36C24618R0840-0004002.pdf

REPORT

OF

SUBSURFACE EXPLORATION

VAMC SALISBURY BUILDING 11 ADDITIONS

SALISBURY, NORTH CAROLINA

ECS PROJECT NO. 08-9011

JUNE 24, 2013

REPORT OF SUBSURFACE EXPLORATION

VAMC Salisbury Building 11 Additions Salisbury, North Carolina

Prepared For:

Mr. C Harmon Reed, Jr. AIA Odell International 13620 Reese Blvd.

Huntersville, NC 28078

Prepared By:

ECS Carolinas, LLP 1812 Center Park Drive

Suite D Charlotte, NC 28217

ECS Project No:

08-9011

Report Date:

June 24, 2013

Report of Subsurface Exploration Mr. C. Harmon Reed Jr.

VAMC Salisbury Building 11 Additions Odell International Salisbury, North Carolina ECS Project No. 08-9011 Page 2 June 24, 2013

1. INTRODUCTION

1.1. Project Information

The project site is located on the campus of W.C. Hefner Veterans Administration Medical Center (VAMC) at 1601 Brenner Avenue in Salisbury, North Carolina as shown in the Site Vicinity Map (Figure 1) in the Appendix. We understand the project will include four (4) additions to the existing VAMC including two (2) patient wings (one on each end of the existing building), a dining room addition, and a conference room addition.

The two patient wing structures will be one-story steel frame structures over a crawl space. The finished floor elevation of the patient wings is anticipated to be at or near elevation 715.5 feet.

The dining room and conference room additions are anticipated to be slabs-on-grade at or near elevation 704.5 feet. Maximum column and wall footing loads are not anticipated to exceed 350 kips and 7 kips per linear foot, respectively.

1.2. Scope of Services

Our scope of services for this phase of the project included a subsurface exploration with soil test borings, shear wave velocity testing, engineering analysis of the foundation support options, and preparation of this report with our recommendations. The subsurface exploration included ten (10) soil test borings (B-1 through B-10) to depths ranging from 19.5 to 29.5 feet below existing grades. Approximate boring locations are shown on the Boring Location Diagram (Figure 2) included in the Appendix. The soil borings were performed using a SIMCO 2400 ATV-mounted drill rig using continuous-flight, hollow-stem augers.

2. FIELD SERVICES

2.1. Test Locations

The soil boring locations and depths were selected by Fitzpatrick Engineering Group, PLLC and located in the field by ECS using existing landmarks as reference. The approximate test locations are shown on the Boring Location Diagram (Figure 2) presented in the Appendix of this report and should be considered accurate only to the degree implied by the method used.

Ground surface elevations were interpolated from the existing conditions plan provided by ColeJenest & Stone and should be considered accurate only to the degree implied by the method used.

2.2. Soil Test Borings

Ten (10) soil test borings were drilled to evaluate the stratification and engineering properties of the subsurface soils at the project site. Standard Penetration Tests (SPT’s) were performed at designated intervals in general accordance with ASTM D 1586. The Standard Penetration Test is used to provide an index for estimating soil strength and density. In conjunction with the penetration testing, split-barrel soil samples were recovered for soil classification at each test interval. Boring Logs are included in the Appendix.

The drill crew also maintained a field log of the soils encountered at each of the boring locations.

After recovery, each sample was removed from the auger and visually classified.

Representative portions of each sample were then sealed and brought to our laboratory in Charlotte, North Carolina for further visual examination. Groundwater measurements were attempted at the termination of drilling at each boring location.

Salisbury, North Carolina ECS Project No. 08-9011 Page 3 June 24, 2013

2.3. Shear Wave Velocity Testing

ECS performed one (1) Refraction Microtremor (ReMi) survey as indicated on the Test Location Diagram (Figure 2) included in the Appendix. The ReMi survey was performed by ECS field personnel using a 280-foot array along the existing ground surface adjacent to the proposed building footprint. Twelve (12) 10-Hz vertical P-wave geophones connected to a cable along the array at 8-meter intervals were used to perform the ReMi survey. At the end of the array the cable was connected to a Seistronix twelve-channel Exploration Seismograph capable of storing record lengths up to 100 seconds. For this study, all twelve channels were used. Ambient vibrations or microtremors were recorded for ten (10) 30-second intervals (unfiltered).

The field data recorded was processed using SeisOpt® ReMi™ software to reveal a one-dimensional average shear-wave (S-wave) velocity profile for the traverse. The weighted average shear wave velocity of materials from the ground surface to a depth of 100 feet is used to determine the seismic site class. The Shear Wave Velocity Profile (Figure 3) is included in the Appendix of this report.

3. LABORATORY SERVICES

Soil samples were collected from the borings and examined in our laboratory to check field classifications and to determine pertinent engineering properties. Data obtained from the borings and our visual/manual examinations are included on the respective boring logs in the Appendix.

A geotechnical engineer classified each soil sample on the basis of color, texture, and plasticity characteristics in general accordance with the Unified Soil Classification System (USCS). The soil engineer grouped the various soil types into the major zones noted on the boring logs. The stratification lines designating the interfaces between earth materials on the boring logs and profiles are approximate; in situ, the transition between strata may be gradual in both the vertical and horizontal directions. The results of the visual classifications are presented on the Boring Logs included in the Appendix.

4. SITE AND SUBSURFACE FINDINGS

4.1. Area Geology

The site is located in the Piedmont Physiographic Province of North Carolina. The native soils in the Piedmont Province consist mainly of residuum with underlying saprolites weathered from the parent bedrock, which can be found in both weathered and unweathered states. Although the surficial materials normally retain the structure of the original parent bedrock, they typically have a much lower density and exhibit strengths and other engineering properties typical of soil. In a mature weathering profile of the Piedmont Province, the soils are generally found to be finer grained at the surface where more extensive weathering has occurred. The particle size of the soils generally becomes more granular with increasing depth and gradually changes first to weathered and finally to unweathered parent bedrock. The mineral composition of the parent rock and the environment in which weathering occurs largely control the resulting soil's engineering characteristics. The residual soils are the product of the weathering of the parent bedrock.

Salisbury, North Carolina ECS Project No. 08-9011 Page 4 June 24, 2013

In addition, it is apparent that the natural geology within the site has been modified in the past by grading that included placement of fill materials. The quality of man-made fills can vary significantly, and it is often difficult to access the engineering properties of existing tests performed in soil test borings and the degree of compaction of existing fill soils; however, a qualitative assessment of existing fills can sometimes be made based on the N-values obtained and observations of the materials sampled in the test borings.

4.2. Subsurface Conditions

The subsurface conditions at the site, as indicated by the borings, generally consisted of fill, residual soil, partially weathered rock, and refusal materials to the depths explored. The generalized subsurface conditions are described below. For soil stratification at a particular test location, the respective Boring Log found in the Appendix should be reviewed.

Approximately 1 to 2 inches of topsoil was encountered at the ground surface at each Boring.

Fill soils were encountered below the topsoil at Borings B-1, B-2, B-3, B-6, B-8, and B-10 and extended to depths ranging from 3 to 17 feet below the existing ground surface. The fill soils generally consisted of Silty SAND (SM), Sandy/Clayey SILT (ML) exhibiting SPT N-values ranging from 4 to 27 blows per foot (bpf), with the majority between 10 and 14 bpf. Auger refusal was encountered within the fill at Boring B-10 at a depth of 14.5 feet below existing grade. Auger refusal indicates the presence of material that permitted no further advancement of the hollow stem auger or split spoon sampler. No sample was recovered in the split-spoon sampler. The boring was then offset approximately 5 feet to the south (Boring B-10A) and terminated at 29.5 feet.

Residual soil was encountered below the topsoil at Borings B-4, B-5, B-7, and B-9, and below the fill at the remaining boring locations. Residual soils are formed by the in-place chemical and mechanical weathering of the parent bedrock. The residual soils encountered in the borings generally consisted of Silty CLAY (CL), Sandy SILT (ML) and Silty SAND (SM), exhibiting SPT N-values ranging from 7 to 80 bpf. Borings

Partially weathered rock (PWR) was encountered below the residual soils at all boring locations.

PWR is defined as residual material exhibiting SPT N-values greater than 100 bpf. The PWR encountered generally consisted of Sandy SILT (ML) and Silty SAND (SM) exhibiting SPT N-values ranging from 50 blows per 5 inches to 50 blows per 1 inch. All boring locations were terminated in PWR.

4.3. Groundwater Observations

Groundwater measurements were attempted at the termination of drilling and prior to demobilization from the site. Groundwater was encountered at Borings B-1 and B-6 at a depth of

24.8 and 23.5 feet below the ground surface, respectively. Fluctuations in the groundwater elevation should be expected depending on precipitation, runoff, utility leaks, and other factors not evident at the time of our evaluation. Normally, highest groundwater levels occur in late winter and spring and the lowest levels occur in late summer and fall.

4.4. Shear Wave Velocity Measurements

The weighted average shear wave velocity of the soils encountered in the upper 100 feet near the ReMi array performed was approximately 1,775 feet per second (fps). The Shear Wave Velocity Profile (Figure 3) is presented in the Appendix of this report.

Page 5 June 24, 2013

5. CONCLUSIONS AND RECOMMENDATIONS

The borings performed at this site represent the subsurface conditions at the location of the borings. Due to inconsistencies associated with the prevailing geology, there can be changes in the subsurface conditions over relatively short distances that have not been disclosed by the results of the test location performed. Consequently, there may be undisclosed subsurface conditions that require special treatment or additional preparation once these conditions are revealed during construction.

Our evaluation of foundation support conditions has been based on our understanding of the site, project information and the data obtained in our exploration. The general subsurface conditions utilized in our foundation evaluation have been based on interpolation of subsurface data between and away from the borings. In evaluating the boring data, we have examined previous correlations between penetration resistance values and foundation bearing pressures observed in soil conditions similar to those at your site.

5.1. Organic Laden Soils

A layer of organic laden soil, ranging in thickness from approximately 1 to 2 inches, was encountered at each boring location. The surficial organic laden soil is typically a dark-colored soil material containing roots, fibrous matter, and/or other organic components, and is generally unsuitable for support of engineering fill, foundations, or slabs-on-grade. ECS has not performed laboratory testing to determine the organic content or other horticultural properties of the observed surficial organic laden soils. Therefore, the phrase “surficial organic laden soil” is not intended to indicate suitability for landscaping and/or other purposes. The surficial organic laden soil depths provided in this report and on the individual Boring Logs are based on driller observations and should be considered approximate. Please note that the transition from surficial organic laden soils to underlying materials may be gradual, and therefore the observation and measurement of the surficial organic laden soil depth is approximate. Actual surficial organic laden soil depths should be expected to vary and generally increases with the amount of vegetation present over the site.

5.2. Undocumented Fill Materials

Fill soils were encountered below the topsoil at Borings B-1, B-2, B-3, B-6, B-8, and B-10 and extended to depths ranging from 3 to 17 feet below the existing ground surface. The fill soils generally consisted of Silty SAND (SM), Sandy/Clayey SILT (ML) exhibiting SPT N-values ranging from 4 to 27 blows per foot (bpf), with the majority between 10 and 14 bpf. Auger refusal was encountered within the fill at Boring B-10 at a depth of 14.5 feet below existing grade. Auger refusal indicates the presence of material that permitted no further advancement of the hollow stem auger or split spoon sampler. No sample was recovered in the split-spoon sampler. The boring was then offset approximately 5 feet to the south (Boring B-10A) and terminated at 29.5 feet.

ECS was not provided with documentation of the earthwork activities, thus the fill should be considered undocumented. If the owner possesses compaction data from previous earthwork activities, ECS should be given the opportunity to review this data and make revisions to this report if needed. However, based on the results of the soil test borings, it appears that some level of compactive effort was utilized during fill placement with the exception of Boring B-10.

The fill encountered at Boring B-10 varied from 4 to 27 bpf.

Salisbury, North Carolina ECS Project No. 08-9011 Page 6 June 24, 2013

Undocumented fill poses risks associated with undetected deleterious inclusions within the fill and/or deleterious materials at the virgin ground fill interface that are covered by the fill.

Deleterious materials can consist of significant amount of organics derived from organic rich strippings, rubbish, construction or demolition debris, stumps and roots, and logs. If these materials are covered over by or are within undocumented fill, the organic materials tend to decompose slowly in the anaerobic conditions in or under the fill. Decomposition can occur over periods ranging from several years to several decades. As the organic materials decompose, a void is created which can create soft conditions and even subsidence in areas above the organics. Where these types of conditions exist under or within undocumented fill, they are sometimes in discreet pockets that can go undetected by normal subsurface exploration techniques, i.e., soil test borings and test pits.

The magnitude of settlement or subsidence associated with the organic materials is generally related to the volume of organic materials. Therefore, when undocumented fill is present, soil test borings and test pits can indicate generally good conditions when, in fact, undiscovered pockets of organics occur under buildings or parking lots. After the structure has been in place for some time, the extra load, or pressure, caused by new facility or new fill constructed on the undocumented fill causes subsidence and consolidation which is reflected in settlement, sometimes excessive, in the parking lot surface or in the structure. Resurfacing of parking lots can be utilized to repair “bird baths” created by subsidence at a generally acceptable cost.

The problem with uncontrolled fill is that the degree of risk associated with the above factors and consequences cannot be quantified. Soil test borings on a very close grid of 20 to 30 ft could still miss significant discreet volumes of organics such as a stump pile. The only way to totally eliminate the risk associated with undocumented fill is to remove it, exposing the original ground and allowing evaluation of the quality of the material in the fill volume for reuse as engineered fill.

ECS does not recommend supporting foundations, slabs-on-grade, or project pavements on undocumented fill. Additionally, ECS recommends performing additional soil test borings and/or test pits in the vicinity of Boring B-10 to further delineate the presence of undocumented fill.

5.3. Seismic Site Classification

The Shear Wave Velocity Profile (Figure 3) is presented in the Appendix of this report. The site class definitions for the weighted average of shear wave velocity in the upper 100 feet of the soil profile are presented in Table 1613.5.2 of the North Carolina Building Code, which we have reproduced in the table below for reference.

Site Class

Soil Profile Name Average Soil Shear Wave Velocity (Vs-bar) in the Top 100 feet, as per

Section 1615.1.5 A Hard Rock Vs-bar > 5,000 ft/sec B Rock 2,500 ft/sec < Vs-bar ≤ 5,000 ft/sec C Very dense soil and soft rock 1,200 ft/sec < Vs-bar ≤ 2,500 ft/sec D Stiff Soil Profile 600 ft/sec ≤ Vs-bar ≤ 1,200 ft/sec E Soft Soil Profile Vs-bar < 600 ft/sec

Based on the results obtained from the Shear Wave Velocity testing, a seismic site class of “C” should be used for design purposes.

Salisbury, North Carolina ECS Project No. 08-9011 Page 7 June 24, 2013

5.4. Structure Foundations

East Patient Wing, Dining Room Addition, & Conference Room Addition

Provided the recommendations outlined herein are implemented, the proposed buildings may be adequately supported on a shallow foundation system consisting of spread footings bearing on firm undisturbed low plasticity residual soil or newly-placed engineered fill. A bearing capacity of up to 3,000 psf is recommended for foundations bearing on firm undisturbed low plasticity residual soil or newly-placed engineered fill.

For this project, minimum wall and column footing dimensions of 18 and 24 inches, respectively, should be maintained to reduce the possibility of a localized, “punching” type, shear failure.

Exterior foundations and foundations in unheated areas should be embedded deep enough below exterior grades to reduce potential movements from frost action or excessive drying shrinkage. For this region, we recommend footings bear at least 18 inches below finished grade.

Total settlement is anticipated to be less than 1 inch, while differential settlement between columns is anticipated to be less than ½ inch for shallow foundations bearing on low plasticity residual soil or newly-placed engineered fill. Foundation geometry, loading conditions, and/or bearing strata different than those described in this report may result in magnitudes of settlement inconsistent with the previous estimates.

West Patient Wing

Provided the recommendations outlined herein are implemented, the proposed building may be adequately supported on a shallow foundation system consisting of spread footings bearing on firm undisturbed low plasticity residual soil or newly-placed engineered fill. A bearing capacity of up to 3,000 psf is recommended for foundations bearing on firm undisturbed low plasticity residual soil or newly-placed engineered fill in the vicinity of Borings B-7, B-8, and B-9. ECS does not recommend supporting the structure on the undocumented fill encountered in Boring B-

10. Therefore, ECS recommends the following alternatives for foundation support in the vicinity of Boring B-10.

1) Remove and Replace: This method requires the complete removal of the existing undocumented fill within the vicinity of Boring B-10 and replacement with engineered fill.

The area of undercut should be extended outward from the edge of the building a minimum of one foot in horizontal distance for every one foot of excavation. Based on our findings, the majority of the undocumented fill appears suitable for re-use as engineered fill. A bearing capacity of up to 3,000 psf is recommended for foundations bearing on newly-placed engineered fill with a minimum embedment depth of 5 feet below finished grade. Based on the anticipated depth of existing undocumented fill (up to 17 feet), this may not be the most economical approach.

2) Ground Improvement: An aggregate pier foundation system can provide support of the structure. Aggregate piers are a displacement foundation element that replaces weak soil with a column of compacted stone. A stone column is installed by a specially designed vibrator or tamp that penetrates through the ground with a combination of self-weight, vibrations, augers and/or water jets. Once the system has reached the desired bearing depth, stone backfill is introduced in lifts in the created void. Each lift is exposed to compactive effort until the desired compaction is achieved. The tamping or vibration

Page 8 June 24, 2013 action compacts the stone and, to a lesser degree, the surrounding soil. The process is completed up to ground level, forming a stone column surrounded by relatively dense in-situ soil. The probe should extend to the top of a dense bearing stratum. Depending upon the column layout and size, four to five stone columns may be installed at each column location. After installation, spread footings can be designed for an allowable bearing pressure based on the specialty contractor’s design recommendations.

3) Deep Foundations: There are many options available for deep foundation systems such as helical anchors, driven (timber, concrete, or steel) piles, augered piles, or drilled shafts. The purpose of the deep foundation system is to extend the loads imposed by the structure into a bearing stratum that can adequately support the loads. A specialty foundation contractor should be contacted to determine the feasibility and design of a pile foundation system. Based on the findings, helical anchors or augered piles may be an alternative. If deep foundations are selected, additional drilling and analysis will likely be required in order to obtain adequate geotechnical data for more detailed pile foundation recommendations.

5.5. Slab-On-Grade Support

Slabs-on-grade can be adequately supported on undisturbed low plasticity residual soils or on newly-placed engineered fill provided the site preparation and fill recommendations outlined herein are implemented. For a properly prepared site, a modulus of subgrade reaction (ks) for the soil of 100 pounds per cubic inch for the soil can be used. This value is representative of a 1-ft square loaded area and may need to be adjusted depending the size and shape of the loaded area depending on the method of structural analysis.

We recommend the slabs-on-grade be underlain by a minimum of 4 inches of granular material having a maximum aggregate size of 1½ inches and no more than 2 percent fines. Prior to placing the granular material, the floor subgrade soil should be properly compacted, proofrolled, and free of standing water, mud, and frozen soil. A properly designed and constructed capillary break layer can often eliminate the need for a moisture retarder and can assist in more uniform curing of concrete. If a vapor retarder is considered to provide additional moisture protection, special attention should be given to the surface curing of the slabs to minimize uneven drying of the slabs and associated cracking and/or slab curling. The use of a blotter or cushion layer above the vapor retarder can also be considered for project specific reasons.

Please refer to ACI 302.1R96 Guide for Concrete Floor and Slab Construction and ASTM E 1643 Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs for additional guidance on this issue.

ECS recommends that the slab be isolated from the footings so differential settlement of the structure will not induce shear stresses on the floor slab. Also, in order to minimize the crack width of shrinkage cracks that may develop near the surface of the slab, we recommend mesh reinforcement as a minimum be included in the design of the floor slab. For maximum effectiveness, temperature and shrinkage reinforcements in slabs on ground should be positioned in the upper third of the slab thickness. The Wire Reinforcement Institute recommends the mesh reinforcement be placed 2 inches below the slab surface or upper one-third of slab thickness, whichever is closer to the surface.

Salisbury, North Carolina ECS Project No. 08-9011 Page 9 June 24, 2013

Adequate construction joints, contraction joints and isolation joints should also be provided in the slab to reduce the impacts of cracking and shrinkage. Please refer to ACI 302.1R96 Guide for Concrete Floor and Slab Construction for additional information regarding concrete slab joint design.

5.6. Pavement Considerations

For the design and construction of exterior pavements, the subgrades should be prepared in accordance with the recommendations in the “Site and Subgrade Preparation” and “Engineered Fill” sections of this report.

An important consideration with the design and construction of pavements is surface and subsurface drainage. Where standing water develops, either on the pavement surface or within the aggregate base course layer, softening of the subgrades and other problems related to the deterioration of the pavement can be expected. This is particularly important at the site due to the moisture sensitive near-surface soils. Furthermore, good drainage should help reduce the possibility of the subgrade materials becoming saturated during the normal service period of the pavement.

Based on our past experience with similar facilities and subsurface conditions, we present the following design pavement sections on the next page, provided the recommendations contained in this report are strictly followed. We have developed the pavement sections recommended below using AASHTO guidelines with a CBR value of 4, assuming the existing subgrades are satisfactorily evaluated during proofroll and repaired in accordance with the geotechnical engineer’s recommendations. Based upon our previous experience with similar projects, ECS has estimated the provided pavement sections based upon a 20 year life, 500 cars per day, 5 delivery trucks per day, 1 garbage truck per day, and 4 semi-trucks per day. We have calculated approximate equivalent axle loadings of 8,470 and 104,290 ESALs for light-duty and heavy-duty pavements, respectively.

PAVEMENT SECTION RECOMMENDATIONS

Material Designation Light Duty

Asphalt Pavement

Heavy Duty Asphalt

Pavement

Portland Cement Concrete (PCC)

Pavement Asphalt Surface Course 3 inch 1.5 inches - Intermediate Coarse - 2.5 inches - Portland Cement Concrete - - 6 inches Aggregate Base Course 6 inches 8 inches 6 inches

ECS should be allowed to review these recommendations and make appropriate revisions based upon the formulation of the final traffic design criteria for the project. It is important to note that the design sections do not account for construction traffic loading. The aggregate base course materials beneath pavements and sidewalks should be compacted to at least 95 percent of their modified Proctor maximum dry density (ASTM D 1557).

Front-loading trash dumpsters frequently impose concentrated front-wheel loads on pavements during loading. This type of loading typically results in rutting of bituminous pavements and ultimately pavement failures and costly repairs. Similarly, drive-thru lanes also create severe risk of rutting and scuffing. Therefore, we suggest that the pavements in trash pickup and drive-thru areas utilize the aforementioned Portland Cement Concrete (PCC) pavement section. It may be prudent to use rigid pavement sections in all areas planned for heavy truck traffic. Such

Salisbury, North Carolina ECS Project No. 08-9011 Page 10 June 24, 2013 a PCC section would typically consist of 6 inches of 4,000 psi, air-entrained concrete over not less than 6 inches of compacted aggregate base course. Appropriate steel reinforcing and jointing should also be incorporated into the design of all PCC pavements.

It should be noted that these design recommendations may not satisfy the North Carolina Department of Transportation traffic guidelines. Any roadways constructed for public use and to be dedicated to the State for repair and maintenance must be designed in accordance with the State requirements.

5.7. Lateral Earth Pressures

ECS understands that retaining walls will be utilized at the project site. Specifics regarding the retaining walls (i.e. location, height, length, loading, etc.) were unknown at the time of this report.

Retaining walls should be designed to withstand the lateral earth pressures exerted upon them, and to resist additional lateral pressures generated by surcharge loads such as traffic loads, adjacent slab loads or from foundations bearing behind the walls.

For wall conditions where wall movement cannot be tolerated or where the wall is restrained at the top, such as basement walls, the “At Rest” earth pressure should be used. For wall conditions where outward wall movement on the order of 0.5 percent of the wall height can be tolerated, the “Active” earth pressure should be used. In the design of retaining walls to restrain compacted backfill, engineered fill or in-situ residual soils, the coefficient of lateral earth pressure can be used to determine lateral earth pressure loads. Please note that the values presented below are for on-site ML and SM materials. If the wall backfill is imported to the site, ECS should be contacted to review the lateral earth pressure coefficients provided. Moderately to highly elastic/plastic soils (MH, CL, and CH) should not be utilized behind earth retaining structures.

Soil Parameter Coefficient of Lateral Earth Pressure

“At Rest” Earth Pressure (Ko) 0.56 “Active” Earth Pressure (Ka) 0.39

“Passive” Earth Pressure (Kp) 2.56

The lateral earth pressure values presented above assume level backfill fill behind the wall, and do not account for hydrostatic pressures against the walls or surcharge loads from overlying or nearby construction.

Resistance to sliding can be provided by friction between the bottom of the wall foundation and the underlying soils and by passive resistance of soil adjacent to the wall foundation. The passive resistance should only be used in situations where the soil adjacent to the toe of the wall will not be eroded or otherwise removed in the future. A coefficient of friction of 0.35 for concrete bearing on approved soils is recommended.

Drainage behind freestanding retaining walls is considered essential towards relieving hydrostatic pressures. Drainage can be established by providing a perimeter drainage system located just above the below grade/retaining wall footings which discharges by gravity flow to a suitable outlet. This system should consist of “perforated pipe” or “porous wall”, closed-joint drain lines. These drain lines should be surrounded by a minimum 6 inches of free-draining, granular filter material having a gradation compatible with the size of the openings utilized in the drain lines and the surrounding soils to be retained, or by gravel wrapped in filter fabric. The

Salisbury, North Carolina ECS Project No. 08-9011 Page 11 June 24, 2013 space between the interior face of the wall and the earth fill should be backfilled with a granular fill of porous quality or better extending from the perimeter drainage system to just below the top of the wall. To prevent frost heave effects from acting against these walls, the granular backfill should extend a minimum of 12 horizontal inches behind the wall. The granular backfill should be capped with pavement, concrete, or a 12-inch layer of low permeable silt or clay to minimize the seepage of water into that backfill from the surface. The ground surface adjacent to the below-grade walls should be kept properly graded to prevent ponding of water adjacent to the walls.

The type of retaining wall used should be carefully selected considering adjacent areas and construction. Irrespective of the retaining wall system chosen, we recommend that the design of the new retaining walls consider their global stability. We recommend that the global factor of safety should be at least 1.5. Other factors of safety shall be as follows:

Factor of Safety against Sliding > 1.5 Factor of Safety against Overturning > 1.5 Factor of Safety against Bearing Capacity Failure > 2.0

5.8. Below Grade Excavation

Partially weathered rock (PWR) was encountered relatively shallow in Borings B-5 and B-9.

Based on the anticipated minor cut and fill depths, difficult excavation is not anticipated during site development; however, the deep of utility trenches was not known at the time of this report.

Therefore, difficult excavation may be encountered in the vicinity of Boring B-5 and B-9. We have generally found that material that our soil drilling augers can penetrate can also be excavated with a large backhoe or ripped with a dozer mounted ripper. Weathered rock or rock that cannot be penetrated by the mechanical auger will normally require blasting to loosen it for removal.

As noted in the Geology section of this report, the weathering process in the Piedmont can be erratic and significant variations of the depths of the more dense materials can occur in relatively short distances. In some cases, isolated boulders or thin rock seams may be present in the soil matrix.

5.9. Cut and Fill Slopes

ECS does not anticipate cut or fill slopes greater than 5 feet in height. We recommend that permanent cut slopes with less than 5 feet crest height through undisturbed residual soils be constructed at 2:1 (horizontal: vertical) or flatter. Permanent fill slopes less than 5 feet tall may be constructed using controlled fill at a slope of 2:1 or flatter. A slope of 3:1 or flatter may be desirable to permit establishment of vegetation, safe mowing, and maintenance. The surface of all cut and fill slopes should be adequately compacted. All permanent slopes should be protected using vegetation or other means to prevent erosion.

The outside face of building foundations and the edges of pavements placed near slopes should be located an appropriate distance from the slope. Buildings or pavements placed at the top of fill slopes should be placed a distance equal to at least 1/3 of the height of the slope behind the crest of the slope. Buildings or pavements near the bottom of a slope should be located at least ½ of the height of the slope from the toe of the slope. Slopes with structures located closer than these limits or slopes taller than the height limits indicated should be specifically evaluated by the geotechnical engineer and may require approval from the building code official.

Salisbury, North Carolina ECS Project No. 08-9011 Page 12 June 24, 2013

Temporary slopes in confined or open excavations should perform satisfactorily at inclinations of 2:1. All excavations should conform to applicable OSHA regulations. Appropriately sized ditches should run above and parallel to the crest of all permanent slopes to divert surface runoff away from the slope face. To aid in obtaining proper compaction on the slope face, the fill slopes should be overbuilt with properly compacted structural fill and then excavated back to the proposed grades.

6. CONSTRUCTION CONSIDERATIONS

6.1. Site Preparation

Prior to construction, the proposed construction area should be stripped of all topsoil, organic material, construction debris, undocumented fill, and other soft or unsuitable material. Upon completion of these razing and stripping operations, the exposed subgrade in areas to receive fill should be proofrolled with a loaded dump truck or similar pneumatic-tired vehicle having a loaded weight of approximately 25 tons. After excavation, the exposed subgrades in cut areas should be similarly proofrolled.

Proofrolling operations should be performed under the observation of a geotechnical engineer or his authorized representative. The proofrolling should consist of two (2) complete passes of the exposed areas, with each pass being in a direction perpendicular to the preceding one. Any areas which deflect, rut or pump during the proofrolling, and fail to be remedied with successive passes, should be undercut to suitable soils and backfilled with compacted fill.

The ability to dry wet soils, and therefore the ability to use them for fill, will likely be enhanced if earthwork is performed during summer or early fall. If earthwork is performed during winter or after appreciable rainfall then subgrades may be unstable due to wet soil conditions, which could increase the amount of undercutting required. Drying of wet soils, if encountered, may be accomplished by spreading and disking or by other mechanical or chemical means.

6.2. Fill Material and Placement

The project fill should be soil that has less than five percent organic content and a liquid limit and plasticity index less than 50 and 30, respectively. Soils with Unified Soil Classification System group symbols of SP, SW, SM, SC, and ML are generally suitable for use as project fill. Soils with USCS group symbol of CL that meet the restrictions for liquid limit and plasticity index are also suitable for use as project fill. Soils with USCS group symbol of MH or CH (high elasticity or plasticity soil) or corrosive soils are generally not suitable for use as project fill.

The fill should exhibit a maximum dry density of at least 90 pounds per cubic foot, as determined by a standard Proctor compaction test (ASTM D 698). We recommend that moisture control limits of -3 to +2 percent of the optimum moisture content be used for placement of project fill with the added requirement that fill soils placed wet of optimum remain stable under heavy pneumatic-tired construction traffic. During site grading, some moisture modification (drying and/or wetting) of the onsite soils will likely be required. The majority of the onsite soils appear suitable for use as project fill.

Project fill within the building footprint should be compacted to at least 98 percent of its Standard Proctor maximum dry density except within 24 inches of finished soil subgrade elevation beneath slab-on-grade and pavements. Within the top 24 inches of finished soil subgrade elevation beneath slab on grade and pavements, the approved project fill should be compacted to at least 100 percent of its standard Proctor maximum dry density. Aggregate base course

Salisbury, North Carolina ECS Project No. 08-9011 Page 13 June 24, 2013

(ABC stone) should be compacted to 100 percent of standard Proctor maximum dry density.

However, for isolated excavations around footing locations or within utility excavations, a hand tamper will likely be required. ECS recommends that field density tests be performed on the fill as it is being placed, at a frequency determined by an experienced geotechnical engineer, to verify that proper compaction is achieved.

The maximum loose lift thickness depends upon the type of compaction equipment used. The table below provides maximum loose lifts that may be placed based on compaction equipment.

LIFT THICKNESS RECOMMENDATIONS

Equipment Maximum Loose Lift

Thickness, in.

Large, Self-Propelled Equipment (CAT 815, etc.) 8 Small, Self-Propelled or Remote Controlled (Rammax, etc.) 6

Hand Operated (Plate Tamps, Jumping Jacks, Wacker- Packers)

ECS recommends that fill operations be observed and tested by an engineering technician to determine if compaction requirements are being met. The testing agency should perform a sufficient number of tests to confirm that compaction is being achieved. For mass grading operations we recommend a minimum of one density test per 2,500 SF per lift of fill placed or per 1 foot of fill thickness, whichever results in more tests. When dry, the majority of the site soil should provide adequate subgrade support for fill placement and construction operations. When wet, the soil may degrade quickly with disturbance from construction traffic. Good site drainage should be maintained during earthwork operations to prevent ponding water on exposed subgrades.

We recommend at least one test per 1 foot thickness of fill for every 100 linear ft of utility trench backfill. Where fill will be placed on existing slopes, we recommend that benches be cut in the existing slope to accept the new fill. All fill slopes should be overbuilt and then cut back to expose compacted material on the slope face. While compacting adjacent to below-grade walls, heavy construction equipment should maintain a horizontal distance of 1(H):1(V). If this minimum distance cannot be maintained, the compaction equipment should run perpendicular, not parallel to, the long axis of the wall.

6.3. Foundation Construction & Testing

Foundation excavations should be tested to confirm adequate bearing prior to installation of reinforcing steel or placement of concrete. Unsuitable soils should be undercut to firm soils and the undercut excavations should be backfilled with compacted controlled fill. Exposure to the environment may weaken the soils at the footing bearing level if the foundation excavations remain open for too long a time; therefore, foundation concrete should be placed the same day that foundations are excavated. If the bearing soils are softened by surface water intrusion or exposure, the softened soils must be removed from the foundation excavation bottom immediately prior to placement of concrete. If the excavation must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, a 1- to 3-inch thick "mud mat" of "lean" concrete may be placed on the bearing surface to protect the bearing soils. The mud mat should not be placed until the bearing soils have been tested for adequate bearing capacity.

Foundations undercut should be backfilled with engineered fill. If lean concrete is placed within the undercut zone, the foundation footprint does not require oversizing. However, if soil or ABC

Salisbury, North Carolina ECS Project No. 08-9011 Page 14 June 24, 2013 stone is used in lieu of lean concrete, the foundation footprint should be oversized on a minimum 1V:1H scale.

We recommend testing all shallow foundations to confirm the presence of foundation materials similar to those assumed in the design. We recommend the testing consist of hand auger borings with Dynamic Cone Penetrometer (DCP) testing performed by an engineer or engineering technician.

7. GENERAL COMMENTS

The borings performed at this site represent the subsurface conditions at the location of the borings only. Due to the prevailing geology and presence of existing undocumented fill, changes in the subsurface conditions can occur over relatively short distances that have not been disclosed by the results of the borings performed. Consequently, there may be undisclosed subsurface conditions that require special treatment or additional preparation once these conditions are revealed during construction.

Our evaluation of foundation support conditions has been based on our understanding of the site and project information and the data obtained in our exploration. The general subsurface conditions utilized in our foundation evaluation have been based on interpolation of subsurface data between and away from the test holes. If the project information is incorrect or if the structure locations (horizontal or vertical) and/or dimensions are changed, please contact us so that our recommendations can be reviewed. The discovery of any site or subsurface conditions during construction which deviate from the data outlined in this exploration should be reported to us for our evaluation. The assessment of site environmental conditions for the presence of pollutants in the soil, rock, and groundwater of the site was beyond the scope of this exploration.

The recommendations outlined herein should not be construed to address moisture or water intrusion effects after construction is completed. Proper design of landscaping, surface and subsurface water control measures are required to properly address these issues. In addition, proper operation and maintenance of building systems is required to minimize the effects of moisture or water intrusion. The design, construction, operation, and maintenance of waterproofing and dampproofing systems are beyond the scope of services for this project.

REVISIONS

DRAFTSMAN

PROJ. MGR.

DATE

FIGURE

PROJECT NO.

SCALESource:

JBB

LEGEND:

Google Maps

LJM

08-9011

06-11-13

N.T.S.

FIGURE 1

SITE VICINITY MAP

VAMC Salisbury Building 11 Additions

B-1

B-2

B-3

B-4

B-5

B-6 B-7

B-8

B-9

B-10

REVISIONS

DRAFTSMAN

PROJ. MGR.

DATE

FIGURE

PROJECT NO.

SCALEBackground Image Provided by:

JBB

LEGEND:

N.T.S.EHF

08-9011

06-11-13

FIGURE 2

BORING LOCATION DIAGRAM

VAMC Salisbury Building 11 Additions

Salisbury, North Carolina

= Approximate Location of Boring

Google Maps

= Approximate Location of ReMi Array

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0 1000 2000 3000 4000 5000 6000 7000

Shear-Wave Velocity, ft/s

D ep th , f t

Vs100' = 1775 ft/s

Project Salisbury VAMC 8m spacing: Vs Profile

FIGURE 3

ARRAY 1

GEOPHONE SPACING = 8 m

SHEAR WAVE VELOCITY PROFILE

VAMC Salisbury

ECS Project 08-9011

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

SS

SS

SS

SS

SS

SS

SS

SS

Topsoil Depth [2"]

FILL - Stiff, Light Brown, Sandy SILT, Moist

(FILL - ML)

RESIDUAL - Stiff, Red, Sandy SILT, Moist

(ML)

Hard, Tan, Silty CLAY, Moist (CL)

Very Dense, Tan, Silty fine to medium SAND, Moist (SM)

Very Stiff, Tan, Sandy SILT, Moist (ML)

PARTIALLY WEATHERED ROCK - Sampled As: Tan, Sandy SILT, Dry (PWR)

END OF BORING @ 29.5'

50/5

50/5

CLIENT

Odell International

JOB #

BORING #

B-1

SHEET

PROJECT NAME

VAMC Salisbury Building 11 Additions - DTR

ARCHITECT-ENGINEER

SITE LOCATION

1601 Brenner Ave, Salisbury, Rowan County

NORTHING EASTING STATION

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL.

WL 28.5 WS WD BORING STARTED 05/29/13

WL(BCR) WL(ACR) 24.8 BORING COMPLETED 05/29/13 CAVE IN DEPTH @ 25.3'

WL RIG SIMCO 2400 FOREMAN Cody DRILLING METHOD 2.25 HSA

D E

P T

H

F T

S A

M P

L E

N O

S A

M P

L E

T Y

P E

S A

M P

L E

D

IS

T (I

N

R E

C O

V E

R Y

IN

SURFACE ELEVATION

DESCRIPTION OF MATERIAL

W A

T E

R L

E V

E L S

E L E

V A

T

IO

N

F T

B L O

W S

/6

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS

BOTTOM OF CASING LOSS OF CIRCULATION

CALIBRATED PENETROMETER TONS/FT2

PLASTIC

LIMIT %

WATER

CONTENT %

LIQUID

LIMIT %

ROCK QUALITY DESIGNATION & RECOVERY

RQD% REC.%

STANDARD PENETRATION

BLOWS/FT708

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

SS

SS

SS

SS

SS

SS

SS

SS

Topsoil Depth [1"]

FILL - Stiff, Reddish Orange, Clayey SILT, Moist (FILL - ML)

RESIDUAL - Medium Stiff to Stiff, Green to Tannish Green, Sandy SILT, Moist (ML)

Very Stiff, Tan, Sandy CLAY, Moist (CL)

Very Dense, Gray, Silty fine to medium SAND, Moist (SM)

Dense to Very Dense, Tannish Green to Green, Silty fine to medium SAND, Moist (SM)

PARTIALLY WEATHERED ROCK - Sampled As: Green, Silty fine to medium SAND, Dry

(PWR)

END OF BORING @ 29.0'

50/5

50/5

CLIENT

Odell International

JOB #

BORING #

B-2

SHEET

PROJECT NAME

VAMC Salisbury Building 11 Additions - DTR

ARCHITECT-ENGINEER

SITE LOCATION

1601 Brenner Ave, Salisbury, Rowan County

NORTHING EASTING STATION

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL.

WL GNE WS WD BORING STARTED 05/29/13

WL(BCR) WL(ACR) GNE BORING COMPLETED 05/29/13 CAVE IN DEPTH @ 24.5'

WL RIG SIMCO 2400 FOREMAN Cody DRILLING METHOD 2.25 HSA

D E

P T

H

F T

S A

M P

L E

N O

S A

M P

L E

T Y

P E

S A

M P

L E

D

IS

T (I

N

R E

C O

V E

R Y

IN

SURFACE ELEVATION

DESCRIPTION OF MATERIAL

W A

T E

R L

E V

E L S

E L E

V A

T

IO

N

F T

B L O

W S

/6

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS

BOTTOM OF CASING LOSS OF CIRCULATION

CALIBRATED PENETROMETER TONS/FT2

PLASTIC

LIMIT %

WATER

CONTENT %

LIQUID

LIMIT %

ROCK QUALITY DESIGNATION & RECOVERY

RQD% REC.%

STANDARD PENETRATION

BLOWS/FT706

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

SS

SS

SS

SS

SS

SS

SS

SS

Topsoil Depth [2"]

FILL - StifF, Brown, Sandy SILT, Moist (FILL -

ML)

RESIDUAL - Stiff, Red, Clayey SILT with Mica, Moist (ML)

Very Stiff, Green, Sandy SILT with Mica, Moist

(ML)

Hard, Light Brown, Sandy CLAY, Moist (CL)

PARTIALLY WEATHERED ROCK - Sampled As: Tan to Gray, Silty fine to medium SAND, Dry (PWR)

END OF BORING @ 29.0'

50/5

50/5

50/4

50/5

50/5

50/4

CLIENT

Odell International

JOB #

BORING #

B-3

SHEET

PROJECT NAME

VAMC Salisbury Building 11 Additions - DTR

ARCHITECT-ENGINEER

SITE LOCATION

1601 Brenner Ave, Salisbury, Rowan County

NORTHING EASTING STATION

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL.

WL GNE WS WD BORING STARTED 05/29/13

WL(BCR) WL(ACR) GNE BORING COMPLETED 05/29/13 CAVE IN DEPTH @ 24.7'

WL RIG SIMCO 2400 FOREMAN Cody DRILLING METHOD 2.25 HSA

D E

P T

H

F T

S A

M P

L E

N O

S A

M P

L E

T Y

P E

S A

M P

L E

D

IS

T (I

N

R E

C O

V E

R Y

IN

SURFACE ELEVATION

DESCRIPTION OF MATERIAL

W A

T E

R L

E V

E L S

E L E

V A

T

IO

N

F T

B L O

W S

/6

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS

BOTTOM OF CASING LOSS OF CIRCULATION

CALIBRATED PENETROMETER TONS/FT2

PLASTIC

LIMIT %

WATER

CONTENT %

LIQUID

LIMIT %

ROCK QUALITY DESIGNATION & RECOVERY

RQD% REC.%

STANDARD PENETRATION

BLOWS/FT715

S-1

S-2

S-3

S-4

S-5

S-6

S-7

SS

SS

SS

SS

SS

SS

SS

Topsoil Depth [2"]

RESIDUAL - Very Stiff, Brown, Sandy SILT, Moist (ML)

Medium Dense, Red, Silty fine to medium SAND, Moist (SM)

Very Stiff, Reddish Orange, Sandy SILT, Moist

(ML)

Medium Dense, Brown, Silty fine to medium SAND, Moist (SM)

PARTIALLY WEATHERED ROCK - Sampled As: Gray, Silty fine to medium SAND, Dry

(PWR)

END OF BORING @ 24.0'

50/3

50/3

50/5

50/3

50/3

50/5

CLIENT

Odell International

JOB #

BORING #

B-4

SHEET

PROJECT NAME

VAMC Salisbury Building 11 Additions - DTR

ARCHITECT-ENGINEER

SITE LOCATION

1601 Brenner Ave, Salisbury, Rowan County

NORTHING EASTING STATION

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL.

WL GNE WS WD BORING STARTED 05/29/13

WL(BCR) WL(ACR) GNE BORING COMPLETED 05/29/13 CAVE IN DEPTH @ 19.8'

WL RIG SIMCO 2400 FOREMAN Cody…