cac meeting may 20, 2008 storm water issue # 109
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CAC MeetingMay 20, 2008
Storm WaterIssue # 109
Presentation Plan
Issue raised by Community Working Group
Overview of PN Storm Water drainage
Overview of Previous Studies
Conclusion of Studies
Issue resolution
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?
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
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
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)
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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