Two of the worst bridges in Colorado are going to be replaced, but not until 2012.Replacement of the Bronco Arch Bridge on Interstate 25 and the Santa Fe Street Bridge, both in Denver, have been set as two of the states highest priority bridges.The bridges are two of the most heavily traveled in the state and both are corroded, crumbling and rusting. The steel Bronco Arch bridge is full of holes. Its concrete pillars are cracked and crumbling and pedestrians said they cross under the bridge at their own risk.Its a little scary, said Evin OCleary, who rides his bicycle under the bridge on the way to school daily. It's really dirty and all the bolts look rusty and it shakes and makes weird noises while cars are going over it.Jake Fink, a pedestrian who also happens to be an engineer said to his trained eye, the bridge appeared to be a patchwork of repair projects.It looks like it's all sort of rigged together, said Fink. It doesn't necessarily look strong enough for the job that it's doing.Colorado Department of Transportation spokeswoman Stacey Stegman said most Colorado bridges are meant to last 40 or 50 years. The Bronco Arch bridge will turn 60 next year.It gets a lot of truck traffic, heavy traffic pounding on it every day, said Stegman. It's really just had a lot of wear and tear and it's tired and ready to be replaced.But Stegman maintained that engineers have deemed the bridge safe until it is replaced.If we had any inkling that it was unsafe, we'd close it right now, said Stegman.7News asked why it has taken so long to replace a bridge that is well past its prime.Its a very costly bridge, said Stegman.For years, CDOT has been forced to place emergency patches on the Bronco Arch bridge rather than replace it. Now, $30 million in state and federal dollars will allow them to replace the bridge altogether with a brand new concrete structure.Stegman said $60 million to repair the Santa Fe Bridge will come from the passage of FASTER, the transportation bill that increased vehicle registration fees to pay for repairs to Colorados poorest bridges.Both projects are slated to begin in April. Stegman said the spring start date will mean less traffic on the Bronco Arch bridge due to football season.