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ODP Drainage
Memorandum
For
Spring Creek Farms North
Fort Collins, Colorado
For:
ST. CHARLES INVESTMENT COMPANY
C/O STEPHEN MAGUIRE
6300 S. SYRACUSE WAY, SUITE 293
Centennial, CO 80111 .
Lo
As en
Engineering
238 Walnut Street, Suite 200
Fort Collins, CO 80524
970-420-5345
MARCH 2, 2011
ODP Drainage Memorandum for Spring Creek Farms North
TABLE OF CONTENTS
Title Page
Table of Contents
I.
INTRODUCTION...................................................................................................2
H.
GENERAL LOCATION AND DESCRIPTION....................................................2
A.
Property Location................................................................................................2
B.
Description of Property........................................................................................2
M.
DRAINAGE BASINS AND SUB-BASINS.............................................................2
A.
Major Basin Description......................................................................................2
B.
Existing Drainage Conditions/Patterns.................................................................3
C.
Future Drainage Conditions/Patterns....................................................................4
IV.
DRAINAGE DESIGN CRITERIA.........................................................................6
A.
Development Regulations....................................................................................6
B.
Development Criteria Reference and Constraints.................................................6
C.
Hydrological Criteria...........................................................................................6
D.
Hydraulic Criteria................................................................................................6
VIII.
REFERENCES..........................................................................o-o...................7
ODP Drainage Memorandum for Spring Creek Farms North
I. INTRODUCTION
The purpose of this ODP Drainage Memorandum is to provide clarification and
document the existing drainage patterns, requirements, and overall function of the
existing Spring Creek Farms North site in relation to the future development of the
remaining portions/parcels within the Spring Creek Farms North site.
II. GENERAL LOCATION AND DESCRIPTION
A. Property Location
The Spring Creek Farms North property is located at the northwest comer of the
Timberline Road and Drake Road intersection, in Fort Collins, Colorado. The
property is bounded to the north by the Timberline Center Subdivision, to the east
by Timberline Road, to the south by Drake Road, and to the west by the Railroad.
More specifically, the property is located in the southeast quarter of Section 19,
Township 7 North, Range 68 West of the 6`h Principal Meridian, County of
Larimer, State of Colorado.
B. Description of Property
Per the Spring Creek Farms North Plat, by Stantec Consulting, the property
contains approximately 51.05 acres, of which approximately 7.54 acres (Lot 1)
contains the existing Police Facility development. The remaining site area is
undeveloped (Outlot A), with the exception of the roadway infrastructure
surrounding and constructed with the Police Facility Development.
Current zoning provides for "LMN", "MMN", and "E" for the remaining
undeveloped portions of the Spring Creek Farms North site (Outlot A).
Future development of the remaining portions of the site may entail roadway, water,
sewer and private infrastructure improvements. Please refer to the attached "ODP
Overall Drainage Exhibit" for schematic details off the site drainage.
III. DRAINAGE BASINS AND SUB -BASINS
A. Major Basin Description
The Spring Creek Farms North property lies within the City of Fort Collins
Foothills Basin. The majority of the property runoff is conveyed from the
northwest to the southeast and into the North Tributary Storm Sewer, located
southeast of the property in Drake Road. The runoff is conveyed to the Fossil
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ODP Drainage Memorandum for Spring Creek Farms North
Creek Reservoir Inlet Ditch, which drains to Fossil Creek Reservoir. Fossil Creek
Reservoir ultimately drains to the Poudre River.
The maximum allowable release rate (for the developed property) into the North
Tributary Storm Sewer is 20 cfs, per the City of Fort Collins SWMM modeling and
the "Drainage and Erosion Control Study for: Spring Creek Farms, Fort Collins,
CO", by Stantec Consulting, dated September 28, 2005.
B. Existing Drainage Conditions/Patterns
The existing Spring Creek Farms North property (approximately 51.05 acres)
consists of the existing Police Facility Development, with the remaining portion of
the property being undeveloped. There are two major drainage patterns for the
Spring Creek Farms North property.
The first drainage pattern for the existing site provides for the Police Facility
Development and the adjacent roadway infrastructure (Basins 3-5, 9, & 12 = 10.39
acres +/- from Stantec Report) and the majority of undeveloped portions of the
major property (Basins 1 & 2 = 39 acres +/-) being ultimately conveyed to the
southeast comer of the Spring Creek Farms North property and into ,the North
Tributary Storm Sewer.
Basins 1 & 2 comprise native grasses and weeds, with these areas also being
previous farm ground. The topography slopes from the northwest to southeast at
approximately 0.90%. Today, the majority of runoff infiltrates into the existing
ground, with very little runoff anticipated to ever reach the existing area inlet in the
southeast comer of the site, due to the flat grades over the existing site.
The existing Police Facility site and adjacent roadway infrastructure (Basins 3-5, 9,
& 12 of Stantec Report) conveys its runoff to an existing detention pond within and
along the south side of the police facility property. Flows are ultimately conveyed
to -the southeast comer of the pond (Pond 5 of Stantec Report), where a water
quality/detention pond outlet structure provides a controlled maximum release of
3.7 cfs into an existing storm sewer that conveys flows south towards the southeast
comer of the Spring Creek Farms North property. Here, the flow is routed through
an existing area inlet, which discharges the flow south and into the existing North
Tributary storm sewer, located in Drake Road and southeast of the Spring Creek
Farms North property.
It's important to note that the existing pipe running south, along the west side of
Timberline Road was sized to allow for 20 cfs to be conveyed in the existing pipe,
which assumes the controlled runoff from the remaining and future developed
attributable basins for the Spring Creek Farms North property (Basins 1 and 2) will
be conveyed to this storm sewer line. This is an option for future development, but
may be unlikely if two separate projects are constructed on the west and east sides
of the future Joseph Allen Drive Extension between Drake Road and Charles
Brockman Drive.
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ODP Drainage Memorandum for Spring Creek Farms North
The second drainage pattern for the remaining portion of the existing Spring Creek
Farms North property and offsite basin on Timberline Road (Basins 6-8, & 10 =
7.59 acres +/-) provides for runoff being conveyed from the west to east and into a
temporary/existing pond (Pond 8 of Stantec report), located at the far northeast
comer of the Spring Creek Farms North property, and west and adjacent to
Timberline Road. The existing/temporary pond currently provides water quality
and detention for the developed condition of Basins 6, 7, and 10, but only the
historic condition (`c' =0.25) for Basin 8. Therefore, as future development occurs
within Basin 8, the existing/temporary pond will either require enlargement or
additional ponds added within the basin to meet the required water quality and
detention requirements. Currently, the pond releases at the attributable basins 2-
year historic rate, which was calculated at 1.1 cfs (see Stantec Report).
It's important to note that the Timberline Subdivision (north of the Spring Creek
Farms site) has allowed for the historic runoff from the far west portion of Basin 8
(west of the existing Joseph Allen Drive) and the roadway portions within Basin 8
to flow north in the curb and gutter along Joseph Allen Drive and into an existing
detention pond (Pond A) on the Timberline Subdivision property. However, future
development within Basin 8, excluding the roadway portions of Joseph Allen Drive,,
will require that runoff be conveyed to the on -site existing/temporary pond or
future, additional pond(s) or drainage systems within Basin 8 and the Spring Creek
Farms North property.
C. Future Drainage Conditions/Patterns
The ODP Overall Drainage Exhibit and ODP Drainage Memorandum, by Aspen
Engineering, provides for the anticipated drainage patterns and options for the
future development of the remaining portions of the Spring Creek Farms North
property.
The ODP Drainage Exhibit depicts the existing basins for the Spring Creek Farms
North property (from Stantec Report) and shows the future layout of the Joseph
Allen Drive Extension. For the purposes of this memorandum, Aspen Engineering
has assumed the possibility of two separate projects being constructed along the
west and east sides of the future Joseph Allen Drive Extension (within Basin 1),
with developed parcels (Basins 1 & 2) providing their own on -site water quality and
detention.
It is anticipated that parcels to the west of the future extension will provide their
own on -site water quality and detention, with controlled releases into the future
storm sewer in the Joseph Allen Drive Extension, while parcels east of the future
Joseph Allen Drive Extension will provide their own on -site water quality and
detention, with controlled releases into the existing storm sewer on the west side of
Timberline Road.
The anticipated future storm sewer in the Joseph Allen Drive Extension will serve
as an outfall for developed parcels along the west side of Joseph Allen Drive and
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ODP Drainage Memorandum for Spring Creek Farms North
possibly areas/portions adjacent to and on the east side of Joseph Allen Drive, with
controlled releases being conveyed south in Joseph Allen Drive, then east along the
north side of Drake Road and into the existing inlet structure, located at the
northwest corner of the Drake Road and Timberline Road intersection. Runoff will
be routed south and into the North Tributary Storm sewer. It's important to note
that the existing inlet structure will be replaced or modified to accept the storm
sewer pipe connection(s).
The remaining parcels east of the future Joseph Allen Drive Extension will provide
their own on -site water quality and detention, with controlled releases being
conveyed east and into the existing storm sewer, running south along the west side
of Timberline Road. The release rates from the developed portions/parcels will
combine with that from the existing Police Facility Development (Qioo = 3.7 cfs)
and will be conveyed south to the existing area inlet, where the flow will combine
with the controlled flow from parcels west of Joseph Allen Drive. The combined,
controlled flow from these areas (Basins 1-5, 9, & 12 of Stantec Report) will be
released south and into the North Tributary Storm Sewer.
It's important to note that the combined maximum release rate from future
developed areas west and east of Joseph Allen Drive (Basins 1 & 2) and the existing
Police Facility development (Basins 3-5, 9, & 12) into the North Tributary Storm
Sewer is 20 cfs.
Future development of the remaining areas/portions of the Spring Creek Farms
North property will be provided for in Basin 8 (5.4 acres +/-). The future
development within Basin 8 will require that the existing/temporary detention pond
be enlarged or that additional ponds be added within the basin to meet the required
water quality and detention requirements, with the maximum allowable release rate
from the developed basins being the 2-year historic rate.
It's important to note that the roadway portions of Joseph Allen Drive, within Basin
8, will continue to be conveyed to and detained within Pond A of the Timberline
Subdivision, in accordance with the "Final Drainage and Erosion Control Report for
Timberline Center Subdivision", by North Star Design, dated February, 21, 2006;
revised April 12, 2006.
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ODP Drainage Memorandum for Spring Creek Farms North
IV. DRAINAGE DESIGN CRITERIA
A. Development Regulations
Design criteria from the City of Fort Collins Storm Drainage and Design Criteria
and Construction Standards shall be followed for future development of the Spring
Creek Farms North property.
B. Development Criteria Reference and Constraints
The City of Fort Collins Stormwater staff was consulted with to obtain their
position on conformance to the Foothills Basin master plan release rates. The City
requested that attributable, developed portions of the site (Basins 1-5, 9, & 12)
release at no more than 20 cfs into the North Tributary Storm Sewer, with
remaining attributable portions of the site (Basins 6-8, & 10) being allowed to
release at the 2-year historic rate, in accordance with the "100% Design Drainage
Report for Interim Timberline Road Widening, Drake to Prospect', dated July 20,
2005, by North Star Design and Interwest Consulting Group. The 2-year historic
release rate for the future development shall be calculated, and must conform to the
allowable release rate allowed by the above mentioned drainage report and those
requirements called for and required for the Foothills Basin.
C. Hydrological Criteria
Peak flow rates for the 2-year and 100-year storms shall be calculated for future
development and shall be in accordance with the City of Fort Collins Storm
Drainage and Design Criteria and Construction Standards.
D. Hydraulic Criteria
Hydraulic analysis of the future storm sewer conveyance systems shall be provided
for and calculated in accordance with the City of Fort Collins Storm Drainage and
Design Criteria and Construction Standards.
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ODP Drainage Memorandum for Spring Creek Farms North
VIIL REFERENCES
a) City of Fort Collins Storm Drainage and Design Criteria and Construction Standards,
March 1986.
b) "Drainage and Erosion Control Study for: Spring Creek Farms, Fort Collins, CO",
September 28, 2005, by Stantec Consulting.
c) "Final Drainage and Erosion Control Report for Timberline Center Subdivision",
February 21, 2006; revised April 12, 2006, by North Star Design.
d) North Star Design and Interwest Consulting Group, "100% Design Drainage Report for
Interim Timberline Road Widening, Drake to Prospect", dated July 20, 2005.
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