Water Supply Wells
Water Supply Wells
A well uses the groundwater in the rock under your property as a water supply. The system typically includes a narrow well (usually about 6 inches in diameter) with a submersible electric pump that connects directly to a home or business.
Illustration of a Hand-Pumped Well
(Not acceptable for a drinking water source)
Illustration of a Modern Well (U.S.EPA)
The well is drilled to a depth below the level of the water table so that the well shaft can store water for periods of higher-water demand. (The water table is that level in the ground below which the ground is saturated.) An impervious sleeve lines the upper part of the well shaft to prevent surface water and shallow groundwater from entering, which might contaminate the well water supply. As the pump removes water from the well shaft, groundwater flows in from fissures in the rock to replace what has been used (although not necessarily as quickly as it is withdrawn).
Illustration of Groundwater and the Water Table
Illustration Source: U.S. Geological Survey
Depending on the volume of groundwater supplied or the quality of the groundwater, you might also need an aboveground storage/pressure tank or onsite water treatment. Current standards require that you identify two reserve well sites for future use in the event of a well failure. Wells must be sited at least 100 feet from and should be uphill from any existing or proposed septic system.
DEP estimates that approximately 17,500 properties in the county use a groundwater well for their water supply.
Groundwater Source
Groundwater is water held in the cracks and other spaces in layers of rock and sand, deep underground in an aquifer. When it rains or snows, some water flows into lakes and streams, some evaporates back into the air, and some water seeps into the ground. This water infiltrates the upper soil layers and eventually reaches the saturated zone of the aquifer, where all the interconnected openings between rock particles are filled with water.
Diagram Showing a Typical Water Table Source for Water Supply Wells
An aquifer is much like a giant sponge and your well taps into the water held in the opening of the sponge." Groundwater flows slowly through the pores and fractures in the aquifer rocks, supplying your well with fresh, naturally filtered water. Water infiltration through the soil above from rain and snow melt replenishes the groundwater.
Well Water Testing
Your well should be tested once a year, or more frequently if you suspect a problem. Also, testing should be done whenever:
- work is done on the well;
- if there is a notable change in water taste, smell, color, or clarity;
- if neighbors discover a contaminant in their well water; or
- if there is an unexplained illness in humans or animals.
Water should be tested by a certified, qualified, public or private lab. Contact DPS for a list of qualified labs: call 311 within the county and 240-777-0311 outside the county. At a minimum, test water for bacteria and nitrates, in addition to any contaminants likely on your property. A good initial set of tests for a private well includes hardness, alkalinity, pH, conductivity and chloride. Contact DPS for testing suggestions based on your location and risk.
Water Well Use and Maintenance
Just as public sanitary utilities must monitor and maintain their water supply and wastewater disposal systems, a property owner needs to perform periodic maintenance and testing of private on-site wells and septic systems. This helps to ensure the maximum life of the systems, to reduce replacement and repair costs, and to protect the health of users and the environment.
Careful attention to activities at the surface, along with minor maintenance efforts, will keep your well providing clean water for many years. There are responsibilities you have as a well owner:
Careful attention to activities at the surface, along with minor maintenance efforts, will keep your well providing clean water for many years. There are responsibilities you have as a well owner:
- Periodically inspect the well cover and casing for wear, holes, and proper fit.
- Make sure that the ground slopes down, away from the well, for proper drainage.
- Take care when working or mowing near the well to prevent damage to the well cover and to keep the area clean and accessible.
- Keep hazardous chemicals (pesticides, fertilizers, gasoline) away from the well, and prevent spills or dumping of any harmful substance in the area.
- Always use qualified well diggers or pump installers when servicing your well and be sure to abide by state and county regulations.
- Test water annually, and keep a record of the results, along with records of well maintenance and conditions.
- Dispose of chemicals and hazardous substances appropriately: don't flush, dump down drains, or dump on the ground! Call DEP's Recycling & Resource Management Division at 311 (240-777-0311 out of County) for details on proper disposal.
- Clean up any oil, gasoline, pesticides, fertilizers, or household chemical spills as thoroughly and as quickly as possible. If necessary, call the Fire Department (911) or DEP (311/240-777-0311) for help.
- Minimize your use of fertilizers and pesticides and encourage your neighbors to do the same. These substances can easily seep into groundwater through the soil layers, where collective accumulation can lead to unhealthy levels. Be aware of the County’s regulations concerning the use of pesticides
- If you have an unused well on your property, make sure it is properly abandoned by filling and capping the well. Abandoned wells are a direct connection to the aquifer, providing an easy means of contamination. Contact the DPS, Well and Septic Section about requirements for abandoning old wells 311 (240-777-0311 out of County).
- Underground storage tanks are a common cause of groundwater contamination. Be aware of the condition and location of septic or fuel tanks and keep your septic system pumped and inspected. Underground storage tanks are permitted and regulated by the Maryland Department of the Environment.
Well Use and Maintenance Resources
The County’s Department of Permitting Services (DPS), Well and Septic Section, has prepared a useful brochure about well maintenance.
The University of Maryland Extension also has prepared a useful document that address well maintenance. Anyone who uses or contemplates using a well should review Water Wells and Their Maintenance Guidelines
Maryland Department of the Environment has useful information provided by the MDE Water Supply Program.
WellOwner.org Information provided by the National Groundwater Association and the Rural Community Assistance Program.
EPA's Private Drinking Water Wells: According to this site, EPA estimates that approximately 13 million American households obtain water from their own private drinking water supplies. The site also notes that "EPA neither regulates private wells nor does it provide regulatory standards or criteria for individual wells." EPA does encourage these households to take special precautions to ensure the protection and maintenance of their drinking water supplies.
Safe Drinking Water Information: According to this website, "The Environmental Protection Agency's Safe Drinking Water Information webpage provides link to an online form and a mailing address for questions about drinking water. The webpage also provides links to a variety of drinking water topics including those related to wells."