RMA_Geotech_Report_20190627.pdf

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Attached to: CO FLAP DEN 56(1) Access Connections to ROAR Federal contract opportunity
Solicitation number: 6982AF19B000013
Issued by: Department of Transportation Federal Highway Administration

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SUBMITTED TO:

Atkins North America, Inc.

7604 Technology Way, Suite 400 Denver, Colorado 80237

BY:

Shannon & Wilson, Inc.

1321 Bannock Street, Suite 200 Denver, Colorado 80204

(303) 825-3800 www.shannonwilson.com

GEOTECHNICAL AND PAVEMENT DESIGN REPORT

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

COMMERCE CITY, COLORADO

June 2019

Shannon & Wilson No: 23-1-01437-003

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019 ii

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CONTENTS

1 Introduction

2 Project and Site Description

3 Subsurface Explorations and Laboratory Testing

3.1 Field Investigation

3.2 Geotechnical Laboratory Testing

4 Regional Geology and Subsurface conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.3 Groundwater

5 Geologic Hazard Evaluation

5.1 Seismic Hazards

5.2 Swelling Soil and Bedrock

5.3 Corrosion

6 Geotechnical Recommendations

6.1 Driven Piles

6.1.1 Axial Design

6.1.2 Minimum Tip Depth

6.1.3 Lateral Resistance

6.1.4 Corrosion Resistance

6.2 Retaining Walls

6.2.1 Design Parameters

6.2.2 Wall Drainage

7 Pavement Recommendations

7.1 Design Methodology

7.2 Swelling Soil

7.3 Traffic Loading

7.4 Subgrade Soils

7.5 Recommended Pavement Sections

8 Construction Considerations iii

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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

8.1.5 Overdriving

8.2 Earthwork and Grading

8.2.1 Excavation

8.2.2 Subgrade Preparation and Proof Rolling

8.2.3 Fill Placement and Compaction

8.3 Paving Materials

9 Closure

10 References

Exhibits Exhibit 5‐1: Seismic Design Ground Motion Parameters

Exhibit 6‐1: Recommended Minimum Tip Elevations

Exhibit 6‐2: Recommended Retaining Wall Design Parameters

Exhibit 8‐1: Recommended Materials for Pavements

Table Table 1: Geotechnical Parameters for Deep Foundation Design

Figures Figure 1: Vicinity Map

Figure 2: Site and Exploration Plan (8 sheets)

Figure 3: Subsurface Profile A‐Aʹ Sand Creek Pedestrian Bridge

Figure 4: Subsurface Profile B‐Bʹ Uvalda Ditch Pedestrian Bridge

Figure 5: Subsurface Profile C‐Cʹ North High Line Canal Pedestrian Bridge

Figure 6: Subsurface Profile D‐Dʹ South High Line Canal Pedestrian Bridge

Figure 7: Estimated Axial Pile Resistance Sand Creek Pedestrian Bridge

Figure 8: Estimated Axial Pile Resistance Uvalda Ditch Pedestrian Bridge

Figure 9: Estimated Axial Pile Resistance North High Line Canal Pedestrian Bridge

Figure 10: Estimated Axial Pile Resistance South High Line Canal Pedestrian Bridge iv

C O

Figure 11: Recommended P‐Multipliers For Laterally Loaded Groups of Piles of Shafts

Figure 12: Pile and Driving Equipment Data

Figure 13: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Subsurface Explorations

Appendix B: Laboratory Test Results

Appendix C: Site Photographs

Appendix D: Pavement Calculations

Important Information v

A C

R O

ACRONYMS

AASHTO American Association of State Highway and Transportation Officials

CAPWAP Case Pile Wave Analysis Program

CDOT Colorado Department of Transportation

ESAL Equivalent Single Axle Loading

FHWA Federal Highway Administration

HACP Hot Asphalt Concrete Pavement

H:V Horizontal to Vertical

LRFD Load and Resistance Factor Design

NWR National Wildlife Refuge

PDDM Project Development and Design Manual

PGA Peak Ground Acceleration

RMA Rocky Mountain Arsenal

USGS United Stated Geological Survey

USDOT United States Department of Transportation

UTBC Untreated Base Course

WEAP Wave Equation Analysis of Pile Driving

Geotechnical and Pavement Design Report

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1 INTRODUCTION

This report summarizes the results of our subsurface exploration and laboratory testing program and presents geotechnical and pavement design recommendations and construction considerations for the proposed Rocky Mountain Arsenal (RMA) National

Wildlife Refuge (NWR) Project (the Project) in Commerce City, Colorado. Our services were completed in general accordance with our Task Order Agreement No. 005/1005073 with Atkins North America, Inc. (Atkins) dated February 25, 2019. Our conclusions and recommendations in this report are based on:

The limitations of our approved scope, schedule, and budget described in our contract;

Our understanding of the Project and information provided by Atkins;

Subsurface conditions observed in the borings at the time our explorations were completed; and

The results of testing performed on samples collected from the explorations.

The objective of our geotechnical studies was to provide recommendations and construction considerations, as presented herein, for the proposed pedestrian bridges and parking lots.

The authorized scope of services was based on this objective and this report should not be used for other purposes without Shannon & Wilson, Inc.’s (Shannon & Wilson’s) review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located within the RMA in Commerce City, Colorado (Figure 1). The proposed work within the RMA consists of adding new trails and parking lots. Four new pedestrian bridges, identified as the Sand Creek Pedestrian Bridge, Uvalda Ditch Pedestrian

Bridge, North High Line Canal Pedestrian Bridge, and South High Line Canal Pedestrian

Bridge are proposed to be constructed within the RMA. We understand that the proposed pedestrian bridges will consist of prefabricated single span bridges founded on driven H‐ piles. Based on preliminary plans provided by Atkins the bridge lengths will be between

25 and 60 feet. Each bridge will be approximately 10 feet wide. As part of the project the grades will be raised approximately 3 to 5 feet at the bridge locations and may require short abutment and wing walls. Nominal (less than 2 feet) cuts and fills are anticipated at all other locations.

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In addition, four parking lots are also proposed throughout the RMA at the following locations:

Parking Lot 1 ‐ E. 64th Avenue and Woodland Trail

Parking Lot 2 ‐ E. 56th Avenue and Uvalda Street

Parking Lot 3 ‐ E. 56th Avenue near the High Line Canal

Parking Lot 4 ‐ E. 96th Avenue near Chambers Road

The proposed parking lots will be surfaced with hot asphalt concrete pavement (HACP).

Refer to Figure 2 for a project map with the bridge and parking lot locations.

3 SUBSURFACE EXPLORATIONS AND LABORATORY

TESTING

3.1 Field Investigation

Shannon & Wilson conducted a field exploration program from March 25 through 27, 2019, to explore subsurface conditions at the project site. The subsurface exploration program consisted of drilling and sampling twelve borings (designated SW‐01 through SW‐12). The locations of the borings are shown in Figure 2.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used. Photographs of the drilling locations and pavement cores are included in Appendix C.

3.2 Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index and engineering properties. Index tests included natural water content, grain size analysis, percent fines, and Atterberg limits. Engineering properties tests included corrosion, swell/consolidation, and R‐Value. Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content, fines content, and Atterberg limits are also shown on the individual boring logs included in

Appendix A.

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4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

The RMA lies east of the basin axis of the Denver Basin, a structural depression that occupies much of eastern Colorado. Geologic mapping in the area indicates the site is underlain by Holocene and Pleistocene eolian deposits overlying Denver and Arapahoe

Formations (Lindvall, 1983). The eolian deposits are described as primarily sand, sandy‐silt and clay deposits ranging from 10 to 20 feet thick. The underlying Denver and Arapahoe

Formations are described as brown, yellowish‐brown, gray, and blueish gray interbedded sandstone, claystone, siltstone, and shale.

4.2 Subsurface Conditions

Borings SW‐01 and SW‐02 were drilled at the Sand Creek Pedestrian Bridge and interbedded very loose to loose sand and medium stiff to stiff, sandy clay to a depth of approximately 27 feet. Medium dense to dense sand with silt was then encountered to a depth of 78 feet. Claystone and sandstone bedrock were then encountered to a depth of

90 feet.

Borings SW‐03 and SW‐04, located at the Uvalda Ditch Pedestrian Bridge, encountered very loose to loose, silty sand to a depth of 15 feet underlain by soft to stiff clay to a depth of

42 feet. Medium dense, silty sand was then encountered overlaying claystone bedrock at a depth of 50 feet to the termination depth of the boring at approximately 65 feet.

At the North High Line Canal Pedestrian Bridge, borings SW‐05 and SW‐06 encountered

12 feet of loose to medium dense, silty sand overlying 40 feet of stiff clay. Sandstone and claystone bedrock was encountered from 52 feet to the termination depth of the boring at

85 feet.

Borings SW‐07 and SW‐08 were completed at the South High Line Canal Pedestrian Bridge and encountered 15 feet of medium dense sand with silt overlying claystone and sandstone to the termination depth of the boring at a depth of 45 feet. An approximately 3‐foot thick weak layer of lignite and claystone was encountered at a depth 27 feet.

Borings SW‐09 through SW‐12 were drilled at the parking lot locations and generally encountered very loose to medium dense sand with varying percentages of silt and clay along with isolated layers of medium stiff to stiff clay.

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Subsurface profiles for each bridge are provided in Figures 3 through 6.

The explorations were performed to evaluate geotechnical soil conditions at the project site.

Our observations are specific to the locations, depths, and times noted on the logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions.

Potential variation includes, but is not limited to:

The conditions between explorations may be different.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

If conditions different from those described herein are encountered during construction, we should review our description of the subsurface conditions and reconsider our conclusions and recommendations.

4.3 Groundwater

During drilling, groundwater was encountered in pedestrian bridge borings SW‐01 through

SW‐08 at depths ranging from about 9 to 30 feet below the existing ground surface.

Groundwater was not encountered in borings SW‐06 and SW‐07, as well as in the parking lot borings SW‐09 through SW‐12. The groundwater level at the time of drilling is noted on each boring log included in Appendix A. 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 ditches and flood events.

5 GEOLOGIC HAZARD EVALUATION

5.1 Seismic Hazards

The Front Range of Colorado is an area of low potential for damaging earthquakes.

Unfortunately, it is not possible to accurately estimate the timing or location of future earthquakes, because the occurrence of earthquakes is relatively infrequent and the historical earthquake record in Colorado is short (about 130 years). Based on a recent geologic map by the U.S. Geological Survey (USGS), the nearest fault to the proposed project is the Golden Fault, approximately 20 miles to the west (Rogers and others, 1998).

However, there is only refuted evidence that this fault has been active in the Quaternary

Period, or last 1.6 million years. Therefore, in our opinion, the potential for ground surface fault rupture is low.

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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, it is our opinion that the risk of liquefaction is low.

Using the American Association of State Highway and Transportation Officials (AASHTO)

Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2017) criteria, and based on subsurface conditions encountered in our borings at the proposed

RMA pedestrian bridges (assuming that similar conditions are present from the maximum depth of our boring to a depth of 100 feet), Site Class E is recommended for the proposed bridge structures.

Ground motion parameters were determined for the project site using the USGS AASHTO

2009 Web Service Documentation Web Application (USGS, 2009) and procedures recommended by AASHTO (2017). Exhibit 5‐1 presents recommended seismic design ground motion parameters.

Exhibit 5-1: Seismic Design Ground Motion Parameters

Design Parameter Value

Peak Ground Acceleration 1 (PGAB) 0.055 g

Site Class E

Short-period Spectral Acceleration, SS 0.119 g

Long-period Spectral Acceleration, S1 0.033 g

Site Factor, FPGA 2.5

Site Factor, Fa 2.5

Site Factor, FV 3.5

Peak Design Spectral Acceleration, AS 0.138 g

Short-period Design Spectral Acceleration, SDS 0.297 g

Long-period Design Spectral Acceleration, SD1 0.114 g

TO 0.077 sec.

TS 0.384 sec.

NOTES:

PGAB = peak ground acceleration for a site underlain by Site Class B soil (soft rock) Based on AASHTO 2009 Guide Specifications.

g = gravity; sec. = seconds

5.2 Swelling Soil and Bedrock

Swell susceptible soil and rock are common along the Front Range of Colorado. In general, the overburden material encountered in the borings consisted of sand with a lesser portion

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019 of clay and were judged to be non‐expansive. To assist us in determining the swell potential through the project area, we reviewed a published geologic map of potentially swelling soil and rock of the Front Range urban corridor, developed by Hart (1974). The map indicates that the site has low swell potential.

To further evaluate the potential for swell at the site, we performed Atterberg limits, moisture contents, and a swell/consolidation test on soil samples encountered in our explorations. The swell tests indicated nil swell potential. Based on these results, it is our opinion that the swell susceptibility of the subgrade at the project site is low.

5.3 Corrosion

The clay soil and bedrock materials in the Colorado Front Range area can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, samples of sandstone bedrock and sandy lean clay were 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 samples ranged from 755 to 9,000 ohm‐centimeters. Based on correlations developed by Roberge (2012), these values suggest an extremely corrosive to moderately corrosive subsurface.

The concentration of water soluble sulfates measured in the samples was 0.01 percent by weight (100 parts per million). Based on classifications as defined by ACI‐318‐14 (ACI, 2014), these test results suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0). Based on standard construction specifications prepared by the

Colorado Department of Transportation (CDOT), these test results correspond to Class 0 requirements for sulfate resistance (CDOT, 2011).

6 GEOTECHNICAL RECOMMENDATIONS

As discussed in Section 2.0, we understand the proposed pedestrian bridges will consist of prefabricated single span bridges founded on driven 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.

6.1 Driven Piles

We understand that driven HP 14x89 or HP 12x53 piles will be used to support the proposed pedestrian bridges and that the piles will be designed for a factored maximum load of up to approximately 60 kips per pile. The design criteria presented herein were

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23-1-01437-003 June 2019 developed based on recommendations presented in the AASHTO LRFD Bridge Design

Specifications (AASHTO, 2017). In addition, the 2016 Federal Highway Administration

(FHWA) Manual “Design and Construction of Driven Pile Foundations” (FHWA, 2016) was used to supplement driven pile design procedures and develop the axial resistance parameters.

6.1.1 Axial Design

Plots of the geotechnical pile capacity for each bridge are provided in Figure 7 through 10.

The geotechnical resistance should be confirmed by dynamic testing (i.e., the nominal geotechnical resistance indicated by the dynamic testing multiplied by the resistance factor should be greater than or equal to the factored structural axial load on the pile). AASHTO

(2017) recommends a strength limit resistance factor of 0.65, assuming dynamic testing is completed as described in Section 8.1.4. A resistance factor of 1.0 is recommended for the service limit state. A resistance factor of 1.0 is recommended for the extreme limit states, except a resistance factor of 0.8 is recommended for uplift.

A minimum spacing of three widths (center‐to‐center) for axial loads is recommended to reduce the stress overlap between the adjacent piles. If this condition cannot be met, a reduction in axial resistance parameters (i.e., consideration of group effects) may be necessary. Lateral resistance of driven piles is discussed in Section 6.1.3. If battered piles are to be implemented for lateral loading, we recommend that the pile be battered no flatter than 1 horizontal to 4 vertical (1H:4V).

For properly designed and installed piles, we estimate settlement to be on the order of

1 inch or less. This settlement value does not include elastic compression of the pile under service conditions. Differential settlement across the bridge would be expected to be about

50 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.

6.1.2 Minimum Tip Depth

Relatively soft and loose overburden soils were encountered at each bridge location.

Considering the variability of these materials we recommend extending all piles below the recommended minimum tip elevation to reduce the likelihood of both total and differential settlements at the abutment locations. Refer to Exhibit 6‐1 for our recommended minimum tip elevations at each bridge location.

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Exhibit 6-1: Recommended Minimum Tip Elevations

Location Minimum Tip

Elevation Depth Below Existing

Ground Surface

Sand Creek Pedestrian Bridge 5,199 feet 40 feet

Uvalda Ditch Pedestrian Bridge 5,235 feet 40 feet

North High Line Canal Pedestrian Bridge 5,255 feet 40 feet

South High Line Canal Pedestrian Bridge 5,279 feet 35 feet

6.1.3 Lateral Resistance

To determine the lateral resistance of an individual driven pile, and the deflection, shear, and moment along the pile, we have provided input parameters for the commercial software LPILE by Ensoft, Inc. (2017) in Table 1. Group action can be analyzed using p‐ multipliers within LPILE. P‐multipliers (i.e., group reduction factors) for loading perpendicular and parallel to a line of piles are presented on Figure 11.

6.1.4 Corrosion Resistance

Based on corrosion testing of the subgrade soils, the H‐Piles will be subjected to an aggressive soil environment as discussed in Section 5.3. The FHWA Pile Design Manual

(2016) recommends a corrosion rate for steel piles buried in fill or disturbed soils; however, subgrade soils encountered at the site did not encounter fill or disturbed soils. As such, we used guidance from the CDOT Bridge Design Manual (2019) in recommending corrosion rates. Based on CDOT, we recommend designing the H‐piles to include sacrificial steel assuming a minimum corrosion rate of 0.001 inches per year.

6.2 Retaining Walls

We anticipate that abutment and wing walls will be located on either side of the bridges to accommodate the approach embankments.

6.2.1 Design Parameters

Our recommended lateral earth pressures for design of retaining walls are provided in

Exhibit 6‐2. The parameters are based on AASHTO (2017) criteria and assume Backfill

Material in accordance with FP‐14 Section 704.03 or onsite overburden granular material is used within the retained zones (i.e., the 1H:1V zone extending upward from the heel of the reinforced zone). We recommend that onsite soils used within the retained zone have a maximum fines content of 35 percent. Clayey materials should be excluded from use within the retained zone. The static earth pressures assume a vertical wall face with a horizontal backslope and do not include any hydrostatic pressure related to accumulation of water in

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019 the backfill. Active earth pressures assume walls are free to displace a minimum of

0.001 times the height of the wall (0.001H). If the conditions and assumptions discussed above are not met, the recommendations should be revised.

Exhibit 6-2: Recommended Retaining Wall Design Parameters

Design Parameter Value

Backfill Material

Total Unit Weight (pcf) 125

Effective Friction Angle (degrees) 32

Cohesion (psf) 0

Active Earth Pressure Coefficient, KA 0.31

Equivalent Fluid Density for Active Conditions (pcf) 39

Bearing Resistance

Strength Limit Nominal Bearing Resistance (psf) 1 4,500

Strength Limit Resistance Factor for Bearing 2 0.55

Nominal Coefficient of Friction for Sliding 3 0.40

Strength Limit Resistance Factor for Sliding 4 0.80

NOTES:

Nominal bearing resistance assumes a minimum footing width of 3 feet and a minimum embedment depth of 3 feet.

Bearing resistance factor based on AASHTO (2017), Table 11.5.7-1.

Value assumes cast-in-place concrete. If the concrete is precast, the provided value should be multiplied by a factor of 0.80.

Sliding resistance factor based on AASHTO (2017), Table 10.5.5.2.2-1.

Passive pressure should be ignored in front of walls.

pcf = pounds per cubic foot; psf = pounds per square foot

We anticipate on the order of 1 inch of settlement at wing wall locations with the majority of the settlement will occur during wall construction. Settlement will be roughly proportional to loading (i.e., for a nominal bearing resistance of 2,250 psf, approximately ½ inch of settlement would be anticipated).

Surcharge loads from motor vehicles/traffic and construction equipment will induce additional lateral loads on retaining walls. The pressures provided in Exhibit 6‐2 do not account for surcharge loads. Lateral loads due to various types of surcharges may be calculated by multiplying the surcharge by the active earth pressure coefficient (KA). The earth pressure coefficients are also shown in Exhibit 6‐2. Surcharge loads should be applied as recommended on Figure 13.

6.2.2 Wall Drainage

The earth pressure parameters provided for the proposed retaining walls assume a free‐ draining backfill condition. As such, it will be important to control surface water and to

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019 provide drainage measures that reduce the potential for water to accumulate behind walls, particularly considering the proximity of walls to the creek and ditch channels.

Surface water behind the wall should not be allowed to discharge directly into the wall backfill materials. In addition, water should not be allowed to discharge or pond around retaining structures. We recommend sloping the ground surface in front of walls a minimum of 5 percent away from the wall face for a minimum horizontal distance of 10 feet measured from the face of the wall (or until a paved surface is encountered, whichever is less).

In general, materials with greater than about 3 percent fines content are not considered free draining. If the backfill is not free draining, a rapid drawdown condition could occur following flood events, i.e., water could be trapped in the backfill after flood waters recede.

This condition could be addressed by designing the wall for appropriate water pressures or by including internal drainage features to reduce the potential for water to accumulate in the backfill. Appropriate drainage features could include:

Placement of a 12‐inch thick drainage layer (CDOT Filter Material) on the back face of the wall, with a discharge system (e.g., weep holes or a perforated collector pipe at the base of the drainage layer, daylighting to a suitable discharge point).

Installation of geocomposite drainage boards on the back face of the wall, with a suitable discharge system (e.g., weep holes or a perforated collector pipe, daylighting to a suitable discharge point)

Limiting the fines content of the wall backfill to 3 percent.

7 PAVEMENT RECOMMENDATIONS

Performance of a pavement system depends on the pavement material and thicknesses, subgrade strength, traffic loads and repetitions, design life, and subgrade drainage characteristics. The following sections discuss each of these aspects as they relate to the project.

7.1 Design Methodology

Our pavement design and results are based on the design procedures presented in the

1993 AASHTO Guide for the Design of Pavement Structures with guidance from the U.S.

Department of Transportation and FHWA Federal Lands Highway Project Development and Design Manual (PDDM), dated March 2008, and the CDOT Pavement Manual (2019).

Pavement design inputs and calculations are presented in Appendix D.

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7.2 Swelling Soil

As indicated in Section 5.2, we anticipate low swell potential at the RMA parking lots where granular soils are anticipated at the subgrade elevation. Overexcavation is not necessary for swell mitigation based on the anticipated subgrade material.

7.3 Traffic Loading

Based on discussions with Atkins, traffic counts are not available for the parking lots;

however, we understand that the lots will have low volumes and be primarily used by passenger vehicles. For design of the parking lots, we assumed an equivalent single axle loading (ESAL) of 50,000 based on the minimum recommend ESAL in the PDDM.

7.4 Subgrade Soils

As discussed in Section 4.2, the subsurface explorations completed at the parking lots primarily encountered granular material consisting of sands with varying percentages of silt and clay. To estimate the strength of the subgrade materials, a Hveem Stabilometer (R‐

Value) test was completed on a bulk sample from boring SW‐09 resulting in a R‐Value of 37.

Laboratory index testing indicated the bulk sample consisted of AASHTO classification A‐2‐

4. For the design subgrade strength, we used a CDOT correlation between R‐Value and resilient modulus, which calculates a resilient modulus value of 8,498 pounds per square inch.

7.5 Recommended Pavement Sections

Using the PDDM procedures and the parameters outlined in Appendix D, we recommend the following pavement section for the Project:

3.0 inches of HACP overlying 5 inches of untreated base course (UTBC).

Refer to Section 8.2 for subgrade preparation recommendations for the parking lots.

8 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

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019 driving equipment. Information required for such an analysis is presented on Figure 12.

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 determining 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.

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8.1.4 Dynamic Testing of Pile Driving

Dynamic testing during pile driving is required by AASHTO (2017) 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.

The resistance factor of 0.65 (on the resistance determined from dynamic testing) recommended in Section 6.1.1 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. In our opinion, considering the short length of spans, this criteria could be changed to one pile per bridge for this project. 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.

8.1.5 Overdriving

Exhibit 6‐1 indicates minimum tip elevations for the piles based on the subsurface profile at the bridge sites. To achieve the minimum tip elevations, the piles may have to be overdriven to capacities greater than those required to achieve the structural resistance. We anticipate maximum driving resistances up to 150 kips for the project. The Contractor should choose a hammer that will be able to drive the piles to the minimum tip elevations without damaging the piles.

8.2 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).

8.2.1 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.

Geotechnical and Pavement Design Report

23-1-01437-003 June 2019

8.2.2 Subgrade Preparation and Proof Rolling

All wall, embankment, and pavement 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.

8.2.3 Fill Placement and Compaction

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 walls. Therefore, small equipment that is hand‐operated should be required 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).

8.3 Paving Materials

The following exhibit summarizes our recommendations for pavement material selection.

All specification sections reference the FP‐14 U.S. Customary Units, (USDOT and FHWA, 2014).

Exhibit 8-1: Recommended Materials for Pavements

Material Specification Additional Requirements/Comments

UTBC Section 301 Use Gradation C, D, or E

HACP Section 403 (FP-14)

Division 400

(CDOT, 2011)

Aggregate Gradation: Grade SX (1/2-inch NMAS)

PG Binder: PG 64-22

Gyratory Number (N): 50 or 75

NOTES:

HACP = Hot Asphalt Concrete Pavement; NMAS = Nominal Maximum Aggregate Size; UTBC = Untreated Base Course

The recommended SuperPave Binder is based on LTPP Bind Version 3.1Beta and guidance from the CDOT Standard Specifications for Road and Bridge Construction (2011). We recommend one 3‐inch thick lift.

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23-1-01437-003 June 2019

9 CLOSURE

This report has been prepared for the exclusive use of Atkins and Central Federal Lands

Highway Division for the purpose of providing geotechnical recommendations for the

Rocky Mountain Arsenal National Wildlife Refuge project. This geotechnical design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analyses and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule and budget, the analyses, conclusions and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

Shannon & Wilson, Inc. has prepared “Important Information about Your Geotechnical

Report,” to assist you and others in understanding the use and limitations of our reports.

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23-1-01437-003 June 2019

10 REFERENCES

American Concrete Institute (ACI), 2014, Building code requirements for structural concrete and commentary, Farmington Hills, Mich., ACI 318‐14.

American Association of State Highway and Transportation Officials (AASHTO), 1993, AASHTO guide for design of pavement structures: Washington, D.C., AASHTO, 2 v.

American Association of State Highway and Transportation Officials (AASHTO), 2017, AASHTO LRFD bridge design specifications, Customary U.S. units, 8th edition:

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

Officials.

Colorado Department of Transportation (CDOT), 2019, Bridge Design Manual.

Colorado Department of Transportation (CDOT), 2019, M‐E Pavement Design Manual.

Colorado Department of Transportation (CDOT), 2011, Standard Specifications for Road and Bridge Construction.

Ensoft, Inc., 2017, LPILE 2017, A Program for Analyzing Stress and Deformation of

Individual Piles or Drilled Shafts Under Lateral Load, Austin, Texas.

Hart, S.S., 1974, Potentially swelling soil and rock in the front range urban corridor, Colorado: Colorado Geological Survey, Denver, Colorado, 4 sheets.

Lindvall, R.M., 1983. Geologic Map of the Sable Quadrangle, Adams and Denver Counties, Colorado: Colorado Geological Survey, Geologic Quadrangle Map GQ‐1567, scale

1: 24,000.

Roberge, P.R., 2012, Handbook of corrosion engineering, Second Edition: McGraw‐Hill, New York, New York.

Rogers, W.P., Kirkham, R.M., and Widmann, B.L., compilers, 1998, Fault number 2324, Golden fault, in Quaternary fault and fold database of the United States: U.S.

Geological Survey website, http://earthquakes.usgs.gov/hazards/qfaults, accessed

October, 2016.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2016, Design and Construction of Driven Pile Foundations. Publication No.

FHWA‐NHI‐16‐009. Available from:

https://www.fhwa.dot.gov/engineering/geotech/pubs/gec12/nhi16009_v1.pdf.

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U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2008, Federal Lands Highway project development and design manual (PDDM):

U.S. Department of Transportation and Federal Highway Administration.

Available from: http://flh.fhwa.dot.gov/resources/manuals/pddm/.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2014, Federal standard specifications for construction of roads and bridges on

Federal Highway projects, FP‐14 English Units: U.S. Department of

Transportation and Federal Highway Administration.

U.S. Geological Survey (USGS) AASHTO 2009 Web Service Documentation Web

Application (USGS, 2009). Available from:

https://earthquake.usgs.gov/ws/designmaps/

Geotechnical and Pavement Design Report

Location Top Bottom Top Bottom Lpile

Soil Type

Total Unit

Weight 7

Drained Friction Angle

Undrained Shear

Strength (Boring ID) (ft) (ft) (ft) (ft) (ft) (pcf) (deg) (psf)

0 7 5,239 5,232 Very Loose Silty Sand Sand (Reese) 115 28 -

7 12 5,232 5,227 Stiff Clay Stiff Clay w/o Free Water

120 - 1,000

12 22 5,227 5,217 Loose Sand with Silt Sand (Reese) 115 30 -

22 27 5,217 5,212 Stiff Clay Stiff Clay w/o Free Water

120 - 1,500

27 78 5,212 5,161 Medium Dense to

Dense Sand with Silt Sand (Reese) 120 34 -

78 90 5,161 5,149

CLAYSTONE/

SANDSTONE: very weak

Stiff Clay w/o Free Water

130 - 6,000

0 15 5,275 5,260 Very Loose to Loose

Silty Sand Sand (Reese) 115 28 -

15 25 5,260 5,250 Soft Clay Soft Clay 115 - 500

25 42 5,250 5,233 Stiff Clay Stiff Clay w/o Free Water

120 - 1,500

42 50 5,233 5,225 Medium Dense Silty

Sand Sand (Reese) 125 34 -

50 65.5 5,225 5,210 CLAYSTONE: very weak Stiff Clay w/o Free Water

125 - 4,000

0 12 5,295 5,283 Loose to Medium Dense Silty Sand

Sand (Reese) 115 30 -

12 52 5,283 5,243 Stiff Clay Stiff Clay w/o Free Water

115 - 1,500

52 62 5,243 5,233

SANDSTONE/

CLAYSTONE: very weak

Stiff Clay w/o Free Water

125 - 2,500

62 85.5 5,233 5,210 SANDSTONE: very weak Stiff Clay w/o Free Water

125 - 2,500

0 15 5,313 5,298 Medium Dense Sand with Silt Sand (Reese) 120 30 -

15 25 5,298 5,288 CLAYSTONE: very weak Stiff Clay w/o Free Water

125 - 3,000

25 33 5,288 5,280

CLAYSTONE:

extremely weak Stiff Clay w/o Free Water

125 - 2,000

25 45 5,280 5,268 SANDSTONE: very weak Stiff Clay w/o Free Water

125 - 4,000

NOTES:

4 The LPile parameters shown are for a horizontal ground surface. Sloping ground surface modifications should be included per Ensoft, Inc.'s recommendations for Lpile.

7 For design below the water table, the effective unit weight (' = - w , w = 62.4 pcf) must be used.

ksf = kips per square foot; psf = pounds per square foot; pcf = pounds per cubic foot; deg = degrees; ft = foot

2 The groundwater elevation is based on the observerved groundwater at the time of drilling. Design groundwater elevations should correspond to ditch flood elevation.

Table 1 - Geotechnical Parameters for Deep Foundation Design

Groundwater

Elevation 2 Representative

Soil/Rock Description

LPILE PARAMETERS FOR

LATERAL ANALAYSIS 3, 4, 5, 6

South High Line Canal (SW-07 and

SW-08)

5,227

5,260

5,266

5,283

Elevation 1

Depth Below Existing Ground

Surface

Sand Creek (SW-01 and

SW-02)

Uvalda Ditch (SW-03 and

SW-04)

North High Line Canal (SW-05 and

SW-06)

1 Ground surface elevations were based on electronic topographic files provided by Atkins.

3 The LPile parameters shown are for a single shaft or pile. For group effects, see Figure 5 for recommended p-multipliers.

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

6 The lateral loading analysis should consider the potential for loss of material from flooding and scour.

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VICINITY MAP

FIG. 1

PROJECT

LOCATIONS

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

Map adapted from aerial imagery provided by Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Miles

0 2 4

Denver

Project Location

Colorado

June 2019 23-1-01437-003

Fi le na m e:

\E F\

-1

D E

N \0 s\

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E 96th Ave

E 56th Ave

To Denver

Fig. 2 S.1

Fig. 2 S.3

Fig. 2 S.4

Fig. 2 S.8

Fig. 2 S.2

Fig. 2 S.5 Fig. 2 S.6

Fig. 2 S.7

Rocky Mountain Arsenal

LEGEND Fig. 2 S.1 Figure 2 Index Map and Reference Sheet Number

AutoCAD SHX Text I-70

AutoCAD SHX Text I-25

EL 5232.50'

E 3180514.11'

N 1721407.85'

SET #5RB PPC CNT PNT

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SITE AND EXPLORATION PLAN

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

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dw e:

-2

A ut ho r:

K W

SW-09

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTES

LEGEND

Boring Designation and Approximate Location

SW-02

Sheet 1 of 8

A A' Profile Designation and Approximate

Location

AutoCAD SHX Text

E 64TH AVENUE

AutoCAD SHX Text

WOODLAND TRAIL

AutoCAD SHX Text

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SITE AND EXPLORATION PLAN

SAND CREEK

PEDESTRIAN BRIDGE

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

SW-02

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTESLEGEND

Boring Designation and Approximate Location

SW-01

SW-02

Sheet 2 of 8

A A' Profile Designation and Approximate

Location

SAND CREEK

PEDESTRIAN BRIDGE

AutoCAD SHX Text

SET #5 REBAR W/

PINK PLASTIC CAP

STAMPED: CONTROL POINT

23-1-01437-003

SITE AND EXPLORATION PLAN

UVALDA DITCH

PEDESTRIAN BRIDGE

FIG. 2

CO FLAP DEN 56 (1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

SW-04

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTESLEGEND

Boring Designation and Approximate Location

SW-03

SW-02

Sheet 3 of 8

A A' Profile Designation and Approximate

Location

UVALDA DITCH

PEDESTRIAN BRIDGE

AutoCAD SHX Text

WATER

SET #5 REBAR W/

PINK PLASTIC CAP

STAMPED: CONTROL POINT

SET #5 REBAR W/

PINK PLASTIC CAP

STAMPED: CONTROL POINT

SET #5 REBAR W/

PINK PLASTIC CAP

STAMPED: CONTROL POINT

24" CORRIGATED METAL PIPE

INV=5278.10

24" CORRIGATED METAL PIPE

INV=5278.03

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SITE AND EXPLORATION PLAN

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

SW-10

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTESLEGEND

Boring Designation and Approximate Location

SW-02

Sheet 4 of 8

A A' Profile Designation and Approximate

Location

AutoCAD SHX Text

AutoCAD SHX Text G

AutoCAD SHX Text W

AutoCAD SHX Text

SET #5 REBAR W/

PINK PLASTIC CAP

STAMPED: CONTROL POINT

23-1-01437-003

SITE AND EXPLORATION PLAN

NORTH HIGH LINE CANAL

PEDESTRIAN BRIDGE

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTESLEGEND

Boring Designation and Approximate Location

SW-02

Sheet 5 of 8

SW-05

SW-06

A A' Profile Designation and Approximate

Location

C C'

NORTH HIGH LINE CANAL

PEDESTRIAN BRIDGE

AutoCAD SHX Text

SW-08

SW-07

BENCH MARK

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SITE AND EXPLORATION PLAN

SOUTH HIGH LINE CANAL

PEDESTRIAN BRIDGE

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTESLEGEND

Boring Designation and Approximate Location

SW-02

Sheet 6 of 8

A A' Profile Designation and Approximate

Location

SOUTH HIGH LINE CANAL

PEDESTRIAN BRIDGE

AutoCAD SHX Text

SW-11

VENT

WATER

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SITE AND EXPLORATION PLAN

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTES

LEGEND

Boring Designation and Approximate Location

SW-02

Sheet 7 of 8

E 56th Ave

A A' Profile Designation and Approximate

Location

AutoCAD SHX Text

SW-12

23-1-01437-003

SITE AND EXPLORATION PLAN

FIG. 2

CO FLAP DEN 56(1)

Rocky Mountain Arsenal NWR

Commerce City, Colorado

June 2019

0 50 100

Scale in Feet

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Fi le

: I :\E

-1 D

E N

\0 s\

A tk in s C

R oc ky M tn A rs en al \D ra fti ng \F ig

\F ig

.2 S ite a nd E xp lo ra tio n P la n.

-2 ho r:

K W

1. Map adapted from aerial imagery provided by Google Earth Pro, reproduced with permission granted by Google Earth Mapping Service.

NOTES:LEGEND

Boring Designation and Approximate Location

S…

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