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Review File: Brookfield 8th Addition <br />Final Plat Exhibits <br />Engineering Review <br />February 7, 2017 <br />Page 4 of 5 <br />C 2.1 <br />1. Correct the plat name in all instances in this sheet. The plat name is "Brookfield 8th <br />Addition". <br />2. Revise paragraph "... or as directed by the City." to read " The City requires a sweeper on <br />site or the ability to have one on site within 3 hours after notification by the City that <br />sweeping is required" <br />C 2.2 <br />1. The MPCA will be assigning a TMDL for dissolved oxygen to Trott Brook. Information <br />in the SWPPP will need to be revised to reflect this change. <br />Detail Sheets <br />1. Add typical section for 168th Circle with dimensions, grades, and pavement section. <br />2. Remove detail SEW-6. <br />Stormwater Calculations <br />A stormwater summary report was provided. The stormwater modeling identifies 3 existing <br />drainage areas and 4 proposed drainage areas. The model routes all flows to a central point for <br />comparison of the flows. The report indicates that the volume reduction required by the <br />LRRWMO for the 10 and 100 year events is achieved. Our review indicates the volume control <br />is not achieved as shown below. <br />Existing <br />Area Description <br />Al SE Side <br />A2 Trott Brook Side <br />A3 Mitigation Area <br />2 yr. 10 yr. <br />0.48 2.13 <br />2.18 7.72 <br />0.86 2.24 <br />100 yr. <br />6.66 <br />22.3 <br />5.65 <br />Proposed <br />Area Description 2 yr. 10 yr. 100 yr. <br />1 SE Side 0.88 2.56 6.69 <br />2 Trott Brook Back yards 2.68 6.5 15.62 <br />X "Pond 1 Front Yards and Street" 3.79 6.54 13.42 <br />Total to Trott Brook 6.47 13.04 29.04 <br />3 Mitigation Area 0.67 1.63 3.91 <br />Difference <br />Area Description 2 yr. 10 yr. 100 yr. <br />1 SE Side 0.4 0.43 0.03 <br />2 Trott Brook Side 4.29 5.32 6.74 <br />3 Mitigation Area -0.19 -0.61 -1.74 <br />Net Change in Runoff <br />4.5 5.14 5.03 <br />