Parts of the city’s sewer system will get a major overhaul starting mid-month. Spanning nearly 4 miles, the renovation effort aims to modernize the century-old piping within the densely populated area bounded by Mainzer Strasse, Fischer/Altenwoogstrasse, Hilgardring and Gaustrasse, city officials said. The work will be phased to minimize road closures and parking restrictions. Work is expected to last through the end of the year, weather permitting, officials said.