1. You are planning to build a three story above ground building with a basement parking garage below ground. The bottom of your slab/foundation will be 17 ft below existing grade. You plan to keep the ground water level in the excavation 3.0 ft below the bottom of the foundation for approximately 3 months. The water table is 11 ft below existing grade. The soil is uniform medium
sand down to a depth of approximately 50 ft. The soil below 50 ft is an impervious clay. Your excavation will be 320 ft x 150 ft. You have determined that a 4 ft wide x 3 ft deep sump around the perimeter of your excavation will provide adequate dewatering capacity. Based on test wells on site, you determined that the medium sand has a k value of .058 ft/min and that the D factor is 50 ft.

a. Calculate the flow rate, q
b. Calculate the total volume (V) of water that will need to be pumped in gallons per minute (GPM)

If q and V are calculated in Question 1 and found to be 143.93 ft³/min and 1076.60 GPM respectively:

2. For the previous problem, assume that you found the total volume to be pumped is 250 GPM. You will place your pump inside of the excavation and run a flexible line 500 ft to a storm drain on the existing grade (you have obtained the proper permits to discharge into the drain). Use the given tables and include them marked as part of your answers to select:

a. Choose from one of the given pumps and choose the smallest possible hose diameter for it. Explain and numerically justify all your choices. Include friction losses. Show choices in the tables.
Transcribed Image Text:TABLE 20.11 Water friction loss, in feet per 100 ft of smooth bore hose. Flow in U.S. (gpm) 5 10 15 20 25 30 35 40 50 60 70 80 90 100 125 150 175 200 250 300 350 400 450 1 21.4 76.8 2 8.9 31.8 68.5 1 1/1/ 2.2 7.8 16.8 0.74 2.64 5.7 28.7 9.6 43.2 14.7 Actual inside diameter of hose (in.) 2 2/1/ 3 61.2 20.7 80.5 27.6 1/1/2 NO 0.3 1.0 2.3 3.9 6.0 8.5 11.2 35.0 14.3 52.7 21.8 73.5 30.2 40.4 0.2 0.5 0.9 1.4 2.0 2.7 3.5 5.2 52.0 12.6 64.2 15.7 77.4 0.32 0.51 18.9 28.6 0.70 0.93 7.3 2.5 9.8 3.3 1.2 1.8 4.3 5.3 6.5 9.8 40.7 13.8 53.4 18.1 68.5 23.4 35.0 49.0 0.3 0.4 0.5 0.7 1.0 1.3 1.7 2.1 2.6 4.0 5.6 7.4 9.6 14.8 20.3 27.0 4 0.5 0.6 0.9 1.3 1.8 2.3 3.5 4.9 6.6 8.4 10.5 5 0.8 1.2 1.7 2.3 6 0.32 0.49 0.69 0.90 2.9 1.1 3.6 1.4 8 0.28 0.35
Transcribed Image Text:Total head including 5 (1.5) friction [ft (m)] 5 (1.5) 300 10 (3.0) 295 20 (6.1) 277 30 (9.1) 260 40 (12.2) 241 50 (15.2) 225 60 (18.3) 197 70 (21.3) 160 80 (24.4) 125 90 (27.4) 96 Model 18-M (3-in.) Height of pump above water [ft (m)] 10 (3.0) 15 (4.6) 20 (6.1) Capacity [gpm (1/min)*] 12 Total head including friction [ft (m)] # F Total head including friction [ft (m)] 30 (1,136) (1,117) 40 (1,048) 259 (980) 50 (802) 209 (9.1) 333 (1,260) (12.2) 315 (1,192) (15.2) 290 (1,098) (984) 250 (946) 210 (795) 200 (757) 60 (18.3) 255 (965) 235 (912) 241 (912) 207 (784) 177 (670) 70 (21.3) 212 (852) 225 (852) 202 (765) 172 (651) 80 (24.4) 165 (746) 197 (746) 197 (746) 169 (640) 90 (27.4) 116 (606) 160 (606) 160 (606) 160 (606) 100 (30.5) 60 (473) 125 (473) 125 (473) 125 (473) (363) 96 (363) 96 (363) 96 (363) (625) 165 (439) 116 (227) 10 (3.0) 10 Model 20-M (3-in.) Height of pump above water [ft (m) 15 (4.6) 20 (6.1) 25 (7.6) 667 (2,525) 30 (9.1) 660 (2,498) 575 40 (12.2) 645 (2,441) 565 50 (15.2) 620 (2,347) 545 60 (18.3) 585 (2,214) 70 (21.3) 535 (2,025) 475 80 (24.4) 465 (1,760) 410 90 (27.4) 375 (1,419) 325 100 (30.5) 250 (946) 215 110 (33.5) 65 (246) 60 (3.0) Model 40-M (4-in.) Height of pump above water [ft (m) 15 (4.6) 20 (6.1) Capacity [gpm (1/min)*] # # *** A **** (2,176) 475 (1,798) (2,139) 465 (1,760) (2,063) 455 (1,722) 510 (1,930) 435 (1,647) (1,798) 410 (1,551) 365 (1,552) (1,382) (1,230) 300 (1,136) (815) 195 (227) 50 ** (738) (189) Capacity [gpm (1/min)*] 280 (1,060) 235 (890) 270 (1,022) 230 255 (965) 220 205 (890) (791) 184 (625) 157 116 (439) 60 (227) 60 (871) (833) (776) (696) (594) (439) (227)

Question

1. You are planning to build a three story above ground building with a basement parking garage below ground. The bottom of your slab/foundation will be 17 ft below existing grade. You plan to keep the ground water level in the excavation 3.0 ft below the bottom of the foundation for approximately 3 months. The water table is 11 ft below existing grade. The soil is uniform medium
sand down to a depth of approximately 50 ft. The soil below 50 ft is an impervious clay. Your excavation will be 320 ft x 150 ft. You have determined that a 4 ft wide x 3 ft deep sump around the perimeter of your excavation will provide adequate dewatering capacity. Based on test wells on site, you determined that the medium sand has a k value of .058 ft/min and that the D factor is 50 ft.

a. Calculate the flow rate, q
b. Calculate the total volume (V) of water that will need to be pumped in gallons per minute (GPM)

If q and V are calculated in Question 1 and found to be 143.93 ft³/min and 1076.60 GPM respectively:

2. For the previous problem, assume that you found the total volume to be pumped is 250 GPM. You will place your pump inside of the excavation and run a flexible line 500 ft to a storm drain on the existing grade (you have obtained the proper permits to discharge into the drain). Use the given tables and include them marked as part of your answers to select:

a. Choose from one of the given pumps and choose the smallest possible hose diameter for it. Explain and numerically justify all your choices. Include friction losses. Show choices in the tables.

TABLE 20.11 Water friction loss, in feet per 100 ft of smooth bore hose.
Flow
in U.S.
(gpm)
5
10
15
20
25
30
35
40
50
60
70
80
90
100
125
150
175
200
250
300
350
400
450
1
21.4
76.8
2
8.9
31.8
68.5
1 1/1/
2.2
7.8
16.8
0.74
2.64
5.7
28.7
9.6
43.2 14.7
Actual inside diameter of hose (in.)
2 2/1/
3
61.2 20.7
80.5
27.6
1/1/2
NO
0.3
1.0
2.3
3.9
6.0
8.5
11.2
35.0
14.3
52.7 21.8
73.5
30.2
40.4
0.2
0.5
0.9
1.4
2.0
2.7
3.5
5.2
52.0 12.6
64.2
15.7
77.4
0.32
0.51
18.9
28.6
0.70
0.93
7.3 2.5
9.8
3.3
1.2
1.8
4.3
5.3
6.5
9.8
40.7 13.8
53.4 18.1
68.5
23.4
35.0
49.0
0.3
0.4
0.5
0.7
1.0
1.3
1.7
2.1
2.6
4.0
5.6
7.4
9.6
14.8
20.3
27.0
4
0.5
0.6
0.9
1.3
1.8
2.3
3.5
4.9
6.6
8.4
10.5
5
0.8
1.2
1.7
2.3
6
0.32
0.49
0.69
0.90
2.9
1.1
3.6 1.4
8
0.28
0.35

Total head
including 5 (1.5)
friction
[ft (m)]
5 (1.5) 300
10
(3.0) 295
20
(6.1) 277
30 (9.1) 260
40 (12.2) 241
50 (15.2) 225
60 (18.3) 197
70 (21.3) 160
80 (24.4) 125
90 (27.4) 96
Model 18-M (3-in.)
Height of pump above water [ft (m)]
10 (3.0) 15 (4.6) 20 (6.1)
Capacity [gpm (1/min)*]
12
Total head
including
friction
[ft (m)]
#
F
Total head
including
friction
[ft (m)]
30
(1,136)
(1,117)
40
(1,048) 259 (980)
50
(802) 209
(9.1) 333 (1,260)
(12.2) 315 (1,192)
(15.2) 290 (1,098)
(984) 250 (946) 210 (795) 200 (757) 60 (18.3) 255 (965) 235
(912) 241 (912) 207 (784) 177 (670) 70 (21.3) 212
(852) 225 (852) 202 (765) 172 (651) 80 (24.4) 165
(746) 197 (746) 197 (746) 169 (640)
90
(27.4) 116
(606) 160 (606) 160 (606) 160 (606) 100 (30.5) 60
(473) 125 (473) 125 (473) 125 (473)
(363) 96 (363) 96 (363) 96 (363)
(625) 165
(439) 116
(227)
10 (3.0)
10
Model 20-M (3-in.)
Height of pump above water [ft (m)
15 (4.6) 20 (6.1)
25 (7.6) 667 (2,525)
30 (9.1) 660 (2,498)
575
40 (12.2) 645 (2,441) 565
50 (15.2) 620 (2,347) 545
60 (18.3) 585 (2,214)
70 (21.3) 535 (2,025) 475
80 (24.4) 465 (1,760) 410
90 (27.4) 375
(1,419)
325
100 (30.5) 250 (946) 215
110 (33.5) 65 (246) 60
(3.0)
Model 40-M (4-in.)
Height of pump above water [ft (m)
15
(4.6)
20
(6.1)
Capacity [gpm (1/min)*]
#
#
***
A ****
(2,176) 475 (1,798)
(2,139) 465 (1,760)
(2,063) 455
(1,722)
510 (1,930) 435 (1,647)
(1,798) 410
(1,551) 365
(1,552)
(1,382)
(1,230) 300
(1,136)
(815) 195
(227) 50
**
(738)
(189)
Capacity [gpm (1/min)*]
280 (1,060) 235 (890)
270 (1,022) 230
255 (965) 220
205
(890)
(791) 184
(625)
157
116
(439)
60 (227) 60
(871)
(833)
(776)
(696)
(594)
(439)
(227)

Accepted Answer

The water table is 11 ft below the existing gradeThe soil below 50 ft is an impervious clayk value…