Subway is by far the most expensive form of mass transportation system development. The Los Angeles subway extension tunnel construction and track placement is projected to cost $540,000,000 per mile. In addition to tunneling excavation and track installation, significant resources are required for construction of stations as much as 100 feet below grade and requiring elaborate access facilities between the street and underground platform elevations, while maintaining high levels of reliability for the environmental and life safety systems necessary for safe and convenient use of the subway.
Impacts of construction activity frequently affect structures and property outside of or beyond the tunnel or station construction areas. Destabilizing, undermining, and disruption of surrounding and adjacent structures, properties and public works infrastructure require significant corrective measures, at equally significant costs. Disruption of business, street traffic and access in the vicinity of subway construction has consistently occurred throughout the duration of subway construction, and should be anticipated and planned for in all future projects.
The extensive excavation and construction activities associated with subway development affect virtually all properties adjacent to station excavations, tunnel drilling and earth removal access points, as well as, the excavation and construction required for relocation of utilities, storm drains and other underground facilities. Most adjacent properties, and the businesses located on them, will be rendered partially or completely inaccessible during construction in the immediate vicinity, while blocks and districts may experience extended periods of congestion or limited access during construction of tunnel, station and access facilities.
Impacts of typical monorail foundation excavation are generally limited to guide way column foundations, which are commonly pad or spread footings poured just below ground or pavement surface elevations. Where geologic, soil or other conditions require different, or more elaborate foundation designs, monorail guideway and station foundations are broadly adaptable to existing ground, infrastructure, utility and development conditions. Requiring one tenth or less of the mass and weight of elevated roadways, light rail or heavy rail facilities, monorail guide way structures are inherently more compatible with a majority of construction conditions and locations; while the distinct advantages of off site modular construction and assembly enable monorail builders to minimize disruption of existing development, business and traffic in construction areas.