ABSTRACT
Subsurface drainage systems installed along interstate or limited access highways are designed to remove runoff quickly in order to maintain high speed traffic flow. When these subsurface drain pipes leak or fail during storms however, large water volumes are injected into the substrate where they flush out bedrock channels. Most of the sinks that have developed on a section of interstate highway I-78 in western New Jersey have occurred after periods of heavy rain, and have been associated with failures or ruptures at joints in the subsurface drainpipes. As long as these drains overflow and leak, they will continue to produce sinkhole development along the route. Although grouting is an essential part of sinkhole remediation, it is not a panacea, because grouting some areas will only divert underground water flow elsewhere, and new sinks will appear at other locations along the highway. A more radical alternative would be to replace the underground drains with welded pipe to prevent leakage into the substrate, and place grout curtains parallel to the travel lanes in the affected area in order to isolate it completely from the movement of ground water.
