HomeMy WebLinkAboutHEARTSIDE HILL ACCESSORY BUILDING AND CHILD CARE CENTER - FDP240007 - SUBMITTAL DOCUMENTS - ROUND 1 - Drainage Related Document
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, P.E.
DATE: 5/01/24
PROJECT: Heartside Hill – Accessory Building & Child Care Center
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 Accessory Building and Child Care Center 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 Accessory Building and Child Care Center 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 Accessory Building and Child Care Center
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 Accessory Building and Child Care Center 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
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NYLOPLAST DUCTILE IRON
DO NOT POLLUTE DRAINS TO WATERWAYS
NYLOPLAST DUCTILE IRON
DO NOT POLLUTE DRAINS TO WATERWAYS
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ONOTPOLLUTE
UCTILEIRON
DRAINSTOWATERWAYS
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COMMUNITY BLDG
FFE=4936.85
(BLDG PHASE 1)
DAYCARE
FFE=4937.85
(BLDG PHASE 2)
LOT 1
BLOCK 3
TRACT A
Heart of the Rockies
Forth Subdivision
LOT 1
BLOCK 2
Existing Church Building
FFE = 4933.70
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.
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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.
8.THE ESTIMATED DISTURBED AREA IS 31,400± SF.
0
SCALE: 1" =
307.5 1515
15'
CONSTRUCTION ENTRANCE W/
VEHICLE TRACKING CONTROL
INLET PROTECTION
LIMITS OF DISTURBANCE (APPROX)
SILT FENCE
PERMANENT RIPRAP APRON
ROCK SOCKS
SEEDING, MULCHING AND CRIMPING
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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)
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5/1/24
1" = 15'
N/A
ZMW
JTC
21-1045-02
C2.00
6 10
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 28 2024
Heartside Hill - Community Building - Forebay Weir
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 15.71
Total Depth (ft) = 0.25
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 2.83
Highlighted
Depth (ft) = 0.14
Q (cfs) = 2.830
Area (sqft) = 2.24
Velocity (ft/s) = 1.26
Top Width (ft) = 15.71
0 2 4 6 8 10 12 14 16 18 20
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 = 2*π*5/2 = 15.71 ft (5 ft radius forebay)
1-11/16" Depth