17M7972E__Geotechnical_Report_FS_371-B_Updated.PDF

Geotechnical Evaluation Report Revision 1

Timber Bridge Replacement over Eighteenmile Creek

(FS 371-B)

Town of Grandview, Bayfield County, Wisconsin

Prepared for:

WSP USA

Brett Carlson

October 29, 2018

TPT Project Number: 17M7972E

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

October 29, 2018 TPT Project No. 17M7972E

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300 Herndon, Virginia 20171

Re: Geotechnical Evaluation Report – Revision 1 Timber Bridge Replacement over Eighteenmile Creek (FS 371-B)

FR 371 (Deer Lick Lake Road) Town of Grandview, Bayfield County, Wisconsin

Dear Ms. Alunkal:

Enclosed is our revised geotechnical evaluation report for the above referenced project. We have prepared this report and based our conclusions upon current applicable professional standards.

If you have any questions concerning the data, the recommendations presented, or if we may be of further service on this project, please contact us at (715) 392-7114. We appreciate the opportunity to be of service to you.

Sincerely, Twin Ports Testing II, Inc.

Brett Carlson Project Engineer

Michael A. Haapala

Principal Engineer

Attachment:

Geotechnical Evaluation Report

Contents

1 Introduction

1.1 Scope of Services

1.2 Proposed Project

2 Site Conditions

2.1 Site Location and Existing Conditions

2.2 Topography

2.3 Geologic Setting

3 Field Procedures

3.1 Boring Locations and Elevations

3.2 Sampling

3.3 Boring Logs

3.4 Water Level Readings

4 Subsurface Conditions

4.1 Soil

4.2 Groundwater

5 Laboratory Testing

5.1 Water Content

5.3 Sieve Analysis

6 Analyses and Design Recommendations

6.1 Design Considerations

6.2 Site Preparation and Approach Grading

6.3 Shallow Foundations

6.4 Driven Timber Piles

6.5 Slopes

6.6 Backfill and Fill

6.7 Scour and Riprap

7 Recommendations for Construction

7.1 Excavation

7.2 Driven Piles

7.3 Observation

7.4 Materials Testing

8 Limitations of Evaluation and Report

8.1 Site Variations

8.2 Design Review

8.3 Continuity of Professional Responsibility

8.4 Safe Working Conditions

8.5 Exclusive Use

Appendix:

Boring Location Sketch (1 Page), Boring Logs B-1 and B-2 (2 Pages), Estimated Ultimate Pile Resistance Graphs (4 Pages), Sieve Analysis (1 Page), Soil Classification Data/Boring Log Notes (2 Pages)

17M7972E Revision 1 1

1 Introduction

This report presents the results of our revised geotechnical evaluation for the proposed replacement of the culvert over Eighteenmile Creek on Forest Road 371 (Deer Lick Lake Road) in the Town of Grand View, Bayfield County, Wisconsin. This work covers DSR FS 371-B as part of the WI ERFO FS 2016-1(3) project.

Our initial geotechnical report included recommendations for 12 inch diameter timber piles.

During the design and review process it was determined by WSP that the proposed bridge would need to be lengthened from 45 feet to 75 feet and that design load of piles would be increased to 90 kips per pile. Based upon our initial analysis the use of timber piles was not a feasible option for the longer bridge and increased structural loads. This revised report presents our results for the use of closed ended steel pipe piles.

1.1 Scope of Services

The scope of our geotechnical evaluation as outlined in our Cost Estimate 17M7972R1, dated January 4th 2018, included:

Performing a field exploration program consisting of two (2) Standard Penetration Test (SPT) borings, one at each bridge abutment, to depths of 20 feet below creek bottom or refusal.

Performing observations and laboratory testing of soil samples to evaluate pertinent engineering properties of materials encountered.

Preparing a report including boring logs with a boring location sketch, a summary of subsurface conditions encountered at the site, recommendations for site preparation, recommendations for bridge foundation design, and recommendations for construction.

We were authorized to proceed with the proposed scope of services in a signed subcontractor agreement dated February 26, 2018.

Twin Ports Testing II, Inc. (TPT) has prepared this report for design purposes only. It may not have sufficient subsurface information to prepare an accurate construction bid. We recommend that contractors preparing bids or proposals for this project be provided with a complete copy of this report as a supplement to the plans and specifications.

1.2 Proposed Project

We understand that WSP is working on the designs for a bridge structure and approach grading to replace a corrugated steel pipe culvert along the existing alignment. The culvert below the road for Eighteenmile Creek was washed out during a large rain event in July 2016.

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We understand that horizontal and vertical alignments of the approaches on either side are not expected to change significantly from the existing alignment. We also understand that a single-span timber bridge is the preferred replacement structure. The proposed bridge will have a span length of 75 feet and will require design loads of 90 kips per pile.

Changes in the nature, design, and location of all or parts of this project will likely occur. The conclusions and recommendations contained in this report shall not be considered applicable to changes unless they are reviewed by the geotechnical engineer of record. We will then make necessary changes or modifications to this report in writing only.

1.2.1 Reference Information

We referenced the following documents as part of this project:

“Pleistocene Geology of the Superior Region, Wisconsin,” dated 1985, prepared by Lee Clayton – University of Wisconsin

“Project Development and Design Manual,” dated July 2012, prepared by Federal Lands Highway Divisions - FHWA.

Web Soil Survey website, prepared by the United States Department of Agriculture and the Natural Resources Conservation Service. http://websoilsurvey.nrcs.usda.gov.

2 Site Conditions

2.1 Site Location and Existing Conditions

This site is located on Forest Road (FR) 371 (Deer Lick Lake Road) in the Town of Grand View in Bayfield County, approximately 1,600 feet west of the intersection with FR 376 (also known locally as Otto Olson Road). The approximate site location is shown in Figure 1. The existing road is gravel surfaced and ditches slope downward on either side of the roadway.

Eighteenmile Creek runs north and south under the road which runs generally east to west.

Areas directly adjacent to the roadway and river are wooded and consist of trees, grass and brush. Current conditions at this site consist of a washed out road with berms on the roadway on both sides of the washout. Pictures of the site are shown in Figures 2 and 3 below.

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Figure 1: Approximate Site Location

Figure 2: Site Looking West

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Figure 3: Site Looking West

2.1.1 Review of Historical Images

As part of our evaluation we looked at historical images of the site using Google Earth. Based upon available aerial photographs, this site has changed little since the first available image dated 1991.

2.2 Topography

Site topography is relatively flat on either side of the roadway with ditches in the immediate vicinity sloping downward towards the stream and away from the roadway. Based on information collected during our field exploration, the creek water level was approximately 14 feet below the surface of the roadway at the time field procedures were performed.

2.3 Geologic Setting

Through an understanding of the geologic history and processes of an area, we are better able to define and understand the range of geotechnical properties observed in the geological materials encountered at the site. Knowledge of the anticipated subsurface profile at the site is important for interpreting and correlating the borings from the field exploration program.

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Based upon information from geologic survey reports and previous soil explorations in the area, the geology local to the site generally consists of pre-pleistocene rock. This unit is described as Cambrian or Precambrian rock at the surface in much of the area, but till or stream sediment may be a few meters or more thick in many areas. (Clayton)

2.3.1 Results of Web Soil Survey

As part of our evaluation for this project we reviewed the Web Soil Survey website. The Web Soil Survey consists of publically available soils information prepared by the United States Department of Agriculture and the Natural Resources Conservation Service. Our review of this information identified one primary soil unit throughout the immediate project site consisting of the Vilas-Lindquist complex. The Web Soil Survey suggests that soils at this site consist primarily of sandy outwash soils described as loamy sand over sand.

2.3.2 Geologic Hazards

The potential for most geologic hazards is generally medium for the proposed structure. A hazard potential summary is shown in Table 1 below.

Table 1: Geologic Hazard Summary

Geologic Hazard Present? Comments

Earthquake/Seismic Activity No The site is in an area of low seismic activity.

Flooding

Yes This site is located within the floodplain of the

Eighteenmile Creek and has experienced flood damage.

Slope Failure/Landslides

Some Slopes and embankments exist at this site.

Structures constructed near slopes without proper protection could cause slope instabilities.

Made Ground

Yes Fill soils are present at this site associated with roadway and culvert construction.

Swelling/Shrinking Soil

No Outwash soils encountered at this site have low swelling and shrinking potential when exposed to changes in water content.

3 Field Procedures

The subsurface exploration program for this project consisted of two SPT borings. Boring FS 371-B (West) encountered initial auger refusal at a depth of 14.1 feet. Additional attempts encountered auger refusal at depths ranging from 3 ½ feet and 10 ½ feet. Multiple offset attempts were required to get to 31 feet in Boring FS 371-B (East). Boring FS 371-B (East) was performed to a depth of 31 feet. It is our opinion that refusal is due to the presence of cobbles and boulders. We were unable to penetrate past a depth of 14.1 feet on the west side of the site.

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SPT borings were performed using a Geoprobe 7822DT rubber track-mounted drill rig using hollow stem auger drilling methods. Field procedures for Boring FS 371-B (East) were performed on May 7th, 2018 which encountered shallow refusal, field procedures were continued on June 13th, 2018. Field procedures for Boring FS 371-B (West) were performed on June 13th, 2018.

3.1 Boring Locations and Elevations

Boring locations were staked in the field by TPT personnel. Approximate boring locations are shown on the Boring Location Sketch in the Appendix. Boring FS 371-B (East) was performed at the east end of the washout and Boring FS 371-B (West) was performed at the west end of the washout. Both borings were performed within the existing roadway, as close to the washout as safely possible.

Surface elevations at the boring locations were determined in the field by TPT personnel on May 7th, 2018 and June 13th, 2018. Surface elevations at Boring FS 371-B (East) were referenced to benchmark 3351 and referenced to benchmark 3350 at Boring FS 371-B (West). It is our understanding that benchmark 3350 has an elevation of 1229.5 feet and that benchmark 3351 has an elevation of 1,228.5 feet. Surface elevations at the boring locations are shown on the boring logs in the Appendix. The approximate benchmark locations are shown on the Boring Location Sketch in the Appendix.

3.2 Sampling

3.2.1 Standard Penetration Tests

At selected depth intervals in the borings, Standard Penetration Tests (SPT) were conducted in substantial compliance with ASTM Method D1586. The SPT “N” values shown on the boring logs are the number of blows required to drive a standard split barrel sampler 12 inches (two six-inch increments) into undisturbed soil using a 140 pound drive hammer dropped 30 inches per blow after an initial “set” of six inches. The “N” value is an index of the relative density of cohesionless soils and consistency of cohesive soils. The values shown on the boring logs are field values and have not been corrected for hammer energy, surcharge, etc. Partially disturbed samples obtained from the SPT were sealed in glass jars and returned to the laboratory for testing.

3.3 Boring Logs

A field log was prepared for each boring location by our field supervisor. These logs contain factual information and field interpretation of the soil conditions observed, as described in compliance with ASTM D420 and D2488.

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Final boring logs are included in the Appendix. The final logs represents our interpretation of the contents of the field logs after laboratory observations by a geotechnical engineer and laboratory tests of the field samples were complete. Soils are described in this report according to the Unified Soil Classification System (USCS) and AASHTO System, as outlined in the Boring Log Notes and Soil Classification Data in the Appendix.

3.4 Water Level Readings

Water level readings were observed in the borings at the times and under the conditions stated on the boring logs. We have reviewed the data and have reported interpretations in the text of this report. However, it must be noted that fluctuations in the level of ground water may occur due to variations in rainfall, temperature, subsurface materials and other conditions or factors different from those observed at the time of our measurements. It should be noted that such conditions are subject to change.

4 Subsurface Conditions

The subsurface conditions encountered at this site generally consist of two stratigraphic units;

(1) Fill and (2) Poorly Graded Sand.

4.1 Soil

4.1.1 Fill

Fill soils, consisting of silty sand, were encountered at the surface in both borings to depths up to seven feet. The fill soils generally contained gravel, ranged from fine to coarse grained, were moist, and were brown in color. Apparent cobbles and boulders were observed within the fill.

4.1.2 Poorly Graded Sand (AASHTO A-1-a, A-1-b, and A-3)

Native poorly graded sand soils were encountered beneath the fill in both boring locations to the boring termination depths. Poorly graded sand soils contained varying amounts of gravel, ranged from fine grained to coarse grained, were moist to waterbearing, and were brown in color. Apparent cobbles and boulders were observed throughout the sand. Three feet of heaving sand (sand blowup) was encountered within the auger at a depth of 30 feet in Boring FS 371-B (East). We had to terminate the boring once heaving sands were encountered.

SPT N-values suggest that poorly graded sand soils ranged from very loose to dense in relative density.

4.2 Groundwater

Groundwater was observed at a depth of 19 ½ feet in Boring FS 371-B (East) and was not encountered prior to the refusal depth of 14.1 feet in Boring FS 371-B (West) during drilling and

17M7972E Revision 1 8 sampling, respectively. Groundwater levels at this site are expected to be directly related to the level of the adjacent Eighteenmile Creek. Based on our information obtained in our elevation survey, the water surface of Eighteenmile Creek was about 14 feet below the surface of the roadway at the time of our field exploration. A hydrostatic groundwater distribution starting at a depth of 14 feet was used in our analysis. A detailed evaluation of groundwater levels at the site would require long term monitoring of piezometers and was not included in the scope of this evaluation.

5 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.

5.1 Water Content

Laboratory water content testing was performed in general accordance with ASTM D2216 on collected samples from the field exploration. Values of water content ranged from two percent to 19 percent. Results of water content tests are shown on the borings logs in the Appendix.

5.2 Sieve Analysis

Sieve analysis testing of material passing the #200 sieve was performed in general accordance with ASTM D114 procedures on two samples from Boring FS 371-B (East). Test results are provided in Table 2 below and on the boring logs in the Appendix. Test results for full sieve analysis are attached in the Appendix.

Table 2: Summary of Sieve Analysis Results

Boring Depth (feet) Description of

Material % Passing #200

FS 371-B

(East)

2-3.5 SM (Fill) 48

FS 371-B

(East)

7-8.5 SP-SM 5.8

SP-SM = Poorly Graded Sand with Silt SM = Silty Sand

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6 Analysis and Design Recommendations

6.1 Design Considerations

Shallow Groundwater: Groundwater was encountered in Boring FS 371-B (East) at a depth of 19 ½ feet during drilling and sampling at this site. Groundwater elevations are expected to be directly related to the level of Eighteenmile Creek. At the time of our field exploration, the water level of Eighteenmile Creek was approximately 14 feet below the existing roadway surface. Encountered soils at this site have a high hydraulic conductivity and groundwater will flow into excavations below the groundwater level.

Shallow Refusal: Shallow refusal was encountered at multiple offset locations at both boring locations. The cause of refusal is unknown and is likely due to the presence of cobbles and boulders. Determining the cause of refusal would require test pits or rock coring and was not included in the scope of our evaluation.

Soils information below a depth of 14 feet in Boring FS 371-B (West) was not able to be collected during our field exploration due to auger refusal. Based upon soil conditions encountered at sites nearby we anticipate that soil conditions below a depth of 14 feet will likely be consistent with soils encountered in Boring FS 371-B (East). This assumption was used in our analysis.

A bridge bearing on spread footings or driven piles appear to be feasible options for this site.

Driven piles may be difficult to install due to the presence of apparent cobbles and boulders; it will likely be necessary to remove soils containing cobbles and boulders to depths up to 14 feet for pile installation. We recommend that additional testing consisting of test pits or rock coring be performed to confirm the cause of refusal at depths affecting construction. If driven piles are the preferred foundation option, recommendations are provided in Section 6.4 below.

6.2 Site Preparation

6.2.1 Removal of Fill Soils

Field explorations at this site encountered fill soils at the surface to depths of up to seven 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.

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 shallow foundations should be excavated to a minimum depth of one foot below the bottom of footing elevation to insure the removal of any projections or boulders and should be brought up to design elevations with compacted engineered fill.

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After initial grading procedures, subgrade soils should be proof rolled and observed by a geotechnical engineer to determine if soft areas are still present. We recommend that any observed soft or otherwise unsuitable soils be removed and replaced with compacted fill.

6.2.2 Approach Grading

Horizontal and vertical changes to the existing approach grading are expected to be minimal.

During approach grading, we recommend that all existing pavements and observed soft soils be removed and replaced with compacted engineered fill to reach pavement section design elevations. The roadway subgrade should then be scarified and re-compacted prior to placing subbase and base materials.

If roadway widening is required as part of this project, we recommend that all existing vegetation and topsoil within widened areas be stripped prior to placement of roadway materials. Excavations should avoid extending below groundwater due to potentially difficult backfilling conditions and difficulties achieving adequate compaction. If excavations do extend below water consideration should be given to using coarse grained material as backfill below the water table. All approach grading should be properly crowned to promote drainage away from the roadway.

6.3 Shallow Foundations

It appears that shallow foundations, consisting of spread footings, may be used for foundation support when bearing on native sand soils or engineered fill over sand native soils. It is expected that bridge foundations will be placed on a minimum of twelve inches of engineered fill overlying native soil. Recommendations for foundation design are provided below.

6.3.1 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 4,000 psf (pounds per square foot) may be used to design footings placed on native soils or engineered fill over native soils.

6.3.2 Settlement Estimate

For foundations bearing on native sand 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.

6.3.3 Frost Protection

We recommend that bridge foundations be placed at a minimum depth of eight 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.

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

6.4 Driven Piles

Driven closed ended steel pipe piles are a feasible foundation option for this site and are recommended for support of the bridge and abutments. It will likely be necessary to remove soils containing cobbles and boulders to depths up to 14 feet to install piles.

6.4.1 Pile Types

We evaluated two pile types for this project; 14 and 16 inch outside diameter close-ended pipe (CEP) piles. Other types and sizes of driven piles can be evaluated upon request.

6.4.2 Calculation Method

There are multiple methods of performing static analysis of pile resistance. Most methods are developed from empirical correlations with long term unit shaft and toe resistances being a function of effective stress. We strongly recommend that any static analysis be correlated with dynamic or static field tests in order to properly determine design effectiveness and assumptions.

Ultimate pile resistances for two pile sizes and associated lengths in Borings FS 371-B (East) and FS 371-B (West) were estimated using the software AllPile developed by CivilTech Software.

Field measured resistance depends on the control method used (dynamic formula, wave equation, Pile Dynamic Analyzer (PDA), or static load test).

6.4.3 Driven Pile Capacities

LRFD Geotechnical Resistances: We used the computer program, AllPile, to estimate the geotechnical static resistances (Rη) of steel pipe piles with minimum specified outside diameters of 14 inches and 16 inches.

Factored Geotechnical Capacities: Factored geotechnical pile capacities are determined by multiplying the pile driving resistance factor (Фdyn) by the total drive resistance (Rη). AASHTO recommends that Фdyn be related to the degree of construction control. For situations where subsurface exploration and static calculations have been completed, we recommend factors for Фdyn as shown in the following table.

Table 3: Resistance Factors

Specified Field Control Method Фdyn

Dynamic Formula (Modified Gates formula - FHWA) 0.40

Wave Equation and Pile Driving Analyzer (PDA) 0.65

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The following tables summarize estimated ultimate pile capacities at each location based on depth and should be multiplied by the LRFD reduction factors outlined above for the appropriate method of field control.

Estimated ultimate resistances for two pile sizes, 14-inch and 16-inch diameter piles, are shown in Tables 4 and 5 for pile toe depths of 35 feet and 40 feet below existing grade, bearing in the loose sand soils encountered at this site. Depths are referenced from the surface of existing grade of our borings. We assumed piles will be cut-off at around elevation 1,232.0 feet. We also assumed that any removal or excavation of soils contatining cobbles and boulders prior to pile installation will be properly backfilled with compacted engineered fill.

Table 4: Estimated Ultimate Axial Resistance – 14-inch diameter Closed Ended Steel Pipe Pile

Boring Assumed Pile Cutoff Elevation

(feet)

Estimated Minimum Pile Length (feet)

Toe Elevation (feet)

Estimated Ultimate Resistance (kips)

East 1232.0 35 1197.0 160

East 1232.0 40 1192.0 190

West 1232.0 35 1197.0 145

West 1232.0 40 1192.0 165

Table 5: Estimated Ultimate Axial Resistance – 16-inch diameter Closed Ended Steel Pipe Pile

Boring Assumed Pile Cutoff Elevation

(feet)

Estimated Minimum Pile Length (feet)

Toe Elevation (feet)

Estimated Ultimate Resistance (kips)

East 1232.0 35 1197.0 180

East 1232.0 40 1192.0 230

West 1232.0 35 1197.0 160

West 1232.0 40 1192.0 190

Graphs depicting estimated ultimate pile resistance vs. pile depth for each pile type and location are included in the Appendix. The estimated resistances assume that piles will by protected from scour.

Factored Tensile Capacities: Geotechnical capacities for tension are dependent upon the shaft resistance of a pile. A reduction factor (Фdyn) of 0.3 is common when using the dynamic formula control method. We do not anticipate that tensile pile capacity will be a limiting factor in design. If necessary, tensile capacity can be estimated using skin friction values from the bearing capacity charts in the Appendix and applying the desired reduction factor.

6.4.4 Settlement

Using the estimated pile capacities presented above with the appropriate reduction factors, we anticipate total and differential deformation at the pile heads will be less than one inch.

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6.4.5 Drag Load and Downdrag

Drag load is the integration of the unit negative skin friction and usually benefits foundation performance by prestressing the pile (assuming adequate structural strength is provided).

Downdrag refers to settlement from soils above the neutral plane “hanging” on the pile and pulling it down. Where piles are driven into a very dense soil layer or bedrock, drag load is maximized and downdrag is minimal. Downdrag is of most concern for shallow, predominately “shaft-bearing” piles where outside influences (fill loads, groundwater table changes, adjacent foundations, etc.) cause settlement of the soils above the neutral plane.

Bridge abutment elevations are assumed to be at existing grade plus no more than two feet. As such, embankment induced settlement and associated drag load are expected to be minimal.

We do not recommend reducing loads or increasing pile lengths to account for drag load in geotechnical design. This practice effectively increases the factor of safety and typically results in a less economical design.

6.4.6 Lateral Design Parameters

Lateral earth pressures are an important aspect of designing underground structures including driven piles, sheet piles, and abutment walls. Lateral earth pressures are generally calculated for three modes of soil stress referred to as the at-rest condition, active condition, and the passive condition. For cohesionless soils or cohesive soils under long term loading, lateral earth pressures for each of the three conditions are calculated based upon soil friction angle and the respective earth pressure coefficients (Ko, Ka, and Kp) using an effective stress analysis.

Estimated lateral earth pressure coefficients and soil parameters for use in LPILE or GROUP software are shown in the Tables 6 and 7 below.

Table 6: Coefficients of Lateral Earth Pressure

Depth (feet) Ko Kp Ka

0-7 0.45 3.4 0.30

7-31 0.45 3.4 0.30

Table 7: LPILE/GROUP Estimated Design Parameters

Dep th (ft) p-y Curve Soil Model

Effective/Dry Unit Weight (pcf) φ' (deg)

Cu (psf)

Kh (pci) E50

0-7 Sand (Reese) 57.6/120 33 - 25 -

7-14 Sand (Reese) 57.6/120 33 - 90 -

14-31 Sand (Reese) 57.6/120 33 - 20 -

As part of determining lateral parameters we estimated the depth of fixity of driven piles.

Depth of fixity will be dependent upon the design lateral loads of the structure and pile size.

Based upon the pile sizes discussed above and assumed lateral loads of 5 kips, we estimate that the depth of fixity of piles will be located 6 feet to 8 feet below the ground surface.

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We recommend providing drainage behind abutment walls to reduce the potential for water collecting behind the walls.

6.4.7 Uplift

Driven piles may be designed to resist uplift using the dead weight of the pile section and the frictional resistance along the pile shaft. We recommend that a resistance factor of 0.3 be used to determine the factored resistance of piles in uplift.

6.4.8 Structural Pile Strength

After pile diameters, lengths, and design loads have been determined, an analysis of structural strength should be performed. We recommend limiting the maximum load (dead load + drag load at the neutral plane) to 50% of the pile axial strength.

6.4.9 Pile Spacing

We recommend minimum pile spacing based on the following equation:

c/c = 2.5b where c/c = minimum center to center spacing b = pile diameter

If piles are spaced closer than outlined above, we should be consulted to evaluate group effects.

6.4.10 Frost Protection

If a concrete pile cap is used, we recommend that frost protection be provided. To provide frost protection, we recommend that a minimum of 6 feet of soil cover be provided above bottom of pile cap (BOPC) elevation. If pile caps are placed at shallower depths, we recommend providing frost protection as outlined in ASCE 32-01 Design and Construction of Frost-Protected Shallow Foundations. Piles extending above the ground surface do not require frost protection.

Structural slabs, grade beams, and pile caps constructed on void forms have successfully been used on past projects in this area. This frost protections option results in a void below the concrete to allow the ground to move from frost.

6.2.11 Concrete Pile Fill

We recommend filling closed-end pipe piles with concrete having a 28 day compressive strength of at least 3,000 psi.

6.2.12 Toe Protection

Dense sand layers, cobbles, and boulders were encountered at this site during field procedures.

We recommend that closed ended pipe piles be driven with a hardened steel plate to protect

17M7972E Revision 1 15 the toe of the piles.

6.5 Slopes

It is anticipated that temporary and permanent embankments will be required for this project.

If clean granular material is used, permanent slopes should be constructed at a minimum 2:1 (H:V) in order to achieve a factor of safety against sliding of at least two. Permanent slopes constructed using clayey or silty soils should have a minimum slope of 3:1 (H:V) Temporary slopes for construction purposes may be constructed at a 1.5:1 (H:V) if granular borrow (or similar material) is used. Material used for construction of slopes should be approved by a geotechnical engineer or direct representative.

6.6 Backfill and Fill

A wide variety of materials can be considered as suitable for engineered backfill and fill. 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 or SP-SM in the Unified Soil Classification System (ASTM D2487) are usually the most available suitable soils for engineered backfill and fill.

6.6.1 Recommended Gradation for Engineered Backfill and Fill

We recommend that engineered fill meet the gradation requirements outlined in the table below.

Table 8: Recommended Gradation for Engineered Backfill and Fill

Sieve Size Percent Passing

3'' 100

2'' 85-100

3/4'' 71-100

#4 35-100

#200 0-7

Alternative gradations should be evaluated by a geotechnical engineer for acceptability if these guidelines cannot be satisfied by locally available backfill materials.

Existing soils at this site may be considered for reuse based upon results of laboratory testing. If soils are encountered during excavation activities that are desired for re-use we recommend that the suitability for re-use be confirmed with laboratory testing of bulk samples.

6.6.2 Compaction Standard

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

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6.6.3 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 9: Compaction Recommendation

Type of Engineered Fill % Minimum Compaction

Foundation Structural Backfill 98%

Non-structural Foundation Backfill 95%

Within 3 Feet of Pavement Section 100%

6.6.4 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.

6.6.5 Moisture

In general, granular fill materials should be placed and compacted within two percent of optimum moisture content, as determined by the above applicable compaction standard.

When fill materials are not in this range of moisture content, 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.

6.7 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. A detailed scour analysis was not included in our scope of work.

7 Recommendations for Construction

We offer the following recommendations for use during the construction of this project.

7.1 Excavation

7.1.1 Dewatering

Groundwater was encountered in Boring FS 371-B (East) at this site around a depth of 19 ½ feet below existing ground surface. Groundwater within excavations for construction of the structure is expected to be directly related to the levels of the adjacent Eighteenmile Creek. 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 stream around the excavations or installing temporary sheet pile cofferdams with sumps and pumps.

17M7972E Revision 1 17

7.1.2 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.

7.1.3 Temporary Shoring

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

7.1.4 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.

7.2 Driven Piles

7.2.1 Wave Equation Analysis

A wave equation driveability analysis should be performed to evaluate the contractor’s proposed driven pile installation method. A wave equation analysis will also help to determine a restrike criteria for field evaluation of pile resistance and can be used in combination with high-strain dynamic pile testing.

7.2.2 High-Strain Dynamic Pile Testing

We recommend that high-strain dynamic pile testing (HSDPT) with a Pile Driving Analyzer (PDA) be performed in accordance with ASTM D4945 on at least two piles at the project site. HSDPT provides an evaluation of pile hammer performance, pile integrity, pile stresses during driving, and pile resistance.

7.2.3 CAPWAP

CAPWAP analysis of PDA data is an essential part of HSDPT and should be performed on each test pile. CAPWAP provides an estimate of soil resistance distribution along the pile and is correlated with static analysis to provide verification of design assumptions.

7.2.4 Restrikes

Restrikes should be performed on at least two production piles to confirm estimates of long-term capacity from static analysis, HSDPT, and CAPWAP data.

7.3 Observation

7.3.1 Excavations

Excavation bottoms and engineered fill operations should be observed by a geotechnical

17M7972E Revision 1 18 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.

7.3.2 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.

7.3.3 Driven Piles

We recommend full time observation of driven piles by an experienced technician or engineering assistant working under the supervision of a geotechnical engineer for recording pile types, lengths, hammer performance, and penetration resistance.

7.4 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.

8 Limitations of Evaluation and Report

8.1 Site Variations

We have based the analyses and recommendations submitted in this report in part on the data obtained from two SPT borings. The nature and extent of variations at the site will not become evident until construction. Where major variations appear it will be necessary for us to re-evaluate the recommendations of this report.

8.2 Design Review

As the geotechnical engineer for this project, we recommend that we be provided an opportunity to perform a general review of final plans and specifications for this project to determine that recommendations provided have been properly interpreted and included. We assume no responsibility for misinterpretation or improper application of our recommendations and conclusions by others.

17M7972E Revision 1 19

8.3 Continuity of Professional Responsibility

We recommend that we be retained to provide geotechnical engineering services during construction. This would allow us to observe compliance with the plans, specifications and our recommendations, provides continuity of professional responsibility, and allows design changes to be made in the event that subsurface conditions differ from those anticipated.

8.4 Safe Working Conditions

Responsibility to provide safe working conditions for earthwork and below grade aspects of this project is solely that of the contractors working on the project. It appears that the on site soils are generally OSHA Type B and C soils. However, our site exploration was limited to two test locations and therefore all excavations should be evaluated individually at the time of construction by the contractor. All local, state and federal requirements, statutes, ordinances, or building codes relating to slopes or temporary sheeting and bracing of trenches and excavations must be observed during construction.

8.5 Exclusive Use

We have prepared this report for the exclusive use of WSP USA for specific application to the proposed replacement timber bridge on FS 371 over Eighteenmile Creek in the Town of Grandview, Bayfield County, Wisconsin. Professional services provided to this project by TPT were completed, findings obtained, and recommendations prepared using generally accepted engineering principles and practices. Conclusions and recommendations contained herein are based upon the applicable standards of our profession at the time this report was prepared. No warranty, express or implied, is made.

17M7972E Revision 1 20

APPENDIX

Boring Location Sketch (1 Page) Boring Logs B-1 and B-2 (2 Pages)

Estimated Ultimate Pile Resistance Graphs (4 Pages) Sieve Analysis (1 Page)

Boring Log Notes/Soil Classification Data (2 Pages)

N

Approximate Boring Location

DRAWN BY: CHECKED BY:

DATE: SCALE:

DRAWING NO:

TPT PROJECT NO:

DRAWING NO:

1/1

REV:

DCS BMC

6/20/2018 N/A

17M7972E-01

17M7972E

A

BORING LOCATION SKETCH

DSR FS 371-B

Town of Grandview

Bayfield County, Wisconsin

T win

P orts

T esting

FS 371

FS 371-B (EAST)

FS 371-B (WEST)

Benchmark 3351

Benchmark 3350

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

7.0

9.0

19.0

28.0

31.0

(FILL) Silty Sand, trace gravel, fine to medium grained, brown, moist, loose to medium dense

*Sieve analysis performed at 3 feet

(SP-SM) POORLY GRADED SAND with Silt, fine to coarse grained, brown, moist, medium dense (AASHTO A-1-b) *Percent passing the #200 sieve test performed at 8 feet = 5.8% (SP) POORLY GRADED SAND with Gravel, fine to coarse grained, brown, moist to wet, medium dense (AASHTO A-1-b) *pieces of fractured rock in sample at ten feet Auger Refusal at 10.5 feet, move 5 feet east, refusal at 3 1/2 feet move 10 feet east, blind drill to 9 1/2 feet

(SP) POORLY GRADED SAND, fine grained, brown, waterbearing, very loose to medium dense (AASHTO A-3)

(SP) POORLY GRADED SAND, trace gravel, fine to medium grained, brown, waterbearing, loose, (AASHTO A-1-a) *3 feet of sand blow up at 29.5 feet

Boring then Backfilled with Bentonite End of Boring

CLIENT:

DSR FS371-B

PROJECT:

6/13/18

19.5 ft WD

River elev. 1219.5 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

JMJ

WATER LEVEL

WSP USA Town of Grandview, Bayfield County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

05/07/18 06/12/18

REPORT DATE:

7822DT

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

17M7972E

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

1234.3

1224.3

1214.3

1204.3

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 371-B (East)

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 17M7972E DSR FS371B.GPJ TWINPORT.GDT 7/17/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1234.3 ftST

R

AT

A C

H

AN

G E

D

EP

TH

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

6.0

11.0

14.1

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

(SP) POORLY GRADED SAND, fine to medium grained, brown, moist, dense (AASHTO A-1-a) *apparent cobbles at 8 feet

(SP) POORLY GRADED SAND, trace gravel, fine to coarse grained, brown, moist, dense (AASHTO A-1-a) *rock fragments in sample at 12 feet

*Auger refusal at 14 feet, move 10 feet west, refusal at 6 feet, move 10 feet west, refusal at 8 feet Boring then Backfilled with Bentonite End of Boring

CLIENT:

DSR FS371-B

PROJECT:

6/13/18

NE WD

River elev. 1219.5 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

MLH

WATER LEVEL

WSP USA Town of Grandview, Bayfield County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

06/13/18 06/13/18

REPORT DATE:

7822DT

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

17M7972E

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

1232.5

1222.5

1212.5

1202.5

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 371-B (West)

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 17M7972E DSR FS371B.GPJ TWINPORT.GDT 7/17/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1232.5 ftST

R

AT

A C

H

AN

G E

D

EP

TH

50/1

0 0

30 30

60 60

90 90

120 120

150 150

180 180

210 210

240 240

270 270

300 300

0 04 48 812 1216 1620 2024 2428 2832 3236 3640 40

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972 Figure 1

DSR FS 371-B (East) 14 inch OD close ended steel pipe pile

60 60

90 90

120 120

150 150

180 180

210 210

240 240

270 270

300 300

0 04 48 812 1216 1620 2024 2428 2832 3236 3640 40

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972 Figure 1

DSR FS 371-B (East) 16 inch OD close ended steel pipe pile

20 20

40 40

60 60

80 80

100 100

120 120

140 140

160 160

180 180

200 200

0 04 48 812 1216 1620 2024 2428 2832 3236 3640 40

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972 Figure 1

DSR FS 371-B (West) 14 inch OD close ended steel pipe pile

60 60

90 90

120 120

150 150

180 180

210 210

240 240

270 270

300 300

0 04 48 812 1216 1620 2024 2428 2832 3236 3640 40

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972 Figure 1

DSR FS 371-B (West) 16 inch OD close ended steel pipe pile

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