The Dirty Truth About Turbidity

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Zone 4 Line A
Sources Pathways and Loadings Workgroup May 22nd
2007
Rand Eads RiverMetrics LLC www.rivermetrics.com ri
vermetrics_at_gmail.com 503-435-7516
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SiteLocation
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Estudillo Canal
San Lorenzo Creek
Bockman Canal
Sulphur Creek
Zone 4 Line A
Old Alameda
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Watershed Description
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• 4.5 km2 area
• 1.7 km upstream of the bay
• Above the tidal influence
• 65 industrial-commercial, 33 residential
• 4 km of rail bed
• Large impervious surfaces
• Engineered urban channel, with numerous side
  drains

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Instrumentation
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• Campbell data logger
• DTS-12 turbidity sensor
• Pressure transducer (stage)
• ISCO automatic pumping sampler
• Tipping bucket rain gage
• Cellular modem
• Solar panel

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Turbidity Threshold Sampling
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• Continuous, high-quality SSC records
• Estimates concentration from turbidity
• Obtains samples from every storm event
• Samples validate the turbidity record
• Reduces the cost of monitoring
• Automates sample collection
• Uses real-time turbidity to sample efficiently
• More accurate sediment loads

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Time of Concentration in Bay Area Watersheds
Guadalupe R. (8-10 hrs)
(40 acres)
(4 acres)
(Ref McKee et al., 2003)
San Francisco Estuary Institute
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Boom Configuration
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• Bridge-mounted boom
• Hydroplaned on water surface at stage gt2 feet
  (with added weight)
• Debris buildup
• Range of sampling depth is more variable that
  with a bed-mounted boom
• HY08 recommend small expenditure (1-2k) on
  redesign and redeployment of the current boom to
  a bed-mounted boom

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