|Citation||Wilson, J , Schreier, H and Brown, S. 2008. Arsenic in groundwater in the Surrey-Langley Area. Prepared for Fraser Health Authority and BC Ministry of Environment.|
|Abstract/Description or Keywords||This study was initiated by Fraser Health Authority and BC Ministry of Environment to
provide a greater understanding of the extent, concentrations and possible sources of
arsenic in drinking water from private wells in the White Rock-Surrey-Langley area.
Elevated arsenic levels have been reported in a number of locations in B.C. in the past
few years, and because arsenic is a carcinogen that can cause cancers and other
chronic health effects over a lifetime of ingestion, it has become a source of increased
concern. Health Canada recently reduced the maximum acceptable concentration
(MAC) for arsenic from 0.025 to 0.010 mg/L, based on municipal and residential scale
treatment achievability and a consideration of the health effects (2006 Guideline for
Canadian Drinking Water Quality – GCDWQ). Chronic health effects may be observed
after long-term ingestion of lower levels of arsenic in drinking water (Wang and Mulligan,
2006). Health Canada considers arsenic concentrations below 0.0003 mg/L to have
risk of health effects over a lifetime of exposure. However, arsenic
concentrations above 0.0003 mg/L in surface and groundwater wells are recorded in BC,
Canada and globally, in natural and untreated spring water.
The aim of the project was to determine the spatial extent of arsenic concentrations in
groundwater in relation to geology and land use in the White Rock-Surrey-Langley area.
Private well owners were invited to participate on a voluntary basis in a survey and 98
well sites were tested in August 2007 to ensure that the spatial distribution of the
samples covered the extent of the White Rock-Langley-Surrey area and the major
groundwater aquifers in the area.
The results showed that 43% of privately owned ground-water wells had total arsenic
levels above the MAC of 0.010 mg/L. A further 40% fell between 0.0003 mg/L and 0.010
mg/L, levels which may still be associated with chronic adverse health effects. There is a
significant relationship between arsenic and well depth with deeper wells having
generally higher arsenic levels. The majority of well owners that obtain their groundwater
from deposits associated with marine and glaciomarine materials have a high probability
of elevated arsenic contamination. Given that the majority of the high arsenic levels
occurred in deep wells and in marine types of deposits it is postulated that the arsenic
originates from natural sources in marine deposits that accumulated in the area after
Significant positive correlations were found between arsenic and boron, and to a much
lesser extent between arsenic and chlorine, further suggesting that the occurrence of
arsenic is from natural geological sources.
82 of the wells analysed in August were re-tested in October 2007 to assure that the
elevated arsenic concentrations could be corroborated. A high level of agreement was
found between the two test results. It was also possible to test the effectiveness of filter
systems that were used in 13 of the 98 wells. The results indicate that only about half of
the different types of filter systems were effective in reducing arsenic levels in the
drinking water by more than 10%. Because all available filter systems were of different make and vintage no detailed testing was pursued and well owners are urged to contact
different suppliers for information on effective treatment systems.
Historic data on arsenic from wells that serve multiple users and are under the
jurisdiction of the Fraser Health Authority were also included in the analysis and the
results confirmed that arsenic is primarily associated with marine and glacial-marine
deposits. Only data since 2000 were included because the analytical detection limits
were insufficient prior to that date.
All well owners were informed of their individual results. The Fraser Health Authority
issues a public media release outlining the preliminary results of the study and provided
the public with information on the best available options to reduce the health risks of
arsenic in their drinking water and well owners are encouraged to conduct regular testing
using a certified water analysis lab.
|Regional Watershed||Lower Fraser|
|Sub-watershed if known|