HomeMy WebLinkAboutGrading Plans - 11/30/2020Brown Farm 3rd
Lot 35, Block 4
���
� \
� -
�
, , �
� - - —_ —�--
_ _�--� � --�> ��
_�� �� � � •
���� av��
November 24, 2020
Stormwater Engineering & Development Review Division
City of Fort Collins Utilities
700 Wood Street
Fort Collins, Colorado 80522
RE: 2436 Farghee Court Drainage Memo
Parcel # 9602400032
Dear City of Fort Collins:
Grading/Stormwater Plan Accepted
(Building Permit Released)
Accepted by: Matt Simpson
Date: 11/30/2020
KEEFE CNIL,INC
825 Union Street
Golden, Colorado 80401
(970) 215-6808
meg@keefecivil.com
Keefe Civil Project Number: 2020-015
The purpose of this letter is to describe the proposed site improvenlents and potential drainage
impacts at 2436 Farghee Court (Exhibit A). The 0.33-acre project site is a developed single-family
residential lot with established landscaping located northwest of South Taft Hill Road and West
Drake Road in Fort Collins, Colorado. Current conditions at the site include a split-level house
with garden level windows, a small garden shed, a concrete patio with partial wood deck overlay,
established trees, several garden areas, and a concrete driveway.
The lot is bound by existing single-family residential properties on all rear and side lot lines.
Approximately 90% if the site consists of Altvan-Satanta loams, while the northwestern boundary
consists of Poudre fine sandy loam per the NRCS Soil Survey of Larimer County (E�ibit B). The
entire site has been classified as being within hydrologic soil group B. These soils are anticipated
to have a inoderate rate of water transmission.
Historically, site stormwater has drained with gentle slopes from the west to east via overland
flows. When stormwater does not infiltrate the established yard, it eventually flows into Farghee
Court right-of-way.
Per the flood insurance rate map (Exhibit C), the lot is located within Zone X. Zone X is defined as
an area of minimal flood hazard and does not have a base flood elevation associated with it.
The proposed site improvements include a single-story house addition with no basement and a
concrete patio area (Exhibit A). Due to the requirement of constructing a handicap accessible
addition for the homeowner, the finished floor must match the existing home. Therefore, the
addition will have a proposed hanging floor installed. Since there is a lack of adequate fall in the
backyard to allow for proper drainage swale slopes, the top of foundation will be 0.3 ft lower than
the finished grade along the western edge of the addition. The foundation will have damp-proofing
designed and installed by others.
The lot's total impervious area will be approximately 39%, which is less than the 45% maximum
for the City of Fort Collins' drainage master plan in this area. The site's total adjusted impervious
� _� _, � -�
� T'i' � - - - :� fi� '
� a�� �i a a c� a a� e��� a a a a� a� d a�� a���
a a a v v a v� v a v a v v v v a v a a a a v a�v �
r ��, �.1� fl� �4� fl� fl� �'� �Q� ,�� �Q� ,�'� �� ,�'� �� fl� �`e ,�'� p� �� ,�� ,�1� Q� �� �� �tr '
������������������������#�
2436 Farghee Court Drainage Memo
Pa�e 2 of 2
Keefe Civil Project No.: 2020-015
November 24, 2020
area will increase by 2,614 square feet (s�, as indicated in the following calculations.
Historic Adjusted Developed Adjusted
Total Lot Hardscape or Hard Lot Area Historic Area Lot Area Developed
Surface Areas (st� (s� (sf� Area (sf�
Concrete 1,060 1,060 1,740 1,740
Rooftop 1,625 1,625 3,605 3,605
Patio and Pavers (40%) 340 136 225 90
Total Impervious Area 3,025 2,821 5,570 5,435
Net Increase in Imperviousness 2,614 sf
The composite runoff coefficient and drainage basin runoff calculations for the historic and
developed site are included in the enclosed tables (Exhibit D). Using the Fort Collins Stormwater
Criteria Manual (2018), the proposed stormwater runoff will increase at the site, as indicated in the
summary table below. However, the newly developed stormwater will flow towards Farghee Court
right-of-way without negatively impacting neighboring properties with the construction of the
proposed 70 ft retaining wall along the southeastern property line.
2-year 10-year 100-year
Total Historic Runoff 0.22 cfs 0.37 cfs 1.02 cfs
Total Developed Runoff 0.39 cfs 0.66 cfs l.81 cfs
Based on the enclosed design, it is my professional opinion the additional runoff generated by
these site improvements will not cause adverse impacts to downstream private properties.
I herby attest that this letter for the final drainage design for 2A�36 Farghee Court was prepared by
me or under my direct supervision, in accordance with the provisions of the Fort Collins
Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not
assume liability for drainage facilities designed by others.
Thank you for the opportunity to submit this drainage memo. Please do not hesitate to reach out
to me if you have any questions or comments regarding the above items.
Best regards,
r� � � �
Megan L. Keefe, PE / Manager
Keefe Civil, Inc.
Enclosures
��o�P D O L�CF2s
,,,......
O � � N L. k�. �FO
. �
: � -� :
i � 39378 m i
. �e.M�s,� .
����' ,,,,:o�a,,�`=:,,,�a.�����
FSS�ONAL ENG�
Cc: David Kaplan, Elevated Design Build
John Motley, Elevated Design Build
� -� -� -� -G� -�. -� -G3 _� -G� _L� -p -� -� -� _� -G� -� -� -n -P -� -L� -� -L� -P
V O� D O r1 O O O O Q O O O O�7 O O� V Q � O � O
r� a d d e e e a d d d d e a d d e e d d a d d d d �
a a a a a a a a a a a a a a a a v a a a v v a a a c
> �� �'� do �d �Q �� Qo ao �d �� Q� Qa d� �d �� �d �d Q� �� �� Q� d� a� �� a�
AAAA�A�AA�AAAAA�►AA�AA'AAG�A�
� Hydrologic Soil Group—Larimer County Area, Colorado �
F (2436 Farghee Court, Fort Collins, CO) _
0 0
489616 489G23 489f'i30 489G37 489644 489f,51 489658 A89665 489Ci72 489679 489686
40° 33' 2T' N I I -.- -—Iq � :,,.�� — I__-- I . v I I _ �� I I _ I 40° 33' 2T' N
,
.
t' .' ,. �. : .
. > .n
d�
��.
�- � ,� .� � ,. � •� t. ��� _ � : , �� � �
` �-- � � ,�; �,
�II
, �� •� ��' - - � � �
• ' _ k � r. =��'°ry G.,
�:� � - _ . -���lM
�a .� -
� . . �. �
� b • �Y Ii
� .
. �. . � �.� ` � � -
6 xy,� � n - ii . — F r ,
4i'' ��• .A.� 9.' -� .���' .� � � F-
� ' � , Va _ � n , `di
_ �,.. _ �� �; �
- ; �� :
�.� �.�� , ° - .�
� �,- �t _, �. -
�,.� � r.. . �h� :.�` ���t ii u_� :;- .
� � - ` � � �
�_ �o .�� _ n _a= —�
� ��
,��.��`� . .�.: F ��..: . .
� � .a n? �� L� �. � � �� ' w -� � � � �� � �
k�` ry � � �
: .. . , � �'• • A� -���N ". " , k :� -_ _
m,
� ,
T
° .�� m : - �
� • �:
. . ��i — �i _ •� r` _, .A .. ' - - �
� '�� y;n - ��' -�
.� � .
' ,-� e .
• - e��. .. t,r .. _
�— � �� � .2�' i � ,�� . � _ � '3 .o.,� _y.l — �
� ,��° , . . 4... +i� •3 ` r�. • *Y 'p - y ' `
' . p � ,". � . ' � . ���1�'� �,, y� ,,74 y� � o u , �
, " y. ii� ?'�� ��-� � a � � � r?�' 1� � �!I � . ' ,
. _ ..
o ' . �
� Soil Ma m, ma not be Valid at�th �: � �• . "� .� ` "r _ ' ° �' � — �
`��` � " �
� is s ;ale. .0 .—� R' � Y
.� . ' � �
� • e�" �p �" Y�, �^ �' , . r. 4 . W L.. _ ,
. .-�
40° 33' 25° N I�`.� � . I a`a� "_i+fi: �.I m� AI� I '� ��ii�"-d�" i �.� I ."� i�-� I "�' ' 40° 33' 25" N
489616 489623 489630 48.9637 489694 489651 489658 489665 489672 489G79 489GB6
3 3
= ro
F Map Scale: 1:334 if pnnted on A landscape (11" x 8.5") sheet. '"
�
N Meters
0 4 9 18 27
/V �
0 15 30 60 90
Map projection: Web Merotor Comer coordinates: WGS84 Edge ti6: UTM Zone 13N WGS84
Natural Resources Web Soil Survey 8/2/2020
Conservation Service National Cooperative Soil Survey Page 1 of 4
Hydrologic Soil Group—Larimer County Area, Colorado
(2436 Farghee Court, Fort Collins, CO)
MAP LEGEND
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
� A
o A�o
0 B
� B/D
0 C
� C/D
� D
� Not rated or not available
Soil Rating Lines
� � A
r r A/D
rr B
M � B/D
rr C
r r C/D
� � D
r r Not rated or not available
Soil Rating Points
o A
0 A/D
0 B
o B�o
0 C
0 C/D
0 D
0 Not rated or not available
Water Features
Streams and Canals
Transportation
� Rails
� Interstate Highways
US Routes
Major Roads
Local Roads
Background
�i Aerial Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:24, 000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 15, Jun 9, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Natural Resources Web Soil Survey 8/2/2020
Conservation Service National Cooperative Soil Survey Page 2 of 4
Hydrologic Soil Group—Larimer County Area, Colorado
Hydrologic Soil Group
2436 Farghee Court, Fort Collins,
CO
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
Altvan-Satanta loams, 0 B
to 3 percent slopes
84
Poudre fine sandy loam, B
0 to 1 percent slopes
Totalsfor Area oflnterest
Description
0.3
0.1
0.4
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
84.8%
15.2%
100.0%
Natural Resources Web Soil Survey 8/2/2020
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group—Larimer County Area, Colorado
Component Percent Cutoff.• None Specified
Tie-break Rule: Higher
2436 Farghee Court, Fort Collins,
CO
Natural Resources Web Soil Survey 8/2/2020
Conservation Service National Cooperative Soil Survey Page 4 of 4
NOTES TO USERS
_ � -
unity �map repos:tory s .._ ..c
' Base Flood Elevatlons
-e=Es z � tiooewaVs - ;.:i
ne � _ � �:� � .
I ucq iF .�,a �ie
orl M1 c FiF, 1 F'e.�ti
c i , �ien.ss,. . � f:,,,;;
(,'�•/ tl, t:� .. �; � 11C S
�.C'�._' � AtC'.1 [�./. �,c.� W FIS
.:� Iv � A�•.1,. ne ."�Ne .V !il' 4c.CS .,
w � �...'JC��' i , .. _1..
COJ9tal B�s Flootl Elevations '.�:U'�y u y i�f�.:.r�1
v_ � �eP .nnv �`e��.. u �
.y� . �.� ..�,o arc.
s��m y . . ,ero �pc i
� n. �S'�Nt,i.e. I �
'�iL'c . c � a U.�.,es'
.. .,,. . r c w. . s s .c.. � � n . .-,,nn. te . .
^ _fi d V � � e �. _C
h_�,�.. asac � �a��+s
e �a
- tl A�eas r ; tlood
om�ol strucNres . c.4 - Veas�..es'
_ P � t _ _ _
- _z.,�_ ., eor:o��ai dammv. � <a,.z�
_ _ _ \ ' G:..e,:, Von,,�,:
V¢�tC i tl t m
' '� \ - _ ,92�
\� 4" e
' ; ., . ..�. e h��... . .e�.,e �
\Gb �_�
n:;nN � � ...
�,, . i
a=.+,:.�^' _ ' '
:3t5cys.'� _�pnv:::;
l .e r a 5-�''L':i:i .-.......
b h arks
�.x:H �,c , -
n i�� ,vov �.�f3oil �ia-azaz�.. , �, _.
6ase p � f M1 a �. C��� : '!y .
va::� 4 rrnli. c�-�u:,� u: �rv�
�. , _ _._ .....os..v� .u_�,..�.. c. _ ,�v �o;o�
' e tl<",y.,�� z stream channel co�f�9urations
H\ ,.ulv
� prn� � [ b.- 'nay
5. AS r�
�;1� u �aG i:1od (
E4'h. _0 2 tl..._ .naJ rP dG. _.�0_
COrporat¢ IlmitS 5""..:n C . e G25P� Cr '.ne :PS� C '
ae�
_ _ M p 1 tl
- > ,e > � v �> �.� _ «�,-
- v �
' _ - x�
- - �=FEMAMapServiceCe ter,��_5����,_
F.�
�Y=PG P
_ - = S;P FEMA Map
Se�v'�aeCe te u__s _ � � _. � c ...,_ �
�
�
sq,;,,s o
fLOC�iNG EFFECTS
SPHING CANVOI
FHRiC �!VEi7Jl01
3�
. �'��i'.'-.E�.•CTg�iVAd
ZONEAEJ�.-". r.,rEE�
�i N
LEGEND
� SPECIAL F!00� H(+ZQRD AREAS (SF4AsJ SUBIER T6
IfvUN�ATiON BV THE 1°/u ANNUAL Ch:ANCE FLOO�
e r
ee ctl'.. ry g.ven ' Sceial
a n�a�y � e n�e- r��.
i__e f ✓. T�..es P , A99�eV a J E. IMe �ise
�d��_icr„ e�.�s.z.ee<e,.no.et�r�a�..ieov�.
2crvE n �,.. �_ .��,. n s cu. r r .
2o,uCae „ . Yena� .. .-w.
zo�uCaH :i rcc• (�s� ,..Fas o ,i, xc nor.
ZONLaJ �eP �• �( 1 to ::mIY � z'e),
....nW. F�r ��.� o a�.0 an J�viuLr.v
L NL pH _ erminuo_ merN Orotc-c1eA f�an
�o_J s�bfn e tM
nJxa
, �e �o. � _ �da � i �„ u�� � � �� �an.� �,
�e�u�n�a n<. P.ocecka c no« o koc,ni
or sy tm u Ji w s. �c.0 ��� tN�.. �d k�vntv_
riM
xmEv no�d r � �r.iu,�ry nmT.n P�+�a em „. hnsP i�oN
�nWns o .ri �� . �
Zc'�uEVE I , �m vs«�n na:rro (.�.c rc.>,, �,.� no�
ev,c, s are. -rea. �
� FLOODWAY AREAS M 20NE AE
A .,.I f 1�� t!i'r-� LA t
vn tl���2 t tt I x �� 2nnu�l t a'rcx 10.J ixn t� ,crr. vvR out
..,ztanl_ n.. 5 n� �oa�' ..xig��:s.
0 OTHERhLOOD AREAS
zeNe x . a< � , ��w�.
. ae.�.;. or ie:: M.!� �.,m a.a��:
r�..3
e�,.e, a. a..a: a���-.�: . p.eg �� i q a. ..r .. �..<e
0 OTFERAREAS
zONE x tl terr��n�tl , x aisee c. . . a cnoncE �01=N.
ZONE J eas n n. t .,..d . ozutls a�. ir0 .e .�' eo, but rqssible_
� COASTAL BARRIER RESOURCES SVSfEM (CB'nS) AR'0.5
,�Di O'iHERN.'ISE PROTEC�EU AREAS (OPAs)
._,.�s.,�� .r,��� , .�...�-�,��a�u�.�.osce.� ..ar�..M�,s.
Fncaouirn no�:�a�.r
- - - Fbc., a�.Wury
- - (enc� 9aw�✓nJz�v
,... fJ •���������������• L'oF:..iJO�PLu�:.J.iv
0� ' �wanr ren.
�,� i v� _, �r arnms �� im ���
5t3^^^�^ �ase.iomi-k�.aooni�^emo.x�i:c;ec+.tm����.eei
.... - . a. �e ui .n I. . . t.� . i. �,
• r.<a
�7��re...�«�wn�n��n«, e c i �w� o �9av tw;vu su,
�i U^ c�,�x��mi.��
��_3�� -23� �r�..��-i1'.nc
Gth"rapn' cwrE �atec .rfrv��ncef, :n .ne I.mtl nnn an
' �� -' DaWm pf �983 (M� b'i)
-., �-� +wo�. e.e. u�.esa ra�s.e e we.ac,. g o.e�s ore �3
— svuamoc �ra u �. <mornoo s�re >iz�e roo
"•"`"� rynem��o��zo^e5(F:�ZOnE0503),Lam[ar:Cc�rtormal�Cnnic
��x��t � �.s e ,. ��a�ni� .� .o� v ��R seno� or
. 3 av¢ �-_5
. �2 ��.��' ,Y�! P�i9,�JEr M�,r�.�ry
P �� o Itr �n Lhe '.� 5� once SN Y� 0. fu !h�s 1�:- .
o tlere�mine If f v.oilaUle ir ywr „�wa�ce
nry ro
nyan[ a[ rell [r�e M1aM,�el Flcvio Ir,.ureric �rugrert` nl L�OMJF.�B 6C2� �
:.,E. _ . N ���j;'^>..
MAP SCALE �"=500'
25f �� - ��G�EET
�_,'� � ��= PANEL 0986G
_5,.�_�::.: �
`J:
�
��
<
;?
7G
/ �•
l.1_
i
FIRM
FLOOD INSURANCE RATE MAP '
L;1RI�tPR CO['\Tl',
COLOR:IDO
a\U ISCORYORA'S'ElldRti.aS
PANEL 986 OF 1420 ���,
r�r r_., �= Av�m I
CO�'TPK+IJ�. �'.
j :.�= -=iY. ����..
��m��
�� MAP NUMBER
,,����"=: 68669C6486G ,
c MAP REVISED
MAY 2, 2012 ����.
-���� }'i•derallmergi�nc� 1�fanaKement.�,i�ne;�
�^�,ao.o" �90eenmE "'..._.....__'""" °91soo�.F '�2
Composite Runoff Coefficient Calculations
2436 Farghee Court, Fort Collins, CO
� (�',����+� )
� _ ;-�
A,
Where: C= Composite Runoff Coefficient
C; = Runoff Coefficient for Specific Area (A;), dimensionless
A; = Area of Surface with Runoff Coefficient of C;, acres or square feet
n= Number of different surfaces to be considered
A, = Total Area over which C is applicable, acres or square feet
Equation 5-2
Historic Drainage Areas Developed Drainage Areas
Runoff Minor (2- and 10-yr) Major (300-yr) Minor (2- and 30-yr) Major (300-yr)
Surface Type Coefficientsl Area (sf) Composite CZ Composite C3 Area (sf) Composite CZ Composite C3
Hardscape or Hard Surface
Concrete 0.95 1,060 1,740
Pavers 0.50 135 135
Rooftop 0.95 1,625 3,605
Patio 0.50 205 90
Total Impervious Area 3,025 5,570
Landscape or Pervious Surface
Lawns, Clayey Soil, Flat Slope < 2% 0.20 11,170 8,625
Total Lot Area 14,195 0.35 0.44 14,195 0.49 0.61
Notes:
1. Runoff coefficients per Fort Collins Stormwater Criteria Manual Table 3.2-2.
2. Composite runoff coefficient per Fort Collins Stormwater Criteria Manual Equation 5-1.
3. Frequency adjustment factor per Fort Collins Stormwater Criteria Manual Table 3.2-3.
Table 3.2-3. Frequency Adjustment Factors
Storm Return Period Frequency Adjustment
(years) Factor (C�)
2, 5, 10 1.00
25 1.10
SO 1.20
100 1.25
Table 3.2-2. Surface Type - Runoff Coefficients
Surface Type Runoff Coefficients
Hardscape or Hard Surface
Asphalt, Concrete 0.95
Rooftop 0.95
Recycled Asphalt 0.80
Gravel 0.50
Pavers 0.50
Landscape or Pervious Surface
Lawns, Sandy Soil, Flat Slope < 2% 0.10
Lawns, Sandy Soil, Avg Slope 2-7% 0.15
Lawns, Sandy Soil, Steep Slope >7% 0.20
�awns, Clayey Soil, Flat Slope < 2% 0.20
Lawns, Clayey Soil, Avg Slope 2-7% 0.25
Lawns, Clayey Soil, Steep Slope >7% 0.35
Hartman - drainage.xlsx
Drainage Basin Runoff Calculations
2436 Farghee Court, Fort Collins, CO
Area Minor Major
Initial/Overland Timel Travel Timez Final T� Intensity (in/hr)° Basin Flow (cfs)5
Basin Length Slope Minor to Major to Length Slope Channel Velocity tt Minor Tc Major Tc
(acres) Composite C Composite C 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr
(ft) (%) (min) (min) (ft) (%) Type (fps) (min) (min) (min)
Historic
A 0.326 0.35 0.44 100 1 14.0 12.4 NA 14.0 12.4 1.92 3.29 7.16 0.22 0.37 1.02
Developed
A 0.326 0.49 0.61 50 2 6.4 5.2 120 1%o swale 1.5 1.3 7.8 6.5 2.44 4.16 9.11 0.39 0.66 1.81
Notes:
1. Per Fort Collins Stormwater Criteria Manual Section 3.3.2.
i.s��i.i-cxcf>�
T' 3�
Where: C= Runoff Coefficient, dimensionless
Cr = Frequency Adjustment Factor, dimensionless
L= Length of Overland Flow, feet
S = Slope, percent
2. Per Fort Collins Stormwater Criteria Manual Section 3.3.3.
V _ 1.49 R2/3S1/2
n
Where: V = Velocity, feet/second
n = Roughness Coefficient, dimensionless
R= Hydraulic Radius, feet (Hydraulic Radius = area / wetted perimeter, feet)
S = Longitudinal Slope, feet/feet
And:
L
T� - vxbo
3. Per Fort Collins Stormwater Criteria Manual Section 3.3.4. A minimum T� of 5 minutes is required.
T� iso + 10
4. Per IDF Table for Rational Method, Table 3.4-1 Fort Collins Stormwater Criteria Manual.
5. Per Fort Collins Stormwater Criteria Manual Equation 5-1.
Q = CIA
Where: Q= Peak Rate of Runoff, cfs
C = Runoff Coefficient, dimensionless
I = Rainfall Intensity, in/hr
A= Area of the Basin or Sub-basin, acres
Hartman - drainage.xlsx