T-1795-0150- Addendum No. 5.pdf

FROM: Maryland Transit Administration

SUBJECT: Addendum No. 5

T-1795-0150 METRO WABASH VEHICLE WASH UPGRADE

DATE: January 25, 2024

Addendum No. 5 is One-Thousand eleven (1011) pages and includes the following:

ITEM No. 1 --- Provides the “RFI” questions and answers for the project.

ITEM No. 2 --- Provides the “Geotechnical Engineering Report” for the project.

ITEM No. 3 --- Provides the “Limited Lead Base Paint Screening” for the project.

ITEM No. 4 --- Provides the “Lead Base Paint Inspection Report” for the project.

ITEM No. 5 --- Provides a revised “SPEC BOOK” for the project.

ITEM No. 6 --- Provides the “Appendix F CDRL Report” for the project.

ITEM No. 7 --- Provides the updated “BID FORM” for the project.

All other terms and conditions remain unchanged.

Acknowledgement of receipt of Addendum No. 5 to T-1795-0150.

Vendor Name: ___________________________________________________________

Responses to Contractor’s Questions for T-1795-0150

1) There are no electrical disconnects shown on the unit heaters per the line diagram on drawing

EL-300. Is this the intent of the design?

Response: Unit heaters UH-1 to UH-13 have a built in disconnect as per the schedule on ME-

502. A disconnect is to be provided for UH-14 as shown on EL-105.

2) There appears to be more light fixtures coming out than getting installed. If this is the case, is the contractor responsible for supplying a certain Lumen/FC rating throughout the affected area? If so, please provide the minimum Lumen/FC ratings.

Response: The fixtures shown on EL-102 to 104 provide adequate illumination for the facility.

No additional fixtures will be required other than those shown.

3) Please provide the As-Built Plans dated 01/18/83 which are listed in Note 2 on dwg ST-101.

These are needed to estimate the Demolition work.

Response: All pertinent information has been transferred to contract drawings and as stated in the note it is up to the contractor to field verify.

4) There is no bid item on the unit price schedule for light fixtures. Can you please clarify where we should include the cost associated with the light fixture installation?

Response: As per specification 265101 section 4.1B, Light fixture cost should include under panelboards section 262416.

5) Please provide a specification for the fire sprinkler work.

Response: See drawing FP-101 for fire sprinkler specifications.

6) Please define the constraints of accessing the site from the two ends of the building

Response: Access to both ends of the car wash will be allowed but it will have to be coordinated with MTA metro RCM and YTOCC following the RWP rules. The Railcar maintenance shop will continue to operate during the carwash construction. The west end of the car wash is the preferred entrance.

7) Will the contractor be required to have a full-time flagman on the project when entering and exiting the building?

Response: No.

8) The Bid item 0003 Quality Control Allowance shall cover the cost of the project quality control. In addition to the full-time no other duties QC Manager, this allowance is to cover the cost of the project testing and inspection. If the allowance amount is insufficient to cover all of the QC cost, will MTA provide a change for any additional cost or shall the contractor carry these costs in our bid?

Response: If allowance cost is not sufficient to cover QC manager a change may be provided for additional funding.

9) Will the contractor be required to provide a full-time safety officer when onsite working at the site. If so, will the safety officer be allowed to have other project duties?

Response: The contractor is required to have an approved safety representative onsite whenever any work is being performed onsite. The safety representative cannot perform any other duties while in this position.

10) Demolition drawing AR005 indicates saw cutting a door opening into the existing precast wall, however Structural drawing ST-101 indicated the removal of the precast panel and replacement.

Please define if we are to modify the precast in place or if we are to removal full panels and replace.

Response: The information provided on ST-101 is the preferred method of replacement. The

Contractor may choose to sawcut the egress opening into the existing precast panel. The

Contractor will be responsible for any damage caused to the existing structure during the sawcutting process.

11) If the precast removal and replacement scope is included in the bid, please define the constraints and phasing associated with the removal and replacement of the pre-cast panels located at column lines 17 -18.

Response: The only constraints during replacement of the precast wall panels are the load path of the panels to the main building structure (if the details shown ST-801 are followed there should not be any other constraints). Contractor will be responsible for safe handling during the removal and replacement of the precast panels as noted in the Specification 034000. There are no phasing requirements for the removal and replacement of the precast wall panels, refer to sheet ST-801 for notes regarding precast wall panels.

12) Will the contractor be allowed to connect to the existing utilities (power and water) at the site?

Response: Yes.

13) Will the contractor be permitted to drain ground water encountered in the deep excavations or piles into the existing storm system, provided the water is adequately filtered prior to discharge?

Response: Yes.

14) At the site visit we noticed the on the northeast side of the building there are trailers and seacans near the location of the proposed new door. Will these items be removed before the start of the work?

Response: No, one new door is on the exit wall of the train wash bay. There is no conflict. The other door is near column 18 on the Northeast wall of the train wash bay.

15) ) Does the facility contain lead-based paint? Has an environmental report been prepared and if so, please provide.

Response: Report attached.

16) As a U.S. manufacturer of vehicle wash systems for mass transit since 1961, we respectfully request that our equipment be considered as approved equal for the Vehicle Washing

Equipment (NS Corporation)

Response: NS Corporation is an engineer approved equal to basis of design Train Wash vendor.

Contractor is responsible for any differences or alterations from the design documents to incorporate the NS Corporation Train Wash system, per drawing EQ-110, General Note #1 and other applicable sections of contract documents.

17) Are contaminated soils anticipated?

Response: Contaminated soils are not anticipated.

18) Please provide Geotech report if available.

Response: Report attached.

19) What is the preferred method of sheeting the trench?

Response: Support of excavation (SOE) is typically design-built by the Contractor. Also, without knowing details of the location and purpose of the excavation, we cannot comment on the

SOE. Site conditions indicate shallow depth of rock in some areas. In areas of shallow rock, and considering limited space, a trench box or a custom designed (or modular) internally braced excavation support system would work. Final SOE design is ultimately the Contractors responsibility.

GEOTECHNICAL ENGINEERING REPORT

FOR:

MTA WABASH MAINTENANCE SHOP UPGRADES

BALTIMORE CITY, MARYLAND

E2CR PROJECT NO. 21521-04

Prepared For:

HNTB Corporation 120 E. Baltimore Street, Suite 1810

Baltimore, MD 21202

Consultant To:

Maryland Transit Authority

Prepared by:

E2CR, Inc.

1405 Parker Road Suite A Baltimore MD 21227

Phone: 410-737-9100 Fax: 410-737-9101 E-mail: email@e2cr.com

December 6, 2021

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 PROJECT DESCRIPTION

3.0 PURPOSE AND SCOPE

4.0 FIELD INVESTIGATION

5.0 LABORATORY TEST RESULTS

6.0 SUBSURFACE CONDITIONS

6.1 Site Geology

6.2 Generalized Subsurface Conditions

6.2.1 Wash Bay Area

6.2.2 Wheel Lathe Pit

6.3 Groundwater

7.0 EVALUATIONS AND RECOMMENDATIONS

7.1 General

7.2 Wheel Lathe Pit

7.3 Wash Bay Area

7.3.1 Spread Footing

7.3.2 Deep Foundation

7.4 Soil Parameters

7.5 Lateral Earth Pressures

7.6 Earthwork and Grading Considerations

7.7 Temporary Support of Excavation

7.8 Construction Dewatering Considerations

8.0 REMARKS

LIST OF TABLES

Table 1: Micropile Details

Table 2: Drilled Shaft Details

Table 3: Soil Parameters for Design of Structures

Table 4: Equivalent Fluid Pressures

LIST OF APPENDICES

APPENDIX A: Figures

Figure 1: Site Vicinity Map

Figure 2: Aerial Photograph

Figure 3: Proposed Construction – Wash Bay Area

Figure 4: Boring Location Plan – Wash Bay Area

Figure 5: Boring Location Plan – Wheel Lathe Pit Area

Figure 6: Boring Location Plan – Existing Borings (1976)

Figure 7: Subsurface Profile for Wash Bay Area

Figure 8: Subsurface Profile for Wash Bay Area

APPENDIX B: Boring Logs

Table B-1: Summary of Boring Data

Boring Logs

Existing Boring Logs by Balter, Inc. (1976)

APPENDIX C: Laboratory Test Results

Table C-1: Summary of Laboratory Test Data

Laboratory Test results (Graphical Format)

APPENDIX D: ALLPILE Analysis

Re: MTA Wabash Maintenance Shop Upgrades

Baltimore City, Maryland

E2CR Project No. 21521-04

December, 2021 Page 1 of 19

1.0 INTRODUCTION

This report presents the results of the geotechnical investigation conducted in association with the design of the proposed MTA Wabash Vehicle Wash Upgrade Project in

Baltimore, Maryland. The investigation was conducted for HNTB Corporation (HNTB), in general accordance with our proposals dated April 2, 2021, July 1, 2021, and October

14, 2021. The investigation was authorized by HNTB, Principal Consultants to Maryland

Transit Authority (MTA).

This Geotechnical Engineering Report (GER) summarizes our findings from the investigations and provides evaluations and recommendations for the proposed upgrades.

2.0 PROJECT DESCRIPTION

The project site is located at the MTA Wabash Avenue Maintenance Facility, which is located on the northwest side of the intersection of Wabash Avenue and Northern

Parkway in Baltimore, Maryland. The Site Vicinity Map and the Aerial Photograph are included as Figure 1 and Figure 2 in Appendix A.

The project consists of upgrading the existing metro car wash facility on Track 11 and the existing wheel lathe pit on Track 13, within the existing MTA’s Wabash Avenue

Maintenance Facility. The existing car wash equipment will be removed, and new equipment will be installed. The existing platform will be removed and a new and longer platform will be installed. The shop floor drains will be upgraded. The proposed construction for the wash bay area is included in Figure 3 in Appendix A.

In addition, upgrades are proposed within the main shop area to install MTA’s new wheel lathe within the existing wheel lathe pit located on Track 13, inside the MTA

Maintenance Facility.

3.0 PURPOSE AND SCOPE

The basic purpose of this investigation was to evaluate the subsurface conditions at the location of the proposed upgrades for the wash bay and wheel lathe pit area for the design and construction aspects of the project.

As directed by HNTB, the scope of our services for the wash bay upgrades as outlined in our proposal dated April 2, 2021, are described below.

December, 2021 Page 2 of 19

Wash Bay Subsurface Exploration Scope:

1) Meet/conference call with the Design Team to discuss the scope, borings and/or test pit locations, schedule, etc.

2) Visit the site to assess the site conditions, access, type of equipment required, etc.

3) Review all available information (locations of new equipment, access issues, etc.) and prepare a Test Pit Location Plan, jointly with HNTB, and submit for review.

4) E2CR and HNTB will jointly stake the test pit locations in the field. However, the test pit locations, once drilled, will be surveyed by HNTB or Others.

5) E2CR will call Miss Utility. However, private utility lines within the Facility should be marked by MTA or Others.

6) Mobilize vacuum test pit equipment (including compressor), coring machine, Dynamic Cone Penetrometer (DCP) equipment, etc.

7) Perform a total of 3 days of fieldwork, which will consist of excavating 5 to 7 vacuum test pits to depths of 4 feet to 10 feet each. The test pits will be excavated as follows:

First, perform a 6 inch to 8-inch diameter core through the existing floor slab. The floor slab is estimated to be 8 inches to 12 inches thick, depending on the location of the test pit.

Vacuum excavate the gravel base, if any, and measure its thickness.

Perform DCP tests in the soil subgrade and also obtain soil samples.

Continue vacuum excavation with DCP tests and obtaining soil samples, at about

1 foot intervals, through the fill, if any, until the test pit encounters good bearing soils. The maximum depths of the test pits are anticipated to be about 8 feet to 10 feet, depending on whether the vacuum test pit hole(s) can stay open.

Based on the previously drilled borings, hard/dense soils consisting of decomposed rock or rock could be encountered at shallow depths.

The test pits will be terminated once good bearing soils are encountered.

8) The vacuum test holes will be backfilled and grouted with high strength non-shrink grout.

9) Measure groundwater levels, if encountered. Where possible, the test holes will be left open overnight for 24-hr groundwater reading. However, holes located in critical areas cannot be left open and will be grouted at completion.

10) Conduct laboratory tests on subsurface samples as follows:

Moisture Content on selected jar and bag samples.

One set of Atterberg Limits and Sieve Analysis, on different soil types encountered.

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Additional USCS classifications (Atterberg Limits and Sieve Analysis tests or percentage fines tests) will be conducted at the location of equipment or where additional testing is required to analyze the subsurface conditions

11) Analyze the subsurface soil and groundwater conditions and prepare a geotechnical report for the design and construction of the project. The report will include:

a) Summary of field exploration including Test Pit Location Plan, Test Pit Logs, Groundwater Levels, Subsurface Strata, etc.

b) Summary of Laboratory test results

c) Evaluations and recommendations, including,

i. Design Soil Parameters,

ii. Seismic design parameters,

iii. Later Earth Pressures (if and where required),

iv. Dewatering,

v. Support of Excavation,

vi. Earthwork (Soil types, suitability, placement, compaction, etc.),

vii. Bearing Conditions, Bearing Capacity & Settlement of Structures, etc.,

viii. Soil parameters as needed if deep foundations (like micropiles, etc.) are suggested.

12) Coordinate with HNTB during the final design phase to provide geotechnical information to support LRFD/Limit State Design.

a) This includes assisting HNTB with defining the requirement for additional borings during the construction phase.

Wheel Lathe Pit Upgrades Scope: Subsequent to the submission of our proposal dated

April 2, 2021, it was decided that one additional boring/vacuum test pit was required in the main shop area for installation of MTA’s new wheel lathe.

The scope for the additional services required for the Wheel Lathe Pit Upgrades are detailed in our proposal dated July 1, 2021, and include the following:

1) Mobilize a drill rig with a short tower; vacuum test pit equipment (including compressor), coring machine, DCP equipment, etc.

2) Perform a total of 1 additional day of fieldwork, which will consist of excavating 1 vacuum test pit to a depth of 4 feet to 10 feet and drill 1 soil boring to refusal on bedrock. The test pit will be excavated as described in the previous wash bay section.

The vacuum test pit would be terminated on hard/dense material and the boring would be terminated once auger refusal was encountered on bedrock.

3) Conduct laboratory tests on selected soil samples

December, 2021 Page 4 of 19

4) Analyze the subsurface soil and groundwater conditions and include recommendations in the geotechnical report for the design and construction of the wheel lathe facility.

Our scope of work did not include the following:

1) Obtaining ROE for private property, if required.

2) Environmental Sampling and Testing.

3) Corrosion Tests on Soils.

4) Cost Estimating

5) Preparation and/or Review of contract Drawings and Specifications.

6) Assistance during bidding process

7) Post award construction services.

4.0 FIELD INVESTIGATION

The field investigation was conducted in August and October 2021. A total of three (3) locations (B-1 through B-3) were investigated at the wash bay area, and two (2) locations

(TW-1 and TW-2) were investigated at the wheel lathe pit area.

Wash Bay Field Investigation:

It was initially proposed to perform test pits at five (5) locations (i.e. B-1 through B-5).

The proposed test pit locations are shown in the Boring Location Plan, i.e. in Figure 4 in

Appendix A. The top of the existing slab at the wash bay is at about EL+429.0 feet and therefore all the test pits were excavated from EL. 429.0 feet.

The field investigations started on August 27, 2021. At test pit location B-1, during coring of the concrete slab, an unknown and unmarked electric conduit was encountered at a depth of about 10.5 inches. The conduit was embedded within the concrete slab. An

MTA on-site representative was informed, and MTA decided to stop further coring operations until the site could be scanned for utilities. HNTB mobilized a Ground

Penetrating Radar (GPR) and scanned the existing utilities around the proposed test pit locations. The drill crew was re-mobilized to the site on August 30, 2021. An offset core was performed at test pit location B-1. The offset core again encountered an unknown and unmarked electric conduit at a depth of 10.5 inches. The coring operations were again suspended by MTA.

After additional scanning for utilities by HNTB, the drill crew started work in the wash bay area on October 19, 2021. A total of three (3) locations (B-1 through B-3) were investigated to depths of up to about 9.5 feet using vacuum excavating equipment, December, 2021 Page 5 of 19 including a lance and hand augers. Dynamic Cone Penetrometer (DCP) tests were conducted in the test pits at 1-foot depth intervals. Soil samples were retrieved using a hand auger. A representative portion of each hand auger sample was placed in a glass jar and was appropriately marked. The test pits B-1 and B-2 were terminated at depths of 9.5 feet and 9.1 feet, respectively, after encountering hard material (i.e., possible decomposed rock or bedrock). Test pit B-3 was terminated at a depth of 7.5 feet because the hole kept caving in and it was difficult to keep the hole open. Test pit B-3 did not encounter hard material at the termination depth.

During coring of the concrete slab at test pit B-4 location, an unmarked electric conduit was encountered at a depth of about 9.5 inches below the top of the concrete slab. After discussions with HNTB and MTA, it was decided to stop further investigation in the wash bay area, since there were several unknown and unmarked utility lines that could pose a significant risk to the drill crew.

All the test pits were backfilled with concrete and the surface grouted with high strength grout after completion of the test pits.

Wheel Lathe Pit Field Investigation:

At the wheel lathe pit, one test pit (i.e. TW-1) was excavated and one boring (i.e. TW-2) was drilled at the locations shown on the Boring Location Plan, i.e. in Figure 5 in

Appendix A.

After the two locations were scanned for utilities and cleared by HNTB, the drill crew was mobilized on October 18, 2021. The test pit location TW-1 was located at the bottom of the existing wheel lathe pit (i.e. at or about EL +423.0 feet). The test pit was performed using a coring machine and vacuum excavating equipment. In TW-1, 44.0 inches of concrete and 6.0 inches of No. 57 Stone was encountered. Below the No. 57

Stone, hard/dense material was encountered, which appeared to be the bedrock. The bedrock was encountered below the stone at a depth of about 50.0 inches.

The boring TW-2 was drilled from the shop floor (i.e. from about EL +429.0 feet) using a truck mounted D-50 drill rig, using a short tower due to height restrictions. While drilling, the exhaust from the drill rig was piped outside the maintenance shop in order to remove exhaust fumes from the shop. The boring TW-2 encountered auger refusal at a depth of about 8.67 feet below the existing ground surface, i.e. existing shop floor. The boring was terminated upon encountering bedrock.

December, 2021 Page 6 of 19

The boring TW-2 encountered 16.5 inches of concrete at the surface. The boring was advanced using 3¼- inch (ID) hollow stem augers, following ASTM D6151 - Standard

Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil Sampling.

Standard Penetration Tests (SPTs) were conducted and split spoon samples were obtained in the borings using a 2-inch outer diameter (OD) and 13/8-inch ID sampler. The SPTs were performed per "Standard Test Method for Standard Penetration Test (SPT) and

Split-Barrel Sampling of Soils," ASTM D1586. The SPTs were generally performed continuously with depth using 1.5-foot sample intervals to the bottom of the boring. A representative portion of each SPT sample was placed in a glass jar and was appropriately marked.

The test pits and the boring were backfilled with concrete mixed with some auger cuttings, and the surface patched with high strength grout upon completion.

All field operations were monitored by a geologist or a geotechnical engineer, who also visually classified the samples per the Unified Soil Classification System (USCS). A summary of the test pit data and boring data is included in Table B-1 in Appendix B. The edited test pit and boring logs, which contain a detailed description of the subsurface conditions encountered during the investigation, are included in Appendix B.

Existing Boring Information

The existing boring information provided to us by HNTB indicated that several borings were drilled by Robert B. Balter, Inc. from September, 1976 through October, 1976 prior to the construction of the existing MTA maintenance facility. The locations of the existing borings are shown in Boring Location Plan, i.e. in Figure 6 in Appendix A.

The relevant borings in the vicinity of the wash bay area are numbered NWJ-12, NWJ-

14, NWJ-17, NWJ-28, and NWJ-29. The ground elevation at the time of drilling the borings in 1976 varied from about EL 434.7 feet to EL 441.4 feet. The borings were drilled to depths of up to about 49.5 feet, and bedrock was cored in almost all of the borings. Boring logs of these 5 previously drilled borings by Balter, Inc. in the vicinity of the wash bay area, have also been included in Appendix B.

5.0 LABORATORY TEST RESULTS

All soil samples recovered from the test borings were transported to our laboratory and were visually inspected by a geotechnical engineer to corroborate and/or modify the field classification. Selected samples were subjected to various testing to determine additional engineering characteristics of the on-site soils.

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Laboratory tests on soil samples included natural moisture content, sieve analyses, percentage fines, and Atterberg limit tests. All tests were performed in general accordance with ASTM procedures.

The results of these laboratory tests are summarized in Table C-1 in Appendix C. The graphical outputs of the test results are also included in Appendix C.

6.0 SUBSURFACE CONDITIONS

The site geology and the site subsurface stratigraphy are discussed in the section below.

6.1 Site Geology

According to the Geologic Map of Maryland (Wetherill et al., 1968), the site is located in the alluvium deposits of the western shore uplands of the Coastal Plain Physiographic

Province, which consists of Gravel, Sand, Silt, and Clay materials that have been deposited by the receding seas.

The surficial soils at the site consist of sedimentary soils that belong to the Sand-Gravel facies of the Lower Cretaceous Potomac Group. This formation consists of Gravel and sand, commonly orange-brown and locally limonite-cemented. The presence of silt and red, white, or gray clay is expected (includes Brandywine, Bryn Mawr, and Sunderland

Formations). The strata surface is up to 50 feet.

Surrounding geologic formations (including Baltimore Gabbro Complex and Ultramafic

Rocks) consist of Hypersthene gabbro with subordinate amounts of olivine gabbro, norite, anorthositic gabbro, and pyroxenite. Igneous minerals and textures are well preserved in some rocks while others exhibit varying degrees of alteration and recrystallization, and still, others are entirely recrystallized with a new metamorphic mineral assemblage. Depth to bedrock within this project's scope is shallow (from 15 feet to 50 feet) from the natural ground surface.

6.2 Generalized Subsurface Conditions

The subsurface conditions encountered in the borings or test pits are contained on the individual Boring or Test Pit Logs. The transitions between strata may be gradual and indistinct. The subsurface conditions described below are generalized, and the strata type and depths could vary between the investigation Locations. The Subsurface conditions are summarized in the following sections:

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6.2.1 Wash Bay Area

The subsurface stratigraphy at the wash bay area is shown in Figure 7 and Figure 8, in

Appendix A. Since E2CR could perform only limited test pits/borings within the Wash

Bay Facility, the existing boring data from the previously drilled borings by Balter in

1976 were also used to evaluate the subsurface conditions at the Wash Bay Facility.

6.2.1.1 E2CR Field Investigation

The investigation performed by E2CR included vacuum test pit excavations along with

DCPs at three locations (i.e. B-1 through B-3).

All the test pits were excavated from the top of the existing floor slab of the Facility which was at about EL+429 feet. The test pits encountered 15 inches to 15.5 inches of concrete underlain by about 6 inches of Stone which appeared to be No. 57 Stone.

Below the No. 57 stone, Fill was encountered up to a depth of about 7.5 feet. The fill material is believed to have been placed during the construction of the existing facility and consisted of Clayey SAND, Sandy CLAY, and GRAVEL. The DCP tests performed on the fill material yielded values that generally deteriorated with depth, indicating that the fill was well compacted within the top about 3.0 feet and was loosely placed and not well compacted below about 3 feet. No deleterious materials were encountered in the fill.

Test pits B-1 and B-2 encountered hard material (i.e. possible decomposed rock or rock) at depths of 9.5 feet and 9.1 feet, respectively. The DCP tests performed on the hard material yielded values from 15 to 30 blows.

In test pit B-3, gravel fill was encountered from a depth of 2.5 feet to about 7.5 feet. The test pit was terminated at 7.5 feet because the gravel kept caving in and the hole could be kept open. The DCP tests performed at a depth of 7.5 feet had blow counts of about 9 to

17 blows. The test pit did not extend to the natural soils.

6.2.1.2 Balter Field Investigation

Robert B. Balter, Inc. drilled several borings from September through October of 1976, prior to construction of the existing MTA Maintenance Facility. The relevant borings in the vicinity of the Wash Bay area are numbered NWJ-12, NWJ-14, NWJ-17, NWJ-28, and NWJ-29, with a surface elevation of EL. 434.7 feet, EL. 441.0 feet, EL. 440.6 feet, EL. 441.4 feet and, EL. 440.2 feet, respectively. Note that the ground surface elevation at

December, 2021 Page 9 of 19 the time of drilling these borings is considerably higher than the top of slab elevation of

EL+429 feet within the Wash Bay Facility.

The borings drilled by Balter indicate that the subsurface stratigraphy at the site consists of residual soils, underlain by decomposed rock and bedrock. The residual soils consist of red, brown, green, SILT, CLAY, and Clayey SAND. The standard penetration resistance

(N value) in the residual soils varies from about 4 blows per foot (bpf) to over 50 bpf and generally increases with depth. The residual soils are underlain by the decomposed rock, i.e. residual soils or saprolite with SPT N-values of more than 50 blows/foot. The decomposed rock is underlain by the bedrock.

The borings indicate that the depth to bedrock varies significantly from about 8.0 feet to about 40.3 feet, i.e., EL 399.9 feet to EL. 426.7 feet, as shown on the subsurface profiles, Figure 7 and Figure 8, in Appendix A. The bedrock was classified as green, gray, Tremolite GNEISS with a recovery of 33 percent to 100 percent and Rock Quality

Designation (RQD) of 0 percent to 100 percent.

6.2.2 Wheel Lathe Pit

The field investigation in the wheel lathe pit area included one vacuum test pit excavation

(TW-1) and one drilled boring (TW-2). The test pit TW-1, located in the existing pit (EL

423.0 feet) encountered 44.0 inches of concrete and 6.0 inches of No. 57 Stone. The bedrock was encountered below the stone at a depth of about 50.0 inches (i.e., EL 418.8).

Boring TW-2 was drilled from the existing slab elevation (i.e. from EL 429.0 feet). The concrete slab was about 16.5 inches thick and was underlain by about 6 inches of No. 57

Stone. The No. 57 Stone was underlain by Fill, which consisted of poorly graded Sand with Clay (SP-SC). The SPT N-values within the fill varied from about 2 blows/foot to about 10 blows/foot. The SPT N-value was 10 blows/foot from a depth of 2 feet to 3.5 feet. Below 3.5 feet and to a depth of 7 feet, the SPT N-values were 2 blows/foot to 5 blows/foot. It appears that the top 1.5 feet of fill was well compacted and was loosely placed below 1.5 feet. The fill extended to a depth of 8.3 feet. The boring encountered auger refusal at a depth of 8.7 feet (i.e., EL. 420.3 feet) below the existing ground surface. Since the bedrock was not cored, it is not possible to identify the type of rock at the site.

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6.3 Groundwater

Groundwater was not encountered in any of the investigated locations. The existing borings by Balter, Inc. indicated the presence of groundwater at depths of 10.2 feet to

18.5 feet (i.e., EL. 422.1 to EL. 429.5). Since the site was significantly graded after Balter drilled their borings, it is possible that the changed grades also resulted in changed groundwater elevations at the site.

Please note that fluctuation in precipitations, seasonal conditions, construction activity, surface runoff, and site-specific factors could cause groundwater conditions to be different from those observed. Additionally, perched water could be encountered on top of clay layers/lenses or on top of decomposed rock/rock.

7.0 EVALUATIONS AND RECOMMENDATIONS

7.1 General

The evaluations and recommendations presented in subsequent sections of this report are based on our understanding of the proposed construction and the general subsurface conditions encountered. Should the project characteristics be altered significantly from those discussed, or should different subsurface conditions be encountered during construction, our office should be consulted, as the evaluations and recommendations presented herein may no longer be valid.

7.2 Wheel Lathe Pit

For satisfactory performance, the foundation of any structure must satisfy two independent design criteria. First, it must have an acceptable factor of safety against bearing failure in the foundation soils under maximum design load. Second, the settlements during the life of the structure must not be of a magnitude that will cause structural distress or impair the operational efficiency of the facility. Selection of the foundation type to satisfy these criteria depends on the nature and magnitude of dead and live loads, the base of the structure, and the settlement tolerances. Where more than one foundation type satisfies these criteria, cost, scheduling, material availability, and local practice will probably influence or determine the final selection of the type of foundation.

The test pit TW-1 encountered 44 inches of concrete slab underlain by 6 inches of #57 stone. Under the stone, hard material (possible bedrock) was encountered. Based on the

December, 2021 Page 11 of 19 test pit, the bedrock is at a depth of about 50 inches or 4.2 feet below the existing wheel lathe pit. The exact elevation of the floor of the wheel lathe pit is not known at this time.

The boring TW-2 encountered decomposed rock at about 8.3 feet and auger refusal at a depth of 8.7 feet. Considering the shop floor elevation of EL+429, the bedrock was encountered at about EL+420.3 feet.

The exact elevation of the floor of the wheel lathe pit is not known at this time. However, it appears that the pit is at least 6 feet below the floor slab of the shop. Considering the boring and the test pit information, it appears that about 2+ feet of rock was probably excavated during the construction of the existing wheel lathe pit.

The spread footing foundations for the wheel lathe pit upgrades will be bearing on bedrock. Rock was not cored or tested during this investigation. Robert B. Balter, Inc.

previously drilled borings at the site in 1976 before the construction of the existing facility. The geotechnical engineer for the construction of the existing facility recommended an allowable bearing pressure of 15 ksf for footings bearing on the bedrock.

Based on the available information, the wheel lathe pit upgrades bearing on rock, should be designed for a factored bearing resistance of 15 ksf. The estimated total and differential settlements are estimated to be less than about 1 inch. The proposed foundation should be checked for uplift due to buoyancy.

7.3 Wash Bay Area

The Wash Bay improvements include the removal of the existing platform and installation of a new platform. The new platform will be longer than the existing platform and is proposed to be supported on columns.

The foundation type to support the columns will depend on the nature and magnitude of dead and live loads, the base of the structure, and the settlement tolerances. Where more than one foundation type satisfies these criteria, cost, scheduling, material availability, and local practice will probably influence or determine the final selection of the type of foundation.

The following sections provide evaluations and recommendations for the different types of foundation options for the Wash Bay area:

December, 2021 Page 12 of 19

7.3.1 Spread Footing

The subsurface investigations performed in the Wash Bay area (i.e., test pits B-1 through

B-3) encountered up to 7.5 feet of uncontrolled Fill in different areas. The DCP tests performed on subsurface material yielded values that generally deteriorated with depth, indicating that the fill was well compacted within the top 3.0 feet and was loosely placed and not well compacted below about 3 feet. The natural material encountered below the fill was generally saprolite or decomposed Rock.

Several borings in the vicinity of the car wash bay were drilled by Robert B. Balter, Inc.

in 1976 during the construction of the maintenance facility. The relevant borings are numbered NWJ-12, NWJ-14, NWJ-17, NWJ-28, and NWJ-29. These previously drilled borings indicate that the depth to decomposed Rock/bedrock varies considerably, as shown below.

Boring No. Decomposed Rock EL Bedrock EL

NWJ-12 EL+426.7

NWJ-14 EL+426

NWJ-17 EL+425.6 EL+424.6

NWJ-28 EL+411.4 EL+405.2

NWJ-29 EL+420.2 EL+399.9

Test Pit No. Depth to DR/Rock Elevation of DR/Rock

B-1 9.5 feet EL+419.5

B-2 9.1 feet EL+419.9

B-3 Below 7.5 feet DR/Rock not enc, hole collapsed

Note that the top of the floor slab is at EL+429 feet.

Based on the test pit data, it appears that the depth to decomposed rock/rock is about 9 feet to 10 feet. It also appears that the existing fill to a depth of about 7.5+ feet was not placed and compacted properly. Foundations founded on this fill could experience settlements and differential settlements of more than 1 inch. Due to the uncertainty associated with miscellaneous fill, it is not recommended to design the footings to bear on the existing fill.

Option 1: An option would be to excavate or remove the uncontrolled Fill material, which is estimated to be up to a depth of about 7.5+ feet, and replace it with structural fill

December, 2021 Page 13 of 19 that is compacted in layers to the existing ground elevation. In this case, a factored bearing resistance of 3.0 ksf should be used to design the spread footings.

Option 2: In case higher factored bearing resistance is required, the existing uncontrolled fill should be excavated, and the footing should be founded directly on the decomposed rock/bedrock at an estimated depth of 9.0 feet. The spread footing foundations bearing directly on the decomposed rock could be designed for a factored bearing resistance of

6.0 ksf. The total and differential settlements are estimated to be less than 1.0 inches.

Due to space limitations, Options 1 or 2 may not be feasible, and a deep foundation will probably be a better option.

7.3.2 Deep Foundation

As mentioned in the previous sections, extensive excavation and backfill operations will be required due to the uncontrolled and miscellaneous nature of the existing fill. The deep excavations will be difficult in the limited space. To minimize excavation, the proposed upgrades could be supported on a deep foundation. Two options are discussed below:

7.3.2.1 Micropiles

Due to the constructability and site limitations, micropiles are the preferred option to support the proposed foundation. Micropiles can be installed from the existing slab, and no excavation will be required since micropiles can be installed through the existing slab.

Micropile rigs come in small sizes and should be able to install the micropiles in the limited headroom of the Wash Bay area.

The evaluations indicate that 7-inch micropiles with about 10 feet embedment into the underlying bedrock could be designed for a factored resistance of 50 tons. The actual length of individual micropiles will vary. The governing criteria would be 10+ feet embedment into rock. The depth to rock would vary, and so the lengths of the micropiles would vary. This should be considered while estimating micropile quantities. The estimated length of the proposed micropiles according to the bedrock encountered in the borings is shown in Table 1 below.

December, 2021 Page 14 of 19

Table 1: Micropile Details

Boring #

Existing

Floor

Elevation

(ft)

Bedrock

Elevation

(ft)

Bedrock

Depth (ft)

Micropile Length (ft)

Unbonded Bonded*

(Embedded) Total

NWJ-12 429.0 426.7 2.3 2.3 10 12.3

NWJ-14 429.0 426.0 3.0 3.0 10 13

NWJ-17 429.0 424.6 4.4 4.4 10 14.4

NWJ-28 429.0 405.2 23.8 23.8 10 33.8

NWJ-29 429.0 399.9 29.1 29.1 10 39.1

* The governing criteria for micropile installation is 10 feet of rock embedment.

Although borings NWJ-12, NWJ-14, and NWJ-17 indicate shallow bedrock, the recently concluded field investigation at the existing facility didn’t encounter shallow refusal. It is possible that the grades were changed during construction of the facility.

Based on the current investigation, decomposed rock/bedrock appears to be at depths of

9.5 feet or more. Based on these findings, the length(s) of the micropiles, with 10 feet of rock embedment, is estimated to be between 20 feet and 40+ feet. Allpile program was used to analyze the capacity of the micropiles. The Allpile runs are included in Appendix

D.

The micropile should be installed with a casing, and the casing should be driven to the top of the rock and filled with concrete. The micropile should also have a center rebar, which would extend to the bottom of the micropile, i.e., into the 10 feet (minimum) bonded zone in the bedrock. It is recommended that a minimum of 2 micropiles be installed for each column footing to account for possible eccentricities. The total and differential settlement is estimated to be less than about 1.0 inches.

It is to be noted that micropiles are proprietary and should be designed and installed by a specialty contractor based on a performance specification. It will be difficult to conduct pile load tests within the confined space. In lieu of the pile load test, the micropile designer should demonstrate that the micropiles have the nominal pile resistance of 2 times the factored pile resistance, or 100 tons per micropile.

7.3.2.2 Drilled Shafts

Drilled shafts could also be used to support the column footings. Preliminary evaluations indicate that a 24-inch diameter drilled shaft, with a 2+ feet minimum embedment into the underlying bedrock, could be designed for a factored resistance of 100 tons. Each

December, 2021 Page 15 of 19 column footing could be supported on one drilled shaft. The governing criteria for drilled shaft installation is a minimum of 2 feet of embedment into the bedrock. Therefore, the lengths of the drilled shafts will vary based on the depth to bedrock. The estimated length(s) of the proposed drilled shafts according to the bedrock encountered in the borings is shown in Table 2.

Table 2: Drilled Shaft Details

Boring #

Existing

Floor

Elevation

(ft)

Bedrock

Elevation

(ft)

Bedrock

Depth (ft)

Drilled Shaft Length (ft)

Unbearing Bearing*

(Embedded) Total

NWJ-12 429.0 426.7 2.3 2.3 2 4.3

NWJ-14 429.0 426.0 3.0 3.0 2 5

NWJ-17 429.0 424.6 4.4 4.4 2 6.4

NWJ-28 429.0 405.2 23.8 23.8 2 25.8

NWJ-29 429.0 399.9 29.1 29.1 2 31.1

* The governing criteria for drilled shaft installation is 2 feet of rock embedment.

Although borings NWJ-12, NWJ-14, and NWJ-17 indicate shallow bedrock, the recently concluded field investigation at the existing facility didn’t encounter shallow refusal. It is possible that the grades were changed during construction of the facility.

Based on the current investigation, decomposed rock/bedrock appears to be at depths of

9.5 feet or more. Based on these findings, the length of the drilled shafts, with 2 feet of rock embedment, is estimated to be between 12 feet and 32 feet. The total and differential settlement is estimated to be less than about 1.0 inches. Allpile program was used to analyze the capacity of the drilled shafts. The Allpile runs are included in Appendix D.

The installation of the drilled shafts should be per MDSHA Standard Specifications.

Even though drilled shafts are a viable option, the drilled shaft rigs are larger, and there may be access issues with a drilled shaft rig. It may not be possible to operate a drilled shaft rig within the wash bay area which has low ceiling.

7.4 Soil Parameters

As described in Section 6.2, the subsurface stratigraphy at the site consists of fill, residual soils, decomposed rock and rock.

December, 2021 Page 16 of 19

Based on the available information and laboratory tests, the following design parameters were utilized in the geotechnical analysis:

Table 3: Soil Parameters for Design of Structures

Strata Depth

(feet)

Moist Unit

Weight

(pcf)

Elastic

Modulus

(ksf)

Strength Parameters

Cohesion

(psf)

Friction

Angle ()

Fill 0 to 7.5 120 200 0 30

Residual Soil Below 7.5 120 300 0 30

Decomposed

Rock

Varies 125 1,500 300 36

Rock Varies 140 10,000 10,000 36

Select Borrow

120 200 0 30

No. 57 Stone

(Backfill)

- 110 1,200 0 36

Please note that the unit weight values provided in Table 2 are moist unit weight values.

An ultimate friction factor of 0.35 should be used between concrete and soil.

An ultimate friction factor of 0.25 should be used between DIP and soil.

An ultimate friction factor of 0.20 should be used between PVC pipe and soil.

7.5 Lateral Earth Pressures

Unbalanced below ground walls will be subjected to lateral earth pressures. Walls that are braced should be designed for at-rest pressures. The design should be checked for seismic conditions. Table 4 below shows the equivalent fluid pressures for below grade walls.

Table 4: Equivalent Fluid Pressures

Stratum Equivalent Fluid Pressure (psf)

At Rest Active Passive

Existing Fill 60 40 360

Compacted Select Borrow 60 40 360

Compacted Stone 50 32 450

Residual Soil 60 40 360

Decomposed Rock 50 32 450

Rock 50 32 450

December, 2021 Page 17 of 19

The lateral earth pressures do not include hydrostatic pressures and lateral surcharge loads. The coefficient of sliding for concrete and subgrade is 0.35.

Groundwater could be encountered at deeper depths. Depending on the type of construction and the depth of construction, hydrostatic pressure may have to be considered

7.6 Earthwork and Grading Considerations

The existing platform and floor drains are proposed to be replaced at approximately the same location as the existing platforms and floor drains, resulting in minimal re-grading.

There will be some excavation and backfill activities during the construction of the proposed improvements. All grading and construction operations should be performed per Maryland State Highway Standard Specifications, Latest Edition.

In case a spread footing is used to support the proposed improvements, all fill selection, placement, and compaction should be done per Maryland State Highway Administration

Standard Specifications.

All structural backfill should consist of select borrow; should be placed in 6 inch to 8 inch lifts; and should be compacted to 95 percent of the maximum dry density and within

2% of the optimum moisture content as determined by AASHTO T180 (ASTM D1557).

The backfill could also consist of CR-6, GAB, or AASHTO No. 57 Stone. If No. 57 is used, the AASHTO No. 57 Stone must meet the requirements of Section 901 of the latest edition of Maryland State Highway Administration (MDSHA) Standard Specifications for Construction and Materials. The No. 57 Stone also be wrapped in geotextile Type SE, to prevent migration of fines.

The field density of compacted borrow backfill should be determined per ASTM D1556

(sand cone method) or ASTM D6938 (nuclear method). These tests should be performed on each lift of fill with a frequency of one (1) or more per 2,500 square feet of fill and one (1) per every 50 linear feet in utility trenches. The compaction test is not required for

AASHTO No. 57 Stone backfill. Compaction testing is required for GAB and CR-6.

7.7 Temporary Support of Excavation

In case of using a spread footing for the proposed updates, the excavation is anticipated to be up to about 10 feet. Excavations deeper than 4 feet will require lateral support (if the

December, 2021 Page 18 of 19 excavations cannot be laid back on a temporary slope of 1.5 horizontal: 1 vertical, under applicable OSHA regulations). The temporary support can consist of methods such as sheeting and shoring, mules, etc.

Construction dewatering should be considered in association with the design of the support of excavation. The design and implementation of the support of excavation should be left to the Contractor.

7.8 Construction Dewatering Considerations

Groundwater was encountered in the previously drilled borings from 1976 at about El.

422.1 feet to El. 429.2 feet. However, the current investigation did not encounter groundwater.

Typically, groundwater levels could fluctuate by about 3+ feet due to seasonal variations.

Also, the groundwater is typically encountered just above the decomposed rock or rock.

Therefore, control of water and dewatering, in association with the support of excavation, is anticipated during the construction of the spread footing. In addition, any water that enters the excavation due to changes in seasonal conditions, rainwater, or surface infiltration, will also require dewatering. The method of groundwater control and dewatering should be left to the contractor.

8.0 REMARKS

This report has been prepared solely and exclusively for HNTB to provide guidance to design professionals in developing facilities plans for the MTA Wabash Maintenance

Shop Upgrades project located in Baltimore City, Maryland. It is considered that adequate evaluations and recommendations have been provided to serve as a basis for the design requirements for the project.

This report is not intended for use by others, and the information contained herein is not applicable to other sites. The Consulting Engineer cannot be held accountable for any problems which occur due to the application of this report to other than its intended purpose. This report in its entirety should be attached to the project specifications.

This report does not contain environmental considerations for the proposed construction.

Additional recommendations can be provided as needed.

December, 2021 Page 19 of 19

These analyses and recommendations are based on information made available to us at the time of our investigation, the actual conditions encountered at the test boring locations, and the existing borings performed by Balter, inc. in 1976. General assumptions have been made that the limited exploratory test borings represent the site conditions in relation to the aerial extent and depths of the borings. However, it should be noted that the actual subsurface conditions between the test boring locations might vary from the conditions indicated on the appended test boring logs. Should the actual conditions encountered during construction differ significantly from those indicated by the test boring logs, we should be notified immediately so that the analyses and recommendations can be reviewed and/or revised as necessary.

Our professional services have been performed, and this report has been prepared in accordance with generally accepted engineering principles and practices. E2CR, Inc.

assumes no responsibility for interpretations made by others based upon our work or our recommendation.

APPENDICES

APPENDIX A – FIGURES

E2CR, INC.

MTA Wabash Maintenance Shop Updates FIGURE: 1 DRAWN BY: MK CHECKED BY:NS

Site Vicinity Map DATE: November 2021 JOB NO.: 21521-04 SCALE: NTS

SITE

MTA Wabash Maintenance Shop Updates FIGURE: 2 DRAWN BY: MK CHECKED BY:NS

Aerial Photograph DATE: November 2021 JOB NO.: 21521-04 SCALE: NTS

SITE

MTA Wabash Maintenance Shop Updates FIGURE: 3 DRAWN BY: MK CHECKED BY:NS

Proposed Construction – Wash Bay DATE: November 2021 JOB NO.: 21521-04 SCALE: NTS

MTA Wabash Maintenance Shop Updates FIGURE: 4 DRAWN BY: MK CHECKED BY:NS

Boring Location Plan – Wash Bay DATE: November 2021 JOB NO.: 21521-04 SCALE: NTS

MTA Wabash Maintenance Shop Updates FIGURE: 5 DRAWN BY: MK CHECKED BY:NS

Boring Location Plan – Wheel Lathe Pit DATE: November 2021 JOB NO.: 21521-04 SCALE: NTS mkarimpour Call Out

TW-2

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