Incorporating Condition Assessment of “Aerial Crossings” Into Your Asset Management Program

Authors:

  • Aditya Ramamurthy PMP, ENV SP - Hazen and Sawyer
  • Nelson Navarro PE - City of Virginia Beach Department of Public Utilities

Like most water and sanitary sewer utilities around the nation, rehabilitation and/or replacement of aging sanitary sewer and water infrastructure is a top priority for the City of Virginia Beach Department of Public Utilities (DPU). The City is currently mandated to be in compliance with the regional Consent Order and is also in the process of developing a mandatory, multi-year, rehabilitation implementation plan. As a result, limited capital improvement program (CIP) funds are available for other programs. With an industry “new-normal” of having to do more with less, prioritization and effective program/project management of all capital programs (including the aerial crossing CIP) is critical and necessary.

DPU owns and operates approximately 1,620 miles of gravity sewer lines, 190 miles of sewer force main, 407 sewer pump stations, 1,580 water distribution and transmission mains, 11 water tanks, and 8 water pump stations. Included in this asset inventory are approximately 50 water and sanitary sewer aerial crossings. Aerial crossings are defined as water and sanitary sewer pipelines that cross over water bodies either attached to bridges or mounted on stand-alone piles. The area served by DPU contains many water bodies including lakes, rivers, inlets, and bays which ultimately discharge to the Atlantic Ocean. The challenges and risks associated with the installation of distribution and collection systems across these natural barriers are commonly mitigated by the suspension of piping from bridges or the support of piping by pile structures.

Given the increased possibility and risk (ex. discharge of sewage to a water body) of a potential aerial crossing failure due to exposure to natural elements and forces, DPU has established an annual CIP project dedicated to the renewal and replacement of aerial crossings.

This presentation will explore the methodologies used by DPU to conduct a risk-based criticality and physical condition assessment for DPU’s 53 water and sanitary sewer aerial crossings. To properly incorporate DPU’s aerial crossings into the asset management program, the condition assessment of these aerial crossings included inspection of piles, bents, hangers, spindles, and tie-downs, in addition to the typical structural features of the pipe. In addition to these specific asset components, other physical features need be included in the assessment; namely adequacy of accessibility for inspection and maintenance, security, erosion of stream banks, accumulation of debris and potential for damage as a result of storms.

This presentation will also review the unique inspection procedures utilized by DPU staff to conduct condition assessments of their aerial crossing assets, provide examples of identified defects, and discuss the process used to rank and prioritize each aerial crossing for rehabilitation and/or replacement.

For more information, please contact the author at aramamurthy@hazenandsawyer.com.

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