A paving project that started two months ago on Ocean Street in South Portland remains incomplete because the Portland Water District plans to replace a water main in front of Mahoney Middle School in September. The mile-long paving project, from Broadway to the Cape Elizabeth line, started June 22 and was expected to be completed by the end of July, according to the Maine Department of Transportation. It’s a heavily traveled stretch of Route 77, where commuter backups are often evident at intersections with Broadway, Highland Avenue and Sawyer Street, especially when school is in session. Glidden Excavating & Paving of Gorham completed most of the paving project several weeks ago, except for the section in front of Mahoney Middle School, where Ocean Street meets Broadway.