Letter of Geotechnical Findings - USFS Bridge on Jordan Road over Pedlar R.pdf

Letter of Geotechnical Findings

Prepared for:

TGS Engineers, Inc.

804-C N. Lafayette Street Shelby, North Carolina 28150

October 25, 2019

2400 Crownpoint Executive Drive

Suite 800

Charlotte, NC 28227

(980) 339-8684 contact@carolinasgeotech.com www.carolinasgeotech.com

October 25, 2019 Mr. Leonard G. Fletcher, PE

TGS Engineers, Inc.

804-C N. Lafayette Street

Shelby, North Carolina 28150

SUBJECT: Letter of Geotechnical Findings

USFS Bridge on Jordan Road over Pedlar River

Vesuvius, Virginia

CG2 Project No.: 240019042

Carolinas Geotechnical Group, PLLC (CG2) has completed the subsurface exploration for the replacement bridge located on Jordan Road over the Pedlar River. Our services were performed in general accordance with the agreement between CG2 and TGS Engineers, Inc. Our Boring Location Plan, and Soil Test Boring Records are attached to this letter. We have also provided a summary of our findings from the exploration.

CG2 performed the exploration on October 14 and 15, 2019 with a track-mounted drill rig equipped with an automatic hammer. Standard Penetration Testing (SPT) was performed at regular intervals.

The test locations were marked in the field prior to our mobilization to the site. Our test locations marked on the attached boring location plan should be considered approximate.

SUBSURFACE CONDITIONS

Fill, or soil placed by man, were encountered at the ground surface at each of the borings. The fill soils consisted of very loose to medium dense, silty sand (SM). Our field personnel noted the presence of 12 to 18-inch boulders in the existing fill. Fill was encountered in the borings to a depth of approximately 12 feet below the existing ground surface.

Alluvial soils were encountered below the existing fill soils in each of the borings. The alluvial soils encountered consisted of dense to very dense, silty, sandy gravel (GP) and sand (SP) with silt and gravel. The alluvial soils were encountered in the borings to depths ranging from approximately 17 to

18.5 ft below the existing ground surface.

Residual soils were encountered at Boring B-1 below the alluvial soils. The residual soils generally consisted of dense, silty sand (SM) and hard, sandy silt (ML). The residual soils were encountered in Boring B-1 to a depth of approximately 28.5 feet below the existing ground surface.

Each of the borings encountered partially weathered rock at depths ranging from 18.5 to 28.5 feet below the existing ground surface. Partially weathered rock is defined as material requiring 100 blows with less than 1 ft of penetration from the SPT hammer. The partially weathered rock encountered in the boring was sampled as brown, silty sand (SM).

Letter of Geotechnical Findings

USFS Bridge on Jordan Road over Pedlar River

Vesuvius, Virginia

October 25, 2019

Each of the borings encountered auger refusal material at depths ranging from approximately 21 to

37.5 feet below existing grades. Upon encountered auger refusal at Boring B-2, our field crew attempted to offset the boring and encountered casing advancer refusal at a similar depth.

OPINIONS

CG2 has been requested to provide an opinion on estimated pile lengths for the subject bridge. Our summary is included below in Table No. 1:

Table No. 1: Estimated Pile Length Summary

Factored Pile Resistance: 125 tons (250 kips) Required Driving Resistance: 210 tons (420 kips)

End Bent

End Bent

Bottom of Cap Elevation (ft)* 94.5 94.5

Estimated Pile Embedment into Cap (ft) 2 2

Estimated Penetration into Rock (ft) 3 3

Estimated Tip Elevation (ft)** 69.4 76.7

Estimated Pile Length (ft) 28 20

Average Pile Length (ft) 30 25 *Bottom of cap elevation provided by TGS Engineers, Inc.

**Elevations based on project specific datum provided by TGS Engineers, Inc.

It has been estimated that a pile driving hammer with a maximum rated energy in the range of 35,000 ft-lbs to 42,000 ft-lbs per blow will be required to drive the piles at the subject bridge. This estimated energy range should not release the contractor from providing equipment capable of installing the piles to the estimated tip elevation or Required Driving Resistance. Pile excavation or other installation methods may be required where appropriate to install the piles.

CLOSING

CG2 is pleased to have the opportunity to provide these services to you. If you have questions concerning the content of this letter, or if CG2 can be of further service, please contact CG2 at (980) 339-8684.

Sincerely, Carolinas Geotechnical Group, PLLC

D. Matthew Brewer Robert E. Kral Senior Project Manager Senior Project Manager

Attachments:

Boring Location Plan Soil Test Boring Records

TES

TES

TES

TES

-L- STA 11+67.39

BEGIN BRIDGE

-L- STA 12+59.64

END BRIDGE

-L- POT 10+00.00

-L- POT 15+02.37

-L- STA 10+25.00

BEGIN PROJECT

END PROJECT

-L- STA 14+65.00

2 3.9'

7.6'0

5.1

7.9

10'10'

TYP. +

TYP.

50' TRANS. TO EXIST.

5 50' TRANS. TO EXIST.

REMOVE EXIST. BRIDGE

POSTS AND NO WIDENING FOR GUARDRAIL.

USE 8' EXTRA DEPTH GUARDRAILNOTE:

B-1 B-2

BORING PLAN

PROJECT REFERENCE NO.

Bridge on Jordan Road over Pedlar River

FEET

0 60 120

CG2 No. 240019042

FIGURE NO.

P

IP

E 18 " P

IP

E

ELEV:92.02'

E:100.27'

N:306.68'

CP1

ELEV:92.23'

E:65.46'

N:522.00'

CP2

ELEV:95.43'

OF TREE

NAIL IN BASE

BM

SIGN POST

SIGN POST

S

IG

N

O L

D

R O

A D

B E

D

EXISTING TRUSS BRIDGE

EXISTING GRAVEL ROAD EXISTING GRAVEL ROAD

EXISTING FENCE

OVERFLOW AREA

O V E

R F

L O

W

A

E A

P E

D L

A

IV

E R

P E

D

LAR

R

IVE

R

LEXINGTON TURNPIKE

TO PEDLAR RIVER RD AND

TO BLUE RIDGE PARKWAY

DATUM DESCRIPTION

THE LOCALIZED COORDINATE SYSTEM DEVELOPED FOR THIS PROJECT

IS BASED ON THE COORDINATES ESTABLISHED BY

TGS ENGINEERS FOR MONUMENT "CP1"

NORTHING: 306.68(ft) EASTING: 100.27(ft)

ELEVATION: 92.02(ft)

THE BEARING AND

LOCALIZED HORIZONTAL GROUND DISTANCE FROM

"CP1" TO -L- STATION 10+00.00 IS

S 33°39'20.6" E 195.46'

ALL LINEAR DIMENSIONS ARE LOCALIZED HORIZONTAL DISTANCES

VERTICAL DATUM USED IS ASSUMED

C

C

F

F

F

F

F

F

F

F

F

F

F

F

F

C

C

C

C

C

C

C

C

C

FILL: Very Loose to Medium Dense, Brown-Black-Orange, Silty Fine to Medium SAND (SM), contains gravel-size rock fragments

12 to 18-inch diamater boulders encountered during drilling from 0 to 10 ft below existing ground surface

ALLUVIAL: Very Dense, Brown-Gray, Silty, Fine to Medium Sandy

GRAVEL (GP)

*Blow Counts likely influenced due to the presence of gravel

RESIDUAL: Dense, Brown-Black-Orange, Silty Fine to Medium SAND (SM), contains gravel-size rock fragments

Hard, Orange-Brown, Fine to Medium Sandy SILT (ML)

Cave-in Depth: 25.5 ft

PARTIALLY WEATHERED ROCK: Sampled as Brown, Silty Fine to Medium SAND (SM)

Refusal at 37.5 feet.

Boring terminated at a depth of 37.5 feet.

W

W

W

Sat

Sat

Sat

Sat

14-9-7 (16)

7-4-3 (7)

4-1-3 (4)

5-7-9 (16)

100/3"

41-19-20 (39)

15-24-33 (57)

50/3"

50/2"

50/0"

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SS

SS

SS

SS

SS

SS

SS

SS

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D E

P T

H (f t)

G R

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MATERIAL DESCRIPTION

M oi st ur e D es cr ip tio n

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S (N

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S A

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20 40 60 80

PL LLMC

SPT N VALUE

20 40 60 80

FINES CONTENT (%)

20 40 60 80

GROUND ELEVATION 100.9 ft

LOGGED BY C. Keeten

DRILLING METHOD H.S. Augers

DRILLING CONTRACTOR C. Odom - Diedrich D-50 - 89% GROUND WATER LEVELS:

CHECKED BY M. Brewer, P.E.

DATE STARTED 10/14/19 COMPLETED 10/14/19 HOLE SIZE 6 inches

NOTES Project-specific coordinate system and datum EASTING 165 ftNORTHING 306 ft

STABILIZED WATER LEVEL 18.00 ft / Elev 82.90 ft

0-HR WATER LEVEL 25.50 ft / Elev 75.40 ft

BORING NUMBER B-1

CLIENT TGS Engineers, Inc.

PROJECT NUMBER 240019042

PROJECT NAME USFS Bridge on Jordan Road over Pedlar River

PROJECT LOCATION Vesuvius, Virginia

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J Carolinas Geotechnical Group, PLLC 2400 Crownpoint Executive Drive, Suite 800 Charlotte, North Carolina 28227

FILL: Medium Dense, Brown-Black, Silty Fine to Medium SAND (SM), contains gravel-sized rock fragments

12 to 18-inch diamater boulders encountered during drilling from 0 to 10 ft below existing ground surface

Cave-in Depth: 9.5 ft

ALLUVIAL: Dense, Brown-Gray, Fine to Coarse SAND (SP) with silt, contains angular gravel

*Blow Counts likely influenced due to the presence of gravel

PARTIALLY WEATHERED ROCK: Sampled as Brown, Silty Fine to Medium SAND (SM)

Refusal at 21.0 feet.

Boring terminated at a depth of 21.0 feet.

M

M

M

M

M

5-8-13 (21)

5-5-6 (11)

6-5-10 (15)

7-5-6 (11)

5-7-25 (32)

50/1"

50/0"

SS

SS

SS

SS

SS

SS

SS

D E

P T

H (f t)

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MATERIAL DESCRIPTION

M oi st ur e D es cr ip tio n

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W C

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N T

S (N

V A

LU

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C O

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T

Y P

E N

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B E

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20 40 60 80

PL LLMC

SPT N VALUE

20 40 60 80

FINES CONTENT (%)

20 40 60 80

GROUND ELEVATION 100.7 ft

LOGGED BY C. Keeten

DRILLING METHOD H.S. Augers

DRILLING CONTRACTOR C. Odom - Diedrich D-50 - 89% GROUND WATER LEVELS:

CHECKED BY M. Brewer, P.E.

DATE STARTED 10/15/19 COMPLETED 10/15/19 HOLE SIZE 6 inches

NOTES Project-specific coordinate system and datum EASTING 141 ftNORTHING 395 ft

STABILIZED WATER LEVEL --- FIAD

0-HR WATER LEVEL --- Dry

BORING NUMBER B-2

CLIENT TGS Engineers, Inc.

PROJECT NUMBER 240019042

PROJECT NAME USFS Bridge on Jordan Road over Pedlar River

PROJECT LOCATION Vesuvius, Virginia

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