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TypeWastewater
nameCahaba WRF Electrical System Sustainability/Redundancy Improvements – A Case Study
Speaker 1Bernard Pettiford
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Mr. Pettiford has been in the Environmental Engineering field in one way shape of form since 1997. He is an electrical engineer with experience developing detailed electrical designs for new/existing water and wastewater treatment facilities, performing power system analysis, developing electrical safety programs, performing electrical safety training and performing electrical oversight during construction. Mr. Pettiford has experience with startup commissioning, NFPA, and OSHA requirements. He is client focused and results driven.

Abstract Text

CDM Smith performed an Arc Flash Study Report at the Cahaba Water Reclamation Facility (WRF) in Jefferson County, AL. The study noted four key concerns, which were out-of-scope for the arc flash study but required attention. Those concerns included:

  • National Electrical Code (NEC) working clearance violations; mechanical and structure restricting access to equipment.
  • Age and condition of electrical equipment, including obsolete equipment dating back to 1970.
  • Lack of EPA Class I Reliability for electrical distribution equipment supplying power to wastewater treatment process through a radial, 2.4kV, electrical distribution system.
  • Concerns of system reliability and safety due to using an ungrounded delta distribution voltage of 2.4kV.

As a result of the information learned in the Arc Flash Study, CDM Smith was contracted to develop an Electrical Master Plan and electrical design to address the concerns. The new design replaces the existing 2.4kV radial system to 12.470kV dual radial, secondary main-tie-main configuration. This presentation will cover the following:

  • Configuration and condition of the existing electrical distribution system; 2.4kV simple radial distribution system.
  • Criteria used during the evaluation process; consensus regulatory criteria, reliability/redundancy criteria, and maintainability.
  • Challenges faced during the design phase; new infrastructure requirements, electrical equipment space constraints in existing locations and maintaining plant operations during construction.