The URL can be used to link to this page

Home My WebLink AboutSERRANO TOWNHOMES - FDP - 41-04A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT,70 PROJEC LOCATIO �°0 0 0 DATE: 10/8/04 SCALE: 1" = 500' DRAWN BY: SB JOB NO.: 223-01 BD RDWKK DRN M9181 � \•••i�r�rrr�. • SERRANO TOWNHOMES VICINITY MAP 0 N North Star design, inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 Phone: 970-686-6939 Fax: 970-686-1188 APPENDIX A VICINITY MAP I 7. REFERENCES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March 1999. 3, RBD, Inc. Engineering Consultants, "Final Drainage and Erosion Control Study for the Hamlet at Miramont P.U.D.", dated March 29, 1996. 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September 2001. 6 effectiveness of the erosion protection but would increase the costs with no added benefit. ' All erosion control calculations are included in Appendix C of this report. Specific erosion control measures during and after construction are shown on the Drainage and Erosion Control Plan in the back pocket. ' The erosion control escrow amount is $5,955. r 6. CONCLUSIONS ' 6.1 Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Storm Drainage Design Criteria Manual. 6.2 Drainage Concept ' The proposed drainage concepts presented in this report and on the construction plans adequately provide for conveyance of stormwater runoff to the existing detention area. The private storm sewer system has been designed to adequately pass required flows and will be maintained by the Homeowner's Association for this development. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 5 Basin 4 (0.09 acres) is located in the northwestern portion of the site. Runoff from this I basin will sheet flow to the north and into the Boardwalk Drive curb and gutter. Runoff from Basin 4 is 0.3 cfs for the 10-year storm and 0.8 cfs for the 100-year storm. ' Basin 5 (0.18 acres) is located in the northeastern portion of the site. Runoff from this basin will sheet flow to the north and into the Boardwalk Drive curb and gutter. Runoff from Basin 5 is 0.5 cfs for the minor storm and 1.3 cfs for the major storm. I 1 4.3. Drainage Summary The proposed development has been divided into five subbasins. Runoff from all subbasins will be routed to the north and into the Boardwalk Drive curb and gutter or be collected in the on site storm drain and conveyed to the existing inlet in Boardwalk Drive. The runoff will then be piped to the existing downstream detention pond. 5. 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 the existing storm system during construction. Potential also exists for tracking of mud onto existing streets which could then wash into existing storm systems. 5.2 Specific Details To limit the amount of silt leaving the site several erosion control measures shall be implemented during construction. All inlets shall be protected with gravel filters, straw bales will be placed in the swale on the west side of the site and the west, north and east boundaries shall have silt fence installed. A vehicle tracking pad shall be used to control the mud being tracked onto the existing pavement in Boardwalk. During overlot grading, disturbed areas are to be kept in a roughened condition and watered to reduce wind erosion. The required performance standard for the site is 79.5%. Based on the effectiveness calculations, this performance standard is not being met but adequate erosion control measures are being provided on this site. Any additional measures would not increase the 4 4. DRAINAGE FACILITY DESIGN 4.1. General Concept The runoff from the proposed development will flow to the north to existing Boardwalk Drive via sheet flow and proposed private storm drains. Runoff will be conveyed via Boardwalk Drive curb and gutter or on site storm pipe to the existing Type R inlet and ultimately to the downstream detention pond in the Lodge at Miramont. Based on the SWM Model updated with the Lodge at Miramont development, this site was included in the sizing of the detention pond. The model indicates that Basin 212 (which includes this development) is 4.2 acres and has an imperviousness of 80%. Based on a composite calculation of the actual area in Basin 212, the imperviousness is slightly less than 57%. Therefore, based on the model and the actual conditions, adequate detention is provided in the Lodge pond 4.2. Specific Flow Routing A summary of the drainage patterns within each basin is provided in the following paragraphs. Basin 1 (0.43 acres) is located in the western portion of the site. Runoff from this basin will be collected in the west proposed private storm pipe and conveyed, with runoff from Basin 3, to the inlet in Boardwalk Drive. Basin 1 runoff is 1.0 cfs for the 10-year minor storm and 2.8 cfs for the 100-year major storm. Basin 2 (0.60 acres) is located in the eastern portion of the site. Runoff from this basin will be collected in the east proposed storm pipe and conveyed to the inlet in Boardwalk Drive. Basin 2 runoff is 1.3 cfs for the 10-year storm and 3.5 cfs for the 100-year storm. Basin 3 (0.99 acres) is located in the interior portion of the site and encompasses all of the proposed drives and parking and a majority of the buildings. Runoff from this basin is conveyed through the site via curb and gutter and concrete pans. The runoff is conveyed to an inlet in the proposed drive entrance. The flow will be collected in the west storm pipe and conveyed with runoff from Basin 1 to the inlet in Boardwalk Drive. Runoff from Basin 3 is 3.2 cfs for the 10-year storm and 8.2 cfs for the 100-year storm. SWMM Model. In the TST report, this site is included in Basin OS8. With existing drainage patterns, runoff sheet flows to Boardwalk Drive, then is collected in an existing Type R inlet, and then is piped to the existing detention pond. 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), 2001 has been used. I3.2. Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City Stormwater Department and the Master Drainage Reports governing this site. Neither stormwater detention nor extended water quality detention are provided on this site but the required storage volume is provided in the Lodge at Miramont pond on the north side of Boardwalk Drive. The pond certification by TST is included in Appendix D. 3.3. Hydrologic Criteria Runoff computations were prepared for the 10-year minor and 100-year major storm frequencies utilizing the Rational Method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Detention for this site will be provided by Detention Pond 340 located on the north side of Boardwalk Drive in the Lodge at Miramont. 3.4. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are included in Appendix B of this report. There are no public storm sewer improvements proposed with this project. All storm sewers shown on site will be privately maintained by the homeowner's association. All basins will release into the existing curb and gutter of Boardwalk Drive or into the storm pipe that will tie into the back of the existing type R inlet in Boardwalk Drive. 2 1. GENERAL LOCATION AND DESCRIPTION 1.1. Location The proposed Serrano Townhomes is located in Fort Collins at the southwest corner of the intersection of South Lemay Avenue and Boardwalk Drive. This project is located in the Southeast Quarter of Section One, Township Six North, Range Sixty-nine West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. The site is bounded on the north by Boardwalk Drive, on the west by an existing private drive within the Hamlet development, on the south by the Mail Creek Ditch and on the east by South Lemay Avenue. See the Vicinity Map in Appendix A. 1.2. Description of Property The project consists of approximately 2.3 acres of land. The proposed improvements on this site consist of 18 units in six buildings with associated drives, walks, and parking. ' Access is obtained on the north from Boardwalk Drive. No portion of the proposed project is within a designated floodplain area. Existing development on the site includes a single-family residence, along with drives and walks all of which will be removed with this project. Existing drainage patterns are to the north at approximately 4%. 1 2. I DRAINAGE BASINS AND SUB -BASINS 2.1. Major Basin Description The proposed development lies within the McClellands Mail Creek Drainage Basin. Detention for this site is provided by a downstream detention pond in the Lodge at Miramont. This detention pond is designated as Detention Pond 340 in the SWMM Model as shown in the "Final Drainage and Erosion Control Study for the Hamlet at Miramont P.U.D." by RBD, Inc., dated March 29, 1996 and the subsequent "Final . Drainage Report for the Lodge at Miramont P.U.D. by TST Inc. dated March 13, 2001. Excerpts of these reports are included in Appendix D of this report. 2.2. Sub -basin Description The site currently drains from south to north, with an existing slope of approximately 4%. According to the RBD, Inc. drainage report, this site is a portion of Basin 212 of the 1 TABLE OF CONTENTS TABLEOF CONTENTS............................................................................................................... iii ' 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location...................................................................................................................1 1.2 Description of Property............................................................................................1 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description..........................................................................................1 2.2 Sub -Basin Description.............................................................................................1 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations..............................................................................................................2 3.2 Development Criteria Reference and Constraints....................................................2 3.3 Hydrologic Criteria..................................................................................................2 3.4 Hydraulic Criteria....................................................................................................2 4. DRAINAGE FACILITY DESIGN 4.1 General Concept.......................................................................................................3 4.2 Specific Flow Routing.............................................................................................3 4.3 Drainage Summary ...................................................................................................4 5. EROSION CONTROL 5.1 General Concept......................................................................................................4 5.2 Specific Details........................................................................................................4 6. CONCLUSIONS 6.1 Compliance with Standards....................................................................................5 6.2 Drainage Concept.....................................................................................................5 7. REFERENCES....................................................................................................................6 APPENDICES A Vicinity Map B Hydrologic & Hydraulic Computations C Erosion Control Calculations D Excerpts from Previous Reports E Figures and Tables iii �1 North Star &me, design, inc. June 21, 2005 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage & Erosion Control Report for Serrano Townhomes I Dear Basil, I am pleased to submit for your review and approval, this Final Drainage & Erosion Control Report for Serrano Townhomes. I certify that this report for the drainage design of Serrano Townhomes was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Prepared by: f ` Shane Boyle, BIT North Star Design, Inc. Reviewed By: Patric4L i Kroetch, PE North Star Design, Inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 970-686-6939 Phone • 970-686-1 188 Fax FINAL DRAINAGE & EROSION CONTROL REPORT FOR SERRANO TOWNHOMES Prepared for: TREADSTONE DEVELOPMENT 231 S. Howes Street Fort Collins, CO 80522 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970)686-6939 June '21, 2005 Job Number 223-01