HomeMy WebLinkAboutDrainage Reports - 02/06/2017City offt: Collins v Pam:
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FINAL DRAINAGE REPORT
FOR
MAJESTIC ESTATES
Prepared For:
Suburban Land Reserve, Inc.
79 South Main Street, Suite 500
Salt Lake City, LIT 841 1 1
(801) 321-7567
Prepared By:
JR Engineering, LLC
2900 South College Avenue, Suite 3D
Fort Collins, CO 80525
(970) 491-9888
Contact: Tim Halopoff,.P.E.
December 2016
fob No. 39699.01
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TABLE OF CONTENTS
TABLE OF CONTENTS..........................................................................................................I
'
APPENDIX............. ...................................................................................................................
I
VICINITYMAP........................................................................................................................1
'
GENERAL DESCRIPTION AND LOCATION......................................................................2
LOCATION AND EXISTING SITE CHARACTERISTICS....................................................................2
'
SITESOILS...............................................................................................................................2
FLOODPLAIN............................................................................................................................2
DRAINAGE BASINS AND SUB-BASINS...............................................................................3
'
MAJORBASIN..........................................................................................................................3
HISTORIC SUB-BASINS.............................................................................................................3
'
DEVELOPED SUB-BASINS.........................................................................................................5
DRAINAGE DESIGN CRITERIA...........................................................................................6
'
REGULATIONS..........................................................................................................................6
LOW -IMPACT DEVELOPMENT...................................................................................................6
HYDROLOGIC CRITERIA............................................................................................................7
,
HYDRAULICCRITERIA..............................................................................................................7
DRAINAGE FACILITY DESIGN...........................................................................................8
'
GENERALCONCEPT..................................................................................................................8
OFFSITEFLOWS.......................................................................................................................8
WATER QUALITYJDETENTION FACILITIES.................................................................................8
,
STORMWATER POLLUTION PREVENTION..................................................................10
TEMPORARY EROSION CONTROL............................................................................................10
'
PERMANENT EROSION CONTROL............................................................................................10
MAINTENANCE...... .................................................................................................................10
SUMMARY AND CONCLUSIONS......................................................................................11
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EXISTING AND PROPOSED CONDITIONS ...................... .............................................................
I I
REFERENCES........................................................................................................................12
APPENDIX
Appendix A — Figures
Appendix B — Hydrologic Calculations
Appendix C — Hydraulic Calculations
Appendix D — Referenced Information
Appendix E— LID Exhibits
Appendix F — Drainage Plans
Page i
(V J•R ENGINEERING
' Engineer's Certification Block
1 hereby certify that this Preliminary Drainage Report for Majestic Estates was prepared by me
(or under my direct supervision) for JR Engineering, LLC and the owners thereof and meets or
texceeds the criteria of the City of Fort Collins Stormwater Design Standards.
Timothy J. Halopoff, P.E.
Registered Professional Engineer
State of Colorado No. 31453
' J•R ENGINEERING
Page ii
VICINITY MAP
VICINITY MAP
SCALE: 1'=2000'
FOM CREEK REMOVA
Page I
J-R ENGINEERING
GENERAL DESCRIPTION AND LOCATION
LOCATION AND EXISTING SITE CHARACTERISTICS
Majestic Estates is located in the northwest quarter of Section 17, Township 6 North, Range 68
West of the 6th Principal Meridian in the City of Fort Collins, Larimer County, Colorado. More
specifically, the Majestic Estates site is a 19.90 acre property that is currently undeveloped fallow
farmland previously planted with hay and is currently covered in native grasses and sparse alfalfa.
The site is zoned UE (Urban Estates) and will support single family estate lots once developed. The
proposed use of the site is 8 single family estate lots and about 13.5 acres of open space.
' The existing site generally slopes to the east and is split into two drainage directions. The northern
portion of the site drains to the northeast corner of the property, with slopes ranging between
0.60% and 2.5%, into an existing water quality pond. The southern portion of the site sheet flows to
the southeast corner of the property, with slopes ranging between 0.60% and 2.5%, where runoff is
collected in an existing ditch and piped through existing 12" pipe under Rock Castle Lane to the
south.
' SITE SOILS
The Majestic Estates site soils consist of loamy soil, predominately Nunn clay loam and Fort Collins
loam. Nunn clay loams belong to hydrologic soils Group C. Group C soils have 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. Nunn clay loam with 0-3 percent slopes generally has a combined surface
layer thickness of approx. 30 inches. Runoff is moderately high, and the hazards of wind erosion are
moderately low. Fort Collins loams belong to the hydraulic soils Group B. Group B soils have a
moderate infiltration rate when thoroughly west. These consist mostly of moderately deep or deep,
moderately well drained or well drained soils that have moderately fine testier to moderately
coarse texture. These soils have a moderate rate of water transmission. Supporting figures can be
found in Appendix A
' FLOODPLAIN
The site is shown on FEMA FIRM panel 08069C 120OF which is a non -printed panel. There are no
major drainage ways located within or immediately adjacent to the site.
t
' J•R ENGINEERING
Page 2
DRAINAGE BASINSAND SUB -BASINS
MAJOR BASIN
The proposed Majestic Estates site is located in the Fossil Creek major basin. The Fossil Creek
Basin encompasses approximately 32 square miles in south Fort Collins and Larimer County. The
basin extends from the foothills across Interstate 25 past County Road 5. Historically, the Fox
Meadows basin consisted of agricultural land, but has experienced significant development in the
recent years.
The site is shown on FEMA FIRM panel 08069C 1200F which is a non -printed panel. There are no
major drainage ways located within or immediately adjacent to the site.
HISTORIC SUB -BASINS
The site has existed as agricultural farmland for years and runoff from the site has generally been
split in half by a raised earthen tributary ditch that bisected to property in an L-shape. The
northeast zone of the property traditionally drains to the northeast corner of the site, where the
flows are conveyed to the Westchase Tract N detention pond through a 15" ADS pipe. The
southern portion of the site drains to the north borrow ditch of Rock Castle Drive and crossed
under the drive through existing 12" CMP at the southeast corner of the property.
The Majestic Estates site was previously a part of the Final Drainage Report for the Church of Jesus
Christ of Latter Day Saints Temple (LDS) completed by Landmark Engineering, LTD, in September
2013. In accordance with the previous report the existing irrigation channel that bisects the
property has been abandoned and will be regarded to accommodate the proposed site layout.
Wetland Mitigation Areas were added to replace the low quality natural habitat removed with the
irrigation ditch. The wetlands areas are located in both the northeast corner of the property and in
an offsite pond southwest of the property. According to the previous drainage report, the
Westchase offsite detention pond has been designed to handle up to 216 cfs from the LDS site and
the Majestic Estates site. Referring to the "Existing Drainage Plan", included in Appendix F, the
following describes the existing condition drainage basins.
'
J-R ENGINEERING Page 3
■
Existing Ofisite Drainage Basins (OS):
Sub -basin OS I consists of 6.61 acres of LDS temple site that drains in an easterly direction and is
captured by existing storm sewer and released by a 36" RCP storm pip onto the subject property
via the existing Swale. From the LDS Final Drainage report Basin OS I runoff in the I00yr event is
58.39 cfs thru the 36" RCP.
Existing Onsite Sub -Basins:
The site has three existing onsite drainage basins approximately delineated by the previous LDS
Final Drainage report.
Sub -basin EX-D58 consists of 12.09 acre area of undeveloped open space with native grasses and
weeds covering the majority of the ground and is assumed to have a 100 year runoff coefficient of
0.25. Runoff generally flows southeasterly across basin EX-D58, at slopes ranging from 0.60% to
2.0%, into the existing north borrow ditch of Rock Castle Lane and east to the existing 12" CMP
under Rock Castle Lane.
Sub -basin EX-D59 consists of 6.76 acre area of undeveloped open space with the same ground
cover and runoff coefficient as sub -basin EX-D58. Runoff generally flows northeasterly, at slopes
ranging from 0.60% to 4.0% into the exiting wetlands area/ water quality pond in the northeast
corner of the site.
Sub -basin EX-D60 consists of 2.41 acre area of undeveloped open space with the same ground
cover and runoff coefficient as sub -basin EX-D58 and EX-D59. Runoff generally sheet flows
northeasterly offsite at slopes ranging from 0.60% to 2.0%.
Page 4
J-R ENGINEERING
DEVELOPED SUB -BASINS
The proposed developed condition sub -basins have been designed to mimic the historic basins'
runoff patterns, for both on- and off -site basins. The following describes the proposed conditions
on -site drainage basins. Refer to the "Proposed Drainage Plan" in Appendix F for reference.
Proposed Onsite Sub -Basins:
Sub -basin A consists of 12.04 acres on the south side of the subject property. Runoff from the
proposed lots and open space travels southeast to the existing north borrow ditch of Rock Castle
Lane. Collected flows are conveyed east to the existing 12" CMP under Rock Castle Lane at DPI.
Sub -basin A has a runoff coefficient of 0.25 in the 100yr event, matching the previous LDS Final
Drainage Report. Sub -basin A has a total discharge of 17.9 cfs in the 100 year event which is less
than the 23.85 cfs from the previous LDS Final Drainage Report.
Sub -basin B I consists of 1.30 acres on the west side of the subject property. Runoff from the
proposed lots sheet flows to Majestic Drive where it is collected in curb and gutter and is conveyed
to an existing sump inlet at DP2. Piped flows are conveyed in the storm sewer under Majestic Drive
and east to the proposed Swale eventually discharging into the existing wetland/ WQ pond in the
northeast corner of the site.
Sub -basin B2 consists of 5.00 acres in the northern portion of the subject property. Runoff from
the proposed lots and open space flow over a grass buffer and into the proposed Swale eventually
discharging into the existing wetland/ WQ pond in the northeast corner of the site.
Sub -basin B3 consists of 1.48 acres on the north side of the subject property and includes the
existing wetland/ WQ Pond. Runoff is captured in the existing WQ pond and released over 40
hours to the existing Westchase detention pond to the northeast of the site.
Sub -basin C consists of 1.47 acres along the eastern edge of the subject property. Runoff from
this sub -basin sheet flows east off site similar to historic conditions.
Page 5 ,
J•R ENGINEERING 11
■
I DRAINAGE DESIGN CRITERIA
REGULATIONS
This report was prepared to meet or exceed the City of Fort Collins stormwater criteria. The City
of Fort Collins Storm Drainage Design Criteria and Construction Manual (with all current 2011
Revisions)(FCSDDCCM) and the Urban Drainage Flood Control District's (UDFCD) Drainage
Criteria Manual (USDCM) Volumes I, 2 and 3 were referenced as guidelines for this design. This
report was also prepared in accordance with the previous drainage report for the site, Final
Drainage Report for the Church of Jesus Christ of Latter Day Saints Temple, completed by
Landmark Engineering, LTD. in September 2013. Please see Appendix D for excerpts from this
report.
Low -IMPACT DEVELOPMENT
Volume reduction is an important part of the .Four Step Process and is fundamental to effective
stormwater management. Per City criteria, a minimum of 50 percent of new impervious surface
area must be treated by a Low -Impact Development (LID) best management practice (BMP) as well
as 25% of the new pavement area must be treated by porous pavement unless 75% of the site is
treated by LID then porous pavement is not needed. The proposed LID BMPs will have the effect of
slowing runoff through the site lot and increasing infiltration and rainfall interception by encouraging
infiltration and careful selection of vegetative cover. The improvements will decrease the composite
runoff coefficient of the site and are expected to have no adverse impact on the timing, quantity, or
quality of stormwater runoff. The proposed site uses grass buffers for the LID/BMP design
elements. In total 80.6% of the new impervious area is treated by an LID thus eliminating the need
for porous pavement, see the tables below for treatment ratios and additional detail on each LID.
An illustrative LID/Surface Maps well as sizing of the grass buffers is provided in Appendix F.
On -Site Treatment by LID Requirement
New Impervious Area
44,900
sq. ft.
Required Minimum Impervious Area to be Treated
22,450
sq. ft.
(=50% of new impervious area)
Impervious Area Directly Treated by LID Treatment Method #1 — Grass Buffer
10,900
sq. ft.
impervious Area Directly Treated by LID Treatment Method #2 - Grass Buffer
25,300
sq. ft.
Total Impervious Area Treated
36,200
sq. ft.
Actual % of Impervious Area Treated
80.6
%
Page 6
j-R ENGINEERING
HYDROLOGIC CRITERIA
The rational method was performed to calculate the peak runoff rates for each basin. Weighted
runoff coefficients were calculated for each basin using Tables RO- I I based on Natural Resources
Conservation Service (NRCS) Type C and Type B hydrologic soil classifications and surface
characteristics of each basin. The time of concentration was calculated using USDCM Equation RO-
3 and the intensity was calculated using the corresponding storm rainfall depth and USDCM
Equation RA-3. To more closely match the City of Fort Collins IDF Curve, Coefficient 3 of the
UDFCD's intensity formula was adjusted to 0.786. The City of Fort Collins area has 2-year, I -hour
rainfall depth of 0.82 inches and a 100-year, I- hour rainfall depth of 2.86 inches. These depths do
account for the 1997 adjusted rainfall depths. The 2- hour 100-year rainfall total is 3.67 inches,
based on the rainfall frequencies adopted by the City of Fort Collins.
HYDRAULIC CRITERIA
The ultimate Majestic Estates storm drainage system will be designed to convey the minor and
major storm events through the property with the inlets, storm sewer pipes, and swales for the
flows being calculated by this report. Per the requirements provided by the City of Fort Collins
Storm Drainage Design Criteria and Construction Manual, all inlets and storm pipes will be
designed to convey the 100-year storm flows. Pipe capacities were modeled in Bentley Storm CAD
V8i. All pipes have been designed to be in accordance with the Fort Collins Amendments to the Urban
Drainage and Flood Control District Criteria Manual with respect to pipe slope, capacity, velocity, and
HGL/EGL elevation.
An existing onsite wetland/ WQ pond will be used to capture the developed conditions runoff from
the site as well as the contributing runoff from the LDS temple that flows onto the site. An existing
outfall from the site will be used to convey detained releases northeast to the existing Westchase
detention pond.
All Swale and pipe outlets will be protected with turf mat or riprap; whichever is most appropriate.
Storm sewer pipe outlets will be protected using the requirements set by the USDCM for the
protection of downstream conveyance channels and culverts. LID measures have been integrated
into this design. In all, 80.6 percent of this project's impervious areas pass through and are treated
in LIDS prior to reaching the wetland/ WQ pond, which exceeds the minimum requirement of 50
percent, set by the City of Fort Collins.
Page 7
J•R ENGINEERING
■
DRAINAGE FACILITY DESIGN
GENERAL CONCEPT
The proposed improvements to the Majestic Estates site will result in developed condition runoff
' being conveyed across the proposed lots and to the east via surface flow and a proposed swale.
Low -impact development best management practices are proposed to improve the quality of runoff
' and aid in reducing peak flows and attenuating stormwater peaks. Specifically, a grass buffers are
proposed to improve water quality.
' The existing wetland/ WQ pond outfall has been designed to capture flows from the Majestic
Estates site and discharge to the existing Westchase detention pond located to the northeast of the
site.
' OFFSITE FLOWS
A portion of offsite flows from the LDS temple enter the site through the 36" RCP and are
conveyed to the existing wetland/WQ pond via the proposed Swale. The amount of flow from the
offsite basin was determined from the Final Drainage Report for the LDS temple, 22.57 cfs in the
minor storm event and 58.39 cfs in the major storm event. The offsite flows are collected in the
grass lined swale and conveyed to the north where they are detained in the existing wetland/ WQ
pond.
WATER QUALITY/DETENTION FACILITIES
' Proposed grass buffers will provide water quality for Basin A and Basin B2 of the site. The existing
wetland/ water quality pond will provide water quality for the remainder of the site as well as the
' offsite flows.
There is no detention proposed for Basin A since the amount of runoff calculated in the proposed
condition does not exceed the flow rate assumed in the previous drainage analysis. The previous
LDS temple drainage report determined a I00yr flow of 23.85 cfs for Basin A with 26% impervious.
The total runoff for the 100yr storm event for Basin A is 17.9 cfs with 8.8% impervious; which is
' lower than the previous report and thus no detention is necessary for Basin A. The existing offsite
Westchase detention pond will provide detention for Majestic Estates Basins BI-B3 and Basin C as
well as the offsite flows. According to the Final Drainage report for the LDS Temple the existing
wetland/ WQ pond in the northeast corner of the site was designed to capture the flows from the
Majestic Estates Basins 13I-133 and Basin C as well as the contributing flows from the LDS Temple
' site. The existing pond was designed to capture 18.7 cfs from the contributing basins of the Majestic
Estates site in the 100 year event. The 100 year storm event calculated by the Rational Method for
' the contributing basins of the Majestic Estates is 16.3 cfs (-Basins BI-B3 and Basin C), less than the
18.7 cfs it was designed for. The existing water quality pond was designed to capture flows from
Basin C although all of the runoff from Basin C may not necessarily get to the outlet structure. The
' ' J•R ENGINEERING Page 8
existing water quality structure was designed to release the water quality volume over 40 hours and ,
release the I00yr storm event over a weir and into the existing Westchase detention pond. Please
see Appendix D for excerpts from this report and the memo referencing the conditions for Basin ,
A.
'
J•R ENGINEERING Page 9
■
STORMWATER POLLUTION PREVENTION
TEMPORARY EROSION CONTROL
A temporary erosion control plan is to be implemented for the site during construction.
' Temporary erosion control measures include, but are not limited to, slope and swale protection,
silt fence placed around downstream areas of disturbance, construction vehicle tracking pad at
entrances, a designated concrete truck washout basin, designated vehicle fueling areas, inlet
protection, and others. All temporary erosion control measures are to be removed after they are
deemed unnecessary.
' PERMANENT EROSION CONTROL
' Permanent erosion control measures include, but are not limited to, the constructed
detention/water quality ponds, riprap pads placed for culvert outlet protection, seeding and mulch
placed to enable and established vegetative growth, etc. Long-term maintenance of these erosion
' control measures shall be the responsibility of the owner of the property. A detailed Erosion
Control Report, plan, and cost estimate meeting all City requirements is submitted under a
separate cover.
MAINTENANCE
' The owner of the drainage facility is responsible for the maintenance of all components of the
drainage system located on their property; including inlets, pipes, culverts, channels, ditches,
hydraulic structures, detention basins or other such appurtenances unless modified by development
' agreement.
' Annual inspections should take place on detention facilities to ensure they are functioning as
intended. At no time should the outlet structure be blocked by sediment or debris, and
consequently, minor maintenance should take place after significant storm events to remove trash
' and debris buildup from the outlet structures of both facilities. Removal of accumulated debris
should be scheduled annually as well, typically no later than May to ensure that each facility is
' operating as designed before each storm season. Frequent mowing of vegetation will help the ponds
with odor and insect control.
Annual maintenance operations should include:
• Inspect outlet structure and pipes, check structural integrity
• Check pond sedimentation levels
• Trash and debris removal (each spring, before storm season)
• Wetland vegetation overgrowth mitigation, odor control, insect control as needed based on
observation or complaints
• Scheduled sediment removal and disposal for every 5 years, or as needed to keep forebays
to less than 1 /3 full of sediment at all times.
Page 10
I ) J-R ENGINEERING
SUMMARY AND CONCLUSIONS
The proposed concept for the development of the Majestic Estates site involves surface flows and
piping of developed conditions flows to an existing wetland/ WQ pond. LID site enhancements will
treat the site runoff at the source before allowing the runoff to be conveyed to the existing
wetland/ WQ pond. Offsite flows from the west will be conveyed through the site and captured in
the wetland/ WQ pond.
EXISTING AND PROPOSED CONDITIONS
The existing conditions drainage has three onsite sub -basins with different outfall points, one to the
southeast side and one to the northeast side of the subject property. The existing conditions
drainage patterns are maintained in the proposed conditions. The proposed improvements will have
no adverse impacts on the flow rate, character, or quality of runoff leaving the site.
The hydrologic and water quality calculations were performed using the required methods as
outlined in the City of Fort Collins Amendments to the Urban Drainage and Flood Control District
Criteria Manual. The proposed drainage improvements meet or exceed the City's requirements.
This report exhibits that the proposed drainage improvements are also in accordance with the
previous drainage report for the site, Final Drainage Report for the Church of Jesus Christ of Latter
Day Saints Temple, completed by Landmark Engineering, LTD. in September 2013.
'
J-R ENGINEERING Page 11
■
I REFERENCES
Final Drainage Report for the Church of Jesus Christ of Latter Day Saints Temple, Landmark
Engineering, LDT., September 2013.
Hydrologic Group Rating for Larimer County Area, Colorado; USDA -Natural Resources
Conservation Service, National Cooperative Soil Survey. Web Soil Survey URL:
http://websoilsurvey.nres.usda.gov. Quly 21, 2010]
Storm Drainage Criteria Manual and Construction Standards; City of Fort Collins Storm Water
Utility, City of Fort Collins, Colorado, Updated January, 1997.
Urban Storm Drainage Criteria Manual (Volumes I. 2, and 3); Urban Drainage and Flood Control
District, June 2001.
Page 12
J•R ENGINEERING
APPENDIXA- FIGURES
J•R ENGINEERING
4 M N
4 ZrbN
Hydrologic Soil Group—Larimer County Area, Colorado
�5
496520 496000 496WO 4%760 496840 496920
3
Map Scale: 1:3,450 M prkftd m A (11" x 8.5") slaet.
N Mmtm
0 50 100 200 300
A0 150 300 600 900
Map proje m: Web Maramr Caner mordwates: WGS84 Fie tks: UTM Zone 13N WG484
i It A Natural Resources Web Soil Survey
r Conservation Service National Cooperative Soil Survey
497000 497060
Hydrologic Soil Group—Larimer County Area, Colorado
1 I
MAPLEGEND
Area of Interest (AOI)
0
Area of Interest AOI)
Solis
Soil Rating
Polygons
Q
A
Q
AID
Q
B
Q
BID
0
C
Q
CID
Q
D
Q
Not rated or not available
Soil Rating
Lines
ns
A
.v
AID
ti
B
N
BID
C
y
CID
ti
D
r
Not rated or not available
Soil Rating Points
■
A
®
NO
■
B
■
BID
ISDA Natural Resources
Conservation Service
®
C
®
CID
®
D
E3
Not rated or not available
Water Features
Streams and Canals
Transportation
ty t Rails
N Interstate Highways
US Routes
Major Roads
Local Roads
Background
® Aerial Photography
MAP INFOR
The soil surveys that comprise you'
Warning: Soil Map may not be valid
Enlargement of maps beyond the I
misunderstanding of the detail of
placement. The maps do not show
soils that could have been shown at
Please rely on the bar scale on ea
measurements.
Source of Map: Natural Resour
Web Soil Survey URL: hftp:Ilwe
Coordinate System: Web Merca
Maps from the Web Soil Survey are
projection, which preserves direct)
distance and area. A projection th
Albers equal-area conic projection
calculations of distance or area are I
This product is generated from the
the version date(s) listed below.
Soil Survey Area: Larimer County
Survey Area Data: Version 10,
Soil map units are labe:I
or larger.
Date(s) aerial images were photog�
2011
The orthophoto or other base map c
compiled and digitized probably difff
imagery displayed on these maps.
of map unit boundaries may be evi
Web Soil Survey '
National Cooperative Soil Survey
Hydrologic Soil Group—Larimer County Area, Colorado
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
35
Fort Collins loam, 0 to 3
percent slopes
C
2.7
6.6%
36
Fort Collins loam, 3 to 5
percent slopes
B
21.7
52.2%
55
Kim loam, 5 to 9 percent
slopes
B
0.5
1.1%
63
Longmont clay, 0 to 3
percent slopes
D
0.3
0.8%
74
Nunn day loam, 1 to 3
percent slopes
C
16.3
39.3%
Totals for Area of Interest
41.6
100.0%
usnA Natural Resources Web Soil Survey 3/15/2016
r Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group—Larimer County Area, Colorado
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, B, C, and D) and
three dual classes (A/D, B/D, and C/D). 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 D. 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 (A/D, B/D, or C/D), 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 D are assigned to dual classes.
Rating Options
Aggregation Method. Dominant Condition
Component Percent Cutoff: None Specified
Tie -break Rule: Higher
usnA Natural Resources Web Soil Survey - 3/15/2016
Conservation Service National Cooperative Soil Survey Page 4 of 4
APPENDIX B - HYDROLOGIC CALCULATIONS
' J•R ENGINEERING
Subdivision: Majestic Estates
Location: Fort Collins
COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 10/5/16
0
Basin ID
Total Area
(ac)
Paved Roads/ Roofs
Lawns, Sandy Soil (Type B)
Lawns, Heavy Soils (Type C)
Basins
Weighte�
Runoff Co
C2
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
A
12.04
0.95
- 0.50
0.04
0.15
6.86
0.09
0.25
4.68
0.10
0.23
B1
1.30
0.95
0.25
0.18
0.15
0.50
0.06
0.25
0.55
0.11
0.3
B2
5.00
0.95
0.32
0.06
0.15
2.00.'
0.06
0.25
2.68
0.13
0.2
B3
1.48
0.95
0.06
0.04
0.15
1.17
0.12
0.25
0.25
0.04
0.26
C
1.47
0.95
0;11
0.07
0.15
1-..17- -
0.12
0.25
0.19
0.03
0.22
Basin B
7.78
0.2
TOTAL
21.29
0.2
C100= 1.25' Basin Total Weighted Runoff Coeff
Table RO-11
Rational lfethod Runoff Coefficients for Composite Analysis
Character of Surface
Runoff Coefficient
Sucets, Parking Lots.
Daves:
Asphalt
0.95
Concrete
0.95
Gravel
0.5
Roofs
0.95
Recycled Asphalt
0,8,
Laams, Sandy Soil:
Flat <2-;
0.1
Average 2 to 706
0.15
Steep >7°u
0.2
IanmS,.fleavy Soil_
Flat <20;
0.2
Average 2 to 7%
0.25
Steep?74B
0.35
OOO.dN969901'Fxcd'Dmimge DminW_CeIm 3969901_v2.0.ffim
Table RO-12
Rational Alethod Runoff Coefficients for Composite A
Storm Return Period
Frequency Factor
veers
Ct__
2 to 10
1.00
171 to 21
1.10
2610 50
1:20
51 to 100
1.25
Subdivision: Majestic Estates
Location: Fort Collins
COMPOSITE PERCENT IMPERVIOUS CALCULATIONS
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 10/5/16
Pavement
Roofs
Lawns/ Grass
Basin ID
Total Area
(ac)
-;imp-
(%)
Area (ac)
Weighted%
Imp. (%).
%Imp. (%)
Area (ac)
Weighted%
Imp. (%).
%Imp. (%)
Area (ac)
e
Weighted% Y
Imp. (%).
A
12.04
100%
0.17
1.4%
95%
0.33
2.6%
5%
11.54
4.8%
BS
1.30
100%
0.10
7.7%
95%
0.15
11.0%
5%
1.05
4.0%
B2
5.00
100%
0.12
2.4%
95%
0.20
3.8%
5%
4.68
4.7%
B3
1.48
100%
0.06
4.1%
95%
0.00
0.0%
5%
1.42
4.8%
C
1.47
100%
0.11
7.5%
95%
0.00
0.0%
5%
1.36
4.6%
Basin B
7.78
TOTAL
21.29
X',3960000.a1f'3969901E=dDmbagDnomp C&1M 3%"01_a2.0als
STANDARD FORM SF-2 '
TIME OF CONCENTRATION
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 10/5/16
SUB -BASIN
INITIAL/OVERLAND
TRAVELTIME
tc
DATA
(TJ
(Tj
(URBANIZE
BASIN
ID
D.A.
(ac)
Hydrologic
SoilsGroup
Impervious
(%)
Cz
CIN
L
(ft)
S.
(%)
t,
(min)
L,
(ft)
S.
(%)
K
VEL
(ft/s)
t,
(min)
COMP. t,
(min)
TOTA
LENG
A
12.04
B/C
9%
0.23
0.29
'. - 200
2.0%
83.7
200
0.5%
7.0
0.5
6.7
90.4
4
Bl
1.30
B/C
23%
0.35
0.44
' - 80
2.00A
45.6
270
1.00A
-20.0
2.0
2.3
47.9
B2
5.00
B/C
11%
0.25
0.31
130
2.0%
65.9
70
0.5%
20.0
1.4
0.8
66.7
B3
1.48
B/C
9%
0.20
0.25
75
2.0%
53.0
320
0.5%
20.0
1.4
3.8
56.8
C
1.47
B/C
12°%
0.22
0.28
- 'W
1.0%
47.6
Soo
1.0%
7.0
0.7
11.9
59.5
i
NOTES:
t,=ti+t,
t; =(1.87•(1.1-C•Cf)'(L)A0.5)/((S,)-0.33)
L= length of overland flow ( 500' max)
C= runoff coefficient
Cf= Frequency adjustment factor
t; = overland (initial) flow time (minutes)
5 = Average Slope along the overland flow path, ft/ft
t,=L/(60K•(5°)A0.5
t, = channelized flow time (minutes)
S = waterway slope, ft/ft
V, = travel time velocity (ft/sec) = V%40.5
(Equation 6-2)
Table 6-2. NRCS Conveyance Fa
Type of Land Surface
Heavy Meadow
(Equation 6-4) Tillage/field
Short pasture and lawns
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
First Design Point Time of Concentration:
t,=(18-15•i)+L/(60•(24•i+12)•(S°)A0.5) (Equation 6-5)
i = imperviousness (expressed as a decimal)
t, is lesser of Equation 6-2 and Equation 6-5.
For Urbanized basins a minimum t, of 5.0 minutes is required.
For non -urbanized basins a minimum t, of 10.0 minutes is required.
X.3960000a1Ri969901'ExcetDraimplDramage_Cala_:969901_W1.0x1sm
K
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Subdivision: Majestic Estates
Location: Fort Collins
Design Storm: 2-Year
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 10/5/16
DIRECT RUNOFF
TOTAL
RUNOFF
STREET
PIPE
TRAVEL TIME
V
N
�
N
t
u
STREETS
d
Q
Q
o
V
:ESE
_
y
o
2
`r
C
O
4!
N
M
�•
V
•
OCf
1
A
12.04
0.23
23.4
2.77
1.48
4.1
Add Ex. Majestic Dr. Flow
2
Bl
1.30
0.35
17.9
0.46
1.71
0.8
3.5
3.5
Add LDS Temple Rows
3a
23.4
Add 36" RCP Flow
3
B2
5.00
0.25
19.6
1.25
1.63
2.0
25.4
Add Bio-Swale Flow
4
B3
1.48
0.20
23.3
0.30
1.49
0.4
25.8
S
C
1.47
0.22
22.2
0.32
1.52
0.5
X:`.960(g0 W\s969901tE�tcl�Aainax�Uaiw�e_fala i969901 W_.Oxlsm
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Subdivision: Majestic Estates
Location: Fort Collins
Design Storm: 100-Year
PIPE TRAVEL
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 10/5/16
TI
DIRECT RUNOFF
TOTAL RUNOFF
STREET
c
?C:3960000 n1N9699011Eur73haomgclD�aimgc_Ca1e 3969901 v2.0[Ivu
APPENDIX C - HYDRAULIC CALCULATIONS
J•R ENGINEERING
4Ywksheef ?roterned
DESIGN PEAK FLOW FOR ONE-HALF OF STREET _
OR GRASS -LINED CHANNEL BY THE RATIONAL METHOD
Protect Majestic Estates
Inlet ID: DP 2 EX Fort ColSIDE lllins Single Curb Inlet I
�w D I I I 17 STREET XI I I I OVERLANFLOW
1
GUTTER FLOWS
IY _ yl IV I. '
GUTTER PLUS CARRYOVER FLOW- Show Deleils
ROADWAY CENTERLINE
On ennined
thoughother me s: Minor Storm Major Storm
<—
(bd gale Powfa lR of sewt OR pnasew4 then»IY. *Qanxn= cis
FlLL IN THIS SECTION
ou enter values In Row 14. sWp She rest of this sheet and proceed to sheet QAdow or Area Inlet
OR_
;raphoorma in the
blue mby
FILL IN THE
S,bcatdmera Area
SECTIONS BELOW.
�-f�j����9^I,aas
Percent Imperviousness
—
Sae Type:
O Ste is Urban
Raw O'n'Jppcl Fa: NRCS Soil Type - A, B, C. or D
Sad-1 1
Qet Slope(Mt) Length(ft)
Q SaIs
Q6erland Flow
Chanvel Flow =
- r US minorsionn MajorStonn
Design Stone Retum Period. T, -1 1yters
Rehm Period On Hou Predpilation P, =l I linches
User-De(urd Storm Ruoff Coefficient (leave Ws blard(to &Mept a cakliate0 veke), C -
Usa-0efbed Syr. Ruoff Coeffident (leave dris blank to aocept a relndated.v ka:). Cs =
Bypass (Carry-Ovu) Flow from upstream Subcatchnwnts, Os c 0.0 cfs
Total Design Peak Flow, D = 3.5 8.8 cfa
UD-Inlet v3.14-DP2.tdsm, O-Peak 5f2/2016, 1:41 PM
Project:
Inlet ID:
11 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) 11
1 g T, Tp
SAM W — Tx
ffQw Qx/
H T�—
Gutter Geometry Enter data in the blue cells
Maximum Allowable Width for Spread Behind Curb
T� =
15.0
ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb)
SeAcK =
0.002
ft(ft
anning's Roughness Behind Curb (typically between 0.012 and 0.020)
naACK
Height of Curb at Gutter Flow Line
Houae =
6,00
inches
Distance from Curb Face to Street Crown
T. =
18.0
R
utter Width
W =
2.00
it
Street Transverse Slope
Sx =
0.002
ftM
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/R)
Sw =
0.083
ftM
Street Longitudinal Slope - Enter 0 for sump condition
So =
0.000
Nft
anning's Roughness for Street Section (typically between 0.012 and 0.020)
nsmFFr =
0.013
Minor Storm Major Stone
Max. Allowable Spread for Minor & Major Storm
Truv<=
9.0
18.0
it
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm
d� =1
6.0
1 6.0
inches
Allow Flow Depth at Street Crown (leave blank for no)
LJ check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion
Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion
O,r,,, = SUMP I SUMP cfs
inor stone max. allowable capacity GOOD - greater than flow given on sheet'O-Peak'
ajor storm max. allowable capacity GOOD - greater than flow given on sheet'O-Peak'
UD-Inlet v3.14-DP2.xlsm, C-Allow 5/2/2016, 1:41 PM
INLET IN A SUMP OR SAG LOCATION
Project = Majestic Estates
Inlet ID = DP 2 EX Fort Collins Single Cum Inlet
4' Lo (C) 4
H-Curb _
H-Vert
Wo
Wp
W
Lo(G)
minterrelation (hilaugl
of Inlet
Inlet Type
Depression (additional to mrtinuus gutter depression'a' hom'QAbw)
em
ter of Unit Wets (Grate or Cub Opening)
No
r Depth M Flow4m (outside of local depression)
Pending Depth
16lformallon
h of a Uric Grate
L. (G)
I of a Unit Grate
W.
Opersng Ratio for a Grate (typical vales 0.15-0.90)
A.
prig Factor for a Single Grate (typical vale 0.50 - 0.70)
C, (G)
Weir Coefficient (typical vale 2.15 - 3.60)
C. (G)
Critics Coefficient (typical vahe 0.60 -0.60)
C. (G)
Opening Information
h of a Unit Cub Opering
L. (C)
t of Vertical Cub Opering in Inches
H.
it of Cub Orifice Throat in Inches
Ham
of Throat (see USDCM Figue ST-5)
Theta
WMN for Depression Pan (typically the putter widh of 2 feel)
Wr
Iug Factor for a Single Cub Opening (typical vale 0.10)
Cr (C)
Opening Weir Coefficient (typical vale 2.3-3.7)
C. (C)
Opering Odom Coefficient (typical vale 0.60 - 0.70)
Co (C)
ll Inlet Interception Capacity (assumes clogged condition)
Q.
Capacity IS GOOD for Minor and Major Storms (10 PEAK)
- O Fua mouse
Warning 1: Di nensen entered Is not a typical dimension for Inlet type specified.
MINOR MAJOR
CDOT/Demer Dinstion
2.00 13 Com2:'0 inches
6.0 10.5 inches
MINOR MAJOR � O.aride �los
3.00 3."0 feet
2.00 G:. feet
0.43 ., 3
0.50 0.50
3.30
0.60 fi.GO
3.00
6,50
5.25
5 "5
0.00
!:A
2.00
2"
0.10
0.10
3.70
..70
0.66
n <i
set
Iles
Iches
egress
:et
UD-Inlet v3.14-DP2.rdsm, Inlet In Sump 51212016, 1:43 PM
3969901 StormCAD.stsw
5/2/2016
Plan View
Connect to EX. 36"
MH-1
Bentley Systems, Inc. Haestad Methods Solution Center
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203
-755-1666
O-1
2yr Results
'
Label flow
Capacity
Line
Line
Line
Invert Up
Invert
HGL Up
HGL EGL Up
EGL
Velocity
Velocit
Velocity
(cfs)
(Design)
Size
Length
Slope
(ft)
Down
(ft)
Down (ft)
Down
Avg
y Up
Down
(cfs)
(in)
(ft)
(ft/ft)
(ft) °
(ft)
(ft) `
(ft/s)
(ft/s)
(ft/s)
CO-1
1 23.401
36.53
36.0
190.()l
0.0031
4,911.41
1 4,910.84
4:913.18
1 4,912.781
4,913.63
1 4,913.15
5.481
5.381
4.83
CO-2
1 23.401
37.00
36.0
39.01
0.0031
4,910.84
4,910.72
4912.53
4,912,281
4,913.04
1 4,912.90
5.541
5.701
6.31
3969901StormCAD.stsw Bentley Systems, Inc. Haestad Methods Solution Center
11/16/2016 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755
-1666
100yr Results
Label Flow
Capacity
. Line
Line
Line
Invert Up
Invert
HGL Up
HGL EGL Up _ EGL :
Velocit
Velocit
Velocit
N-vale
'
(cfs)
(Design
Size
Length
Slope
(ft)
Down
(ft)
Down, (ft) Down
y Avg
y Up
y
Pipe
(in)
(ft)
(ft/ft)
(ft)
(ft) (ft)
(ft/5)
(ft/s)
Down
(cfs). .:
..
(fUS)
..'
CO-1
61.80
36.53
36.01
190.01
0.003
4911.41
4,910.84
4,916.05
4,914.42
4,917.24
1 4,915.61
1 8.74
8.74
8.74
07
CO-2
1 61.80
37.00
1 36.01
39.01
0.003
4:910.84
4,910.72
4,913.83
4,913.25
4,915.011
4,914.72
1 8.741
8.75
9.71
0.t
�969901IStormCAD.stsw Bentley Systems, Inc. Haestad Methods Solution Center
1/16/2016 27 Siemon Company Drive Suite 200 W Watertown. CT 06795 USA +1-203-755
-1666
Profile - 1 - 2 yr
4;9;88J
a.9.S.60
�9:8 t0
{,9:BA0
4,917.80
{,9:) 60
1,917 b
4,91d.90
a,9:6b0
{,916.b
4,916.90
4.91dA0
4.935.80
a.9]5.60
{,9:9 W
9:S M
C
a,9:5.00
4,9Ia.60
W 4,9:a 10
9:4 20
a,9i'm
a,911 M
{,S:0.60
419:).b
a,91].]0
a;90.00
4.9:2.80
ar9 -'AO
4.911
4,9:2.00
0,9:1.Y0
4.91:.40
{9:: M
4.9:J.b
0 ;OA 20.0 J^.i 4L.G 50.0 60.0 Y(i.0 :OO.0 M4 120.0 :30.0 ]AM ]a..0 W.0 110.0 :04
6 wn(IS)
I
Profile - 1 - 300yr
a,930.00
a,918.80
1,918.60
6914.30
s,s36.�
a.918.00
1,91]AO
6,91).b0
49v-a0 -
a,91>.20
4,917.00
a.915.90
a,936
a,916 a0
a,91630
1.916.00
t,915d0 �',
a,915.40
G 4,919.14
♦,915.3C
a,915.00
j a,91<.60
d a,91t.60
a,93a.aC
1,91630
C914.00
1,91}6C
J,91).40
1.111.4
4,91 20
4,9UM
.,W."
a,912.60
4,912.40
41912.20
a,913.00
4101140
a,911.50
a,913 p'
3933."
4910.5'
1,910.6'
0.0 10.9 ::.0 33.0 10,0 55.0 50.0 70.0 00,0 S0.0 1C0.0 1190 3e0.0 130.0 1J0.0 35^,.0 AM t%:.0 12C0 1:(J V0 :t00
M.U.n (it)
PIPE OUTFALL RIPRAP SIZING CALCULATIONS
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.: 39699.0
Calculated By: BAB
Checked By:
Date: 5 18 16
STORM DRAIN SYSTEM
36" RCP DESIGN POINT
Q100 (cfs)
61.8
Flows are the greater of proposed
vs.future
D or H (in)
36
W (ft)
Slope (%)
0.50
Yn (in)
8.74
Yt (ft)
Unknown
If "Unknown" Yt/D=0.4
Yt/D, Yt/H
0.40
Per Chapter 9, Section 3.2.3
Supercritical (yes/no)
no
Da, Ha (in) *
Da=0.5(D+Yn), Ha=0.5(H+Yn)
dso (in), Required
1.42
Required Riprap Size
L
Fig. 9-38 or Fig. 9-36
Use Riprap Size
L
dso (in)
9
Table MD-7
Expansion Factor, 1/(2 tan0)
4.50 :
Fig. 9-35 OR 9-36
0
0.11
Erosive Soils?
Yes
At
11.23
At=Q/V
Lp
28.6
L=(1/(2 tan q))(At/Yt - D)
Min Length (ft)
9.0
Min L=31) or 3H
Max Length (ft)
30.0
Max L=10D or 10H
Min Bottom Width, T (ft)
12.4
T=2*(LP*tan0)+W
Design Length (ft)
29.0
Design Width (ft)
12.4
Riprap Depth (in)
18
Depth=2(d5o)
Type II Base Depth (in)
6
*Not used if Soil Riprap
Cutoff Wall
Yes
Cutoff Wall Depth (ft)
24.0
Depth of Riprap and Base
Cutoff Wall Width (ft)
9.3
Note: No Type II Base to be used if Soil Riprap is specified within the plans
* For use when the flow in the culvert is supercritical (and less than full).
X.'3960000.all`3969901\Exccl,Dmin ge\Dminage_Cales_3969901_e2.0.xlsm Page 1 or2 5i2R016
U
ZE
O
rn
Z
a
x
w
8
7
WN
6 = Expansion Angle
St
Imo/mmmmmum
O .1 2 .3 .4 .b b .I .a
TAILWATER DEPTH/CONDUIT HEIGHT, Yt/D
Figure 9-35. Expansion factor for circular conduits
t3= Expansion Angie
TAILWATER DEPTH/CONDUIT HEIGHT—Yt/H
Figure 9-36. Expansion factor for rectangular conduits
X'3960000.dr3969901\Excell)minkdDmimge_Cales_3969901_v2.0.xlsm Paget oft 5.+22016
APPENDIX D - REFERENCED INFORMATION
J•R ENGINEERING
FINAL DRAINAGE REPORT
FOR THE CHURCH OF JESUS CHRIST
OF LATTER DAY SAINTS TEMPLE,
FORT COLLINS, COLORADO
Prepared for:
Church of Jesus Christ of Latter Day Saints
50 E. North Temple Street, 10th Floor
Salt Lake City, Utah 84150-6300
Contact: Mark Tingey P.970.391.0212
mtingey@comcast.net
' September, 2013
Project No. ARCHNE-I L8A-01-301
Consulting Engineer
LANDMARK ENGINEERING, LTD.
3521 West Eisenhower Blvd.
Loveland, CO 80537
Ph: (970) 667-6286/Toll Free (866)-379-6252
Northeast Pond D-59 Outlet Structure
The detention pond on Tract N (Westchase) has been designed to handle up to 216 cfs from the LDS
site (+ 3S acres) during the 100-year storm event in order to accommodate as much storm runoff as
possible from the LDS site, an overflow weir structure has been designed for the outlet of the northeast
pond. Due to width constraints between properties and cover issues with existing utilities, the design of
the outlet structure was only able to accommodate approximately 112 cfs from the LDS site.
Approximately 41-feet of existing 36-inch storm pipe, a manhole, and a headwall have to be removed 7
shortened in order to accommodate the spillway. After the 36-inch storm pipe has been cut back, a
new headwall will be installed with a concrete channel that will accompany the spillway to the Tract N
Westchase detention pond. The 100-year flow from the Westchase drainage report of 93 cfs for the
existing 36-inch storm pipe has been calculated into the lower spillway total flow of 155.16 cfs at a
depth of 0.81 feet.
The spillway structure consists of a number of concrete walls in order to contain storm flows within
certain areas so as not to encroach on adjacent properties under required grading criteria. The spillway
's co be covered in ShoreM2X Solt revetment scour protew m mat for erosion protection. The %W-
ear storm event calculated by the Rational Method for the northeast pond is approximately 94 cfs. The
overflow spillway for this pond has been sized to accommodate 1.2 times 94 cfs or 112.54 cfs.
The stormwater quality outlet structure for the pond is piped under the spillway in an easterly fashion
o a concrete channel that also flows to the main spillway structure. The concrete channel for this was
designed due to grading constraints. Unlike most outlet structures, this one only discharges the water
lquality volume over 40-hours. Since there is no detention volume associated with this pond, the height
of the water quality structure has to be equal to the elevation of the spillway weir. Therefore the water
quality structure is to have solid cover placed on the top instead of a grated one. The average discharge
over 40-hours through the pipe is 0.09 cfs. Additional storm water volume has been provided in the
concrete channel servicing the outlet structure for Basin D-60 of 4.84 cfs. All of the runoff from Basin
D-60 may not necessarily get to the outlet structure. Future detention release from the proposed
housing development may also utilize the concrete channel of the outlet structure.
3-11
Water Quality Pond D59 (Northeast):
Calculated Required Water Quality Pond Volume = 0.31 Acre -Feet @ EL=4904.23
Water Quality Capture Volume at Structure = 0.31 Acre -Feet
Overflow/Outlet Weir Height = 4904.23
Overflow/Outlet Weir Length = 107.00 feet
Water Height Calculated at Weir = 0.5 feet @ Qioo = 112.54 cfs
Refer to the next page for the water quality outlet structure detail for Pond D59.
Water Quality Ponds
As previously mentioned, the LDS water quality ponds take two forms. The northeast pond is solely
designed as a natural habitat buffer zone and water quality pond (D59). Pond (D59) allows 100-year
storm flows to pass over its weir and become detained by the detention pond on Westchase Tract N.
The second pond (D54) is a true detention pond, with additional volume for water quality. Pond (D54)
is located in the Southwest portion of this site.
When calculating water quality and detention volumes, the ponds are sized to stack the required
Eivolumes upon one another, instead of combining the two. This provides for the rare situation that
loccurs when the 100-year storm event follows a smaller event that has recently filled the pond's water
quality space. The overall goals of the LDS water quality ponds are to cleanse the developed condition
storm water of particulates (suspended solids) and chemicals (Dissolved solids) from the runoff prior to
release to the receiving waters/dry swales. By correctly sizing the LDS water quality steel perforated
' plates, low flows and smaller storms can be detained for longer periods (24-40 hrs) prior to release, so
that particulates can settle out and chemicals can have a chance to be absorbed by plant material and
soils within the pond. Water Quality Ponds D54 and D59 have WQCV of 0.08 ac: ft- and 0.31 ac.-ft.,
respectively. These volumes are designed to abate over a period of 40 hours. The water quality system
characteristics on the LDS project are appropriately sized and will be enhanced by the wetland
mitigation areas that we have incorporated in this design.
A constructed wetland area is a conveyance BMP that is built, in part, to enhance stormwater quality.
Constructed wetlands use dense vegetation to slow down runoff and allow time for both biological
;uptake and settling of sediment. Both of the LDS outfall detention/water quality ponds will utilize
wedand mitigation areas. These areas are to be constructed flat with a ponding depth of six -inches. An
overflow weir shall be constructed to control the ponded water and dissipate outgoing runoff. The LDS
Church sub -contracted Western Ecological Resource, Inc., to consult on the wetland areas. They
advised on how much ponding and which plant species should be introduced in and around the natural
,fearures. Refer to the NAturat Habitat buffer Zones Ptah in the map packets of this repast for derails.
4-2
CALCU ATtOH OF A PEAK RUNOFF USING RATIONAL METkt00
Project Title: LDS
Catchment ID: D58
1. Catchment Hydrologic Data
Catchment ID = D58
Area = 12.09 Acres
Percent Imperviousness = 26.00 %
NRCS Soil Type = D A, B, C, or D
IL Rainfall Information
I (inchlhr) = C7 ' P1 l(C2 + Td)"C3
Design Storm Return Period, Tr =
10 years (input return period for design storm)
C1 =
28.50 (input the value of C1)
C2=
. 10.00 (input the value of C2)
C3=
0.786 (input the value of C3)
P1=
1.40 inches (input one-hr precipitation —see Sheet "Design Info'
III. Analysis of Flow Time (Time of Concentration) for a Catchment
Runoff Coefficient, C =
0.37
Overide Runoff Coefficient. C =
(enter an overide C value if desired, or leave blank to accept calculated C.)
5-yr. Runoff Coefficient, C-5 =
0.29
Overide Syr. Runoff Coefficient, C = .
.. (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.)
Illustration
."--Cl
-11W B°4
11 Catchment
Reach 3 Hawiarr
NRCS
7ypea�
Heavy
MeadowJ11 Fliegd
PL �
Nearly
sere G nd
Waterway
Paved Areas &
Shall awed Swates
Conveyance If
2.5 0O7
10
15
20 --
Calculations:
Reach
Slope
Length
5-yr
NRCS
Flaw --.,
Flow
ID
S
L
Runoff
Convey-
Velocity
Time-,
Coeff
ante
V
Tf
Nit
ft
C-5
fps
minutes
4
�97 ��_ �� tTc= 17.17
User -Entered Tc = 17.17
I
IV. Peak Runoff Prediction
Rainfall Intensity at Computed Tc, I = 1.63 inch/hr Peak Flowrate, Qp =
Rainfall Intensity at Regional Tc, I = 2.98 inchihr Peak Flowrate, Qp = -.1341"Cfs
Rainfall Intensity at User -Defined Tc, I = 2.98 inchihr Peak Flowrate, Qp = ___A-_9-cfs
Q,o=6Z4(Z97)f2,09
H4-2YR, Tc and PeakQ
�),^ ^ =1.7C*;%u)G,07 09
1012612012, 4.11 PM '
CALCULATION Of A PEAK RUTAOFF USMG RAT101AAL MET"013
Project Title: LDS
Catchment ID. D59
1. Catchment Hydrologic Data
Catdumtt 1.0 = USS
Area = 6,76 Acres
Percent Imperviousness = 25.00 %
NRCS Soil Type = D A, B, C, or D
11. Rainfall Information I (inchlhr) = C1 ' P1 I(C2 Td)AC3
Design Storm Return Period, Tr = 10 years (input return period for design storm]
C1 = 28.50 (input the value of Cl)
C2= 10:00 Gnput the value of C2)
C3= 0.786 (input the value of C3)
P1= 1.40 inches (input one-hrprecipitation--see Sheet "Design Info")
Ill. Analysis of Flow Time (Time of Concentration) for a Catchment
Runoft Coefficient, C = 026
Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.)
5-yr. Runoff Coefficient, C-5 = . 028
Overide 5-yr: Runoff Coefficient, C = (enter an overide C-5 value if desired, or, leave blank to accept calculated C-S.)
Illustration
° LEr"m
Z= Reach IIwr
Z Reach O.Rqor�
-10 ' 3 nm.Mutton
�rDO b �' catchanent
ieZ
Reach 3 Boundary
MRCS Land
Heavy
Tillage/
Short
Nearly
Grassed
Paved Areas &
Type
Meadow
Freld
Pasture/
Bare
Sw as/
Shaliaw Paved Swales
Lawns
Ground
Waterwa
Sheet
Can nce
2.5I
7 1"
10
15
20
Calculations:
Reach
ID
Overland
Slope
S
wa
input
Length
L
It
Input
0.02W0'
' 259:`.
A
0.0132'
1 SON
3
4.
IV. Peak Runoff Prediction
Rainfall Intensity at Computed Tc, I = 2.45 inchfhr
Rainfall Intensity at Regional Tc, 1= 3.20 inchfhr
Rainfall Intensity at User-0erined Tc, I = _ _ 3.20 inch/hr
517
NRCS
Flow
Flow
Runoff
Convey-
Velocity
I
Tune
Coeff
ante
V
Tl
C-5
rps
minutes
Computed Tc = 1t 24:73 . .
Regional Tc = 14.79 �—
User -Entered Tc = 14.79
Peak Fiowrate, Op = er.ST"tis
Peak Fiowrate, Op = —4-Wefs--
Peak Flowrate, Op _ZS&-ens
059 10YR.xts, Tc and PeakO /� ^� _ I' �� /�Z 5 )/ � /, 7� \ / pb �^ 612012013, 6:10 PM
CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD
Project Title: LDS
Catchment ID: D60
I. Catchment Hydrologic Data
Catchment ID = D60
Imperviousness
= 2.41 Acres
Percent = 25.00 %
NRCS Soil Type = D A, B. C, or D
fl. Rainfall information
i (incWhr)= C1' P7 /(C2+Td)^C3
Design Storm Return Period, Tr =
10 years (input return period for design storm)
C1 =
28.50 (input the value of C1)
C2=
10.00 (input the value of C2)
C3=
D388 (input the value of C3)
P1=
1.40 inches (input one-hr precipitation —see Suet "Design Info")
Ill. Analysis of Flow Time (Time of Concentration) for a Catchment
Runoff Coefficient, C =
0.36
Overide Runoff Coefficient, C =
(enter an overide C value if desired, or leave blank to accept calculated C.)
5-yr. Runoff Coefficient, C-5 =
0.28
Overide 5-yr. Runoff Coefficient, C =
(enter an overde C-5 value if desired, or leave blank to accept calculated C-5.)
Illustration
�" Z i �5
►a = 31
rlana LEGEND
Reach 1 pay.
Reath Bed
` )17
f
Reach)
Flow Directio
f-
Catrlunenc
Bounawy
NR d
TF
�
Meadow
Pasturet
Bare
watesJ
Spat o Swaies
11
Lawns
lived
Con nce
7 IF77T6'7
0... 15 11
20 J
Calculations: Reach Slope Length
ID S L
Wit I ti
1
2
5•yr
NRCS
Flow
Flow
Runoff
Convey-
Velocity
Time
Coeff
ante
I
V
I I
If
C-5
fps
minutes
- DZ5(3 15 Z I S
IV. Peak Runoff Prediction
Rainfall Intensity at Computed Tc, I = 1.97 inch/hr
i Rainfall Intensity at Regional Tr, I = 3.14 inch/hr
Rainfall Intensity at User -Defined Tc, I = 3.14 inch/hr
OD
)643
D60-10YRxls, Tc and PeakQ
4t�I,nn2lTc= 15.44 :c—"
User-EnteredTc=1 15.40
Peak Flowrate, Op = "44z tfa--
Peak Fiowrate, Op = ?44-cfs
Peak Flowrate, Op = ^.ccg-6;o-
6/2012D13, 6:11 PM
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DONALD & ROBIN
MILDRUM
LOT 3
wk
-cb
TIN!136UN6., ROAD
---4885
7
90..
.. ........ ---------
ROBERT KOEHLER S.W. 1/4,
N.W. 1/4 SECTION 17
A.P. No. 86170-00-012
EQND D54
WOCV RELEASE=40 HRS.
W0CV--0.08 ACRE FEET
TOTAL POND VOLUME=0.55 ACRE FEET
mj
QUALITY OUTLET STRUCTUREOP
w
TOP OF WELL SCREEN = 490&28 = WOCV
OUT = 4906.08
OUTLET BOX I RELEASE RATE = 2.45 CFS
OUTLET BOX I GRATE ELEVATION = 4908.28
OUTLET BOX 2 RELEASE RATE = 20.44 CFS
OUTLET BOX 2 GRATE ELEVATION=4911.15
100YR WSEL=4911.15
BOX I TO BOX 2 ORIFICE = 5-INCH SQUARE
OVERFLOW GRATE CAPACITY = 21.98 CFS 0 50% REDUCTION
LOWEST TOP OF BERM ELEVATION = 4913-00
POND FREEBOARD = 1.85 FEET
POND D59
WOCV RELEASE=40 HRS.
WOCV=0.31 ACRE FEET=TOTAL POND VOLUME
WATER QUALITY OUTLET STRUCTURE
TOP OF WELL SCREEN = 4904.23
Lij
z
FL OUT=4901.90
OVERFLOW/OUTLET WEIR ELEVATION = 4904.23
WEIR LENGTH = 107.00 FEET
DEPTH OF WATER OVER WEIR = 0.5 FEET 0 0100 = 112.54 CFS
LOWEST TOP OF BERM ELEVATION = 4905-23
POND FREEBOARD = 1 FOOT
' MEMORANDUM
To: Heather McDowell
From: Becky Brush, EIT
Date: April 20, 2016
Subject: Majestic Estates- Drainage Analysis
J•R ENGINEERING
A Westrian Company
JR Engineering, LLC has completed a conceptual storm drainage evaluation for the Majestic Estates project.
The following is a summary of the findings discovered while performing an analysis of the proposed Majestic
Estates project in order to determine the basin's 100yr runoff and LID requirements. It is our understanding
that by showing the amount of runoff in the proposed condition does not exceed the flow rate assumed in the
previous drainage analysis, no detention will be necessary for the southeastern drainage basin area. We have
also shown that the LIDS depicted on the attached exhibit, are able to adequately treat at least 75% of the
project's new impervious area.
' This memo relies upon a previous drainage study for the site, which was completed in September 2013, entitled
Final Drainage Report for the Church of Jesus Christ of Latter Day Saints Temple. The previous report
determined a 100yr flow of 23.85 cfs for the southeast basin, which JR Engineering identifies as Basin A for
' this analysis. Basin A is 12.42 acres and consists of 4 proposed lots and one existing lot. For this analysis it was
assumed that the average impervious area per lot would be approximately 3,800 square feet ( 600 sf driveway,
700 sf garage, and 2500 sf home footprint) and that the lots will be graded as type B lots with about 75% of
each lot's impervious area draining to the rear of the lot and the rest draining to the front. The area that drains to
the front of the lots is conveyed to a large natural Swale and into an existing wetland/ water quality pond. These
flows are not included in those being treated by an official LID.
Using the City of Fort Collins Stormwater Criteria Manual, JR Engineering found the following for the
southeast basin A: a composite runoff coefficient of 0.28, a composite percent impervious of 8.7%, a time of
concentration of 23.4 minutes, and a total discharge of 17.7 cfs in the 100 year event. See the .attached
spreadsheet calculations for more details.
Our conclusion is that, using the assumed 3,800 sf of impervious area per lot and the existing soil types B and
C( as shown in the exhibit), the total runoff for the 100yr storm event for the southeast Basin A of the Majestic
Estates project is 17.7 cfs; which is lower than the previous report. Thus we will propose no detention for Basin
A. Water quality for the site will be provided for 75% of the entire site's new impervious area via a grass buffer
in the southeast and a sand filter in the northeast. The grass buffer will provide water quality for Basin A before
flowing into the existing northern roadside Swale of Rock Castle Lane. The sand filter will provide water quality
for Basin B2 which will fill and then flow directly into the proposed Swale, via a level spreader, draining to the
existing wetland/ WQ pond in the northeast corner of the site. Ultimately, we plan to proceed with a formal
submittal, using these hydrologic methods to achieve substantial compliance with the City of Fort Collins's
Stormwater Criteria Manual. Please contact me if you find that any changes should be implemented prior to our
formal submittal.
Sincerely,
Becky Brush
07200 South Alton Way, Suite C400 0130 East Kio%a Street, Suite 400 E12900 South College Avenue; Suite 3D
Centennial, C080112 Colorado Springs, C080903 Fort Collins, C080525
303-740-9393 • Fax 303-921-7320 719-593-2593 • Fax 303-921-7320 970491-9888 • Fax 303-921-7320
Subdivision: Majestic Estates
Location: Fort Collins
COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
Paved Roads/ Roofs
Lawns, Sandy Soil (Type B)
Lawns, Heavy Soils
(Type C)
Basins T
Basin ID
Total Area
(ac)
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Weightei
Runoff C
C2
A
12.42
0.95
0.50
0.04
0.15
7.24''
0.09
0.25
4.68
0.09
0.22
BI
1.30
0.95
0.25
0.18
0.15
0.50
0.06
0.25
0.55
0.11
0.35
B2
4.82
0.95
0.32
0.06
0.15
1.83
0.06
0.25
2.67
0.14
0.26
83
1.48
0.95 -
0.06
0.04
0.15
1.17
0.12
0.25
0.25
0.04
0.20
C
127
0.95
0.11
0.08
0.15
0.97
0.11
0.25
0.19
0.04
0.23
Basin B
7.60
0.26
TOTAL
21.29
0.24
C100= 1.250 Basin Total Weighted Runoff Coeff
Table RO-11
Rational Methed.Runoff Coefficient, for Composite Analysis
Character of Surface
Runoff Coefficient
Streets, parking Lots,
Drives:
Asphalt
0.95
Concrete
0.95
Gravel
0.5
Roofs
0.95
Recycled asphalt
0..8
Lawns, Sandy Soo'
Flah:2%
0.1
Average 2 io 7%
0.15
Steep>79b
0.2
Lama, Aeavy Soil:
Flat <;2%
0:2
Acernue 2 to 7-6
0.25
Steep>7%
0.35
000,alPJ969%1'Excd'Dnmage'DminW_Cdes_3969901 c2.0.aiem
Table RO-12 '
Rational Method Runoff Coefficients for Composite A
Storm Return Period
Frequency Factor
rears
C
.2do 10
1.00
11 to 25
1.10
16 to 50
1.20
Si to too
135
COMPOSITE PERCENT IMPERVIOUS CALCULATIONS
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
Basin ID
Total Area
(ac)
Pavement
Roofs
Lawns/ Grass
%Imp.
I%)
Area (ac)
Weighted%
Imp, (%)•
%Imp. (%)
Area (ac)
Weighted%
Imp. (%).
%imp. (%)
Area (ac)
Weighted%
Imp. (%).
-A
;12.42 -
100%
'.. 0.17 `:
1.4%
95%
"` 0.33
2.5%
5%
11.92
4.8%
" -'B1
::1.30 -
100%
`: 0.10.
7.7%
95%
015
11.0%
5%
-1.05 -'
4.0%
82
'-4.82 ' ,:
100%
..0.06 .
1.2%
95%0.26
5.1%
5%
- 4.50 ;.
4.7%
`.B3
1.48
100%
20.06
4.1%
95%
0.00 '
0.0%
5%
1.42
4.8%
C
1.27 ` '"
100%
0.11-P
8.7%
95%
�0.00 . "
0.0%
5%
1.16
4.6%
TOTAL
21.29
X:',3960000.aE3969901'EXM\DDULW D amage_Cala_3969901 -vM xls
STANDARD FORM SF-2
TIME OF CONCENTRATION
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
SUB -BASIN INITIAL/OVERLAND TRAVELTIME tc
DATA (TI) (Tj (URBANIZEI
BASIN D.A. Hydrologic Impervious Cz C. L S. t, L, S. K VEL t, COMP. t, TOT
ID (ac) Soils Group (%) (fill (%) (min) (it) (%) (ft/s) (min) (min) LENG
A I 1i 6i I R/r I Q-A I n 97 1 n 7R -)nn] 7 rml Ad rl inn n;-Al 7 nI n S 6.7 Q1 4 4
61
1.30 -.
B/C-
23%
1 0.35
1 0.44 1-',
, 801
2.0%1
45.61
270
,:
1.0%1
-20.01
2.01
2.31
47.9
82
4.82 -
B/C
11%
1 0.26
1 0.33
1301
2.0%
65.1
701
0.5%1
20.01
1.41
0.81
66.0
NOTES:
t,=tr+t, (Equation 6-1)
tr =(1.87•(1.1-C`Cf)-(L)A0.5)/((St,)A0.33)
L= length of overland flow ( 500' max)
C= runoff coefficient
Cf= Frequency adjustment factor
t; = overland (initial) flow time (minutes)
S = Average Slope along the overland flow path, ft/ft
t,=L/(60K-(Sa)A0.5 (Equation 6-4)
t, = channelized flow time (minutes)
S = waterway slope, ft/ft
V t = travel time velocity (ft/sec) = K•S,A0.5
First Design Point Time of Concentration:
t,=(18-15"i)+L/(60'(24•i+12)'(S,)A0.5) (Equation 6-5)
i = imperviousness (expressed as a decimal)
t, is lesser of Equation 6-2 and Equation 6-5.
For Urbanized basins a minimum tc of 5.0 minutes is required.
For non -urbanized basins a minimum t, of 10.0 minutes is required.
X.3960000AR3969901�FxcetAamage�a amage_Cda_3969901 _V2.0.akw
I
Table 6-2. NRCS Conveyance Factors, K
Type of Land Surface
K
Heavy Meadow
2.5
Tillage/field
5
Short pasture and lawns
7�
Nearly bare ground
10
Grassed waterway
15
Paved areas and shallow paved swales
2CM
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Subdivision: Majestic Estates
Location: Fort Collins
Design Storm: 2-Year
PIPE TRAVEL TIM
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
E
DIRECT RUNOFF
TOTAL
RUNOFF
STREET
W
N
�
U
X'G96000D.aW3969901\F_x¢PDMWage Dmimge_Celcs_3969901_%..O.xhm
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Subdivision: Majestic Estates
Location: Fort Collins
Design Storm: 100-Year
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
DIRECT RUNOFF
TOTAL
RUNOFF
STREET
PIPE
TRAVELTI
U
t
c
w
3
3
c
a
STREET
o
o
_
o
o
,r
�
¢
r
�
¢
�
C
c
`G
E
o
.
�.
.Cy
o
w
o
a
w
v
1
A
12.42
0.28
23.4
3.42
5.17
17.7
-6a-
Add Ex. Majestic Dr. Flow
2
Bl
1.30
0.44
17.9
0.57
5.95
3.4
8.8
8.8
Add 36" RCP Flow
3
B2
4.82
0.33
19.6
1.57
5.69
8.9
1 1
70.7
Add Swale Flow
4
63
1.48
0.25
23.3
0.37
5.19
1.9
72.6
5
C
1.27
0.29
21.9
0.37
5.35
2.0
Y 3960000.aflU969901\Ex rl)miioa c\Draim,c Clics_3969901 _v2A.xls
t - Excerpt from " Final Drainage Report
for LDS Temple" dated September
2013.
CALCULAiM OF A. PEAK IkUNOFF USMG WtONAL METHOQ
Project Title: LDS
Catchment ID: D58
1. Catchment Hydrologic Data
' Catchment ID = D58
Area = 12.09 Acres
Percent Imperviousness = 26.00 %
NRCS Soil Type = D A, B, C, or D
It. Rainfall Information I (inchibr)= C1 * Al f(C2 + Td)AC3
Design Storm Return Period, Tr = 10 years (input return period for design storm).
C1 = 28.50 (input the value of Cl)
C2- MOO OO (input the value of C2)
C3= 0.786 (input the value of C3)
P1= 1.40 inches (inputone-hr precipitation -see Sheet "Design Info'
III. Analysis of Flow Time (Time of Concentration) for a Catchment
Runoff Coefficient, C = 0.37
Overide Runoff Coefficient, C = (enter an ovedde C value if desired, or leave Wank to accept catculated C.)
5-yr. Runoff Coefficient, CS = 0.29
Overide Syr, Runoff Coefficient, C = (enter an overide C-5 value if desired, of leave blank to accept calculated C-5.)
Illustration
' - - - orertand
L�GIIYD'
Rcxch 1, now
Reach 2 BLS
Fhnr Dbmcfw -
Calchrneni
- Reaeh3 Bouadacy.
NRCS Lard'
-. Heavy
Tillage/
Grassed
Paved Areas 8 "-
Type
Meadow
Field. -
PasWrei
Bare ..
Swalest
Shallow Paved Swales
I
t.avms
Ground
waterwa
Sheet Flow)
conveyance . "
- 2.5
5
7 '"
f0:.
15-'
" - -
'
Calculations: Reach Slope Length 5-yr
NRCS Flom . , Flow
'
.. :.
ID
S
L
Runoff
Convey-
Velocity
-Time_..__
-
Coeff
once
V
Tr
n!ft
ft
C-5
fps
rninutes
input
input
output
input
cutout
output
'
Overland
0:0200.:
- 450
0.29
NIA ,.
%, 0.30
24:77
1- "
0.0070
840
7.00 ' `:
0 59
23.90
3 .
4
'S
Suml
1,290
1
Computed Tc =
48.67
�� pp��i �%
—f ZZ
CO
%
Y-1, � Z97 4�� / (97
(p
Regional Tc=
User-EnteredTc=
17,17
17.17
-
IV. Peak Runoff Prediction
Rainfall Intensity at Computed Tc I = 1.63 inctdhr
Peak Flowrate Op
'
Rainfall Intensity, at Regional Tc, I = 2.98 inchfir
Peak Flowrate, QP s
Rainfall Intensity at User -Defined Tc, I = 2.98 inchthr
Peak Fiowrate, Op = 3-49' cfs
H4-2YR. Tc and PeakQ r r y GL ` �� /�
' IA^ � r
p 1012612012, 4:11 PM
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Subdivision: Majestic Estates
Location: Fort Collins
Design Storm: 100-Year
Project Name: Majestic Estates
Project No.: 39699.01
Calculated By: BAB
Checked By:
Date: 3/20/16
DIRECT RUNOFF
TOTAL RUNOFF
STREET
PIPE
TRAVEL
TI
w
.V..
m
t
U
STREET
c¢
W
t
E
Q
Cii
o
N
a
o
Q
O
a
y
D58
12.09
0.325
17.17
3.93
6.08
23.89
'LDS Temple basin with City of Fort Collins rainfall data
R:'5960000all\39699011EucrDnimgelDnimgc_Caks 3969901 _v2AXIM
' Grass Buffer
T-1
Description
Grass buffers are densely vegetated
strips of grass designed to accept sheet
flow from upgradient development.
t Properly designed grass buffers play a
key role in LID, enabling infiltration and
slowing runoff. Grass buffers provide
' filtration (straining) of sediment.
Buffers differ from swales in that they
are designed to accommodate overland
' sheet flow rather than concentrated or
channelized flow.
Site Selection
Grass buffers can be incorporated into a
wide range of development settings.
Runoff can be directly accepted from a
Photograph GB-1. A flush curb allows roadway runoff to sheet flow
through the grass buffer. Flows are then further treated by the grass
al Ph fM II E
parking lot, roadway, or the roof of a sw e. oto courtesy o u er. ng neenng.
structure, provided the flow is distributed in a uniform manner over the width of the buffer. This can be
achieved through the use of flush curbs, slotted curbs, or level spreaders where needed. Grass buffers are
often used in conjunction with grass swales. They are well suited for use in riparian zones to assist in
stabilizing channel banks adjacent to major drainageways and receiving waters. These areas can also
sometimes serve multiple functions such as recreation.
Hydrologic Soil Groups A and B provide the best infiltration
capacity for grass buffers. For Type C and D soils, buffers still
serve to provide filtration (straining) although infiltration rates are
lower.
Designing for Maintenance
' Recommended ongoing maintenance practices for all BMPs are
provided in Chapter 6 of this manual. During design the
following should be considered to ensure ease of maintenance
' over the long-term:
■ Where appropriate (where vehicle safety would not be
impacted), install the top of the buffer 1 to 3 inches below the
adjacent pavement so that growth of vegetation and
accumulation of sediment at the edge of the strip does not
prevent runoff from entering the buffer. Alternatively, a
sloped edge can be used adjacent to vehicular traffic areas.
■ Amend soils to encourage deep roots and reduce iffigation
trequirements, as well as promote infiltration.
Grass Buffer
`Functions
LIDNolume Red.
Yes
W CV Capture
No
W CV+Flood Control
No
Fact Sheet Includes
EURV Guidance
No
Typical Effectiveness for Targeted<
Pollutants';
Sediment/Solids
Good
Nutrients
Moderate
Total Metals
Good
Bacteria
Poor
Other Considerations
Life- cycle Costs
Low
'Based primarily on data from the
International Storntwater BMP Database
(www.b mpdatabase. org).
November 2010 Urban Drainage and Flood Control District GB-1
Urban Storm Drainage Criteria Manual Volume 3
T-6
Sand Filter
O 4:1 SIDESLO 6 WITH NO AREAS
GREATER THAN kt. WHEN USING
WAILS, THE DESIGN SHOULD ALLOW
FUR (REMOVAL AND REPLACEMENT
OF THE FILTER (AVER WITHOUT
JEOPARDIZ14 THE INTEGRITY OF
ME WALL /
LEND H ND L PoPRAP
TYPE OR VMM SHOULD
EXTEND TO AT LEAST D
TIMES ME PIPE DMEfER
PROVIDE MAINTENANCE —
ACCESS TO FILTER
SURFACE
INFLOW
AM
NTS
RACK
`— FLAT AREA OF SAND"MTER
— CLEAN. OUT (TYP)•
4".SLOTTED PIPE., AT 20' D.C. SEETAaLE. SF-2.
OUT MTTH. (2) 45' BENDS AND WATERTIGHT CAP
TIONAL: FLOW CONTROL VOLUME -
RIPRAP FILL VOIDS WITH �-=SF-1,4'
FILTER MATERIAL I-MINORIFICE PLATE.FOR 12 HOUR GRAIN OF WOM
FILTER MATERIAL SEE TABIL MIN. UNDER DRAIN MEETING TABLE SF-2,
SLOPE AT OS% MIN.
ppppO
NTS
NUM' THIS OEAIL SHOWS A.PARML IWILTRATION'SEC110N. FOR FULL INFILTRATION EUMIATE
UNDERORNN AND PROVIDE --V-6" OF FILTER MATERIAL FOR NO INFILTRATIONFRINGE
OMPERYFAME MEMBRANE S=RED TO UST -IN -PACE CONCRETE WALLSEEOETAILS SF-2 AND
SF -a
(D SLOPE MRA1GHT GRADE) SUOGRADE(2-10%) TO UNOERDRNN TO REDUCE.
SATURATED SOIL -CONDITIONS BETWEEN STORM. EVENTS (OPTIONAL)
SECOMONZ
wsa A
Figure SF-1. Sand Filter Plan and Sections
OUTFLOW
SF-8 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
wwe
Design Procedure Form: Grass Buffer (GB)
Sheet 1 of 1�
-
Designer: BAB
r-
yrev
ln
.ga
Company: JR Engineering
-
Date: April 20, 2016
�0
-
Project: Majestic Estates
`-P
-
Location:
1. Design Discharge
;
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer
Oz = 4.0 cis
a
'
2. Minimum Width of Grass Buffer
We =� 80 �' it
-
3. Length of Grass Buffer (14' or greater recommended)
Lo = 14 it
4. Buffer Slope (in the direction of flow, not to exceed 0.1 it / ft)
So = 0.007 it / It
-
5. Flow Characteristics (sheet or concentrated)
.
.`
-.
A) Does runoff flow into the grass buffer across the
Ox Ones
�!� yes."-) No
entire width of the buffer?
_..._.__.. .......
B) Watershed Flow Length
Fr= 480 ft
-
C) Interface Slope (normal to flow)
S'= 0.001 Ulf
s
D) Type of Flow
' �'- � >> SHEET FLOW
Sheet Flow: FL * Sx < 1
Concentrated Flow: FL* Si > 1
6. Flow Distribution for Concentrated Flows
me (sheet flow)
_
Slotted Curblxj
Level Spreader
Other (Explain):
--'
7 Soil Preparation
-
(Describe soil amendment)
1=~
e
8 Vegetation (Check the type used or describe "Other")
r Ch �p P��
I U 0 Exsmg Xerk Turf Grass
F
3 Irrigated Turf Grass
Otter (Explain):
s+ `
Choose ne
=
9. Irrigation
" i Temporary
ry
'
('Select None if existing buffer area has 80% vegetation
- x Permanent
.-
AND will not be disturbed during construction.)
,. ,
u
None*
10. Outflow Collection (Check the type used or describe "Other")
Gras Swale
�) Street Gutter
;.; Storm Sewer Inlet
Other (Explain):.
A
Notes:
aR1
,„a;,'$_S'issc3
`.4'.°.,i l�-•wiw'• -r�..sA A .,r,'d0. e951�e v - �3r °care o-.a°'iM.�,sq'` qw Iqy JN .t1 �drea �'."m 6P'� P.i1 �A�:
3969901 UD-BMP_v3#1- grass buffer.xlsm. GB 4/20/2016, 2:56 PM
m- #�'. �'&n.�a�.'s
Design Procedure Form: Sand Filter (SF)
'-
sheet 1 of 2.
Designer. BAB
iAe
Company: JR Engineering
Date: April 20, 2016
Project: Majestic Estates
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tdbulary Area, I,
a
I, = 11.0 %
(100% if all paved and roofed areas upstream of sand filter)
B) Tributary Area's Imperviousness Ratio (i = 1.1100)
.. 0.110
i=i
C) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time
WQCV = 0.07 watershed inches '
WQCV= 0.9' (0.91" 0- 1.19 - F+ 0.78 - i)
D) Contributing Watershed Area (including sand filter area)
Area = 115,434 sq it
E) Water Quality Capture Volume (WQCV) Design Volume
Vwwv =� - .. 629
Vwacv = WQCV 1 12' Area
F) For Watersheds Outside of the Denver Region, Depth of
ds = 1.40 in
Average Runoff Producing Storm
-
G) For Watersheds Outside of the Denver Region,
Vwocv onmr =7 ' 2.047' cu ft
Water Quality Capture Volume (WQCV) Design Volume
-
H) User Input of Water Quality Capture Volume (WQCV) Design Volume
VWocyuaa, = cu ft
(Only if a different WQCV Design Volume Is desired)
2. Basin Geometry
-
A) WQCV Depth
Dw,,v= 1.0 If
B) Sand Fitter Side Slopes (Horizontal distance per unit vertical,
Z = 4.00 ft / ft
4:1 or flatter preferred). Use "0" if sand filter has vertical wall,.
C) Mimimum Fi ter Area (Fiat Surface Area)
AM„ ' 455 ' 7 sq ff a
D) Actual Fitter Area
A� 3201 sq it n
E) Volume Provided
VT = 3201 cur ft
3. Filter Material
QQ 18" CDOT Ciao C Filter Material
�........0
Other (Expiain
............. .............................................._...............
a
4. Underdrain System
Choose One
A) Are underdrains provided?
O YES
NO
B) Underdram system orifice diameter for 12 hour drain tlme
i) Distance From Lowest Elevation of the Storage
y= NIA ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours
Volrz-; N/A _aft
io) Orifice Diameter, 3!$' Minimum
fi
Da =�� N/A � � in
r
_
3969901 UD-BMP_v3#1- sad filter.xlsm. SF 4/20/2016, 2:55 PM
r' Fm rah.
ae.
Design Procedure Form: Sand Fitter (SF)
V
0
Sheet 2 of 2
Designer: BAB
Company: JR Engineering -
-
Date: April 20, 2016
Project: Majestic Estates
s
t.
Location:
Oroose Ore
5. Impermeable Geomembrane Liner and Geotexble Separator Fabric
vE5 NO
A) Is an impermeable liner provided due to proximity
- of structures or gmundwater contamination?
m
6-7. Inlet / Outlet Works
-
A) Describe the type of energy dissipation at inlet points and means of
conveying flows in excess of the WOCV through the outlet
Notes:
d+k' MR�^_iu{'"'i f„ri ai r�.i34 G �4a 3
1 3969901 UD-BMP v3#1- sad filter.xlsm, SF 4/20/2016, 2:55 PM
APPENDIX E - LID EXHIBITS
J•R ENGINEERING
I / PIT
/
I /
I / /
I /
I
I
I I
I 1
1
I / I
I /
/
/
I
l
TRILBY ROAD - -
N4
I W 1 \
r , `��
B
II
-- 'I
�\ \ TYPE C SOIL \ TYPE B SOIL 1.48. 0 EX YETLANDS/ WO PONDov
.25
\\` ♦ \\ \ \\ \\ ram' \ \
1 I I I ID I i \I I I
I111� llll, r' \\lli III ill � I/ � I I\ I1\\I
II I I I i I PROPOSED SAM FILTER \
I, \
II I I 6 1 I I V YI
II I I I es c
I I / .B2 .26 / I/ T _� �I� II 1.27
It v
.29 I i I 1 .33 I,
� \ 1 \I
�yg,D I
DR WAIF \ \I
2110,
I /BI
�
r\
,.30 .44
Ex sWALE ro aE cRADEo
/ TYPE C SqL /
\ / --TYPE B SOIL.
\ I
— I
I �\
IF
AS SUM 38M S
OF IMPERVKfUS AREA PER LOT'
WITH ABOUT )SA DRAININGM
THE.
ri�24
-
/ 49,5
22
/TYPES SOIL
--_ i ..,
\ /
//
I
♦_-N.- -
TYPE B SOIL
+•
TYPE C SOL
TYPE B SOIL
TYPE CSO4
/
_ s .e a W ,F. ♦
-
CR
- �a910 LANDMARK
I
_'
- 1 7 C
A0100 Cis _
m
PROPOSED NON IRRIGATED GRASS BUFFER
—
EX NORTH BORROW DITCH -' / Qj ` r
OF ROCK CASTLE LANE
EX 1Y• GNP
U
Zw NZ
XH-0�.. s'
aawwz ¢-•
wm�SOma
�U 6'wIJW YZ
SAND FILTER
' (LOOKING NORTH)
LEVEL SPREADER
wy"<�
SCALE: N.T.S.
ma0
rc a O0
NAIURAL. SYNALE ro
�' F
z
F waawa. �rn�
NE 1IAIpS/
z 0000 wo
1
IN)P
,�p�0
Or UNDER ORAIN
W N O
18• CCOT GLASS C FILL MATEWW.
O N O J
a
Q N M
MUj CD Eli
mZ
�N]C
¢
C, Z N Q
Q
�o
GRASS BUFFER
= M - ME
Ell
(LOOKING NEST)
SCALE: N.T.S.
FASTING DITCH SIDEWALK ACTS AS
LEVEL SPREADER
FOR 1011
10%
14 WN.
v
fO
i5h
AMENDED SOILS
NOTE: SEE ATTACHED URBAN DRAINAGE DETAILS
FOR SPECIFICATIONS
Fi
ENGINEER'S ST
>o Rr,.,
e
PREPARED UNDER MY DIRECT SUPERVISION
1AMF3 •'•�90
z
oQy
Y$:
e
37953 �:
o
ME <cED
CO
w
A'•
\o<<
Z
m
m
TIMOTHY JAMES HALOPOFF, P.E.
.•
o•
B AE,,,,.•• 6�
v
OLORAp O N0. 37953
S/ E�
J Ofl6L
>
F
FOR ANO ON BEHALF OF JR ENGINEERING, LLL.
ry �
m
m
m
60 30 0 60 120
ORIGINAL SCALE: 1• = 60'
•
Know what's NOW.
Cell6Bfore you dW
City D(Fort Collins, Colorado
o
GAS
UTILITY PLAN APPROVAL
p
u
u
APPROVED:
Ciry EnKium Dam
CHECKED BY:
Wa¢m A waalewav Utility Dare
CHECKED Or.
ILL
Smmwamr Ulm,, Dam
V)
C.0
CHECKED BY:
LLJ
Q
Pulm A R—firm Dam
l'—
Z
CHECKED BY:
F
Q Z
Tral6c EnAvuv Dam
V)
Q. O
CKC`oO Br
Lu
p I-
En —nvuat PUm- Dam
CHECKED BY:
L)
V)
Z
Dare
� O
U
Lazimer County, Colorado
d
UTILITY PLAN APPROVAL
Q
RENEWED BY:
a
Lrim°r CP tyEngii- Due
THESE BANS HAW BEEN RENEWED BY THE OTY OF FORT COLUNS
FOR CONCEPT ONLY. THE REDREW DOES NOT IMRY RESPONSIBILITY BY
ME RENEWNG DEPARTMOST. THE CITY ENGINEER. ON TIE CITY OF
TIE
FORT COLONS FOR ACCURACY AND CORRECTNESS Al
CALCIILATONB. FURTHERMORE. THE REDREW DOES NOT IMPLY THAT THE
CUANOTES OF THE ITEMS ON ME PLANS ARE ME FINAL WANTITIR
REWIRED. THE REDREW SHALL NOT BE CONSTRUED IN ANY REASW AS
SHEET
11 OF 1rJ
ACCEPTANCE OF DNAIIGAL RESI'MSOLITY BY ME OTY OF FONT
COLLINS FOR AODIFONAL WANTTIES OF ITEMS 940M THAT MAY BE
JOB NET
3969901
REWIRED DURING THE CONSTRUCTION PHA"
-l! e r,
.rtIry
Design Procedure Form: Grass Buffer (GB)
Sheet 1 of 1
Designer. BAB
Company: JR Engineering
a
Date: October 3, 2016
Project: Majestic Estates
-
Location: Grass Buffer North
1. Design Discharge
a
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer
Qz = 2.0 off;
2. Minimum Width of Grass Buffer
WG= 46' ;it
{
=
tM
m
�
3. Length of Grass Buffer (14' or greater recommended)
Lo= 450 ft
gyp.
pia
4. Buffer Slope (in the direction of flow, not to exceed 0.1 It / ft)
So = 0.020 ft / ft
-
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
(hcoser ; No
entire width of the buffer?
_
B) Watershed Flow Length
Fr= 145 ft
"
C) Interface Slope (normal to flow)
Si= 0.001 hilt
D) Type of Flow
SHEEP FLOW
Sheet Flow: FL Si 11
W
. Concentrated Flow: FtSi > 1
6. Flow Distribution for Concentrated Flows
*nose j w (street flay)
i.i Slotted [ubig
Si Level Spreader
{ ` Other (Explain):
7 Soil Preparation
(Describe soil amendment)
50% sand and 50% topsoil
8 Vegetation (Check the type used or describe "Other")
�:Clioose f#NBt9 Xetk Turf tress
v
_) angated Turf Crass
Other (Explain):
< `
3
9. Irrigation
r Chat pomryiv
('Select None if existing buffer area has 80% vegetation
permanent
'
„.
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other) 'wose Oniss Swale
0 Street Gutter
Stonn Sewer Inlet
[: Other (Explain):
Notes:
tea:
3969901 UD-BMP_v3#1- grass buffer north.xlsm, GB 101312016, 3:15 PM
V".-..
Design Procedure Form: Grass Buffer (GB)
221,
Sheet 1 of 1
Designer: BAB
Company: JR Engineering
Date: October 5" 2016
Project: Majestic Estates
-�
Location: Grass Bunner South
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer
Oz = 4.1 cis
g{"
2. Minimum Width of Grass Buffer
Wo=' 82 it
e
+x
3. Length of Grass Buffer (14' or greater recommended)
Lo = 14 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / it)
So = 0.007 fl/ ff
"
-
5. Flow Characteristics (sheet or concentrated)
"
'-
A) Does runoff flow into the grass buffer across the
I *N.o
_
entire width of the buffer?""-""
T-
B) Watershed Flow Length
FL= 480 ft
C) Interface Slope (normal to flow)
Si= 0.001 ft 1 ft
D) Type of Flow
( SHEET FLOW
Sheet Flow: FLS, < 1
,
Concentrated Flow: FL ' Si > 1
6. Flow Distribution for Concentrated Flows
*o,,, qp@e (sheet flow)
(} Slotted Curbhg
j Level Spreads
l.r Other (Explain):
)a
w,
f`
7 Soil Preparation
(Describe soil amendment)
50% sand and 50% topsoil
8 Vegetation (Check the type used or describe "Other")
(�^9 xak Tirf tress
t✓ Irrigated Turf Grass
Other (Explain): i
9. Irrigation
•oose Comporary
_.
('Select None if existing buffer area has 80% vegetation
permanent 3
AND will not be disturbed during construction.)
7 None'
... _.__.._.._ .
10. Outflow Collection (Check the type used or describe "Other")
C*a @ass Swale
Street Gutter �
*;
Storm Sewer Inlet
10,
�,•; Other (Explain):
I
ry
Notes:
3969901 UD-BMP v3#1- grass buffer south.xlsm, GB 1101312016,313 PM
APPENDIX F - DRAINAGE PLANS
1
J•R ENGINEERING
MILBY 90M
I /
/
/
/
I/
\A
1
os1
8.81
I
TYPE OWL
6
/
I 1
I
1
1
I 1 1
I ; I
1
_ 1
\ THE OWL \ I ttP
`' SOL
TYPE IS SPL \ /
TYPE c SOIL
a WE
4911,
Y TYPE L SQL
/ Ii
i
/ \ i i49/D- — IX NDION B �i-- \`1
J a ROCIt cAsO" nc LANE
ANE+E
/' IX 1Y tlIP ))
CRIMINAL SCALE 1T - 60,
w=
Om -
OEM
wM€pa¢a
m
iso v!V:€ F
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