S02 Geotechnical Report Ft. Sam Houston - Additional Road Repairs_F.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report

Ft. Sam National Cemetery Phase 3 Expansion & Improvements

San Antonio, TX

May 5, 2020

Terracon Project No. 90195179

Prepared for:

Anderson Engineering of Minnesota, LLC

Plymouth, Minnesota

Prepared by:

Terracon Consultants, Inc.

San Antonio, Texas

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

DEEP FOUNDATIONS

SEISMIC CONSIDERATIONS

FLOOR SLABS

PAVEMENTS

GENERAL COMMENTS

ATTACHMENTS

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

PHOTOGRAPHY LOG

EXPLORATION RESULTS (Boring Logs)

FIGURES (GeoModel)

SUPPORTING INFORMATION (General Notes and Unified Soil Classification System)

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INTRODUCTION

Geotechnical Engineering Report

Ft. Sam National Cemetery Phase 3 Expansion & Improvements

1520 Harry Wurzbach Road

San Antonio, TX Terracon Project No. 90195179

May 5, 2020

INTRODUCTION

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed cemetery expansion to be located at 1520 Harry Wurzbach

Road in San Antonio, TX. The purposes of these services are to provide information and geotechnical engineering recommendations relative to:

◼ Subsurface soil conditions ◼ Foundation design and construction

◼ Groundwater conditions ◼ Site preparation and earthwork

◼ Seismic site classification per IBC ◼ Excavation considerations

◼ Pavement design and construction

The Geotechnical Engineering Scope of Services for this project included the advancement of fifty-five (55) test borings to depths ranging from about 8 to 40 feet below existing site grades.

Maps showing the site and boring locations are shown in the Site Location and Exploration

Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the boring logs in the

Exploration Results section.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel Information

The project is located at 1520 Harry Wurzbach Road in San Antonio, Texas.

GPS coordinates of the site are: 29.47676o and -98.43270o

See Site Location

Existing

Improvements Existing buildings, asphalt pavements and cemetery

Current Ground

Cover Asphalt, landscape, grass and bare soil.

Ft. Sam National Cemetery Phase 3 Expansion & Improvements ■ San Antonio, TX

May 5, 2020 ■ Terracon Project No. 90195179

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PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions are as follows:

Item Description

Information Provided The project information was provided by Mr. Eric Sautbine with Anderson

Engineering of Minnesota, LLC.

Proposed Structures

The development will include:

■ New honor guard building;

■ Expansion to the existing administration building;

■ New equipment storage and material storage building;

■ Associated parking/driveway areas;

■ Repair of existing pavement sections on the west side of the property as well as a construction of a new access road in the east side of the property;

■ Expansion of graveyard area.

Footprint area of the buildings are:

■ Approximately 1,200 square feet for the honor guard building;

■ Approximately 800 square feet for the material storage building;

■ Approximately 2,300 square feet for the equipment storage building.

■ Approximately 2,500 square feet for the addition to the existing administration building.

■ New columbaria (maximum of 10,784 niches)

Existing Topography

Based on grading plan provided by Mr. Eric Sautbine, P.E., with Anderson

Engineering of Minnesota, LLC., existing grades at the building locations are:

◼ Existing grade at the honor guard building is about EL. 720.0 feet;

◼ Existing grade at the equipment storage and material storage building is about EL. 676.0 feet;

◼ Existing grade at the addition to the existing administration building is about EL. 677.0 feet.

◼ Existing grade at columbaria location is about EL. 672.0 feet.

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Item Description

Finished Floor Elevation

Based on grading plan provided by Mr. Eric Sautbine, P.E., with Anderson Engineering of Minnesota, LLC., finished floor elevations the building locations are:

◼ Finished floor elevation (FFE) at the honor guard building is set at

EL. 722.0 feet;

◼ Finished floor elevation (FFE) at the equipment storage building is set at EL. 675.6 feet;

◼ Finished floor elevation (FFE) at the material storage building is set at EL. 676.6 feet;

◼ Finished floor elevation (FFE) at the addition to the existing administration building is set at EL. 677.3 feet.

GEOTECHNICAL CHARACTERIZATION

Site Geology

The San Antonio Sheet (1983) of the Geologic Atlas of Texas published by the Bureau of

Economic Geology at the University of Texas at Austin has mapped Fluviatile Terrace Deposits

(Qt) underlain by the Navarro Group and Marlbrook Marl - Undivided (Kknm) at the project site.

The Fluviatile Terrace Deposits are of the Pleistocene period and consist of gravel, sand, silt and clay. These deposits are found along the banks of streams, creeks and rivers and are the result of water born deposition and generally consist of the weathered products of rock located at higher elevations.

The Fluviatile Terrace Deposits are likely underlain by the Navarro Group and Marlbrook Marl

- Undivided formation. The upper part of this geologic unit typically consists of marl, clay, sandstone, and siltstone. The lower part of this geologic unit typically consists of montmorillonitic, unctuous, greenish gray to brownish gray clay which weathers to a very thick, black, clayey soil.

Subsurface Conditions

We have developed a general characterization of the subsurface conditions at the building locations based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. As part of our analyses, we identified the following model layers within the subsurface profile in the areas of the building pads.

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Honor Guard Building

Model Layer # Description General Description

1 Fat Clay1 Dark Brown, Yellowish Brown and Brown; Medium Stiff to Hard

1/ The FAT CLAY materials could undergo high volumetric changes (shrink/swell) should they experience changes in their in-place moisture content.

Equipment and Material Storage Building

Model Layer # Description General Description

Clayey Gravel1

(Fill) Light Brown, Brown, Yellowish Brown; Medium Dense to Dense

2 Clayey Gravel2 Light Brown; Dense to Very Dense

3 Fat Clay3 Dark Brown, Light Brown and Brown; Stiff to Hard

4 Lean Clay4 Light Brown, Brown and Light Gray; Stiff to Hard

5 Shale5 Gray; Hard

1/The FILL CLAYEY GRAVEL materials are primarily granular in nature and are expected to possess a negligible potential for volumetric changes due to moisture fluctuations. However, uncontrolled fill material may be subject to excessive settlement if not properly compacted. Also, uncontrolled fills may contain debris and other unsuitable material not detected by our widely spaced borings.

2/The CLAYEY GRAVEL materials are primarily granular in nature and are expected to possess a negligible potential for volumetric changes due to moisture fluctuations.

3/ The FAT CLAY materials could undergo high volumetric changes (shrink/swell) should they experience changes in their in-place moisture content.

4/ The LEAN CLAY materials could undergo moderate volumetric changes (shrink/swell) should they experience changes in their in-place moisture content.

5/ The CLAY-SHALE materials are volumetrically stable when considered for expansive soil-related movements.

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Administration Building Expansion

Model Layer # Description General Description

Clayey Gravel1

(Fill) Yellowish Brown

2 Clayey Gravel2 Light Brown; Dense

3 Fat Clay3 Brown; Stiff

4 Lean Clay4 Light Brown, Brown; Stiff to Hard

5 Shale5 Light Gray, Gray; Hard

1/The FILL CLAYEY GRAVEL materials are primarily granular in nature and are expected to possess a negligible potential for volumetric changes due to moisture fluctuations. However, uncontrolled fill material may be subject to excessive settlement if not properly compacted. Also, uncontrolled fills may contain debris and other unsuitable material not detected by our widely spaced borings.

2/The CLAYEY GRAVEL materials are primarily granular in nature and are expected to possess a negligible potential for volumetric changes due to moisture fluctuations.

3/ The FAT CLAY materials could undergo high volumetric changes (shrink/swell) should they experience changes in their in-place moisture content.

4/ The LEAN CLAY materials could undergo moderate volumetric changes (shrink/swell) should they experience changes in their in-place moisture content.

5/ The CLAY-SHALE materials are volumetrically stable when considered for expansive soil-related movements.

This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs and GeoModel can be found in the

Exploration Results section and Figures section of this report respectively. It can be emphasized that the stratification boundaries on the boring logs represent the approximate location of changes in native soil types; in situ, the transition between materials may be gradual.

Groundwater Conditions

Groundwater generally appears as either a permanent or temporary water source. Permanent groundwater is generally present year-round, which may or may not be influenced by seasonal and climatic changes. Temporary groundwater water is also referred to as a “perched” water source, which generally develops because of seasonal and climatic conditions.

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The borings were advanced to the required depths using dry drilling techniques to evaluate groundwater conditions at the time of our field program. The boreholes were observed for the presence of groundwater during and after completion of drilling. The water levels observed in the borings can be found on the boring logs in the Exploration Results section of this report and are summarized in the table below.

Boring # Approximate Depth to Water from Existing Grade while Drilling

(feet)

B-21 11

B-26 11

B-27 8

B-28 9

B-53 28

B-54 31

B-57 34

Note: No free water was observed during drilling of the borings not listed here

Seasonal variations such as amount of rainfall and runoff, climatic conditions and other factors generally result in fluctuations of the groundwater level over time. The granular strata can easily transmit water. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The foundation contractor should check the groundwater conditions just before foundation excavation activities.

In addition to observations for water made during the drilling, five 20-foot deep piezometers were installed at the site. Piezometer locations are provided in the table below and illustrated on the exploration plan.

Piezometer Latitude Latitude Ground Surface

Elevation above MSL

P-1 29.47825° -98.41792° 677 feet

P-2 29.47430° -98.41890° 669 feet

P-3 29.47180° -98.41878° 671 feet

P-4 29.47283° -98.41444° 667 feet

P-5 29.47780° -98.41457° 662 feet

Water readings at the piezometers to date are provided below. Two more sets of water readings will be taken at about two week intervals in January 2020. The wells then be will be abandoned

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Date of Reading

Depth of Water (feet)

P-1 P-2 P-3 P-4 P-5

December 13, No water observed

No water observed

No water observed

No water observed

GEOTECHNICAL OVERVIEW

The buildings may be supported by

◼ Shallow grade supported slab with grade beams (Stiffened), or

◼ Structurally suspended slab supported on drilled shafts.

The foundations being considered must satisfy two independent engineering criteria with respect to the subsurface conditions encountered at this site. One criterion is the foundation system must be designed with an appropriate factor of safety to reduce the possibility of a bearing capacity failure of the soils underlying the foundation when subjected to axial and lateral load conditions.

The other criterion is that the movement of the foundation system due to compression

(consolidation or shrinkage) or expansion (swell) of the underlying soils must be within tolerable limits.

Expansion Potential

Expansive soils are present at this site. The near surface, high plasticity fat clay could become unstable with typical earthwork and construction traffic, especially after precipitation events.

Effective drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

Based on our findings, the subsurface soils at this site generally exhibit moderate to high shrink/swell potential in their current condition. Estimated Potential Vertical Rise (PVR) values at the project site are summarized in the table below.

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Building Boring # Approximate Potential Vertical Rise

(inches)

Honor Guard Building B-3 and B-4 5.5

Equipment Storage Building B-53 and B-54 4.5

Material Storage Building B-55 and B-56 4.5

Administration Building Expansion B-57 and B-58 4.0

We estimated the potential shrink/swell at the site using the information from our field and laboratory programs and based on method TEX-124-E of the Texas Department of Transportation

(TxDOT) Manual of Testing Procedures. It can be emphasized that the actual movements could be greater than the values presented in this report because of inadequate drainage, ponded water and moisture infiltration beneath the structures after construction.

This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and (at least minor) cracking in the structure should be anticipated. The severity of cracking and other damage such as uneven floor slabs will probably increase if modification of the site results in excessive wetting or drying of the expansive soils. Eliminating the risk of movement and distress may not be feasible unless the floor slab is suspended and supported by drilled pier foundations.

Therefore, we strongly recommend the floor slabs at the buildings be structurally suspended and supported by drilled pier foundations.

Demolition Considerations

If any existing buildings and sidewalks at this site will be demolished prior to construction work, abandoned (or to be abandoned) underground utilities may be present within the footprint area of the planned structures. Utilities and associated backfill and granular bedding material can provide avenues for subsurface water to enter under the structure subgrade. We recommend that all abandoned utility lines be completely removed from the proposed structure areas. Abandoned pipes which remain underground should be grouted.

Removal of any below-grade foundation or structures will likely create large subsurface voids. It is very important that all subsurface voids formed from the removal of the foundation system be backfill completely with moisture conditioned, compacted, engineered fill as described Earthwork section of this report. It is our experience that improperly backfilled excavations can cause significant settlement under and around the proposed structures.

As an alternative to compacted soil backfill, a flowable fill material may be considered. Flowable fill, or slurry, when properly designed provides a competent subgrade and can still be readily excavated if the utilities require repair or maintenance. In addition, flowable fill does not need to be placed in lifts, compacted, or tested.

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Interaction with Existing Structures

We understand the Administration Building expansion will be connected to the existing building.

The construction of additions to an existing structure can often create a situation that leads to the formation of distress in both structures if both structures are connected to each other. Typically, such distress occurs due to the use of different foundations and different framing stiffness of the structures. These differences often lead to dissimilar performances between the additions and existing structure. Such performance dissimilarities typically manifest themselves as differential movements and can cause significant amount of distress. The risks associated with dissimilar performances between the additions and existing structure may be reduced by adopting the following ways:

◼ Designing the foundation of the addition using the type and geometry similar to the existing foundation system (when appropriate);

◼ Dowel the addition and existing foundations/floor slabs together to prevent differential vertical movements across the joint; and

◼ Constructing an expansion joint between the new and existing structure to allow for differential horizontal movement between the addition and existing structure.

◼ Installing new piers at least 2 pier diameters away from the closest existing piers.

Excavating adjacent to the existing foundation should be performed with care. Excavations adjacent to the existing structure could cause the foundation to become undermined and as a result the foundation or structure could suffer damages. We recommended that the contractor monitor the existing foundation carefully during construction and be prepared to brace the existing foundation if necessary.

EARTHWORK

Earthwork will include clearing and grubbing, excavations, and fill placement. The following sections provide recommendations for use in the preparation of specifications for the work.

Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations.

General Site Preparation

Construction operations may encounter difficulties due to the wet or soft surface soils becoming a general hindrance to equipment due to rutting and pumping of the soil surface, especially during and soon after periods of wet weather. If the subgrade cannot be adequately compacted to

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◼ removal and replacement with select fill;

◼ chemical treatment of the soil to dry and increase the stability of the subgrade; or

◼ drying by natural means if the schedule allows.

Prior to construction, all vegetation, pavements, loose topsoil and any otherwise unsuitable materials should be removed from the construction area. The stripped materials consisting of vegetation and organic materials should be wasted from the site or used to revegetate landscaped areas or exposed slopes after completion of grading operations. Wet or dry material should either be removed, or moisture conditioned and recompacted. After stripping and grubbing, the subgrade should be proof-rolled where possible to aid in locating loose or soft areas. Proof-rolling can be performed with a fully loaded dump truck or comparable pneumatic tired vehicle. Soils that are observed to rut or deflect excessively (typically greater than 1-inch) under the moving load should be undercut and replaced with properly compacted on-site soils. The proof-rolling and undercutting activities should be witnessed by a representative of the Geotechnical Engineer and should be performed during a period of dry weather.

Building Pad Preparation

Average existing grades and planned Finished Floor Elevations (FFEs) within the Honor Guard

Building, Equipment Storage Building, Material Storage Building and Administration Building

Expansion are given in the table below.

Structure

Approximate

Existing

Grade

(feet)

Planned

Finished

Floor

Elevations

(feet)

Finished Building

Pad Elevation 1

(feet)

Honor Guard Building EL. 720.0 feet EL 722.0 feet EL 721.5 feet

Equipment Storage Building EL. 676.0 feet EL 675.6 feet EL 675.1 feet

Material Storage Building EL. 676.0 feet EL 676.6 feet EL 676.1 feet

Administration Building Expansion EL. 677.0 feet EL 677.3 feet EL 676.8 feet

Columbaria2 EL. 672.0 feet EL 672.0 feet EL 671.5 feet file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Fill_Compaction_Requirements

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1/ Assuming a slab thickness of about 6 inches.

2/ FFE of the columbaria is assumed to be at or near existing grades

As previously mentioned, the Potential Vertical Rise (PVR) is about 4 to 5½ inches for the current conditions at the site. Therefore, use of a grade supported slab will entail proper subgrade preparation to reduce expansive soil related movements. These recommendations may change if the FFE changes.

For a structurally suspended slab carried on drilled shafts (with void boxes and/ or crawl space), building pad preparation will not be necessary.

Honor Guard Building Pad (Borings B-3 and B-4)

◼ After completing stripping operations as discussed in the General Site Preparation section, excavate all subgrade in the building area to an elevation of EL. 710.0 feet (about

10 feet excavation). The building pad area is defined as the area that extends at least 5 feet (horizontal) beyond the perimeter of the proposed building or to the outside edge of any movement sensitive flatwork.

◼ After excavating to the depth specified above, the exposed subgrade should be proof rolled with a fully loaded dump truck or comparable pneumatic tired vehicle to evidence any weak yielding zones. A Terracon geotechnical engineer or their representative should be present to observe proof rolling operations.

◼ Over-excavate any confirmed weak yielding zones, both vertically and horizontally, to expose competent soil. The exposed subgrade should be moisture conditioned between

+2 and +6 percentage points of the optimum moisture content and compacted to at least

95 percent of the maximum dry density determined in accordance with ASTM D 698.

◼ Place 11 feet of imported cohesive select fill soil in loose lifts of about 8 inches to achieve an elevation of about EL. 721.0 feet. Each lift should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content and compacted to at least 95 percent of the maximum dry density determined in accordance with ASTM D 698.

◼ Place ½ foot (6 inches) of Granular Select Fill to achieve the proposed FBPE (EL. 721.5 feet). The material should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content, and then compacted to at least 100 percent of the maximum dry density determined in accordance with ASTM D 698. The layer of Granular

Select Fill will help to serve as an all weathering working surface.

◼ If grades are to be raised further, then Granular Select Fill should be used to achieve finished building pad elevation (FBPE).

file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Site_Preparation

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Equipment Storage Building Pad (Borings B-53 and B-54)

◼ After completing stripping operations as discussed in the General Site Preparation section, excavate all subgrade in the building area to an elevation of EL. 667.0 feet (about

9 feet excavation). The building pad area is defined as the area that extends at least 5

◼ Place 7 feet of imported cohesive select fill soil in loose lifts of about 8 inches to achieve an elevation of about EL. 674.0 feet. Each lift should be moisture conditioned between -2

◼ Place a minimum of 1 feet of Granular Select Fill to achieve proposed FBPE (EL. 675.1 of the optimum moisture content, and then compacted to at least 100 percent of the maximum dry density determined in accordance with ASTM D 698. The layer of Granular

Select Fill will help to serve as an all weathering working surface and will also improve the modulus of subgrade reaction that in turn will provide slab support for floor loads.

◼ Please refer to the Floor Slabs Section of this report for options on K values for slab support.

Material Storage Building Pad (Borings B-55 and B-56)

◼ After completing stripping operations as discussed in the General Site Preparation section, excavate all subgrade in the building area to an elevation of EL. 667.0 feet (about

9 feet excavation). The building pad area is defined as the area that extends at least 5 file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Site_Preparation file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Site_Preparation

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◼ Place 8 feet of imported cohesive select fill soil in loose lifts of about 8 inches to achieve an elevation of about EL. 675.0 feet. Each lift should be moisture conditioned between -2

◼ Place a minimum of 1 feet of Granular Select Fill to achieve proposed FBPE (EL. 676.1 of the optimum moisture content, and then compacted to at least 100 percent of the maximum dry density determined in accordance with ASTM D 698. The layer of Granular

Select Fill will help to serve as an all weathering working surface and will also improve the modulus of subgrade reaction that in turn will provide slab support for floor loads.

Building Pad for Administration Building Expansion (Borings B-57 and B-58) section, excavate all subgrade in the building area to an elevation of EL. 668.0 feet (about

9 feet excavation). The building pad area is defined as the area that extends at least 5 file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Site_Preparation

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◼ Place 8 feet of imported cohesive select fill soil in loose lifts of about 8 inches to achieve an elevation of about EL. 676.0 feet. Each lift should be moisture conditioned between -2

◼ Place a minimum of ½ foot (6 inches) of Granular Select Fill to achieve proposed FBPE

(EL. 676.8 feet). The material should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content, and then compacted to at least 100 percent of the maximum dry density determined in accordance with ASTM D 698. The layer of Granular Select Fill will help to serve as an all weathering working surface.

Columbaria (Borings B-44 through B-47) section, excavate all subgrade in the columbaria area to an elevation of EL. 664.0 feet

(about 8 feet excavation). The pad area is defined as the area that extends at least 5 feet

(horizontal) beyond the perimeter of the proposed columbaria or to the outside edge of

+2 and +6 percentage points of the optimum moisture content and compacted to at least file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Site_Preparation

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◼ Place 7 feet of imported cohesive select fill soil in loose lifts of about 8 inches to achieve an elevation of about EL. 671.0 feet. Each lift should be moisture conditioned between -2

◼ Place a minimum of ½ foot (6 inches) of Granular Select Fill to achieve proposed FPE

(EL. 671.5 feet). The material should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content, and then compacted to at least 100 percent of the maximum dry density determined in accordance with ASTM D 698. The layer of Granular Select Fill will help to serve as an all weathering working surface.

finished pad elevation (FPE).

It can be emphasized that the recommendations are based on the current moisture conditions at the site. To maintain the moisture and to protect the soils from further moisture fluctuations, construction should proceed fairly rapidly, and the subgrade soils should not be exposed to the elements for a long period of time.

Details regarding fill materials, placement and compaction are presented in Fill Material Types and Fill Compaction Requirements sections.

Clay Cap- If not covered with concrete flatwork or pavements, the upper 2 feet (clay “cap”) of the

5-foot (horizontal) overbuild should consist of a cohesive clay with a plasticity index greater than

25. The purpose of the clay cap is to reduce the potential for water to infiltrate the building pad causing the subgrade soils to swell. The clay "cap" material should have at least 70 percent by weight passing the No. 200 Sieve and no more that 15 percent by weight retained in the No. 4

Sieve. The clay “cap” may be replaced with concrete flatwork or pavement extending to the edge of the foundation. Properly compacted, this clay layer should help to reduce migration of moisture into the select fill below.

Flatwork

As previously stated, the subgrade soils exhibit Potential Vertical Rise (PVR) that ranges from about 4 inch to 5½ inches for the current conditions at the site. It will be necessary to perform modifications beneath the movement sensitive flatwork to reduce the PVR to a desirable level.

The pad beneath the movement sensitive flatwork should be prepared as described under

Building Pad Preparation section of this report to reduce soil movement. The pad should extend only to the edge of the movement sensitive flatwork. If the flatwork is not prepared as recommended under the Building Pad Preparation section, then movement and cracking should be expected that may result in uneven flatwork which in turn may cause trip hazards, reverse file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Fill_Material_Types file://///sanantonio1/Data/Projects/2018/90185355/Working%20Files/DRAFTS%20(Proposal-Reports-Communications)/90185355%20GRIT.docx%23_Fill_Compaction_Requirements

Responsive ■ Resourceful ■ Reliable 16 surface flow or doors which drag on the flatwork when opened. Consider including the door stoops as part of the building pad to prevent interference with door operations.

Fill Material Types

Earthen materials used for structural and general fill should meet the following material property requirements:

Fill Type 1 USCS Classification Comments

Select fill CL (LL≤40) and (7≤PI≤20) Can be placed at all locations and elevations.

On-Site Soil CH, GC, CL Not to be used as Select Fill.

Granular Select Fill2 See Note 2 -----

1/ Prior to any filling operations, samples of the proposed borrow and on-site materials should be obtained for laboratory moisture-density testing. The tests will provide a basis for evaluation of fill compaction by in-place density testing. A qualified soil technician should perform sufficient in-place density tests during the filling operations to evaluate that proper levels of compaction, including dry unit weight and moisture content, are being attained.

2/ Granular select fill should consist of 2014 TxDOT Item 247, Type A, Grade 1-2 crushed limestone base material.

Plasticity Index (PI) should range from 5 to 15.

Fill Compaction Requirements

Select and general fill should meet the following compaction requirements.

Item Description

Fill Lift Thickness All fill should be placed in thin, loose lifts of about 8 inches, with compacted thickness not exceeding 6 inches.

Compaction of On-Site Soil and Select Fill At least 95 percent of the material’s Standard Proctor maximum dry density (ASTM D 698).

Compaction of Granular Select Fill At least 100 percent of the material’s Standard Proctor maximum dry density (ASTM D 698).

Moisture Content of On-Site Soil Between +2 and +6 percentage points of the optimum moisture content.

Moisture Content of Select Fill and

Granular Select Fill

Between -2 and +3 percentage points of the optimum moisture content.

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Grading and Drainage

Effective drainage should be provided during construction and maintained throughout the life of the new improvements. After pad construction, we recommend verifying final grades to document that effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary, as part of the structure’s maintenance program.

Proper site drainage should be maintained during the entire construction phase so that ponding of surface runoff does not occur and cause construction delays and/or inhibit site access, particularly in cut areas. During construction, it is possible that the surficial soils may become excessively wet as a result of inclement weather conditions. When the moisture content of these clay soils elevates above what is considered to be the optimum range of moisture for compaction operations, they can become difficult to handle and compact. If such conditions create a hindrance to compaction operations or site access, lime or cement may be mixed with these soils to improve their workability. The additive can be mixed as per 2014 TxDOT Item 275 (cement) or 2014

TxDOT Item 260 (lime). The subgrade should be tested for sulfates prior to the use of lime. The purpose of the additive is to dry out the subgrade and improve sire access. The strict requirements for curing and actual quantity of additive can be at the discretion of the contractor. The subgrade, however, should be compacted to at least 95 percent of the maximum dry density as per ASTM

D 698 at moisture contents ranging from +2 to +6 percentage points of the optimum moisture content.

Flatwork and pavements will be subjected to post-construction movement. Maximum grades that are feasible should be used for paving and flatwork to prevent water from ponding. Allowances in final grades should also consider post-construction movement of flatwork, particularly if such movements are deemed critical. Where paving or flatwork abuts the structure, joints should be effectively sealed and maintained to prevent surface water infiltration. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a grade of at least five percent for at least 10 feet from perimeter walls (except in areas where ADA ramps are required; these should comply with state and local regulations).

Backfill against grade beams, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of construction debris to reduce the possibility of moisture infiltration.

Planters and other surface features which could retain water in areas adjacent to the structures should be properly drained, designed, sealed or eliminated. Landscaped irrigation adjacent to the foundation systems should be properly designed and controlled to help maintain a relatively constant moisture content within 5 feet of the structure.

Utility trenches are a common source of water infiltration and migration. Infiltration of water into utility trenches or foundation excavations should be prevented during construction. Utility trenches that penetrate beneath the structure should be effectively sealed to restrict water intrusion and flow through the trenches that could migrate below the pad. We recommend constructing an vacomathij Highlight

Responsive ■ Resourceful ■ Reliable 18 effective clay “trench plug” that extends at least 5 feet out from the face of the building exterior.

The plug material should consist of clay compacted at a water content at or above the soil’s optimum water content. The clay fill should be placed to completely surround the utility line and be compacted in accordance with recommendations in this report. The combination of 10 mil poly and flowable fill backfill can be used in place of a clay plug.

Consideration should be given to the use of utility trenches outside of the building area as interceptor drains. For instance, these excavations can be backfilled near full depth with granular material and sloped to drain into storm sewers or similar outflow areas. In addition, 20 mil PVC vapor barrier (ASTM E 1745 Class A) may be placed on the downhill side (building pad side of the trench). In order to separate granular backfill materials within drainage system and trench backfill materials, geotextiles should be placed or wrapped around drainage system. As a result, some additional “protection” from the negative effects of subsurface water flow may be gained with little extra cost.

Earthwork Construction Considerations

It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of floor slabs. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over, or adjacent to, construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted, prior to floor slab construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local, and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred.

SHALLOW FOUNDATIONS

A stiffened slab on grade foundation may be considered to support the structures at the project site provided the building pad is prepared as per the Building Pad Preparation section. A strip footing may be used to support the columbaria.

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Design Parameters – Slab on Grade Foundation

Parameters commonly used to design this type of foundation are provided on the table below.

The slab foundation design parameters presented in the table are based on the criteria published by the Wire Reinforcement Institute (WRI). These are essentially empirical design methods and the recommended design parameters are based on our understanding of the proposed project, our interpretation of the information and data collected as a part of this study, our area experience, and the criteria published in the WRI design manual.

Conventional Method Parameters Value

Net Allowable Bearing Pressures 1 2,000 psf

Subgrade Modulus (k) 80 pci

Potential Vertical Rise (PVR) 1 to 1½ inches

WRI Method Parameters

Design Plasticity Index (PI) 2 26

Climatic Rating (Cw) 17

Soil – Climate Support Index (1-C) 0.11

We recommend that exterior grade beams be at least 30 inches below the finished exterior grade.

Interior grade beams (if any) should be at least 24 inches below the Finished Floor Elevation

(FFE). These recommendations are for a proper development of bearing capacity for the continuous beam sections of the foundation system and to reduce the potential for water to migrate beneath the slab foundation. These recommendations are not based on structural considerations. Grade beam depths may need to be greater than recommended herein for structural considerations and should be properly evaluated and designed by the Structural

Engineer. The grade beams or slab portions may be thickened and widened to serve as spread footings at concentrated load areas.

For a slab foundation system designed and constructed as recommended in this report, post construction settlements should be less than 1 inch. Settlement response of a select fill supported slab is influenced more by the quality of construction than by soil-structure interaction. Therefore, it is essential that the recommendations for foundation construction be strictly followed during the construction phases of the pad and foundation.

The use of a vapor retarder should be considered beneath concrete slabs-on-grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slabs will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 for procedures and cautions about the use and placement of a vapor retarder.

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Design Parameters – Strip Footing

Allowable bearing pressure along the base of the wall should be 2,000 psf. This bearing pressure includes a factor of safety against a bearing capacity failure of at least 3. Allowable bearing pressures are also based on the bearing surface being comprised of compacted soil that is free and clean of all debris and loose material. To calculate the resistance to sliding, a value of 0.4 should be used as the ultimate coefficient of friction between the footing and the underlying soil or select fill.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction of the

Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable bearing soils are encountered at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. This is illustrated on the sketch below.

Over-excavation for structural fill placement below footings should be conducted as shown below.

The over-excavation should be backfilled up to the footing base elevation, with select fill placed, as recommended in the Earthwork section.

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DEEP FOUNDATIONS

Drilled Shaft Design Parameters

The structures may be supported on straight-sided (non-underreamed) drilled piers. Soil design parameters for the design of drilled shaft foundations are provided in the table below. Due to the presence of gravel zones, underreamed piers are not deemed a viable option at the project site.

The drilled shafts for the Honor Guard Building should be installed to a minimum depth of 25 feet below existing site grades.

Drilled Shaft Design Summary (Honor Guard Building)

Approximate Elevation

(feet)

Allowable Skin Friction 1,3

(psf)

Allowable End Bearing Pressure

EL. 720 – EL. 715 --- ---

EL. 715 – EL. 705 500 ---

EL. 705 – EL. 695 600 ---

EL. 695 – EL. 680 750 10,000

1/ The allowable skin friction values include a factor of safety of 2.

2/ The bearing pressure includes a factor of safety of 3.

3/ Top 5 feet of the soil are considered not to contribute towards side friction due potential separation of the surficial soil due to desiccation and construction disturbance.

The drilled shafts for the Equipment Storage and Material Storage Buildings should be socketed at least 5 feet into the underlying shale.

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Drilled Shaft Design Summary (Equipment Storage and Material Storage Building)

Approximate Elevation

(feet)

EL. 676 – EL. 671 --- ---

EL. 671 – EL. 661 650 ---

EL. 661 – EL. 640 500 ---

EL. 640 – EL. 636 950 18,000

1/ The allowable skin friction values include a factor of safety of 2.

2/ The bearing pressure includes a factor of safety of 3.

3/ Top 5 feet of the soil are considered not to contribute towards side friction due potential separation of the

The drilled shafts for the Administration Building Expansion should be socketed at least 5 feet into the underlying shale.

Drilled Shaft Design Summary (Administration Building Expansion)

Approximate Elevation

(feet)

EL. 677 – EL. 672 --- ---

EL. 672 – EL. 662 350 ---

EL. 662 – EL. 642 500 ---

EL. 642 – EL. 637 1,000 20,000

1/ The allowable skin friction values include a factor of safety of 2.

2/ The bearing pressure includes a factor of safety of 3.

3/ Top 5 feet of the soil are considered not to contribute towards side friction due potential separation of the

The bearing pressures presented in the table assume that the bearing surface will be free and clean of soft or moist material and loose debris. The allowable end bearing and skin friction values presented in this report are based on center-to-center spacing of at least three shaft diameters.

A closer spacing may be considered but it may reduce the axial capacity of the foundation depending on the spacing pattern of the foundations. If a clearance of three diameters cannot be maintained in every case, the above bearing capacities should be reduced by 20 percent. Drilled piers installed at a center-to-center clearance of two diameters or less are not recommended.

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In addition to the axial compressive loads on the piers, these piers will also be subjected to axial tension loads due to the expansive soil conditions and possibly due to other induced structural loading conditions. To compute the axial tension force due to the swelling soils along the pier shaft, the following equation may be used.

Qu = 65•d

Where: Qu = Uplift force due to expansive soil conditions in kips (k) d = Diameter of pier shaft in feet (ft)

This calculated force may be used to compute the longitudinal reinforcing steel required in the pier to resist the uplift force induced by the swelling clays. However, the cross-sectional area of the reinforcing steel should not be less than 1 percent of the gross cross-sectional area of the drilled pier shaft. The reinforcing steel should extend from the top to the bottom of the shaft to resist this potential uplift force.

For the straight-sided drilled piers, the uplift force due to swelling soils and any other axial tension forces due to structural loading conditions can be resisted by the allowable side-shear of the drilled pier. The allowable uplift resistance of the straight sided drilled piers can be evaluated using the following equation:

Qar = 2.6· d · Dp + 0.9Wp + PDL

Where: Qar = Allowable uplift resistance of pier in kips (k) d = Diameter of pier shaft in feet (ft)

Dp = Anchorage length which is the pier length minus the upper

15 feet of shaft in contact with the soil in feet (ft)

Wp = Weight of the drilled pier in kips (k)

PDL = Permanent sustained dead Load acting on the drilled pier in kips (k)

Total settlements, based on the indicated bearing pressures, should be approximately ¾ inch or less for properly designed and constructed drilled piers. Differential settlement may also occur between adjacent piers. The amount of differential settlement could approach 50 to 75 percent of the total pier settlement. For properly designed and constructed piers, differential settlement between adjacent piers is estimated to be less than ½ of an inch. Settlement response of drilled piers is impacted more by the quality of construction than by soil-structure interaction.

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Improper pier installation could result in differential settlements significantly greater than we have estimated. In addition, larger magnitudes of settlement should be expected if the soil is subjected to bearing pressures higher than the allowable values presented in this report.

Drilled Shaft Construction Considerations

The pier excavations should be augered and constructed in a continuous manner. Steel and concrete should be placed in the pier excavation immediately following drilling and evaluation for proper bearing stratum, embedment, and cleanliness. In no circumstances should the pier excavation remain open overnight. Due to the presence of dense Gravel and strong Shale zones, high powered, high torque rock excavation equipment will be necessary.

Due to the presence of subsurface water and some gravel layers, we recommend that the foundation contractor be prepared to control sloughing of the excavation sidewalls or control water seepage into the pier excavations should they occur. Prior to any excavation, the foundation contractor should verify the subsurface water levels.

Two (2) methods to control sloughing and water seepage include the use of casing and slurry displacement. The casing and slurry methods are discussed in the following paragraphs.

Casing Method - Casing will provide stability of the excavation walls and will reduce water influx; however, casing may not completely eliminate subsurface water influx potential. In order for the casing to be effective, a “water tight” seal must be achieved between the casing and surrounding soils.