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SD GFP - Sylvan Lake (Custer State Park)

Sewage treatment plant, Custer, South Dakota. NPDES permit SD0024279, in force until May 31, 2031. Last 12 months: no values over a limit. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: outfall 002 form A monthly (19 values), outfall 003 form A monthly (8 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 0 of 36 reports late

Limits in force (47)

ParameterStatisticLimitMonthsOutfall
Temperature, water deg. fahrenheit30-day averagereport only (deg F)all year002
Temperature, water deg. fahrenheitdaily maximumreport only (deg F)all year002
Flow rate30-day averagereport only (MGD)all year002
Flow ratedaily maximumreport only (MGD)all year002
BOD, 5-day, 20 deg. C30-day average≤ 10 mg/Lall year002
BOD, 5-day, 20 deg. Cdaily maximum≤ 17.5 mg/Lall year002
pHdaily minimum≥ 6.5 SUall year002
pHdaily maximum≤ 8.8 SUall year002
Solids, total suspended30-day average≤ 10 mg/Lall year002
Solids, total suspendeddaily maximum≤ 17.5 mg/Lall year002
Nitrogen, total [as N]daily maximumreport only (mg/L)all year002
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LJun–Sep002
Nitrogen, ammonia total [as N]30-day average≤ 1.1 mg/LMay002
Nitrogen, ammonia total [as N]30-day average≤ 3.7 mg/LFeb, Mar002
Nitrogen, ammonia total [as N]30-day average≤ 3.7 mg/LApr002
Nitrogen, ammonia total [as N]30-day average≤ 1.3 mg/LOct002
Nitrogen, ammonia total [as N]30-day average≤ 3.6 mg/LJan, Nov, Dec002
Nitrogen, ammonia total [as N]daily maximum≤ 1.1 mg/LJun–Sep002
Nitrogen, ammonia total [as N]daily maximum≤ 5.1 mg/LMay002
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LFeb, Mar002
Nitrogen, ammonia total [as N]daily maximum≤ 11.3 mg/LApr002
Nitrogen, ammonia total [as N]daily maximum≤ 2.3 mg/LOct002
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LJan, Nov, Dec002
Phosphorus, total [as P]daily maximumreport only (mg/L)all year002
Chlorine, total residualdaily maximum≤ .019 mg/Lall year002
E. coli, colony forming units [CFU]30-day geometric mean≤ 126 #/100mLMay–Sep002
E. coli, colony forming units [CFU]daily maximum≤ 235 #/100mLMay–Sep002
Flow, totalmonthly totalreport only (Mgal)all year002
Duration of dischargemonthly totalreport only (d)all year002
Temperature, water deg. fahrenheit30-day averagereport only (deg F)all year003
Temperature, water deg. fahrenheitdaily maximumreport only (deg F)all year003
Flow rate30-day averagereport only (MGD)all year003
Flow ratedaily maximumreport only (MGD)all year003
pHdaily minimum≥ 6 SUall year003
pHdaily maximum≤ 8.8 SUall year003
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LJun–Sep003
Nitrogen, ammonia total [as N]30-day average≤ 1.1 mg/LMay003
Nitrogen, ammonia total [as N]30-day average≤ 3.7 mg/LFeb, Mar003
Nitrogen, ammonia total [as N]30-day average≤ 3.7 mg/LApr003
Nitrogen, ammonia total [as N]30-day average≤ 1.3 mg/LOct003
Nitrogen, ammonia total [as N]30-day average≤ 3.6 mg/LJan, Nov, Dec003
Nitrogen, ammonia total [as N]daily maximum≤ 1.1 mg/LJun–Sep003
Nitrogen, ammonia total [as N]daily maximum≤ 5.1 mg/LMay003
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LFeb, Mar003
Nitrogen, ammonia total [as N]daily maximum≤ 11.3 mg/LApr003
Nitrogen, ammonia total [as N]daily maximum≤ 2.3 mg/LOct003
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LJan, Nov, Dec003

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/SD0024279 · MCP: https://passage-data.com/mcp