high infiltration rates (i.e., sandy or gravelly soils).

-  A downspout can empty directly into a rain garden. Just add some stones or a splash pad to prevent erosion.

Rain garden (Photo CMCH: bit.ly/dCOkur)

Some really helpful tips on installing and maintaining rain gardens can be found from the Canadian Mortgage and Housing Corporation's factsheet 'Improving Stormwater Management in Your Yard'.  

More great information on rain gardens, including a list of native, water-loving plants, can be on the Clean Annapolis River Project website. 

Do you have a photo of a rain garden or maintenance tips that you'd like to share? We'd love to see them! 

Beautiful! (Photo: www.atlantic.sierraclub.ca)

Continuous Deflection Separation (CDS)

This week we wanted to find out more about stormwater quality treatment technologies, so we contacted The Shaw Group. They have installed over 150 Continuous Deflection Separation (CDS) systems across the Maritimes. CDS units improve water quality of stormwater runoff by removing sediment, floatables, oil and grease. 

CDS unit (image:www.shawpipe.com)

CDS units have a screen filter that removes all floatable materials and a separate treatment chamber which captures sediment and hydrocarbons. Due to potential high volumes of trapped pollutants, maintenance on these systems is very important. At a minimum they should be maintained twice per year, which includes sucking out the floatable debris and sediment with a vacuum truck.

We went to visit Portland Hills Estates, a large development surrounding Russell Lake, where several CDS units are installed at different stormwater outfalls around the Lake. We saw a ‘56/40 unit’, the largest CDS system which can filter up to 56 cubic feet of water per second.  This system is designed to capture the 1 in 25 year storm (as opposed the 1 in 100 year storm), and as a result it functions very effectively 80% of the time. The other 20% of the time surplus flows through a by-pass valve. 

Let's life the lid and see what is inside!

Wow! Tennis balls, water bottles and several other floatables from the development and neighbouring school are trapped by the CDS. These items would otherwise eventually end up in Russell Lake.

The stormwater outfall is virtually garbage-free!

The impetus for filtering stormwater came from the Russell Lake community group who were concerned about how the Portland Hills Estates development would impact lake water quality. This concern lead to the developer, Clayton Development, including the purchase and installation of these systems into the development agreement. Using these CDS systems is now common practice for Clayton Development.