A prospective buyer's summary of 3845 Bloomfield Road — a 51.15-acre agriculturally-zoned parcel on the south side of Bloomfield Road, just southeast of Burnside Road, in the Twin Hills area of west Sonoma County. This brief consolidates the public record (Permit Sonoma, Sonoma County Assessor & GIS, Cal Fire, DWR) into the facts that matter for a purchase decision — with particular attention to the two items that drive diligence here: the water/well situation and the engineered motocross track and its lapsed grading permits.
What it is: a mid-size, legal-nonconforming agricultural parcel with a small 1925 farmhouse, two 1971 outbuildings, a county-standard driveway, and an engineered, permit-graded motocross track the owners built between 2009 and 2015. It carries the Valley Oak Habitat (OAK) and Scenic Resources (SR) combining districts but no riparian-corridor overlay — no designated stream crosses the land. Hazards are benign (moderate fire zone, neither floodway nor floodplain, very-low liquefaction).
The two things a buyer must underwrite: (1) water — the parcel runs on a grandfathered, undocumented 1925-era well with no flow test or water-quality data on file; and (2) the motocross track — its three grading permits all expired without being finaled, so any plan to keep, modify, or remove it has a defined county path and cost that should be priced into the offer. Both are covered in detail below.
The parcel is zoned LEA B6 160 (Land Extensive Agriculture, 160-acre minimum density). At 51.15 acres it sits well under that minimum, so it is a legal nonconforming lot. The practical consequence: the existing 1925 dwelling is a legal nonconforming use that may be maintained, repaired, and in most cases replaced in place, but a buyer generally cannot layer a brand-new primary residence on top of the existing one — this sub-160-acre LEA constraint is the dominant cap on residential development potential. Confirm the specific replacement/expansion path with Permit Sonoma before pricing any residential upside.
Overlays add review, not prohibition. OAK (Valley Oak Habitat) means removing or disturbing valley oaks triggers a permit; the standard approach is to preserve in place and design around them. SR (Scenic Resources) adds a height/materials/visibility review for anything visible from Bloomfield Road. Neither is a hard "no," but both add a step. The parcel does not carry the RC50/50 riparian overlay — no designated stream crosses it.
Soils & terrain. The land grades from flatter Steinbeck loam (SnD2, 9–15%) near the road up to steeper Los Osos clay loam (LsE, 15–30%) toward the eastern ridge, with a "Mostly Landslide" rating. The lower SnD2 band is classed Farmland of Statewide Importance and is the same vineyard-suitable belt as the adjacent 5 Wells / 3545 Bloomfield vineyard — relevant if a buyer is evaluating plantable upside. The clay-loam-on-slope profile is exactly why any grading on this parcel requires engineered cut/fill, drainage, and erosion control (see the track section).
Hazards are mild. Moderate Fire Hazard Severity Zone in the Cal Fire State Responsibility Area; FEMA Zone X (minimal flood, outside the SFHA); neither floodway nor floodplain; Very Low liquefaction; no overlap with the 2017/2019/2020 fire perimeters.
The assessor records three structures totaling 2,352 sq ft. No building, septic, or well permits exist in the Permit Sonoma system — the structures pre-date it.
| Structure | Size | Year | Notes |
|---|---|---|---|
| Principal residence | 804 sq ft | 1925 | 2 BR / 1 BA, low-average class. Small; effectively a teardown/replacement candidate for most contemporary uses (subject to the LEA legal-nonconforming path). |
| Detached garage | 396 sq ft | 1971 | — |
| "Other structure" | 1,152 sq ft | 1971 | The substantive secondary building — likely a barn / equipment shed. Identify and assess on a site walk. |
Permitted additions since 2008: a new + upgraded driveway entrance built to county standard (ENC09-0030, finaled), a recorded boundary survey (R/S 13-126, 2013), and the motocross track. No documented ag-exempt outbuildings (no AEX filings) — anything beyond the three listed structures is pre-system, ≤120 sq ft exempt, or unpermitted, so walk the site before pricing.
This is the single biggest open question on the parcel. The property is served by a grandfathered well of 1925 vintage with no permit, no flow test, and no water-quality data on file at Permit Sonoma. There is no surface water right, no irrigation district, and no municipal water — the parcel is entirely on its own groundwater. For a 51-acre property, the well's yield and quality are make-or-break for any use beyond the status quo, and they are currently unverified.
What the public record does tell us (favorable backdrop):
What a buyer must do (well diligence checklist):
Like the well, the septic system is the original grandfathered 1925 system with no SEP record in Permit Sonoma. It serves the existing 804 sq ft dwelling under grandfathered status. Any new dwelling, expanded bedroom count, or change of use triggers a fresh septic capacity review (Sonoma sizes systems by bedroom count) and likely a new on-site wastewater permit. The clay-heavy soils mean a buyer should not assume a conventional system will perc for an expanded program — a soils/perc evaluation should be part of diligence if expansion is the plan. Verify current system location, type, and condition on the site walk.
Between 2009 and 2015 the owners built an engineered motocross track on the parcel, designed by Adobe Associates (a Santa Rosa civil-engineering firm) to handle the clay-loam slopes with proper cut/fill, drainage, and erosion control. The track is real, professionally graded, and described in the final permit as "@ 100%" complete. The complication for a buyer is in how the permits closed out — or didn't.
| Permit | Type | Filed | Status | Description |
|---|---|---|---|---|
| ENC09-0030 | Encroachment | 2009-02 | Finaled ✓ | New + upgraded driveway entrances to county standard (south side of Bloomfield Rd) |
| GRD09-0106 | Grading | 2009-06 | Expired | "Grading for moto-cross track" |
| GRD12-0080 | Grading | 2012-06 | Expired | "To complete GRD09-0106 grading for moto-cross track" |
| R/S 13-126 | Record of Survey | 2013-12 | Map approved | Boundary survey, recorded Book 762 Maps 11 |
| GRD15-0104 | Grading | 2015-06 | Expired (2018) | "To complete prior grading for moto-cross track @ 100%" |
The key facts: all three grading permits (GRD09 → GRD12 → GRD15) expired without being finaled — a re-pull-instead-of-close-out pattern. At the same time, there is no code-enforcement case on file (no VBU/VPL/COD record): Permit Sonoma is currently treating the track as a permitted, not a violating, use. So the track exists in a stable-but-unclosed state. The engineered grading plans are archived (Accela document box 14528, document IDs 4738926 & 4740155) and the Record of Survey is at the County Recorder — both pullable for cut/fill volumes, drainage design, and exact track footprint.
Bottom line: the track is value-additive for a motocross household and a priced remediation item for everyone else. Either way, the lapsed-permit status means a buyer should resolve the track's standing with the County before close rather than inherit ambiguity — the cost is bounded and known, not open-ended.
The parcel last sold in October 2008 for $1,100,000 ($21,506/acre) and is currently assessed at $1,421,692. The most directly relevant transaction is the adjacent 4201 Bloomfield Road, which traded in December 2025 for $2,485,000 across 46.15 acres — $53,847/acre. Applied straight-line to this parcel's 51.15 acres, that implies roughly $2.75M, before adjusting for differences in improvements (4201 has a working residence; 3845 has only the small 1925 farmhouse) and the track.
| Comparable | Date | Price | Acres | $/ac | Note |
|---|---|---|---|---|---|
| 4201 Bloomfield Rd (adjacent) | Dec 2025 | $2,485,000 | 46.15 | $53,847 | The comp — directly adjacent, similar size, fresh |
| 3545 Bloomfield (5 Wells Vineyard) | Active | $6,500,000 | 72 | $90,278 | Immediate neighbor; estate home + planted vineyard; cut from $10.5M |
| 12760 Green Valley Rd | Listed 2024 | $3,499,000 | 80 | $43,738 | Best raw vacant-ag-land $/ac benchmark |
| 2836 Bloomfield Rd | Jul 2024 | $2,699,000 | 3.9 | $691,795 | Small-lot residential estate (house + barns) |
| 4050 Bloomfield Rd | Dec 2017 | $1,099,000 | 5.23 | $210,134 | Small residential parcel |
$/acre tiers in this corridor (2023–2026): raw vacant ag land at 50–100 ac runs $25K–$50K/ac; plantable-but-unplanted vineyard-belt land $50K–$80K/ac; land with a developed vineyard + estate home $90K–$160K/ac. 3845 sits in the first-to-second tier.
Independent buyer-side estimate: a working as-is value range of $2.5M–$3.0M, capped by the LEA-160 constraint on new residential development and softened by signs of cooling at the high vineyard end (5 Wells' 38% list-price cut). Vineyard-development potential, validated by the planted neighbor, is the main upside lever; the well's unverified yield and the track's remediation cost are the main downside adjustments. This is an analytical estimate, not an appraisal — an MAI appraisal and the well/septic diligence above should set the actual number.