SPSA Steam Plant - Portsmouth, VA

Thursday, November 13th, 2014 by John Siwicki

Challenge

January 2009 -The Southeastern Public Service Authority (SPSA) Steam Plant is located along the Elizabeth River and adjacent to the Norfolk Naval Shipyard. The plant burns trash to generate steam and power for local authorities. The administration building at the Steam Plant had visible signs and symptoms of foundation settlement, such as gaping cracks in the concrete block walls, separation between the block walls and ceiling, racked door frames, and cracked floor slabs. Settlement ranged from 1 inch to 3 inches. Differential movement within the block walls threatened to bind or break utility lines and piping that extended through wall penetrations. Signs of settlement were reportedly first noticed in the late 1990’s, but had become increasingly worse in the last year. A geotechnical report with soil boring information had been completed for the project. One of the probable causes of settlement was identified as dewatering activities at the neighboring shipyard.

Solution

Twenty-nine (29) hydraulically-driven push piers were used to stabilize and lift the settled area of the building. The piers were installed on the inside of the building, so excavation was done by hand and excess material hauled outside in wheel barrows. While preparing the footings for bracket installation, the crew encountered sections of wooden piles, abandoned sewer and electrical lines, and an old concrete foundation, all from an old building that sat on this site prior to the construction of the SPSA Steam Plant facility. The geotechnical investigation identified suitable bearing soils at a depth of about 60 feet. However, the subsurface conditions varied significantly, and pier depths ranged throughout the building from about 50 feet to over 100 feet. The settled area of the administration building was stabilized and then lifted 1 ½ inches back toward its original elevation.

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