Abstract
The proposed route for a new interstate highway traverses the recharge area of a spring-fed wetland. An investigation was conducted to determine whether the potential loss of recharge would significantly decrease groundwater discharge to the wetland. The local ground-water flow system consists of: a) downward saturated flow through a fine-grained, low-permeability unit, b) downward, unsaturated flow through the upper portion of an underlying coarse-grained, high-permeability unit, c) horizontal saturated flow through the base of the high-permeability unit, and d) discharge to the spring-fed wetland and a nearby creek, both of which are incised into the high-permeability unit. The spring occurs where the water table intersects the land surface. A loss of recharge water may result in a lower water table elevation, which could cause a reduction in overall discharge at the spring. Modeling of ground-water flow suggests that spring discharge may be reduced by 8 to 35 percent after the highway is constructed. The reduction is dependent upon highway alignment and drainage options. The most likely scenarios cause an 8 to 13 percent decrease in discharge.
