Laserfiche WebLink
<br />kimley-horn.com 767 Eustis Street, Suite 100, St. Paul, MN 55114 651-645-4197 <br /> <br />MEMORANDUM <br />To: City of Hugo <br />From: Stephanie Thulien, PE <br /> Ron Leaf, PE <br />Justin Conner, PE <br />Date: June 1, 2020 <br />Subject: City of Hugo Maintenance Facility Preliminary Stormwater Design Summary <br /> <br />The purpose of this memo is to summarize the stormwater permitting requirements for the City of <br />Hugo Maintenance Facility site and the corresponding preliminary design approach to address these <br />requirements. <br />SITE DESCRIPTION <br />The Maintenance Facility site is located north of 140th Street North between Irish Ave N and Hyde <br />Ave N in the City of Hugo. Proposed improvements include a new building, entrance driveway and <br />parking/storage lot. The site is proposing to create 7.33 acres of new impervious surface. <br />Future improvements include a community room and additional parking areas. These improvements <br />are included in the proposed stormwater management approach and are included in the 7.33 acres of <br />new impervious. The existing site generally drains in two directions; to the north and to the south. <br />Proposed site conditions will generally follow existing drainage patterns. <br />STORMWATER MANAGEMEN T REQUIREMENTS <br />The Maintenance Facility site will trigger the following stormwater management rules, that the City of <br />Hugo enforces, and issues permits for, based on Rice Creek Watershed District (RCWD) stormwater <br />requirements. A stormwater permit is required for any development that creates 10,000 square feet <br />or more of new impervious surface. <br />Volume Control/Water Quality <br />Water quality volume is required for 1.1 inches off the proposed new impervious for the site. A TP <br />removal factor of 0.65 must be applied where infiltration is not feasible and biofiltration is used. Based <br />on soil borings, a biofiltration basin is proposed to treat the north drainage and an infiltration basin is <br />proposed to treat drainage to the south. Pretreatment structures will be added in any locations where <br />stormwater discharges into the basins. Below is a summary of sizing of the basins. <br />• North drainage <br />o New impervious: 5.23 acres <br />o Water quality volume (based on 1.1 inches): 0.48 ac-ft <br />o Water quality volume with TP removal factor of 0.65: 0.74 ac-ft