Felts Avenue Water Quality Study

Felts Avenue is located one block east of Old 41 Road and south of the Imperial River. The focus of this 36.6-acre residential and commercial project was to treat the stormwater runoff in the Felts Avenue outfall basin prior to its discharge into the Imperial River. The majority of the existing drainage found in the basin was open swale, and the conveyance of plant material, silt and trash was compounding the nutrient load being exported into the river.

To reduce detritus, a baffle box upstream of a dry retention area eliminates discharge of the larger debris and provides an important treatment prior to outfall into the river. The pretreatment baffle box provides a preliminary treatment while the second component of the treatment train is a diversion to dry retention area with a 1.5’ storage depth which will treat 0.30” of runoff for the 36.6-acre basin. In the case of a storm event where the runoff exceeds the volume of the treatment area, a diverter within the baffle box sends the remaining pre-treatment runoff down the existing swale and into the river.

A nutrient-separating baffle box acts as a pre-treatment device which will be given a removal rate of 19% for Nitrogen and 15.5% for Phosphorus. Total removal for the baffle box and the dry retention diversion equals 70% total TN removal and 69% total TP removal.
The existing hydrology was modeled in XP-SWMM 2009. The resulting flow rate was used to do a preliminary design of the proposed retention pond and control structures. The proposed hydrology was modeled by modifying the existing hydrology model to reflect the proposed improvements to show proposed drainage equal to existing conditions. The significance of this project is that it is designed so a large volume of runoff can percolate through the dry retention area, although there is very little elevation change prior to outfall into the river. The custom design of the floating weir allows this additional water quality treatment to occur while maintain volume capacity to a flood sensitive area.