The Montana Water Quality Act (§75-5-605 ) requires a valid permit for the following activities:

(a) construct, modify, or operate a disposal system that discharges into any state waters;

(b) construct or use any outlet for the discharge of sewage, industrial wastes, or other wastes into any state waters; or

(c) discharge sewage, industrial wastes, or other wastes into any state waters.

MGWPCS permits are for discharge to state groundwaters. They are not applicable for discharges occurring within the boundaries of federally recognized Indian Lands. For additional information on discharges occurring within Indian Lands please refer to the USEPA Underground Injection Control Program

MGWPCS permits may also not be applicable for discharges located near state surface waters. For additional information on surface water discharge permits, please refer to the Surface Water Discharge (MPDES) program.

An individual MGWPCS permit is a stand-alone permit issued for a site-specific activity. Each individual permit may differ as they are based on the specifics of each discharge site and of each proposed discharge activity.

Each individual permit is placed into a category based on the type of wastewater to be discharged; either domestic (e.g. sinks, toilets, showers) or non-domestic (industrial or other wastewater). The most convenient way to apply or renew an individual permit is to use our online system FACTS. To file a paper application please see information below.

• Domestic Wastewater-Groundwater Permit Application
• Must be accompanied by MPDES General Information Form (DEQ-Form 1)
• Industrial & Other Wastewater- Groundwater Permit Application
• Must be accompanied by MPDES General Information Form (DEQ-Form 1)

Maintenance of an existing permit is sometimes needed in order to keep the permit up to date with proposed facility or administration changes. A Modifications may be classified as either a minor or major depending on the proposed changes.

Major Modifications are typically required when the permittee plans to alter their collection system, treatment facility, or disposal structures (e.g. addition of a discharging structure, increase in design capacity). A modification may not be required when replacing like-for-like equipment, or improving the existing treatment methods.

The application procedures for major modification of an individual permit mirrors the administrative procedure in applying for a new permit. For more information, please refer to the Individual Permit Application Information.

Minor Modifications are typical when the permittee plans on undergoing minor administrative changes such as transfer of permit ownership. In order to transfer ownership, a complete PTN form, along with a $500 minor modification fee is required.