Dreaming of more elbow room, space for horses, and a slower pace just minutes from Silicon Valley? You are not alone. Many buyers look to San Martin for acreage and equestrian living, only to find that local rules, wells and septic, and hazard zones can shape what is possible. In this guide, you will learn how to protect your plan with a practical checklist, local resources, and the key decisions that matter most. Let’s dive in.
The big picture: lifestyle and limits
San Martin is an unincorporated, rural community guided by Santa Clara County’s General Plan, which preserves a non‑urban character. That rural charm is real, but so are the rules that come with it. The County uses zoning and special combining districts in San Martin to direct how land can be used and developed. You will want to confirm the exact status of any parcel early in your due diligence. You can review the County’s planning framework and local processes on the County’s General Plan and ordinances page.
Bottom line: buying acreage in San Martin can deliver space and lifestyle close to Silicon Valley, but entitlements, water and septic capacity, and hazard‑mitigation obligations often determine what you can actually build and operate.
Here is your short checklist to keep handy:
- Zoning and recorded notices
- Well type, capacity, and water quality
- Septic system records and feasibility
- Fire hazard and defensible space
- Flood risk near creeks and drainage ways
- Easements, access, and private road agreements
- Barns, outbuildings, and any unpermitted work
Start with entitlements and zoning
Before you picture new barns, an arena, or a second dwelling, verify the parcel’s zoning and any combining districts. In much of South County, County ordinance language includes an “Onsite Agriculture” requirement that can affect new residential development on parcels over five acres. On those parcels, a new single‑family residence may only be allowed as ancillary to onsite agriculture, and the term “onsite agriculture” is defined with minimum activity thresholds. The County also records a notice to memorialize that restriction. Review the code language and treat this as a critical check for your target parcel by starting with the County and the zoning and ordinance text.
Practical tip: ask a County planner to confirm the parcel’s base zoning, any San Martin combining district overlays, and whether a recorded notice applies to new residential use. If you plan to subdivide, add a primary home, or claim a residential entitlement on 5+ acres, confirm whether current agricultural activity meets the County’s test.
Taxes, easements, and right‑to‑farm notices
Some San Martin parcels participate in the California Land Conservation Act, known as the Williamson Act, or carry open‑space easements. Enrolled parcels gain agricultural tax valuation but are restricted to agricultural and compatible uses. Buyers should confirm enrollment because it affects permitted uses and the tax basis. County guidance also notes that certain equine uses, such as boarding or training, may not be considered a commercial agricultural commodity for Williamson Act purposes. Learn more on the County’s page for Williamson Act and open‑space easements.
Expect standard local disclosures in escrow, including right‑to‑farm notices and, where applicable, private well or Williamson Act disclosures. Read them carefully. For a general overview of local advisory items, see the regional disclosure advisory used by many transactions in this area, such as the RSMSCA advisory overview.
Water: public system vs private well
Much of San Martin relies on groundwater through private wells or small water systems. Each option has different implications for inspections, permits, quality, and financing. If the property has a private well, request the permit history, recent lab test results, and pump information. The local water agency recommends annual testing and offers guidance for private well owners on permitting, construction, and destruction rules. Start with Valley Water’s Well Ordinance and private well owner resources.
Groundwater quality varies by location and over time. Valley Water reports that South County, including areas of Morgan Hill and San Martin, has seen localized issues such as elevated nitrate and perchlorate levels. Private wells do not receive the same routine testing as public systems, so make lab testing a priority. Review Valley Water’s notes on groundwater quality and testing recommendations and obtain recent results during escrow.
Recommended minimum testing panel for a private well:
- Nitrate and nitrite
- Total coliform and E. coli
- Arsenic
- Hardness
- Consider perchlorate and other local contaminants if the parcel is near known monitoring areas
Wastewater: septic systems and feasibility
Most acreage in San Martin uses onsite wastewater treatment systems. The Santa Clara County Department of Environmental Health (DEH) must clear septic feasibility for new development and for projects that change sewage generation, including many additions or ADUs. DEH’s process often includes a site assessment, soil analysis, and percolation testing. For marginal sites, extra geotechnical or hydrogeologic reports may be required. DEH typically stamps OWTS design plans during the building‑permit process, and an OWTS construction permit is issued with the building permit. You can review DEH’s process on the OWTS clearance page.
During escrow, request copies of as‑built septic plans, the most recent septic pumper’s report, and a 30‑minute water test if you plan to reuse the system. If an ADU or bedroom addition is part of your plan, consult DEH early so you know what tests or upgrades they will require.
Inspections that matter most
Use this prioritized list to structure your due diligence. Start the first three items as soon as possible.
- Zoning and recorded notices
- Confirm base zoning, combining districts, and any recorded notice affecting new residences or use. Review the ordinance text for “Onsite Agriculture” and San Martin combining rules through the County and the zoning code reference.
- Septic and DEH records
- Order a septic pumper’s report, request as‑builts, and ask DEH about required testing or design upgrades. See DEH’s OWTS clearance steps.
- Private well inspection and lab testing
- Verify well permits, capacity, and water quality. Valley Water’s private well guidance outlines owner responsibilities and permits.
- Barns and outbuildings
- Inspect structure, electrical, water supply to troughs, ventilation, animal containment, and drainage. Verify whether buildings were permitted. The County building permit packet explains inter‑agency clearances such as DEH or Roads and Airports. Review the building permit requirements.
- Survey and title review
- Confirm boundaries, easements, access, and any shared road or well agreements. A survey and title exceptions can reveal limits that affect usage and financing.
- Fire hazard and defensible space
- Check whether the parcel lies in a high or very high fire hazard area. New construction and major remodels in these zones can trigger stronger building standards and defensible space rules. See local maps and guidance via the County Fire Department’s LRA wildfire map portal.
- Flood risk and Llagas Creek
- Some parcels near Llagas Creek are affected by flood risk and recent flood‑protection improvements. Review the status of the Upper Llagas Creek Flood Protection project and check current FEMA mapping.
- Environmental hazards
- If your parcel is near known groundwater plumes or past industrial sites, search local and state records. Valley Water’s groundwater quality page explains where to find monitoring data.
Equestrian must‑haves to verify
If horses are central to your plan, inspect with an equine lens. Focus on function, safety, and drainage.
- Stall layout and ventilation in barns
- Drainage from wash racks and around paddocks
- Manure storage or composting location and runoff controls to protect creeks
- Fencing condition and suitability for horses
- Gates, driveway width, and turning radius for hay and manure trucks
- Trailer parking and safe loading areas
If you plan commercial boarding or training, confirm whether a separate use permit is required and how added activity affects water and septic demand. If the parcel is under a Williamson Act contract, confirm which equine activities are compatible on the County’s Williamson Act program page.
Ongoing costs to plan for
Rural properties carry recurring costs that scale with herd size and acreage. Build a reserve for the following:
- Septic maintenance. Pumping and inspection are routine, often every 3 to 5 years depending on usage.
- Well service and treatment. Plan for annual lab tests and periodic pump or control replacements.
- Fencing and pasture care. Expect repairs, reseeding, weed control, and irrigation for paddocks.
- Hay, bedding, and manure removal. Costs track herd size and local market conditions.
- Fire mitigation. Tree and brush clearance for defensible space can affect insurance and is often an annual task in high hazard areas. Check the LRA wildfire guidance for local requirements.
- Private road maintenance. If you share a private road, review the agreement and budget for your portion of upkeep.
Permits you may need
Most projects on acreage require coordination across County departments. Expect some or all of the following:
- Building permit for houses, major remodels, or barns with electrical or plumbing. See the County’s building permit submittal.
- Septic plan review and OWTS construction permit through DEH. Refer to DEH’s OWTS clearance.
- Well permits for new construction, destruction, or standby status through Valley Water. See well owner and permitting guidance.
- Use permits or Architectural and Site Approval for uses not by right or for commercial equestrian operations. Review the County’s rules and the zoning code reference.
- Recorded notices for residences on 5+ acre parcels where dwelling use is ancillary to onsite agriculture. Confirm with the County and through title.
Quick due diligence checklist
Print this and use it during early inspections and calls:
- Run the parcel APN through County planning to confirm base zoning, any San Martin combining districts, and recorded notices. Start with the County’s General Plan and ordinance portal and request a planner pre‑check.
- Order a septic pumper’s report, request as‑builts, and ask DEH about needed tests or upgrades for your intended use. See DEH’s OWTS guidance.
- Schedule a well inspection and lab testing panel. Review owner rules on Valley Water’s private well resources and read about groundwater quality considerations.
- Order a boundary survey and request preliminary title exceptions. Confirm easements, access, and any shared road or well agreements.
- Verify fire hazard status and any defensible space obligations using the County Fire LRA map.
- If near Llagas Creek, check current risk and the status of the Upper Llagas Creek Flood Protection project.
- Have a qualified equine facilities specialist walk the property before you waive contingencies if you plan to keep or board horses.
Why work with a South County acreage team
Country properties demand a different playbook. You want an agent who knows the local entitlement rules, can coordinate with DEH and Valley Water, and can pull the right specialists fast. With a team model and deep South County roots, you get faster answers, better vendor coverage, and a smoother path from offer to close.
If you are weighing two parcels, planning an ADU, or mapping out an arena and barn layout, a responsive, local team can help you pressure‑test the plan against wells, septic, zoning, and hazards before you commit.
Ready to find the right acreage or equestrian property in San Martin? Reach out to The Palacios Group to start a focused search and a clean, confident due diligence plan.
FAQs
What does “Onsite Agriculture” mean for 5+ acre parcels in San Martin?
- County code often requires new residences on parcels over five acres to be ancillary to onsite agriculture, with activity thresholds and a recorded notice that buyers should verify through planning and title.
How do I verify a private well before I buy?
- Request the well’s permit history, recent lab tests, and pump details, and follow Valley Water’s private well guidance on permitting, testing, and destruction rules.
What septic documents should I ask for in escrow?
- Ask for as‑built septic plans, the latest septic pumper’s report, and a 30‑minute water test if reusing the system; consult DEH for feasibility and required upgrades.
Can I add an ADU on acreage in San Martin?
- It depends on zoning and septic and well capacity; DEH must clear projects that change sewage generation, so consult DEH early to learn testing and design requirements.
How do I check fire hazard and insurance implications?
- Look up the property on the County Fire LRA map to see hazard levels and defensible space rules, which can affect building standards and insurance availability.
Is horse boarding considered an agricultural use under the Williamson Act?
- County guidance indicates boarding or training may not qualify as a commercial agricultural commodity under the Williamson Act, so confirm compatibility before you buy.
