11/30/2021 EB Packet - Laserfiche WebLink

Home Search

Five soil borings were performed. All borings detected primarily poorly graded, fine grained sand. Ground water was detected at 10-12 feet in the 3 boring in area of the proposed building pad, and at 7 feet in one of the borings associated with the infiltration basin. Stormwater Management A stormwater management plan has been submitted and will receive a full review by the Engineering Department. The following summary review is based upon the same stormwater management plan and drainage calculations. Development of the site includes 10,873 sq. ft. (24.6%) of the total 44,258 sq. ft. area of the site becoming impervious surface. While zoning requirements allow for up to 65% impervious surface, the fact that the parcel is in the Shoreland Overlay brings the allowable impervious surface down to 60%. The site as proposed is in compliance with this requirement. Existing Conditions Per the Drainage Calculations Report, most stormwater (approximately 0.81 acres) currently drains to the wetland in the northwest. The rest (approximately 0.21 acres) drains southeast to Blue Heron Drive where the water enters the stormwater system through an inlet and heads to wetland and ultimately to Rice Lake. Proposed Conditions No impacts are proposed to the wetland in the northwest. An infiltration basin, along with a rain guardian and forebay for pretreatment, will ensure that the proposed impervious surface addition will not increase rate or volume of stormwater runoff for the 2-, 10-, or 100-year storm events. 2-YEAR 10-YEAR 100-YEAR EXISTING (CFS) (CFS) JCFS) WETLAND (111) 0.14 0.57 2.05 BLUE HERON DRIVE (1121 0.06 0.28 0.99 2-YEAR 10-YEAR 100-YEAR PROPOSED (CFSI (CFS) (CF5) WETLAND (111) 0.05 0.40 1.89 BLUE HERON DRIVE (RI) 0.06 0.17 0.47 Stormwater Pollution Prevention The Stormwater Pollution Prevention Plan (SWPPP) notes the locations of several Best Management Practices (BMPs) that will be installed to minimize erosion and sediment leaving the site. 3