FINAL_LAFB_TCF_Norfolk_District_USACE_Geotechnical_Report.pdf

RE-SITE LOCATION

AIR FORCE TARGETING CENTER FACILITY

LANGLEY AIR FORCE BASE

HAMPTON, VIRGINIA

Limited Subsurface Exploration and Preliminary

Geotechnical Engineering Report

January 2017

PREPARED BY:

Geo Environmental Section, Norfolk District U.S. Army Corps of Engineers Fort Norfolk, 803 Front Street Norfolk, VA 23510 ii

INTRODUCTION

This report has been prepared by Norfolk District U.S. Army Corps of Engineers (NAO) to provide a general characterization of the subsurface conditions at the project site and provides a general overview of the soil and geologic conditions with detailed descriptions at discrete soil boring locations.

SUMMARY

It is our understanding that the Air Force is planning for the design and construction of a building to house the proposed Air Force Targeting Center at LAFB. A site was initially selected at LAFB near the intersection of Helms Road and South Roma Road; however, the location has now been re-sited in an area approximately ½ mile west of the former site. As part of Norfolk District’s Services to LAFB, the Geo-Environmental Section performed a limited subsurface exploration and prepared a preliminary geotechnical engineering report within the boundaries of the re-sited location as specified by LAFB personnel. The report provides a general characterization of the subsurface conditions at the project site, provides an overview of the soil conditions, and provides general guidance with respect to geotechnical engineering considerations. This report is for information only and presents our understanding of the project, reviews the exploration procedures, and presents our observations. The preliminary geotechnical report is for planning purposes and is not suitable for design purposes.

Due to very loose to loose soils, and shallow water table conditions, it is our opinion that the proposed facility should be supported by means of a deep foundation system. Square precast pre-stressed concrete piles (SPPC) will be the most economical of the driven pile options and are one of the most widely utilized deep foundation systems in the Tidewater Area.

Groundwater was encountered in all borings at a relatively shallow depth ranging from 4.7 to 6.0 feet below ground surface. Based on our observations the relatively shallow groundwater will impact most excavations performed on this site. Dewatering such as sumps with pumps, well points or deep wells will be required for most utility excavations. Temporary drainage ditches should also be employed by the Contractor to accentuate drainage during construction.

Seven (7) buildings, known as Temporary Living Facilities in historical Norfolk District USACE project files, previously existed on the site. The former buildings were located around the existing parking areas. Although no evidence of previous building foundations were encountered during the limited subsurface exploration, it is possible that the building foundations may not have been completely removed during their demolition. Limited project information does not indicate the kind of foundations (deep or shallow) that were constructed for the Temporary Living Facilities. There is also a possibility that abandoned utility lines from the demolished buildings may be present within the project area. It is our understanding that there are several active underground utilities that cross the site.

No historical environmental research was performed for the site as part of our scope for the geotechnical evaluation. During the subsurface exploration, no indications of visual staining, odor, or elevated Photo-Ionization Detector readings (a measure of some common Volatile iii

Organic Compounds) were noted in the soil samples. The LAFB environmental office may have additional information of the former use of this site and whether the demolition of the old site buildings was properly performed and all hazardous materials were properly disposed.

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TABLE OF CONTENTS

1. PURPOSE

2. PROJECT INFORMATION

2.1 Scope of Work

2.2 Proposed Facility

2.3 Site Description

2.4 Historical Information

3. LIMITED SUBSURFACE EXPLORATION

3.1 General

3.2 Location

3.3 Soil Testing and Sampling

3.4 Laboratory Soil Testing

3.5 Cone Penetration Test

4. SUBSURFACE CONDITIONS

4.1 Regional Geology

4.2 Subsurface Stratigraphy

4.3 Groundwater Conditions

5. PRELIMINARY GEOTECHNICAL ENGINEERING CONSIDERATIONS

5.1 Preliminary Foundation Design

5.2 Ground Floor Slab-on-Grade

5.3 Seismic Site Classification for Design

5.4 Pavement Design Recommendations

5.5 Groundwater and Site Drainage

6. PRELIMINARY EARTHWORK CONSIDERATIONS

6.1 Site Preparation

6.2 Foundation Construction

6.3 Controlled Structural Fill

6.4 Suitability of On-site Material

6.5 Compaction Requirements

7. LIMITED ENVIRONMENTAL FIELD ASSESSMENT

7.1 Field Assessment

REFERENCES

Appendix A: Location and Geologic Maps Appendix B: Boring Location Plan, Boring Logs, and Profiles Appendix C: Laboratory Test Results Appendix D: CPT Results Appendix E: Pictures

1. PURPOSE

This report has been prepared to provide a general characterization of the subsurface conditions at the project site and to provide a general overview of the soil and geologic conditions with detailed descriptions at discrete boring locations. It is furnished for information purposes.

The purpose of the report is to summarize the results of a subsurface exploration and laboratory testing performed by the Norfolk District, U.S. Army Corps of Engineers for the proposed Air Force Targeting Center Facility at Langley Air Force Base (LAFB). The report is for information only and presents our understanding of the project, reviews the exploration procedures, and presents our observations, and provides general guidance with respect to geotechnical engineering considerations.

2. PROJECT INFORMATION

2.1 Scope of Work: It is our understanding that the Air Force is planning for the design and construction of a building to house the proposed Air Force Targeting Center at LAFB. A site was initially selected at LAFB within an existing ballfield near the southeast corner of the intersection of Helms Road and South Roma. A new site is currently being considered which is approximately ½ mile west of the former site. As part of the planning process for the development at the new site, an additional surface exploration and preliminary geotechnical report was prepared by the Geo-Environmental Engineering Section, Norfolk District, US Army Corps of Engineers. The purpose was to provide general subsurface conditions and to determine if any special foundation requirements such as deep foundations or other modifications would be needed. The preliminary geotechnical report is for planning purposes and is not suitable for design purposes.

2.2 Proposed Facility: According to information provided by the Norfolk District, Engineering Management Section, it our understanding that the proposed Air Force Targeting Center Facility (AFTCF) is to be constructed as a single story building, high bay, masonry construction and shall contain a total area of 95,000 square feet.

The 1391 developed for the initial site location was considered valid for the re-site option. The proposed facility must include space for 1,750 workstations and associated racks and communications equipment, mechanical space, conditioned computer warehouse space, and command staff offices for Center and three Squadrons. The facility space must accommodate crew size based on number, duration and frequency of worldwide targeting and geospatial intelligence operations in support of Allied Forces. The facility must also include space for operations, mission support, logistics support, and administrative support. It was also suggested that the facility include an emergency generator, site improvements, a foundation so that the building finished floor is at least ten (10) feet above mean high tide sea level, parking, and all necessary support. Due to the flooding in the Langley area, the building shall have finished floors above the appropriate design flood. A preliminary map of the proposed building location, titled Siting Option #1, was provided by the Norfolk District, USACE Design Management Section. This map is provided in Appendix A.

2.3 Site Description: The Air Force Targeting Center Facility will be constructed at Langley Air Force Base, Hampton, Virginia. The proposed building location will be constructed due south of the intersection of Worley Road and Weyland Road, and east of the 497th ISR Group building, located in the parking area off Sperry Court.

The site is located within the Lighter-Than-Air (LTA) visual area as indicated in the Design Compatibility Guidelines March 2006. According to this report, certain architectural criteria may be required for buildings constructed within the LTA area which include and are not limited to site planning, building forms, roof design, window design, and landscaping. A ground surface elevation for the site was interpreted to be seven (7) feet NAVD 88 from USGS/FEMA LiDAR-2014 contour elevation maps provided by the Geospatial Section, Water Resources Division, at Norfolk District USACE. Location maps and project site contour elevation maps are also provided in Appendix A.

The existing project site currently consists of three (3) separate parking lots, which are currently utilized by base personnel operating in the 497th ISR Group building.

The parking areas are occupied 24-hours, 7-days a week for building operations.

According to historical Norfolk District USACE project files and, as described in further detail in Section 2.4 of this report, seven (7) buildings, known as Temporary Living Facilities previously existed on the site. The former buildings were located around the existing parking areas. Project files indicate a subsurface site investigation was performed in 1982, and 1994 Google Earth Pro imagery verifies that these buildings existed on the site. A LAFB Base Map, dated 2005 and provided by the Project Manager of the LAFB 633 Civil Engineer Squadron, also identifies these seven (7) buildings on site as building numbers 1092 to 1098. The building number map is provided in Appendix A, Figure 6. The building numbers in Figure 6 differ from those provided in Figures 9 and 10. The map shown in Figure 6 was provided to Norfolk District USACE by the 633 Civil Engineer Squadron at LAFB, whereas the original source of the CADD drawings provided in Figures 9 and 10 are unknown. It is assumed, based on Google Earth Pro imagery, that sometime between 2011 and 2014, the seven (7) buildings were demolished.

As shown in in the enclosed photographs in Appendix E, several repairs have been made to the pavement in areas of the parking lots due to underlying utilities. While clearing the utilities for the subsurface exploration, it was brought to our attention that utility lines from NASA Langley were located near the southern area of the site, and active gas lines, electrical lines, sanitary sewer lines, and an active force main were located within the project limits. Cone Penetration Tests one and two (CPT-1 and CPT-2) were carefully located during the subsurface exploration between active electrical and sanitary sewer lines on the site. CPT locations are provided on the boring location map in Appendix B. There is also a possibility that abandoned utility lines from the demolished buildings may be present within the project area.

2.4 Historical Information: Historical project files, historical drawings, and Google Earth Pro imagery show seven (7) buildings around the existing parking areas, which according to the project file, were considered to be Temporary Living Facilities. A subsurface investigation consisting of ten (10) borings extending to a depth of 20 feet below ground surface, was performed by ATEC Associates, Inc. and submitted to LAFB on 30 September 1982. Hollow stem auger method was used and soils encountered in the subsurface investigation were Very Loose to Medium Dense Silty and Clayey Sands. A boring location plan was provided with the report, and a preliminary not for construction drawing, which correlates the boring locations with the proposed parking area and seven (7) buildings, was also provided in the historical file and was dated 16 July 1983. The drawing also provides the proposed locations for some of the utilities, such as sanitary and electrical, and shows elevations at locations within the site area. Historical elevations varied on the site from approximately 8.5 feet to 10.0 feet. The datum used by the survey team was not identified in the drawing. The drawing states that the coordinates were based on an assumed coordinate system, and were not related to a state plane coordination system.

The historical boring location plan is provided in Appendix A.

Satellite imagery provided by Google Earth Pro, shows a timeline of site images extending from 21 March 1994 through 23 April 2014. The seven (7) buildings were shown in the images until 23 April 2014. The previous imagery dating 27 September 2011 shows the buildings still on site. It is believed that the buildings were demolished sometime between 27 September 2011 and 23 April 2014. Also looking at the satellite imagery from 29 April 2006, Appendix A Figure 11, it appears the northern and eastern areas of the site contained smaller structures and even what appears to be a playground or fitness area in the eastern portion of the site. Refer to Appendix A, Figures 11 through 13 for a general timeline of Google Earth Pro images of the proposed project site.

Although no evidence of previous building foundations were encountered during the limited subsurface exploration, it is possible that the building foundations may not have been completely removed during their demolition. Limited project information does not indicate the kind of foundations (deep or shallow) that were constructed for the Temporary Living Facilities.

3 LIMITED SUBSURFACE EXPLORATION

3.1 General: A limited subsurface exploration was performed to identify the subsurface material properties and define the subsurface stratigraphy. The subsurface exploration program consisted of soil borings with standard penetration tests (SPT) and Cone Penetration tests (CPT). The soil borings and CPT tests were performed by Savannah District, U.S. Army Corps of Engineers under the supervision of an Engineer from Norfolk District, U.S. Army Corps of Engineers.

3.2 Location: A limited number of borings and CPTs were spaced across the site relative to the proposed location of the facility. Locations were flagged in the field based on measurements from existing features. Northing and Easting coordinates for each boring location were interpolated using a Langley Air Force Base CADD drawing from the Norfolk District USACE project files titled LAFB-Base Map.dwg.

The CADD file was revised on 21 May 2002. Ground surface elevations for each boring were interpolated by USGS/FEMA LiDAR-2014 contour elevation maps provided by the Geospatial Section, Water Resources Division, Norfolk District, USACE. The location and elevation are accurate only to the degree implied by these methods used to their determination. Prior to drilling, all locations were cleared for underground utilities by Virginia Miss Utility, personnel from Safety and Quality Assurance Alliance (SQA2) at NASA Langley Research Center, and utility personnel at LAFB. Boring locations are shown on the enclosed subsurface exploration plan, provided in Appendix B.

3.3 Soil Testing and Sampling: Six (6) Standard Penetration Test (SPT) borings, designated as DH-1 through DH-6, were drilled at the proposed site, each to an approximate depth of 100 feet below ground surface (bgs). SPT boring: DH-5 was performed on 12 and 13 April 2016; DH-6 was performed on 13 April 2016; DH-4 was performed on 14 April 2016; DH-3 was performed on 14 and 15 April 2016; and DH-2 was performed on 15 April 2016; and DH-1 was drilled on 16 April 2016.

SPT borings were performed in accordance with ASTM D 1586 with a track-mounted drill rig utilizing 4 ¼-inch I.D. hollow stem auger procedures. Soil samples were obtained with a standard 2-inch outer diameter and 24-inch long split-spoon sampler driven with a 140-lb automatic hammer falling 30 inches. The number of blows required to drive the sampler for each six (6) inch penetration increment was recorded. The recovered soil samples were visually classified in the field in general accordance with ASTM D 2488. The samples were then returned to the Norfolk District Office for review. Boring logs are included in Appendix B. Portions of the recovered soil were placed in plastic jars and tested for Volatile Organic Compounds (VOCs) using a MiniRAE 2000 portable VOC monitor, also known as a Photo- Ionization Detector (PID). The detector stores hundreds of Low, High, Time Weighted Average (TWA), and Short Term Exposure Limits (STEL) in its library.

The preset limits vary and depend on which gas is detected by the device. If VOC exposures exceed preset limits, an alarm will sound on the detector emitting three (3) beeps and flashes per second.

3.4 Laboratory Soil Testing: Laboratory soil testing was performed by Savannah

District, U.S. Army Corps of Engineers Materials Testing Regional Technical Center of Expertise, located in Marietta, Georgia. Twenty-four (24) soil samples, which were generally representative of the subsurface materials, were selected for classification tests (ASTM D 422, D 2216, D 2487, and D 4318). The laboratory test results were used to aid in soil classifications of the in-situ soils. Laboratory test results are provided in Appendix C.

3.5 Cone Penetration Test: The subsurface exploration program also included Cone Penetration Tests (CPT), which was designated as CPT-1 and CPT-2. The cone penetration tests were performed by Savannah District, U.S. Army Corps of Engineers in accordance with ASTM D 3441. The CPT was performed at approximate 0.164 foot depth intervals beginning at approximately 0.164 feet below the existing ground surface. The test cone was advanced through the soil by the hydraulic jacking system of a SCAPS rig. The tests were performed to an approximate depth of 100 feet below the existing ground surface, and the test data was reduced by Savannah District. The results of the data reduction are provided in Appendix D.

4. SUBSURFACE CONDITIONS

4.1 Regional Geology: Langley Air Force Base is located approximately four (4) miles north-northwest of Hampton, Virginia and approximately 10 miles east of Newport News, Virginia. It is located in the Coastal Plain Physiographic Province.

Numerous transgressions and regressions of the Atlantic Ocean have deposited marine, lagoonal, and fluvial (stream lain) sediments. The regional geology is very complex, and generally consists of interbedded layers of varying mixtures of sands, silts, and clays. According to the Geologic Map of Virginia, the surficial soils belong to the Lynnhaven Member (Qtl) of the Tabb formation. These soils are described as pebbly and cobbly, fine to coarse gray sand grades upward into clayey and silty fine sand and sandy silt. Thickness varies from 0 to 20 feet (USGS). A copy of the geologic map of the site can be seen in Appendix A. These surficial deposits are underlain by the soils of the Yorktown formation. The Yorktown formation is Miocene in age. The top of the Yorktown formation typically consists of a relatively thin layer of bluish gray to gray highly plastic clay. The layer typically acts as an aquaclude between overlying soils and the underlying Yorktown soils. The underlying soils of the Yorktown formation typically consist of bluish gray to gray, fossiliferous, medium dense silty sands, and firm to very stiff sandy silts and silty sands. Shell beds are often abundant in this formation. The Yorktown stratum, once encountered, generally extends to depths in excess to 150 feet below sea level.

4.2 Subsurface Stratigraphy: The subsurface conditions discussed in the following section and those shown on the boring test logs represent interpretations of the boring data and are for information only. The lines designating strata breaks on the boring logs and those indicated below represent approximate boundaries between soil types, as the transition may be gradual or may occur between samples. The generalized subsurface stratigraphy is our interpretation of the soil stratigraphy and subsurface condition at the project site based on our subsurface exploration and available information. The interpretation necessarily assumes uniform subsurface conditions across the site, which is probably, but not necessarily, correct. The general descriptions, below, should not be considered as a substitute for the boring logs.

Generalized subsurface profiles for the site are also included in Appendix B of this report.

A FILL layer was encountered to range in depth of approximately 4-inches to 9-inches bgs in the soil borings. This soil is typically a Very Loose to Loose, Brown, Dark Brown, Orangish Brown, and Black Clayey Fine to Coarse SAND with roots, or Soft, Brown, Gray, and Dark Brown, CLAY with some fine to coarse sand with roots.

SPT N-values ranged from 1 to 2 blows per foot (bpf) with an average of 1.8 bpf.

Photo-ionization Detector (PID) readings were recorded as zero (0) parts per million (ppm) for this layer.

Underlying the FILL layer, is a layer which consists of Very Loose to Medium Dense, Brown, Orangish Brown, Yellowish Brown, Reddish Brown, Tan and Black, Fine to Coarse Silty and Clayey SAND, classified as SM, SC, or SP-SM. This material was encountered to an approximate depth of 8.3 to 12.0 feet bgs. Rocks were encountered in the split spoon for borings DH-3 and DH-4 at a depth of 1.58 feet and 3.5 feet bgs. Trace gravel was encountered in boing DH-3 from approximately 2-feet to 4-feet bgs, and low recovery occurred for depth interval 4-feet to 6-feet. Shell fragments were encountered in all borings ranging in depths from approximately 6.0 to 12.0 feet bgs. SPT N-values ranged from 0 to 23 bpf with an average of 6.9 bpf. PID readings were recorded as zero (0) ppm for this layer. This material has been designated as Stratum I for this site.

According to the laboratory soil tests results on selected samples listed in Table 1 in Appendix C, the moisture content for the Stratum I ranged from 11.3 to 36.4 percent with an average of 25.9 percent. The percent passing the No. 200 Sieve ranged from

15.5 to 35.5 percent with an average of 23.4 percent.

Underlying Stratum I was a Very Loose to Medium Dense, Dark Gray and Bluish Gray, Silty and Clayey Fine SAND with varying sizes and amounts of shell fragments, classified as SP-SM, SM, or SC. This material was encountered from approximately 8.3 to termination for all borings. Intermittent layers of Soft to Stiff, Bluish Gray and Dark Gray CLAY or Plastic CLAY with some fine sand, classified as CL or CH, was encountered between the approximate depths of 65 to 92 feet bgs.

SPT N-values ranged from 0 to 36 bpf with an average of 7.2 bpf. PID readings were recorded as zero (0) ppm for this layer. This material has been designated as Stratum II for this site.

According to the laboratory soil test results on selected samples listed in Table 2 in Appendix C, the moisture content for the Stratum II ranged from 22.0 to 37.4 percent with an average of 31.2 percent. The percent passing the No. 200 Sieve range from 7 to 79 percent with an average of 24.7 percent.

4.3 Groundwater Conditions: Groundwater was measured at each borehole approximately after auger removal and 24 hours after drilling operations. The water level was observed to range approximately 4.7 to 5.9 feet bgs approximately 24 hours after drilling operations were complete. A temporary piezometer was also installed within 10 feet of boring location DH-3 on 15 April 2016. It was installed to a depth of approximately 10.0 feet bgs with approximately 5.0 feet of screen and 5.0 feet of riser. The water level was observed at approximately 5.7 feet approximately 48 hours after installation.

The depth to groundwater that was observed at time of the exploration does not reasonably represent the conditions that will be encountered during construction or for the life of the building. Due to the shallow water table conditions encountered in the borings, groundwater could be found close to the ground surface. Groundwater levels are expected to fluctuate with seasonal changes, periods of heavy or little rainfall, tides, pumping from wells, and other factors. The near surface soils can become soft and wet.

5. PRELIMINARY GEOTECHNICAL ENGINEERING

CONSIDERATIONS

5.1 Preliminary Foundation Design: Based on the results of the subsurface exploration program, it is our opinion that the proposed facility should be supported by means of a deep pile foundation system. Square precast pre-stressed concrete piles (SPPC) will be the most economical of the driven pile options and are one of the most widely utilized deep foundation systems in the Tidewater Area. The piles are available in sizes from 10 to 24 square inches, and are typically designed for allowable pile loads of between 35 to 250 tons (70 to 500 kips). Lengths of piles typically in the Tidewater Area may vary between 40 to 80 feet to obtain the required capacity.

Table 3 below provides our preliminary estimate of pile capacities for three (3) SPPC dimensions with a tip depth of 75 feet below the ground surface for the facility’s foundation system while using a factor of safety of 3. These values are not for design but for general planning. The design needs to consider other factors but not limited to building loads, site grading, and horizontal deflections. Verification load testing shall be included as part of the contract for production piles during construction. The capacity of a group of piles should not be spaced less than three (3) pile diameters apart, center to center, and a reduction of capacity will be needed for pile groups.

The final order lengths and tip elevations shall be adjusted based on the results of the test piles and load test programs.

Table 3. Square Precast Pre-stressed Concrete Pile Sizes and Approximate Capacities

SPPC

Dimensions

(ft)

Embedment Depth

(ft)

Approximate Allowable

Compression Capacity (tons)

Approximate Allowable

Tension Capacity (tons)

12-in x 12-in

21 12 16-in x 16-in 36 19 18-in x 18-in 45 23

The piles are expected to derive the majority of their capacity from shaft friction with minor end bearing in sand layers at deeper depths. The soil materials typically exhibit time-dependent strength characteristics. The dynamics of driving piles will cause excess pore pressures to develop, thereby decreasing driving resistance during initial pile installation. Once driving is complete, the excess pore pressures dissipate with time and the bearing capacity of the pile increases. Several days will be required for the excess pore pressures to dissipate. Due to these reasons, it will not be possible to confirm pile capacities with a simple driving criterion such as number of hammer blows per foot or advanced pile. Instead, driving criteria will likely consist of a target tip elevation and/or certain embedded length in a bearing material with specified driving resistance. The specified driving resistance should be based on a Wave Equation Analysis of the Contractor’s selected hammer.

The proposed facility finished floor shall be constructed above the appropriate design flood elevation. Compacted controlled selected structural fill will be necessary to raise the final floor of the facility above future flood elevation. Refer to section 6.3 for controlled structural fill recommendations.

5.2 Ground Floor Slab-on-Grade: The ground floor slab for the proposed building can be designed as a slab-on-grade provided the ground floor slab is lightly loaded with general office furniture. If the slab will support heavy equipment then the slab will need to be designed as a structural slab which shall be supported on the pile foundations. Some undercutting and replacement of existing in-situ soils may be required if soils are soft or unsuitable as identified during the proof-rolling procedure of the subgrade.

A four-inch thick granular base layer consisting of open-graded crushed stone (VDOT 57 crushed stone) or clean sand (ASTM C-33 Sand) should be placed beneath the floor slabs. This granular base would function as a leveling and load disturbing material for the slab and provide a capillary break beneath the slab.

A vapor barrier should be used beneath ground floor slabs that will be covered by tile, wood, carpet, impermeable floor coatings, and/or if other moisture-sensitive equipment or materials will be in contact with the floor. Utility and other excavations within the subgrade of the floor slabs shall be backfilled with properly compacted structural fill in accordance with the project specifications to provide uniform floor slab support.

5.3 Seismic Site Classification for Design: The site soils were classified in accordance with ASCE Standard ASCE 7-05, Chapter 20 based on the Standard Penetration Resistance (N) obtained from boring locations DH-1 through DH-6. The average N values over the upper 100 feet of soil was determined to be less than 15 bpf, and in accordance with this method the site class is defined as Site Class E. The most accurate site classification can be obtained by using the average shear wave velocity procedure; however, this requires special testing such as surface wave tests or seismic cross-hole tests. Performing such tests may lead to a more favorable site classification which will lead to lower design forces and possible savings in the building structure.

5.4 Pavement Design Recommendations: The following general pavement recommendations are made: design adequate grading to provide runoff away from paved surfaces and beyond the limits of paved area and building areas. We recommend underdrains at low points in the pavement to limit water penetration into the base course and subbase.

The ability of the existing subgrade soils to support pavement structures may be variable across the site. The existing subgrade soils are moisture sensitive and will lose stability when subjected to moisture and construction traffic. It is recommended that pavement construction be performed during the summer months and to provide positive drainage to prevent moisture from ponding on the subgrade.

5.5 Groundwater and Site Drainage: Groundwater was encountered in all borings at a relatively shallow depth. Approximately 24 hours after drilling the water level in the borings ranged from 4.7 to 5.9 feet below the surface. Based on our observations the relatively shallow groundwater will impact most excavations performed on this site. Dewatering such as sumps with pumps, well points or deep wells will be required for most utility excavations. Temporary drainage ditches should also be employed by the Contractor to accentuate drainage during construction.

6. PRELIMINARY EARTHWORK CONSIDERATIONS

6.1 Site Preparation: Proper site preparation will be critical to this project in order to achieve satisfactory performance of the structure. It is recommended that a Geotechnical Engineer be retained to provide soil engineering services during the actual site preparation and foundation construction phase of the project to perform appropriate evaluations to help assure that conditions encountered during construction are similar to the conditions encountered in the subsurface exploration. The Geotechnical Engineer can also assist in interpretation of differing subsurface conditions that may be encountered and recommend remedial work, if needed.

Site preparation for the building pad and pavements should include complete removal of surface vegetation, surficial soils, organic material, trees, tree stumps, roots and organic soils. Measured topsoil in the borings was generally four (4) inches thick.

However, some roots were encountered in borings extending 2.0 to 6.0 feet below the surface. Topsoil is defined as the upper surface soils that contain roots and other organic material. Due to groundwater conditions encountered on the site, all excavations for this site will require dewatering methods.

Stripping of topsoil should be performed to a horizontal distance of at least 10 feet beyond the limits of the building footprints, and five (5) feet beyond the limits of pavement in the undeveloped areas. Areas of construction should also be cleared of soft, wet, or disturbed soils. Over-excavated areas should be backfilled with properly compacted suitable fill. During the clearing and stripping operations, positive surface drainage should be maintained to prevent the accumulation of water.

After stripping, the exposed subgrade soils in the areas of development should be proof-rolled with a 15-ton loaded dump truck or other pneumatic-tired vehicle of similar size and weight. Proof-rolling should be observed by a Geotechnical Engineer and the Contracting Officer. Proof-rolling should be performed during a period of favorable weather and not while the site is wet, frozen, above planned grade, or severely desiccated. Any unsuitable materials that are observed to yield or rut noticeably during proof-rolling should be under and replaced with compacted imported controlled structural fill or stabilized in-place as recommended by the Geotechnical Engineer and approved by the Contracting Officer. Although no building debris was observed during the limited subsurface exploration, building remains from the former structure may still exist buried on site, along with possible underground utilities. We recommend that several tests pits be performed by the contractor and the contractor’s geotechnical engineer to verify that all building remains have been removed from the site prior to filling the site with structural fill.

The near surface subgrade soils are moisture sensitive and will lose stability if these soils become wet and are subjected to construction traffic. As a result, site preparation should be performed during an extended period of dry weather.

Undercutting or reworking by aerating or discing or the near surface soils may be necessary if the exposed subgrade soils become unstable during construction. Any fill materials, aggregates, and/or concrete should be placed as soon as possible over the approved subgrade in order to reduce exposure of the subgrade to weather and construction activity. It is important to stress that the subgrade needs to be properly prepared and protected during construction to minimize the degradation of these soils.

6.2 Foundation Construction: Test piles should be driven at the site within the proposed foundation areas prior to installation of production piles. The purpose of the test piles is to attempt to verify bearing depths, axial compressive capacities, and driving conditions across the site. Test piles should be 10 feet longer than the anticipated pile design length and should be driven to the indicated design bearing depth. The Geotechnical Engineer of record should witness the test pile installation.

The test piles should be located to provide coverage over the planned foundation areas. The number of test piles will be dependent upon the combination of the pile types and bearing elevations selected for the project. Test piles may be installed at planned permanent pile locations and utilized if adequate capacity is achieved. The test pile locations should be reviewed and approved by the Geotechnical Engineer of record. As a minimum, two static load tests per ASTM D 1143 shall be performed for the building. Pile re-strikes shall be performed in accordance with ASTM D 4945. A dynamic pile analysis shall be performed on each pile. The pile re-strikes shall not be performed until at least 3-days after test pile installation. The pile hammer used in the test pile program shall have sufficient energy to “prove” at least

250% of the specified allowable pile design capacity(ies). Application of the test load should be performed under the direction of a Geotechnical Engineer.

A wave equation and drivability evaluation should be performed for the proposed pile hammer assembly prior to the start of the test pile program. CAPWAP analyses should be performed on the PDA measurements obtained from the test piles indicated. Depending on the findings of the dynamic testing, the specified pile load test may be deleted at the discretion of the Geotechnical Engineer of record. In addition, some adjustment of the design capacities or bearing depths may be necessary.

6.3 Controlled Structural Fill: Fill placed beneath buildings, structures, and under roadways which will raise the site to the finished subgrade shall be compacted structural fill. Controlled structural fill material under buildings and the roadways should be non-expansive and free of organic matter, debris, and particles larger than two (2) inches in size. Proposed fill materials should be subjected to laboratory tests consisting of, but not necessarily limited to, moisture density determinations, Atterberg limits, and sieve analysis. Controlled Structural Fill under buildings, pavements, and structures should classify per USCS as SW, SP, SP-SM, SM, or SC with a maximum of 35 percent fines passing the No. 200 sieve.

6.4 Suitability of On-site Material: Due to existing fill, groundwater elevations, and debris encountered in the borings on the site, it is our opinion that structural fill will need to be imported from off-site. The imported fill shall conform to the recommendations above. The on-site soils will not be suitable for reuse as backfill in excavated utility trenches. Backfill material in utility trenches within the construction areas should consist of structural fill (as described in the previous section), and should be compacted to at least 95 percent of the standard Proctor maximum dry density in accordance with ASTM D 698. This fill should be placed in 4 to 6 inch loose lifts when hand compaction equipment is used.

6.5 Compaction Requirements: The contractor shall provide proper equipment to meet compaction requirements based on a modified Proctor (ASTM D 1557). Due to the higher energy from the modified Proctor, the optimum moisture content of the material will be lower than a standard Proctor. The in-situ moisture content of the subsurface material is expected to be higher than the optimum moisture content from a modified Proctor. The contractor should be prepared to adequately dry the in-situ soils prior to placement as backfill. The compaction requirements for this project are listed below:

Structures, Foundations, and Concrete Slabs: Compact top 12 inches of subgrade and subsequent structural fill to 95 percent of ASTM D 1557.

Roads and parking areas: Compact top 12 inches of subgrade and subsequent fill to 95 percent of ASTM D 1557.

Green Areas: Compact to 85 percent of ASTM 1557.

Maximum loose lift thickness shall be eight (8) inches and 12 inches under buildings and pavements, respectively. Proper compaction equipment should be utilized by the contractor to achieve the required compaction. For areas which do not permit the use of heavy compaction equipment (utility trenches) lift thickness shall be reduced to six

(6) inch loose lifts to achieve the required compaction. During fill operations, positive surface drainage should be maintained to prevent the accumulation of water.

Each lift of fill should be tested in order to confirm that the degree of compaction is attained. Field density tests to verify fill compaction should be as required by the earthwork specification.

The moisture of backfill material should be maintained within three (3) percentage points of the optimum moisture content as determined from the modified Proctor.

Compaction requirements may be reduced by five (5) percent for cohesive material, defined as material contained more than 50 percent fines (material passing the No.

200 sieve).

Care should be used when operating the compactors near existing structures to avoid transmission of the vibrations that could cause settlement damage or disturb occupants. In this regard, it is recommended that the vibratory roller remain at least 25 feet away from existing structures; these areas should be compacted with small, hand-operated compaction equipment.

7. LIMITED ENVIRONMENTAL FIELD ASSESSMENT

7.1 Field Assessment: No historical environmental research was performed for the site as part of our scope for the geotechnical evaluation. A photo-ionization detector (PID) was used to detect volatile organic compounds (VOCs), if any, in the soil during the subsurface exploration. Soil sample readings were measured to be 0 ppm during the subsurface exploration. It was determined that no environmental laboratory testing for soil samples would be required due to no indications of visual staining, odor, or elevated PID readings of the soil. The LAFB environmental office may have additional information of the former use of this site and whether the demolition of the old site buildings was properly performed and all hazardous materials were properly disposed.

REFERENCES

Design Capability Guidelines, Langley Air Force Base, Virginia. Prepared by PBS&J.

March 2006.

Google. Map of Langley Air Force Base, Hampton, Virginia.

<https://www.google.com/maps/place/Langley+Air+Force+Base,+Hampton,+VA +23665/@37.0365511,- 76.3717956,13z/data=!4m2!3m1!1s0x89ba8409e3715e9f:0xc526abdf8b222536?hl =en>

USACE. GIS Map of Virginia. < http://nao‐ap‐ oracle.nad.ds.usace.army.mil:7777/pls/apex/f?p=106:1:15492078822174:::::>

USGS. “Tabb Formation, Lynnhaven Member.”

<http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=VAQtl%3B0>

APPENDIX A:

LOCATION AND GEOLOGIC MAPS

Figure 1. Langley Air Force Base located in Hampton, Virginia. Red circle indicates general location.

Figure 2. Targeting Center Facility project site located off of Sperry Court. Red circle indicates proposed project location.

Figure 3. Proposed project site is located east of the 497th ISR Group Building, south of the intersection of Worley Road and Weyland Road.

Figure 4. The proposed project site is located within the Lynnhaven member of the Tabb formation

[Qtl]. Red circle indicates general project site location.

Worley Road

Weyland Road

497th ISR Group Building Sperry Court

Proposed Project Site

Figure 5. Close up map showing the proposed project site location, within the Lynnhaven member of the Tabb formation [Qtl]. Red circle indicates proposed project site.

Figure 6. Map shows the Temporary Living Facilities previously located on the proposed project site.

Seven buildings were once present on the site numbering 1092 through 1098. Red circle indicates previous building locations before demolition.

Figure 7. Yellow area indicates the Lighter than Air District at Langley Air Force Base, Hampton, Virginia (PBS&J 2005).

Figure 8. Yellow area shows location of Lighter than Air District. Red circle indicates general project area (PBS&J 2005).

Figure 9. Norfolk District USACE LAFB Utilities CADD drawing, last updated 2002, shows the site utility locations in 2002. Utility key is indicated below. The yellow lines indicate fencing, and the white lines indicate structures. Each corresponding building number is labeled outside of the white boundary lines. The green line in the southern area of the site, as indicated above, is labeled in the drawing as a

NASA electrical line 110 kV.

Sanitary Lines

Electrical Lines

Water Lines

NASA Electrical Line

Figure 10. Norfolk District USACE 2002 CADD drawing shows a closer view of the site utility locations in 2002. Utility key is indicated below. The yellow line indicates fencing, and the white lines indicate buildings. Each corresponding building number is labeled outside of the white lines. Sewer pump station is indicated above.

Sanitary Lines Electrical Lines Water Lines

Sewer Pump Station

Figure 11. Google Earth Pro satellite image of proposed project site dated 4/29/2006 (Google Earth

Pro).

Figure 12. Google Earth Pro satellite image of proposed project site dated 4/30/2011 (Google Earth

Pro).

Figure 13. Google Earth Pro Satellite of proposed project site dated 4/23/2014.

I n t e g r i t y - S e r v i c e - E x c e l l e n c e

Siting Option # 1 FY17 Air Force Targeting Center Facility, Langley (JBLE), VA

QD-Arc Area

CONCEPTUAL

F u t u r e

As of: 19 Jan 16

US Army Corps of Engineers Norfolk District

Map: Targeting_Facility_Contours Developed By: Jason O'Neal Date: 5/17/2016

7 7

1 in = 67 feetAir Force Targeting Center Facility Langley Air Force Base

Hampton, Va

Elevation Data Source:

USGS/FEMA LiDAR - 2014

Coordinate System:

NAD_1983_HARN_StatePlane_Virginia_South

0 10050 Feet

Norfolk District

Map: Targeting_Facility_Contours Developed By: Jason O'Neal Date: 5/17/2016

7 7

NAVD88 (feet) High : 10

Low : 5

1 in = 67 feetAir Force Targeting Center Facility Langley Air Force Base

Hampton, Va

Elevation Data Source:

USGS/FEMA LiDAR - 2014

Coordinate System:

NAD_1983_HARN_StatePlane_Virginia_South

Norfolk District

Map: Targeting_Facility_Contours Developed By: Jason O'Neal Date: 5/17/2016

1 in = 67 feetAir Force Targeting Center Facility Langley Air Force Base

Hampton, Va

Elevation Data Source:

USGS/FEMA LiDAR - 2014

Coordinate System:

NAD_1983_HARN_StatePlane_Virginia_South

APPENDIX B:

BORING LOCATION PLAN, BORING LOGS,

AND PROFILES

Subsurface Exploration Plan for the Proposed Targeting Center Facility Langley Air Force Base, Hampton, Virginia

DH-2DH-1

DH-4

DH-3

DH-5

DH-6

CPT-2

CPT-1

Standard Penetration Test Locations (SPT) Cone Penetration Test (CPT) Locations

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

E4TSEJLS

Oval

0.5 2.0

4.0

6.0

9.3 9.6

12.0

[FILL] Very Loose to Loose, Brown, Clayey Fine to Coarse SAND, moist, roots (6-inches) [SM] Medium Dense, Light Brown and Orangish Brown, Silty Fine to Medium SAND, moist (0.5 to 2.0 feet) [SC] Loose, Orangish Brown Mottled Yellowish Brown and Tan, Clayey Fine SAND, moist (2.0 to 4.0 feet) [SC] Very Loose, Orangish Brown Mottled Yellowish Brown, Tan, and Black, Clayey, Fine SAND, moist to wet (4.0 to 6.0 feet) [SC] Loose to Medium Dense, Orangish Brown, Reddish Brown, Yellowish Brown, Clayey Fine SAND with mostly shell fragments, wet (6.0 to 9.3 feet) [SM] Medium Dense, Bluish Gray, Silty Fine SAND with mostly shell fragments, moist to wet (9.3 to 9.6 feet) [SM] Loose, Reddish Brown and Brown, Silty Fine SAND with mostly shell fragments, wet to moist (9.6 to 12.0 feet) [SM] Medium Dense to Very Loose, Bluish Gray, Silty Fine SAND with shell fragments varying with depth, wet (12.0 to 62.0 feet)

+6.5 +5.0

+3.0

+1.0

-2.3 -2.6

-5.0

SS-1

0' to 2'

SS-2

2' to 4'

SS-3

4' to 6'

SS-4

6' to 8'

SS-5

8' to 10'

SS-6

13' to 15'

SS-7

18' to 20'

SS-8

23' to 25'

SS-9

28' to 30'

SS-10

33' to 35'

SS-11

38' to 40'

SS-12

43' to 45'

SS-13

48' to 50'

Sample SS-3 4' to 6' WC=35.6%, LL=41, PL=23, PI=18

Water level recorded at 5.15' bgs on 4/17/2016 approximately 24-hour reading Water level recorded at 5.55' bgs on 4/16/2016 time 1500 after auger removal

Little shell fragments from 18' to 27' bgs

Water level recorded at 22.45' bgs on 4/16/2016 time 1335 before auger removal

Sample SS-9 28' to 30' WC=37.1%, LL=NP, PL=NP, PI=NP

Cave-in depth approximately 30' bgs on 4/16/2016 time 1458

Trace shell fragments from 27' to 42' bgs

Few shell fragments from 42' to 47' bgs

2-5-8-4 N=13

2-2-3-3 N=5

1-0-1-0 N=1

1-2-3-2 N=5

5-7-9-7 N=16

9-5-5-5 N=10

2-1-1-2 N=2

1-2-2-2 N=4

1-1-1-1 N=2

2-1-1-1 N=2

1-1-2-2 N=3

1-1-2-3 N=3

1-2-2-3 N=4

REMARKS

(Drilling time, water loss, depth weathering, etc., if significant)

LEGEND

CLASSIFICATION OF MATERIALS

(Description)

ELEVATION DEPTH

a fc eb gd

SAMPLE

DEPTH

(feet)

SAMPLE

BLOWS

1.9

4 1/4 HSA

INSTALLATION SHEET

John Verrett

Jennifer Spitz100.0

7. THICKNESS OF OVERBURDEN

8. DEPTH DRILLED INTO ROCK

9. TOTAL DEPTH OF HOLE

17. ELEVATION TOP OF HOLE

15. ELEVATION GROUND WATER

SHEETS

STARTED COMPLETED

Hole No. DH-1

Langley Air Force Base

11. DATUM FOR ELEVATION SHOWN (TBM or MSL)

DISTURBED

1. PROJECT

+7.0

US Army Corps of Engineers, Savannah District UNDISTURBED13. TOTAL NO. OF OVERBURDEN

SAMPLES TAKEN

18. TOTAL CORE RECOVERY FOR BORING

3. DRILLING AGENCY

5. NAME OF DRILLER

6. DIRECTION OF HOLE

DEG. FROM VERT.

4. HOLE NO. (As shown on drawing title and file number)

14. TOTAL NUMBER CORE BOXES

16. DATE HOLE

DIVISION

4/16/2016---

12. MANUFACTURER'S DESIGNATION OF DRILL

OF

DH-1

10. SIZE AND TYPE OF BIT

LOCATION (Coordinates or Station) Hampton, Virginia N 3,565,381.86 E 12,106,954.89

2.

19. GEOLOGIST

CME-850 Track Rig

VERTICAL INCLINED

Air Force Targeting Center Facility

4/16/2016

DRILLING LOG 2

Hole No. DH-1

/2 8/

PROJECT HOLE NO.

Air Force Targeting Center Facility DH-1PREVIOUS EDITIONS ARE OBSOLETE.1836MAR 71

ENG FORM

62.0

67.0

72.0

77.0

88.9

92.0

100.0

[SM] Medium Dense to Very Loose, Bluish Gray, Silty Fine SAND with shell fragments varying with depth, wet (12.0 to 62.0 feet) (continued)

[SC] Very Loose, Bluish Gray, Clayey Fine SAND with shell fragments, wet

[CL] Soft, Bluish Gray CLAY with some fine sand and trace shell fragments, wet

[SC] Medium Dense, Bluish Gray, Clayey Fine SAND with shell fragments, moist to wet

[SP-SM] Medium Dense, Bluish Gray, Silty Fine SAND with and no shell fragments, wet

[CL] Hard, Bluish Gray and Dark Gray CLAY with some fine sand, wet

[SP-SM] Medium Dense to Loose, Bluish Gray Silty Fine SAND with mostly to little shell fragments, wet

Boring terminated at approximately 100 feet below ground surface.

-55.0

-60.0

-65.0

-70.0

-81.9

-85.0

-93.0

SS-14

53' to 55'

SS-15

58' to 60'

SS-16

63' to 65'

SS-17

68' to 70'

SS-18

73' to 75'

SS-19

78' to 80'

SS-20

83' to 85'

SS-21

88' to 90'

SS-22

93' to 95'

SS-23

98' to 100'

Some shell fragments from 47' to 62' bgs

Sample SS-17 68' to 70' WC=30.9%, LL=37, PL=20, PI=17

While advancing auger to 73'-75' interval, added approximately 5-gallons of water to auger to remove sand heave from augers

Sample SS-19 78' to 80' WC=22.1%, LL=NP, PL=NP, PI=NP

Trace to little shell fragments from 77' to 82' bgs

No shell fragments from 82' to 88.9' bgs

While advancing auger to 98'-100' interval, added approximately 5-gallons of water and used bailer to remove sand heave from augers PID readings were recorded for each soil…