17M7972_Geotechnical_Letter_of_Results_FS_344-A_and_344-B.PDF

17M7972 Page 1 of 6

September 10, 2018 TPT Project 17M7972

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300

Herndon, Virginia 20171

Re: Letter of Results and Recommendations

DSR FS 344-A and DSR FS 344-B

Culvert Replacement and Roadway Reconstruction

Town of Gordon, Ashland County, Wisconsin

Dear Ms. Alunkal:

This letter presents the results of our field explorations performed at two culvert washouts along two unnamed creek crossings located on FS 344 in the Town of Gordon, Ashland County, Wisconsin. The DSR

FS 344-A site is located around 4,800 feet north of the intersection of FS 193 with FS 344. The DSR FS 344-B site is located around 5,900 feet north of the intersection of FS 193 with FS 344. This work covers

DSR FS 344-A and DSR 344-B as part of the WI ERFO FS 2016-1(5) project.

Project

It is our understanding that WSP USA is in the design process for culvert replacements and roadway reconstruction at the above referenced sites. It is our understanding that the culverts and roadway sustained damage from a large rain event in July 2016. It is our understanding that the replacement culvert located at site FS 344-A will consist of a 64 inch by 43 inch corrugated metal pipe (CMP) and that the replacement culvert located at site FS 344-B will consist of a 77 inch by 52 inch CMP. As part of the design process geotechnical services were requested.

Our scope of services for this project consisted of performing one (1) Standard Penetration Test (SPT) boring at each site to a depth of 20 feet below creek bottom or refusal. We were authorized to proceed with the proposed scope of services in a signed subcontractor agreement dated February 26, 2018.

Field Exploration

Field procedures for this project were performed on May 15th, 2018 using our Geoprobe Systems

7822DT track mounted drill rig and hollow stem auger drilling methods. Boring FS 344-A (North) was performed to the north of the roadway washout to the auger refusal depth of 12 ½ feet. Boring FS 344-B

(South) was performed to the south of the roadway washout to a depth of 25 feet; five feet of sand blow up was encountered in the auger at a depth of 25 feet and the boring was terminated at this depth. The boring locations are shown on the Boring Location Sketch attached to this letter. Surface elevations were recorded by our field crew using a surveyors level and rod and were referenced to a benchmark labeled 5650. It is our understanding that this benchmark has an elevation of 1485.9 feet.

1301 N 3 rd St. Superior WI 54880 715 - 392 - 7114 1 - 800 - 373 - 2562 F 715 - 392 - 7163 www.twinportstesting.com

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Laboratory Testing Results of the field testing and observed subsurface conditions were evaluated to develop a laboratory testing program. The final laboratory testing program included visual classification by a geotechnical engineer, water content testing, and sieve analysis testing.

Laboratory water content testing was performed in general accordance with ASTM D2216 on collected samples from the field exploration. Results of water content tests are shown on the borings logs in the

Appendix. In general water content ranged from eight percent to 26 percent.

Sieve analysis testing was performed in general accordance with ASTM D422 procedures on two samples.

Test results for percent passing the #200 sieve are provided in Table 1 below and on the boring logs in the

Appendix. Test results for full gradation sieve testing are attached to this letter.

Table 1: Summary of Sieve Analysis Results

Boring Depth (feet) Description of

Material % Passing #200

FS 344-A

(North)

0-2 SP-SM (Fill)

AASHTO A-2-4

FS 344-B

(South)

0-2 SM (Fill)

AASHTO A-2-4

*SM = Silty Sand

Subsurface Conditions - Soil DSR FS 344-A (North)

Fill soils consisting of poorly graded sand with silt (AASHTO A-1-b) and silty sand (AASHTO A-2-4) were encountered at the surface to depths up to six feet. Fill soils generally contained gravel, ranged from fine to coarse grained, were brown in color, and were moist.

Native clayey sand soils (AASHTO A-2-4) were encountered below the fill soils to the refusal depth of

13½ feet. Clayey sand soils were generally fine to coarse grained, contained trace gravel, were brown in color, and were wet. Based upon results of SPT N-values native clayey sand soils appear to be generally range from loose to medium dense in relative density.

Rock coring would be required to determine the cause of refusal and was not included in our scope of services for this project.

Subsurface Conditions - Groundwater DSR FS 344-A (North)

Groundwater was not encountered in Boring FS 344-A (North) while drilling and sampling at this site.

Groundwater levels at this site are anticipated to correspond with the surface level of the adjacent unnamed creek which had a surface elevation of 1482.9 feet.

Subsurface Conditions - Soil DSR FS 344-B (South)

Fill soils consisting of silty sand (AASHTO A-2-4) were encountered at the surface to depths up to 12 feet.

Fill soils generally contained gravel, ranged from fine to coarse grained, were brown in color, and ranged from moist to waterbearing. Pieces of wood were encountered in the sample collected at ten feet and trace organics were encountered around a depth of 12 feet.

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Native poorly graded sand with silt soils (AASHTO A-1-b) were encountered below the fill soils to the boring termination depth of 25 feet. Poorly graded sand with silt soils were generally fine to medium grained, were brown in color, and were waterbearing. Based upon results of SPT N-values native poorly graded sand with silt soils appear to generally range from very loose to medium dense in relative density.

Subsurface Conditions - Groundwater DSR FS 344-B (South)

Groundwater was encountered in Boring FS 344-B (South) at a depth of six feet while drilling and sampling at this site. Groundwater levels at this site are anticipated to correspond with the surface level of the adjacent unnamed creek which had a surface elevation of 1480.2 feet.

Design Considerations and Recommendations Culverts bearing on aggregate bedding or spread footings appear to be the most economical options for this site. Alternative structure options for this site include bottomless arches or bridges bearing on spread footings.

Site Preparation

Field explorations at the DSR FS 344-A site encountered fill soils at the surface to depths of about six feet and at the DSR FS 344-B site to depths of about 12 feet. Fill soils in Boring FS 344-B (South) contained pieces of wood and organics at depths of 10 feet and 12 feet. The conditions and compactive effort under which fill soils were placed is unknown and it is possible that these soils would settle significantly when loaded. Soils containing organics and wood are highly compressible and are not suitable for structure support.

Although soils beneath new construction are expected to experience little to no increase in net stresses, we do not recommend placing shallow foundations over uncontrolled fill soils. We recommend stripping all surface fill soils and any organic soils encountered within the footprint and influence area (1H:1V out from the outside edge of footings) of the proposed foundations and replacing with compacted engineered fill to reach design elevations. Excavations for the placement of culverts should be excavated to a minimum depth of six inches below the bottom of culvert elevation to insure the removal of any projections or boulders.

Minimum excavations for the removal of fill soils at the DSR FS 344-A site are expected to be about six feet and at the DSR FS 344-A site are expected to be about 12 feet.

Shallow Foundations It appears that shallow foundations, consisting of spread footings or culverts bearing on aggregate bedding, may be used for foundation support when bearing on native sands or engineered fill over native sands. It is expected that culverts will be placed on a minimum of six inches of aggregate bedding overlying native soil.

Recommendations for foundation design are provided below.

Net Allowable Bearing Stress

Results of the field and laboratory testing program were used to evaluate the net allowable bearing stress for shallow foundations. In our opinion, a net allowable bearing stress (with a minimum factor of safety of at least 2.5) of 3,000 psf (pounds per square foot) may be used to design footings placed on native soils or engineered fill over native soils.

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Settlement Estimate

For foundations bearing on native soils or engineered fill over native soils and designed according to the net allowable bearing stresses outlined above, we estimate total settlement of less than one inch and differential settlements less than one-half inch.

Frost Protection We recommend that culvert foundations be placed at a minimum depth of six feet below finished exterior grade (surface of soil directly above foundation) to provide frost protection. We also recommend that roadway surface be a minimum of five feet above the water table to minimize frost heave.

In areas where new culvert construction tie into existing roadways, we recommend that excavations extend from the bottom of culverts at a slope of 1:20 (Vertical:Horizontal) to provide frost differential protection.

Backfill and Fill A wide variety of materials can be considered as suitable for engineered backfill placed in a controlled manner or for general fill soils at non-structural locations. The choice of materials is a function of structural requirements, water table conditions, seasonal construction constraints, placement and compaction methods, and other site or project specific needs. Soils which classify as SP, SP-SM, or SM in the Unified Soil Classification System (ASTM D2487) or AASHTO A-1 and AASHTO A-2 in the AASHTO Soil Classification System are usually the most available suitable soils for engineered backfill and fill.

For this project, we recommend that Aggregate Bedding meeting the gradation outlined below for direct culvert support/bedding.

Table 2: Gradation for the entire sample

Sieve Percent Passing by Weight (%)

1 ¼ inch 100

No. 4 25-100

Table 3: Gradation for the portion of the sample passing the No. 4 sieve, conform to the following limits

Sieve Percent Passing by Weight (%)

No. 4 100

No. 40 --

No. 100 0-30

No. 200 0-15

Other gradations for backfill of over excavations or embankment construction may also be suitable as approved by the project geotechnical engineer. Existing fill and native soils may be suitable for re-use, but should be verified through sieve analysis of representative bulk samples.

We recommend that a geotextile fabric (WisDOT Type SAS or equivalent) be placed between native soils and engineered fill/aggregate bedding to promote drainage and provide separation.

Compaction Standard We recommend using ASTM D698 - Standard Proctor as the laboratory compaction standard.

Density

We recommend compacting each lift to a minimum of the following percentage of the above compaction standard for the respective types of fill materials:

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Table 4: Compaction Recommendation

Type of Engineered Fill % Minimum Compaction

Foundation Structural Backfill 98%

Aggregate Bedding 98%

Non-structural Foundation Backfill 95%

Within 3 Feet of Pavement or Aggregate Base Section 100%

Lift Thickness Place engineered backfill and fill materials in lifts not to exceed eight inches in a loose condition, unless the contractor can demonstrate satisfactory results when placing thicker lifts. Maximum compacted lift thickness should not exceed 12 inches in a loose condition.

Moisture In general, granular fill materials should be placed and compacted within two percent of optimum moisture content, as determined by the above referenced compaction standard. When the moisture content of fill materials is not in this range, compaction to the required density may be difficult if not impossible. The excavating contractor is responsible for controlling and adjusting moisture content of backfill materials.

Scour and Riprap We recommend the use of concrete end treatments (headwalls and wingwalls) combined with riprap to prevent the erosion of embankment soils and to provide protection against scour. Culvert foundations should be placed at an adequate depth to avoid scour. A detailed scour analysis was not included in our scope of work.

Dewatering Groundwater was not observed in Boring FS 344-A (North) and was observed at a depth of six feet in Boring FS 344-B (South) during drilling and sampling. Groundwater within excavations for construction of the proposed culverts is expected to be directly related to the levels of the adjacent unnamed creeks at the respective sites. If excavations extend below the groundwater surface and dewatering is necessary for construction, a large scale dewatering plan will be required. Dewatering options include diverting the unnamed creeks around the excavations or installing temporary sheet pile cofferdams with sumps and pumps.

Over Sizing Excavations for the placement of engineered backfill should extend horizontally at least a minimum of one foot beyond the bottom edge of footing for every one foot of over excavation depth required below the footing.

Temporary Shoring Temporary shoring of excavations may be required for this project. Any temporary shoring systems should be designed by a registered professional engineer.

Frozen Materials If construction occurs during temperatures below freezing, the base of all excavations and backfill materials should be protected from freezing. Excavated surfaces which become frozen should be completely thawed prior to placing backfill, concrete, or pavements. If freezing has loosened and reduced the bearing capacity of the excavation surface, remove the frozen material to the undisturbed surface. Frozen material should not be used as backfill.

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Observation - Excavations Excavation bottoms and engineered fill operations should be observed by a geotechnical engineer or a designated representative to assure that the recommendations in this report are being followed. In-place density testing should be performed to document that project specifications are met.

Observation - Foundations Installation of foundations should be observed and documented by a qualified technician or engineer. We recommend that at a minimum, concrete be tested for air content, temperature, slump, and compressive strength.

Frequency of Testing

For this project, we recommend a minimum density testing frequency of one test per 1,000 square feet of backfill area per lift. If the project area is smaller than this, we recommend a minimum of one test per lift. For isolated locations or questionable areas, we recommend a minimum of one test per occasion.

General

If you have any questions regarding our results, or if we may be of further service on this project, please call us at 715.392.7114.

Twin Ports Testing II, Inc.

Brett Carlson, PE

Project Engineer

Martin L. Halvorson, PE

Senior Engineer

Attachments:

Boring Location Sketch (1 Page)

Boring Logs (2 Pages)

Sieve Analysis (1 Page)

Boring Log Notes (2 Pages)

N

Approximate Boring Location

DRAWN BY: CHECKED BY:

DATE: SCALE:

DRAWING NO:

TPT PROJECT NO:

DRAWING NO:

1/1

REV:

DCS BMC

7/13/2018 N/A

17M7972J-01

17M7972J

A

BORING LOCATION SKETCH

Culvert Replacement and Roadway Reconstruction

DSR FS 344-A and DSR FS 344-B

Town of Gordon, Ashland County, Wisconsin

T win

P orts

T esting

344-B SOUTH

344-A NORTH

F

R

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

2.0

6.0

13.5

(FILL) Poorly Graded Sand with silt and gravel, fine to coarse grained, brown, moist

*Sieve analysis test performed at 1 foot

(FILL) Silty Sand with gravel, fine to coarse grained, brown, moist

(SC) CLAYEY SAND, trace gravel, fine to coarse grained, brown, wet, loose to medium dense (AASHTO A-2-4)

*Auger refusal at 12 1/2 feet

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 344-A

PROJECT:

5/21/18

NE WD

River Elev 1482.9 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Observed

BORING STARTED

CREW CHIEF

MLH

WATER LEVEL

WSP USA Town of Gordon, Ashland County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

05/15/18 05/15/18

REPORT DATE:

WATER LEVEL BORING COMPLETED ABBREVIATIONS: ACR-After Casing Removal, BCR-Before Casing Removal, AB-After Boring, WD-While Drilling, WS-While Sampling, NE-None Encountered, DB-Diamond Bit, HSA-Hollow Stem Auger, RB-Rock Bit, SS-Split Spoon, ST-Shelby Tube, PA-Power Auger, MR-Mud Rotary, CS-Continuous, RP-Rock Probe, PH-Percussion Hammer, WL-Water Level, WOH-Weight of Hammer, EIL-Exceeds Instrument Level, TS-Topsoil, PP-Pocket Penetrometer

17M7972J

SA

M

PL

E

N O

D

EP

TH

(f t)

EL

EV

AT

IO

N

(f t)

0.0

10.0

1487.4

1477.4

SA

M

PL

E

D

IS

TA

N

C E

PLASTIC

LIMIT %

TPT Project No.:

UNCONFINED COMPRESSIVE STRENGTH (TONS/FT2)

PERCENT PASSING #200 SIEVE

10 20 30 40 50

1 2 3 4 5

10 20 30 40 50

FS 344-A (North)

See Boring Location Sketch

R

EC

O

VE

R Y

10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

W

AT

ER

L

EV

EL

SA

M

PL

E

TY

PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972J DSR FS 344A.GPJ TWINPORT.GDT 7/12/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1487.4 ftST

R

AT

A C

H

AN

G E

D

EP

TH

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

12.0

25.0

(FILL) Silty Sand with gravel, fine to coarse grained, brown, moist to waterbearing *Sieve analysis of % passing #200 sieve test performed at 1 foot = 26.1 %

*pieces of wood at 10 feet

*trace organics at 12 feet

(SP-SM) POORLY GRADED SAND with Silt, fine to medium grained, brown, waterbearing (AASHTO A-1-b)

*Five feet of sand blow up at 25 feet Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 344-B

PROJECT:

5/21/18

6.4 ft WD

River Elev 1480.2 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

13.4 ft

BORING STARTED

CREW CHIEF

MLH

WATER LEVEL

WSP USA Town of Gordon, Ashland County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

05/15/18 05/15/18

REPORT DATE:

WATER LEVEL BORING COMPLETED ABBREVIATIONS: ACR-After Casing Removal, BCR-Before Casing Removal, AB-After Boring, WD-While Drilling, WS-While Sampling, NE-None Encountered, DB-Diamond Bit, HSA-Hollow Stem Auger, RB-Rock Bit, SS-Split Spoon, ST-Shelby Tube, PA-Power Auger, MR-Mud Rotary, CS-Continuous, RP-Rock Probe, PH-Percussion Hammer, WL-Water Level, WOH-Weight of Hammer, EIL-Exceeds Instrument Level, TS-Topsoil, PP-Pocket Penetrometer

17M7972K

SA

M

PL

E

N O

D

EP

TH

(f t)

EL

EV

AT

IO

N

(f t)

0.0

10.0

20.0

30.0

1487.7

1477.7

1467.7

1457.7

SA

M

PL

E

D

IS

TA

N

C E

PLASTIC

LIMIT %

TPT Project No.:

UNCONFINED COMPRESSIVE STRENGTH (TONS/FT2)

PERCENT PASSING #200 SIEVE

10 20 30 40 50

1 2 3 4 5

10 20 30 40 50

FS 344-B (South)

See Boring Location Sketch

R

EC

O

VE

R Y

10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

W

AT

ER

L

EV

EL

SA

M

PL

E

TY

PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972K DSR FS 344B.GPJ TWINPORT.GDT 7/12/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1487.7 ftST

R

AT

A C

H

AN

G E

D

EP

TH

WOH

BORING LOG NOTES

Water Level Water levels indicated on the boring logs are as measured at stated times. In clean sand soils, the elevations indicated are considered relatively reliable levels. However, in less permeable soils, even after several days of monitoring, accurate determinations may not be possible. Therefore, additional/alternative methods of groundwater elevation monitoring should be sought.

Commonly Used Moisture Conditions of Soils Term Meaning Dry Requires the addition of considerable moisture to attain optimum for compaction Moist Near optimum moisture for compaction Wet Requires drying to attain optimum moisture for compaction Waterbearing Saturated granular soils

Gradation Description and Terminology Soil Type Particle Name Size Range Coarse Grained Soils Boulders Over 12”

Cobbles 3”-12” Gravels #4-3” Gravels – Coarse ¾”-3” Gravels – Fine #4-¾” Sands #200-#4 Sands – Coarse #10-#4 Sands – Medium #40-#10 Sands – Fine #200-#40

Fine Grained Soils Silt 0.005 mm-#200 Clay Less than 0.005 mm

Descriptive Terms of Components Present in Sample (other than ASTM D 2487) Term Percent of Dry Weight Trace 1-5% With 5-12% Some 12-30% And 30-50%

Relative Density of Granular Soils N-Value (SPT) Relative Density Standard “N” Penetration 0-4 Very Loose Blows per foot of a 140 pound hammer 5-10 Loose falling 30” on a 2” outside diameter 11-30 Medium Dense split barrel sampler 31-50 Dense Over 50 Very Dense

Consistency of Cohesive Soils N-Value (SPT) Consistency (Q, tsf or kg/cm2) 0-2 Very Soft Less than 0.25 3-4 Soft 0.25-0.50 5-8 Medium 0.50-1.00 9-15 Stiff 1.00-2.00 16-30 Very Stiff 2.00-4.00 Over 30 Hard 4.00-8.00

UNIFIED SOIL CLASSIFICATION SYSTEM – ASTM D 2487