No Dig Pipe Rehabilitation Saves Cost and Keeps Airport in Operation

No Dig Pipe Rehabilitation Saves Cost and Keeps Airport in Operation


Xiangquan Li, Kennedy/Jenks Consultants, Santa Clara, CA
Tom Kapushinski, City of Palo Alto, Palo Alto, CA

Abstract: The City of Palo Alto owns and operates a 54-inch diameter concrete outfall that conveys tertiary wastewater effluent from the City’s Regional Water Quality Control Plant (Plant) to a shallow-water discharge in San Francisco Bay. The pipeline was constructed in the 1960s in Bay Mud, a very soft, saturated clay material typically encountered in the San Francisco Bay area. The depth of cover above the outfall in some locations is less than two feet and this pipeline has settled in the Bay Mud over the years creating leakage at multiple pipe joints. Further settlement is expected if future construction activities near the pipeline place additional fill above the outfall. Since the pipeline alignment crosses the City of Palo Alto Airport, one of the busiest general aviation airports in California, open excavation to repair the outfall would negatively impact Airport operation. Additionally, the existing pipeline alignment was not documented in the field and was only generally known. To select an appropriate pipeline rehabilitation alternative, the Plant engineering team successfully implemented an innovative pipeline location and inspection method, while maintaining the pipeline in service. Using pipe condition assessment data, the existing pipe alignment, and sensitive biological habitat survey results, the Plant engineering team evaluated multiple trenchless pipe rehabilitation alternatives, including cured-in-place pipe (CIPP), spray-on lining technologies, swagelining, sliplining and internal joint seals. The evaluation was used to identify an approach that provided the least impact to the Airport and environment, while identifying a cost-effective rehabilitation solution for the existing outfall.

Publication Date: 2018

Presented at:
NASTT’s 2018 No-Dig Show Palm Springs, California
March 25-29, 2018 | Paper Number: MM-T1-05

Non-Member Price: $10.00

Discounted Member Price: $0.00

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