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Hill City, City of

Sewage treatment plant, Hill City, South Dakota. NPDES permit SD0020885, in force until Feb 28, 2027. Last 12 months: over a limit once (last June 2026), 2 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (24 values)
Renewal application due
Sep 1, 2026 · 180 days before expiry; your permit may set another date
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 5 of 12 reports late

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

Period endingParameterReportedLimitOver by
June 2026Nitrogen, ammonia total [as N], daily maximum3.12 mg/L≤ 1.75 mg/L78%

Limits in force (26)

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≤ 10 mg/Lall year
BOD, 5-day, 20 deg. Cdaily maximum≤ 17.5 mg/Lall year
BOD, 5-day, 20 deg. C30-day averagereport only (mg/L)all year
pHdaily minimum≥ 6.6 SUall year
pHdaily maximum≤ 8.6 SUall year
Solids, total suspended30-day average≤ 10 mg/Lall year
Solids, total suspendeddaily maximum≤ 17.5 mg/Lall year
Solids, total suspended30-day averagereport only (mg/L)all year
Nitrogen, total [as N]daily maximumreport only (mg/L)all year
Nitrogen, ammonia total [as N]30-day average≤ .9 mg/LSep
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LJan, Feb, Mar, Apr, May, Jun, Jul, Aug, Oct, Nov, Dec
Nitrogen, ammonia total [as N]daily maximum≤ 1.5 mg/LSep
Nitrogen, ammonia total [as N]daily maximum≤ 1.75 mg/LJan, Feb, Mar, Apr, May, Jun, Jul, Aug, Oct, Nov, Dec
Nitrogen, nitrate total [as N]30-day average≤ 50 mg/Lall year
Nitrogen, nitrate total [as N]daily maximum≤ 88 mg/Lall year
Phosphorus, total [as P]daily maximum≤ .1 mg/Lall year
Floating solids, waste or visible foam-visualdaily maximum< 0 abst=0;prst=1all year
E. coli, colony forming units [CFU]30-day geometric mean≤ 126 #/100mLMay–Sep
E. coli, colony forming units [CFU]daily maximum≤ 235 #/100mLMay–Sep
BOD, 5-day, percent removalmonthly average minimum≥ 85 %all year
Solids, suspended percent removalmonthly average minimum≥ 85 %all year
Turbidity, lab, NTUdaily maximumreport only (NTU)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/SD0020885 · MCP: https://passage-data.com/mcp