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Over millions
of years
and thousands of miles,
following the trail of road salt
Chicago Tribune
- 2/27
In
a conference room on the seventh floor of City Hall, three Department
of Streets and Sanitation honchos recently discussed a subject
so constantly on their minds that, as deputy commissioner Dan
Katalinic said, "We're thinking about the weather even when
we don't know we're thinking about it."
"Snow's
supposed to miss us again," Commissioner Al Sanchez said.
Katalinic, a 30-year department veteran, cautioned, "Just
watch it hook around over the lake and come back."
Bill
Bonko, head of operations and, like Katalinic, a former plow driver,
added the most ominous note. "The ground's frozen,"
he said. "If it comes, it'll stick."
Despite
a winter that, so far, has had way more barks than bites, the
three know that snow can smite this city any time before -- and
sometimes well after -- the season's official March 21 end. This
season has seen only about 20 inches of snow -- most of that early
on and limited to the lakefront -- compared with a winter average
nearly twice that.
Mindful
of the capricious weather here, Sanchez and his lieutenants frequently
checked in with the Snow Command Center just down the hall. There,
monitors displayed data on the storm, information on road conditions,
air and ground temperatures -- intelligence the department needs
as it braces for possible battle.
When,
as Ralph Waldo Emerson wrote, "Announced by all the trumpets
of the sky, arrives the snow," Streets and San stomps it
as though it were a roach.
In
January 1979, 83.7 inches of snow fell over a span of just a few
weeks (average for the season is 39 inches). With far less snow-fighting
equipment then, the city was overwhelmed. Citizens were outraged
that snow was not removed and so voted to ensure that then-Mayor
Michael Bilandic was.
Snow
removal became politics. An armada of equipment was ac quired.
An army of drivers was trained to operate any piece of equipment
in that fleet. Battle plans were drawn charting priority streets,
optimal driver routes and call-up procedures.
But
all the tactics and weapons are of little use without ammunition,
which consists of half-inch and smaller crystals that are about
40 percent sodium and 60 percent chloride, sodium chloride, NaCl,
salt. The stuff the city shakes on Western Avenue and King Drive
is the same stuff you shake on your fries, just a much chunkier
grind.
Road
salt lives to absorb moisture. As it sucks water out of snow,
it becomes brine, a mix of water and salt, with a freezing temperature
of minus 6 degrees, well below that of water. Aided by the heat
of tires passing over, the brine melts the snow around it, and,
assuming plowing has removed much of the snow already, eventually
rids the streets of snow and ice to create what the department
calls "running water," roadways cleared curb to curb.
"Without
salt, you could push snow all day and not do much good."
Bonko said. "It's like having a gun without any bullets."
The
lexicon of Streets and San has embraced the ammo analogy. In the
heat of battle, when seconds count, an emptied plow/spreader will
come thundering up to a city salt pile. The driver will call out
to the front-loader operator, "Quick, give me bullets."
None
of Chicago's great snowfalls -- the repeated hammering in '79
or that 2 feet in two days monster in '67, or the April Fools'
Day surprise in 1970 -- would have happened in the good old days
420 million years ago. Then, about the middle of the Silurian
era, this was a tropical place. Much of what now is the Great
Lakes region and, in fact, much of the United States, lay beneath
a warm, shallow sea edged by coral reefs in which mollusks, squid
and other sea critters frolicked. Life was beginning the evolutionary
crawl up from water onto the land. Dinosaurs were still in the
future.
In
the Silurian seas, depressions (such as the one called the Michigan
basin) formed. There, poor water circulation allowed salts to
settle to the bottom where they crystallized into halite (rock
salt). Over eons, the salt layer was covered by as little as 800
to as much as 6,800 feet of other geologic stuff atop which Michiganders
now ski, make automobiles, cheer for the hapless Lions and otherwise
go about their daily business.
On
the southwest side of Detroit, there's a portal leading back those
hundreds of millions of years. A shaft at the Detroit Salt Co.
descends 1,200 feet (about a quarter mile) into the Earth, terminating
in a series of spaces that spread out horizontally to cover an
underground area of almost 1,500 acres.
The
mine's first shaft was sunk in 1906. Back then, mined salt was
primarily for food processing, and anyone scattering salt on streets
would have been considered daffy. But as more and more people
bought more and more cars and more and more traffic moved by truck
over more and more miles of roadways, more and more urbanites
saw clear streets as a birthright. In 1940, 164,000 tons of road
salt were sold in the U.S. By 2001, the number had multiplied
a hundred-fold to 16,845,000 tons.
According
to "Salt, a World History," just 8 percent of salt produced
in this country is used for food, while 51 percent is used to
de-ice American roads. The Detroit mine sells nothing but road
salt now (The remaining 41 percent is used for water softening,
chemical production, etc.).
In
the "room and pillar" style of mining used here, salt
is extracted leaving rooms 50 to 60 feet square with salt floors
about a foot thick, salt ceilings 4 to 6 feet thick and salt walls
22 feet tall awaiting further excavation. Pillars of salt larger
than the rooms are left in place to ensure that the Motor City
stays up where it should be. An X-ray view from above would show
a checkerboard pattern of voids and pillars. Historically, salt
mining has been far safer than coal mining, the latter now done
with toothed machines that constantly gnaw away at the coal deposit.
It's also more comfortable. Inside the mine, it's dry, clean,
55 to 75 degrees with fresh air pumped in from above. The decorating
scheme is total off-white.
Using
an electric-powered, 16-foot-long, chainsaw-looking piece of equipment,
a salt wall is undercut at floor level. Explosives are stuffed
into holes drilled into the face and detonated, dropping about
800 tons in each blast.
"A
structure tends to amplify the vibrations," company spokesman
Charles Dixon said, "You can hear it in a house up on top."
The
hunks of salt are run through an underground crusher and several
screeners (bigger equipment is lowered into the mine in pieces
and reassembled). The goal is the American Society for Testing
and Materials D-632 standard, the standard for incremental road
de-icing salt, the standard used by all cities that salt.
Conveyor
belts run the salt up into waiting rail cars, each carrying 100
tons. Some of those cars will make the 3 1/2-hour trip to Chicago.
(The city also gets salt from a mine near Hutchinson, Kan. 7 1/2
hours away). Salt is off-loaded and stored at South Side rail
yards and then trucked to 19 salt storage sites around the city.
Once,
there was a theatrical term, "The Chicago Howdy." It
referred to the savagely harsh reviews that often greeted touring
plays here. The term might well be applied today to the welcome
that awaits a visiting storm.
Streets
and Sanitation can call on as many as 261 big blue trucks, each
with a 10-foot-wide plow in the front, a load of up to 10 tons
(that's 20,000 pounds) of salt aboard and, mounted on the back,
a spreader to lay that NaCl down. In bitterly cold weather, side-mounted
tubes can add liquid calcium chloride to the salt spray. The chemical,
more expensive than salt but with a freezing point of minus 58,
helps salt work longer and more efficiently. When you see blue-tinted
salt, the color comes from calcium chloride.
The
city also uses a dozen Tigers (smaller, narrower trucks with an
under-mounted scraper and 7 tons of salt) for side streets. Eleven
4-by-4 pickup trucks, each carrying a ton and a half of salt,
are available for finer cleanup work. In the unlikely event that
snowfall somehow survives the city's counterassault, quick-hitch
plows can be mounted on 150 garbage trucks.
The
Illinois Department of Transportation plows and salts the expressways.
The city's responsibility is arterial streets, side streets, Lake
Shore Drive and the Skyway and add up to 5,573 lane miles, more
than the distance, a department press release notes, "between
Chicago and Buenos Aires."
Streets
and San doesn't plow alleys. Plowing, it believes, just stacks
snow in front of garage doors. Their trucks will make tracks in
alley snow, and it's up to motorists to get into those grooves.
Also, though the department gets many such requests each winter,
it won't send someone out to shovel your sidewalk.
The
Snow Command Center is able to tap the most sophisticated weather
forecasting techniques to spy out the oncoming enemy and track
it as, for instance, it whitens the fields of Iowa, leaps the
Mississippi into Illinois, races through Warren County, Marshall,
Grundy, raging ever closer. On one table within the center sits
a red phone. Pick it up, and the National Weather Service is on
the line. Local weather forecasters appear on various video screens.
"Some," Katalinic noted, "are more accurate than
others."
Lit
mostly by the glow of those monitors, the center also displays
the whole citywide battlefield, enabling decisions to be made
as to when and where to move the troops. All across the city,
remote cameras are trained on key roadways. Air and ground temperatures
and humidity levels around town are projected on the screens.
Global Positioning System equipment in the trucks generates triangular,
orange blips on the monitors with numbers next to them that identify
each individual truck and, hence, its driver. When a storm is
anticipated, the triangles can be seen moving to their battle
stations then waiting for the order to attack.
"The
GPS technology is great," Katalinic said, "before we
had it, there was a blinding snowstorm one year, and we found
one of our guys had gotten lost and was plowing streets in Hammond,
Ind."
`In
July I'm thinking about salt," Bill Bonko said. "That's
when we start moving it to storage areas. The commissioner wants
our supply at full strength by Halloween."
Bonko
was conducting a tour of some of the salt storage piles around
the city. As part of his job, he is in and out of these storage
areas so often that other Streets and San employees joke that
his car has great traction from the salt embedded in its tire
treads.
Chicago
entered the 2002-2003 snow season with about 410,000 tons of salt
on hand, and an option to buy, if needed, an additional 160,000
tons, creating a potential ammo dump of 570,000 tons. Some of
the city's 19 salt storage piles are outdoors; others are protected
by plywood sheathed domes; two are inside buildings. Recently,
the city has been trying out movable, tube-shaped, canvas-covered
shelters. There's one near State Street and 23rd.
Lake
Shore Drive is served on the north by salt at Wilson Avenue and
on the south by salt piled at McCormick Place. The city's busiest
pile is near North and Throop, tucked pretty much out of sight
behind a Home Depot store. The biggest, 60,000 tons, is at Grand
and Rockwell. A greater trucking distance from the South Side
rail yards makes the pile at O'Hare, per ton, the city's costliest.
Department
people call smaller piles "lumps." Big ones are called
"awesome" by anyone who sees them.
Bonko
turned off West Grand Avenue a few blocks west of Western, headed
through a wide chain-link gate, up an incline and stopped at the
base of the city's biggest pile, four-stories of salt. This likely
is the only view in which a mountain-like shape and the skyline
of Chicago are combined.
Bonko
told a story that has become a legend in Streets and Sanitation.
When the Radio City Music Hall Rockettes were in town a few years
ago. "Someone wanted a picture of them posed like they were
in the Swiss Alps," he said. "They brought them here."
He
has come to show off a piece of equipment the department has developed.
"Outside, a pile will absorb enough water to form a crust
about a foot thick that protects the rest of the pile," he
said. "The salt sort of makes it's own dome."
That
crust used to be discarded until the department figured a way
to turn it back into spreadable salt. "We took a really big
wood chipper," he said, "and asked the manufacturer
to make some different teeth and another conveyor belt. The result:
The world's first salt crust recycler.
Speaking
of recycling, in the summer, plow/spreader trucks are converted
to lay asphalt. The Tiger snow fighters convert to graffiti blasters.
Much
of the stockpile was laid in back in the 2000-2001 winter when
the city was able to acquire additional salt at the previously
contracted price of about $22.50 a ton. The market price was far
higher then, greatly inflated by the harshness of that winter
throughout the Midwest. The average price for salt is around $24.50.
So
far this season, some 123,000 tons of salt have been spread on
Chicago's streets. For comparison, the winter beginning in 2000
was one of the worst in the city's history in terms of road salt
consumption. The city used 324,000 tons then.
Once
again, the order to attack doesn't come to the drivers stationed
all over the city, their trucks loaded with salt, the motors idling.
The storm has veered away to become the problem of road crews
south and east of Chicago. On the big screen in the command center,
the orange blips representing plow/spreaders can be seen leaving
their stations to return their salt loads to storage piles.
"We're
always at the mercy of Mother Nature and Lady Luck," Bonko
said. "So far this winter, those women have been good to
us."
Where
does it end up? Salt of the earth
Where
does all that salt end up?
As
you've noticed, in an unusually precipitation-free winter, a lot
of salt dust has been left to whiten our streets and sidewalks,
our cars, our shoes. This is not as bad a thing as some angry
letters to the editor have stated. Even salt dust retains some
melting ability, potentially speeding up the melting of, for instance,
rain that freezes upon hitting the pavement, creating dangerous
slick spots. Most of the rest of the salt is absorbed into the
ground, settles into small cracks in concrete making them bigger,
corrodes steel, runs off into the lake and rivers, etc.
The
local office of the U.S. Environmental Protection Agency said
that Lake Michigan is big enough that it doesn't show any effects
from road salt runoff. That's not to say there are no effects.
"Any
wetlands adjacent to major roads will show an increase in salinity
over time," said Wayne Lampa, now retired but an ecologist
for 25 years with the Forest District of DuPage County. In that
role, he has measured salinity in the ditches next to routes 53
and 83, in the streams and ponds and rivers of the county, in
its forests and marshes.
What
he found surprised him.
"I
had no concept how heavy the concentrations were," he said.
"Areas completely isolated from roadways have water with
salt content about that of drinking water, 6 to 10 parts per million.
I've found [roadside water] with upwards of 600 parts per million,
almost the salinity of salt-water, which is 800 parts per million."
Salinity
seems to be cumulative. In the fall, after a spring and summer
of rains and no new salt, Lampa has found high concentrations
awaiting another season of salt deposits.
In
a project to preserve a prairie along U.S. Highway 355, he had
berms built to contain the salt, but found salinity still infiltrating
far from the road.
"With
high traffic volume and speed, salt becomes airborne," he
said. "The berm just launched it higher and farther."
Salt
accumulation is worst in areas of poor drainage like roadside
ditches. If you consult your notes taken earlier in this story,
you'll remember the Michigan basin in the Silurian Sea 420 million
years ago. Roadside ditches are acting like miniature versions
of that as salts settle to the bottom, returning whence they came.
Lampa
noted that expressways are creating corridors in which native
plants are being replaced by salt loving species.
"Native
vegetation is not very tolerant of salt," he said, "so
plants from the East Coast and the Gulf Coast come here following
the interstates," he said. We now have salt marshes in Illinois."
He
said that, no doubt, microorganisms in water and soil and animal
life also are affected by road salt, but that not enough study
has been done to tell the extent.
Working
with a list generated by the Morton Arboretum, Bob Benjamin, head
forester in the city's Department of Forestry, has been planting
relatively salt-tolerant species.
"There's
Kentucky Coffee Tree, Bald Cypress, Ohio Buckeye, Northern Catalpa,"
he said, "and a lot of smaller shrubs and other plants. I'm
always looking for new stuff, always thinking where does this
fit in the ecosystem, where will it work in the city?"
When
Benjamin gets a new cultivar, he'll try it in maybe 10 test sites
around town and see how it does.
--
Charles Leroux
The
real deal easier on budget
"You'll
see a big city like Chicago use manufactured salt about the time
my car runs on water," said Bill Bonko, head of operations,
Chicago's Department of Streets and Sanitation.
He
was talking about salt alternatives that have been developed,
some of which you may have used on your front steps and sidewalk.
In
the volume the city requires, though, the cost -- 10 times that
of road salt -- is prohibitive.
Sand
can be used instead of salt and is in some places far from the
city. But because it just helps traction and does nothing to clear
the roadway, the usage is mostly on rural secondary roads.
In
Chicago, sand clogs sewer systems and isn't used at all.
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