The region has scrapped a plan to replace a broken 45-year-old watermain on the Concession Street bridge by boring a tunnel under the Grand River and will instead relocate the main to the other side of the bridge.
The region made the decision earlier this year after realizing that boring a hole through bedrock was too costly.
Unfortunately that realization came after staff completed a Class Environmental Assessment last year on the preferred option of installing a trenchless watermain under the Grand River.
During the implementation stage of the project earlier this year, however, "prohibitively higher" construction costs came to light.
The region recently hired Stantec Consulting Ltd. to revise the Class EA with a new preferred solution to install the watermain on the downstream side of the Concession Street bridge.
The damaged water main has been out of service since February 2018 when extreme temperature fluctuations led to an ice jam above the Park Hill dam.
Coupled with rain that raised water levels across the watershed, the resulting thaw sent massive ice chunks down river and into the side of the bridge.
Large sections of the watermain were crushed by the ice and fell into the river, leaving almost half the city without water for several hours while repairs were completed to divert the water supply.
City water operations crews were able to isolate the water main at both ends of the bridge but couldn’t replace the missing segments.
Mike Parsons, director of environmental services for the city, told CambridgeToday last year that the "ductile iron water main", which was installed by the region when the bridge was constructed in 1977, served the southern half of Cambridge.
In the four years since the ice jam destroyed it, water supply has been maintained using redundant mains in the city-owned system.
Originally budgeted at $1.3 million, the watermain's replacement cost was reset at $1.58 million in this year's budget, including design and construction costs. The region estimates more detailed cost estimates will be developed once the detailed design phase of the project gets underway later this year.
Starting Aug. 9, a Revised Project File Report will be prepared to summarize the project and will be available for a minimum 30-day public review period.
- With files from CambridgeToday.