On April 3, Soundkeeper sent a letter to the King County Council in support of the independent investigation of the West Point Sewage Treatment Plant failure. In that letter, we pose detailed questions that we would like to see addressed in the investigation, including:
Comparison of an event at West Point in 2009 to the 2017 failure. In June of 2009, ten million gallons of untreated effluent were discharged into Puget Sound when the switch that controlled the emergency bypass gate malfunctioned. The 2009 event identified the failing float switches and bypass gate issues as vulnerabilities in the design and operation of the West Point facility.
System designs and potential failures. The Wastewater Treatment Divison uses its automated Supervisory Control and Data Acquisition (SCADA) system to maximize flow to West Point’s secondary treatment plants, while protecting the biological treatment system, via operation of regulators and pump stations. Clearly, in the course of the Feb 2017 bypass emergency event, the design approach of the plant, its control system, and/or the operation of the plant failed to protect the biological treatment system.
Vulnerability of the emergency bypass gate. The ability to operate the emergency bypass gate at West Point appears to be a proven point of dangerous vulnerability in this facility. Whenever a facility has a recognized point of weakness such as this, a risk management approach should be employed to either modify the design to reduce the vulnerability, or implement an asset management plan to reduce the risk of failure at this vulnerable point.
Worker safety risks. King County staff have stated that had this event occurred during the day, multiple workers would have been in the below ground galleries that were flooded – implicating severe worker safety risks. We are concerned that the potential loss of life associated with the Feb 2017 incident points to a serious facility design flaw, and are urging the Council to ensure that the independent investigation addresses these risks head on, and issues recommendations around whatever design flaws must be corrected to prevent future loss of life or injury.