2001 Annual Water Quality Report

General Water Chemistry

The quality of drinking water is a subject that is frequently discussed, but more often misunderstood. Just a few years ago we seldom questioned the water we drank. In the past few years technology has given us the ability to measure small amounts of contaminates. Along with technology comes public awareness and more Federal and State regulations. Even with today's technology some people still question the safety of their public water supply and turn to alternative sources with less stringent testing requirements for drinking water. Sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs, and wells. As water travels over the surface of the land or through the ground, it dissolves naturally-occurring minerals, and in some cases, radioactive material, and can pick up substances resulting from the presence of animals or from human activity. Contaminants that may be present in source water include: (A) Microbial contaminants-such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife. (B) Inorganic Contaminants-such as salts and metals, which can be naturally-occurring or result from urban storm water runoff, industrial, or domestic wastewater discharges, oil and gas production, mining, and farming. (C) Pesticides and herbicides-which may come from a variety of sources such as agriculture, urban runoff, and residential uses. (D) Organic chemical contaminants-including synthetic and volatile organic chemicals, which are by products of industrial processes and petroleum production, and can also come from gas stations, urban storm water runoff, and septic systems. (E) Radioactive contaminants -which can be naturally occurring or be the result of oil and gas production and mining activities.

In order to ensure that tap water is safe to drink, the Department of Environmental Protection (DEP) and U.S. Environmental Protection Agency (EPA) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. The Food and Drug Administration (FDA) and Massachusetts Department of Public Health (DPH) regulations establish limits for contaminants in bottled water. All drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk. More information about contaminants and potential health effects can be obtained by calling the EPA's Safe Drinking Water Hotline (800-426-4791).

Some people may be more vulnerable to contaminants in drinking water than the general population. Immune-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and some infants can be particularly at risk from infections. These people should seek advice about drinking water from their health agents. EPA/Centers for Disease Control and Prevention (CDC) guidelines on lowering the risk of infection by microbial contaminants are also available from the Safe Drinking Water Hotline.

Monomoy Lens Let's Protect It

Understanding the Monomoy Lens

How does the Lens work?
Protecting the Monomoy Lens starts with understanding how it works - its hydrogeology. Lenses can be thought of as mounds of groundwater bordered by marine water at the edge, bedrock on the bottom, and separated from each other by tidal rivers, such as Bass River, that cut across the Cape peninsula. Groundwater refers to subsurface water located beneath the water table, in soils and geologic formations that are fully saturated. The entire layer of fresh groundwater beneath the Cape is referred to as the Cape Cod Sole Source Aquifer. Recharge to this lens comes from precipitation and snow fall.

Who uses this water?
Monomoy is the second largest lens, and is located under the towns of Dennis, Harwich, Brewster, Chatham, Orleans and a section of Yarmouth. It is approximately 300 feet thick, and is the source of drinking water to over 40,000 homes and businesses that are served by 49 municipal public water supply wells and an estimated 1,000 private wells. In the 1999 off-season, Cape municipal water suppliers pumped an average of five million gallons per day. In-season this figure almost triples.

How is the groundwater quality?
The Monomoy Lens supplies generally excellent drinking water from its porous sand and gravel deposits. The water is considered "soft" due to the lack of calcium and magnesium. The pH of the water is naturally low, which can cause blue staining on plumbing fixtures from copper piping. Municipal water supplies are treated to neutralize the pH. Naturally occurring iron and manganese can cause staining, odor and taste problems. Sodium chloride can be elevated in coastal areas due to salt spray or saltwater intrusion.

How do surface waters fit in?
The Monomoy Lens also boasts over 200 freshwater lakes and ponds, 20 streams, and 150 miles of coastal shoreline. The inland surface water bodies are windows on the aquifer that reflect the intersection of low areas in the ground surface with the water table. Groundwater typically discharges into a pond on one side and then pond water recharges the lens on the other side. Streams and rivers act as drains that skim groundwater off the surface of the water table. The large Monomoy ponds (Long, Seymour and Hinkleys) receive groundwater discharge from the lens, which in turn, feeds the Herring River so that groundwater ultimately discharges as stream flow into Nantucket Sound. Where there is only coastal shoreline, groundwater discharges directly into marine water as fresh water seepage. Because of this interconnection, all uses of water- whether for drinking, swimming, boating, clamming, cranberry farming, or wetland habitat - are dependent upon maintaining the quantity and quality of the lens.
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