Authors: P. Doig, A. Page
Proceedings of the North American Tunneling 2006 Conference; Pgs: 437-443; June 10 - June 15, 2006; Chicago, United States
Abstract
The Lower Northwest Interceptor project in Sacramento involves the installation of 19 miles of twin 60-inch and 66-inch diameter force main. The line extends from the rapidly growing Natomas region in the northwest of the city, to the existing treatment plant in the south. The line features two tunnelled crossings of the Sacramento River, and five open-cut pipeline sections, each in excess of three miles in length. The open-cut sections include numerous crossings of waterways and highways, and these are being constructed by micro-tunneling. The microtunnels are up to 30 feet in depth and are located in river sediments, with a high water table. Hatch Mott MacDonald is part of a team managing the construction of two of the five pipeline sections for the Sacramento Regional County Sanitation District. The two sections were designed by different engineers and were constructed by different contractors.
This paper compares tunnels completed on the two projects and comments upon factors such as ground conditions, design approach, machine performance, ground stabilization, and productivity. The lessons learned are detailed for future consideration.
