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Watertown, City of

Sewage treatment plant, major discharger, Watertown, South Dakota. NPDES permit SD0023370 expired Jun 30, 2009; its limits still apply. Last 12 months: over a limit once (last March 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (34 values), form W quarterly (2 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 0 of 16 reports late

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

Period endingParameterReportedLimitOver by
March 2026Nitrogen, ammonia total [as N], daily maximum15.7 mg/L≤ 5.5 mg/L185%

Limits in force (45)

ParameterStatisticLimitMonths
Temperature, water deg. centigrade30-day averagereport only (deg C)all year
Temperature, water deg. centigradedaily maximumreport only (deg C)all year
Flow rate30-day averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
Conductivity30-day averagereport only (umho/cm)all year
Conductivitydaily maximumreport only (umho/cm)all year
Oxygen, dissolved [DO]daily minimum≥ 7 mg/Lall year
BOD, 5-day, 20 deg. C30-day average≤ 20 mg/LApr–Oct
BOD, 5-day, 20 deg. C30-day average≤ 15 mg/LJan, Feb, Mar, Nov, Dec
BOD, 5-day, 20 deg. Cmaximum 7-day average≤ 20 mg/LApr–Oct
BOD, 5-day, 20 deg. Cmaximum 7-day average≤ 15 mg/LJan, Feb, Mar, Nov, Dec
BOD, 5-day, 20 deg. Cdaily maximum≤ 35 mg/LApr–Oct
BOD, 5-day, 20 deg. Cdaily maximum≤ 26 mg/LJan, Feb, Mar, Nov, Dec
BOD, 5-day, 20 deg. C30-day averagereport only (mg/L)all year
pHdaily minimum≥ 6.5 SUall year
pHdaily maximum≤ 9 SUall year
Alkalinity, total [as CaCO3]30-day averagereport only (mg/L)all year
Alkalinity, total [as CaCO3]daily maximumreport only (mg/L)all year
Solids, total suspended30-day average≤ 30 mg/Lall year
Solids, total suspendedmaximum 7-day average≤ 45 mg/Lall year
Solids, total suspended30-day averagereport only (mg/L)all year
Oil & Greasedaily maximum≤ 10 mg/Lall year
Nitrogen, ammonia total [as N]30-day average≤ 2 mg/LApr
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LMay–Sep
Nitrogen, ammonia total [as N]30-day average≤ 1.4 mg/LOct
Nitrogen, ammonia total [as N]30-day average≤ 2 mg/LJan, Feb, Mar, Nov, Dec
Nitrogen, ammonia total [as N]daily maximum≤ 3.3 mg/LApr
Nitrogen, ammonia total [as N]daily maximum≤ 1.4 mg/LMay–Sep
Nitrogen, ammonia total [as N]daily maximum≤ 2.4 mg/LOct
Nitrogen, ammonia total [as N]daily maximum≤ 5.5 mg/LJan, Feb, Mar, Nov, Dec
Nitrogen, nitrate total [as N]30-day averagereport only (mg/L)all year
Nitrogen, nitrate total [as N]daily maximumreport only (mg/L)all year
Floating solids, waste or visible foam-visualdaily maximum≤ 0 N=0;Y=1all year
Coliform, fecal general30-day geometric mean≤ 1000 #/100mLMay–Sep
Coliform, fecal generaldaily maximum≤ 2000 #/100mLMay–Sep
Coliform, total general30-day geometric mean≤ 5000 #/100mLall year
Coliform, total generaldaily maximum≤ 20000 #/100mLall year
CBOD5+NH3-N30-day averagereport only (mg/L)all year
CBOD5+NH3-Ndaily maximumreport only (mg/L)all year
BOD, 5-day, percent removalmonthly average minimum≥ 85 %all year
Solids, suspended percent removalmonthly average minimum≥ 85 %all year
Hydrocarbons, petroleumdaily maximum≤ 1 mg/Lall year
Oil and grease visualdaily maximum≤ 0 N=0;Y=1all year
Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubiadaily maximum≤ 0 pass=0;fail=1all year
Pass/Fail Static Renewal 7Day Chronic Pimephales promelasdaily maximum≤ 0 pass=0;fail=1all year

How strict are these limits?

Cited limits by parameter: South Dakota'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/SD0023370 · MCP: https://passage-data.com/mcp