North Shore Force Main Emergency Rehabilitation – San Francisco Public Utilities Commission
San Francisco California
Due to repeated failures of an existing 36-inch steel force main, the San Francisco Public Utilities Commission (SFPUC) elected to rehabilitate the sewer force main under an emergency procured design-build contract. The existing steel force main was installed along the historic road, The Embarcadero. The shoreline drives along San Francisco Bay adjacent to the Ferry Building. LAN provided technical support for the contractor, Shimmick Construction Company.
Because of the deteriorating state of the existing 36-inch steel force main, the sliplining 28-inch HDPE pipe was designed to withstand the full internal pressure and external loading which included grouting of the annular space. Due to the obstructions in place during the construction of the original 36-inch force main, there were multiple double offsets throughout the line (ranging from 5 degrees to 14 degrees). In a few locations, the bends were within a few feet of each other presenting complications in the necessary sliplining process, utilizing 2,550-ft of HDPE pipe as a replacement for the original pipeline.
LAN provided recommendations for annular space-grouting, thrust restraints, and using controlled low strength material (CLSM) as backfill during construction.
At a glance
$4.1 million Design-Build contract
2,600 LF of 36-inch pipe rehabilitation
120 calendar day emergency contract
40,000 vehicles per day traffic count
Remove the bullets for Work Hours and Constant Pedestrian Traffic
Design Constraints: Pressure class of pipe & fittings; Multiple/sequential bends; Presence of prior repairs; Limited accessible points; Temporary reconnections
Evaluation of grouting options: Cement + bentonite; Injected from low point @ max 30 psi
Determination of allowable pull stresses
Flexibility in design
Method of thrust restraint
San Francisco Public Utilities Commission (SFPUC)