HomeMy WebLinkAboutDrainage Reports - 11/23/1993Final Approved Report
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ENGLISH RANCH 4TH AND 5TH FILINGS
PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT
PREPARED
FOR
BARTRAN &•COMPANY, INC.
NOVEMBER 2, 1993
STEWART & ASSOCIATES, INC.
103 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
303/482-9331
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ENGLISH RANCH 4TH AND 5TH FILINGS
PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT
INTRODUCTION:
The proposed English Ranch 4th and 5th Filings consist of a 39.6627 acre
parcel of land located in the Northeast ; of Section 32, Township 7 North,
Range 68 West of the Sixth P.M., Fort Collins, Larimer County, Colorado. This
parcel is an extension to the east of the existing English Ranch 1st, 2nd and
3rd Filings.
The proposed improvements for this parcel consist of 94 single—family
lots, 40 paired —housing lots, streets and two proposed detention ponds on the
north end of the site. The proposed 4th Filing (21.1 acres) is planned for
construction in 1994, and the 5th Filing (18.6 acres) is planned for
construction in 1995.
The site is bordered on the north by East Horsetooth Road, on the east
by County Road No. 9, on the west by English Ranch lst and 3rd Filings, and
on the south by farm land.
EXISTING DRAINAGE BASIN AND SUB —BASINS:
The proposed site is in the Fox Meadows Basin Drainage Master Plan which
was developed for the City of Fort Collins by Resource Consultants, Inc. and
dated February 1981. Runoff from this basin is north to East Horsetooth Road
then east in a 36" existing storm drain to the existing drainage outfall channel
from the Foothills Basin. The Sunstone development and English Ranch lst,
2nd and 3rd Filings have been developed, and all the storm drainage facilities
are in place.
The existing basin is presently undeveloped, consisting of existing
irrigated farm land.:. The upper reach of this site slopes east at approximately
0.5% then north at approximately 1.0% grade.
There is no offsite runoff from the south, east, north or west onto this
site. Overflow may enter the site on the north end of the project from
overspill created by plugging or overtopping of the Sunstone and English Ranch
detention ponds. s..
DRAINAGE CRITERIA:
Due to the small size, the Rational Method has been utilized to determine
peak runoff rates and required detention pond. volumes. Design factors used
are in accordance with the recommendations of the City of Fort Collins Storm
Drainage Design Criteria and Construction Standards Manual. In.accordance
with City of Fort Collins drainage policy, the 100—year runoff from the
developed site will be. detained in two onsite detention ponds and released
at the 2—year undeveloped rate.
English Ranch 4th and 5th Filings
Page 2
PROPOSED DRAINAGE FACILITIES:
Design calculations and a grading and drainage plan have been included
at the end of this report. The proposed drainage.facilities for the site are
summarized as follows:
1. There will be two onsite detention ponds on the south side of East
Horsetooth Road on the north end of the site. Pond l (west pond) will
be sized•to store a minimum of 98,665 C.F. The pond area is 50,400 square
feet and, at an average depth of 3 feet, will have the capacity to store
130,000 cubic feet more or less. Release rate from this pond is 2.48
c.f.s. The pond will release into the existing 36" pipe in East Horsetooth
Road. All pond sideslopes shall be a maximum slope of 4:1.
Pond 2 will be sized to store a minimum of 122,661 cubic feet. Release
rate from this pond is 3.08 c.f.s. to the existing 36" pipe. All pond
sideslopes shall be a.maximum slope of 4:1
2. Curb inlets will. be required at Concentration Point (CP) Nos. 1 through
8. Use a 4—foot-inlet at CP Nos. 1, 2, 6, 7 and 8. Use an 8—foot inlet
at CP Nos. 3, 4 and 5.
3. A storm sewer system will be constructed to the concentration points.
Pipes are sized using K ters flowing full diagram.
4. A temporary drain Swale from Stockbury Drive at the east end of the 4th
Filing to Pond 2 will be required to be constructed until the 5th Filing
is constructed.
EROSION CONTROL:
This site is scheduled to be constructed in three phases. The 4th Filing
will be constructed in two phases, and the 5th Filing will be constructed in
one phase. The developer will only strip the phase ready to be constructed.
Pond outlets will require a gravel filter to be in place during construction.
All constructed inlets will also be required to have a gravel filter in place.
Additional erosion control may be required at the time of final submittal.
Franklin D. Blake, P.E. & -L. S.
enclosures
STEWART&NSSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: Date: 9 _ 9 Client: �f.•'�T/�p/ti% E' CEO Sheet No. —/— of
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5 -1-84
URBAN DRAINAGE & FLOOD CONTROL DISTRICT
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5 -1-84
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5 -1-84
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