HAMILTON, ON - July 8, 2009 –A Drinking Water Advisory (DWA) is being issued today for those who use Lynden’s Municipal Drinking Water System. Lynden residents were notified today that lead has been intermittently detected at concentrations above the Maximum Acceptable Concentration (MAC) in the Lynden water system. The DWA will remain in effect until several months (12 weeks +/-) of consecutive acceptable lead results are obtained in order to determine a reasonable trend of acceptable lead concentrations.
“The recent and intermittent detection of lead above the Maximum Allowable Concentration (MAC) in the Lynden drinking water system is not perceived to be a risk to the health of the users of the Lynden water system in the short term,” said Dr. Chris Mackie, Associate Medical Officer of Health for the city of Hamilton. “We are confident that following the recommendations in the Drinking Water Advisory will protect the residents of Lynden from the potential health effects.”
Lynden residents who receive water from the Lynden drinking water system can use a water filter as a temporary intervention to ensure their tap water has acceptable lead concentrations. Public Works will be providing two of these filters to each affected household over the next couple days.
Lead has not been found above the MAC in the source of the Lynden drinking water or in the distribution system in the past five years, and the water well and distribution system do not contain lead pipes.
-30-
Media Contacts:
Dan McKinnon,
Acting Director
Water and Wastewater
Public Works
905-546-2424 ext. 5941
Eric Mathews
Manager, Health Protection
Public Health Services
905-546-2424 ext. 2186
BACKGROUND INFORMATION
Hamilton Public Health Services has been working with the City of Hamilton Public Works Department regarding recent detections of lead concentrations above the Maximum Acceptable Concentration (MAC) in the Lynden Municipal Drinking Water System. Historically, lead concentrations been very low to non-detectable in the source of the Lynden drinking water or in the distribution system. The water well and distribution system do not contain lead pipes. Over the past five years (since February 2002) lead has not been detected above the MAC in the Lynden drinking water system.
However, a water sample collected on February 18, 2009 from the treated water near the well/source had a lead concentration of 0.0103 milligrams per litre of water (mg/L) which is above the MAC of 0.0100 mg/L. The MAC for lead in drinking water can also be expressed as 10 parts per billion (10 ppb). Subsequent resampling and testing of this location and locations in the distribution system were subsequently below the MAC.
Public Works increased the lead monitoring to a monthly schedule, which did not detect lead concentrations above the MAC in the Lynden water system until May. A sample collected on May 5th had a high lead concentration, at 0.0690 mg/L. Immediate re-sampling and testing over the next two days indicated that lead concentrations were acceptable.
In late May and early June Public Works implemented additional corrective action by emptying and cleaning the water reservoirs at the beginning of the Lynden water system. This action was taken in order to remove sediment that may have accumulated over time and that might be intermittently causing the elevated lead concentrations.
After the reservoirs were cleaned the lead monitoring schedule was increased to once every two weeks. Water samples collected in June after the reservoirs were cleaned yielded lead concentrations that were well below the MAC.
One out of three water samples collected on June 30th had an elevated lead concentration of 0.0143 mg/L; the other two water samples had lead concentrations of 0.0027 and 0.0025 mg/L. Re-sampling and testing was conducted immediately after the lab results were reported. Two out of three samples collected on July 6th had elevated lead concentrations (0.0216 mg/L and 0.0105 mg/L); the other sample was 0.0074mg/L.
Due to the return of lead concentrations above the MAC in the Lynden water supply after the reservoirs were cleaned, it became apparent that the recent and intermittent source of the lead was not corrected by cleaning the reservoir. Public Health Services decided that the precautionary and prudent approach would be to issue a Drinking Water Advisory (DWA) and notify the users of the Lynden drinking water system that lead has been intermittently detected at slightly elevated concentrations in the Lynden water system. The DWA will remain in effect until several months (12 weeks +/-) of consecutive acceptable lead results are obtained in order to determine a reasonable trend of acceptable lead concentrations.
The level of exposure that has occurred to date does not represent a health risk to the residents of Lynden. This drinking water advisory is to prevent long-term exposure to this level of lead in water, which may represent a small risk of health impact.
Lynden residents who receive water from the Lynden drinking water system can use a water filter as a temporary intervention to ensure their tap water has acceptable lead concentrations. These filters should meet NSF Standard #53 for lead removal, as indicated on the filter packaging. Public Works will be providing two of these filters to each affected household over the next couple days.