Attachment 3 - Joliet CBOC Geotech Proposed Parking.pdf

ECS Midwest, LLC Geotechnical Engineering Report

Proposed Parking Lot Addition

1201 Eagle Road Joliet, Illinois

ECS Project No. 16:13974

September 20, 2021

September 20, 2021 Ms. Suzette Evans, PE, LEED AP David Mason and Associates 333 South Desplaines Street, Suite 200 Chicago, Illinois 60661 Email: sevans@davidmason.com

ECS Project No. 16:13974

Reference: Geotechnical Engineering Report Proposed Parking Lot Addition 1201 Eagle Road Joliet, Illinois

Dear Ms. Evans:

ECS Midwest, LLC (ECS) has completed the subsurface exploration, laboratory testing, and geotechnical engineering analyses for the above-referenced project. Our services were performed in general accordance with our agreed to scope of work. This report presents our understanding of the geotechnical aspects of the project along with the results of the field exploration and laboratory testing conducted, and our design and construction recommendations.

It has been our pleasure to be of service to David Mason and Associates during the design phase of this project. We would appreciate the opportunity to remain involved during the continuation of the design phase, and we would like to provide our services during construction phase operations as well to verify subsurface conditions assumed for this report. Should you have any questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, ECS MIDWEST, LLC

Bernardo Martinez-Tarin, P.E.* Mark J. Carlson, RPG, D.GE, P.E.

Geotechnical Project Engineer bmartineztarin@ecslimited.com *Licensed in MI, IA

Chief Engineer MCarlson@ecslimited.com Renews 11/30/21 https://ecslimited365.sharepoint.com/sites/16Chicago/16 GEO Rept 100139/Job 13000 - 13999/13974 - Proposed Parking Adition/Report/13974 - Proposed Parking Addition.docx mailto:sevans@davidmason.com mailto:bmartineztarin@ecslimited.com mailto:MCarlson@ecslimited.com

Parking Lot Addition – Joliet, IL September 20, 2021 ECS Project No. 16:13974 Page i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 Project Location/current site use/Past site use

2.2 Proposed Construction

3.0 FIELD EXPLORATION AND LABORATORY TESTING

3.1 Subsurface characterization

3.2 Groundwater Observations

3.3 Field Infiltration Testing

3.4 Laboratory Testing

4.0 DESIGN RECOMMENDATIONS

4.1 Pavements

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 Subgrade Preparation

5.1.1 Stripping, Grubbing and Probing

5.1.2 Proofrolling

5.1.3 Site Temporary Dewatering

5.2 Earthwork Operations

5.2.2 Engineered fill

5.4 Utility Installations

6.0 CLOSING

APPENDICES

Appendix A – Drawings & Reports

• Site Location Diagram

• Boring Location Diagram

Appendix B – Field Operations

• Reference Notes for Boring Logs

• Subsurface Exploration Procedures

• Boring Logs

Appendix C – Supplemental Report Documents

• Important Information about This Geotechnical Engineering Report

ECS Project No. 16:13974 Page 1

EXECUTIVE SUMMARY

The following summarizes the main findings of the exploration, particularly those that may have a cost impact on the planned development. Further, our principal foundation recommendations are summarized. Information gleaned from the Executive Summary should not be utilized in lieu of reading the entire geotechnical report.

• The project is planned to consist of an at-grade parking expansion.

• Based on the results of the subsurface exploration, we recommend a design Illinois Bearing Ratio (IBR) of 2.5 and a modulus of subgrade reaction (kv) of 100 pci. Pavement design recommendations are included in the body of the text of this report.

ECS Project No. 16:13974 Page 2

1.0 INTRODUCTION

The purpose of this study was to provide geotechnical information for the design of drive lanes and parking lots for the proposed project to be constructed in Joliet, Illinois. The recommendations developed for this report are based on project information supplied by Ms. Suzette Evans and Mr. Jonathan Stitgen with David Mason and Associates, and Mr. Gary Collins with Virtual Energy Solutions.

Our services were provided in accordance with our proposal no. 16:20826-GP, dated April 2, 2021, and revised August 18, 2021 which includes our terms and conditions of service.

This report contains the procedures and results of our subsurface exploration and laboratory testing programs, review of existing site conditions, engineering analyses, and recommendations for the design and construction of the project.

The report includes the following items.

• A brief review and description of our field and laboratory test procedures and the results of testing conducted.

• A review of surface topographical features and site conditions.

• A review of subsurface soil stratigraphy with pertinent physical properties.

• Final soil exploration/test boring logs.

• Recommendations for site preparation and construction of compacted fills, including an evaluation of on-site soils for use as compacted fills and identification of potentially unsuitable soils and/or soils exhibiting excessive moisture at the time of sampling.

• General recommendations for pavement design, including a recommended design CBR.

• Evaluation and recommendations relative to groundwater control, including recommendations for pavement underdrains.

ECS Project No. 16:13974 Page 3

2.0 PROJECT INFORMATION

2.1 PROJECT LOCATION/CURRENT SITE USE/PAST SITE USE

The project site is located at 1201 Eagle Road, Joliet, Will County, Illinois and is bounded to the north and east by undeveloped land, to the south by the existing structure at 1201 Eagle Street and to the west by Walnut Street. The site location is shown below, and in wider scope on the Site Location Diagram in Appendix A.:

Site Location Map

The project site is currently an undeveloped, grassed lot, although based on available historic imagery, the project site was formerly developed by a hospital structure which was demolished in Summer 2018.

Based on our review of the ‘ALTA/NSPS Land Title Survey’ (prepared by RT&A and dated October 31, 2018), the existing site grades in the project areas range from EL. 590 feet to EL. 616 feet above MSL.

2.2 PROPOSED CONSTRUCTION

The following information explains our understanding of the planned development including proposed buildings and related infrastructure.

Pavement: The development will include paved parking and drive lanes. The design traffic was not provided to us. Based on our conversation with you and our review of the documents provided by email on September 15, 2021. Therefore, it was necessary for ECS to use arbitrarily selected design traffic volumes. The information below summarizes our understanding and assumptions of the traffic.

ECS Project No. 16:13974 Page 4

PAVEMENT DESIGN INFORMATION

Pavement Area Maximum Daily Traffic

Light Duty 250 personal vehicles and 5 vans

Heavy Duty 1,000 personal vehicles, 10 vans and 2 minibuses

Based on the anticipated site grades, we understand the proposed parking lot will approximately match the existing site grades along Walnut Street (therefore sloping down from about EL. 606 feet to EL. 594 feet above MSL). A 2% traffic growth factor and a 20-year design period were considered for this analysis.

If ECS’ understanding of the project is not correct, especially if the structural loads or elevations are different, please contact ECS so that we may review these changes and revise our recommendations, as appropriate.

ECS Project No. 16:13974 Page 5

3.0 FIELD EXPLORATION AND LABORATORY TESTING

Our exploration procedures are explained in greater detail in Appendix B including the insert entitled ‘Subsurface Exploration Procedures: SPT’. Our scope of work included drilling eight (8) borings. Our borings were located with a handheld GPS unit and their approximate locations are shown on the Boring Location Diagram in Appendix A.

3.1 SUBSURFACE CHARACTERIZATION

The subsurface conditions encountered were generally consistent with published geological mapping. The following sections provide generalized characterizations of the soil strata. Please refer to the boring logs in Appendix B.

GENERAL SUBSURFACE CHARACTERISTICS

Approximate Depth Range

(feet) Stratum Description

Calibrated Penetrometer

Resistance (tsf)

Water Content

SPT(1) N-

values (bpf)

Near-Surface Cover

N/A Topsoil: 3 to 12 inches N/A N/A N/A

¼-7½ I(3)

Fill or Possible Fill: Construction Debris, consisting of:

Sand and gravel (SP) – dark brown, moist, medium dense to very dense

Gravel, Crushed limestone with fines (GP) – gray, moist, loose

NA NA 17-55(2)

½-7½ II(4) Silty Clay (CL/ML) – brown, moist, hard to very hard

4-9 14-21 11-22

Notes:

(1) Standard Penetration Testing

(2) SPT N-values in fill or possible fill may not be representative of actual in-situ conditions.

(3) Stratum I was not encountered at boring B-1. Stratum I was observed to overlie Stratum II at borings B-2, B-3 and B-6.

Borings B-4, B-5 and B-7 were terminated within Stratum I due to refusal on undetermined obstructions.

(4) Stratum II was only encountered at borings B-1, B-2 (2 feet below grades), B-3 and B-6 (6 feet below grades).

It should be noted that given the history of the site (which was determined from our review of historical aerial imagery), we understand the project site was previously occupied with a hospital structure. It is apparent from the result of the subsurface exploration that the excavations resulting from the demolition of the former structure (and possibly a basement or crawl space) were backfilled with demolition debris.

Based on refusal encountered at several locations, large remnants of the former structure (including possible slab fragments) are likely to be found below the site. It should also be noted that in certain locations (such as towards the west end of the site) natural soil deposits were encountered either from below the surficial materials or below a certain amount of debris fill. At borings B-1 and B-2, no fill to very shallow fill was encountered. After a detailed review of the historical aerial imagery, it was observed that those locations correspond to a former at-grade driveway, which would justify the conditions revealed by the borings at those locations.

The soil stratification shown on the boring logs represents the interpreted soil conditions at the actual boring locations. Variations in the stratification can occur between sample intervals and boring locations.

The subsurface conditions at other times and locations on the site may differ from those found at the boring locations. If different site conditions are encountered during construction, ECS should be contacted to review our recommendations relative to the new information.

ECS Project No. 16:13974 Page 6

3.2 GROUNDWATER OBSERVATIONS

Ground water levels were measured in our boring logs in Appendix B. During conventional auger drilling, water or drilling fluid is not injected into the open borings to help support the soils. As such, free-flowing groundwater can be observed flowing naturally into and out of the soil borings. Free-flowing groundwater was not observed at the boring locations, neither during drilling nor after boring completion. Soils in the Midwest frequently oxidize from gray to brown above the level where the soil remains saturated. The ground water table is frequently interpreted to be located near this zone of change, which may be an indication of the static long-term water level. Gray or wet soils were not identified at the soil boring locations, indicating the groundwater table may be located deeper than the extents of the current subsurface exploration.

It should be noted that based on the nature of the fill materials encountered on site, and the predominantly cohesive materials encountered below the fill, perched water conditions are possible to be encountered on site, during the thawing season or times of heavy rain. and Based upon our interpretation of the test boring observations, it appears that the static groundwater level may be found deeper than our boring depths. However, perched water conditions may develop or exist seasonally particularly in areas with clayey soils. Variations in the long-term water table elevation may occur as a result of changes in precipitation, evaporation, surface water runoff, construction activities, and other factors.

3.3 FIELD INFILTRATION TESTING

ECS attempted to perform a field infiltration test at about the center of the site. Due to the obstructions encountered, ECS was unable to install the infiltrometer to the specified depth (5 feet). In an attempt to complete the field infiltration test, ECS’ subcontracted driller offset up to 3 times the proposed location, twice in the northerly direction (away from the building) and once in the southerly direction (towards the building), with similar results. As such, ECS was unable to perform infiltration testing and to measure the permeability of the soils on site.

The permeability of site soils will vary based on soil composition, in-place condition, and others. Based on the results of the infiltration testing, the tested soils were observed to exhibit medium to high permeability, typical of poorly graded granular soils. We recommend the project Civil Engineer review the infiltration test results and determine if the infiltration rates of the tested soil are suitable for the anticipated drainage and infiltration requirements at the project site.

3.4 LABORATORY TESTING

The laboratory testing consisted of selected tests performed on samples obtained during our field exploration operations. Classification and index property tests were performed on representative soil samples. These tests included:

• Natural Moisture Content (ASTM D2216)

• Calibrated Penetrometer Resistance

Each sample was visually classified on the basis of texture and plasticity in accordance with ASTM D2488 Standard Practice for Description and Identification of Soils (Visual-Manual Procedures) and including USCS classification symbols. After classification, the samples were grouped in the major zones noted on the boring logs in Appendix B. The group symbols for each soil type are indicated in parentheses along with the soil descriptions. The stratification lines between strata on the logs are approximate; in situ, the transitions may be gradual.

ECS Project No. 16:13974 Page 7

The soil samples will be retained in our laboratory for a period of 60 days, after which, they will be discarded, unless other instructions are received as to their disposal.

ECS Project No. 16:13974 Page 8

4.0 DESIGN RECOMMENDATIONS

4.1 PAVEMENTS

Subgrade Characteristics: Based on the results of our borings, it appears that the pavement subgrades in cuts will consist mainly of granular construction debris or natural silty clay. Illinois Bearing Ratio (IBR) or other means to evaluate the bearing characteristics of soils on site were not part of this project. However, since natural soil deposits are cohesive and do not drain well, as well as due to the presence of construction debris (which may lead to potential of dips and pockets in the clay), we recommend utilizing an IBR value of 2.5 for design purposes. For rigid pavements, a modulus of subgrade reaction, kv, of 100 pounds per cubic inch (pci) (based on a 1 foot by 1 foot plate test) was considered.

The pavement design recommendations assume the subgrade consists of suitable materials evaluated by ECS, and the subgrade is prepared as recommended in the Subgrade Preparation and Earthwork Operations sections of this report.

The preliminary pavement sections below are guidelines that may or may not comply with local jurisdictional minimums. The pavement sections below assume a pavement life of 20 years and traffic loading as indicated in Section 2.2 of this report:

PROPOSED PAVEMENT SECTIONS

FLEXIBLE PAVEMENT RIGID PAVEMENT

MATERIAL Heavy Duty Light Duty Heavy Duty

Portland Cement Concrete (f’c = 4000 psi)

- - 6 in.

Bituminous Surface Course (SM- 9.5)

1½ in 1½ in -

Bituminous Binder Course (BM- 25.0)

3 in 2 in -

Graded Aggregate Base Course

(AASHTO #21A/21B)

10 in 8 in 6 in

TOTAL 14½ in 11½ 12

In general, heavy duty sections are areas that will be subjected to trucks, or other similar vehicles including main drive lanes of the development. Light duty sections are appropriate for automobile traffic, light duty truck traffic and parking areas.

Large, front loading trash dumpsters frequently impose concentrated front wheel loads on pavements during loading. This type of loading typically results in rutting of asphalt pavement and ultimately pavement failures. For preliminary design purposes, we recommend that the pavement in trash pickup areas consist of a 6-inch thick, 4,000 psi, reinforced concrete slab over 8-inches of dense graded aggregate.

When traffic loading becomes available ECS or the Civil Engineer can design the pavements.

ECS Project No. 16:13974 Page 9

5.0 SITE CONSTRUCTION RECOMMENDATIONS

5.1 SUBGRADE PREPARATION

5.1.1 Stripping, Grubbing and Probing

The subgrade preparation should consist of stripping all vegetation, rootmat, topsoil, and any soft or unsuitable materials from the 10-foot expanded building, 5-foot expanded pavement limits, and 5 feet beyond the toe of Engineered fills. Most borings (except for B-1) encountered debris fill to varying depths.

Based on the observed conditions and the history of the site, it is deemed impractical to remove the observed fill to support the proposed pavements on natural soils or engineered fill. As such, we recommend the subgrade elevation is exposed, and the subgrade is proofrolled in accordance with the provisions of the following section. In addition, any large construction debris fragment exposed during the stripping process should be removed and the resulting excavations be backfilled with engineered fill in accordance with the provisions of this report. As an alternative, large fragments that cannot be removed (such as slabs on grade) should be probed with 3-inch holes in a 10-foot by 10-foot grid pattern to prevent water from storing within the pavement subbase materials.

5.1.2 Proofrolling

After removing all unsuitable surface materials, cutting to the proposed grade, and prior to the placement of any engineered fill or other construction materials, the exposed subgrade should be observed by ECS.

The exposed subgrade should be thoroughly proofrolled with previously approved construction equipment having a minimum axle load of 10 tons (e.g., fully loaded tandem-axle dump truck). The areas subject to proofrolling should be traversed by the equipment in two perpendicular (orthogonal) directions with overlapping passes of the vehicle under the observation of ECS. This procedure is intended to assist identification of yielding materials. In the event that unstable or “pumping” subgrade is identified during the proofroll, those areas should be marked for repair prior to the placement of any subsequent engineered fill or other construction materials. Methods of repair of unstable subgrade, such as undercutting, moisture conditioning and recompaction, or chemical stabilization, should be discussed with ECS to determine the appropriate procedure with regard to the existing conditions causing the instability. Test pits may be excavated to explore the shallow subsurface materials in the area of the instability to help determine the appropriate remedial action to stabilize the subgrade.

If construction will occur during wet times of the year (such as during the spring or fall months) or immediately following extended periods of rain, then seasonal reduction of the near surface soil strength will occur. This may cause additional unstable or pumping subgrade areas for constructability concerns.

The high moisture content clayey and silty materials, present near surface at several of the boring locations, may not pass a proofroll, and may need to be undercut or repaired. Some undercutting or repair of unstable subgrade soils should be anticipated during slab and pavement subgrade preparation. The actual quantity of the subgrade undercut or stabilization should be determined at the time of construction.

Undercut or repair of unstable subgrades to establish a suitable support condition may be needed. The improvement method chosen may be influenced by several factors such as weather and schedule, as well as the area, depth, and nature of the unstable subgrade soils. Depending on the aforementioned and other factors, subgrade repair methods may include:

Scarification and Compaction: Soils can be scarified, moisture conditioned (i.e., dried or wetted) to within a narrow range of the material’s optimum moisture content and compacted. Scarification and compaction is generally most applicable where very shallow unstable conditions are encountered and at times when the soil can be properly dried or wetted to within a narrow range of the materials optimum moisture content.

ECS Project No. 16:13974 Page 10

Undercut and Replacement: We recommend soft or yielding soils be evaluated in approximately 6 to 12-inch intervals to help limit the volume of undercuts. If soft or yielding soils are identified, the contractor should remove only 6 to 12 inches of material at a time in the subject area and then proofroll/evaluate the undercut subgrade to determine if additional undercut is needed. This may take more time but could potentially reduce the removal of more soil than necessary.

5.1.3 Site Temporary Dewatering

Limited Excavation Dewatering: Based upon our subsurface exploration at this site, as well as significant experience on sites in nearby areas of similar geologic setting, we believe construction dewatering at this site will be mainly limited to removing accumulated rainwater or perched water if it becomes an issue. It appears that the permanent static groundwater for this site is well below the planned deepest excavation and deeper than the extents of the present subsurface exploration.

5.2 EARTHWORK OPERATIONS

5.2.2 Engineered fill

Prior to placement of Engineered fill, representative bulk samples (about 50 pounds) of on-site and/or off-site borrow should be submitted to ECS for laboratory testing, which will typically include Atterberg limits, natural moisture content, grain-size distribution, and moisture-density relationships (i.e., Proctors) for compaction. Import materials should be tested prior to being hauled to the site to determine if they meet project specifications. Alternatively, Proctor data from other accredited laboratories can be submitted if the test results are within the last 90 days.

Satisfactory Engineered Fill Materials: Materials satisfactory for use as Engineered fill should consist of inorganic soils with the following engineering properties and compaction requirements.

ENGINEERED FILL INDEX PROPERTIES

Subject Property

Building and Pavement Areas LL < 40, PI<20

Max. Particle Size 3 inches

Max. organic content 5% by dry weight

ENGINEERED FILL COMPACTION REQUIREMENTS

Subject Requirement

Compaction Standard Modified Proctor, ASTM D1557

Required Compaction 95% of Max. Dry Density

Moisture Content ±3 % points of the soil’s optimum value

Loose Thickness 8 inches prior to compaction

On-Site Borrow Suitability: The on-site natural silty clay soils may be feasible to use as engineered fill but should be further evaluated by ECS prior to its use. Existing debris fill soil must not be utilized as engineered fill unless debris can be crushed to acceptable particle sizes in accordance with the parameters included in the Tables above. It is possible that localized sinkholes can develop over the deleterious fill materials due to the large void spaces between debris fragments. The use of a biaxial

ECS Project No. 16:13974 Page 11 geogrid will assist in limiting small detrimental sinkholes. On-site soil used as engineered fill must not contain more than 3 percent organic matter as determined by ASTM D2974, and must be free of frozen matter, deleterious materials, over-sized material (maximum 3-inch particle diameter), or chemicals that may result in the material being classified as “contaminated.” Some conditions at the time of construction, such as wet or freezing weather, may preclude the use of on-site soil, and use of an imported less moisture sensitive or less frost susceptible granular material may be needed. The soils must be compacted within a narrow range of the material’s optimum moisture content. The soil should not be compacted too dry as it may lose its apparent stability if it later becomes wet. Soil chemical modification may be helpful to reduce moisture contents of subgrade soils and fills. The suitability of engineered fill materials is recommended to be checked by ECS prior to placement.

Fill Placement: Fill materials should not be placed on frozen soils, on frost-heaved soils, and/or on excessively wet soils. Borrow fill materials should not contain frozen materials at the time of placement, and all frozen or frost-heaved soils should be removed prior to placement of Engineered fill or other fill soils and aggregates. Excessively wet soils or aggregates should be scarified, aerated, and moisture conditioned.

5.4 UTILITY INSTALLATIONS

Utility Subgrades: The soils encountered in our exploration are expected to be generally suitable for support of utility pipes. The pipe subgrades should be observed and probed for stability by ECS. Any loose or unsuitable materials encountered should be removed and replaced with suitable compacted Engineered fill, or pipe stone bedding material.

Utility Backfilling: The granular bedding material (AASHTO No. 57 stone) should be at least 4 inches thick, but not less than that specified by the civil engineer’s project drawings and specifications. We recommend that the bedding materials be placed up to the spring line of the pipe. Fill placed for support of the utilities, as well as backfill over the utilities, should satisfy the requirements for Engineered fill and Fill Placement.

Excavation Safety: All excavations and slopes should be constructed and maintained in accordance with OSHA excavation safety standards. The contractor is solely responsible for designing, constructing, and maintaining stable temporary excavations and slopes. The contractor’s responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations. ECS is providing this information solely as a service to our client. ECS is not assuming responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred.

ECS Project No. 16:13974 Page 12

6.0 CLOSING

ECS has prepared this report to guide the geotechnical-related design and construction aspects of the project. We performed these services in accordance with the standard of care expected of professionals in the industry performing similar services on projects of like size and complexity at this time in the region.

No other representation expressed or implied, and no warranty or guarantee is included or intended in this report.

The description of the proposed project is based on information provided to ECS by Client. If any of this information is inaccurate or changes, either because of our interpretation of the documents provided or site or design changes that may occur later, ECS should be contacted so we can review our recommendations and provide additional or alternate recommendations that reflect the proposed construction.

We recommend that ECS review the project plans and specifications so we can confirm that those plans/specifications are in accordance with the recommendations of this geotechnical report.

Field observations, and quality assurance testing during earthwork and foundation installation are an extension of, and integral to, the geotechnical design. We recommend that ECS be retained to apply our expertise throughout the geotechnical phases of construction, and to provide consultation and recommendation should issues arise.

ECS is not responsible for the conclusions, opinions, or recommendations of others based on the data in this report.

Site Location Diagram Boring Location Diagram

APPENDIX A - Drawings & Reports

Service Layer Credits: Sources: Esri, HERE, Garmin, USGS, Intermap, INCREMENT P, NRCan, Esri Japan, METI, Esri China

²

DAVID MASON AND ASSOCIATES

PARKING LOT ADDITION

1201 EAGLE STREET, JOLIET, ILLINOIS

SITE LOCATION DIAGRAM

0 1,200600 Feet

9/16/2021

ENGINEER

SCALE

16:13974

PROJECT NO.

SHEET

DATE

BMT

AS NOTED

B-1

B-2

B-3

B-4

B-5

B-6

B-7

B-8

Service Layer Credits: Esri, HERE, Garmin, (c) OpenStreetMap contributors

²

Legend Approximate boring locations

DAVID MASON AND ASSOCIATES

PARKING LOT ADDITION

1201 EAGLE STREET, JOLIET, ILLINOIS

BORING LOCATION DIAGRAM

0 16080 Feet

9/16/2021

ENGINEER

SCALE

16:13974

PROJECT NO.

SHEET

DATE

BMT

AS NOTED

APPENDIX B - Field Operations

Reference Notes for Boring Logs Subsurface Exploration Procedures: SPT Laboratory Testing Procedures: Index Properties Boring Logs

REFERENCE NOTES FOR BORING LOGS

MATERIAL1,2

1Classifications and symbols per ASTM D 2488-17 (Visual-Manual Procedure) unless noted otherwise.

2To be consistent with general practice, “POORLY GRADED” has been removed from GP, GP-GM, GP-GC, SP, SP-SM, SP-SC soil types on the boring logs.

3Non-ASTM designations are included in soil descriptions and symbols along with ASTM symbol [Ex: (SM-FILL)].

4Typically estimated via pocket penetrometer or Torvane shear test and expressed in tons per square foot (tsf).

5Standard Penetration Test (SPT) refers to the number of hammer blows (blow count) of a 140 lb. hammer falling 30 inches on a 2 inch OD split spoon sampler required to drive the sampler 12 inches (ASTM D 1586). “N-value” is another term for “blow count” and is expressed in blows per foot (bpf). SPT correlations per 7.4.2 Method B and need to be corrected if using an auto hammer.

6The water levels are those levels actually measured in the borehole at the times indicated by the symbol. The measurements are relatively reliable when augering, without adding fluids, in granular soils. In clay and cohesive silts, the determination of water levels may require several days for the water level to stabilize. In such cases, additional methods of measurement are generally employed.

7Minor deviation from ASTM D 2488-17 Note 14.

8Percentages are estimated to the nearest 5% per ASTM D 2488-17.

Reference Notes for Boring Logs (1-29-2021).doc © 2021 ECS Corporate Services, LLC. All Rights Reserved

COHESIVE SILTS & CLAYS

UNCONFINED

COMPRESSIVE

STRENGTH, QP4

<0.25

0.25 - <0.50

0.50 - <1.00

1.00 - <2.00

2.00 - <4.00

4.00 - 8.00

>8.00

SPT5

(BPF)

CONSISTENCY7

(COHESIVE)

GRAVELS, SANDS & NON-COHESIVE SILTS

SPT5

DENSITY

<5 5 - 10

11 - 30 31 - 50

>50

Very Loose Loose

Medium Dense Dense

Very Dense

WATER LEVELS6

RELATIVE

AMOUNT7

Trace

With

Adjective (ex: “Silty”)

COARSE

GRAINED

(%)8

<5

FINE

GRAINED

(%)8

<5

DRILLING SAMPLING SYMBOLS & ABBREVIATIONS

PARTICLE SIZE IDENTIFICATION

DESIGNATION PARTICLE SIZES

Hollow Stem Auger Power Auger (no sample) Bulk Sample of Cuttings Wash Sample Shelby Tube Sampler Split Spoon Sampler

Rock Quality Designation % Rock Sample Recovery % Rock Core, NX, BX, AX Rock Bit Drilling Pressuremeter TestSS

ST

WS

BS

PA

HSA

RQD

PM

RD

RC

REC

Boulders Cobbles

Gravel:

Sand:

Silt & Clay (“Fines”) Fine Medium

Coarse Fine Coarse

0.074 mm to 0.425 mm (No. 200 to No. 40 sieve) <0.074 mm (smaller than a No. 200 sieve)

0.425 mm to 2.00 mm (No. 40 to No. 10 sieve)

2.00 mm to 4.75 mm (No. 10 to No. 4 sieve)

4.75 mm to 19 mm (No. 4 sieve to ¾ inch) ¾ inch to 3 inches (19 mm to 75 mm) 3 inches to 12 inches (75 mm to 300 mm) 12 inches (300 mm) or larger

>50 31 - 50 16 - 30

9 - 15 5 - 8 3 - 4 <3

Very Hard Hard

Very Stiff

Stiff Firm Soft

Very Soft

ASPHALT

CONCRETE

GRAVEL

TOPSOIL

VOID

BRICK

AGGREGATE BASE COURSE

GW

GP

GM

GC

SW

SP

SM

SC

ML

MH

CL

CH

OL

OH

PT

WELL-GRADED GRAVEL

gravel-sand mixtures, little or no fines

POORLY-GRADED GRAVEL

gravel-sand mixtures, little or no fines

SILTY GRAVEL

gravel-sand-silt mixtures

CLAYEY GRAVEL

gravel-sand-clay mixtures

WELL-GRADED SAND

gravelly sand, little or no fines

POORLY-GRADED SAND

gravelly sand, little or no fines

SILTY SAND

sand-silt mixtures

CLAYEY SAND

sand-clay mixtures

SILT

non-plastic to medium plasticity

ELASTIC SILT

high plasticity

LEAN CLAY

low to medium plasticity

FAT CLAY

high plasticity

ORGANIC SILT or CLAY non-plastic to low plasticity

ORGANIC SILT or CLAY high plasticity

PEAT

highly organic soils

WL (First Encountered)

WL (Completion)

WL (Seasonal High Water)

WL (Stabilized)

FILL POSSIBLE FILL PROBABLE FILL ROCK

FILL AND ROCK

25 - 45

10 - 20

30 - 45

10 - 25

Standard Penetration Testing, or SPT, is the most frequently used subsurface exploration test performed worldwide. This test provides samples for identification purposes as well as a measure of penetration resistance, or N-Value. The N-Value, or blow counts, when corrected and correlated, can approximate engineering properties of soils used for geotechnical design and engineering purposes.

Involves driving a 2-inch outside diameter hollow tube (split-spoon) into the ground by dropping a 140-lb hammer a height of 30 inches at desired depth

Recording the number of hammer blows required to drive the split-spoon a distance of 12 inches (in 3 or 4 Increments of 6 inches each)

Auger is advanced* and an additional SPT is performed

One SPT test is typically performed every 2½ to 5 feet.

Obtain a 1⅜-inch diameter soil sample

*Drilling Methods May Vary – The predominate drilling methods used for SPT are open hole fluid rotary drilling and hollow-stem auger drilling.

SUBSURFACE EXPLORATION PROCEDURE:

STANDARD PENETRATION TESTING (SPT)

ASTM D 1586

Split-Barrel (Split-Spoon) Sampling

SPT Procedure:

Moisture content determination was performed on select fine-grained soil samples in accordance with ASTM D 2216.

Calibrated hand penetrometer tests (Qp) were performed on select cohesive soil samples. In the hand penetrometer test, the unconfined compressive strength of a soil sample is estimated, to a maximum of 4.5 or 6 tons per square foot (tsf), depending on the penetrometer model, by measuring the resistance of a soil sample to penetration by a small, calibrated, spring-loaded cylinder.

Atterberg limits determination was performed on select fine-grained soil samples in accordance with ASTM D 4319. The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its liquid limit, plastic limit, and shrinkage limit. Depending on its water content, a soil may appear in one of four states: solid, semi-solid, plastic and liquid. In each state, the consistency and behavior of a soil is different and consequently so are its engineering properties.

Atterberg limits can also be used to help distinguish between silt and clay, and to distinguish between different types of silts and clays.

Particle size distribution, also referred to as gradation or sieve analysis, refers to the proportions by dry mass of a soil particles distributed over specified particle-size ranges. The particle size distribution is used to help classify soils for engineering purposes. Particle size distribution determination was performed on select fine-grained soil samples in accordance with ASTM D 421, D 422 and/or D 1140.

A loss on ignition (LOI) test is used to estimate the organic content of the soil. In the LOI test a dry sample is heated to 440o C to burn off organic matter within the sample. The lost weight is compared to the initial dry weight to estimate the percentage of organics in the material. LOI determination was performed in accordance with ASTM D 2974.

LABORATORY PROCEDURES:

Index Testing https://en.wikipedia.org/wiki/Soil https://en.wikipedia.org/wiki/Water_content https://en.wikipedia.org/wiki/Silt https://en.wikipedia.org/wiki/Clay

DE

PT

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [7"] (+/-) (CL/ML) SILTY CLAY, trace sand, trace gravel, brown, moist, very hard to hard

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

3-4-7 (11)

4-7-11 (18)

4-7-11 (18)

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

9.00

8.00

6.00

17.0

16.2

19.4

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-1

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780768.7

EASTING:

2875283.8

STATION: SURFACE ELEVATION:

594.9

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

CALIBRATED PENETROMETER TON/SF

[FINES CONTENT] %

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [6"] (+/-)

(SP/GP FILL) FILL, SAND WITH GRAVEL/

GRAVEL WITH SAND, contains brick, brown, moist, medium dense (CL/ML) SILTY CLAY, trace gravel, grayish brown, moist, hard (CL/ML) SILTY CLAY, trace gravel, trace sand, brown, moist, hard

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

11-10-7 (17)

5-8-11 (19)

4-6-8 (14)

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

6.00

7.00

6.00

15.5

21.1

14.0

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-2

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780653.5

EASTING:

2875286.1

STATION: SURFACE ELEVATION:

596.9

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [12"] (+/-)

(SP/GP FILL) FILL, SAND WITH GRAVEL/

GRAVEL WITH SAND, contains concrete, dark brown and gray and black, moist, medium dense

(CL/ML) SILTY CLAY, trace sand, trace gravel, brown, moist, hard

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

11-13-15 (28)

7-8-9 (17)

11-11-11 (22)

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

7.00

2215.1

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-3

DRILLER/CONTRACTOR:

Groundbreaking Explora on

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780776.0

EASTING:

2875375.1

STATION: SURFACE ELEVATION:

592.2

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [3"] (+/-)

(SM/GM FILL) FILL, SILTY SAND WITH

GRAVEL/GRAVEL WITH SAND, contains brick, brown, moist, dense

(SP/GP FILL) FILL, SAND WITH GRAVEL/

GRAVEL WITH SAND, contains wood brick and concrete, brown, moist, very dense to dense

Refusal encountered at 6.9 feet.

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

13-19-22 (41)

22-31-24 (55)

38-50/5" (50/5")

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

50/5"

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-4

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780667.6

EASTING:

2875383.5

STATION: SURFACE ELEVATION:

593.9

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1 S-2

SA

M

PL

E

TY

PE

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [3"] (+/-)

(SP/GP FILL) FILL, SAND WITH GRAVEL/

GRAVEL WITH SAND, contains brick and metal, brown, moist, very dense Apparent obstruc on; possible buried slab

Refusal encountered at 2.5 feet.

END OF DRILLING AT 2.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

30-46-50/3" (96/9") 15/0"

(15/0")

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

96/9"

15/0"

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-5

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780787.7

EASTING:

2875478.4

STATION: SURFACE ELEVATION:

588.6

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [9"] (+/-)

(SM/GM FILL) FILL, SILTY SAND WITH

GRAVEL/GRAVEL WITH SAND, contains brick, brown, moist, very dense

(CL/ML) SILTY CLAY, trace gravel, trace sand, brown, moist, hard

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

14-16-36 (52)

26-10-20 (30)

15-10-12 (22)

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

4.00

2217.3

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-6

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780683.2

EASTING:

2875484.5

STATION: SURFACE ELEVATION:

596.3

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

SA

M

PL

E

TY

PE

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [3"] (+/-) (CL/ML FILL) FILL, SILTY CLAY, trace gravel, trace sand, brown, moist (SC FILL) FILL, CLAYEY SAND, trace gravel, contains brick, brown, moist, medium dense Apparent obstruc on; possible buried slab

Refusal encountered at 3.1 feet.

END OF DRILLING AT 3.1 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

40/1" (40/1")

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

40/1"

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-7

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

19495028.6

EASTING:

2296583.3

STATION: SURFACE ELEVATION:

588.6

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

H (F

T)

SA

M

PL

E

N U

M

BE

R

S-1

S-2

S-3

SA

M

PL

E

TY

PE

SS

SS

SS

SA

M

PL

E

DI

ST

IN

RE

CO

VE

RY

(I N

DESCRIPTION OF MATERIAL

Topsoil [9"] (+/-)

(SM/GM FILL) FILL, SILTY SAND WITH

GRAVEL/GRAVEL WITH SAND, contains brick, brown, moist, dense

(GP POSSIBLE FILL) POSSIBLE FILL,

GRAVEL, gray, moist, loose

END OF DRILLING AT 7.5 FT

W

AT

ER

L

EV

EL

S

EL

EV

AT

IO

N (F

T)

BL

O

W S/

6"

39-50

5-5-5 (10)

6-5-5 (10)

Plas c Limit Water Content Liquid Limit X─────────⚫─────────△

CLIENT:

David Mason and Associates

PROJECT NAME:

Parking Lot Addi on

PROJECT NO.: BORING NO.:

16:13974 B-8

DRILLER/CONTRACTOR:

SHEET:

SITE LOCATION:

1201 Eagle Street, Joliet, Illinois 60432

LOSS OF CIRCULATION

NORTHING:

1780659.9

EASTING:

2875559.3

STATION: SURFACE ELEVATION:

598.7

BOTTOM OF CASING

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL

WL (First Encountered)

WL (Comple on)

WL (Seasonal High Water)

WL (Stabilized)

Dry

Dry

BORING STARTED:

BORING

COMPLETED:

EQUIPMENT:

ATV

Aug 26 2021

Aug 26 2021

LOGGED BY:

BM08

CAVE IN DEPTH:

HAMMER TYPE:

DRILLING METHOD:

Auto

HSA

GEOTECHNICAL BOREHOLE LOG

STANDARD PENETRATION BLOWS/FT

ROCK QUALITY DESIGNATION & RECOVERY

RQD

REC

APPENDIX C - Supplemental Report Documents

Important Information about This Geotechnical-Engineering Report

Geotechnical-Engineering Report Important Information about This

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

While you cannot eliminate all such risks, you can manage them. The following information is provided to help.

The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer.

Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.

The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations.

Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.

Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client.

Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical-engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project.

Do not rely on this report if your geotechnical engineer prepared it:

• for a different client;

• for a different project or purpose;

• for a different site (that may or may not include all or a portion of the original site); or

• before important events occurred at the site or adjacent to it;

e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations.

Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems.

Read this Report in Full Costly problems have occurred…