17 - Discuss failure and repair of newly placed water main at 100 block of South Main Street

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bore methods. These two pipe sections were connected at the bore pit located just south of Clarksville using Certa-Lok PVC pipe in the trench. This pipe joint is where the leak occurred. Certa-Lok pipe is designed with an interlocking mechanism that seals the pipe joints and locks them together such that two sections of pipe cannot be pulled apart when pulling through the ground during a bore installation. Two sections of pipe are interlocked at an integral bell restrained joint that has a gasket and a secondary channel inside the joint where a plastic rod (nylon spline) is inserted during the bore. This rod restrains the two pipes together. Certa-Lok is ideal for usage in congested environments and boring operations. Because these two sections of pipe where installed by bore from different ends, the joint at their connection was installed in an open trench by the utility crew. The pipes were connected and scaled properly, but the plastic rod used to fuse them together to create the restraint, was apparently not installed. This missing rod was unknown until time of the repair. In 2018, the water main passed all required inspections under the contract, and has been water tight for about two years. However, because all buried pressure pipes vibrate and have potential for movement over time, it appears that the absence of the rod in the Certa-Lok pipe allowed enough movement at this joint to result in a leak. The contractor is responsible for repairing defective work under the contract. They repaired the pipe at no cost to the city. The final street repair is scheduled for next week. Please note, this contract is $24 Million and includes utility replacements across town. The city has contracted with a professional engineering firm AECOM for the design and limited support during construction phase, as well as a third parry inspection firm EST Inc. to oversee daily operations and construction activities. Staff is involved with approval of field or design changes that affect the overall contract scope or budget, and we work closely with AECOM and EST for project management. After reviewing the testing reports, we agree that this water main passed all required inspections in 2018, and the leak was caused by defective work of the construction crew. Note that for this project, there has been about 46,000 LF of water line pipe installed, and over 2500 joints. There have been only two issues with defective joints in over 4 years of work, which is less than 0.1% of the total project. Below is a list of required inspections under the contract, and a corresponding report is attached for each. 1. Specification 33 04 40 — 3.0l.D.l.d Hydrostatic Test (pressure test) 2. Specification 33 04 40 — 3.01.E Disinfection (chlorine residual in water sample)