HomeMy WebLinkAboutEVERGREEN PARK REPLAT (NO. 1), BLOCK 5, LOTS 1 & 2 - PDP/FDP - 24-96A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTAPPENDIX V
Stuffer Envelope
Grading, Drainage and Erosion Control Plan
Easement dedication exhibit for Lots 1 and 2, Block 5
No Text
easterly to Pond 5 (conceptual). The detention volume required for the basin, in order
to meet the prescribed release rate, was estimated to be 6.4 acre-feet.
Basin 5A. The basin was assumed to be completely developed for commercial use with
an estimated imperviousness of 90 percent. On -site detention is required for this basin.
The allowable release from this basin is 5 cfs, or 0.40 cfs/acre. The designated release
point for Basin SA is Pond 5; this pond will release flows to Dry Creek. The detention
volume required for the basin, in order to meet the prescribed release rate, was estimated
to be 2.3 acre-feet.
Basin 5B. The basin was assumed to be completely developed for commercial use with
an estimated imperviousness of 90 percent. On -site detention is required for this basin.
The allowable release from this basin is 11 cfs, or 0.36 cfs/acre. The designated release
point for Basin 5B is Dry Creek at the southeast corner of the basin. The detention
volume required for the basin, in order to meet the prescribed release rate, was estimated
to be 5.6 acre-feet.
Basin 6. The basin was assumed to be primarily developed for commercial use (79
percent), with 8 percent devoted to medium density residential housing. The remaining
13 percent was assumed to be open space associated with existing wetland, which is
functioning as a detention pond (Pond 6). It is noted that 13 percent is probably a
conservatively low estimate of the wetland area within this basin. The resulting average
imperviousness is 75 percent. On -site detention is not required for this basin; however
the integrity of the downstream storm drainage system requires that "Pond 6" continue
to operate as a detention pond. In fact, this Master Plan specifies that Pond 6 act as a
regional detention pond, receiving on -site detention releases from Basins 7A, 7B and 9.
Assuming that the pond will receive releases from these three basins as well as runoff
from Basin 6, the existing pond and outlet will limit the developed condition 100-year
release to 13.8 cfs. The detention volume required for the basin, based on the current
release rate of 13.8 cfs, was estimated to be 15.5 acre-feet. It is imperative that this
pond release rate be maintained due to the capacity of downstream conveyance and
detention facilities. The designated release point for Basin 6 is the upstream end of the
Blue Spruce Drive roadside channel/culvert system which conveys flow to the Evergreen
West Pond.
Basin 7A. The basin was assumed to be fully developed with medium and low density
residential housing at 32 and 68 percent, respectively. Consequently, the estimated
imperviousness is 42 percent. On -site detention is required for this basin, with releases
routed through Pond 6 for additional attenuation of the flood peak. The allowable
release from this basin is 12 cfs, or 0.51 cfs/acre. The designated release point for Basin
7A is a conceptual drainage channel/ pipe system through Basin 7B which will convey
flows to Pond 6. The detention volume required for the basin, in order to meet the
prescribed release rate, was estimated to be 3.7 acre-feet.
Basin 7B. The basin was assumed to be fully developed with a combination of
commercial, and low and medium residential housing. The resulting imperviousness was
20
MAR-21-97 FRI 13:02
1 . UV/ VV
Basin 1F. The basin is part of Greenbriar Village PUD, Second and Fourth Filings.
Consequently, the basin was assumed to be fully developed with medium residential land
use. An imperviousness of 40 percent was assumed. Runoff will concentrate along the
west side of Redwood Street near the end of Fox Glove Court; it will then eyed
under Redwood Street in a proposed pipe system designed to carryyflbe
ows-
Therefore, on -site detention is not required for this basin, as all storm proposed Greenbriar tivetiand nd. runoff
will
conveyed under Redwood Street to the p op
Basin 1G. The basin is part of the Greenbriar Village PUD, Third Filing, therefore,
it was assumed to be 40 percent impervious. Runoff from the basin will be conveyed
directly (undetained) to the outfall pipe for the Greenbriar Wetland Pond, thereby being
routed directly to the Redwood Pond. The Greenbriar Wetlandond not has resultbein co adverse
n configured
to over -detain such that undetained runoff from Basin
IG will impact to the Redwood Pond. Consequently, on -site detention is not required for this
basin.
Bassin 2. The basin was assumed to be developed with commercial, and both high and
ing to 5, 35 and 60 percent levels, respectively; the result
low density residential hous
being an average imperviousness of about 50 percent. On -site detention is not required
for this basin; storm rwt ff %W be conveyed to the existing Redwood Pond. Oufl flows
discharges from this pond will enter the proposed outlet channel which will carry
easterly to Lemay Avenue while picldng up runoff from Basin OB and outflows from the
Evergreen Fast Pond near the east end of the channel.
Basin 3A. The basin was assumed to be completely developed for commercial use with
an estimated imperviousness of 90 percent. On -site detention is not required for this
basin; storm mnoy will be transported to the existing inlet channel far the Evergreen
West Pond.
Basin B. The basin was assumed to be developed for 37 percent com�nerc 1 set of the ance
63 percent residential housing at levels representing
respectively.
The reessult is a developed
basin for high, medium and low densities; respec ' y
imperviousness of 63 percent. On site detention is not be required for this basin; storm
Outflow from this pond
rwio will a tr
will enter the existing outlet channel which will transport flow southerly to Pond 5
(conceptual).
Basin 4D. By definition, the basin is currently fully developed for commercial Due e;
the amount of impervious area for the basin was determined to be 97 percent.easible.
10
the fulty-developed condition of to pond 5 (conceptual)-
4,. on -site detention is not f
Storm runoff will be conveyed
Basln4U. The basin was assumed to�Ent On siteydetention f re or commercial
th basin
an estimated imperviousness of
The allowable release from this basin is 17 c or .47 cfs/acre The desisnated release
s
.,,,;�► fnr rtnsin 4U is the storm sewer and street along Conifer Street which convey flows
19
Table 5.3. Summary of Hydraulic Analysis and Design Information for the Existing Conveyance Facilities Which Require Modu►cations or
.,.,a a.o r^nvav9nnP Rarilitiec which Have Been Desiened but Not Constructed.
11111JlVYGIIIGIIIJ, ullu
lllV �v..•v�•.
•.v.. ...�-------
------- ---
.-
Description:Wtdtii
Bottom
(R) or
' Stde Slopa
Invert Slope
Mannrrtg's
100-Xea
ptscharge'
F►ow
0606,
Flow
Velocity
Commeiits
EleMerif
Number.
v)
(R/R)
W....
est
Area
Basins 7A and 7B Outlet
36" RCP.
n/a
0.0040
0.013
28
-
-
Pipe full capacity = 42 cfs
PI
Pipe to Pond 6
P2
Evergreen West Pond
30 ft
4
0,0025
0.060
(Nod 252)
1.5
1.5
Freeboard provided = 1.0 ft.
Inlet Channel
Evergreen West Pond
7 ft
4
0.0019
0.060
24
1.6
1.1
Freeboard provided = 2.5 ft (min.)
P3
Outlet Channel
P4
Conifer Street Channel
7 ft
4
0.0025
0.035
(Node20132)
3.2
3.2
Freeboard provided = 3.8 ft
;: Noitheast
Area .....
PS
PVE-B Perimeter
0 ft
4
0.0068
0.060
16
1.5
1.7
Freeboard provided = 0.5 ft (min.)
Channel, East Reach (A)
P6
PVE-B Perimeter
25 ft
4
0.0043
0.035
445
2.8
4.6
Freeboard provided = 0.7 ft (min.)
Channel, East Reach (B)
P7
PVE-B Perimeter
0 ft
4
0.0080
0.060
8
1.2
1.5
Freeboard provided = 0.8 R (min.)
Channel, West Reach
P8
PVW-B Perimeter
0 ft
4
0.0070
0.060
17
1.6
1.7
Freeboard provided = 0.8 ft (min.)
Channel, East Reach
East Pipe Crossing of
tripple 42"
n/a
0.0067
0.013
445
-
-
Available driving head 2 9.5 ft
(see Appendix F.2)
I arimer and Weld
Canal
RCPs
P10
West Pipe Crossing of
single 42"
n/a
0.0063
O.o13
111
--
_
Available driving h = 12.8 ft
(see Appendix F.2)
Iead
arimer and Weld Canal
RCP
:Southeast:Aiea
.
P11
Greenbriar Wetland Pond
15" RCP
n/a
0.0033
0.013
4
--
-
Pipe full capacity = 4 cfs
Outlet Pipe
P12
Redwood Pond Outlet
5 ft
4
0.0025
0.060
17
1.4
1.2
Freeboard provided = 1.6 ft (min.)
Channel
P13
Evergreen East Pond
3 ft
1
0.0025
0.016
49
2.0
5.1
Freeboard provided = 1.1 ft
Outlet Channel (concrete)
P14
Greenbriar Outfall
12 ft
4
0.0020
0.060
64
(Node 269)
2.2
1.4
Freeboard provided = 0.3 ft
Channel, North Reach
P15
Greenbriar Outfall
16 ft
4
0.0020
0.060
77
(Node 270)
2.1
1.5
Freeboard provided = 0.4 ft
Channel, South Reach
' Refer to Appendix F for explanation of design discharges.
FBI
FINAL REPORT
GREENBRIAR-EVERGREEN BASIN
MASTER DRAINAGE PLAN
PREPARED. FOR:
City of Fort Collins
Stormwater Utility
235 Mathews
Fort Collins, CO 80524
PREPARED BY:
Lidstone & Anderson, Inc.
736 Whalers Way, Suite F 200
Fort Collins, CO 80525
(LA Project No. COTST05.4)
May 1, 1996
Appendix IV
Greenbriar-Evergreen Basin Master Drainage Plan;
Lidstone & Anderson, Inc.;
Project No COTST05.4; dated May, 1996
SECTION 3. HYDROLOGY STANDARDS
3.1 General Design Storms
All drainage systems have to take into consideration two separate and distinct drainage problems. The
storm, depending on land use The runoff l storm which occurs at frular intervals,
o this type of storm ssconlside considered the" "nuisance flow". based on 'the two to he
second is the major storm which is usually based on an infrequent storm, such as the 100-year storm.
In some instances the major storm routing will not be the same as the initial storm. In this case, a
complete set of drainage plans shall be submitted for each storm system.
3.1.1 Initial Storm Provisions
As stated before, the initial storm shall be based on the two to ten-year storm. The objectives
of such drainage system planning are to minimize inconvenience, to protect against recur-
ring minor damage and to reduce maintenance costs in order to create an orderly drainage
system at a reasonable cost for the urban resident. The initial storm drainage system may in-
clude such lacilities as curb and gutter, storm sewer and open drainageways, and detention
facilities.
3.1.2 Major Storm Provisions
The major storm shall be considered the 100-year storm. The objectives of the major storm
planning are to eliminate substantial property damage or loss of life. Major drainage systems
may include storm sewers, open drainageways, and detention facilities. The correlation
between the initial and major storm system shall be analyzed to insure a well coordinated
drainage system.
3.1.3 Storm Frequency
The initial and major storm design frequencies shall not be less than those found in the fol-
lowing table:
Table 3-1
DESIGN STORM FREQUENCIES
Design Storm Return Period
Initial Storm Major Storm
Land Use or Zoning t
Residential:
(RE, RL, RLP, RP, ML, RM, RMP, ................ Par 100-year
................
2-y _
RLM, MM. RH) ......................... ..
Business: .............10 -year 100 year
(BG, BL, BP. HB, C. IL, IP, lG) ............... 10-year 100-ye?r
................ 100-year
Public Budding Areas ................................. ..... 2-year
......................................... 100-year
Parks, Greenbelts, etc ............... —
Open Channels & Drainageways.............................................
................................. 100-year
Detention Facilities .............................................
See Table 3-2 !or zoning delinitions.
3.1.4 Rainfall Intensities
sed in the computation of runoff shall be obtained from the
The rainfall intensities to be u
Rainfall Intensity Duration Curves for the City of Fort Collins, included in these specifications
as Figure 3.1.
3.1.5 Runoff Computations with the criteria
Storm Runoff computations for both the initial and All unoffor storm calculations lmadle in the design of
set forth in Section 3.2 "Analysis Methodology."
both initial and major drainage systems shall be in with the storm have
atyped
narrative
form of a Drainage Report. Reports submitted for approval should have a typ
with computations and maps in a legible form.
3-1
MAY 1984
DESIGN CRITERIA
No Text
R-M-P Medium Density Planned Residential District — designation for medium density
areas planned as a unit (PUD) to provide a variation in use and building placements
with a minimum lot area of 6,000 square feet.
R-L-M Low Density Multiple Family District — areas containing low density multiple family
uniith a minimum
ot area of
ts or any other use in the R-L District one -family or two-family dwellings lingswlmultiple-family0
and 9 000 square feet for0
square feet
for
dwellings.
M-L Low Density Mobile Home District — designation for areas for mobile home parks
containing independent mobile homes not exceeding 6 units per acre.
M-M Medium Density Mobile Home District — designation for areas of mobile home
parks containing independent mobile homes not exceeding 12 units per acre.
B-G General Business District — district designation for downtown business areas,
including a variety of permitted uses, with minimum lot areas equal to 1 /2 of the total
floor area of the building.
B-P Planned Business District — designates areas planned as unit developments to
provide business services while protecting the surrounding residential areas with
minumum lot areas the same as R-M.
H B Highway nses witBusiness District
h am'in mum lot area equalto 1/2 ofthe totalfloorta etautomobile-orientated
of the building.
B-L Limited. Business District — designates areas for neighborhood convenience
centers, including a variety of community uses with minimum lot areas equal to two
times the total floor area of the building.
C Commercial District —designates areas of commercial, service and storage areas.
I-L Limited Industrial District —designates areas of light industrial uses with a minimum
area of lot equal to two times the total floor area of the building not to be less than
20,000 square feet.
I-P Industrial Park District —designates light industrial park areas containing controlled
industrial uses with minimum lot areas equal to two times the total floor area of the
building not to be less than 20,000 square feet.
I-G General Industrial District — designates areas of major industrial development.
T Transition District —designates areas which are in a transitional stage with regard
to ultimate development.
For current and more explicit definitions of land uses and zoning classifications, refer to the
Code of the City of Fort Collins, Chapters 99 and 118.
Table 3-3
RATIONAL METHOD RUNOFF COEFFICIENTS FOR COMPOSITE ANALYSIS
Runoff Coefficient
Character of Surface
Streets, Parking Lots, Drives:
0.95
Asphalt................................................................................................
0.95
Concrete............................................................................................. 050
Gravel.................................................................................................
Roofs ....................................
.......................................... 0.95
Lawns, Sandy Soil: 0.10
Flat<2% ............................................................................................. 0.15
Average2 to 7%.................................................................................. 0.20
Steep>7%..........................................................................................
Lawns, Heavy Soil: 0.20
Flat<2%............................................................................................. 0.25
Average 2 to 7%.................................................................................. 0.35
Steep>7%......... :......................................... .......................................
MAY 1984 3-4 DESIGN CRITERIA
3.1.7 Time of Concentration
In order to use the Rainfall Intensity Duration Curve, the time of concentration must be
known. This can be determined either by the following equation or the "Overland Time of
Flow Curves" from the Urban Storm Drainage Criteria Manual, included in this report (See
Figure 3-2).
TC =1.87 (1.1 — CC,) D "Z
S3
Where Tc = Time of Concentration, minutes
S = Slope of Basin, %
C = Rational Method Runoff Coefficient
D = Length of Basin, feet
Cl = Frequency Adjustment Factor
Time of concentration calculations should reflect channel and storm sewer velocities as well
as overland flow times.
3.1.8 Adjustment for Infrequent Storms
The preceding variables are based on the initial storm, that is, the two to ten year storms. For
storms with higher intensities an adjustment of the runoff coefficient is required because of
the lessening amount of infiltration, depression retention, and other losses that have a
proportionally smaller effect on storm runoff.
These frequency adjustment factors are found in Table 3-4.
Table 3-4
RATIONAL METHOD FREQUENCY ADJUSTMENT FACTORS
Storm Return Period
Frequency Factor
(years)
C,
2 to 10
1.00
11 to25
1.10
26 to 50
1.20
51 to 100
1.25
Note: The product of C times C, shalt not exceed 1.00
3.2 Analysis Methodology
The methods presented in this section will be instituted for use in the determination and/or verification
of runoff at specific design points in the drainage system. These methods are (1), the Rational Method
and (2) the Colorado Urban Hydrograph Procedure (CUHP). Other computer methods. such as
SWMM, STORM, and HEC-1 are allowable if results are not radically different than these two. Where
applicable, drainage systems proposed for construction should provide the minimum protection as
determined by the methodology so mentioned above.
3.2.1 Rational Method
For drainage basins of 200 acres or less, the runoff may be calculated by the Rational
Method, which is essentially the following equation:
Q = C1CIA
Where O = Flow Quantity, cfs
A =Total Area of Basin, acres
C1= Storm Frequency Adjustment Factor (See Section 3.1.8)
C = Runoff Coefficient (See Section 3.1.6)
1 = Rainfall Intensity, inches per hour (See Section 3.1.4)
3.2.2 Colorado Urban Hydrograph Procedure
For basins larger than 200 acres, the design storm runoff should be analyzed by deriving
synthetic unit hydrographs. It is recommended that the Colorado Urban Hydrograph
Procedure be used for such ana!ysis. This procedure is detailed in the Urban Storm Drainage
Criteria Manual, Volume 1, Section 4.
MAY 1984 3-5 DESIGN CRITERIA
APPENDIX III
Backup Diagrams and Exhibits
Table 3-3; Rational Method Runoff Coefficients for Composite Analysis
Table 3-4; Rational Method Frequency Adjustment Factors
Figure 3-2; Estimate of Average Flow Velocity for Use with the Rational Formula
Figure 3-1; City of Ft. Collins Rainfall Intensity Duration Curve
March 24, 1997
Project No: 1466-14-96
Re: EROSION CONTROL SECURITY DEPOSIT REQUIREMENTS:
Lots 1 & 2, Block 2, Replat (No. 1) of Evergreen Park; Fort Collins, Colorado
A. An erosion control security deposit is required in accordance with City of Fort Collins
policy (Chapter 7, Section C: SECURITY; page 7.23 of the City of Fort Collins
Development Manual). In no instance shall the amount of the security be less than
$1000.00.
1. According to current City of Fort Collins policy, the erosion control security deposit
is figured based on the larger amount of 1.5 times the estimated cost of installing
the approved erosion control measures or 1.5 times the cost to re -vegetate the
anticipated area to be disturbed by construction activity.
a. The cost to install the proposed erosion control measures is approximately
$ 1,875.00 Refer to the cost estimate attached in Appendix I. 1.5 times the cost
to install the erosion control measures is $ 2,812.50
b. Based on current data provided by the City of Fort Collins Stormwater Utility,
and based on an actual anticipated net affected area which will be disturbed by
construction activity (approximately 2.12 acres), we estimate that the cost to re -
vegetate the disturbed area will be $ 1,126.21 ($ 531.00 per acre x 2.12 acres).
1.5 times the cost to re -vegetate the disturbed area is $ 1,689.31. The $ 531.00
per acre for re -seeding sites of less than 5 acres was quoted to us by the City of
Fort Collins Stormwater Utility staff.
CONCLUSION:
The erosion control security deposit amount required for Lots 1 & 2, Block 5, Replat (No.
1) of Evergreen Park will be $2,812.50
4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-031 1
March 24, 1997
Project No: 1466-14-96
Basil Hamdan
City of Fort Collins Stormwater Utility
P.O. Box 580
Ft. Collins, Colorado 80522
Re: Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park; Fort Collins, Colorado
Dear Basil,
Attached is the erosion control security deposit estimate for Lots 1 & 2, Block 5, Replat (No. 1)
of Evergreen Park.
ESTIMATE 1:
600 LF of Silt Fence @ $ 3.00 per LF
1 - Gravel Inlet Filter ® $ 75.00 each
TOTAL ESTIMATED COST:
ESTIMATE 2:
re -vegetate the disturbed area of 2.12 acres at $ 531.00 per acre
TOTAL ESTIMATED COST:
$ 1,800.00
$ 75.00
$ 1,875.00
x 1.50
$ 2,812.50
$ 1,126.21
$ 1,126.21
x 1.50
$ 1,689.31
In no instance shall the amount of the security be less than $ 1,000.00. Therefore, the total
required erosion control security deposit for Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen
Park will be $ 2,812.50
' - can at 226-5334.
Shear Engineering Corporation
BW S / meo
cc: Premier Custom Homes
Dave Stringer, City of Fort Collins
4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-031 1
APPENDIX II
Erosion Control Calculations
Erosion Control Sequencing schedule
Erosion Control security deposit estimates
SHEAR ENGINEERING CORPORATION
PAGE e
OUTLET STRUCTURE FOR LOT 1 & 2 EVERGREEN PARK
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE: 03/24/97
PROJECT NO 1466-14-96 BY MEG
PROJECT LOCATION :FORT COLLINS PILE: PREMOUT
INPUT FOR OUTLET STRUCTURE
LOWER ORIFICE DIAM. (ft) = 0.33 WHIR TYPE BROADCRESTED DETERMINE ORIFICE SIZE
LOWER ORIFICE INV. (ft) = 70.34 WEIR LENGTH (ft) = 4.00 FOR MINOR STORM
LOWER ORIFICE CORP. (Cl) = 0.65 WEIR INVERT (ft) = 71.75 Q= CA(2gH)^O.5
UPPER ORIFICE DIAM.(ft) = NA WHIR COHF. (CW) = 2.60 A = Q/(C(2gH)^0.5
UPPER ORIFICE INV. (ft) = NA TOP OF BERM (ft) = 72.02 H (ft) = 1.35
UPPER ORIFICE COBF. (Cu) = NA INIT. DELTA (ft) = 0.66 C = 0.65
100 YR. RELEASE RATE (cfs)= 0.49 DELTA HEAD (ft) = 0.50 Q (cfe)= 0.49
CHANNEL WIDTH (ft) = 4.00 100 YR WSBL REQUIRED (£t)- 71.69 A (sf) = 0.08
CHANNEL DEPTH (ft) = 0.50 OVER FLOW YES R (ft) = 0.160
PIPE SLOPE (t) = 0.005 WHIR TYPE BROADCRESTED D (ft) = 0.321
MANNINGS n = 0.016 WEIR LENGTH (ft) = 100.00 USE 0.33' DIAMETER (4")
WHIR INVERT (ft) = 72.02
WHIR COHF. (Cwo) = 2.60
*rrrrr+x r+rrrrrrt rr+rrrrr *OUTPUT* ***rr**r ***rrrrr trtr+r+rx r+rrrr+*
CHANNEL AREA (SF) 2.00 WETTED PERIMETER = 5.00 FEET
HYD. RAD (FT) = 0.400 FEET R^2/3 = 0.5427
OUTLET CHANNEL CAPACITY = 0.71 CPS
LOWER ORIFICE AREA (A) = 0.0855 SQUARE PERT
UPPER ORIFICE AREA (A) = 0.0000 SQUARE FEET
rrtrtrrxrrtrrrrrrrxrr+rr*+rrrrr+rtrrrrrxrtrr+rrtxrtrrrrtrtrr+rrrxtrrrrrrrrrrtr+rxxtrtrrtrr+rrrr**rrtrrrrr****rrrrr***r
LOWER ORIFICE UPPER ORIFICE PRIMARY WHIR OVERFLOW SPILLWAY
rrrrr*rt **rrrrr **rrrrr rrrr rrr xr+rrr+ •rrr+trt +rrrttr r+r:rrr rr+rrrr rr+rrrr
HEAD HEAD HEAD SUB HEAD '
BLEV. OVER LOWER OVER UPPER OVER WHIR TOTAL OVER WHIR TOTAL ELEV.
LOWER ORIFICE UPPER ORIFICE WHIR FLOW PLOW WEIR FLOW FLOW
ORIFICE FLOW ORIFICE FLOW
ft ft cfe ft cfe ft cfe cfe ft cfe cfs ft
70.34 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 70.34
71.00 0.49 0.31 0.00 0.00 0.00 0.00 0.31 0.00 0.00 0.31 71.00
71.50 0.99 0.45 0.00 0.00 0.00 0.00 0.4S 0.00 0.00 0.45 71.50
72.00 1.49 0.55 0.00 0.00 0.25 1.30 1.85 0.00 0.00 1.85 72.00
72.02 1.51 0.55 0.00 0.00 0.27 1.46 2.01 0.00 0.00 2.01 72.02
72.10 1.59 0.56 0.00 0.00 0.35 2.15 2.72 0.08 5.88 8.60 72.10
71.69 1.18 0.49 0.00 0.00 0.00 0.00 0.49 0.00 0.00 0.49 71.69
71.75 1.24 0.50 0.00 0.00 0.00 0.00 0.50 0.00 0.00 0.50 71.75
71.69 1.18 0.49 0.00 0.00 0.00 0.00 0.49 0.00 0.00 0.49 71.69
r xrtrrrrr *rrrrr*r rrrrrrrr rrr+rrrr rrrrrtrrr rrrtxrrr rrxtrtrrr rxrrtr+rx rrrrrrrtr rrr*rtrrr +rrrrrrr *rrrrr**
ORIFICE EQUATION: CA(2gH)'1/2 WEIR PLOW EQTN. : CWLH^3/2
NOTE: HEAD OVER ORIFICE = HEAD OVER CENTER OF ORIFICE
APPROXIMATE W.S.EL. FOR Qrel = 0.49 CPS = 71.69 OK
FREEBOARD = 0.33 REQUEST VARIANCE
CONCLUDE: OUTLET STRUCTURE IS ADEQUATE
SHEAR ENGINEERING CORPORATION
PAGE 7
AVERAGE END AREA METHOD
FOR WEST DETENTION POND
VOLUMES
PROJECT :LOTS 1 & 2 EVERGREEN PARK DATE: 03/24/97
PROJ. NO:1466-14-96
LOCATION:BLUE SPRUCE DRIVE BY MBO
NOTES FILE: PRSMAVG
CONSTANT: 65 = 1 SQ IN. FIRST EVEN CONTOUR 71 FEET
INVERT 70.34 FEET TOP BLEV 72 FEET
INCREMENT 1 FOOT SCALE: 1• = 30 FEET
t trtrtrrrr •f rrrttr trtttttt rtrtxrtttrtr rf rfrr+f r+fr+t+t xtrxxxxrt xrxfrrrr rf rrf rfr
STAGE BLHV PLANI- AREA AREA VOLUME CUM. CUM. CUM.
METER (Al) (A2) (V1) VOLUME VOLUME VOLUME
ft ft READING sq in sq ft cf cf cy ac-ft
+:rtrrrfr rrrf rrr+ xfrtrtf rff rrf rrf rf rf+fr+f+ +rt+r+tt trtxftxtr •r•rrrrf rrffr•rr
0.00 70.34 0 0.00 0 0 0 0 0.00
0.66 71.00 158 2.43 2188 722 722 27 0.02
1.66 72.00 1146.5 17.67 15902 9045 9767 362 0.22
---------------------------------------------------------------------------------
FORMULAH:A1= (PLANIMETBR READING)/CONSTANT
A2= (Al) *SCALE SQUARED
VOLUME REQUIRED WITH 1/2 ROW = 7006 CP
WATER SURFACE ELEVATION REQUIRED = 71.69 FEET
FINISHED FLOOR ELEVATION = 72.76 FEET LOT 2
FINISHED FLOOR ELEVATION = 73.35 PBBT LOT 1
SEPARATION PROVIDED = 1.07 FEET REQUEST VARIANCE BECAUSE < 1.5 PBBT
MAXIMUM WATER DEPTH = 1.35 FEET REQUEST VARIANCE BECAUSE > 1.0 FOOT
FREEBOARD PROVIDED = 0.31 FEET REQUEST VARIANCE BECAUSE < 1.0 FOOT
CONCLUDB:SET PRIMARY WHIR HEIGHT AT 71.76
POND WILL BE ADEQUATE
SHEAR ENGINEERING CORPORATION
PAGE 6
DETENTION VOLUME REQUIRED FOR
DETENTION POND OF LOT 1 & 2 EVERGREEN PARK
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE: 03/24/97
PROJ.NO. 1466-14-96 BY MEO
FILE: PREMCUHP NOTE: 1/2 ROW INCLUDED IN AREA
CUMULATIVE RUNOFF METHOD
FOR
SIZING DETENTION PONDS
DESIGN STORM: 100 YEAR RUNOFF COEFFICIENT 0.89
RELEASE RATE: 0.49 CPS AREA: 1.05 ACRES
RELEASE RATE IS BASED ON 0.47 CPS PER ACRE OF CONTRIBUTING AREA
INITIAL TIME: 5 MINUTES TIME INCREMENT: 5 MINUTES
CONTRIBUTING AREA
ONSITE SUBBASIN = Aw AREA = 0.92 ACRES
ROW AREA = 0.13 ACRES
INFLOW INFLOW RELEASE STORAGE STORAGE
TIME TIME INTENSITY RATE VOLUME VOLUME VOLUME VOLUME
min Dec iph cfs cf cf cf ac-ft
rt+ttxxrrxtl ttl txxttl ttttt+trttttYtf t+tt+txtfi ttt4rfffif tf tfi tfitttrftttit x.
5 300 9.30 8.69 2607.3 148.1• 2459.2 0.06
10 600 7.14 6.67 4003.4 296.1 3707.3 0.09
15 900 6.06 5.66 5096.8 444.2 4652.6 0.11
20 1200 5.21 4.87 5842.5 592.2 5250.3 0.12
25 1500 4.63 4.33 6490.1 740.3 5749.9 0.13
30 1800 4.20 3.92 7064.8 888.3 6176.5 0.14
35 2100 3.81 3.56 7476.9 1036.4 6440.6 0.15
40 2400 3.60 3.36 8074.1 1184.4 6869.7 0.16
45 2700 3.28 3.07 8275.9 1332.5 6943.5 0.16
50 3000 3.02 2.82 8466.6 1480.5 6986.1 0.16
55 3300 2.80 2.62 8634.8 1628.6 7006.2 0.16 ***
60 3600 2.60 2.43 8746.9 1776.6 6970.3 0.16
65 3900 2.43 2.27 6856.3 1924.7 6931.6 0.16
70 4200 2.30 2.15 9027.3 2072.7 6954.6 0.16
75 4500 2.17 2.03 9125.4 2220.8 6904.6 0.16
80 4800 2.07 1.93 9285.2 2368.8 6916.4 0.16
85 5100 1.96 1.83 9341.3 2516.9 6824.4 0.16
90 5400 1.87 1.75 9436.6 2664.9 6771.7 0.16
95 5700 1.77 1.65 9428.2 2813.0 6615.2 0.15
100 6000 1.70 1.59 9531.9 2961.0 6570.9 0.15
105 6300 1.63 1.52 9596.4 3109.1 6487.3 0.15
110 6600 1.57 1.47 9683.3 3257.1 6426.2 0.15
115 6900 1.50 1.40 9672.1 3405.2 6266.9 0.14
120 7200 1.44 1.35 9688.9 3553.2 6135.7 0.14
trrrtttt+xrtrttr+xrxfifrrttrrtttrr+r+rfixxrx+xtffrtfftrtrrxtf tff tf ttf rx+rf
DETENTION VOLUME REQUIRED = 7006.23 cf = 0.16 ac-ft
NOTE: RELEASE RATE BASED ON AREA OF 1.05 ACRES & 0.47 CPS/ACRE.
SHEAR ENGINEERING CORPORATION
DEVELOPED
PLOW TO CONCENTRATION POINT 2
FROM SUBBASIN As & ROWNORTH
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE 03/24/97
LOCATION:FORT COLLINS PROS. NO.1466-14-96
PILE: PREMRAT BY MHO
AREA (A)= 1.290 ACRES
RUNOFF COBF. (C)
PAGE S
2 YEAR 10
YEAR
100
YEAR
C = 0.65
0.65
0.81
SEE SPREAD SHEET ATTACHED ON PAGE
2
TIME OF CONCENTRATION (Tc)
OVERLAND TRAVEL TIME (Ti)'
LENGTH =? FEET SLOPE
_?
%
2 YEAR 10
YEAR
100
YEAR
C _? ?
?
Ti (min)= 0.00
0.00
0.00
TRAVEL TIME (Tt)=L/(60*V)
PLOW TYPE
L (ft) _? S (%) _?
?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (&) _?
?
•
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S ($) _?
?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (%) _?
?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (%) _?
?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S 00 _?
?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (%) _?
?
V (fps)
_?
Tt(min)=
0.00
NOTE: ALL VELOCITIES TAKEN
FROM FIGURE
3-2
TOTAL TRAVEL TIME
(min) =
0.00
Tc =Ti+TOTAL TRAVEL TIME
2 YEAR 10
YEAR
100
YEAR
Tc (min)= 0.00
0.00
0.00
USE Tc = 30
10
10
assumed
verify at
final
INTENSITY (I) (iph)
2 YEAR
10 YEAR
100 YEAR
I
= 2.54
4.45
7.14
NOTE:
INTENSITIES TAKEN
FROM FIGURE
3-1
RUNOFF
(Q= CIA) (cfe)
2 YEAR
10 YEAR
100 YEAR
Q
= 2.13
3.72
7.47
CONCLUDE: RELEASE UNDETAINED INTO EVERGREEN WEST POND
SHEAR ENGINEERING CORPORATION
DEVELOPED
FLOW TO CONCENTRATION POINT 1
FROM SUBBASIN Aw & ROWSOUTH
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE 03/24/97
LOCATION:FORT COLLINS PROJ. NO.1466-14-96
FILE: PREMRAT BY MHO
AREA (A)= 1.050 ACRES
RUNOFF COEF. (C)
PAGE 4
2 YEAR
10 YEAR
100
YEAR
C = 0.71
0.71
0.89
SSE SPREAD SHEET ATTACHED
ON PAGE
2
TIME OF CONCENTRATION (TO
OVERLAND TRAVEL TIME (Ti)
LENGTH =? FEET
SLOPE _?
k
2 YEAR
10 YEAR
100
YEAR
C =?
?
?
Ti (min)= 0.00
0.00
0.00
TRAVEL TIME (Tt)=L/(60*V) FLOW TYPE
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
L (ft) _? S (k)
_? ?
V (fps)
_?
Tt(min)=
0.00
NOTE: ALL VELOCITIES TAKEN FROM FIGURE
3-2
TOTAL TRAVEL TIME
(min) =
0.00
Tc =Ti+TOTAL TRAVEL TIME
2 YEAR
10 YEAR
100
YEAR
Tc (min)= 0.00
0.00
0.00
USE Tc = 10
10
10
assumed
verify at
final
INTENSITY (I) (iph)
2 YEAR
10 YEAR
100
YEAR
I = 2.54
4.45
7.14
NOTE: INTENSITIES TAKEN FROM FIGURE
3-1
RUNOFF (Q= CIA) (C£s)
2 YEAR
10 YEAR
100
YEAR
Q = 1.91
3.34
6.69
CONCLUDE:DETAIN IN PARKING LOT
RELEASE RATE = 0.47
cfs/acre*
ACREAGE =
0.49 CPS
0
SHEAR ENGINEERING CORPORATION
HISTORIC PAGE 3
PLOW TO CONCENTRATION POINT 2
PROM SUBBASIN Aw & As
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE 03/24/97
LOCATION:FORT COLLINS PROJ. NO.1466-14-96
PILE: PREMRAT BY MRO
AREA (A)= 2.120 ACRES
RUNOFF CORP. (C)
2 YEAR
10 YEAR
100
YEAR
C = 0.20
0.20
0.25
LAWN CLAY SOIL, FLAT
TIME OF CONCENTRATION (TO
OVERLAND TRAVEL TIME (Ti)
LENGTH = 400 FEET
SLOPE = 1.00
$
2 YEAR
10 YEAR
100
YEAR
C = 0.20
0.20
0.25
Ti (min)= 33.66
33.66
31.79
TRAVEL TIME (Tt)=L/(60*V) FLOW TYPE
L (ft) _? S ($)
_? ?
L (ft) _? S (%)
_? ?
L (ft) _? S ($)
_? ?
L (ft) _? S ($)
_? ?
L (ft) _? S ($)
_? ?
L (ft) _? S ($)
_? ?
L (ft) _? S ($)
_? ?
NOTE: ALL VELOCITIES TAKEN FROM FIGURE
3-2
Tc =Ti+TOTAL TRAVEL TIME
2 YEAR
10 YEAR
100
YEAR
Tc (min)= 33.66
33.66
31.79
USE Tc = 33.5
33.5
32
INTENSITY (I) (iph)
2 YEAR
10 YEAR
100
YEAR
I = 1.47
2.60
4.20
NOTE: INTENSITIES TAKEN PROM FIGURE
3-1
RUNOFF (Q= CIA) (cfs)
2 YEAR
10 YEAR
100
YEAR
Q = 0.62
1.10
2.23
V (fps) _?
Tt(min)=
0.00
V (fps) _?
Tt(min)=
0.00
V (fps) _?
Tt(min)=
0.00
V (fps) _?
Tt(min)=
0.00
V (fps) _.
Tt(min)=
0.00
V (fps) _?
Tt(min)=
0.00.
V (fps) _?
Tt(min)=
0.00
TOTAL TRAVEL TIME
(min) =
0.00
CONCLUDE: HISTORIC FLOW TO EVERGREEN WEST DETENTION POND
DEVELOPMENT WILL REDUCE CONTRIBUTING AREA TO POND TO MATCH
MASTER PLAN BASIN DELINEATION AS BEST AS POSSIBLE
SHEAR ENGINEERING CORPORATION
SUBBASIN BREAKDOWN PAGE 2
PROJECT: LOT 1 & 2 EVERGREEN PARK DATE 03/24/97
LOCATION:FORT COLLINS BY MEO
PROD. NO.1466-14-96
TOTAL SITE AREA = 2.12 ACRES Ae = 1.20 ACRES- SITE ONLY
TOTAL BASIN AREA = 2.34 ACRES Aw = 0.92 ACRES- SITE ONLY
SUB BASINS
Aw Ae ROW ROWNORTH ROWSOUTH BASIN
ASPHALT 0.39 0.53 0.15 0.06 0.09 0.92
CONCRETE 0.02 0.02 0.03 0.01 0.02 0.04
GRAVEL 0.00 0.03 0.00 0.00 0.00 0.03
ROOFS 0.20 0.14 0.00 0.00 0.00 0.34
LAWNS,SANDY SOIL
FLAT < 2% 0.00 0.00 0.00 0.00 0.00 0.00
AVERAGE 2 TO 7% 0.00 0.00 0.00 0.00 0.00 0.00
STEEP > 7% 0.00 0.00 0.00 0.00 0.00 0.00
LAWNS, HEAVY SOIL:
FLAT < 2% 0.31 0.48 0.04 0.02 0.02 0.79
AVERAGE 2 TO 7% 0.00 0.00 0.00 0.00 0.00 0.00
STEEP > 7% 0.00 0.00 0.00 0.00 0.00 0.00
TOTAL 0.92 1.20 0.22 0.09 0.13 2.12
RUNOFF COEFFICIENT SUB BASINS
Aw Ae ROW ROWNORTH ROWSOUTH BASIN
C2-CID 0.70 0.64 0.81 0.78 0.83 0.66
C100 = 1.25*C2 0.87 0.80 1.00 0.98 1.00 0.83
DESIGN POINT AREA C2 C100
1 1.05 0.71 0.89
2 1.29 0.65 0.81
PLOW SUMMARY FOR LOT & 2 EVERGREEN PARK PAGE 1
0
DESIGN CONTRIBUTING AREA C2 C10 C100 Tc Tc I2 ISO I100 Q2 Q10 Q100 DESIGN
POINT SUB 2,10 100
BASINS) ac. min. min iph iph iph cfe cfe cfe
w rtrtwwrtt+xrtwwrrrxx+xrtwwrtwrrtwrrr+♦rxxxrtrtwrrrrrr+xwwrrrr+ttxxrtwrtrt+r+++xrxrwxwxrtxxxrtwxxtxxxrtxrrtiwrrwrrw
DEVELOPED SITE
1 Aw & ROWSOUTH 1.05 0.71 0.71 0.89 10.00 10.00 2.54 4.45 7.14 1.91 3.34, 6.69 DETAIN
2 Ae & ROWNORTH 1.29 0.65 0.65 0.81 10.00 0.00 2.54 4.45 7.14 2.13 3.72 7.47 UNDET
HISTORIC SITE
2 Aw & Ae 2.12 0.20. 0.20 0.25 33.50 32.00 1.47 2.60 4.20 0.62 1.10 2.23 HISTORIC
APPENDIX I
Storm Drainage Calculations
PAGE 8
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
VI. VARIANCE REQUEST:
A. Variance from City of Fort Collins requirements (Continued)
2. The constraints on the grading caused by the site topography and the ADA requirements
do not allow us to provide the required freeboard.
3. The detention requirements within the Evergreen - Greenbriar basin and the topography
of the site do not allow us to meet the separation or maximum depth requirements.
VII. CONCLUSIONS:
A. Compliance with Standards
1. All drainage analysis has been performed according to the requirements of the City of
Fort Collins Storm Drainage Criteria Manual and the City of Fort Collins policy.
2. All Erosion Control design complies with the City of Fort Collins Erosion Control
Reference Manual and generally accepted practices.
B. Drainage Concept
1. The drainage design for Lots 1 and 2, Block 5, Replat (No: 1) of Evergreen Park is in
accordance with the City of Fort Collins requirements, except as noted in the variance
requests, and the recommendations of the Amended Greenbriar/Evergreen Master
Drainage Plan.
2. There will be no adverse downstream effects due to the development of the site.
VIM REFERENCES:
1. Fort Collins Storm Drainage Criteria Manual
2. Urban Drainage and Flood Control District Drainage Criteria Manual
3 Greenbriar-Evergreen Park Master Drainage Plan; Engineering Professionals
4. Final Utility plans for MAJOR STORM DRAINAGEWAY FOR EVERGREEN PARK;
Engineering Professionals; EPI Project No: 97-1; plans dated March, 1981
5. The Amended Greenbriar-Evergreen Basin Master Drainage Plan; Lidstone & Anderson,
Inc.; Project No COTST05.4; dated May, 1996
PAGE 7
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
V. EROSION CONTROL:
A. General Concept
1. Erosion control measures will be as identified on the Drainage and Erosion Control Plan.
2. An erosion control security deposit is required in accordance with City of Fort Collins
policy (Chapter 7, Section C : SECURITY; page 7.23 of the City of Fort Collins
Development Manual). In no instance shall the amount of the security be less than
$ 1000.00.
3. According to current City of Fort Collins policy, the erosion control security deposit is
figured based on the larger amount of 1.5 times the estimated cost of installing the
approved erosion control measures or 1.5 times the cost to re -vegetate the anticipated
area to be disturbed by construction activity.
4. Refer to the security deposit document located in Appendix Il of this report.
B. Specific Details
1. Temporary erosion control measure to be installed on the site during construction
include:
a. Silt fence along the south and east property lines
b. Gravel inlet filter at the outlet device on the west side of the site.
VI. VARIANCE REQUEST:
A. Variance from City of Fort Collins requirements
1. With this report, the developer is formally requesting the following variances from:
a. the requirement that one (1') foot of freeboard be provided in the detention pond,
b. the requirement that a foot and a half (1.5') of vertical separation between the 100-
year water surface elevation and the proposed finished floor of the buildings be
provided. We are requesting that the minimum separation be reduced to one (1.0)
foot.
c. the requirement that the maximum depth of water in a parking lot be less than one
(1') foot. We are requesting that the maximum depth be increased to one and a half
(1.5') feet.
PAGE 6
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
IV. DRAINAGE FACILM DESIGN:
B. Specific Details (continued)
3 The detention pond in the western portion of the site is sized using the Cumulative
Runoff method.
a. The runoff coefficient utilized with the Cumulative Runoff method for sizing the
detention pond is 0.89.
b. The release rate from the western detention pond is 0.50 cfs. This is based on the
0.47 cfs/acre recommended by the amended Greenbriar-Evergreen Master Drainage
Plan.
4 The area used to determine the release rate from the western pond consists of the 1/2
R.O.W. of Blue Spruce Drive and sub -basin Aw. The total area equals 1.05 acres.
(Refer to page 6 in the calculations).
a. The required detention pond storage volume according to the Cumulative Runoff
method, utilizing a runoff coefficient of 0.89 is 7006 cubic feet. Refer to page 6,
Appendix I for the detention pond volume calculations.
b. The actual volume provided in the detention pond is 9767 cubic feet. Refer to page 7,
Appendix I for the Stage -Storage calculations. The required 100-year W.S.EI based
on the stage storage curve is 71.69 feet.
c. The finished floor elevation for the building on lot 1 is set at an elevation of 73.35
feet.
d. The finished floor elevation for the building on lot 2 is set at an elevation of 72.76
feet.
e. The estimated 100-Year Water Surface Elevation (W.S.EI.) in the pond is 71.76 feet.
Refer to page 8, Appendix I for the hydraulic analysis of the outlet structure.
f. The freeboard provided is 0.26 feet.
g. The separation provided between the estimated 100-Year W.S.EI. and the finished
floor elevation of the building on lot 1 is 1.59 feet.
h. The separation provided between the estimated 100-Year W.S.EI. and the finished
floor elevation of the building on lot 2 is 1.0 feet.
5. The outlet structure will consist of a headwall with a 15" pipe and an orifice plate with a
4" diameter hole at the upstream invert. A 4' wide curbed channel and a sidewalk culvert
will also be installed to convey the stormwater to Blue Spruce Drive. Refer to page 8,
Appendix I for the hydraulic analysis of the outlet structure.
PAGE 5
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
IV. DRAINAGE FACILITY DESIGN:
A. General Concept
1. The stormwater from the site will be directed to the east and west by creating a high point
approximately 260 feet east of the west property line.
2. Detention pond release from the western portion of the property (sub -basin Aw) will
occur near the southwest corner of Lot 2.
a. The outlet will consist of curbed channel and sidewalk culvert to the flowline of the
existing Blue Spruce Drive curb and gutter.
b. A restriction device will reduce flows to Blue Spruce Drive and create a detention
pond in the parking area.
c. Flows are conveyed south in the Blue Spruce Drive flowline to Conifer Street.
B. Specific Details
1 A preliminary channel design was done for the channel on the north side of the site by
Lidstone and Anderson in the amended Greenbriar-Evergreen Master Drainage Plan. The
preliminary channel geometry, design flow and capacity are summarized below.
a.
Bottom width
b.
Marmings n
C.
Slope
d.
Side slopes
e.
Design Flow
f.
Depth
g.
Top width
h.
Flow depth
i.
Freeboard
j.
Flow capacity
= 30.0 feet
= 0.060
= 0.0025 ft/ft
= 4:1 (Run: Rise)
= 80.0 cfs
= 2.5 feet
= 50.0 feet
= 1.52 feet
= 0.98 feet
= 195.0 cfs
2 Channel cross sections done with this project indicate that the channel does not conform
to the original design by EPI or the design by Lidstone and Anderson done with the
Amended Greenbriar-Evergreen Master Drainage Plan.
PAGE 4
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
M. DRAINAGE AND EROSION CONTROL DESIGN CRITERIA:
B. Development Criteria Reference and Constraints
1. Previous studies which were considered include:
a. Greenbriar-Evergreen Park Master Drainage Plan; Engineering Professionals
b. The Amended Greenbriar-Evergreen Basin Master Drainage Plan; Lidstone &
Anderson, Inc.; Project No COTST05.4; dated May, 1996.
2. Blue Spruce Drive is developed and paved.
3. New American Disabilities Act (ADA) requirements affect the final parking lot grading
design. Maximum allowable design grades for handicap parking, and access from the
public right-of-way effect the drive and parking lot final grading which typically affects
detention volumes.
C. Hydrological Criteria
1. The Rational method (Q = CIA) was used to determine the pre -developed and post
development peak flows for the 10 and 100-year storm events (commercial
requirements).
2. The Cumulative Runoff Method was used to determine the required detention volume for
the portion of the property that will be located in basin 4U after development of the site.
a. The 100-Year storm was used as the design storm.
3. The release rate from the onsite detention pond located in the western portion of the site
is based on the requirements of the Amended Greenbriar-Evergreen Basin Master
Drainage Plan (0.47 cfs/acre).
a. The area used to size the pond consists of that portion of the site and 1/2 ROW of
Blue Spruce Drive which are located in Basin 4U as delineated on this Drainage and
Erosion Control plan
4. Stormwater from Basin 3B is released undetained to the Evergreen West regional
detention pond in accordance with the recommendations of the Amended Greenbriar-
Evergreen Basin Master Drainage Plan.
D. Hydraulic Criteria
1. Orifice and weir equations and coefficients suggested by the City of Fort Collins Storm
Drainage Criteria Manual were used.
PAGE 3
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
II. DRAINAGE BASINS AND SUB -BASINS:
B. Sub -Basin Description (continued)
5. Existing site grades indicate that historic flows are conveyed east and north towards the
Evergreen West detention pond and outfall channel which are located within Basin 3B of
the preliminary amended Greenbriar-Evergreen Master Drainage Plan.
6. We met with the City of Fort Collins Stormwater Utility to discuss the master plan basin
delineation and the actual basin delineation. The grading of the site will create a new
basin delineation between basin 4U and 3B. This new delineation will not affect the
overall areas of the basins as shown on amended Greenbriar-Evergreen Master Drainage
Plan.
7. There is an existing drainage channel along the north property line of Lot 1, Block 5
which conveys storm water from the storm sewer under Blue Spruce Drive to the
Evergreen West Pond.
a. The channel is located along the common property line of Lot 1, Block 5 of
Evergreen Park and Coachlight Plaza PUD.
b. There is an existing sixteen (16') foot Utility and Drainage easement along the south
side of the north property line of lot 1 as shown on the plat of Replat (No. 1) of
Evergreen Park.
c. There is an existing thirty (38') foot Utility and Drainage easement along the north
side of the south property line of lot 1 as shown on the replat of Coachlight Plaza
PUD.
III. DRAINAGE AND EROSION CONTROL DESIGN CRITERIA:
A. Regulations
1. All storm drainage design criteria from the City of Fort Collins Drainage Criteria Manual
was followed.
2. Storm Drainage design criteria modification was considered based on data provided by
City of Fort Collins Stormwater Utility personnel concerning conclusions presented with
the amended Greenbriar-Evergreen Park Master Drainage Plan.
3. All erosion control design criteria from the City of Fort Collins Erosion Control
Reference Manual.
PAGE 2
Final Drainage and Erosion Control Report
Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park
II. DRAINAGE BASINS AND SUB -BASINS:
B. Sub -Basin Description
1. According to the Amended Greenbriar-Evergreen Master Drainage Plan the western
portion of both lots are situated within Basin 4U (undeveloped) as defined on the
amended Greenbriar-Evergreen Basin Master Drainage Plan. See the Exhibit from the
amended Greenbriar-Evergreen Basin Master Drainage Plan included with the Drainage
and Erosion Control Plan in the stuffer envelope. Based on the existing site topography
the entire site should be situated in Basin 3B.
a. Page 20 of the draft of Amended Greenbriar-Evergreen Basin Master Drainage Plan
states the following:
BASIN 4U. The basin was assumed to be completely developed for commercial use
with an estimated imperviousness of 90 percent. On -site detention would be required
for this basin. The allowable release from this basin is 17 cfs, or 0.47 cfs/acre. The
designated release point for Basin 4U is the storm sewer and street along Conifer
Street which convey flows easterly to Pond 5 (conceptual). The detention volume
required for the basin, in order to meet the prescribed release rate, was estimated to be
6.4 acre feet.
2. According to the Amended Greenbriar-Evergreen Master Drainage Plan the eastern
portion of both lots are situated within Basin 3B as defined the amended Greenbriar-
Evergreen Basin Master Drainage Plan. See the Exhibit from amended Greenbriar-
Evergreen Park Master Drainage Plan included with the Drainage and Erosion Control
Plan in the stuffier envelope.
a. Page 19-20 of the draft of the Amended Greenbriar-Evergreen Basin Master Drainage
Plan states the following:
BASIN 3B. The basin was assumed to be developed for 37 percent commercial use,
and 63 percent residential housing at levels representing 11, 49 and 3 percent of the
entire basin for high, medium and low densities, respectively. The result is a
developed imperviousness of 63 percent. On -site detention would not be required for
this basin: storm water runoff would be transported to the existing Evergreen West
Pond. Overflow from this pond would enter the existing outlet channel which would
transport flow southerly to Pond 5 (conceptual).
3. All of Lot 1 is situated in Basin 3B based on the existing topography of the site and the
street. There is a high point located approximately 40' north of the south property line of
lot 1 and the existing site topography slopes to the east.
4. All of Lot 2 is is situated in Basin 3B based on the existing topography of the site.
PAGE 1
Final Drainage and Erosion Control Report
Lots 1 & 2,1 Block 5, Replat (No. 1) of Evergreen Park
L GENERAL LOCATION AND DESCRIPTION:
A. Location
1. Lots 1 and 2, Block 5, Replat (No. 1) of Evergreen Park is located in the Northeast One -
Quarter of Section 1, 17N, R69W of the 6th P.M., Ft. Collins, (Larimer County),
Colorado. These are existing platted lots.
2. More specifically, Lots 1 and 2, Block 5, Replat (No. 1) of Evergreen Park are located on
the east side of Blue Spruce Drive approximately 1000 feet north of Conifer Drive in the
Northeast part of Fort Collins, Colorado (See Vicinity Map).
a. Blue Spruce Drive is an existing street with sewer, water, curb and gutter and street
paving installed. These improvements were installed with the final utility plans for
Replat (No. 1) of Evergreen Park.
3. This project will consist of two (2) warehouse style buildings and the necessary parking
for the intended use.
B. Description of Property
1. There is an existing foundation on the site. This foundation will be removed and two (2)
buildings will be constructed. The remainder of the site is undeveloped. Existing ground
cover consists primarily of native dry land grasses.
2. The site area of lot 1 is approximately 54,087 square feet (1.24 acres).
3. The site area of lot 2 is approximately 38,300 square feet (0.88 acres).
4. An existing regional detention pond (Evergreen West Pond) and outfall channel is located
south and east of this property (See Drainage and Erosion Control Plan in stuffer
envelope).
5. There is an existing channel along the north property line of lot 1 which conveys
stormwater to the Evergreen West Pond.
6. There are no irrigation canals or systems located on or within 100' of the project site.
II. DRAINAGE BASINS AND SUB -BASINS:
A. Major Basin Description
1. The site is situated within the Greenbriar-Evergreen Drainage Basin as designated on the
City of Fort Collins Stormwater Basin Map. The Master Drainage Plan for the
Greenbriar-Evergreen Basin is currently being amended.
a. The Basin fee rate for the Greenbriar-Evergreen Basin is $ 10,000 per gross acre
according to the development fee section of . the City of Fort Collins Development
Manual. This may be reduced if detention is provided.
No Text
March 24, 1997 IZCNO6R
H E A A
INEERING
Project No: 1466-14-96 PORATION
Basil Hamdan
City of Ft. Collins Stormwater Utility
P.O. Box 580
Ft. Collins, Colorado 80524
Re: Lots 1 & 2, Block 5, Replat (No. 1) of Evergreen Park; Ft. Collins, Colorado
Dear Basil,
Enclosed, please find the Final Drainage and Erosion Control Report for Lots 1 & 2, Block 5,
Replat (No. 1) of Evergreen Park. The hydrology data and the hydraulic analysis presented in this
report complies with the requirements of the City of Fort Collins Storm Drainage Criteria Manual;
dated March, 1984, and the Erosion Control Reference Manual.
The report also complies with the recommendations of the Amended Greenbriar-Evergreen Basin
Master Drainage Plan; Lidstone & Anderson, Inc.; Project No COTST05.4; dated May, 1996.
If you have any questions or comments, please call me or Mark Oberschmidt at 226-5334.
Sincerely,
Brian W. Shear, P.E.
Shear Engineering Corporation
BWS / meo
cc: Premier Custom Homes
4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-031 1
Final Drainage and Erosion Control Report
for
LOTS 1 & 2, BLOCK 5, REPLAT (NO. 1) OF EVERGREEN PARK
Fort Collins, Colorado
Prepared for:
Premier Custom Builders,,Inc.
401A South Link Lane
Ft. Collins, Colorado 80524
1N5 TEAL ZU MITTAL
Prepared by:
SHEAR ENGINEERING CORPORATION
Project No: 1466-14-96
DATE: March, 1997
4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-031 1