McMahon Associates, Inc. was engaged by Carusone Construction, Inc. to provide survey services at the Southwest Water Pollution Plant located in Philadelphia, PA as part of the construction of the Dissolved Air Flotation System Improvements project.  This project included temporary excavation support and protection required to build the PWD Dilution Water Tank and 30” diameter Underflow Bypass.  McMahon Associates was first tasked with the horizontal layout of the limit of disturbance for the exaction and prior to excavation, installing a monitoring system for the purpose of monitoring the adjacent building for movement during sheeting, excavation, and tank construction.  As the excavation got underway, the survey crews also began layout of the solider beams that were to be used in the temporary excavation support. McMahon Associates was also tasked with establishing vertical control based upon finished floor elevations, existing plans, and utility depths.

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During the excavation it was necessary to monitor the adjacent building’s walls for movement due to the proximity of the excavation.  Multiple reflective targets were placed on the building columns which were sighted from project control points.  Each of the targets were located from multiple control points over the course of the excavation to ensure there was no movement.  An analysis of the position of the target was performed after each day’s observation to ensure the existing building showed no signs of disturbance.