Complex sentence: A $10.5 million dam for the reservoir was scheduled to be completed by mid-October 2011, with the site was expected to be underwater by November 2011, and for that reason any paleontological excavation had to be done quickly.
Split into simpler sentences: A $10.5 million dam for the reservoir was scheduled to be completed by mid-October 2011, with the site was expected to be underwater by November 2011. For that reason, any paleontological excavation had to be done quickly.