The process of dividing land into parcels is a necessary and important function in the growth of a community. When, where, and how development occurs establishes land division patterns for the community that will last for generations.
The DEQ Subdivision Program reviews divisions of land comprising less than 20 acres, as well as condominiums and recreational camping vehicle and mobile home parks, regardless of the size of the parcel where they are located. This review is limited to sanitation facilities, including the water supply, sewage disposal, solid waste disposal, and storm drainage systems.
Subdivisions are reviewed prior to creating the parcels to assure that adequate sanitation facilities can be constructed, operated, and maintained to support each parcel. Planning ahead for proper design and location of the facilities helps protect both our surface and ground water in Montana.
Design manuals have been developed to provide standards for wastewater treatment systems, water supply development, and storm drainage systems. The regulations also set out minimum separation distances between water supply sources and potential contamination sources such as wastewater treatment systems, surface waters, and floodplains.
The regulations and subdivision review are structured to prevent pollution problems through the proper design, location, operation, and maintenance of sanitation facilities.
Subdivision Review Fee Calculation - Effective April 22, 2016
Before DEQ Subdivision approval can be finalized (allowing you to move forward with your project), you must first obtain a water right or have a letter provided by the Department of Natural Resources & Conservation indicating that your usage does not require a beneficial water use permit. For instructions on requesting a determination by DNRC regarding water right requirements visit: DNRC Water Right Inquiry Instructions
Montana’s Water Quality Act requires the Department of Environmental Quality to protect high quality waters from degradation. Nondegradation rules apply to all Montana Pollutant Discharge Elimination System (MPDES) permits, Montana Ground Water Pollution Control System (MGWPC) permits, and any activities that may affect the quality of surface or ground water.
Nondegradation determinations are typically associated with “mixing zones.” A mixing zone is defined by law and by rules as an area of wastewater discharge as it enters either receiving surface water or ground water. The zone is established in the wastewater permit or by final decision by DEQ on nondegradation. Water quality standards may be exceeded within the zone; however, the mixing zone must have: a definable boundary; be of the smallest practicable size; and a minimum effect on water uses. Water quality standards must be met at the end of a mixing zone. A mixing zone cannot be granted for a surface water discharge permit if it would threaten or impair existing beneficial uses. For ground water, human health-based standards must not be exceeded beyond the boundaries of the mixing zone. A proposed activity may not begin until DEQ has issued a nondegradation determination. Certain exemptions may apply to the nondegradation requirements. More information about mixing zones and nondegradation can be found in Water Quality Standards and in the Mixing Zone Rules
How to Perform a Nondegradation Analysis for Subsurface Wastewater Treatment Facilities
- Appendix A: SWTS - Nondegradation Checklist (xls)
- Appendix B: SWTS - Significance Determination Checklist (pdf)
- Appendix C: SWTS - Ground Water Mixing Zone Determination Checklist (pdf)
- Appendix D: SWTS - Surface Water Mixing Zone Determination Checklist (pdf)
- Appendix E: Nitrate Sensitivity Analysis Spreadsheet (xls)
- Appendix E: Nitrate Sensitivity Analysis Spreadsheet - Cumulative Effects (xls)
- Appendix F: Bauman and Schafer Paper (pdf)
- Appendix G: Calculating Hydraulic Conductivity from Well Log Pumping Test Data (pdf)
- Appendix H: Hydraulic Gradient Three Point Solution Worksheet (pdf)
- Appendix I: Hydraulic Gradient Example (gif)
- Appendix J: Allowed Nitrate Concentrations (ARM 17.30.715) (pdf)
- Appendix K: Examples of Accepted Methods for Drawing Mixing Zones (pdf)
- Appendix L: Nitrate Sensitivity Analysis: Cumulative Effects Example (pdf)
- Appendix M: Identification of Confined Aquifers (1/3) (pdf)
- Appendix M: Identification of Confined Aquifers (2/3)(pdf)
- Appendix M: Identification of Confined Aquifers (3/3) (pdf)
- Appendix N: Phosphorus Breakthrough Analysis Spreadsheet (xls)
- Appendix O: Calculation of Cumulative Phosphorus Impacts (pdf)
- Appendix O: Calculation of Cumulative Phosphorus Impacts Figure (jpg)
- Appendix P: Summary of Categorical Exemptions (pdf)
- Appendix Q: Adjacent to Surface Water Dilution Analysis (xls)
- Appendix R: Darcy's Law for Calculating Ground Water Flow Volumes (pdf)
- Appendix S: Estimating 7Q10 on an Ungauged Stream (pdf)
- Appendix T: Trigger Value Calculations for Impacts of Nitrates to Surface Water (pdf)
- Appendix U: Pathogen Transport (xlsx)
Proposed Rule and Circular DEQ-8 Changes