HomeMy WebLinkAboutHANSEN FARM FIRST REPLAT - BDR210010 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: Hansen Farms Minor Amendment
FORT COLLINS | GREELEY 1 | 1
September 22nd, 2021
City of Fort Collins
Community Development and Neighborhood Services
281 North College Avenue
Fort Collins, CO 80522
RE: DRAINAGE MEMORANDUM FOR HANSEN FARMS MINOR AMENDMENT
FORT COLLINS, COLORADO
NE PROJECT #: 167-021
Dear Staff:
Northern Engineering Services is pleased to submit this Drainage Memorandum for the Hansen Farms Minor
Amendment application for your review. The proposed amendment will entail a replat of the area previously
designated for townhomes in the Hansen Farms subdivision in Fort Collins, CO. The subject site is located in the
east half of section 7, Township 6 North, Range 68 west of the 6th P.M. Fort Collins, Larimer County, Colorado.
The site is bounded to the south by Fallen Branch Drive, to the west by Knobby Pine Drive, to the north by Happy
Woodland Drive, and to the east by Floating Leaf Drive, all of which are platted streets in the Hansen Farms
Subdivision.
This Drainage Memorandum has been prepared in accordance with the Fort Collins Stormwater Criteria Manual
(FCSCM) and Mile High Flood District (MHFD) standards.
The intent of this project is to replat to construct lots for duplexes as opposed to townhomes. The duplexes
(including sidewalks and driveways) will overall have smaller footprints than the previously planned townhome
layout, and as such the decrease in new planned roof and concrete area of the subject site will be used for
landscaping. The new proposed lots have been designed to maintain the same drainage profiles as the currently
approved plan, however there will be a significant reduction in impervious area, thus contributing to lower the
projected runoff rates and decrease LID requirements. Upon completion of the amendment, subject area will
exhibit the same drainage patterns with a reduction in peak runoff rates as compared to the original approved
drainage report for Hansen Farms, while still utilizing the same LID structures designed for the original
subdivision drainage plan.
If you have any questions, please feel free to contact us at your earliest convenience.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Sterling Hallauer, EI Danny Weber, PE
Project Engineer Project Manager
Project:
Calc. By:
Date:
Description Surface Area
(sq ft)
Percent
Impervious Impervious Area (sq ft)
Rooftop 66402.90 90% 59762.61
Concrete 48346.91 100% 48346.91
Asphalt 18413.35 100% 18413.35
Pavers 0.00 40% 0.00
Gravel 0.00 40% 0.00
Landscaping 136729.80 2% 2734.60
Total 269892.97 129257.48
Description Surface Area
(sq ft)
Percent
Impervious Impervious Area (sq ft)
Rooftop 55232.82 90% 49709.54
Concrete 40765.43 100% 40765.43
Asphalt 18302.17 100% 18302.17
Pavers 0.00 40% 0.00
Gravel 0.00 40% 0.00
Landscaping 157567.51 2% 3151.35
Total 271867.93 111928.49
-17328.99Difference in Impervious Area (sq ft)
Minor Amendment Impervious Areas
Approved Hansen Farm Impervious Areas
IMPERVIOUS AREA CALCULATIONS
167-021Hansen Duplexes Minor Amendment
S. Hallauer
September 22nd, 2021
XXXXXXFLOATING LEAF DRKNOBBY PINE DRA
L
L
E
Y
K
NO
B
B
Y
P
I
N
E
D
R FALLEN BRANCH DRHAPPY WOODLAND DR
LEGEND
CONCRETE
ASPHALT
ROOFTOP
LANDSCAPE
APPROVED HANSEN FARM IMPERVIOUS AREAS
FORT COLLINS, CO
HANSEN DUPLEXES
E N G I N E E R N GI
EHTRON R N
09.22.21
P:\167-021\DWG\EXHIBITS\167-021_IMPERV.DWG
( IN FEET )
1 inch = ft.
Feet08080
80
Approved Hansen Farm Impervious Areas
Description Surface Area
(sq ft)
Percent
Impervious
Impervious Area
(sq ft)
Rooftop 66402.90 90%59762.61
Concrete 48346.91 100%48346.91
Asphalt 18413.35 100%18413.35
Pavers 0.00 40%0.00
Gravel 0.00 40%0.00
Landscaping 136729.80 2%2734.60
Total 269892.97 129257.48
Difference in Impervious Area (sq ft)-17328.99
Minor Amendment Impervious Areas
Description Surface Area
(sq ft)
Percent
Impervious
Impervious Area
(sq ft)
Rooftop 55232.82 90%49709.54
Concrete 40765.43 100%40765.43
Asphalt 18302.17 100%18302.17
Pavers 0.00 40%0.00
Gravel 0.00 40%0.00
Landscaping 157567.51 2%3151.35
Total 271867.93 111928.49
XXXXXXFLOATING LEAF DRKNOBBY PINE DRA
L
L
E
Y
K
NO
B
B
Y
P
I
N
E
D
R FALLEN BRANCH DRHAPPY WOODLAND DR
LEGEND
CONCRETE
ASPHALT
ROOFTOP
LANDSCAPE
( IN FEET )
1 inch = ft.
Feet08080
80
PROPOSED MINOR AMENDMENT IMPERVIOUS AREAS
FORT COLLINS, CO
HANSEN DUPLEXES
E N G I N E E R N GI
EHTRON R N
09.22.21
P:\167-021\DWG\EXHIBITS\167-021_IMPERV.DWG
Approved Hansen Farm Impervious Areas
Description Surface Area
(sq ft)
Percent
Impervious
Impervious Area
(sq ft)
Rooftop 66402.90 90%59762.61
Concrete 48346.91 100%48346.91
Asphalt 18413.35 100%18413.35
Pavers 0.00 40%0.00
Gravel 0.00 40%0.00
Landscaping 136729.80 2%2734.60
Total 269892.97 129257.48
Difference in Impervious Area (sq ft)-17328.99
Minor Amendment Impervious Areas
Description Surface Area
(sq ft)
Percent
Impervious
Impervious Area
(sq ft)
Rooftop 55232.82 90%49709.54
Concrete 40765.43 100%40765.43
Asphalt 18302.17 100%18302.17
Pavers 0.00 40%0.00
Gravel 0.00 40%0.00
Landscaping 157567.51 2%3151.35
Total 271867.93 111928.49