In Tehama County, a septic tank has to sit at least 50 feet from an individual water well, and the leach field (disposal field) at least 100 feet. Property lines need 5 feet for the tank and field, and a perennial stream needs 150 feet from the field. Those septic setback distances in Tehama County come from Table III under County Code section 9.22.180, and they decide where your system can go before anyone talks about soil or tank size.
Most people find out about setbacks late. They pick a nice spot for the house, then learn the only legal spot for the drainfield is the one they wanted for the shop. We'd rather you learn it now, with a tape measure and a site plan, than after the engineer's drawings come back.
The numbers from the county table
Here's the table as the county publishes it, trimmed to the items that come up most on rural lots around Corning, Red Bluff and Los Molinos. All distances are minimum horizontal feet.
| Measured from | Septic tank | Disposal field | Seepage pit |
|---|---|---|---|
| Buildings or structures | 5 | 8 | 8 |
| Property line | 5 | 5 | 8 |
| Individual water supply well | 50 | 100 | 150 |
| Public water supply well | 100 | 100 | 150 |
| Spring | 50 | 100 | 150 |
| Drainage ditch or ephemeral stream | 25 | 25 | 25 |
| Intermittent stream | 50 | 50 | 50 |
| Perennial stream | 100 | 150 | 150 |
| Lake or reservoir | 50 | 100 | 100 |
| Drinking supply lake or reservoir | 50 | 200 | 200 |
| Cut or fill bank | 10 | 4 times bank height | 4 times bank height |
Two details trip people up. "Buildings or structures" includes porches, steps, carports, covered walks and roofed patios, not just the house. And the cut or fill bank rule is four times the vertical height of the bank, measured from the top edge, capped at 35 feet. A 6-foot cut behind a pad means 24 feet of clearance for the field.
The county's table is a living document, so check the current version at the Tehama County septic setback table before you design anything. Tehama County Environmental Health issues the permits and has the last word.
Why wells control the whole layout
On a typical five-acre parcel off Highway 99W or Gerber Road, the well is already in the ground. The 100 feet from well to disposal field is a hard circle on your site plan, and it doesn't care that your neighbor's well may sit close to the line too. Wells on the adjoining parcel count.
That's the first thing we draw. Well, then the 100-foot circle, then the creek or ditch, then the property lines. What's left is where the field can actually go. Sometimes that's a big open area. Sometimes it's a strip 20 feet wide along a fence.
If you have a seepage pit design (not common, and many soils won't allow it), the numbers jump to 150 feet from a well. For most Tehama County lots, a conventional trench or bed field is what pencils out.
Creeks and ditches: dry doesn't mean exempt
The county splits water features into three types. A drainage ditch or ephemeral stream (one that runs a day or two after rain) needs 25 feet. An intermittent stream (comes and goes) needs 50 feet. A perennial stream, the kind that runs all year, needs 100 feet for the tank and 150 for the field.
Here's where owners get surprised. That swale along the back of your lot that's bone dry in October still counts as a ditch or ephemeral stream. And in a wet January it may be moving a lot of water. Environmental Health decides how it's classified, not you, so ask early. We'd rather have the call made in November, with the ground wet and the channel visible, than guess in August.
Slopes, fill and cut banks
If you're building a pad first, the pad can wreck your septic plan. Cut a 5-foot bank for a house pad and you've just created a 20-foot no-go zone for the disposal field above or below it. Fill is the same. Plan the pad and the septic layout together, not one after the other. Our grading and site prep work and our septic installation work are services we do together, which is why we push owners to settle both on one drawing.
This is also why we'd rather not start excavating a leach field right after a big storm. Saturated clay smears, and a smeared trench wall doesn't take water the way the soil test said it would. Two dry weeks is a good rule, and if the forecast turns, we'd wait.
When the setbacks leave you nowhere to go
Sometimes the table beats the lot. A narrow parcel with a well in the wrong place, a creek along one edge and a steep bank on the other can leave no compliant spot for a conventional system. Your options then are usually these:
- Move the house or shop footprint so the field has room.
- Look at an engineered or alternative system, which Environmental Health has to approve and which costs more.
- Ask whether a shared or off-site field makes sense with a neighbor.
- Walk away from the parcel, if you haven't bought it yet.
That last one is the honest answer more often than people like to hear. If you're under contract on raw land, get the perc test and a setback sketch before the contingency period ends. The percolation test tells you if the soil works. The setbacks tell you if there's room to use it.
What to bring to the planning conversation
A site sketch with the well, the house location, any creeks or ditches, and the property lines gets you most of the way. Add the approximate height of any bank you plan to cut. If you're rebuilding after a burn, tell us where the old system was, and ask Environmental Health early whether it can be reused or has to be redesigned to today's table.
Walberg, Inc. has worked across Tehama, Butte and Shasta counties since 1999, and each county sets its own rules. Tehama's numbers above are Tehama's, so don't assume they carry over to a parcel in another county. For the state-level rules that sit above the county ones, see the State Water Board's onsite wastewater treatment program.
Common Questions
How far does a septic tank have to be from a well in Tehama County?
Under County Code 9.22.180, the septic tank must be at least 50 feet from an individual water supply well and 100 feet from a public water supply well. The disposal field must be at least 100 feet from either. Seepage pits need 150 feet.
How close can a leach field be to a property line in Tehama County?
The disposal field must be at least 5 feet from a property line, and a seepage pit at least 8 feet. The septic tank also needs 5 feet. Those are minimums from the county table, and Environmental Health makes the final call on your parcel.
How far does a septic system need to be from a creek?
It depends on the type of creek. A drainage ditch or ephemeral stream needs 25 feet, an intermittent stream needs 50 feet, and a perennial stream needs 100 feet for the tank and 150 feet for the field. A dry channel can still count, so have Environmental Health classify it.
Can a septic tank be under a driveway or patio?
The county table treats roofed patios, carports and covered driveways as structures that need setbacks. Even where a tank could technically sit under paving, access for pumping matters, and we'd steer you away from it. Ask us and Environmental Health before you pour anything.
The bottom line
Draw your well, creeks, property lines and any planned cut banks on one sketch before you lay out the house. The setbacks will tell you where the field can go, and the house should work around that, not the other way around. When you have a sketch, request a free estimate from Walberg, Inc. and we'll walk the lot with you. If your project also needs a pad or driveway, we can plan the dirt work with it, and you can see how that looks on our projects page or in our Corning service area.