Water, Water Everywhere

Thinking of building a home? Then you may want to give some thought to the depth and direction of underground rivers called aquifers.

Such underground water - or "groundwater" - tends to "follow the surface topography," say hydrogeologists. In other words, watch which way storm runoff drains, and you'll be able to tell which way the water you can't see runs "downhill."

Rivers and creeks in your area flow in a certain direction. Chances are the aquifers beneath your property flow that direction, too. "Surface water" like rivers and lakes "recharge" aquifers as does rain. Aquifers "discharge" into lakes and rivers.

While you may be lucky enough to have purchased a property with hilly terrain, and decide to perhaps build into one of the hills to take advantage of a particular view - if your new home sits directly in the path of storm runoff, basement flooding could be a periodic problem.

That's not to say the problem can't be solved. Installing a landscaped swale can divert water away from your home, discharging it harmlessly down a part of the hill on which there are no structures, and perhaps into a newly constructed pond.

Besides noting the direction surface and groundwater flow, you will also want to consult soil maps on file with your county. Through them, you can learn the "depth to groundwater." If an aquifer is "shallow" - digging into it while laying a foundation could mean an expensive "dewatering" project to keep the construction site dry while the basement is being poured.

Also important, testing groundwater for quality should your property be rural and require a well. Bedrock groundwater is safer than shallow groundwater. Surface contaminants, such as farm field runoff which can elevate nitrate levels in water and be a risk to babies and small children, is a greater threat to shallow aquifers, particularly groundwater 10 feet or less from the surface. Not all bedrock is created equal. Limestone, for example, is more susceptible to contamination because of fractures or "karst" features - which can allow contaminated water to travel quickly over large distances. To learn what sort of bedrock you have, ask a neighbor for a copy of his/her "well log." When wells are drilled, the sorts of soil and rock encountered are logged and filed. Local governments will have well logs on file because a permit is required to drill a new well. Another source of this information is well drilling companies.

Certain activities can impact groundwater quality and potentially compromise the safety of your drinking water. The University of Missouri (http:extension.missouri.edu) lists common practices that can help you consider how human activity and site conditions such as soil types can affect water quality:

• Washing spilled motor oil and grass clippings into storm drains or surface waters
• Storing gasoline and other hazardous chemicals near children's toys
• Paving walkways instead of using porous material, thus increasing runoff
• Not separating garbage for recycling
• Placing sprinklers so the water runs onto a sidewalk or street
• Planting flowers and other vegetation that may require fertilizers and pesticides near a wellhead
• Burning garbage, which may add toxins to air that eventually settle on the ground surface

Soil types play an important role in determining where contaminants go and how water moves. Nearly all soils are permeable, which means water and other fluids can percolate, or seep, through them, according to the university. Different soils, such as sand, or clay, have different properties that permit water (and contaminants) to percolate through the soil or run off at variable rates. Your county's Soil and Water Conservation District can help you determine what types of soils underlie your building site.

Lawn chemicals and leachate from a leaking septic tank, for example, can flow downward into groundwater or across the land into surface water. Many household activities, such as those listed above, can also produce problems that go beyond property boundaries. For example, contaminants that enter groundwater through a neighbor's abandoned well may flow underground until they reach your well.

The following are additional potential sources of contamination:

• Improperly located or poorly maintained septic system or sewage lagoon
• Pipes that discharge sewage to the surface
• Underground or aboveground storage tank containing fuel oil, gasoline, or other petroleum products
• Improperly constructed or abandoned well
• Stockpiled animal manures or animal pens, corrals or kennels close to a well or surface water body
• Improper storage, use or disposal of yard and garden chemicals and other hazardous products like paints and solvents
• Machine maintenance workshop near well
• Road de-icing materials (salt, cinders) that flow toward a well or nearby surface water body

By carefully mapping your homesite before you build, you can avert pitfalls, protect groundwater, and help keep your family safe.

Picturing an aerial view of your property, the university suggests graphing the following:

Graph Paper for Homesite Map

One block = 1/10 inch = 10 feet

• Property boundaries
• House and garage
• Outbuildings, sheds
• Septic system, drain field
• Nearest surface water
• Water wells
• Dry or abandoned wells
• Heating oil or other fuel
• Storage tanks
• Building perimeter drains
• Lawn areas
• Vegetable and flower gardens
• Other cultivated areas
• Animal manure storage areas
• Roads, driveways
• Drainage ditches
• Impervious surfaces (such as patios or sidewalks)
• Refuse piles or storage
• Drainage swales and gullies

On your map, note the areas where you store and use chemicals and other potential hazards by using letter codes. Make up your own code letters or symbols as needed.

For example:

• F = Fuel tanks for gasoline or heating oil
• A = Automotive products like motor oil, gasoline and antifreeze
• P = Pesticides, herbicides
• H = Hazardous products like solvents, acids, paints and thinners

For larger-view maps, add landscape features such as hills, rivers and ponds and human-built features such as runoff drainways, roads and bridges. Note potential sources of contamination beyond the boundaries of your property such as farm fields, dumps and gas stations. Indicate seasonal changes at your homesite, such as wet areas in the spring. Wet areas might indicate a high water table.

Other things to consider include asking about previous or current industrial or agricultural activities in the area, such as old landfills and buried fuel tanks on neighboring properties. Any source of contamination uphill from your well could potentially impact the safety of your drinking water.