City of Columbus Big Walnut Sanitary Trunk Sewer Extension 6F1, Part 1

H.R. Gray provided critical path method (CPM) scheduling and construction management services on the Big Walnut Sanitary Trunk Sewer Extension project. This project consisted of the installation of 9,900 lineal feet of 72-inch sanitary sewer using Reinforced Concrete Pipe (RCP) with PVC T-Lock liner for the tunnel lining. This project also included the installation of five access shaft/manhole structures and the installation of tangential inlet drop structure and associated deaeration chamber and appurtenances as well as the installation of 15 lineal feet of 16-inch and 18-inch ductile iron pipe (DIP), 20 lineal feet of 36-inch sanitary PVC sewer pipe and two Type "C" manholes. Also, a 105-inch diameter, 9,300 linear foot tunnel was constructed through Ohio shale and 600 linear feet was constructed through soft ground/mixed face conditions.

H.R. Gray encountered two major challenges on this project. The first was mining through 600 feet of soft ground/mixed face conditions containing several nests of boulders and cobbles underneath and within the groundwater table. The second challenge was mining through a 200 foot soft ground buried valley with a hard rock tunnel boring machine by implementing a consolidation grouting operation. Both challenges resulted in potential claims situations for additional time and compensation. However, because of H.R. Gray's on-site management, extensive documentation, rescheduling and negotiations with the contractor, the project remained on time and budget. Several other challenges were overcome by H.R. Gray maintaining open communications with the contractor and the city's management team and addressing every issue immediately and in good faith.

The project was completed in May 2009 within budget.

 

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