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: May 2, 2019 - ATU's must be listed to match registered tanks, FEMA requirements, operating capacity
• 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.
• Certified Sewage Site Plan

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.20.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
• Application of Recommended Standards and Guidance for Pressure Distribution Sewage Systems - February 2022 Version – ONST.22.POL.802
• Interlacing Drainfields ONST.20.POL.847.pdf
• Application of Recommended Standards & Guidance for Sand Lined Trench Systems - March 2014 Version – ONST.20.POL.822
• Determination of Highest Seasonal Water Table - ONST.20.POL.841
• Representative Rainy Season Policy - ONST.20.POL.843
• Representative Rainy Season Guideline - ONST.20.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
• Procedure for Wet Season Study – ONST.20.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
• Maximum Density Requirements in Category I Aquifer – ONST.20.POL.856
• Policy to Clarify How the Term Unit Volume of Sewage will be applied to Multi-Unit Residential Development – ONST.20.POL.858
• 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.22.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 - ONST.20.POL.814
• Record Drawing Submittal Requirements - ONST.20.POL.860
• Requirements for by-passing an Intermittent Sand Filter – ONST.20.POL.845
• Requirements for Rebuilding Mounds, Intermittent Sand Filters, Sand-Lined Trench/Beds and Glendon Biofilters - Thurston County Policy – ONST.20.POL.853
• Sewage System Design Standards for Summit Lake - ONST.20.POL.801
• Use of Sand-Lined Trench/Beds - Technical Guidelines - ONST.20.GUI.822
• 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: Identify wells within 100 feet of property, submit 3 copies of designs, pump chamber size and timed dosing for repairs, independent float trees, staking. 
• Memorandum dated July 10, 2003 regarding use of designer stamps/seals
• Memorandum dated February 4, 2004 listing miscellaneous information & requirements: Setback from water lines to onsite components, water line record drawing requirement, signage and site flagging, dose timers. 
• Memorandum dated November 4, 2004 listing miscellaneous information & requirements: Effluent filters and ATU's, design submittals, design revisions, changes to designs during installation, waiver requests, Record Drawing submittals, test pit excavations. 
• Memorandum dated March 8, 2006 listing miscellaneous information and requirements: test pits, seven time rule, soil log descriptions, model homes, length of time between field and site work and actual submittal of designs, notice of expectations for licensed designers and professional engineers, COSS and conforming OSS defined in January 1, 2006 version of Article IV.
• Memorandum dated December 22, 2006 listing miscellaneous information and requirements: sewer/water line crossing/reduced setbacks, record drawing requirements, water line installations, fee charges and policy, July 2, 2007 Article IV update
• 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: Article I and Article IV updates, January 1, 2010, mandatory submission of pumper reports and fees, inspection of septic system when property sells, risers and access ports at or above finished grade. Also, implementation of 2009 version of DOH RS&G for Pressure Distribution, Mound and Sand Lined Trench and 2007 version of intermittent Sand Filter. Mound reserve areas required to be staked, reference to new Sand Lined Trench policy, WAC 246-272C adopted by DOH, list pf permit applications and scenarios with fees.
• 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
• Memorandum dated March 26, 2007 - Lot Failing to Meet Minimum Land Area

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: May 2, 2019 - ATU's must be listed to match registered tanks, FEMA requirements, operating capacity
• 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
• Installer Completion Form

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" - (WA DOE) (533 page document)
• Chapter 246-272A WAC, On-Site Sewage Systems

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

• Application of Recommended Standards and Guidance for Pressure Distribution Sewage Systems - ONST.22.POL.802
• Pressure Distribution System Recommended Standards and Guidance - 07/2012 (WA DOH) 
• Application of Recommended Standards & Guidance for Sand Lined Trench Systems - March 2014 Version - ONST.20.POL.822
• Recommended Standards and Guidance for Sand Lined Trench System - 03/2014 (WA DOH) 
• Recommended Standards and Guidance for Intermittent Sand Filter System - 12/2016 (WA DOH)
• Recommended Standards and Guidance for Mound System - 05/2020 (WA DOH)
• Requirements for Rebuilding Mounds, Intermittent Sand Filters, Sand-Lined Trench/Bed and Glendon Biofilter - Policy ONST.20.POL.853
• Use of Table VI for Sewage System Repairs and Modifications - ONST.20.POL.814
• Repair and Certification of Failing Sewage Tanks - Thurston County Policy Number ONST.21.POL.607
• Record Drawing Submittal Requirements - ONST.20.POL.860
• Use of Sand-Lined Trench/Beds - Technical Guidelines - ONST.20.GUI.822
• Miscellaneous Info and Requirements Memo 02/11/2003
• Miscellaneous Items Memo 02/04/2004
• County Changes and Requirement Update Memo 12/22/2006
• Solids Pump Tanks Memo 06/29/2007
• Environmental Health Updates Memo 01/04/2010
• Proper Abandonment of Septic Tanks 08/29/2011
• Several Onsite Updates Memo 03/01/2012

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

• Certification Steps
• 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.20.POL.605
• Contract Requirements for Third Party Maintenance - ONST.20.POL.830

Website Links

• Glossary of Sewage Related Terms (WA DOH)
• Washington State Onsite Sewage Regulations - (246-272A WAC)
• Approved Onsite Products (WA DOH)
• Property Owners/Property Manager Publications (WA DOH)
• Design Standards for Large Onsite Sewage Systems (WA DOH)
• Recommended Standards & Guidance for Documents Listed Below
  • 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

• Certification Steps
• 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 DOH)
• 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)

• Use of Sand-Lined Trench/Bed (Technical Guide) - ONST.20.GUI.822
• Representative Rainy Season (Technical Guide) - ONST.20.GUI.843 New Format Only
• Sewage System Design Standards for Summit Lake - ONST.20.POL.801
• Use of Table VI for Sewage System Repairs and Modifications - ONST.20.POL.814
• Application of Recommended Standards and Guidance for Sand Lined Trench Systems - ONST.20.POL.822
• Contract Requirements for Third Party Maintenance - ONST.20.POL.830
• Additional Fees Required for Sewage System Design Review - ONST.20.POL.832 New Format Only
• Determination of Highest Seasonal Water Table - ONST.20.POL.841 New Format Only
• Representative Rainy Season - ONST.20.POL.843
• Requirements for Bypassing an Intermittent Sand Filter - ONST.20.POL.845
• Requirements for Rebuilding Mounds, Intermittent Sand Filters, Sand Lined Trench/Bed and Glendon Biofilter - ONST.20.POL.853
• Maximum Density Requirements in Category I Aquifer Recharge Area - ONST.20.POL.856
• Policy to Clarify How the Term "Unit Volume of Sewage" Will be Applied to Multi-Unit Residential Development - ONST20.POL.858 New Format Only
• Record Drawings Submittal Requirements - ONST.20.POL.860
• Procedure for Wet Season Study - ONST.20.PRO.840 New Format Only
• Non-Conforming Septic System Mitigation - ONST.21.POL.859
• Application of Recommended Standards and Guidance for Pressure Distribution Sewage Systems - ONST.22.POL.802
• Requiring Service Contracts with Certified Monitoring Specialist - ONST.20.POL.605

List is in Date Order - Most Recent at the Top

• Updated Supplemental Application - Effective 03/22/2021
• 2022 Common Fees for Septic and CSA Submittals 01/01/2022
• Program for Financial Assistance for Septic System Repairs 07/22/2016
• OSS Application Process Changes - Effective 07/31/2015
• On-Site Sewage Program Updates 03/01/2012: Record drawings, adult family homes, pump and inspection reports, Sand Filter Pump basins and Operational Certificate renewals and Time of Transfers, testing options for certification of industry professionals, reminders for designers. Vertical separation, valves and valve boxes, minimum width of gravelless chambers
• Ordinance H-1-2023 Amending Article IV of the Sanitary Code
• Memo - Who Can Work on Proprietary Devices or Disinfection Units 

List in Order of Update

Current Policies

• Requirements for Siting Glendon Biofilters and Lowridge Oscars  ONST.22.POL.819   
• Adult Family Homes - ONST.21.POL.857   
• Interlacing Drainfields ONST.20.POL.847.pdf   Revised 05/01/2020
• Minimum OPC Requirements in MRA - ONST.12.POL.837
• Non-Conforming Septic System Mitigation - ONST.21.POL.859 (Certified Sewage Site Plan Guidance)
• OSS-Effluent-Monitoring-ONST.17.POL.606.pdf (see note on page two)  Revised 11/16/2017
• Owner Inspections of OSS In MRA's - ONST.13.POL.834
• Owner Certification to Self-Inspect Septic System - ONST.13.POL.846
• OSS System Inspections in the MRA Operation and Maintenance Program - ONST.13.POL.833
• Repair and Certification of Failing Sewage Tanks - ONST.21.POL.607        
• Contract Requirements for Third Party Maintenance - ONST.20.POL.830
• Sewage Systems Requiring Operational Certificates - ONST.13.POL.808
• Use of Table VI for Sewage System Repairs/Modifications - ONST.20.POL.814
• Use of Terralift Machine on Sewage Systems in Thurston County - ONST.96.POL.801
• Requirements for Rebuilding Mounds, Intermittent Sand Filters, Sand-Lined Trench/Bed and Glendon Biofilter - ONST.20.POL.853

​Listed in Order of Date Cancelled

Cancelled Policies

• Inspection Reports for Annual OPC Renewals   Cancelled 08/10/2017
• O&M Requirements for Community OSS (COSS)   Cancelled 08/10/2017
• Requirements for Siting Glendon Biofilters Cancelled 8/18/2022

Building Development Center Hours (TC BDC)

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

OnlineRME

Water Waste Management (WA DOH)

Septic & Sewage Publications (WA DOH)