HomeMy WebLinkAboutEAST OAK TOWNHOMES - FDP240009 - SUBMITTAL DOCUMENTS - ROUND 1 - Drainage Related Document
FINAL
DRAINAGE AND EROSION CONTROL REPORT
EAST OAK TOWNHOMES SUBDIVISION
Prepared for:
CCC Development
221 East Oak Street, Unit A
Fort Collin, CO 80524
Prepared by:
Wilson & Company
4065 St Cloud Drive, Suite 201
Loveland, Colorado 80538
970-834-6364
June 26, 2024
Job Number 22-100-645-00
4065 St. Cloud, Suite.201
Loveland, CO 80538
970-834-6364 phone
June 26, 2024
Mr. Wes Lamarque
City of Fort Collins Stormwater Engineering
700 Wood Street
Fort Collins, CO 80522
RE: Final Drainage and Erosion Control Report for East Oak Townhomes Subdivision
Dear Wes,
I am pleased to submit for your review and approval, this Final Drainage and Erosion
Control Report for East Oak Townhomes Subdivision development. I certify that this
report for the drainage design was prepared in accordance with the criteria in the Fort
Collins Stormwater Criteria Manual.
City of Fort Collins PDP comments dated March 29, 2024 have been addressed in this
report.
I appreciate your time and consideration in reviewing this submittal. Please call if you
have any questions.
Sincerely,
Abigail Wright, EIT Michael Oberlander, P.E.
Civil Engineer in Training Colorado Professional
Engineer No. 34288
4065 St. Cloud, Suite.201
Loveland, CO 80538
970-834-6364 phone
ENGINEER’S CERTIFICATION
“I hereby attest that this report for the final drainage design for the East Oak Townhomes
Subdivision development 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.”
___________________________________________ _______________________
Registered Professional Engineer Date
Michael Oberlander, PE
Registered Professional Engineer
State of Colorado No. 34288
For and on behalf of Wilson & Company
Lots 1-15 East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page i
Table of Contents
1. GENERAL LOCATION AND DESCRIPTION ........................................................... 1
1.1 Location ............................................................................................................ 1
1.2 Description of Property and Project ............................................................... 1
1.3 Floodplain Submittal Requirements ............................................................... 1
2. DRAINAGE BASINS AND SUB-BASINS ................................................................. 2
2.1 Major Basin Description .................................................................................. 2
2.2 Sub-basin Description ..................................................................................... 2
3. DRAINAGE DESIGN CRITERIA ............................................................................... 2
3.1 Regulations ....................................................................................................... 2
3.2 Directly Connected Impervious Area (DCIA) Discussion ............................. 2
3.3 Development Criteria Reference and Constraints ......................................... 3
3.4 Hydrological Criteria ........................................................................................ 4
3.5 Hydraulic Criteria ............................................................................................. 6
3.6 Low Impact Development (LID) Conformance ............................................... 7
3.7 Water Quality (WQ) Treatment Criteria ........................................................... 7
3.8 Detention Requirements .................................................................................. 8
3.9 Floodplain Regulations Compliance .............................................................. 8
3.10 Modifications of Criteria .................................................................................. 8
4. DRAINAGE FACILITY DESIGN ............................................................................... 8
4.1 General Concept .............................................................................................. 8
4.2 Specific Details ................................................................................................. 8
4.3 LID, WQ and Detention .................................................................................. 10
5. SEDIMENT AND EROSION CONTROL ................................................................... 9
6. CONCLUSIONS ...................................................................................................... 12
6.1 Compliance with Standards .......................................................................... 12
6.2 Drainage Concept .......................................................................................... 12
7. REFERENCES ........................................................................................................ 12
APPENDIX A VICINITY MAP, DRAINAGE & EROSION CONTROL PLANS ................ A
APPENDIX B HYDROLOGIC COMPUTATIONS .......................................................... B
APPENDIX C HYDRAULIC CALCULATIONS ...............................................................C
APPENDIX D IMPERVIOUS AREA & BMP EXHIBITS AND LID CALCULATIONS ......D
APPENDIX E SOILS AND FLOODPLAIN INFORMATION ............................................ E
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 1
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location
East Oak Townhomes Subdivision is in the Southwest ¼ of Section 12, Township
7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County
of Larimer, State of Colorado. It is in Old Town Fort Collins and is bounded on the
north by Lot 26, Block 131 of the Original Town Plat (the McIntyre House), on the
east by Mathews Street, on the south by East Oak Street and on the west by an
alley and Lots 17 and 18 and the east half of Lots 19-22 of Block 131 of the Original
Town. Please refer to the Vicinity Map located in Appendix A.
1.2 Description of Property and Project
The project area is 0.48 acres and is currently occupied by Northern Colorado Real
Estate Brokers, LLC and the Community of Christ- Fort Collins Congregation.
The project proposes to develop a single family attached project including attached
multi-story units with associated drive aisle and sidewalk, wet and dry utilities, and
alley improvements.
Offsite flow does not contribute to the site from any direction.
According to Natural Resources Conservation Service Web Soil Survey, the soils
onsite consist of Santana loam, 0 to 1 percent slopes, Soil Group C. Please refer
to Appendix E for the Hydrologic Soil Group – Larimer County Area map that
includes this site.
1.3 Floodplain Submittal Requirements
The area is designated as Zone X, Area of Minimal Flood Hazard, on FIRM Panel
08069C0979H, dated 5/02/2012 and is therefore not within any FEMA mapped
floodplain. The site does not have any adjacent City of Fort Collins local
floodplains. A Floodplain Submittal is not required and has not been included with
this report. Please refer to Appendix E for the National Flood Hazard Layer
FIRMette.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 2
2. DRAINAGE BASINS AND SUB-BASINS
2.1 Major Basin Description
East Oak Townhomes Subdivision is part of the Old Town Basin Master Drainage
Plan. The basin is in north-central Fort Collins and is urbanized. All the water from
the basin drains to the Poudre River located north and east of the site.
2.2 Sub-basin Description
The property is in the north central part of the Old Town Basin and drains to the
existing storm systems in Mathews and Oak Street.
3. DRAINAGE DESIGN CRITERIA
3.1 Regulations
This report was prepared to meet or exceed the “Fort Collins Stormwater Criteria
Manual” (FCSCM) specifications. Where applicable, the criteria established in the
Mile High Flood District’s (MHFD) “Urban Storm Drainage Criteria Manual”
(USDCM), developed by the Denver Regional Council of Governments, has been
used.
3.2 Directly Connected Impervious Area (DCIA) Discussion
The USDCM recommends a four-step process for receiving water protection that
focuses on reducing runoff volumes, treating the water quality capture volume
(WQCV), stabilizing drainageways and implementing long-term source controls.
The Four Step Process applies to the management of smaller, frequently occurring
events.
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).
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 3
Runoff from the site shall be conveyed to a permanent water quality facility (ADS
Stormtech system) which promotes settlement of particles and will slow the "first
flush" from all storms entering the public street and storm sewer system.
Step 2: Implement BMPs that Provide a Water Quality Capture Volume with
Slow Release
Runoff from the site shall be conveyed to an underground water quality facility
which reduces the rate of runoff and promotes settlement of particles.
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
The proposed project will control pollutants by encouraging them to settle out
inside the isolator row of the ADS Stormtech system before being released from
the site. The proposed project will proactively control pollutants at their source by
preventing pollution rather than removing contaminants once they have entered
the stormwater system as compared to historic conditions.
3.3 Development Criteria Reference and Constraints
All basins in Fort Collins are required to provide LID water quality. This will be
discussed in subsequent sections of the report.
The stormwater outfall for this site is the northeast corner into the curb of Mathews
that flows north. The Cache la Poudre River is the ultimate outfall.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 4
3.4 Hydrological Criteria
The City of Fort Collins requires that all drainage system design and construction
take into consideration two design storms: the minor storm and the major storm.
The “minor storm” is the 2-year storm or the 50th percentile storm event. The
“major storm” is the 100-year storm or the one percentile storm event.
Runoff computations were prepared for the 2-year minor and 100-year major storm
frequencies utilizing the Rational Method. The study was divided into five onsite
basins that can be identified on the Drainage Plan in Appendix A.
Percentage impervious values were based on proposed land surface types and
are specified in the following table from the FCSCM.
Table 1. Recommended Percentage Imperviousness Values.
The runoff coefficients are based on surface type and specified in the following
table from the FCSCM. The site is classified as NRCS Hydrologic Soil Group C.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 5
Table 2. Surface Type – Runoff Coefficients.
The City of Fort Collins requires a Frequency Adjustment Factor for the 100-year
Storm Return Period. The following table lists this factor, Cf.
Table 3. Frequency Adjustment Factors.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 6
The rainfall intensities used in the Rational Method computation of runoff were
obtained from the Fort Collins Rainfall IDF Curve contained in the figure below.
Figure 1. Rainfall IDF Curve – Fort Collins.
All hydrological calculations including a summary of the calculated minor and major
rainfall event flows are provided in Appendix B.
3.5 Hydraulic Criteria
All hydraulic calculations within this report have been prepared in accordance with
the FCSCM and/or the USDCM. Final hydraulic calculations (inlet sizing and weir
analysis) are included in Appendix C. The pipes within the project have not been
sized as the entire system floods the ADS Stormtech system and then discharges
over a weir prior to exiting the site.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 7
3.6 Low Impact Development (LID) Conformance
Integration of LID systems into the drainage design is required for all development
projects. The implementation of LID systems requires one of the following two
options:
1. 50% of the newly added or modified impervious area must be treated
by LID techniques and 25% of new paved (vehicle use) areas must
be pervious.
2. 75% of newly added or modified impervious area must be treated by
LID techniques.
Pervious pavement is not proposed; therefore, 75% of the newly added or modified
impervious area must be treated by LID techniques. This is accomplished with an
underground water quality treatment system (ADS Stormtech system). For this
site, more than 75% is provided in the ADS Stormtech system. The actual treated
area at this time is 88% and the remaining 12% of water quality treatment is in the
Udall Natural Area regional pond.
Please refer to the Impervious Area Exhibit in Appendix D for comparison of the
existing and proposed impervious areas.
3.7 Water Quality (WQ) Treatment Criteria
The City requires stormwater quality treatment of all new or modified impervious
areas. For this site, 25% of the standard water quality requirement is already
provided for in the City’s Udall Natural Area water treatment facility. The site will
provide water quality for 88% of the newly added or modified impervious area with
the LID facility.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 8
3.8 Detention Requirements
Because the development is not increasing impervious area greater than 5,000
square feet, detention is not required. The increase in impervious area has been
calculated to be 2,814 square feet.
3.9 Floodplain Regulations Compliance
The project is not within any FEMA mapped floodplain. Therefore, a Floodplain
Submittal is not required and has not been included with this report.
3.10 Modifications of Criteria
There are currently zero Modifications of Criteria for this project.
4. DRAINAGE FACILITY DESIGN
4.1 General Concept
The storm runoff of the proposed development will be conveyed to the Mathews
Street curb and gutter in the northeast corner of the site after being treated through
the LID system. 88% of the impervious area of the site will pass through a
proposed underground water quality treatment system (ADS Stormtech system).
The Stormtech system will receive the building roof drains (except Lot 7) and the
courtyard / drive area. A weir will be placed downstream of the collection system
and Stormtech chambers forcing the water to backflow into the treatment system
and through the fabric on the bottom of the chambers. In larger events, the weir
will overtop (maximum elevation 4980.1 during the major event) into an outlet pipe,
concrete channel, and new Mathews Street sidewalk culvert system to the curb of
Mathews. It will then follow existing conditions and flow north to the existing triple
combination inlets in Mathews just south of the intersection with Mountain Avenue.
4.2 Specific Details
A summary of the drainage patterns within each basin is provided in the following
paragraphs. Please refer to Appendix A for the drainage plan and Appendix B for
a hydrologic summary of each basin.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 9
Basin A is 0.27 acres and contains the proposed building. This basin will produce
0.7 cfs and 2.7 cfs during the 2-year and 100-year events, respectively. Roof drains
from all lots (except Lot 7) will drain to adjacent 6-inch collection pipes. Both
systems will direct the roof flow north to a structure with a sump that will then
backwater into the ADS Stormtech system for treatment.
Basin B is 0.17 acres and is located in the center and north side of the site and
contains the landscaping and drive/courtyard between buildings. This basin drains
to proposed landscape area inlets located in the landscape areas adjacent to the
west building, and to a 24” inch area inlet and a 2’x3’ ADS Nyloplast curb inlet on
the north side of the site. The landscape area inlets will drain to a 12-inch system
and the sump structure north of the ADS Stormtech system. The remainder of the
basin flow and what is not captured in the landscape inlets will be captured in the
24-inch area inlet and 2’x3’ ADS Nyloplast curb inlet and will drain to the proposed
storm system where a weir in the last structure of the storm system will force the
flooding of the ADS Stormtech chambers. The treated water from Basins A and B
will outlet through the fabric and underdrain of the system. The underdrain will
drain to the weir structure (on the downstream side of the weir) and to a channel
and pipe system under the Mathews sidewalk that will discharge to the curb on
Mathews.
Basin B will produce 0.4 cfs and 1.2 cfs during the 2-year and 100-year events,
respectively. The proposed 2’x3’ ADS Nyloplast inlet and the 24” area inlet were
analyzed to ensure that the 100-year flow from both basins A and B (3.9 cfs) can
be captured in one or both inlets in case of failure of the Stormtech system.
Basin C is 0.08 acres and is located west of the building in the alley and south of
the building. The basin contains the concrete walk on East Oak Street and a most
of the alley west of the site. The basin drains south through the alley and then
along the curb and gutter of East Oak Street to an existing storm inlet, design point
c. This basin will produce 0.2 cfs and 0.8 cfs during the 2-year and 100-year
events, respectively.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 10
Basin D is 0.04 acres and contains the north portion of the alley on the west side
of the development. The basin contains concrete walks and a concrete drive. The
basin drains to the center of the alley and continues to drain north as it does today.
This basin will produce 0.1 cfs and 0.4 cfs during the 2-year and 100-year events,
respectively.
Basin E is 0.02 acres and contains the roof of Lot 7. The basin drains west to the
alley as it does today and then along the curb and gutter of East Oak Street to an
existing storm inlet at design point c. This basin will produce 0.0 cfs and 0.2 cfs
during the 2-year and 100-year events, respectively.
4.3 LID, WQ and Detention
The project is required to treat 75% of on-site new impervious area with LID. LID
treatment has been identified as an underground water quality system (entirely
isolator rows of a proposed ADS Stormtech system). The LID will treat 88% of the
on-site impervious area. Appendix D includes the Impervious Area Exhibit and
calculations for LID treatment.
Table 4. LID Summary Table
75% On-Site Treatment by LID Requirement
New or Modified Impervious Area 17,716 sf
Required Minimum Impervious Area to be Treated 13,287 sf
Total impervious Area Treated 15,567 sf
Actual % of Impervious Area On-Site Treated by LID 88%
On-site detention for this site is not required.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 11
5. SEDIMENT AND EROSION CONTROL
The disturbed area is less than one-acre and will not require a State of Colorado
Discharge Permit or City of Fort Collins plan and report.
Temporary Sediment and Erosion Control
Erosion and sedimentation will be controlled on-site during construction by use of
vehicle tracking control pad, concrete washout area, silt fence, rock socks in
adjacent existing curb and gutter, inlet protection, and seeding and mulch. The
measures will be designed to limit the overall sediment yield increase due to
construction as required by the City of Fort Collins. During 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 to comply with applicable permits. 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.
Wherever construction vehicles access routes or intersect paved public roads,
provisions must be made to minimize the transport of sediment by runoff or
vehicles tracking onto the paved surface. The contractor will be responsible for
clearing mud tracked onto city streets daily.
All temporary erosion and sediment control practices must be maintained and
repaired as needed to assure continued performance of their intended function.
An Erosion Control Plan with schedule and escrow calculation is included in the
plan set and Appendix A.
East Oak Townhomes Subdivision
4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone:
970.834.6364
Page 12
6. CONCLUSIONS
6.1 Compliance with Standards
All computations that have been completed within this report are in compliance
with the City of Fort Collins Storm Drainage Design Criteria Manual.
6.2 Drainage Concept
The proposed drainage concepts presented in this report and on the preliminary
construction plans adequately provide for stormwater quantity and quality
treatment of proposed impervious areas. Conveyance elements have been
designed to pass required flows and to minimize future maintenance.
If, at the time of construction, groundwater is encountered, a Colorado Department
of Health Construction Dewatering Permit will be required.
7. REFERENCES
1. City of Fort Collins, “Fort Collins Stormwater Criteria Manual”, adopted
December 2018.
2. Mile High Flood District, “Urban Storm Drainage Criteria Manual”, Volume
1 (partially updated March 2024), Volume 2 (updated January 2016), and
Volume 3 (partially updated March 2024).
A
APPENDIX A
VICINITY MAP
DRAINAGE PLAN
EROSION CONTROL PLAN
SITE
VICINITY MAP
SCALE: 1"=500'
LOTS 1-15
EAST OAK TOWNHOMES SUBDIVISION
A1
EB
RD
RD
SCB
W
AC SCBRD
TEL
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X X X X X X X X
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LOT 26, BLOCK 131
ORIGINAL TOWN
GARAGE
LOT 1
LOT 2
LOT 3
LOT 4
LOT 5
LOT 6
LOT 7 LOT 8 LOT 9
LOT 10
LOT 11
LOT 15
LOT 14
LOT 13
LOT 12
LOT 17-18, BLOCK 131
ORIGINAL TOWN
EAST 1/2 OF LOTS
19-22, BLOCK 131
ORIGINAL TOWN
LOT 7-16, BLOCK 131
ORIGINAL TOWN
TRACT A
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PRIVATE AE
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5
EX COMBINATION INLET
(ON-GRADE)
FLOW NORTH TO EX
TRIPLE COMBINATION
INLETS IN MATHEWS
2'X3' CURB INLET
ADS NYLOPLAST
24" AREA INLET
W/ DOME GRATE
6" ROOF DRAIN
FOR EAST
BUILDINGS
36" NYLOPLAST JUNCTION
W/ SOLID LID
STORMTECH 160 LP (12X2)
15" HP
36" NYLOPLAST BASIN W/ WEIR
AND SOLID LID
TOP OF WEIR=4979.5
H ON WEIR=4980.1
36" NYLOPLAST BASIN
W/ SOLID LID
15" HP
8"X12" 90° BEND
6" ROOF C/O
4" PERF PVC
(2) 8" HP
12" HP
15" HP
12" AREA INLET
W/ DOME GRATE
AND 8" LEADER
(TYP)
12" HP
36 LF OF 4" C900 FIRE SERVICE
8"X12" TEE
(TYP)
12" 90° BEND
6" ROOF C/O
12"X15" TEE
4" SOLID
PVC
8"X8" TEE
8" 90° BEND
2' CONC CHANNEL
12" DEEP
6" ROOF C/O
6" ROOF DRAIN
FOR WEST BUILDINGS
6" ROOF C/O
12" HP
DRAINAGE
PLAN
9
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22-100-645-00
JUNE 26, 2024
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EXISTING MAJOR CONTOUR
BASIN COEFFICIENT (100-YR)
DRAINAGE BASIN AREA
DRAINAGE BASIN NUMBER
DESIGN POINT
PROPOSED DRAINAGE BASIN DIVIDE LINE
FLOW PATH
LEGEND
EXISTING MINOR CONTOUR
PROPOSED MINOR CONTOUR
PROPOSED MAJOR CONTOUR
811
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E
W
S
S
T
R
E
E
T
E OAK STREET
AL
L
E
Y
MCINTYRE HOUSE
LOT 26, BLOCK 131
ORIGINAL TOWNGARAGE
LOT 1
LOT 2
LOT 3
LOT 4
LOT 5
LOT 6
LOT 7 LOT 8 LOT 9
LOT 10
LOT 11
LOT 15
LOT 14
LOT 13
LOT 12
LOT 17-18, BLOCK 131
ORIGINAL TOWN
EAST 1/2 OF LOTS
19-22, BLOCK 131
ORIGINAL TOWN
LOT 7-16, BLOCK 131
ORIGINAL TOWN
TRACT A
DE, PRIV. UE,
PRIV. AE
TRACT B
9' PRIV. UE,
PRIV. AE
PUBLIC
UE
PUBLIC
UE
RS-1RS-1 RS-1
RS-1
RS-1
SSA
4
9
8
1
49
8
1
4980
498
0
49
7
9
497
8
4979
4978
49
7
8
497
9
4982
49
8
1
498
2
49
8
2
4982
4981
4979
497
9
4979
497
9
49
7
8
49
7
9
4
9
7
8
49
8
2
36" NYLOPLAST JUNCTION W/ SOLID LID
STORMTECH 160 LP (12X2)
EX STORM INLET
2'X3' CURB INLET
ADS NYLOPLAST 36" NYLOPLAST BASIN W/
WEIR AND SOLID LID
36" NYLOPLAST BASIN W/ SOLID LID
24" AREA INLET
W/ DOME GRATE
12" AREA INLET
W/ DOME GRATE
12" AREA INLET
W/ DOME GRATE
12" AREA INLET
W/ DOME GRATE
12" AREA INLET
W/ DOME GRATE
CF
CF
CF
CFCF
CF
SAWCUT (TYP)
CWA SSA
STAGING IN ROW WILL REQUIRE A
PERMIT FROM THE CITY
STAGING IN ROW WILL REQUIRE A
PERMIT FROM THE CITY
EROSION
CONTROL PLAN
10
MPO
AGW
MPO
22-100-645-00
JUNE 26, 2024
40
6
5
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DRAWN BY:
CHECKED BY:
DATE:
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PROJECT NO:
DESIGNED BY:
SHEET NO:
SHEET TITLE
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BY
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NOTES:
1. CONTRACTOR TO PROVIDE AND MAINTAIN ALL NECESSARY EROSION
CONTROL MEASURES PRIOR TO AND THROUGHOUT CONSTRUCTION. EROSION
CONTROL PROTECTION SHALL REMAIN IN PLACE UNTIL CONSTRUCTION IS
COMPLETE AND ALL DISTURBED GROUND IS ADEQUATELY VEGETATED WITH
OWNER'S APPROVAL FOR REMOVAL.
2. THE EXTENT OF EROSION CONTROL PROTECTION SHALL BE OBSERVED AND
ADJUSTED AS NEEDED DURING CONSTRUCTION BASED ON SITE CONDITIONS
AND THE PERFORMANCE OF THE EROSION CONTROL MEASURES SHOWN, TO
SUPPLY SUFFICIENT EROSION CONTROL AND MINIMIZE DOWNSTREAM
WATERWAY POLLUTION.
3. LIMIT DISTURBANCE TO AREAS WITHIN EROSION CONTROL BOUNDARIES.
ADJUST EROSION CONTROL BOUNDARIES AS NECESSARY TO ADEQUATELY
COMPLETE PROPOSED WORK. ALL DISTURBED AREAS SHALL BE PREPARED
(SEEDED & MULCHED, SURFACE ROUGHENING, ETC.) TO MINIMIZE EROSION
POTENTIAL AND SOIL MIGRATION.
4. SEE LANDSCAPE PLAN FOR REVEGETATION METHODS AND DETAILS.
DURING CONSTRUCTION, ANY SOIL DISTURBED AND NOT UNDER ACTIVE
CONSTRUCTION SHALL BE SEEDED AND MULCHED PER LCUASS STANDARDS.
5. ALL ROCK SOCKS ALONG COLLEGE AVENUE AND KENSINGTON DRIVE TO
INCLUDE WARNING MARKERS. ROCK SOCKS ALONG COLLEGE AVENUE SHALL
NOT IMPEDE TRAFFIC BY PROTRUDING INTO THE TRAFFIC LANE.
6. NO TRACKING OF MUD AND DEBRIS WILL BE ALLOWED ONTO THE
SURROUNDING STREETS AND PROPERTIES. IN CASE ANY TRACKING OCCURS,
IT SHALL BE CLEANED IMMEDIATELY BY THE CONTRACTOR.CC
C
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22
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8
0
5
2
4
811
LEGEND
SCL SCL
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
PROPOSED MINOR CONTOUR
PROPOSED MAJOR CONTOUR
FLOW PATH
ROCK SOCK AREA INLET PROTECTION
ROCK SOCK
BLOCK AND ROCK SOCK INLET PROTECTION
TEMPORARY CONSTRUCTION FENCE
SEDIMENT CONTROL LOG AT BACK OF CURB
STABILIZED STAGING AREA
VEHICLE TRACKING CONTROL PAD
NOTES REGARDING CONSTRUCTION AND PROTECTION OF STORMTECH DRAINAGE SYSTEM:
1. THE CONTRACTOR WILL BE RESPONSIBLE FOR KEEPING THE SYSTEM CLEAR OF SEDIMENT DURING CONSTRUCTION.
2. THE SYSTEM SHALL BE INSTALLED AS LATE IN THE CONSTRUCTION PHASING AS POSSIBLE.
3. DURING EXCAVATION FOR THE CHAMBERS AND ROCK, SOILS SHALL BE REMOVED FROM THE SITE OR MOVED TO AN AREA
THAT DOES NOT FLOW TOWARD THE EXCAVATION.
4. FABRIC, ROCK AND CHAMBER INSTALLATION SHALL BE COMPLETED AS QUICKLY AS POSSIBLE WITH MO LOOSE SOIL ABOVE
OR AROUND THE EXCAVATION.
5. THE FABRIC AND ROCK SHALL BE COVERED WITH PAVEMENT AS QUICKLY AS POSSIBLE AFTER CONSTRUCTION.
6. IF PAVING IS NOT IMMEDIATELY AFTER INSTALLATION, THE EDGE OF THE EXCAVATION SHALL BE PROTECTED WITH AN
EDGE PROTECTION BMP (ROCK SOCK OR SEDIMENT CONTROL LOG).
7. PIPES AND INLETS THAT ARE DESIGNED TO DRAIN INTO THE FACILITY SHALL HAVE INLET PROTECTION INSTALLED
IMMEDIATELY TO KEEP SEDIMENT OUT OF THE SYSTEM.
8. THE ISOLATOR ROW SHALL BE INSPECTED AFTER CONSTRUCTION AND CLEANED IF NECESSARY.
LIMITS OF DISTURBANCE
CONCRETE WASHOUT BERM
A3
B
APPENDIX B
HYDROLOGIC COMPUTATIONS
Wilson & Company
DRAINAGE SUMMARY TABLE
Design Tributary Area C (2 & 10) C (100) tc (2 & 10) tc (100) Q(2)tot Q(10)tot Q(100)tot
Sub-basin REMARKS
Point (ac) (min) (min) (cfs) (cfs) (cfs)
a A 0.27 0.95 1.00 5.0 5.0 0.7 1.3 2.7 Roof drain system to StormTech Chambers
b B 0.17 0.76 0.95 5.0 11.1 0.4 0.6 1.2 Inlets to StormTech Chambers
c C 0.08 0.83 1.00 5.0 5.0 0.2 0.3 0.8 Alley south to Oak Street ex inlet
d D 0.04 0.95 1.00 5.0 5.0 0.1 0.2 0.4 Alley north to north alley
e E 0.02 0.95 1.00 5.0 5.0 0.0 0.1 0.2 Lot 7 Roof west to alley
231128 COFC FLOW.xls B1
Wilson & Company
RUNOFF COEFFICIENTS & % IMPERVIOUS
LOCATION:East Oak Townhomes
PROJECT NO:22-100-645-00
COMPUTATIONS BY:AGW
DATE:6/20/2024
Recommended Runoff Coefficients from Table 3.2-2 of City of Fort Collins Stormwater Criteria Manual
Recommended % Impervious from Table 4.1-3 of City of Fort Collins Stormwater Criteria Manual
Hydrologic Soil Group Type C
Runoff %
coefficient Impervious
C
Streets, parking lots (asphalt): 0.95 100
Sidewalks (concrete): 0.95 100
Roofs: 0.95 90
Pavers: 0.50 40
Landscape Areas (Flat slope, clay) : 0.20 2
Landscape Areas (Avg slope, clay) : 0.25 2
SUBBASIN TOTAL TOTAL ROOFS STREETS, PARKING LOTS PAVERS SIDEWALK LANDSCAPE RUNOFF %
DESIGNATION AREA AREA (asphalt) (concrete) (Flat slope, clay) COEFF. Impervious REMARKS
(ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft)
(C)
Existing
Ex Site 0.48 20,932 9,905 4,819 0 1,065 5,143 0.77 71 Total Site Impervious Area=14,902
ROW to EX TBC 0.22 9,457 0 3,337 0 1,813 4,307 0.61 55
TOTAL 0.70 30,389 9905 8156 0 2878 9,450 0.72 66
Proposed
Site 0.48 20,932 12,544 0 0 6,390 1,851 0.88 85 Total Site Impervious Area=17,716
ROW to EX TBC 0.22 9,457 0 228 0 5,089 4,140 0.62 57
TOTAL 0.70 30,389 12544 228 0 11479 6,138 0.80 76
Added Impervious Area=2814 sf
Equations
- Calculated C coefficients & % Impervious are area weighted
C = (Ci Ai) / At
Ci = runoff coefficient for specific area, Ai
Ai = areas of surface with runoff coefficient of Ci
n = number of different surfaces to consider
At = total area over which C is applicable; the sum of all Ai's
231128 COFC FLOW.xls B2
Wilson & Company
RUNOFF COEFFICIENTS & % IMPERVIOUS
LOCATION:East Oak Townhomes
PROJECT NO:22-100-645-00
COMPUTATIONS BY:AGW
DATE:6/20/2024
Recommended Runoff Coefficients from Table 3.2-2 of City of Fort Collins Stormwater Criteria Manual
Recommended % Impervious from Table 4.1-3 of City of Fort Collins Stormwater Criteria Manual
Hydrologic Soil Group Type C
Runoff %
coefficient Impervious
C
Paved Area (asphalt-streets, parking lots): 0.95 100
Concrete (alley and sidewalks): 0.95 100
Roofs: 0.95 90
Gravel or Pavers: 0.50 40
Landscape Areas (Flat slope, clay) : 0.20 2
Landscape Areas (Avg slope, clay) : 0.25 2
SUBBASIN TOTAL TOTAL ROOF PAVED GRAVEL/PAVERS CONCRETE LANDSCAPE RUNOFF %
DESIGNATION AREA AREA AREA AREA AREA AREA AREA COEFF. Impervious REMARKS
(ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C)
A 0.27 11,859 11,859 0 0 0 0 0.95 90
B 0.17 7,221 0 0 0 5,370 1,851 0.76 75
C 0.08 3,665 0 0 0 3,077 588 0.83 84
D 0.04 1,674 0 0 0 1,666 8 0.95 100
E 0.02 685 685 0 0 0 0 0.95 90
Area Treated 0.44 19,080 11289 0 0 5370 1851 0.85 82 Total Impervious area treated=15,567
Equations
- Calculated C coefficients & % Impervious are area weighted
C = (Ci Ai) / At Equation 5-2
Ci = runoff coefficient for specific area, Ai
Ai = areas of surface with runoff coefficient of Ci
n = number of different surfaces to consider
At = total area over which C is applicable; the sum of all Ai's
231128 COFC FLOW.xls
B3
Wilson & Company
STANDARD FORM SF-2
TIME OF CONCENTRATION - 2 and 10 YR
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-645-00
COMPUTATIONS BY: AGW
DATE: 6/20/2024
2 and 10-yr storm Cf = 1.00 from Table RO-12 of City of Fort Collins Stormwater Code, Volume I
SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS
DATA TIME (ti) (tt) (URBANIZED BASIN) tc
DESIGN SUBBASIN(s) Area C Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10
PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min)
(1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14)
a A 0.27 0.95 5 2.0 0.5 0 2.0 0.012 3.8 0.0 0.5 5 10.0 5.0
b B 0.17 0.76 31 1.0 3.6 170 1.7 0.012 3.5 0.8 4.4 201 11.1 5.0
c C 0.08 0.83 17 2.0 1.7 95 1.2 0.012 2.9 0.5 2.2 112 10.6 5.0
d D 0.04 0.95 17 2.0 0.9 56 0.9 0.012 2.5 0.4 1.3 73 10.4 5.0
e E 0.02 0.95 5 2.0 0.5 0 0.9 0.012 2.5 0.0 0.5 5 10.0 5.0
EQUATIONS:Overland Flow Length
tc = ti + tt Equation 5-3 L=200' Max in developed areas
L=500' Max in undeveloped areas
ti = [1.87 (1.1 - CCf ) L0.5 ] / S Equation 3.3-2
tt = L/(V*60)Equation 5-5
V=1.49/n * R^2/3*S^1/2 Equation 5-4
12611.0079 6103.3
final tc = minimum of ti + tt and urbanized basin check
min. tc = 5 min. due to limits of IDF curves
231128 COFC FLOW.xls
B4
Wilson & Company
STANDARD FORM SF-2
TIME OF CONCENTRATION - 100 YR
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-645-00
COMPUTATIONS BY: AGW
DATE: 6/20/2024
100-yr storm Cf = 1.25 from Table RO-12 of City of Fort Collins Stormwater Code, Volume I
SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS
DATA TIME (ti) (tt) (URBANIZED BASIN) tc
DESIGN SUBBASIN(s) Area C C*Cf Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10
PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min)
(1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14)
a A 0.27 0.95 1.00 5 2.0 0.3 0 2.0 0.012 3.8 0.0 0.3 5 10.0 5.0
b B 0.17 0.76 0.95 31 1.0 1.6 170 0.0 0.012 0.3 9.7 11.2 201 11.1 11.1
c C 0.08 0.83 1.00 17 2.0 0.6 95 1.2 0.012 2.9 0.5 1.2 112 10.6 5.0
d D 0.04 0.95 1.00 17 2.0 0.6 56 0.9 0.012 2.5 0.4 1.0 73 10.4 5.0
e E 0.02 0.95 1.00 5 2.0 0.3 0 0.9 0.012 2.5 0.0 0.3 5 10.0 5.0
EQUATIONS:Overland Flow Length
tc = ti + tt Equation 5-3 L=200' Max in developed areas
L=500' Max in undeveloped areas
ti = [1.87 (1.1 - CCf ) L0.5 ] / S Equation 3.3-2
tt = L/(V*60)Equation 5-5
V=1.49/n * R^2/3*S^1/2 Equation 5-4
final tc = minimum of ti + tt and urbanized basin check 12,611 6,103
min. tc = 5 min. due to limits of IDF curves
231128 COFC FLOW.xls
B5
Wilson & Company
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 2-Yr Storm)
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-645-00
COMPUTATIONS BY: AGW
DATE: 6/20/2024
2 yr storm, Cf = 1.00
DIRECT RUNOFF CARRY OVER TOTAL REMARKS
Design Tributary A C Cf tc i Q (2) from Q (2) Q(2)tot
Sub-basin Design
Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs)
a A 0.27 0.95 5.0 2.85 0.7 0.7
b B 0.17 0.76 5.0 2.85 0.4 0.4
c C 0.08 0.83 5.0 2.85 0.2 0.2
d D 0.04 0.95 5.0 2.85 0.1 0.1
e E 0.02 0.95 5.0 2.85 0.0 0.0
Q = Cf C iA
Q = peak discharge (cfs)
C = runoff coefficient
Cf = frequency adjustment factor
i = rainfall intensity (in/hr) from City of Fort Collins IDF curve
A = drainage area (acres)i = 24.221 / (10+ tc)0.7968
231128 COFC FLOW.xls
B6
Wilson & Company
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 10-Yr Storm)
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-645-00
COMPUTATIONS BY: AGW
DATE: 6/20/2024
10 yr storm, Cf = 1.00
DIRECT RUNOFF CARRY OVER TOTAL REMARKS
Design Tributary A C Cf tc i Q (10) from Q (10) Q(10)tot
Sub-basin Design
Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs)
a A 0.27 0.95 5.0 4.87 1.3 1.3
b B 0.17 0.76 5.0 4.87 0.6 0.6
c C 0.08 0.83 5.0 4.87 0.3 0.3
d D 0.04 0.95 5.0 4.87 0.2 0.2
e E 0.02 0.95 5.0 4.87 0.1 0.1
Q = Cf C iA
Q = peak discharge (cfs)
C = runoff coefficient
Cf = frequency adjustment factor
i = rainfall intensity (in/hr) from City of Fort Collins IDF curve
A = drainage area (acres)i = 41.44 / (10+ tc)0.7974
231128 COFC FLOW.xls
B7
Wilson & Company
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 100-Yr Storm)
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-645-00
COMPUTATIONS BY: AGW
DATE: 6/20/2024
100 yr storm, Cf = 1.25
DIRECT RUNOFF CARRY OVER TOTAL REMARKS
Des. Area A C Cf tc i Q (100) from Q (100) Q(100)tot
Design
Point Design. (ac) (min) (in/hr) (cfs) Point (cfs) (cfs)
a A 0.27 1.00 5.0 9.95 2.7 2.7
b B 0.17 0.95 11.1 7.44 1.2 1.2
c C 0.08 1.00 5.0 9.95 0.8 0.8
d D 0.04 1.00 5.0 9.95 0.4 0.4
e E 0.02 1.00 5.0 9.95 0.2 0.2
Q = C iA
Q = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from City of Fort Collins IDF curve
A = drainage area (acres)i = 84.682 / (10+ tc)0.7975
231128 COFC FLOW.xls
B8
12611.01 6103.25
City of Fort Collins Stormwater Criteria Manual
B9
City of Fort Collins Stormwater Criteria Manual
B10
C
APPENDIX C
HYDRAULIC CALCULATIONS
EB
RD
RD
SCB
W
AC SCBRD
TEL
TEL
TEL
E
SCBSCB
RD
P
E
E
RD
RD
SCB
G
W
W
W
W
FI
B
E
R
SS
E
E
SS SS SS SS SS SS SS SS SS SS SS
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
X X
X X X X X X X X
X
X X X X X X X X X X X X X X X X X X X X X X X
XX
X
X
MA
T
H
E
W
S
S
T
R
E
E
T
AL
L
E
Y
36" NYLOPLAST JUNCTION W/ SOLID LID
15" INV (N) = 4978.30
SUMP = 4975.0
RIM = 4981.57
6" ROOF
INV = 4978.50
MCINTYRE HOUSE
LOT 26, BLOCK 131
ORIGINAL TOWN
GARAGE
LOT 1
LOT 2
LOT 3
LOT 4
LOT 5
LOT 6
LOT 7 LOT 8
LOT 9
LOT 10
LOT 11
LOT 15
LOT 14
LOT 13
LOT 12
LOT 17-18, BLOCK 131
ORIGINAL TOWN
EAST 1/2 OF LOTS
19-22, BLOCK 131
ORIGINAL TOWN
LOT 7-16, BLOCK 131
ORIGINAL TOWN
STORMTECH 160 LP (12X2)
BOTTOM ROCK = 4977.90
BOTTOM CHAMBERS = 4978.40
TOP CHAMBERS = 4979.40
TOP ROCK = 4979.90
MIN FG = 4981.07
119.7 LF @ 0.4%
6" ROOF DRAIN
FOR EAST BUILDINGS
TRACT A
UE,DE,
PRIVATE AE
2'X3' CURB INLET
ADS NYLOPLAST
CURB FL = 4981.20
12" INV= 4978.45
15" HP INV = 4977.50
9.0 LF 15" HP @ 4.4%
36" NYLOPLAST BASIN W/ WEIR
AND SOLID LID
12" HP INV= 4978.00
15" HP INV=4977.55
4" HP INV = 4977.55
TOP OF WEIR = 4979.50
RIM=4981.53
36" NYLOPLAST BASIN
W/ SOLID LID
12" HP INV (NW)=4978.40
15" HP INV (S, NE)= 4978.40
RIM=4981.53 9.5 LF 15" HP @ 0.5%
12" INV = 4978.50
8" PVC INV = 4978.30
4" PERF INV = 4977.70
8" PVC INV = 4978.40
8" PVC INV = 4978.40
8"X12" INV = 4979.50
4" PERF INV = 4978.0
6" ROOF C/O
INV = 4979.00
4" PERF PVC @ 0.3%
(2) 17 LF 8" HP @ 0.5%9.0 LF 12" HP
@ 0.6%
95 LF 12" HP @ 1%
18.0 LF 15" HP @ 0.6%
8" HP INV=4977.29
8" HP
INV=4977.2024" AREA INLET
W/ DOME GRATE
12" INV = 4978.60
6" INV=4978.60
GRATE= 4981.00
12" AREA INLET
W/ DOME GRATE
AND 8" LEADER
INV = 4979.60
GRATE=4981.48
12" AREA INLET
W/ DOME GRATE
AND 8" LEADER
INV = 4979.50
GRATE=4981.32
12" AREA INLET
W/ DOME GRATE
AND 8" LEADER
INV = 4979.30
GRATE=4981.34
12" AREA INLET
W/ DOME GRATE
AND 8" LEADER
INV = 4978.90
GRATE=4981.34
18.0 LF 12" HP @ 0.5%
36 LF OF 4" C900 FIRE SERVICE
TRACT
B
9' PRIV. UE,
PRIV. AE
PUBLIC
UE
PUBLIC
UE
UTILITY CROSSING
6" SAN INV=4974.84
15" HP INV=4978.37
8"X12" TEE
INV=4979.34
8"X12" TEE
INV=4979.17
8"X12" TEE
INV=4978.80
12" 90° BEND
6" ROOF C/O
INV=4978.60
12"X15" TEE
30 LF 4" SOLID
PVC @ 0.5%
UTILITY CROSSING
6" SAN INV=4975.02
4" PERF INV=4977.62
8"X8" TEE
8" 90° BEND
W
2' CONC CHANNEL
12" DEEP
STORM OUTFALL
2' CONC CHANNEL
FF=81.80
FF=81.80
FF=81.80
FF=81.80
FF=81.80
FF=81.80
6" ROOF C/O
INV=4979.10
117.6 LF @ 0.4%
6" ROOF DRAIN
FOR WEST BUILDINGS
6" ROOF C/O
INV=4978.65
40
6
5
S
A
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C
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D
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5
3
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PH
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9
7
0
-
8
3
4
-
6
3
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UTILITY PLAN
STORM
7
MPO
AGW
MPO
22-100-645-00
JUNE 26, 2024
DRAWN BY:
CHECKED BY:
DATE:
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PROJECT NO:
DESIGNED BY:
SHEET NO:
SHEET TITLE
RE
V
.
BY
EA
S
T
O
A
K
T
O
W
N
H
O
M
E
S
SU
B
D
I
V
I
S
I
O
N
90%
S
U
B
M
I
T
T
A
L
NOT
F
O
R
CON
S
T
R
U
C
T
I
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NOTES:
1. ALL STORM, SANITARY, AND WATER AS WELL AS POWER AND
OTHER "DRY" UTILITY INSTALLATIONS, SHALL CONFORM TO THE CITY
OF FORT COLLINS STANDARDS AND SPECIFICATIONS CURRENT AT
THE DATE OF APPROVAL OF THE PLANS BY THE LOCAL ENGINEER.
2. STORM SEWER PIPE SHALL BE ADS HP WITH WATER TIGHT JOINTS
AS SPECIFIED ON THE PLAN OR OTHERWISE NOTED. ALL STORM
SEWER SHALL BE INSPECTED BY THE CITY OF FORT COLLINS (COFC).
3. LENGTH OF PIPE IS MEASURED FROM CENTER OF STRUCTURE TO
CENTER OF STRUCTURE.
4. WATER MAINS AND FIRE LINES SHALL BE PVC(C900) AS SPECIFIED
BY THE COFC. THE MINIMUM COVER OVER WATER LINES IS 4.5 FEET
AND THE MAXIMUM COVER IS 5.5 FEET UNLESS OTHERWISE
APPROVED BY THE COFC.
5. ALL WATER SERVICES SHALL BE INSTALLED AT A MINIMUM OF 5
FEET BELOW FINISHED FLOOR ELEVATION AND SHALL BE TYPE K
COPPER AS SPECIFIED BY COFC.
6. ALL SANITARY SEWER PIPE SHALL BE PVC (SDR35) UNLESS
OTHERWISE NOTED ON THE PLAN. SEWER PIPE SHALL BE AS
SPECIFIED BY THE CITY OF FORT COLLINS STANDARD PLANS AND
SPECIFICATIONS.
7. SEE ARCHITECTURAL DRAWINGS FOR WALL LOCATION DETAILS OF
GAS METERS, ELECTRIC METERS, AND TELEPHONE TERMINALS.
8. LIMITS OF STREET CUT SHOWN ARE APPROXIMATE. FINAL LIMITS
ARE TO BE DETERMINED IN THE FIELD BY CITY ENGINEER INSPECTOR.
ALL REPAIRS TO BE IN ACCORDANCE WITH THE CITY STREET REPAIR
STANDARDS.
9. ANY DAMAGED CURB, GUTTER AND SIDEWALK EXISTING PRIOR TO
CONSTRUCTION, AS WELL AS STREETS, SIDEWALKS, CURBS AND
GUTTERS DESTROYED, DAMAGED OR REMOVED DUE TO
CONSTRUCTION OF THIS PROJECT, SHALL BE REPLACED OR
RESTORED TO CITY OF FORT COLLINS STANDARDS AT THE
IMPROVEMENTS AND/OR PRIOR TO THE ACCEPTANCE OF COMPLETED
IMPROVEMENTS AND/OR PRIOR TO THE ISSUANCE OF THE FIRST
CERTIFICATE OF OCCUPANCY.
CC
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8
0
5
2
4
811
C1
0.23 ft Head required
0.5 ft provided, OK
Q100 Basins
A+B=3.9
This analysis is to determine
if the major storm event will
be captured if failure of the
StormTech system occurs.
C2
0.33 ft Head required
0.5 ft provided, OK
Q100 Basins
A+B=3.9 cfs
This analysis is to determine
if the major storm event will
be captured if failure of the
StormTech system occurs.
C3
Worst case H=0.08 ft
Q capture
=0.25 cfs
C4
Worksheet for 36" Basin w/ weir
Project Description
DischargeSolve For
Input Data
ft80.07Headwater Elevation
ft79.50Crest Elevation
ft0.00Tailwater Elevation
ft^(1/2)/s3.00Weir Coefficient
ft3.0Crest Length
0Number Of Contractions
Results
cfs3.87Discharge
ft0.57Headwater Height Above
Crest
ft-79.50Tailwater Height Above Crest
ft²1.7Flow Area
ft/s2.26Velocity
ft4.1Wetted Perimeter
ft3.00Top Width
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/24/2024
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
Center36in basin with weir.fm8
Basin A+ Basin B Q100=3.9 cfs
C5
Cross Section for 36" Basin w/ weir
Project Description
DischargeSolve For
Input Data
cfs3.87Discharge
ft80.07Headwater Elevation
ft79.50Crest Elevation
ft0.00Tailwater Elevation
ft^(1/2)/s3.00Weir Coefficient
ft3.0Crest Length
0Number Of Contractions
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/24/2024
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
Center36in basin with weir.fm8
Basin A+ Basin B Q100=3.9 cfs
C6
D
APPENDIX D
IMPERVIOUS AREA EXHIBIT,
BMP EXHIBIT AND
LID CALCULATIONS
RD
RD
SCB
W
AC SCBRD
RD
SCBSCB
RD
RDRD
SCB
ST
W W
W
W
X
X X X X
X X X X X X X X X X X
X X
E OAK STREET
MA
T
T
H
E
W
S
S
T
R
E
E
T
RD
RD
SCB
W
AC SCBRD
RD
SCBSCB
RD
RDRD
SCB
ST
W W
W
W
E OAK STREET
MA
T
T
H
E
W
S
S
T
R
E
E
T
40
6
5
S
A
I
N
T
C
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O
U
D
D
R
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E
,
S
U
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T
E
2
0
1
LO
V
E
L
A
N
D
,
C
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8
0
5
3
8
PH
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SURFACE AREA (SF)% IMPERVIOUS IMPERVIOUS AREA
(SF)
ROOF 12544 90 11289
CONCRETE/ASPHALT 6390 100 6390
GRAVEL 0 40 0
LANDSCAPE 1851 2 37
TOTAL 1530 17716
SURFACE AREA (SF)% IMPERVIOUS IMPERVIOUS AREA
(SF)
ROOF 9905 90 8915
CONCRETE/ASPHALT 5884 100 5884
GRAVEL 0 40 0
LANDSCAPE 5143 2 103
TOTAL 20932 14902 IMPERVIOUS
AREA
EXHIBIT
1
MPO
AGW
MPO
DRAWN BY:
CHECKED BY:
DATE:
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PROJECT NO:
DESIGNED BY:
SHEET NO:
SHEET TITLE
RE
V
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BY
EXISTING PROPOSED
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JUNE 26, 2024
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22-100-645-00
D1
EB
RD
RD
SCB
W
AC SCBRD
TEL
TEL
TEL
E
SCBSCB
RD
P
E
E
RD
RD
SCB
G
W
W
W
W
FI
B
E
R
SS
E
E
SS SS SS SS SS SS SS SS SS SS SS
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
X X
X X X X X X X X
X
X X X X X X X X X X X X X X X X X X X X X X X
XX
X
X
MA
T
H
E
W
S
S
T
R
E
E
T
E OAK STREET
AL
L
E
Y
MCINTYRE HOUSE
LOT 26, BLOCK 131
ORIGINAL TOWN
GARAGE
LOT 1
LOT 2
LOT 3
LOT 4
LOT 5
LOT 6
LOT 7 LOT 8 LOT 9
LOT 10
LOT 11
LOT 15
LOT 14
LOT 13
LOT 12
LOT 17-18, BLOCK 131
ORIGINAL TOWN
EAST 1/2 OF LOTS
19-22, BLOCK 131
ORIGINAL TOWN
LOT 7-16, BLOCK 131
ORIGINAL TOWN
TRACT A
UE,DE,
PRIVATE AE
4981.5
4
9
8
1
49
7
7
.
5
497
8
4978.
5
49
7
9
4979.5
4979.5
49
8
0
49
8
0
.
5
STORMTECH 160 LP (12X2)
PERMANENT
BMP
EXHIBIT
2
MPO
ES
MPO
22-100-645-00
JUNE 26, 2024
40
6
5
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DRAWN BY:
CHECKED BY:
DATE:
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DA
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PROJECT NO:
DESIGNED BY:
SHEET NO:
SHEET TITLE
RE
V
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BY
EA
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811
EXISTING MAJOR CONTOUR
LEGEND
EXISTING MINOR CONTOUR
PROPOSED MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PERMANENT STORMWATER QUALITY
BMP (ADS STORMTECH SYSTEM)
STORMWATER QUALITY BMP
AREA TREATED BY PERMANENT
D2
Design Procedure Form: Extended Detention Basin (EDB) - Sedimentation Facility
Project Name: East Oak Townhomes
Project Number: 22-100-645-00
Company: Wilson & Co
Designer: MPO
Date: 6/20/2024
1. Basin Storage Volume
A) Tributary Area's Imperviousness Ratio (i=Ia/100) Ia = 82 %
i = 0.82
B) Contributing Watershed Area (Area) A = 0.44 acres
C) Water Quality Capture Volume (WQCV) WQCV = 0.27 watershed inches
12-hour Drain Time
(WQCV = 0.8 * (0.91 * i3 - 1.19 * i2 + 0.78i) )
D) Design Volume: Vol = WQCV/12 * Area Vol. = 0.010 ac-ft 436 cf
Volume in Chambers:
24 chambers x 15 CF per chamber= 360 cf
Volume in Pipe System:
LF Diameter, in
27 15 33 cf
122 12 96 cf
Total volume in pipes= 129 cf
Total Volume in System= 489 cf
D3
DETENTION VOLUME CALCULATIONS
Rational Volumetric (FAA) Method
ISOLATOR ROW
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-635-00
COMPUTATIONS BY: es
DATE: 6/24/2024
Equations:Area trib. to pond =0.44 acre
Developed flow = QD = CIA C (2) =0.85
Vol. In = Vi = T C I A = T QD Developed C A = 0.37 acre
Vol. Out = Vo =K QPO T Release rate, QPO =0.1980 cfs
storage = S = Vi - Vo K =1.0 (from fig 2.1)
Rainfall intensity from City of Fort Collins IDF Curve (half of 2-year)
Storm Rainfall QD Vol. In Vol. Out Storage Storage
Duration, T Intensity, I (cfs)Vi Vo S S
(min) (in/hr)
(ft3) (ft
3) (ft
3) (ac-ft)
5 1.43 0.5 160 59 101 0.00
10 1.11 0.4 249 119 130 0.00
20 0.81 0.3 364 238 126 0.00
30 0.65 0.2 438 356 81 0.00
40 0.54 0.2 485 475 10 0.00
50 0.46 0.2 516 594 -78 0.00
60 0.41 0.2 552 713 -161 0.00
70 0.0 0 832 -832 -0.02
80 0.0 0 950 -950 -0.02
90 0.0 0 1069 -1069 -0.02
100 0.0 0 1188 -1188 -0.03
110 0.0 0 1307 -1307 -0.03
120 0.0 0 1426 -1426 -0.03
Provided Volume: 130 ft
3
0.003 acre-ft
240626 FAA isolator row.xls,FAA-100yr
D4
LOCATION: East Oak Townhomes
PROJECT NO: 22-100-635-00
COMPUTATIONS BY: es
DATE: 6/24/2024
A***B C D*E G H I J K
WQCV (12
Hr.) for info
only
WQ Flow
(1/2 Q2)
Chamber
Type
Single
Chamber
Release Rate
Through
Fabric*
Volume in one
Chamber
Chambers
Provided
Actual
Release Rate
Thru Fabric
Required
Storage
Volume by
FAA Method
with Qin=B
and Q out=H
Min Number
of Chambers
for FAA
Release
Volume in Isolator
Rows
cf cfs cfs cf (G*D) cfs CF (I/E) (G*E)
436 0.6 SC-160LP 0.00824 6.85 24 0.198 130 19 164.4
* -SC160LP Single Chamber = 10.6 SF FABRIC (Area in ACAD detail)
Fabric Release @ 0.35 gal/min/SF = 3.7 gal/min/chamber
3.7 gal/min = 0.008241 cfs/chamber
WQ FLOW= (Q2A+Q2B)/2=(0.7+0.4)/2=0.6 CFS
Isolator Row Volume Check
*** - Water Quality Volume shown for information only.
The design approach is that all rows are "isolator rows" and the volume
within the chambers is adequate to allow the water quality flow to pass
through the fabric. All other flow will bubble up on the north end of the
chambers and leave the site over land.
D5
New or Modified Impervious Area 17,716 sf
Required Minimum Impervious Area to be Treated 13,287 sf
Treatment - Underground WQ System (ADS) 15,567 sf
Actual % of Impervious Area On-Site Treated by LID 88 %
75% On-Site Treatment by LID Requirement
LID Table
D6
E
APPENDIX E
SOILS
AND
FLOODPLAIN INFORMATION
Hydrologic Soil Group—Larimer County Area, Colorado
(220 East Oak Townhomes Subdivision)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/29/2023
Page 1 of 4
44
9
2
7
5
0
44
9
2
7
6
0
44
9
2
7
7
0
44
9
2
7
8
0
44
9
2
7
9
0
44
9
2
8
0
0
44
9
2
8
1
0
44
9
2
8
2
0
44
9
2
8
3
0
44
9
2
7
5
0
44
9
2
7
6
0
44
9
2
7
7
0
44
9
2
7
8
0
44
9
2
7
9
0
44
9
2
8
0
0
44
9
2
8
1
0
44
9
2
8
2
0
44
9
2
8
3
0
493670 493680 493690 493700 493710 493720
493670 493680 493690 493700 493710 493720
40° 35' 10'' N
10
5
°
4
'
2
9
'
'
W
40° 35' 10'' N
10
5
°
4
'
2
6
'
'
W
40° 35' 7'' N
10
5
°
4
'
2
9
'
'
W
40° 35' 7'' N
10
5
°
4
'
2
6
'
'
W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:413 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
E1
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
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 18, Aug 24, 2023
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
(220 East Oak Townhomes Subdivision)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/29/2023
Page 2 of 4 E2
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
94 Satanta loam, 0 to 1
percent slopes
C 0.8 100.0%
Totals for Area of Interest 0.8 100.0%
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.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Hydrologic Soil Group—Larimer County Area, Colorado 220 East Oak Townhomes
Subdivision
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/29/2023
Page 3 of 4
E3
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado 220 East Oak Townhomes
Subdivision
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/29/2023
Page 4 of 4
E4
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOOD
HAZARD AREAS
Without Base Flood Elevation (BFE)
Zone A, V, A99
With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areas
of 1% annual chance flood with average
depth less than one foot or with drainage
areas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard information is derived directly from the
authoritative NFHL web services provided by FEMA. This map
was exported on 11/29/2023 at 9:58 AM and does not
reflect changes or amendments subsequent to this date and
time. The NFHL and effective information may change or
become superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximate
point selected by the user and does not represent
an authoritative property location.
1:6,000
105°4'45"W 40°35'22"N
105°4'8"W 40°34'54"N
Basemap Imagery Source: USGS National Map 2023 E5
4065 St. Cloud, Suite.201
Loveland, CO 80538
970-834-6364 phone