C109584- Attachment G - Duct Bank Report.pdf
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- Solicitation number
- C109584
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This document is a report of a subsurface investigation conducted by GeoTechnologies, Inc. for an existing 200-foot-long utility duct bank located at the National Institutes of Environmental Health Sciences (NIEHS) campus in Research Triangle Park, North Carolina. The investigation included drilling four borings to depths of 9 to 20 feet below grade and found the subsurface conditions consisting primarily of variable fill material mixed with some rock fragments, underlain by very hard silt and partially weathered rock. The report recommends that helical anchors be used to underpin the duct bank, extending through the fill material to the underlying harder strata to provide high-capacity support.
The related federal contract opportunity is a solicitation (Solicitation Number C109584) from the Department of Health and Human Services, National Institutes of Health, to improve the reliability of the Central Utility Plant at the Research Triangle Park campus by providing standby power for chilled water generation. This $25 million to $100 million Design-Build project aims to correct medium voltage and low voltage duct bank settlement issues, replace feeders, install medium voltage switches, and construct a new generator yard and electrical vault. The solicitation is open to small business joint ventures, and responses are due by September 23, 2024.
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Text version
February 17, 2022
Rick Sykes Foundation Solutions, LLC 4122 Bennett Memorial Road, Suite 304 Durham, NC 27705
Re: Report of Subsurface Investigation NIEHS Duct Bank Research Triangle Park, North Carolina GeoTechnologies Project No. 1-21-1304-EA
Gentlemen:
GeoTechnologies, Inc. has completed the authorized evaluation for underpinning the existing duct bank with helical anchors. Our evaluation included drilling four borings to depths of 9 to 20 feet below existing grade.
The borings were completed using hollow stem augering techniques and soils were sampled at selected intervals using standard penetration testing techniques (ASTM D-1586). This report presents our recommendations regarding foundation support of the proposed facility.
PROJECT DESCRIPTION
The site is located at 111 TW Alexander Drive in Research Triangle Park, North Carolina. We understand that an existing 200-foot-long utility duct bank has settled and will require underpinning with helical anchors. The duct bank is reportedly 3 feet below grade and is overlain with an asphalt parking lot.
SUBSURFACE CONDITIONS
Subsurface conditions on the site were generally characterized by fill material that extended to depths of 4 to 19 feet below existing grade. The fill was comprised of a mixture of silt and clay of varying plasticity, intermixed with some blast rock. The fill material exhibited penetration resistances of 6 to 17 blows per foot (bpf). Some of the penetration resistances were likely elevated due to the rock fragments mixed in the fill.
Underlying the fill, the borings generally encountered very hard silt and partially weathered rock (PWR). PWR is described as material that can be penetrated with the soil drilling augers but that exhibits penetration resistances in excess of 100 bpf. Borings B-2, B-3 and B-4 were terminated at depths of 19 to 20 feet in PWR.
Boring B-1 was terminated at 9 feet when an unknown obstruction was encountered. Groundwater was not encountered in the borings at the time of boring completion.
RECOMMENDATIONS
Information regarding the depth of the base of the duct bank was not provided. We are assuming that the duct bank is likely bearing on the existing fill material. The fill is variable and is mixed with some rock
Foundation Solutions, LLC Re; Niehs Duct Bank February 17, 2022 Page: 2 fragments. If helical anchors are used for the underpinning we recommend that they extend through the fill material to the underlying PWR or hard silt. The hard silt and PWR will support high capacity anchors and the maximum capacity will be controlled by the strength of the anchor materials. A 40-kip anchor can easily be developed on the hard silts and PWR underlying the fill material. During installation, the operations should be monitored to verify that the anchors extend to near the anticipated embedment depth and that an appropriate torque is achieved. If shallow refusal is encountered on rock mixed in the fill material it may be necessary to predill a pilot hole or to use an excavator to remove the obstruction.
GeoTechnologies, Inc. appreciates the opportunity to be of service on this phase of the project. Please contact us if you have any questions concerning this letter or if we may be of additional service on this or other projects.
Sincerely, GeoTechnologies, Inc.
David L. Israel, P.E.
NC Registration No. 14319
DLI/pr-ch Attachments 1211304ea
GoMaps
Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community
February 17, 2022
0 0.0095 0.0190.00475 mi
0 0.015 0.030.0075 km
1:564 disrael.VBN Oval disrael.VBN Oval disrael.VBN Oval disrael.VBN Oval disrael.VBN Typewritten Text B-1 disrael.VBN Typewritten Text B-2 disrael.VBN Typewritten Text B-3 disrael.VBN Typewritten Text B-4 disrael.VBN Typewritten Text Figure 1
50/0"
B-1
50/3.5"
50/5.5"
50/3"
B-2
50/1.5"
B-3
50/2"
B-4
Durham, NC
SCALE: As Shown
FIGURE No: 2 NIEHS Duct Bank
Depth (Feet)
JOB No:1-21-1304-EA
PROJECT:
GENERALIZED SUBSURFACE PROFILE LEGEND
Asphalt
Low Plasticity Clay to Silt
Moderate Plasticity Clay
Partially Weathered Rock
Low Plasticity Silt
Moderate Plasticity Silt
Low Plasticity Clay
CABC Stone
High Plasticity Clay
Auger Refusal
Standard Penetration Resistance
Fill
1.1
9.0
CL
ML
Asphalt (13").
FILL: Firm, reddish brown, clay and silt.
Boring terminated at 9 feet on concrete.
3-3-4
50/0"
No groundwater encountered upon completion.
DEPTH
(FT.)
0.0
TEST BORING RECORD
PENETRATION
(BLOWS/FT.)
BLOWS PER
SIX INCHES
ELEVATION
(FT.)
1 OF 1PAGE
JOB NUMBER
BORING NUMBER
DATE
1-21-1304-EA
B-1 2-14-22
100 20 40 60 100
DESCRIPTION
3200 Wellington Court, Ste 108 Raleigh, NC 27615
G T
I_ M
A
IN
E A
.G P
J G
T I.G
D T
/1
6/
1.0
4.0
7.5
13.0
19.3
CL
CH
ML
Asphalt (12").
FILL: Brown, silty CLAY.
Partially Weathered Rock (PWR): sampled as brown sandy silt.
Very Hard, reddish brown and gray, SILT.
Partially Weathered Rock (PWR): sampled as reddish brown silt.
Boring terminated at 19.3 feet.
45-50/3.5"
40-40-40
50/5.5"
50/3"
No groundwater encountered upon completion.
DEPTH
(FT.)
0.0
TEST BORING RECORD
PENETRATION
(BLOWS/FT.)
BLOWS PER
SIX INCHES
ELEVATION
(FT.)
1 OF 1PAGE
JOB NUMBER
BORING NUMBER
DATE
1-21-1304-EA
B-2 2-14-22
100 20 40 60 100
DESCRIPTION
3200 Wellington Court, Ste 108 Raleigh, NC 27615
G T
I_ M
A
IN
E A
.G P
J G
T I.G
D T
/1
1.0
8.0
13.0
19.0 19.3
ML
MH
ML
CL
Asphalt (12").
FILL: Stiff, brown, clayey SILT with rocks.
FILL: Very Stiff, brown clayey SILT with rocks.
FILL: Stiff, brown, silty CLAY with rocks.
Partially Weathered Rock (PWR).
Boring terminated with auger refusal at 19.3 feet.
7-7-8
5-7-10
9-7-4
50/1.5"
No groundwater encountered upon completion.
DEPTH
(FT.)
0.0
TEST BORING RECORD
PENETRATION
(BLOWS/FT.)
BLOWS PER
SIX INCHES
ELEVATION
(FT.)
1 OF 1PAGE
JOB NUMBER
BORING NUMBER
DATE
1-21-1304-EA
B-3 2-14-22
100 20 40 60 100
DESCRIPTION
3200 Wellington Court, Ste 108 Raleigh, NC 27615
G T
I_ M
A
IN
E A
.G P
J G
T I.G
D T
/1
1.5
6.5
12.0
17.5
19.5 19.8
ML
CH
CH
ML
Base Course Stone.
FILL: Firm, reddish brown, SILT.
FILL: Firm, reddish brown, silty CLAY.
FILL: Stiff, reddish brown, silty CLAY.
Hard, light gray, SILT with rock fragments.
Partially Weathered Rock (PWR): sampled as brown silt.
Boring terminated at 19.8 feet.
3-3-3
3-4-2
2-4-5
40-50/2"
No groundwater encountered upon completion.
DEPTH
(FT.)
0.0
TEST BORING RECORD
PENETRATION
(BLOWS/FT.)
BLOWS PER
SIX INCHES
ELEVATION
(FT.)
1 OF 1PAGE
JOB NUMBER
BORING NUMBER
DATE
1-21-1304-EA
B-4 2-14-22
100 20 40 60 100
DESCRIPTION
3200 Wellington Court, Ste 108 Raleigh, NC 27615
G T
I_ M
A
IN
E A
.G P
J G
T I.G
D T
/1
| NIEHS_DB_Elect_Final_Report 06.14.22 |
| GEO TEST RESULTS |
| SUBSURFACE CONDITIONS |
| RECOMMENDATIONS |
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