What type of system is an underdrain typically connected to?

An underdrain is typically connected to a nearby waterway or storm water drainage system because its primary function is to manage excess water. Underdrains are installed beneath roads and bridges to collect groundwater and prevent water buildup, which can lead to structural issues or deterioration. By directing this water toward an external drainage system, such as a storm drain or nearby waterway, underdrains effectively help maintain the integrity of the bridge and surrounding infrastructure. This connection is essential in ensuring proper drainage away from the bridge, reducing the risk of flooding, erosion, or damage caused by water accumulation.

In contrast, the other options do not align with the specific purpose of an underdrain. The main water supply line and the electrical system of the bridge are unrelated to water drainage management, while a backup drainage reservoir is not a typical connection for an underdrain, as its role is more about managing and distributing unwanted water rather than storing it.