The Alameda Siphon No. 4 Project involved the construction of a new 66-inch diameter pipeline that extends across Sunol Valley from the existing Coast Range Tunnel to the Irvington Tunnel. The new pipe includes a connection to the existing pipeline exiting the east portal upstream of the existing connections for Alameda Siphon No. 2 and No. 3; new chemical feed points, crossings of the Calaveras Fault and the Alameda Creek, and cross-connections to the existing three siphons, and the Irvington Tunnel at the west portal. The entire pipeline alignment is located in a seismic hazard zone.
AGS, as a Joint Venture Partner, was responsible for the design of a seismically resistant welded steel pipe, approximately 3,000 feet long and 66-inches in diameter that extends across Sunol Valley from the existing Coast Range Tunnel connecting to either the existing or new Irvington Tunnels.
Significant elements of AGS’ scope included:
Pipeline
• Assistance to City staff in site improvements
• Design of pipeline and micro tunnel extending below Alameda Creek.
• Design of pipeline and micro tunnel extending below Alameda Creek.
• Design of (5) large underground valve vaults to resist large thrust loads, soil pressure, and dynamic soil loads.
• Design of a pipeline fault crossing.
Facilities
• Evaluation and seismic retrofit of (2) existing valve houses and underground valve vaults.
• Design of (4) new 20-foot high tower structures and horizontal frames to support vertical and horizontal ventilation ducts.
• Design of foundation structures to support miscellaneous mechanical buildings.
• Design of elevated steel platforms for the valve vaults.
• Design of equipment support structures.
Roadway and Retaining Walls
• Realignment of an approximately 1,000-foot section of Calaveras Road.
• Redesign of existing Alameda East Portal Road intersection.
• Geometric design of new intersection into Calaveras Road and miscellaneous access roads.
• Street improvements and storm drainage facilities, including hydrology and hydraulic calculations.
• Design of retaining walls employing soil nail, soldier pile, and lagging, interlocking blocks, etc.
Geotechnical, Fault Crossing/Creek Crossing
• Investigation to explore and evaluate the subsurface conditions for pipeline design and construction.
• Assessments of fault rupture hazard, liquefaction potential, and landslide conditions.
• Analysis of aquifer characteristics.
• Particular emphasis was made to assist in the development of design parameters for the Calaveras Fault crossing and the Alameda Creek crossing.
AEP Security Structure– Antiterrorism
• Design of an arch and a dome steel structure to protect the portal from blast loads in a postulated explosive attack.
• Design of an elevated steel platform over the arch-and dome structure.
• Design of a foundation consisting of concrete wall/grade beam on concrete piles to support the arch- and- dome upper structure.
• Design of a concrete headwall to resist the blast loads over the portal.
Tunnel Design
The AS4 Project involved the construction of a new water transmission pipeline that extends across Sunol Valley from the existing Coast Range Tunnel (CRT) to a new Irvington Tunnel. The 96-inch diameter tunnel advanced underneath Alameda Creek, and cross-connections to the existing three siphons and the proposed new Irvington Tunnel. The Tunnel was excavated using a Tunneling Boring Machine(TBM) with pressure head capability.
