USGS Groundwater Monitoring Well Redevelopment Using Air Lift Method


How to Redevelop Groundwater Monitoring Wells
Using the Air Lift Method [Narrator]
Hi, my name is Randy Bayless. I am the Groundwater Specialist for the Indiana
Kentucky Water Science Center of the U.S. Geological Survey and today, we are going
to talk about the air-lift method for well redevelopment. Over time, groundwater wells may become partially
or even fully blocked by accumulation of materials at the well screen or openings. This blockage is typically the result of sediment,
chemical or biological accumulation of materials which may restrict the connectivity between
a well and an aquifer. If left unresolved, the water data collected
from the affected well might not be representative of the aquifer and the data will be biased
or even erroneous. There are several methods can be used to identify
a well that needs to be redeveloped, including hydrograph inspection, annual total depth
of well measurements, regular well integrity tests (slug tests) and inspection with a borehole
camera. This will allow you to identify potential
problems as they arise. Comparing these results with a drillerís
log will provide you the best standard for what the total depth should be. Safety is a very high priority. Please read, understand and follow your Centerís
Safety Plan and all pertinent equipment manuals to prevent injuries. It is highly recommended to consult your local
safety coordinator for additional safety concerns. Minimum safety equipment but not limited to:
Steel toe boots Safety glasses or goggles
Ear plugs or muffs Leather gloves
Nitrile gloves The standard 185 CFM, 125 psi compressor should
work at most sites. Air hoses
Electrical (E) and weighted steel tapes Misc. tools: wrenches, screwdrivers, hammers,
etc. Field computer with field forms
Station description Drillerís well log
Deionized water Inspect the Gage Read the station description for the driving
directions, site specific safety requirements and to become familiar with the gage and equipment. Read the well log, including the casing/screen
information, the depth of water and previous redevelopment information. Prior to redeveloping any well, you will want
to complete a thorough gage inspection. First, make consecutive tape downs to water
surface using an E-tape until two measurements agree within 0.02 feet. Record all values and corresponding times
in your field notes. Measure and record the total depth of the
well using a weighted steel tape. Preparing the Well Remove all equipment from the well, including
the shelter above well casing. Place the equipment a safe distance from the
well to prevent creating a trip hazard. The water in the well needs to rise and fall
several feet to flush the screen. This causes water to rapidly enter the screen
during the rise and then during the fall forces the water inside the well out the screen,
removing clogging material and debris from the well and well screen, and cleaning the
gravel pack surrounding the screen. Well Screen Cleaning Lower the air hose several feet below the
water surface. Set the E- tape to stop several feet above
the water surface. Partially open the air supply to start raising
the water level and listen and watch for the alarm on the E-tape to go off. Shut off air supply. Allow the well to stabilize. If possible make TDs to water surface as the
well stabilizes Repeat the process 2 or more times. Redeveloping Remove the E-tape from the well. Lower the air hose down 60 percent of distance
from water surface to well screen for most wells. For deep wells (greater than 300 feet) less
submergence is needed. Start the maximum flow of air. Within a short period of time the air should
force a powerful burst of water and debris from the well. Shut off air supply and allow the well to
stabilize. Repeat the process until visual observation
indicates that the water is relatively clean. Shut off the air compressor and remove hose. Final Inspections Measure and record the final Total Depth of
the well using a weighted steel tape. If all of the debris at the bottom of the
well has been removed from the well, the final total depth measurement should generally be
in closer agreement with the original drillerís log. Re-install gage structures and all equipment. Make consecutive tape downs to water surface
using an E-tape until two measurements agree within 0.02 feet. Record these measurements in your field notes. At continuous recording sites and set the
recorder to the tape down to water surface measurement and start the recordings and transmission
of data. Decontaminate all equipment using deionized
water. Caution Please consult your local groundwater specialist
or the Office of Groundwater before attempting any of this method on your own. The air lift method can change the geochemistry
of the formation surrounding the well or the water quality within the well. If your well is sampled for water quality,
another method should be considered. How to Redevelop Groundwater Monitoring Wells
Using the Air Lift Method [Narrator]
Hi, my name is Randy Bayless. I am the Groundwater Specialist for the Indiana Kentucky Water
Science Center of the U.S. Geological Survey and today, we are going to talk about the
air-lift method for well redevelopment. Over time, groundwater wells may become partially
or even fully blocked by accumulation of materials at the well screen or openings. This blockage
is typically the result of sediment, chemical or biological accumulation of materials which
may restrict the connectivity between a well and an aquifer. If left unresolved, the water
data collected from the affected well might not be representative of the aquifer and the
data will be biased or even erroneous. There are several methods can be used to identify
a well that needs to be redeveloped, including hydrograph inspection, annual total depth
of well measurements, regular well integrity tests (slug tests) and inspection with a borehole
camera. This will allow you to identify potential problems as they arise. Comparing these results
with a drillerís log will provide you the best standard for what the total depth should
be. Safety is a very high priority. Please read, understand and follow your Centerís
Safety Plan and all pertinent equipment manuals to prevent injuries.
It is highly recommended to consult your local safety coordinator for additional safety concerns.
Minimum safety equipment but not limited to: Steel toe boots
Safety glasses or goggles Ear plugs or muffs
Leather gloves Nitrile gloves The standard 185 CFM, 125 psi compressor should
work at most sites. Air hoses
Electrical (E) and weighted steel tapes Misc. tools: wrenches, screwdrivers, hammers,
etc. Field computer with field forms
Station description Drillerís well log
Deionized water Inspect the Gage Read the station description for the driving
directions, site specific safety requirements and to become familiar with the gage and equipment.
Read the well log, including the casing/screen information, the depth of water and previous
redevelopment information. Prior to redeveloping any well, you will want
to complete a thorough gage inspection. First, make consecutive tape downs to water
surface using an E-tape until two measurements agree within 0.02 feet.
Record all values and corresponding times in your field notes.
Measure and record the total depth of the well using a weighted steel tape. Preparing the Well Remove all equipment from the well, including
the shelter above well casing. Place the equipment a safe distance from the
well to prevent creating a trip hazard. The water in the well needs to rise and fall
several feet to flush the screen. This causes water to rapidly enter the screen
during the rise and then during the fall forces the water inside the well out the screen,
removing clogging material and debris from the well and well screen, and cleaning the
gravel pack surrounding the screen. Well Screen Cleaning Lower the air hose several feet below the
water surface. Set the E- tape to stop several feet above
the water surface. Partially open the air supply to start raising
the water level and listen and watch for the alarm on the E-tape to go off.
Shut off air supply. Allow the well to stabilize.
If possible make TDs to water surface as the well stabilizes
Repeat the process 2 or more times. Redeveloping Remove the E-tape from the well.
Lower the air hose down 60 percent of distance from water surface to well screen for most
wells. For deep wells (greater than 300 feet) less submergence is needed.
Start the maximum flow of air. Within a short period of time the air should
force a powerful burst of water and debris from the well.
Shut off air supply and allow the well to stabilize.
Repeat the process until visual observation indicates that the water is relatively clean.
Shut off the air compressor and remove hose. Final Inspections Measure and record the final Total Depth of
the well using a weighted steel tape. If all of the debris at the bottom of the
well has been removed from the well, the final total depth measurement should generally be
in closer agreement with the original drillerís log.
Re-install gage structures and all equipment. Make consecutive tape downs to water surface
using an E-tape until two measurements agree within 0.02 feet. Record these measurements
in your field notes. At continuous recording sites and set the
recorder to the tape down to water surface measurement and start the recordings and transmission
of data. Decontaminate all equipment using deionized
water. Caution Please consult your local groundwater specialist
or the Office of Groundwater before attempting any of this method on your own.
The air lift method can change the geochemistry of the formation surrounding the well or the
water quality within the well. If your well is sampled for water quality,
another method should be considered. Credits U.S. Geological Survey, U.S. Department of
the Interior Special Thanks to Office of Groundwater, U.S.
Geological Survey, Reston, VA Produced by J. H. Poehler, Hydrologic Technician,
U.S. Geological Survey, IN-KY-WSC Field Assistant: B. C. Long, Hydrologic Technician,
U.S. Geological Survey, IN-KY-WSC Technical Advisors:
R. A. Sheets, Acting Assistant Chief of Office of Groundwater, U.S. Geological Survey, Reston,
VA E. R. Bayless, Groundwater Specialist, U.S.
Geological Survey, IN-KY-WSC J. S. Woods, Supervisor Hydrologist, U.S.
Geological Survey, IN-KY-WSC Post processing and IT Support:
J. H. Poehler, Hydrologic Technician, U.S. Geological Survey, IN-KY-WSC
M. N. Gonzales, Information and Technology Specialist, U.S. Geological Survey, IN-KY-WSC
M. Worland, Computer Assistant, U.S. Geological Survey, IN-KY-WSC Narrated by:
E. R. Bayless, Groundwater Specialist, PhD., U.S. Geological Survey, IN-KY-WSC Resources
Cunningham, W.L., and Schalk, C.W., 2011, Groundwater Technical Procedures of the U.S.
Geological Survey, Techniques and Methods 1-A1.
Driscoll, F.G., 2nd ed. 1986, Groundwater and Wells. St. Paul, MN: Johnson Screens.
USGS Guide for Social Media, http://communities.usgs.gov/blogs/vis/audiovisual/video-and-film/

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