5.8: Lab Exercise (Part C)

Part C – Groundwater Flow

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 the UST). These UST’s could leak, and gasoline could possibly reach the water table. In the diagram below, a business using a well has detected gasoline in their groundwater. To detect the source of the potential leak, contour the water table’s surface and determine its flow path. There are several gas stations in the diagram, and each has the potential to have the leaking UST. Seven monitoring wells are installed in the area, and you have data about the water table elevation within each well. Using that data (in elevation above sea level), contour this map as you would any other. Add the water table elevations to the map, and using pencil, contour the groundwater elevations using a contour interval of 2 feet. Noting that the gas should flow with the groundwater, determine the direction of groundwater flow and note the most likely gas station to be the source of the gasoline leak (in a real-world scenario, once the likely culprit was determined, more monitoring wells would be installed and they would be tested for gasoline residue).

 Table 5.1 Monitoring Well Water Table Elevation (feet) 1 794' 2 790' 3 788' 4 786' 5 786' 6 783' 7 780'

18. Which gas station is the most likely source of the gasoline leak?

a. Station A                         b. Station B                         c. Station C

19. Is the school likely to be at risk of contamination from this same leak?

a. Yes                                b. No

20. Is the church likely to be at risk of contamination from this same leak?

a. Yes                                b. No