SEPTIC SYSTEMS
​​Common Questions Related to Septic Systems:
When do you need an approved qualified professional?
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When you are developing a vacant lot and there is no sewer system nearby.
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If your property is currently on Septic and you are adding an ADU or addition to your property that will increase the total property’s bedroom count.
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If you are planning to split your lot to create additional dwellings (Using SB-9 or Traditional Methods)
What are the different types of OWTS?
The County of San Diego allows different types of OWTS that include:
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Standard Systems (Leach Lines, Deep Bed Dispersal Systems)
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Vertical Seepage Pits (These systems are only allowed in certain areas)
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Supplemental Treatment Systems (Drip Dispersal Systems)
What type of System do I need for my project?
The proposed OWTS system is dependent on your project’s scope (number of proposed bedrooms), parcel size, groundwater limitations, percolation rates, space available to accommodate the septic system, etc. We are happy to help you determine the correct type of system and answer any questions you have.​
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How much do you charge for percolation testing and septic design?
Each septic project comes with its own challenges, and these challenges determine the final cost. At Strike Engineers, we like to be as transparent as possible, which is why we post a range for our fees related to septic as-built locates, percolation testing, and septic design.
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Septic As-Built Locates: $1,800.00 - $3,000.00
Percolation Testing: $4,500.00 - $8,050.00
Septic Design: $4,000.00 - $5,200.00
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How much does it cost to install a Septic System?
It really depends on the type and size of the system, and we always suggest getting quotes directly from an approved septic contractor. We work closely with contractors to help estimate the range of installation costs. Based on our research, we estimate that a standard system installation will range from $30,000.00 - $40,000.00, while a supplemental treatment system installation will range from $55,000.00 – $65,000.00.
The County of San Diego Septic System Approval Process
(A Step-by-step overview)
Here’s our step-by-step overview of what we do to get a septic system (onsite wastewater treatment system, OWTS) approved under the current San Diego County Local Agency Management Program (LAMP), effective February 1, 2025. (County of San Diego)
1. Preliminary Site Evaluation & Planning
- We can help you determine if your property is served by a public sewer system or not. Only properties without sewer access need an OWTS. If your property is within 200 ft of a sewer system the local jurisdiction will ask you to connect. We can help you with the permitting for sewer connection as well.
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- We will conduct a desktop study of your project to get an understanding of the existing site characteristics including soil type, possible percolation capacity, groundwater depth, topography/slope, distance to surface waters, and nearby environmental sensitivity. The LAMP evaluates septic suitability on a per-site basis.
2. Conduct Percolation Testing
- We will complete a percolation test permit application and submit it to the County of San Diego Department of Environmental Health and Quality. Once approved and the application fee of $952 is paid, we will notify the County of when the pre-soak and percolation test will be conducted.
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- Percolation testing is conducted over the course of two days. On day 1, the percolation test holes are drilled and presoaked with water for a minimum of 4 hours. On day 2, the percolation test is conducted to determine a percolation rate. This percolation rate will contribute to the design of your septic system. A County Inspector will be on site while we are conducting either the presoak or percolation test.
- Once we complete percolation testing, we compile the field data into an official percolation test results form, and we will submit to the County of San Diego.
3. Prepare and Submit the OWTS Layout Report (Design)
- As a licensed OWTS Professional (for standard systems, vertical seepage pits, and supplemental treatment systems) we are qualified to design your system based on tested percolation rates.
- Our design will include, but not be limited to, septic tank size, disposal field/leach lines or drip dispersal, spacing, separation from groundwater, etc. Supporting calculations will be prepared and included in the OWTS Layout Report, which will be submitted to the County of San Diego Department of Environmental Health and Quality (DEHQ) for review.
- Once we have compiled your application with calculations and design/layout, we will submit the completed “OWTS Layout Report” (Septic Application) to the San Diego County Department of Environmental Health and Quality (DEHQ) for review. The County Fee for a new layout application is $1,789.
4. County Review and Approval of Layout
- Once submitted, DEHQ reviews the layout/package. Under the 2025 LAMP there will likely be more involvement from county agents, potentially including inspections of test holes or site visits before design approval.
- If approved, DEHQ issues a Layout Approval (often identified by a Record ID). This approval confirms that the design meets LAMP requirements for that parcel/site.
- This is the final step of the permit and approval process and where you will choose a septic contractor to install your system. We work with septic contractors throughout the County of San Diego and are happy to give you contractor referrals.
5. Apply for and Obtain the Installation Permit
- With the approved layout, you can submit an “OWTS Installation Permit Application” form to DEHQ and pay the County fee of $994.
- Ensure that installer is properly licensed: a licensed contractor (e.g., C-36, C-42, Class A or B) must perform the installation — or if owner is acting as builder, they must follow the rules and understand restrictions. We will only refer you to a properly licensed, approved qualified service provider.
6. Inspections & Final Certification / “As-built” Documentation
- After installation, DEHQ inspects the work to ensure compliance with the approved design and LAMP standards.
- A “final approval” typically requires written certification and as-built drawings from the design engineer (especially for supplemental treatment systems). We are happy to help you with this on a time & material basis.
7. Operation, Maintenance & Long-term Compliance
- For systems requiring monitoring/maintenance (e.g., supplemental treatment systems), the owner must hold a valid annual operating permit at all times. Use of the system without a valid permit is a violation.
- Owners must comply with all conditions of the installation permit, including monitoring, maintenance, operation, and record-keeping.