UTRCA hosts symposium about 'Low Impact...
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Mar 20, 2014  |  Vote 0    0

UTRCA hosts symposium about 'Low Impact Development' technologies

St. Marys Journal Argus

Stew Slater

St. Marys Journal Argus

FANSHAWE PARK — As the temperatures rose a few degrees above freezing this week, Imtiaz Shah found himself getting up from his desk in the lower level of the new headquarters building of the Upper Thames River Conservation Authority (UTRCA) and going outside — to a location overlooking Fanshawe Lake.

He did the same thing in the summer, whenever it rained.

Shah, an environmental engineer for the conservation authority, was waiting to see how long it would take for rainwater or meltwater to reach to top of the pond designed to manage stormwater from the entire five-hectare piece of cleared land upon which the headquarters and its adjacent parking lots sit. Once at that level, by design of the pond, the water would spill through a single concrete outflow, about six metres long, and be released into a naturally-vegetated channel that meanders its way slowly down the embankment to the lake.

Sometimes, Shah waited a long time. Often, he went back inside without ever seeing the water reaching the top.

Those were the times he was most satisfied with the result.

It’s all part of what’s called Low Impact Development (LID), a concept Shah says is gaining ground among municipal planning departments in other parts of Ontario, and the UTRCA is hoping to see become more established here.

When the UTRCA opened what it calls the Watershed Conservation Centre on May 31, 2013, it boasted about its first-in-London status as a “Platinum”-rated building under the Leadership in Energy and Environmental Design (LEED) system. Development of the surrounding property, conservation authority officials asserted, was likewise undertaken with the utmost in environmental stewardship — with LID principals — in mind.

On Thursday, March 20, about 200 planners and engineers from across Ontario gathered at the Watershed Conservation Centre for a day-long opportunity to learn about LID techniques for stormwater. They took in indoor presentations from people like Shah, and went outside to see the various innovative techniques used in the development of the surrounding property.

The most highly-noticeable among the LID innovations is the Watershed Centre’s “green roof.” From above, it looks like a lawn. But it actually forms the roof of a large storage building adjoining the main Centre.

And instead of having rainwater flow off a steel or asphalt roof through eavestroughs in a single, fast-flowing stream, the green roof allows water to infiltrate into the surface and be released slowly in the following days and weeks.

According to Shah, some municipal governments in the Greater Toronto Area have changed their planning regulations over the past couple of years, and now require a certain square footage of green roof structures in any new development over a certain threshold in area. He concedes that green roofs remain a considerably more expensive option for buildings, but adds that there are also considerable long-term savings for municipalities when it comes to erosion control and repairs to stormwater management infrastructure.

It’s clear, however, that what Shah is most proud about is the way in which stormwater and meltwater are managed on the rest of the Watershed Centre property.

“There are no storm sewers or sanitary sewers on this site,” he states. “This (stormwater management) pond has no inlet pipes. All the water that flows into it flows in over naturally vegetated areas.”

There’s one metal culvert allowing water to flow from a parking lot area to a down-slope grassy area. And there’s the not-so-often-needed concrete outflow from the pond. But other than that, water either flows across vegetated soils, in what are called “bio-swale” trenches also covered in grass, or onto “pervious parking lot” material. All of these surfaces allow the water to flow more slowly than it would in an underground pipe, and allow a good portion of it to percolate slowly through to the groundwater.

“What we’re trying to do is mimic the natural hydrological cycle of the site,” the environmental engineer explains.

Developers of any property within the Upper Thames watershed are required to inform the UTRCA about their intentions; the UTRCA is welcome to submit comments about the development proposals but, in most cases, the developer is not bound by any recommendations made.

In so-called “regulated” areas, by contrast, permits must be obtained from the conservation authority. In general, these areas include floodplains or slopes leading to floodplains.

In either case, Shah is confident that LID approaches will continue to gain popularity in the district. In the past few months, he noted, municipal planning departments and developers of residential subdivisions in Sebringville (four homes on large, 1 ½-acre lots) and Ingersoll (a suburban setting of 40-50 homes) have agreed to implement some UTRCA suggestions.

In Sebringville, Shah said, the traditional run-off control approach called for catchbasins along a 750-metre underground pipe, leading into a management pond. On the conservation authority’s advice, the plan was altered to include bioswales. Shah says it became easier to convince municipal officials when it was shown that potential long-term maintenance costs for the subterranean run-off control would far outweigh maintenance of the LID-style structures.

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