17M7972T_Letter_of_Results__FS_187.pdf

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October 8, 2018 TPT Project 17M7972T

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300

Herndon, Virginia 20171

Re: Letter of Results and Recommendations

DSR FS 187

Culvert Replacement and Roadway Reconstruction

Town of Marengo, Ashland County, Wisconsin

Dear Ms. Alunkal:

This letter presents the results of our field explorations performed at the culvert for an unnamed creek crossing under Forest Road (FR) 187 (Mineral Lake Road) in the Town of Marengo, Ashland County, Wisconsin. The DSR FS 187 site is located around 5,200 feet north of the intersection of FR 199 (Four Corners Store Road) with FR 187 (Mineral Lake Road). This work covers DSR FS 187 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 replacement and roadway reconstruction at the above referenced site. It is our understanding that the culvert and roadway sustained damage from a large rain event in July 2016. It is our understanding that the replacement culvert located at site FS 187 will consist of a pipe culvert. 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 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 1st, 2018.

Field Exploration

Field procedures for this project were performed on September 19th, 2018 using our Diedrich D-120 track mounted drill rig and hollow stem auger drilling methods. Boring FS 187 was performed to the south of the culvert to a depth of 16 feet. The boring location is 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, the base of a tree marked with a wooden stake and pink flagging. We assigned an elevation of 100.0 feet to this benchmark.

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.

Subsurface Conditions - Soil

Fill soils consisting of silty sand (AASHTO A-2-4) were encountered at the surface to a depth of nine feet.

Fill soils generally ranged from fine to coarse grained, were brown in color, and were moist to wet.

Native silty sand soils (AASHTO A-2-4) were encountered below the fill soils to a depth of around 14 feet. Silty sand soils were generally fine to medium grained, were brown in color, and were waterbearing. SPT N-values suggest that native silty sand soils were generally medium dense in relative density.

Native silt soils (AASHTO A-4) were encountered below the silty sand soils to the boring termination depth of 16 feet. Silt soils generally contained trace sand, were brown in color, and were waterbearing.

SPT N-values suggest that native silt soils were generally medium dense in relative density.

Subsurface Conditions - Groundwater

Groundwater was not encountered in Boring FS 187 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 98.6 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 187 site encountered fill soils at the surface to a depth of around nine feet and will likely be encountered deeper during excavation activities. 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. We recommend that full time excavation observation by a geotechnical engineer be performed during construction to confirm the removal of fill soils prior to placement of any engineered fill, aggregate bedding, and/or foundations.

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 one foot 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 187 site are expected to be around nine feet.

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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 soils or engineered fill over native soils. 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.

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.

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.

Table 2: Gradation for the entire sample

Sieve Percent Passing by Weight (%)

1 ¼ inch 100

No. 4 25-100

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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.

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:

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 187 during drilling and sampling but will be encountered during excavation activities at this site. Groundwater within excavations for construction of the proposed culvert is expected to be directly related to the level of the adjacent unnamed creek which had an elevation of 98.6 feet during field procedures. If excavations extend below the groundwater surface and dewatering is necessary for construction, a large scale dewatering plan will be required.

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Dewatering options include diverting the unnamed creek around the excavation 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.

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

Project Engineer

Michael A. Haapala

Senior Engineer

Attachments:

Boring Location Sketch (1 Page), Boring Log (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:

BMC MAH

10/8/18 N/A

17M7972T-01

17M7972T

A

BORING LOCATION SKETCH

DSR FS 187

Town of Marengo

Ashland County, Wisconsin

T win

P orts

T esting

FS 187

F S

M i n e r a l

L a k e

R o a d

FS 199 (Four Corners Store Road)

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

9.0

14.0

16.0

(FILL) Silty Sand with gravel, fine to coarse grained, brown, moist to wet (AASHTO A-2-4)

(SM) SILTY SAND, fine to medium grained, brown, waterbearing, medium dense (AASHTO A-2-4)

(ML) SILT, trace sand, brown, waterbearing (AASHTO A-4)

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 187

PROJECT:

9/27/18

NE WD

2.3 ft surveyed creek elev

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

Lou Dinnan

WATER LEVEL

WSP USA Town of Marengo, Ashland County, WI

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

09/18/18 09/18/18

REPORT DATE:

D-120

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

17M7972T

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PL

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N O

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(f t)

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(f t)

0.0

10.0

20.0

100.9

90.9

80.9

SA

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PL

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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

FS187

See Boring Location Sketch

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10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

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PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972T DSR FR187.GPJ TWINPORT.GDT 10/8/18

G R

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SURFACE ELEVATION:

100.9 ftST

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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