glacial till or to bedrock. To reduce the risk of damaging the piles during anticipated hard driving and for sloping rock conditions, Hard-Bite 77600-B driving points were specified where bedrock surface slopes were anticipated to be flatter than two horizontal to one vertical (2H:1V). Rock Injector driving points were specified where bedrock surface slopes were anticipated to be steeper than 2H:1V. Pile Driveability and Testing Pile driveability was evaluated via wave equation analyses for each substructure to check that driving equipment could efficiently drive the piles to the required nominal bearing resistances without overstressing the piles. Dynamic testing of piles at each substructure was specified to confirm nominal bearing resistances, monitor pile driving stresses and develop production driving criteria. Construction The northbound foundations and superstructure were constructed first, beginning in spring 2017. Doing so allowed the existing southbound bridge to be used to accommodate traffic in both directions. To access the north piers, a temporary trestle spanned the river from staging areas on its south bank. Piers - The pile cap elevations necessary for scour protection at the central and northern piers required approximately 20 ft (6 m) deep excavations that extended below river level and the use of internally braced sheet pile cofferdams toed into glacial till. Pile-driving templates were mounted to the top of the cofferdam to assist with maintaining location and plumbness of the piles. They were installed from a crane adjacent to the cofferdam. Pier foundation pile lengths typically ranged from 20 to 70 ft (6 to 21 m) deep and typically developed required Mid-construction view of the northbound alignment, looking north axial resistance in glacial till or on bedrock. The south abutment piles typically developed required axial capacities at driven lengths between 90 and 110 ft (27 and 34 m) on bedrock. Pile Driving Analyzer (PDA) testing restrike data suggested slight relaxation on average, which was considered in developing driving criteria. PDA testing also indicated typical skin friction contributions of 25%, indicating predominantly end bearing piles. Abutments - Northbound north abutment piles, on the order of 155 to 180 ft (47 to 55 m) in length, were advanced through the dense embankment fill and into the underlying glacial till to develop required axial resistance. The design-build team revisited the AASHTO criteria requiring piles extend 10 ft (3 m) below original ground; that was done in evaluating whether the southbound north abutment foundation could be redesigned with a larger number of lower-capacity piles bearing Bedrock subgrade preparation for central southbound pier spread footing 88 * DEEP FOUNDATIONS * JULY/AUG 2021