The ground is still shifting in Nutana after a chunk of riverbank collapsed behind a row of houses.

City officials lifted the voluntary evacuation order today for about 50 residences in the 200 and 300 block of 11th Street East, and across the alley on Saskatchewan Crescent East.

Despite the order being lifted, however, Saskatoon's infrastructure general manager Mike Gutek said residents should continue to exercise precaution in the affected areas and to stay out of the back lanes.

"[The ground] is moving a bit. From last night to now, we've seen some portions of the failure move about a foot vertically and also horizontally," he said, adding that he's seen additional cracks in the ground, but that the failure appears localized.

"The only thing at risk now is the danger of accoutrements in some of the affected backyards falling over."

Gutek said the cause of the slump "is what it's always been for a thousand years" and there's also no indication that an infrastructural issue, such as a broken water main, was the catalyst of the slump.

"All of the slopes on the South Saskatchewan River are unstable," he said. The dirt that sits on top is stable however the sandy sills are unstable, explained Gutek.

On Thursday, city staff and emergency workers were on site to assess the damage.

The naturally occurring slope failure caused significant damage to a backyard in the 200 block of 11th Street East, sinking a patio by about four feet and tilting a power pole on a 40 degree angle.

Both power and gas were shut off early Thursday afternoon as a precautionary measure.

City officials said power was expected to be switch back on by 1 p.m., and natural gas service is expected to be restored to more than half of the 500 affected customers. 

City workers are now working to drill holes in the hill to insert piezometers - an instrument used to measure groundwater pressures - and an inclinometer - a device used to measure the tilt of a slope - in the alley by Saturday.

"That will give us an idea of the elevation of the slip plane," said Gutek.

Scheduled power outages on Saturday (between 8 a.m and 5 p.m.) and possibly Sunday (between 8 a.m. and noon) will be done in order to drill and install the equipment. Only houses in the 200 and 300 block of Saskatchewan Crescent East and 11th Street East will be affected.

Gutek said the cost and scope of the repairs are still being assessed and that it's "still too early" to know what the next steps are.

"Determining what we do afterwards will a separate process," said Gutek, adding that property owners will be responsible for the damage on their own property.

See related: Residents asked to evacuate after 'naturally' occurring slope failure

fsuen@rawlco.com

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