NORTH SIDE SEWER RELIEF TUNNEL, HOUSTON, TEXAS

When corrosion measures protecting the North Side Sewer Relief Tunnel’s liner failed causing massive wastewater overflows into a bayou, OTHON was retained by the City of Houston to evaluate the problem and provide recommendations for rehabilitating approximately 5,000 lf of this 84-inch sanitary sewer line. OTHON first provided physical inspection and evaluation of the tunnel which runs through an area featuring residential developments, schools, and heavily traveled thoroughfares. Two major challenges that the evaluation team faced were the inaccessibility of the existing line, which was 50 to 60 feet deep, and the requirement to keep the highly used line in service. This required all fieldwork to be conducted between midnight and 5 am to take advantage of minimum flows in pipe.

OTHON then developed an alternative analysis to determine the most cost-effective techniques for rehabilitating the tunnel. The alternative evaluation focused on the impacts of various construction requirements, such as cost, bypass pumping, structural integrity, host pipe condition (wet/dry), effects of changed field conditions, corrosion resistance, construction sequencing, and flow diversion. OTHON also developed a Site Safety and Health Plan for the project and prepared plans, specifications, and estimate for rehabilitation.

Completion Date: 2001
Construction Cost: $6,000,000
Owner: City of Houston