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Session 26B: Collection, Pump Stations and Conveyance
10:30am - 12:00pm
Session Chair: Andrew Matsumoto, Civil West Engineering Services;
10:30am - 11:15am
Sealing the Collection System with a Focus on Main to Lateral Rehabilitation
Cities who are trying to reduce costs associated with excessive I&I and/or root intrusion are finding that rehabilitating manholes and lining city owned sewer pipe does not always produce the results they desire because the failing laterals remain an unmitigated source of clear water inflow. The focus of this session is on proper techniques and materials to renew lateral services using CIPP technology with special emphasis on restoring the connection of the lateral to the mainline sewer in accordance with the ASTM F2561 and ASTM F3240.
• A permanently sealed connection means service life equals design life.
• Specification is the key to a successful project; ASTM F2561 is the industry best practice standard.
11:15am - 12:00pm
One Liner to Rule Them All
Jeff Schmidt1, Matt Tooley1, Ray Nickel2, Mark Slepski3, Stephen Lindsey1
1Jacobs, United States of America; 2Parametrix; 3King County WTD; , ,
This presentation explores the unique performance parameters of a pressure sewer rehabilitation that experiences up to full vacuum, the current available alternatives and their limitations and what the rehabilitation manufacturers promise to deliver versus what the industry has installed.
King County’s Interbay forcemain was constructed in 1967 and consists of approximately 3,000 linear feet of dual 36-inch steel pipes and dual 48-inch reinforced concrete pipes (RCP) between the Interbay Pump Station and the sewer interceptor discharge, with an overall rated capacity is 133 mgd. Given the criticality of the system, a failure of the pipework would result in significant overflows into the Puget Sound.
The pipeline has only experienced a single failure in the 36-inch steel main in 2013. Inspections of the 48-inch RCP mains indicate that the RCP has a remaining service life of 10-20 years, leading to the need for rehabilitation or replacement. This paper will focus primarily on the alternatives for replacement or rehabilitation of the dual 48-inch RCP segment to extend design life by 50 years.
The system pressures include a steady state condition of 27 feet, shut of head of 90 feet, and a negative surge pressure of -25 feet. The site and construction constraints pose further project challenges including a short summer construction period targeting low flows, tidal groundwater table, site contamination from a historical landfill, adjacent rail road, adjacent armory, works underneath a freeway bridge and the need to keep a single main online at all times.
The alternatives considered include:
Open cut replacement
Nonstructural CIPP Hot Water Cure
Structural CIPP Hot Water Cure
Structural CIPP UV Cure
Spiral Wound Pipe
Alternatives were evaluated on a range of technical performance requirements, focusing on the ability to hydraulically meet the required minimum internal diameter and maximum and minimum pressures. The refined CIPP alternatives were further compared against available resin alternatives (such as “green” resins, vinyl ester, and epoxy) considering their performance capabilities, environmental impacts, historical cure performance and the current manufacturer endorsements versus proven installed track record.