Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)
2026 303(d) list Waterbody ID CAR4036400020020226083118 River & Stream Region 4 · Los Angeles
At a glance
- 2026 listing Evidence: State-published
- On the 2026 303(d) list · 22 Appendix A decisions
- Category 5: a TMDL is required
- What a listing means
- Pollutants and stressors
- 22 pollutants in 8 Appendix A categories
- Nutrients (2) · Pathogens (1) · Pesticides (13) · SALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES (2) · Total Toxics (1) · Toxic Inorganics (1) · Toxic Organics (1) · Trash (1)
- Listing decisions
- TMDL information Evidence: State-published
- 22 decisions with a TMDL requirement status; 14 name a TMDL project
- Status codes as published: 5A, 5B
- TMDL details
- Industrial stormwater facilities
- 0 report it as their receiving water Evidence: identification corroborated
- 8 within 1 km Evidence: geographic proximity
- Neither count establishes a discharge · Facilities
What a 303(d) listing means
The Clean Water Act section 303(d) list names waters that do not meet water quality standards for one or more pollutants or stressors. California publishes it in the Integrated Report; this page shows the 2026 decisions from Appendix A as published.
- A listing describes the condition of the waterbody. It does not identify which sources cause the impairment, and it does not by itself place a requirement on any particular facility.
- Listed waters do not all have the same status. The Integrated Report category says how an impairment is being addressed: 5, a TMDL is required; 4a, addressed by a USEPA-approved TMDL; 4b, addressed by other pollution control requirements; 4c, impairment not caused by a pollutant. This waterbody's decisions are in category 5.
- TMDL requirement status values (such as 5A or 5B) are shown exactly as published in Appendix A.
2026 listing status Evidence: State-published
- On the 2026 303(d) list
- Yes
- Appendix A decisions
- 22
- Integrated Report category
- 5 (a TMDL is required)
- Listing cycle
- 2026
- State Board adoption
- 2026-02-03 (Resolution 2026-0005)
- USEPA approval
- not confirmed — submittal letter to USEPA published; no approval found on the report page (checked 2026-10-22)
- Regional Water Board
- 4 — Los Angeles
Published by the State Water Resources Control Board (2026 California Integrated Report, Appendix A). Listing status is taken from Appendix A only. A listing describes the condition of this waterbody, not of any facility.
Location
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Open this area on the statewide map · Browse impaired waters
Listing decisions and pollutants Evidence: State-published
Grouped by the Pollutant Category published in Appendix A. Pollutant names, categories and decisions are exactly as published.
Nutrients (2 decisions)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Ammonia | Nutrients | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Nonpoint Source Point Source | 69681 |
| Nitrogen, Nitrite | Nutrients | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Nonpoint Source Point Source | 68707 |
Pathogens (1 decision)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Indicator Bacteria | Pathogens | 5 | Do Not Delist from 303(d) list (TMDL required list) | Original | A Source Unknown | 68657 |
Pesticides (13 decisions)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Bifenthrin | Pesticides | 5 | List on 303(d) list (TMDL required list) | Revised | A Source Unknown | 137449 |
| ChemA (tissue) | Pesticides | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Agriculture-storm runoff | 72430 |
| Chlordane | Pesticides | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Revised | A Source Unknown | 137433 |
| Chlorpyrifos | Pesticides | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Revised | A Source Unknown | 137434 |
| Cyfluthrin | Pesticides | 5 | List on 303(d) list (TMDL required list) | Revised | A Source Unknown | 137453 |
| Cypermethrin | Pesticides | 5 | List on 303(d) list (TMDL required list) | Revised | A Source Unknown | 137450 |
| DDT (Dichlorodiphenyltrichloroethane) | Pesticides | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Revised | See TMDL documentation | 149454 |
| DDT (tissue) | Pesticides | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Nonpoint Source | 71546 |
| Malathion | Pesticides | 5 | Do Not Delist from 303(d) list (TMDL required list) | Revised | A Source Unknown | 137441 |
| Permethrin | Pesticides | 5 | List on 303(d) list (TMDL required list) | Revised | A Source Unknown | 137455 |
| Pyrethroids | Pesticides | 5 | List on 303(d) list (TMDL required list) | Revised | A Source Unknown | 137448 |
| Toxaphene | Pesticides | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Revised | See TMDL documentation | 137447 |
| Toxaphene (tissue & sediment) | Pesticides | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Original | Nonpoint Source | 69944 |
SALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES (2 decisions)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Chloride | SALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Atmospheric Deposition Domestic Use of Ground Water Groundwater Loadings Irrigated Crop Production Major Municipal Point Source-dry weather discharge Surface Runoff | 72395 |
| Total Dissolved Solids | SALINITY/TOTAL DISSOLVED SOLIDS/CHLORIDES/SULFATES | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Atmospheric Deposition Domestic Use of Ground Water Groundwater Loadings Irrigated Crop Production Major Municipal Point Source-dry weather discharge Surface Runoff | 70554 |
Total Toxics (1 decision)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Toxicity | Total Toxics | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Nonpoint Source Point Source | 69136 |
Toxic Inorganics (1 decision)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Sulfates | Toxic Inorganics | 5 | List on 303(d) list (being addressed by USEPA approved TMDL) | Original | Atmospheric Deposition Domestic Use of Ground Water Groundwater Loadings Irrigated Crop Production Major Municipal Point Source-dry weather discharge Surface Runoff | 76412 |
Toxic Organics (1 decision)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| PCBs (Polychlorinated biphenyls) | Toxic Organics | 5 | Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL) | Revised | See TMDL documentation | 137445 |
Trash (1 decision)
| Pollutant | Pollutant category | Category | Final listing decision | Decision status | Sources | Decision ID |
|---|---|---|---|---|---|---|
| Trash | Trash | 5 | List on 303(d) list (TMDL required list) | Original | A Source Unknown | 76966 |
TMDL information Evidence: State-published
| Pollutant | TMDL requirement status | TMDL project | Priority | USEPA approval of TMDL | Expected attainment |
|---|---|---|---|---|---|
| Ammonia | 5B | Calleguas Creek Nitrogen (1) | — | 2003-06-20 | — |
| Bifenthrin | 5A | — | Low | — | — |
| ChemA (tissue) | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-24 | — |
| Chlordane | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-14 | — |
| Chloride | 5B | Calleguas Creek Chloride (3) | — | 2008-12-02 | — |
| Chlorpyrifos | 5B | Calleguas Creek Toxicity (2) | — | 2006-03-14 | — |
| Cyfluthrin | 5A | — | Low | — | — |
| Cypermethrin | 5A | — | Low | — | — |
| DDT (Dichlorodiphenyltrichloroethane) | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-24 | — |
| DDT (tissue) | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-14 | — |
| Indicator Bacteria | 5A | — | Low | — | — |
| Malathion | 5A | — | Low | — | — |
| Nitrogen, Nitrite | 5B | Calleguas Creek Nitrogen (1) | — | 2003-06-20 | — |
| PCBs (Polychlorinated biphenyls) | 5B | Calleguas Creek PCBs (7) | — | 2006-03-14 | — |
| Permethrin | 5A | — | Low | — | — |
| Pyrethroids | 5A | — | Low | — | — |
| Sulfates | 5B | Calleguas Creek Boron/Sulfate/TDS (4) | — | 2008-12-02 | — |
| Total Dissolved Solids | 5B | Calleguas Creek Boron/Sulfate/TDS (4) | — | 2008-12-02 | — |
| Toxaphene | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-24 | — |
| Toxaphene (tissue & sediment) | 5B | Calleguas Creek Historic Pesticides (5) | — | 2006-03-14 | — |
| Toxicity | 5B | Calleguas Creek Toxicity (2) | — | 2010-03-14 | — |
| Trash | 5A | — | Low | — | — |
This is TMDL information for the waterbody. It does not establish that a TMDL applies to any particular facility. Facility-specific TMDL requirements recorded in SMARTS appear on facility pages and are not linked to this waterbody until reviewed.
HUC12 watersheds
Published with the listing Evidence: publisher-reported
- Upper Arroyo Conejo 180701030104
- Lower Arroyo Conejo 180701030105
Overlapping the waterbody's shape Evidence: spatial
- Upper Arroyo Conejo 180701030104 also published
- Lower Arroyo Conejo 180701030105 also published
Industrial stormwater facilities
Evidence: identification corroborated
Shows: the facility named this waterbody as its receiving water in SMARTS, and the name and the facility's location are consistent with it. Does not establish: a discharge pathway, a discharge of any pollutant, or a cause of the listing.
Evidence: geographic proximity
Shows: the facility's reported location is within 1 km of the waterbody's mapped shape. Does not establish: that the facility discharges to this waterbody, or any other relationship.
Report this waterbody as their receiving water Evidence: identification corroborated
No facility's reported receiving water is identified as this waterbody.
Within 1 km of a facility's reported location Evidence: geographic proximity
Spatial proximity only; discharge pathway not established. Being near this waterbody does not mean a facility discharges to it.
| Facility | WDID | Status | Distance | Map |
|---|---|---|---|---|
| City of Thousand Oaks Hill Canyon Wastewater Treatment Plant | 4 56NNA000224 | NONA Submitted | 49 m | map |
| City of Thousand Oaks Hill Canyon Wastewater Treatment Plant | 4 56I001584 | Terminated | 596 m | map |
| Baxalta US Inc | 4 56I025374 | Active | 661 m | map |
| Baxter BioScience | 4 56I015568 | Terminated | 802 m | map |
| Municipal Ser Ctr | 4 56I011736 | Terminated | 902 m | map |
| Municipal Ser Ctr | 4 56I011763 | Terminated | 902 m | map |
| City of Thousand Oaks | 4 56I018843 | Active | 902 m | map |
| Atara Biotherapeutics Inc | 4 56NEC004603 | Terminated | 956 m | map |
8 facilities, nearest first.
Sources and provenance
| Information | Source | Retrieved |
|---|---|---|
| Watershed Boundary Dataset HU2 GeoPackages 15, 16, 18 (WBDHU12) | USGS | 2026-10-22 |
| 2026 California Integrated Report, Appendix A: 2026 303(d) List (final) | SWRCB | 2026-10-22 |
| Final_2026_Rivers_and_Streams + Final_2026_Lakes_and_Reservoirs (FeatureServer 0) | SWRCB GIS | 2026-10-22 |
| SMARTS TMDL requirements | SMARTS | 2026-10-21 |
Relationships computed 2026-10-22 (facility_huc12/1, proximity/1, receiving_water/2, tmdl_reference/1, waterbody_huc12_ovl/1, waterbody_huc12_pub/1).
Integrated Report categories: 5, a TMDL is required; 4a, addressed by a USEPA-approved TMDL; 4b, addressed by other pollution control requirements; 4c, impairment not caused by a pollutant.