GEO TECH REPORT_F-35 Hangar_2020-08-28_FINAL9-10-2020.pdf

GEOTECHNICAL ENGINEERING REPORT

Air National Guard F-35 Hangar Facility

Truax Field

Madison, Wisconsin

GESTRA Project No.: M20046-10

September 10, 2020

Prepared For:

Hanson Professional Services, Inc.

13801 Riverport Drive, Suite 100

Maryland Heights, MO 63043

Geotechnical Engineering Report

Air National Guard F-35 Hangar Facility

GESTRA Project No. M2046-10

September 10, 2020

Prepared For:

Hanson Professional Services, Inc.

277 W. Nationwide Blvd.

Columbus, OH 43215

Prepared By:

GESTRA Engineering, Inc.

2223 Industrial Drive

Monona, WI 53713

(608) 222-9406

Table of Contents

1.0 INTRODUCTION

1.1 PROJECT INFORMATION

2.0 SCOPE OF WORK

3.0 EXPLORATION RESULTS

3.1 SITE CONDITIONS

3.2 PEDOLOGICAL INFORMATION (USED IN PAVEMENT DESIGN)

3.3 SUBSURFACE SOIL PROFILE

3.4 GROUNDWATER OBSERVATIONS

3.5 LABORATORY TEST SUMMARY

4.0 ANALYSIS AND RECOMMENDATIONS

4.1 GEOTECHNICAL CONSIDERATIONS

4.2 SITE PREPARATION

4.3 FOUNDATION RECOMMENDATIONS

4.3.1 SHALLOW FOUNDATIONS

4.3.2 ALTERNATIVE FOUNDATION OPTIONS

4.4 FLOOR SLAB RECOMMENDATIONS

4.5 SEISMIC SITE CLASSIFICATION

4.6 LATERAL EARTH PRESSURES FOR BELOW GRADE WALLS

4.7 PAVEMENT DESIGN

4.8 SITE EVALUATION OF STORM WATER INFILTRATION

4.9 SOIL CORROSIVITY

4.10 CONSTRUCTION CONSIDERATIONS

5.0 EXPLORATION AND TESTING PROCEDURES

5.1 LAYOUT AND ELEVATION PROCEDURES

5.2 FIELD TESTING PROCEDURES

5.3 LABORATORY TESTING PROCEDURES

STANDARD OF CARE

APPENDIX I BOREHOLE LOCATION MAP, TEST BORING LOGS, SOIL AND SITE

EVALUATION – STORM FORMS, GENERAL NOTES AND SOILS

CLASSIFICATION

APPENDIX II LABORATORY TEST RESULTS

APPENDIX III WEB SOIL SURVEY

APPENDIX II RESULTS OF FIELD RESISTIVITY AND PLATE LOAD TESTS

© GESTRA Engineering, Inc. 2020

Page 1 M20046-10

Geotechnical Engineering Report

Air National Guard Medical Readiness Building

1.0 INTRODUCTION

GESTRA Engineering, Inc. (GESTRA) was authorized by Hanson Professional Services, Inc.

(Hanson) to complete a subsurface exploration and geotechnical engineering report for the new

Air National Guard (ANG) F-35 Hangar Facility located at Truax Field in Madison, Wisconsin.

This report presents the results from the subsurface soil exploration and describes the field exploration, laboratory test results, and provides recommendations pertaining to the design and construction of the proposed building and new pavements.

The engineering recommendations and analysis contained within this report are based on the following project information which is a projection of GESTRA’s understanding of the project. If for any reason the actual project information differs from what is reported below, GESTRA should be contacted so that we can review our recommendations in light of any new information.

1.1 PROJECT INFORMATION

The project will include the construction of a new 3-Bay Hangar Facility with asphalt access roads surrounding the building.

The building is planned to be located in the area south of Building 414 within the ANG facility.

The floor slab will be at an approximate elevation of 857.5 feet. The maximum load at a typical structural column is planned to be approximately 120 kips. There will be one location where the anticipated column load will be approximately 220 kips. Maximum walls loads are anticipated to be 4.6 kips per linear foot.

The apron and access road to the apron are the only areas expect to have F-35 traffic. The pavement for the apron will consist of 12 inches of concrete over 6 inches of aggregate and the pavement for the access road to the apron will consist would consist of 4 inches of asphalt over 8 inches of aggregate. It is our understanding that the weight of the F-35 vehicle when loaded are between

45,000 and 70,000 pounds.

The pavement area northeast of the eastern bay and on the northwest side of the western bag will consist of 3 inches of asphalt, over 6 inches of aggregate and a 4 inch drainage layer. These areas are expected to only have small military and delivery vehicle traffic.

2.0 SCOPE OF WORK

GESTRA has performed the following services for the project:

Contacted Diggers Hotline to locate public utilities at the site.

Staked borehole locations in the field using tape and stake methods. Elevation and coordinates of boring locations B-2 through B-3 were determined by using a Geomax

Zenith 35 GNSS-INS receiver and referenced to Wisconsin Carrier Registration System

ANG F-35 Hangar Facility September 10, 2020

Page 2 M20046-10

(WisCRS) Dane County (NAVD88). Elevation for boring B-1 was estimated from the topographic map on the Dane County LIO website.

Completed a total of four (4) standard penetration test (SPT) soil borings, 3 to a depth of

31 feet and 1 to a depth of 76 feet. At the completion of drilling, the spoils produced from the drilling activity were containerized in 55 gallon drums and the boreholes were abandoned per WDNR requirements.

Performed laboratory soil testing to assign classification and engineering properties to the soils encountered. Laboratory testing included hand penetrometer, moisture and organic content, hydrometer, modified Proctor, California Bearing Ratio (CBR) test, pH and Miller

Box resistivity. GESTRA subcontracted Testing Engineers International, Inc. to perform sulfate testing.

Subcontracted GEI Consultants, Inc. to preform field Electrical Resistivity and Static Plate

Load Testing.

Prepared this geotechnical engineering report presenting the results of the field and laboratory testing as well as providing the following recommendations:

a. Building: recommendations for shallow foundations, allowable soil bearing capacity, estimates of settlement, floor slab recommendations, recommendations for compacted aggregate piers and helical piers, seismic site classification, site preparation/ soil correction and construction considerations.

b. Pavement: soil parameters for the pavement design consisting of an estimated CBR value for design of asphalt pavement, and subgrade modulus of soil reaction value for design of rigid pavement (including hangar floor slab).

c. Storm Water Feature (Drainage Layer below Pavement): soils were classified per the USCS system and the Field Book for Describing and Sampling Soils, USDA

NRCS, 2012, provided soil infiltration rates, and a discussion to the design and construction of the drainage layer.

3.0 EXPLORATION RESULTS

3.1 SITE CONDITIONS

The existing site has a concrete drive along the southeast side of the existing building (Bldg. 414).

On either side of the drive, the area is grass covered with a parking lot south of the project site. On the northwest side of the building the area is grass covered. Based on the topographic map on the

Dane County Land Information Office website, the grade of the site is relatively flat. The ground surface elevation at the boring locations varied between 855 and 857 feet.

Historical aerial photos indicate that the site was farm fields in 1937. By 1954, the surrounding area was developed for the Truax Air Field and access roads and a small building were constructed surrounding the project site. By 1968, a hangar building, which is currently there, was constructed north of the project site. By 1995, Building 414 and the road southeast of the building was constructed. By 2005, the parking lot and by 2010 the building south of the site were constructed.

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3.2 PEDOLOGICAL INFORMATION (USED IN PAVEMENT DESIGN)

The USDA NRCS Web Soil Survey was used to research the pedologic mapping within the project limits. We have included the Web Soil Survey map in Appendix III of this report for your reference. Wacousta Silty Clay Loam was mapped within the project limits.

Wacousta series consists of very deep, very poorly drained soils formed in silty lacustrine sediments. These soils are in broad depressions and swales on till plains, moraines, and stream terraces. These soil types are considered common subgrade material, and have generally fair to poor strength characteristics.

3.3 SUBSURFACE SOIL PROFILE

All of the borings were performed in the grass landscaped areas. Four to twelve inches of topsoil was encountered at the surface. Fill was encountered in two of the borings, B-1 and B-2. The fill material consisted of clay soil to a depth of 3 feet at boring B-1, and mixture of granular soils (sand and gravel) to a depth of 7.1 feet at boring B-2.

The native soils consisted of a thin layer of clay soil near the surface. The native clay soil had moisture contents values between 17% and 23% and unconfined strengths between 1.0 and 2.5 tons per square foot (tsf). In boring B-1, a 9-inch thick organic clay layer was encountered below the clay. Loss on ignition content of the organic clay layer tested was 13.6%. Below the clay layer and organic clay, very loose to loose sand was encountered. The very loose to loose sand typically had N-values between 2 and 9 blows per foot (bpf). Between depths of 16 to 27 feet, the native very loose to loose sand soil became denser with N-values typically between 11 and 30 bpf. The medium dense sand was also observed to have a higher fine (silt) content.

Results of the field and laboratory tests and observations are depicted on the individual boring logs included in Appendix I. Soils were grouped together based on similar observed properties. The stratification lines were estimated by the reviewing engineer based on available data and experience. The actual in-situ changes between layers may differ slightly and may be more gradual than depicted on the boring logs. Subsurface and groundwater conditions can vary between borehole locations and in areas not explored.

It is important to note that the soil observations, fill depths and topsoil thickness estimates were made in small diameter boreholes. Therefore, it should be understood that thicker or thinner deposits of the individual strata are likely to be encountered within other portions of the project.

Furthermore, the estimation of strata thickness at a particular location can differ from person to person due to a sometimes indistinct transition between the soils encountered. Additionally, it must be recognized that in the absence of foreign substances and/or debris within the soil samples obtained, it is sometimes difficult to distinguish between natural soils and clean soil fill.

3.4 GROUNDWATER OBSERVATIONS

Groundwater observations were made during drilling operations. Groundwater was observed to vary between depths of 4 to 5 feet below the existing ground surface. Accurate water level readings could not be made at the completion of drilling, due to the driller using mud rotary drilling techniques and introducing drilling fluid into the borehole.

Groundwater level fluctuations may occur with time and seasonal changes due to variations in precipitation, evaporation, surface water runoff and local dewatering. Perched water pockets and a higher water table may also be encountered during wet weather periods, particularly in more

Page 4 M20046-10 permeable silt and sand seams or granular fill material overlying less permeable clays. Installation and monitoring of an observation well would be required to assess true groundwater elevation.

3.5 LABORATORY TEST SUMMARY

GESTRA collected one (1) bulk sample from the auger cuttings from each borehole during drilling.

The bulk samples were combined to create a composite sample to represent the generalized soil profile of the upper 5 feet of soil. Based on design pavement loads, CBR tests were performed using modified Proctor density (ASTM D1557). The details of laboratory results for the standard

Proctor and CBR tests are provided in Appendix II. Following Table 3-4 summarizes the standard

Proctor and CBR test results.

Table 3-1: Summarized Modified Proctor and CBR Test Results of Subgrade Materials

Sample

Designation Sample Location

Modified Proctor (ASTM D1557) % CBR at 0.1 in penetration, 95% compaction

Max. Dry

Density

(pcf)

% Optimum

Moisture

Content

CBR-1 B-1 through B-4 122.8 11.0 18

Select samples of the subgrade soils were submitted for laboratory gradation testing. Table 3-2 provides a summary of the tests performed and associated USCS soil classification.

Table 3-2: Subgrade Soil Tests

Soil

Sample Sample Location

Grain Size Results

(% passing)

Atterberg Limit

Results (%) Soil Type

P4 P200 LL PI

CBR-1 B-1 through B-4 85.8 46.1 32 11 CLAYEY SAND

SS-4 B-1 97.2 11.0 NP NP

SAND WITH

SILT

P4= Percent passing sieve #4; P200= Percent passing sieve #200; all the samples were non plastic;

NP=not performed

4.0 ANALYSIS AND RECOMMENDATIONS

4.1 GEOTECHNICAL CONSIDERATIONS

A concern with construction of shallow foundations is the observed shallow groundwater table and excavations extending near or below the groundwater table. For excavations extending below the groundwater table, a formal dewatering plan will need to be prepared to lower the groundwater table to a recommended depth of 2 feet below the bottom of the excavation. Excavations for shallow foundations may also require additional excavation and replacement with open graded granular fill overlying a geotextile to provide a stable working surface. In addition, since the

Page 5 M20046-10 excavations will extend through loose sand fill and native sand, shoring may be required if the excavations cannot be sloped back to prevent caving. Additional recommendations for dewatering and shoring are presented in Section 4.9.

As an alternative option to shallow foundations, the building could be supported on either compacted aggregate piers or helical piers. However, excavations for both will have the same concerns as noted above for shallow foundations. Recommendations for each alternative foundation option is presented in Section 4.3.2. We also reviewed other foundation options such as auger cast piles and micropiles, but these systems are typically more expensive and may not be the most economical for the site.

4.2 SITE PREPARATION

Site preparation should start with removal of surficial topsoil, buried organic soil like that encountered in B-1, vegetation, and debris or other deleterious material, if encountered. In addition, all unused utilities should be properly rerouted, removed or abandoned. Material removed from the project site should be disposed in accordance with all applicable federal, state, and local regulations. Soil should not be stockpiled near or adjacent to the excavations.

In the building slab on grade and pavement areas, after the initial site preparation described above, we recommend compacting the exposed material. Any areas of significant deflection during compaction may be disked, dried, and re-compacted if weather permits, or removed and replaced with engineered fill. After compaction is completed, we recommend the subgrade area should be proof rolled with a minimum 20-ton tandem axle duel wheel dump truck. A geotechnical engineer or their designated representative should be present during the proof roll in order to identify soft or unstable areas, if any, and subsequently recommend remediation procedures. Per FAA AC

150/5370-10H, Section 152-2.9, soft areas of subgrade that deflect more than 1-inch or show permanent deformation greater than 1-inch shall be remediated. Where subgrade remediation is needed, the type of remediation and the depth needed should be determined at the time of construction based on drainage, weather and soil conditions. The following options may be considered for subgrade soil correction.

Mechanical Stabilization: Areas of subgrade remediation could be reworked to correct the moisture content and recompacted in accordance with the project specification. If the underlying soil becomes soft and unstable due to presence of water and existing soil cannot be recompacted, localized soft areas may require bridging of the unstable weak soils to facilitate construction.

Bridging can be accomplished with the use of thick layers of granular engineered fill. If open-graded aggregate layers are used for subgrade replacement, we recommend a geotextile fabric be placed to prevent migration of fine soil particles into the layer.

Geogrid: Removal and replacement or mechanical stabilization can include the placement of a geogrid material with an approved granular fill. Various options of geogrid strength and related thickness of granular fill are available, but the system selected should be designed by an experienced contractor or geogrid supplier based on the site soil conditions. By using a geogrid, the soil excavation and replacement depth can be reduced.

Removal and Replacement: Removal and replacement of the soft or unstable soils can be performed and replaced with similar suitable material that exists in the other areas of the subgrade or replaced with engineered fill. Based on FAA AC 150/5370-10H, Section P-152-2.5, the subgrade under areas to be paved shall be compacted to a depth of 12 inches and to a density of

Page 6 M20046-10 not less than 100 percent of the maximum dry density for non-cohesive soils and for cohesive soils as determined by ASTM D1557. Non-cohesive soils in this specification defined as soils having a plasticity index (PI) of less than 3 as determined by ASTM D4318. If an open graded clean stone is used as fill, a geotextile might be necessary to provide an adequate separation between the underlying subgrade and new fill and to prevent migration of the finer subgrade soils into the void space of the new fill. The subgrade in areas outside the limits of the pavement areas shall be compacted to a depth of 12 inches and to a density of not less than 95 percent of the maximum density as determined by ASTM D1557.

Based on the relatively high moisture contents (above 20%) and buried organic clay observed in boring B-1, it is likely that northwest portion of the project site will show instability when exposed to construction traffic and proof rolls. It is recommended that buried organic soil like that encountered in B-1 be removed in its entirety.

Site grading should direct runoff away from the planned building slab on grade and pavement areas, and should be maintained throughout construction so that the potential for softening of the subgrade soils is reduced. Equipment and working traffic should also be kept to a minimum on subgrade surfaces, especially during times of precipitation or following spring thaw. The contractor is responsible for maintaining completed earthwork areas. Consideration should be given to installing construction roads or utilizing the existing pavement for construction traffic to reduce disturbance to the subgrade soils.

Per FAA AC 150/5370-10H, Item 152-2.8, the fill materials shall be constructed in lifts as established in control strip per Item 152-2.7. However, the lift thickness should not be less than 6 inches nor more than 12 inches of compacted thickness. The material in each lift shall be within

±2% of optimum moisture content before rolling to obtain the prescribed compaction. Engineered fill placed within the building pad, below foundations or in the pavement subgrade/base course should be compacted to a minimum of 95% of the modified Proctor dry density value. Structural soil fill should be placed a minimum of five feet beyond the edges of the new building and pavement areas, and an additional foot horizontally for each vertical foot of new fill to be placed to provide adequate lateral confinement. The inorganic site soils free of any construction debris that would be removed from excavations could be reused as structural fill; however, moisture conditioning of the material may be necessary.

The information presented in this report may be used to evaluate the site conditions for construction, but the contractor is responsible for determining site preparation means and methods required to complete the project. An aggressive construction schedule or construction during seasons with limited drying time may not allow for reconditioning of the subgrade and soil correction may require removal and replacement with imported granular fill or use of geogrid with granular fill.

4.3 FOUNDATION RECOMMENDATIONS

4.3.1 SHALLOW FOUNDATIONS

The proposed building can be supported on a typical shallow spread/strip footing system designed for a maximum net allowable soil bearing pressure of 1,500 pounds per square foot (psf) provided the recommendations in this report are followed. Spread foundations designed for a maximum net allowable soil bearing capacity of 1,500 psf should be supported by the native sand soils with a minimum N-value of 4 blows per foot or new engineered fill placed over recommended sand soil.

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Table 4-1 provides the depths at each of the test boring locations to the soil recommended for an allowable bearing capacity of 1,500 psf.

Table 4-1: Recommended Excavation Depths

Boring

Location

Existing Surface

Ground Elevation (ft)

Estimated Depth to 1,500 psf

Allowable Bearing Capacity (ft)

Depth (ft) Elevation (ft)

B-1 864.7 3.8 1 860.9

B-2 856.9 10 1, 2 846.9

B-3 857.1 4.5 1 852.6

B-4 855.5 1.6 853.9

1. Groundwater encountered near (within 2 feet) or above the planned excavation depth.

2. Boring encountered deeper fill material.

Where unsuitable soils are encountered at the foundation elevation, soil correction should consist of additional excavation to remove the unsuitable soils. If the over-excavation is being filled with engineered fill, we recommend the over-excavation be widened at a minimum 1H:1V ratio from the edge of the foundation. The over-excavation can then be filled to grade with suitable engineered fill consisting of a well graded granular material placed in lifts not exceeding 12 inches and compacted to at least 95% of the maximum dry density as determined by the modified Proctor

(ASTM D1557). Alternatively, lean concrete with a minimum compressive strength of 500 psi could be used to fill the over-excavation to grade and lateral over-excavation will not be required.

A dewatering plan should be in place prior to excavations near or deeper than water levels encountered.

The depth of excavation required to expose suitable bearing material may vary in areas not explored by GESTRA; therefore, we recommend the foundation excavations be reviewed by a geotechnical engineer or their designated representative to determine when soil suitable to support the recommended bearing capacity is observed.

The shallow foundation design should incorporate a minimum strip footing width of 18 inches and column pad width of 24 inches, even if the allowable bearing capacity has not been fully utilized.

All foundations should bear a minimum of 48 inches below grade for heated structures and 60 inches for unheated structures in order to protect the structure from frost heave. We recommend that foundations also be suitably reinforced in order to compensate for the effects of minor differential movements due to subsurface soil variations.

If the recommendations as stated in this report are used in the design and construction of the proposed buildings, it is our opinion that total settlements will be less than 1 inch.

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4.3.2 ALTERNATIVE FOUNDATION OPTIONS

HELICAL PIERS

A helical pier foundation system can be considered as an option to support the building. Helical piers would extend loading through existing fill material to an underlying more competent material. Helical piers consist of a solid steel plate or plates (helical plate) attached at the lower end of a steel shaft. The piers are turned into the ground to suitable soils until the necessary resistance is met to provide the designed bearing strength. A concern with helical piers is the loose fill and sand soils above the bearing soils. The loose fill and sand soils could be a concern for lateral confinement of the pier and may result in the pier buckling. The requirement for a grout column around the shaft of the pier to prevent buckling should be evaluated by the pier installer.

For planning purposes, we estimate that helical piers extending through the existing fill and loose sand into the medium dense sand soil could achieve an allowable capacity on the order of 8-10 kips per pier. The anticipated capacity assumes the helical piers will have 3 helical flight plate (8, 10 and 12 inches), estimated deepest length of 35 feet from existing grade, and includes a factor of safety of 3.

Higher or lower allowable capacity may be achieved through alternate arrangement of helical flight plates and variations in the installed depth. As a minimum, we recommend the top helical flight be embedded a minimum of 5 feet into the medium dense sand. This depth will vary and the helical pier installer should use their system to develop the final design details, number of flights, pier depth, and allowable capacity.

As listed below, the Wisconsin Building Code – SPS 362.1810 identifies that the Factor of Safety used for deep foundation design depends on the extent of field testing performed to verify capacity.

Our recommendations are based on static analysis and a factor of safety of 3. Through additional field load testing, a lower factor of safety may be used in the design capacity.

“If the ultimate capacity is assessed solely by static analysis, a minimum factor of safety of 3.0 shall be applied to the ultimate capacity to determine allowable load capacity.”

“If one or more static load tests are performed, in addition to a static analysis, a minimum factor of safety of 2.0 shall be applied to the ultimate capacity to determine allowable load capacity...”

The design grades will partially dictate the shaft length of the helical piers. The design should consider the structural capacity of the pier as there is a maximum load allowed on the pier that depends on the shaft design.

COMPACTED AGGREGATE PIERS

As an alternative to shallow foundation design, compacted aggregate piers could be used beneath the building foundations to provide a higher allowable design soil bearing pressure and eliminate the need for excavation below bottom of foundation elevation. In general, aggregate piers consist of drilling a hole into suitable bearing soil and backfilling the excavation with crushed stone in lifts and compacting each lift using a crane-suspended downhole vibrator to densify the stone.

Aggregate pier system will generate spoil; however, alternate displacement systems are available that can be installed without generating spoil. The evaluation of the soil and groundwater conditions along with the specific design is typically provided by a specialty contractor and the

Page 9 M20046-10 soil and groundwater conditions may require unique construction methods beyond the general description provided above.

A more in depth cost analysis should be performed by a specialty contractor to determine if the cost of aggregate piers will result in an overall lower project cost. The specialty contractor should also determine if vibrations from installing the aggregate piers will affect any nearby utilities or buildings.

4.4 FLOOR SLAB RECOMMENDATIONS

We recommend that a subgrade reaction modulus of 200 pounds per square inch per inch of deflection (pci) be used in the design of the floor slab at grade. The modulus value was assumed based on clay fill or native clay or loose sand as the subgrade soils, and assumes a 1-foot plate is used to determine the modulus and should be adjusted for the size of the foundation and confinement effect. We recommend that the floor slabs be suitably reinforced and designed to be separate from the foundation system in order to allow for separate movements. It is recommended that the structural engineer specify the floor slab thickness, reinforcing, joint details and other parameters. At a minimum, the floor slabs are recommended to be reinforced or the concrete contain an appropriate fiber mesh additive to help control shrinkage cracking.

We recommend the installation of a capillary moisture break directly below the slab. It should consist of at least 6 inches of sand or gravel with a maximum particle size of 1 inch containing no more than 10% passing the number 200 sieve (fines) and follow the recommendations of ACI

302.1, Section 4.1. The structural engineer, architect, or manufacturer of a floor covering should determine the need of a vapor barrier, specify the vapor barrier location and consider the concrete curing and the effects of moisture on future flooring materials or building end use. If a vapor retarder is used, we recommend it be placed in accordance with ACI 302.1 Section 3.2 and should meet the requirements of ASTM E1745. The vapor retarder should include proper sealing at penetrations, overlap at joints, and sealing at the interface of the wall and slab and may require an adequate cushion material to prevent damage.

4.5 SEISMIC SITE CLASSIFICATION

Section 1613 of the International Building Code 2015 (IBC) was used to assign a soil site classification. Based on the native soil conditions observed and assuming these are consistent or better to a depth of 100 feet, the soil site classification D (stiff soil) should be used in the structural design of the proposed building. Based on site class D, and mapped spectral response acceleration

Ss and S1 for Madison, Wisconsin, the site coefficient Fa and Fv are 1.6 and 2.4, respectively.

4.6 LATERAL EARTH PRESSURES FOR BELOW GRADE WALLS

Below grade walls will need to be designed to resist lateral earth pressures. The values presented in Table 4-2 assume that the walls are vertical; that a clean, free-draining granular fill is used as backfill within 2 feet behind the wall; the backfill condition at the ground surface is level; the walls are above the groundwater table; and that adequate drainage is provided to prevent the buildup of any hydrostatic pressure. In addition, the below grade walls will also be required to resist the surcharge of traffic that may occur during or after construction.

Page 10 M20046-10

Table 4-2: Below-Grade Wall Design Parameters

Below-Grade Wall Design Parameters 1

Total Unit Weight of Backfill () 120

Angle of Internal Friction (Φ) 28

At-Rest Earth Pressure Coefficient, (Ko) 0.53

Active Earth Pressure Coefficient, (Ka) 0.36

Passive Earth Pressure Coefficient, (Kp) 2.77

Coefficient of sliding friction (ultimate) 0.34

1. Based on very loose to loose sand soil encountered

For walls that are free to rotate at least 0.001 times the height of the wall, such as a temporary earth retention system and retaining walls, then an active earth pressure condition will develop.

Equivalent fluid densities can be calculated by multiplying unit weight by the listed pressure coefficients at different conditions. Using an assumed total unit weight of soil of 120 pounds per cubic foot (pcf), these results in an equivalent active fluid pressure of 43 psf/foot. For walls that will be restrained, such as permanent basement walls, then an at-rest condition will pertain. In this case, we recommend an equivalent at-rest fluid pressure of 64 psf/foot.

For passive resistance, we recommend an equivalent passive fluid pressure of 332 psf/foot. We also recommend using a minimum factor of safety of 2.0 in passive earth pressure calculations because of the large strains required to mobilize the full passive resistance, ignoring the upper 1 foot of soil in frost protected areas and ignoring the soil within the frost depth for other areas.

Our recommendations assume the walls are above the groundwater table. Drainage should be provided behind below-grade and retaining walls to prevent the buildup of hydrostatic pressures.

We recommend that free-draining granular drainage aggregate be placed within 2 feet behind the back face of the below grade walls. Drainage pipes are recommended to be installed behind the walls and be drained by gravity or a sump pit and pump system. The drainage pipes should be surrounded by a minimum of 6 inches of drainage aggregate. Due to the existing fill soils containing a significant percentage of fine material, the drainage aggregate should be completely wrapped in a non-woven, high survivability, geotextile fabric with an apparent opening size (AOS) in the range of 70 to 100. The geotextile fabric should prevent migration of any adjacent soil into the drainage aggregate. We do not recommend using a drainage pipe that includes a geotextile sleeve in immediate contact with the pipe.

We recommend a relatively impermeable barrier that may consist of a minimum 2 foot thick clay cap or Bituminous or Portland cement concrete (i.e. walkways and drives) be placed around each of the below-grade structures to minimize surface water infiltration into the backfill against the walls. The clay material, if used, should be placed and compacted as recommended in this report and should extend from final grade to a depth of at least 2 feet. The clay cap or impermeable barrier should slope away from the structure at a minimum 2 percent grade. Surcharge loads, including

Page 11 M20046-10 those from adjacent (present and future) structures, as well as temporary construction equipment, within a zone defined by a plane extending at a 45 degree angle above the base of the wall should also be included in the design. The size of the compactor used behind the wall should be limited to less than 500 pounds to minimize stresses on the wall. The backfill should be compacted to a minimum of 90 percent of the maximum dry density as determined by the modified Proctor test

(ASTM D1557).

4.7 PAVEMENT DESIGN

SOIL PARAMETERS FOR PAVEMENT DESIGN

From an evaluation of the subsurface conditions, FAA AC No.: 150/5320-6F, and FAA AC No.:

150/5370-10H, we recommend that the specific pavement design values outlined below be used in establishing the appropriate pavement section(s) for the project.

The parameters in Table 4-3 assume soil subgrade preparation has been performed as identified in this report and are based on Unified Soil Classification System (USCS) classification of lean clay

(CL). If the existing upper clay fill or native clay soils are removed in their entirety and underlying sand soils are exposed, the soils parameters may be modified from what is reported in Table 4-3 for soils with a Frost Group Index of FG-2.

Table 4-3: Estimated Average Soil Parameters

Design Parameters

USCS Soils Classification CL

Reduced Subgrade Strength for Flexible Pavement CBR value a, (%) 4

Frost Group Index b FG-3

Frost Penetration depth c, (Inches) 60

Maximum Dry Density d, (pcf) 123

Optimum Moisture Content d, (%) 11

Poisson’s Ratio e 0.35

Modulus of Subgrade Reaction Based on Plate Load Tests (pci) 455-515 h

Revised Modulus of Subgrade Reaction Based on Frost Group Index f (k)

(pci)

Elastic Modulus of Subgrade for Rigid Pavement h (E), (psi) 6,000 g

Elastic Modulus of Subgrade for Flexible Pavement g (E), (psi) 6,000 a Based on FAA AC No.: 150/5320-6F, Chapter 3. Section 3.12.18.3, Table 3-5 b Based on FAA AC No.: 150/5320-6F, Chapter 2. Section 2.7.1, Table 2-2 c Based on Hammerpedia website, Wisconsin Frost Line (https://www.hammerpedia.com/wisconsin-frost-line/) d Based on Proctor test ran on the auger cuttings collected from upper 5 feet of borings.

e Based on FAA AC No.: 150/5320-6F, Chapter 3. Section 3.12.11, Table 3-2 f Based on FAA AC No.: 150/5320-6F, Appendix A:Soil Characteristics Pertinent to Pavement Foundations g Estimated using empirical formula per FAA AC No.: 150/5320-6F, Chapter 2. Section 2.5.3 h Value is based on test data performed, Design value should be adjusted to account for variations in subgrade conditions and material saturation.

Page 12 M20046-10

FAA AC No: 150/5320-6F suggests subgrade stabilization may be necessary where the elastic modulus of subgrade is less than 7,500 psi (or CBR of 5%). The above elastic modulus of subgrade value is reduced due to seasonal frost (see discussion below). If subgrade stabilization is planned, FAA AC No: 150/5320-6F, Section 2.6.1 recommends subgrade stabilization by chemical, mechanical methods or replacement with suitable subgrade material.

DISCUSSION OF SEASONAL FROST

The airport is located in a seasonal frost area. The design of an airport pavement should address the adverse effects of seasonal frost. Per FAA AC No: 150/5320-6F, the design of pavement can be based on either of two approaches: Frost Protection or Reduced Subgrade Strength (RSS). The estimated soil parameters in Section 4.7.1 are presented to be used for RSS approach.

SUBSURFACE DRAINAGE

One of the important considerations in designing a high quality and durable pavement is providing adequate drainage. Drainage design for the proposed pavement section is out of GESTRA’s scope for this project. Subsurface drainage is discussed in Appendix G of FAA AC No. 150/5320-5D

Airport Drainage Design dated May 13, 2013. The effectiveness of subsurface drainage will be impacted by the site groundwater.

4.8 SITE EVALUATION OF STORM WATER INFILTRATION

The pavement section for the access roads to the paint booth and apron for the snow plows and towing will consist of an asphalt layer over aggregate base and 4 inch drainage layer. It is our understanding that the drainage layer will need to be designed for infiltration.

The samples collected in the upper 18 feet for borings were evaluated for the above storm water feature, and the WDNR Soil and Site Evaluation-Storm forms are included in Appendix I. The texture of the samples collected was identified visually. Typically, the upper 1.5 to 4.5 feet of the soil in the borings consisted of fill or native Clay, Sandy Clay, Sandy Clay Loam, Silt Loam. The only exception was in boring B-2 where Sand fill was encountered to a depth of 7.1 feet.

Underlying the above soil layers, native Loamy Sand was encountered to a depth of 18 feet. Water was observed to be between depths of 4 to 5 feet bgs during drilling operations.

The stratification lines between the soil types were identified based on the available data. The actual in-situ changes between layers may differ slightly and may be more gradual than depicted on the evaluation form. Subsurface and groundwater conditions can vary in areas not explored by

GESTRA.

Infiltration rates for the observed soil textures were estimated based on the information provided in WDNR Technical Standard 1002, Table 2 (dated September 2017), and are presented in the Soil and Site Evaluation-Storm form attached in Appendix I. At the anticipated design elevation, the design bottom of infiltration elevation is within fill or native Clay, Sandy Clay, Sandy Clay Loam, Silt Loam. Based on our interpretation of the Wisconsin Department of Natural Resources

(WDNR) NR 151.12(5)(c)6.a and Conservation Standard Practice 1002, the soils encountered, assuming that the grade of the site will not change significantly, assuming that no additional soil improvements will be made (removal and replacement), and based on the infiltration rates presented in Table 2 of WDNR Conservation Standard Practice 1002, the site could be considered exempt from infiltration requirements.

Page 13 M20046-10

However, if the upper fill or native Clay, Sandy Clay, Sandy Clay Loam, Silt Loam are removed to expose the existing Sand fill and native Loamy Sand soils, the storm water features could be designed for infiltration. Additional exploration through test pits and laboratory testing (grain size analysis) is required if the Sand fill and native Loamy Sand soils will be designed for infiltration per WDNR Conservation Standard Practice 1002. Additional evaluation of infiltration device is also recommended to establish if the soil meets the filtering layer requirements as the bottom of the storm water feature will likely be within 3 feet of the groundwater levels encountered. NR 151 requires the soil between the bottom of the infiltration system and seasonal high groundwater have at least a 3-foot layer of soil with 20% fines or greater or a 5-foot soil layer with 10% fines or greater. Grain size analysis tests performed on the native Loamy Sand soils collected from borings

B-1 and B-4 indicate that the percentage of fines will be between 10% and 20%.

4.9 SOIL CORROSIVITY

GESTRA subcontracted GEI to complete the electrical resistivity testing. Resistivity testing was performed at 3 locations within the grassy landscaped area surrounding the existing building. A map showing the location of each test and results from the tests are included in Appendix IV.

In addition, GESTRA completed Miller Box resistivity, pH testing was performed on two samples collected from borings B-2 and B-3. Table 4-4 provides a summary of the test results, and detailed results are included in Appendix II.

Table 4-4: Summary of Laboratory Testing (Corrosivity)

Test Test Method Results

Electrical

Resistivity Testing G57 1,410 to 6,310 Ω*cm

Resistivity (Miller

Box) G187 4,500 to 10,000 Ω*cm pH G51 7.7 to 8.2

Sulfate C1580 < 0.1 percent by mass

Based on the results from the electrical resistivity testing and Table 2-3 in the FHWA NHI-09-

087, the existing onsite soils are Corrosive to Mildly Corrosive.

The sulfate content determined for the sample was compared to the values in Table 19.3.1.1 of

ACI 318R. Based on this table, the soil samples test are categorized as “Exposure Class S0” and injurious sulfate attack is not a concern.

4.10 CONSTRUCTION CONSIDERATIONS

The detailed means and method of excavation and construction should be decided by the contractor and approved by the project design team. Based on the specific site information, geotechnical exploration results and requirements for the proposed structure and pavement, the following issues should be taken in consideration during construction.

Page 14 M20046-10

Dewatering

Based on the soil borings performed, substantial water is not anticipated to be encountered for shallow excavations of less than 4 feet below existing grades. If water is encountered during the shallow excavations, we anticipate the appropriate number of temporary sump pits and pumps should be sufficient to remove water in the excavation. If excavations are anticipated to extend below 4 feet, a formal dewatering plan should be prepared so that the groundwater level is maintained to a depth of 2 feet below the excavation. The formal dewatering plan should also address the effects of lowering the groundwater table will have on nearby structures. The contractor should also be prepared to control water from surface run-off and rain, and prevent it from accumulating in excavations or otherwise affecting construction.

Excavation Stability

Caving is a common issue for excavation side walls during construction, especially if fill material, granular soils, and/or water seepage are observed. An excavation plan should be developed and the length of excavation left open should be limited to prevent caving soil from covering the suitable bearing soils.

A temporary soil retention system may also be necessary in order to prevent caving or provide support of surrounding structures or utilities during construction. Providing recommendations or designing the retention system is out of the scope for GESTRA. The contractor must comply with the federal, state, local and updated OSHA regulations during excavation and in retention system design to ensure excavation safety and a retention system should consider the site groundwater in the design.

Occupational Safety and Health Act (OSHA) has instituted strict standards for temporary construction excavations. These standards are outlined in 29 CFR Part 1926 Subpart P.

Excavations within unstable soil conditions or extending five feet or more in depth should be adequately sloped or braced according to these standards. Excavation safety is the responsibility of the contractor. Material stockpiles or heavy equipment should not be placed near the edge of the excavation slopes. The actual stable slope angle should be determined during construction and will depend upon the loading, soil, and groundwater conditions encountered.

Weather Implications

The subgrade soil or the soil at foundation level might become unstable with exposure to adverse weather such as rain, snow and freezing temperatures. The unstable areas due to weather exposure may require an additional undercut or stabilization and the representative geotechnical engineer should assist with the determination of the depth of additional undercut or stabilization procedure based on observation of the field condition.

Soil Sensitivity

Soil at the construction site will be exposed to moisture and disturbance from construction traffic, construction equipment and human factors. Due to the disturbance, soil may become sensitive with contact of water. Contractor should try to lessen the exposure the soil at the construction site may encounter to moisture and disturbances. Therefore, the foundations, floor slabs and pavements should be constructed immediately after the review of the representative geotechnical engineer.

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Existing Fill

The project may require excavation of existing fill material or dewatering during construction.

Handling existing fill material or site water may have special requirements. GESTRA has not evaluated the subsurface conditions with respect to environmental considerations.

5.0 EXPLORATION AND TESTING PROCEDURES

5.1 LAYOUT AND ELEVATION PROCEDURES

A total of four (4) soil borings were completed at the locations shown on the attached Borehole

Location Map in Appendix I. The location of the borings were selected by Hanson and located in the field by GESTRA.

Elevation of boreholes B-2 through B-4 were obtained by GESTRA using a Geomax Zenith 35

GNSS-INS receiver. Elevations shown on the boring logs are reference to the Wisconsin Carrier

Registration System (WisCRS) Dane County (NAVD88). Coordinates and elevation were not obtained by a licensed surveyor. Elevation for boring B-1 was estimated from the topographic map on the Dane County LIO website.

5.2 FIELD TESTING PROCEDURES

The boreholes were drilled using a truck mounted drill rig. The boreholes were initiated and advanced by using hollow stem augers. At a depth between 14 and 16 feet, the driller converted to mud rotary drilling. Twenty-four-inch split spoon samples were collected continuously to a depth of 18 feet and then at 5-foot intervals to the assigned termination depth of the boring.

All representative soil samples were taken in general accordance with the “Standard Method for

Penetration Test and Split-Barrel Sampling of Soils” (ASTM D1586). After each sampling, a soil sample was retained and placed in a jar and recorded for type, color, consistency, and moisture, sealed and then transported to the laboratory for further review and testing, if required. The specific drilling method used including the depth, rig type, and crew chief, are included on each of the individual boring logs as it may change for each borehole.

In addition, GESTRA subcontracted GEI to performed Electrical Resistivity and Static Plate Load testing. Electrical resistivity and static plate load testing were performed in accordance with ASTM

G57 and CRD-C-655-95 standards, respectively. A full description of the testing procedures are included in Appendix IV.

5.3 LABORATORY TESTING PROCEDURES

After completion of drilling operations, all of the retained soil samples were transported to

GESTRA’s laboratory and classified by a geotechnical engineer using the Unified Soil

Classification System (USCS) and the Field Book for Describing and Sampling Soils, USDA, NRCS, 2012. Charts describing the classification systems used are included in Appendix I. The engineer assigned laboratory testing suited to extract important index properties of the soil layers.

These tests included hand penetrometer, moisture and organic content, hydrometer, modified

Proctor, CBR, pH, resistivity using Miller box and sulfate. The methods used are presented on the individual lab forms.

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STANDARD OF CARE

Our exploration was limited to evaluating subsurface soil and groundwater conditions pertaining to the proposed project. GESTRA did not perform any environmental, chemical, or hydrogeologic testing as these were not part of our work scope.

This report should be made available in its entirety to bidding contractors for information purposes.

The soil borings and site sketch should not be detached from this report. Our report is not valid if used for purposes other than what is described in the report.

All OSHA regulations such as those regarding proper sloping and temporary shoring of excavations should be followed during the entire construction process.

GESTRA has presented our professional opinions in this report in the form of recommendations.

Our opinions are based on our understanding of current project information and related accepted engineering practices at the time of this report. Other than this, no warranty is implied or intended.

Sincerely, GESTRA Engineering, Inc.

Report Prepared By: Report Reviewed By:

Eric Jeske, P.E. Douglas Dettmers, P.E.

Staff Engineer Senior Engineer

Digitally signed by Eric Jeske

Date: 2020.09.10 09:10:38 -05'00' Digitally signed by Douglas Dettmers

Date: 2020.09.10 09:12:02 -05'00'

M20046-10

APPENDIX I

BOREHOLE LOCATION MAP, TEST BORING LOGS, SOIL AND SITE EVALUATION – STORM FORMS,

GENERAL NOTES AND SOILS CLASSIFICATION

Project Name & Location:

Truax F-35 Hangar Facility (W9133L-16-D-0005)

GESTRA Engineering, Inc.

2223 Industrial Drive Monona, WI 537013 Phone: (608) 222-9406 Fax: (608) 222-9408

Checked by: DD

Date: July 14, 2020

Scale: 1” = 100’

Drawing Title:

Borehole Location Map

Drawing No.: 1 of 1

Project No.: M20046-10

Prepared by: ESJ Madison, Wisconsin

= Approximate Borehole Location (Elevation WisCRS - Dane County NAVD88)

N

Base map obtained from Dane County LIO website

Building

B-1 (856.9)

B-2 (856.9)

B-3 (857.1)

B-4 (855.5)

2.50

TOPSOIL (8")

0.7 (855.3)

LEAN CLAY, dark brown with dark gray, moist, very stiff

3 (853) ORGANIC CLAY, black, moist, loose

3.8 (852.2) POORLY GRADED SAND WITH SILT, brown, wet, loose to medium dense

Color change to gray at 6'

22.8 (833.2) SANDY SILT, gray, wet, medium dense

27.8 (828.2) SAND WITH SILT, gray, wet, medium dense

31 (825) End of Boring at 31.0 ft.

Elevation estimated for topographic map on Dane County Land Information Office website.

LOI = 13.6%

Gravel = 2.8% Sand = 86.2% P200 = 11.0%

Driller converted to mud rotary at 16'

SS

-1

SS

-2

SS

-3

SS

-4

SS

-5

SS

-6

SS

-7

SS

-8

SS

-9

SS

-1

SS

-1

SS

-1

CL

OH

SP-SM

ML

SP-SM

DATE DRILLING ENDED

PROJECT NAME