HomeMy WebLinkAboutROHRBACKER PUD - PRELIMINARY & FINAL - 41-89C - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT0
STt MART&kSSOCIATES
Consulting Engineers and Surveyors
May 7, 1990
Mr. Glen Schlueter
Storm Water Utility
City Of Fort Collins
P 0 Box 580
Fort Collins, CO 80522
RE: Supplemental Storm Drainage Information for Rhorbacker P.U.D.
Dear Glen:
At the Planning and Zoning Board meeting held March 21, 1990, it was
said that quite a bit of water has been seen running east on Magnolia
Street, through the Rhorbacker property. I believed that this could
not possibly have been from rain storms due to the small runoff basin.
The Rhorbacker porperty only generates 3.0 c.f.s. during a 10 year storm
and the offsite field, lying to the west, which might contribute runoff,
generates 4.9 c.f.s. during a 10 year storm. I thought the water seen
in the street was probably from irrigation overflow, and Mrs. Rohrbacker
confirmed this. She told me that on occasions during the past her husband
had complained to the person irrigating the field to the west when his
irrigation water broke out of the ditches and flooded through the
Rohrbacker property. As I pointed out in the March 16, 1990 Rohrbacker
P.U.D. storm drainage report, this irrigation overflow from the west
can be diverted by constructing an earthen berm along the west property
line of the Rohrbacker P.U.D.
The proposed filter berm to the downstream side of the auto storage area
is to stop oil and grease drippings from being washed onto adjoining
properties by lesser storms. We realize that the 100 year storm will
inundate the entire area and cause the filter berm to be non —effective.
As we discussed previously, the 100 year stom flow will so dilute any
oil or grease washed from this site, that it will not be a hazard.
The installation of the filter berm and the possible construction of
a berm to divert irrigation overflows will make the Rohrbacker P.U.D.
a safe and practical site for the storage of vehicles.
I am attaching a copy of the March 16th 1990 Storm Drainage Report.
Please call if you have any questions or additional ideas regarding this
project.
Sincerely,
Phillip f. Robinson, P.E. & L.S.
Vice President
I k k
enclosure James H. Stewart
and Associates, Inc.
214 N. Howes Street
PO. Box 429
Ft. Collins, CO 80522
303/482-9331
0
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STORM DRAINAGE REPORT
ROHRBACKER P.U.D.
PREPARED FOR
AUTO SALVAGE - MR. WAYNE SPECHT
STEWART & ASSOCIATES, INC.
MARCH 16, 1990
% 0 •
ROHRBACKER P.U.D. DRAINAGE REPORT.
The Rohrbacker P.U.D. is a 3.6 acre site located at 1200 East Magnolia
Street, which is 400 feet North of East Mulberry Street and 600 feet
west of Link Lane. The site presently has two metal buildings and a
250 foot long by 35 foot wide asphalt strip, and the remainder of the
property is gravel and earthen surfaced. The site is located in the
Cache La Poudre River flood plain, according to FEMA map 080101 0179 C
as revised March 18, 1986. The 100 year flood water elevation is
approximately 4932, which is about 3 feet above the existing ground
elevation. The floor elevations of the two existing buildings are below
the 100 year flood water elevation, therefore, they will be
non —conforming. The west building is now used by Sipes Concrete
Contractors as a shop and office, and a portion of the west yard is used
for storage of concrete forms and related equipment. The Sipes' operation
will remain the same; therefore, there will be no change in storm water
run—off from the westerly portion of the site.
The east building, which is now vacant will be occupied by the Auto
Salvage operation as a sales office and for storage of auto parts. The
lots to the south will be used for storage of salvagable vehicles. The
ground surface will not be changed from that which now exists, and the
storm run—off quantities will remain the same. Hazardous wastes, such
as oil or grease, shall not be drained from the vehicles onto the ground,
but since there may be drips or spills, a filter berm shall be constructed
around the run—off from the vehicle storage area. This filter berm will
be constructed from compacted road base, which will hold its shape and
which will allow water to pass through while filtering out oil and grease.
Any offsite flows onto the Rohrbacker P.U.D. would come from the upstream
property lying to the west. This property to the west is farm laQd which
is irrigated from north to south and which has a waste water ditch running
north to south along its east edge. The Lemay Avenue dike stops the
flood waters which would come directly from the Cache La Poudre River;
therefore, only the rain falling on the field will contribute to runoff
flows, and the irrigated rows running north to south and the waste waters
ditch will intercept all storm waters before they flow onto the Rohrbacker
P.U.D. The attached calculation sheet shows the existing runoff
quantities from this offsite field. Whenever this offsite property is
developed, and Magnolia Street is constructed through from the east,
a complete drainage study of the area will be required; but until that
happens, the drainage patterns are such that this field will not
contribute offsite flows to the Rohrbacker P.U.D. In case the irrigation
row direction is changed and the waste water ditch is done away with,
offsite flow onto the Rohrbacker P.U.D. can be diverted by constructing
an earthen berm along its west property line.
a
Rohrbacker P.U.D Drainage Report
March 16, 1990
Page 2
The proposed uses of the Rohrbacher P.U.D. will not change the ground
surfacing from that which now exists; therefore, the quantity of run—off
and drainage patterns will remain the same. The construction of the
filter berm will stop any hazardous wastes from leaving the site. The
proposed uses will not cause any risk to the safety or welfare of the
public.
This storm drainage report is only for the immediate use of the site
as an auto salvage operation; and any further development, such as new
paving or buildings, shall require a complete new utility and drainage
plan review.
The attached calculation sheet shows the composite C factor along with
the 2 year, 10 year, and 100 year storm run—off quantities from the
existing conditions of the Rohrbacker P.U.D.
Phillip 1V Robinson, P. E. & L.S.
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Stewart & Associates, Inc. / 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
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