Insights

Greene Economics led the 2025 update of Thurston County’s On-Site Sewage System Management Plan to meet new state code and strengthen public and environmental health protections for drinking water, shellfish beds, and Puget Sound. The plan targets vulnerable on-site sewage systems—especially in sensitive and flood-prone areas—enhances data and climate change planning, protects sensitive watershed, and supports more than 55,000 systems serving homes and businesses countywide.

Case Study: Greene Economics’ cost analysis helped King County prioritize investments in aging on-site septic systems and equitable infrastructure solutions.