Large On-site Sewage System (LOSS) Information and Guidance

The following information is offered to assist you in planning your LOSS project and complying with regulatory requirements. 

Rules and Regulations

• Chapter 246-272B WAC - Large On-site Sewage Systems Regulations
• Fees and Billable Hours
• Statutory Authorities: RCW 43.20.050, 43.70.110; 43.70.250, 70A.115, and Chapter 246-272-3000 WAC

Best Management Practices, Tech Tips, Fact Sheets, and Frequently Asked Questions

Best Management Practices

• Best Management Practice Explanation Form (PDF)
• Commercial Kitchens (PDF)
• Disposal of Pharmaceuticals (PDF)
• Kitchen Waste (PDF)
• Marinas (PDF)
• RV Parks (PDF)
• Schools (PDF)

Tech Tips

• How to Calculate Your Wastewater Flows Using Your Dose Counter (PDF)
• How to Calculate Your Wastewater Flows Using Your Elapsed Time Meter (PDF)
• Sampling Effluent in a LOSS (PDF)
• Wildfires / Water Outage / Power Outage (PDF)
• Before, During, and After a Flood (PDF)

Fact Sheets

• Do's and Don'ts of Septic System Care (PDF)
  • Spanish: Qué hacer y qué no hacer en el cuidado del sistema séptico (PDF)
• Drainfield Care for LOSS (PDF) - Fact sheet discusses protecting the drainfield and reserve areas.
• Drainfield Reductions for LOSS (PDF) - Fact sheet helps clarify when reductions in drainfields are appropriate.
• Enforcement Process for LOSS (PDF) - Outlines the steps taken when a LOSS is not in compliance with state rules.
• Signs of Septic System Failure or Malfunction (PDF) - A failed or malfunctioning LOSS is a risk to human and animal health and can pollute the environment.
• Cross Reference: Health & Ecology, Large On-site Sewage System (LOSS) Documents (PDF) - A comparison of LOSS submittal requirements for the Department of Health and the Department of Ecology.
• Glossary of Terms (LOSS) (PDF)
• Guidelines for Test Pit Construction for On-site Sewage Systems (PDF)
• Large On-site Sewage System Online Payment Guide - An invoice must exist in order to make a LOSS payment online.

Operating Permit Renewal Forms

An annual operating permit renewal application is mailed in advance to each system by Department of Health.

• Flowchart of the LOSS Renewal Process (PDF)
• Annual Maintenance and Monitoring Report forms for LOSS:
• Operating Permit expires March 31 (Word)
• Operating Permit expires September 30 (Word)

Operating Permit for Existing LOSS: First Application

• Existing System Review and Operating Permit Process Flowchart (PDF) for existing Large On-site Sewage Systems (LOSS) without a DOH permit.
• Existing System Questionnaire (Word) for existing Large On-site Sewage Systems without a DOH Permit.
• Operating Permit Application (Word)

Designing and Building a New LOSS or Modifying an Existing LOSS

• Flowchart of the Large On-site Sewage System (LOSS) New Project Review & Approval Process (PDF)
• Flowchart of the Large On-site Sewage System (LOSS) Operating Permit & Approval to Construct Process (PDF)
• Sustainable Infrastructure for Small System Public Services - A Planning and Resource Guide (PDF)
• Project Submittal form for Large On-site Sewage System (LOSS) (Word) AKA Application for a New LOSS or Modification to an Existing LOSS
• Predesign Report Requirements, Large On-site Sewage System (LOSS) (PDF)
• Site Evaluation and Environment Review
• Guidelines for Test Pit Construction for On-site Sewage Systems (PDF)
• Engineering Report Checklist (PDF)
• Plans & Specifications Checklist (PDF)
• Operating Permit Application (Word)
• Public Notice Requirements for LOSS greater than 14,500 gallons per day
• Construction Completion Report for Large On-Site Sewage System (LOSS) (Word)
• Fact Sheet about Large On-site Sewage System (LOSS) Drainfield Reductions (PDF)
• Model Operation and Maintenance Manual (Word)
• Monitoring and Reporting Plan Manual (Word)

Environmental Review Forms and Guidance

• Guidelines for Test Pit Construction for On-site Sewage Systems (PDF)
• Monitoring and Reporting Plan Manual (Word)
• Monitoring Report Cover Sheet (Excel) - This form must be submitted along with your lab reports.
• Soil & Site Inspection Guidance - under development
• Search for an Accredited Laboratory - Washington State Department of Ecology website
• Site Risk Survey for Large On-site Sewage System (LOSS) (PDF)
• Level 1 Nitrate Balance Instructions (PDF)
• Level 1 Nitrate Balance Spreadsheet (Excel)

Inspecting and Evaluating Existing LOSS

• Inspection, Schematic, and Engineering Evaluation Guidance for Existing Large On-site Sewage Systems (Word)
• System Abandonment Report (PDF) - Large On-site Sewage System (LOSS)
• Infiltration and Inflow can be Costly - good article in the Spring 1999 "Pipeline" publication, including helpful tips to find and resolve.

LOSS Management

• Management of Large On-site Sewage Systems (LOSS) (PDF) - Guidelines that set forth the minimum information to be included in any LOSS Management Plan.
• Search for an Accredited Laboratory - Washington State Department of Ecology

Related Resources

• Criteria for Sewage Works Design (Orange Book) - Guide for the design of sewage collection, treatment, and reclamation systems. Developed and published by Washington State Department of Ecology.
• Glossary of Terms (LOSS) (PDF)
• How to Hire a Professional Engineer (PDF)
• Pressure Distribution Systems (RS&G) (PDF)
• Search for an Accredited Laboratory - Washington State Department of Ecology

More Resources

Wastewater Forms and Publications

Contact Wastewater Program Staff

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