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Recharge The process by which water—from rainfall, snow- melt, and other sources—flows into a water-bearing geologic formation (aquifer) is known as recharge. Water first passes through the unsaturated zone, where soil pores are filled partly with air and partly with water. The water then flows downward through the unsaturated zone into the saturated zone, where the soil pores are completely filled with water. The boundary between these two zones is called the water table (see Figure The water table rises when water enters the saturated zone and falls when water is discharged from the saturated zone either naturally springs, lakes, or rivers) or by pump- ing wells). The unsaturated zone is important to the groundwater underlying it. As incoming water seeps down through the unsaturated zone, impurities are removed, helping to cleanse the water. Both the quantity and quality of groundwater is affected by the condition of the unsaturated zone in a recharge area. SEPTIC SYSTEMS A properly designed, installed, and maintained septic system poses no threat to groundwater. However, inadequately functioning and/or failing septic systems can contribute to the contamination of groundwater. Wastewater from septic systems may include many types of contaminants, such as nitrates, harmful bacteria, and viruses. Trace amounts of metals may be contributed to the system from persons using some medications. Also, commonly used chemical substances, such as pesticides, paints, varnishes, and thinners, can contaminate the groundwater if they are not disposed of properly. Some chemicals, even in small amounts, can be dangerous to both the environment and public health. Through physical, chemical, and biological pro- cesses, the soil acts as a natural buffer to remove bacteria and viruses in the unsaturated zone. How- ever, various geologic conditions, such as fractured bedrock and shallow groundwater tables, may allow these bacteria and viruses to be transported very rapidly and could contaminate nearby drinking water supplies. Therefore, it is critical that your drinking water well is properly sited, has a sealed casing, and the required distances from nearby septic systems are maintained. This will help prevent contaminants from seeping into and mixing with your drinking water (see Figure Separation Distances A septic system must be located a certain distance away from drinking water wells, streams, lakes, and houses. These distances are referred to as horizontal separation distances. Figure 4 (see back) shows a typical layout of a conventional onsite wastewater disposal system. Actual horizontal separation distances have been established and are specified in local regulations. In order to maintain aerobic digestion processes and remove contaminants effectively, the absorption field must be adequately separated from the groundwater or other limiting layer. This is known as the vertical separation distance and is also specified by local regulations. Determining System Size and Water Usage Water use in rural households can be predicted from the house plan, depending on the number of bed- rooms, water-using appliances, and potential addi- tions. Although the actual number of residents determines water use in a house, the house plan determines the potential number of residents number of bedrooms), water usage, and subsequent wastewater flow. Typical wastewater flow rates range from 60–120 gallons per person per day. Typical minimum septic tank sizes range from 750–1000 gallons. The flow estimate, plus the soil permeability estimate how easily water moves through the soil), is used to determine the area of the absorption field needed for the system. Installing a drainfield of sufficient size is critical to the proper functioning of your septic system. Local regulations should always be reviewed before installing a septic system. Are Contaminants Reaching the Water? Signs that wastewater from your septic system could be reaching water sources include: • Unpleasant odors persistent rotten egg smell), soggy soil, liquid waste flow, or excessive grass growth over the soil absorption area. These often indicate failure of the system and the need for repairing, expanding, or replacing the absorption area. Groundwater protection and your septic system continued . . . 1 2 3 4 5 6 1 2 3 4 5 6 evapotranspiration evaporation runoff water-vapor transport precipitation groundwater flow Hydrologic cycle Fig. 1 Water table Fig. 2 well saturated zone surface water unsaturated zone water table Correct location of septic systems and drinking water wells Fig. 3 well septic tank drainfield groundwater movement saturated unsaturated water table WHAT IS GROUNDWATER? Water in the saturated zone beneath the soil surface is commonly referred to as groundwater. Groundwater is but one stage, or form, through which water passes in the earth’s hydrologic cycle (see Figure The hydrologic cycle is the continual movement of water over, in, and through the earth and its atmosphere as it changes from one form—solid, liquid, or vapor—to another. The water you use today may have evaporated from an ocean, traveled through the atmosphere, fallen back to the earth’s surface, gone under- ground, and flowed through streams leading back to the oceans. Water is readily visible in many forms, including clouds, rain, snow, fog, lakes, streams, oceans, and polar ice caps. However, groundwater located beneath the soil surface is a vital resource for the success and survival of the entire ecosystem. Groundwater has been tapped for thousands of years, but only recently have we started to understand its importance and how to manage this precious resource. Much remains to be discovered about groundwater, and wider public awareness of its nature and properties is an important first step. ---PAGE BREAK--- Helping America's small communites meet their wastewater needs Helping America's small communites meet their wastewater needs • Excessive weed or algae growth in the water near shorelines. Nutrients leaking from septic systems could be a cause of this type of growth. • Health department test results of well water indicate the presence of contamina- tion. These tests may show the presence of indicator bacteria total coliform, fecal coliform) in the water. Nitrate testing is not commonly performed and may need to be requested. Although wastes from septic systems are not the only source of these contaminants, they can be likely suspects. • Indicator dye put into your septic system reaches nearby ditches, streams, lakes, or drinking water supplies. Special dyes are available from your local health department that may help find problems that otherwise are difficult to detect. This method can also help verify the other listed above. How to Prevent Problems • Before installation is complete, have the septic tank tested for watertightness. • Maintain your septic system by having it inspected and pumped regularly. • Conserve water in your home by using low-flow fixtures and by implementing water conservation practices to avoid hydraulic overload of your septic system. • Redirect surface water flow away from your soil absorption field. • Do not drive vehicles or heavy equipment over the absorption field. This will compact the soil and reduce its ability to absorb water. • Plant a greenbelt (grassy strip or small, short-rooted vegetation) between your soil absorption field and the shoreline of any nearby surface water body. • Keep chemicals and other hazardous wastes out of the septic system. • If you have a drinking water well, have it tested yearly for contaminants. If you suspect a contamination problem, have it tested more often. Typical layout of a septic system Fig. 4 house septic tank well drainfield 100 feet 100 feet 10 feet property line stream 20 feet 10–15 feet For more information regarding the care of your septic system, contact your local health department. More information about septic systems is available from the National Small Flows Clearinghouse (NSFC) through other brochures in this series: So . . . now you own a septic system, Item The care and feeding of your septic system, Item For more information about this or other NSFC products, please contact us by writing to: National Small Flows Clearinghouse West Virginia University P.O. Box 6064 Morgantown, WV 26506-6064 or phone: (800) 624-8301, (304) 293-4191 or fax: (304) 293-3161 www.nsfc.wvu.edu Helping America’s small communities meet their wastewater needs Helping America’s small communities meet their wastewater needs One in a series of three brochures designed to aid you in caring for your septic system. Groundwater protection and your septic system