1. Some Observations from Using a Colloidal Borescope in Basalt Aquifers Gerry Winter

3. What You See in the Field

4. Objectives  Locate flow zone(s)  Determine dominant ground water flow direction(s) in each well  Estimate ground water flow velocity in the flow zones

5. Location of Wells near Bliss 

6. Basalts

7. Bliss Results  #1 Well - Best record at depth of 112.5 ft  Flow direction 321º or to the northwest  Flow velocity estimated at 16 ft/day  Interesting oscillations – pumping well

8. Bliss #1 - Oscillations

9. Bliss Results  #3 Well - Best records at depths of 80, 86.2, 95, & 99 ft  Flow directions 256, 290, 230, & 130 degrees (to the west in shallow zones)  Flow velocities estimated at 44 to 97 ft/day

10. Bliss Results  #5 Well - Best records at depths of 84, 84.5, 87, & 87.5 ft  Flow directions 133, 90, 94, & 133 degrees (to the southeast or east)  Flow velocities estimated at 10 ft/day in shallowest zone and 14 to 18 ft/day other zones

11. Air Base

12. Air Base Results  Flow velocities estimated at 12 ft/day, 28 ft/day, 10 ft/day, 13 ft/day, & 7 ft/day  Flow directions variable, appear to be dependent upon production well pumping even with production wells are off

13. Air Base

14. Near Surface Source of TCE  Monitoring well almost below source; ground water concentrations near detection limits  Ground water flow zone about 32 ft below “water table”  If vapor phase partitioning is dominant transport mechanism – concentrations may be low because ground water samples reflect deeper ground water

15. Observations  Ground water flow zones found at contacts between basalt flows  Production & irrigation wells can have strong effects on flow directions  Irrigation ditches/canals can affect flow directions  Monitoring wells typically have 20 slot screen and sand pack but set length may not include basalt flow contact

16. Observations continued  Source of contamination above “water table” may not be detected if flow zone is deeper in well  Flow velocities often 10-20 feet/day  Pressure pulses can be observed at distance from pumping well  Flow directions can be affected long after pumping stops