It takes three things to get 21 inches of snow off the nearly 1,200 miles of streets and… It takes three things to get 21 inches of snow off the nearly 1,200 miles of streets and sidewalks that lattice the city: hard work, planning and patience, local officials said.

Patience is the virtue they’re emphasizing today.

Fifth and Forbes avenues in Oakland remain covered in snow, four days after this weekend’s historic storm.

Joanna Doven, a spokeswoman for Mayor Luke Ravenstahl, said the Public Works Department is “working as hard as they can.”

“This is the most snow we’ve seen in [nearly] 20 years. It’s historic,” she said. “Pitt students and the other residents in Oakland have to be patient. Twenty-one inches of snow represents a serious problem for even the most capable recovery teams.”

Tony Barbarino, the manager of Bellevue’s Public Works Department, said his borough uses a strategy almost identical to the plan Pittsburgh typically uses.

“Because the entire community of Bellevue covers only about one square mile, it offers a comprehensible portrait of the snow removal process,” Barbarino said. “It was definitely a struggle to get our streets cleaned during and after the storm, but we had a lot of dedicated people working, and we were able to get the job done. We had a seven-man crew working overnight Friday, and they have cleared all the streets.”

Barbarino said Pittsburgh Public Works employees will work around the clock to finish the job, and that they will follow a strict pattern in clearing streets and sidewalks with snowplows and backhoes.

Crews salt and plow roads in order of traffic levels, he said.

Crews clear primary routes first, he said. These are main business arteries that provide access to hospitals, schools, police and fire stations. Primary routes continue to receive salt treatment as required to maintain traffic flow.

Workers plow secondary roads, such as those running through residential areas, after they’ve finished the primary roads. They make exceptions for extreme situations, such as fires and medical emergencies, Barbarino said.

Last, workers plow and salt tertiary roads. These are streets and alleyways that have little traffic on a regular basis and are cleared only after the secondary routes are completely cleaned.

Doven did not respond to additional calls asking why Forbes and Fifth avenues, which help provide access to UPMC Presbyterian Hosptial, hadn’t been cleared. An insider in the Pittsburgh Public Works Department, who asked to remain anonymous because he is not authorized to discuss the department’s activities, said those two primary routes are “part of the ongoing plan to clear Oakland’s streets.”

“We are working to clear all the streets in Oakland, but it is a slow process because of the huge pileups,” he said.

Earlier in the day, Doven said people with questions or concerns should visit the Pittsburgh Public Works website, which explains the city’s snow-removal procedures.

The goal of the snow and ice control program is to keep vehicular traffic moving on Pittsburgh’s streets during and following snowstorms, the site says. To accomplish this goal, Public Works’ fleet uses plows and computerized salt spreaders, and personnel continually receive training in the use of snow-removal and salting equipment to ensure high efficiency.

Barbarino said one of the chief difficulties in removing such large amounts of snow is that simply plowing and salting is not enough. Huge snowbanks pile up beside roads and in parking lots, sometimes burying cars and blocking entrances to shops and businesses. Private contractors are often called in to remove these nuisance snowbanks, which must be moved to locations approved by the city.

To avoid flooding and any other environmental damage, workers avoid dumping snow into or around any of Pittsburgh’s rivers, Barbarino said.

“The whole process of snow removal is even more time consuming than plowing and salting,” Barbarino said. “We have to work around parked and snowed-in vehicles. We have to work around traffic patterns and make sure we are dumping the snow in the right places. It’s a pain, but we are going to start pecking away at the job tonight and hope to finish up sometime this week.”

But the snow that they can’t remove quickly often becomes packed, making conditions more dangerous.

The snow that’s expected to fall today and tomorrow will fall on top of inches of packed snow.

“It will compact the snow underneath it and make it almost like ice,” said Rich Redmond, a meteorologist for the National Weather Service.

And Allegheny County 911 is already receiving a high volume of calls. This weekend, it received more than three times as many calls as normal.