HomeMy WebLinkAboutDrainage Reports - 04/13/1994DRAINAGE AND EROSION REPORT
for
Convenience Store, Gas Station and Car Wash
At The Market At Horsetooth Commons P.U.D
At Horsetooth Road and South Shields Street
Fort Collins, Colorado
by
ADVANCED PROFESSIONAL ENGINEERING INC.
P.O. Box 1391
Fort Collins, CO 80522
Phone A Fax (303)-484-0533
Project # 69-7N-27-124
March 28, 1994
ADVANCED PROFESSIONAL ENGINEERING INC.
A
'
REGISTERED PROFESSIONAL, CONSULTANT ENGINEERS AND LAND SURVEYORS
P.O. BOX 1391, FORT COLLINS, COLORADO 80522-1391 USA
'
p
PHONE & FAX (303) 484-0533
March 28, 1994
'
E
Wickham Gustafson Architects
c/o Bob Gustafson
1730 South College Ave. Suit 202
Fort Collins, CO 80525
'
RE: Drainage and Erosion Report for Convenience Store, Gas
Station And Car Wash at Horsetooth Road and Shields Street,
'
Fort Collins, Colorado.
Dear Bob:
tThis
is the final drainage and erosion control report for the
proposed convenience store, gas station and car wash with two
'
drive -ways and parking lots to be located At the Northwest corner
of Horsetooth Road and Shields Street. The legal description
of
the site is Lot 1 of The Market At Horsetooth Commons P.U.D. a
Replat of Tract D of Horsetooth Commons PUD, in the City of Fort
tCollins,
State.of colorado.
The hydrology data and the hydraulic analysis presented here are
in compliance with the City of Fort Collins " Storm Drainage
Design Criteria", dated May 1984. The data and the analysis are
determined based on the historic, proposed developed conditions
and according to the Drainage Master Plan for Foothills Basin
'
(Basin G), dated February 1981.
A variance is requested here for the size of the orifice to be
installed at the inlet of the 15 inch storm drainage pipe, from 2
'
inch to 4 inch, since a 2 inch is very small and may plug the
entrance which will cause obstruction of flow at the inlet and
since the size of the pipes downstream are large enough (15 inch
'
and 36 inch) to carry 0.94 cfs instead of 0.50 cfs. If you have
any further questions or need any more information please feel
free to call me at (303)-484-0533
Sincerely,
k d
Colorado Reqistered
H
' SUBDIVISION PLANNING AND DESIGN - SOIL AND GEO-TECHNICAL INVESTIGATIONS - FOUNDATION, STRUCTURE DESIGN AND
INSPECTION - DRAINAGE, FLOOD CONTROL PLANNING AND DESIGN - ENVIRONMENTAL ASSESSMENT - CONSTRUCTION MANAGEMENT
TABLE OF CONTENTS
Title
?Age -
INTRODUCTION
1
SITE LOCATION AND CONDITIONS
1
HYDROLOGY AND HYDRAULICS ANALYSIS
2
PROPOSED CONSTRUCTION
5
SUMMARY
6
DISCUSSION
7
DETENTION POND SIZE
7
EROSION CONTROL REPORT
9
OVERLAND TIME OF FLOW
16
RAINFALL INTENSITY DURATION CURVE
17
l
I DRAINAGE REPORT
' INTRODUCTION
This drainage report provides the hydrology data using City of
' Fort Collins rainfall data and utilizes hydraulic analysis to
determine historic, existing and proposed drainage conditions for
the proposed convenience store, gas station and car wash to be
located at Northwest Corner of Horsetooth Road and Shields
' Street. The site legal description is Lot 1 of The Market At
Horsetooth Commons P.U.D., a Replat of Tract D of Horsetooth
Commons PUD. This drainage report is prepared and compiled based
' on the following references;
1- Storm Drainage Criteria, City of Fort Collins, May 1984.
' 2- Drainage Master Plan for Foothills Basin (Basin G), by
Resource Consultants, dated February 1981.
3- The Market at Horsetooth Commons PUD Plat by King &
Associates, approved and recorded on July 1987, # M-74-1438.
' 4- Drainage, grading and Utility Plans for The Market at
Horsetooth Commons PUD Tract D by Redpeak Engineering dated
January, May and revised in June 1987. All plans were
approved by the City of Fort Collins July 1987.
5- As built survey, topographic and contour maps prepared by
Advanced Professional Engineering Inc., October 1993.
' SITE LOCATION AND CONDITIONS
The site is located at Northwest Corner of Horsetooth Road and
' South Shields Street, Fort Collins, Colorado. The site is
bordered by S. Shield Street on the East side, Horsetooth on the
South side and by three other private drives along the West,
' Northwest and North sides. The site is located in the Foothills
basin (Basin G). The site is part of The Market At Horsetooth
Commons P.U.D., which is located in Southeast 1/4 of Section 27,
Township 7 North, Range 69 West of the 6th P.M. All the streets
have curbs, gutters and sidewalks. There are two curb cuts and
driveways existing on two of the private drives.
The existing condition of the lot is vacant and situated in a
depression below the adjacent streets. The existing general
topography of the site is relatively flat with slight overall
' slope of 1.7%.from Southwest to Northeast. The runoff is drained
by an intake storm drainage box connected to an 15 inches storm
sewer. The ground is covered with local Hay, native grasses and
wild weeds which grow all over the field. There are no trees on
' the property. The total area of the site is 0.906 acres or 39,475
square feet. The total area was obtained from the recorded Plat
of The Market At Horsetooth Commons PUD, by King & Associates,
' approved and recorded on July 1987, # M-74-1438.
[]
11
1
HISTORIC DRAINAGE CONDITIONS
The site is part of Tract D of Horsetooth Commons PUD. The site
is called area III in the drainage study by Redpeak Eng., June
1987. The site has a native hay ground cover. The topography of
the site is generally flat with a slight slope of 1.0% from West
to East. The runoff was generally flowing from West to East as a
sheet flow. Under historical conditions for grass land with 1.33%
slope is equal to 0.30 (based on Redpeak Eng. report Appendix I).
HYDROLOGY DATA AND HYDRAULICS ANALYSIS
The site is part of the Market at Horsetooth Commons PUD Overall
Drainage & grading Plan dated January 1987. Which is also a part
of the Drainage Master Plan for Foothills Basin (Basin G), dated
February 1981. This report will present and discuss the historic,
existing and the proposed conditions. Since the site had been
developed, streets, curbs, gutters and sidewalks have already
been built around the lot. There are two curb cuts and drive
approaches existing on two of the private drives.
The total area involved in this drainage study is 39,475 square
feet or 0.906 acres gross. Since the area is far less than 200
acres, the Rational Method to calculate the storm runoff quantity
can be used. The site is zoned commercial (business), although a
10 year initial historic storm is assumed, this report will use
the 2 year initial historic storm since Redpeak Eng. report used
the 2 year historic storm (from table # 3-1, page 3-1 Storm
Drainage Design Criteria). The historic runoff is calculated for
the site as follows;
I. Estimated runoff quantity "Q" in cfs, under historic
conditions for 2 year storm, based on design storm
frequencies for natural ground area;
1. The Rational Method runoff coefficient for 39,475 square
feet under historic conditions for grass land with 1.33%
slope is equal to 0.30 (based on Redpeak Eng. report).
2. Time of concentration in minutes;
T� = 1.87 x (1.1 - CXCf) x (L1 1/2 = 21.08
SI/j
Where;
TC Time of Concentration, minutes
A Area of the site in acres = 0.91 acres
S = Slope of basin S8 = 1.33%
Cf = Frequency adjustment factor for 10 yr = 1.0
C = Rational Method Runoff Coefficient = 0.30
L Length of Basin in feet = 240 feet
Also, from Figure 3-2, Ta = 21.0 minutes
2
3. Precipitation in inches/hour using Rainfall Intensity
Duration Curves for 2 year frequency for City of Ft.
' Collins, from figure 3-1.
I = Rainfall intensity = 1.80 inches/hour
' 4. Runoff quantity for undeveloped conditions;
Q = C (C{) IA Where;
' Q = Flow quantity, cfs
A = Total area of basin = 0.91 acres
' C = Runoff coefficient = 0.30
Cf = Frequency adjustment factor = 1.0
I = Rainfall intensity = 1.80 inches/hour
Then Q2 = 1.0 x 0.3 x 1.80 x 0.91 - 0.50 cfs
Qio = 1.0 x 0.3 x 3.2 x 0.91 - 0.87 cfs
' And Qioo = 1.25 x 0.30 x 5.10 x 0.91 = 1.73 cfs
' EXISTING DRAINAGE CONDITIONS
The streets, curb, gutter and sidewalks are already built around
the site as part of development of The Market PUD. The existing
' flow around the streets is a gutter flow as shown on the drainage
plan of Redpeak Eng. The runoff along the South side of
Horsetooth Road drains along the gutter to the East and via a
t sidewalk chase inlet on Shields Street at the corner. The runoff
along the East side of South Shields Street drains along the
gutter to the South and into the storm drainage intake at the
' corner of Richmond Dr., and Shields Street. The runoff pattern of
the streets is not changing.
According to Redpeak Eng's drainage report and plans, the
' northwest portion of lot 1 is used as 100 year flood and as a
detention pond (A) for Area I of Tract (D). This portion of lot
1, which includes also portions of streets (private driveways) is
' equal to 3,485.00 square feet or 0.08 acres. This area is
draining into detention pond (A).
' The Existing drainage condition over the undeveloped area is a
sheet flow over the entire site from the Southwest to the
Northeast with an average slope of 1.7%, which help provide a
sufficient drainage condition. There is a 2x3 feet intake storm
' drainage box connected to a 15 inch• reinforced concrete (RCP)
storm sewer pipe, which is connected to a 36 inch RCP main storm
sewer line. In Redpeak drainage report, the report shows a four
inch orifice to be installed on the inlet of the pipe.
1 3
' The following is the site data;
Site Area Gross = 39,475 S.F. ( 0.91 Acres)
' Net _ 33,421 S.F. ( 0.767 Acres)
Street R.O.W 6,054 S.F. (15.3%)
Conc. Drive & Side Walk = 11350 S.F. ( 3.4%)
' Undeveloped Area 32,071 S.F. (81.3%)
II. Estimated runoff quantity "Q" in cfs, under existing
' conditions for 10 year storm, based on design storm
frequencies for existing paved, concrete and natural ground
areas.
' 1. The runoff coefficient for roof, concrete and pavement is
equal to 0.95. The runoff coefficient for grass with a
slope of 1.7% is equal to 0.20.
' land Cover Area Area Runoff
sq.ft. Acres Coeff.
' Perimeter streets 61,054 0.14 0.95
Sidewalks/Curb & Gut. 1,350 0.03 0.95
Natural Open Space 32,071 0.74 0.20
' Total Area 39.475 0.91 0.34
' 2. Time of concentration in minutes;
A = Area of the site in acres = 0.91 acres
S = Slope of basin S% = 1.70%
' Cf = Frequency adjustment factor for 10 yr = 1.0
C = Weighted Runoff Coefficient = 0.34
L = Length of Basin in feet - 190 feet (from the
' highest point at the Southwest corner to the
existing intake drainage box).
Then
' TC 16.5 minutes, from Figure 3-2.
3. Precipitation in inches/hour using Rain Fall Intensity
Duration Curves for 2 year frequency for City of Ft.
' Collins, from figure 3-1.
I = Rainfall intensity = 2.05 inches/hour
' 4. Runoff quantity for existing conditions;
' Q2 = 1.0 x 0.34 x 2.05 x 0.91 - 0.63 cfs
Q,0 = 1.0 x 0.34 x 3.6 x 0.91 = 1.11 cfs
' Qioo = 1.25 x 0.34 x 5.85 x 0.91 = 2.25 cfs
1]
4
I
' PROPOSED DEVELOPMENT The proposed construction consists
ofdone story building, convenience store, gas station with
' attached car wash, a paved parking lot, two driveways and
landscaped areas. The following is the site data;
' Site Area Gross = 39,475 S.F. ( 0.91 Acres)
Less R.O.W. Net = 33,421 S.F. ( 0.767 Acres)
Building Area 3,125 S.F. ( 7.9%)
Parking & Drives = 19,138 S.F. (48.5%)
Landscape Area = 11,158 S.F. (28.3%)
Street R.O.W 6,054 S.F. (15.3%)
' DEVELOPED DRAINAGE CONDITIONS
III Estimated Runoff Quantity "Q" for 100 year in cfs for the
developed conditions; The runoff coefficient for Roof,
Concrete and pavement is equal to 0.95. The runoff coefficient
for grass is equal to 0.20.
land Cover Area/sq.ft. Area/acre Runoff/Coeff.
' Building Area = 3,125 S.F. 0.07 0.95
Parking & Drives = 19,138 S.F. 0.44 0.95
Street R.O.W = 61054 S.F. 0.14 0.95
' Landscape Area = 11,158 S.F. 0.26 0.20
Total Area = 39,475 S.F. 0.91 0.74
BASIN DELINEATION: The site including the private driveways and
' the surrounding area is divided into 3 basins. The following are
the three basins;
' Basin "A" is the main basin for the site which includes the
building, gas pump area and the parking lot, it is called area
III in Redpeak drainage report. The total area of Lot 1 is equal
39,475 square feet. Total area of basin "A" is 30,407 square feet
or 0.70 Acres. Since the slope of this basin is toward the
northeast and since the existing storm sewer inlet box is in the
northeast corner, then the location of the detention pond is
chosen at the northeast corner of the lot. Basin "A" runoff
drains into a 2x3 feet intake storm drainage box connected to an
15 inches reinforced concrete (RCP) storm sewer pipe, with a 4
t inch orifice. The 15 inch storm sewer pipe is connected to a 36
inch RCP main storm sewer line (see drainage plan).
' Basin "B" is for area I and area II (Redpeak drainage report)
which includes the northwest portion of the site (Lot 1) and
portions of private driveways. The area of lot 1 that is located
in basin "B" is 4,716 square feet or 0.11 Acres. All of basin "B"
' drains through detention pond "A", which drains into the inlet H-
3 (Redpeak drainage report). The inlet is connected to 15 inch
storm sewer pipe which is connected to a 36 inch RCP main storm
' sewer line. Portion of lot 1 is used as 100 year flood and
detention pond (A) for Area I of Tract (D). This portion of lot 1
is also draining into detention pond (A). (see drainage plan).
' 5
' Basin "C" is that portion along the north side of Horsetooth Road
and along the west side of Shields Street. The area of Lot 1 that
is located in basin "C" is 4,300 square feet or 0.10 Acres.
' Portion of basin "C" runoff drains into a storm drainage inlet at
the northwest corner of Horsetooth Road and Shields street. The
inlet is connected to a 36 inch RCP main storm sewer line. The
' other portion of the runoff drains south along the west side of
Shields Street and into an inlet at the southwest corner of
Shields Street and Richmond Drive (see drainage plan).
' BASIN "A"
The total area contributing to basin A runoff is equal to 30,459
' square feet. The net area contributing to the detention pond on
lot 1 is equal to the followings;
' land Cover Area/sq.ft. Area/Acr Runoff/Coeff.
Building Area = 3,125 S.F. 0.07 0.95
Parking & Drives = 19,138 S.F. 0.44 0.95
' Street R.O.W 2,254 S.F. 0.05 0.95
Landscape Area 5,942 S.F. 0.14 0.20
Total Area = 30,459 S.F. 0.70 0.80
' 1. Calculated composite runoff coefficient is equal to
C = (0.07+0.44+0.05)x0.95 + 0.14x0.20 = 0.80
0.70
2. Time of concentration in minutes; Basin Length -flow path;
' Overland Flow from high point to he gutter 70 feet with
slope of 0.4%, then T� = 6.5 Min. Gutter Flow for 260 feet
with 1.0% Slope and an average velocity of 2.0 fps, then TC
' = 2.2 Min.
Total TC = 6.5 + 2.20 = 8.70 minutes,
' 3. Precipitation in inches/hour from figure 3-1.
I = 7.30 inches/hour
' 4. Runoff quantity for proposed development;
' Qz = 1.0 x 0.80 x 3.0 x 0.70 = 1.68 cfs
Q,0 = 1.0 x 0.80 x 5.20 x 0.70 = 2.90 cfs
' Qioo = 1.25 x 0.80 x 7.30 x 0.70 = 5.11 cfs
1 6
I
' SUMMARY OF RUNOFF
The developed area is divided into three basins "A", "B" and "C".
' The total runoff for the 100 year major storm is equal to Qoo =
5.11 cfs. The developed runoff from basin B and C is minima . The
total runoff for the 2 year minor storm for the entire area is
' equal to 0.50 cfs. The difference between 100 year storm and 2
year storm which is equal to 4.61 cfs will be required to be
detained. The discharge out of the detention pond will be limited
' to the allowable historical release flow of 0.50 cfs. A 4 inches
orifice will be installed at the inlet of the 15 inches storm
sewer pipe to regulate the flow.
' Orifice equation to determine discharge through a 4" pipe orifice
is: Q = AxV = AxC(2xgxh)1/2 Where g = 32.2 ft2/sec.
A = Area of the orifice, V = Velocity of flow.
h = Head of water in feet, C = Discharged Coefficient.
Then the discharge = 0.087x0.6(2x32.2x 5.0)1/2 = 0.94 cfs.
DISCUSSION
1 According to the City of Fort Collins's Drainage Design Criteria,
a detention pond is needed to detain the difference between the
' 100 year major flood storm and the 2 year minor flood storm. The
following assumptions have been considered in determining the
location, type and size of the detention ponds;
1. No other off site runoff is entering the proposed developed.
Except for basin B and C runoff there is no other runoff
from lot 1 is exiting the site.
' 2. Since the slope of the site is toward the Northeast, and
since the storm sewer inlet box with 15 inches storm sewer
' pipe is in the Northeast corner, then the location of the
detention pond is chosen at the Northeast corner of the lot.
The site of the detention pond is shown on drainage plan.
3. All surface drainage from the site except basin B and C will
be directed to the Northeast and into the detention pond,
then through the 15 inch storm drainage sewer pipe, then
' into a 36 inch storm sewer pipe along the west side of
Shields Street.
' 4. The historical and developed runoff of lot 1 as determined
in this report is within the values of that in Redpeak
drainage report, which is already planned in Drainage Master
' Plan for Foothills Basin (Basin G), dated February 1981.
5. The existing flow around the streets surrounding the site is
a gutter flow as shown on drainage plan. The runoff along
north side of Horsetooth Road drains along the gutter to the
east, then south along Shields Street into a sidewalk inlet
' 7
1
I
I
1
1
[1
1
1
1
d
IJ
at the northwest corner of Shields and Horsetooth Road. The
inlet is connected to 36 inches RCP storm sewer pipe
draining south along Shields Street. The runoff along west
side of South Shields Street drains south along the gutter
into storm drainage intake at southwest corner of Richmond
Dr., and Shields Street. Drainage runoff pattern of all
streets is still the same as planned by Redpeak report.
DETENTION POND SIZE
Mass Diagram;
Total Discharge Historic Required
Time I CfCA Q,00 Volume QZ Volume Storage
Min. Sec. In /hr Acre cfs Ft3 cfs Ft3 Ft3
5
300
8.6
0.70
6.0
1,806
0.50
150
11,656
10
600
7.2
0.70
5.0
3,024
0.50
300
2,724
20
1,200
5.2
0.70
3.6
4,368
0.50
600
3,768
30
10,800
4.15
0.70
2.9
5,229
0.50
900
4,329
40
21,400
3.5
0.70
2.5
5,880
0.50
1,200
4,680
60
3,600
2.6
0.70
1.8
6,552
0.50
1,800
4,752*
90
5,400
.1.87
0.70
1.3
7,068
0.50
2,700
4,368
120
7,200
1.43
0.70
1.0
7,207
0.50
3,600
31,607
180
10,800
1.05
0.70
0.7
7,938
0.50
5,400
2,538
From the Mass diagram the maximum difference between 100 and 2
year storm is 4,752 cubic feet, which is required to be detained.
Discharge out of detention pond will be limited to the allowable
historical release flow of 0.50 cfs by using a 4" orifice.
STORAGE VOLUME
The volume needed to be retained is 4,752 cubic feet. The volume
in the detention pond area is the storage volume between contour
line of 5079.70 feet and contour line of 5081.50. The volume
needed is determined using the following formula;
Volume = d (A + B + (AB) 1/2 )
3
Where; d = Depth between contour line ft.
A = Surface area of top contour line.
B = Surface area of bottom contour line.
I
t Storage volume between contours 5,079.70 and 5,080.00 is:
A = 600.00 sq. ft., Surface area at contour line 5,079.70.
B = 1,200.00 sq. ft., Surface area at contour line 5,080.00.
' with a depth of d = 0.30 feet, Then V, = 265.00 cubic feet
Storage volume between contours 5,081.00 and 5,080.00 is:
A = 1,200.00 sq. ft., Surface area at contour line 5,080.00.
B = 3,317.00 sq. ft.,,Surface area at contour line 5,081.00.
with a depth of d = 1.00 feet, Then V, = 2,170.00 cubic feet
' Storage volume between contours 5,081.00 and 5,081.50 is:
A = 6,265.00 sq. ft., Surface area at contour line 5,081.50.
B = 3,317.00 sq. ft., Surface area at contour line 5,081.00.
' with a depth of d = 0.50 feet, Then V, = 2,357.00 cubic feet
The drainage inlet box has the size of 2.2x3.67x3.2 which can
' hold 25.84 ft3. Then total volume of detention pond is equal to =
25.84 + 265.00 + 2,170.00 + 2,357.00 = 4,817.84 ft3. Total
storage volume provided by detention pond is equal to 4,817.84
ft3, which exceeds the needed storage volume of 4,752 ft3.
The slope of the detention pond should not exceed 4:1. The inlet
drainage box should be cleaned once a year at least before the
' rain season. The flow through the 15" storm seer pipe will be
restricted to the allowable flow of 2.year storm of O.,Sp cfs by
installing a 4" orifice at the inlet. The finished floor
' elevations of the proposed building is 5083.00. The high water
line is at 5081.50.
II EROSION CONTROL REPORT
' INTRODUCTION
' This erosion report provides the wind and rainfall erosion
control plan using City of Fort Collins wind and rainfall data,
for the new proposed convenience store, gas station and car wash
to be located at Northwest Corner of Horsetooth Road and Shields
Street, in the city of Fort Collins, State of Colorado. The total
area of the site is 0.91 acres or 39,475 square feet.
WIND AND RAINFALL EROSION CONTROL DURING CONSTRUCTION
The entire site is in a moderate wind and rainfall erodibility
zone. The undeveloped portion of the site is covered with local,
native and wild grasses and weeds. There are no trees on the
property. The development will consist of one story building of
' 2,515 square feet to be used as a convenience store, which is
attached to 610 square feet car wash. A paved small parking lot
and two driveways, staging and vacuum area totaling 19,138 square
feet. The total landscaped area is equal to 11,158 square feet.
' There are 6,054 square feet of paved streets as half wright-of-
away. The following is a break down of the site;
' 9
1
I
' Site Area Gross = 39,475 S.F. ( 0.91 Acres)
Less R.O.W. Net = 33,421 S.F. ( 0.767 Acres)
Building Area = 3,125 S.F. ( 7.9%)
' Parking & Drives = 19,138 S.F. (48.5%)
Landscape Area = 11,158 S.F. (28.3%)
Street R.O.W = 6,054 S.F. (15.3%)
' The landscaped area will be covered with sod, irrigated lawn,
shrubs and trees (see landscape plan). All runoff flows from the
' site will be directed toward detention pond on site and then
through drainage box inlet into 15" storm sewer pipe.
WIND EROSION CONTROL PLAN
Since the total area of the site is equal to 0.91 Acres which is
less than one acre, then according to the City of Fort Collins
' Storm Drainage Criteria, May 1984, a wind erosion control plan is
not required, but a rainfall erosion control plan is required.
' RAINFALL EROSION CONTROL PLAN
The existing conditions of the site is covered with local, native
and wild weed and grasses. Since the inlet drainage box and storm
' sewer pipe are in existing on site at the location of the
detention pond then an area inlet filter will be installed around
the existing drainage inlet box. The filter can be consisted of
hay or straw bales to be placed around drainage inlet (as shown
in the drainage plan) to prevent erosion and sediments from
entering the storm sewer system. A silt fence is also proposed
around the site as a silt and sediment trap which will reduce any
' additional erosion effect.
A strip of 18' x 18' x 6" deep of gravel or crushed rocks are to
' be laid on the bare ground surface at both driveways during
construction period to prevent dropping of sediment, silt and
deposits from the work site to the streets.
' A = Area of the site in acres = 0.91 acres
S = Average slope of basin = 1.70%
Flow path (Labl) = 290 feet
RAINFALL WIND
' 100% moderate 100% moderate
1
10
' RAINFALL PERFORMANCE STANDARD
Lb = Lebl = 290 feet
' Sb = 1.70%
' Performance Standard = 78.80% ( from table 8-A)
RAINFALL EROSION CONTROL EFFECTIVENESS
EFF = (1 - C x P) x 100
where EFF = Effectiveness M
C = C-Factor (cover factor)
P = P-Factor (Practice factor)
' Erosion Control C-Factor P-Factor Area
Method Value Value Ac. Comment
Established Grass 0.04 1.00 0.26 At landscaped area
' Roads & Streets 0.01 1.00 0.14 Existing
Roughened ground 1.00 0.90 0.51 Construction site
Sediment trap 1.00 0.50 N/A At inlet
' Straw filter 1.00 0.80 N/A At inlet
Silt fence 1.00 0.50 N/A Around the site.
' Net C-Factor = (0.04x0.26 + O.01x0.14 + 1.Ox0.51)/0.91 = 0.59
(grass) (Street) (rough ground)
Net P-Factor =(1.Ox0.26+1.Ox0.14+0.9x0.51)0.5x0.8x0.5/0.91 =0.19
(grass) (Street) (rough ground)
' EFFebl- (1 -C x P) x 100
_ (1 - (0.59 x 0.19) x 100 = 89% > 78.8%
' Since the net EFF is greater than PS (89% > 78.80%), the proposed
erosion control methods will meet the City of Fort Collins
requirements.
11
RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: Lot 1, The Market at Horsettoth Commons STANDARD FORM A
COMPLETED BY: Advanced Professaional Eng. Inc. DATE: 3/30/94
DEVELOPED
ERODIBILITY
Asb
Lsb..
Ssb
Lb
Sb
PS
SUBBAgIN
ZONE
(ac)
(ft)
(%)
(feet)
M
M
Basin A
Moderate
0.406
190
1.7
190
1.7
78.8
MARCH 1991
9.14 DESIGN CRITERIA
1
C
[1
1
1
EFFECTIVENESS CALCULATIONS
PROJECT: Lot 1 The Market at Horsetooth Commons STANDARD FORM B
COMPLETED BY: Advanced Professional Eng Inc. DATE: 3/30/94
Erosion Control C-Factor P-Factor
Method Value Value Comment
Established Grass 0.04 1.0 0.26 acres at landscaped
Roads & Streets 0.01 1.0 Already existing 0.14 Ac.
Roughened ground 1.0 0.9 0.51 ac. construction area
Sediment trap 1.0 0.5
At inlet
Straw filter 1.0 0.8
Silt fence 1.0 0.5 Around the site
MAJOR
PS
SUB
AREA
BASIN
($)
BASIN
(Ac)
CALCULATIONS
A
78.8%
Net C-Factor=(0.04x0.26+O.O1x0.14+1.Ox0.51)/0.91=0.5
Net P-Factor=(1.Ox0.26+1.Ox0.14+0.9x0.51)0.5xO.8x0.5/
= 0.19
EFF.=(1-CxP)x100
_ (1 - (0.59 x 0.19) x 100 = 89% more than 78.82
%I
' MARCH 1991 8.15 DESIGN CRITERIA
' CONSTRUCTION SEQUENCE
' PROJECT: Lot 1 The Market at Horsetooth Commons STANDARD FORM C
SEQUENCE FOR 19 94 ONLY COMPLETED BYs Advanced Professional EngDATEs3/30/94
' 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 Enginoer.
' YEAR 1994 1995
MONTH IAIMIJIJIAISIOIN IDIJ IF I M
■ I
OVERLOT GRADING
' WIND EROSION CONTROL
Soil Roughening
Perimeter Barrier
Additional Barriers
' Vegetative Methods
Soil Sealant
Other
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
Netting,/Mats/Blankets
Other
STRUCTURES, INSTALLED BY General Contractor MAINTAINED BY _ Schrader Oil Co.
' VEGETATION/MULCHING CONTRACTOR General Contractor
' DATE SUBMITTED3hn./94
APPROVED BY CITY OF FORT COLLINS ON
I
MARCH 1991 9-16 DESIGN CRITERIA
I
[1
[1
1
1
1
0
1
1
COST ESTIMATE FOR EROSION CONTROL PLAN
The erosion control plan requires the following:
1- Silt fence is proposed around the site.
800 liner feet of silt fence x 4 feet high of 6 mill at
$ 20.00/100 feet long = 20 x 8 = $ 160.00
2- 10 pieces of hay or straw bales to be placed around drainage
inlet. 10 pieces x $ 4.0 = $ 40.00
3- A strip of 18' x 18' x 6" deep of gravel or crushed rocks
are to be laid on the bare ground surface at both driveways
during construction period.
The cost = 18x18x0.5x2 = 324 cubic feet = 12.00 cubic yard
The cost = $ 250.00
4- 6,000 square feet of landscaped grass at the end of project
cost = 6,000 x $ 0.25 = $ 1,500.00
Total cost = 160.00 + 40.00 + 250.00 + 1,500 = $ 1,950.00
Then 150% of the cost = 1.5 x 1,950.00 = $ 2,925.00, which is
greater than the $ 1,000.00 minimum.
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6tormttor Mantas
1. 1f desatesing is "ad to mats It uti I it l at, a Rate ^c..
construction DasatermP wastewater Discharge Perms it required it
discharged into s storm sewer, channel, irrigation ditch, or any
warars of the United State• w
3. All Construction activities nn this site must comply with the S
State of Colorado Permitting Process for Ltormater Discharges p
Associated with Construction Activity For Information, please
contact Colorado Department of Held Motor Guallty control E,j/
Division wQCp PS P=, 4300 Cherry Creel Drive South, Denver, IT/
Colorado 80222 153o Attention permits and Enforcement Section J
Phone (303) 6921550 2 I
3. Prior to final inspection and acceptance by the City, a L
certification f the drainage facilities by a registered engineer, YI _
most be submitted to and approved by the Ste rlmltter Utility.
ALI
t. Maintenance f all onslts and affairs drainage facilities will Ay
be the responsibility of the owners
s of the property. She owners 'I
of the property at the present are Schrader Oil Co. ; Y „II
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TYPICAL SECTION GRASS LOVED CHANNEL rYP nL SEI CONCRETE
AD [role T iCw LE PAN
10 score
G,.
CLIC Veal Food
Code =0,42 dnc •. 1_
yl Yl .wY OL NISL DATA:
Site Are 6voe.e IF 09,475 S.P. 1 U.11 Acres)
Lend RAM" Net - 33,421 S.F. C, 167 Lyres,
H ildirg 111 3,125 S.F. 7.19)
talking A F i - L9 30 5-1". 148.A)
nddce from
-e 11 1 6 .,I. 120. 1%)
e2roet 8.0.14 - EFTA F.E. INS. 1\)
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wre
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y VMMARY OF µAIHAGE IV 1�0 P_ 1 - (tllJLITED INTO 67Y
Historic Existing pevelaped /
'1 L. Area Acred 0.91 0 91 0.70
1 4 240 nJ 26d.J L
1 Iel[h 1 : tl 3i0 :90 :e360 - 330
T:m 23.0 8 70 Ad. J
'(F (' hrl 0.50 [.US ],loin / .
Runoff [ 1 y (oft] 0.50 16 31 1.60
Runoff f 10 y 1_ 1=foI 0.8] It .90
Runoff for 100 yr lots) 1.73 2.a3 5.11 �. fly WTb 4 lTdAdEl
BY Y/ECM1l.E fo HATCu
1 pESLNS[OX PO$0 6S0Ml < ORIGILE FELL
ELATE
Aliownblo I'll retel9e . p,s` -ty. A 6 inches orifice 'i1 he installed at the inlet of CM 15
The Jiff na - 4.61 fa. mats StOTM sewer pipe to regulate the flea.
VI-VIld renpl R, 1. 1 Ro,two. Swi-
volume, provided - e,. 81' 84 LL, feet.I
100 year high water RRS,, COI 50 Alan Inlet v ,
s,NA1,L DRAINAGE p]?SM-f419Y1
0
0 t 1
V: y IaQ',
CI,Iddl 12. 0 12 EtHao
Depth =001 RR 0.41 feet
De
pth f2, 25 en..
lope
AREA IM ET FILTER
STRAW BALES
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