In 2011; the Minnesota Department of Transportation (MnDOT) installed an iron-enhanced sand filter (IESF) at Trunk Highway (TH) 610 and County Road 81 in Maple Grove; Minnesota. This feature is a two-cell filtration system into which part of Trunk Highway 610 and County Road 81 drain. From 2012 through 2018; MnDOT monitored the influents and effluents into the IESF to determine its effectiveness in removing particulate and dissolved phosphorus from stormwater runoff from the nearby highways. MnDOT also retained Barr Engineering Co. (Barr) to analyze the data collected during this period. As part of the data analysis; Barr developed a hydrologic model to account for all inflows and outflows from the system. The model was calibrated to the data collected in 2018 and applied to the prior years. The results of data analysis and watershed modeling showed that all influents and effluents have not been accounted for and the collected data were inconclusive in assessing the effectiveness of this IESF. This report summarized the analyses performed on the data collected; determined the potential effectiveness of the IESF; and provided some guidelines for design and future monitoring of other IESFs.