HomeMy WebLinkAboutNORTHFIELD FILING 1 EXPANDED - PDP180011 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
FOR
Northfield
Prepared by:
Highland Development Services
6355 Fairgrounds Ave, Suite 100
Windsor, Colorado 80550
Phone: 970.674.7550
Prepared for:
Landmark Real Estate Holdings, LLC
6341 Fairgrounds Ave, Suite 100
Windsor, Colorado 80550
Office: 970.460.0567
January 23, 2019
Job Number 18-1000-00
6355 FAIRGROUNDS AVE, SUITE 100, WINDSOR, COLORADO 80550 | PHONE 970.674.7550
January 23, 2019
Mr. Shane Boyle
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Preliminary Drainage Report for Northfield
Dear Shane,
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 will consist of 139 single family attached (fee simple) units and 301
condominium units, a mixed-use building with a combination of retail and apartments, and a
community clubhouse.
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 FEMA regulatory, Dry Creek
100-year Floodplain 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, and a portion of the improvements 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 2019. 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 Use 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 Fort Collins Municipal Code Chapter 10 requirements. A portion of the site is
located within the Cache la Poudre River 500-yr floodplain. Critical facilities are prohibited
Page 2
within the 100-yr and/or 500-yr floodplains. Critical facilities include facilities for at-risk
populations (daycares, schools, nursing homes, etc) and emergency service facilities (urgent
care, hospitals, fire stations, police stations, etc).
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. Due to the groundwater elevations and in consideration of the
infiltration galleries, pond bottoms, and building foundations, the site is anticipated to be
dewatered, utilizing the NECCO pipe as the dewatering outfall. A groundwater study is
currently in process and will be reviewed with staff when complete.
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 1999 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
Page 4
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
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
pipes, 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 developed drainage basins are 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 developed
runoff is 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 8.12 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 9.45 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 7.71 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 3.10 acres of single-family attached and condominium residential
lots, public roadways and private drives. Runoff is conveyed along Schlagel St, Toomey
Drive, and the private drives, is captured by Type R inlets and area inlets. Runoff is then
conveyed to detention Pond B1 via 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 1.07 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. Approximately 60% 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 7.12 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. Stormwater 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 established 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 17.57 acres draining to the detention Pond A1 and Pond A2, which allows a release
rate of 3.51 cfs. 3.89 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 20.76 acres which allows a release rate of 4.15 cfs. This requires
4.60 acre-ft of detention storage volume with 0.42 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.
Page 8
Drainage System C:
Drainage System C’s basin is 2.46 acres which allows a release rate of 0.49 cfs. This requires
0.54 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 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 particles 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. The
preliminary area of treatment calculations will be further detailed and coordinated with staff
during 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
Page 10
controls. The Four Step Process applies to the management of smaller, frequently occurring
events.
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
stormwater 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 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 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 2018]
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
SUBJECT
PROPERTY
(APPROX.)
SUBJECT
PROPERTY
(APPROX.)
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
DITCH
DRY CREEK
LAKE CANAL
DITCH
N. LEMAY AVENUE
TOOMEY DRIVE
PIONEER TRAIL ROAD
STEELEY DRIVE
LANDMARK WAY
N. LEMAY AVENUE
POND D
POND C POND B1
POND B2
POND A2
POND A1
SCHLAGEL STREET
BASIN COEFFICIENT (100-YR)
BASIN DESIGNATION
BASIN AREA
DESIGN POINT
DRAINAGE FLOW ARROW
DRAINAGE BASIN BOUNDARY
DRAINAGE BASIN FLOW PATH
LEGEND
EX MAJOR CONTOUR
EX MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
0
100'
100 50 100 200
SCALE: 1" =
NO. REVISION BY DATE
HIGHLAND
DEVELOPMENT SERVCIES
6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550
PHONE: 970.674.7550 | FAX: 970.674.7568 | www.Highland-DS.com
PREPARED BY OR UNDER THE
DIRECT SUPERVISION OF:
FOR AND ON BEHALF OF HIGHLAND
DEVELOPMENT SERVICES
REVIEW SET
NOT FOR
CONSTRUCTION
SHEET OF
DRAWN BY
CHECKED BY
DATE
SCALE (H)
HDS PROJECT #
SCALE (V)
NORTHFIELD
OVERALL DRAINAGE EXHIBIT
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 353,688 8.120 212,213 0 0 0 141,475 60.0% 0.67 0.84
A2 411,678 9.451 247,007 0 0 0 164,671 60.0% 0.67 0.84
B1 335,799 7.709 201,479 0 0 0 134,319 60.0% 0.67 0.84
B2 135,085 3.101 81,051 0 0 0 54,034 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 46,517 1.068 27,910 0 0 0 18,607 60.0% 0.67 0.84
C2 60,493 1.389 36,296 0 0 0 24,197 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 37,716 0 0 0 123,205 23.4% 0.41 0.52
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 2,529,863 58.078 1,459,081 0 0 0 1,070,782 57.7% 0.65 0.82
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:
Highland Development Services
% Impervious values from Table RO-11 in the Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
J.Claeys
18-1000-00
January 23, 2019
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 8.120 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 9.451 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 7.709 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 3.101 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 1.068 200 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 1.389 200 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 23.4% 0.41 3.694 115 0.0050 17.33 285 0.0050 Paved Areas 20 1.41 3.36 20.69 0.0050 19.83 19.83
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
January 23, 2019
Northfield
DEVELOPED TIME OF CONCENTRATION
J.Claeys
18-1000-00
Highland Development Services
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 8.120 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 9.451 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 7.709 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 3.101 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 1.068 200 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 1.389 200 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 23.4% 0.52 3.694 115 0.0050 14.72 285 0.0050 Paved Areas 20 1.41 3.36 18.07 0.0050 19.83 18.07
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
January 23, 2019
Northfield
DEVELOPED TIME OF CONCENTRATION
J.Claeys
18-1000-00
Highland Development Services
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 8.120 19.05 0.67 5.44 1.65 8.98 19.05 0.67 5.44 2.82 15.33 17.12 0.84 6.80 6.08 41.33
A2 A2 9.451 18.74 0.67 6.33 1.66 10.54 18.74 0.67 6.33 2.84 18.00 16.80 0.84 7.92 6.14 48.56
B1 B1 7.709 17.31 0.67 5.16 1.73 8.95 17.31 0.67 5.16 2.96 15.28 15.38 0.84 6.46 6.40 41.34
B2 B2 3.101 9.72 0.67 2.08 2.24 4.65 9.72 0.67 2.08 3.82 7.94 7.79 0.84 2.60 8.47 21.99
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 1.068 14.05 0.67 0.72 1.91 1.37 14.05 0.67 0.72 3.27 2.34 13.06 0.84 0.89 6.90 6.17
C2 C2 1.389 14.24 0.67 0.93 1.90 1.77 14.24 0.67 0.93 3.25 3.02 13.31 0.84 1.16 6.85 7.96
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 19.83 0.41 1.53 1.62 2.47 19.83 0.41 1.53 2.76 4.22 18.07 0.52 1.91 5.91 11.31
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)
J.Claeys
Highland Development Services
18-1000-00
January 23, 2019
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 0.41 3.89 4.31 4.69
B Basins 0.49 4.60 5.09 3.42
C Basins 0.06 0.54 0.60 1.30
D Basins 0.23 1.24 1.47 3.55
11.47 12.96
North of Suniga
Total
Pond Summary
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
Pond Summary Table
J.Claeys
Highland Development Services
18-1000-00
January 23, 2019
18-1000-00 PondCalcs.xls Page 1 of 5 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
17.570 acres 169,646 3.89
3.51 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Accumulative
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 146.42 43,925 1,054 42,871 0.98
10 7.72 113.60 68,161 2,108 66,052 1.52
15 6.52 95.94 86,349 3,163 83,186 1.91
20 5.60 82.41 98,886 4,217 94,669 2.17
25 4.98 73.28 109,923 5,271 104,652 2.40
30 4.52 66.51 119,723 6,325 113,398 2.60
35 4.08 60.04 126,080 7,380 118,700 2.72
40 3.74 55.03 132,084 8,434 123,650 2.84
45 3.46 50.91 137,470 9,488 127,981 2.94
50 3.23 47.53 142,590 10,542 132,048 3.03
55 3.03 44.59 147,137 11,596 135,541 3.11
60 2.86 42.09 151,508 12,651 138,857 3.19
65 2.72 40.03 156,099 13,705 142,394 3.27
70 2.59 38.11 160,072 14,759 145,313 3.34
75 2.48 36.49 164,222 15,813 148,408 3.41
80 2.38 35.02 168,107 16,868 151,239 3.47
85 2.29 33.70 171,859 17,922 153,937 3.53
90 2.21 32.52 175,611 18,976 156,635 3.60
95 2.13 31.34 178,657 20,030 158,627 3.64
100 2.06 30.31 181,880 21,084 160,796 3.69
105 2.00 29.43 185,412 22,139 163,273 3.75
110 1.94 28.55 188,414 23,193 165,221 3.79
115 1.89 27.81 191,901 24,247 167,654 3.85
120 1.84 27.08 194,947 25,301 169,646 3.89
Northfield
100-yr Detention Volume - FAA Method
Highland Development Services
January 23, 2019
18-1000-00
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 17.570 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.415 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond A1
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4948.00 0 0.00 0.00 0.00 0.00
4949.0 23600 0.54 0.18 1.00 0.18
4950.0 67420 1.55 1.00 2.00 1.18
4951.0 80448 1.85 1.70 3.00 2.88
4951.6 86080 1.98 1.15 3.60 4.02
Pond A2
CONTOUR (FT) AREA (FT
2
) 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
Critical Pond Elevations - A Basins
J.Claeys
Highland Development
18-1000-00
January 23, 2019
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
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.67
1.25
0.84 ft3 acre-ft
20.764 acres 200,484 4.60
4.15 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Accumulative
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 51,909 1,246 50,664 1.16
10 7.72 134.25 80,551 2,492 78,059 1.79
15 6.52 113.38 102,045 3,738 98,308 2.26
20 5.60 97.38 116,862 4,983 111,878 2.57
25 4.98 86.60 129,904 6,229 123,675 2.84
30 4.52 78.60 141,486 7,475 134,011 3.08
35 4.08 70.95 148,998 8,721 140,277 3.22
40 3.74 65.04 156,094 9,967 146,127 3.35
45 3.46 60.17 162,458 11,213 151,246 3.47
50 3.23 56.17 168,510 12,459 156,052 3.58
55 3.03 52.69 173,884 13,704 160,179 3.68
60 2.86 49.74 179,049 14,950 164,098 3.77
65 2.72 47.30 184,474 16,196 168,278 3.86
70 2.59 45.04 189,170 17,442 171,728 3.94
75 2.48 43.13 194,074 18,688 175,386 4.03
80 2.38 41.39 198,665 19,934 178,731 4.10
85 2.29 39.82 203,099 21,180 181,920 4.18
90 2.21 38.43 207,534 22,425 185,108 4.25
95 2.13 37.04 211,133 23,671 187,462 4.30
100 2.06 35.82 214,942 24,917 190,025 4.36
105 2.00 34.78 219,115 26,163 192,952 4.43
110 1.94 33.74 222,663 27,409 195,254 4.48
115 1.89 32.87 226,784 28,655 198,130 4.55
120 1.84 32.00 230,384 29,901 200,484 4.60
Northfield
100-yr Detention Volume - FAA Method
January 23, 2019
Highland Development Services
18-1000-00
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 20.764 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)
4949.0 0 0.00 0.00 0.00 0.00
4950.0 9,741 0.22 0.07 1.00 0.07
4951.0 28,648 0.66 0.42 2.00 0.50
4952.0 48,037 1.10 0.87 3.00 1.37
4953.0 67,627 1.55 1.32 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
J.Claeys
Highland Development
18-1000-00
January 23, 2019
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
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Detention Volume Calculation - C Basins
0.67
1.25
0.84 ft3 acre-ft
2.457 acres 23,719 0.54
0.49 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Accumulative
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 20.47 6,141 147 5,994 0.14
10 7.72 15.88 9,530 295 9,235 0.21
15 6.52 13.41 12,073 442 11,631 0.27
20 5.60 11.52 13,826 590 13,236 0.30
25 4.98 10.25 15,369 737 14,632 0.34
30 4.52 9.30 16,739 884 15,855 0.36
35 4.08 8.39 17,628 1,032 16,596 0.38
40 3.74 7.69 18,467 1,179 17,288 0.40
45 3.46 7.12 19,220 1,327 17,894 0.41
50 3.23 6.65 19,936 1,474 18,462 0.42
55 3.03 6.23 20,572 1,621 18,951 0.44
60 2.86 5.88 21,183 1,769 19,414 0.45
65 2.72 5.60 21,825 1,916 19,909 0.46
70 2.59 5.33 22,381 2,064 20,317 0.47
75 2.48 5.10 22,961 2,211 20,750 0.48
80 2.38 4.90 23,504 2,358 21,146 0.49
85 2.29 4.71 24,028 2,506 21,523 0.49
90 2.21 4.55 24,553 2,653 21,900 0.50
95 2.13 4.38 24,979 2,801 22,178 0.51
100 2.06 4.24 25,430 2,948 22,482 0.52
105 2.00 4.11 25,923 3,095 22,828 0.52
110 1.94 3.99 26,343 3,243 23,100 0.53
115 1.89 3.89 26,831 3,390 23,441 0.54
120 1.84 3.79 27,257 3,538 23,719 0.54
Northfield
100-yr Detention Volume - FAA Method
January 23, 2019
Highland Development Services
Northfield
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV):
Tributary Area, A 2.457 acres
Imperviousness, I 60.0%
WQCV (watershed inches) 0.236 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.058 acre-feet Including 20% for Sedimentation
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
Pond C1
CONTOUR (FT) AREA (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4953.20 0 0.00 0.00 0.00 0.00
4954.0 2550 0.06 0.02 0.80 0.02
4955.0 12625 0.29 0.16 1.80 0.18
4956.0 15228 0.35 0.32 2.80 0.49
4957.0 17591 0.40 0.38 3.80 0.87
4958.0 20183 0.46 0.43 4.80 1.30
Critical Pond Elevations - C Basins
J.Claeys
Highland Development
18-1000-00
January 23, 2019
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
=
18-1000-00 PondCalcs.xls Page 4 of 5 Highland Development Services
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)
Accumulative
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
Runoff Coefficient (C )
Frequency Factor (C f )
100-yr Detention Volume - FAA Method
Northfield
January 23, 2019
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 (FT
2
) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4945.62 0 0.00 0.00 0.00 0.00
4946.00 272 0.01 0.00 0.38 0.00
4947.00 3426 0.08 0.04 1.38 0.04
4948.00 16131 0.37 0.21 2.38 0.24
4949.0 41269 0.95 0.64 3.38 0.88
4950.0 60269 1.38 1.16 4.38 2.04
4951.0 71520 1.64 1.51 5.38 3.55
Critical Pond Elevations - D Basins
J.Claeys
Highland Development
18-1000-00
January 23, 2019
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
=
18-1000-00 PondCalcs.xls Page 5 of 5 Highland Development Services
Appendix D
APPENDIX D – STREET CAPACITIES
CONNECTOR LOCAL
NTS
MAJOR ARTERIAL
NTS
NOTES:
1. MINOR STORM - NO CURB-TOPPING. MAXIMUM SIX (6) INCH FLOW DEPTH AT GUTTER. FLOW SPREAD MUST LEAVE AT LEAST A TWELVE (12) FEET WIDE CLEAR TRAVEL LANE IN EACH DIRECTION.
2. MAJOR STORM - THE DEPTH OF WATER MUST NOT EXCEED THE BOTTOM OF THE GUTTER AT THE MEDIAN TO ALLOW OPERATION OF EMERGENCY VEHICLES, THE DEPTH OF WATER OVER THE GUTTER FLOW LINE SHALL
NOT EXCEED TWELVE (12) INCHES, AND THE FLOW
MUST BE CONTAINED WITHIN THE RIGHT-OF-WAY OR EASEMENTS PARALLELING THE RIGHT-OF-WAY. THE MOST RESTRICTIVE OF THE THREE CRITERIA SHALL GOVERN.
NOTES:
1. MINOR STORM - NO CURB-TOPPING. FLOW MAY SPREAD TO CROWN OF STREET.
2. MAJOR STORM - THE DEPTH OF WATER AT THE STREET CROWN SHALL NOT
EXCEED SIX (6) INCHES TO ALLOW OPERATION OF EMERGENCY
VEHICLES, THE DEPTH OF WATER OVER THE GUTTER FLOW LINE SHALL
NOT EXCEED TWELVE (12) INCHES, AND THE FLOW MUST BE CONTAINED
WITHIN THE RIGHT-OF-WAY OR EASEMENTS PARALLELING THE
RIGHT-OF-WAY. THE MOST RESTRICTIVE OF THE THREE CRITERIA SHALL
GOVERN.
DEVELOPMENT HIGHLAND SERVCIES
6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550
PHONE: 970.674.7550 | FAX: 970.674.7568 | www.Highland-DS.com
SHEET OF
DRAWN BY
CHECKED BY
DATE
SCALE (H)
HDS PROJ #
SCALE (V)
NORTHFIELD
STREET CAPACITY EXHIBIT
1/23/19
N/A
N/A
JTC
JTC
18-1000-00
1 1
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
A2 418,325 60% 250,995 Infiltration Gallery 0.19 6,586 SC-310 5,207
B2 159,134 60% 95,480 Infiltration Gallery 0.19 2,505 SC-740 1,264
B3 433,610 60% 260,166 Infiltration Gallery 0.19 6,827 SC-310 5,405
D1 172,132 60% 103,279 Rain Garden 0.19 2,710
706,400
709,920
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.
J.Claeys
Highland Development Services
18-1000-00
January 23, 2019
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
WQCV12-hr
(ft
3
)
WQCV12-hr
(watershed
inches)
Impervious Area
Treated (ft
2
)
Treatment Method
StormTech
Chamber Model
Infiltration Gallery
Footprint (ft
2
)
(from StormTech)
N/A (See UD BMP)
Highland Development Services
18-1000-00
J.Claeys
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
18-1000-00
J.Claeys
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 )
=
18-1000-00 PondCalcs.xls Page 3 of 5 Highland Development Services
J.Claeys
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
=
18-1000-00 PondCalcs.xls Page 2 of 5 Highland Development Services
J.Claeys
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
t c
P
I
+
=
18-1000-00 Rational Calcs (FC).xlsx Page 4 of 4 Highland Development Services
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 − ��
��
) �
� �
18-1000-00 Rational Calcs (FC).xlsx Page 3 of 4 Highland Development Services
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 − ��
��
) �
� �
18-1000-00 Rational Calcs (FC).xlsx Page 2 of 4 Highland Development Services
Atotal
(acres)
Weighted %
Impervious
A COMPOSITE
paved
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
18-1000-00 Rational Calcs (FC).xlsx Page 1 of 4 Highland Development Services
1/23/19
1" = 100'
N/A
JTC
JTC
18-1000-00
----
1 1
N
W E
S
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