A.03.09 Attachment 11 Appendix B - Final Geotechnical Report.pdf.pdf

REPORT OF GEOTECHNICAL EXPLORATION

POL – Increase Fuel Storage Capacity

Kecskemet Air Base, Bacs-Kiskun County, Hungary

Contract No. W912GB-16-D-0019

LHKE 180001

Prepared for:

Black and Veatch Special Projects Corporation

6800 W., 115th street, Suite 2200

Overland Park, KS, USA 66211

Prepared by:

Amec Foster Wheeler E & I GmbH

Weserstrasse 4, 60329 Frankfurt, Germany

February 16, 2018

Amec Foster Wheeler Project No. 580930001G

Amec Foster Wheeler E & I GmbH.

Weserstrasse 4, 60329 Frankfurt, Germany www.amecfw.com

February 16, 2018

Mr. Shaun Quigley Black & Veatch Special Projects Corporation 6800 W. 115th street, Suite 2200 Overland Park, KS 66211

Subject: Report of Geotechnical Exploration POL – Increase Fuel Storage Capacity Project

Kecskemet Air Base, Bacs-Kiskun County, Hungary Contract No. W912GB-16-D-0019

LHKE 180001

Amec Foster Wheeler Project No. 580930001G

Dear Mr. Quigley:

Amec Foster Wheeler E & I GmbH (Amec Foster Wheeler) has recently completed the authorized geotechnical exploration for the proposed POL – Increase Fuel Storage Capacity project at the Kecskemet Air Base in Kecskemet, Hungary. This exploration was conducted in general accordance with Amec Foster Wheeler’s Geotech Scope POL, dated 14 July 2017, and authorized under BVSPC Agreement 17-5041 dated 25 September 2017.

The following report discusses our exploration, subsurface conditions, and provides recommendations for design and construction of the project.

We have enjoyed assisting you and look forward to serving as your geotechnical and construction materials testing consultant on the remainder of this project and on future projects.

If you have any questions concerning this report, please contact us.

Sincerely, Pieter J. DePree, P.E. Larry Sciple, P.G.

Sr. Assoc. Geotechnical Engineer Senior Geologist II Registered Georgia 19637 Registered Tennessee TN1573

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page ii

TABLE OF CONTENTS

1 INTRODUCTION

1.1 PURPOSE

1.2 SITE DESCRIPTION

1.3 PROJECT DESCRIPTION

2 DATA GATHERING

2.1 FIELD EXPLORATION

2.1.1 Soil Borings

2.1.2 Dynamic Penetrometer Heavy (DPH)

2.2 LABORATORY TESTING

3 SITE AND SUBSURFACE CONDITIONS

3.1 AREA AND SITE GEOLOGY

3.2 SUBSURFACE CONDITIONS

3.3 GROUNDWATER

4 ANALYSIS

4.1 SETTLEMENT

4.2 LIQUEFACTION AND EARTHQUAKE RELATED SETTLEMENT

5 CONCLUSIONS AND RECOMMENDATIONS

5.1 TANK FOUNDATIONS

5.1.1 Predicted Settlement

5.1.2 Recommendation – Ground Improvement by Preloading

5.1.3 Tank Footprint Preparation

5.1.4 Filling around the Enclosure

5.1.5 Other Foundation Approaches

5.1.6 Effect on Existing Tanks and other Facilities

5.1.7 Piping Connections

5.2 FILLED POND

5.3 SWELLING AND COLLAPSIBLE SOILS

5.4 LATERAL EARTH PRESSURE FOR ENCLOSURE WALL DESIGN

5.5 SITE GRADING

5.5.1 Excavation

5.5.2 Fill Placement

5.6 FROST ZONE

5.7 FUEL OPERATION BUILDING FOUNDATION

5.8 PAVEMENT DESIGN

5.9 UTILITY INSTALLATION

5.10 SEISMIC DESIGN

5.10.1 Site Class

5.10.2 Liquefaction

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page iii

5.10.3 Seismic Related Settlement

5.11 CORROSION POTENTIAL

6 QUALIFICATIONS OF RECOMMENDATIONS

Figure 1: Field Exploration Plan POL A

Figure 2: Field Exploration Plan POL B Figure 3: Seismic Hazard Map Figure 4: Settlement Plate Detail Appendix A: Field Exploration including Boring Logs (with DPH) Appendix B: Laboratory Test Results Appendix C-1: Static Settlement Analysis Appendix C-2: Liquefaction and Earthquake Related Settlement Analysis ASFE Information on Geotechnical Reports

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 1

1 INTRODUCTION

Amec Foster Wheeler has completed the authorized geotechnical exploration for the proposed POL – Increase Fuel Storage Capacity project at the Kecskemet Air Base in Kecskemet, Hungary.

1.1 Purpose

The purpose of this study was to explore the subsurface conditions in the area of the two planned POL (petroleum, oil, and lubricants) tanks and related improvements and to analyze these conditions as they relate to proposed construction. This report briefly discusses our understanding of the project, describes our exploratory procedures, and presents our conclusions and recommendations.

1.2 Site Description

The Kecskemet Air Base was constructed in about 1951 under the Warsaw Pact. The base is centered around an approximately 2,500 meter long by 60 meter wide main runway (Runway 12- 30), oriented northwest to southeast (azimuth 120-300 degrees). Most of the air base support facilities including aprons, hangars, taxiways, fuel storage, munitions storage, warehousing, etc.

are located on the southwest side of the runway. Two POL facilities, POL A and POL B are located southwest of the runway, near the north end of the support area. Each POL facility includes two existing fuel tanks. Existing tanks were constructed in 2004-5 and are above grade but covered with a cone of soil for protection. Based on review of documents provided, we understand that the existing steel tanks are encased in concrete enclosures and supported on shallow mat foundations. Details of site preparation for the existing tanks, including ground improvement, if any, were not available.

The base is located at about elevation 115 meters above mean sea level. It lies in the Hungarian plain and the surrounding countryside includes agricultural and wooded tracts and is relatively level. The town of Kecskemet is located to the southwest of the airfield. Undeveloped areas within the base are generally grassed. A topographic survey was not available but, based on elevations from public sources, the overall site appears to have a few meters of relief, though the slopes are gentle.

1.3 Project Description

Our understanding of the proposed airfield improvements is based on documents provided by Black and Veatch (B&V) and serves as the basis for our recommendations. The primary construction at each of the two sites will be a 2.5 million liter capacity fuel tank. Detailed drawings of the proposed tanks were not available, but we assume the tanks will be similar to, though larger than, the existing tanks. The steel, interior tanks will be surrounded by a concrete enclosure about 22 meters in diameter with about a 1.3 meter access area between.

Like the existing tanks, new tanks will be at grade but covered with a cone of soil (termed “cut and cover”) sloping up the sides with about 1 meter on top of the concrete enclosure. The steel tank and concrete enclosure will be on a shared mat foundation or slab, with a slope toward the middle of the tank for the outlet piping. Soil fill around and over each tank is expected to total about 3,716 M3 (PDR page C-7) creating a footprint of about 79 meters in diameter to the outside edge of the cover. The fill is anticipated to have a compacted density in the order of 2 metric tons per cubic meter, though this could vary somewhat depending on the fill source, which is not known at this time. Total weight of each tank, fuel, enclosure, and soil is expected to be about 10,000 metric tons.

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At site A, the new tank will be located at least 72 meters (outer enclosure wall to outer enclosure wall) of the existing tanks and the soil cover will be about 20 meters from the soil cover of the existing tank. However, at site B the new tank will be only about 22 meters (out to out) of the nearest existing tank and the new soil cover will substantially overlap that of the existing.

In addition to the new tank at each of the two sites, other improvements will include a new 33 square meter fuel operation building as well as related fuel piping, other utilities, and pavements.

No grading plan was available, but the sites are relatively level, so the main earthwork is expected to be the burial of the tanks and backfill of various utility lines. Fill will be imported to the site.

Apart from the containment outer wall, no below grade walls are anticipated.

2 DATA GATHERING

2.1 Field Exploration

The exploration included borings, heavy dynamic penetrometer (DPH) in the two POL areas in and around new tank footprints, as follows:

1. Subsurface utilities and UXO were cleared by site personnel.

2. Eight borings, designated PB-01 through PB-08 were conducted at the approximate locations indicated on Figures 1 and 2. An offset boring (PB-05A) was conducted next to PB-05 for additional sampling.

3. Heavy Dynamic Penetrometer (DPH) probes were conducted adjacent to (about 1 meter offset) each boring to obtain consistency data on the subsurface materials.

The boring locations were marked in the field by the field geologist using a hand-held GPS device (positional error about 3-5 meters) and estimating distances and right angles from existing site features. As such, the boring locations shown on Figure 1 should be considered approximate.

The Soil Boring Records, in Appendix A, show the DPH penetration resistances and present the soil descriptions. The stratification lines and depth designations on the boring records represent the approximate boundaries between soil types. In some instances, the transition between soil types may be gradual.

2.1.1 Soil Borings

The borings were drilled by a Bohrgeraet DA-72 drill mounted on a MAN truck chassis. A sampling tube was driven into the soil using a percussion method with a pneumatic downhole hammer. Drilling was performed without the use of drilling fluid. Soil samples were extracted at one-meter intervals for observation, logging, and photo documentation by the field geologist and driller. Grab samples of representative materials were selected by the field geologist and placed in air-tight containers for transport to the lab. Thin-walled samplers were used to attempt to obtain relatively undisturbed samples at selected intervals, using similar techniques (driving).

Boreholes were left open overnight to obtain stabilized groundwater measurements and then backfilled with drilling spoils.

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2.1.2 Dynamic Penetrometer Heavy (DPH)

The DPH test was conducted in general accordance with DIN 4094. The DPH is widely used in Europe. The test consists of continuously driving a rod with a pointed tip with an area of 15 cm2 into the ground with a 50 kg hammer falling 0.5 M. The number of blows to drive each 10 cm increment is recorded. The tip has a slight bulge to break friction with the soil above. The test provides reasonable correlation with Standard Penetration Test (ASTM 1586) and a variety of soil mechanics parameters in some conditions, notably at shallow depths above the groundwater.

However, at depth and especially below the water table, soft or loose soils can collapse around the rod, increasing the driving resistance. As the operators cannot detect this collapse, soft or loose materials may not be detected as the high driving resistance may indicate either a high tip resistance and no shaft friction or low tip resistance and elevated shaft friction due to collapse of soils at some point above the increment.

2.2 Laboratory Testing

Laboratory testing included classification tests (moisture content, grain size, and plasticity), strength tests (unconfined compression), compressibility (Consolidation) tests of fine grained samples, California Bearing Ratio tests for pavement support, and moisture/density (Proctor) tests. Results are included in Appendix B and indicated on the boring logs in Appendix A.

3 SITE AND SUBSURFACE CONDITIONS

3.1 Area and Site Geology

The Kecskemet Air Base lies in the Pannonian Plain, an ancient sea filled with several kilometers of sediments of Paleogene to Holocene Age. The stratigraphy is characterized by a Tertiary basin-fill sequence resting on a highly deformed substrate of Proterozoic, Paleozoic, and Mesozoic rocks of the Inner Carpathian foldbelt. The sediments derive from the surrounding mountainous areas and include gravels, sands, and fines. Near surface materials have been altered in the recent past by aeolian and alluvial processes as well as over a thousand years of cultivation. In the late 18th century, overgrazing denuded the area such that aeolian transport occurred.

3.2 Subsurface Conditions

The subsurface conditions discussed in the following paragraphs and those shown on the soil Test Boring Records represent an interpretation of the field and laboratory data using normally accepted geotechnical engineering judgments considering local geology and experience.

The Boring Logs in Appendix A represent our interpretation of the field conditions based on the field geologist’s classification of the core samples confirmed by subsequent laboratory testing and DPH results. The lines designating the interfaces between various strata represent approximate boundaries only, as transitions between materials may be gradual. Soil conditions may vary between and away from the boring locations.

Borings generally encountered a layer of slightly organic topsoil or cultivated soil at the surface, likely related to recent agricultural activity. Borings in the POL A area encountered up to about 6 meters of very loose, sandy fill, which may represent fill placed in a former pond in that area. A zone of finer grained material was encountered at the base of the fill which may be a pond liner or accumulated fine grained pond sediment.

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The natural soils below the topsoil were primarily poorly graded fine sand but contained variable fractions of generally low-plasticity fines. Some zones of predominantly silty or clayey soils, generally of low to moderate plasticity, were encountered at depth, but sandy layers appear to predominate through the profile. Soil densities were generally above the range expected for collapsible soil (< 1.6 gm/cm2) and the water table is shallow so that soils are generally saturated and so cannot be collapsible. Observation of samples and DPH data indicated the natural soils were generally of moderate consistency.

3.3 Groundwater

Groundwater was encountered in all the borings and stabilized rapidly in the generally sandy soils at depths of 1.2 to 2.5 meters. Once topographic information becomes available, groundwater elevations and gradients can be developed.

Groundwater levels can fluctuate with changes in weather, drainage, and ground disturbance in the area. The relatively flat terrain, shallow groundwater, and generally sandy soils suggest that groundwater levels at the site will be closely related to local rainfall. Kecskemet has a relatively dry climate, with average annual rainfall of about 60 cm and monthly rainfall typically between about 3 and 8 cm. September and October are typically the driest months, so groundwater levels during our exploration in November were probably low relative to seasonal highs.

4 ANALYSIS

Analyses included settlement analysis of the tanks at the two POL sites due to consolidation of underlying soils as well as analysis of liquefaction and earthquake related settlement.

4.1 Settlement

Unisettle® software was used to estimate settlement at the center and edges of the proposed tanks as well as key points (existing tanks) near the proposed tanks. Soil compression properties were estimated from field and laboratory data. The tanks were modeled using step-wise approximations, essentially a three layer system to simulate the conical tank and fill. Software output is included in Appendix C-1.

4.2 Liquefaction and Earthquake Related Settlement

Calculations of liquefaction potential and related settlement of nearly liquefied soils were calculated based on published methods. Calculations are included in Appendix C-2.

5 CONCLUSIONS AND RECOMMENDATIONS

The following evaluations and recommendations are based upon the previously presented project information and data obtained in this exploration, and our previous experience with similar projects. If the structural information is incorrect, or if the location of the proposed construction is changed, please contact us so that our recommendations can be reviewed and modified, if necessary.

The discovery of site and/or subsurface conditions during construction different from the data obtained in this exploration should be reported to us for our evaluation. The assessment of site environmental conditions or the presence of pollutants in the soil, rock, or groundwater of the site is beyond the scope of this geotechnical exploration.

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5.1 Tank Foundations

The key geotechnical issues with this project will be support of the new tanks and impact of the new tank loads on one of the existing tanks at Site B. The weight of the fuel, tank, and enclosure, probably in the order of 2,500 metric tons, is a relatively small part of the total weight of the new construction, with the main portion being the weight of about 3,700 cubic meters of fill, likely at a moisture conditioned density in the order of 2 metric tons per cubic meter or 7,400 metric tons.

The total load of fuel plus dead load of the steel tank, concrete enclosure and foundation, and soil will produce a total added load on the tank footprint in the order of 10,000 metric tons.

5.1.1 Predicted Settlement

Nearly all of the load (soil fill and fuel) will be placed after the tank is constructed, so that the tank and containment will experience the full magnitude of settlement. Based on our field and laboratory testing and assuming the weight of tank, enclosure, foundations, and backfill at 10,000 tons over the footprint indicated, we anticipate on the order of 28 cm of settlement of the planned tank at Site A and 23 cm at Site B. Assuming backfill is placed uniformly around the tank (such that the difference between the backfill level on different sides of the tank at any time is 60 cm or less), differential settlement within the tank footprint at POL A is expected to be about 4 cm. Since there is some existing fill associated with the existing tank on the west side of the new tank at POL B, the weight of additional fill to be placed on that side will be less, which will increase the potential differential settlement to about 6 cm at the POL B tank.

The large footprint of the new tanks and fill around them will increase vertical stresses in the soil profile to a considerable depth. Most of the soil profile beneath the tanks is relatively low-compressibility (medium dense to dense sand) but much settlement will come from consolidation of layers of more compressible, fine-grained materials (silty and clayey) at depth. Sandy soils above and below these layers will allow relatively rapid drainage of the fine-grained layers, so that most consolidation and settlement should occur within 8-10 weeks after the full load is in place.

At Site A, more settlement is expected due to the upper 6 meters of the profile that appear to be sandy backfill of a former pond, which, based on the DPH data, may have been placed without engineering control and compaction. This sandy backfill, apparently relatively free of fines will compress/consolidate rapidly, as porewater can exit laterally and upward if the thin zone of possible pond liner or fine-grained sediments inhibits downward drainage.

5.1.2 Recommendation – Ground Improvement by Preloading

We anticipate settlement of the magnitude predicted will be unacceptable for the new tanks. To reduce settlement for the planned new tanks, we recommend preloading. Preloading would involve placing a load similar to the planned new tank/soil load (about 10,000 metric tons, based on available information) and allowing consolidation of the underlying soil to occur, then removing the load and constructing the tanks. The planned imported fill for cover of the two tanks could be used to preload one tank location then moved to preload the other location. Preload can be placed in approximately the shape of the finished tank/fill. The fill planned for the other tank site can replace the volume of the tank enclosure. Preload need not be compacted, but the surface should be sloped and rolled to promote runoff so the fill does not become excessively wet, which could delay its later compaction.

Settlement plates (see Figure 4) should be placed prior to preload placement and monitored prior to, during, and after preload fill is placed to allow a determination of when settlement has largely ceased. When settlement has ceased, preload can be removed, the bearing area prepared, and tank construction begun. The profile contains numerous sandy layers between finer grained

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 6 layers, so the duration required for preloading should be in the order of 8 weeks after placement of the full preload.

Assuming settlement is largely complete before pre-load is removed and the exposed surface is prepared so as to avoid/repair any disturbance, total settlement of the new tanks/enclosures should be limited to about 3 cm or less over the life of the structure due to potential slight fluctuation in groundwater levels, slight rebound after pre-load removal, and long term secondary compression. A modulus of subgrade reaction (k) of 4 MPa/M may then be used for mat design.

5.1.3 Tank Footprint Preparation

Preload will improve the overall soil profile, but greater improvement will likely be required on the soils immediately below the tank to provide a stable working surface for foundation construction and fill compaction. To this end, either before placement of the preload or after the preload is removed, the topsoil, including root systems should be removed. The area should then be proofrolled with a fully loaded, tandem axle dump truck (gross vehicular weight about 25 metric tons) under the observation of the geotechnical engineer who can recommend measures to address any areas of rutting or instability noted. Such measures may include rolling with heavy compaction equipment, undercut and replacement with compacted fill, and stabilization with geotextile or large, angular stone (20-40 cm). Shallow (~1-2 meter), short duration dewatering using sumps may be required to achieve local undercut. At POL A, most of the footprint will likely require such measures to improve the pond fill.

5.1.4 Filling around the Enclosure

Although preloading will substantially reduce expected settlement, we recommend placement of fill around the new tank enclosure be conducted uniformly, with no more than 60 cm of variation in the fill level around the tank during filling.

5.1.5 Other Foundation Approaches

Other approaches are possible and may save somewhat on the schedule, but have significant drawbacks so are not recommended. Note that any but the first option will involve some schedule impacts, though possibly less than preloading. Other approaches include:

1. Tank construction without ground improvement – if settlement in the order of that predicted is tolerable, the tank could be constructed without special measures.

2. Undercut and replacement – ground improvement by undercut and replacement with less compressible material would have little effect, since most settlement will occur due to compressible soils well below practical excavation depths.

3. Deep foundations – deep foundations such as bored piles or driven precast, steel pipe or H-sections could be considered. These would be subject to considerable downdrag which would reduce their capacity. Some settlement would still be expected, depending on the pile lengths, due to the effect of the pile group on deeper compressible zones. Pile selection will require balancing spacing in the tank foundation mat/pile cap, tolerable settlement, and pile length considering capacities that can be developed from side friction (little end bearing will be available) for various pile types and installation methods.

4. Rigid Inclusions – Rigid inclusions are vertical elements similar to piles but installed without direct connection to the tank foundation to reinforce the foundation soils, improve

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 7 the modulus of the profile, and reduce settlement. Compaction grout columns serve a similar function.

5. Stone columns – Stone columns are like rigid inclusions but using stone (gravel) rather than rigid elements to replace a portion of the compressible soils and improve the overall modulus of the foundation zone.

6. Smaller tanks – construction of multiple, smaller tanks (similar to the existing) to provide the same capacity could be considered. Tanks with smaller footprints and less load would produce significantly less settlement. Existing tanks are understood to have performed acceptably so either withstood settlement or had prior ground improvement. Tanks should be spread out to minimize interaction.

7. Alternate protection – The soil fill protection around and over the tanks is a significant driver of settlement concerns. If alternative approaches not involving this fill load are available, settlement risk may be less. For example, the total weight of an enclosure twice as thick will be considerable less than the weight of soil fill.

8. Dewatering – lowering groundwater in the new tank footprints could produce effects similar to preloading. The most compressible zones are fine grained and will drain slowly.

However, the thick zones of relatively permeable (sandy) soil will produce large volumes of water such that it is likely impractical to pump sufficient water quantity to achieve effective drainage and drawdown. The radius of effect of dewatering is likely to be much greater than for preloading, and could cause settlement of the existing tanks and structures farther from the new tanks.

9. Other ground improvement options – a range of other ground improvement options are available, including other grout injection techniques, dynamic compaction, vibroflotation, etc. However, these are generally poorly suited to conditions and/or less effective than methods described in the previous sections.

5.1.6 Effect on Existing Tanks and other Facilities

Construction and filling of the new tanks, or preloading, will produce settlement in the area around the new tanks. Significant settlement due to the new tanks and fill loads could impact existing tanks and other existing structures, including roads, utilities, etc. in the immediate vicinity, generally a radius of about 70 meters from the center of the new tank.

We anticipate the existing tanks experienced some settlement in the weeks and months after their construction and filling. Drawings do not indicate deep foundations, but it is possible that some form of ground improvement may have been used to limit the settlement at the time of the existing tank’s construction and was not indicated on the available documents. Since the existing tanks are smaller with less soil backfill, they have significantly less total load and smaller footprints than the planned tanks. Therefore, vertical stress increase through the profile is less and decreases with depth more quickly than predicted for the new tanks, such that settlement of those tanks may have been significantly less and so tolerable. Survey comparison of current tank elevations to the as-built elevations (if available) along with estimates of the existing tank loading would provide valuable data for confirmation of our settlement calculations.

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Assuming subsurface conditions under the nearby existing tanks are similar to the boring data and no significant ground improvement was performed under the existing tanks, the new tank and related fill at POL B will produce significant settlement of the easternmost of the two existing tanks (nearest the new tank), in the order of 7 cm on the east side of the existing tank and about 2 cm on the opposite side. Therefore, the northeastern existing tank at POL B could experience considerable differential settlement, in the order of 5 cm, during construction and filling of the new tank there. This settlement would be in addition to any settlement of the existing tanks that may have occurred to date. For the western tank at POL B and at POL A, the separation of the existing tanks to the new tanks is greater, so settlement of the existing tanks should be in the order of about 2 cm.

We recommend establishing a tolerance for additional settlement of all of the existing tanks and then monitoring the existing tank’s settlement by means of monuments fixed in or on the enclosures during placement of pre-load. Should settlement magnitude approach acceptable limits, the pre-load could be removed pending implementation of other measures.

At POL B, we recommend relocating the new tank farther from the existing tanks. A separation of 70 meters from the existing edge of enclosure to the proposed edge of the new tank enclosure will largely eliminate the risk, though lesser separation would reduce the risk/settlement magnitude as compared to the current planned separation of less than 20 meters edge to edge.

If relocation is not possible and the settlement of the expected magnitude is unacceptable, ground improvement could be conducted beneath the existing tank or tanks. Some ground improvement measures, notably compaction grouting, can be conducted in tight areas with minimal intrusion.

Improvement would need to be substantial (and hence will be costly) due to the large loads and depth of the zone requiring treatment. Additional investigation of conditions at the existing tank is recommended for design of the compaction grouting.

Compaction grouting involves injecting low-mobility (near zero slump) cementitious grout into the subsurface using injection rods driven to depth. The method produces a column of grout surrounded by improved soils at each injection location. Angle drilling could be used to treat zones beneath the steel tank from within the enclosure access. Grout injection can be used to lift settled structures to some degree, and the existing tanks which are founded on relatively rigid mats should be robust and so likely to withstand high grout pressures. Treatment should consider possible issues associated with differential support of the existing tank foundation/mat. Grout columns/injection may be required under the whole mat, though possibly at wider spacing in areas farther from the new tank. Grouting will improve the soil profile and reduce (though not eliminate) expected settlement.

Alternately, deep foundations such as micropiles could be advanced into the subsurface through the existing enclosure or tank. Low headroom measures, such as micropiles are likely possible.

Depending on the existing mat and its ability to span, piles would likely need to be installed under the tank area as well as under the enclosure, requiring the tank to be taken out of service to allow access to the interior for pile installation.

For new and existing roads, settlement may impact drainage. Settlement may impact gravity utilities (sewer and storm drain) but the gradual settlement expected is unlikely to damage most utility lines. Measures to prevent/limit settlement of pavements and utilities are likely to be much more costly than repairs. The most practical approach is likely to monitor critical lines, delay installation of new lines, roads, and other structure until preloading is completed, and conduct any

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 9 necessary repairs near the end of the project. Such repairs may include fine grading and repaving to restore surface drainage and, possibly, replacement of some utility lines.

5.1.7 Piping Connections

A common practice with above ground tanks subject to settlement is to make settlement sensitive piping connections after the tank has settled, but we anticipate that, for this project, most of the pipe connections will need to be made prior to filling around the enclosure, which will produce most of the expected settlement.

5.2 Filled Pond

Base personnel reported that the tank location at POL A is underlain by a former pond which was filled at some time in the past. Borings encountered loose, sandy fill with a layer of finer grained material near the bottom that may have been a liner or accumulated fine sediment in the former pond. The pond/fill extends to over 6 meters in PB05 and may be deeper elsewhere. The extents of the former pond are not known, but over 4 meters of apparent pond fill was encountered in PB06 and slightly less in PB07. PB08 encountered about a meter of fill, which may or may not be related to the pond.

Assuming the pond was filled with sandy material as encountered in the borings and generally free of significant trash or organic matter, pre-loading should effectively consolidate and improve the fill to allow tank construction. The sandy fill should drain rapidly – within the time anticipated for preloading to consolidate deeper fine layers. We recommend review of any available records as well as excavation of at least 3 test pits within the tank footprint to increase confidence that pond fill is free of trash, debris, logs, topsoil, etc., though there would remain a risk of such materials beneath the pond. Decay of organic debris below the zone of groundwater fluctuation will occur very slowly, so small amounts of such material remaining below the groundwater should not have a significant impact on tank settlement.

Overexcavation of the entire pond fill would reduce risk of organic debris or other deleterious material being left beneath the tank. To excavate 6 meters or more, when groundwater is at about 2 meters and may be higher during construction, would require extensive dewatering. The goal of dewatering should be to lower the groundwater to at least 1 meter below the anticipated bottom of the excavation to allow stabilization for equipment access and maintain side slope stability.

Dewatering to 7 meters is approaching the limit of effective well-point vacuum systems, so more than one level of well points may be required.

If the pond was lined and the liner is intact, it could aid in dewatering by limiting inflow, depending on the pond size. If no liner is present, volumes of groundwater entering the pond could be considerable given the relatively permeable sandy soils.

Drawdown of water in the pond area could lower groundwater for a considerable distance around and potentially cause damaging settlement of the existing tanks, roads, or other structures in the area.

If overexcavation of the pond is envisioned, we recommend at least 1 pumping well test to better assess the aquifer flow characteristics of the shallow soils. This will aid in design of a dewatering system which will likely include well-points, possibly on at least 2 levels and possibly a cut-off wall around the pond to limit inflow for practical pump capacity and/or to limit the radius of effect and potential impacts on existing construction.

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5.3 Swelling and Collapsible Soils

Plastic clays can undergo volume change with changes in moisture content, causing swelling, heave, or settlement. The climate in Kecskemet is relatively dry, but rainfall is well distributed throughout the year and, as noted, groundwater is relatively shallow. Little plastic clay was encountered in the borings at depths shallow enough to allow moisture content change. If pockets exist at shallow depth, we anticipate they can be detected during site preparation.

Some soil deposits can be collapsible, that is, the soil particles are cemented (typically by lime or clay) into a low-density, high void ratio configuration but, when wetted, experience a significant void ratio change (collapse). This is common in aeolian deposits (loess), which may be present in the Kecskemet area. Collapsible soils would not occur beneath the seasonal high groundwater.

Indications of collapsible soil, such as cementation, were not noted in our field investigation and in-situ density measurements in the soils were above the range where collapse is expected.

Further observations of subgrade are warranted, but the risk of collapsible soils at the site should be low.

5.4 Lateral Earth Pressure for Enclosure Wall Design

No below grade walls are anticipated, but imported backfill will be placed over and around the proposed tank enclosures. The tank enclosure walls are not anticipated to be flexible so will be subject to the at-rest lateral earth pressure. The at-rest earth pressure will depend on the material imported, but assuming a relatively clean fine sand (SP or SP-SM), as is common in the area, we anticipate the compacted material will have an angle of internal friction of at least 30 degrees and a unit weight (moist) of about 2 gm/cm2. This would give a coefficient of at-rest lateral earth pressure of 0.5 and an equivalent fluid unit weight of 1 gm/cm2. No special drainage requirements are anticipated for the sandy fill, however, if fill with greater fines content is used, we recommend drainage be installed around the base of the enclosure wall to prevent hydrostatic pressures on the enclosure wall. Design parameters described should be confirmed once the borrow source is determined.

5.5 Site Grading

We anticipate site grading will be limited due to the relatively level site. Apart from treating the former pond at POL A, the main grading activities are expected to include excavation and backfill of utility trenches and placement of the fill around the tank enclosure at each site.

5.5.1 Excavation

Except for possible excavation of the former pond as discussed above, excavation at the POL sites is expected to be limited to shallow trenches for utilities. Soils can generally be excavated with conventional equipment (excavators, pan-scrapers, loaders). The most significant excavation difficulty anticipated will be groundwater if the pond at POL A is to be excavated, as discussed above. Shallow excavation for piping and other utilities is unlikely to encounter groundwater. If groundwater is encountered in shallow excavations, the geotechnical engineer can observe conditions and recommend dewatering measures, which will likely include shallow local sumps. If the work is conducted during relatively dry weather, excavation should be routine.

We recommend segregating soils during excavation into select granular soils (SP or SP-SM, generally less than 12 percent fines) for use in pavement subgrade, other inorganic soils for general fill, and organic or other deleterious soils for wasting or re-use as topsoil in final site stabilization.

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 11

5.5.2 Fill Placement

Granular material (SP or SP-SM soils) should be used for the pavement subgrade, defined as a zone at least 60 cm thick beneath planned pavement and extending 60 cm horizontally outside the pavement limits. The thickness of the subgrade may need to be greater based on pavement design requirements, including vehicle loads and frequency of operations, but we recommend not less than 60 cm be considered in the subgrade zone. Outside this zone, a wider range of soils should be acceptable for fill for other site grading including fine grading outside the pavement areas, replacement of undercut below the pavement subgrade zone, backfill of utility trenches, revetments, blast containment berms, etc.

Fill for general grading should be low plasticity (PI less than 30) soil generally free of organic matter and other deleterious materials and rock fragments larger than 3 inches in any dimension.

Most site soils should meet these criteria, except for topsoil (both at the current surface and buried in some areas). Fill should be placed in maximum 200 mm thick loose lifts assuming standard heavy compaction equipment (at least 10,000 kg operating weight, Cat CS54 or similar). Lighter equipment should be used within about 3 meters of the enclosure wall and in utility trenches or areas inaccessible to the heavy compactors. If lighter equipment is used, thinner lifts may be required to achieve compaction. Fill placed over and around the tanks and other site fill outside the pavement or foundation subgrade zone should be compacted to at least 95 percent of the MPMDD (soil's maximum dry density as determined by the modified proctor compaction test - ASTM D 1557 or AASHTO T180 or approximate Hungarian Equivalent of MSZ 14043-7:1981).

Within the pavement subgrade zone, fill should be compacted to 100 percent of MPMDD.

Pad-Foot or Sheep’s Foot rollers are required for silty or clayey soils (SM, SC, ML). Smooth drum vibratory rollers should be used for granular (SP, SP-SM) soils and to roll down the surface at the end of each shift to reduce surface water infiltration.

Soil moisture during placement should be maintained within three percent above or below the optimum moisture content as determined by ASTM D1557. The contractor should be prepared to adjust moisture contents by wetting or drying of the soils. Relatively clean sands (SP or SP-SM) should drain and dry rapidly, but greater drying effort may be required for soils with greater fines content, especially those excavated from near the groundwater.

Laboratory testing of proposed fill will be necessary during site grading to evaluate the compaction characteristics of the fill. All fill placement should be witnessed by a qualified soils technician under the direction of the geotechnical engineer who should make periodic density tests, at least one per 5,000 M2 of pavement area or 30 linear meters of trench backfill. Areas that do not meet the compaction specifications should be reworked to achieve the specified density and retested for compliance.

Fill material should be placed in horizontal lifts and adequately keyed into stripped and scarified subgrade soils. In confined areas such as utility trenches, portable compaction equipment and thin lifts of three to four inches may be required to achieve specified degrees of compaction.

Given the disparity in permeability between the subgrade fill and some of the natural soils with more fines, care should be taken to avoid forming subsurface traps where water could accumulate and be trapped in the subgrade fill. Anticipated drainage measures (edge drains or French drains) should substantially address this risk.

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5.6 Frost Zone

The PDR reports frost depth at 51 cm. Other sources (L. Gaspar, 1959) give depths as great as

0.9 meters in Budapest, which is at a similar elevation in the Hungarian Plain about 80 km north of Kecskemet. In either case, the frost line should fall within the SP or SP-SM subgrade zone if not the pavement base, which, with drainage measures and treatment as described above should provide acceptable frost resistance. Utilities should generally be buried beneath the frost depth, unless other protection measures are provided, including frost resistant bedding.

5.7 Fuel Operation Building Foundation

Details of the fuel operation building loadings were not available, but we anticipate a pre-fabricated one-story structure with relatively low foundation loads. We recommend the building footprint be treated as for pavement areas, with a minimum of 60 cm of compacted granular (SP or SP-SM) fill beneath the footings. Footings should bear at least 60 cm below finished grade.

Footings for the building may be shallow spread or continuous foundations designed for a maximum allowable bearing pressure of 1,500 pounds per square foot (psf) based on total load.

We recommend widths of not less than 60 cm for footings for ease of construction and to eliminate the possibility of localized shear failures.

A qualified geotechnical engineer should observe the footing or mat excavation and assess if the further improvement in the footings may be required. Such improvement would likely consist of overexcavation and replacement with additional select fill. The maximum depth of overexcavation will depend on actual footing loads and dimensions, but we anticipate it would be 2 meters or less. Footing concrete should not be placed on wet or frozen subgrade.

5.8 Pavement Design

Relatively small changes in fines content of soil can have significant impacts on the pavement soil support values. For SP and SP-SM soils, the fines content is such that compaction tends to force the larger sand particles into intimate contact, with finer particles in spaces between the sand. Thus, the soil support/CBR/modulus of subgrade reaction are relatively constant through the range of fines content from about 0 to 12 percent. The fines generally do not completely fill voids between sandy particles, so acceptable drainage is maintained. However, with increasing fines content, sufficient fines are present to separate and fill voids between the sandy particles, so that permeability and soil support values decrease significantly. At about 25 to 30 percent fines in fine sand, the drainage and soil support values may be little different from soils that are primarily silt or clay soils.

Laboratory testing confirmed this range, with CBR values ranging from 1.1 to 13.8. Plate load test results on SP soils returned values of about 100 and 250 MPa/M at locations near TB-04 and TB-10 respectively.

Assuming that the subgrade zone soils consist of in-situ SP or SP-SM soils prepared and densified as described above or SP/SP-SM fill placed and compacted per the recommendations above, we recommend design based on a modulus of subgrade reaction of 80 MN/M3 (~300 pci) or a CBR value of 12.

5.9 Utility Installation

Excavation for trenches for shallow utilities such as power for lighting should be routine and possible using conventional equipment. Shallow groundwater may be encountered. Utilities should be designed considering possible buoyancy issues during seasonal high groundwater.

Report of Geotechnical Exploration – POL – Increase Fuel Storage Capacity, Kecskemet Air Base, Hungary February 16, 2017 Project No. 580930001G Page 13

Deeper utility excavations, such as for stormwater or other gravity lines, will likely require substantial dewatering and shoring measures.

5.10 Seismic Design

The Kecskemet Base is in a relatively low seismicity area. Figure 3 and Global Seismic Hazard Assessment Program (GSHAP) indicate the 475-year return period PGA of about 0.11g at Kecskemet. Other sources (see References, Appendix C-2) indicate a horizontal PGA of 0.2g and a vertical PGA in excess of 1.0g in a 1911 seismic event in the area, but we understand that USACE concurs with use of the 0.11 g as the design PGA.

5.10.1 Site Class

As noted above, DPH correlations to SPT can be unreliable below the groundwater. Also, DPH were not able to penetrate to 30 M. However, based on DPH data as well as observations of the soil cores, the natural profile appears to be Site Class D. IBC allows use of Site Class D if evidence of liquefiable soils is not present, therefore, Site Class D may be assumed for seismic design of POL B. Based on DPH and boring information, the pond fill will render POL A site a Site Class E (for very loose pond fill soils) and Site Class F (for liquefaction potential of the very loose pond fill soils). We anticipate preloading will improve these soils considerably to allow design based on Site Class D. Direct shear wave velocity measurement using various geophysical techniques (such as Spectral Analysis of Surface Waves) can be used to further assess site class and liquefaction potential after preloading.

5.10.2 Liquefaction

Liquefaction occurs when excess pore pressures develop due to earthquake shaking, causing a substantial loss of shear strength in the affected soils. Soils that liquefy may flow to the surface, causing loss of support for overlying structures. Liquefaction risk is a function of the degree of shaking (normally measured as a Peak Ground Acceleration or PGA) but also the duration of shaking or number of cycles of shaking near the PGA, which can approximately be correlated to earthquake magnitude. Liquefaction risk is greatest for saturated, low-consistency, sandy soils with low fines content and decreases rapidly with increasing soil density and fines content.

Based on calculations (see Appendix C-2) a PGA of 0.11g for short duration (magnitude ~5.6, likely 2-3 significant cycles near PGA) seismic events is unlikely to produce significant liquefaction. This is confirmed by reports of the 1911 event, where only one small area of liquefaction (sand boil) was noted in or near Kecskemet. Few if any cases of liquefaction within the design earthquake parameters (PGA = 0.11g and Magnitude ~5.6) have been documented.

For this project, calculations indicate the liquefaction risk is highest in the unimproved, very loose, sandy pond fill soils at POL A. Shallow soils at POL B are generally higher consistency and contain significant fines, such that liquefaction risk should be substantially…