Geo Technical Exploration Report

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THIELE GEOTECH, INC.13478 Chandler Road

Omaha , Nebraska 68138-3716

402.556.2171 Fax 402.556.7831

www.thielegeotech.com

G EO TEC H N I C A L M A TERI A L EN V I R O N M EN TA L EN G I N E ERI N G

Geotechnical Exploration Report

Pump Station

Railroad Street and Herbert StreetBeatrice, Nebraska

Prepared for:WLA Consulting, Inc.1640 L Street, Suite DLincoln, Nebraska 68508

March 9, 2010

TG Project No. 10026.00


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T h i e l e G e o t e c h I n c

Geotechnical Exploration Report

Pump Station

Table of Contents

INTRODUCTION ................................................................................................................................................. 1PROJ ECT DESCRIPTION .................................................................................................................................. 2SURFACE AND SUBSURFACE CONDITIONS ............................................................................................... 3

SITE CONDITIONS ............................................................................................................................................................ 3LOCAL GEOLOGY ............................................................................................................................................................ 3SOIL CONDITIONS ........................................................................................................................................................... 3GROUND WATER OBSERVATIONS .............................................................................................................................. 4

ANALYSIS AND RECOMMENDATIONS ........................................................................................................ 5GENERAL ........................................................................................................................................................................... 5EXCAVATION DEWATERING ........................................................................................................................................ 5SHORING ............................................................................................................................................................................ 5PUMP STATION ................................................................................................................................................................. 6EARTHWORK AND EXCAVATIONS ............................................................................................................................. 7OTHER RECOMMENDATIONS ....................................................................................................................................... 7

APPENDIX


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Geotechnical Exploration Report March 9, 2010TG #10026.00 Page 1


INTRODUCTION

Thiele Geotech, Inc. has completed a geotechnical exploration study for the proposed pump station to

be located near Railroad Street and Herbert Street in Beatrice, Nebraska. The purpose of this study

was to identify the general soil and ground water conditions underlying the site, to evaluate

engineering properties of the existing soils, to provide earthwork and site preparation

recommendations, and to recommend design criteria and parameters for foundations and other earth

supported improvements.

This study included soil borings, laboratory testing, and engineering analysis. One test boring was

drilled at the location of the new pump station. The field and laboratory data are presented in the

Appendix, along with a description of investigative methods.

The drilling and testing performed for this study were conducted solely for geotechnical analysis. No

analytical testing or environmental assessment has been conducted. Any statements or observations in

this report regarding odors, discoloration, or suspicious conditions are strictly for the information of

our client. If an evaluation of environmental conditions is desired, a separate environmental

assessment should be conducted. This study did not include biological assessment (e.g. mold, fungi,

bacteria) or evaluation of measures for their control.

It should also be noted that this report was prepared for design purposes only, and may not be

sufficient for a contractor in bid preparation. Prospective contractors should evaluate potential

construction problems on the basis of their own knowledge and experience in the local area and on

similar projects, taking into account their own intended construction methods and procedures.

This report is an instrument of service prepared for use by our client on this specific project. The

report may be duplicated as necessary and distributed to those directly associated with this project,

including members of the design team and prospective contractors. However, the technical approach

and report format shall be considered proprietary and confidential, and this report may not be

distributed in whole or in part to any third party not directly associated with this project. By using and

relying on this report, all other parties agree to the same terms, conditions, and limitations to which the

client has agreed.


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PROJECT DESCRIPTION

The project consists of a 28-foot deep wet well for a new pump station. We assume that the structure

will consist of reinforced concrete floors, walls, and top. The new pump station will be located

adjacent to an existing pump station near the intersection of Railroad Street and Herbert Street in

Beatrice, Nebraska. The site is located on the north bank of Indian Creek on the east side of Railroad

Street.


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SURFACE AND SUBSURFACE CONDITIONS

SITE CONDITIONS

The project site is located north of Railroad Street and east of Herbert Street, immediately north ofIndian Creek in Beatrice, Nebraska. The pump station site is built up by several feet. The site is in an

open area which is grass and tree covered.

LOCAL GEOLOGY

The surface geology of eastern Nebraska is Pleistocene in age and consists of eolian (wind-blown)

deposits of Peoria and Loveland loess. The loess formed in dune-shaped hills west of the Missouri

River. The Peoria loess typically consists of silty lean clays that are stiff when dry but become softer

with increasing moisture content. The Peoria often exhibits low unit weight and is collapse

susceptible. The Loveland loess is an older deposit, and typically consists of lean clays. TheLoveland generally exhibits higher unit weights and shear strengths than the Peoria.

The loess overlies Pleistocene glacial deposits of Kansan and Nebraskan till. The till consists of lean

to fat clays mixed with sand, gravel, and occasional cobbles. The glacial deposits are generally fairly

deep, but are sometimes near the surface at lower elevations on steep slopes. Cretaceous sandstone or

Pennsylvanian limestone and shale form the bedrock unit below the glacial deposits. The depth to

bedrock is normally great, and rock is rarely encountered in construction.

Along drainageways, alluvial and colluvial deposits are typically present. These soils were formed by

erosion of the adjoining loess-mantled hills. Alluvial deposits are generally present along creeks andin major drainageways. The upper several feet of alluvium are usually stiffer due to the effects of

desiccation. Colluvial soils are usually located at the base of steep slopes and in upland draws, and are

formed by local creep and sloughing.

SOIL CONDITIONS

The soils encountered in the test borings generally consisted of man-placed fill over alluvium.

Man-placed fill was encountered in the upper 7 feet of the boring. It was described as dark gray,

moist, hard lean clay. Based on an assumed Standard Proctor the fill had compaction levels of roughly

100 percent.

Alluvium was encountered below the fill, and extended to a 28 foot depth. It was described as light

brown to reddish brown, slightly moist to wet, loose, poorly-graded sand.

Shale and limestone rock was encountered at 28 feet below grade. It was described as light brown,

wet, and very hard in consistency. Drilling refusal was encountered at 30 feet, where a Standard

Penetration Test blow count of 50 for 2 inches of penetration was recorded.


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Ranges of engineering properties from laboratory tests on selected samples are presented in Table 1.

Table 1 - Laboratory Results

Soil Layer

Moisture

Content (%)

Dry Unit

Weight (pcf)

Unconfin

edCompressive

Strength(tsf)

Classification (LL/PI)

Man-placed fill 17 to 18 103 to 111 2.3 CL (36/20)

Alluvium 2 to 15 -- -- SP (P-200=4.3%)

GROUND WATER OBSERVATIONS

Ground water levels were observed in the borings as presented in Table 2. Note that ground water

levels may fluctuate due to seasonal variations and other factors.

Table 2 - Water Level Observations

Boring

Number

Water Level (ft. below grade)

During Drilling End of Drilling

B-1 15.0 15.0


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ANALYSIS AND RECOMMENDATIONS

GENERAL

The soils encountered in the test boring were variable with depth. Soil in the upper 7 feet consistedof lean clay which was hard in consistency. Below the lean clay fill, alluvial poorly-graded sand was

encountered to a 28 foot depth. Shale and limestone rock was found at 28 feet. The rock was very

hard at 30 feet. Excavation into the rock will likely require pneumatic or hydraulic rock breakers.

Ground water was fairly shallow in the boring, and dewatering will be a major consideration in

making the excavation to construct the pump station.

EXCAVATION DEWATERING

Ground water was present at roughly 15 feet below existing grade. The proposed excavations extend

below the water table and will require dewatering to facilitate construction.

Soils encountered below the water table consist predominantly of poorly-graded sand. Since the soils

beneath the water table are mainly sand, we expect seepage rates to be high. Sump pumps will not be

sufficient to control the inflow of water into excavations. A well point or deep well system will be

necessary to adequately dewater the excavations. We expect that multiple dewatering points will be

necessary around the excavation to maintain a stable bottom condition.

SHORING

OSHAs Construction Standards for Excavations require that the contractors excavation activitiesfollow certain worker safety procedures. These include a requirement that excavations over 4 feet

deep be sloped back, shored, or shielded. The soils encountered in the test borings generally classify

as type B and C soils according to the OSHA standard. The maximum allowable slope for an

unbraced excavation in these soils is 1H:1V and 1.5H:1V, respectively, although other provisions and

restrictions apply. Excavations over 20 feet deep require specific design by a licensed Professional

Engineer. The contractor is solely responsible for site/excavation safety and compliance with OSHA

regulations. The geotechnical engineer assumes no responsibility for site safety, and the above

information is provided only for consideration by the designers.

For braced excavation design, we recommend using a cohesion of 1,000 psf where clay is

encountered, and a friction angle of 30 degrees where sand is present. A soil unit weight of 120 pcf is

recommended above the water table, and buoyant unit weight of 65 pcf is recommended below the

water table. Dewatering will have a significant impact on shoring loads. The shoring design should

carefully consider water levels, hydrostatic loads, and dewatering requirements.


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PUMP STATION

The structure is planned for a 28-foot depth, which puts it very close to the rock layer at 28 to 30

feet. We recommend extending the foundation to bear on the hard rock at roughly 30 feet below grade

instead of bearing on a thin layer of sand at 28 feet. The following paragraphs include discussion

about bearing on sand in case the structure becomes shallower than originally planned.

The allowable bearing pressure for a buried structure would be the gross bearing pressure, which is the

net allowable bearing pressure derived from the shear strength of the soil plus the surrounding

overburden pressure. During construction, the net allowable bearing pressure controls before the

structure is backfilled. Thus, we recommend that both the construction case and long-term case be

considered in sizing the mat foundation for the structure.

The net allowable bearing pressure for the saturated sand would be approximately 1,000 psf. The

overburden pressure at a depth of 28 feet would be approximately 1,820 psf, based on a soil unit

weight of 65 pcf and assuming the water table at the ground surface. Thus, the gross allowablebearing pressure for the lift station bearing on sand would be approximately 2,820 psf. A conservative

net allowable bearing pressure for the hard rock would be approximately 5,000 psf. The overburden

pressure at a depth of 30 feet would be approximately 1,950 psf, based on a soil unit weight of 65 pcf

and assuming the water table at the ground surface. Thus, the gross allowable bearing pressure for the

lift station bearing on rock would be approximately 6,950 psf. The actual contact pressure should be

calculated by dividing the maximum operating weight of the lift station structure across the outside

diameter of the lift station walls. Any footing projection outside of the walls should be neglected in

the gross bearing calculation due to the balancing overburden pressure above this section of the

foundation. For structural design of the base, this contact pressure should be uniformly distributedacross the interior slab as a conservative practice. The same contact pressure should be separately

applied to the footing projection as a cantilever. In addition, the footing projection should be designed

to support the full weight of the overlying soil acting downward to resist buoyant effects.

Since the net contact pressure for the completed/backfilled structure is actually negative, resulting in a

reduction in the effective stress below the structure, there should be minimal settlement due to

compression of the underlying soil. Actual settlement will be a function of the installation process, but

should be minor (less than 1 inch if supported on sand, and negligible if supported on rock) if the

contractor can maintain a stable excavation. If the bottom of the excavation ends in sand, we

recommend placing a layer of crushed rock below the base to provide a stable work platform. This

layer should be 12 inches thick, consisting of a 6-inch thick layer of 3-inch stabilization rock and a 6-

inch thick layer of pipe bedding material. A lean concrete mix may be placed as a mud slab in lieu of

the bedding layer for construction convenience.

For uplift design, we recommend that the design ground water level be taken at the ground surface.

The uplift resistance should be calculated as the minimum operating weight of the lift station structure

plus the effective weight of the soil mass above the footing projection outside of the barrel section.


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An effective unit weight of 65 pcf should be used for the backfill soil above the footing projection.

The hydrostatic pressure and resisting loads should also be applied across the bottom of the structure

to check the structural capacity of the base slab under this loading condition.

For evaluating lateral pressures on the barrel section, we also recommend using the design ground

water level at the ground surface. Lateral loads on the walls should be calculated at 30 pcf (equivalent

fluid) for the effective soil pressure (at rest condition) plus full hydrostatic pressure.

EARTHWORK AND EXCAVATIONS

The excavated site soils will generally be suitable for reuse as structural fill, although significant

moisture conditioning may be required. Any off-site borrow should be a clean, inorganic silt or lean

clay with a liquid limit less than 45 and a plasticity index less than 20, or poorly-graded sand similar to

the on-site soil. Borrow material should not contain an appreciable amount of roots, rock, or debris,

and should not contain any foreign material with a dimension greater than 3 inches.

All fills and backfill around the structure should be placed and compacted as structural fill. Fill should

be placed in thin lifts not to exceed 8 inches loose thickness. Structural fill should be compacted with

a sheepsfoot type roller to a minimum of 95 percent of the maximum dry density (ASTM D698,

Standard Proctor). Moisture content should be controlled to between -3 and +4 percent of optimum.

Quality control testing is an important part of any earthwork operation. It is recommended that a

representative of the geotechnical engineer periodically monitor earthwork operations to verify proper

compliance with these recommendations, including compaction levels.

OTHER RECOMMENDATIONS

During detailed design, additional issues may arise and possible conflicts may occur with our

recommendations. Such issues and conflicts should be resolved through dialogue between the

geotechnical engineer and designers. It is recommended that the geotechnical engineer review the

final design, including the plans and specifications, to verify that our recommendations are properly

interpreted and incorporated into the design.

If any changes are made in the design of the project, including the nature or location of proposed

facilities on the site or significant elevation changes, the analysis and recommendations of this report

shall not be considered valid unless the changes are reviewed. The analysis and recommendations ofthis report should not be applied to different projects on the same site or to similar projects on different

sites.

The analysis and recommendations in this report are based upon borings at specific locations. The

nature and extent of variation between boring locations is impossible to predict. Because of this,

geotechnical recommendations are preliminary until they have been confirmed through observation of

site excavation and earthwork preparation. If variations appear during subsequent exploration or


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during construction, we may reevaluate our recommendations and modify them, if appropriate. The

geotechnical engineer should be retained during construction to observe compliance with the

recommendations of this report and to provide quality control testing of earthwork construction. If

these services are provided by others, including the contractor, the entity that provides construction

phase observation and testing shares responsibility as the geotechnical engineer of record forimplementing or modifying these recommendations.

Respectfully submitted,Thiele Geotech, Inc.

Prepared by,

John A. Christiansen, P.E.Nebraska License E-7821

P:\10026.00\GEOTECHNICAL EXPLORATION REPORT.DOC


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Geotechnical Exploration Report March 9, 2010TG #10026.00 Appendix


APPENDIX

Subsurface Exploration Methods

Legend of Terms

Boring Location Plan

Boring Logs

Soil Test Summary


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Geotechnical Exploration Report March 9, 2010TG #10026.00 Appendix


SUBSURFACE EXPLORATION METHODS

The fieldwork for this study was completed on February 15, 2010. The exploratory program consisted

of 1 test boring drilled at the approximate location shown on the Boring Location Plan. Boring

locations were selected to provide the desired site coverage and were adjusted to accommodate access

conditions. The boring location was laid out by estimating angles and measuring with a cloth tape

from existing site features. The boring location should only be considered accurate to the degree

implied by the methods used to define them.

The test boring was advanced using hollow stem augers powered by a truck-mounted drill rig. Soil

samples were obtained at selected depths as indicated on the boring logs. A 3-inch nominal diameter

thin-walled sampler was hydraulically pushed to obtain undisturbed samples. Disturbed samples were

obtained by driving a 2-inch nominal diameter split barrel sampler while conducting standard

penetration tests (SPT).

The boring log was prepared based on visual classification of the samples and drill cuttings, and by

observation of the drilling characteristics of the subsurface formations. The log was supplemented and

modified based on the laboratory test results and further examination of the recovered samples. The

stratification lines on the boring log represent the approximate boundary between soil types, but the

insitu transition may be gradual.

Water level observations were made at the times stated on the boring log. The boring was backfilled

with drill cuttings at the completion of the fieldwork.

The field boring logs were reviewed to outline the depths, thicknesses, and extent of the soil strata. A

laboratory testing program was then developed to further classify the basic soils and to evaluate the

engineering properties for use in our analysis.

Laboratory tests to further classify the soils included visual classification, moisture content, dry unit

weight, Atterberg limits, and fraction passing the #200 sieve. The shear strengths of cohesive samples

were evaluated using the unconfined compression test.

The boring log and related information in this report are indicators of subsurface conditions only at the

specific locations and times noted. Subsurface conditions, including ground water levels, at other

locations of the site may differ significantly from conditions that exist at the sampling locations. Also

note that the passage of time may affect conditions at the sampling locations.


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LEGEND OF TERMSSoil Description Terms

Consistency - Fine Grained Consistency - Coarse Grained Moisture Conditions

Very Soft, Soft, Firm, Very Loose, Loose, Medium Dry, Slightly Moist, Moist

Hard, Very Hard Dense, Dense, Very Dense Very Moist, Wet (Saturated)

Sample Identification Sample Type Sample Data Laboratory Data

U -- Undisturbed (Shelby Tube) No. -- Number MC -- Moisture contentS -- Split barrel (disturbed) SPT -- Standard penetration test d -- Dry unit weight

C -- Continuous sample bpf -- blows per foot qu -- Unconfined compression

A -- Auger cuttings (disturbed) Rec -- Recovery LL/PI -- Liquid limit & plasticity index

Unified Soil Classification System Peat Pt Highly organic soils

Fat Clay CH Clay - Liquid Limit >50 * 50% or more

Elastic Silt MH Silt - Liquid Limit >50 * smaller than

Lean Clay CL Clay - Liquid Limit % sand

Poorly-Graded Gravel GP Gravels with less than 5 percentWell-Graded Gravel ** GW smaller than No. 200 sieve *

* See Plasticity Chart for definition of silts and clays ** See Criteria for Sands and Gravels for definition of well-graded

Plasticity Chart

Pl

as

tic

ity

In

d

e

x

60

50 CH or OH

40

30MH or OH

20 CL or OL

10CL-ML ML

0 10 20 30 40 50 60 70 80 90 100

L i q u i d L i m i t

Criteria for Sands and Gravels Coarse Fine Coarse Medium Fine FINES

Boulders Cobbles Gravel Gravel Sand Sand Sand (silt or clay)

Sieve size 10" 3" " #4 #10 #40 #200

Well-graded sands (SW) Cu=D60/D106 and Cc=(D30)2/(D10 x D60) 3 and 1

Well-graded gravels (GW) Cu=D60/D104 and Cc=(D30)2/(D10 x D60) 3 and 1


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15/17

WAT

D

E

DEP(ft.)

bori

5

10

15

20

25

ER LEVEL OB

uring Drilling

nd of Drilling

COLOR M

ng backfilled

darkgray

light slibrown

grayishbrown

ERVATIONS

VIS

IST. CONSI

15.0

15.0

ith cuttings

oist hard

htly loosoist

et

LO

AL/MANUAL

T.SOILTYPE

Railroad St

see B

lean clay

poorlygradedsand

PROJECT

LOCATION

ATION OF BO

ESCRIPTION

GEOLOGICORIGIN

Pump Statio

& Herbert St,

oring Locatio

fill

alluvium

ING

REMA

eatrice, NE

n Plan

light bmottl

fine tosa

minor fin

DRILLER

DRILLI

TYPE O

S

RKSNTY

Epley

3.2

g

U

rown Uling

oarse Ud

S

S

gravel

S

LOGGER

G METHOD

F SURFACE

AMPLE DATA

. &PE

SPT(bpf)

RE(in.

Kalbach

5 HSA

rass

-1 11

-2 11

-3 12

-4 3

-5 5

-6 5

BOJOB NO.

DRILL RI

ELEVATIO

LABORAT

)

MC(%)

d(pcf)

10026.0

CME 45

16.9 111.4

18.3 103.0

2.3

11.0

15.2

ING LDATE

BORING

N DEPT

ORY DATA

qu(tsf)

LL/PICLASS

0 2/15/1

B-1

30

LL=36

2.25 PI=20

CL

P200

4.3%

SP

D


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WAT

D

E

DEP(ft.)

bori

30

35

40

45

50

ER LEVEL OB

uring Drilling

nd of Drilling

COLOR M

ng backfilled

reddishbrown

lightbrown

ERVATIONS

VIS

IST. CONSI

15.0

15.0

ith cuttings

et loos

et veryhard

LO

AL/MANUAL

T.SOILTYPE

Railroad St

see B

poorlygradedsand

rock

PROJECT

LOCATION

ATION OF BO

ESCRIPTION

GEOLOGICORIGIN

Pump Statio

& Herbert St,

oring Locatio

alluvium

ING

REMA

eatrice, NE

n Plan

weathewith lim

bottom of h

DRILLER

DRILLI

TYPE O

S

RKSNTY

Epley

3.2

g

shaleestone S

ole @ 30

LOGGER

G METHOD

F SURFACE

AMPLE DATA

. &PE

SPT(bpf)

RE(in.

Kalbach

5 HSA

rass

-7 50/2

BOJOB NO.

DRILL RI

ELEVATIO

LABORAT

)

MC(%)

d(pcf)

10026.0

CME 45

ING LDATE

BORING

N DEPT

ORY DATA

qu(tsf)

LL/PICLASS

0 2/15/1

B-1(con

30

D


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SOIL TEST SUMMARProject J ob No.

Pump Station 10026.00Location Date

Railroad St & Herbert St, Beatrice, NEUNIT UNCONFINED SOIL CLASSIFICATION

BORING SAMPLE SAMPLE SAMPLE MOISTURE WEIGHT VOID SAT. COMPRESSION ATTERBERG PASS REMARK

NO. NO. DEPTH DIA. CONTENT WET DRY RATIO (%) qu STRAIN LIMITS #200

(ft.) (in.) (%) (pcf) (pcf) (e) (tsf) (%) LL PL PI (%)

B-1 U-1 1.5-3 16.9 130.2 111.4 0.512 89

U-2 3.5-5 2.85 18.3 121.8 103.0 0.636 78 2.25 4.7 36 16 20 CL

U-3 8.5-10 2.3

S-4 13.5-15 11.0

S-5 18.5-20 15.2 4.3 SP

S-6 23.5-25

S-7 28.5-30

2/22/2010

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