Clarksburg Vineyards: Delta Islands, Levees, Winery Overlay and Primary Zone Rules

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

The Clarksburg AVA lies in the northern Sacramento-San Joaquin Delta, just south of Sacramento, on reclaimed river islands and tracts in Yolo, Sacramento and Solano Counties. It is flat, close to sea level, crossed by sloughs and protected by levees, which makes drainage, flood exposure and Delta land-use review the core questions for anyone buying or selling vineyard land here. Since 2022 the appellation has also reached south to take in Grand Island and Ryer Island.

Clarksburg at a glance

Where the appellation runs

The boundary in 27 CFR 9.95 is drawn on waterways, levees and roads. It starts at Jefferson Boulevard and Burrows Avenue near West Sacramento, follows the Sacramento River Deep Water Ship Channel about 17 miles southwest, then Miner Slough and Cache Slough to the Sacramento River. From there it follows the river upstream to the Delta Cross Channel, runs east along the railroad and a levee to Interstate 5, north along I-5 to Hood Franklin Road, and back north along the Southern Pacific railroad levee to Freeport before crossing the river and returning to Burrows Avenue. The approved maps include the Clarksburg, Courtland, Bruceville, Isleton, Liberty Island and Rio Vista quadrangles.

The 2022 expansion to Grand and Ryer Islands

TTB’s expansion rule, T.D. TTB-178, took effect April 8, 2022. It added about 27,945 acres in Sacramento and Solano Counties next to the southern part of the AVA, taking in all of Grand Island and Ryer Island, where the petition counted about 350 acres of vines on Grand Island and three vineyards on Ryer Island. The rule describes the AVA’s defining features: poorly drained clay and clay loam soils, drainage by ditches, canals, tile drains and vine-row berms, frequent use of wet-tolerant rootstocks, elevations from roughly 10 feet below to 10 feet above sea level, and about 16 inches of average annual rain in the original findings. If a ranch’s grape contract or label history predates April 2022, blocks on those islands may have been sold under a different appellation name.

Merritt Island

Inside Clarksburg sits Merritt Island, 27 CFR 9.68, established in 1983 and amended in 1987. It lies in Yolo County about six miles south of Sacramento, bounded by Sutter Slough, Elk Slough (running about 9.6 miles up to the community of Clarksburg) and the Sacramento River. The TTB AVA list confirms Merritt Island is within Clarksburg and that Clarksburg covers Sacramento, Solano and Yolo Counties.

For how the Delta fits into California’s wine regions, see our California wine regions guide.

Winery rules: Yolo County’s Clarksburg Agricultural District

On the Yolo side, the county adopted a special overlay for the Clarksburg area. Yolo County Code Sec. 8-2.401, the Clarksburg Agricultural District Overlay Zone, applies to land designated Agriculture in the Clarksburg Area Plan. Its use table sorts winery activity into categories, each tied to a permit level (allowed with zoning clearance, site plan review, minor use permit or major use permit):

• Stand-alone tasting rooms under or over 2,000 square feet
• Small wineries under 100,000 cases a year
• Medium wineries from 100,000 to 1,000,000 cases a year
• Large wineries above 1,000,000 cases a year

The overlay also sets operating standards: outdoor events between 9 a.m. and 10 p.m., special event facilities tiered at 18 events a year, permeable surfaces for permanent parking, no on-street parking, direct public-road access (with exceptions), one entry sign up to 40 square feet, and shielded lighting near homes. The Clarksburg Citizens Advisory Committee serves as the district’s advisory committee. Read the table for the exact permit level that applies to each category before you plan a winery or tasting room.

Parcels on the Sacramento County side (Hood, Courtland, Grand Island) and the Solano County side (Ryer Island) follow those counties’ codes instead; see the Sacramento County vineyards page and the Solano County vineyards page. State and federal permits sit on top of local approval: winery license transfer and custom crush and alternating proprietorships are useful reads.

The Delta Primary Zone

Much of the Clarksburg area falls in the legal Delta, and parts of it in the Primary Zone. The Delta Protection Commission, a state agency, reviews certain Primary Zone land-use decisions for conformity with its Land Use and Resource Management Plan and can appeal local decisions that do not conform. The Commission describes the Delta as about 738,000 acres across parts of Contra Costa, Sacramento, San Joaquin, Solano and Yolo Counties and a corner of Alameda. Check the Commission’s Primary Zone map for the parcel; a subdivision, new non-farm use or large facility there can draw a second layer of review beyond the county.

Flood, levees and drainage

Clarksburg’s vineyards sit behind levees on land at or below sea level, so flood is the first physical risk to review. Pull the FEMA flood zone for each building and well, ask which reclamation district maintains the levee and what assessments the parcel pays, and read any history of seepage or levee work. Drainage is just as important for the vines: TTB’s findings note growers rely on ditches, canals, tile drains and berms. Ask for maps of drain lines and pumps and who owns them. Our Yolo County flood zone and levee insurance guide, Courtland flood and levee records and Sacramento County Delta land and homes go deeper.

Water typically comes from river and slough diversions or wells. Surface rights in the Delta are a specialized area; confirm the right, the diversion point and recent reporting, and check DWR’s basin prioritization for wells. See vineyard water rights.

Williamson Act and farmland rules

Delta farmland is often under Williamson Act contracts. The Department of Conservation explains that contracts bind all later buyers, roll over yearly on 10-year terms (20 for Farmland Security Zones), and can be cancelled only at the owner’s request with a 12.5% fee. On the Yolo side, conversion of farmland to non-agricultural use can also trigger agricultural mitigation; see our Yolo County farmland and Williamson Act mitigation guide and Williamson Act guide.

A due diligence list for a Clarksburg vineyard

• Map each block against 27 CFR 9.95 and, near Elk and Sutter Sloughs, against Merritt Island (9.68).
• For Grand Island or Ryer Island blocks, check how fruit was labeled and contracted before the April 2022 expansion.
• Confirm the county (Yolo, Sacramento or Solano) and, in Yolo, the Clarksburg Agricultural District permit level for any winery or tasting use.
• Check whether the parcel is in the Delta Primary Zone and how the Delta Protection Commission’s plan applies.
• Get FEMA flood zones, the reclamation district, levee assessments and any seepage or flood history.
• Map drain tile, ditches and pumps; confirm who maintains them.
• Verify surface water rights and diversion reporting, or well logs and pump tests.
• Obtain any recorded Williamson Act or Farmland Security Zone contract.
• Review grape contracts, rootstocks (wet tolerance), vine age and trellis.
• Use the full vineyard due diligence checklist.

Questions people ask

Sources & notes

1. 27 CFR 9.95 Clarksburg, 2025 CFR edition via GovInfo (current text at eCFR Part 9)
2. 27 CFR 9.68 Merritt Island, 2025 CFR edition via GovInfo
3. TTB final rule: T.D. TTB-178, Expansion of the Clarksburg Viticultural Area, 87 FR 13157 (Mar. 9, 2022)
4. TTB: Established American Viticultural Areas
5. Yolo County Code: Sec. 8-2.401, Clarksburg Agricultural District Overlay Zone (American Legal Publishing, the county’s code host)
6. Delta Protection Commission: About the Commission
7. DWR: Basin prioritization
8. California Department of Conservation: Williamson Act questions and answers

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

Related: Yolo County vineyards · Sacramento County vineyards · Clarksburg real estate guide · Courtland real estate guide · El Dorado vineyards · Vineyard due diligence · Vineyard water rights · All vineyard and winery guides