LAB 11: GROUNDWATER PROCESSES AND WATER RESOURCES

Transcription

1 Environmental Geology 103L team Fall 2015 names LAB 11: GROUNDWATER PROCESSES AND WATER RESOURCES The objectives of this lab are to: Understand the relationship between sedimentary rock types and groundwater processes. Construct and understand water-table topography. Determine the rate and direction of groundwater movement. Evaluate the hazards and risks associated with groundwater contamination. PART 1: LOVE CANAL THE GROUNDWATER CONTAMINATION CASE THAT SHOOK AMERICA Open the websites below and read about the landmark environmental disaster at Love Canal NY, near Niagara Falls. Love Canal PROVES why understanding how groundwater functions is so very VITAL to the health of every community, as well as how grassroots America changed the accountability of corporations and government to these disasters. History: Love Canal: the Start of a Movement: elf.html After reading the websites, watch the video clip summary of the terrifying tragedy of Love Canal, and answer the questions below. 1. What was the original purpose of Love Canal? 2. What events led to the contamination of the site? How did the hazardous waste get there in the first place? 1

2 3. What types of chemicals were in the soils? 4. What were the health effects on the people who lived in or went to school at Love Canal? 5. How did the government finally respond? What is Superfund? 6. What is Black Creek Village? Has the cleanup been effective? Would you live there? 7. Is the situation at Love Canal unique? Visit this website showing the locations of other Superfund sites: Are there any superfund sites in SC? How many? PART II: POROSITY AND PERMEABILITY Read sections 12.1 and 12.2, pages , in your lab manual. You will be conducting the experiments in Exercise 12.1 on page Observation Container A Container B Container C Container D Grain Size Sorting Grain Shape Porosity Permeability 8. Before the experiments, in the table above, describe each material using qualitative observations (i.e. large or small grains; well or poorly sorted; rounded or angular; low-med-high porosity). Then, predict which material will have the greatest permeability. Which will be the least permeable? Why did you make these predictions? 9. How did the results compare to your predictions? Was there anything surprising in the results? 2

3 PART III: SEDIMENTARY ROCKS AND AQUIFERS Rocks: 13, 16, 19, 20, and 23 What types of earth materials are most likely to be contaminated by groundwater? Which ones are more likely to hold water and which materials are more likely to cause water to be repelled? The following section explores the different types of sediments and rocks that are affected by groundwater processes. An aquifer is an underground layer of water bearing rock, which transmits water to wells and springs. Sediments and sedimentary rocks play a critical role in the groundwater story. For sedimentary rocks to be good aquifers they must have high porosity and permeability. Porosity is a measure of the void spaces in a material. Permeability is the measure of the ability of a material to transmit fluids. Many sedimentary rocks consist of grains such as sand, silt or clay. Aquifers: When sediment is deposited and lithified there may be spaces or pores between the grains. For example, sandstone is a sedimentary rock that often makes an excellent aquifer. While limestoness do not have high porosity initially, they dissolve in slightly acidic groundwater so they also can make good aquifers. Aquitards: Some sediment, such as clay, does not have much pore space when lithified to form shale. Shale is often an aquitard. 10. What is the significance in relation to groundwater systems of each of the rocks above? In other words, how would an aquifer be affected if the bedrock consisted of #13 (sandstone)? Specimen Number 13 Rock/Sediment Name Significance to groundwater systems N/A Sand Example: Uncemented sand is typically porous and permeable therefore it would make a good aquifer. N/A Clay N/A Gravel 3

4 PART IV: GROUNDWATER MODELING To enhance your understanding of groundwater, you will observe the movement of water through different types of sediments in a groundwater model. You or your instructor will do the following: Fill the plastic water bottles, insert stopper assembly, and invert it at the ends of the groundwater model tank. Allow the water to run through the groundwater model. Add dye to one of the monitoring wells. DO NOT PLACE DYE INTO THE SMALL POND!! BE SURE TO ONLY PLACE DYE INTO ONE OF THE WELLS! Observe the direction and rate of groundwater movement as the dye flows through the aquifer sediments. The porosity and permeability of the different sediments will affect the direction and rate of groundwater movement. You can time the rate of groundwater movement either using stopwatches, your watch, or your cell phone. 11. What direction does the groundwater flow left or right? 12. Why? 13. Use the box as the edge of the model and make a sketch of the sediment layers in the groundwater model. Label the types of sediment and location of the river and wells. 14. Using the syringe, withdraw water from one of the wells, simulating pumping. Observe what happens to the groundwater motion. Draw arrows on your sketch to illustrate. 15. What happened to the direction of the groundwater flow when you began pumping from the well? 16. What happened to the direction of the groundwater flow when you STOPPED pumping? Why did this happen? 17. Suppose a company that manufactures solvents dumped nasty chemicals into the ground in the middle of the night. What would happen to the farmer s well water next door? 4

5 PART IV: GROUNDWATER CONTAMINATION Section A: Rate of Contaminant Transport In 1985, Voldemort Industries paint manufacturing company dumped chemical wastes (containing chromium, lead, and zinc compounds) from their paint pigment operations in a landfill near River Hogwarts (Figure 1). In response to concerns expressed by nearby residents, Voldemort Industries conducted an investigation of the landfill in 2010 in which they installed the groundwater monitoring wells T-1, T-2, T-3, and T-4. The 2010 water sample results from these wells are listed below. Well Number Depth to water table (m) Contaminants Present T-1 11 None T-2 14 None T-3 17 Pb, Cr, Zn T-4 18 None Well at Hagrid s Residence 6 None Using the depth to water table for each well, draw the water table with a dashed line on Figure 1. Measure the depth to water from the top of the well - not from the ground surface Show the direction of groundwater flow with arrows on Figure 1. In 2010, the water sample from T-2 was not contaminated. When T-2 was sampled in 2011 it showed significant levels of lead, chromium, and zinc. Sketch the approximate boundaries of the contaminant plume (area of contaminated groundwater) on Figure How many years, since the chemical waste was dumped in the landfill, has it taken for the contaminant plume to reach well T-2? Show your work! (HINT: when did contamination BEGIN?) 19. Approximately how fast is this plume moving (in m/year)? Measure the horizontal distance from the middle of the landfill and well. Show your work! years m/yr 20. In what year will the contamination reach the well at Hagrid s residence? Show your work! 21. Why were no contaminants found in well T-4? 22. Is the Dumbledore Formation likely to act as an AQUIFER or AQUITARD? 23. Will the plume contaminate the well water at Hogwarts? YES NO 24. Why or why not? 5

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7 Section B: Exercise 12.7 Someone is Polluting My Water! In this scenario, homeowners noticed a strange smell in whenever they took showers, washed dishes, or ran the tap for drinking water. Many complained of the water smelling and tasting suspiciously of gasoline! Your Environmental Assessment company has been hired to determine if there has been a gas leak from one of the nearby gas stations and if so, which one is causing the contamination of the homeowners drinking water. The background information in Section 12.4 & 12.5, pages and questions for this scenario are found in Exercise 12.7 on pages in your lab manual. Be sure to READ the exercise background before answering the questions! You and your teammates will need to determine what you need to know in order to find a solution for these homeowners. 1. What information do you need to solve this case? 2. Does either gas station have a leakage problem? Explain 3. Which homes or neighborhoods will be affected next? Indicate on the map below where the gasoline contamination will go. 4. Gasoline concentrations of 50 ppm and higher are considered dangerous. Highlight or circle those locations on the figure below. 5. Are there other locations on this map that are likely to be in danger of contamination in the future? 6. If so, indicate those locations on your map. 7. How do you know? 7

8 Contour Interval: 10 ppm