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4.a 3 Comments submitted by Watershed District via email 11 01 2016COMMENTS FROM CARNELIAN MARINE ST. CROIX WATERSHED DISTRICT From: Carl Almer Sent: Wednesday, October 19, 2016 11:07 AM To: 'ishaver@croscwd.org' Subject: RE: variance application in Scandia (Smith Garage) Jim, If approved by the City, the variance for setback from the St. Croix River would trigger a CMSCWD Permit and compliance with Rules 2 (Stormwater Management), 3 (Erosion and Sediment Control) and 4 (Buffers). The proposed 24x24 ft garage result in a net increase in impervious surface of approximately 440 SF. Per the District's Small Residential Project Stormwater Worksheet, this project would require a stormwater BMP sized with a treatment volume of approximately 65 CF. With the SP -SM soils onsite, stormwater management would best be in the form of a small infiltration trench or french drain, maybe paired with a rain barrel if the garage is guttered. Additional detail is required for proposed excavation into the hillside, retaining wall and finished grades. A grading plan with proposed erosion and sediment control will be necessary to assess compliance with Rule 3. Rule 4 Exceptions 4.9.4 & 4.9.5 are likely applicable in determining the St. Croix River buffer width: • 4.9.4 For properties where the existing primary structure location does not conform to the setback under the applicable shoreland ordinance and the structure location is not required to be brought into conformance with the applicable setback, the buffer width shall be 50% of the existing distance between the structure and the OHWL, delineated wetland edge, or top of bank as applicable to the resource. • 4.9.5 A 30 -ft clear zone from primary structures may be maintained within the Outer zone of a stream buffer. Carl K. Almer EOR: water I ecology I community d: 651.203.6024 o: 651.770.8448