1. CAC Meeting May 20, 2008 Storm Water Issue # 109

2. Presentation Plan Issue raised by Community Working Group Overview of PN Storm Water drainage Overview of Previous Studies Conclusion of Studies Issue resolution

3. 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?

4. 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

5. 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

6. 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)

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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.