Jennifer Bardenheuer, REHS
So, you’ve found your perfect slice of California heaven. A piece of land with a view and a few oaks and the price is right! Right?! But much of rural California has no public sewer, so one question decides whether you can build a home on it at all: can the parcel support a permitted septic system?
Without an approved septic site, the county generally won’t issue a building permit for a house. That’s why I tell buyers to answer the septic question before they close, not after.
In California, septic systems (onsite wastewater treatment systems, or OWTS) are regulated locally. Each county’s environmental health department, or in some places the city, permits them under state standards and its own local rules, so the process and testing can differ from one county to the next.
A parcel can look perfect and still fail
What makes a good septic site is mostly underground, so you can’t judge it from the driveway. Common problems include:
Poor soils. Soil that’s too tight, like heavy clay, holds water. Soil that’s too coarse, like loose gravel, lets wastewater pass through before it’s treated.
Shallow groundwater or bedrock. The leach field needs enough good soil below it. A high water table, especially in wet months, or rock close to the surface can rule out an area.
Steep slopes. Steep ground limits where a leach field can go and may call for a different design.
A smaller lot. Sizing of the system is largely based on bedroom count, and the system has to fit, along with room for a replacement system.
Setbacks. The system has to stay certain distances from wells (yours and the neighbors’), creeks, ponds, property lines, easements, buildings and cut banks. On a small or narrow parcel, those distances add up fast.
Flood areas and drainage. Low spots, drainage courses and flood zones can be off limits.
What a pre-purchase septic evaluation involves
These are some variables I look at when I evaluate a parcel for a buyer:
Records and rules. I start with what’s already on file with the county and what that county’s rules require. Because every California county runs its own program, I don’t assume.
Site visit. I walk the property to look at slopes, drainage, wells, creeks, easements and likely house and septic locations.
Soil profile holes. An excavator digs test holes so I can see and describe the soil layers and check for groundwater, bedrock or other limits.
Percolation (perc) tests, where required. A perc test measures how fast water soaks into the soil. Not every county or site requires one, but many do.
Mapping a usable area. The goal is to find an area that meets the setbacks and soil requirements for the primary leach field, plus a reserve area for a future replacement. Many counties require that reserve.
Timing: do it during your contingency period
The best time to do this is during your due diligence or contingency period, while you can still walk away or renegotiate. A few things affect timing:
Seller permission. Testing means digging on someone else’s land, so you’ll need the seller’s written permission to access the property.
Excavator scheduling. Profile holes and perc tests need an excavator on site. I coordinate that as part of testing.
County scheduling. Some counties want to witness the testing, which means fitting into their calendar.
The season. Some counties want testing done when groundwater is highest, often in wet months. A test done in a dry month may not tell the whole story.
If that looks tight, ask for a longer contingency up front.
Interpreting the results
The results usually land in one of three places:
A conventional system works. This is generally the simplest and least expensive option.
An alternative or engineered system is needed. Sites with limits may still work with a different design, such as a pressure-dosed or mound system, or added treatment. These usually cost more to build and may come with ongoing maintenance, monitoring or permit requirements.
A septic system isn’t feasible. Sometimes the site just doesn’t work. It’s far better to learn that before you buy.
Watch out for old perc tests and approvals
Sometimes a listing says the parcel “perked” or “has an approved septic site.” That’s a good start, but verify it with the county’s environmental health department. An old test may have been done under older rules, may not cover where you want to build, or may have expired. An earlier approval may not carry over to a new owner or a new project.
Questions to ask before you make an offer
Is public sewer available, or will this need septic?
Are there any septic records, perc tests or approvals on file with the county? How old are they?
Is there a well on the property or on neighboring parcels?
Are there creeks, ponds, easements or flood areas on or near the parcel?
Will the seller allow testing, and does my contingency period allow enough time?
How many bedrooms am I planning? Do I want an ADU, a shop or a future lot split? Bigger plans may need more septic area.
Let’s check before you buy
I help land buyers all across California, including Tuolumne, Calaveras, Mariposa, Yolo, Amador, Contra Costa and Alameda counties, find out whether a parcel can support a septic system and what the county will need.
If you’re looking at a piece of land, give me a call at (209) 536-8048 before your contingency runs out. We can talk through the parcel and the best next step.
— Jennifer Bardenheuer, REHS
