The City of Tacoma Public Works Environmental Services Wastewater Management operates two wastewater treatment plants, maintains more than 700 miles of sewer pipeline, and serves more than 90,000 customers. In 2008, Environmental Services staff were challenged with a directive to
increase operational efficiency by improving process automation. However, the existing distributed control system (DCS) is more than 20 years old and in need of replacement. The DCS consists of database servers, operator and engineering workstations, controllers with local input/output (I/O)
subsystems, and remote I/O subsystems with limited connectivity to other systems. In addition to this existing control system, several processes within the facility were either operated via local stand-alone programmable logic controllers (PLCs) of various makes and models or operated manually.
The DCS and PLC control systems had minimal as-built software or hardware documentation. To achieve this directive, City staff formed an Automation Team consisting of key Operations, Maintenance, Engineering, and Management staff, and Brown and Caldwell to develop a Master Automation Plan
(MAP). The primary goals envisioned for the MAP were to provide a roadmap and framework for all future automation projects, build consensus around the future control system, institute control system standards, and provide a tool for long-term capital improvement planning. Completed in the
first quarter of 2009, the MAP established a model for the Automation Team to review newly requested automation projects against the City's defined automation needs, rather than an Automation Team member's personal interests or the project initiator's influence. During the
MAP project, a project evaluation model was developed and applied to a backlog of 41 existing automation project requests from Operations, Maintenance, and Engineering personnel. The Automation Team has been given the authority to evaluate and prioritize new automation projects and make
recommendations for the Capital Improvement Plan (CIP) funding based on criteria established and documented in the MAP. However, full acceptance of the Automation Team as a decision-making body has been difficult for the City and is still evolving to support Management needs and staff desires.
While the concept has been embraced, the difficulties of deferring decisions and relinquishing funding authority have been challenging. The MAP has achieved the goal of bringing together competing groups within the City's Engineering, Operations, and Maintenance staff to discuss the
long-term automation objectives. While all staff are moving forward to optimize the control system's applications, the approach to achieving the long-term goals and objectives provided in the MAP are still being defined in detail by the City of Tacoma.
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