Method and apparatus for a drywell retrofit

Abstract

The present invention is a drywell retrofit top that can either replace the top portion of an existing drywell or be placed upon a newly placed drywell. The drywell retrofit top provides a flow path for storm water run-off from the top of the drywell directing the storm water run-off that falls into the drywell retrofit top trap chamber and then directs the water to a treatment system. After the treatment system process the water, the water is flows back to the drywell retrofit top to a drop chamber and then discharged into a drywell chamber where the water is able to percolate of filtrate back to surrounding native soils. The drywell retrofit top uses a precast concrete cylinder that has an integral bottom piece that is placed on top of a perforated precast concrete cylinder from the previous drywell. The drywell retrofit top has a vertical dividing wall separating the precast concrete cylinder into two chambers with a larger chamber collecting the storm water run-off. While the water is collected, sediment and heavier than water pollutants settle out in the trap chamber. An outlet pipe is place several inches or some way up the side wall of the drywell retrofit top cylinder. Once the water reaches the level of the outlet pipe, the water then flows out of the trap chamber to a treatment system that is typically situated near the drywell.

1 . A drywell retrofit diverter top comprising;
 a precast concrete vessel having an integral bottom, a trap chamber, a drop chamber with the two chambers being separated by a vertical dividing wall that sits upon the integral bottom;   a precast concrete cover that integrates with the precast concrete vessel and sits above the trap and drop chambers with a manhole and a grated top to direct storm water runoff to drain into the trap chamber;   the trap chamber having an outlet hole in which storm water runoff is directed to a treatment system;   a return line from the treatment system to the drop chamber through an inlet hole in which the inlet hole is lower than the outlet hole of the trap chamber to facilitate treated storm water runoff to gravity drain from the drywell to the treatment system and back to the drywell;   a drain hole in the drop chamber that is located in the integral bottom; and   one or more perforated precast concrete cylinders situated below the integral bottom in which the storm water runoff is deposited through the drain hole of the drop chamber.   
     
     
         2 . The drywell retrofit diverter top of  claim 1  wherein the vertical dividing wall runs from the integral bottom to just below the level of the precast concrete cover to allow storm water runoff to spill into the drop chamber from the trap chamber and directly into the perforated precast concrete cylinders if the outlet hole is unable to direct storm water runoff to the treatment system. 
     
     
         3 . The drywell retrofit diverter top of  claim 1  wherein the integral bottom is sized and shaped to fit a cylindrical shaped perforated precast concrete cylinder of an already existing drywell. 
     
     
         4 . The drywell retrofit diverter top of  claim 3  in which the integral bottom is notched to align with the top of cylindrical shaped perforated precast concrete cylinder. 
     
     
         5 . The drywell retrofit diverter top of  claim 1  further comprising an access hole in the precast concrete cover situated above the drop chamber in which samples of storm water runoff can be drawn and tested. 
     
     
         6 . The drywell retrofit diverter top of  claim 1  wherein the materials used to make the various components of the drywell retrofit diverter top include; steel, plastic, concrete or a combination of these materials. 
     
     
         7 . The method of retrofitting a drywell with a drywell diverter top, comprising
 excavating around a preexisting drywell;   exposing a precast concrete cone of an already existing drywell;   removal of the precast concrete cone;   fabricating a precast concrete vessel having a bottom that integrates with a remaining drywell chamber, a trap chamber, a drop chamber with the two chambers being separated by a vertical dividing wall that sits upon the bottom, a precast concrete cover that integrates with the vessel and sits above the trap and drop chambers with a manhole and a grated top which directs storm water runoff to drain into the trap chamber, the trap chamber having an outlet hole situated above a floor of the trap chamber, the outlet hole directing the storm water runoff to a treatment system that is gravity fed through the outlet hole, a return line from the treatment system to the drop chamber through an inlet hole in which the inlet hole is lower than the outlet hole of the trap chamber to facilitate gravity drainage from the drywell to the treatment system and back to the drywell, a drain hole in the drop chamber that is located in the integral bottom;   placing the fabricated precast cast concrete vessel upon a precast perforated concrete cylinder within the drywell;   locating and placing a treatment system to allow for gravity feed of storm water runoff to drain from the trap chamber to the treatment system and back to the drop chamber;   excavating a line from the drywell to the treatment system;   inserting a pipe from the drywell diverter top outlet hole of the trap chamber to the treatment system;   inserting a pipe from the treatment system to the drop chamber inlet hole; and   backfilling around the drywell for proper runoff.