HomeMy WebLinkAboutDrainage Reports - 02/23/2018TAIT
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December 27'h, 2016
City of Fort Collins Engineering Division
281 N College
Fort Collins, CO 80524
1 6163 E. County Rood 16, to l..d. CO 80s37 i
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Drainage Letter for the Proposed Site Development located at
Harmony Rd and Ziegler Rd, Fort Collins, CO 80528
Lot 13, Front Range Village
Dear Rick Richter
City of Ft. Collins pro d Plans
Approved By_
Date
This drainage letter is to convey the proposed site development conforms to the overall report, which is
titled Final Drainage and Erosion Control Study for Front Range Village, Fort Collins, Colorado prepared
by Stantec Consulting Inc (February, 2007), and will hereafter be referred to as the Master Report.
The subject property currently consists of drive aisles, an undeveloped building pad, and the Front Range
Village Dog Park. The area of disturbance for these improvements is 65,340 SF (1.540 acres). The
development is located in the southeast quarter of Section 32, Township 7 North, Range 68 West of the
61h Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado, on the northwest corner
of Harmony Rd and Ziegler Rd. The subject property lies on Lot 13 of Front Range Village. The site is
bound to the west by existing parking lot and commercial retail, to the north by Council Tree Avenue, to
the east by an existing drive aisle, and to the south by Lot 7 (Famous Dave's BBQ).
Proposed improvements for this lot include a building constructed on the north side of the site with a total
footprint of 13,880 square feet, consisting of a strip mall with restaurant, retail, and office space. The site
consists of Type C Soils Nunn clay loam, and existing backfill. This site is located in flood Zone X, "Areas
determined to be outside the 0.2% annual chance floodplain."
' Existing drainage patterns on the west side of site direct flows to either a curb inlet or an area inlet in the
drives. The east side of the site spills into the parking lot to the east where it sheet flows to an inlet across
the parking lot. Master Report was calculated using a minimum overall imperviousness of 84-percent for
' this basin. The proposed lot is accounted for in the Final Drainage Report as includes a portion of basin
201, along with basins 202, 203, 204, 206, and 209. These basins have a combined Clio of 6.27 cfs and
Q1oo of 13.98 cfs. The post developed site will discharge at rates less than or equal to these flows in the
10 and 100 year storm events.
' Post -development drainage will be conveyed via sheet flow and curb and gutter to a combination of
existing inlets and a couple of proposed inlets. See drainage plan sheet at the end of this letter for
additional information.
The post development property consists of nine on -site sub -basins. See drainage sheets for additional
information.
Post -development Sub -basin C1 consists of 0.48 acres of drive aisle, parking lot and landscaping along
the southwest side of the site. This basin is 68% impervious. Runoff from this basin drains via sheet flow
and curb and gutter to an existing area inlet in the parking lot. Sub -basin C1 discharges at a rate of 0.91
cfs in the 10-year storm event and 3.86 cfs in the 100-year storm event.
' Post -development Sub -basin C2 consists of 0.23 acres of parking lot, sidewalk and landscaped area on
the northwest side of the site. This basin is 82% impervious. Runoff from this basin generally sheet flows
' to a curb inlet on the east side of the parking area. Sub -basin C2 has a discharge rate of 0.91 cfs in the
10-year event and 2.00 cfs in the 100-year storm event.
Post -development Sub -basin C3 consists of 0.01 acres of paved walkway and landscape area near the
' northwest corner of the building. This basin drains to an existing grate inlet in the landscape area. This
basin is 46% impervious. Sub -basin C3 discharges at 0.03 cfs in the 10-year event and 0.07 cfs in the
100-year storm event.
Post -development Sub -basin C4 consists of 0.02 acres of paved walkway and landscaped area on the
near the northwest corner of the building. This basin drains into a proposed grate inlet in the landscape
area. This basin is 46% impervious. Sub -basin C4 discharges at 0.05 cfs in the 10-year event and 0.14
' cfs in the 100-year storm event.
Post -development Sub -basin C5 consists of 0.01 acres of paved walkway near the northwest corner of
the building. This basin drains into the street to the north to continue existing drainage patterns. This
basin is 90% impervious. Sub -basin C5 discharges at 0.04 cfs in the 10-year event and 0.09 cfs in the
100-year storm event.
' Post -development Sub -basin C6 consists of 0.03 acres of paved walkway and patio. This basin drains
into a proposed trench drain inlets on the north side of the building. This basin is 90% impervious. Sub -
basin C6 discharges at 0.13 cfs in the 10-year event and 0.27 cfs in the 100-year storm event.
Post -development Sub -basin C7 consists of 0.32 acres of the proposed building. This basin drains into
all surrounding sub -basins and follows the drainage patterns of those sub -basins. This basin is 90%
impervious. Sub -basin C7 discharges at 1.36 cfs in the 10-year event and 2.90 cfs in the 100-year storm
event.
Post -development Sub -basin C8 consists of 0.27 acres of paved walkway, parking lot, and landscape
area. This basin drains to the southeast corner of the proposed parking spaces to a proposed storm drain
inlet, which connects to the existing storm drain system in the drive aisle on the west of the site. This
basin is 80% impervious. Sub -basin C8 discharges at 1.05 cfs in the 10-year event and 2.33 cfs in the
100-year storm event.
Post -development Sub -basin C9 consists of 0.03 acres of landscaping. This basin drains to the private
drive aisle on the south side of the property. This basin is 2% impervious. Sub -basin C9 discharges at
0.04 cfs in the 10-year event and 0.18 cfs in the 100-year storm event.
Post -development Sub -basin C10 consists of 0.08 acres of landscaping and sidewalk. This basin drains
to the private drive aisle on the east side of the property. This basin is 54% impervious. Sub -basin C10
discharges at 0.25 cfs in the 10-year event and 0.63 cfs in the 100-year storm event.
The overall post -development site imperviousness is 75%, compared to the minimum 85% previously
designed conditions. After improvements, the site will discharge at a total rate of 12.49 cfs in the 100-
year storm event, generating 1.49 cfs less than existing conditions, as determined in the master drainage
report. See drainage plan for additional information.
The overall drainage concept for this site is to convey flows via sheet flow and curb and gutter to a number
' of inlets throughout the site. The drainage patterns and flow rates generally conform to the original design
intent.
' Since
Alex
' Direc
RUNOFF COEFFICIENT CALCULATIONS
Project Name: C01303C - Front Range Village - Lot 13
Calculated By: NE
Check By: AH
Date: 12/27/2016
RECOMMENDED RUNOFF COEFFICIENT AND PERCENT IMPERVIOUS
Runoff Coefficients, C-value
LAND USE
°k IMPERVIOUS
10 YEAR 100 YEAR
LANDSCAPE
2
1
0.22
0.52
DRIVES AND WALKS
90
0.87
1
0.91
ROOFS
90
0.87
0.91
POST -DEVELOPMENT CONDITIONS:
AREA
DESIGN
A(LAND.)
AC
A(D&W)
AC
A(ROOFS)
AC
A(TOTAL)
AC C10 C100
%
IMPERVIOUS
C1
0.12
0.36
0.00
0.48
0.71
0.81
68
C2
0.02
0.21
0.00
0.23
0.81
0.88
82
C3
0.01
0.01
0.00
0.01
0.55
0.72
46
C4
0.01
0.01
0.00
0.02
0.55
0.72
46
C5
0.00
0.01
0.00
0.01
0.87
0.91
90
C6
0.00
0.03
0.00
0.03
0.87
0.91
90
C7
0.00
0.00
0.32
0.32
0.87
0.91
90
CS
0.03
0.24
0.00
0.27
0.80
0.87
80
C9
0.03
0.00
0.00
0.03
0.22
0.52
2
C10
0.03
0.05
0.00
0.08
0.61
0.75
54
TOTAL: 1.49
WEIGHTED:
0.84
75
1 Runoff coefficients and percent impervious per UDFCD Stormwater Design Manual
10-YEAR INDIVIDUAL BASIN FLOWS
' Project Name: C01303C - Front Range Village - Lot 13
Calculated By: NE
Check By: AH
Date: 12/27/2016
' POST -DEVELOPMENT CONDITIONS:
SUB -BASIN DATA
DIRECT RUNOFF
CONTRIBUTING
BASIN
EFFECTIVE
I
SUB BASIN
BASINS
AREA acre
C10
AREA acre
in/hr
Q cfs
C1
0.48
0.71
0.34
4.87
1.65
C2
0.23
0.81
0.19
4.87
0.91
C3
0.01
0.55
0.01
4.87
0.03
C4
0.02
0.55
0.01
4.87
0.05
C5
0.01
0.87
0.01
4.87
0.04
C6
0.03
0.87
0.03
4.87
0.13
C7
0.32
0.87
0.28
4.87
1.36
C8
0.27
0.80
0.22
4.87
1.05
C9
0.03
0.22
0.01
5.87
0.04
C10
0.08
0.61
0.05
4.87
1 0.25
TOTAL: 1
5.50
I per City of Fort Coillins stormwater design standards.
Q10= C*I*A
1
100-YEAR INDIVIDUAL BASIN FLOWS
' Project Name: C01303C - Front Range Village - Lot 13
Calculated By: NE
' Check By: AH
Date: 12/27/2016
POST -DEVELOPMENT CONDITIONS:
SUB -BASIN DATA
DIRECT RUNOFF
CONTRIBUTING
BASINS
BASIN
AREA acre
C100
EFFECTIVE
AREA acre
I
in/hr
SUB BASIN
Q cfs
C1
0.48
0.81
0.39
9.95
3.86
C2
0.23
0.88
0.20
9.95
2.00
C3
0.01
0.72
0.01
9.95
0.07
C4
0.02
0.72
0.01
9.95
0.14
C5
0.01
0.91
0.01
9.95
0.09
C6
0.03
0.91
0.03
9.95
0.27
C7
0.32
0.91
0.29
9.95
2.90
C8
0.27
0.87
0.23
9.95
2.33
C9
0.03
0.52
0.02
10.95
0.19
C10
0.08
0.75
0.06
1 9.95
1 0.63
TOTAL: 12.49
1 I per City of Fort Coillins stormwater design standards.
Q100= C'I'A
Channel Report
' Hydraflow Express Extension for Autodesk® AutoCADO Civil 3D® by Autodesk, Inc.
6 inch Roof Drain
Circular
Diameter (ft)
Invert Elev (ft)
Slope (%)
N-Value
Calculations
Compute by:
Known Q (cfs)
Elev (ft)
11.00
10.75
1 10.50
' 10,25
10.00
' 9.75
Highlighted
= 0.50
Depth (ft)
Q (cfs)
Area (sqft)
= 10.00
Velocity (ftls)
= 99.00
Wetted Perim (ft)
= 0.013
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Known Q
= 2.90
0 1
Monday, Nov 21 2016
= 0.26
= 2.900
= 0.10
= 27.97
= 0.81
= 0.50
= 0.50
= 12.42
Section
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCADO Civil 3D® by Autodesk. Inc.
12 Inch PVC
'
Circular
Diameter (ft)
= 1.00
Invert Elev (ft)
= 100.00
Slope (%)
= 1.50
N-Value
= 0.013
'
Calculations
Compute by:
Known Q
Known Q (cfs)
= 3.12
'
Elev (ft)
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Section
' 102.00
101.50
101.00
v
' 100.50
100.00
99 50
0 1
1 Reach (ft)
I
Wednesday, Dec 21 2016
= 0.63
= 3.120
= 0.52
= 5.98
= 1.83
= 0.76
= 0.97
= 1.19
3
Depth (ft
..00
1.50
1.00
1 11
-0.50
Channel Report
' Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
<Name>
' Circular
Diameter (ft) = 1.50
Invert Elev (ft) = 100.00
tSlope (%) = 1.50
N-Value = 0.013
'Calculations
Compute by: Known Q
Known Q (cfs) = 4.90
1
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Wednesday, Dec 21 2016
= 0.65
= 4.900
= 0.74
= 6.65
= 2.16
= 0.86
= 1.49
= 1.34
Depth I
2.00
0
1
0
1
0
1
Section
2
3
4
1.5C
1.0C
0.5C
O.00
-0.5 1
Reach (ft)
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GENERAL NOTE:
MY FUTURE UND DISTURBANCE. INCREASE IN IMPERNWS AREA
MD/OR CHANGE IN RUNOFF CONDITIONS ON THIS 511E MAY REQUIRE
MDITU)NAL STORM WATER MANAGEMENT PER FORT CQ1NS
REQAANXIS IN PUCE AT THAT TINE (INCLUDING TOTAL LND
OSNRBAJICF AND/OR IMPERVIOUSNESS ADDED W THIS PLAN).
STORMWATER RUNOFF NOTES
TDTM DISTURBED AREA: 1.49 ACE
PRENOUAY APPROVED DEVELOPMENT X IMPERNWS: 85
POST -DEVELOPMENT X IMPERNWS: 25
POST -DEVELOPMENT 10-YR STORM RUNOFF: 9.50 CFS
POST -DEVELOPMENT 100-YR STORM RUNOFF: 1149 CIS
A = BASIN DESIGNATION
6 � B =AREA IN ACRES
C = X IMPERVIOUSNESS
SUMMARY RUNOFF TABLE
CONTRIBUBASH D AREA
(ACRES)
C N1WE .
ROOM
1PEmM
(CRS)
P�
(OS)
Cl 0.411
O.D
1.0
3.86
CZ 0.23
ON
0.91
2.00
C3 0.01
On
0.03
0.07
04
O02
en
0.05
0.14
CS 0.0
E91
0.N
0.W
CS 0.03
E91
0.13
0.27
C9
0.32
0.91
1.36
29O
N
0.28
1.05
1.05
112
N
0.0
0.52
ON
0.15
CIO
0.0N
On
125
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R UNAUTHORIZED CHANGES & USES: r ,TQI
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`! THE ENGINEER PREPARING THESE PUNS Mill NOT BE RESPOMMWE FOR. OR UABFE FOR, UNAUTHORIZED ENGINEERS NOTE TO CONTRACTOR
AIANGES TO OR ENGINEERS
DATUM: NGVO29 UNAANSRD (CID CITY OF FMT GER DATUM)
USES Of THESE PANS, ALL CHANGES OF THESE RUNS MUST BE IN MIRING AND MUST BE APPROVED F THE PREPARED?: *= W BENCHMARK /II-9C ALUMINUM CAP 300' HEST OF COIDETT GRIM ON 1W OF c
OF THESE PUNS PRIOR TO CONSTRUCTION. CONSTRUCTOR CONTRACTOR AGREES THAT IN ACCORDANCE AFF GENERALLY CONCNEHE VIAL OF IRRIGATON STRUCTUR[ ELEVATOR 4950.01
ACCEPTED CONSTRUCTION PRACTCES, CONSTRUCTOR CONTRACTOR WLL BE REWIRED TO ASSUME SOFT AND COMPEER THE EYSIENLE AND LOCATOR Of ANY UNDERGROUND UTUTES, PIPE$ AND/DI SiRUCTNLS BENCHMARK 15-07: SOUTHEAST OWNER Of HARMONY ED. MD A QER ED. SO ifA
RESPONSBIUTY FOR JOB SR CONDITONS DURING THE COURSE OF CONSTRUCTON OF THE PROJECT, INQADING SUETY OF SHOW W THESE PUNS RETIE WTANED BY A SEARCH OF AVAIUME REGORGS THERE MAYBE ♦ _ SOUTH OF THE EDGE OF ASPHALT ON THE WALL QI A DOME!WIGAMIN DROP
ALL PERSONS AND PROPERTY. THAT THIS REWIREMSNT SHALL BE MADE TO APPLY CONTINUOUSLY AND NOT BE UNITED TO EDSTNG UTUUTES NOT SOW W THESE PUNS. THE CONTRACTOR SHAM ASCERT1 THE 10.UE /
Y NORMAL "KING HWR% AND CONSTRUCTION CONTRACTOR FURTHER AGREES TO DEFEND, INDEMNIFY ANI) HOD DENG4 VERTCM AND HORIZONTAL LOCATOR OF THOSE UNDERGROUND UTUTES TO BE USED POOR 10 THE BFAMNCS BASD QI THE SOUTH UNE Q TH7�M�ST SiRUMINE. ELENATON 492/.N9 FEET.NOM W NAAIL HARMUSS PROECT, MGM MY NG FIAD A- M9 t FRRE L ORAUFEGED, IN SOF£ NEWQNCOE E DEIGN PRCHLSSO�IALMMGE OF �TES,CSIONAND N OR HA BE RESPONSINFE FW ANY DAMAGE TO MY PUBLIC OR PRIVATE WAIN OF S TpN 32 AS BEMING NORTH N9' 26 If RANI M DATUM IS REWIRED FOR MY PURPOSE. TE FOUL EWATON SHG FIRM RAT Q FRONT RANGE VILLBE USFb. MONK = NGw29 UNADJUSTED i z20'
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