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

Turbidity measurement Sadar, Hach Co., 2005

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)

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

Results

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

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.