Reports state 2 freighters have gone aground in 1 week at the entrance to the port of Barranquilla, Columbia.   The 40,709 dwt freighter Chios Wind went aground with 25,000 metric tons of grain aboard.  The 53,632 dwt freighter Magnum Power was reporated aground earilier.   The grounded vessels has blocked all commerical traffic to and out of the port.   One report states the cause of the groundings is due to the build up of a sand bank at the entrance to the channel.   Harbour officials have stated the cause was due to the current, the underpowered vessels and lack of seamanship of the masters of each vessel.   A tug has been requested to help free both vessels.   No reports of injuries or pollution being released.