Geotech Report 878-95047-2 Schenck Dining Hall_07132009.pdf

Professional Service Industries, Inc. 534 St. Andrews Road, Suite C • Columbia, SC 29210 • Phone 803/776-6050 • Fax 803/772-2803

July 13, 2009

Mr. Chris Garrett PBDewberry 2101 Wilson Boulevard, Suite 200 Arlington, Virginia 22201

Geotechnical Engineering Services Report Proposed Site Adapt For a New Dining Hall

Schenck Civilian Center Conservation Center Pisgah Forest, North Carolina

PSI Project 878-95047-2

Dear Mr. Garrett

Thank you for choosing Professional Service Industries, Inc. (PSI) as your geotechnical consultant for your project in Pisgah, North Carolina.

In accordance with your authorization, we have completed a subsurface exploration for the referenced project. The findings of the exploration and our recommendations for the project are discussed in the accompanying report. As requested, three copies of the report are being submitted to you.

The soil samples obtained during this exploration that were not consumed in laboratory testing will be retained in our laboratory for sixty days, unless otherwise noted.

If you have any questions, please do not hesitate to contact our office. PSI would be pleased to continue providing geotechnical services throughout the implementation of the project, and we look forward to working with you and your organization on this and future projects.

Respectfully Submitted, PROFESSIONAL SERVICE INDUSTRIES, INC.

David McKee, PE Principal Consultant

GEOTECHNICAL ENGINEERING

SERVICES REPORT

PROPOSED SITE ADAPT FOR A NEW DINING HALL

SCHENCK CIVILIAN CONSERVATION CENTER

PISGAH FOREST, NORTH CAROLINA

PREPARED FOR

PBDEWBERRY

2101 WILSON BOULEVARD, SUITE 200

ARLINGTION, VIRGINIA 22201

PREPARED BY

PROFESSIONAL SERVICE INDUSTRIES, INC.

534 ST. ANDREWS ROAD

COLUMBIA, SOUTH CAROLINA 29210

PHONE: (803) 776-6050

FAX: (803) 776-4682

David M. McKee, P.E.

Principal Consultant

July 13, 2009 PSI Project Number: 878-95047-2

Keith Ingram, PE Branch Manager

TABLE OF CONTENTS

PROJECT INFORMATION

• PROJECT AUTHORIZATION

• PROJECT LOCATION AND DESCRIPTION

• PURPOSE AND SCOPE OF SERVICES

SITE AND SUBSURFACE CONDITIONS

• SITE CONDITIONS

• EXPLORATORY PROCEDURES

• SUBSURFACE CONDITIONS

• GROUNDWATER INFORMATION

EVALUATIONS AND RECOMMENDATIONS

• SITE PREPARATION

• STRUCTURAL FILL SELECTION AND PLACEMENT

• DRAINAGE AND GROUNDWATER CONSIDERATONS

• FOUNDATION RECOMMENDATIONS

• FLOOR SLAB RECOMMENDATIONS

• PAVEMENTS

• CONSTRUCTION EXCAVATION CONSIDERATONS

REPORT LIMITATIONS

APPENDIX

BORING LOCATION PLAN

BORING LOGS

LABORATORY TEST RESULTS

GENERAL NOTES

Proposed Site Adapt for a New Dining Hall July 13, 2009 PSI Project 878-95047-2 Page 1 of 10

PROJECT INFORMATION

Project Authorization

This report presents the results of our geotechnical exploration services for the proposed Site Adapt of a New Dining Hall at the Schenck Civilian Conservation Center in Pisgah Forest, North Carolina. Our services have been performed in general accordance with PSI Proposal Number PO-878-950098 dated May 15, 2009 and Subconsultant Agreement dated June 16, 2009. Written authorization was given in the form of a signed proposal to perform the scope of services referenced within the proposal.

Project Location and Description

The proposed new Dining Hall will be located to the northwest of the existing Gymnasium (Building 30) and to the northeast of the existing Wellness center (Building 53 ) at the Schenck Civilian Conservation Center in Pisgah Forest, North Carolina. The proposed Dining Hall will be about 9,230 square feet in size and will have associated parking on the east side. The structure will be single story and will have CMU walls and a concrete slab-on-grade floor. Structural loads were not available at this time. However, based on experience with similar projects column and wall loads are estimated to be on the order of 50 to 70 kips and 2 to 3 kips per linear foot, respectively. A grading plan was not available at this time. However, based on observations of the site during field operations, PSI anticipates that cut excavations or fill placement in the building pad area will be on the order of one to two feet.

The information presented in this section was used in the evaluation. Estimated loads and corresponding foundation sizes have a direct affect on the recommendations, including the type of foundation, the allowable bearing pressure, and the estimated settlement. In addition, estimated subgrade elevations and cut/fill quantities can have a direct affect on the provided recommendations. If any of the noted information is incorrect or has changed, please inform PSI so that we may amend the recommendations presented in this report, if appropriate. If PSI is not retained to perform this function, PSI can not be responsible for the impact of the changes on the performance of the project.

Purpose and Scope of Services

The purpose of this exploration was to evaluate the subsurface conditions at the site and to provide recommendations regarding foundation bearing capacity, as well as general site development for the proposed structure. The scope of the exploration and analysis included the following:

• PSI performed five soil test borings which were advanced in the area of the planned building and pavement area. The borings were advanced to depths ranging from 5 ½ to 25 feet below existing grades.

• PSI prepared a Boring Log for each of the borings which described the

PSI Project 878-95047-2 Page 2 of 10 subsurface conditions encountered and other pertinent information.

• We conducted a geotechnical engineering evaluation of the available data to provide recommendations regarding foundation type, including allowable foundation bearing pressure, pavement design and construction considerations, such as subgrade preparation, excavation characteristics and fill placement at the site.

• PSI prepared this engineering report presenting data, evaluations and recommendations.

Please note that the scope of services did not include an environmental assessment for determining the presence or absence of wetlands or hazardous or toxic materials in the soil, bedrock, surface water, groundwater, or air, on, below or around this site. Any statements in this report or on the boring log regarding odors; colors, unusual or suspicious items or conditions are strictly for the information of the client.

SITE AND SUBSURFACE CONDITIONS

Site Conditions

At the time of field exploration, the site was mainly grass covered with an existing roadway that crossed the northern half of the building area. An existing drainage ditch with wooden cross walks was located along the southern side of the proposed building area. Scattered trees were located throughout the grassed areas.

The topography of the property, with the exception of the ditch area, appeared to be relatively level.

The surface of the site was firm and supported our ATV mounted drill rig.

Exploratory Procedures

Five soil test borings were advanced at the approximate locations shown on the Boring Location Plan in the Appendix of this report. In addition, two shallow offset borings, (B-1A and B-2A), were advanced in an attempt to retrieve undisturbed samples in the upper five feet. The test borings were drilled to a depth of 5½ to 25 feet below existing grades. The boring locations were established in the field by PSI personnel by approximating distances and angles from known references, as shown on the provided site plan in the appendix of this report.

The borings were advanced with a CME 550X ATV mounted drill rig using hollow stem augers. Standard penetration testing (ASTM D-1586) was performed at selected depths in the test borings. The soil samples obtained from the drilling operations were classified in general accordance with ASTM D-2488 (Visual-Manual Procedure for Description of Soils). Soil classifications include the use of the Unified Soil Classification System described in ASTM D-2487 (Classification of Soils for Engineering Purposes).

PSI Project 878-95047-2 Page 3 of 10

Subsurface Conditions

Topsoil was encountered in all of the test borings and extended to depths of about 2 to 3 inches below the existing ground surface. Below the topsoil, FILL soil consisting of very soft to stiff sandy SILT (ML), elastic SILT (MH) and silty SAND (SM) was encountered in test borings B-3, B-4 and B-5 and extended to a depth of about 6 feet below existing grades.

Alluvial soil consisting mainly of very loose to dense, silty or clayey SAND (SM or SC) and gravel (GM) was encountered below the topsoil in test borings B-1 and B-2 and below the fill soil in test borings B-3, B-4, and B-5. The alluvial soil extended to termination depths of about 11½,11½ and 10½ feet in test borings B-1, B-3 and B-5, respectively, and to depths of 11 and 12 feet below existing grades in test borings B-2 and B-4, respectively. Residual soil consisting of medium stiff SILT (ML) and medium dense silty SAND (SM) was encountered below the alluvium in test borings B-2 and B-4 and extended to the maximum 25 foot depth explored.

The above subsurface description is of a generalized nature, provided to highlight the major soil strata encountered. The boring logs presented in the Appendix should be reviewed for specific information as to the individual soil strata locations. The stratifications shown on the boring log represent the conditions at the actual boring locations only. Variations may occur and should be expected outside the boring location. The stratifications represent the approximate boundary between subsurface materials and the transition may be gradual.

Groundwater Information

Groundwater was encountered in the test borings at depths ranging from about 2 ½ to 5 feet below existing grades at the time of field exploration. Although groundwater was encountered at these depths, groundwater levels can often fluctuate and can be encountered at shallow depths during periods of heavy rainfall. We recommend that the Contractor determine the actual groundwater levels at the time of construction to determine the groundwater impact on the construction procedures.

PSI Project 878-95047-2 Page 4 of 10

EVALUATION AND RECOMMENDATIONS

Based upon review of the data obtained from the borings, the proposed structure can be supported on shallow foundations provided remedial measures are taken to improve unsuitable surface soil in the upper 6 to 8 feet. Remedial measures will also be required to improve subgrade conditions in parking areas depending on location. Detailed discussion of our recommendations for design and construction are presented in the following sections of this report.

Site Preparation

Initially, all surface materials including grass, topsoil, pavement structures and any other unsatisfactory/deleterious materials should be removed from the proposed areas scheduled for site development for a lateral distance of 5 feet beyond the limits of new construction.

After designated areas of the site have been stripped, the removal of unsuitable soil within the proposed building footprint and pavement areas can begin.

Building Area: We recommend existing fill soil and loose, alluvial soil be undercut from within the building area as well as an area at least 5 feet beyond the building footprint.

Based on the test boring data, it is anticipated that the depth of undercut will vary from about 6 to 8 feet below existing grades depending on location. The final depth of undercut should be determined by PSI at the time of grading. We recommend all undercutting operations be observed by PSI to document and check that all of the loose fill and alluvial soil have been removed as recommended. Based on the groundwater levels recorded in the test borings, dewatering during undercutting and replacement fill operations should be anticipated. Dewatering may consist of ditching or other means. The contractor should be responsible for selecting the most optimal dewatering method. Prior to commencing backfilling operations, the undercut subgrade may require stabilization. Placement of a 12 inch layer of open graded stone such as #57 stone and a woven geotextile fabric (placed above and below the stone) is often a suitable method for providing a stable base. It is recommended that an allowance for these materials be included for budgeting purposes.

Parking Areas: Following clearing and stripping of site, the exposed subgrade, final subgrades in cut excavations and all areas receiving new fill should be proof rolled.

Proof rolling should be performed using a loaded dump truck, or similar rubber-tired equipment, weighing at least 20 tons. Proof rolling operations should be observed by a representative of PSI. Subgrades exhibiting excessive deflection during proof rolling should be undercut as recommended by PSI at the time of grading.

All areas receiving fill should be compacted to 95 percent of the maximum dry density as determined by ASTM D-698 laboratory procedure. The upper 12 inches of subgrade for

PSI Project 878-95047-2 Page 5 of 10 slabs and pavements should be compacted to at least 98 percent of the maximum dry density as determined by ASTM D-698.

Following undercutting and proofrolling, structural fill may be placed as recommended in this report.

During site preparation, burn pits, trash pits or other such buried disposal areas are all too frequently encountered in isolated areas outside the boring locations. If such items are encountered during construction, PSI should be notified immediately to address the situation and have the opportunity to provide recommendations on how to proceed with construction.

Structural Fill Selection and Placement

After completion of the site preparation, the placement of any fill required to achieve finished subgrade level can proceed. Any material utilized as fill should not contain rocks greater than 3 inches in diameter or greater than 30% retained on the ¾-inch sieve. Fill material should not contain more than 4 percent (by weight) of organic matter or other deleterious material. Typically, the Plasticity Index (PI) for the material should not exceed 25, and the Liquid Limit (LL) for the material should not exceed 50 (Unified Soil Classifications of GW, GM, GC, SW, SM, ML and some SC and CL), as determined by Atterberg Limit (AL) testing (ASTM D 4318). Use of material with AL values in excess of these limits can sometimes be used if the owner acknowledges and accepts the associated risks. Structural fill should possess a maximum dry density (MDD) of at least 95 pounds per cubic foot (pcf) as determined by the standard Proctor compaction test

(ASTM D-698).

The onsite near surface soils which will be undercut are unsuitable for use as structural fill due to their moisture content, moisture sensitivity and organic content. The construction budget should provide an allowance for proper disposal of unsatisfactory materials that will exist within the building and parking areas.

Structural fill required to achieve subgrade elevations should be placed in loose lifts of 8 inches or less in thickness, unless otherwise specified. Fill soils within the upper 12 inches of finished grade should be compacted to at least 98 percent of the material’s standard Proctor maximum dry density (MDD). Below 12 inches structural fill should be densified to at least 95 percent of the MDD. The moisture content of the controlled fill should be maintained within 3 percent of the material’s optimum moisture content as determined by the standard Proctor compaction test.

It is recommended that the placement and compaction of any fill be monitored by a Soil Technician, working under the direction of the Geotechnical Engineer, to document that the specified degree of compaction is being obtained. We recommend compaction testing be performed at a rate of one test per lift per lift.

Drainage and Groundwater Considerations

In general, water should not be allowed to collect near the foundations either during, or after construction. Undercut or excavated areas should be sloped toward one corner to

PSI Project 878-95047-2 Page 6 of 10 facilitate the removal of any collected rainwater, groundwater or surface runoff. Positive site drainage should be provided to reduce infiltration of surface water around the perimeter of the building and parking areas. All grades should be sloped away from the building and surface drainage should be collected and discharged such that water is not permitted to infiltrate the building area.

Foundation Recommendations

Based on the subsurface conditions encountered by the field exploration program, the estimated loads of the proposed structure, anticipated grading and the remedial earthwork recommendations stated herein, it appears that conventional spread footings will be a satisfactory foundation system for the proposed structure. The following design parameters are recommended for foundation design and construction.

• Foundations bearing on new structural fill may be designed using a maximum net allowable bearing pressure of 2,000 pounds per square foot. The allowable bearing pressure should include factored dead load plus sustained live load.

• Footings should be embedded at least 1½ feet below the lowest adjacent grade to reduce the detrimental effects of seasonal moisture variations in the soils, for frost protection and for bearing considerations. We anticipate that they may be embedded more deeply to resist overturning forces.

• PSI recommends that the foundations be designed in accordance with the 2006 North Carolina Building Code.

Footing excavations should be protected from surface water run-off and freezing. If water is allowed to accumulate within a footing excavation and soften the bearing soils, or if the bearing soils are allowed to freeze, the deficient soils should be removed from the excavation prior to concrete placement.

Floor Slab Recommendations

Where concrete slabs are designed as beams on an elastic foundation, the residual soil or structural fill that will comprise the subgrade should be assumed to have a modulus of subgrade reaction (k) of 130 pounds per cubic inch (pci). This value is estimated based on the expected result of a plate load test of the subgrade using a nominal 30-inch plate.

However, if the floor slab design is sensitive to K, plate load tests should be performed to establish a site-specific value. In order to provide uniform support beneath any proposed floor slab-on-grade, we recommend that floor slabs be underlain by a minimum of 4 inches of compacted aggregate subbase material. The estimated modulus of subgrade reaction after the addition of 4 inches of aggregate subbase material is 160 pci.

PSI Project 878-95047-2 Page 7 of 10

The aggregate base course material should be compacted to at least 98 percent of its standard Proctor maximum dry density. Open-graded crushed stone, such as No. 57 stone may also be used; however, it is our experience that open graded crushed stone can collect water during periods of rain and cause saturation and softening of the subgrade soils prior to placement of the floor slab concrete. Therefore, construction sequencing/timing, and the season in which the stone is placed, should be taken into consideration.

The crushed rock is intended to provide a capillary break to limit migration of moisture through the slab. If additional protection against moisture vapor is desired, a vapor retarding membrane may also be incorporated into the design. Factors such as cost, special considerations for construction, and the floor coverings suggest that decisions on the use of vapor retarding membranes be made by the architect and owner. Vapor retarders should be installed in accordance with ACI 302.1, Chapter 3.

The precautions listed below should be closely followed for construction of slabs-on-grade. These details will not prevent the amount of slab movement, but are intended to reduce potential damage should some settlement of the supporting subgrade take place.

• Cracking of slabs-on-grade is normal and should be expected. Cracking can occur not only as a result of heaving or compression of the supporting soil, but also as a result of concrete curing stresses. The occurrence of concrete shrinkage cracks, and problems associated with concrete curing may be reduced and/or controlled by limiting the water to cement ratio of the concrete, proper concrete placement, finishing, and curing, and by the placement of crack control joints at frequent intervals, particularly, where re-entrant slab corners occur. The American Concrete Institute (ACI) recommends a maximum panel size (in feet) equal to approximately three times the thickness of the slab (in inches) in both directions. For example, joints are recommended at a maximum spacing of 12 feet assuming a four-inch thick slab. We also recommend that control joints be scored three feet in from and parallel to all foundation walls.

Using fiber reinforcement in the concrete can also control shrinkage cracking.

• Some increase in moisture content is inevitable as a result of development and associated landscaping; however, extreme moisture content increases can be largely controlled by proper and responsible site drainage, building maintenance and irrigation practices.

• All backfill in areas supporting slabs should be moisture conditioned and compacted as described earlier in this report. Backfill in all interior and exterior utility line trenches should be carefully compacted.

• Exterior slabs should be isolated from the building. These slabs should be reinforced to function as independent units. Movement of these slabs should not be transmitted to the building foundation or superstructure.

Foundation and utility line installation, weather and other construction activities can disturb the subgrade between completion of grading and slab construction. For this reason, the

PSI Project 878-95047-2 Page 8 of 10

Geotechnical Engineer should evaluate the subgrade immediately prior to placing the base materials or slab concrete. During this evaluation, the subgrade should be proofrolled with heavy rubber-tired equipment if practical. Areas judged by the Geotechnical Engineer to be unstable should be undercut and replaced with structural fill compacted to at least 98 percent of its standard Proctor maximum dry density.

Pavements

The following pavement recommendations are presented as preliminary for your consideration. The civil engineer for the project may have more traffic and project design data available than is presently known, and may wish to modify and refine these pavement sections. We will, upon request, be pleased to provide a more detailed pavement design when definite traffic and building plans are available.

Prior to placing the base or leveling course, the subgrade should be proof rolled with a fully- loaded, tandem axle dump truck, or similar rubber tired vehicle, in order to detect areas or pockets of unusually soft material. It should be noted that the pavement section may not be adequate for the support of heavy construction traffic.

Asphalt Pavement

Based on our experience and using a design California Bearing Ratio (CBR) value of 5 (estimated) for the subgrade soils, a design life period of 20 years suggests the following pavement thicknesses. For entrance and dumpster truck drive areas, we assumed traffic will not exceed 4 equivalent 18-kip single axle loads (ESALs) per day. For car parking areas, we assumed 1 ESAL per day. If the anticipated traffic exceeds these values, we should be informed so that a specific pavement design can be made for the project, or the design can be modified by the site civil engineer. A typical asphalt pavement section would be:

Table 1. Typical Asphalt Pavement Section Minimum Recommended Thickness

Material

Driveways

Car Parking

Asphalt Pavement

3 inches 2 inches

Aggregate Base Course

6 inches 6 inches

Asphalt pavement base course material should consist of a well-graded, 1½-inch or ¾-inch-minus, crushed rock, having less than 5 percent material passing the No. 200 sieve.

The base course and asphaltic concrete materials should conform to the requirements set forth in the latest edition of the North Carolina Department of Transportation, Standard Specifications for Highway Construction. Base course material should be moisture conditioned to within 2 percent of the optimum moisture content and compacted by mechanical means to a minimum of 95 percent of the material's maximum dry density as determined in accordance with ASTM D-1557 (Modified Proctor). Fill

PSI Project 878-95047-2 Page 9 of 10 materials should be placed in layers that, when compacted, do not exceed approximately 6 inches. The asphaltic concrete material should be compacted to at least 92 percent of the material’s theoretical maximum density as determined in accordance ASTM D-2041 (Rice Specific Gravity).

Construction Excavation Considerations

In Federal Register Volume 54, No. 209 (October 1989), the United States Department of Labor, Occupational Safety and Health Administration (OSHA) amended its "Construction Standards for Excavations, 29 CFR, Part 1926, Subpart P." This document was issued to better insure the safety of workmen entering trenches or excavations. It is mandated by this federal regulation that all excavations, whether they be utility trenches, basement excavations, or footing excavations, be constructed in accordance with the revised OSHA guidelines. It is our understanding that these regulations are being strictly enforced and if they are not closely followed, the owner and the contractor could be liable for substantial penalties.

The contractor is solely responsible for designing and constructing stable, temporary excavations and should shore, slope, or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. The contractor's responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor's safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations.

We are providing this information solely as a service to our client. PSI is not assuming responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred.

PSI Project 878-95047-2 Page 10 of 10

REPORT LIMITATIONS

The recommendations submitted are based on the available soil information obtained and the assumptions made by PSI, for the proposed project. The results are considered reliable to the degree implied by the location of the borings. If there are any revisions to the plans for this project or if deviations from the subsurface conditions noted in this report are encountered during construction, PSI should be notified immediately to determine if changes in the foundation, or other recommendations, are required. If PSI is not retained to perform these functions, PSI cannot be responsible for the impact of those conditions on the performance of the project.

The geotechnical engineer warrants that the findings, recommendations, specifications, or professional advice contained herein have been made in accordance with generally accepted professional geotechnical engineering practices in the local area at the time of this report. No other warranties are implied or expressed.

PSI did not provide any service to investigate or detect the presence of moisture, mold or other biological contaminants in or around any structure, or any service that was designed or intended to prevent or lower the risk of the occurrence of the amplification of the same. The client acknowledges that mold is ubiquitous to the environment with mold amplification occurring when building materials are impacted by moisture. The client further acknowledges that site conditions are outside of PSI’s control and that mold amplification will likely occur, or continue to occur, in the presence of moisture. As such, PSI cannot, and shall not, be held responsible for the occurrence or recurrence of mold amplification.

After the plans and specifications are more complete, the geotechnical engineer should be provided the opportunity to review the final design plans and specifications to assess that our engineering recommendations have been properly incorporated into the design documents. At that time, it may be necessary to submit supplementary recommendations. This report has been prepared for the exclusive use of PBDewberry for the specific application to the proposed Site Adapt for a New Dining Hall, Pisgah Forest, North Carolina.

We appreciate the opportunity to have provided you with our geotechnical engineering services and look forward to participation in the construction phase of this project. If you have any questions concerning this report or if we may be of further service in any manner, please contact our office.

APPENDIX

BORING LOCATION PLAN

BORING LOGS

LABORATORY TEST RESULTS

GENERAL NOTES