Thursday, August 2, 2012

Purchasing a Home with a Water Well-Caveat Emptor

In rural areas or here on the edge of nowhere private wells supply water to homes. If you are thinking about buying a home with a private water well you need to understand at a minimum the basics about groundwater, the local geology, water quality, how the well system works, how deep the well is and how old and what size pump it has. These are the factors that will impact water reliability, water quantity, and water quality.  It would be a real shame to discover after closing on home that the drinking water well does not supply enough water for you to do laundry in the summer, goes dry in a drought or that the water is contaminated or has an unpleasant taste or smell. It can be very expensive to replace a well or well components, engineer solutions to water supply problems and install and maintain a water treatment systems. A home inspection tells you nothing about the well or septic system.  

About 15% of households in the United States depend on private wells including over a million each in Virginia and Pennsylvania where I once lived. In its most basic sense a private water well is a hole in the ground that is drilled, driven, or hand dug to supply water for a household. Most wells today are drilled by a cable tool or by air-rotary drill. Hand-dug wells are usually very old but still exist; and are very susceptible to pollution from surface sources and may also present easy routes for surface contaminants to enter the aquifer. If considering purchasing a home with an old hand dug or driven well factor in the cost of replacing the well with a modern drilled well in the price and be aware that not all pieces of land have suitable aquifers to tap.

The aquifer is the groundwater. Aquifers may occur a few feet below the land surface, but useful aquifers are more commonly found at depths greater than 100 feet in Pennsylvania and 100-400 feet beneath the bedrock in Virginia. Some groundwater occurs in the pore spaces of solid rock, but most usable groundwater occurs in cracks and fractures in rock layers or between sand and gravel particles of unconsolidated layers. Except in Karst terrain which has its own special problem, groundwater normally occurs in small spaces within the geological layers and not as underground lakes or rivers.

 Geologic formations called aquitards are usually made of clay or dense solid rock. The aquidards inhibit groundwater infiltration, and restrict groundwater movement into and between aquifers. Aquitards located above and below an aquifer form a confined aquifer. If a well is drilled into a confined aquifer, artesian pressure forces the trapped water to rise in the well above the aquifer if the pressure is great enough, the water may even flow without pumping to the land surface creating an artesian well. The downside to a confined aquifer is that recharge is limited. The coastal plain in Virginia has a confined aquifer and is really only recharged at the “fall line.” A groundwater aquifer without an aquitard above it is an unconfined aquifer and more susceptible to contamination, but more easily recharged by precipitation. Without pumping, the water level in wells in unconfined aquifers is the same as the aquifer. The county department of health, the extension office, the local offices of the U.S. Geological survey are good places to find out about the local geological and groundwater conditions. You need to understand what type of aquifer you are dealing with to be aware of the factors that impact water quantity and quality. There are dry years and wet years and water availability will vary, though it is not always obvious. The groundwater aquifer tapped for water is not seen so you need to understand it to be aware of the water budget that you will have to live within before you run out of water.

In many locations private wells are not regulated or only minimally regulated. Virginia now has well drilling regulations and standards, but those only apply to wells drilled after 1992 and require a health department permit for drilling new wells and repairs of older wells.  If you buy a home with an existing well- buyer beware. It is your responsibility to make sure that you know what you are buying. The type of well, the well yield, the condition of the well and the quality of the water is your responsibility to determine before purchase. The type of well and the configuration will be determined by the age of the well and geology.  While there was a time when some wells were hand dug with a shovel or hand driven using connected pieces of pipe (as featured in Hallmark channel movies) most wells use equipment to drill, dig or drive pipe and by and large modern wells are drilled. Nonetheless, there are thousands of home supplied with water from older wells. Ask, look, investigate. Check driller’s logs filed with the health department.

The type of well is determined by geology and history. Sitting as my home does in the Culpeper groundwater basin above fractured rock and bedrock, drilled wells are predominant. When drilling a well, it is typical here and now in Prince William Virginia in the twenty-first century to drill the well through a first and second layer of groundwater. I have a second groundwater level I can drop my pump down to if need be in a drought.

Drilled wells penetrate about 100-400 feet into the bedrock. To continually supply water, a drilled well must intersect bedrock fractures containing ground water. The art of well drilling is having a feel for what a fracture looks like at the surface- knowing where the water is. A trained and experienced hydro-geologist can generally find the fractured rock zones, or the intersection of two fractured rock zones using aerial photography and the fracture trace technique. It can be expensive to hire a professional hydro geologist, but the cost is worthwhile for difficult areas.  Where I live in the Piedmont region of Virginia the local geology is a fractured rock system that is water rich with more than one groundwater layer, so using hydro geologists is not common, but I do know of a couple of instances where several wells were drilled before obtaining adequate water flow and it might have been more cost effective to locate water before the house was built or to design a different well system. The Piedmont tends to be so water rich that alternatives are not in common use. In some regions low production wells are common.

If a property has a low producing well, there are ways to deal with it. First is water conservation and the second is to increase water storage within the system. Water conservation involves changing water–use behavior such as taking shorter showers, but usually involves installing water saving devices like a front-loading washer (saves 20 gallons of water for each load),low flush toilets, flow restricting faucets and shower heads. Installing watersaving appliances can reduce household water use by up to 30%. Water conservation may solve the problem of a 5 gallon a minute well, but increasing water storage can make a reliable 1 gallon a minute well viable for a modern household. An intermediate storage system consisting of a storage tank ,reservoir or cistern that can be installed between the well and pressurized distribution system. The reservoir serves as the primary source of supply for the pressure pump supplying peak demand. Ideally, the storage tank or cistern should be able to hold at least a day’s water supply and be regulated by a float switch or water level sensor. A 1 gallon a minute well can pump 1,440 gallons per day more than adequate for a household of almost any size.  The rule of thumb is to size a storage tank or cistern at 100 gallons per person in the household. It is much cheaper to installed intermediate storage than keep drilling wells.   

Once you have determined that the water supply is adequate, the water quality should be checked. The quality of the groundwater is a characteristic of the aquifer and the ability of your local geology to protect or impact your aquifer. The most common sources of pollution to groundwater supplies come from two categories; naturally occurring ones and those caused by human activities. Naturally occurring contamination are produced from the underlying soil and rock geology. Microorganisms in the soil can travel into groundwater supplies through cracks, fissures, and other pathways. Nitrates and nitrites from the nitrogen compounds in the soil can also enter the groundwater. From the underlying rocks radionuclides and heavy metals can enter the groundwater. There are areas with natural occurring arsenic, cadmium, chromium, lead, selenium and fluoride. While many natural contaminants such as iron, sulfate, and manganese are not considered serious health hazards, they can give drinking water an unpleasant taste, odor, or color.

Human activities can also introduce contaminants into thegroundwater. Bacteria and nitrates can be caused by human and animal waste. Improperly constructed and sealed wells can allow surface contamination to enter the well. Improperly maintained septic systems containing human waste and any chemical you flush down the drain, horses, and backyard poultry can contaminate the groundwater. Leaks from underground storage tanks, surface disposal of solvents, motor oil, paint, paint thinner, termite treatment or nearby or historic landfills or industrial operations can contaminate groundwater. A confining geological layer can protect groundwater from surface contaminants more effectively than a fractured rock system, and there is extremely limited natural protection in karst terrain. Though it is cost prohibitive to test for every potential contaminant, a broad baseline analysis should be performed before purchasing a home (and every few years). A bacteria test is not enough. The cheapest way to do this is a commercial product aimed at the private homeowner. One product I have used is the WaterCheck with Pesticides. This product covers 15 heavy metals, 5 inorganic chemicals, 5 physical factors (like hardness and pH), 4 trihalo methanes, 43 volatile organic chemicals (solvents), and 20 pesticides, herbicides and PCB’s. The analysis takes two weeks and so the contingency period must allow for that or a more expensive analysis must be used. Whatever analysis you use, make sure you use an EPA certified laboratory that is also certified in the State where the property is located.

All private wells should be have as a water-tight, vermin-proof well cap and a cement or bentonite grout seal between the borehole and the well casing to prevent surface contamination and bacteria from entering the well. In coal or gas country, a well should include a vent. Well water should be tested annually to ensure a safe drinking water supply for your family. The supply of water should be adequate. In our modern world household water demand is not spread evenly over the day. There are peak usage times driven by washing machines, dish washers, showers. An adequate water system must be able to yield enough water to satisfy peak demand. Look for a minimum of 10 gallons a minute from a modern drilled well to supply a household or a system with intermediate storage (remember in some instances the well itself can provide storage). To live comfortably with your well, your water system has to be able to deliver an entire day’s worth of clear uncontaminated water within a 90 minute window.  

1 comment:

  1. Great information on wells and aquifers! Thanks, Elizabeth!

    I minored in geology, so I try to pay attention to bedrock type when I buy a home; but you remind me that I should examine the local aquifers, too, whenever a home is not on city water and sewer.

    Karst terrain can be a problem, and most homebuyers may have no idea. Prone to contamination – and at times, sinkholes. I mean, well, karst terrain is where we find caves, if that tells folks anything.

    We have karst not far from where I live. They already got sinkholes and failed wells locally in our karst region (not my neighborhood, but nearby), and our local developers (Clarke Co. VA, Jefferson Co. WV, Frederick Co. VA and formerly in Loudoun Co. VA) don't seem to pay much attention to karst. They just seem to keep building on the stuff, and the county governments for whatever reason will seem to let them keep doing that.

    I worry that in time, something may give. Not sure, but then, I prefer other types of rock under my home, and try to plan that accordingly.