USGS Groundwater Monitoring Well Redevelopment Using Air Lift Method

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Detailed Description

This video documents a U.S. Geological Survey technical procedure for groundwater well redevelopment using the air lift method. 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. When blockage of a well screen or opening occurs, there are multiple well redevelopment methods hydrologists can use to remove the blockage. The redevelopment method selected depends, in part, on the well construction and on the use of the well. For example, the air-lift method may change the water-quality characteristics of the water in a well and may not be appropriate in some cases. This training video for USGS hydrologists and hydrologic technicians documents a USGS procedure for using the air lift method to redevelop a USGS groundwater well. This USGS video was released in 2016 and is in the public domain.​

Details

Image Dimensions: 480 x 360

Date Taken:

Length: 00:06:53

Location Taken: US

Transcript

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/