GTA provided geotechnical services for the construction of a six-level precast concrete parking structure in Lancaster, Pennsylvania. The garage required excavations up to 17 feet in depth within an urban environment with existing structures on two sides of the proposed garage. Based on the original design, the proposed foundations could not be economically installed using conventional shoring systems. GTA designed a permanent shoring system that would also function as a permanent pressure relief wall. This allowed the proposed footings to be redesigned and conventional shoring systems to be economically installed. For the permanent pressure relief wall, GTA designed a soldier pile wall with shotcrete lagging and a soil nail wall with shotcrete facing. GTA provided observation and testing during construction, including test nail evaluation.
GTA designed the micropile system to support the proposed garage footings on the underlying limestone bedrock. Two types of micropiles, consisting of 7-inch and 9 5/8-inch diameter, were designed. GTA provided observation and testing for the test pile. GTA also designed an underpinning system to support an adjacent structure. The underpinning design used a pit system that extended to depths of up to 7 feet.