HomeMy WebLinkAbout05 - Design Report - Baxter Meadow Ph 2A - Addendum DESIGN REPORT ADDENDUM
BAXTER MEADOWS
PHASE 2A
BOZEMAN, MONTANA
November 10, 2005
Prepared for.•
BAXfER MEADOWS, LLC
Prepared by.,
Thomax, [)van k- Hoski"s,Inc. I THOMAS, DEAN AND HOSKINS, INC.
TD &14-1)- 215 W MENDENHALL, SUITE C-1
Eaginearingc� � t: Y '.` ' BOZEMAN, MT 59715
Project No. B05-016-021
Introduction
The purpose of this report is to support design alterations that have occurred for Baxter
Meadows Phase 2A since the original Phase 2 report submitted by Robert Peccia and Associates
(RPA), October 2003. This report documents changes occurring to storm drain systems in Phase
2A. Water and sewer systems have been vertically adjusted to assist in raising the road grades,
but the basis of design has come from the original Peccia plans. All other aspects of this design
shall adhere to the original design.
The Baxter Meadows subdivision is located in the northeastern area of the City of Bozeman,
Montana. The project is bounded by Davis Lane on the east, Oak Street on the south, Harper's
Puckett to the west, and Cattail Street on the north. Phase 2A is enclosed to the south by Baxter
Lane, west by Vaquero Parkway, north by Equestrian Street, and east by Caballo Avenue.
Design Report
Stormwater
The original design report broke Phase 2 into seven distinct drainage basins each flowing to its
respective pond. Phase 2A alterations have impacted basins 2 and 3. Master planning by PC
Development called for pond 2 to be eliminated. To facilitate this, runoff from basin 2 shall be
piped directly to pond 3. See attached map in appendix.
Stormwater Conveyance
PVC pipe with a minimum cover of 3' shall be used throughout the project in accordance with
City standards. All inlets shall conform to City of Bozeman Standard Drawing number 02720-1A.
Neenah R-3067 grates shall be utilized in all locations. All inlets and pipes have been sized for
the 25-year event. Inlets locations shall adequately collect water to limit the water surface
elevation to a max of .3'within the flowline.
Pipe flow analysis was conducted for the 25-year event. Time of concentrations and "C" values
were per RPA calculations and were not revised. Flows were generated via the rational method
and flow capacity was checked using Manning's equation. All calculations can be seen in the
appendix.
Stormwater Detention
Stormwater ponds are used to provide detention so that the peak outflow after development is
less than or equal to the peak outflow from the property before development. The original Pond
3 was built in conjunction with the Tracker Building project. Recently, the pond was altered to
make it more aesthetically pleasing. The new pond shall have 13,029 cf of storage.
Original calculations by Peccia derived a required volume of 1264 cf for Basin 2 and 10,882 cf for
Basin 3. By combining the areas and recomputing required volume we derived 12,824 cf. At this
time, we believe that the existing pond will be adequate for this increase in runoff.
APPENDIX
ORIGINAL STORM DRAIN CALCULATIONS
ROBERT PECCIA & ASSOCIATES
OCTOBER 2003
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Baxter Meadows-Phase 11
Detention Basin 2
Design Storm Frequency 10 yr
Basin Area(Ac) 2.17
Pro-Development Coefficient C Post-Development Coefficient C
Area(Ac) C .Area(Ac) C
Open Space 2.17 0.20 Open Space 0.20
Med.Res. 0.35 Med.Res. 0.35
Dense Res. 0.50 Dense Res. 2.17 0.50
Comm.Neigh. 0.60 Comm.Neigh. 0.60
Comm.Down 0.80 Comm.Down 0.80
Industrial 0.80 Industrial 0.80
Total Area: 2.17 Composite C: 0.2 Total Area: 2.17 Composite C: 0.5
Pre-Development Post-Development
Runoff Distance 500 it Runoff Distance 650 It
Average Slope 1.20% Average Slope 0.90%
Time of Concentration 36 min Time of Concentration 32 min
Average Rainfall Intensity 0.89 Inft Average Rainfall Intensity 0.96 Irdhr
Maximum Runoff 0.39 cis Maximum Runoff 1.04 cis
�I
Stone Intensity Developed Developed Undeveloped Required
Duration 10 Yr Flow Runoff Runoff Storage
(minl pnAu) (cfs) (cf) (CO (cf)
1 6 3.22 3.49 1048 116 931
10 2.05 2.23 1335 232 1103
15 1.68 1.71 1639 348 1190
20 1.31 1.42 1702 466 1237
25 1.13 1.23 1840 581 1259
36 0.91 0.99 2070 813 1257
40 0.83 0.90 2169 929 1240
46 0.77 0.84 2260 1045 1215
50 0.72 0.78 2345 1161 1184
55 0.68 0.13 2425 1278 1147
60 0.64 0.69 2500 1394 1106
65 0.61 0.66 2571 1510 1061
70 0.58 0.63 2638 1626 1012
75 0.55 0.60 2703 1742 961
80 0.53 0.58 2765 1858 906
85 0.51 0.55 2824 1974 850
90 0.49 0.63 2581 2091 790
95 0.47 0.62 2936 2207 729
100 0.46 0.50 2989 2323 666
105 0.44 0.48 3041 2439 602
110 0.43 0.47 3091 2555 535
116 0.42 0.46 3139 2671 468
120 0.41 0.44 3186 2787 399
125 0.40 0.43 3232 2904 328
130 0.39 0.42 3277 3020 257
135 0.38 0.41 3320 3136 184
140 0.37 0.40 3363 3252 111
145 0.36 0.39 3404 3308 36
150 0.35 0.38 3445 3484 -39
Minimum Basin Area
Minimum Volume= 1264 cf
Minimum Area(18"basin depth) 843 sf Actual Area(shaped to drain)= 1685 sf
Minimum Area for Sediment Control->145 of per 1 cfs
Peak Developed Flow-> 1.09 cis
Minimum Area= 158 of
I
Baxter Meadows-Phase II
Detention Basin 3
Design Storm Frequency 10 yr
Basin Area(Ac) 12.15
it
Pro-Development Coefficient C Post-Development Coefficient C
Area(Ac) C Area(Ac) C
Open Space 12.16 0.20 Open Space 0.20
Mod.Res. 0.35 Mod.Res. 0.35
Dense Res. 0.50 Dense Res. 3.15 0.50
Comm.Neigh. 0.60 Comm.Neigh. 9 0.60
Comm.Down 0.80 Comm.Down 0.80
Industrial 0.80 Industrial 0.80
Total Area: 12.15 Composite C: 0.2 Total Area: 12.16 Composite C: 0.57
Pre-0evelopment Post-Development
Runoff Distance 1300 ft Runoff Distance low it
Average Slope 0.80 % Average Slope 0.50 %
i Time of Concentration 87 min Time of Concentration 38 min
Average Rainfall Intensity 0.80 haft Average Rainfall Intensity 0.86 INhr
Maximum Runoff 1.45 ofs Maximum Runoff 8.01 cfs
Storm Intensity Developed Developed Undeveloped Required
Duration 10 Yr Flow Runoff Runoff Storage
(min) (INfv) (cfs) (cf) (co (cf)
' 5 3.22 22.46 6735 434 6300
10 2.05 1431 8684 869 7715
15 1.58 10.99 9892 1303 8690
20 1.31 9.12 10940 1737 9203
25 1.13 7.89 11829 2171 9668
30 1.00 7.00 12609 2606 10003
35 0.91 6.34 13308 3040 10208
40 0.83 5.81 139" 3474 10470
45 0.77 5.38 14531 3908 10623
50 0.72 5.03 15077 4343 10734
65 0.68 4.72 15588 4777 10811
60 0.64 4.46 16070 5211 10856
70 0.58 4.04 16961 6080 10882
76 0.65 3.86 17376 6514 10662
80 0.53 3.70 17773 6948 10824
85 0.51 3.56 18154 7383.r. 10771
90 0.49 3.43 18521 7817 10704
95 0.47 3.31 18875 8251 10623
100 0.46 3.20 19216 8685 10631
105 0.44 3.10 19547 9120 10428
110 0.43 3.01 19868 9554 10314
115 0.42 2.92 20180 9988 10192
120 0.41 2.84 20483 10422 10060
125 0.40 2.77 20777 10857 9921
130 0.39 2.70 21065 11291 9774
135 0.38 2.64 21345 11725 9620
140 0.37 2.57 21618 12159 9459
145 0.36 2.52 21885 12594 9292
150 0.35 2.46 22147 13028 9119
Minimum Basin Area
Minimum Volume= 10882 of
Minimum Area(18"basin depth) 7255 sf Actual Area(shaped to drain)■ 14509 of
Minimum Area for Sediment Control->145 sf per 1 cfs
Peak Developed Flow-> 4.24 cis
Minimum Area= 615 of
I `
REVISED CALCULATIONS
Baxter Meadows Phase 2A
Stormdrain Design - 25 Year Storm Event
Location Runoff Calculation Storm Drain Design Comments
From To Drainage Runoff CA (acre) Sum CA Tc Across Cumulative Tc Rainfall Runoff (cfs) Pipe Dia. Manning's Pipe Pipe Velocity Pipe Flow Pipe Pipe Pipe
Area A Coeff. C (acre) Area(min) (min) Intensity (in) coefficient Slope Length Of Flow Time(min) Capacity Velocity Capacity
(acre) (in/hr) ..n" (ft/ft) (ft) (ft/s) (cfs) Check Check
3.1 MH A 0.40 0.50 0.20 0.20 13.4 13.40 2.04 0.41 12 0.013 0.50% 62 3.21 0.32 2.52 OK 1ADEQUATE
3.2 MH A 1.21 0.50 0.61 0.81 15.4 15.40 1.86 1.13 12 0.013 0.50% 18 3.21 0.09 2.52 OK ADEQUATE
MH A MH C 0.00 0.00 0.81 15.49 1.86 1.49 15 0.013 0.35% 37 3.11 0.20 3.82 OK !ADEQUATE
3.3 MH B 0.22 0.60 0.13 0.13 10.0 10.00 2.46 0.32 12 0.013 0.50% 20 3.21 0.10 2.52 OK JADEQUATE
3.4 MH B 0.15 0.60 0.09 0.22 10.0 10.00 2.46 0.22 12 0.013 0.50% 45 3.21 0.23 2.52 OK JADEQUATE
MH B MH C 0.00 0.00 0.22 10.23 2.42 0.54 15 0.013 0.35% 76 311 0.41 3.82 OK JADEQUATE
MH C MH D 0.00 0.00 1.03 15.69 1.84 1.89 15 0.013 0.35% 305 3.11 1.63 3.82 OK ADEQUATE
3.5 MH D 0.47 0.60 0.28 0.28 10.0 10.00 246 0.69 12 0.013 0.50% 62 3.21 0.32 2.52 OK ADEQUATE
3.6 MH D 1.79 0.60 1.07 1.36 16.6 16.60 1.78 1.91 12 0.013 0.50% 18 3.21 0.09 2.52 OK ADEQUATE
MH D MH E 0.00 0.00 2.38 17.32 1.73 4.12 15 0.013 0.42% 35 3.41 0.17 4.18 OK ADEQUATE
MH E MH F 0.00 0.00 2.38 17.50 1.72 4.09 15 0.013 0.42% 374 3.41 1.83 4.18 OK ADEQUATE
3.8 MH F 0.98 1 0.60 0.59 2.97 18.2 1.67 0.98 12 0.013 0.50% 58 3.21 0.30 2.52 OK ADEQUATE
3.9 MH F 0.26 0.60 0.16 3.13 10.0 2.46 0.38 12 0.013 0.50% 18 3.21 0.09 2.52 OK ADEQUATE
MH F MH I 0.00 0.00 313 19.32 1.61 5.04 18 0.013 0.30% 39 3.25 0.20 5.75 OK ADEQUATE
2.1 2.2 0.18 0.50 0.09 0.09 10.0 2.46 0.22 12 0.013 0.50% 65 3,21 0.34 2.52 OK ADEQUATE
2.2 MH G 1.71 1 0.50 0.86 0.95 1 10.34 2.40 2.27 15 0.013 2.28% 89 7.95 1 0.19 9.74 OK ADEQUATE
2.3 2.4 0.16 0.50 0.08 0.08 10.0 2.46 0.20 12 0.013 0.50% 63 3.21 0.33 2.52 OK ADEQUATE
2.4 MH G 0.12 0.50 0.06 0.14 10.33 2.41 0.34 15 0.013 0.50% 37 3.72 0.17 4.56 OK ADEQUATE
MH G IMH H 0.00 1 0.00 1.09 10.52 2.38 2.58 1 15 0.013 0.33% 261 3.02 1.44 3.71 OK JADEQUATE
3.9 MH H 0.26 0.60 0.16 1.24 10.0 1 2.46 0.38 12 0.013 0.50% 43 3.21 0.22 2.52 OK ADEQUATE
3.10 MH H 1.95 0.60 1.17 2.41 16.4 1.79 2.09 12 0.013 0.95% 22 4.42 0.08 3.47 OK ADEQUATE
MH H MH I 0.00 0.00 2.41 16.48 1 78 4.30 18 0.013 0.33% 35 3.41 0.17 6.03 OK ADEQUATE
MH I MH J 0.00 0.00 5.54 19.52 1.60 8.86 21 0.013 0.57% 199 4.97 0,67 11.95 OK i ADEQUATE
3.A MH J 0.29 0.50 0.15 5.68 10.0 1 2.46 0.36 12 0.013 4.80% 17 9.94 1 0.03 7.80 OK ]ADEQUATE
3.13 MH J 0.48 0.50 0.24 5.92 10.0 246 0.59 12 0.013 1.67% 57 5.86 0.16 4.60 OK ADEQUATE
MH J MH K 0.00 0.00 5.92 20.19 1.57 9.28 21 0.013 0.57% 183 4.97 0.61 11.95 OK ADEQUATE
3.15 MH K 0.29 0.50 0.15 6.07 10.0 2.46 0.36 1 15 0.013 1.00% 15 526 0.05 6.45 OK ADEQUATE
MH K 3.16 0.00 0.00 6.07 20.80 1.54 9.32 21 0.013 0.50% 1 59 4.66 0.21 11.19 OK ADEQUATE
3.16 MH M 0.48 0.50 0.24 6.31 1 21.01 1.53 9.63 21 0.013 0.50% 48 4.66 0.17 11.19 OK ADEQUATE
3.11 3.12 1.15 0.60 0.69 0.69 10.0 2.46 1.69 15 0.013 0.71% 131 4.43 0.49 5.44 OK ADEQUATE
3.12 MH N 0.75 0.60 0.45 1.14 10.49 238 2.71 15 0.013 1.54% 109 6.53 0.28 8.01 OK ADEQUATE
3.14 MH N 0.29 0.60 0.17 017 10.0 2.46 0.43 15 0.013 0.50% 24 3.72 1 0.11 4.56 OK ADEQUATE
MH N MH L 0.00 0.00 1.31 10.11 2.44 320 15 0.013 2.38% 38 8.12 0.08 9.96 OK ADEQUATE
3.13 MH L 0.23 0.60 0.14 0.14 10.0 246 0.34 15 0.013 0.50% 58 3.72 0.26 4.56 OK ADEQUATE
MH L MH M 1 0.00 0.00 1.45 10.26 242 1 3.51 1 15 0.013 0.84% 82 4.82 0.28 1 5.91 OK ADEQUATE
MH M OUTLET 0.00 1 0.00 1 7.76 21.19 1 1.52 1 11.78 1 21 0.013 0.59% 1 131 5.06 0.43 12.16 OK ADEQUATE
i25 = 0.78 • T,- 64 Q = C i A V = 1 . n R2i3 s'12 t= I Q = V A
Project: B05-016-021
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