05/12/2004 P&Z Packet - Laserfiche WebLink

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Engineering Review Page 3 April 8, 2004 ox Den Acres ity of Lino Lakes, Minnesota 4. Minimum grades and slopes must be provided and shown on the Plans as follows: 0.5% for streets (including curb and gutter), and 2.0% for turfed/non -paved areas including all swales and slopes. 5. Proposed house pad information, including floor elevations are provided on the Plans, including the City's requirements for floor elevations. The minimum lowest floor must be the greater of 2 feet above the HWL, 4 feet above the NWL, 4 feet above the groundwater elevation, and 1 -foot above the emergency overflow. The emergency overflow elevation and location is shown on some but not all ponds. In addition, it appears that at least some of the units do not meet the minimum 4 feet separation from the NWL. The emergency overflow information must be provided at all locations on the Plan, and the proposed floor elevations shall be reviewed and adjusted as needed. The Grading Plans shall specify that all house pads on filled areas shall be designed by a registered Professional Engineer (per geotechnical recommendations) and approved by the City of Lino Lakes. 6. The submittal of a geotechnical and groundwater investigation and report is essential for determining pond capacities and minimum low floor elevations. For example, the Ordinary High Water Elevations of many of the existing wetlands are higher than the lower elevations of some of the proposed NURP /detention ponds. This must be investigated further to assure that drainage will function as required. 7. At Lot 17, Block 4, it is indicated that a future retaining wall will be needed. A wall location and additional information to clarify must be provided. 8. On the Preliminary Plat, drainage and utility easements along all property lines shall be provided per typical detail provided. In addition, drainage easements shall be provided around all wetland and detention areas to cover the 100 -year levels and provide access for maintenance vehicles /equipment. 9. At least three of the lots are indicated as "custom graded ". Additional grading information shall be submitted. 10. A Certified As -built Survey shall be provided by the Developer's Engineer upon completion of grading, certifying that all grading complies with the Grading Plan. This Certification shall be required prior to the issuance of any building permits. Final certification that the grading meets City requirements for adequate drainage and minimum slopes will be required prior to the issuing of building permits. Percent grades shall be shown on the Plan. 11. Storm Sewer System and Drainage Calculations: a. Existing condition computations are acceptable. Proposed condition curve numbers and time of concentration are acceptable. However, the discharge rates from the proposed 2 -, 10 -, and 100- year design rainfall events cannot exceed the existing conditions discharge rates. It is helpful to provide a discharge rate comparison table with the revised discharge rate calculations. b. The City Standard for storm sewer systems is the 5 -year rainfall event for this type of residential development. However, a 10 -year design storm system will also be accepted. c. Minimum storm sewer pipe full velocity is 3 feet per second; 2.5 feet per second was used on the submitted Plans and calculations.