HomeMy WebLinkAboutMOURNING SUBDIVISION 2ND REPLAT LOTS 1 AND 2 - 13 91A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFinal Drainage and Erosion Control Report
for
CHILI'S GRILL AND BAR
(Lot 2, Second Replat of Mourning Subdivision)
Fort Collins, Colorado
Prepared for
CHILI'S, INC.
c/o Brinker International
6820 LBJ Freeway
Dallas, Texas 75240
Project No: 1270-01-91
Date: December 2, 1991
4836 S. College, Suite 12 Fort Collins, CO 80525 (303)226-5334
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DRAINAGE CRITERIA ANUAL
RUNOFF
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VELOCITY IN FEET PER SECOND
FIGURE 3-2.' ESTIMATE OF AVERAGE FLOW .VELOCITY .FOR
USE WITH THE RATIONAL FORMULA.
*MOST FREQUENTLY OCCURRING"UNDEVELOPED"
LAND SURFACES. IN ,THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
Release No. 55, USDA, SCS Jan. 1975.
5 -1-84
URBAN DRAINAGE &.FLOOD CONTROL DISTRICT
APPENDIX B
' Offsite Contributing Basin Plan
Grading, Drainage and Erosion Protection Plan
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PAGE 1
Chili's Grill and Bar
I GENERAL LOCATION AND DESCRIPTION
A. Location
1. Chili's Grill and Bar will be located on the northwest
corner of the intersection of South College Avenue and
Foothills Drive, just east of Steele's grocery store.
2. The property is described as Lot 2, Second Replat of
Mourning Subdivision, City of Fort Collins located in the
Southeast 1/4 of Section 26, T7N, R69W of the 6th P.M.
B. Description of property
1. The proposed Lot 2 contains 36,134 square feet more or
less.
2. The site is currently undeveloped.
3. The site slopes moderately toward the north and east with
offsite runoff contribution. There is an existing 24"x24"
curb inlet near the northeast corner of the site. This inlet
is in a sump condition, currently accepting stormwater from
the existing frontage road north and south and its
contributing areas and from the immediate property.
4. The site is zoned HB (Highway Business).
II DRAINAGE BASINS AND SUB -BASINS
A. Major Basin description
1. Chili's is located within the Foothills Basin (BASIN G) as
defined by the City of Fort Collins Drainage Basin map.
B. Sub -basin description
1. The site is contained within a sub -basin of the Foothills
Drainage Basin. It is included in Reach 3 of the Foothills
Basin Drainage Master Plan.
2. The Foothills Basin Drainage Master Plan indicates that this
site could pond water 3' deep prior to overtopping South
College Avenue. The 100-year high water level is defined at
elevation 5025.00 in the Foothills Basin Drainage Master
Plan.
III DRAINAGE -DESIGN CRITERIA
A. Regulations:
1. City of Fort Collins Storm Drainage Criteria and Erosion
Control Criteria was used.
B. Development criteria reference and constraints:
1. Previous studies
a. The Foothills Basin Drainage Master Plan study.
b. There was a drainage study prepared for the site in
1988 by Stewart and Associates, Inc. for Foothills
Parkway P.U.D.
2. The surrounding properties are fully developed. The existing
grades are the primary grading design constraint. All
grading and facility design must accomodate existing grades
on all four (4) sides of the property. South College Avenue
exists on the east and wont be changed. Foothills Parkway
exists on the south and wont be changed. Dellenbach
Chevrolet and Steele's Market to the north and west
respectively, have improvements which will not change.
PAGE 2
Chili's Grill and Bar
C. Hydrological criteria
1. The Rational method for determining peak flows was used for
the evaluation of the 10 and 100 year storm events
(commercial requirements). The calculation of all flows for
each sub -basin and combinations thereof, appear in the
appendix. Peak flows are designated on the Drainage plans.
D. Hydraulic criteria
1. The grading of the parking lot will provide the main
conveyance of storm runoff through the site and to the
existing inlet at the sump or low point. No modifications to
the main storm sewer system are anticipated.
2. Runoff from Foothills Parkway will be conveyed to the
parking lot via a sidewalk culvert and a curbed channel. The
Mannings equation for open channels was used to determine
sidewalk culvert and curbed channel width requirements.
IV DRAINAGE FACILITY DESIGN
A. General concept
1. Generally, all runoff which currently contributes to the
existing inlet at the northeast corner of the site will
continue to be conveyed to the existing inlet at the
northeast corner of the site.
a. A series of draiange facility improvements will direct
Foothills Parkway contributing runoff to the Chili's
site after vacation of the existing Frontage Road.
These improvements will consist of the following:
i. a concrete sidewalk culvert
ii. a curbed channel
iii. a valley pan in the parking lot area to the
existing inlet.
b. The top of the existing inlet will be modified from a
curb inlet to an area inlet.
2. Erosion control facilities will be utilized during
construction in order to protect downstream drainage
facilities as well as surrounding properties. — --- ---- ---_-
V CONCLUSIONS
A. Compliance with standards
1. All drainage calculations comply with the requirements of
the City of Fort Collins Storm Drainage Criteria Manual.
2. Temporary erosion control calculations and facility design,
comply with the requirements of the City of Fort Collins
Erosion Control Manual.
B. Drainage concept
1. The grading plan allows for the effective conveyance of all
contributing onsite and offsite storm water runoff through
the site, to the existing inlet at the southeast corner of
the site and to the existing 48" RCP storm sewer.
2. Detention will be provided on the Chili's site because of
the limited capacity of the existing 48" RCP storm sewer
which runs east -west adjacent to the north property line.
PAGE 3
Chili's Grill and Bar
3. Developed peak flows at several concentration points are
documented on the Grading and Drainage Plan. In summary the
developed peak flows at the concentration points studied,
are as follows:
C10/C100 Q10/Q100
Study Pt. developed developed
cfs
A 0.95/1.00 8.B/14.7
B 0.95/1.00 13.1/21.9
C 0.95/1.00 16.6/27.8
4. The 100-year high water level is defined at elevation
5025.00 in the Foothills Basin Drainage Master Plan. At this
elevation, stormwater will overflow into South College
Avenue.
5. Temporary Erosion control protection will be provided
according to the requirements of the City of Fort Collins
Erosion Control Reference Manual.
a. Wind erosion requirements are excluded according to
Section 4.2.1 since the site is less than 1 acre.
b. Haybales around the area inlet will be the primary
erosion control feature for the project.
VI REFERENCES
1. City of Fort Collins Storm Drainage Criteria Manual
2. City of Fort Collins Storm Erosion Control Manual
3. City of Fort Collins topographic Aerial for the NE 1/4 of Section
13, T7N, R69W
4. City of Fort Collins Storm Drainage Utility inventory mapping
APPENDIX A
Storm Drainage Calculations
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