Information septic system designers and engineers, who work in Thurston County, must be familiar with and utilize when designing systems that will be put in to use in our county.

Links to Documents May Not Work on All Browsers

General Information

• Updates for Designers and Installers
• Designer List Application
• Introduction to Designer Program
• Sewage System Project Matrix
• Thurston County Onsite Wastewater System Construction Manual — Minimum standards and recommendations for the construction of onsite wastewater treatment and disposal systems in Thurston County.

Rules, Regulations and Fees Policy, Procedure, RS&G's

• Washington State Department of Licensing
• Chapter 196-33 WAC, Rules of Professional Practice for Licensees Designing On-Site Wastewater Treatment Systems
• Article I of the Thurston County Sanitary Code, General Provisions
• Article IV of the Thurston County Sanitary Code, Sewage Disposal Regulations
• Table 24.10-4 in Appendix B of the Critical Areas Ordinance. This is associated with Article IV, Section 11, Table II foodnote 2. Updated from Chapter 17 of a previous version of the Critical Areas Ordinance.
• Thurston County Environmental Health Fee Schedule

Memos, Letters and Policies

• Additional Fees Required for Sewage System Design Reviews - ONST.07.POL.832
• Policy on Expiration and Renewal of Sewage System CSAs - PRMT.POL.809-99-15-640
• Policy on Expiration and Renewal of Sewage System Applications and Permits - PRMT.POL.809.99 15-639
• Standards and Guidance for Pressure Distribution Systems – July 2009 Version and Record Drawing Requirements – ONST.11.POL.802
• Interlacing/Fingering Drain Fields Accepted Criteria –  ONST.11.POL.847
• Memorandum and Policy on Application of WSDOH Recommended Standards & Guidance for Sand Lined Trench Systems – ONST.09.POL.822
• Policy on Determination of "Highest Seasonal Water Table" - ONST.07.POL.841
• Representative Rainy Season Policy - ONST.07.POL.843
• Representative Rainy Season Guideline - ONST.07.GUI.843
• Wet Season Study Application - ONST.07.POL.842
• Wet Season Study Policy - ONST.07.POL.840
• Wet Season Study Procedure – ONST.07.PRO.840
• Wet Season Study Water Table Evaluation – ONST.07.GUI.840
• Policy on Minimum Land Area Requirements for Existing Legal Lots – ONST.POL.806.98
• Policy on the Review of Technical Justification and Preliminary Designs for Subdivisions – ONST.08.POL.839
• Policy on Maximum Density Requirements in Category I Aquifer Recharge Areas – ONST.14.POL.856
• Policy to Clarify How the Term "Unit Volume of Sewage" will be applied to Multi-Unit Residential Development – ONST.21.POL.857
• Policy on Common Drainfield Areas – ONST.01.POL.820
• Policy on Protection of Existing Water Supplies Adjacent to Property Being Developed – ONST.96.POL.602
• Policy on Requirements for Siting of Glendon Biofilters – ONST.11.POL.819
• Policy on Siting of Single Family Wells for Subdivision Projects – ONST.08.POL.815
• Policy on Review of Single Family Wells for the Sewage System Design Process – ONST.00.POL.816
• Policy on Sewage System and Water System Standards in Seasonally Flooded Areas – ONST.08.POL.818
• Policy on Repair and Certification of Failing Sewage Tanks – ONST.21.POL.607
• Use of Table VI for Sewage System Repairs and Modifications - Thurston County Policy – ONST.12.POL.814
• Requirements for by-passing an Intermittent Sand Filter – ONST.09.POL.845
• Requirements for Rebuilding Mounds and Intermittent Sand Filters - Thurston County Policy – ONST.12.POL.853
• Policy On Sewage System Design Standards for Summit Lake Basin - ONST.05.POL.801
• Information on Retention and Disposition of Public Records for Certified Installers, Monitoring Specialists, & Pumpers
• Letter to Septic System Professionals - OSS Application Process Changes Effective 7/31/15
• Memorandum and Policy on Waivers
• Memorandum on Application of WSDOH Recommended Standards & Guidance for Many Different Systems
• Memorandum on Urban Area Requirements for Land Development Projects
• Memorandum dated February 11, 2003 listing miscellaneous information & requirements
• Memorandum dated July 10, 2003 regarding use of designer stamps/seals
• Memorandum dated February 4, 2004 listing miscellaneous information & requirements
• Memorandum dated November 4, 2004 listing miscellaneous information & requirements
• Memorandum dated March 8, 2006 listing miscellaneous information and requirements
• Memorandum dated December 22, 2006 listing miscellaneous information and requirements
• Memorandum dated June 29, 2007 Regarding Solids Pump Tanks
• Memorandum dated October 12, 2009 Regarding Record Drawing Submittals
• Memorandum dated January 4, 2010 Environmental Health Updates
• Abandonment of Septic Tanks Memo Dated 8-29-11 
• Memorandum dated March 1, 2012 - Onsite Program Updates to Sewage System Professionals
• Memorandum on Article IV Clarification on Designs with Repair Applications
• McAllister Geologically Sensitive Area Requirements - Part of Article I, Appendix B

Information for those who want to be certified and operate to install septic systems in Thurston County.

Links to Documents May Not Work on All Browsers

General Information

• Updates for Designers and Installers
• Certified Installer Application
• Procedures for Certification as Sewage System Installer in Thurston County
• Thurston County Onsite Wastewater System Construction Manual — Minimum standards and recommendations for the construction of onsite wastewater treatment and disposal systems in Thurston County

Rules, Regulations & Fees 

• Thurston County Environmental Health Fee Schedule
• Article IV Rules and Regulations Governing Treatment and Dispersal of Sewage
• Department of Ecology's "Criteria for Sewage System Works Design" - DOE Website (533 page document)
• Chapter 246-272A WAC, On-Site Sewage Systems

Policy, Procedures, RS&G's Memos and Letters

• Standards and Guidance for Pressure Distribution System - Thurston County Policy Number ONST.11.POL.802
• Pressure Distribution System Recommended Standards and Guidance - July 2012 - DOH Document
• Standards and Guidance for Sand Lined Trench System - Thurston County Policy Number ONST.09.POL.822
• Recommended Standards and Guidance for Sand Lined Trench System - March 2014 - DOH Document
• Recommended Standards and Guidance for Intermittent Sand Filter System - December 2016 - DOH Document
• Recommended Standards and Guidance for Mound System - May 2020 - DOH Document
• Requirements for Rebuilding Mounds and Intermittent Sand Filters-Thurston County Policy ONST.12.POL.853
• Use of Table VI for Sewage System Repairs and Modifications-Thurston County Policy ONST.12.POL.814
• Repair and Certification of Failing Sewage Tanks - Thurston County Policy Number ONST.13.POL.607
• Miscellaneous Info and Requirements Memo dated 2-11-03
• Miscellaneous Items Memo dated 2-4-04
• County Changes and Requirement Update Memo dated 12-22-06
• Solids Pump Tanks Memo dated 6-29-07
• Environmental Health Updates Memo dated 1-4-10
• Proper Abandonment of Septic Tanks dated 8-29-11
• Several Onsite Updates Memo dated 3-1-12

Information for those who want to be certified as septic system monitoring specialists in Thurston County.

Links to Documents May Not Work on All Browsers

• Application - CMS
• Performance Expectations - 2009
• General Onsite Procedures
• Major Microbial Diseases in Domestic Wastewater
• Thurston County Septic Tank Pumper's Manual
• Onsite Sewage System Construction Manual
• Technical Paper Diagnostic Techniques Utilized in Analysis of Failed Systems for Residential Waste
• Inspecting Your Septic Tank
• Understanding and Caring for Your Pressure Distribution System
• Article IV, Thurston County Sanitary Code
• Memo and Policy for Implementation of DOH-TRC Sand Filter Guidelines
• Contracts Requiring Third Party Maintenance - ONST.08.POL.605
• Policy Requiring Service Contracts with CMS - ONST.08.POL.830

Website Links

• Glossary of Sewage Related Terms - WSDOH
• Washington State Onsite Sewage Regulations - WAC
• Approved Onsite Products - WSDOH
• Property Owners/Property Manager Publications - WSDOH
• Design Standards for Large Onsite Sewage Systems - WSDOH
• Recommended Standards & Guidance for Documents Listed Below - WSDOH
  • Aerobic Treatment Units (Proprietary Treatment Products) / Alternating Drainfields
    Dosing Gravity Drainfield Systems / Glendon®  BioFilters / Gravelless Drainfields
    Holding Tank Sewage Systems / Intermittent Sand Filter Systems / Mound Systems
    Pressure Distribution / Proprietary Packed Bed Filter Systems
    Proprietary Treatment Products - Replaces Aerobic Treatment Units, Proprietary Packed Bed /
    Filters and Upflow Media Filters / Recirculating Gravel Filters
    Sand Lined Trench Systems / Stratified Sand Filters / Subsurface Drip System
    Water Conserving Onsite Wastewater Treatment Systems

Information for those who want to be certified and operate to pump septic systems in Thurston County.

Links to Documents May Not Work on All Browsers

• Cover Letter
• Pumper Application
• Pumper and Pumper Firm Performance Expectations
• Summary of Septic System Operation and Maintenance Program for the Henderson Watershed Protection Area
• Thurston County Septic Tank Pumpers' Manual
• Article IV Section 23.3 Pumping Firm
• List of Approved On-site Sewage Disposal System Additives — WA Dept of Health
• Thurston County Septic Tank Pumper / Facility Inspection Report

Sample information packet provided to property owners served by a septic system.

• Septic Inspection and Pumping Guide
• Inspecting Your Septic Tank, It's not so bad... really!
• Understanding and Caring for Your Sand Filter System
• Understanding and Caring for Your Septic Tank System
• Understanding and Caring for Your Mound System
• Understanding and Caring for Your Pressure Distribution System
• Septic Tank Additives— Small Flows Quarterly, Winter 2002
• Your On-Site Sewage System (used as the holder for the handouts)

List is in Date Order - Most Recent at the Top

• Updated Supplemental Application - Effective 3-22-2021
• 2022 Common Fees for Septic and CSA Submittals - 1/1/2022
• Program for Financial Assistance for Septic System Repairs - 7-22-2016
• OSS Application Process Changes - Effective 7-31-2015
• On-Site Sewage Program Updates - 3-1-2012

List in Order of Update

Current Policies

• Requirements for Siting Glendon Biofilters and Lowridge Oscars  ONST.22.POL.819   New  3-23-2022
• Adult Family Homes   New 3-23-2021
• Interlacing Drainfields ONST.20.POL.847.pdf   Revised 5-1-2020
• OSS-Effluent-Monitoring-ONST.17.POL.606.pdf (see note on page two)   Revised 11-16-2017
• Owner Inspections of OSS In MRA's
• Owner Certification to Self-Inspect Septic System
• OSS System Inspections in the MRA Operation and Maintenance Program
• Repair and Certification of Failing Sewage Tanks
• Systems Requiring Service Contracts with Monitoring Specialist          
• Contract Requirements for Third Party Maintenance 
• Sewage Systems Requiring Operational Certificates
• Use of Table VI and Sewage System Repairs/Modifications
• Requirements for Rebuilding Mounds and Intermittant Sand Filters

​Listed in Order of Date Cancelled

Cancelled Policies

• Inspection Reports for Annual OPC Renewals   Cancelled 8-10-2017
• O&M Requirements for Community OSS (COSS)   Cancelled 8-10-2017
• Requirements for Siting Glendon Biofilters Cancelled 8-18-2022

Building Development Center Hours (BDC)

OSS Tank Pump Out Report - Electronic Submittal Only: $15

OnlineRME

Washington State Department of Health (WDOH)

RS&G's (WDOH)