limited geotechnical engineering evaluation...2300 missile drive, cheyenne, wyoming 82001 phone...

2300 Missile Drive, Cheyenne, Wyoming 82001 Phone 307-635-0222 www.stratageotech.com

Limited Geotechnical Engineering Evaluation

Classroom Additions Albany County Campus

Laramie, Wyoming

Limited Geotechnical Engineering Evaluation Classroom Additions

Albany County Campus Laramie, Wyoming

PREPARED FOR: Laramie County Community College

Mr. Tim Macnamara 1400 College Drive

Cheyenne, Wyoming 82007 [email protected]

307.778.1256

PREPARED BY: STRATA, A Professional Services Corporation

2300 Missile Drive Cheyenne, Wyoming 82001 Telephone (307) 635.0222

January 5, 2017

www.stratageotech.com

© 2016 by Strata, A Professional Services Corporation. All rights reserved.

TABLE OF CONTENTS

Page

INTRODUCTION ............................................................................................................................................. 1

Project understanding .................................................................................................................................. 2

Existing Conditions .................................................................................................................................... 2

Proposed Construction ............................................................................................................................. 2

FIELD EXPLORATION ...................................................................................................................................... 2

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

SUBSURFACE CONDITIONS ........................................................................................................................... 3

GEOTECHNICAL OPINIONS AND RECOMMENDATIONS ................................................................................ 4

Drilled Pier Foundation Design ................................................................................................................. 5

EVALUATION LIMITATIONS ........................................................................................................................... 5

Plate 1 Location of Exploratory Borings Appendix A Exploratory Boring Logs USCS Information Appendix B Laboratory Test Results



Limited Geotechnical Engineering Evaluation Classroom Additions

Albany County Campus Laramie, Wyoming

INTRODUCTION

STRATA, A Professional Services Corporation (STRATA) is pleased to provide our limited

geotechnical engineering evaluation for the classroom additions to be constructed onto the Albany

County Campus facility in Laramie, Wyoming. The purpose of this evaluation is to assess the

subsurface conditions at the two classroom areas and to prepare geotechnical engineering

opinions and recommendations that may be used for planning, design and construction of the

new classroom foundations that are adjacent to the existing building. The scope of this report is

intended solely to address concerns relative to the new classroom addition foundations that are

immediately adjacent to the existing building and within the stress influence zone of the existing

shallow spread footings supported at frost depth within the overburden soils. The scope of this

report specifically excludes geotechnical information relative to other aspects of the project such

as, the use of spread footings in other areas of the new additions, floor slabs, drainage and

earthworks. We understand that geotechnical information relative to the use of spread footings,

slabs on-grade and other aspects of the project is presented in the original geotechnical report

prepared by Terracon Consultants for the initial building development; and that the project design

team intends to use the original report to the extent possible for the current project.

This report must be read, understood and implemented in its entirety. Report portions

cannot be relied upon individually without the supporting text of remaining sections, appendices

and figures. Our opinion is that the success of the proposed construction will depend on following

the report recommendations, good construction practices, and providing the necessary

construction monitoring, testing, and consultation to verify that work has been completed as

recommended. We accomplished this evaluation referencing our proposal dated November 11,

2016. To accomplish our evaluation, STRATA performed the following services:

1. One exploratory boring was drilled to an approximate depth of 19 feet within the eastern classroom addition area.

2. The soils encountered were visually described, classified, and logged referencing the

Unified Soil Classification System (USCS). The soil and rock samples were returned to our laboratory for additional visual assessment and testing.

Classroom Additions – Albany County Campus Laramie, Wyoming

File: WY16316A Page 2



3. Laboratory testing was performed in general accordance with ASTM procedures including in-situ moisture, Atterberg limits, grain-size analysis and consolidation. We utilized these laboratory results to help characterize the soil and rock properties for use in our engineering analyses.

4. Engineering analyses were performed in order to provide geotechnical design and

construction recommendations for the new foundations adjacent to the existing building.

PROJECT UNDERSTANDING

Existing Conditions

The project is located on the Albany County Campus at 1125 Boulder Drive in Laramie,

Wyoming. The Campus site is situated on the east side of Boulder Drive, south of the Farm

Bureau and east of the Laramie Rec Center. The existing building is a single-story, metal framed

structure with masonry veneer and slab on-grade floor. The structure is comprised of two square

buildings that are connected at the corners with a tall steel-frame structure with glass atrium area.

The existing building is supported on spread footing foundations that presumably bear at a

minimum 42-inch frost depth. The overall site slopes down to the west at an approximate 2 percent

grade.

Proposed Construction

The new classroom additions will be situated on the southern corners of each of the two

main buildings and within areas that are currently paved patios. The new structures will each be

approximately 40 feet by 45 feet and will utilize similar steel framing and masonry veneer as the

existing buildings. Elevation Structural Design reports the maximum column and wall loads are

16 kips and 1.4 kips per linear foot, respectively. Tolerable settlement criteria for the additions

have not been specifically defined, although in our conversations with the design team it was

agreed that differential movements between the existing and new structures should be minimal.

We assume that differential movements on the order of ½-inch or less are acceptable.

FIELD EXPLORATION

STRATA drilled a single exploratory boring within the proposed eastern classroom

addition on December 14, 2016. The boring was advanced to an approximate depth of 19 feet.

The location of the boring is presented on Plate 1 and the log of boring is presented in Appendix

A. The boring was staked in the field by Strata personnel and the ground surface elevation at the

boring was determined based on a survey referencing the finished floor elevation of the existing

building.





STRATA advanced the boring using a CME-55 track-mounted drill rig equipped with 4-

inch diameter solid-stem augers. An experienced geotechnical engineer logged and visually

classified the soil encountered in the boring referencing the Unified Soil Classification System

(USCS). Soil samples were obtained within the boring via 2-inch and 2.5-inch outside diameter

split-barrel samplers driven with a 140-pound automatic hammer falling 30 inches. The N values

presented on the logs have not been corrected for sampler size, overburden stress or hammer

efficiency. Sampling was performed in general conformance with ASTM D1586 and samples

were collected at selected depth intervals as indicated on the logs.

LABORATORY TESTING

The soil samples collected in the field were returned to our laboratory for further

classification and testing in accordance with ASTM procedures. We completed the following

laboratory testing, the results of which are presented on the boring logs and in Appendix B:

Natural moisture content Sieve analyses Plasticity indices Consolidation

SUBSURFACE CONDITIONS

The soil conditions encountered in the boring generally consist of unconsolidated sand,

silt and clay overlying siltstone bedrock. A more specific discussion of each stratum encountered

is presented below:

Silty clayey sand (SC-SM) – Below a thin surficial layer of landscaping gravel, medium dense, reddish-brown silty clayey sand extended to an approximate depth of 3 feet. The sand fraction of the soil consisted of fine to medium grained particles and the silty clay fraction exhibited low plasticity.

Poorly graded sand with silt (SP-SM) – Below the silty clayey sand layer, reddish-brown poorly graded sand with silt extended to an approximate depth of 4.5 feet. The sand fraction varied from fine to medium grained and the relative density of the soil was loose.

Silty sand (SM)– Below the poorly graded sand layer, medium dense, reddish brown, silty sand extended to an approximate depth of 8 feet. This soil is effectively a residual siltstone/sandstone material that is weathered to the point that little to no structure remains. The sand fraction was primarily of fine grained particle size and the silt fraction was non-plastic

Siltstone bedrock – Below the silty sand layer, moderately hard, reddish-brown siltstone extended to the maximum depth of exploration.





Groundwater – Groundwater was not encountered at the time of drilling. Based on the moisture content data for the various material within the foundation influence zone, we do not anticipate significant effects associated with groundwater. However, numerous factors can contribute to the presence or fluctuation of groundwater levels. The evaluation of these factors is beyond the scope of this study.

GEOTECHNICAL OPINIONS AND RECOMMENDATIONS

The primary concern for the support of the new building columns is differential movements

between the existing and new foundations. The existing spread footing foundations supported on

soil are assumed to have reached a condition of equilibrium and for the purpose of this study can

be taken to be stable with no expected additional movements. On the other hand, any new

footings can be expected to settle to some extent due to the addition of foundation loads. For

practical purposes, it can be taken that the total settlements of the new foundations will define the

differential movements between the new and existing foundations. In addition, new spread

footings can impose additional stresses on the adjacent existing footings, resulting in potential

additional movements of the existing footings. In order to maintain strain compatibility between

the existing footings and adjacent new footings, it is necessary to limit the potential settlement of

the new footings to a negligible value. For this reason, and based on the conditions encountered

and our knowledge of the site, it is our opinion that the limited column supports for the classroom

additions that are adjacent to the existing building should be supported on the siltstone bedrock.

There are at least three feasible alternative foundation systems that can provide adequate

support, including drilled piers, helical piers and direct footing embedment in the siltstone. Based

on our initial conversations with Mr. Ken Tobin and Mr. Jeremy Tuck of the design team, we

understand that conventional drilled piers are preferred due to availability of local contractors and

cost. Therefore, design and construction recommendations for drilled piers are presented in the

following sections. The recommendations presented reflect our understanding of the proposed

classroom addition locations, configuration, loading conditions, existing topography, existing

geotechnical data, and subsurface conditions as encountered. Subsurface conditions may vary

from what was observed during our subsurface evaluation and the extent of this variation is

unknown and will not be known until construction, and may impact foundation design and

construction cost and/or schedule.





Drilled Pier Foundation Design

The following design and construction recommendations should be observed for drilled

pier foundation systems for the proposed classroom structure supports located adjacent to the

existing building foundations.

1. Design straight shaft drilled piers using a maximum allowable end bearing pressure of 9,000 psf.

2. Piers must penetrate the competent siltstone bedrock a minimum of one foot. We

anticipate pier lengths may vary from approximately 8 to 10 feet. Provide a contingency in the pier schedule to allow for additional length to be added in the field. Reinforce the full length of drilled piers as required per ACI.

3. Design piers with a minimum diameter of 16 inches to facilitate proper cleaning,

observation of the pier hole, and concrete placement.

4. Use a concrete with a fluid mix with a slump range of 6 to 8 inches so that it will fill voids between reinforcing steel and the pier hole. Construct individual piers and place concrete immediately after the excavation is performed.

5. We anticipate only single piers will be used at each column location. However, if multiple piers are used then capacity reduction factors and minimum pier spacing must be included in the pier design. We can provide these values if requested.

6. We anticipate the use of a tremie and concrete pump to place the pier concrete. Due to anticipated raveling and sloughing of the overburden sands, pier concrete quantities may exceed calculated neat-line volumes.

EVALUATION LIMITATIONS

This geotechnical engineering evaluation has been prepared to assist the planning, design

and construction of the new classroom column foundations adjacent to existing building. Our

services consist of professional opinions and recommendations made in accordance with

generally accepted geotechnical engineering principles and practices as they exist in Wyoming

at the time of this report.

The geotechnical recommendations provided herein are based on the premise that an

adequate program of tests and observations will be conducted during construction in order to

document compliance with our recommendations and to confirm conditions exposed during

subgrade preparations. Further, the method of exploration used allows observation of a relatively

small sample of the subsurface conditions at the site. Variations may exist beyond the exploration

locations. These variations would not be apparent until construction. Where such variation does





exist, it may affect the options and recommendations presented in this report, as well as

construction timing and costs.

B-1

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VICINITY MAP

NOT TO SCALE

PROJECT SITE

LARAMIE

I-80

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(HW

Y 8

0)

BASE IMAGE CREATED FROM:

GOOGLE EARTH(Dated 7-27-15)

LEGEND:

EXPLORATORY BORING DRILLED

NOVEMBER 12, 2016

B-1

Drawn By:

Project No.:

Copyright: STRATA

Date:

12/28/2016 8:31:01 A

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WY16316A

December 2016

MAT

2300 Missile Drive

Cheyenne, Wyoming 82001

PHONE: 307-635-0222

CLIENT: Laramie County Community College

Albany County Campus Classroom Additions

Laramie, Wyoming

EXPLORATION LOCATION

1

N

THIS PLAN COMPRISES A PORTION OF STRATA'S REPORT AND THE TEXT OF THE REPORT CONTAINS ESSENTIAL INFORMATION: BEFORE UTILIZING THIS PLAN FOR ANY PURPOSE WHATSOEVER, THE REPORT

SHOULD BE READ COMPLETELY. THIS PLAN IS INTENDED TO HELP VISUALIZE THE INFORMATION PROVIDED IN THE REPORT. THESE LOCATIONS AND INFORMATION WERE ADDED TO EXISTING PLANS OF THE

SITE PREVIOUSLY PREPARED BY OTHERS AND NO CHECK OF ACCURACY, CURRENCY, APPROPRIATENESS, ETC., OF INFORMATION PROVIDED BY OTHERS WAS PERFORMED, SINCE SUCH CHECKS WERE NOT

PART OF STRATA'S SCOPE OF SERVICES.

SCALE IN FEET

(APPROXIMATE)

0 40 80

APPENDIX A Exploratory Boring Log

USCS Information

4553

5535

68912

1011

50/6.0"

50/6.0"

50/2.0"

50/2.0"

7302.2

7299.7

7298.0

7294.7

7283.5

LANDSCAPING ROCK

SILTY CLAYEY SAND, (SC-SM)reddish brown, fine to mediumsand, medium dense, moist,trace gravel

POORLY GRADED SANDWITH SILT, (SP-SM) reddishbrown, fine to medium sand,loose, moist, trace gravel

SILTY SAND, (SM) light brown,fine sand, medium dense, moist,highly weathered residualsiltstone, varies to sandy silt

SILTSTONE, reddish brown,medium hard, damp, trace clay

Elevation based on finish floor ofexisting building = 7303.5'Borehole Terminated at 19.2Feet.

non-plastic

non-plastic

10

8

17

100+

100+

100+

Pocket Penetrometer, TSF 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Sheet 1 Of 1

Sam

ple

Typ

e

% Passing No. 200 Sieve

TEST RESULTS

SP

TB

low

s P

er6

Inch

es

20 40 60 80

PL LLMC

Sym

bol

Dry

Den

sity

(pcf

)

7302.7

Project Name: Classroom Additions - Albany County Campus

Date Drilled: 12/22/20161

BORING LOG

Ele

vatio

n

USCS Description

Groundwater Depth: N.E.

Client: Laramie County Community College

Remarks

Note: BGS =Below Ground Surface

Logged By: T. Olson

Project #: WY16316A

Drill Rig: CME 55

Drilled By: Strategic Expl.

Borehole Dia.: 4" SFA

SP

T -

N

SPT, N-Value

Dep

th(f

t)

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1/5

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6 -

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DIT

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.GP

J

10

4

7

10

10

7

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

50

50

50

SC-SM

SP-SM

SM

Well-Graded Gravel,

Gravel-Sand Mixtures.

Poorly-Graded Gravel,

Gravel-Sand Mixtures.

Silty Gravel, Gravel-

Sand-Silt Mixtures.

Clayey Gravel, Gravel-

Sand-Clay Mixtures.

Well-Graded Sand,

Gravelly Sand.

Poorly-Graded Sand,

Gravelly Sand.

Silty Sand,

Sand-Silt Mixtures.

Clayey Sand,

Sand-Clay Mixtures.

Inorganic Silt, Sandy

or Clayey Silt.

Inorganic Clay of Low

to Medium Plasticity,

Sandy or Silty Clay.

Organic Silt and Clay

of Low Plasticity.

Inorganic Silt, Mica-

ceous Silt, Plastic

Silt.

Inorganic Clay of High

Plasticity, Fat Clay.

Organic Clay of Medium

to High Plasticity.

Peat, Muck and Other

Highly Organic Soils.

TYPICAL NAMES

LETTER

SYMBOL

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

COARSE

GRAINED

SOILS

GRAVELS

SANDS

CLEAN

GRAVELS

GRAPH

SYMBOL

GRAVELS

WITH

FINES

CLEAN

SANDS

SANDS

WITH

FINES

FINE

GRAINED

SOILS

SILTS AND CLAYS

LIQUID LIMIT

LESS THAN 50%

SILTS AND CLAYS

LIQUID LIMIT

GREATER THAN 50%

MAJOR DIVISIONS

Standard 2-Inch OD Split-Spoon

Sample

California 2.5-Inch OD

Split-Spoon Sample

Rock Core

Shelby Tube 3-Inch OD

Undisturbed Sample

Groundwater After

24 Hours

Groundwater

at Time of Drilling

BG

BK

RG

Baggie Sample

Bulk Sample

Ring Sample

Shorthand Notation:

BGS = Below Existing Ground Surface

N.E. = None Encountered

HSS = Hollow Stem Auger

SSS = Solid Stem Auger

Indicates Date of

Reading

APPENDIX B Laboratory Test Results

CONSOLIDATION TEST RESULTSASTM D 2435 (Method A)

Water added @ .92 ksf

0.1 1 100.2 0.3 0.4 0.5 0.6 0.7 0.80.9 2 3 4 5 6 7 8 9 20 30

Load, ksf

-5

-4

-3

-2

-1

0

Ver

tical

Stra

in, %

-0.7

-1.4

-2.6

-4.5

-4.9

-0.5-0.7

0.0 -0.1

-0.3-0.5

Project: Classroom Addition Albany County CampusClient: LCCCProject Number: WY16316ALab Number: B-1 at 7'Sample Classification: Reddish Brown SILTY SAND (SM)Sample: In-Situ Tube (Condition: Good)Date Tested: 12/30/16 By: JFSample Dry Unit Weight: 115.5 pcfMoisture Content: 10.0%

limited geotechnical engineering evaluation...2300 missile drive, cheyenne, wyoming 82001 phone...

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