COUNCIL BLUFFS — Workers are dredging in Council Bluffs’ Lake Manawa for the first time in decades as part of an effort to improve its water clarity and eliminate algae blooms. A dredging barge is slowly making its way across the 715-acre lake, removing sand from the lake bottom. Crews are concentrating on a 60-acre area, where they want to increase depths to a maximum of 16 feet deep.