HomeMy WebLinkAboutNORTHFIELD FILING 1, EXPANDED - PDP - PDP180011 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
FOR
Northfield
Prepared by:
Interwest Consulting Group
1218 West Ash, Suite A
Windsor, Colorado 80550
Phone: 970.674.3300
Fax: 970.674.3303
Prepared for:
Landmark Real Estate Holdings, LLC
1170 Ash Street, Suite 100
Windsor, Colorado 80550
Office: 970.460.0567
August 22, 2018
Job Number 1282-168-03
1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
August 22, 2018
Ms. Heather McDowell
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Preliminary Drainage Report for Northfield
Dear Heather,
We are pleased to submit for your review, the Preliminary Drainage Report for the Northfield
subdivision. This report describes the drainage design intent to be in accordance with the criteria
in the City of Fort Collins Storm Drainage Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
Jason T. Claeys, P.E., LEED AP
Interwest Consulting Group
Page i
TABLE OF CONTENTS
Table of Contents ............................................................................................................................. i
Engineer’s Certification Block ....................................................................................................... ii
General Description and Location .................................................................................................. 1
Site Description and Location ..................................................................................................... 1
Site Soils ...................................................................................................................................... 2
Storm Drainage Criteria .................................................................................................................. 3
Hydrologic Criteria ...................................................................................................................... 3
Hydraulic Criteria ........................................................................................................................ 3
Drainage Basins .............................................................................................................................. 5
Drainage Facility Design ................................................................................................................ 7
Drainage Conveyance Design ..................................................................................................... 7
Detention/Water Quality Pond Design ........................................................................................ 7
Low Impact Development ............................................................................................................... 9
Stormwater Pollution Prevention .................................................................................................. 11
Conclusions ................................................................................................................................... 12
References ..................................................................................................................................... 13
Appendix ....................................................................................................................................... 14
Appendix A – Site Descriptions, Characteristics, & References ............................................... A
Appendix B – Rational Calculations ........................................................................................... B
Appendix C – Detention Pond Calculations ................................................................................ C
Appendix D – Street Capacities ................................................................................................. D
Appendix E – Low Impact Development Calculations ............................................................... E
Page ii
ENGINEER’S CERTIFICATION BLOCK
I hereby certify that this Preliminary Drainage Report for Northfield was prepared by me (or
under my direct supervision) for the owners thereof and meets or exceeds the criteria of the City
of Fort Collins Stormwater Design Standards.
________________________________________
Jason T. Claeys, PE
Registered Professional Engineer
State of Colorado No. 42122
Page 1
GENERAL DESCRIPTION AND LOCATION
SITE DESCRIPTION AND LOCATION
Northfield is located in the Southeast Quarter of Section 1, Township 7 North, Range 67 West of
the Sixth Principal Meridian, City of Fort Collins, County of Larimer, within the State of
Colorado. More specifically, Northfield is located north of the ALTA Vista Subdivision, west of
N. Lemay Avenue, and southeast of the Lake Canal irrigation ditch.
The project site is approximately 55.26 acres currently and is undeveloped agricultural land. The
site appears to be vegetated with grasses harvested for livestock feed. The site generally slopes
from the northwest to the southeast at about 0.5% slope. There are no existing surface
improvements currently on the property.
The property is proposed to be subdivided into multiple single family lots and condominium
tracts. Northfield and will consist of 138 single family attached (fee simple) units and 302
condominium units.
Northfield is located within the City’s Dry Creek Drainage Basin. In addition to the City of Fort
Collins Stormwater Design Standards, drainage requirements are also described in the “North
East College Corridor Outfall (NECCO) Design Report”, prepared by Ayres Associates, dated
August 2009. The improvements associated with Northfield are located within basins 115, 116,
117, 414, 950, 951, 960, 961, 970, 971, 980, and 981 as delineated in the above report.
A portion of the Northfield improvements are located within the 100-yr FEMA Flood Hazard
Area as shown on FEMA FIRM map numbers 08069C0977G (revised June 17, 2008), and
08069C0981G (revised June 17, 2008). All improvements are outside of the 100-yr floodway,
but are within the 100-yr floodplain. The first phase of the NECCO improvements were
completed early in 2017 with the remaining improvements completed in the spring of 2018. It is
anticipated that the LOMR associated with these improvements will be completed by the end of
year in 2018. Once the LOMR is complete, the 100-yr floodplain is anticipated to be removed
from the site. If circumstances occur that the LOMR is not complete at the time of construction
for the Northfield improvements, a floodplain development permit will be required. It is
anticipated that the floodplain limits will be adjusted prior to the construction of the residential
units. If buildings are constructed prior to the map revision, the buildings will be elevated above
the Regulatory Base Floodplain Elevation and adhering to LUC Chapter 10 requirements. A
portion of the site is located within the Cache la Poudre River 500-yr floodplain. Critical
facilities are prohibited within the 500-yr floodplain. Critical facilities such as facilities for at-
rick populations (daycares, schools, nursing homes, etc) and emergency access service facilities
(urgent care, hospitals, fire stations, police stations, etc).
Page 2
Site Soils
The Northfield site consists of Loveland clay loam and Nunn clay loam and are classified as
Type C hydrologic group. According to USDA/Natural Resource Conservation Group, this soil
has a slow infiltration rate when thoroughly wet. These soils 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.
Per the “Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property”,
prepared be Earth Engineering Consultants (EEC), dated August 16, 2017:
Vegetation growth and topsoil was encountered at the surface of each boring. Underlying the
topsoil/vegetation layer was a zone of cohesive subsoils classified lean to fat clay with varying
amounts of sand and clayey sand to approximate depths of 2 to 5-1/2 feet. Underlying the
cohesive subsoils was a granular layer of poorly to well graded sand with silt and gravel
extending to the depths explored at approximately 14 to 21-1/2 feet or to underlying bedrock.
It appears that below the lean to fat clay, there is a granular materials that would inhibit more
moderate infiltration rates then the surface materials.
Groundwater was also observed during the subsurface soil exploration:
Groundwater and/or the presence of a piezometric water surface, was generally observed at
depths ranging from approximately 3 to 7 feet below ground surface as indicated on the
enclosed boring logs.
EEC has continued to monitor the groundwater level depths over the last 12 month period after
the original borings. Groundwater elevations are taken into consideration for the pond bottoms
and building foundations.
Supporting figures can be found in the Appendix A.
Page 3
STORM DRAINAGE CRITERIA
This preliminary report was prepared to meet or exceed the City of Fort Collins storm water
criteria. The City of Fort Collin’s Storm Drainage Design Criteria and amendments to the Urban
Drainage Flood Control District’s (UDFCD) Drainage Criteria Manual (USDCM) Volumes 1, 2
and 3 were referenced as guidelines for this design.
HYDROLOGIC CRITERIA
The rational method was performed to calculate the peak runoff rates for each basin. Percent
impervious were estimated based on land use and the associated runoff coefficients were
calculated. The time of concentration was calculated using City of Fort Collins initial time of
concentration and the intensity was calculated using the corresponding storm rainfall depth and
USDCM Equation 4-3. To account for the City of Fort Collins’ IDF Curve, Coefficient 3 of the
UDFCD’s intensity formula was adjusted to 0.7867. The City of Fort Collins area has 2-yr 1-hr
rainfall depth of 0.82 inches and a 100-yr 1 hr rainfall depth of 2.86 inches. These depths do
account for the 1997 adjusted rainfall depths.
HYDRAULIC CRITERIA
The hydraulic calculations provided for in this report are limited to maximum street capacities
based on the minimum street slopes. The Street Sections and Allowable Half-Street spreadsheets
for 0.5% longitudinal slope are provided in the Appendix.
The final Northfield storm drainage system will be designed to convey the minor and major
storm events through the combination of streets, inlets, storm sewer pipes, and swales. Per the
requirements provided by the City of Fort Collins Storm Drainage Design Criteria, all inlets and
storm pipes will be designed such that, during the minor initial storm event, the 2-yr storm, the
flows for the Local Street will not top the curb and may only rise to the street crown elevation,
and for an Arterial (with Median) will not top the curb and the flow spread will leave at least one
12 ft lane width free of water in each direction. During the major storm event, the 100-yr storm,
the water depth for the Local Street will be held to a maximum depth of 6” at the street crown,
12” at the gutter flow line, and/or flow must be contained within right-of-way or easements
paralleling the right-of-way. The Arterial (with Median) will be held to a maximum depth that
will not exceed the median gutter elevation, 12” at the gutter flowline, and/or flow must be
contained within right-of-way or easements paralleling the right-of-way.
Within the Final Drainage Report, peak basin runoff flows from the rational calculations will
then be used to determine the street capacities, and on-grade inlet locations. The on-grade and
sump inlet capacities will be calculated using UDFCD’s spreadsheet UD-Inlet_v4.05.xlsm. The
inlet capacities will be analyzed and the necessary adjustments will be applied to the street
Page 4
runoff flows based on the amount of runoff collected by on-grade inlets. The sump inlets will be
sized using the previous mentioned street capacity allowances with overtopping if needed.
The captured flows will then be analyzed using EPA’s SWMM program to design pipe size and
slopes. UD-Inlet applies a clogging factor while sizing the inlets, but while sizing the storm
sewer, it is assumed that the inlets are free of clogging debris and capturing the maximum
amount of street runoff. Orifice rating curves will be utilized for the inlet capture capacities and
route the captured runoff through the storm drain system. The program accounts for head losses
within manholes and bends and head losses associated with pipe friction.
Hydraflow will be used to compute the open channel hydraulics and check the capacities of the
drainage swales throughout the site. Flow velocities within these swales will be reviewed and
where flows are found to be supercritical, the swales will be protected with turf reinforcement
mat.
All swale and pipe outlets will be protected with riprap or suitable erosion protection methods.
Storm sewer pipe outlets will be protected using the requirements set by the USDCM for the
protection downstream of culverts.
All supporting calculations for street sections are located in the Appendix.
Page 5
DRAINAGE BASINS
The Northfield improvements proposed drainage basins were delineated by areas draining to
major drainage elements (such as ponds and roadway sumps). The final drainage report will
further detail the drainage basins. For the purposes of this preliminary drainage study, it is
assumed that the project is 60% impervious for medium density residential sites, slightly higher
than the 50% listed for LMN land use zone. Detailed percent imperviousness will be determined
with the final drainage study. Historical drainage analysis was completed for the areas of
Northfield located within the NECCO basin map that allows the runoff to be released at historic
rates. The remaining areas of Northfield did not calculate the historic runoff rates since the
proposed improvements are within basins that are restricted to 0.2 cfs/acre release rate. The
basins are broken into 5 main drainage systems:
Drainage System A:
Drainage System A pertains to the improvements along the east side of the project site.
Majority of this basin’s improvements are proposed for future phases.
Sub-basin A1 consists of 8.39 acres of single-family attached and condominium residential
lots, public roadways and private drives. The basin includes a portion of Schlagel Street and
N. Lemay Avenue. Flows from this basin is mainly conveyed along roadways and will be
collected by a Type R inlets and conveyed to detention Pond A1.
Sub-basin A2 consists of 9.60 acres of single-family attached and condominium residential
lots, public roadways and private drives. The basin includes a portion of Schlagel Street,
Harvest Sun Street, and Pioneer Road. Runoff from this basin will be conveyed along
roadways and directed to detention Pond A2 and ultimately to detention Pond A1. All of
basin A2 will be treated by a LID infiltration gallery.
Drainage System B:
Sub-basin B1 consists of 7.16 acres of single-family attached and condominium residential
lots, public roadways and private drives. This basin includes portions of Landmark Way
Road, Steeley Drive, and Schlagel Street. Runoff is mainly conveyed along roadways and
directed to detention Pond B1.
Sub-basin B2 consists of 3.65 acres of single-family attached and condominium residential
lots, public roadways and private drives. Runoff is conveyed along Schlagel St, Harvest Sun
Street, and the private drives, is captured by Type R inlets and area inlets. Runoff is then
conveyed to detention Pond B1via storm drain pipes. All of basin B2 will be treated by a LID
infiltration gallery.
Page 6
Sub-basin B3 consists of 9.95 acres of single-family attached lots, multifamily residential
buildings and private drives. Runoff is conveyed along streets and private drives and
captured by area inlets. Runoff is then conveyed to detention Pond B2 via storm drain pipes
and ultimately conveyed to detention Pond B1. All of basin B3 will be treated by a LID
infiltration gallery.
Drainage System C:
Sub-basin C1 consists of 1.09 acres of multifamily residential buildings and open space.
Runoff is conveyed along an open channel swale to culverts crossing Steeley Drive to
detention Pond C.
Sub-basin C2 consists of 1.39 acres of commercial lots and detention Pond C. Flows drain to
the swale, running southwesterly along the northwest property line of the site, then into pond
C. A concrete pan conveys all of the collected flow to the outlet structure, restricting flows to
the allowed release rate.
Drainage System D:
Drainage System D consists of the area south of Suniga Rd.
Sub-basin D1 consists of 6.47 acres of future multifamily residential buildings, a
commercial lot, public roadway, and private drives. Runoff is conveyed to detention Pond D
via open channel swales and storm drains. All of basin D1 will be treated by a LID
bioretention/rain garden.
Sub-basin D2 consists of 3.69 acres of commercial property, detention Pond D, and portions
of N. Lemay Ave and Suniga Rd. Runoff from the roadways is conveyed along Suniga Rd
and N. Lemay Ave to two Type R sump inlets. Runoff outside of the roadways is conveyed
to detention Pond D. This basin’s detention requirements allows a release rate equal to the
current/historic runoff rates and is accounted for in the Pond D detention volume
calculations.
Drainage System E:
Sub-basins E1 & E2 consist of two basins, combining for a total of 7.19 acres of public
roadways along Suniga Rd. Runoff is conveyed along Suniga Rd and collected by Type R
sump inlets. The locations of these inlets were depicted in the conceptual design of the “East
Vine Drive Relocation” utility plans. Runoff captured by these inlets is conveyed to the
existing NECCO reinforced concrete box culvert storm drain, undetained.
Page 7
DRAINAGE FACILITY DESIGN
DRAINAGE CONVEYANCE DESIGN
Storm infrastructure to convey runoff will include overland grass-lined swales, concrete trickle
pans, inlets, storm sewer and culverts. Storm water detention and water quality enhancement
will be achieved through the use of an extended detention basin. Storm inlets, storm sewers and
the roadway culverts will be appropriately sized with the final drainage design
DETENTION/WATER QUALITY POND DESIGN
Multiple extended detention basins (EDB) with a dry bottom will be utilized as the detention and
water quality facility for Northfield. The EDBs along the north side of Suniga Road are
designed to reduce the 100-yr developed runoff to the allow 0.2 cfs/acre. A portion of the area
south of Suniga Road is allowed release rates equal to current/historic rates with the remaining
restricted to the 0.2 cfs/acre. For the preliminary drainage study, the FAA method was used to
determine the detention volume needed. EPA SWWM will be utilized for the final drainage
design. UDFCD is referenced for the water quality capture volume (WQCV) with a 40-yr drain
time. Due to the limited grades on the site, multiple ponds are proposed throughout the site with
the main detention ponds being located along Suniga Rd. The pond bottoms have been graded to
be 2 ft above the measured groundwater levels. The ultimate outfall will be the existing NECCO
storm drain system. Below is a description of the pond networks:
Drainage System A:
This basin is 17.99 acres draining to the detention Pond A1 and Pond A2, which allows a release
rate of 3.60 cfs. 3.99 acre-ft of detention storage is required with 0.42 acre-ft WQCV. To
achieve the total detention volume, a network of two detention ponds, Pond A1 and Pond A2,
will provide the total volume. At final design, SWMM will be utilized to maximize the
detention volume in Pond A2 by determining the appropriate release rate, while only allowing
the 0.2 cfs/acre from Pond A1.
Drainage System B:
Drainage System B’s basin is 20.77 acres which allows a release rate of 4.15 cfs. This requires
4.60 acre-ft of detention storage volume with 0.49 acre-ft WQCV. To achieve the total detention
volume, a network of two detention ponds, Pond B1, and Pond B2, along with Pond A1 will
provide the volume. At final design, SWMM will be utilized to maximize the detention volume
in upstream ponds by determining the appropriate release rate, while only allowing the 0.2
cfs/acre from Pond A1.
Drainage System C:
Page 8
Drainage System C’s basin is 2.48 acres which allows a release rate of 0.50 cfs. This requires
0.55 acre-ft of detention storage volume with 0.06 acre-ft WQCV. During final design the
release rate from Pond C may need to be reduced to ultimately only allow 0.2 cfs/acre release
rate from Pond A1.
Drainage System D:
This basin is 10.16 acres which allows a release rate of 9.15 cfs, requiring 1.24 acre-ft of
detention storage 0.23 acre-ft WQCV. 6.47 acres are required to detain to 0.2 cfs/acre while the
remaining will be detained to historic rates. The release rate from Pond D will account for the
portions of Lemay that are not able to be conveyed to the detention pond.
Page 9
LOW IMPACT DEVELOPMENT
The City of Fort Collins updated the Low Impact Development ordinance in 2016 (Ordinance
No. 007, 2016) to require:
• Treat at least 75% of any newly developed or redeveloped impervious area using one or a
combination of LID techniques, or
• Treat at least 50% of any newly developed or redeveloped impervious area using one or a
combination of LID techniques when 25% of private driveable surfaces are permeable.
To satisfy the required implementation of Low Impact Development (LID) techniques,
Northfield will utilize below grade infiltration galleries (such as ADS StormTech chamber
system) and bioretention ponds/rain gardens. Other LID techniques were explored, but due to
the limited grade available and the amount of detention volume required, shallow infiltration
galleries assisted in maintaining storm drain grades and detention volumes. Pavers within the
private drives did not treat enough contributing area to justify their use. Infiltration galleries will
promote infiltration while capturing fine sediment that drains off of the impervious areas. Further
soil investigation will occur to confirm the infiltration capacities within the sandy/gravel soil
layers approximately 2’ to 5 ½’ below existing grades. It is anticipated that the infiltration
gallery aggregates will extend to this sandy/gravel layer. Isolator rows will be implemented at
the headworks to the infiltration galleries to allow larger sediment particle to settle prior to
entering the infiltration gallery. The isolator rows will be accessible to remove sediments.
Standard water quality is also provided within the detention ponds in addition to these LID
infiltration galleries. A Standard Operations Procedure will be provided at final design to assist
in ensuring that these BMPs will adequately perform over time.
It was discussed with staff that there may be consideration on lowering the percent of area
treated for single-family areas to 50%. Though the current design exceeds the 50% treatment, it
is slightly under 75% treatment. For the purposes of the preliminary design, the area of
treatment was calculated, rather than the area of impervious area. This approach assumes that
the area of treatment has similar correlation to the impervious area treated. These area of
treatment calculations will be further detailed in the final drainage design.
Below is a description of the 4 step process for selecting structural BMPs:
Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for
receiving water protection that focuses on reducing runoff volumes, treating the water quality
capture volume (WQCV), stabilizing drainageways and implementing long-term source controls.
The Four Step Process applies to the management of smaller, frequently occurring events.
Page 10
Step 1: Employ Runoff Reduction Practices
To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low
Impact Development (LID) strategies, including Minimizing Directly Connected Impervious
Areas (MDCIA).
Captured runoff from strategic areas are routed through below grade infiltration galleries and
bioretention pond/rain gardens. Infiltration galleries and rain gradens will slow runoff, promote
infiltration, and filter runoff prior to being released into the adjacent storm drain system.
Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release
The infiltration galleries and rain gardens are designed to provide water quality capture volume
per Urban Drainage’s recommendations and calculations. The captured runoff is design for a 12-
hr drain time.
Step 3: Stabilize Drainageways
Natural Drainageways are subject to bed and bank erosion due to increases in frequency,
duration, rate and volume of runoff during and following development. Because the site will
drain to an existing storm system, bank stabilization is unnecessary with this project.
Step 4: Implement Site Specific and Other Source Control BMPs
Proactively controlling pollutants at their source by preventing pollution rather than removing
contaminants once they have entered the stormwater system or receiving waters is important
when protecting storm systems and receiving waters. This can be accomplished through site
specific needs such as construction site runoff control, post-construction runoff control and
pollution prevention / good housekeeping. It will be the responsibility of the contractor to
develop a procedural best management practice for the site.
All calculations are attached for reference.
Page 11
STORMWATER POLLUTION PREVENTION
Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet
protection, a gravel construction entrance, seeding, mulch, and turf. The measures are designed
to limit the overall sediment yield increase due to construction as required by the City of Fort
Collins. During overlot and final grading the soil will be roughened and furrowed perpendicular
to the prevailing winds.
During the performance of the work required by these specifications or any operations
appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the contractor
shall furnish all labor, equipment, materials, and means required. The Contractor shall carry out
proper efficient measures wherever and as necessary to reduce dust nuisance, and to prevent dust
nuisance that has originated from his operations from damaging crops, orchards, cultivated
fields, and dwellings, or causing naissance to persons. The Contractor will be held liable for any
damage resulting from dust originating from his operations under these specifications on right-
of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-
way. Wherever construction vehicles access routes or intersect paved public roads, previsions
must be made to minimize the transport of sediment by runoff or vehicles tracking onto the
paved surface. Stabilized construction entrances are required with base material consisting of 6”
coarse aggregate. The contractor will be responsible for clearing mud tracked onto city streets
on a daily basis.
All temporary and permanent erosion and sediment control practices must be maintained and
repaired as needed to assure continued performance of their intended function. Silt fence and
sediment control logs will require periodic replacement. Maintenance is the responsibility of the
contractor.
All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall
not be considered established until a ground cover is achieved which is demonstrated to be
mature enough to control soil erosion to the satisfaction of the City Inspector and to survive
severe weather condition.
Page 12
CONCLUSIONS
This Preliminary Drainage Report for Northfield has been prepared to comply with the storm
water criteria set by the City of Fort Collins. The proposed preliminary drainage system
presented in this report is designed to convey the developed peak storm water runoff through the
site to the existing storm drain system and to the development’s LID features, detention and
water quality facilities. Storm drains will be sized to provide the required roadway relief in both
the 2-yr and 100-yr storm events, and to adequately convey the released runoff from the
detention ponds disbursed throughout the site. Overland relief will be provided at all sump
locations. The calculated 100-yr peak flows released from the Northfield will adhere to the
allowed rates as established in the NECCO drainage studies. This preliminary drainage report
anticipates the implementation of best management practices for erosion control, temporary and
permanent, and on-site construction facilities that will be further designed and details in the Final
Drainage Report.
It can therefore be concluded that development of Northfield will comply with the storm water
jurisdictional criteria and will not adversely affect the adjacent properties, streets, storm drain
system and/or detention/water quality facilities. Controlling the developed runoff from these
improvements will actually improve the current situations currently existing on the site.
Therefore, this preliminary report satisfies the burden of proof needed to proceed to a Final
Drainage Report.
Page 13
REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood
Control District, June 2001, Revised November 2010.
2. Storm Drainage Criteria Manual and Construction Standards, City of Fort Collins Storm
Water Utility, City of Fort Collins, Colorado, Updated January, 1997 with 2012
amendments.
3. Fort Collins Stormwater Criterial Manual (Draft for Council), Fort Collins Utilities, City
of Fort Collins, Colorado, Dated November 2017 [Anticipated to be adopted by City
Council in 2017]
4. “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. [12/06/2017]
5. “Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property”,
prepared by Earth Engineering Consultants, LLC, Dated August 16, 2017
6. “Public Improvement Plans, East Vine Drive Relocation”, prepared by Ayres Associates,
Dated February 2009, obtained from City of Fort Collins.
7. “Utility Plans for NECCO Ponds and Backbone” – Record Drawings, prepared by Ayres
Associates, Dated June 2017, obtained from the City of Fort Collins.
8. “Flood Insurance Rate Map, Larimer County, Colorado – Map Number 08069C0977G”,
Federal Emergency Management Agency, Map Revised June 17, 2008.
9. “Flood Insurance Rate Map, Larimer County, Colorado – Map Number 08069C0981G”,
Federal Emergency Management Agency, Map Revised June 17, 2008.
Page 14
APPENDIX
Appendix A – Site Descriptions, Characteristics, & References
Appendix B – Rational Calculations
Appendix C – Detention Pond Calculations
Appendix D – Street Capacities
Appendix E – Low Impact Development Calculations
Appendix A
APPENDIX A – SITE DESCRIPTIONS, CHARACTERISTICS, & REFERENCES
SITE
Vicinity Map
PROJECT DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK #43-97
ON THE SOUTH END OF THE WEST HEADWALL OF THE LAKE CANAL BRIDGE AT NORTH LEMAY
AVENUE, 200 FEET SOUTH OF THE INTERSECTION OF LEMAY AVENUE. AND CONIFER STREET
ELEV= 4960.11
CITY OF FORT COLLINS BENCHMARK #12-07
SOUTH SIDE OF VINE DRIVE ON THE SOUTH HEADWALL OF THE BRIDGE OVER DRY CREEK
BASIN 0.4 MILES EAST OF NORTH LEMAY AVENUE
ELEV= 4947.86
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM.
IF NGVD29 UNADJUSTED IS REQUIRED FOR ANY PURPOSE,
THE FOLLOWING EQUATIONS SHOULD BE USED:
NGVD UNADJUSTED = 4960.11 (NAVD88) - 3.17
NGVD UNADJUSTED = 4947.81 (NAVD88) - 3.18
NTS
Hydrologic Soil Group—Larimer County Area, Colorado
(NorthField)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/6/2017
Page 1 of 4
4494130 4494220 4494310 4494400 4494490 4494580 4494670
4494130 4494220 4494310 4494400 4494490 4494580 4494670
494350 494440 494530 494620 494710 494800 494890 494980 495070 495160
494350 494440 494530 494620 494710 494800 494890 494980 495070 495160
40° 36' 11'' N
105° 4' 2'' W
40° 36' 11'' N
105° 3' 23'' W
40° 35' 52'' N
105° 4' 2'' W
40° 35' 52'' N
105° 3' 23'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,140 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
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:
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
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
64 Loveland clay loam, 0 to
1 percent slopes
C 11.9 20.9%
73 Nunn clay loam, 0 to 1
percent slopes
C 16.6 29.2%
76 Nunn clay loam, wet, 1
to 3 percent slopes
C 28.3 49.9%
Totals for Area of Interest 56.7 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, 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.
Hydrologic Soil Group—Larimer County Area, Colorado NorthField
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/6/2017
Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado NorthField
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/6/2017
Page 4 of 4
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
Intensity (in/hr)
City of Fort Collins
Rainfall Intensity-Duration-Frequency Curve
2-yr (FTC)
10-yr (FTC)
100-yr (FTC)
2-yr (UD)
10-yr (UD)
100-yr (UD)
100-yr
10-yr
0.0
1.0
2.0
3.0
4.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0
Duration (min)
2-yr
10-yr
Duration
(minutes)
2-yr
Intensity
(in/hr)
10-yr
Intensity
(in/hr)
100-yr
Intensity
(in/hr)
Duration
(minutes)
2-yr
Intensity
(in/hr)
10-yr
Intensity
(in/hr)
100-yr
Intensity
(in/hr)
5 2.85 4.87 9.95 33 1.22 2.08 4.24
6 2.67 4.56 9.31 34 1.19 2.04 4.16
7 2.52 4.31 8.80 35 1.17 2.00 4.08
8 2.40 4.10 8.38 36 1.15 1.96 4.01
9 2.30 3.93 8.03 37 1.13 1.93 3.93
10 2.21 3.78 7.72 38 1.11 1.89 3.87
11 2.13 3.63 7.42 39 1.09 1.86 3.80
12 2.05 3.50 7.16 40 1.07 1.83 3.74
13 1.98 3.39 6.92 41 1.05 1.80 3.68
14 1.92 3.29 6.71 42 1.04 1.77 3.62
15 1.87 3.19 6.52 43 1.02 1.74 3.56
16 1.81 3.08 6.30 44 1.01 1.72 3.51
17 1.75 2.99 6.10 45 0.99 1.69 3.46
18 1.70 2.90 5.92 46 0.98 1.67 3.41
19 1.65 2.82 5.75 47 0.96 1.64 3.36
20 1.61 2.74 5.60 48 0.95 1.62 3.31
21 1.56 2.67 5.46 49 0.94 1.60 3.27
22 1.53 2.61 5.32 50 0.92 1.58 3.23
23 1.49 2.55 5.20 51 0.91 1.56 3.18
24 1.46 2.49 5.09 52 0.90 1.54 3.14
25 1.43 2.44 4.98 53 0.89 1.52 3.10
26 1.40 2.39 4.87 54 0.88 1.50 3.07
27 1.37 2.34 4.78 55 0.87 1.48 3.03
28 1.34 2.29 4.69 56 0.86 1.47 2.99
29 1.32 2.25 4.60 57 0.85 1.45 2.96
30 1.30 2.21 4.52 58 0.84 1.43 2.92
31 1.27 2.16 4.42 59 0.83 1.42 2.89
32 1.24 2.12 4.33 60 0.82 1.40 2.86
Figure 3-1a
City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for using the Rational Method
Duration 2-yr 10-yr 100-yr 2-yr ∆∆∆∆ 10-yr ∆∆∆∆ 100-yr ∆∆∆∆
5 2.85 4.87 9.95 2.78 -0.07 4.74 -0.13 9.68 -0.27
6 2.67 4.56 9.31 2.64 -0.03 4.51 -0.05 9.20 -0.11
7 2.52 4.31 8.80 2.52 0.00 4.30 -0.01 8.78 -0.02
8 2.40 4.10 8.38 2.41 0.01 4.11 0.01 8.39 0.01
9 2.30 3.93 8.03 2.31 0.01 3.94 0.01 8.04 0.01
10 2.21 3.78 7.72 2.21 0.00 3.78 0.00 7.72 0.00
11 2.13 3.63 7.42 2.13 0.00 3.64 0.01 7.43 0.01 2-yr 0.82
12 2.05 3.50 7.16 2.05 0.00 3.51 0.01 7.16 0.00 10-yr 1.40
13 1.98 3.39 6.92 1.98 0.00 3.39 0.00 6.92 0.00 100-yr 2.86
14 1.92 3.29 6.71 1.92 0.00 3.28 -0.01 6.69 -0.02
15 1.87 3.19 6.52 1.86 -0.01 3.17 -0.02 6.48 -0.04
16 1.81 3.08 6.30 1.80 -0.01 3.08 0.00 6.28 -0.02 C 1 28.5
17 1.75 2.99 6.10 1.75 0.00 2.99 0.00 6.10 0.00 C 2 10
18 1.70 2.90 5.92 1.70 0.00 2.90 0.00 5.93 0.01 C 3 0.786651
19 1.65 2.82 5.75 1.65 0.00 2.82 0.00 5.77 0.02
20 1.61 2.74 5.60 1.61 0.00 2.75 0.01 5.61 0.01
21 1.56 2.67 5.46 1.57 0.01 2.68 0.01 5.47 0.01
22 1.53 2.61 5.32 1.53 0.00 2.61 0.00 5.34 0.02
23 1.49 2.55 5.20 1.49 0.00 2.55 0.00 5.21 0.01
24 1.46 2.49 5.09 1.46 0.00 2.49 0.00 5.09 0.00
25 1.43 2.44 4.98 1.43 0.00 2.43 -0.01 4.97 -0.01
26 1.40 2.39 4.87 1.39 -0.01 2.38 -0.01 4.86 -0.01
27 1.37 2.34 4.78 1.36 -0.01 2.33 -0.01 4.76 -0.02
28 1.34 2.29 4.69 1.34 0.00 2.28 -0.01 4.66 -0.03
29 1.32 2.25 4.60 1.31 -0.01 2.24 -0.01 4.57 -0.03
30 1.30 2.21 4.52 1.28 -0.02 2.19 -0.02 4.48 -0.04
31 1.27 2.16 4.42 1.26 -0.01 2.15 -0.01 4.39 -0.03
32 1.24 2.12 4.33 1.24 0.00 2.11 -0.01 4.31 -0.02
33 1.22 2.08 4.24 1.21 -0.01 2.07 -0.01 4.23 -0.01
34 1.19 2.04 4.16 1.19 0.00 2.03 -0.01 4.15 -0.01
Coefficients
Intensity (in/hr)
Urban Drainage
Intensity (in/hr)
City of Fort Collins
Urban Drainage
Inputs
Urban Drainage Intensity Equation
1-hr Rainfall Depths (P 1 )
City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
Use of Urban Drainage Intensity Equation for CoFC IDF Values
This cell was determined
using Solver to best match
intensities given from the
Fort Collins IDF values.
C 3
2
1 1
( c )
C t
C P
I
+
=
34 1.19 2.04 4.16 1.19 0.00 2.03 -0.01 4.15 -0.01
35 1.17 2.00 4.08 1.17 0.00 2.00 0.00 4.08 0.00
36 1.15 1.96 4.01 1.15 0.00 1.96 0.00 4.01 0.00
37 1.13 1.93 3.93 1.13 0.00 1.93 0.00 3.94 0.01
2-year 5-yr 10-yr 25-yr 50-yr 100-yr
5 0.29 0.40 0.49 0.63 0.79 1.00
10 0.33 0.45 0.56 0.72 0.90 1.14
15 0.38 0.53 0.65 0.84 1.05 1.33
20 0.64 0.89 1.09 1.41 1.77 2.23
25 0.81 1.13 1.39 1.80 2.25 2.84
30 1.57 2.19 2.69 3.48 4.36 5.49
35 2.85 3.97 4.87 6.30 7.90 9.95
40 1.18 1.64 2.02 2.61 3.27 4.12
45 0.71 0.99 1.21 1.57 1.97 2.48
50 0.42 0.58 0.71 0.92 1.16 1.46
55 0.35 0.49 0.60 0.77 0.97 1.22
60 0.30 0.42 0.52 0.67 0.84 1.06
65 0.20 0.28 0.39 0.62 0.79 1.00
70 0.19 0.27 0.37 0.59 0.75 0.95
75 0.18 0.25 0.35 0.56 0.72 0.91
80 0.17 0.24 0.34 0.54 0.69 0.87
85 0.17 0.23 0.32 0.52 0.66 0.84
90 0.16 0.22 0.31 0.50 0.64 0.81
95 0.15 0.21 0.30 0.48 0.62 0.78
100 0.15 0.20 0.29 0.47 0.60 0.75
105 0.14 0.19 0.28 0.45 0.58 0.73
110 0.14 0.19 0.27 0.44 0.56 0.71
115 0.13 0.18 0.26 0.42 0.54 0.69
120 0.13 0.18 0.25 0.41 0.53 0.67
City of Fort Collins
Design Storms
for using SWMM
Figure 3-1c
Time
(min)
Intensity (in/hr)
These are the 1-hour storm
2-year 5-yr 10-yr 25-yr 50-yr 100-yr
1-hr 0.82 1.14 1.40 1.81 2.27 2.86
2-hr 0.98 1.36 1.71 2.31 2.91 3.67
Storm
Duration
Rainfall Depth (in)
Note: The City of Fort Collins SWWM input hyetopgrah is used to calculate the
1-hr and 2-hr storm rainfall depths for the different storm events.
These are the 1-hour storm
depths that are used in the
Urban Drainage intensity
equation, derived from the CoFC
Hyetograph.
Table RO-13
SWMM Input Parameters
Depth of Storage on Impervious Areas 0.1 inches
Depth of Storage on Pervious Areas 0.3 inches
Maximum Infiltration Rate 0.51 inches/hour
Minimum Infiltration Rate 0.50 inches/hour
Decay Rate 0.0018 inches/sec
Zero Detention Depth 1%
Manning’s n Value for Pervious Surfaces 0.025
Manning’s n Value for Impervious Surfaces 0.016
4.3.2 Pervious-Impervious Area
Table RO-14 should be used to determine preliminary percentages of impervious land
cover for a given land-use or zoning. The final design must be based on the actual
physical design conditions of the site.
Table RO-14
Percent Imperviousness Relationship to Land Use*
LAND USE OR ZONING
PERCENT IMPERVIOUS
(%)
Business:
T
CCN, CCR, CN
E, RDR, CC, LC
C, NC, I, D, HC, CS
20
70
80
90
Residential:
RF,UE
RL, NCL
LMN,NCM
MMN, NCB
30
45
50
70
Open Space:
Open Space and Parks (POL)
Open Space along foothills ridge
(POL,RF)
RC
10
20
20
*For updated zoning designations and definitions, please refer to Article Four of the City Land
Use Code, as amended
LEGEND
DRAINAGE BASIN
BASIN NUMBER
BASIN AREA (ACRES)
EXHIBIT 4.2
FUTURE DETENTION AND WATER QUALITY REQUIREMENTS
RESTRICT AMOUNT OF RUNOFF
TO EXISTING CONDITIONS IF
RE-DEVELOPED. WATER QUALITY
PROVIDED IN REDWOOD POND
REQUIRE FUTURE ON-SITE
DETENTION & WATER
QUALITY. RELEASE RATE
@ 0.20 cfs/acre
REQUIRE FUTURE ON-SITE
DETENTION.
WATER QUALITY PROVIDED
IN REGIONAL POND.
FUTURE RE-ALIGNED VINE
DRIVE. WATER QUALITY
PROVIDED WITH SNOUTS.
DISCHARGE INTO
REGIONAL POND WITHOUT
FUTURE DETENTION OR
WATER QUALITY.
RESTRICT AMOUNT OF RUNOFF
TO EXISTING CONDITIONS IF
RE-DEVELOPED. FUTURE WATER
QUALITY REQUIRED.
RESTRICT AMOUNT OF RUNOFF
TO EXISTING CONDITIONS IF
RE-DEVELOPED. WATER QUALITY
PROVIDED IN REGINAL POND.
BASIN 103: NO DETENTION OR
WATER QUALITY REQURED IF
DISCHARGING INTO
EVERGREEN WEST POND
COLLEGE AVENUE
RED CEDAR CIRCLE
LEMAY AVENUE
DRY CREEK
BRISTLECONE DRIVE
CONIFER STREET
NOKOMIS COURT
BLUE SPRUCE DRIVE
CONIFER STREET
LUPINE DRIVE
REDWOOD
POND
REGIONAL
POND
REDWOOD STREET
COLLEGE AVENUE
JEROME STREET
BONDELL STREET
OSIANDER STREET
EAST VINE DRIVE
70.0 ac
68.2 ac
13.2 ac
1
Jason Claeys
From: Jaclyn Michaelsen <jmichaelsen@iconeng.com>
Sent: Thursday, October 12, 2017 11:50 AM
To: Jason Claeys
Cc: Linsey Chalfant
Subject: RE: Necco-Construction Plans
The manhole on the northwest corner of Suniga and Lemay is MH Riser A-7. It is approximately 500-ft to the west of
Lemay. The invert of the riser is at a 4943.68. The HGL is at a 4947.68 in the Master Plan condition. The Master Plan
had the Schlagel property connecting into the system at this junction. I would check with the City, but I would assume
tat you could connect into the storm sewer anywhere downstream of this location. Let me know if you need another
elevation.
Thanks
Jaclyn Michaelsen
970.310.1547
From: Jason Claeys [mailto:jclaeys@interwestgrp.com]
Sent: Wednesday, October 11, 2017 10:54 AM
To: Jaclyn Michaelsen <jmichaelsen@iconeng.com>
Cc: Linsey Chalfant <lchalfant@fcgov.com>
Subject: RE: Necco-Construction Plans
Hi Jackie,
I hope that all is well. I am digging deeper into our stormwater design for the Schlagel property. I am anticipating tying
to the NECCO line near the northwest corner of (Old) Lemay and Suniga. There were a few HGL’s in the report Lindsey
sent but not near this intersection. Would you be able to send me appendixes to the report for reference and possibly
the SWMM model? I want to review how the HGL’s in the NECCO pipe will affect our detention.
Thanks!
Jason T. Claeys, P.E., LEED AP
Interwest Consulting Group | jclaeys@interwestgrp.com
1218 W Ash St, Suite A | Windsor, CO 80550
D 970.347.8917 | M 970.817.1712 | www.interwestgrp.com
PZ-2
MW-1
PZ-1
PZ-5 PZ-6 MW-2
PZ-3 PZ-4
PZ-7
(4956.1)
[4948.9]
(4957.3)
[4951.3]
(4956.1)
[4951.0]
(4953.5)
[4948.5]
(4954.2)
[4947.4]
(4951.8)
[4946.5]
(4953.2)
[4948.6]
(4954.6)
[4958.5]
(4956.5)
[4950.8]
4951
4950
4949
4948
4947
Figure 2: Groundwater Contour Map
Schlagel Property
Fort Collins, Colorado
EEC Project #: 1172056 Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
MW-1 & MW-2:
Approximate Monitor
Well Locations
Legend
PZ-1 thru PZ-7:
Approximate
Piezometer Locations
Approximate Ground
Surface Elevation
Approximate
Groundwater Elevation
(4950.8)
[4950.8]
Approximate
Groundwater Contours
Approximate
Groundwater
Directional Flow
4950.8
4951.8
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 3.0 4951.6 4957.6 5.0 4946.8 4952.8 5.0 4951.5 4957.5
7/27/2017 3.8 4950.8 4956.8 5.3 4946.5 4952.5 4.7 4951.8 4957.8
9/19/2017 4.0 4950.6 4956.6 5.7 4946.1 4952.1 5.2 4951.3 4957.3
10/19/2017 4.0 4950.6 4956.6 5.6 4946.2 4952.2 5.0 4951.5 4957.5
2/12/2017 5.7 4948.9 4954.9 7.0 4944.8 4950.8 6.8 4949.7 4955.7
6/7/2018 3.7 4950.9 4956.9 5.2 4946.6 4952.6 4.4 4952.1 4958.1
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 5.5 4947.7 4953.7 5.0 4951.1 4957.1 5.0 4948.5 4954.5
7/27/2017 4.6 4948.6 4954.6 5.1 4951.0 4957.0 5.0 4948.5 4954.5
9/19/2017 4.7 4948.5 4954.5 5.8 4950.3 4956.3 5.3 4948.2 4954.2
10/19/2017 4.6 4948.6 4954.6 5.9 4950.2 4956.2 5.1 4948.4 4954.4
2/12/2017 6.2 4947.0 4953.0 7.5 4948.6 4954.6 6.5 4947.0 4953.0
6/7/2018 4.6 4948.6 4954.6 4.4 4951.7 4957.7 5.3 4948.2 4954.2
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Appendix B
APPENDIX B – RATIONAL CALCULATIONS
ONLY
ONLY
ONLY
ONLY
ONLY
ONLY
lake canal
dry creek
lake canal
N. LEMAY AVENUE
HARVEST SUN STREET
PIONEER TRAIL ROAD
STEELEY DRIVE
LANDMARK WAY ROAD
N. LEMAY AVENUE
POND D
POND C
POND B1
POND B2
POND A2
POND A1
SCHLAGEL STREET
1218 W. Ash, Suite A
Windsor , Colorado 80550
Phone: (970) 674-3300
Fax: (970) 674-3303
I N T E R W E S T C O N S U L T I N G G R O U P
PREPARED FOR
PROJ. NO.
DATE:
SCALE (H):
SCALE (V):
CHECKED BY:
DESIGNED BY:
PROJECT NAME
NORTHFIELD
OVERALL DRAINAGE EXHIBIT
08/22/18
1"= 100'
N/A
LAJ
JTC
1282-168-03
1 of 1
1170 West Ash Street, Suite 100
Windsor, Colorado 80550
Office: 970.460.0567
BASIN COEFFICIENT (100-YR)
BASIN DESIGNATION
BASIN AREA
DESIGN POINT
DRAINAGE FLOW ARROW
DRAINAGE BASIN
BOUNDARY
DRAINAGE BASIN
FLOW PATH
LEGEND
EX MAJOR CONTOUR
SPILL GUTTER
EX MINOR CONTOUR
Design Engineer:
Design Firm:
Project Number:
Date:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf
)
100% 0.95
2-year to
10-year
1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
0% 0.25
C2
to C10
C100
A1 365,366 8.388 219,219 0 0 0 146,146 60.0% 0.67 0.84
A2 418,325 9.603 250,995 0 0 0 167,330 60.0% 0.67 0.84
B1 311,766 7.157 187,060 0 0 0 124,707 60.0% 0.67 0.84
B2 159,134 3.653 95,480 0 0 0 63,654 60.0% 0.67 0.84
B3 433,610 9.954 260,166 0 0 0 173,444 60.0% 0.67 0.84
C1 47,357 1.087 28,414 0 0 0 18,943 60.0% 0.67 0.84
C2 60,578 1.391 36,347 0 0 0 24,231 60.0% 0.67 0.84
D1 281,776 6.469 169,065 0 0 0 112,710 60.0% 0.67 0.84
D2 160,920 3.694 88,255 0 0 0 72,666 54.8% 0.63 0.79
E1 49,837 1.144 29,902 0 0 0 19,935 60.0% 0.67 0.84
E2 260,459 5.979 156,276 0 0 0 104,184 60.0% 0.67 0.84
Overall 2,549,128 58.520 1,521,179 0 0 0 1,027,949 59.7% 0.67 0.83
Historic D2 160,920 3.694 21,754 0 0 0 139,166 13.5% 0.34 0.43
Northfield
DEVELOPED IMPERVIOUS AREA CALCULATION
DESIGN CRITERIA:
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
BASINS:
% Impervious values from Table RO-11 in the Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
L. Johnson
Interwest Consulting Group
1282-168-03
August 22, 2018
Land Use
Paved
Roof
Walks
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Gravel/Pavers
Lawns
(Heavy, 2-7% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
Type of Travel
Surface
Cv
A1 A1 60.0% 0.67 8.388 52 0.0050 7.31 1074 0.0050 Paved Areas 20 1.41 12.66 19.96 0.0050 19.05 19.05
A2 A2 60.0% 0.67 9.603 55 0.0050 7.51 1036 0.0050 Paved Areas 20 1.41 12.21 19.72 0.0050 18.74 18.74
B1 B1 60.0% 0.67 7.157 24 0.0050 4.96 1048 0.0050 Paved Areas 20 1.41 12.35 17.31 0.0050 18.57 17.31
B2 B2 60.0% 0.67 3.653 24 0.0050 4.96 404 0.0050 Paved Areas 20 1.41 4.76 9.72 0.0050 12.82 9.72
B3 B3 60.0% 0.67 9.954 300 0.0050 17.55 491 0.0050 Paved Areas 20 1.41 5.79 23.33 0.0050 16.06 16.06
C1 C1 60.0% 0.67 1.087 200 0.0050 14.33 366 0.0050 Paved Areas 20 1.41 4.31 18.64 0.0050 14.05 14.05
C2 C2 60.0% 0.67 1.391 200 0.0050 14.33 387 0.0050 Paved Areas 20 1.41 4.56 18.89 0.0050 14.24 14.24
D1 D1 60.0% 0.67 6.469 42 0.0050 6.57 776 0.0050 Paved Areas 20 1.41 9.15 15.71 0.0050 16.30 15.71
D2 D2 54.8% 0.63 3.694 115 0.0050 11.78 285 0.0050 Paved Areas 20 1.41 3.36 15.14 0.0050 13.52 13.52
E1 E1 60.0% 0.67 1.144 42 0.0050 6.57 348 0.0050 Paved Areas 20 1.41 4.10 10.67 0.0050 12.48 10.67
E2 E2 60.0% 0.67 5.979 42 0.0050 6.57 1132 0.0050 Paved Areas 20 1.41 13.34 19.91 0.0050 19.48 19.48
HD2 Historic D2 13.5% 0.34 3.694 300 0.0048 31.32 478 0.0029 Tilage/Field 5 0.27 29.44 60.76 0.0036 30.08 30.08
August 22, 2018
Northfield
DEVELOPED TIME OF CONCENTRATION
L. Johnson
Interwest Consulting Group
1282-168-03
LENGTH
(ft)
DESIGN CRITERIA:
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
Overland Flow Equations for City of Fort Collins - Storm Water Criteria Manual
SUB-BASIN DATA
INITIAL/OVERLAND TIME
(ti)
TRAVEL TIME (tt)
tc
=ti
+tt
(min)
Urban Check Final
tc
(min)
DESIGN
POINT
Sub-basin
%
Impervious
C2-10
AREA
(acres)
tt
(min)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (100-yr)
Type of Travel
Surface
Cv
A1 A1 60.0% 0.84 8.388 52 0.0050 4.46 1074 0.0050 Paved Areas 20 1.41 12.66 17.12 0.0050 19.05 17.12
A2 A2 60.0% 0.84 9.603 55 0.0050 4.59 1036 0.0050 Paved Areas 20 1.41 12.21 16.80 0.0050 18.74 16.80
B1 B1 60.0% 0.84 7.157 24 0.0050 3.03 1048 0.0050 Paved Areas 20 1.41 12.35 15.38 0.0050 18.57 15.38
B2 B2 60.0% 0.84 3.653 24 0.0050 3.03 404 0.0050 Paved Areas 20 1.41 4.76 7.79 0.0050 12.82 7.79
B3 B3 60.0% 0.84 9.954 300 0.0050 10.71 491 0.0050 Paved Areas 20 1.41 5.79 16.50 0.0050 16.06 16.06
C1 C1 60.0% 0.84 1.087 200 0.0050 8.75 366 0.0050 Paved Areas 20 1.41 4.31 13.06 0.0050 14.05 13.06
C2 C2 60.0% 0.84 1.391 200 0.0050 8.75 387 0.0050 Paved Areas 20 1.41 4.56 13.31 0.0050 14.24 13.31
D1 D1 60.0% 0.84 6.469 42 0.0050 4.01 776 0.0050 Paved Areas 20 1.41 9.15 13.15 0.0050 16.30 13.15
D2 D2 54.8% 0.79 3.694 115 0.0050 7.77 285 0.0050 Paved Areas 20 1.41 3.36 11.13 0.0050 13.52 11.13
E1 E1 60.0% 0.84 1.144 42 0.0050 4.01 348 0.0050 Paved Areas 20 1.41 4.10 8.11 0.0050 12.48 8.11
E2 E2 60.0% 0.84 5.979 42 0.0050 4.01 1132 0.0050 Paved Areas 20 1.41 13.34 17.35 0.0050 19.48 17.35
HD2 Historic D2 13.5% 0.43 3.694 300 0.0048 27.75 478 0.0029 Tilage/Field 5 0.27 29.44 57.19 0.0036 30.08 30.08
August 22, 2018
Northfield
DEVELOPED TIME OF CONCENTRATION
L. Johnson
Interwest Consulting Group
1282-168-03
LENGTH
(ft)
DESIGN CRITERIA:
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
Overland Flow Equations for City of Fort Collins - Storm Water Criteria Manual
SUB-BASIN DATA
INITIAL/OVERLAND TIME
(ti)
TRAVEL TIME (tt)
tc
=ti
+tt
(min)
Urban Check Final
tc
(min)
DESIGN
POINT
Sub-basin
%
Impervious
C100
AREA
(acres)
tt
(min)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS: I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs) P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-2yr = 0.82 in
A n = Basin drainage area (ac) P 1-10yr = 1.40 in
P 1-100yr = 2.86 in
BASIN SUMMARY:
tc (min)
Runoff Coeff
(C2-10)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s) tc (min)
Runoff Coeff
(C2-10)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s) tc (min)
Runoff Coeff.
(C100)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s)
A1 A1 8.388 19.05 0.67 5.62 1.65 9.28 19.05 0.67 5.62 2.82 15.84 17.12 0.84 7.02 6.08 42.69
A2 A2 9.603 18.74 0.67 6.43 1.66 10.71 18.74 0.67 6.43 2.84 18.29 16.80 0.84 8.04 6.14 49.34
B1 B1 7.157 17.31 0.67 4.80 1.73 8.31 17.31 0.67 4.80 2.96 14.19 15.38 0.84 5.99 6.40 38.38
B2 B2 3.653 9.72 0.67 2.45 2.24 5.48 9.72 0.67 2.45 3.82 9.35 7.79 0.84 3.06 8.47 25.91
B3 B3 9.954 16.06 0.67 6.67 1.80 11.99 16.06 0.67 6.67 3.07 20.47 16.06 0.84 8.34 6.27 52.28
C1 C1 1.087 14.05 0.67 0.73 1.91 1.39 14.05 0.67 0.73 3.27 2.38 13.06 0.84 0.91 6.90 6.29
C2 C2 1.391 14.24 0.67 0.93 1.90 1.77 14.24 0.67 0.93 3.25 3.03 13.31 0.84 1.16 6.85 7.97
D1 D1 6.469 15.71 0.67 4.33 1.82 7.88 15.71 0.67 4.33 3.10 13.45 13.15 0.84 5.42 6.88 37.29
D2 D2 3.694 13.52 0.63 2.34 1.95 4.56 13.52 0.63 2.34 3.33 7.79 11.13 0.79 2.93 7.40 21.65
E1 E1 1.144 10.67 0.67 0.77 2.16 1.65 10.67 0.67 0.77 3.68 2.82 8.11 0.84 0.96 8.35 8.00
E2 E2 5.979 19.48 0.67 4.01 1.63 6.54 19.48 0.67 4.01 2.79 11.16 17.35 0.84 5.01 6.04 30.23
HD2 Historic D2 3.694 30.08 0.34 1.27 1.28 1.63 30.08 0.34 1.27 2.19 2.79 30.08 0.43 1.59 4.47 7.11
10-yr Peak Runoff 100-yr Peak Runoff
Northfield
DEVELOPED PEAK RUNOFF
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
DESIGN CRITERIA:
Design
Point
Sub-basin Area (acres)
L. Johnson
Interwest Consulting Group
1282-168-03
August 22, 2018
2-yr Peak Runoff
Q n = C n I n A n
(0.786651)
1
( 10 )
28 . 5
Appendix C
APPENDIX C – DETENTION POND CALCULATIONS
Basin
Req'd
WQCV
(ac-ft)
Req'd
Detention
Volume (ac-ft)
Total Volume
Req'd
(ac-ft)
Total Volume
Provided
(ac-ft)
A Basins 0.42 3.99 4.41 4.72
B Basins 0.49 4.60 5.09 3.43
C Basins 0.06 0.55 0.61 1.96
10.11 10.11
D Basins 0.23 1.24 1.47 2.07
L.Johnson
Interwest Consulting Group
1282-163-03
August 22, 2018
North of Suniga
South of Suniga
Total
Pond Summary
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
Pond Summary Table
1282-168-03 PondCalcs.xls - Pond Summary Page 1 of 5 Interwest Consulting Group
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
17.991 acres 173,707 3.99
3.60 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 149.92 44,977 1,079 43,897 1.01
10 7.72 116.32 69,793 2,159 67,634 1.55
15 6.52 98.24 88,416 3,238 85,178 1.96
20 5.60 84.38 101,254 4,318 96,936 2.23
25 4.98 75.04 112,554 5,397 107,157 2.46
30 4.52 68.11 122,589 6,477 116,112 2.67
35 4.08 61.48 129,098 7,556 121,542 2.79
40 3.74 56.35 135,246 8,636 126,610 2.91
45 3.46 52.13 140,761 9,715 131,046 3.01
50 3.23 48.67 146,004 10,795 135,210 3.10
55 3.03 45.65 150,660 11,874 138,786 3.19
60 2.86 43.09 155,135 12,954 142,182 3.26
65 2.72 40.98 159,836 14,033 145,803 3.35
70 2.59 39.02 163,904 15,112 148,792 3.42
75 2.48 37.37 168,153 16,192 151,961 3.49
80 2.38 35.86 172,131 17,271 154,860 3.56
85 2.29 34.50 175,973 18,351 157,623 3.62
90 2.21 33.30 179,816 19,430 160,385 3.68
95 2.13 32.09 182,935 20,510 162,425 3.73
100 2.06 31.04 186,234 21,589 164,645 3.78
105 2.00 30.14 189,851 22,669 167,182 3.84
110 1.94 29.23 192,924 23,748 169,176 3.88
115 1.89 28.48 196,495 24,828 171,668 3.94
120 1.84 27.72 199,614 25,907 173,707 3.99
125 1.79 26.97 202,281 26,987 175,295 4.02
130 1.75 26.37 205,672 28,066 177,605 4.08
135 1.71 25.77 208,700 29,146 179,555 4.12
140 1.67 25.16 211,367 30,225 181,142 4.16
145 1.63 24.56 213,672 31,304 182,368 4.19
150 1.60 24.11 216,972 32,384 184,588 4.24
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
20.765 acres 200,487 4.60
4.15 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 173.03 51,910 1,246 50,665 1.16
10 7.72 134.25 80,552 2,492 78,061 1.79
15 6.52 113.39 102,047 3,738 98,309 2.26
20 5.60 97.39 116,864 4,984 111,880 2.57
25 4.98 86.60 129,906 6,229 123,677 2.84
30 4.52 78.60 141,489 7,475 134,013 3.08
35 4.08 70.95 149,001 8,721 140,280 3.22
40 3.74 65.04 156,096 9,967 146,129 3.35
45 3.46 60.17 162,461 11,213 151,248 3.47
50 3.23 56.17 168,513 12,459 156,054 3.58
55 3.03 52.69 173,887 13,705 160,182 3.68
60 2.86 49.74 179,052 14,951 164,101 3.77
65 2.72 47.30 184,478 16,196 168,281 3.86
70 2.59 45.04 189,173 17,442 171,731 3.94
75 2.48 43.13 194,077 18,688 175,389 4.03
80 2.38 41.39 198,668 19,934 178,734 4.10
85 2.29 39.82 203,103 21,180 181,923 4.18
90 2.21 38.43 207,537 22,426 185,111 4.25
95 2.13 37.04 211,137 23,672 187,465 4.30
100 2.06 35.82 214,946 24,918 190,028 4.36
105 2.00 34.78 219,119 26,164 192,956 4.43
110 1.94 33.74 222,667 27,409 195,258 4.48
115 1.89 32.87 226,789 28,655 198,133 4.55
120 1.84 32.00 230,388 29,901 200,487 4.60
125 1.79 31.13 233,466 31,147 202,319 4.64
130 1.75 30.43 237,379 32,393 204,986 4.71
135 1.71 29.74 240,875 33,639 207,236 4.76
140 1.67 29.04 243,953 34,885 209,068 4.80
145 1.63 28.35 246,614 36,131 210,483 4.83
150 1.60 27.82 250,422 37,376 213,046 4.89
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Detention Volume Calculation - C Basins
0.67
1.25
0.84 ft3 acre-ft
2.478 acres 23,924 0.55
0.50 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 20.65 6,194 149 6,046 0.14
10 7.72 16.02 9,612 297 9,315 0.21
15 6.52 13.53 12,177 446 11,731 0.27
20 5.60 11.62 13,945 595 13,351 0.31
25 4.98 10.33 15,502 743 14,758 0.34
30 4.52 9.38 16,884 892 15,992 0.37
35 4.08 8.47 17,780 1,041 16,740 0.38
40 3.74 7.76 18,627 1,189 17,438 0.40
45 3.46 7.18 19,386 1,338 18,048 0.41
50 3.23 6.70 20,109 1,487 18,622 0.43
55 3.03 6.29 20,750 1,635 19,114 0.44
60 2.86 5.94 21,366 1,784 19,582 0.45
65 2.72 5.64 22,014 1,933 20,081 0.46
70 2.59 5.37 22,574 2,081 20,493 0.47
75 2.48 5.15 23,159 2,230 20,929 0.48
80 2.38 4.94 23,707 2,379 21,328 0.49
85 2.29 4.75 24,236 2,527 21,709 0.50
90 2.21 4.59 24,765 2,676 22,089 0.51
95 2.13 4.42 25,195 2,825 22,370 0.51
100 2.06 4.27 25,649 2,973 22,676 0.52
105 2.00 4.15 26,147 3,122 23,025 0.53
110 1.94 4.03 26,571 3,271 23,300 0.53
115 1.89 3.92 27,063 3,419 23,643 0.54
120 1.84 3.82 27,492 3,568 23,924 0.55
125 1.79 3.71 27,859 3,717 24,143 0.55
130 1.75 3.63 28,326 3,865 24,461 0.56
135 1.71 3.55 28,744 4,014 24,729 0.57
140 1.67 3.47 29,111 4,163 24,948 0.57
145 1.63 3.38 29,428 4,311 25,117 0.58
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.66
1.25
0.83 ft3 acre-ft
10.163 acres 53,806 1.24
9.15 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 83.42 25,027 2,744 22,284 0.51
10 7.72 64.73 38,837 5,488 33,349 0.77
15 6.52 54.67 49,200 8,232 40,968 0.94
20 5.60 46.95 56,343 10,976 45,368 1.04
25 4.98 41.75 62,631 13,719 48,912 1.12
30 4.52 37.90 68,215 16,463 51,752 1.19
35 4.08 34.21 71,838 19,207 52,630 1.21
40 3.74 31.36 75,258 21,951 53,307 1.22
45 3.46 29.01 78,327 24,695 53,632 1.23
50 3.23 27.08 81,245 27,439 53,806 1.24
55 3.03 25.40 83,836 30,183 53,653 1.23
60 2.86 23.98 86,326 32,927 53,399 1.23
65 2.72 22.81 88,942 35,670 53,271 1.22
70 2.59 21.72 91,205 38,414 52,791 1.21
75 2.48 20.79 93,570 41,158 52,412 1.20
80 2.38 19.95 95,783 43,902 51,881 1.19
85 2.29 19.20 97,921 46,646 51,275 1.18
90 2.21 18.53 100,059 49,390 50,670 1.16
95 2.13 17.86 101,795 52,134 49,661 1.14
100 2.06 17.27 103,631 54,878 48,754 1.12
105 2.00 16.77 105,643 57,622 48,022 1.10
110 1.94 16.27 107,354 60,365 46,988 1.08
115 1.89 15.85 109,341 63,109 46,232 1.06
120 1.84 15.43 111,076 65,853 45,223 1.04
125 1.79 15.01 112,561 68,597 43,963 1.01
130 1.75 14.67 114,447 71,341 43,106 0.99
135 1.71 14.34 116,132 74,085 42,047 0.97
140 1.67 14.00 117,616 76,829 40,788 0.94
145 1.63 13.67 118,899 79,573 39,327 0.90
150 1.60 13.42 120,735 82,316 38,419 0.88
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 17.991 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.425 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond A1
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4948.00 0 0.00 0.00 0.00 0.00
4949.0 22759 0.52 0.17 1.00 0.17
4950.0 65432 1.50 0.97 2.00 1.14
4951.0 81095 1.86 1.68 3.00 2.82
4951.6 86080 1.98 1.15 3.60 3.97
Pond A2
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4950.21 0 0.00 0.00 0.00 0.00
4951.0 6116 0.14 0.04 0.79 0.04
4952.0 15342 0.35 0.24 1.79 0.28
4953.0 18370 0.42 0.39 2.79 0.66
4953.2 18809 0.43 0.09 2.99 0.75
Critical Pond Elevations - A Basins
L.Johnson
Interwest Consulting Group
1282-163-03
August 22, 2018
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
=
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 20.765 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.490 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond B1
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4949.00 0 0.00 0.00 0.00 0.00
4950.0 9,697 0.22 0.07 1.00 0.07
4951.0 28,631 0.66 0.42 2.00 0.49
4952.0 48,045 1.10 0.87 3.00 1.37
4953.0 68,191 1.57 1.33 4.00 2.69
Pond B2
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4952.04 0 0.00 0.00 0.00 0.00
4953.0 8,592 0.20 0.06 0.96 0.06
4954.0 23,159 0.53 0.35 1.96 0.41
4954.5 32,929 0.76 0.32 2.46 0.73
Critical Pond Elevations - B Basins
L.Johnson
Interwest Consulting Group
1282-163-03
August 22, 2018
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 2.478 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.059 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond C1
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4953.20 0 0.00 0.00 0.00 0.00
4954.0 2345 0.05 0.01 0.80 0.01
4955.0 16096 0.37 0.19 1.80 0.20
4956.0 20990 0.48 0.42 2.80 0.63
4957.0 24661 0.57 0.52 3.80 1.15
4958.0 28514 0.65 0.61 4.80 1.76
4958.3 29724 0.68 0.20 5.10 1.96
Critical Pond Elevations - C Basins
L.Johnson
Interwest Consulting Group
1282-163-03
August 22, 2018
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
=
1282-168-03 PondCalcs.xls - Pond Stage (Prelim C) Page 4 of 5 Interwest Consulting Group
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 10.163 acres
Imperviousness, I 58.1%
WQCV (watershed inches) 0.230 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.234 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond D
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4948.00 0 0.00 0.00 0.00 0.00
4949.0 18909 0.43 0.14 1.00 0.14
4950.0 42621 0.98 0.69 2.00 0.83
4951.0 46562 1.07 1.02 3.00 1.86
4951.2 47220 1.08 0.22 3.20 2.07
Critical Pond Elevations - D Basins
L.Johnson
Interwest Consulting Group
1282-163-03
August 22, 2018
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
=
1282-168-03 PondCalcs.xls - Pond Stage (Prelim D) Page 5 of 5 Interwest Consulting Group
Appendix D
APPENDIX D – STREET CAPACITIES
CONNECTOR LOCAL
NTS
MAJOR ARTERIAL
NTS
1218 W. Ash, Suite A
Windsor , Colorado 80550
Phone: (970) 674-3300
Fax: (970) 674-3303
I N T E R W E S T C O N S U L T I N G G R O U P
PREPARED FOR
PROJ. NO.
DATE:
SCALE (H):
SCALE (V):
CHECKED BY:
DESIGNED BY:
PROJECT NAME
NORTHFIELD
STREET CAPACITY EXHIBIT
08/22/18
1"=10'
1"=1'
LAJ
JTC
1282-168-03
1 of 1
1170 ASH STREET, SUITE 100
WINDSOR, CO 80550
OFFICE: 970.460.0567
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 19.5 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.015
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 = 0.020 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 = 0.005 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.015
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 18.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 5.8 10.5 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 = 9.5 61.8 cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Northfield
Connector Local
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
1282-168-03 Inlet Calcs_Connector Local.xlsm, Inlet 1 8/21/2018, 5:11 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 13.8 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.015
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 32.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 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 = 0.005 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.015
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 18.67 32.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 9.2 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Spread Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 10.3 45.4 cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Northfield
Major Arterial
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
1282-168-03 Inlet Calcs_Major Arterial.xlsm, Inlet 1 8/21/2018, 5:13 PM
Appendix E
APPENDIX E – LOW IMPACT DEVELOPMENT CALCULATIONS
Northfield
Low Impact Development
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Low Impact Development Summary
Sq-Ft Acres % Impervious Impervious Area (ft
2
)
% of Impervious Area
Requiring Treatment
Impervious Area
Requiring Treatment
512,841 11.77 60% 307,704 50% 153,852
1,227,884 28.19 60% 736,731 75% 552,548
107,764 2.47 90% N/A 75% (future treatment) N/A
304,152 6.98 60% 182,491 0% N/A
360,777 8.28 0% 0 0% N/A
2,513,418 57.70 1,226,927 - 706,400
Infiltrator Depth &
Area (ft
2
)
2 ft
A2 418,325 60% 250,995 Infiltration Gallery 0.19 0.43 6,586 3,293
B2 159,134 60% 95,480 Infiltration Gallery 0.19 0.43 2,505 1,253
B3 433,610 60% 260,166 Infiltration Gallery 0.19 0.43 6,827 3,413
D1 286,887 60% 172,132 Rain Garden 0.19 0.43 4,517 -
706,400
778,773
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped impervious area using one or a combination of LID techniques, or
- Treat at least 50% of any newly developed or redeveloped impervious area using one or a combination of LID techniques when 25% of private driveable surfaces are permeable.
L. Johnson
Interwest Consulting Group
1282-168-03
August 22, 2018
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Development Area Breakdown
Area Drainage to
LID (ft
2
)
% Impervious
Totals
Description
Single Family Area
Multifamily Area
Commercial Area (future treatment)
Suniga (no treatment)
Detention / Landscape Areas (no treatment)
Total Impervious Area Treated (ft2)
Total Impervious Area Required for Treatment (ft2)
Basin(s)
Treatment Areas
Summary
Req'd WQCV
(12 hr Release Rate)
(cu-ft)
Depth of Average Runoff
Producing Storm
(watershed inches)
WQCV
(watershed
inches)
Impervious Area
Treated (ft
2
)
Treatment Method
=
1282-168-03 PondCalcs.xls - Pond Stage (Prelim B) Page 3 of 5 Interwest Consulting Group
1282-168-03 PondCalcs.xls - Pond Stage (Prelim A) Page 2 of 5 Interwest Consulting Group
155 1.57 13.16 122,421 85,060 37,360 0.86
160 1.54 12.91 123,955 87,804 36,151 0.83
165 1.51 12.66 125,338 90,548 34,790 0.80
170 1.48 12.41 126,571 93,292 33,279 0.76
175 1.45 12.16 127,652 96,036 31,617 0.73
180 1.42 11.91 128,583 98,780 29,803 0.68
185 1.40 11.74 130,294 101,524 28,770 0.66
190 1.38 11.57 131,903 104,268 27,636 0.63
195 1.36 11.40 133,413 107,011 26,401 0.61
200 1.34 11.24 134,821 109,755 25,066 0.58
205 1.32 11.07 136,129 112,499 23,630 0.54
210 1.30 10.90 137,336 115,243 22,093 0.51
215 1.28 10.73 138,443 117,987 20,456 0.47
220 1.26 10.56 139,449 120,731 18,718 0.43
225 1.24 10.40 140,355 123,475 16,880 0.39
230 1.22 10.23 141,160 126,219 14,941 0.34
235 1.21 10.15 143,046 128,962 14,084 0.32
240 1.20 10.06 144,882 131,706 13,176 0.30
Adjusted Runoff Coefficient (CC f )
Area (A )
Allowed Release Rate
Required Detention
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
City of Fort Collins - Storm Water Criteria Manual
Detention Volume Calculation - D1 Basin
August 22, 2018
Runoff Coefficient (C )
Frequency Factor (C f )
100-yr Detention Volume - FAA Method
Northfield
L. Johnson
Interwest Consulting
1282-168-03
150 1.60 3.32 29,883 4,460 25,423 0.58
155 1.57 3.26 30,300 4,609 25,691 0.59
160 1.54 3.20 30,680 4,757 25,922 0.60
165 1.51 3.13 31,022 4,906 26,116 0.60
170 1.48 3.07 31,327 5,055 26,272 0.60
175 1.45 3.01 31,595 5,203 26,391 0.61
180 1.42 2.95 31,825 5,352 26,473 0.61
185 1.40 2.91 32,249 5,501 26,748 0.61
190 1.38 2.86 32,647 5,649 26,997 0.62
195 1.36 2.82 33,020 5,798 27,222 0.62
200 1.34 2.78 33,369 5,947 27,422 0.63
205 1.32 2.74 33,693 6,095 27,597 0.63
210 1.30 2.70 33,992 6,244 27,748 0.64
215 1.28 2.66 34,266 6,393 27,873 0.64
220 1.26 2.61 34,515 6,542 27,973 0.64
225 1.24 2.57 34,739 6,690 28,049 0.64
230 1.22 2.53 34,938 6,839 28,099 0.65
235 1.21 2.51 35,405 6,988 28,417 0.65
240 1.20 2.49 35,859 7,136 28,723 0.66
Area (A )
Allowed Release Rate
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
City of Fort Collins - Storm Water Criteria Manual
Runoff Coefficient (C )
Frequency Factor (C f ) Required Detention
Adjusted Runoff Coefficient (CC f )
August 22, 2018
Northfield
100-yr Detention Volume - FAA Method
L. Johnson
Interwest Consulting
1282-168-03
155 1.57 27.30 253,918 38,622 215,295 4.94
160 1.54 26.78 257,100 39,868 217,232 4.99
165 1.51 26.26 259,969 41,114 218,855 5.02
170 1.48 25.74 262,526 42,360 220,166 5.05
175 1.45 25.22 264,769 43,606 221,163 5.08
180 1.42 24.69 266,700 44,852 221,848 5.09
185 1.40 24.35 270,247 46,098 224,150 5.15
190 1.38 24.00 273,586 47,343 226,243 5.19
195 1.36 23.65 276,716 48,589 228,127 5.24
200 1.34 23.30 279,638 49,835 229,803 5.28
205 1.32 22.96 282,351 51,081 231,270 5.31
210 1.30 22.61 284,855 52,327 232,528 5.34
215 1.28 22.26 287,151 53,573 233,578 5.36
220 1.26 21.91 289,238 54,819 234,419 5.38
225 1.24 21.56 291,116 56,065 235,051 5.40
230 1.22 21.22 292,785 57,311 235,475 5.41
235 1.21 21.04 296,698 58,556 238,142 5.47
240 1.20 20.87 300,507 59,802 240,704 5.53
Area (A )
Allowed Release Rate
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
City of Fort Collins - Storm Water Criteria Manual
Runoff Coefficient (C )
Frequency Factor (C f ) Required Detention
Adjusted Runoff Coefficient (CC f )
Detention Volume Calculation - B Basins
August 22, 2018
Northfield
100-yr Detention Volume - FAA Method
L. Johnson
Interwest Consulting
1282-168-03
155 1.57 23.66 220,001 33,463 186,537 4.28
160 1.54 23.20 222,758 34,543 188,215 4.32
165 1.51 22.75 225,244 35,622 189,622 4.35
170 1.48 22.30 227,459 36,702 190,757 4.38
175 1.45 21.85 229,403 37,781 191,622 4.40
180 1.42 21.40 231,075 38,861 192,215 4.41
185 1.40 21.09 234,149 39,940 194,209 4.46
190 1.38 20.79 237,042 41,020 196,022 4.50
195 1.36 20.49 239,754 42,099 197,655 4.54
200 1.34 20.19 242,286 43,179 199,107 4.57
205 1.32 19.89 244,636 44,258 200,378 4.60
210 1.30 19.59 246,806 45,337 201,468 4.63
215 1.28 19.29 248,795 46,417 202,378 4.65
220 1.26 18.99 250,603 47,496 203,106 4.66
225 1.24 18.68 252,230 48,576 203,654 4.68
230 1.22 18.38 253,677 49,655 204,021 4.68
235 1.21 18.23 257,067 50,735 206,332 4.74
240 1.20 18.08 260,367 51,814 208,552 4.79
Area (A )
Allowed Release Rate
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
City of Fort Collins - Storm Water Criteria Manual
Runoff Coefficient (C )
Frequency Factor (C f ) Required Detention
Adjusted Runoff Coefficient (CC f )
Detention Volume Calculation - A Basins
August 22, 2018
Northfield
100-yr Detention Volume - FAA Method
L. Johnson
Interwest Consulting
1282-168-03
t c
P
I
+
=
1282-168-03 Rational Calcs (FC).xlsx Page 4 of 4 Interwest Consulting Group
OVERALL SLOPE
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
��
=
1.87(1.1 − ��
��
) �
� �
1282-168-03 Rational Calcs (FC).xlsx Page 3 of 4 Interwest Consulting Group
OVERALL SLOPE
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
��
=
1.87(1.1 − ��
��
) �
� �
1282-168-03 Rational Calcs (FC).xlsx Page 2 of 4 Interwest Consulting Group
Atotal
(acres)
Weighted %
Impervious
A COMPOSITE
paved
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
1282-168-03 Rational Calcs (FC).xlsx Page 1 of 4 Interwest Consulting Group
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
BFE (FEMA)
CROSS-SECTION (FEMA)
100-YR FLOODPLAIN (FEMA)
0
100'
100 50 100 200
SCALE: 1" =
AH
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 5.0 4952.3 4958.3 6.5 4947.7 4953.7 7.0 4949.1 4955.1
7/27/2017 6.0 4951.3 4957.3 6.8 4947.4 4953.4 7.2 4948.9 4954.9
9/19/2017 7.0 4950.3 4956.3 6.7 4947.5 4953.5 7.3 4948.8 4954.8
10/19/2017 7.1 4950.2 4956.2 6.6 4947.6 4953.6 7.3 4948.8 4954.8
2/12/2017 8.8 4948.5 4954.5 8.0 4946.2 4952.2 8.9 4947.2 4953.2
6/7/2018 5.1 4952.2 4958.2 7.2 4947.0 4953.0 7.0 4949.1 4955.1
4957.3 4954.2 4956.1
4953.5
PZ-7
PZ-4
4953.2
4954.6 4951.8 4956.5
4956.1
MW-1 MW-2 PZ-1
PZ-2 PZ-3
PZ-5 PZ-6
Northfield - (AKA Schalagel Property)
Earth Engineering Consultants, LLC (EEC) - Project No. 1172056
Groundwater Monitoring - Summary Table
18.5 ac
8.7 ac
29.3 ac
11.4 ac
9.8 ac
11.4 ac
4.8 ac
16.4 ac
3.3 ac
1.3 ac
31.6 ac
52.7 ac
21.3 ac
7.4 ac
18.1 ac
17.0 ac
2.5 ac
2.7 ac
2.0 ac
4.6 ac
2.5 ac
13.1 ac
3.9 ac
13.7 ac
1.8 ac
0.2 ac
7.2 ac
6.0 ac
3.8 ac
0.6 ac
2.4 ac
5.2 ac
1.6 ac
2.6 ac
35.7 ac
2.6 ac
1.8 ac
1.8 ac
1.6 ac
1.2 ac
0.7 ac
4.2 ac
2.6 ac
13.6 ac
13.0 ac
8.6 ac
7.1 ac
5.1 ac
4.5 ac
4.2 ac
10.9 ac
8.2 ac
19.2 ac
16.0 ac
32.4 ac
17.5 ac
9.8 ac
16.6 ac
29.3 ac
6.0 ac
10.3 ac
5.9 ac
1.5 ac 1.3 ac
21.2 ac
1.ac5 ac 1.2
1.1 ac
1.1 ac
8.2 ac
1.0 ac
8.6 ac
5.2 ac
14.8 ac
2.0 ac
1.6 ac
3.3 ac
1.4 ac 5.3 ac
1.2 ac
1.0 ac
2.7 ac 2.2 ac
3.9 ac
3.3 ac
3.4 ac
4.4 ac
7.9 ac
0.2 ac
4.2 ac
1.1 ac 1.7 ac
2.4 ac
2.0 ac
1.0 ac
36.2 ac
5.5 ac
49.1 ac
APPROX NORTHFIELD
PROPRETY LINE
38 1.11 1.89 3.87 1.11 0.00 1.90 0.01 3.88 0.01
39 1.09 1.86 3.80 1.09 0.00 1.87 0.01 3.82 0.02
40 1.07 1.83 3.74 1.08 0.01 1.84 0.01 3.76 0.02
41 1.05 1.80 3.68 1.06 0.01 1.81 0.01 3.70 0.02
42 1.04 1.77 3.62 1.04 0.00 1.78 0.01 3.64 0.02
43 1.02 1.74 3.56 1.03 0.01 1.76 0.02 3.59 0.03
44 1.01 1.72 3.51 1.01 0.00 1.73 0.01 3.54 0.03
45 0.99 1.69 3.46 1.00 0.01 1.71 0.02 3.48 0.02
46 0.98 1.67 3.41 0.99 0.01 1.68 0.01 3.44 0.03
47 0.96 1.64 3.36 0.97 0.01 1.66 0.02 3.39 0.03
48 0.95 1.62 3.31 0.96 0.01 1.64 0.02 3.34 0.03
49 0.94 1.60 3.27 0.95 0.01 1.61 0.01 3.30 0.03
50 0.92 1.58 3.23 0.93 0.01 1.59 0.01 3.25 0.02
51 0.91 1.56 3.18 0.92 0.01 1.57 0.01 3.21 0.03
52 0.90 1.54 3.14 0.91 0.01 1.55 0.01 3.17 0.03
53 0.89 1.52 3.10 0.90 0.01 1.53 0.01 3.13 0.03
54 0.88 1.50 3.07 0.89 0.01 1.51 0.01 3.09 0.02
55 0.87 1.48 3.03 0.88 0.01 1.50 0.02 3.06 0.03
56 0.86 1.47 2.99 0.87 0.01 1.48 0.01 3.02 0.03
57 0.85 1.45 2.96 0.86 0.01 1.46 0.01 2.98 0.02
58 0.84 1.43 2.92 0.85 0.01 1.44 0.01 2.95 0.03
59 0.83 1.42 2.89 0.84 0.01 1.43 0.01 2.92 0.03
60 0.82 1.40 2.86 0.83 0.01 1.41 0.01 2.88 0.02
0.00 -0.02 0.00
C 3
2
1 1
( c )
C t
C P
I
+
=
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 12, Oct 10, 2017
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2015—Oct
15, 2016
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
(NorthField)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/6/2017
Page 2 of 4