Continuity mistake: When Clark lifts Lana back onto the bridge, from a shot from above, we see that Lana puts her left leg onto the bridge into a sitting position. They then cut to a different angle but now both her legs are still dangling and she eventually puts her right leg on the bridge first.
Continuity mistake: When Ian is dragging Lana towards the dam, his double can be seen in the background dragging Chloe. The double is on Chloe's right side pushing her. Cut to a close up as Chloe says "Ian you need help" but now the double is behind Chloe and is pulling her.