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Hundreds of abandoned wells in each and every Iowa county expose valuable groundwater resources to contamination and create a safety hazard that can result in serious injury to humans and animals.

The only sure way to reduce the damage done by abandoned wells is to have them properly plugged. The following information summarizes the content of 26 slides contained in a "Power Point"presentation developed by Dr. Tom Glanville, Department of Ag and Biosystems Engineering, Iowa State University for a three-day workshop for County Sanitarians and Environmental Specialists. The "Private Water Well Systems" workshop, sponsored by the Iowa Department of Public Health and Kirkwood Community College will be held on October 2-4, 1995 at the Environmental Training Center, Kirkwood Community College, Cedar Rapids, Iowa.

County Extension Offices and others interested in obtaining a copy of this presentation for use in their environmental programs may obtain a complete copy by clicking here Plugging Abandoned Wells - Power Point Presentation (205K). (Note: you must have the Microsoft Power Point software or a Power Point viewer to view and use the presentation).

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Plugging Abandoned Wells

(image)

=============== Abandoned Wells - How Many??

• 36,000 (based on county assessors' survey of landowners in 1983-84)
• Long-term census data suggest 100,000 or more
• about 225,000 inhabited farmsteads in year 1900 (most hadat least one well)
• only about 105,00 active farmsteads today
• implies 120,000 abandoned farm wells

=============== Concerns About Abandoned Wells

• Threaten ground water quality...
• permit surface contaminants to enter
• may allow poor quality water from one formation to enter an aquifer of higher quality
• Pose a safety hazard to unsuspecting children, pets, livestock.

=============== Objective of Well Plugging

• Re-establish the natural ground water protection that existed before the well was constructed

=============== Well plugging techniques must consider:

• Well construction
• Type of geology the well penetrates
• Potential for contaminant migration
• Cost

=============== Typical types of well used in Iowa

• Bored or dug wells
• drilled wells
• driven wells

=============== Large diameter "bored" or "dug" wells

• common in southern and western Iowa
• 18 - 48 inch diameter (large interior volume)
• usually < 100 feet deep
• leaky casing - tile, brick, rock
• tap only upper-most saturated zone
• often at loess/till interface
• small low-yield aquifers that are not likely to affect another well
• defined as a "Class I" well in Chapter 39 of IAC

=============== Small diameter "drilled" wells

• 5 - 12 inch diameter (relatively small interior volume)
• typically 20 - 500 feet deep
• often tap highly productive bedrock or sands/gravel aquifersof regional importance
• defined as "Class II" wells in Chapter 39 of IAC

=============== Driven wells

• 1-2 inch diameter
• generally < 50 feet deep
• tap shallow sand/gravel aquifers
• defined as "Class III" wells in IAC

=============== Types of Plugging Materials

• "Sealing" Materials
• "Fill" materials

=============== Sealing materials

• Sealing materials are watertight materials that prevent water and contaminants from migrating into or through a plugged well
• Examples: bentonite products, neat cement

=============== Fill materials

• Not watertight - fill up space but do not prevent contaminant migration
• Generally less costly than sealing materials

Examples: clean sand, gravel, pea gravel, agricultural lime, crushed stone, and soil (soil recommended ONLY for large diameter wells)

=============== Key Point about Fill Materials

• Iowa well plugging rules require sealing materials to be used in EVERY plugged well
• Fill materials are optional and recommended only for very large or deep wells

=============== Plugging Procedures

• Remove pumps, piping, and other internal obstructions
• Remove casing to 4-foot depth
• Measure depth and diameter of well
• Calculate quantities of plugging materials needed
• Install plugging materials in proper location
• Mound compacted soil over top of plugged well

=============== Lineal feet of well casing filled by various

plugging materials

(table)

=============== Placing plugging materials in well

• To avoid dilution and poor sealing, neat cement and bentoniteslurries should be pumped into bottom of well through a tremie pipe
• Granular sealing materials (graded bentonite chips) and "fill" materials may be poured (very slowly) into top of well

=============== Beware of "bridging"

• caused by pouring granular plugging materials into well too rapidly
• Bridging and subsequent collapse of bridge leads to settling and ineffective plugging

=============== To avoid bridging

• Screen graded bentonite chips as they are poured into the well to remove fines that may cause bridging.
• Graded bentonite and granular fill materials should be poured through a funnel having a diameter approximately one-half the diameter of the well casing

=============== To avoid bridging (more...but worth it!)

• Use a weighted line to "monitor" progress as granular plugging materials are added
• Compare measurements with length of casing that should be filled by the amount of material added
• If level rises too rapidly, this signals bridging -- stop immediately and break up the bridge
• If level rises too slowly, this signals loss of plugging material into the formation

=============== Location of sealing and fill materials is crucial

• Sealing materials above or at the top of important water-yielding zones
• Fill material (if used) below or between zones of sealing material

=============== Plugging Large Diameter
(Class I) Wells

(Graphic)

=============== Plugging Sand & Gravel
(Class II) Wells

(Graphic)

=============== Plugging Bedrock Wells
(Class II single aquifer)

(Graphic)

Plugging Bedrock Wells (multiple aquifer)

(Graphic)

Warning about use
of fill material

Proper positioning of fill (and sealing) materials requires detailed information regarding local geology and construction of the well

For most old wells, this information is not available....in these instances complete filling with sealing materials is recommended

=============== For Further Information

Guidelines for Plugging Abandoned Water Wells: Technical Information Series # 15 by Donivan L. Gordon, Geological Survey Bureau, Iowa Dept. of Natural Resources, 1988.

Successfully Plugging Your Abandoned Well by Tom Glanville, Department of Agricultural & Biosystems Engineering, Iowa State University, Revised September 1995. (available in all County Extension offices)

Plugging Abandoned Wells (slide/tape presentation) funded by Iowa Dept. of Agriculture & Land Stewardship, produced by Tom Glanville and Don Wishart, Iowa State University Extension Service (available through county Extension offices) September 1990 (available in all County Extension offices)

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