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How does groundwater level affect your development plans?

Groundwater comes from precipitation, like rain, snow or sleet. 
Groundwater comes from precipitation, like rain, snow or sleet. 
Ryan McVay/Lifesize/Thinkstock

One of the most important sources of our water is a natural resource we call groundwater. Groundwater makes up 98 percent of the usable water on Earth [source: Groundwater Foundation]. Not to be confused with surface water that we see in lakes, rivers and oceans, groundwater comes from rain, snow, sleet and hail that soaks into the ground. It fills the spaces between rocks, soil, gravel and sand, with gravity pulling it down until it reaches a level that is fully saturated. The top of this level of saturated water is known as the water table.

Groundwater comes to us mostly clean and free from pollution, but it can become contaminated, making it unfit for human use. Some of the most common contaminants are gasoline, oil, road salts and chemicals. One of the biggest sources of groundwater contamination is corroding, cracking or leaking storage tanks. Experts estimate that more than 10 million storage tanks are buried in the United States and that more than 20,000 abandoned and uncontrolled hazardous waste sites litter the country [source: Groundwater Foundation].

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Septic systems used by those not connected to a city sewer system are another source of contamination and landfills can leak contaminants through cracks in their bottom layer. Rain even washes fertilizers, pesticides and road salts into the groundwater.

Those who drink contaminated water or come in contact with it can contract serious bacterial diseases, nervous system disorders, cancer and even liver or kidney failure. Wildlife and fish also experience adverse effects from contaminated groundwater [source: Groundwater Foundation].

Because it is deep in the ground, cleaning up contaminated groundwater can be difficult and costly, to the tune of millions of dollars. If you're a landowner considering the development of your property, you would be prudent to test the waters, so to speak, when planning your development. Local health agencies can assist in obtaining a water analysis.

In addition to groundwater quality, consider groundwater quantity when making your development plans. Low and high groundwater levels each come with their own set of issues. Read on for more details on how groundwater levels might change your development plans and what you can do to mitigate the effects.

If you plan to construct a well on your property, groundwater levels might determine the type of well you build
If you plan to construct a well on your property, groundwater levels might determine the type of well you build
Hemera/Thinkstock

As our society grows and evolves, shifts in population and changes in land use can deplete water supplies or result in flooding. The amount of precipitation we receive can also affect groundwater levels.

If you plan to construct a well on your development property, groundwater levels might determine the well you build. Wells pump water from an aquifer, an area that holds a lot of groundwater. If groundwater levels are low, you'll have the expense of digging a deeper well. More energy will be required to drive your well pump because the water must be lifted higher to reach the surface, which will also cost you more [source: U.S. Department of the Interior].

Deep wells may affect the quality of your water as well. The pumping can cause salt water that lies deep below the surface to be sucked inland and contaminate the groundwater. Land subsidence is another issue with low groundwater levels. With no support from water, the land caves in and sinkholes develop.

There are also problems with high groundwater levels. Water coming from a shallow well is more acidic than water from a deeper well, making it more corrosive to plumbing. It can dissolve your metal pipes and fittings, and cause leakage.

Although the June 1986 amendment to the federal Safe Drinking Water Act banned extensive use of lead in pipes, you'll still find it in limited amounts [source: Woodward]. Since exposure can severely affect your health, if you have a shallow well you should have water samples analyzed for lead content at a certified water-testing laboratory just to be sure.

The good news is that the alternative products that have replaced lead in piping are more resistant to the dissolving action of corrosive water. Plastic piping is also an option where building codes allow.

Proper drainage is a crucial consideration in land development. Groundwater can be blocked from its normal course of flow by new construction and accumulate in the ground. Water close to the underside of the basement floor can rise up through the slab and cause dampness. If groundwater levels are higher than the basement floor, water can leak in through the walls and floor and you'll have standing water. Ideally, a building should be constructed so that even during rainy seasons the groundwater level is at least 10 feet below the finished ground [source: Al's Home Improvement Center].

We know the problems of low and high groundwater levels, but how do you know what the level is on your property? Regional agencies measure groundwater levels at area well locations or you can measure your personal well. However, if you do your own measurement, be sure to obtain good instructions before proceeding, so as not to damage your well equipment.

Changes in land and water use, such as new residential, industrial or agricultural development, might influence where and when to measure. Measuring at different times of year also provides different information. Spring and fall measurements determine elevation gradients and groundwater flow direction. Spring measurements also indicate the extent the storage in the aquifer system has recharged from winter precipitation. In summer, wells in operation are measured to determine pump lifts instead of groundwater levels to determine pump efficiency and pumping costs [source: Fulton].

There are a variety of techniques used to monitor groundwater levels. Metal tape sounding devices can be lowered into the well until they contact water. The length of tape that was submersed in water is subtracted from the total length of tape inserted in the well to determine the level. Electrical sounding devices are used with a cable lowered into the well until continuity occurs. Pressure transducer sounding devices, the most expensive method, connect to a data logger, enabling continuous monitoring [source: Fulton].

It is important to monitor groundwater levels over time to obtain valuable information such as supply levels, annual changes in levels and the direction of the flow. This information helps the region protect the quantity of groundwater and ensure a dependable and affordable supply. It also helps developers gain insight for well construction and placement to assist in the efficient extraction of the water.

Groundwater is essential to life and a key consideration when planning land development. Before beginning the development process make sure to determine the quality and quantity of the groundwater on your property and take the necessary actions to ensure health, comfort and a successful development project.

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Sources

  • Al's Home Improvement Center. "Waterproofing Basements." (February 3, 2011) http://alsnetbiz.com/homeimprovement/basement.html
  • Fulton, Allan; Dudley, Toccoy; Staton, Kelly. "Groundwater Level Monitoring: What Is It? How Is It Done? Why Do It?" University of California Agriculture and Natural Resources. (February 2, 2011) http://cetehama.ucdavis.edu/files/20592.pdf
  • Groundwater Foundation. "Sources of Contamination." (February 3, 2011) http://www.groundwater.org/gi/sourcesofgwcontam.html
  • Groundwater Foundation. "What is Groundwater?" (February 3, 2011) http://www.groundwater.org/kc/whatis.html
  • Groundwater Foundation. "Groundwater Basics." (February 3, 2011) http://www.groundwater.org/gi/docs/GWBASICS2.pdf
  • Jaben, Jan. "Environmental audits and expertise have become industry necessities." National Real Estate Investor. August 1991. (February 2, 2011) http://find.galegroup.com.remote.scccld.lib.mo.us:8080/gps/infomark.do?&contentSet=IAC-Documents&type=retrieve&tabID=T003&prodId=IPS&docld=A11281946&source=gale&srcprod=ITOF&userGroupName=scccld_main&version=1.0
  • Kernen, Brandon. "Federal and State Agencies Investigate Changing Groundwater Levels in New Hampshire Wells." New Hampshire Department of Environmental Services. January 10, 2011 (February 3, 2011) http://des.nh.gov/media/pr/2011/20110111-wells.htm
  • Oregon Water Resources Department. "How to Measure the Water Level in a Well." June 2009 (February 17, 2011) http://www1.wrd.state.or.us.pdfs/NGWN/Water_Level_Booklet.pdf
  • U.S. Department of the Interior. U.S. Geological Survey. "Groundwater depletion." December 14, 2010 (February 3, 2011) http://ga.water.usgs.gov/edu/gwdepletion.html
  • U.S. Department of the Interior. U.S. Geological Survey. "How urbanization affects the hydrologic system." December 14, 2010 (February 3, 2011) http://ga.water.usgs.gov/edu/urbaneffects.html
  • Woodward, Janice; Ross, Blake; Parrott, Kathleen. "Lead in Household Water." National AG Safety Database. April 2002. (February 2, 2011) http://nasdonline.org/document/1436/d001230lead-in-household-water.html

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