Prologis Park-LR150602
GEOTECHNICAL ENGINEERING REPORT
PROPOSED PROLOGIS PARK ONE TWENTY ONE
BUILDINGS 1, 2 AND 3
NEAR NWC OF WEST SANDY LAKE RDAND NORTH COPPELL RD
COPPELL, TEXAS
Prepared For:
Prologis
2501 North HardwoodStreet, Suite 2450
Dallas, Texas 75201
Attention: Mr.Kyle Low
JUNE2015
PROJECT NO. 15-20061.2
G EOTECHNICAL E NGINEERING
E NVIRONMENTAL C ONSULTING
C ONSTRUCTION M ATERIAL T ESTING
June 2, 2015
Mr.Kyle Low
Prologis
2501 North Hardwood Street, Suite 2450
Dallas, Texas 75201
Re:Geotechnical Engineering Report
Proposed Prologis Park One Twenty One
Buildings 1, 2 and 3
Near NWC of West Sandy Lake Rdand North Coppell Rd
Coppell, Texas
Rone Project No. 15-20061.2
Dear Mr.Low:
Submitted herewith are the results of a geotechnical investigation conducted for the
referenced project. This investigation was performed in accordance with our proposal P-
20883-15 dated March 18, 2015 (Revision #2).
This report presents engineering analyses and recommendations for site grading,
foundations, and pavements. Results of our field and laboratory investigation aresubmitted
in detail in the Appendix section of the report.
We appreciate the opportunity to be of service to you on this project, and we would appreciate
the opportunity to provide the materials engineering testingand geotechnical observation
servicesduring the construction phase of this project. Please contact us if you have any
questions or need any additional services.
Respectfully Submitted,
Thusha P. Thushanthan, P.E. Xuhui Chang, P.E.
Geotechnical EngineerGeotechnical ManagerI Dallas Division
Texas Engineering Firm License No. F-1572
D ALLAS |F ORT W ORTH |A USTIN |S AN A NTONIO |H OUSTON
TABLE OF CONTENTS
Page
1.0 INTRODUCTION........................................................................................................... 1
2.0 BACKGROUND............................................................................................................ 1
3.0 PURPOSES AND SCOPE OF STUDY........................................................................ 2
4.0 FIELD OPERATIONSAND LABORATORY TESTING............................................... 3
5.0 GENERAL SITE CONDITIONS.................................................................................... 4
5.1 Site Geology.............................................................................................................. 4
5.2 Subsurface Soil Conditions....................................................................................... 4
5.3 Groundwater............................................................................................................. 5
6.0 ANALYSIS AND RECOMMENDATIONS.................................................................... 7
6.1 Seismicity Site Class................................................................................................. 7
6.2 Potential Vertical Soil Movements............................................................................ 7
6.3 Foundation Recommendations................................................................................. 8
6.3.1 General Discussion............................................................................................ 8
6.3.2 Shallow Spread Footing Foundations – Building 1........................................... 8
6.3.3 Underreamed Drilled Pier Foundations – Buildings 2 and 3............................. 9
6.3.4 Construction Considerations for Drilled Piers – Buildings 2 and 3................... 9
6.3.5 Grade Beams/Tilt Panels – Buildings 1, 2 and 3.............................................10
6.3.6 Graded-Supported Floor Slab – Buildings 1, 2 and 3.....................................11
6.4 Subgrade Treatment – Buildings 1, 2 and 3...........................................................11
6.5 Pavement Design Recommendations....................................................................13
6.6 Pavement Subgrade Preparation...........................................................................15
6.7 General...................................................................................................................16
7.0 GENERAL EARTHWORK RECOMMENDATIONS...................................................17
7.1 General Discussion................................................................................................. 17
7.2 Site Grading............................................................................................................17
7.3 Site Preparation......................................................................................................17
7.4 Select Fill.................................................................................................................19
7.5 Density Tests.......................................................................................................... 19
8.0 CONSTRUCTION OBSERVATIONS.........................................................................20
9.0 REPORT CLOSURE..................................................................................................20
APPENDIX A
Plate
VICINITY MAP………………………………………………………………………………….............. ……A.1
GEOLOGY MAP…………………………………………………………………………………..............….A.2
BORING LOCATION DIAGRAM.........................................................................................................A.3
LOGS OF BORING.....................................................................................................................A.4-A.39
KEY TO CLASSIFICATIONS AND SYMBOLS.................................................................................A.40
UNIFIED SOIL CLASSIFICATION SYSTEM....................................................................................A.41
SWELL TEST RESULTS(CURRENT INVESTIGATION)................................................................A.42
SWELL TEST RESULTS(PRELIMINARY INVESTIGATION).........................................................A.43
APPENDIX B
Page
FIELD OPERATIONS......................................................................................................................... B-1
LABORATORY TESTING................................................................................................................... B-2
GEOTECHNICAL ENGINEERING REPORT
PROPOSED PROLOGIS PARK ONE TWENTY ONE
BUILDINGS 1, 2 AND 3
NEAR NWC OF WESTSANDY LAKE RD AND NORTH COPPELL RD
COPPELL, TEXAS
1.0INTRODUCTION
The proposedPark One Twenty One is located near the northwest corner ofWest Sandy Lake
Road and North Coppell Road, eastof State Highway 121 in Coppell, Texas. Comprising
approximately 120 developable acres, we understand the project will consist of fiveindustrial
office/warehouse buildings, with associatedpaved parking, drive areasand stormwater detention
locations.The city of Coppell, Texas will construct Freeport Parkwaythat will result in connecting
LakesideParkwayfrom its current terminus atState Highway 121 to the north with Freeport
Parkway’s current terminus at West Sand Lake Roadto the south. Fourof the fiveproposed
buildings will be onthe east side of Freeport Parkway, west of North Coppell Road. The fifth
buildingwill be on the southwestside of Freeport Parkway at the frontage with State Highway 121.
One building designated as a Build-To-Suit for Subaru is currently underconstruction(Building 4).
The remaining buildings are designated by building numbers 1, 2, 3 and 5.This report provides
recommendations for the design and construction of Buildings 1, 2 and 3. A brief summary of each
building is provided in the following table.
Building FootprintAreaFinished Floor Elevation
BuildingNo
(Square feet) (feet)
Building 1108,360506.5
Building 2142,080494.5
Building 3382,500489.0
2.0 BACKGROUND
Based on 1968 aerial maps, it appears the project site was strip mined in the past. Rone completed
a preliminary geotechnical study for the site that included test pits to evaluate fill soils used to cover
the site after strip-mining (Rone Report Number 14-18896). Mass grading of the entire site began in
March 2015before this investigation.Therefore, the borings drilled forthis investigation would have
differentsurface elevations asthose from the preliminary study.
Project No. 15-20061.2Page 1
Mass grading of the site included placing several feet of fill in Building Pads 2 and 3.Building 1
received less fill.Building 5was a cut condition and was reported separately (Rone Report Number
15-20061.1 dated May 20, 2015). Rone personnel were onsite fulltime during mass grading and all
fills were placed with moisture and density control.
Preliminary infrastructure plansprepared by HalffAssociates, Inc.,dated January 16, 2015were
provided to Rone.The originalground at Buildings 1, 2 and 3 generally slopeddowntoward the
east and northeast with elevations varying approximately from 517 to 476feetprior to mass grading.
Based on the providedinfrastructure plans, the original ground elevations variedapproximately from
508feet in the southwest corner to493feet in the northeast corner within the footprint of Building1
prior to mass grading.Similarly, original ground variedapproximately from 498 to 479 feet for
Building 2and from 501 to 476 feet for Building 3 within their respective footprints prior to mass
grading.The building padswerenear their final pad elevationsat the time of this investigationas
mass grading was nearly complete.
As stated previously, Rone performed a preliminary geotechnical study for this site and issued Rone
report number 14-18896 dated February 24, 2014.Sixborings were completed within thebuilding
footprint for Buildings 1, 2 and 3during the preliminary geotechnical investigation. The findings from
the preliminary study as well as the Subaru report and Building 5 report were also used to develop
the final geotechnical recommendations.
Structural loads imposed by the proposeddevelopmentarenot known at this time, but are expected
to be relatively light (less than 500 kips). A site vicinity map and geological map are attached as
Plates A.1 and A.2, respectively. The general location and orientation of the site are shown on the
Boring Location Diagram, Plate A.3, in the Appendix section of this report.
3.0 PURPOSES AND SCOPE OF STUDY
The principal purposes of this investigation were to evaluate the general soiland rockconditions at the
proposed site and to develop geotechnical recommendations for the design and construction of
foundations. To accomplish its intended purposes, the study was conducted in the following phases:
(1) drilledsample borings to evaluate the soil conditions at the boring locations and to obtain
soil and rock samples;
Project No. 15-20061.2Page 2
(2) conductedlaboratory tests on selected samples recovered from the boringsto establish the
pertinent engineering characteristics of the foundation soilsand rocks; and
(3) performedengineering analyses, using field and laboratory data, to develop foundation
design criteria.
4.0 FIELD OPERATIONS ANDLABORATORY TESTING
In addition to the six borings (B-7 through B-12) completed during the preliminary study, soil and
rock conditions were determined by 30 additional borings (B-14 through B-43). Borings B-14
through B-43 were drilled to a depth of 30feet(except Boring B-30, which was terminated at a depth
of about 18½feet)below site grade within the footprint areas of the proposed Buildings 1, 2 and 3.
Preliminary Borings B-7 through B-12 were completed to a depth of 25 feet below site grade. Table
provided belowsummarizes the field explorations scenario for each building.The preliminary
borings (B-7through B-12) and the additional borings (B-14 through B-43) were drilled in February,
2014 and May, 2015, respectively.Locations of all 36 borings are shown on Plate A.3, Boring
Location Diagram. Sample depth, description of soils, and classification (based on the Unified Soil
Classification System) are presented on the Logs of Boring, Plates A.4through A.39. Keys to terms
and symbols used on the logs are shown on Plates A.40and A.41.
Borings Completed for
BuildingPreliminary Boring(s)
Current Investigation
Building 1B-12B-14 through B-21
Building 2B-10 and B-11B-22 through B-29
Building 3B-7through B-9B-30 through B-43
Laboratory soil tests were performed on selected samples recovered from the borings to confirm
visual classification and determine the pertinent engineering properties of the soils encountered.
Classification test results are presented on the Logs of Boring.Swell tests were performed on
selected clay samples and the results are tabulated and presented in the Appendix section of this
report on PlatesA.42 and A.43.
As mentioned previously, the site appeared to have beenstrip mined in the 1960s and fill was
confirmed to bepresent at this site.To better define thickness, quality and composition of possible
Project No. 15-20061.2Page 3
fill at thesite, a total of 26 test pits were excavated to depths of about 5.5 to 12.5 feet below the
existing ground surface during our preliminary investigation.Fiveof those test pits(TP-22through
TP-26)were excavatedin or near the proposed Buildings1, 2 and 3locations.The test pit locations
are shown on the boring locationdiagram. The test pits confirmed the existence of foreign fill, but
no unsuitable materials were encountered.
Descriptions of the procedures used in the field and laboratory phases of this study are presented in
the Appendix of this report.
5.0 GENERAL SITE CONDITIONS
5.1Site Geology
Based on the Geologic Atlas of Texas, Dallas Sheet, and our borings, this site appears to be located
inFluviatile Terrace Deposits underlain by the Woodbine Formation. Fluviatile Terrace Deposits
generally consist of gravel, sand, silt, and clay. The Woodbine formation generally consists of sand,
clays, sandstones and shales. Dense and irregular shaped masses of hard sandstone occur at
random throughout the formation. It is often difficult, if not impossible, to trace a particular bed for
any distance. Water is found at various levels in the formation, some as perched tables in sand
lenses.As mentioned previously, the site also holds imported fill. Descriptions of the various strata
and their approximate depths and thickness are shown on the Logs of Boring.
5.2Subsurface Soil Conditions
The subsurface conditions are indicated in detail for each boring location in the Logs of Boring. The
stratification boundaries shown on the Logs of Boring represent the approximate locations of
changes in types of soiland rock; in situ, the transition between material types may be gradual and
indistinct. A brief summary of the stratigraphy encountered at the borings is given below.
Based on the classification test results and visual inspection, Borings B-15, B-26, B-27, B-31, B-34,
B-35, B-37, B-38, B-39, B-41, B-42 and B-43generally encountered reddish brown, brown,light
brown,dark brown and gray clay and sand fills, sandy leanclays (CL), fat clays(CH),clayey sands
(SC), silty sands (SM) and sands (SP-SC & SP-SM)with varying amounts of gravelfrom the ground
surface to depthsof about 23½to 28feet, followed by gray shale to their termination depth of 30
feet.BoringB-30encounteredreddish brown, brown, light brown and gray sandy leanclays (CL)
from the ground surface to a depthof about 18 feet, followed by sandstoneto the termination depth
of 18½ feet.The remaining 17boringsencounteredsimilar clays and sands from the ground
Project No. 15-20061.2Page 4
surfaceto the termination depth of 30 feet.Clay and sand fills were encounteredin 21 borings up to
depthsof about 2 to 13½ feet below grade.
BoringsB-7throughB-11completed during the preliminary investigationgenerally encountered fat
clays (CH), sandyclays(CL), clayey sands(SC), sands (SP & SP-SM) andclayeygravel (GC) to
depths of about 11 to 18½feet, followed by shale andsandstone to thetermination depths of 25
feet.BoringB-12 encountered silty-clayey sand (SC-SM), sand (SP), sandy clays (CL), and sandy
gravel (SG)from the ground surfaceto its termination depthof 25 feet.It should be noted that these
preliminary borings were completed before the mass grading; thus, these borings would have the
different surface elevations asthose completed forthe currentinvestigation.
As mentioned previously, fivetest pits were excavated in or near the Buildings 1, 2 and 3areas
during the preliminary investigation.The test pits generally encountered sandy clay, clayey sand,
sand and gravel.No obvious debris, trash, or other unsuitable materials were observed to the test
pit termination depths of about 5.5 to 12.5 feet.Based on our visual observation of the test pit
excavations, many pockets of on-site soils appear to be suitable to use as select fill.
The Plasticity Index (PI) of the samples tested varied from non-plasticto 45,indicating lowto high soil
plasticity. A highPlasticity Index is generally associated with a highpotential for the active clay soils to
shrink and swell with changes in moisture content.A summary of the PIof the samples tested within
the active zone of each buildingis provided below.
PI within the Active Zone of
BuildingSwellPotential
12 feet
Building 1Non-plastic to 40low to high
Building 213 to 45low to high
Building 315 to 35low to high
5.3Groundwater
The borings were advanced using auger drilling and intermittent sampling methods in order to
observe groundwater seepage levels.Groundwater seepage was encountered in 22 borings at
various depths during and upon completion of drilling, and at the end of the day after boring
Project No. 15-20061.2Page 5
completion. The remaining 14borings didnot encountergroundwater seepage during drilling and
thoseboreholes appeared dry atcompletion of drilling. Please refer to the table below for details
regarding groundwater depths from the boring surface.
Depth to Water During Depth to water Upon Depth to water at the
Boring
Drilling (ft.)Completion (ft.)End of the Day
3
B-819.515Not Measured
3
B-98Not EncounteredNot Measured
2
B-101316Not Measured
2
B-1112Not EncounteredNot Measured
1
B-122319Not Measured
1
B-142323Not Measured
1
B-1513Not EncounteredNot Measured
1
B-172728Not Measured
1
B-192119Not Measured
1
B-201717Not Measured
2
B-232627Not Measured
2
B-242121Not Measured
2
B-252124Not Measured
2
B-261924Not Measured
2
B-272323Not Measured
2
B-282024Not Measured
2
B-292426Not Measured
3
B-321924Not Measured
3
B-371927Not Measured
3
B-381726Not Measured
3
B-401927Not Measured
3
B-412424Not Measured
Note: Superscripts 1, 2 and 3 denote the buildingnumbers in which those borings were drilled.
It is difficult to accurately predict the magnitude of subsurface water fluctuations that might occur
based upon short-term observations. The risk of encountering seepage is increased during or after
periods of precipitation. Groundwater should be anticipated during the construction phase of this
Project No. 15-20061.2Page 6
project. Groundwater levels should be expected to fluctuate throughout the year with variations in
precipitation, runoff, and the water levels in nearby surface water features.
6.0 ANALYSIS AND RECOMMENDATIONS
6.1 Seismicity Site Class
The site class for seismic design is based on several factors that include soil profile (soil or rock),
shear wave velocity, density, relative hardness, and strength, averaged over a depth of 100 feet.
The borings for this project did not extend to a depth of 100 feet; therefore, we assumed the soil
conditions below the depth of the borings to be similar to those encountered at the termination depth
of the borings. Based on Section 1613.5.2 of the 2012International Building Codeand our local
experiences, we recommend using Site Class C(soft rock/stiffsoil profile)for seismic design.
6.2 Potential Vertical Soil Movements
Potential Vertical Movement calculations were performed in general accordance with the Texas
Department of Transportation (TxDOT) Method 124-E. The TxDOT 124-E method is empirical and
is based on the Atterberg limits and moisture content of the subsurface soils. Swell test results were
also used in the estimation of the PVR.
The Potential Vertical Rise (PVR) calculated using the TxDOT method ranges from about1to 3
inches based on in-situ soil being at a dry antecedent condition, existing site grades at the time of
our drilling and the depth of theactive zone at 12feet for this site.At the time of drilling, the soils at
the borings were in a slightlydry to slightly moistcondition. Results of free swell testsas reported
on Plate A.42range between 0.0 and 5.6percent, with an average swell of 0.8 percent.The current
moisture profile andfree swell test results indicate the PVR to be on the order of 1 inch or less
except at some isolated locations, where the PVR may be up to 3 inches. Therefore,the design
should be based on the 3-inchPVR.The building pads should be protected from moisture loss until
ready for construction in order to preserve the current PVR conditions.
As presented on Plate A.42, results of the free swell test from aspecimen sampled at 6 to 8 feet in
Boring B-21 drilled withinBuilding 1 indicate a swell of 5.6 percent. Similarly, samples obtained from
BoringsB-30 and B-41, both were drilled within Building 3, showa swell of 4.4 and 4.8 percent,
respectively.These three swell test results indicate that there are some isolated areas with higher
swell potential than other areas.The moisture profile and swell potential of the soils near these boring
locations(B-21, B-30 and B-41)should be re-evaluated just prior to the construction.
Project No. 15-20061.2Page 7
6.3Foundation Recommendations
6.3.1 General Discussion
Based on conditions encountered at the time of our investigationand our understanding of the project,
the proposed Building 1 can be supported onshallow spread footing foundationswith a grade-
supported interior floor slab, provided some floor movements can be tolerated.The proposed
Buildings 2 and 3 can be supported onauger-excavated, underreamed, cast-in-placeconcrete pier
foundations with a grade-supportedinterior floor slab, provided some floor movements can be
tolerated.Subgrade treatment maybenecessary toreduce the PVR to more tolerable levels (1 inch)
and this is discussed below in Section“6.4Subgrade Treatment”.Recommendations for foundations
are presentedbelow.
6.3.2 Shallow SpreadFooting Foundations–Building 1
Shallow spread footing foundations can be used for support of the structural loads ofthe proposed
Building1. Spread footing foundations should be proportioned using a maximum net allowable
bearing pressure of 2,500psf and are recommended to bear in the natural soilor moisture-density
controlled fillat a depth of at least 6feetbelow the final grade. This bearing pressure contains a
safety factor of at least 3 against shear failure of the foundation bearing soils.Foundation settlement
due to applied loads should be anticipated to be on the order of 1 inch. Foundation movements due to
shrinking and swelling of active soils should be less than 1 inch. Individual spread footings should be
atleast 30 inches wide, and strip footings should be at least 18 inches wide.
The geotechnical engineer should monitor spread foundation construction to confirmconditions are as
anticipated. Foundation excavations should be dry and free of loose material.It is recommended that
the final 6-inches of the footing bottom be excavated with a smooth mouthed bucket. Excavations for
foundations should be filled with concrete before the end of the workday or sooner if necessary to
prevent deterioration of the bearing surface. Prolonged exposure or inundation of the bearing surface
with water will result in changes in strength and compressibility characteristics. If delays occur, the
excavation should be deepened as necessary and cleaned, in order to provide a fresh bearing surface.
If more than 24 hours of exposure of the bearing surface is anticipated in the excavations, a “mud slab”
should be used to protect the bearing surfaces. If a mud slab is used, the foundation excavations
should initially be over-excavated by approximately 4 inches and a lean concrete mud slab of
approximately 4 inches in thickness be placed in the bottom of the excavations immediately following
exposure of the bearing surface by excavation. The mud slab will protect the bearing surface, maintain
Project No. 15-20061.2Page 8
more uniform moisture in the subgrade, facilitate dewatering of excavations if required, and provide a
working surface for the placement of formwork and reinforcing steel.
6.3.3Underreamed Drilled Pier Foundations–Buildings 2 and 3
Drilled pier foundations can be utilized to support the structural loads of the proposed Buildings2 and
3. We recommend auger excavated, underreamed, steel-reinforced, cast-in-place concrete piers
bearing within the claysor clayey sandsat a depth of 15feet below the existing grade at the time of
Rone’s field investigation for support of the proposed buildings. These piers may be proportioned
using a net allowable end bearing pressure of 3,500 pounds per square foot (psf). The allowable
bearing value includes a minimum factor of safety of 3 against shear failure of the foundation bearing
soils. Foundation piers designed and constructed in accordance with the information provided in this
report will experience a total settlement equal to or less than 1 inch.
The piers will be subjected to vertical uplift pressures caused by expansion within the near surface clay
soils. Therefore, each pier must contain reinforcing steel throughout the full length of the shaft to
counteract these pressures. These vertical uplift pressures are expected to be up to 1,800 psf of
perimeter surface area over a depth of up to 12 feet. Uplift forces should not be developed on piers
penetrating through the select fill.Uplift forces can be reduced to 800 psf in the moisture-conditioned
subgrade. The uplift force can be resisted by the dead load on the shafts plus the uplift resistance
provided by the underream portion of the piers. The passive failure plane originates from the bottom
edge of the bell and radiates outward at an angle of 30 degrees from the vertical.
The piers should be provided with an underream diameter to shaft diameter ratio not less than 2 to 1,
and not greater than 3 to 1. For uplift considerations, piers should not be spaced closer than 2
underream diameters(edge to edge) based on the diameter of the larger pier. Closer pier spacing
may result in reduced uplift capacity. We should be contacted to review closer pier spacing on a case-
by-case basis.
6.3.4Construction Considerations for Drilled Piers–Buildings 2 and 3
The construction of all piers should be observed by experienced geotechnical personnel during
construction to assure compliance with design assumptions and to confirm:
(1)the bearing stratum;
(2)the underream size;
Project No. 15-20061.2Page 9
(3)the removal of all smear zones and cuttings;
(4)that groundwater seepage, when encountered, is correctly handled; and
(5)that the shafts are vertical (within the acceptable tolerance).
Groundwater seepage was encountered in mostof the borings during our field investigation.
Groundwater seepage may be encountered during pier installation. The risk of encountering seepage
is increased during and after periods of precipitation. It would be beneficial to determine the depth to
groundwater just prior to construction.Reinforcing steel and concrete should be ready and placed
immediately after the excavation has been completed, dewatered, cleaned, and observed to reduce
the risk of groundwater seepage and deterioration of the foundation-bearing surface.In no event
should a completed pier excavation be allowed to remain open for more than 2hours.
It should be noted that based on the borings, anticipated bearing stratum may consist of clayey sands
which will increase the possibility of the underream collapse. The underreamangle can be increased
to 60 degrees to help limit the possibility of collapse.Careful measures should be taken to ensure that
the underream is stable before placing the concrete. We highly recommend underream pier
installation be monitored on a full-time basis by Rone’s experienced geotechnical personnel to confirm
conditions are as anticipated and to assure compliance with design assumptions.The use of straight-
shafts should be considered if the underreamscollapse.Generally,the straight-shaft is made the
same diameter as the underreamusing the same allowable end bearing.
Concrete should have a slump of 5 to 7 inches, and should not be allowed to strike the shaft sidewall
or steel reinforcement during placement. Submersible pumps may be required to control seepage.
We should be contacted for further evaluation and recommendations if excessive groundwater
seepage and/or underream collapse occurs.
6.3.5Grade Beams/Tilt Panels–Buildings 1, 2 and 3
Grade beams/tilt panels should be structurally connected into the top of the piers/footings. A
minimum void space of 4inchesshould be provided between the subgrade and the grade beams/tilt
panels for the structures,provided the subgrade treatmentis performed as described in section “6.4
SubgradeTreatment”. The void space allows movement of the soils below the grade beams/tilt
panels without distressing the structure. The excavation in which the void box lays must remain dry.
In addition, backfill material must not be allowed to enter the voidarea below grade beams/tilt
panels, since this reduces the void space.
Project No. 15-20061.2Page 10
Typically, a soil retainer in the form of a thin pre-cast panel or pieces of wood is placed along the
outside edge of the grade beams/tilt panelsto prevent the aforementioned soil intrusion. On-site
soil then may be placed against the sides of the grade beams/tilt panels.
6.3.6Graded-Supported Floor Slab–Buildings 1, 2 and 3
As mentioned earlier, potential ground movements up to 3inchesare possible at this site.
Subgrade treatment as describedbelow in Section “6.4 Subgrade Treatment” maybe necessaryto
reduce the PVR to about 1 inchfor grade-supported interior floor slabs.
We understand that the floor slabs are generally structurally connected to the perimeter beam or tilt
panels. Given that a grade-supported floor slab will be constructed with a PVR of approximately 1
inch, interior wall connections and racking systems should either be designed or placed such that
the potential movement can be tolerated. If the floor slab is structurally connected to the perimeter
wall and/or interior pier caps, we recommend that at a minimum, the following tasks be completed:
1.Backfill of the perimeter leave-out should be placed as moisture conditioned on-site soils as
outlined in Section “7.0 General Earthwork Recommendations”to reduce the potential for
differential swell near perimeter walls;
2.Moisture conditioning should extend at least 5 feet beyond the perimeter of the structure and
any adjacent flatwork sensitive to movement; and
3.A saw-cut joint should be installed approximately 6 to 8 feet inside the building perimeter to
assist in controlling potential hinge cracks that may occur.
A moisture barrier should be used beneath the interior floor slab in areas where floor coverings
will be utilized or in areas that are sensitive to moisture.
6.4Subgrade Treatment–Buildings 1, 2 and 3
Swell test results indicate that a PVR of up to 1inchshould be anticipated based on the current site
conditionsexcept at some isolated locations, such as Borings B-21, B-25, B-30 and B-41.However,
the TxDOT method shows that swellpotential could beas high as 3 inches at this site.Therefore,
we recommend the moisture profile and swell potential for each building be re-evaluated just prior to
theconstructionof each building. Supplemental moisture check borings shouldbe advanced to a
depth of about 12 feet just prior to the constructionof each buildingin order to determine the depth
and the extent of the areaforsubgrade treatment.Subgradetreatmentshould consist of removing
Project No. 15-20061.2Page 11
the active subgrade soils,replacing with moisture and density control,and capping with 1-footselect
fill. The depth and the extent of rework will be determined based on the results of the supplemental
moisture check borings.
Reworking of existing soilsshould be performed to increase the moisture of the soils to a level that
reduces their ability to absorb additional water that could result in post-construction heave in these
soils. Moisture-conditioned soils should extend at least 5 feet outside the foundation perimeter, or any
other adjacent features sensitive to differential movement. The subgrade should be excavated to the
planned depth below the final pad elevation. Any deleterious materials or rock fragments greater than
4 inches in diameter encountered within the soils should be removed, or rock may be processed to
less than 4 inches in size. The subgrade to receive moisture-conditioned soils should be scarified to a
depth of 6 inches, and compacted to 92to 96 percent of the material’s Standard Proctor dry density
(ASTM D698) at a workable moisture content at least 3percentage points above optimum. On-site
soils, select fill and imported fill material to be used as moisture-conditioned structural fill can then be
placed in loose lifts less than 9 inches, and placed and compacted as recommended in Section “7.0
General Earthwork Recommendations” to within 1 foot of final grade. The remaining upper 1 foot of
material placed should consist of select fill asdescribed in Section 7.0.
As an alternative to a select fill moisture cap, the upper 8 inches of the fill mayconsist of lime-treated
on-site clays. Lime treatmentof on-site claysgenerally requires approximately 6to 8percent lime by
dry weight; however, actual treatment ratios should be confirmed during construction. Crushed
limestone or concrete can also be used as select fill.
All fill placed on site within the building padshould be placed following the moisture treatment
guidelines provided herein.
There is a tendency for the subgrade to dry out after the subgrade treatment is complete. The
reworked/moisture-conditioned soilsshould be covered with select fill or lime-treated soil
immediately after completion of the subgrade treatment, and the surface should be kept moist prior
to slab construction.Select fill/ lime-treated soilshould not extend beyond the perimeter beam.
Moisture conditioned clay fill should be monitored and tested on a full-time basis by Rone Engineers to
confirmconditions are as anticipated and to confirmthe fill is placed with the proper moisture content
and degree of compaction. Density tests should be performed on each lift of fill placed.
Project No. 15-20061.2Page 12
6.5Pavement Design Recommendations
When designing proposed pavement sections for driveways and parking areas, subgrade conditions
must be considered along with expected traffic use/frequency, pavement type, and design period.
For this project, traffic loading and frequency conditions were assumed for various conditions as no
specific traffic information was provided. The following information and assumptions were used in
our analysis:
1.45,000 total design equivalent single axle load (ESAL) repetitions for parking areas
subjected to automobiles and light trucks;
2.100,000 total design ESAL repetitions for drive/fire lanes subjected to automobile, light
trucks and fire trucks;
3.500,000 total design ESAL repetitions for heavy duty pavements subjected to semi-
tractor trailers and dumpster trucks, or equivalent;
4.A concrete modulus of rupture of 530 psi;
5.A design life of 20years;
6.Initial serviceability, p, of 4.5 and a terminal serviceability, p, of2.0 for concrete
ot
pavements;
7.Reliability, 85 percent
8.Standard deviation, 0.35
9.Load transfer (“J” factor), 3.1 (doweled concrete pavement with edge support)
10.Drainage coefficient, 1.0
11.A k-value of 100 pci for subgrade consisting of clay soils and 150 pci for lime-stabilized
subgrade.
The pavement thickness determinations were performed in accordance with the “AASHTO Guide for
the Design of Pavement Structures (current edition)” guidelines. The minimum pavement sections
arepresented in the table below.Thesepavement sections are estimatedbased on assumed traffic
volumes. A more precise design can be made with detailed traffic loading information.
Project No. 15-20061.2Page 13
Portland Cement
Traffic UseDesignESAL CountConcrete (PCC)
Thickness (inches)
Parking Areas for Autos
45,0005
and Light Trucks
Drive Lanes for Autos and
100,0006
Light Trucks/Fire Lanes
Light Semi-Truck
500,0007
Traffic/Dumpster Areas
Concrete with a minimum 28-daycompressive strength of 3,500 pounds per square inch should be
used. As a minimum, reinforcing steel should consist of #3 bars spaced at amaximum of 18 inches
on centerin each direction.
Lime treatment of the pavement subgrade is recommended for PCC pavements subjected to heavy
truck traffic (7-inchpavement section). In small localized areas (dumpster pads, etc.), it may not be
practical to perform lime treatment. In these areas, the concrete thickness may be increasedby one
(1) inch and lime treatment omitted. Increased periodic maintenance (i.e. sealing of cracks/joints) is
critical to the long-term performance of the pavement in areas without subgrade treatment. Lime
treatment will improve pavement performance forthe 5-and 6-inch PCC sections; however, it is not
required. Periodic maintenance (i.e. sealing of cracks and joints) should be performed to prevent
water intrusion into the underlying clay subgrade. The pavement surface should be contoured such
that surface water drains off and away from the pavement or into inlets. Water allowed to pond on or
adjacent to pavement surfaces could saturate the subgrade soils leading to premature pavement
failure.
Pavement recommendations are based on the assumed loadingconditions and commonly accepted
design procedures that should provide satisfactory performance for the design life of 20 years for
the assumed traffic loadings. The concrete pavement should have between 4 and 6 percent
entrained air. Hand-placed concrete should have a maximum slump of six inches. A sand-leveling
course should not be permitted beneath pavements. All steel reinforcement, dowel
spacing/diameter, and pavement joints should conform to applicable city standards.
Project No. 15-20061.2Page 14
6.6Pavement Subgrade Preparation
All topsoil, vegetation, and any unsuitable materials should be removed. The pavement subgrade
should be proofrolled with a fully loaded tandem axle dump truck or similar pneumatic-tire equipment
to locate areas of loose subgrade. In areas to be cut, the proofroll should be performed after the
final grade is established. In areas to be filled, the proofroll should be performed prior to placement
of engineered fill and after subgrade construction is complete. Areas of loose or soft subgrade
encountered in the proofroll should be removed and replaced with engineered fill, or moisture
conditioned (dried or wetted, as needed) and compacted in place.
Grading and compaction of pavement subgrade should follow the recommendations in the “General
Earthwork Recommendations” section. The final grades must be such that drainage is facilitated,
and access of surface water to the subgrade materials is prevented.
The existingsoils in the area are plastic and can undergo some volume change when subjected to
moisture variations. If the moisture contents of these soils reduce, they may shrink and cracks may
develop. If the moisture content of these materials increases, they could swell and lose strength.
Shrinkage, swelling, or strength loss could be detrimental to the proper function of the pavement.
Lime treatment of clay subgrade willprovide more uniform subgrade support and improve these
soil's strength characteristics. Where used, we recommend a minimum of 7percent lime (by dry soil
weight) to a depth of 6 inches. However, the actual percentage lime required should be determined
during site development by completing a lime series test. Lime stabilization should be performed in
accordance with Item 260, current Standard Specifications for Construction of Highways, Streets,
and Bridges, Texas Department of Transportation (TxDOT) or applicable standards.
Clayey sand, sandy clay or sandy soils will not benefit from lime treatment. In these areas, cement
treatment may be necessary. Portland cement treatment should be in accordance with TxDOT Item
275, "Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges." It
is anticipated that 5 percent by dry weight of Portland cement will be required to stabilize the clayey
sand or sandy clay subgrade to a depth of 6 inches. The cement treated subgrade should be
thoroughly mixed and compacted to 95 percent of standard Proctor density at optimum moisture
content to + 3 percent. Compaction of the treated subgrade should be performed no later than 4 hours
after adding and mixing the cement into the subgrade.The actual percentage of cement required
should be confirmed in the field by collecting soil samples during construction once pavement
Project No. 15-20061.2Page 15
subgrade elevation is attained. A cement series test should be performed on the sample collected and
the results should be used to determine the actual percentage of cement required.
The amount and type of stabilization should be determined when the site is graded and the
pavement subgrade exposed. The readers should understand that lime/cementstabilizing the
upper 6 inches of the subgrade soils will not reduce the shrinking and swelling of the subgrade,
which normally occurs with the seasonal moisture fluctuations. Therefore, some differential vertical
movements of the pavements should be expected.
Water can be introduced beneath the pavement through granular materials used for aggregate
bases and utility line embedment, and can cause differential movement in the pavement. Aggregate
base or a granular leveling course should not be used beneath pavements, and all utilities should
have clay plugs substituted for granular embedment material at the edges of the pavement to
reduce the risk of moisture access and possible swelling.
6.7 General
All grade supported slabs, outward swinging doors, outside stairs, etc. should be designed to
accommodate anticipated potential movements at this site as presented at the beginning of this
section.
Every attempt should be made to limit the extreme wetting or drying of the subsurface soils because
swelling and shrinkage of these soils will result. Standard construction practices of providing good
surface water drainage should be used. A positive slope of the ground away from any foundation
should be provided. Also, ditches or swales should be provided to carry the run-off water both
during and after construction. Lawn areas should be watered moderately, without allowing the clay
soils to become too dry or too wet. Roof runoff should be collected by gutters and downspouts, and
should discharge away from the building.
Backfill for utility lines or along the perimeter beams should consist of site-excavated soil. If the
backfill is too dense or too dry, it will swell and a mound will form along the trench line. If the backfill
is too loose or too wet, it will settle and a sink will form along the trench line. Backfill should be
compacted as recommended in the section titled “General Earthwork Recommendations” below.
Project No. 15-20061.2Page 16
If granular material is used for embedment in utility trenches,we recommend placing a clay plug, as
a replacement for the granular embedment, at the location where the city line is located, at the
location where the utility enters the structure and at other connections. The intent is to limitany free
moisture from passing through the granular embedment and entering the soil beneath the
structures.
Root systems from trees and shrubs can draw a substantial amount of water from the clay soils at
this site, causing the clays to dry and shrink. This could cause settlement beneath grade-supported
slabs such as foundation slabs, walks and paving. Trees and large bushes should be located a
distance equal to at least one-half their anticipated mature height away from grade slabs.
All excavations should be sloped, shored, or shielded in accordance with OSHA requirements.
7.0 GENERAL EARTHWORK RECOMMENDATIONS
7.1 GeneralDiscussion
The following recommendations for site preparation and fill placement may contain elements that do
not appear to apply to the presently known conditions at the project site. These items have been
included in this appendix since our experience has been that unforeseen obstacles are encountered
on some project sites, and progress can be delayed while written guidance is prepared. While we
cannot cover every possible circumstance, we have attempted to address the most frequently
occurring issues in this report section.
7.2Site Grading
Site grading operations, where required, should be performed in accordance with the
recommendations provided in this report. The site grading plans and construction should strive to
achieve positive drainage around all sides of the proposed Buildings 1, 2 and 3. Inadequate
drainage around structures built on-grade will cause excessive vertical differential movements to
occur.
7.3 Site Preparation
Preparation of the site for any future construction should include the removal and proper disposal of
all obstructions that would hinder construction. These obstructions should include all abandoned
structures, foundations, debris, water wells, septic tanks and loose material. It is the intent of these
Project No. 15-20061.2Page 17
recommendations to provide for the removal and disposal of all obstructions not specifically provided
for elsewhere by the plans and specifications.
All concrete, trees, stumps, brush, abandoned structures, roots, vegetation, rubbish and any other
undesirable matter should be removed and disposed of properly. It is the intent of these
recommendations to provide a loose surface with no features that would tend to prevent uniform
compaction by the equipment to be used.
In general, we recommend that all active utilities that would extend beneath the building and are not
intended to provide service to the structure be rerouted around the building footprint, and the
abandoned lines be removed and disposed of properly. All abandoned utilities within the building
that are not removed represent a risk to future building performance; if the lines are abandoned in
place, they must be fully grouted and capped so that the pipes do not provide a ready conduit for
water.
The exposed surface should be proofrolled with a fully loaded, tandem-axle dump truck or similar
pneumatic-tire equipment to locate areas of unsuitable subgrade. In areas to be cut, the proofroll
should be performed after the final grade is established. In areas to be filled, the proofroll should be
performed prior to placement of engineered fill and after subgrade construction is complete. Areas
of loose or soft subgrade encountered in theproofroll should be removed and replaced with
engineered fill, or moisture conditioned (dried or wetted, as needed) and compacted in place.
All areas to be filled should be disced or bladed until uniform and free from large clods. Soils should
be brought to the proper moisture content and compacted as indicated in the following “Fill
Placement Criteria”table.
Fill Placement Criteria
Plasticity Compaction Moisture
Item DescriptionDensity Requirement
RequirementStandard Requirement
Optimum moisture to
General 95% to 100% of
On-site soilsNoneASTM D698
4% above optimum
grading
maximum dry density
moisture
Optimum moisture to
Imported General Liquid Limit (LL) 95% to 100% of
ASTM D6984% above optimum
general fillgradingless than 60 maximum dry density
moisture
Moisture
92% to 96% of At least 3% above
conditioned Structural fillNoneASTM D698
maximum dry densityoptimum moisture
on-site soils
Project No. 15-20061.2Page 18
Plasticity Compaction Moisture
Item DescriptionDensity Requirement
RequirementStandard Requirement
Select fill
95% to 100% of Within 2% of optimum
(sandy clay or Structural fillASTM D698
maximum dry densitymoisture
clayey sand)
Select fill Per TxDOT Item
95% to 100% of Within 2% of optimum
(crushed rock Structural fill247, Type A or ASTM D698
maximum dry densitymoisture
or concrete)C, Grade 2 or 3
Pavement Pavement 95% to 100% of 0% to 4% above
See report textASTM D698
subgradesupportmaximum dry densityoptimum moisture
7.4Select Fill
Select fill should consist of a clean, natural soil meeting the criteria listed in the table above. The fill
should have a moisture content within the specified range, be placed in loose lifts less than 9 inches
thick, and compacted as indicated. Lime-treated, on-site soils may also be used as the select fill
cap, provided the PI of the material meets the specifications for select fill. Lime treatmentof on-site
claysgenerally requires approximately 6 to 8 percent lime by dry weight; however, the actual
percentage of lime should be determined once soils have been stockpiled and sampled.
Crushed limestone or concrete can also be used as select fill. Crushed limestone or concrete used
as select fill should be placed in loose lifts less than 9 inches thick and meet the material, moisture,
and compaction criteria indicated in the table above.
All fills should be placed in level, uniform layers, which, when compacted, should have a moisture
content and density conforming to the stipulations called for herein. Each layer should be
thoroughly mixed during spreading to provide uniformity of thelayer. The fill thickness should not
exceed 9-inch loose lifts.
7.5Density Tests
Field Density tests should be made by the Soils Engineer or his representative. Density tests should
be taken in each layer of the compacted material below the disturbed surface. If the materials fail to
meet the density specified, the course should be reworked as necessary to obtain the specified
compaction.
Project No. 15-20061.2Page 19
8.0 CONSTRUCTION OBSERVATIONS
In any geotechnical investigation, the design recommendations are based on a limited amount of
information about the subsurface conditions. In the analysis, the geotechnical engineer must
assume the subsurface conditions are similar to the conditions encountered in the borings.
However, during construction quite often anomalies in the subsurface conditions are revealed.
Therefore, it isrecommended that Rone Engineering Services, Ltd. be retained to observe
earthwork and foundation installation and perform materials evaluation and testing during the
construction phase of the project. This enables the geotechnical engineer to stay abreast of the
project and to be readily available to evaluate unanticipated conditions, to conduct additional tests if
required and, when necessary, to recommend alternative solutions to unanticipated conditions. Until
these construction phase services are performed by the project geotechnical engineer, the
recommendations contained in this report on such items as final foundation bearing elevations, final
depth of undercut of expansive soils for non-expansive earth fill pads, and other such subsurface-
related recommendations should be considered as preliminary.
It is proposed that construction phase observation and materials testing commence by the project
geotechnical engineer at the outset of the project. Experience has shown that the most suitable
method for procuring these services is for the owner to contract directly with the project geotechnical
engineer. This results in a clear, direct line of communication between the owner and the owner's
design engineers, and the geotechnical engineer.
9.0 REPORT CLOSURE
The analyses, conclusions and recommendations contained in this report are based on site
conditions as they existed at the time of the field investigation and further on the assumption that the
exploratory borings are representative of the subsurface conditions throughout the site; that is, the
subsurface conditions everywhere are not significantly different from those disclosed by the borings
at the time they were completed. If during construction, different subsurface conditions from those
encountered in our borings are observed, or appear to be present in excavations, we must be
advised promptly so that we can review these conditions and reconsider our recommendations
where necessary. If there is a substantial lapse of time between submission of this report and the
start of the work at the site, if conditions have changed due either to natural causes or to
construction operations at or adjacent to the site, or if structure locations, structural loads or finish
grades are changed, we urge that we be promptly informed and retained to review our report to
Project No. 15-20061.2Page 20
determine the applicability of the conclusions and recommendations, considering the changed
conditions and/or time lapse.
Further,it is urgedthat Rone Engineering Services, Ltd. be retained to review those portions of the
plans and specifications for this particular project that pertain to earthwork and foundations as a
means to determine whether the plans and specifications are consistent with the recommendations
contained in this report. In addition, we are available to observe construction, particularly the
compaction of structural fill, or backfill and the construction of foundations as recommended in the
report, and such other field observations as might be necessary.
This report has been prepared for the exclusive use of the Clientand theirdesignated agents for
specific application to design of this project. We have used that degree of care and skill ordinarily
exercised under similarconditions by reputable members of our profession practicing in the same or
similar locality. No warranty, expressed or implied, is made or intended.
Project No. 15-20061.2Page 21
APPENDIX A
APPENDIX B
FIELD OPERATIONS
Subsurface conditions were defined by 36sample borings located as shown on the Boring Location
Diagram, Plate A.3. The borings were drilled at locations staked in the field by Rone. The borings
were advanced between sample intervals using continuous flight auger drilling procedures. The
results of each boring are shown graphically on the Logs of Boring, Plates A.4 throughA.39.
Sample depth, description, and soil classification based on the Unified Soil Classification System
are shown on the Logs of Boring. Keys to the symbols and terms used on the Logs of Boring are
presented on Plates A.40and A.41.
Relatively undisturbed samples of cohesive soils were obtained with Shelby tube samplers in general
accordance with ASTM D1587 at the locations shown on the Logs of Boring. The Shelby tube sampler
consists of a thin-walled steel tube with a sharp cutting edge connected to a head equipped with a ball
valve threaded for rod connection. The tube is pushed into the undisturbed soils by the hydraulic pull-
downof the drilling rig. The soil specimens were extruded from the tube in the field,logged, tested for
consistency with a hand penetrometer, sealed, and packaged to maintain "in situ" moisture content.
The consistency of cohesive soil samples was evaluated in the field using a calibrated hand
penetrometer. In this test,a 0.25-inch diameter piston is pushed into the undisturbed sample at a
constant rate to a depth of 0.25-inch. The results of these tests are tabulated at respective sample
depths on the logs. When the capacity of the penetrometer is exceeded, the value is tabulated as
4.5+.
Samples of cohesive and granular soil wereobtained using split-barrel sampling procedures in
general accordance with ASTM D1586. In the split-barrel procedure, a disturbed sample is obtained
in a standard 2 inch OD split barrel-sampling spoon driven into 18 inches into the ground using a
140-pound hammer falling freely 30 inches. The number of blows for the last 12 inches of a
standard 18-inch penetration is recorded as the Standard Penetration Test resistance (N-value).
The N-values are recordedon the boring logs at the depth of sampling. The samples were sealed
and returned to our laboratory for further examination and testing.
The shaleand sandstoneencountered werealso evaluated with a modified version of the Texas Cone
Penetration test. Texas Department of Transportation (TX-DOT) Test Method Tex-132-E specifies
driving a 3-inch diameter cone with a 170-pound hammer freely falling 24 inches. This results in 340
B-1
foot-pounds of energy for each blow. This method was modified by utilizing a140-pound hammer
freely falling 30 inches. This results in 350 foot-pounds of energy for each hammer blow. In relatively
soft materials, the penetrometer cone is driven 1 foot and the number of blows required for each 6-inch
penetration is tabulated at respected test depths, as blows per 6 inches on the log. In hard materials
(rock or rock-like), the penetrometer cone is driven with the resulting penetrations, in inches, recorded
for the first and second 50 blows, a total of 100 blows. The penetration for the total 100 blows is
recorded at the respective testing depths on the boring logs.
Groundwater observations during and after completion of the boring are shown on the upper right of
the boring logs. Upon completion of the boring, the boreholes werebackfilled from the top and
plugged at the surface.
B-1
LABORATORY TESTING
General
Laboratory tests were performed to define pertinent engineering characteristics of the soils
encountered. The laboratory tests included moisture content, gradation (percentage of material
passing through a standard U.S. No. 200 sieve), Atterberg limits determination, free swell,
unconfined compressive strength,dry unit weight and visual classification.
Classification Tests
Classification of soils was verified by natural moisture content and Atterberg limits determinations.
These tests were performed in general accordance with American Society for Testing and Materials
(ASTM) procedures. The Atterberg limits, gradationsand natural moisture content determinations
are presented at the respective sample depths on the Logs of Boring.
Free Swell Tests
Selected samples of the near-surface cohesive soils were subjected to free swell tests. In the free
swell test, a sample is placed in a consolidometer and subjected to the estimated overburden
pressure. The sample is then inundated with water and allowed to swell. Moisture contents are
determined both before and after completion of the test. Test results are recorded as the percent
swell, with initial and final moisture content.
Strength Tests
Unconfined compression tests were performed on selected samples of cohesive soils. In the
unconfined compression test, a cylindrical specimen is subjected to axial load at a constant rate of
strain until failure occurs. Test procedures were in general accordance with ASTM D2166.
Strengths determined by this test are tabulated at their respective sample depths on the logs of
borings. Results of natural moisture content and dry unit weight determinations are also tabulated at
the respective sample depths on the logs.
B-2