Land Planning

Big Horn County

Land Planning Office

Paul Thur
Land Planner

P.O. Box 29
425 Murphy Street
Basin, WY 82410

Phone: 307-568-2424
Fax: 307-568-2461

Stephanie May - Land Planner Assistant

Office Hours
Monday - Friday: 8:00am – 5:00pm*

Due to fieldwork and meetings, appointments are strongly recommended.

What is a Subdivision?

A subdivision is the creation or division of a lot, tract, parcel or other unit of land for the immediate or future purpose of sale, building development or redevelopment, for residential, recreational, industrial, commercial or public uses. The process for subdividing depends on the number of lots being created, the size of the lots being created and the type of subdivision. We encourage landowners to become familiar with the Subdivision Regulations prior to submitting an application for a subdivision.

The Big Horn County Subdivision Regulations were modeled directly from the Wyoming State Statutes, Title 18, Chapter 5, Article 3 and customized to meet the specific needs of our county. They were amended on January 18, 2022. The amendments consist of clarifications of Wyoming Statutes, clarification of Big Horn County Road and Address Management Palicy, clarification of development agreements, clarification of water supply and water rights, additional definitions, addition of an Application for Exemption for an Affidavit of Exemption, additional plat requirements, amended fees, various grammatical errors.

Types of Subdivisions

Exempt Subdivisions

Important Update:

In 2019, The State of Wyoming Legislature passed House Bill 196. This bill changed the requirements for Subdivisions using the family exemption portion of Wyoming State Statue 18-5-303. The 5 and 1 year requirements have changed. Under the revised 18-5-303 (a) (i) (C) adopted on 02/27/2019, any Subdivsion of land using the family exemption must now be titled in the name of the grantor for a period of not less than 10 years prior of the division of land and the creation of a new parcel. The Immediate family member gaining title must now remain the titled owner for a period of not less than 5 years, unless one of the conditions set in  18-5-303 (a) (i) (C) are met.

Our policy is, any Subdivision using the Family exemption filed with the County Clerk on or before 02/26/2019 will use the 5 and 1 year requirements, and filings on or after 02/27/2019 will use the 5 and 10 year requirements. If you have any questions regarding this change please contact the Big Horn County Land Planner.

Use the following link to see the bill: Wyoming State Legislature 2019 House Bill 196  (will open in new window with state website)

A land division that is not required to go through the formal subdivision process, however, an exempt subdivision requires an Affidavit of Exemption to be filed with the Surveyor's Final Plat. Please contact the Land Planning Department for the Application for Exempt Land Division.

Click on the image below to see a graphic that shows some examples of exempt subdivisions:


Note: Not all exemptions are cut and dry; special conditions apply in most cases.  All exemptions and conditions for exemptions are explained in Chapter III, Section 3 of the Big Horn County Subdivision Regulations.

Simple Subdivision

A division of one unit of land into one or up to 5 lots, each smaller than 35 acres. Parcels greater than or equal to 35 acres that are created as part of land division are exempt from the subdivision process.

Major Subdivision

A division of one unit of land into three or more lots, each smaller than 35 acres. A major subdivision includes any subdivision that does not qualify as a simple subdivision.

See the graphic below that shows various types of subdivisions by lot number/size:

LP Examples subdivisions

Process Checklists

We have developed a few checklists to help our customers visualize and keep track of all the moving pieces throughout the process.

Simple Subdivision Process Checklist


To start the process on a new simple subdivision, complete and submit a Simple Subdivision Application to the Land Planning Department. 

To modify any part of an existing subdivision, complete and submit a Subdivision Amendment Application to the Land Planning Department.

To start the process on a new major subdivision, please consult with the Land Planner directly.


Delegated Official

The Wyoming Department of Environmental Quality delegated the authority and responsibility to enforce and administer the provisions of W.S. 35-11-301(a)(iii) and (v) for small wastewater facilities to Big Horn County. The delegation agreement includes the authority to do the following:

  • Develop necessary rules, regulations, standards and permit systems
  • Review and approve construction plans
  • Conduct inspections
  • Issue permits
  • Enforce against violations
  • Develop rules governing the review and appeal of any decision made by Big Horn County

Septic Permit

A septic permit is required before construction of a small wastewater treatment facility can commence.

Septic Permit Application Package

A Septic Permit Application Package is required for any new construction/install, replacement or repair of a small wastewater treatment facility within unincorporated areas of Big Horn County. The application should ONLY be used for conventional systems (septic tank and leachfield) with a wastewater flow of less than 2,000 gallons per day. The system design must comply with the minimum requirements of the Wyoming Water Quality Rules and Regulations, Chapter 25. Only those pages which are applicable to your system must be submitted in addition to the application.

Basic Septic Installation Process Overview

*Not all installations will follow this exact process. Exceptions are possible.*

  1. Obtain a Septic Permit Application from Land Planning
  2. Conduct groundwater exploration cut and percolation tests
  3. Submit Septic Permit Application to Land Planning
  4. Design system
  5. Submit design to Land Planning
  6. Obtain county-issued Permit to Construct
  7. Install system according to approved design specifications
  8. Land Planning inspects system before backfilling occurs
  9. Obtain county-issued permission to backfill

PLEASE CALL OR STOP BY IF YOU NEED HELP! We will try to make the process as simple as possible.


  • Water leakage
  • Introduction of non-domestic waste products into the system (e.g., dental floss, feminine hygiene products, diapers, condoms, cotton swabs, coffee grounds, cat litter, paper towels, household chemicals, oil, gasoline, pesticides, paint, antifreeze)
  • Buildup of oil and grease
  • Buildup of solids and sludge
  • Heavy internal water usage
  • Heavy external watering (e.g., irrigation, excessive rain or runoff water, pooled water)
  • Poor system design
  • Dense soil
  • Crushed or damaged system components (e.g., driven over, parked on, tree root growth, livestock grazing)

The Land Planning Department is responsible for assigning all physical addresses in the unincorporated areas of Big Horn County.

The County requires the assignment of a physical address for all residences, businesses, seasonally-occupied structures (e.g., cabins and ranger stations), high-frequency public use structures (e.g., comfort stations, rest areas, and similar), and unmanned facilities connected to a utility in unincorporated Big Horn County. Addressing of other structures may be required or taken into consideration at the discretion of the Land Planning Department. Addresses will generally not be assigned to vacant lots or parcels where no development is planned in the near future.

How to Request a Physical Address

Self-assignment of addresses is prohibited in Big Horn County, the County Land Planner assigns all addresses based on the County Road and Address Management Policy (RAMP). In order to assign an address in unincorporated Big Horn County, you must submit an Address Application and fee to the Land Planning Department. 

The following will be verified before an address is issued:

  • Applicant is the owner of the property upon which an address is being requested. If the applicant is not the landowner, approval from the landowner is required
  • Verification of legal passage to the land, verification of direct access to a permitted County ROW, WYDOT, or easement through private land to a public ROW.
  • Does the parcel meet the road name requirements of the RAMP?

How is an address number determined?

If the address location is on a currently named road, the address number will be assigned based on a number range defined by the Big Horn County Address System. Using geographic information systems (GIS), the road will be segmented into sections that match the range of numbers defined. In most cases, the address number assigned will be chosen where the access road to the address location meets the named road. Generally, addresses north or east of the named road will have an odd number assigned and addresses south or west of the named road will have an even number assigned.

If the address location is on an unnamed road and there are two or fewer addressed locations along the access, a number will be assigned based on the named road that the access road intersects. If the address location is on an unnamed road and there are three or more addressed locations along the access, the private road will first be named using the process defined in the Big Horn County Road and Address Management Policy, then all addresses along the road will be reassigned accordingly.

Address Changes

There are occasions where addresses are modified. One example is when more than two residences share a common access road that has not yet been named. In this case, the road will be named and any existing addresses along the road will be changed to match the newly named road. Each addressee will be notified of the change, as well as all emergency services and dispatch offices, utility companies, county offices, the postal service, and other interested parties.

If an existing address does not conform to the County address system or policy, the County Planner will initiate the process for changing an address.

See the Big Horn County Road and Address Management Policy for more information.

Reporting Damaged Signs

To report a down, missing, or damaged sign call the Land Planning Department at (307) 568-2424 or send an email to

Addresses for In-Town Residents

If the structure you are seeking an address for is within a municipal boundary (i.e., Basin, Burlington, Byron, Cowley, Deaver, Frannie, Greybull, Lovell, or Manderson), please contact the appropriate municipality. The Land Planning Department only issues in-town addresses upon the request of the town administration.