A construction barge working near part of the riverwalk expansion project sank in the Chicago River on Thursday morning. The barge, which sank near the LaSalle Street Bridge, is estimated to be about 15-20 square feet and began taking on water overnight, according to CDOT spokesman Pete Scales. The barge is out of the way of traffic and is not hampering boat traffic on the river, Scales said. Walsh Construction, which owns the barge, has called in a marine salvage company to retrieve it, Scales said.