please answer all the above questions.

Context 1 The Smith Family is still dealing with the aftermath of their TCE spill. The Joneses, whose property adjoins the Smiths' property, have noticed the coming and going of environmental consultants and have discovered that there has been an uncontrolled release of TCE. Because they get their drinking water from a well on their property, they are worried about potential groundwater impacts. They phone the Department of Environmental Quality to ask for an investigation. The DEQ organizes the installation of monitoring wells around the Smiths' property to detect potential off-site migration. (Monitoring wells are porous tubes installed from the ground surface to below the water table to enable measurement of water levels and groundwater sampling; see Figure 1 for an example.) The location of monitoring wells, drinking water wells and various buildings is displayed (with respect to groundwater flow contours determined by measuring depth to groundwater) in Figure 2. The Smiths agree to follow up with periodic sampling (performed by an independent consultant) and reporting to the DEQ. WW1 MWZ DWI Smith Cleaners . MW3 MW7 Smith residence . MW4 Jones residence MW6 MWS 100 200 300 yds. 0 DW2 Iloi Legend Property line Direction of groundwater flow Building WW1-7 Monitoring well DW1-2 Drinking water wel Figure 2. Position of Smith and Jones residences, Figure 1. A technician takes a sample from a the Smith dry cleaning business (the site of the monitoring well in Jacksorwille, NC. The red TCE spill) and various groundwater wells with tape measure in the background is used to respect to groundwater flow contours. measure depth to groundwater. (Photo via NC DEO) The soil bored out the ground for the development of the monitoring wells is analyzed to determine properties of the aquifer. On the Smiths' property, the water table is at a depth of roughly 10 ft from the ground surface. Below this depth, the soil consists of coarse sand with a hydraulic conductivity of roughly 1 cm/s. The bulk density of the soil is 1.4 g/cm. By volume, the soil is 40% void space. After the water levels in the monitoring wells stabilize, exact depth to groundwater is measured at each well. The wells are purged, allowed to refill with fresh groundwater and sampled. The samples are analyzed for TCE. A TCE sample is also taken from the Joneses' drinking water well. The results are shown in Table 1. MWS MW6 MW7 DW2 Table 1: Results of groundwater sampling Well MW1 MWZ MW3 MW4 Depth to 3.10 3.14 3.16 3.22 GW (m) TCE (ug/L) ND ND ND ND ND- not dected (detection limit -1 ug/L); NM-nat measured. 3.14 3.13 NM 3.21 ND ND ND ND 7. What is the minimum time required for TCE that reaches the groundwater immediately below the Smiths' dry-cleaning business to reach the Joneses' drinking water well? 8. Based on the above calculations, you decide that monthly sampling of the groundwater wells is adequate to ensure that there is no undetected off-site migration of TCE. For five months, TCE is not detected in any of the samples taken. On the sixth month, the TCE concentration in the sample for MW4 is 2 wg/L. What could explain this? 9. Upon seeing this result, what do you recommend? Base your recommendations on information you find for TCE reference doses, drinking water criteria, etc. Context 1 The Smith Family is still dealing with the aftermath of their TCE spill. The Joneses, whose property adjoins the Smiths' property, have noticed the coming and going of environmental consultants and have discovered that there has been an uncontrolled release of TCE. Because they get their drinking water from a well on their property, they are worried about potential groundwater impacts. They phone the Department of Environmental Quality to ask for an investigation. The DEQ organizes the installation of monitoring wells around the Smiths' property to detect potential off-site migration. (Monitoring wells are porous tubes installed from the ground surface to below the water table to enable measurement of water levels and groundwater sampling; see Figure 1 for an example.) The location of monitoring wells, drinking water wells and various buildings is displayed (with respect to groundwater flow contours determined by measuring depth to groundwater) in Figure 2. The Smiths agree to follow up with periodic sampling (performed by an independent consultant) and reporting to the DEQ. WW1 MWZ DWI Smith Cleaners . MW3 MW7 Smith residence . MW4 Jones residence MW6 MWS 100 200 300 yds. 0 DW2 Iloi Legend Property line Direction of groundwater flow Building WW1-7 Monitoring well DW1-2 Drinking water wel Figure 2. Position of Smith and Jones residences, Figure 1. A technician takes a sample from a the Smith dry cleaning business (the site of the monitoring well in Jacksorwille, NC. The red TCE spill) and various groundwater wells with tape measure in the background is used to respect to groundwater flow contours. measure depth to groundwater. (Photo via NC DEO) The soil bored out the ground for the development of the monitoring wells is analyzed to determine properties of the aquifer. On the Smiths' property, the water table is at a depth of roughly 10 ft from the ground surface. Below this depth, the soil consists of coarse sand with a hydraulic conductivity of roughly 1 cm/s. The bulk density of the soil is 1.4 g/cm. By volume, the soil is 40% void space. After the water levels in the monitoring wells stabilize, exact depth to groundwater is measured at each well. The wells are purged, allowed to refill with fresh groundwater and sampled. The samples are analyzed for TCE. A TCE sample is also taken from the Joneses' drinking water well. The results are shown in Table 1. MWS MW6 MW7 DW2 Table 1: Results of groundwater sampling Well MW1 MWZ MW3 MW4 Depth to 3.10 3.14 3.16 3.22 GW (m) TCE (ug/L) ND ND ND ND ND- not dected (detection limit -1 ug/L); NM-nat measured. 3.14 3.13 NM 3.21 ND ND ND ND 7. What is the minimum time required for TCE that reaches the groundwater immediately below the Smiths' dry-cleaning business to reach the Joneses' drinking water well? 8. Based on the above calculations, you decide that monthly sampling of the groundwater wells is adequate to ensure that there is no undetected off-site migration of TCE. For five months, TCE is not detected in any of the samples taken. On the sixth month, the TCE concentration in the sample for MW4 is 2 wg/L. What could explain this? 9. Upon seeing this result, what do you recommend? Base your recommendations on information you find for TCE reference doses, drinking water criteria, etc