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Walnut Ridge, City of - Walnut Ridge WWTP

Sewage treatment plant, major discharger, Walnut Ridge, Arkansas. NPDES permit AR0046566, in force until Dec 31, 2027. Last 12 months: over a limit 70 times (last August 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 25 days after each period: outfall 001 form A monthly (23 values), outfall 001 form A2 monthly (22 values), outfall 001 form Q quarterly (6 values), outfall 001 form Q2 quarterly (4 values), outfall TX1 form Q quarterly (14 values)
Renewal application due
Jul 4, 2027 · 180 days before expiry; your permit may set another date
Last report on file
August 2026
Oct 2024 – Sep 2025
108 values over a limit, 0 required values missing, 1 of 36 reports late

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

All 70 values over a limit
Period endingParameterReportedLimitOver by
October 2025BOD, carbonaceous [5 day, 20 C], 7-day average26 mg/L≤ 15 mg/L73%
October 2025BOD, carbonaceous [5 day, 20 C], monthly average14.1 mg/L≤ 10 mg/L41%
October 2025Mercury, total recoverable, monthly average.017 ug/L≤ .0134 ug/L27%
October 2025Mercury, total recoverable, monthly average.036 lb/d≤ .00014 lb/d25614%
November 2025BOD, carbonaceous [5 day, 20 C], 7-day average25 mg/L≤ 15 mg/L67%
November 2025BOD, carbonaceous [5 day, 20 C], monthly average14.7 mg/L≤ 10 mg/L47%
November 2025Coliform, fecal general, 7-day geometric mean2790 #/100mL≤ 2000 #/100mL40%
November 2025Mercury, total recoverable, monthly average.015 ug/L≤ .0134 ug/L12%
November 2025Mercury, total recoverable, monthly average.0355 lb/d≤ .00014 lb/d25257%
November 2025Nitrogen, ammonia total [as N], 7-day average13 mg/L≤ 9 mg/L44%
November 2025Peracetic Acid, instantaneous maximum1.18 mg/L≤ 1 mg/L18%
November 2025pH, minimum5.6 SU≥ 6 SU—
December 2025BOD, carbonaceous [5 day, 20 C], 7-day average27.3 mg/L≤ 15 mg/L82%
December 2025BOD, carbonaceous [5 day, 20 C], monthly average18.5 mg/L≤ 10 mg/L85%
December 2025Mercury, total recoverable, 7-day average.055 ug/L≤ .0269 ug/L104%
December 2025Mercury, total recoverable, monthly average.055 ug/L≤ .0134 ug/L310%
December 2025Mercury, total recoverable, monthly average.1349 lb/d≤ .00014 lb/d96257%
January 2026BOD, carbonaceous [5 day, 20 C], 7-day average35.2 mg/L≤ 15 mg/L135%
January 2026BOD, carbonaceous [5 day, 20 C], monthly average24.4 mg/L≤ 10 mg/L144%
January 2026Mercury, total recoverable, monthly average.015 ug/L≤ .0134 ug/L12%
January 2026Mercury, total recoverable, monthly average.0313 lb/d≤ .00014 lb/d22257%
January 2026Solids, total suspended, 7-day average31 mg/L≤ 22.5 mg/L38%
January 2026Solids, total suspended, monthly average20.5 mg/L≤ 15 mg/L37%
February 2026BOD, carbonaceous [5 day, 20 C], 7-day average33.3 mg/L≤ 15 mg/L122%
February 2026BOD, carbonaceous [5 day, 20 C], monthly average21.9 mg/L≤ 10 mg/L119%
February 2026Mercury, total recoverable, 7-day average3.4 ug/L≤ .0269 ug/L12539%
February 2026Mercury, total recoverable, monthly average18.7433 lb/d≤ .00014 lb/d—
February 2026Mercury, total recoverable, monthly average3.4 ug/L≤ .0134 ug/L25273%
February 2026Peracetic Acid, instantaneous maximum2.05 mg/L≤ 1 mg/L105%
February 2026Solids, total suspended, 7-day average42 mg/L≤ 22.5 mg/L87%
February 2026Solids, total suspended, monthly average20.3 mg/L≤ 15 mg/L35%
March 2026BOD, carbonaceous [5 day, 20 C], 7-day average27.5 mg/L≤ 15 mg/L83%
March 2026BOD, carbonaceous [5 day, 20 C], monthly average19.1 mg/L≤ 10 mg/L91%
March 2026Mercury, total recoverable, 7-day average13 ug/L≤ .0269 ug/L48227%
March 2026Mercury, total recoverable, monthly average.0342 lb/d≤ .00014 lb/d24329%
March 2026Mercury, total recoverable, monthly average13 ug/L≤ .0134 ug/L96915%
March 2026pH, minimum5.87 SU≥ 6 SU—
April 2026BOD, carbonaceous [5 day, 20 C], 7-day average27 mg/L≤ 15 mg/L80%
April 2026BOD, carbonaceous [5 day, 20 C], monthly average20.9 mg/L≤ 10 mg/L109%
April 2026Mercury, total recoverable, 7-day average.2 ug/L≤ .0269 ug/L643%
April 2026Mercury, total recoverable, monthly average.0003 lb/d≤ .00014 lb/d114%
April 2026Mercury, total recoverable, monthly average.2 ug/L≤ .0134 ug/L1393%
April 2026Solids, total suspended, 7-day average28 mg/L≤ 22.5 mg/L24%
May 2026BOD, carbonaceous [5 day, 20 C], 7-day average24.1 mg/L≤ 15 mg/L61%
May 2026BOD, carbonaceous [5 day, 20 C], monthly average13.2 mg/L≤ 10 mg/L32%
May 2026Coliform, fecal general, 7-day geometric mean4030 #/100mL≤ 400 #/100mL908%
May 2026Mercury, total recoverable, 7-day average4.7 ug/L≤ .0269 ug/L17372%
May 2026Mercury, total recoverable, monthly average.0087 lb/d≤ .00014 lb/d6114%
May 2026Mercury, total recoverable, monthly average4.7 ug/L≤ .0134 ug/L34975%
May 2026Peracetic Acid, instantaneous maximum3.05 mg/L≤ 1 mg/L205%
May 2026Solids, total suspended, 7-day average28 mg/L≤ 22.5 mg/L24%
June 2026BOD, carbonaceous [5 day, 20 C], 7-day average24.1 mg/L≤ 15 mg/L61%
June 2026Coliform, fecal general, 7-day geometric mean612 #/100mL≤ 400 #/100mL53%
June 2026Mercury, total recoverable, 7-day average.035 ug/L≤ .0269 ug/L30%
June 2026Mercury, total recoverable, monthly average.035 ug/L≤ .0134 ug/L161%
June 2026Peracetic Acid, instantaneous maximum1.25 mg/L≤ 1 mg/L25%
July 2026BOD, carbonaceous [5 day, 20 C], 7-day average24.1 mg/L≤ 15 mg/L61%
July 2026BOD, carbonaceous [5 day, 20 C], monthly average< 10.7 mg/L≤ 10 mg/L7%
July 2026Coliform, fecal general, 30-day geometric mean> 2886 #/100mL≤ 200 #/100mL—
July 2026Coliform, fecal general, 7-day geometric mean> 2000 #/100mL≤ 400 #/100mL—
July 2026Mercury, total recoverable, 7-day average.08 ug/L≤ .0269 ug/L197%
July 2026Mercury, total recoverable, monthly average.0002 lb/d≤ .00014 lb/d43%
July 2026Mercury, total recoverable, monthly average.08 ug/L≤ .0134 ug/L497%
July 2026Nitrogen, ammonia total [as N], 7-day average8.2 mg/L≤ 6 mg/L37%
July 2026Solids, total suspended, 7-day average27 mg/L≤ 22.5 mg/L20%
August 2026Coliform, fecal general, 30-day geometric mean3109 #/100mL≤ 200 #/100mL1455%
August 2026Coliform, fecal general, 7-day geometric mean12700 #/100mL≤ 400 #/100mL3075%
August 2026Mercury, total recoverable, 7-day average9.5 ug/L≤ .0269 ug/L35216%
August 2026Mercury, total recoverable, monthly average.0156 lb/d≤ .00014 lb/d11043%
August 2026Mercury, total recoverable, monthly average9.5 ug/L≤ .0134 ug/L70796%

Limits in force (81)

ParameterStatisticLimitMonthsOutfall
Oxygen, dissolved [DO]instantaneous minimum≥ 6 mg/LJan, Feb, Mar, Apr, Nov, Dec001
Oxygen, dissolved [DO]instantaneous minimum≥ 5 mg/LMay–Oct001
Oxygen, dissolved [DO]instantaneous minimum≥ 5 mg/LMay–Oct001
Oxygen, dissolved [DO]instantaneous minimum≥ 6 mg/LJan, Feb, Mar, Apr, Nov, Dec001
pHminimum≥ 6 SUall year001
pHminimum≥ 6 SUall year001
pHmaximum≤ 9 SUall year001
pHmaximum≤ 9 SUall year001
Solids, total suspendedmonthly average≤ 15 mg/Lall year001
Solids, total suspendedmonthly average≤ 15 mg/Lall year001
Solids, total suspended7-day average≤ 22.5 mg/Lall year001
Solids, total suspended7-day average≤ 22.5 mg/Lall year001
Solids, total suspendedmonthly average≤ 148.9 lb/dall year001
Solids, total suspendedmonthly average≤ 156.4 lb/dall year001
Nitrogen, ammonia total [as N]monthly average≤ 4 mg/LMay–Oct001
Nitrogen, ammonia total [as N]monthly average≤ 6 mg/LJan, Feb, Mar, Apr, Nov, Dec001
Nitrogen, ammonia total [as N]monthly average≤ 4 mg/LMay–Oct001
Nitrogen, ammonia total [as N]monthly average≤ 6 mg/LJan, Feb, Mar, Apr, Nov, Dec001
Nitrogen, ammonia total [as N]7-day average≤ 6 mg/LMay–Oct001
Nitrogen, ammonia total [as N]7-day average≤ 9 mg/LJan, Feb, Mar, Apr, Nov, Dec001
Nitrogen, ammonia total [as N]7-day average≤ 6 mg/LMay–Oct001
Nitrogen, ammonia total [as N]7-day average≤ 9 mg/LJan, Feb, Mar, Apr, Nov, Dec001
Nitrogen, ammonia total [as N]monthly average≤ 39.7 lb/dMay–Oct001
Nitrogen, ammonia total [as N]monthly average≤ 59.5 lb/dJan, Feb, Mar, Apr, Nov, Dec001
Nitrogen, ammonia total [as N]monthly average≤ 41.7 lb/dMay–Oct001
Nitrogen, ammonia total [as N]monthly average≤ 62.6 lb/dJan, Feb, Mar, Apr, Nov, Dec001
Nitrite + Nitrate total [as N]monthly averagereport only (mg/L)all year001
Nitrite + Nitrate total [as N]monthly averagereport only (mg/L)all year001
Nitrite + Nitrate total [as N]7-day averagereport only (mg/L)all year001
Nitrite + Nitrate total [as N]7-day averagereport only (mg/L)all year001
Nitrite + Nitrate total [as N]monthly averagereport only (lb/d)all year001
Phosphorus, total [as P]monthly averagereport only (mg/L)all year001
Phosphorus, total [as P]monthly averagereport only (mg/L)all year001
Phosphorus, total [as P]7-day averagereport only (mg/L)all year001
Phosphorus, total [as P]7-day averagereport only (mg/L)all year001
Phosphorus, total [as P]monthly averagereport only (lb/d)all year001
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all year001
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all year001
Flow, in conduit or thru treatment plantdaily maximumreport only (MGD)all year001
Flow, in conduit or thru treatment plant7-day averagereport only (MGD)all year001
Chlorine, total residualinstantaneous maximum< .011 mg/Lall year001
Peracetic Acidinstantaneous maximum≤ 1 mg/Lall year001
Peracetic Acidinstantaneous maximum≤ 1 mg/Lall year001
Mercury, total recoverablemonthly average≤ .0134 ug/Lall year001
Mercury, total recoverablemonthly average≤ .0134 ug/Lall year001
Mercury, total recoverable7-day average≤ .0269 ug/Lall year001
Mercury, total recoverable7-day average≤ .0269 ug/Lall year001
Mercury, total recoverablemonthly average≤ .00013 lb/dall year001
Mercury, total recoverablemonthly average≤ .00014 lb/dall year001
Coliform, fecal general30-day geometric mean≤ 200 #/100mLMay–Sep001
Coliform, fecal general30-day geometric mean≤ 1000 #/100mLJan, Feb, Mar, Apr, Oct, Nov, Dec001
Coliform, fecal general30-day geometric mean≤ 1000 #/100mLJan, Feb, Mar, Apr, Oct, Nov, Dec001
Coliform, fecal general30-day geometric mean≤ 200 #/100mLMay–Sep001
Coliform, fecal general7-day geometric mean≤ 400 #/100mLMay–Sep001
Coliform, fecal general7-day geometric mean≤ 2000 #/100mLJan, Feb, Mar, Apr, Oct, Nov, Dec001
Coliform, fecal general7-day geometric mean≤ 2000 #/100mLJan, Feb, Mar, Apr, Oct, Nov, Dec001
Coliform, fecal general7-day geometric mean≤ 400 #/100mLMay–Sep001
Overflowsmonthly totalreport only (occur/mo)all year001
Overflowsmonthly totalreport only (occur/mo)all year001
Overflow volume [SS0 volume, CSO volume]monthly totalreport only (gal)all year001
Overflow volume [SS0 volume, CSO volume]monthly totalreport only (gal)all year001
BOD, carbonaceous [5 day, 20 C]monthly average≤ 10 mg/Lall year001
BOD, carbonaceous [5 day, 20 C]monthly average≤ 10 mg/Lall year001
BOD, carbonaceous [5 day, 20 C]7-day average≤ 15 mg/Lall year001
BOD, carbonaceous [5 day, 20 C]7-day average≤ 15 mg/Lall year001
BOD, carbonaceous [5 day, 20 C]monthly average≤ 99.2 lb/dall year001
BOD, carbonaceous [5 day, 20 C]monthly average≤ 104.3 lb/dall year001
Whole Effluent Toxicity [WET] - C. dubia7-day minimum≥ 80 %all yearTX1
Whole Effluent Toxicity [WET] - C. dubia7-day minimum≥ 100 %all yearTX1
Whole Effluent Toxicity [WET] - P. promelas7-day minimum≥ 80 %all yearTX1
Whole Effluent Toxicity [WET] - P. promelas7-day minimum≥ 100 %all yearTX1
Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubia7-day minimumreport only (pass=0;fail=1)all yearTX1
Pass/Fail Static Renewal 7Day Chronic Pimephales promelas7-day minimumreport only (pass=0;fail=1)all yearTX1
Low Flow Pass/Fail Survival Test Static Renewal 7 Day Chronic Ceriodaphnia dubia7-day minimumreport only (pass=0;fail=1)all yearTX1
Low Flow Pass/Fail Survival Test Static Renewal 7 Day Chronic Pimephales promelas7-day minimumreport only (pass=0;fail=1)all yearTX1
NOEC Lethal Static Renewal 7 Day Chronic Ceriodaphnia dubia7-day minimumreport only (%)all yearTX1
NOEC Lethal Static Renewal 7 Day Chronic Pimephales promelas7-day minimumreport only (%)all yearTX1
NOEC Sub-Lethal Static Renewal 7 Day Chronic Ceriodaphnia dubia7-day minimumreport only (%)all yearTX1
NOEC Sub-Lethal Static Renewal 7 Day Chronic Pimephales promelas7-day minimumreport only (%)all yearTX1
Coef Of Var Static Renewal 7Day Chronic Ceriodaphnia dubia7-day minimumreport only (%)all yearTX1
Coef Of Var Static Renewal 7Day Chronic Pimephales promelas7-day minimumreport only (%)all yearTX1

How strict are these limits?

Cited limits by parameter: Arkansas's rules and the federal ones.

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