HomeMy WebLinkAboutHORSETOOTH EAST BUSINESS PARK PUD - PRELIMINARY/FINAL - 43-94 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTCOMPUTATIONS
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Stewart & Associates, Inc. 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
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Stewart & Associates, Inc. 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
Date 2 Client: Tie Srn o/d S Sheet No. :_of 13
Chkd By: Date Project: IL)O rs 6rc4-4 Ous i n Cff Park r—1 r-s+
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COMPUTATIONS
Stewart & Associates, Inc. 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
P11-S Date ti Client: I^% 0• F-Sczv r7o/ck Sheet No. of 13
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I USE WITH THE RATIONAL FORMULA.
*MOST FREQUENTLY OCCURRING "UNDEVELQPED"
LAND SURFACES IN THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
Release No. 55, USDA, SCS Jan. 1975.
5 -1-84
URBAN DRAINAGE & FLOOD CONTROL DISTRICT
COMPUTATIONS
Stewart & Associates, Inc. 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
F PI(Z —Date zl Client: kA/ Tie'✓,r70/01"5 Sheet No. of 13
ChkdBy: Date Project: PuldiG Ser✓Icy �a. - /�orse�oo�h 3US ��_rt lark_
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Horsetooth Business Park, First Filing
April 4, 1991
Page 3
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 allowable release rate for
all of the future parcels to be developed in the Horsetooth Business Park
shall be 0.17 c.f.s, per gross acre.
There is an existing 18 inch storm drain running east from the manhole.
at the intersection of Automation Way and Elk Road. This 18 inch line
flows to the east and is part of a previously proposed system which will
possibly be abandoned, therefore,we are plugging the 18 inch pipe in the
manhole and outflowing the manhole via a new 15 inch pipe draining to the
south.
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.
Sheet 3
Horsetooth Business Park, First Filing
April 4, 1991
Page 2
We propose to use 15 inch RCP storm drains for all the pipes in the
Horsetooth Business Park. Sheet 12 of this report is a profile of the
proposed storm pipe system. Also shown on sheet 12 is the calculated
hydraulic grade line, along with calculations of pipe flow velocity and
capacity at critical points. We calculated all of the velocities and
capacities in the pipe system based on the pipe outflow going into a
completely filled Collindale Business.'Pa.rk detenti.on pond. This is the
most conservative situation, since the high water line elevation of the
Collindale Business Park pond will be lower for all storms except the 100
year storm, and even during the 100 year ,storm, it will not reach the full
level for 3 hours. The calculated capacity of the outfall pipe as it enters
the Collindale Business Park pond is 5.3 c.f.s., which is close enough
to the 5.5 c.f.s. allowable release rate.
The hydraulic grade line is a maximum 0.22 feet above manhole lids,
which is not enough to pop the manhole lids. There is a safety valve built
into the storm pipe system, which is that when there is more runoff entering
the pipe system through street catch basins than the downstream pipes can
carry, there will be backflow into the detention ponds. Detention ponds
constructed in the Horsetooth Business Park shall have an outflow
restriction plate which is hinged, to that it will allow backflow to enter
the pond through a 15 inch opening. Sheet 13 of this report shows the
detention ponds for this filing, along with the approximate location, size,
and high water line of future ponds.
The small detention pond located in the north parking lot will provide
14,594 cubic feet of the total required 96,433 cubic feet of detention
volume. The outflow from the small pond is 0.57 c.f.s., of the allowed
1.76 c.f.s., therefore, the outflow from the large pond located at the
south end of the site will be the difference, which is 1.19 c.f.s. The
proper volume will accumulate in the north detention pond due to the fact
that we have used the 0.57 c.f.s. release rate and the basin area of 1.9
acres to calculate a detention requirement of 14608 cubic feet, which is
substantially the same as the maximum pond volume of 14594 cubic feet.
This release rate of 0.57 c.f.s. is larger than the allowable (1.9) (0.17)
= 0.32 c.f.s., but we have compensated for this by decreasing the release
rate of the south pond from (8.48) (0.17) = 1.44 c.f.s. to 1.19 c.f.s.
The large detention pond located at the south end of the site has
a proposed capacity of 110563 cubic feet, and a required detention volume
of 81839 cubic feet, so there is 28724 cubic feet excess capacity. The
bottom of this pond is to be left flat so that it will become a wetlands,
with cattails and wetlands grasses. The wetland will become an effective
settling basin and will provide a better water quality into the storm
drainage system. The restricted outflow of 1.19 c.f.s. will slow the flow
through the pond and allow the wetland settling area to be more effective.
Sheet 2
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 a gross area of 10.38
acres to the center of adjoining streets. 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 10.38 acres,.
7.93 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 2.21 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 outflow from the total 32.2 acres of the
Horsetooth Business Park site is 5.5 c.f.s. The 5.5 c.f.s. outflow is
determined by the available capacity of the existing 24 inch pipe under
Timberline Road. The 24 inch pipe was installed in 1989 as a part of the
Foothills Drainage Basin major improvements, its purpose being to carry
storm flows from the Collindale Business Park and from the Horsetooth
Business Park. The allowable outflow per gross acre of the Horsetooth
Business Park is 5.5 divided by 32.2, equals 0.17 c.f.s. per acre, therefore
the total outflow from the 10.38 acre site is 1.76 c.f.s.
Sheet 1
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C,OLF
COURSE
VICINITY MAP
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STORM DRAINAGE REPORT
OF
HORSETOOTH BUSINESS PARK
FIRST FILING
IW:19' , 7l7flL`7
W.W. REYNOLDS COMPANIES
PREPARED BY
STEWART & ASSOC.IATES, INC.
FEBRUARY 4. 1991
REVISED 3118 j91
REVISEC7 415) 9I
No Text
cTr\AiApTRAr,r,nnAT c 103 S. PH482-9331 MELDRUMFAX 482-938, FORT COLLINS, CO 80521
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Consulting Engineers and Surveyors
By: PI7Z Date: Z-21- cN- Client: T1 t--A �r /["% e YcK rl ACrl Sheet No. of
Project: 40vsej(ja�FqS4- )�5US(,ie5f Pbflr
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CONSTRUCTION SEQUENCE
PROJECT: 1-�Orse4ocA P.G,s1
SEQUENCE. FOR 1994- ONLY COMPLETED BY:
61r.,RU1.:1 112mo
DATE:
Indicate by use of a bar line or symbols when erosion control measures will be installed.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engineer.
YEAR
MONTH
------------ - -I
OVERLOT GRADING I
WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other comic fod4c-
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving!
Other
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettinas/Mats/Blankets
Other
STRUCTURES: INSTALLED BY
1444- !f9 �
N I D I T
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
HDI/SF-C:1989
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MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS Off
Je�`Il �?': 1991 8-20 DESIGN CP.T_TE.'.T'•.
-------EFFECTIVENESS CALCULATIONS
------------ ---------------------------------------------
PROJECT: STANDARD FORM B
COMPLETED BY: DATE:
Erosion Control
C-Factor
P-Factor
Method
Value
Value Comment
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( RAINFALL PERFORMANCE STANDARD EVALUATION
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Horsetooth East Business Park Minor Subdivision
Page 2
There will be no development on Lot 3 at this time, and in the future
when Lot 3 is developed, the existing detention pond along the north boundary
of Lot 3 will be enlarged to supply detention necessary. A separate drainage
report shall be necessary for the development of Lot 3.
The release rate for the 4.41 acre development of Lots 1 and 2 and Tract
A is 0.17 c.f.s. per acre, per the 1991 Horsetooth Business Park report. The
release rate from the Tract A pond shall be 0.75 c.f.s., and the required pond
volume shall be 37533 cubic feet. Release from the Tract A pond will be through
a 15—inch pipe with a restricted opening. This restriction plate shall be
the "flap gate" type, as utilized by the Horsetooth Business Park First Filing,
to allow backflow from the 15—inch storm pipe system to flow into the detention
pond.
EROSION CONTROL
Horsetooth East Business Park is located in a moderate rainfall and wind
erodibility zone.
Lot 1 will be developed at this time, and Lots 2 and 3 will be developed
in the future. The existing heavy grass vegetation on Lots 2 and 3 will not
be disturbed at this time.
Tract A is on existing wetland ponding area which will be utilized as
the stormwater detention area for runoff from Lots 1 and 2. A restrictd outlet
from the pond will be protected by a sediment trap.
The construction sequence will be that the building foundation will be
constructed this fall and winter and, weather permitting, the curbs and pavement
will follow. If it is impractical to.begin the curb and pavement due to
weather, the building construction can still proceed, and the existing
vegetation on the parking lot area of Lot 1 can remain undisturbed.
The erosion control procedures shall comply with City of Fort Collins
criteria.
FINAL STORM DRAINAGE AND EROSION CONTROL REPORT
HORSETOOTH EAST BUSINESS PARK MINOR SUBDIVISION
SITE LOCATION
The Horsetooth East Business Park Minor Subdivision is located in the
Fox Creek Drainage Basin. The site is the southerly 8.9 acres of a 32.2 acre
development located in the Northeast a of Section 31, Township 7 North, Range
68 West, of the Sixth P.M., City, of Fort Collins, Colorado. The site is bounded
on the west by the Union Pacific Railroad, on the north by Bighorn Drive, on
the east by Timberline Road, and on the south by the Collindale Business Park.
Automation Way runs north —south through the approximte middle of the site.
EXISTING CONDITIONS
The site drains from northwest to southeast at 0.7 percent slope. The
site is covered with heavy vegetation consisting of broad leaf grass. There
is a dirt stockpile on the westerly portion of the site, and there is a wetland
ponding area in the southeast corner of the site (Tract A). This ponding area
will be utilized as a detention pond for the east half of the site (Lots 1
and 2). There is an existing detention pond located along the north boundary
of the west half of the site (Lot 3). This pond was constructed by the
Horsetooth Business Park First Filing in 1991. Lot 3 will not be developed
at this time and will be left as is. The existing vegetation on Lot 3 will
not be disturbed.
OFFSITE FLOWS
There are no major offsite flows onto the three lots of Horsetooth East
Business Park. The east one—half of the Union Pacific railroad right—of—way
drains onto Lot 3, but the railroad embankment stops flows from the Collindale
Golf Course which lies west of the railroad. There is an open irrigation ditch
across the south edge of the site. This open ditch picks up runoff from the
golf course and from the railroad right—of—way. The ditch is piped under the
railroad by a 24—inch steel pipe, and then runs east in an open ditch to
Timberline Road where it enters a 24—inch diameter concrete pipe and is then
piped on east to County Road 9. We plan to place this open ditch in a pipe
from Timberline Road to the west side of Automation Way: This shall require
approval of the ditch owner, Mr. Robert Shields.
PROPOSED STORM DRAINAGE DEVELOPMENT
The existing ponding and wetland area located on Tract A will be utilized
as the detention pond for Lots 1 and 2. Lot 1 will be developed at this time
with an office building and parking, and Lot 2 will be developed in the future
with buildings and parking lots. We will provide, at this time, the required
detention ponding and drainage facilities for Lot 2 so that when it is developed
in the future, it can drain directly into the detention pond which will be
constructed at this time. The total area which will drain into the Tract A
detention pond is 4.41 acres. This includes Lots 1 and 2, Tract A, and Bighorn
Drive. Automation Way and the west one—half of Ti.mberline Road drain into
the existing Collindale Business Park detention pond through existing curb
inlets. The Collindale Business Park pond is almost four acres in size and
has a foot of freeboard, so it can easily accommodate this street runoff.
9
STEWART$,06SOCIATES
Consulting Engineers and Surveyors
August 22, 1994
Mr. Basil Hamdan
Storm Water Utility
City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522
Dear Basil:
The following drainage and erosion control report is prepared for the
Horsetooth East Business Park Minor Subdivision. Horsetooth East Business
Park Minor Subdivision is the second phase of a 32.2 acre business and
industrial development which was begun in 1991.
A drainage report titled "Horsetooth Business Park First Filing" was
prepared for this 1991 development. I am including a copy of this report in
the appendix and will follow the design guidelines established by this 1991
report.
This report complies with the City of Fort Collins Storm Drainage Design
Criteria.
Sincerely,
e 1. n V
c/r.lJ�rl
Phillip I. Robinson, P.E. & L.S.
Vice President Z* 4502
jrr
enclosures
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
Ft. Collins, CO 80522
303/482-9331
Fax 303/482-9382
FINAL
STORM DRAINAGE AND EROSION CONTROL REPORT
FOR
HORSETOOTH EAST BUSINESS PARK MINOR SUBDIVISION
TIMBERLINE PARTNERS LIMITED
AUGUST 22, 1994
STEWART & ASSOCIATES. INC.
102 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
303/482-9331