This section will eventually have information about the MIDS calculator, including a Manual and a link to the calculator. Below is a tentative outline for the section. Pages highlighted in blue are partly populated.
A Minimal Impact Design Standards (MIDS) best management practice (BMP) calculator was developed to assist designers and regulators in determining conformance to the MIDS performance goals The MIDS BMP calculator is a tool used to determine stormwater runoff volume and pollutant reduction capabilities of various low impact development (LID) BMPs. The MIDS calculator estimates the stormwater runoff volume reductions for various BMPs based on the MIDS performance goal (1.1 inches of runoff off impervious surfaces) and annual pollutant load reductions for total phosphorus (including a breakdown between particulate and dissolved phosphorus) and total suspended solids (TSS).
The MIDs calculator is designed in Microsoft Excel with a graphical user interface (GUI), packaged as a windows application, used to organize input parameters. The Excel spreadsheet conducts the calculations and stores parameters, while the GUI provides a platform that allows the user to enter data and presents results in a user-friendly manner.
The MIDS calculator is divided into four main components: the “Site information” tab, “Schematic” tab, “BMP Properties” window, and “Results” tab. The “Site information” tab is where the user enters information for the entire site being studied. This includes information used to calculate annual precipitation for the study area, average pollutant concentrations in runoff from the entire site, as well as land used areas for the entire study area. The “Schematic” tab is where the user adds or removes BMPs to the site and provides a visual diagram of all BMPs and routing between BMPs. In the “BMP Properties” window the user enters land use areas, routing information, and design parameters specific to an individual BMP. Finally, in the “Results” tab, results are displayed for the entire site as well as individual BMPs. Results include pollutant removal rates and loads, annual volume reduction, as well as conformance to the MIDS performance goal. A detailed overview of individual input parameters and workflows is presented in the MIDS Calculator User Documentation. Below is a detailed discussion of the main objectives of the MIDS calculator and the calculations that take place to meet those objectives.
The calculator has five main objectives:
1) Calculates the stormwater runoff volume reduction performance goal for a site.
2) Calculates annual stormwater runoff volumes and pollutant loads (total suspended sediment, dissolved phosphorus, and particulate phosphorus) from site.
3) Provides a method to add stormwater BMPs, input BMP specific parameters, and route overflow stormwater and pollutants to downstream practices.
4) Calculate stormwater runoff volume reduction achieved toward the performance goal and annual stormwater volume and pollutant load reductions for each individual BMP and the entire site.
5) Report results, including stormwater runoff volume reduction applied toward the performance goal, annual pollutant load reductions for TSS, dissolved phosphorus, and particulate phosphorus, as well as annual stormwater volume reduction for the entire site and individual BMPs.
The MPCA trained over 50 people across the state to become “Super Users” of the MIDS Calculator. People on the list have agreed to help others use the calculator. Feel free to contact them if you have a question on how to use the calculator.