Baltimore's Pilot Water Main Inspection Program Becomes Emergency Rehab/Replacement Project

This paper reviews the results of the City of Baltimore's pilot large-diameter pipe inspection program, originally undertaken to develop and implement an inspection, condition assessment and asset management program for raw and finished water mains within the Baltimore Metropolitan Area. The transmission mains of primary concern are those of prestressed concrete cylinder pipe (PCCP), with a particular emphasis on those constructed in the early 1970's. Many of these PCCP transmission mains were fabricated with Class IV prestressing wire and such mains have had a significant history of breaking. An unexpected outcome of the inspections was the identification of a large number of 54- and 36-inch pipe sections in deteriorating condition which posed the threat of incipient main failure if returned to service. These findings required that the joint owner/operators of the system repair or replace the identified pipe reaches on an emergency basis, while at the same time maintaining adequate water supply for the system's customers. The paper describes the two types of internal inspections that were employed for this project, the action plan developed in response to the defective pipes identified, and the design and construction of repairs and replacements of the damaged pipes. It also discusses the careful coordination required between Baltimore City, and Baltimore, Howard, and Anne Arundel Counties in response to the inspection findings.