Environmental Health
Septic Systems
On-Site Sewage Management Plan
Thurston County OSS Management Plan  
  Background  l  Recommendations & Summary  l  Additional Info  


This management plan was developed in response to state law that requires the County to identify areas where septic systems (on-site sewage systems or OSS) might pose a risk to public health and develop strategies for managing systems in those areas.

This legislation directed local health officers of the twelve Puget Sound counties bordering Puget Sound to take further actions to reduce fecal coliform pollution and the degradation and loss of marine life in Puget Sound caused by low-dissolved oxygen conditions. The legislation directed local health officers to create Marine Recovery Areas in areas where on-site sewage systems are polluting Puget Sound.

The Marine Recovery Area (MRA) strategy must specify how, by July 12, 2012, the local health officer will:

  • Find existing failing systems and ensure that system owners make necessary repairs, and
  • Find unknown systems and ensure that they are inspected and functioning properly and repaired, if necessary.

In November 2006, an advisory committee was convened to develop recommendations for the Countyís on-site sewage system management plan and the revision of Article IV of the Thurston County Sanitary Code (on-site sewage system regulations). Their recommendations are the backbone of this plan.

Management Plan Recommendations and Summary

Database Enhancements

This part of the plan will allow the County to:

  • Develop and maintain an inventory of all known septic systems in operation within Thurston County
  • Require septic system be inspected when the properties are sold or transferred unless the system is required to have and is in full compliance with a renewable operational certificate

The plan recommends that the existing AMANDA electronic database be enhanced. AMANDA currently requires sewage system operation and maintenance (O&M) and permit data to be entered manually. This plan recommends that a web-based system be developed to allow O&M records to be submitted electronically and transferred to and managed by AMANDA. This will allow Health Department staff to better meet the O&M monitoring and management goals, and will be a step towards setting up systems to remind all OSS owners of the O&M needs for their system.

Identification of Sensitive Areas

Health Department staff and the advisory committee evaluated land use, shellfish closure data and existing water quality information to identify areas where OSS could pose an increased public health risk or where existing OSS are a significant factor contributing to concerns. They identified nine areas where OSS could pose an increased public health risk:

  • Henderson Watershed Protection Area
  • Nisqually Reach Shellfish Protection Area
  • Eld Inlet
  • Totten Inlet
  • Budd Inlet
  • Summit Lake
  • Southern Thurston County (Scatter Creek Area)
  • McAllister Springs Aquifer Recharge Area (southeast of Lacey)
  • Shana Park/East Olympia Wellhead Areas

After further evaluation, they concluded:

  • The Henderson Inlet Watershed Protection Area and Nisqually Shellfish Protection District should be recognized as Marine Recovery Areas.
  • OSS monitoring, maintenance and education programs for OSS in the Nisqually area should be modeled after the Henderson Watershed Protection Area.
  • The Eld Inlet watershed should be more carefully evaluated to determine if it should be established as Marine Recovery Area.
  • Other areas be evaluated further to determine if OSS are causing or have the potential to create water quality and public health problems.

Operation, Monitoring and Maintenance in Sensitive Areas

The plan recommends that Article IV be amended to:

  • Require a property is evaluated before the property is sold or transferred, and the inspection report submitted to the Health Department
  • Require septic tank pumpers records for each OSS tank that is pumped or serviced in Thurston County

Due to incomplete records, there is also a need to inventory systems in urban areas where sewer service is provided to confirm whether the home or business is served by OSS or sewer.

Marine Recovery Area Strategy

This part of the plan recommends that Article IV be amended to:

  • Create Marine Recovery Areas for Henderson Inlet, Nisqually Reach and other areas as needed.
  • Identify the responsibility and role of the sensitive area committee in Article IV.


The County currently offers advanced OSS training classes to Henderson Watershed Protection Area residents. It is recommended these classes be offered countywide.

Currently, certain septic systems require renewable operational certificates. OSS owners are notified when the certificates are about to expire and homeowners must have the system inspected and pumped, if necessary, before they can be renewed.

The plan recommends a more formal notification procedure to advise owners of systems that donít have renewable operational certificates about what they should do to monitor and maintain their system.

Implementation Strategy

This plan recognizes that resources are needed to evaluate the data that is submitted to both identify failing on-site sewage systems and to evaluate the quality of work being done.

A mechanism for funding these plan elements needs to be developed. While some funding is being provided through the Washington State Department of Health, additional resources are needed to sustain current programs and those envisioned by this plan.

Based on the current resource limitations in Thurston County, the implementation schedule and work plan have been split into:

  • Activities that can be achieved with currently available funding and resources
  • Activities that require additional resources

This strategy proposes to allocate resources to complete activities that will achieve the greatest results while laying the groundwork that will allow other plan elements to proceed. These include regulation updates needed to implement the OSS inventory elements of this plan, database enhancements to allow O&M records to be submitted on-line, and creation of the sensitive area workgroup. Because funding is assured only through June 2009, this strategy focuses on activities that can be completed within that window of time. Other plan elements are put on a workplan for the future.

Additional Information

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This page last updated: 11/09/17