HomeMy WebLinkAboutDrainage Reports - 09/23/2008CIVIL ENGINEERS
3400 WEST 1 STD STREET
BUILDING 5, SUITE Z
GREELEY, CO B0634
(970) 37B-6935, FAx (970) 37B-6997
WWW.DMWCIVILENGINEERS.COM
Drainage Letter
August 28, 2008 City) of Ft.:.Collins rov2dPlans
City of Fort Collins
Stormwater Utility Date 9-aJ-oB
700 Wood Street
Fort Collins, CO 80521
Re: Research Innovation Center - CSU Foothills Campus
Overland Trail at Rampart Road Improvements
Project No. 0801.00-RIC
Dear Staff:
On behalf of our client, Colorado State University, with the above referenced project, we
are providing this letter in lieu of a drainage report. A drainage report is not being
provided for this project due to the fact that the the overall post construction drainage
patterns for the Overland Trail and Rampart Road improvements will remain unchanged
from existing conditions.
The proposed construction on Overland Trail will affect only the runoff from the west
side of the road crown. All runoff from the east side of the crown will be unaffected by
the proposed construction.
The improvements to Rampart Road minimally extend the width of the asphalt road
surface but do not add curb and gutter. ,The existing flow pattern of runoff sheet flow
will be maintained.
Approximately 0.33 acres of existing asphalt on both roads will be either removed and
replaced or milled and re -surfaced. 0.40 acres of new asphalt surfacing will be placed
and 0.24 acres of new concrete will also be placed. This results in a net of 0.31 acres
of new surfacing.
EXISTING CONDITIONS - Overland Trail
The existing west side of Overland Trail in the construction area does not have curb and
gutter. Pre -construction runoff is conveyed off the road as sheet flow. Flow north of
Rampart Road is then conveyed north to an existing curb and gutter. Flow south of
Rampart Road sheet flows into an existing ditch on the west side of the road, and then
south to an existing culvert under Overland Trail.
PROPOSED CONDITIONS — Overland Trail
Asphalt without curb and gutter will be added to Overland Trail north of Rampart Road.
Runoff in this area will sheet flow to the west, similar to the existing conditions. This
flow will be captured and conveyed north in a proposed road -side ditch. The ditch
discharges into the existing curb and gutter in the same manner as under existing
conditions.
Street runoff south of Rampart Road will be captured by the proposed curb and gutter
and conveyed south to the curb cut on the west side of Overland Trail at Station 13+08.
The curb cut discharges into the existing road -side ditch. Runoff flows south to an
existing culvert approximately at Station 12+13 and is conveyed east under Overland
Trail. This matches the flow pattern under existing conditions. The 100-yr runoff routed
to the curb cut is 4.9 cfs for an area of 0.5 acres.
Please contact me if you should have any questions.
Sincerely,
DMW Civil Engineers, Inc.
33885
Jade P. Miller, P.E. (CO #33885) �•., • 07
Project Engineer �SSro�vn; EN61