Look where we got to go! (40 photos of an empty lock)

Normally, there's enough water to drown a whale in the Sault Ste. Marie recreational lock. This summer, however, the water flowing over the century-old wooden lock floor is just enough to preserve it.

On Monday, after construction finished for the day, a few of us were treated to a rare walk on the bottom of the lock at the Sault Ste. Marie Canal National Historic Site.

Members of the media joined Parks Canada, City of Sault Ste. Marie and project employees on the muddy floor, gazing up the 16-metre walls at visitors passing overhead across the gate bridges.

Under normal circumstances, water from the upper St. Marys River comes in through two 11-tonne butterfly valves, down four two-metre square historic tunnels, up through the historic lock sub-floor, filling the recreational lock.

Today, we wandered around the floor, trying to catch a glimpse of the four historic butterfly valves at the downriver side of the lock.

Those are under a series of white steel beams.

We climbed down a ladder to inspect the inside of the coffer dam, installed over a three-week period ended last week.

The last of the 16 million litres of water it normally takes to fill the lock to the upriver side, about 7.3 metres above the downriver side, has been fully removed from the lock for the first time in 13 years.

The lock was 'unwatered' to allow crews to inspect it, complete any needed maintenance and try to find where water is leaking into the historic powerhouse, said Barry Guzzo, a technical services coordinator with Parks Canada.

"This project will set us up for the next 10-year cycle which we require for maintenance," Guzzo said. "We're doing some structural repairs to the walls. Downstream we're unwatering the sills and a small wall that has failed and we're changing the configuration of our baffle wall which is on the discharge side of the functional lock chamber."

Guzzo explained that the southwest wall of the historical lock - further upstream from where the current lock is - failed in 1986.

That resulted in the closure of the lock until a new concrete lock liner was essentially placed within the historical lock, making it a few metres narrower and much shorter.

At 77 metres, it's now only about a third of the length it was when the lock was originally completed in 1895.

"This project, basically on the heavy construction and structural stuff, picks up where that reconstruction ended in 1997 and is taking us a little bit further down the canal approach to the location of that coffer dam," Guzzo said.

The current lock is used only for recreational boats and is closed to marine traffic until the project is complete and the lock recommissioned in spring 2011.

The project has been ongoing for the past eight months and Guzzo said it appears they will be able to alleviate much of the leakage problem in the powerhouse while also completing the scheduled maintenance and re-engineering aspects of the project.

Meyknecht-Lischer, based out of Kanata, Ontario, is undertaking the contract work.

The same company also successfully completed repairs and restoration work to the historic Rideau Canal wall last winter.

Later this week, workers hope to have a crane bring in an excavator to do some clean-up on the downriver side of the lock, removinh the two modern butterfly valves on the upriver side for maintenance.

To lift out the 11-tonne valves, 68 bolts bigger than a man's fist have to be removed from each valve before they can be disconnected and hoisted out of the lock.