September 8, 2010

CH2M HILL

Amherstburg’s new treatment plant is being built around the existing facility.

Stimulus makes Amherstburg, Ontario’s long overdue wastewater plant a reality

RON STANG

correspondent

AMHERSTBURG, Ont.

It’s been a long time coming for the southwestern Ontario town of Amherstburg. So long, in fact, that Lou Zarlenga, the municipality’s manager of public services, calls this project his “favourite subject” to talk about.

“I’ve been working on that project nine years,” the senior administrator laughs. Now, with the aid of some senior government dollars, the town will soon have a sewage-treatment plant with current technology.

Amherstburg, located at the juncture of the Detroit River and Lake Erie, is one of the very last communities on the Great Lakes to upgrade its treatment plant from primary to secondary treatment.

The town has been operating with an existing plant dating from 1962. But with continued growth in this Windsor bedroom community and a couple of subdivisions in effect on hold by order of the province, the town had no alternative but to update what had become a bit of an embarrassment for a municipality otherwise modernizing its infrastructure and seeking to be a tourist destination.

The old plant, for example, just had primary treatment with solids removal and chlorine disinfection.

The $10.6 million federal and provincial COMRIF funding for the new one has been in addition to major sums of government stimulus dollars flowing to Amherstburg — $16 million for an almost-completed recreation complex and $11.3 million for street rebuilds and landscaping in the town’s historic core.

When it came to sewage, one of the biggest problems the town had was old, combined lines.

When storms or spring runoff occurred sewage got dumped into the adjacent Detroit River. Provincial officials “were not thrilled with the bypassing,” Zarlenga said understatedly.

So, construction crews have been a frequent sight throughout the town over the last two years, digging up streets and replacing most of those pipes with separated lines.

The final piece is the treatment plant.

Construction began in February on the $34.1 million plant and is to wrap up by June 2012. The design is by CH2M Hill’s Guelph office and construction by Windsor-area contractor Facca Inc., a longtime bridge builder that in recent years has branched into underpass pump work, leading in turn to small municipal sewage plant contracts.

The main parts of the plant are a two-storey head works and dewatering building. This will contain screens and including a sludge-dewatering centrifuge, along with a truck loading bay.

There will also be a UV disinfection building and a prominent administration building with landscaping.

Between the head works and UV buildings are a gallery containing twin primary clarifiers with chain-and-flight sludge scrapers, twin three-pass aerated bioreactors fed by turbine blowers and equipped with fine bubble diffusers and twin secondary clarifiers with chain-and-flight sludge scrapers.

Whereas previously the public never saw the sewage plant from the busy street leading out of town, the new plant will get some notice. In fact the administration building’s design has similarities to the 18th century soldiers’ barracks in the town’s Fort Malden, a national historic site.

Part of the challenge for designers was that the new plant is being overlaid on the old one. This required some design rethinking on CH2M Hill’s part.

The old plant had to keep running until phases of the new one come on stream.

“The main constraint features that we had to deal with at that site were the physical constraints, the physical space aspects, building around the existing plant without disrupting operations and working with what little space that we had available,” CH2M Hill’s project manager Dave Arsenault said.

“It’s more in the specifics of the layout, dimensional ratios of different tanks and how they’re oriented with the other buildings,” he said.

“It was a lot of trial and error involved in trying to fit all that together.”

This “shoehorning” led to the design of rectangular rather than circular tanks to “take better advantage of space,” he said. The tanks stick up only about two-and-a-half metres above ground.

Construction crews also have had to essentially wrap new structures around the existing buildings.

“We’re building around the whole plant basically right now,” Darrin Murphy, Facca’s site superintendent, said.

“The primary gallery gets built last and that’s basically kind of the footprint of the existing building so we have to kind of do some bypass pumping to the plant, make the plant work around the existing structure and then take down the existing structure and then complete the primary gallery in the last phase,” he said.

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