Geotech_Reoport_November_2024_4588.x_WS_City_Hall_Outdoor_Plaza_RCP.pdf

Prepared for:

255 Miller Avenue Mil l Va l ley, CA 94941

Prepared by :

11521 Blocker Drive, Suite 110 Auburn, CA 83854

(530) 887-1494

GEOTECHNICAL REPORT

City of West Sacramento

City Hall Outdoor Plaza

West Sacramento, CA

November 2024

Auburn Office:

11521 Blocker Drive, Ste 110 Auburn, CA 95603 Fresno (559) 438-8411

(530) 887-1494 West Sacramento (916) 375-8706

Blackburn File No. 4558.x November 18, 2024

Kendra Manning RHAA Landscape Architecture & Planning 225 Miller Avenue Mill Valley, CA 94941

Subject: Geotechnical Report City of West Sacramento – City Hall Outdoor Plaza West Sacramento, California

Dear Kendra, Blackburn Consulting (Blackburn) is pleased to submit this Geotechnical Report for the City of West Sacramento City Hall Outdoor Plaza project. Blackburn prepared this report in accordance with our January 8, 2024, Proposal for Geotechnical Engineering Services for the project.

Thank you for selecting Blackburn to be on your design team. Please call if you have questions or require additional information.

Sincerely, BLACKBURN CONSULTING

Reviewed by:

Haze M. Rodgers, P.E., G.E. Rob Pickard, P.G., C.E.G.

Director of Geotechnical Services Senior Engineering Geologist

Copies: 1 PDF Copy to the City of Roseville

City of West Sacramento – City Hall Outdoor Plaza November 18, 2024

Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope of Services

1.3 Project Description

1.4 Site Description

2 SUBSURFACE CONDITIONS

2.1 Exploratory Borings

2.2 Soil Conditions

2.3 Groundwater

3 LABORATORY TESTS

4 GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS

4.1 Expansive Soil

4.2 2022 California Building Code Seismic Parameters

4.3 Soil Corrosivity

4.4 Grading

4.4.1 Original Ground and Subgrade Preparation

4.4.2 Fill and Compaction

4.4.3 Over-optimum Soil Moisture

4.5 Spread Footings

4.6 Shade Structure Drilled Pier Foundations

4.7 Concrete Pavement Recommendations (Includes Pedestrian Concrete Flatwork)

4.8 Construction Considerations

5 RISK MANAGEMENT

6 LIMITATIONS

Table of Contents (cont.)

FIGURES

Figure 1: Vicinity Map Figure 2: Site Plan

APPENDIX A

Legend of Boring Logs Boring Log

DRAFT GEOTECHNICAL REPORT

November 18, 2024

APPENDIX B

Paragon boring Log

APPENDIX C

Laboratory Test Results

APPENDIX D

Important Information about this Geotechnical Engineering Report, Geoprofessional Business Association, 2019

November 18, 2024

1 INTRODUCTION

1.1 Purpose

Blackburn Consulting (Blackburn) prepared this Geotechnical Report for design and construction of the proposed City of West Sacramento City Hall Outdoor Plaza Project (Project), located at 1110 West Capitol Blvd., in West Sacramento, California. This report contains a brief project description, surface and subsurface conditions, laboratory tests, and geotechnical recommendations for design and construction of the Project. This report was prepared for the City of West Sacramento and the design team and shall not be used or relied upon by others, or for different locations or improvements without the written consent of Blackburn.

1.2 Scope of Services

To prepare this report, Blackburn:

Discussed the proposed improvements with you.

Reviewed Schematic Design (SD) summary dated September 9, 2024, prepared by RHAA.

Reviewed USDA soil survey data, geologic maps, historic topographic maps, and California Department of Water Resources groundwater data covering the site.

Reviewed the report of March 30, 2016 Geotechnical Investigation, City of west Sacramento Solar Shade Structures, prepared by Paragon Geotechnical, Inc.

Drilled, logged, and sampled one exploratory boring drilled at the site on September 25, 2024.

Performed laboratory tests on soil samples obtained from the exploratory boring.

Performed engineering analysis and calculations to develop our conclusions and recommendations.

1.3 Project Description

The City of West Sacramento plans to expand the facilities on the east side of the existing City Hall building.

The project will replace existing landscaping and concrete flatwork. The new outdoor plaza will include:

Outdoor workspaces Outdoor meeting areas Break/lunch areas Shade structures Concrete flatwork Landscaping Fencing or walls to provide secure access to the area

1.4 Site Description

The project site is located at 1110 West Capitol Blvd in West Sacramento, California. Figure 1 shows the site Vicinity Map. Figure 2-Site Plan. Photos 1 and 2 show the site conditions on June 18, 2024.

November 18, 2024

Photo 1

South side of the Site, looking north. Existing solar canopies over the parking lot can be seen in the right background.

Photo 2

Southwest corner of the Site looking northeast.

November 18, 2024

2 SUBSURFACE CONDITIONS

2.1 Exploratory Borings

Blackburn’s drilling subcontractor Taber Drilling (Taber) drilled one auger boring to a depth of 21.5 feet to explore the site subsurface conditions. Figure 2 shows the approximate boring location.

Taber drilled the boring using 4-inch solid flight augers. Blackburn obtained soil samples at various intervals using a 3.0-inch outside diameter (O.D.) Modified California sampler (equipped with 2.4-inch diameter liners) and 2.0-inch O.D. Standard Penetration Test (SPT) samples. The Sampler was driven with an automatic hammer, weighing 140-pounds, and falling approximately 30-inches per blow. We also collected bulk samples at various depths within the borings. the boring log is included in Appendix A.

Paragon drilled three borings for the geotechnical investigation for the solar canopies. Paragon Boring B2 was drilled in the parking area east of the planned outdoor plaza project. The approximate location of the B2 is shown on Figure 2, and a copy of the log is in Appendix B.

2.2 Soil Conditions

The subsurface conditions encountered by Blackburn and Paragon include:

Medium stiff to soft silt, sandy silt, and lean clay to depths of 4 to 7 feet.

Approximately 4 feet of loose to medium dense silty/clayey sand and poorly graded sand.

Soft to medium stiff to clay and silt with variable percentages of sand interbedded with layers of loose clayey sand to the full depth of exploration (21.5 feet bgs).

More detailed information is presented on the boring logs in Appendices A and B.

2.3 Groundwater

We observed groundwater at a depth of 9 feet below ground surface (bgs) during our subsurface exploration. Paragon encountered groundwater at 10 feet bgs. We reviewed groundwater level data for nearby wells available at the California Department of Water Resources website (http://www.water.ca.gov/waterdatalibrary/), which indicate that seasonal groundwater levels at the site can rise wit within a 2 to 3 feet of the ground surface. The depth to groundwater is dependent upon the water levels in the nearby Sacramento River. Groundwater levels are anticipated to fluctuate seasonally due to changes in precipitation, irrigation, pumping of wells, Sacramento River level, and other factors.

3 LABORATORY TESTS

We performed the following laboratory tests on representative soil samples from the exploratory boring:

Sieve analysis and Atterberg Limits for soil classification and expansion potential.

Triaxial strength (unconsolidated undrained) for lateral capacity analysis.

Soil corrosivity (pH, resistivity, sulfate, and chlorides).

Test results are included on the logs in Appendix A and complete test reports are included in Appendix C.

November 18, 2024

4 GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS

4.1 Expansive Soil

Our visual/manual soil classification indicates the near-surface soil at the site has low to moderate expansion potential. Provided the recommendations in Section 4.4 of this report are followed, expansive soil should not impact the project improvements.

4.2 2022 California Building Code Seismic Parameters

Blackburn used the SEAOC/OSHPD Seismic Design Maps Tool1 to determine our recommended 2022 California Building Code (CBC) seismic design parameters and considered:

ASCE 7-16 Reference Standard

Risk Category III

Site Class D – Stiff Soil (default)

Latitude: 38.582032 Longitude: -121.523393

Structures will meet one or more of the exceptions identified in ASCE 7-16 Section 11.4.8.

Table 2 presents our recommended 2022 CBC seismic design parameters.

Table 2: 2022 CBC Seismic Design Parameters

Ss – Acceleration Parameter 0.589

S1 – Acceleration Parameter 0.259

Fa – Site Coefficient 1.329

Fv – Site Coefficient 2.082*

SMS – Adjusted MCE Spectral Response Acceleration Parameter 0.783

SM1 – Adjusted MCE Spectral Response Acceleration Parameter 0.809**

SDS – Design Spectral Response Acceleration Parameter 0.522

SD1 – Design Spectral Response Acceleration Parameter 0.539**

PGAM – MCEG peak ground acceleration 0.334

TL – Long Period Transition Period 12

* Blackburn calculated values assuming the exception for a ground motion hazard analysis per ASCE 7-16, 11.4.8.

** Recommended SM1 and SD1 values are increased by 50% from mapped values in accordance with ASCE 7-16 Supplement 3, Section 11.4.8 Exception.

Blackburn should be notified if the assumptions listed above are incorrect. If project structural design does not meet the exception noted above Blackburn should perform a site-specific response analysis for final design.

1 URL: https://seismicmaps.org

November 18, 2024

4.3 Soil Corrosivity

Table 3 presents soil corrosivity test results.

Table 3: Soil Corrosivity Test Results

Sample No. Depth (ft.) pH Minimum Resistivity (ohm-cm)

Sulfate Content (ppm)

Chloride Content (ppm)

B1-2B 6.0-6.5 6.56 1,470 18.5 10.2

Based on our soil corrosivity test results, structural concrete in contact with the ground should meet the concrete and reinforcing steel requirements of American Concrete Institute ACI-318-19 (Building Code Requirements for Structural Concrete) for Exposure Class S0 (Sulfates) and Exposure Class C1 (Chlorides).

The corrosion test results indicate that the soil at the site is likely mildly to moderately corrosive to steel and other metals. Corrosivity test results for the sample tested are included in Appendix C for further evaluation of soil corrosivity by a corrosion consultant.

We are not corrosion consultants and cannot evaluate the potential corrosion impacts to metallic elements embedded in or in contact with the ground. A corrosion consultant should evaluate whether specific corrosion mitigation measures are necessary for the project improvements.

4.4 Grading

Where referenced in this report, use ASTM D1557 test methods to determine relative compaction and optimum moisture. Compacted soil should not be considered suitable (even if it meets relative compaction requirements) if it is unstable and pumps or flexes excessively under construction equipment loads.

4.4.1 Original Ground and Subgrade Preparation

We anticipate that the site soil will be excavatable with conventional earthmoving equipment. Prior to site grading, remove vegetation, debris, planters, unwanted pavement, abandoned utilities, abandoned foundations, soft or unstable areas, or other deleterious materials. Remove loose and disturbed soil caused by the removal(s) and widen the excavation/depression so it is accessible to compaction equipment. Strip the site to a depth of approximately 2 inches to remove surface vegetation and associated organics where present. Do not use strippings as fill in exterior flatwork, wall, or other structural areas. Consult the landscape architect to determine if strippings are acceptable for use as fill in landscape areas.

Process and compact the exposed subgrade in areas for the shade structure, wall, and new concrete flatwork as follows:

Scarify the subgrade to a depth of 8 inches.

Uniformly moisture condition scarified subgrade material to at least 2% above the optimum moisture content.

Compact the scarified soil to at least 95% percent relative compaction.

November 18, 2024

4.4.2 Fill and Compaction

On-site soil may be used as fill provided it is free of debris and visible concentrations of vegetation and has a maximum particle size of 1 inch.

Imported fill must meet the following requirements:

No concentrations of organics, debris, and other deleterious materials, Maximum particle size of 1 inch, with at least 75 percent passing the No. 4 Sieve, and at least 20 percent passing the No. 200 Sieve.

Plasticity Index less than or equal to 12, per ASTM D4318.

Minimum R-value of 10, per California Test Method 301.

Place and compact fill as follows:

1. Place fill in loose lifts no thicker than 8 inches prior to compaction.

2. Uniformly moisture condition to at least 2% above the optimum moisture content and compact to at least 95% relative compaction. Maintain this moisture content until additional fill is placed or the fill (including finish pavement/flatwork subgrade) is covered by concrete or aggregate base.

Place and compact Aggregate Base (AB) as follows:

1. Place AB in loose lifts no thicker than 12 inches prior to compaction.

2. Uniformly moisture condition to -1% to 2% above the optimum moisture content and compact to at least 95% relative compaction.

4.4.3 Over-optimum Soil Moisture

Excessively over-optimum (wet) soil conditions can make proper compaction difficult or impossible. Wet soil is commonly encountered during the winter and spring months, or in excavations where groundwater or perched water is encountered.

In general, wet soil can be mitigated by discing the soil during prolonged periods of dry weather or over excavation and replacement with drier material.

If wet, unstable soil is encountered, Blackburn can observe the conditions and provide more specific mitigation recommendations.

4.5 Spread Footings

Use the following recommendations for design of the continuous (strip) and isolated spread footings:

Strip footings should be at least 18 inches wide and extend a minimum of 18 inches below the lowest adjacent soil grade. Isolated spread footings should have a minimum width of 24 inches.

Use an allowable bearing capacity of 1,250 psf (dead plus live load) to design footings bearing on undisturbed on-site soil. The allowable bearing capacity may be increased by one-third for transient loads.

For the above allowable bearing capacity, we estimate total settlement < 1-inch and differential settlement < ½-inch.

November 18, 2024

To resist lateral movement, use an ultimate (no factor of safety) coefficient of friction of 0.30 and allowable passive earth pressure of 200 psf per foot of depth (safety factor of 1.5 applied to ultimate value). If both friction and passive pressure are used, reduce the allowable passive pressure by half.

Clean footing excavations of debris and loose soil prior to placing concrete.

Slope the ground surface away from foundations at a minimum of 2 percent for a distance of at least 5 feet.

Blackburn must observe all footing excavations prior to concrete placement to verify that competent bearing materials have been exposed.

4.6 Shade Structure Drilled Pier Foundations

Design reinforced cast-in-place concrete piers for the proposed shade structures in accordance with the following recommendations:

Provide a minimum pier diameter of 18 inches, minimum pier depth of 4 feet below adjacent grade, and minimum pier spacing of 3 diameters center-to-center.

Use the allowable skin friction values in Table 5 to resist uplift and compression loads:

Table 5: Allowable Skin Friction

Pier Length Depth Below Finish Grade

(feet)

Average Allowable Compression Skin Friction Side Resistance

Over Pile Length (psf)

Average Allowable Uplift Skin Friction Side

Resistance Over Pile Length (psf)

4 115 87 5 141 106 6 166 125 7 191 143 8 214 161 9 208 156

10 202 152 11 198 148 12 194 146 13 191 143 14 189 141 15 186 140

Allowable values based on safety factor = 2.0 applied to ultimate skin friction values.

Use an allowable passive pressure of 200 psf/ft (safety factor of 1.5 applied to ultimate value) to resist pier lateral loads.

November 18, 2024

The above allowable skin friction and passive pressure values may be increased by one-third for transient loads such as wind or seismic.

Group reduction factors for axial and lateral resistance are not necessary provided the minimum 3D pier spacing is maintained.

For drilled pier foundations not located within concrete flatwork or pavement areas, neglect skin friction and passive pressure resistance within the upper 1 foot of finish grade.

For reinforced piers designed in accordance with the above recommendations, we estimate total settlement < ½-inch.

Pier bottoms must be cleaned to remove any loose soil or debris prior to concrete placement.

4.7 Concrete Pavement Recommendations (Includes Pedestrian Concrete Flatwork)

We provide the following recommendations for pedestrian concrete flatwork:

A minimum pavement section of 6 inches of concrete over 6 inches of Class 2 aggregate base (AB) for both concrete subject to vehicular loads and for concrete flatwork subject to pedestrian loads to mitigate potential distress due to expansive soil movement. The vehicular concrete pavement section corresponds to a traffic index of 6 or less. Contact Blackburn for additional concrete pavement section recommendations if a higher traffic index is warranted based on the anticipated traffic/vehicular loads, as determined by the civil engineer and/or City.

Provide minimum concrete reinforcement consisting of No. 4 bars on 18-inch centers (each way) for expansive soil mitigation.

Concrete should have a minimum 28-day compressive strength of 3,000 psi minimum for pavement with pedestrian traffic only.

Provide a maximum joint spacing of 11 feet.

Compact subgrade and AB per Sections 4.4.

The Civil Engineer is responsible for designing the final joint types/spacing and concrete reinforcement/doweling, and for specifying the appropriate concrete mix design.

4.8 Construction Considerations

Drilled pier excavations will likely extend below groundwater and into sands and soft clays and silts.

Temporary casing might be required to prevent the drilled holes from collapsing. Drilled pier excavations should not remain open longer than necessary to construct the pier. Reinforcing steel and concrete should be placed as soon as possible after excavation to reduce the potential for hole collapse. The drilled holes should be dewatered, or concrete be placed by tremie methods below groundwater.

5 RISK MANAGEMENT

Our experience and that of our profession clearly indicates that the risks of costly design, construction, and maintenance problems can be significantly lowered by retaining the geotechnical engineer of record to provide additional services during design and construction. For this project, retain Blackburn to:

November 18, 2024

Attend a preconstruction meeting with the owner, general contractor, earthwork contractor, underground contractor, and other parties associated with the management, oversight, and process of demolition and earthwork to review geotechnical recommendations, testing requirements and project schedule.

Observe removal of underground utilities, foundations, vegetation, and other underground features in accordance with the project plans, specifications and this Geotechnical Report including loose soil generated from the removal.

Monitor construction to check and document our report assumptions. At a minimum, Blackburn should monitor grading, trench backfill, pavement subgrade and aggregate base compaction, and footing/pier excavations.

Update this report if design changes occur, 2 years or more lapse between this report and construction, and/or site conditions have changed.

If Blackburn is not retained to perform the above applicable services, we are not responsible for any other party’s interpretation of our report, and subsequent addendums, letters, and discussions.

6 LIMITATIONS

Blackburn performed services in accordance with generally accepted geotechnical engineering principles and practices currently used in this area. Where referenced, we used ASTM standards as a general (not strict) guideline only. We do not warranty our services.

Blackburn based this report on the current site conditions. We assume the soil and groundwater conditions encountered in our explorations are representative of the subsurface conditions throughout the site. Conditions at locations other than our explorations could be different.

Our scope did not include evaluation of on-site hazardous material, flood potential, aerial photograph review, or biological pollutants. Please contact Blackburn if you would like an evaluation of one or more of these potential issues.

Appendix A presents our boring logs. The lines designating the interface between soil types are approximate. The transition between material types may be abrupt or gradual. Our recommendations are based on the final logs, which represent our interpretation of the field logs/data, laboratory test results and general knowledge of the site and geological conditions.

Modern design and construction are complex, with many regulatory sources/restrictions, involved parties, construction alternatives, etc. It is common to experience changes and delays. The owner should set aside a reasonable contingency fund based on complexities and cost estimates to cover changes and delays.

Refer to Appendix D (Important Information about This Geotechnical Engineering Report, Geoprofessional Business Association, 2019) for additional limitations regarding this report.

FIGURES

Figure 1: Vicinity Map

Figure 2: Site Plan

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F ig ur e

Vi ci ni ty M ap .d w g

Figure 1

November 2024

File No. 4588.x

DISTANCE, MILE

0 1 2

VICINITY MAP

West Sacramento City Hall Outdoor Plaza

1110 West Capital Ave.

West Sacramento, California

SCALE: 1"= 1 MILE

Source: Autodesk Civil 3D 2024, CA State Plane 2.

PROJECT

LOCATION

W. Capital Ave.

Casa M obile Circle

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Si te

P la n.

dw g

Figure 2

Source: Aerial - Autodesk Civil 3D, 2024. NAD83, CA State Plane 2. SITE PLAN

L E G E N D

DISTANCE, FEET

0 50 100

SCALE: 1"= 50

Approximate Location of Blackburn Boring (2024)

BC-24-001

Approximate Location of Paragon Boring (2016)

B-1

November 2024

File No. 4588.x

West Sacramento City Hall Outdoor Plaza 1110 West Capital Ave.

West Sacramento, California

B-2

BC-24-001

City Hall Outdoor Plaza

West Sacramento, CA

November 2024

APPENDIX A

Legend of Boring Logs

Boring Log

Graphic / Symbol Group Names

Well-graded GRAVEL

GW

Well-graded GRAVEL with SAND

CL

Poorly graded GRAVEL

GP

Poorly graded GRAVEL with SAND

Well-graded GRAVEL with SILT

GW-GM

Well-graded GRAVEL with SILT and SAND

Well-graded GRAVEL with CLAY (or SILTY CLAY)

GW-GC

GP-GM

Poorly graded GRAVEL with SILT and SAND

ML

GP-GC

GM

SILTY GRAVEL with SAND

OL

CLAYEY GRAVEL

GC

CLAYEY GRAVEL with SAND

SILTY, CLAYEY GRAVEL

GC-GM

SILTY, CLAYEY GRAVEL with SAND

OL

SW

SP

SW-SM

Well-graded SAND with SILT and GRAVEL

Well-graded SAND with CLAY (or SILTY CLAY)

SW-SC

SP-SM

Poorly graded SAND with SILT and GRAVEL

Poorly graded SAND with CLAY (or SILTY CLAY)

SP-SC

SM

SILTY SAND with GRAVEL

CLAYEY SAND

SC

CLAYEY SAND with GRAVEL

OH

SILTY, CLAYEY SAND

SC-SM

SILTY, CLAYEY SAND with GRAVEL

PT PEAT

OL/OH

COBBLES

COBBLES and BOULDERS

BOULDERS

Poorly graded SAND with CLAY and GRAVEL (or SILTY CLAY and GRAVEL)

SILTY SAND

OH

Well-graded SAND with CLAY and GRAVEL (or SILTY CLAY and GRAVEL)

Poorly graded SAND with SILT

MH

Well-graded SAND

Well-graded SAND with GRAVEL

Poorly graded SAND

Poorly graded SAND with GRAVEL

CH

Well-graded SAND with SILT

Poorly graded GRAVEL with CLAY (or SILTY CLAY) Poorly graded GRAVEL with CLAY and SAND (or SILTY CLAY and SAND)

SILTY GRAVEL

Well-graded GRAVEL with CLAY and SAND (or SILTY CLAY and SAND)

Poorly graded GRAVEL with SILT

CL-ML

GROUP SYMBOLS AND NAMES

Graphic / Symbol

Lean CLAY Lean CLAY with SAND Lean CLAY with GRAVEL SANDY lean CLAY

GRAVELLY lean CLAY SANDY lean CLAY with GRAVEL

GRAVELLY lean CLAY with SAND

SILTY CLAY

SILTY CLAY with SAND SILTY CLAY with GRAVEL

SANDY SILTY CLAY

SANDY SILTY CLAY with GRAVEL

GRAVELLY SILTY CLAY

GRAVELLY SILTY CLAY with SAND

SILT

SILT with SAND SILT with GRAVEL

SANDY SILT

SANDY SILT with GRAVEL

GRAVELLY SILT

GRAVELLY SILT with SAND

ORGANIC lean CLAY ORGANIC lean CLAY with SAND ORGANIC lean CLAY with GRAVEL SANDY ORGANIC lean CLAY SANDY ORGANIC lean CLAY with GRAVEL GRAVELLY ORGANIC lean CLAY GRAVELLY ORGANIC lean CLAY with SAND

ORGANIC SILT

ORGANIC SILT with SAND ORGANIC SILT with GRAVEL

SANDY ORGANIC SILT

SANDY ORGANIC SILT with GRAVEL

GRAVELLY ORGANIC SILT

GRAVELLY ORGANIC SILT with SAND

Fat CLAY Fat CLAY with SAND Fat CLAY with GRAVEL SANDY fat CLAY SANDY fat CLAY with GRAVEL GRAVELLY fat CLAY GRAVELLY fat CLAY with SAND

Elastic SILT Elastic SILT with SAND Elastic SILT with GRAVEL SANDY elastic SILT SANDY elastic SILT with GRAVEL GRAVELLY elastic SILT GRAVELLY elastic SILT with SAND

ORGANIC fat CLAY ORGANIC fat CLAY with SAND ORGANIC fat CLAY with GRAVEL SANDY ORGANIC fat CLAY SANDY ORGANIC fat CLAY with GRAVEL

GRAVELLY ORGANIC fat CLAY with SAND

ORGANIC elastic SILT ORGANIC elastic SILT with SAND ORGANIC elastic SILT with GRAVEL SANDY elastic ELASTIC SILT SANDY ORGANIC elastic SILT with GRAVEL GRAVELLY ORGANIC elastic SILT GRAVELLY ORGANIC elastic SILT with SAND

ORGANIC SOIL

ORGANIC SOIL with SAND ORGANIC SOIL with GRAVEL

SANDY ORGANIC SOIL

SANDY ORGANIC SOIL with GRAVEL

GRAVELLY ORGANIC SOIL

GRAVELLY ORGANIC SOIL with SAND

Shelby Tube

NX Rock Core

Bulk Sample

Piston Sampler

HQ Rock Core

Other (see remarks)

SAMPLER GRAPHIC SYMBOLS

Standard Penetration Test (SPT)

California Sampler (2" ID)

Modified California Sampler (2.4" ID)

Group Names C Consolidation (ASTM D2435)

FIELD AND LABORATORY TESTS

DRILLING METHOD SYMBOLS

WATER LEVEL SYMBOLS

Auger Drilling Rotary Drilling Dynamic Cone or Hand Driven Diamond Core

Static Water Level Reading (short-term)

First Water Level Reading (during drilling)

Static Water Level Reading (long-term)

CL Collapse Potential (ASTM D5333) CP Compaction Curve (ASTM D696, D1557, CTM 216) CR Corrosion, Sulfates, Chlorides (CTM 643, CTM 417, CTM 422)

CU Consolidated Undrained Triaxial (ASTM D4767) DS Direct Shear (ASTM D3080) EI Expansion Index (ASTM D4829) M Moisture Content (ASTM D2216) OC Organic Content (ASTM D2974) P Permability (ASTM D5084) PA Particle Size Analysis (ASTM D6913 or D422) PI Liquid Limit, Plastic Limit, Plasticity Index

(ASTM D4318)

PL Point Load Index (ASTM D5731)

PM Pressure Meter

PP Pocket Penetrometer R R-Value (CTM 301) SE Sand Equivalent (CTM 217) SG Specific Gravity (AASHTO T100) SL Shrinkage Limit (ASTM D4943) SW Swell Potential (ASTM D4546)

UC Unconfined Compression - Soil (ASTM D2166) Unconfined Compression - Rock (ASTM D7012)

UU Unconsolidated Undrained Triaxial (ASTM D2850) UW Unit Weight (ASTM D7263)

TV Pocket Torvane

VS Vane Shear (AASHTO T223 / ASTM D2573)

ASPHALT CONCRETE CONCRETE

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Bo rin g Le ge nd fo r R ep or ts A

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BORING RECORD LEGEND

Descriptor Very Soft

Unconfined Compressive Strength (tsf)

< 0.25

CRITERIA FOR DESCRIBING CONSISTENCY OF COHESIVE SOIL

Torvane (tsf) Pocket Penetrometer (tsf)

< 0.25

Descriptor

Angular

Subangular Subrounded

Rounded

CRITERIA FOR DESCRIBING ANGULARITY OF COARSE-GRAINED PARTICLES

Criteria

Particles have sharp edges and relatively plane sides with unpolished surfaces

Particles are similar to angular description but have rounded edges Particles have nearly plane sides but have well-rounded corners and edges

Particles have smoothly curved sides and no edges

< 0.12

Field Approximation Extrudes between fingers when squeezed

CRITERIA FOR DESCRIBING MOISTURE CONDITION

Descriptor

Dry

Moist

Wet

Criteria Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, usually soil is below water table

Descriptor

Boulder

Cobble

Gravel

Sand

Fines (Silt and Clay)

CRITERIA FOR DESCRIBING PLASTICITY OF FINE-GRAINED SOIL

Descriptor

Nonplastic Low

Medium

High

Criteria

A 1/8-inch (3-mm) thread cannot be rolled at any water content.

The thread can barely be rolled, and the lump cannot be formed when drier than the plastic limit.

The thread is easy to roll, and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. The lump crumbles when drier than the plastic limit It takes considerable time rolling and kneading to reach the plastic limit. The thread can be rerolled several times after reaching the plastic limit. The lump can be formed without crumbling when drier than the plastic limit.

Descriptor

Medium Dense

Loose

Very Loose

CRITERIA FOR APPARENT DENSITY OF COHESIONLESS SOIL

SPT N60 - Value (blows/foot) 0 - 4

CRITERIA FOR SOIL PARTICLE SIZE

Size

Coarse

Fine

Coarse

Medium

Fine

> 12 inches

3/4 inch to 3 inches

3 to 12 inches

No. 4 Sieve to 3/4 inch

No. 10 Sieve to No. 4 Sieve

No. 40 Sieve to No. 10 Sieve

No. 200 Sieve to No. 40 Sieve

Passing No. 200 Sieve

Soft 0.25 - 0.50 0.25 - 0.50 0.12 - 0.25 Medium Stiff 0.50 - 1.0 0.50 - 1.0 0.25 - 0.50

Easily penetrated several inches by thumb Can be penetrated several inches by thumb with moderate effortStiff

2.0 - 4.0 2.0 - 4.0 1.0 - 2.0 Readily indented by thumb but penetrated only with great effort Hard > 4.0 > 4.0 > 2.0 Readily indented by thumbnail

< 2 2 - 4 4 - 8 8 - 15

> 30

(blows/ft) SPT N60 - Value

Descriptor

Strong

Moderate

Weak

CRITERIA FOR DESCRIBING CEMENTATION OF COARSE-GRAINED SOIL

Criteria

Crumbles or breaks with handling or little finger pressure

Crumbles or breaks with considerable finger pressure

Will not crumble or break with finger pressure

Dense

Very Dense

4 - 10

10 - 30

30 - 50

>50

Very Stiff 15 - 30

1.0 - 2.0 1.0 - 2.0 0.50 - 1.0

Flat

Elongated

Flat and elongated

CRITERIA FOR DESCRIBING PARTICLE SHAPE (Gravel, Cobbles, Boulders) The particle shape shall be described as follows where length, width, and thickness refer to the greatest, intermediate, and least dimensions of a particle, respectively

Particles with width/thickness > 3

Particles with length/width > 3

Particles meet criteria for both flat and elongated

Descriptor Stratified

Laminated

Fissured

Slickensided

Blocky

Criteria Alternating layers of varying material or color with layers at least 1/4 in. (6 mm) thick; note thickness Alternating layers of varying material or color with the layers less than 1/4 in. thick; note thickness Breaks along definite planes of fracture with little resistance to fracturing Fracture planes appear polished or glossy, sometimes striated Cohesive soil that can be broken down into small angular lumps which resist further breakdown Inclusion of small pockets of different soils, such as small lenses of sand scattered through a mass of clay; note thickness

Descriptor

None

Slow

Rapid

CRITERIA FOR DESCRIBING DILATANCY OF FINE-GRAINED SOIL

Criteria

No visible change in the specimen

Water appears slowly on the surface of the specimen during shaking and does not disappear or disappears slowly upon squeezing

Water appears quickly on the surface of the specimen during shaking and disappears quickly upon squeezing

CRITERIA FOR DESCRIBING STRUCTURE

Lensed

Homogeneous Same color and appearance throughout CRITERIA FOR PERCENTAGE OF MATERIAL (Gravel, Sand, and Fines) Estimate percentages to the closest 5%. All percentages must add up to 100%.

For Percentages present but less than 5%, use trace but do not use in sum total.

NOTE: This legend sheet provides descriptors and associated criteria for select soil description components only. Refer to the most recent version of ASTM D2488, Standard Practice and Identifcation of Soils (Visual-Manual Procedure) for field classification. Laboratory test results are considered on the final logs.

Criteria based on 2022 Caltrans Soil and Rock Logging, Classification, and Presentation Manual and USACE EM 1110-1-1804 Geotechnical Investigations

PAGE 23/

/2

Bo rin g Le ge nd fo r R ep or ts A

ST

M

_2

4.

dw g

BORING RECORD LEGEND

CR

SILT (ML); stiff; dark yellowish brown; moist; mostly fines; little fine SAND; low plasticity

SANDY SILT (ML); soft; dark yellowish brown; moist; mostly fines; some fine SAND; nonplastic to low plasticity interbedded lenses of SILT (ML) and SANDY SILT (ML) Lean CLAY (CL); soft; very dark gray; moist; mostly fines; trace fine SAND; medium plasticity

CLAYEY SAND (SC); medium dense; dark gray; moist; mostly fine SAND; some fines

Poorly-graded SAND (SP); very loose to loose; dark gray;

moist; mostly fine to medium SAND; trace fines

SILT with SAND (ML); medium stiff; dark brown; moist; mostly fines; little fine SAND; low to medium plasticity

Lean CLAY (CL); medium stiff; dark grayish brown; moist;

mostly fines; trace fine SAND;

wet

Bottom of exploration at 21.5 ft below ground surface (bgs) Backfill Tremie Neat Cement Grout Ground water encountered at 10.5 ft bgs

Groundwater Rosed to 9.0 ft bgs Bulk-A 0.0 - 5.0 ft bgs

UU

UU

1.25

0.25 push

OPERATOR'S NAME

David

LOCATION (Lat/Long or North/East and Datum)

EQUIPMENT

CME 55 Crawler

DRILLING ROD TYPE AND DIAMETER / BUCKET WIDTH

AFTER (DATE)BACKFILL AND COMPLETION

Backfill Tremie Neat Cement Grout

EXCAVATION METHOD

Solid-Stem Auger

HOLE ID

B1

DURING

COMPLETION DATE

9-25-24

BEGIN DATE

9-25-24

GROUND WATER

READINGS

SAMPLER TYPE(S) AND SIZE(S) (ID)

SPT (1.4"), CalMod (2.4")

HELPER'S NAME

Moises

HAMMER TYPE

Safety semi-automatic drop (140#/ 30")

LOGGED BY

JB

CASING TYPE AND DIAMETER(in)

HAMMER EFFICIENCY, ERi

BOREHOLE DIAMETER

4 in

TOTAL DEPTH

21.5 ft

SURFACE ELEVATIONLOCATION (Offset, Station, Line)CONTRACTOR Taber

Not measured10.5 ft on 9-25-24

P la st ic ity In de x

E

LE

V A

T

IO

N ft)

A dd iti on a l

La b

T es ts

D ril lin g

M et ho d

Laboratory Data

#2

CHECKED BY

RCP

SHEET

D E

P T

H ft)

S am pl e

N um be r

PROJECT NAME

West Sacramento City Hall Outdoor Plaze

FILE NO.

4588.x

CLIENT

COUNTY

YOL

PREPARED BY

AG

POSTMILE

D

ROUTE

DESCRIPTION

N fie ld

P us h P re ss ur e

Li qu id Li m it

S he ar S tr en gt h

T es t

M oi st ur e C on te nt

HOLE ID

B1

P oc ke t

P en tr om et er

R ec ov er y

M at er ia l G ra ph ic s

D ry

D en si ty

(p cf

S am pl e

Lo ca tio n

B lo w s pe r in

N

A

S T

M

B C

I L O

G F

O R

S O

IL

.X B

O R

IN

G

L O

G S

.G P

J L

IB

R

A R

Y _2

.G

LB

1/

/2

APPENDIX B

Paragon Boring Log

APPENDIX C

Laboratory Test Results

TRIAXIAL SHEAR TEST REPORT

Blackburn Consulting W. Sacramento, CA

Client: RHAA

Project: West Sacramento City Hall Outdoor Plaza

Source of Sample: B1 Depth: 3.5-4'

Sample Number: 1C

Proj. No.: 4588.X Date Sampled:

Type of Test:

Unconsolidated Undrained

Sample Type: CalMod

Description: Top 1": SILTY SAND, brown

Bottom 4": SILT, brown

Assumed Specific Gravity= 2.7

Remarks:

Figure

Sample No.

Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in.

Height, in.

Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in.

Height, in.

Strain, %

Strain, %

Strain rate, in./min.

Back Pressure, psf

Cell Pressure, psf

Fail. Stress, psf

Ult. Stress, psf s1 Failure, psf s3 Failure, psf

In iti a l

A t T e st

33.2 85.0 91.1

0.9837 2.37 4.99

33.2 85.0 91.1

0.9837 2.37 4.99

0.030

8.5

D e vi a to r

S tr e ss p sf

Axial Strain, %

0 5 10 15 20

S h e a r S tr e ss p sf

Normal Stress, psf

0 400 800 1200 1600 2000 2400

C, psf f, deg

Tan(f)

Results

Client: RHAA

Project: West Sacramento City Hall Outdoor Plaza

Source of Sample: B1 Depth: 3.5-4' Sample Number: 1C

Project No.: 4588.X Figure Blackburn Consulting q , p sf p, psf

0 500 1000 1500 2000 2500 3000

Peak Strength

Total a= a= tan a=

960 psf

0.0 deg

0.00

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

TRIAXIAL SHEAR TEST REPORT

W. Sacramento, CA

Client: RHAA

Project: West Sacramento City Hall Outdoor Plaza

Source of Sample: B1 Depth: 16-16.5'

Sample Number: 5C

Proj. No.: 4588.X Date Sampled:

Type of Test:

Unconsolidated Undrained

Sample Type: CalMod

Description: Lean CLAY, brown

Assumed Specific Gravity= 2.7

Remarks:

Figure

Sample No.

Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in.

Height, in.

Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in.

Height, in.

Strain, %

Strain, %

Strain rate, in./min.

Back Pressure, psf

Cell Pressure, psf

Fail. Stress, psf

Ult. Stress, psf s1 Failure, psf s3 Failure, psf

In iti a l

A t T e st

42.3 80.0

103.4 1.1057

2.41 4.97

42.7 80.0

104.3 1.1057

2.41 4.97

0.030

5.3

D e vi a to r

S tr e ss p sf

Axial Strain, %

0 5 10 15 20

S h e a r S tr e ss p sf

Normal Stress, psf

0 400 800 1200 1600 2000 2400

C, psf f, deg

Tan(f)

Results

Client: RHAA

Project: West Sacramento City Hall Outdoor Plaza

Source of Sample: B1 Depth: 16-16.5' Sample Number: 5C

Project No.: 4588.X Figure Blackburn Consulting q , p sf p, psf

0 400 800 1200 1600 2000 2400

Peak Strength

Total a= a= tan a=

372 psf

0.0 deg

0.00

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

D e vi a to r

S tr e ss p sf

0% 8% 16%

Particle Size Distribution Report

ASTM D1140

P E

R C

E N

T F

IN

E

R

GRAIN SIZE - mm.

0.00010.0010.010.1110100

% +3" Coarse

% Gravel

Fine Coarse Medium

% Sand

Fine Silt

% Fines

Clay in in in

½ in in

¾ in

½ in

/8 in

Test Results (ASTM D1140) Material Description

Atterberg Limits

Coefficients

Classification

Test Remarks

Sample Date:

Source of Sample: B1 Depth: 8-8.5' Sample Number: 3B

Client:

Project:

Project No: Figure

Sieve Size or

Diam. (mm.)

Finer

Spec.*

Out of Spec.

Pct.

of

Fines

CLAYEY SAND, very dark grayish brown

#200 45

18 34 16

SC

RHAA

West Sacramento City Hall Outdoor Plaza

4588.X

PL= LL= PI=

D90= D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

* (no specification provided)

W. Sacramento, CA

LIQUID AND PLASTIC LIMITS TEST REPORT

P

LA

ST

IC

IT

Y

IN

D

EX

LIQUID LIMIT

0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

CL o r O

L

CH o r O

H ML or OL MH or OH

Dashed line indicates the approximate upper limit boundary for natural soils

MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS

Project No. Client: Remarks:

Project:

Blackburn Consulting

W. Sacramento, CA Figure

Source of Sample: B1 Depth: 8-8.5' Sample Number: 3B

CLAYEY SAND, very dark grayish brown 34 18 16 45 SC

4588.X RHAA

West Sacramento City Hall Outdoor Plaza

HazeRodgers Text Box Paragon Geotechnical, Inc. Laboratory Testing

City Hall Outdoor Plaza

West Sacramento, CA

November 2024

APPENDIX D

Important Information about this Geotechnical Engineering Report, Geoprofessional Business Association, 2019

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 because those relying on a geotechnical-engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full.

You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys.

Typical changes that could erode the reliability of this report include those that affect:

• the site’s size or shape;

• the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria;

• the composition of the design team; or

• project ownership.

As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.

Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed.

This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation.

This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical-engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to:

specifications; and

• be available whenever geotechnical-engineering guidance is needed.

You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.

Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect.

Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes.

To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions.

Your geotechnical engineer should respond fully and frankly.

Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance.

Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies.

Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team.

Geotechnical engineers are not building-envelope or mold specialists.

Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review.