Lou Harmon, Program Manager  
Phone 307-777-7088
email: lharmo@wyo.gov

SMALL WASTEWATER FACILTIES
(Septic Tanks and Leachfields)

APPLICATION PACKAGE

Counties Giving Local Approval (Delegated Programs)

Counties Requiring DEQ/WQD Approval (non-delegated)

APPROVED SEPTIC TANK LIST

GENERAL INSTRUCTIONS for DESIGN:
Less than 2000 Gallons Per Day GRAVITY SEPTIC SYSTEM utilizing a LEACHFIELD

Introduction - The following instructions are provided to assist you in submitting a properly completed application, design calculations, plan and detail sheets for a small wastewater treatment and disposal system (less than 2000 gallons per day). By carefully following the instructions and submitting all of the required information, delays can be avoided and a permit issued promptly.

Professionally Engineered Design - This design information package with the various system handouts for small wastewater treatment facilities has been prepared by registered professional engineers employed by the Wyoming Department of Environmental Quality (DEQ) / Water Quality Division (WQD).

Properly conducting the site evaluation including percolation tests, determination of seasonal high groundwater depth, important surface features, and other pertinent factors, will provide the applicant with the data needed for the system design. Using this data, following the instructions, and accurately completing the necessary sheets for the chosen system, should ensure that the applicant’s design will comply with the minimum requirements of the DEQ Water Quality Rules & Regulations, Chapter 11, Part D, effective date May 10th 1984.
Lead Engineer: Ronald L. Ewald, Wyoming PE No. 6279

Disposal Field Alternatives - The selection of the type of disposal system depends upon site conditions such as terrain, lot layout, soil percolation rates, seasonal high groundwater levels, and subsurface geology. The standard trench or bed type disposal system can be used under most conditions. A trench system tends to require less earthwork and leach field materials than a bed system. However, a bed system is more compact and may be desirable in situations where land area is limited. Trench or bed systems can be constructed with either perforated pipe and washed rock, or manufactured chambers.

If the site conditions are hilly such that the bottom of the disposal area cannot be kept level, then a side hill type of disposal field layout may be desirable. A separate side-hill handout is available.

If the seasonal high groundwater level, bedrock, or an impervious clay layer is within four feet of the bottom of the proposed leachfield, then a mounded, partially mounded, non-discharging pond, or evapotranspiration system may be required. Since these types of facilities are more difficult to design and construct, separate handouts have been prepared for each and are available upon request.

A pumping system may sometimes be necessary to pump the sewage uphill from the house or septic tank to the leachfield. A separate handout is also available to assist you with this design.

Application Submittal Requirements - A complete application package is necessary before a permit can be approved and issued. Three copies of the application form along with three copies of each pertinent page of the design package must be submitted with the application. Only those pages used for your individual design need to be submitted. There may be several pages in the design package which do not apply to your system - these pages need not be included. Additionally, any pages marked as “Example” or “Instructions” can be omitted.

Design Information - The instructions and examples will help you to calculate the size of your wastewater system and to supply the information that is necessary for us to review your project. The design information should then be transferred to the appropriate detail sheets as needed for your system. The following abbreviations are used throughout the design package:

gpd = gallons per day

sf or sq ft = square feet

mpi = minutes per inch

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