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Discovery Bay, Town of, Community Services District

Sewage treatment plant, major discharger, Contra Costa County, California. NPDES permit CA0078590, in force until Jan 31, 2030. Last 12 months: over a limit once (last December 2025), 3 of 30 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 30 days after each period: outfall EFF1 form A monthly (23 values), outfall EFF1 form Q quarterly (4 values), outfall INF1 form A monthly (11 values), outfall EFF1 form Y yearly, outfall INF1 form Y yearly
Last report on file
September 2026
Oct 2024 – Sep 2025
1 value over a limit, 0 required values missing, 0 of 17 reports late

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

Period endingParameterReportedLimit
December 2025%Effect Static 4 Day Chronic Raphidocelis subcapitata, weekly average> 100 % effect≤ 50 % effect

Limits in force (47)

ParameterStatisticLimitMonthsOutfall
Temperature, water deg. fahrenheitinstantaneous maximumreport only (deg F)all yearEFF1
Specific conductancedaily maximumreport only (umho/cm)all yearEFF1
Oxygen, dissolved [DO]instantaneous minimumreport only (mg/L)all yearEFF1
BOD, 5-day, 20 deg. Cmonthly average≤ 10 mg/Lall yearEFF1
BOD, 5-day, 20 deg. Cweekly average≤ 15 mg/Lall yearEFF1
pHinstantaneous minimum≥ 6.5 SUall yearEFF1
pHinstantaneous maximum≤ 8.5 SUall yearEFF1
Solids, total suspendedmonthly average≤ 10 mg/Lall yearEFF1
Solids, total suspendedweekly average≤ 15 mg/Lall yearEFF1
Nitrogen, ammonia total [as N]monthly average≤ .84 mg/Lall yearEFF1
Nitrogen, ammonia total [as N]weekly average≤ 1.8 mg/Lall yearEFF1
Nitrite + Nitrate total [as N]monthly average≤ 10 mg/Lall yearEFF1
Nitrite + Nitrate total [as N]weekly average≤ 17 mg/Lall yearEFF1
Carbon, dissolved organic [as C]daily maximumreport only (mg/L)all yearEFF1
Hardness, total [as CaCO3]daily maximumreport only (mg/L)all yearEFF1
Chloride [as Cl]daily maximumreport only (mg/L)all yearEFF1
Boron, total recoverabledaily maximumreport only (ug/L)all yearEFF1
Copper, total recoverablemonthly average≤ 45 ug/Lall yearEFF1
Copper, total recoverabledaily maximum≤ 72 ug/Lall yearEFF1
Chlorpyrifosdaily maximumreport only (ug/L)all yearEFF1
Diazinondaily maximumreport only (ug/L)all yearEFF1
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all yearEFF1
Flow, in conduit or thru treatment plantdaily maximumreport only (MGD)all yearEFF1
Temperature Increase Deg. Finstantaneous maximum≤ 20 deg Fall yearEFF1
Diazinon + Chlorpyrifosmonthly average≤ 1 ug/Lall yearEFF1
Diazinon + Chlorpyrifosweekly average≤ 1 ug/Lall yearEFF1
Solids, total dissolveddaily maximumreport only (mg/L)all yearEFF1
Mercury, total recoverabledaily maximumreport only (ug/L)all yearEFF1
Mercury, total recoverableannual total≤ 24 g/yrall yearEFF1
Methylmercurydaily maximumreport only (ug/L)all yearEFF1
BOD, 5-day, percent removalmonthly average minimum≥ 85 %all yearEFF1
Solids, suspended percent removalmonthly average minimum≥ 85 %all yearEFF1
%Effect Static 4 Day Chronic Raphidocelis subcapitataweekly average≤ 50 % effectall yearEFF1
Pass/Fail Static 4 Day Chronic Raphidocelis subcapitataweekly average≤ 0 pass=0;fail=1all yearEFF1
Pass/Fail Static 4 Day Chronic Raphidocelis subcapitatamonthly median≤ 0 pass=0;fail=1all yearEFF1
Temperature, water deg. fahrenheitinstantaneous maximumreport only (deg F)all yearINF1
Specific conductancedaily maximumreport only (umho/cm)all yearINF1
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all yearINF1
BOD, 5-day, 20 deg. Cdaily maximumreport only (mg/L)all yearINF1
pHinstantaneous minimumreport only (SU)all yearINF1
pHinstantaneous maximumreport only (SU)all yearINF1
Solids, total suspendedmonthly averagereport only (mg/L)all yearINF1
Solids, total suspendeddaily maximumreport only (mg/L)all yearINF1
Boron, total recoverabledaily maximumreport only (ug/L)all yearINF1
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all yearINF1
Flow, in conduit or thru treatment plantdaily maximumreport only (MGD)all yearINF1
Solids, total dissolveddaily maximumreport only (mg/L)all yearINF1

How strict are these limits?

Cited limits by parameter: California'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/CA0078590 · MCP: https://passage-data.com/mcp