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Most of Maine’s aquifers are at risk

Mark Holden, Portland Press Herald, June 10, 2009

“DEP has found that of the 29,000 acres of high-yield sand and gravel aquifers in Maine, only about 1,200 acres are not at risk.”

Drill into the ground in Maine and eventually you’ll find water. This groundwater can be found in the cracks in rock or in the spaces between soil grains. Rock or soil formations that contain water and allow it to move are called aquifers.

Sand and gravel deposits make aquifers that are especially productive and are sources for many town and city water supplies and for businesses requiring lots of water.

The sand and gravel deposits were left behind by the melting of the huge ice sheet that covered all of Maine 18,000 years ago. Water ran under and downstream of the melting ice in gravel-choked streams, leaving deposits of sand and gravel in what are today’s river valleys.

Over the years, people have found many uses for these deposits, such as construction fill or to mix with cement. Just as it is easy to dig in a sandbox, it is easy to dig into sand and gravel deposits. Since these deposits also tend to be well-drained (rain water sinks right in), people have built cities, cemeteries and farms over the sand and gravel.

People figured out that groundwater wells were easy to dig in these “big sandboxes.” Industrious Mainers put these great sand and gravel aquifers to use, not just as fill or for concrete but also as sources of drinking water.

Because of their resource value, the Maine Geological Survey has mapped the state’s sand and gravel aquifers. The society has also mapped areas in these aquifers that produce large amounts of water, called “high-yield” sand and gravel aquifers.

The Department of Environmental Protection has found that many high-yield aquifers are at risk from pollution. In fact, the DEP has found that of the 29,000 acres of high-yield sand and gravel aquifers in Maine, only about 1,200 acres are not at risk. The DEP has published this information on its Web site at: www.maine.gov/dep/blwq/docgw/aqua_index .

What does “at risk” mean? An aquifer that is at risk could be contaminated by activities happening on the overlying land. Examples of risks include storing large amounts of gasoline at a filling station or dumping waste in a landfill.

Another type of risk comes from rainwater that washes over buildings, parking lots and roads, carrying oil that drips from cars and road salt used to melt ice. These chemicals and many others can soak into the aquifer or wash into streams, ponds, rivers and wetlands. The DEP tracks 38 different types of land-use risks.

It is up to everyone to conserve aquifers that are not yet at risk and protect those which are threatened. We can all do our part to protect these vulnerable groundwater supplies by being thoughtful about our activities on the land.

What can you do to protect groundwater? Be aware that spilled chemicals could be washed into the ground by the rain. Dispose of old paint, solvents, gas and waste oil at a waste recycling facility or household hazardous waste collection day. If you must use insecticides, fertilizers and household chemical, use them sparingly.

Mark Holden is an environmental specialist with the Maine DEP’s Bureau of Land and Water Quality. “In Our Backyard” is a weekly column of the Maine Department of Environmental Protection. E-mail your environmental questions to infodep@maine.gov or send them to “In Our Backyard,” Maine DEP, 17 State House Station, Augusta, ME 04333.

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