Drainwater treatment system for use in a horizontal passageway

A drainwater treatment system for installation in an underground location of a drainage system having a upstream pipe portion which conducts drainwater to the underground location and a downstream pipe portion which conducts drainwater from the underground location, the system comprising:

• an upwardly-opening box structure positionable within the underground location and connectable in series with the upstream and downstream pipe portions so that drainwater which flows out of the upstream pipe portion flows into one end of the structure and drainwater which enters the downstream pipe portion flows out of the other end of the structure, the structure having an interior and a bottom;
• a partition supported within the structure for dividing the interior of the structure into an upstream chamber into which drainwater flows from the upstream pipe portion and a downstream chamber from which drainwater flows out of the structure by way of the downstream pipe portion, the partition having an upper edge and an opening adjacent the upper edge through which the interior of the upstream chamber communicates with the interior of the downstream chamber;
• flow-channeling means for decelerating the flow of drainwater which enters the upstream compartment including a mid-panel supported within the upstream chamber for dividing the interior of the upstream chamber into an upper section and a lower section and disposed beneath the elevation of the upstream pipe portion and the partition opening so that drainwater which enters the upstream chamber through the drain pipe flows directly into the upper section of the upstream chamber, and wherein the mid-panel provides a first opening through which drainwater is permitted to flow from the upper section to the lower section and provides a second opening;
• a conduit joined between the mid-panel and the partition permitting communication between the second opening of the mid-panel and the partition opening for conducting drainwater from the lower section of the upstream chamber to the downstream section when the level of the drainwater collected within the upstream compartment rises to the elevation of the partition opening so that the drainwater which enters the upper section from the upstream pipe portion and flows into the lower section is decelerated to flow conditions at which debris and suspended solids are permitted to separate and settle from the drainwater before being conducted from the lower section and into the downstream chamber through the conduit;
• at least one filter supported within the downstream chamber so that drainwater which flows into the downstream chamber from the upstream chamber by way of the conduit flows through the at least one filter for filtering contaminants from the drainwater before flowing out of the structure by way of the downstream pipe portion.