Groundwater Pollution Remediation NOTE 5 Aquifer Evaluation & Pumping Test Methods

What are purposes of pumping tests?

General Procedure 1)Preliminary Studies: Collection and review of all geological & hydrological site information 2) Site selection, well drilling and development 3) Pretest conceptual modeling effect 4) Piezometers 5) Pump test performance 6) Data analysis

Here σ = Ф o – Ф (draw down) Steady Flow (large time): Thiem Method Step 1: Plot drawdown-vs-log t for each piezometer to verify large time (or steady flow). Step 2: Use Thiem equation to get estimate for T or K. Step 3: Repeat for all well pairs and average. Limitations?

Unsteady flow (confined aquifer): Theis’ Method

Unsteady Flow: Theis Method Step 1: Prepare ‘type curve’ (log W(u)-vs-log 1/u plot) Step 2: Plot log σ vs log r 2 /t in a separate paper with same scale. Step 3: Place observed data over type curve and place position of best match. Step 4: Select match point & determine associated coordinates (W(u), u, σ and r 2 /t) Step 5:Substitute values of W(u), σ, and Q into Theis equation, and solve for T (and K). Step 6: Calculate S

Cooper-Jacob Solution (For a small u) When u is smaller than 0.01, then, In which conditions is the u small? Radius of Influence (u < 0.01)

Jacob Method (For a small u < 0.01) Step 1: Plot log σ vs log t & fit straight line Step 2: Extend line until it intercepts time axis. Step 3: Determine slope of line. Step 4: Solve for T using the determined slope value. Step 5: Solve for S using the estimated intercept at the time axis. Step 6: Repeat for all piezometers Step 7: Check that u < 0.01

Unsteady flow unconfined aquifer: Neuman’s Method Early time, type A curve Late time, type B curve Family of Neuman type curves Here S A =S y

Unsteady flow unconfined aquifer: Neuman’s Method Step 1: Construct Family of Neuman type curves Step 2: Prepare observed data curve (Plot log σ vs log t) Step 3: Superpose data plot on type A curves and match β value. Step 4: Select match point, and calculate K H H O and S for early time. Step 5: Repeat procedure for late time data and type B curve with selected β value. Step 6: Select match point, and calculate K H H O and Sy for late time. Step 7: Calculate Kv Step 8: Repeat procedure with data from other piezometers. Comments: This method makes sense but too sensitive with beta values.