Environmental studies and Forestry A tank farm at a local chemical distribution facility is leaking and is contaminating the groundwater, causing a concentration directly beneath the site of 14.5 milligrams per liter (mg/L). The groundwater is flowing at the rate of 0.25 meters per day toward a public drinking water well one kilometer away. Preliminary measurements indicate that the chemical is subject to degradation in the aquifer with a half –life of 11 years. It also appears that there is a retardation factor in effect, whereby the rate at which the chemical flows is only half the rate of groundwater flow. To be conservative, assume the pollutant does not disperse within the aquifer, but merely flows along with it. The public well pumps 75,000 gallons of water per day, delivered to 50,000 customers. 1. How do you set this problem up? 1. What is given in the problem? 2. How do these factors relate to one another? 1. Estimate the steady-state pollutant concentration expected at the well. 2. Estimate daily dose for a 70-kg adult ingesting 2 L/day of this water. USEPA default of 30 years 3. If the carcinogenic potency of the contaminant is 0.02 (mg/kg/day)-1, estimate the excess cancers per year in this population if they were to drink this water for 70 years

Environmental studies and Forestry

A tank farm at a local chemical distribution facility is leaking and is contaminating the groundwater, causing a concentration directly beneath the site of 14.5 milligrams per liter (mg/L). The groundwater is flowing at the rate of 0.25 meters per day toward a public drinking water well one kilometer away. Preliminary measurements indicate that the chemical is subject to degradation in the aquifer with a half –life of 11 years. It also appears that there is a retardation factor in effect, whereby the rate at which the chemical flows is only half the rate of groundwater flow. To be conservative, assume the pollutant does not disperse within the aquifer, but merely flows along with it. The public well pumps 75,000 gallons of water per day, delivered to 50,000 customers.

1. How do you set this problem up?

1. What is given in the problem?

2. How do these factors relate to one another?

1. Estimate the steady-state pollutant concentration expected at the well.

2. Estimate daily dose for a 70-kg adult ingesting 2 L/day of this water. USEPA default of 30 years

3. If the carcinogenic potency of the contaminant is 0.02 (mg/kg/day)-1, estimate the excess cancers per year in this population if they were to drink this water for 70 years