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Home My WebLink AboutC.A.T. 22ND FILING, COMMUNITY HORTICULTURE CENTER PDP & FDP - 53-85AV / AZ - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTEDAW INC 240 FASi MOUfviAIN AVENUE November 1 _5, 2000 FORT COLLINS COLORADO Mr. Basil Hamdan e°52� City of Fort Collins Stormwater Utility 700 Wood Street rE� Q;o aea eo�3 Fort Collins, C� g�$2,4 Fnx s�o aea es�e Re: Project Development Drainage and Erosion Control Report for www.edaw.com Fort Collins Community Horticultural Center Dear Basil: We are pleased to submit for your review and approval this Project Development Drainage and Erosion Control Report for the Fort Collins Community Horticultural Center. We appreciate your consideration in reviewing this submittal. Please call if you have questions. Best Regards, /, l� �' ��____�`�1�� ,��%- �`% , . _ , .- �� , , ; Kay Force Gre�ory-�Turst, P.E. Design Engineer Principal in Charge cc: Encl. UNITED STATES EUROPG AUSTRALIA A$ I A I]�; 1�;: i 1 f' '. ,9 N � 1'. .<. , i f J D '� f � b' ' I i O N I v1 -,l � f C W C' f- L") 'v1� - f'. F Project Development Drainage and Erosion Control Report Fort Collins Community Horticultural Center November 15, 2000 Prepared for: City of Fort Collins Prcp�u-ed b� : EDAW Inc. 240 East Mountain Avenue Fort Collins, CO 80524 (970)484-6073 Tob No. 7F082.10 TABLE OF CONTENTS Page No. INTRO DUC T ION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . HISTORIC OFF-SITE DRAINAGE ...... ...... ......... ... 1. PROPOSED OFF-SITE DRAINAGE ... ...... ...... ... ..... 1. HISTORIC ON-SITE DRAINAGE .. . . . . . . . . . . . . . . . . . . . . . . . 1. PROPOSED ON-SITE DRAINAGE ... ... ... ... ... ... ... ... 1. DRAINAGE DESIGN CRITERIA ... ... ... ... ... ... ... ...... 1. DETENTION STORAGE ..................................... 1. BEST MANAGAMENT PRACTICE ... ...... ... ...... ...... 2. EROSION CONTROL ...... ... ...... ... ... ... ... ... ... ... ..... �. CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. APPENDIX — DRAINAGE CALCULATIONS EROSION CONTROL CALCULATIONS n Introduction This report is submitted as a Project Development Drainage and Erosion Control Report for the Fort Collins Community Horticultural Center, a parcel in a portion of Tract C, Windtrail Townhomes PUD 1�` Replat and in the NE '/a of Section 23, T7N, R 69 W, Fort Collins, Colorado. The parcel is 18.7 acres, bounded on the east by Center Avenue, on the south by the proposed extension of Rolland Moore Drive, on the west by Hill Pond and on the north by Spring Creek. This north property line defines a 100-foot wide buffer strip on the north bank of Spring Creek. Drainage elements on the site interact with Spring Creek, Hill Pond, the Sherwood Ditch Lateral and CSURF property south of the proposed Rolland Moore Drive. The site is located within the Spring Creek Draina�e Basin and tlood plain, and no detention is required ✓ The northern portion ofthe site currently drains at less tlian I% to tl�e north, directly into Spring Creek, while the southern portion is interrupted by the Sherwood Ditch LateraL An existin� suspended 1 Z" CNIl' currently conveys runoff from CSURF property to the south across this ditch and towards Sprin� Creek. The project proposes to maintain these drainage patterns by replacing the suspended CMI' with RCP culverts under the Sherwood Ditch. Portions of the project lie within the 100-year flood plain of Spring Creek. Minor re-grading of the site has increased the flood storage of the Spring Creek channel, and this evaluation is contained in the FEMA Flood Mapping Study by Anderson Consulting Engineers Although no detention is required on the site, BMP's will address stormwater quality. This will consist of porous landscape that will treat low flow, while allowing high flow events to bypass into Spring Creek. An erosion control plan and report will address erosion potential during construction. Historic Off-Stte Drainage — Historic offsite draina�e comes from 1 1.0 acres of CSURF property to the south, as well as from 0.7 acres immediately west of the property. PrOpoSed Off-Site Dralnage — The construction of Rolland Moore Drive will intercept existing flows from the south. A culvert will convey these flows under the street. Existing flows from the west will be routed throu�h a water quality pond. HtstortC On-Site Drainage — The northern portion of the site currently drains at less than 1% to the north, directly into Spring Creek, while the southern portion is interrupted by the Sherwood Ditch Lateral. An existing suspended 12" CMP currently conve_ys runofffrom CSURF property to the south across this ditch and towards Spring Creek. PropOsed On-Slte Drainage — Development of the property will cause an increase of discharge into Sprin� Creek. Approximately 10% of the site will be impervious, with the remaininb portion developed as play�rounds and gardens. Culverts will convey the historic 100-year runoff from the south under the Sherwood Ditch Lateral and into Spring Creek. Drainage Deslgn Criteria — Drainage criteria are based on the City of Fort Collins Storm Drainage Design Criteria, and calculations use the rational method. Best Management Practice Eroslon Control Design — The Community Horticultural Center site lies within moderate rainfall and wind erodability zones per City of Fort Collins zone maps. Potential for erosion exists as construction commences and until paving and landscaping are completed. The site is required to meet a rainfall erosion performance standard of 79 during construction and a performance standard of 93 after construction. Wind erodability will also be addressed. Overlot grading will begin in spring of 2001. The northern portion will immediately be re-seeded. Paving should be installed within 12 weeks of the overlot grading, and permanent landscaping should follow as soon as possible after pavin� is complete. Prior to construction, silt fencing will be installed around the entire site. Basi�ls BZa, B2b and BZc will drain to inlets interior to the site. Basin B 1 w�ill drain to a water quality pond. These facilities will be installed within approximately 8 weeks. During construction straw bale dikes will protect these inlets. At completion of construction, the entire site will be hard-surfaces or landscaped. Erosion Control Security — Temporary erosion control measures: Measure Unit ( ty Silt fence LF 0 Erosion mat SY 0 Straw bale dike E.A 0 Unit Cost Total 0.73 $0 l.11 $0 90 $0 Total $0 2 Security = $0000 x 1.5 = $0000 Co�lclusion — All design and computations will be completed in compliance with the City of Fort Collins storm drainage design criteria. The site does not substantially change existin� drainage patterns. All site drainage will be directed to Spring Creek through existing and new conveyances. Erosion control measures will protect Spring Creek from excessive wind and water-born sediment. The project will also be scheduled to minimize the time bare ground is exposed to the elements. Appendix e • � ___________________EFFECTIVENE55_CALCULATIONS_________________________ PROJECT: STANDARD FORM B COMPLETED BY: DATE: Erosion Control C-Factor P-Factor � Method Ualue Value Comment � ---------------------------------------------------------- � - . . . . �„ � � _.� �, . � � �1 L- y� i. i �� G . � � � , -' � I ��.i��Cw�t�� tYlp 59 p C '"� - i ;, c+ � � _ , � �„ � � r .t-� ��C�.4��'w l� Op �" • 5 Q I :�JIa.�J . L-,te �.' C.�q+'�� ,a� 1 , e0 � � g D � `� r�- � ' � .- i ' ° � I -----------=----------------,_-----------------------------------------I MAJOR� PS � SUB � AREA � I BASIN� (ro� �BASIN� (Ac) � CALCULATIONS � -----�------�-----�------�--------------------------------------------� � � �� Z � � � � � � � � I I I I I i---------------------------------------------------------------------- HDI/SF-B:1989 , • �� RAINFALL PERFORMANCE STANDARD EVALUATION --------------------------------------------------------------------- PROJECT: STANDARD FORM A COMPLETED BY: ' ^ DATE: - --------------------------------------------------------------------- DEVELOPED�ERODIBILITY� Asb � Lsb � Ssb � Lb ( Sb � PS SUBBASIN � ZONE �(ac) �(ft) �(%) �(feet) �(q) �(o) -- �-----------�-------�-------� �-------� I------- � I I � �:�: �� i i i (( i i . i`� � � � � � � . I ��, � � � � � � I I � � � � �?-: I' I � I t ` I I i I I I l I I I _ l I I_ I � I I � �, � I i � � � - f� I i I i ► ,--------------------------------------------------------------------- HDI/SF-A:1939 � � � � I% , - � CONSTRUCTION SEQUENCE • PROJECT: � -- - SEQUE�ICE. �OR �i9 ONLY COMPLETED BY: STANDARD FORM C DATE: '1 Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. YEAR MONTH � ----------------------------�----- OVERLOT GRADING I WINO EROSION CONTROL Soil Roughing Perimeter Barrier Additional Barriers Vegetative Methods Soil Sealant Other RAINFALL EROSION CONTROL STRUCTURAL: ' Sediment Trap/Basin ' Inlet Filters ' • Straw Barriers I Silt Fence Barriers � Sand Bags � Bare Soil Preparation j Contour Furrows � Terracing � Asphalt/Concrete Paving� Other I VEGETATIVE: � Permanent Seed Planting� Mulching/Sealant � Temporary Seed Planting� Sod Installation Nettings/Mats/Blankets Other I � ----------------------------------------------------------------------------------------� STR�JCTURES: INSTALLED BY MAINTAINED BY VEGETATION/MULCHING CONTRACTOR DAiE SUBMITTED APPROVED BY CITY OF FORT COLLINS ON 0 � � � � � � � � � � � -----------------------------------------------------' � � . � � I • iDI/SF-C:1989 project:: Fort Collins Hort. Center - South Water Quality Pond prepared by : EDAW inc date: 05/01/00 Q req'd > 3464 gpm Includes entrance/exit losses by: mm Enclosed flow under head tlifferential C Hazen-Williams pipe roughness D Pipe diameter h water surface elevation differential Vo velocity L pipe length Hf Headloss due to friction (ft per 100ft) K Loss coefficient PIPE DATA K D L h C Pick initial V� Hf Computed Vo Repeat until Vi and Vo converge Result Sch. 40 & 80 PVC PE Type K copper Sch. 40 steel Concrete in. ft (2g(h-Hf))^.5 (ft/s) ft Hf=.2083(100/C)^1.852`QM.852/D^4.866 square pipe end 0.50 18.00 in. 170 ft 0.860 ft 135.0 5.1 fUsec 0.447 ft 5.2 f/sec (98.50-96.80-0.84) 4096 gpm submerged pipe flow Increase or decrease pipe size and repeat process if required, for desired flow. Add entrance and exit loss if applicable. PROJECT: Fort Collins Hort. Center - Basin 2 Prepared by : EDAW inc. Date: 10/26/00 Manning's Equation, Pipe & Channel Q-100 His.=16.6 cfs, Basin B2c CHANNEL AND PIPE DATA Mannings n = OAl2. Side Slope = 0.00 x:1 Base Width = 10.00 feet Bottom S+ope = 0.005 ft/ft Flow Depth = 2.50 feet ADDITIONAL PIPE DATA � Pipe Diam. = 15:00 inches �i Prcnt Full = 85 percent RESULTS - CHANNEL Area [sq.ftJ = 25.00 Hyd. Radius = 15.00 Flow [cfs] = 307.78 Flow [gpm] = 138130 Vel [fps] = 12.31 Width [ft] = 10.00 RESULTS - PIPE Flow [cfs] _,�� ' 5.10 ( 16.6 cfs req'd) Flow [gpm] = 2288 Vel�� [�ps] _ �� ., ,: �� 4.58 Use 4 culverts 11x18 RCP arch PROJECT: Fort Collins Hort. Center - Sherwood Ditch Prepared by : EDAW inc. Date: 11 /13/00 Manning's Equation, Pipe & Channel CHANNEL AND PIPE QATA Mannings n = 0.035 ' Side Slope = 2.00 x:1 Base Width = 10.00 feet Bottam Slope = 0.00160 ftift Flow Depth = 2.00 feet ADDITIONAL PIPE DATA Pipe Diam. = 18.00 inches Prcnt Full = 90 percent RESULTS - CHANNEL Area [sq.ftJ =, 28.00 ,' ' Hyd. Radius = 18.94 Flow [cfs] = 61.71 ( 55 cfs req'd) Flow [gpmj = 27695 Vel [fps] = 220 Width [ft] = 1$.00 RESULTS - PIPE Flow [cfs] = 1.66 ;� Flow [gpm] = 746 � Vel [fps] _ ' ' 0.99 This slope is based on 1-foot drop in ditch water surface aong 586-foot length of open channel. This is an "order of magnitude" calculation, and will be finalized with HEC-2 analysis.