20_12_Geotech_240726.pdf

REVISED

GEOTECHNICAL ENGINEERING REPORT

for

C.O.P. – Firehouse 20/Medic Station 12

Relocation

Pittsburgh, Allegheny County, Pennsylvania

Prepared For:

AE7

2840 Liberty Avenue, Suite 403

Pittsburgh, PA 15222

Prepared By:

Langan Engineering and Environmental Services, LLC.

2400 Ansys Drive, Suite 403

Canonsburg, PA 15317

Jeffrey A. Anthony, PE

Pennsylvania Professional Engineer License Number PE 063001

Jared M. Green, PE, D.GE

Pennsylvania Professional Engineer License Number PE 077115

1 June 2022

Revised 26 July 2024

250129401

REVISED Geotechnical Engineering Report

C.O.P. – Fire Station 20 / Medic Station 12 (the “Project”)

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

Revised 25 July 2024

Page i of ii

TABLE OF CONTENTS

Page No.

INTRODUCTION

PROJECT UNDERSTANDING

Existing Conditions

Proposed Development

REVIEW OF AVAILABLE INFORMATION

Historical Aerial Photographs

Historical Topographic Maps

Soil Survey Data

Regional Geology

Mining

Landslide Hazards

Langan Preliminary Geotechnical Report

SUBSURFACE EXPLORATION

Laboratory Testing

SUBSURFACE CONDITIONS

Surface Materials

Fill

Residual Soils

Bedrock

Groundwater

EVALUATION AND RECOMMENDATIONS

Mine Remediation

Subgrade Preparation

Installing Compacted Stone Columns

Slab-on-grade and pavement Subgrade Preparation

Engineered Fill

Reuse of Existing Site Soils

Imported Fill

Fill Placement and Compaction

Foundations and Floor Slabs

Shallow Foundations on Improved Ground

Floor Slabs

Seismicity

Pavement Design

Flexible Pavement

Rigid Pavement

Corrosion Test Results

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Revised 25 July 2024

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Utilities

Sloped Excavations and Temporary Excavation Support

Groundwater Control During Construction

SERVICES DURING DESIGN, CONSTRUCTION DOCUMENTS AND CONSTRUCTION

QUALITY ASSURANCE

OWNER AND CONTRACTOR RESPONSIBILITIES

LIMITATIONS

LIST OF FIGURES

Figure 1 Site Location Map

Figure 2 Location Plan

Figure 3 USDA Soils Map

Figure 4 Bedrock Geology Map

Figure 5 Pittsburgh Coal Map

Figure 6 Mine Map

Figure 7 Landslide Hazard Map

LIST OF APPENDICES

Appendix A Boring Logs and Boring Log Legend

Appendix B Rock Core Photographs

Appendix C Laboratory Test Results

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

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INTRODUCTION

This report presents the findings of a geotechnical engineering study performed by Langan

Engineering and Environmental Services, Inc. (Langan) on behalf of AE7 (the “Client”) for the proposed C.O.P. – Fire Station 20 / Medic Station 12 in West Mifflin, Allegheny County, Pennsylvania. Langan’s scope of services included (1) researching and reviewing available site information; (2) obtaining subsurface information by subcontracting to drill at accessible site areas and performing laboratory testing of soil samples; (3) analyzing the collected information and data;

and, (4) providing recommendations for earthwork and foundation design and other geotechnical aspects of the proposed construction.

Our services were completed in two phases. Langan completed three preliminary borings, in

April 2021, to investigate the mine workings conditions in the Pittsburgh coal seam and provided a preliminary memorandum to assist with building location. Subsequent to receiving a proposed building location, Langan completed seven additional borings to develop foundation and slab design and geotechnical-related site preparation recommendations. Following the issuance of our 1 June 2021 report, the building footprint was moved over the mined out area to avoid relocation of a deep sanitary sewer line; this revised report addresses the changes to the mined-out area.

All elevations given in this report are referenced to the North American Vertical Datum of 1988

(NAVD 88) and are in feet, unless otherwise noted.

PROJECT UNDERSTANDING

Existing Conditions

The ±5.9-acre lot identified by Allegheny County Parcel Number 184-E-80 (the “Site”) is bounded by Mifflin Road to the southwest, a commercial property to the southeast, and residential properties to the northeast and northwest and is currently undeveloped. However, the city of

Pittsburgh uses the Site as a repository for demolition debris. See Figure 1 for a Site Location

Map.

Existing ground surface elevations (el) at the Site range from el ±1,079 feet in the northeast corner of the Site to el ±1,136 feet in the southwest corner. See Figure 2 for a Location Plan.

Proposed Development

We understand that the City of Pittsburgh intends to construct a new two-story combined firehouse and EMT building with a ±19,600 square-foot footprint, associated asphalt and concrete surface parking, and one detention basin. We understand that the proposed finished floor elevation of the proposed building will be el 1,096.5 feet. A 7 February 2024 grading plan prepared by Langan indicates that maximum cuts of roughly 11 feet and fills of roughly 6 feet will be required to reach proposed grades. Atlantic Engineering Services, the project structural engineer, provided the following preliminary maximum column and wall compressive loads:

Pittsburgh, Allegheny County, Pennsylvania

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• Maximum column load: 100 kips; and,

• Maximum continuous wall footing load: 2 kips/linear foot (klf).

When available, we should be provided final column and wall compressive loads for evaluation, if different than described herein. When the final Site and grading plans are available, we should be provided the opportunity to review the building location and final grades to confirm that the recommendations provided herein are appropriate.

REVIEW OF AVAILABLE INFORMATION

We reviewed available aerial photographs and topographic maps; soil survey data; regional geologic information; and Langan’s preliminary geotechnical report for the Site. Pertinent information obtained from these documents is summarized in the following subsections.

Historical Aerial Photographs

Available historical aerial photographs for the Site were dated 1947, 1948, 1949, 1952, 1956, 1959, 1969, 1973, 1983, 1993, 1995, 2004, 2005, 2006, 2008, 2009, 2010, 2012, 2013, and 2015.

The aerial photographs indicate that the Site was occupied by a mobile home park prior to 1947.

Each of the aerial photographs show additional mobile homes on the Site until the 2004 photograph, which shows the removal of the mobile homes. Aerial photographs after 2004 depict the Site is in its present configuration.

Historical Topographic Maps

Available historical topographic maps for the Site were dated 1904, 1907, 1908, 1910, 1915, 1926, 1928, 1932, 1937, 1946, 1949, 1955, 1957, 1961, 1967, 1971, 1980, 1998, 2013, 2016, and 2019. The topographic maps indicate that the Site was occupied by a railway and several residential buildings prior to 1904. The topographic maps indicate the Site was unchanged until the 1955 map which shows the removal of the railway line and residential buildings. No changes are visible to the Site following the 1955 topographic map.

Soil Survey Data

The USDA soil survey for the Site indicates the soil present at the Site consists of Urban land-

Culleoka complex, 8 to 25 percent slopes (UCD) and the Gilpin, Weikert, Culleoka channery silt loams and 25 to 80 percent slopes (GSF). Urban land – Culleoka complex consists of human transported materials over fine-loamy residuum weathered from sandstone and siltstone. The

Gilpin, Weikert, Culleoka channery silt loams consist of acid fine-loamy residuum weathered from shale and siltstone. The depth to restrictive features is reportedly between 20 and 40 inches. The depth to the water table is reportedly greater than 80 inches. See Figure 3 for the USDA Soils

Map.

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Regional Geology

A review of the Bedrock Geology Map of Pennsylvania (Berg et. al., 1980) indicates the bedrock beneath the Site consists of Pennsylvanian age Monongahela Group. The Monongahela Group consists of cyclic sequences of limestone, shale, sandstone, and coal. The base of the formation is at the bottom of Pittsburgh Coal. See Figure 4 for Bedrock Map.

Mining

According to the Coal Resources of Allegheny County, Pennsylvania mine maps, the Pittsburgh

Coal has reportedly been deep mined beneath the Site. The Coal Crop Line and Structure

Contours map of the Glassport Quadrangle indicates that the crop line of the Pittsburgh coal beneath the site is roughly el 1040, approximately 40-to-70 feet below the surface. The Site is bisected by the Amity Anticline. See Figure 5 for Pittsburgh Coal Map and Figure 6 for Mine Map.

Landslide Hazards

According the Landslides and Related Features map (Pomeroy, 1979) of the Glassport

Quadrangle, the Site contains material susceptible to rockfalls and coal refuse piles, not burnt or on fire. See Figure 7 for Landslide Hazard Mapping.

Langan Preliminary Geotechnical Report

Langan completed a preliminary subsurface exploration and memo comprised of recommendations for the proposed development dated 28 May 2021. Langan’s preliminary memo documented the exploration consisted of drilling three (3) borings, identified as LB-1 through LB-3, to depths between roughly 62 and 72 feet. LB-1 is located in an area where mine maps indicate mining did not occur; whereas LB-2 and LB-3 are located in areas indicated by former underground mining.

In general, subsurface conditions consist of between 5 and 35 feet of loose to medium dense, predominately granular, fill over dense granular residual soil over bedrock consisting of sandstone, shale, and coal. Boring LB-1 encountered no evidence of mining; however, both borings LB-2 and LB-3 encountered tool drops while drilling and evidence of mine gob.

SUBSURFACE EXPLORATION

Our final field exploration consisted of drilling seven (7) borings, identified as FB-1 through FB- 7, to depths of about 10-to-57 feet. The boring locations were marked in the field by Langan field personnel at the approximate locations shown on the Location Plan (see Figure 2). The borings were drilled by Test Boring Services, Inc. (TBS) of Washington, Pennsylvania on 1 and 4 April

2022, under the direct observation of Langan geotechnical engineers, under the direct supervision of the project Professional Engineers. TBS drilled the borings using a track-mounted

Diedrich D-50 drill rig, hollow-stem auger drilling, and NX rock coring techniques.

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Standard Penetration Test (SPT) procedures were used to obtain samples from all borings in general accordance with the provisions of ASTM D1586; a 140-pound automatic hammer was used to drive the standard 2-inch OD split-spoon soil sampler. SPTs were performed in a near continuous manner to the proposed termination depth or to split-spoon refusal. Split-spoon refusal is defined as 50 or more hammer blows to drive the sampler 6 inches or less. Following

SPT refusal, in select borings, rock was cored using an NX-size double-tube core barrel equipped with a diamond cutting bit in accordance with ASTM D2113 to obtain up to 5-foot-long rock cores.

The soil and rock samples were classified in the field by our engineer in accordance with ASTM

D2488 (visual method) and the Unified Soil Classification System (USCS). Groundwater levels were recorded upon completion of soil sampling and after rock coring. Soil classifications, SPT blow counts and N-values, and other field observations were recorded on the boring logs. Rock type, percent core recovery, and Rock Quality Designation (RQD - i.e., the sum of rock pieces 4 inches long or longer divided by the rock core run length) were recorded by our geotechnical engineer and retrieved rock cores were photographed. Field records including individual boring logs are provided in Appendix A, and rock core box photographs are provided in Appendix B.

The SPT samples were obtained using a hydraulically driven automatic trip hammer. Most correlations with SPT data are based on N-values collected with a safety hammer. The hammer efficiency for the Diedrich D-50 hammer is not known, however it is estimated to be roughly 20% greater than that applied using the safety hammer. The hammer blows shown on the boring logs are uncorrected for the higher energy; however, we correct SPT N-values for the higher energy

(N60) when using N-values in our analyses.

Laboratory Testing

Soil samples from the geotechnical exploration were visually examined in the field and classifications were confirmed by re-examination in our Canonsburg, Pennsylvania office.

Representative disturbed soil samples were selected for testing and sent to our subcontracted laboratory, Geotechnical Testing Services, Inc. of Coraopolis, Pennsylvania, to determine physical and engineering properties for use in our analyses and evaluations. The following laboratory tests were performed for the project:

• Grain-Size Analysis; ASTM D422;

• Moisture Content; ASTM D2216;

• Atterberg Limits; ASTM D4318;

• Standard Proctor; ASTM D698;

• California Bearing Ratio (CBR); ASTM D1883;

• Soil Corrosivity:

o Soil pH (AASHTO T289);

o Soil resistivity (AASHTO T288);

o Sulfates (AASHTO T290);

o Sulfides (AWWA 4500-S);

o Soil ORP (ASTM G200); and

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The results of the geotechnical testing are discussed under the soil strata descriptions in the following sections. The laboratory test results are provided in Appendix C.

SUBSURFACE CONDITIONS

In general, subsurface conditions encountered in the borings consisted of fill over residual soils, over bedrock. More detailed descriptions of the encountered material are described in the following paragraphs.

Surface Materials

Boring FB-2 identified about 5 inches of topsoil at the surface. All other borings identified fill at the surface.

Fill

In borings FB-1 through FB-7 and LB-1 through LB-3, a roughly 5 to 35 foot thick layer of fill was encountered, starting from ground surface or below topsoil, where present. Borings FB-1 and

FB-2 were terminated in the fill stratum. The fill in all borings, except in FB-4 and FB-7, consisted predominately of sand and gravel with varying amounts of silt and clay and deleterious materials

(i.e., slag, cinders, and brick and concrete fragments). The granular fill was generally observed to be loose to medium dense as evidenced by SPT N60-values generally ranging from 5 to 28 blows/foot, and averaging about 16 blows/foot.

In borings FB-4 and FB-7, fill consisted predominantly of silt and clay with varying proportions of gravel and sand. The fine grained fill was observed to be firm to very stiff as evidenced by SPT

N60-values ranging from 7 to 23 blows/foot, and averaging about 13 blows/foot.

Laboratory classification tests were completed on selected fill samples and the results are summarized in Table 1 below.

Table 1 – USCS Soil Classification Results

Boring

Sample

Depth

(feet)

Water

Content

Liquid

Limit

Plasticity

Index

USCS

Gravel

Fraction

USCS

Sand

Fraction

USCS

Fines

Fraction

USCS

Material

Classification

FB-7 0.0-10.0 11.7 32 12 5.9 28.1 66.0 CL

FB-4 9.0-10.5 19.4 40 15 16.7 24.7 58.6 CL

FB-6 15.0-16.5 11.6 28 9 31.1 31.0 37.9 GC

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Residual Soils

Residual soils, which are formed in-place by the complete weathering of the underlying rock, were encountered immediately beneath the fill in borings FB-6 and FB-7 and LB-1 through LB-3.

The residual soils consisted of predominately of sand and gravel with a lesser and varying amounts of rock fragments, silt, and clay.

The granular residual soils consisted of dry silty or clayey sand having varying proportions of gravel, and was generally found to be loose to very dense as evidenced by SPT N60-values generally ranging from 9 to greater than 100 blows/foot, and averaging about 43 blows/foot.

Bedrock

Immediately beneath the residual soils, roughly 1 to 3 feet of weathered bedrock was encountered in all borings, except in FB-1 and FB-2 which were terminated in the fill stratum.

The weathered rock was observed to be very dense as evidenced by SPT N-values greater than

50 blows/foot, and was generally found to be dry.

Rock cores collected from boring FB-3, LB-1, LB-2 and LB-3 were comprised of sandstone, shale, sandstone, coal, limestone and claystone of varying hardness, weathering, and quality (i.e., fracture density). The rock core recovery (REC), defined as the ratio of total length of core recovered to the length of the core run, ranged from 0% to 100%, and averaged 80%. The rock quality designation (RQD) of the bedrock, defined as the sum of pieces 4 inches or more in length divided by the core length, ranged from 0% to 100%, and averaged about 29% indicating generally poor quality rock.

Coal was encountered in boring FB-3, between depths of about 45-to-56 feet, corresponding to about elevations 1,049 feet and 1,038 feet, respectively. Coal was also encountered in boring

LB-1, between depths of about 46 to 57 feet, corresponding to about elevations 1,044 feet and

1,033 feet, respectively. RQD for coal is commonly zero or very low.

Voids, as evidenced by loss of drilling water and tool drops during drilling, were encountered during preliminary subsurface exploration in April 2021, in Borings LB-2 and LB-3, at depths of about 49 and 58 feet, respectively, corresponding to about elevations1,046 and 1,042 feet, respectively. Voids were not encountered in other borings.

Groundwater

Water was encountered during soil sampling in Borings FB-2 and LB-1 at about 6 feet and 3 feet below existing grade, and was determined based on the wetness of the soil samples and pooling of water in the bore hole. The wet samples are likely the result of perched water, which occurs when groundwater becomes trapped above cohesive soil with low permeability. Perched groundwater within the fill stratum should be anticipated. Water was not encountered in other borings and the remaining samples in other borings were generally dry or moist.

Pittsburgh, Allegheny County, Pennsylvania

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These observations represent the groundwater at the time of the exploration only. Seasonal and yearly fluctuations in groundwater elevation should be expected with variations in precipitation and other hydrologic factors.

EVALUATION AND RECOMMENDATIONS

Our test borings encountered fill material to a depth of up to about 35 feet below existing grade.

The fill contains deleterious materials (i.e., brick fragments, slag, cinder, etc.) and does not appear as though it was placed in controlled and compacted lifts, as evidenced by wide variations in SPT

N-values. The subsurface condition on this Site is not suitable to support the structural loads via a conventional shallow foundation system, consisting of spread and strip footings bearing on unimproved existing material. We recommend that the proposed building be supported on footings bearing on soil improved by stone columns.

Additionally, based on available mining information and boring data, the Site underground abandoned coal mines occupy the northern and eastern portions of the Site. Because the proposed building will partially span the undermined portion of the Site, mine stabilization using saturation grouting is required to minimize the risk of ground subsidence and settlement.

The following sections present our recommendations regarding the geotechnical aspects of the proposed Site work and construction based on the subsurface conditions established by our geotechnical exploration, laboratory testing, and analysis.

Mine Remediation

Saturation grouting should be performed beneath the portion of the building that extends over the mined out area - roughly 80% of the building footprint in all portions excepting the western corner. Saturation grouting is accomplished by drilling percussion holes into the mine void on a grid pattern extending in approximately a 5 foot offset from the building footprint and gravity-injecting a fluid (i.e., high-slump) cement grout to fill the void space. A low-slump mix of concrete should be injected around the perimeter of the new building (or portions thereof) to create a barrier that prevents the fluid grout from flowing beyond the proposed limits of the remediation.

The grouting program should be developed based on the available mine maps and exploration findings.

Based on the area of the mapped mine openings, and verified by our borings, approximate height of voids, but unknown coal extraction ratio (estimated to range from 40 to 60%, which is common for the region), we preliminarily estimate a theoretical range of grout/concrete volume take for the proposed building in its current proposed location could be on the order of 4,000 to 9,000 cubic yards. Additional mine research, exploration, characterization, and finite element modelling could be performed to refine these estimates.

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Subgrade Preparation

After removal of surficial material, and excavation to final subgrade (within cut areas), and before placing compacted fill to raise site grades, the following subgrade preparation procedures must be implemented prior to fill placement and construction of the building slab.

Installing Compacted Stone Columns

Compacted Stone Columns are columns constructed of rammed aggregate which act as a soil reinforcing element. We recommend that the Impact Pier System by Geopier® or approved equivalent method be used to construct the compacted stone columns. The Impact Pier method displaces the soil during stone column installation rather than creating an augered hole with spoils. The cavity associated with the Impact Pier is created by a specially designed mandrel that is pushed and vibrated into the ground. Stone is placed into the cavity as the mandrel is withdrawn. The mandrel also acts as a tamper to compact the stone. The compacted stone columns improve the ground conditions by providing a stiff composite ground mass.

We expect that the stone column lengths will extend through the fill and bear on dense residual soil or decomposed rock, which was encountered at about elevations 1,070 to 1,082 feet, in borings FB-3 through FB-6, advanced within the proposed building footprint. The stone columns are typically on a grid pattern spaced at 4 to 8 feet on center.

Because stone column installation methods are proprietary, the stone column design and layout should be prepared, signed, and sealed by a Professional Engineer licensed in Pennsylvania that specializes in that design and submitted to our firm for review. The design and improved ground must simultaneously provide the design bearing pressure specified herein and satisfy the long term post construction settlement requirements.

Pre-augering or excavation of obstructions in the fill should be performed as necessary to facilitate stone column installation.

One on-site modulus test should be conducted in the weakest area of the Site. The test pier should be loaded to approximately 150% of the maximum theoretical load. The settlement should not exceed 1 inch at 100% of the maximum theoretical load.

Slab-on-grade and pavement Subgrade Preparation

After completion of site clearing, installing ground improvement elements and excavation to plan subgrade elevation, but before placing compacted fill, we recommend that the subgrade within the proposed development areas be proof-compacted with a minimum of six overlapping passes of a vibratory sheeps-foot or pad-foot roller having a minimum static drum weight of 10 tons.

Additional proof-compacting coverages should be completed in any areas deemed necessary based on observations made by a qualified inspecting geotechnical engineer.

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Before constructing finished surfaces (i.e., building slabs, asphalt and concrete pavement), we also recommend that the sub-base be proof-rolled using a fully-loaded tri-axle dump truck in the presence of a qualified geotechnical engineer. Soft areas identified during proof-rolling should be excavated to a firm, unyielding surface, and replaced with approved, compacted fill. If the over-excavation fails to observe competent subgrade within 2 feet, other options of stabilization should be considered (i.e., chemical stabilization or placing a layer of triaxial geogrid); we should be consulted to provide supplemental recommendations based on the field conditions.

Fill should not be placed on wet or loose subgrade. Sufficient time should be provided to dry and re-compact loose, wet soils. In the event such time is not available, such unsuitable subgrade soils, as determined by the inspecting geotechnical engineer, should be excavated and replaced with approved compacted fill or the subgrade should be stabilized by adding lime to dry the wet soils. When sufficient time to air dry excessively wet Site soils is not available, lime dry the soils by blending 1 to 4% lime, by weight, to facilitate handling, placement, and compaction.

All approved subgrade surfaces should be graded and sealed to facilitate drainage and prevent loss of support. During the cutting and filling operations, construction equipment should follow consistent traffic patterns throughout the Site to minimize disturbance of the subgrade during wet periods. The contractor should preferentially stabilize and protect approved subgrade soils from damage.

Do not place fill material on areas where free water is standing, on frozen subgrade areas, or on surfaces which have not been approved by the inspecting geotechnical engineer.

For pavement and building slab areas, the sub-base material can be placed as a protective layer as soon as practical upon completing Site grading and subgrade preparation work. Before floor slab construction and pavement installation, this aggregate sub-base layer should be repaired, re-graded, and re-compacted, when necessary as determined by the inspecting geotechnical engineer.

Engineered Fill

All fill placed in structural areas, including the building pad and parking lots, is considered structural fill. All fill placed in landscaped areas is considered general fill. All structural fill must be free of organics, wood, metal, debris, or other deleterious materials and should conform to any environmental requirements for this project.

Reuse of Existing Site Soils

The Site is used by the city of Pittsburgh as a repository for demolition debris. As such, there are numerous piles of concrete chunks; brick and concrete masonry fragments; and asphalt fragments and millings throughout the Site. This debris is generally unsuitable for use as structural fill; however, can be crushed or processed to particles have dimensions less than 3 inches in any direction and used as slab or pavement subbase.

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The majority of the on-Site fill to be excavated for construction contains deleterious materials

(e.g., bricks, cinder, slag, etc.), and is not suitable for reuse as structural fill; however, on Site soils can be used as non-structural fill to raise grades in landscaped areas. A portion of the on-

Site soils have a relatively high percentage of fines and should be blended with predominantly granular soil when placed in fills. The blending ratio should be 1:1 fine-grained to granular soils.

The fine-grained soils are expected to be difficult to handle, place, and compact if they become excessively wet. Before placing and compacting the excavated soils, moisture conditioning to an acceptable moisture content such as by discing or air drying, as determined by a qualified geotechnical engineer, may be necessary. We recommend minimizing the duration of exposure to precipitation of the on-Site soils to be reused as fill. Soils should be placed as fill as soon as possible following excavation, with stockpiling of on-Site soil minimized where construction allows. Stockpiled soil should be protected from precipitation when practical. We also recommend that earthwork take place during dry weather. Lime can be used to improve the material handling characteristics of these soils. Should stabilization be required, appropriate blends should be designed and reviewed by the Owner’s engineer.

Imported Fill

Imported fill should consist of a relatively well-graded mixture of sand and gravel with not more than 30 percent (by weight) finer than the No. 200 sieve and with a maximum particle size of 6 inches. The use of any imported fill containing a higher percentage of fines would need to be evaluated by a qualified geotechnical engineer during construction.

Suitable fill should be free of all organics, metal, debris, or other deleterious materials and should conform to any environmental requirements for this project. Imported fill should not contain sulfates or chlorides detrimental to buried concrete and metal. Imported fill should also be free from slag and pyrite. The Contractor should provide documentation of compliance before delivery of any fill to the Site.

The Contractor should submit laboratory test results to certify the fill is free from these materials.

Grain size distribution, maximum dry density, and the optimum water content determinations should be made on representative samples of the backfill and fill materials proposed by the

Contractor.

Fill Placement and Compaction

Structural fill (i.e., beneath the building and pavement areas) should be placed in uniform lifts and compacted to at least 95 percent of the material’s maximum dry density as determined by the

Modified Proctor Compaction Test (ASTM D1557). Fill placed in landscape areas should be compacted to at least 90 percent of the material’s maximum dry density as determined by the

Modified Proctor Compaction Test (ASTM D1557). Imported select fill should be placed in 12-

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1 June 2021 inch-thick loose lifts and compacted using a smooth-drum vibratory roller having a minimum static drum weight of 5 tons. Site fine-grained soils should be placed in 8-inch-thick loose lifts and compacted using a sheeps-foot roller having a minimum static drum weight of 5 tons. Smaller compaction equipment (i.e., walk-behind trench roller or jumping jack compactor) and thinner lifts

(maximum 6-to-8 inches thick) should be used in areas of limited maneuverability.

For fill containing oversized rock or material with greater than 40% of gravel-sized rock fragments, a Proctor Compaction Test does not accurately represent in situ conditions. Therefore, individual lifts should be compacted with a minimum of six overlapping coverages using a vibratory roller to provide a firm, unyielding surface as determined and approved by the inspecting geotechnical engineer.

The water content at the time of compaction should be within 3 percentage points of the optimum water content. All fill placement should be subject to observation and testing by a qualified geotechnical engineer. No fill material should be placed on areas where free water is standing, on frozen subgrade areas, or on surfaces which have not been approved by a qualified geotechnical engineer.

Foundations and Floor Slabs

Shallow Foundations on Improved Ground

We expect that following ground improvements, bearing capacities of 4 kips per square foot (ksf) can be achieved. Footing design should consider the influence stress from adjacent footings. The design of improved ground must simultaneously provide the design bearing pressure specified herein and satisfy the long term post construction settlement criteria of no more than 1 inch total settlement, and no more than 0.5 inches differential settlement between adjacent columns. For mass concrete poured against approved compacted soil subgrade, we recommend using a coefficient of sliding friction of 0.3.

Perimeter strip footings should have a minimum width of 24 inches and interior strip footings should have a minimum width of 18 inches; even if smaller dimensions can be justified using the allowable bearing pressure indicated above. The minimum dimension for isolated footings should be 3 feet by 3 feet. Perimeter foundations and foundations in unheated parts of the building must be a minimum depth of 3 feet below final grade to reduce the potential for frost heave. Interior footings in heated areas are not subject to this requirement.

The final footing subgrade on stone column improved soil must be approved by a qualified inspecting geotechnical engineer. Detailed recommendations for subgrade preparation are provided in the Subgrade Preparation section of this report.

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Floor Slabs

The building ground-floor slab can be conventional slab-on-grade construction bearing on proofrolled/compacted soil subgrade areas. The floor slab can be designed using a modulus of subgrade reaction of 100 pounds per cubic inch (lbs/in3).

Slab areas should be proof-rolled with a drum roller having a minimum static drum weight of

10 tons. Slab bearing areas must be inspected and approved by a qualified geotechnical engineer before steel reinforcement or concrete placement. Any soft, loose, or unsuitable soils identified by the inspecting geotechnical engineer during proof-rolling should be removed and replaced with approved compacted fill.

We recommend that a minimum 6-inch-thick layer of ¾-inch clean crushed stone be constructed beneath the slabs of the buildings to protect the subgrade after it has been properly prepared and to serve as a capillary break. We recommend a 10 mil vapor retarder be placed between the slab and crushed stone. Because the development program is not known at this time, the designer should refer to the decision flowchart in ACI 302.2 Figure 7.1 for the location and placement of the retarder. Construction and/or saw cut joints should be provided as necessary for crack control.

Concrete mixes with high water/cement (w/c) ratios result in excess water in the concrete, which increases the cure time and results excessive vapor transmission through the slab. Therefore, concrete for the floor slab should have a low w/c ratio – less than 0.45. The slab should be properly cured. Construction and/or saw cut joints should be provided as necessary for crack control.

Seismicity

Seismic coefficients are based on the 2018 IBC (i.e., ASCE 7-16) and the U.S. Geological Survey.

Based on the limited boring information obtained, we expect the proposed development can be designed using the seismic parameters listed below.

• Site Class = D

• Maximum Considered Earthquake Ground Motions

• 0.2 Second Spectral Response Acceleration, Ss = 0.089g

• 1.0 Second Spectral Response Acceleration, S1 =0.045g

The above ground motions should be adjusted for site class “D” effects using coefficients

Fa = 1.6 and Fv = 2.4.

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

Pavement Design

Flexible Pavement

We have provided recommendations for minimum asphalt and concrete pavement sections based on assumed traffic loading data, and the anticipated subgrade soils. Our design was based on Equivalent Single Axle Loads (ESAL) of 100,000. The pavement sections were designed using a 20-year life expectancy, and California Bearing Ratio (CBR) of 2, as determined by laboratory test results, was used in our analysis. This CBR value is expected to generally represent the compacted Site soils while in service. Based on our analysis, we recommend the following pavement sections for this project:

Table 2 – Recommended Standard Duty Flexible Pavement Minimum Sections

Material Thickness

Bituminous Concrete Wearing Course, PennDOT 9.5mm Wearing Course 2 inches

Bituminous Concrete Binder Course, PennDOT 19 mm Binder Course 3 inches

Subbase Course

PennDOT No. 2A Aggregate Base Course 12 inches

Rigid Pavement

We also analyzed and provided design recommendation for Portland cement concrete (PCC) paving for heavy duty sections in lieu of the above noted flexible pavement. This pavement was designed following the rigid pavement design guidelines given in the AASHTO Guide for Design of Pavement Structures. The aforementioned Heavy Duty Pavement vehicular loading data with a 20-year design life, and a soil subgrade reaction (k) of 100 lbs/in3 was utilized in our analysis.

We recommend the following PCC pavement sections for this project:

Table 3 – Recommended Pavement Section

Material Thickness

Top (Finish) Course (4000 psi Portland cement) 6 inches

Subbase Course

PennDOT No. 2A Aggregate Base Course 12 inches

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

The concrete pavement should include steel reinforcement consisting of Grade 60 No. 3 deformed bars. Slab reinforcement longitudinal and transverse spacing should be a maximum of

48 inches on center. Reinforcement should be properly supported on chairs during concrete placement.

Reinforcement should be placed so that 3 inches of concrete coverage is provided between the steel reinforcement and the aggregate subbase. Sawcut joints should be provided as necessary for crack control. The actual expansion joint longitudinal and transverse spacing should be determined after the Site plan drawings, including the dimensions of the loading and approach slab area, are finalized.

The pavement design parameters recommended herein will require a properly prepared subgrade prepared in accordance with the Subgrade Preparation section of this report. Drainage is essential for adequate pavement performance. Therefore, we recommend the design include surface and subsurface drainage systems that maintain the subgrade near optimum moisture conditions. In addition, the subgrade should be compacted, fine graded, and constructed to drain without ruts or low areas that could collect water. The granular base should be allowed to drain freely and should not be used to fill low areas.

Pavement materials should be selected, installed, and placed in general accordance with the applicable specifications and procedures as recommended by reputable controlling agencies such as PennDOT, AASHTO, Asphalt Institute, American Concrete Institute, etc.

Pavement subgrade preparation work should be inspected by a qualified geotechnical engineer.

Should isolated areas exhibit unsuitable conditions, the isolated areas should be over-excavated to a depth as determined by the Geotechnical Engineer and immediately replaced with approved compacted fill or aggregate base.

Corrosion Test Results

The results of the corrosion testing of the composite bag sample from boring FB-1 collected between 0 and 10 feet, indicate that the soil is corrosive to ductile iron and steel. Utilities that come in contact with existing soils should be constructed using plastic pipes or appropriate corrosion protection. Epoxy coated reinforcing steel should be used in concrete elements that will be in contact with existing soils. The results are summarized in the Table 4 below.

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

Table 4 – Corrosion Potential Test Results

Parameter Test Result Points1 Total Points2

Corrosive

Ductile Iron Concrete Steel

Moisture Content Fair 1

14.5 Yes No Yes

pH 7.7 0

Min. Resistivity 360 Ω-cm 10

Soil ORP 215 mV 0

Sulfides Very High 3.5

Chloride-Ion 884 ppm N/A

Sulfate 783 ppm N/A

• Points based on the 10-Point Soil Evaluation Procedure outlines in ANSI/AWWA C105-72 (R77)

• The points from all five areas are totaled, and if the sum is 10 or greater, the soil is considered corrosive.

Utilities

All excavations should be properly sloped and/or braced in conformance with applicable OSHA regulations. Before utility installations, exposed utility trenches should be proof-rolled with at least six (6) overlapping coverages of a double-drum walk-behind vibratory roller such as a vibratory plate or equivalent. Any soft or unstable areas identified by the proof-rolling should be removed and replaced with compacted fill. Backfill in utility excavations should meet the previously discussed requirements for engineered fill, including fill placement and compaction requirements.

Sloped Excavations and Temporary Excavation Support

Excavations should be sloped or stepped whenever possible to minimize the need for temporary excavation support. The excavation side slopes should be no steeper than 1.5H:1V. Any stepped excavations should also be performed using the same criterion. Where limited space availability does not allow for sloping or stepping of an excavation, a temporary excavation support system will be required.

The final design of temporary excavation support systems should be the responsibility of the contractor’s Professional Engineer licensed in Pennsylvania. The foundation contractor should submit design calculations and drawings signed and sealed by a licensed Pennsylvania

Professional Engineer showing his proposed temporary excavation support and underpinning systems, if such systems are required. The design soil and rock loads should be reviewed before constructing the support structures, and the design should also take into account the loads from adjacent structures, surface traffic, other construction surcharge loading (i.e., construction equipment, material storage, etc.), and hydrostatic pressure arising from incidental water accumulation behind the excavation support and underpinning elements.

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

Excavation support construction should be performed under the special inspection of an

Pennsylvania-licensed Professional Engineer. The contractor should perform excavation support construction and underpinning work without causing loss of support or other adverse impacts to the neighboring structures, utilities, sidewalks, and streets. The excavation support system and neighboring structures being underpinned should be monitored for vertical and lateral movements using survey control points periodically.

Groundwater Control During Construction

Groundwater was not encountered in our borings. However, perched water may still be encountered in these excavations for proposed building foundations or utilities. Groundwater can be expected to fluctuate with weather, seasonal conditions, or construction activity. Should shallow groundwater be encountered during construction, shallow interceptor trenches should be installed to divert water away from the building and improve Site subgrade conditions.

We expect that groundwater, perched water, and collected stormwater can be controlled using conventional submersible pumps in conjunction with gravel sumps. Water should not be allowed to pond over soil subgrades. Proper grading and trenching along with pumping are needed to maintain the Site in a dry and workable condition, and to prevent disturbance of the bearing subgrades. The pumping, handling and discharge of all dewatering effluent should be performed in accordance with all applicable regulations and any environmental requirements established for the Site.

SERVICES DURING DESIGN, CONSTRUCTION DOCUMENTS AND CONSTRUCTION

QUALITY ASSURANCE

During final design we should be retained to consult with the design team as geotechnical questions arise. Technical specifications and design drawings should incorporate

Langan’s recommendations. When authorized, Langan will assist the design team in preparing specification sections related to geotechnical issues such as earthwork, ground improvement, shallow foundations, backfill, and excavation support. Langan should also, when authorized, review the project plans, as well as Contractor submittals relating to materials and construction procedures for geotechnical work, to confirm the designs incorporate the intent of our recommendations.

Langan has explored and interpreted the Site subsurface conditions and developed the foundation design recommendations contained herein, and is therefore best suited to perform quality assurance observation and testing of geotechnical-related work during construction. The work requiring quality assurance confirmation and/or special inspections per the Building Code includes, but is not limited to, earthwork, backfill, ground improvements, shallow foundations, and excavation support.

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021

Recognizing that construction observation is the final stage of geotechnical design, quality assurance observation during construction by Langan is necessary to confirm the design assumptions and design elements, to maintain our continuity of responsibility on this project, and allow us to make changes to our recommendations, as necessary. The foundation system and general geotechnical construction methods recommended herein are predicated upon Langan assisting with the final design and providing construction observation services for the Owner.

Should Langan not be retained for these services, we cannot assume the role of geotechnical engineer of record, and the entity providing the final design and construction observation services must serve as the engineer of record.

OWNER AND CONTRACTOR RESPONSIBILITIES

The Contractor is responsible for construction quality control, which includes satisfactorily constructing the foundation system and any associated temporary works to achieve the design intent while not adversely impacting or causing loss of support to neighboring property, structures, utilities, roadways, etc. Construction activities that can alter the existing ground conditions such as excavation, fill placement, foundation construction, dewatering, etc. can also induce stresses, vibrations, and movements in nearby structures and utilities, and disturb occupants. Contractors are solely responsible to ensure that their activities will not adversely affect the structures and utilities, and will not disturb occupants. Contractors must also take all necessary measures to protect the existing structures, utilities, etc. during construction. By using this report, the Owner agrees that Langan will not be held responsible for any damage to adjacent structures, utilities, etc.

The preparation and use of this report is based on the condition that the project construction contract between the Owner and their Contractor(s) will include: 1) Langan being added to the

Project Wrap and/or Contractor’s General Liability insurance as an additional insured, and 2) language specifically stating the Foundation Contractor will defend, indemnify, and hold harmless the Owner and Langan against all claims related to disturbance or damage to adjacent structures, utilities, etc. or properties.

LIMITATIONS

The conclusions and recommendations provided in this report result from our interpretation of the geotechnical conditions existing at the Site inferred from a limited number of borings and architectural and structural information provided by AE7 and Atlantic Engineering Services. Actual subsurface conditions may vary. Recommendations provided are dependent upon one another and no recommendation should be followed independent of the others.

Any proposed changes in structures or their locations should be brought to Langan’s attention as soon as possible so that we can determine whether such changes affect our recommendations.

Information on subsurface strata and groundwater levels shown on the logs represent conditions

Pittsburgh, Allegheny County, Pennsylvania

Langan Project No.: 250129401

1 June 2021 encountered only at the locations indicated and at the time of exploration. If different conditions are encountered during construction, they should immediately be brought to Langan’s attention for evaluation, as they may affect our recommendations.

This report has been prepared to assist the Owner, architect, and structural engineer in the design process and is only applicable to the design of the specific project identified. The information in this report cannot be utilized or depended on by engineers or contractors who are involved in evaluations or designs of facilities (including underpinning, grouting, stabilization, etc.) on adjacent properties which are beyond the limits of that which is the specific subject of this report.

Environmental issues (such as permitting or potentially contaminated soil and groundwater) are outside the scope of this study and have been addressed in a separate evaluation.

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Combined Safety Facility Geotechnical Report.docx

FIGURES

Figure 1 – Site Location Map

Figure 2 – Location Plan

Figure 3 – USDA Soils Map

Figure 4 – Bedrock Geology Map

Figure 5 – Pittsburgh Coal Map

Figure 6 – Mine Map

Figure 7 – Landslide Hazard Map

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Date: 7/24/2024 Time: 14:58 User: adjacobs Style Table: Langan.stb Layout: 2 Document Code: 250129401-0501-BL101-0101 www.langan.com

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APPENDIX A

BORING LOGS AND BORING LOG LEGEND

APPENDIX A1

PRELIMINARY BORING LOGS

S -1

S -2

S -3

S -4

S -5

S -6

S -7

S -8

S -9

S -1

S

-1

S S

S S

S S

S S

S S

S S

S S

S S

S S

S S

S S

Brown Sandy medium GRAVEL, some silt (moist) [FILL]

Brown to black Silty fine-coarse SAND, trace gravel, coal…