The explosions planned near the crossing of Lavergne and Lawrence avenues are part of a broader project aimed at improving drainage and preventing basement flooding in the surrounding area, according to a city document explaining the project. The Northwest Side work, scheduled to end in December 2015 at an approximate cost of $19.7 million, will involve installing shafts to tie the sewers into the Deep Tunnel system, the massive regional flood and pollution control project that remains under construction, Litherland said.