Attach II - Final Geotechnical Report - 610A4-23-101.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report

6104A4-23-101 Upgrade Campus Electrical Systems

Fort Wayne, Allen County, Indiana September 21, 2020

Terracon Project No. N1205233

Prepared for:

FFE, Inc.

Cincinnati, Ohio

Prepared by:

Terracon Consultants, Inc.

Cincinnati, Ohio

Re: Geotechnical Engineering Report 610A4-23-101 Upgrade Campus Electrical Systems 2121 Lake Avenue Fort Wayne, Allen County, Indiana Terracon Project No. N1205233

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

SEISMIC CONSIDERATIONS

FLOOR SLABS

LATERAL EARTH PRESSURES

PAVEMENTS

GENERAL COMMENTS

FIGURES

Note: This report was originally delivered in a web-based format. Orange 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

GeoReport logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

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INTRODUCTION

Geotechnical Engineering Report 610A4-23-101 Upgrade Campus Electrical Systems

2121 Lake Avenue

Fort Wayne, Allen County, Indiana Terracon

Project No. N1205233

September 21, 2020

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed 610A4-23-101 Upgrade Campus Electrical Systems project to be located at the Veterans Affairs Medical Center at 2121 Lake Avenue in Fort

Wayne, Allen County, Indiana. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Foundation design and construction

■ Groundwater conditions ■ Floor slab design and construction

■ Site preparation and earthwork ■ Seismic site classification per IBC

■ Demolition considerations ■ Lateral earth pressures

■ Excavation considerations ■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of six test borings to depths ranging from approximately 25 to 35 feet below existing site grades.

Maps showing the site and boring locations are shown in the Site Location and Exploration

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

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 the existing Veteran’s Affairs Medical Center at

2121 Lake Avenue in Fort Wayne, Allen County, Indiana.

See Site Location

Existing

Improvements

Existing Veteran’s Affairs Medical Center with existing 1- to 5-story buildings, paved surface parking lots and paved access drives.

610A4-23-101 ■ Fort Wayne, Allen County, Indiana

September 21, 2020 ■ Terracon Project No. N1205233

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Item Description

Current Ground

Cover

Proposed sites are currently covered with Portland cement pavement, exposed earth and grass.

Existing Topography

Elevations within the Building 1 project site range from about Elevation 768 to 770 feet and are nearly level. Elevations within the Building 2 project site range from about Elevation 756 feet to 767 feet. Grades gradually decrease from east to west across the Building 2 site.

Geology

Our experience near the vicinity of the project site, previous geotechnical studies (performed by others) and our current borings indicate the site is in a glaciated area. The subsurface soils typically consist of variable depths of man-placed fill underlain by natural clay and granular soils and then glacial till and outwash soils. The existing fill and upper native soils near Building

No. 1 have high silt and sand contents and vary between cohesive and cohesionless sand and silt soils. The site is mapped as having Devonian

Age bedrock underlying the natural soil. Bedrock was not encountered within the current exploration depths.

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Information Provided

■ E-mail and telephone conversations with FFE, Inc. in June 2020 and

August 2020.

■ Building 1 Schematic Design, Drawing A101, undated by FFE, Inc.

■ Building 2 Schematic Design, Drawing A101, undated by FFE, Inc.

■ Grading Concept, dated 8/8/2019 provided by FFE, Inc.

■ Foundation Plan, Design Drawing SB101, undated by FFE, Inc.

■ Slab and Foundation Plan, Design Drawing 1-SB101, undated by FFE, Inc.

■ Email from FFE, Inc. on September 9, 2020 regarding column loads and building construction.

Project Description

The project consists of two building additions. Building 1 addition is located on the south side of existing Building No. 1 and will be an electrical addition.

Building 2 addition will be located on the south side of existing Building No. 2, which will contain emergency power generators. The project also includes replacing 3 boilers within existing Building 2.

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Proposed Structure

The Building 1 addition has plan dimensions of about 48 feet by 66 feet and initially will be a single-story, slab-on-grade, below-grade structure with a walk-out on the south wall. The Building 1 addition could eventually be expanded to include 5-stories. Building 1 addition will require foundation walls/wing walls on the south side extending east and west of the building addition. Future plans could include the removal of the wing walls if possible future additions are constructed along the south side of existing Building 1.

The Building 2 addition includes a one-story building addition with plan dimensions of about 36 feet by 127 feet. The Building 2 addition will be slab-on-grade (non-basement). Foundation walls will be required on the east side of the building.

Building Construction

Anticipated building construction:

Steel frame for above grade portions

Reinforced concrete subsurface walls

Concrete and masonry bearing walls

Slab-on-grade

Finished Floor

Elevation

The proposed Building No. 1 addition finished floor elevation is Elevation

760.0 feet. Existing finished floor elevation of Building No. 2 is about Elevation

758.97 feet, based on provided topographic information.

Maximum Loads

(need to be confirmed)

■ Columns Building 1: 280 to 475 kips

■ Columns Building 2: 100 to 150 kips

■ Walls: 3 to 6 kips per linear foot (klf)

■ Slabs: 150 pounds per square foot (psf)

■ Building 1 Equipment loads:

■ Unit Substation – 22,450 lbs.

■ 208V Gear – 41,145 lbs.

■ 480V Gear – 56,860 lbs.

■ ATS – 3,600 lbs.

■ Building 2 Equipment Loads:

■ Generators – 55,200 lbs.

■ Generator accessories – 18,400 lbs.

■ Electrical Equipment – 7,500 lbs.

■ DA/Condensate tank – 25,000 lbs.

■ Water Softener Package – 5,000 lbs.

Grading/Slopes Up to 10 feet of cut at Building No. 1 addition and up to about 8 feet of cut and

3 feet of fill at Building No. 2 addition will be required to develop final grade.

Below-Grade

Structures

Foundation walls up to about 10 feet in height will be required for the Building

No. 1 addition. Foundation walls up to 8 feet high at the east end of the

Building No. 2 addition may be required to achieve the proposed finished floor elevation.

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Free-Standing

Retaining Walls

Wing walls (retaining walls) up to about 8 to 10 feet in height will be required along to the west and east sides of the Building No. 1 south wall to support proposed cut for the building and allow the south wall to be constructed as a walk-out at finished grade. If future additions are constructed along the south side of existing Building 1, these retaining walls may get removed.

Pavements Repair of existing Portland cement concrete pavement will likely be required

No pavement loading has been provided at this time.

Estimated Start of

Construction Spring/summer 2021

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 site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs can be found in the

Exploration Results section and the GeoModel can be found in the Figures section 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.

Model Layer Layer Name General Description

Existing Fill Clayey sand, poorly graded sand and silty clay with sand, with various gravel and clay seams, brown some gray

Upper

Cohesionless

Silty sand, clayey sand, and silt, trace interbedded clay seams, brown to gray, loose to medium dense

3 Upper Cohesive

Silty clay, lean clay or sandy lean clay with various amounts of sand and silt seams to pockets, trace gravel, brown, gray or dark gray, stiff to very stiff

4 Outwash

Silty sand or poorly graded sand, trace gravel, fine to medium grained, some coarse grained sand, brown and gray, very dense with occasional medium dense seams

No records have been provided to indicate the degree of control used during placement of the existing fill soils. The N-values from the borings indicates that the consistency of the existing fill is variable. As a result, it is our opinion that the existing fill should be considered undocumented in nature and is not considered suitable for direct foundation or floor slab support.

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The upper cohesionless and cohesive soils appear to be glacial in nature. Several of the cohesive soils appear to be glacial till, which is mixture of clay, silt, sand and gravel that was deposited beneath the glacial ice and is overconsolidated in nature. It is common in glacial till soils to have seams, layers or pockets of silt, sand or gravel sandwiched between the lower permeability silty clay, sandy lean clay or lean clay soils.

Groundwater Conditions

The boreholes were observed while drilling and immediately after completion for the presence and level of groundwater. The water levels observed in the boreholes can be found on the boring logs in

Exploration Results and are summarized below.

Boring

Approximate Depth to

Groundwater while Drilling

(feet)

Approximate Depth to

Groundwater Immediately after Drilling (feet)

B20-1A 11.5 12

B20-2 18.5 Not observed

B20-3 23.5 Borehole Caved Dry at 25

B20-4 23.5 Borehole Caved Dry at 23

B20-5 23.5 Borehole Caved Dry at 24

B20-6 20 17

1. Below ground surface

The short-term groundwater levels summarized above do not necessarily indicate stable ground water levels. Long-term observations in piezometers, or observation wells sealed from the influence of surface water, are often required to define groundwater levels in profiles of this type. Perched groundwater is often encountered at the existing fill/natural soil interface, within existing fill or within native granular soil seams/layers. As a result, perched water could be encountered during construction.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. There is a potential for perched water in the granular seams in the natural soils and at the existing fill/natural soil interface. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

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GEOTECHNICAL OVERVIEW

The encountered sandy and silty native soils and existing fill soils encountered in the borings are subject to disturbance due to construction and foot traffic when exposed during construction, particularly after precipitation events. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter or wetter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist.

Temporary and permanent drainage controls should be established as early as possible during construction to limit the amount of surface water directed within the construction areas. In addition, over excavation and placement of a minimum 12-inch thick compacted crushed stone

(crushed limestone or other crushed rock material with angular faces) or a minimum 4-inch thick lean concrete mudmat to protect and seal the silty and sandy soils encountered in the borings would improve the trafficability of the on-site soils from construction and foot traffic during construction. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

The soils that will support the foundations are glacial soils and have a high sand and silt content.

The glacial soils are generally lean clay or sandy lean clay with seams, layers and pockets of silt, silty sand and sand. Again, these soils have the potential to become easily disturbed during construction activities after the bearing soils are exposed. Overexcavation of the bearing soils 3 to 4 inches below the design bearing elevation and pouring a lean concrete mudmat to protect the approved bearing soils should be considered to limit disturbance of the foundation soils by foot and construction activities after the bearing soils are approved. Also, if silt and sand soils are encountered at the bearing elevation, extra care will need to be taken when excavating these soils to limit disturbance of the soils, which could result in unplanned undercuts at foundation locations. Where undocumented fill soils are encountered at the foundation locations, these existing fill soils will need to be undercut to expose firm native soils and bear at a lower elevation or be replaced with either lean concrete backfill or compacted structural backfill. The Shallow

Foundations section addresses support of the building additions and equipment mat foundations bearing on native firm soils or engineered fill overlying native firm soils. The Floor Slabs section addresses slab-on-grade support of the building additions.

The planned retaining walls located east and west of the planned Building 1 Addition will need to be supported on firm native soil or new structural fill overlying firm native soil. The encountered undocumented fill at our test boring locations varied in depth from about 6 to 11 feet below existing grade. The existing fill in the vicinity of the planned retaining walls was described as clayey sand, poorly graded sand or silty clay with sand. Temporary excavations through the clayey sand and sand soils will not stand vertically to allow trenching through the undocumented fill and replacement with lean concrete backfill. As a result, it is anticipated that the excavation for the

Building 1 Addition will need to be expanded laterally and safe temporary slopes constructed in the existing fill soils to allow the retaining wall foundations to be constructed at a lower elevation on firm native soils or on structural fill placed and compacted over the firm native soils. Either

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These clayey sand and sandy soils can also ravel and slough, which can result in undermining of adjacent structures. Any structures adjacent to temporary excavations will need to consider potential undermining of the foundation soils. These soils may also impact the type of underpinning/shoring required for the Building 2 Addition, where it is anticipated the eastern end of the addition will extend below the existing Building 2 foundations.

It is anticipated that some areas of existing pavements will need to be replaced after the planned building additions are completed. The Pavements section addresses the recommended design subgrade support values for both flexible and rigid pavement systems.

Support of pavements on or above existing fill materials is discussed in this report. However, even with the recommended construction procedures, there is inherent risk for the owner 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. To take advantage of the cost benefit of not removing the entire amount of undocumented fill, the owner must be willing to accept the risk associated with building over the undocumented fills following the recommended reworking of the material. Should this be the case, development can be supported on a shallow foundation system.

The General Comments section provides an understanding of the report limitations.

EARTHWORK

Earthwork is anticipated to include clearing and grubbing, removal of existing pavements, excavations, and 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.

Site Preparation

At the proposed Building 1 addition prior to performing the required excavation, it is anticipated that the west end of Building 16 will need to be demolished and underground utilities will need to be rerouted accordingly. In addition, any air conditioning units or other equipment in the vicinity of the new addition and within the anticipated excavation area for the new addition will need to be temporarily or permanently relocated beyond the limits of the anticipated excavation for the new addition. Any vegetation and root mat should be removed from the excavation area. Complete stripping of the topsoil should be performed within the limits of the anticipated excavation area.

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At the proposed Building 2 addition, site preparation is anticipated to start with removal of existing pavements and relocation or removal of existing underground utilities within the planned construction area. In addition, prior to performing the required excavation at the east end of the proposed addition, all existing vegetation and root mat should be removed. Complete stripping of the topsoil should be performed in the proposed building and planned excavation area. Any excavations resulting from the relocation of underground utilities should be backfilled with structural fill as recommended later in this report.

Several areas of the exposed subgrade are anticipated to consist of silt or sand soils. Proof-rolling these types of soils with rubber-tired construction equipment is not recommended. The subgrade should be proofrolled with a minimum 20-ton, smooth-drum roller without vibration. The proofrolling should be performed under the direction of the Geotechnical Engineer. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should either be removed and replaced with structural fill as recommended later in this report. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

Due to the high sand and silt content of the anticipated subgrade soils at both building additions, consideration should be given to either placing a minimum 4-inch thick lean concrete mudmat or a 12-inch thick protective layer of compacted INDOT No. 53 crushed rock with angular faces (no rounded river gravel is recommended).

Existing Fill

As noted in Geotechnical Characterization, all the borings encountered existing fill to depths ranging from about 3.5 to 11 feet below existing grades. The fill appears to have been placed with some compactive effort, but we have no records to indicate the degree of control. The planned excavation in the Building 1 Addition area will likely remove most if not all the undocumented fill, but some areas of existing fill may remain after the area is cut to grade. In the Building 2 Addition area it is anticipated that some undocumented fill will be present once the existing pavement is removed and the east end of the addition is cut to grade. All existing fill within the proposed addition footprints and at least 5 feet beyond the addition footprints should be completely undercut until firm native soil is exposed. Once undocumented fill materials have been removed, the entire area should be proofrolled with a heavy, smooth drum roller, to aid in delineating areas of weak or otherwise unsuitable soil. Once unsuitable materials have been remediated, and the subgrade has passed the proofroll test, the existing and undocumented fill that was removed can be evaluated for reuse as structural fill.

Support of pavements, on or above existing fill soils, is discussed in this report. However, even with the recommended construction procedures, there is inherent risk for the owner that compressible fill or unsuitable material, within or buried by the fill will, not be discovered. This risk

Responsive ■ Resourceful ■ Reliable 9 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, as previously discussed. Areas of soft, weak or otherwise unsuitable material should be undercut and replaced with either new structural fill or suitable, existing on site materials.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill is material used below, or within 10 feet of structures, pavements or constructed slopes. General fill is material used to achieve grade outside of these areas. Earthen materials used for structural and general fill should meet the following material property requirements:

Soil Type USCS Classification Acceptable Parameters (for Structural Fill)

Low Plasticity

Cohesive

CL, CL-ML,

SM

Liquid Limit less than 40 Plasticity index less than 20

High Plasticity

Cohesive

CH, MH Not recommended at this site

Granular

GW, GP, GM, GC,

SW, SP, SM

Less than 10% Passing No. 200 sieve

On-Site Soils

CL, CL-ML, SP, SM,

SC and ML

The encountered CL, CL-ML, SP , SM and SC soils are anticipated to be acceptable as new structural fill materials, provided they are adequately moisture conditioned and compacted using suitable compaction equipment. The ML soils were encountered in one of the borings, but could be encountered at other locations and can be very difficult to work with, since slight variations in moisture content can cause these soils to become unstable. If encountered, silt soils should be wasted off-site or in non-structural areas, if possible.

1. Structural and general fill should consist of approved materials free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

2. CH or MH soils are not recommended as fill materials at this site.

Fill Compaction Requirements

Structural and general fill should meet the following compaction requirements.

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Item Structural Fill General Fill

Maximum Lift Thickness

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

4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used

Same as Structural fill

Minimum Compaction

Requirements 1, 2

98% of maximum dry density within all building areas, beneath foundations and in all pavement areas.

95% of max.

Water Content

Range

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

Granular: -3% to +3% of optimum

As required to achieve min.

compaction requirements

1. Maximum dry 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).

Excavation

About 9 to 11 feet of excavation is anticipated to reach the Building 1 Addition subgrade elevation and about 8 to 9 feet of excavation is anticipated to achieve the subgrade elevation near the east end of the Building 2 Addition. The excavation for the building additions can be accomplished with conventional excavation equipment, such as track hoes, backhoes, etc. One item that will need to be considered is that a large amount of the existing fill was described as clayey sand, which will likely become unstable when subjected to wheel-supported construction equipment, such as dump trucks. Temporary haul roads to support the wheeled-construction equipment will likely be required where existing pavements will not remain or there are no paved areas.

Based on current plans, the finished floor at the east end of the proposed Building 2 Addition (FFE is about 759 feet) extends below the existing Building 2 finished floor elevation (FFE is about

767.8 feet). As a result, the proposed Building 2 Addition excavation will extend about 9 feet below the existing Building 2 finished floor and an estimated 5 to 6 feet below the existing Building

2 footings at the east end of the building. Provided archive drawings (Sheet A2 dated November

1947) indicate that the bearing elevation of the footings at this end of existing Building 2 range from about Elevation 764.0 feet to 757.0 feet. Where the excavation for the Building 2 Addition extends below the existing building footings, this portion of the proposed excavation will need to be shored and/or the footings underpinned. Typically, shoring and underpinning is designed by the contractor or his subcontractor. Alternatively, the designers could step the new floor load down in this area and step the proposed footings to avoid undermining the existing building footings. The new footings should not extend below an imaginary 2H:1V line extending from the bearing elevation of the existing building footings. Prior to commencing construction, the contractor should perform test pits to confirm the actual elevation of the existing building footings.

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The following tables contain recommended soil parameters that can be used for design of shoring and/or underpinning based upon soil conditions encountered in Boring B20-2. The design will need to consider the surcharge loads of the existing Building 2 footings, floor loads and any equipment loads. The contractor should be required to submit the design for review by the project design team prior to construction. Review of the shoring/underpinning drawings should not relieve the contractor of his responsibility to properly design and construct the shoring/underpinning system.

Recommended Soil Parameters and Earth Pressure Coefficients for for Temporary Shoring System Design – Boring B20-2

Material

Angle of

Internal

Friction, ()

Total Unit

Weight

(pcf)

Ko

(At-Rest)

Ka

(Active)

Kp

(Passive)

Existing fill - sand 30° 120 0.50 0.33 3.0

Clayey Sand (loose) 28° 120 0.53 0.36 2.77

Lean Clay with Sand (stiff to very stiff)

28° 125 0.53 0.36 2.77

1. For level backslope; no hydrostatic pressures. Need to include effects of adjacent surcharge loads in the lateral earth pressures for design.

Recommended Soil Parameters for for Underpinning System Design Boring B20-2

Material

Angle of

Internal

Friction, ()

Total Unit

Weight

(pcf)

Undrained

Cohesion (psf)

Clayey Sand (loose) 28° 120 --

Lean Clay with Sand (stiff to very stiff)

-- 125 1,500

Poorly Graded Sand (dense to very dense)

28° 130 0.56

Gray soft shale and limestone 32° 140 0.50

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. Based on the borings, a large portion of the soils at the site will be classified as

Type “C” and this will need to be taken into the construction plan and construction limits.

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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

Due to the sandy nature of the soils anticipated in most of the excavations, it will be important to direct surface water run-off away from the temporary excavations, in order to limit erosion of the temporary slopes. Erosion can destabilize temporary slope and result in undermining and/or result in sloughing of temporary slopes.

The contractor should also make allowances for temporary sumps in the excavation areas to remove precipitation and other sources of water within the excavation areas. The borings did not encounter groundwater seepage within the anticipated excavation depths. However, glacial soils generally contain cohesionless silt, sand and gravel pockets, seams or layers sandwiched between less permeable cohesive soil , which can contain perched water. Depending on the areal extent of and the amount of recharge to these cohesionless soils, perched water can become an issue during excavation, particularly after precipitation events and during wetter seasons of the year.

Utility Trench Backfill

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 structural fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the building additions 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 into approved storm water collection systems or alternatively onto splash blocks at a distance of at least 10 feet from the building.

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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 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

Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of floor slabs. 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.

The encountered sandy and silty native soils and existing fill soils encountered in the borings are subject to disturbance due to construction and foot traffic when exposed during construction, particularly after precipitation events, if possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter and wetter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist.

Temporary and permanent drainage controls should be established as early as possible during construction to limit the amount of surface water directed within the construction areas. In addition, over excavation and placement of a minimum 12-inch thick compacted crushed stone

(crushed limestone or other crushed rock material with angular faces) or a minimum 4-inch thick lean concrete mudmat to protect and seal the silty and sandy soils encountered in the borings would improve the trafficability of the on-site soils from construction and foot traffic during construction.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer.

Monitoring should include documentation of adequate removal of vegetation and topsoil, proofrolling, and mitigation of areas delineated by the proofroll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, until approved 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 and 5,000 square feet in pavement areas. One density and water content test should be performed for every 50 linear feet of compacted utility trench backfill.

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In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. If unanticipated conditions are encountered, 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 building column and wall foundations for the Building 1 Addition and the Building 2 Addition. For the retaining walls planned at the east and west sides of the south Building 1 Addition wall, the method of construction will determine the design bearing foundations for these retaining walls. If the retaining wall foundation is lowered to bear on firm native soils, the recommendations for the Building 1 Addition apply. If the retaining foundation is stepped up away from the Building 1 Addition and supported on new compacted structural fill, then the recommendations for the Building 2 Addition apply. See the further discussion in the Foundation Construction Considerations.

Design Parameters – Compressive Loads – Building 1 Addition

Item Description

Maximum Net Allowable Bearing pressure

5,000 psf (foundations bearing within undisturbed soils)

3,500 psf (foundation bearing on undisturbed soils)

Required Bearing Stratum

Native at least stiff lean clay soil or medium dense granular soil or medium silt soil

Minimum Foundation Dimensions Columns: 30 inches

Continuous: 18 inches

Ultimate Passive Resistance

(equivalent fluid pressures)

250 pcf (cohesive backfill)

350 pcf (granular backfill)

Ultimate Coefficient of Sliding Friction

0.3 (native soil)

Minimum Embedment below

Finished Grade

Exterior footings in unheated areas: 42 inches

Interior footings in heated areas: 12 inches

Estimated Total Settlement from

Structural Loads

Less than about 1 inch

Estimated Differential Settlement 2, 7

About 1/2 of total settlement

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1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied. Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description.

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

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face. The recommended values are only applicable below frost depth (42 inches) for exterior footings and below a depth of 12 inches below finished floor elevation in interior areas.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. 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.

7. Differential settlements are as measured over a span of 50 feet or between adjacent column footings.

Design Parameters – Compressive Loads – Building 2

Maximum Net Allowable Bearing pressure

3,500 psf (foundations bearing within undisturbed soils)

2,500 psf (foundation bearing on undisturbed soils)

Native at least stiff lean clay soil or medium dense granular soil or medium silt soil or new structural fill overlying native firm soil

Minimum Foundation Dimensions Columns: 30 inches

Continuous: 18 inches

250 pcf (cohesive backfill)

350 pcf (granular backfill)

Ultimate Coefficient of Sliding Friction

0.3 (native soil or new structural fill)

Minimum Embedment below

Exterior footings in unheated areas: 42 inches

Estimated Total Settlement from

About 1/2 of total settlement

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1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied. Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description.

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

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face. The recommended values are only applicable below frost depth (42 inches) for exterior footings and below a depth of 12 inches below finished floor elevation in interior areas.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. 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.

7. Differential settlements are as measured over a span of 50 feet or between adjacent column footings.

Design Parameters – Mat Foundations

These recommendations are applicable to the anticipated mat foundation supporting the generators and the electrical equipment at the additions at Buildings 1 and 2.

Item Description

Foundation Subgrade Modulus (Building

1)

15 psi/inch (limit mat foundation net contact pressure to 500 psf or less)

Foundation Subgrade Modulus (Building

2)

10 psi/inch (limit mat foundation net contact pressure to 750 psf or less)

Natural stiff cohesive soil, natural medium dense cohesionless soil or new structural fill overlying natural firm soils.

250 pcf (native soil or compacted fill)

Ultimate Coefficient of Sliding Friction

0.3 (native soil and new structural fill)

Minimum Embedment below

Exterior footings: 42 inches

Estimated Total Settlement from

About 1/3 of total settlement along the mat foundation length

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1. The net contact pressure is the pressure in excess of the minimum surrounding overburden pressure at the mat foundation base elevation. Values assume level grades adjacent to mat foundation.

2. Values provided are for maximum loads noted in Project Description.

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

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations.

7. Differential settlements are as measured over the length of the mat foundation and assume rigid foundation conditions.

At the mat foundations, the structural engineer will need to evaluate the foundation thickness required to distribute the load of the equipment across the mat area. Where mat foundations abut the planned floor slabs, there should be a construction joint provided between the mat foundation perimeter and the adjacent building floor slab.

Construction Adjacent to Existing Buildings

Differential settlement between the additions and the existing building is expected to approach the magnitude of the total settlement of the addition. Expansion joints should be provided between the existing building and the proposed addition to accommodate differential movements between the two structures. Underground piping between the two structures should be designed with flexible couplings and utility knockouts in foundation walls should be oversized, so minor deflections in alignment do not result in breakage or distress. Care should be taken during excavation adjacent to existing foundations, to avoid disturbing existing foundation bearing soils.

New footings should bear at or near the bearing elevation of immediately adjacent existing foundations. Depending upon their locations and current loads on the existing footings, footings for the new addition could cause settlement of adjacent walls. To reduce this concern and risk, clear distances at least equal to the new footing widths should be maintained between the addition’s footings and footings supporting the existing building.

We understand existing foundations will not support additional load from the walls of the new additions. If this is not correct, we request that we be given the opportunity to evaluate the additional load being applied to the existing footings, which will require that the existing estimated footing loads be provided.

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Design Parameters - Uplift Loads

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils. As illustrated on the subsequent figure, the effective weight of the soil prism defined by diagonal planes extending up from the top of the perimeter of the foundation to the ground surface at an angle, , of 20 degrees from the vertical can be included in uplift resistance.

The maximum allowable uplift capacity should be taken as a sum of the effective weight of soil plus the dead weight of the foundation, divided by an appropriate factor of safety. A maximum total unit weight of 100 pcf should be used for the backfill. This unit weight should be reduced to

40 pcf for portions of the backfill or natural soils below the groundwater elevation.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction 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.

The native soils at the site have a high sand and silt content. These soils tend to become easily disturbed when subjected to foot and construction traffic, particularly after precipitation events. In order to limit disturbance of foundations soils after excavation and approval, it would be beneficial to place a minimum 3- to 4-inch-thick lean concrete mud mat to protect the approved bearing soils, particularly for mat foundations where the bearing soils will be exposed for longer periods of time while the reinforcing steel is tied and placed in the foundation excavation. However, the

Responsive ■ Resourceful ■ Reliable 19 lean concrete mud mats would also help protect the bearing surface in column and wall footing excavations, as well.

If silt and sand soils are encountered at the design bearing elevation, the use of excavation buckets without teeth help limit disturbance of the bearing soils. Excavating the soil by peeling the soil in smaller thicknesses or lift, as compared to taking the material out in large chunks or thicknesses will also help limit the disturbance to the exposed sandy or silty foundation soils. If the soils are dry, the surface of the exposed sandy and silty soils can be compacted with a vibratory plate compactor.

If unsuitable bearing soils are encountered at the base of the planned footing excavation (existing fill, water softened soils or disturbed soils), 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. This is illustrated on the sketch below.

Over-excavation for structural fill placement below footings should be conducted as shown below.

The over-excavation should be backfilled up to the footing base elevation, with granular soils such as INDOT No. 53 crushed limestone placed, as recommended in the Earthwork section.

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Retaining Wall Building 1 Addition Foundation Construction Considerations

At the retaining wall footings extending east and west of the south Building 1 Addition wall, it is anticipated that existing fill, which is unsuitable for direct support of the retaining wall footings will be exposed. It is anticipated that the existing fill will need to be undercut and replaced. The encountered clayey sand, silty sand and sandy existing fill soils will need to be properly laid back to safe slopes per OSHA guidelines or need temporary support during construction. It may be advantageous to extend the proposed lower level excavation of the Building 1 Addition to the limits of the proposed retaining walls or to a level where native firm soil is exposed and construct the retaining wall footings at the lower level and backfill the retaining walls. Alternatively, the excavation below the retaining wall footings could be backfilled with structural backfill, after firm native soils are exposed, which would allow the retaining wall footings to be stepped as the retaining walls extend away from the new building addition. Either method will require larger than normal excavation volumes to allow safe egress into the excavation and larger quantities of structural backfill.

SEISMIC CONSIDERATIONS

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

Category. Site Classification is required to determine the…