HomeMy WebLinkAboutRIDGEWOOD HILLS RESIDENCES 4TH FILING - MAJOR AMENDMENT - MJA130003 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT (3)PRELIMINARY DRAINAGE REPORT
Ridgewood Hills Fourth Filing
Multi-Family Residential Development
Triangle Drive & Avondale Road
Fort Collins, Colorado
Prepared For:
M. Timm Development, Inc.
233 E. Carrillo St., Suite 0
Santa Barbara, CA 93101
(805) 963-0358
Prepared By:
.aI B CONSULTING
OWEN
GROUP, INC.
3715 Shallow Pond Drive,
Fort Collins, CO 80528
Phone: 970-226-0264
Fax: 970-226-3760
April 2013
Proj . No.: 12-390
RIDGEWOOD HILLS FOURTH FILING
MULTI-FAMILY RESIDENTIAL DEVELOPMENT
PRELIMINARY DRAINAGE REPORT
Table of Contents
ENGINEER'S CERTIFICATION ........... ............................................................. ..................... 1
I. LOCATION AND DESCRIPTION OF PROPERTY AND PROPOSED DEVELOPMENT ...... 2
A. Location ........................................... .............................................. ................................... 2
B. Description of Property ....... .. .. .... ... ........... ........................................................................ 2
C. Description of Proposed Development ........................................ .... ................................. 2
II. DRAINAGE BASINS AND SUB-BASiNS ..... .. ....... .. ........ .. ............... .. ..... ... ..... ........................ 3
A Major Basin Description ...... .. ....... ............... ... .. .. ... .. .. ... .... ... ..... ... ..... .... ..... ............. ......... .. 3
B. Sub-Basin Description .. ... ........... .......... ................................... .. ... ..... ..... .... .. ........... ....... .. 3
III. DRAINAGE DESIGN CRITERIA.. ..... ...... .............................................. .... .................... ......... 4
A. Regulations ..................... ..... ... .. .. ..... ......... .................................... ...................... .. ............ 4
B. Development Criteria Reference and Constraints ............................................................ 4
C. Hydrologic Criteria ........... .. .. ......... .... ....................................... .... .... .................. ............... 4
D. Hydraulic Criteria ............. .. .. ...... .. .......................................... ... ....... ...... ........................... 5
E. Floodplain Impacts .......... .. ... ... ... ..... ... ..................................... ..... .... .... ............................. 6
F. Waiver I Variance from Criteria .... ............................................. ........................................ 6
IV. WETLAND PRESERVATION AND MITIGATION ......................................... .......................... 6
V. DRAINAGE FACILITY DESiGN.. .... .................... ................. ... ....... ......... .......... .... .. ... ... ..... .. ... 6
A. General Concept .................. .... .. ........ ... ....... ................... .. .. .... .. ....... ..... ... .. .. .. ... ..... ...... ..... 6
B. Specific Details ................ .. ... ... ........................................ .... .. ....... .. .. .............. .. ....... .. .... .. . 7
C. Erosion Control and Storm Water Considerations ................. ... .... .................. ............ ...... 9
VI. CONCLUSiONS......................... ........................................................................................... 10
A Compliance with Standards ... ... .. .... ............................................... ................................. 10
B. Drainage Concept ...................... .................................................... .. ... ............................ 10
VII . REFERENCES ................................. .............................................. ..... .... .. ...... ............ ......... 11
VIII. ATTACHMENTS
IX. DRAWINGS
RIDGEWOOD HILLS FOURTH FILING
MULTI-FAMILY RESIDENTIAL DEVELOPMENT
PRELIMINARY DRAINAGE REPORT
ENGINEER'S CERTIFICATION
I hereby certify that this Preliminary Drainage Report for the design of stormwater management
facilities for the Ridgewood Hills Fourth Filing multi-family residential development was prepared
by me, or under my direct supervision, in accordance with the provisions of the City of Fort
Collins Storm Drainage Design Criteria and Construction Standards for the owners thereof.
Larry C. Owen, P.E. mm,,~ i~
Registered Professional Engineer
State of Colorado No. 29871
1
RIDGEWOOD HILLS FOURTH FILING
MULTI-FAMILY RESIDENTIAL DEVELOPMENT
PRELIMINARY DRAINAGE REPORT
I. LOCATION AND DESCRIPTION OF PROPERTY AND PROPOSED DEVELOPMENT
A. LOCATION
The proposed development is located in the Southeast Quarter of Section 14, Township 6
North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado. The site is bounded on the west, south of Avondale Rd., by single-family
residential lots fronting onto Triangle Dr. , on the north and west, north of Avondale Rd., by
Triangle Dr., on the east by vacant land, and on the south by single-family residential lots
fronting onto Peyton Dr. Adjacent land use to the south, west and north of the project site is
single-family residential , and to the east of the site, the vacant land immediately adjacent to
the site is designated for medium-density mixed-use neighborhood development, and
beyond that for neighborhood commercial development. The site is entirely within the
bounds of the City of Fort Collins.
B. DESCRIPTION OF PROPERTY
The site comprises a total area of 10.4 acres. The property is currently vacant, but has
been used for agriculture in past. The current ground cover is a mix of native grasses.
The site slopes generally from west to east, at surface gradients ranging between 3.5% and
15%. There is a gentle ridge, however, that bisects the site along an axis aligned roughly
from northwest to southeast and generally corresponding to the alignment of Avondale
Road, which effectively subdivides the site into two natural drainage basins, both ultimately
draining to the east, but in the context of the site alone, one drains to the northeast and the
other to the southeast.
The native soils underlying the site are predominantly silty loams (Wiley loam - 65.6% of
site area; Fort Collins loam - 27.7% of site area; and Satanta loam - 6.7% of site area). All
of these soils fall within NRCS Hydrologic Soil Group B. A geotechnical engineering
investigation that was conducted at the site in 2004 characterized the subsurface soils as
sandy, lean clays, extending to depths in excess of 15 feet, in most areas of the site. At one
boring location in the northern portion of the site and at two locations in the southern portion
of the site, weathered siltstone/claystone bedrock was encountered at depths of
approximately 11 - 12 feet. No groundwater was encountered during initial boring or when
the borings were reinspected several days later.
Flood plain mapping for the vicinity of the development site indicates that no portion of the
site lies within any mapped floodplain area.
C. DESCRIPTION OF PROPOSED DEVELOPMENT
The proposed development of the site will consist of multi-family residential buildings,
including 146 dwelling units in 11 buildings (2-story and 3-story); 33 enclosed garages in
2
three buildings; a clubhouse, with adjoining pool I spa, sports court, tot lot and recreation
area; paved access driveways, sidewalks, and outdoor parking areas; and landscaped open
space. Buildings will cover approximately 19.8% of the site; paved drive aisles, sidewalks
and vehicle parking areas will cover approximately 29.2% of the site; and landscaped open
space will account for 51.0% of the site area.
Access to the development will be via the eastward extension of Avondale Road from
Triangle Drive. The layout of the proposed development is shown as the base of the
Drainage Plan, which is included as an attachment to this report.
Municipal infrastructure for supply of potable water and collection of sanitary sewage is
available adjacent to the site in Triangle Drive, as well as at the end of Peyton Dr., south of
the site. Appropriate utility mains will be extended throughout the site to serve the
development. Electric power, natural gas, telephone and cablevision services are also
available to serve the development.
Stormwater runoff from the development will be directed via overland flow to appropriately
sized and located storm drain inlets and drainage piping, and conveyed to one of two
existing off-site detention basins; one located across Triangle Dr. from the north tip of the
site, and the other located south of Peyton Dr., approximately 250 feet south of the site.
II. DRAINAGE BASINS AND SUB-BASINS
A. MAJOR BASIN DESCRIPTION
The proposed development lies within the Fossil Creek Master Drainage Basin, as
delineated in the City of Fort Collins Drainage Basin Master Plan (City of Fort Collins, June
2004).
B. SUB-BASIN DESCRIPTION
The site is located in Basins OS-4, 821 and 918, as well as a portion of Basin 917, as
delineated in the Ridgewood Hills PUD, Filing 3, Final Drainage & Erosion Control Study
(Nolte Associates, June 2000).
The northern portion of the site (Tract B) drains to the east and is Basin OS-4. According to
the Nolte report, development of Basin OS-4 was anticipated to include multi-family
residential dwellings, and runoff was to be routed through one of the two Ridgewood Hills 3rd
Filing detention basins (labeled as Detention Ponds #1 and #2). Both of the detention
ponds were reported to have sufficient capacity to accommodate developed runoff from
Tract B.
The southern portion of the site (Tract A) consists of Basin 821 and a portion of Basin 917.
Tributary flows include those from on-site areas, as well as the rear portions of the
developed single-family lots along the east side of Triangle Dr., between Avondale Rd., and
Peyton Dr., and the rear portions of the developed single-family lots along the north side of
Peyton Dr., east of Triangle Dr. This basin also includes the front halves of the first 3 Yz lots
on the east side of Triangle Dr., south of Avondale Rd., and the east half of Triangle Dr.,
abutting those lots. The total off-site area that is tributary to the southern drainage system is
approximately 1.59 ac.
3
A portion of the site along the east perimeter slopes away sharply from the remainder of the
site. Runoff from this area cannot reasonably be captured and directed to the detention
basins. Thus, runoff will flow overland from this area onto the adjacent undeveloped land,
as it does currently. There are no improvements proposed in this area of the site, aside
from grading and landscaping, so the rate of runoff from this area will be essentially the
same as it is for the historic, undeveloped condition. The total area of the undetained
portion of the site is approximately 1.25 ac (0.90 ac. north of Avondale Rd., and 0.35 ac.
south of Avondale Rd.).
For purposes of analyzing the drainage regime for the proposed development, the project
site and off-site tributary areas have been subdivided into 27 drainage sub-basins, reflective
of the anticipated final topography of the site. These drainage sub-basins range in size from
0.04 acres to 1.87 acres. These on-site and off-site sub-basins comprise the drainage
regime for the project and are accounted for in the stormwater management analysis and
the design of stormwater management improvements for the project.
While final grading of the development site will result in localized ridges and depressions,
the overall direction of storm flow will continue to be generally consistent with the existing
predevelopment drainage patterns of the site.
III. DRAINAGE DESIGN CRITERIA
A. REGULATIONS
The proposed stormwater management improvements for the development of Ridgewood
Hilts Fourth Filing are designed in accordance with the requirements of the City of Fort
Collins Storm Drainage Design Criteria and Construction Standards (City of Fort Collins,
May 1984, March 1991 and January 1997). The recently approved amendment to the Fort
Collins Stormwater Criteria Manual, requiring the incorporation of Low-Impact Development
(LID) principles and criteria, is also expected to apply to this development. The specific
requirements of the LID amendment, as they may apply to this site, have not yet been
determined and, thus, are not reflected in this Preliminary Drainage Report. Those
requirements will be clarified through meetings and discussions with City staff, and will be
incorporated, as necessary, into the final design of stormwater management improvements
for the project.
B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
The criteria used as the basis for analysis and design of stormwater management
improvements for this site are those found in the references cited in the section immediately
above.
To the knowledge of the author, there are no other capital drainage improvements planned
for this portion of the Fossil Creek Master Drainage Basin, aside from those referred to
above, that would constrain or otherwise influence the design of the stormwater
improvements for this site.
C. HYDROLOGIC CRITERIA
Stormwater runoff from the respective sub-basins of the Ridgewood Hills Fourth Filing site is
analyzed for storms with 2-year and 1 ~O-year return frequencies.
4
Due to the relatively small aggregate area of the tributary drainage sub-basins
(approximately 13.5 acres, including off-site tributary areas), the Rational Method was
chosen for use in the design of the stormwater management improvements. The Rational
Method provides that:
Q =CIA, where:
Q = Design flow in cubic feet per second (cfs)
C = Coefficient of runoff for the area under consideration
I = Rainfall intensity for the design storm duration (in/hr)
A =Area of the drainage sub-basin under consideration (a c)
Composite coefficients of runoff were calculated for the two design storm events, based on
the applicable percent imperviousness of the respective surfaces (roof, pavement,
landscaped areas, etc.) within the various sub-basins. Rainfall intensities were determined
using information presented in the City of Fort Collins Storm Drainage Design Criteria and
Construction Standards.
For this Preliminary Drainage Report the adequacy of the two off-site detention basins is
accepted, per the Nolte report. Tract B (the northern portion of the site) will, for the most
part, drain to the northeast and into existing Detention Pond #1 and Tract A (the southern
portion of the site), plus a small portion of Tract B, will drain to the southeast and into
existing Detention Pond #2.
Analyses that were conducted by Interwest Consulting Group for a previously proposed
development of this same site included recommendations that some modifications be made
to the flow control orifices in the outlet control structures for both existing detention ponds,
and to the emergency overflow spillway in Detention Basin #2, in order to properly reflect the
City's revised rainfall criteria and the specific runoff characteristics of the proposed
development. Similar analyses will be conducted for the currently proposed development,
as part of the final design process, and appropriate design revisions will be included in the
final design submittal. The detention analyses will also reflect application of the newly
adopted LID criteria, as necessary.
The design worksheets included in the Attachments to this Preliminary Drainage Report
present documentation of the hydrologic calculations for the on-site storm drainage systems.
D. HYDRAULIC CRITERIA
Within the development, a significant portion of the runoff will be conveyed on the surface,
initially as sheet flow and subsequently as concentrated flow in shallow pans and gutters, as
well as in grassed swales. In order to minimize surface accumulations of runoff, the
assessment of required capacity and the sizing of the respective components of the
drainage system are based on the anticipated runoff from the 100-year storm event. No
detention is planned within any of the traffic circulation or parking areas, and it is the intent
of the design that there be minimal, if any, accumulation of runoff in paved parking or travel
areas. Inevitably, however, some accumulation will occur under extreme storm events, due
to the constriction presented by inlet openings. In all cases, it is the intent of the design that
the maximum depth of accumulation be less than one foot and that the duration of localized
impoundment be short.
5
Where the site grading design in localized areas precludes continuous surface migration of
runoff to the respective detention basins, appropriately sized inlets and storm drain piping
are included to convey the accumulated runoff from these localized collection points to the
detention basins. Inlet locations and sizing will be refined in the final design phase of the
project.
The calculation spreadsheets included in the Attachments to this Preliminary Drainage
Report reflect this design approach.
E. FLOODPLAIN IMPACTS
As stated in Section I B (Description of Property) above, there are no mapped floodplains
that impact this property.
F. WAIVER I VARIANCE FROM CRITERIA
There are currently no waivers or variances from the City of Fort Collins Storm Drainage
Design Criteria and Construction Standards requested in connection with the design of the
stormwater management facilities for the Ridgewood Hills Fourth Filing development.
IV. WETLAND PRESERVATION AND MITIGATION
There are no wetlands within the boundaries of the site.
V. DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
In general , developed flows will follow the intent of the Ridgewood Hills PUD, Filing 3
drainage report, with all tributary flows updated to reflect 1997 Rainfall. As stated above,
Tract B will, for the most part, drain to existing Detention Pond #1 and Tract A , plus a small
portion of Tract B, will drain to existing Detention Pond #2. Water quality requirements will
be addressed through implementation of LID principles, on-site, as well as within the
detention basins. Off-site migration of runoff will be minimized to the extent practical.
The design of the stormwater management systems for the Ridgewood Hills development is
based on the premise that runoff generated within the site should be managed within the
site, to the greatest extent practicable, such that there is no adverse impact to either the
development or to adjacent or downstream properties, drainage facilities and waterways.
The grading plan for the site has been designed to promote positive drainage away from all
building envelopes, and to direct collectable runoff flow to the collection system and then to
the detention basins.
The design worksheets included in the attachments to this Preliminary Drainage Report
present details of the hydrologic and hydraulic calculations pertinent to the design of the on
site storm drainage system. A Preliminary Drainage Plan, showing the Concept Plan for
development of the site and proposed developed drainage patterns is included in the map
pocket following the attachments.
6
B. SPECIFIC DETAILS
There are a number of collection and conveyance scenarios within the drainage regime
associated with this development. The respective scenarios are described below.
Runoff from all buildings and the immediately adjacent landscaped areas will migrate via
overland flow to either an adjacent paved parking area and drive aisle or to an area inlet in a
nearby landscaped collection area.
Within Tract B, runoff from the buildings along the west side of this portion of the site
adjacent to Triangle Drive will be, for the most part, directed to a series of connected area
inlets and a piping network beneath the landscaped area between the buildings an the
street. These sub-basins comprise an aggregate area of approximately 1.14 ac and
generate a 100-yr flow of 7.56 cfs.
Runoff from the adjacent drive aisle and parking area, including the west half of the garages,
will flow overland to a low-point inlet at the north end of the drive aisle. This sub-basin
comprises an area of 0.83 ac and generates a peak design runoff of 8.22 cfs.
Runoff from the clubhouse and amenities area in the central region of Tract B, as well as
from the adjacent drive aisles to the south and east, and the north half of the two residential
buildings fronting onto Avondale Road will migrate via overland flow to the drive aisles and
to a low-point inlet toward the north end of the east drive aisle. This SUb-basin comprises an
area of 1.87 ac and will generate a peak design runoff of 15.79 cfs.
The runoff accumulating at the inlet in the east drive aisle, along with that accumulating at
the inlet at the north end of the west drive aisle, will be piped northward to the existing inlet
in the east gutter of Triangle Drive, and from there to existing Detention Pond #1. At a point
in this piped system just upstream of the existing Triangle Drive inlet, the accumulated runoff
from the buildings and surrounding landscaping along the Triangle Drive frontage of Tract B
will be coming led with the flows from the interior areas of the site. The total design flow
entering the existing Triangle Drive inlet from the drainage systems serving Tract B is
calculated to be 30.55 cfs. In addition to this collected runoff, there will be uncollected runoff
from the landscaped area along the east perimeter of Tract B. That runoff is calculated to
be 2.60 cfs, which will exit the site in a relatively uniform sheet flow across a property line
measuring approximately 706 feet in length (0.037 cfs 1ft).
Within Tract A, there will also be a blend of overland flow and piped flow, but the areas
tributary to the piped collection system are more broadly integrated than those in Tract B.
Runoff from the southern portions and surrounding landscaping of the Tract B buildings
fronting onto Avondale Dr., as well as from a corner of the building and adjacent
landscaping in the northwest corner of Tract A, and from the off-site single-family area
draining to Triangle Drive and then to Avondale Road either migrates to the adjacent street
gutter and flows to one of several street inlets, or is collected in a series of area inlets in the
respective landscaped areas, from where it is piped to the storm main to be located within
the Avondale Road right-of-way. The aggregate tributary area within this collection of sub
basins is 2.12 ac, and the peak design runoff generated from this area amounts to 12.08 cfs.
Runoff from the buildings, adjacent landscaped areas and paved drive aisle and parking
area in the northeast quadrant of Tract A will be collected in area inlets and a parking lot
inlet at the east end of the drive aisle, and piped to the storm main that will be an extension
of the storm main serving the Avondale Road sub-basins. The aggregate area of these
7
northeast sub-basins is 0.68 acres, and the incremental peak design runoff from these sub
basins is calculated to be 3.95 cfs.
Runoff from the buildings, driveways, parking areas and landscaped space within the three
interior sub-basins in Tract A, comprising the majority of the area tributary to this drainage
system, will migrate via overland sheet flow and shallow gutter flow, to an inlet near the
southeast corner of the site, from where it will be piped to the a connection point with the
storm drain serving the Avondale Road sub-basins and those in the eastern region of the
site, and from there to existing Detention Pond #2. The aggregate area of these three
interior sub-basins is 3.22 acres and the peak design flow generated from these sub-basins
is calculated to be 21.15 cfs.
There is a drainage sub-basin along the southern perimeter of Tract A, which includes a
landscaped buffer area along between this site and the adjacent single-family lots, the
southern half of the most southwesterly building on this site, the southeast quarter of the
most southeasterly building on this site, and the rear portions of the single-family lots.
Runoff from this tributary area will migrate via overland sheet flow to a grassed swale
running along the southern perimeter of the site, and eventually into an area inlet near the
southeast corner of the site. Flows accumulated at the area inlet will be comingled with the
runoff piped from the central region of Tract A and piped to the connection with the main
north-south storm drain along the eastern perimeter of the site. The aggregate area of this
southern perimeter drainage basin is 1.80 acres, and the incremental peak design runoff
from this area is calculated to be 5.12 cfs.
The drainage sub-basins, overland flow directions and the piped drainage systems serving
the proposed development are shown on the drawings included with this report.
The following table presents a summary of the tributary sub-basins and corresponding
calculated hydrology for the proposed Ridgewood Hills Fourth Filing development.
8
DRAINAGE DATA SUMMARY TABLE
SUB-BASIN DESIGN BASIN COMP. RUNOFF COEFF. CUMMDES.RUNOFF (cfs)
1.0. POINT AREA (ac) C2 C100 0 2 0100
North System
N1 1 0.353 0.53 0.66 0.66 2.31
N2 2 0.276 0.52 0.66 1.18 4.11
N3 3 0.301 0.57 0.72 1.79 6.26
N4 4 0.211 0.50 0.62 2.08 7.56
N5 5 1.872 0.68 0.85 4.08 15.79
N6 6 0.830 0.80 1.00 2.35 8.22
7 6.08 23.69
8 7.87 30.55
OS-1 9 0.401 0.71 0.89 8.76 34.01
N7 0.900 0.25 0.31 0.73 2.60
N8 0.163 0.68 0.85 0.39 1.37
South System
S1 10 0.560 0.58 0.73 1.00 3.73
S2 11 0.125 0.41 0.52 1.05 3.85
S3 12 0.235 0.46 0.57 0.38 1.34
13 1.35 4.93
S4 14 0.121 0.47 0.59 0.20 0.71
S5 15 0.125 0.46 0.57 0.20 0.71
S6 16 0.154 0.73 0.91 1.96 7.20
S7 17 0.155 0.41 0.51 0.22 0.78
S8 18 0.412 0.68 0.85 1.14 4.26
S9 19 0.112 0.74 0.92 0.29 1.03
20 3.09 11.40
S10 21 0.119 0.69 0.86 3.27 12.08
S11 22 0.201 0.62 0.77 0.44 1.55
23 3.56 13.15
S12 24 0.436 0.64 0.81 0.90 3.49
25 4.28 15.90
S13 26 0.041 0.61 0.76 0.08 0.31
27 4.30 16.03
S14 28 1.866 0.64 0.80 3.01 11.80
S15 29 1.153 0.77 0.96 5.09 20.03
S16 30 0.204 0.78 0.98 5.39 21.15
S17 31 0.810 0.32 0.41 0.94 2.84
S18 32 0.990 0.28 0.35 6.70 26.27
33 10.56 41 .62
S19 0.352 0.25 0.31 0.31 1.10
C. EROSION CONTOL AND STORM WATER QUALITY CONSIDERATIONS
Permanent water quality enhancement will be provided through the design of on-site LID
improvements, as necessary, as well as the outlet control structure components of the
detention facilities, as addressed above.
In addition, storm water quality and erosion control during construction will be addressed
through the application of Best Management Practices (BMPs), as recommended in Volume
III of the Urban Storm Drainage Criteria Manual (UDFCD, April 2008).
9
Throughout the course of construction and until such time as permanent drainage surfaces
and/or vegetation are established throughout the development, appropriate measures will be
implemented and maintained to minimize erosion and limit the transport and migration of
sediment. Silt fencing will be installed along the downstream perimeters of the site (south
and east), as well as around sub-sites or work areas within the site, as appropriate.
Temporary drainage swales will be established throughout the site, as necessary, to collect
and convey storm runoff from the work areas, and temporary sediment barriers will be
installed at regular intervals along the lengths of these swales to slow the runoff flows and
promote deposition of sediment and other suspended solids. The anticipated locations of
the temporary swales, as well as details of erosion control Best Management Practices
(BMP's) will be shown on the Erosion Control Plan, submitted as part of the Final
Compliance drawing set.
All runoff from the disturbed portions of the site will be intercepted and directed to one of the
temporary sediment traps within the site, and discharge from these facilities will be
controlled. Accumulated sediments will be periodically removed from these facilities and
properly disposed of.
Permanent landscaping will be installed within the developed area, as soon as practical, and
temporary revegetation or mulching will be implemented if there are any areas disturbed by
construction activities, but not scheduled for immediate implementation of development
improvements.
VI. CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
The design of the storm water management improvements to serve the Ridgewood Hills
Fourth Filing development is in compliance with the City of Fort Collins Storm Drainage
Design Criteria and Construction Standards. The criteria and recommendations of the
Urban Storm Drainage Criteria Manual are also reflected in the design of the drainage
systems.
B. DRAINAGE CONCEPT
The proposed drainage improvements for the Ridgewood Hills Fourth Filing development
will effectively protect the proposed development, as well as downstream properties,
drainage facilities and natural waterways, from the potential impacts of storm runoff,
resulting in no adverse impacts from the improvements proposed for this site. Development
of the site, as proposed, should have a beneficial impact on water quality in downstream
drainage facilities and drainage ways by reducing of delaying the initial discharge of runoff
from the site such that sediments and other potential pollutants typically carried by this first
flush are removed from the flow.
10
VII. REFERENCES
"City of Fort Collins Storm Drainage Design Criteria and Construction Standards" City of Fort
Collins, May 1984, March 1991 and January 1997
"Urban Storm Drainage Criteria Manual", Volumes 1 & 2, UDFCD, April 2008
"Urban Storm Drainage Criteria Manual", Volume 3, UDFCD, April 2008
11
ATTACHMENTS
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VICINITY MAP
Hydrologic Soil Group-------Larimer County Area, Colorado
(Ridgewood Hills Fourth Filing)
40· 29' 7"
40· 2S' 54"
40· 29' 7"
40· 28' 54"
Map Scale: 1:1,S80 W printed on Asize (S.S" x 11") sheet.
__-==:::::II____-=====Meters
A N o 15 W ~ 00
O!"""...~50:==1~01llll0---·211110"'0===~30~eel
USDA Natural Resources Web Soil Survey 4/3/2013
= Conservation Service National Cooperative Soil Survey Page 1 of 4
Hydrologic Soil Group-Larimer County Area, Colorado
(Ridgewood Hills Fourth Filing)
MAP LEGEND
Area o of Interest Area (AOI) of Interest (AOI)
Soils
Soil Map Units
Soil Ratings
D A
D ND
D B
D BID
D C
D CID
D D
Not rated or not available
Political Features
o Cities
Water Features
Streams and Canals
Transportation
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MAP INFORMATION
Map Scale: 1: 1 ,880 if printed on A size (8.5" x 11 ") sheet.
The soil surveys that comprise your AOI were mapped at 1 :24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for accurate map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: UTM Zone 13N NAD83
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 7, May 1, 2009
Date(s) aerial images were photographed: 8/6/2005
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
USDA ~iiiiji Natural Resources Web Soil Survey 4/3/2013
Conservation Service National Cooperative Soil Survey Page 2 of 4
Hydrologic Soil Group-larimer County Area, Colorado Ridgewood Hills Fourth Filing
Hydrologic Soil Group
Hydrologic Soil Group-- Summary by Map Unit - Larimer County Area, Colorado (C0644)
Map unit symbol
37
Map unit name Rating Acres in AOI Percent of AOI
Fort Collins loam, 5 to 9
percent slopes
B 3.1 27.7%
96 Satanta loam, 3 to 5 percent
slopes
B 0.8 6.7%
118 Wiley silt loam, 1 to 3 percent
slopes
B 0.4 3.9%
119 Wiley silt loam, 3 to 5 percent
slopes
B 7.0 61.7%
Totals for Area of Interest 11.3 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, S, C, and D) and
three dual classes (NO, BID, and C/O). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group O. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (NO, BID, or C/O), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group 0 are assigned to dual classes.
USDA Natural Resources Web Soil Survey 4/3/2013
=-iiiiii
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group-Larimer County Area, Colorado Ridgewood Hills Fourth Filing
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
USDA Natural Resources Web Soil Survey
=-jjjj=
Conservation Service National Cooperative Soil Survey Page 4 of 4
4/3/2013
RIDGEWOOD HILLS APARTMENTS
DRAINAGE BASIN COMPONENT AREA DATA
3/29/13
Basin 1.0. Total Area Pavement Buildings Landscaped
North System (s.f.) (ae) (s.f. ) (ae) (s.f. ) (ae) (s·U (ae)
N1 15,358 0.353 0 0.000 6 058 0.139 9,300 0.213
N2 12037 0.276 a 0.000 4,723 0.108 7314 0.168
N3 13 116 0.301 0 0.000 6,058 0.139 7058 0.162
N4 9,185 0.211 0 0.000 3,248 0.075 5,937 0.136
N5 81,554 1.872 42,000 0.964 7875 0.181 31679 0.727
N6 36,142 0.830 24,914 0.572 3,293 0.076 7,935 0.182
N7 39187 0.900 0 0.000 0 0.000 39,187 0.900
N8 7,103 0.163 4,331 0.099 0 0.000 2,772 0.064
OS-1 17473 0.401 11603 0.266 0 0.000 5870 0.135
North System Subtotal 231155 5.307 82848 1.902 31255 0.718 117052 2.687
South System
S1 24413 0.560 9554 0.219 2,000 0.046 12,859 0.295
S2 5,428 0.125 0 0.000 1,269 0.029 4159 0.095
S3 10,225 0.235 0 0.000 3,029 0.070 7196 0.165
S4 5,270 0.121 0 0.000 1,683 0.039 3,587 0.082
S5 5,443 0.125 0 0.000 1 599 0.037 3,844 0.088
S6 6,714 0.154 4,556 0.105 0 0.000 2,158 0.050.
S7 6,757 0.155 0 0.000 1 509 0.035 5,248 0.120
S8 17,943 0.412 10972 0.252 0 0.000 6,971 0.160
S9 4,872 0.112 3394 0.078 0 0.000 1478 0.034
S10 5191 0.119 3226 0.074 0 0.000 1,965 0.045,
S11 8,767 0.201 0 0.000 4611 0.106 4,156 0.095
S12 18,992 0.436 7457 0.171 3245 0.074 8290 0.190
S13 1,804 0.041 0 0.000 931 0.021 873 0.020
S14 81287 1.866 29061 0.667 16184 0.372 36042 0.827
S15 50,233 1.153 28576 0.656 8392 0.193 13,265 0.305
S16 8,874 0.204 4,865 0.112 1 881 0.043 2128 0.049
S17 35304 0.810 0 0.000 3764 0.086 31 ,540 0.724
S18 43,113 0.990 0 0.000 1 878 0.043 41,235 0.947
S19 15348 0.352 0 0.000 0 0.000 15348 0.352
South System Subtotal 355978 8.172 101 661 2.334 51975 1.193 202342 4.645
Tributary Area Total 587,133 13.479 184,509 4.236 83,230 1.911 319,394 7.332
RIDGEWOOD HILLS APARTMENTS
RUNOFF COEFFICIENTS & PERCENT IMPERVIOUSNESS
Rational Method Runoff Coefficients & % Imperviousness
Runoff Coeff % Imprerv.
Roof 0.95 90
Pavement 0.95 100
Landscaped 0.25 0
Basin 1.0. Total Basin Bldg Footprint Pavement Landscaped Composite Composite
Area Area Area Area Runoff Coeff. % Imperv.
(ac) (ac) (ac) (ac)
North &ystem
N1 0.353 0.139 0.000 0.213 0.53 35.50
N2 0.276 0.108 0.000 0.168 0.52 35.31
N3 0.301 0.139 0.000 0.162 0.57 41.57
N4 0.211 0.075 0.000 0.136 0.50 31.83
N5 1.872 0.181 0.964 0.727 0.68 60.19
N6 0.830 0.076 0.572 0.182 0.80 77.13
N7 0.900 0.000 0.000 0.900 0.25 0.00
N8 0.163 0.000 0.099 0.064 0.68 60.97
OS-1 0.401 0.000 0.266 0.135 0.71 66.41
South System
S1 0.560 0.046 0.219 0.295 0.58 46.51
S2 0.125 0.029 0.000 0.095 0.41 21.04
S3 0.235 0.070 0.000 0.165 0.46 26.66
S4 0.121 0.039 0.000 0.082 0.47 28.74
S5 0.125 0.037 0.000 0.088 0.46 26.44
S6 0.154 0.000 0.105 0.050 0.73 67.86
S7 0.155 0.035 0.000 0.120 0.41 20.10
S8 0.412 0.000 0.252 0.160 0.68 61.15
S9 0.112 0.000 0.078 0.034 0.74 69.66
S10 0.119 0.000 0.074 0.045 0.69 62.15
S11 0.201 0.106 0.000 0.095 0.62 47.34
S12 0.436 0.074 0.171 0.190 0.64 54.64
S13 0.041 0.021 0.000 0.020 0.61 46.45
S14 1.866 0.372 0.667 0.827 0.64 53.67
S15 1.153 0.193 0.656 0.305 0.77 71.92
S16 0.204 0.043 0.112 0.049 0.78 73.90
S17 0.810 0.086 0.000 0.724 0.32 9.60
S18 0.990 0.043 0.000 0.947 0.28 3.92
S19 0.352 0.000 0.000 0.352 0.25 0.00
North System Total 4.905 0.718 1.636 2.552 0.59 46.51
South System Total 8.172 1.193 2.334 4.645 0.55 41 .70
Tributary Area Tot. 13.078 1.911 3.969 7.198 0.56 43.50
RIDGEWOOD HILLS APARTMENTS
Prepared by: ~
TImes of Concentration
2-yr Storm Event
Date: 3/29/13
Frequency Adjustment Factor: 1.00
Sub-Basin Data Initial 1Overland TIme
Basin I Area Runoff Coeff LenQth Slope TI
1.0. I (ac) (It) (%) (min)
North System
N1 0.353 0.53 35 6.0% 3.51
N2 0.276 0.52 35 10.0% 2.98
N3 0.301 0.57 35 15.0% 2.38
N4 0.211 0.50 30 100% 2.89
N5 1.872 0.68 95 6.0% 4.26
N6 0.830 0.80 20 5.0% 1.49
N7 0.900 0.25 83 11.0% 6.56
N8 0.163 0.68 42 5.0% 3.02
OS-1 0.401 0.71 54 2.0% 4.21
South System
S1 0.560 0.58 75 2.0% 6.68
S2 0.125 0.41 57 2.0% 7.71
S3 0.235 0.46 45 15.0% 3.30
S4 0.121 0.47 24 2.0% 4.57
S5 0.125 0.46 23 2.0% 460
S6 0.154 0.73 30 2.0% 306
S7 0.155 0.41 25 5.0% 3.81
S8 0.412 0.68 35 2.0% 3.71
S9 0.112 0.74 20 2.5% 2.24
S10 0.119 0.69 33 3.0% 3.10
S11 0.201 0.62 22 2.0% 3.36
S12 0.436 0.64 63 2.0% 5.38
S13 0.041 0.61 50 1.0% 6.46
S14 1.866 0.64 156 1.0% 10.75
S15 1.153 0.77 28 2.0% 2.64
S16 0.204 0.78 40 1.0% 3.76
S17 0.810 032 28 25.0% 2.65
S18 0.990 0.28 18 20.0% 2.42
S19 0.352 0.25 78 20.0% 5.22
Total 13.48
Channel Travel TIme
Length Slope Velocity
(ft) (%) (fps)
200 Pipe Flow
200 Pipe Flow
220 Pipe Flow
120 Pipe Flow
460 2.65% 3.20
515 4.47% 4.20
368 Pipe Flow
135 2.20% 2.90
596 3.36% 3.60
81 1.23% 1.60
375 2.40% 3.00
165 Pipe Flow
167 2.40% 3.00
35 Pipe Flow
64 Pipe Flow
80 Pipe Flow
400 2.25% 2.90
RIDGEWOOD HILLS APARTMENTS
Prepared by: ~
Times of Concentration
100-yr Storm Event
Date: 3!29/13
Frequency Adjustment Factor: 1.25
Sub-Basin Data Initial! Overland Time
Basin Area Runoff Coeff LenQlh Slope Ti
1.0. ae ft % min
North System
N1 0.353 0.53 35 6.0% 2.71
N2 0.276 0.52 35 10.0% 2.30
N3 0.301 0.57 35 15.0% 1.74
N4 0.211 0.50 30 10.0% 2.29
N5 1.872 0.68 95 6.0% 2.55
N6 0.830 0.80 20 5.0% 0.51
N7 0.900 0.25 83 11 .0% 6.08
N8 0.163 0.68 42 5.0% 1.81
OS-1 0.401 0.71 54 2.0% 2.26
South System
S1 0.560 0.58 75 2.0% 4.81
S2 0.125 0.41 57 2.0% 6.55
83 0.235 0.46 45 15.0% 2.71
84 0.121 0.47 24 2.0% 3.70
S5 0.125 0.46 23 2.0% 3.78
86 0.154 0.73 30 2.0% 1.58
87 0.155 0.41 25 5.0% 3.25
S8 0.412 0.68 35 2.0% 2.22
89 0.112 0.74 20 2.5% 1.10
810 0.119 0.69 33 3.0% 1.82
811 0.201 0.62 22 2.0% 2.28
812 0.436 0.64 63 2.0% 3.48
813 0.041 0.61 50 1.0% 4.44
814 1.866 0.64 156 1.0% 7.02
815 1.153 0.77 28 2.0% 1.13
816 0.204 078 40 1.0% 1.45
817 0.810 0.32 85 10.0% 5.60
818 0.990 0.28 18 20.0% 2.21
S19 0.352 0.25 78 20.0% 4.84
Total 13.48
- L "---- '------ -
Channel Travel Time
LenQlh Slope Velocity
ft %) (fps)
200 Pipe Flow
200 Pipe Flow
220 Pipe Flow
120 Pipe Flow
460 2.65% 3.20
515 4.47% 4.20
368 Pipe Flow
135 2.20% 2.90
596 3.36% 3.60
81 1.23% 1.60
375 2.40% 3.00
165 Pipe Flow
167 2.40% 3.00
35 Pipe Flow
64 Pipe Flow
80 Pipe Flow
Figure 3·1
City of Fort Collins, Colorado
Rainfallintensity-Duration-Frequency Curve
City of Fort Collins Precipitation Frequency Analysis, 1999 (Regional Analysis)
11,00
10,00 · : · ·~:;; tc-· , ,'.~ ' -;l ' '. .' r' ': '"~ I. I . .~ I : :; ':~~ ~~·~~~:...-" .,...;;.}/::,;, :..,;,.~~ : ':~.;}t ; ~' ;;;' :; -_ }~-j:i fJ;:" ·; ~~;if:4;~!
9.00
.•.• j
·' · :~:~T: ' ':::'::ET ' ~: /~ . .~ " ", ' ",. ; : ~~ ., ..,. .: . ; '.
•'.-,--' ~.!.."..; . ;.:... .. ;,. . " ~ ' -.' ~. " "'1 --;, ..~ : ' :
7,00 '- ~ ;. ,
-- .~r.l.t: c: ., .- ~,.:.-.~ " ·~": '~ :.,:~. . _:~.·_~~: ~t. ": ;, ,_{r~ } ,'~-~ : :;- ~}-; ). ~. i ':4", ',-:'.". ."~., ~ . i , .._.._ :. .. :.. ,'.:. :~ ';':' '.•." .,.~~ ..:,. "7-•.
• • '- . ~~~~ -';~,: . ; .. ~ r -~~~~:;;
.- .'",":..' :TO" ',.' ..:<',,-..._> . j 1-- ·-- 25-year
~ ' - ' ~ " . : : .~ r :'~..; .," :_ '':- or ; 0,:. .~ : :.' , ! 1- I
>. · ·.l ' t l ' , .. ' • ' ; , : .•• ' .. . . ;' : ., - ~O-ye"r
~ - _ ".0•• , ~
II) 5.00 ~ .:~!:~'. ~: :... '. ~~'~ . -. - " + . : ; ,- - - 5-year
t: 1- --- 2~y~_a~ ._
.<..ll . I •• , ' ,•
t: 4.00 ....;.. .. : ~ : ;i,:~ : ~ ; ,~:,:<~~ ;~;:,,{ , =+ ;; n'>
.! ,.. ~ •.... ..•.....•- ~ ~ -. . ,.;. ," ,; '"
3.00
: :'..:; . : , . ; . , : ;:,:;: ~~ , .: -:::::: . :;: . : : ; ~ t'. ~:~')c~:
2.00 .\..,:..Z':... . ' :'7'~;" ;r ~.; ~ . :. ' :' ;..!. :. >~: ~~ '1
1.00
0.00
o 20 40 60 80 100 120
Duration (minutes)
City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for using the Rational Method
(5 minutes - 30 minutes)
Figure 3-1a
-
Duration : 10-year
2-year 100-
I (minutes) Intensity Intensity Intensity yen
(in/hr) (in/hr) (in/hr
5.00 2.85 4.87 9.95 I
2.67 4.56 i
I 6.00 I 9.31 , I
-
7.00 2.52 4 .31 8.80
8.00 2.40 4.10 8 .38
.- -.
9.00 2.30 I 3.93 8.03
10.00 2.21 3.78 I 7.72 ,
11.00 2.13 3.63 ! 7.42
I i 12.00 2.05 I 3.50 7.16
13.00 1.98 i 3.39 I 6 .92
14.00 1.92 3.29 6.71
15.00 1.87 3.19 6.52 I
16.00 1.81 3.08 6.30 i I
17.00 1.75 2.99 6.10 !
18.00 1.70 2.90 5.92 !
19.00 1.65 2.82 I 5.75
-20.00 i 1.61 2.74 5.60
, !
! 21 .00 ; 1.56 2.57 5.46
22.00 1.53 2.61 5.32
23.00 1.49 2.55 5.20
24.00 1.46 2.49 f 5.09
1__- 25.00 1.43 2.44 t 4.98 --1;
26.00 1.40 i 2 .39 4.87
27.00 1.37 2.34 4.78
28 .00 1.34 2.29 I 4.69 i
29.00 1.32 ! 2.25 ! 4.60
30.00 ;
; 1.30 2.21 4.52
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
z-
W
o Q.
.J
CI)
1
I I II ! iI I ;fj
IlL:I II I. I
j I I i It I II: I i
..J:/ 1 I .2.3 I 4tiil/If i/if ~J 11!!Ij'! l ' !i i 12 I 3 5 10 20
t---~-;- - "'t~ tiFI(i~~E I~l RO~~' ~11 PER SECOND
Estimate of Average Overland Flow Velocity for Use With the Rational Formula
06/2001 RO-13
Urban Drainage and Flood Control District
I ,. I .. I I I
RIDGEWOOD HILLS APARTMENTS
ON·SITE STORM DRAINAGE SYSTEM DESIGN
(Rational Method Procedure)
2·YR STORM EVENT
Prepared by: ~ Date: 3/29/13
Direct Runoff
Basin Des! n Sub-Basin Runoff lime of C'A Rainfall Des igrJ
I. D. Point Area Coe ffi c Concenl1 Intensit R.un off
ac min ac mtho els
North System
Nl 1 0.353 0.53 3.5 0.19 2.85 0.66
N2 2 0.276 0.52 3.0 0.14 2.85 0.52
N3 3 0.301 0.57 2.4 0.17 2.85 0.61
N4 4 0.211 0.50 2.9 0.10 2.85 0.37
N5 5 1.872 0.68 6.7 1.27 2.57 4.08
N6 6 0.830 0.80 3.5 0.66 2.85 2.35
7
8
OS-l 9 0.401 0.71 7.0 0.29 2.52 0.90
N7 0.900 0.25 6.6 0.22 2.58 0.73
N8 0.163 0.68 3.8 0.11 2.85 0.39
South System
Sl 10 0.560 0.58 7.5 0.33 2.46 1.00
S2 11 0.125 0.41 9.8 0.05 2.23 0.14
53 12 0.235 0.46 3.3 0.11 2.85 0.38
13
S4 14 0.121 0.47 5.5 0.06 2.76 0.20
55 15 0.125 0.46 4.6 0.06 2.85 0.20
S6 16 0.154 0.73 3.1 0.11 2.85 0.40
S7 17 0.155 0.41 3.8 0.06 2.85 0.22
58 18 0.412 0.68 6.0 0.28 2.67 0.93
S9 19 0.112 0.74 3.0 0.08 2.85 0.29
20
S10 21 0.119 0.69 3.9 0.08 2.85 0.29
S11 22 0.201 0.62 4.8 0.12 2.85 0.44
23
S12 24 0.436 0.64 6.8 0.28 2.55 0.90
25
513 26 0.041 0.61 6.5 0.03 2.60 0.08
27
S14 28 1.866 0.64 12.5 1.19 2.02 3.01
S15 29 1.153 0.77 4.2 0.88 2.85 3.14
S16 30 0.204 0.78 4.7 0.16 2.85 0.57
S17 31 0.810 0.32 4.4 0.26 2.85 0.94
S18 32 0.990 0.28 6.0 0.28 2.67 0.93
33
S19 0.352 0.25 5.2 0.09 2.81 0.31
~--'-- - '---- -
Cummulatlve Runoff Chann el ' Gutter Flow
Total Time Cumm . Rainfall Cumm. Channel Flow
of Cone. C'A Intensity Run off Slope Depth
min ac 101M cfs % ft
3.5 0.19 2.85 0.66
4.4 0.33 2.85 1.18
4.7 0.50 2.85 1.79
5.6 0.61 2.74 2.08
6.7 1.27 2.57 4.08
3.5 0.66 2.85 2.35
7.0 1.93 2.52 6.08
7.3 2.54 2.48 7.87
RIDGEWOOD HILLS APARTMENTS
ON-SITE STORM DRAINAGE SYSTEM DESIGN
(Rational Method Procedure)
100-YR STORM EVENT
Prepared by: ~ Date: ~
Direct Runoff
Basin Desigfl Sub-Basin Runoff Time ot C'A Rainfall
1.0. Point Area Coeffic Concentr. Jntensttv
ao min ae mlhr)
North System
Nl 1 0.353 0.53 2.7 0.19 9.95
N2 2 0.276 0.52 2.3 0.14 9.95
N3 3 0.301 0.57 1.7 0.17 9.95
N4 4 0.211 0.50 2.3 0.1 0 9.95
N5 5 1.872 0.68 4.9 1.27 9.95
N6 6 0.830 0.80 2.6 0.66 9.95
7
8
OS-l 9 0.401 0.71 5.0 0.29 9.95
N7 0.900 0.25 6.1 0.22 9.26
N8 0.163 0.68 2.6 0.11 9.95
South System
Sl 10 0.560 0.58 5.7 0.33 9.16
S2 11 0.125 0.41 8.6 0.05 8.17
53 12 0.235 0.46 2.7 0.11 9.95
13
S4 14 0.1 21 0.47 4.6 0.06 9.95
55 15 0.125 0.46 3.8 0.06 9.95
56 16 0.154 0.73 1.6 0.11 9.95
S7 17 0.155 0.41 3.3 0.06 9.95
58 18 0.412 0.68 4.5 0.28 9.95
59 19 0.112 0.74 1.9 0.08 9.95
20
510 21 0.119 0.69 2.6 0.08 9.95
511 22 0.201 0.62 3.8 0.12 9.95
23
S12 24 0.436 0.64 4.8 0.28 9.95
25
S13 26 0.041 0.61 4.4 0.03 9.95
27
514 28 1.866 0.64 9.4 1.19 7.91
S15 29 1.153 0.77 2.7 0.88 9.95
S16 30 0.204 0.78 2.4 0.1 6 9.95
517 31 0.810 0.32 7.4 0.26 8.63
S18 32 0.990 0.28 5.7 0.28 9.50
33
519 0.352 0.25 4.8 0.09 9.95
De sian
Runoff
cfs
2.31
1.80
2.15
1.30
15.79
8.22
3.57
2.60
1.37
3.73
DRAINAGE DATA SUMMARY TABLE
SUB-BASIN DESIGN BASIN COMP. RUNOFF COEFF. CUMM.DES.RUNOFF (cfs)
I.D. POINT AREA (ae) C? Cwo Q? Qmo
North S"'y"stem
N1 1 0.353 0.53 0.66 0.66 2.31
N2 2 0.276 0.52 0.66 1.18 4.11
N3 3 0.301 0.57 0.72 1.79 6.26
N4 4 0.211 0.50 0.62 2.08 7.56
N5 5 1.872 0.68 0.85 4.08 15.79
N6 6 0.830 0.80 1.00 2.35 8.22
7 6.08 23.69
8 7.87 30.55
OS-1 9 0.401 0.71 0.89 8.76 34.01
N7 0.900 0.25 0.31 0.73 2.60
N8 0.163 0.68 0.85 0.39 1.37
South S'l.stem
S1 10 0.560 0.58 0.73 1.00 3.73
S2 11 0.125 0.41 0.52 1.05 3.85
S3 12 0.235 0.46 0.57 0.38 1.34
13 1.35 4.93
S4 14 0.121 0.47 0.59 0.20 0.71
S5 15 0.125 0.46 0.57 0.20 0.71
S6 16 0.154 0.73 0.91 1.96 7.20
S7 17 0.155 0.41 0.51 0.22 0.78
S8 18 0.412 0.68 0.85 1.14 4.26
S9 19 0.112 0.74 0.92 0.29 1.03
20 3.09 11.40
S10 21 0.119 0.69 0.86 3.27 12.08
S11 22 0.201 0.62 0.77 0.44 1.55
23 3.56 13.15
S12 24 0.436 0.64 0.81 0.90 3.49
25 4.28 15.90
S13 26 0.041 0.61 0.76 0.08 0.31
27 4.30 16.03
S14 28 1.866 0.64 0.80 3.01 11 .80
S15 29 1.153 0.77 0.96 5.09 20.03
S16 30 0.204 0.78 0.98 5.39 21.15
S17 31 0.810 0.32 0.41 0.94 2.84
S18 32 0.990 0.28 0.35 6.70 26.27
33 10.56 41.62
S19 0.352 0.25 0.31 0.31 1.10
DRAWINGS
0.53
1.34
0.71
0.71
1.39
0.78
3.47
1.03
1.02
1.55
3.49
0.31
11.80
10.97
1.98
2.84
3.30
1.10
Cummulative Runoff Channell Gutter Flow
Total Time Cumm. Ra infall Cumm. Channel Flow
of Conc. C'A [ntenm Runoff Slope De th
min se inlhrl cfs % ft
2.7 0.19 9.9 5 2.31
3.3 0.33 9.95 4.11
3.6 0.50 9.95 6.26
4.4 0.61 9.95 7.56
4.9 1.27 9.95 15.79
2.6 0.66 . 9.95 8.22
5.2 1.93 9.82 23.69
5.5 2.54 9.63 30.55
5.5 2.82 9.63 34.01
2.60
1.37
37.98
5.7 0.33 9.16 3.73
8.6 0.38 8.17 3.85
2.7 0.1 1 9.95 1.34
8.7 0.48 8.14 4.93
4.6 0.06 9.95 0.7 1
3.8 0.06 9.95 0.71
8.8 0.71 8.10 7.20
3.3 0.06 9.95 0.78
4.5 0.34 9.95 4.26
1.9 0.08 9.95 1.03
9.0 1.14 8.03 11.40
9.3 1.22 7.94 12.08
3.8 0.12 9.95 1.55
9.6 1.34 7.84 13.15
4.8 0.28 9.95 3.49
9.6 1.62 7.84 15.90
4.4 0.03 9.95 0.31
9.8 1.65 7.78 16.03
9.4 1.19 7.91 11 .80 3.09% 0.36
10.0 2.08 7.72 20.03 1.22% 0.48
10.5 2.24 7.57 21.15
7.4 0.26 8.63 2.84 3.45% 0.61
10.5 2.78 7.57 26.27
10.5 4.40 7.57 41 .62
4.8 0.09 9.95 1.10
42.72
Pioe Flow Travel Time
DeslQn Pi e Pice Pice Lena th Velocity Time
Flow Slop~ Size Cmci\y_
cfs % ,n cfs ft :105) min
2.31 1.80 12 4.79 222 5.98 0.62
4.11 4.44 12 7.52 135 9.77 0.23
6.26 3.20 12 6.39 388 8.14 0.79
7.56 4.50 12 7.57 103 9.65 0.18
15.79 2.30 18 15.92 164 9.01 0.30
8.22 0.70 18 8.78 14 5.67 0.04
23.69 1.10 24 23.70 102 7.54 0.23
30.55 2.50 24 35.73 17 12.85 0.02
34.01 1.57 30 28.32 80 36.07 0.04
This runoff exits the site undetained, as is the current condition.
This runoff exits the Site undetained, as is the current condition .
Total Design Runoff from the North Drainage System
3.73 8.70 12 10.53 23 9.00 0.04
3.85 2.15 18 15.40 41 7.23 0.09
1.34 1.14 12 3.81 166 4.42 0.63
4.93 2.15 18 15.40 30 7.67 0.07
0.71 1.47 12 4.33 101 4.85 0.35
0.71 0.54 12 2.62 60 3.97 0.25
7.20 2.00 18 14.85 126 8.32 0.25
0.78 4.18 12 7.30 126 6.14 0.34
4.26 1.71 18 13.73 41 6.76 0.10
1.03 4.17 18 21.44 12 6.31 0.03
11.40 2.00 18 14.85 151 9.16 0.27
12.08 1.76 18 13.93 142 8.91 0.27
1.55 28.92 8 6.51 30 15.29 0.03
13.15 1.76 18 13.93 30 8.99 0.06
3.49 2.69 18 17.22 19 7.60 0.04
15.90 6.98 18 27.74 179 16.17 0.18
0.31 25.00 8 6.05 8 9.19 0.01
16.03 7.80 18 29.32 8 16.76 0.01
236 6.53 0.60
130 5.18 0.42
21.15 14.20 18 39.57 70 22.84 0.05
566 3.85 2.45
26.27 1.40 24 26.74 30 15.44 0.03
41 .62 1.04 30 41.81 74 8.52 0.14
This runoff exits the site undetained, as is the current condition.
Total Design Runoff from the South Drainage System
7.3 2.82 2.48 8.76
0.73
0.39
9.88
7.5 0.33 2.46 1.00
9.8 0.38 2.23 1.05
3.3 0.11 2.85 0.38
9.9 0.48 2.22 1.35
5.5 0.06 2.76 0.20
4.6 0.06 2.85 0.20
10.0 0.71 2.21 1.96
3.8 0.06 2.85 0.22
6.0 0.34 2.67 1.14
3.0 0.08 2.85 0.29
10.4 1.1 4 2.18 3.09
10.8 1.22 2.15 3.27
4.8 0.12 2.85 0.44
11.1 1.34 2.12 3.56
6.8 0.28 2.55 0.90
11 .2 1.62 2.11 4.28
6.5 0.03 2.60 0.08
11 .5 1.65 2.09 4.30
12.5 1.19 2.02 3.01 3.09% 0.24
13.3 2.08 1.96 5.09 1.22% 0.32
13.9 2.24 1.93 5.39
4.4 0.26 2.85 0.94 3.45% 0.40
13.9 2.78 1.93 6.70
14.0 4.40 1.92 10.56
5.2 0.09 2.81 0.31
-
10.87 - L_
Pi e Flow TravelTime
De sigrl Pipe Pllil Pi e Len.q1h Velocity TIme
Flow Slope Size Capacity
cfs % 10 cfs ft :!ps min
0.66 1.80 12 4.79 222 4.33 0.85
1.18 4.44 12 7.52 135 6.90 0.33
1.79 3.20 12 6.39 388 7.00 0.92
2.08 4.50 12 7.57 103 8.20 0.21
4 .08 2.30 18 15.92 164 7.57 0.36
2.35 0.70 18 8.78 14 4.18 0.06
6.08 1.10 24 23.70 102 6.26 0.27
7.87 2.50 24 35.73 17 8.98 0.03
8.76 1.57 30 28.32 80 31 .74 0.04
This runoff exits the site undetained. as is the current condition.
This runoff exits the site undetained. as is the current condition.
Total Design Runoff from the North Drainage System
1.00 8.70 12 10.53 23 9.00 0.04
1.05 2.15 18 15.40 41 4.97 0.14
0.38 1.14 12 3.81 166 3.11 0.89
1.35 2.15 18 15.40 30 5.31 0.09
0.20 1.47 12 4.33 101 2.76 0.61
0.20 0.54 12 2.62 60 3.97 0.25
1.96 2.00 18 14.85 126 5.88 0.36
0.22 4.18 12 7.30 126 4.18 0.50
1.14 1.71 18 13.73 41 4.74 0.14
0.29 4.17 18 21.44 12 3.03 0.07
3.09 2.00 18 14.85 151 6.64 0.38
3.27 1.76 18 13.93 142 6.46 0.37
0.44 28 .92 8 6.51 30 10.63 0.05
3.56 1.76 18 13.93 30 6.62 0.08
0.90 2.69 18 17.22 19 5.17 0.06
4.28 6.98 18 27.74 179 11.46 0.26
0.08 25.00 8 6.05 8 4.33 0.03
4.30 7.80 18 29.32 8 11 .95 0.01
236 4.90 0.80
130 3.77 0.57
5.39 14.20 18 39.57 70 15.90 0.07
566 2.93 3.22
6.70 1.40 24 26.74 30 12.56 0.04
10.56 1.04 30 41.81 74 7.15 0.17
This runoff exits the site undetained . as is the current condition.
~lpesign Runoff from_the South_ Drainag~System I
400 2.25% 2.90
120 1.70% 2.60
137 2.19% 2.80
150 1.33% 1.70
140 0.70% 1.70
0 0.00% 1.00
291 1.03% 2.00
306 2.55% 3.30
103 2.00% 1.80
215 1.86% 2.00
573 3.49% 2.70
0 0.00% 0.00
TI
(min)
2.40
2.04
0.78
2.76
0.84
2.08
0.93
2.30
0.77
0.82
1.47
1.37
0.00
2.43
1.55
0.95
1.79
3.54
Tc Check Final Tc Remarks
CompTc Tot. LenQth Tc =(Ll180)+10
(min) (ft) (min) (min)
2.71 235 11.3 2.7
2.30 235 11.3 2.3
1.74 255 11.4 1.7
2.29 150 10.8 2.3
4.94 555 13.1 4.9
2.56 535 13.0 2.6
6.08 451 12.5 6.1
2.59 177 11.0 2.6
502 650 13.6 5.0
5.65 156 10.9 5.7
8.63 432 12.4 8.6 I
2.71 210 11.2 2.7 I
4.63 191 11.1 4.6
3.78 58 10.3 3.8
1.58 94 10.5 1.6 I
3.25 105 10.6 3.3
4.52 435 12.4 4.5
1.87 140 10.8 1.9 I
2.64 170 10.9 2.6
,
3.75 172 11.0 3.8
4.85 203 11.1 4.8
4.44 50 10.3 4.4 I
9.44 447 12.5 9.4
268 334 11.9 2.7
2.40 143 10.8 2.4
7.39 300 11.7 7.4
,
5.75 591 13.3 5.7
4.84 78 10.4 4.8
I
120 1.70% 2.60
137 2.19% 2.80
150 1.33% 1.70
140 0.70% 1.70
0 0.00% 1.00
291 1.03% 2.00
306 2.55% 3.30
103 2.00% 1.80
215 1.86% 2.00
573 3.49% 2.70
0 0.00% 0.00
Tt
(min)
2.40
2.04
0.78
2.76
0.84
208
0.93
2.30
0.77
0.82
1.47
1.37
0.00
2.43
1.55
0.95
1.79
3.54
Tc Check Final Tc Remarks
CompTe Tot. LenQth Tc =(U180)+10
(min) (It) (min) (min)
3.51 235 113 3.5
2.98 235 11.3 3.0
2.38 255 11.4 2.4
2.89 150 10.8 2.9
6.65 555 13.1 6.7
3.54 535 13.0 3.5
6.56 451 12.5 6.6
3.79 177 11.0 3.8
6.97 650 13.6 7.0
7.53 156 10.9 7.5
9.79 432 12.4 9.8
3.30 210 11.2 3.3
5.49 191 11.1 5.5
4.60 58 10.3 4.6
3.06 94 10.5 3.1
3.81 105 10.6 3.8
6.01 435 12.4 6.0
3.01 140 10.8 3.0
3.92 170 10.9 3.9
4.83 172 11.0 4.8
6.75 203 11.1 6.8
6.46 50 10.3 6.5
13.18 447 12.5 12.5
4.18 334 11.9 4.2
4.71 143 10.8 4.7
4.44 243 11.4 4.4
5.96 591 13.3 6.0
5.22 78 10.4 5.2