1. Turbidity measurements in Alameda Creek and selected tributaries: August through December 2007 Alicia N. Gilbreath and Lester J. McKee San Francisco Estuary Institute

2. Turbidity measurement Sadar, Hach Co., 2005

3. Turbidity WQ objective “Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses. Increases from normal background light penetration or turbidity relatable to waste discharge shall not be greater than 10 percent in areas where natural turbidity is greater than 50 NTU.” - San Francisco Regional Water Quality Control Board (SFRWQCB) Basin Plan (2007), Turbidity water quality objective (3.3.19)

4. Thresholds used in analysis 10 NTU > 50% exposure time 25 NTU > 20% exposure time and 50 NTU > 10% exposure time Klein and Trush (in prep), in McBain and Trush, 2007

7. Results

10. Results compared to thresholds Percentage of Sampling Events: ≥ 10 NTU≥ 25 NTU≥ 50 NTUCount (n) Alameda Ck @ Ardenwood100%95%63%19 Alameda Ck @ Alvarado39%0% 18 Alameda Ck @ Decoto11%0% 9 Alameda Ck @ Mission33%8% 12 Alameda Ck @ Stonybrook Ck10%0% 10 Alameda Ck @ frmr Sunol Dam8% 12 Alameda Ck @ Sunol Temple20%0% 5 Alameda Ck @ 6800% 3 Alameda Ck @ Welch Ck0% 8 Arroyo De La Laguna @ Paloma53%5% 19 Arroyo De La Laguna @ Verona89%5% 19 Arroyo De La Laguna @ Bernal84%5% 19 Arroyo Del Valle @ Valley5%0% 19 Arroyo Del Valle @ Bernal0% 3 Alamo Canal @ 58041%6% 17 Arroyo Mocho @ Hopyard100%95%53%19 Tassajara Ck @ W. Las Positas94%71%24%17 Arroyo Mocho @ Santa Rita100%71%29%17 Line G-3 @ Arroyo Mocho92%69%31%13 Arroyo Mocho above Line G-377%15%8%13 Arroyo Mocho @ El Charro50% 2 Arroyo Las Positas @ El Charro21%5% 19 Arroyo Las Positas @ Livermore0% 3 Arroyo Las Positas @ First20%10%0%10 Altamont Ck @ Bristlecone67%33%0%6

11. Recommendations 1)Conduct a bioenergetics study in areas where turbidity may impact the fish. 2)Investigate sources and management options for inputs into Arroyo Mocho.