Tuesday, October 18, 2016

Environmental Studies Field Trips: Street Maintenance

CGEE Student Voice
Environmental Studies Field Trip Series
by Jenni Abere

This week, my class went to the street maintenance yard for St. Paul to learn about the work that is done at different times of the year, such as leaf sweeping, snow and ice removal, and storm water management. We learned about the common practices as well as what can be done to reduce the impact on the environment.

Street Sweeping

While busy roads are swept more frequently, all the streets in St. Paul are swept once in the spring and once in the fall. In the few weeks of sweeping, 10-15 thousand cubic yards of leaves are collected. This is an important task. Leaves are a major source of phosphorous pollution in water. Once the leaves are collected, they are composted or put on farm fields.

The streets around Hamline's campus were swept this week!

This subject was very topical for me. For the past month, I've been working on Adopt-a-Storm-Drain, to raise awareness that streets are directly connected to lakes and rivers. We encourage people to rake up leaves, pick up trash and dog poop, and use less salt in the winter. Recently, we have been in the Hamline-Midway neighborhood and Lake Hiawatha area. The fall is a good time for outreach because the leaves are falling.

City-wide street sweeping has a huge impact, but it can only be done a few times a year. For all the other times, it's up to citizens to keep the streets -- and rivers -- clean.

Snow and Ice Control

Snow removal is a huge part of street maintenance in Minnesota. For this field trip, we looked at the snow plows and discussed the different ways salt is used. Regular rock salt is only effective when the road temperature is about 15°F. There are ways to make the salt more effective, so that less is needed. Chloride pollution is an emerging concern for waterways, so we need strategies to reduce salt use.

A mountain of salt in the storage shed.

Pre-wetting the ice with salt brine makes the rock salt more effective. There are also preventative measures, where liquids are applied before it snows and this prevents ice from forming. Magnesium and calcium chloride can be used with salt to make it effective at temperatures as low as -10 to -20°F.

Of course, a lot of salt is still used, and this salt ends up in waterways and vegetation. One alternative to salt is "abrasives," or sand. This usually has some level of salt in it as much, but not enough to really melt the ice. It just provides traction. This is a good alternative for sidewalks and home driveways. However, for roads it is not really a viable option. Sand will also enter into waterways in the spring.

Storm Water Management

Before and after the visit to the maintenance yard, we saw some storm water retainment features, including a rain garden by the Hamline Church and plants along the Green Line. The goal of these features is to prevent the runoff from streets from going into storm drains and then into the river.

A rain garden by the Hamline Church.

One of the problems with preventing runoff is that the groundwater can become contaminated with phosphorous and chloride and other pollution. Plants can help absorb some of this, but salt and other pollution can be harmful to the plants. The gardens along the Green Line are experimental -- time will tell if these plants can withstand high levels of runoff and pollution.

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