A GUIDE FOR THE PRIVATE WELL OWNER ON THE COVER The Santa Clara Valley Water District Administration Building, formerly its headquarters, boasts a mosaic depicting the layers beneath the valley floor. Water seeps from the surface through these layers to replenish the groundwater basin. The water district’s formation in 1929 was in response to the over- pumping of groundwater and the need to have an agency dedicated to protecting and preserving this critical water resource. TABLE OF CONTENTS INTRODUCTION » 4 WELL OWNER RESPONSIBILITIES » 5 WELL CONSTRUCTION AND WELL MAINTENANCE » 6 WATER QUALITY PROTECTION » 9 WATER QUALITY SAMPLING AND TREATMENT » 12 RESOURCE GUIDE » 17 INTRODUCTION This guidebook is intended to make private well ownership a The thousands of water supply wells that draw water from little easier. It is designed to: the county’s groundwater basins have traditionally produced very high quality drinking water. In recent years, however, • Alert private well owners to the potential for contamination our drinking water aquifers have been threatened by toxic and the need for water quality testing; chemicals from industrial spills, leaking underground storage tanks, and agricultural applications, as well as biological • Introduce well owners to the basics of proper well pathogens from sewers, septic systems and animal facilities. construction, destruction and maintenance; These contaminants can find their way through the natural protective layers of clay and silt and into our drinking water • Inform well owners of their responsibilities in Santa Clara aquifers. This problem can be exacerbated by the presence County. of improperly constructed wells, abandoned wells, or wells located too near a potential contaminant source like a Nearly half of all water used in Santa Clara County comes septic system. These wells can act as vertical pathways, from below the valley floor, where layers of sand and gravel allowing chemicals and pathogens on the surface or in provide a natural reservoir for water in underground aquifers. shallow aquifers to migrate into our deep drinking water In addition to being an extraordinary storage facility, the aquifers. To help control and prevent the contamination groundwater basin also serves as an inexpensive and of our groundwater basins and to protect public health, efficient treatment and distribution system. The groundwater we need the cooperation of private well owners. We have basin provides some natural treatment and filtration as water produced this pamphlet to help you help us protect our percolates through the soil and rock. It also transmits large groundwater resources and your health. quantities of water over long distances without the need for infrastructure, such as pipelines or pumping plants. This guidebook is meant only as a guide for well owners. We do not claim that the recommendations made in this document will work in every situation, nor do we claim to have covered every possible scenario or contaminant. GROUNDWATER BASIN IN SANTA CLARA COUNTY DIABLO RANGE SANTA CRUZ MOUNTAINS INDUSTRIAL RECHARGE POND GAS ANIMAL FACILITY STATION SEWER AGRICULTURAL SHALLOW LINE APPLICATION WELL CREEK STORAGE WATER TANK SEPTIC SUPPLY WATER TABLE SYSTEM WELL GROUNDWATER BASIN BEDROCK DEEP DRINKING CLAY & SILT WATER IN SHALLOW SAND & GRAVEL WATER AQUIFER LAYER FRACTURED BEDROCK AQUIFER 4 WELL OWNER RESPONSIBILITIES To protect public health and to maintain the high quality • Properly maintain the well so that it remains in compliance of water in our drinking water aquifers, well owners are with the district and state well standards. Wells must be required to adhere to various state and local laws relating maintained so that they do not allow the introduction to wells. In general, well owners are required to: of surface waters or other materials into them through improperly sealed well casings or gravel fill/sounding • Obtain permits from the Santa Clara Valley Water District tubes. Wells must be secured so that children or animals before any well construction, destruction, or modification. cannot enter them. • Complete any well construction, destruction, or • File Water Production Statements to report to the water modification according to water district and state well district the amount of water that was produced from standards. Wells must be constructed so that they do not the well, if the well is located within one of the defined allow poor quality surface water or water from shallow Groundwater Charge Zones. aquifers to migrate into drinking water aquifers. There are specific well construction practices that must be followed • Properly destroy any wells that are not being used. When to ensure that wells are constructed properly. Note: all no longer in use, wells must be destroyed so that they can well construction, destruction, or modification activities never act as vertical conduits or endanger public health. must be completed by a C-57 licensed contractor. Generally, wells must be completely filled with impervious sealing materials. • Register all wells with the water district. For more information on your responsibilities as a well owner, • Obtain water system clearance from the Santa Clara contact the Wells Unit at (408) 630-2660 or visit the water County Department of Environmental Health before district’s web site at www.valleywater.org. a well is used for drinking water purposes. 5 WELL CONSTRUCTION AND WELL MAINTENANCE WELL CONSTRUCTION The typical domestic well in Santa Clara County is constructed by Wellhead drilling a hole in the ground to a depth of 100 to 300 feet. As the well driller is drilling the hole, the type and depth of materials that Well the bit passes through are noted. This information is recorded Casing on the driller log that is submitted to the permitting agency and provided to the well owner by their drilling contractor. The well is constructed once the driller finds layers of sand or SAND & GRAVEL gravel that produce enough water to meet the well owner’s Blank needs. These water producing layers are called aquifers. Casing To construct the well, the driller installs a length of plastic or steel pipe called the well casing into the hole. The well casing keeps the hole from collapsing and allows pumping CLAY & SILT Annular or Sanitary Seal equipment to be installed. By regulation, the well casing must have a diameter at least four inches smaller than the diameter of the hole. SHALLOW AQUIFER Where the hole intersects the best water producing layers (the sand and gravel aquifers), the driller installs well casing with thin cuts or perforations. This portion of the well is called the well screen. The well screen allows water to pass into the casing but keeps out sand and gravel. Where the hole CLAY & SILT intersects layers of clay or fine silt (layers that don’t typically produce significant quantities of water), the driller installs unperforated pipe called blank casing. To keep fine sand, silt, and clay from entering the well screen, Filter Pack the driller installs a sand and gravel mix called the filter pack into the space between the casing and the hole. To protect the water quality in the deeper, drinking water aquifers from poor DEEP Well AQUIFER Screen quality surface water and shallow aquifer water, the driller also installs a concrete or cement seal (annular or sanitary seal) between the blank casing and the hole. In Santa Clara County, the minimum annular seal depth is 50 feet. The Santa Clara Valley Water District requires a deeper annular seal if the well is to be installed in the valley floor (vs. mountainous regions) and may also require that specific clay layers be sealed off. Typical well seal depths are 150 feet in the north county and 100 feet in the south county. The annular seal extends to the surface of the ground where it is extended out to create a concrete pad with the well casing extending out of the middle of it. These surface features are called the wellhead. At the wellhead, the casing extends at least one foot above the ground surface and is securely capped to prevent anything, including surface water, from entering the well. The concrete pad is sloped away from the casing to protect the well from damage and from surface water contamination. 6 WELL CONSTRUCTION AND WELL MAINTENANCE A poorly maintained well can lead to a variety of problems Inspect your wellhead including poor water quality and reductions in the amount Get in the habit of doing a visual check on your well at least of water your well can produce. To minimize these potential once a year. More often is better. See below for some of the problems, a well maintenance program is an important part things to look for when inspecting your well. of a well owner’s responsibilities. WELLHEAD INSPECTION 6 REGISTRATION NUMBER 1 MISSING PLUG 7 STANDBY WELL 3 ARTESIAN 1' FLOW 5 GROUND SLOPE 2 CRACK or GAP 4 WEEDS or DEBRIS 1 Look for openings that insects, rodents, water, or anything 5 Make sure the ground slopes away from your well and else can enter. Cap, seal, or otherwise plug them. that your well casing extends at least one foot above the ground to ensure that surface water does not collect or flow 2 Look for cracks in the concrete pad that would allow near the well. water, and any contaminants it may be carrying, to follow the well casing down into your drinking water aquifer. 6 Make sure your well registration number is still visible Seal cracks, or re-pour a new concrete pad. on your well. This is a local legal requirement. Call the water district at (408) 630-2660 if you need a new, free 3 If water is flowing out the top of the well, call a licensed registration tag. well contractor to stop the flow. In addition to being a waste of water, if water can leak out, contaminants can 7 If you have an inactive well, turn the pump on several seep in.