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3.8 Water Monitoring Programs

  • Issued: September 2014
  • Content last reviewed: September 2014

3.8.1  General information

This program is designed to monitor for fisison and activation products that may be distributed in sources that are used to supply public drinking water. Drinking water is sampled from the water treatment plants (WTPs) within each surveillance area which are closest to the nuclear installations being monitored. Regular sampling of drinking water is an important component of an emergency preparedness program.

The WTPs in the eastern part of the Toronto Surveillance Area are used to monitor drinking water for emissions from the Pickering nuclear generating facility. This is because there are no WTPs in the Pickering Surveillance Area.

Lorne Park and Lakeview WTPs are located in Peel Region, just west of the Toronto boundary. Samples from these facilities, along with tap water samples taken at the Radiation Protection Service, form a subset of the Toronto Surveillance Area called "Toronto-west". This will be referred to in the data tables presented for this section.

Drinking water monitoring in the Bruce Surveillance area consists of two facilities; the Kincardine and Southampton WTPs.

The WTPs for all surveillance areas are listed in Tables 2a and 2b and their locations shown on the respective maps.

3.8.2  Drinking Water Monitoring Program

WTPs personnel collect a fixed volume of treated water every day and combine this to form either weekly or monthly composite samples. The weekly composites are from WTPswithin the Bruce, Darlington, Pickering and Toronto Surveillance Areas. Every four weeks an RPMS staff member collects the weekly composite samples. Monthly water sample composites are collected from WTPs in the Essex and Ottawa Surveillance Areas. At the end of each month, these samples are shipped to the RPMS via courier. Refer to Table 2 for the names of the individual WTPs.

Monthly composite tap water samples are collected at the Radiation Protection Service, Etobicoke. This is done to provide a distribution evaluation sample of drinking water in the Metropolitan Toronto area.

The composites are analysed for tritium using liquid scintillation counting. Once completed, the composites are combined with samples received during the previous three months, to form a quarterly composite. The quarterly composites are screened for gross-α and gross-β activities, and analysed for γ-emitters by gamma spectroscopy. The concentrations of the isotopes Cobalt-60, Iodine-131, Cesium-134 and Cesium-137 are reported in Bq/L.

The routine sampling of drinking water involves the cooperation and support of the WTPs which participate in the ORSP.

3.8.3  Drinking Water Monitoring Results

There were 564 weekly and 108 monthly drinking water samples collected and individually analysed for tritium content. A total of 80 quarterly composites were prepared. As previously described, these were screened for gross-α and gross-β activity, and analysed for γ-emitters by gamma spectroscopy. A total of 1152 analyses were completed on the water samples in 2012. The results of these measurements are summarized in the following tables.

The results of the tritium analysis for drinking water samples that are collected weekly at the water treatment plants in the Bruce, Darlington and Pickering (Toronto) Surveillance Areas are presented in graphical form in Appendix 4. Measurements that were reported as less than the laboratory-MDC of 5 Bq/L are shown on the graphs as 2.5 Bq/L. The graphs have been included to demonstrate the range and variability that is seen in the sampling results from location to location.

Table 4a: Drinking Water Monitoring – Tritium Analysis
Surveillance Area Number of Samples Median Value[ 1 ]
(Bq/L)
Measurements
> DSC[ 2 ]
Bruce 104 8.4 0
Darlington 258 4.4 0
Essex 36 < 5 0
Ottawa 36 < 5 0
Toronto 202 4.3 0
Toronto-West 36 4.5 0

The median concentrations of tritium in drinking water range from 4.3 Bq/L in the Toronto-west Surveillance Area to 8.4 Bq/L in the Bruce Surveillance Area. As in 2011, the upper value presented here is just under 0.10% of the DSC of 7000 Bq/L for tritium in drinking water.

There has been little change in the results from the Bruce and Pickering Surveillance Areas when compared with previous years as shown in Figure 1 "10-year Results – Tritium in Drinking Water". This figure does show there has been a steady decrease in concentration of tritium in drinking water the Darlington Surveillance Area.

The results of the γ analysis, as shown in Table 4b, were consistently less than the MDC for each nuclide throughout all regions. These results remain comparable to measurements made in previous years.

Table 4b: Drinking Water Monitoring – Gamma Analysis
Surveillance Area Number of Samples Co–60
(Bq/L)
I–131
(Bq/L)
Cs–134
(Bq/L)
Cs–137
(Bq/L)
Bruce 8 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]
Darlington 20 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]
Essex 12 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]
Ottawa 12 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]
Toronto 16 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]
Toronto-West 12 < 0.2[ 3 ] < 0.6[ 3 ] < 0.7[ 3 ] < 1.0[ 3 ]

In 2012, the results of the gross-α analysis were found to be consistently less than the MDC. While some gross-β activity was detected, the median value remains close to the β-MDC of 0.04 Bq/L. This is far below the gross-βscreening level action concentration of 0.5 Bq/L - established from the Ontario Drinking Water Standards. [R-5] Very little change has been seen in these concentrations when compared with those of 2011 or other years.

Table 4c: Drinking Water Monitoring – Gross-Alpha/Gross-Beta Analysis
Surveillance Area Number of Samples Gross-α
(Bq/L)
Gross-β
(Bq/L)
Bruce 8 < 0.04[ 4 ] 0.04
Darlington 20 < 0.04[ 4 ] 0.06
Essex 12 < 0.04[ 4 ] 0.05
Ottawa 12 < 0.04[ 4 ] < 0.04[ 4 ]
Toronto 16 < 0.04[ 4 ] 0.06
Toronto-West 12 < 0.04[ 4 ] 0.06

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[ 1 ] DSC – Determined using Linear Regression

[ 2 ] LaboratoryMDC Tritium-in-Drinking Water = 5 Bq/L

[ 3 ] MDC = 10% DSC for each nuclide

[ 4 ] MDC

ISSN 1929-2899