Report of Geotechnical Study

Transcription

1 Report of Geotechnical Study Leakes Mill Park Phase 2 Goochland County, Virginia F&R Project No. 60S-0585 Prepared For: Dewberry 4085 Lake Brook Drive, Suite 200 Richmond, Virginia Prepared By: Froehling & Robertson, Inc Dumbarton Road Richmond, Virginia March 11, 2015 Corporate HQ: 3015 Dumbarton Road Richmond, Virginia T F VIRGINIA NORTH CAROLINA SOUTH CAROLINA MARYLAND DISTRICT OF COLUMBIA A Minority-Owned Business

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3 SECTION TABLE OF CONTENTS 1.0 PURPOSE & SCOPE OF SERVICES PROJECT INFORMATION SITE DESCRIPTION PROPOSED CONSTRUCTION EXPLORATION PROCEDURES SUBSURFACE EXPLORATION LABORATORY TESTING REGIONAL GEOLOGY & SUBSURFACE CONDITIONS REGIONAL GEOLOGY SUBSURFACE CONDITIONS General Surficial Soils Possible Fill Residual Soils SUBSURFACE WATER LABORATORY TEST RESULTS GEOTECHNICAL DESIGN RECOMMENDATIONS GENERAL PAVEMENT DESIGN RECOMMENDATIONS GEOTECHNICAL CONSTRUCTION RECOMMENDATIONS SITE PREPARATION SURFACE WATER/GROUNDWATER CONTROL STRUCTURAL FILL PLACEMENT AND COMPACTION TEMPORARY EXCAVATION RECOMMENDATIONS CONTINUATION OF SERVICES LIMITATIONS PAGE Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - i -

4 APPENDICES APPENDIX I Site Vicinity Map (Drawing No. 1) Boring Location Plan (Drawing No. 2) APPENDIX II Key to Soil Classification Unified Soil Classification Chart Boring Logs APPENDIX III Standard Proctor Test Results APPENDIX IV ASFE Document Important Information about Your Geotechnical Engineering Report Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - ii -

5 1.0 PURPOSE & SCOPE OF SERVICES The purpose of the subsurface exploration and geotechnical engineering evaluation was to explore the subsurface conditions in the area of the Leakes Mill Park Phase 2 Project, and provide geotechnical engineering design and construction recommendations that can be used during the design and construction of the proposed soccer field and parking lot. F&R s scope of services included the following: Completion of nine soil test borings, to a depth of 10 feet below the existing ground surface; Preparation of typed Boring Logs; Perform select laboratory testing to assist with geotechnical evaluation and construction. Performing a geotechnical engineering evaluation of the subsurface conditions with regard to their suitability for the proposed construction; Preparation of this geotechnical report by professional engineers. Our scope of services did not include a survey of the boring location, quantity estimates, preparation of plans or specifications, or the identification and evaluation of environmental aspects of the project site. 2.0 PROJECT INFORMATION 2.1 Site Description The project site is located at 3951 River Road West in Goochland County, Virginia. On site is a parking lot with two soccer fields to the west. 2.2 Proposed Construction Project information was provided in and phone correspondences with Dewberry, dated August 25, Project information included a sketch of the site showing the stock pile area and the new parking lot area. We understand the improvements will consist of the construction of a new irrigated soccer field and expanding the existing parking lot to the south. The new field will be located west of the existing two playing fields, and have an approximate footprint of 250 feet by 350 feet. Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 1 -

6 3.0 EXPLORATION PROCEDURES 3.1 Subsurface Exploration The subsurface exploration program was performed on February 16, 2015 and consisted of nine soil test borings, designated as B-1 through B-9. The borings were terminated at a depth of 10 feet below existing site grade. The boring locations were selected and staked by F&R personnel, and the approximate location of the boring is shown on the attached Boring Location Plan (Drawing No. 2, Appendix I). In consideration of the methods used in their determination, the boring locations shown on the attached Boring Location Plan should be considered approximate. The soil test boring was performed in accordance with generally accepted practice using an ATVmounted CME 55rotary drill rig equipped with an automatic hammer. Hollow-stem augers were advanced to pre-selected depths, the center plug was removed, and representative soil samples were recovered with a standard split-spoon sampler (3-1/4 in. ID, 3-1/2 in. OD) in general accordance with ASTM D 1586, the Standard Penetration Test. For these tests, a weight of 140 pounds was freely dropped from a height of 30 inches to drive the split-spoon sampler into the soil. The number of blows required to drive the split-spoon sampler four consecutive 6-inch increments was recorded, and the blows of the second and third increments were summed to obtain the Standard Penetration Resistance (N-value). The N-value provides a general indication of in-situ soil conditions and has been correlated with certain engineering properties of soils. An automatic hammer was used to perform the Standard Penetration Test (SPT) on this project. Research has shown that the Standard Penetration Resistance (N-value) determined by an automatic hammer is different than the N-value determined by the safety hammer method. Most correlations that are published in the technical literature are based on the N-value determined by the safety hammer method. This is commonly termed N 60 as the rope and cathead with a safety hammer delivers about 60 percent of the theoretical energy delivered by a 140-pound hammer freely falling 30 inches. Several researchers have proposed correction factors for the use of hammers other than the safety hammer to correct the values to be equivalent to the safety hammer SPT N 60 -values. The correction is made using the following equation: N 60 = N field x C E N field is the value recorded in the field and C E is the energy ratio for the hammer utilized in the field. The guidelines provided in the Performance and Use of the Standard Penetration Test in Geotechnical Engineering Practice manual, published by the Center for Geotechnical Practice and Research at the Virginia Polytechnic Institute and State University, recommend that a correction factor (C E ) be used to covert N field values to N 60 values, when using an automatic hammer. The N- Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 2 -

7 values reported on the Boring Logs included in this report are the actual, uncorrected, field derived values (N field ). It is recommended that corrected N 60 values be used for engineering analysis. F&R regularly calibrates our automatic hammers and for the hammer used on this project, we recommend that a correction factor (C E ) of 1.32 be used to convert N field values to N 60 values. In addition to the spilt spoon sampling described above, a bulk sample was collected from the boring. The bulk sample consisted of auger cuttings from the top ten feet of the boring. Prior to demobilization, the borehole was backfilled with auger cuttings. Periodic observation of the backfilled boring should be performed, as the boring backfill could settle over time resulting in subsidence of the ground around the borehole. Representative portions of the split-spoon soil samples obtained throughout the exploration program were placed in glass jars and transported to our laboratory. In the laboratory, the soil samples were evaluated by a member of our engineering staff, in general accordance with techniques outlined in the visual-manual identification procedure (ASTM D 2488). The soil descriptions and classifications discussed in this report and shown on the attached Boring Logs are based on visual observation and should be considered approximate. A copy of the boring logs are provided and classification procedures are further explained in Appendix II. Split-spoon soil samples recovered on this project will be stored at F&R s office for a period of 60 days. The samples will be discarded after 60 days, unless prior notification is provided to us in writing. 3.2 Laboratory Testing In addition to soils examined using the visual/manual method, the bulk sample was subjected to moisture-density relationship (Standard Proctor) testing as well as California Bearing Ratio testing. The results of the testing are summarized in Section 4.4 and is included in Appendix III of this report. 4.0 REGIONAL GEOLOGY & SUBSURFACE CONDITIONS 4.1 Regional Geology The Geologic Map of Virginia (1993) reports that the project site lies within the Central Piedmont Physiographic Province of Virginia. The Piedmont province is the largest physiographic province in Virginia. It is bounded on the east by the Coastal Plain Province and on the west by the mountains of the Blue Ridge Province. The Piedmont Province is characterized by gently rolling topography, Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 3 -

8 deeply weathered bedrock, and a relative scarcity of solid rock outcrop. Rock is strongly weathered in the Piedmont's humid climate and competent bedrock is generally buried under a thick (5-65 feet) blanket of saprolite. The saprolite is a residual soil that consists of thoroughly decomposed rock formed in place by chemical weathering of igneous or metamorphic rock in humid climates such as is found in Central Virginia. Locally, the site may be underlain by the Proterozoic-aged Porphyroblastic Garnet-Biotite Gneiss. The residual soil profile generally grades downward gradually from fine-grained plastic soils near the ground surface to coarse-grained soils at greater depth, as observed in our boring logs. 4.2 Subsurface Conditions General The subsurface conditions discussed in the following paragraphs and those shown on the attached Boring Logs represents an estimate of the subsurface conditions based on interpretation of the boring data using normally accepted geotechnical engineering judgments. The transitions between different soil strata are usually less distinct than those shown on the boring logs. Sometimes the relatively small sample obtained in the field is insufficient to definitively describe the origin of the subsurface material. In these cases, we qualify our origin descriptions with possible before the word describing the material s origin (i.e. possible residuum, etc.). Although individual soil test borings are representative of the subsurface conditions at the boring locations on the dates shown, they are not necessarily indicative of subsurface conditions at other locations or at other times. Data from the specific soil test boring is shown on the attached Boring Logs in Appendix II. The boring encountered surficial soils underlain by residual soils and soft weathered rock which extended to the boring termination depth. The soils are generally discussed in the following paragraphs Surficial Soils Surficial Soil was encountered in all of the borings to an approximate depth of 0.5 feet (6 inches). Surficial Soil is typically a dark-colored soil material containing roots, fibrous matter, and/or other organic components, and is generally unsuitable for engineering purposes. F&R has not performed any laboratory testing to determine the organic content or other horticultural properties of the observed Surficial Soil materials. Therefore, the term Surficial Soil is used instead of Topsoil to indicate that the soil has not been evaluated for its suitability for landscaping and/or other purposes. The surficial soil depth provided in this report is based on driller observations and should be considered approximate. We note that the transition from Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 4 -

9 Surficial Soil to underlying materials may be gradual, and therefore, the observation and measurement of surficial soil depths is subjective. Actual surficial soil depths should be expected to vary across the site, especially where tree roots exist Possible Fill Fill may be any material that has been transported and deposited by man. Materials described as fill were encountered from the surface at the boring, to depths ranging from 2 to 6 feet below existing grade. The sampled fill materials were generally described as Clayey SAND (SC) or Sandy Fat CLAY (CH). Standard penetration resistances (N-values) in the fill material ranged between 5 and 22 blows per foot (bpf), indicating a variable degree of compaction Residual Soils Residual soils were encountered beneath the surficial soil and extend to the boring termination depth, as noted on the attached boring logs. Sampled natural residual soils consist of Sandy Fat CLAY (CH), Silty SAND (SM), Sandy SILT (ML), and Clayey SAND (SC). The field N-values for the coarse-grained SAND range from 10 to 100+ bpf, indicating that these soils have a relative density from loose to very dense. The field N-values for the fine-grained CLAY and SILT range from 10 to 19 bpf, indicating that these soils have a consistency from stiff to very stiff. 4.3 Subsurface Water The test boring was monitored during drilling, upon completion of drilling operations and at the end of the work day to obtain short-term subsurface water information. Subsurface water was not encountered during drilling operations. It should be noted that the location of the subsurface water could vary by several feet because of seasonal fluctuations in precipitation, evaporation, surface water runoff, local topography, and other factors not immediately apparent at the time of this exploration. Normally, the highest subsurface water levels occur in the late winter and spring and lowest levels occur in the late summer and fall. It should also be noted that boreholes often cave in where wet soil conditions, or flowing water is encountered. 4.4 Laboratory Test Results As discussed in Section 3.2, laboratory testing was performed on split spoon samples and a bulk sample taken from the soils in the upper 10 feet for natural moisture content, moisture density relationship, and California Bearing Ratio testing. The result from the laboratory testing is included in the table below. Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 5 -

10 Boring No. Sample Depth (ft) Natural Moisture Content (%) Maximum Dry Density (pcf) Optimum Moisture (%) B CBR 5.0 GEOTECHNICAL DESIGN RECOMMENDATIONS 5.1 General The following evaluations and recommendations are based on our observations at the site, interpretation of the field data obtained during this exploration, as well as the field and laboratory data obtained during the previous exploration and our experience with similar subsurface conditions and projects. Subsurface conditions in unexplored locations may vary from those encountered. If the locations, loading, or elevation are changed, we should be notified and requested to confirm and, if necessary, re-evaluate our recommendations. Identification of an appropriate pavement system for a given parking lot is dependent upon the proposed loads, soil conditions, and construction constraints, such as proximity to other structures, etc. The subsurface exploration aids the geotechnical engineer in identifying the soil stratum appropriate for structural support. This identification includes considerations with regard to both allowable bearing pressure and compressibility of the soil strata. In addition, since the method of construction greatly affects the soils intended for structural support, consideration must be given to the implementation of suitable methods of site preparation, fill compaction, and other aspects of construction. 5.2 Pavement Design Recommendations The thickness of the recommended pavement section is directly related to the service life, the initial cost of placement, the preparation of the soil subgrade, and the method by which the granular base and the pavement are placed. We anticipate that the parking areas will service automobile traffic. The following pavement sections have been designed and evaluated using VDOT s Pavement Design Guide for Subdivision and Secondary Road (July 2009) for the parking area. The design and analysis of the pavement structure is based on a performance period of 20 years and a Design CBR value of 6.2. The DCBR value was calculated by taking 2/3 of the laboratory determined CBR values presented in Section 4.4 of this report. If the desired design life differs Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 6 -

11 from our assumed values, F&R should be notified so that we can adjust our pavement design recommendations as necessary. The following flexible pavement section is provided: Layer Light Duty Flexible Pavement Parking Stalls and Drive Lanes VDOT Specification Recommended Minimum Thickness (Inches) Surface Course Asphalt Concrete (SM-9.5) 2.0 Base Aggregate (21B) 8.0 The final subgrade within the pavement area should be carefully evaluated by the geotechnical engineer to determine its suitability for pavement and/or new fill support. Any unsuitable materials encountered in pavement areas should be undercut and either replaced with engineered fill or re-compacted in accordance with the recommendations of this report. An important consideration with the design and construction of pavements is surface and subsurface drainage. Where standing water develops, softening of the subgrade and other problems related to the deterioration of the pavement can be expected, especially with clay subgrades. Furthermore, good drainage should minimize the possibility of the subgrade materials becoming saturated over a long time. Based upon the results of the soil test borings, the groundwater table should not significantly affect the performance of pavements; however, surface runoff water that is trapped during construction on the exposed subgrade soils or that may enter through future cracks could create localized deterioration of the soil's bearing capacity. Standing water that may develop on the surface of the pavement may be minimized by: Adequate design (surface graded to control runoff to desired locations - catch basins, drain inlets, gutters, etc.); Accurate grading of each lift of pavement section component material (to achieve the desired design grades); Adequate compaction of each lift of pavement section component material (to minimize localized settlements that result in ponding); Installing temporary weep holes in drainage structures, construction of drainage swales and diversion ditches and proper backfill and grading behind curbs to minimize water intrusion from behind the curbs. Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 7 -

12 Installation of standard underdrains and edge drains across and along paved areas will also prevent water that infiltrates through cracks and joints from accumulating within the pavement section and weakening the subgrade. 6.0 GEOTECHNICAL CONSTRUCTION RECOMMENDATIONS 6.1 Site Preparation Before proceeding with construction, surficial soils and other deleterious non-soil materials (if any) should be stripped or removed from the proposed construction area. During the stripping operations, positive surface drainage should be maintained to prevent the accumulation of water. After stripping, areas intended to support pavement should be carefully evaluated by a geotechnical engineer. Any unsuitable materials observed during the evaluation should be undercut and replaced with approved compacted fill or stabilized in-place. The possible need for, and extent of, undercutting and/or in-place stabilization required, if needed, can best be determined by the geotechnical engineer at the time of construction. Once the site has been properly prepared, at-grade construction may proceed. 6.2 Surface Water/Groundwater Control Subsurface water, for the purposes of this report, is defined as water encountered below the existing ground surface. Based on the subsurface water data obtained during our exploration program, we do not anticipate that subsurface water will be encountered during anticipated earthwork and shallow excavations for the pavement construction. An important aspect to consider during development of this site is surface water control. During the construction, we recommend that steps be taken to enhance surface flow away from any excavations and promote rapid clearing of rainfall and runoff water following rain events. It should be incumbent on the contractor to maintain favorable site drainage during construction to reduce deterioration of otherwise stable subgrades. 6.3 Structural Fill Placement and Compaction Controlled structural fill may be constructed using the non-organic on-site soils or off-site borrow having a classification of CL, ML, SC, SM, or better, as defined by the Unified Soil Classification System (USCS). Other materials may be suitable for use as general controlled structural fill materials and should be individually evaluated by the geotechnical engineer. Controlled structural fill should be free of boulders, organic matter, debris, or other deleterious materials and should Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 8 -

13 have a maximum particle size no greater than 3 inches. It should be noted that the on-site soils do not meet the requirements given above. We recommend that structural fill be compacted to at least 95 percent of the Standard Proctor (ASTM D 698 or AASHTO T 99) maximum dry density and that the moisture content be maintained within three percentage points of the optimum moisture content, as determined from the Standard Proctor density test. Fill materials should be placed in horizontal lifts with maximum loose thickness of 8 inches. New fill should be adequately keyed into stripped and scarified subgrade soils. During fill operations, positive surface drainage should be maintained to prevent the accumulation of water. In confined areas such as may be used for this project, portable compaction equipment and thin lifts of 3 to 4 inches may be required to achieve specified degrees of compaction. Generally, we do not anticipate significant problems controlling moistures within approved fill during periods of dry weather, but moisture control may be difficult during winter months or extended periods of rain. We recommend that the contractor have equipment on site during earthwork for both drying and wetting of fill soils. Attempts to work the soils when wet can be expected to result in deterioration of otherwise suitable soil conditions or of previously placed and properly compacted fill. If construction traffic or weather has disturbed the subgrade, the upper 8 inches of soils intended for structural support should be scarified, moisture conditions, and re-compacted. Each lift of fill should be tested to confirm that the recommended degree of compaction is attained. In confined areas, a greater frequency may be required. 6.4 Temporary Excavation Recommendations Mass excavations and other excavations required for construction of this project must be performed in accordance with the United States Department of Labor, Occupational Safety and Health Administration (OSHA) guidelines (29 CFR 1926, Subpart P, Excavations) or other applicable jurisdictional codes for permissible temporary side-slope ratios and/or shoring requirements. The OSHA guidelines require daily inspections of excavations, adjacent areas and protective systems by a competent person for evidence of situations that could result in cave-ins, indications of failure of a protective system, or other hazardous conditions. All excavated soils, equipment, building supplies, etc., should be placed away from the edges of the excavation at a distance equaling or exceeding the depth of the excavation. F&R cautions that the actual excavation slopes will need to be evaluated frequently each day by the competent person and flatter slopes or the use of shoring may be required to maintain a safe excavation depending upon excavation specific Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page - 9 -

14 circumstances. The contractor is responsible for providing the competent person and all aspects of site excavation safety. F&R can evaluate specific excavation slope situations if we are informed and requested by the owner, designer or contractor s competent person. 7.0 CONTINUATION OF SERVICES We recommend that we be given the opportunity to review the grading plan and project specifications when construction documents approach completion. This review evaluates whether the recommendations and comments provided herein have been understood and properly implemented. We also recommend that Froehling & Robertson, Inc. be retained for professional and construction materials testing services during construction of the project. Our continued involvement on the project helps provide continuity for proper implementation of the recommendations discussed herein. As the Geotechnical Engineer of Record, F&R should be retained to monitor and test earthwork activities, and subgrade preparations, and excavations. It should be noted that the actual soil conditions at the various subgrade levels will vary across this site and thus the presence of the Geotechnical Engineer and/or his representative during construction will serve to validate the subsurface conditions and recommendations presented in this report. We recommend that F&R be employed to monitor the earthwork and backfilling operations, and to report that the recommendations contained in this report are completed in a satisfactory manner. Our involvement on the project will aid in the proper implementation of the recommendations discussed herein. The following is a recommended scope of services: Review of project plans and construction specifications to verify that the recommendations presented in this report have been properly interpreted and implemented; Observe all excavations for compliance with the geotechnical recommendations. These services are not included in our current scope of services and can be rendered for an additional cost. 8.0 LIMITATIONS This report has been prepared for the exclusive use of Dewberry or their agent, for specific application to the Leakes Mill Park Phase 2 project, in accordance with generally accepted soil engineering practices. No other warranty, express or implied, is made. Our evaluations and Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page

15 recommendations are based on design information furnished to us; the data obtained from the previously described subsurface exploration program, and generally accepted geotechnical engineering practice. The evaluations and recommendations do not reflect variations in subsurface conditions which could exist intermediate of the boring locations or in unexplored areas of the site. Should such variations become apparent during construction, it will be necessary to re-evaluate our recommendations based upon on-site observations of the conditions. There are important limitations to this and all geotechnical studies. Some of these limitations are discussed in the information prepared by ASFE, which is included in Appendix IV. We ask that you please review this ASFE information. Regardless of the thoroughness of a subsurface exploration, there is the possibility that conditions between borings will differ from those at the boring locations, that conditions are not as anticipated by the designers, or that the construction process has altered the soil conditions. Therefore, experienced geotechnical engineers should evaluate earthwork, and pavement construction to verify that the conditions anticipated in design actually exist. Otherwise, we assume no responsibility for construction compliance with the design concepts, specifications, or recommendations. In the event that changes are made in the design or location of the proposed structure, the recommendations presented in the report shall not be considered valid unless the changes are reviewed by our firm and conclusions of this report modified and/or verified in writing. If this report is copied or transmitted to a third party, it must be copied or transmitted in its entirety, including text, attachments, and enclosures. Interpretations based on only a part of this report may not be valid. Dewberry Leakes Mill Park Phase 2 Goochland County, Virginia F&R File No. 60S-0585 March 11, 2015 Page

16 APPENDIX I

17 Froehling & Robertson, Inc. SITE VICINITY MAP Drawing No. 1 Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland County, Virginia Source: DeLORME Scale: Not to Scale Date: February 2015 Approximate Site Location

18 Froehling & Robertson, Inc. BORING LOCATION PLAN Drawing No. 2 Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland County, Virginia Source: Google Earth Scale: Not to Scale Date: February 2015 B-1 B-2 B-3 B-4 B-5 B-6 B-7 B-8 B-9 - Approximate Boring Location

19 APPENDIX II

20 COARSE-GRAINED SOILS Gravels Clean gravels Cu 4 and 1 Cc 3 D GW Well-graded gravel E (More than 50% (Less than 5% fines C ) of coarse fraction Cu < 4 and/or [Cc < 1 or Cc > 3] D GP Poorly graded gravel E retained on No. 4 Gravels with fines Fines classify as ML or MH GM Silty gravel E,F,G sieve) (More than 12% fines C ) More than 50% retained on the No. 200 sieve Clean Sands Fines classify as CL or CH Cu 6 and 1 Cc 3 D GC SW Clayey gravel E,F,G Well-graded sand I Sands (50% or more of (Less than 5% fines H ) Cu < 6 and/or [Cc < 1 or Cc > 3] D SP Poorly graded sand I coarse fraction Sands with fines Fines classify as ML or MH SM Silty sand F,G,I passes No. 4 sieve) (More than 12% fines H ) Fines classify as CL or CH SC Clayey sand F,G,I HIGHLY ORGANIC SOILS Primarily orgainic matter, dark in color, and organic in odor PT Peat Elastic silt K,L,M Organic clay K,L,M,P Organic silt K,L,M,Q A Based on the material passing the 3-in. (75-mm) sieve. G If fines are organic, add "with organic K If soil contains 15 to < 30 % plus No. 200, add B If field sample contained cobbles or boulders, or both, fines" to group name. "with sand" or "with gravel", whichever is add "with cobbles or boulders, or both" to group name. H Sands with 5 to 12 % fines require dual predominant. C Gravels with 5 to 12 % fines require dual symbols: symbols: L If soil contains 30 % plus No. 200, GW-GM well-graded gravel with silt SW-SM well-graded sand with silt predominantly sand, add "sandy" to GW-GC well-graded gravel with clay SW-SC well-graded sand with clay group name. GP-GM poorly graded gravel with silt SP-SM poorly graded sand with silt M If soil contains 30 % plus No. 200, GP-GC poorly graded gravel with clay SP-SC poorly graded sand with clay predominantly gravel add "gravelly" to D I If soil contains 15 % gravel, add "with group name. Cu = D 2 60 D Cc = 30 D gravel" to group name. 10 D 10 X D 60 PI 4 and plots on or above "A" line. E If soil contains 15 % sand, add "with sand" J If Atterburg limits plot in hatched area, O PI < 4 or plots below "A" line. to group name. F If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. CLASSIFICATION OF SOILS FOR ENGINEERING PURPOSES ASTM Designation: D 2487 (Based on the Unified Soil Classification System) Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Silts and Clays Liquid limit 50 or more Inorganic Organic soil is a CL-ML, silty clay. FROEHLING & ROBERTSON, INC. Engineering Stability Since 1881 PI plots below "A" line Group Symbol MH OH P PI plots on or above "A" line. Q PI plots below "A" line. Soil Classification Group Name B FINE-GRAINED SOILS PI > 7 and plots on or above "A" line J CL Lean clay K,L,M Inorganic Silts and Clays PI < 4 or plots below "A" line J ML Silt K,L,M Liquid limit less than 50 Organic clay K,L,M,N Liquid limit oven dried Organic OL Liquid limit not dried < 0.75 Organic silt K,L,M,O 50% or more passes the No. 200 sieve PI plots on or above "A" line CH Fat clay K,L,M Liquid limit oven dried Liquid limit not dried < 0.75

21 Particle Size and Proportion KEY TO BORING LOG SOIL CLASSIFICATION Visual descriptions are assigned to each soil sample or stratum based on estimates of the particle size of each component of the soil and the percentage of each component of the soil. Particle Size Proportion Descriptive Terms Descriptive Terms Soil Component Particle Size Component Term Percentage Boulder > 12 inch Major Uppercase Letters > 50% Cobble 3-12 inch (e.g., SAND, CLAY) Gravel-Coarse 3/4-3 inch -Fine #4-3/4 inch Secondary Adjective 20% - 50% Sand-Coarse #10 - #4 (e.g., sandy, clayey) -Medium #40 - #10 -Fine #200 - #40 Minor Some 15% - 25% Silt (non-cohesive) < #200 Little 5% - 15% Clay (cohesive) < #200 Trace 0% - 5% Notes: 1. Particle size is designated by U.S. Standard Sieve Sizes 2. Because of the small size of the split-spoon sampler relative to the size of gravel, the true percentage of gravel may not be accurately estimated. Density or Consistency The standard penetration resistance values (N-values) are used to describe the density of coarse-grained soils (GRAVEL, SAND) or the consistency of fine-grained soils (SILT, CLAY). Sandy silts of very low plasticity may be assigned a density instead of a consistency. DENSITY CONSISTENCY Term N-Value Term N-Value Very Loose 0-4 Very Soft 0-1 Loose 5-10 Soft 2-4 Medium Dense Firm 5-8 Dense Stiff 9-15 Very Dense > 50 Very Stiff Hard > 30 Notes: 1. The N-value is the number of blows of a 140 lb. Hammer freely falling 30 inches required to drive a standard split-spoon sampler (2.0 in. O.D., 1-3/8 in. I.D.) 12 inches into the soil after properly seating the sampler 6 inches. 2. When encountered, gravel may increase the N-value of the standard penetration test and may not accurately represent the in-situ density or consistency of the soil sampled. F:\Branch 62\GEOWORD\REPORTS\keyblsc.enc.doc

22 SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS GRAPH LETTER TYPICAL DESCRIPTIONS GRAVEL AND GRAVELLY SOILS CLEAN GRAVELS (LITTLE OR NO FINES) GW GP WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES COARSE GRAINED SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE GRAVELS WITH FINES (APPRECIABLE AMOUNT OF FINES) GM GC SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE SAND AND SANDY SOILS CLEAN SANDS (LITTLE OR NO FINES) SW SP WELL-GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES POORLY-GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE SANDS WITH FINES (APPRECIABLE AMOUNT OF FINES) SM SC SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES ML INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY FINE GRAINED SOILS SILTS AND CLAYS LIQUID LIMIT LESS THAN 50 CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE SILTS AND CLAYS LIQUID LIMIT GREATER THAN 50 MH CH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS EXISTING FILL FILL EXISTING FILL MATERIALS NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS

23 R Froehling & Robertson, Inc. BORING LOG Boring: B-1 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL RESIDUUM Stiff, Red, Sandy Fat CLAY, Trace Mica (CH) Dense, Tan to Tan and White, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

24 R Froehling & Robertson, Inc. BORING LOG Boring: B-2 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL POSSIBLE FILL Loose, Dark Brown, Clayey SAND, Trace Roots (FILL-SC) RESIDUUM Stiff, Red, Sandy Fat CLAY, Trace Mica (CH) Very Stiff, Red to Brown, Sandy SILT, Trace Mica (ML) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

25 R Froehling & Robertson, Inc. BORING LOG Boring: B-3 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL POSSIBLE FILL Medium Dense, Brown, Clayey SAND, Trace Wood (FILL-SC) RESIDUUM Stiff to Very Stiff, Red, Sandy Fat CLAY, Trace Mica (CH) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

26 R Froehling & Robertson, Inc. BORING LOG Boring: B-4 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL POSSIBLE FILL Loose, Brown, Clayey SAND, Trace Roots (FILL-SC) RESIDUUM Medium Dense, Red, Clayey SAND, Trace Mica (SC) Dense to Very Dense, Gray and Tan, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

27 R Froehling & Robertson, Inc. BORING LOG Boring: B-5 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth 0.5 Description of Materials (Classification) SURFICIAL SOIL Elevation: Total Depth: 9.8' RESIDUUM Loose to Very Dense, Brown and Red, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling /4" Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

28 R Froehling & Robertson, Inc. BORING LOG Boring: B-6 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL RESIDUUM Medium Dense, Red, Clayey SAND, Trace Mica (SC) Medium Dense to Dense, Red and Gray, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

29 R Froehling & Robertson, Inc. BORING LOG Boring: B-7 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL RESIDUUM Stiff, Red, Sandy Fat CLAY, Trace Mica (CH) Dense, Red to Brown, Silty SAND, Trace Mica (SM) Medium Dense to Dense, Tan and Red, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

30 R Froehling & Robertson, Inc. BORING LOG Boring: B-8 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL POSSIBLE FILL Medium Dense, Dark Brown and Black, Clayey SAND, Trace Roots (FILL-SC) RESIDUUM Medium Dense, Gray and Red, Silty SAND, Trace Mica (SM) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

31 R Froehling & Robertson, Inc. BORING LOG Boring: B-9 (1 of 1) Project No: 60S-0585 Client: Dewberry Project: Leakes Mill Park Phase 2 City/State: Goochland, Virginia Elevation Depth 0.5 Elevation: Total Depth: 10.0' Description of Materials (Classification) SURFICIAL SOIL POSSIBLE FILL Stiff to Firm, Dark Brown and Black, Sandy Fat CLAY, Trace Roots, Trace Gravel (FILL-CH) Boring Location: See Boring Location Plan * Sample Blows Sample Depth N-Value (feet) (blows/ft) Drilling Method: HSA 3-1/4 in Hammer Type: Automatic Date Drilled: 2/16/15 Driller: Sequist Remarks Subsurface water was not encountered during drilling 6.0 RESIDUUM Medium Dense, Red, Clayey SAND, Trace Mica (SC) Boring terminated at 10 feet. Boring backfilled upon completion. BORING_LOG (LONG NAME) 60S-0585.GPJ F&R.GDT 3/11/15 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

32 APPENDIX III

33 MOISTURE/DENSITY RELATIONSHIP Curve No.: 1 Project No.: 60S0585 Date: Project: Leakes Mill Park Client: Dewberry Sample Number: 1 [Control #120338] Depth: 0-5' Remarks: N/A MATERIAL DESCRIPTION Description: Reddish Brown Sandy Clay [Sample Marked B-6] Classifications - USCS: CL AASHTO: Nat. Moist. = 22.3 % Sp.G. = Liquid Limit = 46 Plasticity Index = 22 %<No.10 = %<No.60 = 95.8 % %<No.40 = %<No.200 = 85.3 % 60.2 % Maximum dry density = pcf Optimum moisture = 20.9 % TEST RESULTS 140 Test specification: ASTM D Method A Standard 130 Dry density, pcf % SATURATION CURVES FOR SPEC. GRAV. EQUAL TO: Sp. gr. for ZAV is an assumed value Water content, % Figure FROEHLING & ROBERTSON, INC.

34 FROEHLING & ROBERTSON, INC. Engineering Stability Since Dumbarton Road Richmond, Virginia I USA T I F California Bearing Ratio Project No.: 60S-0585 Test Date: 3/9/2015 Client: Dewberry Tested By: C.M. Project: Leakes Mill Park Phase 2 Compaction method: ASTM D1883/AASHTO T193/VTM8 Location: Goochland County, Virginia X Soaked CBR X 65 Blows Stress on Piston (psi) Penetration (inches) Soaked Dry 0.1 in. penetration (wet): in. penetration (wet): 9.6 Maximum Dry Density (pcf): Swell (%): 0.6 Optimum Moisture Content (%): 20.9 Dry Density Before Soaking (pcf): Dry Density After Soaking (pcf): Visual Description: Retained on 3/4 inch sieve (%): 0.0 Reddish Brown Sandy CLAY Surcharge Weight (pounds): 10.0 F&R Lab No.: Moisture Content Before Soaking (%): 15.6% Moisture Content After Soak, Top in. (%): 23.1% Source: Moisture Content After Soak, Ave. (%): 21.6% B-6

35 APPENDIX IV

36 Important Information About Your Geotechnical Engineering Report Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. The following information is provided to help you manage your risks. Geotechnical Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engineer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solely for the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one not even you should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary. Do not read selected elements only. A Geotechnical Engineering Report Is Based on A Unique Set of Project-Specific Factors Geotechnical engineers consider a number of unique, project-specific factors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates otherwise, do not rely on a geotechnical engineering report that was: not prepared for you, not prepared for your project, not prepared for the specific site explored, or completed before important project changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, elevation, configuration, location, orientation, or weight of the proposed structure, composition of the design team, or project ownership. As a general rule, always inform your geotechnical engineer of project changes even minor ones and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineering report whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctuations. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engineers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ sometimes significantly from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. A Report's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those recommendations are not final, because geotechnical engineers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual