Thurston County adopts 2025 On-Site Sewage Management Plan 

A septic management overhaul in Thurston County is complete, though builders and environmental advocates remain at odds on costs and protections. 

The Thurston County Board of Health adopted the 2025 Thurston County On-Site Sewage (OSS) Management Plan at a meeting on Tuesday, Dec. 9.

The plan, which serves as a framework for future septic oversight, was approved in accordance with the Revised Code of Washington 70.118A and Washington Administrative Code 246-272A.

The six categories of approved recommendations in the plan are “septic-to-sewer planning, designation of sensitive areas and marine recovery areas, database and dashboard development, climate change planning, quality assurance control and county-led septic programs.” 

The new plan recommends the establishment of new marine recovery area designations in Eld Inlet and Deschutes River Watershed, climate change response protocols for coastal septic systems, and expanded operation and maintenance requirements over the coming years. 

Septic systems treat wastewater from homes not connected to municipal sewer lines by filtering household sewage through underground tanks and drain fields before entering the groundwater. Failing systems can leak untreated waste into streams, lakes and South Puget Sound, contaminating drinking water wells and shellfish harvesting areas. 

Thurston County Environmental Health Division Director Season Long told the board the plan binds shared responsibility between septic owners and the health department. 

"This updated OSS management plan ensures the county remains compliant with new state requirements, while continuing to improve septic system management and protect water quality in our community," Long said.

"This is just the overall arching plan. It's just really a framework. Implementation is the next phase where we'll talk about what are we going to prioritize and how are we going to fund it." 

Of the county's approximately 55,400 systems, 16,203 require renewable operational certificates due to complexity or location in sensitive areas. Complex systems requiring operational certificates show 86% compliance, but standard systems outside the program lag at 35%. 

The operational certificate program in the Henderson and Nisqually watershed protection areas has driven compliance to 85% and cut failure rates from 13-14% in the early years to about 2-4% per year from 2009 through 2021. 

"By requiring regular maintenance, we're catching those small things early," said Thurston County Septic Operation and Maintenance Program Supervisor Jean Frost. 

The plan recommends Eld Inlet as a marine recovery area due to its threatened status as a shellfish growing area, elevated total phosphorus concentrations, and 69% noncompliance rate among septic owners. 

The Budd Inlet/Deschutes River watershed is also recommended to be designated as a watershed protections area due to elevated phosphorus levels and its connection to Budd Inlet, a shellfish growing area. Only 37% of septic systems in that watershed currently meet compliance standards. 

Summit Lake is recommended for sensitive area designation because residents rely on the lake for drinking water. The lake experienced severe harmful algal blooms in 2017 and 2019, which forced the county to provide potable water to shoreline residents for extended periods. 

The plan also flags Scatter Creek Aquifer, the county's only sole source aquifer, which contains several nitrate hotspots exceeding both county and federal safe drinking water contaminant levels of 4.0 milligrams per liter (mg/L) and 10.0 mg/L respectively, according to a 2022 county analysis. 

Public comment 

Industry representatives and environmental advocates squared off during the public hearing. 

Christine Erica Marbet, water resources biologist for the Squaxin Island Tribe, endorsed the plan and noted the tribe holds treaty-reserved fish and shellfish resources in Thurston County. 

"I support a robust septic system management plan because it protects access to safe shellfish for harvest for the Squaxin Island Tribe and all residents of Thurston County," Marbet said. 

Olympia resident Betsy Norton connected failing septic systems to "toxic algae blooms and low dissolved oxygen in the surface waters," urging the county to use accessory dwelling unit permits as an opportunity to inspect existing systems. 

Septic system owner Jane Mountjoy-Venning backed the plan and called for "a little bit more oversight" of systems that have never been inspected because the property never sold. 

On the other side of the issue, Jessie Simmons, of Olympia Master Builders, warned "any expansion of marine recovery areas should be first preceded by economic impact review," recommending a builder and stakeholder advisory panel for annual reviews. 

Christina Janis, of the Thurston County Realtors Association, questioned the timing of adoption. 

"Funding should be first, adopting should be second," Janis said. "I think in this day and age, we've found budget after budget after budget being in crisis." 

Septic system designer Adam Hunter said Thurston County levies the highest repair fees in the region and stressed finding efficiencies rather than raising fees.

Also, Jim Hunter, a septic designer since 1978, questioned prioritizing septic oversight when municipal sewer systems discharge millions of gallons of raw sewage into Puget Sound during storm events. 

Local real estate agent Paul Oczkewicz said current septic programs already work well and suggested the county focus on sewer system problems. 

Project outlook 

Meanwhile, Thurston County Manager Leonard Hernandez told the board the adopted plan does not impose new fees or rate structures. 

The plan estimates total program costs at $2,324,600 annually, if all the recommendations are implemented in full. The Pollution Identification and Correction Program alone would require $900,000, with dye testing at $132,000, time of transfer processing at $432,600 and groundwater quality monitoring at $60,000. 

The operation and maintenance program generated $1,065,240 in revenue in 2023. That total included $325,513 from Henderson Inlet assessments, $343,167 from Nisqually Reach assessments and $281,075 from operational certificate fees. 

The county processed 1,545 time of transfer applications in 2023 and 1,535 in 2024. From 2016 through 2024, 1,518 repair permits were issued countywide. 

Staff emailed the plan to 134 Thurston County certified septic professionals during the public comment period, drawing a 63.5% open rate. Social media posts on Facebook generated 3,483 views, and the public comment web page received 181 views and 37 written comments. 

Moving forward, the plan advances to Phase 2, where county staff is going work with the Board of Health to prioritize implementation of and adopt funding mechanisms. 

Later phases would target identifying and prioritizing marine recovery areas and other sensitive areas based on public health risk and impacts to key industries, including shellfish harvesting and recreation. Any such designations would require additional public input before new requirements could take effect. 

Those efforts would build on existing programs and partnerships, with implementation proceeding in stages rather than all at once. 

Editor's note: This story has been updated to reflect clarifications and corrections to a number of sentences.