Description of a Sinusoidal Slug Testing Device and Trial Testing in an Unconfined Aquifer

Transcription

1 GROUNDWATER & ENVIRONMENTAL SERVICES,INC. Description of a Sinusoidal Slug Testing Device and Trial Testing in an Unconfined Aquifer Don A. Lundy, PG GES, Lilburn, GA John F. Dowd and Todd C. Rasmussen, UGA, Athens, GA

2 Topics to Cover Review of Sinusoidal Aquifer Tests Sinusoidal Slug Test Device Field Trail Testing Data Analysis Method Findings and Conclusions

3 Sinusoidal Aquifer Tests Tidal fluctuations > Shoreline is line source > Wave amplitude and lag time used to estimate aquifer diffusivity (T/S) Sinusoidal pumping > Pumping and injecting water at sinusoidal rates > Analytical soln. to estimate aquifer parameters (T & S)

4 Set-up for Sinusoidal Pumping Source: Rasmussen et. al. 2003

5 Analytical Solution Solving the Flow Equation: Source: Rasmussen et. al. 2003

6 Analysis of Savannah River Tests Best-Fit of Steady-State Analytical Soln. Source: Rasmussen et. al. 2003

7 Best-Fit AQTESOLV Theis (1935) Soln. at Observation Well 101D Source: G. Duffield, 2010

8 Transfer Sinusoidal Pumping to Slug Testing Research Steps > Obtain Funding > Conceptual Design > Detailed Design > Construction > First Trial Test (EON Products, Snellville) > Second Trial Test (Research Site, Bemidji, MN) > Data Analysis for T & S > Validate Results against Conventional Pumping Test Sinusoidal Slug Tester Grant Proposal

9 First Trial for Equipment Functionality 4-inch well in Saprolite 5-ft by 3-inch diameter slug Transducer in control well Water level response: > Four oscillations > Peaks sharper than troughs > Downward trend

10 Second Trial Test at USGS Crude Oil Site

11 North Pool Hydrogeologic Cross Section 2cd Trial Test Wells

12 Equipment Set-up at the Bemidji Site

13 Transducer Responses Observations: Wave shape imperfections at control well filtered. Amplitudes diminish with distance. Background fluctuations large relative to obs. well responses. Lag times small. Waves propagate quickly.

14 Conversion of Slug Movement to Q Rates Arm rotation moves slug Insertion = Injection Withdrawal = Pumping Constant angular velocity Equal θ change per time step Wire cable length change is sinusoidal Q rates based on slug length changes with time

15 Calculating Pumping/Injection Q Rates Model slug movement Calculate changes in leader wire length Known: slug length and diameter Changes in cylindrical volume/time = Q-rates But

16 Imperfect Sine Waves at the Control Well Cause: > Slug submergence into rising water level > Slug emergence from falling water level Solution: > Determine when these happen > Assign zero Q rates If it is periodic, wave doesn t need to have a perfect shape. Trial test data at control well 531A.

17 Data Analysis with AQTESOLV

18 Comparison to USGS Pumping Test Results Sinusoidal Slugger > 531A, 9205A, 9205B > Ave. Trans. = 14,810 ft 2 /d > Ave. Storativity = 1.56E-03 Conventional Pumping > 501, 505, 506, 507 > Ave. Trans. = 13,425 ft 2 /d > Ave. Storativity = 1.84E-03 Agreement of Results > Ave. Trans. within ~10% > Ave. Storage within ~16% Printout for pumping well 501.

19 Data Analysis Findings for the Control Well Modeling slug movement relative to pretest static water level gives first-approximation of Q rates. Sine waves at the control well will have slightly distorted shapes, i.e. imperfections. Imperfections are understood by comparing slug movement to recorded water-level changes. Zero Q rate occurs when the slug moves completely below or out of the water column. With distance, the aquifer filters the imperfections, but the Q rates should still account for them in the analysis phase.

20 Data Analysis Findings for the Observation Wells Distance from control well should be limited. Water-level trends should be removed by analyst. Speed of propagating waves are consistent with confined aquifer behavior. Confined aquifer solutions can estimate aquifer parameters (T and S values). Partial penetration of the aquifer allows for estimating K v /K h ratio. Directional transmissivities can be obtained.

21 Sinusoidal Slug Test Conclusions Observation wells must be located near control well. Provides comparable results to conventional 24-hour pumping tests. No need to store, treat, haul, or dispose of contaminated groundwater. Equipment set-up and take-down: ~ hr. Duration of test: 10 to 20 min. Analysis can be made with existing commercial software.

22 GROUNDWATER & ENVIRONMENTAL SERVICES,INC. Practical Solutions. Sustainable Results. LAND AIR WATER ENERGY Thank you.