Ameren Transmission Company's Illinois Rivers Transmission Line River Crossings Foundation Design

摘要

Three (3) major river crossings [one (1) across the Mississippi River and two (2) across the Illinois River] with tower spans potentially as great as 3,700 feet are part of Ameren Transmission Company of Illinois ("Ameren") Illinois Rivers Transmission Line Project. Hanson Professional Services Inc. ("Hanson") is working closely with Ameren to provide geotechnical, civil, structural, and hydrologic and hydraulic engineering services to design steel tripod foundations for the 14 lattice towers, potentially as tall as 470 feet, that are part of these crossings, as well as the necessary access roads and barge landings. Soil test borings advanced to rock depths up to 120 feet at each tower location; soil laboratory testing; land and bathymetric surveying; and engineering analysis of design load cases, geotechnical parameters, and hydraulic aspects of the river crossings, were utilized to develop foundation design parameters and performance criteria (strength and displacement) for the evaluated conditions, including flood levels, scour, debris forces, hydraulic forces, and ice forces. This paper summarizes how accessibility and permit-related challenges can be overcome on major transmission line projects such as this project. Many of the towers are on the river side of flood protection levees and in wetland areas. Some are on islands within the rivers. Part of the strategy to overcome such challenges was to design 100% steel foundations to preclude the need for concrete and minimize ground disturbance areas and required earth excavation. Additionally, barges will be utilized to transport all necessary components, machinery, and workforce to many of the tower locations. In the interest of brevity, this paper focuses on the Mississippi River crossing.