The Gleaner
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An aquifer lesson

In a temperate region like eastern Canada, people tend to take the blessing of abundant clean water for granted, but the Chateauguay River watershed, which covers most of this MRC, is vulnerable. It has been extensively studied by the provincial government and by universities, most recently by McGill’s L4E doctorate project on the watershed’s state of contamination.

Most people think of drinkable water as “ours,” paid for by taxation in towns with water services, or by personal investment in the case of private wells. However, studies show that it’s better to picture this aquifer like a big bathtub, with straws reaching down at intervals to suck up its contents. The straws are public and private wells, drilled down as far as 400 feet. Naturally the situation is more complex, especially in areas with limestone bedrock where the system is more like a series of underground veins and pools, with wells going down and hitting this vein or that pool. The main point to remember is that water flows between wells.

If the water in one end of the bathtub or one vein of an artery-like system is contaminated with chemicals and heavy metals, the rest of the water will inevitably receive that contamination, unless the source is removed. Simply put: if one well gets polluted, especially with chemicals, it’s only a question of time until the rest receive their share.

Organic vs. chemical

In the case of organic contamination, distancing dumps of organic materials such as manure from wells can provide protection. Microorganisms and chemical reactions in the soil can eventually break down organic contaminates like E. coli bacteria and viruses. Protecting water from this kind of contamination is the basis upon which Franklin and then the Haut-Saint-Laurent MRC designed protection plans last year, after continuing reports of construction-waste dumping. This precaution, if enforced by town inspectors (who can authorize hefty daily fines), would indeed mostly protect that water from organic contamination.

Unfortunately, the biggest threat to the Valley’s water supply comes from the dumping of chemical contaminates. These materials, often found in construction waste, can include carcinogens in petrochemicals as well as lead and other heavy metals that will never break down (“forever chemicals”), and they can cause serious adverse effects on humans such as cancers and birth defects. Chemical contaminates have been found in the few areas where local and provincial governments finally performed scientific testing, like at the Jodoin site on Route 201 and on Rang Dumas last summer.

Filling the bathtub

Aquifers have natural areas of recharge that replenish at least some of the water removed by pumping. According to a 2004 hydrogeological overview of the aquifers in the Chateauguay River basin, the Chateauguay Valley aquifer, upon which 65 per cent of the population in our MRC depends for water, has large recharge areas, mostly in constantly shrinking wetlands.

On what is called The Rock, an area between Ormstown and Franklin, the bedrock is porous and the soil is sandy, so rainwater can trickle down to the underground basins. Old gravel pits and quarries also help replenish the water supply. However, a 2013 study on the regional sustainability of the Chateauguay River aquifers, as well as research investigating the impacts of decreasing recharge rates on groundwater management, shows that hydrologists have learned well-pumping or other activities, including plugging up porous rock with fill, adversely affect the aquifer’s ability to recharge; the whole aquifer can start to fail, providing less and less water.

 

A diagram of water tables wells and springs published by the Utah Geological Survey depicts how aquifer systems work DIAGRAM Utah Geological Survey geologyutahgov

 

The Rock – the major recharge area of the Chateauguay Valley aquifer – is topped by exposed stone and scrub and runs along Route 201 between Franklin and Ormstown. The area was zoned industrial in the 1990s, and has attracted a staggering amount of backfill, especially in recent years when road construction ramped up in Montreal and regulations on dumping remained lax. The Rock is very porous, and although unsuited for pasture or growing crops, it has been storing up rainwater for many hundreds or even thousands of years. Now, areas of that porous surface have been blocked by dumped material, and some wetlands in the area are plugged.

Chemical dumping can affect water quality, but even clean fill, if it blocks aquifer recharge areas, can affect water quantity. The growing population and increased water use for crops and livestock has already put pressure on Valley supply, with wells having to be dug much deeper than before; it’s important for citizens to become more aware of the increasing fragility of their water supply – both in quality and in quantity.

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