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Groton, City of

Sewage treatment plant, Groton, South Dakota. NPDES permit SD0022187 expired Mar 31, 2026; its limits still apply. Last 12 months: over a limit 2 times (last April 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (18 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 0 of 12 reports late

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

Period endingParameterReportedLimitOver by
April 2026Nitrogen, ammonia total [as N], 30-day average16.9 mg/L≤ 3.5 mg/L383%
April 2026Nitrogen, ammonia total [as N], daily maximum20.9 mg/L≤ 7.5 mg/L179%

Limits in force (20)

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
BOD, 5-day, 20 deg. C30-day average≤ 30 mg/Lall year
BOD, 5-day, 20 deg. Cmaximum 7-day average≤ 45 mg/Lall year
pHdaily minimum≥ 6 SUall year
pHdaily maximum≤ 9 SUall year
Solids, total suspended30-day average≤ 90 mg/Lall year
Solids, total suspendedmaximum 7-day average≤ 135 mg/Lall year
Nitrogen, total [as N]daily maximumreport only (mg/L)all year
Nitrogen, ammonia total [as N]30-day average≤ 3.5 mg/LJan, Feb, Mar, Apr, Nov, Dec
Nitrogen, ammonia total [as N]30-day average≤ 2.1 mg/LMay–Oct
Nitrogen, ammonia total [as N]daily maximum≤ 7.5 mg/LJan, Feb, Mar, Apr, Nov, Dec
Nitrogen, ammonia total [as N]daily maximum≤ 11 mg/LMay–Oct
Phosphorus, total [as P]daily maximumreport only (mg/L)all year
E. coli, colony forming units [CFU]30-day geometric mean≤ 630 #/100mLMay–Sep
E. coli, colony forming units [CFU]daily maximum≤ 1178 #/100mLMay–Sep
Flow, totalmonthly totalreport only (Mgal)all year
Duration of dischargemonthly totalreport only (d)all year

How strict are these limits?

Cited limits by parameter: South Dakota'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/SD0022187 · MCP: https://passage-data.com/mcp