HomeMy WebLinkAboutWater, Sewer & Drainage Compliance MITCHELL
M M
MORGAN August 16, 2011
Erika Bridges
City of College Station
Planning and Development Services
P.O. Box 9960
College Station, TX 77842
Re: Lakeridge Townhomes Ph. 2A(SP) — Water, Sewer & Drainage Compliance Letter
Dear Erika,
Water
Phase 2A was designed in accordance with the overall waterline design for the Lakeridge
Townhomes. The fire flow report previously submitted with Phase 1A dated January 2010
anticipated the construction of Phase 2 and models a fire flow of 1500 gpm at Building 10 and
maintains adequate velocity and pressure within the system.
The original Phase 2 is now being split into Phase 2A and 2B. Because of this split, the original
loop for Phase 2 will not be complete until Phase 2B is complete. So an additional modeling run
was performed to assure adequate pressure and velocity could be maintained with a radial feed
line to serve the fire hydrant at node 59318. Exhibit 8, attached, shows the original loop that
was being constructed with the Phase 2 project (Line 4027 around to line 4019). Phase 2A will
now end construction at line 4022 and 4007. The modeling run has closed line 4027 and 4022
(as depicted with the 0.00 flowrate in these pipes). With a fire flow of 1500 gpm on node 59318,
the maximum velocity occurs in line 4019 and is 9.7 fps and the minimum pressure is 68 psi
occurring at node 59318. This pressure and velocity in the system meets the minimum design
standards.
All waterlines for Phase 2A were designed in accordance with the City of College Station Unified
Development Standards.
Sewer
Phase 2A was designed in accordance with the overall sanitary sewer design for the Lakeridge
Townhomes. A master sewer layout was designed for the entire project and Phase 2A is
following that layout, sizing and depth.
Drainage
Similarly Phase 2A was designed in accordance with the overall drainage design for the
Lakeridge Townhomes. The detention pond and storm sewer system within Lakeridge was
sized for ultimate development which included Phase 2A. There is one new storm sewer
system being constructed with Phase 2A and we have attached the inlet sizing, HGL
calculations and drawings for that system. All impervious cover being constructed within Phase
2A was accounted for in the overall drainage report for Lakeridge Townhomes dated January
2010.
As seen on the attached Exhibit 6.1, the HGL's have been calculated for both the 10 and 100
year storm events. These HGL's can also be seen on the storm sewer plan & profile sheet also
attached. Exhibits 7.1 and 7.2 illustrate the sizing of the storm inlets and grate inlet. Both IN15
and IN16 are sized as 5 foot inlets and have less than 8" of ponded depth at the inlet during a
511 UNIVERSITY DRIVE EAST, SUITE 204 • COLLEGE STATION, TX 77840 • T 979.260.6963 • F 979.260.3564
CIVIL ENGINEERING • HYDRAULICS • HYDROLOGY • UTILITIES • STREETS • SITE PLANS • SUBDIVISIONS q
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100 -year storm event. The grate inlet is sized as an EJIW V5728 with 2.57 sq in of open area
which allows only .25 ft of ponded depth over the inlet during the 100 -year storm event, however
the HGL will force water to pond to a depth of 9" at this point. Because there is an overflow path
within the parking lot to the inlet just downstream, the depth of ponding will really only reach .31'
or 4" during the 100 -year storm event.
One noteworthy point is that there will be a temporary grate inlet constructed on the west side of
the site until Phase 2B is constructed. This occurs because the grades are such that the
overland flow is blocked by the new parking lot grades. This is just a temporary situation until
the parking lot is expanded. Once Phase 2B is constructed, flow from the undeveloped tract will
be intercepted by the ultimate storm line that will serve this area. This grate inlet is called out as
an EJIW V5728 with 2.57 sq in of open area but it doesn't matter what size is used here as it is
only temporary and serves only to drain a ponding area. If water backs up into the graded
swale during storm events it doesn't matter as : it only acts as an additional temporary storage
area while the system drains.
If ou have any questions or comments,,��e to call our office at 979 - 260 -6963.
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EXHIBIT 7.1
LAKERIDGE TOWNHOMES PHASE 2A
INLET CAPACITY
10 -YEAR STORM
SUMP CU RB (recessed) >, (10 Year: Storni)
1N15 1N16
Q = 2.10 cfs Q = 5.00 cfs
clog = 10% clog = 10%
Q clogged = 2.31 cfs Q clogged = 5.5 cfs
y= 0.83 ft y= 0.83ft
L =1 1021ft L =I 2.421ft
SUMP CURB:
Q = 3.0 *L *y "1.5
L= Q/(3.0 *y "1.5)
SUMP RATE ,. (10 Year Storm)
Q = 3.40 cfs
clog = 25% SUMP GRATE:
Q clogged = 4.25 cfs Q = 4.82 *A *h ^0.5
h = 0.50 ft A = Q/(4.82 *y "0.5)
. Open Area =l 1.00Ift
Note*
Recessed inlets curb opening =
Height of curb +depression
y = 6 " +4" =equal 10"
EXHIBIT 7.2
LAKERIDGE TOWNHOMES PHASE 2A
INLET CAPACITY
100 -YEAR STORM WSE
SU MP'u.CURB {recessed) 1100 Year Storm) 4'
IN15 IN16
Q = 3.10 cfs Q = 7.30 cfs
clog = 10% clog = 10%
Q clogged = 3.41 cfs Q clogged = 8.03 cfs
Chosen L= 5.00 ft Chosen L= 5.00 ft
Flowline= 315.67 ft Flowline= 315.89 ft
y = 0.37 ft y =) 0.66Ift
WSE= 316.04 ft WSE= 316.55 ft
SUMP:, GRATE, " (100 Year Storm)-
GT14
Q = 5.00 cfs
clog = 25%
Q clogged = 6.25 cfs
Inlet Selected= V5728
Open Area
Selected= 2.57 ft
T /G= 314.55 ft
h =) 0.25Ift
WSE= 314.80 ft
Note* SUMP CURB:
Recessed inlets curb opening = Q = 3.0 *L *y ^1.5
Height of curb +depression L= Q/(3.0 *y ^1.5)
y = 6 " +4" =equal 10"
SUMP GRATE:
Q = 4.82 *A *h ^0.5
A = Q/(4.82 *y ^0.5)
EXHIBIT 8
Analysis Type: Steady State
Project Description: Peak Day Conditions, Phase 2A, Fireflow of 1500 gpm on Node 59318
{
f� 5930
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59314
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59334 \ 9 1.
35312
59301
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403 59335
59322 59321 369
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EXHIBIT 8
Results - Junctions
Time Level: 0; 0 day 0:00 hr
Number of Junctions: 25(Selection)
Junction ID Elevation Demand Grade Pressure
[ft] [gPm] [ft] [psi]
35312 308.000 0.000 494.507 80.814
59301 308.000 0.000 494.094 80.634
59302 311. 000 5.650 492.578 78.678
59303 309. 000 0.000 492.583 79.546
59304 308.000 6.680 492.443 79.919
59305 309.000 0.000 491.664 79.148
59306 310.000 6.680 489.757 77.889
59307 314.000 11.820 487.014 74.967
59308 314.000 11.820 487.341 75.109
59309 315. 000 0.000 487.960 74.943
59310 315.500 0.000 488.370 74.905
59311 316.500 0.000 488.683 74.607
59312 317.750 6.680 489.319 74.341
59313 312.000 0.000 491.477 77.767
59314 309. 000 0.000 492.413 79.473
59318 317.000 1500.000 474.368 68.187
59320 314.500 13.360 481.987 72.572
59321 317.500 0.000 476.182 68.757
59322 319.500 0.000 - 2575095.00 ! - 1115927.12
59323 318.000 0.000 - 2575095.00 - 1115926.50
59324 318.000 16.440 - 2575095.00 ! - 1115926.50
59325 318.250 0.000 - 2575095.00 - 1115926.50
59326 318.500 0.000 - 2575095.00 - 1115926.62
59334 314.875 13.360 490.460 76.081
59335 318.500 6.680 - 2575095.00 - 1115926.62
EXHIBIT 8
Results - Pipes
Number of Pipes: 26(Selection)
Pipe ID Node 1 Node 2 Diameter Length Roughness Flow Velocity Headloss
[in] [ft] [millift] [gpm] [ft /s] [ft]
3997 35312 59301 12.000 68.370 130.000 1599.170 4.537 0.413
3998 59302 59303 4.000 140.322 140.000 -5.650 -0.144 0.004
3999 59303 59301 8.000 234.743 140.000 - 613.280 -3.914 1.511
4000 59301 59304 8.000 106.460 140.000 985.890 6.293 1.651
4001 59304 59305 8.000 50.825 140.000 979.210 6.250 0.778
4002 59305 59306 8.000 124.542 140.000 979.210 6.250 1.907
4003 59306 59307 8.000 181.383 140.000 972.529 6.207 2.743
4004 59307 59308 8.000 59.338 140.000 - 564.210 -3.601 0.327
4005 59308 59309 8.000 107.870 140.000 - 576.030 - 3.677 0.618
4006 59309 59310 8.000 71.557 140.000 - 576.030 -3.677 0.410
4007 59310 59311 8.000 54.617 140.000 - 576.030 -3.677 0.313
4008 59311 59312 8.000 106.905 140.000 - 587.590 -3.750 0.636
4009 59312 59334 8.000 187.883 140.000 - 594.270 ! - 3.793 1.141
4010 59313 59314 8.000 147.907 140.000 - 607.630 -3.878 0.936
4011 = 59314 59303 8.000 26.817 140.000 - 607.630 ! -3.878 0.170
4019 59307 59320 8.000 144.496 140.000 1524.920 9.733 5.027
4020 59320 59321 8.000 169.613 140.000 1511.560 9.648 5.805
4021 59321 59318 8.000 53.777 140.000 1500.000 9.574 1.815
4022 59321 59335 8.000 114.189 140.000 0.000 0.000 0.000
4023 59322 59323 8.000 128.439 140.000 4.880 0.031 0.000
4024 59323 59324 8.000 116.150 140.000 4.880 0.031 0.000
4025 59324 59325 8.000 81.659 140.000 - 11.560 - 0.074 0.000
4026 59325 59326 8.000 42.083 140.000 - 11.560 -0.074 0.000
4027 59326 59311 8.000 131.660 140.000 0.000 0.000 0.000
4037 59334 59313 8.000 160.626 140.000 - 607.630 ! -3.878 1.017
4038 59335 59322 8.000 115.267 140.000 4.880 0.031 0.000
EXHIBIT 8
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I
EXHIBIT 9
Analysis Type: Steady State
Project Description: Average Day Conditions, Phase 2A
593 , ' N/
r F �g19
y 5931'
/ 4010 a ° f •
��, 593
•
f 59314 -'
i
9334 ,g
l' • 35312 \ \LO , , ,g
f f
1' 59301 '
f oy t A dd
D
•
,' 13 59.
f 0E '04 ' 'ti
/ 312
4006 59309
° 08 /59310 O 59305
f 0 17 0
o 06
59311
a o 5 • vQ
F �.
59326 •02
s - 5930
59325 phi v�9
'� 59324
•
v 59320
59323 p. i `
0 s
b
4022 4021 ,
•59 403 •59 • 59318
59321 3 69
Jr„, 91
- m
EXHIBIT 9
Results - Junctions
Time Level: 0; 0 day 0:00 hr
Number of Junctions: 25(Selection)
Junction ID Elevation ' Demand Grade Pressure
[ft] [gpm] [ft] [psi]
35312 308.000 0.000 499.536 82.993
59301 308.000 0.000 499.536 82.993
59302 311.000 1.530 499.535 81.692
59303 309.000 ! 0.000 499.535 82.559
59304 308.000 1.810 499.535 82.992
59305 309.000 0.000 499.535 82.559
59306 310.000 1.810 499.535 82.125
59307 314.000 i' 3.190 499.534 80.392
59308 314.000 3.190 499.534 80.392
59309 315.000 0.000 499.534 79.959
59310 315.500 0.000 499.534 79.742
59311 316.500 0.000 499.534 79.309
59312 317.750 1.810 499.534 78.767
59313 312.000 0.000 499.535 81.259
59314 309.000 0.000 499.535 82.559
59318 317.000 0.000 499.534 79.092
59320 314.500 3.610 499.534 80.175
59321 317.500 0.000 499.534 78.875
59322 319.500 0.000 - 695753.063 - 301608.250
59323 318.000 0.000 - 695753.063 - 301607.594
59324 318.000 4.440 - 695753.063 - 301607.594
59325 318.250 0.000 - 695753.063 - 301607.688
59326 318.500 0.000 - 695753.063 - 301607.813
59334 314.875 3.610 499.534 80.013
59335 318.500 1.810 - 695753.063 - 301607.813
EXHIBIT 9
•
Results - Pipes
Number of Pipes: 26(Selection)
Pipe ID Node 1 Node 2 Diameter Length Roughness Flow Velocity Headloss
[in] [ft] [millift] [gpm] [Ws] [ft]
3997 35312 59301 ' 12.000 68.370 130.000 26.810 ' 0.076 0.000
3998 59302 59303 4.000 140.322 , 140.000 -1.530 - 0.039 ' 0.000
3999 59303 59301 i 8.000 234.743 140.000 - 11.763 -0.075 0.001
4000 ! 59301 59304 8.000 106.460 140.000 15.047 0.096 i 0.001
4001 59304 59305 ' 8.000 50.825 140.000 13.237 0.084 0.000
4002 59305 59306 8.000 124.542 ' 140.000 13.237 0.084 0.001
4003 59306 59307 8.000 181.383 !, 140.000 11.427 0.073 0.001
4004 ! 59307 59308 8.000 59.338 140.000 1.502 0.010 0.000
4005 59308 59309 8.000 107.870 " 140.000 -1.688 - 0.011 0.000
4006 59309 59310 8.000 71.557 140.000 -1.688 -0.011 0.000
4007 59310 59311 8.000 54.617 140.000 - 1.688 -0.011 0.000
4008 59311 59312 8.000 106.905 140.000 -4.813 - 0.031 0.000
4009 59312 59334 8.000 187.883 140.000 -6.623 - 0.042 0.000
4010 59313 59314 8.000 147.907 140.000 - 10.233 -0.065 0.000
4011 59314 59303 8.000 26.817 140.000 - 10.233 -0.065 0.000
4019 59307 59320 8.000 144.496 140.000 6.735 0.043 0.000
4020 59320 59321 8.000 169.613 140.000 3.125 0.020 0.000
4021 59321 59318 8.000 53.777 140.000 -0.000 -0.000 0.000
4022 59321 59335 8.000 114.189 140.000 0.000 0.000 0.000
4023 59322 59323 8.000 128.439 140.000 1.315 0.008 0.000
4024 59323 59324 8.000 116.150 140.000 1.315 0.008 0.000
4025 59324 59325 8.000 81.659 140.000 -3.125 -0.020 0.000
4026 59325 59326 8.000 42.083 140.000 -3.125 -0.020 0.000
4027 59326 59311 8.000 131.660 140.000 0.000 0.000 0.000
4037 59334 59313 8.000 160.626 140.000 - 10.233 -0.065 0.000
4038 59335 59322 8.000 115.267 140.000 1.315 0.008 0.000
EXHIBIT 9