GeoTech Rpt-Terracon.pdf

Proposal Cover Page

F-35 Consolidated Weapons Training Facility – JAX ANG Geotechnical Engineering Report

March 5, 2024 | Terracon Project No. EQ235134

Prepared for:

Parsons Corporation 100 W. Walnut Street Pasadena, California 91124-0001

8001 Baymeadows Way, Suite 1

Jacksonville, FL 32256 P (904) 549-7376

Terracon.com

Facilities | Environmental | Geotechnical | Materials

This item has been digitally signed and sealed by Thomas E. Selfridge, P.E. on the date adjacent to the seal. Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies.

Report Cover Letter to Sign

March 5, 2024

Parsons Corporation 100 W. Walnut Street Pasadena, California 91124-0001

Attn: Mr. Zachary Dineen P: (315) 751-4449 E: Zachary.Dineen@Parsons.com

Re: Geotechnical Engineering Report F-35 Consolidated Weapons Training Facility – JAX ANG 14300 Fang Drive Jacksonville, Florida 32218 Terracon Project No. EQ235134

Dear Mr. Dineen:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PEQ235134 dated September 14, 2023. This Geotechnical Engineering Report presents the results of the subsurface exploration, laboratory testing, engineering analyses and geotechnical engineering recommendations with regard to the design and construction of the proposed improvements for the F-35 CWTF project at the Florida Air National Guard base in Jacksonville, Florida.

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 Consultants, Inc.

Tom D. Hallahan Thomas E. Selfridge, P.E.

Project Manager Senior Geotechnical Engineer Geotechnical Services Florida P.E. No.: 41199

F-35 Consolidated Weapons Training Facility – JAX ANG | Jacksonville, Florida 32218

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i Introduction Project Description Site Conditions Geotechnical Characterization

General Area Geology Soil Survey GeoModel and Site Subsurface Conditions Groundwater Field Electrical Resistivity

Geotechnical Overview Earthwork

Demolition Site Preparation

General Site Drainage Surface Water Control Surficial Soil Compaction (Subgrade Preparation) Proofrolling

Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Earthwork Construction Considerations Groundwater Considerations Construction Observation and Testing

Shallow Foundations Design Parameters – Compressive Loads Design Parameters – Overturning and Uplift Loads Seismic Site Class Foundation Construction Considerations

Floor Slabs Floor Slab Design Parameters Floor Slab Construction Considerations

Lateral Earth Pressure Design Considerations General Comments

Figures GeoModel Generalized Subsurface Profile

Facilities | Environmental | Geotechnical | Materials ii

Attachments

Exploration and Testing Procedures 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.

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Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic 1 Overview Statement 2

Project Description

New structures with total plan area of 22,696 square feet including new Weapons Release Systems Shop (WRSS) and Weapons Loading Training Hangar (WLT)

Estimated maximum loads: columns 140 kips, bearing wall loads: 5 kips/ft, floor slab live loads 250 psf

Minimal cut or fill to achieve final grade

Minor excavation other than foundation construction and utility installation

Geotechnical Characterization

The soil borings generally encountered loose to dense fine sand of varying fines content, (Unified Soil Classification System of SP, SP- SM, SP-SC,SM, SC) to an approximate depth of 25 to 26 feet below the existing ground surface, underlain by a layer of very loose silty clayey sand and very soft silty clay (SC, CL, CH) to an approximate depth of 30 feet. The borings then typically encountered medium dense to very dense sandy soils (SP, SP-SM, SM, SC) to an approximate depth of 63 to 68 feet below the existing ground surface, underlain by stiff to hard lean clay with silt and trace phosphates to the deepest termination depth of approximately 100 feet beneath the ground surface. Groundwater observed at an approximate depth range of 3.5 to 5 feet below the existing ground at time of drilling.

Earthwork Earthwork is anticipated to include demolition, excavations, and engineered fill placement as required to achieve site grading.

Shallow Foundations

Shallow foundations are recommended for building support.

Allowable bearing pressure = 3,000 psf Expected settlements: < 3/4-inch total, < 1/2-inch differential

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed new Weapons Loading Training Hangar (WLT) and Weapons Release Systems Shop (WRSS) to be located at the Florida Air National Guard Base, located at 14300 Fang Drive in Jacksonville, Florida 32218. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ SPT Boring logs with field and laboratory data

■ Groundwater levels observed during exploration

■ Site Location and Exploration Plans

■ A Generalized Subsurface Profile

■ Subsurface exploration and laboratory testing procedures

■ Description of subsurface conditions

■ Results of all laboratory testing performed

■ Recommendations for shallow foundations, including but not limited to; allowable soil bearing pressures, estimated settlement, and suitability of excavated material as engineering fill.

■ Shallow foundation bearing surface preparation recommendations

■ Recommendations for design and construction of interior soil supported floor slabs

■ Site preparation recommendations

■ Lateral earth pressure design recommendations

■ Seismic design considerations (Site Class and liquefaction potential)

The geotechnical engineering Scope of Services for this project included drilling four Standard Penetration Test (SPT) borings to an approximate depth of 100 feet each below the existing ground, two SPT borings to a depth of approximately 32 to 35 feet, engineering analysis, a field electrical resistivity survey, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and Exploration Plans in the Appendix. 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 as separate tables in the Exploration Results section.

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:

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Information Provided

Via e-mail correspondence with Phuc Abrego, and David Pratt of Parsons Corporation on September 12 and 13, 2023. Further information was furnished by Richard Jones and Ed Hickey of Parsons in December 2023.

Project Description

The project will include the demolition of existing structures and pavements within the project footprint and construction of a new 11,456 square-foot plan area Weapons Loading Training Hangar (WLT) and a 11,240 square-foot plan area Weapons Release Systems Shop (WRSS) as part of the proposed F-35 Concealed Weapons Training Facility.

Proposed Structures

The WLT consists of a high bay hangar, with associated offices, storage areas, locker rooms with other mechanical and electrical facilities.

The WRSS includes a weapons loading storage bay, weapons loading and release shops, cleaning and service areas, and other training facilities.

A 10-foot-tall CMU perimeter barrier wall is planned around the hangar building.

Finished Floor Elevation

The proposed finished floor elevation(s) for the proposed buildings are not known at this time; however, we assume that minimal grading cut or fill will be required to achieve plan elevations.

Maximum Loads

■ Individual Columns: 140 kips (WRSS) 100 kips(WLT)

■ Bearing Walls: 5 kips per linear foot (klf)

■ Floor Slab Live Load: 250 pounds per square foot (psf)

Grading/Slopes Minimal earthwork grading cut and fill will be required.

Retaining Walls As necessary to provide design grade separation

Stormwater Management

Stormwater run-off will be directed to existing water management facilities on site. Expected range of permeability values for the upper 80 inches of the natural on-site soils are indicated in the Soil Survey section.

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

Facilities | Environmental | Geotechnical | Materials 3

Site Conditions

The following description of site conditions is derived from our site visits during November 2023 through February 2024, 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 14300 Fang Drive at the Florida Air National Guard base in Jacksonville, Florida with a total floor plan of approximately 22,696 square feet.

Latitude: 30.489506 Longitude: -81.702786 See Site Location and Exploration Plans

Existing Improvements

The project area currently has several structures present, presumably for aircraft maintenance and storage, which are scheduled for demolition.

Current Ground Cover

The existing ground cover consists of buildings, pavements, and grassy areas, adjacent to aircraft hangars and taxiways associated with the Air National Guard Military Base

Existing Topography

According to a topographic survey of the project site by Southeastern Surveying, the existing ground elevations range from approximately 23.5 to 26.5 feet AMSL.

Geotechnical Characterization

General Area Geology

The site area lies within the Atlantic Coastal Plain physiographic province, which in northeast Florida encompasses a series of ancient marine terraces. These terraces mark the ocean bottom during the Pleistocene Epoch when the sea, having transgressed beyond the present shoreline, remained stationary for long periods of time punctuated by episodic regressions. As the sea regressed to a lower level, the sea floor became exposed as a flat plain with a low scarp and sand dune ridge along the landward edge marking the abandoned shoreline. The flat plains and abandoned shorelines have, since their deposition been dissected and eroded by streams, wind, and rainfall, leaving only remnants of their original structure.

The shallowest consolidated rock formations underlying the area occur at approximately 400 feet below ground surface where the Ocala Group limestone formations begin. The Ocala Group is comprised of the Crystal River Formation, Williston Formation and the Inglis Formation and represents the uppermost host rock for the Floridan aquifer. These deposits

Facilities | Environmental | Geotechnical | Materials 4 are composed primarily of light colored, granular, massive fossiliferous marine limestone.

Limestone was not encountered in the borings drilled for this preliminary exploration.

Between the Floridan aquifer system and the shallow aquifer system is the Hawthorn Group, an aquiclude unit comprised of gray to green, silty to sandy, phosphatic clay deposits. The Hawthorn Group has thin discontinuous interbedded lenses of black, fine to pebbly, phosphatic sand, phosphatic sandy limestone, and gray, hard dolomite. The limestone and dolomite lenses are more predominant near the base of the formation. The Hawthorn Group acts as an aquitard between the surficial aquifer system and the Floridan aquifer. The Hawthorn Group was not encountered in this preliminary study.

The Hawthorn Group is unconformably overlain by Pleistocene to recent deposits of sand, silt, silty sand, clayey sand and shelly, clayey sand in the upper portions, and interbedded sandy clay, clay and soft to hard limestone in the lower portion. The sands, silts and clays are associated with geologically recent marine and estuarine deposits. The limestone, together with a coarse phosphatic sand and gravel bed that marks the contact with the Hawthorn Group, are the host rock for the most laterally extensive aquifer in the shallow aquifer system. These deposits vary in thickness and composition across northeast Florida.

Hydraulic pressure from the artesian conditions in the Floridan aquifer percolates water slowly upward through the Hawthorn Group into the surficial aquifer; however, the majority of water in the surficial aquifer is recharged by rainwater infiltration. The shallow aquifer unit is widely used in Duval County for private domestic water supply and irrigation purposes.

Soil Survey

The Soil Survey for Duval County, Florida, as prepared by the United States Department of Agriculture (USDA), Soil Conservation Service (now renamed the Natural Resource Conservation Service - NRCS), identifies seven soil types at the subject site as shown below.

The Web Soil Survey (WSS) map of the project area was reviewed and a map encompassing the project area is included as Exhibit A-2 in Site Location and Exploration Plans. The WSS presents shallow (typically upper 80 inches) soil stratification information produced and compiled by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). Exhibit A-2 identifies the soil map units documented by the NRCS in the project area.

The map units are indicated in the following table.

Facilities | Environmental | Geotechnical | Materials 5

SUMMARY OF SOILS IN PROJECT VICINITY – FROM NRCS WEB SOIL SURVEY

Map Unit No.

And Name

Stratification Estimated Seasonal High Groundwater Level (feet)

Depth Range

(inches)

Unified Soil Classification

Permeability

(in/hour)

Mascotte Fine Sand

0 to 2% slopes

0 - 5 5 - 15 15 - 25 25 - 28 28 – 58 58 – 80

SP-SM, SM

SP-SM, SM

SP-SM, SM

SP-SM, SM

SC, SC-SM, SM

SP-SM, SM

6.0 – 20

6.0 - 20

0.6 – 2.0

6.0 - 20

0.2 – 0.6

0.6 – 2.0

0.5 – 1.5 Apparent Jan - Oct

Urban Land No data for urban Land due to variability

In general, the soils encountered in the borings were similar to the soils described in the Soil Survey in the upper 80 inches or so.

GeoModel and Site Subsurface Conditions

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 and Generalized Subsurface Profile in the Appendix.

Model Layer

Layer Name General Description

1 FINE SAND

Sandy soils with varying fines content, loose to very dense. (SP, SP-SM, SP-SC)

2 SILTY SAND Silty fine sand, loose to dense. (SM)

3 CLAYEY SOIL

Clayey sand and sandy clay, loose to medium dense and medium stiff to very stiff (SC, CL)

4 SOFT CLAYEY SOIL

Silty clayey sand and silty clay, very loose and very soft to medium stiff (SM-SC, CL, CH)

5 HAWTHORN GROUP

Lean clay with silt, trace phosphates, medium stiff to hard (CL)

6 ASPHALT Asphalt pavement

The Boring Logs provide detailed descriptions of the subsurface conditions encountered at each boring location. When reviewing the boring logs and the subsurface profile, it should be understood that soil conditions might vary between and away from boring

Facilities | Environmental | Geotechnical | Materials 6 locations. Stratification boundaries on logs represent the approximate depth of changes in soil types; the transition between materials may be gradual.

The soil borings generally encountered loose to dense fine sand of varying fines content, (Unified Soil Classification System of SP, SP-SM, SP-SC,SM, SC) to an approximate depth of 25 to 26 feet below the existing ground surface, underlain by a layer of very loose silty clayey sand and very soft silty clay (SC, CL, CH) to an approximate depth of 30 feet. The borings then typically encountered medium dense to very dense sandy soils (SP, SP-SM, SM, SC) to an approximate depth of 63 to 68 feet below the existing ground surface, underlain by stiff to hard lean clay with silt and trace phosphates to the deepest termination depth of approximately 100 feet beneath the ground surface. This deeper layer is considered the upper portion of the Hawthorn Group, which is believed to extend to a depth of at least 400 feet beneath the site.

Groundwater

Each borehole was observed during drilling for the presence and depth of groundwater.

The SPT soil borings were advanced from the ground surface with continuous split spoon sampling and then a mud rotary drilling technique in which a drilling slurry was circulated in the borings while drilling to flush soil cuttings to the surface. The use of drilling fluid in the boreholes and the need for backfilling prevented stabilized groundwater observations.

The soil borings typically encountered groundwater at depths ranging from about 3.5 feet (Borings B-3 and B-4) to 5 feet (Borings B-1, B-2, and B-6) below the ground surface.

The other boring, B-5, encountered groundwater at approximately four feet depth.

It should be recognized that the groundwater level will fluctuate due to seasonal climatic variations, previous rainfall, construction operations, surrounding development, and other interrelated factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the boring profile sheets. It should be noted that changes in on-site or adjacent off-site surface hydrology and subsurface drainage could have significant effects on the seasonal high groundwater levels in the project area.

Field Electrical Resistivity

Field measurements of soil electrical resistivity were performed by GeoView. The soil resistivity testing was performed at a central location identified in the Field Exploration Plan in the attachments. The Wenner arrangement (equal electrode spacing) was used with “a” spacings of 2, 5, 10 and 20 feet. The “a” spacing is generally considered to be the depth of influence of the test. The testing was performed in perpendicular orientations at each test location as shown on the test report. The test results of the soil resistivity measurements are presented in the Exploration and Laboratory Results section in the attachments.

Facilities | Environmental | Geotechnical | Materials 7

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided that the recommendations in this report are implemented in the design and construction phases of this project.

Based on the conditions encountered and estimated load-settlement relationships, the proposed structures can be supported on conventional Shallow Foundations. It should be noted that although the upper portion of the soil profile consisted mainly of loose to dense sandy soils, layers of very loose clayey sand and very soft silty clay were encountered in the borings from an approximate depth of 25 to 30 feet. Consolidation testing of relatively undisturbed Shelby tubes of this material and subsequent settlement analyses indicated that compression of these layers under the proposed loading conditions should be insignificant.

The Floor Slabs section addresses slab-on-grade support of structures. The groundwater level should be considered during design and construction of the development.

Due to the existing development, complete demolition and removal of existing foundations and utilities within the footprint area of the new construction should be conducted prior to site preparation. Earthwork provides detailed considerations for demolition, site preparation and fill placement.

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, 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

The proposed new construction footprint will encompass several existing structures which will need to be demolished, including a one-story metal building, metal sheds, a one-story masonry building, and a large metal canopy, along with exterior sidewalks, Facilities | Environmental | Geotechnical | Materials 8 pavements, and utilities. We recommend existing foundations, slabs, pavements, and utilities be completely removed from within the proposed building footprint and extending at least 5 feet beyond the outer edge of proposed new building foundations.

For areas outside the proposed building footprints and foundation influence zones, existing foundations, pavements, floor slabs, and utilities should be removed where they conflict with proposed utilities, any retaining walls, and any new pavements. In such cases, existing foundations, pavements, floor slabs, and utilities should be removed to a depth of at least 2 feet below the affected utility or design pavement subgrade elevation.

Site Preparation

General Site Drainage

Site drainage measures should be implemented prior to or concurrent with initial mass grading and may include excavation of perimeter ditches with supplemental lateral ditches extending into the site, as required. The ditches should be constructed and maintained to gravity drain throughout the site preparation process. Failure to protect the subgrade soils and control surface water runoff can significantly impact the earthwork construction schedule and result in unnecessary reworking of the subgrade.

Surface Water Control

Surface water should not be allowed to pond on the site and soak into the soil during construction. Construction staging should provide for drainage of surface water and precipitation away from the structure areas. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils.

Surficial Soil Compaction (Subgrade Preparation)

Throughout most of the project area, a veneer of sandy surficial soils (Model Layer 1 and

2) is present. Sandy soils typically respond well to mechanical densification using a heavy vibratory drum roller. This densification process, conducted prior to proofroll, will improve the uniformity of the subsurface and may reduce the amount of overexcavation (undercutting). The exposed sandy subgrade soils within 5 feet of the planned building and pavement areas should be compacted with at least eight overlapping passes of a vibratory drum roller with a static operating weight of no more than 15,000 pounds and a drum diameter of no more than 36 inches. Use of a larger vibratory roller is not recommended at this site due to the proximity of the groundwater level to the ground surface. It is possible that vibratory compaction operations may induce pumping of the ground surface due to generation of excess pore water pressures. If pumping of the ground surface occurs, the vibratory component of the roller should be disengaged to

Facilities | Environmental | Geotechnical | Materials 9 allow the pore pressures to dissipate. Continued compaction of the surface soils in non-vibratory/static mode may be necessary until adequate separation between the compaction surface and groundwater level can be achieved via placement of any necessary grading fill. A minimum number of eight roller passes is recommended. The roller passes should be divided into an equal number of passes in perpendicular directions. A compaction criterion of 95% of the native soil’s maximum dry density (ASTM D1557) should be achieved to a depth of 12 inches. The effectiveness of the densification will be dependent on the moisture content of the subsoils at the time of construction. Moisture conditioning of the soils may be required.

Proofrolling

Following the densification program and prior to any grading fill placement, the exposed subgrade soils should be proofrolled by the contractor and observed by Terracon personnel. Proofrolling may be accomplished using a suitable vehicle such as a fully loaded tandem axle dump truck. The proofroll vehicle should systematically traverse the entire project area with multiple overlapping passes. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Excessively wet or dry material should either be removed, or moisture conditioned and recompacted.

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.

Reuse of On-Site Soil: Excavated on-site soil is likely to be suitable for reuse as structural or general fill. Material property requirements for on-site soil for use as general fill and structural fill are noted in the table below:

Property General and Structural Fill

Composition Free of deleterious material

Maximum particle size 3 inches

Fines content No more than 12% Passing No. 200 sieve

Plasticity Non-plastic

GeoModel Layer Expected to be Suitable1 1

1. Based on subsurface exploration. Actual material suitability should be determined in the field at time of construction.

Facilities | Environmental | Geotechnical | Materials 10

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.

Fill Type 1 USCS Classification Desired Parameters (for Structural Fill)

Structural Fill SP, SP-SM, SP-SC No more than 10% Passing No. 200 sieve

General Fill SP, SP-SM, SP-SC, SM2 No more than 15% passing No. 200 sieve

1. Structural and general fill should consist of approved materials free of organic matter and debris. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

2. Acceptable soils with an SM classification should have a fines content of 15 percent or less to help reduce moisture conditioning requirements and the potential for disturbance of the compacted surface following periods of prolonged or intense rainfall. Fines content of silty sand borrow soils can be reduced by thoroughly blending this material with lower fines content material. Use of higher fines content silty sands (SM) as grading fill may be considered if the contractor can demonstrate the ability to acceptably dry and compact these materials.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift Thickness

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

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

Same as structural fill

Minimum Compaction

Requirements 1,2,3

■ 98% of max. in first 12 inches below foundations and within 1 foot beneath pavement base

■ 95% of max. above foundations, below floor slabs, and more than 1 foot below finished pavement subgrade or foundations

92% of max.

Water Content

Range 1,4 -3% to +3% of optimum

As required to achieve min.

compaction requirements

Facilities | Environmental | Geotechnical | Materials 11

Item Structural Fill General Fill

1. Maximum density and optimum water content as determined by the modified Proctor test (ASTM D 1557).

2. Engineered fill materials should be placed in horizontal, loose lifts not exceeding 12 inches in thickness and should be thoroughly compacted. Where light compaction equipment is used, as is customary within a few feet of retaining walls and in utility trenches, the lift thickness will need to be reduced to achieve the desired degree of compaction.

3. We recommend that engineered fill be tested for moisture content and compaction during placement. Should the results of the in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved.

4. Specifically, moisture levels should be achieved and maintained low enough to allow for satisfactory compaction to be achieved without pumping when using suitable vibratory compaction equipment.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural 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 backfills 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.

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

Facilities | Environmental | Geotechnical | Materials 12 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 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 desiccates, saturates, or is disturbed, the affected material should be removed, , 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

Facilities | Environmental | Geotechnical | Materials 13 instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Groundwater Considerations

The Contractor should be prepared to implement a dewatering program for excavations made below existing site grades, such as those for installation of stormwater pipes or other utilities.

Based on observations at our soil borings, it is anticipated that groundwater could be encountered in excavations on site, particularly in topographically lower areas of the site.

Dewatering procedures used by the contractor will be dependent on a number of factors such as the areas and depths of excavations, prevalent groundwater conditions, and prevalent weather conditions at the time of construction.

Dewatering procedures employed should be capable of maintaining groundwater levels at least 2 feet below the lowest point of the excavation being dewatered, or as deep as required to achieve the required compaction or suitable subgrade conditions. In addition, the dewatering procedures should be maintained until all construction operations are above the groundwater levels that existed prior to dewatering, or until all structural bearing subgrades are adequately protected.

We expect that installation of deeper drainage pipes and drainage structures will require vacuum-type dewatering systems such as wellpoints or horizontal sock-type vacuum dewatering systems. Groundwater control in shallower excavations (e.g., spread footings) in sandy soils can typically be accomplished by excavating sumps in non-structural bearing areas of the excavation and pumping of the accumulated water from the sumps as needed to maintain a dry excavation.

Construction Observation and Testing

The earthwork efforts should be observed by Terracon. Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of 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 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.

Facilities | Environmental | Geotechnical | Materials 14

In areas of foundation excavations, the prepared bearing subgrade should be tested for density and water content at a frequency of at least one test for every 100 square feet for footings (at least one per column) and at least one test per 50 feet for continuous strip footings. 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 foundations.

Design Parameters – Compressive Loads

Item Description

Net Allowable Bearing Pressure 1, 2 3,000 psf

Required Bearing Stratum 3 GeoModel Layer 1 and 2 or structural fill extending to undisturbed native soils.

Minimum Foundation Dimensions Isolated – 24 inches Continuous – 18 inches

Sliding Resistance 4 0.45 ultimate coefficient of friction

Minimum Embedment below

Finished Grade 5 18 inches

Estimated Total Settlement from

Structural Loads 2 Less than about 0.75 inch

Estimated Differential Settlement 2, 6 About 2/3 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. 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. 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

Facilities | Environmental | Geotechnical | Materials 15 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 permit use of the 3,000 psf allowable soil bearing pressure.

For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

6. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Design Parameters – Overturning and Uplift Loads

Shallow foundations subjected to overturning loads should be proportioned such that the resultant eccentricity is maintained in the center-third of the foundation (e.g., e < b/6, where b is the foundation width). This requirement is intended to keep the entire foundation area in compression during the extreme lateral/overturning load event.

Foundation oversizing may be required to satisfy this condition.

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils with consideration to the IBC basic load combinations.

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 / 30 meters 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). It is our opinion that Site Class D may be considered for the project site.

Item Description

Soil Moist Unit Weight 110 pcf

Soil Effective Unit Weight1 50 pcf

Soil weight included in uplift resistance

Soil included within the prism extending up from the top perimeter of the footing at an angle of 20 degrees from vertical to ground surface

1. Effective (or buoyant) unit weight should be used for soil above the foundation level and below a water level. The high groundwater level should be used in uplift design as applicable.

Facilities | Environmental | Geotechnical | Materials 16

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of Terracon. 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.

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 structural fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with fine sand (SP, SP-SM) placed, 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.

Floor Slab Design Parameters

Item Description

Floor Slab Support1

Floor slabs should be constructed over a uniform and stable subgrade compacted to a depth of at least 12 inches. The subgrade should be constructed as described below:

■ On-site sand soil (Model Layer 1) or imported sand meeting the requirements of Structural Fill should be placed for the first 12 inches immediately below the slab.

Subgrade should be compacted to recommendations outlined in Earthwork

Estimated Modulus of Subgrade Reaction 2

150 pounds per square inch per inch (psi/in) for anticipated slab loading conditions

Compaction Requirements

At least 95 percent of the material’s Modified Proctor maximum dry density (ASTM D 1557) in each lift of structural fill. In areas where floor slabs will be subjected to transient, rolling loads (such as from aircraft traffic), the compaction criterion should be increased to at least 98 percent of the material’s Modified Proctor maximum dry density in the upper 12 inches.

Minimum Testing Frequency3

One field density test per 2,500 square feet (or fraction thereof).

1. Floor slabs should be structurally independent of any building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation. Narrower, turned-down slab-on-grade foundations may be utilized at the approval of the structural engineer. The slabs should be appropriately reinforced to support the proposed loads.

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.

3. We recommend that subgrades be maintained at the proper moisture condition until floor slabs are constructed. If the subgrade should become desiccated prior to construction of floor slabs, the affected material should be removed, or the materials moistened and recompacted. Upon completion of grading

Facilities | Environmental | Geotechnical | Materials 18 operations in the building areas, care should be taken to maintain the recommended subgrade moisture content and density prior to construction of the building floor slabs.

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 control 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 beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient control joints, appropriate reinforcing, or other means.

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.

Terracon 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.

Facilities | Environmental | Geotechnical | Materials 19

Lateral Earth Pressure Design Considerations

Design of any earth retaining walls associated with the project should consider either the active or at rest lateral earth pressures generated by the backfill soils placed against the completed walls depending on designer’s assumption of allowable wall movement. The following table presents soil properties for compacted sandy backfill placed against the completed retaining wall.

Compacted Structural Fill or Backfill Material1

Unit Weight (pcf)

A ng le o f In te rn al

Fr ic ti on

2 , D eg

W al l F ri ct io n R at io

3 , Earth Pressure Coefficients4

D am p

S at ur at ed

S ub m er g ed

A ct iv e5

(K a)

A t-

R es t6

K o)

P as si ve

(K p)

Fine SAND to fine SAND with silt (SP, SP-SM)

110 125 63 33 0.5 0.28 0.46 6.4

1. These materials are granular and do not exhibit appreciable cohesion.

2. The friction angle value is based upon a compacted density equivalent to 95 percent of the

Modified Proctor maximum dry density (ASTM D 1557).

3. Wall friction ratio – assumed smooth, formed concrete against granular soil.

4. Short-Term (immediately after backfilling) and long-term conditions should be essentially equivalent due to the relatively free draining granular nature of the backfill.

5. The active and passive coefficients were determined by the Log-Spiral Method which considers the effects of wall friction. (See Figure 5a, USS Steel Sheet Piling Design Manual).

A level backfill condition was assumed. Coefficients for sloping backfill should be appropriately adjusted. A factor of safety of at least 2 should be applied to the tabulated Kp value for use in design.

6. The at-rest earth pressure coefficient was estimated using the Jaky formula: ko = 1-sin .

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 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.