A06_GEOTECH_RPT_FLNI_200729.pdf

GARVIN

BOWARD BEITKO

BUILT ON REPUTATION

CONSULTING GEOTECHNICAL,

FORENSIC & ENVIRONMENTAL

ENGINEERS

FINAL

GEOTECHNICAL ENGINEERING

INVESTIGATION

PROPOSED

TOWER OF VOICES STRUCTURE

FLIGHT 93 NATIONAL MEMORIAL IMPROVEMENTS

STONEYCREEK TOWNSHIP

SOMERSET COUNTY, PENNSYLVANIA

For:

PAUL MURDOCH ARCHITECTS

8820 WILSHIRE BOULEVARD #330

BEVERLY HILLS, CA 90211

Garvin Boward Beitko Engineering, Inc.

180 Bilmar Drive Suite IV

Pittsburgh, PA 15205 September 9, 2016 Phone: (412) 922-4440 GBBE 15107

Fax: (412) 922-3223

BUILT ON REPUTATION

CONSULTING

GEOTECHNICAL / FORENSIC / ENVIRONMENTAL

ENGINEERS

September 9, 2016

Paul Murdoch Architects 8820 Wilshire Boulevard #330 Beverly Hills, CA 90211

Attn: Paul Murdoch, AIA, LEED AP President

Subject: Final Geotechnical Engineering Investigation Proposed Tower of Voices Structure

Flight 93 National Memorial Improvements Stonycreek Township, Somerset County, Pennsylvania Garvin Boward Beitko Project 15107.1

We completed our geotechnical engineering investigation for the subject project. This report describes the findings of the investigation and presents recommendations for the design and construction of foundations, and related geotechnical project elements, for the Tower of Voices (TOV) structure at the subject site.

As shown on the

1.0 – SITE LOCATION AND CONDITIONS

Site Location Plan of Figure 1, the site is located at the existing Flight 93 National

Memorial Park, east of Approach Road, approximately 530 yards south of its intersection with U.S. Route

30, in Stonycreek Township, Somerset County, Pennsylvania. As shown on the Boring Location Plan

(BLP) of Figure 2, the grass- and weed-covered ground surface at the site falls relatively gently southwest between approximate elevations 2410 ft and 2375 feet. Wetlands occupy various zones about the area, as shown on the BLP, although – based on that drawing – none appears to be located at the proposed TOV development area.

The H.F. Lenz Company, Inc., survey crew staked the test boring locations in the field. All elevations in this report are referenced to the ground surface elevation contours shown on the February 22, 2016, AutoCAD drawing file provided to us by Paul Murdoch Architects (PMA). They appear to be referenced to

United States Geological Survey (USGS) datum.

Garvin Boward Beitko Engineering, Inc.

180 Bilmar Drive Suite IV Pittsburgh, PA 15205 Phone: (412) 922-4440 Fax: (412) 922-3223

GARVIN Proposed Tower of Voices BOWARD BEITKO Page 2 of 20

The BLP shows the locations of four test borings – Borings 101, 102, 103 and 104 – drilled by Test Boring

Services, Inc., during July 11 and 12, 2016, to delineate general subsurface conditions at the proposed TOV construction area.

2.0 – SUBSURFACE EXPLORATIONS

Standard penetration tests (SPTs) were conducted in the soil mantle of all borings in general compliance with American Society for Testing and Materials (ASTM) Test Designation: D1586-11. These tests provide a measure of the shearing resistance, or strength, of cohesive soils and the relative density of granular soils; they also provide soil specimens for laboratory evaluation. At Boring 101, the SPTs were continued to refusal on bedrock, from which level continuous NQ-2 (nominal 2” diameter) rock cores were procured to a depth of 83.5 feet. Borings 102, 103 and 104 were terminated in the soil mantle at depths between 10.3 ft and 10.5 feet. The subsurface exploratory program for this investigation entailed 91.4 lin ft of soil boring and 23.4 lin ft of rock coring. The borings were backfilled with cement-bentonite grout upon completion.

As indicated on the Summary of Subsurface Explorations table on Page 3, the borings encountered about

0.4 ft of topsoil atop strip-mine backfill (a.k.a. strip-mine spoil). Boring 101 extended through the strip-mine backfill and revealed approximately eight feet of residual soil (the product of in-place decomposition of bedrock), giving a total soil mantle thickness of about 60 feet. Borings 102, 103 and 104 were terminated within the strip-mine backfill at depths slightly greater than 10 feet.

The strip-mine spoil consists of materials resulting from strip-mining operations at the site, which reportedly occurred between about 20 and 40 years ago. During that time, the Upper Kittanning, Middle

Kittanning and Lower Kittanning coal seams were mined from the site via stripping operations, wherein the original overburden (interval between the then-existing ground surface and the floor of the coal seam(s)) was removed and the coal seams were excavated from the site. Upon completion of mining operations, the site was backfilled. The backfill was composed of materials interlaced with spoils resulting from the coal mining operations. The strip-mine backfill includes erratic boulders, apparently predominately of sandstone origin, although boulders of other lithologic characteristics are also present in the boring samples. The boulders are mixed with a heterogeneous, anisotropic mixture of rock fragments, sand, silt and clay, varying from loose to dense on the relative density scale, where basically granular.

BOWARD BEITKO Page 3 of 20

The residual soil is composed of decomposed claystone. It grades into bedrock composed of generally massive and hard sandstone. The rock quality designation (RQD) of the rock cores ranges from 46 to 98 percent.

Observations for groundwater were conducted during the progress of the subsurface explorations and upon completion of boring operations. The borings encountered no consistent groundwater table. Boring 101 encountered an apparent pocket of perched water at a depth of 48 feet. This likely represents storm runoff that percolated through the more porous strip-mine backfill and became trapped atop a less permeable layer of soil or a boulder. It should be realized that seeps and springs and/or relatively substantial groundwater not intercepted by the borings may be present at the site. The drill tool lubricating water used for rock coring operations obscured potential groundwater below the bedrock surface. Therefore, groundwater that may be present in the more porous rock strata could not be measured and is not herein identified.

The following table summarizes the subsurface explorations.

Boring Designation

Existing Ground Surface Elevation

(feet)

Fill/Strip-Mine Spoil Thickness

(feet)

Residual Soil Thickness

(feet)

Total Depth to Bedrock

Surface (feet)

Bedrock Surface

Elevation (feet)

101 2391 52 8 60 2331 102 2395 + + + + 103 2393 + + + + 104 2388 + + + +

+ extends beyond boring

SUMMARY OF SUBSURFACE EXPLORATIONS

Pertinent geotechnical terminology and detailed test boring records of the soils and rocks encountered are appended.

Bulk bag and rock cores were submitted to Geotechnical Testing Services, Inc. (GTS), for physical laboratory testing, including: water content determinations; Atterberg (liquid and plastic) limits tests;

particle grain size analyses; modified proctor (moisture-density relationship) tests; and unconfined compression tests. The tests were performed in accordance with applicable ASTM procedures. Test results are appended.

3.0 – LABORATORY TESTING

BOWARD BEITKO Page 4 of 20

Based on our interpretation of mining maps provided to us by PMA, and information related to previous geotechnical engineering studies completed by us and others at the site, the site is underlain by strip-mine backfill, as confirmed by the test boring results summarized in Section 2.0 of this report. Research completed by a prior project geotechnical engineer indicates that the spoil thicknesses may reportedly approach 250 ft in some areas. However, based on our interpretation of the appended copy of the

September 19, 1995, Exhibit 9,

4.0 – MINING STUDY

Diamond T Coal Company, Job No. 15 Lambert and Farkas-Stahl Strip map (Mine Map), the strip-mine backfill in the vicinity of the proposed TOV location should be less than

100 ft thick, as confirmed by Boring 101, which, at a depth of 52 ft, encountered the apparent underclay – decomposed claystone – of the strip-mined Lower Kittanning coal seam. The base of the former Lower

Kittanning coal seam appears to have resided at about elevation 2339. This coal seam base elevation appears to be within reasonable proximity to deep mine elevation 2323, the nearest deep-mined coal seam elevation that we could locate on the Mine Map.

As determined from the appended copy of a similar, although less detailed deep-mine map, the deep mine workings appear to be situated at least 250 ft to the east of the proposed TOV structure area. This appears to represent the shortest distance between the structure construction area and the deep mine, where we understand at least 40 percent of the coal was removed, leaving coal pillars and barriers in place to provide nominal roof and overburden (interval between ground surface and the roof of the mine) support. Based on a typical 15° angle-of-draw extending upward and outward from the closest deep-mine wall and on a coal mine void extending up to about an estimated depth of 80 ft below the ground surface, should deep-mine workings collapse, the closest that the subsidence zone should approach the TOV structure should be on the order of approximately 220 ft or more. Thus, based on the mining information provided, the proposed

TOV, as located, does not appear to be at risk of mine subsidence damage.

This report is based on proposed conditions as shown on the drawings attached to the

5.0 – DISCUSSION AND RECOMMENDATIONS

Tower of Voices Pre-

Design Report Update (Pre-Design Report), which namely include the: February 8, 2016, Sub Sheet No.

A1.01, Tower of Voices Site Plan and February 8, 2016, Sub Sheet No. A1.11, Tower of Voices Area Plan both by PMA; and an undated, un-named AutoCAD drawing, XA-MINE, emailed to us by E. Cunningham, with PMA, on February 17, 2016. It is also based on the appended cross-section drawings provided to us by PMA. Should any aspect of the proposed schemes depicted on the drawings and/or discussed herein be altered, we should be immediately notified to determine if revisions to this report are required.

BOWARD BEITKO Page 5 of 20

5.1 – Proposed Fill Mound and TOV Structure Considerations

It is our understanding that the proposed TOV will be a 93-ft-high, C-shaped, cast-in-place concrete tower with an approximate diameter of 12 feet. It is estimated that approximately 2,800 cu yd of material will be required to construct the 156 ft by 130 ft, in plan, oval-shaped fill “mound” to immediately underlie the

TOV structure. We have not been provided with a grading plan for the mound at this time. The tower will be surrounded by light poles reportedly expected to be about 20 ft high and one foot in diameter; the quantity, type, and detailed dimensions of the light standards are uncertain at the time of this report. We further understand that driveways and parking lots have already been completed and do not require further investigation; hence, they are not considered in this report. At this time, no retaining walls of any significant height are anticipated at the TOV; thus, no geotechnical engineering recommendations related to retaining walls are herein included. Should additional structures, pavements or any other site elements or appurtenances, beyond those specifically addressed in this report, require geotechnical engineering recommendations or considerations, we would be pleased to consult with you regarding the additional engineering analysis and associated costs that will be required to address them.

As described above, the site was backfilled with non-engineered strip-mine backfill. End-dumped mine backfill possesses the potential to significantly settle under its own weight, with settlement continuing for long periods of time after placement. Factors affecting the magnitude and duration of total and differential settlements include placement procedures, material composition, depth of fill, age of fill, groundwater levels, rate of surface water infiltration and loading conditions. Most of these factors are difficult to quantify; while others are impossible to estimate. Due to the relatively extended time that the strip-mine backfill has been in place, most of the immediate settlement caused by the weight of the placed materials has likely already occurred. However, long term settlements related to predominately boulder-laden strip-mine spoil can occur for many years to come. Based on our professional geotechnical engineering experience and as indicated in references1, 2

1 Kareem, Ph.D., P.E., Wayne A. and Lee, P.E., Craig S., Settlement Evaluations of End Dumped Coal Mine Spoil Fill, 2008 National Meeting of the American Society of Mining and Reclamation, Richmond, VA, New Opportunities to Apply Our Science, June 14-19, 2008, Published by ASMR, 3134 Montavesta Rd, Lexington, KY 40502.

, end-dumped boulder-laden fills undergo long-term secondary settlements due to several factors including: compression or crushing of the boulder point contacts;

degradation of the boulders via weathering and long-term exposure to groundwater and storm water percolating through the fill; sudden stress/strain adjustments and sliding at boulder-on-boulder contact

2 Zipper, C.E. and Winter, Steve, Stabilizing Reclaimed Mines to Support Buildings and Development, Virginia Cooperative Extension, Powell River Project, Reclamation Guidelines for Surface Mined Land, Publication 460-130, Communications and Marketing, College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, 2009.

BOWARD BEITKO Page 6 of 20 zones, especially where subsurface voids resulted from poor boulder placement; and “piping” of the finer-grained soils into inter-boulder voids in the strip-mine spoils, wherein the fines are washed into voids via water seeping through the spoils, resulting in settlements and “sinkhole-like” depressions at the ground surface superjacent to the void zones. We are not aware of an accepted method to predict or quantify potential ground movements or settlements from such boulder and void effects. We can only estimate elastic compression (i.e., immediate settlement) of predominately coarse-grained strip-mine backfill materials under the weight of the proposed fill mound and TOV structure. This method ignores potential boulder and void effects, which can be substantial.

Using the Schmertmann method3,4

, and based on the findings of the four widely-spaced borings for the proposed TOV structure area, it appears that the proposed fill mound, estimated to be on the order of 10 ft thick, will result in at least 2.8 in. of elastic settlement of the underlying subgrade. This estimate does not include the settlement of the fill mound material. Assuming that the fill mound is properly compacted and verified via compaction testing during earthwork operations, as discussed in Section 5.3 of this report, based on a rule-of-thumb of five percent of elastic compression per thickness of new fill placed, an estimated additional one-half inch of settlement strictly due to the compression of the new fill is conceivable. This totals (2.8 in. + 0.5 in. =) 3.3 inches. Although some of this settlement will occur during fill placement, a substantial portion will not. This settlement estimate does not include consolidation of clay layers or the aforementioned boulder effects, both of which are difficult to predict for such a thick, heterogeneous and anisotropic strip-mine backfill soil mantle. Nonetheless, it is our subjective professional opinion that the settlements, including those factors, could be twice as much, or possibly more, than the elastic compression movement. This results in six to seven inches, and possibly more, of anticipated total settlement.

Consultations with Mr. Murdoch, AIA, LEED AP, reveal that the project schedule may allow for placing the fill mound and allowing it to rest for several months. We recommend this procedure be implemented, as it should allow much of, and possibly most, of the settlement to occur due to the fill mound surcharge load. We further recommend that the fill mound settlement be monitored via strategically-placed survey monitoring points. Five survey monument points, placed in a basic “domino” pattern throughout the final ground surface of the fill mound, would likely suffice; we should be consulted regarding further

3Schmertmann, J. H., Static Cone to Compute Static Settlement over Sand, ASCE Journal of Soil Mechanics & Foundations Division, 96 (3), pp. 1011-1043, 1970.

4 Schmertmann, J. H., Hartmann, J. P. and Brown, P. R., Improved Strain Influence Factor Diagrams, ASCE Journal of the Geotechnical Engineering Division, 104 (GT8), pp. 1131-1135, 1978.

BOWARD BEITKO Page 7 of 20 consideration of the final quantity and location of the monuments. The survey monuments should be installed so that they are not disturbed during the reading interval and so that they are not affected by frost heave; hence, they should extend at least 48 in. deep. We recommend that their elevations be immediately accurately determined upon installation, which should occur within one to two days of completing the fill mound placement. This reading will serve as the baseline. Due to reading problems we have experienced from surveyors using GPS instruments at other sites, we recommend that, if you engage a surveyor to obtain the monument readings, that surveyor consult with us prior to initiating reading measurements at the site. We would be pleased to consult with you regarding the cost for our personnel to read the monuments.

The monuments should be read once per week for at least six weeks after installation. After that time interval, readings can likely be extended to once every two weeks. The survey data should be submitted to us for evaluation. Upon approval by us, wherein it appears that adequate settlement has transpired and/or the monument movements have abated, survey monument readings can likely be terminated. Although the elastic compression settlements should occur relatively quickly, potential consolidation- and boulder-movement/crushing-related settlements may take much longer as they are essentially impossible to predict for this material. Thus, at least several months may be required to reach a reasonable degree of confidence regarding the disposition of potential continued ground movements at the proposed fill mound.

Although the above-described measure should substantially mitigate settlement-related effects to the final grade at the proposed fill mound, as well as associated distresses to relatively lightly-loaded proposed construction elements, such as sidewalks, paving, light bollards, etc., it will not eliminate settlement of substantial structures, such as the TOV structure or approximately 20-ft-high light standards that we understand may be installed. The location of such light standards was not provided to us. We further discuss the light standards in Section 5.2 of this report. If proposed fill mound settlement is not allowed to occur prior to installing sidewalks, slabs, and other walkway finishes that cannot withstand distortions and distresses from such settlements, such elements should be designed as structural members – similar to a structural floor slab supported with deep foundations, such as the micropiles discussed later in this report.

Our elastic settlement analysis of the proposed TOV structure, supported on conventional isolated spread footing foundations designed for a total combined uniform contact bearing pressure of 2500 lb/sq ft, indicates that it will experience at least 1.1 in. of total settlement and on the order of at least three-fourth inch of differential settlement. This does not include settlement due to consolidation or boulder effects, as described earlier in this report. Thus, settlements to the proposed structure could be much more severe, BOWARD BEITKO Page 8 of 20 possibly over twice the elastic compression estimates. Due to the height of the TOV structure, it is our opinion that such settlement could be catastrophic. Hence, we do not recommend that the TOV be supported with footings, and they are not further discussed in this report.

We expressed similar concerns regarding structure support in our July 6, 2012, Geotechnical Engineering

Investigation report, which addresses several structures at the facility, most of which we understand were constructed. We recommended that those structures be supported with micropiles. We herein recommend that the proposed TOV structure be supported with micropile foundations. Using this foundation system can avoid the above-outlined settlement concerns.

The cost effectiveness of micropiles is a function of site features, such as significant geologic features, structural concerns and/or environmental concerns. They are an especially favorable option where:

subsurface conditions are difficult (i.e., boulders and other subsurface obstructions); subsurface voids are or may be present, and; structural settlements must be minimized5

. All of these factors apply to this site.

Although none of the borings encountered voids, there exists the potential that they exist where boulder on boulder conditions may have occurred within the strip-mine backfill soil mantle.

Micropile foundations, installed by a contractor that specializes in such piling, entail drilling vertical shafts via a hammer drill and simultaneously installing steel casing. The steel casing, exhibiting a nominal yield stress of 80 kip/sq in., is typically either 5-1/2-in.- or 7-in.-outside-dia, with 7-in.-dia generally considered the most common size used. The casing is typically “seated” slightly into the bedrock. Drilling continues, without casing, into the bedrock to a depth necessary to achieve the bond resistance for the pile design load.

A steel bar, typically sized between a No. 10 and No. 28, is centered vertically in the casing/shaft and the annulus is backfilled with cement grout. The steel bar requires a structural engineering analysis, beyond the scope of our geotechnical engineering analysis. Permanent steel casing should be used to avoid bonding between potentially unstable boulders and the grout. Boring 101 indicates that micropiles should extend into sandstone bedrock. The unconfined compression tests of the sandstone cores (copies appended with laboratory test results), compared to typical values of sandstone bedrock in Pennsylvania6

5 Bruce, D.A., Cadden, A.W., Sabatini, P.J., Practical Advice for Foundation Design – Micropiles for Structural Support, Proceedings Of Sessions Of The Geo-Frontiers 2005 Congress, January 24-26, 2005, Austin, Texas Sponsored by Deep Foundations, Shallow Foundations, and Risk Management Committees the Geo-Institute of the American Society of Civil Engineers, Reston, VA: ASCE, 978-0-7844-0777-6 or 0-7844-0777-0, 2008.

, reveal that, 6 Geyer, Alan R., and Wilshusen, J. Peter, Engineering Characteristics of the Rocks of Pennsylvania, Environmental Geology Supplement to the State Geologic Map, Environmental Geology Report 1, Pennsylvania Geological Survey Fourth Series, First Edition 1972, Second Edition, Revised 1982, Sate Books Store, Harrisburg, PA.

BOWARD BEITKO Page 9 of 20 although the sandstone cores appear relatively fresh, massive and hard, the strength of the site sandstone lies only within the lower 50 percent of the typical range of values. The weakest core, procured at a depth of about 62 ft – within the anticipated micropile bond zone – is only about 16 percent of the afore-referenced sandstone strength range. Based on this sandstone strength as a guide, our analysis7 reveals that a 7-in.-dia permanently-cased micropile, with an appropriately design-sized steel bar, backfilled with grout exhibiting an appropriate compressive strength (often a minimum 28-day strength of 3000 psi, although it depends on structural design), installed via the industry-accepted Type A gravity-injected grouting procedure, should be suitable for an allowable load capacity of: 54 ton/pile with a 10 ft competent sandstone rock socket; 65 ton/pile with a 12 ft competent sandstone rock socket; and 82 ton/pile with a 15 ft competent sandstone rock socket. These pile capacity estimates include a factor of safety of 2.5. Type A piles are typically assumed to have a group efficiency of unity. Piles should be spaced no closer than three pile diameters from adjacent piles.

It should be understood that micropiles include both geotechnical and structural design aspects. This report presents recommendations and parameters related to the geotechnical engineering design. Structural design, not included in our scope of services or this report, should be completed by a structural engineer that is part of the piling contractor team or that is engaged by him.

Contracting the pile foundation design and installation as essentially a design-build component of the project is a common practice in this locale, especially as local competent piling contractors have access to extensive in-house empirical data and are often aware of capacities exceeding conventional analytical methods. Hence, this practice may represent a cost savings to the project owner. We recommend that the micropiles be designed and installed via the design-build practice. To do otherwise would not only be in contradiction to industry practices (subjecting the owner to increased scrutiny and responsibility/liability should problems occur with the piles), but expose the owner to increased risk, as well as potential increased costs. Please see the appended excerpt from a distinguished reference7 regarding this practice. Using the design-build practice, we recommend that the project specifications included with bid documents require that a minimum 10-ft-deep rock socket be used for the micropiles. Coal and clay seams should not be included as part of the rock socket as these strata are not considered competent. Permissible structural movements, determined by the project structural engineer, should also be provided to the contractor, so that

7 Micropile Design and Construction Guidelines, Implementation Manual, U.S. Department of Transportation, Federal Highway Administration, Priority Technologies Program, Publication No. FHWA-SA-97-070, June 2000.

BOWARD BEITKO Page 10 of 20 he can select the appropriate drilling and grouting procedure, as well as a structural pile section that exhibits the required stiffness.

Regardless of the method used to estimate the micropile capacity for design, it should be verified via a static pile load test, performed in accordance with ASTM Test Designation: D1143-81 (1994), wherein the test pile is subjected to at least twice its design load. The Procedure B Maintained Test should be used.

The location of the test pile(s) should be approved by us.

Micropile uplift capacity should be based on the bonded zone resistance, analyzed as the skin friction developed at the grout/bedrock interface. An allowable skin friction value of 15 lb/sq in. should be used for design.

The best method to obtain lateral resistance from micropiles entails battering specific piles, as needed, to transfer lateral loads along the piles axes. This method is always recommended over the attribution of lateral stresses to vertically installed micropiles, which are not known for sustaining high lateral loads.

Nonetheless, in certain conditions (i.e., micropiles subjected to downdrag forces), the designer is compelled to assign some lateral loads to vertically-installed micropiles.

If lateral loads are assigned to vertical micropiles, it should be realized that the micropile casing is typically installed in sections as the drilling proceeds. One section of casing is threaded to the next section. Hence, piles under lateral loading will impose bending and tensile stresses on such joints, which can have an impact on the integrity of the pile casing primarily due to the reduced thickness of the casing over the length of the threaded area. If the piles are subjected to lateral loads, we recommend that the project specifications require that the piling contractor demonstrates the adequacy of the proposed joint details to the satisfaction of the project engineer.

Micropile behavior in a group configuration is influenced by the pile spacing. The deflection of a pile group under a lateral load may be two to three times larger than the deflection of a single pile loaded to the same intensity. Piles in trailing rows of groups have significantly less resistance to a lateral load than piles in the lead row and, therefore, exhibit greater deflections. This is due to the pile-soil-pile interaction that takes place in a pile group. The pile-soil-pile interaction results in the lateral capacity of a pile group being less than the sum of the lateral capacities of the individual piles comprising the group. Hence, laterally

BOWARD BEITKO Page 11 of 20 loaded pile groups have efficiency less than one. Typically, for in-line piles, group effects are negligible for micropile spacing between six to seven diameters and, for micropiles arranged in a row (i.e., perpendicular to the direction of loading), group effects are negligible for micropile spacing just greater than three diameters5. It has been proposed by others8 that a p-multiplier, Pm, be used to modify the load-deflection (p-y) curve of an individual pile based upon the pile row position. P-y curves graphically portray the pile movement or deflection over its length while imposed to loads. For piles in a given row, the same Pm value is applied to all p-y curves along the length of the pile. As discussed in a reference6, in a lateral load test of a three by three pile group with the piles spaced at three diameters apart, the leading row of piles had a Pm of 0.8 times that of an individual pile. The Pm values for the middle and back row of the group were 0.4 and 0.3, respectively. We recommend that, if possible, assigning lateral loads to micropiles be avoided, as they often exhibit lateral capacities less than one ton per pile. If the structural design team determines that assigning lateral loads to the micropiles cannot be avoided, the piling contractor designer should perform an evaluation of lateral capacity. Lateral capacity, if needed, should be analyzed based on the following parameters.

Estimated Parameters for Laterally Loaded Pile Design

Soil Density, γ 115 lb/cu ft s

Bedrock Density, γ 175 lb/cu ft r

Soil Modulus, k 90 lb/ cu in. s

Soil Strain at 50% Stress, E 0.007 50

Angle of Internal Friction for Bedrock, φ 42° r

Bedrock Shear Strength, S 4800 lb/sq in. r

If pile uplift and/or lateral loading is required per design, we recommend that they be verified via field tests performed in accordance with ASTM Test Designations: D3689 and D3966, respectively.

If the above-recommended proposed fill mound settlement waiting and monitoring period is undertaken, downdrag loads on the micropiles should be relatively minor, assuming that little additional vertical soil mantle movements/settlements will occur. However, if the fill mound is not allowed to complete most to all of the settlement, as reviewed and approved by us, then the piles should be designed to sustain the

8 Brown, D.A., Morrison, C., and Reese, L.C., Lateral Load Behavior of Pile Group in Sand, ASCE Journal of Geotechnical Engineering, Vol. 114, No. 11, pp. 1261-1276, 1988.

BOWARD BEITKO Page 12 of 20 downdrag forces in addition to the structure loads to which they will be subjected. Downdrag loads imposed on each pile should be estimated based on the following equation.

D = 6.8x10-3

(t)(L)(d)

Where:

t = fill thickness (ft)

D = downdrag load (tons)

L = pile length from top of pile to bedrock surface (ft) d = outside diameter of pile (in.)

If downdrag forces are not properly considered, there is a risk that pile foundations may fail. Battered micropiles should not be considered where downdrag forces are a concern. In that case, there is a risk that the micropiles may bend and shear from such soil mantle settlement stresses and strains. In our professional opinion, regardless of downdrag loads, due to the slenderness and relative weakness of micropiles in shear and bending, it is always prudent to design micropiles as compression and tension members, rather than designing them to directly resist lateral loads.

5.2 – Light Standards

As discussed in Section 5.1, we understand that approximately 20-ft-high light standards are planned for the general TOV area. Although no light standard locations were provided to us, based on the soil mantle revealed by the borings, supporting them on conventional footings entails risk that would be assumed by the owner. This is due to the risk of soil mantle settlement. Although no light standard loads were provided to us, considering their height, even slight settlement may result in noticeable rotation. Should they rotate beyond their center of gravity, or are laterally overloaded (i.e., from wind loads), there is a risk that they will topple. This would, of course, subject pedestrians and park visitors to potential health and safety hazards. Therefore, our primary recommendation is that such light standards be supported with micropiles, as outlined in Section 5.1.

However, supporting such structures with micropiles will likely be relatively expensive and, possibly, not cost effective. Therefore, to reduce the risk of them becoming hazardous to the public, their center of gravity could be lowered by supporting them with wide and relatively heavy isolated block spread footings.

BOWARD BEITKO Page 13 of 20

Depending on the final selected block footing dimensions, they will provide a resisting moment to offset the worst lateral loads to the light standards. If the light standards settle and rotate, it will require substantially greater movements before they exceed their center of gravity. Based on the boring findings, we recommend that each block footing foundation “footprint,” plus minimum two-foot-wide perimeter strips, be over-excavated to a depth of four feet below the planned foundation bearing horizon. The exposed undercut surfaces should be proof-rolled, to the satisfaction of our field personnel, with a suitable steel smooth-drum vibratory roller compactor exerting a minimum centrifugal force of 5000 lb/drum. Soft or loose zones delineated via proof-rolling should be further undercut to competent material, as determined by us, or to an additional depth of two feet, whichever is first encountered. Especially soft or loose zones may require enhancement with a combination of polymeric geogrid and select crushed stone; we will provide field/condition-specific recommendations should this worst-case condition occur. The vacated volumes should be backfilled with suitable inert (non-expansive) crushed limestone meeting the size and grading requirements for AASHTO No. 1 to within 18 in. of the planned bearing subgrade elevation. The

AASHTO No. 1 limestone should be capped by six inches of inert AASHTO No. 57 crushed limestone.

The remaining volumes may be backfilled to final bearing subgrade with suitable inert on- or off-site fill materials. All fill and backfill, including the crushed limestone, should be placed and compacted as recommended in Section 5.3 of this report. The footings should extend at least 48 in. below final adjacent exterior grade for frost protection. With proper implementation of the above subgrade enhancement scheme, the light standard block footings should be designed based on an allowable total combined (dead and live) load contact bearing pressure of 2000 lb/sq foot. Depending on the analysis by your structural engineer, such an allowable bearing pressure may be required in cases where the light standards are resisting lateral wind loads, subjecting the footings to moments.

Lateral resistance developed at the footings should be designed based on: a concrete footing base / subgrade interface coefficient of friction value, δb, of 0.3; an angle of internal friction, øb, of 28°; a cohesive intercept value, cb, of zero, and; a soil density, γb

, of 115 lb/cu foot. Uplift resistance will likely be controlled by the mass weight of the foundations plus the weight of any backfill placed atop them.

Considering the risk of settlement of the light standards, it would be prudent to provide conduits carrying the electrical supply to the standards with flexible couplings.

Temporary sidewalls of the above-described foundation over-excavation should be no steeper than two horizontal to one vertical (2:1). Methods to control surface water entering and/or percolating into the excavations, such as sumps and pumps, may be required, as determined by the contractor and his engineer.

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5.3 Fill Considerations

Suitable fill/backfill should not contain topsoil, organics, frozen materials, potentially expansive materials, pyrite or marcasite, carbonaceous materials, slag, compressible materials, trash, or rock fragments larger than five inches in dimension when using large compaction equipment, and three inches when using relatively small compaction equipment, such as mechanical tampers, plate vibrators, or walk-behind roller compactors. We should be provided with the opportunity to evaluate all proposed fill materials, whether obtained from on- or off-site sources.

In general, fill material should consist of inorganic, low-plasticity soil with a liquid limit less than 45 and a plasticity index less than 25. All cohesive fill/backfill should be compacted to at least 95 percent of its maximum modified proctor dry density as determined by ASTM Test Designation: D1557-12e1, at water contents within three percent (±3%) of the optimum water content established by that test. Granular fill/backfill, including aggregates/crushed stone, should be compacted to a minimum of 70 percent relative density as defined by ASTM Test Designations: D4253-16 and D4254-16.

Prior to placing fill, the exposed fill area subgrade should be proof-rolled with a suitable ten-ton (static weight) vibratory roller compactor, such as a Raygo 400A, or equal approved by us. Soft or loose zones delineated by the proof-rolling should be undercut to competent material or to a depth of three feet below final subgrade elevation, whichever is first encountered. If the undercut surface remains incompetent to receive backfill, as determined by our field personnel, suitable inert AASHTO No. 1 crushed limestone should be “punched” into the exposed undercut surface until adequate shear strength is achieved, as judged by us. The vacated volume(s) should be backfilled with at least one foot of AASHTO No. 1 limestone, and possibly a thicker layer if required to provide stability, as determined by our field personnel, capped with six inches of AASHTO No. 57 crushed limestone. The remaining volume should be backfilled to final subgrade elevation with suitable inert on- or off-site fill materials.

Once the subgrade is proof-rolled and prepared/enhanced, as recommended above, the exposed subgrade at the proposed fill mound area should be thoroughly scarified, via such methods as cross-etching into it with the teeth of earthmoving equipment, to the satisfaction of our field personnel. The mound fill should be bonded to the existing ground with “stair-step” benches or notches. The benches/notches should be cut into the exposed existing subgrade so that the horizontal “treads” are at least six feet wide. The height of their vertical “risers” will depend on existing grade. A minimum three-foot-deep permanent field drain, shown typically on Figure 3, should be installed about the entire circumference of the proposed fill mound to assist

BOWARD BEITKO Page 15 of 20 with maintaining a relatively dry interface between the existing grade and the newly-placed fill. The field drain should be properly tied into stormwater facilities. Final grades at the proposed fill mound should not exceed 2:1. With proper implementation of the herein-recommended construction of the proposed fill mound, its slopes should be stable in the long term.

Loose lifts of fill should not exceed eight inches in thickness, except where approved by our field personnel. All fill and backfill should be placed so that they can be quantitatively tested for compaction with conventional field testing equipment, such as nuclear densometers. Our review of the stockpile fill materials, discussed further below, reveals that they are not too rocky for field compaction testing. At least one field compaction test should be performed for every 4000 square feet of area in each lift of fill. At least two tests should be performed for each lift, regardless of the area it encompasses. Compaction tests should be completed at 50 ft intervals in each lift of backfill in narrow trenches, such as utility or footing trenches. Granular fill/backfill materials, except AASHTO No. 1 aggregate/stone, should also be field-tested for compaction. If testing personnel indicate that the fill is too rocky to compaction test, or that it cannot be compaction tested for any other reason, we recommend that we be consulted to review the reported conditions.

The borings revealed that the on-site soils contain concentrations of silts and clays, rendering them sensitive to moisture increases. Such materials, if moist to wet in their excavated state, or if exposed to precipitation, will be difficult or impossible to immediately properly compact. Those soils will either need to be mixed with drier materials or should be spread in thin layers, disked and turned over to dry adequately for compaction, all of which is labor intensive and time consuming. Further, if material drying operations are attempted, the contractor must stage the site grading and subgrade preparation operations to maintain relatively large open fields for spreading and drying materials. Precipitation on a drying field would re-saturate the exposed soils, and drying operations would need to be started over. Of course, replacing all unsuitable and/or wet/saturated excavated on-site materials with suitable and drier off-site soil would expedite earthmoving operations.

In accordance with our scope of services, we collected four samples of stockpiled material at the Park. The locations of the sampled soils are superimposed in red on the appended copy of Flight 93 National

Memorial Soil Testing Area of Exhibit A. The samples were submitted to GTS for physical laboratory testing, including Atterberg (liquid and plastic) limits, gradation, modified proctor, and as-collected water content. Detailed laboratory test results, with aspects we deem important as tabulated below, are appended.

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Sample

SUMMARY OF STOCKPILE MATERIAL LABORATORY TESTING

Description Liquid

Limit

Plastic Limit

Plasticity Index

As- Collected

Water Content

Unified Soil Classification

Modified Proctor

Maximum Dry

Density (lb/cu ft)

Modified Proctor

Optimum Water

Content

Brown siltstone and sandstone fragments and silty clay

33 21 12 5.5 SC 129.5 8.6

Brown clayey silt and siltstone, sandstone, shale and claystone fragments

28 18 10 5.3 SC 135.9 7.5

Brown clayey silt and siltstone, sandstone, shale and claystone fragments

32 19 13 5.9 CL 129.4 8.9

Brown clayey silt and siltstone, sandstone, shale and claystone fragments

33 20 13 7.0 SC 130.7 8.5

Based on the test results, the sampled stockpile materials appear suitable for use as fill. We collected the samples from the surface of the stockpile, which appeared to have significantly dried in the sun. Hence, the as-collected water contents, as tabulated above, were low. This dry material will likely require wetting to achieve adequate compaction. It is possible that the soils deeper within the stockpile, which are more protected from the drying effects of the sun and wind, may be wetter. The tabulated proctor results are strictly limited to the materials sampled. Should the material composition vary as the pile is excavated for use, it is possible that the above proctor results will no longer be representative. In that case, supplemental modified proctor testing will be required. Further, additional Atterberg limit and grain size analyses may be required if it is suspected that the material consists of fat clay or other potentially problematic materials.

In that case, we recommend that we be contacted to review the exposed materials.

The surfaces of fill/backfill lifts should be near horizontal or retrograde to the proposed final slope grade.

At the end of each day of earthwork operations, fill surfaces should be graded with adequate fall to an area that will allow potential storm runoff to drain or collect so that the entire lift of fill is not detrimentally affected. Such water should be removed and the saturated fill zone reworked and/or the wet/saturated fill material removed, as required to achieve proper compaction. Further, it would be prudent for the

BOWARD BEITKO Page 17 of 20 earthmoving contractor to “seal” the surface of the final lift of fill at the end of each work day with a smooth-drum roller compactor, or equal, to mitigate infiltration of potential precipitation into the fill.

In western Pennsylvania, typically the most effective time of year for earthmoving operations is between

June and early September. Earthmoving operations during seasons outside of this period often encounter delays due to weather. Earthmoving operations during about November through April are never recommended, except during those rare, unpredictable, and usually very limited instances where short periods of dry and relatively warm weather occur.

As a general “rule of thumb,” fill/backfill borrow materials excavated at sites similar to this site may experience a “shrinkage” factor (a.k.a. volume decrease) of less than or equal to approximately five percent after being compacted. This factor does not include materials that fall off hauling trucks/equipment or are otherwise inefficiently transported or handled.

5.4 Seismic Considerations

Our evaluation indicates that the foundation subgrade material at site correlates to a Site Class “C” according to our interpretation of the International Building Code.

5.5 Damaged Subgrade Areas

All subgrade areas disturbed by construction equipment/activities and/or precipitation should be recompacted. However, depending on the degree of “damage” inflicted on such subgrade areas, additional measures - such as deeper cuts, crushed stone backfill and/or geotextile stabilization fabric - may be required to properly repair them. It is not possible at this time to determine remedial measures required for such potential subgrade damage until the actual damage occurs. All such disturbed subgrade areas should be evaluated in the field by us prior to undertaking any attempted remedial measures.

5.6 Groundwater

Although little groundwater was encountered at the borings, as indicated in Section 2.0, there is, nonetheless, the risk that some excavations may intercept underground seeps and springs. Should such groundwater be encountered in excavations, based on the borings, we anticipate that most of it should be controllable with conventional sumps and pumps. If underground seeps and springs are intercepted at pavement subgrade excavations, it may be necessary to divert such water with field drains, as typically shown on Figure 3. Other methods, such as blanket drains, etc., may be required to address such

BOWARD BEITKO Page 18 of 20 groundwater. However, such groundwater control measures, if needed, will need to be determined in the field during construction. We recommend that, if such groundwater is encountered, we be contacted to review the condition and provide recommendations to address it.

5.7 Pavement Subgrade Preparations

We understand that concrete slab-on-grade construction, including steel reinforcing bars and structural composite section design, will be used for “pavements” about the TOV. We recommend that the aforementioned proposed fill mound be allowed to settle under its own weight, as discussed in Section 5.1, prior to constructing the slab-on-grade pavements. Otherwise, there is risk that the slab pavements will be distressed from settlements. After the settlement has occurred, and the condition is approved by us, the exposed pavement slab subgrade areas, plus three-foot-wide perimeter strips, should be proof-rolled to the satisfaction of our field personnel with a minimum ten-ton (static weight) vibratory roller compactor, such as a Raygo 400A, or equal approved by our field personnel. Confined pavement areas that will not facilitate the aforementioned relatively large roller compactor can be proof-rolled with a steel smooth-drum walk-behind roller compactor exerting a minimum centrifugal compactive force of 3500 pounds, as approved by us. All soft or loose zones delineated by our personnel during proof-rolling operations should be undercut to competent material or to a maximum depth of three feet below final subgrade elevation, whichever is first encountered. Should our field personnel determine that the exposed undercut surface is unsuitable to receive backfill, it should be enhanced. Such subgrade enhancement can be attempted by

“punching” a layer of suitable inert AASHTO No. 1 crushed limestone into it until adequate shear strength is achieved. If the subgrade does not allow the stone to be punched into it, the vacated volume may need to be backfilled with up to about two feet of AASHTO No. 1 limestone to bridge over poor subgrade areas, as judged in the field by our personnel. If adequate shear strength is still not achieved, we should be consulted. In such extreme cases, a combination of geotextile stabilization fabric and/or geogrid with crushed limestone may be required to stabilize the subgrade. The AASHTO No. 1 limestone should be capped with a minimum six-inch-thick layer of suitable inert AASHTO No. 57 crushed limestone. All crushed limestone should be compacted as recommended in Section 5.3.