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Colusa, City of

Sewage treatment plant, Colusa, California. NPDES permit CA0078999, in force until May 31, 2027. Last 12 months: over a limit 14 times (last July 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 32 days after each period: outfall 001 form A monthly (27 values), outfall 001 form C monthly (2 values), outfall 001 form D monthly (2 values), outfall 001 form Q quarterly (2 values), outfall 001 form Y monthly (16 values), outfall INF form A monthly (7 values)
Renewal application due
Dec 2, 2026 · 180 days before expiry; your permit may set another date
Last report on file
August 2026
Oct 2024 – Sep 2025
39 values over a limit, 0 required values missing, 0 of 64 reports late

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

All 14 values over a limit
Period endingParameterReportedLimitOver by
October 2025% Survival Flow Through 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
October 2025% Survival Flow Through 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
October 2025% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
October 2025% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
October 2025Coliform, total general, 7-day median6.8 MPN/100mL≤ 2.2 MPN/100mL209%
November 2025% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
November 2025% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
January 2026% Survival Flow Through 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
January 2026% Survival Flow Through 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
January 2026% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
January 2026% Survival Static Renewal 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
February 2026% Survival Flow Through 96Hr Acute Pimephales promelas, minimum median0 % survival≥ 90 % survival100%
February 2026% Survival Flow Through 96Hr Acute Pimephales promelas, minimum0 % survival≥ 70 % survival100%
July 2026Coliform, total general, 7-day median4.5 MPN/100mL≤ 2.2 MPN/100mL105%

Limits in force (58)

ParameterStatisticLimitMonthsOutfall
Temperature, water deg. fahrenheitinstantaneous maximumreport only (deg F)all year001
Turbiditydaily averagereport only (NTU)all year001
Turbidityinstantaneous maximumreport only (NTU)all year001
Specific conductancemonthly averagereport only (umho/cm)all year001
Specific conductancedaily maximumreport only (umho/cm)all year001
Oxygen, dissolved [DO]instantaneous minimumreport only (mg/L)all year001
BOD, 5-day, 20 deg. Cmonthly average≤ 10 mg/Lall year001
BOD, 5-day, 20 deg. Cweekly average≤ 15 mg/Lall year001
pHminimum≥ 6.5 SUall year001
pHmaximum≤ 8.5 SUall year001
Solids, total suspendedmonthly average≤ 10 mg/Lall year001
Solids, total suspendedweekly average≤ 15 mg/Lall year001
Nitrogen, ammonia total [as N]monthly average≤ 1.1 mg/Lall year001
Nitrogen, ammonia total [as N]monthly average≤ .6 mg/Lall year001
Nitrogen, ammonia total [as N]weekly average≤ 3.8 mg/Lall year001
Nitrogen, ammonia total [as N]weekly average≤ 1.4 mg/Lall year001
Carbon, dissolved organic [as C]daily maximumreport only (mg/L)all year001
Carbon, dissolved organic [as C]daily maximumreport only (mg/L)all year001
Hardness, total [as CaCO3]daily maximumreport only (mg/L)all year001
Zinc, total recoverablemonthly average≤ 42 ug/Lall year001
Zinc, total recoverablemonthly average≤ 530 ug/Lall year001
Zinc, total recoverabledaily maximum≤ 84 ug/Lall year001
Zinc, total recoverabledaily maximum≤ 1100 ug/Lall year001
Flow, in conduit or thru treatment plantEPA's "M2 Average"report only (MGD)all year001
Flow, in conduit or thru treatment plantdaily maximum≤ .7 MGDall year001
Ultraviolet light transmittanceminimum hourly averagereport only (%)all year001
Ultraviolet light transmittancedaily minimumreport only (%)all year001
Ultraviolet light dosageminimum hourly averagereport only (mJ/cm2)all year001
Ultraviolet light dosagedaily minimumreport only (mJ/cm2)all year001
Ultraviolet light dosagedaily averagereport only (mJ/cm2)all year001
Coliform, total general30-day maximum≤ 23 MPN/100mLall year001
Coliform, total general7-day median≤ 2.2 MPN/100mLall year001
Coliform, total generalinstantaneous maximum≤ 240 MPN/100mLall year001
BOD, 5-day, percent removalmonthly average minimum≥ 85 %all year001
Solids, suspended percent removalmonthly average minimum≥ 85 %all year001
%Effect Static 4 Day Chronic Raphidocelis subcapitatamedianreport only (% effect)all year001
%Effect Static 4 Day Chronic Raphidocelis subcapitatamaximumreport only (% effect)all year001
%Effect Static Renewal 7 Day Chronic Ceriodaphnia dubiamedianreport only (% effect)all year001
%Effect Static Renewal 7 Day Chronic Ceriodaphnia dubiamaximumreport only (% effect)all year001
%Effect Static Renewal 7Day Chronic Pimephales promelasmedianreport only (% effect)all year001
%Effect Static Renewal 7Day Chronic Pimephales promelasmaximumreport only (% effect)all year001
% Survival Static Renewal 96Hr Acute Pimephales promelasminimum≥ 70 % survivalall year001
% Survival Static Renewal 96Hr Acute Pimephales promelasminimum median≥ 90 % survivalall year001
% Survival Flow Through 96Hr Acute Pimephales promelasminimum≥ 70 % survivalall year001
% Survival Flow Through 96Hr Acute Pimephales promelasminimum median≥ 90 % survivalall year001
TU Static Renewal 7-Day Chronic Ceriodaphnia dubiamedianreport only (tox chronic)all year001
TU Static Renewal 7-Day Chronic Ceriodaphnia dubiamaximumreport only (tox chronic)all year001
TU Static Renewal 7-Day Chronic Pimphales promelasmedianreport only (tox chronic)all year001
TU Static Renewal 7-Day Chronic Pimphales promelasmaximumreport only (tox chronic)all year001
Static 96Hr Chronic Selen. Capricornutummedianreport only (tox chronic)all year001
Static 96Hr Chronic Selen. Capricornutummaximumreport only (tox chronic)all year001
Specific conductancedaily maximumreport only (umho/cm)all yearINF
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all yearINF
BOD, 5-day, 20 deg. Cdaily maximumreport only (mg/L)all yearINF
Solids, total suspendedmonthly averagereport only (mg/L)all yearINF
Solids, total suspendeddaily maximumreport only (mg/L)all yearINF
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all yearINF
Flow, in conduit or thru treatment plantdaily maximumreport only (MGD)all yearINF

How strict are these limits?

Cited limits by parameter: California'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/CA0078999 · MCP: https://passage-data.com/mcp