HomeMy WebLinkAboutDrainage Reports - 02/02/1993FINAL DRAINAGE INVESTIGATIOH
FOR
319 M..Z\.T H EW S STREET
LOT 4, BLOCK 13 3
CITY 0~ FORT COLLINS
FINAL DRAINAGE INVESTIGATIOH
FOR
319 Mll.T HEWS STREET
LOT 4 , BLOCK 133
CI TY 0~ FORT COL LI NS
Prepare d f o r
CONTEMPORJI.RY BUI L DI NG CONCEPT S
713 De n n i s on Avenue
F o rt Co llins, Co l orado 80526
Gf -e t
January 20, 1993
Commission No.: 1163-11-01-02
CONSULTING ENGINEERS
G~ Eas t Th i rd St r ee t
Lo .~l a d , Colora d o 80537
(303) 663-0138
FOUNDATION II Engineering,
AND SOILS Inc.
January 20, 1993
Commission No.: 1163-11-01-02
Mr. Bret Larimer
Contemporary Building Concepts
713 Dennison Avenue
Fort Collins, Colorado 80526
Dear Mr. Larimer,
The enclosed report represents the results of the final d r ainage
inve s tigation for t h e 0.16 acres located at 319 Mathews S t reet, Lot
4 , Bl o ck 1 3 3, City of Port Co ll ins , in th e Sou t hea s t Qu a r ter o f
S ect i on 12, Townsh i p 7 North , Range 69 Wes t of the 6 th P .M .
This investigation was based upon the proposed site development
p l an and plnt ; proposed site development co n s t ruc tio n p l a ns; o n -
site observcttions; and available topographic information. The
lnveFtigation was performed in accordan ce with the criteria
established in the City of Fort Collins - ''Storm Drainage Design
Criteria and Construction Specification Stnadards" manual.
It ls our opinion
feasible provided
attached report and
~ccordance wlth the
that t he c onstruction of the f our--p x: is
that the recommendati ons con taired in t he
the incorporated fin :;l design are performed 1.1:
final approvc<l plans for the project.
C_RY2f ~u;::; <y7(
. Robert N . Sencenbaugh
?OUUDATI0N ENGINEERL'G , CO'SULJ::e: G r:;G:;:HEE~S , LT"C.
/1/ed by :
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100 East 3rd Street • Loveland, Colorado 80S37 • (303) 663-0138
Letter of Trans~ittal
Table of Content s
Scope
Site Description
Ex is ti ng Conditions
TABLE OF CONTENTS
Proposed De velopment
Conc1usions ·and Recommendations
Vici nity Map
Cal cu lat i orrn
Draina ge Plan/Site Plan
2XHIB I 'l'S
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Sxhibit: A
E.x:hi.bit B
Ex h i bit C
S C O P E
The following report represents the results of a d rainage
investigatio n for a proposed development t o be known as 319 Math ews
Street , Lot 4 , Blo c k 133 , City of Fort Collins, located on a par c e l
of land s i tuated i n t h e South eas t Qu arte r o f Section 1 2 , Town s h i up
7 North , Rang e 69 Wes t of the 6th P .M., Larime r County , Col o rado.
The inv es tigat io n was performed for Mr . Br e t Lar i mer . The purpose
of this i nvestigation is to determine the effects of the pr o posed
dev el opment of the a r ea 's e xis ting drain age c ond itions and to
determine the improvements , i f any , and th e appropriate sizing f or
proposed i mpr o vements so that it may be inco r p o rated with the
construction fo th e project . The conc l us i ons and recommendati o ns
presented in this report are based upon the propose d s ite
development plan and plat ; proposed site development const r ucti o n
plans; on -s ite ob~ervat i ons ; and the availab l e topographic
informalion . The analys is was perc1frmcd in accordance ,1ith the
City of Fort: Collins -" Sto rm Drainage Design Cr i tc r-ia and
Co ns truction Standards " manual .
S I T E D E S C R I P T I O N
The site is r e c t angular in s h ape and contain s appro x imately 0.17
acr es . T he s it e 's Ea st-Wes t dim e nsion is a p pr oxima t e l y 140 feet
and its Nor t h-South dim e nsio n is 50 f e et . The site abuts the
westerly right-of-way o f Mathews Street in the South 300 bl ock .
E X I S T I N G C O N D I T I O N S
The sit e i s curr en t l y not d eve l ope d, a n d i s na turally vegetated
wi th grasses and weeds and some e xi st i ng s mall trees . Ther e is a
natu ra l slope fr o m t he southwe st to the no r theast with a 2. 9%
slope. Dr aina ge and runoff are carried in curb and gutter of
mathews street flowing to the north.
Th e area surro u ndin g the site i s developed wi th mu lti-fa mi l y units.
The site re c e iv es ve ry littl e r u nof f from t his development.
Dra i na g e from o f f site i s sh o wn on th e g r a d ing plan submitted with
this report.
P R O P O S E D D E V E L O P M E N T
The proposed construction is to consists of developing the 0.17
acres into a multi-unit residential structure. Small parking areas
are proposed for the east and west ends of the site, and an access
driveway is proposed to connect to Mathews Street.
C O N C L U S I O N S A N D R E C O M M E N D A T I O N S
1 . The proposed development will retain existing drainage
patterns.
2 . The park i ng structure at the east end of the site wi ll be
constructed to serve as a catc~ bas i n. Drainage wil l be
installed to discharge into Mathews Street curb and gutter .
3 . The s ite is not located with i n a floodway or flood plan .
4. All development is to be performed in accordance with City of
Fort Collins Standards and Specifications .
5. On-site detention of stormwater is recommend ed . The
parking area proposed for the east end o f the lot will be used
for this purpose. The area will be excavated and backfilled
with gravel.
6. Erosion control during construction will be required. During
overlot grading a sediment trap shall be constructed, which
will eventually be the detention pond. Further, asphalt paving
as well as foundations will be completed first, to include
installation of detention facility.
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Runoff Coefficient
Current 0.20
Proposed, by composite method
C = (Sum of i =l to N (Ci/ Ai)) / At
C = (( 0.5 Gravel/1756 Sq F t ) + (0.95 Roof/1902 Sq Ft)
+ (0.95 Con cr ete /617 Sq Ft ) + (0.15 Gr ass/2707 Sq F t ) /
7000 Sq Ft
C = 0.53
Time Concentratio n
D = 152Ft
s = 3 %
C = 0.53
Tc = ( 1. 8 7 * ( 1. 1
Cf 2 to 10 year
to 25 year
to 50 year
=
=
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(C * Cf)) * DA0 .5 )/ SA .33 3
1. 0
1.10
1. 20
to 10 0 year = 1 .25
Tc 2 = 8.84 min
Tc 25 = 8.02 min
Tc 50 = 7.20 min
Tc 100 = 6.79 min
Analysis Methodology
Rational Method
Q = Cf*C*l*A
Q2 = .22cfs
QlO = .39cfs
Q200 = .74cfs
(from chart 3-2)
12 = 2.6 in/hr
110 = 4.6 in/hr
125 = 5.8 in/hr
150 = 6.9 in/hr
ilOO = 7+ in/hr
Release Rate
. 2 cfs per city Fort Collins
Time I Cf*C*A Vin
(sec)
408 7.75 .113 357
600 7.20 .113 487
900 6.05 .113 613
1200 5.2 .113 703
1800 4.2 .113 851
2700 3.25 .113 988
3600 2.6 .113 1054
5400 1. 85 .113 1125
Minimum De tention Required 500 CFt
···+··
Vout
81. 6
120
180
2 40
360
540
720
1080
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Det Req
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367
433
463
491
448
334
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EDGE <A' E XI STING PARK.ING L~T ~ \O
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RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: STANDARD FORM A
COMPLETED BY: Rw--s DATE: 1017[9?___
DEVELOPED ERODIBILITY Asb Lsb Ssb Lb Sb PS
SUBBA!i;rN ZONE . (ac) (ft) (%) (feet) (%) (%)
N\A f'f)o D E..12.A, £.. • 17 \'32. -"3, 0 \ ?'-
\52.. 3,o 8 \,CJ
MARCH 1991 8-14 DESIGN CRITERIA
EFFECTIVENESS CALCULATIONS
PROJECT:
COMPLETED BY:
Erosion Control
Method
.--PAe..~ \tvG r\ e..sR
C::S£1:::;\l"Y1~~,J-r If::~.~
MAJOR
BASIN
A
MARCH 1991
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f2.cuc:. ~ ~CD
PS SUB
(%) BASIN
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AREA
(Ac)
STANDARD FORM B
DATE: /0 / 7 / q L
C-Factor
Value
0 .0\
I . o o
P-Factor
Value
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a.so
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CALCULATIONS
Comment
---U ~-:-E ''-> n 0 "-) y O N D f'\ 'i<-~ Q.
(7') (3 E., C.0'\'\c,,\2.\)<::.,-lc..O ~ 1<;':..s ,)
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csoo ~ :r.'S :z /<:> 1o
~06'~r0 "'S'olL .: ~ 76
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-(99 * . o?<.\ + 79. t. ,. . 130/. J7
-:: 63.',8 fo
DESIGN CRITERIA
CONSTRUCTION SEQUENCE
PROJECT: Fove PIE.-'>< STANDARD FORM C
SEQUENCE FOR 19 ~ ONLY COMPLETED BY: DATE:
Indicate by use of a bar line or symbols when erosion control measures will be installed.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engin~er.
OVERL OT GRADING
IND EROSION CONTROL
Soil Ro u g h e ning
Perime t er Bar r ier
Addi tion a l Barriers
Vegetative Me t h od s
So il Sealant
Ot h er
YEAR
MONTH
INFALL EROSI ON CO NTROL
STRUCTU RAL :
Sediment T rap /Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare So i l Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettings/Mats/Blankets
other
INSTALLED BY
GETATION/MULCHING CONTRACTOR
TE SUBMITTED
MARCH 1991
I I I I 2. I -z.,l3
MAINTAINED BY
--------------
APPROVED BY CITY OF FORT COLLINS ON ----------
8-16 DESIGN CRITERIA
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OFF SITE FLOW CALCULATIONS
RUNOFF COEFFICIENT
COMPOSITE METHOD
C = (Sum of i = 1 to N ( Ci/ Ai )) / At
C = ((0.5 (Asphalt) / 10560 Sq Ft) + (0.95 (Roof) / 3000 Sq Ft)
+ (0.15 (Grass) / 1500 Sq Ft )) / 15061 Sq Ft
C = . 55 /
TIME CONCENTRATION
Tc= (1.87 * (1.1 -C * Cf)) * D A.5 / S A.33
D = 106 Ft S = 2 % Cf=
Tc = 7. 65 ~ S,Wl~ul)
IlOO = 6.35 (from chart
Q =Cf* C *I* A
p_ "'?
Q 1 0 0 = 1 . 5 3 Cf S J. 'o 2 0""""S "
1. 25
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