King County Council Independent Assessment of the West Point Treatment Plant July 18, 2017 AECOM Presentation • Background • Incident Summary • Investigation Approach • HAZOP Analysis • Failure Mechanisms • Findings and Lessons Learned • Life Safety Management • Recommendations West Point Independent Assessment Background • Combined sewage treatment plant (stormwater and sewage) • 440 mgd capacity primary treatment, 300 mgd secondary treatment • Constrained Site West Point Independent Assessment 3 Incident Summary 2:12:30 AM – Power outage to A-side panel Pumps 1 & 2 fail; Hydraulic System fails 2:14:40 AM – Pumps 3 & 4 fail 2:14:59 AM – High level alarm in Effluent Pump Station triggers interlock with Primary Effluent gates to close 2:25:00 AM – High-High level floats failed to activate (flooding of WPTP begins) 3:04:00 AM – Raw Sewage Pumps manually stopped; Emergency Bypass initiated 3:05:00 AM – Flooding stops [2,315 Alarms in 51 minutes] High-High B-side Panel Level Floats PE Gate Effluent 4 3 Primary Sedimentation Tanks 2 Influent 1 Pre-Aeration A-side Panel Effluent Channel Critical Failures During Event • Power Outage to half of Effluent Pumps • Hydraulic Controls for all Effluent Pump Control Valves had no backup power • High Level Float Switches in Primary Tanks did not activate • Control System Alarms were not prioritized • No automated indication of flooding conditions • Manual operation required to shut off Raw Sewage Pumps West Point Independent Assessment Assessment Approach • Incident Review • Review of Process Areas • HAZOP Analysis • Failure Mode Evaluation • Mitigation Strategies • Recommendations West Point Independent Assessment Capacity Analysis 600 500 Capacity (MGD) 440 mgd 400 300 mgd 300 200 100 0 Firm Capacity West Point Independent Assessment Max Capacity Evaluation Process - HAZOP Select Process Area Repeat for all Process Areas Repeat for all Process Variables Define nodes (pump, valve, etc.) for each area Repeat for Additional Design Intent Define Design Intent Develop Action Items OK Select Process Variable (outage, loss of signal) Define individual Deviation or Failure Consequences of Deviation or Failure From BS IEC 61882 Assess Acceptability of Risk None None Possible Causes of Deviation or Failure Identify Existing Safeguards Potential Failure Mechanisms Technical Failure Mechanism Plant Hydraulics 1 Influent Control Structure 7 Preliminary Treatment 2 Raw Sewage Pump Station 5 Preaeration and Sedimentation Tanks 7 Flow Diversion Structure 3 Effluent Pump Station 5 Electrical 7 Instrumentation & Control 7 Operational Areas Risk Factors Staffing 3 Operations 8 Training 5 Equipment & Systems Testing Procedures 8 Maintenance Procedures 3 West Point Independent Assessment Findings and Lessons Learned • WPTP has many physical constraints • Lack of redundancy in key process areas. - Plant requires ALL systems to be fully functional to handle peak flow conditions. • WPTP requires a higher level of operational integration to manage interdependencies. • Emergency response training did not prepare for this type of incident - Operators did everything that could reasonably be expected of them • Current Systems are not optimized for an emergency event - Control system alarms were not prioritized for emergency situations West Point Independent Assessment Recommendations • Implement Life Safety Management System for all critical systems • Conduct comprehensive emergency response training in different failure scenarios. Develop guidelines for bypass decision-making by operations staff. • Conduct an integrated system-wide evaluation to address capacity constraints, redundancy and reliability. More passive systems are needed for relief from loss of automation or power outages. • Optimize capital investment to maximize redundancy. West Point Independent Assessment Life Safety Management Industry Standard Practice Proposed change to asset or function Maintenance Supervisor Plant Manager Recommendation to change Life Safety Management Health & Safety • Operating procedures • Employee training Proposed change to asset or function Engineering • Quality assurance • Risk Analysis Operations • Safety Reviews • Maintenance Systems • Change Management Maintenance Recommendation to change Operational Integration Moving Forward Level of Evaluation Before Feb 9 Event PSM With Life Safety Management System (January 2018) PSM Innovative Approach Industry Standard Chemical Systems Rest of Plant Chemical Systems Rest of Plant PSM = Process Safety Management – Required for Chemical Systems in Plant Recommendations • Implement Life Safety Management System for all critical systems • Conduct comprehensive emergency response training in different failure scenarios. Develop guidelines for bypass decision-making by operations staff. • Conduct an integrated system-wide evaluation to address capacity constraints, redundancy and reliability. More passive systems are needed for relief from loss of automation or power outages. • Optimize capital investment to maximize redundancy. West Point Independent Assessment Thank you AECOM