1. Groundwater Modeling 4: GW-3 Tips Groundwater Hydraulics Daene C. McKinney

2. Setup – Part (a) Create the “working directory” – C:\temp\P20a_work Download the GW-3.zip file (from class webage) Un-Zip the GW-3.zip file to get the file P20a.gwv Place the file P20a.gwv in the directory – C:\temp\P20a_work Open the model P20a (just double click on the P20a.gwv file) Run the model P20a

3. P20a.GWV When you open the P20a.GWV file, you should see :

4. P20a.GWV When you run the P20a.GWV file you should get a solution that looks like:

5. Setup – Part (b) Create a new “working directory” named P20b_work – C:\temp\P20b_work – Keep a separate working directory for each part, so you can back up if you make a mistake Copy the file P20a.gwv to the directory C:\temp\P20b_work Change the name of the file to P20b.gwv Open the model P20b (just double click on the P20b.gwv file)

6. Setup – Part (b) – Cont. Select “MODELS – PATHS TO MODELS” Set working directory to: C:\temp\P20b_Work

7. Part b – Impermeable Cap Create the Impermeable Cap: – Select: Props  Recharge – Select: Props  Property Values  Matrix Editor

8. Impermeable Cap Change the Recharge values for appropriate rows and cells from 6.34e-008 to 0.00e+00 in the cells representing the Impermeable Cap Note the zeros

9. Recharge for Impermeable Cap You should end up with a Recharge distribution that looks like this:

10. Transient Model Setup Convert the model to a transient model with 1 stress period

11. Stress period Types Set: Stress Period Type to 1 (for transient) Set up the Stress periods Stress period length = 972,000,000 seconds (= 30.82 years) 20 time steps Time step multiplier of 1.5

12. Specific Yield Set specific yield = 0.28

13. Initial Heads for Part (b) Select: Model  MODFLOW  Package Options Select: Initial Heads tab Select: Initial Head Location: Read Heads Directly from Binary Head Save File Select: Browse Select: P20a_Assign.hds file Note

14. Result – Last time step – Part (b) Results for the last time step should look like this. Next Time Step Ctrl+Shift+N Previous Time Step Ctrl+Shift+P

15. Setup – Part (x) x= c, d, e, f, g Create a new working directory “C:\temp\P20x_work” Make a copy of the file P20x-1.gwv (x-1 = previous version) Place the file P20x-1.gwv in the directory – C:\temp\P20x_work Rename the copy P20x.gwv Copy the file “P20a_Assign.hds” to the directory “P20x_work” Select: Initial Head Location: Read Heads Directly from Binary Head Save File Select: P20a_Assign.hds file

16. Part (c) – Slurry Wall What’s a slurry wall? Slurry walls are non-structural barriers (Cutoff Walls, Slurry Trenches) that are constructed underground to impede groundwater flow. (www.slurrywall.com)

17. Part (d) – Drain BC In the table, the elevation is the stage and the last column is the "conductance” Fll in the "Drain" BC form as: – Stage: Elevation from table – Width: 1 – Length: 1 – Thickness: 1 – Hydraulic Conductivity: 10 – This gives a "Conductance" = 10 ft2/sec cruxper.com

18. Part (x) What solution does your team recommend? Feel free to suggest solutions that are – modifications of those suggested here or – have not been discussed in the assignment or these slides.