Alabama Department of Transportation (ALDOT) changed the delivery method to a P3 delivery. The project is currently under procurement with three shortlisted teams working with ALDOT and its owner representatives. Proposals are expected to be due at the end of 2019. The project is located along the U.S. Interstate I-10 corridor, which connects California to Florida, covering about 2,420 mi (3,895 km) of roadway. As I-10 traverses through Mobile, Ala., it passes beneath the Mobile River in a dual tunnel system constructed in the 1970s, with two lanes in each direction. The tunnel was designed for average daily traffic (ADT) of 35,000; however, the ADT is in excess of 75,000 and is more than 115,000 on peak holidays, creating a pinch point along the corridor. The purpose of the project is to increase capacity on I-10 and minimize impact to the maritime industry. To alleviate the congestion and increase capacity, the project will include the design, construction, operation and maintenance (O&M) of a new six lane cable-stayed bridge crossing the Mobile River. The bridge will require a minimum of 215 ft (65.5 m) of clearance above the river channel and will span approximately 2,550 ft (777 m) in length. The project will also require the design, construction and O&M of a new, 7 mi (11.3 km) long Bayway structure to replace the existing Bayway. The structure will be required to have eight lanes (an increase over the existing four lanes) and will connect Baldwin County to the new cable- stayed bridge. The project also includes seven interchanges along the proposed alignment. The majority of the project spans water with bridge structures, therefore, bridge foundations represent a major component of the overall cost to the project. Load testing of substructures has been and is recognized as a key step in the overall design and construction process of bridges. Load tests allow engineers to verify design parameters and assumptions, and to optimize their design. Agencies/owners require load testing on projects to reduce risk, as it relates to subsurface conditions, safety and increased efficiency in the design. Typical practice is for load testing to be performed during the construction phase, limiting the ability for designers to fully understand the performance of substructures during the design phase. As alternative delivery projects increase in size and complexity, the need for more detailed and greater quantities of subsurface information (including load tests) during the procurement phase increases. A robust foundation testing program is essential to provide information for preliminary design, planning and bidding for large projects, reducing risks for both owners and concessionaires/contractors. Pre-bid Load Testing Foundation design, which contains significant risks relative to both engi- neering performance and construction, is typically a critical path item early in the schedule. Performing a load test program prior to letting of an alternative delivery project has many benefits and advantages to the overall execution of the project from procurement to completion. Contractors assign a monetary value to each risk item, so reducing foundation related risks through pre-bid testing can significantly reduce the contingency costs included in a proposal to cover those risks. Project risks for foundations are significant in a project of the magnitude of the MRB including the following: • High foundation loads from vessel impact, storm events, wind and wave loads • Performance issues, including axial side and base resistance values/lateral soil resistance in different soil strata • Drivability, needs for pile driving aids (i.e., jetting, predrilling, etc.), hammer size, required bearing without pile damage To reduce or minimize some of the risks mentioned above, Dan Brown and Associates and Thompson Engineering (part of ALDOT’s representative team) recommended a pre-bid load test program that would address key concerns from a foundation design and construction standpoint. The program included axial loading tests, lateral loading tests and variation of installation techniques for several different foundation types and sizes. The information obtained through the load testing was provided to all concessionaire teams. Subsurface Information Baseline subsurface information was provided to the three concessionaire teams. The exploration program included 24 cone penetration test (CPT) soundings, 186 borings including standard penetration test (SPT) and undisturbed sampling techniques, which totaled over 24,000 ft (7,315 m) of soil drilling. Borings near the main pylons were drilled to a depth of up to 320 ft (97.5 m) below the existing ground surface or mud line. Lab testing of soil samples included classification, shear strength and consolidation information. The subsurface information given to the proposing teams provides valuable information to be considered when preparing their bids. The winning team will supplement the pre-bid data with its own field exploration. Providing load test information to the teams during pro- curement allows the teams to “calibrate” or refine their evaluations of the subsurface data and increase the level of confidence in their design parameters. Load Testing Program Following a review of the benefits, estimated cost and interest from the teams, ALDOT approved a pre-bid load test program in August 2017. Plans were assembled; the project was advertised and then awarded in December 2017. The concessionaire teams were allowed to bid on the load test program to help ensure there was adequate interest of qualified foundation contractors to assist in making the bids competitive. The award bid was approximately $3.4 million to Jordan Pile Driving, who is a member of one of the concessionaire teams. The Notice to Proceed was provided to the contractor in January 2018 with an expected completion date of May-June 2018. Liquidated damages were included in the contract for scheduling purposes, as ALDOT wanted to make sure the results of the load test program could be used in a timely manner for the conces- sionaire’s design and cost estimating. The load test program consisted of numerous deep foundation systems, including driven piles of differing types/sizes and a drilled shaft. Axial load testing on the driven piles was performed using static, high strain dynamic and rapid load testing. Bi-directional load cells were DEEP FOUNDATIONS • JULY/AUG 2019 • 15
