Switching from Magnesium to Salt-based Deicer

by jhwygirl

I can’t seem to vanquish this now untimely thought from my head, so consider this some blog-pimping self-therapy.

Last Monday’s city council voted 10-2 (Rye, Strohmaier voting nay) to approve a 90-day emergency ordinance that would allow the use of salt as deicer on Missoula’s roadways.

One would have thought something like that would have been dealt with handily and quickly, but the hearing lasted nearly an hour (maybe more) on the issue.

More than a decade ago, Missoula’s air quality rules were rewritten to prohibit the use of salt with the belief that the use of magnesium would help keep dust down and it would reduce the need for particulate-producing sand.

Now, I listened to the better part of the hearing, and I had read the pre-hearing Missoulian article on the matter, and one of the things that struck out to me is that there wasn’t any real cost analysis done on the issue.

Yep – unless I’m missing something – there was no real true cost analysis done on the matter.

During the hearing Jaffe asked about whether a cost study had been done, and staff basically reiterated what had been said in the Missoulian article. I’ll paraphrase: “Not really (in reference to the cost analysis), but what I can tell you is that the stuff (magnesium chloride) that I buy is diluted down to 30% strength. We’re basically paying for water. The salt we’d buy would be 95% salt. You do the math.”

Now – that isn’t a cost analysis.

Magnesium is $130/ton, salt is $110. Last year the city had $135,000 allocated, but spent $220,000.

Didn’t we have a big winter last year? I remember shoveling a bit more. Plus there were more than the usual ice storms.

What was the de-icing allocation the fiscal year before last year? Did the $135,000 represent a cut to the typical budget allocation?

Do some minor look-see into the issue and you’ll find that magnesium chloride is less caustic than salt. That’s pretty well known. You’ll also find that magnesium chloride is more effective at lower temperatures. That’s a plus, no?

Steve Robertson, of Missoula, points out in a Missoulian letter to the editor that “once salt is applied, more is needed to prevent liquid refreezing.”

So salt isn’t as effective as magnesium chloride at lower temperatures, and salt has to be reapplied once it melts the ice to keep from refreezing the road surface.

One thing that I couldn’t find, but you can see how the stuff works, is what is the cost-per-yard or cost-per-square mile of application? I’m talking just the product. I see the mag chloride being put down and it’s being dripped down on the roads. Salt – that stuff is tossed out at a much heavier ration that the dripping of liquid. So it appears to me – and I am admittedly no expert on the matter – that there is less mag chloride being used to cover the same area on a pound-per-pound basis. Remember – we’re buying both by the ton.

Beyond that, Missoula is going to have to retool equipment to spread salt. Now, maybe we’ve got the stuff in stash, I don’t know, but that is going to cost labor. Labor that might be better spent elsewhere. It’s a cost. Regardless.

Plus – the city doesn’t even have enough equipment to spread salt – it’ll have to phase in new equipment over the next few years to move to salt.

Further – did I mention salt is caustic? – is equipment going to break and have to be replaced at a higher rate with the use of salt?

Then I could ask what the salt is going to do to our fisheries, as opposed to magnesium. And if we’re using more salt that magnesium..well….

Regarding that – the Health Board had to make a change to its regulations for water quality to allow for the use of salt.

Read: Missoula just lowered its water quality standards so that we can use salt.

AND, the whole water quality thing’ll have to come back to the Health Board and the Missoula County Commissioners to allow for the use of salt.

Seriously? Am I reading that correctly?

Anyways…there it is. Had to get it out of my head.

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  1. Ed Childers

    Geez, it sounds awful when you put it that way.
    On the other hand, we’ve basically OK’d a trial of stuff called “IceSlicer” (www.iceslicer.com) which has been reviewed by the Health Department, the Health Board, the Water Quality Advisory Council. And of course by Public Works; Brian Hensel who runs the Street Department has been looking for something to supplement rust-inhibited mag chloride (the liquid stuff) and sand (has some uses). He wants something that costs less. He conservatively figures the cost per mile of IceSlicer at about half that of mag chloride. Application is with sanding trucks. “IceSlicer” claims to have the same corrosivity as mag chloride, about 30% that of white salt. Councilwoman Walzer found something that indicated IceSlicer is 80% as corrosive as white salt. She’s looking into it. I found an apparent 2002 comparison of Ice Slicer to Kansas Rock Salt, done by the University of Colorado for Fort Collins, that found no significant difference.
    Did I mention we OK’d a *trial* of “IceSlicer?” By the way, PW has used some of it under some conditions in previous years with no apparent ill effects on anything.
    The emergency ordinance has some minor changes, plus the following.

    THIS WAS ADDED TO THE EMERGENCY ORDINANCE:
    Liquid products shall be analyzed in the concentration they are applied to the street and directly compared to Table 1. Solid products shall be liquefied at specifications approved by the Department prior to analysis. In general products will be analyzed in accordance
    with product category test protocols developed by the Pacific Northwest Snowfighter’s Association (PNS) before being compared to Table 1.

    THIS WAS ELIMINATED FROM THE EMERGENCY ORDINANCE: Corrosivity to Steel 30% as corrosive as salt.

  2. goof houlihan

    Doesn’t the sand have 10% salt anyway, just to keep it from clumping?

  3. Ed – Missoula did have to lower its water quality standards, no?

  4. Ed Childers

    Good morning.
    No, we didn’t lower water quality standards.
    The Council minutes are at:
    ftp://www.ci.missoula.mt.us/packets/council/2008/2008-12-01/081124minutes.doc
    Check out Jim Carlson’s (Health Dept.) comments. And Brian Hensel’s.
    And Goof, I remember something about salt keeping sand from freezing, but I don’t recollect any percentages.




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