Mono County California
Published on Mono County California (https://monohealth.com)


Onsite Wastewater Treatment Systems (OWTS)

Septic [1]

Onsite Wastewater Treatment Systems (OWTS) Program

The OWTS Program protects people and the environment by making sure sewage and greywater are handled safely. We:

  • Review and issue permits for on-site sewage systems
  • Regulate greywater systems
  • Oversee septage haulers (pump/transport companies)

Quick Links

Septic System Permit Application (OWTS Permit) — PDF [2] Construction Guide for Conventional Septic — PDF [3]

Building or Repairing a Septic System (Conventional)

This section summarizes key steps. See the full guide for details. Seepage pits and cesspools are prohibited in Mono County.

Permit Steps (At-a-Glance)

  1. Apply: Submit application, fee, a to-scale plot plan, and a simple site map.
  2. Site evaluation & testing: Test trenches and percolation tests (by a licensed professional/REHS) as required.
  3. Review & decision: We review submittals and field conditions; if approved, a permit is issued.
  4. Build with inspections: Schedule required inspections at each stage (see below).

Required Inspections

  • Site & soil profile (before permit issuance)
  • Open trench (before placing rock/pipe)
  • Final (tank, leach lines, distribution)

Key Site Basics

  • Adequate soil and acceptable percolation (typ. 5–60 min/in)
  • Vertical separation ≥ 5 ft from trench bottom to groundwater/bedrock
  • Reserve area equal to 100% of the leach field
  • Slope under 30%
  • Example setbacks: wells 100 ft; buildings 5 ft (tank) / 8 ft (leach lines)

Operation & Maintenance (O&M)

  • Do not flush wipes/solids or pour grease/harsh chemicals down drains
  • Protect the leach field (no parking, paving, or heavy landscaping on top)
  • Pump the septic tank every 5–7 years (more often with heavy use)
Download Full Construction Guide (PDF) [3] California Environmental Reporting System (CERS) [4]

Important

Permits must be issued before construction begins. Commercial systems require design by a licensed professional and soil testing verified by Environmental Health. Please submit three copies of your permit application. 

Supporting Documents

PDF icon OWTS Permit Application [2] (33 KB)
PDF icon OWTS Construction Guide [3] (126 KB)

Web Links

California Environmental Reporting System [5]

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Source URL: https://monohealth.com/environmental-health/page/onsite-wastewater-treatment-systems-owts

Links
[1] https://monohealth.com/sites/default/files/styles/gallery500/public/imageattachments/environmental-health/page/29328/360_f_219747651_vzd6azcz72tde4drce7fjjkakxuwrzrc.jpg?itok=WtOypdgV
[2] https://monohealth.com/sites/default/files/fileattachments/environmental_health/page/29328/1septic_app.pdf
[3] https://monohealth.com/sites/default/files/fileattachments/environmental_health/page/29328/constr_guide_conv08-2.pdf
[4] https://cers.calepa.ca.gov/
[5] https://cers.calepa.ca.gov/about-cers/help-materials/