High on the Mountain Top
Join Date: Jan 2004
Location: North Vancouver, BC, Canada.
Interest: Mountain biking, hiking, nature photography, astronomy, music...
"Heavy metal contamination is possible without a bad taste, that's true but rare. Usually there is enough other dissolved solids for the taste to be a warning flag"
This statement is misleading. It is certainly not true for southwestern BC. Metals can exceed safe levels when Total Dissolved Solid concentraion is low and there is no odd taste. It all depends on local geology. Areas with un-metamorphosed sedimentary and/or volcanic rocks would typically have higher Total Dissolved Solid concentrations but not necessarily higher heavy metals. Most of the gulf islands and parts of the southern interior would fall into that category. Areas of metamorphosed older clastic marine sedimentary and volcanic rocks typically would have low total dissolved solids, but groundwater in areas with those types of rocks, intrusions within volcanic rocks in particular, can be anomalous in heavy metals. This is exactly the case in parts of the north shore mountains, Howe Sound and on the sunshine coast. The sources of arsenic are the commonly occurring Gambier group rocks (Mt. Seymour, much of Howe Sound/Sea to Sky) and Bowen group rocks (upper Lynn Headwaters, Cypress Bowl, Bowen Island, Sunshine Coast) found throughout the region. Groundwater in all of these areas is typically low in total dissolved solids and has no odd taste, but metal concentrations vary greatly and naturally exceed safe levels in several locations tested. There is no way you would be able to taste the difference between 5 ppb and 50 ppb arsenic, though the latter is five times the maximum safe limit for drinking water but only 1/1000 of the maximum allowable TDS. You can't make a direct correlation with high TDS and high heavy metals as that would also be stating that you are not likely to have heavy metals unless you also have high TDS - our local geology proves that wrong.
I see that on the findaspring.com site people have suggested having the Lynn Headwaters spring tested. As far as metals detection goes, my recommendation would be to take a sample during a dry period after at least a week of no rain. This will minimize the dilution effect that rainwater/ditch water will have during rainy periods. Based on local geology (granitic rocks) I'm going to guess that arsenic will not be an issue. However, other sources of contamination, such as fertilizer, weed killer and bacteria, will vary greatly throughtout the year and a single test will be inconclusive. Periodic monitoring would be required for those things.
During dry parts of the year the water from this spring is likely close to 100% groundwater sourced. For much of the year much of the water in the pool is surface runoff (ditchwater) that has only been diluted by the spring, yet I still see people filling water bottles from it.