HomeMy WebLinkAboutDrainage Reports - 10/07/1996 (2)PROPERTY OF Final A ved ReP01t
FORT COLD NS UTI ITIES Z f
DRAINAGE INVESTI ON
FOR
WEST PLUM STREET - P.U.D.
CITY OF FORT COLLINS, LARIMER COUNTY, COLORADO
Prepared for
Vista Building Company
P. O. Bog 885
Fort Collins, Colorado 80522
May 14,1996
(Revised August 9,1996)
Project No. PLA -195 - 96
AUG2 p,
HI9001MR Engineetg Associates
150 E. 29th Street, #238 Loveland, Colorado 80538 Telephone: (970) 663 - 2221
1
1
' Engineering Associates
August 8, 1996
Project No. PLA - 195 - 96
Mr. Basil Y. Hamdan
Stormwater Utility
235 Mathews
' P. O. Box 580
Fort Collins, Colorado 80522-0580
Dear Mr. Hamdan,
The enclosed report represents the results of the drainage investigation for the
proposed "West Plum Street - P.U.D." to be located in the City of Fort Collins,
Larimer County, Colorado.
' This investigation was based upon the proposed site development plan; proposed
site grading plan; on -site observations; and available topographic information.
' The investigation was performed in accordance with the criteria established in
the City of Fort Collins "Storm Drainage Design Criteria and Construction
Specification Standards" manual.
If you should have any questions, please feel free to contact this office.
' Respectfully Submitted,
MESS Engineering Associates
' Dennis R. Messner, P.E.
DRM/mkm
1
tEnclosures
' cc: Mr. Doug Viita
Civil and Environmental Engineering Consultants
150 E. 29th Street, Suite 238 Loveland, Colorado 80538 Telephone: (970) 663-2221
TABLE OF CONTENTS
Letter of Transmittal
Table of Contents
Scope
Site Description
"Historic" Conditions
Proposed Development
Erosion Control Measures
Conclusions and Recommendations
Drainage Summary
Erosion Control Cost Estimate letter
EXHIBITS
Vicinity Map
"Historic" Conditions Exhibit
Proposed Conditions Exhibit
Calculations
ii
SCOPE
' The following report represents the results of a drainage investigation for a
proposed single family residential development to be located in the North Half of
Section 16, Township 7 North, Range 69 West of the 6th P.M.in the City of Fort
' Collins, Larimer County, Colorado. The investigation was performed for the
project developer, Viita Building Company. The purpose of this investigation is to
determine the effects of the proposed development on the area's existing drainage
' conditions and to determine the improvements, if any, and the appropriate sizing
for the proposed improvements so that it may be incorporated with the
construction of the project. The conclusions and recommendations presented in
' this report are based upon the proposed site development plan; proposed building
construction plans; on -site observations; and the available topographic
information. The analysis was performed in accordance with the City of Fort
Collins "Storm Drainage Design Criteria and Construction Standards" manual.
SITE DESCRIPTION
' The site is considered to be rectangular and contains approximately 3.05 acres,
exclusive of the adjacent 2.5 acre tract to the South that is to remain undeveloped.
The site's East-West dimension is approximately 395 feet and its North -South
' dimension is 335 feet. The site abuts the southerly right-of-way of West Plum
Street and the tract that is to remain undeveloped abuts the northerly right-of-way
of West Elizabeth Street. The site is located in the CANAL IMPORTATION
DRAINAGE BASIN.
"HISTORIC" CONDITIONS
' The site is vacant and has been utilized as irrigated pasture. A small depression
has been dug near the Northeast corner of the site to capture surface runoff for
' stock watering. The ground surface has been- roughly graded and a moderate
ground cover of grasses is found on the parcel. The "historic" direction that the
site slopes is from South to North. A small lateral ditch is situated along the crest
of a hill adjacent to the southerly boundary of the development. The site is
' considered to be moderate with slopes ranging from 1 % to 6 %. The major portion
of the site currently drains onto West Plum Street. The run-off generated on the
rear yards of the adjacent lots to the West and East flows onto the site and then
' flows northerly across the site to West Plum Street. The runoff from the tract to
the South that is to remain undeveloped flows to the South and East toward West
Elizabeth Street. An existing developed area of approximately one acre situated
' immediately West of the site contributes run-off to the street flow along the North
side of the site. The run-off in the street flows to the East along Plum Street to the
intersection with Timber Lane. The flow travels North along Timber Lane for
' approximately four hundred feet where it is intercepted by storm drain inlets. The
-run-off is directed through the inlets to an open drainage channel that flows
easterly.
1
PROPOSED DEVELOPMENT
The proposed development of the site is to consist of developing thirteen single
family residences to be located on the northern three acres of the site. The homes
are to be considered as affordable housing. The average proposed lot size is
approximately 7,000 square feet. The house "foot print" is anticipated to be from
1,200 square feet to 1,500 square feet depending on the style of house to be
constructed. A paved driveway and attached two -car garage are to be constructed
with each home. The proposed site plan indicates that a cul de sac is to be
constructed at the southerly boundary of the site. The proposed development plan
indicates that the southern two and one-half acres of the site is to remain vacant.
with a potential for future development.The cul de sac is intended ultimately
provide access to the southerly portion of the site that is to remain undeveloped.
This investigation has not considered this as tributary to the development that is
currently proposed.
As previously stated the run-off from the site flows onto West Plum Street. There
are no other drainage facilities available to accept run-off from the site.
The current City policies require that the difference between the historic rate of
run-off and the developed rate of run-off be detained onsite. The release rate is to
be no greater than the 2 Year Storm historic rate.
The City's policies normally require that the adjacent street flows be incorporated
with the onsite detention requirements. This policy applies most efficiently when
the street construction and onsite detention are performed concurrently. In this
instance, it is not physically feasible to combine the two flows since the flow
generated on the streets can not be intercepted and directed into an on -site
detention facility and then routed back into the curb and gutter. The area within
the southerly half of the Plum Street right-of-way has been considered as tributary
to the detention facility for sizing purposes.
There are long term plans for improvements to be made within the Importation
Canal Drainage Basin. These improvements could provide facilities that would
eliminate the need to provide onsite detention for the proposed development.
Therefore, the onsite detention facility may be considered to be temporary and may
be better utilized for open space purposes when its function as a drainage facility
is no longer necessary. L
2
EROSION CONTROL MEASURES
Erosion control considerations are based upon the short term activities that occur
during construction and the long term measures that are to be placed for the life
of the facility. The long term erosion control measures are the proposed methods
and materials to be used to provide surface treatments for the driveways, parking
areas, walkways and the landscaped open areas. Landscape materials and
plantings in the open areas will provide a combination of ground covers to deter
erosion.
The anticipated construction schedule should have the site grading completed,
within one (1) month after commencing construction. The schedule for
construction activities is anticipated to be: September 15 - September 20, perform
site grading; September 23: - October 5 install water and sewer lines; October 7 -
October 15 construct curb,'gutter and sidewalks and drainage related facilities;
October 21 - October 24 place pavement; October 15 - October 25 install
landscaping. The recommended short term erosion control methods to be
incorporated with the construction activities consist of the following: upon
completion of grading operations and at the time that the drainage outlet is
installed a "Straw Bale Filter" is to be placed at the inlet; and a "Silt Fence is to
be placed along the northern boundary of the site in order to control and contain
mud and debris onsite.
Wind erosion measures are to consist of water application and roughening of
exposed surfaces.
3
CONCLUSIONS AND RECOMMENDATIONS
1. The proposed development will retain the "historic" drainage patterns.
2. The site is located in the IMPORTATION CANAL DRAINAGE BASIN. The
site is not located within a defined floodway or flood plain.
3. All development is to be performed in accordance with City of Fort Collins
criteria. A variance to the City's policies is requested from detention of
adjacent street flows due to physical impracticality.
4. Onsite detention of storm water is required by the City of Fort Collins. The
volume of run-off to be detained is estimated to be 10,836 cu. ft. The detention
volume has been determined based upon the calculated volume of run-off
generated by a 100 Year Storm. The entire site, one-half of the adjacent W.
Plum Street, and the adjacent rear yards at the West side of the site have
been considered as the tributary area to determine the volume of the
detention pond. The calculated volume generated from the tributary area
is to be released at a controlled rate determined by the sum of the `historic'
rate of run-off from the site for a 2 Year Storm plus the rate of run-off for the
rear yards of the area to the West of the site. The calculated release rate is
1.92 c.f.s.
5. The City of Fort Collins Standards for temporary erosion control measures
are to be incorporated with the construction activities. Specifically, the
following are to be incorporated in the site construction activities:
a. A "Silt Fence" is to be placed along the northerly border of the site.
b. "Straw Bale Filters" are to be placed at the the inlet end of the outfall
pipe until inlet structures are in place.
c. Water application is to be made to prevent dust during the site
development phase of the project.
d. Roughening of the exposed earth surfaces shall take place during the
site development phase of the project.
9
STORM WATER DETENTION SUMMARY
SITE DRAINS TO "IMPORTATION CANAL" DRAINAGE BASIN
GROSS SITE AREA (includes 1/2 of W. Plum Street) = 144,935 Sq. Ft. = 3.31 Ac. ±
NET SITE AREA = 132,858 Sq.Ft. = 3.05 Ac. ±
HISTORIC "C" = 0.20
DEVELOPED "C" = 0.45
HISTORIC "Q2" = 1.39 c.f.s.
CRITERIA BASED DETENTION VOLUME = 10,836 Cu.Ft. ±
PLAN DETENTION VOLUME = 10,937 Cu.Ft.
MAXIMUM DEPTH OF DETAINED WATER = 2.25 Ft. Q Elevation 5097.50
PEAK DISCHARGE FROM DETENTION, Q = "HISTORIC" Q2 + QOFFSITE
= 1.92 c.£s. ±
RUN-OFF SUMMARY
Basin
Area
`C'
—Ql_
Oloo
(Acres)
(c.f.s.)
(c.f.s.)
A
0.80
0.45
0.67
1.92
B
0.56
0.45
0.53
1.51
C
0.40
0.45
0.38
1.08
1
0.56
0.45
0.63
3.75
2
2.75
0.45
3.09
8.97
' Engineering
Mr. Basil Hamdan
Stormwater Utility
' City of Fort Collins
235 Mathews
P. O. Box 580
Fort Collins, Colorado 80522 - 0580
Re: West Plum Street - P.U.D., Fort Collins, Colorado
Dear Mr. Hamdan,
May 16, 1996
Project No. PLA-195-96
The estimated cost for erosion control devices for the subject site has been
' estimated to be:
1. Silt Fence 4751.f. @ $2.50/ft. _ $1,187.50
2. Straw Bale Filter 2 Each @ $75.00/Ea. $150.00
Total $1,337.50
Cost @ 150% = 1.5_x $1,337.50 = $2,006.25
' The cost to re -seed the 132,850 square foot site at $0.0298/sq.ft. _ $3,959.17
150% of the re -seeding cost = 1.5 x $3,959.17 = $5,938.75
Therefore, the subject project's estimated erosion control security amount is
determined to be $5,938.75. This amount is to be included as surety for the erosion
control guarantee along with any other surety requirements that may be a part of
the City's "Developer's Agreement" requirements.
If you should have any questions or desire additional information, please feel free
to contact this office.
Submitted,
ngineering Associates
Dennis R. Messner, P.E.
cc: Mr. Doug Viita, Viita Building Company
Civil and Environmental Engineering Consultants
150 E. 29th Street, Suite 225 Loveland, Colorado 80538 Telephone: (970) 663-2221
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for
WEST PLUM STREET - P.U.D.
to be located in the North Half of Section 16, Township 7 North,
Range 69 West of the 6th PJL in the City of Fort Collins,
T arimer County, Colorado
I
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Conc. Pt. "A" Conc. Pt. "B"
(Offsite Run-off to W. Plum St.) (Combined Offsite & Onsite Run-off on W. Plum St.)
Area = 0.8 Acres ± Area=Offsite[0.8+0.6+0.4]+Onsite[3.3]=5.1 Acres ±
02 = 0.7 c.f.s. ± 02 = 3.3 c.f.s. ±
0100 = 1.9 c.f.s.+ 0100 = 10.7 c.f.s.±
� �c1J�C(��[Ja��fiIO��(u
DRAINAGE INVESTIGATION CALCULATIONS
Client: VIITA BUILDING COMPANY Project No: PLA-195-96
Project: WEST PLUM STREET - P.U.D. Date: 14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO By: D.R.M.
Rev. 6/28/96
This investigation is being performed to determine the required detention volume, discharge rates, channel
and structure sizing for the subject project site.
The site is located in the "Importation Canal' Drainage Basin.
RATIONAL METHOD Runoff Coefficients, "C
Larimer County Storm -Water Management Manual
Land Use Description
"C
Building/Roofs
0.95
Drives and Walks
0.95
Gravel Surfaced
0.50
Undeveloped n Areas
0.20
Grassed Landscaped Areas
0.15
RATIONAL METHOD
Frequency Adjustment Factors
Storm Return
Period ears
Freq. Factor
"Cr,
2
1.00
5
1.00
10
1.00
100
1.25
EXISTING CONDITIONS: (Note that only the northern 3 ± acres of the site is considered in this investigation.)
Building/Roof
Street, Drives and Walks
Gravel Surfaced Landscape
Undeveloped Open Areas
Landscaped Areas
Area=
0
Sq.Ft.
Area=
0
Sq.Ft.
Area=
0
Sq.Ft.
Area=
144,395
Sq.Ft.
Area= 0 1 Sq.Ft.
TOTAL SITE AREA Area= 144,395 Sq.Ft.
Avg. C2 = ([(0.90 x 8,845)+(0.20 x 135,550)] + 144,395) x 1.00
Avg. C2 = 0.20
Avg. C5 = ([(0.90 x 8,845)+(0.20 x 135,550)] + 144,395) x 1.00
Avg. C5 = 0.20
Avg. C10 = ([(0.90 x 8,845)+(0.20 x 135,550)] + 144,395) x 1.00
Avg. C10 = 0.20
Avg. C100 = ([(0.90 x 8,845)+(0.20 x 135,550)] + 144,3951 X 1.25
Avg. C100 = 0.25
(Existing W. Plum St.)
3.31 Acres
Page 1 of 7
DRAINAGE INVESTIGATION CALCULATIONS
' Client: VIITA BUILDING COMPANY
Project No:
PLA-195-96
Project: WEST PLUM STREET - P.U.D.
Date:
14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO
By:
D.R.M.
'
Rev. 8/9/96
EXISTING CONDITIONS: (cons.)
Time of Concentration
Consider sheet flow across site from South to North
' L = 420 ft. Elev. Diff. 5106 - 5096 =
10.00
ft.
Slope, S = 2.38 %
'
T = 1.87(1.1-CCf)4L+(SAl/3)=1.87(1.1-(0.25x1.00))4143+( 2.38A1/3) =
25.84
Minutes
' Since surrounding area is developed consider for 'urbanized' condition as a check
Tc = L / I80 + 10 for 'urbanized' condition with longest flow path
considered
' Length, L = 600 ft. Tc = 600 / 180 + 10 =
13.33
minutes
Average of the two methods = (24.41 + 13.33) / 2 =
19.59
minutes
' USE Tc = 15 minutes since area is mostly developed
' Rainfall Intensifies based upon 15 minute Time of Concentration:
I2 = 2.10 in./hr. I5 =
3.00
in./hr.
' I10 = 3.70 in./hr. I100 =
6.00
in./hr.
Determine Run-off from Site under present conditions:
Q = CIACf
Q2 = 0.20 x 2.10 x 3.31 x 1.00 =
1.39
c.f.s.
' Q5 = 0.20 x 3.00 x 3.31 x 1.00 =
1.99
c.f.s.
Q10 = 0.20 x 3.70 x 3.31 x 1.00 =
2.45
c.f.s.
' Q100 = 0.20 x 6.00 x 3.31 x 1.25 =
4.97
c.f.s.
' Offsite Run-off @ Existing Conditions:
Area "B": Consider the run-off generated from the rear lot areas of the single-family residential lots
immediately West of the Site.
' Area = 65 x 375 + 43,560 =
0.56
Acres
Time of Concentration = 15 minutes from previous calculations.
' "C" = 0.45 from Table 3-2
Page 2 of 7
DRAINAGE INVESTIGATION CALCULATIONS
' Client:
VIITA BUILDING COMPANY
Project No:
PLA-195-96
Project:
WEST PLUM STREET - P.U.D.
Date:
14-Mar-96
Location:
N 1/2 16 - 7 - 69, City of Fort -Collins, Larimer County, CO
By:
D.R.M.
'
Rev. 8/9/96
EXISTING CONDITIONS: (cons.)
' Area "B":
Q = CIACf Q2 = 0.45 x 2.10 x 0.56 x 1.00 =
0.53
c.f.s.
Q5 = 0.45 x 3.00 x 0.56 x 1.00 =
0.76
c.f.s.
'
Q10 = 0.45 x 3.70 x 0.56 x 1.00 =
0.93
c.f.s.
Q 100 = 0.45 x 6.00 x 0.56 x 1.25 =
1.51
c.f.s.
'
Area "C":
Consider the run-off generated from the rear lot areas of the single-family residential
lots
immediately East of the Site.
'
Area = 50 x 350 + 43,560 =
0.40
Acres
Time of Concentration = 15 minutes from previous calculations.
' "C" =
0.45 from Table 4.2.6-1
Area "C":
Q = CIACf Q2 = 0.45 x 2.10 x 0.40 x 1.00 =
0.38
c.f.s.
'
Q5 = 0.45 x 3.00 x 0.40 x 1.00 =
0.54
c.f.s.
'
Q10 = 0.45 x 3.70 x 0.40 x 1.00 =
0.67
c.f.s.
Q 100 = 0.45 x 6.00 x 0.40 x 1.25 =
1.08
c.f.s.
' Area "A":
Consider the run-off generated on the developed area to the West
that drains onto
Plum Street
from Rocky Road.
' Time of Concentration = L / 180 + 10 Tc = (550 / 180) + 10 =
13.06
Minutes
Length, L =
550 feet Therefore consider Tc = 15 minutes
Area = [(425 x 75) + (50 x 60)] / 43,560 =
0.80
Acres
' Therefore the gutter flow from the West
Area "A":
Q = CIACf Q2 = 0.45 x 2.10 x 0.80 x 1.00 =
0.67
c.f.s.
Q5 = 0.45 x 3.00 x 0.80 x 1.00 =
0.96
c.f.s.
Q10 = 0.45 x 3.70 x 0.80 x 1.00 =
1.18
c.f.s.
'
Q100 = 0.45 x 6.00 x 0.80 x 1.25 =
1.92
c.f.s.
Page 3 of 7
I
DRAINAGE INVESTIGATION CALCULATIONS
1
1
1
Client: VIITA BUILDING COMPANY
Project No:
PLA-195-96
Project: WEST PLUM
STREET - P.U.D.
Date:
14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO
By:
D.R.M.
Rev. 8/9/96
PROPOSED CONDITIONS:
Building/Roof
Area=
18,600
Sq.Ft.
Drives and Walks
Area=
36,400
Sq.Ft.
Gravel Surfaced Landscape
Area=
0
Sq.Ft.
Undeveloped Open Areas
Area=
0
Sq.Ft.
Landscaped Areas
Area=
89,395
Sq.Ft.
TOTAL SITE AREA
Area=
144,395
Sq.Ft. =
3.31
Acres
Avg. C = [(0.95 x 18,600)+(0.95 x 36,400)+(0.50 x 0)+(0.35
x 0)+(0.20 x 89,395)]
+ 144395
Avg. "C" =
0.45
Flow path through back yard swales from Lots 6 to 2 and then in concrete pan to detention pond,
therefore, Tc = 10 minutes
I2 = 2.50 in./hr. I5 = 3.65 in./hr.
110 = 4.45 in./hr. I100 = 7.25 in./hr.
Determine Peak Rate of Run-off at Proposed Condition:
Area #1 - Area that is to flow undetained onto W. Plum street: Area #1 =
0.56
acres
Q2 = 0.45 x 2.50 x 0.56 x 1.00 =
0.63
c.f.s.
Q5 = 0.45 x 3.65 x 0.56 x 1.00 =
0.92
c.f.s.
Q10 = 0.45 x 4.45 x 0.56 x 1.00 =
1.12
c.f.s.
Q100 = 0.45 x 7.25 x 0.56 x 1.25 =
1.83
c.f.s.
Area #2 - Area onsite that drains to the proposed detention pond: Area #2 =
2.75
acres
Q2 = 0.45 x 2.50 x 2.75 x 1.00 =
3.09
c.f.s.
Q5 = 0.45 x 3.65 x 2.75 x 1.00 =
4.52
c.f.s.
Q10 = 0.45 x 4.45 x 2.75 x 1.00 =
5.51
c.f.s.
Q100 = 0.45 x 7.25 x 2.75 x 1.25 =
8.97
c.f.s.
Page 4 of 7
DRAINAGE INVESTIGATION CALCULATIONS
Client: VIITA BUILDING COMPANY Project No:
PLA-195-96
Project: WEST PLUM STREET - P.U.D.
Date:
14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO
By:
D.R.M.
Rev. 8/9/96
DETENTION VOLUME CALCULATION FOR PROPOSED SITE CONDITIONS
QRelease = Q2 (Exist. Conditions) + Q Offsite thru Det. Pond = 1.39 + 0.53 =
1.92
c.f.s.
At Q100 Proposed = CIACf = 0.45 x I x 3.31 x 1.25 =
1.86
x I (in./hr.)
Time
min.
Rainfall Int., I
in./hr.
Q100 Prop.
c.f.s.)
Vol. @ Q100
(cuft)
Q Rel. @ 2 Yr.
(c.f.s.
Vol. Rel.
cuff[
Vol. Diff.
cu.ft.
10
7.10
13.21
7,926
1.92
1,152
6,774
15
6.00
11.16
10,044
1.92
1,728
8,316
20
5.15
9.58
11,496
1.92
2,304
9,192
25
4.55
8.46
12,690
1.92
2,880
9,810
30
4.10
7.63
13,734
1.92
3,456
10,278
40
3.45
6.42
15 408
1.92
4,608
10,800
50
2.95
5.49
16 470
1.92
5.760
10,710
60
2.65
4.93
17 748
1.92
6,912
10,836
70
2.35
4.37
18,354
1.92
8,064
10,290
80
2.15
4.00
19,200
1.92
9,216
9,984
90
1.95
3.63
19,602
1.92
10,368
9,234
100
1.75
3.26
19,560
1.92
11,520
8,040
110
1.60
2.98
19,668
1.92
12 672
6,996
120
1.45
2.70
19,440
1.92
13 824
5,616
' Therefore, a minimum of 10,836 cu. ft. of Detention Storage Volume is desired for the site.
' DETERMINE POND SIZE:
High Water Surface Area, At (175 x 40) = 7,000 sq.ft.
' Pond Bottom Surface Area, Ab (150 x 20) = 3,000 sq.ft.
Max Depth, It = 2.25 ft.
' - Vol. = 1/3 ( Ab + At + 4AbAt) h = 10,937 cu.ft.
10,937 = 10,836 Therefore, OK
' Provide minimum of 1.0 ft. freeboard or additional 33% of total volume for safety factor.
' Elevation of Low Point = 5095.25
Design Top of Berm Elev. w/ 1.0' freeboard = 5095.25 + 2.25 + 1.0 = 5098.50
' To attain 33% of total volume an additional depth of approximately 1.0' would be required.
Therefore, maintain 1.0' freeboard.
Page 5 of 7
' DRAINAGE INVESTIGATION CALCULATIONS
' Client: VIITA BUILDING COMPANY
Project No:
PLA-195-96
Project: WEST PLUM STREET - P.U.D.
Date:
14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO
By.
D.R.M.
Rev. 8/9/96
DETENTION OUTLET CALCULATION FOR PROPOSED SITE CONDITIONS
Determine sizes to provide control at the outlet from the Detention Pond.
Determine Orifice Opening Area for Discharge at Q2:
' Orifice Equation: Q = CA 42gh h = Depth - 0.5' =
1.75
ft.
Q Release = 1.92 c.f.s. C =
0.65
'
A = Q / (C42gh) = 1.92 / [0.65 4(2 x 32.2 x 1.75] =
0.28
sq ft.
tWith Round Opening A = 7rrA2 Radius, R = JA/n = J 0.28/7r =
0.30
ft.
Radius, R = ft. x 12 in./ft. =
3.60
in.
With Square Opening A = wA2 Width of Opening, W = qA = 40.28 =
0.53
ft.
Width of Opening, W = ft. x 12 in./ft. =
6.36
in.
' Use 7-1/4" dia. Round Opening or 6-3/8" Square Opening for
outlet control
device.
CHECK FLOW DEPTH IN PLUM STREET
'
Q2 = 0.63 + 0.38 + 0.67 + 1.74 =
3.42
c.f.s.
' Q100 = 1.83 + 1.08 + 1.92 + 1.74 =
6.16
c.f.s.
Theoretical Street Capacity, Q = 0.56 Z/n CIS yA8/3
' n =
0.016
Z = 1 / Cross Slope = 1/0.02 =
50
' S = Gutter Slope = 1.2 % =
0.012
ft. / ft.
At Depth of Flow, y Minor Storm Allowable Depth, y = 6" =
0.5
ft.
' Q = 0.56 x (50 / 0.016) x 40.012 x 0.5A8/3 =
30.19
c.f.s.
Reduction Factor=
0.80
'
Design Capacity = Theoretical Capacity x Reduction Factor = 30.19 x 0.80 = 1
24.15
c.f.s.
' 24.15 >> 6.16 Therefore, the existing street's Design Capacity
greatly exceeds
estimated flow for either the Minor or Major Storms.
Page 6 of 7
DRAINAGE INVESTIGATION CALCULATIONS
' Client: VIITA BUILDING COMPANY
Project No:
PLA-195-96
Project: WEST PLUM STREET - P.U.D.
Date:
14-Mar-96
Location: N 1/2 16 - 7 - 69, City of Fort Collins, Larimer County, CO
By:
D.R.M.
'
Rev. 8/9/96
CROSS PAN CAPACITY AT PEAR STREET
' At 3" Flow Depth Pan Slope, S =
0.007
ft./ft.
Pan Area, A =
3.06
sq. ft.
' Wetted Perimeter, Wp =
24.5
ft.
R = A / Wp = 3.06 / 24.5 =
0.125
ft.
' n =
0.016
' Q=1.486/n A RA2/3 SA1/2 = 1.486x3.06x(0.125)A2/3x(0.007)Al/2/0.016=
5.94
c.f.s.
Flow over Cross -Pan from West side of Pear Street
' Q100 + Q Offsite = (0.45 x 7.25 x 1.0 x 1.25) + 1.83 =
5.91
c.f.s.
5.94 = 5.91 Therefore depth of flow at 3" - OK
' Determine Flow depth at Drainage Swale along rear lot -lines of Lots 11, 12 & 13
' At 6 Flow Depth Swale Slope, S =
0.01
ft./ft.
"V" shaped Swale 10 ft. wide by 6 in. Deep Swale Area, A =
5
sq. ft.
' Wetted Perimeter, Wp =
10.05
ft.
R=A/Wp=2.5/10.05=
0.50
ft.
' n =
0.025
Q=1.486/n A RA2/3 SA1/2 = 1.486x2.5x(0.25)A2/3x(0.01)Al/2/0.025=
18.72
c.f.s.
'
Flow over Cross -Pan from West side of Pear Street
' Q100 + Q Offsite = (0.45 x 7.25 x 1.0 x 1.25) + 1.83 =
5.91
c.f.s.
Q x 1.33 = 5.91 x 1.33 =
7.86
c.f.s.
18.72 >> 7.86 Therefore depth of flow less than 6" - OK
1
Page 7 of 7
RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: West Plum Street - P.U.D. STANDARD FORM A
COMPLETED BY: Messner Engineering Associates DATE: 3-14-96
DEVELOPED
ERODIBILITY
Asb
Lsb
Ssb
Lb
Sb
PS
SUBBA�IN
ZONE
(ac)
(ft)
($)
(feet)
($)
($)
Entire
Moderate
3.05
525
1.9%
79.6
Site
MARCH 1991 8-14 DESIGN CRITERIA
EFFECTIVENESS CALCULATIONS
PROJECT: West Plum Street - P.U.D. STANDARD FORM B
COMPLETED BY: Messner Engineering Associates DATE: 3-14-96
Erosion Control C-Factor P-Factor
Method Value Value Comment
Bare Soil 1.00 1.00
Road/Walks 0.01 1.00
Silt Barrier 1.00 0.50
Sediment Trap 1.00 0.50
Gravel Filter 1.00 0.80
MAJOR
PS
SUB
AREA
BASIN
($)
BASIN
(Ac)
CALCULATIONS
Entire
79.6
3,:05
3.05
Bare Soil = 2.05 ac.
Site
Road/Walk = 1.0 ac.
wtd 'C' _ (1.0 x 2.05) + (0.01 x 1.00) / 3.05
= 0.68
wtd 'P' = 0.5 x 0.5 x 0.8
= 0.2
EFF. _ (1 - (0.68 x 0.2)) x 100
= 86.4,-- 79.6
OK
MARCH 1991
1
8-15
DESIGN CRITERIA
CONSTRUCTION SEQUENCE
' PROJECT:
West
Plum
Street
- P.U.D.
5EOUENCE.
FOR
19 96
ONLY
COMPLETED BY: Messner Engineering Assoc.DATE
STANDARD FORM C
3-14-96
' 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 1 -1996
MONTH I JANIFEB ! MARIAPR MAY IJUNEIJULYIAUG ISEP IOCT INOV IDEC
'
----------------------------
1----------------------------------------------------------� OVERLOT GRADING xx
'WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier.
Additional Barriers
'Vegetative Methods
Soil Sealant
Other(Water Application)
' 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
t Mulching/Sealant
Temporary Seed Planting
Sod Installation
' Nettings/Mats/Blankets
Other
' STRUCTURES: INSTALLED BY
' VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
HOI/SF-C:1989
MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS ON
xxx
XXXX
xxxx
xxxxxxxx
xxx
xxx
FOR,
aaairz '�� •1 TO SON 2
L I PLAT Rigooy Mal
�roRE W
( THE PROAR OF 7a PRE
mill rux ww"
_SmiI ON) le -I oA u I FORT
uu 5. IL rS• 4. - ESs'
ORIFICE PLATE DETAIL
-- 7xoi=ro=srn '
_T
I 55
f7771
J'=e % J
w , . P�'l LT �"imu ro zTAa
${� $
Ic.`a R-
PIPE
'Ire4rL19;51".�aIT T
rcw.urc� •_•
SECTION AT DETENTION POND OUTLET
--NOf ro srA,E - - --
I.
IF y
�1wE1 - j[fi 4N 24
rmwaRNORICTURE Wol M ORMA. x PAY
INLET STRUCTURE DETAIL_
OR
-FILTERaL FASSID
WOOD TOST
-RACKLUED TRENCH
Ehr_
FARES
gP OR R SE J,F
oOD POST To POST
E RE Plum
TFRE] W CON J 3tr
offRUNOFFE
far OF FTNI
R
eas
iCalOry vEw
DR GMG fRTERNG velSaRE
SILT FENCE DETAIL
- o0T
-0 SCAE
L12._.
_.
rr„
F � Mal sic £on'"E a !Y
ImmroiIDEEvo7�=01,
MRm�+Arz,
Is NMAffro A= { rax OR m mi ASS 3ErnaM A-6
T� WAY°Y7MMOM Wwumc.
£2EA INLET FILTER STRAW BALES
A NOT TO SCALE
F'11ne r 1 1 It
e a eMx e�
HPo Al MOM SLCPES To Se 441
m we wne .wo emrzR.`
SECTION_A-A. AT DETENTION POND
NOT TO SfAL1- - -`
I
I
I -
Propbsed Slit Fence
5100_47-
_ 1�
if ro
Mal
•2Zf '
-'
ALL
aer swra TO % It
SECTION B-8 AT DETENTION POND
f'ore3eae
OVERFLOW SECTION
1NOTT6-9511
a
-g-
a�nO'w�ic tii: Ir -
i,p5
SECTION C C
(A4woN PmPa,llu=1
Exii Gmund an tolia"i
USER Gmrxary Safes To and
one Pmwny G(mRM y
Dle Pam L. I'M al
IT
lIV
Rsrudune r�
20%Mu. I,J
1s so
0 30 9a
1" = 3G-
Contour Interval 1'
Cur - propgeed Silt Fence _�
Sid Ik _ ----
s
PropOaed Sidewalk Culvert
Overflow -,Proposed 12"0
_-=j� S: N-12 Pipe Outlet
%A' OOW D.D
�fi - J
T.O.F.Elev.= /
5102 5
/
I1 0 1.00 Ele'v. TQF: Nav
=B' 4 1 5.7 1 51005
I
v- Ile
13 12 L�
"OF P posed Sidewalk r
61027 - I�
Cu erl (Safe Dethil Sheet'&) C
- -
z r --em�l ,r{, + �'� Detention
2,4 c 0 I' �� ' +� ate_ ss. - sa.9 C 7. Area
2' Wide IT
HS Elev.-
Proposed.r
a a 0 Concrete Pan
% E.O.F. Elev.- - _ '10 ti10.7 I I,
51030 _ MID
+ 5a95-.
2.6� L05i �' * 02 - -- �� 1
a o.'. Eev A-
_ l 51027 - DOIL-
5104.0 r' �
3.3 .. _
3.0 21
\ 8
i Ij s
t
-
T.O.F. v. I li� \ TA cep= 5105.2,
5105.2 L1 i 5 045 -
a.37 5 a�`O 5D
♦ 3 4.5
t_.-3to5r_ 4�j_*tl ITO F. Elev.-
5105.7
T.O_F_
5105 _ 5106.7
e
1 Fall 7`6_
�
SLOE 72 60 ®b - .a--- -�.
NOTE: SITE GRADING OPERATIONS RHALL BE RESTRICTED TO THE
IN PLUM STREET - P.UDP LIMITS. J,10 GRADING -OPERATIONS SHALL
4) x'` OCCUR ON THE PROPERTIES TO THE WEST OR EAST OFTHE,SITE.-
j
Oct
_Inlet Str)Contro:
Orifice
Release (SEE DETAIL
A^
yo
/ IeR'
y0
Proposed I
-Sdt °-ence
O13-, i I
STORK WATER DETENTION SUMMARY
SITE DRNNS TO
7MPORTATON CANAL'
DRAINAGE BASIN
GROSS SITE AREA (Including 1/2 of
adjacent
W. Plum
9L)-I44.935 III
-3.31 Acrn!
NET SITE AREA
- 132.1555 Sa R. -
3.05 Acreei
HISTORIC 'C -
020
DEVELOPED 'C'
- aeE5
,
HISTORIC O2 1.39 c 1 e.
CRITERIA BASED
DETENTION VOLUME
- 10,836
cu.N.!
PUN DETENTION
VOLUME - 10937
cu.l
MAXIMUM DEPTH
OF DUNNED WATER - 2.0
FILL e Devotion 5097.50
PEN( DISCHARGE FROM DETENTION,
0 HISTORIC' 02
+ oaR919
- 1.92
cI
RUN-OFFSUMMARY
B6�tl
(Acres)
yy22.�,,
(c.l.0.)
c.f.e.
A
0.80 0.0
0.67
1.92
B
0.54 0.465
D M
1.51
C
01 0A5
0.3e
1.05
1
0.50 OA5
0.63
1.75
2
2.75 0.0
3.09
&97
City
of Fort Conine, Colorado
UTILITY
PLAN APPROVAL
APPROVED.
f _.
ON -
ra/
�9
CHECKED
BY
l�yt
Vote3G
" W-
r t t r-7Cli I'ty
CHECKED
BY
role.y
CHECKED
BY.
Ts003 TiRecreotion'- --
-- "
CHECKED
BY
-
CHECKED
BY
CONIRRUCTON SEQUENI
PROJEU YI E.U=Eii. _Rua c
SMENCE MR 19% ONLY ea OF s,�.ecsae. EMIL ua_re.
•GT E
E_� rr'N,.NJI
-
-
Typically Indicates Existing
Ground Surface Contour
1
I
.�1ar/
Tyyp call Indicates Proposed
- 5101
Fmsh Surface Contour
Typically Indicates Proposed Gurb,
Gutter & Sidewalk
- Tr'
Typically Indicates Existing Cufb,
Gutter & Sidewalk
10
x---x--
Typically Indicates 'Silt Fence'
t
(
Typically Indicates Drainage
Flow Direction
Typically Indicates Drainage
Basin Limit
Typically Indicates Concentrrat.On
. OAF er0�
Paint Identifier -
SCALE:
DRAWN
CHKD
Project No.
PLA I95-96
SHEET
3 of '3
e-; .596