Country property, wells, septic and acreage.

Have a well yield or flow test performed by a qualified well professional, and review the well completion report on file for depth, construction and static level. Yield varies seasonally, so ask the well professional to time and interpret the test with the dry season in mind. Water quality testing is a separate exercise from quantity.

Lenders and insurers may require specific tests. Ask early, because scheduling a well test can take longer than a standard inspection period allows.

SourceCalifornia Department of Water Resources ↗ (opens in a new tab)

Tank condition and capacity, the leach field's condition and location, evidence of surfacing or failure, the permitted design against actual bedroom count, and the maintenance and pumping history. On many rural properties the leach field's remaining capacity is the single most consequential unknown.

A septic system sized for a three-bedroom house constrains an addition that adds a fourth, which is a common and expensive surprise.

SourceState Water Board · onsite wastewater (OWTS) program ↗ (opens in a new tab)

The system has to be repaired or replaced to current standards, permitted through the local agency, and in some cases relocated. Costs vary widely with soil, slope, setbacks from wells and waterways, and whether an engineered or alternative system is required.

Replacement standards are usually stricter than the standards the original system was built to, so a like-for-like replacement is not a safe assumption.

SourceState Water Board · onsite wastewater (OWTS) program ↗ (opens in a new tab)

Not always. Physical access and legal access are different things. Legal access usually means recorded frontage or a recorded easement giving you the right to reach the parcel, and it should appear in the title report. Access rights can also arise without a recorded grant, which is exactly the kind of gap a title officer and a real estate attorney should look at. A driveway that has been used for decades is not proof of a recorded right.

Shared roads also raise maintenance-agreement questions, which lenders on some loan types will want to see documented.

General informationNo single public source governs this. It depends on the property and the contract, and this page is general information, not advice for your situation. Confirm specifics with the appropriate professional.

It is a contract restricting land to agricultural or open-space use in exchange for a reduced property tax assessment. Contracts renew automatically each year unless a notice of nonrenewal is filed, which starts a nine-year phase-out. Early cancellation is a separate, exceptional process that requires county findings and a substantial fee.

For a buyer this can be an advantage or a constraint depending on your intended use. Confirm the contract status for the specific parcel before assuming either.

SourceCalifornia Department of Conservation · Williamson Act ↗ (opens in a new tab)

State law has substantially expanded accessory dwelling unit rights, but rural parcels add water supply, septic capacity, fire access, setback and zoning constraints that can still decide what is buildable within the limits state ADU law places on local rules. Density for a full second dwelling is a separate question from ADU eligibility.

The realistic sequence is to confirm zoning, then septic and water capacity, then fire access, before designing anything.

SourceCalifornia HCD · accessory dwelling units ↗ (opens in a new tab)

Sonoma County uses several agricultural and resource designations that differ in minimum parcel size, permitted uses, density and the kinds of structures and commercial activity allowed. Two adjacent parcels can carry different designations with meaningfully different rights.

Read the designation for the specific parcel rather than for the area, then confirm permitted uses with the planning department in writing.

SourcePermit Sonoma · zoning codes ↗ (opens in a new tab)

Yes. Well construction, modification and destruction require permits from the local permitting agency, and the work must be done by a licensed contractor to state and local standards. Setbacks from septic systems, property lines and potential contamination sources apply.

In areas subject to groundwater management, additional requirements or restrictions may apply to new extraction.

SourcePermit Sonoma ↗ (opens in a new tab)

It has to be tested to know. Common tests cover bacteria, nitrates, arsenic and general mineral content, and results vary by aquifer and by depth even between neighboring properties. Treatment systems can address many issues, but they are an ongoing cost and maintenance obligation.

Test during the inspection period rather than after closing, and retest periodically as an owner.

SourceCalifornia Department of Water Resources ↗ (opens in a new tab)

Any structure that was built without a permit, converted to a use it was not designed for, or is being counted as living space. Barns converted to studios, guest quarters or rentals are often unpermitted, which affects insurance, financing and legal occupancy.

Check the permit record for every structure on the parcel, not just the main house.

SourcePermit Sonoma · permit record search ↗ (opens in a new tab)

It sets defensible space obligations and, in some zones, building requirements for materials, vents and access. It is not what insurers price from: carriers use their own address-level risk models, so a very high fire hazard severity zone designation does not by itself decide whether a property can be insured or what it will cost. Price the actual quote into your carrying cost before you commit.

Get an insurance quote for the specific address during the inspection period. Availability can differ significantly between neighboring parcels.

SourceCAL FIRE OSFM · fire hazard severity zones ↗ (opens in a new tab)

It measures how quickly soil absorbs water, one of the inputs that decide whether and how a septic system can be designed on a site. The county decides when one is required, typically for new septic design, many replacements, and before anyone should assume vacant land can be developed.

A failed or marginal result can make a parcel undevelopable for conventional systems, or require a costlier engineered alternative.

SourceState Water Board · onsite wastewater (OWTS) program ↗ (opens in a new tab)

Usually yes. Tree removal, grading, vegetation management and work near watercourses are commonly regulated, and unpermitted work can trigger enforcement and restoration requirements that far exceed the original cost.

Confirm the rules for the specific parcel before clearing anything, including work you consider routine maintenance.

SourcePermit Sonoma ↗ (opens in a new tab)

Federally backed lenders generally require flood insurance for properties in high-risk flood zones. Properties outside those zones can still flood, and coverage is often available at lower cost. Flood is not covered by a standard homeowner's policy.

Check the flood map for the exact parcel, and remember that maps are periodically revised.

SourceFEMA Flood Map Service Center ↗ (opens in a new tab)