Attachment 7 VB16 137G Ord and Weitzel Area Road Repair Report.pdf

REPORT OF

SUBSURFACE

EXPLORATION

AND

GEOTECHNICAL

ENGINEERING

SERVICES

Ord & Weitzel Area Road Repair – ANC

Arlington National Cemetery Arlington, Virginia

G E T Project No.: VB16-137G (Revision 3) PB Project No.: 185671

August 16, 2016

PREPARED FOR:

204 Grayson Road · Virginia Beach, VA 23462 Phone: (757)-518-1703 www.getsolutionsinc.com

204 Grayson Road Virginia Beach, VA 23462 Phone: (757)-518-1703 Fax: (757)-518-1704 info@getsolutionsinc.com

August 16, 2016

TO: WSP | Parsons Brinkerhoff 277 Bendix Road

Suite 300 Virginia Beach, VA 23452

Attn: Mr. Chris Moore, P. E.

RE: Report of Subsurface Exploration and Geotechnical Engineering Services

Ord & Weitzel Area Road Repair - ANC Arlington National Cemetery Arlington, Virginia G E T Project No.: VB16-137G (Revision 3) PB Project No.: 185671

Dear Mr. Moore:

In compliance with your instructions, we have completed our Subsurface Exploration and Geotechnical Engineering Services for the above referenced project. The results of this study, together with our recommendations, are presented in this report.

Often, because of design and construction details that occur on a project, questions arise concerning subsurface conditions. G E T Solutions, Inc. would be pleased to continue its role as Geotechnical Engineer during the project implementation.

We appreciate the opportunity to work with you on this project. We trust that the information contained herein meets your immediate need, and should you have any questions or if we could be of further assistance, please do not hesitate to contact us.

Respectfully Submitted, G E T Solutions, Inc.

Matthew R. English, E.I.T.

Project Engineer

Bruce R. Spiro, P.E.

Principal Engineer Virginia Reg. # 015791

Copies: (1) Client

TABLE OF CONTENTS

Arlington National Cemetery Arlington, Virginia G E T Project No.: VB16-137G (Revision 3) | PB Project No.: 185671

EXECUTIVE SUMMARY ............................................................................................................ i

1.0 PROJECT INFORMATION

1.1 Project Authorization

1.2 Project Site Location and Description

1.3 Project Construction Description

1.4 Purpose and Scope of Services

2.0 FIELD AND LABORATORY PROCEDURES

2.1 Field Exploration

2.2 Laboratory Testing

3.0 SITE AND SUBSURFACE CONDITIONS

3.1 Site Geology

3.2 Existing Pavement Section Conditions

3.3 Subsurface Soil Conditions

3.4 Groundwater Discussion

3.5 Shrink-Swell Soils Discussion

3.6 Frost-Susceptible Soils Discussion

3.7 Slope Stability Discussion

4.0 EVALUATIONS AND RECOMMENDATIONS

4.1 Clearing and Grading

4.2 Subgrade Preparation

4.3 Structural Fill and Placement

4.4 Suitability of On-site Soils

4.5 Pavement Design

4.6 Seismic Evaluation

5.0 CONSTRUCTION CONSIDERATIONS

5.1 Anticipated Excavation Characteristics

5.2 Excavation Stability

5.3 Dewatering

5.4 Site Utility Installation

5.5 Structure Protection and Monitoring

5.6 Construction Monitoring and Inspections

5.7 Excavations

6.0 REPORT LIMITATIONS

APPENDIX I BORING LOCATION PLAN

APPENDIX II SUMMARY OF SOIL CLASSIFICATION

APPENDIX III SUMMARY OF LABORATORY CLASSIFICATION RESULTS

APPENDIX IV BORING LOGS

APPENDIX V GENERALIZED SOIL PROFILE

APPENDIX VI CBR TEST RESULTS

APPENDIX VII PAVEMENT SECTION COMPOSITION AND DESCRIPTION

APPENDIX VIII PHOTOGRAPHS OF POTENTIALLY PROBLEMATIC SLOPES

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671 i

EXECUTIVE SUMMARY

The project site is located within the northern most tip of the Arlington National Cemetery (ANC) in the town of Arlington, Virginia. More specifically, the project area encompasses Ord & Weitzel Drive, Lincoln Drive, L’Enfant Drive, and Mitchell Drive; totaling roughly 5,000 LF of paved roadway. Repairs are expected to include the replacement of the existing curbs and gutters, roadway, subgrade, inlets, drain pipes, and underdrains associated with the roads. It should be noted that the roadway has experienced numerous areas of “alligator” and transverse cracking as well as small and large pavement patches throughout. New pipe alignment is expected to go alongside or under the roadways before tying into existing outfall(s). The finish grades are expected to coincide with the current grades, thus cuts and fills are not expected to exceed 1 to 2 feet.

Our field exploration program included three (3) 25-foot deep Standard Penetration Test (SPT) borings (designated as B-1, B-2, and B-3) within the vicinity of slopes to assess the potential for slope failures and twelve (12) 10-foot deep SPT borings (designated as CBR-1 through CBR-

12) within the proposed pavement renovation areas. Bulk subgrade samples were collected at each CBR boring within the proposed pavement renovation areas. The bulk subgrade samples were returned to our laboratory and subjected to CBR testing in accordance with ASTM standards.

The results of our field exploration program indicated natural subsurface soils generally arranged in a 3-layer configuration composed varying layers of Sand, Silt, Clay, and Gravel.

Groundwater was not encountered at the SPT boring locations during the drilling operations.

The following evaluations and recommendations were developed based on our field exploration and laboratory-testing program:

§ A field testing program is recommended during construction. This testing program should include as a minimum, subgrade load testing (proofrolling) and compaction testing.

§ The shallow subsurface CLAY (CH, CL) and SAND (SC-SM, SC) materials encountered at the boring locations are unsuitable for reuse as structural fill;

however, these soils may be used as fill in green areas.

§ The shallow subsurface soils recovered during our field exploration were determined to have shrink-swell characteristics (potential to expand or contract with moisture changes) and to be susceptible to frost action. These concerns should be addressed to avoid poor pavement performance.

§ The project site is located within the physiographic province called the Piedmont and associated with this province is the Potomac Formation. Naturally occurring and construction-related landslides are common and widespread in the weathering zone of areas associated with the Potomac Formation; thus, any slopes (naturally occurring or to be constructed) should be monitored for any evidence of potential landslide characteristics.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671 ii

§ The California Bearing Ratio (CBR) test results indicated CBR values ranging from 3.0 to 15.3 with an average value of 8.4. A CBR value of 5.6 should be used in designing the pavement sections.

§ Due to the shallow subsurface soils’ shrink-swell characteristics, frost action susceptibility, and mica content (in isolated areas as indicated on the Boring Log sheets), it will be necessary to undercut a minimum of 18 inches (possibly up to 24 inches), line the subgrade with a geosynthetic, and backfill with compacted structural fill or aggregate base material

§ The project’s budget should include an allowance for subgrade improvements (undercut and backfill with structural fill).

§ Based on the information obtained at the boring locations (to a maximum depth of 15 feet) and our experience within the vicinity of the project site, it is our opinion that this site may be classified as a Site Class “D” in accordance with Table 20.3-1 of ASCE 7-10 as referenced by the 2012 International Building Code (IBC).

This summary briefly discusses some of the major topics mentioned in the attached report.

Accordingly, this report should be read in its entirety to thoroughly evaluate the contents.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

1.0 PROJECT INFORMATION

1.1 Project Authorization

G E T Solutions, Inc. has completed our subsurface exploration and geotechnical engineering services for the proposed Ord & Weitzel Area Road Repair project located at the Arlington National Cemetery in Arlington, Virginia. The geotechnical engineering services were conducted in general accordance with the scope presented in G E T Proposal No. PVB16-207G.

Authorization to proceed with our services was received from the client in the form of an executed Task Order No. 2 issued under the Professional Services On-call/Task Order Subcontract between Parsons Brinkerhoff and G E T Solutions, Inc. dated September 26, 2014.

1.2 Project Site Location and Description

The project site is located within the northern most tip of the Arlington National Cemetery (ANC) in the town of Arlington, Virginia. More specifically, the project area encompasses Ord & Weitzel Drive, Lincoln Drive, L’Enfant Drive, and Mitchell Drive; totaling roughly 5,000 LF of paved roadway. The existing grades throughout this project site vary from roughly 40 to 130 feet NAVD88 with slopes as steep as 1H:1.5V to 1H:2V. A site vicinity map is provided in Figure 1.

Figure 1: Project Site Vicinity Map

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

1.3 Project Construction Description

Repairs are expected to include the replacement of the existing curbs and gutters, roadway, subgrade, inlets, drain pipes, and underdrains associated with the roads mentioned in Section

1.2. It should be noted that the roadway has experienced numerous areas of “alligator” and transverse cracking as well as small and large pavement patches throughout the project site.

Drain lines, drain inlets, manholes, and roadways are to also be reconstructed. New pipe alignment is expected to go alongside or under the roadways before tying-into existing outfall(s).

Abandoned storm drain structures are expected be removed or pumped with flowable fill materials. Curbs will be raised where needed to be 2 inches above grade on the back of the curb. In addition, a 4-inch, Schedule 40 conduit (for Wi-Fi) will be installed 1 foot from the proposed curb and gutters 2 feet deep along all roadways. Roadways are expected to be designed for proper drainage. Construction is not expected to impact existing trees and root systems along the roadways. The finish grades are expected to coincide with the current grades, thus cuts and fills are not expected to exceed 1 to 2 feet.

If any of the noted information is incorrect or has changed, please inform G E T Solutions, Inc. so that we may amend the recommendations presented in this report, if appropriate.

1.4 Purpose and Scope of Services

The purpose of this study was to obtain information on the general subsurface conditions at the proposed project site. The subsurface conditions encountered were then evaluated with respect to the available project characteristics. In this regard, engineering assessments for the following items were formulated:

1. General assessment of the soils revealed by the borings performed at the proposed renovation area.

2. General location and description of potentially deleterious material encountered in the borings that may interfere with construction progress or structure performance, including existing fills or surficial/subsurface organics.

3. Construction considerations for subgrade preparation including stripping, grading, fill placement and compaction, and excavations.

4. Evaluation of the on-site soils for re-use as structural fill.

5. Pavement design recommendations based on the field exploration activities (12 borings and associated CBR tests) and our experience with similar soil conditions.

6. Seismic site class determination in accordance with the 2012 International Building Code.

The scope of services did not include an environmental assessment for determining the presence or absence of wetlands or hazardous or toxic material in the soil, bedrock, surface water, groundwater or air, on or below or around this site.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

2.0 FIELD AND LABORATORY PROCEDURES

2.1 Field Exploration

In order to explore the general subsurface soil types and to aid in developing project design recommendations, the following exploration program was performed:

§ Three (3) 25-foot deep Standard Penetration Test (SPT) borings (designated as B-1 through B-3) were drilled within the vicinity of slopes to assess the potential for slope failures.

§ Twelve (12) 10-foot deep SPT borings (designated as CBR-1 through CBR-12) were drilled within the proposed pavement renovation areas. Bulk subgrade samples were collected from each of the CBR boring locations. The bulk subgrade samples were collected from approximately 1 to 4 feet below existing grades and were returned to our laboratory and subjected to CBR testing in accordance with ASTM standards.

6-inch pavement cores were drilled at all boring locations to determine the existing pavement section and base course thicknesses as well as to facilitate drilling.

Standard Penetration Tests were performed in the field in general accordance with ASTM D 1586. The tests were performed continuously from the existing ground surface to a depth of 10 to 12 feet, and between 13 to 15 feet below existing grades. The soil samples were obtained with a standard 1.4” I.D., 2” O.D., 30” long split-spoon sampler. The sampler was driven with blows of a 140 lb. hammer falling 30 inches, using an automatic hammer. The number of blows required to drive the sampler each 6-inch increment of penetration was recorded and is shown on the boring logs. The sum of the second and third penetration increments is termed the SPT N-value (uncorrected for automatic hammer and overburden pressure). A representative portion of each disturbed split-spoon sample was collected with each SPT, placed in a glass jar, sealed, labeled, and returned to our laboratory for review.

The SPT boring locations were established and staked in the field by a representative of G E T Solutions, Inc. using a Global Positioning System (GPS) device and by measuring from existing landmarks. These locations were first approved by the client. The approximate boring locations are shown on the attached “Boring Location Plan” (Appendix I), which was developed based on a site plan provided by the client.

2.2 Laboratory Testing

Representative portions of all soil samples collected during drilling were sealed in glass jars, labeled and transferred to our laboratory for classification and analysis. A Project Engineer performed the soil classification in general accordance with ASTM Specification D 2487 and D 2488. A summary of the soil classification system is provided in Appendix II.

Representative split-spoon soil samples were selected and subjected to natural moisture, full sieve gradation, -#200 sieve, and Atterberg Limits testing in order to corroborate the visual classification. These test results are presented on the “Summary of Laboratory Classification Results” (Appendix III) and “Boring Log” sheets (Appendix IV) of this report.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

The bulk soil samples were subjected to Atterberg Limits, natural moisture content, full sieve gradation, Standard Proctor, and CBR testing in general accordance with ASTM standards. A summary and comprehensive test results are provided in Appendix VI.

3.0 SITE AND SUBSURFACE CONDITIONS

3.1 Site Geology

The project site lies within two major physiographic provinces: the Piedmont and the Atlantic Coastal Plain. Geology of the Piedmont and the Atlantic Coastal Plain is complex. A geologic formation known as the Potomac Formation is noted to occur in this region. The Potomac Formation is comprised of fluvial (stream lain) and possibly deltaic sediments and is characterized by interbedded layers of varying mixtures of sands, silts, and clays, rapid pinching and thickening of beds, and varying grain size grading. The clays of the Potomac Formation are highly plastic due to the high percentage of montmorillonite clay. Due to sediments being deposited and subsequently eroded from above the Potomac Formation, the fine-grained sediments of some areas have been consolidated to a generally stiff to hard consistency.

Although sediment of the Potomac has experienced much stress relief from this erosion, Potomac sediments have been exposed to extreme physical and chemical weathering which creates joints and fractures in the near-surface soils. Commonly associated with joints and fractures are slickensides. Slickensides are polished, grooved surfaces that occur along shear planes within the soil which result from shrink-swell action of clays. Slickensides form along the internal shear planes as soil aggregates move past one another in response to these volume changes. The abundance of joints and fractures within the Potomac Formation and related slickensides ultimately weakens the formation and has led to slope instability throughout.

Much of the Atlantic Coastal Plain is separated from the Piedmont province by the Fall Line.

Numerous transgressions and regressions of the Atlantic Ocean have deposited marine, lagoonal, and fluvial sediments within the Coastal Plain which generally consists of interbedded layers of varying mixtures of sands, silts, and clays.

Based on our review of existing geologic and soil boring data, the geologic stratigraphy encountered in our subsurface explorations generally consisted of Potomac Formation sands, silts and clays.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

3.2 Existing Pavement Section Conditions

As previously mentioned, the borings were facilitated by coring or augering through the existing pavement section. The results of our coring/augering and soil boring exploration program indicate the presence of asphalt underlain by aggregate base material and CLAY (CL/CH) and SAND (SM, SC-SM, SC). Asphalt was underlain by concrete at boring location CBR-7 only.

These sections are presented in Table I and presented in Appendix VII (Existing Pavement Section and Composition). The pavement materials and thicknesses should be expected to vary at other locations along the project alignment. That said the Contractor should anticipate the possibility of encountering concrete pavement and wire mesh beneath the asphalt pavement sections. Although concrete was encountered at only one coring location, per the Owner, these conditions have been encountered during previous roadway repair projects at Arlington National Cemetery.

Table I - Existing Pavement Section and Composition Boring

No.

Asphalt

(in.)

Concrete

(in.)

Aggregate Base Material

(in.)

Shallow Subgrade Soils

(USCS)

B-1 6 - 10 GRAVEL (GC)

B-2 2.75 - 14 SAND (SM)

B-3 2.75 - 13 CLAY (CL)

CBR-1 2.75 - 15 CLAY (CL)

CBR-2 2.75 - 20 SAND (SC)

CBR-3 4 - 13 CLAY (CH)

CBR-4 2.75 - 11 SAND (SC)

CBR-5 5 - 15 SAND (SC)

CBR-6 6.25 - 6 SAND (SC)

CBR-7 5.25 6.75 - SAND (SC)

CBR-8 6.5 - 4.5 SAND (SC)

CBR-9 3 - 13 SAND (SC-SM)

CBR-10 3.25 - 12.5 SAND (SC)

CBR-11 3.5 - 13 SAND (SC)

CBR-12 5 - 10 SAND (SC)

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

3.3 Subsurface Soil Conditions

A summary of our SPT borings is presented below in Table II.

Table II - Subsurface Soil Conditions

AVERAGE

DEPTH (ft) STRATUM DESCRIPTION RANGES OF

SPT(1) N-VALUES

to

1 – 1.9

Pavement Section See Table I –

1 – 1.9 to

I

Ø Red-brown, orange, brown, tan, and gray SAND (SM, SC-SM, SC) with varying amounts of Silt, Clay, Gravel, and mica

Ø Red-brown, orange, brown, tan, and gray CLAY (CH, CL) with varying amounts of Sand, Silt, Gravel, and mica

*Deposits of GRAVEL (GM, GC) were encountered at borings B-1 and B-2 between the depths of 1.33 and 2 feet and 4 and 6 feet below existing grades, respectively.

Non-cohesive 6 – 59

Cohesive 9 – 69 to

16.5 – 21.5 II Ø Orange, tan, and gray CLAY (CH) with varying amounts of Sand, Silt, Gravel 6 – 32

16.5 – 21.5 to

III

Ø Red, orange, tan, and gray SAND (SC) with varying amounts of Silt, Clay, and Gravel

*Penetration refusal was encountered at approximately 25 feet below existing grades at borings B-1, B-2, and B-3.

34 – 97

Notes:

(1) SPT = Standard Penetration Test, N-Values in Blows-per-foot (uncorrected)

The subsurface descriptions are of a generalized nature provided to highlight the major soil strata encountered. The records of the subsurface exploration are included in Appendix IV (Boring Log sheets) and in Appendix V (Generalized Soil Profile) which should be reviewed for specific information as to the individual borings. The stratifications shown on the records of the subsurface exploration represent the conditions only at the actual boring locations. Variations may occur and should be expected between boring locations. The stratifications represent the approximate boundary between subsurface materials and the transition may be gradual.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

3.4 Groundwater Discussion

Groundwater was not encountered at the SPT boring locations during the drilling operations.

The boreholes were backfilled upon completion for safety considerations. As mentioned in Section 3.2, the majority of the shallow subsurface soils consist of relatively impermeable CLAY.

As such, perched water conditions should be expected across the project site. Controlling the perched water, if encountered, should be addressed by the contractor prior to proceeding with construction.

Groundwater conditions will vary with environmental variations, tidal fluctuations, and seasonal conditions, such as the frequency and magnitude of rainfall patterns, as well as man-made influences, such as existing swales, drainage ponds, underdrains and areas of covered soil (paved parking lots, sidewalks, etc.). Seasonal groundwater fluctuations of 3(+/-) feet are common in the project’s area; however, greater fluctuations have been documented. We recommend that the contractor determine the actual groundwater levels at the time of the construction to determine groundwater impact on the construction procedures.

3.5 Shrink-Swell Soils Discussion

The shallow subsurface soils recovered during our field exploration were determined to have shrink-swell characteristics (potential to expand or contract with moisture changes). Pavements constructed on expansive soils at certain depths may be subjected to detrimental uplift or horizontal forces caused by the swelling of these soils as a result of an increase in the moisture content. Conversely, as these Clays lose moisture they may shrink, adversely affecting the pavements.

The following preventative measures are recommended from Sta 249+25.71 to Sta 232+31.32 and from Sta 320+70.10 to Sta 114+22.90 within the roadway alignment, approximately 1800 linear feet total, in order to minimize shrink-swell concerns:

· Increase aggregate base course and/or structural fill depth to a minimum of 30 inches below finished grade (below the pavement surface).

· Do not plant deep-rooted trees and shrubs within 10 feet of the pavement.

· Moderately moisten the soils within 5 feet of the pavement during hot weather conditions.

· Tie drains to the storm water system and situate downspouts in such a manner to prevent ponding water near the pavement.

3.6 Frost-Susceptible Soils Discussion

The shallow subsurface soils recovered during our field exploration were determined to be susceptible to frost action. Frost action can cause differential heaving, surface roughness and cracking, blocked drainage, and a reduction in bearing capacity during thaw periods. Little to no frost action occurs in clean, free draining sands, gravels, crushed rock, and similar granular materials, under normal freezing conditions. The large proportion of intergranular void space permits water to freeze in-place without segregation into ice lenses. Conversely, Silts and some Clays are highly frost-susceptible. The condition of relatively small intergranular void space, high capillary potential/action, and moderate to low permeability of these soils accounts for this characteristic.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

The following preventative measures are recommended in all areas in order to minimize frost action concerns:

· Place and compact select non-frost-susceptible borrow materials to a thickness or depth to prevent subgrade freezing for frost susceptible soil.

· Stabilize the frost-susceptible soil by eliminating the effects of soil fines by reducing the quantity of soil moisture available for within the freezing zone by blocking and/or rerouting off all possible paths.

· Soil moisture available for frost heave can be mitigated through the installation of deep drains and/or a capillary barrier such as an open graded drainage layer sandwiched between two geotextiles, or a horizontal geocomposite drain. The installation of a capillary barrier requires the removal of the frost susceptible material to a depth either below frost penetration (estimated to be roughly 18 to 20 inches) or sufficiently significant to reduce the influence of frost heave on the pavement and pavers. The capillary break must be drained.

· Increase the pavement thickness to account for strength reduction in the subgrade during the spring-thaw period.

3.7 Slope Stability Discussion

As previously mentioned in Section 3.1, physical and chemical weathering of the fine-grained sediments of the Potomac Formation has led to the creation of numerous joints and fractures with associated slickensides; thus, weakening the near-surface soils. Naturally occurring and construction-related landslides are common and widespread in the weathering zone of areas associated with the Potomac Formation. Landslides can be immediate during excavations or can often take place many years after slopes are excavated in predominantly clay sediments of the Potomac Formation. Sloughing can occur even on relatively flat slopes. Many flat and steep slopes may show no evidence of landslides or sloughing; however they will display evidence of creep in the form of trees bent at the base. Photographs of potential problematic slopes encountered at the project site are provided in Appendix VIII. Included in these photographs are slopes where slight sloughing has occurred and bent trees were present. These areas as well as any other areas noticed should be monitored for any increasing evidence of potential landslide characteristics.

4.0 EVALUATIONS AND RECOMMENDATIONS

Our recommendations are based on the previously discussed project information, our interpretation of the soil test borings, and our observations during our site reconnaissance. If the proposed construction should vary from what was described, we request the opportunity to review our recommendations and make any necessary changes.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

4.1 Clearing and Grading

The proposed construction areas should be cleared by means of demolishing and removing any pavement, other site features, and any other unsuitable materials. It is estimated that a cut of up to 6 inches will be required to remove the existing pavement. As mentioned in Section 3.2, concrete pavement and/or wire mesh beneath the asphalt pavement sections is a distinct possibility based on previous roadway repair projects at Arlington National Cemetery. It is recommended that the clearing operations extend laterally at least 5 feet beyond the perimeter of the proposed construction area. The Contractor should use extreme caution during all clearing and undercut operations as to not disturb tree roots, graves, and other features to remain; thus, clearing and undercut operations should be reduced as necessary. The excavations associated with the site demolition and removal should be backfilled with compacted structural fill as described herein this report.

As previously mentioned in Sections 3.5 and 3.6 of this report, the shallow subsurface soils encountered at the boring locations possess shrink-swell characteristics and are susceptible to frost action. Therefore, it is recommended to undercut a minimum of 12 inches (possibly up to 24 inches) within the proposed pavement areas, line the subgrade with a geosynthetic, and backfill with compacted structural fill or aggregate base material. The undercut is considered necessary within the proposed construction areas to remove these problematic soils to a depth significant to reduce or eliminate their impact on the pavements. It is recommended that the undercutting operations extend laterally at least 3 feet beyond the edge of the proposed pavement.

To reduce the potential for subgrade improvements (undercutting due to saturated soils in conjunction with heavy construction traffic), it is recommended that the grading operations be performed during the drier months of the year (historically April through November). This should minimize these potential problems, although they may not be eliminated. If grading is attempted during the winter months, undercutting of wet soils should be anticipated. However, during the drier months of the year, wet soils could be dried by disking or implementing other drying procedures to achieve moisture contents necessary to achieve adequate degrees of compaction.

The site should be graded to enhance surface water runoff to reduce the ponding of water.

Ponding of water often results in softening of the near-surface soils. In the event of heavy rainfall within areas to receive fill, we recommend that the grading operations cease until the site has had a chance to dry.

Any undercut and backfill should be performed under the observation of a qualified Geotechnical Engineer (or designated representative) who will evaluate the composition of the recovered soils. Recommendations concerning the subgrade improvements (as necessary) will be provided in the field following the testing procedures.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

4.2 Subgrade Preparation

Following the clearing operation, the exposed subgrade soils should be densified with a large static drum roller. After the subgrade soils have been densified, they should be evaluated by a qualified Geotechnical Engineer (or designated representative) for stability. Accordingly, the subgrade soils should be proofrolled to check for pockets of loose material hidden beneath a crust of better soil. Several passes should be made by a large rubber-tired roller or loaded dump truck over the parking lot area. The number of passes will be determined in the field by the Geotechnical Engineer depending on the soils conditions. Due to size constraints of some of the construction areas, the use of large construction equipment such as those just described may not be feasible. In these cases, the subgrade soils should be densified with portable, mechanical tampers. After these subgrade soils have been densified, the Geotechnical Engineer should visually verify the relative compaction and advance hand auger borings to verify the subsurface soils are consistent with those described in this report. Any pumping or unstable areas observed during proofrolling (beyond the initial cut) or visual inspection should be undercut and/or stabilized at the direction of the Geotechnical Engineer.

4.3 Structural Fill and Placement

Following the approval of the natural subgrade soils by the Geotechnical Engineer, the placement of the fill required to establish the design grades may begin. Any material to be used for structural fill should be evaluated and tested by a qualified construction materials testing laboratory prior to placement to determine if they are suitable for the intended use. Suitable structural fill material should consist of sand or gravel containing less than 25% by weight of fines (SP, SM, SW, GP, GW), having a liquid limit less than 20 and plastic limit less than 6, and should be free of rubble, organics, clay, debris and other unsuitable material.

All structural fill should be compacted to a dry density of at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557) unless recommended otherwise in this report. In general, the compaction should be accomplished by placing the fill in maximum 10-inch loose lifts and mechanically compacting each lift to at least the specified minimum dry density. A qualified Geotechnical Engineer (or designated representative) should perform field density tests on each lift as necessary to assure that adequate compaction is achieved.

Backfill material in utility trenches within the construction areas should consist of structural fill (as previously above), and should be compacted to at least 95 percent of ASTM D 1557. This fill should be placed in 4 to 6 inch loose lifts when hand compaction equipment is used.

Care should be used when operating the compactors near existing structures to avoid transmission of the vibrations that could cause settlement damage or disturb occupants. In this regard, it is recommended that the vibratory roller remain at least 25 feet away from existing structures; these areas should be compacted with small, hand-operated compaction equipment.

4.4 Suitability of On-site Soils

Based on the laboratory testing program, the shallow subsurface CLAY (CH, CL) and SAND (SC-SM, SC) materials encountered at the boring locations are unsuitable for reuse as structural fill; however, may be used as fill in green areas.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

4.5 Pavement Design

Based on the results of the laboratory test program, the collected bulk soil samples in the footprint of the proposed new pavement have an average soaked CBR value of 8.4. The highest and lowest CBR values from the twelve (12) tests were omitted in conformance with the VDOT Pavement Design Guide for Subdivision and Secondary Roads in Virginia; thus the above value is the average of the remaining CBR test values. The average soaked CBR value was multiplied by a factor of two-thirds to determine a pavement design CBR value. The two-thirds factor provides the necessary safety margins since the specified time for soaking may not be long enough to give the minimum CBR strength of some soils, to compensate for any non-uniformity of the soil, and to account for any low test results not considered when computing the average.

Therefore, a CBR value of 5.6 should be used in designing the pavement sections.

Due to the shallow subsurface soils’ shrink-swell characteristics, frost action susceptibility, and mica content (in isolated areas as indicated on the Boring Log sheets of Appendix IV), subgrade improvements will be required. Subgrade improvements should consist of undercutting the natural subgrade soils to at least below the frost penetration depth as presented in Section 3.6;

therefore, it will be necessary to undercut the natural subgrade a minimum of 18 inches (possibly up to 24 inches), line the subgrade with a geosynthetic, and backfill with compacted structural fill or aggregate base material. This undercut should also accomplish the previous recommendation in Section 3.5 of increasing the aggregate base course and/or structural fill depth to a minimum of 30 inches below finished grade (below the pavement surface) based on the pavement section recommended in Table III. In addition to the undercut, it is recommended that a drainage layer be included directly beneath the asphalt pavement (directly above the base course layer) accompanied by an underdrain system to be designed by the Civil Engineer.

These measures should be implemented in all pavement areas.

The results of our laboratory testing program indicated that the pavement subgrade soils will generally be comprised of CLAY (CH, CL) and SAND (SC-SM, SC) with an appreciable amount of fines (Silt/Clay). These soils are particularly susceptible to deterioration due to high moisture content and construction traffic. The construction of the pavement sections is expected to be performed during the fall/winter (wet) months. As a result, the bearing capabilities of the surface soils are expected to be compromised. As such, it may be necessary to stabilize the subgrade through undercut and replacement with structural fill or aggregate base materials or otherwise stabilized through lime, cement, or the use of a geosynthetic. If the subgrade is improved by means of applying soil/cement or lime stabilization techniques, it should be noted that the subgrade soils are nearly 50% Sand and 50% fines, and the selection of the improvement method should be made by the specialty contractor based on their local experience. This will alleviate additional undercutting requirements if instabilities are noted during proofroll testing operations.

Precise traffic design data was unknown at the time of this reporting; however, based on the type of facility and known types of vehicular traffic, it is expected that the traffic category will be Category III or IV leading to a maximum possible design index of 5. Thus, based on a design index of 5, the minimum pavement design recommendations for the proposed pavement areas are presented in Table III. These recommended minimum pavement sections presume an undercut, use of geosynthetic, and replacement of the shallow subsurface CLAY (CH, CL) and SAND (SC-SM, SC) soils (where encountered) as described previously.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

To substantiate our pavement design, we utilized Pavement-Transportation Computer Assisted Structural Engineering (PCASE) Version 2.09 computer software. PCASE is supported by the Tri-Services (Army, Air Force, and Navy) and is based on current Tri-Service Criteria. The comprehensive results of the PCASE analysis are provided in Appendix IX.

Table III - Minimum Pavement Sections

Section Hot Mix Asphalt

Drainage Layer(1)

Aggregate Base(2)

Structural Fill(3) Subgrade(4)

Surface

(SM-12.5A)

Base

(BM-25.0A)

Light Duty Flexible

(Parking Bays) 2” - 4” 8” 18-24” Stable, lined with geosynthetic(5)

Heavy Duty Flexible

(Drive Aisles) 1.5” 2” 4” 8” 18-24” Stable, lined with geosynthetic (54)

Note(s): (1) VDOT Open Graded Drainage Layer (OGDL)

(2) VDOT Type 21-A or 21-B, compacted to a dry density of at least 100% of the Modified Proctor maximum dry density (ASTM D 1557).

(3) Undercutting poor-quality subgrade soils a minimum 18 inches (possibly up to 24 inches) and backfilling with structural fill (minimum CBR = 20) will be necessary. The structural fill should be compacted to a dry density of at least 95% of the Modified Proctor maximum dry density (ASTM D 1557).

(4) The natural subgrade should be compacted to a dry density of at least 95% of the Modified Proctor maximum dry density (ASTM D 1557) to a minimum depth of 6 inches below the recommended structural fill.

(5) Geotextile: Mirafi HP270N or equivalent, Geogrid: Tensar TriAx TX130S, TX160, or equivalent

In preparation for a stable subgrade support for pavement, the following construction steps are recommended:

1. Following pavement rough grading operations, the exposed subgrade should be observed under proofrolling. This proofrolling should be accomplished with a fully loaded dump truck or 7 to 10 ton drum roller to check for pockets of soft material hidden beneath a thin crust of better soil. Any unsuitable materials thus exposed should be removed and replaced with a well-compacted material. The inspection of these phases should be performed a qualified Geotechnical Engineer or designated representative.

2. Where excessively unstable subgrade soils are observed during proofrolling and/or fill placement, it is expected that these weak areas can be stabilized by means of thickening the base course layer. These alternates are to be addressed by a qualified Geotechnical Engineer or designated representative during construction, if necessary, who will recommend the most economical approach at the time.

Actual pavement section thicknesses and asphalt types should be provided by the design civil engineer based on traffic loads, volume, and the owners design life requirements. All pavement material and construction procedures should conform to Unified Facilities Criteria (UFC) requirements.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

4.6 Seismic Evaluation

Based on our experience in the vicinity of the project site and the composition of the soils recovered within the upper 25 feet (maximum explored depth) at the boring locations, it is our opinion that the site characteristics are indicative of a Site Class “D” in accordance with Table 20.3-1 of ASCE 7-10 as referenced by the 2012 International Building Code (IBC).

5.0 CONSTRUCTION CONSIDERATIONS

5.1 Anticipated Excavation Characteristics

Based on the results of this exploration, varying soil conditions and compositions are expected to be encountered throughout the project limits. Open-cut excavations will extend through natural soils containing appreciable amounts of fines. Based on these characteristics, the shallow subsurface materials encountered within the project alignment are unsuitable for reuse as backfill. Soils containing appreciable amounts of deleterious debris should be discarded;

however, an effort should be made during excavation to segregate potentially suitable in-situ fill soils for reuse. Information pertaining to backfill criteria was provided previously in Section 4.3.

5.2 Excavation Stability

The shallow subsurface within the project limits is comprised of clayey and granular soils;

however, the Contractor should anticipate these soils to have relatively little cohesion and have a high potential for caving. Based on these mentioned characteristics, it is recommended that all subsurface soils be considered Type C in accordance with Occupational Safety and Health Administration (OSHA) criteria.

Temporary Slopes

Due to the limited space for construction, temporary slopes may not be a feasible option. The Contractor should be aware that temporary slope height, slope inclination, or excavation depths should in no case exceed those specified in local, state and/or federal safety regulations (e.g.

OSHA Safety and Health Regulations for Construction, 29 CFR Part 1926, or successor regulations). Where temporary slopes are not feasible, shoring by means of sheeting and/or trench shields may be appropriate. Where the stability of adjoining structures, pavements, or other improvements is endangered by excavation operations, support systems such as shoring, bracing, or underpinning may be required to provide structural stability. Shoring, bracing, or underpinning required for this project (if required) should be designed by a professional engineer.

Any slopes (temporary or permanent) required on site should take in to account the characteristics of the Potomac Formation sediments and the concerns highlighted in Section 3.1 and Section 3.7. Slope failures including sloughing and landslides can occur immediately without any indication.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

Shoring

Shoring design and installation should be the responsibility of the Contractor. Shoring systems required for this project should be designed by a professional engineer. Shoring systems should be designed to provide positive restraint of trench walls in an effort to protect against lateral deformation that may result in ground cracks, settlement, and/or other ground movements that may affect adjacent underground utilities and pavements as well as surface improvements. The Contractor should be made aware of this potential condition in order that preventative measurers can be implemented or repair measures provided for.

Depending on the shoring system used, the removal process may create voids along the walls of the excavations. If these voids are left in place and are significant, backfill and/or the retained soil may shift laterally resulting in settlement of overlying structures/pavements. As such, care should be taken to remove the shoring systems and backfill the trenches in a manner as to not create these voids.

In all cases, the Contractor should select an excavation and/or shoring scheme that will protect adjacent and overlying improvements, including below grade utilities.

5.3 Dewatering

It is expected that dewatering will not be required for excavations; however, if necessary, dewatering above the groundwater table could probably be accomplished by pumping from sumps. Since temporary dewatering will impact construction and be dependent on construction methods and scheduling, we recommend the Contractor be solely responsible for the design, installation, maintenance, and performance of all temporary dewatering systems. Where shoring is employed, the dewatering system should be compatible with the type of shoring to be used.

We recommend the Contractor verify groundwater conditions and evaluate dewatering requirements prior to construction.

5.4 Site Utility Installation

The base of the utility trenches should be observed by a qualified inspector prior to the pipe placement to verify the suitability of the bearing soils. Based on the results of our field exploration program, it is expected that the utilities will be located within CLAY (CH, CL) soils. In these instances, the bearing soils may require some stabilization to provide suitable bedding.

This stabilization is commonly accomplished by adding 12 inches or more of bedding stone (Type VDOT # 57). The resulting excavations should be backfilled with structural fill, as described in Section 4.3 of this report. Imported fill should be included in the construction budget to backfill the utility excavations within the construction areas.

Report of Subsurface Exploration & Geotechnical Engineering Services August 16, 2016

Arlington National Cemetery Arlington, Virginia G E T Project No: VB16-137G (Revision 3) | PB Project No.: 185671

5.5 Structure Protection and Monitoring

Excavation for the proposed utility pipes will be made within the zone of influence of existing structures and/or under existing roadways or utilities. The Contractor must take adequate measures to protect existing structures and utilities from movement and must perform all work in such a way as to limit damage to existing structures, utilities, and/or roadways. All structures within 100 feet of the proposed construction should be monitored during construction.

Monitoring should include, but not be limited to, visual inspections, and the placement of crack monitors and monitoring points on the exterior of structures. Ground deformation monitoring monuments should be installed along and to each side of any excavations in order to assess the performance and any ground subsidence. The Contractor should install and obtain monitoring point readings prior to beginning excavation or operation of groundwater control system at the site.

The reading schedule of all monitoring points should be daily during excavation and then at least weekly until all excavation, dewatering, and all work has been completed. Additional surveys should be made if excessive ground movement is noticed.

Ground vibrations resulting from construction activities should be monitored with one or more seismographs. The seismographs should be placed on solid ground adjacent to vibration-sensitive locations.

A preconstruction survey should be conducted on existing structures within 100 feet of construction areas prior to any work along the alignment. Additional structures may be surveyed as deemed necessary by the Contractor. The preconstruction survey should consist of visual inspection and documentation (written, photographic, and/or video) of the existing structure. If damage to adjacent structures is reported, a similar survey should be conducted at the end of the work and the conditions recorded in the two surveys should be compared for indications of construction related damage to the existing structures.

5.6 Construction Monitoring and Inspections

The recommendations provided in this report are based on our understanding of the proposed project and on our evaluation of the data collected based on subsurface conditions observed in widely spaced exploratory borings. It is imperative that a qualified Geotechnical Engineer or designated representative be present during construction to observe the subsurface soil conditions and confirm that the Contractor complies with the intent of the earthwork recommendations contained…