HomeMy WebLinkAboutDrainage Reports - 10/20/1995' 1tiAOPERT- OF
PUT COLLM v2MXr F.s
' FINAL DRAINAGE REPORT
FOR
' HARMONY MELJ,
PREPARED FOR
N.R.C.E.
' September 13,1995
[]
STEWART & ASSOCIATES, INC.
' 103 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
i ' 970/482-9331
I
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September 13, 1995
Mr. Basil Hamdan
Stormwater Utility
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522
Dear Mr. Hamdan:
STEWART&A SSOCIATES
Consulting Engineers and Surveyors
The following is the storm drainage report for Harmony Mill located at 131 North Lincoln
Avenue, Fort Collins, Colorado. The site is a use by right and has an existing four story brick
building which is being remodeled into an office building. The site is a part of Block 9 and a part
of vacated Chestnut Street and a part of a vacated alley, all in the original plat of the City of Fort
Collins. It is bounded on the Northeast by Willow Street, and on the Southeast by Lincoln
Avenue and on the Southwest by an existing Union Pacific railroad spur. The net area of the lot
is 0.60 acres and the gross area of the lot, including half of Willow Street and half of Lincoln
Avenue, is 1.19 acres. The site is approximately 200 feet Southwest of the Cache la Poudre
River. The site drains Southeasterly along Willow Street and Northeasterly along Lincoln
Avenue. The historic ground cover is asphalt, gravel and bare ground. A part of the original
building has already been demolished.
The proposed development of the site is to remodel the building and construct two asphalt
parking lots and construct curb, gutter and sidewalk along Lincoln Avenue. Also, 22 parking
spaces will be constructed with concrete partly in the Willow Street right-of-way and partly on
site. The remainder of the lot will be landscaped.
There is an existing 12 inch diameter storm drain along the Northwesterly line of Lincoln
Avenue which is draining Northeasterly to the Cache la Poudre River. There are two area inlets
at the comer of Lincoln Avenue and Willow Street which presently accept storm water from the
site and will remain in place in the new landscaped area. All of the storm water runoff from the
newly developed site will continue to discharge into the two inlets. An existing 24 inch diameter
storm drain carries the storm water from the inlets to the Cache la Poudre River. If the inlets
cannot accept the storm water, it will pond in the landscape area and overtop the new curb and
gutter and flow overland in Lincoln Avenue to the Cache la Poudre River.
Due to the very close proximity to the Cache la Poudre River, no onsite storm water
detention is being provided.
The historic runoff coefficient based on the actual impervious surface before the
demolition was done was 0.67 and the time of concentration was 20 minutes because the runoff
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
Ft. Collins, CO 80522
303/482-9331
Fax 303/482-9382
' Harmony Mill
' Page 2
' was all sheet flow over a gravel surface. The proposed development increases the hard surfacing
but replaces much of the gravel surface with turf The total runoff coefficient will be reduced
from 0.67 to 0.61. The time of concentration is significantly reduced due to the runoff being
' changed from sheet flow to channelized flow in new curb and gutter. The time of concentration is
reduced from 20 minutes historically to 11 minutes on the developed proposal. The two year and
ten year frequency developed runoff rates are a little higher than the historic runoff rates, but the
' 100-year frequency developed runoff rate is smaller than the historic rate.
The summation of the above narrative of the drainage system for this site is that with the
proposed landscaping and the proposal parking improvements, the developed runoff rates are not
significantly increased and the storm water will continue to flow to the existing inlets without
creating a hazardous condition. The proposed curb and gutters will control the traffic and control
the storm water runoff.
Erosion control for the site is different than many projects. The building is existing so
there is no disturbance for it. The existing concrete pavement on Lincoln Avenue and much of
the existing asphalt on Willow Street will remain as constructed. The curb and gutter will be
constructed adjacent to the existing roadway. The main areas that will be disturbed will be the
two parking areas. Silt fences will be erected on the downstream side of both areas prior to
preparing the subgrade. Straw bales will be placed around both existing area inlets. The existing
gravel areas that become turf areas will not be disturbed until the landscaping is started after the
other site construction is completed. At that time the existing gravel will be removed, and top soil
will be placed immediately. The areas will then be sodded as soon as possible after the top soil is
in place. If there is going to be more than a few days in between tasks, silt fences will also be
erected on the downstream sides of the turf areas.
The storm water calculations and the grading plan and the erosion control calculations are
included as a part of 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 questions regarding this
report, please call.
Sincerely,
Richard A. Rutherford, P.E. & L.S.
President
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�4�P,��CIST�q�`,�FG
5028
I
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CONSTRUCTION SEQUENCE
PROJECT: HAzMOa Mimic STANDARD FORM C
SEQUENCE. FOR 19 qs ONLY COMPLETED BY: ,e Ad- DATE: 3/io f y.r
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 Engineer.
IOIqS- YEAR
MONTH J F dt A A S O I �v
---------------------------- ----T--------------------------7 ---t --- ---- --} ---
OVERLOT GRADING I I 1 I I I
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
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettings/Mats/Blankets
Other
'-----------
"99 G 1
STRUCTURES: INSTALLED BY MAINTAINED BY
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED APPROVED BY CITY OF FORT COLLINS ON
-HDI/SF-C:1989
JANUA_'.Y 1901 8-20
DESIGN CRITERIA
I
STEWART&ASSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: P. A'.k Date: 3 / / o/ 4S Client: /J. R , G, E , Sheet No. 3 of
'
Project: N A tz nA 5 A, ./ M i I_c_
Subject: ,s �- o P 1�1 I A l A u ,y 0 ,C C
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STEWART&kSSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: )z Ap- Date: '3/o .S Client: ^) . P, C. F. Sheet No. 4 of
Project:
Subject:
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-------------RAINFALL PERFORMANCE STANDARD EVALUATION
-.-----------------------------------------------------
PROJECT: 14AeMo,.vy M/-L STANDARD FORM A
COMPLETED BY: ,eA,P DATE: 3 /o
---------------------------------------------------------------------�
DEVELOPED ERODIBILITY Asb Lsb Ssb Lb Sb PS
tj
SUBBASI__---ZOtIE---- -(ad-(ft)_---(�)-_ (feet)---(q)----(0)--
G.eors Atoa&e47& 1•19A,. 43o' 0•collo 430' O•Go% � 73.1,
AREA
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-EFFECTIVENESS CALCULATIONS
------------------ ----------------=---------
PROJECT: H-4.,e /u.o v y /4
COMPLETED BY: Ae- .
----------------
STANDARD FORM B
DATE: 3 0
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Erosion Control
C-Factor
P-Factor
1
Method
Value
Value Comment
----------------------------------------------------------
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0.80
--------------------------------------------------------------------
SILT FENG'�
/.O
,.O'eo
MAJORI
PS
SUB AREA
BASINI
BASIN
(Ac)
CALCULATIONS
------------------------
A e--------------------
eA
WTD C=(/.0xozS)+4CO-01A6,07)-4
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w'r o ? = 0.6 A o. f3 = C . 6 4-
E rF. = C-(O,ZSx o G9-) jx/0o = gG,O%
Ok? 73.4%
----------------------------------------------------------------------�
HDI/SF-B:1989
STEWART&ASSOCIATES
Consulting Engineers and Surveyors
April 5, 1995
Mr. Basil Hamdan
Stormwater Utility
P.O. Box 580
Fort Collins, CO 80522
Dear Mr. Hamdan:
The following is the Erosion Control Cost Estimate for Harmony Mill located at 131
Lincoln Avenue, Fort Collins, Colorado.
1. 105 L.F. Silt Fence @ $2.00/ft. $210
2. Two Area Inlet Straw Bale Filters @ $75 $150
3. Reseeding 30,000 S.F. $894
The amount of the Erosion Control Escrow Bond will be 150% of $894, which is $1,341.
ffyou have any questions regarding this cost estimate, please call.
Sincerely,
a.
Richard A. Rutherford, P.E. & If.S.
President
rsc
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
Ft. Collins, CO 80522
303/482-9331
Fax 303/482-9382
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