HomeMy WebLinkAboutEAST RIDGE C-STORE - PDP - 33-98G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTThe C-Store project site is divided into four developed basins (Refer to Sheet 5 of 5, Preliminary
Drainage and Erosion Control Plan). Basins 100, 101, and 200 have similar internal developed
drainage patterns. The overland flow from landscaped areas and the sheet flow from parking and
sidewalk areas spills to curb and gutter that, in turn, spills on to Vicot Way (Basins 100 & 101)
and Sykes Drive (Basins 101 & 200). At this time, we do not plan to construct any below grade
infrastructure (e.g., storm drain pipe, inlets, and etc.). Basin 300 is a short and wide basin along
the north property line of the project site that will be landscaped and drain to the north.
The attached 10-year. (minor storm) and 100-year (major storm) developed runoff calculations
are based on the Rational Method procedure. This calculation method is recommended by the
City of Fort Collins for sites less than 5 acres. During the minor and major storm events, the
estimated develop runoff is Qlo=2.77 cfs and Qi00=7.40 cfs, respectively. If the Qioo estimate is
converted into a unit release rate, which is done by dividing the area of the project site into the
developed runoff value for the site, we found that our unit release rate is less than what TST
estimated with SWMM (8.09 cfs/ac versus 9.94 cfs/ac). Despite this difference, the rational
method estimate is reasonable and valid for the proposed land use.
Please feel free to contact me at (970) 484-1921 at your convenience if you have any questions
regarding this .report. We thank you for your time and consideration in. reviewing this drainage
report submittal.
Sincerely,
JIM SELL DESIGN, INC.
Herman Feissner, P.E.
Enclosure
cc: File
March 16, 2007
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City of Fort Collins Stormwater Utility
700 Wood Street
PO Box 580
Fort Collins, CO 80522
RE: East Ridge C-Store PDP Submittal
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Dear Basil:
LANDSCAPE ARCHITECTURE
PLANNING
ENGINEERING
GRAPHIC DESIGN
The following letter report has been prepared for the East Ridge C-Store in accordance with the
storm drainage design guidelines set forth in the City of Fort Collins Stormwater Drainage
Design Criteria and Construction Standards (Dated: January 1997).
The C-Store project site is an undeveloped lot within the East Ridge Subdivision. It is bounded
to the north by undeveloped land; to the east by Vicot Way (proposed); to the south by Sykes
Drive (proposed); . and to the west by Timberline road. We assume herein that construction
progress, within the East Ridge Subdivision will be far enough along that the necessary storm
drainage conveyance, storage, and water quality infrastructure will be in place and serviceable
prior to the development of the C-Store project site.
TST, Inc. (TST) recently submitted the Final Drainage Report for East Ridge Subdivision to the
City -of Fort Collins for review and approval. According to this report, the project site straddles
basins 50 and 54. With respect to the contours shown on TST's Final. Drainage Plan, it looks
like the C-Store project site should fall within the limits of basin 50. Basin 54 should tftverse
along the north property line of the subject site. Basin 50 is comprised of f2.82 acres of mostly
undeveloped land, except for .the existing Timberline _Road improvements, set aside for
commercial development and an improved Timberline Road section and alignment. Basin 54 is
comprised of t4.70 acres of undeveloped land, except for the improved Timberline- Road
improvements, set aside for multi -family development and an improved Timberline Road section
and alignment. The commercial land use proposed by TST is consistent with the current
proposed land use. The soils within the project site are NRCS Hydrologic Soil Group `B'.
The proposed C-Store grading is consistent with TST's proposed overlot grading plan. There are
no off -site areas that drain on to the project site. In general, the developed site runoff will sheet
flow to Vicot Way and Sykes Drive and combine with developed runoff from other developed
areas in basin 50. In Sykes Drive at TST's design point 50, the developed runoff spills into a
proposed Type `R' Inlet (Sump). This inlet discharges into storm drain infrastructure proposed by
TST that outfalls into Detention Pond I. -No on -site detention or water quality is required because
it is provided in Detention Pond 1.
153 WEST MOUNTAIN AVENUE F0RT COLLINS, C0LORADO 80524 P970.484.1921 F970.484.2443 INFO@JIMSELLDESIGN.COM JIMSELLDESIGN.COM