In an increasingly common refrain, three U.S. senators from Wisconsin and Minnesota are demanding release of federal funds to enable work to move forward on the $1.8-billion replacement of Blatnik Bridge—a key freight and commuter link between Duluth, Minn. and Superior, Wis. that dates to the early 1960s,Sens.Tammy Baldwin (D-Wisc.), Amy Klobuchar (D-Minn.) and Tina Smith (D-Minn.) wrote a joint letter March 2 to U.S. Transportation Secretary Sean Duffy seeking final approval and release of a $1.05-billion federal grant for the project, which is set to start this fall. The bridge carries Interstate-535 and serves an average of 33,000 daily vehicles traveling over St. Louis Bay. It is essential for freight movement and commercial traffic serving the Duluth and Superior but is in poor condition with significant structural deterioration, creating serious capacity, mobility and safety concerns, the letter says.…