HomeMy WebLinkAboutGrading Plans - 10/22/2025D RAINAGE L ETTER
1224 W M AGNOLIA S TREET
F ORT C OLLINS , CO
19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | 970-530-4044 | www.unitedcivil.com
10/3/2025
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: 1224 W MAGNOLIA STREET RESIDENCE
FORT COLLINS, COLORADO
PROJECT NUMBER: U23010
BUILDING PERMIT #2208586 (HOUSE)
BUILDING PERMIT #2504177 (GARAGE)
Dear Staff,
United Civil Design Group, LLC. is pleased to submit this Drainage Letter for the 1224 W Magnolia Street Residence in Fort
Collins, Colorado. In general, this summary serves to document the stormwater impacts associated with the proposed site
improvements.
SITE LOCATION AND PROJECT DESCRIPTION
The 1224 W Magnolia Street Residence site (referred herein as ”the site”) is situated in the Southeast Quarter of Section 10,
Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, Larimer County, State of Colorado. More
specifically, the site is located at the northeast corner of W Magnolia Street and Scott Avenue. The planned improvements
consist of the demolition of existing features and construction of a residence and accompanied garage structure.
EXISTING CONDITIONS
Hydrology
The site, located within the Old Town Drainage Basin, is approximately 0.22 acres. Draining by way of overland flow, runoff
from the site generally drains to the southeast and the northwest. Runoff is ultimately conveyed to street inlets in both
Magnolia Street and Scott Ave, and is ultimately further conveyed downstream within the Old Town Basin Portions.
Floodplain
The site is not located within a FEMA floodplain or – FEMA Map No. 08069C0978G (see attachments). The site is also not
located within a City of Fort Collins regulatory floodplain (see Fort Collins Floodplain mapping attached).
CITY REQUIREMENTS
As discussed above, the site is located within the Old Town Drainage Basin. Per information provided by the City of Fort
Collins, drainage requirements for residential projects state that, “The water quantity detention requirements can be waived
if less than 5,000 square feet of hard surface is being added in the Old Town Drainage Basin or if the final percentage of hard
surfaces including one-half the adjacent streets or alleys is equal to or less that the percentage the City’s master drainage
plan for your area of town.” Given these criteria, detention is not proposed with the site improvements.
IMPROVED CONDITIONS
The proposed site improvements include the re-construction of a single-family residence and garage, in addition to the
replacement of the existing driveway and concrete walks in support of the residence. The proposed residence is larger than
that of the existing home, resulting in an overall increase in impervious area. The table on the following page summarizes the
hydrologic impact associated with the proposed site improvements relative to existing conditions. Refer to the attached
Impervious Area Exhibits to see the location of the existing and proposed impervious areas.
Grading/Stormwater Plan Accepted
(Building Permit Released)
Accepted by:
Date :
SW - DEREK LUTZ
10/22/2025
D RAINAGE L ETTER
1224 W M AGNOLIA S TREET
F ORT C OLLINS , CO
19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | 970-530-4044 | www.unitedcivil.com
HYDROLOGIC SUMMARY TABLES
Impervious Area Summary Table
Existing Proposed Difference
Overall Area (Acre) 0.22 0.22 -
Roof (sf) 1,746 3,080 +1,334
Concrete (sf) 802 611 -191
Total Increase in Hard Surface Area (sf) +1,143
Note that the area used in these calculations considers area within the 0.22-acre property. Runoff flows and drainage patterns
for the improved site remain largely unchanged from existing conditions. A breakpoint exists at the intersection of W
Magnolia St and Scott Ave, therefore on-site drainage flows are directed generally southeast to northwest to existing
discharge locations offsite within the Old Town Basin. Downspouts from the proposed residence are planned to be piped by
the contractor away from the proposed buildings.
Runoff does drain to the neighboring properties immediately to the north and east in accordance with historic conditions,
however, the net increase in hard surface area that ultimately drains to the neighboring lots is less than 350 s.f. Refer to the
attached Impervious Area Exhibits for further information.
DETENTION & WATER QUALITY
Provided that the net increase in hard surface area (i.e., 1,143 s.f.) is less than 5,000 s.f., detention requirements are waived
for this residential project per City of Fort Collins drainage criteria for residential lots within the Old Town Drainage Basin.
Proposed improvements include disconnected impervious areas separated by landscaped areas. Runoff from proposed
impervious areas discharge to landscape areas that act as grassed buffers before reaching existing discharge locations offsite.
EROSION CONTROL
Erosion control, both temporary and permanent, is a vital part of any development project. For this project, the site
disturbance is less than 1 acre; therefore, a CDPHE Stormwater Management Plan (SWMP) is not required. However,
comprehensive erosion control measures are included with the site improvements. Refer to the Civil Construction Plans for
additional information. At a minimum, the following temporary BMP’s will be installed and maintained to control on-site
erosion and prevent sediment from traveling off-site during construction:
Sediment Control Log – a linear roll made of natural materials to trap sediment from sheet flow. Sediment Control
Log is a temporary BMP placed at the perimeter of disturbed area.
The contractor shall store all construction materials and equipment and shall provide maintenance and fueling of equipment
in confined areas on-site from which runoff will be contained and filtered. Temporary Best Management Practices (BMP’s)
will be inspected by the contractor at a minimum of once every two weeks and after each significant storm event.
CONCLUSIONS
The drainage system proposed within this Drainage Letter provides adequate conveyance of the developed stormwater
runoff from the proposed improvements to existing discharge locations. Existing drainage patterns remain with the proposed
site improvements; negative impacts new to the site are not anticipated to the City of Fort Collins Master Drainage Plan or
adjacent properties and infrastructure due to the proposed improvements; the net increase in hard surface area that
ultimately drains to the neighboring lots is less than 300 s.f. No detention is required for onsite runoff per City of Fort Collins
D RAINAGE L ETTER
1224 W M AGNOLIA S TREET
F ORT C OLLINS , CO
19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | 970-530-4044 | www.unitedcivil.com
requirements for this residential development as the proposed site increase in imperviousness is less 5,000 square feet.
Water quality considerations are being provided by the grassed buffers on the site.
We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in
the Fort Collins Stormwater Criteria Manual (FCSCM). This summary was prepared in compliance with technical criteria set
forth in both the Mile High Flood District (MHFD) Urban Storm Drainage Criteria Manual and the FCSCM.
If you should have any questions or comments as you review this drainage summary, please feel free to contact us at your
convenience.
Sincerely,
United Civil Design Group, LLC
Prepared by:
Brady Kirkbride, EI
Design Engineer
Sam Eliason, PE
Principal
ATTACHMENTS
- Existing Impervious Area Exhibit
- Proposed Impervious Area Exhibit
- FEMA Firmette (covering FEMA FIRM Panel 08069C0978G)
- City of Fort Collins Floodplain Map
10/3/2025
A TTACHMENTS
EXISTING CONCRETE 802 SF
EXISTING ROOF 1,746 SF
TOTAL = 2,548 SF
PROPERTY BOUNDARY
MAGNOLIA STREET
70'-80' RIGHT OF WAY (PLAT)
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IMPERVIOUS AREA CONVEYED TO
326 SCOTT AVENUE 730 SF
TOTAL = 730 SF
620 SF
IMPERVIOUS AREA CONVEYED TO
1218 W MAGNOLIA STREET
260 SF
TOTAL = 880 SF
1218 W MAGNOLIA
STREET
326 SCOTT
AVENUE
BASIN BOUNDARY (TYP)
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SCALE: 1" = 20'
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1224 W MAGNOLIA STREET RESIDENCE
EXISTING IMPERVIOUS AREA EXHIBIT
DATE:June 2, 2023 PREPARED FOR:ARCHER HOMES INC.JOB NUMBER:U23010 NOTE:THIS EXHIBIT WAS PREPARED FOR INFORMATION ONLY AND THE ENGINEER PREPARING THESE PLANS WILL NOT BE RESPONSIBLE FOR UNAUTHORIZED USE OF THEM.SHEET OF1 1
NO
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19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | (970) 530-4044 | www.unitedcivil.com
UNITED CIVIL
Design Group
PROPOSED CONCRETE 611 SF
PROPOSED ROOF 3,080 SF
MAGNOLIA STREET
70'-80' RIGHT OF WAY (PLAT)
SC
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TOTAL = 3,691 SF
NET INCREASE IN HARD SURFACE AREA = 1,143 SF
IMPERVIOUS AREA CONVEYED TO
326 SCOTT AVENUE 1013 SF
TOTAL = 1013 SF
IMPERVIOUS AREA CONVEYED TO
1218 W MAGNOLIA STREET
335 SF
TOTAL = 335 SF
1218 W MAGNOLIA
STREET
326 SCOTT
AVENUE
NET INCREASE = 283 SF
NET DECREASE = 545 SF
PROPERTY BOUNDARY
DOWNSPOUT
DOWNSPOUT
BASIN BOUNDARY (TYP)
DOWNSPOUT
DOWNSPOUT
DOWNSPOUT
DOWNSPOUT
DOWNSPOUT
DIRECTED WEST
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SCALE: 1" = 20'
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1224 W MAGNOLIA STREET RESIDENCE
PROPOSED IMPERVIOUS AREA EXHIBIT
DATE:October 3, 2025 PREPARED FOR:ARCHER HOMES INC.JOB NUMBER:U23010 NOTE:THIS EXHIBIT WAS PREPARED FOR INFORMATION ONLY AND THE ENGINEER PREPARING THESE PLANS WILL NOT BE RESPONSIBLE FOR UNAUTHORIZED USE OF THEM.SHEET OF1 1
NO
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19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | (970) 530-4044 | www.unitedcivil.com
UNITED CIVIL
Design Group
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 5/24/2023 at 3:48 PM 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°6'9"W 40°35'12"N
105°5'32"W 40°34'45"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020