Des_Lacs_Final_Revised_Geotech_Report.pdf

Revised Geotechnical Design Report Des Lacs Refuge

County Road 2 Bridge Replacement Kenmare, North Dakota

March 31, 2016

Submitted To:

AECOM

8181 E. Tufts Avenue Denver, Colorado 80237

By:

Shannon & Wilson, Inc.

1321 Bannock Street, Suite 200 Denver, CO 80204

23-1-01372-101

ALASKA

CALIFORNIA

COLORADO

FLORIDA

MISSOURI

OREGON

WASHINGTON

WASHINGTON DC METRO

WISCONSIN

1321 BANNOCK STREET, SUITE 200

DENVER, COLORADO 80204

PHONE 303•825•3800

FAX 303•825•3801

www.shannonwilson.com 23-1-01372-101

March 31, 2016

AECOM

8181 E. Tufts Avenue Denver, Colorado 80237

Attn: Ms. Tammy Eggers

RE: REVISED GEOTECHNICAL DESIGN REPORT, DES LACS REFUGE,

COUNTY ROAD 2 BRIDGE REPLACEMENT, KENMARE, NORTH DAKOTA

We are pleased to submit our revised geotechnical design report for the above-referenced project.

The enclosed report discusses subsurface conditions encountered during the exploration program, summarizes laboratory tests, and provides geotechnical engineering recommendations for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have questions or require further information, please contact me at (303) 825-3800.

Sincerely, SHANNON & WILSON, INC.

Mark J. Vessely Vice President

JXC:MJV:GRF/lmr

Enc: Revised Geotechnical Design Report

23-1-01372-101_L1_rev1/wp/lmr

23-1-01372-101_R1_rev1.docx/wp/lmr 23-1-01372-101 i

TABLE OF CONTENTS

Page

1.0 INTRODUCTION

2.0 SCOPE OF WORK

3.0 SITE AND PROJECT DESCRIPTION

4.0 FIELD EXPLORATIONS AND LABORATORY TESTING

5.0 SUBSURFACE CONDITIONS

5.1 Regional Geology

5.2 Subsurface Conditions

6.0 GEOLOGIC HAZARD EVALUATION

6.1 Seismic Hazards

6.2 Sulfates and Corrosion

7.0 GEOTECHNICAL RECOMMENDATIONS

7.1 Abutment Foundations

7.1.1 Driven Piles

7.1.2 Lateral Load Capacity

7.2 Retaining Walls

7.2.1 Lateral Earth Pressures

7.2.2 Sliding and Bearing Resistance

7.2.3 Embedment Depth

7.2.4 Global Stability

8.0 CONSTRUCTION CONSIDERATIONS

8.1 Driven Pile Installation

8.1.1 Wave Equation Analysis of Pile Driving

8.1.2 Pile Driving Equipment

8.1.3 Monitoring of Pile Driving

8.1.4 Dynamic Testing of Pile Driving

8.2 Temporary Excavations and Support

8.3 Earthwork and Grading

8.3.1 Excavation

8.3.2 Subgrade Preparation and Proof Rolling

8.3.3 Fill Placement and Compaction

9.0 PLAN REVIEW AND CONSTRUCTION OBSERVATION

10.0 LIMITATIONS

TABLE OF CONTENTS (cont.)

ii

11.0 REFERENCES

TABLES

1 2014 AASHTO Seismic Design Criteria 2 Corrosivity Ratings Based on Soil Resistivity 3 Sulfate Exposure 4 Geotechnical Parameters for Deep Foundation Lateral Load Analysis 5 Rrecommended Design Parameters for Lateral Earth Pressures

FIGURES

1 Vicinity Map 2 Site and Exploration Plan 3 Generalized Subsurface Profile A-A’ 4 Estimated Axial Pile Resistance, HP 14 X 102 5 Estimated Axial Pile Resistance, HP 14 X 89 6 Estimated Axial Pile Resistance, HP 12 X 74 7 Recommended P-multipliers for Group Effects 8 Recommended Surcharge Loading for Temporary and Permanent Walls 9 Pile and Driving Equipment Data

APPENDICES

A Subsurface Explorations and Field Methods B Laboratory Test Results C Global Stability Calculations D Important Information About Your Geotechnical Report

REVISED GEOTECHNICAL DESIGN REPORT

DES LACS REFUGE

COUNTY ROAD 2 BRIDGE REPLACEMENT

KENMARE, NORTH DAKOTA

1.0 INTRODUCTION

This report presents geotechnical engineering recommendations for the replacement of the bridge on County Road 2 over Des Lacs River. The report summarizes our subsurface explorations, laboratory testing and geotechnical engineering studies, and presents conclusions and recommendations for design of walls and bridge foundations.

2.0 SCOPE OF WORK

Our work was completed in general accordance with AECOM Technical Services, Inc.

(AECOM) Task Order number 08 of Master Services Agreement 12S-15391-C005 dated March 10, 2015. We completed the following tasks for the project.

Coordinated subcontractors for drilling borings

Observed, logged, and collected soil samples from two 100-foot deep borings

Completed laboratory testing on selected soil samples from the borings

Evaluated geotechnical data and completed geotechnical engineering analyses to develop conclusions and recommendations for design of the project

Evaluated subsurface conditions relative to construction of the project and prepared this report

3.0 SITE AND PROJECT DESCRIPTION

The proposed bridge over Des Lacs River is located within the Des Lacs Wildlife Refuge outside of Kenmare, North Dakota city limits in Ward County (Figure 1). The bridge currently has a load restriction with indications of concrete spalling and honeycombed areas on the underside of the deck and rail posts. The current bridge is a two-span 80-foot long 27-foot-wide structure oriented in the east and west directions over the Des Lacs River. The bridge foundation is unknown and both roadway approaches are built on embankments with a maximum height of about 8 feet.

We understand that the replacement bridge over the Des Lacs River will be a single-span structure approximately 80 feet long and 36 feet wide at the same location of the current bridge.

Minor repaving will be performed to connect the existing road to the new abutments.

4.0 FIELD EXPLORATIONS AND LABORATORY TESTING

Shannon & Wilson conducted a field exploration program to explore subsurface conditions at the project site. Two borings, designated SW-01 and SW-02, were drilled on April 2 and April 3, 2015 to explore subsurface conditions at the proposed bridge area. The locations of the borings are shown in Figure 2.

Appendix A describes the procedures used to complete the drilling and sampling of the geotechnical borings and presents the individual exploration logs and an explanation of the symbols and terminology used on the logs.

Shannon & Wilson completed geotechnical laboratory testing to determine index properties and engineering properties of selected samples from the borings. The laboratory program included tests for natural water content, Atterberg limits, mechanical gradation, and corrosion. Laboratory test methods and results are provided in Appendix B.

5.0 SUBSURFACE CONDITIONS

We based our understanding of the geology and subsurface conditions at the project site on a review of regional geologic maps and the results of our field exploration program. A generalized subsurface profile of geologic conditions at the bridge location is provided in Figure 3. We have grouped the subsurface materials into three general geologic units, which include from top to bottom: fill, alluvium, and glacial till. The geologic units are described below.

5.1 Regional Geology

The project area is within the Central Lowlands province which is east of the Great Plains and extends from Canada to northern Texas. The project area has been heavily glaciated and there have been multiple events of glacial advancement and retreat. The resulting geology is an area dominated by deposits of glacial till and outwash (alluvium). Glacial features include max moraines, ground moraines, linear ridge deposits, river terrace deposits, kames, and eskers (Lemke, 1960). The project area is chiefly mapped as a ground moraine that is composed of stony clay till (Lemke, 1960). The map does not differentiate small alluvial and lacustrine deposits from small filled depressions such as kettle lakes.

5.2 Subsurface Conditions

Fill may represent in-place material that has been disturbed through excavation or grading activities, or materials brought from off site and placed for construction needs. Fill was encountered in both borings and extended to depths of about 7 feet below the ground surface. A pavement section consisting of 10 to 11 inches of asphalt overlying 4 to 5 inches of aggregate base course was encountered in both borings. Underlying the pavement section, fill encountered in boring SW-01 consisted of medium stiff to stiff, sandy lean clay. In boring SW-02, fill consisted of mostly medium dense to dense, clayey sand.

Underlying the fill, the borings encountered alluvium consisting of very loose to dense, clayey and silty sand and soft to very stiff, sandy lean clay. Trace to few gravel was observed throughout various samples.

Underlying the alluvium, glacial till was encountered and consisted of medium stiff to hard, lean clay with trace to some gravel. From the boring logs we interpret that the glacial till and outwash may interfinger and alluvium is observed above and below the glacial till. In boring SW-01 there are two intervals of glacial till from 48 to 63 feet and another from 73 to 83 feet.

The glacial till was separated by a layer of medium dense alluvium. In boring SW-02 there was interval of glacial till from 34 to 78 feet.

From a depth of 78 and 83 feet to the maximum depth of exploration, a medium dense to dense layer of alluvial outwash was encountered. This generally consisted of silty sand to a poorly graded sand.

Groundwater levels were recorded in each boring after drilling. Groundwater was encountered in both borings within the alluvium at depths between about 12 and 14 feet below ground surface. Groundwater fluctuations are likely and will depend on seasonal variations, local precipitation and runoff, and other factors, but will primarily be influenced by water levels in the Des Lacs River and Middle Des Lacs Lake.

6.0 GEOLOGIC HAZARD EVALUATION

6.1 Seismic Hazards

Based on data from the quaternary fault and fold database of the United States, there are no faults near the site and the nearest active fault is 450 miles southwest of the project site (USGS, 2006).

Therefore, in our opinion, the potential for ground surface fault rupture and damaging earthquakes is low.

Liquefaction may occur in loose, saturated, cohesionless soils when subjected to earthquake ground shaking. Based on the subsurface conditions encountered at the project site and the relatively low peak ground acceleration (PGA) for this area (see Table 1), it is our opinion that the liquefaction potential is low.

Using the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2014) criteria, and based on subsurface conditions encountered in borings at the proposed Des Lacs Bridge, Site Class E is recommended for the proposed bridge structure.

Ground motion parameters were determined for the project site using the USGS U.S. Seismic Design Map Web Application and the 2009 AASHTO LRFD Bridge Design Criteria (the design parameters have not changed in the current 2014 manual). Table 1 presents recommended seismic design ground motion parameters.

TABLE 1

2014 AASHTO SEISMIC DESIGN CRITERIA

Ground Motion Parameters Value Peak Ground Acceleration1 (PGAB) 0.020 g Site Class E Short-period Spectral Acceleration, Ss 0.046 g Long-period Spectral Acceleration, S1 0.013 g Site Factor, Fpga 2.5 Site Factor, Fa 2.5 Site Factor, Fv 3.5 Peak Design Spectral Acceleration, AS 0.050 g Short-period Design Spectral Acceleration, SDS 0.114 g Long-period Design Spectral Acceleration, SD1 0.045 g T0 0.079 s TS 0.395 s Seismic Design Category A Notes: 1) PGAB = peak ground acceleration for a site underlain by Site Class B rock.

2) Seismic parameters developed in accordance with AASHTO Guide Specifications for LRFD Seismic Bridge Design (2009).

6.2 Sulfates and Corrosion

To assist in estimating the corrosion potential for the substructure, a sample of clay was tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Table B-1 in Appendix B.

The resistivity measured in the sample was 1,060 ohm-cm. Based on the FHWA 2010 Drilled Shaft Manual (Brown and others, 2010), the resistivity values suggest an aggressive subsurface environment for metal in contact with these materials. Roberge (1999) also provides corrosivity ratings based on soil resistivity (Table 2). The resistivity values measured in the sample indicates highly corrosive subsurface conditions.

TABLE 2

CORROSIVITY RATINGS BASED ON SOIL RESISTIVITY

ROBERGE (1999)

Soil Resistivity (ohm-cm) Corrosivity Rating > 20,000 Essentially noncorrosive

10,000 – 20,000 Mildly corrosive 5,000 – 10,000 Moderately corrosive 3,000 – 5,000 Corrosive 1,000 – 3,000 Highly corrosive

< 1,000 Extremely corrosive

The concentration of water soluble sulfates measured in the sample was 0.02 percent by weight.

Based on classifications as defined by ACI-318-11 (ACI, 2011) (Table 3), this test result suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0).

TABLE 3

SULFATE EXPOSURE

ACI (2011)

Water Soluble Sulfate in Soil (Percent by Weight) Sulfate Exposure

< 0.10 Negligible (S0)

0.10 – < 0.20 Moderate (S1)

0.20 – 2.00 Severe (S2)

> 2.00 Very Severe (S3)

We recommend that a specialist in corrosion-resistance design review the results included in Table B-1 to determine actual construction materials and methods based on the test results.

7.0 GEOTECHNICAL RECOMMENDATIONS

7.1 Abutment Foundations

As discussed in Section 3.0, we understand the proposed replacement bridge over the Des Lacs River will consist of a single span bridge founded on piles. In our opinion, driven piles are a cost-effective and appropriate foundation system for the bridge abutments based on the subsurface conditions encountered at the site and local practices.

7.1.1 Driven Piles

Based on our analyses and the subsurface conditions encountered in our explorations, the driven piles used to support the bridge abutments should extend through the upper alluvium and glacial till, and develop capacity in the lower, granular alluvium. The design criteria presented herein were developed based on recommendations presented in the AASHTO LRFD Bridge Design Specifications (AASHTO, 2014). In addition, the 2006 FHWA Manual “Design and Construction of Driven Pile Foundations” (FHWA, 2006) was used to supplement driven pile design procedures and develop the axial resistance parameters.

We understand steel H-piles (HP) are the preferred pile type and steel pipe piles are not being considered at this time. Therefore, we assumed pile sizes of HP 14 X 104, HP 14 X 89, and HP 12 X 74 for our analyses. Based on the subsurface conditions and driven pile design procedures discussed above, we developed axial resistance curves for each pile type. The unfactored, nominal axial resistance curves for the HP 14 X 104, HP 14 X 89, and HP 12 X 74 pile sizes are presented on Figures 4 through 6, respectively. The recommended resistance factors are provided in the notes of each figure.

Based on our understanding, HP 14 X 89 piles will provide the required resistance;

however, the pile size was increased to HP 14 X 104 for corrosion protection. As such, the nominal axial resistance curve for the HP 14 X 104 pile size (Figure 4) will be used to establish pile driving installation criteria.

The geotechnical resistance should also be confirmed by dynamic testing, i.e., the nominal geotechnical resistance indicated by the dynamic testing multiplied by the appropriate resistance factor should be greater than or equal to the factored structural axial resistance of the pile section. Assuming dynamic testing is completed as described in Section 8.1, a resistance factor of 0.65 on the geotechnical resistance indicated by the dynamic testing is appropriate

(AASHTO, 2014).

To further estimate pile penetration and select a hammer that will not overstress the piles, we recommend completing a wave equation analysis (see Section 8.1). A resistance factor of 1.0 is appropriate for the structural resistance of the pile during driving. Further discussion on wave equation analysis and pile installation is provided in Section 8.1.

A minimum spacing of 2.5 widths (center-to-center) for axial loads is recommended to reduce the stress overlap between the adjacent H-piles. If this condition cannot be met, a reduction in axial capacity parameters, i.e., consideration of group effects, may be necessary.

Lateral capacity of driven piles is discussed in Section 7.1.2 and assumes vertical piles.

However, if battered piles are to be implemented for lateral loading, we recommend that the pile be battered no flatter than 4V:1H (vertical to horizontal).

For properly designed and installed piles, we estimate settlement to be on the order of 1 inch or less based on our experience with similar projects. This settlement value does not include elastic compression of the pile under the allowable design load. Differential settlement between adjacent piles would be expected to be about 50 to 75 percent of this value. About 75 percent of the settlement is anticipated to occur as the load is applied with the remaining settlement occurring within the first year following construction.

7.1.2 Lateral Load Capacity

Lateral loads acting on the structure from wind, seismic, and other loadings are typically resisted by the passive earth pressure against the caps, the frictional resistance developed between the sides of the cap and surrounding soils, and the lateral resistance provided by the deep foundation members. The lateral behavior of the piles is highly dependent on the degree of fixity of the top of the pile.

Frictional sliding resistance at the base of the cap should be ignored because a deep foundation-supported structure may not transmit load directly to the soil beneath the cap. The degree of movement required to initiate passive soil pressure and pile cap movement will depend on the degree of fixity to the deep foundation element. Passive soil resistance against the cap and frictional resistance along the sides of the cap should be ignored because of the relatively small allowable design deflections, the comparatively larger movements required to mobilize the passive soil and frictional resistance, and the potential loss of support against the cap during a scour event. As a result, we recommend the lateral resistance be determined based only on the deep foundation elements.

We assume that the computer program LPILEPLUS (Ensoft, 2012) will be used to evaluate the lateral behavior of the driven piles, including estimating lateral deflections and determining required embedment depths. LRFD design methods for lateral loading of driven piles utilize a resistance factor of 1.0 and are controlled by allowable movement criteria. Geotechnical parameters required for input into LPILEPLUS are presented in Table 4. These input parameters are for an individual driven pile. If groups of driven piles are used, the effects of group interaction should be considered when evaluating the horizontal load-deflection behavior. When using the P-Y method of analysis, the values of P (load) should be factored appropriately to account for the group effects. Recommended values of P-multipliers for loading perpendicular and parallel to a line of piles are provided on Figure 7.

TABLE 4

GEOTECHNICAL PARAMETERS FOR DEEP FOUNDATION LATERAL LOAD ANALYSIS

Location (Boring

ID)

DEPTH

RANGE

Representative Groundwater

Depth1 (ft)

Soil Description

Representative Equivalent SPT

Blowcount, NSPT

(bpf)

LPILE PARAMETERS FOR LATERAL ANALYSIS2, 3, 4, 5, 6

Effective

Unit Weight γ' (pcf)

Drained Friction Angle φ'

(deg)

Undrained Shear

Strength SU Modulus k-Value (pci)

Strain at 50%

Maxiumum Stress, ε50

Top Depth

Bottom Depth LPile Soil

Type (ft) (ft) (psf)

Bridge Abutments (SW-01 and

SW-02)

0 7

Medium Stiff Fill 8 Soft Clay

(Matlock) 115 - 1,000 - 0.010

7 48 Medium Stiff Alluvium 6 Soft Clay

(Matlock) 58 - 750 - 0.010

48 65 Stiff Till 10 Stiff Clay without

Free Water 58 - 1,200 - 0.007

65 83 Very Stiff Till 20 Stiff Clay without

Free Water 63 - 2,500 - 0.005

83 101 Medium Dense Alluvium 26 Sand

(Reese) 63 34 - 60 -

NOTES:

1. Groundwater depth was assumed to be at the base of the existing fill. Design should consider flood stage of the Des Lacs River.

2. The LPile parameters shown are for a single pile. For pile group effects, see Figure 7 for recommended P-multipliers.

3. A resistance factor of 1.0 should be used for lateral analyses.

4. The LPile parameters shown are for a horizontal ground surface. Sloping ground modifications should be included, as necessary, per Ensoft, Inc.’s recommendations for the LPile program (2012).

5. The lateral resistance values provided assume that the lateral loads are short-term (non-sustained) loads. If sustained loads are anticipated, we should be notified to provide additional parameters.

6. Analyses should consider the potential loss of ground due to scour.

7. ft = foot; bpf = blows per foot; ksf = kips per square foot; pcf = pounds per cubic foot; deg = degrees; psf = pounds per square foot; pci = pounds per square inch.

7.2 Retaining Walls

We anticipate that cantilevered wing walls will be located on either side of the bridge and on both sides of the roadway to accommodate the proposed widening for the new bridge. Design recommendations for retaining walls are presented in the following sections.

7.2.1 Lateral Earth Pressures

The lateral earth pressures against retaining walls depend on many factors, including surcharge loads, the type of adjacent soil, drainage provisions, and whether or not the top of the wall can yield or deflect laterally/rotate during and after excavation. Recommended lateral earth pressure parameters for the walls were developed based on recommendations by AASHTO (2014). Our recommended earth pressure parameters are provided in Table 5. Additional recommendations and assumptions are as follows:

We recommend Structural Backfill conforming to the requirements provided in the latest edition of the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (2014).

Active and at-rest earth pressures provided in Table 5 assume the walls are backfilled with properly compacted (see Section 8.3.3), Structural Backfill, in a 1H:1V (horizontal to vertical) zone (or flatter) extending upward from the base of the wall and from a point 1.5 feet behind the heel of the wall.

Active earth pressures assume walls are free to displace a minimum of 0.001 times the height of the wall (0.001H). If the walls are not able to displace this amount, at-rest earth pressures should be used for design.

The earth pressures provided in Table 5 assume the walls have a vertical wall face and horizontal back slope, and drainage measures are provided such that hydrostatic pressures do not develop in the retained backfill.

If the conditions and assumptions above are not met, the recommendations should be revised.

TABLE 5

RECOMMENDED DESIGN PARAMETERS FOR LATERAL EARTH PRESSURES

Design Parameter Structural

Backfill Total Unit Weight of Backfill (pcf) 135 Friction Angle (degrees) 34 Cohesion (psf) 0 Active Earth Pressure Coefficient 0.28 Active Equivalent Fluid Density (pcf) 40 At-Rest Earth Pressure Coefficient 0.44 At-Rest Equivalent Fluid Density (pcf) 60 pcf = pounds per cubic foot

Surcharge loads from motor vehicles/traffic and construction equipment will induce additional lateral loads on retaining walls. The pressures provided in Table 5 do not account for surcharge loads. Lateral loads due to various types of surcharges may be calculated by multiplying the surcharge by the at-rest earth pressure coefficient (K0) or active earth pressure coefficient (Ka), depending on if the wall is free to yield as discussed above. The earth pressure coefficients are also shown in Table 5. Surcharge loads should be applied as recommended on Figure 8.

7.2.2 Sliding and Bearing Resistance

Based on our analyses and the subsurface conditions encountered in the borings, we recommend a coefficient of friction for sliding resistance of 0.30. This value assumes cast-in-place concrete bearing on subgrade soil prepared as specified in Section 8.3.2. If the concrete is precast, the provided value should be multiplied by a factor of 0.80. AASHTO (2014) recommends a resistance factor of 1.0 for sliding analyses

7.2.3 Embedment Depth

Where the ground surface in front of the wall face is near horizontal, the base of the walls should be a minimum of 18 inches below the ground surface. However, we also recommend the cantilevered walls be embedded below the frost line for frost mitigation. If the ground surface in front of the wall is sloped, the bottom of the walls should be located a minimum of 18 inches below the elevation at which there is a 4-foot horizontal distance from the wall face to the slope face in front of the wall. A 4-foot wide horizontal bench should also be provided in front of walls bearing on sloping ground.

7.2.4 Global Stability

As part of our evaluation, we performed global stability analyses for the proposed bridge abutments in a fully saturated condition. Based on AASHTO (2014), the guidance for minimum factor of safety is 1.5 for slopes that contain or support a structural element. Our global stability calculations and model output are provided in Appendix C of this report. Based on the model results, the estimated global stability factors of safety are greater than the minimum guidance in

AASHTO (2014).

8.0 CONSTRUCTION CONSIDERATIONS

8.1 Driven Pile Installation

8.1.1 Wave Equation Analysis of Pile Driving

In accordance with Section 551 of FP-14 (FHWA, 2014), a wave equation analysis of pile driving (WEAP) should be completed using the selected pile type and the Contractor’s pile driving equipment. Information required for such an analysis is presented on Figure 9. The wave equation analysis should be completed prior to the start of driving production piles at the site. The WEAP analysis should be used to establish preliminary driving criteria and to confirm that the Contractor’s selected hammer is capable of installing the pile and mobilizing adequate axial resistance without damaging the pile. Production driving criteria should be determined by dynamic testing (see Section 8.1.4) in accordance with Section 551 of FP-14 (FHWA, 2014).

8.1.2 Pile Driving Equipment

Fixed-lead pile driving equipment is recommended for driving the piles. The use of hanging or swinging leads is not recommended unless they are constructed to be held in a fixed position during driving operations. Similar to Section 551.05 of FP-14 (FHWA, 2014), the recommended ranges of hammer energies for driving the piles may be determined using a WEAP. All pile-driving equipment should be designed, constructed, and maintained in a manner suitable for the work to be accomplished for this project. Per FP-14 (2014), the Contractor will be responsible for installing the piles, including the appropriate hammer-cushion system to drive the piles to the depths required without damaging the piles during installation.

8.1.3 Monitoring of Pile Driving

Pile driving should be monitored by taking a continuous driving record of each pile. For this purpose, the Contractor should mark the pile in 1-foot increments. During re-strike (if required), additional 1-inch increments between the 1-foot marks would be necessary.

The pile-driving record should be complete. The form should have spaces to record hammer stroke (diesel hammers), blows per foot, time, date, reasons for delays, and other pertinent information. In addition, the record should include tip elevation, driving criteria, and initials of inspectors making final acceptance of the pile. The pile-driving records should be reviewed on a daily basis. For this purpose, we recommend that an experienced and qualified geotechnical engineer familiar with the subsurface conditions at the project site be assigned to assist in construction monitoring.

It is often difficult to estimate the energy delivered by diesel hammers with visual observation. The Saximeter, developed by Pile Dynamics, Inc., can be used to record hammer strokes and provide an estimate of the driving energy of diesel hammers. If the Contractor selects a diesel hammer, we recommend a Saximeter be considered by the inspection staff to monitor pile driving.

8.1.4 Dynamic Testing of Pile Driving

Dynamic testing during pile driving is required by AASHTO (2014) to confirm that piles are not damaged during installation and is specified in Section 551 of FP-14 (FHWA, 2014).

Dynamic testing should also be completed to confirm adequate geotechnical axial resistance.

Based on subsurface explorations, restrikes of piles in these soils may have an increased capacity

1.2 times larger compared to end of driving capacities (Pile Dynamics, 2010). The resistance factor of 0.65 (on the resistance determined from dynamic testing) recommended in Section 7.1.1 assumes that dynamic pile testing with signal matching, e.g., Case Pile Wave Analysis Program (CAPWAP), is completed on a minimum of two piles, but no less than 2 percent of the production piles at the bridge, and that production driving criteria are developed based on the results of the dynamic testing. As a result, and as presented in Section 551.13 of FP-14 (FHWA, 2014), the Contractor’s pile driving schedule should consider that acceptance criteria for production piles will not be available prior to completing dynamic testing.

8.2 Temporary Excavations and Support

The safe slope for the excavation of subsurface materials depends on many factors, including:

(1) the presence of groundwater; (2) the type, density, and shear strength of the subsurface materials; (3) the depth of excavation; (4) the presence of adjacent facilities; (5) surcharge loading adjacent to the excavation (including excavated material, existing dead or live loads, and construction equipment); and (6) time of construction. Considering these factors, unshored, temporary excavation slopes may be possible. However, we recommend that unshored, temporary excavation slopes only be utilized above the groundwater level (either current level or lowered by dewatering). Constructing excavation slopes below the groundwater level may cause slope instability due to the seepage of groundwater into the excavation. For cost estimating and planning purposes only, we recommend assuming temporary excavations above groundwater level are sloped at 1.5H:1V, consistent with OSHA Type C soils. Temporary excavations should be in accordance with Section 208.03 of FP-14 (FHWA, 2014)

8.3 Earthwork and Grading

Earthwork, including site preparation, embankment construction, placement of fill, and subgrade preparation, should conform to the requirements provided in Division 200 of the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (2014).

8.3.1 Excavation

The fill and native soil can likely be excavated using conventional excavating equipment, such as a rubber-tired backhoe or tracked hydraulic excavator. To reduce disturbance of subgrade soils, the last foot of excavation can be completed with an excavating bucket that has a flat plate over the teeth.

8.3.2 Subgrade Preparation and Proof Rolling

All wall and embankment subgrades (including areas requiring excavation) should be stripped, moisture conditioned, and compacted to a dense and unyielding condition per the requirements described in Section 204 and 208 of FP-14 (2014). Additionally, subgrades should be protected from drying or wetting in excess of what is required to achieve the specified compaction requirements.

8.3.3 Fill Placement and Compaction

Structural Backfill conforming to FP-14 (2014) should be used to backfill zones behind retaining walls. Fill materials should be placed in horizontal lifts, with the loose lift thickness not to exceed 6 inches. Thinner lifts may be required, depending on the contractor’s equipment.

Compaction of backfill adjacent to walls can result in higher lateral earth pressures against the wall. Therefore, small equipment that is hand-operated can be used within a line extending upward from the base of the structure at 0.5H:1V, to a maximum horizontal distance of 5 feet from the face of the wall to reduce this potential.

All fill material should be placed in horizontal lifts and be compacted to a dense and unyielding condition. Granular soils (AASHTO classification A-1, A-3, A-2-4, and A-2-5 soils) should be moisture treated to within 2 percent of optimum moisture content and compacted to at least 95 percent of the maximum dry density, as determined by AASHTO T99 (per Section 208 of FP-14).

9.0 PLAN REVIEW AND CONSTRUCTION OBSERVATION

We recommend that we be retained to review the geotechnical aspects of the plans and specifications prior to bidding the work to determine that they are in accordance with our recommendations.

Geotechnical design recommendations are developed from a limited number of explorations and tests. Therefore, recommendations may need to be adjusted in the field. To this end, we recommend that a construction observation and monitoring program be implemented for the project and that Shannon & Wilson be retained to monitor the geotechnical aspects of construction, particularly the installation of driven piles for the bridge foundations. This monitoring would allow us to confirm that conditions encountered are consistent with those indicated by the explorations and provide recommendations should conditions be revealed during construction that are different from those anticipated.

10.0 LIMITATIONS

The analyses, conclusions, and recommendations presented in this report are based on a limited number of subsurface explorations and laboratory test results. We assume that these explorations are representative of the subsurface conditions beneath the site; that is, the subsurface conditions everywhere are not significantly different from those disclosed by the explorations.

11.0 REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 2014, AASHTO LRFD bridge design specifications, Customary U.S. units, 7th edition:

Washington, D.C., American Association of State Highway and Transportation Officials.

AASHTO, 2009, AASHTO LRFD bridge design specifications: customary U.S. units (4th ed.

with 2008 & 2009 interim revisions): Washington, D. C., AASHTO, 1 v.

American Concrete Institute (ACI), 2011, Building code requirements for structural concrete and commentary, Farmington Hills, Michigan, ACI 318-08.

Brown, D.A, Turner, J.P, Castelli, R.J., 2010, Drilled Shafts: Construction Procedures and LRFD Design Methods: NHI Course No. 132014, Geotechnical Engineering Circular No. 10.

Washington, D.C., Report No. FHWA-NHI-10-016.

Ensoft, Inc., 2012, LPILE Plus 2012, A Program for Analyzing Stress and Deformation of Individual Piles or Drilled Shafts Under Lateral Load, Austin, Texas.

Lemke, R. W., 1960, Geology of the Souris River area, North Dakota: U.S. Geological Survey Professional Paper 325, 138 p., 8 plates.

Pile Dynamics, Inc., 2010, GRLWEAP 2010, Cleveland, Ohio.

Roberge, P.R., 1999, Handbook of corrosion engineering, Second Edition: McGraw-Hill, New York, New York.

U.S. Department of Transportation, Federal Highway Administration (FHWA), National Highway Institute (NHI), 2006, Design and Construction of Driven Pile Foundations, Publication No. FHWA NHI 05-042, April.

U.S. Department of Transportation, Federal Highway Administration (FHWA), 2014, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14.

U.S. Geological Survey (USGS), 2006, Quaternary fault and fold database for the United States, accessed April, 16 2015, from USGS web site: http://earthquake.usgs.gov/regional/qfaults.

http://earthquake.usgs.gov/regional/qfaults

PROJECT

LOCATION

t h

S r e e t

N

W r e e t

N

W

415th Avenue NW

6th Street NE

VICINITY MAP

FIG. 1

Des Lacs Refuge

County Road 2 Bridge Replacement

Kenmare, North Dakota

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Feet

3000 6000

February 2016 23-1-01372-101

F i l e n a m e

I W

I P s

C

F L

H D

A

E C

O M

N o r a k o t a e s

L a c s

B r i d g e

R e p o r t F i g u r e s D r a f t i n g

F g d w t e

L o g i n m a o

MT

Pro

Kenmare

North Dakota

Judson

Bismarck

83 281

Hebron

Des Lacs

Middle Des

Lacs Lake

SW-02

SW-01

6th Street Avenue

D s c

R v e r v e n u e

F i l e n a m e

I W

I P s

C

F L

E C

O M

N o r k o t a s

L a c s

B r i d g e

R e p o r t F i g u r e s D r a f t i n g

F d t e g i n m a o

FIG. 2

SITE AND EXPLORATION PLAN

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth™ Mapping Service.

NOTE

SW-01

200 400

Approximate Scale in Feet

Boring Designation and

Approximate Location

LEGEND

Des Lacs Refuge

County Road 2 Bridge Replacement

Kenmare, North Dakota

February 2016 23-1-01372-101

MT

Pro

A

A

A A'

Generalized Subsurface

Section

West

A

East

A'

A p p r o x i m a t e

E l e v a t i o n i n

F e e t

Till

Alluvium

Glacial Till

Medium Dense to Dense Alluvium

Fill Fill

A p p r o x i m a t e

E l e v a t i o n i n

F e e t

A

17301730

16901690

16801680

ST

SW-01

04-03-15

ST

SW-02

04-02-15

PROJ. 9' N

PROJ. 7' S

Medium Dense Alluvium

Glacial Till

Mixed Alluvium

F i l e n a m e

I W

I P s

C

F L H

D

A

E C

O M

N o r t h

D a k o t a s

L a c s

B r i d g e R e p o r t F i g u r e s

P l a n a n d

P r o f i l e d t e g i n m a o

FIG. 3

GENERALIZED SUBSURFACE

PROFILE A-A'

23-1-01372-101February 2016

0 20 40

Scale in Feet

LEGEND

SW-01

(Proj. 34' N) Water Level Measured from

Monitoring Well and Date Measured

Water Level at Time of Drilling

USCS or Fill/Rock Symbol

Approximate Bedrock Contact

Monitoring Well and/or Boring Designation

Projected Distance and Direction

Standard Penetration Test Blows/Foot or Blows/ Inches Driven

Modified California Sampler

Approximate Geologic Contact

Bottom of Boring

Date Completed

30/6"

1. Figure adapted from AECOM file

RG1504_S-01_GL.dgn

2. Groundwater levels shown were measured at the time of drilling. Groundwater levels will vary.

3. The subsurface profile is generalized from materials observed in soil borings. Variations may exist between profile and actual conditions.

NOTES

Des Lacs Refuge

County Road 2 Bridge Replacement

Kenmare, North Dakota

Vertical = Horizontal

Fill - Medium stiff to stiff, sandy lean clay and medium dense to dense, clayey sand.

Mixed Alluvium - Very loose to dense, clayey and silty sand and soft to very stiff, sandy lean clay.

Glacial Till - Medium stiff to hard, sandy lean clay.

Medium Dense Alluvium - Medium dense, silty sand.

Medium Dense to Dense Alluvium - Medium dense to dense, silty sand and well to poorly graded sand with gravel.

GENERALIZED SOIL UNIT DESCRIPTION

3/30/2016-HP 14X102_GDM_DP_Axial_v2.3_rev1 (plugged side, half plugged tip).xlsm

NOTES:

1.

2.

3.

ASSUMED SUBSURFACE

PROFILE

Based on Nearby Explorations:

SW-01 and SW-02

February 2016

ESTIMATED AXIAL PILE RESISTANCE

HP 14 X 102

Des Lacs Refuge County Road 2 Bridge Replacement

Kenmare, North Dakota

Total pile capacity is a summation of its side and base resistances. Unfactored nominal resistances shown on plots above are to be multiplied by the appropriate resistance factors (RFs). For strength limit state, RF = 0.45 for side resistance and RF = 0.45 for base resistance. A resistance factor of 0.35 should be used for uplift in the strength limit state. For extreme limit state, RF = 1 for side resistance, and RF = 1 for base resistance. A resistance factor of 0.8 should be used for uplift in the extreme event limit state.

23-1-01372-101

The analyses were performed based on recommendations outlined in the AASHTO LRFD Bridge Design Specifications (2014), the FHWA Design and Construction of Driven Pile Foundations (FHWA, 2006), and our experience. The analyses are based on a single pile and do not consider group action of closely spaced piles (closer than 2.5 widths, center to center). Once final pile group sizes and spacings are determined, the axial capacity of the pile group should be re-evaluated.

FIG. 4

Estimated capacities assume that the piles will be installed after construction of the widened approach embankments. Downdrag loads due to potential fill embankment settlement have not been included because of the minor anticipated increase in new surcharge.

0 50 100 150 200 250 300

PI

LE

T

IP

D

EP

TH

B

EL

O

W E

XI

ST

IN

G

G R

A D

E (fe et

UNFACTORED NOMINAL RESISTANCE (tons)

Total Resistance - Strength Limit Side Resistance - Strength Limit Tip Resistance - Strength Limit

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Medium Stiff Fill

0'

Medium Stiff Alluvium

7'

Stiff Till

48'

Very Stiff Till

65'

Medium Dense Alluvium

83'

Boring Extends to

101.5 feet

3/30/2016-HP 14X89_GDM_DP_Axial_v2.3_rev1 (plugged side, half plugged tip).xlsm

1.

2.

3.

February 2016

ESTIMATED AXIAL PILE RESISTANCE

HP 14 X 89

Des Lacs Refuge County Road 2 Bridge Replacement

Kenmare, North Dakota

Total pile capacity is a summation of its side and base resistances. Unfactored nominal resistances shown on plots above are to be multiplied by the appropriate resistance factors (RFs). For strength limit state, RF = 0.45 for side resistance and RF = 0.45 for base resistance. A resistance factor of 0.35 should be used for uplift in the strength limit state. For extreme limit state, RF = 1 for side resistance, and RF = 1 for base resistance. A resistance factor of 0.8 should be used for uplift in the extreme event limit state.

23-1-01372-101

The analyses were performed based on recommendations outlined in the AASHTO LRFD Bridge Design Specifications (2014), the FHWA Design and Construction of Driven Pile Foundations (FHWA, 2006), and our experience. The analyses are based on a single pile and do not consider group action of closely spaced piles (closer than 2.5 widths, center to center). Once final pile group sizes and spacings are determined, the axial capacity of the pile group should be re-evaluated.

FIG. 5

Estimated capacities assume that the piles will be installed after construction of the widened approach embankments. Downdrag loads due to potential fill embankment settlement have not been included because of the minor anticipated increase in new surcharge.

ASSUMED SUBSURFACE

PROFILE

Based on Nearby Explorations:

SW-01 and SW-02

0 50 100 150 200 250 300

PI

LE

T

IP

D

EP

TH

B

EL

O

W E

XI

ST

IN

G

G R

A D

E (fe et

UNFACTORED NOMINAL RESISTANCE (tons)

Total Resistance - Strength Limit Side Resistance - Strength Limit Tip Resistance - Strength Limit

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Medium Stiff Fill

0'

Medium Stiff Alluvium

7'

Stiff Till

48'

Very Stiff Till

65'

Medium Dense Alluvium

83'

3/30/2016-HP 12X74_GDM_DP_Axial_v2.3_rev1 (plugged side, half plugged tip).xlsm

1.

2.

3.

February 2016

ESTIMATED AXIAL PILE RESISTANCE

HP 12 X 74

Des Lacs Refuge County Road 2 Bridge Replacement

Kenmare, North Dakota

Total pile capacity is a summation of its side and base resistances. Unfactored nominal resistances shown on plots above are to be multiplied by the appropriate resistance factors (RFs). For strength limit state, RF = 0.45 for side resistance and RF = 0.45 for base resistance. A resistance factor of 0.35 should be used for uplift in the strength limit state. For extreme limit state, RF = 1 for side resistance, and RF = 1 for base resistance. A resistance factor of 0.8 should be used for uplift in the extreme event limit state.

23-1-01372-101

The analyses were performed based on recommendations outlined in the AASHTO LRFD Bridge Design Specifications (2014), the FHWA Design and Construction of Driven Pile Foundations (FHWA, 2006), and our experience. The analyses are based on a single pile and do not consider group action of closely spaced piles (closer than 2.5 widths, center to center). Once final pile group sizes and spacings are determined, the axial capacity of the pile group should be re-evaluated.

FIG. 6

Estimated capacities assume that the piles will be installed after construction of the widened approach embankments. Downdrag loads due to potential fill embankment settlement have not been included because of the minor anticipated increase in new surcharge.

ASSUMED SUBSURFACE

PROFILE

Based on Nearby Explorations:

SW-01 and SW-02

0 50 100 150 200 250 300

PI

LE

T

IP

D

EP

TH

B

EL

O

W E

XI

ST

IN

G

G R

A D

E (fe et

UNFACTORED NOMINAL RESISTANCE (tons)

Total Resistance - Strength Limit Side Resistance - Strength Limit Tip Resistance - Strength Limit

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Medium Stiff Fill

0'

Medium Stiff Alluvium

7'

Stiff Till

48'

Very Stiff Till

65'

Medium Dense Alluvium

83'

Row 1 Row 2 Row 3 and higher Row 1 Row 2 Row 3 and higher

2.0D 0.54 0.33 0.25 2.0D 0.53 0.27 0.20

3.0D 0.80 0.50 0.38 3.0D 0.80 0.40 0.30

5.0D 1.00 0.85 0.70 5.0D 1.00 0.85 0.70

NOTES:

1. Linear interpolation can be used to calculate the P-Multipliers for the shaft spacings which are not listed above.

2. P-Multipliers are based on AASHTO 2014 LRFD Bridge Design Specifications.

3. The P-Multipliers should be applied to the load portion of the P-Y curve in the LPILE software.

Group Type

Shaft Spacing (Dia.)

1.00 Groups with 2 or

more Rows

Groups with 1 Row

Recommended P-Multipliers Loading Type-3

Group Type

Shaft Spacing (Dia.)

Recommended P-Multipliers

Loading Type-1 Row 1

Loading Type-2

Applied Load

LOADING TYPE - 1

Applied Load

LOADING TYPE - 3

ROW 1 ROW 2 ROW 3 & higher

Applied Load

LOADING TYPE - 2

ROW 1 ROW 2 ROW 3 & higher

Des Lacs Refuge County Road 2 Bridge Replacement

Kenmare, North Dakota

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

RECOMMENDED P-MULTIPLIERS

FOR GROUP EFFECTS

FIG. 7

February 2016 23-1-01372-101

FIG

. 6

RECOMMENDED SURCHARGE

LOADING FOR TEMPORARY AND

PERMANENT WALLS

FIG. 8

Des Lacs Refuge

County Road 2 Bridge Replacement

Kenmare, North Dakota

February 2016

SHANNON & WILSON, INC.

F i l e

I E

F

D

E N s

C

F L H

D

A

E C

O M

N o r t h

D a k o t a s

L a c s

B r i d g e R e p o r t F i n a l

R e v

F i g u r e s N a t i v e S u r c h a r g e

F i g u r e d t e u t h o r j x c

W a l l

PLAN VIEW

H

2.0B

) (psf) cos (1.1' = 2

1.5B e p t h

Z

1.0B

0.0B

0.5B W a l l

ELEVATION VIEW

Z

Wall Line p

L/B =

L/B = 0.25

L/B = 0.5

L/B = 1

UNIFORM SURCHARGE

= (K)q

H q2

/2

< 15 Feet H

EARTH BERM

(psf)s q

(K) (H )

(see Note 3)

Note:

< 33°

H z=nH

Bottom of

Excavation x = mH Q

Point Load in Pounds

(psf)

H

ELEVATION VIEW

x = mH

H

Bottom of

Excavation

W a l l z=nH

(psf)

H

Line Load in Pounds l

Q

B) LATERAL PRESSURE DUE TO LINE LOAD

i.e. NARROW CONTINUOUS FOOTING

PARALLEL TO WALL

C) LATERAL PRESSURE DUE TO STRIP LOAD

( - sin cos2) (psf)

W a l l

W a l l s

W a l l

A) LATERAL PRESSURE DUE TO POINT LOAD

i.e. SMALL ISOLATED FOOTING OR WHEEL LOAD

D) LATERAL PRESSURE DUE TO EARTH BERM

OR UNIFORM SURCHARGE

Bottom of

Excavation

Bottom of

Excavation

E) LATERAL PRESSURE

BENEATH CORNER OF

ADJACENT FOOTING

0 0.25 0.5 sq

L

B

NOTES

Figures are not drawn to scale.

Applicable surcharge pressures should be added to appropriate permanent wall lateral earth and water pressure.

See Table 5 for recommended K values.

W a l l

Bearing

Pressure q (psf)

1.

2.

3.

(see Note 3)

I , Influence Factor

(I ) q p

Lateral Footing

Pressure on Wall

(derived from NAVFAC DM 7.2, 1986; and Sandhu, Earth Pressure on Walls Due to Surcharge, 1974)

(derived from Poulous and Davis, Elastic Solutions for

Soil and Rock Mechanics, 1974; and Terzaghi and

Peck, Soil Mechanics in Engineering Practice, 1967)

(NAVFAC DM 7.2, 1986)

(derived from Fang, Foundation

Engineering Handbook, 1991)

(NAVFAC DM 7.2, 1986)

= 1.28 (psf)

H

H m n l

Q

(m + n )H

2 2 2

(0.16 + n ) l

Q

H n

2 2

= 0.20 (psf) For m < 0.4:

For m > 0.4: = 1.77 (psf)

H

H m np Q

(m + n )H

2 2 3

(0.16 + n ) p

Q

H n

2 3

= 0.28 (psf) For m < 0.4:

For m > 0.4:

p

Point Load in Pounds

= Unit Weight of Earth Berm s

Q p

Bearing

Pressure

Earth

Berm

= Lateral Pressure in radians

PILE AND DRIVING

EQUIPMENT DATA

FIG. 9

SHANNON & WILSON, INC.

Cushion Material: Area:

Thickness:

Modulus of Elasticity - E: (psi) Coefficient of Restitution - e:

Material: Area:

Thickness:

Modulus of Elasticity - E: (psi) Coefficient of Restitution - e:

Manufacturer: Model:

Type: Serial No.:

Rated Energy: @ Length of Stroke Explosive Force:

Type:

Pile Size: Length (in leads):

Diameter:

Wall Thickness: Taper:

Material: Weight/Ft.:

Design Pile Capacity: (tons) Description of Splice:

Tip Treatment Description:

(with diesel hammers) Anvil weight:(with diesel hammers) Anvil weight:

Ram Weight: Ram Length:

Ram Cross Sectional Area:

PILE

PILE CAP

CUSHION

Helmet Bonnet Anvil Block Drivehead

Contract No.:

Project:

County:

HA

MM

ER

CO

MP

ON

EN

TS

CAPBLOCK

ANVIL

RAM

HAMMER

ANVIL

RAM

Weight:

(for diesel hammers)

(piles driven by)

(for diesel hammers)

Structure Name and/or No.:

Pile Driving Contractor or Subcontractor:

23-1-01372-101February 2016

Des Lacs Refuge

Kenmare, North Dakota

APPENDIX A

SUBSURFACE EXPLORATIONS

23-1-01372-101_R1_AA_rev1.docx/wp/lmr 23-1-01372-101 A-i

A.1 INTRODUCTION .......................................................................................................... A-1

A.2 EXPLORATIONS .......................................................................................................... A-1 A.2.1 Soil Classification System ................................................................................ A-1 A.2.2 Standard Penetration Test (SPT) ...................................................................... A-2 A.2.3 Shelby Tube Sampling ..................................................................................... A-2

A-1 Soil Classification and Log Key (3 sheets) A-2 Log of Boring SW-01 (2 sheets) A-3 Log of Boring SW-02 (2 sheets) A-4 Exploration Photographs (2 sheets)

A-1

A.1 INTRODUCTION

The field exploration program for the County Road 2 Bridge Replacement Project consisted of drilling and sampling two geotechnical borings, designated SW-01 and SW-02, on April 2 and 3, 2015. A representative from Shannon & Wilson observed the drilling and sampling operations, retrieved representative samples for laboratory testing, and prepared descriptive field logs of the borings. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The borings were coordinated (including subcontractor coordination, utility locates, and traffic control) and observed by Shannon & Wilson. Individual boring logs are presented on Figures A- 2 and A-3. These exploration logs represent our interpretation of the contents of the field logs and the results of laboratory testing. The location of each boring (Figure 2) was measured relative to existing features at the site and should be considered accurate to the degree implied by the method used. Photographs of the site at the time of drilling are presented on Figure A-4.

The borings were drilled by Interstate Drilling Services under subcontract to Shannon & Wilson using a truck-mounted Diedrich D-50 drill rig. The borings were drilled within the roadway and advanced to an approximate depth of 101.5 feet below the road surface.