Opinion ID: 804324
Heading Depth: 3
Heading Rank: 1

Heading: The Big Dig's Need for Concrete

Text: Boston's Central Artery/Tunnel project (the Big Dig), lasting from 1991 to 2007, was one of the largest public works projects in United States history at the time of its completion. The project entailed replacement of a major elevated highway that passed through central Boston with an underground expressway, as well as the extension of I-90 to Logan Airport. The Massachusetts Highway Department, and later the Massachusetts Turnpike Authority -4- (MTA), both agencies of the Commonwealth of Massachusetts (the Commonwealth), had primary responsibility for the project. The final cost of the project, approximately $14 billion, was funded jointly by the Commonwealth and the federal government. Numerous private contractors were hired to help with the construction, and many management responsibilities were delegated to a joint venture between Bechtel Infrastructure and Parsons, Brinkerhoff, Quade & Douglas, Inc. (B/PB). These two companies worked as design consultants, performed engineering reviews, and managed much of the construction. Because of the scale and cost of the project, responsibility for construction of various sections was apportioned among different general contractors, and B/PB worked with each in a coordinating role. The general contractors in turn contracted with various sub-contractors. In total, there were approximately 150 individual construction contracts awarded to private companies in connection with the Big Dig. Each of the subcontractors was bound by the contract specifications and schedules that were set out in general contracts with the Commonwealth. The Big Dig required approximately 4.2 million cubic yards of concrete, 60 percent of which was provided by Aggregate. For suppliers of concrete, the construction contracts required that: 1) there be a certain mix design, or recipe, for the concrete, based on the intended use; 2) the supplier have plants with an automatic batching system that ensured the proper mixture -5- of each load, or batch, of concrete; 3) the sub-contractor have in place recorders that captured information regarding the mix design, as well as the date and time of batching for each load of concrete, and provided a printout, called a batch ticket, containing all of the required information; 4) no additional water be added after the concrete mixture was loaded into trucks for delivery; and 5) in most circumstances, the concrete be in place at the construction site within ninety minutes of the time it was mixed and loaded onto trucks. The batch tickets were especially important because they served as a quality control mechanism. Aggregate's drivers would give the batch tickets to B/PB inspectors as they delivered their loads, and the tickets were left in a holding area close to the placement so that inspectors or field engineers could check on the characteristics of the concrete being placed. In particular, inspectors needed to know the time that the concrete was loaded, the mix design, the volume loaded, and the amount placed.