Sinkholes have plagued the Pennsylvania King of Prussia region for years. The causes are many - karst topography, a deep water table, shallow overburden, and ever-changing drainage networks formed by new construction. Sinkholes appear suddenly and without warning. In a populous area, these represent a serious geological hazard.

A new major interchange on State Road 202 (SR 202) involving many bridges, ramps, roads, retaining walls, communication conduits, and sewers was recently impacted by a series of these sinkholes. Structural Preservation Systems (SPS) was retained by the general contractor to grout the existing sinkholes.

SPS implemented low mobility grouting (LMG) to blanket grout the upper strata of karst limestone bedrock and to stabilize the loose, void-filled overburden. During construction, many new sinkholes developed. The new sinkhole activity drastically increased the scope of work-ultimately impacting the original construction schedule, road openings, and future contract work. To combat the challenges, SPS worked around the clock, incorporated six experienced grouting crews, and built an onsite grout plant to accelerate the work and minimize the impact to the highway's construction schedule. The final completion of SPS's drilling and grouting quantities were in excess of 162,000 lineal feet drilled and 1.35 million cubic feet of grout installed. This grouting project stands as the one of the largest LMG projects in karst terrain ever completed in the world.