HomeMy WebLinkAboutBANK ONE PUD - PRELIMINARY & FINAL - 54-87W - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE AND
EROSION CONTROL REPORT FOR
BANK ONE AT HARMONY MARKET
Prepared for
Meline & Irelan, Inc.
471.0 S. College Avenue
Fort Collins, Colorado 80525
To Meet the Preliminary/Final Submittal Requirements for the
City of Fort Collins
256 West Mountain Avenue
Fort Collins, Colorado 80521
Prepared by
Resource Consultants & Engineers
A Division of Owen Ayres & Associates, Inc.
3665 JFK Parkway
Building 2, Suite 300
Fort Collins, Colorado 80525
RCE Ref. No. 34-0144
JAI MME
June 1994 ASSOCIATES
RCEciates
June 6, 1994
Mr. Basil Hamdan
City of Fort Collins
Stormwater Utility
281 North College Avenue
Fort Collins, Colorado 80521
Re: Bank One at Harmony Market
Dear Basil:
Enclosed please find the "Final Drainage and Erosion Control Report for Bank One at
Harmony Market." This report was prepared in accordance with the City of Fort Collins
Storm Drainage Criteria as revised in May 1991.
We appreciate your time and consideration in reviewing this submittal. Please call if you
Nhave any questions.
Sincerely,
Resource Consultants & Engineers
A Division of Owen Ayres & Associates, Inc.
Chris Carlson, EIT
MR.
4P.E.
Manager, Civil Engineering
CAC:-PRB:bbv
Enclosure
cc: Vic Meline
Re-outce Consultants & Engineers
Engineers/Scientists/Surveyors
665 JFK Parkway, Building 2, Suite 300, P.O. Box 270460, Fort. Collins; CO 80527
(303) 223-5556, Denver Metro (303) 572-1806, FAX (303) 223-5578
Ili inted on re,:yded ?aper
BANK-ONE.LTR
34-0144.00
TABLE OF CONTENTS
Page
1. INTRODUCTION..............................................1
2. PREVIOUS STUDIES ................ .. ...................... . 1
3. DRAINAGE PATTERNS..........................................1
4. HYDRAULIC ANALYSIS.........................................5
5. EROSION CONTROL PLAN ...................................... 7
5.1. Overview .............................................. 7
5.2. Wind Erosion ............................................ 7
5.3. Rainfall Erosion ................ .......... .............. 7
LIST OF FIGURES
Figure 1. Vicinity map. ..... ...... ..... ............................ 2
Figure 2. Existing drainage patterns .................................. .. 3
Figure 3. Time schedule . ............................................. 8
LIST OF TABLES
Table 1. Results of Detention Pond Sizing .................................. 5
Table 2. Construction Cost Estimate . .................................... 9
Resource Consultants & Engineers
ii A Division of Ayres Associates
1. INTRODUCTION
This report summarizes the storm drainage investigations performed for the
proposed Bank One At Harmony Market in Fort Collins, Colorado. A hydrologic analysis of
the proposed development was completed to determine the magnitude and location of
storm runoff, effects on Boardwalk Drive, and to develop a detention pond. The analysis
was completed to meet City of Fort Collins Storm Drainage Design Criteria and
Construction Standards Manual.
The Bank One development is located at the southwest corner'of Harmony Road
and Boardwalk Drive and to the north of Miramont First Filing. Preliminary/final drainage
report requirements as shown in Figure 1. It consists of approximately 2.0 acres
occupying the east half of Section 1, Township 6 North, Range 69 West, of the 6th
Principal Meridian. A site master drainage plan for the overall development of the
Oak/Cottonwood Farm was prepared by RBD, Inc. to meet the City's submittal
requirements for Overall Development Plans and is contained in the April 1994 report
"Overall Drainage Study, Oak/Cottonwood Farm, Fort Collins, Colorado." This study was
used as basis for the proposed drainage facilities of this development.
2. PREVIOUS STUDIES
Previous drainage studies of the area include (1) "Overall Drainage Study,
Oak/Cottonwood Farm, Fort Collins, Colorado" by RBD, Inc. (RBD), April 20, 1994 (has not
been approved by the City); (2) "Final Drainage and Erosion Control Study For The Upper
Meadow At Miramont First Filing, Fort Collins, Colorado" by RBD, November 10, 1992;
and (3) "Final Drainage and Erosion Control Study for The Upper Meadow at Miramont
Second Filing, Fort Collins, Colorado" by RBD. These were reviewed to assist with the
preparation of this report.
3. DRAINAGE PATTERNS
The Bank One site lies along the east border of.the Front Range Baptist Church
property and immediately to the west of Boardwalk Drive. It is in the north east corner of
a 22.9 acre offsite basin in the Oak/Cottonwood Farm Overall Drainage Study (RBD).
Besides the church, there is an �irrigation ditch running east - west across the basin. The ' basin is currently at historic conditions with native grasses north of the irrigation ditch and
alfalfa planted south of the ditch. As shown in the grading and drainage plan, runoff
sheet flows into the west Boardwalk Drive gutter where it is conveyed southeasterly to a
curb inlet constructed as part of Miramont Second Filing. A landscaped berm was
constructed along the north property line of the First Filing of Miramont that prevents flow
from crossing existing residential lots and redirects to Boardwalk Drive.
Existing runoff calculations were performed to determine the 10- and 100-year
runoffs for the site using the rational method. Concentration point 1 (Figure 2) is the area
along the northern boundary of the project which runoff flows directly into the drainage
ditch along Harmony Drive. The area of this basin is 0.08 acres and runoff is 0.09 and
Resource Consultants & Engineers
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,P
1-25 NORTH
TO CHEVENNE
'4
MULBERRY ST. TO 11-25 --b- EXIT 269
LAUREL
ST.
COL.ORADO
STATE
UNNERSITY
CAMPUS
PROSPECT
RD. TO 1-25 - EXIT 268
DRAKE
RD.
N
I
8
N
HOR.SETOOTH
RD.
il
HARMONY
W
Z
W
m
RD. F
TO 1-25 EXIr 265
PROJECT
LOCATION
VICINITY MAP
N.T.S.
Figure 1. Vicinity map.
2
Resource Consultants & Engineers
A Division of Ayres Associates
W
MI
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0 0
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LEGEND
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BASIN DESIGNATION
3.44oc
BASIN AREA
OCONCENTRATION
POINT
BASIN LIMITS
15
30 I5 0 30
SCALE IN FEET
.EAST HARMONY ROAD ,a '
A
0.080C
....
o.�..o
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. .. apt ...... �' � ..wp' � .. � ' � .. ♦oo�- ..
i a
Of 4 Located at east side of
Boardwalk Drive
22:9ao North of Miramont
First Filing
Figure 2. Existing drainage patterns.
0.18 cfs, respectively, for the 10- and 100-year events. Concentration point 2 is the
offsite drainagefrom the adjacent church property to the east. The area is 1.47 acres and
the 10- and 100-year runoff is 2.62 and 5.57 cfs, respectively. Concentration point 3 is
the remainder of the project site, including the offsite drainage to the east. The area of the
basin if 3.44 acres and the runoff is 2.19 and 4.53 cfs, respectively, for the 10- and 100-
year events. Existing runoff was also computed for the entire drainage basin (offsite basin
0-1, RBD, Miramont First Filing) which includes this site to assist with the design of the
detention pond. The concentration point is located at Broadwalk Street just north of
Miramont First Filing. The basin area is 22.9 acres and the runoff for the 2-, 10-, and 100-
year events is 5.94, 10.66, and 22.53, respectively.
A detailed grading, drainage, and erosion control plan (enclosed in pocket) shows
the building layout and storm drainage facilities that will be used for the Bank One
development. The map uses a contour interval of 1 foot. Flow from the adjacent church
property, Basin A, is carried through a short swale into a 15-inch RCP storm drain which
crosses the site to Inlet 2. At Inlet 2, this pipe connects to a 24-inch RCP storm drain and
is located near the east edge of the property and south of the Bank One building. It is a
13-foot type R curb inlet with a 14.30 cfs capacity and drains Basin B. The 5-foot type R
curb, Inlet 3, which is southeast of Inlet 2, connects to the 24-inch pipe. Inlet 3 has a
capacity of 4.80 cfs and drains water from Basin C. Runoff collected from the church
property and these two inlets will be directed into a drainage swale which runs south into a
proposed detention pond located just north of Miramont First Filing and adjacent to
Broadwalk Drive. The swale is 2 feet deep with 4 to 1 sideslopes and will be contained in
an 18-foot easement. Runoff from Basin E will flow into the existing concrete channel
along Harmony Road. Calculations show that this flow is too small to cause hydraulic
problems in the ditch and does not effect the overall development plan. Runoff from Basin
D will flow into the Boardwalk Drive gutter instead of being routed through the swale and
detention pond. This will not have a negative effect on the gutter nor will it exceed its
capacity.
As part of the Overall Drainage Study, a detention pond is proposed just north of
Miramont First Filing adjacent to Broadwalk Drive, at the southeast corner of the 22.9 acre
basin. This basin was noted as having the same storm water runoff discharge requirement.
of 0.5 cfs/acre as the remainder of the Oak/Cottonwood Farm development. Also shown
on the Overall Drainage Plan, a storm drain would be used to convey water from. the
detention pond to the Boardwalk Drive gutter. With development of The Upper Meadow at
Miramont First Filing and Boardwalk Drive, the conveyance capacity of Boardwalk Drive
during the 10-year storm was found to be 12.90 cfs (RBD, 1992). Basin 1 of the First
Filing will be contributing 7.33 cfs of storm water onto Boardwalk Drive during the 10-year
storm and 2.43 cfs will come down the gutter from Basin D, leaving a maximum of 3.14
cfs that can be released out of the detention pond. This corresponds to 0.14 cfs/acre,
Which is below the 0.5 cfs/acre maximum and therefore acceptable.
For the 100-year storm event, the detention pond is entitled to release 1 1.38 cfs of
storm water onto Boardwalk Drive. Basin 1 of the Miramont First Filing will contribute
15.70 cfs and 10.03 cfs will come down the gutter from Basin D. The capacity of
Boardwalk Drive during a 100-year storm is 107.7 cfs (RBD, 1992). Assuming a maximum
"I amount of water leaving the detention pond (11.38 cfs), Boardwalk Drive can adequately
convey the 100-year storm runoff.
Resource Consultants & Engineers
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r--
4. HYDRAULIC ANALYSIS
The Bank One at Harmony Market property consists of four basins, labeled Basins
B, C, D, and E, that contribute drainage to separate outlets from the property. There is
also one offsite basin that contributes drainage, namely Basin A. Design points were
identified at all locations where storm runoff will leave the property and at inlets. The
rational method, which was used for the Overall Drainage Study, was used to determine
the 10- and 100- year discharges that would occur as a result of the proposed Bank One
development. The cumulative runoff method was used to size the detention pond. Results
are summarized in Table 1. Calculations supporting these numbers can be found in the
Appendix.
Table 1. Results of Detention Pond Sizing.
Basin
Area
(ac)
Cumulative
Area
(ac)
Runoff
Coeff
(C)
CR
Overland
Flow
Length
(ft)
Average
Overland
Slope
M
Gutter
Flow
Length
(ft)
Average
Gutter
Slope
M
Gutter
Flow
Velocity
(fps)
2-Yr
A
1.39
1.39
0.41
1
1.25
35
1 1.8
465
1.8
2.1
B
1.42
1.42
9.5
1
1.25
41
2
379
0.8
1.8
A+B
2.81
2.81
0.68
1
1.25
35
1.8
712
1.45
1.65
C
1 0.7
0.7
0.95
1
1.25
12
1
1 281
0.8
1.8
D
0.14
0.14
0.95
1
1.25
-
-
213
1.5
2.2
E
0.8
0.8
0.15
1
1.25
15
20
223
1.5
1.8
Basin
Overland Time of
Concentration
Gutter
Travel
Time
(min)
Total Net Time
Tc
Rainfall Intensity
I
Peak Discharge
Q
10-Yr
(min)
100-Yr
(min)
10-
Yr
(min)
100-Yr
(min)
10-Yr
(in/hr)
100-Yr
(in/hr)
10-Yr
(cfs)
100-Yr
(cfs)
A
6.3
5.3
3.7
10
9
4.35
7.4
2.48
5.27
B
1.4
0.7
3.5
4.9
4.2
5.6
9.6
7.55
16.19
A+B
6.3
5.3
6
12.3
11.3
5.2
8.5
10.08
20.3
C
1
0.6
2.6
3.6
3.2
6
9.6
3.99
7.98
D
-
-
1.6
1.6
1.6 1
6
9.6
0.8
1.6
E
2.5
2.4
2.1
4.6
4.5
5.6
9.6
0.7
0.14
Basin A, an offsite basin having an area of 1.39 acre, will drain southeasterly into a
short Swale tapering in a 15-inch RCP storm drain labeled Concentration Point #1. The
storm drain runs to across the property where it connects to Inlet 2. The storm drain was
sized to carry the entire 100-year storm runoff.
Basin B, having an area of 1.42 acre, will drain by gutter and sheet flow to the
southeast corner of the parking lot at Inlet 2 (Concentration Point #2). Drainage through
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Inlet 2 will flow through a 24-inch RCP to Inlet 3 (Concentration Point #3). A 5.55 cfs
capacity overflow swale beginning at point #2 also flows to point #3. This swale will only
carry overflow from the 100-year storm. Flow in the swale will spill over the walk into
Inlet 3.
Basin C, which has an area of 0.70 acre, will drain along the entrance road north
gutter and the west Boardwalk Drive gutter to Inlet 3 (Concentration Point #3). Offsite
area on Boardwalk Drive contributes 0.21 acre to Basin C. Runoff above Inlet 3's
capacity, which occurs only in the 100-year storm, will cross the access road and flow
into the Boardwalk Drive gutter. The capacity in the gutter will not be exceeded.
Basin D, having an area of 0.14 acre, is the south half of the access road. All
runoff from Basin D will leave the property at Concentration Point #4 and enter the
Boardwalk Drive gutter.
Basin E, which has an area of 0.08 acre, will drain into an existing concrete channel
parallel to Harmony Road. The amount of runoff is very small and will not effect the
channel or any downstream facilities.
The sump curb inlets at points #2 and #3 are 13 feet and 5 feet in length,
respectively. For a curb full condition, they have capacities of 14.30 cfs and 4.80 cfs,
respectively. The storm drain pipes to and from the inlets are designed to carry the
maximum amount of flow the inlets will allow. In a 10-year storm all the runoff from
Basins A, B, and C will be intercepted by the inlets and flow into the storm drains. During
a 10-year storm the runoff leaving the storm drain system and entering the drainage swale
is 10.83 cfs. This is less than the capacity of the storm drain system. During the 100-
year storm, 5.27 cfs flows through the 15-inch pipe from point #1 to #2. The inlet
capacity at point #2 of 14.30 cfs is added to the storm drain, while 1.89 cfs overflows
into the 8 foot wide overflow swale. At point #3 the inlet capacity of 4.80 cfs is added to
the storm drain and 5.07 cfs flows into the Boardwalk Drive gutter. During the 100-year
storm the runoff leaving the storm drain system and entering the drainage swale is 24.37
cfs. The capacity of the drainage swale is 38.94 cfs at 2-foot depth and minimum slope.
Using the most restrictive conditions, the Boardwalk Drive gutter capacity will not
be exceeded by the development of the Bank One property. During a 10-year storm the
discharge into the gutter at Concentration Point #4 is 0.80 cfs. During the 100=year storm
the discharge is 6.67 cfs. Further downstream, just above the detention pond outlet, the
10-year storm runoff is 2.43 cfs and the 100-year storm runoff is 10.03 cfs. The
allowable gutter capacity is 12.90 cfs for the 10-year storm and 107.7 cfs for the 100-
year storm (RBD, 1992), neither of which are ever exceeded.
The detention pond was sized to contain the 100-year storm runoff from the
developed Bank One and church property and the historic flow from the remaining
property, 22.97 acres total. The drainage swale will capture all sheet flow from the
undeveloped land that originally flowed into the Boardwalk Drive gutter. Using the
cumulative runoff method, the storage volume required to contain the 10-year storm is
0.605 ac-ft and 1.474 ac-ft for the 100-year storm. This corresponds to depths of 1.0
feet and 1.4 feet of water for the 10- and 100-year storm, respectively. Using a 15-inch
ADS pipe to drain the detention pond into the street gutter, the maximum flow rates are
Resource Consultants & Engineers
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2.9 cfs and 4.6 cfs for the 10- and 100-year storms, respectively. These are both below
the approved maximum flow rates of 3.14 cfs for the 10-year storm and 11.38 cfs for the
100-year storms. A 16-inch by 24-inch area inlet will direct water into the storm drain
from the detention pond. Calculations are shown in the appendix.
5. EROSION CONTROL PLAN
5.1. Overview
The Bank One at Harmony Market will be a 2.05 acre development zoned C on
moderate erodibility soil. Overlot grading will begin the first week of August and building
construction will be completed in March, 1995 (Figure 3). Both wind and water erosion
will be addressed in this plan.
The property is divided into two individual basins. Basin 1 contains subbasins B, C,
and D and drains to the southeast corner of the property.. Basin 2 contains only Basin E of
the drainage plan. Erosion control for the detention pond area will be considered as a third
basin, Basin 3, even though it is not on the Bank One property. Subbasin B contains 1.42
acre, of which 1.37 acre will be disturbed. Subbasin C contains 0.49 acre, of which 0.46
acre will be disturbed. The undisturbed portions of these two basins exist as part of the
developed church property. The 0.14 acre of subbasin D will all be disturbed.. Basin E
contains 0.08 acre, of which 0.05 acre will be disturbed. The undisturbed portion
currently exists as the concrete drainage channel along Harmony Road.
5.2. Wind Erosion
Since construction will occur during the winter months, effective wind erosion plans
must be established. On moderate erodibility soil, significant erosion could occur without
steps taken to protect the soil. Those portions of Basins 1 and E not planted with sod
grass or covered with pavement, will have 2 tons/acre of straw mulch applied for water
erosion control, which also meets the requirements for minimum wind erosion protection.
All mulches will be properly anchored:
5.3. Rainfall Erosion
Subbasin B, of which 1.37 acre will be disturbed, lies in the north half of the
Property, just south of the small Basin 1. The majority of subbasin A will. be covered with
asphalt and concrete, however, 0.31 acre will have sod grass planted and the remaining
0.19 acre will be covered with 2 tons/acre of straw mulch either crimped 4 or more inches
into the soil or sprayed with a tackifier. A gravel sediment filter will be place at the storm
sewer inlets 1 and 2.
Subbasin C. of which 0.46 acre will be disturbed, lies immediately to the south of
subbasin B. Sod grass will cover 0.08 acre, pavement will cover 0.17 acre, and the
remaining disturbed area will have 2 tons/acre of straw mulch anchored in the same
manner as subbasin B. A gravel inlet filter will be placed at Inlet 3.
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PROJECT: Bank One At Harmony Market
SEQUENCE FOR 1994/95 ONLY
COMPLETED BY Chris Carlson
DATE: 6/6/94
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 Engineer.
August
September
November
December
January
--February
March
OVERLOT GRADING
WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier
Vegetative Methods
Soil Sealant
RAINFALL EROSION
CONTROL
STRUCTURAL:
Sediment Trap / Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare. Soil Preparation
Contour Furrows
Asphalt / Concrete Paving
VEGETATIVE:
Permanent Seed Planting
Mulching / Sealant
Temporary Seed Planting
Sod Installation
Nettings / Mats / Blankets
BUILDING CONSTRUCTION:
STRUCTURES: INSTALLED BY: Contractor MAINTAINED BY: Contractor
VEGETATION / MULCHING CONTRACTOR: Contractor
DATE SUBMITTED: 6/6/94 APPROVED BY CITY OF FORT COLLINS ON
Figure 3. Time schedule.
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Subbasin D, all of which is disturbed, will have 0.13 acre covered with asphalt and
0.01 acre of sod grass. A silt fence will be placed along the south border of subbasin D to
prevent sediment from leaving the project before asphalt is in place.
Basin E, of which 0.05 acre will be disturbed, lies along north border of the property
1 and contains the existing concrete channel, which runs parallel to Harmony Road. All of
the disturbed area in Basin E will be covered with sod grass.
'i
Basin 2, which is the detention pond, is 2.21 acres total area. There will be a
concrete trickle channel on 0.02 acre and sod grass on the remaining 2.19 acre. A gravel
inlet filter will be placed at the detention pond outlet pipe.
In addition to the required erosion control measures taken for the basins, 3 straw
bale dikes will be placed in the drainage swale between the storm drain and the detention
pond.
The calculations for performance standards and effectiveness are shown in the
Appendix as well as the supporting calculations.
Security requirements for erosion control are shown in Table 2. The largest
amount, the cost for erosion control measures, will be submitted.
Table 2. Construction Cost Estimate.
Item
Description
Units
Quantity
Unit Cost
Total
Comments
EROSION CONTROL MEASURES
1
Silt fence
ft
210
$ 1
$ 210
2
Sod grass
ac
2.64
500
1,320
3
Straw bales
ea
12
4
48
4
Inlet filter
ea
4
300
1,200
5
Straw mulch at 2
tons/acre
ac
0.4
250
100
Total
$2,878
1.5 x
Total
$4,317
Total security
required
GROSS AREA REVEGETATION
1
Revegetation of
disturbed area
ac
4.23
$ 500
$2,115
Total
$2,115
1.5 x
Total
$3,173
Total security
required
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