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
Topics to Cover
Review of Sinusoidal Aquifer Tests
Sinusoidal Slug Test Device
Field Trail Testing
Data Analysis Method
Findings and Conclusions
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)
Set-up for Sinusoidal Pumping
Source: Rasmussen et. al. 2003
Analytical Solution Solving the Flow Equation:
Source: Rasmussen et. al. 2003
Analysis of Savannah River Tests Best-Fit of Steady-State Analytical Soln.
Source: Rasmussen et. al. 2003
Best-Fit AQTESOLV– Theis (1935) Soln. at Observation Well 101D
Source: G. Duffield, 2010
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
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
Second Trial Test at USGS Crude Oil Site
North Pool Hydrogeologic Cross Section 2cd Trial Test Wells
Equipment Set-up at the Bemidji Site
Transducer Responses
• 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.
Observations:
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
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…
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.
Data Analysis with AQTESOLV
Comparison to USGS Pumping Test Results
Sinusoidal Slugger > 531A, 9205A, 9205B > Ave. Trans. = 14,810 ft2/d > Ave. Storativity = 1.56E-03
Conventional Pumping > 501, 505, 506, 507 > Ave. Trans. = 13,425 ft2/d > Ave. Storativity = 1.84E-03
Agreement of Results > Ave. Trans. within ~10% > Ave. Storage within ~16%
Printout for pumping well 501.
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.
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 Kv/Kh ratio.
Directional transmissivities can be obtained.
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: ~ 0.5 – 1.5 hr. Duration of test: 10 to 20 min. Analysis can be made with existing commercial
software.
GROUNDWATER & ENVIRONMENTAL SERVICES,INC.
Practical Solutions. Sustainable Results.
Thank you.
LAND AIR WATER ENERGY
