HomeMy WebLinkAboutCompliance LetterMITCaHE�LL
MORGAN September 19, 2011
Erika Bridges
City of College Station
Planning and Development Services
P.O. Box 9960
College Station, TX 77842
Re: Lakeridge Townhomes Ph. 2B(SP) — Water, Sewer & Drainage Compliance Letter
Dear Erika,
Wafer
Phase 2B 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 18 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 be completed in Phase 2B. Exhibit 8, attached, shows the original loop
that will be constructed with the Phase 2 project (Line 4027 around to line 4019). The Phase 2B
modeling run completes the loop at line 4022 and 4027. With a fire flow of 1500 gpm on node
59322, the maximum velocity occurs in line 4000 and is 5.9 fps and the minimum pressure is 70
psi occurring at node 59322. This pressure and velocity in the system meets the minimum
design standards.
Exhibit 9 attached is the Average Day Run with Phase 2B complete.
All waterlines for Phase 2B were designed in accordance with the City of College Station Unified
Development Standards.
Sewer
Phase 2B 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 2B is
following that layout, sizing and depth.
Drainage
Similarly Phase 2B 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 2B. There is one new storm sewer
system being constructed with Phase 2B and we have attached the inlet sizing, HGL
calculations and drawings for that system. All impervious cover being constructed within Phase
2B 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 IN24
and IN25 are sized as 5 foot inlets and have less than 8" of ponded depth at the inlet during a
100-year storm event. The grate inlets, GT29, GT29A and JB30, are sized as an EJIW V5728
511 UNIVERSITY DRIVE EAST, SUITE 204 • COLLEGE STATION, TX 77840 • T. 979,260.6963 • F. 979.260.3564
CIVIL ENGINEERING • HYDRAULICS HYDROLOGY UTILITIES • STREETS • SUE PLANS. • SUBDIVISIONS
info@mitchellandmorgan,com w .mitchellandmorgan.com
with 2.57 sq in of open area which allows only .82', 0.62' and 1.03' respectively of ponded depth
over the inlet during the 100-year storm event.
have any questions or comgpVtlfxb�jLfeel free to call our office at 979-260-6963.
77689
Veronica Ay. Mo P.E.,
naging MaPartne
Cc: File
EXHIBIT 8
Analysis Type: Steady State
Project Description: Peak Day Conditions, Phase 2 complete, Fireflow of 1500 gpm on Node 59322
59326
EXHIBIT 8
Time Level: 0; 0 day 0:00 in
Number of Junctions: 25(Selection)
Junction ID
Flevation Demand
Grade
Pressure
[ft] ( ]BPm]
(ft]
(psi) (
r--
--
-I
35312
308.000 0.000
494.507
80.814
t _
59301
0.000
494.094
80.634
^�308.000
59302
_
311.000 5.650
492.299
78.557
59303
-
( 309.000 0.000
--
492.303
�79.425
5-930
f 308.000 ( 6.680
492.620
79.996
59305
309.000 0.000
491.926
79.262
r- -
59306
310.000 6.680
(490.226
78.092
r- -
59307
1
314_000 11.820
487.782
75.300
_
59308
(314.000 (11.820
�487.755
75.288
59309
( 315.000 0.000
487.715
74.837
_
59310
( 315.500 0.000
487.688-�
74.609
r
59311
316.500 0.000
1487.667
74.167
E _59-
312
317.750 6 680
488.426
73.954
59313
1312.000 ( 0_000
( 490.991
77.557
59314
309.000 �0.000
492.102
79.338
59318
317.000 0.000
( 484.844
72.727
59320
1314.500- 13.360
486.406
74.487
59321
317,500 0000
484.844
72.510
59322
319.500 1500.000
482.748
70.735
59323
318.000 0.000
483.986
71.922
59324
318.000 16.440
485.106-�
72.407
59325
318.250 0.000
485.925
i
( 72.653
59326
318.500 0.000 I486.347I72.728
59334
314 875 i 13 360
489.785
75,788
-
59335
i
318.500 ( 6.680
483.792
71.621
EXHIBIT 8
Results -Pipes
Number of Pipes: 26(Selection)
Pipe ID (
Node 1
Node 2
Diameter Length
Roughness l Flow
Velocity Headloss
[in]
[ftl
[millift]
[gpm]
[ft/s] [it]
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 0004�
3999 1
59303
59301
1 8.000
234.743
�140.000
I-672.077
4.290 ( 1.791
4000
59301
1 59304
8.000
�106.460
140.000
927.093
[5.917 1.473
4001
( 59304
159305
1 8.000
1 50.825
1 140.000
920.413
5.875 1 0.694
4002
�9305
59306
8.000
�124.542
140.000
920.413
1 5.875 T1.701
4003
159306
59307
8.000
�181.383
140.000
913.733
5.832 2.444
4004
59307
59308
8.000
59.338
140.000
144.472
0.922 0.026
4005
159308
59309
8.000
107.870
140.000
132.652
0.847 0.041
4006
59309
59310
1 8.000
1 71.557
140.000
132.652
0.847 0.027
4007
159310
I59311
18.000
54.617
140.000
132.652
10.847 0.021
4008
59311
59312
8.0007106.905
1 140.000
F-646 387
4.126 0.759
009
59312
�59334
�8.000
1 187 883
1 140.000
1-653.067
1 -4.168 1-359
4010
59313
1 59314
8.000
147.907
140 000
-666 427T
4.254 11.111
-
4011 �59314
-
�59303
1 8.000
26.817
140.000
1 666.427
J4.254 0.201 I
4019
, 59307
(59320
8.000
( 144.4961
140 000
757.440
1
-1
4.835 �1.375
III
4020
59320T9321
8000
169.613
(140.000
744.081
(4.749 11562
�- -
4021
1 59321
59318
�8.000
r
53.777
1 140.000
-0.000
-
1-0.0000 0.000
4022
�59321
(59335
_-
1 8 000
__-
114.189
--
140.000
4.749- 1.052
4023
1 99322
59323
�8.000
1 128.439
140.000
r�744.081
1-762.599
�4.868 1 1.238
__.
4024
59323
59324
8.000
116.150
140.000
762 599-
4.868 L 120
4025
59324
59325
8.000
81.659
140.000
-779 039
-4.972 0.819
4026
159325
( 59326
( 8.000
42.083 1
140.000
1 779.039
-4.972 0.422
r4027
59326 1
59311
1 8.000
131.660
1 140.000
-779 039
1 _4.972 1.320
4037
59334
59313
8.000
160.626
140.000
666.427
1 4.254 1.206
4038
59335
59322
8.000
r
115.267
140.000
737 401
4.707 1.044
EXHIBIT 8
EXHIBIT 9
Analysis Type: Steady State
Project Description: Average Day Conditions, Phase 2 complete
59326
EXHIBIT 9
Time Level: 0; 0 day 0:00 hr
Number
of Junctions: 25(Selection)
Junction
ID I Elevation
( Demand
Grade
Pressure
[ft]
( IZ;pm]
IN
[Psil
35312
) 308.000
0.000
( 499.310
82.894
C
59301
_
1308.000
0.000
, 499.307
( 82.893
-
59302
- - -
311.000
15 650
- --
499.292
( 81.587
59303
309.000
0.000
499.296
82.455
308.000
6.680
499.299
82.890
59305
-
, 309.000
-�59304
0.000
( 499.296
( 82.455 f
59306
-
( 310.000
6.680
-
499.288
82.019
59307
314 00-0
( 11 820
( 499 280
1 80.282
59308
T ---
314 000
11.820
�499.280
-
80.282
59309
315.000
0.000
( 499.280
79.848�
r59310
315.500
0.000
499.280
179.632
59311
-
) 316.500
0.000
499.280
79.198
59312
) 317.750
�6.680
-�
499.281
1 78.657
59313
312.00�000
499.290
81.153
i
59314
309.000
) 0_000
499.295
82.455�
59318
317.000
0.000
-�
499.278
78.981
59320
--
314.500
13.360
-
T 499.278,
-
80.064 J
59321
( 317.500
0.000
499.278,
78-764
59322
-�
319.500
�0.000
499.278
77.898
59323
318 000
1 0.000
499.278
) 78.548
59324
318.000
16.440
499.278
78.548
59325
1318.250
0.000
499.278
.)
178.440-
59326
318.500
( 0.000
499.279
78.331
59334
314.875
13.360
499.284
79.904
59335
--- 318.500
6.680 -
499.278
78.331 '
EXHIBIT 9
Number of Pipes:
26(Selection)
Pipe ID
Node 1 (Node 2 Diameter Length
Roughness l Flow
Velocity
Headloss
[in]
[ft]
[nulhft]
[gpm]
[ft/s]
( [ft] �I
3997
35312
59301 12.000
68.370
130.000
99.170
0.281
0.002
3998 �59302
59303 4.000
140 322
140.000
5.650
0 144 J0.004
3999
59303
59301 8
000
234.743
140.000
-43.182
-0.276
0.011
4000
59301
59304 1 8.000
1 106.460
140.000
55.988
0.357
0.008
4001 (
59304
] 59305 8.000
50.825
140.000
49.308
0.315
0.003
4002 (
59305
1 59306 8.000
124.542
140.000
49.308
0.315
0.008�
-
4003
59306
59307 8.000
161.363
140.000
42.628
0.272
0.008
4004
59307
59308 8000
(59.338
140.000
10.445
0.067
0.000
4005 r59308
�59309� 8.000
107.870
140.000
j-1.375
-0.009�0.000
4006
59309
T59310 8.000
T71.557
140.000
(-1.375
-0.009
III
0.000
4007
59310
59311 8.000
54.617
140.000
( -1.375
0.009
0.000
4008
59311
59312 8.000
106.905
140.000
-17 492
0 112
0.001
4009
59312
99334 8.000
187.883
140.000
-24.172
-0.154
0.003
4010
59313
59314 1 8.000
147 907
140.000
37.532
0.240
0.005
4011
59314
( 59303 8.000
26.817
140.
000
37.532
0.240
0.001
4019
59307
59320 ( 8.000
144.496
�140.000
20.363
III
0_130
�0A02
4020
59320
( 59321 1 8.000
169.613
140.000
7.003
0.045
0.000
4021
59321
59318 8.000
53.777
140.000
0.000
0.000
0.000
-
4022 j5932�
59335 8.000
114.189
1 140.000
7.003
-
0045
�0.000
4023
59322
59323 1 8.000
128.439
140.000
0.323
0 002
0.000
4024
59323
�9324 8.000
116.150
140.000
(0.323
0_002
0 000
4025 159324
59325 8.000
81.659
140.000
16.117
-0.103
0.001
4026
--
59325
1 59326] 8.000
42.083
I
( 140.000
-16.117
0.103
�0.000
4027
59326
59311 8.000
( 131.660
140.000
-16.117
-0.103
( 0.001
4037 159334
4037
59334
59313 8.000
160.626
140.000
-37.532
-0.240
0.006
4038
59335
59322 8.000
T 115_267
1 140,000
0_323
0.002
0.000
EXHIBIT 9
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EXHIBIT 7.1
LAKERIDGE TOWNHOMES PHASE 2B
INLET CAPACITY
10-YEAR STORM
IN24
IN31
Q =
4.60 cfs
Q = 3.40 cfs
clog =
10%
clog = 10%
Q clogged =
5.06 cfs
Q clogged = 3.74 cfs
y =
0.83 ft
y = 0.83 ft
L= 223 ft
L= 1.65 ft
SUMP CURB:
Q = 3.0*L*y^1.5
L= Q/(3.0*y^1.5)
GT29 GT29A
Q = 2.80 cfs Q = 2.10 cfs
clog = 25% clog = 25%
Q clogged = 3.5 cfs Q clogged = 2.625 cfs
h = 0.50 ft h = 0.50 ft
Req. Open
Area= 0.82 ft2 Req. Open Area= 0.82 ft2
SUMP GRATE M r _ >(10_.Year rn)777777
JB30(Temp grate)
Q = 3.50 cfs
clog = 25% SUMP GRATE.,
Q clogged = 4.375 cfs Q = 4.82*A*h^0.5
h = 0.50 ft A = Q/(4.82*y^0.5)
Req. Open
Area= 1.03 ft2
Note*
Recessed inlets curb opening =
Height of curb +depression
y = 6"+4"=equal 10"
EXHIBIT 7.2
LAKERIDGE TOWNHOMES PHASE 213
INLET CAPACITY
100-YEAR STORM WSE
IN24
IN31
Q =
6.60 cfs
Q = 4.90 cfs
clog =
10%
clog = 10%
Q clogged =
7.26 cfs
Q clogged = 5.39 cfs
Chosen L=
5.00 ft
Chosen L= 5.00 ft
Flowline=
317.67 ft
Flowline= 319.48 ft
Y = .; :762 ft
y= 0ft 51
WSE=
318.28 ft
WSE= 319.99 ft
SUMP GRATE „v; r
,;,{100 Year.";Storm) =,,_„
GT29
GT29A
Q = 4.10 cfs
Q = 3.10 cfs
clog = 25%
clog = 25%
Q clogged = 5.13 cfs
Q clogged = 3.88 cfs
Inlet Selected= V5728
Inlet Selected= V5728
Open Area
Open Area
Selected= 2.57 ft2
Selected= 2.57 ft'
T/G= 319.13 ft
T/G= 319.09 ft
h= 0.17ft
h= -0.10ft
WSE= 319.30 ft
WSE= 319.19 ft
(100Year=Storm)
J1330(Temp grate)
Q = 5.10 cfs
clog = 25%
Q clogged = 6.38 cfs
Inlet Selected= V5728
Open Area
Selected= 2.57 ft2
T/G= 318.45 ft
In = 0.26 ft
WSE= 318.71 ft
Note*
SUMP CURB:
Recessed inlets curb opening =
Q = 3.0*L*yA1.5
Height of curb +depression
L= Q/(3.0*yA1.5)
y = 6"+4"=equal 10"
SUMP GRATE:
Q = 4.82*A*hA0.5
A = Q/(4.82*yA0.5)
October 17. 2011
Erika Bridges
City of College Station
Planning and Development Services
P.O. Box 9960
College Station, TX 77842
Re: Amended Lakeridge Townhomes Ph. 2B(SP) — Water, Sewer & Drainage Compliance
Letter
Dear Erika,
Water
Phase 2B 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 18 and
maintains adequate velocity and pressure within the system.
All buildings will be constructed as TYPE V-B construction with an automatic fire sprinkler
system and the largest building requires a fire flow of 1500 gpm.
The original Phase 2 is now being split into Phase 2A and 2B. Because of this split, the original
loop for Phase 2 will be completed in Phase 2B. Exhibit 8, attached, shows the original loop
that will be constructed with the Phase 2 project (Line 4027 around to line 4019). The Phase 2B
modeling run completes the loop at line 4022 and 4027. With a fire flow of 1500 gpm on node
59322, the maximum velocity occurs in line 4000 and is 5.9 fps and the minimum pressure is 70
psi occurring at node 59322. This pressure and velocity in the system meets the minimum
design standards.
Exhibit 9 attached is the Average Day Run with Phase 2B complete.
All waterlines for Phase 2B were designed in accordance with the City of College Station Unified
Development Standards.
Sewer
Phase 2B 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 2B is
following that layout, sizing and depth.
Drainage
Similarly Phase 2B 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 2B. There is one new storm sewer
system being constructed with Phase 2B and we have attached the inlet sizing, HGL
calculations and drawings for that system. All impervious cover being constructed within Phase
2B was accounted for in the overall drainage report for Lakeridge Townhomes dated January
2010.
511 UNIVERSITY DRIVE EAST, SUITE 204 COLLEGE STATION, TX 77840 • T. 979.260.6963 • E. 979.260.3564 /1l
CIVIL ENGINEERING • HYDRAULICS HYDROLOGY MILMES • STREETS • SITE PLANS • SUBDIVISIONS \1 " Ili
info@mitchellandmorgan.com w .mitchellandmorgan.mm
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 IN24
and IN25 are sized as 5 foot inlets and have less than 8" of ponded depth at the inlet during a
100-year storm event. The grate inlets, GT29, GT29A and J1330, are sized as an EJIW V5728
with 2.57 sq in of open area which allows only .82', 0.62' and 1.03' respectively of ponded depth
over the inlet during the 100-year storm event.
If you have any questions or comments, please feel free to call our office at 979-260-6963.
Veronica J.B. r an, �E , C.F.M. .�nyri�na,ts.
Managing Parther U �y9`• 77
Cc: File