Shown above is the driller's log for well 1 presented as a table and pictorially as a vertical cross section down through the alluvium to the bottom of each well. The driller's log also identifies the approximate depth to the water table at the time the well was constructed and developed. For the purposes of this exercise, the most likely interval considered to be the primary source of water for the well is labeled the Main Aquifer.
Included on each driller's log page is a table of average porosity values for each type of sediment described in the driller's logs.
Sediment type | Average porosity (%) |
Boulder size gravel | 30 |
Pea size gravel | 32 |
Unsorted sand & gravel | 27 |
Coarse sand | 40 |
Medium sand | 41 |
Fine sand | 43 |
Unsorted sand | 28 |
Use the descriptions provided in graphical and tabular form and the table of average porosity values to compute the average porosity for the Main Aquifer interval at each well site. Once you computed the average porosity values for each well site, compute the average porosity of the Main Aquifer between the spill site and the Buffalo River. You will use this estimate to compute the average ground-water velocity.
To estimate the average porosity of the main aquifer at well 1:
Click on the green arrow to return to the page showing the well locations and click on well 2. Repeat the steps you followed to calculate the average porosity values for the Main Aquifer at well 2. Continue with the other wells 3 through 6.