Municipal Highway Garage

Project Details:

Owner: Wawarsing Highway Department
General Contractor: Darlind Construction 
Date of Work: July 2023 
Engineer: Delaware Engineering D. P.C. 
Approximate Key Quantities: Rapid Impact Compaction - 312 EA.


Project Overview:

The Town of Wawarsing, NY, solicited the services of Delaware Engineering to provide design and engineering for a new eight-bay garage to be used to for the Town’s vehicles. Estimated cost of the structure was $7 million. The new garage would replace an existing three-bay masonry structure, designated for demolition as part of the project. An existing six-bay highway garage would be rehabilitated and remain at the site. The new highway garage would include spaces for personnel, eight bays of vehicle storage and repairs/maintenance, and administrative offices. The design of the 1-story garage includes a footprint of 17,000 sq-ft , utilizing pre-engineered steel for the superstructure, and reinforced concrete foundations. Design considerations such as eave height, man and overhead door width and height, drive-through capability, and equipment to facilitate vehicle maintenance (e.g., air stations) and repairs as well as safety (e.g., slop sink, eyewash station, etc.) were incorporated into the design. Due to the presence of loose ground fill soils at the site, Menard USA was contracted to perform Rapid Impact Compaction (RIC) beneath the proposed building.

Ground Conditions:

The soils consisted of upper 10-12 ft of loose granular fill. Beneath the fill is a medium dense to dense sand and gravel layer to roughly 87 ft below working surface, underlain by shale bedrock. Based on the subsurface exploration boring, the only soil requiring improvement was the upper fill layer with low blow counts. It was
determined that RIC was optimal for improving the upper 12ft of soil.


The implementation of RIC offered an economical solution when compared to a mass excavation and subgrade replacement. After implementation of RIC, shallow footing foundation and slab-on-grade systems could be utilized. Menard was contracted to perform 312 RIC prints -- performed by using a 9-ton hammer on a 5 ft
diameter bell. Each print would achieve 50 drops per point to meet Menard’s design parameters while improving the upper 12 ft of fill. As a factor of safety against perimeter settlement, RIC was performed across a 21,000 sq. ft area. This provided five additional ft of RIC around all sides of the structure. RIC targeted an allowable bearing capacity of 4 ksf and up to 1-in total settlement, with ¾-inch differential settlement. A total of 15,600 drops was performed.

While performing RIC, two-dimensional crack monitors were placed on nearby buildings, which were monitored throughout. Vibration monitoring was also performed in conjunction with RIC. Vibration levels did not exceed the threshold of 1 in/sec at any time during RIC. Five post RIC borings were performed by a subcontractor to confirm soil improvement. All RIC points were successfully completed in one pass, with the exception of one print that was backfilled twice to achieve the 50 drops. Menard successfully completed RIC for the Municipal Highway Garage in July 2023.

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