The geologic setting of the Maricopa Site is very favorable for rapid and cost-effective construction of the SSC facility. To correlate geology with tunneling construction methods, the collider ring was divided into ten Construction Units (Table 3-1). A Construction Unit may include several different rock types with varying support requirements but uses a single tunneling construction method. In some units tunnel excavation and lining will be accomplished exclusively by tunnel-boring machine (TBM) systems (see Section 3.5.4.2). In other units either proven cut-and-fill methods or TBM may be used depending upon the depth of the ring below ground surface (see Section 3.5.4.1). The ideal geologic conditions not only allow construction of the coIlider ring in a near surface plane tilted 0.30 from the horizontal, but also provide considerable flexibility for relocation of the proposed ring alignment or for location of future additions to the facility if desired by DOE. The injector complex, experimental chambers, and future facility additions can be built with cut-and-fill methods. Construction problems are not anticipated from geotechnical factors such as collapse-susceptible soils, seismic events (natural or man made), ground water, regional subsidence, expansive clays, or naturally-occurring gases