INTERSTATE POWER AND LIGHT COMPANY

NPDES permit IA0060909 · Major NON-POTW · effective, expires 2029-05-31 · EPA's file as of 2026-09-19

Check this month's numbers before you file
Watch this permit — $79 a month. Every Monday, from EPA's newest files: the next report due and when, whether EPA's file holds your last one, any change to this permit's limits or status, and the renewal date.

EPA's record, 2025-09-01 to 2026-08-31

1values over a limit
0required values missing, on 0 form(s)
0of 60 forms filed late

Last period with anything received: 2026-08-31. Most often over: pH (1).

Reporting

Reports are due about 15 days after each monitoring period ends (read off this permit's own late-day counts in EPA's filings).

Limits in force (35)

OutfallParameterStatisticLimitMonths
002pHDAILY MN >= 6 SU all year
002pHDAILY MX <= 9 SU all year
002Solids, total suspendedDAILY MX <= 50 mg/L all year
003pHDAILY MN >= 6 SU all year
003pHDAILY MX <= 9 SU all year
003Solids, total suspended30DA AVG <= 30 mg/L all year
003Solids, total suspendedDAILY MX <= 45 mg/L all year
003Solids, total suspended30DA AVG <= .5 lb/d all year
003Solids, total suspendedDAILY MX <= .751 lb/d all year
003BOD, carbonaceous [5 day, 20 C]30DA AVG <= 25 mg/L all year
003BOD, carbonaceous [5 day, 20 C]DAILY MX <= 40 mg/L all year
003BOD, carbonaceous [5 day, 20 C]30DA AVG <= .417 lb/d all year
003BOD, carbonaceous [5 day, 20 C]DAILY MX <= .667 lb/d all year
005pHDAILY MN >= 6 SU all year
005pHDAILY MX <= 9 SU all year
005Chromium, total [as Cr]30DA AVG <= .2 mg/L all year
005Chromium, total [as Cr]DAILY MX <= .2 mg/L all year
005Zinc, total [as Zn]30DA AVG <= 1 mg/L all year
005Zinc, total [as Zn]DAILY MX <= 1 mg/L all year
005Chlorine, free available30DA AVG <= .2 mg/L all year
005Chlorine, free availableDAILY MX <= .5 mg/L all year
005Chlorination durationDAILY MX <= 2 hr/d all year
007pHDAILY MN >= 6 SU all year
007pHDAILY MX <= 9 SU all year
007Solids, total suspended30DA AVG <= 30 mg/L all year
007Solids, total suspendedDAILY MX <= 100 mg/L all year
007Oil & Grease30DA AVG <= 15 mg/L all year
007Oil & GreaseDAILY MX <= 20 mg/L all year
008Iron, total [as Fe]30DA AVG <= 2.156 mg/L all year
008Iron, total [as Fe]DAILY MX <= 2.156 mg/L all year
008Iron, total [as Fe]30DA AVG <= 54.8 lb/d all year
008Iron, total [as Fe]DAILY MX <= 54.8 lb/d all year
008E. coliGEO MEAN <= 126 #/100mL Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov
008Toxicity [acute], Ceriodaphnia dubiaDAILY MX <= 1 N=0;Y=1 all year
008Toxicity [acute], Pimephales promelas [Fathead Minnow]DAILY MX <= 1 N=0;Y=1 all year

Built from EPA's ECHO bulk files. EPA's file, not the permit document, is the source: read your permit. Check a report before you file it · All states