ECS Project No. 01:22399 - Soils Report.pdfECS and the site layout plan provided to us by The KDL...

March 27, 2014 Mr. Thomas Burson 43441 Blair Park Square Ashburn, VA 20147

ECS Project No. 01:22399 Reference: Report of Subsurface Exploration and Geotechnical Engineering Analysis,

Weller’s Corner, 20711-20719 Ashburn Road, Ashburn, Loudoun County, Virginia

Dear Mr. Burson: As authorized by the acceptance of our proposal No. 01:46499-GPR2 dated December 30, 2013, and the subsequent change order No. 01:46499-CO, ECS Mid-Atlantic, LLC (ECS) has completed the subsurface exploration and geotechnical engineering analysis for the above-referenced project. The enclosed report discusses the exploration procedures and presents the results of our subsurface exploration and laboratory testing program. The report also provides recommendations regarding site development, pavement design, stormwater management, design of foundation systems, as well as construction considerations for the project. As part of our recent study, ECS performed a total of four soil borings (referenced as B-1 through B-2 and I-1 through I-2) within the proposed development limits. Boring B-1 was performed within the proposed building footprint, Boring B-2 was performed within the proposed paved parking areas, and Borings I-1 through I-2 were performed within the proposed infiltration trenches. After completion of our field exploration, portions of the site plan were altered and the location of the infiltration trenches was changed. Based on the results of our testing, the subsurface profile appears consistent over the site, and we expect our test results to be representative of the materials on site and additional testing should not be necessary. Each of the borings were extended to auger/sampler refusal, which was encountered at depths ranging from 5± feet to 8.5± feet below existing ground surface on the underlying siltstone bedrock. At Boring I-1, an auger probe offset was performed to 2± feet below the existing ground surface, at which point, 4” PVC casing was installed. At Boring I-2, two auger probe offsets were performed to 5± feet and 2± feet below the existing ground surface, at which point, 4” PVC casing was installed at both locations. An infiltration test was performed at each location. The recommendations outlined in this report are based on the four soil borings performed by ECS and the site layout plan provided to us by The KDL Group via email in March 2014. The site generally appears suitable for the design and construction of the proposed development, which will include a two-story multi-family condominium building, associated parking and paved areas, infiltration trenches, and underground utilities.

ECS Project No. 01:22399 March 27, 2014 Page 2 We appreciate this opportunity to be of service to you on this project. If you have any questions regarding the information and recommendations contained in the accompanying report, or if we may be of further assistance to you in any way during planning or construction of this project, please do not hesitate to contact us. Respectfully, ECS MID-ATLANTIC, LLC Ian J. Whitehead, E.I.T. Nicholas C. Meloy, P.E. Staff Project Engineer Senior Project Engineer Andrew R. Shontz, P.G. Principal Engineering Geologist cc: Mr. John Davis – The KDL Group (3 copies) IJW/blm \\s01-ares\data\geotechnical\{eprojects}\22300-22399\01-22399\e-report prep\22399rse.doc

REPORT

PROJECT

Report of Subsurface Exploration and Geotechnical Engineering Analysis

Weller’s Corner 20711-20719 Ashburn Road,

Ashburn, Loudoun County, Virginia

CLIENT

Mr. Thomas Burson 43441 Blair Park Square

Ashburn, VA 20147

_________________________________________

PROJECT NO. 01:22399

_________________________________________

_________________________________________

DATE: March 27, 2014 _________________________________________

TABLE OF CONTENTS PAGE

PROJECT OVERVIEW

Introduction 1 Proposed Construction 1 Scope of Work 1 Purposes of Exploration 2

EXPLORATION PROCEDURES

Subsurface Exploration Procedures 4 Field Infiltration Investigation and Testing Procedures 4 Laboratory Testing Program 5

EXPLORATION RESULTS

Site Conditions 6 Regional Geology and Soils Mapping 6

Regional Geology 6 Soils Mapping 6 Seasonal High/Perched Water Tables and Low Soil Strength 7

Subsurface Conditions 7 Groundwater Observations 8 Infiltration Test Results 9

ANALYSIS AND RECOMMENDATIONS

Subgrade Preparation and Earthwork Operations 10 Fill Placement 11 Highly Plastic Soils 12 Rock Excavation and Blasting Operations 13 Siltstone Considerations 14 Construction Groundwater Control 15 Building Foundations 16 Ground-Supported Slabs 17 Below Grade Walls and Drainage 18 Seismic Site Classification (IBC) 19 Infiltration Trench Facilities 19 Pavements 21 Utility Installation 22 Temporary and Permanent Slopes 23 General Construction Considerations 23 Closing 25

APPENDIX

PROJECT OVERVIEW Introduction This report presents the results of our subsurface exploration and geotechnical engineering analysis for the Weller’s Corner development in Ashburn, Loudoun County, Virginia. A Vicinity Map, located on the diagrams included in the Appendix of this report, show the approximate location of the project site. Authorization to perform this study was provided by the acceptance of ECS Proposal No. 01:46499-GPR2 dated December 30, 2013, and the subsequent change order, ECS Proposal No. 01:46499-CO dated January 9, 2014. Proposed Construction Based on the information provided to us, we understand the development will include the design and construction of a two-story multi-family condominium building with a footprint of approximately 3,760 square feet (sf), associated parking areas, infiltration trenches and underground utilities. The building is divided into two areas, each with an approximate square footage of 1,720 sf, and an interior stairwell connecting the two areas. The eastern half of the proposed condominium building is designed to have a below grade basement. The finished floor elevation of the proposed condominium building is EL. 305.27 feet, while the basement floor elevation of the eastern half of the condominium building is EL. 296.86, feet. Structural loading was not available at the time of this report preparation; therefore, we have assumed that column loads will be on the order of 100 kips or less and wall loads will be on the order of 3 kips/linear foot or less for the building. If actual structural loads differ from our assumed values, ECS must be informed so that we may re-evaluate our recommendations. Based on the site plan provided to us by The KDL Group via email in March 2013 and our site observations of the existing conditions, the site is currently partially developed with three, two-story buildings, a two-story barn, several sheds, a gravel driveway and fences. We understand that the existing structures are planned to remain on-site. The northwest corner of the site is currently undeveloped, and was observed to be a relatively flat, open grassy area. Based on existing site topography from the site plan, the site ranges from a topographic high of elevation EL. 306± feet along the western boarder of the site, to a topographic low of elevation EL. 294± along the eastern boarder of the site. Based upon this information, we do not anticipate large cuts or fills at the site to establish finished grades. The largest cuts will be in the area of the below grade basement, where according to the site plan, cuts on the order of 6 feet to 8 feet can be expected. This description of the proposed project is based on information provided to us by your office or other design team members. If any of this information is inaccurate, either due to our misunderstanding or due to design changes that may occur later, we recommend that we be contacted in order to provide additional or alternate recommendations that may be required. Scope of Work The conclusions and recommendations contained in this report are based on the four soil borings (referenced as B-1 through B-2 and I-1 through I-2) performed by ECS within the proposed building pad, infiltration trenches, and parking areas on January 2, 2014. Boring B-1

ECS Project No. 01:22399 March 27, 2014

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was performed within the proposed building footprint, Boring B-2 was performed within the proposed paved parking areas, and Borings I-1 through I-2 were performed within the proposed infiltration facilities. After completion of our field exploration, portions of the site plan were altered and the location of the infiltration trenches was changed. Based on the results of our testing, the subsurface profile appears consistent over the site, and we expect our test results to be representative of the materials on site and additional testing should not be necessary. Each of the borings were extended to auger/sampler refusal, which was encountered at depths ranging from 5± feet to 8.5± feet below existing ground surface on the underlying siltstone bedrock. At Borings I-1 and I-2, an auger probe offset was performed to 2± feet below the existing ground surface, at which point, 4” PVC casing was installed. An infiltration test was performed in an auger hole offset 5 feet from the original location at each location. Boring locations were selected by ECS in collaboration with the civil engineer based on the site plan available to us at the time of the field exploration. Each of the borings were located in the field by representatives of ECS using our Global Positioning System (GPS) equipment. The GPS unit used for the boring layout is capable of locating horizontal position to sub-meter accuracy. Therefore, we consider the boring locations in the field to be within about 3± feet of the locations indicated on the diagrams in the Appendix. The GPS layout was based on the site plan provided to us by The KDL Group via email on December 26, 2013. A revised site plan and grading information was sent to us in March 2014. The most recent plan was used in this report. The ground surface elevations noted on the boring logs were interpolated from the survey prepared by The KDL Group. Based on the contour interval utilized on the site plan, and considering the accuracy with which the borings were located in the field, the elevations noted on the remaining logs are considered to be accurate to about 1± foot. Please note the elevations shown on our boring logs are only considered to be as accurate as the topographic survey from which they were obtained. Following drilling operations, laboratory tests were performed on selected soil samples to identify the soils and to assist in the determination of properties of the site soils. The results of the subsurface exploration, along with a Boring Location Diagram, are also included in the Appendix of this report. The Boring Location Diagram depicts the boring locations with respect to the provided survey and proposed conditions. The Boring Location Diagram was developed from the site plan provided by The KDL Group. A number of publicly available sources were utilized in addition to the traditional geotechnical services that were performed in order to increase our knowledge of the subsurface conditions across the project site. These services included a review of USGS mapping of geology in the project vicinity as well as the review of Natural Resource Conservation Service (NRCS) soil mapping of the project site. In order to summarize this information concerning the site soil and rock conditions, and their variations across the site, AutoCAD drafting procedures were utilized to “overlay” these geotechnical and geologic maps onto our boring plan. Each of these overlay drawings (Sheets 2 and 3 of 3) are also included within the Appendix of this report. Purposes of Exploration The purposes of this exploration were to explore the soil, weathered rock, and groundwater conditions (if encountered) at the site and to develop engineering recommendations to guide design and construction procedures.


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We accomplished these purposes by:

1. drilling borings to explore the subsurface soil and groundwater conditions,

2. performing infiltration testing at two locations around the site selected by the client,

3. performing laboratory tests on selected representative soil samples from the borings to evaluate pertinent engineering properties,

4. analyzing the field and laboratory test results to develop appropriate engineering recommendations, and

5. preparing this report summarizing our findings and recommendations.


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EXPLORATION PROCEDURES Subsurface Exploration Procedures The soil borings were performed with a truck-mounted auger drill rig, which utilized continuous flight, hollow stem augers to advance the boreholes. Drilling fluid was not used in the boring exploration. The borings were subsequently backfilled with the auger spoils generated during drilling procedures after their completion. In the soil borings, representative soil samples were obtained by means of the split-barrel sampling procedure in general accordance with ASTM Standard D 1586. In this procedure, a 2-inch O.D., split-barrel sampler is driven into the soil a distance of 18 inches by a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler through a 12-inch interval is termed the Standard Penetration Test (SPT) value and is indicated for each sample on the boring logs. This value can be used as a qualitative indication of the in-place relative density of cohesionless soils. Upon completion of drilling operations, the borings were backfilled with the spoils generated during the drilling process. A field log of the soil encountered in the borings was maintained by the drill crew. After recovery, each sample was removed from the sampler and visually classified. Representative portions of each sample were then sealed and brought into our laboratory. Field Infiltration Investigation and Testing Procedures Our infiltration exploration and testing program was developed to help characterize the infiltration potential of soils at specific locations and depths. The depths and locations were selected by the civil engineer. ECS was instructed to perform infiltration testing 5± feet below the existing ground surface. Auger refusal was encountered in Boring I-1 at 4± feet; therefore, the infiltration tests were performed 2± feet below the existing ground surface in both locations. The soils upon which our evaluations are based were recovered by continuous soil profile development via hollow-stem auger drilling/standard split spoon sampling operations. Following drilling of test borings, an offset probe boring was completed to 2± feet below the existing ground surface at each location, and infiltration tests were performed. Once the infiltration test location was prepared, the actual infiltration presoak and infiltration testing was carried out as described below. Infiltration tests were performed at two locations. In both cases, the infiltration testing was performed utilizing a modified constant head method. Each test location was presoaked approximately 24 hours to 30 hours before the actual test was performed. Following the presoak, each infiltration test was performed over a four-hour test duration with the drop in water head being monitored and recorded at regular intervals and then recharged at each reading. The average water level drop recorded over the four hour test period is used to determine the field infiltration rate. The final design rate is one half the field rate. A table containing the raw infiltration test data and the recommended design rate for each test location is included in the Appendix of the report.


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Laboratory Testing Program Representative soil samples were selected and tested in our laboratory to check the field classification and to determine pertinent engineering properties. The laboratory testing program included visual classifications, natural moisture content tests, gradation analysis, and Atterberg Limits testing of selected soil samples. All data obtained from the laboratory testing program is included on respective boring logs and/or on separate laboratory sheets within the Appendix of this report. Each soil sample was classified on the basis of texture and plasticity in accordance with the Unified Soil Classification System (USCS). The group symbols for each soil type are indicated in parentheses following the soil descriptions on the boring logs. A brief explanation of the USCS is included with this report. The samples were grouped by 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 transitions may be gradual, rather than distinct. The soil samples obtained from this exploration were retained at our laboratory for a period of 60 days from the time drilling was completed. The samples obtained during the field exploration have since been discarded.


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EXPLORATION RESULTS Site Conditions The project site is currently a partially developed lot, consisting of two parcel located in the southwest quadrant of Ashburn Road and Hay Road in Ashburn, Loudoun County, Virginia. The site is partially developed with three, two-story buildings, a two-story barn, several sheds, a gravel driveway and fences. The northwest corner of the site is currently undeveloped, and was observed to be a relatively flat, open grassy area. Based on existing site topography from the site plan, the site ranges from a topographic high of elevation EL. 306± feet along the western boarder of the site, to a topographic low of elevation EL. 294± along the eastern boarder of the site. The specific project details, including the existing site features, are shown on the diagrams included in the Appendix of this report. Regional Geology and Soils Mapping Regional Geology The site is located within the central portion of the Culpeper Triassic Basin which extends from the Rapidan River near Madison, Virginia to just west of Frederick, Maryland. The Culpeper Basin is a structural trough, or half-graben, that formed as a result of tensional tectonic activity during the Triassic Geologic Period (±250 million years ago). The tensional tectonic activity that formed the Culpeper Basin ultimately grew to form the current Atlantic Ocean. In the down dropped portion of the basin, a playa lake formed which was subsequently filled by erosional deposits primarily from the Blue Ridge to the west and, to a lesser extent, from the Piedmont to the east. During sedimentation of the basin, the western border fault periodically reactivated which has lead to the shallow (8 to 11º) westward dip of basin strata observed today. After sedimentation of the basin, border fault reactivation resulted in cyclic layers of basalt and sandstone rock along the western margin of the basin. Late in the formation of the basin, local tectonic activity occurred which caused the basin sediments to be intruded by igneous magma forming dikes, sills, and lopoliths of diabase granite bedrock. The Geologic Map of Loudoun County, Virginia indicates that the site is underlain by the Lacustrine Shall and Siltstone Member of the Balls Bluff Siltstone (TRbs). The natural soils in this region are derived from the in-place weathering of the underlying parent bedrock. The residual soils that form above siltstone bedrock generally have low to moderate plasticity and low to moderate shrink/swell potential. Soils Mapping The natural soils which have resulted from the in-place physical and chemical weathering of the underlying bedrock are composed primarily of residual clayey or silty soils with increasing amounts of sand with depth. The granular nature of the residual soils generally increases with depth as does the percentage of rock fragments. These layers are termed weathered rock due


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to their rocklike structure but exhibit characteristics which qualify them as soil. The soil to rock transition in siltstone lithology is generally gradual. In addition, we have also reviewed the available Loudoun County Soils Mapping. Table 1 briefly presents the pertinent characteristics of the soil types mapped at this site. Table 1: Soil Type Characteristics by Mapping Unit (per Loudoun County)

Mapping Unit

Soil Group Typical Terrain Parent Rock Problems/Limiting

Factors Soil

Class

67B Haymarket and Jackland Soils

Convex Ridgetops and

Sideslopes Diabase and Basalt

Highly Plastic Clays, Seasonal Perched

Water Table IV

73B Penn Silt Loam Sloping Convex

Landscapes Siltstones and

Shales Shallow Rock Surface I

74B Ashburn Silt

Loam Sloping

Landscapes Siltstones

Wetness, Low Bearing Capacities

II

According to the Loudoun County Soils Mapping, the site is generally in an area mapped with Class I to Class IV soils corresponding to good to very poor potential for general site development. The majority of the site is located in an area primarily mapped with Class I and II soils, however, a relatively small area, along the western border of the site, is mapped as to contain Class IV soils, typically associated with Diabase geologies. An area mapped with Class II soils spans the eastern portion of the site along, running north to south along Ashburn Road, while the remainder of the site explored, consists of Class I soils. The soils mapped as Class IV soils are typically due to highly plastic clays and due to the possibility of perched water and flooding conditions. No soil points are mapped on the site. Seasonal High/Perched Water Tables and Low Soil Strength Engineering recommendations addressing the possible presence of soils with seasonal high/perched water tables, such as Soil Mapping Units (SMU) 74B are addressed in the Groundwater Observations section on page 8, in the section entitled Construction Groundwater Control on page 15, and in the General Construction Considerations section on page 23. Soils with low strength are discussed in the Building Foundations section on page 16. Recommendations for highly plastic soils are discussed in the Highly Plastic Soils section on page 12. Subsurface Conditions The soils identified in the attached boring logs are generally consistent with the regional geology and soils mapping. The predominant soil profile appears to have been derived from the in-place physical and chemical weathering of the underlying siltstone bedrock materials. Our field exploration indicated surface materials consisting of 3 inches to 11 inches of topsoil in Borings B-1, I-1, and I-2, and 7 inches of compacted gravel in Boring B-2 underlain by natural soils.


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Existing fill was noted in Boring B-2. Existing fill extends from the bottom of the topsoil to 2.5± feet below the existing grades, and consisted of CLAY (CL) with varying amounts of sand and rock fragments. The fill is assumed to be related to the prior site grading activities. The natural residual soils that were encountered generally consisted of low to moderate plasticity Lean CLAY (CL) with varying amount of gravel, sand, and silt. Standard Penetration Test (SPT) N-values within the underlying soils and weathered bedrock materials ranged from weight of hammer material to material 50 blows per foot (bpf) with no visible sampler penetration, indicating loose to extremely dense relative density for cohesionless soils or very soft to very hard consistencies for cohesive soils. For the purposes of this report, weathered rock is any residual soil material having an SPT blow count of 60 bpf or greater. Each of the borings was extended to auger/sampler refusal, which was encountered at a depths ranging from 5± feet to 8.5± feet below existing ground surface on the underlying siltstone bedrock. High plasticity soils (CH or MH) were not encountered in the recently performed borings, and highly plastic soils are not typically encountered in areas underlain by siltstone bedrock. Although highly plastic soils were not encountered in our borings, they may be encountered in unexplored areas of the site or between sampled locations. It is noted that the soils mapped by Loudoun County indicate the presence of highly plastic soils at the northwestern most corner of the site. Groundwater Observations Observations for groundwater were made during sampling and upon completion of drilling operations in each of the boring locations. In auger drilling operations, water is not introduced into the boreholes during soil drilling, and the groundwater position can often be determined by observing water flowing into or out of the borings. Groundwater was not encountered in any of the borings performed to the depths observed while drilling, but was observed after the completion of drilling within each boring at depths ranging from 2± feet to 2.5± feet below the existing ground surface. Perched groundwater conditions can develop in areas with shallow rock. Specifically, rainfall that enters the site, either directly or from overland flow, begins to percolate through the low to moderately permeable surficial soils. Once the water percolation reaches the bedrock, which is significantly less permeable, it begins to flow at the interface of the rock and the soil and within the fractured surface of the bedrock. The groundwater conditions at this site are expected to be significantly influenced by surface water runoff and rainfall. The highest groundwater observations are normally encountered in the late winter and early spring. Variations in the location of the long-term water table may occur as a result of changes in precipitation, evaporation, surface water runoff, and other factors not immediately apparent at the time of this exploration. The site may also be subject to severe desiccation during extended dry periods. Therefore, earthwork operations in the winter and spring are more likely to encounter difficulties with perched conditions than those operations undertaken in the summer or fall. For long-term planning purposes, we strongly urge that mass grading operations be undertaken to coincide with favorable weather periods.


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Infiltration Test Results An infiltration test was conducted at both Borings I-1 and I-2 within Sandy CLAY (CL) with varying amounts of silt and gravel, at depths of approximately 2± feet below existing site grades. Field rate tests were on the order of 7.06 to 9.48 inches per hour. A summary of the findings are provided below: Table 2: Infiltration Test Results

Boring No.

Existing Grade EL. (feet)

Test Elevation EL. (feet)

Field Infiltration Rate (in/hr)

Recommended Infiltration Rate (in/hr)

I-1 300 298 9.48 4.7 I-2 298 293 7.06 3.5


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ANALYSIS AND RECOMMENDATIONS The recommendations outlined in this report are based on the four soil borings and infiltration testing program recently performed by ECS and the site layout plan provided to us by The KDL Group via email in March 2014. The site generally appears suitable for the design and construction of the proposed development, which will include a two-story, multi-family condominium building, associated parking and underground infrastructure. The primary factors that could affect the proposed development are a shallow rock surface, low bearing capacity soils, the possibility of highly plastic soils, and the possibility of perched groundwater conditions. More detailed analysis and recommendations are included in the following sections. Subgrade Preparation and Earthwork Operations The subgrade preparation should consist of stripping all surface cover materials, topsoil, gravel, unsuitable existing fill, and any other soft or unsuitable material from the building and pavement areas. We recommend that site stripping depths account for the topsoil and possible variations in topsoil thickness between boring locations. We recommend the earthwork clearing be extended a minimum of 10 feet beyond the building and pavement limits. Stripping limits should be extended an additional 1 foot for each foot of fill required at the building's exterior edge. The limits discussed in this paragraph define the expanded building and pavement limits. The preparation of fill subgrades, as well as proposed buildings or pavement subgrades should be observed on a full-time basis. These observations should be performed by the Geotechnical Engineer of Record (GER), or their representative, to document the unsuitable materials that have been removed, and that the subgrade is suitable for support of the proposed construction and/or fills. Procedures such as proofrolling, observation, or test pitting operations may be utilized to assist in identifying the presence of unsuitable materials, as required. Existing fill/disturbed surficial materials were encountered at Boring B-2, and will likely be encountered in other areas of the site, particularly adjacent to the existing roadways or utility easements, or in areas between borings. This fill material is likely associated with the previous site development and may be suitable provided it was properly placed, compacted, and tested under the observation of an experienced geotechnical engineering technician. We recommend that documentation from the previous construction activities related to the fill operations be reviewed. If documentation of previous fill placement is not available, we recommend that any existing fill be completely removed from the building area. Based on the boring data, it appears that the existing fill material was placed with some compactive effort and may be suitable for support of pavements. Pavement areas should be thoroughly evaluated with proofrolling at the time of construction to identify areas that may be unsuitable. We recommend that the GER or their authorized representative be present during initial stripping and during excavation of the building footprint to help in delineating suitable and unsuitable materials. Any unsuitable areas identified should be undercut and replaced with suitable fill material compacted as described in this report or otherwise remediated as directed by the GER. After stripping to the desired grade, and prior to fill placement, the stripped surface should be observed by the GER or their authorized representative. Proofrolling using a loaded dump truck, having an axle weight of at least 10 tons, may be used at this time to aid in identifying


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localized soft or unsuitable material which should be removed. Any soft or unsuitable materials encountered during this proofrolling should be removed and replaced with an approved backfill compacted to the criteria given below in the section entitled Fill Placement. Soil bridging lifts within the expanded building and pavement limits should not be used. Excessive settlement of the structures may occur when bridging lifts are utilized in structural areas. Any soft areas should be removed or stabilized in place with geosynthetics and engineered fill as necessary. Recommendations regarding in-place stabilization of soft or unsuitable subgrade materials should be provided by the GER at the time of construction. Fill Placement In general, new engineered fill materials for use as backfill, or for support of pavements should consist of an approved material, free of organic matter, debris, cobbles, and rock fragments greater than 4 inches in diameter. The engineered fill should also have a Liquid Limit and Plasticity Index less than or equal to 45 and 20, respectively, unless they are shown to have “very low” expansion potential. Unacceptable fill materials include topsoil and organic materials (OH, OL, and PT), and high plasticity SILTS (MH) or CLAYS (CH) that cannot be shown to have “very low” expansion potential. The onsite soil may be reused as engineered fill provided that it does not contain organic matter or foreign debris, are not highly plastic, are not environmentally impacted and conform to the criteria outlined above. The suitability of any on-site materials for reuse as engineered fill should be evaluated at the time of construction by the GER or their representative. In general, the soils encountered in the borings appear suitable for reuse as fill material. The suitable on-site soil may require moisture content adjustments, such as the application of discing or other drying techniques or spraying of water prior to use as controlled fill materials. The planning of earthwork operations should recognize and account for these efforts and increased costs. Fill materials should be placed in lifts not exceeding 8 inches in loose thickness and moisture conditioned to within ±2 percentage points of the optimum moisture content. Where controlled fill will have a total thickness not exceeding 8 feet, the soil should be compacted to a minimum of 95% of the maximum dry density obtained in accordance with ASTM Standard D 698, Standard Proctor Method or Virginia Test Method (VTM-1). The upper 1-foot of subgrades for pavement areas should be compacted to a minimum of 100% of VTM-1 or ASTM D 698. Although not anticipated based on the provided site plan, in any areas where the total depth of fill will exceed 8 feet, such as in the proposed sanitary sewer alignments, we recommend that these fill zones be placed as early as possible in the earthwork operations phase. Where the fill depth will be 8 feet or more, we recommend that the fill soils be compacted to a minimum of 98% of the maximum dry density obtained in accordance with ASTM D-698 or VTM-1, for the full depth of the fill. The purpose of the higher compaction criteria is to reduce differential settlement between natural cut soils and controlled fill soils. Because of the moisture and disturbance sensitive nature of the clay soils at the site, the initial one to two lifts of fill may need to be compacted without vibratory efforts. Vibratory compaction equipment may cause disturbance of the near surface site soil and upward migration of


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moisture into the engineered fill which could inhibit compaction efforts. After placement of the initial one to two lifts, vibratory compaction can proceed, if appropriate. The expanded footprint of the proposed structures or pavement and fill areas should be well-defined, including the limits of the fill zones at the time of fill placement. Grade control should be maintained throughout the fill placement operations. All fill operations should be observed on a full-time basis by a qualified soil technician to determine that the specified compaction requirements are being met. A minimum of one compaction test per 2,500 square feet of area should be tested in each lift placed. The elevation and location of the tests should be clearly identified at the time of fill placement. Compaction equipment suitable to the soil type used as fill should be used to compact the fill material. Theoretically, any equipment type can be used as long as the required density if achieved. Ideally, a steel drum roller would be most efficient for compacting and sealing the surface soils. All areas receiving fill should be graded to facilitate positive drainage from building pad and pavement areas of any free water associated with precipitation and surface runoff. Fill materials should not be placed on frozen soil, and all frozen soil should be removed prior to continuation of fill operations. Borrow fill materials should not contain frozen materials at the time of placement. All frost-heaved soil should be removed prior to placement of fill, stone, concrete, or asphalt. Highly Plastic Soils Highly plastic soils were not encountered within the borings performed and are not generally expected to exist in siltstone geologies. However, highly plastic soils are mapped by Loudoun County in the northwestern most portion of the site and may be encountered between intervals sampled, and/or boring locations. These types of soils can develop significant shrink/swell problems with variations in moisture content. If field work is conducted during the winter or early spring months, it is expected that even the non-plastic clay soils at the surface may need to be removed or dried prior to fill placement. As earthwork operations proceed, additional Atterberg Limits tests and Expansion Index tests are recommended in order to evaluate suitability of questionable on-site soils. Highly plastic soils that cannot be shown to have “very low” expansion potential should be dealt with in accordance with the recommendations presented below. Where expansive soils are encountered within two feet below the foundation bearing level, the foundations may either step down to bear at a depth of 5 feet below finished exterior grade, or the footings may be undercut and backfilled to the original bearing elevation. Undercutting of the footings and backfilling with granular backfill or gravel is not recommended, as this would create a reservoir condition that could saturate the plastic soils. Undercut footings shall be backfilled with properly compacted, suitable fine grained soil or preferably, lean concrete to the original bearing elevation. Footings constructed in plastic clay soils should be excavated using a neat excavation and backfilled entirely with lean concrete. If the footings are stepped down to bear at a minimum depth of 5 feet below the finished exterior grades, the footings may bear on either high or low plasticity soils. At this depth, the footings are considered to be below the depth of typical seasonal moisture change. In addition, floor slabs and pavements constructed in areas of high plasticity soils should be underlain by at least 2 feet of compacted, non-expansive suitable fill.


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Rock Excavation and Blasting Operations Rock excavation or blasting should be anticipated at the site in the areas of underground utilities. Rock excavation should also be anticipated to reach the basement floor elevation and foundations in the building area. Utility plans were not provided, so specific depths of utilities was not known at the time of this report. As given in the enclosed boring logs, all borings encountered auger/sampler refusal at a depth between 5± feet and 8.5± feet below existing site grades. It should be noted that unanticipated variations in the rock surface may occur between boring locations. Excavations beyond these levels may require controlled blasting operations. The rippability of bedrock is highly dependent on the amount and nature of fracturing within the rock, the strength of the rock, and the type of equipment used. It should be noted that many site excavation contractors reportedly use 50 blows for 6 inches of penetration as a criteria to define “rock”. Within individual footing excavations and in local excavations for utility lines, however, we anticipate that hoe-ramming will be feasible if excavation is to extend below these levels. For the construction planning and final pay quantities, we recommend that the following definition be used to define hard rock excavation material for the project specification:

“Rock shall be defined as those natural materials which cannot be excavated in an open excavation with a Caterpillar Model D-8, heavy duty track-type tractor, weighted at not less than 285 hp flywheel power and equipped with a single-shank hydraulic ripper, capable of exerting not less than 45,000 lbs. breakout force, or equivalent machinery. For trenches and pits, rock shall be defined as those materials that cannot be excavated with a Caterpillar Model No. 345 L track-type hydraulic excavator, weighing not less than 99,000 lbs., equipped with a 30-inch wide short-tip radius rock bucket, rated at not less than 345 hp flywheel power with bucket-digging force of not less than 39,000 lbs, or equivalent machinery. Boulders or masses of rock exceeding one-half cubic yard in volume shall also be considered rock excavation. This classification does not include materials such as loose rock, concrete, or other materials that can be removed by means other than drilling and blasting, rock trenching, or hoe-ramming, but which for reasons of economy in excavating, the contractor chooses to remove by drilling and blasting, rock trenching, or hoe-ramming techniques.”

When reviewing this data for planning purposes, consideration of the excavation capabilities of different equipment will be necessary. For example, a backhoe will likely not be able to excavate weathered rock materials as easily as a track hoe or ripper. At the same time, ripping may not be an appropriate excavation method for the desired activities. The values derived herein have been provided for informational purposes and are not intended to suggest or recommend excavation methods. Where overblasting occurs, it is often necessary to remove the disturbed materials and replace them with new engineered fill. In situations where blasting is required to reach footing subgrades, it is common practice to set charges so that rock can be removed to a depth corresponding to about 2 feet below the lowest finished floor level. The blast-disturbed material is then either removed and replaced with engineered fill during the grading stage, or it is removed during the foundation construction stage and replaced to subbase level using well-graded coarse


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aggregate. In either case, it should be recognized that perched water will have a tendency to collect in the “bathtub” created as a result of the isolated blast zone. It has been our experience that the use of well graded crushed aggregate, such as VDOT 21A, (and geotextiles, when necessary), in lieu of engineered soil fill, for backfilling these areas will reduce the likelihood for undercutting along footing lines and in slab areas. A well graded aggregate can also serve as a groundwater reservoir where temporary sumps collect and discharge the trapped water during construction. Therefore, we recommend that the grading contractor provide the GER with details regarding the proposed blasting operations prior to performing those operations. With care, this problem can be substantially reduced, and should be a consideration when grading contractors are determining whether to approach the site using blasting or ripping procedures. Of paramount concern and a problem of significant potential cost is that of "overshooting" the rock during site preparation, should rock blasting be deemed necessary. This is especially true within the siltstone areas where blasting will cause fracture along naturally occurring horizontal bedding planes with a typical 8° to 11° dip. As a result, the rock delaminates and “swells” or expands vertically along the bedding planes in the rock. If excessive charges are set, or if the charge pattern is too close or too deep, the siltstone materials will delaminate and “swell” along natural planes of weakness, this expansion can occur below the depth of excavation and the looser material left in place below the foundation element can cause significant settlement of foundations which bear on it. Once foundation loads are placed on the expanded siltstone materials, then the open fractures tend to close up, causing settlement. Therefore, it is strongly recommended that the charge patterns and depths be carefully selected, to avoid overblasting. Irregularities in the base of the footing foundation are acceptable, if rock materials are encountered. For the purposes of bid documentation, any irregularity of up to one foot vertically for ten feet of horizontal distance is acceptable. If the rock is overshot, it will typically excavate in a fairly platy structure. Although it may be possible to remove the larger broken plates with a backhoe, the fracture force may create sufficient voids in the rock plane to induce unacceptable settlement. Therefore, proper control of blasting operations is critical at the site, along with timing of blasting operations. In general, all blasting on the site should be completed, to the extent practical, prior to the placement of concrete. In the event it is necessary to blast additional locations, then the use of vibration monitoring equipment to monitor the performance of placed concrete will be necessary. The potential for overblasting should be recognized during both the design and construction phases. We strongly recommend that the geotechnical consultant meet with the grading contractor and any blasting specialists to review shot patterns and blasting procedures at the time of construction to reduce difficulties associated with overblasting. If overshooting occurs, the loose or disturbed materials should be removed and replaced with controlled, compacted fill placed in accordance with the recommendations included in this report. Siltstone Considerations Siltstone bedrock was encountered within all of the borings performed to the depths observed. We expect that any siltstone materials removed during grading operations will likely be used as engineered fill. Reuse of these materials as engineered fill will require that they be properly manipulated to a suitable gradation prior to placement. The siltstone bedrock at this site will typically excavate in relatively large, blocky and platy pieces, which are difficult to compact for suitable long-term performance. Also, these materials experience rapid degradation due to weathering over relatively short periods of time, once exposed to air and water conditions.


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Therefore, these larger pieces of siltstone, which break up as rock-like fragments in the initial excavation, must be compacted with sufficient compaction energy to substantially break them down into soil size particles during construction. Nondurable siltstone materials removed in blast and ripping excavations may be used as fill if suitably decomposed by mechanical effort. For the purposes of this report, all siltstone materials at the site will be considered nondurable. Durability is the term used to describe the ability of a rock or rock-like material to withstand long-term chemical and mechanical weathering without size degradation. Any siltstone excavated from the site and used as earthwork fill should have a well-graded grain size distribution with rock and soil particles ranging from clay or silt size particles to a maximum size of 6-inches in diameter with 2-inch thick siltstone plates. Particles larger than this should be decomposed by mechanical compaction equipment to achieve the desired grain size distribution. A minimum uniformity coefficient, Cu, of 6 should be used to identify the proper grain size distribution and the samples should have a minimum of 20% passing the #200 sieve and 50% passing the #40 sieve. Variations from these recommendations should be evaluated by the GER prior to fill placement. Laboratory classification and Proctor compaction tests should be performed on samples that have been broken down by compaction equipment to be used for compaction of the fill. This may require manipulation of the material prior to obtaining samples for testing. Samples obtained should be representative of the materials intended to be used as fill with respect to gradation. It has been our experience that engineered fills constructed of siltstone materials tend to perform better when placed at moisture contents slightly wet of optimum. The water associated with moisture levels on the wet side of the optimum moisture content is believed to aid in the physical and mechanical breakdown of siltstone particles, as well as reduce the tendency of the soil matrix to absorb water after fill placement. Construction Groundwater Control The long term continuous groundwater table at the site is expected to be well below the depth of auger/sampler refusal. However, groundwater was encountered in all borings at the site. Groundwater conditions at the site are strongly influenced by surface water flow and infiltration. Specifically, water that enters the site migrates downward to the interface of the fill soils, natural soil, and rock. Once the water reaches the less permeable natural soil or rock, the water travels laterally, often over large distances. Such perched groundwater conditions may be encountered during construction operations. The perched groundwater conditions are seasonal in nature. While perched groundwater conditions may not be encountered during the summer months, such conditions can occur in the winter and late spring months. The degree of fracturing within the rock materials can be increased and altered significantly by blasting operations. Therefore, it is common to have “springs” develop in areas which where previously dry once initial grading operations have commenced. These conditions should be anticipated and can be handled through the use of French drains installed on the uphill side of any excavations performed on site. In addition, French drains may need to be installed in areas where springs develop. The surface of the site should be kept properly graded in order to enhance drainage of the surface water away from the proposed building and pavement areas during the construction


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phase. We recommend that an attempt be made to enhance the natural drainage without interrupting its pattern. It is critically important that planning operations consider construction groundwater control. One of the more cost effect techniques that can be utilized for groundwater control, we believe, is through the prudent utilization of French drains, and in planning utility installations. For example, any utility installation that requires a gravity feed, such as sewer lines, can be effectively converted into “French drains” to help assist in groundwater control. A French Drain Installation Detail in included in the Appendix of this report. Building Foundations The proposed building will be a two story, multi-family condominium building with a footprint of approximately 3,760 square feet (sf). Structural loading was not available at the time of this report preparation; therefore, we have assumed that column loads will be on the order of 100 kips or less and wall loads will be on the order of 3 kips/linear foot or less for the sheriff station. We anticipate the proposed building will bear on new engineered fill or natural soils or a combination of these materials. Based on the available subsurface information, we anticipate that for design purposes, the proposed buildings may be supported by shallow foundations consisting of a spread and/or continuous footing system. For foundations which will bear on natural soils or in properly placed engineered fill, an allowable bearing pressure of 3,000 psf may be used in design. Natural soils capable of supporting this allowable bearing capacity are identified on the boring logs as those natural soils exhibiting SPT N-Values of 10 bpf or higher. The allowable soil bearing pressure refers to that pressure which may be transmitted to the foundation bearing soils in excess of the final minimum surrounding overburden pressure. During construction, the bearing capacity at the final footing excavation should be tested in the field by the GER or authorized representative to document that the in-situ bearing capacity at the bottom of each footing excavation is adequate for the design loads. High plasticity soils were not encountered within the borings performed; however, if high plasticity soils are encountered at footing subgrades, the recommendations provided in the Highly Plastic Soils section of this report should be followed. The presence or absence of highly plastic soils should be documented by the soils technician using hand auger probes at the time of footing observation and testing. 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 excavations are made. 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, we recommend that a 1 to 3-inch thick "mud mat" of "lean" concrete be placed on the bearing soils before the placement of reinforcing steel. Settlement of a structure is a function of the compressibility of the natural soils, the design bearing pressure, column loads, fill depths, and the elevation of the footing with respect to the original ground surface. For the anticipated loads of the condominium building, total settlement values of less than 1 inch are expected. At this site, differential settlement between individual column locations and along any 30-foot wall length within the building should be relatively


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minor, on the order of 50 percent of the maximum total settlement. The settlement estimates stated above apply to individual column footings and wall footings We recommend that continuous footings have a minimum width of 18 inches and that isolated column footings have a minimum lateral dimension of 24 inches. The minimum dimensions recommended above help reduce the possibility of foundation bearing failure and excessive settlement due to local shear or "punching" action. In addition, footings should be placed at a depth to provide adequate frost cover protection. Therefore, we recommend footings be placed at a minimum depth of 2 feet below the finished grade. A Typical Foundation Detail is included in the Appendix of the report. All continuous load-bearing wall foundations should be suitably reinforced. To provide continuity and to reduce the effects of differential settlements, the longitudinal reinforcing steel should be extended into any column footings situated along the wall footings and the foundations should be constructed as a continuous unit though monolithic concrete placement to the greatest extent practical. The reinforcing steel also should be continuous through the building corners. Where top and bottom steel is included in the continuous wall foundations, a minimum footing thickness of 1 foot should be provided. Prior to the placement of any foundation concrete, the steel reinforcement should be examined to document that the bars are properly sized and positioned in accordance with the foundation plans and specifications. Ground-Supported Slabs For the design and construction of any interior slabs-on-grade for the proposed structure, the recommendations provided in the section entitled Subgrade Preparation and Earthwork Operations and Fill Placement should be followed. We recommend that the GER or his authorized representative be present at the beginning of slab subgrade construction to help in delineating suitable and unsuitable materials. Any unsuitable areas identified should be undercut and replaced with suitable fill material compacted as described in this report or otherwise remediated as directed by the GER. Subgrades should then be thoroughly compacted to the criteria of structured fill given within this report.

We recommend that the floor slab be isolated from the column footings so that differential settlement of the structure will not induce shear stresses in the floor slab. Furthermore, in order to reduce the crack width of any shrinkage cracks that may develop near the surface of the slab, we recommend mesh reinforcement be included in the design of the floor slab. The mesh should be in the top half of the slab to be effective. Special attention should be given to the surface curing of the slab in order to reduce uneven drying of the slab and associated cracking. We also recommend that the slabs-on-grade be underlaid by a minimum of 4 inches of granular material having a maximum aggregate size of 1.5 inches and no more than 2% fines. This granular layer will facilitate the fine grading of the subgrade and will provide a path for water below the slab. Prior to placing the granular fill, the floor slab subgrade soils should be properly compacted, and be free of standing water, mud, or frozen soil. Before the placement of concrete, a vapor barrier should be placed on top of the granular material to provide additional moisture protection.


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If high plasticity soils are encountered at or within 2 feet below the slab subgrade surface, it is recommended that the high plasticity soils be removed to a depth of 2 feet below the bottom of slab and replaced with a non-expansive, granular fill material that is placed and compacted in accordance with the recommendation contained within this report.

In the event there is a significant time lag between the site grading work and fine grading of the slab area prior to the placement of stone or concrete, the GER should document the condition of the prepared subgrade. Prior to final slab construction, the subgrade may require scarification and recompaction to provide firm and unyielding conditions. Below Grade Walls and Drainage Below grade walls for the basement below the eastern portion of the condominium building should be designed to withstand lateral earth pressures and surcharge loads. We recommend that the below grade walls be designed for a laterally increasing at-rest earth pressure of 60 psf per vertical foot of wall. This lateral pressure assumes that native CL materials (or more granular) with LL less than or equal to 40, PI less than or equal to 15 and Expansion Index less than or equal to 20 are used for wall backfill. In order to maintain a 60 psf lateral earth pressure, drainage of the backfill must be provided. The design should also account for any surcharge loads within a 45 degree slope from the base of the wall. An example Lateral Earth Pressure Diagram and Zone of Influence Diagram are included in the Appendix of this report. At least a one-foot annular space between the outside of the walls and excavation should be backfilled with an inorganic, free draining granular material, free of debris. Outside this zone, the below-grade walls may be backfilled with low plasticity soils with maximum Liquid Limit and Plasticity Index less than or equal to 40 and 15, respectively. High plasticity soils are not acceptable for use as below grade wall backfill. To achieve a desirable balance between minimizing excessive pressures against the below grade walls and reducing the settlement of the backfill, we recommend that the wall backfill be compacted on the order of 92% to 95% of the maximum dry density determined in accordance with ASTM D 698, Standard Proctor Method. The fill placed adjacent to the below grade walls should not be over compacted. Heavy earthwork equipment should maintain a minimum horizontal distance away from the below grade walls of 1 foot per foot of vertical wall height. Lighter compaction equipment should be used close to the below grade walls. Suitable manmade drainage materials may be used in lieu of the free draining granular backfill, adjacent to the below grade walls. Examples of suitable materials include Enka-Mat, Mirafi, or J-Drain drainage composites. These materials should be covered with a filter fabric having an Apparent Opening Size (AOS) consistent with the size of the soils to be retained. The material should be placed in accordance with the manufacturer's recommendations and connected to either the perimeter drainage system or the underslab granular mat, which in turn should be properly drained. The ground surface adjacent to the below grade walls should be kept properly graded to prevent ponding of water adjacent to below grade walls. We recommend that any below grade spaces of the proposed structure be provided with a perimeter drainage system. This system may consist of 4-inch perforated, closed joint drain tiles located around the perimeter of the lowest level, outside the walls, slightly below the lowest floor level. These drain lines should be surrounded by a minimum of 6 inches of free draining


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granular filter material having a gradation compatible with the size of the openings utilized in the drain lines and surrounding soils to be retained. The granular drainage material should be wrapped with geotextile fabric. As previously mentioned, we recommend that the floor slab be underlain by a minimum of 4-inches of free draining granular material. The underslab drainage blanket and the drain tiles should either be hydraulically connected and either outlet to daylight or connected to a storm sewer, if allowed by the County, to remove any water that may accumulate or directed to an interior sump pit and pumped for removal.

Seismic Site Classification (IBC) The International Building Code (IBC) 2009 requires site classification for seismic design based on the upper 100 feet of a soil profile. Where site specific data are not available to a depth of 100 feet, appropriate soil properties are permitted to be estimated by the registered design professional preparing the soils report based on known geologic conditions. The seismic site class definitions for the weighted average of either the SPT N-values or the shear wave velocities in the upper 100 feet of the soil profile are presented in Table 1613.5.2 of the 2009 IBC Code and in the table below. Table 3: IBC Seismic Site Classification

Site Class

Soil Profile Name Shear Wave Velocity, Vs,

(feet/s) Standard Penetration

Test (SPT) N-value

A Hard Rock Vs > 5,000 fps N/A

B Rock 2,500 < Vs ≤ 5,000 fps N/A

C Very dense soil and soft rock 1,200 < Vs ≤ 2,500 fps NAVG > 50 bpf

D Stiff Soil Profile 600 ≤ Vs ≤ 1,200 fps 15 ≤ NAVG ≤ 50 bpf

E Soft Soil Profile Vs < 600 fps NAVG < 15 bpf In the absence of actual shear wave (Vs) data, we utilized the Standard Penetration Test (SPT) N-values recorded from the borings. Considering the shallow rock surface encountered at this site and on our experience with other projects in the area, we recommend that the design for the buildings be based on a seismic site classification of Site Class C. Infiltration Trench Facilities As we understand, there are currently two proposed infiltration areas. According to The KDL Group, the two infiltration areas are being designed as infiltration trenches. We understand these facilities are currently designed to infiltrate the water runoff from various portions of the site. In the evaluation and design of infiltration facilities, there are 3 primary factors that affect the suitability of the subsurface conditions for practical infiltration design. These factors include 1) presence and depth to a restrictive/impermeable layer (i.e. clay or competent bedrock), relative to the design invert elevation, 2) depth of the seasonal high water table, and 3) in-situ infiltration rates for the soils at or below the proposed invert elevation. During our field exploration, relatively granular fine-grained soils (CL) were encountered in each of the borings performed within the infiltration trench locations which was then underlain by relatively shallow bedrock. Currently, we understand that the proposed invert elevation of these


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infiltration trenches is between EL. 298± feet and EL. 302± feet. Sampler refusal was encountered within Borings I-1 and I-2 at 5.5± feet and 8.5± feet below the existing ground elevation, respectively. As noted previously, a field infiltration test was performed at each location. The field infiltration tests were performed in the weathered rock stratum. This stratum is overlain by fined grained clay materials. It will be necessary to verify that the bottom of the trench is in the weathered rock material in order for infiltration to be possible. Undercutting of the trenches should be expected in some areas to reach the weathered rock layer. The undercut portion of the trench should be backfilled with a free draining sand material such as ASTM C33 sand or other material approved by the GER. The results of the infiltration testing are presented below. Table 4: Infiltration Test Results

Boring No.

Approximate Existing Surface

Elevation (ft)

Proposed Facility Invert Elevation (ft)

Preliminary Infiltration

Test Elevation (ft)

Field Infiltration Rate (in/hr)

Recommended Infiltration Rate (in/hr)

I-1 300 298 298 9.48 4.7 I-2 298 296 296 7.06 3.5 The field infiltration test results indicate a recommended infiltration rate of 4.7 inches/hour and 3.5 inches/hour at locations I-1 and I-2, respectively. The locations of the soil test boring/infiltration test locations can be referenced on the Boring Location Diagram, included in the report Appendix. The results of the infiltration testing performed are also included in the Appendix of this report for reference. After completion of our field exploration, portions of the site plan were altered and the location of the infiltration trenches was changed. Based on the results of our testing, the subsurface profile appears consistent over the site, and we expect our test results to be representative of the materials on site and additional testing should not be necessary. The following table presents depth to watertable information for the soil mapping units on-site. Table 5: Soil Type Depth to Water Table by Mapping Unit (per NRCS)

Mapping Unit Soil Group NRCS Published Depth to

Water Table (in) Soil Class

67B Haymarket and Jackland

Soils > 80 IV

73B Penn Silt Loam > 80 I 74B Ashburn Silt Loam 30 II

Based on the NRCS mapping, the seasonal high groundwater table for the soils mapped on this site, mapped within the proposed rain garden area, is indicated as 30± inches to greather than 80± inches, respectively, below the existing ground surface. Please note that although this seasonal high watertable is most likely due to a perched groundwater condition as previously noted in the Groundwater Observations section, Loudoun County does not differentiate between


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the seasonal high groundwater table and the long term continuous groundwater table. Our borings encountered groundwater between 2 feet and 2.5 feet below existing grade. Although the NRCS website notes a seasonal high groundwater table of 30± inches and greater than 80± inches below the existing ground surface, this typically is a generalized and conservative value that is not determined on a site specific basis. That being said, Loudoun County recognizes two alternative ways to determine the site specific seasonal high groundwater table. A certified professional soil scientist or geologist can perform a series of hand augers or test pits and observe the soils for water indicators or a temporary monitoring well can be installed on the site and observed periodically for a year. Should the results of this testing indicate a seasonal high groundwater level greater than 2-feet below the proposed invert elevation, the clay liner (and engineered media/underdrains) will not be necessary. ECS has the capability to perform either of these options should either be more favorable than installing a clay liner. Based on recent discussions and our experience with Loudoun County, several options exist to address these areas. One option is to install a 1-foot clay liner in the bottom of the facility. The clay liner should consist of a moderate to high plasticity clay, classified as CL or CH and have no more than 10% returned on a No. 200 sieve or larger. We also recommend the soils for the liner be installed at 2 to 3 percentage points above optimum moisture content. We should stress that final approval of all recommendations contained herein concerning infiltration facility design will be determined by Loudoun County. The test procedures utilized and the results of testing herein submitted will be reviewed as part of that approval process. While we do not anticipate additional requests for field testing, the County always reserves the right to clarify any questions which might impact the proper function of the facility. Pavements For the design and construction of any pavements, we recommend that any soft or unsuitable materials be removed from the proposed paved areas. Approximately 2.5± feet of existing fill material was encountered within the proposed paved area during our explorations. Based on the boring data, it appears that the existing fill material may have been placed with some compactive effort and may be suitable for support of pavements. The stripped surface should be proofrolled and carefully observed at the time of construction in order to aid in identifying localized soft and unsuitable materials which should be removed. Due to the potential variability in the strength characteristics of existing fill and natural soils, localized areas requiring additional undercutting and/or alternate stabilization methods should be anticipated during initial subgrade preparation, particularly in areas with existing fill material. In areas where new engineered fill is required to establish the final pavement subgrade elevations, new fill should be placed and compacted in accordance with the Fill Placement section of this report. High plasticity soils were not encountered within the borings performed and are not expected to be a significant consideration on this project. If encountered at the proposed pavement subgrade elevation, highly plastic soils should be undercut to a depth of 2 feet below subgrade or to the depth of the highly plastic soils, whichever is less, and replaced with a non-expansive, engineered fill as outlined above.


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An important consideration in the design and construction of pavements is surface and subsurface drainage. Where standing water develops, either on the pavement surface or within the base course layer, softening of the subgrade and other problems related to the deterioration of the pavement can be expected. Furthermore, good drainage should reduce the possibility of the subgrade materials becoming saturated over a long period of time. We would be pleased to be of further assistance to you in the design of the project pavements by providing additional recommendations during construction of the project. For preliminary design purposes, we recommend using a design California Bearing Ratio (CBR) value of 6 and a Resiliency Factor (RF) of 1.0 for the native soil material. We suggest that, at the time of construction, additional laboratory testing, i.e. Atterberg limit and CBR tests be performed in the proposed pavement areas on representative subgrade materials to permit proper design of these pavements. CBR values in excess of 10 can theoretically be obtained on many of the weathered rock materials encountered at the site. However, the CBR values are influenced by the presence of hard rock particles in the test sample, which can eventually break down with time, thereby giving CBR values that are not representative of the long term soil conditions. The CBR values that we recommend are based on expectations of long-term performance of the material. We recommend that once areas proposed for pavements are roughly placed within 12 inches of final pavement soil subgrade elevation, CBR samples be taken in order to confirm the aforementioned laboratory results. In order to facilitate final test results and submission of an adequate pavement design, we recommend that the samples be taken at locations specified by the active project civil engineer or the GER. Any roadways constructed for public use, to be dedicated to the State for repair and maintenance must be designed in accordance with the State requirements. We would be pleased to provide such pavement designs as an additional service, if provided with traffic frequency information. Depending upon the time in which the temporary construction is used as a service road, some failures should be expected. If the construction pavement system fails, it will be necessary to remove this failed section and replace it with the initial design section or an equivalent repaired section. Large, front loading trash dumpsters frequently impose concentrated front-wheel loads on pavements during loading. In a similar manner, truck loading docks can also experience very high turning wheel loads. This type of loading typically results in rutting of the pavement and ultimately pavement failures. Therefore, we recommend that the pavement in trash pickup areas consist of a 6-inch thick, mesh reinforced concrete slab with a minimum unconfined compressive strength of 4,000 psi. Utility Installation Each of the borings generally encountered natural residual soils, weathered rock and rock which are firm and are expected to be suitable for support of the utility pipes. Where rock is encountered at the subgrade, the rock should be removed to at least 6-inches below and 8-


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inches outside the pipe. All loose or organic materials encountered at the utility pipe subgrade should be removed. The pipe subgrade should be observed and probed for density by the GER to evaluate the suitability of materials encountered. Any relatively isolated, thin soft or yielding areas should be undercut or replaced with suitable compacted fill or pipe bedding material. It is recommended that fill placed for support of the utilities meet the requirements for compacted backfill given in this report. The utility pipes should be provided with granular bedding material. The granular bedding material should consist of at least 6-inches of coarse, open-graded gravel or crushed stone. Compacted backfill should be free of topsoil, root, ice or any other material designated by the GER as unsuitable. The backfill should be placed in shallow horizontal layers of maximum 8 inch loose thickness and compacted with necessary type of compaction equipment to obtain at least 95% and 90% of the maximum dry density per ASTM D 698 or VTM-1 in paved and nonpaved (landscaped) areas, respectively. In areas within a VDOT right-of-way an increased compaction density of 100% of the maximum dry density will apply for the upper 6 inches of the pavement subgrade. All backfill should be placed and compacted at a moisture content to facilitate adequate compaction without significant yielding of the surface, and should generally be within 2 percentage points of the optimum moisture content per standard Proctor tests. The backfill below buildings and pavements should consist of materials meeting the requirements for compacted fill given in this report. The backfill in unpaved areas can consist of the material removed from the trench excavation. The on-site fine-grained soils, as well as some of the coarse-grained soils or weathered rock materials are generally considered suitable for reuse as backfill; however, the moisture content of these soils may be excessively high to obtain adequate compaction, and drying of these materials may be necessary. Where significant pumping or yielding of the surface observed during compaction, the materials should either be removed or scarified and allowed to dry to a moisture content that will permit adequate compaction. In many cases the underlying soils may be dry of optimum moisture and thus, will require wetting in order to achieve good compaction. Temporary and Permanent Slopes Temporary fill slopes constructed of on site native silty or clayey soils should be limited to a maximum gradient of approximately 2H:1V. The temporary slopes should also be thoroughly vegetated to help reduce erosion of the surficial soils. Temporary excavation slopes cut in the native silty or clayey soils should be no steeper than 1H:1V and no steeper than 1.5H:IV, or as indicated by OSHA and VOSHA protocol. Permanent slopes constructed of native soils should generally be 3H:1V or flatter. Slopes steeper than 3H:1V should be designed by the GER. Gradients as steep as 2H:1V may be achieved through the use of select aggregate or engineered rock fills, as well as through the installation of geosynthetics in native soils, but again, must be designed by the GER. Small landscape berms (4 feet in height or less) may be as steep as 1H:1V but should be compacted as structural fill and thoroughly vegetated immediately upon completion. General Construction Considerations The seasonal groundwater conditions at this site may be highly variable and may depend on precipitation, the effects of grading operations, levels in the adjacent streams, and rock fracture patterns. Groundwater conditions at this site are strongly influenced by surface water flow and


-24-

infiltration. Specifically, water that enters the site migrates downward to the interface of the soil and rock. Once the water reaches the relatively impermeable rock, the water perches and travels laterally, often over large distances. Depending on the season, such perched groundwater conditions may be encountered during construction operations. Also, the degree of fracturing within the rock materials can be increased and altered significantly by blasting operations. Therefore, it is common to have "springs" develop in areas which were previously dry once initial grading operations have commenced. The use of sump pits or trenching may be necessary to control any seasonal groundwater encountered. During the field exploration, approximately 2.5± feet of existing fill material was encountered. Existing undocumented fill material should be considered unsuitable for support of structures and be completely removed from the building area unless documentation of previous site activity indicating proper placement and compaction of fill materials can be provided. The removed material may be suitable for reuse in other locations on-site, but should be evaluated further at the time of construction. Based on the boring data, it appears that the existing fill material may have been placed with some compactive effort and may be suitable for support of pavements. Pavement areas should be thoroughly evaluated with proofrolling at the time of construction to identify areas of existing fill that may be unsuitable. Any unsuitable areas identified should be undercut and replaced with suitable fill material compacted as described in this report or otherwise remediated as directed by the GER. Any existing utilities that are not planned to be reused should be removed, along with any unsuitable backfill materials, and capped at the property lines, or rerouted around the property and reconnected. The suitability of any existing utilities and utility trench backfill that will remain in place should be evaluated for structural support in the field by the GER. Care should be exercised during site grading operations so as not to damage any utilities that are to remain. Major soils related difficulties during construction of this project are not anticipated, provided that some precautionary measures are taken to document that preparation of the subgrade and footing bearing surfaces are accomplished by the recommended procedures. These precautions are necessary, as the materials observed in our borings are moisture and disturbance sensitive, and will become weakened if water intrudes into the footing excavations. Prior to the placement of footing concrete, the footings should be cleaned and free of standing water, mud, or other deleterious materials that may affect the performance of the footings. Furthermore, the GER should carefully observe and test all footing subgrades to determine that they are representative of the soil types identified in our soil borings. Exposure to the environment may weaken the soils at the footing bearing level if the foundation excavations remain open for too long a time. We recommend that the building excavations be excavated to approximately one foot above the design finish floor elevation. The remaining one foot grading and footing excavation can then be made the same day the concrete placement is scheduled. 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, we recommend that a 1 to 3-inch thick "mud-mat" of "lean" concrete be placed on the bearing soils before the placement of reinforcing steel. Proper compaction of controlled fill is an important aspect of this project. Therefore, we recommend that all fill operations be observed on a full-time basis by a qualified soil technician to determine if minimum compaction requirements are being met.


-25-

The surficial soils contain fines that are considered moderately to highly erodible. The Contractor should provide and maintain good site drainage during earthwork operations to help maintain the integrity of the surficial soils. All erosion and sedimentation shall be controlled in accordance with sound engineering practice and current County requirements. In a dry and undisturbed state, the majority of the soil at the site will provide good subgrade support for fill placement and construction operations. However, when wet, this soil will degrade quickly with disturbance from contractor operations. Therefore, good site drainage should be maintained during earthwork operations which would help maintain the integrity of the soil. Closing This report has been prepared in order to aid in the evaluation of this project. The analysis and recommendations submitted in this report are based upon the data obtained from the soil borings and tests performed at the locations as indicated on the Boring Location Diagram and other information referenced in this report. This report does not reflect any variations that may occur between the test locations. In the performance of the subsurface exploration, specific information is obtained at specific locations at specific times. However, it is a well known fact that variations in soil and rock conditions exist on most sites between boring locations and also such situations as groundwater levels vary from time to time. The nature and extent of variations may not become evident until the course of construction. If variations then appear evident, it will become necessary for a reevaluation of the recommendations for this report after performing onsite observations during the construction period and noting the characteristics and variations. This report was prepared for the sole use of Mr. Thomas Burson, and his consultants, the only intended beneficiaries of our work. The scope is limited to this specific project and locations described herein and our description of the project represents our understanding of the significant aspects relative to it. In the event of any change in the nature or location of the proposed construction outlined in this report or the accompanying plans and specifications, we should be informed so that the changes can be reviewed and the conclusions of this report modified or approved in writing by the design engineer. No other party should rely on the information contained herein without prior written consent of ECS Mid-Atlantic, LLC.

APPENDIX

Unified Soil Classification System Reference Notes for Boring Logs Boring Logs B-1 through B-2 and I-1 through I-2 (December 2013) Laboratory Testing Summary Liquid and Plastic Limits Test Report Particle Size Distribution Report

Infiltration Test Data (2 Sheets) Typical Foundation Detail Lateral Earth Pressure Diagram Zone of Influence Diagram French Drain Installation Procedure Boring Location Diagram (Sheet 1 of 3) Geology Mapping Diagram (Sheet 2 of 3) Soils Mapping Diagram (Sheet 3 of 3)

0

1.5

3

4.5

6

7.5

9

301.5

300

298.5

297

295.5

294

S-1

S-2

S-3

SS

SS

SS

18

5

0

15

5

0

Topsoil Depth [9"]

CLAY, With Sand, Brown, Moist, Very Soft (CL)

Weathered SILTSTONE, Purplish to ReddishBrown, Moist, Extremely Dense

SPOON REFUSAL @ 5.00'

WOHWOHWOH

50/5

50/0

0 342228.3

50/5

50/0

CLIENT

Mr. Thomas G. Burson

JOB #

22399

BORING #

B-1

SHEET

PROJECT NAME

Weller's Corner

ARCHITECT-ENGINEER

KDL GroupSITE LOCATION

20711 Ashburn Rd, Ashburn, Loudoun County, VANORTHING EASTING STATION

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

WL DRY WS WD BORING STARTED 01/02/14

WL(BCR) DRY WL(ACR) DRY BORING COMPLETED 01/02/14 CAVE IN DEPTH

WL 2.00 RIG CME 75 FOREMAN J. Leatherman DRILLING METHOD 3.25 HSA

DE

PT

H (

FT

)

SA

MP

LE

NO

.

SA

MP

LE

TY

PE

SA

MP

LE

DIS

T.

(IN

)

RE

CO

VE

RY

(IN

)

SURFACE ELEVATION

DESCRIPTION OF MATERIAL

WA

TE

R L

EV

ELS

ELE

VA

TIO

N (

FT

)

BLO

WS

/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

PLASTICLIMIT %

WATERCONTENT %

LIQUIDLIMIT %

ROCK QUALITY DESIGNATION & RECOVERY

RQD% REC.%

STANDARD PENETRATIONBLOWS/FT302

1 OF 1

0

1.5

3

4.5

6

7.5

9

301.5

300

298.5

297

295.5

294

S-1

S-2

S-3

S-4

SS

SS

SS

SS

18

18

6

0

12

14

6

0

Gravel Depth [7"]

CLAY, With Sand, Brown, Moist, Very Stiff (CL-FILL)

Sandy Silty CLAY, Dark Reddish Brown, Moist,Medium Dense (CL-ML)

Weathered SILTSTONE, Reddish Brown, Moist,Extremely Dense


81113

5411

50/6

50/0

24

15 27

22

17.4

50/6

50/0

CLIENT


JOB #

22399

BORING #

B-2

SHEET

PROJECT NAME

Weller's Corner

ARCHITECT-ENGINEER





WL(BCR) DRY WL(ACR) DRY BORING COMPLETED 01/02/14 CAVE IN DEPTH @ 2.00'

WL 2.0 RIG CME 75 FOREMAN J. Leatherman DRILLING METHOD 3.25" HSA

DE

PT

H (

FT

)

SA

MP

LE

NO

.

SA

MP

LE

TY

PE

SA

MP

LE

DIS

T.

(IN

)

RE

CO

VE

RY

(IN

)

SURFACE ELEVATION


WA

TE

R L

EV

ELS

ELE

VA

TIO

N (

FT

)

BLO

WS

/6"

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS



PLASTICLIMIT %

WATERCONTENT %

LIQUIDLIMIT %


RQD% REC.%


1 OF 1

0

1.5

3

4.5

6

7.5

9

300

298.5

297

295.5

294

292.5

291

S-1

S-2

S-3

S-4

SS

SS

SS

SS

24

11

6

0

20

11

6

0

Topsoil Depth [11"]

Sandy CLAY, With Gravel, Brown to ReddishBrown, Moist, Medium Stiff (CL)



12311

3450/5

50/6

50/0

519.9

50/5

50/6

50/0

CLIENT


JOB #

22399

BORING #

I-1

SHEET

PROJECT NAME

Weller's Corner

ARCHITECT-ENGINEER







DE

PT

H (

FT

)

SA

MP

LE

NO

.

SA

MP

LE

TY

PE

SA

MP

LE

DIS

T.

(IN

)

RE

CO

VE

RY

(IN

)

SURFACE ELEVATION


WA

TE

R L

EV

ELS

ELE

VA

TIO

N (

FT

)

BLO

WS

/6"

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS



PLASTICLIMIT %

WATERCONTENT %

LIQUIDLIMIT %


RQD% REC.%


1 OF 1

0

1.5

3

4.5

6

7.5

9

297

295.5

294

292.5

291

289.5

S-1

S-2

S-3

S-4

S-5

SS

SS

SS

SS

SS

24

23

6

5

6

24

23

6

5

6

Topsoil Depth [3"]

Sandy CLAY With Silt, Reddish Brown, Moist,Medium Dense to Very Dense (CL)



67611

182534

50/5

50/6

50/5

50/6

13

59

19.9

50/6

50/5

50/6

CLIENT


JOB #

22399

BORING #

I-2

SHEET

PROJECT NAME

Weller's Corner

ARCHITECT-ENGINEER







DE

PT

H (

FT

)

SA

MP

LE

NO

.

SA

MP

LE

TY

PE

SA

MP

LE

DIS

T.

(IN

)

RE

CO

VE

RY

(IN

)

SURFACE ELEVATION


WA

TE

R L

EV

ELS

ELE

VA

TIO

N (

FT

)

BLO

WS

/6"

10 20 30 40 50+

20% 40% 60% 80% 100%

1 2 3 4 5+

ENGLISH UNITS



PLASTICLIMIT %

WATERCONTENT %

LIQUIDLIMIT %


RQD% REC.%


1 OF 1

B-1S-1 0.00 - 1.50 28.3 CL 34 22 12 84.7

B-2S-2 2.50 - 4.00 17.4 CL-ML 27 22 5 61.3

I-1S-1 0.00 - 2.00 19.9

I-2S-2 2.00 - 3.92 19.9

Laboratory Testing Summary

Notes: 1. ASTM D 2216, 2. ASTM D 2487, 3. ASTM D 4318, 4. ASTM D 1140, 5. See test reports for test method, 6. See test reports for test method

Definitions: MC: Moisture Content, Soil Type: USCS (Unified Soil Classification System), LL: Liquid Limit, PL: Plastic Limit, PI: Plasticity Index, CBR: California Bearing Ratio, OC: Organic Content (ASTM D 2974)

Project No. 22399

Project Name: Weller's Corner

PM: Ian J. Whitehead

PE: Andrew R. Shontz

Printed On: Friday, January 10, 2014

SampleSource

SampleNumber

Depth(feet)

MC1(%)

SoilType2 LL

Atterberg Limits3

PL PI

PercentPassingNo. 200Sieve4

MaximumDensity

(pcf)

Moisture - Density (Corr.)5

OptimumMoisture

(%)

CBRValue6 Other

Page 1 of 1

Tested By: HTN1 HNT1 Checked By: DVT

Lean Clay with Sand Dark Reddish Brown (CL) 34 22 12 87.4 84.7 CL

Sandy Silty Clay Dark Reddish Brown (CL-ML) 27 22 5 69.5 61.3 CL-ML

22399 Mr. Thomas G. Burson

MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS

Project No. Client: Remarks:Project:

Figure

Source of Sample: B-1 Depth: 0.00-1.50 Sample Number: S-1Source of Sample: B-2 Depth: 2.50-4.00 Sample Number: S-2

PL

AS

TIC

ITY

IN

DE

X

0

10

20

30

40

50

60

LIQUID LIMIT0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

CL or OL

CH or OH

ML or OL MH or OH

Dashed line indicates the approximateupper limit boundary for natural soils

4

7

LIQUID AND PLASTIC LIMITS TEST REPORT

Data Entered: 1/10/14Data Entered: 1/10/14

Weller's Corner

Tested By: DNN Checked By: DVT

Lean Clay with Sand Dark Reddish Brown (CL)

Sandy Silty Clay Dark Reddish Brown (CL-ML)

Data Entered: 1/10/14

Data Entered: 1/10/14

inches numbersize size

0.0 0.0 15.3 84.7 CL 34 22 120.0 6.8 31.9 61.3 CL-ML 27 22 5

.75.375

100.099.4

#4#10#40#60#80

#100#200

100.094.687.486.485.885.684.7

93.279.369.567.466.065.361.3

Source of Sample: B-1 Depth: 0.00-1.50 Sample Number: S-1Source of Sample: B-2 Depth: 2.50-4.00 Sample Number: S-2

Mr. Thomas G. Burson Weller's Corner

22399

PL PI+3" % GRAVEL % SAND % SILT % CLAY USCS LL

SIEVE PERCENT FINER SIEVE PERCENT FINER Material Description

GRAIN SIZE REMARKS:

D60

D30

D10

COEFFICIENTS

Cc

Cu

Client:

Project:

Project No.: Figure

PE

RC

EN

T F

INE

R

0

10

20

30

40

50

60

70

80

90

100

PE

RC

EN

T C

OA

RS

ER

100

90

80

70

60

50

40

30

20

10

0

GRAIN SIZE - mm.

0.0010.010.1110100

6 in

.

3 in

.

2 in

.

1½

in.

1 in

.

¾ in

.

½ in

.

3/8

in.

#4

#10

#20

#30

#40

#60

#100

#140

#200

Particle Size Distribution Report

Job No: 22399 Job Name: Weller's Corner Date: 01/03/14

Boring No: I-1Reference Depths for Test (In):

Perc Hole Depth (in.): 24.0 12" = 12.0 24"= 0.00

Test Intervals/Duration (Hrs.) 0.00 1.00 2.00 3.00 4.00Duration 0:00 1:00 2:00 3:00 4:00Actual Test Time (Start/Finish) 13:00 14:00 15:00 16:00 17:00Measured Depth to water (in.) 18.48 5.52 4.68 5.16 4.92Measured Depth. Added -4.08 -5.28 -3.84 -4.44Head (in.) 28.1 29.3 27.8 28.4 Fall (in.) 9.6 10.0 9.0 9.4

Calculated Infiltration Rate (in./hr.):Avg. Fall Over 4 hours: 9.48

Recommended Rate-1/2 Avg. Fall: 4.7Comments:



Test Intervals/Duration (Hrs.) 0.00 1.00 2.00 3.00 4.00Duration 0:00 1:00 2:00 3:00 4:00Actual Test Time (Start/Finish) 12:00 13:00 14:00 15:00 16:00Measured Depth to water (in.) 14.00 3.50 2.50 3.00 3.00Measured Depth. Added or initia -2.50 -4.50 -4.50 -4.75Head (in.) 26.5 28.5 28.5 28.8 Fall (in.) 6.0 7.0 7.5 7.8



INFILTRATION TEST RECORD/CALCULATION SHEET

Job No: 22399 Job Name: Weller's Corner Date: 01/03/14



Test Intervals/Duration (Hrs.) 1.00 2.00 3.00 4.00Actual Test Time (Start/Finish) 13:00 14:00 15:00 16:00Start Depth -4.08 -5.28 -3.84 -4.44End Depth 5.52 4.68 5.16 4.92Initial Head 28.1 29.3 27.8 28.4Fall after 1hr 9.6 10.0 9.0 9.4





Test Intervals/Duration (Hrs.) 0.00 1.00 2.00 3.00 4.00Duration 0:00 1:00 2:00 3:00 4:00Actual Test Time (Start/Finish) 12:00 13:00 14:00 15:00 16:00Measured Depth to water (in.) 14.00 3.50 2.50 3.00 3.00Measured Depth. Added or initial (i -2.50 -4.50 -4.50 -4.75Head (in.) 26.5 28.5 28.5 28.8 #VALUE!Fall (in.) 6.0 7.0 7.5 7.8



INFILTRATION TEST RECORD/CALCULATION SHEET

TYPICAL FOUNDATION DETAIL

CONTINUOUS FOOOTING

q = 3,000 psf B (footing width) =18 inch minimum

Q

(wall load)

Wall Length

Df = 24 inches (min)

Finish Grade

COLUMN FOOOTING

q = 3,000 psf

Finish Grade

B (footing width) =2 feet minimum

Df= 24 inches (min)

Q(column load)

B

i:\geotechnical\{eprojects}\[standard forms]\report diagrams\typical_foundation.doc

LATERAL EARTH PRESSURE DIAGRAM - DRAINED

H (feet)

Surcharge Load (psf)

Lateral Earth Pressure = 60 H psf (For below grade walls restrained from movement at top and bottom, drained conditions presumed)

Horizontal Pressure from Surcharge = 0.5 x Vertical Surcharge

This diagram is not suitable for the design of

Support of Excavation or temporary shoring

systems.

SUBSOIL

FINAL CONFIGURATION STEP 1

STEP 2 STEP 3

FRENCH DRAIN

INSTALLATION PROCEDURE

VDOT #57

AGGREGATE

AMOCO 4551

GEOTEXTILE

FABRIC

SUBDRAIN USING FILTER FABRIC FABRIC IS UNROLLED DIRECTLY OVER TRENCH

THE TRENCH IS FILLED WITH AGGREGATE THE FABRIC IS LAPPED CLOSED AND

COVERED WITH BASE STONE

NOT TO SCALE

CO

NC

CA

P

EX

. TE

LE P

ED

7" MA

PLE

10" MA

PLE

36" WA

LNU

T

20" 2X M

ULB

ER

RYGU

Y

PO

LE

PO

LE

PO

LEP

OLE

S 04°44'16" W14.52'

C1

ASHBURN ROAD

EX

. RE

T WA

LL

EX.RET WALL

EX. GRAVELDRIVEWAY

DRIVEWAY

I.P.F

.

I.P.F

.

NA

ILF

ND

EX

. CO

NC

WA

LK

EX. GRAVELDRIVEWAY

GAS

AC

C/O

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

I.R.F.

EX

.T

ELE

PE

D

N/F

HU

RD

LE

RE

NT

AL

EN

TE

RP

RIS

E,

LLC

PIN

085-1

6-5792-000

Acreage: 0.37

Use

: CO

MM

ER

CIA

LZ

onin

g: RC

N/F

GU

YT

ON

, NIC

HO

LAS

& G

RE

TT

AP

IN 0

85-16-22

95-000A

creage: 0.47U

se: SIN

GL

E-F

AM

ILYZ

onin

g: CR

-2

EX

. EP

EX

. EP

EX. EP

EX

. EP

EX

. EP

EX

. STM

GR

ATE

TO

P=293.73

308

306

304

302

300

298

296

294

302

298

296

N 70°07'40" W

~ 280.44'

308

306

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

ASHBURN ROAD

XX

XX

XX

X

OEOE

OEOE

OEOE

OEOE

OEOE

OEOE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OEOE

OEOE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE

15" MULBERRY15" MULBERRY15" MULBERRY

12" CHERRY

15" ASH24" MAPLE

24" MULBERRY

24" MAPLE

24" MULBERRY

24" MULBERRY

24" ASH

30" MAPLE

60" MAPLE

20" WALNUT

40" ASH

20" WALNUT

SAN MHTOP=306.21

INV OUT=297.11

SAN MHTOP=307.41

INV IN=295.41

N/F

CH

UG

HT

AI, M

OS

SA

DA

Q F

AR

HA

NP

IN 0

85-16-36

75-000A

creage: 0.75U

se: C

OM

ME

RC

IAL

Zon

ing: R

-C

22'

12

7

7

9

3

22'

22'

18'

CG

-2

EP

EP

CG

-2

CG-2

EP

40'

40'

EX. EP

EX. EP

(TO REMAIN)

(TO REMAIN)

(TO REMAIN)

ele

c room

sp

rinkle

r equip

lan

dlord

storage

SE

WE

R C

ON

NE

CT

ION

WA

TE

R C

ON

NE

CT

ION

SP

RIN

KL

ER

CO

NN

ECT

ION

ELE

C ME

TE

RS

/ SER

VIC

E

ho

use

panel

tele

. / ca

bel / internet

water m

anifold / m

eters

/

ac

ces

sibles

torag

e shed

ff = 304.7

ba

sem

en

t ff = 295.72

DN

UP

softner / s

ump / etc.

ff = 304.7

43'

43'

CG

-2

CG

-2EP

CG-22 Q

R-1

1 QR

-1

3 QR

-1

B-1

B-2

I-1

I-2

N 5

03

00

0

E 2287500

N 5

03

00

0

E 2287250

N 5

02

75

0

E 2287500

N 5

02

75

0

E 2287250

SC

ALE

PR

OJ

EC

T N

O.

SH

EE

T

DA

TE

EN

GIN

EE

RD

RA

FT

IN

G

EC

S R

EV

IS

IO

NS

BORING LOCATION

DIAGRAM

MR. THOMAS BURSON

WELLER'S

CORNER

LOUDOUN COUNTY, VA

22

39

9

IJ

WRAC

1"=4

0'

1 O

F 3

01-07-14

03-21-14

TO

PO

GR

APH

IC

RE

FE

RE

NC

E:

DIA

GR

AM

S W

ER

E D

EV

EL

OPE

D F

RO

M T

HE

SI

TE

PLA

N P

RO

VID

ED

BY

TH

E K

DL G

RO

UP, T

HE

PR

OJ

EC

T C

IV

IL

EN

GIN

EE

R.

TH

ES

E E

LE

VA

TI

ON

S A

RE

RE

PO

RT

ED

BY

TH

E K

DL G

RO

UP A

T

A C

ON

TO

UR

IN

TE

RV

AL O

F 2

FT

.

*F

OR

IN

FO

RM

AT

IO

NA

L P

UR

PO

SE

S O

NL

Y*

SE

E A

PPR

OV

ED

SI

TE

PLA

N F

OR

SPE

CIF

IC

GR

AD

IN

G I

NF

OR

MA

TIO

N0

SC

ALE

(IN

FE

ET

)

20

40

40

VICIN

IT

Y M

AP

APPR

OX

. SC

ALE

: 1"=2

00

0'

CO

PY

RIG

HT

AD

C -

TH

E M

AP P

EO

PLE -

PERM

IT

TED

US

E N

UM

BER 2

0904131

SIT

E

LE

GEN

D

APPRO

X. B

OR

IN

G L

OC

AT

IO

N

EX

IS

TIN

G G

RA

DES

PR

OPO

SE

D G

RA

DES

GR

ID

CO

OR

DIN

AT

E S

YS

TEM

ACCO

RD

IN

G T

O L

OU

DO

UN

CO

UN

TY

SO

IL M

APPIN

G, T

HE

SIT

E I

S M

APPE

D A

S H

AV

IN

G C

LA

SS

IV

SO

ILS

.

I:\Geotechnical\{eProjects}\22300-22399\01-22399\b-Drafting\22399_BLD.dwg, 3/27/2014 1:57:35 PM, ECS Mid-Atlantic, LLC Chantilly, VA

CO

NC

CA

P

EX

. TE

LE P

ED

7" MA

PLE

10" MA

PLE

36" WA

LNU

T

20" 2X M

ULB

ER

RYGU

Y

PO

LE

PO

LE

PO

LEP

OLE

S 04°44'16" W14.52'

C1

ASHBURN ROAD

EX

. RE

T WA

LL

EX.RET WALL

EX. GRAVELDRIVEWAY

DRIVEWAY

I.P.F

.

I.P.F

.

NA

ILF

ND

EX

. CO

NC

WA

LK

EX. GRAVELDRIVEWAY

GAS

AC

C/O

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

I.R.F.

EX

.T

ELE

PE

D

N/F

HU

RD

LE

RE

NT

AL

EN

TE

RP

RIS

E,

LLC

PIN

085-1

6-5792-000

Acreage: 0.37

Use

: CO

MM

ER

CIA

LZ

onin

g: RC

N/F

GU

YT

ON

, NIC

HO

LAS

& G

RE

TT

AP

IN 0

85-16-22

95-000A

creage: 0.47U

se: SIN

GL

E-F

AM

ILYZ

onin

g: CR

-2

EX

. EP

EX

. EP

EX. EP

EX

. EP

EX

. EP

EX

. STM

GR

ATE

TO

P=293.73

308

306

304

302

300

298

296

294

302

298

296

N 70°07'40" W

~ 280.44'

308

306

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

ASHBURN ROAD

XX

XX

XX

X

OEOE

OEOE

OEOE

OEOE

OEOE

OEOE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OEOE



12" CHERRY

15" ASH24" MAPLE

24" MULBERRY

24" MAPLE

24" MULBERRY

24" MULBERRY

24" ASH

30" MAPLE

60" MAPLE

20" WALNUT

40" ASH

20" WALNUT

SAN MHTOP=306.21

INV OUT=297.11

SAN MHTOP=307.41

INV IN=295.41

N/F

CH

UG

HT

AI, M

OS

SA

DA

Q F

AR

HA

NP

IN 0

85-16-36

75-000A

creage: 0.75U

se: C

OM

ME

RC

IAL

Zon

ing: R

-C

22'

12

7

7

9

3

22'

22'

18'

CG

-2

EP

EP

CG

-2

CG-2

EP

40'

40'

EX. EP

EX. EP

(TO REMAIN)

(TO REMAIN)

(TO REMAIN)

ele

c room

sp

rinkle

r equip

lan

dlord

storage

SE

WE

R C

ON

NE

CT

ION

WA

TE

R C

ON

NE

CT

ION

SP

RIN

KL

ER

CO

NN

ECT

ION

ELE

C ME

TE

RS

/ SER

VIC

E

ho

use

panel

tele

. / ca

bel / internet

water m

anifold / m

eters

/

ac

ces

sibles

torag

e shed

ff = 304.7

ba

sem

en

t ff = 295.72

DN

UP

softner / s

ump / etc.

ff = 304.7

43'

43'

CG

-2

CG

-2EP

CG-22 Q

R-1

1 QR

-1

3 QR

-1

B-1

B-2

I-1

I-2

Trbs

N 5

03

00

0

E 2287500

N 5

03

00

0

E 2287250

N 5

02

75

0

E 2287500

N 5

02

75

0

E 2287250

SCALE

PROJECT NO.

SHEET

DATE

ENGINEER

DRAFTING

ECS REVISIONS

GEOLOGY MAPPING

DIAGRAM

MR. THOMAS BURSON

WELLER'S

CORNER

LOUDOUN COUNTY, VA

22

39

9

IJ

WRAC

1"=4

0'

2 O

F 3

01-07-14

03-21-14

TOPOGRAPHIC REFERENCE:

DIAGRAMS W

ERE DEVELOPED FROM THE SITE PLAN PROVIDED

BY THE KDL GROUP, T

HE PROJECT CIVIL ENGINEER.

THESE ELEVATIONS ARE REPORTED BY THE KDL GROUP AT

A CONTOUR INTERVAL OF 2FT.

*FOR INFORMATIONAL PURPOSES ONLY*

SEE APPROVED SITE PLAN FOR SPECIFIC GRADING INFORMATION

0

SC

ALE

(IN

FE

ET

)

20

40

40

VICIN

IT

Y M

AP

APPR

OX

. SC

ALE

: 1"=2

00

0'

CO

PY

RIG

HT

AD

C -

TH

E M

AP P

EO

PLE -

PERM

IT

TED

US

E N

UM

BER 2

0904131

SIT

E

GEO

LO

GY

MA

PPIN

G

BA

LLS

BLU

FF S

ILT

ST

ON

ET

rbs

NO

SO

IL P

OIN

TS

MA

PPED

WIT

HIN

DE

VE

LO

PM

EN

T L

IM

IT

S.

GEOLOGIC MAP OF LOUDOUN COUNTY, V

IRGINIA, U

SGS OF-99-15

0, S

COTT SOUTHWORTH, W

.C.

BURTON, J

.S. S

CHINDLER, A

ND A.J. FROELICH W

ITH CONTRIBUTIONS ON THE GEOLOGY OF THE

PIEDMONT PROVINCE BY A.A. D

RAKE, J

R., A

ND R.E. W

EEMS AND AN AEROMAGNETIC SURVEY BY D.L.

DANIELS, W

.F. H

ANNA, A

ND R.E. BRACKEN.

LE

GEN

D

APPRO

X. B

OR

IN

G L

OC

AT

IO

N

EX

IS

TIN

G G

RA

DES

PR

OPO

SE

D G

RA

DES

GR

ID

CO

OR

DIN

AT

E S

YS

TEM

ACCO

RD

IN

G T

O L

OU

DO

UN

CO

UN

TY

SO

IL M

APPIN

G, T

HE

SIT

E I

S M

APPE

D A

S H

AV

IN

G C

LA

SS

IV

SO

ILS

.


CO

NC

CA

P

EX

. TE

LE P

ED

7" MA

PLE

10" MA

PLE

36" WA

LNU

T

20" 2X M

ULB

ER

RYGU

Y

PO

LE

PO

LE

PO

LEP

OLE

S 04°44'16" W14.52'

C1

ASHBURN ROAD

EX

. RE

T WA

LL

EX.RET WALL

EX. GRAVELDRIVEWAY

DRIVEWAY

I.P.F

.

I.P.F

.

NA

ILF

ND

EX

. CO

NC

WA

LK

EX. GRAVELDRIVEWAY

GAS

AC

C/O

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

I.R.F.

EX

.T

ELE

PE

D

N/F

HU

RD

LE

RE

NT

AL

EN

TE

RP

RIS

E,

LLC

PIN

085-1

6-5792-000

Acreage: 0.37

Use

: CO

MM

ER

CIA

LZ

onin

g: RC

N/F

GU

YT

ON

, NIC

HO

LAS

& G

RE

TT

AP

IN 0

85-16-22

95-000A

creage: 0.47U

se: SIN

GL

E-F

AM

ILYZ

onin

g: CR

-2

EX

. EP

EX

. EP

EX. EP

EX

. EP

EX

. EP

EX

. STM

GR

ATE

TO

P=293.73

308

306

304

302

300

298

296

294

302

298

296

N 70°07'40" W

~ 280.44'

308

306

(30' PR

ES

CR

IPTIV

E E

AS

EM

EN

T)

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

ASHBURN ROAD

XX

XX

XX

X

OEOE

OEOE

OEOE

OEOE

OEOE

OEOE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OE

OEOE



12" CHERRY

15" ASH24" MAPLE

24" MULBERRY

24" MAPLE

24" MULBERRY

24" MULBERRY

24" ASH

30" MAPLE

60" MAPLE

20" WALNUT

40" ASH

20" WALNUT

SAN MHTOP=306.21

INV OUT=297.11

SAN MHTOP=307.41

INV IN=295.41

N/F

CH

UG

HT

AI, M

OS

SA

DA

Q F

AR

HA

NP

IN 0

85-16-36

75-000A

creage: 0.75U

se: C

OM

ME

RC

IAL

Zon

ing: R

-C

22'

12

7

7

9

3

22'

22'

18'

CG

-2

EP

EP

CG

-2

CG-2

EP

40'

40'

EX. EP

EX. EP

(TO REMAIN)

(TO REMAIN)

(TO REMAIN)

ele

c room

sp

rinkle

r equip

lan

dlord

storage

SE

WE

R C

ON

NE

CT

ION

WA

TE

R C

ON

NE

CT

ION

SP

RIN

KL

ER

CO

NN

ECT

ION

ELE

C ME

TE

RS

/ SER

VIC

E

ho

use

panel

tele

. / ca

bel / internet

water m

anifold / m

eters

/

ac

ces

sibles

torag

e shed

ff = 304.7

ba

sem

en

t ff = 295.72

DN

UP

softner / s

ump / etc.

ff = 304.7

43'

43'

CG

-2

CG

-2EP

CG-22 Q

R-1

1 QR

-1

3 QR

-1

B-1

B-2

I-1

I-2

N 5

03

00

0

E 2287500

N 5

03

00

0

E 2287250

N 5

02

75

0

E 2287500

N 5

02

75

0

E 2287250

73B

67B

74B

SC

ALE

PR

OJ

EC

T N

O.

SH

EE

T

DA

TE

EN

GIN

EE

RD

RA

FT

IN

G

EC

S R

EV

IS

IO

NS

SOILS MAPPING

DIAGRAM

MR. THOMAS BURSON

WELLER'S

CORNER

LOUDOUN COUNTY, VA

22

39

9

IJ

WRAC

1"=4

0'

3 O

F 3

01-07-14

03-21-14

TO

PO

GR

APH

IC

RE

FE

RE

NC

E:

DIA

GR

AM

S W

ER

E D

EV

EL

OPE

D F

RO

M T

HE

SI

TE

PLA

N P

RO

VID

ED

BY

TH

E K

DL G

RO

UP, T

HE

PR

OJ

EC

T C

IV

IL

EN

GIN

EE

R.

TH

ES

E E

LE

VA

TI

ON

S A

RE

RE

PO

RT

ED

BY

TH

E K

DL G

RO

UP A

T

A C

ON

TO

UR

IN

TE

RV

AL O

F 2

FT

.

*F

OR

IN

FO

RM

AT

IO

NA

L P

UR

PO

SE

S O

NL

Y*

SE

E A

PPR

OV

ED

SI

TE

PLA

N F

OR

SPE

CIF

IC

GR

AD

IN

G I

NF

OR

MA

TIO

N0

SC

ALE

(IN

FE

ET

)

20

40

40

VICIN

IT

Y M

AP

APPR

OX

. SC

ALE

: 1"=2

00

0'

CO

PY

RIG

HT

AD

C -

TH

E M

AP P

EO

PLE -

PERM

IT

TED

US

E N

UM

BER 2

0904131

SIT

E

SO

ILS

MA

PPIN

G

AS

HBU

RN

SILT

LO

AM

(CLA

SS

II)

HA

YM

ARKET

AN

D J

ACKLA

ND

SO

ILS

(CLA

SS

IV)

PEN

N S

ILT

LO

AM

(CLA

SS

I)

74B

67B

73B

LE

GEN

D

APPRO

X. B

OR

IN

G L

OC

AT

IO

N

EX

IS

TIN

G G

RA

DES

PR

OPO

SE

D G

RA

DES

GR

ID

CO

OR

DIN

AT

E S

YS

TEM

ACCO

RD

IN

G T

O L

OU

DO

UN

CO

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TY

SO

IL M

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SIT

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IN

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LA

SS

IV

SO

ILS

.


ECS Project No. 01:22399 - Soils Report.pdfECS and the site layout plan provided to us by The KDL...

Documents

Transcript of ECS Project No. 01:22399 - Soils Report.pdfECS and the site layout plan provided to us by The KDL...