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Twin Lakes Utilities

Sewage treatment plant, Rockwell City, Iowa. NPDES permit IA0070114, in force until Jun 30, 2030. Last 12 months: over a limit 6 times (last September 2026), 2 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: form A monthly (10 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
4 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
May 2026BOD, carbonaceous [5 day, 20 C], 30-day average26.5≤ 25 mg/L6%
July 2026Solids, total suspended, 30-day average106≤ 80 mg/L33%
July 2026pH, daily maximum9.41≤ 9 SU—
September 2026Solids, total suspended, 30-day average118.5≤ 80 mg/L48%
September 2026Solids, total suspended, 7-day average121≤ 120 mg/L1%
September 2026pH, daily maximum9.22≤ 9 SU—

Limits in force (10)

ParameterStatisticLimitMonths
pHdaily minimum≥ 6 SUall year
pHdaily maximum≤ 9 SUall year
Solids, total suspended30-day average≤ 80 mg/Lall year
Solids, total suspended7-day average≤ 120 mg/Lall year
Chloride [as Cl]30-day average≤ 389 mg/Lall year
Chloride [as Cl]daily maximum≤ 629 mg/Lall year
Chloride [as Cl]30-day average≤ 1997 lb/dall year
Chloride [as Cl]daily maximum≤ 3231 lb/dall year
BOD, carbonaceous [5 day, 20 C]30-day average≤ 25 mg/Lall year
BOD, carbonaceous [5 day, 20 C]7-day average≤ 40 mg/Lall year

New limits from May 1, 2028

ParameterNew limitNew or tighterMedian, last 12 months× new limit
E. coli, geometric mean126 #/100mL (Mar–Nov)new——

How strict are these limits?

Cited limits by parameter: Iowa'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/IA0070114 · MCP: https://passage-data.com/mcp