17M7972B_Geotechnical_Report_FS_377-A.PDF

Geotechnical Evaluation Report

Timber Bridge Replacement over Twentymile Creek

(FS 377-A)

Town of Grandview, Bayfield County, Wisconsin

Prepared for:

WSP USA

Martin L. Halvorson, PE

License Number: E-45212-6

September 10, 2018

TPT Project Number: 17M7972B

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

September 10, 2018 TPT Project No. 17M7972B

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300 Herndon, Virginia 20171

Re: Geotechnical Evaluation Report Timber Bridge Replacement over Twentymile Creek (FS 377-A)

FR 377 (Camp 8 Road) Town of Grandview, Bayfield County, Wisconsin

Dear Ms. Alunkal:

Enclosed is our 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, PE Project Engineer

Martin L. Halvorson, PE

Senior 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

5.2 Sieve Analysis

6 Analyses and Design Recommendations

6.1 Design Considerations

6.2 Site Preparation and Approach Grading

6.3 Driven Timber Piles

6.4 Slopes

6.5 Backfill and Fill

6.6 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)

17M7972B 1

1 Introduction

This report presents the results of our geotechnical evaluation for the proposed replacement of the timber bridge over Twentymile Creek on Forest Road 377 (Camp 8 Road) in the Town of Grand View, Bayfield County, Wisconsin. This work covers DSR FS 377-A as part of the WI ERFO FS 2016-1(3) project.

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 design of a bridge structure and approach grading to replace a single span timber bridge along the existing alignment. The existing bridge structure is supported on timber piles and consists of a wood deck. The existing bridge was heavily damaged during an extreme rain even in 2016.

We understand that horizontal and vertical alignments of the approach 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 replacement bridge will have a length of 60 feet and width of 25 feet. Additional work consists of placement of rip rap around the abutments and removal on stream debris.

Changes in the nature, design, and location of all or parts of this project will likely occur. The

17M7972B 2 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

“Timber Pile Design and Construction Manual,” dated 2002, prepared by James G.

Collin, PHD, PE – Timber Piling Council.

“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) 377 (Camp 8 Road) in the Town of Grandview in Bayfield County, approximately 100 feet west of the intersection with Koski Road. The approximate site location is shown in Figure 1. The existing road and bridge deck is asphalt surfaced and ditches slope downward on either side of the roadway. Twentymile Creek runs north and south through the bridge. Areas directly adjacent to the roadway and river are wooded and consist of trees, grass and brush. A picture of the existing bridge is shown in Figure 2 below.

Damage to the existing bridge consists of the approach on the west side of the bridge being washed out leaving around an approximately 30 foot gap between the roadway edge and bridge and scour observed at the piles and abutments.

Figure 1: Site Location

17M7972B 3

Figure 2: Existing Bridge Looking East

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 creek and away from the roadway. Based on information collected during our field exploration, the creek water level was approximately eight feet below the surface of the bridge 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.

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

17M7972B 4

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 two primary soil units throughout the immediate project site. A summary of the soil units and their approximate extents are provided in Table 1 below. In general, the Web Soil Survey suggests that soils at this site consist primarily of loamy sand.

Table 1: Results of Web Soil Survey

Soil Unit USCS

Classification

Parent Material Comments

3888 – Pelkie SM, SP Sandy Alluvium Loamy fine sand over sand

809C – Gogebic-

Metonga Rock outcrop complex

SM, SP

Modified loamy eolian deposits Fine sandy loam

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 2 below.

Table 2: 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 flood plain of the

Twentymile 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 bridge construction.

Swelling/Shrinking Soil

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

17M7972B 5

3 Field Procedures

The subsurface exploration program for this project consisted of two SPT borings. Boring FS 377-A (East) was performed to a nominal depth of 31 feet and Boring FS 377-A (West) was performed to a nominal depth of 41 feet. Boring FS 377-A (West) encountered sand blow up at a depth of 15 feet and auger refusal at a depth around 3 feet.

Boring FS 377-A (West) was performed using a Geoprobe Systems 7822DT rubber track-mounted drill rig using hollow stem auger drilling methods on June 13th, 2018. Sand blow up was encountered at a depth of 15 feet and the boring was discontinued at this depth. Field procedures were resumed on June 14th, 2018 using a Diedrich D-120 rubber track-mounted drill rig using hollow stem auger and mud rotary drilling methods. Boring FS 377-A (West) was blind drilled to a depth of 15 feet and advanced to a depth of 41 feet. Boring FS 377-A (East) was performed to a nominal depth of 31 feet on June 14th, 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 377-A (West) was performed at the west end of the bridge. Boring FS 377-A (East) was performed at the east end of the bridge.

Surface elevations at the boring locations were determined in the field by TPT personnel on June 13th, 2018. Surface elevations were referenced to the benchmark labeled 3250 located on the west side of the river on the north side of the road. An elevation of 1572.9 feet was assigned to this benchmark. Surface elevations at the boring locations are shown on the boring logs in the Appendix. The approximate benchmark location is 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.

17M7972B 6

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.

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), 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 five stratigraphic units;

(1) Asphalt Pavement, (2) Fill, (3) Silty Sand, (4) Poorly Graded Sand, and (5) Poorly Graded Gravel.

4.1 Soil

4.1.1 Asphalt Pavement

Asphalt pavement was encountered at the surface to a depth of 2½ inches in Boring FS 377-A (East).

4.1.2 Fill

Fill soils, consisting of silty sand with gravel, were encountered at the surface in Boring FS 377-A (West) to a depth of six feet. The fill soils generally ranged from fine to coarse grained, were moist, and were brown in color. Auger refusal in Boring FS 377-A (West) indicates that cobbles and boulders are present within the fill.

4.1.3 Silty Sand (AASHTO A-2-4)

Native silty sand soils were encountered at a depth of two feet in Boring FS 377-A (West) to a depth of 14 feet. Silty sand soils generally contained gravel, were fine to coarse grained, and

17M7972B 7 were brown in color.

SPT N-values suggest that silty sand soils were dense in relative density.

4.1.4 Poorly Graded Sand (AASHTO A-1-b and A-3)

Poorly graded sand soils were encountered beneath the fill in Boring FS 377-A (West) and beneath the native silty sand soils in Boring FS 377-A (East) to depths of 28 feet at 31 feet respectively. Poorly graded sand soils generally contained varying amounts of silt, ranged from fine grained to coarse grained, and were brown in color. The soils ranged from wet to waterbearing.

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

4.1.5 Poorly Graded Gravel (AASHTO A-1-b)

Poorly graded gravel soils were encountered beneath the poorly graded sand soils in Boring FS 377-A (West) to the termination depth of 41 feet. Poorly graded gravel soils generally contained sand, were waterbearing, and were brown in color.

SPT N-values suggest that poorly graded gravel soils range from medium dense to dense in relative density.

4.2 Groundwater

Groundwater was observed in Boring FS 377-A (East) and Boring FS 377-A (West) at depths of 13½ feet and 11 feet respectively. Groundwater levels at this site are expected to be directly related to the level of the adjacent Twentymile Creek. Based on our information obtained in our elevation survey, the water surface of the Twentymile Creek was about nine feet below the elevation of Boring FS 377-A (East) at the time of our field exploration. A hydrostatic groundwater distribution starting at a depth of nine 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, sieve analysis (passing the #200 sieve only), Atterberg limits testing, and pocket penetrometer testing.

17M7972B 8

5.1 Water Content

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.

5.2 Sieve Analysis

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 3 below and on the boring logs and in the Appendix. Test results for full gradation sieve testing are attached in the Appendix.

Table 3: Summary of Sieve Analysis Results

Boring Depth (feet) Description of

Material

% Passing

#200

FS 377-A

(East)

4.5-6 SP-SM (Native) 11.0

FS 377-A

(East)

9.5-11 SM (Native) 12.4

6 Analyses and Design Recommendations

6.1 Design Considerations

Shallow Groundwater: Groundwater was encountered in both borings at this site.

Groundwater elevations are expected to be directly related to the level of Twentymile Creek. At the time of our field exploration, the water level of Twentymile Creek was approximately nine feet below the elevation of Boring FS 377-A (East).

Based on the encountered soils and the presence of shallow groundwater, shallow foundations are not recommended at this site. It appears that deep foundations, consisting of driven piles, are a feasible option for foundation support at this site. We anticipate that driven timber piles will be the preferred foundation system. Recommendations for driven piles are provided in Section 6.3 below.

6.2 Site Preparation and Approach Grading

6.2.1 Removal of Existing Structures and Fill Soils

We recommend that all existing structures, foundations, and any encountered fill soils containing organics or debris be completely removed from proposed construction areas at this

17M7972B 9 site prior to construction and replaced with compacted engineered fill.

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 fill soils be removed and replaced with compacted engineered fill to reach pavement section design elevations. The roadway should then be scarified and re-compacted prior to placing subbase and base materials. Where base or subbase materials are placed over fine grained soils, we recommend that a woven geotextile fabric be used to provide separation and promote drainage. Geotextile fabrics should be installed and seam connected according to the manufacturer’s recommendations.

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 not extend below groundwater due to potentially difficult backfilling conditions and difficulties achieving adequate compaction. All approach grading should be properly crowned to promote drainage away from the roadway.

6.3 Driven Timber Piles

Driven timber piles are a feasible foundation option for this site and are recommended for support of the bridge and abutments.

6.3.1 Pile Types

We evaluated two timber pile sizes for this project; 8-inch and 12-inch diameter piles. At a minimum, piles should meet the specifications of ASTM D25-12. Other types and sizes of driven piles can be evaluated upon request.

Timber piles should be provided with end protection with the use of a metal boot or point to reduce the potential for damage during installation. If environmental restrictions will allow, timber piles should be treated with preservative treatments to reduce the risk of pile deterioration.

6.3.2 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.

17M7972B 10

Ultimate pile resistances for two pile sizes and associated lengths in Borings FS 377-A (East) and FS 377-A (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).

6.3.3 Driven Pile Capacities

LRFD Geotechnical Resistances: We used the computer program, UniPile 5.0, to estimate the geotechnical static resistances (Rη) of timber piles with minimum specified tip diameters of 8 inches and 12 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 4: Resistance Factors

Specified Field Control Method Фdyn

Dynamic Formula (Compression) 0.40

Wave Equation and Pile Driving Analyzer (PDA) 0.65

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, 8-inch and 12-inch diameter timber piles, are shown in Table 5 for pile toe depths of 25 feet and 30 feet below existing grade, bearing in the dense sand soils or dense gravel soils encountered at this site. Depths are referrenced from the surface of existing grade of our borings. We assumed piles will be cut-off at around elevation

1160.0 feet.

Table 5A: Estimated Ultimate Axial Resistance – 8-inch diameter Timber Pile

Boring Assumed Pile Cutoff Elevation

(feet)

Estimated Minimum Pile Length (feet)

Toe Elevation (feet)

Estimated Ultimate Resistance (kips)

East 1160.0 25 1135.0 105

East 1160.0 30 1130.0 130

West 1160.0 25 1135.0 65

West 1160.0 30 1130.0 85

17M7972B 11

Table 5B: Estimated Ultimate Axial Resistance – 12-inch diameter Timber Pile

Boring Assumed Pile Cutoff Elevation

(feet)

Estimated Minimum Pile Length (feet)

Toe Elevation (feet)

Estimated Ultimate Resistance (kips)

East 1160.0 25 1135.0 250

East 1160.0 30 1130.0 310

West 1160.0 25 1135.0 145

West 1160.0 30 1130.0 185

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.

6.3.4 Settlement

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

6.3.5 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 an less economical design.

6.3.7 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

17M7972B 12 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 7 through 10 below.

Table 7: Coefficients of Lateral Earth Pressure Boring FS 377-A (East)

Depth (feet) Ko Kp Ka

0-14 0.45 3.4 0.30

14-24 0.45 3.4 0.30

24-31 0.45 3.4 0.30

Table 8: LPILE/GROUP Estimated Design Parameters Boring FS 377-A (East)

Depth (ft) p-y Curve Soil Model Effective/Dry Unit

Weight (pcf) φ'

(deg) Cu

(psf) Kh

(pci) E50

0-14 Sand (Reese) 57.6/120 33 - 61 -

14-24 Sand (Reese) 57.6/120 33 - 125 -

24-31 Sand (Reese) 57.6/120 33 - 60 -

Table 9: Coefficients of Lateral Earth Pressure Boring FS 377-A (West)

Depth (feet) Ko Kp Ka

0-9 0.45 3.4 0.30

9-28 0.45 3.4 0.30

28-31 0.43 3.7 0.27

Table 10: LPILE/GROUP Estimated Design Parameters Boring FS 377-A (West)

Depth (ft) p-y Curve Soil Model Effective/Dry Unit

Weight (pcf) φ'

(deg) Cu

(psf) Kh

(pci) E50

0-6 Sand (Reese) 57.6/120 33 - 90 -

6-28 Sand (Reese) 57.6/120 33 - 20 -

28-41 Sand (Reese) 62.6/125 35 - 60 -

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

As part of determining lateral parameters we estimated the depth of fixity of drive timber 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 later loads of 5 kips, we estimate that the depth of fixity of timber piles will be located 6 feet to 8 feet below the ground surface.

17M7972B 13

6.3.8 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.

6.3.9 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.

6.3.10 Pile Spacing

We recommend minimum pile spacing based on the following equation:

c/c = 2.5b+0.02D where c/c = minimum center to center spacing b = pile diameter D = pile embedment length

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

6.3.12 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. Timber piles extending above the ground surface do not require frost protection.

6.4 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.

17M7972B 14

6.5 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.

6.5.1 Recommended Gradation for Engineered Backfill and Fill

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

Table 6: 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.

6.5.2 Compaction Standard

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

6.5.3 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 7: Compaction Recommendation

Type of Engineered Fill % Minimum Compaction

Foundation Structural Backfill 98%

Non-structural Foundation Backfill 95%

Within 3 Feet of Pavement Section 100%

6.5.4 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.

17M7972B 15

6.5.5 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.

6.6 Scour and Riprap

We recommend the use of timber or 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 construction of this project.

7.1 Excavation

7.1.1 Underground Utilities

Contractors must make all necessary steps to completely locate all underground utilities at this site prior to performing any excavations.

7.1.2 Dewatering

Groundwater was encountered in both boring locations performed at this site around a depth of six 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 Twentymile 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.

7.1.3 Over Sizing

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

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 before placement of backfill or pavement. If freezing has

17M7972B 16 loosened the excavation surface, remove the frozen material to the undisturbed surface.

Frozen material should not be used as backfill.

7.1.5 Temporary Shoring

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

7.2 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

We recommend close observations be made by a geotechnical engineer or a certified technician on the subgrade soils prior to the placement of fills or pavements. The technician should verify that the soils are similar to those found in the soil borings and that they are suitable for support of the proposed construction.

7.3.2 Driven Piles

An experienced engineering technician working under the supervision of the geotechnical engineer or experienced technician should observe the installation of driven piles in general accordance with Timber Pile Design and Construction Manual prepared by APWI. The engineering technician should record pile information such as lengths, elevations, and driving resistances.

17M7972B 17

7.4 Materials Testing

We recommend AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing be followed for the materials certification of the project.

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.

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.

17M7972B 18

8.5 Exclusive Use

We have prepared this report for the exclusive use of WSP USA for specific application to the proposed replacement of the timber bridge on FS 377 over Twentmile Creek in the Town of Grand View, 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.

17M7972B 19

APPENDIX

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

Estimated Ultimate Pile Resistance Graphs (4 Pages) 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

17M7972B-01

17M7972B

A

BORING LOCATION SKETCH

DSR FS 377-A

Town of Grand View

Bayfield County, Wisconsin

T win

P orts

T esting

DSR FS 377-A (EAST)

DSR FS 377-A (WEST)

FS 377

K O

S K

I

R

O

A D

F

S

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

MR

SS

MR

SS

0.3

2.0

14.0

24.0

31.0

2.5 inches of Asphalt Pavement (SP-SM) POORLY GRADED SAND with Silt, fine to coarse grained, brown, moist, dense (AASHTO A-1-b) (SM) SILTY SAND with Gravel, fine to coarse grained, brown, moist, dense (AASHTO A-2-4)

*Sieve analysis test performed at 5 feet

*Sieve analysis of % passsing #200 sieve test performed at 10 feet = 12.4 %

(SP) POORLY GRADED SAND with Gravel, fine to coarse grained, brown, waterbearing, medium dense to dense (AASHTO A-1-b)

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

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 377-A

PROJECT:

6/14/18

13.5 ft WD

River Elev. 1150.4 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

CB

WATER LEVEL

WSP USA Town of Grand View, Bayfield County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

06/14/18 06/14/18

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

17M7972B

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

1158.5

1148.5

1138.5

1128.5

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

DSR FS 377-A (EAST)

See Boring Locaiton 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 17M7972B DSR FS377 A.GPJ TWINPORT.GDT 7/17/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1158.5 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

SS

MR

SS

MR

SS

MR

SS

6.0

14.0

22.0

28.0

41.0

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

*Auger refusal at 3 feet, move 5 feet west

(SP) POORLY GRADED SAND, trace to with gravel, fine to coarse grained, brown, wet to waterbearing, loose to medium dense (AASHTO A-1-b)

(SP) POORLY GRADED SAND, fine grained, brown, waterbearing, loose (AASHTO A-3) *2 feet of sand blow up at 15 feet

(SP) POORLY GRADED SAND, fine to coarse grained, brown, waterbearing, medium dense to dense (AASHTO A-1-b)

(GP) POORLY GRADED GRAVEL with Sand, fine to coarse grained, brown, waterbearing, medium dense to dense (AASHTO A-1-b)

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 377-A

PROJECT:

6/14/18

11 ft WD

River Elev. 1150.4 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 Grand View, 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 06/14/18

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

17M7972B

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

40.0

1163.1

1153.1

1143.1

1133.1

1123.1

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

DSR FS 377-A (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 17M7972B DSR FS377 A.GPJ TWINPORT.GDT 7/17/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1163.1 ftST

R

AT

A C

H

AN

G E

D

EP

TH

0 0

9 9

18 18

27 27

36 36

45 45

54 54

63 63

72 72

81 81

90 90

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

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 # 17M7972A FS 377-A Figure 1

DSR FS 377-A (West) 8 inch diameter pile

20 20

40 40

60 60

80 80

100 100

120 120

140 140

160 160

180 180

200 200

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

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 # 17M7972A FS 377-A Figure 1

DSR FS 377-A (West) 12 inch diameter pile

40 40

80 80

120 120

160 160

200 200

240 240

280 280

320 320

360 360

400 400

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

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 # 17M7972A FS 377-A Figure 1

DSR FS 377-A (East) 12 inch diameter pile

20 20

40 40

60 60

80 80

100 100

120 120

140 140

160 160

180 180

200 200

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

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 # 17M7972A FS 377-A Figure 1

DSR FS 377-A (East) 8 inch diameter 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