Science
EVS 111 Middlesex Community College Migration of Groundwater Pollution Lab

EVS 111

Middlesex Community College - Middletown

EVS

Question Description

Can you help me understand this Environmental Science question?

Calculate the speed at which polluted groundwater travels from the Weapons Center using Darcy's

Law, in which velocity (Q) is equal to a constant (in this case 100 feet/day) times the change in

water table elevation between two wells (Δh), divided by the distance between the wells (l).

a. Using Well Q1 in the path of the plume from the Weapons Center, subtract its water table

elevation from the water table elevation at the Weapons Center (show work):

Well Q

Δh = height at pollution source - height at polluted well

b. Measure and record the horizontal distance between the chosen well and the Weapons Center

(Map scale: 1 cm = 300 ft)

distance (l) = __________ cm on map = __________ ft on ground

c. Calculate groundwater velocity Q = 100 ft/day x Δh (in feet) / distance (l, in feet)

Show your work, including units

see attachment

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MxCC EVS 111 Environmental Science Lab Spring 2020 Migration of Groundwater Pollution at Groton Sub Base An activity based on actual data collected in the summer of 2000 Background In the summer months of 2000, an extensive groundwater study was conducted at the Naval Base in Groton, an area that has a long history of industrial and commercial development. The BGOURI (Basewide Groundwater Operable Unit Remedial Investigation) study was conducted to make recommendations to the Department of the Navy for any needed cleanup of ten sites on the Naval Base to prevent further contamination and to assess the possibility of changing the water classification from GB/GA to GB only. The GB classification is used for water that should not be used as a drinking source. The data from this activity was taken from a revised report of this study written in February 2001 by the US Environmental Protection Agency (EPA). Cleanup has been ongoing at the Sub Base since 1990, when nearly all of the 687-acre base was named to the EPA's Superfund list. The activity will concentrate on two of the area's test sites: Site 20 and Site 7. Site 7, the area around the Torpedo Shops, was historically used for wastewater disposal. In addition to wastewater, contaminants associated with road tars, polyaromatic hydrocarbons (PAHs), were also found in the area. Some PAH-contaminated soil had previously been removed from this area and disposed of at an off-site location. As a result, the site was not found to be a health risk, but the water was deemed unsuitable for human consumption. The soil in Area A, Weapons Center (Site 20) was also found to contain PAHs, as well as the metals antimony, arsenic, nickel, silver, thallium, and zinc. The groundwater at Site 20 was found to contain trichloroethylene (TCE) and benzo(a) pyrene (BaP). Workers at Site 20 were not considered to be at risk because of relatively low levels of contamination, but the groundwater was found to be unsuitable for human consumption. A recommendation was made for a Feasibility Study of this area because of the risk to future residents should land use change. This recommendation was made primarily because there are no controls in place on land use in this area. Objectives  Use real-world data from the Groton Sub-Base to illustrate basic concepts of groundwater flow and groundwater contamination.  Map the elevations of the water table at the Naval Base and contour its slope to estimate hydraulic head.  Evaluate the direction the groundwater is moving in order to predict if any wells could become contaminated.  Calculate the velocity of groundwater movement to determine how long it will take for contamination to reach the wells in its path and the nearby river. Procedure 1. Using the data table "Groton Naval Base, Groundwater Data: June-August 2000" determine the elevation of the water table at each well by subtracting the Depth to Water (ft) from the Surface Elevation Above MSL (ft). Do this for the data from June and record the number in the appropriate blank column in the table. Migration of Groundwater Pollution at Groton Sub Base v. 032420 Page 1 2. Using the June Water Elevation (ft), record water table heights for each well on the map of the Naval Base. The heights should be recorded as close to each well as possible and in ink, preferably in a bright color that will be easy to see. 3. Using a contour interval of ten feet, draw contour lines to show the slope and shape of the water table. Be sure to use pencil to draw the contour lines because you will most likely need to erase your lines several times before you are satisfied with their accuracy.  Remember that contour lines may not cross each other.  Contour lines should be drawn as smooth curves, not jagged lines.  All lines should be labeled with the appropriate elevation (intervals of ten feet). 4. Once you are satisfied with your contour lines of the water table, draw enough water direction flow arrows so that you can see at a glance the direction that the groundwater flows in different parts of the map.  Water always takes the steepest, shortest path downward from one contour line to the next.  Water flow arrows are drawn perpendicular across each contour line to represent the shortest flow path. 5. Mark the two sources of contaminants on the map: a. Draw a vertical bar scaled to 300 ft on top of the word "Torpedo" to represent the wastewater contamination at the Torpedo Shops. b. Draw a vertical bar scaled to 300 ft below the word "Center" to represent the contamination source at the Weapons Center. 6. Show the spread of the contaminants from each source in the direction of groundwater flow by shading in the area that you think will contaminate over time (the "plume").  Outline and shade in pollution plumes covering as long a distance as you think they may travel.  Make sure the pollution plumes follow the direction of groundwater flow that you indicated on the map. Identify here the wells affected by each plume: Torpedo Shops Weapons Center 7. Calculate the speed at which polluted groundwater travels from the Weapons Center using Darcy's Law, in which velocity (Q) is equal to a constant (in this case 100 feet/day) times the change in water table elevation between two wells (Δh), divided by the distance between the wells (l). a. Using Well Q1 in the path of the plume from the Weapons Center, subtract its water table elevation from the water table elevation at the Weapons Center (show work): Well Q Δh = height at pollution source - height at polluted well b. Measure and record the horizontal distance between the chosen well and the Weapons Center (Map scale: 1 cm = 300 ft) distance (l) = __________ cm on map = __________ ft on ground c. Calculate groundwater velocity Q = 100 ft/day x Δh (in feet) / distance (l, in feet) Show your work, including units Migration of Groundwater Pollution at Groton Sub Base v. 032420 Page 2 8. Calculate how long it will take for the contaminants from the Weapons Center to reach Well Q. Show your work including all units. Time (days) = distance (ft) / velocity (ft/day) If your answer is greater than 365 days, convert your answer into years. 9. Repeat the calculation to determine how long it would take for contaminants from the Weapons Center to reach the Thames River. 10. Write a paragraph summarizing the situation at the Groton Sub Base, including your findings and conclusions.  Check your contours again for accuracy, and turn in your completed map and calculations. Groton Naval Base Groundwater Data June-August 2000 Well # (on map) L F D H E C Q A B T S J G K I M N O R P Well Name 2DMW10D 2DMW15D 2DMW16D 2DMW23D 2DMW24D 2DMW25D 2DMW26D 2DMW27D 2DMW28D 2WCMW3S 4MW2S 7MW1D 7MW2D 7MW4S 7MW5D 19MW2 19MW3 MW4-6RI 2WMW22S 3MW14S Surface Elevation Above MSL (in ft) 52.13 41.7 35.3 80.99 33.68 33.09 26.8 25.56 33.01 83.56 96.4 51.69 40.63 44.45 54.18 4.59 4.50 4.51 118.82 34.42 June Depth to Water (ft) 9.36 6.0 2.97 17.14 2.62 6.89 9.06 11.55 15.58 9.53 4.5 9.25 4.1 2.08 11.84 4.27 4.1 3.32 6.42 1.7 August Depth to Water (ft) 10.3 8.01 4.97 29.34 3.77 8.98 10.21 13.94 16.91 10.27 9.0 9.98 5.4 2.71 18.63 5.21 4.31 3.92 7.31 2.05 Water Table Elevation Aquifer Type Bedrock Bedrock Bedrock Bedrock Bedrock Bedrock Overburden Bedrock Bedrock Overburden Overburden Bedrock Bedrock Bedrock Bedrock Overburden Overburden Overburden Overburden Overburden MSL = mean sea level (1988) Migration of Groundwater Pollution at Groton Sub Base v. 032420 Page 3 Migration of Groundwater Pollution at Groton Sub Base v. 032420 Page 4 ...
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