HomeMy WebLinkAboutNORTHFIELD FILING 1 - PDP - PDP170041 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
FOR
Northfield – Filing 1
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
December 13, 2017
Job Number 1282-168-03
1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
December 13, 2017
Ms. Heather McDowell
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Preliminary Drainage Report for Northfield – Filing 1
Dear Heather,
We are pleased to submit for your review, the Preliminary Drainage Report for the Northfield –
Filing 1 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 ................................................................................................................ 8
Drainage Conveyance Design ..................................................................................................... 8
Detention/Water Quality Pond Design ........................................................................................ 8
Low Impact Development ............................................................................................................. 10
Stormwater Pollution Prevention .................................................................................................. 12
Conclusions ................................................................................................................................... 13
References ..................................................................................................................................... 14
Appendix ....................................................................................................................................... 15
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
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ENGINEER’S CERTIFICATION BLOCK
I hereby certify that this Preliminary Drainage Report for Northfield – Filing 1 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 – Filing 1 is the first phase of the ultimate subdivision and will consist of 112
single family attached (fee simple) units and 84 condominium units. There is an Overall
Development Plan (ODP) being submitted concurrently with this Project Development Plan
(PDP). This report is intended to include the preliminary drainage design for the Northfield
Filing 1 PDP and conceptual design review for future phases for the Northfield ODP.
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 – Filing 1 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 Northfield – Filing 1 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 to be 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 Northfield – Filing 1 improvements, a floodplain development permit will be
required. No residential units are proposed within the 100-yr floodplain limits with Northfield –
Filing 1. It is anticipated that the floodplain limits will be adjusted prior to future development
submittals and/or buildings will be elevated above the Regulatory Base Floodplain Elevation and
adhering to LUC Chapter 10 requirements. A large portion of the site is located within the
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Cache la Poudre River 500-yr floodplain limiting any critical facilities being constructed on the
site.
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 Ground water 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. Further investigation of the percolation
rates of the deeper soils are anticipated with the final design and drainage report.
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 is continuing to monitor the groundwater level depths over the 12 month period after the
original borings. Based on the couple observations to date, there has not been a significant
change in groundwater elevations. Groundwater elevations are taken into consideration for the
pond bottoms and building foundations.
Supporting figures can be found in the Appendix A.
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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 USDCM Equation 6-5 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 – Filing 1 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 a Major Arterial will not top the curb and the flow spread will leave at least
one 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 that will not inundate the
ground line of structures and shall not exceed 6” depth at the roadway centerline, and for the
Major Arterial will be held to a maximum depth that will not inundate the ground line of
structures and shall not exceed 6” depth at the roadway centerline or 18” depth at the gutter
flowline.
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
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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.
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DRAINAGE BASINS
The Northfield – Filing 1 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 not completed since
the Filing 1 proposed improvements are within basins that are restricted to 0.2 cfs/acre release
rate. The conceptual future filing improvements and associated drainage basins are delineated
for planning purposes. 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 10.63 acres of single-family attached residential lots, public
roadways and private drives. The basin includes portion of Schlagel Street, Pioneer Trail
Road, Snyder Drive, Harvest Sun Street and Landmark Way Road. Flows from this basin is
mainly conveyed along said roadways and will be collected by a Type R inlets and a
sidewalk culvert, ultimately to detention Pond A1. Future phases will construct much of
Drainage System A storm infrastructure. During the interim condition, runoff will be
conveyed south via open swales to detention Pond A1.
The remaining undeveloped area of Filing 1 will continue to follow the historic drainage
pattern southeasterly across the site. The swales will capture these flows coming from
undeveloped areas to the northwest, and the rest of the undeveloped basin will continue the
historic drainage pattern southeasterly across the site.
Sub-basin A2 consists of 0.81 acres of future private drives and multifamily residential
buildings. This basin will remain undeveloped with the Filing 1 and during the interim
condition will continue to follow the historic drainage patterns southeasterly across the site.
Most of the basin will be intercepted by the interim swale, conveying runoff to detention
Pond A1.
Sub-basin A3 consists of 2.13 acres and includes future multifamily residential buildings
and private drives. This basin will remain undeveloped with Filing 1 and will continue to
follow the historic drainage pattern southeasterly across the site.
Sub-basin A4 consists of 3.42 acres of future single-family attached residential lots,
multifamily residential buildings, public roadways and private drives. This basin will remain
undeveloped with Filing 1 and will continue to follow the historic drainage patterns southerly
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along N. Lemay Ave. A portion of N. Lemay Ave will be improved to accommodate the
intersection with Suniga Rd. Runoff from these improvements will be collected by two Type
R sump inlets and conveyed to the NECCO reinforced concrete box culvert storm drain
without detention.
Sub-basin A5 consists of 2.64 acres of future multifamily residential buildings, private
drives and detention Pond A1. This basin will remain mainly undeveloped with Filing 1. The
basin will continue to follow the historic drainage patterns southeasterly across the site, with
the exception of the runoff captured by the interim detention pond.
Drainage System B:
Drainage System B mainly pertains to the improvements west of Drainage System A basins.
This basin’s improvements are proposed with this current filing.
Sub-basin B1 consists of 5.24 acres of single-family attached residential lots, public
roadways and private drives. Runoff is mainly conveyed along Schlagel St and private
drives, captured by a Type R sidewalk culvert and area inlets. Runoff is then conveyed to
Pond B4 and ultimately to detention Pond B1 via storm drain pipes.
Sub-basin B2 consists of 3.29 acres of single-family attached residential lots, the community
clubhouse, public roadways and private drives. Runoff is conveyed along Schlagel St,
Snyder Dr, and the private drives, is captured by Type R inlets and area inlets. Runoff is
then conveyed to Pond B3 and ultimately to detention Pond B1 via storm drain pipes.
Sub-basin B3 consists of 2.38 acres of multifamily residential buildings and private drives.
Runoff is conveyed along the private drives and captured by area inlets. Runoff is then
conveyed to detention Pond B1 via storm drain pipes.
Sub-basin B4 consists of 4.30 acres of multifamily residential buildings, single-family
attached residential lots, public roadways and private drives. Runoff is conveyed along
Schlagel St and Harvest Sun Street to a sump Type R sidewalk culvert. Runoff is then
conveyed to Pond B2 and ultimately to detention Pond B1 via storm drain pipes. There is a
small portion of this basin that flows to a swale running southwesterly along the northwest
property line of the site. These flows are conveyed to a culvert pipe that runs underneath
Meadow Spring Drive and into the Sub-basin C of Drainage System C, where the swale
continues southwesterly to Pond C. (This basin will be detailed futher in the final drainage
report.)
Sub-basin B5 consists of 0.73 acres of multifamily residential buildings and public
roadways. Runoff is conveyed along Landmark Way Road and captured by Type R sump
inlets before the street intersects with Suniga Road. Runoff is then conveyed detention Pond
B1 via storm drain pipes.
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Sub-basin B6 consists of 2.55 acres of multifamily residential buildings and detention Pond
B1. Runoff is mainly conveyed by sheet flow to the detention pond. A concrete pan conveys
all of the collected flow to the outlet structure, restricting flows to the allowed release rate,
and ultimately to the existing NECCO reinforced concrete box culvert storm drain.
Drainage System C:
Drainage System C mainly consists of the area south of Meadow Spring Dr and a portion of
Schlagel St north of Suniga Rd. This basin’s improvements are proposed with this current
filing.
Sub-basin C1 consists of 1.39 acres of single-family attached residential lots and public
roadways. Runoff is conveyed along Meadow Spring Dr and Schlagel St to a Type R sump
inlet. Runoff captured by this inlet is then conveyed to Pond C via storm drain pipes.
Sub-basin C2 consists of 1.78 acres of single-family attached residential 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, and ultimately to the existing NECCO
reinforced concrete box culvert storm drain.
Drainage System D:
Drainage System D consists of the area south of Suniga Rd.
Sub-basin D1 consists of 9.21 acres of future multifamily residential buildings, a
commercial lot, public roadway, and private drives. This basin will remain undeveloped
with the Filing 1 and during the interim condition will continue to follow the historic
drainage patterns easterly across the site.
Sub-basin D2 consists of 0.91 acres of public roadway along N. Lemay Ave and Suniga Rd.
Runoff is conveyed along Suniga Rd and N. Lemay Ave to two Type R sump inlets. Runoff
captured by these inlets is conveyed to the existing NECCO reinforced concrete box culvert
storm drain, undetained.
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.
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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 – Filing 1. The EDBs are designed to reduce the 100-yr
developed runoff to the allow 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. Not all of the storm infrastructure shown on the Grading
& Drainage Plan will be constructed with this filing. Below is a description of the pond
networks:
Drainage System A:
Drainage System A is not proposed to be fully constructed with Filing 1. For planning purposes,
the ultimate and interim conditions were studied. This basin is 16.21 acres draining to the
detention pond, which allows a release rate of 3.24 cfs. Under the ultimate condition, 3.59 acre-
ft of detention storage is required with 0.383 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.
Under the interim condition, runoff from approximately 16.21 acres will be directed to the
detention pond, 1.44 acre-ft of detention storage is required with 0.275 acre-ft WQCV. This
volume will be achieved in a single pond north of Suniga Rd with a release rate of 3.24 cfs.
Drainage System B:
Drainage System B’s basin is 17.85 acres which allows a release rate of 3.57 cfs. This requires
3.96 acre-ft of detention storage volume with 0.422 acre-ft WQCV. To achieve the total
detention volume, a network of four detention ponds, Pond B1, Pond B2, Pond B3, and Pond B4,
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will provide the total 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 B1.
Drainage System C:
Drainage System C’s basin is 3.80 acres which allows a release rate of 0.76 cfs. This requires
0.84 acre-ft of detention storage volume with 0.090 acre-ft WQCV and is provided in Pond C1.
Drainage System D:
Drainage System D is not proposed to be constructed with Filing 1 with exception of the inlets
and storm drain constructed within N. Lemay Ave. Based on discussions with staff and the
existing impervious area associated with the existing N. Lemay Ave improvements, runoff from
Lemay is not required to be detained. This basin is 10.11 acres which allows a release rate of
2.02 cfs, requiring 2.24 acre-ft of detention storage 0.239 acre-ft WQCV. It should be noted that
the release rates and volumes above assume the 0.2 cfs/acre requirement. The area of the future
detention pond and commercial area are within a NECCO basin that restricts runoff rates to the
existing conditions. The release rate would likely increase and pond volumes reduced when this
is accounted for.
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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 area using one or a
combination of LID techniques, or
• Treat at least 50% of any newly developed or redeveloped 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 - Filing 1 will utilize below grade infiltration galleries. 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. Sumps
will be implemented at the headworks to the infiltration galleries to allow larger sediment
particle to settle prior to entering the infiltration gallery. The sumps 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.
Conceptual areas shown outside of the Filing 1 improvements are shown for planning purposes.
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.
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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.
Infiltration galleries 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 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.
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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.
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CONCLUSIONS
This Preliminary Drainage Report for Northfield – Filing 1 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 Filing 1 will adhere to the
allowed rates as established in the NECCO drainage studies. In this preliminary drainage report,
we have shown the conceptual future improvements for planning purposes and confirm that the
ultimate buildout of the Northfield future phases are appropriately anticipated. 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 – Filing 1 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.
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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 15
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.
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
Appendix B
APPENDIX B – RATIONAL CALCULATIONS
ONLY
ONLY
ONLY
ONLY
ONLY
ONLY
ONLY
lake canal
dry creek
lake canal
POND A1
POND A2
N. LEMAY AVENUE
SNYDER DRIVE
HARVEST SUN STREET
PIONEER TRAIL ROAD
MEADOW SPRING DRIVE
LANDMARK WAY ROAD
SCHLAGEL STREET
SCHLAGEL STREET
N. LEMAY AVENUE
SNYDER DRIVE
POND B1
POND B2
POND B3
POND B4
POND C
POND D
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
12/13/17
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
Northfield
DEVELOPED IMPERVIOUS AREA CALCULATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
BASINS:
%
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 463,045 10.630 60.0% 0.67 0.84
A2 35,384 0.812 60.0% 0.67 0.84
A3 92,687 2.128 60.0% 0.67 0.84
A4 148,850 3.417 60.0% 0.67 0.84
A5 115,077 2.642 60.0% 0.67 0.84
B1 228,242 5.240 60.0% 0.67 0.84
B2 143,112 3.285 60.0% 0.67 0.84
B3 103,867 2.384 60.0% 0.67 0.84
B4 187,106 4.295 60.0% 0.67 0.84
B5 31,832 0.731 60.0% 0.67 0.84
B6 110,921 2.546 60.0% 0.67 0.84
C1 60,327 1.385 60.0% 0.67 0.84
C2 77,729 1.784 60.0% 0.67 0.84
D1 401,014 9.206 60.0% 0.67 0.84
D2 39,433 0.905 60.0% 0.67 0.84
E1 49,549 1.137 60.0% 0.67 0.84
E2 263,309 6.045 60.0% 0.67 0.84
Overall 2,551,484 58.574 60.0% 0.67 0.84
A1 (interim) 463,045 10.630 16.2% 0.36 0.45
Interim Basins A
to Pond A1
706,193 16.212 10.6% 0.32 0.41
L. Johnson
Interwest Consulting Group
1282-168-03
December 13, 2017
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Land Use
Paved
Roof
Walks
Gravel/Pavers
Northfield
DEVELOPED TIME OF CONCENTRATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
-Equation 6-3
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
BASINS
Type of Travel
Surface
Cv
A1 A1 60.0% 0.67 10.630 300 0.0100 13.66 571 0.0061 Paved Areas 20 1.57 6.07 19.73 0.0075 15.36 15.36
A2 A2 60.0% 0.67 0.812 68 0.0201 5.14 186 0.0100 Paved Areas 20 2.00 1.55 6.69 0.0127 10.42 6.69
A3 A3 60.0% 0.67 2.128 227 0.0076 13.02 322 0.0050 Paved Areas 20 1.41 3.80 16.82 0.0061 13.45 13.45
A4 A4 60.0% 0.67 3.417 300 0.0100 13.66 1133 0.0035 Paved Areas 20 1.19 15.87 29.53 0.0049 21.94 21.94
A5 A5 60.0% 0.67 2.642 95 0.0630 4.16 330 0.0029 Paved Areas 20 1.07 5.14 9.31 0.0163 11.10 9.31
B1 B1 60.0% 0.67 5.240 133 0.0050 11.45 492 0.0058 Paved Areas 20 1.52 5.41 16.86 0.0056 14.28 14.28
B2 B2 60.0% 0.67 3.285 19 0.0265 2.45 362 0.0102 Paved Areas 20 2.02 2.98 5.43 0.0110 11.29 5.43
B3 B3 60.0% 0.67 2.384 300 0.0066 15.68 178 0.0066 Paved Areas 20 1.62 1.82 17.51 0.0066 12.71 12.71
B4 B4 60.0% 0.67 4.295 82 0.0329 4.79 373 0.0050 Paved Areas 20 1.41 4.42 9.21 0.0100 11.88 9.21
B5 B5 60.0% 0.67 0.731 60 0.0083 6.50 271 0.0169 Paved Areas 20 2.60 1.74 8.24 0.0154 10.69 8.24
B6 B6 60.0% 0.67 2.546 177 0.0343 6.95 688 0.0050 Paved Areas 20 1.41 8.10 15.06 0.0110 14.21 14.21
C1 C1 60.0% 0.67 1.385 24 0.0302 2.68 345 0.0090 Paved Areas 20 1.90 3.02 5.71 0.0104 11.28 5.71
C2 C2 60.0% 0.67 1.784 251 0.0214 9.69 561 0.0050 Paved Areas 20 1.41 6.62 16.31 0.0101 14.11 14.11
D1 D1 60.0% 0.67 9.206 300 0.0085 14.43 936 0.0058 Paved Areas 20 1.52 10.25 24.68 0.0064 18.72 18.72
D2 D2 60.0% 0.67 0.905 19 0.0274 2.43 384 0.0052 Paved Areas 20 1.44 4.45 6.89 0.0062 12.23 6.89
E1 E1 60.0% 0.67 1.137 43 0.0334 3.47 346 0.0062 Paved Areas 20 1.58 3.65 7.11 0.0093 11.55 7.11
E2 E2 60.0% 0.67 6.045 43 0.0331 3.47 1135 0.0073 Paved Areas 20 1.71 11.06 14.53 0.0083 17.18 14.53
A1
(interim)
A1 (interim) 16.2% 0.36 10.630 300 0.0090 24.20 945 0.0064 Grassed Waterway 15 1.20 13.16 37.36 0.0070 31.18 31.18
SUB-BASIN DATA
%
Impervious
Urban Check
tc
(min)
OVERALL SLOPE
(ft/ft)
TRAVEL TIME (tt)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
tt
(min)
AREA
(acres)
LENGTH
(ft)
REMARKS
Final
Northfield
DEVELOPED PEAK RUNOFF
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
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:
Runoff Coeff.
(C2
)
C(A)
(acres)
Intensity
(in/hr)
Q (ft
3
/s)
Runoff Coeff.
(C10
)
C(A)
(acres)
Intensity
(in/hr)
Q (ft
3
/s)
Runoff Coeff.
(C100
)
C(A)
(acres)
Intensity
(in/hr)
Q (ft
3
/s)
A1 A1 10.630 15.36 0.67 7.12 1.84 13.08 0.67 7.12 3.14 22.33 0.84 8.90 6.41 57.03
A2 A2 0.812 6.69 0.67 0.54 2.55 1.39 0.67 0.54 4.36 2.37 0.84 0.68 8.90 6.06
A3 A3 2.128 13.45 0.67 1.43 1.95 2.78 0.67 1.43 3.34 4.75 0.84 1.78 6.81 12.14
A4 A4 3.417 21.94 0.67 2.29 1.53 3.51 0.67 2.29 2.62 5.99 0.84 2.86 5.34 15.29
A5 A5 2.642 9.31 0.67 1.77 2.28 4.03 0.67 1.77 3.89 6.88 0.84 2.21 7.94 17.57
B1 B1 5.240 14.28 0.67 3.51 1.90 6.67 0.67 3.51 3.25 11.39 0.84 4.39 6.63 29.09
B2 B2 3.285 5.43 0.67 2.20 2.71 5.98 0.67 2.20 4.64 10.20 0.84 2.75 9.47 26.05
B3 B3 2.384 12.71 0.67 1.60 2.00 3.20 0.67 1.60 3.42 5.46 0.84 2.00 6.99 13.95
B4 B4 4.295 9.21 0.67 2.88 2.29 6.58 0.67 2.88 3.90 11.23 0.84 3.60 7.97 28.68
B5 B5 0.731 8.24 0.67 0.49 2.38 1.17 0.67 0.49 4.06 1.99 0.84 0.61 8.30 5.08
B6 B6 2.546 14.21 0.67 1.71 1.91 3.25 0.67 1.71 3.25 5.55 0.84 2.13 6.65 14.17
C1 C1 1.385 5.71 0.67 0.93 2.68 2.48 0.67 0.93 4.57 4.24 0.84 1.16 9.34 10.83
C2 C2 1.784 14.11 0.67 1.20 1.91 2.29 0.67 1.20 3.26 3.90 0.84 1.49 6.67 9.96
D1 D1 9.206 18.72 0.67 6.17 1.67 10.27 0.67 6.17 2.84 17.54 0.84 7.71 5.81 44.79
D2 D2 0.905 6.89 0.67 0.61 2.53 1.53 0.67 0.61 4.32 2.62 0.84 0.76 8.82 6.69
Appendix C
APPENDIX C – DETENTION POND CALCULATIONS
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
16.212 acres 156,530 3.59
3.24 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 9.95 135.10 40,529 973 39,556 0.91
10 7.72 104.82 62,891 1,945 60,946 1.40
15 6.52 88.53 79,673 2,918 76,755 1.76
20 5.60 76.03 91,241 3,891 87,350 2.01
25 4.98 67.62 101,424 4,864 96,561 2.22
30 4.52 61.37 110,467 5,836 104,631 2.40
35 4.08 55.40 116,332 6,809 109,523 2.51
40 3.74 50.78 121,872 7,782 114,090 2.62
45 3.46 46.98 126,841 8,754 118,087 2.71
50 3.23 43.86 131,566 9,727 121,839 2.80
55 3.03 41.14 135,762 10,700 125,062 2.87
60 2.86 38.83 139,794 11,673 128,122 2.94
65 2.72 36.93 144,031 12,645 131,385 3.02
70 2.59 35.17 147,697 13,618 134,079 3.08
75 2.48 33.67 151,525 14,591 136,935 3.14
80 2.38 32.31 155,110 15,564 139,546 3.20
85 2.29 31.09 158,572 16,536 142,036 3.26
90 2.21 30.01 162,034 17,509 144,526 3.32
95 2.13 28.92 164,845 18,482 146,363 3.36
100 2.06 27.97 167,819 19,454 148,364 3.41
105 2.00 27.16 171,077 20,427 150,650 3.46
110 1.94 26.34 173,847 21,400 152,447 3.50
115 1.89 25.66 177,065 22,373 154,692 3.55
120 1.84 24.98 179,875 23,345 156,530 3.59
125 1.79 24.30 182,279 24,318 157,961 3.63
130 1.75 23.76 185,334 25,291 160,043 3.67
135 1.71 23.22 188,063 26,263 161,799 3.71
140 1.67 22.67 190,466 27,236 163,230 3.75
145 1.63 22.13 192,543 28,209 164,334 3.77
150 1.60 21.72 195,517 29,182 166,335 3.82
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.32
1.25
0.40 ft3 acre-ft
16.212 acres 62,565 1.44
3.24 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 64.52 19,357 973 18,384 0.42
10 7.72 50.06 30,038 1,945 28,092 0.64
15 6.52 42.28 38,053 2,918 35,135 0.81
20 5.60 36.31 43,578 3,891 39,687 0.91
25 4.98 32.29 48,441 4,864 43,578 1.00
30 4.52 29.31 52,760 5,836 46,924 1.08
35 4.08 26.46 55,562 6,809 48,753 1.12
40 3.74 24.25 58,208 7,782 50,426 1.16
45 3.46 22.44 60,581 8,754 51,827 1.19
50 3.23 20.95 62,838 9,727 53,111 1.22
55 3.03 19.65 64,842 10,700 54,142 1.24
60 2.86 18.55 66,768 11,673 55,095 1.26
65 2.72 17.64 68,791 12,645 56,145 1.29
70 2.59 16.80 70,542 13,618 56,924 1.31
75 2.48 16.08 72,370 14,591 57,780 1.33
80 2.38 15.43 74,082 15,564 58,519 1.34
85 2.29 14.85 75,736 16,536 59,200 1.36
90 2.21 14.33 77,390 17,509 59,881 1.37
95 2.13 13.81 78,732 18,482 60,250 1.38
100 2.06 13.36 80,152 19,454 60,698 1.39
105 2.00 12.97 81,708 20,427 61,281 1.41
110 1.94 12.58 83,031 21,400 61,632 1.41
115 1.89 12.26 84,568 22,373 62,196 1.43
120 1.84 11.93 85,911 23,345 62,565 1.44
125 1.79 11.61 87,058 24,318 62,740 1.44
130 1.75 11.35 88,518 25,291 63,227 1.45
135 1.71 11.09 89,821 26,263 63,558 1.46
140 1.67 10.83 90,969 27,236 63,733 1.46
145 1.63 10.57 91,961 28,209 63,752 1.46
150 1.60 10.38 93,381 29,182 64,200 1.47
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
17.853 acres 172,374 3.96
3.57 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 9.95 148.77 44,631 1,071 43,560 1.00
10 7.72 115.43 69,257 2,142 67,115 1.54
15 6.52 97.49 87,738 3,214 84,524 1.94
20 5.60 83.73 100,477 4,285 96,192 2.21
25 4.98 74.46 111,691 5,356 106,335 2.44
30 4.52 67.58 121,649 6,427 115,221 2.65
35 4.08 61.00 128,108 7,498 120,610 2.77
40 3.74 55.92 134,208 8,569 125,639 2.88
45 3.46 51.73 139,681 9,641 130,040 2.99
50 3.23 48.29 144,884 10,712 134,172 3.08
55 3.03 45.30 149,504 11,783 137,721 3.16
60 2.86 42.76 153,945 12,854 141,090 3.24
65 2.72 40.67 158,610 13,925 144,684 3.32
70 2.59 38.73 162,647 14,997 147,650 3.39
75 2.48 37.08 166,863 16,068 150,795 3.46
80 2.38 35.59 170,810 17,139 153,671 3.53
85 2.29 34.24 174,623 18,210 156,413 3.59
90 2.21 33.04 178,436 19,281 159,155 3.65
95 2.13 31.85 181,531 20,352 161,178 3.70
100 2.06 30.80 184,805 21,424 163,382 3.75
105 2.00 29.90 188,394 22,495 165,899 3.81
110 1.94 29.01 191,444 23,566 167,878 3.85
115 1.89 28.26 194,988 24,637 170,350 3.91
120 1.84 27.51 198,083 25,708 172,374 3.96
125 1.79 26.76 200,729 26,780 173,950 3.99
130 1.75 26.17 204,093 27,851 176,243 4.05
135 1.71 25.57 207,099 28,922 178,177 4.09
140 1.67 24.97 209,745 29,993 179,752 4.13
145 1.63 24.37 212,033 31,064 180,968 4.15
150 1.60 23.92 215,307 32,135 183,172 4.21
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Detention Volume Calculation - C Basins
0.67
1.25
0.84 ft3 acre-ft
3.797 acres 36,661 0.84
0.76 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 31.64 9,492 228 9,264 0.21
10 7.72 24.55 14,730 456 14,274 0.33
15 6.52 20.73 18,660 683 17,977 0.41
20 5.60 17.81 21,370 911 20,458 0.47
25 4.98 15.84 23,755 1,139 22,615 0.52
30 4.52 14.37 25,872 1,367 24,505 0.56
35 4.08 12.97 27,246 1,595 25,651 0.59
40 3.74 11.89 28,544 1,823 26,721 0.61
45 3.46 11.00 29,707 2,050 27,657 0.63
50 3.23 10.27 30,814 2,278 28,536 0.66
55 3.03 9.64 31,797 2,506 29,291 0.67
60 2.86 9.09 32,741 2,734 30,007 0.69
65 2.72 8.65 33,733 2,962 30,772 0.71
70 2.59 8.24 34,592 3,189 31,402 0.72
75 2.48 7.89 35,489 3,417 32,071 0.74
80 2.38 7.57 36,328 3,645 32,683 0.75
85 2.29 7.28 37,139 3,873 33,266 0.76
90 2.21 7.03 37,950 4,101 33,849 0.78
95 2.13 6.77 38,608 4,329 34,280 0.79
100 2.06 6.55 39,305 4,556 34,748 0.80
105 2.00 6.36 40,068 4,784 35,284 0.81
110 1.94 6.17 40,717 5,012 35,705 0.82
115 1.89 6.01 41,470 5,240 36,230 0.83
120 1.84 5.85 42,128 5,468 36,661 0.84
125 1.79 5.69 42,691 5,696 36,996 0.85
130 1.75 5.56 43,407 5,923 37,484 0.86
135 1.71 5.44 44,046 6,151 37,895 0.87
140 1.67 5.31 44,609 6,379 38,230 0.88
145 1.63 5.18 45,095 6,607 38,489 0.88
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
10.111 acres 97,624 2.24
2.02 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 84.26 25,277 607 24,670 0.57
10 7.72 65.37 39,224 1,213 38,010 0.87
15 6.52 55.21 49,690 1,820 47,870 1.10
20 5.60 47.42 56,905 2,427 54,478 1.25
25 4.98 42.17 63,256 3,033 60,222 1.38
30 4.52 38.28 68,895 3,640 65,255 1.50
35 4.08 34.55 72,554 4,247 68,307 1.57
40 3.74 31.67 76,008 4,853 71,155 1.63
45 3.46 29.30 79,108 5,460 73,648 1.69
50 3.23 27.35 82,055 6,067 75,988 1.74
55 3.03 25.66 84,671 6,673 77,998 1.79
60 2.86 24.22 87,186 7,280 79,906 1.83
65 2.72 23.03 89,828 7,887 81,942 1.88
70 2.59 21.93 92,114 8,493 83,621 1.92
75 2.48 21.00 94,502 9,100 85,403 1.96
80 2.38 20.15 96,738 9,707 87,031 2.00
85 2.29 19.39 98,897 10,313 88,584 2.03
90 2.21 18.71 101,057 10,920 90,137 2.07
95 2.13 18.04 102,810 11,527 91,283 2.10
100 2.06 17.44 104,664 12,133 92,531 2.12
105 2.00 16.94 106,696 12,740 93,956 2.16
110 1.94 16.43 108,424 13,347 95,077 2.18
115 1.89 16.00 110,431 13,953 96,478 2.21
120 1.84 15.58 112,184 14,560 97,624 2.24
125 1.79 15.16 113,682 15,167 98,516 2.26
130 1.75 14.82 115,588 15,773 99,815 2.29
135 1.71 14.48 117,290 16,380 100,910 2.32
140 1.67 14.14 118,789 16,986 101,802 2.34
145 1.63 13.80 120,084 17,593 102,491 2.35
150 1.60 13.55 121,939 18,200 103,739 2.38
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 16.212 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.383 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 22111 0.51 0.17 1.00 0.17
4950.0 53203 1.22 0.84 2.00 1.01
4951.0 59483 1.37 1.29 3.00 2.30
4952.0 63661 1.46 1.41 4.00 3.71
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 6205 0.14 0.04 0.79 0.04
4952.0 15932 0.37 0.25 1.79 0.28
4953.0 19106 0.44 0.40 2.79 0.68
3.59 ac-ft 4.40 ac-ft
Critical Pond Elevations - A Basins
J.Claeys
Interwest Consulting Group
1282-163-03
December 13, 2017
Volume Required: Combined Volume Provided:
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001
(Revised November 2010)
( )
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 16.212 acres
Imperviousness, I 36.3%
WQCV (watershed inches) 0.170 inches 40-Hour Drain Time (Table 3-2)
Required WQCV 0.275 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
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 16146 0.37 0.12 1.00 0.12
4950.0 38428 0.88 0.61 2.00 0.73
4951.0 54071 1.24 1.06 3.00 1.79
4951.5 60342 1.39 0.66 3.50 2.44
1.44 ac-ft 2.44 ac-ft
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001
(Revised November 2010)
Pond A1 Interim
Volume Required: Combined Volume Provided:
Critical Pond Elevations - A Basins (Interim)
J.Claeys
Interwest Consulting Group
1282-163-03
December 13, 2017
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
=
1282-168-03 PondCalcs.xls - Pond Stage (Prelim A Interim) Page 2 of 5 Interwest Consulting Group
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 17.853 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.422 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 8530 0.20 0.07 1.00 0.07
4951.0 21199 0.49 0.33 2.00 0.40
4952.0 34540 0.79 0.63 3.00 1.03
4953.0 47409 1.09 0.94 4.00 1.97
Pond B2
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4954.15 0 0.00 0.00 0.00 0.00
4955.0 7126 0.16 0.05 0.85 0.05
4956.0 23453 0.54 0.33 1.85 0.38
4957.0 31454 0.72 0.63 2.85 1.01
Pond B3
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4953.46 0 0.00 0.00 0.00 0.00
4954.0 2872 0.07 0.01 0.54 0.01
4955.0 17409 0.40 0.21 1.54 0.22
Pond B4
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 3.797 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.090 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond C
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4953.17 0 0.00 0.00 0.00 0.00
4954.0 1168 0.03 0.01 0.83 0.01
4955.0 13987 0.32 0.15 1.83 0.15
4956.0 28723 0.66 0.48 2.83 0.63
4957.0 36143 0.83 0.74 3.83 1.38
Volume Required: 0.84 ac-ft Volume Provided: 1.38 ac-ft
Critical Pond Elevations - C Basins
J.Claeys
Interwest Consulting Group
1282-163-03
December 13, 2017
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001
(Revised January 2016)
( )
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 10.111 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.239 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 18908 0.43 0.14 1.00 0.14
4950.0 43159 0.99 0.69 2.00 0.84
4951.0 63984 1.47 1.22 3.00 2.06
4951.5 77038 1.77 0.81 3.50 2.87
Volume Required: 2.24 ac-ft Volume Provided: 2.87 ac-ft
Critical Pond Elevations - D Basins
J.Claeys
Interwest Consulting Group
1282-163-03
December 13, 2017
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001
(Revised January 2016)
( )
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 - FILING 1
STREET CAPACITY EXHIBIT
12/13/17
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 = 20.5 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 = 16.8 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 10.8 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 = 8.0 66.8 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 12/12/2017, 12:09 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 16.0 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 = 16.8 32.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 10.8 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 = 8.0 78.6 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 12/12/2017, 12:10 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
960,287 22.05
920,610 21.13
56,625 1.30
245,118 5.63
224,315 5.15
2,406,955 55.26
Infiltrator Depth &
Area (ft2)
% Area (ft2) % of Total Req'd % Area (ft2) % of Total Req'd 2 ft
B1 & B2 371,354 60% Infiltration Gallery 99% 366,784 38% 0% 0 0% 0.19 0.43 5,847 2,923
A1, A2, & A3 591,116 60% Infiltration Gallery 57% 335,371 35% 49% 289,489 31% 0.19 0.43 9,307 4,653
B3 103,867 60% Infiltration Gallery 0% 0 0% 133% 138,032 15% 0.19 0.43 1,635 818
D1 286,887 60% Rain Garden 0% 0 0% 100% 286,887 31% 0.19 0.43 4,517 -
Total Treatment 702,155 73% Total Treatment 714,407 78%
Basin (s)
Area Treated
by LID (ft2)
%
Impervious
Req'd WQCV
(12 hr Release Rate)
(cu-ft)
WQCV
(watershed inches)
Depth of Average Runoff
Producing Storm
(watershed inches)
Single Family
(Fee Simple)
Multi-Family
(Condos)
Development Area Breakdown
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID techniques, or
- Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID techniques when 25% of private driveable surfaces are permeable.
J.Claeys
Interwest Consulting Group
1282-168-03
December 13, 2017
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Total
Description
Treatment Method
Single Family Area
Multifamily Area
Commercial Area (future treatment)
Suniga (no treatment)
Detention Areas (no treatment)
(ACRE-FT)
4953.41 0 0.00 0.00 0.00 0.00
4954.0 3459 0.08 0.02 0.59 0.02
4955.0 11947 0.27 0.17 1.59 0.18
4956.0 14331 0.33 0.30 2.59 0.48
4957.0 16316 0.37 0.35 3.59 0.84
Volume Required: 3.96 ac-ft Combined Volume Provided: 4.03 ac-ft
Critical Pond Elevations - B Basins
J.Claeys
Interwest Consulting Group
1282-163-03
December 13, 2017
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised
January 2016)
( )
3
AAAADepth 1 2 1 2
V
+ +
=
* * 1 . 2
12
Area
WQCV
Volume
=
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 1 of 5 Interwest Consulting Group
155 1.57 13.29 123,641 18,806 104,834 2.41
160 1.54 13.04 125,190 19,413 105,777 2.43
165 1.51 12.79 126,588 20,020 106,568 2.45
170 1.48 12.53 127,832 20,626 107,206 2.46
175 1.45 12.28 128,925 21,233 107,692 2.47
180 1.42 12.02 129,865 21,840 108,025 2.48
185 1.40 11.86 131,592 22,446 109,146 2.51
190 1.38 11.69 133,218 23,053 110,165 2.53
195 1.36 11.52 134,742 23,660 111,082 2.55
200 1.34 11.35 136,165 24,266 111,898 2.57
205 1.32 11.18 137,486 24,873 112,613 2.59
210 1.30 11.01 138,705 25,480 113,226 2.60
215 1.28 10.84 139,823 26,086 113,737 2.61
220 1.26 10.67 140,839 26,693 114,146 2.62
225 1.24 10.50 141,754 27,300 114,454 2.63
230 1.22 10.33 142,567 27,906 114,660 2.63
235 1.21 10.25 144,472 28,513 115,959 2.66
240 1.20 10.16 146,326 29,120 117,207 2.69
December 13, 2017
Runoff Coefficient (C )
Frequency Factor (C f )
100-yr Detention Volume - FAA Method
Northfield
J.Claeys
Interwest Consulting
1282-168-03
Adjusted Runoff Coefficient (CC f )
Area (A )
Allowed Release Rate
Required Detention
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
City of Fort Collins - Storm Water Criteria Manual
Detention Volume Calculation - Future D Basins
150 1.60 5.09 45,792 6,835 38,957 0.89
155 1.57 4.99 46,431 7,062 39,369 0.90
160 1.54 4.90 47,013 7,290 39,723 0.91
165 1.51 4.80 47,538 7,518 40,020 0.92
170 1.48 4.71 48,005 7,746 40,259 0.92
175 1.45 4.61 48,415 7,974 40,442 0.93
180 1.42 4.52 48,768 8,202 40,567 0.93
185 1.40 4.45 49,417 8,429 40,988 0.94
190 1.38 4.39 50,028 8,657 41,370 0.95
195 1.36 4.32 50,600 8,885 41,715 0.96
200 1.34 4.26 51,134 9,113 42,021 0.96
205 1.32 4.20 51,630 9,341 42,290 0.97
210 1.30 4.13 52,088 9,568 42,520 0.98
215 1.28 4.07 52,508 9,796 42,712 0.98
220 1.26 4.01 52,890 10,024 42,865 0.98
225 1.24 3.94 53,233 10,252 42,981 0.99
230 1.22 3.88 53,538 10,480 43,059 0.99
235 1.21 3.85 54,254 10,708 43,546 1.00
240 1.20 3.82 54,950 10,935 44,015 1.01
December 13, 2017
Northfield
100-yr Detention Volume - FAA Method
J.Claeys
Interwest Consulting
1282-168-03
Area (A )
Allowed Release Rate
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
City of Fort Collins - Storm Water Criteria Manual
Runoff Coefficient (C )
Frequency Factor (C f ) Required Detention
Adjusted Runoff Coefficient (CC f )
155 1.57 23.47 218,313 33,207 185,106 4.25
160 1.54 23.03 221,049 34,278 186,771 4.29
165 1.51 22.58 223,516 35,349 188,167 4.32
170 1.48 22.13 225,714 36,420 189,294 4.35
175 1.45 21.68 227,642 37,491 190,151 4.37
180 1.42 21.23 229,302 38,562 190,740 4.38
185 1.40 20.93 232,352 39,634 192,719 4.42
190 1.38 20.63 235,223 40,705 194,518 4.47
195 1.36 20.33 237,914 41,776 196,138 4.50
200 1.34 20.04 240,426 42,847 197,579 4.54
205 1.32 19.74 242,759 43,918 198,840 4.56
210 1.30 19.44 244,912 44,990 199,922 4.59
215 1.28 19.14 246,886 46,061 200,825 4.61
220 1.26 18.84 248,680 47,132 201,548 4.63
225 1.24 18.54 250,295 48,203 202,091 4.64
230 1.22 18.24 251,730 49,274 202,456 4.65
235 1.21 18.09 255,094 50,345 204,749 4.70
240 1.20 17.94 258,369 51,417 206,952 4.75
December 13, 2017
Northfield
100-yr Detention Volume - FAA Method
J.Claeys
Interwest Consulting
1282-168-03
Area (A )
Allowed Release Rate
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
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
155 1.57 10.18 94,685 30,154 64,530 1.48
160 1.54 9.99 95,871 31,127 64,744 1.49
165 1.51 9.79 96,941 32,100 64,842 1.49
170 1.48 9.60 97,895 33,072 64,822 1.49
175 1.45 9.40 98,731 34,045 64,686 1.48
180 1.42 9.21 99,451 35,018 64,433 1.48
185 1.40 9.08 100,774 35,991 64,783 1.49
190 1.38 8.95 102,019 36,963 65,056 1.49
195 1.36 8.82 103,186 37,936 65,250 1.50
200 1.34 8.69 104,276 38,909 65,367 1.50
205 1.32 8.56 105,287 39,882 65,406 1.50
210 1.30 8.43 106,221 40,854 65,367 1.50
215 1.28 8.30 107,077 41,827 65,250 1.50
220 1.26 8.17 107,855 42,800 65,056 1.49
225 1.24 8.04 108,556 43,772 64,783 1.49
230 1.22 7.91 109,178 44,745 64,433 1.48
235 1.21 7.85 110,637 45,718 64,919 1.49
240 1.20 7.78 112,057 46,691 65,367 1.50
December 13, 2017
Northfield
100-yr Detention Volume - FAA Method
J.Claeys
Interwest Consulting
1282-168-03
Adjusted Runoff Coefficient (CC f )
Area (A )
Allowed Release Rate
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
City of Fort Collins - Storm Water Criteria Manual
Detention Volume Calculation - A Basins (Interim)
Runoff Coefficient (C )
Frequency Factor (C f ) Required Detention
155 1.57 21.32 198,246 30,154 168,091 3.86
160 1.54 20.91 200,730 31,127 169,603 3.89
165 1.51 20.50 202,971 32,100 170,871 3.92
170 1.48 20.09 204,967 33,072 171,894 3.95
175 1.45 19.69 206,718 34,045 172,673 3.96
180 1.42 19.28 208,225 35,018 173,207 3.98
185 1.40 19.01 210,995 35,991 175,004 4.02
190 1.38 18.74 213,602 36,963 176,639 4.06
195 1.36 18.47 216,046 37,936 178,110 4.09
200 1.34 18.19 218,327 38,909 179,418 4.12
205 1.32 17.92 220,445 39,882 180,564 4.15
210 1.30 17.65 222,400 40,854 181,546 4.17
215 1.28 17.38 224,193 41,827 182,366 4.19
220 1.26 17.11 225,822 42,800 183,022 4.20
225 1.24 16.84 227,288 43,772 183,516 4.21
230 1.22 16.56 228,592 44,745 183,847 4.22
235 1.21 16.43 231,647 45,718 185,929 4.27
240 1.20 16.29 234,620 46,691 187,930 4.31
December 13, 2017
Northfield
100-yr Detention Volume - FAA Method
J.Claeys
Interwest Consulting
1282-168-03
Area (A )
Allowed Release Rate
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
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 - Future A Basins
E1 E1 1.137 7.11 0.67 0.76 2.50 1.91 0.67 0.76 4.27 3.26 0.84 0.95 8.73 8.32
E2 E2 6.045 14.53 0.67 4.05 1.89 7.64 0.67 4.05 3.22 13.04 0.84 5.06 6.58 33.29
A1
(interim) A1 (interim) 10.630 31.18 0.36 3.86 1.25 4.84 0.36 3.86 2.14 8.27
0.45 4.83 4.38 21.12
Design
Point
Sub-basin Area (acres) tc
(min)
2-yr Peak Runoff 100-yr Peak Runoff
L. Johnson
Interwest Consulting Group
1282-168-03
December 13, 2017
10-yr Peak Runoff
Q n = C n I n A n
0.786651)
1
( 10 )
28 . 5
t c
P
I
+
=
tc
(min)
tc=ti+tt
(min)
L. Johnson
Interwest Consulting Group
1282-168-03
December 13, 2017
SLOPE
(ft/ft)
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
ti
(min)
LENGTH Table RO-2
(ft)
INITIAL/OVERLAND
TIME (ti)
DESIGN
POINT
Sub-basin C5
( )
0 .33
0 . 395 1 . 1 5
S
C L
ti
−
=
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
Lawns
(Heavy, 2-7% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
Weighted %
Impervious
COMPOSITE
DRAINAGE BASIN
FLOW PATH
LEGEND
EX MAJOR CONTOUR
SPILL GUTTER
EX MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
BFE (FEMA)
CROSS-SECTION (FEMA)
100-YR FLOODPLAIN (FEMA)
0
100'
100 50 100 200
SCALE: 1" =
AH
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