Castro Valley Creek Castro Valley Creek Stormwater Quality MonitoringStormwater Quality Monitoring

Brake Pad Partnership Meeting

June 22, 2005

Copper Source Loading Estimates (Process Profiles)

Physical & ChemicalCharacterization of

Wear Debris (Clemson University)

WaterQuality

Monitoring (ACCWP)

Steering Committee, Scientific Advisory Team, andStakeholder Involvement Process (Sustainable Conservation)

AirDepositionModeling

(AER)

WatershedModeling

(U.S. EPA)

BayModeling (URS)

Final ReportData Assessment

Conclusions

Air Deposition

Monitoring (SFEI)

Representative Sample of Brake PadWear Debris

(BMC/Link Test Labs)

BPP Technical Studies BPP Technical Studies

Scope of WorkScope of Work

Collect runoff samples from Castro Valley Creek during five to ten storm events

Analyzes samples for total copper and total suspended solids.

Obtain rainfall and stream flow data

BackgroundBackgroundCastro Valley Creek Watershed

– 5.51 square miles– Predominantly low-density residential w/ some

commercial development and open space– Mean Annual Rainfall: 21 inches

Rainy season: October through May

– Elevation: 200 to 500 feet above sea level– Mean Annual Stream Flow: 123 million cu. ft. – Stream channels mostly incised or culverted

BACKGROUND (Cont.)BACKGROUND (Cont.)

Long history of monitoring watershed– USGS stream flow from 1971– Hourly rainfall from 1970– Extensive Water Quality sampling

USGS from 1971 to 1989 Flow-weighted composite sampling 1990-95 90 discrete samples from 2002/2003

Overview of Sampling EffortOverview of Sampling Effort

Sampled Nine Storm Events from October 2003 through February 2004– Time-weighted: composites of four hourly

samples– Flow-weighted discrete samples: every 240,000

cubic feet of flow Consistent with previous sampling regime First flush as discrete sample

12/29/03

0

100

200

300

400

500

600

700

800

8:20 10:25 12:30 14:35 16:40 18:45 20:50 22:55

Time

cfs

Sampling Intervals

Flow

Flow-weighted

Time-weighted

Overview of Sampling (cont.)Overview of Sampling (cont.)

Samples collected using an ISCO automated sampler located at USGS gaging station– Bubbler records stage at two-minute intervals– Converts to flow using USGS rating curve

Overview of Sampling (cont.)Overview of Sampling (cont.)

Samples analyzed by ToxScan Laboratories– Total Copper: EPA Method 160.2– Total Suspended Solids: EPA Method 200.8

109 samples Analyzed– 62 time-weighted samples – 47 flow-weighted samples

Number of Samples Collected and AnalyzedNumber of Samples Collected and Analyzed

Date # Time samples # Flow samples

10/31/03 0 5

11/8/03 12 6

11/14/03 10 2

12/6/03 6 5

12/9/03 6 4

12/14/03 5 6

12/23/03 12 7

12/29/03 7 12

2/17/04 4 0

Total 62 47

Overview of Sampling (cont.)Overview of Sampling (cont.)

5-minute instantaneous flow record for entire season: USGS

One-hour rainfall record for four gauges: ACFC&WCD

Castro Valley Creek Average Daily Flow and Samples Collected

0.00

20.00

40.00

60.00

80.00

100.00

120.00

10/15/03 11/14/03 12/14/03 01/13/04 02/12/04 03/13/04

Date

Flow

(cfs)

0

5

10

15

20

25

Sam

ples

Flow (cfs)

Samples

Copper vs. TSS in Flow-Weighted Samples

0102030405060708090

100

1 11 21 31 41

Sample Number

Tota

l Cop

per

ug/L

0

500

1000

1500

2000

TSS

(mg/

l)

Total Copper

TSS

Event #1

0

20

40

60

80

100

5:44 6:33 8:18

10/31/2003 10/31/2003 10/31/2003

Date/Time

Tota

l Cop

per u

g/l

0

500

1000

1500

2000

TSS

mg/

l

Copper

TSS

Event # 2

0

20

40

60

80

100

17:16 17:53 18:17 18:44 20:12

11/8/2003 11/8/2003 11/8/2003 11/8/2003 11/8/2003

Tota

l Cop

per u

g/l

0

500

1000

1500

2000

TSS

mg/

l

Copper

TSS

Event # 4

0

20

40

60

80

100

18:32 19:01 19:23 19:46 20:30

12/6/2003 12/6/2003 12/6/2003 12/6/2003 12/6/2003

Date/Time

To

tal C

op

pe

r u

g/l

0

500

1000

1500

2000

TS

S m

g/l

Copper

TSS

Event # 5

0

20

40

60

80

100

14:48 0:01 0:53 3:41

12/9/2003 12/10/2003 12/10/2003 12/10/2003Date/Time

To

tal

Co

pp

er u

g/l

0

500

1000

1500

2000

TS

S m

g/l

Copper

TSS

Event # 8

0

20

40

60

80

100

29-Dec-03

To

tal C

op

pe

r u

g/l

0

500

1000

1500

2000

TS

S m

g/l

Copper

TSS

Issues Raised in Peer ReviewIssues Raised in Peer Review

Potential bias due to fixed-point sampling

Appropriateness of suspended sediment analytical method

Fixed–Point SamplingFixed–Point Sampling

Issue: Fixed-point sampling with an automated sampler may introduce a bias.– Larger grain sizes not evenly distributed

Magnitude: ? Potential Resolution:

– Simultaneous fixed point and equal width integrated sampling.

Drawbacks– Difficult logistically / expensive.– Not consistent with previous data/calibration

Total Suspended Solids AnalysisTotal Suspended Solids Analysis

Issue: – Total suspended solids analysis may underestimate

suspended sediment concentrations.

Magnitude: ? Potential Resolution:

– TSS and suspended sediment concentration (SSC) analysis on split samples.

Drawback: – Previous data: TSS

SummarySummary

Samples were collected during nine storm events

109 Flow and Time-weighted samples collected and analyzed

Good coverage of storm flow during first half of wet season

Some uncertainty regarding potential bias