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Plymouth WPCF

Sewage treatment plant, major discharger, Pequabuck, Connecticut. NPDES permit CT0100463 expired May 31, 2021; its limits still apply. Last 12 months: over a limit once (last October 2025), 1 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: form 1 monthly (55 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
8 values over a limit, 0 required values missing, 1 of 12 reports late

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

Period endingParameterReportedLimit
October 2025pH, instantaneous minimum4.9 SU≥ 6 SU

Limits in force (112)

ParameterStatisticLimitMonths
Flow ratemonthly averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
Oxygen, dissolved [DO]instantaneous minimum≥ 7 mg/Lall year
BOD, 5-day, 20 deg. Cmonthly average≤ 20 mg/LMay–Oct
BOD, 5-day, 20 deg. Cmonthly average≤ 30 mg/LJan, Feb, Mar, Apr, Nov, Dec
BOD, 5-day, 20 deg. Cdaily maximum≤ 33 mg/LMay–Oct
BOD, 5-day, 20 deg. Cdaily maximum≤ 50 mg/LJan, Feb, Mar, Apr, Nov, Dec
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all year
BOD, 5-day, 20 deg. Cdaily maximumreport only (mg/L)Jan, Apr, Jul, Oct
pHinstantaneous minimum≥ 6 SUall year
pHinstantaneous maximum≤ 9 SUall year
Solids, total suspendedmonthly average≤ 30 mg/LJan, Feb, Mar, Apr, Nov, Dec
Solids, total suspendedmonthly average≤ 13 mg/LMay–Oct
Solids, total suspendeddaily maximum≤ 50 mg/LJan, Feb, Mar, Apr, Nov, Dec
Solids, total suspendeddaily maximum≤ 22 mg/LMay–Oct
Solids, total suspendedmonthly averagereport only (mg/L)all year
Solids, total suspendeddaily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Solids, total suspendeddaily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Nitrogen, ammonia total [as N]monthly average≤ 2.5 mg/LJul–Sep
Nitrogen, ammonia total [as N]monthly average≤ 9 mg/LMar, Apr
Nitrogen, ammonia total [as N]monthly average≤ 8 mg/LMay
Nitrogen, ammonia total [as N]monthly average≤ 4 mg/LJun, Oct
Nitrogen, ammonia total [as N]monthly average≤ 6 mg/LJan, Feb
Nitrogen, ammonia total [as N]monthly average≤ 5 mg/LNov, Dec
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Jul–Sep
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Mar, Apr
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)May
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Jun, Oct
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Jan, Feb
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Nov, Dec
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Nitrogen, nitrite total [as N]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Nitrogen, nitrite total [as N]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Nitrogen, nitrate total [as N]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Nitrogen, nitrate total [as N]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Phosphorus, total [as P]monthly average≤ .78 mg/LApr–Oct
Phosphorus, total [as P]daily maximum≤ 1.56 mg/LApr–Oct
Phosphorus, total [as P]daily maximumreport only (mg/L)Jan, Feb, Mar, Nov, Dec
Phosphorus, total [as P]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Phosphorus, total [as P]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Cyanide, total [as CN]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Cyanide, total [as CN]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Cyanide, free [amenable to chlorination]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Cyanide, free [amenable to chlorination]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Arsenic, total [as As]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Arsenic, total [as As]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Beryllium, total [as Be]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Beryllium, total [as Be]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Cadmium, total [as Cd]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Cadmium, total [as Cd]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Chromium, hexavalent [as Cr]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Chromium, hexavalent [as Cr]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Chromium, total [as Cr]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Chromium, total [as Cr]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Copper, total [as Cu]monthly average≤ .123 kg/dall year
Copper, total [as Cu]daily maximum≤ .227 kg/dall year
Copper, total [as Cu]monthly averagereport only (kg/d)all year
Copper, total [as Cu]daily maximumreport only (kg/d)all year
Copper, total [as Cu]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Copper, total [as Cu]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Iron, total [as Fe]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Iron, total [as Fe]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Lead, total [as Pb]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Lead, total [as Pb]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Thallium, total [as Tl]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Thallium, total [as Tl]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Nickel, total [as Ni]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Nickel, total [as Ni]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Silver, total [as Ag]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Silver, total [as Ag]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Zinc, total [as Zn]monthly average≤ .304 kg/dall year
Zinc, total [as Zn]daily maximum≤ .574 kg/dall year
Zinc, total [as Zn]monthly averagereport only (kg/d)all year
Zinc, total [as Zn]daily maximumreport only (kg/d)all year
Zinc, total [as Zn]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Zinc, total [as Zn]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Antimony, total [as Sb]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Antimony, total [as Sb]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Aluminum, total [as Al]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Aluminum, total [as Al]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Selenium, total [as Se]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Selenium, total [as Se]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Polychlorinated biphenyls [PCBs]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Phenolsdaily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Phenolsdaily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Ultraviolet light intensityminimum≥ 6.1 mW/cm2Apr–Oct
Chlorine, total residualdaily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Chlorine, total residualdaily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
E. coli30-day geometric mean≤ 126 #/100mLApr–Oct
E. colimaximum≤ 410 #/100mLApr–Oct
Phosphorus, Total [Avg Seasonal Load Cap]monthly averagereport only (lb/d)Oct
Arsenic, sludge tot. dry wt [as As]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Beryllium, sludge, tot. dry wt [as Be]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Solids, total, percentinstantaneous minimumreport only (%)Jan, Apr, Jul, Oct
Solids, fixed, % of total solidsinstantaneous minimumreport only (%)Jan, Apr, Jul, Oct
Solids, volatile % of total solidsinstantaneous minimumreport only (%)Jan, Apr, Jul, Oct
Mercury, total [as Hg]daily maximumreport only (mg/L)Jan, Apr, Jul, Oct
Mercury, total [as Hg]daily maximumreport only (mg/L)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
Zinc, sludge, total, dry weight [as Zn]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Lead, sludge, total, dry weight [as Pb]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Nickel, sludge, total, dry weight [as Ni]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Mercury, sludge, total, dry weight [as Hg]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Chromium, sludge, total, dry weight [as Cr]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Copper, sludge, total, dry weight [as Cu]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
Cadmium, sludge, total, dry weight [as Cd]instantaneous maximumreport only (mg/kg)Jan, Apr, Jul, Oct
BOD, 5-day, percent removalmonthly average minimum≥ 85 %all year
Solids, suspended percent removalmonthly average minimum≥ 85 %all year
NOAEL Static 48Hr Acute D. pulexminimum≥ 90 % survivalJan, Apr, Jul, Oct
NOAEL Static 48Hr Acute D. pulexminimumreport only (% survival)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec
NOAEL Static 48Hr Acute Pimephales promelasminimum≥ 90 % survivalJan, Apr, Jul, Oct
NOAEL Static 48Hr Acute Pimephales promelasminimumreport only (% survival)Feb, Mar, May, Jun, Aug, Sep, Nov, Dec

How strict are these limits?

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

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On EPA ECHO: Facility report · DMR history

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