HomeMy WebLinkAboutHORSETOOTH BUSINESS PARK, 1ST FILING - PRELIMINARY & FINAL - 78-88B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT•
STORM DRAINAGE REPORT
OF
HORSETOOTH BUSINESS PARK
FIRST FILING
PREPARED FOR
W.W. REYNOLDS COMPANIES
PREPARED BY
STEWART & ASSOCIATES, INC.
FEBRUARY 4, 1991
•
LOCATION:
The Horsetooth Business Park is located on the southwest corner of
Horsetooth Road and Timberline Road. The property is bounded on the north
by Horsetooth Road, on the east by Timberline Road, on the west by the Union
Pacific Railroad, and on the south by Collindale Business Park. The total
Horsetooth Business Park contains 32.2 acres. The Horsetooth Business Park
First Filing is located at the northwest corner of the site, adjacent to
the Union Pacific Railroad, and contains 9.2 acres. Horsetooth Business
Park is located in the Foothills Drainage Basin. Portions of the site have
been previously platted as South Collins Tech Center First, Second, and
Third Filings.
EXISTING CONDITIONS:
The pavement, curbs, and sidewalks on Horsetooth Road are completed,
and portions of the pavement, curb, and sidewalk on Timberline Road are
constructed. Some of the utilities, pavement, curbs, and walks shown on
the South Collins Tech Center First Filing plans have been installed,
although a part of these improvements do not fit the present plan, and will
be removed. Other than the previously installed streets, the site is a
pasture covered with vegetation.
There are no offsite flows onto the site. There is an irrigation ditch
which flows from west to east across the south edge of the site. This ditch
belongs to Mr. Bob Shields, and delivers water from Warren Lake to sites
east of Timberline Road. This ditch is open from a point on the west side
of the Union Pacific Railroad to the west side of Timberline Road, and picks
up historic surface flow from the railroad right—of—way, along with some
run—off from the Horsetooth Business Park site. We anticipate that in the
future this ditch will be put in a pipe from Timberline Road to the east
side of the Union Pacific Railroad, and that it will still carry historic
surface run—off from the railroad right—of—way.
PROPOSED IMPROVEMENTS:
The Horsetooth Business Park First Filing consists of 9.2 acres, 6.9
acres of which are to be impervious. We plan to provide stormwater detention
for the difference between the 2 year historic runoff and the 100 year
developed runoff. This calculates to be 1.93 acre feet of detention. There
will be a small detention pond located in the parking lot at the northeast
corner of the site, and a large detention pond located along the south side
of the site.
The maximum allowable runoff from the total Horsetooth Business Park
site is 5.5 c.f.s. We plan to install 15 inch pipes to carry the outflow
from the detention ponds and to pick up street flows at catch basins. The
15 inch pipes will have a hydraulic slope of approximately 1.0 percent,
which will make its capacity 5.3 c.f.s. The 15 inch pipe will then restrict
the outflow to the allowed amount. The 15 inch pipe will drain to the
existing 24 inch pipe under Timberline Road. This 24 inch pipe was installed
as a part of the Foothills Basin project and was meant to carry water from
the Collindale Business Park and from the Horsetooth Business Park area.
• 0
Horsetooth Business Park, First Filing
February 4, 1991
Page 2
There will be additional detention ponds constructed as more of the
Horsetooth Business Park is developed. These additional ponds will be tied
into the 15 inch outfall pipe line.
The attached computation sheets show how we arrived at the allowable
outflow, required detention volume and volume of the detention ponds. The
attached grading and drainage plan shows the proposed grades and drainage
facilities.
Phillip I. Robinson, P.E. & L.S.
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