Anna's Hummingbird photo: Ed Stetson

PRERAB will be applying a dust suppressant, magnesium chloride, or MgCl2, as a trial on a few places on PRE roads to see how well it works and whether it is worth the expense to treat our most dusty dirt roads in future years. This work ideally would happen in the late spring after grading is complete and most of the rains have ended. This dust palliative is a sea salt harvested from the salt ponds in south San Francisco Bay. It is certified organic for use on farms and has no additives. Having less dust in the air benefits both plant and animal respiration .

Here are some questions and answers about the use of magnesium chloride.

How does it work?

It works by absorbing atmospheric moisture, and our local summer foggy climate is ideal for it to work well. The more fog we get, the better it will work.

Where does it come from?

This magnesium chloride comes from the Cargill salt flats in the San Francisco Bay.

Is it toxic?

It is not toxic to animals and is, in fact, an additive in certain foods, like Nigari Tofu in which it is used as a natural firming agent.

How does it affect plants?

Since this is essentially a salt, it will burn plants if it gets directly on them. The truck's nozzles spray straight down, 11" above the road surface, so the only plants at risk are the ones growing in the road itself. Plants in drainages close to the treated road could show some burning with rain runoff but as more water moves through the drainage, the effect should diminish.

Why does it need to be reapplied?

With heavy rains much of the material is washed off and hence reapplication is necessary every year or two. Also the more it is driven on, the more often it needs to be reapplied.

How will winter runoff affect Tomales Bay?

In discussion with experts concerning the Tomales Bay, we confirmed that any of this material running off into the bay will have little impact because it is a component of seawater. Of course, long-term use could reveal unforeseen consequences so monitoring with any new program is appropriate.

How much will it cost?

If we agree that this is an effective treatment, the cost of treating 2.5 to 3 miles of dirt roads would be around $6000/year.

How long will it take to apply?

It would take about half a day to do all the dirt roads in PRE. The initial trial of 1000 linear feet applied in a couple locations in PRE will be very quick.

How will we know where it was applied?

We'll place flagging on either side of the treated strips and the locations will be posted on the IRA website.

Top banner photo credit: Ed Stetson