From 9News.com (Marshall Zelinger):
The lowered section of I-70 opened May 24, taking traffic off the remaining portion of the viaduct near the Purina plant.
Before the roadway was built, pipes were laid down. Some are 20 feet by 6 feet and can be driven through. Others are 6 feet by 6 feet and big enough to walk through.
The water from Central 70 flows to one of eight detention ponds. According to CDOT, the largest can hold 26 football fields worth of water: 8.5 million gallons. The smallest can hold 6,400 bathtubs full of water: 320,000 gallons.
The water from the tunnel portion of Central 70 gets some help getting back to the surface.
“We pump it to a very large holding tank,” said Inzeo…
A pump station near York Street brings the water to one of the detention ponds. From there, the water goes through a micro-pool, to get the solids and sediments taken out before the water ends up in the South Platte River behind the Denver Coliseum.
Half of the pump station is for taking water out, the other half is to support the fire suppression system inside the tunnel.