Moon Mountain District Vineyards: Hillside Planting, Tree Removal, Water and Permits

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

The Moon Mountain District Sonoma County AVA covers the western slopes of the Mayacamas ridge above the town of Sonoma and Glen Ellen, from the Napa County line down to roughly the 400-foot contour. It is a mountain appellation carved out of the Sonoma Valley AVA, and owning land here is mostly about slope: how steep each block is, which trees would have to come out, and where water comes from once you are above the valley floor.

Moon Mountain District at a glance

Where the appellation runs

The boundary in 27 CFR 9.231 starts at a 2,188-foot point on the Sonoma–Napa county line and follows that meandering line south to Lovall Valley Road. It then cuts west past a 692-foot peak to Thornsberry Road, north-northwest to the Castle Road and Bartholomew Road corner, and west past the southernmost quarry on Schocken Hill to the 400-foot contour. That contour carries the line about 7.4 miles northwest, across the Glen Ellen map and onto the Kenwood map, to Nelligan Road near the mouth of Nunns Canyon. From there it climbs to the 600-foot contour, passes near a 973-foot peak, and returns east by way of a 1,483-foot peak to the start.

Two practical points follow. The southern end dips lower than the rest, reaching a 218-foot point at Castle and Bartholomew Roads on the edge of Sonoma, so some lower ground near town is inside. Elsewhere, the 400-foot and 600-foot lines mean a ranch that runs from the valley floor up the hill can be split, with upper blocks in the district and lower blocks only in Sonoma Valley. Have a surveyor or GIS consultant plot each block against the contour before you price a label.

The final rule places the district entirely within the Sonoma Valley AVA, which is entirely within the North Coast AVA, and says it overlaps no other existing or proposed appellation. Land in the district keeps both parent names. TTB received 11 comments on the proposal, all supportive. The petition reported about 1,500 acres in commercial vineyards, 40 vineyards and 11 bonded wineries at the time; those figures describe 2013, not today. For how this fits the wider county, see our Sonoma County appellations overview and the Sonoma Valley vineyards guide. Our blog also covers Moon Mountain and Mount Veeder geology.

Hillside planting and tree removal: the core question

On mountain parcels, the Sonoma County Agricultural Commissioner’s vineyard and orchard site development program (VESCO) usually decides how much new vineyard is realistic. The county’s site development FAQ (an archived 2012 revision; confirm the current ordinance) explains the rules that matter most on a ridge like this:

• Review level is based on the steepest natural slope in the planting area; averaging is not allowed.
• New planting above 15% natural slope is Level II, which requires an engineered erosion control plan. Replanting moves to Level II above 30%.
• Planting is prohibited on natural slopes over 50%.
• Where more than half an acre of tree canopy comes out, tree-removal standards apply: a Certified Engineering Geologist report, a soil-loss analysis showing no net increase in erosion (RUSLE2 on slopes over 25%), and a slope stability analysis on cohesionless soils.
• Tree removal is prohibited on slopes over 40% in cohesionless soils, and ridgetop projects need a 50-foot setback from the defined ridgetop.
• Conifer removal may need CAL FIRE permits, and valley oak removal may need a county permit.
• New-vineyard site work is limited to April 1 through October 15.

The upshot: on a Moon Mountain listing, "plantable acres" is a claim that needs a slope map, a tree survey and a consultant’s read of VESCO before you rely on it. Our vineyard development guide and environmental constraints guide cover what a planting study should include.

Water: valley subbasin below, hard-rock wells above

The lower slopes sit at the edge of the Sonoma Valley Subbasin, which is managed under SGMA by the Sonoma Valley Groundwater Sustainability Agency. The state announced approval of the subbasin’s Groundwater Sustainability Plan on January 26, 2023, and in 2022 the county announced groundwater sustainability fees for non-municipal users in Sonoma Valley, billed per acre-foot pumped (with a flat charge for single-home wells) on the property tax bill. The agency’s online GUIDE tool shows the estimated use assigned to a parcel. Rates change, so pull the current figure for the parcel.

Higher up, many parcels may fall outside the mapped alluvial subbasin altogether, where wells draw from bedrock and yields can vary widely from one well to the next. That makes well history the most important water document on a mountain ranch: the driller’s log, pump tests at the end of a dry season, and any storage ponds with their water-right filings. See Sonoma County groundwater rules, vineyard water rights and vineyard ponds and reservoirs.

The state frost rule at 23 CCR 862 covers only the Russian River stream system, and this district sits on the Sonoma Valley side of the hills, so that rule should not be the operative one here. Confirm any frost or irrigation diversion right with the State Water Board.

Winery and tasting permits on a mountain road

Sonoma County’s winery standards, Sec. 26-18-260, adopted by Ordinance 6404 in March 2023, apply on LIA, LEA and DA agricultural parcels. Several provisions bite harder on steep, narrow-road sites than on the valley floor. Parking must be on site at one space per 2.5 guests plus one per employee, with no parking on public or private roads. Visitor and event capacity is sized to septic, water supply, emergency access and parking. Events over 100 participants need a traffic management plan. If a parcel is zoned for rural residential use rather than agriculture, a winery may not be available at all. Start with our Sonoma County agricultural zoning and winery use permit guides, and the winery due diligence checklist.

Fire hazard, smoke and insurance

Wooded ridges above Sonoma and Glen Ellen are the kind of terrain the state’s Fire Hazard Severity Zone maps are built to classify. The State Responsibility Area maps took effect April 1, 2024, and rate land Moderate, High or Very High; the Fire Marshal describes them as a hazard measure, not a risk score, and notes that the maps do not set insurance rates. Even so, a mountain vineyard home should be quoted for insurance before contingencies run out, and defensible space and access for fire engines on a long private drive should be part of the inspection. See vineyard and winery insurance, wildfire smoke taint and our home hardening guide.

A due diligence list for a Moon Mountain District vineyard

Use our full vineyard due diligence guide alongside these district-specific checks:

• Plot every block against the 400-foot and 600-foot contours in 27 CFR 9.231.
• Get a slope map showing the steepest natural slope in each planned planting area.
• Commission a tree survey if any canopy removal is planned; confirm conifer and valley oak permit needs.
• Ask whether a geologist’s report or slope stability analysis will be required under VESCO.
• Confirm whether the parcel lies inside the Sonoma Valley Subbasin and pull its GSA fee estimate.
• Collect well logs, dry-season pump tests and any pond water-right filings.
• Check road width, grade and turnouts for both farm equipment and fire access.
• Confirm zoning before assuming a winery or tasting room is possible.
• Review on-site parking, septic and water capacity against Sec. 26-18-260 limits.
• Check the fire hazard zone and get insurance quotes early.
• Review smoke-exposure history and any grape contract language on smoke.

Questions people ask

Sources & notes

1. eCFR: 27 CFR 9.231, Moon Mountain District Sonoma County
2. Federal Register: T.D. TTB-117, Establishment of the Moon Mountain District Sonoma County Viticultural Area (Oct. 2, 2013)
3. Sonoma County Agricultural Commissioner: Vineyard and orchard site development FAQ (archived, rev. 2012)
4. California Natural Resources Agency: DWR approves groundwater sustainability plans for four Northern California basins (Jan. 26, 2023)
5. Sonoma County: Groundwater users can now review fee information online (Sept. 2022)
6. Sonoma County: Zoning Code Sec. 26-18-260, Winery Definitions and Standards (Ord. 6404, 2023)
7. Cornell LII: 23 CCR 862, Russian River frost protection
8. Office of the State Fire Marshal: Fire Hazard Severity Zones

The final rule gives both 17,633 and 17,663 acres for the district; vineyard and winery counts are from the 2013 petition. General information, not legal or tax advice. Last reviewed November 2026 by Matthew Martinez.

Related: Sonoma County vineyards · Sonoma real estate guide · Glen Ellen real estate guide · Sonoma Valley vineyards · Petaluma Gap vineyards · Vineyard due diligence · Vineyard water rights · All vineyard and winery guides