The City of Houston's small diameter tunnels and pipe jacking projects

In 1987 the U.S. Environmental Protection Agency (EPA) and the Texas Natural Resource Conservation Commission (TNRCC) mandated that the City of Houston upgrade its sanitary sewer system to control overflows. Houston encompasses nearly 600 square miles (1550 km2) making it the fourth largest city in the United States. A total of 190 miles (305 km) of sewer lines had to be rehabilitated or constructed by December, 1997 to meet the EPA and TNRCC mandates. The cost of this project is $1.2 billion. In 1992, in order to achieve the objective, the City of Houston established the Greater Houston Wastewater Program (GHWP), comprising a combined team of City staff and consultants. A significant portion of GHWP consists of tunnels, including 14 miles (23 km) of man-entry TBM/shield tunnel both primary lined and pipe-jacked with sewer pipe diameter of 48 to 78 inch (1.2 to 2.0 m).