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Waterbody profile

Official Water Board record · 2026 cycle

Oso Flaco Creek

Waterbody ID (WBID)
CAR3121003020020124122144
County / counties
San Luis Obispo
Regional Water Board
Regional Board 3 - Central Coast Region
Waterbody type
River & Stream
Condition category
Category 5 — 303(d) listed, TMDL required
Integrated Report cycle
2026

303(d) listings (16)

Each row is one official listing decision from Appendix A of the Final 2026 California Integrated Report. Source terminology is preserved as published.

Pollutant / stressorDecision IDFinal listing decisionDecision statusTMDL requirement statusTMDL projectTMDL priority
AmmoniaNutrients126615Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Nitrogen Compounds and Orthophosphate TMDL
Benthic Community EffectsOther Cause145727List on 303(d) list (TMDL required list)Revised5A TMDL still requiredLow
BifenthrinPesticides109876List on 303(d) list (being addressed by USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
ChlorideSALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES109826Do Not Delist from 303(d) list (TMDL required list)Revised5A TMDL still requiredLow
ChlorpyrifosPesticides109829Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
Cyhalothrin, LambdaPesticides109894List on 303(d) list (being addressed by USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
DDD (Dichlorodiphenyldichloroethane)Pesticides130059List on 303(d) list (being addressed by USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
DDE (Dichlorodiphenyldichloroethylene)Pesticides130119List on 303(d) list (being addressed by USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
ImidaclopridPesticides109872List on 303(d) list (TMDL required list)Revised5A TMDL still requiredHigh
MalathionPesticides109844Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
NitrateNutrients127241Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Nitrogen Compounds and Orthophosphate TMDL
OxyfluorfenPesticides109881List on 303(d) list (TMDL required list)Revised5A TMDL still requiredLow
PyrethroidsPesticides144902List on 303(d) list (being addressed by USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
SodiumSALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES109863Do Not Delist from 303(d) list (TMDL required list)Revised5A TMDL still requiredLow
ToxicityTotal Toxics109866Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)Revised5B Addressed by USEPA-approved TMDLSanta Maria River Watershed Toxicity and Pesticides TMDL
TurbiditySediment109868Do Not Delist from 303(d) list (TMDL required list)Revised5A TMDL still requiredLow

Source & provenance

Agency
California State Water Resources Control Board
Report
Final 2026 California Integrated Report
Dataset
Appendix A — 2026 303(d) List of Impaired Waters
Imported
Sep 16, 2026, 10:56 PM UTC
Waterbody ID
CAR3121003020020124122144
CALWNUM
3312.1003
WBD code
180600060704
Geometry
Official Water Board GIS (CA_WATERBOARDS_GIS_FINAL_2026)

Location

Official 2026 Water Board geometry. Demonstration facility markers are shown for context only.

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Watershed
Assessed size
5.68 Miles

Derived facility associations

Industrial stormwater facilities geographically associated with this waterbody. These are derived spatial associations, not Water Board findings.

Derived
Alliance Ready Mix, Inc.

Arroyo Grande · Notice of Intent

derived_watershed_association

Derived by California Stormwater Intelligence

Gator Crushing and Recycling

Arroyo Grande · Notice of Intent

derived_watershed_association

Derived by California Stormwater Intelligence

Phillips 66 Company

Arroyo Grande · Notice of Non-Applicability · 0.08 km away

derived_nearby_in_watershed

Derived by California Stormwater Intelligence

Sammys Auto Dismantling

San Luis Obispo · Notice of Intent

derived_watershed_association

Derived by California Stormwater Intelligence

Facility records are official Industrial General Permit registrations, but the association between a facility and this waterbody is derived geographically (proximity or shared HUC12 subwatershed) and is not a Water Board receiving-water determination. Where a permit carries a Water Board-stated TMDL requirement naming this water, it is listed separately above.