What matters most
Inyo County Environmental Health permits and inspects residential septic systems and requires a detailed plot plan with the application. Soil permeability, unsaturated depth, groundwater, setbacks, usable area, proposed flow, and the County’s site evaluation determine whether a conventional or alternative approach may be considered.
Key takeaways
- The current County page directs applicants to its OpenGov permitting portal.
- The Inyo LAMP describes a general starting pattern for soil profiles and percolation tests, but County staff determine actual locations and quantity.
- Plans must preserve a replacement area equal to 100% of the dispersal field.
- Some communities or areas have additional prohibition or Water Board review considerations; obtain current parcel-specific direction.
Application and plot-plan basics
A useful initial package includes the address and APN, property boundaries and easements, existing and proposed structures, wells, nearby water features, the proposed primary dispersal field, a replacement area, separation distances, use, and anticipated wastewater flow.
The LAMP describes County review of the completed application, plot plan, and fee before the site evaluation. Do not begin system construction before the required evaluation and permit authorization.
How many soil profiles and perc tests are needed?
The Inyo LAMP describes a general starting point of two soil profiles and two percolation tests in the proposed construction area, plus one profile and one test in the replacement area. It generally discusses profile excavations to ten feet.
Those numbers are not a universal promise. The administrative authority determines the number and location during the site evaluation, may waive work in some circumstances, and may require more where conditions vary or tests do not establish suitability.
Conventional and alternative systems
Where conditions allow, a conventional septic tank and dispersal field may be used. Where permeability, groundwater separation, available area, flow, or setbacks do not support that system, an engineered alternative may be required—or the proposed development may need reconsideration.
Published baseline lot-density provisions are not automatic approval. The system type and size depend on site evaluation, usable area, soil, separation, and design flow.
Special prohibition and review areas
The Water Board-hosted Inyo LAMP identifies areas around Aspendell, Mountain View Estates, the Rocking K Subdivision, and the City of Bishop where additional prohibition or Water Board review considerations apply to new leaching and percolation systems.
Boundaries, sewer availability, and agency interpretation can change. Applicants in or near these areas should obtain current written direction from Inyo County Environmental Health before authorizing testing or design.
Confirm who may perform the testing
The LAMP contains provisions that vary with work and site complexity. It describes qualified-professional supervision for the formal procedure and also allows administrative approval of certain licensed contractors for uncomplicated sites. Alternative-system sites call for an appropriately qualified licensed professional.
Confirm the accepted tester and responsible report preparer with Inyo County before scheduling field work. The person excavating is not necessarily the professional responsible for locations, procedure, interpretation, and submittal.
What to send Calicore for a proposal
Send the APN or address, proposed building use and bedroom count, preliminary site layout, water-source information, access, grading, prior records, and written Environmental Health direction. Calicore is based in Bishop and can combine related field tasks where the scope and agency process allow.
Services may include septic soil testing, OWTS design support, topographic mapping for civil design, grading and drainage, and permit coordination.
A parcel’s acreage alone does not establish septic suitability. Soil, groundwater, slope, setbacks, flow, usable primary and reserve area, and agency review all matter.
This page provides general educational information based on agency materials available when reviewed. Septic, grading, building, and wastewater requirements can change and may vary by parcel, jurisdiction, proposed use, site conditions, and agency interpretation. The permitting agency determines the required scope and whether a project is approved. Confirm current requirements before testing, design, excavation, or construction.
Frequently asked
Questions about this topic
How many perc tests does Inyo County require?+
The LAMP describes a general starting point of two profiles and two tests in the proposed area and one of each in the replacement area. County staff determine the actual scope and locations.
Is a 15,000-square-foot lot automatically approved for septic?+
No. Published density criteria do not override soil, groundwater, setbacks, design flow, usable area, and County review.
Does my plan need a replacement area?+
Yes. The LAMP requires a 100% replacement dispersal area on the plans.