hi mate,

Thornton Quarry is one of the largest aggregate quarries in the world, located in Thornton, Illinois just south of Chicago. The quarry is 1.5 miles (2.5 km) long, 0.5 miles (1 km) wide, and 450 feet (137.16 m)deep at its deepest point.

• Thornton Quarry is one of the largest aggregate quarries in the world, located in Thornton, Illinois just south of Chicago. The quarry is 1.5 miles (2.5 km) long, 0.5 miles (1 km) wide, and 450 feet (137.16 m) deep at its deepest point. Gallagher Asphalt Corporation has been operating on the grounds of the quarry since 1928. A dryland dike carries Interstate 80/Interstate 294/Tri-State Tollway over the quarry.
• As part of the Chicago Deep Tunnel project, both Thornton Quarry and McCook Quarry will serve as reservoirs to reduce the backflow of stormwater and sewage from Chicago area rivers into Lake Michigan. Thornton Transitional Reservoir contributes a 3.1-billion-US-gallon (12,000,000 m3) capacity to the system, and is expected to contribute 7.9 billion US gallons (30,000,000 m3) when the system is completed in 2014.
• It is estimated that the reservoir will help protect 500,000 people who live in the surrounding 14 suburbs it serves, and will save the city around $40 million worth of damages each year.
• The quarry contains Silurian reefs which formed when the Michigan Basin was covered in sea water more than 400 million years ago.

i hope it helps you..