Ready Mix Sommeliers
In my experience, Open House Chicago’s most popular sites are the ones that reach high in the sky. People love the views, and for good reason. Having said that, I should note that people like much of what is on display during Open House Chicago, be it old new, high or low Chicago is renowned for its architecture.
Yet, I find the birth process to be far more interesting, which is why I love construction sites. It has been fascinating to watch the Vista rise from lower Wacker Drive. By my count, it’s approaching 80 stories, with 20 or so to go. It should top out sometime this winter.
For a number of years, I have failed to make it to Prairie Material’s Yard 32, located at the intersection of Chicago Avenue and Halsted. Following my visit this year, I can report that it is by far Open House Chicago’s best site.
No fooling around once you arrive. Several of the tour guides drive the familiar green and grey Prairie Material trucks. The walking tour takes you virtually everywhere: down to the river to see the barges filled with limestone and sand; up to the room that controls the flow of the materials from start to finish; into the gigantic silos where conveyor belts move the material as it is mixed; and if you are a little kid, one guide made sure you had the opportunity to sit in the driver’s seat of a cement truck. He even let the kids honk the horn.
The statistics are overwhelming. Yard 32 supplies ninety percentage (90%) of the cement for the major projects in the downtown area. The gravel and sand are delivered daily on barges that begin their journey in Romeoville, Illinois, where the quarry is located. Over the course of a year, Yard 32 produces close to 500,000 yards of concrete. A yard weighs 4,000 pounds.
During a given day, the drivers make 65 deliveries, with each truck carrying nine yards of concrete (the legal limit)—best characterized as the whole nine yards. From the time the truck is loaded with the mix, the driver has roughly 90 minutes to make the delivery—that time varies by mix. Don’t worry, if the traffic is slow, the driver has ways to prevent the concrete from hardening in the truck. They can add water, but there is an outer limit. When it is reached, the batch can’t be used.
Not all concrete is the same. There are over 5,000 recipes, but much of the plant’s production comes from just 50 to 65 of those recipes.
The entire process is controlled on the second floor of a tower clad in corrugated metal. An operator sits in a small office with linoleum tile flooring and filled with wood office furniture. On one side, a large black control panel is flush against the wall. The switches and diagrammatic lines that visually connect them control the entire operation. The ones at the top of the panel control the flow of materials being unloaded from the barrages. The switches located further down the panel control the disbursement of the materials among the silos.
Keep moving down the panel: The next row of switches control the flow and mix of the materials as the stone, sand, and aggregate drop to one of two conveyor belts at the bottom of the silos. As the finished product emerges, it flows upward. Another row of switches control the finished product’s descent into the trucks waiting below.
On the other side of the room, there is an interior window. Through it, the operator can see the machinery that pumps the ready mix into the trucks It includes what appears to be a large spinning vat that presumably keeps the mix from hardening. Everything is covered in a white powdery substance. Mixing cement is a dusty business.
I learned a few other interesting facts along the way. First, you don’t unload a barge filled with gravel starting at one end, working your way to the other. You take some gravel from the left side, then from the right side, and keep alternating until the barge is empty. If you take all the gravel from one side, you will create a teeter-totter, with half the gravel ending up in the river. You only make that mistake once. Sort of like in kindergarten, when I got off the down-end of the teeter-totter to see what would happen.
Second, winter can be a problem in the cement business. As the compound moves along the conveyor belts, bits can become dislodged. If those those bits freeze, they clog the chutes at strategic points. One of our guides is tasked with unclogging the system when necessary, which requires the use of a shovel and some dexterity.
Third, there may be more than one check on the quality of the mix before it rolls out of the yard, but there is one critical check: Color. Yep, the folks producing the ready mix can judge whether the mix is a good one by inspecting its color. They are the sommeliers of the ready mix world. Ah, but do not fear. If the person checking the color is wearing sunglasses or the color temperature is higher or lower than normal, the architects at the job site provide another check to assess whether the mix is the right one. They do so by taking core samples.
Fourth, another one of our guides loves to drive his truck, but he won’t drive his car in the city because of all the congestion and crazy drivers. Given the disparity between a cement truck and the family SUV, I fully understand his reasoning. People yield when they see a cement truck coming.
And so the afternoon went. On my way out, I learned one of the main reasons Prairie Material opens Yard 32 to the public. Since Prairie began using the site in 1972, the neighborhood has changed dramatically, with hip urban residential sites encroaching from the south and the west. Prairie wants the public to understand just how significant the role it plays in Chicago’s ongoing development. I was told that if the plant were forced to move just five miles west, the price of concrete would soar, which is a perfectly plausible consideration given Chicago’s perpetual traffic jam and the delivery time tolerances.
[Click on an image to enlarge it]
Caution (Do Not Stop on the Tracks)
Two Barges Waiting to Unloaded
The Crane: First the Left Side, Then the Right Side, Repeat Until Empty
A Conveyor Inside the Silos
The Nerve Center
Operator 8338 at the Big Board
S.T. Mary Is Holcim
Waiting Under a Blue Sky
Catch Me If You Can
Staging for the Load
Put Out to Pasture
It All Starts with Prairie Material, Yard 32