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NORTHERNENGINEERING.COM | 970.221.4158 OVERALL DRAINAGE MEMO: RED ROCKS SELF-STORAGE
FORT COLLINS | GREELEY 1 | 2
February 22, 2022
Stormwater Department
City of Fort Collins
700 Wood Street
Fort Collins, Colorado 80521
RE: OVERALL DRAINAGE MEMORANDUM FOR WORTHINGTON SELF STORAGE
FORT COLLILNS, COLORADO
NE PROJECT NUMBER: 1853-001
Dear City Staff:
This letter report accompanies the submittal for the Worthington Self Storage Overall Development Plan (ODP).
Specifically, this letter report serves to document the overall drainage impacts associated with the proposed
development.
The proposed development site is located in the Centre for Advanced Technology P.U.D. development in Fort
Collins, Colorado. The site is situated west of Worthington Circle and surrounded by private development. The
overall site is roughly 3.2 acres in size. The approved drainage report for this property is the ‘Final Drainage
Report and Erosion Control Study for Cinema Savers’, Center for Advanced Technology Sixteenth Filing, Fort
Collins, Colorado.
The proposed development site is in the City of Fort Collins Spring Creek Master Drainage Basin. Detention
requirements for this basin are to detain the difference between the 100-year development inflow rate and the
historic 2-year release rate. Based on the previous drainage report the calculated required detention volume is
1.51 acre-feet, this includes runoff from C.A.T Tenth filing. There is an existing outfall pipe at the northeast
corner of the project site with a manhole and orifice plate down-stream of the existing detention pond. The
required release rate is 1.91-cfs. Stormwater release is conveyed to the north, across Centre Ave, and discharges
to Spring Creek. This outfall is planned to remain for the entire site.
Per chapter 6, Section 1.3 (FCSCM), onsite detention is required when there is an increase in impervious area
greater that 1000-sqft. Attachment A to this memo shows the planned development of the subject property and
the comparison to the existing imperious area. There is no expected rise in the impervious area with the
proposed project. Existing detention volume is a combination of the existing detention pond and ponding in the
existing parking lot. With the development of the parking lot, the existing detention pond will be modified to
hold the volume required by the previously approved report and the existing release rate will not need to be
adjusted. The entire lot (Basin 1) will be routed to the proposed detention pond in the northeast corner of the
site. Due to the modification of the impervious area, LID systems and water quality treatment will be included in
the drainage design of the entire site.
No floodplains are located on this site. This project will maintain the 100-yr WSEL and the proposed building will
be constructed with a finish floor elevation of at least 1.5’ above the spillway elevation.
NORTHERNENGINEERING.COM | 970.221.4158 OVERALL DRAINAGE MEMO: RED ROCKS SELF-STORAGE
FORT COLLINS | GREELEY 2 | 2
In summary, this Overall Drainage Memo addresses any potential stormwater changes associated with the
proposed Overall Development Plan. In general, there is no significant changes proposed at a major drainage
level. The ODP complies with the governing City of Fort Collins Master Drainage Plans, and the previously
approved drainage report for the subject property.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
MASON RUEBEL, PE
Project Engineer
Attachments
· Attachment A – Impervious Area Computations
· Attachment B – Drainage & Erosion Control Plan – Centre for Advanced Technology Sixteenth Filing
SSSCVAULTELECSSSELECCELECEDDDTCONTROLIRRGXXVAULTF.O.XXXXSSSCVAULTELECSSSELECCELECEDDDTCONTROLIRRGXXVAULTF.O.DRAWN BY:SCALE:DATE:EXISTING VS PROPOSEDIMPERVIOUS AREASHEET NO:FORT COLLINS: 301 North Howes Street, Suite 100, 80521GREELEY: 820 8th Street, 80631ENGINEERNGIEHTRONRN970.221.4158northernengineering.comP:\1853-001\DWG\DRNG\1853-001_IMPV.DWG
2525 WORTHINGTON MINI-STORAGEFORT COLLINSCOLORADOMCREXISTINGPROPOSED( IN FEET )01 INCH = 60 FEET6060ROOFTOPCONCRETEASPHALTSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)19,2207,17986,223100%100%100%112,622TOTAL=19,2207,17986,223GRAVEL040%01" = 60'2/23/2022IMP 1LANDSCAPING27,0230%0ROOFTOPCONCRETEASPHALTSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)52,9838,73849,667100%100%100%111,388TOTAL=52,9838,73849,667GRAVEL040%0LANDSCAPING28,2570%0WO
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