What activity involving roads can lead to water supply contamination?

The activity that can lead to water supply contamination is road salting. This practice is commonly used to de-ice roads during winter months to enhance safety and mobility. However, the salt (often sodium chloride) used during road salting can run off into nearby water bodies during precipitation events, particularly when snow or ice melts. This runoff can increase the salinity levels in surface waters, potentially leading to harmful effects on aquatic life and posing risks to drinking water supplies.

In contrast, while road construction, paving, and repair activities can also pose risks to water quality—such as sediment runoff or the introduction of pollutants from construction materials—they do not have the direct and immediate impact on water supply contamination that road salting does. Road salting's ability to significantly alter the chemical composition of water bodies, especially in terms of salinity, makes it a critical factor in assessing contamination risks to water supplies.