HomeMy WebLinkAboutDrainage Reports - 08/30/20021
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FINAL DRAINAGE REPORT
FOR
REPLAT OF LOTS 7 AND 8, BLOCK 152
CITY OF FORT COLLINS
OLD TOWN MASTER DRAINAGE BASIN•
PREPARED FOR
ROCKY MOUNTAIN CONSTRUCTION MANAGEMENT
B
May 30, 2001
PREPARED BY
STEWART & ASSOCIATES
103 SOUTH MELDRUM STREET
P.O. BOX 429
FORT COLLINS, CO 80522
TEL. 970-482-9331
FAX. 970-482-9382
FI --
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Table of Contents
I
1 Vicinity Map
2-3 Teat of Report
4-7 Runoff Calculations & Drainage Table
8-11 Erosion Control Calculations
Pocket Grading, Drainage & Erosion Control
Plan2
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VICINITY MAP
SCALE: 1 "= 1000'
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STEWART8406SOCIATES
Consulting Engineers and Surveyors
May 30, 2001
Mr. Basil Harridan
Stormwater Utilities
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522-0580
Dear Basil,
' The following is the final drainage report for the Replat of Lots 7 and 8, Block 152, City of
Fort Collins. The site is in the OLD TOWN MASTER DRAINAGE BASIN. It contains 19,000
square feet which is 0.4362 acres. The site is bounded on the North by single family residences, on
the East by an alley, on the South by a single family residence and on the West by Peterson Street.
The site is not in a flood plain.
' The site has two existing single family houses on the West 100 feet. A frame garage was
removed from Lot 7. The site slopes from Southwest to Northeast at an approximate slope of 2.0 %.
The proposal is to divide the two lots into four lots. The West 100.00 feet of Lots 7 and 8
will have the existing two houses. The East two lots will be the East 90.00 feet of Lots 7 and 8 for
' two proposed alley houses. The two existing house lots will not be regraded. The East lots will be
regraded but will continue to drain to the alley.
' The existing gravel alley will be concreted from East Oak Street South for 220 feet. The alley
will be from 16.00 feet to 20.00 feet wide with an inverted crown on the centerline.
' The Historic Basin is all of Lots 7 and 8 and it drains East from the West property line to the
alley. The historic two year runoff rate is 0.24 c.f.s. and the historic 100 year runoff rate is 1.13 c.f.s.
' The Developed Basin is all of Lots 7 and 8 and it also drains East from the West property line
to the alley. The runoff coefficient increases from 0.34 for the historic runoff to 0.49 for the
developed runoff. The developed two year runoff rate is 0.40 c.f.s. and the developed 100 year
runoff rate is 1.91 c.f.s.
' There is an existing storm sewer in Oak Street and an existing storm sewer in Whedbee Street.
The outfall from the intersection of these two storm sewers flows Northerly across Riverside to the
Cache la Poudre River. The outfall storm sewer length is approximately 640 feet. Due to the
' closeness to the River, on site detention is not warranted. The timing of the down -stream runoff
should be to flow out before up stream flows arrive.
James H. Stewart and Associates, Inc.
103 S. Meldrum Street • P.O. Box 429 • Ft. Collins, CO 80522
' 970/482-9331 • Fax 970/482-9382
I (3)
The Old Town Master Drainage Basin Plan has a percentage of impervious area in Table 4.3.
For this Subcatchment No. 201, the percentage of impervious area is 40%. The coefficient of runoff
' is then 0.50. The coefficient of runoff for this site is 0.49. Since the coefficients are similar, on -site
detention is not warranted.
' The fact that the alley is being concreted also facilitates the runoff flowing North to Oak
Street. The increase in runoff will be able to be carried in the concrete alley invert.
' The area that will be disturbed will be the East 90 feet of the site to construct the proposed
alley houses. As soon as the foundations are poured there will be very little need for a water quality
pond. Therefore we are requesting that a variance to the requirement of a water quality pond being
' constructed be granted.
' EROSION CONTROL: The site is in the moderate rainfall erodibiilty zone and in the moderate wind
erodibility zone.
' A silt fence will be placed along the East 90 feet of the North property line. The site will be
sodded after the construction of the alley houses are completed.
' The historic and developed runoff calculations and the erosion control calculations are
enclosed as a part of this report. The Grading, Drainage and Erosion Control Plan is also enclosed
with this report.
This drainage report and the design of the drainage system are in compliance with the City
of Fort Collins Storm Drainage specifications and criteria. If you have any questions regarding this
report, please call
' Sincerely,
63.(A� a'
Richard A. Rutherford, P. . & L.S.
RAR/meh
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STEWART&ASSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
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STEWART&SSOCIATES 103 S. MELDRUM, FORT COLLINS, CO 80521
Consulting Engineers and Surveyors
PH. 482-9331 FAX 482-9382
By: jk% A. P—, — Date: 10, 7-ov Client: g,qe: TMnu.vral.v C - 9, Sheet No. 'S' of
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STEWART&ASSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: Date: -P �.l 7_a 0 Client: kougy A47-Ail Sheet No. of
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STEWART9 ASSOCIATES 103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors
BY: P A-./L. Date: AML- ZJ ofCIient: tQoc,1tyAiouu7-,t1A1 C-, M, Sheet No. 7 of_
Project: R�pLAT- nF 1-n-rs -7� 9 / R C I zx at= 1-'7, 6/7 1- e- t'U'r
Subject: u)j a g=r- 1-c L/ L q -no Als rp p- A e E',4 T') Az A 1,-Je,, Tip A Le, �z
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CONSTRUCTION SEQUENCE
PROJECT: ,2enLATocLo-rs -71L3, �3cock- 15Z, C/ry o<STANDARD FORM C
5EQLENCE. FOR z6ol ONLY COMPLETED BY: ,e•Ae- DATE: Dec.t2, zxo
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Indicate by use of a bar line or symbols when erosion control measures will be installedt.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engineer.
Z 001 YEAR
----------------------MONTH T F I AA I A M J- J- A $• D �Ai
OVERLOT GRADING
WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other— Ccuc2ErE rW0VATr
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettinas/Mats/Blankets
Other
-----------------------------
STRUCTURES: INSTALLED BY MAINTAINED BY
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED APPROVED BY CITY OF FORT COLLINS ON
HOI/SF-C:1989
J?LNUi?'1 1991 8-20 DESIGN CRITERIA .
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RAINFALL PERFORMANCE STANDARD EVALUATION
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PROJECT: 9P5PLA7 Or- 607r 748,BzoeE
ISL,
City
STANDARD - FORM A
I COMPLETED BY: ,-,4,,e.
DATE: va, laz0a�
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(DEVELOPED�ERODIBILITY1
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Lsb•
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HOI/SF-A:1989
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EFFECTIVENESS CALCULATIONS
PROJECT: R EpLAT OF t oTs 7e8, Beak 152, Ctry OF FoLTGoccnvs STANDARD FORM B
COMPLETED BY: %e 4 Q DATE: Deo. /z• zoon
Erosion Control C-Factor P-Factor
Method Value Value Comment
B A e S S'0 j 1- /. o o A. 00 0. 18 A c.
S T-e .4w BA LE- -DIA-,c 1,60 6. so
Ex/jr 14OvJ6S 0.01 1.00 0. 09.4c.
FOJ.uDATIOAJ O.01 /•DO 0.094c.
eA IS TWI. CojeAg D•OB hoo 0.09 qc.
S ii7 FE,vc& /•00 D.SO
MAJOR
PS
SUB
AREA
BASIN
(*)
BASIN
(Ac)
CALCULATIONS
OtbTowu
74,E
L.rrJ�6
6.43(,
U%TD. C = (1•oox 0•te� } (6.01x 0.17) }- �0•oBhO.tYl�
0. 44
= 0. 19 + 0. 001.7 4- '0, DO 7Z __ 0• IgBq
0.44- o • 49-
a 4.3
WTD P = 0,80 A 0•S0 = 0.9b
O.43 X 0.40) x /00 = 82.8 /o of
� 7a•/qo
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EROSION CONTROL COST ESTIMATE
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1. 90 L.F. Silt Fiance @ $3.00 / Ft. $ 270.00
2. Reseeding Site 0.436 Acres @ $650.00 / Acre $ 283.00
Collateral = 1.50 X $283 = $ 425.00
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N
EAST OAK STREET
'WRIGHT-OF-MY SCALE.' l ",, 20'
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-- NOTES: a: N
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--- r. Cue to the amoo site one the neort to keep the alley ad cloak. the miron ZO
r----�-------T— i + r-+-----_ `, central will as artt fence along the North line o the site an c eanirg fM mW
tlp n IIr. from the [mcmle apron of the North end of the alley as needed. U
— ILq<• i_ Gr i ef Grading and 0onoe Plan ern e submitted if a euWrom system O
s epument for basement construction alter he open nob inspection a Ide Is by the foundo6oe engines p
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w �I B 8 -' r n m PROPOSED SPOT ELEV. r n Q II o
EXIST. CONTOUR W 5I m.9 PROPOSED CONTOUR
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LOT LINE Ljj O DC
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,I b ." i , City o/ Fort Collins, Colorado o
Ii 7 UTIUTY PLAN APPROVAL
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