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Water Facts
• Potential Groundwater Contamination Sources
• Natural Contaminants
• Septic Systems
• La Plata County Individual Sewage Disposal System (ISDS) Permits
Information in this section was found at Groundwater Basics > Sources of Contamination, and Sustainability of Ground-Water Resources from United States Geologic Survey (USGS), and USGS reports and papers.
Additional information about selenium can be found at the EPA's selenium page.
Groundwater contamination occurs when man-made products such as gasoline, oil, road salts and chemicals get into the groundwater and cause it to become unsafe and unfit for human use. Some of the major sources of these products, called contaminants, are storage tanks, septic systems, hazardous waste sites, landfills, and the widespread use of road salts and chemicals.
A [domestic] well can be easily contaminated if it is not properly constructed or if toxic materials are released into the well. Toxic material spilled or dumped near a well can leach into the aquifer and contaminate the groundwater drawn from that well. Contaminated wells used for drinking water are especially dangerous. Wells can be tested to see what chemicals may be in the well and if they are present in dangerous quantities.
Septic systems can be serious contamination sources. Septic systems are for homes, offices or other buildings that are not connected to a city sewer system. Septic systems are designed to slowly drain away human waste underground at a slow, harmless rate. An improperly designed, located, constructed, or maintained septic system can leak bacteria, viruses, household chemicals, and other contaminants into the groundwater causing serious problems.
Chemicals include products used on lawns and farm fields to kill weeds and insects and to fertilize the plants. When the rain comes, these chemicals get washed into the ground and eventually into the water.
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Contamination of ground water is not always a result of the introduction of contaminants by human activities. Possible natural contaminants include trace elements such as arsenic and selenium, radionuclides such as radon, and high concentrations of commonly occurring dissolved constituents.
In La Plata County, water was sampled from local aquifers and tested by the United States Geologic Survey during studies in the 1970s (USGS Water Resources Investigations Report 76-69, and USGS Water Supply Paper 1576-J). Many of the samples contained arsenic, chloride, dissolved solids, fluoride, iron, magnesium, manganese, nitrate, nitrite-plus-nitrate as nitrogen, selenium and sulfate in concentrations exceeding recommended or mandatory standards for drinking water established by the Colorado Department of Health, the EPA and the U.S. Public Health Service. The USGS studies emphasize possible health hazards associated with naturally occurring contaminants in ground water, especially selenium and fluoride in some areas of the county.
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Information in this section was found at San Juan Basin Health Department, "Individual Sewage Disposal System Regulations," Colorado Department of Public Health and Environment, and the CDPHE report "Individual Sewage Disposal Systems, A Preliminary Risk Assessment, November 1999,"
Additional information about septic systems is available on the Internet at Septic System FAQs, and The Home Buyer's Guide to Septic Systems.
An individual sewage disposal system (ISDS) provides wastewater treatment and disposal, primarily for individual homes (as well as some commercial and business facilities) in areas not served by central sewer systems and wastewater treatment plants. Traditionally, an individual system consists of a septic tank and an absorption area or leach field. Primary treatment occurs in the septic tank due to removal of suspended solids through settling, flotation and anaerobic digestion of the solids. Additional treatment occurs in the soils around the absorption area through natural physical, chemical and biological processes. These systems are prevalent throughout Colorado, but most particularly in rural and suburban areas where densities are not adequate to support central collection and treatment systems.
The owner of any structure where people live, work or congregate shall insure that the structure contains adequate convenient, sanitary toilet and sewage disposal systems in good working order. Any person who wishes to install, alter or repair and ISDS in La Plata County shall obtain a permit from the Health Officer. The property owner shall be responsible for proper installation and maintenance of the system and for abatement of any nuisance arising from its failure. The Health Officer may issue an order to cease and desist from the use of any system, which is found to be out of compliance or which otherwise constitutes a nuisance or hazard to public health and which has not received timely repairs.
To obtain an ISDS permit, file an application at San Juan Basin Health Department, 281 Sawyer Drive, PO Box 140, Durango, CO 81302
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The existing regulatory framework for individual sewage disposal systems in Colorado is based primarily on human health risks as understood in the 1950s and 1960s, and not directly on potential risks to the quality of surface and ground water resources. For example, setback requirements are designed to protect human health and are based on the limited movement of bacteria through soil systems. However, many chemicals found in septic tank effluent can be transported beyond the immediate vicinity of the treatment system and reach nearby surface waters or underlying ground water systems. Currently, what is considered an adequate ISDS does not directly take into account nutrient, viral or chemical components of wastewater. Consequently, an emerging concern in Colorado is the potential for surface water and ground water contamination caused by discharges from ISDSs.
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