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HomeMy WebLinkAbout6.5.2013 plan review(Health and Wellness Suites)Health and Wellness Suites of Carmel American Structurepoint, Inc. June 5, 2013 Page 1 of 4 June 5, 2013 1st Review Mr. Ross L. Nixon, P.E. American Structurepoint, Inc. 7260 Shadeland Station Indianapolis, IN 46256 RE: Health and Wellness Suites of Carmel Drainage Review Technical Advisory Committee Engineering Review for Development Drainage Designs Dear Mr. Nixon: The stormwater review of the construction plans dated May 17, 2013 and drainage calculations dated May 17, 2013 for the above referenced project has been completed. The submittal is in need of additional information in order to be in compliance with the City of Carmel Stormwater Technical Standard Manual (the Manual). Please revise the plans and calculations in accordance with the comments below: 1. Per Section 102.02 v.b, please provide normal water elevation for the pond adjacent to the southeast corner of the project site. 2. Per Section 102.02 v.g, please provide the land uses of the adjacent properties. 3. Per Section 102.02 vii, please revise the plan/profile sheets to include the elevations, location of all proposed storm sewers, including subsurface drains, top of casting elevations, structure numbers, pipe invert elevations, casting type, structure type, and all existing and proposed utility crossings also shall be indicated. Plan and profile sheets are subject to further review and comment after aforementioned information is provided. 4. Per Section 102.02 xi, a grading plan shall include the following: g. Please provide the 100 year overflow paths ponding areas shown as hatched areas with all associated easements. h. Indication as to the system being public or private. j. Location, size and dimensions of detentions facilities including pond elevations, pond bottom elevations, top of bank elevations, spillway location and elevations, and transverse slopes of dry detention areas. k. Emergency flood routing path(s) and their invert elevations from detention facilities to the receiving system. l. One or more typical cross sections of all existing/proposed channels (swale at the outlet of the detention pond) and other open drainage facilities (detention pond) carried to a point above the 100-year high water and showing the existing land and proposed changes together with the high water elevation expected from the 100- year storm. Please provide typical cross sections of the detention facility. Grading sheets are subject to further review and comment after aforementioned information is provided. Health and Wellness Suites of Carmel American Structurepoint, Inc. June 5, 2013 Page 2 of 4 5. Per Section 102.02 xiv, please revise the Structure Data Table in the plan set to include, at minimum, the following: upstream structure number, downstream structure number, upstream pipe elevation, downstream pipe elevation, pipe length, pipe material, type of structure, and detail reference to the type of structure and any notes related to the structure. Please review and revise accordingly. 6. Per Section 102.03 i.a.i, the pre-development watershed map shall include the drainage area designation corresponding to the designation in the drainage calculations, the area in acres for each drainage area and any off-site drainage areas that need to be accommodated by the system, including the fully developed right-of-way per the City of Carmel Thoroughfare Plan. It appears the fully developed Right-of-Way per the City of Carmel Thoroughfare Plan was not included in the existing drainage basin. Please review and revise accordingly. 7. Per Section 102.03 i.b.ii, the proposed watershed map shall show that all off-site acreage draining through the site is accommodated, including the fully developed right-of-way per the City of Carmel Thoroughfare Plan. It does not appear the fully developed Right-of-Way was included in the proposed watershed map. Please review and revise accordingly. 8. Per Section 102.03 i.b.iv, please include the runoff curve numbers and time of concentration on the existing drainage basin map. 9. Per Section 104.02, the buildings lowest entry elevation that is adjacent to and facing the road shall be a minimum of 15 inches above the road. Also, finished floor elevations or the lowest building entry elevations shall be no less than 6 inches above the finished grade around the building. Also, minimum flood protection grade of all structures fronting a pond shall be no less than 2 feet above any adjacent 100-year local or regional flood elevations, whichever is greater. Please provide elevations for the finished floor and the minimum lowest adjacent grade, as well as the 100-year elevation in all storage basins including underground storage facilities in the pervious pavement. 10. Per Section 302.04, the initially determined hydrologic group for disturbed areas should be changed to the next less infiltrating capacity category (i.e., A to B, B to C, and C to D). It does not appear that the on-site soils have been adjusted accordingly. Please review and revise accordingly. 11. Per Section 302.06.1, the detention facility shall be designed in such a manner that a minimum of 90% of the maximum volume of water stored and subsequently released at the design release rate shall not result in storage duration in excess of 48 hours from the start of the storm. Please review and revise accordingly. 12. Per Section 302.06.4, all stormwater detention facilities shall be separated from any road right of way by no less than fifty (50) feet. Please review and revise accordingly. 13. The proposed wet detention basin shall be designed in accordance with allowable release rates per Section 302.03 of the Manual and the restricted release rates of the Hamilton County surveyor. Detention calculations are required to be provided that indicates the orifice size required to limit the release to acceptable rates, the resulting critical pond and spillway Health and Wellness Suites of Carmel American Structurepoint, Inc. June 5, 2013 Page 3 of 4 elevations, and that sufficient volume provided to accommodate the release rates being limited to the acceptable rates ( they have been provided within the submitted drainage report). The critical pond elevations resulting from this method of modeling shall be used in the MFPG/MLAG determinations. Since the resulting orifice size is less than the minimum 6-inch orifice requirement of Section 302.06.07, the lower orifice shall be upsized to a 6-inch diameter orifice. The upper orifice should then be sized appropriately to restrict the 100-year storm to the required restricted release rate. Stormwater modeling information shall be provided for both scenarios in the drainage report. Please note that the invert elevations of the orifices shall be designed so that the outlet structure can be revised to meet the restricted release rates, if required in the future. Please review and revise accordingly. 14. Per Section 302.06.12, detention basins shall be sized to detain the runoff from the fully developed right-of-way per the City of Carmel 20-year Thoroughfare Plan across all frontages, regardless of existing watershed boundaries or drainage breaks/divides. The acreage of the full right-of-way width may be included in the overall acreage of the development in determining the allowable release rates. Please review and revise accordingly. 15. Per Section 303.07, the ponding and overflow path throughout the development resulting in the 100-year storm event, in the instance the drainage system is completely plugged should be clearly shown in a hatched area. Also, all buildings shall have a minimum flood protection grade no less than 2 feet above any adjacent 100-year local or regional flood elevation. 16. Per Section 305.05, the inlet grate design shall be adequate to pass the design 10-year flow with 50% of the sag inlet clogged. It does not appear this was taken into account, please review and revise accordingly. 17. Per Section 306.02.D, a minimum of 15 feet beyond the actual footprint (top of the bank or the 100-year pond elevation if no top of bank is present) of stormwater detention facilities shall be designated as drainage easement. A minimum 20-foot width easement shall also be required as access easement from a public right-of-way to the facility. 18. Based on concerns raised by the HCSO and the Carmel Engineering Department, please revise the drainage report to include calculations for a downstream analysis of the proposed receiving system for the discharge from the site. The analysis should verify the required and provided capacity of the swale at the outfall of the detention outlet and of the receiving regulated drain storm sewer system. Also, peak flood elevations should be analyzed within the receiving swales in comparison to the eastern adjacent development (invert elevation of the detention outlet appears to be higher than spot grades at the property line and within the adjacent parking lot). And lastly, the condition and flow characteristics of the receiving swale should be analyzed. 19. In review of the existing drainage conditions on site, it appears that the project area currently drains south/southeast to the adjacent off-site detention pond. Depending on the results of the downstream analysis requested in Comment #18, this off-site detention pond may be a more adequate receiving system for the detained site discharge. It will need to be verified that the approved drainage calculations for the off-site pond accounted for this watershed area, and that the detention facility is sufficient to handle the project’s detained flow prior to approval. Also, additional coordination should be completed with the HCSO and the Carmel Engineering Department for this scenario prior to approval. Health and Wellness Suites of Carmel American Structurepoint, Inc. June 5, 2013 Page 4 of 4 Please include with your construction plans, and secondary plat submittal, one (1) copy of the comments indicating the action taken or a written explanation for action not taken in respect to the above comments. The construction plans, drainage calculations and secondary plat are not to be submitted without implementing changes with respect to these comments, and any and all review comments from the City of Carmel and the Hamilton County Surveyor’s Office. CrossRoad Engineers, P.C. 3417 South Sherman Drive. Beech Grove, IN 46107 Once all other agency approvals are obtained, a .pdf of the final drainage report shall be supplied to the Carmel Engineering Department when the final construction sets of plans are submitted for stamped approval. Please contact me at (317) 780-1555 ext. 112 with any questions. Sincerely, CrossRoad Engineers, P.C. Gregory J. Ilko, P.E. Senior Project Manager copy: Gary Duncan, City of Carmel Assistant Engineer Greg Hoyes, Hamilton County Surveyors Office John Thomas, City of Carmel MS-4 Operator Amanda Foley, City of Carmel Engineering Department File