HomeMy WebLinkAboutEVERGREEN PARK SECOND FILING FIRST REPLAT LOT 19 BLOCK 2 - 50 91E - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1
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STORM DRAINAGE REPORT
FOR THE REPLAT OF LOT 19 IN BLOCK TWO
'
OF THE REPLAT OF EVERGREEN PARK, SECOND FILING
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LOCATED IN THE EVERGREEN PARK BASIN
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PREPARED FOR
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LISA AND SHANE HARDEN
JANUARY 4,1999
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PREPARED BY
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STEWART & ASSOCIATES, INC.
103 S. MELDRUM STREET
P.O. BOX 429
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FT. COLLINS, CO 80522
TEL. 970-482-9331
'
FAX 970-482-9382
TABLE OF CONTENTS
1 & 2. Letter and Teat
3. Vicinity Map
4. Calculation Sheet
5. Copy of Sheet 6 of
Evergreen Park 1981 study
6. Copy of Subdivision Plat
Pocket Utility and Grading Plan
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STEWART&ASSOCIATES
' Consulting Engineers and Surveyors
' January 4, 1999
' Mr. Basil Hamdan
Storm Water Utility
' City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522-0580
Dear Basil,
Lot 19 in Block Two of Evergreen park, Second Filing contains 24,773 square feet. The
owners, Lisa and Shane Harden, propose to replat the lot into two single family lots. The minimum
' area of the new lots will be over 11,000 square feet, which is larger than most of the lots in the
development.
' This project is located in the Evergreen Park Drainage Basin. Runoff from the site drains on
the surface along Monterey Drive, to the south across Conifer Street and then into the Evergreen
Park 2nd, 3rd and 4th detention pond.
According to the Evergreen Park Basin Major Storm Drainage Study prepared by Engineering
' Professionals in 1981, the area which includes the Lot 19 site is 40 percent impervious. This
calculates to a runoff coefficient of 0.53.
' We propose that there be no onsite detention required on the two new lots. Although there
are being two lots made from one, the two new lots are larger than most lots in the subdivision, and
the developed runoff coefficient for the site, including hard surface for the two proposed residences,
and the hard surface for the adjoining streets, is not greater than the runoff coefficient used by
' -- Engineering Professionals for their study. A copy ofpage 6 of the 1981 Evergreen Park Basin Major
Storm Drainage Study is included in this report. This page 6 shows the 40 percent imperviousness
' used by that report for the area which includes the lot 19 block 2 site.
A calculation of the developed runoff coefficient is shown on the calculation sheet in this
' report.
The topography of lot 19 block 2 slopes from the northwest comer toward the southeast
' comer, but the slope is very flat. There are existing houses on the adjacent lots to the west and to
the north. The rear yards of these existing residences drain onto the westerly portion of lot 19 block
2 and then onto Foxtail Street and Monterey Drive. We proposed to construct the two new
residences on lot 19 block 2 on the easterly portion of the lots and leave the westerly portion of the
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
lots at approximately the present grade so that the offsite flows are not blocked. A grading plan
showing the proposed floor grades and lot grading is included in the pocket of this report.
' There are no specific erosion control procedures planned for this project since it is the
construction of standard single residences on already developed single family lots. We have though,
' placed a copy of the standard erosion control construction notes on the grading and utility plan.
' The site is located in a moderate wind erodibility zone, so the existing adjacent houses and
streets will provide adequate wind erosion control measures. There have been no additional water
quality measures planned for this project other than those which normally occur when the runoff
' drains across the lawn and landscaping of the lots.
The drainage and erosion control procedures proposed for this project comply with the
' criteria of the City Stormwater Utility.
Please call if you need additional information.
Sincerely, �.•�''i�icpo_
' .�v.......;
�G��T E
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' Philhp I. Robinson, P.E. & L.S.
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STEWART&ASSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: P I R Date: 2 o Client: /_ isa Serra n e. 14cr 4 e oi Sheet No. _ of _
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The coefficients are:
finitial = 2.19 in./hr.
fultimate = 0.05 in./hr.
decay rate = 0.0071 1/sec.
Percent impervious and.Manning's 'n' values were taken from
the recommendations in the City of Fort Collins "Storm Drainage
Design Criteria". The values are:
Land Use
Industrial/Commercial
Residential - Condominium
Residential - 4 units/acre
Open
Conveyance Type
Street
Grassed Channel - Depth >2'
Concrete Channel or Pipe
Overland Flow
Percent Impervious
90
60
40 LOT- l 13/ock 2
10
ManninQ's Coefficient of Roughness
0.016
0.035
0.013
0.250
Where appropriate, an average imperviousness was calculated
from the various land uses within a subcatchment. The area,
length of channel, and slope of each subcatchment were scaled
from available topographic mapping.
IV. (B) Models
As mentioned in the introduction, both the Colorado
Urban Hydrograph Procedure (CUHP) and the Stormwater Management
Model (SWMM) were used in this study. The CUHP can run on a
desktop computer while SWMM is available only on large mainframe
computers. Thus our in-house version of CUHP was used. to do
preliminary routing and evaluation of alternate drainage patterns.
The results were then used to size conduit and channels as initial
input to SWMM.
Frorn Evergreeh Park aclsi^
A4ct r Storms 171-01'n a5 e Stvd�l
-6- by G_, p. 1. in l96/