Q2 — Designing for the Quality as well as the Quantity of Water: A Review of the Kansas City Manual of Best Management Practices

The Kansas City metropolitan area chapter of the American Public Works Association (APWA) adopted a new Best Management Practices Manual for Stormwater Management (BMP manual) in November 2003 as a reference document. The chapter did not adopt the BMP manual as a standard because the membership believed many communities were not ready to fully implement BMP programs. Since that time, a few communities in the KC metro have adopted the BMP manual as a design standard for new development. The BMP manual uses TR-55 methodology for calculating changes in volumes of runoff and peak rates as its basis. The changes in volume and rate of runoff are related to a required level of service to be provided by BMPs to minimize impacts of development. BMP level of service is defined by the overall percent removal provided by each type of BMP and its ability to detain or infiltrate runoff. This methodology was developed to allow design engineers flexibility in choosing the BMPs that best fit the site being developed based on common calculations that most engineers understand and have completed. By incorporating the ability of a BMP to detain or infiltrate runoff in the assigned level of service, the BMP manual places a high priority on those BMPs that minimize volume of runoff. The manual steers the design engineer towards maintaining natural areas and minimizing imperviousness to minimize impacts. The City of Lenexa conducted a series of evaluations where site designs were modified to incorporate the requirements of the BMP manual. Residential and commercial sites were chosen for the evaluation. This was an office exercise to show the community leaders that the BMP manual would not increase the costs of site development and that its methodology was practical and achieved the goal of minimizing impacts of new development. Several new developments have been designed using the BMP manual. The lessons learned and an assessment of the BMP manual's effectiveness will be provided.