[xoxoxoBruce]

The number of natives in the western hemisphere circa 1492 seems to be about 40 million. Working back the 25,000 years or so there seems to have been natives, it's easy to come up with maybe 100 million have lived (and left trash behind) in the Americas.

Of course most of their trash was organic, therefore long gone, but of the more durable stuff of metal/stone/bone/clay, I'd guess we haven't seen most of it.

As I understand it the Poplar St Bridge carries I-70, I-64, I-55, and sundry traffic over the river into St Louis. The new bridge will carry a rerouted I-70 over the river further north entering St Louis at Cass St. This is quite a ways from the Cahokia Mounds Park which is already penned in by I-70, I-55, I-64, I-255 and suburbia, so I don't see how this project affects that. If they're saying the Cahokia site should be much bigger, the new bridge is the least of their problems.
Methinks the Mail is hyperboling.