Local zoning · Imperial County

Imperial County — Overlay Districts

Overlay Districts under the Imperial County local zoning and planning code, with the controlling citations.

Last reviewed: July 6, 2026

Overview

In unincorporated areas of Imperial County, overlay districts “layer” additional rules on top of a property’s base zoning. The county establishes and applies overlays by ordinance and on its official zoning maps; multiple overlays can apply to the same parcel. Overlays commonly address hazards (floodplain, geology), infrastructure/airspace (airport approach), policy areas (specific plans, urban areas), and special land uses (mixed use, geothermal/renewable energy) (§ 90501.03 ; § 90501.04 ).

Key concept: A parcel in unincorporated Imperial County has a base zone (e.g., A‑2, C‑1, M‑1). One or more overlay designations can be added, and new overlays are established only through a zone change approval process (§ 90501.03 ).

Before using this page, confirm your base zoning and any overlays on the county’s official zoning map and then cross‑check applicable development standards and any required design review or parking requirements (§ 90501.04 ; § 90501.11.B for MU site plan review ).

Overlay districts established by the Imperial County zoning ordinance

Imperial County lists the following overlay zoning area designations; each may be combined with a base zone (examples shown in the code include “A‑2‑G,” “A‑2‑U,” “C‑2‑PE”) (§ 90501.03 ; map examples: § 92503.03, § 92533.01, § 92514.04 ).

L‑(x) Lot Size Minimum
G‑ Geothermal Overlay
REG Renewable Energy/Geothermal Overlay
GH‑ Geological Hazard Area
FP‑ Flood Plain Hazard Area
H‑ Airport Approach Height Restriction
SH‑ Specific Hazard Restriction
MP‑ Multipurpose (Restricted)
PE‑ Pre‑Existing Allowed/Restricted
U‑ Urban Areas
N‑ No Residential
SPA‑ Specific Plan Area
MU Mixed Use
C Conditional Zone Change (§ 90501.03 )

L-(x) Lot Size Minimum Overlay (L-)

Purpose: Sets a minimum lot size above the base zone minimum (e.g., “A‑2‑L‑1” requires a 1‑acre minimum lot) (§ 90501.03, L‑(x) ).
Typical permitted uses: Not changed by L‑; uses remain those of the base zone. Not found in retrieved materials.
Key dimensional standards: Lot‑size minimum per suffix (e.g., L‑1 = 1 acre). Specific numeric menu beyond example: Not found in retrieved materials (§ 90501.03 ).
Where it applies: Anywhere the official map applies an “‑L‑(x)” suffix (§ 90501.04 ).

Geothermal Overlay (G-)

Purpose: Identifies areas where geothermal resources affect land use; often shown in combination with agricultural/industrial base zones (e.g., “A‑2‑G,” “M‑1‑G”) (map amendments show widespread “‑G” usage: § 92533.01, § 92534.01, § 92514.04 ).
Typical permitted uses: Not found in retrieved materials.
Key dimensional standards: Not found in retrieved materials.
Where it applies: As shown on official maps; see multiple Mesquite Lake/SP area examples with “‑G” retained after base‑zone changes (§ 92533.01, § 92534.01, § 92514.04 ).

Renewable Energy/Geothermal Overlay (REG) and Renewable Energy Overlay (RE)

Purpose: Implements the county’s Renewable Energy and Transmission Element. The ordinance text establishes an “RE” overlay with two mapped categories: geothermal energy overlay and renewable/geothermal overlay (§ 91701.01.A–B ).
Typical permitted uses: Renewable energy projects (geothermal, solar, wind, biofuel, biomass, algae, concentrated solar‑thermal, concentrated PV) with a Conditional Use Permit in applicable base zones (§ 91701.03 ).
Key dimensional standards: General submittal and development standards are listed for projects in the overlay; parcel‑level dimensional standards otherwise default to base zone unless modified by permit conditions (§ 91701.04.A–B ). Specific height/setback numbers for RE projects: Not found in retrieved materials.
Where it applies: Within RE overlay areas shown on the RE overlay map. The overlay may be amended if adjacency or “island” criteria are met (e.g., near transmission or existing solar, no significant environmental impacts) (§ 91701.02; § 91701.01 “adjacent” and “island” criteria ). Note: § 90501.03 lists “REG,” while Division 17 uses “RE.” Verify current mapping label with the county.

Geological Hazard Area (GH-)

Purpose: Identifies geologic hazard constraints; may limit or condition development (§ 90501.03, GH‑ listing ).
Typical permitted uses: Not found in retrieved materials.
Key dimensional standards: Not found in retrieved materials.
Where it applies: Where mapped on the official zoning map (§ 90501.04 ).

Flood Plain Hazard Area (FP-)

Purpose: Applies special flood hazard regulations and review processes to mapped areas (§ 90501.03, FP‑ listing ).
Typical permitted uses: Not found in retrieved materials.
Key dimensional standards: Not found in retrieved materials. However, appeals and review fees for structures/subdivisions “lying within an area of special flood hazard” are codified (§ 91606.02–.03 ).
Where it applies: Areas of special flood hazard indicated on official mapping; verify with county flood hazard resources (§ 90501.04; § 91606.02–.03 ).

Airport Approach Height Restriction (H-)

Purpose: Protects airport approach airspace; listed as an overlay in § 90501.03 (H‑) and also addressed as an “H” airport use/height restriction zone at § 90501.10 (; ).
Typical permitted uses: The “H” airport use zone section describes airport‑related uses and requires a recorded covenant limiting land to permitted uses for at least 10 years (§ 90501.10.A–B ). Overlay‑specific permitted uses/height planes: Not found in retrieved materials; verify if the mapped H‑ overlay references the § 90501.10 standards.
Key dimensional standards: Height plane parameters in approach areas: Not found in retrieved materials.
Where it applies: Where H‑ is mapped; confirm if your parcel is within an airport approach corridor (§ 90501.04 ).

Specific Hazard Restriction (SH-)

Purpose, uses, standards: Not found in retrieved materials (§ 90501.03, SH‑ listing ).
Where it applies: As mapped (§ 90501.04 ).

Multipurpose (Restricted) (MP-)

Purpose, uses, standards: Not found in retrieved materials (§ 90501.03, MP‑ listing ).
Where it applies: As mapped (§ 90501.04 ).

Pre‑Existing Allowed/Restricted (PE-)

Purpose: Flag for parcels with pre‑existing allowances/restrictions appended to the base zone label (e.g., “C‑2‑PE”) (§ 90501.03, PE‑ listing ).
Typical permitted uses and standards: Not found in retrieved materials.
Where it applies: As mapped; check case‑specific ordinance/conditions on file (§ 90501.04 ).

Urban Areas (U-)

Purpose: Indicates an “Urban Area”; upon permit/development, applicable Urban Area regulations will apply (§ 90501.03, U‑ listing ).
Typical permitted uses: Base‑zone uses, with urban‑area rules layered at the time of development. Specific urban rules: Not found in retrieved materials.
Key dimensional standards: Not found in retrieved materials.
Where it applies: As mapped; frequent in the Calexico area (e.g., “A‑2‑U” to “M‑1‑U” rezones) (§ 92503.03, § 92503.05 ).

No Residential (N-)

Purpose, uses, standards: Listed as “No Residential” in § 90501.03; implementing standards: Not found in retrieved materials .
Where it applies: As mapped (§ 90501.04 ).

Specific Plan Area (SPA-)

Purpose: Identifies parcels governed by an adopted specific plan and its sub‑zoning map(s). The code repeatedly ties zone changes to “Sub‑zoning Map No. 14A — Mesquite Lake Specific Plan Area,” directing reviewers to that map for the controlling standards (§ 92533.01; § 92534.01 notes to Sub‑zoning Map 14A ).
Typical permitted uses: As specified by the applicable specific plan/sub‑zoning map. Not found in retrieved materials.
Key dimensional standards: As specified by the applicable specific plan/sub‑zoning map. Not found in retrieved materials.
Where it applies: Within mapped SPA areas; consult the specific plan document and sub‑zoning map referenced on the county map sheet (§ 90501.04; § 92533.01 ).

Mixed Use (MU)

Purpose: Encourages pedestrian‑oriented, compatible mixes of residential and nonresidential uses; discourages single‑use projects (§ 90501.11.A ).
Typical permitted uses: Residential integrated with compatible commercial (office, retail, personal services), public spaces, and community amenities; stand‑alone uses may be allowed when they foster an overall mix (§ 90501.11.A ).
Key dimensional standards and process: Established only within base zones C‑1 and C‑2; new development in MU requires site plan review with required findings (§ 90501.11.A–B ). Numeric height/setbacks unique to MU: Not found in retrieved materials; base‑zone and development standards continue to apply unless modified by approval.
Where it applies: Parcels in commercial base zones C‑1 or C‑2 where the MU overlay is mapped (§ 90501.11.A; § 90501.03 “MU” listing ).

Conditional Zone Change (C)

Purpose: Indicates a conditional zone change overlay attached to a parcel (§ 90501.03, C listing ).
Typical permitted uses/standards: Tied to the specific adopting ordinance. Not found in retrieved materials.
Where it applies: As mapped and as specified by the adopting ordinance file (§ 90501.04 ).

Quick reference — decision‑relevant overlays and processes

Overlay	What it does	Where allowed / trigger	Process or key standard	Code Reference
MU Mixed Use	Allows integrated residential + commercial; pedestrian‑oriented	Only within base zones C‑1 or C‑2 when MU is mapped	Site plan review required with findings	§ 90501.11.A–B
RE / REG Renewable Energy	Enables renewable energy projects (geo/solar/wind, etc.) in mapped areas	Must be inside RE overlay area; overlay amendments allowed under adjacency/island criteria	Projects require a CUP; comply with general standards	§ 91701.01–.04; § 91701.03 (CUP)
FP‑ Flood Plain Hazard	Flags special flood hazard areas	As mapped on official zoning/flood maps	County flood‑hazard review; published fees/appeals	§ 91606.02–.03
H‑ Airport Approach	Protects airport approach surfaces	As mapped near airports/airfields	Related “H” airport zone requires covenants; overlay height planes not retrieved	§ 90501.03; § 90501.10.B
U‑ Urban Areas	Applies urban‑area regs at time of permit/development	When a “‑U” suffix appears on the zone label	Apply “urban area” regulations; details not retrieved	§ 90501.03; examples § 92503.03, § 92503.05
SPA‑ Specific Plan Area	Subjects parcel to a specific plan’s sub‑zoning rules	Where SPA is mapped and a plan adopted	Use the referenced sub‑zoning map (e.g., Mesquite Lake)	§ 90501.03; § 92533.01 notes to Map 14A
L‑(x) Lot Size Min.	Raises minimum lot size above base‑zone minimum	Any base zone, when “L‑(x)” suffix is mapped	Minimum lot size equals “x” (e.g., L‑1 = 1 acre)	§ 90501.03 (L‑(x))

How overlays interact with base zoning and other approvals

Overlays do not replace the base zone in unincorporated areas; they add conditions or enable special uses. Always check your base zone in the Imperial County Zoning matrix first (§ 90501.02 ).
The official zoning maps control whether an overlay applies. Only maps “sealed” by the Planning Department Director are official; consult the department for a current copy (§ 90501.04 ).
Some overlays require permits beyond standard entitlements:
- MU: site plan review with findings (§ 90501.11.B ).
- RE: CUP within the overlay (§ 91701.03 ).
- FP: flood‑hazard review and fees/appeals are codified (§ 91606.02–.03 ).
Specific plan areas (SPA) shift standards to the plan’s sub‑zoning rules; the county’s map sheets reference which sub‑map to use (e.g., “Sub‑zoning Map No. 14A — Mesquite Lake Specific Plan Area”) (§ 92533.01; § 92534.01 notes ).
If an overlay appears to restrict a previously legal use, consult Imperial County Nonconforming Uses and/or Imperial County Variances and Exceptions for potential relief where allowed by code.

Checklist

Confirm your parcel is in the unincorporated area (overlays here do not govern incorporated cities).
Identify the base zone and all suffixes/overlays on the official zoning map (§ 90501.02; § 90501.04 ).
For any “MU” mapping in C‑1/C‑2, plan for site plan review and show a compatible residential‑commercial mix (§ 90501.11.A–B ).
For any “RE/REG” mapping, confirm your project technology is eligible and prepare a CUP per the county’s renewable‑energy submittal standards (§ 91701.03–.04 ).
If “FP‑” appears, contact the county regarding flood‑hazard review steps, timelines, and applicable fees/appeals (§ 91606.02–.03 ).
If “SPA‑” appears, obtain the relevant specific plan and referenced sub‑zoning map (e.g., 14A) (§ 92533.01/notes ).
Verify whether other overlays (G‑, GH‑, H‑, SH‑, MP‑, PE‑, U‑, N‑, C) impose conditions not evident in the base district. Not found in retrieved materials: request parcel‑specific conditions from the county.
Cross‑check applicable development standards and any required design review, parking, and land use permissions.

Risks & Ambiguities

Issue	Why it matters	What to verify
“REG” vs “RE” naming	§ 90501.03 lists “REG,” while Division 17 implements an “RE” overlay. Labeling affects map interpretation.	Ask Planning which label governs current overlay mapping; confirm eligibility and CUP pathway (§ 90501.03; § 91701.01–.03)
H‑ overlay vs H “zone”	§ 90501.03 lists H‑ as an overlay; § 90501.10 describes an “H” airport use zone with covenants.	Confirm whether mapped H‑ overlay references § 90501.10 standards or a separate approach‑surface standard set (§ 90501.03; § 90501.10)
U‑ (Urban Area) rules	Text says urban regs apply upon permit/development; details not retrieved.	Request the applicable “Urban Area” standards for your map sheet (§ 90501.03)
GH‑/SH‑/MP‑/PE‑/N‑ standards	Overlays are listed but standards and permitted‑use impacts are not in the retrieved text.	Obtain parcel‑specific conditions or adopting ordinances; confirm if any use prohibitions apply (§ 90501.03; § 90501.04)
SPA‑ sub‑zoning	Specific plans control where mapped; ignoring them can misapply standards.	Pull the referenced SPA sub‑zoning map (e.g., Map 14A) and plan‑text for your project (§ 92533.01/notes)
Floodplain scope	FP‑ triggers review and fees; dimensional/constructability limits weren’t retrieved.	Coordinate with the county’s flood review program for exact constraints and timelines (§ 91606.02–.03)

Plain-English Summary

In unincorporated Imperial County, overlays are suffixes added to your base zone that either enable a special use (like renewable energy or mixed use) or flag extra rules (like floodplain or airport approach). Check the official map to see your overlays, then follow any special processes (site plan review for MU, CUP for RE) and apply any referenced plan or review steps before designing your project (§ 90501.03; § 90501.11; § 91701.03; § 91606.02–.03 ). For day‑to‑day standards, also consult base‑zone rules and countywide development standards.

Source References

§ 90501.02 Base zoning areas established (R‑, A‑, C‑, M‑, S‑, G.S.)
§ 90501.03 Creation of overlay zoning areas (L‑, G‑, REG, GH‑, FP‑, H‑, SH‑, MP‑, PE‑, U‑, N‑, SPA‑, MU, C)
§ 90501.04 Zoning maps; official copies and use
§ 90501.10 “H” airport use/height restriction zone (uses, covenants)
§ 90501.11 Mixed‑Use (MU) overlay (purpose, applicability in C‑1/C‑2, site plan review)
Division 17, §§ 91701.00–91701.04 Renewable Energy Overlay (purpose; categories; CUP requirement; general standards; overlay map)
§ 91606.02–.03 Flood hazard review fees and appeals (areas of special flood hazard)
Map examples with overlays/sub‑zoning references: § 92503.03 (U‑ overlay in Calexico area), § 92514.04/§ 92534.01/§ 92533.01 (Mesquite Lake Specific Plan sub‑zoning; “‑G” geothermal)

Sources

Retrieved passages

Imperial County Zoning Code (§ 3) High relevance
Imperial County Zoning Code (§ 3) High relevance
Imperial County Zoning Code (§ 1) High relevance
Imperial County Zoning Code (SECTION 27) High relevance
California Building Code High relevance
Imperial County Zoning Code (§ 3) High relevance
Imperial County Zoning Code (§ 3) Medium relevance
Imperial County Zoning Code (SECTION 34) Medium relevance

Cited sections

Official Imperial County code library

Frequently asked questions

How do I tell if my unincorporated parcel is in an overlay district in Imperial County?

Check the official zoning map, which shows the base zone plus any overlay suffixes (e.g., A‑2‑U, C‑2‑PE, A‑2‑L‑1). The county’s sealed map is the controlling source (§ 90501.04) and overlays are listed in § 90501.03 .

What does the MU mixed‑use overlay allow in unincorporated Imperial County?

MU is intended to combine residential with compatible commercial uses in a walkable format. It applies only within base zones C‑1 or C‑2 and requires a site plan review with findings before development can proceed (§ 90501.11.A–B) .

Can I build a solar or geothermal project anywhere if I get a CUP?

No. Renewable energy projects must be inside the Renewable Energy (RE) overlay and then obtain a CUP in applicable base zones. Overlay amendments are possible under specific adjacency/“island” criteria (§ 91701.01–.03) .

I see “A‑2‑U” on my map label. What does the “‑U” overlay do?

“U‑” marks an Urban Area. Upon permit or development, the county applies the applicable Urban Area regulations. The code notes this in § 90501.03; request the specific urban‑area standards for your site from Planning (§ 90501.03) .

Does the FP‑ floodplain overlay change my setbacks or building height?

The code provided lists flood‑hazard review fees and appeals for projects “lying within an area of special flood hazard,” but specific dimensional limits were not retrieved. Coordinate with the county’s flood review board for exact constraints (§ 91606.02–.03) .

How do specific plans interact with overlays?

If your parcel carries an SPA‑ overlay, the adopted specific plan and its referenced sub‑zoning map (e.g., Mesquite Lake Map 14A) control key standards and land uses. The county’s map sheets include notes directing you to the correct sub‑map (§ 92533.01, § 92534.01 notes) .

What’s the difference between “REG” and “RE” renewable‑energy overlays?

§ 90501.03 lists “REG” in the overlay index, while Division 17 codifies an “RE” overlay with mapped categories and CUP requirements. Confirm with Planning which label governs current mapping and entitlement steps (§ 90501.03; § 91701.01–.03) .

Are airport height limits part of the overlay or a separate zone?

The overlay list includes H‑ (Airport Approach Height Restriction), and the ordinance also contains an “H” airport use/height restriction zone section requiring covenants. Ask Planning whether your mapped H‑ overlay references the § 90501.10 standards (§ 90501.03; § 90501.10) .

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