Agenda - Council Work Session - 02/23/2021

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Permit Extensions Extensions to LRRWMO permits may be granted. When an extension is granted, the LRRWMO stormwater standards in effect at the time of the original permit issuance shall continue to apply. The procedure for extensions varies for platted and non -platted projects as follows: For Aatted, )ro'ects„ LRRWMO permit extensions shall automatically follow extensions granted by the City for that same project. The applicant is responsible for notifying the LRRWMO in writing if such an extension is granted by the city. In cases where a project must reapply to the City for a preliminary plat, either because of expiration of the original permit or changes to the project, the permitee must also reapply for a LRRWMO permit and will be subject to any new LRRWMO stormwater standards enacted since the issuance of the original permit. For non -platted projects, the applicant must apply to the LRRWMO for a permit extension before the end the two year permit life. Such requests will be considered by the LRRWMO Board on a case -by -ease basis, and will only be granted if the proposed project has not changed since the issuance of the original permit. Satisfaction of Pe The LRRWMO stormwater treatment permit requirements shall be deemed satisfied when stormwater infrastructure has been built to meet LRRWMO permit requirements and required performance has been verified (other permit aspects, such as erosion control, may remain outstanding). Activities or construction consistent with the original permitted project plan occurring at a later date do not require a new LRRWMO permit nor are they subject to new LRRWMO stormwater treatment standards that may have been enacted since the issuance of the original permit. The following example serves to clarify how this provision would apply to a phased common plan of development. Consider an example where a common plan of development will be built in several phases, including grading, stormwater infrastructure, and several phases of building construction. A LRRWMO permit must be secured for the multi -phase common plan of development. Once stormwater infrastructure is constructed and found to be performing to the standards required by the permit, the stormwater standards for all phases of the common plan of development will be considered satisfied. Subsequent phases of construction will not be subject to additional LRRWMO stormwater standards, even in the event that the LRRWMO standards are changed. However, if later building construction occurs that is not consistent with the original common plan of development, then a new LRRWMO permit would be triggered and stormwater standards in effect at that time would apply. Storm Sewer Design Except as noted in this document (LRRWMO Stormwater Standards), the design of storm sewers shall be reviewed and approved by the municipality, not the LRRWMO. The LRRWMO must review and approve basin inlets and outlets. Stormwater Basin Sizin and Desi )n Hydrologic and hydraulic design of stormwater basins shall be based upon: For basins that are not landlocked —Available storage volume shall be based on 100-year return period, 24-hr, duration, Atlas 14 rainfall using the NRCS MSE-3 distribution with average soil moisture conditions (AMC 2). Rainfall amounts using the National Oceanic and Atmospheric Administration's update Precipitation Frequency Atlas for the Midwestern States (Atlas 14, Volume 8) can be found at v, Comprehensive Watershed Management Plan Lower Rum River Watershed Management Organization October 2011 E-3