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Home My WebLink AboutHEARTSIDE HILL COMMUNITY FACILITY - PDP230016 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT Highland Development Services, Inc. 6355 Fairgrounds Avenue, Suite 100 | Windsor, CO 80550 | 970.674.7550 Memorandum TO: Basil Hamdan, P.E. FROM: Zach Wiele, Jason Claeys DATE: 2/7/24 PROJECT: Heartside Hill – Community Building HDS JOB NO: 21-1045-02 SUBJECT: Developed Impervious Area Memorandum Please accept the following memorandum describing the proposed developed impervious area for the Heartside Hill Community Building as compared to the assumed developed impervious area originally proposed in the “Final Drainage Report for Heartside Hill” for the final approved Heartside Hill project, prepared by Highland Development Services, dated 9/27/23. This memo is prepared to confirm the developed impervious area complies with the assumed developed impervious area of 70% referenced in the previous study. Previous Study: The Heartside Hill Community Building is located within Basin D1 of the original drainage report. The previous study applied a 70% impervious assumption to the future development area. Assuming 90% impervious value for the roofs and sidewalks derives an impervious area of 18,163.4 sq ft. Proposed Development: An analysis of the proposed Community Building development shows the site will be 59% impervious, less than originally assumed 70%. This was calculated using the combined area of 3,141.8 sq ft for the proposed sidewalk and 12,193.1 sq ft for the proposed roof, giving a total area of 15,353 sq ft. Using the 90% impervious value from the referenced drainage report, the total developed impervious area equates to 59%. Low Impact Development (LID): The improvement area withing Basin D1 is is provided water quality enhancement through Rain Garden D1. These improvements were anticipated within the previous drainage study and Rain Garden D1 satisfies the City LID requirements. In addition to the rain garden treatment, a forebay and level spreader are proposed at the storm drain outfall draining the roof and some walk area. the level spreader provided additional water quality enhancement as runoff sheet flows over open space prior to concentrating within curb/gutter, and storm pipes, providing a grass buffer. Conclusion: The proposed Community Building development will have a 59% developed impervious area, less than the assumed developed impervious area of 70%. The reduced area confirms that the proposed development is in compliance with the drainage report referenced from the Heartside Hill project, approved September 27th, 2023. All references, calculations, and exhibits are attached for reference. NYLOPLAS T D U C T I L E I R O N DO NOT P O L L U T E D R A I N S T O W A T E R W A Y S NYLOPLAST DUCTILE IRON DO NOT POLLUTE DRAINS TO WATERWAYS NYLOPLAST DUCTILE IRON DO NOT POLLUTE DRAINS TO WATERWAYS D N D YLOPLAST ONOTPOLLUTE UCTILEIRON DRAINSTOWATERWAYS COMMUNITY BLDG FFE=4936.85 (BLDG PHASE 1) DAYCARE FFE=4937.85 (BLDG PHASE 2) LOT 1 BLOCK 2 TRACT A Heart of the Rockies Forth Subdivision LOT 1 BLOCK 3 Existing Church Building FFE = 4933.70 RE V I S I O N NO . BY DA T E HI G H L A N D DE V E L O P M E N T S E R V I C E S 63 5 5 F A I R G R O U N D S A V E N U E , S U I T E 1 0 0 | W I N D S O R , C O 8 0 5 5 0 PH O N E : 9 7 0 . 6 7 4 . 7 5 5 0 | E M A I L : I n f o @ H i g h l a n d - D S . c o m | w w w . H i g h l a n d - D S . c o m PREPARED BY OR UNDER THE DIRECT SUPERVISION OF: FOR AND ON BEHALF OF HIGHLAND DEVELOPMENT SERVICES REVIEW SET NOT FOR CONSTRUCTION OFSHEET DRAWN BY CHECKED BY DATE SCALE (H) HDS PROJECT # SCALE (V) HE A R T S I D E H I L L - C O M M U N I T Y B U I L D I N G DR A I N A G E & E R O S I O N C O N T R O L P L A N 2/7/24 1" = 15' N/A ZMW JTC 21-1045-02 C2.00 4 7 CALL UTILITY NOTIFICATION CENTER OF COLORADO CALL 2-BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. before you dig.CallKnow what's below. R N W E S LEGEND EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR BASIN COEFFICIENT (100-YR) BASIN DESIGNATION BASIN AREA DESIGN POINT DRAINAGE FLOW ARROW DRAINAGE BASIN BOUNDARY DRAINAGE BASIN FLOW PATH NOTES 1.CONTRACTOR TO PROVIDE AND MAINTAIN ALL NECESSARY EROSION CONTROL MEASURES PRIOR TO AND THROUGHOUT CONSTRUCTION. PLACE EROSION CONTROL PROTECTION AT ALL EXISTING INLETS DOWNSTREAM FROM THE CONSTRUCTION AREA. EROSION CONTROL PROTECTION SHALL REMAIN IN PLACE UNTIL CONSTRUCTION IS COMPLETE AND ALL DISTURBED GROUND IS ADEQUATELY VEGETATED WITH OWNER'S APPROVAL FOR REMOVAL. 2.THE EXTENT OF EROSION CONTROL PROTECTION SHALL BE OBSERVED AND ADJUSTED AS NEEDED DURING CONSTRUCTION BASED ON SITE CONDITIONS AND THE PERFORMANCE OF THE EROSION CONTROL MEASURES SHOWN, TO SUPPLY SUFFICIENT EROSION CONTROL AND MINIMIZE DOWNSTREAM WATERWAY POLLUTION. 3.LIMIT DISTURBANCE TO AREAS WITHIN EROSION CONTROL BOUNDARIES. ADJUST EROSION CONTROL BOUNDARIES AS NECESSARY TO ADEQUATELY COMPLETE PROPOSED WORK. ALL DISTURBED AREAS SHALL BE PREPARED (SEEDED & MULCHED, SURFACE ROUGHENING, ETC.) TO MINIMIZE EROSION POTENTIAL AND SOIL MIGRATION. 4.STORMWATER MANAGEMENT PLAN SHALL BE PREPARED AND SUBMITTED BY CONTRACTOR PRIOR TO CONSTRUCTION COMMENCEMENT. 5.SEE LANDSCAPE PLAN FOR REVEGETATION METHODS AND DETAILS. DURING CONSTRUCTION, ANY SOIL DISTURBED AND NOT UNDER ACTIVE CONSTRUCTION SHALL BE SEEDED AND MULCHED PER LCUASS STANDARDS. 6.ANY DISTURBED LAND MUST RECEIVE SURFACE ROUGHENING, INCLUDING BUT NOT LIMITED TO SLOPED AREAS. 7.AREAS THAT EXPERIENCE EROSION ISSUES FROM STEEP SLOPES OR WATER EROSION RESULTING IN SEED NOT BEING ABLE TO ESTABLISH DURING THE FIRST GROWING SEASON SHALL REQUIRE RESEEDING AND EROSION CONTROL BLANKETS TO STABILIZE THE SOIL. 0 SCALE: 1" = 307.5 1515 15' CONSTRUCTION ENTRANCE W/ VEHICLE TRACKING CONTROL INLET PROTECTION LIMITS OF DISTURBANCE (APPROX) CONSTRUCTION FENCE PERMANENT RIPRAP APRON ROCK SOCKS Addition landscape area contributing to Basin D2c (considered negligible) Design Engineer: Design Firm: Project Number: Date: % Impervious Runoff Coefficient C Return Period Frequency Adjustment Factor (Cf) 100% 0.95 2-year to 10-year 1.00 90% 0.95 100-year 1.25 90% 0.95 45% 0.55 70% 0.65 0% 0.25 C2 to C10 C100 OS1 88,538 2.03 48,364 3,889 6,687 0 0 29,598 65.4% 0.72 0.89 D1 163,080 3.74 24,710 3,742 5,916 33,798 23,353 71,561 39.8% 0.52 0.65 D2a 48,086 1.10 0 12,931 1,430 0 0 33,725 26.9% 0.46 0.57 D2b 42,280 0.97 231 12,931 1,857 0 0 27,262 32.0% 0.50 0.62 D2a+D2b 90,366 2.07 231 25,861 3,287 0 0 60,987 29.3% 0.48 0.60 D2c 67,394 1.55 44,316 0 4,531 0 0 18,546 71.8% 0.76 0.95 D2d 44,606 1.02 0 0 2,055 0 0 42,551 4.1% 0.28 0.35 D2 202,366 4.65 44,547 25,861 9,874 0 0 122,084 37.9% 0.53 0.66 Total 453,984 10.42 117,621 33,492 22,476 33,798 23,353 223,244 44.0% 0.56 0.70 COMPOSITEApaved (sq feet) Aroof (sq feet) Awalk (sq feet) Alawn (sq feet) ASF Lot (sq feet) ACC Lot (sq feet) Lawns (Heavy, 2-7% Slope) Sub-basin Designation Atotal (sq feet) Atotal (acres) Weighted % Impervious Single-Family (SF) Lots Community Center (CC) Lot Paved Roof Walks Land Use Heartside Hill DEVELOPED IMPERVIOUS AREA CALCULATION DESIGN CRITERIA: Fort Collins Stormwater Criteria Manual BASINS: Highland Development Services Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual % Impervious values from Table 3.2.2 in the Fort Collins Stormwater Criteria Manual J.Claeys 20-1045-00 May 10, 2023 21-1045-00 Rational Calcs.xlsx Page 1 of 5 Highland Development Services (R+W)(.9) = 23,353(0.7) R+W = 18,163.4 sqft Originally assumed impervious area Proposed Walk = 3,141.9 Roof = 12,193.1 R+W = 15,335 sqft Community Center Lot Total (sq ft) (R+W)(.9) = 13,817.7 13,818/23,353 = 59% Impervious Weir Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Feb 7 2024 Heartside Hill - Community Building - Forebay Weir Rectangular Weir Crest = Sharp Bottom Length (ft) = 31.00 Total Depth (ft) = 0.25 Calculations Weir Coeff. Cw = 3.33 Compute by: Known Q Known Q (cfs) = 3.00 Highlighted Depth (ft) = 0.09 Q (cfs) = 3.000 Area (sqft) = 2.93 Velocity (ft/s) = 1.03 Top Width (ft) = 31.00 0 5 10 15 20 25 30 35 40 45 Depth (ft)Depth (ft)Heartside Hill - Community Building - Forebay Weir -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft)Weir W.S. Basin Area Contributing to Forebay = 13,920 sqft => 0.32 acres Impervious Area = 13,000 sqft @ 90% Impervious (Roof & Walk) Estimated % Impervious = 84% 100-yr Runoff Coefficient = 0.89 Assume 5 min time of concentration Intensity = 9.95 in/hr Q100 = CIA = 0.89*9.95*0.32 = 2.83 cfs Forebay Weir Length = 2πr = 2*π*5 = 31.42 ft (5 ft radius forebay)