Three hundred homes and businesses across the city of Ottawa spent a 12th night without power, as the cleanup continues from a devastating storm that knocked out power and damaged the power grid, and a few pockets remained Thursday morning.

Hydro Ottawa reported Wednesday evening that power had been "successfully restored" to 179,700 of the 180,000 customers that were knocked off the grid by a derecho storm on May 21.

"Crews are working as quickly and safely as possible to restore the approx. 300 who remain without," Hydro Ottawa said on Twitter.

Early Thursday morning, Hydro Ottawa's outage map showed no outages of note, but by 9:30 a.m., pockets reappeared, affecting more than 300 customers in different areas, including Grenfell Glen in the west and along Leitrim Road in the east. The map is offering estimated restoration times in the evening hours of Thursday.

Hydro Ottawa said on Twitter Thursday morning that 153 customers in Grenfell Glen were disconnected for an emergency outage to remove trees in the area.

"Restoration is expected overnight, with another planned outage set tomorrow. This work is vital as the system is still vulnerable," Hydro Ottawa said.

REMAINING WORK COMPLICATED, TACTICAL

Joseph Muglia, director of systems operation and grid automation for Hydro Ottawa told Newstalk 580 CFRA’s “The Morning Rush with Bill Carroll” that the last pockets of outages require complicated work.

“We’re away from those bigger pole lines and the bigger circuits that you’ve seen the crews out working on. Now, we’re into the tactical, closer-to-home type of work,” he said. “It’s smaller pockets in neighbourhoods and there’s one circuit that relies on another circuit, so we have to make sure the upstream circuit is fine and it’s been patrolled. It’s extremely complicated, the way things have to be brought back.”

Muglia said he expects the city to be in “pretty good shape” by Friday, but there could be a few individuals who need extra work.

“Maybe there’s a tree on their line, maybe there’s a neighbour’s tree on their line, so it gets a bit more complicated just doing that cleanup and then doing the restoration, but we’ve been mandated to just clear the path. Whatever the conditions are at the house, we’re going to get it on, we’re going to do the work that we have to do.”

He says forestry crews and electrical contractors are riding with hydro crews for the remaining outages.

“We can get almost a one-stop shop when we show up at these houses,” he said.

WHY NOT BURY THE CABLES?

The windstorm last month destroyed more than 300 hydro poles and even buckled metal towers, prompting the question of burying hydro wires to prevent future damage from high winds.

Muglia said, however, that buried wires encounter other issues.

“They’re affected in other ways: by freeze-thaw, by flooding; if it’s not one thing, it’s another,” he explained. “Just to bury everything would be so cost prohibitive. It would be a massive undertaking.”

Muglia said there would be a “huge debrief” in the days and weeks after the work is done.

“We certainly plan for weather events. We take all of that into consideration when we’re planning. This will definitely play into it,” he said.

SCHOOLS

The Ottawa-Carleton District School Board announced Wednesday that power has been restored at Merivale High School. All OCDSB schools will be open for in-person learning on Thursday, June 2.

The Ottawa Catholic School Board says Sacred Heart High School and St. Monica Elementary School remain closed. Students who attend those two schools will continue with virtual learning Thursday.

TWO COMMUNITY SUPPORT CENTRES CLOSING WEDNESDAY

The city of Ottawa says two community support centres that have been open through the recovery are now closed.

Support services at the François Dupuis Recreation Complex and the CARDELREC Recreation Complex ceased their role as support centres Wednesday.

Other community support centers at the Howard Darwin Centennial Arena (1765 Merivale Rd.) and the Hunt Club-Riverside Park Community Centre, (3320 Paul Anka Dr.) will remain open from 10 a.m. to 7 p.m. daily until further notice.

"With many (city of Ottawa) recreation and cultural facilities back to normal operations, residents can access washrooms, showers or charge devices at other facilities, as available," the city said on Twitter.