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Mason County Dept of Utilities & Waste Management

Sewage treatment plant, Shelton, Washington. NPDES permit WA0038075, in force until Jun 30, 2029. Last 12 months: no values over a limit, 9 required values missing, 6 of 52 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: outfall 001 form MM monthly (18 values), outfall 001 form QQ quarterly (1 value), outfall 0RF form MM monthly (2 values), outfall CL2 form MM monthly (2 values), outfall INF form MM monthly (9 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
2 values over a limit, 12 required values missing, 12 of 52 reports late

Limits in force (32)

ParameterStatisticLimitMonthsOutfall
Temperature, water deg. centigrademonthly averagereport only (deg C) (alert, not enforceable)all year001
Temperature, water deg. centigradeweekly averagereport only (deg C) (alert, not enforceable)all year001
BOD, 5-day, 20 deg. Cmonthly average≤ 30 mg/Lall year001
BOD, 5-day, 20 deg. Cweekly average≤ 45 mg/Lall year001
BOD, 5-day, 20 deg. Cmonthly average≤ 13.8 lb/dall year001
BOD, 5-day, 20 deg. Cweekly average≤ 20.7 lb/dall year001
pHsingle readingreport only (SU) (alert, not enforceable)all year001
Solids, total suspendedmonthly average≤ 30 mg/Lall year001
Solids, total suspendedweekly average≤ 45 mg/Lall year001
Solids, total suspendedmonthly average≤ 13.8 lb/dall year001
Solids, total suspendedweekly average≤ 20.7 lb/dall year001
Nitrogen, ammonia total [as N]monthly averagereport only (mg/L) (alert, not enforceable)all year001
BOD, percent removal [total]monthly average minimum≥ 85 %all year001
Enterococcisingle readingreport only (#/100mL) (alert, not enforceable)all year001
Coliform, fecal generalmonthly geometric mean≤ 117 #/100mLall year001
Coliform, fecal generalweekly geometric mean≤ 175 #/100mLall year001
Flowmaximumreport only (gal/d) (alert, not enforceable)all year001
Flowmonthly averagereport only (gal/d) (alert, not enforceable)all year001
Solids, suspended percent removalmonthly average minimum≥ 85 %all year001
Rainfallmaximumreport only (in) (alert, not enforceable)all year0RF
Rainfallmonthly averagereport only (in) (alert, not enforceable)all year0RF
Chlorine, total residualaverage≤ .5 mg/Lall yearCL2
Chlorine, total residualweekly average≤ .75 mg/Lall yearCL2
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L) (alert, not enforceable)all yearINF
BOD, 5-day, 20 deg. Cweekly averagereport only (mg/L) (alert, not enforceable)all yearINF
BOD, 5-day, 20 deg. Cmonthly averagereport only (lb/d) (alert, not enforceable)all yearINF
BOD, 5-day, 20 deg. Cweekly averagereport only (lb/d) (alert, not enforceable)all yearINF
Solids, total suspendedmonthly averagereport only (mg/L) (alert, not enforceable)all yearINF
Solids, total suspendedweekly averagereport only (mg/L) (alert, not enforceable)all yearINF
Solids, total suspendedmonthly averagereport only (lb/d) (alert, not enforceable)all yearINF
Solids, total suspendedweekly averagereport only (lb/d) (alert, not enforceable)all yearINF
Flowmonthly averagereport only (MGD) (alert, not enforceable)all yearINF

How strict are these limits?

Cited limits by parameter: Washington'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/WA0038075 · MCP: https://passage-data.com/mcp