e-Newsletter | 03/13/2012

Isn't it a great mood changer when five inches of March snow melts on one 62º day and the sun shines brightly? Every year when this happens, people ask me, "How does this impact the MMSD system?" The answer varies, but, generally, it is not the snowstorm that causes me concerns. It is the melting of that snow!

Snow cover acts very much like a storage tank. When it is cold, the water stays in its solid form, and we see very little in the way of increased runoff to the system. When it warms up, the snow melts, and that water flows right to our rivers and to the sanitary sewers.

If we look at the March 2 storm, that snowfall was estimated to have about a half of an inch of "liquid equivalent". From March 6-8, when temperatures warmed to over 40º, our South Shore Water Reclamation Facility in Oak Creek was running at nearly two to three times the normal rate that we see during dry weather, but there was no rain. Why? Melting snow saturated the ground and found its way into leaky sewer pipes and foundation drains. It is this increase in flows that MMSD's private property inflow and infiltration strives to reduce.

For the MMSD system, a half-inch of melt off is not a problem. When this melt off occurs along with a rainstorm, we basically have to manage the melt off along with the new rainfall. What compounds the problem is that the soils are usually saturated and will not absorb more water. The result is more runoff and more water to deal with.

It is not only the quantity of water with which we have to deal, but it is the quality of that water as well. This melted water usually has a high concentration of salt and other surface pollutants. If it runs into the sanitary system, we treat that water. If it runs into a storm sewer or directly to the rivers, we see an increase in the pollutants that enter Lake Michigan. If you are interested in seeing the monitoring data that shows the increased pollutants when we have the melt off, go to www.mmsd.com and select the "H2OInfo” button to pull up the most recent water quality information.

"Snow-maggedon” is not a problem, but "melt-aggedon" can be worrisome.

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Milwaukee Metropolitan Sewerage District

260 W. Seeboth Street | Milwaukee, WI 53204