Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
Prepared For:
Larry H. Miller
LHM Thornton
Landmark
Towers
10289 Quivas Street
Thornton, Colorado
Anderson, Wahlen & Associates, Inc.
2010 North Redwood Road
Salt Lake City, Utah 84116
Phone: (801) 521-8529
Fax: (801) 521-9551
Project #: 14-116
Date: December 27, 2016
Final Drainage Report
1/17/2017
December 30, 2016
City of Thornton, Colorado
Engineering Department
Re: Final Drainage Report
To Whom It May Concern:
AWA is submitting this Final Drainage Report for the LHM Thornton Landmark Towers project
located at 10289 Quivas Street, Thornton, Colorado.
This report includes, pre-development conditions and peak release rates as well as post-
development peak release rates for this site. In addition this report provides mitigation options
and detention per City standards and regulations. All calculations included in this report follow
the City of Thornton – Standards and Specifications Manual which references the Urban
Drainage and Flood Control District (UDFCD) Manual Volumes 1, 2, and 3.
If you have any questions regarding this report, please feel free to contact me, Arverd Taylor, at
Sincerely,
Arverd Taylor
Project Manager
Responsible Party Certification
“________ hereby certifies that the sewer and water systems for Landmark Towers will be constructed
according to the design presented in this report. I understand that the City of Thornton does not and
shall not assume liability for the sewer and water system designed and/or certified by my engineer. I
understand that the City of Thornton reviews utility plans, but cannot, on behalf of Landmark Towers,
guarantee that final utility design review will absolve ________ and/or their successors and/or assigns of
future liability for improper design. I further understand that approval of the Plat and/or Development
Permit does not imply approval of my engineer’s utility design.”
Attest:
“I hereby certify that this report (plan) for the Final Utility Design of Landmark Towers was
prepared by me (or under my direct supervision) in accordance with the provisions of the City of
Thornton Standards and Specifications for the Design and Construction of the Public and Private
Improvements for the Responsible Parties thereof. I understand that the City of Thornton does
not and shall not assume liability for utilities designed by others.”
XRegistered Pro fession al En g ineer
State of Co lo rado No. ____________________
XName of Respon sib le Party
XNotary Pu b lic
XAuth orized Sign atu re
Table of Contents GENERAL LOCATION MAP ............................................................................................................................. 1
PROPERTY LOCATION & DESCRIPTION ......................................................................................................... 2
PROPERTY LOCATION ................................................................................................................................ 2
DESCRIPTION OF PROPERTY ..................................................................................................................... 2
DRAINAGE BASINS AND SUB-BASINS ............................................................................................................ 2
MAJOR BASIN AND SUB-BASIN DESCRIPTION .......................................................................................... 2
DRAINAGE DESIGN CRITERIA ........................................................................................................................ 3
REGULATIONS ........................................................................................................................................... 3
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ...................................................................... 3
HYDROLOGICAL CRITERIA ......................................................................................................................... 3
DRAINAGE FACILITY DESIGN ..................................................................................................................... 4
HYDRUALIC CRITERIA ................................................................................................................................ 6
CONCLUSION ................................................................................................................................................. 6
APPENDICES .................................................................................................................................................. 7
REFERENCES .................................................................................................................................................. 8
1
GENERAL LOCATION MAP
Landmark Towers: 10289 Quivas Street
Thornton, Colorado
2
PROPERTY LOCATION & DESCRIPTION
PROPERTY LOCATION
The proposed property is a Portion of the Northwest Quarter of Section 16, Township 2 South, and
Range 68 West of the 6th P.M. City of Thornton, County of Adams, in the State of Colorado. The address
of the site is 10289 Quivas Street, Thornton, Colorado.
The 6.55 acre site is currently undeveloped. The property is bound on the north by a Five Star Collision
Center-Auto Repair shop, to the east by Quivas Street, to the south by residential housing and a
developed commercial lot, and to the west the Alpine Glen Veterinary Clinic.
DESCRIPTION OF PROPERTY
Existing conditions of, the 6.55 acre, site consist primarily of undeveloped land covered by soil and
weeds. The site is relatively flat with the soils containing Platner loam and Ulm loam, corresponding to
soil class C (Web Soil Survey, Appendix I). Existing drainage of the site occurs from the west to the
northeast side of the property. The 6.55 acre site will be constructed in two phases. This report will
account for the full buildout of both phases to adequately size the detention pond.
The proposed project’s land use will be for Vehicle Service and Storage with a majority of the area
consisting of a parking lot. The site will contain a 4,010 square foot building, parking lot, and landscape
area located within the parking lot. A 10.0’ Public Service Utility Easement will be located south of the
proposed parking lot and a 10’ Gas Easement will be located through the north portion of the site
(Appendix II, Civil Sheets - Utility Plan).
DRAINAGE BASINS AND SUB-BASINS
MAJOR BASIN AND SUB-BASIN DESCRIPTION
The site is located within Zone X (unshaded) of the FEMA floodplain, as determined by the Flood
Insurance Rate Map for Adams County, Colorado, Panel 294 and Map Number 08001C0294H, revised on
March 5, 2007 (Appendix III).
The existing drainage for the site consists of overland sheet low to the northeast onto the neighboring
property. After construction all storm water generated onsite will be collected and detained onsite
before being released at a metered rate.
3
The property was separated into 8 different sub-basins. Each sub-basin area was determined based on
site grading and subsequent drainage patterns. Storm water is collected in each sub-basin by catch
basins which ultimately is conveyed to the onsite detention pond. The detention pond has a low flow
trickle channel that drains to an inlet/outlet structure before connecting to a curb drain in Quivas Street
(Utility Plan, Appendix II).
DRAINAGE DESIGN CRITERIA
REGULATIONS
It is not foreseen that there will be any deviations from the criteria. All waterlines, sanitary sewer lines,
storm drain networks, and site improvements shall be constructed per the City of Thornton Standards
and Specifications.
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
At this time there are no known utility studies (i.e., utility reports, project master plans, etc.) done for
this site in question, and no adjacent utility studies. All storm water produced on site will be contained
and will not drain to neighboring property.
HYDROLOGICAL CRITERIA
In accordance with the City of Thornton’s Standards and Specifications, the methodologies and design
standards for determining rainfall, runoff conditions, and detention pond sizing for the project are based
on the standards prescribed in the Urban Drainage and Flood Control District (UDFCD), with local revisions
defined in the Standards and Specifications manual.
Rainfall data was gathered from the NOAA precipitation data frequency server based on latitude and
longitude (Appendix IV). The runoff calculation used was the rational method, as was specified within the
UDFCD manual as an acceptable runoff method for sites smaller than 90 acres. This site was divided into
roof area, landscaping and hard surfaces to determine the runoff coefficient. Individual runoff coefficients
of 0.13, 0.85, and 0.9 were used for landscape, roof and impervious surfaces respectively. The overall
calculated peak runoff for the site for the developed phase is approximately 36 cfs (see calculations
below).
4
Site characteristics:
Area: 6.55 acres
Roof: 4,010 sq. ft.
Hard Surfaces: 234,941 sq.ft.
Landscape: 46,527 sq.ft.
Corresponding Runoff Coefficient = 0.77
Time of Concentration (UDFCD Volume 1, Equation 6-5)
�� = �18 − 15 +�
60�24 + 12���=
�� = ����� ��� �� ������������ ��� �� �� !���ℎ����#
= �$��%��#��## �� #�� �%/100
�� = �(�$� �� �(�) $��ℎ ���/�� � = (��*�ℎ �� �(�) $��ℎ ���
�� = �18 − 15�0.82 +1000
60�24�0.82 + 12√0.03= ~ 10 �����#
Rational Method (UDFCD Volume 1)
/ = $��0 ���� �� ������ ���#
! = ������ ���������
1 = �%���*� ����#�2 �� �����(( ��� � 3������ �4��( �� �ℎ� ��� �� ������������, ����/ℎ� 6 = �� ����2 ���� �����#
/ = !16
/ = �0.77�7.13 �/ℎ��6.55 ����# = 36 ��#
DRAINAGE FACILITY DESIGN
Within the Standards and Specifications section 402.12 (Detention Pond Design), the requirement states
“storage volumes must be calculated using the Full Spectrum Detention Pond sizing method.” Based on
the Full Spectrum Detention Volume specifications within the UDFCD manual, three different volumes are
associated with the design of a full spectrum detention facility. These three different volumes are:
1. WQCV (Water Quality Capture Volume)
2. EURV (Excess Urban Runoff Volume)
3. 100-Year Volume
*Calculations using equations from the UDFCD manual can be found below.
5
1. WQCV (UDFCD Volume 3, Equation 3-1)
8/!9 = ��0.911; − 1.191< + 0.78
� = ��������� �����#$��3�* �� 8/!9 3��� ��� ��=>!= 9�(�� 3, ?� (� 3 − 2
1 = 1�$��%��#��## �%/100
8/!9 = 1�0.91�0.82; − 1.19�0.82< + 0.78�0.82 = 0.34 )����#ℎ�3 − ��ℎ�# = 8084��;
2. EURV (UDFCD Volume 2, Equation 12-3)
@�A9B = 1.20C.�D
= �$��%��#��## ����
@�A9B = 1.20�0.82C.�D = 0.969 )����#ℎ�3 − ��ℎ�# = 23,027 ��;
3. 100-Year Volume (UDFCD Volume 2, Equation 12-4)
9C�� = EC[�0.728C.<GD + 0.15�.<GD6% + �0.364C.<DH + 0.381C.<DHI% + �0.306C.<DH
+ 0.402�.<DH!=%]
=100-year 1-hour rainfall depth= 2.69 in. (Standards and Specifications manual, Section 402.1)
Site Soil Classification = 100% Soil C (Web Soil Survey, Appendix I)
9C�� = 2.69[�0.306�0.82C.<DH + 0.402�0.82�.<DH1] = 1.66 )����#ℎ�3 − ��ℎ�# = 39,456��;
The Full Spectrum Detention Volume Specifications method is also designed to reduce the developed
condition 100-year peak discharge to 90% of the pre-developed 100-year peak flow rate. Table 12-5
within Volume 2 of the UDFCD manual denotes that the specified site can utilize the simplified
equations for the detention pond sizing method. Pre-development peak unit discharge rates are based
on NRCS hydrologic soil group, total flow length and general site slope. Based on the characteristics
listed above Table 12-8 of Volume 2 was utilized to determine the pre-development rate to be 1.49 cfs,
corresponding to a 1.34 cfs release rate for the developed site.
Taking into account the release discharge rate of 1.34 cfs from the 100-Year Volume calculation above,
the site requires a total storage volume of 34,632 ft^3 for the 100-year return period. The onsite
6
detention pond has been adequately sized to detain the required storage volume by providing 56,148
ft^3 of storage capacity. Detention and the specified release rate will be accomplished by two orifice
plates. The first orifice, with a 1.4“ diameter, has been sized to release the EURV in 72 hours as per city
requirements. The second orifice, with a 5” diameter, has been sized to release storm water at the
calculated 1.34 cfs. All orifice calculations can be found in Appendix V.
HYDRUALIC CRITERIA
A private pipe network will be constructed onsite to route storm water runoff to the detention pond
before it is released at a metered rate to Quivas Street. All storm drain, sewer, and additional utility
piping shall be installed per manufacturer’s recommendations and shall meet the City of Thornton’s
Standards and Specifications layout in Section 200, 300, and 400.
CONCLUSION
The LHM Thornton site is in compliance with the City of Thornton’s Standards and Specifications manual.
The calculated developed site has a peak runoff of 46 cfs generated onsite. This 46 cfs peak runoff is
calculated prior to detention and a metered outfall from the site. The detention pond has been sized
using Full Spectrum Detention Specifications method outlined in the UDFCD manual. Equations utilized
within the UDFCD manual calculated a 100-year volume of 39,456 cubic feet, a WQCV volume of 8,084
cubic feet, and a EURV volume of 23,027 cubic feet. A release rate for the developed site was calculated
to be 1.34 cfs. This release rate requires a storage volume of 34,632 cubic feet, which is adequately
stored in the designed detention pond, which has 56,148 cubic feet of storage capacity. Detention will
be accomplished by the use of two orifice plates. The first orifice, with a 1.4“ diameter, has been sized to
release the EURV in 72 hours as per city requirements. The second orifice, with a 5” diameter, has been
sized to release storm water at the calculated 1.34 cfs. All flows larger than the detention basin will be
directed to Quivas Street before flooding the building or neighboring properties.
7
APPENDICES
APPENDIX I – WEB SOIL SURVEY (SOIL CLASSIFICATION)
APPENDIX II – CIVIL SHEETS
APPENDIX III – FEMA FLOOD MAP
APPENDIX IV – NOAA RAINFALL DATA
APPENDIX V – ORIFICE CALCULATIONS
8
REFERENCES
City of Thornton (2012, October). City of Thornton – Standards and Specifications. Retrieved from
https://cityofthornton.net/government/citydevelopment/Pages/standards-specifications.aspx
Urban Drainage and Flood control District (2016, January). Urban Storm Drainage Criteria
Manual – Volume 1. Retrieved from http://udfcd.org/volume-one
Urban Drainage and Flood control District (2016, January). Urban Storm Drainage Criteria
Manual – Volume 2. Retrieved from http://udfcd.org/volume-two
Urban Drainage and Flood control District (2016, January). Urban Storm Drainage Criteria
Manual – Volume 2. Retrieved from http://udfcd.org/volume-three
United States Department of Agriculture, Natural Resources Conservation Service (n.d.). Web Soil
Survey. Retrieved from https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx
FEMA (n.d.). FEMA Flood Map Service Center. Retrieved from http://msc.fema.gov/portal
APPENDIX I WEB SOIL SURVEY (SOIL CLASSIFICATION)
Hyd
rolo
gic
Soi
l Gro
up—
Ada
ms
Cou
nty
Are
a, P
arts
of A
dam
s an
d D
enve
r Cou
ntie
s, C
olor
ado
(LH
M -
Thor
nton
)
Nat
ural
Res
ourc
esC
onse
rvat
ion
Serv
ice
Web
Soi
l Sur
vey
Nat
iona
l Coo
pera
tive
Soi
l Sur
vey
12/2
6/20
16P
age
1 of
4
4414610441464044146704414700441473044147604414790
4414610441464044146704414700441473044147604414790
4991
1049
9140
4991
7049
9200
4992
3049
9260
4992
9049
9320
4993
5049
9380
4991
1049
9140
4991
7049
9200
4992
3049
9260
4992
9049
9320
4993
5049
9380
39° 5
2' 5
9'' N
105° 0' 37'' W
39° 5
2' 5
9'' N
105° 0' 25'' W
39° 5
2' 5
3'' N
105° 0' 37'' W
39° 5
2' 5
3'' N
105° 0' 25'' W
N
Map
pro
ject
ion:
Web
Mer
cato
r C
orne
r coo
rdin
ates
: WGS
84
Edge
tics
: UTM
Zon
e 13
N W
GS84
050
100
200
300Fe
et0
1530
6090M
eter
sM
ap S
cale:
1:1
,330
if p
rinte
d on
A la
ndsc
ape
(11"
x 8
.5")
shee
t.
Soi
l Map
may
not
be
valid
at
this
sca
le.
MA
P LE
GEN
DM
AP
INFO
RM
ATIO
N
Are
a of
Inte
rest
(AO
I)A
rea
of In
tere
st (A
OI)
Soils So
il R
atin
g Po
lygo
nsA A
/D
B B/D
C C/D
D Not
rate
d or
not
ava
ilabl
e
Soil
Rat
ing
Line
sA A
/D
B B/D
C C/D
D Not
rate
d or
not
ava
ilabl
e
Soil
Rat
ing
Poin
tsA A
/D
B B/D
C C/D
D Not
rate
d or
not
ava
ilabl
e
Wat
er F
eatu
res
Stre
ams
and
Can
als
Tran
spor
tatio
nR
ails
Inte
rsta
te H
ighw
ays
US
Rou
tes
Maj
or R
oads
Loca
l Roa
ds
Bac
kgro
und A
eria
l Pho
togr
aphy
The
soil
surv
eys
that
com
pris
e yo
ur A
OI w
ere
map
ped
at1:
20,0
00.
War
ning
: Soi
l Map
may
not
be
valid
at t
his
scal
e.
Enl
arge
men
t of m
aps
beyo
nd th
e sc
ale
of m
appi
ng c
an c
ause
mis
unde
rsta
ndin
g of
the
deta
il of
map
ping
and
acc
urac
y of
soi
llin
e pl
acem
ent.
The
map
s do
not
sho
w th
e sm
all a
reas
of
cont
rast
ing
soils
that
cou
ld h
ave
been
sho
wn
at a
mor
e de
taile
dsc
ale.
Ple
ase
rely
on
the
bar s
cale
on
each
map
she
et fo
r map
mea
sure
men
ts.
Sou
rce
of M
ap:
Nat
ural
Res
ourc
es C
onse
rvat
ion
Ser
vice
Web
Soi
l Sur
vey
UR
L:C
oord
inat
e S
yste
m:
Web
Mer
cato
r (E
PS
G:3
857)
Map
s fro
m th
e W
eb S
oil S
urve
y ar
e ba
sed
on th
e W
eb M
erca
tor
proj
ectio
n, w
hich
pre
serv
es d
irect
ion
and
shap
e bu
t dis
torts
dist
ance
and
are
a. A
pro
ject
ion
that
pre
serv
es a
rea,
suc
h as
the
Alb
ers
equa
l-are
a co
nic
proj
ectio
n, s
houl
d be
use
d if
mor
eac
cura
te c
alcu
latio
ns o
f dis
tanc
e or
are
a ar
e re
quire
d.
This
pro
duct
is g
ener
ated
from
the
US
DA
-NR
CS
cer
tifie
d da
ta a
sof
the
vers
ion
date
(s) l
iste
d be
low
.
Soi
l Sur
vey
Are
a:
Ada
ms
Cou
nty
Are
a, P
arts
of A
dam
s an
dD
enve
r Cou
ntie
s, C
olor
ado
Sur
vey
Are
a D
ata:
Ve
rsio
n 13
, Sep
22,
201
6
Soi
l map
uni
ts a
re la
bele
d (a
s sp
ace
allo
ws)
for m
ap s
cale
s1:
50,0
00 o
r lar
ger.
Dat
e(s)
aer
ial i
mag
es w
ere
phot
ogra
phed
: A
ug 3
0, 2
014—
Sep
18, 2
014
The
orth
opho
to o
r oth
er b
ase
map
on
whi
ch th
e so
il lin
es w
ere
com
pile
d an
d di
gitiz
ed p
roba
bly
diffe
rs fr
om th
e ba
ckgr
ound
imag
ery
disp
laye
d on
thes
e m
aps.
As
a re
sult,
som
e m
inor
shift
ing
of m
ap u
nit b
ound
arie
s m
ay b
e ev
iden
t.
Hyd
rolo
gic
Soi
l Gro
up—
Ada
ms
Cou
nty
Are
a, P
arts
of A
dam
s an
d D
enve
r Cou
ntie
s, C
olor
ado
(LH
M -
Thor
nton
)
Nat
ural
Res
ourc
esC
onse
rvat
ion
Serv
ice
Web
Soi
l Sur
vey
Nat
iona
l Coo
pera
tive
Soi
l Sur
vey
12/2
6/20
16P
age
2 of
4
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Adams County Area, Parts of Adams and Denver Counties, Colorado(CO001)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
PlC Platner loam, 3 to 5percent slopes
C 5.7 85.6%
UlD Ulm loam, 5 to 9 percentslopes
C 1.0 14.4%
Totals for Area of Interest 6.7 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils areassigned to one of four groups according to the rate of water infiltration when thesoils are not protected by vegetation, are thoroughly wet, and receiveprecipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) andthree 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) whenthoroughly wet. These consist mainly of deep, well drained to excessivelydrained sands or gravelly sands. These soils have a high rate of watertransmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. Theseconsist chiefly of moderately deep or deep, moderately well drained or welldrained 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 consistchiefly of soils having a layer that impedes the downward movement of water orsoils of moderately fine texture or fine texture. These soils have a slow rate ofwater transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) whenthoroughly wet. These consist chiefly of clays that have a high shrink-swellpotential, soils that have a high water table, soils that have a claypan or claylayer at or near the surface, and soils that are shallow over nearly imperviousmaterial. 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 isfor drained areas and the second is for undrained areas. Only the soils that intheir natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—Adams County Area, Parts of Adams and Denver Counties, Colorado LHM - Thornton
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
12/26/2016Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Adams County Area, Parts of Adams and Denver Counties, Colorado LHM - Thornton
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
12/26/2016Page 4 of 4
APPENDIX II - CIVIL SHEETS (UTILITY PLAN)
APPENDIX III FEMA FLOOD MAP
APPENDIX IV - NOAA RAINFALL DATA
NOAA Atlas 14, Volume 8, Version 2 Location name: Thornton, Colorado, USA* Latitude: 39.8825°, Longitude: -105.0079°
Elevation: 5520.06 ft** * source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
AMS-based point precipitation frequency estimates with 90% confidence intervals (in
inches/hour)1
DurationAnnual exceedance probability (1/years)
1/2 1/5 1/10 1/25 1/50 1/100 1/200 1/500 1/1000
5-min2.89
(2.24-3.72)4.15
(3.22-5.36)5.26
(4.04-6.80)6.88
(5.18-9.41)8.24
(6.06-11.4)9.73
(6.90-13.7)11.3
(7.72-16.4)13.6
(8.93-20.2)15.5
(9.84-23.1)
10-min2.12
(1.64-2.72)3.04
(2.36-3.93)3.85
(2.96-4.98)5.03
(3.80-6.88)6.04
(4.43-8.32)7.13
(5.05-10.0)8.30
(5.65-12.0)9.98
(6.53-14.8)11.4
(7.21-16.9)
15-min1.72
(1.34-2.22)2.48
(1.92-3.19)3.12
(2.41-4.05)4.10
(3.09-5.60)4.91
(3.60-6.76)5.79
(4.11-8.16)6.75
(4.59-9.75)8.12
(5.31-12.0)9.24
(5.86-13.7)
30-min1.21
(0.942-1.56)1.74
(1.35-2.25)2.19
(1.69-2.84)2.86
(2.16-3.90)3.42
(2.51-4.71)4.02
(2.85-5.66)4.68
(3.18-6.75)5.60
(3.67-8.29)6.36
(4.03-9.46)
60-min0.746
(0.580-0.960)1.08
(0.834-1.39)1.36
(1.05-1.76)1.77
(1.33-2.41)2.11
(1.55-2.90)2.48
(1.75-3.48)2.87
(1.95-4.14)3.43
(2.24-5.07)3.88
(2.46-5.77)
2-hr0.443
(0.348-0.564)0.642
(0.502-0.818)0.809
(0.630-1.04)1.05
(0.800-1.42)1.25
(0.928-1.70)1.47
(1.05-2.04)1.70
(1.17-2.42)2.03
(1.34-2.96)2.29
(1.47-3.37)
3-hr0.319
(0.252-0.403)0.461
(0.363-0.584)0.580
(0.455-0.738)0.753
(0.575-1.01)0.895
(0.667-1.21)1.05
(0.754-1.44)1.21
(0.836-1.71)1.44
(0.957-2.09)1.63
(1.05-2.37)
6-hr0.189
(0.151-0.236)0.268
(0.214-0.336)0.335
(0.265-0.422)0.431
(0.333-0.568)0.510
(0.384-0.679)0.594
(0.432-0.808)0.684
(0.478-0.954)0.811
(0.545-1.16)0.913
(0.596-1.31)
12-hr0.116
(0.094-0.143)0.160
(0.129-0.199)0.197
(0.158-0.245)0.251
(0.196-0.326)0.294
(0.224-0.387)0.341
(0.251-0.458)0.391
(0.276-0.538)0.461
(0.313-0.650)0.517
(0.341-0.734)
24-hr0.071
(0.058-0.087)0.098
(0.079-0.119)0.119
(0.096-0.146)0.149
(0.117-0.191)0.174
(0.133-0.224)0.199
(0.148-0.263)0.226
(0.161-0.305)0.262
(0.180-0.365)0.292
(0.195-0.409)
2-day0.041
(0.034-0.050)0.057
(0.047-0.069)0.070
(0.057-0.085)0.087
(0.069-0.109)0.100
(0.077-0.126)0.113
(0.084-0.146)0.126
(0.091-0.168)0.145
(0.100-0.197)0.159
(0.107-0.220)
3-day0.030
(0.025-0.036)0.041
(0.034-0.049)0.049
(0.040-0.059)0.060
(0.048-0.075)0.069
(0.054-0.087)0.078
(0.059-0.101)0.088
(0.063-0.116)0.100
(0.070-0.136)0.110
(0.075-0.151)
4-day0.024
(0.020-0.028)0.032
(0.026-0.038)0.038
(0.031-0.046)0.047
(0.037-0.058)0.053
(0.042-0.067)0.060
(0.046-0.077)0.067
(0.049-0.088)0.077
(0.054-0.104)0.084
(0.057-0.115)
7-day0.015
(0.013-0.018)0.020
(0.017-0.024)0.024
(0.020-0.028)0.029
(0.023-0.035)0.032
(0.026-0.040)0.036
(0.028-0.046)0.041
(0.030-0.053)0.046
(0.033-0.062)0.051
(0.035-0.068)
10-day0.012
(0.010-0.014)0.015
(0.013-0.018)0.018
(0.015-0.021)0.021
(0.017-0.026)0.024
(0.019-0.030)0.027
(0.021-0.034)0.030
(0.022-0.039)0.034
(0.024-0.045)0.037
(0.026-0.049)
20-day0.008
(0.007-0.009)0.010
(0.008-0.011)0.011
(0.009-0.013)0.013
(0.011-0.016)0.014
(0.012-0.018)0.016
(0.012-0.020)0.017
(0.013-0.022)0.019
(0.014-0.025)0.021
(0.015-0.028)
30-day0.006
(0.005-0.007)0.007
(0.006-0.009)0.009
(0.007-0.010)0.010
(0.008-0.012)0.011
(0.009-0.013)0.012
(0.010-0.015)0.013
(0.010-0.017)0.015
(0.011-0.019)0.016
(0.011-0.020)
45-day0.005
(0.004-0.005)0.006
(0.005-0.007)0.007
(0.006-0.008)0.008
(0.007-0.009)0.009
(0.007-0.010)0.010
(0.008-0.012)0.010
(0.008-0.013)0.011
(0.008-0.014)0.012
(0.009-0.016)
60-day0.004
(0.004-0.005)0.005
(0.004-0.006)0.006
(0.005-0.007)0.007
(0.006-0.008)0.008
(0.006-0.009)0.008
(0.006-0.010)0.009
(0.007-0.011)0.010
(0.007-0.012)0.010
(0.007-0.013)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of annual maxima series (AMS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and annual exceedance probability) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
Page 1 of 4Precipitation Frequency Data Server
12/22/2016http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=39.8825&lon=-105.0079&d...
PF graphical
Back to Top
Page 2 of 4Precipitation Frequency Data Server
12/22/2016http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=39.8825&lon=-105.0079&d...
Maps & aerials
Small scale terrain
Large scale terrain
Large scale map
+
–3km
2mi
+
–100km
60mi
+
–100km
60mi
Page 3 of 4Precipitation Frequency Data Server
12/22/2016http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=39.8825&lon=-105.0079&d...
Back to Top
US Department of CommerceNational Oceanic and Atmospheric Administration
National Weather ServiceNational Water Center
1325 East West Highway Silver Spring, MD 20910
Questions?: [email protected]
Disclaimer
+
–100km
60mi
Page 4 of 4Precipitation Frequency Data Server
12/22/2016http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=39.8825&lon=-105.0079&d...
APPENDIX V - ORIFICE CALCULATIONS
Q=CdAo(2gh)^1/2 Q=CdAo(2gh)^1/2
Flow (Q) = 0.09 Flow (Q) = 1.34
Head (h) = 3 Head (h) = 4
Cd= 0.62 Cd= 0.62
Area (in^2)= 1.50 Area (in^2)= 19.39
Dia (in) = 1.38 Dia (in) = 4.97
*Use 1.4" Diameter * Use 5" Diameter
EURV - 72 Hour
(100 Year Event) Total 100 Year Event
Orifice Calculations