Att12e_CSF_Geotechnical_Report.pdf

Engineering from the ground down

GEOTECHNICAL INVESTIGATION REPORT

NATIONAL PARK SERVICE

GRCA 250176 SUPPORT FACILITIES

PACKAGE A – HELIBASE IMPROVEMENTS

GRAND CANYON NATIONAL PARK

DECEMBER 3, 2020

2750 South Wadsworth Blvd, Suite D-200 Denver, CO 80227

303.625.9502 www.LithosEng.com

December 3, 2020

Project No. 16066

HDR Engineering, Inc.

1670 Broadway, Suite 3400

Denver, CO 80202

Attention: Mr. Ryan Rhoades, PE

Project Manager

Regarding: Geotechnical Investigation Report

GRCA 250176 Support Facilities

Package A – Helibase Improvements

Grand Canyon National Park

Mr. Rhoades, This report presents the results of our geotechnical investigation and recommendations for the Waterline

Replacement Support Facilities – Helibase project. This study was conducted in general accordance with our agreement with HDR Engineering, Inc., dated September 29, 2019. Contained herein are discussions of the general subsurface conditions, geotechnical engineering design recommendations, and construction considerations in support of the subject project.

If you have any questions regarding the contents of this report, please contact the undersigned.

Sincerely, Lithos Engineering

Amber Hill, EI Nate Soule, PE*, PG**

Staff Engineer Vice President

*AZ, CO, PA **WY

Grand Canyon Transcanyon Waterline Replacement HDR Engineering, Inc. Package A – Support Facilities - Helibase Page I of II

TABLE OF CONTENTS

INTRODUCTION

PROJECT BACKGROUND

GEOTECHNICAL INVESTIGATION

3.1 Subsurface Investigation

3.2 Geotechnical Laboratory Testing

3.3 Previous Investigations

SUBSURFACE CONDITIONS

4.1 Subsurface Materials

4.1.1 Fill

4.1.2 Eolian Deposits

4.1.3 Sandy Limestone (Kaibab Formation)

4.2 Groundwater

GEOTECHNICAL DESIGN RECOMMENDATIONS

5.1 Foundation Recommendations for Helibase Building

5.2 Foundation Recommendations for Helibase Active Deck

5.3 Lateral Earth Pressures

5.4 Frost Protection for Utilities and Structures

5.5 Pavement Design

5.6 Seismic Site Classification

5.7 Water Soluble Sulfate

CONSTRUCTION CONSIDERATIONS

6.1 Temporary Excavations

6.2 Site Grading and Earthwork

6.2.1 Structure Site Preparation

6.2.2 Trench Backfill Material

6.3 Fill Placement and Compaction

6.4 Bedrock Excavation

CONSTRUCTION OBSERVATION AND QUALITY ASSURANCE

LIMITATIONS

REFERENCES

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page II of II

LIST OF FIGURES

Figure Number Title

1 Site Vicinity and Boring Location Maps

APPENDICES

Appendix Title

A Boring Log Key and Boring Logs

B Geotechnical Laboratory Testing Results

C Reference Report: Geotechnical Study, Work Directive 03, Phase 1, by

Chen and Associates

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 4 of 14

INTRODUCTION

The National Park Service (NPS) intends to improve upon and construct structures in support of the existing helibase generally located to the south of the South Rim Grand Canyon Village and to the west of

State Highway 64. The Support Facilities – Helibase project (Project) consists of the construction of a new

80x73-foot helibase support building, 100-foot diameter active deck, and contractor access route. The support building will be founded at grade. No major cuts or fills are anticipated for the contractor access route. The Project site includes an active helibase and services the NPS for official business and rescue operations in the National Park.

HDR Engineering, Inc. (HDR) is the prime design engineer for the project and has retained Lithos

Engineering (Lithos) to serve as the project Geotechnical Engineer. This Geotechnical Investigation Report

(GIR) provides data on subsurface conditions encountered in borings in the general vicinity of the proposed helibase improvements and geotechnical recommendations in support of the Project.

PROJECT BACKGROUND

As part of the Grand Canyon Transcanyon Waterline Replacement (GCTWR) project, the NPS intends to relocate the water supply from the Roaring Springs Cave to the Bright Angel Creek in Phantom Ranch. The

GCTWR project consists of the construction of various water conveyance, storage facilities, and ancillary structures servicing visitors and residents of the Grand Canyon. Package A of this project includes the improvement of ancillary structures at the South Rim Park area, specifically the Park helibase. The Project site location is illustrated in Figure 1.

GEOTECHNICAL INVESTIGATION

Lithos conducted a geotechnical investigation for the project consisting of a subsurface investigation and a geotechnical laboratory testing program. The subsurface investigation included 7 borings completed on

October 21, 2020. Results from the subsurface investigation and the laboratory testing program are presented in Section 4 and were utilized in producing design recommendations and construction considerations provided in Sections 5 and 6, respectively.

3.1 Subsurface Investigation

Seven (7) geotechnical borings were conducted in the vicinity of the proposed helibase improvements;

two were drilled in the footprint of the proposed helibase building, one was drilled at the proposed helibase active deck, and the remaining four were drilled along the future contractor access route (Figure

1). Boring depths for LE-3 through LE-9 ranged from 1.5-feet to 15-feet, where all but LE-5 met practical auger refusal in bedrock. Geotechnical drilling was conducted by Enviro-Drill Inc., utilizing a truck-mounted rig. The sampling procedure was conducted in general accordance with American Society for

Testing and Materials (ASTM) standards identified in the following table:

Subsurface Investigation ASTM Standards Procedure ASTM Standard

Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils

D 1586

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 5 of 14

Continuous-flight, hollow-stem augers were used to advance the borings to the maximum exploration depths. During auger drilling, split-spoon (1.375-inch inner diameter) samples were obtained in even intervals. The split-spoon sampler was used to obtain disturbed samples of the encountered materials.

The number of blows by a 140-pound hammer falling 30-inches required for 12 inches of sampler penetration (recorded in 6-inch increments) are presented on the boring logs (Appendix A). Blow counts with less than 6-inches of penetration are presented showing the number of blows for the resulting depth of penetration (50/2” = 50 blows to drive the sampler 2-inches).

3.2 Geotechnical Laboratory Testing

A geotechnical laboratory testing program was conducted on representative samples collected during the subsurface investigation. A laboratory summary table and graphical testing results are provided in

Appendix B. Laboratory tests conducted in general accordance with associated ASTM standards are presented in the table below. If field-determined soil and bedrock descriptions differed from results indicated by laboratory classification testing, the boring logs presented in Appendix A were amended to reflect laboratory testing results. Geotechnical laboratory testing results were utilized in developing engineering design and construction recommendations presented in this report.

Geotechnical Laboratory Testing Geotechnical Test ASTM Standard

200 Sieve Wash D 1140

Atterberg Limits D 4318

Water Soluble Sulfates D 4327

Particle Size Distribution (Gradation) D 6913

3.3 Previous Investigations

In 1984, Chen and Associates performed a geotechnical investigation at the South Rim of the Park to assist with installation of a waterline and water storage tank. Chen and Associates drilled 14 exploratory boreholes and conducted 18 seismic refraction lines. Reference is made in this report to the relevant exploratory results of this investigation. The report is included in Appendix C for reference.

SUBSURFACE CONDITIONS

Subsurface conditions were identified based on the geotechnical investigation, as discussed in Section 3.

Soil and bedrock descriptions noted on the boring logs and in the following sections are in general accordance with ASTM D 2487 – Standard Practice for Classification of Soils for Engineering Purposes

(Unified Soil Classification System, USCS) and ASTM D 2488 – Standard Practice for Description and

Identification of Soils (Visual-Manual Procedure). Appendix A contains boring logs and a supplementary boring log key further describing subsurface investigation procedures and material classification descriptions.

4.1 Subsurface Materials

Primary materials encountered during the subsurface investigation include fill, eolian deposits, and sandy limestone bedrock of the Kaibab Formation. Encountered materials are described in detail below.

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 6 of 14

4.1.1 Fill

Imported fill was encountered in four of the seven borings, LE-6 through LE-9 between the ground surface and depths ranging from 4-feet to 9-feet below ground surface. Fill material was classified in accordance with the Unified Soil Classification System (USCS) as follows:

Poorly Graded Sand (SP)

Silty Sand (SM)

Fill material included primarily fine- to medium-grained sand with lesser amounts of lean silt. Based upon recorded blow counts at each sample interval, the consistency of the fill material was generally medium dense to very dense. This material was further described as being reddish brown to gray and olive as well as dry throughout.

4.1.2 Eolian Deposits

Windblown eolian deposits were encountered in borings LE-3, 4, 5, 8, and 9 between the ground surface and 4-feet to depths ranging from 1.5-feet to 13-feet below ground surface. Eolian deposits were classified in accordance with the USCS as follows:

Silt (ML)

Silty Sand (SM)

Sandy Silt (ML)

Eolian deposits included mostly lean silts and fine- to medium-grained sands. Based upon recorded blow counts at each sample interval, the consistency of the eolian deposits was generally very stiff and very hard. This material was further described as being reddish to olive yellow and gray as well as dry throughout.

Particle size distribution tests were conducted on 7 representative samples of the eolian deposit and the results are provided in Appendix B. Water soluble sulfates tests were performed on 5 representative samples and the results are provided in Appendix B as well as summarized in Section 5.7 of this report.

4.1.3 Sandy Limestone (Kaibab Formation)

Sandy limestone of the Kaibab Formation was encountered at the maximum depth of exploration and resulted in practical auger refusal in all borings except LE-5. Sample recovery was little to none and classification was performed on chips of bedrock broken by the sampler and the augers. Due to the behavior of the drill rig, bedrock was classified as hard very hard and slightly weathered to fresh.

Based on test results on the limestone from Chen and Associates, the unconfined compressive strength ranges from 43 to 286 psi with rock velocities from seismic refraction surveys ranging from 2,900 to 11,500 feet per second.

4.2 Groundwater

Groundwater was not encountered during the subsurface investigation. Based on the proposed construction depths, groundwater is not anticipated to be encountered during construction.

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 7 of 14

GEOTECHNICAL DESIGN RECOMMENDATIONS

The following sections are included primarily for the Engineer designing the Helibase structures and access road. The following design recommendations are based on the project understanding described in Section

2. If additional geotechnical design recommendations are necessary, Lithos can be contacted to provide the required information.

5.1 Foundation Recommendations for Helibase Building

Based on data presented in this report, our experience, and proposed excavation depths, we recommend that a spread footing or mat foundation be utilized for the proposed building. Borings LE-8 and 9 suggest that the limestone bedrock is between nine and 13-feet below ground surface at the proposed building location. Approximately 4-feet of fill exists over eolian deposits. Based on the borings, it appears the fill material is very dense and likely suitable in situ. The base of the subgrade excavation should be inspected to determine if the fill material meets criteria discussed in Section 6.2 of this report. If the fill material is not suitable it should be removed and replaced with native soil from elsewhere on site or imported soils should be used.

Design criteria for shallow foundations are presented below:

1. The foundations should be designed to withstand a total settlement of 1.0 inches and differential settlements of 0.5 inches.

2. Spread footings and mat foundations should be designed using a maximum allowable bearing pressure of 3,000 psf. This value includes appropriate allowable stress design safety factors.

3. It is acceptable to increase the net allowable bearing capacity by one-third if the load combination utilized considers infrequent loads such as wind or earthquake. Snow loading is not considered an infrequent load condition.

4. A frictional coefficient of 0.4 may be used to determine lateral sliding resistance between the foundation and underlying compacted backfill.

5. A shear modulus of 5 ksi may be used for compacted fill against foundation elements.

6. The coefficient of subgrade reaction (k) is typically used for flexible foundation analysis and describes the load intensity per unit of displacement. For recompacted onsite fill or structural backfill, a k value of 115 psi/in is recommended.

5.2 Foundation Recommendations for Helibase Active Deck

Boring LE-7 drilled at the proposed location of the Helibase Active Deck suggests that up to 4-feet of fill material exists above native sand. Limestone bedrock was encountered at a depth of 9-feet. Based on the borings, it appears the fill material is very dense and likely suitable in situ. The base of the subgrade excavation should be inspected to determine if the fill material meets criteria discussed in Section 6.2 of this report. If the fill material is not suitable it should be removed and replaced with native soil from elsewhere on site or imported soils should be used. The Helibase Active Deck should be constructed with a minimum of 6-inches of concrete over minimum 8-inches of moisture conditioned and compacted

Arizona DOT Class 3 aggregate base. The pavement section should be constructed atop a minimum 8-inch thick zone of moisture conditioned and compacted subgrade. The resulting subgrade should be proof-rolled to verify stability and if the proof-roll reveals soft or loose soils, the subgrade should be stabilized.

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 8 of 14

Stabilization can be accomplished by replacing soft soils with compacted, moisture conditioned backfill or by using geotextile stabilization under the 8-inches of backfill.

5.3 Lateral Earth Pressures

Lateral earth pressures presented in the table below should be considered during structural design for permanent below-grade walls and other soil retention structures. Lateral earth pressure values are a function of the properties and the geometry of the retained soil and anticipated magnitude of lateral retention deflection. Groundwater will not be encountered during construction, and thus was not considered for lateral retention deflection.

Additional information regarding acceptable backfill material and allowances for the presented material types will be discussed in Section 6.

Lateral Earth Pressures

Backfill Material Type

Earth Pressure Coefficients

Equivalent Fluid Pressure (pcf)

Active At-Rest Passive Active At-Rest Passive

Onsite Soil 0.36 0.53 2.77 45 65 350

In order for the lateral earth pressures presented above to remain applicable, backfill material placement adjacent to below-grade walls should be in accordance with procedures outlined in Section 6.3. In order for the tabulated lateral earth pressures to apply, backfilled material must be placed within a 1 horizontal to 1 vertical (1H:1V) backfill geometry, up and away from the base of the structure. The recommended equivalent fluid pressures for conditions below the water table include hydrostatic pressures and assume a horizontal backfill surface.

Consideration has not been given to vertical loads applied to the backfill surfaces during or after construction as a result of traffic and/or other surcharge loads, sloping backfill, or soil-wall interfacial friction. Standard design values for typical, non-construction related vehicular traffic result in an additional 250 psf vertical pressure.

5.4 Frost Protection for Utilities and Structures

The base of all foundations and buried wet utilities should extend a minimum of 24-inches below the exterior grade for frost protection.

5.5 Pavement Design for Access Road

On-site pavement for the contractor access road and parking areas should consist of 6-inches of full-depth asphalt (without base course) or 4-inches of asphalt over 8-inches of moisture conditioned and compacted

Arizona DOT Class 3 aggregate base. In high traffic areas and where semi-trucks make tight turns, a minimum of 6-inches of concrete over minimum 8-inches of moisture conditioned and compacted Arizona

DOT Class 3 aggregate base should be used. The pavement sections should be constructed atop a minimum 1-foot thick zone of moisture conditioned and compacted backfill. The resulting subgrade should be proof-rolled to verify stability and if the proof-roll reveals soft or loose soils, the subgrade should

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 9 of 14 be stabilized. Stabilization can be accomplished by over excavating existing soil to bedrock and replacing with compacted, moisture conditioned Engineered Fill or by using geotextile stabilization under the 12-inches of Engineered Fill.

5.6 Seismic Site Classification

Based on the International Building Code and the American Society of Civil Engineers Minimum Design

Loads for Buildings and other Structures, our subsurface investigation, and our experience and knowledge of seismic conditions in the area, a Site Classification A, Hard Rock is recommended for seismic design.

5.7 Water Soluble Sulfate

Water soluble sulfate testing was conducted on five representative samples. The test results ranged from

0.5 to 0.22 percent which would characterize the concrete risk between the ranges of “Not Applicable” to

“Severe” as defined by ACI and shown in the table below. These results should be considered when specifying the allowable cement types and concrete mixes. We recommend HDR take proper precautions to prevent degradation of concrete structures in contact with the ground from sulfate attack. The results all sulfate testing are provided in Appendix B.

American Concrete Institute Code 318-14 Water Soluble Sulfates

Class Water-Soluble Sulfate in Soil SO4, Percent by Mass Risk

S0 SO4 <0.10 Not Applicable

S1 0.10< SO4 <0.20 Moderate

S2 0.20< SO4 <2.00 Severe

S3 SO4 >2.00 Very Severe

CONSTRUCTION CONSIDERATIONS

The following sections are intended for the Engineer producing specifications and the Contractor constructing the proposed structures and pipeline. Construction considerations include temporary excavations, site grading and earthwork, and bedrock excavation.

6.1 Temporary Excavations

General site safety including temporary excavations are the sole responsibility of the Contractor performing construction. Lithos is providing temporary excavation information strictly as an informational benefit to the project team. An Occupational Safety and Health Administration (OSHA) defined competent person should be identified by the Contractor to be in charge of temporary excavations. In general, the

Contractor’s competent person shall have experience or training in determining soil types, benching, and shoring and have the ability to detect potential temporary slope stability and protective system issues.

OHSA defines an excavation as a man-made cut, cavity, trench, or depression formed by the removal of earth. A trench is a specific type of narrow excavation with a geometry including a greater depth than width and a width of 15-feet or less. Trenches or excavations 5-feet deep or greater shall be sloped, retained with shoring, or shielded appropriately. Shielding most commonly includes trench boxes. In general, shoring can include inclined, horizontal, or vertical systems depending on the excavation

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 10 of 14 geometry and availability of retention alternatives. Sloping and benching shall be in accordance with

OSHA recommendations. Benching shall include a maximum 4-foot vertical face for each bench and the overall excavation geometry less than or equal to the OSHA defined slope.

Temporary excavations and trenches are anticipated during utility installation and structure construction.

Lithos has evaluated the soil conditions likely to be penetrated by the proposed construction. Based on the OSHA determined soil types, the following table presents maximum recommended temporary excavation slopes:

OSHA Temporary Excavation Slopes

Backfill Material Type OSHA Classification Maximum Recommended

Slope (H:V) 1,2

Onsite Surficial Deposits Type B 1:1

Onsite Bedrock Type A Vertical 1 H:V = Horizontal:Vertical 2 Valid for trench excavations less than 20 feet in depth

During construction, heavy equipment or excavated material stockpiles shall be kept away from excavation edges to the extent possible. Underground utilities shall be fully understood and documented prior to initiating excavations. Finally, the Contractor’s competent person shall inspect excavations routinely for signs of instability including sliding, toppling, subsidence and bulging, heaving or squeezing, boiling, and/or other visual concerns.

6.2 Site Grading and Earthwork

Site grading and earthwork considerations are presented in the following sections.

6.2.1 Structure Site Preparation

In general, site preparation for the Helibase building and active deck will consist of removal of excavated material as required for the desired construction. If existing site soil is suitable as backfill, excavated materials should be stockpiled conveniently and processed prior to use. Based on the soil encountered in the borings, we believe the fill and native soil will be suitable for use as backfill.

Native soil and/or excavated fill material encountered during excavation that is desired to be reused as backfill shall not contain unsuitable material as determined by a qualified geotechnical engineer.

Generally, processing onsite material shall include removing frozen soil, wood, trash, organic material, cobbles and boulders larger than 3 inches in longest dimension, and other deleterious materials. If other fill materials are preferred for any of the presented applications, Lithos should be contacted to review submitted particle size distributions. Excavated bedrock should not be used as backfill.

Subgrade shall be scarified, moisture conditioned (as necessary), and recompacted to a minimum depth of eight inches below the entire footprint of both the proposed Helibase Building and active deck.

Subgrade moisture and compaction specifications are provided in later sections.

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 11 of 14

6.2.2 Trench Backfill Material

Trench backfill is anticipated within excavated trenches for below grade installation of support utilities to the Helibase Building. Based on our understanding that the pipes will be bedded in clean granular material, recommendations are provided below:

Processed onsite soil should be suitable for backfill within trenches above the pipe bedding zone.

For all utilities, the recommended pipe bedding zone extends a minimum of 2 inches above the crown and 2 inches below the invert of the backfilled pipe.

Recommended gradation for pipe bedding material is provided in the table below. Assuming processed onsite material can meet the recommended gradation, onsite material should be considered suitable for use as pipe bedding.

Pipe Bedding Material

Particle Size % Passing

3/4 inch (19 mm) 100 min

No. 50 (0.297 mm) 25 max

N0. 200 (0.074 mm) 5 max

Processing onsite material shall include removing frozen soil, wood, trash, organic material, cobbles and boulders, and other deleterious materials. If other fill materials are preferred for any of the presented applications, Lithos should be contacted to review submitted particle size distributions.

6.3 Fill Placement and Compaction

Fill placement is anticipated during construction of the helibase building, active deck, and during pipe bedding and trench backfilling. Settlement of the backfill cannot be eliminated but can be greatly reduced by employing proper fill placement techniques, materials testing, and construction oversight discussed in this section. Backfill placement shall occur in maximum 8-inch loose lifts. Minimum recommended compaction specifications are outlined in the table below. Adequately processed onsite soil should be considered suitable as fill material.

Soil Compaction Recommendations

Backfill Material Type

Moisture and Compaction Specifications

Minimum Relative Density

(ASTM D 4253 and

D 4254) Moisture Content1

Dry Density2

Backfill under and around Helibase building, active deck, and pavement

-2% to +2% ≥ 98% N/A

Native soil for trench backfill except if under any structure listed above

-2% to +2% ≥90% N/A

Pipe bedding -3% to +3% N/A 65% 1 Moisture content relative to the optimum moisture content as determined by Standard proctor compaction testing (ASTM D698)

2 Dry density relative to the maximum dry density as determined by Standard proctor compaction testing (ASTM D698)

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 12 of 14

Lithos recommends testing each lift of placed material to determine if compaction specifications are achieved. Adequate moisture control will substantially aid in achieving the desired compaction and shall be carefully controlled throughout fill placement. If fill materials visibly exceed moisture specifications, Lithos recommends working and handling the materials until a moisture content near optimum is obtained. Non-cohesive, granular soils typically achieve a denser configuration if they are placed at a relatively high moisture content. Lithos can also be consulted to aid in the further defining testing specifications for placed fill materials.

Mechanical compaction is required for all materials placed as fill during construction. Compaction of cohesive materials is best accomplished with equipment such as a jumping jack or padfoot roller. Non-cohesive soils are best compacted with a vibratory plate or vibratory smooth-drum roller. Compaction utilizing any flooding type technique is not recommended. Care should specifically be taken when compacting backfill in the pipe bedding zone and on the first lift above the crown of the pipe. We recommend operating only lightweight compaction equipment such as jumping jacks and vibratory plates within the pipe bedding zone and close to the crown of installed pipelines as well as within six inches of newly poured concrete such as foundation walls.

6.4 Bedrock Excavation

Bedrock was encountered in borings along the contractor access road as shallow as 1.5-feet below the ground surface. Depending on the necessary grading for the road and the need to bury utilities below this depth, bedrock excavation may be necessary. Bedrock is anticipated to be difficult to excavate with increasing resistance with depth. Seismic velocities for the Kaibab Formation from previous studies range between 2,900 and 11,500 ft/s. Based on this range, rippability per the Caterpillar Handbook of Ripping is between Rippable to Marginally Rippable using a D11 dozer. Additional methods for excavation of rock include an impact hammer attachment to an excavator or blasting. If blasting is used the contractor must take all necessary precautions for site safety and observe all applicable laws and guidelines for storage and use of explosives.

CONSTRUCTION OBSERVATION AND QUALITY ASSURANCE

Site observations by Lithos during construction are recommended, specifically to address the geotechnical components of the project including structure subgrade preparation, trench and bedrock excavations, pipe bedding, and backfill placement and compaction. Quality assurance of compaction and backfill materials are necessary to ensure long-term performance of the proposed pipeline and to avoid differential settlements in foundations. Lithos recommends that a qualified testing agency is retained during construction to monitor backfill materials and compaction, if possible. Lithos should be notified if unanticipated subsurface conditions are encountered during construction in order to re-evaluate and potentially change the design and/or construction recommendations presented in this report.

LIMITATIONS

This study was conducted in accordance with generally accepted geotechnical engineering and engineering geologic practices and principals; no warranty, express or implied is made. The subsurface conditions described in this report were based on data obtained from widely spaced exploratory borings, geotechnical laboratory testing, information provided by the client, engineering judgement, and our

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 13 of 14 experience with similar subsurface conditions and projects. The boring logs presented in this report only depict the subsurface conditions at the actual boring locations. Subsurface conditions are typically variable, both laterally and vertically and the nature and extent of the subsurface variations across the site(s) may not become evident until construction. The boundaries between different soil types and bedrock presented in this report are approximate and, in some cases, may be more abrupt or gradational than described herein. Groundwater levels may vary with time, precipitation, and changes to the hydrogeological conditions at and/or surrounding the project site.

This report has been prepared exclusively for our client for design purposes for the subject project. Lithos

Engineering is not responsible for technical interpretations by others of the data presented in this report or use of this report by others for the subject project or other projects. If differing site conditions are encountered during further evaluation of the subsurface conditions by others or during construction, Lithos Engineering should be notified immediately to determine if any changes to our recommendations presented in this report are warranted.

The recommendations presented in this report are only intended for the proposed design and construction as understood by Lithos Engineering at the time of issuing this report. If the proposed design and construction changes, Lithos Engineering should be notified immediately and given the opportunity to review the proposed changes and if necessary, modify our recommendations presented herein.

An environmental assessment was not included in the Lithos Engineering scope of work for this project.

Any statements regarding the absence or presence of hazardous and/or toxic substances presented herein are only intended for informational purposes. If the client is concerned about the environmental conditions at the site, Lithos Engineering recommends the client and/or owner retain a qualified environmental firm to conduct an environmental site assessment.

HDR Engineering, Inc. Package A – Support Facilities - Helibase Page 14 of 14

REFERENCES

American Concrete Institute, Building Code Requirements for Structural Concrete (ACI 318-14), January 2008.

ASTM Standards, ASTM International, West Conshohocken, PA (2012).

Maxon, J. H., 1961, Geologic map of the Bright Angle quadrangle, Grand Canyon National Park, Arizona: Grand Canyon Natural History Association, scale 1:48,000

International Building Code, Section 1613 (2018).

Occupational Safety and Health Administration (OSHA), Excavations: Hazard Recognition in Trenching and Shoring, Section V: Chapter 2.

Cat handbook

FIGURES

APPENDIX – A

Boring Logs

Soil Classifications:

Relative Density or Consistency of Non-cohesive and Cohesive Soils Non-cohesive Soils Cohesive Soils

Classification Blows per 12 in Classification Blows per 12 in Very Loose 0 to 4 Very Soft 0 to 2

Loose 5 to 10 Soft 3 to 4

Medium Dense 11-30 Medium Stiff 5 to 8 Stiff 9 to 15

Dense 31 to 50 Very Stiff 16 to 30 Very Dense >50 Hard >30

Description of Odor Description Criteria No Organic

Odor Organic odor is not present

Trace Organic Odor

Mild organic odor; mixture of soil and organics

Strong Organic Odor

Prominent organic odor; sample is primarily organic

Sample Graphics and Descriptions:

California Barrel Sampler: Barrel sampler loaded with sample liners and driven to collect a relatively representative and intact specimen of soil or weak rock.

Split-Spoon Sampler: Split-barrel sampler driven in accordance with ASTM D1586 used to provide visual material descriptions and collect a disturbed specimen.

Shelby Tube Sampler: Thin wall tube hydraulically pushed into the subsurface to collect a representative and intact specimen of soil.

Groundwater Monitoring Well Graphics:

Riser Pipe with Auger Cuttings

Well Screen with Silica Sand

Riser Pipe with Silica Sand

BORING LOG KEY

STANDARD GEOTECHNICAL DRILLING

Gradation Estimates by Field Observation

Description Quantity (%) Trace <5 Few 5 to 10 Little 15 to 25 Some 30 to 45 Mostly > 50

Color: Sample colors are in general accordance with basic brown, red, yellow, and gray combinations

Geologic Interpretation:

A Geologic Interpretation of encountered soil and bedrock units is provided for each specific Visual Material Description. Examples of geologic interpretations for soil that may be presented include: FILL, ALLUVIUM, AEOLIAN, AND GLACIAL TILL, AND RESIDUUM. Rock geologic interpretations are referenced based on a combination of field classifications and applicable geologic maps.

Riser Pipe with Bentonite Chips

Flush Mounted Cap

Boring Graphics:

Cementation Description Criteria

Weak Crumbles with light finger pressure Moderate Crumbles with considerable finger pressure Strong Will not crumble with finger pressure Rock Descriptions:

Field Hardness

Description Criteria

Very Hard Cannot be scratched with a knife or sharp pick.

Hard Can be scratched with a knife or pick only with difficulty

Medium Can be gouged 1 16" deep by firm pressure on knife or pick point Soft Can be grooved or gouged readily with knife or pick point Very Soft Can be carved with knife and scratched readily by fingernail

Weathering

Description Criteria

Fresh No visible sign of rock material weathering: perhaps slight discoloration on major discontinuity surfaces.

Slightly Weathered Discoloration of rock material on discontinuity surfaces.

Moderately Weathered Less than half of the rock material is decomposed and/or disintegrated to soil. Fresh or discolored rock is present either as a continuous framework or as corestones.

Highly Weathered More than half of the rock material is decompsed and/or disintegrated to a soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones

Completely Weathered All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact.

Texture

Description Criteria

Very Fine Grained Grains not individually visible to the unaided eye

Fine Grained Grains barely visible to the unaided eye, up to 1 16" diameter

Medium Grained Grain diameter between 1 16" and 3

16"

Coarse Grained Grains diameter between 3 16" and 14"

Very Coarse Grained Grains larger than 14" in diameter

12"

Boulders Cobbles Gravel Sand Silts and ClaysCoarse Fine Coarse Medium Fine

3" 3/4" 4 10 40 200

300mm 75mm 19mm 4.75mm 2.0mm 0.42mm 0.075mm

U.S. Standard Series Sieve SizesClear Square Sieve Openings

Description of Moisture Description Criteria

Dry Absence of moisture, dusty, dry to the touch Moist Damp but no visible water Wet Visible free water, usually soil below the groundwater table

Auger Cuttings Stick-Up Well

Lean Clay Silt Fat Clay Elastic Silt

Well Graded Gravel

Poorly Graded Gravel

Poorly Graded Sand Sandstone ClaystoneWell Graded

Sand

Below are the primary boring log graphics. Any classification combinations will result in a combination of graphics.

First Groundwater Reading

Second Groundwater Reading

Third Groundwater Reading

Plasticity Description Criteria Nonplastic A 18" diameter thread cannot be rolled

Low A 18" in diameter thread can be rolled with difficulty; a lump cannot be formed at a moisture lower than the plastic limit

Medium A 18" in diameter thread can be rolled easily; a crumbly lump can be formed at a moisture lower than the plastic limit

High A 18" in diameter thread can be rolled very easily; a lump can be formed at a moisture lower than the plastic limit

Bulk Sample: Bulk or bagged sample taken from auger cuttings.

2.5

7.5

12.5

6887.5

6882.5

6877.5

50/1"

EOLIAN DEPOSIT

SILT (ML), trace fine-grained sand, hard, dark brown to olive brown, dry

1.5 ft.

END OF EXPLORATION - TOTAL AUGER REFUSAL

BORING: LE-3 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Access Road @ 64

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,892-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

*Elevation data collected from Google

Earth

7.5

12.5

6892.5

6887.5

6882.5

EOLIAN DEPOSIT

Sandy LEAN CLAY, few fine-grained sand, trace silt, very stiff, dark brown an olive, dry

3.0 ft.

END OF EXPLORATION - TOTAL AUGER REFUSAL

9 0.22 79 30 14

BORING: LE-4 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Access Road South

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,895-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

7.5

12.5

6872.5

6867.5

6862.5

50/0"

50/2"

50/4"

EOLIAN DEPOSIT

Silty SAND (SM), mostly fine- to medium- grained sand, few silt, trace gravel up to 1/2-inch in diameter, dense, pale olive, dry

4.0 ft.

KAIBAB FORMATION

No recovery, very hard

SANDY LIMESTONE, very hard, highly weathered, fine-grained, dry

As above except trace interbedded SILTSTONE

15.0 ft.

END OF EXPLORATION

BORING: LE-5 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Access Road West

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,875-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

7.5

12.5

6872.5

6867.5

6862.5

50/3"

50/4"

FILL

Clayey SAND with Gravel (SC), mostly fine- to medium-grained sand, little lean clay, few gravel up to 1/2-inch in diameter, medium dense, gray to olive, dry

As above except very dense, some trash in sampler

9.0 ft.

KAIBAB FORMATION

SANDY LIMESTONE, trace silt, very soft, completely weathered, pale olive, fine-grained, dry, thinly bedded

13.0 ft.

END OF EXPLORATION - TOTAL AUGER REFUSAL

6 0.15 22 53 25 27 10

BORING: LE-6 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Access Road

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,877-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

7.5

12.5

6882.5

6877.5

6872.5

FILL

Silty SAND (SM), mostly fine-grained sand, few silt, trace gravel up to 1/4 inch in diameter, medium dense, gray to olive, dry

Clayey SAND with Gravel (SC), mostly fine- to medium-grained sand, little lean clay, few gravel up to 1/2-inch in diameter, medium dense, reddish brown to gray, dry

9.0 ft.

END OF EXPLORATION - TOTAL AUGER REFUSAL

11 19 70 33 17

BORING: LE-7 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Access Road

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,885-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

7.5

12.5

6877.5

6872.5

6867.5

50/5"

FILL

Silty, Clayey SAND with Gravel (SC-SM), mostly fine- to medium-grained sand, little lean clay, little silt, few gravel up to 1/4-inch in diameter, dense, reddish brown, dry

4.0 ft.

EOLIAN DEPOSIT

Clayey SAND (SC), mostly fine-grained sand, little lean clay, trace silt very stiff, olive, dry

As above except hard

13.0 ft.

END OF EXPLORATION - TOTAL AUGER REFUSAL

0.21

0.08

BORING: LE-8 Drilling and Sampling Methods Project Name: Grand Canyon Waterline Drill Make and Model: Truck-Mounted

Project Number: 16066 - Phase 5 Drilling Method: Hollow Stem Auger

Client's Name: HDR Engineering, Inc. Bit Type: Cutting Head

Owner's Name: National Park Service Casing Description: Hollow Stem Auger Boring Location: Helibase Deck Northwest

Drilling Subcontractor: Enviro-Drill Hammer Weight (lbs)/Fall (in): 140 lbs. / 30 in. Boring Elevation: 6,881-feet*

Lithos Representative: A. Hill Sampler Type(s): Split Spoon Notes:

Date(s) of Drilling: 10/21/20 Sampler Diameter(s): 1.2 in.

General Notes: Groundwater Data:

1) Soil classifications are in general accordance with ASTM D2487 Standard Practice for Classification of Date: Elapsed Time: Depth to Groundwater:

Soils for Engineering Purposes (Unified Soil Classification System) 10/21/20 0 hrs N/A

2) The maximum particle size identified in the material description is dependent on sampler dimensions.

3) Additional information is provided on the Boring Log Key.

D ep th ft

Sampling Data

E le va tio n (f t)

S am pl e

Id en tif ic at io n

B lo w C ou nt

/6 in

R ec ov er y (in

R Q

D

D ril lin g

R at e (m in ft

G eo lo gi c G ra ph ic Visual Material Description

Soil:

-GEOLOGIC INTERPRETATION-

USCS Classification (group symbol), particle sizes, density or consistency, color, moisture, odor, other descriptions

Rock:

-GEOLOGIC INTERPRETATION-

Bedrock Classification, hardness, weather, color, texture, joint size, other descriptions G ro un dw at er D ep th

M on ito rin g

W el l C on fig ur at io n

M oi st ur e C on te nt

Laboratory Testing Results

In-Situ States

D ry

U ni t W ei gh t (p cf

W at er S ol ub le S ul fa te s

G ra ve l C on te nt

INDEX DATA

S an d C on te nt

F in es C on te nt

Li qu id L im it

P la st ic ity I nd ex

U C

S ps f)

Strength & Compressibility

S w el l P re ss ur e

(p sf

S w el l P er ce nt

7.5

12.5

6877.5

6872.5

6867.5

50/5"

FILL

Poorly-Graded SAND (SP), mostly fine- to medium-grained sand, little silt, trace gravel up to 1/2-inch in diameter, very dense, gray, dry

4.0 ft.

EOLIAN DEPOSIT

Clayey SAND with Gravel (SC),…