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• Mr. Steve Wensman November 22, 2000 Page Two • In the northeast corner of the plat, there is a very steep rear yard on Lot 2, Block 4, and there are proposed contour lines that end in the existing 196th Lane. Clearly, this is not how the road is or will be graded in the future. This area should be reviewed and adjusted. • After reviewing the comments on drainage relative to the high water level, the grading plan should be re-checked to ensure that all pads reflect minimum openings, at least one foot above the high water level or emergency overflow elevation. 2. Drainage Calculations The following is a list of general comments regarding the review of the drainage calculations submitted from Pioneer Engineering: • A 100-year rainfall event versus a 10-day snowmelt event was used to analyze the runoff from the development. Three major ponds have high water levels based on a 10- day snowmelt event. The rest of the ponds appear to have high water elevations based on a 100-year rainfall event. Since the ponds are interconnected, a 10-day snowmelt event is likely the most critical for all the ponds. New high water elevations should be calculated for all ponds using a 10-day snowmelt event. • With the re-analysis of the pond high water level, the building pad elevations and minimum opening elevations need to be verified for each lot adjacent to the ponding • areas. Also, the size of the drainage and utility easement needs to be re-verified to ensure that it encompasses the entire inundated area. • Emergency overflows with spot elevations need to be shown for all ponds where necessary. • An existing conditions model should be provided for the site along with a corresponding drainage map. • Additional storm sewer and inlet structures will need to be provided along several of the streets, such as Dodge Avenue, which shows 1650 LF of street drainage flowing to one set of inlets. 195th-196th Circle, Baldwin Street, and 196th Lane also should be re- analyzed for additional storm sewer. 3. Miscellaneous Items The following items should be considered in the re-submittal. • There are several places where the grading of the site impacts wetlands on the site. It appears there is sufficient impact on the wetlands that this project will need to go through the Wetland Conservation Act process. • Phasing of the development has been discussed. Staff feels that phasing should be accomplished such that none of the new traffic from the Hillside Estates 8th Addition is encouraged to use Auburn Street for ingress or egress. In other words, the phasing should start on the west side of the development and direct traffic either down Dodge Street to 1931d Avenue or westerly on 196th Lane to Evans Street. ID Ltr 112200 Wensman.doc Howard R. Green Company CONSULTING ENGINEERS