Friday, February 15, 2019
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Land Planning - Subdivisions

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 last amended in April of 2012. We anticipate significant revisions in the coming year to provide better clarification of the legal language, process maps to guide landowners through the subdivision process and affidavits for exemptions.

Types of Subdivisions

Exempt Subdivision: A land division that is not required to go through the formal subdivision process with oversight by the Land Planning Department. The most common exemptions seen in Big Horn County are >35-acre parcel splits, boundary line adjustments, family exemptions and mortgages.

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

ExemptSubdiv Example Graphic

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 two 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.



Click on the image below to see a graphic that shows various types of subdivisions by lot number/size:

TypesOfSubdivisions LotNumberSizeOnly

Process Checklists

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

Basic Simple Subdivision Process Checklist

Detailed 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.

Land Planning - Septic Systems


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; and
  • 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)

Land Planning - Rural Addressing

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

  • A physical address will not be assigned unless an existing structure is on site or active, permitted development of a structure is in progress.
  • Your physical address may differ from your mailing address; this is determined by your post office.
  • Proof of permitted access to the site to be addressed may be required before an address will be assigned.
  • A county-issued fire marker displaying the address number is placed where the driveway to the addressed structure meets a named road.

How to Request a Physical Address:
In order to get an address in unincorporated Big Horn County, you must submit an Address Application and fee to the Land Planning Department. The Land Planning staff will review your application, assign an address and contact you (and any appropriate agencies) with your new address.

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 less 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, WY, Rural Addressing 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, WY, Rural Addressing 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.

Contact Land Planning

Land Planning Office
P.O. Box 29
417 Murphy Street
Basin, WY 82410
Phone: 307-568-2424
Fax: 307-568-2461

Office Hours
Monday - Friday
8:00am – 5:00pm*
Due to fieldwork and meetings,
appointments are strongly recommended.