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Geosciences LibreTexts

12.2: Activity 12A - Groundwater Flow

  • Page ID
    14568
  • Many gas stations use underground storage tanks (UST) to store fuel below the ground. You have likely seen a tanker truck at a gas station filling up an UST. These UST’s can leak, and, as a result, gasoline can percolate down to the water table. On Figure 12.9 below, a business using a well has detected gasoline in their groundwater. There are several gas stations in the diagram, and each has the potential to have a leaking UST. Seven monitoring wells are installed in the area; you are provided the data about the water table elevation within each well (Table 12.1). To detect the source of the potential leak, you will need to determine its flow path.

    12.9.png
    Figure 12.9: Groundwater map to use in Activity 12A: Groundwater Flow.

    Table 12.1: Water table elevations for the monitoring wells located on Figure 12.9.

    Monitoring Well

    Water Table Elevation (feet)

    1

    794

    2

    790

    3

    788

    4

    786

    5

    786

    6

    783

    7

    780

    1. Draw (either in pencil or digitally) contour lines for the water table (WT) elevation. Use an interval of 2 feet. Add WT elevations to each of the wells on the map.
    2. Determine the direction of groundwater flow. Draw arrows to illustrate the direction.
    3. Indicate, with a star, the gas station most likely to be the source of the leak.
    4. Which gas station is the most likely source of the gasoline leak?
      1. Station A
      2. Station B
      3. Station C
    5. How do you know?
    6. Is the school likely to be at risk of contamination from this same leak?
      1. Yes
      2. No
    7. How do you know?
    8. Is the church likely to be at risk of contamination from this same leak?
      1. Yes
      2. No
    9. How do you know?

    Attributions

    • Figure 12.9: “Groundwater Map” (CC-BY 4.0; Emily Haddad, own work)​
    • Table 12.1: “Groundwater Monitoring” (CC-BY 4.0; Chloe Branciforte, own work)