Water wells must be properly located and constructed to provide safe water at all times and under all conditions. The purpose of this publication is to describe approved methods for the construction of driven wells. Driven wells as used in this publication also are referred to as sand-point wells.
Description of A Driven Well
A driven well is a small diameter well, assembled by joining lengths of steel pipe, 1¼ inches or 2 inches in diameter, with threaded couplings. Each section of steel pipe is 4 feet or 5 feet in length. A drive-point well screen, consisting of a screen 2 feet or 3 feet in length and attached to a hardened steel tip, is couple threaded to the bottom of the string of pipe. The screen allows groundwater to flow into the well, while keeping the sand out. Depending on the tightness of the soil, hand driven wells can extend to depths of about 30 feet. Driven by weighted hammers, they can extend to depths of 50 feet and further under ideal conditions.
To make the starting of the driving much easier, a pilot hole is first dug or augured at the ground surface to accommodate the drive-point well screen and part of the first section of pipe. To protect the pipe threads while driving, a drive cap is threaded onto the top of the pipe. It is not uncommon to drive the pipe with a post driver, made of a short length of weighted steel pipe with handles. Weighted driving tools, suspended from a tripod or derrick are sometimes used. Some driven well installers use specially made motorized equipment to drive the pipe. Sections of steel pipe are added as the driving progresses. The driving process continues until the sand point extends far enough below the static or non-pumping water level to allow a sufficient depth for drawdown while the well is pumping.
Areas Where Driven Wells Are Constructed
Driven wells are usually constructed in areas of sand and gravel. Figure 1 will assist you in determining if you are in a sandy area where it is more likely to construct a driven point well. More detailed surficial geologic maps are available through the Illinois State Geological Survey. Sandy areas with deep water tables are not conducive to driven wells. If encountered, large boulders or layers of compacted soil, e.g., clay or “hardpan,” can slow or completely stop the driving process. To see if driven wells can successfully be constructed in your area, look at water well construction logs of nearby wells. Water well data is available through the Illinois Environmental Protection Agency, the Illinois State Water Survey, and the Illinois Geological Survey.
Susceptibility of Driven Wells to Contamination
Who May Construct a Driven Well
Proper Construction (Illinois Water Well Construction Code and the Illinois Water Well Pump Installation Code)
(See Figure 2)
The drive-point well screen, drive pipe, and joints must be structurally suitable to prevent rupture during the driving of the well. Steel piping for driven wells shall be a minimum of schedule 40. If aids to driving are used, such as an augured starting hole or water jetting, the annular space around the drive pipe must be sealed with cement grout or puddle clay. The type of pump proposed will determine how the top 10 feet or more of the well shall be completed. A minimum of 20 feet of casing must be provided for the pump drop pipe.
The well casing must terminate at least 8 inches above ground level. An approved well cap or seal must be installed at the top of the well casing to prevent any contamination from entering the well at the surface. A watertight seal must be used when suction, pressure, and electric lines exit the well through the top of the casing. Frost protection should be provided by use of an insulated pump house, if the discharge pipe exits the well above grade. An approved pitless adapter must be used when the discharge pipe exits the well below grade.
Suction and jet pumps are the more common types of pumps installed on driven wells. If the pump is located away from the well, the buried pipe leading to the pump from the well must be encased in another pipe maintained at system pressure. Hand pumps equipped with a packing gland around the pump rod; an enclosed, turned-down spout; and a bell-type, one piece base made as a part of the pump stand or attached to the pump column in a watertight manner, are approved for this use. A down-turned smooth nose sampling faucet shall be installed not less than 18 inches above the floor in a convenient location between the water well and the pressure tank or as near to the well as possible.
The Illinois Water Well Construction Code and the Illinois Water Well Pump Installation Code are available on the Internet at http://www.ilga.gov/commission/jcar/admincode/077/07700920sections.html, and http://www.ilga.gov/commission/jcar/admincode/077/07700925sections.html. Copies also can be obtained from your local health department or from one of the regional offices listed below.
Eliminating Existing Pits
Existing well pits that are not structurally sound and watertight or do not have well casing that extends at least 12 inches above the pit floor should be eliminated. Breaking or removing the floor or one wall of the pit accomplishes this task. The well casing must be extended to at least 8 inches above the finished grade. Fill in the pit with compacted earth. If the pump discharge line exits the top of the well, a well seal and insulated pump house are necessary. If the pump discharge line passes through the well casing underground, an approved pitless adapter must be installed.
Rehabilitation, reconstruction or repair of wells shall be done in compliance with the Illinois Water Well Construction Code.
A new, cleaned or a repaired well normally contains contamination that may remain for weeks unless the well is thoroughly disinfected. This may be accomplished by the use of ordinary laundry bleach in a solution concentration of 100 parts per million (ppm) of chlorine. To give a dosage of 100 ppm, the amount of laundry bleach (5.25% chlorine) required for each 100 gallons of water equals three 8-ounce cups. The amount of bleach required is determined by the amount of water in the well and the water distribution system.
When working with chlorine, you should always be in an open or well-ventilated place. Do not allow the strong liquid to remain in contact with the skin or clothing. Solutions are best handled in plastic containers since strong chlorine solutions corrode metal containers.
Directions for Disinfection
Since the capacity of most driven wells and their water distribution systems is 50 gallons to 100 gallons of water, assume that the total water system contains 100 gallons of water.
Disinfect the well as follows:
- Flush the well.
- Mix three 8-ounce cups of liquid laundry bleach in about 1 gallon of water and stir thoroughly.
- Remove the well cap and pour this solution into the top of the well between the casing and the drop pipe.
- Connect a hose from a faucet on the discharge side of the pressure tank to the top of the well casing and start the pump, recirculating the water back into the well for at least 15 minutes. Then open each faucet in the system until a chlorine smell is noticeable. Close all faucets.
- Rinse chlorine solution off any wires and the pitless adapter in the well casing. Seal the top of the casing with a sanitary well seal and let stand for several hours, preferably overnight.
- After standing, operate the pump, and discharge water from all outlets until all chlorine odor disappears. After several days use, submit a sample of the water to a laboratory for analysis.
Bacterial Analyses and Samples
To obtain bacterial and nitrate analyses of drinking water, submit well samples to a laboratory certified for coliform bacteria by the Illinois Department of Public Health, and certified for nitrate testing by the Illinois Environmental Protection Agency.
Water Well Data Bases
Driven Well Related Internet Sites
Illinois Department of Public Health
Private Water Systems Program
Illinois Environmental Protection Agency
What You Need to Know About Private Drinking Water Wells
Illinois State Geological Survey
Maps – Surficial Geology and Features
Illinois State Water Survey
Domestic Well General Information
University of Minnesota Extension
Driving a Wellpoint
U.S. Environmental Protection Agency
Private Drinking Water Wells
U.S. Geological Survey
Groundwater and the Rural Homeowner
Wisconsin Department of Natural Resources
Driven Point (Sand-Point) Wells
Driscoll, Fletcher G., 1986, Groundwater and Wells: Johnson Division, St. Paul, MN, 1089 p.
Masters, John M., 1983, Geology of Sand and Gravel Aggregate Resources of Illinois: Illinois State Geological Survey Illinois Mineral Notes 88, 10 p.
Berg, Richard C., and John P. Kempton, 1983, Stack-unit mapping of geologic materials in Illinois to a depth of 15 meters: Illinois State Geological Survey Circular 542, 23 p.
Illinois Department of Public Health, Division of Environmental Health, 525 W. Jefferson St., Springfield, IL 62761, 217-782-5830, TTY (hearing impaired use only) 800-547-0466. Questions may be directed to your local health department, to one of the Illinois Department of Public Health regional offices or to the Department’s central office in Springfield.