On the sidewalk in front of 27 Walden, one square of concrete sidewalk is missing. The square has been filled in with tar, but that tar is concave and sits well below grade level. As a result, it is usually filled with rainwater, which means that people have to step around the square and onto the street to avoid it. It is likely to turn to ice and become treacherous in the cold weather. Possible to replace with the standard concrete? (Note: there is a second square that is also filled with tar, but it is not as concave or dangerous as the one just described. It would be ideal to fix both of them.) Thanks.