HomeMy WebLinkAboutMAJESTIC ESTATES - PDP - PDP160016 - REPORTS - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
FOR
MAJESTIC ESTATES
Prepared For:
Suburban Land Reserve, Inc.
79 South Main Street, Suite 500
Salt Lake City, UT 84111
(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.
July 6, 2016
Job No. 39699.01
X:\3960000.all\3969901\Word\Reports\Drainage Report\3969901 Drainage Report.docx
Page i
TABLE OF CONTENTS
TABLE OF CONTENTS .......................................................................................................... I
APPENDIX ................................................................................................................................ I
VICINITY MAP ........................................................................................................................1
GENERAL DESCRIPTION AND LOCATION ......................................................................2
LOCATION AND EXISTING SITE CHARACTERISTICS ....................................................................2
SITE SOILS ...............................................................................................................................2
FLOODPLAIN ............................................................................................................................2
DRAINAGE BASINS AND SUB-BASINS ...............................................................................3
MAJOR BASIN ..........................................................................................................................3
HISTORIC SUB-BASINS .............................................................................................................3
DEVELOPED SUB-BASINS .........................................................................................................5
DRAINAGE DESIGN CRITERIA ...........................................................................................6
REGULATIONS ..........................................................................................................................6
LOW-IMPACT DEVELOPMENT ...................................................................................................6
HYDROLOGIC CRITERIA............................................................................................................7
HYDRAULIC CRITERIA ..............................................................................................................7
DRAINAGE FACILITY DESIGN ...........................................................................................8
GENERAL CONCEPT ..................................................................................................................8
OFFSITE FLOWS .......................................................................................................................8
WATER QUALITY/DETENTION FACILITIES .................................................................................8
STORMWATER POLLUTION PREVENTION .................................................................. 10
TEMPORARY EROSION CONTROL ............................................................................................ 10
PERMANENT EROSION CONTROL ............................................................................................ 10
MAINTENANCE....................................................................................................................... 10
SUMMARY AND CONCLUSIONS ...................................................................................... 11
EXISTING AND PROPOSED CONDITIONS ................................................................................... 11
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 ii
Engineer’s Certification Block
I 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
exceeds the criteria of the City of Fort Collins Stormwater Design Standards.
Timothy J. Halopoff, P.E.
Registered Professional Engineer
State of Colorado No. 39753
Page 1
VICINITY MAP
Page 2
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 08069C1200F which is a non-printed panel. There are no
major drainage ways located within or immediately adjacent to the site.
Page 3
DRAINAGE BASINS AND 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 08069C1200F 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.
Page 4
Existing Offsite Drainage Basins (OS):
Sub-basin OS1 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 OS1 runoff in the 100yr 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 5
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 12.42 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 DP1.
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 17.7 cfs in the 100 year event which is less
than the 23.85 cfs from the previous LDS Final Drainage Report.
Sub-basin B1 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 4.82 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 1.27 acres along the eastern edge of the subject property. Runoff from
this sub-basin sheet flows east off site similar to historic conditions.
Page 6
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 1, 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 75% 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 30,400 sq. ft.
Required Minimum Impervious Area to be Treated 15,200 sq. ft.
(=50% of new impervious area)
Impervious Area Directly Treated by LID Treatment Method #1 – Grass Buffer 11,400 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #2 - Grass Buffer 11,400 sq. ft.
Total Impervious Area Treated 22,800 sq. ft.
Actual % of Impervious Area Treated 75.0 %
Page 7
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-11 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, 1-hour
rainfall depth of 0.82 inches and a 100-year, 1- 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, 75 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 8
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
A proposed grass buffer 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 100yr flow of 23.85 cfs for Basin A. The total runoff for
the 100yr storm event for Basin A is 17.7 cfs; 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 B1-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 B1-B3 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 16.2 cfs (-Basins B1-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 existing water quality
Page 9
structure was designed to release the water quality volume over 40 hours and release the 100yr
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.
Page 10
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:
x Inspect outlet structure and pipes, check structural integrity
x Check pond sedimentation levels
x Trash and debris removal (each spring, before storm season)
x Wetland vegetation overgrowth mitigation, odor control, insect control as needed based on
observation or complaints
x 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 11
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.
Page 12
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.nrcs.usda.gov. [July 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 1, 2, and 3); Urban Drainage and Flood Control
District, June 2001.
APPENDIXA–FIGURES
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/15/2016
Page 1 of 4
4482230 4482310 4482390 4482470 4482550 4482630 4482710
4482230 4482310 4482390 4482470 4482550 4482630 4482710
496520 496600 496680 496760 496840 496920 497000 497080 497160 497240
496520 496600 496680 496760 496840 496920 497000 497080 497160 497240
40° 29' 42'' N
105° 2' 28'' W
40° 29' 42'' N
105° 1' 56'' W
40° 29' 26'' N
105° 2' 28'' W
40° 29' 26'' N
105° 1' 56'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 150 300 600 900
Feet
0 50 100 200 300
Meters
Map Scale: 1:3,450 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
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 map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
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
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 clay loam, 1 to 3
percent slopes
C 16.3 39.3%
Totals for Area of Interest 41.6 100.0%
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/15/2016
Page 3 of 4
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
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/15/2016
Page 4 of 4
APPENDIX B – HYDROLOGIC CALCULATIONS
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 5/18/16
A 12.42 0.95 0.50 0.04 0.15 7.24 0.09 0.25 4.68 0.09 0.22 0.28
B1 1.30 0.95 0.25 0.18 0.15 0.50 0.06 0.25 0.55 0.11 0.35 0.44
B2 4.82 0.95 0.32 0.06 0.15 1.83 0.06 0.25 2.67 0.14 0.26 0.33
B3 1.48 0.95 0.06 0.04 0.15 1.17 0.12 0.25 0.25 0.04 0.20 0.25
C 1.27 0.95 0.11 0.08 0.15 0.97 0.11 0.25 0.19 0.04 0.23 0.29
Basin B 7.60 0.26 0.33
TOTAL 21.29 0.24 0.30
C100= 1.25* Basin Total Weighted Runoff Coeff
COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Total Area
(ac)
Basin ID
Area (ac)
39699.01
Weighted
Runoff Coeff.
Basins Total
Weighted Runoff
Coeff. C100
Runoff
Coeff.
Area (ac)
Lawns, Heavy Soils (Type C)
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Paved Roads/ Roofs Lawns, Sandy Soil (Type B)
Weighted
Runoff Coeff.
Basins Total
Weighted
Runoff Coeff.
C2
Runoff
Coeff.
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 5/2/2016
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 5/18/16
A 12.42 100% 0.17 1.4% 95% 0.33 2.5% 5% 11.92 4.8% 8.7%
B1 1.30 100% 0.10 7.7% 95% 0.15 11.0% 5% 1.05 4.0% 22.7%
B2 4.82 100% 0.06 1.2% 95% 0.26 5.1% 5% 4.50 4.7% 11.0%
B3 1.48 100% 0.06 4.1% 95% 0.00 0.0% 5% 1.42 4.8% 8.9%
C 1.27 100% 0.11 8.7% 95% 0.00 0.0% 5% 1.16 4.6% 13.2%
Basin B 7.60 12.6%
TOTAL 21.29 10.4%
Weighted %
Imp. (%).
% Imp. (%) Area (ac)
Weighted %
Imp. (%).
% Imp. (%)
COMPOSITE PERCENT IMPERVIOUS CALCULATIONS
39699.01
Basin ID
Total Area
(ac)
Pavement Roofs Lawns/ Grass
Basins Total
Weighted %
Imp. (%)
% Imp.
(%)
Area (ac)
Weighted %
Imp. (%).
Area (ac)
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 5/2/2016
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 5/18/16
FINAL
BASIN D.A. Hydrologic Impervious C2
C100 L S
o t i
L t S
o K VEL. t t
COMP. t c TOTAL Urbanized t
c t c
ID (ac) Soils Group (%) (ft) (%) (min) (ft) (%) (ft/s) (min) (min) LENGTH (ft) (min) (min)
A 12.42 B/C 9% 0.22 0.28 200 2.0% 84.6 200 0.5% 7.0 0.5 6.7 91.4 400.0 23.4 23.4
B1 1.30 B/C 23% 0.35 0.44 80 2.0% 45.6 270 1.0% 20.0 2.0 2.3 47.9 350.0 17.9 17.9
B2 4.82 B/C 11% 0.26 0.33 130 2.0% 65.1 70 0.5% 20.0 1.4 0.8 66.0 200.0 19.6 19.6
B3 1.48 B/C 9% 0.20 0.25 75 2.0% 53.0 320 0.5% 20.0 1.4 3.8 56.8 395.0 23.3 23.3
C 1.27 B/C 13% 0.23 0.29 40 1.0% 47.0 500 1.0% 7.0 0.7 11.9 58.9 540.0 21.9 21.9
NOTES:
t c =t
i +t t
(Equation 6-2)
t i = (1.87*(1.1 -C*Cf)*(L)^0.5)/((S
o)^0.33)
L= length of overland flow ( 500' max)
C= runoff coefficient
Cf= Frequency adjustment factor
t i = overland (initial) flow time (minutes) K
S = Average Slope along the overland flow path, ft/ft 2.5
t t =L/(60K*(S
o)^0.5 (Equation 6-4) 5
t t = channelized flow time (minutes) 7
S = waterway slope, ft/ft 10
V t = travel time velocity (ft/sec) = K*S
o^0.5 15
20
First Design Point Time of Concentration:
t c =(18-15*i )+L/(60*(24*i +12)*(S
o)^0.5) (Equation 6-5)
i = imperviousness (expressed as a decimal)
t c is lesser of Equation 6-2 and Equation 6-5.
For Urbanized basins a minimum t c of 5.0 minutes is required.
For non-urbanized basins a minimum t c of 10.0 minutes is required.
DATA (URBANIZED BASINS)
INITIAL/OVERLAND
(Ti)
TRAVEL TIME
(Tt)
STANDARD FORM SF-2
TIME OF CONCENTRATION
SUB-BASIN tc CHECK
39699.01
Table 6-2. NRCS Conveyance Factors, K
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Project Name: Majestic Estates
Subdivision: Majestic Estates Project No.:
Location: Fort Collins Calculated By: BAB
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
Sheet flow to EX. Borrow Ditch
1 A 12.42 0.22 23.4 2.73 1.48 4.0
Add Ex. Majestic Dr. Flow Street Flow to EX. Inlet
2 B1 1.30 0.35 17.9 0.46 1.71 0.8 3.5 3.5 Piped to proposed swale via 36" RCP
Add LDS Temple flows
3a 23.4 Flow coming out of 36" RCP
Add 36" RCP Flow Sheet flow to swale
3 B2 4.82 0.26 19.6 1.25 1.63 2.0 25.4 Swale flow to EX. Wetland/ WQ Pond
Add Bio-Swale Flow Sheet flow to EX. Wetland/ WQ Pond
4 B3 1.48 0.20 23.3 0.30 1.49 0.4 25.8 Total flow into EX. Wetland/ WQ Pond
Sheet flow offsite
5 C 1.27 0.23 21.9 0.29 1.54 0.4
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
2-Year
39699.01
5/18/16
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 7/5/2016
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Project Name: Majestic Estates
Subdivision: Majestic Estates Project No.:
Location: Fort Collins Calculated By: BAB
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
Sheet flow to EX. Borrow Ditch
1 A 12.42 0.28 23.4 3.42 5.17 17.7
Add Ex. Majestic Dr. Flow Street Flow to EX. Inlet
2 B1 1.30 0.44 17.9 0.57 5.95 3.4 8.8 8.8 Piped to proposed swale via 36" RCP
Add LDS Temple flows
3a 61.8 Flow coming out of 36" RCP
Add 36" RCP Flow Sheet flow to swale
3 B2 4.82 0.33 19.6 1.57 5.69 8.9 70.7 Swale flow to EX. Wetland/ WQ Pond
Add Swale Flow Sheet flow to EX. Wetland/ WQ Pond
4 B3 1.48 0.25 23.3 0.37 5.19 1.9 72.6 Total flow into EX. Wetland/ WQ Pond
Sheet flow offsite
5 C 1.27 0.29 21.9 0.37 5.35 2.0
39699.01
PIPE
100-Year
DIRECT RUNOFF TOTAL RUNOFF STREET
5/18/16
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 7/5/2016
APPENDIX C – HYDRAULIC CALCULATIONS
Worksheet Protected
Project:
Inlet ID:
Design Flow: ONLY if already determined through other methods: Minor Storm Major Storm
(local peak flow for 1/2 of street OR grass-lined channel): *QKnown = 3.5 8.8 cfs
* If you enter values in Row 14, skip the rest of this sheet and proceed to sheet Q-Allow or Area Inlet.
Geographic Information: (Enter data in the blue cells):
Subcatchment Area = Acres
Percent Imperviousness = %
NRCS Soil Type = A, B, C, or D
Slope (ft/ft) Length (ft)
Overland Flow =
Channel Flow =
Rainfall Information: Intensity I (inch/hr) = C1 * P
1 / ( C2
+ Tc ) ^ C
3 Minor Storm Major Storm
Design Storm Return Period, Tr = years
Return Period One-Hour Precipitation, P1 = inches
C1 =
C2 =
C3 =
User-Defined Storm Runoff Coefficient (leave this blank to accept a calculated value), C =
User-Defined 5-yr. Runoff Coefficient (leave this blank to accept a calculated value), C5 =
Bypass (Carry-Over) Flow from upstream Subcatchments, Qb = 0.0 cfs
Total Design Peak Flow, Q = 3.5 8.8 cfs
<---
FILL IN THIS SECTION
OR…
FILL IN THE
SECTIONS BELOW.
<---
DESIGN PEAK FLOW FOR ONE-HALF OF STREET
OR GRASS-LINED CHANNEL BY THE RATIONAL METHOD
Majestic Estates
DP 2 EX Fort Collins Single Curb Inlet
Site is Urban
Site is Non-Urban
Show Details
Site Type:
Street Inlets
Area Inlets in a Median
Flows Developed For:
UD-Inlet_v3.14-DP2.xlsm, Q-Peak 5/2/2016, 1:41 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK
= 15.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK
= 0.002 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK
= 0.013
Height of Curb at Gutter Flow Line HCURB
= 6.00 inches
Distance from Curb Face to Street Crown TCROWN
= 18.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX
= 0.002 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW
= 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO
= 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET
= 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX
= 9.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX
= 6.0 6.0 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow
= SUMP SUMP cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
Majestic Estates
DP 2 EX Fort Collins Single Curb Inlet
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
UD-Inlet_v3.14-DP2.xlsm, Q-Allow 5/2/2016, 1:41 PM
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 10.5 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = 3.00 3.00 feet
Width of a Unit Grate Wo
= 2.00 2.00 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat
= 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw
(C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 3.6 8.8 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED
= 3.5 8.8 cfs
Warning 1: Dimension entered is not a typical dimension for inlet type specified.
INLET IN A SUMP OR SAG LOCATION
Majestic Estates
DP 2 EX Fort Collins Single Curb Inlet
CDOT/Denver 13 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
Override Depths
UD-Inlet_v3.14-DP2.xlsm, Inlet In Sump 5/2/2016, 1:43 PM
CO-2
CO-1
O-1
Connect to EX. 36"
MH-1
Plan View
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203 Page 1 of 2
-755-1666
5/2/2016
Bentley StormCAD V8i (SELECTseries 3)
3969901StormCAD.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.03.84]
2yr Results
J-loss
Coeff
N-value
Pipe
Velocity
Down
(ft/s)
Velocity
Up
(ft/s)
Velocity
Avg
(ft/s)
EGL
Down
(ft)
EGL Up
(ft)
HGL Down
(ft)
HGL Up
(ft)
Invert
Down
(ft)
Invert Up
(ft)
Line
Slope
(ft/ft)
Line
Length
(ft)
Line
Size
(in)
Capacity
(Design)
(cfs)
Flow
(cfs)
Label
CO-1 23.40 69.78 36.0 190.0 0.011 4,911.41 4,909.33 4,912.97 4,911.20 4,913.59 4,911.60 8.89 6.31 5.06 0.013 1.700
CO-2 23.40 46.55 36.0 39.0 0.005 4,909.33 4,909.14 4,910.89 4,910.65 4,911.51 4,911.32 6.59 6.31 6.59 0.013 0.500
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203 Page 1 of 1
-755-1666
5/3/2016
Bentley StormCAD V8i (SELECTseries 3)
3969901StormCAD.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.03.84]
100yr Results
J-loss
Coeff
N-value
Pipe
Velocity
Down
(ft/s)
Velocity
Up
(ft/s)
Velocity
Avg
(ft/s)
EGL
Down
(ft)
EGL Up
(ft)
HGL Down
(ft)
HGL Up
(ft)
Invert
Down
(ft)
Invert Up
(ft)
Line
Slope
(ft/ft)
Line
Length
(ft)
Line
Size
(in)
Capacity
(Design)
(cfs)
Flow
(cfs)
Label
CO-1 61.80 69.78 36.0 190.0 0.011 4,911.41 4,909.33 4,914.45 4,912.82 4,915.64 4,914.01 8.74 8.74 8.74 0.013 1.700
CO-2 61.80 46.55 36.0 39.0 0.005 4,909.33 4,909.14 4,912.21 4,911.67 4,913.43 4,913.14 8.74 8.86 9.71 0.013 0.500
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203 Page 1 of 1
-755-1666
5/3/2016
Bentley StormCAD V8i (SELECTseries 3)
3969901StormCAD.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.03.84]
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.: 39699.01
Calculated By: BAB
Checked By: 0
Date: 5/18/16
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)
d50 (in), Required 1.42
Required Riprap Size L Fig. 9-38 or Fig. 9-36
Use Riprap Size L
d50 (in) 9 Table MD-7
Expansion Factor, 1/(2 tanT) 4.50 Fig. 9-35 OR 9-36
T 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=3D or 3H
Max Length (ft) 30.0 Max L=10D or 10H
Min Bottom Width, T (ft) 12.4 T=2*(Lp
*tanT)+W
Design Length (ft) 29.0
Design Width (ft) 12.4
Riprap Depth (in) 18 Depth=2(d50
)
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).
STORM DRAIN SYSTEM
PIPE OUTFALL RIPRAP SIZING CALCULATIONS
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 2 5/2/2016
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 2 of 2 5/2/2016
APPENDIX D – REFERENCED INFORMATION
!&$ *!& * ('*,
'* , -* ' " +-+ *!+,
' $,, * 1 +!&,+ , %($
'*, '$$!&+ '$'*'
(C7B3C76 8AC
:FC5: A8 "7DFD :C;DE A8 $3EE7C 3I +3;@ED
7200 South Alton Way, Suite C400
Centennial, CO80112
303-740-9393 x Fax 303-921-7320
130 East Kiowa Street, Suite 400
Colorado Springs, CO80903
719-593-2593 x Fax 303-921-7320
2900 South College Avenue, Suite 3D
Fort Collins, CO80525
970-491-9888 x Fax 303-921-7320
MEMORANDUM
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
To: Heather McDowell
From: Becky Brush, EIT
Date: April 20, 2016
Subject: Majestic Estates- Drainage Analysis
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 3/20/16
A 12.42 0.95 0.50 0.04 0.15 7.24 0.09 0.25 4.68 0.09 0.22 0.28
B1 1.30 0.95 0.25 0.18 0.15 0.50 0.06 0.25 0.55 0.11 0.35 0.44
B2 4.82 0.95 0.32 0.06 0.15 1.83 0.06 0.25 2.67 0.14 0.26 0.33
B3 1.48 0.95 0.06 0.04 0.15 1.17 0.12 0.25 0.25 0.04 0.20 0.25
C 1.27 0.95 0.11 0.08 0.15 0.97 0.11 0.25 0.19 0.04 0.23 0.29
Basin B 7.60 0.26 0.33
TOTAL 21.29 0.24 0.30
C100= 1.25* Basin Total Weighted Runoff Coeff
Lawns, Sandy Soil (Type B)
Weighted
Runoff Coeff.
Basins Total
Weighted
Runoff Coeff.
C2
Runoff
Coeff.
COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Total Area
(ac)
Basin ID
Area (ac)
39699.01
Weighted
Runoff Coeff.
Basins Total
Weighted Runoff
Coeff. C100
Runoff
Coeff.
Area (ac)
Lawns, Heavy Soils (Type C)
Runoff
Coeff.
Area (ac)
Weighted
Runoff Coeff.
Paved Roads/ Roofs
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 3/20/16
A 12.42 100% 0.17 1.4% 95% 0.33 2.5% 5% 11.92 4.8% 8.7%
B1 1.30 100% 0.10 7.7% 95% 0.15 11.0% 5% 1.05 4.0% 22.7%
B2 4.82 100% 0.06 1.2% 95% 0.26 5.1% 5% 4.50 4.7% 11.0%
B3 1.48 100% 0.06 4.1% 95% 0.00 0.0% 5% 1.42 4.8% 8.9%
C 1.27 100% 0.11 8.7% 95% 0.00 0.0% 5% 1.16 4.6% 13.2%
TOTAL 21.29 10.4%
Area (ac)
Weighted %
Imp. (%).
% Imp. (%)
COMPOSITE PERCENT IMPERVIOUS CALCULATIONS
39699.01
Basin ID
Total Area
(ac)
Pavement Roofs Lawns/ Grass
Basins Total
Weighted %
Imp. (%)
% Imp.
(%)
Area (ac)
Weighted %
Imp. (%).
Area (ac)
Weighted %
Imp. (%).
% Imp. (%)
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
Subdivision: Majestic Estates Project Name: Majestic Estates
Location: Fort Collins Project No.:
Calculated By: BAB
Checked By: 0
Date: 3/20/16
FINAL
BASIN D.A. Hydrologic Impervious C2
C100 L S
o t i
L t S
o K VEL. t t
COMP. t c TOTAL Urbanized t
c t c
ID (ac) Soils Group (%) (ft) (%) (min) (ft) (%) (ft/s) (min) (min) LENGTH (ft) (min) (min)
A 12.42 B/C 9% 0.22 0.28 200 2.0% 84.6 200 0.5% 7.0 0.5 6.7 91.4 400.0 23.4 23.4
B1 1.30 B/C 23% 0.35 0.44 80 2.0% 45.6 270 1.0% 20.0 2.0 2.3 47.9 350.0 17.9 17.9
B2 4.82 B/C 11% 0.26 0.33 130 2.0% 65.1 70 0.5% 20.0 1.4 0.8 66.0 200.0 19.6 19.6
B3 1.48 B/C 9% 0.20 0.25 75 2.0% 53.0 320 0.5% 20.0 1.4 3.8 56.8 395.0 23.3 23.3
C 1.27 B/C 13% 0.23 0.29 40 1.0% 47.0 500 1.0% 7.0 0.7 11.9 58.9 540.0 21.9 21.9
NOTES:
t c =t
i +t t
(Equation 6-2)
t i = (1.87*(1.1 -C*Cf)*(L)^0.5)/((S
o)^0.33)
L= length of overland flow ( 500' max)
C= runoff coefficient
Cf= Frequency adjustment factor
t i = overland (initial) flow time (minutes) K
S = Average Slope along the overland flow path, ft/ft 2.5
t t =L/(60K*(S
o)^0.5 (Equation 6-4) 5
t t = channelized flow time (minutes) 7
S = waterway slope, ft/ft 10
V t = travel time velocity (ft/sec) = K*S
o^0.5 15
20
First Design Point Time of Concentration:
t c =(18-15*i )+L/(60*(24*i +12)*(S
o)^0.5) (Equation 6-5)
i = imperviousness (expressed as a decimal)
t c is lesser of Equation 6-2 and Equation 6-5.
For Urbanized basins a minimum t c of 5.0 minutes is required.
For non-urbanized basins a minimum t c of 10.0 minutes is required.
DATA (URBANIZED BASINS)
INITIAL/OVERLAND
(Ti)
TRAVEL TIME
(Tt)
STANDARD FORM SF-2
TIME OF CONCENTRATION
SUB-BASIN tc CHECK
39699.01
Table 6-2. NRCS Conveyance Factors, K
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Project Name: Majestic Estates
Subdivision: Majestic Estates Project No.:
Location: Fort Collins Calculated By: BAB
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
Sheet flow to EX. Borrow Ditch
1 A 12.42 0.22 23.4 2.73 1.48 4.0
Add Ex. Majestic Dr. Flow Street Flow to EX. Inlet
2 B1 1.30 0.35 17.9 0.46 1.71 0.8 3.5 3.5 Piped to proposed LID Bio-Swale via 36" RCP
Add 36" RCP Flow Sheet flow to LID Bio-Swale
3 B2 4.82 0.26 19.6 1.25 1.63 2.0 25.4 Swale flow to EX. Wetland/ WQ Pond
Add Bio-Swale Flow Sheet flow to EX. Wetland/ WQ Pond
4 B3 1.48 0.20 23.3 0.30 1.49 0.4 25.8 Total flow into EX. Wetland/ WQ Pond
Sheet flow offsite
5 C 1.27 0.23 21.9 0.29 1.54 0.4
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
2-Year
39699.01
3/20/16
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Project Name: Majestic Estates
Subdivision: Majestic Estates Project No.:
Location: Fort Collins Calculated By: BAB
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
Sheet flow to EX. Borrow Ditch
1 A 12.42 0.28 23.4 3.42 5.17 17.7
Add Ex. Majestic Dr. Flow Street Flow to EX. Inlet
2 B1 1.30 0.44 17.9 0.57 5.95 3.4 8.8 8.8 Piped to proposed LID Bio-Swale via 36" RCP
Add 36" RCP Flow Sheet flow to LID Basin and swale
3 B2 4.82 0.33 19.6 1.57 5.69 8.9 70.7 Swale flow to EX. Wetland/ WQ Pond
Add Swale Flow Sheet flow to EX. Wetland/ WQ Pond
4 B3 1.48 0.25 23.3 0.37 5.19 1.9 72.6 Total flow into EX. Wetland/ WQ Pond
Sheet flow offsite
5 C 1.27 0.29 21.9 0.37 5.35 2.0
39699.01
PIPE
100-Year
DIRECT RUNOFF TOTAL RUNOFF STREET
3/20/16
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Project Name: Majestic Estates
Subdivision: Majestic Estates Project No.:
Location: Fort Collins Calculated By: BAB
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
D58 12.09 0.325 17.17 3.93 6.08 23.89
*LDS Temple basin with City of Fort Collins rainfall data
39699.01
100-Year
3/20/16
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
Grass Buffer T-1
November 2010 Urban Drainage and Flood Control District GB-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph GB-1. A flush curb allows roadway runoff to sheet flow
through the grass buffer. Flows are then further treated by the grass
swale. Photo courtesy of Muller Engineering.
Description
Grass buffers are densely vegetated
strips of grass designed to accept sheet
flow from upgradient development.
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
parking lot, roadway, or the roof of a
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 irrigation
requirements, as well as promote infiltration.
Grass Buffer
Functions
LID/Volume Red. Yes
WQCV Capture No
WQCV+Flood Control No
Fact Sheet Includes
EURV Guidance No
Typical Effectiveness for Targeted
Pollutants3
Sediment/Solids Good
Nutrients Moderate
Total Metals Good
Bacteria Poor
Other Considerations
Life-cycle Costs Low
T-6 Sand Filter
SF-8 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Figure SF-1. Sand Filter Plan and Sections
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer Q2 = 4.0 cfs
2. Minimum Width of Grass Buffer WG = 80 ft
3. Length of Grass Buffer (14' or greater recommended) LG = 14 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / ft) SG = 0.007 ft / ft
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
entire width of the buffer?
B) Watershed Flow Length FL= 480 ft
C) Interface Slope (normal to flow) SI= 0.001 ft / ft
D) Type of Flow SHEET FLOW
Sheet Flow: FL * SI < 1
Concentrated Flow: FL * SI > 1
6. Flow Distribution for Concentrated Flows
7 Soil Preparation
(Describe soil amendment)
8 Vegetation (Check the type used or describe "Other")
9. Irrigation
(*Select None if existing buffer area has 80% vegetation
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other")
Notes:
Design Procedure Form: Grass Buffer (GB)
BAB
JR Engineering
Majestic Estates
April 20, 2016
Existing Xeric Turf Grass
Irrigated Turf Grass
Other (Explain):
Choose One
Choose One
Grass Swale
Street Gutter
Storm Sewer Inlet
Other (Explain):
None (sheet flow)
Slotted Curbing
Level Spreader
Choose One
Other (Explain):
Choose One
Yes No
Choose One
Permanent
None*
Temporary
3969901 UD-BMP_v3#1- grass buffer.xlsm, GB 4/20/2016, 2:56 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 11.0 %
(100% if all paved and roofed areas upstream of sand filter)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.110
C) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 0.07 watershed inches
WQCV= 0.9 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including sand filter area) Area = 115,434 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 629 cu ft
VWQCV = WQCV / 12 * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = 1.40 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 2,047 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth DWQCV = 1.0 ft
B) Sand Filter Side Slopes (Horizontal distance per unit vertical, Z = 4.00 ft / ft
4:1 or flatter preferred). Use "0" if sand filter has vertical walls.
C) Mimimum Filter Area (Flat Surface Area) AMin = 455 sq ft
D) Actual Filter Area AActual = 3201 sq ft
E) Volume Provided VT = 3201 cu ft
3. Filter Material
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Majestic Estates
Design Procedure Form: Sand Filter (SF)
BAB
JR Engineering
April 20, 2016
Choose One
Choose One
18" CDOT Class C Filter Material
Other (Explain):
YES
NO
3969901 UD-BMP_v3#1- sad filter.xlsm, SF 4/20/2016, 2:55 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6-7. Inlet / Outlet Works
A) Describe the type of energy dissipation at inlet points and means of
conveying flows in excess of the WQCV through the outlet
Notes:
Design Procedure Form: Sand Filter (SF)
BAB
JR Engineering
April 20, 2016
Majestic Estates
Choose One
YES NO
3969901 UD-BMP_v3#1- sad filter.xlsm, SF 4/20/2016, 2:55 PM
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
MAJESTIC DRIVE
ROCK CASTLE LANE
TRILBY ROAD
TIMBERLINE ROAD
APPENDIX E – LID EXHIBITS
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer Q2 = 2.0 cfs
2. Minimum Width of Grass Buffer WG = 40 ft
3. Length of Grass Buffer (14' or greater recommended) LG = 450 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / ft) SG = 0.020 ft / ft
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
entire width of the buffer?
B) Watershed Flow Length FL= 145 ft
C) Interface Slope (normal to flow) SI= 0.001 ft / ft
D) Type of Flow SHEET FLOW
Sheet Flow: FL * SI < 1
Concentrated Flow: FL * SI > 1
6. Flow Distribution for Concentrated Flows
7 Soil Preparation
(Describe soil amendment)
8 Vegetation (Check the type used or describe "Other")
9. Irrigation
(*Select None if existing buffer area has 80% vegetation
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other")
Notes:
Design Procedure Form: Grass Buffer (GB)
BAB
JR Engineering
Majestic Estates
June 20, 2016
Grass Buffer North
50% sand and 50% topsoil
Existing Xeric Turf Grass
Irrigated Turf Grass
Other (Explain):
Choose One
Choose One
Grass Swale
Street Gutter
Storm Sewer Inlet
Other (Explain):
None (sheet flow)
Slotted Curbing
Level Spreader
Choose One
Other (Explain):
Choose One
Yes No
Choose One
Permanent
None*
Temporary
3969901 UD-BMP_v3#1- grass buffer 2.xlsm, GB 6/20/2016, 2:01 PM
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer Q2 = 4.0 cfs
2. Minimum Width of Grass Buffer WG = 80 ft
3. Length of Grass Buffer (14' or greater recommended) LG = 14 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / ft) SG = 0.007 ft / ft
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
entire width of the buffer?
B) Watershed Flow Length FL= 480 ft
C) Interface Slope (normal to flow) SI= 0.001 ft / ft
D) Type of Flow SHEET FLOW
Sheet Flow: FL * SI < 1
Concentrated Flow: FL * SI > 1
6. Flow Distribution for Concentrated Flows
7 Soil Preparation
(Describe soil amendment)
8 Vegetation (Check the type used or describe "Other")
9. Irrigation
(*Select None if existing buffer area has 80% vegetation
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other")
Notes:
Grass Bunner South
50% sand and 50% topsoil
Design Procedure Form: Grass Buffer (GB)
BAB
JR Engineering
Majestic Estates
May 25, 2016
Existing Xeric Turf Grass
Irrigated Turf Grass
Other (Explain):
Choose One
Choose One
Grass Swale
Street Gutter
Storm Sewer Inlet
Other (Explain):
None (sheet flow)
Slotted Curbing
Level Spreader
Choose One
Other (Explain):
Choose One
Yes No
Choose One
Permanent
None*
Temporary
3969901 UD-BMP_v3#1- grass buffer.xlsm, GB 6/20/2016, 2:00 PM
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
LID Measure Impervious Area
Treated Sq. ft.
Area of LID sq.ft. Ratio
Northern Grass Buffer 11,400 23,000 0.5
Southern Grass Buffer 11,400 27,100 0.4
LID Sizing
New Impervious Area 30,400 sq. ft.
Required Minimum Impervious Area to be Treated 15,200 sq. ft.
(=50% of new impervious area)
Impervious Area Directly Treated by LID Treatment Method #1 - Northern Grass Buffer 11,400 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #2 - Southern Grass Buffer 11,400 sq. ft.
Total Impervious Area Treated 22,800 sq. ft.
Actual % of Impervious Area Treated 75.0 %
On-Site Treatment by LID Requirement
MAJESTIC DRIVE
ROCK CASTLE LANE
TRILBY ROAD
TIMBERLINE ROAD
APPENDIX F – DRAINAGE PLANS
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
MAJESTIC DRIVE
ROCK CASTLE LANE
TRILBY ROAD
TIMBERLINE ROAD
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
MAJESTIC DRIVE
ROCK CASTLE LANE
TRILBY ROAD
TIMBERLINE ROAD
3 Based primarily on data from the
International Stormwater BMP Database
(www.bmpdatabase.org).
Short pasture and lawns
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 4/20/2016
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Short pasture and lawns
X:\3960000.all\3969901\Excel\Drainage\Drainage_Calcs_3969901_v2.0.xlsm Page 1 of 1 5/2/2016
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
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.
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/15/2016
Page 2 of 4