Status and Trends for PCBs and Mercury in San Francisco Bay - - PowerPoint PPT Presentation

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Status and Trends for PCBs and Mercury in San Francisco Bay - - PowerPoint PPT Presentation

Oct 01, 2022 258 likes •382 views

Status and Trends for PCBs and Mercury in San Francisco Bay Implicat ions of t he TMDL t o Dredging Bridgette DeS hields S eptember 17, 2014 Topics Background History of RMP sediment monitoring TMDLs and dredging TMDL and

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Status and Trends for PCBs and Mercury in San Francisco Bay

Implicat ions of t he TMDL t o Dredging

Bridgette DeS hields

S eptember 17, 2014

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Topics

  • Background

— History of RMP sediment monitoring — TMDLs and dredging

  • TMDL and DMMO thresholds
  • Changes in monitoring program
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Regional Monitoring Program (RMP)

  • S

tarted in 1993 as a collaborative effort between regulators and regulated community

  • Collect water, sediment, and tissue samples from

S an Francisco Bay and its tributaries

  • Provides water quality regulators and

managers with information they need to manage the estuary effectively

  • Oversight by steering committee and

technical review committee

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RMP S ediment Monitoring

Original Design: Fixed Stations Redesign: Fixed & Random Stations

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Dredging and TMDLs

  • Dredging results in an overall net loss of PCBs and

Hg from the Bay

  • No load is allocated
  • S

ediments disposed of in Bay should have PCB & Hg concentrations no greater than that in ambient surface sediments in the Bay.

—not to exceed the 99th percentile of total PCB and Hg concentrations of the previous 10 years of Bay surface sediment samples collected through the RMP

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http://www.sfei.org/content/dmmo- ambient-sediment-conditions

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Current Thresholds

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Trends in TMDL/ DMMO Limits

  • 34%

increase for PCBs and 6% decrease for PAHs from 2011 to 2014

  • Hg concentrations stable

5 10 15 20 25 30 35 2011 2012 2013 2014

90% UTL of 99th Percentile (ug/kg)

PCB

0.4 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.5 2011 2012 2013 2014

90% UTL of 99th Percentile (mg/kg)

Hg

4000 4200 4400 4600 4800 5000 2011 2012 2013 2014

90% UTL of 90th Percentile (ug/kg)

PAH

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Change in S ampling Frequency

27 stations for sediment, 2014 - 2023

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S ummary

  • Thresholds vary each year

—Material acceptable one year may be unacceptable the next due to changes in 10-year averages —PCBs currently increasing, but management actions are intended to lower concentrations over time —Future TMDLs (S e, PAHs)

  • Change in testing frequency

—Effect is unknown —Fewer data points; introduces some uncertainty

  • S

hould testing frequency be reconsidered?

  • S

hould averaging period be reconsidered?