Nearly a year ago, HGC Construction gave me a tour of the second phase of Mercer Commons, a $13 million project that included the historic rehabilitation of 13 buildings and new construction that will result in 67 mixed-income apartments and 10,600 square feet of commercial space. Last week, I got a look at the finished product. To view a slideshow of before and after pictures, click on the image to the right. Walnut Hills-based HGC Construction served as the construction manager and general contractor…