1. Sediment – Causes & Prevention Improving Water Quality- Well Rehab & Downhole Camera Applications
Michael L. Vaught, PG
Hydrogeologist
Certified Well Contractor
EGIS
Downhole Video, & Well Repairs
441 Northside Drive
Chapel Hill, NC 27516
Phone:
Fax:

2. Introduction
This presentation shows examples of using downhole equipment to limit microbial contaminants and achieve the highest quality water from supply wells.

3. Rock Type Hard to crystalline rock and granular type aquifer systems.
Sedimentary, Metamorphic, and Igneous rocks.
Reference the Ground Water Atlas of the United States and the Geological Surveys Maps.
Qualify the environment of reference.

4. Well Construction Geographic or Physiographic location Type of Well
Coastal Plain
Piedmont
Mountains
Type of Well
large or small diameter
shallow or deep
cased or “open hole”
Groundwater level in surficial and confined aquifers varies from the natural shallow availability because of general and specific uses within the state and region. Lowering of the water table by Industrial and mining uses is more predictable; whereas, the impact from agricultural and urban uses are less easy to control. Well depth is usually as shallow as possible for most private wells because drillers typically charge by the foot. At the coast wells are shallow to avoid salty water. In the piedmont and mountains, wells are usually deeper than 50 feet. On the coastal plain wells may be more shallow than 50’.
Shallow wells intersect the water table. Deep wells draw their water from a minimum of 30 to 50 feet below the water table.
Large size wells can be considered as greater than eight inches in diameter.
Cased wells are fully cased such as a bored, or jetted, or deep drilled and allow infiltration through screens and gravel packs; in unconsolidated and weathered formations. Open hole wells have casing at the top sitting on the rock borehole in consolidated formations.

5. Poor Water Quality Near surface - Rapid Infiltration
Biofouling (iron, mineral, slime growth)
Faulty well construction
Geologic strata and formation
Natural or manmade disturbances
Declining yield indicates the water producing zone is undergoing changes and the well bore may be clogged. Incorrect pumping depth combined with a leaky well casing generates a vigorous bioslime in the borehole. Highly fractured crystalline rock may allow infiltration of poorly filtered water down into the aquifer. Catastrophic storms, explosions, vibrations, and nearby excavations can change water wells.

6. Analysis of Problem Well Records Borehole Camera Survey
passive well inspection
active well investigation
identify source of well problem
verify results
Traditional the water well pump was removed and the borehole was videoed. Newer slim line and low power camera systems allow inspections with the pump in place and pumping. Versatile and durable underwater cameras are taking the guess work out of well service. Real time doownhole inspections are critical to saving time and directing the operations.

7. Slim-line downhole camera
Smann diameter cameras can travel down many wells without pulling the pump. This is an extended light camera. They are often better in turbid water than rear or face lit cameras. Glare is the difference in turbid water, caused by different types of lights. When the pump remains in placethe size of the well determines the choice of camera size. Large diameter wells need larger sized cameras with more powerful lights. Size or diameter of the well determines equipment needs, size of the camera.
Suppliers of cameras, Laval, CCV, Marks Products, Accu-Vue, …….

8. New state of the art downhole camera from Laval
New state of the art downhole camera from Laval. Combination downhole and side view images. Useful for direct fracture identification, and geologic interpretation. More detail is evident in direct side views. Unobstructed downhole view give the entire at 0once. .

9. Casing Unconsolidated formations
65 GPM Withdrawal
15’
Static WL
65’
Pumping WL
65gpm / (65-15)ft
= specific capacity of
1.3 gpm/ft of drawdown
Specific Capacity after 15 years
100GPM Withdrawal
15’
Static WL
45’
Pumping WL
100gpm / (45-15)ft
= specific capacity of
3.3 gpm/ft of drawdown
Specific Capacity of a newer well

10. Unconsolidated formations
Confined Aquifer

12. Sealing the Annulus
Bentonite, Cement, Concrete, Mixtures

13. Consolidated formations
Casing
Consolidated formations

16. Reasons For Contaminated Water
Distribution system
Well configuration
Shallow rapid infiltration
Poor well head protection
Surface water influence

17. Microbial Contamination Sources
Shallow rapid infiltration
Nutrient rich water
Biofouling within the well
Distribution system backflow
Dirty wells produce positive bacteria samples. Natural accumulations within the well and system grow many types of bacteria, including coliforms.

18. Well Maintenance Exercise (water usage) Chlorination Record keeping
200 ppm
Record keeping
Testing for Bacteria
Chlorination not recommended for coliform

19. Well Maintenance
Landscape so surface water drains away from the wellhead

20. Test Yield Specific Capacity
65 GPM Withdrawal
15’
Static WL
65’
Pumping WL
65gpm / (65-15)ft
= specific capacity of
1.3 gpm/ft of drawdown
Specific Capacity after 15 years
100GPM Withdrawal
15’
Static WL
45’
Pumping WL
100gpm / (45-15)ft
= specific capacity of
3.3 gpm/ft of drawdown
Specific Capacity of a newer well

21. Well Characterization
Construction method
Water levels
Casing amount
Well depth
Pump location
Pumping rates

22. Well Characterization
Water bearing fractures
Cascading water zone
Geological structure
Surface infiltration
Circulation cell size
Dead or non-circulating zones

23. Downhole Video & Pumping
Observe All Three Stages
Static rest.
Pumping stress.
Recharge.
Characterize well
Construction (leaky casing?)
Borehole stability
Water zones

24. Video Clips
Geology
Biofouling
Oxygen Enrichment
Pumping Effect

25. Repairs/Rehab Cleaning, flow sleeves, recirculation Liners Biofouling
Mud and Sand
Eliminate dead zones.
Prevent concentration within the well.
Liners
Seal out shallow water veins.
Pathogenic Contaminates
Stabilize the well.

26. Minimize Storage and Enlarge Flow Cells
Excess storage generates uncontrolled growth of naturally occurring biofilms
Enrichment of excess or retained storage accelerates biofouling from the top down
Set the pumping depth in a well
based on actual maximum demand
generate 3/4 drawdown or to the water vein

27. Well Storage Stored water lies
above the intake
above the highest water zone
Well storage is the zone of a water column within or draining to the bore-hole
above the pump
above the most shallow production zone
called the Storage Cell
Water level in a storage type well falls continuously during the stress test

28. Wellhead Protection

29. Wellhead Protection WHPA Delineation Methods
Arbitrary fixed or calculated fixed radius method

30. References
Anderson, K.E. (1998) Ground Water Handbook, National Ground Water Association
Driscoll, F.G. (1986) Ground Water and Wells, Second Edition, Jonhson Screens
Smith, S. A., Borch, M. A., and Noble, L. N. (1993) Evaluation and Restoration of Water Supply Wells, AWWA Research Foundation
Waller, R.M. (1994) Ground Water and the Rural Homeowner, U.S. Geological Survey

31. Presented by Mike Vaught
Groundwater and Well Service.
441 Northside Drive, Chapel Hill, NC 27516
Telephone
Fax