Mammoth Lakes — Overlay Districts

Last reviewed: July 2, 2026

Overview

Mammoth Lakes' Title 17 establishes three special-purpose overlay zones that layer additional rules on top of the underlying zoning: the Equestrian Overlay Zone (E), the Open Space/Stream Corridor Protection Overlay Zone (OSSC), and the Snow Deposition Design Overlay Zone (SDD). These overlays modify permitted uses, require special reports or use permits, and set dimensional or performance limits intended to protect natural resources and public safety. The overlay types and their place on the Town Zoning Map are adopted in the Zoning Code and on the map on file with the Department; see § 17.32.010 and § 17.16.030 for the controlling provisions .

District-by-district breakdown

Equestrian Overlay Zone (E)

• Purpose: The E overlay is intended to permit the keeping of horses or pack stock in limited, accessory situations while minimizing impacts on neighbors and resources; see § 17.32.020 .
• Typical permitted uses: Keeping horses or pack stock only as an accessory use to an existing permitted use and only for personal/family use. Commercial boarding or riding operations on non-owner property are not permitted under the overlay; see § 17.32.020 .
• Key dimensional/operational standards (code-based):
  • Minimum lot size to keep horses: 20,000 sq ft (minimum) and the overlay initiation minimum is 5 acres for creating an E zone; see § 17.32.020 and initiation rules in § 17.32.020(d) .
  • Number of animals: Maximum of two horses on a 20,000 sq ft lot; add one horse per additional 10,000 sq ft of lot area (explicit in § 17.32.020(c)(2)) .
  • Setbacks and structure limits: No horse/pasture closer than 50 ft to an adjoining dwelling (never closer than 25 ft to a property line); barns/stables subject to main-building setbacks but in no case closer than 10 ft to side/rear lot lines and max 15 ft height (see § 17.32.020(c)(3)-(5)) .
  • Environmental controls: Animal confinement areas must be kept clean; confinement areas must be at least 50 ft from any permanent lake or stream and waste must not run into water bodies (§ 17.32.020(c)(6)-(7)) .
• Where it applies: Overlay boundaries are shown on the adopted Town Zoning Map; initiating or amending an E overlay follows the map amendment procedures of Chapter 17.108 (§ 17.16.030 and § 17.32.020(d)) .

Practical note: If you propose horse facilities on a property that touches an OSSC or watercourse, confirm the 50‑ft water setback and streambed mapping requirements in § 17.36.100 (streambed info) as part of permitting .

Open Space / Stream Corridor Protection Overlay Zone (OSSC)

• Purpose: The OSSC is intended to protect sensitive stream and drainage corridors, preserve wetland habitat, and protect water quality; see § 17.32.030 .
• Typical permitted uses: Uses default to the underlying zoning classification, but the OSSC makes land use more restrictive in practice:
  • A use permit is required for all uses except a single‑family dwelling on a single lot (explicit in § 17.32.030(b)) .
  • The code allows transfer of development rights associated with private property in OSSC to other private holdings by use permit (§ 17.32.030(b)) .
• Key standards and application items:
  • Any project adjacent to a permanent stream or lake must submit a site‑specific streambed analysis prepared by a qualified professional to identify the top of bank; see § 17.36.100(3) for streambed information requirements .
  • Development standards, parking, and mitigation will normally be set in the use permit or conditions of approval for OSSC properties (§ 17.32.030(c)) .
• Where it applies: Shown on the Town Zoning Map as OSSC; see § 17.16.030 for the map adoption and legend that lists OSSC as a zoning overlay .

Practical note: Expect the department to treat OSSC parcels as environmentally constrained — most non‑minor work will be subject to discretionary review and conditions tied to water quality (Lahontan RWQCB) and streambed mapping requirements .

Snow Deposition Design Overlay Zone (SDD)

• Purpose: The SDD is specifically focused on avalanche/snow deposition hazards: identify areas with avalanche potential and minimize health and safety hazards tied to avalanche deposition; see § 17.32.040 .
• Applicability and permitted uses:
  • The SDD applies to areas located immediately above, adjacent to, or within 150 feet of the 30‑degree point of an avalanche starting zone as shown on the Town Zoning Map (§ 17.32.040(b)) .
  • No development (including building permits and subdivisions) is allowed without first obtaining a use permit; roads, driveways, and utilities are not included in that prohibition (§ 17.32.040(c)) .
• Required technical submittals:
  • Use permit applications must include certification by a recognized avalanche expert that there will be no greater snow deposition and no overall increase in avalanche hazard; Town may require a second opinion at applicant expense (§ 17.32.040(c)(1)-(2)) .
  • The SDD contains a strong disclaimer: the Town does not warrant ultimate safety; development in SDD is at owner risk and permitting does not eliminate hazard potential (§ 17.32.040(d)) .
• Where it applies: SDD boundary is mapped on the Zoning Map and listed in Table 17.16.030 as the SDD overlay; check the map on file with the Department and verify with staff for parcel‑level applicability (§ 17.16.030 and § 17.32.040) .

Practical note: In SDD areas expect detailed geotechnical / avalanche engineering and strict findings before discretionary permits will be approved; the code contemplates hiring outside experts paid by applicants for second opinions (§ 17.32.040(c)(2)) .

Quick reference table — decision‑relevant overlay rules

How overlays interact with other standards (practical guidance)

• Overlays layer on top of the underlying zone standards in Chapters 17.16–17.32; if there is a conflict, the specific zoning district standards override the general standards in Chapter 17.36, but overlay rules add constraints that must be satisfied in addition to base zone standards; see § 17.36.010 for the interplay of general site‑planning standards and district rules .
• Projects in overlays commonly trigger discretionary review (use permit) and therefore may require design review and conditions tied to parking, landscaping, signage, or other requirements; linkages to parking standards and design review processes are routine and you should plan to address them in permit submittals (see cross-references to parking Chapter 17.44 and design review Chapter 17.88 in district tables) .
• For projects near watercourses, the streambed information requirement under § 17.36.100 applies in addition to OSSC rules; provide a hydrologist/civil engineer report early in the process .
• For accessory dwelling units (ADUs) or residential modifications on overlayed parcels, state ADU law interacts with local standards; local ADU rules require building-code compliance and other local site standards — consult § 17.36.x ADU provisions and the California Building Standards Code for construction requirements; verify the ADU policy in Title 17 before relying on a blanket approach .

Inline resources you should consult on applications: Mammoth Lakes Zoning & planning overview, the Zoning chapter, Development Standards, Parking, Design Review, Landscaping and Screening, Signage, and the ADU guidance pages.

Checklist — what an applicant must satisfy for overlayed parcels

• Confirm overlay designation on the Town Zoning Map (verify OSSC/SDD/E presence) and record it on the project cover sheet (§ 17.16.030) .
• Determine whether the proposed activity is allowed by the underlying zone; if not, plan a zoning amendment per Chapter 17.108 (§ 17.108.010–.030) .
• If in OSSC, prepare to submit a use permit for all but single‑family on a single lot and include any required streambed information as specified in § 17.36.100 .
• If in SDD, include avalanche expert certification and any avalanche‑mitigation design; expect Town review and possible independent second‑opinion at applicant expense (§ 17.32.040(c)) .
• If proposing horse keeping under E, show lot area calculations, animal counts, confinement layout, setbacks, and compliance with County Environmental Health / Animal Control standards (§ 17.32.020(c)) .
• Address general site standards: snow storage (§ 17.36.110), setback rules (§ 17.36.100), and landscaping/screening conditions (see Landscaping and Screening) .
• Expect conditions, possible mitigation, and design review (see Design Review) if discretionary approvals are required .
• Verify building permits follow the California Building Standards Code and local building/fire rules; technical reports required by overlays do not replace building‑code submittals (see California Building Standards Code) .

Risks & Ambiguities

Information Gaps

• Parcel‑level overlay boundaries and exact SDD mapped extents: Not found in retrieved materials (verify with Department/Zoning Map) .
• Exact application fees, hearing timelines, and step‑by‑step submittal checklists for overlay use permits: Not found in retrieved materials (verify with the Department).
• Specific standards for the content and format of avalanche expert reports (scope, required analyses): The code requires certification but does not specify report format; clarify with the Department (§ 17.32.040(c)) .
• Any recent amendments or overlay additions after the print export provided here: Verify with the Town’s online code or Department for updates.

Plain-English Summary

If your property in Mammoth Lakes sits inside one of three overlays—E (horses), OSSC (stream/open‑space protection), or SDD (avalanche/snow deposition)—you must follow extra rules beyond the base zone: E limits horses to accessory, family use with lot‑size and setback rules; OSSC generally requires a use permit (except for a single family on a single lot) and streambed studies for projects near water; and SDD requires a use permit plus an avalanche expert certification before most types of development can proceed. See the specific code sections § 17.32.010–.040 and check the Town Zoning Map to confirm whether your parcel is inside an overlay .

Source References

• Title 17 — ZONING (Town Zoning Code, print export). Overlay zones listed in § 17.32.010 (special purpose overlay zones list) .
• § 17.32.020 — Equestrian Overlay Zone (E): purpose, permitted uses, lot/animal/setback/structure standards and initiation rules .
• § 17.32.030 — Open Space/Stream Corridor Protection Overlay Zone (OSSC): purpose, use permit requirement, development rights transfer option .
• § 17.32.040 — Snow Deposition Design Overlay Zone (SDD): purpose, applicability (150 ft rule), use permit and avalanche expert certification requirements, Town disclaimer of liability .
• § 17.16.030 — Zoning Map adoption and legend listing overlay map symbols (OSSC, SDD, etc.) .
• § 17.36.100 and § 17.36.110 — Streambed information, permanent lake/stream setbacks and snow storage requirements (applies to projects in overlays) .
• Chapter 17.108 — Procedures for map and text amendments (initiation and processing of overlay changes) .
• Mammoth Lakes zoning/navigation pages noted inline: Mammoth Lakes zoning & planning overview, Mammoth Lakes Zoning, Mammoth Lakes Development Standards, Mammoth Lakes Parking, Mammoth Lakes Design Review, Mammoth Lakes Landscaping and Screening, Mammoth Lakes ADUs, California Building Standards Code.

Retrieved passages

• Mammoth Lakes Zoning Code (§ 17.28.030) High relevance show source text
• Mammoth Lakes Zoning Code (Chapter 17.116.) Medium relevance show source text
• CBC § 17.28.030 (Chapter 17.88) Medium relevance show source text
• Mammoth Lakes Zoning Code (Title 17) Medium relevance show source text
• Mammoth Lakes Zoning Code Medium relevance show source text
• Mammoth Lakes Zoning Code (§ 17.52.120) Medium relevance show source text
• Mammoth Lakes Zoning Code (§ 65800) Medium relevance show source text
• Mammoth Lakes Zoning Code (Chapter 17.60) Medium relevance show source text
• Mammoth Lakes Zoning Code (§ 17.32.040) High relevance show source text
• Mammoth Lakes Zoning Code (Chapter 17.108.) High relevance show source text
• Mammoth Lakes Zoning Code (Section 17.04.010) High relevance show source text
• Mammoth Lakes Zoning Code (§ 17.32.070) High relevance show source text
• Mammoth Lakes Zoning Code (Chapter 17.56) Medium relevance show source text

Cited sections

• Title 17 — ZONING (Town Zoning Code, print export). Overlay zones listed in **§ 17.32.010** (special purpose overlay zones list) . (Title 17)
• **§ 17.32.020** — Equestrian Overlay Zone (E): purpose, permitted uses, lot/animal/setback/structure standards and initiation rules . (§ 17.32.020)
• **§ 17.32.030** — Open Space/Stream Corridor Protection Overlay Zone (OSSC): purpose, use permit requirement, development rights transfer option . (§ 17.32.030)
• **§ 17.32.040** — Snow Deposition Design Overlay Zone (SDD): purpose, applicability (150 ft rule), use permit and avalanche expert certification requirements, Town disclaimer of liability . (§ 17.32.040)
• **§ 17.16.030** — Zoning Map adoption and legend listing overlay map symbols (OSSC, SDD, etc.) . (§ 17.16.030)
• **§ 17.36.100** and **§ 17.36.110** — Streambed information, permanent lake/stream setbacks and snow storage requirements (applies to projects in overlays) . (§ 17.36.100)
• **Chapter 17.108** — Procedures for map and text amendments (initiation and processing of overlay changes) . (Chapter 17.108)
• Mammoth Lakes zoning/navigation pages noted inline: Mammoth Lakes zoning & planning overview, Mammoth Lakes Zoning, Mammoth Lakes Development Standards, Mammoth Lakes Parking, Mammoth Lakes Design Review, Mammoth Lakes Landscaping and Screening, Mammoth Lakes ADUs, California Building Standards Code.
• MammothLakes_ZoningCode.md

• Official Mammoth Lakes code library