Updates to the MIDS calculator
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This page is under construction
This page is under construction
Version 2 of the MIDS calculator was updated in 2016. Version 3.0 includes the following changes from Version 2.
- When a user opens the calculator (either an existing file or a new file), the Site Information tab appears. In Version 3 of the calculator, the user must specify whether they are using the calculator to determine compliance with a Construction Stormwater permit. If the user answers "YES", the Stormwater disconnection (Impervious disconnection) BMP will not be available. The Stormwater disconnection (Impervious disconnection) BMP does not meet the permit requirement that "The Permittee(s) must design infiltration or filtration systems that provide a water quality volume (calculated as an instantaneous volume) of one (1) inch of runoff (or one (1) inch minus the volume of stormwater treated by another system on the site) from the new impervious surfaces created by the project." The Results tab indicates whether the calculations are for compliance with a Construction Stormwater permit. If the user selects "NO" to the question about whether the calculator is being used for permit compliance, the Stormwater disconnection (Impervious disconnection) BMP will be available. For a description of this BMP, see the next bullet.
- A Stormwater disconnection (Impervious disconnection) BMP was created. Stormwater disconnection/Impervious surface disconnection spreads runoff generated from parking lots, driveways, rooftops, sidewalks and other impervious surfaces onto adjacent pervious areas where it can be infiltrated. All pollutants in the infiltrated water are credited as being reduced. Pollutants in the stormwater that bypasses the best management practice (BMP) receive 68 percent removal for total suspended solids (TSS) and 0 percent reduction for both dissolved and particulate phosphorus. Guidance, methodology, and an example are provided on this page. A summary of the calculation methodology is found at this link.