The Urban Stormwater and Aquifer Improvement Project

Great news!  This year, the EAC has launched a project in Porters Lake aiming to explore innovative stormwater management practices in new residential developments.  The project will involve collaborating with the local community and discussing water, stormwater management, and building healthy water neighbourhoods. We will share results from our pilot site, a new development that is implementing low impact development practices.  We will be monitoring groundwater levels and surface water quality around this new development as it is built and during ongoing construction.  This project is an exciting collaboration between an environmental organization, a developer, university and a community to explore how innovative stormwater management techniques can improve groundwater availability and surface water quality.  We are very proud to share this project with you.

(Photo: during a site visit the team stopped by Bell Lake- Jenny and Rob from the Centre for Water Resources Studies (CWRS), Kyle from genivar, Jocelyne from the Ecology Action Centre (EAC), Brad from Seven Lakes, Rick from CWRS, and Jennifer from the EAC).

Public Outreach

Our project is focused on the Porters Lake area, and we want to connect with this community on freshwater issues.  To share information on these topics, we will launch a series of talks in Lake Echo, Porters Lake, and Musqodoboit in fall 2013 and winter-spring of 2014.  Topics include "Healthy rainwater on your property", "How do we know a lake or stream is healthy?" and "Building a healthy water neighbourhood". Dates and locations for the fall talks are nearly confirmed, so stay tuned to this site so you can attend these events.  Stay tuned for more talks and events in the winter and spring of 2014!

Community Showcase

Bell Lake, in the community of Porters Lake

The EAC believes that seeing is believing, and we have the rain gardens, stormwater demonstration sites and living shorelines to prove it!  The EAC is keen to be working with a developer in the Halifax Regional Municipality using low impact development and open-space principles in their planning.  The Villages of Seven Lakes are in the beginning stages of development in the Porters Lake.  We encourage you to explore their website to find out about their design ideas which include 60% open space, clustered communities, rain gardens, bioswales, and infiltration areas for managing stormwater, innovative stormwater management systems, wetland restoration, tertiary wastewater treatment and many more interesting features.

Research

We are very fortunate to work with a developer that is keen to have ongoing monitoring of their development on lakes and groundwater near their sites.  We have partnered with the Dalhousie Centre for Water Resources Studies who will help us understand the natural conditions of lake and groundwater before homes and roads are built.  They will generate digital models of the site and the impact it has on the surrounding water systems.  These impacts will be compared to that of a conventional development using computer modeling.  This is the beginning of a long and beautiful relationship that will help us understand and hopefully promote low impact development practices elsewhere in HRM and Nova Scotia.

We would love to know your thoughts on stormwater in your community and on your property.  Consider taking our short survey to help us learn more!

Stay tuned for updates on this project, and for information on upcoming talks.

Permeable Pavement

Permeable pavement allows precipitation to slowly soak into the ground, thereby reducing runoff from driveways, roads and parking lots. There are two main types of permeable pavement – permeable pavers (also known as interlocking concrete blocks) and porous pavement. These BMPs can be incorporated into designs for new developments, or used as a retrofit option for existing homes and buildings. 

Permeable Pavers consist of impervious concrete blocks or tiles that allow water to infiltrate between blocks in voids filled with gravel or grass.  

Permeable Paver (photo: bit.ly/be1x3a)

Parking space at the Ecology Action Centre

Porous Asphalt or Concrete consists of standard asphalt or concrete mixes with the finer aggregates removed resulting in pores within the pavement that allows water to permeate through the surface. 

A parking lot on the Dalhousie University campus uses porous pavement  to reduce stormwater runoff. The lot was graded allowing runoff to flow towards the strip porous pavement area at one end of the lot. There is a clear stone base under the permeable area with a perforated PVC pipe leading to catch basin in the corner of the lot.  Water that infiltrates through the pavement has a chance to soak into the ground before being picked up by the perforated pipe. A strip of permeable pavement on a graded lot works well, therefore repaving the entire parking lot is not necessary. Some concern exists about how porous pavements can withstand Nova Scotia's harsh winter conditions, however this was put in during the Fall of 2010, and there has been no damage reported to date.

Strip on porous pavement on a Dalhousie University parking lot (width of the car)

Regular asphalt on the left, porous pavement on the right

The City of Vancouver is using an alternative approach to reduce imperviousness on residential side streets called ‘Country Lane Treatment’. This design incorporates a soil and grass covered plastic mat between two parallel concrete driving strips. Permeable pavers were used to connect driveways to the driving strips. Click here to see more examples of road treatments from Vancouver. 

'Country Lane' in Vancouver (Photos: http://bit.ly/A4s9Os)

More information on permeable pavements and other stormwater management technologies can be found on the Sustainable Technologies Evaluation Program (STEP) website, an initiative led by the Toronto and Region Conservation Authority.

Retention Basins (Wet Ponds)

In a recent blog post we talked about dry detention basins which hold water temporarily and release it slowly into the environment.  A retention basin works in a similar way but retention basins can store water for longer periods of time, mimicking a real lake or pond.  Retention basins are effective in storing and slowing runoff, thereby improving water quality by allowing pollutants to filter out of the water column. 

To find some examples of retention basins, we visited Dartmouth Crossing to see how stormwater runoff was collected from the large roofs and parking lots at the shopping centre.

Retention pond behind Walmart

We were pleasantly surprised to see and hear a gurgling stream in this landscape with so much pavement and hard surface cover.  The stream, Grassy Brook, is largely fed by runoff collected off parking lots and rooftops. A drop of water that lands on Walmart’s roof or parking lot is collected underground then released into Grassy Brook which flows behind the building. Marsh vegetation and willow trees were planted to enhance habitat and slow the flow of water, thereby helping to remove pollutants. Since white surfaces absorb less heat and stay cooler on sunny days, Walmart's roof is painted white to keep water temperature cool, as warm water entering a natural system can harm fish and other species. The increased flow of water into the retention basin and into Grassy Brook has created an active spawning site for trout.

White roof

 The wet pond shown below has both aesthetic and functional purposes. The pond is surrounded by a walking path, and an amphitheatre, so people can listen to concerts and enjoy the scenery. Trout also use this pond as a spawning area.

Pondside amphitheatre retention basin.The pipes in the background (left)
collect overflow during extreme precipitation events.

Runoff is slowly released into the pond through this small opening
to avoid a high peak flow.

Stormwater Basins

A common method to manage stormwater runoff is through stormwater basins or ponds, which collect and release runoff at a controlled rate to avoid flooding or erosion of downstream areas. Stormwater basins can either be detention basins, which are dry between storms, or retention basins, which have a permanent pool of water. Detention basins only contain water after a rain event, while retention basins always hold water.

The Canada Games Centre on Lacewood Drive in Halifax has an underground detention basin on-site that collects stormwater runoff from the building’s roof, parking lot and lawn area. Underneath a field beside the Centre lies a 10m deep hole that is filled with rock. Large, boulder size rocks were used to increase infiltration. Two metres beneath the surface lies a perforated pipe that runs across the length of the field and catches any overflow. During a heavy precipitation event, water enters the dry detention pond and infiltrates the rock layer. Water only enters the perforated pipe if the water level rises to 2 metres below the surface, and Jeff Pinhey, the site engineer has never witnessed an overflow event. The detention pond was built during the construction of the building. 

Underground detention pond at the Canada Games Centre

Underground detention ponds are safe, do not need to be fenced and provide additional space for on-site recreation. Detention ponds can also be above ground, such as this example in Dartmouth Crossing. We’ll explore wet retention ponds in more detail in future posts.

Above-ground dry detention pond in Dartmouth Crossing

Bioswales

The Prospect Road Community Centre was built in 2010 with several stormwater features  incorporated into the building's design. Runoff from the roof is collected in a large underground cistern and reused in the building for non-potable uses such as flushing toilets.

Runoff from the site and parking lot are collected in bioswales, which are vegetated depressions where water collects and soaks into the ground. This filtration improves water quality by removing pollutants and allows for water to re-enter the ground, recharging groundwater supply.

Water enters the bioswale through curb openings

The bioswales are composed of an underground perforated pipe surrounded by 5 feet of rock and gravel. During an extreme precipitation event, high volumes of water flow overland into the bioswales, flooding the rock area and overflowing into the perforated pipe. The water is then collected and piped off-site, ultimately draining into a natural wetland adjacent to the building. 

 Bioswales reduce strain on built stormwater systems and reduce likelihood of flooding and infrastructure damage by passively allowing water to move off-site. This engineered system mimics how water would naturally flow in an unaltered environment. Bioswales are not only useful, but also can be an attractive landscape feature.

Water drains off-site into a natural wetland