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.