Draft California 2026 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 8 - Santa Ana Region

Water Body Name:	Box Springs Channel (Riverside County)
Water Body ID:	CAR8012700020210720040419
Water Body Type:	River & Stream


DECISION ID	149135	Region 8
Box Springs Channel (Riverside County)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 149135, Indicator Bacteria	Region 8
Box Springs Channel (Riverside County)

LOE ID:

300935

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Middle Santa Ana River TMDL Monitoring Project data for Box Springs Channel (Riverside County) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the geomean water quality threshold for E. coli. This is a six week rolling geomean that is calculated weekly.

Data Reference:

Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 8.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use for waters where the salinity is equal to or less than 1 part per thousand 95 percent or more of the time applies a rolling six-week geometric mean of E. coli, not to exceed 100 cfu/100 mL (ISWEBE 2018).

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): US-BXSP (Box Springs Channel at Tequesquite Avenue).

Temporal Representation:

The samples were collected between the days of 2011-04-19 and 2011-05-19 .

Environmental Conditions:

QAPP Information:

CDM Smith. 2019. Santa Ana River Watershed Bacteria Monitoring Program.

QAPP Information Reference(s):

Santa Ana River Watershed Bacteria Monitoring Program

Line of Evidence (LOE) for Decision ID 149135, Indicator Bacteria	Region 8
Box Springs Channel (Riverside County)

LOE ID:

300903

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Middle Santa Ana River TMDL Monitoring Project data for Box Springs Channel (Riverside County) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the Statistical Threshold Value (STV) water quality threshold for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 8.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use where the salinity is less than 1 parts per thousand 95 percent or more of the time applies a statistical threshold value to E. coli of 320 cfu/100 mL, not to be exceeded by more than 10 percent of samples within a calendar month (ISWEBE 2018).

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): US-BXSP (Box Springs Channel at Tequesquite Avenue).

Temporal Representation:

The samples were collected between the days of 2011-04-19 and 2011-05-19 .

Environmental Conditions:

QAPP Information:

CDM Smith. 2019. Santa Ana River Watershed Bacteria Monitoring Program.

QAPP Information Reference(s):

Santa Ana River Watershed Bacteria Monitoring Program