contracting packages coming from different contractors must be identified and actively managed. Other systems engineering assignments may include configuration management (assuring system function and performance are consistent with design) and change control management. A small, well-lead group of experienced procurement practitioners will prepare and proof contract documents and oversee procurement processes for the several underground contracts to be bid and built.

Site Characterization and Environmental Protection

Engineers with training in many disciplines are necessary to characterize the underground, re-engineer existing infrastructure, and create the environment necessary to support the proposed underground infrastructure. The expertise of civil engineers trained in the design, construction, and maintenance of public works is augmented with expertise of those with graduate training in areas such as geotechnical and geological engineering, rock and soil mechanics, and geophysics.

Geotechnical engineers classify the engineering behavior of earth materials through field and laboratory testing. Geological engineers interpret how the geology and geologic origins of an area might influence planning, mining, construction, and operation of the infrastructure. Understanding the soil and rock mechanical properties at and near a job site is necessary for smart and safe design and construction of proposed underground structures. Rock mechanics engineers describe expected in situ strengths, stresses, strains, elasticity, and other rock mass properties where work will occur. Soil mechanics engineers similarly describe the nature and behavior of the less consolidated materials—soils—in the area. In the early design and development of the project, these various specialists prepare a geotechnical baseline report (GBR),2 take part in specifying and selecting tunnel boring machines (TBMs), and, as designs develop, work with the design and specification drafting team. Geophysical engineers noninvasively measure physical properties of an area using equipment and analytical techniques to infer geology, geologic structure, groundwater conditions, to identify geologic anomalies where they exist, and the presence of manmade artifacts or potentially dangerous gases. This aids production of three-dimensional models of soil and rock characteristics. Gaseous ground mitigation specialists will design measures to mitigate and control each type of gas.

Groundwater Protection and Control

Environmental engineers and planners identify potential impacts to the environment associated with underground infrastructure construction and work with

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2 A GBR is used to define the baseline conditions on which contractors will base their bids and select their means, methods, and equipment (FHWA, 2011a).



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