Prior to placement of the dredge fill, the site consisted of ~50 to 60 ft of water underlain by a 10-ft mud line that transitioned to sand deposits at depth. Fill placement was completed using hydraulic and mechanical processes. The fill was variable, but generally, it could be described as silty sand with pockets of soft fine-grained material and other manmade fill.
For large areal fill placement, a wick-drain and surcharge program often provide the most economical solution. Typically less costly than traditional deep foundations or other ground improvement techniques, the wick drains, with surcharge, allow the fill material to undergo rapid consolidation within a relatively short duration. The various methods of fill placement – along with the placement of the heterogeneous material -- proved to be challenging. Consequently, pre-augering across different portions of the work area, as well as the development of special wick installation equipment to overcome dense layers at depth, was required. Despite the challenges, Menard installed 7 million LF of wick drains ranging in depth from 30 to 100 ft in multiple phases.
As part of the POLB's efforts to rebuild America's Greenest Port, Menard completed wick-drain installation within the scheduled time frame and within the project’s budget.
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.