HomeMy WebLinkAboutDrainage Reports - 10/16/1997DRAINAGE IIWESTIGATION
I 1
A PROPOSED'AAMCO' TRANSMSSION SHOP
TO BE LOCATED ON
LOT 1% CREGER PLAZA SECOND REPLAT
FORT COUPrN COLORADO
Prepared for
Cottier Construction, Inc.
P. O. Bog 1051
Fort Collin., Colorado, 80522
June 1994
(Revised July 1994)
Project No. PLA 140.94
PREPARED BY.
MESSNER Engineering associates
150 East 29th Street, Suite 225 Loveland, Cobrado 80538 ' . Telephone: (303) 663-2221
Civil and Environmental Engineering Consultants
Project No. PIA-140-94
June 3,1994
Revised July 12,1994
Mr. Pete Cottier
Cottier Construction, Inc.
P.O. Bog 1051
Fort Collins, Colorado 80522
Dear Mr. Cottier,
The enclosed report represents the results of the drainage investigation for the
proposed "AAMCO Transmission" facility to be located on Lot 10 of the Creger Plaza -
2nd Replat in the City of Fort Collins, Larimer County, Colorado. The report and the
related grading and drainage plan have been revised to comply with the City of Fort
Collins' Stormwater Utility's staff review comments.
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.
We sincerely appreciate the opportunity to be of service to you. If you should have any
questions, please feel free to contact this office.
Respectfully Submitted,
cee zti
Dennis R. Messner, P.E.
MESSNER Engineering Associates
DRWmkm
lly-V
Enclosures
Civil and Environmental Engineering Consultants
150 E. 29th Street, Suite 225 Loveland, Colorado 80538 Telephone: (303) 663-2221
-W*)-AXQ ZMYZM_ .
Letter of Transmittal
Table of Contents
Scope
Site Description
Existing Conditions
Proposed Development
Erosion Control Measures
Conclusions and Recommendations
n
1
2
2
3
Vicinity Map
Existing Conditions Exhibit
Proposed Conditions Exhibit
Calculations
Drainage Summary
n
The following report represents the results of a drainage investigation for a proposed
"AAMCO" transmission repair shop to be located on a parcel of land situated in the
Northeast Quarter of Section 35, Township 7 North, Range 69 West of the Sixth P.M.,
Larimer County, Colorado. The site description is: Lot 10 of Creger Plaza Second Replat
in the City of Fort Collins. The investigation was performed for the project contractor,
Cottier Construction, Inc. 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 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 site development 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.
The site is rectangular and contains approximately 0.73 acres, including the adjacent
South Mason Street right-of-way. The site's East-West dimension, including the westerly
half of the Mason Street right-of-way, is approximately 320 feet and its North -South
dimension is 100 feet. The site abuts the easterly right-of-way of the Burlington Northern
Railroad and the westerly right-of-way of South Mason Street. The site is located on the
drainage basin boundary between the FOOTHILLS BASIN and the MAIL CREEK
BASIN. Surface run-off from the site will flow southerly along South Mason Street and
therefore the site is considered to be in the MAIL CREEK BASIN.
The site is presently vacant. The ground surface has been roughly graded and native
vegetation is sparse to moderate across the site. The site has been used to dispose of
excess excavated material from the nearby construction sites. Due to the dumping of
material on the site, a ridge has been created in the middle of the lot. Run-off on the west
side of the ridge flows toward the southwest to a drainage course that is situated along
the Burlington Northern Railroad. The run-off that is generated on the east side of the
ridge flows toward the southeast and into a depression located at the west side of South
Mason Street. The "historic" direction that the site slopes is from Northwest to Southeast.
The slopes range in rates varying from 0.5% to 5%. The site does receive a minor amount
of run-off from the property to the North. The run-off from the north will be retained on
the adjacent site after the development of the site has been completed. The run-off
generated on the adjacent railroad right-of-way flows southerly along the railroad
right-of-way. The existing curb and gutter along the west side of Mason Street is
constructed with a grade break located at the center of the common driveway for Lots 10
and 11. The flow in the gutter to the north of this point is northerly toward Horsetooth
Road. The flow in the gutter to the south of this point is southerly toward an existing
storm drain inlet. The run-off which is directed southerly along the curb and gutter
ultimately flows into the Mail Creek Basin outfall system.
The proposed development of the site is to consist of constructing a commercial structure
to be located on the eastern third of the site. The structure is to contain a total building
"foot -print" of 5,060 square feet. A paved parking area is to be provided for 16 vehicles and
will be located between the structure and South Mason Street. Access to the site is to be
provided through a shared driveway to be located at the northeast corner of the site. The
proposed site plan indicates that the western portion of the site is to be used for the
storage of vehicles and to provide an emergency access. The western vehicle storage area
is to have a paved surface.
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. According to the City's Stormwater Utility staff the
site has previously been included in a Special Improvement District that established a
peak rate of discharge of 0.5 c.f.s. per acre as the controlling factor in determining the
size of detention facilities onsite.
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 developed concurrently. In this instance, it is not
physically feasible to combine the two flows since the flow generated on the street would
have to be intercepted and directed onto the site at its lowest point. Consideration is being
given to the volume of run-off that is generated within the street right-of-way by providing
the detention volume onsite for the adjacent portion of South Mason Street. It is intended
that this will reduce the net discharge to the area system.
Erosion control considerations have been made based upon the short term, activities
occurring during construction and the long term, measures considered through the life
of the facility. The long term measures incorporated to eliminate erosion are the
proposed methods and materials to be used to provide surface treatments for the
structure and associated driveways, parking areas, walkways and the landscaped open
areas. The landscape materials and plantings in the open areas will provide a
combination of living and inert ground covers to deter erosion.
The recommended short term erosion control methods to be incorporated with the
construction activities are: the placement of a "Gravel Filter' at the proposed inlet; and
placing a "Silt Fence" along the southern boundary of the site in order to control and
contain mud and debris onsite. The proposed construction site is exempt from providing
wind erosion measures since its area is less than one acre. The schedule for
construction activities is anticipated to be: August 15 - August 30, perform site grading
and access related construction; September 1- January 1, structure construction;
November 1- November 20, construct parking and drives, and install landscaping and
signage.
2
1. The proposed development will retain the "historic" drainage patterns.
2. The site is located in the MAIL CREEK 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 for detention of adjacent street flows due to
physical impracticality.
4. Onsite detention of stormwater is required by the City of Fort Collins. The volume of
run-off to be detained is estimated to be 5,519 cu. ft. The detention volume has been
determined based upon the calculated volume of run-off from a 100 Year Storm with
the site considered at the proposed conditions being released at a controlled rate of
0.37 c.f.s. The release rate of 0.37 c.f.s. has been based upon discharging the detained
flow at a maximum rate of 0.50 c.f.s. per acre of developed site.
5. The City of Fort Collins Standards for temporary erosion control measures are to be
incorporated with the construction activities.
3
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2 aHECNEO: D.R.Y
Area of Basin in Acres
Q.46 OC. Pmfec! No.
Q1Da-100 Year Runoff Rate PtA-140-94
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Client: Cottier Construction, Inc.
By. DRM
Project No. PLA-140-94
June 3, 1994
Revised July 12,1994
Calculations for Drainage Investigation for Lot 10 of Creger Plaza - 2nd Replat located
in the NE 114 of Section 35, Township 7 North, Range 69 West of the 6th P.M., City of Fort
Collins, Larimer County, Colorado
Total On -Site and Off -Site Areas = 0.843 t acres (including South Mason Street
right-of-way and BN Railroad Right-of-way)
The proposed development of the site is to consist of the construction of a commercial
structure together with the associated parking and access drives. The area of the site
excluding the railroad right-of-way is:
Net Site Area = 31,737 sq.ft. = 0.729 t acres
Rational "Coo Factor = 0.20 for Lawns and Landscaped Areas
to = 0.95 for Roofs, Decks, Patios, etc.
it it = 0.95 for Asphalt and Concrete Streets, Drives, and Parking
to of
to = 0.50 for Gravel Drive and Parking
it 11 = 0.20 for Unimproved and Open Areas
of to
" = 0.20 for Railroad Right -of -Way
"C"avg (Undeveloped) All area considered to be "Unimproved"
"C" avg = 0.20
Time of Concentration overland from grade break point onsite to Railroad swale:
Time of Concentration across undeveloped area Considered as:
Toverland =1.8 (1.1- C) qL + S^1/3
OS=2.8% L=90ft. C=0.20
T=1.8( 1.1-0.20)490f.2.8^1/3=10.9min.
Tswale = L(ft.) + [Vel. (ftlsec.) x 60 minJsec.] per Fig. 3-2
0 S = 1.5% & L = 110 ft. Vel. = 1.3 Wsec.
T=110+[1.3x601=1.4min.
Therefore, Tc =10.9 + 1.4 =12.3 min.
USE 10 minutes as Time of Concentration
12 010 min. = 2.50 inJhr.
Iwo 0 10min. a 7.25 Whr.
Page 1
Client: Cottier Construction, Inc.
By: DRM
Run-off,Q=CxIxARCif
Cf at 2 year Storm =1.0
Project No. PIA-140-94
June 3,1994
Revised July 12, 1994
Cf at 100 Year Storm =1.25
The "Western Area" contains approximately 0.36 acres onsite plus 0.13 acre
contributing from the adjacent BN Railroad r-o-w
Offsite Area ® Railroad
(Does not drain onto site)
Onsite Area "A"
(Drains onto Railroad)
Q2 = 0.20 x 2.50 x 0.13 x 1.00 = 0.07 c.£s.
Qioo = 0.20 x 7.25 x 0.13 x 1.25 = 0.24 c.£s.
Q2 = 0.20x2.50x0.36x1.00=0.18c.£s.
Qioo = 0.20 x 7.25 x 0.36 x 1.25 = 0.65 c.is.
The "Eastern Area" contains approximately 0.30 acres that drains toward Mason Street.
Onsite Area'B"
Q2 = 0.20x2.50x0.30x1.00=0.15c.£s.
Qioo = 0.20 x 7.25 x 0.30 x 1.25 = 0.54 cl.&
The proposed grading plan is designed to direct run-off to two (2) separate points of
concentration. The "Western Area - #1" is to concentrate at an inlet with an orifice
control plate that is to be located in the middle of the storage area on the west side of the
building. The "Eastern Area - #2" is to concentrate at an inlet that is to be located
approximately 50 feet west of the Southeast corner of the parking lot. The flow out of the
inlet will be restricted by an orifice plate. The run-off will flow from Inlet #1 to Inlet #2
and then be piped to the 18" RCP City storm drain located in Mason Street.
#1- West "C"avg: Lawns and Landscaped Areas
Roofs, Decks, Patios, etc.
Streets, Drives, and Parking
Gravel Drive and Parking
Unimproved and Open Area
Railroad Right -of -Way
Total Area
#2 - East "C"avg: Lawns and Landscaped Areas
Roofs, Decks, Patios, etc.
Streets, Drives, and Parking
Gravel Drive and Parking
Unimproved and Open Area
Railroad Right -of -Way
Total Area
0 sq.ft.f
0 sq.ft.f
= 7,720 sq.ftt
0 sq.ft.t
1,000 sq.fta
= 0 sa.ft.t
8,720 sq.ft.t "Cavg = 0.86
3,850 sq.ft.t
5,060 sq.ft.t
= 14,107 sq.ft.t (including Mason St.)
0 sq.ft.t
0 sq.ft.t
0 sg,ft.+
23,017 sq.fta lice 8vg = 0.82
Page 2
Client: Cottier Construction, Inc. Project No. PIA-140-94
By: DRM June 3, ..,
Revised July 12, ••,
RUN-OFF FROM _ Y Y AT PROPOSED • 11 _ • , _ WffHOUT DETENTION
11 • N
Consider that the Time of Concentration to remain as the undeveloped Tc.
USE 10 minutes as Time of Concentration
12 0 10 min. = 2.50 inJhr. Iioo 010 min. = 7.25 inJhr.
Western Area #1 Q2 = 0.86 x 2.50 x 0.20 x 1.00 = 0.43 c.£s.
Qioo =1.00 x 7.25 x 0.20 =1.45 c.fs. (CCf > 1.00 therefore, 1.00 used)
Eastern Area #2 Q2 = 0.82 x 2.50 x 0.53 x 1.00 =1.09 c.£s.
Qioo =1.00 x 7.25 x 0.53 = 3.84 c.£s. (CCf > 1.00 therefore, 1.00 used)
Determine Release Rate ,Q, at 0.50 c.f.s./acre:
Qrelease = 0.50 x 0.73 = 0.37 c.f.s. = Maximum rate of Total of flow released.
Western Area #1- Q released = 0.20 x 0.50 = 0.10 c.fs.
Eastern Area #2 - Q released = Total Site = 0.73 x 0.50 = 0.37 c.£s.
The calculations to determine the detention storage volumes for the two separate
detention areas are shown on the following pages.
Page 3
Client: Cottier Construction, Inc.
By: DRM
Proj. No.: PLA-140-94
Date: June 3,1994
Rev.July 12,1994
DETENTION VOLUME DETERMINATION FOR "RATIONAL METHOD"
Detention Volume determination for the Eastern portion of the site.
Time
(min.)
Q100 Prop.
(c.f.s.)
Vol. ® Q100
(cu.ft.)
Q dis. 0 2 Yr.
(c.f.s.)
Vol. dis.
(cu.ft.)
Vol. Diff.
(cu.ft.)
10
3.94
2,366
0.37
219
29147
15
3.28
2,952
0.37
329
2,624
20
2.86
3,427
0.37
438
2,989
25
2.54
3,807
0.37
548
3,260
30
2.30
4,139
0.37
657
3,482
40
1.96
4,692
0.37
876
3,816
50
1.69
5,070
0.37
1,095
3,975
60
1.48
5,321
0.37
1,314
41007
70
1.32
5,540
0.37
1,533
49,007
80
1.19
5,695
0.37
11752
3,943
90
1.08
5,835
0.37
1,971
3,864
100
1.00
6,006
0.37
29190
3,816
110
0.92
6,082
0.37
2,409
3,673
120
0.87
1 6,253
0.37
2,628
3,625
Q = CIACf
QRelease = 0.5 x Area = 0.5 x 0.73 = 0.37 c.f.s.
At Q100 Proposed =1.00 x I x 0.53 = 0.53 x I
Therefore, a minimum of 4,007 cu. ft. of Detention Storage Volume is desired for the
Eastern portion of the site that is to discharge to the existing storm drain.
Note that the Q inflow is considered for the area oonoentrating at the Eastern Inlet
but that the discharge rate is that determined for the entire site since the western
Area is being released at a controlled rate thru the Eastern Inlet.
Page 4
Client: Cottier Construction, Inc.
By: DRM
Proj. No.: PIA-140-94
Date: June 3,1994
Rev. July 12,1994
DETENTION VOLUME DETERMINATION FOR "RATIONAL METHOD"
Detention Volume determination for the Western portion of the site.
Time
(min.)
Q100 Prop.
(c.f.s.)
Vol. ® Q100
(cu.ft.)
Q dis. ® 2 Yr.
(c.f.s.)
Vol. dis.
(cu.ft.)
Vol. Diff.
(cu.ft.)
10
1.45
870
0.10
60
810
15
1.20
1,080
0.10
90
990
20
1.04
1,248
0.10
120
1,128
25
0.92
1,380
0.10
150
1,230
30
0.83
11494
0.10
180
1,314
40
0.70
1680
0.10
240
1440
50
0.60
1,800
0.10
300
1,500
60
0.52
1,872
0.10
360
1512
70
0.46
1,932
0.10
420
1,512
80
0.41
1,968
0.10
480
1,488
90
0.37
1,998
0.10
540
1,458
100
0.34
2 040
0.10
600
1440
110
0.31
2,046
0.10
660
1,386
120
0.29
1 2,088
1 0.10
1 720
1 1,368
Q = CIACf
QRelease = 0.5 x Area = 0.5 x 0.20 = 0.10 c.f.s.
At Q100 Proposed =1.00 x I x 0.20 =
0.20 x I
Therefore, a minimum of 1,512 cu. ft. of Detention Storage Volume is desired for the
Western portion of the site.
Page 5
Client: Cottier Construction, Inc. Proj. No.: PLA-140-94
By: DRM Date: June 3,1994
Rev. July 12,199z.
DETENTION VOLUME CHECK OF PROPOSED DETENTION IN PARKNG LOT
(EASTERN AREA #2)
Elevation
Area
( .Ft.)
Avg. Area
(S .Ft.)
Elevation Diff.
(Ft.)
Volume
(Cu.Ft.)
Sum of Volume
(Cu.Ft.)
(Outlet)
35.50
25
275
0.5
138
138
36.00
525
1,253
0.25
313
451
36.25
1,980
2 660
0.25
665
1,116
36.50
3,340
4,508
0.25
1,127
2,243
36.75
5,675
6,625
0.25
1,656
3,899
37.00
71575
3,899 - 4,007 Therefore, sufficient volume is available in the ponded parking lot area
at a depth of 1.5 feet with High Water Elevation ® 37.0
DETENTION VOLUME CHECK OF PROPOSED DETENTION IN PARKING LOT
(WESTERN AREA #1)
Elevation
Area
( .Ft.)
Avg. Area
(S .Ft.)
Elevation Diff.
(Ft.)
Volume
(Cu.Ft.)
Sum of Volume
(Cu.Ft.)
(Outlet)
35.75
50
440
0.25
110
110
36.00
830
1,720
0.25
430
540
36.25
2,610
3,930
0.25
983
11523
36.50
5,250
1,523 -1,512 Therefore, sufficient volume is available in the ponded storage area at a
depth of 0.75 feet with High Water Elevation ® 36.5
Page 6
Client: Cottier Construction, Inc.
By. DRM
Project No. PIA-140-94
June 3,1994
Revised July 12,1994
Calculations to determine orifice opening size to control the rate of outflow from the two
detention areas:
Orifice Equation, Q = CA42gh
A = Q + C42gh
At East Area #2
Q = 0.37 c.f.s. (See Page 3)
h = 37.0 - 33.9 = 3.1 ft.
Coefficient "C" = 0.65
g = 32.2 ftJsec.^2
A = 0.37 + [0.65 x A 2 x 32.2 x 3.1)] = 0.040sq. ft.
A=w*2 w=CIA
w = 40.040 = 0.2 ft. = 2.4 inches
Therefore, Use 2-3/8" x 2-3/8" as Maximum Orifice Opening
At West Area #1
Q = 0.10
h=36.5-34.75=1.75
A=0.10+[0.65x4(2x32.2x1.75)]=0.014
A=40.014 w = 0.12 ft. = 1.4 inches
Therefore, Use 1.3/8" x 1.3✓8" as Maximum Orifice Opening
A = n Rad.^2 Rad. = 4A/x = 40.014/x = 0.07 ft.
Rad. = 0.80 inches Diameter = 1-1/2 inches
Use 1-1/2" dia. pipe as orifice as alternate to square orifice plate.
Page 7
RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: Lot 10 Creger Plaza second Replat STANDARD FORM A
COMPLETED BY: Dennis Messner, Messner Engr. Assoc. DATE: June 3, 1994
DEVELOPED
ERODIBILI Y
Asb
Lsb
Ssb
Lb
Sb
PS
SUBBAgIN
ZONE
(ac)
(ft)
($)
(feet)
M
M
Moderate
0.66
150
2.25
79.5
MARCH 1991 8.14 DESIGN CRITERIA
EFFECTIVENESS CALCULATIONS
PROJECT: :__Lot .10 Creger Plaza Second Replat STANDARD FORM B
COMPLETED BY: Dennis Messner, Messner Engr. Assoc. DATE: June 3, 1994
Erosion Control C-Factor P-Factor
Method Value Value Cominent
Bare Soil 1.00 1.00 Graded Lot
Building Foundation 0.01 1.00
Silt Fence 1.00 0.50
Inlet filter 1.00 0.80
MAJOR
PS
SUB
AREA
BASIN
(t)
BASIN
(AC)
CALCULATIONS
79.5
0.66
Bare Soil = 0.54 ac. Building = 0.12 ac.
Wtd. "C" - Factor = [(0.54 x 1.00) + (0.12 x 0.01)
=0.82
Wtd. "P" -'Factor = 1.Oxl.OxO.5xO.8 = 0.40
Eff. _ [1 - (0.,82 x 0.40)] x 100 = 67.2 > 79.5 OK
MARCH 1991
8.15
DESIGN CRITERIA
CONSTRUCTION SEQUENCE
PROJECT: Lot j 0 CrPPA p1A7A SP41and RPplat
STANDARD FORM C
SEQUENCE FOR 19 94 ONLY COMPLETED BY: Dennis Messner DATE: June 3, 1994
V. Indicate.. by use of a bar line- or e e �6 s ailed0 74/ ��("
y symbols when erosion control measures wi 1 be installed.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engineer.
YEAR 1 1114
MONTH Aug. Sept Oct.l Nova Dec.
OVERLOT GRADING
WIND EROSION CONTROL
Soil Roughening
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other
RAINFALL EROSION CONTROL
STRUCTURALs
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other (Foundation)
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettinge/Mate/Blankets
Other
NOT APPLICABLE
STRUCTURESs INSTALLED BY MAINTAINED BY
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
APPROVED BY CITY OF FORT COLLINS ON
MARCH 1991 8.16 DESIGN CRITERIA
STORMWATER DETENTION SUMMARY
SITE DRAINS TO MAIL CREEK BASIN
GROSS SITE AREA = 31,737 SO.FT. = 0.73 ACRES t
NET SITE AREA EXCLUDING SOUTH MASON STREET R-O-W - 28,724 SOFT. - 0.66 ACRES t
HISTORIC "C" = 0.20
DEVELOPED "C" = 0.82
CRITERIA BASED DETENTION VOLUME - 5,519 cU.ft.
PLAN DETENTION VOLUME - 5,422 cu.ft.
MAXIMUM DEPTH OF DETAINED WATER =1.2 ft.
PEAK DISCHARGE, O = 0.33tc.f.s.
June 3,1994
Project No. PIA-140-94
Mr. Glen D. Schlueter
Stormwater Utility
City of Fort Collins
235 Mathews
P. O. Bog 580
Fort Collins, Colorado 80522 - 0580
Re: Lot 10 Creger Plaza - 2nd Replat, Fort Collins, Colorado
Dear Mr. Schlueter,
The subject project's estimated erosion control security amount has been determined to
be the minimum amount required by the City of Fort Collins. Therefore, the amount of
$1,000.00 should be included for the erosion control guarantee along with any other
surety requirements that are to be a part of the City's "Developers Agreement."
If you should have any questions or desire additional information, please feel free to
contact this office.
Respectfully Submitted,
MESSNER Engineering Associates
Dennis R. Messner, P.E.
DRM/mkm
cc: Mr. Pete Cottier, Cottier Construction, Inc.
Civil and Environmental Engineering Consultants
150 E. 29th Street, Suite 225 Loveland, Colorado 80538 - Telephone: (303) 663-2221