Geotechnical Report.pdf

102283EX09ROtisANGGeotechFinal

June 2, 2009 Project No. 102283

Mr. Josh Bergsten Burns and McDonnell Engineering Company, Inc.

9400 Ward Parkway Kansas City, Missouri 64114

Reference: Geotechnical Engineering Evaluation Report Proposed Intel Facility Otis Air National Guard Base Bourne, Massachusetts

Dear Mr. Bergsten:

Kleinfelder has completed the authorized subsurface exploration and geotechnical engineering evaluation for the above-referenced project in general accordance with our proposal dated February 20, 2009 and the Technical Guidelines provided by Burns and McDonnell dated February 3, 2009. The purpose of the geotechnical engineering evaluation was to explore and evaluate the subsurface conditions at the project site and develop geotechnical design and construction recommendations for the project. The attached report contains a description of the findings of our field exploration and laboratory testing program, our engineering interpretation of the results with respect to the project characteristics, and our geotechnical site development recommendations as well as construction guidelines for the planned project.

We appreciate the opportunity of providing our services for this project. If you have questions regarding this report or if we may be of further assistance, please contact the undersigned.

Sincerely, KLEINFELDER EAST, INC.

Derek Pagel, E.I.T.

Staff Engineer

Reviewed By:

Jonathan Morrison, P.E.

Geotechnical Project Manager

William C. Rinker, P.E.

Geotechnical Group Manager

Enclosures DP/JM:lmc

180 Sheree Blvd., Suite 3800 Exton, PA 19341 p| 610.430.7866 f| 610.430.7872 kleinfelder.com

GEOTECHNICAL ENGINEERING EVALUATION

REPORT

PROPOSED INTEL FACILITY

OTIS AIR NATIONAL GUARD BASE

BOURNE, MASSACHUSETTS

JUNE 2, 2009

Project No. 102283

This document was prepared for use only by the Client, only for the purposes stated, and within a reasonable time from issuance. Non-commercial, educational and scientific use of this report by regulatory agencies is regarded as a "fair use" and not a violation of copyright. Regulatory agencies may make additional copies of this document for internal use. Copies may also be made available to the public as required by law. The reprint must acknowledge the copyright and indicate that permission to reprint has been received.

180 Sheree Blvd., Suite 3800 Exton, PA 19341 p| 610.430.7866 f| 610.430.7872 kleinfelder.com

TABLE OF CONTENTS

SECTION PAGE

1.0 INTRODUCTION

1.1 GENERAL

1.2 PURPOSE AND SCOPE OF SERVICES

1.3 SITE DESCRIPTION

1.4 PHYSICAL SETTING

2.0 SITE INVESTIGATION

2.1 SUBSURFACE CONDITIONS

2.1.1 Surface Materials

2.1.2 Existing Fill and Apparent Buried Asphalt

2.1.3 Coastal Plain Sand

2.1.4 Groundwater

2.2 LABORATORY TESTING

3.0 SITE DEVELOPMENT RECOMMENDATIONS

3.1 SITE PREPARATION

3.2 SUBGRADE PREPARATION

3.3 EARTHWORK

3.4 BACKFILL AND FILL

3.5 UTILITIES

3.6 SEISMIC CONSIDERATIONS

4.0 DESIGN RECOMMENDATIONS

4.1 FOUNDATION DESIGN

4.2 SLAB-ON-GRADE

4.3 MOISTURE VAPOR TRANSMISSION

4.4 PAVEMENT DESIGN

4.5 GROUNDWATER MANAGEMENT

4.6 CORROSION AND SULFATE ATTACK

4.7 RETAINING WALLS AND BELOW-GRADE WALLS

5.0 LIMITATIONS

PLATES

PLATE 1 GENERAL SITE LOCATION MAP

PLATE 2 BORING LOCATION PLAN

APPENDICES

APPENDIX A TEST BORING LOGS

APPENDIX B LABORATORY DATA

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1.0 INTRODUCTION

1.1 GENERAL

Kleinfelder has completed the authorized geotechnical engineering evaluation for the proposed Intel facility to be located to the south of the intersection of Izzea Street and Corn Street at the Otis Air National Guard Base in Bourne, Massachusetts. The project site location is shown on a USGS base map included as Plate 1, General Site Location Map.

This report includes our recommendations related to the geotechnical aspects of project design and construction. Conclusions and recommendations presented in this report are based on the subsurface conditions encountered at the locations of our explorations and the provisions and requirements outlined in the limitations section of this report. Recommendations presented herein should not be extrapolated to other areas or used for other projects.

1.1 PROPOSED SITE DEVELOPMENT

We understand that the proposed Intel Facility will be constructed in two phases. The first phase will include the construction of a two-story, 33,000 square-foot Ops and Support building. The second phase includes the construction of a single-story, 7,600 square-foot Administration building. The Administration building will connect with the Ops and Support building’s second floor due to site topography and proposed grading.

It is anticipated that the lower level of the two-story building will be constructed with concrete walls and the upper level and single-story building will be steel-framed construction. Ground level floors will consist of slabs-on-grade. As discussed in the RFP, isolated and continuous shallow footings are the anticipated foundation type for the structures. The roof system for the buildings will consist of standing seam metal over wide rib steel roof deck. The non load-bearing exterior walls will consist of concrete masonry units with metal studs and/or horizontal wall girts above supporting metal panel. Interior walls will be non-load-bearing and will consist of concrete masonry units or gypsum wallboard over cold-formed steel studs.

Ancillary development at the site is anticipated to include retaining walls to support the grading plan and topography, as well as parking lots and other exterior pavements.

Based on information provided by the Structural Engineer for the two-story structure, the maximum dead and live interior column loads are 266 kips (133 kips dead load and 133 kips live load), the maximum exterior dead and live column loads are 126 kips (76 kips dead load and 50 kips live load), and the maximum exterior dead and live corner column loads are 60 kips (35 kips dead load and 25 kips live load).

Loads for the single-story structure and information regarding proposed site grading are not available at this time.

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1.2 PURPOSE AND SCOPE OF SERVICES

The purpose of this geotechnical evaluation was to explore and evaluate subsurface conditions at the site and to develop recommendations for the geotechnical aspects of the design and construction of the project. The Scope of Services performed for this geotechnical evaluation consisted of a subsurface exploration program, laboratory testing of selected soil samples, engineering analysis of the field and laboratory data, and the preparation of a written report presenting the results of our field exploration, laboratory tests and engineering analyses.

The scope of the exploration and engineering evaluation for this study, as well as the conclusions and recommendations in this report, were based on our understanding of the project as described above. If pertinent details of the project have changed or otherwise differ from our descriptions, we must be notified and engaged to review the changes and modify our recommendations, if needed.

1.3 SITE DESCRIPTION

Based on observations made during the field evaluation, the existing site slopes generally downward from Izzea Street to Grandville Avenue and includes an existing single-story building, associated asphaltic concrete and gravel paved parking areas and driveways, grass-covered landscaped areas, and many mature trees in the eastern quadrant of the site. Based on the preliminary topographic plan provided by Burns and McDonnell Engineering Co., Inc. the project site generally slopes downward from northwest to southeast with elevations ranging from approximately 106 feet along Izzea Street to approximately 95 feet along Grandville Avenue.

Based on information provided by Otis Air National Guard Base personnel, we understand that existing utilities are present within the site, and that the area near Izzea Street may have once been part of a historical runway system.

1.4 PHYSICAL SETTING

The project site is located within the Otis Air National Guard Base in Bourne, Massachusetts.

Based on the Bedrock Geologic Map of Massachusetts (1983) by the Commonwealth of Massachusetts Department of Public Works, the site is underlain by the Connecticut Valley Belt.

This formation reportedly consists of Silurian shallow water sediments and Connecticut Valley synclinorium, intruded by devonian quartz monzodiorite, tonalite, and granite, with the particular site area dominated by augite-hornblende quartz monzodiorite. Quaternary deposits are generally characterized as fluvial outwash plains and ice contact zones. In most places the debris was sorted by meltwater streams and deposited as stratified drift. In the ice-contact zone the depositional environment was chaotic. It was characterized by rapid changes in stream volume and stream course. In this zone the stratified drift is coarsest, mostly gravel and sand, and includes till and boulders deposited by the ice. Away from the ice-contact zone, the stratified drift becomes increasingly more sorted and finer grained. These outwash deposits are mostly sand and gravelly sand.

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2.0 SITE INVESTIGATION

2.1 SUBSURFACE CONDITIONS

Subsurface conditions at the site were explored by eleven test borings using hollow-stem auger drilling techniques. The subsurface exploration program was performed on March 5 and 6, 2009 under the technical supervision of Mr. Derek Pagel of Kleinfelder.

The test borings were performed using a CME 850 track-mounted drill rig to depths ranging between approximately 6 and 52 feet below the existing ground surface, in general accordance with the Technical Guidelines.

The locations of the test borings are shown on Plate 2 - Test Boring Location Plan. Descriptions of the soil strata encountered are included in the boring logs provided in Appendix A. The major soil groups encountered during the field evaluation are described below in the general order of their occurrence.

2.1.1 Surface Materials

The borings (except B-9) encountered approximately six inches of topsoil below the ground surface (bgs). Boring B-9 was drilled within an existing asphalt parking lot, and encountered approximately two inches of asphalt.

2.1.2 Existing Fill and Apparent Buried Asphalt

Beneath the surface materials, the borings encountered existing fill materials that generally consisted of olive and olive-brown, loose to medium dense poorly-graded sand (SP) and silty sand (SM), along with soft, low plasticity sandy silt (ML). The existing fill materials extended to depths that ranged from approximately 2 feet bgs to 8 feet bgs. In borings B-2, and B-11, a 4-inch layer of apparent buried asphaltic material was encountered below the fill.

2.1.3 Coastal Plain Sand

Underlying the existing fill and apparent buried asphalt materials, the borings encountered a stratum of coastal plain sand that generally consisted of light-brown to olive-brown, loose to medium dense silty sand (SM), poorly graded sand with silt (SP-SM), poorly graded sand (SP), and some thin layers of sandy silt (ML). The sand stratum extended to the limits of the borings.

2.1.4 Groundwater

Groundwater was encountered during the subsurface evaluation only in boring B-5 at a depth of approximately 48 feet bgs. It should be noted that groundwater is known to fluctuate due to local and regional factors including, but not limited to, precipitation events, tides, seasonal changes, and periods of wet or dry weather.

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2.2 LABORATORY TESTING

Laboratory testing was performed on select soil samples obtained from the test borings to further evaluate physical and chemical soil properties. Laboratory testing included 9 sieve tests, 1 Atterberg Limits, 15 natural moisture content determinations, one laboratory compaction (proctor), and one corrosion series test. The corrosion series included one soil pH determination, one redox potential (Eh) test, one sulfides test, one soluble sulfate test, one chloride ion test, and one resistivity test. Results of the laboratory tests can be found on the boring logs provided in Appendix A, and the Laboratory Data provided in Appendix B.

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3.0 SITE DEVELOPMENT RECOMMENDATIONS

3.1 SITE PREPARATION

The proposed development area includes an existing single-story building, gravel and asphaltic concrete paved parking areas, and grass-covered areas with some trees and shrubbery. Refer to Plate 2 - Boring Location Plan, for approximate locations of the proposed redevelopments. We understand that the existing building will be removed prior to commencement of the proposed construction activities. Site preparation should commence with removal of the existing building and asphalt concrete pavements, and stripping of vegetation and topsoil within the development areas.

Removal of trees and excavation of root systems and excessive organic material should be performed and backfill in these excavations should be placed in accordance with the requirements for load-bearing fill as described in Section 3.4.

In the area of the proposed building footprints and the area extending 5 feet beyond the building footprints, completely remove any slabs and subsurface building elements associated with the existing single-story building at the site. In proposed pavement areas completely remove any existing slabs and remove existing subsurface building elements within two feet vertically of the bottom of the proposed pavement sections. Existing utilities within the proposed building areas should be re-routed or properly removed. As an alternative to removal, utilities may be abandoned in place by grouting. As part of the removal process, portions of utilities remaining should be properly capped and sealed. Backfill the demolition excavations as well as any basements, crawlspaces, or vaults in accordance with the guidelines for Load Bearing Fill as defined in Section 3.4.

Rubble from demolition may be crushed and re-used as load-bearing fill as defined in Section 3.4, provided unsuitable materials are removed. Suitable fill material includes brick rubble, concrete rubble, asphalt, mortar, concrete block, grout, gravel, sand, and rock fragments. Unsuitable material includes all other materials. Larger pieces of material should be crushed or not used. On-site sorting of materials should be anticipated to remove unsuitable items from otherwise suitable fill material.

A representative of the Geotechnical Engineer should monitor the site preparation operations to observe that unsuitable materials have been removed.

3.2 SUBGRADE PREPARATION

Identification of unstable areas is critical to the successful redevelopment of the site. A representative of the Geotechnical Engineer should observe all excavations to evaluate potential loose or soft zones within the existing fill and native site soils. After site preparation procedures have been performed, subgrades scheduled to receive load-bearing fill to achieve proposed grades, or subgrades in cut areas should be proof-rolled under the observation of a representative of the Geotechnical Engineer to evaluate the suitability of the subgrade. Loose and/or soft zones identified by the representative of the Geotechnical Engineer should be removed and replaced at the recommendation of the representative of the Geotechnical Engineer. Excavated soils may be re-used provided they meet the requirements of Section 3.4 of this report.

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The proof-rolling should be performed with a loaded tri-axle dump truck, or other means approved by the representative of the Geotechnical Engineer. Proof-rolling should uniformly cover the subgrade in accordance with recommendations by the representative of the Geotechnical Engineer. Suspect areas should be further investigated by a representative of the Geotechnical Engineer, by methods that may include test pits or laboratory testing, to identify causes and/or extents of instability. The proof-rolling objective should be to identify zones of weakness in the subsoil that may require stabilization. Soils which exhibit excessive rutting, pumping, or other signs of instability as determined by a representative of the Geotechnical Engineer should be stabilized, or removed and replaced with compacted fill in accordance with Section 3.4 of this report, at the recommendation of a representative of the Geotechnical Engineer. The development areas should be stable as determined by a representative of the Geotechnical Engineer prior to construction of structural elements.

3.3 EARTHWORK

Based on the soils encountered in the borings, site grading for the slab placement and excavations for the footings are anticipated to primarily encounter loose to medium dense silty sand fill materials, as well as sandy silt and poorly-graded sand, beneath the surface materials.

The soils encountered during our evaluation are generally considered suitable for reuse as load-bearing fill material as defined in Section 3.4. However, reworking of the on-site soils to be used as compacted fill may be required if they are not within the range of acceptable moisture content. Standard Proctor compaction tests (ASTM D698) should be performed on representative samples of the proposed fill material to determine the range of acceptable moisture content and density.

Load-bearing fills placed within the building area should generally have their moisture contents controlled to within three percent of optimum, and load-bearing fills placed outside the building area should generally have their moisture contents controlled to within five percent of optimum.

The moisture content of proposed fill material can be greatly influenced by seasonal changes and precipitation events. Depending on the moisture content of the proposed backfill material at the time of proposed reuse, wetting or drying of the proposed backfill material may be required.

The greatest success in reusing on-site materials as compacted backfill and fill is generally achieved during periods of warm dry weather, however, fill material can be placed during any season provided the moisture content permits adequate workability and compaction. If the moisture contents of the proposed on-site fill materials are too high and the schedule does not allow for drying, import material as defined in Section 3.4 may be used.

Construction site safety is the sole responsibility of the contractor, who shall also be solely responsible for the means, methods and sequencing of construction operations. Excavations should be performed under the direction of the contractor’s “Competent Person” as defined by OSHA. The contractor should also be aware that slope height, slope inclination or excavation depths (including utility trench excavations) should in no case exceed those specified in local, state and/or federal safety regulations, such as OSHA Health and Safety Standard for Excavations, or more stringent applicable regulations. According to OSHA standards, the sandy soils encountered in the borings are classified as Type C soils, and should maintain a maximum slope inclination of 1 vertical to 1 ½ horizontal for temporary slopes. Stockpiles should be placed a minimum distance equal to that of the adjacent excavation height, from the edge of excavations and their heights should be controlled so they do not surcharge the sides of the excavation. Surface drainage should be carefully controlled to prevent flow of water into the excavations. The site should be

102283EX09ROtisANGGeotechFinal Page 7 June 2, 2009 graded to prevent surface water from ponding in construction areas and accumulating in excavations.

If site grading and construction is to be performed during or shortly after the rainy months, the owner and contractors should be fully aware of the potential impact of wet weather. Rainstorms can cause delay to construction and damage to previously completed work, such as saturating a compacted pad or subgrade, or flooding an excavation. Runoff can also cause erosion. Earthwork during rainy months will require extra effort and caution by the contractors. The soils may be too wet to compact which will require processing to dry the soil. The grading contractor should be responsible to protect work to avoid damage by rainstorms, including, but not limited to, smooth rolling the seal off a pad or subgrade surface to facilitate drainage and to reduce rain damage, and the covering of trenches and stockpiles with plastic sheeting. Ponded water should be pumped out of excavations and subgrade areas immediately. Construction in wet weather, if a possibility for project construction, should be addressed in the project construction bid documents and/or specifications. We recommend the grading contractor submits a wet weather construction plan outlining procedures they will employ to protect their work and to minimize damage to their work by rainstorms.

3.4 BACKFILL AND FILL

The two types of backfill and fill proposed to support the structures and site features previously described are defined herein as follows:

General Load-Bearing Fill: Used for support of pavements, curbs, sidewalks, and finished site grades outside the building areas. General Load-Bearing Fill should consist of or a combination of GW, GP, GM, GC, SW, SP, SM, SC, ML, and CL materials as classified by ASTM D2487.

The General Load-Bearing Fill should consist of inorganic and readily compactable site soils, inert rubble or rock fragments. Fragments larger than eight inches (any dimension) should be excluded from General Load-Bearing Fills. The on-site soils encountered in the borings are generally considered suitable for use as General Load-Bearing Fill provided the moisture content and particle sizes are controlled. General Load-Bearing Fills should have a moisture content controlled to within 5 percent of optimum as determined by ASTM D-698.

Select Load-Bearing Fill: Recommended for fills exclusively in the building areas. Select Load- Bearing Fill should consist of inorganic and readily compactable site soils, inert rubble or rock fragments. Fragments larger than four inches (any dimension) should be excluded from Select Load-Bearing Fills. Select Load-Bearing Fill should consist of or a combination of GW, GP, GM, GC, SW, SP, SM, and SC materials as classified by ASTM D2487. The on-site sandy soils encountered in the test borings are generally considered suitable for use as Select Load-Bearing Fill provided the moisture content and particle sizes are controlled. Select Load-Bearing Fills should have a moisture content controlled to within three percent of optimum as determined by

ASTM D-698.

If imported fills are necessary, imported soils should meet the above requirements, and based on their intended use, should have less than 35 percent by weight passing a No. 200 sieve, and should have a liquid limit below 40 and a plasticity index of 12 or less. Proposed import fill should be approved by the project Geotechnical Engineer prior to delivery to the site.

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Load-bearing fills should be placed on a stable, near level subgrade prepared by the removal of weak soil deposits. The load-bearing fills should be placed in lifts not exceeding a loose thickness of 12 inches, and 8 inches in confined trench and wall backfills.

It is recommended that Select and General Load-Bearing Fills have each lift compacted to at least 98 percent and 95 percent, respectively, of the optimum Standard Proctor dry density as determined by ASTM D-698. In addition, fills should be stable without significant movement under construction equipment as judged by a representative of the Geotechnical Engineer. Quality control observation and testing of in-place fill densities throughout construction should be performed by a representative of the Geotechnical Engineer. However, conformance with the specifications remains the contractor’s responsibility.

The contractor should not place backfill or fill material on subgrade surfaces that are muddy, frozen, or contain frost/ice. Frozen soils are not suitable fill sources.

3.5 UTILITIES

Utility excavations should comply with local codes, ordinances and OSHA requirements.

Excavation side slopes are to be maintained in a safe condition, in accordance with Section 3.3 of this report, until completion of backfilling.

The backfilling of utility trenches in the building area must meet the same compaction criteria as the surrounding subgrade soil (i.e. 98 percent of the optimum dry density as determined by the Standard Proctor Test, ASTM D-698, most recent edition). Since a nuclear density gauge may read the conduit or pipe as a void, visual observations of backfill materials and manual techniques, performed by a representative of the Geotechnical Engineer, should supplement nuclear density testing.

3.6 SEISMIC CONSIDERATIONS

Based on the properties of the soils encountered in our test borings and our knowledge of geologic conditions in the area of the site, a site class of ‘D’ (“stiff soil” profile) is considered appropriate as determined from Table 1613.5.2 of IBC 2006.

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4.0 DESIGN RECOMMENDATIONS

4.1 FOUNDATION DESIGN

Based on our evaluation, Kleinfelder recommends that the proposed Air National Guard Base Intel facility be supported on shallow continuous wall-footings and isolated spread-footings bearing on either approved undisturbed native soils or engineered fill. The undocumented fills encountered up to a depth of about 8 ft bgs appear to be composed predominantly of disturbed native materials, and may not have been placed under engineering controls. Therefore, these materials may not provide adequate uniform foundation support and present a risk for damaging differential settlements. To mitigate the potential for damaging differential settlements to occur, we recommend that undocumented fills, buried asphaltic materials and soft native deposits be overexcavated and replaced with select load-bearing fill beneath the area of the footings. Based on conditions encountered in the test borings, this may include excavations of about 2 to 8 ft below existing grades to extend into undisturbed native materials.

Footings constructed in accordance with the above recommendations may be designed for a maximum net allowable soil bearing pressure of 3,000 pounds per square foot (psf) bearing on approved foundation subgrades. Considering the allowable bearing pressure, the factor of safety with respect to shear failure is greater than 3. A one-third increase in allowable bearing pressure may be used for load combinations that include all transient loads including seismic and wind.

Continuous wall footings should be designed as “light” grade beams to reduce the potential for differential settlement. Continuous footings should have a minimum width of 24 inches and isolated spread footings should have a minimum width of 36 inches. Post-construction total and differential settlements of the shallow foundation system are estimated to be less than 1 inch and ½ inch respectively.

During construction, footing excavations should be observed by a representative of the Geotechnical Engineer to evaluate the supporting capabilities of the bearing materials. The representative of the Geotechnical Engineer should “probe” the foundation subgrade with a manually operated soil-probe to identify potential loose or soft zones. If unsuitable bearing conditions or debris are encountered, the area should be over-excavated, and backfilled with compacted, select load-bearing fill at the recommendation of a representative of the Geotechnical Engineer.

Footings subject to frost are recommended to be located at least 48 inches below the lowest adjacent exterior grade. Construction schedules which include a winter season may require temporary frost protection for interior footings and other building features which are not designed to be subject to frost upon building completion.

For resistance to lateral loading, we anticipate the foundations will be constructed on sandy soils or approved Load-Bearing Fills. An ultimate coefficient of friction of 0.35 may be assumed for calculation of frictional resistance along the bottom of the foundation. We recommend a minimum factor of safety of 1.5 to resist sliding.

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4.2 SLAB-ON-GRADE

It is Kleinfelder’s opinion that the proposed slabs-on-grade may be supported on a subgrade consisting of suitable proof-rolled existing materials or new properly compacted select-load-bearing fills used to construct the building pad. The slabs-on-grade should be designed and constructed in accordance with the recommendations of ACI Committee Reports 360R-92 and 302.1 R-96.

Concrete floor slabs are recommended to be simply supported at wall junctures to allow unrestricted rotation of the slab's edges. Alternatively, the slabs should be free to undergo vertical deflection at the joints. Control joints should be used to control shrinkage cracks. Based on the subgrade preparation procedures recommended herein and the existing soil conditions, a subgrade modulus (k) of 150 pci is estimated for slab design.

Conventional ground floor slab design should include a vapor retarder located immediately below the slab and at least six inches of free draining granular material below the vapor retarder as a capillary break. If the materials underlying the vapor retarder contain sharp or angular particles, a geotextile fabric should be provided to protect the vapor retarder from puncture.

Portions of the floor slabs may not be subjected to building heat during freezing weather and may be susceptible to frost heave. The soils beneath these slabs should consist of a non-frost susceptible, free-draining granular material for a minimum one-foot of depth. The soil should contain drainage provisions to ensure that surface water is not trapped.

It is typical for construction activities to “damage” the building pad between the time the building pad is prepared and the new floor slab is constructed. Kleinfelder recommends that just prior to vapor retarder installation and slab construction, the building area subgrade be proof-rolled and any unstable zones be stabilized at the recommendation of the Geotechnical Engineer representative.

4.3 MOISTURE VAPOR TRANSMISSION

Subsurface moisture and moisture vapor naturally migrate upward through the soil and, where the soil is covered by a building or pavement, this subsurface moisture will collect. To reduce the impact of the subsurface moisture and potential impact of future introduced moisture (such as landscape irrigation or precipitation) the current industry standard is to place a vapor retarder on the compacted crushed rock layer. This membrane typically consists of visqueen or polyvinyl plastic sheeting of at least 10 mil in thickness. It should be noted that although vapor barrier systems are currently the industry standard, this system may not be completely effective in preventing floor slab moisture problems. These systems typically will not necessarily assure that floor slab moisture transmission rates will meet floor-covering manufacturer standards and that indoor humidity levels be appropriate to inhibit mold growth. The design and construction of such systems are totally dependent on the proposed use and design of the building and all elements of building design and function should be considered in the slab-on-grade floor design.

Building design and construction have a greater role in perceived moisture problems since sealed buildings/rooms or inadequate ventilation may produce excessive moisture in a building and affect indoor air quality.

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Various factors such as surface grades, adjacent planters, the quality of slab concrete and the permeability of the on-site soils affect slab moisture and can control future performance. In many cases, floor moisture problems are the result of either improper curing of floors slabs or improper application of flooring adhesives. We recommend contacting a flooring consultant experienced in the area of concrete slab-on-grade floors for specific recommendations regarding your proposed flooring applications.

Special precautions must be taken during the placement and curing of all concrete slabs.

Excessive slump (high water-cement ratio) of the concrete and/or improper curing procedures used during either hot or cold weather conditions could lead to excessive shrinkage, cracking, or curling of the slabs. High water-cement ratio and/or improper curing also greatly increase the water vapor permeability of concrete. We recommend that all concrete placement and curing operations be performed in accordance with the American Concrete Institute (ACI) manual.

It is emphasized that we are not floor moisture proofing experts. We make no guarantee nor provide any assurance that use of a capillary break/vapor retarder system will reduce concrete slab-on-grade floor moisture penetration to any specific rate or level, particularly those required by floor covering manufacturers. The builder and designers should consider all available measures for floor slab moisture protection.

4.4 PAVEMENT DESIGN

We understand that pavement will include flexible or rigid pavements for parking and drivelanes.

Traffic loadings were not available; however, for the general vehicular and light-truck traffic, we would anticipate that the pavement section would typically include a minimum of 3 inches of asphalt concrete placed on top of a minimum of 6 inches of crushed stone sub-base and placed on approved subgrade materials as described in Section 3.2 of this report. Rigid concrete pavements should be placed on top of a minimum of 6 inches of crushed stone sub-base and placed on approved subgrade materials as described in Section 3.2 of this report. For design of pavement sections, we recommend a subgrade modulus of 150 pci, a CBR value of 8, and a resilient modulus of 12,000 psi based on the properties of the soils encountered in our borings.

4.5 GROUNDWATER MANAGEMENT

Groundwater was encountered at approximately 48 feet bgs at the time of our exploration. It should be noted that groundwater is known to fluctuate due to local and regional factors including, but not limited to, precipitation events, tides, periods of wet or dry weather, and seasonal changes. Dewatering of excavations may be required due to infiltrating surface water or pockets of “trapped” water. During construction, surface water may infiltrate along more permeable sand seams and act as perched groundwater above soils with a higher silt and clay content. To reduce the need for dewatering, surface water should be prevented from ponding in construction areas and accumulating in excavations by such means including, but not limited to, grading, ditches, swales, or diversion berms. Dewatering systems, if needed, should be designed and operated to prevent pumping of soil, disturbance of subgrades, and adverse effects to existing site features. Pumped water should be detained properly on site prior to discharge off site.

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4.6 CORROSION AND SULFATE ATTACK

Corrosivity testing was performed on one composite soil sample, combined from two discrete samples collected from the split-spoon sampler. The results of the corrosivity testing are provided in Table 1:

Table 1 – Summary of Laboratory Soil-Corrosivity Testing

Bor. No. Samples Depth pH Redox Potential Chloride Sulfate Sulfide Elec.

Resist.

B-5 B + C 2 to 6 ft 6.92 270 mV 75 mg/kg 93 mg/kg <27 mg/kg

4,100 ohm-cm

These soil corrosivity laboratory results were compared to guidelines in the following references to evaluate the potential of corrosion and attack to concrete and metal:

• Building Code Requirements for Reinforced Concrete, ACI 318, ,Part 3, Chap. 4;

• Naval Facilities Engineering Command, Design Manual 7.02, NAVFAC DM7.2, Chap. 4;

• Permanent Ground Anchors, FHWA DP-68-1R; and

• Polyethylene Encasement for Ductile Iron Pipe Systems, ANSI/AWWA C105/A21.5, Appendix A.

The soil is considered to present low potential for corrosion and attack to concrete and metal pipe. Standard mix design for concrete and standard corrosion protection for metal for buried structures is recommended. These analytical laboratory tests were preformed on discrete samples and do not provide a complete representation of all soil types at the site. The soil corrosion laboratory test results are general and should be considered only a random survey.

Kleinfelder does not practice corrosion engineering and, therefore, detailed analysis of corrosion test results is not included in this report. We make no guarantee nor provide any assurance regarding the risk for corrosion potential. We recommend a qualified corrosion engineer be retained to review the test results and design protective systems that may be required.

4.7 RETAINING WALLS AND BELOW-GRADE WALLS

We understand that the proposed site development may include the construction of below grade walls and/or site retaining walls 15 feet in height or less.

Any walls subject to unbalanced earth pressure should be designed as earth retaining walls. Floor and overhead loads as well as surcharge loads such as sloped backfill, line loads, and adjacent traffic should be included in the retaining wall design. Walls structurally connected to the proposed building or braced at the wall top such that lateral deflection is not permitted, should be designed for an at-rest earth pressure. Free standing walls not connected to the proposed building or braced at the wall top may be designed for an active earth pressure, provided lateral movements at the top of the wall are acceptable. Parameters in the following table assume horizontal backfill behind retaining walls and no hydrostatic pressure.

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Retaining Wall Design Parameters

Angle of Internal Friction (for granular soil meeting the requirements included herein) φ = 30°

Total Unit Weight 120 pcf

Lateral Earth Pressure Coefficients KO (at-rest) = 0.50;

Ka (active) = 0.33;

Kp (passive) = 3.00

Equivalent Fluid Pressures At rest = 60 pcf Active = 40 pcf

Retaining walls should be designed with backdrains to mitigate build-up of hydrostatic pressures. A typical backdrain system consists of an 18-inch wide (horizontal measure) zone of crushed, free-drainage gravel with less than five-percent fines, wrapped in a geotextile filter fabric (Mirafi 140N or equivalent) immediately behind the walls. A drainage mat may be used as an alternative to the drainage stone layer. The gravel section or drainage mat should be drained by a 4-inch minimum diameter PVC perforated pipe placed at the base of the wall. The pipe should drain by gravity to discharge at a suitable location as determined by the Civil Engineer. We recommend below-grade walls include full-height water proofing.

Backfill or fill material placed behind retaining walls should consist of select load-bearing fill, as defined in Section 3.4, with the additional requirement of having less than 30 percent by weight passing a No. 200 sieve. Onsite soils may be re-used provided they meet the requirements noted above. Over-compaction should be avoided because increased compactive effort can result in lateral pressures significantly higher than those recommended above.

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5.0 LIMITATIONS

Recommendations contained in this report are based on our field observations and subsurface explorations, laboratory tests, and our present knowledge of the proposed development. It is possible that soil or groundwater conditions could vary between or beyond the points explored.

If soil or groundwater conditions are encountered during construction that differ from those described herein, we should be notified immediately so a review may be made and any supplemental recommendations provided. If the scope of the proposed construction, including the proposed loads or structural locations, changes from that described in this report, our recommendations should also be reviewed.

We have prepared this report in accordance with generally accepted geotechnical engineering practices. No warranty, either expressed or implied, is made. The recommendations provided in this report are based on the assumption that an adequate program of tests and observations will be conducted by Kleinfelder during the construction phase in order to evaluate compliance with our recommendations. Other standards or documents referenced in any given standard cited in this report, or otherwise relied upon by the author of this report, are only mentioned in the given standard; they are not incorporated into it or “included by reference,” as that latter term is used relative to contracts or other matters of law.

This report may be used only by Burns and McDonnell Engineering Co., Inc. and only for the purposes stated within a reasonable time from its issuance, but in no event later than one year from the date of the report. Land or facility use, on and off-site conditions, regulations, or other factors may change over time, and additional work may be required with the passage of time.

Based on the intended use of the report, Kleinfelder may recommend that additional work be performed and that an updated report be issued. Non-compliance with any of these requirements by Burns and McDonnell Engineering Co., Inc. or other parties will release Kleinfelder from any liability resulting from the use of this report by any unauthorized party and Burns and McDonnell Engineering Co., Inc. agrees to defend, indemnify and hold harmless Kleinfelder from any claim or liability associated with such unauthorized use or non-compliance.

The scope of work for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site.

Kleinfelder has conducted subsurface exploration and provided recommendations for this project. We recommend that Kleinfelder be given the opportunity to provide final design for this project, if required. In the event Kleinfelder is not, at a minimum, retained to review the final project plans and specifications to evaluate if our recommendations have been properly interpreted, we will assume no responsibility for misinterpretation of our recommendations.

We recommend that all earthwork during construction be monitored by a representative from Kleinfelder, including site preparation, installation of foundation elements, and placement of structural fill and/or backfill. The purpose of these services would be to provide Kleinfelder the opportunity to observe the actual soil conditions encountered during construction, evaluate the applicability of the recommendations presented in this report to the soil conditions encountered, and recommend appropriate changes in design or construction procedures if conditions differ from those described herein.

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