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Storm Water Issue 109
CAC Meeting May 20, 2008
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Presentation Plan

• Issue raised by Community Working Group
• Overview of PN Storm Water drainage
• Overview of Previous Studies
• Conclusion of Studies
• Issue resolution

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Issue 109 Effects of Storm Water Management on
the Local Environment

• What are the effects of storm water run-off on
  the environment?
• How significant are the concentrations (loadings)
  of contaminants in the run off during a storm
  event at PNGS?
• Can these concentrations affect the surrounding
  environment?

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Issue 92 Patterns of Storm Water Run-off from
the site and effect on the local environment

• Are the patterns of storm-water run-off at PNGS
  understood?
• Does PNGS know the fate of storm-water run-off
  from each drainage area?
• Can storm-water runoff have negative effects on
  the surrounding environment (e.g. nearby creeks
  and Hydro Marsh)
• Is PNGS or Town of Pickering responsible for
  maintaining the storm-water outfall that empties
  into Hydro Marsh via a ditch that crosses Kinsmen
  park? Are there plans to avoid outfalls from
  PNGS into the sensitive Marsh area?
• Dispositioned as Category 1 in 2002

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Discharge Areas Common To PNGS and Associated
Storm Water Concerns

• Paved areas (parking) drained by perimeter
  ditches
• Vehicular fluids, salt, ditch erosion (suspended
  solids)
• Paved areas (non parking) drained by imbedded
  yard drains
• Spill events, outdoor material storage
• Granular fill areas drained by perimeter ditches
• Ditch erosion to a lesser extent
• Granular fill areas drained by imbedded yard
  drains
• Suspended solids in extreme events
• Natural areas drained by natural flow paths

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Storm Water Studies

• Storm Water Control Study (1997)
• Follow-up Storm Water Control Study (2002)
• Pickering A Return to Service Storm Water Quality
  Follow-up Monitoring Program (2007)

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Storm Water Control Study (1997)

• Conducted between 1995 1996, for a 12 month
  period
• Intended to capture seasonal variation
• Intended to monitor non-point source discharges
• 13 discharge points were monitored for 4 seasonal
  storm events
• Monitoring for
• Toxicity
• Metals
• Oil Grease
• Simple chemicals
• Organic compounds

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Storm Water Control Study (1997)

• Conclusions
• Elevated suspended solids seen in many samples
• Areas were observed that were vulnerable to
  erosion and therefore elevated suspended solids
• Sodium (salt) seen as seasonally high
• Toxicity seen at one location
• Oil and grease suggested as a contributing factor
• Contradicted by later studies

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Storm Water Control Study (1997)

• Recommendations
• Numerous recommendations to be considered on a
  priority basis
• Solids management program
• Consideration of oil water separator installation
• Review salt usage
• Consideration of consolidating discharge points

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Storm Water Control Study (1997)

• Subsequent Actions
• Total Suspended Solids Reduction Program
• Cleaned out 250 catch basins and manholes
• Erosion control at ditches
• Elimination of herbicide spray application
• Installed 28 catch basin filter inserts at
  Parking Lots

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Storm Water Control Study (1997)

• Subsequent Activities with Relevant Impacts
• Containment and oil water separator installed
  around PN-A standby generators
• Impermeable containment installed around standby
  generator fuel oil storage tanks
• Ceased storage of waste oil outdoors unless in
  containment
• Used batteries now staged in cargo containers
• Outdoor caustic storage tank at old water
  treatment plant decommissioned

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Follow-up Storm Water Control Study (2002)

• Intended to evaluate and document the
  effectiveness of the action taken after the
  original Storm Water Control Study

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Follow-up Storm Water Control Study (2002)

• Sampling Program (April 2000 Feb 2001)
• 14 Locations Sampled
• 8 in Pickering A area
• 6 covering rest of site
• Covered four seasonal storm events
• Parameters tested
• General Chemistry, organics metals, radionuclides
  (CWG concern), toxicity

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Follow-up Storm Water Control Study (2002)

• Results
• Total Suspended Solids (TSS) reduced compared to
  1997 levels
• Metals generally well below guidelines with some
  transients linked to TSS level
• Radionuclides detectable but within expected
  levels
• Chemicals and Hydrocarbons far below limits
  (generally undetectable)
• One toxicity test failure at same site as 1997
• All parameters at typical levels except zinc
• Study suggest possible linkage to low hardness
  and total metals
• No activities in area that would generate zinc
• No further action recommended

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Follow-up Storm Water Control Study (2002)

• Recommendations
• Continue to operate solids reduction program
• Periodically evaluate salt usage on site
• Salt usage, although in line with urban runoff
  values has been reviewed repeatedly
• Although use of sand has been expanded in some
  usages safety concerns have prevented salt from
  being replaced
• Pickering is going to be testing the pre-wetting
  (brine) technology on site to cut salt usage

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Pickering A Return to Service Storm Water Quality
Follow-up Monitoring Program (2007)

• Intended to
• Quantify storm water quality under post restart
  conditions
• Verify Environmental Assessment conclusion that
  the Pickering A return to service did not have an
  adverse effect on storm water quality

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Pickering A Return to Service Storm Water Quality
Follow-up Monitoring Program (2007)

• Sampling Program (April 2000 Feb 2001)
• 6 PN-A Locations Sampled
• Consistent with 2002 study
• Covered four storm events
• Parameters tested
• General Chemistry, organics metals,
  radionuclides, toxicity

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Pickering A Return to Service Storm Water Quality
Follow-up Monitoring Program (2007)

• Results
• Total Suspended Solids (TSS) comparable to 2002
  levels with less variance
• Metals levels generally decreased from 2002
  levels
• Zinc persisting at levels seen in 2002
• Radionuclides detectable but within expected
  levels
• Hydrocarbons far below limits (generally
  undetectable)
• Toxicity test failure at same site as 1997 and
  2002
• All parameters except zinc at low levels
• Possible linkage to low hardness and total metals
  reiterated
• Hardness will be corrected as this water enters
  the lake

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Pickering A Return to Service Storm Water Quality
Follow-up Monitoring Program (2007)

• Conclusions
• Pickering A return to service has not had a
  detrimental affect on storm water quality
• No further monitoring required

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Conclusion

• The discharges of storm water from the PN site
  have been repeatedly assessed.
• The corrective measures taken in response to the
  initial Storm water Control Study have been
  effective at significantly improving the quality
  of storm water runoff from the PN site.
• Numerous other actions were taken to lessen the
  risk of chemical spills
• Storm water from the PN site exhibits the
  characteristics and variability that would be
  expected from urban run-off
• Erosion control measures are ongoing
• Salt usage reduction will be explored via the use
  of a brine pre-wetting technology field trial
• The intermittent toxicity issue at one location
  are not environmentally significant

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Issue 109 Effects of Storm Water Management on
the Local Environment

• What are the effects of storm water run-off on
  the environment?
• How significant are the concentrations (loadings)
  of contaminants in the run off during a storm
  event at PNGS?
• Can these concentrations affect the surrounding
  environment?
• Dispositioned as Category 1 in 2002

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Suggested Disposition

• Category 1
• No further action required, the issue has been
  dealt with to the extent required or the extent
  possible.
• or
• The issue is being managed satisfactorily and
  would be brought back to the CAC only if an
  unusual result or event arose calling into
  question the managed process for the issue.