Chloride Levels in the Edgewood Retention Pond

The city of Madison uses salt on the roads to break down ice and prevent slippery roads. However, when the snow and ice melts, the runoff has to go somewhere. That runoff goes into our lakes and streams, affecting the wildlife and vegetation. High concentrations of salt can sometimes be harmful to roadside vegetation. The degree of harm to vegetation relates to four factors: the amount of salt, type of soil, total precipitation and plant species (Salt and The Environment). The purpose of our study was to determine whether there was a correlation between the chloride levels in the Edgewood Retention Pond and the use of road salt as a deicer. We measured the amount of chloride at three sites within the Edgewood Retention Pond during the winter months. We used the Hach® Test to measure the chloride in the water and also monitored the conductivity of the water. Throughout the six months, the chloride concentrations greatly increased from about 8 mg/L to 6000 mg/L. Unlike previous years of testing, we did receive record breaking amounts of snow. This study has shown that there was a correlation between the chloride levels in the retention pond and road salt. We understand there is a liability issue regarding the safety of staff and students on the Edgewood campus. The goal is to find a balance between safety and ideal distribution of salt. The following are recommendations for reducing the amount of salt used on the Edgewood campus; monitoring the weather, knowing storm conditions, calibrating spreaders prior to winter, and using good spreading techniques (Salt and The Environment).