# Montana HB 664: Repeal numeric nutrient standards

Montana HB 664, Repeal numeric nutrient standards, is a 69th Legislature, Regular Session (2025) House bill sponsored by Bill Mercer (Republican); status signed, last action 2025-05-05 (Chapter Number Assigned) (as of 2026-10-12).

- Canonical: https://policyrisk.com/state-bill/MT-HB664-2025
- As of: 2026-10-12
- Plain-text twin of the page above; the HTML and this file carry the same facts.

## Facts
- Bill: Montana HB 664
- State: Montana
- Session: 69th Legislature, Regular Session (2025)
- Title: Repeal numeric nutrient standards
- Status: signed
- Chamber: House
- Introduced: 2025-02-22
- Last action: 2025-05-05, Chapter Number Assigned
- Sponsor: Bill Mercer (Republican)
- Cosponsors: 1
- Subjects: Environmental Protection, State Government, Water, Rule Making
- Touches household money: no
- Roll calls: 4 (207 yes, 91 no in all)
- Economic provisions PRIA read: 3

## Summary

No summary available.

## Bill overview: provisions PRIA read

- Numeric nutrient standards repealed, new rules: benefit, medium. The law repeals DEQ-12A, Montana’s numeric nutrient standards. DEQ deletes all references to DEQ-12A in ARM 17.30.507, 17.30.516, 17.30.602, 17.30.619–17.30.629, 17.30.702, and 17.30.715. It also repeals ARM 17.30.660 and 17.30.1388 and removes the old transition statute, 75-5-321. DEQ now sets nut…
- New pollution and mixing zone definitions: mixed, low. The law says groundwater contamination inside a permitted CO2 storage reservoir is not “pollution.” It also says certain contamination does not get a mixing zone. These changes alter permit and enforcement rules for the affected discharges.
- Watershed advisory groups replace workgroup: mixed, low. The law removes the Nutrient Work Group from statute. DEQ no longer uses that group for advice on nutrient rules. Instead, watershed advisory groups advise DEQ on the impaired-waters list and TMDLs under 75-5-702 and 75-5-703.

## Sponsors and cosponsors

- Sponsor: Bill Mercer (Republican), House
- Cosponsor: John Esp (Republican), Senate

## Roll call votes

| Date | Chamber | Motion | Result | Yes | No | Other |
| --- | --- | --- | --- | --- | --- | --- |
| 2025-04-15 | Senate | Do Concur | pass | 34 | 16 |   |
| 2025-04-14 | Senate | Do Concur | pass | 34 | 16 |   |
| 2025-03-07 | House | Do Pass | pass | 69 | 30 |   |
| 2025-03-06 | House | Do Pass | pass | 70 | 29 |   |

## Actions (23)

- 2025-05-05: Chapter Number Assigned (House)
- 2025-05-01: Signed by Governor (House)
- 2025-04-24: Transmitted to Governor (House)
- 2025-04-24: Signed by President (Senate)
- 2025-04-23: Signed by Speaker (House)
- 2025-04-18: Returned from Enrolling (House)
- 2025-04-15: Sent to Enrolling (House)
- 2025-04-15: 3rd Reading (Senate)
- 2025-04-14: 2nd Reading (Senate)
- 2025-04-10: Committee Report (Senate)
- 2025-04-09: Committee Executive Action (Senate)
- 2025-03-27: Hearing (Senate)
- 2025-03-17: Referred to Committee (Senate)
- 2025-03-14: 1st Reading (Senate)
- 2025-03-07: Transmitted to Senate (House)
- 2025-03-07: 3rd Reading (House)
- 2025-03-06: 2nd Reading (House)
- 2025-03-01: Committee Report (House)
- 2025-02-28: Committee Executive Action (House)
- 2025-02-24: Hearing (House)
- 2025-02-22: 1st Reading (House)
- 2025-02-22: Referred to Committee (House)
- 2025-02-22: Introduced (House)

## Bill text

- Enrolled, 2025-04-16: [PDF](https://docs.legmt.gov/download-ticket?ticketId=c4b45d3f-5eb5-4cb1-b0cf-ef09047ae8ee)
- Introduced, 2025-02-22: [PDF](https://docs.legmt.gov/download-ticket?ticketId=f9008209-a778-4b6a-9b41-486053f0b0e2)

## Related bills

- SB 437: Revise definition of sex in Montana law (signed)
- HB 831: Increase elderly homeowner and renter income tax credit (vetoed)
- HB 628: Revise early literacy targeted intervention laws (vetoed)
- SB 410: Provide for Montana genomic security act (vetoed)
- SB 424: Revising the disabled veteran property tax assistance program (vetoed)
- SB 422: Generally revise laws relating to insurance coverage relating to cancer (vetoed)

## Sources
- [Enrolled (PDF)](https://docs.legmt.gov/download-ticket?ticketId=c4b45d3f-5eb5-4cb1-b0cf-ef09047ae8ee)
- [Introduced (PDF)](https://docs.legmt.gov/download-ticket?ticketId=f9008209-a778-4b6a-9b41-486053f0b0e2)

## Related
- [SB 437: Revise definition of sex in Montana law](https://policyrisk.com/state-bill/MT-SB437-2025)
- [HB 831: Increase elderly homeowner and renter income tax credit](https://policyrisk.com/state-bill/MT-HB831-2025)
- [HB 628: Revise early literacy targeted intervention laws](https://policyrisk.com/state-bill/MT-HB628-2025)
- [SB 410: Provide for Montana genomic security act](https://policyrisk.com/state-bill/MT-SB410-2025)
- [SB 424: Revising the disabled veteran property tax assistance program](https://policyrisk.com/state-bill/MT-SB424-2025)
- [SB 422: Generally revise laws relating to insurance coverage relating to cancer](https://policyrisk.com/state-bill/MT-SB422-2025)
- [Montana bills](https://policyrisk.com/states/montana/bills)
- [Montana state hub](https://policyrisk.com/states/montana)
- [All state legislation](https://policyrisk.com/state-bills)

Source: PRIA, https://policyrisk.com/state-bill/MT-HB664-2025 (as of 2026-10-12).