Pollution plume

As MN/DOT eyes more lanes for I-35W, what does it mean for air quality in Southwest?

As the state tries to address traffic growth on I-35W, freeway neighbors face an air-quality Catch 22.

If the state doesn't improve the freeway, the interstate would get more and more clogged.

Cars stuck in stop-and-go traffic run inefficiently and increase pollution, like benzene -- a carcinogen -- and combustion byproducts that cause respiratory problems. Freeway congestion may lead some drivers to opt for neighborhood streets, adding to safety concerns and pollution there.

If the state does add capacity on I-35W, including planned High Occupancy Vehicle lanes north of the Crosstown, cars would move more freely, burn more efficiently, and add relatively less pollution, experts say.

Yet critics say the state can't build itself out of congestion -- and more lanes will increase sprawl. At some point in the future, more cars will be stuck in traffic with the same problem repeating itself, only this time with more cars and more pollution.

"This plan is working real hard to balance the needs of the community around the project with the folks who use the project," said Kevin Gutnecht, a spokesman for the Minnesota Department of Transportation. "The issue of transit is a very important issue. We want the HOV lane."

The air-quality impact of the plan is not known. The environmental assessment is still a work in progress, MN/DOT said.

Rep. Jean Wagenius of Minneapolis has called MN/DOT's plan a "concrete solution" and said legislators should have had information on environmental impacts sooner.

And she said she wanted more than one option to look at -- and options that looked at increasing transit further.

"You could go way down the line and spend millions of dollars on design and it may bring up questions," Wagenius said. "The appropriate time to ask the question is at the time we are looking at alternatives.

"To expand the number of cars without looking at the air-quality issue at this point doesn't make sense."

Focusing on carbon monoxide The state would not build the HOV lanes until 2015, but it is laying the design groundwork now. The work on the Crosstown, is expected to begin in the

next few years.

MN/DOT's consultants estimate that, under this plan, traffic in the I-35W corridor will increase 16 percent -- or 31,200 cars a day -- by 2025.

Much of the talk about the I-35W project has centered on making the Crosstown Commons interchange safer, without closing it for construction, and adding new ramp access at Lake Street and 38th Street. Little public attention has focused on air quality.

The environmental assessment will focus on carbon monoxide, said John Crawford of URS/BRW, a consultant with the state. It will take a detailed look at "hot spots," to make sure the project will not violate federal carbon monoxide standards.

The final report will have a subjective discussion of other pollutants, like ozone and fine particles, but "we are not doing a detailed modeling," he said.

Air-quality trends and federal standards The federal government regulates seven air pollutants: ozone, carbon monoxide, lead, sulfur dioxide, nitrogen dioxide, and two types of small particles, coarse and fine.

The state Health Department is creating Health Risk Values for exposure to a number of volatile organic compounds, like benzene, that are tailpipe emissions. They will not have the regulatory clout of the federal standards.

The Twin Cities metropolitan area exceeded the federal carbon monoxide standard a decade ago, and became what technicians term a "non-attainment area."

The state began the vehicle inspection program in 1991. It ended in 1999 as new car technologies improved and carbon monoxide levels dropped, said Rick Strassman, air-monitoring unit supervisor for the Minnesota Pollution Control Agency (MPCA).

The U.S. Environmental Protection Agency recently developed new and stricter rules for fine particle and ozone. Twin Cities' air quality is close to surpassing those federal standards, Strassman said.

If the area exceeds those limits, the state would have to develop a plan to address it -- though no one knows yet what it would be, and the solution depends on the pollutant, he said.

Air quality has improved dramatically in the last 25 to 30 years as the result of regulations, Strassman said. Yet the root causes of pollution are changing.

"You can't go back to the power plant and the oil refinery and get further reductions," he said. "Transportation in the Twin Cities is taking on a major share of a number of these pollutants, especially a group of compounds called air toxics."

John Griffith, MN/DOT's project manager for I-35W at Crosstown Commons, said he believed the environmental study on I-35W would show an air-quality improvement if the freeway upgrades go forward.

A consultant's traffic forecasts say the interstate would have an acceptable level of traffic flow through 2025 -- assuming other improvements happen on Crosstown and further north on I-35W. Smoother traffic means less pollution, he said.

At the point I-35W gets congested again, "we would have to do more measures that would help ease that congestion," he said.

"I am not proposing that MN/DOT is going to be adding general purpose lanes and building our way out of congestion," he said. "There is a limit to what we can do. Certainly, the transit way, the HOV lane, the opportunity for buses, will hopefully carry along with the 25-year forecast."

By the numbers The transit benefit from MN/DOT's HOV lane depends on how one chooses to look at the numbers.

By MN/DOT's consultant's accounting, daily transit trips on I-35W jump more than 100 percent between 2000 and 2025 -- from 11,000 people a day to 22,800 a day.

By Wagenius' accounting, when transit starts with a small number, a 100 percent increase doesn't do much. The 11,000 transit trips in 2000 made up 4 percent of all trips in the I-35W corridor. The 22,800 transit trips projected for 2025 would account for only 7 percent of all trips that year, she said.

Further, in spite of the HOV lane, MN/DOT's consultants say the number of people per car would take a small tick down, from 1.34 per car in 2000 to 1.33 per car in 2025.

The HOV lane can work against higher vehicle occupancy, said Steve Ruegg, an associate with Parsons Brinckerhoff, a MN/DOT consultant working on travel forecasting.

"When those added transit trips get generated, they take disproportionately from car pools," he said. "You sometimes see a slight decrease in occupancy because people who formerly might have carpooled are now saying, 'I don't need that, I can just hop on the bus.'"

Another problem is that the computer model might not be sensitive enough pick up behavior changes with the HOV lane, he said.

"It has to be a clear advantage to carpool," Ruegg said. "Saving one or two minutes is usually not enough to induce more people to carpool. It has to be at least five-minute savings. It is a difficult thing for the model to track down."

Induced Travel Demand While an HOV lane helps with transit, the flip side of the coin is that adding more lanes reduces congestion -- and encourages people to drive more.

"There is something called Induced Travel Demand," said John Hensel, a supervisor with MPCA's Regional Environmental Management Division. "If you think of time as a commodity, which it is, if time becomes cheaper, namely if you can jump on the freeway and get twice as far in a certain amount of time, people will say 'This is a good deal.'"

"The other thing they might say is, 'Since I can get twice as far in a certain amount of time, how about if I move farther out? I can get out to a really nice area that isn't as developed.'"

As more people drive the I-35W corridor, Hensel could not say how much higher pollution levels are for those living near the freeway.

"We are really tight on our monitoring money," he said. "We asked for a couple of positions and got turned down. There is little money coming out of the legislature to deal with this problem, especially when we are not violating existing standards."