HomeMy WebLinkAboutRICHMOND ASSOCIATES RH NON RESIDENTIAL USE - 46 90 - CORRESPONDENCE - STORMWATER-RELATED DOCUMENTSDecember 7, 1990
Project No: 1227-01-90
Mr. Glen D. Schlueter
City of Fort Collins Storm Water Utility
P.D. Box 580
Ft. Collins, Colorado 80522
II
I DEC 7rM
Re: 420 West Oak Street (Richmond Associates), Ft. Collins, Colorado.
Dear Mr. Schlueter,
The proposed improvements to the Richmond property involves the covering
of a present dirt rear yard/parking area and alley with a checker block
paver. The block which will be used allows for 277 of its surface area to
be planted to grass. The dirt that is existing in the rear yard/parking
area ranges from a semi -Packed to hard -packed clay and road base material.
The slope of the existing area appears to be towards the private alley,
then into a public alley which conveys the runoff to Mountain Avenue.
The affected area contains approximately 3,497 square feet of pervious
area with an approximate runoff coefficient of 0.40 because there is
little or no grass or overgrowth to slow the water down. The gravel area
also increases the runoff coefficient somewhat. Once the pavers are in
place, this area will be approximately 272 pervious and 73% impervious,
with an average runoff coefficient of 0.75. A sand or gravel base for the
block may help reduce the runoff coefficient. All other property runoff,
south of the proposed parking area, will continue to be directed south to
West Oak Street. There is little or no offsite contribution from the east
or west.
The storm runoff generated within this small area will obviously increase
slightly due the the placement of the block, but not to the point of
impacting the existing surrounding and downstream drainage system. We
calculate that the increase in runoff due to the addition of the paver
block over the proposed area will be 0.10 cfs for a 2-year storm and 0.30
cfs for a 100-year storm, utilizing City of Fort Collins Storm Drainage
Design Criteria.
We feel that the insignificant potential increase in runoff does not
warrant further improvement to the proposed parking area and alleyway,
than that already proposed by Richmond and Associates. We also feel that
the paver block will establish a more acceptable and direct route for
storm water runoff than currently exists.
If you have
Sincere
Shear Engineering Corpor
Brian W. Shear, P.E.
BWS/so
cc: Ted Shepard; City Planning
Richmond Associates
at 226-532"4.
4836 S. College, Suite 12 Fort Collins, CO 80525 (303)226-5334