GEOTECHNICAL INVESTIGATION

CITY OF COLLEGE STATION

SANDY POINT PUMP STATION IMPROVEMENTS

7290 SANDY POINT ROAD

BRYAN, TEXAS

Reported to

Malcolm Pirnie/Arcadis

Houston, Texas

by

Aviles Engineering Corporation

5790 Windfern

Houston, Texas 77041

713-895-7645

REPORT NO. G118-13

May 2013

TABLE OF CONTENTS

1.0 INTRODUCTION ................................................................................................................................... 1

1.1 Project Description .............................................................................................................................. 1

1.2 Authorization ....................................................................................................................................... 1

1.3 Purpose and Scope .............................................................................................................................. 1

2.0 SUBSURFACE EXPLORATION .......................................................................................................... 2

3.0 LABORATORY TESTING .................................................................................................................... 3

3.1 Geotechnical Laboratory Testing ....................................................................................................... 3

3.2 Chemical Analyses ............................................................................................................................... 3

4.0 SITE CONDITIONS ............................................................................................................................... 4

4.1 Subsurface Conditions ........................................................................................................................ 4

4.2 Subsurface Variations ......................................................................................................................... 5

5.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS ............................................................ 6

5.1 Abandonment of Existing Wet Well .................................................................................................. 6

5.2 Cooling Tower ..................................................................................................................................... 7

5.2.1 Option 1 - Mat Foundation ............................................................................................................ 8

5.2.2 Option 2 - Straight Sided Drilled Shafts ........................................................................................ 8

5.2.3 Concrete Basin............................................................................................................................. 10

5.3 Sodium Hypochlorite Bulk Storage Tanks ...................................................................................... 12

5.3.1 Drilled-and-Underreamed Footings ............................................................................................. 12

5.3.2 Floor Slab .................................................................................................................................... 14

5.3.2.1 Option 1 - Structural Floor Slab .............................................................................................. 16

5.3.2.2 Option 2 - Subgrade Supported Floor Slab .............................................................................. 16

5.4 Precast Concrete Building ................................................................................................................ 18

5.5 Installation of Underground Utilities by Open-Cut Method ......................................................... 18

5.5.1 Geotechnical Parameters for Underground Utilities .................................................................... 18

5.5.2 Loadings on Pipes ........................................................................................................................ 19

5.5.3 Deflections of Flexible Pipes ....................................................................................................... 20

5.5.4 Trench Stability ........................................................................................................................... 21

5.5.5 Thrust Force Design Recommendations ...................................................................................... 24

5.5.6 Bedding and Backfill ................................................................................................................... 25

5.6 Asphalt Pavement Driveway ............................................................................................................ 25

5.6.1 Flexible Pavement ....................................................................................................................... 25

5.6.2 Pavement Subgrade ..................................................................................................................... 27

5.7 Fill Requirements .............................................................................................................................. 27

5.7.1 Select Fill ..................................................................................................................................... 27

5.7.2 General Fill .................................................................................................................................. 28

5.8 Site Preparation and Grading .......................................................................................................... 29

6.0 CONSTRUCTION MONITORING .................................................................................................... 29

7.0 GENERAL ............................................................................................................................................. 29

8.0 LIMITATIONS ..................................................................................................................................... 30

9.0 CLOSING REMARKS ......................................................................................................................... 30

APPENDICES

Appendix A

Plate A-1 Vicinity Map

Plate A-2 Boring Location Plan

Plates A-3 to A-5 Boring Logs

Plate A-6 Key to Symbols

Plate A-7 Classification of Soils for Engineering Purposes

Plate A-8 Terms Used on Boring Logs

Plate A-9 ASTM & TXDOT Designation for Soil Laboratory Tests

Plate A-10 Sieve Analysis Test Results

Appendix B

Plate B-1 Allowable Accumulative Unit Skin Friction vs. Depth for Straight Sided Drilled Shafts

Plate B-2 Allowable Unit End Bearing vs. Depth for Straight Sided Drilled Shafts

Plate B-3 Allowable Compressive Load vs. Depth for Straight Sided Drilled Shafts

Appendix C

Plate C-1 Recommended Geotechnical Design Parameters for Underground Utilities

Plate C-2 Load Coefficients for Pipe Loading

Plate C-3 Live Loads on Pipe Crossing Under Roadway

Appendix D

Plate D-1 Critical Heights of Cuts in Nonfissured Clays

Plate D-2 Maximum Allowable Slopes

Plate D-3 A Combination of Bracing and Open Cuts

Plate D-4 Lateral Pressure Diagrams for Open Cuts in Cohesive Soil-Long Term Conditions

Plate D-5 Lateral Pressure Diagrams for Open Cuts in Cohesive Soil-Short Term Conditions

Plate D-6 Lateral Pressure Diagrams for Open Cuts in Sand

Plate D-7 Bottom Stability for Braced Excavation in Clay

Plate D-8 Thrust Force Calculation

Plate D-9 Thrust Force Example Calculation

Plate D-10 Design Parameters for Bearing Thrust Block

Appendix E

A&B Laboratories Chemical Analyses

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GEOTECHNICAL INVESTIGATION

CITY OF COLLEGE STATION

SANDY POINT PUMP STATION IMPROVEMENTS

7290 SANDY POINT ROAD

BRYAN, TEXAS

1.0 INTRODUCTION

1.1 Project Description

Aviles Engineering Corporation (AEC) performed a geotechnical investigation for the City of College Station’s

proposed Sandy Point Pump Station Improvements, located at 7290 Sandy Point Road in Bryan, Texas. A

vicinity map is presented on Plate A-1, in Appendix A. Based on information provided by Malcolm

Pirnie/Arcadis, AEC understands that the improvements include: (i) a 20-foot high, 85 foot long by 35 foot wide

cooling tower; (ii) two 9 foot diameter by 10.5 foot high sodium hypochlorite bulk storage tanks within a metal

building canopy structure; (iii) an 8 foot long by 8 foot wide precast concrete building adjacent to the bulk storage

tanks; (iv) an asphalt pavement driveway; and (v) 14- to 48 inch diameter waterlines at the cooling tower. The

waterlines will have a maximum invert depth of approximately 10 feet and will be installed by open cut method.

1.2 Authorization

The investigation was authorized via Subcontract Agreement between AEC and Arcadis on March 26, 2013, by

Mr. Jonathan Howard, Principal of Arcadis, based upon AEC Proposal No. G2013-01-03, dated January 11,

2013.

1.3 Purpose and Scope

The purpose of this geotechnical investigation is to evaluate the subsurface soil conditions at the project site and

develop geotechnical engineering recommendations for design and construction of the proposed cooling tower,

bulk storage tank, precast concrete building, underground utilities, and asphalt driveway. The scope of this

geotechnical investigation is summarized as below:

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1. Soil drilling and sampling of three geotechnical borings to 50 feet deep;

2. Soil laboratory testing on selected soil samples;

3. Engineering analyses and recommendations for foundation type(s) and depth, allowable bearing capacity for

mat foundation, axial capacity for drilled shafts, and subgrade preparation for the cooling tower;

4. Engineering analyses and recommendations for foundation type and depth, allowable bearing capacity, floor

slab, and subgrade preparation for the bulk tanks, canopy structure, and precast concrete building;

5. Engineering analyses and recommendations for installation of underground utilities by open cut method,

including trench shoring, bottom stability, bedding, and backfill

6. Engineering analyses and recommendations for the asphalt driveway, including pavement thickness design

and subgrade preparation;

7. Recommendations for construction of the foundations, utilities, and pavement.

2.0 SUBSURFACE EXPLORATION

Subsurface conditions at the site were investigated by drilling three soil borings to 50 feet below grade; Borings

B-1 and B-2 were performed within the cooling tower footprint and Boring B-3 was performed within the bulk

storage tank footprint. The total drilling footage was 150 feet. Boring locations were selected by AEC and

confirmed by Malcolm Pirnie in the field prior to arrival of the drill rig. Boring survey data was not available at

the time this report was prepared. The approximate boring locations are shown on the attached Boring Location

Plan on Plate A-2, in Appendix A.

The field drilling was performed with a truck-mounted drilling rig initially using dry auger method, then using

wet rotary method once groundwater and granular soils were encountered. Undisturbed samples of cohesive soils

were obtained from the borings by pushing 3-inch diameter thin-wall, seamless steel Shelby tube samplers in

accordance with ASTM D 1587. Granular soils were sampled with a 2-inch split-barrel sampler in accordance

with ASTM D 1586. Standard Penetration Test resistance (N) values were recorded for the granular soils as

“Blows per Foot” and are shown on the boring logs. Strength of the cohesive soils was estimated in the field using

a hand penetrometer. The undisturbed samples of cohesive soils were extruded mechanically from the core

barrels in the field and wrapped in aluminum foil; all samples were sealed in plastic bags to reduce moisture loss

and disturbance. The samples were then placed in core boxes and transported to the AEC laboratory for testing

and further study. The bore holes were left open for 24 hours so that additional groundwater readings could be

obtained. After the 24 hour readings were obtained, the borings were backfilled with bentonite chips. Details of

the soils encountered in the borings are presented on Plates A-3 through A-5, in Appendix A.

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3.0 LABORATORY TESTING

3.1 Geotechnical Laboratory Testing

Soil laboratory testing was performed by AEC personnel. Samples from the borings were examined and classified

in the laboratory by a technician under supervision of a geotechnical engineer. Laboratory tests were performed

on selected soil samples in order to evaluate the engineering properties of the foundation soils in accordance with

applicable ASTM Standards. Atterberg limits, moisture contents, sieve analysis, percent passing a No. 200 sieve,

and dry unit weight tests were performed on typical samples to establish the index properties and confirm field

classification of the subsurface soils. Strength properties of cohesive soils were determined by means of torvane

(TV), unconfined compression (UC), and undrained-unconsolidated (UU) triaxial tests performed on undisturbed

samples. The test results are presented on their representative boring logs. A key to the boring logs, classification

of soils for engineering purposes, terms used on boring logs, and reference ASTM Standards for laboratory testing

are presented on Plates A-6 through A-9, in Appendix A. Sieve analyses are presented on Plate A-10, in

Appendix A.

3.2 Chemical Analyses

To evaluate the potential for sulfate and chloride attack on subgrade stabilization and underground utilities, we

selected one soil sample for chemical analyses. Resistivity, Sulfate, Chloride, and pH analyses were performed by

A & B Laboratories, Inc. A summary of the analysis results are presented on Table 1 below. A copy of the reports

by A&B Laboratories is presented in Appendix E.

Table 1. Resistivity, Sulfate, Chloride, and pH Analysis Results

Sample ID Resistivity

(ohm/cm)

Sulfate

(mg/kg)

Chloride

(mg/kg) pH

Aggressive

Environment

B-2, 8’-10’ 2155 (not tested) 8010 7.64 Yes

B-3, 2’-4’ 14124 10.6 99.6 7.02 No

Whenever the pH value is 4.5 or less, the foundation design should be based on an aggressive subsurface

environment. Alternately, if the resistivity is less than 2,000 ohms/cm, the soils should be treated as aggressive.

If the soil resistivity is between 2,000 and 5,000 ohms/cm, and the chloride ion content is greater than 100 parts

per million (ppm) or the sulfate ion content is greater than 200 ppm, the foundation design should be based on an

aggressive subsurface environment. Resistivity values greater than 5,000 ohms/cm are considered non-aggressive

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environments. Based on the above criteria, the soil sample tested from Boring B-2 at a depth of 8 to 10 feet can

be considered an aggressive environment, while the sample from Boring B-3 at a depth of 2 to 4 feet can be

considered a non-aggressive environment.

4.0 SITE CONDITIONS

Based on our site visit, the proposed improvements will be located primarily on the west side of the existing

facility. The proposed cooling towers will be located on a flat grassy area between two 1 to 2 foot high retaining

walls (from cooling towers that were previously demolished at the site), while the bulk storage tanks will be

located in a flat grassy area to the west of the existing horizontal surge tank.

4.1 Subsurface Conditions

The soil strata encountered in our borings are summarized below:

Boring Depth (ft) Description of Stratum

B-1 0 - 4 Fill: stiff to very stiff, Sandy Lean Clay (CL), with roots, sand and clay

pockets, and gravel

4 - 6 Fill: Poorly Graded Sand w/Silt (SP-SM), with gravel and clay pockets

6 - 10 Fill: Clayey Sand (SC), with lean clay pockets

10 - 14 Fill: stiff to very stiff, Sandy Lean Clay (CL), with abundant sand seams and

pockets

14 - 18 Clayey Sand (SC)

18 - 28 Medium dense to very dense, Silty Sand (SM)

28 - 43 Firm to hard, Fat Clay (CH), with slickensides

43 - 50 Very dense, Silty Sand (SM)

B-2 0 - 2 Fill: hard, Sandy Lean Clay (CL), with silt seams and gravel

2 - 4 Fill: stiff, Lean Clay (CL), with gravel

4 - 12 Fill: hard, Lean Clay (CL), with sand seams and pockets

12 - 14 Medium dense, Silty Sand (SM), with clay pockets

14 - 16 Medium dense, Clayey Sand (SC), with fat clay pockets

16 - 18 Medium dense, Poorly Graded Sand w/Clay (SP-SC)

18 - 22 Stiff to very stiff, Sandy Lean Clay (CL), with silty sand seams

22 - 28 Very dense, Silty Sand (SM), with clayey sand pockets

28 - 43 Very stiff to hard, Fat Clay (CH), with silt layers

43 - 50 Very dense, Clayey Sand (SC), with fat clay pockets

B-3 0 - 10 Hard, Sandy Fat Clay (CH)

10 - 22 Medium dense, Clayey Sand (SC)

22 - 32 Medium dense to dense, Silty Sand (SM)

32 - 45.5 Stiff to hard, Fat Clay (CH), with silt partings

45.5 - 50 Hard, Lean Clay (CL), with abundant silt seams

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The cohesive soils in the borings have Liquid Limits (LL) that varied from 24 to 80 and Plasticity Indices (PI) that

varied from 11 to 47. This indicates that the cohesive soils at the site have low to very high plasticity. The

cohesive soils encountered are classified as “CL” and “CH” type soils and the granular soils encountered are

classified as “SM”, “SC”, “SP-SM”, and “SP-SC” type soils in accordance with the Unified Soil Classification

System (USCS). “CH” soils undergo significant volume changes due to seasonal changes in soil moisture

contents. “CL” type soils with lower LL (less than 40) and PI (less than 20) generally do not undergo significant

volume changes with changes in moisture content. However, “CL” soils with LL approaching 50 and PI greater

than 20 essentially behave as “CH” soils and could undergo significant volume changes.

Groundwater was encountered in the borings at a depth of 18 to 29 feet below grade during drilling and was

subsequently observed at a depth of 14.1 to 23.8 feet approximately 15 minutes after the initial encounter,

indicating that the groundwater at the site could be pressurized. The groundwater levels varied from 11 to 25.1

feet below grade approximately 24 hours after completion of drilling. A summary of groundwater readings is

presented in Table 2.

Table 2. Groundwater Depths below Existing Ground Surface

Boring

No.

Boring

Depth

(ft)

Groundwater Depth

Encountered during

Drilling (ft)

Groundwater Depth

15 min. after Initial

Encounter (ft)

Groundwater

Depth After 24

Hours (ft)

B-1 50 18 n/a 13.1

B-2 50 18 14.1 11.0

B-3 50 29 23.8 25.1

The information in this report summarizes conditions found on the date the borings were drilled. It should be

noted that our groundwater observations are short-term; groundwater depths and subsurface soil moisture

contents will vary with environmental variations such as frequency and magnitude of rainfall and the time of year

when construction is in progress.

4.2 Subsurface Variations

It should be emphasized that: (i) at any given time, ground water depths can vary from location to location, and (ii)

at any given location, ground water depths can change with time. Ground water depths will vary with seasonal

rainfall and other climatic/environmental events. Subsurface conditions may vary away from and between the

boring locations.

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Clay soils in the Brazos Valley area typically have secondary features such as slickensides and contain sand/silt

seams/lenses/layers/pockets. It should be noted that the information in the boring logs is based on 3-inch diameter

soil samples which were generally obtained at intervals of 2 feet in the top 20 feet of the borings and at intervals

of 5 feet thereafter to the boring termination depths. A detailed description of the soil secondary features may not

have been obtained due to the small sample size and sampling interval between the samples. Therefore, while

some of AEC’s logs show the soil secondary features, it should not be assumed that the features are absent where

not indicated on the logs.

5.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS

Based on information provided by Malcolm Pirnie/Arcadis, AEC understands that the improvements include: (i)

a 20-foot high, 85 foot long by 35 foot wide cooling tower; (ii) two 9 foot diameter by 10.5 foot high sodium

hypochlorite bulk storage tanks within a 32 feet long by 18 feet wide metal building canopy structure; (iii) an 8

foot long by 8 foot wide precast concrete building adjacent to the bulk storage tanks; (iv) an asphalt pavement

driveway; and (v) 14- to 48 inch diameter waterlines at the cooling tower. The waterlines will have a maximum

invert depth of approximately 10 feet and will be installed by open cut method.

5.1 Abandonment of Existing Wet Well

According to Malcolm Pirnie, there is an existing abandoned 17 foot deep wet well located to the east of the

proposed cooling tower location; however details regarding existing cooling tower foundation demolition or how

the wet well was abandoned (whether it was backfilled or not) were not available. In addition, the location and

dimensions of the wet well were not available at the time this report was prepared. AEC should be notified if

existing abandoned underground utilities or the wet well are located within (or immediately adjacent to) the

footprint of the proposed cooling tower so that our recommendations can be revised as necessary.

Abandonment of Underground Utilities: Existing drainage pipelines that are to be abandoned and are located

beneath or behind the existing wet well should be fully drained or pumped and backfilled with flowable fill (lean

concrete). Flowable fill should be in accordance with Item 401 of the 2004 Texas Department of Transportation

(TxDOT) Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges, or

equivalent local standards.

7

Partial Breaking of Wet Well Slab: At least twenty-four hours after the drainage pipelines have been backfilled

with flowable fill, the middle portion of the bottom slab should be cut with 2 to 3 inch diameter holes with a 5 foot

center-to-center spacing. A minimum 3 or 4 foot distance should be maintained from the core holes to the walls

of the wet well.

Saw Cut Top of Walls of the Wet Well: To avoid “hard spots” beneath future pavement and/or finished ground

surface, the top 12- to 24-inches of the wet well walls below the existing ground surface should be removed by

saw cutting.

Backfill of Wet Well: We recommend that a minimum 6 inch thick compacted bank sand blanket be placed on top

of the wet well slab. Bank sand should meet the requirements of ASTM C33 concrete sand. The concrete sand

should be placed in maximum 8 inch thick loose lifts and compacted to a minimum of 95 percent of its ASTM

D 698 maximum dry density at a moisture content within 2 percent of optimum. Above the compacted sand

blanket layer, compacted select fill should be used to backfill the wet well to the existing ground surface. The

select fill should be placed in maximum 8 inch thick loose lifts and compacted to a minimum of 95 percent of its

ASTM D 698 maximum dry density at a moisture content between optimum and 3 percent above optimum. Fill

within 3 feet of walls should be placed in loose lifts no more than 4 inches thick and compacted using hand

tampers, or small self-propelled compactors. Select fill requirements are presented in Section 5.7.1 of this report.

5.2 Cooling Tower

According to Malcolm Pirnie, the cooling tower will have a footprint that is approximately 85 feet long by 35 feet

wide. The cooling tower will be supported on concrete plinths within a 2 foot deep concrete basin; the bottom of

the basin slab will be approximately 6 to 12 inches below grade. The combined weight of the cooling tower and

water within the concrete basin will be approximately 500,000 pounds.

Based on Borings B-1 and B-2, the soil conditions at the cooling tower generally consist of approximately 12 to

14 feet of stiff to hard sandy lean clay (CL) and clayey/poorly graded sand (SC/SP-SM) fill at the ground surface,

underlain by approximately 14 to 16 feet of medium dense to very dense silty/clayey sand (SM/SC/SP-SC) and

stiff to very stiff sandy lean clay (CL), followed by approximately 15 feet of firm to hard fat clay (CH), then

approximately 7 feet of very dense clayey sand (SC) to the boring termination depths of 50 feet below grade. AEC

notes that the 12 to 14 feet of fill encountered in Borings B-1 and B-2 are not uniform. It is AEC’s opinion that

8

spread footings should not be used due to the concern of potential differential settlement. AEC recommends that

the cooling tower be supported on either a mat foundation or straight-sided drilled shafts.

5.2.1 Option 1 - Mat Foundation

Based on Borings B-1 and B-2, the top 12 to 14 feet of fill at the site consists of stiff to hard sandy lean clay and

medium dense clayey/poorly graded sand (SC/SP-SM). To reduce the potential of soil movement due to

differential settlement and provide competent and uniform soil support for the mat foundation, we recommend

that the mat foundation be founded at least 5 feet below existing grade. This option assumes that the structural

continuity and flexural strength of the mat foundation can bridge over non-uniform soils underneath, resulting in

smaller differential settlements than spread footings.

Mat Foundation: A mat foundation founded at 5 feet below existing grade can be designed for a net allowable

bearing capacity of 2,000 pounds per square foot (psf) for sustained loads and 3,000 psf for total loads, based on

a minimum factor of safety (FS) of 3 for sustained loads and 2 for total loads; whichever is critical should be used.

Modulus of Subgrade Reaction: The modulus of subgrade reaction (k) is frequently used in the structural analysis

of mat foundations. Based on the soil conditions encountered and the size of the mat foundation, we recommend

using k = 60 pounds per cubic inch (pci) for a mat foundation founded at a depth of 5 feet below the existing

ground surface.

Mat Settlement: A detailed settlement analysis for a mat foundation is beyond the scope of this investigation.

Based on the soil conditions encountered, we estimate that a mat foundation designed and constructed as

recommended will experience total settlements within 1 inch.

5.2.2 Option 2 - Straight Sided Drilled Shafts

Straight-sided drilled shafts can be used as an alternative to a mat foundation. We performed drilled shaft

analyses using O’Neill and Reese’s method, “Drilled Shaft Design and Construction” (1999). In the analyses, we

neglected skin friction from a zone of 5 feet below the ground surface to account for potential construction

disturbance and potential shrinkage of the surficial expansive clay fill soils. We used a FS of 2 and 3 for skin

friction and end bearing, respectively.

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The total allowable compressive axial bearing capacity of a straight-sided drilled shaft is the sum of the allowable

skin friction (obtained by multiplying the shaft perimeter by the allowable unit cumulative skin friction beginning

from 5 feet below existing grade to the design depth) and the allowable end bearing (obtained by multiplying the

drilled shaft cross-sectional area by the allowable unit end bearing at the design depth). The allowable

accumulative unit skin friction capacity vs. depth curve, allowable unit end bearing vs. depth curve, and allowable

compressive load vs. depth curve for 24-, 36-, and 48-inch diameter straight-sided drilled shafts are presented on

Plates B-1 through B-3, in Appendix B.

When a shaft tip is terminated in a strong layer underlain by a weak layer and the thickness between the shaft tip

and the top of the weak layer is less than 2 shaft diameters (feet), we recommend the use of the design end bearing

of the lower weak layer.

Drilled Shaft Spacing: To reduce the influence of adjacent drilled shafts and group effects, the minimum

center-to-center spacing between adjacent shafts should be at least 3 times the diameter of the larger shafts; the

minimum edge-to-edge spacing between adjacent shafts should not be less than 3 feet. For a drilled shaft group

with a pier cap in contact with the ground, the individual capacity of the drilled shaft should be multiplied by an

efficiency factor, η, where η = 0.75 for a center-to-center spacing of 3D (D is the diameter of the larger shaft) and

η = 1.0 for a center-to-center spacing of 6D. The value of η may be linearly interpolated for intermediate spacing.

The group capacity will be the smaller of: (i) the sum of the individual capacities of the drilled shaft multiplied by

η, or (ii) the bearing capacity for the block (i.e., the group of the drilled shafts and their enclosed soil mass acting

as a block foundation) failure. The minimum spacing must include proper allowances for cantilever tolerance of

alignment and possible oversizing of the drilled hole.

Drilled Shaft Settlements: A detailed settlement analysis for drilled shafts is beyond the scope of this

investigation. Based on the soil conditions encountered, we estimate that straight sided drilled shafts designed and

constructed as recommended will experience total settlements within 1 inch.

Drilled Shaft Construction: Drilled shaft foundations should be constructed in accordance with Item 416 of the

2004 TxDOT Standard Specifications, or equivalent local standards. Based on Borings B-1 and B-2, drilled shaft

excavations will encounter saturated granular soils from a depth of 12 to 14 feet below grade and groundwater at

14 to 18 feet below grade, which could cause sidewall sloughing or collapse during shaft excavation. To maintain

integrity of the shaft excavations, we recommend the use of temporary steel casing or bentonite slurry for drilled

shaft construction. AEC does not recommend the use of polymer slurry for shaft construction.

10

For slurry method, the bentonite slurry should be used prior to encountering ground water or granular soils and the

slurry head should be maintained at least 5 feet higher than the ground water at the site during construction. The

concrete should be placed using a tremie to displace the lower density slurry. Care must be taken to ensure that

tremie is positioned and maintained at the bottom of excavation until a height of 5 feet of concrete has been poured.

As more concrete is added, the tremie should be maintained at a minimum distance of 5 feet below the top of the

concrete pour.

New drilled shafts should not be excavated within 3 shaft diameters (edge to edge) of an open shaft excavation,

or one in which concrete has been placed in the preceding 24 hours, to prevent movement of fresh concrete from

the recently filled footing to an adjacent unfilled footing. Placement of concrete should be accomplished as soon

as possible after excavation to reduce changes in the state of stress and possible sloughing in the foundation soils.

No shafts should be left open overnight or poured without the prior approval of the Owner’s Representative.

In addition, each footing excavation should be inspected by a qualified Owner’s Representative prior to placing

concrete, to check that: (1) the footing excavation has been constructed to the specified dimensions at the

recommended depth and formation; and (2) excessive amounts of soil cuttings and any soft-compressible

materials have been removed from the bottom of the excavation.

5.2.3 Concrete Basin

Subgrade Preparation: Subgrade preparation should extend a minimum of 5 feet beyond the cooling tower basin

perimeter. A minimum of 6 inches of surface soils, existing vegetation, trees, roots, and other deleterious

materials should be removed and wasted. The excavation depth should be increased when inspection indicates the

presence of organics and deleterious materials to greater depths.

After surface stripping, existing overburden soils should be excavated to achieve either: (i) the bottom of the mat

foundation elevation at 5 feet below grade; or (ii) if drilled shafts are used to support the cooling tower, the bottom

of the basin slab elevation at approximately 6 to 12 inches below grade. The exposed subgrade should be

proof-rolled in accordance with Item 216 of the 2004 TxDOT Standard Specifications to identify and remove any

weak, compressible, or other unsuitable materials; such materials should be replaced with compacted select fill or

clean stabilized soils.

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Grade Beams: We recommend that foundation grade beams (if drilled shafts are used) be founded at least 30

inches below the lowest final grade. The grade beams can be constructed on 6 inch carton forms. If carton forms

are used, care should be taken so that the carton forms do not collapse during concrete placement and will not be

exposed to water in the grade beam excavations. Surface water should not be allowed to seep into and remain in

the carton form space during the life of the structures. If no carton forms will be used, we recommend that tensile

reinforcement be placed in both top and bottom of the beams. The drilled shafts and beams should be tied

together.

Moisture Barrier: We recommend that a horizontal moisture barrier (minimum 10-mil thick) be placed below the

concrete slab to move edge effects away from the slab and mitigate seasonal fluctuations of water content directly

below the structure.

Lateral Earth Pressures: The magnitudes of the lateral earth pressures on the basin walls will depend on the type

and density of the backfill, surcharge on the backfill, and hydrostatic pressure, if any. If the backfill is

over-compacted or if highly plastic clays are placed behind the walls, the lateral earth pressure could exceed the

vertical pressure.

Lateral pressure resulting from construction equipment, structural loads, or other surcharge on the top of the basin

walls should be taken into account by adding the equivalent uniformly distributed surcharge to the design lateral

pressure. Hydrostatic pressure should also be included in the design (while assuming the basin is drained). We

recommend that at least 240 psf uniform surcharge pressure be considered for design of the walls.

AEC assumes that the basin walls will be cast-in-place reinforced concrete and that no lateral movement is

allowed. As a result, the basin walls which can be designed based on at-rest earth pressure. The at-rest earth

pressure at depth z can be determined by Equation (1). The walls should consider short term and long term

conditions, whichever condition is critical should be used for design. Design soil parameters for retaining wall

design are presented on Plate C-1, in Appendix C.

p0 = (qs+γ h1+γ’ h2)K0 + γwh2 ............ Equation (1)

where, p0 = at-rest earth pressure, psf.

qs = uniform surcharge pressure, minimum 240 psf.

γ, γ’ = wet and buoyant unit weights of soil, pcf.

h1 = depth from ground surface to groundwater table, feet.

h2 = z-h1, depth from groundwater table to point under consideration, feet.

Z = depth below ground surface, feet.

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K0 = coefficient of at-rest earth pressure.

γw = unit weight of water, 62.4 pcf.

Basin Wall Backfill: If the basin excavation will be laid/stepped back, we recommend use of select fill as backfill

behind the basin walls. The excavation area should extend a minimum of 2 feet horizontally beyond the basin

perimeter, then slope upwards at a H:V = 1:1 slope or flatter. Select fill criteria are presented in Section 5.7.1 of

this report.

5.3 Sodium Hypochlorite Bulk Storage Tanks

Based on the drawings provided by Malcolm Pirnie, the two 9 foot diameter bulk storage tanks will be located

within a 32 foot long by 18 feet wide concrete basin, covered by a metal building canopy. Each bulk storage tank

will have an operating weight of approximately 60,000 pounds. Based on Boring B-3, the subsurface conditions

at the storage tanks generally consists of approximately 10 feet of hard fat clay (CH), underlain by approximately

22 feet of clayey/silty sand (SC/SM), followed by approximately 13.5 feet of stiff to hard fat clay (CH), then

approximately 4.5 feet of hard lean clay (CL) with silt to the boring termination depth of 50 feet below grade.

Based on Boring B-3, the surface soils within the structure footprint generally consist of highly expansive clay to

a depth of 10 feet. AEC recommends that the bulk storage tanks and canopy building be supported on

drilled-and-underreamed footings, founded on top of the medium dense clayey sand (SC) stratum at a depth of 10

feet below grade.

5.3.1 Drilled-and-Underreamed Footings

Allowable Bearing Capacity: AEC recommends that drilled-and-underreamed footings be founded at a depth of

10 feet below existing grade, and be designed for a net allowable bearing capacity of 3,500 psf for sustained loads

and 5,250 psf for total loads, based on a minimum FS of 3 for sustained loads and 2 for total loads, whichever is

critical should be used.

Uplift Capacity: According to O’Neill and Reese (1999), the uplift resistance of a drilled-and-underreamed

footing in cohesive soils can be calculated as:

Q (uplift) = (su Nu Au)/FS1 + Wc/FS2 + Ws/FS3 ............ Equation (2)

Nu = 1.5 Db / Bb ≤ 9 ............ Equation (3)

13

where: Q = Allowable uplift resistance of a drilled footing, lbs

su = Average undrained shear strength of the cohesive soil between the base of the bell and

2 Bb above the base; use su = 2,000 psf for this structure (based on Boring B-3)

Nu = Bearing capacity factor for base uplift resistance, Nu ≤ 9

Db = Depth of base below ground surface minus the seasonal moisture change zone for a

drilled and underreamed footing, ft; the seasonal moisture change zone in

Bryan/College Station can be considered as 15 feet below the existing ground surface

Bb = Diameter of the bell, ft

Bs = Diameter of the shaft, ft

Wc = Effective weight of concrete footing, lbs

Ws = Effective weight of projected soil above the bell, lbs (use unit weight, γ = 125 pcf for

soils above water table, and buoyant unit weight γ’ = 65 pcf for soils below water table)

Au = π/4 (Bb2 - Bs

2), projected area of bell over shaft, ft

2

FS1, FS2, FS3 = Factors of Safety for uplift resistance

We recommend that the following safety factors be used for uplift design: FS of 2 for soil cohesion (FS1 = 2), FS

of 1.1 for dead weight of footing (FS2 = 1.1), and FS of 1.5 for weight of soil above the bell (FS3= 1.5). Based

on above equations, the uplift resistance of a drilled-and-underreamed footing can be increased by extending the

founding depth of the footing or increasing the diameter of the bell.

Vertical Reinforcement: To withstand uplift forces resulting from the shrink/swell movements of clay soils in the

moisture active zone, each footing should contain reinforcing steel throughout its full length to sustain an uplift

load of at least 38d kips, where “d” is the diameter of the shaft in feet.

Footing Spacing: To reduce stress overlap from adjacent footings and potential construction problems, the

minimum edge-to-edge clear spacing between the underreams should not be less than 0.6 x diameter of the larger

underream. New foundations for the building should be spaced to reduce the potential of new foundations

affecting existing building foundations (and vice versa) by placing the new foundations outside the bearing (stress)

zone of existing foundations. The bearing (stress) zone can be defined by a line drawn downward from the outer

edge of the existing foundation and inclined at an angle of 45 degrees to the vertical.

Footing Settlements: A detailed settlement analysis for drilled-and-underreamed footings is beyond the scope of

this investigation. Based on the soil conditions encountered and the anticipated structural loads, we estimate that

drilled-and-underreamed footings, designed and constructed as recommended in this report, will experience total

settlements on the order of 1 inch.

14

Drilled-and-Underreamed Footing Construction: Drilled-and-underreamed footings should be constructed in

accordance with Item 416 of the 2004 TxDOT Standard Specifications, or equivalent local standards. A qualified

geotechnical technician should check each footing excavation prior to placing concrete to insure that:

1) The footing has been constructed to the specified dimensions at the recommended depth and founded in

the correct formation as indicated in this report;

2) The column is concentric with the pier cap/grade beam and drilled footing; and

3) Excessive cuttings, any soft or compressible materials, and ponded water are removed from the bottom

of the excavation.

There is a possibility that slickensides and/or pockets/seams of sands/silts within the clay soils may make

underreaming (belling) difficult, and result in potential sloughing or caving-in of the shaft excavation sidewalls

during construction, particularly for underreams over 6 feet in diameter. We recommend that a maximum

diameter ratio of bell to shaft not exceed 2 to 1. Based on Boring B-3, ground water will probably not be

encountered within the drilled shaft excavations; however, the site groundwater level will fluctuate with seasonal

rainfall and other climatic events, and may be higher at the time of construction. If ground water is encountered

within the cohesive soils during construction, sump pumps may be used to pump water out from the excavations

and soft sediments should be removed. However, if significant sloughing or caving occurs during

drilled-and-underreamed shaft excavation, further footing excavation should be stopped and a reduced bell/shaft

ratio or even straight-sided shafts (matching the bell diameter) with bentonite slurry or temporary casing may be

necessary.

Placement of concrete should be accomplished immediately after excavation is completed to reduce potential for

sloughing of the foundation soils. Footing excavations should not be left open overnight. No concrete should be

placed without the prior approval of the Owner’s Representative. New drilled footings should not be excavated

within 2 bell diameters (edge to edge) of an open footing excavation, or one in which concrete has been placed in

the preceding 24 hours, to prevent movement of fresh concrete from the recently filled footing to an adjacent

unfilled footing.

5.3.2 Floor Slab

Estimated Soil Movements: Expansive clays exhibit a potential to shrink and swell with changes in their moisture

contents. The changes in the soil moisture content are usually caused by variations in the seasonal amount of

rainfall and evaporation rates or other localized factors like the moisture withdrawal by nearby trees. The seasonal

15

moisture active zone generally extends to about 15 feet below ground in the Brazos Valley area, and will be deeper

if trees with deep root zones exist adjacent to the structures.

Potential Vertical Rise (PVR) is an estimate of the potential of an expansive soil to swell from its current state.

For the top 15 feet of the existing soils encountered in Boring B-3, the total PVR for the tanks/canopy building is

estimated to be about 3.8 inches based on in-situ moisture conditions. PVR was computed using TxDOT test

method Tex-124-E.

Additional movements can occur in areas if water is allowed to pond during or after construction on soils with

high plasticity, or if highly plastic soils are allowed to dry out prior to fill or concrete placement. High plasticity

clay may also experience shrinkage during periods of dry weather as moisture evaporation occurs at the ground

surface and the groundwater table drops. The actual PVR of the site will be highly dependent upon the actual PI

and moisture regime of the clayey soils at the time of construction. Therefore, uniformity and preservation of the

moisture contents of the near surface clays during construction and during the life of the structure is critical to

reducing potential shrink-swell movement of the floor slab.

Table 3. Estimated PVR vs. Thickness of Replacement Fill (Based on Boring B-3)

Thickness of Replacement Fill Beneath

the Existing Ground Surface (ft) PVR (in)

0 3.8

1 3.3

2 2.8

3 2.2

4 1.5

5 1.1

6 0.6

Floor Slab: In general, the tolerable differential vertical movement for a common building slab is about 1 inch.

To limit the PVR to 1 inch, the following approaches can be used: (1) a drilled-footing supported structural floor

slab in combination with 8 inch carton forms between the bottom of the slab and the subgrade soil; or (2)

excavating approximately 6 feet of existing soils and replacing them with a low-expansive select fill material (in

accordance with Table 3).

16

5.3.2.1 Option 1 - Structural Floor Slab

The most effective method to mitigate movement of subgrade soils due to shrink-swell cycles of expansive soils

is construction of a drilled-footing supported structural floor slab with 8 inch carton forms between the bottom of

the slab and the top of the subgrade soil.

Subgrade Preparation: Subgrade preparation should extend a minimum of 5 feet beyond the floor slab perimeter.

Thereafter, a minimum of 6 inches of surface soils, existing vegetation, trees, roots, and other deleterious

materials shall be removed and wasted. The excavation depth should be increased when inspection indicates the

presence of organics or deleterious materials to greater depths.

The exposed subgrade should then be proof-rolled in accordance with Item 216 of the 2004 TxDOT Standard

Specifications, to identify and remove any weak, compressible, or other unsuitable materials; such materials

should be replaced with clean onsite clay soils. Afterwards, general fill can be placed and compacted to achieve

the design finished floor elevation (FFE) of the building (i.e. the bottom of the carton forms). General fill

recommendations are presented in Section 5.7.2 of this report.

Grade Beams: We recommend that foundation grade beams be founded at least 30 inches below the lowest final

grade. The grade beams should be constructed on 8 inch carton forms. Care should be taken so that the carton

forms do not collapse during concrete placement and will not be exposed to water in the grade beam excavations.

Surface water should not be allowed to seep into and remain in the carton form space during the life of the

structures. The drilled shafts and beams should be tied together.

Moisture Barrier: To prevent mildew or mold growth on the underside of the structural floor slab, we recommend

that a horizontal moisture barrier (minimum 10-mil thick) be placed below the concrete slab (on top of the carton

forms).

5.3.2.2 Option 2 - Subgrade Supported Floor Slab

A less expensive alternative to a structural slab is a reinforced on-grade floor slab. A concrete slab-on-grade in

conjunction with limited fill replacement can be considered, if the Owner is willing to take some risk of floor slab

movement. This option assumes that uniformity and preservation of the moisture contents of the near surface clays

during construction and during the life of the structure are maintained adequately, and that any resultant

17

movements can be adequately sustained by the subgrade soils and foundation system.

Subgrade Preparation: Subgrade preparation should extend a minimum of 5 feet beyond the floor slab perimeter.

A minimum of 6 inches of surface soils, existing vegetation, trees, roots, and other deleterious materials shall be

removed and wasted. The excavation depth should be increased when inspection indicates the presence of

organics and deleterious materials to greater depths.

Afterwards, an additional 3.5 feet (total depth of 4 feet, which includes the 6 inches of surface removal) of existing

soils should be removed. The exposed subgrade should be proof-rolled in accordance with Item 216 of the 2004

TxDOT Standard Specifications to identify and remove any weak, compressible, or other unsuitable materials;

such materials should be replaced with compacted select fill or clean stabilized soils.

After proof-rolling, we recommend that the top 6 inches of exposed subgrade be stabilized with a minimum of 7

percent hydrated lime (by dry soil weight). The actual percentage of lime should be determined by lime-series or

pH method in a laboratory prior to construction. After subgrade stabilization, compacted select fill or clean,

stabilized soils should then be used to achieve the design FFE of the building. Select fill or stabilized soil should

be in accordance with Section 5.7.1 of this report.

According to Table 3 in Section 5.3.2 of this report, the PVR for 4 feet of soil replacement and 6 inches of

subgrade stabilization is 1.3 inches, which is still greater than 1 inch; the Owner should be aware that some risk

of floor slab movement is still present if this floor slab option is selected. If conditions which exacerbate moisture

variations such as the presence of trees, poor drainage, excessive drying, or wetting of subsurface soils, or leaking

underground utilities are located nearby, the floor slab total vertical movements and net differential vertical

movements could be higher than estimated.

Grade Beams: We recommend that foundation grade beams be founded at least 30 inches below the lowest final

grade. The grade beams can be constructed on 8 inch carton forms. If carton forms are used, care should be taken

so that the carton forms do not collapse during concrete placement and will not be exposed to water in the grade

beam excavations. Surface water should not be allowed to seep into and remain in the carton form space during

the life of the structures. If no carton forms will be used, we recommend that tensile reinforcement be placed in

both top and bottom of the beams. The foundations and beams should be tied together.

18

Floor slabs are typically structurally tied to the grade beams. Alternatively, isolating the floor slabs from grade

beams with a flexible impervious compound will be beneficial to reduce the potential for slab cracking due to

differential soil movement; however, its use will not mitigate the total and differential PVR movements and the

floor slabs are expected to move corresponding to the subgrade soils.

Moisture Barrier: We recommend that a horizontal moisture barrier (minimum 10-mil thick) be placed below the

concrete slab to move edge effects away from the slab and mitigate seasonal fluctuations of water content directly

below the structure.

5.4 Precast Concrete Building

Based on information provided by Malcolm Pirnie, the precast concrete control building will be located on the

north side of the proposed bulk storage tanks. The one-story precast building will have a footprint that is

approximately 8 feet long by 8 feet wide, and will weigh approximately 45,000 pounds. AEC assumes that the

FFE of the proposed building will be at or near existing grade. Based on the soil conditions encountered in Boring

B-3, AEC recommends that the precast concrete building also be supported on drilled-and-underreamed footings,

founded at 10 feet below grade.

Recommendations for the building foundations and subgrade preparation for the precast building are presented in

Section 5.3 of this report.

5.5 Installation of Underground Utilities by Open-Cut Method

Underground utilities installed by open-cut methods should be installed in accordance with Item 400 of the 2004

TxDOT Standard Specifications, or equivalent local standards. AEC understands that the proposed underground

water lines will have a maximum invert depth of 10 feet below grade and will be installed by open cut method.

5.5.1 Geotechnical Parameters for Underground Utilities

Recommended geotechnical parameters for the subsurface soils along the alignments to be used for design of

underground utilities are presented on Plate C-1, in Appendix C. The design values are based on the results of

field and laboratory test data on individual boring logs as well as our experience. It should be noted that because

of the variable nature of soil stratigraphy, soil types and properties along the alignment or at locations away from

19

a particular boring may vary substantially.

5.5.2 Loadings on Pipes

Underground utilities support the weight of the soil and water above the crown, as well as roadway traffic and any

structures that exist above the utilities.

Earth Loads: For underground utilities to be installed using open cut methods, the vertical soil load We can be

calculated as the larger of the two values from Equations (4) and (6):

We = Cd γ Bd2 ............ Equation (4)

Cd = [1- e -2Kµ’(H/Bd)

]/(2Kµ’) ............ Equation (5)

We = γBcH ............ Equation (6)

where: We = trench fill load, in pounds per linear foot (lb/ft);

Cd = trench load coefficient, see Plate C-2, in Appendix C;

γ = effective unit weight of soil over the conduit, in pounds per cubic foot (pcf);

Bd = trench width at top of the conduit < 1.5 Bc (ft);

Bc = outside diameter of the conduit (ft);

H = variable height of fill (ft);

when the height of fill above the top of the conduit Hc >2 Bd, H = Hh (height of fill above the

middle of the conduit). When Hc < 2 Bd, H varies over the height of the conduit; and

Kµ’ = 0.1650 maximum for sand and gravel,

0.1500 maximum for saturated top soil,

0.1300 maximum for ordinary clay,

0.1100 maximum for saturated clay.

When underground conduits are located below groundwater, the total vertical dead loads should include the

weight of the projected volume of water above the conduits.

Traffic Loads: The vertical stress on top of an underground conduit, pL (psf), resulting from traffic loads (from a

H-20 or HS-20 truck) can be obtained from Plate C-3, in Appendix C. The live load on top of the underground

conduit can be calculated from Equation (7):

WL = pL Bc ............ Equation (7)

where: WL = live load on the top of the conduit (lb/ft);

pL = vertical stress (on the top of the conduit) resulting from traffic loads (psf);

Bc = outside diameter of the conduit, (ft);

20

Lateral Loads: The lateral soil pressure pl can be calculated from Equation (8); hydrostatic pressure should be

added, if applicable.

pl = 0.5 (γHh + ps) ............ Equation (8)

where: Hh = height of fill above the center of the conduit (ft);

γ = effective unit weight of soil over the conduit (pcf);

ps = vertical pressure on conduit resulting from traffic and/or construction equipment (psf).

5.5.3 Deflections of Flexible Pipes

Deflection is one of the controlling factors in the design of buried flexible or semi-rigid pipes, such as PVC and

ductile iron pipes. These pipes deflect under soil and surcharge loads; the amount of deflection is a function of the

service load on the pipe, the stiffness of the pipe, and the surrounding soil.

The deflection can be calculated using the Modified Iowa Formula, expressed as Equation (9), and the effective

stiffness, E/ of the surrounding soil. The E

/ is a combination of the stiffness of the pipe bedding material, E’B and

the stiffness of the native soil, E’N. Long-term deflection values are typically used for flexible/semi-rigid pipe

design; these values may be obtained by applying an appropriate deflection lag factor, DL, to the short-term

deflection values used in the Modified Iowa Formula.

'061.03

ER

EI

KWDx L

+

=∆ ............ Equation (9)

where: x∆ = pipe deflection (in);

DL = deflection lag factor,

(a) use minimum 1.0 for granular backfill and the full prism load is assumed to act on the

pipe, (b) use minimum 1.5 for granular backfill and assumed trench loadings, (c) use

minimum 2.5 for sandy lean clay (CL) where the backfill can become saturated

K = bedding constant, typically 0.11,

W = [We (from Eq. 6) + WL (from Eq. 7) +Ww], total service load on the crown of the pipe, (lb/in);

Ww = weight of water prism (if any) above the crown of the pipe

E = initial modulus (Young’s modulus) of the pipe material (psi);

I = pipe wall moment of inertia (in.4/in);

R = mean pipe radius (in);

E/ = effective modulus of soil reaction (psi)

The effective modulus of soil reaction, E/, may be obtained from the equations presented below:

E/ = zeta * E’B ............ Equation (10)

21

zeta = '/'*)44.1(

44.1

NB EEff −+ ............. Equation (11)

where: f = )1/(444.0154.1

1/

−+

−

cd

cd

BB

BB ............ Equation (12)

and: Bd = trench width at the top of the pipe (ft);

Bc = outside diameter of the pipe (ft).

For the stiffness of the pipe bedding material E’B, 2,000 psi can be used for granular materials such as clayey sand,

silty sand, silty gravel or clayey gravel (containing less than 12% fines) with a minimum 95 percent ASTM D-698

(Standard Proctor) compaction. Effective Modulus of Soil Reaction for natural soil, E’N is presented on Plate C-1,

in Appendix C.

5.5.4 Trench Stability

Cohesive soils in the Brazos Valley area contain many secondary features which affect trench stability, including

sand seams and slickensides. Slickensides are shiny weak failure planes which are commonly present in fat clays;

such clays often fail along these weak planes when they are not laterally supported, such as in an open excavation.

The Contractor should not assume that slickensides and sand seams/layers/pockets are absent where not indicated

on the logs.

The Contractor should be responsible for designing, constructing and maintaining safe excavations. Care should

be taken so that the excavations do not cause any distress to existing structures.

Trenches 20 feet and Deeper: OSHA requires that shoring or bracing for trenches 20 feet and deeper be

specifically designed by a licensed professional engineer.

Trenches Less than 20 Feet Deep: Trench excavations that are less than 20 feet deep may be shored, sheeted and

braced, or laid back to a stable slope for the safety of workers, the general public, and adjacent structures, except

for excavations which are less than 5 feet deep and verified by a competent person to have no cave-in potential.

The excavation and trenching should be in accordance with Occupational Safety and Health Administration

(OSHA), Safety and Health Regulations, 29 CFR, Part 1926. Recommended OSHA soil types for trench design

for existing soils can be found on Plate C-1, in Appendix C. Fill soils are considered OSHA Class ‘C’; submerged

cohesive soils should also be considered OSHA Class ‘C’, unless they are dewatered first.

22

Critical Height is defined as the height a slope will stand unsupported for a short time; in cohesive soils, it is used

to estimate the maximum depth of open-cuts at given side slopes. Critical Height may be calculated based on the

soil cohesion. Values for various slopes and cohesion are shown on Plate D-1, in Appendix D. Cautions listed

below should be exercised in use of Critical Height applications:

1. No more than 50 percent of the Critical Height computed should be used for vertical slopes. Unsupported

vertical slopes are not recommended where granular soils or soils that will slough when not laterally

supported are encountered within the excavation depth.

2. If the soil at the surface is dry to the point where tension cracks occur, any water in the crack will increase

the lateral pressure considerably. In addition, if tension cracks occur, no cohesion should be assumed for

the soils within the depth of the crack. The depth of the first waler should not exceed the depth of the

potential tension crack. Struts should be installed before lateral displacement occurs.

3. Shoring should be provided for excavations where limited space precludes adequate side slopes, e.g.,

where granular soils will not stand on stable slopes and/or for deep open cuts.

4. All excavation, trenching and shoring should be designed and constructed by qualified professionals in

accordance with OSHA requirements.

The maximum (steepest) allowable slopes for OSHA Soil Types for excavations less than 20 feet are presented

on Plate D-2, in Appendix D.

If limited space is available for the required open trench side slopes, the space required for the slope can be

reduced by using a combination of bracing and open cut as illustrated on Plate D-3, in Appendix D. Guidelines

for bracing and calculating bracing stress are presented below.

Computation of Bracing Pressures: The following method can be used for calculating earth pressure against

bracing for open cuts. Lateral pressure resulting from construction equipment, traffic loads, or other surcharge

should be taken into account by adding the equivalent uniformly distributed surcharge to the design lateral

pressure. Hydrostatic pressure, if any, should also be considered. The active earth pressure at depth z can be

determined by Equation (13). The design soil parameters for trench bracing design are presented on Plate C-1, in

Appendix C.

221 2)'( hKcKhhqp waasa γγγ +−++= ............ Equation (13)

where: pa = active earth pressure (psf);

qs = uniform surcharge pressure (psf);

γ, γ’ = wet unit weight and buoyant unit weight of soil (pcf);

h1 = depth from ground surface to groundwater table (ft);

h2 = z-h1, depth from groundwater table to the point under consideration (ft);

23

z = depth below ground surface for the point under consideration (ft);

Ka = coefficient of active earth pressure;

c = cohesion of clayey soils (psf); c can be omitted conservatively;

γw = unit weight of water, 62.4 pcf.

Pressure distribution for the practical design of struts in open cuts for clays and sands are illustrated on Plates D-4

through D-6, in Appendix D.

Bottom Stability: In open-cuts, it is necessary to consider the possibility of the bottom failing by heaving, due to

the removal of the weight of excavated soil. Heaving typically occurs in soft plastic clays when the excavation

depth is sufficiently deep enough to cause the surrounding soil to displace vertically due to bearing capacity

failure of the soil beneath the excavation bottom, with a corresponding upward movement of the soils in the

bottom of the excavation. In fat and lean clays, heave normally does not occur unless the ratio of Critical Height

to Depth of Cut approaches one. In very sandy and silty lean clays and granular soils, heave can occur if an

artificially large head of water is created due to installation of impervious sheeting while bracing the cut. This can

be mitigated if groundwater is lowered below the excavation by dewatering the area. Guidelines for evaluating

bottom stability in clay soils are presented on Plate D-7, in Appendix D.

Based on a maximum invert depth of 10 feet and our borings, granular fill soils will most likely be encountered

within the open cut excavations from a depth of 4 to 10 feet in the vicinity of Boring B-1, and clayey sands may

be encountered within the trench bedding zones of 10 to 12 feet in the vicinity of Borings B-2 and B-3. If the

excavation extends below groundwater and the soils at or near the bottom of the excavation are mainly sands or

silts, the bottom can fail by blow-out (boiling) when a sufficient hydraulic head exists. The potential for boiling

or in-flow of granular soils increases where the groundwater is pressurized. To reduce the potential for boiling of

excavations terminating in granular soils below pressurized groundwater, the groundwater table should be

lowered at least 3 feet below the excavation.

Calcareous nodules, silt/sand seams, and fat clays with slickensides were encountered in some of the borings.

These secondary structures may become sources of localized instability when they are exposed during excavation,

especially when they become saturated. Such soils have a tendency to slough or cave in when not laterally

confined, such as in trench excavations. The Contractor should be aware of the potential for cave-in of the soils.

Low plasticity soils (silts and clayey silts) will lose strength and may behave like granular soils when saturated.

24

5.5.5 Thrust Force Design Recommendations

Thrust forces are generated in pressure pipes, typically as a result of changes in pipe diameter, pipe direction or

at the termination point of the pipes. The pipes could disengage at the joints if the forces are not balanced and if

the pipe restraint is not adequate. Various methods of thrust restraint are used including thrust blocks, restrained

joints, encasement, and tie-rods.

Thrust restraint design procedure based on the 2008 American Water Works Association (AWWA) Manual

“Concrete Pressure Pipe (M9)” is discussed below. Plate D-8, in Appendix D shows the force diagram generated

by flow in a bend in a pipe and also gives the equation for computing the thrust force. An example computation

of a thrust force for a given surge pressure and a bend angle is presented on Plate D-9, in Appendix D.

Frictional Resistance: The unbalanced force due to changes in grade and alignment can be resisted by frictional

force FR, between the pipe and the surrounding soil. The resisting frictional force per linear foot of pipe against

soil can be calculated from Equation (14):

FR = f (2We + Ww + Wp) ............ Equation (14)

where: f = Coefficient of friction between pipe and soil;

We = Weight of soil over pipe (lb/ft);

Ww = Weight of water inside the pipe (lb/ft);

Wp = Weight of pipe (lb/ft).

The value of the frictional resistance depends on the material in contact with the backfill and the soil used in the

backfill. For a ductile iron pipe or PVC pipe with crushed stone or compacted sand backfill, an allowable

coefficient of friction of 0.3 can be used. To account for submerged conditions, a soil unit weight of 60 pcf should

be used to compute the weight of compacted backfill on the pipe.

Thrust Blocks: Thrust blocks utilize passive earth pressures to resist forces generated by changes in direction or

diameter of pressurized pipes. Passive earth pressure can be calculated using Equation (15); we recommend that

a FS of 2.0 be used when using passive earth pressure for design of thrust blocks. The design soil parameters for

thrust block design are presented on Plate C-1, in Appendix C. Design parameters for bearing thrust blocks are

presented on Plate D-10, in Appendix D.

25

pp = γzKp + 2c(Kp)½ ............ Equation (15)

where, pp = passive earth pressure (psf);

γ = wet unit weight of soil (pcf);

z = depth below ground surface for the point under consideration (ft);

Kp = coefficient of passive earth pressure;

c = cohesion of clayey soils (psf).

5.5.6 Bedding and Backfill

Trench excavation, pipe embedment material, and backfill for the proposed underground utilities should be in

general accordance with Item 400 of the 2004 TxDOT Standard Specifications, or equivalent local standards.

Backfill should be placed in loose lifts not exceeding 8 inches and compacted to 95 percent of its ASTM D-698

(Standard Proctor) maximum dry density at a moisture content ranging between optimum and 3 percent above

optimum.

5.6 Asphalt Pavement Driveway

Based on the provided site plan, an asphalt concrete driveway will be located to the south of the proposed bulk

storage tanks. Traffic volume and vehicle loads were not available at the time this report was prepared. AEC

assumes that the vehicle traffic will consist primarily of passenger vehicles, pickup trucks, operations trucks, and

tanker trucks. AEC also assumes that the final grade of the asphalt pavement will be at or near existing grade.

The pavement design recommendations developed herein are in accordance with the “American Association of

State Highway and Transportation Officials (AASHTO) Guide for Design of Pavement Structures,” 1993 edition.

5.6.1 Flexible Pavement

Pavement Design: Flexible pavement design procedure includes determination of the structural number (SN) for

the proposed pavement, as well as the thickness of individual components of the surface course, base course, and

subgrade. The basic equation developed by the AASHTO Road Test is:

SN = a1(D1) + a2(D2) + a3(D3) ............ Equation (16)

where: SN = Structural Number for the total flexible pavement structure.

a1, a2, a3 = layer coefficients for surface, base and subgrade course respectively.

D1, D2, D3 = thickness of surface, base and subgrade course, respectively, in inches.

26

Layer coefficients used for design are presented on Table 4.

Table 4. Layer Coefficients for Asphalt Pavements

Pavement Layer Layer Coefficient

HMAC a1 = 0.44

Flexible Base a2 = 0.14

Stabilized Subgrade a3 = 0.11

The parameters that were used in computing the flexible pavement section are as follows:

Roadbed Soil Resilient Modulus (MR) 4,500 psi

Drainage Coefficient (Cd) 1.0

Overall Standard Deviation (S0) 0.44

Reliability Level (R) 85%

Initial Serviceability (P0) 4.2

Terminal Serviceability (Pt) 2.0

The recommended flexible pavement section for the driveway is provided on Table 5 below.

Table 5. Recommended Flexible Pavement Section

Pavement Layer Thickness (in)

Hot Mix Asphaltic Concrete 2.5

Flexible Base 12

Stabilized Subgrade1 8

Note: Stabilized subgrade recommendations are presented in Section 5.6.2 of this report.

Given the above design parameters, the driveway section should sustain 776,700 repetitions of 18-kip Equivalent

Single Axle Loads (ESAL). The design engineer should verify whether the proposed pavement section will

provide enough ESALs for the anticipated amount of site traffic. AEC should be notified if different standards or

constants are required for pavement design at the site, so that our recommendations can be updated accordingly.

Asphalt Pavement: HMAC pavement should be constructed in accordance with Item 340 of the 2004 TxDOT

Standard Specifications, or equivalent local standards, and be compacted to obtain 5 to 9 percent air voids.

Flexible base: Crushed limestone base course shall be in accordance with Item 247, Type D, Grade 2 (or

equivalent) of the 2004 TxDOT Standard Specifications, and should be placed in 8 inch loose lifts and compacted

27

to 95 percent of their ASTM D 698 (Standard Proctor) dry density at a moisture content ranging from 2 percent

below to 2 percent above optimum. The surface of the compacted base should be primed with 0.20 gallons per

square yard of MC-30 cutback asphalt.

5.6.2 Pavement Subgrade

Subgrade preparation should extend a minimum of 2 feet beyond the paved area perimeters. We recommend that

a minimum of 6 inches of surface soils, gravel, existing vegetation, trees, roots, and other deleterious materials be

removed and wasted. The excavation depth should be increased when inspection indicates the presence of

existing gravel pavement, organics, and deleterious materials to greater depths. The exposed soils should be

proof-rolled in accordance with Item 216 of the 2004 TxDOT Standard Specifications to identify and remove any

weak, compressible, or other unsuitable materials; such materials should be replaced with compacted fill.

Scarify the top 8 inches of the exposed subgrade and stabilize the underlying soils with a minimum of 7 percent

hydrated lime by dry soil weight. Lime stabilization shall be performed in accordance with Item 260 of the 2004

TxDOT Standard Specifications. The percentage of lime required for stabilization is a preliminary estimate for

planning purposes only; laboratory testing should be performed to determine optimum contents for stabilization

prior to construction. The stabilized soils should be compacted to 95 percent of their ASTM D 698 (Standard

Proctor) dry density at a moisture content ranging from optimum to 3 percent above optimum.

5.7 Fill Requirements

5.7.1 Select Fill

Select fill should consist of uniform, non-active inorganic lean clays with a PI between 10 and 20 percent, and

more than 50 percent passing a No. 200 sieve. Excavated material delivered to the site for use as select fill shall

not have clay clods with PI greater than 20, clay clods greater than 2 inches in diameter, or contain sands/silts with

PI less than 10. Prior to construction, the Contractor should determine if he or she can obtain qualified select fill

meeting the above select fill criteria.

As an alternative to imported fill, on-site soils excavated during construction can be stabilized with either

hydrated lime or lime/fly-ash, depending on the soil type. Excavated sandy clay soils should be stabilized with a

minimum of 7 percent hydrated lime by dry soil weight, while excavated granular soils should be stabilized with

28

a minimum of 3 percent hydrated lime and 8 percent fly ash by dry soil weight. The amount of lime or lime-fly

ash provided is for estimating purposes only, the actual amounts required for stabilization should be determined

by lime-series curve or pH method in a laboratory prior to construction. Lime and lime/fly ash stabilization should

be done in general accordance with Items 260 and 265 of the 2004 TxDOT Standard Specifications. AEC prefers

using stabilized on-site clay as select fill since compacted lime-stabilized clay generally has high shear strength,

low compressibility, and relatively low permeability. Blended or mixed soils (sand and clay) should not be used

as select fill.

All material intended for use as select fill should be tested prior to use to confirm that it meets select fill criteria.

The fill should be placed in loose lifts not exceeding 8 inches in thickness. Backfill within 3 feet of walls or

columns should be placed in loose lifts no more than 4-inches thick and compacted using hand tampers, or small

self-propelled compactors. The lime-stabilized onsite soils or select fill should be compacted to a minimum of 95

percent of the ASTM D 698 (Standard Proctor) maximum dry unit weight at a moisture content ranging between

optimum and 3 percent above optimum.

If imported select fill will be used, at least one Atterberg Limits and one percent passing a No. 200 sieve test shall

be performed for each 5,000 square feet (sf) of placed fill, per lift (with a minimum of one set of tests per lift), to

determine whether it meets select fill requirements. Prior to placement of pavement, the moisture contents of the

top 2 lifts of compacted select fill shall be re-tested (if there is an extended period of time between fill placement

and concrete placement) to determine if the in-place moisture content of the lifts have been maintained at the

required moisture requirements.

5.7.2 General Fill

General fill can be used beneath a structural floor slab (if any). AEC recommends that general fill consist of a

clean, cohesive soil (USCS Classification “CL” or “CH”). Granular soils (i.e. sands, silts, and gravel; not more

than 50 percent retained on No. 200 sieve) should not be used as general fill.

General fill should be placed in loose lifts not exceeding 8 inches in thickness. The fill should be compacted to

95 percent of the ASTM D 698 (Standard Proctor) maximum dry unit weight at a moisture content ranging

between optimum and 3 percent above optimum.

29

5.8 Site Preparation and Grading

To mitigate site problems that may develop following prolonged periods of rainfall, it is essential to have adequate

drainage to maintain a relatively dry and firm surface prior to starting any work at the site. Adequate drainage

should be maintained throughout the construction period. Methods for controlling surface runoff and ponding

include proper site grading, berm construction around exposed areas, and installation of sump pits with pumps.

In addition to the recommended subgrade preparation, measures should be taken to reduce the potential for

moisture changes in the subsurface soils under the proposed structure, which will in turn mitigate the potential for

shrink and swell movements to occur. Measures recommended for consideration include:

- Maintain uniform compaction and moisture content for fill/subgrade soils during construction;

- Do not allow water to pond or allow the soils to dry out prior to constructing floor slabs;

- Locate landscaping away from floor slabs; trees should be located no closer than their mature canopy

radius to the structure and pavements; even so, the tree roots influence zone can extend beyond their

mature canopy radius;

- Design roof drains to discharge into paved areas or into a subsurface drainage system;

- Design final grading to provide site drainage away from the structure.

6.0 CONSTRUCTION MONITORING

Site preparation (including clearing and proof-rolling), earthwork operations, and foundation construction should

be monitored by qualified geotechnical professionals to check for compliance with project documents and

changed conditions, if encountered.

7.0 GENERAL

AEC should be authorized to review the design and construction plans and specifications prior to release to check

that the geotechnical recommendations presented herein are properly interpreted.

The information contained in this report summarizes conditions found on the date the borings were drilled. The

attached boring logs are true representations of the soils encountered at the specific boring locations on the date

of drilling. Due to variations encountered in the subsurface conditions across the site, changes in soil conditions

from those presented in this report should be anticipated. AEC should be notified immediately when conditions

encountered during construction are significantly different from those presented in this report.

APPENDIX A

Plate A-1 Vicinity Map

Plate A-2 Boring Location Plan

Plates A-3 to A-5 Boring Logs

Plate A-6 Key to Symbols

Plate A-7 Classification of Soils for Engineering Purposes

Plate A-8 Terms Used on Boring Logs

Plate A-9 ASTM & TXDOT Designation for Soil Laboratory Tests

Plate A-10 Sieve Analysis Test Results

AEC PROJECT NO.:

G118-13

AVILES ENGINEERING CORPORATION

APPROX. SCALE:

N.T.S.

DATE:

DRAFTED BY:

SOURCE DRAWING PROVIDED BY:

GOOGLE MAPSPLATE NO.:

PLATE A-1

SITE

VICINITY MAP

04-29-13

WlW

SAND POINT PUMP STATION IMPROVEMENTS

BRYAN, TEXAS

AEC PROJECT NO.:

G118-13

AVILES ENGINEERING CORPORATION

BORING LOCATION PLANSANDY POINT PUMP STATION IMPROVEMENTS

BRYAN, TEXAS

APPROX. SCALE:

1” = 40’

DATE:

04-25-13DRAFTED BY:

BpJPLATE NO.:

PLATE A-2

SOURCE DRAWING PROVIDED BY:

MALCOLM PIRNIE

B-1 (50’)

B-3 (50’)

B-2 (50’)

~65’

~85’

~65’

~25’~20’

~20’

LEGEND:

BORING NO. AND (DEPTH IN FEET)BORING LOCATION – APPROXIMATE

B-# (X’)

0

6

12

18

24

30

36

42

Fill: stiff to very stiff, brown Sandy Lean Clay

(CL), with roots, sand and clay pockets, and

gravel

-tan 2'-4'

Fill: tan Poorly Graded Sand w/Silt (SP-SM),

with gravel and clay pockets

Fill: tan Clayey Sand (SC), with lean clay

pockets

-with gravel 6'-8'

-light brown 8'-10'

Fill: stiff to very stiff, light brown and gray

Sandy Lean Clay (CL), with abundant sand

seams and pockets

-gray 12'-14'

Tan and gray Clayey Sand (SC)

Medium dense to very dense, red and tan

Silty Sand (SM)

-with clay partings 23'-25'

Firm to hard, gray Fat Clay (CH), with

slickensides and silt layers

-dark brown 33'-40'

28

50/6"

15

10

2

7

10

18

19

18

18

21

29

24

26

36

116

113

114

98

77

12

23

14

33

29

24

30

62

14

13

13

16

27

19

16

11

14

35

PROJECT: Sandy Point Pump Station, City of College Station BORING B-1

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 18 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 18 FEET WHILE DRILLING

WATER LEVEL AT N/A FEET AFTER N/A

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-3

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

48

54

60

66

72

78

84

Very dense, brown Silty Sand (SM)

-gray 48'-50'

Termination depth = 50 feet

24 hour groundwater @ 13.1'

boring caved @ 15.5' after 24 hours

50/5"

50/6"

32

29

34

PROJECT: Sandy Point Pump Station, City of College Station BORING B-1

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 18 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 18 FEET WHILE DRILLING

WATER LEVEL AT N/A FEET AFTER N/A

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-3

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

0

6

12

18

24

30

36

42

Fill: hard, brown Sandy Lean Clay (CL), with

silt seams and gravel

Fill: stiff, gray and brown Lean Clay (CL), with

gravel and ferrous stains

Fill: hard, brown Lean Clay (CL), with sand

seams and pockets

-gray, red, and brown 6'-8'

-gray 8'-12'

Medium dense, red and tan Silty Sand (SM),

with clay pockets

Medium dense, gray Clayey Sand (SC), with

fat clay pockets

Medium dense, red and tan Poorly Graded

Sand w/Clay (SP-SC)

Stiff to very stiff, light gray and tan Sandy

Lean Clay (CL), with silty sand seams

Very dense, light gray and tan Silty Sand

(SM), with clayey sand pockets

Very stiff to hard, light gray Fat Clay (CH),

with silt layers

-with abundant silt and sand layers 38'-40'

21

17

24

50/4"

16

15

11

10

15

18

12

21

17

10

16

25

30

31

114

110

118

96

51

38

12

27

49

32

26

56

14

14

16

15

26

13

35

16

11

30

PROJECT: Sandy Point Pump Station, City of College Station BORING B-2

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 18 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 18 FEET WHILE DRILLING

WATER LEVEL AT 14.1 FEET AFTER 1/4 HR

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-4

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

48

54

60

66

72

78

84

Very dense, gray Clayey Sand (SC), with fat

clay pockets

-brown, with silty sand 48'-50'

Termination depth = 50 feet

24 hour groundwater @ 11.0'

boring caved @ 13.2' after 24 hours

50/2"

50/5"

31

33

49

PROJECT: Sandy Point Pump Station, City of College Station BORING B-2

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 18 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 18 FEET WHILE DRILLING

WATER LEVEL AT 14.1 FEET AFTER 1/4 HR

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-4

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

0

6

12

18

24

30

36

42

Hard, brown Sandy Fat Clay (CH), with

ferrous stains

-with roots 0'-2'

-brown and gray, with sand partings 4'-6'

-gray and tan 6'-8'

-gray 8'-10'

Medium dense, tan Clayey Sand (SC)

-light gray 12'-16'

-red and tan 16'-20'

-with red and tan sandy clay layer 18'-20'

Medium dense to dense, orange and tan Silty

Sand (SM)

-boring caved at 26'

-red and tan, with fat clay layer 28'-30'

Stiff to hard, dark brown Fat Clay (CH), with

silt partings

-light brown, with silty sand seams 43'-45'

14

20

26

25

41

29

11

18

11

13

15

6

12

10

9

14

12

28

28

32

124

114

92

4.46

65

43

13

100

69

50

22

80

20

18

22

33

49

32

np

47

PROJECT: Sandy Point Pump Station, City of College Station BORING B-3

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 30 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 29 FEET WHILE DRILLING

WATER LEVEL AT 23.8 FEET AFTER 1/4 HR

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-5

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

48

54

60

66

72

78

84

Fat Clay (CH) (cont.)

Hard, dark brown Lean Clay (CL), with

abundant silt seams

Termination depth = 50 feet

24 hour groundwater @ 25.1'

boring caved @ 25.2' after 24 hours

43

33

49

80

PROJECT: Sandy Point Pump Station, City of College Station BORING B-3

DATE 4/4/13 TYPE 4" Dry Auger / Wet Rotary LOCATION See Boring Location Plan

BORING DRILLED TO 30 FEET WITHOUT DRILLING FLUID

WATER ENCOUNTERED AT 29 FEET WHILE DRILLING

WATER LEVEL AT 23.8 FEET AFTER 1/4 HR

DRILLED BY V&S CHECKED BY WLW LOGGED BY V&S

PLATE A-5

DE

PT

H I

N F

EE

T

SY

MB

OL

SA

MP

LE

IN

TE

RV

AL

DESCRIPTION

.

S.P

.T.

BL

OW

S /

FT

.

MO

IST

UR

E C

ON

TE

NT

, %

DR

Y D

EN

SIT

Y,

PC

F

SHEAR STRENGTH, TSF

0.5 1 1.5 2

Torvane

Pocket Penetrometer

Unconfined Compression

Confined Compression

-2

00

ME

SH

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IN

DE

X

PROJECT NO. G118-13

Symbol Description

Strata symbols

Fill

Clayey sand

Silty sand

Low plasticity

clay

Poorly graded sand

with clay

High plasticity

clay

Misc. Symbols

Water table depth

during drilling

Torvane

Pocket Penetrometer

Confined Compression

Subsequent water

table depth

Soil Samplers

Undisturbed thin wall

Shelby tube

Standard penetration test

KEY TO SYMBOLS

PLATE A-6

PLATE A-7

PLATE A-8

PLATE A-9

GRAIN SIZE ANALYSIS - SIEVE

Project : Sandy Point Pump Station Improvements Job No.: G118-13

Location of Project: Bryan, Texas Date of Testing: 4/9/2013

Sand

Gravel Coarse Fine Silt Clay

to Medium

Curve Boring Depth (ft) Cu Cc

1 B-1 4-6 N/A N/A

2 B-2 43-45 N/A N/A

3 B-3 14-16 N/A N/A

PLATE A-10

AVILES ENGINEERING CORPORATION

Consulting Engineers - Geotechnical, Construction Materials Testing, Environmental

Clayey Sand (SC)

Fill: Poorly Graded Sand w/Silt (SP-SM)

Clayey Sand (SC)

Soil Description

3" #43/4" #40 #200

0

10

20

30

40

50

60

70

80

90

100

0.00010.0010.010.1110100

Per

cen

tag

e P

ass

ing

(%

)

Diameter (mm)

Grain Size Analysis

Curve 1 Curve 2 Curve 3

APPENDIX B

Plate B-1 Allowable Accumulative Unit Skin Friction vs. Depth for Straight Sided Drilled Shafts

Plate B-2 Allowable Unit End Bearing vs. Depth for Straight Sided Drilled Shafts

Plate B-3 Allowable Compressive Load vs. Depth for Straight Sided Drilled Shafts

0

5

10

15

20

25

30

35

40

45

50

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Dep

th b

elo

w E

xis

tin

g G

rou

nd

Su

rfa

ce (

ft)

Allowable Accumulative Unit Skin Friction Capacity (kips/ft diameter)

G118-13 Sandy Point Pump StationDrilled Shaft Capacity (Based on Borings B-1 and B-2)

Skin Friction

Notes:

1. Capacity shown is for single, isolated

shafts, spaced at least 6 shaft diameters,

center-to-center (η = 1.0).

2. Neglect capacity to a depth of 5 feet below

existing grade.

3. Capacity includes a Safety Factor of 2 for

skin friction.

Plate B-1

Neglect to 5 feet below grade

0

5

10

15

20

25

30

35

40

45

50

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Dep

th b

elo

w E

xis

tin

g G

rou

nd

Su

rfa

ce (

ft)

Allowable Unit End Bearing (ksf)

G118-13 Sandy Point Pump StationDrilled Shaft Capacity (Based on Borings B-1 and B-2)

End Bearing

Notes:

1. Capacity shown is for single, isolated

shafts, spaced at least 6 shaft diameters,

center-to-center (η = 1.0).

2. Neglect capacity to a depth of 5 feet below

existing grade.

3. Capacity includes a Safety Factor of 3 for

end bearing.

Plate B-2

Neglect to 5 feet below grade

0

5

10

15

20

25

30

35

40

45

50

0 50 100 150 200 250 300 350 400

De

pth

belo

w E

xis

tin

g G

rou

nd

Su

rfa

ce (

ft)

Allowable Compressive Load (kips)

G118-13 Sandy Point Pump StationDrilled Shaft Capacity (Based on Borings B-1 and B-2)

24-in Dia. Shaft

36-in Dia. Shaft

48-in Dia. Shaft

Notes:

1. Allowable total capacity shown includesskin friction and end bearing.

2. Capacity shown is for single, isolated

shafts, spaced at least 6 shaft diameters,

center-to-center.

3. Neglect capacity to a depth of 5 feet below

existing grade.

4. Capacity includes a Safety Factor of 2 for

Plate B-3

Neglect to 5 feet below grade

APPENDIX C

Plate C-1 Recommended Geotechnical Design Parameters for Underground Utilities

Plate C-2 Load Coefficients for Pipe Loading

Plate C-3 Live Loads on Pipe Crossing Under Roadway

G118-13 SANDY POINT PUMP STATION, CITY OF COLLEGE STATION, TEXAS

SOIL PARAMETERS FOR UNDERGROUND UTILITIES

C

(psf)

φ

(deg)Ka K0 Kp

C'

(psf)

φ'

(deg)Ka K0 Kp

0-4 Fill: stiff to very stiff CL 120 58 600 C 1500 0 1.00 1.00 1.00 150 18 0.53 0.69 1.89

4-6 Fill: SP-SM 120 58 300 C 0 26 0.39 0.56 2.56 0 26 0.39 0.56 2.56

6-10 Fill: SC 124 62 1000 C 0 30 0.33 0.50 3.00 0 30 0.33 0.50 3.00

10-14 Fill: stiff to very stiff CL 133 71 600 C 1800 0 1.00 1.00 1.00 175 18 0.53 0.69 1.89

14-15 SC 134 72 300 C 0 28 0.36 0.53 2.77 0 28 0.36 0.53 2.77

0-2 Fill: hard CL 125 63 1000 C 2500 0 1.00 1.00 1.00 250 18 0.53 0.69 1.89

2-4 Fill: stiff CL 120 58 600 C 1500 0 1.00 1.00 1.00 150 18 0.53 0.69 1.89

4-12 Fill: hard CL 126 64 2000 C 3600 0 1.00 1.00 1.00 300 18 0.53 0.69 1.89

12-15 Medium dense SM/SC 120 58 1000 C 0 30 0.33 0.50 3.00 0 30 0.33 0.50 3.00

0-10 Hard CH 138 76 2000 B 3600 0 1.00 1.00 1.00 300 18 0.53 0.69 1.89

10-15 Medium dense SC 121 59 1000 C 0 30 0.33 0.50 3.00 0 30 0.33 0.50 3.00

(1) γ = Unit weight for soil above water level, γ’ = Buoyant unit weight for soil below water level. E'n = Soil modulus for native soils;

(2) C = Soil ultimate cohesion for short term (upper limit of 3,600 psf for design purposes), φ = Soil friction angle for short term;

(3) C' = Soil ultimate cohesion for long term (upper limit of 300 psf for design purposes), φ' = Soil friction angle for long term;

(4) Ka = Coefficient of active earth pressure, K0 = Coefficient of at-rest earth pressure, Kp = Coefficient of passive earth pressure;

(5) CL = Lean Clay, CH = Fat Clay, SC = Clayey Sand; SM = Silty Sand; SP-SM = Poorly Graded Sand w/Silt

(6) OSHA Soil Types for soils in the top 20 feet below grade:

A: cohesive soils with qu = 1.5 tsf or greater (qu = Unconfined Compressive Strength of the Soil)

B: cohesive soils with qu = 0.5 tsf or greater

C: cohesive soils with qu = less than 0.5 tsf, fill materials, or granular soil

C*: submerged cohesive soils; dewatered cohesive soils can be considered OSHA Type C.

Long-Term

Boring Depth (ft) Soil Typeγ

(pcf)

γ'

(pcf)

E'n

(psi)

B-1

B-2

B-3

OSHA

Type

Short-Term

PLATE C-1

PLATE C-2Reference: US Army Corps of Engineers Engineering Manual, EM 1110-2-2909, Oct. 31, 1997, Figure 2-5.

PLATE C-3

APPENDIX D

Plate D-1 Critical Heights of Cuts in Nonfissured Clays

Plate D-2 Maximum Allowable Slopes

Plate D-3 A Combination of Bracing and Open Cuts

Plate D-4 Lateral Pressure Diagrams for Open Cuts in Cohesive Soil-Long Term Conditions

Plate D-5 Lateral Pressure Diagrams for Open Cuts in Cohesive Soil-Short Term Conditions

Plate D-6 Lateral Pressure Diagrams for Open Cuts in Sand

Plate D-7 Bottom Stability for Braced Excavation in Clay

Plate D-8 Thrust Force Calculation

Plate D-9 Thrust Force Example Calculation

Plate D-10 Design Parameters for Bearing Thrust Block

APPENDIX E

A&B Laboratories Chemical Analyses

L A B O R A T O R Y T E S T R E S U L T S

Soil

13041512.01

Sample Matrix

Job Sample ID:

AnalystDate TimeQReg LimitRpt LimitDFUnitsResultParameter/Test DescriptionTest Method

B-3,2'-4'

Other Information:

Time Collected:

Client Sample ID:

Date Collected:

Wilber WangAttn:

G118-13 Sandy Point Pump Station,Bryan, TexasProject Name:

Aviles EngineeringClient Name:

Date13041512Job ID :

5/8/2013

04/04/13

ResistivityEPA 120.1

SR05/08/13 10:50H311ohm-cm14124Resistivity¹

Water Soluble AnionsEPA 300.0

XA04/30/13 08:5311mg/Kg99.6Chloride

XA04/30/13 08:5311mg/Kg10.6Sulfate

Corrosivity, pHSW-846 9045D

SR05/01/13 09:55H31s.u.7.02pH

SR05/01/13 09:55H31s.u.22.5Temperature when read, °C¹

¹-Parameter not available for accreditation

Page 3 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13041512Job ID :

Xan

Samples in This QC Batch :

Qb13043009

Anions

13041512.01

Reporting Units :

04/30/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

mg/KgEPA 300.0

5/8/2013

Prep Date : 04/29/13 14:30EPA 300.0Prep Method :PB13043009Sample Preparation : XanPrep By :

QC Type: Method Blank

D.F. RptLimitParameter Result Units QualCAS #

mg/Kg 1BRL 1Chloride 16887-00-6

mg/Kg 1BRL 1Sulfate

%RecoveryCtrlLimit

LCSDResult

LCSResult

RPDCtrlLimitRPD

LCSSpk Added

LCSD% Rec

LCS% RecParameter

LCSDSpk Added

QC Type: LCS and LCSD

Qual

1.910410 80-120106 2010.6Chloride 10 10.4

5.493.910 80-12099.1 209.91Sulfate 10 9.39

Refer to the Definition page for terms.

Page 4 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13041512Job ID :

Srani

Samples in This QC Batch :

Qb13050636

Corrosivity, pH

13041512.01

Reporting Units :

05/01/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

s.u.SW-846 9045D

5/8/2013

QC Type: Duplicate

13041387.01QC Sample ID:

Parameter UnitsSampleResult QualRPD

RPDCtrlLimit

QCSampleResult

s.u.pH 11.47 0.2 511.49

ToleranceLCSDResult

LCSResult

RPDCtrlLimitRPD

LCSAssignedParameter

LCSDAssigned

QC Type: LCS and LCSD

Qual

4.0 3.95-4.053.98pH

Refer to the Definition page for terms.

Page 5 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13041512Job ID :

Srani

Samples in This QC Batch :

Qb13050837

Resistivity

13041512.01

Reporting Units :

05/08/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

ohm-cmEPA 120.1

5/8/2013

QC Type: Method Blank

D.F. RptLimitParameter Result Units QualCAS #

ohm-cm 1>500000 1Resistivity

QC Type: Duplicate

13041512.01QC Sample ID:

Parameter UnitsSampleResult QualRPD

RPDCtrlLimit

QCSampleResult

ohm-cmResistivity 14471 2.4 2014124

%RecoveryCtrlLimit

LCSDResult

LCSResult

RPDCtrlLimitRPD

LCSSpk Added

LCSD% Rec

LCS% RecParameter

LCSDSpk Added

QC Type: LCS and LCSD

Qual

10000 80-12097.79766Resistivity

Refer to the Definition page for terms.

Page 6 of 8

General Term Definition

BRL

Front-Wt

Below Reporting Limit

Front Weight

Back WeightBack-Wt

cfu colony-forming units

Conc. Concentration

D.F. Dilution Factor

LCS Laboratory Check Standard

LCSD Laboratory Check Standard Duplicate

MS Matrix Spike

MSD Matrix Spike Duplicate

Molecular WeightMW

RPD

ppm parts per million

Relative Percent Difference

TNTC Too numerous to count

Post-Wt

Pre-Wt Previous Weight

Q Qualifier

RegLimit Regulatory Limit

RptLimit Reporting Limit

T Time

Post Weight

surr Surrogate

SDL Sample Detection Limit

13060782

L A B O R A T O R Y T E R M A N D Q U A L I F I E R D E F I N I T I O N R E P O R T

Date:Job ID : 6/24/2013

Qualifier Definition

Sample was received and analyzed past holding time.H3

Page 2 of 8

L A B O R A T O R Y T E S T R E S U L T S

Soil

13060782.01

Sample Matrix

Job Sample ID:

AnalystDate TimeQReg LimitRpt LimitDFUnitsResultParameter/Test DescriptionTest Method

B-2,8'-10'

Other Information:

Time Collected:

Client Sample ID:

Date Collected:

Wilber WangAttn:

G118-13 Sandy Point Pump Station,College Station,TxProject Name:

Aviles EngineeringClient Name:

Date13060782Job ID :

6/24/2013

04/04/13

ResistivityEPA 120.1

BMM06/19/13 12:00H311ohm-cm2155.17Resistivity¹

Water Soluble AnionsEPA 300.0

XA06/18/13 13:33100100mg/Kg8010Chloride

Corrosivity, pHSW-846 9045D

SR06/19/13 09:55H31s.u.7.64pH

SR06/19/13 09:55H31s.u.24.0Temperature when read, °C¹

¹-Parameter not available for accreditation

Page 3 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13060782Job ID :

Bmanley

Samples in This QC Batch :

Qb13061948

Resistivity

13060782.01

Reporting Units :

06/19/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

ohm-cmEPA 120.1

6/24/2013

QC Type: Method Blank

D.F. RptLimitParameter Result Units QualCAS #

ohm-cm 1BRL 1Resistivity

QC Type: Duplicate

13060402.01QC Sample ID:

Parameter UnitsSampleResult QualRPD

RPDCtrlLimit

QCSampleResult

ohm-cmResistivity 537.63 0.9 20533.05

%RecoveryCtrlLimit

LCSDResult

LCSResult

RPDCtrlLimitRPD

LCSSpk Added

LCSD% Rec

LCS% RecParameter

LCSDSpk Added

QC Type: LCS and LCSD

Qual

10000 80-12010310288.07Resistivity

Refer to the Definition page for terms.

Page 4 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13060782Job ID :

Srani

Samples in This QC Batch :

Qb13062438

Corrosivity, pH

13060782.01

Reporting Units :

06/19/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

s.u.SW-846 9045D

6/24/2013

QC Type: Duplicate

13060782.01QC Sample ID:

Parameter UnitsSampleResult QualRPD

RPDCtrlLimit

QCSampleResult

s.u.pH 7.65 0.1 57.64

ToleranceLCSDResult

LCSResult

RPDCtrlLimitRPD

LCSAssignedParameter

LCSDAssigned

QC Type: LCS and LCSD

Qual

4.0 3.95-4.054.0pH

Refer to the Definition page for terms.

Page 5 of 8

Q U A L I T Y C O N T R O L C E R T I F I C A T E

Date :13060782Job ID :

Xan

Samples in This QC Batch :

Qb13062445

Anions

13060782.01

Reporting Units :

06/21/13QC Batch ID :

Method :

Created Date :

Analysis :

Created By :

mg/KgEPA 300.0

6/24/2013

Prep Date : 06/14/13 16:00EPA 300.0Prep Method :PB13062432Sample Preparation : XanPrep By :

QC Type: Method Blank

D.F. RptLimitParameter Result Units QualCAS #

mg/Kg 1BRL 1Chloride 16887-00-6

%RecoveryCtrlLimit

LCSDResult

LCSResult

RPDCtrlLimitRPD

LCSSpk Added

LCSD% Rec

LCS% RecParameter

LCSDSpk Added

QC Type: LCS and LCSD

Qual

10.399.210 90-110110 2011Chloride 10 9.92

Refer to the Definition page for terms.

Page 6 of 8