HomeMy WebLinkAboutMASON STREET INFRASTRUCTURE - ODP - ODP230001 - SUBMITTAL DOCUMENTS - ROUND 1 - Drainage Related Document (2)
NORTHERNENGINEERING.COM | 970.221.4158 OVERALL DRAINAGE MEMO: MASON STREET INFRASTRUCTURE
FORT COLLINS | GREELEY 1 | 2
May 24, 2023
Stormwater Department
City of Fort Collins
700 Wood Street
Fort Collins, Colorado 80521
RE: OVERALL DRAINAGE MEMORANDUM FOR MASON STREET INFRASTRUCTURE
FORT COLLILNS, COLORADO
NE PROJECT NUMBER: 1971-001
Dear City Staff:
This letter report accompanies the submittal for the Mason Street Infrastructure Overall Development Plan
(ODP). Specifically, this letter report serves to document the overall drainage impacts associated with the
proposed developments. As each lot develops it will need to follow the FCSCM and this ODP Memo.
The proposed development is comprised of two properties located east of N College Ave and north of Hickory
Street. The site is situated around N Mason Street and Hibdon Court and will include the development of three
lots (Lot 1, Lot 2, Lot 3), Mason Street right-of-way dedication, and a single tract (Tract A). The overall combined
site is 13.45 acres in size. The site is currently zoned as Service Commercial District (C-S).
The subject properties are not located in a FEMA or City of Fort Collins regulatory floodplain and there are no
existing structures onsite. Any proposed buildings will be constructed with a finish floor elevation of at least 1.5-
ft above the spillway elevation.
The proposed development site is in the City of Fort Collins Dry 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. In the Dry Creek Basin the 2-year historic release rate is 0.2 cfs/acre. With future
development, the lots surrounding N Mason Street will be responsible for providing water quality treatment and
Low impact development (LID) per the Fort Collins Stormwater Criteria Manual.
The proposed site will include the construction of the Interim Hickory Regional Detention Pond located in Lot 1.
The Hickory Pond will provide detention for the adjacent Lot 2 and standard water quality treatment for Lot 1 &
2 in the interim. Water quality treatment and LID will be provided with the future development of Lots 2 & 3 to
meet the city’s current requirements. Lot 3 will maintain historic drainage paths in the interim condition.
Detention location and analysis for Lot 3 will be determined with development. There is an existing site outfall in
the southeast corner of the project site. The Interim Hickory Regional Detention Pond will detain and release
upstream of the existing outfall to minimize impact to downstream infrastructure.
The site does receive notable runoff from adjacent properties which are detained in an existing detention pond
onsite. The interim Hickory Pond will incorporate the existing detention volume and release rate in the interim
condition. Additional analysis of these offsite flows will be performed with the Ultimate Hickory Regional
Detention Pond and designed by the City of Fort Collins.
NORTHERNENGINEERING.COM | 970.221.4158 OVERALL DRAINAGE MEMO: MASON STREET INFRASTRUCTURE
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