HomeMy WebLinkAboutDrainage Reports - 08/05/2014III1GrINS C4of`Ft.Collin prov Plans
J`III Approved By
Date_ 9 -e -r if l`
July 11, 2014
Mr. Glen Schlueter
City of Fort Collins
Stormwater Engineering Division
700 Wood Street
Fort Collins, CO 80521
Reference: Drainage Letter for Kechter Farm Clubhouse
JVA Job No. 1844.6c
Dear Glen:
JVA, Incorporated
25 Old Town Square, Suite 200
Fort Collins, CO 80524
Ph: 970.225.9099
Tall Free:877.444.1951
Web site:
www.ivaiva.com
E-mail:
info(@jvajva.com
This letter is written to describe the drainage impact of a proposed community recreation
clubhouse within the Kechter Farm Development. The clubhouse and its facilities will be
constructed within Lot 13 of the subdivision. Improvements will include a 6,500+ square foot
community building, parking lot, associated walks, plaza areas, playground and swimming pool.
The lot is located at the southwest comer Zepher Road and Trilby Road. It will have two
driveway accesses. One driveway will enter the lot from Eagle Roost Drive and the other will
enter the lot from Heronry Place.
JVA included Lot 13 in a previous drainage study titled, "Final Drainage Report for the Kechter
Farm Development," published on January 21, 2014. Specifically, Lot 13 is included within
major drainage basin B of the study. The developed conditions were assumed to be 47%
imperviousness, similar to that of the surrounding lots for single-family housing. The expected
runoff from Lot 13 would be 1.25 CFS for the minor 2-year storm event and 8.16 CFS for the
major 100-year event.
The majority of the site will be drained by sheet flow to the surrounding landscaping and streets.
Roof drainage will be piped to the existing underground storm sewer system. The calculated
imperviousness for lot 13 with the proposed club house improvements is 49.2%. Outside of the
lot, the sub -basin boundaries for Bl, BI I and B12 will remain unchanged from the previous
study. Grading modifications for the proposed construction, however, will slightly alter the
previous sub -basin boundaries within the lot. The lot has been divided into three sub -basins, DB-
1, DB-I I and DB-12, that more evenly shed from the proposed site into the same corresponding
sub -basins of the original study. Please refer to the attached Figure 1 — Developed Drainage
Map. The analysis herein is similar to that of the original study, using the rational method to
analyze peak flows for individual sub -basins. Please see the attached calculations.
Sub -Basin DB-1 will be approximately 0.78 acres and will shed to Sub -basin B-1 of the original
study. Peak flows are calculated to be 0.56 CFS in the 2-year event and 3.53 CFS in the 100-
year event.
Sub -Basin DB-II will be approximately 0.56 acres and will shed to Sub -Basin B-I1 of the
original study. Peak flows are calculated to be 0.44 CFS in the 2-year event and 2.58 CFS in the
100-year event.
BOULDER I FORT COLLINS I WINTER PARK
Drainage Letter
Kechter Farm Club House
July 11, 2014
2 of 2
Sub -Basin DB-12 will be approximately 0.48 acres and will shed to Sub -Basin B-12 of the
original study. Peak flows will be 0.31 CFS in 2-year event and 2.12 CFS in the 100-year event.
The combined peak flows from Lot 13 are calculated to be 1.30 CFS in the 2-year event and 8.21
CFS in the 100-year event. Each of these peak flows is within 0.1 CFS of what would be
anticipated by the original study. With respect to the 2.2% increase in anticipated impervious
area within the 1.819 acre tot, the effect on the 40.5 acre, major drainage basin B is expected to
be minimal.
In conclusion, the proposed design for the clubhouse and the development of Lot 13 is well
within the design parameters presented in the original study by JVA, Inc. for Kechter Farms.
The site has been designed to comply with all of the stormwater jurisdictional criteria and will
not adversely affect any of the surrounding storm drainage infrastructure.
Sincerely,
JVA, Incorporated
By: L
Robin L. Ki6ss, PE
Project Engineer
Cc: Toll Brothers, Inc.
Attachments:
Drainage Calculations
Figure 1 — Developed Drainage Map
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