Streets Commissioner David Perri Explains Sunday’s Ice Disaster
On Sunday morning, thousands of folks in the Philadelphia region got in their cars, unaware that the roads were about to turn into sheets of ice. We got City of Philadelphia Streets Commissioner David Perri on the phone to get his take on what happened.
Was Sunday one of your more nightmarish days on the job?
Nothing strikes fear in the hearts of highway departments more than an ice storm. They are the most difficult storms to fight. They are so difficult to predict. The weather conditions really have to be, kind of like a perfect storm of conditions for freezing rain to develop.
One problem is, it’s dependent on ground temp. You can be looking at forecasts, the temperature readings in the air, and that air may be at or above freezing. But if your ground temp is below freezing, you’ll have ice develop. If it was just a little bit colder on Sunday, it would have come down as sleet. And sleet is almost gravelly; you can get reasonable traction.
But with freezing rain, it’s basically a glaze. It’s an ice skating rink. Very difficult to deal with.
You didn’t get any warnings about the freezing rain?
The night before — on Saturday night — there were no freezing rain advisories. The highway departments weren’t anticipating that type of event. And then the rain came earlier than expected. The air temp was just at the right point where it fell as rain and hit the cold ground and immediately froze.
What can you do to stop the roads from turning into ice?
The best defense against an ice storm is to tell folks to stay home. There’s not a lot you can do. Even if you salted, you can’t get salt on every square inch of roadway, and any patch of ice sets you up for a major accident.
We hate to see ice storms. It’s the worst type of winter event you have to deal with. We’d much rather have snow.
So once you realize it’s coming, there’s still not much to be done?
We tell people to stay in place. We salt as much as we can. But really, the best message is just to stay at home. The DRPA and turnpike and other entities did the right thing by closing the highways and bridges.
Where does the Streets Department get its weather forecasts?
We use four or five different sources. We have a custom, private weather forecasting service that sends us updates throughout the day. We also contact the airport; they have a private service. And we look at National Weather Service (NWS). Oh, and Weather Underground. I’m not pitching them, but they were pretty accurate last year.
What, no Cecily Tynan or John Bolaris?
We do check in with her, too. She’s actually pretty good. I look at Bolaris, too. Tynan’s a little better.
But we use the National Weather Service as the baseline. If they’re predicting a winter storm warning, that’s our base. If they’re not predicting it, but another is predicting a major event, we’ll deploy based on that one.
Even though we use the National Weather Service as our baseline for snow response we tend to favor forecasts based upon the European weather model. The sad truth is that the European weather model has 10 times more computing power than the NWS model.
What forecast did you get on Sunday?
Our forecast that came in at 6 a.m. had no ice storms. The National Weather Service didn’t issue an ice storm warning until 7 o’clock. And at that point, we tried to get the pieces in place to fight.
We got 40 salt crews out on Sunday morning. By about 10, the local roads were in a reasonable condition. I went out and checked the Roosevelt Boulevard. The inner drives where the tunnels are got closed off — they are notorious for ice. The outer lanes all stayed open. The Boulevard was navigable.
What would you have done had you known this was coming?
We would have had a full deployment of salt trucks that started a couple of hours before and then salted through the event, but we only would’ve gotten primary streets salted and part of the secondary network. We wouldn’t have been able to get the whole city.
A lot of people don’t realize that the city has a snow deployment plan. In the city’s snow deployment plan, we have primary streets, secondary streets and tertiary or neighborhood streets. Anything less than a winter storm warning — so anything less than five inches — we only treat primary. When the snow is at five inches, we deploy to treat and plow and salt primary and secondary streets and higher elevation tertiary streets.
Prior to the Street administration, the city did not have a residential snow removal program. He started that. But back then, the bar was 12 inches. The policy was that the residential network would not be treated until we have a 12-inch snowstorm. Now Nutter has officially changed that to five inches or above.
Compared to last year, you seem to have gotten off pretty easy so far this winter.
Well, we’ve only had an inch-and-a-half. But it felt like a lot more. We’ve had four deployments. Tomorrow will make five.
When we get snow and temps before and during and after it are in the teens, it’s very difficult to completely clear streets. Salt loses effectiveness when it gets into the teens.
Fortunately, we haven’t had to convert the trash compactors into snow plows this year. When that happens, we have delays in trash pickup. Last year, we had problems for weeks on end. Every time we had a snow event, there were major delays. This year, we’re blessed.
So far, I haven’t seen any ridiculous pothole problems. Last year was insane.
We’re actually now starting to see signs of an early pothole season, unfortunately. Some of the seams are starting to open up on Delaware Avenue and Vine Street.
Last year, we did 50,000 repairs, which was an all-time record for us.
We had another phenomenon last year that was amazing. I took pictures. We had trash trucks literally fall into the street. They were cave-ins. The cave-ins were caused by water formed underneath the roadway surface that basically lifted up the surface of the street. The extreme low temperatures caused what’s known as ice lenses to form under the roadway. When it thawed and the first heavy truck went down, it punched right through the street. We had to pull six trucks out of the street. It was just incredible.
Has battling the winter changed much or is it still done the same way it was done 10, 20 years ago?
We have plans for significant changes if future budgets allow it. We’re gonna purchase these gauges to embed in city streets that will give us real-time roadway temperatures. We’ll know the ground temp, whether the streets are wet, whether they are snow-covered or frozen. And we can better deploy our vehicles.
I’ll give you an example as to why this is so important. Last year, we had one winter event where we had spotters in the street. I took a ride up to the Somerton area, which has a higher elevation, because I wanted to see if the streets were clear. And I had another employee in a high elevation in far Northwest Philly. If there’s not ice forming, we should be in good shape. Of course, the higher you go, the colder it is.
Icing was minimal in both places, so we felt good and started rolling up the operation. But then we start getting all these calls about icing in Port Richmond and Delaware Avenue, and I thought, it can’t possibly be icing there.
Then, I figure it out as I am driving down 95. I start seeing this massive fog rolling in off the Delaware River and up Spring Garden. What was happening was, the Delaware River was frozen and the wind was blowing out of the East. Normally, Chestnut Hill is colder than South Philly. But it was the opposite in this particular storm. This is why we need to know the road temperatures.
Beyond these gauges, what else does Streets need to deal with winter more efficiently?
We need to convert to more of a brining operation. Brining is when you use a mixture of salt and water and spray it on the street. You can do that two days before a storm. This is very effective in melting the first inch of snowfall, and the majority of our storms are about an inch.
Right now, we can only brine 30 miles, and we’d like to increase that to 300 miles. There are over 2,500 miles in the city network. Brining would also reduce the amount of salt we have to purchase, because you’re only putting out a thin layer.
And then eventually, we need to outfit our fleet and contractor fleet with GPS equipment, so that we know where the salt trucks are, we know what area is being treated and what remains.
But all of this would require the kind of money that needs a major policy decision.
What are you expecting to do for tomorrow’s snowfall?
At this point, we’re doing a brining operation covering 30 miles. We’re expecting it to be just a salting event, and we’ll salt the primaries and secondaries. We’ll be ready to plow if we get more than two inches. That’s generally the threshold. With the first storm, when we got an inch-and-a-half, I had people telling me, We didn’t see a plow truck. But that’s not enough to plow. There are manhole castings that protrude from the roadway surface. So we plow down to about one inch.
What do people who don’t live on these primary or secondary roadways do?
In any storm, if your street isn’t passable, call 311, and we will deploy to make your street passable.
Within what time period?
That’s the tricky part. First we do the primary and secondary routes. As a general rule of thumb, about 12 hours after we finish the secondary streets. All told, figure 12 to 18 hours after the last snowflake.
Good luck out there.
Thanks. We’re happy to get the word out.
Follow @VictorFiorillo on Twitter.