The first piece of a roadway-topped railroad tunnel that’s part of work to replace the bridge at Washington and Clark streets is lowered into place this morning. Part of the 12-month project — the beginnings of a temporary city street between the DiamondJacks Casino entrance at Washington and the area near the entrance of Ergon, which is near the foot of the hill where Lee Street begins — is under way and expected to be complete within the next week. The 80-year-old bridge was demolished in August and has been closed since January 2009. It is the lone span along Vicksburg’s main north-south corridor connecting downtown and Interstate 20. The project is being handled by Kanzaa Construction of Topeka, Kan., at a cost not to exceed $8.6 million and is expected to be finished by spring’s end.