HomeMy WebLinkAboutWEST VINE STORAGE - PDP - PDP170016 - CORRESPONDENCE - STORMWATER-RELATED DOCUMENTS,� • •
FORBES ENGINEERING
Full Service Civil & Structural Engineering
September 20, 2017
Mark Taylor
Stormwater Department
Arthur Ditch Administrator
City of Fort Collins
RE: Detention pond release into Arthur Ditch
West Vine Storage
1050 West Vine Drive
Fort Collins, Colorado
Dear Mr. Taylor;
This letter is sent to formalize our discussions concerning the storm water release
from this property to the Arthur Ditch. As you may recall the property is boarded
by Vine Drive on the south, Shields Street to the west, and Arthur Ditch to the
north (see attached existing drainage conditions map). The property is fairly flat,
sloping from the south to the north at an approximate grade of one percent and is
by natural contours below the adjacent streets. The storm water drainage from this
property has historically entered the Arthur Ditch along its south side. There are
no other drainage facilities in the area, nor can any be constructed that would
direct water away from the Arthur Ditch. As we discussed it is appropriate that the
drainage from this property continue to flow to the Arthur Ditch.
We have designed the drainage for the property to be released to the Arthur Ditch
from two detention ponds. There is a west pond and an east pond. Each pond
contains approximately half of the drainage from the property. In addition the City
is requiring that we accept onto the site storm water from the right-of-way and
street adjacent to the property. This water is directed to the east detention pond.
Each pond has restricted releases as required by the City of Fort Collins Drainage
Standards.
Each pond employs methods of sediment and pollutant control through a system of
rain gardens that pretreat the water prior to the release to the detention ponds.
There is one rain garden that serves the west detention pond and two rain gardens
that serve the east detention pond. No drainage enters the detention ponds without
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first flowing through the rain gardens. The design of these treatment facilities is in
conformance to the City of Fort Collins current Drainage Standards.
The release to the ditch in two locations reduces the intensity of the point flows
into the ditch and reduces the possibility of wash-out of the backs of the ditch.
Required stabilization rip-rap is used at the headwall release fans to reduce erosion
and maintain the bank structure of the ditches. All of this is detailed with the
drainage report for the project.
We will provide you electronic copies of the Grading and Drainage Plan and the
Erosion Control plan for your use. We will also include an electronic copy of the
Drainage Report for you. We hope these are the documents that you reyuire to
accept the drainage from this property. We appreciate your help in this project.
I hope this letter covers your concerns. Please don't hesitate to call if I can be of
further service or if you have any questions. I can be reached at (970) 232-6014.
Sincerely,
Kevin Forbes, P.E. #35265