07/25/2007 Env Bd Packet - Laserfiche WebLink

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• Modeling must conform to Technical Release #20 of the U.S. Department of Agriculture, Natural Resources Conservation Service, and subsequent guidance, and composite curve numbers may not include directly connected impervious surface (Paragraph 3(a)(i)). • The critical 100 -year precipitation events are explicitly defined as the 24 -hour rainfall and the 10 -day snowmelt (Paragraph 3(a)(iii)). • Stormwater modeling for the peak flow and volume criteria need only consider the two -year and 100 -year critical events, and not the one -year event (Paragraph 4(i)). Also, application submittal requirements would be amended to require soil borings in the locations of all proposed stormwater management facilities (Paragraph 4(d)). G. Easement Requirements and Facility Maintenance Obligations The stormwater rule presently requires an applicant to provide an easement for District review and approval. The proposed rule would clarify the easement requirement (Paragraph 4(m)). First, it would state clearly that a flowage easement is required over the area inundated by the 100 -year, 24 -hour storm for all surface elements of the stormwater system and all on -site floodplain. Second, it would clarify that the easement is for the benefit of the land use authority, in accordance with the nearly universal practice to require easement dedication as a part of platting or municipal development approval. The District does not wish to require property owners to convey duplicative easements. Third, however, the rules would explicitly require that an easement on a public ditch be a minimum of 33 feet on each side of centerline, and that the District's ability to enforce this restriction be established. As ditch authority, the District holds right -of- way for public ditch systems and must keep the area adjacent to its ditches clear so that maintenance can be performed. It was widespread practice at the time the District's public systems were established, early in the previous century, for right -of- way to be set at 66 feet (four rods) on centerline for maintenance access. At this time, some landowners may not be mindful of this constraint. The rule would provide a reminder. 12 • • •