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City of Colstrip

Sewage treatment plant, Colstrip, Montana. NPDES permit MT0030422, in force until Jan 31, 2027. Last 12 months: no values over a limit. Source: EPA ECHO, Oct 22, 2026.

Reports due: About 28 days after each period: form A monthly (10 values)
Renewal application due: Aug 4, 2026 · 180 days before expiry; your permit may set another date
Last report on file: August 2026
Oct 2024 – Sep 2025: 0 values over a limit, 0 required values missing, 1 of 12 reports late

Limits in force (10)

Parameter	Statistic	Limit	Months
Flow rate	monthly average	report only (MGD)	all year
Flow rate	daily maximum	report only (MGD)	all year
pH	minimum	≥ 6.5 SU	all year
pH	maximum	≤ 9 SU	all year
Solids, total suspended	monthly average	≤ 50 mg/L	all year
Solids, total suspended	daily maximum	≤ 75 mg/L	all year
Aluminum, dissolved [as Al]	30-day average	≤ .1 mg/L	all year
Aluminum, dissolved [as Al]	instantaneous maximum	≤ .21 mg/L	all year
Chlorine, total residual	monthly average	≤ .1 mg/L	all year
Chlorine, total residual	daily maximum	≤ .1 mg/L	all year

How strict are these limits?

pH, minimum at least 6.5 SU — stricter than 57% of 26 other minor POTWs in Montana; 42% have the same limit
Chlorine, total residual, monthly average .1 mg/L — stricter than 40% of 1,313 other minor POTWs nationwide; 5% have the same limit
Solids, total suspended, daily maximum 75 mg/L — stricter than 17% of 1,356 other minor POTWs nationwide

Cited limits by parameter: Montana's rules and the federal ones.

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On EPA ECHO: Facility report · DMR history

Your permit document is the final word. As JSON: /api/v1/permits/MT0030422 · MCP: https://passage-data.com/mcp