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August August August August 13131313, , , , 2018201820182018
RE:RE:RE:RE: Fort Collins Brewery (Revisions for Red Truck Brewery Minor Amendment)Fort Collins Brewery (Revisions for Red Truck Brewery Minor Amendment)Fort Collins Brewery (Revisions for Red Truck Brewery Minor Amendment)Fort Collins Brewery (Revisions for Red Truck Brewery Minor Amendment)
This project included very minor modifications to the existing detention/WQL pond,
originally constructed as part of the Fort Collins Brewery project. Those modifications
are shown on Revision 1 to the approved Fort Collins Brewery Utility Plans, dated
12/28/2017, and in the approved Drainage Memorandum, dated 8/23/2017. Both
documents are attached for reference.
Although there were minor deviations from the approved grading plan (greater than
0.2’), the as-built conditions indicate that the project was constructed in general
conformance with the approved revised grading plan and approved Drainage
Memorandum. Adequate slopes are provided to convey runoff from the site to the
existing detention and water quality pond.
The detention volume within the detention pond located on site is in accordance with
the approved Drainage Memo referenced above. As such, there is negligible impact
from the modifications and no modification to the outlet structure is required. The pond
will function in a substantially identical manner as the pre-project conditions.
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4025 Automation Way, Suite C4
Fort Collins, CO 80525
970-232-9645
www.WashburnSurveying.com
Sheet 1 of 1 Project #: 2018-002 Date: July 9, 2018 Scale: 1"=10' Drawn: CDB
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AS-BUILT EXHIBIT
RED TRUCK BEER COMPANY
LOT 2, FORT COLLINS BREWERY, LOCATED IN THE SOUTHEAST OF THE NORTHEAST QUARTER OF SECTION 12, TOWNSHIP 7 NORTH, RANGE 69 WEST OF
THE 6TH P.M., CITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADO
ELEVATIONS SHOWN ARE FROM AN AS-BUILT SURVEY OF THE SITE PERFORMED ON
July 9 & 17, 2018
CHAD R. WASHBURN
COLORADO LICENSED PROFESSIONAL LAND SURVEYOR 37963 FOR
AND ON BEHALF OF WASHBURN LAND SURVEYING, LLC. 970.232.9645
EngineeringEngineeringEngineeringEngineering
908 Laporte Avenue Fort Collins, Colorado 80521 970.219.2834 bob@apex-engineer.com
AugustAugustAugustAugust 23, 201723, 201723, 201723, 2017
Mr. Shane Boyle, P.E.
Stormwater Department
City of Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80521
RE:RE:RE:RE: Drainage Drainage Drainage Drainage MemoMemoMemoMemo
Red Truck Brewery Red Truck Brewery Red Truck Brewery Red Truck Brewery –––– Minor AmendmentMinor AmendmentMinor AmendmentMinor Amendment
Dear Shane,
This purpose of this letter is to examine the potential impacts of the proposed site
improvements associated with the above referenced Minor Amendment (MA) project on
the existing drainage facilities located on the project site. As we discussed in our
meeting on 5/31/2017, the project consists of exterior and interior remodeling of the
existing Fort Collins Brewery located at 1020 East Lincoln Avenue. There is also an
elevated deck proposed over the existing detention pond. The deck is supported by 38
12”x12” concrete piers and four 24”x24” concrete piers. The total plan area of the 42
proposed piers is 54 square feet.
The changes in impervious cover created by the revisions to the site design are as
follows:
• Removal of concrete from parking area and sidewalk (190)
• Expansion of existing patios and sidewalk (906 SF)
• A gravel trail along the west side of the building (1283 SF)
In preparing this drainage memo, the following approved documents prepared by Apex
Engineering for the Fort Collins Brewery (FCB) project are referenced:
• Utility Plans (and subsequent drawings of record), dated 4/20/2009
• Final Drainage, Erosion Control and Water Quality Report, dated 4/20/2009
• Drainage Certification, dated 9/24/2010
RunoffRunoffRunoffRunoff ParametersParametersParametersParameters
The net effect of the removal and additions listed above, the weighted composite runoff
Coefficient (C) and percentage of impervious area changes very slightly. The following is
a comparison of the existing and proposed values (calculations attached):
C % Imp.
Existing 0.852 82.1%
Proposed 0.857 83.0%
Detention StorageDetention StorageDetention StorageDetention Storage
The original FTB detention analysis was based on a proposed C of 0.852 for full build out
of both phases of the project. The original analysis was modified to reflect the higher
proposed C of 0.857. The results indicate that these revisions do not increase required
detention volume. Please note that this result is to be expected since the City’s detention
volume calculation spreadsheet adds a 25% factor of safety to all runoff coefficients.
Basin Roof Area (sqft) Asphalt Area (sqft) Concrete Area (sqft) Gravel Area (sqft) Lawn Area (sqft) Total Area Composite
No."C=0.95" "C=0.95" "C=0.95" "C=0.50" "C=0.25" (sqft) "C"
P-1 38,843 32,013 33,510 1,283 11,927 117,576 0.874
Total SITE 38,843 32,013 33,510 1,283 11,927 117,576 0.874
Total Acreage 0.89 0.73 0.77 0.03 0.27 2.70
Impervious Ratio
Basin Roof Area (sqft) Asphalt Area (sqft) Concrete Area (sqft) Gravel Area (sqft) Lawn Area (sqft) Total Area Imperviousness
No.(sqft) Ratio
P-1 38,843 32,013 33,510 1,283 11,927 117,576 0.830
Total SITE 38,843 32,013 33,510 1,283 11,927 117,576 0.830
Total Acreage 0.89 0.73 0.77 0.03 0.27 2.70
Composite Calculations
Basins Total Area Sum CxA Composite C
P-1, E-4 3.64 3.12 0.857
Business:
Commercial areas
Neighborhood areas
Residential:
Single-family
Multiunit (detached)
Multiunit (attached)
Half-acre lot or larger
Apartments
Industrial:
Light areas
Heavy areas
Parks, cemeteries:
Playgrounds:
Schools:
Railroad yard areas:
Undeveloped areas:
Historical Flow Analysis
Greenbelts, agricultural
Off-site flow analysis
(when land use not defined)
Streets:
Paved
Gravel (packed)
Driveways and sidewalks:
Roofs:
Lawns, sandy soil
Lawns, clayey soil
*Refer to Figures RO-3 through RO-5 in Runoff Chapter
Notes:
1. Net increase in concrete area = 535 SF
2. Net increase in gravel area = 1340 SF
45
0
0
100
40
90
90
10
50
15
2
*
80
80
90
5
95
85
*
60
75
Land Use or Surface Characteristics Percent Imper-viousness
Developed Weighted Runoff Coefficients
Red Truck Beer
APEX ENGINEERING
1:32 AM
8/23/2017
100 Year
This is to convert % imp. to a C value
100-year (must insert % imp. and C pervious).
ft3 acre-ft.
'C' value 0.86 42981.1 0.9867
'C' * 1.25 1
Area 3.64 acres Modified Modified
Release Rate 0.73 M. FATER D. JUDISH C. LI
5/95 Nov-97 Nov-98
DETENTION POND SIZING
TIME TIME INTENSITY Q 100 Runoff Release Required Required
cum 100 year Volume Cum total Detention Detention
(mins) (secs) (in/hr) (cfs) (ft^3) (ft^3) (ft^3) (ac-ft)
0 0 0 0.00 0 0.0 0.0 0.0000
5 300 9.950 36.22 10865.4 218.4 10647.0 0.2444
10 600 7.720 28.10 16860.48 436.8 16423.7 0.3770
15 900 6.520 23.73 21359.52 655.2 20704.3 0.4753
20 1200 5.600 20.38 24460.8 873.6 23587.2 0.5415
25 1500 4.980 18.13 27190.8 1092.0 26098.8 0.5991
30 1800 4.520 16.45 29615.04 1310.4 28304.6 0.6498
35 2100 4.080 14.85 31187.52 1528.8 29658.7 0.6809
40 2400 3.740 13.61 32672.64 1747.2 30925.4 0.7100
45 2700 3.460 12.59 34004.88 1965.6 32039.3 0.7355
50 3000 3.230 11.76 35271.6 2184.0 33087.6 0.7596
55 3300 3.030 11.03 36396.36 2402.4 33994.0 0.7804
60 3600 2.860 10.41 37477.44 2620.8 34856.6 0.8002
65 3900 2.720 9.90 38613.12 2839.2 35773.9 0.8213
70 4200 2.590 9.43 39595.92 3057.6 36538.3 0.8388
75 4500 2.480 9.03 40622.4 3276.0 37346.4 0.8574
80 4800 2.380 8.66 41583.36 3494.4 38089.0 0.8744
85 5100 2.290 8.34 42511.56 3712.8 38798.8 0.8907
90 5400 2.210 8.04 43439.76 3931.2 39508.6 0.9070
95 5700 2.130 7.75 44193.24 4149.6 40043.6 0.9193
100 6000 2.060 7.50 44990.4 4368.0 40622.4 0.9326
105 6300 2.000 7.28 45864 4586.4 41277.6 0.9476
110 6600 1.940 7.06 46606.56 4804.8 41801.8 0.9596
115 6900 1.890 6.88 47469.24 5023.2 42446.0 0.9744
120 7200 1.840 6.70 48222.72 5241.6 42981.1 0.9867
Required detention
Page 1
Red Truck
Detention Pond
As Built Detention Pond Volume Rating Curve
Elevation (ft.)
Area
(ft.2 )
Area
(acre)
Storage
(acre-ft.)
Cumulative Storage
(acre-ft.)
35.01 0 0.000 0.000 0.000
35.50 332 0.008 0.001 0.001
36.00 3,495 0.080 0.019 0.020
36.50 7,007 0.161 0.059 0.079 36.627
37.00 7,059 0.162 0.081 0.160
37.50 7,097 0.163 0.081 0.241
38.00 7,136 0.164 0.082 0.322
38.50 7,518 0.173 0.084 0.406
39.00 9,004 0.207 0.095 0.501
39.50 9,653 0.222 0.107 0.608
40.00 16,220 0.372 0.147 0.755
40.50 28,703 0.659 0.254 1.009
40.60 31,206 0.716 0.069 1.078 40.604
(100 year Volume) Required =0.99 acre-ft
WQCV Required = 0.094 acre-ft
(100 year Volume+ WQCV) Required =1.08 acre-ft
40.60
36.63
where:
V = volume between contour interval
d = elevationn - elevationn-1
A = area of elevationn-1 contour
B = area of elevationn contour
100-year WSEL =
WQ WSEL =
Based on As-Built Topography of Existing Detention Pond
()V d A B AB= + +1
3
APEX ENGINEERING
1:33 AM
8/23/2017