Structural Rehabilitation of the Kenilworth PCCP Transmission Main with Steel Slipliner

Baltimore County's 48-inch PCCP Kenilworth Transmission Main, constructed in four phases between the 1970's and 1990's, serves 125,000 customers in the central part of the County. The main provided potable water, without incident, until it failed catastrophically in June 2003, adjacent to a local high school. Following an emergency repair, the same transmission line failed again nine months later, this time causing more severe damage to roads, underground infrastructure, and homes. After this second event, condition assessments and forensic analysis were conducted in late-2004, employing both visual and electromagnetic inspection technologies to evaluate the overall structural integrity of the pipeline, resulting in an emergency contract to replace four PCCP segments. Six years later in late-2010, in keeping with the County's policy to periodically inspect major transmission mains of questionable integrity, another re-inspection was performed, this time employing more advanced technologies as well as structural risk analysis and 3D finite element modeling. This led to the discovery of 33 PCCP sections that needed to be structurally rehabilitated or removed-and-replaced; decision needed to be made on the rehabilitation of the structurally deficient sections only, or the renewal of the entire length of pipeline in question. After considering various repair options -including carbon fiber reinforced composites (CFRP), removal-and-replacement with new PCCP sections, and structural sliplining with steel pipe or high-density polyethylene (HDPE) pipe - the County decided to slipline the PCCP host pipe with spiral welded steel pipe. This paper not only discusses the history of the pipeline and its condition assessment and forensic analysis in detail, but also reviews the innovative decision processes involved with the selection of the appropriate rehabilitation method, material specification and drawing development. Discussion on the construction process of sliplining with steel pipe along with an evaluation of lessons learned is also provided.