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Home My WebLink AboutHOWES/CANYON MIXED-USE (CORTINA) - PDP - 45-02 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTlu;,A(A vdp�vz?& fcr*ICW 4A,6w,,b2sm Caws, * kAouzootp Kepi — t'dP oil, in one�(3PNAkQl w� � zs� WCJ>Acgp.*e... PROJECT LOCATION VICINITY MAP NOT TO SCALE 7 L 1 0 I I APPENDIX A VICINITY MAP W 1' WA elements have been designed to pass required minor storm flows and to minimize future maintenance. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. REFERENCES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March, 1986. 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated March, 1969, and Volume 3 dated September, 1992. 3. Old Town Master Drainage Basin Plan for the City of Fort Collins Summary Report by Resource Consultants & Engineers, Inc, dated January 7, 1992. 6 5. I 6. I structure will be maintained by the Home Owner's Association. EROSION CONTROL 5.1 General Concept This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins Zone Maps. The potential exists for silt movement from the site and into Spring Creek. Potential also exists for tracking of mud onto existing streets which could then wash into existing storm systems. The erosion control escrow amount is $4,830. 5.2 Specific Details To limit the amount of silt leaving the site several erosion control measures shall be implemented during construction. All existing and proposed inlets shall be protected with gravel filters and all boundaries shall have silt fence installed. A vehicle tracking pad shall be installed at the proposed drive to control the mud being tracked onto the existing pavement. During demolition, disturbed areas are to be kept in a roughened condition and watered to reduce wind erosion. CONCLUSIONS 6.1 Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Erosion Control Reference Manual for Construction Sites and the Storm Drainage Design Criteria Manual. 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans provide for stormwater quality treatment of proposed impervious areas to the greatest extent possible considering the existing improvements surrounding the site. Conveyance 5 5 V is currently no detention or water quality provided on site. It is proposed that a similar runoff pattern be maintained with the redevelopment of this site and water quality will be provided for the building runoff. 4.2 Specific Flow Routing A summary of the drainage patterns within each basin is provided in the following paragraphs. Basin 1 contains the southeastern portion of Canyon Avenue and adjacent buildings and parking. The runoff from this basin currently flows to the existing type r inlet in Canyon Avenue. A new inlet is proposed to capture this runoff and convey it to the existing storm system. Basin 2 contains the proposed parking lot. The runoff from this basin also currently inlet in Canyon Avenue. Another inlet is to flows to the existing type r new proposed capture this runoff and convey it to the existing storm system. Basin 3 contains the northeastern portion of Canyon Avenue and the adjacent walks and landscaped areas. Runoff from this basin will flow to the existing type r inlet as it has historically done. Basin 4 contains the majority of the site including the proposed building. Runoff from this basin will flow to a Stormceptor and be conveyed to the existing storm system. Basin 4A is a small basin that contains only the ramp into the subterranean garage. Runoff from this basin will be collected in a trench drain and conveyed to a sand/oil separator in the garage and then released to the sanitary sewer system. This is being proposed because the elevation of the trench drain into the garage is deeper than the existing storm system. 4.3 Drainage Summary The existing and proposed drainage facilities located outside in the right of way for Canyon Avenue will be maintained by ,the City of Fort Collins. The Stormceptor 4 U streets. 3.3 Hydrologic Criteria Runoff computations were prepared for the 2-year minor and 100-year major storm frequency utilizing the rational method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub - basins. Standard Form 9 (SF-9) provides a summary of the design flows for all Sub - basins and Design Points associated with this site. 3.4 Hydraulic Criteria ® �1 All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are included in Appendix C of this report. The existing storm sewer system and reconfiguration were analyzed with this report. The existing type r inlet on Canyon Avenue currently intercepts the 2 year storm on the southeast half of Canyon Avenue between Olive and Oak Streets. The existing area inlet currently intercepts a very small amount of flow from the landscaped area at the north end of the site. The existing type r inlet will remain but less runoff will flow to this inlet. It is proposed to install a new inlet southwest of the existing type r inlet which will intercept approximately half of the existing 2 year flow on Canyon Avenue. The existing area inlet will be abandoned with this proposed development. A solid top will be installed on the inlet and the minor flows will be redirected to the street. 1 4. DRAINAGE FACILITY DESIGN 1 4.1 General Concept All of the runoff from this site currently drains to the adjacent streets and is either collected in the storm system on Canyon Avenue or is conveyed south in Howes Street to another storm system. Both storm systems convey the runoff to the Poudre River. There 3 1 I I Drainage Basin Plan for this basin has been completed by RCE, Inc. dated January 7, 1993. Portions of this report are in Appendix F. This site is not located in a 100-year floodplain or in a `Flooded Area' designated in Figure 4 of the above reference report. In this same report, Canyon Avenue was recommended for street regrading in Figure 5. 2.2 Sub -basin Description This site drains to the Poudre River either via the storm system at the north end of the site or in Howes Street which conveys the flow south to another storm system. These storm systems have been designed,to carry the 2 year minor storms. The characteristics of the sub -basin are not being modified significantly with the proposed redevelopment. The site is currently paved over the majority of the site and the current proposal will maintain a similar imperviousness. 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage Design Criteria Manual" specifications. Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual" (UDFCD), 1984, developed by the Denver Regional Council of Governments, has been used. 3.2 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City Stormwater Department. Detention is not proposed for this site. Water Quality is being provided for the new building proposed on the site. This is being accomplished by the use of a Stormceptor structure located at the north end of the site. Runoff from the roof will be collected internally in the building and will be discharged to the existing storm system via the proposed Stormceptor structure. The structure has storage capacity for 85 cubic feet of sediment. A maintenance program for this structure will be incorporated into the Home Owners Association documents. The sidewalk areas and the landscaped areas will discharge directly to the adjacent 2 I C I 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location ® The Canyon & Howes Residences is located in Old Town Fort Collins. This project is ■ located in the Southeast Quarter of Section 11, Township 7 North, Range 69 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in Appendix A. The project is located in the southwest corner of the intersection of Oak Street and Howes Street. The project is bounded on the northwest by Canyon Avenue, on the east by the Howes Street and on the south by the Linden Press Building and a single family residence. 1.2 Description of Property The entire project consists of approximately 0.4 acres of land. This property currently has a 900 square foot bank building, drive through area and paved parking. The land currently slopes to the south at a range of approximately 0.5% to 1%. All of the existing improvements on site will be removed with this proposed redevelopment. The proposed redevelopment consists of a single 6 story building with a subterranean parking garage. The building will extend to the right of way on the Canyon Avenue frontage and the Howes Street frontage. The lower two levels of the building will contain commercial uses and the upper 4 levels will contain residential units. Sidewalks, drives Iand curb locations will be reconfigured with this redevelopment. 1 2. n I There is an existing storm sewer system on Canyon Avenue at the north end of this site. This storm system will remain and will be extended south to collect runoff from the proposed parking area and in Canyon Avenue. A Stormceptor inlet will also be added to the system to treat the runoff from the roof of the proposed building. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description The proposed development lies within the Old Town Master Drainage Basin. The Master 1 I I I TABLE OF CONTENTS TABLEOF CONTENTS............................................................................................................... iii ® 1. GENERAL LOCATION AND DESCRIPTION * 1.1 Location...................................................................................................................I 2. 1.2 Description of Property ............................................................................................I DRAINAGE BASINS AND SUB -BASINS ' 2.1 Major Basin Description..........................................................................................I 2.2 Sub -Basin Description.............................................................................................2 ' 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations............................:.................................................................................2 3.2 Development Criteria Reference and Constraints....................................................2 ' 3.3 Hydrologic Criteria..................................................................................................3 3.4 Hydraulic Criteria.....................................................................................................3 ' 4. DRAINAGE FACILITY DESIGN 4.1 General Concept.............................................................................:.........................3 4.2 Specific Flow Routing...........................................................................................:A 4.3 Drainage Summary ...................................................................................................4 5. EROSION CONTROL 5.1 General Concept......................................................................................................5 5.2 Specific Details........................................................................................................5 6. CONCLUSIONS 6.1 Compliance with Standards....................................................................................5 6.2 Drainage Concept......................................................................................................5 7. REFERENCES....................................................................................................................6 ' APPENDICES A . Vicinity Map B Hydrologic Computations C Hydraulic Calculations ' D Erosion Control Calculations E Figures and Tables F Excerpt from Previous Reports I �1 North Star ® design, inc. 1 November 18, 2002 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Study for the Canyon & Howes Residences Dear Basil, I am pleased to submit for your review and approval, this revised Final Drainage and Erosion Control Study for the Canyon & Howes Residences, a multi -family residential project. I certify that this report for the drainage design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. i r r r r L1. I I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. ii 700 Automation Drive, Unit I Windsor, Colorado 80550 970-686-6939 Phone • 970-686-1188 Fax \ n + t ( r i 5� t Y 1 : J i F - FINAL DRAINAGE AND EROSION CONTROL STUDY-. for CANYON & HOWES RESIDENCES Yx � u F r ��{ Prepared for ( Coulson Develo went Group, Inc. p , 516 West Magnolia Street Fort CollinsCO 80521 , ,t I4 � • Prepared by. North Star Design. , ` 700 "Automation' Drive; Unit I, Wmdsor, Colorado 865 0 (97ft68&6039: } M1.. November 18, 2002 .Job Number H4. 26, ' I i c