A chamber having an inlet for receiving polluted storm-water runoff and an outlet for the storm water to flow out. Within the chamber are one or more baffles forming gaps and having apertures. The gaps define a longer water flow route through the chamber and the apertures disperse the storm water within the chamber. This increases storm-water residence time which encourages settling of particulate matter such as sand and grit. In alternative embodiments, there are included a screen, a collection reservoir, and/or a pivotal filter for further dispersing, detaining, and/or filtering the storm water.