Dixon — Overlay Districts

Last reviewed: July 2, 2026

Overview

This page explains how the Dixon Zoning Code defines and applies overlay districts — the special zoning layers that sit on top of base zones and add parcel-specific rules. Dixon’s overlay districts in Title 18 are limited and discrete: the Groundwater Well (GW) Overlay, the Planned Development (-PD) Overlay, and the Specific Plan (SP) Overlay. For how overlays interact with base development rules and site-level requirements, also see the city’s Dixon Zoning and Dixon Development Standards guidance.

How Dixon organizes overlays (quick legal anchors)

• Overlay districts are listed in the Official Zoning Map and in Table 18.03.010; overlays are added to base zones as suffixes (e.g., R-1-PD) (§ 18.03.010) .
• Where map boundaries are unclear, the Official Zoning Map rules apply; verify parcel boundaries with the City Clerk and Director (§ 18.03.020) .

District-by-district breakdown

GW Overlay District — Groundwater Well (-GW)

Purpose and quick effect

• The Groundwater Well (GW) Overlay District is narrowly targeted to control groundwater extraction near an impacted plume at the Municipal Service Center; it is not a citywide policy but applies only to enumerated parcels (§ 18.08.010–.020) .

Where it applies

• The code lists specific parcels by address and Assessor’s Parcel Number where the -GW rules apply; this is a fixed list in the ordinance (e.g., 285 East Chestnut Street and adjacent parcels; see § 18.08.020) .

Typical permitted uses / limits

• The overlay does not create new permitted uses; instead it imposes conditions on certain activities — most importantly the drilling/installation of groundwater extraction wells (§ 18.08.030–.040) .

Key standards (decision-relevant)

• Minimum sanitary seal for any groundwater extraction well: 50 feet measured from ground surface to top of initial screen (§ 18.08.030) .
• Drilling a well in the -GW zone requires a Conditional Use Permit (CUP) under Chapter 18.24; CUP must include reimbursement terms for incremental sanitary seal costs (§ 18.08.040) .

Practical guidance

• If a property is listed in § 18.08.020, expect extra engineering/specification conditions and coordinate with Solano County or the Central Valley Regional Water Quality Control Board where the code references outside agency approval for modifications (§ 18.08.020.B) .

Relevant code: § 18.08.010–.040 .

PD Overlay District — Planned Development (-PD)

Purpose and quick effect

• The Planned Development (PD) Overlay District allows one or more properties to be developed under a site-specific PD Plan that customizes development standards and uses to achieve coordinated, flexible design outcomes (§ 18.09.010) .

Where it applies / map notation

• A PD is shown on the Zoning Map by adding the suffix “-PD” and the adopting ordinance number to the base zone (§ 18.09.020; § 18.32.020) .

Typical permitted uses / limits

• No use other than an existing use is permitted in a -PD unless it is in compliance with an approved PD Plan; the PD Plan may include any permitted or conditional use from the Code consistent with the General Plan (§ 18.09.030) .

Key dimensional and program standards

• Minimum area: 5 acres (City Council may approve smaller where public benefit is demonstrated) (§ 18.09.040.A) .
• Density: total dwelling units cannot exceed General Plan density unless density bonus rules apply (§ 18.09.040.B) .
• Floor Area Ratio (FAR): cannot exceed the maximum permitted by the General Plan for the development area (§ 18.09.040.C) .
• Performance standards of Chapter 18.17 apply; where PD is silent on a design standard, the base district standard applies (§ 18.09.040.D–E) .

Procedures and findings (what the City will check)

• Establishment of a -PD is a zoning amendment (processed under Chapter 18.29) and requires a PD Plan submitted and processed with a Conditional Use Permit-style review (§ 18.32.030.B.1–2) .
• Required findings include General Plan consistency, site suitability, adequate utilities/transportation, compatibility with surrounding uses, compliance with design guidelines, and demonstration that the PD produces a demonstrably superior result to conventional zoning (§ 18.32.040.A–F) .
• PD Plans expire if not acted on within two years unless building permits or conditions of approval specify otherwise; renewals and phased approvals are provided for (§ 18.32.060) .

Practical implications

• A -PD changes how you prepare project-level design documents and often bundles design review, subdivision (tentative map), and entitlement requests; expect to coordinate landscaping, parking, and public improvements as part of the PD Plan (see Dixon Parking, Dixon Landscaping and Screening, and Dixon Design Review for related processes).

Relevant code: § 18.09.010–.050 and § 18.32.010–.080 .

SP Overlay District — Specific Plan (SP)

Purpose and quick effect

• The Specific Plan (SP) Overlay District identifies areas covered by adopted Specific Plans; within SP boundaries the adopted Specific Plan controls uses and development standards, not the base zoning alone (§ 18.10.010–.020) .

Where it applies

• The code lists adopted Specific Plans by name and directs users to the full plan documents on file with the City (for Dixon: the Northeast Quadrant Specific Plan and the Southwest Dixon Specific Plan) (§ 18.10.030) .

Typical permitted uses / limits

• Within an SP area, the Specific Plan’s permitted uses and standards govern; where the Specific Plan is silent, the City’s Zoning Code applies, and the Community Development Director decides which Code provisions apply (§ 18.10.020.A–C) .

Practical guidance

• Always pull the adopted Specific Plan document for the parcel in question. If a use is not expressly listed, the Director will classify the use or refer to the Planning Commission; appeals follow § 18.21.120 (§ 18.10.020.A.2) .

Relevant code: § 18.10.010–.030 .

Quick reference table — overlays, the basics

Checklist — what an applicant must satisfy for overlays

• Confirm whether the parcel is on the Official Zoning Map and whether it carries -GW, -PD, or SP notation (§ 18.03.020) .
• If the parcel is in the -GW list, include well-engineering showing 50 ft sanitary seal and prepare for a CUP under Chapter 18.24 (§ 18.08.030–.040) .
• If applying for -PD, prepare a PD Plan and process it as a zoning amendment with required findings; include tentative subdivision map concurrently if applicable (§ 18.32.030.B.1–3; § 18.32.040) .
• For SP areas, pull the adopted Specific Plan document and show consistency; where the Specific Plan is silent, identify which Dixon Code standards will apply (§ 18.10.020.A.1–3) .
• Provide CEQA and technical studies (traffic, utilities, environmental contamination) as required; PD conditions may require public improvements and performance standards (§ 18.32.050; § 18.09.040.D–E) .
• Coordinate related topic-level requirements early: parking, landscaping, signage, design review, and accessory dwelling unit rules may interact with overlay approvals (see Dixon Parking, Dixon Landscaping and Screening, Dixon Signage, Dixon Design Review, and Dixon ADUs).
• Verify Official Zoning Map boundary determinations and consult the Community Development Director for parcel-split or boundary questions (§ 18.03.020) .

Risks & Ambiguities

Plain-English Summary

Dixon uses three narrow overlay layers in its zoning code: -GW for a handful of parcels near a contaminated groundwater plume (stricter well rules and a CUP), -PD for site-specific planned developments that replace some base rules with a customized PD Plan, and SP where an adopted Specific Plan governs uses and standards. Check the Official Zoning Map and the specific ordinance sections noted here before you design or submit a permit application; verify PD plan conditions and any parcel list in the GW chapter. Relevant legal text: § 18.08, § 18.09 / § 18.32, and § 18.10 .

Source References

• Dixon Zoning Code (Title 18), Table 18.03.010 and Official Zoning Map rules — § 18.03.010; § 18.03.020 .
• Groundwater Well (GW) Overlay — § 18.08.010–.040 .
• Planned Development (PD) Overlay — § 18.09.010–.050 and Planned Development procedures/requirements § 18.32.010–.080 .
• Specific Plan (SP) Overlay — § 18.10.010–.030 (lists Northeast Quadrant and Southwest Dixon Specific Plans) .
• PD findings, conditions, expiration and amendment rules — § 18.32.040–.080 .
• General applicability and relationship to the General Plan — § 18.01.040–.050 .

(If you need the PDF of any Specific Plan or a parcel lookup for overlay notation on the Official Zoning Map, verify with the City Clerk or Planning Division; the ordinances refer to plan documents “on file with the City.”)

Retrieved passages

• Dixon Zoning Code (Chapter 18.24) High relevance show source text
• Dixon Zoning Code (Chapter 18.29) High relevance show source text
• Dixon Zoning Code (Chapter 18.31Prezoning) High relevance show source text
• Dixon Zoning Code (Chapter 18.33Enforcement) High relevance show source text
• Dixon Zoning Code (Chapter 18.12) Medium relevance show source text
• Dixon Zoning Code (Chapter 18.33Enforcement) Medium relevance show source text
• Dixon Zoning Code (Section governs) Medium relevance show source text
• Dixon Zoning Code (Chapter 18.18) Medium relevance show source text

Cited sections

• Dixon Zoning Code (Title 18), Table 18.03.010 and Official Zoning Map rules — **§ 18.03.010; § 18.03.020** . (Title 18)
• Groundwater Well (GW) Overlay — **§ 18.08.010–.040** . (§ 18.08.010)
• Planned Development (PD) Overlay — **§ 18.09.010–.050** and Planned Development procedures/requirements **§ 18.32.010–.080** . (§ 18.09.010)
• Specific Plan (SP) Overlay — **§ 18.10.010–.030** (lists Northeast Quadrant and Southwest Dixon Specific Plans) . (§ 18.10.010)
• PD findings, conditions, expiration and amendment rules — **§ 18.32.040–.080** . (§ 18.32.040)
• General applicability and relationship to the General Plan — **§ 18.01.040–.050** . (§ 18.01.040)
• Dixon_ZoningCode.md

• Official Dixon code library