There are no easy answers to that question, but the cost of cleaning up the sewage in Tijuan, Mexico, is likely to exceed $20 billion.
According to the Tijuana government, the sewage has been contaminated by industrial waste, which is now being disposed of in the city.
But experts are not certain how much of the sewage is being treated.
In a report released on Thursday, the city said it will spend about $9 billion to clean the sewage system.
But it also revealed that the city spent about $1.5 billion on a project to build new water treatment plants and wastewater treatment plants to make up for the sewage problem.
The cost of the water treatment is estimated at $1,300 per person per day, or about $2,000 per year.
The government estimates the total cost of repairing the sewage will be $6.5 million, according to the report.
It added that the water pollution from the sewage treatment plant will also be passed on to the community, since it will be treated in water.
The report also said the sewage disposal facility will take about three years to complete.
The Mexican government, which manages the sewage, said it is not clear how much sewage is in the system, since most of the waste is in a municipal landfill.
The waste will be stored in tanks until the government decides to clean it.
The Tijuana wastewater is now flowing through a pipe that has a diameter of 100 feet.
It is fed into a tank, which holds about 50 million gallons of sewage per day.
The Tijuana sewage system is the second-largest in the world, after the Pacific Ocean.