SA Affordable Housing’s sister publication Plumbing Africa has many interesting articles equally relevant to affordable housing and should be a must-read. Below is an excerpt from an article contributed by the plumbing industry’s international mother body IAPMO (International Association of Plumbing and Mechanical Officials).

Rooftop gardens ease stress on sewage systems. Image credit: Lifestyle Home Garden

Rooftop gardens ease stress on sewage systems. Image credit: Lifestyle Home Garden

It has become common to talk about the impact of climate change not upon the current generations, but on the generations yet to come. Perhaps then it’s fitting that multiple initiatives are proliferating, aimed at addressing stormwater management. “Stormwater pollution in urban centres is one of the biggest sources of water pollution in the country,” says a spokesperson for the US Environmental Protection Agency. “Green infrastructure provides tools to address the threat.”

Existing stormwater systems are being overwhelmed with more frequent and intense storms. As rainwater floods drainage systems, the run-off carries sewage into other bodies of water, including freshwater reservoirs. Along the way, this run-off gathers chemicals from the ground, such as oil dripped from cars.

However, because the transportation and treatment of water requires massive installation, creating change on a systemic level can often be challenging. “Water is the oldest industry on the planet, and it’s also the slowest to innovate,” says Ryan Vogel of PureBlue, a company that incubates many young companies seeking to profitably address the issues of stormwater pollution and wastewater management.

Mitigation can take the form of rain gardens, trenches, and redirection. Toronto’s Green Roof Bylaw began requiring the incorporation of green roofs into the design of new construction projects that are greater than 2 000 m² in gross square footage, and requires coverage of between 20-60% of the available area. For more than ten years, the efficacy of this approach has been studied at the University of Toronto’s Green Roof Innovation Testing Laboratory, known as the GRIT Lab, which carries as its charge “the goal of investigating the environmental performance associated with such ‘green’ and ‘clean’ technologies as green roofs, green walls, and photovoltaic arrays.

“We test aspects of green roofs, using a more evidence-based approach,” says GRIT Lab’s Professor Robert Wright. Wright says that a rooftop garden as simple as a grassy surface will release water more slowly, easing the stress on sewage systems that have often been designed for smaller populations or less density. The gardens can also reflect sunlight, reducing urban heat and the demand on increasingly overtaxed HVAC systems.

When incorporated into the design concept of the building, rooftop gardens can even yield small crops like specialty herbs, vegetables, wildflowers or blueberries. A local Torontonian had even begun harvesting and serving honey from bee colonies installed in a green roof until concerns were raised that construction from neighbouring buildings were introducing too much lead dust into the colony, tainting the honey. Rooftop cisterns can be used to provide irrigation. With tongue only slightly in cheek, Wright suggests that as other neighbourhood regulations shift, other specialty herbs might find their way to rooftop gardens, where they can be securely grown.

Source: Plumbing Africa