W912QR25BA017_GEOTech_FIO-0002.pdf

Solicitation For Indoor Small Arms Range, Rickenbacker, OH

P2: 508679

Design-Bid-Build

GEOTECHNICAL Report (For Information Only) Certified Final Design

03 September 2025

W912QR25BA017-0002

RRS-A: 200A Disposition: Maintain for 15 yrs after construction.

W912QR25BA017_GEOTech_FIO-0002

REPORT OF GEOTECHNICAL EXPLORATION

RICKENBACKER ANGB

SMALL ARMS RANGE FACILITY

LOCKBOURNE, OH

Table of Contents .S::,.C:) � �o

1 GENERAL SITE DESCRIPTION .............................................................. i;;--...._,, ...... ;;s'?f- 2 GENERAL SITE GEOLOGY ................................................................ 0 . ..... ti):.( .1

3 SCOPE OF WORK PERFORMED

y

4 RESULTS OF THE EXPLORATION

" qj. 4.1 GENERAL •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

······················ 2

4.2 SUBSURFACE SOil CONOITIONS

� .... ,;..._.;$;5

4.3 BEDROCK CONDITIONS ••••••••••••••••••••••••••••••••••••• 0······,0C;:j_································· 4

4.4 GROUNDWATER CONDITIONS .................. � .. -

4.5 SEISMIC CONDITIONS ••••••••••••••••••••••• �···�··i

·o·················································· 5

5 ANALYSES AND RECOMMENDAT � ....... (2;

5.1 GENERALSITEWORK ••••••••• 0···········�····························································· 5

5.1.1 Topsoil Stripping(.{J,vemer.($'emoval

5.1.2 Subgrade Eva� ionf_f[!J'1itioning

5.1.3 Constructio�"'!iebrih'\"'!\

5.1.4 On-Site€ps ·····'<('l'\V

5.1.5 Ge�/ Fill RG'i'rements

5.1.6 ,Ji�lace'E!t

5.1.7 �-oilMoqment 5.1.p,� -Si�e z�1.1'ractices

�'9.J E�vation Safety

<f5:, ST�RE FOUNDATIONS

5.i.o' Aggregate Stone c�lumn Rec�mm�ndati�ns

�'2 Recommended Minimum Footing Dimensions

�fli:2.3 Footing Trenches

5.2.4 Grade Supported Floor Slab Recommendations

V O 5.2.5 Below Grade Walls

5.2.6 Potential Foundation Movement

5.3 PAVEMENT CONSIDERATIONS

5.3.1 Rigid Pavement

FIELD TESTING PROCEDURES

The general field procedures employed by the Field Services Center are summarized in the following outline. The procedures utilized by the AEI Field Service Center are recognized methods for determining soil and rock distribution and ground water conditions. These methods include geophysical and in situ methods as well as borings.

Soil Borings are drilled to obtain subsurface samples using one of several alternate techniques depending upon the surface conditions. Borings are advanced into the ground using continuous flight augers. At prescribed intervals throughout the boring depths, soil samples are obtained with a split-spoon or thin-walled sampler and sealed in airtight glass jars and labeled. The sampler is first seated 6 inches to penetrate loose cuttings and then driven an additional foot, where possible, with blows from a 140 pound hammer falling 30 inches. The number of blows required to drive the sampler each six-inch increment is recorded. The penetration resistance, or “N-value” is designated as the number of hammer blows required to drive the sampler the final foot and, when properly evaluated, is an index to cohesion for clays and relative density for sands. The split spoon sampling procedures used during the exploration are in general accordance with ASTM D 1586. Split spoon samples are considered to provide disturbed samples, yet are appropriate for most engineering applications.

Thin-walled (Shelby tube) samples are considered to provide undisturbed samples and obtained when warranted in general accordance with ASTM D 1587.

These drilling methods are not capable of penetrating through material designated as “refusal materials.” Refusal, thus indicated, may result from hard cemented soil, soft weathered rock, coarse gravel or boulders, thin rock seams, or the upper surface of sound continuous rock. Core drilling procedures are required to determine the character and continuity of refusal materials.

Core Drilling Procedures for use on refusal materials. Prior to coring, casing is set in the boring through the overburden soils. Refusal materials are then cored according to ASTM D-2113 using a diamond bit attached to the end of a hollow double tube core barrel. This device is rotated at high speeds and the cuttings are brought to the surface by circulating water. Samples of the material penetrated are protected and retained in the inner tube, which is retrieved at the end of each drill run.

Upon retrieval of the inner tube the core is recovered, measured and placed in boxes for storage.

The subsurface conditions encountered during drilling are reported on a field test boring record by the driller. The record contains information concerning the boring method, samples attempted and recovered, indications of the presence of various materials such as coarse gravel, cobbles, etc., and observations between samples. Therefore, these boring records contain both factual and interpretive information. The field boring records are on file in our office.

The soil and rock samples plus the field boring records are reviewed by a geotechnical engineer. The engineer classifies the soil in general accordance with the procedures outlined in ASTM D 2487 and D 2488 and prepares the final boring records which are the basis for all evaluations and recommendations.

Representative portions of soil samples are placed in sealed containers and transported to the laboratory. In the laboratory, the samples are examined to verify the driller’s field classifications.

Test Boring Records are attached which show the soil descriptions and penetration resistances.

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The final boring records represent our interpretation of the contents of the field records based on the results of the engineering examinations and tests of the field samples. These records depict subsurface conditions at the specific locations and at the particular time when drilled. Soil conditions at other locations may differ from conditions occurring at these boring locations. Also, the passage of time may result in a change in the subsurface soil and ground water conditions at these boring locations. The lines designate the interface between soil or refusal materials on the records and on profiles represent approximate boundaries. The transition between materials may be gradual. The final boring records are included with this report.

Water table readings are normally taken in conjunction with borings and are recorded on the “Boring Logs”. These readings indicate the approximate location of the hydrostatic water table at the time of our field investigation. Where impervious soils are encountered (clayey soils) the amount of water seepage into the boring is small, and it is generally not possible to establish the location of hydrostatic water table through water level readings. The ground water table may also be dependent upon the amount of precipitation at the site during a particular period of time. Fluctuations in the water table should be expected with variations in precipitation, surface run-off, evaporation and other factors.

The time of boring water level reported on the boring records is determined by field crews as the drilling tools are advanced. The boring water level is detected by changes in the drilling rate, soil samples obtained, etc. Additional water table readings are generally obtained at least 24 hours after the borings are completed. The time lag of at least 24 hours is used to permit stabilization of the ground water table which has been disrupted by the drilling operations. The readings are taken by dropping a weighted line down the boring or using as electrical probe to detect the water level surface.

Occasionally the borings will cave-in, preventing water level readings from being obtained or trapping drilling water above the caved-in zone. The cave-in depth is also measured and recorded on the boring records.

Sampling Terminology

Undisturbed Sampling: Thin-walled or Shelby tube samples used for visual examination, classification tests and quantitative laboratory testing. This procedure is described by ASTM D 1587. Each tube, together with the encased soil, is carefully removed from the ground, made airtight and transported to the laboratory. Locations and depths of undisturbed samples are shown on the “Boring Logs.”

Bag Sampling: Bulk samples of soil are obtained at selected locations. These samples consist of soil brought to the surface by the drilling augers, or obtained from test pits or the ground surface using hand tools. Samples are placed in bags, with sealed jar samples of the material, and taken to our laboratory for testing where more mass material is required (i.e. Proctors and CBR’s). The locations of these samples are indicated on the appropriate logs, or on the Boring Location Plan.

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T:\10 PROJECTS\210-000 Folder Template\Geotech\REPORTS\Class System.doc

CLASSIFICATION SYSTEM FOR SOIL EXPLORATION

COHESIVE SOILS

(Clay, Silt, and Mixtures)

CONSISTENCY SPT N-VALUE Qu/Qp (tsf) PLASTICITY

Very Soft 2 blows/ft or less 0 – 0.25 Degree of Plasticity Soft 2 to 4 blows/ft 0.25 – 0.49 Plasticity Index (PI) Medium Stiff 4 to 8 blows/ft 0.50 – 0.99 Low 0 – 7 Stiff 8 to 15 blows/ft 1.00 – 2.00 Medium 8 – 22 Very Stiff 15 to 30 blows/ft 2.00 – 4.00 High over 22 Hard 30 blows/ft or more > 4.00

NON-COHESIVE SOILS

(Silt, Sand, Gravel, and Mixtures)

DENSITY SPT N-VALUE PARTICLE SIZE IDENTIFICATION

Very Loose 4 blows/ft or less Boulders 12 inch diameter or more Loose 4 to 10 blows/ft Cobbles 3 to 12 inch diameter Medium Dense 10 to 30 blows/ft Gravel Coarse – 1 to 3 inch Dense 30 to 50 blows/ft Medium – ½ to 1 inch Very Dense 50 blows/ft or more Fine – ¼ to ½ inch Sand Coarse – 0.6mm to ¼ inch

RELATIVE PROPORTIONS Medium – 0.2mm to 0.6mm Descriptive Term Percent Trace 1 – 10 Fine – 0.05mm to 0.2mm Trace to Some 11 – 20 Some 21 – 35 Silt 0.05mm to 0.005mm And 36 – 50 Clay 0.005mm

NOTES

Classification – The Unified Soil Classification System is used to identify soil unless otherwise noted.

Standard “N” Penetration Test (SPT) (ASTM D1586) – Driving a 2-inch O.D., 1 3/8-inch I.D. sampler a distance of 1 foot into undisturbed soil with a 140-pound hammer free falling a distance of 30 inches. It is customary to drive the spoon 6-inches to seat the sampler into undisturbed soil, and then perform the test. The number of hammer blows for seating the spoon and making the tests are recorded for each 6 inches of penetration on the field drill long (e.g., 10/8/7). On the report log, the Standard Penetration Test result (i.e., the N value) is normally presented and consists of the sum of the 2nd and 3rd penetration counts (i.e., N = 8 + 7 = 15 blows/ft.)

Soil Property Symbols

Qu: Unconfined Compressive Strength N: Standard Penetration Value (see above) Qp: Unconfined Comp. Strength (pocket pent.) omc: Optimum Moisture content LL: Liquid Limit, % (Atterberg Limit) PL: Plastic Limit, % (Atterberg Limit) PI: Plasticity Index mdd: Maximum Dry Density

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Unconfined Compression Test

ASTM D2166

Project Number:

Project:

Sampling Date:

Sample Number:

Client Name:

Remarks:

Rickenbacker ANGB - Small Arms Range Facility 223-064

3/22/2023

ST#1

Benham-Mead & Hunt

6.0 ft - 8.0 ftSample Depth:

Lockbourne, OhioLocation:

Boring Number: B-1

Received Date 3/23/2023

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Before Test

Strain Rate (in/min)

Test Data

Undrained Shear Strength (psf) Unconfined Compressive Strength (psf)

Height (in) Diameter (in)

Void Ratio:

Saturation (%):

Dry Density (pcf)

Moisture Content (%):

Specimen Number 87654321

Strain at Failure (%):

23.6

104.0 101.4 0.633

2.8100 5.7390

1886.06 943.03

0.0978

14.81

Benham-Mead & Hunt

ST#1

3/22/2023 223-064 Rickenbacker ANGB - Small Arms Range Facility

Remarks:

Client Name:

Sample Number:

Sampling Date:

Project:

Project Number:

Liquid Limit: 3517Plastic Limit:2.7Specific Gravity:

UDType:

2.04Height To Diameter Ratio:

Soil Classification: CL

Location: Lockbourne, Ohio

Sample Depth: 6.0 ft - 8.0 ft

Specimen 1 Failure Sketch

Specimen 2 Failure Sketch

Specimen 3 Failure Sketch

Specimen 4 Failure Sketch

Specimen 5 Failure Sketch

Specimen 6 Failure Sketch

Specimen 7 Failure Sketch

Specimen 8 Failure Sketch

128.5Wet Density (pcf)

0.9Strain Limit @ 15% (in)

1.70Strain Rate (%/min):

0Failure Angle (°):

2 3 4 5 6 7 8

Boring Number: B-1

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Project Number:

Project:

Sampling Date:

Sample Number:

Client Name:

Remarks:

Rickenbacker ANGB - Small Arms Range Facility 223-064

3/22/2023

ST#1

Benham-Mead & Hunt

6.0 ft - 8.0 ftSample Depth:

Lockbourne, OhioLocation:

Boring Number: B-2

Received Date 3/23/2023

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Before Test

Strain Rate (in/min)

Test Data

Undrained Shear Strength (psf) Unconfined Compressive Strength (psf)

Height (in) Diameter (in)

Void Ratio:

Saturation (%):

Dry Density (pcf)

Moisture Content (%):

Specimen Number 87654321

Strain at Failure (%):

21.0

106.8 97.1 0.590

2.8700 5.7220

3510.89 1755.45

0.097

10.49

Benham-Mead & Hunt

ST#1

3/22/2023 223-064 Rickenbacker ANGB - Small Arms Range Facility

Remarks:

Client Name:

Sample Number:

Sampling Date:

Project:

Project Number:

Liquid Limit: 3624Plastic Limit:2.7Specific Gravity:

UDType:

1.99Height To Diameter Ratio:

Soil Classification: CL

Location: Lockbourne, Ohio

Sample Depth: 6.0 ft - 8.0 ft

Specimen 1 Failure Sketch

Specimen 2 Failure Sketch

Specimen 3 Failure Sketch

Specimen 4 Failure Sketch

Specimen 5 Failure Sketch

Specimen 6 Failure Sketch

Specimen 7 Failure Sketch

Specimen 8 Failure Sketch

129.3Wet Density (pcf)

0.9Strain Limit @ 15% (in)

1.70Strain Rate (%/min):

0Failure Angle (°):

2 3 4 5 6 7 8

Boring Number: B-2

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Project Number:

Project:

Sampling Date:

Sample Number:

Client Name:

Remarks:

Rickenbacker ANGB - Small Arms Range Facility 223-064

3/22/2023

ST#1

Benham-Mead & Hunt

8.0 ft - 10.0 ftSample Depth:

Lockbourne, OhioLocation:

Boring Number: B-3

Received Date 3/23/2023

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Before Test

Strain Rate (in/min)

Test Data

Undrained Shear Strength (psf) Unconfined Compressive Strength (psf)

Height (in) Diameter (in)

Void Ratio:

Saturation (%):

Dry Density (pcf)

Moisture Content (%):

Specimen Number 87654321

Strain at Failure (%):

19.7

113.3 107.4 0.498

2.8270 5.5950

549.45 274.73

0.095

5.82

Benham-Mead & Hunt

ST#1

3/22/2023 223-064 Rickenbacker ANGB - Small Arms Range Facility

Remarks:

Client Name:

Sample Number:

Sampling Date:

Project:

Project Number:

Liquid Limit: 2115Plastic Limit:2.7Specific Gravity:

UDType:

1.98Height To Diameter Ratio:

Soil Classification: CL-ML

Location: Lockbourne, Ohio

Sample Depth: 8.0 ft - 10.0 ft

Specimen 1 Failure Sketch

Specimen 2 Failure Sketch

Specimen 3 Failure Sketch

Specimen 4 Failure Sketch

Specimen 5 Failure Sketch

Specimen 6 Failure Sketch

Specimen 7 Failure Sketch

Specimen 8 Failure Sketch

135.6Wet Density (pcf)

0.8Strain Limit @ 15% (in)

1.70Strain Rate (%/min):

0Failure Angle (°):

2 3 4 5 6 7 8

Boring Number: B-3

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CBR Test Results

ASTM (D1883) / AASHTO (T193)

Location: Lockbourne, Ohio Sample Depth: 1.0 ft - 4.0 ft

P-4 Benham-Mead & Hunt

BULK#1

223-064 Rickenbacker ANGB - Small Arms Range Facility

Remarks:

Client Name:

Sample Number:

Sampling Date:

Project:

Project Number:

CBR Results Results 1 2 3 4 5 6 7 8

CBR @ 0.10 (in) CBR @ 0.20 (in)

10.7 14.6 6.0

Project Information

10.3 14.1

6.1

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CBR Test

ASTM (D1883) / AASHTO (T193)

1 2 3 4 5 6 7 8 Specimen NumberBefore Soaking

Surcharge Weight (lb) Number of Blows Maximum Dry Density (pcf) Optimum Moisture Content (%) Mold ID Mold Diameter (in) Mold Weight (lb) Sample Height (in) Mold Volume (in³) Moisture Content (%) Weight of Mold + Soil (lb) Weight of Soil (g) Dry Density (pcf) Wet Density (pcf)

87654321After Soaking Soaked Sample Height (in) Soaked Time (Hr) Swell (%) Moisture Content (%) Weight of Mold + Soil (lb) Weight After Soaking (g) Dry Density (pcf) Wet Density (pcf)

12.35

119.4

3D 6.000 17.69 4.584 129.61 13.0 26.81

107.6 121.6

4.604 96.000 0.4 15.7 27.20 4315.5 118.9 137.5

13.0

4136.8

2.72Specific Gravity 29Liquid Limit 9Plastic Limit

2.72 2.72 29 29 9 9

12.56 12.63 56 81

119.4 119.4

13.0 13.0 3C 4C

6.000 6.000

17.51 17.64

4.584 4.584

129.61 129 61

13.0 13.0

26.99 27.35

4298.2 4405 3

111.8 114.6

126.3 129.5

4 606 4.595

96.000 96.000

0.5 0.2

13.8 13.1

27.24 27.53

4411.6 4486.9

118.8 119.1

135.2 134.7

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Pavement Design Report U.S. Army Corps of Engineers

PCASE Version 2.09.08 Date : 4/18/2023

Design Name : FLEXIBLE Design Type : Roads

Pavement Type : Flexible Road Type : Parking Area

Terrain Type : Flat Analysis Type : CBR

Depth of Frost (in) : 19 Wander Width (in) : 33.35

Layer Information

Layer Type Material Type Frost Code Moisture Content

Dry Unit Weight (lb/ft^3)

Analysis (lb/ft^3)

Non frost Design

Thickness (in)

Reduced Subgrade Strength

(in)

Limited Subgrade

Penetration (in)

CBR

Strength

AC AC NFS 0 145 Compute 2 2 2 0 BASE UCS NFS 5 135 Compute 4.92 5.67 1 .31 100 SUBG COHCUT F3/F4 18 100 Manual 0 0 0 5

Traffic Information Pattern Name PARKING LOT

Vehicles Weight (lb) Passes per Life

Span" Equivalent

Passes

CAR - PASSENGER 3000 500000 1

TRUCK, 3 AXLE 35000 1300 1300

TRUCK, 3 AXLE 35000 1301

Estimated AASHTO Equivalent Single Axle Loads 34675

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Pavement Thickness Report U.S. Army Corps of Engineers

PCASE Version 2.09.08 Date : 4/18/2023Design Name : RIGID

Design Type : Roads Pavement Type : Rigid

Road Type : Parking Area Terrain Type : Flat

Analysis Type : K Depth of Frost (in) : 18 Wander Width (in) : 33.35

% Load Transfer : 25 Effective K (pci) : 128

Reduced Sub Effective K (pci) : 25 Joint Spacing : 10 to 15 ft

Dowel Spacing : 12.00 in Dowel Length : 16.00 in

Dowel Diameter: .75 in

Layer Information

Layer Type Material Type Frost Code Moisture Content

Dry Unit Weight (lb/ft^3)

Flexural Strength (lb/ft^3) CbCr (psi) %

Steel Analysis

Non frost Design

Thickness (in)

Reduced Subgrade Strength

(in)

Limited Subgrade Penetratio

(in)

K Strength

(pci)

PCC NA NFS 0 145 600 0 0 Compute 6 6 6 0 BASE UCS NFS 5 135 0 0 0 Manual 4 4 7.98 0 SUBG COHCUT F3/F4 18 100 0 0 0 Manual 0 0 0 100

Traffic Information Pattern Name PARKING LOT

Vehicles Weight (lb) Passes per Life

Span" Equivale nt

CAR - PASSENGER 3000 500000 1

TRUCK, 3 AXLE 35000 1300 1300

TRUCK, 3 AXLE 35000 1301

Estimated AASHTO Equivalent Single Axle Loads 147059

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SS : 0.117

S1 : 0.06

Fa : 1.6

Fv : 2.4

SMS : 0.187

SM1 : 0.145

SDS : 0.125

SD1 : 0.096

TL : 12

PGA : 0.058

PGA M : 0.093

FPGA : 1.6

Ie : 1

Cv : 0.7

Seismic Design Category:

D - Stiff Soil

B Design Response Spectrum

S (g) vs T(s)a

MCE Response SpectrumR

S (g) vs T(s)a

Design Vertical Response Spectrum

S (g) vs T(s)a

MCE Vertical Response SpectrumR

S (g) vs T(s)a

Seismic

Site Soil Class:

Results:

Data Accessed: Tue Apr 04 2023

Date Source:

USGS Seismic Design Maps based on ASCE/SEI 7-16 and ASCE/SEI 7-16 Table 1.5-2. Additional data for site-specific ground motion procedures in accordance with ASCE/SEI 7-16 Ch. 21 are available from USGS.

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The ASCE 7 Hazard Tool is provided for your convenience, for informational purposes only, and is provided “as is” and without warranties of any kind. The location data included herein has been obtained from information developed, produced, and maintained by third party providers;

or has been extrapolated from maps incorporated in the ASCE 7 standard. While ASCE has made every effort to use data obtained from reliable sources or methodologies, ASCE does not make any representations or warranties as to the accuracy, completeness, reliability, currency, or quality of any data provided herein. Any third-party links provided by this Tool should not be construed as an endorsement, affiliation, relationship, or sponsorship of such third-party content by or from ASCE.

ASCE does not intend, nor should anyone interpret, the results provided by this Tool to replace the sound judgment of a competent professional, having knowledge and experience in the appropriate field(s) of practice, nor to substitute for the standard of care required of such professionals in interpreting and applying the contents of this Tool or the ASCE 7 standard.

In using this Tool, you expressly assume all risks associated with your use. Under no circumstances shall ASCE or its officers, directors, employees, members, affiliates, or agents be liable to you or any other person for any direct, indirect, special, incidental or consequential damages arising from or related to your use of, or reliance on, the Tool or any information obtained therein. To the fullest extent permitted by law, you agree to release and hold harmless ASCE from any and all liability of any nature arising out of or result ng from any use of data provided by the ASCE 7 Hazard Tool.

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TABLE 4

Guide for Consistency of Fine-Grained Soils

+)))))))))))))))))0))))))))))))))))))))))))))))))))0)))))))))))))))))))),

* * * Estimated Range of *

* * * Unconfined *

* * * Compressive * *SPT Penetration * * Strength *

* (blows/foot) * Estimated Consistency * tons/sq. ft. * /)))))))))))))))))3))))))))))))))))))))))))))))))))3))))))))))))))))))))1

* <2 * Very soft * <0.25 *

* * (extruded between fingers * *

* * when squeezed) * *

* 2 - 4 * Soft * 0.25 - 0.50 *

* * (molded by light finger * *

* * pressure) * *

* 4 - 8 * Medium * 0.50 - 1.00 *

* * (molded by strong finger * *

* * pressure) * *

* 8 - 15 * Stiff * 1.00 - 2.00 *

* * (readily indented by * *

* * thumb but penetrated with * *

* * great effort) * *

* 15 - 30 * Very stiff * 2.00 - 4.00 *

* * (readily indented by * *

* * thumbnail) * *

* >30 * Hard * >4.00 *

* * (indented with difficulty * *

* * by thumbnail) * * .)))))))))))))))))2))))))))))))))))))))))))))))))))2))))))))))))))))))))-

7.1-17

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Your Geotechnical Engineering Report

To help manage your risks, this information is being provided because subsurface issues are a major cause of construction delays, cost overruns, disputes, and claims.

Geotechnical Services are Performed for Specific Projects, Purposes, and People

Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering exploration conducted for an engineer may not fulfill the needs of a contractor or even another engineer. Each geotechnical engineering exploration and report is unique and is prepared solely for the client. No one except the client should rely on the geotechnical engineering report without first consulting with the geotechnical engineer who prepared it. The report should not be applied for any project or purpose except the one originally intended.

Read the Entire Report

To avoid serious problems, the full geotechnical engineering report should be read in its entirety. Do not only read selected sections or the executive summary.

A Unique Set of Project-Specific Factors is the Basis for a Geotechnical Engineering Report

Geotechnical engineers consider a numerous unique, project-specific factors when determining the scope of a study. Typical factors include: the client’s goals, objectives, project costs, risk management preferences, proposed structures, structures on site, topography, and other proposed or existing site improvements, such as access roads, parking lots, and utilities Unless indicated otherwise by the geotechnical engineer who conducted the original exploration, a geotechnical engineering report should not be relied upon if it was:

• not prepared for you or your project,

• not prepared for the specific site explored, or

• completed before important changes to the project were implemented.

Typical changes that can lessen the reliability of an existing geotechnical engineering report include those that affect:

• the function of the proposed structure, as when it’s changed from a multi-story hotel to a parking lot

• finished floor elevation, location, orientation, or weight of the proposed structure, anticipated loads or

• project ownership

Geotechnical engineers cannot be held liable or responsible for issues that occur because their report did not take into account development items of which they were not informed. The geotechnical engineer should always be notified of any project changes. Upon notification, it should be requested of the geotechnical engineer to give an assessment of the impact of the project changes.

Subsurface Conditions Can Change

A geotechnical engineering report is based on conditions that exist at the time of the exploration. A geotechnical engineering report should not be relied upon if its reliability could be in question due to factors such as man-made events as construction on or adjacent to the site, natural events such as floods, earthquakes, or groundwater fluctuation, or time. To determine if a geotechnical report is still reliable, contact the geotechnical engineer. Major problems could be avoided by performing a minimal amount of additional analysis and/or testing.

Most Geotechnical Findings are Professional Opinions

Geotechnical site explorations identify subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engineers review field logs and laboratory data and apply their professional judgment to make conclusions about the subsurface conditions throughout the site. Actual subsurface conditions may differ from those indicated in the report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risk associated with unanticipated conditions.

The Recommendations within a Report Are Not Final

Do not put too much faith on the construction recommendations included in the report. The recommendations are not final due to geotechnical engineers developing them principally from judgment and opinion. Only by observing actual subsurface conditions revealed during construction can geotechnical engineers finalize their recommendations. Responsibility and liability cannot be assumed for the recommendations

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A Geotechnical Engineering Report Is Subject To Misinterpretation

Misinterpretation of geotechnical engineering reports has resulted in costly problems. The risk of misinterpretation can be lowered after the submittal of the final report by having the geotechnical engineer consult with appropriate members of the design team. The geotechnical engineer could also be retained to review crucial parts of the plans and specifications put together by the design team. The geotechnical engineering report can also be misinterpreted by contractors which can result in many problems. By participating in pre-bid and preconstruction meetings and providing construction observations by the geotechnical engineer, many risks can be reduced.

Final Boring Logs Should not be Re-drawn

Geotechnical engineers prepare final boring logs and testing results based on field logs and laboratory data.

The logs included in a final geotechnical engineering report should never be redrawn to be included in architectural or design drawings due to errors that could be made. Electronic reproduction is acceptable, along with photographic reproduction, but it should be understood that separating logs from the report can elevate risk.

Contractors Need a Complete Report and Guidance

By limiting what is provided for bid preparation, contractors are not liable for unforeseen subsurface conditions although some owners and design professionals believe the opposite to be true. The complete geotechnical engineering report, accompanied with a cover letter or transmittal, should be provided to contractors to help prevent costly problems. The letter states that the report was not prepared for purposes of bid development and the report’s accuracy is limited.

Although a fee may be required, encourage the contractors to consult with the geotechnical engineer who prepared the report and/or to conduct additional studies to obtain the specific types of information they need or prefer. A prebid conference involving the owner, geotechnical engineer, and contractors can prove to be very valuable. If needed, allow contractors sufficient time to perform additional studies. Upon doing this you might be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions.

Closely Read Responsibility Provisions

Geotechnical engineering is not as exact as other engineering disciplines. This lack of understanding by clients, design professionals, and contractors has created unrealistic expectations that have led to disappointments, claims, and disputes. To minimize such risks, a variety of explanatory provisions may be included in the report by the geotechnical engineer To help others recognize their own responsibilities and risks, many of these provisions indicate where the geotechnical engineer’s responsibilities begin and end. These provisions should be read carefully, questions asked if needed, and the geotechnical engineer should provide satisfactory responses.

Environmental Issues/Concerns are not Covered

Unforeseen environmental issues can lead to project delays or even failures. Geotechnical engineering reports do not usually include environmental findings, conclusions, or recommendations. As with a geotechnical engineering report, do not rely on an environmental report that was prepared for someone else.

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