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Oconomowoc Wastewater Treatment Plant

Sewage treatment plant, major discharger, Oconomowoc, Wisconsin. NPDES permit WI0021181 expired Sep 30, 2025; its limits still apply. Last 12 months: over a limit once (last January 2026), 15 required values missing, 1 of 26 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 21 days after each period: outfall 001 form A monthly (9 values), outfall 001 form Q quarterly (3 values), outfall 701 form A monthly (6 values), outfall 001 form AN yearly, outfall 103 form AN yearly, outfall 701 form AN yearly
Last report on file
June 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 1 of 21 reports late

Last 12 months (Oct 1, 2025 – Sep 30, 2026)

Period endingParameterReportedLimitOver by
January 2026BOD, 5-day, 20 deg. C, weekly average7.94≤ 7 mg/L13%

Limits in force (21)

ParameterStatisticLimitMonthsOutfall
Oxygen, dissolved [DO]daily minimum≥ 7 mg/Lall year001
BOD, 5-day, 20 deg. Cweekly average≤ 7 mg/Lall year001
BOD, 5-day, 20 deg. Cmonthly average≤ 7 mg/Lall year001
BOD, 5-day, 20 deg. Cweekly average≤ 233 lb/dall year001
pHdaily minimum≥ 6 SUall year001
pHdaily maximum≤ 9 SUall year001
Solids, total suspendedweekly average≤ 10 mg/Lall year001
Solids, total suspendedmonthly average≤ 10 mg/Lall year001
Nitrogen, total [as N]quarterly maximumreport only (mg/L)all year001
Nitrogen, ammonia total [as N]monthly maximumreport only (mg/L)all year001
Nitrogen, Kjeldahl, total [as N]quarterly maximumreport only (mg/L)all year001
Nitrite + Nitrate total [as N]quarterly maximumreport only (mg/L)all year001
Mercury, total recoverableannual maximumreport only (ng/L)all year001
Mercury, total recoverableannual maximumreport only (ng/L)all year103
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all year701
BOD, 5-day, 20 deg. Cmonthly maximumreport only (mg/L)all year701
Solids, total suspendedmonthly averagereport only (mg/L)all year701
Solids, total suspendedmonthly maximumreport only (mg/L)all year701
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all year701
Flow, in conduit or thru treatment plantmonthly maximumreport only (MGD)all year701
Mercury, total recoverableannual maximumreport only (ng/L)all year701

How strict are these limits?

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

Check this month's numbers Email me before each report is due

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On EPA ECHO: Facility report · DMR history

Your permit document is the final word. As JSON: /api/v1/permits/WI0021181 · MCP: https://passage-data.com/mcp