A Guide for Private Domestic Well Owners
March 2015
Compiled by:
The California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program
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TABLE OF CONTENTS
INTRODUCTION................................................................................................................ 5
GROUNDWATER BASICS .................................................................................................. 7
PRIVATE DOMESTIC WELL USE IN CALIFORNIA ................................................................ 8
WELL CONSTRUCTION ...................................................................................................... 9
WATER QUALITY TESTING .............................................................................................. 10
WATER QUALITY TREATMENT ........................................................................................ 13
WELL DESTRUCTION ...................................................................................................... 13
WATER QUALITY PROTECTION ....................................................................................... 14
RESOURCE GUIDE .......................................................................................................... 16
ACKNOWLEDGEMENTS .................................................................................................. 18
APPENDIX: Photographic Guide to Common Well Maintenance Issues ......................... 18
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DISCLAIMER This document is provided for informational purposes only. Water quality problems in private domestic wells may occur even when precautions are taken. This guide can help well owners with water quality testing and interpretation, and contains tips to help preserve and maintain a problem-free, clean well. For additional questions, please contact your local environmental health agency, or contact The State Water Resources Control Board (State Water Board) Division of Water Quality at 916-341-5455. ACRONYMS and ABBREVIATIONS DDW = State Water Board Division of Drinking Water DTSC = Department of Toxic Substances Control DWR = Department of Water Resources EC = electrical conductivity MCL = maximum contaminant level mg/l = milligrams per liter Mgal = million gallons Mgal/day = million gallons per day State Water Board = State Water Resources Control Board TAF = total acre feet TDS = total dissolved solids g/l = micrograms per liter. (A microgram is 1/1,000th of a milligram, and 1/1,000,000th of a gram.) US EPA = United States Environmental Protection Agency USGS = United States Geological Survey VOCs = volatile organic compounds
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INTRODUCTION What is Groundwater? Groundwater is water that fills spaces between soil and rocks beneath the earths surface. Most groundwater comes from rain and snow that falls to the ground and percolates downward through the soil, until it accumulates above a confining layer (see Figure 1), or aquitard (see Figure 4). The area in the ground that is filled with water is called the saturated zone, and the top of the saturated zone is called the water table. The water table can be very near or far below the ground surface, varying by region, proximity to surface water, amount of precipitation, the season, and many other factors. An aquifer is a formation or group of formations in rocks and soils containing water. Groundwater is accessible for household purposes by drilling a well.
Who Uses Groundwater? California depends heavily on groundwater to meet its water supply needs. Groundwater supplies approximately 40 percent of the states water, with about 60 percent coming from surface water. Households outside of urban areas typically have a private domestic well, as opposed to being connected to a community public water system (water company). As shown in Figure 1, wells are drilled to access groundwater below the land surface. Private domestic wells typically tap the shallower aquifers. Public water systems also use groundwater, but since they are of higher-demand, wells are drilled much deeper, accessing larger aquifers.
Figure 1. Diagram of a typical, though simplified, groundwater system.
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Groundwater Facts: Californians use more groundwater than
any other state in the country, equal to about 11 billion gallons per day.
Approximately 31 million Californians get a portion of their drinking water from a public water system that relies on groundwater.
Annual groundwater extractions in California contribute to about 40 percent of the states total water supply (California Department of Water Resources, 2013).
Evaluation of groundwater supplies by type of use indicates that about 76 percent of the average annual groundwater extraction goes toward agricultural uses, with about 22 and 2 percent going toward urban and managed wetland uses, respectively (California Department of Water Resources, 2013).
Up to two million California residents are served either by the estimated 250,000 to
600,000 private domestic wells, or by water systems serving fewer than 15 service connections.
The Tulare Lake, San Joaquin River, and Sacramento hydrologic regions account for about 75 percent of the average annual groundwater use (California Department of Water Resources, 2013).
Groundwater use increases during drought conditions.
Approximately half the people in the United States use groundwater for drinking water.
Over 11 billion gallons of groundwater per day are used for agricultural irrigation, helping to make Californias agricultural economy one of the largest in the United States.
1 Strategic Plan, California Water Today, Volume 1, Department of Water Resources, 2013
Figure 2. Total Water Supply in California, 2005-2010 average annual data. DWR Magazine, Fall 2014, pg. 12. Continuation of this figure, and legend, on page 7, Figure 3.
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GROUNDWATER BASICS How Do We Get Groundwater? Most wells use a pump to bring groundwater to the surface. There are several types of wells: public supply wells, irrigation wells, industrial supply wells, monitoring wells, and private domestic wells. Artesian wells flow without pumping. What is In Groundwater? Groundwater quality is related to several factors including geology, climate, and land use. Many naturally occurring chemicals in groundwater come from dissolving rocks, soil, and decaying plant material. Well water can become contaminated. Human activities can increase the concentration of
naturally occurring substances like salts, minerals, and nitrate. Poor well construction or placement close to a potential source of contamination can affect domestic well water quality. Domestic well owners are responsible for testing their well water to ensure its quality. Other compounds, such as pesticides and volatile organic compounds (VOCs), do not occur naturally in the environment. These substances can enter groundwater through spills, irrigation, wastewater percolation fields, septic systems, animal facilities, leaking underground fuel storage tanks, and other sources.
Figure 3. Total Water Supply in California, 2005-2010 average annual data. DWR Magazine, Fall 2014, pg. 13.
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PRIVATE DOMESTIC WELL USE IN CALIFORNIA
Over 95 percent of the 38 million California residents get their drinking water from a public or municipal source these supplies are typically treated to ensure that the water is safe to drink.
However, up to 2 million California residents are served either by private domestic wells or by water systems serving fewer than 15 service connections. The State Water Board Division of Drinking Water does not regulate the quality of water from either of these sources. Private domestic well owners are responsible for maintaining their well and are encouraged to test their well water quality.
The Division of Drinking Water maintains a list of certified drinking water laboratories that can provide testing in your area. The State Water Board recommends that you test your well at least once a year to ensure it is safe. If the test results show a chemical above the maximum contaminant level (MCL), it is a good idea to use an alternate drinking water source and look into ways to fix the problem. You may want to consider installing a water treatment system or drilling a new well that taps a less contaminated aquifer. Boiling your water does not remove many of the commonly found chemicals.
Wells draw water from different depths, and can be affected by different pollution sources. Types of wells and possible pollution sources are illustrated in the figure below:
A: Shallow wells capture water from shallow aquifers close to thesurface. Some private domestic wells are shallow wells.
B: Intermediate wells can tap either deep or shallow aquifers, and caninclude private domestic, agricultural, and industrial supply wells.
C: Deep wells tap deep aquifers, and include public supply, agricultural,and industrial supply wells.
Figure 4. Possible pollution sources for groundwater wells.
https://waterboards.maps.arcgis.com/apps/webappviewer/index.html?id=bd0bd8b42b1944058244337bd2a4ebfahttps://waterboards.maps.arcgis.com/apps/webappviewer/index.html?id=bd0bd8b42b1944058244337bd2a4ebfahttp://www.waterboards.ca.gov/drinking_water/certlic/device/watertreatmentdevices.shtml
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WELL
