Amendment 0003 Attachment 02 Geotechnical Report.pdf

Report Cover Page

VISN Warehouse Geotechnical Engineering Report

December 18, 2023 | Terracon Project No. N6235192

Prepared for:

Above Group, Inc.

400 E. Pratt Street, 8th Floor

Baltimore, Maryland 21202

12460 Plaza Drive

Parma, Ohio 44130

P (216) 459-8378

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

December 18, 2023

Above Group, Inc.

400 E. Pratt Street, 8th Floor

Baltimore, Maryland 21202

Attn: Jake Lantz

P: (410) 372-7227

E: jlantz@abovegroupinc.com

Re: Geotechnical Engineering Report

VISN Warehouse

325 New Castle Road

Butler, Pennsylvania

Terracon Project No. N6235192

Dear Mr. Lantz:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PN6235192 dated

October 24, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

Richard Sullivan, P.E. Chett A. Siefring, P.E.

Engineer – Geotechnical Services Manager – Geotechnical Services

VISN Warehouse | Butler, Pennsylvania

Facilities | Environmental | Geotechnical | Materials i

Table of Contents Introduction

Project Description

Site Conditions

Geotechnical Characterization

Seismic Site Class

Percolation

Geotechnical Overview

Earthwork

Demolition

Subgrade Preparation

Site Preparation

Existing Fill

Excavation

Soil Stabilization

Fill Material Types

Fill Placement and Compaction Requirements

Utility Trench Backfill

Grading and Drainage

Earthwork Construction Considerations

Construction Observation and Testing

Shallow Foundations

Design Parameters – Compressive Loads

Foundation Construction Considerations

Floor Slabs

Floor Slab Design Parameters

Floor Slab Construction Considerations

Lateral Earth Pressures

Design Parameters

Subsurface Drainage for Below-Grade Walls

Pavements

Pavement Subgrade Support Characteristics

General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures

Facilities | Environmental | Geotechnical | Materials ii

Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed warehouse to be located at 325 New

Castle Road in Butler, Pennsylvania. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil and rock conditions

■ Groundwater conditions

■ Infiltration

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Demolition considerations

■ Foundation design and construction

■ Floor slab design and construction

■ Lateral earth pressure

■ Pavement design and construction

■ Frost considerations

The geotechnical engineering Scope of Services for this project included the advancement of 11 test borings to depths ranging from 5.75 to 15.5 feet, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and/or as separate graphs in the Exploration Results section.

Project Description

Our understanding of the project conditions is as follows

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Information

Provided

A request for proposal that included the following was provided to Terracon via email from AGI on June 22, 2023:

■ VAMC Butler A/E Scope of Work for Construct a Warehouse for VISN 4 Western Market Distribution Project #529-314

■ An undated Site with New Warehouse Plan prepared by

U.S. Department of Veterans Affairs.

An email from AGI on September 28, 2023 indicated that an infiltration test was to be included as part of the scope of work for the project.

Additional information was emailed on October 19, 2023 and contained the following:

■ Site Grading Plan and Site Layout and Utility Plan prepared by U.S. Department of Veterans Affairs and dated 8/4/23.

Project

Description New warehouse.

Proposed

Structure

Structures associated with the project include an approximate

17,000 to 22,000-square foot building with minimum wall heights of 16 feet. The building is planned to be slab-on-grade.

Building

Construction

Not provided; we anticipate that addition will be constructed using concrete tilt-up panels or structural steel with masonry block walls.

Finished Floor

Elevation

Finished floor elevation for the planned building is 1289.5± feet, MSL.

Maximum Loads

In the absence of information provided by the design team, we will use the following loads in estimating settlement based on our experience with similar projects:

■ Columns: 100 kips

■ Walls: 4 kips per linear foot (klf)

■ Slabs: 125 pounds per square foot (psf)

Grading

Approximately 1 feet of cut and 5 feet of fill will be required to develop final grade for the building, excluding remedial grading requirements.

Below-Grade

Structures

Four recessed loading docks are planned for the southern section of the west wall line.

Pavements It was indicated that asphalt and concrete pavements will be utilized at the site.

Facilities | Environmental | Geotechnical | Materials 3

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project is located at 325 New Castle Road in Butler, Pennsylvania.

Latitude: 40.8725 / Longitude: -79.9468 (approximate)

See Site Location

Existing

Improvements

In the area of the planned warehouse, no existing improvements are present. The overall site has several buildings and parking areas.

Current Ground

Cover Grass with a few trees.

Existing

Topography

Based on elevations taken from the US Department of Veteran

Affairs Grading Plan dated 8/4/23, the existing site grades range from approximately 1284 to 1290 feet MSL for the areas explored across building pad and 1282 to 1290 feet MSL for the areas explored across the site.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Facilities | Environmental | Geotechnical | Materials 4

Model

Layer Layer Name General Description

1 Surface Cover Topsoil or Aggregate

2 Fill Sand

3 Cohesive Soil Stiff silt or medium stiff to hard clay

4 Bedrock Highly weathered and very weak shale

The borings were advanced in the dry using the hollow-stem augers drilling technique that allows short term groundwater observations to be made while drilling. Groundwater conditions may be different at the time of construction than those encountered during completion of our field exploration. Mapping by the Natural Resources Conservation

Service (NRCS) indicates a seasonal high groundwater level within 12 inches of ground surface. Groundwater conditions may change because of seasonal variations in rainfall, runoff, and other conditions not apparent at the time of drilling. Perched water may be present at the site within sand or silt seams within native clay layers, and/or at the interface of the soil/rock boundary and/or fill materials overlying lower permeability cohesive soils. Long-term groundwater monitoring was outside the scope of services for this project.

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic

Design Category. Site Classification is required to determine the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC). Based on the soil/bedrock properties observed at the site and as described on the exploration logs and results, our professional opinion is that a Seismic Site Classification of D be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 15.5 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

Percolation

The percolation tests were performed on November 22, 2023. At each location, a drill rig was used to auger down to the planned test depth. The subsurface conditions encountered at the test locations consisted of granular fill materials. Groundwater was not encountered

Facilities | Environmental | Geotechnical | Materials 5 in the test holes. The tests were run in general conformance with the Pennsylvania

Stormwater BMP Manual dated December 30, 2006.

The test results are summarized in the table below:

Test Location. P-1 P-2

Hole Diameter (in) 8 8

Test Depth (ft) 3 5

Water Depth (inches) 12 12

Soil Type Lean Clay Lean Clay

Drop in water level

1st 30-Minute Pre-Soak Period

(inches)

0 0

Drop in water level

2nd 30-Minute Pre-Soak Period

(inches)

0 0

Reading No. Drop in water level over 30-minute intervals (inches)

Drop in water level over 30-minute intervals (inches)

0 0

2 0 0

3 0 0.125

4 0.125 0

Percolation Rate (in/hr)

0.03 0.03

Reduction Factor

2.99 2.99

Average Stabilized Infiltration Rate

(in/hr)

0.01 0.01

Facilities | Environmental | Geotechnical | Materials 6

Test Location. P-1 P-2

1. Below the existing ground surface.

2. Reduction factor is calculated according to the following: Rf = 2∗d1 – Δd dia + 1; where:

Rf = Reduction Factor d1 = initial water depth (inches)

Δd = final water depth change (inches) dia = test hole diameter (inches)

Geotechnical Overview

The main potential geotechnical concern facing site development is the shallow bedrock.

The majority of the near-surface soils are fine grained in nature. These soils, especially those denoted as silt or containing silt, have the propensity to degrade and become unstable when exposed to dynamic forces, such as those typically associated with construction activities - especially after precipitation events. Positive drainage can help with the stability of the site soils and should be established early in the construction sequence and maintained thereafter to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

Existing fill material (GeoModel Layer 2) was encountered in test boring B-8 to a depth of approximately 3.5 feet below existing grade. While the fill did not contain any man-made inclusions, debris and other deleterious matter it must be considered undocumented unless documentation can be provided to prove otherwise. In undocumented fill there is an inherent risk that compressible fill or unsuitable material, within or buried by the fill, will not be discovered and may lead to excessive amounts of settlement. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fil l.

As such, Terracon does not recommend the existing fill be used for structural support unless the owner is willing to accept the risks of building upon the fill . Additional information regarding the fill can be found in the Earthwork section.

Based upon the proposed finished floor elevation, it is probable that foundations will bear upon both soil and rock. It is generally cautioned against having foundations within the same structure bear upon both soil and rock unless those sections of the same building are designed to be structurally independent of each other. This is because bedrock is inherently stronger than soil

Facilities | Environmental | Geotechnical | Materials 7 and subsequently those foundations bearing upon bedrock will inevitably settle less than those bearing upon soil. Such contrasts in foundation support may lead to potentially excessive differential settlement unless the structures are suitably designed to accommodate such differences. In general, it is advisable to lower all foundations so they bear upon bedrock.

However, where it is necessary to utilize both soil and rock as a bearing media, we propose utilizing a ‘buffer’ between the foundations and bedrock. This buffer should be comprised of engineered fill and proportioned in size to the width of the foundation. Such that strip footings shall have a buffer two times as deep as their width and isolated foundations have a buffer one times as deep as their width. Additional information regarding foundation recommendations can be found in the Shallow Foundations section.

The Floor Slabs section addresses slab-on-grade support of the building and the

Pavements section addresses the design of pavement systems.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

Earthwork

Earthwork is anticipated to include demolition, clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Demolition

Pavements and buried objects encountered within the proposed development area be removed in their entirety. Any existing utilities should also be removed or relocated. Once removed, it is imperative that backfilling is suitably undertaken to ensure the long-term performance of the new structure. Historical evidence indicates that new structures placed over the remnants of previous construction or poorly compacted backfill often result in the new structure performing poorly either with evidence of cracking within wall, foundations, and/or floor slabs or in severe cases settlements beyond the tolerable limits of the structure.

Subgrade Preparation

The subgrade should be proofrolled with an adequately loaded vehicle such as a fully-loaded (minimum 20 ton gross vehicle weight) tandem-axle dump truck. The proofrolling

Facilities | Environmental | Geotechnical | Materials 8 should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should be removed and replaced with properly placed and compacted engineered fill. Excessively wet or dry material should either be moisture conditioned and recompacted or removed and replaced with properly placed and compacted engineered fill.

Where the subgrade has passed a proofroll, compacted engineered fill soils should be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation, slab or pavement construction.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Site Preparation

Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.

Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

Existing Fill

As indicated in the Geotechnical Overview section of this report, fill material was encountered at this site.

If existing fill is encountered within the building pad it should be removed in its entirety so that the foundations and floor slabs can bear on either suitable naturally deposited soils or engineered fill placed upon these soils.

Support of pavements, above, upon or within the exiting fill, is discussed in this report.

However, even with the recommended construction procedures, it must be realized that there is an inherent risk that compressible fill or unsuitable material, within or buried by the fill, will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by following the recommendations contained in this report.

If the owner elects to construct pavements on the existing fill, the following protocol should be followed. Once the planned subgrade elevation has been reached the entire pavement area should be proofrolled. Areas of soft or otherwise unsuitable material should be undercut and replaced with either new structural fill or suitable, existing on site materials.

Facilities | Environmental | Geotechnical | Materials 9

Excavation

We expect that shallow excavations into soil can be accomplished with conventional construction equipment. If excavation into the bedrock is required, then heavy-duty construction equipment equipped with rock teeth or rock hammers will likely be required.

This expectation is based upon the ease at which the sandstone was augured during this geotechnical exploration. We do caution, however, that there is a mechanical difference between auguring and excavation through rock which may determine the ease of bedrock excavation. As such, it is advisable to contract with an excavator who is experienced with rock excavation. The excavator should be afforded the opportunity to conduct test excavations prior to construction so that they can determine their equipment needs.

Soil Stabilization

If the near surface become unstable, they may be improved using one of the following recommend procedures. If earthwork is to take place in the wet season then contingencies for such work should be incorporated into the budget and schedule.

Methods of subgrade improvement, as described below, could include scarification, moisture conditioning and recompaction, removal of unstable materials and replacement with granular fill (with or without geosynthetics), and chemical stabilization. The appropriate method of improvement, if required, would be dependent on factors such as schedule, weather, the size of area to be stabilized, and the nature of the instability. More detailed recommendations can be provided during construction as the need for subgrade stabilization occurs. Performing site grading operations during warm seasons and dry periods would help reduce the amount of subgrade stabilization required.

If the exposed subgrade is unstable during proofrolling operations, it could be stabilized using one of the methods outlined below.

■ Scarification and Recompaction - It may be feasible to scarify, dry, and recompact the exposed soils. The success of this procedure would depend primarily upon favorable weather and sufficient time to dry the soils. Stable subgrades likely would not be achievable if the thickness of the unstable soil is greater than about

1 foot, if the unstable soil is at or near groundwater levels, or if construction is performed during a period of wet or cool weather when drying is difficult.

■ Crushed Stone - The use of crushed stone or crushed gravel is a common procedure to improve subgrade stability. Typical undercut depths would be expected to range from about 6 to 24 inches below finished subgrade elevation.

The use of high modulus geotextiles (i.e., engineering fabric or geogrid) could also be considered after underground work such as utility construction is completed.

Prior to placing the fabric or geogrid, we recommend that all below grade construction, such as utility line installation, be completed to avoid damaging the

Facilities | Environmental | Geotechnical | Materials 10 fabric or geogrid. Equipment should not be operated above the fabric or geogrid until one full lift of crushed stone fill is placed above it. The maximum particle size of granular material placed over geotextile fabric or geogrid should not exceed 1-

1/2 inches.

■ Chemical Modification - Improvement of subgrades with lime, portland cement or class C fly ash could be considered for improving unstable soils. Chemical modification should be performed by a pre-qualified contractor having experience with successfully stabilizing subgrades in the project area on similar sized projects with similar soil conditions. Results of chemical analysis of the additive materials should be provided to the geotechnical engineer prior to use. The hazards of chemicals blowing across the site or onto adjacent property should also be considered. Additional testing would be needed to develop specific recommendations to improve subgrade stability by blending chemicals with the site soils. Additional testing could include, but not be limited to, determining the most suitable stabilizing agent, the optimum amounts required, the presence of sulfates in the soil, and freeze-thaw durability of the subgrade.

Further evaluation of the need and recommendations for subgrade stabilization can be provided during construction as the geotechnical conditions are exposed.

Fill Material Types

Fill required to achieve design grade should be classified as engineered fill . Engineered fill is material used below, or within 10 feet of structures, pavements or constructed slopes.

Reuse of On-Site Soil: Excavated on-site soil may be selectively reused as Engineered

Fill.

Material property requirements for on-site soil for use as engineered fill are noted in the table below:

Property Engineered Fill

Composition Free of deleterious material

Maximum Particle Size 3 inches

Fines Content of Granular Soils Less than 15% Passing No. 200 sieve

Liquid Limit of Cohesive Soils Maximum liquid limit of 50

GeoModel Layer Expected to be

Suitable1 3, 4

1. It may be possible to reuse the fill materials of GeoModel Layer 2 providing that the material is reviewed and approved by the Geotechnical Engineer.

Facilities | Environmental | Geotechnical | Materials 11

Imported Fill Materials: Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Soil Type 1

USCS

Classification

Acceptable Parameters (for Engineered

Fill)

Low Plasticity

Cohesive CL, CL-ML All locations and elevations

Granular

GW, GM, GC,

SW, SM, SC

All locations and elevations

1. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site. Additional geotechnical consultation should be provided prior to use of uniformly graded gravel on the site.

Fill Placement and Compaction Requirements

Engineered fill should meet the following compaction requirements.

Item Engineered Fill

Maximum Lift

Thickness

8 inches or less in loose thickness when heavy (minimum 8 tons), self-propelled compaction equipment is used

6 inches in loose thickness when hand-guided equipment

(i.e. jumping jack or plate compactor) is used

Minimum Compaction

Requirements 1,2

98% of the material’s maximum dry density

Water Content Range

Low plasticity cohesive: -2% to +3% of optimum moisture

Granular: -3% to +3% of optimum moisture or at suitable level to provide sufficient compaction without the material pumping or rutting when proofrolled

1. Maximum density and optimum water content as determined by the standard

Proctor test (ASTM D 698).

2. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least 70% relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the

Geotechnical Engineer or representative.

Facilities | Environmental | Geotechnical | Materials 12

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with engineered fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Flooding or jetting for placement and compaction of backfill is not recommended.

For low permeability subgrades, utility trenches are a common source of water infiltration and migration. Utility trenches penetrating beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for engineered fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least

10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to

Facilities | Environmental | Geotechnical | Materials 13 document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of

Facilities | Environmental | Geotechnical | Materials 14 existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,500 square feet of compacted fill in the building areas or a minimum of 3 tests per lift, and 5,000 square feet in pavement areas. Where not specified by local ordinance, one density and water content test should be performed for every 100 linear feet of compacted utility trench backfill and a minimum of one test performed for every 12 vertical inches of compacted backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical

Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Shallow Foundations

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

Again, foundations should not be brought to bear upon both bedrock and soil. In general it is advisable to lower all foundations so they bear upon bedrock. However, where it is necessary to utilize both soil and rock as a bearing media we propose utilizing a ‘buffer’ between the foundations and bedrock. This buffer should be comprised of engineered fill and proportioned in size to the width of the foundation. Such that strip footings shall have a buffer two times as deep as their width and isolated foundations have a buffer one times as deep as their width.

Design Parameters – Compressive Loads

Item Description

Maximum Net Allowable Bearing

Pressure 1, 2

Layer 3 3,000 psf

GeoModel

Layer 4 5,000 psf

Facilities | Environmental | Geotechnical | Materials 15

Item Description

Required Bearing Stratum

Layer 3

Stiff or better cohesive soils or engineered fill bearing upon these soils or bedrock

GeoModel

Layer 4 Shale bedrock

Minimum Foundation Dimensions

Columns 30 inches

Continuous GeoModel Layer 3= 18 inches

GeoModel Layer 4 = 12 inches

Sliding Resistance

Allowable cohesion

GeoModel Layers 3/4 = 500 psf

Minimum Embedment below

Finished Grade

Exterior footings in unheated areas:

36 inches

Interior footings in heated areas:

12 inches

Estimated Total Settlement from

Structural Loads

Less than about 1 inch

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. A factor of safety of 3 has been applied.

2. Values provided are for maximum loads noted in Project Description. Additional geotechnical consultation will be necessary if higher loads are anticipated.

3. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

4. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Frictional resistance for granular materials is dependent on the bearing pressure which may vary due to load combinations. For fine-grained materials, lateral resistance using cohesion should not exceed ½ the dead load.

5. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

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Facilities | Environmental | Geotechnical | Materials 16

Sensitive soils exposed at the surface of footing excavations may require surficial compaction with hand-held dynamic compaction equipment prior to placing engineered fill, steel, and/or concrete. Should surficial compaction not be adequate, construction of a working surface consisting of either crushed stone or a lean concrete mud mat may be required prior to the placement of reinforcing steel and construction of foundations.

If unsuitable bearing soils are observed at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The lean concrete replacement zone is illustrated on the sketch below.

Overexcavation for engineered fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with approved engineered fill that is placed and compacted, as recommended in the Earthwork section.

Facilities | Environmental | Geotechnical | Materials 17

Floor Slabs

Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

Again, existing fill materials, GeoModel Layer 2, were observed at the site to depths of up to 3.5 feet below existing grade. As previously described, any existing fill present beneath floor slabs should be completely removed and replaced with engineered fill.

Floor Slab Design Parameters

Item Description

Floor Slab

Support1

Use 4 inches of aggregate base course meeting material specifications of ACI 302

Subgrade compacted to recommendations in Earthwork

Estimated Modulus of Subgrade

Reaction 2

125 pounds per square inch per inch (psi/in) for point loads

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, when the project includes humidity-controlled areas, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut contraction joints should be placed in the slab to help determine the location and extent of cracking. For additional recommendations, refer to the ACI Design Manual. Joints or cracks should be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks

Facilities | Environmental | Geotechnical | Materials 18 beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient contraction joints, appropriate reinforcing or other means.

Settlement of floor slabs supported on existing fill, and/or weak soils cannot be accurately predicted but could be larger than normal and result in some cracking. Mitigation measures, as noted in Existing Fill within Earthwork, are critical to the performance of floor slabs. In addition to the mitigation measures, the floor slab can be stiffened by adding steel reinforcement, grade beams, and/or post-tensioned elements.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed, and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should observe the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

Lateral Earth Pressures

Design Parameters

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to values indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction, and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The “at-rest” condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

Facilities | Environmental | Geotechnical | Materials 19

Lateral Earth Pressure Design Parameters

Earth

Pressure

Condition 1

Coefficient for

Backfill Type 2

Surcharge

Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

Active (Ka) Granular - 0.33

Fine Grained - 0.41

(0.33)S

(0.41)S

(40)H

(50)H

(80)H

(85)H

At-Rest (Ko) Granular - 0.50

Fine Grained - 0.58

(0.50)S

(0.58)S

(60)H

(70)H

(90)H

(95)H

1. For active earth pressure, wall must rotate about base, with top lateral movements

0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance. Fat clay or other expansive soils should not be used as backfill behind the wall.

2. Uniform, horizontal backfill, with a maximum unit weight of 120pcf for cohesive soils and 120pcf for granular soils.

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage for Below-Grade Walls below. “Submerged” conditions are recommended when drainage behind walls is not incorporated into the design.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 degrees from vertical for the active case.

Footings, floor slabs or other loads bearing on backfill behind walls may have a significant influence on the lateral earth pressure. Placing footings within wall backfill and in the zone of active soil influence on the wall should be avoided unless structural analyses indicate the wall can safely withstand the increased pressure.

Facilities | Environmental | Geotechnical | Materials 20

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity type concrete walls. These recommendations are not applicable to the design of modular block

- geogrid reinforced backfill walls (also termed MSE walls). Recommendations covering these types of wall systems are beyond the scope of services for this assignment.

However, we would be pleased to develop a proposal for evaluation and design of such wall systems upon request.

Subsurface Drainage for Below-Grade Walls

A perforated rigid plastic drain line installed behind the base of walls and extending below adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage to daylight or to a sump pit and pump. The drain line should be surrounded by clean, free-draining granular material having less than 5% passing the No. 200 sieve, such as No. 57 aggregate. The free-draining aggregate should be encapsulated in a filter fabric.

The granular fill should extend to within 2 feet of final grade, where it should be capped with compacted cohesive fill to reduce infiltration of surface water into the drain system.

As an alternative to free-draining granular fill, a prefabricated drainage structure may be used. A prefabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion and is fastened to the wall prior to placing backfill.

Facilities | Environmental | Geotechnical | Materials 21

Pavements

Pavement Subgrade Support Characteristics

For pavement design by others, we recommend that a subgrade California Bearing Ratio, CBR, of 4 be used for the asphaltic concrete pavement designs. We recommend that a modulus of subgrade reaction of 125 pci be used for the portland cement concrete pavement designs. These values were empirically derived based upon our experience with the subgrade soils encountered at the site and our expectation of the quality of the subgrade as prescribed by the Site Preparation conditions as outlined in Earthwork.

Frost Considerations

The soils on this site are frost susceptible, and small amounts of water can affect the performance of the slabs on-grade, sidewalks, and pavements. Exterior slabs should be anticipated to heave during winter months. If frost action needs to be eliminated in critical areas, we recommend the use of non-frost susceptible (NFS) fill or structural slabs (for instance, structural stoops in front of building doors). NFS materials are generally those that contain less than 20% of the material passing the number 200 sieve. Placement of NFS material in large areas may not be feasible; however, the following recommendations are provided to help reduce potential frost heave:

1. Provide surface drainage away from the building and slabs, and toward the site storm drainage system.

2. Install drains around the perimeter of the building, stoops, below exterior slabs and pavements, and connect them to the storm drainage system.

3. Grade clayey subgrades, so groundwater potentially perched in overlying more permeable subgrades, such as sand or aggregate base, slope toward a site drainage system.

4. Place NFS fill as backfill beneath critical areas of this project.

As an alternative to extending NFS fill to the full frost depth, consideration can be made to placing extruded polystyrene or cellular concrete under a buffer of at least 2 feet of

NFS material.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Variations will occur between exploration point locations or due to the modifying effects

Facilities | Environmental | Geotechnical | Materials 22 of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the Geotechnical

Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design…