A small community pumps groundwater from a confined sandstone aquifer for their drinking water supply (see figure
above).
A recent monitoring study, however, shows that the aquifer is contaminated by a TCE plume near the Boeing and
Cascade sites upgradient. Although the well water is currently not contaminated, the citizens are extremely concerned
since groundwater is their exclusive source of water supply. The fact that groundwater is invisible make them particularly
anxious and has been asking many questions:
1. Will the advancing plume hit the community wells? How long does it take for the plume to reach the wells?
2. Can the community still use the groundwater? Will the community pumping affect the plume migration? What is the
influence area of the community wells?
3. What is the safe yield of the community wells?
4. What is the area of contribution (recharge area) of the community wells?
5. How can the community develop a wellhead protection program that protects the community water supply?
Schematic sketch of
a typical north-south cross-section
Suppose you are hired as a consultant by the local citizens, develop a quantitative analysis for the situation based on
the following preliminary data available from earlier studies:
Current pumpage from each well 80 gpm
Average hydraulic conductivity of the sandstone, 30 m/day
Effective porosity = 0.2
Deep percolation into the deep sandstone aquifer, 10 inch/year
Average Land Surface elevation 10 m
Overbank deposits vertical conductivity, 0.1 ft/day
Sandstone Aquifer top elevation -10 m
Average aquifer thickness, 40 m
Blue Lake,
stage 3m, bottom elevation, -2 m
Fairview Lake, stage 3.5 m, bottom elevation, 0 m
Columbia River, stage 3m, fully penetrating to the aquifer
General regional flow direction: north to the Columbia
Map size, x-length = 6800 ft.
Document your analysis in a concise technical report (approximately 7 to 10 pages). The report must be typed using a Word
Processor and should include the following key elements: background and objectives, approach, conceptual representation,
numerical theory and solution methods, results, analysis and discussion, assumptions and justifications, and conclusions.
Your project will be graded based on both the technical contents and written presentation.