Agenda - Council - 02/23/2016 - Laserfiche WebLink

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Review File: Northfork Alpine Addition Preliminary Plat Request Engineering Review Page 2 of 2 4. The outflow path from the pond to the wetland must be defined with spot elevations and contours. 5. The maximum slope shall not exceed one foot vertical to four feet horizontal. . 6. The font size/ pen weight of labels must be increased to make plan readable. The sizes of the existing and proposed contour labels should be swapped, the proposed labels should be larger than the existing labels. 7. Additional proposed contours are required on lot 2 to show how the house pad will blend in with existing grade. 8. The pond should be moved farther east on lot 4 or the area reserved for the septic system should be made narrower and longer to provide a route to the back yard if the future homeowner desires to build a shed there. 9. The drainfield and alternate areas shown must be protected with fencing prior to any grading on the site. 10. A utility sheet will be required showing the storm sewer structure rims and inverts, pipe sizes, slopes and lengths. 11. A legend must be provided. 12. The details must be Ramsey standard details. 13. The pond outlet to the wetland must have a skimmer structure. 14. The west infiltration basin does not have an outlet. It must be modeled for back to back 100 years storms. The adjacent basement grades must be adjusted to provide the necessary vertical separation per the Lower Rum River Water Management Organization (LRRWMO) rules. Staff offers the following comments on the drainage calculations submitted with this application plan. The calculations indicate adequate infiltration volume is provided on the site in the infiltration basin and ponding area. The plans indicate that all of the runoff from the street is directed to the pond on the east side of the proposed street. It appears that the bottom of this pond is less than 2 feet above the ground water elevation expressed in the wetland. This are is not eligible for infiltration credit. The catch basins should be directed to the infiltration basin. An overflow outlet can be provided in the eastern catch basin to allow flow to go to the pond for 2 year and larger events. This will remove the need for modeling back to back storms listed in note 14. A permit from the LRRWMO has been issued. All provisions of the permit must be complied with. Review of the permit memo indicates additional information was provided to the LRRWMO engineer beyond the information provided to the City. A copy of all data provided to the LRRWMO must be forwarded to the City. Utilities: All lots are proposed to be served by well and septic. The septic design report must show the locations of the borings performed for design of the septic systems.