Marietta NatCem 859CM3021_CD95_Project manual-2 of 2.pdf

PROJECT MANUAL, VOLUME 2

Issued for Construction

MARIETTA NATIONAL CEMETERY

Lodge Rehabi l i ta t ion, Design and Construct New Restrooms, Committa l Shelter , and Miscel laneous Repair I tems

Project Number 915CM3041

Bid Documents

November 18, 2022

Prime Consultant:

Walker Federal Services, LLC

Subconsultants:

Charlotte Engineers Principal Engineering, Inc.

ECS Southeast, LLP

R&R Construction Services, Inc.

WFS

APPENDIX I - Geotechnical Engineering Report

ECS Southeast, LLP

June 9, 2022

Geotechnical Engineering Report

Marietta National Cemetery Restroom Building, Committal Shelter, and Flagpole

500 Washington Avenue Marietta, Georgia, 30060

ECS Project No. 10:11440

Mr. Brian Jacobson Director of Planning and Design Walker Federal Services 7820B Unit 162 Wormans Mill Road, Frederick, Maryland, 21701

ECS Project No. 10:11440

Reference: Geotechnical Engineering Report

Marietta National Cemetery‐ Restroom Building, Committal Shelter, and Flagpole 500 Washington Avenue, Marietta, Georgia, 30060

Dear Mr. Jacobson:

ECS Southeast, LLP (ECS) has completed the subsurface exploration, laboratory testing, and geotechnical engineering analyses for the above‐referenced project. Our services were provided in accordance with the Project Authorization Agreement between Walker Federal Services and ECS dated May 16, 2022. This report presents our understanding of the geotechnical aspects of the project along with the results of the field exploration and laboratory testing conducted, and our design and construction recommendations.

It has been our pleasure to be of service to Federal Walker Services during the design phase of this project.

We would appreciate the opportunity to remain involved during the continuation of the design phase, and we would like to provide our services during construction phase operations as well to verify subsurface conditions assumed for this report. Should you have any questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, Kisan Patel, E.I.T Robert H Barnes, P.E., P.G.

Geotechnical Project Manager Geotechnical Principal Engineer Kpatel2@ecslimited.com rbarnes@ecslimited.com

Marietta National Cemetery‐ Restroom Building, Committal Shelter, and Flagpole June 9, 2022 ECS Project No. 10:11440 Page i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1.1 General

1.2 Scope of Services

2.0 PROJECT INFORMATION

2.1 Project Location

2.2 Proposed Construction

3.0 FIELD EXPLORATION AND LABORATORY TESTING

3.1 Subsurface Characterization

3.1.1 Regional Geology

3.2 Soil Conditions

3.3 Groundwater Observations

3.4 Laboratory Testing

4.0 DESIGN RECOMMENDATIONS

4.1 General

4.2 Impacts on Site Development and Design

4.2.1 Existing Retaining Wall

4.2.2 Design Implications of Undocumented Fill

4.3 Restroom Building

4.3.1 Ground Improvement Alternatives

4.3.2 Foundation Recommendations

4.3.3 Slab on Grade

4.4 Committal Shelter

4.5 POW Memorial Plaza Flagpole

4.6 Pavements

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 Subgrade Preparation

5.1.1 Stripping and Grubbing

5.1.2 Removal of Structures and Utilities

5.1.3 Proofrolling

5.2 Earthwork Operations

5.2.1 Existing Man‐Placed Fill

5.2.2 Suitability of On‐Site Soils for Reuse as Structural Fill

5.3 Foundation and Slab Observations

5.4 Utility Installations

5.5 Additional Considerations

6.0 PLAN REVIEW AND ADDITIONAL STUDY

7.0 CLOSING

ECS Project No. 10:11440 Page ii

APPENDICES

Appendix A – Drawings & Plans

Site Location Diagram

Boring Location Plan

Appendix B – Borings

Reference Notes for Boring Logs

Boring Logs B‐1 through B‐7

Appendix C – Laboratory Testing

Laboratory Test Results Summary

Appendix D – Supplemental Report Documents and Calculations

GBA Important information About This Geotechnical‐Engineering Report

ECS Project No. 10:11440 Page 1

EXECUTIVE SUMMARY

This Executive Summary is intended as a very brief overview of the primary geotechnical conditions that are expected to affect design and construction. Information gleaned from this Executive Summary should not be utilized in lieu of reading the entire geotechnical report.

Prior site grading activity has resulted in portions of the planned improvement areas being filled.

Existing undocumented fills beneath the planned restroom building, committal shelter, and flagpole areas were noted at the boring locations. Undercutting (full or partial) and replacement with structural fill will be required. Additional exploration with hand augers and Wildcat dynamic cone penetrometer (WDCP) testing is recommended to further evaluate the undocumented fill conditions within the planned areas of improvement.

Provided that any soft or poor‐quality existing fill or residual subgrade soils are remediated, and subgrades are prepared, and new structural fill installed in accordance with the Construction Recommendations of this report, the planned structures can be supported by conventional shallow foundations consisting of column or strip footings bearing on engineer‐approved residual soils, new structural fills, and improved existing fill.

A retaining wall was observed near the new proposed restroom building. The proposed building should either be setback from the retaining wall a horizontal distance equal to the height of the wall and/or the new building foundations should be lowered so that the building loads do not impose new loads on the retaining wall. Additionally, the integrity of the existing retaining wall should be evaluated by a qualifies structural engineer.

ECS should also be retained to provide Special Inspections and construction materials testing on behalf of the Owner to facilitate and document proper implementation of our recommendations. We recommend that ECS be retained to apply our expertise throughout the geotechnical phases of construction, and to provide consultation and recommendation should issues arise.

ECS Project No. 10:11440 Page 2

1.0 INTRODUCTION

1.1 General

According to information provided to ECS, the proposed project consists of the construction of a restroom building, a committal shelter, and a flagpole. The purpose of this exploration was to provide geotechnical information for the design of the proposed restroom building and shelter foundations and floor slabs, as well as the flag pole foundation.

The recommendations developed for this report are based on the results of our subsurface exploration and project information provided by Walker Federal Services. This report contains the results of our subsurface exploration and laboratory testing programs, site characterization, engineering analyses, and recommendations for the design and construction of the planned improvements.

1.2 Scope of Services

The purposes of this exploration were to explore the soil and groundwater conditions within the areas of planed improvements and to develop engineering recommendations to guide in the design and construction of the planned improvements. We accomplished the purposes of the study by:

1. Reviewing the available publications concerning local geology of the site and performing a general site reconnaissance.

2. Drilling borings to explore the subsurface soil and groundwater conditions.

3. Performing laboratory tests on selected representative soil samples from the borings to evaluate pertinent engineering properties.

4. Evaluating the field and laboratory data to develop appropriate engineering recommendations.

2.0 PROJECT INFORMATION

2.1 Project Location

The proposed site improvements are located on the grounds of the Marietta National Cemetery off Roswell Street with an address of 500 Washington Avenue, Marietta, Georgia, 30060. A Site Location Diagram is provided in Appendix A (Figure 1). The site is approximately 23 acres and majority of the area is a cemetery with few one‐story structures and associated utilities. Figure 2.1.1 shows the ESRI imagery of the project site and surrounding area with the cemetery highlighted in red.

2.2 Proposed Construction

Based on the information provided by Walker Federal Services and the project structural engineer, the planned improvements at the Marietta National Cemetery include the construction of a restroom building, a committal service shelter, and a flagpole. Currently the restroom building is planned behind a retaining wall on the eastern side of the maintenance building as shown in Figure 2.2.1. The committal service shelter is planned at the existing shelter just south of the vacant office building. The flag pole is

ECS Project No. 10:11440 Page 3 planned as part of the new POW memorial plaza which is currently located in the lawn area to the west of the vacant office building. We understand that the locations of the memorial and flag pole are not finalized and may change.

Figure 2.1.1 Imagery of Project Site and Surrounding Area

Since the proposed areas of improvement are relatively flat, minimal cuts and fills are anticipated for the planned improvements. Based on our conversation with the structural engineer, the restroom building will be a one‐story CMU building with a slab on grade and the committal shelter will be a one‐story steel framed structure with slab on grade. Based on this information, we anticipate the maximum column and continuous wall loads to not exceed 50 kips and 6 kips per linear foot, respectively.

Figure 2.2.1 Proposed Restroom Building Layout

ECS Project No. 10:11440 Page 4

Figure 2.2.2 Proposed Committal Service Shelter Layout

3.0 FIELD EXPLORATION AND LABORATORY TESTING

To explore the subsurface conditions at this site, a total of seven soil test borings (B‐1 to B‐7) were performed in the proposed improvement areas. Borings B‐1, B‐2, and B‐3 were performed in the proposed restroom building area to depths ranging from 10 to 20 feet below existing grade. Borings B‐4, B‐5, and

B‐6 were performed in the proposed committal shelter to depths ranging from 10 to 20 feet below existing grade. Boring B‐7 was performed for the proposed flagpole to a depth of 20 feet below existing grade.

Boring locations were determined in the field by our representative who measured distances and estimated right angles from existing site features. The approximate boring locations are shown on the Boring Location Plan in Appendix A.

The soil test borings were performed with an ATV mounted drill rig, which utilized hollow stem augers to advance the boreholes. No water or drilling fluid was introduced during the process. Representative soil samples were obtained by means of the split‐barrel sampling procedure in general accordance with ASTM

Specification D‐1586 with an automatic drive hammer. In this procedure, a 2‐inch O.D., split‐barrel sampler is driven into the soil 18 inches by a 140‐pound hammer falling 30 inches.

The number of blows required to drive the sampler through the last 12 inches of the sampling interval is termed the Standard Penetration Test (SPT) N‐value and is indicated for each sample on the boring logs.

This value can be used as a qualitative indication of the in‐place relative density of cohesionless soils. In a less reliable way, it also indicates the consistency of cohesive soils.

ECS Project No. 10:11440 Page 5

An automatic trip drop hammer was used for the standard penetration testing, which generally has a higher efficiency than a manual cathead and rope type hammer. Typically, the automatic hammer yields lower standard penetration test resistances (field N‐values) than a manual cathead and rope type hammer. This reduction has been considered in our evaluation. However, the N‐values reported on the logs, and the consistency descriptions on the boring logs are based on the field‐recorded values and not corrected for hammer efficiency.

The drill crew and an ECS representative prepared a field log of the soils encountered in the borings. After recovery, each sample was removed from the sampler and visually classified by the field crew.

Representative portions of each sample were then sealed and brought to our laboratory in Marietta, Georgia for further visual examination and laboratory testing by ECS.

3.1 Subsurface Characterization

3.1.1 Regional Geology

The site is located within the Piedmont Region of Georgia. The natural soils at the site consist primarily of residual materials formed from the in‐place physical and chemical weathering of the underlying parent bedrock. The relative density of the residual soils is primarily dependent upon the degree of weathering, surface disturbance, groundwater action, and residual mineral bonding. The shear strength of residual soils is anisotropic and exhibits great variations from point to point. Soils with the flaky minerals oriented parallel to the potential shear plane and the slickenside surfaces have lower shear strengths.

The boundary between soil and rock is not clearly defined. A transitional zone called partially weathered rock (PWR) is normally found above the parent rock. PWR is defined for engineering purposes, as residual material with standard penetration resistances more than 100 blows per foot. Weathering is facilitated by fractures, joints, and the presence of less resistant rock types. Consequently, PWR and hard rock profiles are irregular and zones of PWR or rock may occur within the soil mantle well above the general bedrock level. Boulders may be found in the upper soil matrix.

The natural geology in portions of the site has been modified in the past by grading that included the placement of fill materials. The quality of man placed fills can vary significantly, and it is often difficult to assess the engineering properties of existing fills. Furthermore, there is no specific correlation between

N‐values from Standard Penetration Tests performed in soil test borings and the degree of compaction of existing fill soils; however, a qualitative assessment of existing fills can sometimes be made based on the

N‐values obtained and observations of the materials sampled in the test borings.

Groundwater levels are irregular in the Piedmont Region. The surface of the groundwater table is largely dependent on the topography and is generally parallel to the ground surface. Localized distortions due to differences in vertical and horizontal permeability may occur. The groundwater table can fluctuate two or more feet with seasonal rainfall.

ECS Project No. 10:11440 Page 6

3.2 Soil Conditions

Data from the soil test borings is included in the Appendix. The subsurface conditions discussed in the following paragraphs and those shown on the boring logs represent an estimate of the subsurface conditions based on interpretation of the boring data using normally accepted geotechnical engineering judgments. We note that the transition between different soil strata is usually less distinct than those shown on the boring logs. Please refer to individual boring logs that are contained in Appendix B.

Stratum Description Ranges of SPT (1) N‐values

(bpf (2))

N/A

Topsoil – The surface layer at boring locations B‐4 through B‐7 consisted of approximately 6 inches of topsoil. Thicknesses are expected to be variable across the project site. Dozer clearing was used to access the borings performed. Observed topsoil depths do not include root balls which could be significantly deeper and are also not recommended for support of structures and/or pavements.

N/A l

FILL – Soils described as fill consisting of firm to stiff sandy Silt (ML) and very loose to loose silty Sand(SM) was encountered at each boring location extending to depths ranging from about 3 to 8 feet below the ground surface.

Traces of rock fragments, where present within the fill, may have cause the SPT blow counts to be amplified.

2 to 29

II

Residual Soils – Beneath the fill soils are residual soils described as loose to very dense silty Sand (SM).

2 to 21

Notes: (1) Standard Penetration Testing.

(2) bpf – Blows per foot.

3.3 Groundwater Observations

Groundwater seepage into our borings was not observed during our exploration at the depths explored.

Stabilized groundwater readings were not measured since all the boreholes were backfilled immediately after sampling due to safety concerns.

3.4 Laboratory Testing

Classification and index property tests were performed by ECS on representative soil samples obtained from the test borings to aid in classifying soils according to the Unified Soil Classification System and to quantify and correlate engineering properties. Laboratory testing included moisture content testing, Atterberg Limits, and washed #200 sieve gradation analyses. The results of the laboratory testing program are included in Appendix C.

Each sample was visually classified based on texture and plasticity in accordance with ASTM D2488 Standard Practice for Description and Identification of Soils (Visual‐Manual Procedures) and including USCS classification symbols, and ASTM D2487 Standard Practice for Classification for Engineering Purposes (Unified Soil Classification System (USCS)). After classification, the samples were grouped in the major zones noted on the boring logs in Appendix B. The group symbols for each soil type are indicated in

ECS Project No. 10:11440 Page 7 parentheses along with the soil descriptions. The stratification lines between strata on the logs are approximate; in situ, the transitions may be gradual.

4.0 DESIGN RECOMMENDATIONS

4.1 General

At the time this report was prepared the project was in the initial planning stages. As such, the building footprint, structural loads, building floor elevations, and site grading plans were not finalized. Once the project drawings and site plans are further developed, copies should be provided to ECS for review. At that time, ECS will determine if changes to the recommendations outlined in this report are needed.

Supplemental exploration, as discussed in this report, is recommended to provide final recommendations for final design and construction.

4.2 Impacts on Site Development and Design

Geotechnical related concerns identified during this study that may impact the project include the presence of existing undocumented fill and the presence of a retaining wall located directly behind the proposed restroom building. The following concerns are discussed in more detail in the following sections of this report.

4.2.1 Existing Retaining Wall

The proposed restroom building is currently planned on the eastern side of the maintenance building. A retaining wall is located on the west side of the proposed restroom building as outlined in red in Figure

4.2.1. The retaining wall was approximately 5 feet in height. The structural integrity of the retaining wall was not evaluated and is outside our scope of work. We recommend the new structure be offset from the wall so that the foundation loads of the new building do not imposes loads on the retaining wall.

Alternatively, the new building footings should be lowered to an elevation such that the zone of influence of the building loads is beneath the retaining wall.

ECS Project No. 10:11440 Page 8

Figure 4.2.1‐ Retaining Wall Outline and Location

4.2.2 Design Implications of Undocumented Fill

Loose/soft existing undocumented fill materials were encountered in each boring extending to depths varying from 3 to 8 feet below the existing ground surface. The undocumented fill in the samples obtained during drill appeared to be relatively free of organic material, including wood fragments and topsoil.

If very loose/soft soils or pockets of debris, organics, stumps, or other poor‐quality materials, exist within the fill and are not removed during construction, then localized excessive differential settlements could occur in response to new structural loads and the on‐going process of volume change which may still occur in the fill. If such non‐uniform settlements occur, then moderate distress could result. In consideration of the depth of the fill and the amount of observed organic materials in the fill soils, this material is not acceptable for support of any future structures, including buildings, walls, and pavements.

Therefore, we recommend supplementary exploratory hand auger borings with Wildcat dynamic cone penetrometer testing (WDCP) be performed around the footprint of the restroom building and the committal shelter at time of construction to further evaluate existing undocumented fill materials prior to site development. Our recommendations for ground improvement are discussed in the following sections of the report.

4.3 Restroom Building

Borings B‐1, B‐2, and B‐3 were performed in the proposed restroom building area. Undocumented fill materials were encountered in borings B‐1 and B‐2 extending to a depth of about 5.5 feet. In boring B‐3, the fill continues to a depth of approximately 8 feet. Based on the varying relative density of the fill materials and possible presence of poor‐quality materials within the fill matrix, we do not recommend the building foundations be installed on the existing fill in its current condition. Ground improvement with either full removal and replacement or partial removal, in place densification of the remaining fill, and new structural fill could be considered. These alternatives are discussed in more detail in Section 4.3.1.

4.3.1 Ground Improvement Alternatives

From experience, we offer the following recommendations on how to prepare the building area for the new structure. Once you have reviewed these scenarios and the recommended exploratory hand auger borings with WDCP testing have been completed, we would be happy to discuss the alternatives further with you and your structural engineer to finalize the foundation recommendations.

Alternative 1 – Complete Removal and Replacement

The most assured means of preparing the expanded building area for new construction would be the complete removal of the undocumented fill materials beneath the building footprint plus a 10‐foot margin where practical. Removal and replacement of the undocumented fill underlying the new building would reduce the settlement to that of any other structure supported by engineered fill.

ECS Project No. 10:11440 Page 9

Alternative 2 ‐ Partial Undercut

As a cost saving option, we considered partial undercut of the highly variable fill. If this option is selected, the Owner accepts the increased risk of potential differential settlement and associated cracking. With that understanding, we recommend over excavating the upper 4 feet in the building area, densifying the remaining fill in‐place with surface compaction equipment, and installing new structural fill. Depending upon the results of the surface compaction, additional undercut may be required to remove localized poor‐quality materials. We believe that replacing these soils with clean, properly compacted engineered fill installed over densified fill soils can reduce the risk of uneven foundation and floor slab settlement.

It is likely that the surficial fill to be removed will require some drying and possibly screening to remove debris if it is to be re‐used to backfill the excavation. We recommend that moisture content tests and standard Proctor tests be performed on the existing fill to determine its compaction characteristics and suitability for re‐use.

4.3.2 Foundation Recommendations

Provided subgrades and structural fills are prepared as recommended by one of the ground improvements presented in this report, the proposed structure can be supported by shallow foundations including column footings and continuous wall footings. We recommend the foundation design use the following parameters:

Design Parameter Column Footing Wall Footing

Net Allowable Bearing Pressure (1) 3,000 psf

Acceptable Bearing Soil Material New structural fill and residual soils

Minimum Width 24 inches 16 inches

Minimum Footing Embedment Depth

(Below slab or outside finished grade) (2) 18 inches

Estimated Total Settlement (3) Less than 1 inch

Estimated Differential Settlement (4) Less than ½‐inch

Notes:

(1) Net allowable bearing pressure is the applied pressure greater than the surrounding overburden soils above the base of the foundation.

(2) For bearing considerations and frost penetration requirements.

(3) Based on assumed structural loads. If final loads are different, ECS must be contacted to update foundation recommendations and settlement calculations.

(4) Based on maximum column/wall loads and variability in borings. Differential settlement can be re‐evaluated once the foundation plans are more complete.

Potential Undercuts: Except as noted, the soils at the foundation bearing elevation are anticipated to be suitable for support of the proposed structure. If soft or poor‐quality soils are observed at the footing bearing elevations, the poor‐quality soils should be undercut and removed. Any undercut should be backfilled with lean concrete (f’c ≥ 1,000 psi at 28 days) up to the original design bottom of footing elevation; the original footing shall be constructed on top of the hardened lean concrete.

ECS Project No. 10:11440 Page 10

4.3.3 Slab on Grade

It appears that the slabs will bear on a combination of new structural fill, densified existing fill, and residual soils. Within the building footprint there may be areas of soft or yielding existing fill or residual soils that should be removed and replaced with compacted structural fill in accordance with the recommendations included in this report. Soft or yielding soils may be encountered during construction. Those soils should be removed and replaced with compacted structural fill in accordance with the recommendations included in this report.

Subgrade Modulus: Provided the structural fill and granular drainage layer are constructed in accordance with our recommendations, the slab may be designed assuming a modulus of subgrade reaction, k1 of 120 pci (lbs./cu. inch).

Vapor Barrier: Before the placement of concrete, a vapor barrier may be placed on top of the granular drainage layer to provide additional protection against moisture vapor penetration through the floor slab.

When a vapor barrier is used, special attention should be given to surface curing of the slab to reduce the potential for uneven drying, curling and/or cracking of the slab. Depending on proposed flooring material types, the structural engineer and/or the architect may choose to eliminate the vapor barrier.

The following graphic depicts our soil‐supported slab recommendations:

1. Drainage Layer Thickness: 4 inches

2. Drainage Layer Material: granular material such as GAB having a maximum aggregate size of 1.5 inches and no more than 10 percent fines.

3. Subgrade compacted to 98% maximum dry density per ASTM D698

Slab Isolation: Soil‐supported slabs should be isolated from the foundations and foundation‐supported elements of the structure so that differential movement between the foundations and slab will not induce excessive shear and bending stresses in the floor slab. Where the structural configuration prevents the use of a free‐floating slab such as in a drop‐down footing/monolithic slab configuration, the slab should be designed with adequate reinforcement and load transfer devices to reduce overstressing of the slab.

The above should be considered general guidance to assist the Owner and design team. Project specific designs, plan details or other input from the Structural Engineer of Record should control.

Concrete Slab Vapor Barrier

Granular Capillary Break/Drainage Layer

Compacted Subgrade

ECS Project No. 10:11440 Page 11

4.4 Committal Shelter

Borings B‐4, B‐5, and B‐6 were performed for the proposed committal shelter. Undocumented fill materials were encountered in borings B‐5 and B‐6 extending to a depth of about 5.5 feet. In boring B‐4, the fill continues to a depth of approximately 3 feet. Based on the varying relative density of the fill materials and possible presence of poor‐quality materials within the fill matrix, we do not recommend the shelter foundations be installed on the existing fill in its current condition. Ground improvement with either full removal and replacement or partial removal, in place densification of the remaining fill, and new structural fill could be considered. These alternatives are discussed in more detail in Section 4.3.1 above. For the committal shelter, we recommend a partial undercut of 3 feet within the expanded shelter footprint.

Shelter Foundations: Provided subgrades and structural fills are prepared as recommended by one of the ground improvements presented in this report, the proposed shelter can be supported by shallow foundations including column footings and continuous wall footings. Alternatively, a turndown slab or thickened slab could be considered. We recommend the foundation design use the parameters presented in Section 4.3.2.

Shelter Pad or Slab: Provided the structural fill and a 4‐inch‐thick granular base layer are constructed in accordance with our recommendations, the slab may be designed assuming a modulus of subgrade reaction, k1 of 120 pci (lbs./cu. inch).

4.5 POW Memorial Plaza Flagpole

The flag pole is planned as part of the new POW memorial plaza which is currently located in the lawn area to the west of the vacant office building. We understand that the locations of the memorial and flag pole are not finalized and may change. Boring B‐7 was advanced for the flagpole. Undocumented fill materials were encountered in the boring extending to a depth of about 3 feet. The flag pole foundation or pier should extend below the undocumented fill and bear in the residual soil. A net allowable bearing pressure of 3 Ksf may be used for design.

4.6 Pavements

Subgrade Characteristics: Based on the results of our soil test borings and anticipated site grading, we anticipate that the soils that will be exposed as pavement subgrades, exposed in cuts, and placed as fill, will consist mainly of sandy Silt (ML) material. The Owner and Contractor should anticipate the undercutting of poor‐quality soils and moisture conditioning will be required during construction.

California Bearing Ratio [CBR] testing was not performed as part of this study. For preliminary design purposes, we recommend assuming a design CBR value of 4 be utilized based upon our visual classification of likely pavement subgrade soils. Prior to subbase placement and paving, CBR testing on the subgrade soils should be performed to confirm the soil engineering properties.

No traffic data was available; therefore, we have made assumptions to provide preliminary pavement sections. The preliminary pavement sections below are guidelines that may or may not comply with local jurisdictional minimums but can be adjusted with more complete traffic data and actual CBR lab testing.

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PROPOSED PAVEMENT SECTIONS

FLEXIBLE PAVEMENT RIGID PAVEMENT

MATERIAL Heavy Duty Light Duty Heavy Duty Light Duty

Portland Cement Concrete with macro‐fiber mesh (f’c = 4000 psi)

‐ ‐ 6 in. 5 in.

AC Surface Course HMA Superpave – 9.5mm or

12.5 mm

1.5 in 2 in ‐ ‐

AC Base Course HMA Superpave – 19mm

2 in ‐ ‐ ‐

Graded Aggregate Base Course

(GAB)

8 in 6 in 6 in 5 in

In general, heavy‐duty sections should be used in areas that will be subjected to trucks or other similar heavily loaded vehicles and main drive lanes of the site. Light duty sections are appropriate for automobile traffic and parking areas.

Large, front loading garbage trucks which empty trash dumpsters frequently impose concentrated front wheel loads on pavements during loading. This type of loading typically results in rutting of asphalt pavement and ultimately pavement failures. For preliminary design purposes, we recommend that the pavement in trash pickup areas consist of a 6‐inch thick, 4,000 psi, reinforced concrete slab over 6‐inches of dense graded aggregate. When traffic loading becomes available ECS, or the Civil Engineer can design the pavements.

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 Subgrade Preparation

5.1.1 Stripping and Grubbing

The subgrade preparation should consist of stripping all vegetation, rootmat, topsoil, and any soft or poor‐ quality materials from the 5‐foot expanded building, expanded pavement limits, and 5 feet beyond the toe of structural fills. Borings performed in “undisturbed” areas of the site contained approximately 6 to 7 inches of topsoil. Topsoil thickness will be variable and deeper topsoil or organic laden soils may be present beyond the test locations. ECS should be retained to verify that topsoil and poor‐quality surficial materials have been removed prior to the placement of structural fill or construction of structures

5.1.2 Removal of Structures and Utilities

At the time of our field work, the existing committal shelter area was developed with a slab and associated utilities in the close vicinity of the proposed structure. The footprint of the new shelter will overlap a portion of the existing slab. The re‐development of the project site will require the demolition and removal of the shelter structure, existing slab, and utilities. This should include the complete removal of all floor slabs, foundations, walls, under slab utilities, pavements, et cetera.

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Existing utilities that will no longer be in service should be completely removed from the new building footprint. Active utilities should be re‐routed around the building, wherever possible, and the abandoned section of utility completely removed from the proposed building area. If active utilities are to remain within the building footprint, these utilities should be reviewed by the project structural engineer for conflicts and clearly identified on the construction plans. Special foundation construction procedures may be required to support the new building foundations over utilities.

Excavations resulting from the removal of the above items and associated loose fill should be backfilled with new structural fill as discussed in the following section of this report. This should be observed on a full‐time basis by a representative of ECS to document that the poor‐quality materials have been removed and that the subgrade is suitable for support of the proposed construction and/or fills.

Any below ground construction/utilities in the vicinity of the proposed building should be removed prior to the initiation of new construction. We suggest that available information regarding the existing utilities at the site be reviewed prior to construction.

5.1.3 Proofrolling

Prior to fill placement or other construction on subgrades, the subgrades should be evaluated by ECS. The exposed subgrade should be thoroughly proofrolled with construction equipment having a minimum axle load of 10 tons [e.g., fully loaded tandem‐axle dump truck]. In confined areas, smaller compaction equipment (e.g., 5‐ to 10‐ton vibratory drum rollers) may be used for proofrolling. Proofrolling should be traversed in two perpendicular directions with overlapping passes of the vehicle under the observation of ECS. This procedure is intended to assist in identifying any localized yielding materials.

Where proofrolling identifies areas that are yielding or “pumping” subgrade those areas should be repaired prior to the placement of any subsequent structural fill or other construction materials. Methods of stabilization include undercutting, moisture conditioning, or chemical stabilization. The situation should be discussed with ECS to determine the appropriate procedure. Test pits may be excavated to explore the shallow subsurface materials to help in determining the cause of the observed yielding materials, and to assist in the evaluation of appropriate remedial actions to create a firm and unyielding subgrade.

5.2 Earthwork Operations

5.2.1 Existing Man‐Placed Fill

Existing fill should be evaluated by ECS personnel at the time of construction using hand auger explorations and Wildcat dynamic cone penetrometer testing (WDCP) to determine the extend undercutting is required in the building and the pavement area based on the options selected from Section

4.3.1 Ground Improvement Alternatives. ECS personnel should confirm that poor‐quality fill materials have either been improved or removed.

5.2.2 Suitability of On‐Site Soils for Reuse as Structural Fill

Laboratory testing on the selected soils from Borings B‐1 and B‐5 between the depths of 3.5 foot and 7.5 feet indicates that the natural moisture content of the tested soils ranged between 20.4 and 21.6 percent.

Laboratory testing indicates that the moisture content of the tested soil samples is likely near optimum or slightly above optimum for proper compaction. The site soils contain about 47.4 to 56.1 percent of fine‐

ECS Project No. 10:11440 Page 14 grained soils (passing the #200) in the samples tested. These types of soils are moisture sensitive and may be difficult to use as structural fill if the material becomes too wet. The fine‐grained soils at the site could become unworkable and require reworking and drying for proper compaction.

Atterberg Limits testing was performed on a soil sample obtained from Borings B‐1. The testing indicated that the tested soil samples had liquid limits (LL) of 56 percent, and a plasticity index (PI) of 19 percent.

The liquid limit of the tested samples above the recommended liquid limit of less than 50 for structural fill. In addition, the plasticity index of the tested sample is below the recommended plasticity index of less than 25 for structural fill. Based on the lab test results, the soil sample from Boring B‐2 is classified as silty Sand (SM). The silty Sand (SM) fill and residual soils appear generally suitable for re‐use as structural fill if they are within the moisture range for proper compaction and are free from deleterious materials, such as organics and debris. The on‐site soils should be tested by ECS prior to use as structural fill.

Prior to placement of structural fill, representative bulk samples (about 50 pounds) of on‐site and/or off‐ site borrow should be submitted to ECS for laboratory testing, which will typically include Atterberg limits, natural moisture content, grain‐size distribution, and moisture‐density relationships (i.e., Proctors) for compaction. Import materials should be tested prior to being hauled to the site to determine if they meet project specifications. Alternatively, Proctor data from other accredited laboratories can be submitted if the test results are within the last 90 days.

Structural Fill Materials: Materials for use as structural fill should consist of inorganic soils with the following engineering properties and compaction requirements.

STRUCTURAL FILL INDEX PROPERTIES

Subject Property

Building and Pavement Areas LL < 40, PI<20

Max. Particle Size 4 inches

Fines Content Less than 65 %

Minimum dry unit weight (in place) > 95 pcf

Max. organic content 5% by dry weight

STRUCTURAL FILL COMPACTION REQUIREMENTS

Subject Requirement

Compaction Standard Standard Proctor, ASTM D698

Required Compaction 95% of Max. Dry Density (98% in the top 1 foot)

Moisture Content +3 % points of the soil’s optimum value

Loose Thickness 8 inches prior to compaction

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Fill Placement Considerations: Fill materials should not be placed on frozen soils, on frost‐heaved soils, and/or on excessively wet soils. Borrow fill materials should not contain frozen materials at the time of placement, and all frozen or frost‐heaved soils should be removed prior to placement of Structural Fill or other fill soils and aggregates. Excessively wet soils or aggregates should be scarified, aerated, and moisture conditioned.

5.3 Foundation and Slab Observations

Protection of Foundation Excavations: Exposure to the environment may weaken the soils at the footing bearing level if the foundation excavations remain open for too long a time. Therefore, foundation concrete should be placed the same day that excavations are made. If the bearing soils are softened by surface water intrusion or exposure, the softened soils must be removed from the foundation excavation bottom immediately prior to placement of concrete. If the excavation must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, a 1 to 3‐inch thick “mud mat” of “lean” concrete should be placed on the bearing soils before the placement of reinforcing steel.

Footing Subgrade Observations: While the soils at the foundation bearing elevation are anticipated to be suitable for support of the proposed structure, it is important to have the Geotechnical Engineer of Record (ECS), or their authorized representative, observe the foundation subgrade prior to placing foundation concrete, to confirm the bearing soils are what was anticipated.

Slab Subgrade Verification: Prior to placement of a drainage layer, the subgrade should be prepared in accordance with the recommendations found in Section 5.1.3 Proofrolling.

5.4 Utility Installations

Utility Subgrades: The soils encountered in our exploration are expected to be generally suitable for support of utility pipes. The pipe subgrades should be observed and probed for stability by ECS. Any loose or poor‐quality materials encountered should be removed and replaced with suitable compacted Structural Fill, or pipe stone bedding material.

Utility Backfilling: The granular bedding material (often sand or processed aggregate) should be at least 4 inches thick, but not less than that specified by the civil engineer’s project drawings and specifications.

We recommend that the bedding materials be placed up to the springline of the pipe. Fill placed for support of the utilities, as well as backfill over the utilities, should satisfy the requirements for Structural Fill and Fill Placement.

Excavation Safety: All excavations and slopes should be constructed and maintained in accordance with OSHA excavation safety standards. The contractor is solely responsible for designing, constructing, and maintaining stable temporary excavations and slopes. The contractor’s responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations. ECS is providing this information solely as a service to our client. ECS is not assuming responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred.

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5.5 Additional Considerations

During the cooler and wetter periods of the year, delays and additional earthwork costs should be anticipated. At these times, reduction of soil moisture may need to be accomplished by a combination of mechanical manipulation and the use of chemical additives, such as lime or cement, to lower moisture contents to levels appropriate for compaction. Alternatively, during the drier times of the year, such as the summer months, moisture may need to be added to the soil to provide adequate moisture for successful compaction according to the project requirements.

Measures should also be taken to limit site disturbance, especially from rubber‐tired heavy construction equipment, and to control and remove surface water from development areas, including structural and pavement areas.

Exposure to the environment may weaken the soils at the footing bearing level if the foundation excavations remain open for too long a time. Therefore, foundation concrete should be placed the same day that excavations are dug. If surface water intrusion or exposure softens the bearing soils, the softened soils must be removed from the foundation excavation bottom immediately prior to placement of concrete. If the excavation must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, we recommend that the foundations be covered or otherwise protected.

Positive site drainage should be maintained during earthwork operations, which should help maintain the integrity of the soil. Placement of fill on the near surface soils, which have become saturated, could be difficult. When wet, these soils will degrade quickly with disturbance from contractor operations and will be extremely difficult to stabilize for fill placement.

Where unacceptable materials are encountered, they must be evaluated by an ECS representative and may need to be undercut and replaced or improved by re‐compaction.

The surface of the site should be kept properly graded to enhance drainage of the surface water away from the proposed structure areas during the construction phase. We recommend that an attempt be made to enhance the natural drainage without interrupting its pattern.

The surficial soils contain fines, which are considered moderately erodible. Erosion and sedimentation shall be controlled in accordance with Best Management Practices and current County and State NPDES requirements. At the appropriate time, we would be pleased to provide a proposal for conducting construction materials testing and NPDES services.

6.0 PLAN REVIEW AND ADDITIONAL STUDY

At the time this report was prepared the project was in the initial planning stages. As such, the restroom building location and floor elevation were not finalized and site layout and grading plans have not been developed. The above analysis and recommendations are specific to the areas explored. If site layout changes, ECS should be notified at that time, ECS will determine if additional exploration and changes to the recommendations outlined in this report are needed. Once the project drawings and site plans are further developed, copies should be provided to ECS for review.

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Undocumented fill material is present at the proposed site improvement locations to depths of up to 12 feet below existing grade. We recommend a series of supplemental hand auger borings with WDCP testing be performed around the planned restroom building, committal shelter, and pavement areas prior to construction to further evaluate the character of the existing undocumented fill materials. Depending upon the findings in the supplemental hand auger borings with WDCP testing, modifications to the above ground improvement and site preparation recommendations may be required.

7.0 CLOSING

ECS has prepared this report to guide the geotechnical‐related design and construction aspects of the project. We performed these services in accordance with the standard of care expected of professionals in the industry performing similar services on projects of like size and complexity at this time in the region.

No other representation expressed or implied, and no warranty or guarantee is included or intended in this report. ECS is not responsible for the conclusions, opinions, or recommendations of others based on the data in this report.

The description of the proposed project is based on information provided to ECS by Walker Federal Services at the time the explorations were performed. If any of this information is inaccurate or changes, either because of our interpretation of the documents provided or due to design or site layout changes that may occur later, ECS should be contacted so we can review our recommendations and provide additional or alternate recommendations that reflect the proposed construction. We recommend that ECS review the final project plans and specifications so we can confirm that those plans/specifications are in accordance with the recommendations of this geotechnical report.

Because undocumented fill is present on this site, the Owner and Contractor must assess the relative risk that unacceptable material could have been buried in the proposed development area which was not detected in the widely spaced borings.

Field observations, monitoring, and quality assurance testing during earthwork and foundation installation are an extension of and integral to the geotechnical design recommendation. We recommend that the owner retain these quality assurance services and that ECS be allowed to continue our involvement throughout these critical phases of construction to provide general consultation as issues arise. We would be pleased to provide an estimated cost for these services at the appropriate time. Please contact Mr. Jorge J. Rodriguez‐Alvarez by email (JRodriguezAlvarez@ecslimited.com) or at our office number (770‐590‐1971).

This report is provided for the exclusive use of Walker Federal Services and their project specific design team. This report is not intended to be used or relied upon in connection with other projects or by other third parties. ECS disclaims liability for any such third‐party use or reliance without express written permission.

APPENDIX A – Diagrams & Plans

Site Location Diagram Boring Location Plan

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APPENDIX B – Borings

Reference Notes for Boring Logs Boring Logs B‐1 through B‐7

REFERENCE NOTES FOR BORING LOGS

MATERIAL1,2

1Classifications and symbols per ASTM D 2488-17 (Visual-Manual Procedure) unless noted otherwise.

2To be consistent with general practice, “POORLY GRADED” has been removed from GP, GP-GM, GP-GC, SP, SP-SM, SP-SC soil types on the boring logs.

3Non-ASTM designations are included in soil descriptions and symbols along with ASTM symbol [Ex: (SM-FILL)].

4Typically estimated via pocket penetrometer or Torvane shear test and expressed in tons per square foot (tsf).

5Standard Penetration Test (SPT) refers to the number of hammer blows (blow count) of a 140 lb. hammer falling 30 inches on a 2 inch OD split spoon sampler required to drive the sampler 12 inches (ASTM D 1586). “N-value” is another term for “blow count” and is expressed in blows per foot (bpf). SPT correlations per 7.4.2 Method B and need to be corrected if using an auto hammer.

6The water levels are those levels actually measured in the borehole at the times indicated by the symbol.