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Item 3.2 Hansen Heights Review No. 1 ENGINEERING REVIEW Residential Subdivision for the City of Otsego by Hakanson Anderson Submitted to: Honorable Mayor and City Council cc: Adam Flaherty, City Administrator Audra Etzel, City Clerk Dan Licht, City Planner Dave Kendall, City Attorney Scott Dahlke, P.E., Civil Engineering Site Design Henry Hansen, VHF Investments, LLC Reviewed by: Ronald J. Wagner, P.E. Brent M. Larson, P.E. Date: August 11, 2021 Proposed Development: Hansen Heights (1st Addition) Street Location A portion of the SE ¼ of Section 28, T121, R23 and a portion of of Property: the SW ¼ of Section 27, T121, R23. East of Odean Avenue NE and North of 70th Street NE. Applicant: Henry Hansen Developer: VHF Investments, LLC 6750 Stillwater Blvd N #4 Stillwater, MN 55082 Owners of Record: VHF Investments, LLC Purpose: Hansen Heights is a proposed preliminary plat of 131 lot (includes 2 existing lots) and final plat of 65 single-family residential development on approximately 92.4 acres in the City of Otsego, Wright County, Minnesota. The proposed development will be served with municipal water, sanitary sewer, storm sewer, and public streets typical of an urban setting. Jurisdictional Agencies: City of Otsego, Wright County, Minnesota Department of (but not limited to) Health, Minnesota Department of Natural Resources, Minnesota Pollution Control Agency, Wright Soil and Water Conservation District. Permits Required: NPDES, Minnesota Department of Health (water), (but not limited to) Minnesota Pollution Control Agency (sanitary sewer), and Wright County PAGE 2 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx TABLE OF CONTENTS INFORMATION AVAILABLE PRELIMINARY PLANS FINAL PLAT GRADING AND DRAINAGE PLANS (PHASE 1) COVER SHEET GRADING AND DRAINAGE PLAN EXISTING CONDITIONS AND REMOVALS SWPPP CONSTRUCTION PLANS (PHASE 1) COVER SHEET OVERALL LAYOUT/NOTES SANITARY AND WATER UTILITY PLANS STORM SEWER AND STREET PLANS DETAILS SURFACE WATER MANAGEMENT WETLANDS OTHER CONSIDERATIONS SUMMARY AND/OR RECOMMENDATION PAGE 3 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx INFORMATION AVAILABLE Preliminary Plans for Hansen Heights, dated 7/27/2021, by Civil Engineering Site Design. Final Plat for Hansen Heights, dated 7/26/2021, by Civil Engineering Site Design Construction Plans for Hansen Heights, dated 7/27/2021, by Civil Engineering Site Design Grading Plans for Hansen Heights, dated 7/27/2021, by Civil Engineering Site Design Landscaping Plan for Hansen Heights, dated 7/27/2021, by Civil Engineering Site Design Storm Water Management Plan for Hansen Heights, dated 3/26/19, by Civil Engineering Site Design. Storm Sewer Design Calculations for Hansen Heights, dated 3/26/19, by Civil Engineering Site Design. Wetland Delineation Report for Henry Hansen, dated 10/30/18, by AG Wetland Services, Inc. Additional Information Minnesota Rules, Chapter 4410 – EAW Requirement City of Otsego Engineering Manual City of Otsego Zoning and Subdivision Ordinances National Wetland Inventory Map PAGE 4 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx PRELIMINARY PLANS 1. Lot 6, Block 5 (Phase 1) is an existing home and will remain until a future phase where it is proposed to be divided into four single family lots. The two west lots would require direct access to Odean Avenue. We recommend that a single driveway be used for these two lots to access Odean Avenue. 2. The future trail from Ohland Avenue to the east has proposed contours only about ½ way down the hill. This trail shall be designed to the end point and shown that the alignment and slopes will meet all ADA and City requirements. FINAL PLAT 3. The east-west street just south of 75th Street is mislabeled Ohland Avenue, this shall be 75th Lane NE. 4. Verify the 20’ wetland buffer around the wetlands in Outlot A are contained within Outlot A. 5. A drainage and utility easement shall be placed over all of Outlots A and B. 6. Minimum 10’ easements shall be provided along all rear lot lines (i.e. lots along Outlot B and rear yards of Block 6, and rear yard of L1, Block 7). 7. The easement between Lot 13 and 14, Block 2 shall be a minimum of 50 feet wide centered on the sanitary sewer along this lot line. Or a drop manhole will be needed near the rear of the adjacent house pads with a shallower sewer pipe between the street and this manhole. 8. All cross drainage shall be covered by drainage easement or the grading plans shall be revised to show all drainage directed to the easement along the lot lines. 9. A utility easement will be needed to cover the sanitary and watermain stubs to the property south of Lot 6, Block 5. 10. A 100’ tangent between the reverse curves is required along 74th Street just west of Odell Avenue. GRADING AND DRAINAGE PLANS Cover Sheet 11. No comments. Grading And Drainage Plan 12. The ponds shall be labeled with a name/number on all sheets. This shall correlate with the naming in the storm water report. PAGE 5 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx 13. A maintenance path is shown for access to the Pond #6 between Lots 17 and 18, Block 2. This maintenance path shall be extended to provide access to the outlet structure at the east side of Pond #6 as well. The top of the berm around the pond shall widened to be a minimum of 10’ wide to accomplish this. 14. The wet pre-treatment basin for Pond #6 requires a 10:1 bench below the NWL. 15. The wetland buffer shall be shown on the grading plans. The buffer shall be 20’ wide. 16. The delineated wetland boundaries shall be labeled in the grading plans. 17. An emergency overflow elevation shall be labeled for the low area in the rare of Lot 1 and 2, Block 4. It appears to be approximately 924.6 over the existing driveway to the north which is sufficient freeboard from the proposed low opening elevations. 18. An EOF is needed for the low point in Odell Avenue, south of 75th Lane. 19. A minimum of 1.5’ of freeboard is required from all EOF’s to the lowest openings for all houses. (i.e. L15, B3 should be a minimum of 920.5). 20. Proposed lot corner elevations shall be provided for all lots (lots along 75th Street are missing rear elevations). 21. Additional spot elevations are required between houses on the side yard lot lines at the front and rear setback lines. Provide a spot elevation at the property line at the front/rear of the house if the adjacent house elevations are + 1.5 feet. The elevations shall be a minimum of 0.3’ below the lower house to provide to the side lot line. A number of lots may require retaining walls. 22. It s unclear why the dual elevations for the lot opening for Lot 3, Block 6 are required. The higher elevation do not agree with the contours in the area. 23. Cross drainage shall be contained with drainage and utility easements. The rear yards of Block 3 appear to have cross drainage that will not be within easements. 24. Draintile shall be installed along the rear lot lines to provide a connection point for all lots sump pumps if they are more than one lot away from a storm catch basin or storm basin. Draintile will be required for some Blocks 3, 5, and 6. Existing Conditions and Removals 25. No comments. SWPPP 26. Inlet protection shall be installed on all of the nearest catch basins and culverts located downstream from the construction entrance(s) along Odean Avenue. 27. A concrete washout area shall be called out. PAGE 6 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx 28. A double layer of erosion control is required around all wetlands if a minimum of 50’ of undisturbed vegetative buffer cannot be maintained. CONSTRUCTION PLANS Cover Sheet 29. No comments. Overall Layout/Notes 30. A water and sanitary sewer stub shall be provided to the west right-of-way at Sanitary Sewer MH 6. 31. The ponds shall be labeled with a name/number on all sheets. This shall correlate with the naming in the storm water report. Provide Pond #5 Normal and High water elevations. Sanitary And Water Utility Plans 32. Water services shall be on the upstream side of the sanitary sewer service. Some services along throughout the plans are switched. 33. The sanitary sewer manholes shall be revised to show 0.1’ of fall across the inverts. 34. The sanitary sewer and watermain crossing shall be directed to the north of the property line on the west side of Odean Avenue. City staff will work with the developers engineer to provide an acceptable stub location. 35. See comment #7 regarding sanitary sewer between 13 and 14, Block 2. Storm Sewer And Street Plans 36. The vertical curve at station 9+00 on Odell Avenue does not meet a 30 mph design speed and shall be revised. 37. No trash guards are required on pipe sizes less than 24” diameter. 38. The outlet pipe and structure for Pond #5 does not appear to provide any rate control or skimming. This will required discussion with the developers engineer. Details 39. Additional detail and spot elevations are required for all pedestrian ramps to depict the comply with ADA requirements. PAGE 7 S:\Municipal\Aotsego23xx\2346 Hansen Heights\A-REVIEW PHASE\OT2346 RVW1.docx SURFACE WATER MANAGEMENT 40. No new stormwater calculations or storm design calculations have been submitted with this resubmittal. A new updated stormwater management plan and storm sewer design calculations shall be submitted to agree with the current revisions. The overall layout of the site has only changed slightly with the exception of some ponding being infiltration basins. We would assume that the changes would be minor and the site will function as originally planned. 41. Submit a geotechnical exploration report. Verify existing ground water elevations are a minimum 3’ below infiltration basin(s) bottom. Percolation tests will be required at the proposed infiltration basin locations to verify designed rates. 42. Pre-treatment of the storm water into infiltration basin 5 is required. 43. Previous comment - Please submit inlet spread calculations (only needed for critical CBs i.e. CB 50 & 51) WETLANDS 44. A Wetland Delineation has been submitted and approved (Notice of Decision dated 12/20/2018). This is still valid as it is within 5 years of the current project. No wetlands are proposed to be impacted by this project. OTHER CONSIDERATIONS 45. A Geotechnical Exploration Report prepared by a professional engineer shall be submitted with a recommended R-value for the street section design. 46. A statement certifying the environmental condition of the site including the presence of any hazardous substance as defined in Minnesota Statutes 115B.02, Subd 8 is required. Developer’s Engineer has indicated that they have confirmed with the property owner that no hazardous substances are known. This shall be confirmed in writing. SUMMARY AND/OR RECOMMENDATION We recommend approval contingent upon the above items being addressed.