Nonpoint source pollution captured by urban stormwater runoff is the greatest challenge for surface water quality improvements. Computer-based design tools have been developed to help mediate this issue by guiding end users through the implementation of decentralized stormwater management. The majority of these tools focus on treatment via biofiltration, yet concern regarding this treatment regime is rising. Case studies from research past clearly indicate the susceptibility of groundwater to contamination from extensive anthropogenic activity at the surface. Contaminants, such as nitrates and pathogens, are not completely removed before runoff enters the underground watercourse. Additionally, national and state legislation, which explicitly lists where neglect for groundwater quality is permissible—exacerbate concerns. This research analyzes the efficiency the BMP Siting Tool developed by the US Environmental Protection Agency and the Grey-to-Green Decision Support Tool developed by the University of South Florida. The tools were used to obtain cartographic data illustrating suitable sites for bioswales and infiltration basins throughout northern portion of Hillsborough County, Florida. This data was then integrated with the Karst Aquifer Vulnerability Index (KAVI) groundwater vulnerability model. The area of bioswales and infiltration basins that intersected areas of the KAVI model listed as ‘highly vulnerable’ or ‘moderate-to-highly vulnerable’ was calculated. This permitted an assessment of which BMP facility had the greatest sitings atop vulnerable areas, respective of the tool. The BMP Siting Tool sited 2.80% of all bioswales and 27.89% of all infiltration basins above vulnerable areas. Likewise, the Grey-to-Green Decision Support Tool sited 21.66% of all bioswales and 9.62% of all infiltration basins above vulnerable areas. These results prompted the development of a supplemental groundwater vulnerability framework to be incorporated into both tools’ analytical process.