On March 7, McMullan’s project for the rehabilitation of C&O Canal Locks 3 & 4 was recognized by Structural Engineers Association - Metropolitan Washington’s (SEA-MW) for Outstanding Specialized (Non-building) Structure as part of their annual Excellence in Structural Engineering Awards gala. Judging criteria included: creativity of structural design; technical innovations and their influence on design; ingenuity of design for efficient use of material and labor; how the design solved unusual problems; and quality of execution.

Under contract with National Park Service, McMullan was the SEOR for the rehabilitation of these two stone masonry locks constructed in 1832 and located between 30th and 31st Streets NW Washington DC. Lock No. 3 required complete reconstruction to address tilting walls due to deterioration of its timber foundation. The timber lock gates were removed; the 15-foot-high ashlar laid stone masonry walls were disassembled, marked, and temporarily stored; and the timber lock foundation was removed. After a concrete mat foundation was installed, the lock walls were reconstructed with the face stones in their original position. Lock No. 4 required repairs to address water leakage through the masonry and deteriorated timber gates. Repairs included partial replacement of deteriorated stones, repointing, and replacement of the wood lock gates and associated hardware.

A key challenge was the requirement to restore both locks reusing as much historic material as possible including deteriorated faced stones and unknown quantities of backing stone. During initial investigations, many of the face stones were found to have cracked or delaminated. Working with the National Park Service, methods for repairing face stones were developed as well as specifications for the disassembly, cleaning, and temporary storage of stones to minimize further damage. In order to quantify the repairs for bidding, photos of existing lock walls were projected onto an elevation plane with individual face stones requiring repair identified. As each stone was removed and closely inspected, a decision was made if the stone should be replaced or repaired. Measurements taken during disassembly were found to be similar to those anticipated by McMullan, minimizing the need for new backing stone.

McMullan’s project management and engineering team comprised Principals Douglas E. Bond, PE, SE and Denis McMullan, PE with Project Structural Engineer Megan Beery, PE and Structural Engineer Rebecca Biskaduros, PE. Other teaming partners included Peck, Peck & Associates; JMT; GeoCapitol Engineering, LLC, A Terracon Company; and Clark Construction.

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