ELLSWORTH, Maine — How much water is in the top inch of Moosehead Lake?
That was the question state geologist Robert Marvinney asked Wednesday night at Striking a Balance, a regular forum that focuses on issues about development.
The answer: There are approximately 2 billion gallons of water in the top 1-inch layer of Moosehead Lake, the 40-mile-long lake that stretches from Greenville north to Seboomook.
That’s just a drop in the state’s proverbial water bucket.
Marvinney, Stephen Norton, professor emeritus of earth sciences at the University of Maine, and John Hopeck, a hydrogeologist with the Maine Department of Environmental Protection, reviewed Maine’s groundwater resources, some of the threats to groundwater quality, and laws surrounding groundwater extraction.
All of Maine’s groundwater comes from precipitation — rain and melting snow. About 10-20 percent of Maine’s annual 42 inches of precipitation — between 2 trillion and 5 trillion gallons annually — infiltrates the soil to recharge the groundwater, Marvinney said.
“The groundwater, the surface water, the rain, they are all connected,” Marvinney said. “Water flows through the soil into the ground. The water flows through geologic materials. The groundwater eventually flows out to the surface.”
Mainers draw groundwater from two sources, Marvinney said: sand and gravel aquifers and bedrock aquifers. Bedrock wells are wells drilled into the bedrock. They tap water running through fractures in the bedrock, which underlies all of Maine.
“They’re just about everywhere,” he said.
Sand and gravel aquifers are “fairly localized” deposits, mostly left by the last glaciers. While wells drilled into bedrock aquifers generally are low-yield wells, the sand and gravel aquifers can store a large amount of water and are a source for many municipal and industrial water supplies.
All three speakers stressed the danger of contamination to the groundwater and the difficulty involved in cleaning up that contamination. Marvinney showed a map of past oil spills in the state, and the orange dots covered much of the populated areas of Maine.
Water, particularly in bedrock fractures, does not move very much, Norton said.
“Water has a long residence time in the ground,” he said. “If it becomes contaminated, it will stay contaminated for a very long time. The soil can be cleaned up, but cleaning up groundwater is very difficult and very expensive.”
Norton focused on water quality and some of the natural threats to quality, including radon, arsenic, salt and fluoride. All of those elements occur naturally in Maine bedrock and can occur in the groundwater. Radon, he noted, is an element that comes from uranium and, like uranium, is radioactive. It also has been shown to cause cancer in high enough doses, he said.
Norton noted, however, that aerating the well water can get rid of the radon.
Mercury contamination, on the other hand, has an almost exclusively human source, he said. Almost all the mercury contamination found in lake sediments in Maine comes from deposits from the atmosphere, the result of burning high amounts of fossil fuels. Studies show those deposits increased significantly until 1970 when the Clean Air Act was enacted, and have declined ever since.
“It shows that if we can recognize the problem, we can alter the problem,” he said.
A number of state and federal laws and regulations are designed to protect groundwater and to ensure that the extraction of groundwater does not affect surface water resources, including wetlands, lakes, rivers and streams.
While the Bulk Water Transport law regulated companies moving water beyond municipal borders, many of those laws were triggered not by water use but by the size of the development. The Site Location Development Act regulated larger developments, defined as those affecting 3 or more acres, such as biomass boilers, air-ports, and big-box stores; and required an evaluation of impacts on water resources both in the ground and on the surface, he said. It did not target the amount of water extracted from the ground.
An addition to the Natural Resources Protection Act in 2007 strengthened regulations on water use and impacts on groundwater sources.
Larger developments, Hopeck said, often are easier to deal with since regulators are looking at site-specific criteria. What is harder to deal with, he said, is smaller, incremental development in communities where road and home construction can take place over significant local aquifers.
In those areas, he said, normal municipal and residential activities such as salting the roads, washing a car or changing its oil can become threats of contamination to that aquifer.
Wednesday’s session was the 18th forum in the Striking a Balance series that meets every three or four months to discuss issues related to personal property rights and development in Hancock County. Partners in the series include the Hancock County Planning Commission, Down East Resource, Conservation and Development Council, the Union River Watershed Coalition, and the Maine Coastal Program. Funding is provided by a donation from Bar Harbor Bank & Trust.