September 9, 2010

CITY OF NANAIMO

Target trees removed for a watermain extension through Colliery Dam Park were chosen carefully.

FOCUS | Sewer and Watermain

Watermain extension to pass through popular park in Nanaimo, British Columbia

PETER KENTER

correspondent

A new $1-million watermain extension project in Nanaimo, B.C. will pass straight through the heart of a park for the good of the greater environment.

It’s a decision that may appear odd to the casual observer, but the path of the new watermain makes sound environmental sense.

The main is designed to enhance the water supply, strengthen the fire-protection system and support future development in the southern part of Nanaimo. Colliery Dam Park, through which the main will pass, contains two dams and features second-growth forest plied by trails.

“We had the choice of following the streets and detouring around the park, but that would have made it a much larger project,” says Tom Kraft, manager of the City of Nanaimo Engineering Department.

The street route would have added about $440,000 in costs to the project. An engineering and environmental assessment indicated that the watermain could be significantly shortened if it passed through the park, although some trees would need to be removed, and the main would have to cross the Chase River.

“The engineers recommended the path through the park based on capital cost and sustainability,” says Kraft.

“If we passed through the park, we would only need two feet of ground cover for the pipe, instead of the typical four that we would need along a road. Less asphalt and gravel would be used and smaller construction equipment could be used to complete the project.”

The route through Colliery Dam Park aimed to minimize impact on the forest, following an asphalt trail for 330 metres before crossing 300 metres of forested area and the river, then linking mains on either side of the park.

Residents were less than pleased when it was announced that some mature trees were slated for removal in order to accommodate the trench and the excavators, which require a four-metre clearance.

The trees were deemed a renewable resource, and the 22 target trees were chosen carefully, with non-native species and sickly trees chosen first. The rumour mill, however, inflated the number wildly, leading to some public opposition in 2009.

“Some people were quoting numbers as high as 200 trees, while others were talking about clear-cutting and desecration of the forest,” says Kraft.

“We held a series of open houses with our engineers, arborists and wildlife experts that summer, in which we walked people along the path of the water main, and showed them where the main actually shifted direction to avoid certain trees, such as a species of yew that’s considered untouchable.”

Residents also voted on how the city would compensate for the trees, either replanting at a ratio of two to one with native species, or building an additional path through the park. The new tree option won by a handy margin.

Concerns over nesting owls and fish runs were mitigated largely through scheduling, with the trees removed in mid-summer, and major construction limited to August and September.

“The owls and fish simply aren’t active in the area at that time,” says Kraft.

An environmental assessment revealed that boring underneath the river presented more environmental challenges than crossing over it.

The main is, instead, suspended inside a second pipe as it crosses the river, a few feet over the water surface. Residents were asked to weigh in on whether they wanted a bridge built across the river to hide the pipe. They opted instead for the minimalist approach.

“What we did, to prevent the pipe from standing out, is to make it look like one of the many trees that have fallen across the river,” says Kraft. “The pipe was designed with a bend in it to make it look more like a fallen tree from a short distance away.”

The City of Nanaimo’s own construction crews are completing the bulk of the project.

“It’s certainly the most unique project we’ve worked on in this department,” says Kraft.

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