Miami Beach is over 100 years old and similar to many other cities, it had a gravity system in place. A gravity system is a series of connecting pipes that redirect storm water that enter the system from the streets. In Miami Beach, the water was carried directly into the bay through the force of gravity. In certain areas, where the bay area is situated at slightly higher elevations, the gravity system could not sufficiently remove water and would instead redirect it back into the system, resulting in flooding.
It’s important to note that most pump station systems in the city were initially converted to direct water into injection wells. Injection wells are devices that help push water and other material underground. However, this option was no longer viable because the city is not only facing the effects of rising sea level but also dealing with a reduced capacity for soil to store rain water which equals to a reduced capacity to push water underground. The existing pump stations are no longer connected to injection wells and are instead directed to outfalls.
As these pumps were being installed, the city saw this as an opportunity to improve water quality over the previous gravity based system which did not have any level of treatment or pollutant capture accepted at the inlets. Most of the components of the existing pump stations are located underground and include several different chambers. The wet-well has a bar rack that collects floatable trash, the second chamber has a vortex structure or eco-sense box that traps sediments and dirt from site run off. The last chamber is known as the aeration chamber, where oil accumulates, remains separated by water and is then removed using vacuum trucks. The filtered water below is then pushed out into the bay. See the video below to learn the difference between a gravity and pump station system.