Percolation Testing and Septic Design in Inyo County California
If you’re planning a new home or septic system installation in Inyo County, California, understanding the county’s requirements for percolation testing, septic sizing, and septic design is essential. While each California county has unique rules, all septic systems must follow state standards to protect public health and the environment. Following proper procedures ensures your system functions safely and receives county approval.
Percolation Testing: Understanding the Process
Percolation testing measures how quickly water drains through the soil on your property. The results determine if the site is suitable for a septic system and guide septic sizing and septic design. In Inyo County, all percolation tests must be conducted under the supervision of a qualified professional and in accordance with the Inyo County Local Agency Management Program (LAMP), which aligns with California OWTS and other state requirements.
Test Pits: Inspection and Purposes
Before conducting a percolation test, test pits must be prepared. Test pits are inspected by a qualified professional and serve multiple critical purposes:
Soil Profile Evaluation: Inspecting the soil layers helps determine texture, composition, and permeability, which are key factors for septic sizing and septic design.
Bedrock Identification: Test pits reveal the depth to bedrock or other restrictive layers that could limit the placement of a leach field.
Water Table Determination: Test pits allow professionals to measure the depth to groundwater, ensuring the septic system will operate safely and avoid contamination risks.
Overall Site Suitability: The combination of soil profile, bedrock depth, and water table information ensures the site can support a septic system that complies with Inyo County requirements.
Who Can Inspect and Conduct the Perc Test
All percolation tests, including test pit inspections, must be overseen by a Registered Environmental Health Specialist (REHS), a licensed Professional Civil Engineer (PE), a registered Geotechnical Engineer (GE), or a licensed Professional Geologist (PG).
How Test Pits Are Dug
Test pits can be dug by a licensed contractor, the property owner, or STL. STL can dig and prepare pits under professional supervision to meet county requirements. Test pits are typically 18 to 24 inches wide and 7 to 8 feet deep, depending on soil conditions and the depth of the proposed leach field.
Performing the Percolation Test
Once test pits are inspected, the percolation test is performed by adding water and measuring how quickly it drains through the soil in minutes per inch. These results determine septic sizing and the type of system appropriate for your property. Detailed logs of test locations, soil conditions, and percolation rates are required for submission to Inyo County Environmental Health.
Septic Design and Sizing
Septic system design in Inyo County follows local LAMP requirements while adhering to California state standards:
System Type: Based on soil and site conditions, systems may be conventional gravity, pressure distribution, or an approved alternative.
Septic Sizing: Leach field size is calculated using percolation rates and projected wastewater flow.
Setbacks and Compliance: Designs must meet minimum distances from water sources, structures, and property lines.
Every County is Unique, But All Follow State Standards
While Inyo County has specific procedures and requirements, every California county must comply with state standards to protect public health. Differences between counties may include test pit preparation, percolation testing procedures, and documentation requirements, but the overall process of soil evaluation, percolation testing, and proper septic system design is consistent statewide. Inyo County’s LAMP which outlines all these requirements can be found here: https://www.waterboards.ca.gov/rwqcb6/water_issues/programs/owts/docs/lamp_tracking/inyolamp.pdf
How STL Can Handle It All
At Soil Tests Laboratory, we provide a full-service solution for Inyo County property owners. Our team includes licensed Professional Civil Engineers who can manage every step—from test pit preparation and inspection, percolation testing, to complete septic sizing and septic design. By working with STL, you can be confident your system is professionally designed, compliant with county and state standards, and ready for approval—making your project seamless from start to finish.
Contact us for a price at: Info@soiltestslab.com or call (951) 345-3509
