Abstract: The present invention is a drywell retrofit sump insert designed to be placed inside an existing drywell or other similar Underground Injection Control (UIC). The drywell insert helps protect groundwater by removing pollutants from raw storm water runoff that enters the drywell before the drywell infiltrates the storm water into the ground. Once the raw storm water enters the drywell retrofit sump insert, sand, silt, grit, and other high-density pollutants settle out of the storm water stream and accumulate in the bottom of the drywell retrofit sump insert. Oil, grease, and other low-density pollutants float on top of the standing water inside the drywell retrofit sump insert and are kept inside by the oil baffles on the outlet holes. The drywell retrofit sump insert is comprised of a rigid cylinder with an integral flanged bottom attached by means of a watertight joint.

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.