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Successful underwater blast at John Hart reservoir

JOC News Service
Successful underwater blast at John Hart reservoir

NANAIMO, B.C. – As part of the scheduled work for the John Hart Generating Station Replacement Project, BC Hydro contractor InPower BC recently completed a rock blast within the John Hart reservoir in Campbell River, B.C.

The blast, which removed a rock area and created an approach channel to the new water intake works at the John Hart dam, took place at about 11:30 p.m. on Oct. 3.

"This is an important milestone and another potential project risk that has been overcome by our contractor," said BC Hydro project spokesperson Stephen Watson, in a statement.

"We’re pleased to see this event completed successfully with no impacts to the project, dam, nor to the City of Campbell River’s domestic water supply – the city draws water from the reservoir only a few hundred meters away from the blast area. It was very carefully carried out."

InPower BC CEO Paul Sawyer said about 154 holes were drilled into the rock outcrop area for the placement of the packaged explosives. The specifications of the blast were to have very little ground vibrations, which was achieved.

"A lot of planning went into this blast event to ensure that it went successfully," Sawyer stated in a release.

"There were many facets to it, and from an external perspective, that also included engagement with government fish agencies, BC Parks and the City of Campbell River. It all went according to plan."

A lot of planning was necessary because the blast happened at night, the period when city domestic water withdrawals from the BC Hydro penstocks are lowest.

Also, to nearly eliminate risk to the city water supply from potential turbidity issues and a resulting public boil water advisory, the John Hart Generating Station was temporarily shut down and all the downstream water flow was redirected down Elk Falls Canyon, adds the release. The closed off BC Hydro penstocks were kept full of water and became the short-term reservoir for the city water supply.

The double silt curtains are now back in place to protect water quality in the John Hart reservoir by separating the work area from the reservoir. InPower BC will now begin the process of removing about 3,000 cubic metres of loose rock from the reservoir bottom by crane and clam-bucket. The new rock approach channel allows water to enter the water intake works and the power tunnel down to the underground powerhouse.

The John Hart project remains on schedule for the new facility to be in full operation by fall 2018.

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