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PRELIMINARY DRAINAGE REPORT
FISCHER PROPERTIES
FORT COLLINS, COLORADO
APRIL 27, 2022
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FORT COLLINS
GREELEY
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PRELIMINARY DRAINAGE REPORT: FISCHER PROPERTIES
COVER SHEET
April 27, 2022
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: PRELIMINARY DRAINAGE REPORT FOR
FISCHER PROPERTIES
Dear Staff,
Northern Engineering is pleased to submit this Preliminary Drainage Report for your review. This
report accompanies the Preliminary Development Plan submittal for the proposed Fischer Properties.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual
(FCSCM) and serves to document the stormwater impacts associated with the proposed Fischer
Properties project. We understand that review by the City of Fort Collins is to assure general
compliance with standardized criteria contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Cassandra Ungerman Danny Weber, PE
Project Engineer Project Manager
Compliance Statement
I hereby attest that this report for the Preliminary drainage design for Fischer Properties was prepared
by me or under my direct supervision, in accordance with the provisions of the Fort Collins
Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume
liability for drainage facilities designed by others.
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TABLE OF CONTENTS
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ....................................................................................... 4
II. DRAINAGE BASINS AND SUB-BASINS ............................................................................................ 6
III. DRAINAGE DESIGN CRITERIA ....................................................................................................... 6
IV. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ............................................................. 7
V. DRAINAGE FACILITY DESIGN ....................................................................................................... 8
VI. CONCLUSIONS......................................................................................................................... 10
VII. REFERENCES ........................................................................................................................... 11
TABLES AND FIGURES
Figure 1 - Vicinity Map ................................................................................................................................ 4
Figure 2 - Aerial Photograph ..................................................................................................................... 5
Figure 3 - Existing Floodplains .................................................................................................................. 5
Table 1 - LID Summary ............................................................................................................................... 8
Table 2 - Detention Summary ................................................................................................................... 9
APPENDICES
APPENDIX A – HYDROLOGIC COMPUTATIONS
APPENDIX B – HYDRAULIC COMPUTATIONS
APPENDIX C – WATER QUALITY / LID EXHIBIT
APPENDIX D – EROSION CONTROL REPORT
APPENDIX E – USDA SOILS REPORT
APPENDIX F – FEMA FIRMETTE
MAP POCKET
C 700 – HISTORIC DRAINAGE EXHIBIT
C 701 – DRAINAGE EXHIBIT
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I. GENERAL LOCATION AND DESCRIPTION
A. LOCATION
1. Vicinity Map
Figure 1 - Vicinity Map
2. Fischer Properties project site is located in the southwest quarter of Section 15, Township 7 North,
Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
3. The project site (refer to Figure 1) is bordered to the north by Westward Drive; to the east by South
Shields Street; to the south by existing developed single-family lots; and to the west by Del Mar
Street.
4. There is existing storm drainage infrastructure within South Shields Street in the form of curb inlets
and storm sewer manholes.
B. DESCRIPTION OF PROPERTY
1. Fischer Properties is comprised of ± 5.34 acres.
2. The site is currently a developed parcel of single-family homes with mostly unpaved drives, and
pasture for horses and livestock.
3. The existing groundcover consists of short grasses, cleared pasture, treated lawns, and existing
single-family homes. The existing on-site runoff generally drains from the southwest to the
northeast across flat grades (e.g., 0.50% - 2.00%) to South Shields Street. From there, the drainage
continues into curb inlets on South Shields Street, which convey runoff south to Canal Importation
Ditch to Spring Creek, and on to the Cache La Poudre River.
4. According to the United States Department of Agriculture (USDA) Natural Resources Conservation
Service (NRCS) Soil Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx),
the site consists primarily of Altvan-Satanta loams (Hydrologic Soil Group B) and Nunn clay loam
(Hydrological Soil Group C).
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Figure 2 - Aerial Photograph
5. Spring Creek and Canal Importation Ditch are the only major drainageways nearby the project site.
6. The proposed development will consist of one (1) apartment building containing 81 units and ten
(10) single-family lots. Other proposed improvements include parking lots, sidewalks, pool,
courtyards, and landscaping.
7. The proposed land use is mixed. This is a permitted use in the Low Density Residential (LDR) District
which will comprise the entirety of the proposed single-family lot area, and the Neighborhood
Conservation Buffer (NCB) District which will comprise the entirety of the multi-family building
development.
C. FLOODPLAIN
1. No portions of the site are located in a FEMA regulatory floodplain, as demonstrated in FEMA
FIRMette map panel 0978 (Product No. 08069C0978G).
Figure 3 - Existing Floodplains
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2. There are no special floodplain considerations required regarding finished floor elevations of
building footprints.
3. No floodplain use permit will be required for this project.
II. DRAINAGE BASINS AND SUB-BASINS
A. MAJOR BASIN DESCRIPTION
The project area of Fischer Properties is located within the City of Fort Collins Old Town major
drainage basin. Detention requirements for this basin are to detain the difference between the 100-
yr developed inflow rate and the historic 2-year release rate.
B. SUB-BASIN DESCRIPTION
1. The outfall for the project site is the Canal Importation Ditch, approximately ½ mile to the south.
2. The existing subject site can be defined with 7 distinct drainage basins.
3. The existing site runoff generally drains from southwest to northeast onto South Shields Street.
4. The project site receives runoff from Del Mar Street and Lakewood Drive to the west, as well as
portions of the single-family lots bordering on the north and south, which are generally B-Type lots.
III. DRAINAGE DESIGN CRITERIA
A. OPTIONAL PROVISIONS
There are no optional provisions outside of the FCSCM proposed with Fischer Properties.
B. STORMWATER MANAGEMENT STRATEGY
The overall stormwater management strategy employed with Fischer Properties utilizes the “Four
Step Process” to minimize adverse impacts of urbanization on receiving waters. The following is a
description of how the proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the
stormwater impacts of this development is the site selection itself. By choosing an already
developed site with public storm sewer currently in place, the burden is significantly less than
developing a vacant parcel absent of any infrastructure.
Fischer Properties aims to reduce runoff peaks, volumes and pollutant loads from frequently
occurring storm events (i.e., water quality (i.e., 80th percentile) and 2-year storm events) by
implementing Low Impact Development (LID) strategies. Wherever practical, runoff will be routed
across landscaped areas or through a rain garden or water quality pond. These LID practices reduce
the overall amount of impervious area, while at the same time Minimizing Directly Connected
Impervious Areas (MDCIA). The combined LID/MDCIA techniques will be implemented, where
practical, throughout the development, thereby slowing runoff and increasing opportunities for
infiltration.
Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow
Release. The efforts taken in Step 1 will help to minimize excess runoff from frequently occurring
storm events; however, urban development of this intensity will still have stormwater runoff
leaving the site. The primary water quality treatment will occur between underground vaults
located at the southeast area of the project, and several rain gardens between the single-family
and multifamily areas of the property. The remaining runoff will be treated for water quality in the
three proposed detention ponds in the center south area and the east parkway between the
apartment building and South Shields Street.
Step 3 – Stabilize Drainageways. While not directly applicable to this site, the project will pay
one-time stormwater development fees as well as ongoing monthly stormwater utility fees, both of
which help achieve citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to
industrial and commercial developments.
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IV. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
1. The subject property is not part of any Overall Development Plan (ODP) drainage study or similar
“development/project” drainage master plan.
2. The site plan is constrained on all sides by public streets, with the exception of the south edge and
the west half of the north edge, which are constrained by existing single-family lots.
A. HYDROLOGICAL CRITERIA
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure 3.4-1 of
the FCSCM, serve as the source for all hydrologic computations associated with Fischer Properties
development. Tabulated data contained in Table 3.4-1 has been utilized for Rational Method runoff
calculations.
2. The Rational Method has been used to estimate peak developed stormwater runoff from drainage
basins within the developed site for the 2-year, 10-year, and 100-year design storms. Peak runoff
discharges determined using this methodology have been used to check the street capacities,
inlets, swales, and storm drain lines.
3. Two separate design storms have been utilized to address distinct drainage scenarios. The first
event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second
event considered is the “Major Storm,” which has a 100-year recurrence interval.
B. HYDRAULIC CRITERIA
1. The drainage facilities proposed with Fischer Properties project are designed in accordance with
criteria outlined in the FCSCM.
2. As stated in Section I.C.1, above, the subject property is not located next to a FEMA designated
floodplain, nor is it located within any identified floodplain limits.
C. FLOODPLAIN REGULATIONS COMPLIANCE
As previously mentioned, this project is not adjacent to a FEMA regulated floodplain and as such, it
will not be subject to any floodplain regulations.
D. MODIFICATIONS OF CRITERIA
There are no formal modifications outside of the FCSCM proposed with Fischer Properties.
E. CONFORMANCE WITH WATER QUALITY TREATMENT CRITERIA
City Code requires that 100% of runoff from impervious surfaces in a project site shall receive some
sort of water quality treatment. This project proposes providing water quality treatment using
several methods. A single rain garden bisected with a sidewalk culvert will be located in the open
space between the single family and multi-family areas. This area treating the single family lots will
discharge into a detention pond south of the rain gardens, which will then discharge to exiting
stormwater infrastructure in South Shields Street. The runoff captured by the parking lot area in
sub-basin 100 will be conveyed to numerous area and curb inlets, which will be treated with
underground storage chambers in area under the parking lot at the southeast corner of the site.
From here, the flows will be discharged to the southeast detention pond. Runoff collected along
the north edge of the apartment building will be directed to several area inlets and be treated in a
detention pond in the northeast corner of the site. All detention ponds and underground storage
will discharge to the existing storm drain in South Shields Street. Due to the physical constraints
associated with an infill project of this nature and the prohibition of providing water quality
facilities within the public right-of-way, there are some small, narrow areas around the perimeter of
the project that cannot be captured. The northeast portion of the site, due to the trussed roof on
the multi-family building, will not be captured. To account for not capturing these flows, there are
several off-site areas that will be treated for water quality. An area swap is being proposed for these
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portions to override the portion of site area that is not being treated. See Appendix C for LID
calculations and exhibit.
F. CONFORMANCE WITH LOW IMPACT DEVELOPMENT (LID)
The project site will conform with the requirement to treat a minimum of 75% of the project site
using a LID technique. A single rain garden and underground chambers will be used to capture and
filter or infiltrate the water quality capture volume.
G. SIZING OF LID & WQ FACILITIES
Rain Gardens/Underground Chambers
1. The rain garden and chambers were sized by first determining the required water quality capture
volume (WQCV) for Basin 200 for the rain garden and Basin 100 for the chambers. A 12-hour drain
time was used in this calculation.
2. Once the WQCV was identified, each rain garden and chamber area were sized for its respective
WQCV. The rain gardens will be constructed with a biomedia filter and underdrain. An overflow
drain will be provided in each rain garden and weir for chambers to pass storms greater than the
WQCV.
Water Quality Pond
1. The water quality pond was sized by first determining the required water quality capture
volume (WQCV) for Basins 100, 101, OS-2, and OS-4. A 40-hour drain time was used in
this calculation. The WQCV that resulted was approximately 4070 ft3, which includes the
additional 20%
Table 1 - LID Summary
LID ID Area (ft2) Weighted %
Impervious
Volume per
UD-BMP (ft3)
Vol. w/ 20%
increase per
FC Manual
(ft3)
Impervious
area (ft2)
Rain Garden A 123,675 55% 1,817 2,080 63,074
Stormtech 1 93,759 66% 1,451 1,741 61,881
V. DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
1. The main objective of Fischer Properties drainage design is to maintain existing drainage patterns,
while not adversely impacting adjacent properties.
2. A list of tables and figures used within this report can be found in the Table of Contents at the front
of the document. The tables and figures are located within the sections to which the content best
applies.
3. Drainage for the project site has been analyzed using three (3) onsite drainage sub- basins,
designated as sub-basins 100, 101 and 200. Furthermore, there are four (4) offsite drainage sub-
basins designated as sub-basins OS-1, OS-2, OS-3, and OS-4. The drainage patterns anticipated for
the sub-basins are further described below.
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Sub-Basin 100 & 101
Sub-Basins 100 and 101 encompass approximately 60% of the total site area. Sub-basin 100
contains Stormtech Chambers 1 which is the collection point of the multi-family building, adjacent
parkways, and parking lot before release into the proposed Pond 2 in sub-basin 101. Sub-basin 101
contains a portion of the multi-family building, landscaped areas, and Detention Pond 2. An outlet
structure with a restrictor plate will be installed in Pond 2 and an outfall pipe will be used for the
discharge into the South Shields Street storm drain.
Sub-Basin 200
Sub-Basin 200 encompasses approximately 40% of the total site area. Basin 200 is comprised
primarily of the single-family lots and the cul-de-sac extension to Lakewood Drive. This basin will
convey runoff to Rain Garden A through a concrete pan on the north edge of the north lots and via
two sidewalk chases connecting the cul-de-sac directly to the two distinct areas of the rain garden.
The rain garden will then convey its drainage to Detention Pond 1, which will discharge to the
existing South Shields Street storm drain.
Sub-Basins OS-1 – OS-4
Sub-Basins OS-1 through OS-4 are offsite basins containing existing single-family residential lots,
open space, and paved roadways. Stormwater runoff from these basins flows via curb and gutter and
overland flow onto the project site. Sub-Basins OS-1 and OS-3 flow to Sub-Basin 200 where their flows
are treated for LID in Rain Garden A. Sub-Basins OS-2 and OS-4 are assumed to pass through Sub-
Basin 100, but these flows are not accounted for in the Stormtech calculations.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report.
B. SPECIFIC DETAILS
1. Two detention ponds are proposed with this development and will detain up to the 100-yr storm
event and release at or below the calculated release rate. See Table 2 for detention summary.
Table 2 - Detention Summary
2. LID treatment is being provided within Rain Garden A and Stormtech Chamber 1. These treat
approximately 86% of the site impervious runoff, which is more than the required 75% LID
treatment. Please see the LID exhibit and calculations in Appendix C. The remainder of water
quality will be provided by extended detention.
3. Detention allowable release rate is based on computed 2-year historic flow for the overall property.
4. Stormwater facility Standard Operations Procedures (SOP) will be provided by the City of Fort
Collins in the Development Agreement.
5. Preliminary Design details, and construction documentation shall be provided to the City of Fort
Collins for review prior to Preliminary Development Plan approval.
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VI. CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
1. The drainage design proposed with Fischer Properties complies with the City of Fort Collins Master
Drainage Plan for the Spring Creek and Canal Importation Basins.
2. The drainage plan and stormwater management measures proposed with Fischer Properties
project are compliant with all applicable State and Federal regulations governing stormwater
discharge.
B. DRAINAGE CONCEPT
1. The drainage plan and stormwater management measures proposed with Fischer Properties
project are compliant with all applicable State and Federal regulations governing stormwater
discharge.
2. Fischer Properties will not impact the Master Drainage Plan recommendations for the Canal
Importation and Spring Creek major drainage basin.
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VII. REFERENCES
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance
No. 159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code.
2. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
3. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright- McLaughlin Engineers, Denver, Colorado, Revised April 2008.
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PRELIMINARY DRAINAGE REPORT: FISCHER PROPERTIES
APPENDIX
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.19
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Residential (Low Density).…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………50%0.55 0.55 0.69
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt/Con
crete
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of Single
Family (ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
H1 2.742 0.00 0.06 0.26 0.28 0.00 0.00 2.49 17% 0.39 0.39 0.48
H2 2.653 0.00 0.00 0.00 0.00 0.00 0.00 2.65 2% 0.25 0.25 0.31
OS-1 0.133 0.105 0.03 80% 0.81 0.81 1.00
OS-2 0.518 0.141 0.38 26% 0.44 0.44 0.55
OS-3 0.397 0.00 0.097 0.30 25% 0.43 0.43 0.54
OS-4 0.928 0.01 0.095 0.82 12% 0.33 0.33 0.41
HISTORIC BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Offsite Basins
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
h1 H1 0.39 0.48 300 1.28%21.2 18.5 208 1.04%0.015 0.59 7.14 0.5 12.8 21.7 19.0 12.8 12.8
h2 H2 0.25 0.31 300 2.27%20.9 19.5 176 1.77%0.015 0.59 9.29 0.3 12.6 21.3 19.8 12.6 12.6
os-1 OS-1 0.81 1.00 49 1.65%3.2 1.1 129 2.32%0.015 0.59 10.64 0.2 11.0 3.4 1.3 5.0 5.0
os-2 OS-2 0.44 0.55 143 1.07%14.4 12.0 N/A 0.015 0.59 N/A N/A 10.8 14.4 12.0 10.8 10.8
os-3 OS-3 0.43 0.54 139 3.58%9.7 8.1 N/A 0.015 0.59 N/A N/A 10.8 9.7 8.1 9.7 8.1
os-4 OS-4 0.33 0.41 100 2.06%11.3 10.1 N/A 0.038 0.50 N/A N/A 10.6 11.3 10.1 10.6 10.1
HISTORIC DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
Offsite Basins
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10 Notes:
1) Add 5000 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per Larimer County
Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a
water depth of 1', fixed side slopes, and a triangular swale section for grass
channelized flow. Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Rational Method Equation:
Rainfall Intensity:
h1 H1 2.74 12.8 12.8 0.39 0.48 2.02 3.45 7.04 2.15 3.68 9.27
h2 H2 2.65 12.6 12.6 0.25 0.31 2.02 2.02 7.04 1.34 1.34 5.79
os-1 OS-1 0.13 5.0 5.0 0.81 1.00 2.85 2.85 9.95 0.31 0.31 1.32
os-2 OS-2 0.52 10.8 10.8 0.44 0.55 2.17 2.17 7.57 0.49 0.49 2.16
os-3 OS-3 0.40 8.1 8.1 0.43 0.54 2.40 2.40 8.38 0.41 0.41 1.80
os-4 OS-4 0.93 10.1 10.1 0.33 0.41 2.21 2.21 7.72 0.68 0.68 2.94
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
Offsite Basins
HSTORIC RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
()()()AiCCQf=
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Residential (Low Density).…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………50%0.55 0.55 0.69
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt/Con
crete
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of Single
Family (ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
100 2.24 1.07 0.19 0.50 0.00 0.00 0.00 0.00 0.67 77% 0.82 0.82 0.88
101 0.84 0.00 0.06 0.26 0.00 0.00 0.00 0.00 0.52 36% 0.52 0.52 0.57
200 2.31 0.35 0.09 0.00 1.51 0.00 0.00 0.00 1.96 54% 0.39 0.39 0.46
Offsite Basins
OS-1 0.13 0.11 0.00 0.00 0.00 0.00 0.00 0.00 0.03 80% 0.81 0.81 0.86
OS-2 0.52 0.00 0.00 0.14 0.00 0.00 0.00 0.00 0.38 26% 0.44 0.44 0.50
OS-3 0.40 0.00 0.00 0.10 0.00 0.00 0.00 0.00 0.30 25% 0.43 0.43 0.49
OS-4 0.93 0.00 0.01 0.09 0.00 0.00 0.00 0.00 0.82 12% 0.33 0.33 0.39
Rain Garden 2.84 0.46 0.10 0.19 1.51 0.00 0.00 0.00 1.03 55%0.34 0.34 0.37
Stormtech 2.20 0.80 0.14 0.52 0.00 0.00 0.00 0.00 0.38 65%0.68 0.68 0.72
Total Release 7.37 1.53 0.36 1.09 1.51 0.00 0.00 0.00 2.40 56%0.47 0.47 0.51
Total On-Site 5.39 1.43 0.34 0.76 1.51 0.00 0.00 0.00 0.88 61% 0.49 0.49 0.52
DEVELOPED BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
100 100 0.82 0.88 39 3.23%2.2 1.7 524 1.09%0.015 0.59 7.31 1.2 13.1 3.4 2.9 5.0 5.0
101 101 0.52 0.57 22 6.09%2.8 4.2 452 1.31%0.015 0.59 8.01 0.9 12.6 3.7 5.1 5.0 5.1
200 200 0.39 0.46 29 4.48%4.3 3.9 330 1.68%0.015 0.59 9.06 0.6 12.0 4.9 4.5 5.0 5.0
os-1 OS-1 0.81 0.86 49 1.65%3.2 2.7 129 2.32%0.015 0.59 10.64 0.2 11.0 3.4 2.9 5.0 5.0
os-2 OS-2 0.44 0.50 143 1.07%14.4 13.1 0 N/A 0.015 0.59 N/A N/A 10.8 14.4 13.1 10.8 10.8
os-3 OS-3 0.43 0.49 139 3.58%9.7 8.8 0 N/A 0.015 0.59 N/A N/A 10.8 9.7 8.8 9.7 8.8
os-4 OS-4 0.33 0.39 100 2.06%11.3 10.4 0 N/A 0.038 0.50 N/A N/A 10.6 11.3 10.4 10.6 10.4
DEVELOPED DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
Offsite Basins
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10 Notes:
1) Add 5000 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per Larimer County
Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a
water depth of 1', fixed side slopes, and a triangular swale section for grass
channelized flow. Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Rational Method Equation:
Rainfall Intensity:
100 100 2.24 5.0 5.0 0.82 0.88 2.85 4.87 9.95 5.24 8.95 19.62
101 101 0.84 5.1 5.1 0.52 0.57 2.85 4.87 9.95 1.25 2.14 4.78
200 200 2.31 5.0 5.0 0.39 0.46 2.85 2.85 9.95 2.57 2.57 10.57
os-1 OS-1 0.13 5.0 5.0 0.81 0.86 2.85 2.85 9.95 0.31 0.31 1.13
os-2 OS-2 0.52 10.8 10.8 0.44 0.50 2.17 2.17 7.57 0.49 0.49 1.96
os-3 OS-3 0.40 8.8 8.8 0.43 0.49 2.35 2.35 8.21 0.40 0.40 1.60
os-4 OS-4 0.93 10.4 10.4 0.33 0.39 2.21 2.21 7.72 0.68 0.68 2.79
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
Offsite Basins
DEVELOPED RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
()()()AiCCQf=
SFW
NYLOPLASTDO NOT POLLUTEDRAINS TOWATERWAYS
DO NOT POLLUTE DRAINS TO WATERWAYS
NYLOPLAST DUCTILE IRONUDT
TXX
XXXXXXXX X
D
D
D
D
D
D
STSTSTST204.5'43
.
6
'76.4'0.52 ac.
OS-2
2.24 ac.
100
2.31 ac.
200
0.40 ac.
OS-3
0.93 ac.
OS-4
0.13 ac.
OS-1
100
200
OS-2
OS-1
OS-3
OS-4
0.84 ac.
101
RAIN
GARDEN A
STORMTECH
CHAMBERS 1
DETENTION
POND 1
100-YR WSEL =
5030.3
DETENTION
POND 2
100-yr
WSEL =
5029.4
DRAWN BY:
SCALE:
ISSUED:
IMPALA
REDEVELOPMENT
SHEET NO:
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
E N G I N E E R N GI
EHTRON R N
970.221.4158
northernengineering.com
LID EXHIBIT
C. Ungerman
1in=120ft
4/27/22
PROPOSED STORM SEWER
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
ADESIGN POINT
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
A
LEGEND:
( IN FEET )
1 inch = ft.
Feet0100100
100
RAIN GARDEN LIMITS
STORMTECH CHAMBERS
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
LID Site Summary - New Impervious Area
Total Area of Current Development 284,256 ft2
Total Impervious Area 144,302 ft2
Total Impervious Area without LID Treatment 13,694 ft2
101
75% Requried Minimum Area to be Treated 108,226
Total Treated Area 124,007 ft2
Percent Impervious Treated by LID 85.94%
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =55.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.550
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.18 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 123,675 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =2,180 cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1360 sq ft
D) Actual Flat Surface Area AActual =sq ft
E) Area at Design Depth (Top Surface Area)ATop =sq ft
F) Rain Garden Total Volume VT=cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
B. Ruch
April 26, 2022
Fischer
Fort Collins
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
SF-UD-BMP_v3.07, RG 4/26/2022, 1:21 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
B. Ruch
April 26, 2022
Fischer
Fort Collins
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
SF-UD-BMP_v3.07, RG 4/26/2022, 1:21 PM
Project Number:Project:
Project Location:
Calculations By:Date:
Sq. Ft. Acres
100 94,906 2.18 64%Stormtech 1 Stormtech 1,523 60,740
101 37,010 0.85 37%n/a n/a 0 13,694
200 100,599 2.31 54%Rain Garden A Rain Garden 930 54,323
Total 232,515 5.34 128,757
LID Summary
Project Number:Project:
Project Location:
Calculations By:Date:
LID Summary
per LID
Structure
Sq. Ft. Acres
Rain Garden A 100,599 2.31 54%200 Rain Garden 1,723 2,068 54,323
Stormtech 1 94,906 2.18 64%100 Stormtech 2,111 2,533 60,740
Total 195,505 4.49 4,601 115,063
232,515 ft2
128,757 ft2
13,694 ft2
96,568 ft3
115,063 ft2
89.36%
LID Summary
AreaBasin ID Treatment TypePercent
Impervious LID ID
Fischer Subdivision
4/25/2022
1382-002
Fort Collins, Colorado
C. Ungerman
Total
Impervious
Area (ft2)
Required
Volume (ft3)
LID Summary per Basin
Area
Weighted %
Impervious
1382-002
Fort Collins, Colorado
C. Ungerman
Impervious
Area (ft2)
Vol. w/20%
Increase per
Fort Collins
Manual (ft3)
Fischer Subdivision
4/25/2022
Subbasin ID Treatment TypeLID ID Volume per
UD-BMP (ft3)
Total Treated Area
Percent Impervious Treated by LID
101
75% Requried Minimum Area to be Treated
LID Site Summary - New Impervious Area
Total Area of Current Development
Total Impervious Area
Total Impervious Area without LID Treatment
X X X XXXXX
XXXXXXXXXXX
XXXXXXXXX X X XD
D
D
D
D
D
STSTSTSTSTSTSTSTSTSTSTSTSTS
T STF.O.
F.O.
D
D
/ / / / / / / /0.52 ac.
OS-2
NYLOPLASTDO NOT POLLUTE
DRAINS TOWATERWAYS
DO NOT POLLUTE DRAINS TO WATERWAYS
NYLOPLAST DUCTILE IRON
UDUDUDUDUDGGGGGGGG
GT
TEEEGG G G GEEEEEEEEEEEEEEEEEEEFDCEEEEE/ / / / / / / /2.24 ac.
100
101
2.31 ac.
200
0.40 ac.
OS-3
0.93 ac.
OS-4
0.13 ac.
OS-1
100
200RAINGARDEN ASTORMTECH
CHAMBERS 1
PROPOSED
STORM DRAIN
PROPOSED
STORM DRAIN
PROPOSED 2'
CONCRETE
PAN
PROPOSED 2'
CONCRETE PAN
OS-2
OS-1
OS-3
OS-4
0.84 ac.
101
PROPOSED
UNDERDRAIN
PROPOSED
SIDEWALK
CULVERT
PROPOSED
SIDEWALK
CULVERT
PROPOSED
UNDERDRAIN
5' SIDEWALK
5' SIDEWALK
SOUTH SHIELDS STREETSPRIN
G
F
I
E
L
D
D
R
I
V
E
WESTWARD DRIVE
DEL MAR STREETLAKEWOOD
DRIVE
EXISTING
STORM DRAIN
EXISTING
STORM DRAIN
9' UTILITY EASEMENT
9' UTILITY EASEMENT
DETENTION
POND 1
100-YR WSEL =
5033.3
DETENTION
POND 2
100-yr WSEL
= 5029.4
PROPOSED 2'
CONCRETE PAN
EXISTING 24"
STORM DRAIN
LOT 3
LOT 4
LOT 1 LOT 2
LOT 5
LOT 8
LOT 6
LOT 7
LOT 10 LOT 9
BLOCK 1
BLOCK 1
TRACT B
TRACT A
PROPOSED CULVERT
PROPOSED CULVERT
6' SIDEWALK
5' SIDEWALK
6' SIDEWALK30'
FL-FL57' ROW
OWNER: POPPE, DAVID A.
1205 WESTWARD DR.
OWNER: MARX,
NICHOLAS J./ JILL B.
JARVIS
1209 WESTWARD DR.
OWNER: GRIFFITHS,
THOMAS
1213 WESTWARD DR.
OWNER: WAYFARE HOME
RENTAL, LLC.
1217 WESTWARD DR.
OWNER: BOWEN,
ZACHARY H.
1200 DEL MAR ST.
OWNER: LAJEUNESSE,
ROBERT M./ IRINA V.
1220 SPRINGFIELD DR.
OWNER: MIRANDA, JOHN
E./ YVONNE C.
1212 SPRINGFIELD DR.
OWNER: MARTINO, MARY
K.
1208 SPRINGFIELD DR.
OWNER: RIEUX SYLVIA
MARIANNE TRUST
1204 SPRINGFIELD DR.
OWNER: JRB HOLDINGS,
LLC.
1200 SPRINGFIELD DR.
OWNER: CARLSON, BEVERLY A.
1301 S. SHIELDS ST.
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
1 inch = ft.
Feet04040
40
80 120
SheetFISCHER PROPERTIESThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETENGINEERNGIEHTRONRNFORT COLLINS: 301 North Howes Street, Suite 100, 80521GREELEY: 820 8th Street, 80631970.221.4158northernengineering.comof 16
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
11
NOTES:
1.REFER TO THE PRELIMINARY DRAINAGE REPORT FOR FISCHER PROPERTIES BY
NORTHERN ENGINEERING, DATED APRIL 27, 2022 FOR ADDITIONAL INFORMATION.
A
LEGEND:
C 701DRAINAGE EXHIBIT 16
Rational Flow Summary | Developed Basin Flow Rates
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100 Q2
(cfs)
Q100
(cfs)
100 2.24 5.0 5.0 0.82 0.88 5.24 19.62
101 0.84 5.1 5.1 0.52 0.57 1.25 4.78
200 2.31 5.0 5.0 0.39 0.46 2.57 10.57
OS-1 0.13 5.0 5.0 0.81 0.86 0.31 1.13
OS-2 0.52 10.8 10.8 0.44 0.50 0.49 1.96
OS-3 0.40 8.8 8.8 0.43 0.49 0.40 1.60
On-Site LID Treatment
Project Summary
Total Impervious Area 144,302 sf
Target Treatment Percentage 86%
Minimum Area to be Treated by LID measures 124,007 sf
Rain Garden Area
Rain Garden Area 3,834 sf
Run-on area for Rain Gardens 218,581 sf
Total Rain Garden Treatment Area 222,415 sf
Overall Run-on Ratio for Rain Garden (50:1 Max) 57 :1
Total Treatment Area 124,007 sf
Percent Total Project Area Treated 85.9%
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION