HomeMy WebLinkAboutAMIGOS AT SHIELDS PRELIMINARY PUD - 47 90A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTNo Text
PROPOSED SITE GRADING
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PRELIMINARY DRAINAGE &
EROSION CONTROL REPORT
FOR
AMIGOS AT SHIELDS P.U.D.
AUGUST 3, 1992
PREPARED FOR:
AMIGOS GROWTH MANAGEMENT CORPORATION
2546 SOUTH 48TH STREET
P.O. BOX 6189
LINCOLN, NEBRASKA 68506
PREPARED BY:
PARSONS & ASSOCIATES
CONSULTING ENGINEERS
432 LINK LANE PLAZA
FORT COLLINS, COLORADO 80524
(303) 221-2400
PROJECT NUMBER: 92.17 AMI
TABLE OF CONTENTS
Introduction
Site Description
Historic Drainage
Drainage Criteria
Drainage Under Developed Conditions
Erosion Control
Conclusions and Recommendations
Calculations
Grading and Drainage Plan
Figure 1 Vicinity Map
Figure 2 Existing Topography
Figure 3 Proposed Site Grading
PRELIMINARY DRAINAGE &
EROSION CONTROL REPORT
FOR
AMIGOS AT SHIELDS P.U.D.
FORT COLLINS, COLORADO
INTRODUCTION
This drainage report has been prepared along with preliminary engineering drawings
to provide design information for the development of an Amigos Restaurant along the west
side of South Shields Street between University Avenue and West Elizabeth Street. This
report was prepared to provide information for on and off site drainage runoff which impacts
this site in accordance with the City of Fort Collins "Storm Drainage Design Criteria and
Construction Standards."
SITE DESCRIPTION
The proposed Amigo at Shields P.U.D. site is at 230' x 132' site location at 1015
South Shields Street. The site is currently being used by Campus West Texaco as a service
station. The 0.697 acre site is located in the Southeast Quarter of Section 15, Township 7
North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, Larimer County,
Colorado (see figure 1).
As a developed commercial site, the existing use generates intense activity. The site
is almost totally impervious except for a small dirt area at the rear of the site. Based on field I
verified topography, drainage from the west one-half of the site runs to the west into a
parking lot. Drainage from the east one-half of the site runs to the east into the existing
Shields Street curb and gutter.
The property to the south is an undeveloped grassy area. The property to the west
is lower than this site and is used as a parking lot. Shields Street, an arterial roadway, forms
the eastern boundary and the Campus West Shops are immediately to the North.
-1-
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FIGURE /
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EAST
BASIN
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- SOU TH .
SITE TOPO EXISTING DRAINAGE BASINS
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HISTORIC DRAINAGE
The existing topography divides the site in one-half with the existing building at the
highest point in the middle of the site. The rear of the lot drains northwesterly into the church
parking lot to the west. The front of the lot drains northeasterly to the Shields Street curb
and gutter.
The site is totally impervious except for a .17 acre packed dirt area along the westerly
56' of the lot.
Composite "C"
* West '/2 of Lot
Area 97' x 132' = 12,804 sq. ft.
Packed Dirt 5 6' x 132' = 7,392 sq. ft. C = Q5
Paved Area & Building 41' x 132' = 5,412 so. ft. C = 10
12,804 sq. ft. C = .71
(7392)(0.5) + (5412)(1.0) _ .71
12,804
* fast '/2 of Lot
Area = 98' x 132' = 12,936 sq. ft.
'Y2 Shields Right -of -Way = 4,620 so. ft.
Total 17,556 sq. ft.
- Composite "C" 1.0
Total Lot Area
West '/2 _
East Y2 _
Shields R/W =
12,804 sq. ft.
.294 Ac
12,936 sq. ft.
.297 Ac
4,620 sq. ft.
.106 Ac
Total = 30,360 sq. ft.
-4-
697 AC
Historic Flow From West '/2 of site
L = 160 ' South edge of building to northwest corner of site
Drop =2.5' S=1.6%
From Figure 3.2 Urban Drainage
V = 2.5 ft/sec Tc = 160/2.5/60 = 1.1 Min.
Assume a Minimum Tc = 5.0 Min.
12 = 2.55 in/hr I = 9.0 in/hr
Q = (cf)(c)(1)(A)
QZ = (1.0) C 71) (2.5 5) (.294) _ .53 cfs
Qioo = (1.25)(.71)(9.0)(.294) = 2.35 cfs
DRAINAGE CRITERIA
The Rational formula was used to develop flows for this project. The Rational Formula
is an excellent predictor of runoff in drainage basins less than 200 acres.
DRAINAGE UNDER DEVELOPED CONDITIONS
exist.
The proposed Amigos Restaurant site will maintain the flow patterns that currently
Front Basin (East 'h & Shields Street Right -of -Way)
The front of the lot will continue to sheet flow runoff to Shields Street.
This basin contains approximately 1400 square feet of landscaped area which
will actually reduce the amount of runoff which flows into the west Shields
Street curb. As a result, no detention is provided and no drainage
improvements are proposed.
Rear -Basin ---(West-'h of -Lot
Site detention will be required for the rear one-half of the existing site.
Only 2,000 square feet of landscaping is provided in this area with the
remainder of the lot being impervious. The detention pond will be designed to
release water at the historic rate. This rate was developed to reflect the 56'
-5-
wide dirt area at the very rear of the lot. The detention pond will be within the
parking lot and an outlet pipe and orifice plate are designed to restrict flows to
the historic rate.
EROSION CONTROL
This project is located within areas of moderate wind and water erosion potential as
identified by the City of Fort Collins wind and water erodibility maps.
Wind Erosion
Since this project is less than one acre, no wind erosion improvements
need to be provided.
Water Erosion
The detention pond will be used as a sediment trap to minimize sediment
runoff due to water erosion: Straw bales will be used around the perimeter of
the site immediately after demolition and striping to control erosion prior to the
paving of the parking lot.
CONCLUSIONS AND RECOMMENDATIONS
The replacement of the existing Texaco Station with an Amigos Restaurant has minimal
impact on this area. The site is divided into front and rear basins. The location of the new
building at the same location and grade of the existing structure will insure that changes to
the flow of runoff is minimal. The front basin with 1400 square feet of landscaping will
actually reduce the amount of runoff to Shields Street. The rear basin will require a small
parking -lot detention area to insure that releases to the west are kept to a historic rate.
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