Sediment – Causes & Prevention Improving Water Quality- Well Rehab & Downhole Camera Applications

1. Sediment – Causes & PreventionImproving 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: 919-929-8363 Fax: 419-858-9118 Email: gwinvest@juno.com

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.

4. Well Construction • Geographic or Physiographic location • Coastal Plain • Piedmont • Mountains • Type of Well • large or small diameter • shallow or deep • cased or “open hole”

5. Poor Water Quality • Near surface - Rapid Infiltration • Biofouling (iron, mineral, slime growth) • Faulty well construction • Geologic strata and formation • Natural or manmade disturbances

6. Analysis of Problem • Well Records • Borehole Camera Survey • passive well inspection • active well investigation • identify source of well problem • verify results

7. Slim-line downhole camera

9. Casing Unconsolidated formations • 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 • 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

10. Unconsolidated formations • Confined Aquifer

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

13. 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

18. Well Maintenance • Exercise (water usage) • Chlorination • 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 YieldSpecific Capacity • 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 • 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

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 • 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 919-929-8363 Fax 509-278-5724