MEMORANDUM – UND-02-DES-MM-030
Memoraadsndum
Email:
s 9(2)(a)
To
s 9(2)(a)
From
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ACT
CC
s 9(2)(a)
Date
22/08/13
Subject
Western Approach Subgrade CBR Analysis
INT R ODU CTI ON
This memo sets out the anticipated subgrade conditions and undercutting requirements of the
approaches to the underpass where the road is not piled or on a floor slab.
This memo supersedes recommendations made in UND/Memo/02/04 (dated 20/11/2012).
The approaches on grade are defined as follows:
Western Approach (Taranaki Street End) – Chainage 210-248m;
Eastern Approach (Basin Reserve End) – Chainage 476-540m.
The depth of the approaches below ground level where it is placed on grade will require cuts of
between 0 and 3.5m below ground level.
ANTIC IPAT ED GROUND C ONDIT I ONS
L INFORMATION
The anticipated ground conditions are highly variable across the site, a summary of the anticipated
geological conditions is below:
Western Approach (Taranaki Street End)
RELEASED UNDER THE
0-2m (variable) – Silt/Gravel Fill.
2-8m (variable) – mix of brown silt and gravel layers, layers vary between 0.3 and 2m
thickness (Holocene).
8m+ - bluish grey interbedded sands, silts and gravels with infrequent organic layers
(Pleistocene).
OFFICIA
Eastern Approach (Basin Reserve End)
0-2m (variable) – Silt/Gravel Fill.
2-6m (variable – mix of brown silt and gravel layers, layers vary between 0.3 and 4m
thickness (Holocene)
Memorial Park Alliance / UND-02-DES-MM-030 West Subgrade CBR.docx (e.g. UND-02-DES-MM Lagging Design)/ Date
2
6m+ - bluish grey interbedded sands, silts and gravels with infrequent organic layers
(Pleistocene)
Investigation data is provided in the Factual Geotechnical Investigation Report (UND-02-DES-RP-
001).
Site walkovers suggest that the cut surface in the western approach is predominantly moderately
dense silty gravels with some silt layers.
CB R DE S IGN
Scala penetrometers have been undertaken in the current excavation surface at the western
approach. This area is currently cut down to 200mm (lower level) to 500mm (upper level) above
the final excavation surface. The scala penetrometer details are outlined in table 1 below:
Table 1: Scala Penetrometer Test Details
ACT
Scala Test
Location
Approximate Level
Test Depth
SC1
CH235 South Wall
Lower Level
1.4m
SC2
CH235 Middle
Upper Level
0.85m
SC3
CH247 South Wall
Lower Level
1.55m
SC4
CH247 Middle
Upper Level
1.5m
SC5
CH248 North Wall
Upper Level
1.4m
The scala penetrometer results and CBR analysis are attached.
The scala CBR interpretation suggest that the CBR is above 15 below the proposed cut level. The
geological cuts on site generally show silty gravels and a minimum CBR of 15 is realistic in this
material. However, there may be sections of the road cut that may expose silt and silty clay layers.
The subgrade CBR in this material could be as low as 3.
There are two options for the pavement design CBR for the site:
1. Design for a worst case subgrade of 3 across the whole site. Some areas of poor materials
may need to be undercut 0.5m below subgrade and replaced with compacted granular fill.
Expensive but conservative option.
2. Multi design road subgrade, design for a subgrade CBR of 15 and 3 across the site, the
majority of the site should be CBR 15+ but there are likely to be areas with a subgrade CBR
L INFORMATION
of 3. The subgrade CBR 3 pavement zone shall be extended 3m into the CBR 15 zone
where encountered. Some areas of poor material may need to be undercut an additional
0.5m below subgrade and replaced with compacted granular fill.
RELEASED UNDER THE
Both these design options assume that good construction practices are used on site during
construction, this includes:
Leaving a protection layer of 150mm of cover over the final subgrade level and cutting to
the final level only hours before placing drainage material.
Final cut surface is not trafficked with construction machinery.
Construction of the basecourse material is undertaken in dry conditions. Subgrade is not
OFFICIA
allowed to get wet.
Geotechnical engineer inspects all +150mm cut surfaces to confirm any areas of soft
material requiring additional undercut.
Subgrade has good quality surface and subsoil drainage installed.
Good construction practices are particularly important for silt and clay subgrades that are very
sensitive to deformation. The subgrade CBR could drop to 1 or 2 if poor construction practices are
used.
These recommendations are for the western approach subgrade only. Once the excavation in the
eastern approach is closer to the final subgrade level we will undertake additional subgrade
analysis to confirm the suitability of CBR 15 for the east.
Attachments:
Scala Logs
Scala CBR analysis (MJ Stockwell 1977)
ACT
L INFORMATION
RELEASED UNDER THE
OFFICIA
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.0000
Date:
16/08/2013
Test No.
SC1
Project:
MPA
Operated by:
DTG
Location:
4.2m out from Post 216 to 140
Logged by:
DTG
Sheet
1
RL:
Lower level
Checked by:
of
1
0
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
50
1
2550
100
3
2600
150
4
2650
500
200
4
2700
250
4
2750
300
4
2800
350
5
2850
400
5
2900
450
5
2950
1000
ACT
500
6
3000
550
5
3050
600
8
3100
650
4
3150
700
9
3200
1500
750
5
3250
800
4
3300
850
7
3350
900
6
3400
950
4
3450
2000
1000
4
3500
1050
4
3550
1100
5
3600
1150
4
3650
1200
5
3700
(mm) 2500
1250
7
3750
th
1300
11
3800
ep
D
1350
8
3850
1400
15
3900
1450
3950
3000
1500
4000
1550
4050
1600
4100
1650
4150
1700
4200
L INFORMATION
1750
4250
3500
1800
4300
1850
4350
1900
4400
1950
4450
RELEASED UNDER THE
2000
4500
4000
2050
4550
2100
4600
2150
4650
2200
4700
2250
4750
4500
2300
4800
OFFICIA
2350
4850
2400
4900
2450
4950
2500
5000
5000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC1
Project:
MPA
Operated by:
DTG
Location:
4.2m out from Post 216 to 140
Logged by:
DTG
Sheet
2
RL:
Lower level
Checked by:
of
2
5000
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
5050
7550
5100
7600
5150
7650
5500
5200
7700
5250
7750
5300
7800
5350
7850
5400
7900
6000
5450
7950
ACT
5500
8000
5550
8050
5600
8100
5650
8150
5700
8200
6500
5750
8250
5800
8300
5850
8350
5900
8400
5950
8450
7000
6000
8500
6050
8550
6100
8600
)
6150
8650
m
6200
8700
(m 7500
6250
8750
th
p
6300
8800
e
D
6350
8850
6400
8900
6450
8950
8000
6500
9000
6550
9050
6600
9100
6650
9150
6700
9200
L INFORMATION
6750
9250
8500
6800
9300
6850
9350
6900
9400
6950
9450
RELEASED UNDER THE
7000
9500
9000
7050
9550
7100
9600
7150
9650
7200
9700
7250
9750
9500
7300
9800
OFFICIA
7350
9850
7400
9900
7450
9950
7500
10000
10000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC2
Project:
MPA
Operated by:
DTG
Location:
6.1m from SC1
Logged by:
DTG
Sheet
1
RL:
Upper level
Checked by:
of
1
0
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
50
1
2550
100
1
2600
150
3
2650
500
200
0.3
2700
250
0.3
2750
300
0.3
2800
350
1
2850
400
1
2900
450
5
2950
1000
ACT
500
5
3000
550
8
3050
600
8
3100
650
6
3150
700
14
3200
1500
750
9
3250
800
9
3300
850
10
3350
900
3400
950
3450
2000
1000
3500
1050
3550
1100
3600
1150
3650
1200
3700
(mm) 2500
1250
3750
th
1300
3800
ep
D
1350
3850
1400
3900
1450
3950
3000
1500
4000
1550
4050
1600
4100
1650
4150
1700
4200
L INFORMATION
1750
4250
3500
1800
4300
1850
4350
1900
4400
1950
4450
RELEASED UNDER THE
2000
4500
4000
2050
4550
2100
4600
2150
4650
2200
4700
2250
4750
4500
2300
4800
OFFICIA
2350
4850
2400
4900
2450
4950
2500
5000
5000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC2
Project:
MPA
Operated by:
DTG
Location:
6.1m from SC1
Logged by:
DTG
Sheet
2
RL:
Upper level
Checked by:
of
2
5000
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
5050
7550
5100
7600
5150
7650
5500
5200
7700
5250
7750
5300
7800
5350
7850
5400
7900
6000
5450
7950
ACT
5500
8000
5550
8050
5600
8100
5650
8150
5700
8200
6500
5750
8250
5800
8300
5850
8350
5900
8400
5950
8450
7000
6000
8500
6050
8550
6100
8600
)
6150
8650
m
6200
8700
(m 7500
6250
8750
th
p
6300
8800
e
D
6350
8850
6400
8900
6450
8950
8000
6500
9000
6550
9050
6600
9100
6650
9150
6700
9200
L INFORMATION
6750
9250
8500
6800
9300
6850
9350
6900
9400
6950
9450
RELEASED UNDER THE
7000
9500
9000
7050
9550
7100
9600
7150
9650
7200
9700
7250
9750
9500
7300
9800
OFFICIA
7350
9850
7400
9900
7450
9950
7500
10000
10000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC3
Project:
MPA
Operated by:
DTG
Location:
2.9m from Post 224 in line with 132
Logged by:
DTG
Sheet
1
RL:
Lower level
Checked by:
of
1
0
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
50
3
2550
100
2
2600
150
1
2650
500
200
2
2700
250
5
2750
300
4
2800
350
5
2850
400
5
2900
450
6
2950
1000
ACT
500
7
3000
550
5
3050
600
9
3100
650
7
3150
700
7
3200
1500
750
8
3250
800
7
3300
850
6
3350
900
5
3400
950
7
3450
2000
1000
6
3500
1050
6
3550
1100
8
3600
1150
13
3650
1200
13
3700
(mm) 2500
1250
10
3750
th
1300
8
3800
ep
D
1350
8
3850
1400
8
3900
1450
11
3950
3000
1500
14
4000
1550
16
4050
1600
4100
1650
4150
1700
4200
L INFORMATION
1750
4250
3500
1800
4300
1850
4350
1900
4400
1950
4450
RELEASED UNDER THE
2000
4500
4000
2050
4550
2100
4600
2150
4650
2200
4700
2250
4750
4500
2300
4800
OFFICIA
2350
4850
2400
4900
2450
4950
2500
5000
5000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC3
Project:
MPA
Operated by:
DTG
Location:
2.9m from Post 224 in line with 132
Logged by:
DTG
Sheet
2
RL:
Lower level
Checked by:
of
2
5000
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
5050
7550
5100
7600
5150
7650
5500
5200
7700
5250
7750
5300
7800
5350
7850
5400
7900
6000
5450
7950
ACT
5500
8000
5550
8050
5600
8100
5650
8150
5700
8200
6500
5750
8250
5800
8300
5850
8350
5900
8400
5950
8450
7000
6000
8500
6050
8550
6100
8600
)
6150
8650
m
6200
8700
(m 7500
6250
8750
th
p
6300
8800
e
D
6350
8850
6400
8900
6450
8950
8000
6500
9000
6550
9050
6600
9100
6650
9150
6700
9200
L INFORMATION
6750
9250
8500
6800
9300
6850
9350
6900
9400
6950
9450
RELEASED UNDER THE
7000
9500
9000
7050
9550
7100
9600
7150
9650
7200
9700
7250
9750
9500
7300
9800
OFFICIA
7350
9850
7400
9900
7450
9950
7500
10000
10000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC4
Project:
MPA
Operated by:
DTG
Location:
7.1m from SC3
Logged by:
DTG
Sheet
1
RL:
Upper level
Checked by:
of
1
0
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
50
4
2550
100
5
2600
150
7
2650
500
200
7
2700
250
8
2750
300
9
2800
350
6
2850
400
6
2900
450
6
2950
1000
ACT
500
9
3000
550
6
3050
600
4
3100
650
6
3150
700
8
3200
1500
750
6
3250
800
5
3300
850
6
3350
900
8
3400
950
8
3450
2000
1000
6
3500
1050
6
3550
1100
8
3600
1150
6
3650
1200
8
3700
(mm) 2500
1250
7
3750
th
1300
5
3800
ep
D
1350
9
3850
1400
11
3900
1450
10
3950
3000
1500
15
4000
1550
4050
1600
4100
1650
4150
1700
4200
L INFORMATION
1750
4250
3500
1800
4300
1850
4350
1900
4400
1950
4450
RELEASED UNDER THE
2000
4500
4000
2050
4550
2100
4600
2150
4650
2200
4700
2250
4750
4500
2300
4800
OFFICIA
2350
4850
2400
4900
2450
4950
2500
5000
5000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC4
Project:
MPA
Operated by:
DTG
Location:
7.1m from SC3
Logged by:
DTG
Sheet
2
RL:
Upper level
Checked by:
of
2
5000
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
5050
7550
5100
7600
5150
7650
5500
5200
7700
5250
7750
5300
7800
5350
7850
5400
7900
6000
5450
7950
ACT
5500
8000
5550
8050
5600
8100
5650
8150
5700
8200
6500
5750
8250
5800
8300
5850
8350
5900
8400
5950
8450
7000
6000
8500
6050
8550
6100
8600
)
6150
8650
m
6200
8700
(m 7500
6250
8750
th
p
6300
8800
e
D
6350
8850
6400
8900
6450
8950
8000
6500
9000
6550
9050
6600
9100
6650
9150
6700
9200
L INFORMATION
6750
9250
8500
6800
9300
6850
9350
6900
9400
6950
9450
RELEASED UNDER THE
7000
9500
9000
7050
9550
7100
9600
7150
9650
7200
9700
7250
9750
9500
7300
9800
OFFICIA
7350
9850
7400
9900
7450
9950
7500
10000
10000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC5
Project:
MPA
Operated by:
DTG
Location:
2.5m from post 132
Logged by:
DTG
Sheet
1
RL:
Upper level
Checked by:
of
1
0
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
50
3
2550
100
3
2600
150
5
2650
500
200
5
2700
250
6
2750
300
6
2800
350
5
2850
400
5
2900
450
6
2950
1000
ACT
500
5
3000
550
5
3050
600
7
3100
650
7
3150
700
8
3200
1500
750
9
3250
800
6
3300
850
6
3350
900
8
3400
950
8
3450
2000
1000
10
3500
1050
10
3550
1100
8
3600
1150
6
3650
1200
4
3700
(mm) 2500
1250
7
3750
th
1300
12
3800
ep
D
1350
14
3850
1400
15
3900
1450
3950
3000
1500
4000
1550
4050
1600
4100
1650
4150
1700
4200
L INFORMATION
1750
4250
3500
1800
4300
1850
4350
1900
4400
1950
4450
RELEASED UNDER THE
2000
4500
4000
2050
4550
2100
4600
2150
4650
2200
4700
2250
4750
4500
2300
4800
OFFICIA
2350
4850
2400
4900
2450
4950
2500
5000
5000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
TONKIN & TAYLOR
Scala logs 16 Aug 2013.xls
SCALA PENETROMETER LOG
Job No:
85700.000
Date:
16/08/2013
Test No.
SC5
Project:
MPA
Operated by:
DTG
Location:
2.5m from post 132
Logged by:
DTG
Sheet
2
RL:
Upper level
Checked by:
of
2
5000
mm
No. of
mm
No. of
Driven
Blows
Driven
Blows
5050
7550
5100
7600
5150
7650
5500
5200
7700
5250
7750
5300
7800
5350
7850
5400
7900
6000
5450
7950
ACT
5500
8000
5550
8050
5600
8100
5650
8150
5700
8200
6500
5750
8250
5800
8300
5850
8350
5900
8400
5950
8450
7000
6000
8500
6050
8550
6100
8600
)
6150
8650
m
6200
8700
(m 7500
6250
8750
th
p
6300
8800
e
D
6350
8850
6400
8900
6450
8950
8000
6500
9000
6550
9050
6600
9100
6650
9150
6700
9200
L INFORMATION
6750
9250
8500
6800
9300
6850
9350
6900
9400
6950
9450
RELEASED UNDER THE
7000
9500
9000
7050
9550
7100
9600
7150
9650
7200
9700
7250
9750
9500
7300
9800
OFFICIA
7350
9850
7400
9900
7450
9950
7500
10000
10000
0
1
2
3
4
5
6
7
8
9
10
Blows / 50 mm
Test Method Used: NZS 4402:1988 Test 6.5.2 Dynamic Cone Penetrometer
MPA
T&T job No.:
85700.000
20/08/2013
CBR and Soil Bearing Pressure given Scala data
SC1
SC2
SC3
SC4
SC5
Depth
Scala WS
Bearing CBR Depth
Scala WS
Bearing CBR Depth
Scala WS
Bearing CBR Depth
Scala WS
Bearing CBR Depth
Scala WS
Bearing CBR Depth
Scala WS
Bearing CBR
mm
mm/blow
kPa
mm
mm/blow
kPa
mm
mm/blow
kPa
mm
mm/blow
kPa
mm
mm/blow
kPa
mm
mm/blow
kPa
50
50
69
3
50
50
69
3
50
16.7
178
12
50
12.5
229
17
50
16.7
178
12
#DIV/0!
####
100
16.7
178
12
100
50
69
3
100
25
126
7
100
10
278
22
100
16.7
178
12
#DIV/0!
####
150
12.5
229
17
150
16.7
178
12
150
50
69
3
150
7.1
374
35
150
10
278
22
#DIV/0!
####
200
12.5
229
17
200
166.7
24
1
200
25
126
7
200
7.1
374
35
200
10
278
22
#DIV/0!
####
ACT
250
12.5
229
17
250
166.7
24
1
250
10
278
22
250
6.25
418
41
250
8.3
327
28
#DIV/0!
####
300
12.5
229
17
300
166.7
24
1
300
12.5
229
17
300
5.5
467
49
300
8.3
327
28
#DIV/0!
####
350
10
278
22
350
50
69
3
350
10
278
22
350
8.3
327
28
350
10
278
22
#DIV/0!
####
400
10
278
22
400
50
69
3
400
10
278
22
400
8.3
327
28
400
10
278
22
#DIV/0!
####
450
10
278
22
450
10
278
22
450
8.3
327
28
450
8.3
327
28
450
8.3
327
28
#DIV/0!
####
500
8.3
327
28
500
10
278
22
500
7.1
374
35
500
5.5
467
49
500
10
278
22
#DIV/0!
####
550
10
278
22
550
6.25
418
41
550
10
278
22
600
10
278
22
550
10
278
22
#DIV/0!
####
600
6.25
418
41
600
6.25
418
41
650
6.25
418
41
700
7.1
374
35
600
7.1
374
35
#DIV/0!
####
650
12.5
229
17
650
8.3
327
28
750
6.7
394
38
800
9.1
302
25
700
6.7
394
38
#DIV/0!
####
700
5.6
460
47
700
3.6
674
84
850
7.7
349
31
900
7.1
374
35
800
6.7
394
38
#DIV/0!
####
750
10
278
22
750
5.6
460
47
950
8.3
327
28
1000
7.1
374
35
900
7.1
374
35
#DIV/0!
####
800
12.5
229
17
800
5.6
460
47
1050
8.3
327
28
1100
7.1
374
35
1000
5.5
467
49
#DIV/0!
####
900
7.7
349
31
850
5
507
55
1150
4.8
525
58
1200
7.1
374
35
1100
5.5
467
49
#DIV/0!
####
1000
12.5
229
17
1250
4.3
578
67
1300
8.3
327
28
1200
10
278
22
1100
11.1
254
20
1350
6.25
418
41
1400
5
507
55
1300
5.3
482
51
1200
11.1
254
20
1450
5.3
482
51
1500
4
615
73
1400
3.4
708
91
1300
5.6
460
47
1550
3.3
727
94
1400
4.4
566
65
L INFORMATION
RELEASED UNDER THE
S:\SOILS\Scala-CBR\Subgrade CBR-Scala.xlsx: Field Data Entry Printed on 20/08/2013
Page 1 of 1
OFFICIA
CBR with Depth derived from Scala Penetrometer
CBR Values
0
10
20
30
40
50
0
200
ACT
400
600
)
m
800
(m
th
p
e
D
1000
1200
L INFORMATION
1400
RELEASED UNDER THE
1600
OFFICIA
1800
SC1
SC2
SC3
SC4
SC5
S:\SOILS\Scala-CBR\Subgrade CBR-Scala.xlsx: Field CBR Chart Printed on 20/08/2013
Page 1 of 1