Chalk Hill Vineyards: Nested Boundary, Frost Water, Groundwater Edges and Zoning

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Chalk Hill is a compact appellation in the hills east of Windsor, tucked into the northeastern corner of the Russian River Valley between Healdsburg, Alexander Valley and Mark West Creek. Owners here deal with a boundary written road by road, an AVA nested two levels deep, Russian River frost rules, and a location close enough to Windsor and the Santa Rosa Plain that jurisdiction and groundwater lines need checking parcel by parcel.

Chalk Hill at a glance

Where the appellation runs

The boundary in 27 CFR 9.52 is unusually detailed for its size: 30 numbered segments drawn on just two USGS quadrangles. It starts and ends where the Redwood Highway (Old Highway 101) meets Arata Lane. Along the way it follows Windsor River Road, Starr Road, Mark West Road, Porter Creek Road, Franz Valley Road, Spurgeon Road, Chalk Hill Road, Reiman Road and Eastside Road, as well as Mark West Creek, Franz Creek, Martin Creek, the north fork of Barnes Creek, Brooks Creek and the Russian River. Landmarks include the Chalk Hill peak, a 737-foot hill and a PG&E transmission line.

Because the line runs along roads and creeks, a single ranch can sit partly inside and partly outside the AVA. Road frontage, especially along Chalk Hill Road and Franz Valley Road, is a common place to find a split.

The border with Alexander Valley shifted in 1988, when T.D. ATF-272 moved vineyards in Chalk Hill’s southeast corner into Alexander Valley, as TTB’s 2008 Alexander Valley ruling recounts. For any parcel on that side, check which rule controls.

Nesting. TTB’s 2011 Russian River Valley expansion states that Russian River Valley entirely encompasses Chalk Hill, which lies in its northeastern corner, and that Chalk Hill is also entirely within Northern Sonoma. Wine from a Chalk Hill vineyard can therefore qualify for Chalk Hill, Russian River Valley, Northern Sonoma or North Coast, subject to TTB’s labeling rules. See our Russian River Valley vineyards guide for the parent appellation.

Neighbors. The Fountaingrove District, established in 2015, lies south of Chalk Hill without overlapping it. In that ruling TTB said Chalk Hill has temperatures and topography similar to Fountaingrove but soils derived mainly from river deposits. Our post on how Chalk Hill got its name looks at the area’s geology from another angle.

Frost protection and creek water

Chalk Hill’s creeks feed the Russian River, so California’s Russian River frost regulation, 23 CCR 862, applies to frost-protection diversions from March 15 through May 15. Each diverter must be covered by a State Water Board-approved water demand management program, submitted by February 1 before the frost season. The program must include a frost system inventory, stream stage monitoring at 15-minute intervals, a stranding-mortality risk assessment and corrective action timelines. Wells count when their pumping contributes to a drop in stream stage during a frost event; an individual diverter can seek exemption by showing its well is not hydraulically connected.

At the county level, the VESCO application requires a frost protection registration or negative declaration for Russian River watershed parcels, with the fee due again on transfer. Ask the seller for both the state program records and the county registration. More on water: vineyard water rights and vineyard ponds and reservoirs.

Groundwater: near the Santa Rosa Plain line

The Santa Rosa Plain GSA describes its subbasin as running from Windsor south to Cotati and from Santa Rosa west to Sebastopol. It charges groundwater users a per-acre-foot fee on the property tax bill, adopted at $46.04 per acre-foot for 2026-27, with rural residential use estimated at half an acre-foot a year. Chalk Hill sits in the hills east of Windsor, mostly above the plain. Parcels on its western edge toward Windsor and Mark West Creek may or may not fall inside the subbasin, so check the GSA’s map and the property tax bill for a groundwater fee line. Higher ground east of the plain is outside the three Sonoma County GSA areas, which also include Sonoma Valley and Petaluma Valley. See Sonoma County groundwater rules.

Hillside blocks and water quality

Chalk Hill’s rolling terrain means many blocks are on slopes, and new planting runs through the county’s VESCO program. Per the county’s site development FAQ, new planting stays at Level I up to 15% natural slope (10% on highly erodible soils), replanting stays at Level I up to 30% (15% on highly erodible soils), and planting over 50% is prohibited. Under the current application, grading becomes "engineered" once combined cut and fill exceeds 5,000 cubic yards, cuts go deeper than 2 feet, or natural slope reaches 15%. Engineered grading needs stamped plans and a geotechnical report. Grading and drainage permits expire three years after issue; VESCO permits expire after five.

The North Coast Regional Water Board approved its commercial vineyard order R1-2024-0056 in June 2025, with enrollment expected from July 1, 2028 to July 1, 2029. Build that into a long-term plan. See vineyard development and environmental constraints.

Zoning, Windsor and wineries

Most Chalk Hill farmland is in unincorporated Sonoma County, where the 2023 winery standards in Sec. 26-18-260 apply to use permits in LIA, LEA and DA zones. With homes in the hills around many ranches, the noise rules can decide a project. Outdoor amplified music needs 1,600 feet from adjacent noise-sensitive property lines, acoustic music or outdoor groups need 625 feet, and parking lots need 450 feet, unless a noise study supports less. Wine trade activities may run until 10 p.m., but outdoor amplified sound ends at 5 p.m. Near Windsor, confirm whether a parcel is inside town limits, because town zoning would govern instead.

Williamson Act contracts are common on larger ranches. The county’s contracted-parcel procedure sets 10-acre (Type I) and 40-acre (Type II) minimums. It lets undersized parcels join a multi-parcel contract if a covenant bars their separate sale during the term. Confirm current rules, since that policy is from 2007. See agricultural zoning, winery use permits and Williamson Act.

Fire and insurance

Wooded slopes along Chalk Hill Road and toward Franz Valley warrant a check of CAL FIRE’s Fire Hazard Severity Zone maps. The state-responsibility map took effect April 1, 2024, and maps for local-responsibility areas were released to local jurisdictions in phases in early 2025. See vineyard and winery insurance, wildfire smoke taint and Windsor fire-resilient home records.

A due diligence list for a Chalk Hill vineyard

Pair with the full vineyard due diligence guide.

• Plot every block against the 30-segment boundary in 27 CFR 9.52 and the 1988 Alexander Valley change.
• Confirm the parcel is in unincorporated Sonoma County, not the Town of Windsor.
• Check whether the parcel is in the Santa Rosa Plain subbasin and whether a GSA fee appears on the tax bill.
• Get 23 CCR 862 water demand management program records and the county frost registration.
• Pull water rights filings, pond permits, well logs and pump tests.
• Collect VESCO, grading and drainage permits and their expiration dates.
• Review any winery use permit for noise, hours, events and parking conditions.
• Confirm Williamson Act contract type, any multi-parcel covenant and any nonrenewal notice.
• Check CAL FIRE hazard zones and FEMA flood maps for creek frontage.
• Plan for North Coast Water Board vineyard order enrollment in 2028–2029.

Questions people ask

Sources & notes

1. Cornell LII: 27 CFR 9.52, Chalk Hill
2. Federal Register: Expansion of the Alexander Valley Viticultural Area (2008)
3. Federal Register: Expansions of the Russian River Valley and Northern Sonoma Viticultural Areas (2011)
4. Federal Register: Establishment of the Fountaingrove District Viticultural Area (2015)
5. Cornell LII: Cal. Code Regs. tit. 23, § 862
6. Santa Rosa Plain GSA: Groundwater Sustainability Fee
7. County of Sonoma: GSAs seek input from agricultural groundwater users
8. Sonoma County Agriculture/Weights & Measures: Site development FAQ and VESCO application
9. North Coast Regional Water Board: Vineyard Order R1-2024-0056
10. Sonoma County: Zoning Code Sec. 26-18-260
11. Permit Sonoma: Policy 8-1-8, Williamson Act parcels
12. CAL FIRE OSFM: Fire Hazard Severity Zones

General information, not legal or tax advice. Last reviewed November 2026 by Matthew Martinez.

Related: Sonoma County vineyards · Windsor real estate guide · Russian River Valley vineyards · Knights Valley vineyards · Vineyard due diligence · Vineyard water rights · All vineyard and winery guides