HomeMy WebLinkAboutAAMCO TRANSMISSION PUD, LOT 10, CREGER PLAZA 2ND REPLAT - PRELIMINARY / FINAL - 32-94 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTEngineering Associates
June 3, 1994
Project No. PLA-140-94
Mr. Glen D. Schlueter
Stormwater Utility
City of Fort Collins
235 Mathews
P. O. Box 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 "Developer's 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
STORMWATER DETENTION SUMMARY
SITE DRAINS TO MAIL CREEK BASIN
GROSS SITE AREA = 31,737 SQ.FT. = 0.73 ACRES ±
NET SITE AREA EXCLUDING SOUTH MASON STREET R-O-W = 28,724 SQ.FT. = 0.66 ACRES ±
HISTORIC "C" = 0.20
DEVELOPED "C" = 0.71
CRITERIA BASED DETENTION VOLUME = 4,358 cu.ft.
PLAN DETENTION VOLUME = 4,738 cu.ft.
MAXIMUM DEPTH OF DETAINED WATER = 1.2 ft.
PEAK DISCHARGE, Q = 0.33±c.f.s.
CONSTRUCTION SEQUENCE
PROJECT: 1,or 10 gar Plaza Sacnnd Replat
STANDARD FORM C
SEQUENCE FOR 19 94 ONLY COMPLETED BY: Dennis Messner DATE: June 3, 1994
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 1994
MONTH Aug.1 Septl Oct.I Nov.I Dec.I
OVERLOT GRADING ax
WIND EROSION CONTROL
Soil Roughening
Perimeter Barrier NOT APPLICABLE
Additional Barriers
Vegetative Methods
Soil Sealant
Other
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters XXXX}CXXXXX
Straw Barriers
Silt Fence Barriers XXXXXXXXXXXXXXXXXXXX
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving DX
Other (Foundation) XXXXXXXXXXXXXXXXX
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation XXX
Nettinge/Mate/Blankets
Other
STRUCTURES: INSTALLED BY
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS ON
MARCH 1991 8-16 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 Comment
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.Ox0.5x0.8 = 0.40
Eff. _ [1 - (0.82 x 0.40)] x 100 = 67.2 > 79.5 OK
MARCH 1991 B-15 DESIGN CRITERIA
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
ERODIBILITY
Asb
Lsb
Ssb
Lb
Sb
PS
SUBBA§IN
ZONE
(ac)
(ft)
($)
(feet)
M
M
Moderate
0.66
150
2.25
79.5
MARCH 1991 8-14 DESIGN CRITERIA
Client: Cottier Construction, Inc.
By: DRM
DETERMINE ORIFICE SIZE
Orifice Equation, Q = CA42gh
A=Q+N2gh
At East Area #2
Q = 0.23 c.f.s.
h = 37.0 - 33.9 = 3.1
C = 0.65
Project No. PLA-140-94
June 3, 1994
A=0.23-i-[0.65x4(2x32.2x3.1)]= 0.025sq. ft.
A=w*2 w=CIA
w = A.025 = 0.16 ft. = 1.9 inches
Therefore, Use T' x 2' as Maximum Orifice Opening
At West Area #1
Q = 0.10
h=35.9-35.0=0.9
A=0.10-[0.65x�(2x32.2x0.9)] =0.02
A = 40.02 w = 0.14 ft. = 1.7 inches
Therefore, Use 1-31T' x 1-3/Vas Maximum Orifice Opening
Page 7
Client: Cottier Construction, Inc.
By: DRM
Proj. No.: PLA-140-94
Date: June 3, 1994
DETENTION VOLUME CHECK OF PROPOSED DETENTION IN PARKING LOT
(EASTERN AREA #2)
Elevation
Area
(S .Ft.)
Avg. Area
(S .Ft.)
Elevation Diff.
(Ft.)
Volume
(Cu.Ft.)
Sum of Volume
(Cu.Ft.)
(Outlet)
35.80
25
275
0.2
55
55
36.00
525
1,205
0.25
301
356
36.25
1,885
2,460
0.25
615
971
36.50
3,035
4,088
0.25
1,022
1,993
36.75
5,140
6,113
0.25
1,528
3,521
37.00
7,085
3,521 = 3,533 Therefore, sufficient volume is available in the ponded parking lot area
at a depth of 1.2 feet with High Water Elevation @ 37.0
DETENTION VOLUME CHECK OF PROPOSED DETENTION IN PARKING LOT
(WESTERN AREA #1)
Elevation
Area
(S .Ft.)
Avg. Area
(S .Ft.)
Elevation Dif. .
(Ft.)
Volume
(Cu.Ft.)
Sum of Volume
(Cu.Ft.)
(Outlet)
35.00
25
275
0.5
138
138
35.50
525
1,205
0.25
301
439
35.75
1,885
2,460
0.15
369
808
35.90
3,035
4,088
0.1
409
1,217
36
5,140
808 = 825 Therefore, sufficient volume is available in the ponded storage area at a
depth of 0.9 feet with High Water Elevation ® 35.9
Page 6
Client: Cottier Construction, Inc.
By: DRM
Proj. No.: PLA-140-94
Date: June 3, 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
0.91
544
0.10
60
484
15
0.75
675
0.10
90
585
20
0.65
780
0.10
120
660
25
0.58
863
0.10
150
713
30
0.52
934
0.10
180
754
40
0.44
1,050
0.10
240
810
50
0.38
1,125
0.10
300
825
60
0.33
1,170
0.10
360
810
70
0.29
1,208
0.1
420
788
80
0.26
1,230
0.1
480
750
90
0.23
1,249
0.1
540
709
100
0.21
1,275
0.1
600
675
110
0.19
1,279
0.1
660
619
120
0.18
1,305
1 0.1
1 720
585
Q = CIACf
QRelease = 0.5 x Area = 0.5 x 0.20 =
At Q100 Proposed = 0.50 x I x 0.20 x 1.25 =
0.10 c.f.s.
0.13 x I
Therefore, a minimum of 825 cu. ft. of Detention Storage Volume is desired for the
Western portion of the site that is to discharge to the existing open swale along the
BN Railroad.
Page 5
Client: Cottier Construction, Inc.
By: DRM
Proj. No.: PLA-140-94
Date: June 3, 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. ® 2 Yr.
(c.f.s.)
Vol. dis.
(cu.ft.)
Vol. Diff.
(cu.ft.)
10
3.38
2,026
0.23
138
1,888
15
2.79
2,515
0.23
207
2,308
2D
2.42
2,906
0.23
276
2,630
25 1
2.14
3,214
0.23
345
2,869
30
1.93
3,479
0.23
414
3,065
40
1.63
3,912
0.23
552
3,360
50
1.40
4,192
0.23
690
3,502
60
1.21
4,359
0.23
828
3,531
70
1.07
4,499
0.23
966
3,533
80
0.95
4,583
0.23
1,104
3,479
90
0.86
4,653
0.23
1,242
3,411
100
0.79
4,751
0.23
1,380
3,371
110
0.72
4,765
0.23
1,518
3,247
120
0.68
4,862
0.23
1,656
3,206
Q = CIACf
QRelease = 0.5 x Area = 0.5 x 0.46 =
At Q100 Proposed = 0.81 x I x 0.46 x 1.25 =
0.23 c.f.s.
0.47 x I
Therefore, a minimum of 3,533 cu. ft. of Detention Storage Volume is desired for the
Eastern portion of the site that is to discharge to the existing storm drain.
Page 4
Client: Cottier Construction, Inc.
By. DRM
Project No. PLA-140-94
June 3, 1994
RUN-OFF FROM SITE AT PROPOSED CONDITIONS WITHOUT DETENTION
Consider that the Time of Concentration to remain as the undeveloped Tc.
USE 10 minutes as Time of Concentration
12 @ 10 min. = 2.50 inJhr.
Iioo @ 10 min. = 7.25 in./hr.
Western Area #1 Q2 = 0.50 x 2.50 x 0.20 x 1.00 =
0.25 c.£s.
Qioo = 0.50 x 7.25 x 0.20 x 1.25 =
0.91 c.fs.
Eastern Area #2 Q2 = 0.81 x 2.50 x 0.46 x 1.00 =
0.93 c.£s.
Qioo = 0.81 x 7.25 x 0.46 x 1.25 =
3.38 c.£s.
Determine Release Rate ,Q, at 0.50 c.f.s./acre:
Qrelease = 0.50 x 0.66 = 0.33 c.f.s. = Maximum rate of Total of flow released.
Western Area #1 - Q released = 0.20 x 0.50 = 0.10 c.f.s.
Eastern Area #2 - Q released = 0.46 x 0.50 = 0.23 c.fs.
The estimated detention storage volumes based for the two detention areas are indicated
on the following pages.
Page 3
Client: Cottier Construction, Inc.
By: DRM
RUN-OFF FROM SITE AT EXISTING CONDITIONS:
Run-off, Q = C x I x A x Cf
Cf at 2 year Storm = 1.0
Project No. PLA-140-94
June 3, 1994
Cf at 100 Year Storm = 1.25
The Western Area contains approximately 0.36 acres plus a 0.13 acre contribution from
the BN Railroad
Offsite Area @ Q2 = 0.20 x 2.50 x 0.13 x 1.00 = 0.07 c.Es.
Railroad
Qioo=0.20x7.25x0.13x1.25=0.24c.fs.
Onsite Area "A" Q2 = 0.20 x 2.50 x 0.36 x 1.00 = 0.18 c.fs.
Qioo = 0.20 x 7.25 x 0.36 x 1.25=0.65c.fs.
The Eastern Area contains approximately 0.30 acres
Onsite Area'B" Q2 = 0.20 x 2.50 x 0.30 x 1.00 = 0.15 c.fs.
Qioo = 0.20 x 7.25 x 0.30 x 1.25 = 0.54 c.fs.
PROPOSED DEVELOPMENT - RUN-OFF COEFFICIENT
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 a small outlet pipe 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 restrcted by an orifice plate.
#1 - West "C"avg: Lawns and Landscaped Areas = 0 sq.ft+
Roofs, Decks, Patios, etc. = 0 sq.ft.±
Streets, Drives, and Parking = 0 sq.ft+
Gravel Drive and Parking = 8,720 sq.ft.±
Unimproved and Open Area = 0 sq.ft.±
Railroad Right -of -Way = 0 sq.ft.±
Total Area = 8,720 sq.ft.±
"C"avg = 0.50
#2 - East "C"avg: Lawns and Landscaped Areas = 3,850 sq.ft.±
Roofs, Decks, Patios, etc. = 5,060 sq.ft.±
Streets, Drives, and Parking = 11,094 sq.ft.±
Gravel Drive and Parking = 0 sq.ft.±
Unimproved and Open Area = 0 sq.ft.±
Railroad Right -of -Way = 0 sq.ft.±
Total Area = 20,004 sq.ft.±
'IC7I 8Vg = ((3,850 x 0.20) + (0 x 0.50) + (5,060 x 0.95) + (11,094 x 0.95)) + 20,004 = 0.81
Page 2
Client: Cottier Construction, Inc. Project No. PIA-140-94
By: DRM June 3, 1994
Calculations for Drainage Investigation for Lot 10 of Creger Plaza - 2nd Replat located
in the NEV4 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 ± 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 net area of the site
after deduction of the existing South Mason Street r-o-w and the railroad r-o-w
Net Site Area = 28,724 sq.ft. = 0.659 ± acres
9 COKKVZ 113 V V Ilk,_ H 101a QKKIJ
Rational "C" Factor = 0.20 for Lawns and Landscaped Areas
= 0.95 for Roofs, Decks, Patios, etc.
" = 0.95 for Asphalt and Concrete Streets, Drives, and Parking
= 0.50 for Gravel Drive and Parking
= 0.20 for Unimproved and Open Areas
" = 0.20 for Railroad Right -of -Way
"C"avg (Undeveloped)
All area considered to be "Unimproved"
"C" avg = 0.20
TIME -OF -CONCENTRATION EXISTING CONDITIONS•
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) AIL + S^1/3
®5=2.8% L=90ft. C=0.20
T = 1.8 ( 1.1 - 0.20) �90 + 2.8A /3 = 10.9 min.
Tswale = L(ft.) + [Vel. (ft./sec.) x 60 minJsec.] per Fig. 3-2
® S = 1.5% & L = 110 ft. Vel. = 1.3 ftJsec.
T = 110 + [1.3 x 60 ] = 1.4 min.
Therefore, Tc = 10.9 + 1.4 = 12.3 min.
USE 10 minutes as Time of Concentration
12 @ 10 min. = 2.50 inJhr.
Iioo @ 10 min. = 7.25 in./hr.
Page 1
K A I
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Is
n3imum 11TE
seat
&IN
No Text
CONCLUSIONS AND RECOMMENDATIONS
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
request for a variance to the City's policies is requested for the detention of adjacent
street flows due to physical impracticallity.
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 4,358 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
0.33 c.f.s. The release rate of 0.33 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.
E
PROPOSED DEVELOPME
The proposed development of the site is to consist of constructing a commmercial
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 area is to be
gravel surfaced.
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 street flows adjacent to the site be
incorporated with the onsite detention requirements. This policy works when the street
construction and onsite detention are developed in conjunction. In this instance it is not
physically feasible to combine the two flows since the street flow would have to enter the
site at its low point. Consideration is being given to the flow from the adjacent railroad
right-of-way which will reduce the the overall discharge to the area streets.
EROSION CQNTROL MEASURE
Erosion control considerations have been made based upon the short term, activities
occuring 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 a 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 method to be incorporated into the
construction activities is the placement of a "Sediment Trap" and "Silt Fence" 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 new parking and drives, and install
landscaping and signage.
2
SCOPE
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 6th 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.
SITE DESCRIPTION
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.
EXISTING CONDITIONS
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.
1
TABLE OF CONTENT'S
Letter of Transmittal
i
Table of Contents
Scope
1
Site Description
1
Existing Conditions
1
Proposed Development
2
Erosion Control Measures
2
Conclusions and Recommendations
3
Vicinity Map
Existing Conditions Exhibit
Proposed Conditions Exhibit
Calculations
Drainage Summary
n
Project No. PLA-140-94
June 3, 1994
Mr. Pete Cottier
Cottier Construction, Inc.
P. O. Box 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.
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,
O�C,� "t_�
Dennis R. Messner, P.E.
MESSNER Engineering Associates
DRM/mkm
Enclosures
J4ne 31
Civil and Environmental Engineering Consultants
150 E. 29th Street, Suite 225 Loveland, Colorado 80538 Telephone: (303) 663-2221
DRAINAGE IIWESTIGATION
o
A PROPOSED'AAMCO' TRANSMLSSION SHOP
TO BE LOCATED ON
LOT 10, CREGER PLAZA SECOND REPLAT
FORT COLLINS, COLORADO
Prepared for
Cottier Construction, Inc.
P. O. Box 1051
Fort Collins, Colorado 50522
June 1994
Project No. PIA-140-94
luotiplMNAMIN
MESSNER Engineering Associates
150 East 29th Street, Suite 225
Loveland, Colorado 80538
Telephone: (303) 663-2221
Civil and Environmental Engineering Consultants