Amendment 0003 - Geo Technical Report 2.pdf

TABLE OF CONTENTS

1.0 INTRODUCTION AND PURPOSES

1.1 Project Description

1.2 Purposes

2.0 FIELD INVESTIGATION

2.1 General

2.2 Drilling Methods and Groundwater Observations

2.3 Sampling Methods

2.4 Field Classifications, Sample Preservation, and Borehole Completion

3.0 LABORATORY INVESTIGATION

3.1 General

3.2 Strength Tests

3.3 Classification Tests

3.4 Water Content Tests

4.0 GENERAL SOIL CONDITIONS

4.1 General

4.2 Soil Stratification

4.3 Groundwater Observations

5.0 DISCUSSION

5.1 General Soil Conditions

5.2 Expansive Clay Considerations

5.3 Design Considerations

6.0 RECOMMENDATIONS

6.1 Bell-Bottom Pier Foundation

6.2 Augered Cast-in-Place Pile Foundation

6.2.1 Axial Capacity

6.2.2 Axial Group effects

6.2.3 Estimated Settlement

6.2.4 Auger-Cast Pile Installation and Construction

6.2.5 Other Pile Foundation Construction Considerations

6.3 Site Preparation and Earthwork Construction

6.4 Other Design Considerations

7.0 REPORT LIMITATIONS

FIGURES

1.0 INTRODUCTION AND PURPOSES

1.1 Project Description

Plans are being made for the construction of a new Mississippi Radiation and Oncology building addition at the VA Medical Center located at 1500 East Woodrow Wilson Drive in

Jackson, Mississippi. The proposed new building addition will abut the northwest corner of an existing building and will be bounded by other buildings to the south and west. The addition will generally consist of a one-story structure encompassing about 4,500 sq ft. Construction details and structural and/or floor loads have not been provided at this time. We understand that the new building addition will house relatively heavy medical equipment that is somewhat sensitive to vibrations and differential movement. We also understand that the existing structure to the south is supported on a deep foundation with the slab entirely above grade, while the existing structure to the west is supported on a shallow foundation. Details regarding grading plans have not been provided; however, we anticipate only nominal cutting and/or filling will be required to match the existing building grade and to provide drainage away from the addition. The proposed construction area is open.

1.2 Purposes

The specific purposes of this exploration were:

1) to make exploratory soil borings within the area planned for construction of the new addition;

2) to verify field classifications and to evaluate pertinent physical properties of the soils encountered in the borings by means of visual examination of the soil samples in the laboratory and tests performed on the samples; and

3) after analysis of the soil boring and laboratory test data, to provide recommendations for site preparation, earthwork construction, and building foundation design and construction.

Our current scope of work does not include: environmental study; detailed slope and trench stability analyses; dewatering analyses; detailed pavement design; structural foundation design;

review of plans and specifications; responses to contractor requests for information (RFIs); and construction phase services.

2.0 FIELD EXPLORATION

2.1 General

Two borings were made at the site in 2016, and two additional borings, Borings 1 and 2, were made to further explore subsurface soil conditions within the proposed construction area for the new addition. The approximate locations of Borings 1 and 2, as well as the approximate locations of the two borings made in 2016, are shown on attached Figure 1. Borings 1 and 2 were made within the proposed construction area for the new addition to an exploration depth of 45 ft.

Borings 1 and 2 were located in the field by means of visual sighting and taped measurements from existing site features using distances scaled from the site plan we were furnished.

All soils were classified in general accordance with the Unified Soil Classification System.

A synopsis of the Unified Soil Classification System is presented on Figure 2 along with symbols and terminology typically utilized on graphical soil boring logs. Graphical logs of Borings 1 and

2 are presented on Figures 3 and 4. Logs of Borings 1 (2016) and 2 (2016) can be found in the appendix. The graphical logs illustrate the types of soil and stratification encountered with depth below the existing ground surface at the individual boring locations. Surface elevations included at the top of the graphical boring logs were estimated from ground elevation contours shown on the furnished site plan and topographic survey map and should be considered approximate.

Approximate GPS coordinates for the boring locations as determined by our drilling personnel using a hand-held device are shown at the bottom of the graphical boring logs within the

“Comments” section.

2.2 Drilling Methods and Groundwater Observations

Borings 1 and 2 were initially advanced to depths of 15 ft and 10 ft, respectively, by dry augering and then were extended to completion using rotary wash drilling procedures.

Observations were made continuously during auger drilling in an attempt to detect groundwater seepage emerging into the open boreholes. Notes pertaining to observed groundwater conditions are indicated in the lower right corner of the graphic logs.

2.3 Sampling Methods

Relatively undisturbed samples of the soil were obtained at approximate 3-ft to 5-ft intervals of depth in the Borings 1 and 2 by pushing a 3-in. OD Shelby tube sampler approximately

2 ft into the soil. The Shelby tube samples were obtained within the depth intervals illustrated as shaded portions of the "Samples" column of the graphic boring logs.

Disturbed auger cutting samples were also taken near the ground surface in Borings 1 and

2. The depths at which the auger cutting samples were taken are illustrated as small I-shaped symbols under the "Samples" column of the graphic boring logs.

2.4 Field Classifications, Sample Preservation, and Borehole Completion

All soils encountered during drilling were examined and classified in the field by a geotechnical engineering technician. The undisturbed Shelby tube samples were extruded from the sampling tubes in the field. An approximate 6-in. long portion of each Shelby tube sample was sealed with melted paraffin in a cylindrical cardboard container to prevent moisture loss and structural disturbance. An additional portion of each Shelby tube sample and auger cutting samples were sealed in jars to provide material for visual examination and testing in the laboratory. Unless other disposition is requested, we routinely discard soil samples after about six months of storage.

In accordance with Mississippi Department of Environmental Quality (MDEQ) regulations, the

45-ft deep boreholes for Borings 1 and 2 were filled with cement-bentonite grout after completion of drilling and sampling.

3.0 LABORATORY INVESTIGATION

3.1 General

All of the soil samples were examined in the laboratory by a geotechnical engineer and tests were performed on the samples to assist in evaluating the strength, classifications and volume change properties of the soils encountered. The types of laboratory tests performed are described in the following paragraphs.

3.2 Strength Tests

The undrained shear strength characteristics of the fine-grained soils encountered in the borings were investigated by means of visual estimates of consistency and from the results of unconfined compression (UC) and unconsolidated undrained (UU) triaxial compression tests performed on selected undisturbed Shelby tube samples. The cohesions resulting from the UC and

UU triaxial compression tests are plotted as small open circles and triangles, respectively, in the data section of the graphic logs. The water content and dry density were also determined for the compression test specimens. The water contents are plotted as small shaded circles in the data section of the graphic boring logs. The dry densities are tabulated to the nearest lb per cu ft under the “Dry Density” column of the logs.

3.3 Classification Tests

The classifications and volume change properties of the soils encountered in the borings were investigated by means of Atterberg liquid and plastic limit tests performed on selected representative samples. The results of the liquid and plastic limit tests are plotted as small crosses interconnected by dashed lines in the data section of the graphic boring logs. In accordance with the Unified Soil Classification System, fine-grained soils are classified as either clays or silts of low or high plasticity based on the results of Atterberg limit tests. The numerical difference between the liquid limit and plastic limit is defined as the plasticity index (PI). The magnitudes of the liquid limit and plasticity index and the proximity of the natural water content to the plastic limit are indicators of the potential for a fine-grained soil to shrink or swell upon changes in moisture content or to consolidate under loading. The proximity of the natural water content to the plastic limit is also an indicator of soil strength.

The classifications of soils consisting predominantly of sand or containing some sand were investigated by means of minus No. 200 sieve tests performed on selected samples. The percentages of fines resulting from the minus No. 200 sieve tests are tabulated at the appropriate depths under the “% Passing No. 200 Sieve” column of the graphic logs.

3.4 Water Content Tests

Water content tests were performed on all samples upon which strength tests were not conducted to corroborate field classifications and to extend the usefulness of the strength and plasticity data. The results of the water content tests are plotted as small shaded circles in the data section of the graphic boring logs. The water content data have been interconnected on the logs to illustrate a continuous profile with depth.

4.0 GENERAL SOIL CONDITIONS

4.1 General

A general description of subsurface soil and groundwater conditions revealed by the borings made for this exploration is provided in the following paragraphs. The graphical logs shown on Figures 3 and 4, as well as in the appendix, should be referred to for specific soil and groundwater conditions encountered at each boring location. Stick logs of the borings are shown in profile on Figure 5 to aid in visualizing subsurface soil conditions. Tabulated adjacent to the stick logs are Atterberg liquid and plastic limits, percentages of fines passing the No. 200 sieve, water contents, dry densities and cohesions.

Some soils encountered at the boring locations appear to be fill materials. It should be understood that it is difficult to distinguish fill from natural soils. The borings are only representative of the conditions at the boring locations. There could be relatively weak and compressible fill materials or large concentrations or organic matter or debris at locations not explored during this study. It is not practical to fully characterize old fill materials by means of borings.

4.2 Soil Stratification

Subsurface soils encountered within the 45-ft completion depth of the borings include fill materials consisting of sandy clay (CL), sand (SM and SP-SM), clays (CH) and Yazoo clays (CH) underlain by natural clays (CH) of the Yazoo formation. The fill materials were encountered from the ground surface to approximate depths ranging from 13 ft to 22 ft below the ground surface.

Styrofoam was encountered below a depth of about 18 ft at Boring 2. The fill soils at the locations of Borings 1 (2016) and 2 (2016) were found to have a faint hydrocarbon odor below a depth of about 8 ft.

Medium stiff Yazoo clay (CH), sandy clay (CL) and clay (CH) fill materials that are considered to have low-moderate strength and moderate-high compressibility were encountered within the approximate depth intervals of 8 ft to 13 ft at Boring 1, 4 ft to 8 ft at Boring 2, 3.5 ft to

9.5 ft at Boring 1 (2016), and 3 ft to 13 ft at Boring 2 (2016). The remaining soils are considered to have moderate to high strength and low to moderate compressibility. The sand (SM and SP-SM) fill materials have no potential for shrinking and swelling. The sandy clay (CL) fill materials are considered to have low shrink/swell potential.

Clay (CH) fill materials, which were encountered within the approximate depth interval of

8 ft to 9.5 ft at Boring 1 (2016), are considered to have moderate to high shrink/swell potential.

Yazoo clay (CH) fill materials were encountered from the ground surface to a depth of about 13 ft at Borings 1 and 2 (2016) and within the approximate depth interval of 3.5 ft to 8 ft at Boring 1

(2016). The Yazoo clay (CH) fill materials are expansive with high to very high shrink/swell potential.

Weathered Yazoo clays (CH) were encountered within the approximate depth intervals of

17 ft to 30 ft at Boring 1, 22 ft to 30 ft at Boring 2, and 13 ft to 33 ft at Boring 2 (2016). Slickensides were noted in the weathered Yazoo clays (CH). Slickensides are randomly oriented micro-failure planes within clays (CH) caused by differential shrink/swell movements in the geologic past. The weathered Yazoo clays (CH) are expansive with high to very high shrink/swell potential.

Hard blue unweathered Yazoo clays (CH) were encountered at a depth of 30 ft at Borings

1 and 2 and at a depth of 33 ft at Boring 2 (2016). The unweathered Yazoo clays (CH) are considered to be expansive with very high shrink/swell potential. The unweathered Yazoo clays

(CH) were encountered to the 45-ft termination depth of Borings 1 and 2 and to the 40-ft termination depth of Boring 2 (2016).

4.3 Groundwater Observations

Free water was not encountered during auger drilling for the borings. In our opinion, groundwater conditions at the site will primarily be influenced by rainfall, surface drainage, and by the rise and fall of water levels in nearby ditches, creeks, ponds or other bodies of water.

Groundwater conditions at the site can also be influenced by man-made changes. Soils which did not exhibit free water during the short time period of drilling may exhibit water seepage at other times during construction and within excavations that remain open for an extended period of time or that are permanent. Surficial soils can become saturated and weak to relatively shallow depths during periods of prolonged and heavy rainfall.

5.0 DISCUSSION

5.1 General Soil Conditions

Subsurface soils encountered within the 45-ft maximum completion depth of the borings made for this exploration include fill materials consisting of sandy clay (CL), sand (SM and SP-

SM), clays (CH) and Yazoo clays (CH) underlain by natural clays (CH) of the Yazoo formation.

The fill materials were encountered at each boring location from the ground surface to approximate depths ranging from 13 ft to 22 ft.

Medium stiff Yazoo clay (CH), sandy clay (CL) and clay (CH) fill materials that are considered to have low-moderate strength and moderate-high compressibility were encountered within the following depth intervals of:

• 8 ft to 13 ft at Boring 1

• 4 ft to 8 ft at Boring 2

• 3.5 ft to 9.5 ft at Boring 1 (2016)

• 3 ft to 13 ft at Boring 2 (2016)

The remaining subsurface soils encountered in the borings are considered to have moderate to high strength and low to moderate compressibility. The sandy clay (CL) fill materials are considered to have low shrink/swell potential. The sand (SM and SP-SM) fill materials are considered to have no potential for shrinking and swelling.

Yazoo clay (CH) and clay (CH) fill materials fill materials were encountered from the ground surface to a depth of about 13 ft at Borings 1 and 2 (2016) and within the approximate depth interval of 3.5 ft at Boring 9 ft at Boring 1 (2016). Natural weathered Yazoo clays (CH) were encountered within the approximate depth intervals of 17 ft to 30 ft at Boring 1, 22 ft to 30 ft at

Boring 2, and 13 ft to 33 ft at Boring 2 (2016). Unweathered Yazoo clays (CH) were encountered from a depth of about 30 ft to the 45-ft termination of Boring 1 and 2 and from a depth of about

33 ft to the 40-ft termination of Boring 2 (2016). The clay (CH) fill materials are considered to have moderate to high shrink/swell potential and Yazoo clay (CH) fill materials and natural soils are expansive with moderate to very high shrink/swell potential. Refer to the profile sheets found on Figure 5 for the approximate depths at which expansive clays (CH) were encountered in the borings.

As previously mentioned, some soils encountered at the boring locations appear to be fill materials. It should be understood that it is difficult to distinguish fill from natural soils. The borings are only representative of the conditions at the boring locations. Pieces of Styrofoam were encountered below a depth of about 18 ft at Boring 2. The fill soils at the locations of Borings 1

(2016) and 2 (2016) were found to have a faint hydrocarbon odor below a depth of about 8 ft.

There could be relatively weak and compressible fill materials or large concentrations or organic matter or debris at locations not explored during this study. It is not practical to fully characterize old fill materials by means of borings. Our concern is that these materials could contain minor amounts of deleterious matter in some locations, and there is a possibility of worse fill conditions not discovered by the borings. Buried construction debris from past activities may also be present.

Efforts should be made to identify possible fill materials and buried debris prior to construction.

Any unstable soils and existing debris should be addressed as discussed later in this report. The risk of unforeseen conditions cannot be eliminated without completely removing the existing questionable fill material or using ground improvement efforts.

5.2 Expansive Clay Considerations

The moderately to very highly expansive clays (CH) can experience significant shrink/swell movements associated with seasonal moisture content fluctuations. Cover materials overlying expansive clay (CH) soils act as a buffer against seasonal moisture content changes caused by rainy weather, droughts and evapotranspiration. Thus, the potential magnitude of moisture content changes and associated shrink/swell movements within expansive clay (CH) soils is proportionate to the thickness of overlying cover materials. Seasonal moisture content changes and shrink/swell movements within expansive clay (CH) soils decrease as the thickness of cover materials increases. There is a general trend for expansive clay (CH) soils under structures to swell due to an increase in water content caused by capillary and vapor phase movement of moisture within the clays (CH). Expansive clay (CH) soils will also experience considerable swelling if directly supplied with water from rainfall, sprinkler systems, broken underground water and sewer pipes, or any other source. Trees growing adjacent to a structure can extract a considerable amount of moisture from the ground resulting in localized shrinkage of expansive clay (CH) soils accompanied by vertical and lateral movements.

Overburden removal associated with the establishment of finished grades lower than existing ground elevations will cause stress relief in expansive clay (CH) soils resulting in long-term rebound. It is roughly estimated that rebound of the expansive clays (CH) due to stress relief could be on the order of 1/4 in. to 1/2 in. for every foot of overburden removal. Expansive clay

(CH) soils will also experience long-term downhill creep movements, depending on slope steepness.

5.3 Design Considerations

The various aspects of expansive clay (CH) soils described in the preceding subsection must be considered in the design and construction of the foundation for the new addition. Also, the weak and compressible fill materials encountered at the boring locations must be taken into consideration. A foundation should be utilized which will accommodate the anticipated structural loads and also minimize future differential vertical movements resulting from settlement due to soil consolidation and/or shrinking/swelling within the expansive clay (CH) soils.

Considering the new addition will house relatively heavy medical equipment that will be somewhat sensitive to vibrations and differential movement and the presence of the highly to very highly expansive Yazoo clays (CH), we recommend that the addition be supported entirely above grade on a deep foundation system of auger-drilled and cast-in-place, reinforced concrete, bell-bottom piers bearing the hard unweathered blue Yazoo clays (CH). Alternatively, the new addition could be supported entirely above grade on augered cast-in-place piles, commonly referred to as auger-cast piles.

Special attention is required at locations where ground supported pavements, sidewalks and other appurtenances either connect to or abut the pier/pile-supported addition. Differential movement between these items and the pier/pile-supported addition will occur. It is our opinion that slabs and sidewalks that abut the addition, particularly at entrances, should also be supported above a void space on deep foundation elements. In areas where some differential movement is acceptable, a buffer of low shrink/swell soils should be provided in order to reduce, but not eliminate, shrink/swell movements and associated differential movements. The appropriate buffer thickness is dependent on the magnitude of potential movement that is considered acceptable, with greater buffer thickness generally resulting in lower shrink/swell movements. Buffer thicknesses on the order of 7 ft to 10 ft are typically used for lightly loaded slab-on-grade structures, and buffer thicknesses in the range of 3 ft to 5 ft are often used for pavements and sidewalks, with the understanding that some movement will occur as a result of normal seasonal fluctuations in water content. Unacceptable shrink/swell movements, on the order of 6 in to 12 in., can result from water leaks or poor drainage, even with a 7 ft to 10 ft thick buffer.

It is generally considered that a buffer thickness on the order of 15 ft will essentially eliminate shrink/swell movements associated with normal seasonal fluctuations in water content.

Details of our recommendations for design and construction of the bell-bottom pier and augered cast-in-place pile foundation are included in a following subsection of this report.

Recommendations for site preparation and earthwork construction for sidewalks and other appurtenances associated with the addition are also provided in a following subsection.

6.0 RECOMMENDATIONS

6.1 Bell-Bottom Pier Foundation

We recommend that the proposed addition be supported entirely above grade by a deep foundation consisting of auger-drilled and cast-in-place, reinforced concrete, bell-bottom piers brought to bear in the hard unweathered blue Yazoo clays (CH). As indicated previously, unweathered blue Yazoo clays (CH) were encountered in Borings 1 and 2 at a depth of about 30 ft and at Boring 2 (2016) at a depth of approximately 33 ft. The piers should extend to a minimum depth of not less than 3 ft into the unweathered blue Yazoo clays (CH). It should be understood that the depth to unweathered blue Yazoo clays (CH) could vary throughout the site.

It might be necessary to increase the pier bearing depths during construction either to penetrate at least 3 ft into totally blue unweathered Yazoo clays (CH) or to avoid caving of the pier bell ceilings caused by slickensided weathered Yazoo clays (CH).

The piers should be designed for end bearing. We recommend that the bell-bottom portions of the piers be dimensioned for maximum combinations of dead, live and wind loads utilizing a net allowable soil bearing pressure of 12,000 lbs per sq ft. The recommended allowable bearing pressure refers to the imposed stress at the base of the piers in excess of the soil overburden pressure that will exist after finished grades have been established. The diameter of the bell-bottom portion of each pier should be at least 2.5 times the diameter of the pier shaft to provide resistance against uplift forces. The piers should be reinforced over their entire length with a net steel area equivalent to not less than 1.25 percent of the gross cross-sectional area of the shaft. If necessary, higher percentages of steel reinforcement within the piers should be based on either structural design for anticipated loading conditions or tensile forces resulting from skin friction between the soil and pier shaft caused by heaving Yazoo clays (CH) along the shaft. An adhesion of 1,500 lbs per sq ft should be utilized to estimate the uplift force caused by heaving soils within about the top

15 ft of the pier shaft. The pier shafts should be interconnected and braced at the void space excavation level by grade beams extending in at least two mutually perpendicular directions. The grade beams should be directly underlain by a void space with a minimum vertical thickness of 24

in. to allow for future unimpeded vertical movement of the underlying soils. The void spaces could be created utilizing wax-coated cardboard box forms that are commonly referred to as J-voids or expanded steel and wood forms manufactured by SuperVoid Systems, LLC. Alternatively, GeoSpan compressible material produced by Plasti-Fab could be utilized. It should be noted that the grade beams must be designed for uplift pressure imposed upon the bottom of the beam considering the complete collapse of the GeoSpan and SuperVoid forms. Estimated uplift pressures for GeoSpan can be provided by Plasti-Fab, and uplift pressures for SuperVoid can be provided by

SuperVoid Systems, LLC. Vertical shields should be provided along the sides of the void space to prevent soil collapse into the voids. The side shields can consist of corrugated fiberglass panels, or other suitable products as determined by the structural designer.

Long-term settlement of the piers is expected to be within normally tolerable structural limits. We roughly estimate that bell-bottom piers supporting the addition could experience settlement on order of ½ in. About one-half of the estimated settlement is expected to occur during and soon after construction, with the remainder of the settlement essentially completed within a few years.

The floor system of the addition should be structurally supported above a crawl space by the bell-bottom pier foundation. The floor system should be designed to span between the piers and grade beams and support the anticipated loadings. All subfloor piping and conduits should be hung from the suspended floor system, and flexible couplings should be utilized at all points where the piping and conduits extend beyond the addition and below ground. The crawl space beneath the addition should be well ventilated and drained. If possible, a means for draining the void spaces beneath the grade beams should also be provided to prevent the accumulation of water.

Normal construction procedures should be employed for the auger-drilled and cast-in-place, reinforced concrete, bell-bottom piers. In the Jackson area, bell-bottom piers are usually constructed without the use of removable steel casing. However, casing will be required at some pier locations to either seal off perched water and/or to prevent sloughing of weak fill materials, silty sand (SM) fill materials, and slickensided weathered Yazoo clays (CH) during drilling and underreaming. Care should be taken to observe each pier excavation, and any loose materials that have sloughed into the drilled and underreamed pier holes should be removed prior to the placement of reinforcing steel and concrete. Concrete should be placed immediately after each pier excavation has been completed and observed. Pier excavations should not be allowed to remain open for more than one hour. All soils excavated during pier construction should be removed from the site and not used as fill material.

6.2 Augered Cast-in-Place Pile Foundation

Alternatively, the new addition can be supported by augered cast-in-place piles, commonly referred to as auger-cast piles. Recommendations for design and construction of augered cast-in-place piles are provided in the following paragraphs. Recommendations for other deep foundation types can be provided upon request.

6.2.1 Axial Capacity. Compression capacities for auger-cast piles were estimated using design procedures established by the Federal Highway Administration (FHWA). The capacity of an individual pile consists of a combination of skin friction around the perimeter of the pile and end bearing at the tip. Typically, a certain portion of the skin friction is neglected near the base of each pile and also near the top. For the auger-cast piles, skin friction was neglected within the depth interval of one pile diameter above the tip and within the top 3 ft of the pile. The pile capacity computations were performed using the ENSOFT computer program SHAFT (2017) which was developed to model FHWA design criteria.

Allowable compression capacity curves for various sizes of auger-cast piles are presented on Figure 6. Ultimate compression capacities were computed for the various pile sizes for average subsurface soil conditions revealed by the borings and soil strength parameters based on laboratory test results and engineering judgment. The computed ultimate skin friction force was divided by a factor of safety of 2.5 and the computed ultimate end bearing force was divided by a factor of safety of 3.0 to arrive at the allowable capacity. The allowable capacities can be increased by 25 percent for short-term loadings such as wind loads. Reinforcing for the auger-cast piles should be as necessary for the applicable compression, tension and lateral loadings. For auger-cast piles subject to uplift loading, a full pile length centered rebar should be utilized with adequate development length embedment into the pile cap.

6.2.2 Axial Group Effects. The reduction in individual pile capacity due to pile group effects depends on a number of factors including the configuration of the group, number of piles in the group, pile size, the depth of installation, and the pile spacing. In our opinion, no reduction in the single-pile capacities is necessary for the effects of group action, provided a center-to-center spacing of no less than 3 pile diameters is utilized. This recommended spacing should also reduce installation problems. If piles are spaced closer than 3 diameters, we recommend that we be retained to review the design and comment on axial group effects.

6.2.3 Estimated Settlement. For the factors of safety used to develop the allowable pile capacity curves, the long-term settlement of piles is expected to be within normal tolerable limits. We roughly estimate that piles supporting the structure should experience settlement of 1/2

in. or less for single piles or pile groups. As noted previously, differential settlement between pile-supported structures and structures supported on shallow foundations may be greater.

6.2.4 Auger-Cast Pile Installation and Construction. Due to the procedures required to properly install an auger-cast pile, special care must be taken by an experienced contractor and independent observer during construction. The auger-cast pile does not permit a down-hole observation as with drilled piers or shafts, nor are there driving records as with driven piles to assess whether the pile has attained the appropriate bearing stratum. Acceptance of the pile requires the qualified assessment of stratum support based on observation of soil cuttings and excavation drilling rates. Also, if the grout is not pumped down the hollow-stem auger at a sufficient pressure to maintain a displacement of the subsurface soils, or if the auger is withdrawn too quickly without maintaining sufficient head or in a jerky random fashion, the surrounding soils may squeeze in, resulting in necking down of the grout column. This necking down could result in a total soil inclusion where the pile is totally displaced and no longer acts as one continuous unit. Therefore, observation of the auger-cast pile installation and preparation of accurate construction records will be a very critical aspect. These services should be performed by a geotechnical engineer and/or geotechnical engineering technician who is knowledgeable concerning auger-cast pile construction methods, material properties and design concepts. A pre-work conference with all involved parties to discuss the work plans and the observation procedures is strongly recommended. The foundation subcontractor should be required to submit a statement of qualifications during bidding that lists previously completed projects similar to this project, and they should also submit a work plan to the owner prior to start of construction that demonstrates an understanding of the work required and also shows that proper equipment will be available to perform the work.

As a general guide, the following items are strongly recommended as part of the specifications for construction. A set of six 2-in. x 2-in. x 2-in. grout cubes should be taken frequently from the concrete deliveries in the first few days and then once per day after it has been shown that grout mixes are adequate. Two cubes of the set should be broken at 7, 28 and 56 days

(reference ASTM C 109 and Corps of Engineers CRD-C 620). Flow cone measurements should be made on each concrete delivery after any water is added to the mix at the site with an acceptable flow being between 16 and 35 seconds (reference Corps of Engineers CRD-C 611). The grout pump should be calibrated and the number of strokes required for a pile installation which includes

15 to 25 percent waste should be established and compared to the actual number of strokes during construction. A 25 to 50 percent waste may be more appropriate to assume for bid purposes, with an add/deduct amount adjusted following the trial test piles as a governing standard for actual grout take.

A trial installation should be utilized to establish generally acceptable grout takes and withdrawal rates, which should be maintained during production. Once the required bearing depth has been achieved, stationary rotating of the auger flights should be kept to a minimum so as not to remove excess volumes of soil which could negatively affect nearby piles or structures as well as the design capacity of the pile being placed. The auger withdrawal should be smooth and continuous during grouting with no variations in withdrawal rate allowed. A minimum grout head of 5 ft should be required before a pile is accepted. This is noted by a clean stream of grout flowing from the ground while the auger tip is still 5 ft below the surface. If the 5 ft of head is not present, the entire pile length should be redrilled and regrouted. Placement of piles adjacent to freshly grouted piles should not be allowed within a distance of 5 ft from edge to edge of the piles until after a period of 24 hours. Detailed specific language to be included in specifications or on drawings addressing minimum requirements for construction of the augered cast-in-place piles are beyond the present work scope, but can be provided upon request. An independent observer should keep an accurate and detailed log of each trial and production pile installed.

6.2.5 Other Pile Foundation Construction Considerations. Pile cap excavations should be protected during construction against the intrusion of storm water. Imported select backfill materials placed around and over the pile caps meeting the classification requirements given in Section 6.1 Site Preparation and Earthwork Construction of this report should be spread in maximum 5-in. thick loose lifts and compacted with hand-operated mechanical tampers to not less than 98 percent of standard Proctor maximum dry density (ASTM D 698). The moisture content of the backfill materials should be within 3 percentage points of the optimum water content as determined by standard Proctor compaction tests.

6.3 Site Preparation and Earthwork Construction

Since the proposed addition is to be supported entirely above grade by a deep pier foundation system, no special earthwork is needed for the addition, except as required either to remove existing subsurface features that might interfere with construction or to grade to provide for drainage within the crawl and/or void spaces beneath the addition. Sidewalks and other appurtenances supported on grade that abut the addition will move differentially with respect to the deep-foundation-supported addition. If the differential movement is considered detrimental or not acceptable, the appurtenances should also be supported on a deep foundation. Otherwise, the expected differential movements resulting from either settlement due to consolidation of weak soils or shrinking and swelling of the expansive clay (CH) soils can be reduced by excavating and replacing the weak soils and expansive clays (CH) with compacted select fill and providing a separating buffer of low permeability and low shrink/swell potential soil between the sidewalks and other appurtenances and the underlying expansive clays (CH). As previously mentioned, buffer thicknesses on the order of 7 ft to 10 ft are typically used for lightly loaded slab-on-grade structures, and buffer thicknesses in the range of 3 ft to 5 ft are often used for pavements and sidewalks, with the understanding that some movement will occur as a result of normal seasonal fluctuations in water content. Unacceptable shrink/swell movements, on the order of 6 in to 12 in., can result from water leaks or poor drainage, even with a 7 ft to 10 ft thick buffer. It is generally considered that a buffer thickness on the order of 15 ft will essentially eliminate shrink/swell movements associated with normal seasonal fluctuations in water content. Undercutting should be performed as required to provide for the placement of the recommended low shrink/swell potential soil buffer thickness.

As an initial step of site preparation, all existing pavement, foundations, utilities or pipes, and any other subsurface obstructions that might interfere with foundation construction for the addition should be removed and/or relocated. Stripping should be performed to remove organic-laden surficial soils, vegetation, debris, brush and roots. Excavation should be performed as required to remove weak soils. Undercutting should be performed as required for sidewalks and other appurtenances that will abut the addition to permit the construction of the low permeability and low shrink/swell potential soil buffer described above. The vertical and lateral extent of excavation required to remove weak soils and undercutting to remove expansive clays (CH) must be determined in the field during earthwork construction. Stripping, excavation and/or undercutting should extend laterally not less than 3 ft beyond the edges of sidewalks and not less than 5 ft beyond the limits of other appurtenances.

Excavation and undercutting should be performed in accordance with all applicable OSHA regulations. Depending on the season when earthwork is performed, groundwater perched within fill and/or natural soils could be encountered during excavation and/or undercutting. The means and methods for intercepting, collecting and removing groundwater entering excavations and undercut areas should be the sole responsibility of the earthwork contractor.

Extreme care should be taken while excavating weak soils and/or undercutting clays (CH) adjacent to the existing buildings to avoid undermining their foundations. For excavations extending below the foundation levels of the existing buildings, it may be necessary to temporarily underpin the foundations or shore the soils underlying the existing foundations. To minimize exposure of the existing building foundations to undermining, excavation/undercutting and backfilling adjacent to the existing buildings should be conducted in relatively narrow segments as measured parallel to the buildings.

In areas to receive fill after stripping, excavation and/or undercutting, the exposed soils should be scarified to a minimum depth of 6 in. and compacted to not less than 95 percent of standard Proctor maximum dry density (ASTM D 698) with stability present. Alternatively, the exposed soils can be proofrolled to demonstrate stability. Stability is defined as the absence of significant pumping, yielding or rutting of soils during compaction or proofrolling. If stability is not evident in some areas, either additional excavation or treatment of the in situ soils with an admixture, or a combination of these approaches, might be required to achieve stable conditions.

It should be noted that fine-grained soils exposed after stripping, excavation and undercutting are susceptible to pumping under wet conditions. The construction techniques and types of equipment utilized and site drainage provided during construction will have a great effect on the performance of these soils throughout the project. The routing of heavy rubber-tired equipment should be controlled to minimize, as much as possible, traffic over the site. All traffic should be discouraged during periods of inclement weather. If pumping is initiated in fine-grained soils, as a construction expedient the pumping can be counteracted by treating these materials with hydrated lime. It is estimated that about 4 to 6 percent hydrated lime by dry weight of soil could be required for silty clays (CL) and sandy clays (CL). It is estimated that about 6 to 8 percent hydrated lime by dry weight of soil could be required for clays (CH).

After stripping, excavation, undercutting, and scarification/compaction or proofrolling have been performed as recommended in the preceding paragraphs, fill materials can be placed to achieve planned grades. Imported fill soils should consist of select, nonorganic and debris-free silty clays (CL) having a plasticity index (PI) within the range of 10 to 24, a liquid limit less than

45, and not less than 70 percent fines passing the No. 200 sieve. Fill materials should be compacted from lifts not exceeding 9 in. in loose thickness to not less than 95 percent of standard Proctor maximum dry density (ASTM D 698) at moisture contents within 3 percentage points of the optimum water content. Where hand-controlled mechanical tampers are utilized for compaction of fill, the loose lift thickness should be limited to 5 in. Stability must be evident during compaction of each lift before any subsequent lifts of fill material are added. As a construction expedient, fill soils that are unstable and/or pumping due to excessive moisture can be treated with hydrated lime in accordance with recommendations given previously for pumping on-site soils. Finished site grades should be sloped to promote quick runoff of storm water away from the addition.

Laboratory classification tests, including Atterberg limit determinations and grain-size analyses, should be performed on the fill soils initially and routinely during earthwork operations to check for compliance with the recommendations provided herein. Field moisture/density tests should be performed frequently in the scarified and compacted on-site soils and in each compacted lift of fill material to assist in evaluating whether the recommended moisture contents and dry densities are being achieved. As a guide for structure and appurtenant features earthwork construction, we suggest a minimum of one test per lift for each 2,000 sq ft of surface area or portion thereof.

6.4 Other Design Considerations

The expansive clays (CH) which underlie the ground surface at the site will swell considerably if directly supplied with water. If flower and shrub beds including sprinkler systems are placed adjacent to the addition, the beds should be prepared such that they do not trap water, and sprinklers should be operated only enough to satisfy the water demands of the plants and shrubs. Excessive watering and ponding adjacent to the addition could result in downward percolation of water to the expansive clays (CH) causing them to swell. Rainwater falling directly on the addition should be collected and prevented from reaching the ground beneath and immediately adjacent to the addition. Downspouts transmitting water to the ground level should emit collected rainwater not less than 10 ft away from the addition. The downspouts could be connected to solid discharge pipes buried beneath the ground. We caution that these pipes should be flexible enough to accommodate some differential movement and all pipe connections must be leak free. Trees remove water from the ground by transpiration causing vertical and horizontal shrinkage of clays (CH). To minimize these effects, any trees planted for landscaping purposes should be located at least one-half their anticipated mature height away from the addition. If the risk of more movement is acceptable, a less strict building-to-tree spacing of about 25 ft for hardwoods and 15 ft for pines could be utilized.

The proposed new addition, supported above grade by a deep foundation, will abut existing structures that we understand are supported on both shallow and deep foundations. Differential movement can occur at the junctures between the structures. Special consideration should be given to the design and construction of floor slab, wall and roof connections between the structures to accommodate some differential movement. An expansion joint could possibly be utilized for that purpose.

The site for the addition at the VA Medical Center in Jackson, Mississippi lies within a relatively low seismic activity region according to the seismic zone mapping referenced in the

International Building Code. Given the site soil profile as revealed by the borings and anticipated for the area based on our experience, a site Class D could be used in a seismic load evaluation.

7.0 REPORT LIMITATIONS

The analyses, conclusions, and recommendations discussed in this report are based on conditions as they existed at the time of our field exploration and further on the assumption that the exploratory borings are representative of subsurface conditions throughout the areas explored.

It should be noted that actual subsurface conditions between and beyond the borings might differ from those encountered at the boring locations. If subsurface conditions are encountered during construction that vary from those discussed in this report, Burns Cooley Dennis, Inc. should be notified immediately in order that we may evaluate the effects, if any, on earthwork and foundation design and construction.

Burns Cooley Dennis, Inc. should be retained for a general review of final design drawings and specifications. It is advised that we be retained to observe earthwork and foundation design and construction for the project in order to help confirm that our recommendations are valid or to modify them accordingly. Burns Cooley Dennis, Inc. cannot assume responsibility or liability for the adequacy of recommendations if we do not observe construction.

This report has been prepared for the exclusive use of ThinkForm Architects for specific application to the geotechnical-related aspects of design and construction of new Mississippi

Radiation and Oncology building addition at the VA Medical Center located at 1500 East Woodrow

Wilson Drive in Jackson, Mississippi. The only warranty made by us in connection with the services provided is that we have used that degree of care and skill ordinarily exercised under similar conditions by reputable members of our profession practicing in the same or similar locality. No other warranty, express or implied, is made or intended.

FIGURES

B-1

B-2

B-1

B-2

JOB NO. SCALE:240684 AS SHOWN FIGURE 1

PROPOSED BUILDING ADDITION

MISSISSIPPI RADIATION AND ONCOLOGY

VA MEDICAL CENTER

JACKSON, MISSISSIPPI

BURNS COOLEY DENNIS, INC.

551 SUNNYBROOK ROAD

RIDGELAND, MISSISSIPPI 39157

Approximate Boring Locations

Legend

2016 BCD Soil Boring (Proj. No. 160366)

2024 BCD Soil Boring (Proj. No. 240684)

0 10 20 40

SCALE: 1" = 20'

N

S

EW

FIGURE 2

MAJOR DIVISIONS

C

O

AR

SE

-G

R

AI

N

ED

S O

IL

S

FI

N

E- G

R

AI

N

ED

S O

IL

S

GRAVELS

SANDS

WELL GRADED GRAVEL, GRAVEL-SAND MIXTURE

POORLY GRADED GRAVEL, GRAVEL-SAND MIXTURE

SILTY GRAVEL, GRAVEL-SAND-SILT MIXTURE

CLAYEY GRAVEL, GRAVEL-SAND-CLAY MIXTURE

WELL GRADED SAND, GRAVELLY SAND

POORLY GRADED SAND, GRAVELLY SAND

SILTY SAND, SAND-SILT MIXTURE

CLAYEY SAND, SAND-CLAY MIXTURE

SILT WITH LITTLE OR NO PLASTICITY

CLAYEY SILT, SILT WITH SLIGHT TO MEDIUM PLASTICITY

SILTY CLAY, LOW TO MEDIUM PLASTICITY

SANDY CLAY, LOW TO MEDIUM PLASTICITY (30% TO 50% SAND)

CLAY, HIGH PLASTICITY

ORGANIC CLAY OR SILT OF MEDIUM TO HIGH PLASTICITY

PEAT, HUMUS, SWAMP SOIL

SAMPLE TYPES

(Shown in Sample Column)

Shelby Tube

Split Spoon

No Recovery

Auger

Dennison Barrel

P L A S T I C I T Y C H A R T

PL

AS

TI

C

IT

Y

IN

D

EX

CH & OH

CL

ML

00 10 20 30 40 50 60 70 80 90 100

FOR CLASSIFICATION OF FINE GRAINED SOILS

LIQUID LIMIT

TERMS CHARACTERIZING SOIL STRUCTURE

DENSITY AND CONSISTENCY

COARSE-GRAINED SOILS FINE-GRAINED SOILS

PENETRATION

RESISTANCE, N

Blows per Foot Blows per FootDENSITY CONSISTENCY Kips/Sq. Ft

Very Loose Loose Medium Dense Dense Very Dense

Very Soft Soft Medium Stiff Stiff Very Stiff Hard

RELATIVE COMPOSITION

With Cobbles Greater than 3 inches Slightly 5 - 15%

Sandy 16 - 29%

30 - 50% (or Gravelly)

Gravel Coarse - 3/4 inch to 3 inches

Coarse - 2 mm to 4.76 mmSand Medium - 0.42 mm to 2 mm Fine - 0.074 mm to 0.42 mm Less than 0.074 mmSilt & Clay

PARTICLE SIZE IDENTIFICATION

SANDY SILT

SILT, FINE SANDY OR SILTY SOIL WITH HIGH PLASTICITY

Fine - 4.76 mm to 3/4 inch

CLASSIFICATION, SYMBOLS AND

TERMS USED ON GRAPHICAL

BORING LOGS

<0.25

0.25 - 0.50

0.50 - 1.00

1.00 - 2.00

2.00 - 4.00

>4.00

0 - 1 2 - 4 5 - 8

9 - 15 16 - 30

>30

0 - 4 5 - 10

11 - 30 31 - 50

>50

More than half of coarse fraction larger than No.4 sieve size

More than half of coarse fraction smaller than No.4 sieve size

Clean Gravels (Little or no fines)

Gravels with fines (Appreciable amount of fines)

Clean Sands (Little or no fines)

Sands with fines (Appreciable amount of fines)

SILTS AND

CLAYS

Liquid limit less than

SILTS AND

CLAYS

Liquid limit greater than 50

M or e th an h al f o f m at er ia l l ar…