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Roger Weller, geology instructor

by Elizabeth Piccolo
Physical Geology
Spring 2013

Soil:  The Foundation of Your Dream Home

            Do you dream of a mountain cabin in the woods?  Or maybe you desire a house on a seaside cliff?  Home buyers often focus on views and floor plans instead of the most important factor in the entire process:  the land upon which their home will be constructed, as well as the location of garages, workshops, and their well and septic systems.  Before purchasing land for your dream home, invest some time researching soil and weather conditions, as well as the history of the area.  Although general contractors, developers, and realtors are responsible for many things; ultimately, it is the homeowner that will pay for mistakes or unknown factors discovered during the construction process.  With a little research, costly repairs and long-term maintenance expenses can be drastically reduced or totally eliminated.  This paper will provide a brief overview of soil survey reports, soil, soil contamination, acid sulfate soil, groundwater, groundwater contamination, septic systems, expansive soils, erosion, and landslides.   Keep in mind your most valuable and inexpensive source of information is your potential neighbor(s).  Speak to them about the history of the area, expansive soil complaints, prevalent rain/snowfall areas of runoff, incidences of flash flooding, irrigation practices, groundwater and drainage issues.  Your neighbor’s problem could be your problem too in the future.  A little time invested upfront prior to your purchase can save you thousands of dollars later and prevent you from buying a piece of property that will be difficult to sell.  Several reference sites are available after the Works Cited for further information on these subjects.

Soil Survey Reports

            Many home developers and realtors will talk about soil survey results, but beware of this information:  who explains it and how it is explained.  Soil Scientists specialize in this subject and could be consulted to clarify the known risks of the area and explain the report results.   Caution should be taken with these results as soil surveys have limits:

            Soil surveys are limited by the chemical and physical data that are collected. Samples for analysis may or may not have been completed for soils located within a soil survey area.  Information learned in one area is extrapolated to other areas. Soil tests are not done for such items as chemical applications and toxic spills (Muckel, 5).  Sampling soil is a complex process.  For a history of Soil Surveys and an online List of Surveys by State, visit:

            According to Gary B. Muckel with the National Soil Survey Center in Lincoln, Nebraska, “Locating facilities in areas with excessive risks contributes to loss of life, health, and property” (5).  Mr. Muckel has published an extremely informative 96 page document on the United States Department of Agriculture website titled, “Understanding Soil Risks and Hazards Using Soil Survey to Identify Areas With Risks and Hazards to Human Life and Property” (Muckel 1).  This document describes some of the many risks and hazards to homeowners.  A call or visit to your state cooperative extension office may have more detailed historical and soil information.   General soil information is available through the Department of Agriculture in your state.  If you are unsuccessful locating information in your state, try the federal government website for more contact information:


            Fellow Cochise College Student, Marti Stoner, prepared a presentation on Soil.  For an overview, check out the presentation:


Soil Contamination

            Typically speaking, there are three contaminant materials most commonly found near homes:  lead, arsenic, and cadmium (Gromicko 1).  Although banned in the 1970s, lead paint is still the largest contributor.  Areas within the “drip zone” (six feet from the structure), are more prone to contamination; however, if pressure washing or sandblasting were used to remove the lead paint, particles can be found in surrounding areas moved by heavy rains or melting snow (Gromicko, 1).  Between 1950 and 2004, outside structures like gazebos, walkways, fences and playgrounds were built with wood sprayed with Arsenic to protect and preserve the wood (Gromicko 1).  Old rural areas, now developed into housing communities, were used for farming and may still contain fertilizer and pesticide residues decades later.  Cadmium has entered our environment and our atmosphere, “as a byproduct of the burning of fossil fuels and municipal wastes, and from the smelting of zinc, lead and copper” (Gromicko 1).  The health risk to humans and animals arises during any type of direct contact -- primarily digging.  Children are at risk because they often play on the ground or put things in their mouth that have been on the ground without washing their hands.  Cats, dogs, and other animals often eat or drink water from the ground that may cause illness or death.  These contaminants can also prevent plants from thriving.  Through leaching:


                                    Courtesy:  Roger Weller

these contaminants, as well as others, could enter the groundwater sources poisoning the water supply.  “Soil tests for metals are different from standard soil fertility tests, though both are needed to give clues on how to address contamination.  Environmental, and some agricultural , laboratories perform soil tests for metals.  Procedures for collecting a soil sample and explanation of test results can be obtained from the laboratory used” (Muckle 18).

Acid Sulfate Soil

            Often mistaken as topsoil due to its dark color, acid sulfate soil “is corrosive to concrete in direct contact” and runoff “is equally corrosive and harmful to plants and soil organisms” (Fanning and Muckel, 7).  Although it is most common along coastlines, it can be found in upland areas as well.  In coastal regions “sulfidic materials are near the surface or at some depth where they are easily exposed during construction activities”; however, in upland areas, sulfidic materials may be found seven meters or more beneath the surface (Fanning and Muckel, 8).  As long as acid sulfate soil remains underground it is safe; however, if the soil is drained or the water table lowered, and/or excavation activities occur, the soil is exposed to oxygen and can form sulfuric acid.  This can release a variety of heavy metals like iron, arsenic, and aluminum which can cause failure in steel and concrete structures (“Acid”).  In the United States, soil samples are typically taken at a depth of two meters, but since land excavation of home sites is often performed, sampling at deeper depths would be wise (Muckel and Fanning,  8).  Also consider if mining operations are conducted nearby, or if there is a history of this type of activity.  If contamination is detected, reclamation measures must be taken, requiring additional costs as well as construction delays. 


            Prior to purchasing any parcel of land, check the Environmental Protection Agency’s Superfund Site to determine its location.  Areas known to have historical damage caused by hazardous material waste, mining and manufacturing, are recorded here:

            Also, prior to purchasing a land parcel, contact your Health and Human Services department to obtain groundwater tests results.  Some lenders require “proof of a bacteria-free water supply” prior to issuing a loan (“Septic”).  Insist on an inspection of an existing septic system to ensure it isn’t failing.  “It pays to be concerned about your water from well to wash to waste” (“Septic”).

            Access to, and availability of, quality water is extremely important.  It is needed for drinking water, food preparation, personal hygiene, as well as landscaping or irrigation.  The site selection process for a well should be considered in advance to ensure an ample supply of clean water is available.  A review of local water table information should be conducted to determine the well depth required to prevent septic and other forms of contamination.

The water table may access resources from the closest aquifer:

water table.jpg


                        Courtesy:  Roger Weller

A test will be required to test for the soils permeability and porosity:



All of these factors impact the cost of groundwater:

             Groundwater costs.jpg

Over long periods of over-pumping, a cone of depression forms:

                cone of depression.jpg

            When water is pumped out of a well faster than the water table can refill, a loss of water supply and water pressure will occur until the water table returns to a normal level.

Groundwater Contamination

            Long term effects of drinking water contaminated with pollutants can cause many types of cancers, but the short term effects caused by septic waste can also cause dysentery and hepatitis.  Contamination can occur several ways:




Atmospheric contaminants, chemicals used outside the home or road salts, uncontrolled hazardous waste, landfills, and storage tanks.   

Septic Systems

            In rural areas not connected to a public sewer system, the installation of a septic system is the most economical and effective method of treating effluent.  Effluent is all wastewater leaving a home or building, including sinks, toilets, dishwashers, washing machines, and bathtubs.  These waters often contain harmful materials to humans, animals, and plant life and must be adequately treated before being released into our environment.





            Location of the septic system is a critical component of rural home site development, and should be a priority decision due to space and distance requirements.  A properly functioning standard septic system requires at least one acre of land, and should be located at least 100 feet from a well to provide safe disposal of septic effluent (“Septic”).   Areas with steep slopes and ravines or flood-prone areas near streams or rivers are not recommended.  The most desirable location for the septic system is at the highest point available, but lower than the well (“Septic”).  The deeper the well, the less likely it will become contaminated by effluent. 

Expansive Soils

            According to Virginia’s Department of Mines, Minerals, and Energy, “Soils that exhibit changes in volume with changing moisture content are called expansive soils” (Virginia Dept.).  Based on the amount of clay minerals present in the soil, specifically montmorillonite, an expansive soil can shrink and swell “up to fifteen times its dry volume and generate pressures in excess of 30,000 pounds per square foot” (Virginia Dept.).  An existing shrink / swell factor may be identified by the existence of cracked foundations, driveways, sidewalks, pipes, and roadways; missing or improper gutter drainage; and the presence of a large amount of landscaping items, primarily large trees. 

Structure damage from shifting soil is the geologic hazard that causes more damage [in dollars] in the United States than all other natural hazards combined, including earthquakes, floods, tornadoes, volcanoes, and hurricanes.1 Despite the significant costs to repair such foundation issues, many people remain unaware of the devastating effects of expansive soils on foundation due to the gradual nature of such damage. This is compounded by the fact that to the untrained eye or new homeowner, the beginning cracks or other signs cannot initially be attributed to a specific event. Expansive soil could be compared to carbon monoxide’s lethal, but undetected, effect on humans –the silent killer (McKnight 2).

Cracked foundation


Corner Walls Separating


Splitting Walls


Use the Expansive Soils Map and Soil Moisture Regimes of the Contiguous United States Map on the next page to locate the property under consideration to identify its regime.  This data can determine if your purchase may be prone to this condition.  Combine this information with the fact that “Suburban developments frequently contain buried construction waste or decaying root systems” (Virginia Dep).  This can aggravate an already “unsettling” experience for the homeowner.    Do you want to build your dream home on top of an old landfill?

Expansive Soil: The hidden force behind basement and foundation problems





Soil Moisture Regimes of the Contiguous United States Map




                                Source: page 1

            Erosion is the process of carrying away material by wind or water.  Former Cochise College student, Jessica Redus, conducted her research on soil erosion, and I will refer you to her paper for more information:




            For a brief history of landslides, check out former Cochise College student, Alex Jirousek’s, presentation:

and Tracy Cottrell’s presentation at:


Two visual indications of previous landslide activity are:



And Scarp:


                        Courtesy:  Roger Weller

            Some preliminary research on your area of interest could begin on a site similar to:

            Sites like this are not always 100% factual, but can provide a valuable overview of weather and natural disaster information.  It can also help begin a dialogue with the neighboring property owners and provide a general overview of the community.  Searches may be conducted by the city name, county or zip code, and will provide a variety of subjects.  Weather information is usually found towards the middle of the page.  All categories are not available for all searches (i.e., San Francisco, CA and St. David, AZ).  Below is a snapshot of city data for Malibu, CA (“Malibu”) regarding natural disasters:

            The number of natural disasters in Los Angeles County (51) is a lot greater   than the US average (12).
            Major Disasters (Presidential) Declared: 24
            Emergencies Declared: 4
            Causes of natural disasters: Fires: 34, Floods: 14, Storms: 8, Landslides: 5,   Winter Storms: 5, Mudslides: 4, Earthquakes: 2, Heavy Rain: 1, Snow: 1, Storm: 1, Tornado: 1,

            Wind: 1, Freeze: 1, Hurricane: 1 (Note: Some incidents may be assigned to more than one category).

            The data above shows that Malibu not only has a history of two earthquakes, but has experienced at least 14 Floods, 5 Landslides, and 4 Mudslides.   The fact remains that considerable soil will be lost through erosion leaving this area a high risk for future landslides. Homeowners in this area pay a high premium for homeowner’s insurance and remain at high risk of experiencing future landslides.

            Consider another coastal location on the east coast.  Information provided for Virginia Beach, VA.. reflects no history of landslides, mudslides or heavy rains, and the absence of earthquake activity is replaced with tornado activity (“Virginia”). 

            Virginia Beach-area historical tornado activity is slightly above Virginia state average. It is 9% smaller than the overall U.S. average.

            On 9/5/1979, a category F3 (max. wind speeds 158-206 mph) tornado 21.0 miles away from the Virginia Beach city center injured 2 people and caused between $500,000 and $5,000,000 in damages.

            On 7/4/1967, a category F3 tornado 33.7 miles away from the city center injured 5 people and caused between $5000 and $50,000 in damages.

            Further research in these areas could eliminate future problems and confirm that some areas are best left alone --  unless money is not an issue of course. 

Works Cited

“Acid Mine Drainage.”  Ground Truth Trekking.  Ground Truth Trekking.  2013.  Web.  20 Apr. 2013.

Gromicko, Nick.  “Soil Contamination Inspection.”  International Association of Certified Home Inspectors, Inc.  Inspecting the World.  2013.  Web.  10 Apr. 2013.


“Malibu, CA.”  2012 Onboard Informatics.  Advameg, Inc. 2012.  Web.   21 Apr.           2013.

McKnight, Kelly.   “Analysis of Expansive Soil and Foundation Damage.”  Dec. 16,             2011.  University of North Texas, Department of Geography, 2013.  Web.  11 Apr.  2013.   


Muckel, Gary B.  “Understanding Soil Risks and Hazards: Using Soil Survey To       Identify Areas With Risks and Hazards to Human Life and Property.”       United States Department of Agriculture.   NRCS.  National Soil Survey      Center.   Lincoln, NE.  2004.  Web.  10 Apr. 2013.

“Septic Systems: What you need to know.”  North Carolina Cooperative Extension Service.  Water Quality and Waste Management.  Publication Number: WM-1.  March 1996 (JWM).  Web.  19 Apr. 2013.


“Soil Survey.”  United States Department of Agriculture.  Natural Resources             Conservation Service.  2013.  Web.  20 Apr. 2013.


“Superfund Sites Where You Live.”  United States Environmental Protection             Agency.  2012.  Web. 20 Apr. 2013.

“Threats to Our Groundwater.”  The Groundwater Foundation.  2013.  Web.  20 Apr. 2013.


“Virginia Beach, VA.”  2012 Onboard Informatics.  Advameg, Inc. 2012.  Web.

Virginia Department of Mines, Minerals and Energy.  “Expansive Soils and Frost             Heave.”  Virginia Department of Mines, Minerals and Energy.     2012.  Web.  20 Apr. 2013.

Additional Resources

Arizona, University of Extension

Before You Build Your Home:


Expansive Soil: (National Soil Survey Center Channel)




Opal’s Pals:

Courtesy of Roger Weller, Cochise College,


Septic Systems:


Topographical Maps:


Weather (Past and Present):


Other Related Student Presentations:


I wish to thank the following students for their research provided above.
Marti Stoner, Spring 2006; Jessica Redus, Fall 2009; Tianya Shemanski, Fall 2007; Casey Fuller, Spring 2010; Tracy Cottrell, Fall 2005; and Alex Jirousek, Fall 2009.