Geotechnical Engineering Report - Brooks · This revised geotechnical engineering report has been prepared for the design and construction of a single story veterinary clinic, being

Revised Geotechnical Engineering Report

Brooks Veterinary Clinic City Base Landing Road and Goliad Road

San Antonio, Texas

Prepared for: Brooks Development Authority

San Antonio, Texas

Prepared by: Drash Consultants, LLC

San Antonio, Texas September 22, 2015

Drash Project No. 115G1063.02

TABLE OF CONTENTS

Page EXECUTIVE SUMMARY ........................................................................................................... i INTRODUCTION ...................................................................................................................... 1

Authorization ................................................................................................................. 1

Purpose and Scope of Services .................................................................................... 1

PROJECT INFORMATION ....................................................................................................... 1 SITE AND SUBSURFACE CONDITIONS ................................................................................ 2

Site Conditions .............................................................................................................. 2

Subsurface Conditions .................................................................................................. 2

Subsurface Stratigraphy ............................................................................................................ 2 Subsurface Water ...................................................................................................................... 3

GEOTECHNICAL RECOMMENDATIONS AND GUIDELINES ................................................ 3 Slab Foundation ............................................................................................................ 3

Lateral Earth Pressures ................................................................................................ 6

Seismic Design Considerations ..................................................................................... 8

Soil Corrosivity .............................................................................................................. 8

Landscape Design ........................................................................................................ 9

Drainage Adjacent To Structure .................................................................................... 9

Utility Trenches .......................................................................................................................... 9

Earthwork .................................................................................................................... 10

Building Pad Preparation .........................................................................................................11 Clay Cap ..................................................................................................................................13 Bathtub Condition ....................................................................................................................13 Fill Materials and Placement ....................................................................................................13

Pavements .................................................................................................................. 15

Pavement Sections ..................................................................................................................15 Pavement Section Materials ....................................................................................................16

INTERPRETATION OF REPORT ........................................................................................... 18 CONSTRUCTION MONITORING AND TESTING .................................................................. 18 LIMITATIONS OF REPORT ................................................................................................... 18 EXHIBITS

Exhibit 1 Project Location Map Exhibit 2 Boring Location Plan Exhibit 3 Log of Boring

APPENDIX – FIELD AND LABORATORY Exploratory Drilling Program Laboratory Testing Program Notes Regarding Soil and Rock

Drash Project No. 115G1063.02 Brooks Veterinary Clinic i

EXECUTIVE SUMMARY

This revised geotechnical engineering report has been prepared for the design and construction of a single story veterinary clinic, being referred to as the Brooks Veterinary Clinic (Project). The building site was moved to an adjacent lot. The Project is currently located on approximately 0.27 acres on the north side of City Base Landing Road, approximately 800 feet west of its intersection with Goliad Road, southwest of the Holiday Inn Express in San Antonio, Texas. Based on the information provided to us for this study and from data developed as part of our engineering service, the site is suitable for the planned improvements. A general summary of our findings, conclusions, and recommendations with regard to the geotechnical engineering aspects of the Project are provided below:

• Subsurface conditions consist of fat clay underlain by lean clay.

• Key design information is as follows:

o The subsurface stratigraphy exhibits a moderate to high potential for volume changes (expansion and contraction) with fluctuations in its moisture content.

o A grade supported slab foundation system may be used to support the veterinary clinic.

o Grade beams shall bear at least 18 inches below the exterior grade. Grade beams may be sized for an allowable total load bearing pressure of 3,000 psf (pounds per square foot) or an allowable dead plus gravity live load bearing pressure of 2,000 psf.

o The estimated settlement beneath the foundation units, provided proper and quality construction is performed, is estimated to be less than ½ inch.

• Pavement recommendations are provided for both asphalt and concrete sections.

This summary is provided for convenience only. For those individuals and entities that may need more details or technical information from this report for their use, it must be read in its entirety to have an understanding of the information and recommendations provided for the Project.

Drash Project No. 115G1063.02 Brooks Veterinary Clinic 1

REVISED GEOTECHNICAL ENGINEERING REPORT BROOKS VETERINARY CLINIC

CITY BASE LANDING ROAD AND GOLIAD ROAD SAN ANTONIO, TEXAS

INTRODUCTION

Drash Consultants, LLC (Drash) is pleased to submit this revised geotechnical engineering report for the design and construction of a single story veterinary clinic, being referred to as the Brooks Veterinary Clinic (Project). The building site was moved to an adjacent lot. The Project is currently located on approximately 0.27 acres on the north side of City Base Landing Road, approximately 800 feet west of its intersection with Goliad Road, southwest of the Holiday Inn Express in San Antonio, Texas. The proposed structure is expected to have footing loads in the range of 100 kips and/or 1.5 kips per linear foot, approximately half of which is sustained load.

Authorization

This Project was authorized by Mr. Leo Gomez with Brooks Development Authority by issuance of BDA purchase order number 10497, Task oder number 002, on August 28, 2015. The scope of services was defined in Drash Proposal No. PG1151072.01, dated August 21, 2015.

Purpose and Scope of Services

The purposes of this engineering service were to evaluate the general subsurface conditions (soil, rock, subsurface water) within the Project limits by drilling exploratory boring, conduct tests on samples recovered during drilling of the exploratory boring, analyze and evaluate the test data, perform engineering analyses using the data analyzed and evaluated from the field and laboratory programs to develop geotechnical engineering recommendations and guidelines with respect to:

• Site conditions as applicable; • Earthwork as applicable;

• Subsurface Stratigraphy; • Foundation design and construction;

• Subsurface water conditions; • Estimate of foundation settlement; and

• Potential for soil expansion-contraction; • Pavement recommendations; The scope of services was performed in general accordance with Exhibit A of our Agreement for Services.

PROJECT INFORMATION

The following information was provided to us by the Client, design professionals working on the Project, or was collected by our firm:


Project Location

The Project is located on approximately 0.27 acres on the north side of City Base Landing Road, approximately 800 feet west of its intersection with Goliad Road, southwest of the Holiday Inn Express in San Antonio, Texas. The general vicinity of the Project is illustrated on Exhibit 1, the Project Location Map.

Project The project will involve design and construction of a single story veterinary clinic.

Current Site Conditions The Project site is currently an undeveloped tract of land with vegetation and brush across the site.

Current Topography Based on our visual observations, the site appeared to be relatively flat and level.

Proposed Topography

Proposed grades and the finished floor elevations (FFE) were not available to us at the time this report was prepared. For our recommendations, we have assumed that the FFE is near the existing grade. Drash should be contacted to re-evaluate the recommendations, once the FFE becomes available.

SITE AND SUBSURFACE CONDITIONS

Site Conditions

The site, as noted previously, is on an undeveloped tract of land with vegetation and brush across the site. Based on visual observations, there were no noticeable or obvious conditions within the site that would affect the geotechnical engineering aspects of this Project.

Subsurface Conditions

Subsurface conditions within the Project limits were evaluated by drilling exploratory boring at the location shown on Exhibit 2, the Bore Location Plan. Information retrieved from the exploratory boring is summarized herein.

Subsurface Stratigraphy Subsurface stratigraphy, based on the exploratory boring, can be generalized as follows:

Layer Identification

Approximate Depth To and Thickness Of

Layer (feet) Description of Layer

Layer 1 0 to 4½ FAT CLAY (CH); dark brown; very stiff with gravel and roots in the upper 2 feet.

Layer 2 4½ to 15 LEAN CLAY (CL); dark brown to tan; very stiff and hard; with interbedded calcium deposits.

The log of boring, presenting more specific information about the subsurface stratigraphy encountered at each exploratory boring location, is provided in the Exhibits section of this report.


Subsurface Water Subsurface water was not encountered during drilling or upon completion of the exploratory boring below existing ground surface (ground surface at the time of our field activities). The exploratory boring was then backfilled with the spoils generated during drilling operations. Subsurface water is generally encountered as a ‘true’ or permanent water source or as a ‘perched’ or temporary water source. Permanent subsurface water is generally present year round, which may or may not be influenced by seasonal and climatic changes. Temporary subsurface water generally develops as a result of seasonal and climatic conditions. Based on the planned development, subsurface water is not expected to affect or impact the planned construction activities.

GEOTECHNICAL RECOMMENDATIONS AND GUIDELINES

Based on the information provided to us by the Client and Project Team, our exploratory boring drilled at the site, results of laboratory tests performed on samples recovered during the subsurface exploration program, and our engineering analyses, the following statements can be made regarding the Project site:

• The site is suitable for the planned construction.

• The subsurface stratigraphy exhibits a moderate to high potential for volume changes (expansion and contraction) with fluctuations in its moisture content.

• A grade supported slab foundation system may be used to support the veterinary clinic.

• Both flexible (asphaltic concrete overlying granular base) and rigid (reinforced concrete) pavements can be used.

The foundations being considered must be designed to reduce the possibility of soil failure when subjected to axial and lateral load conditions. The foundations must also be designed so that foundation movements, whether vertical, horizontal or rotational, are within allowable limits of the soil and within design and operational limits of the proposed structures. The following geotechnical recommendations and guidelines have been prepared based on the data collected or developed during this Project, our experience with similar projects, and our knowledge of sites with similar surface and subsurface conditions.

Slab Foundation

As noted previously, the subsurface soils exhibit a moderate to high potential to undergo expansion and contraction with fluctuations in their moisture contents. Based on our calculations, the subsoils at this site may yield a Potential Vertical Rise (PVR) of about 2 inches. The actual movement could be greater if inadequate drainage or other sources of water are allowed to infiltrate beneath the structure after construction. Recommendations for this foundation type are presented below.


Monolithic Slab with Interior Grade Beams. If the building subgrade and fill pad are prepared for a design PVR of about 1 inch as specified in Option 1 of the Building Pad Preparation section of this report, the slab foundation may be designed in accordance with Chapter 18, Section 1808.6.1 and 1808.6.2 of the 2015 International Building Code (IBC). The slab foundation would consist of perimeter and interior concrete grade beams poured monolithic with the floor slab. Design parameters are provided below for the appropriate slab foundation design method.

Option 1: PTI (Post Tensioning Institute) Method: 3rd Edition1, 2, 3, 4, 7, 8

Edge Moisture Variation Distance (em): Center Lift (ft): 9.0

Edge Lift (ft): 4.7 Maximum Unrestrained Differential Soil Movement or Swell (ym):

Center Lift (in): 1.0 Edge Lift (in): 1.2

Coefficient of Slab-Subgrade Friction (µ): 0.75 Net Allowable Bearing Pressures6:

Total Load Conditions (psf): 3000 Dead Load Plus Gravity Live Load Conditions (psf): 2000

Maximum Allowable Deflection Ratio of Foundation Beam: 1/360

Option 1: CRSI (Concrete Reinforcing Steel Institute) Method 1, 2, 3, 4, 8

Net Allowable Bearing Pressures6 Total Load Conditions (psf): 3000

Dead Load Plus Gravity Live Load Conditions (psf): 2000 Maximum Allowable Deflection Ratio of Beam Footing: 1/360

Subgrade Modulus, k (pci): 50

Option 1: WRI (Wire Reinforcement Institute) Method 1, 2, 3, 4, 8

Design Plasticity Index5: 38 Climatic Rating (Cw): 16

Soil Climate Support Index (1-C): 0.25 Site Slope (%): 0

Soil Unconfined Compressive Strength, qu (tsf) : 1.0 Net Allowable Bearing Pressures6:

Total Load Conditions (psf): 3000 Dead Load Plus Gravity Live Load Conditions (psf): 2000

Maximum Allowable Deflection Ratio of Foundation Beam: 1/360

Monolithic Slab Without Grade Beams. If the building subgrade and fill pads are prepared for a ½-inch PVR as recommended in Option 2 of the Building Pad Preparation section of this Report, the slab foundation may be designed in accordance with Chapter 18, Section 1808.6.3 of the 2015 IBC manual. The slab foundations would essentially consist of a perimeter concrete grade beam that is structurally tied to a concrete floor slab of uniform


thickness (no interior grade beams). At concentrated loads, the grade beams or floor slab sections may be thickened or widened to carry the applied load. The uplift loads can be resisted by the weight of the beam or the floor slab. The grade beam or floor slab sections may be thickened to increase the resistance to the uplift loads. Design parameters are provided below for the appropriate slab foundation design method.

Option 2: Slab Design Parameters 1, 3, 4, 8

Net Allowable Bearing Pressures6: Total Load Conditions (psf): 3000

Dead Load Plus Gravity Live Load Conditions (psf): 2000 Maximum Allowable Deflection Ratio of Foundation Beam: 1/360

Subgrade Modulus, k (pci): 100 Slab Foundation Design Notes. The following notes apply to the slab foundation design methods presented in the previous two subsections.

1 Design parameters are based on preparing the subgrade and constructing a building pad as recommended in Option 1 or 2 of the Building Pad Preparation section of this report.

2 This is essentially an empirical design method 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, PTI, and CSRI design manuals.

3 The width of grade beams should not be less than 12 inches. The bearing depth below final grade should not be less than 18 inches for grade beams. These foundation dimension recommendations are for proper development of bearing capacity for the foundations and to reduce the potential for water to migrate beneath the foundation. These recommendations are not based on structural considerations of the applicable design method. Actual foundation depths and widths may need to be greater than the minimum recommended herein for structural considerations, which should be properly evaluated and designed by the Structural or Foundation Engineer.

4 If the floor slab of the foundation is to be covered with wood, vinyl tile, carpet, or other moisture sensitive or impervious coverings, a vapor barrier should be placed beneath concrete slab foundations or concrete floor slabs if they are bearing directly on the ground. The designer should be familiar with the American Concrete Institute (ACI) 302 for procedures and cautions about the use and placement of a vapor barrier.

5 Based on the weighted average method for a depth of 15 feet. 6 Includes a factor of safety (FS) of at least 2 for total load conditions and at least 3 for dead load plus gravity

live load conditions. 7 According to the PTI 3rd Edition, once the foundation plan has been determined, the Shape Factor (SF)

shall be calculated. If the SF exceeds 24, the designer should contact us to discuss additional geotechnical engineering recommendations to reduce the ym and em values to recommended values.

8 The estimated settlement beneath the foundation units, provided proper and quality construction is performed, is less than 1 inch.

Foundation Construction Considerations. Excavations for the foundations shall be neat excavated with a smooth-mouthed bucket. If a toothed bucket is used, excavation with this bucket should be stopped 6 inches above the final foundation bearing elevation and the foundation excavation completed with a smooth-mouthed bucket or by hand labor. Debris in the bottom of the foundation excavation should be removed prior to steel placement.


The foundation excavations should be sloped sufficiently to create internal sumps for runoff collection and removal of water. If surface runoff water or subsurface water seepage in excess of 1 inch accumulates at the bottom of the foundation excavation, it should be collected and removed so that the ponding water does not adversely affect the quality of the foundation bearing surface. Special care should also be taken to protect the exposed foundation bearing soils from being disturbed or drying out prior to placement of the concrete.

Lateral Earth Pressures

Presented below are at-rest and active earth pressure coefficients and equivalent fluid pressures for various backfill types that may be used to design retaining walls and below grade walls at this site.

Active earth pressures should be used for the site retaining walls since the top of the site retaining walls will not be restrained from horizontal movement. If the below grade walls are restrained along the top from lateral movement; the walls should be designed for “at-rest” earth pressure conditions.

LATERAL EARTH PRESSURE DESIGN CRITERIA

LATERAL EARTH COEFFICIENT FOR

BACKFILL TYPE

EQUIVALENT FLUID DENSITY (pcf)

SURCHARGE PRESSURE, p1

(psf)

EARTH PRESSURE, p2 (psf)

Active (ka) Sand - 0.33 41 (0.33)S (41)H

Gravel - 0.28 35 (0.28)S (35)H On-Site Soil - 0.59 71 (0.59)S (71)H

At-Rest (ko) Sand - 0.50 63 (0.50)S (63)H

Gravel - 0.44 55 (0.44)S (55)H On-Site Soil - 0.74 89 (0.74)S (89)H


A passive equivalent fluid density of 180 pcf may be used for site retaining walls or bearing in soil or compacted fill material. Applicable conditions to the above table include:

• For active earth pressure, the retaining wall must rotate about its base, with top lateral movements of about 0.002 H to 0.004 H, where H is retaining wall height.

• To develop the passive pressure, the retaining wall shall be allowed a movement of 0.005T (T is the thickness of the retaining wall footing plus thickness of the key, if any).

The passive pressure should be neglected in the upper 12 inches below the ground surface in front of the retaining wall footing.

• The passive pressure will be less for a sloped ground surface in front of the retaining wall. If slopes are planned in front of the retaining wall, we should be consulted to provide lower passive pressures than provided above.

• Uniform surcharge, S, should be included where applicable.

• For on-site soil and soil backfill, use a maximum total unit weight of 120 pcf.

• For sand and gravel soil backfill, use a maximum total unit weight of 125 pcf.

• Compact horizontal backfill between 95 and 98 percent of the maximum dry density in accordance with the standard compaction effort.

• The earth pressure criteria presented in the table do not include:

o Hydrostatic conditions developing behind the retaining wall.

o Surcharge loading from compaction equipment and floor slabs.

o A factor of safety.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out from the base of the retaining wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively. Granular backfill should consist of free-draining sand or gravel. The sand should have 100 percent passing the No. 16 sieve and not more than 5 percent passing the No. 200 sieve. The gravel should consist of a washed, evenly graded mixture of crushed stone, or crushed or uncrushed gravel with 100 percent passing the 1½-inch sieve and not more than 5 percent passing the No. 4 sieve. Lean clay backfill should have a plasticity index (PI) equal to or less than 20 percent. Clayey soils with a PI exceeding 20 percent should not be considered for use as retaining wall backfill. To calculate the resistance against sliding, a value of 0.50 should be used as the ultimate coefficient of friction between the footing and the underlying soil. A maximum footing bearing capacity of 2,000 psf should be considered for a footing bearing in soil at least 18 inches below


finished grade. All retaining walls should be checked against failure due to overturning, sliding, and overall global stability. Such an analysis can only be performed once the dimensions of the retaining wall are known. Drash can provide this analysis upon request. Drash also provides design services for concrete retaining walls and MSE retaining walls. A drain is recommended for collection and removal of surface water percolation or subsurface water along the base of any site retaining walls or split level walls. In general, drains should consist of at least a 2-foot thick section of free-draining sand or gravel (as previously described) immediately behind the site retaining wall or split level locations. The free-draining material should be wrapped in a geotextile filter fabric. A slotted or perforated PVC pipe should be situated at the base of the 2-foot section and be sloped to drain to a sump or other appropriate outlet such as weep holes. In unpaved areas, to reduce the chances for surface water infiltration into retaining wall drains or retaining wall backfill, the final 24 inches of backfill for retaining walls should preferably consist of cohesive lean clay soil having a PI between 15 and 25 percent. This will help to reduce percolation of surface water into the backfill.

Seismic Design Considerations

Presented below are the seismic design criteria for the Project site and immediate area.

Description Value 2015 International Building Code Site Classification (IBC) 1 D2

Site Latitude 29.3460○

Site Longitude -98.4294○

Maximum Considered Earthquake 0.2 second Design Spectral Response Acceleration (SDS) 0.092

Maximum Considered Earthquake 1.0 second Design Spectral Response Acceleration (SD1) 0.048 1 The site class definition was determined using SPT N-values in conjunction with Table 1613.3.2 in

the 2015 IBC. The Spectral Acceleration values were determined using publicly available information provided on the United States Geological Survey (USGS) website. The above criteria can be used to determine the Seismic Design Category using Tables 1613.5.6 (1) and 1613.5.6 (2) in the 2015 IBC.

2 Note: Chapter 20 of ASCE 7 requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope does not include the required 100-foot soil profile determination. The boring extended to a maximum depth of 15 feet, and this seismic site class definition considers that hard soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration.

Soil Corrosivity

Laboratory testing was conducted on a soil sample recovered from the boring to assess the corrosivity risk of the soils at the boring locations. The soil sample was submitted to an analytical lab to determine the sulfate content. The result of the laboratory test is provided below.


Summary of Laboratory Sulfate Tests

Boring No. Sample Depth (ft) Sulfate (ppm)

B-2 2½ to 4 198

According to the 2015 IBC, concrete that will be exposed to sulfate-containing solutions should be designed in accordance with ACI 318. The sulfate test results indicate that the sulfate exposure levels are low. Therefore, Type II cement may be used at this site.

Landscape Design

We realize that landscaping is vital to the aesthetics of any project. The Project Owner and Project Design Team, particularly the Architect and Landscape Architect, should be made aware that placing large bushes and trees adjacent to the structure may contribute to future distress to the foundation system and structure. Vegetation placed in landscape beds that are adjacent to the structure should be limited to small plants and shrubs that will not exceed a mature height of about 4 feet and that are not ‘water demanding’. Large bushes and trees that will generally exceed 4-foot heights should be planted at a distance away from the structure so that their canopy or ‘drip line’ does not extend to the structure’s perimeter when the tree reaches maturity. Plants and shrubs that are ‘water hungry’ should not be planted within 5 feet of the structure. Watering of vegetation, particularly landscape beds adjacent to the structure should be performed in a timely and controlled manner. Excessive watering, as well as no consistent watering, should be avoided.

Drainage Adjacent To Structure

The performance of the foundation system for the proposed structure will not only be dependent upon the quality of construction but also upon the stability of the moisture content of the soils underlying the foundation. The Project Civil Engineer should design final site grades so that there is positive surface drainage away from the structure. Post-construction accumulation or ponding of surface runoff near structures must be avoided.

Utility Trenches Various utilities will be installed at the Site. The utilities may include sanitary sewer lines, storm drainage (i.e., sewer lines, concrete drainage channels, culverts, etc.), electrical lines, gas lines, and telecommunication lines. Installation of these utilities should conform to the applicable specifications of the utility entity. Utilities such as telecommunications, small water lines, or sanitary sewer laterals, should meet the following minimum installation guidelines:

• The bottom of the utility trench excavation should be clean of loose soils and debris prior to placement of the utility pipe or cable.

• Backfill above the utility pipe or cable should be as follows:


o Traversing Non-Pavement or Non-Load Bearing Areas

The backfill soils may be the excavated soils.

Place the backfill soils in loose lifts not to exceed 8 inches in thickness to achieve compaction thickness no greater than 6 inches.

Add water as applicable so that the soil moisture content after compaction is between -2 and +3 percent of optimum moisture content.

Compact the backfill soil lift to at least 95 percent of standard moisture-density relationship (ASTM D 698).

o Traversing Pavement or Load Bearing Areas

Place 12 inches of backfill soils, which may be the excavated soils, above the utility pipe or cable. The backfill soils should be placed as follows:

• Place the backfill soils in loose lifts not to exceed 8 inches in thickness to achieve compaction thickness no greater than 6 inches.

• Add water as applicable so that the soil moisture content after compaction is between -2 and +3 percent of optimum moisture content.

• Compact the backfill soil lift to at least 95 percent of standard moisture-density relationship (ASTM D 698).

Place flowable fill in the utility trench, terminating at a depth to accommodate the applicable pavement section or slab.

The flowable fill should have a 28-day compressive strength between 25 and 100 psi.

Earthwork

Recommendations and guidelines for general site preparation, building pad preparation, and placement of fill soils at the Project site are discussed in this section. The recommendations presented for design and construction of earth supported elements including foundations and floor slabs are contingent upon following the recommendations and guidelines outlined in this section. Earthwork on the Project should be evaluated by our firm. The evaluation of earthwork should include observation and testing of all fill soils placed at the site, subgrade preparation beneath buildings and pavements, and any load-bearing requirements within the Project. The contractor or its applicable subcontractor(s) are responsible for designing and constructing stable, temporary excavations, as required to maintain stability of both the excavation sides and bottom. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards.

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 minimum densities as described in the Fill Materials and Placement section of this report, one of the following measures may be required:

• 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.

In our experience with similar soils in this area, chemical treatment may be an effective method to increase the supporting value of wet and weak subgrade. Drash should be contacted for additional recommendations, if chemical treatment of the soils is needed. Prior to placing any fill, all vegetation, 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. Presented below are building pad preparation recommendations for the building.

Building Pad Preparation Proposed grades and the finished floor elevations (FFE) were not available to us at the time this report was prepared. For our recommendations, we have assumed that the FFE is near the existing grade. Drash should be contacted to re-evaluate the recommendations, once the FFE becomes available.

The subsurface soils at this site generally exhibit a moderate to high potential to undergo expansion and contraction during fluctuations in their moisture contents. Based on the information developed from our field and laboratory programs, we calculate that the subgrade soils at this site may yield a PVR of about 2 inches. However, the actual PVR could be greater than calculated, if inadequate drainage or other sources of water are allowed to infiltrate beneath the structures during and after construction.

As noted previously, the slab foundation may be designed in accordance with 2015 IBC Sections 1808.6.1 or 1808.6.2 if the PVR is 1 inch or less (Option 1), or Section 1808.6.3 if the PVR is ½-inch or less (Option 2). The foundation design will depend on the building subgrade and pad preparation option selected below.

Option 1: Excavation & Replacement with Select Fill (1 inch PVR)

• Strip vegetation, loose topsoil and any otherwise unsuitable materials from the building area. The building area is defined as the area that extends at least 3 feet (horizontal) beyond the perimeter of the proposed building and any adjacent flatwork.

• After stripping, excavate the subgrade at least 3 feet below the slab from the building pad area and remove it from the site.


• Before placing any fill, the exposed subgrade in the building area should be proofrolled with at least a 20-ton roller, or equivalent equipment, to evidence any weak yielding zones. A technical representative of our firm should be present to observe proofrolling operations. If any weak yielding zones are present, they should be over excavated, both vertically and horizontally, to expose competent soil. The excavated soil can be used to restore grade provided that the material is relatively free and clean of deleterious material or materials exceeding 3 inches in maximum dimension.

• After proofrolling and replacing any weak yielding zones, scarify the exposed subgrade an additional 6 inches, moisture condition the soils and compact to at least 95 percent of the maximum dry density determined in accordance with the Standard effort (ASTM D 698). The exposed subgrade should be moisture conditioned between optimum and +4 percentage points of the optimum moisture content.

• Select fill should then be placed to achieve the finished building pad elevation (FBPE). Recommendations for select fill are included in the Fill Materials and Placement section of this report.

• To provide uniform slab support and create a more all-weather working surface, we recommend constructing the final 6 inches of the building pad with granular select fill. The granular select fill should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content, and then compacted to at least 95 percent of the maximum dry density determined in accordance with ASTM D 698. Recommendations for granular select fill are included in the Fill Materials and Placement section of this report.

• A clay cap should be installed as described in the Clay Cap section of this report.

Option 2: Excavation & Replacement with Select Fill (½ inch PVR)

• Strip vegetation, loose topsoil and any otherwise unsuitable materials from the building area. The building area is defined as the area that extends at least 3 feet (horizontal) beyond the perimeter of the proposed building and any adjacent flatwork.

• After stripping, excavate the subgrade at least 5 feet below the slab from the building pad area and remove it from the site.

• Before replacing the stockpiled soil, the exposed subgrade in the building area should be proofrolled with at least a 20-ton roller, or equivalent equipment, to evidence any weak yielding zones. A technical representative of our firm should be present to observe proofrolling operations. If any weak yielding zones are present, they should be over excavated, both vertically and horizontally, to expose competent soil. The excavated soil can be used to restore grade provided that the material is relatively free and clean of deleterious material or materials exceeding 3 inches in maximum dimension.


• After proofrolling and replacing any weak yielding zones, scarify the exposed subgrade an additional 6 inches, moisture condition the soils and compact to at least 95 percent of the maximum dry density determined in accordance with the Standard effort (ASTM D 698). The exposed subgrade should be moisture conditioned between optimum and +4 percentage points of the optimum moisture content.

• Select fill should then be placed to achieve the FBPE. Recommendations for select fill are included in the Fill Materials and Placement section of this report.

• To provide uniform slab support and create a more all-weather working surface, we recommend constructing the final 6 inches of the building pad with granular select fill. The granular select fill should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content, and then compacted to at least 95 percent of the maximum dry density determined in accordance with ASTM D 698. Recommendations for granular select fill are included in the Fill Materials and Placement section of this report.

• A clay cap should be installed as described in the Clay Cap section of this report.

Clay Cap If not covered with concrete flatwork or pavements, the final 2 feet of the 3-foot (horizontal) building pad overbuild should consist of a cohesive clay with a plasticity index (PI) between 18 and 25 percent. The 2-foot ‘clay cap’ should have at least 70 percent by weight passing the No. 200 Sieve and no more than 15 percent by weight retained on the No. 4 Sieve. The on-site CH and CL soils do not meet the above requirements. The clay cap may be replaced with concrete flatwork or pavement extending to the edge of the foundation. Properly compacted, this clay cap should help to reduce migration of moisture into the select fill below. The clay cap should be placed and compacted as noted in the following section.

Bathtub Condition Please be aware that select granular fill should only be used for the final 6 inches of the building pad. Excavation and replacement of expansive soils with granular fill may cause water to collect within the building pad. Any water migrating into a granular fill building pad is often confined by the less permeable clay soils that surround the bottom and perimeter sides of the building pad. Since this water has no way to drain out of the building pad, its only escape is to be absorbed by the surrounding clay soils. The result of this collected water within a building pad is commonly referred to as a ‘bathtub’ condition. This collected water results in a moisture increase of the clay soils, which results in a volume change (expansion) or weakening of the clay soils. This expansion or weakening generally results in foundation movements, which can lead to foundation and superstructure distress. Thus, only select clay fill or moisture conditioned on-site soils should be used to construct the building pad.

Fill Materials and Placement Unless noted otherwise in another section of this report, select fill should meet the following criteria.


Specification for Fill Materials

Fill Type USCS Classification Acceptable Location for Placement

Granular Select Fill 1 Varies All locations

Select Fill 2 CL All locations

On-Site Soils CL and CH

The on-site CH and CL materials do not meet select fill specifications. Unless noted otherwise in this Report, on-site material can only be used for grade adjustments within pavements, general, non-structural and common areas. Otherwise it should be removed from the site.

1 Granular Select Fill shall meet one of the following criterion: • Crushed stone (limestone) meeting Type A, Grades 1, 2, or 3 of the 2004 TxDOT Standard

Specifications for Construction and Maintenance of Highways, Streets, and Bridges. Designation as a GC or GM in accordance with the Unified Soil Classification System (USCS).

• Crushed or uncrushed gravel meeting Type B, Grades 1, 2, or 3 of the 2004 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges. Designation as a GC or GM in accordance with the USCS.

• Crushed concrete meeting Type D, Grades 1, 2, or 3 of the 2004 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges. Designation as a GC or GM in accordance with the USCS.

• Clayey gravel (may locally be referred to as “pit-run” material) or caliche having no particle sizes greater than 3 inches in any dimension, at least 50 percent of total material retained on the No. 200 sieve, a Liquid Limit (LL) no greater than 40, and a Plasticity Index (PI) between 7 and 20. Designation as a GC in accordance with the USCS.

• Commercial Grade Base (may locally be referred to as “three-quarters to dust” material) that is produced by some local/regional quarries having nothing retained on the 2 inch sieve, at least 60 percent retained on the No. 40 sieve, at least 80 percent retained on the No. 200 sieve, an LL no greater than 30, and a PI of 7 or less. Designation as a GM in accordance with the USCS.

• Clayey sand or silty clayey sand (may locally be referred to as “pit-run” material) having no particle sizes greater than 3 inches in any dimension, at least 50 percent of total material retained on the No. 200 sieve, an LL no greater than 40, and a PI between 7 and 20. Designation as an SC in accordance with the USCS.

• Silty sand or sand-silt mixtures having at least 50 percent of total material retained on the No. 200 sieve, an LL no greater than 30, and a PI of 7 or less. Designation as a SM in accordance with the USCS. Please note that this material is sensitive to moisture induction, which may create placement and compaction difficulties.

2 Select Fill: Lean clay having no more than 70 percent of total material retained on the No. 200 sieve, a LL no greater than 40, a PI between 10 and 20, and no more than 15 percent by weight retained on the No. 4 sieve. Designation as a CL in accordance with the USCS.

3 Fill, whether select or non-select, that is being placed in a controlled and compacted manner shall meet one of the above specifications, be free of debris (i.e. trash, rubble, organic materials, vegetation, roots), have no particles exceeding 3 inches in maximum dimension.

Prior to any filling operations, samples of the fill materials, whether select or non-select, to be used for construction shall be submitted for approval, which will include performing laboratory tests to verify compliance to the above specifications.


Placement and Compaction Requirements for Fill Materials

Item Description

Fill and Backfill Lift Thickness All fill and backfill, select and non-select, should be placed in thin, loose lifts not to exceed 8 inches, with compacted thickness of about 6 inches.

Moisture Content and Compaction of Select Fill and Select Backfill – all applications

95 percent of the maximum dry density as determined by the Standard effort (ASTM D 698); the materials should be moisture conditioned between -2 and +3 percentage points of the optimum moisture content.

Moisture Content and Compaction of On-Site Soils

95 percent of the maximum dry density as determined by the Standard effort (ASTM D 698); the on-site materials should be moisture conditioned between optimum and +4 percentage points of the optimum moisture content.

Pavements

Both flexible and rigid pavement systems will be used for driveways and parking. Based on our knowledge of the Project, we anticipate that traffic loads will be produced primarily by automobile traffic and occasional delivery and trash removal trucks.

Pavement Sections The flexible pavement section was designed in general accordance with the National Asphalt Pavement Association (NAPA) Information Series (IS-109) method (Class 1 for Light and Class 2 for Heavy). The rigid pavement section was designed using the American Concrete Institute (ACI 330R-01) method (Traffic Category A (ADTT=0) for Light and A-1 (ADTT=10) for Heavy). For this Project, Light and Heavy pavement section alternatives are being provided. Light is for areas expected to receive only vehicle traffic such as cars, pick-ups, and SUV’s. Heavy assumes areas with heavy traffic, such as trash pickup areas and main access drive areas. If heavier traffic loading is expected, Drash should be provided with the information and allowed to review these pavement sections. Based on the subsoil investigation, we understand that the pavement subgrade may consist of clay materials. The pavement sections are provided below:

FLEXIBLE PAVEMENT SYSTEM Raw Subgrade Modified Subgrade

Light Heavy Light Heavy Hot Mix Asphaltic Concrete 2.0 inches 2.0 inches 2.0 inches 2.0 inches

Granular Base Material 1 10.0 inches 14.0 inches 6.0 inches 10.0 inches Modified Subgrade --- --- 6.0 inches 6.0 inches

Moisture Conditioned Raw Subgrade 6.0 inches 6.0 inches --- --- 1 Asphalt treated base (ATB) material may be used in place of granular base material. Every 2

inches of granular base material may be replaced with 1 inch of ATB. However, the minimum thickness of the ATB material shall not be less than 4 inches.


RIGID PAVEMENT SYSTEM Raw Subgrade Modified Subgrade

Light Heavy Light Heavy Reinforced Concrete 6.0 inches 8.0 inches 5.0 inches 6.0 inches

Modified Subgrade --- --- 6.0 inches 6.0 inches

Moisture Conditioned Raw Subgrade 6.0 inches 6.0 inches --- ---

The pavement subgrade is expected to consist of select fill or clayey soils. Proper perimeter drainage is important and should be provided so infiltration of surface water from unpaved areas surrounding the pavement is minimized. We do not recommend installation of landscape beds or islands in the pavement areas. Such features provide an avenue for water to enter into the pavement base section. Water penetration usually results in degradation of the pavement base section with time as vehicular traffic traverses the affected area. Above grade planter boxes, with drainage discharge onto the top of the pavement or directed into sewers, should be considered if landscape features are desired. Also, the Asphalt Institute recommends a minimum of 2 percent slope for asphalt pavements. The importance of proper drainage cannot be overemphasized and should be thoroughly considered by the Project Team. A crack sealant compatible to both asphalt and concrete should be provided at all concrete-asphalt interfaces (i.e. curb to pavements). Pavement areas that will be subjected to heavy wheel and traffic volumes, such as waste bin or "dumpster" areas, entrance/exit ramps, and delivery areas, should be a rigid pavement section constructed of reinforced concrete. The concrete pavement areas should be large enough to properly accommodate the vehicular traffic and loads. For example:

• The dumpster pad should be large enough so that the wheels of the collection truck are entirely supported on the concrete pavement during lifting of the waste bin; and

• The concrete pavement should extend beyond any areas that require extensive turning, stopping, and maneuvering.

The pavement design engineer should consider these and other similar situations when planning and designing pavement areas. Waste bin and other areas that are not designed to accommodate these situations often result in localized pavement failures.

Pavement Section Materials Presented below are selection and preparation guidelines for various materials that may be used to construct the pavement sections. Submittals should be made for each pavement material. The submittals should be reviewed by Drash and any appropriate members of the Project Team. The submittals should provide test information necessary to verify full compliance with the recommended or specified material properties.


Hot Mix Asphaltic Concrete Surface Course - The asphaltic concrete surface course should be plant mixed, hot laid Type C or D Surface meeting the master specifications requirements of 2014 TXDOT Standard Specifications Item 341 and specific criteria for the job mix formula. The mix should be compacted between 91 and 95 percent of the maximum theoretical density as measured by TEX-227-F. The asphalt cement content by percent of total mixture weight should fall within a tolerance of ±0.3 percent asphalt cement from the specific mix. In addition, the mix should be designed so 75 to 85 percent of the voids in the mineral aggregate (VMA) are filled with asphalt cement. The grade of the asphalt cement should be PG 64-22 or higher performance grade. Aggregates known to be prone to stripping should not be used in the hot mix. If such aggregates are used measures should be taken to mitigate this concern. The mix should have at least 70 percent strength retention when tested in accordance with TEX-531-C.

Pavement specimens, which shall be either cores or sections of asphaltic pavement, will be tested according to Test Method TEX-207-F. The nuclear-density gauge or other methods which correlate satisfactorily with results obtained from Project pavement specimens may be used when approved by the Engineer.

Asphaltic Base Course - The asphaltic base material should meet the specification requirements of 2014 TxDOT Standard Specification Item 340, Type A or B.

Prime Coat - The prime coat should consist of sealing the base with an oil such as an MC-30 or an emulsion. The prime coat should be applied at a rate of about 0.2 to 0.5 gallons per square yard with materials which meet TxDOT Item 300. The prime coat will help to minimize penetration of rainfall and other moisture that penetrates the base.

Granular Base Material - Base material may be composed of crushed limestone base meeting all of the requirements of 2014 TxDOT Item 247, Type A, Grade 1 or 2; the material should have no more than 15 percent of the material passing the No. 200 sieve.

The base should be compacted to at least 98 percent of the maximum dry density determined in accordance with the Standard effort (ASTM D 1557) at moisture contents ranging between -2 and +3 percentage points of the optimum moisture content.

Concrete - Concrete should have a minimum 28-day design compressive strength of 4,000 psi and a design flexural strength of 650 psi.


Moisture Conditioned Subgrade - The subgrade should be scarified to a depth of 6 inches and then moisture conditioned and compacted as recommended in this Report.

Pavement Joints, Reinforcement, and Dowels - Refer to ACI 330 “Guide for Design and Construction of Concrete Parking Lots” and TxDOT “Standard Specifications” for this information. Details regarding subgrade preparation, fill materials, placement and compaction are presented in the Earthwork section of this report.

INTERPRETATION OF REPORT

Drash understands that its geotechnical engineering report is used by the Client and various individuals and firms involved with the design and construction of the Project. Drash should be invited to attend Project meetings (in person or teleconferencing) or be contacted in writing to address applicable issues relating to the geotechnical engineering aspects of the Project. Drash should also be retained to review the final construction plans and specifications to evaluate if the information and recommendations in our geotechnical engineering report has been properly interpreted and implemented in the design and specifications.

CONSTRUCTION MONITORING AND TESTING

The performance of the foundation system for the proposed structure will be highly dependent upon the quality of construction. As the Geotechnical Engineer of Record for this Project, Drash should be retained to provide construction observation and materials testing services during the Project, particularly the construction activities relating to foundations, building pad, pavements, excavation and site grading.

LIMITATIONS OF REPORT

This geotechnical engineering report is based upon the information provided to us by the Client and various other individuals and entities associated with the Project, exploratory boring drilled within the Project limits, laboratory testing of randomly selected soil or rock samples recovered during drilling of the exploratory boring, and our engineering analyses and evaluation. The Client and readers of this geotechnical engineering report, should realize that subsurface variations and anomalies can and will exist across the site and between the exploratory boring. The Client and readers should realize that site conditions will change due to the modifying effects of seasonal and climatic conditions. The nature and extent of such site or subsurface variations may not become evident until construction commences or is in progress. If site and subsurface anomalies or variations exist or develop, Drash should be contacted immediately so that the situation can be evaluated and addressed with applicable recommendations. The contractor and applicable subcontractors should familiarize themselves with this report prior to the start of their construction activities, contact Drash for any interpretation or clarification of the report, retain the services of their own


consultants to interpret this report, or perform additional geotechnical testing prior to bidding and construction.

Unless stated otherwise in this report or in the contract documents between Drash and Client, our scope of services for this Project did not include, either specifically or by implication, any environmental or biological assessment of the site or buildings, or any identification or prevention of pollutants, hazardous materials or conditions at the site or within buildings. If the Client is concerned about the potential for such contamination or pollution, Drash should be contacted to provide a scope of services to address the environmental concerns. Also, permitting, site safety, excavation support, and dewatering requirements are the responsibility of others. This geotechnical engineering report has been prepared for the exclusive use of our Client for specific application to this Project. This geotechnical engineering report has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, express or implied, are intended or made.

Should the nature, design, or location of the Project, as outlined in this geotechnical engineering report, be modified, geotechnical engineering recommendations and guidelines provided in this document will not be considered valid unless Drash reviews the changes and either verifies or modifies the applicable Project changes in writing.

EXHIBITS

EXHIBITDrawn By:

Checked By:

Reviewed By:

Project Mngr:

Date:

Scale:

Project No. PROJECT LOCATION MAP

NOT TO SCALE

09-22-2015

115G1063.02GK

AFA

1045 Central Parkway North, Suite 103 ▪ San Antonio, Texas 78232Office: 210.340.5004 ▪ Facsimile: 210.340.5009

1

N

GK

AFABROOKS VETERINARY CLINIC

CITY BASE LANDING AND GOLIAD ROADSAN ANTONIO, TEXAS

PROJECT SITE

TBPE Firm Registration F-13654

City Base Landing

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