Unified Sewer Plan Update

Unified-Sewer-Plan-iconEnvisioning Our Future Sewer System

Wastewater treatment facilities around Puget Sound face regulatory and environmental pressures to develop, implement, and improve wastewater treatment processes to meet increasing water quality regulations for effluent discharge. 

The Unified Sewer Plan will reflect Pierce County’s ongoing commitments to a healthy Puget Sound and strategic goals of supporting vibrant communities, effective government, and an entrepreneurial climate.
About the USP
What is the Unified Sewer Plan?

Pierce County Planning & Public Works is currently updating the Unified Sewer Plan (USP), which is an all-encompassing plan that aligns with the Pierce County Comprehensive Plan and will guide the County’s sewer utility for the next 20 years. The plan describes the sewer service area, existing collection and treatment system and outlines policies, goals, and plans that will guide future expansion and improvements. 

The USP also addresses elements required by the Washington State Department of Ecology, including the General Sewerage Plan, the Puget Sound Nutrient General Permit, expansion of sustainability, and the resource recovery efforts of biosolids, biogas, and reclaimed water.

Unified Sewer Plan

General Sewerage Plan

  • Requires appointment of Review Committee and Hearings Board adoption
  • Planning Commission and Department of Ecology approval
  • Engineering reports developed based on this plan
  • Goals, policies and objectives
  • Require by WACs and RCWs
  • History and overview

Recoverable Resources Management Plan
Biological Nutrient Removal, Biosolids, Biogas & Reclaimed Water

  • Treatment requirements for utilization of wastewater treatment process byproducts
  • Mitigates and minimizes future regulatory risks
  • Align with community and organizational goals
  • Long-range operating strategy

  1. Stakeholders
  2. Goals
  3. Policy Topics

Pierce County’s wastewater utility staff engages with ratepayers, elected officials, tribal partners, stakeholders, and regulators to understand their expectations and develop strategies for how best to balance those expectations while maintaining affordable rates. 

Our business case evaluations include considerations of the environment and social awareness to the standard cost/benefit/risk analysis, and address sustainability, sewer capacity, recovery, and wastewater treatment byproducts (such as reclaimed water, biosolids, biogas and nutrient reduction). 


Pierce County launched the Unified Sewer Plan update project in March of 2020 and expects to finalize the plan in 2025. Stakeholder engagement will assist in initial plan development, analysis and environmental review of alternatives.  
Washington State Department of Ecology and the Pierce County Council have approval oversight of the final plan. See below for more detail about the timing and goals for each phase.  

(Note: Timelines have shifted due to the pandemic response needs, prioritized policy work, and to ensure coordination with broader Pierce County’s Comprehensive Plan timing.)
  1. Prework/Contracting
  2. Phase 1
  3. Phase 2 (Current Phase)
  4. Phase 3
  5. Adoption

The prework and contracting took place in 2019-2020.