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HomeMy WebLinkAboutPVH HEALTH SYSTEMS, HARMONY CAMPUS - ODP - 32-98 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTOil J.1N(100 0 0 0 w o � L a Y Y1ti 7' � I q tij n q �O s Ob'Oa 3NIl2i 8W11 e -q NO/ly avoaiiva �I�I�Yd x No Text 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1997. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991, Revised January 1997. 3. McClellands Basin 100-Year Master Plan Update, by RBD, Inc., Fort Collins, Colorado, April 1, 1996. 4. McClellands Basin Master Drainage Plan, by Greenhorne & O'Mara, Inc., Fort Collins, Colorado, June 20, 1986. 5. Final Drainage Report for Timberline Road, by Northern Engineering Services, Inc., Fort Collins, Colorado, July 15, 1994. 6. Final Drainage and Erosion Control Study for The Hamlet at Miramont P.U.D., Fort Collins, Colorado, by RBD, Inc., March 1996. 2 Ponds 1-3, the release rate for the 10 year storm event is 16.21 cfs and for the 100 year storm event, a release rate of 40.31 cfs. V. STORM WATER QUALITY A. General Concept The State of Colorado requires Stormwater Management Plans as part of their permit process. The Poudre Valley Hospital will use various Best Management Practices for the treatment of storm water runoff that will be implemented in the construction phase of the project. These BMP's and their related calculations will be determined as the site is developed. VI. EROSION CONTROL A. General Concept Erosion control plans and calculations for the Poudre Valley Hospital will be provided as the site is developed. VII. CONCLUSIONS A. Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. B. Drainage Concept The proposed drainage concepts presented in this study and shown on the overall drainage plan adequately provide for the transmission of developed on -site runoff to the proposed detention ponds. C. Storm Water Ouality Preceding development, Best Management Practices will be determined for the treatment of storm water runoff. D. Erosion Control Concept Prior to development, erosion control plans will be produced in accordance to the recommendations provided for in the City of Fort Collins Storm Drainage Design Criteria Manual. 5 The site has been broken into four basins, 1, 2, 3, and 4. Basin 1 contains 80.62 acres, a majority of the site. Runoff generally will flow in a southeasterly direction to three detention ponds along the southern property line. These 3 detention ponds are graded to minimum slope of 0.50%, with concrete trickle pans. They are separated by swales and stormwater will travel through pipes and swales to continue on to the next pond. Basin 2 contains 16.20 acres of the site. Runoff from this area will flow to Detention Ponds 4 & 5, which are connected by an equalizing pipe. Water will be released from the detention ponds through a dual release rate outlet structure into storm pipes that lead to Detention Pond 1. Since it is released at the historical rate, it does not need to be detained in Detention Pond 1. Basins 3 and 4 contain 3.69 acres and 1.83 acres of the site, respectively. These areas flow toward the Spring Canyon Lateral along the northern property line. This area has historically flowed into the concrete ditch and will continue to do so. ' With the additional 12' wide pavement surface on Harmony Road, there is an I additional amount of runoff that is flowing to the Spring Canyon Lateral. Due to grading and layout of Harmony Road, the PVH site and the Spring Canyon Lateral, runoff is unable to flow on to the PVH site. Instead it will continue to flow into p the Spring Canyon Lateral, as it has historically done. The five permanent detention ponds to be constructed on the site will be responsible for collecting runoff for the site. Detention ponds 2-5 will discharge into Detention Pond 1. Detention Pond 1 will release runoff from a dual release rate outlet structure into Conveyance Element 39. Conveyance Element 39 is a grass lined open channel that runs along the southern property line and then south along the Timber Creek PUD and the Stetson Creek PUD's eastern property line. Conveyance Element 39 ultimately drains to the McClellands Basin Drainageway. The peak flow allowed for Conveyance Element 39, from the SWMM Model, is 66.70 cfs. This results in a 2.28' depth in the ditch. The amount of flow being released into Conveyance Element 39 from the Poudre Valley Hospital, at the 100- year release rate of 0.50 cfs/acre, is 48.41 cfs. This will result in a 2.02' depth in I the ditch. Since the amount of flow being released into Conveyance Element 39 is less than the flow allowed for, the ditch capacity will not be exceeded. The Poudre Valley Hospital will discharge into Conveyance Element 39 at the southeast comer of the property. The McClellands Basin has a dual release rate of 0.20 cfs/acre for the 10-year storm event and a 0.50 cfs/acre for the 100-year storm event. The allowable release rate for Detention Ponds 4 & 5 for the 10-year storm event of 3.24 cfs and for the 100-year storm event of 8.10 cfs. For Detention 4 E. Variances from Criteria A variance from the City of Fort Collins Storm Drainage Criteria is being sought for the runoff from Harmony Road flowing into the Spring Canyon Lateral. IV. DRAINAGE FACILITY DESIGN A. General Concept Conveyance Element 39 is currently 2160 feet long and is an open channel that runs along the southern property line of the PVH site. At the southeast corner of the site, Conveyance Element 39 turns the corner and flows south along the east property line of Timber Creek PUD and Stetson Creek PUD. Poudre Valley Hospital plans to modify Conveyance Element 39 in the following ways. PVH plans to shorten Conveyance Element 39 to the southeastern comer of the site. The ditch that currently exists along the southern property line will be re -graded into three small detention ponds connected by swales. Runoff from the Poudre Valley Hospital will be released from the southeasterly detention pond into Conveyance Element 39 and continue to flow south. Flows from the Poudre Valley Hospital site will travel through a system of curb I and gutters, storm drain pipes, concrete pans and swales to reach the seven permanent detention ponds. Preliminary placement of storm pipes can be seen on the Drainage Plan in the back pocket of this report. This plan shows the location I of the pipes that will connect the detention ponds and also includes the proposed locations of the pipes for the Project Development Plan. Once the flow reaches the ponds, it will be released from an outlet structure. This outlet structure will allow runoff to be discharged at a staged release rate for the 10-Yr and 100-Yr storms. Detention Ponds 1-3 will be connected by swales. Ponds 4 & 5 are equalizing ponds and will be connected with a storm drain pipe. Flow from Ponds 4 & 5 will travel through storm drain pipe to release into Pond 1. The flow from Pond 1 will release into the grass lined open channel, conveyance element 39, from an outlet structure. The rational method was used in determining the size of the five permanent detention ponds. The Master Plan for the McClellands Basin requires on -site detention using a staged release rate of 0.20 cfs/acre for a 10-year design storm and 0.50 cfs/acre for a 100 year design storm. Excerpts from McClellands Basin I Master Drainage Plan can be found in the appendix. Calculations used for the Overall Drainage Plan can also be found in the Appendix. A SWMM Model for the McClellands Basin currently exists. For the Project Development Plan, the SWMM model will be updated. 3 At the southeast comer of the site, Conveyance Element 39 turns the corner and flows south along the east property line of the Timber Creek PUD and the Stetson Creek PUD. Excerpts from the McClellands Basin 100-Year Master Plan Update can be found in the appendix of this report. The flow ultimately discharges into the McClellands Basin Drainageway. A portion of Timberline Road will be detained on the Poudre Valley Hospital Site. Sections of the Final Drainage Report for Timberline Road, done on July 15, 1994, by Northern Engineering Services, Inc., which show this area of roadway has been included in the Appendix. These sections specify the area of Timberline to be detained as well as storm flows. No off -site runoff from properties surrounding the Poudre Valley Hospital site pass through the site. With the construction of the site, no additional flows are anticipated. III. DRAINAGE BASIN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Development Criteria Reference and Constraints The criteria and constraints from The McClellands Basin 100-Year Master Plan and the subsequent update dated April 1, 1996 are being utilized in this Overall Drainage Study. The Poudre Valley Hospital site is currently being utilized as agricultural land, and the McClellands Basin Master Plan for the site does not include on -site detention facilities for the future development. C. Hvdrolosic Criteria The Poudre Valley Hospital PDP Drainage Report will utilize the Final Drainage and Erosion Control Study for the Hamlet at Miramont P.U.D.'s SWMM model I and simply expand on it. SWMM computer models will be run for the Project Development Plan. D. Hydraulic Criteria All calculations within this study have been prepared in accordance with the City of Fort Collins Storm Drainage Criteria and are included in the appendix. 2 OVERALL DRAINAGE REPORT FOR THE POUDRE VALLEY HOSPITAL HARMONY CAMPUS FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Poudre Valley Hospital Harmony Campus site is located south of Harmony Road and east of Timberline Road in southeastern Fort Collins, Colorado. The site is shown on the Vicinity Map in the Appendix. More particularly, the site is situated in the northwesterly portion of Section 5, Township 6 North, Range 68 West of the Sixth P.M., City of Fort Collins, Larimer County, Colorado. B. Description of Propertv The Poudre Valley Hospital site contains approximately 102 acres of land, most of which is currently undeveloped and being proposed for the Harmony Campus of Poudre Valley Hospital. The majority of the property currently consists of cultivated farmland. The site generally slopes in a southeasterly direction at approximately 2.0%. There is a concrete irrigation ditch along the northern property line of this site called the Spring Canyon Lateral, owned by the Warren Lake Company. This ditch is to be relocated and will remain active. H. DRAINAGE BASINS A. Major Basin Description The Poudre Valley Hospital site lies entirely within the McClellands Basin. In the Final Drainage and -Erosion Control Study for the Hamlet at Miramont P.U.D., completed by RBD, Inc., the SWMM Model was updated. In the update, the Poudre Valley Hospital is located in Basin 316. Applicable portions of these studies are included in the Appendix. ' Historic drainage patterns on the subject site are in a southeasterly direction per the McClellands Basin 100-Year Master Plan Update. The site historically discharges ' into Conveyance Element 39. Conveyance Element 39 is currently 2160 feet long and is an open channel that runs along the southern property line of the PVH site. 1 APPENDIX PAGE VICINITY MAP 1 HYDROLOGY 3 DETENTION POND SIZING 9 SWALE ANALYSIS - CONVEYANCE ELEMENT 39 16 EXCERPTS FROM McCLELLANDS BASIN MASTER DRAINAGE PLAN 20 EXCERPTS FROM McCLELLANDS BASIN 100-YEAR MASTER PLAN UPDATE 24 EXCERPTS FROM THE FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE HAMLET AT MIRAMONT P.U.D. 27 EXCERPTS FROM FINAL DRAINAGE REPORT FOR 43 TIMBERLINE ROAD TABLES AND FIGURES 55 TABLE OF CONTENTS PAGE I. GENERAL LOCATION AND DESCRIPTION A. LOCATION I B. DESCRIPTION OF PROPERTY I II. DRAINAGE BASINS A. MAJOR BASIN DESCRIPTION I III. DRAINAGE DESIGN CRITERIA A. REGULATIONS 2 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 2 C. HYDROLOGICAL CRITERIA 2 D. HYDRAULIC CRITERIA 2 E. VARIANCES FROM CRITERIA 3 IV. DRAINAGE FACILITY DESIGN A. GENERAL CONCEPT 3 V. STORM WATER QUALITY A. GENERAL CONCEPT 5 VI. EROSION CONTROL A. GENERAL CONCEPT 5 VII. CONCLUSIONS A. COMPLIANCE WITH STANDARDS 5 B. DRAINAGE CONCEPT 5 C. STORM WATER QUALITY 5 D. EROSION CONTROL CONCEPT 5 REFERENCES 6 THE SEAR -BROWN GROUP FULL -SERVICE DESIGN PROFESSIONALS FORMERLY RBD, INC. 209 SOUTH MELDRUM FORT COLLINS, COLORADO 80521-2603 970-482-5922 FAX:970-482-6368 October 14, 1998 Mr. Basil Harridan City of Fort Collins Water Utilities--Stormwater 700 Wood Street Fort Collins, Colorado 80521 RE: Overall Drainage Report for the Poudre Valley Hospital - Harmony Campus Dear Basil: We are pleased to re -submit to you, for your review and approval, this Overall Drainage Report for the Poudre Valley Hospital - Harmony Campus. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. The Preliminary Drainage and Erosion Control Report for the PDP is being submitted simultaneously. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, The Sear -Brown Group Prepared by: Storm Gewirtz, E.I.T. Project Engineer Traci Downs, E.I.T. Project Engineer cc: File 823-001 Albert Kahn Associates Reviewed by: Kevin Gingery, P.E. Engineering Manager NEW YORK•PENNSYLVANIA COLORADO•UTAH STANDARDS IN EXCELLENCE EQUAL OPPORTUNITY EMPLOYER Overall Drainage Report Poudre Valley Hospital Harmony Campus, Fort Collins, Colorado October 1998 THE SEAR -BROWN GROUP Standards in Excellence