512-23-154 - Geotech Report.pdf

Report Cover Page

VAMC Loch Raven Geotechnical Engineering Report

February 22, 2024 | Terracon Project No. JD235427

Prepared for:

Above Group, Inc.

305 East Drive, Suite H

Melbourne, Florida 32904

19955 Highland Vista Drive, #170

Ashburn, Virginia 20147

P (703) 726-8030

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

February 22, 2024

Above Group, Inc.

305 East Drive, Suite H

Melbourne, Florida 32904

Attn: Stephen Kazim, PE, HFDP, EBCP

P: (321) 345-9026

E: skazim@abovegroupinc.com

Re: Geotechnical Engineering Report

VAMC Loch Raven

3900 Loch Raven Blvd

Baltimore, MD

Terracon Project No. JD235427

Dear Mr. Kazim:

We have completed the scope of Geotechnical Engineering services for the above-referenced project in general accordance with Terracon Proposal No. PJD235427 dated

December 29, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

Josh April, PG Paul Burkart, PE

Senior Project Manager Senior Principal

VAMC Loch Raven | Baltimore, MD

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Introduction

Project Description

Site Conditions

Geotechnical Characterization

Groundwater

Seismic Site Class

Corrosivity

Earthwork

Site Preparation

Subgrade Preparation

Existing Fill

Excavation

Fill Material Types

Fill Placement and Compaction Requirements

Utility Trench Backfill

Grading and Drainage

Earthwork Construction Considerations

Construction Observation and Testing

Shallow Foundations

Design Parameters – Compressive Loads

Foundation Construction Considerations

Floor Slabs

Floor Slab Design Parameters

Floor Slab Construction Considerations

Lateral Earth Pressures

Design Parameters

Subsurface Drainage for Below-Grade Walls

General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Facilities | Environmental | Geotechnical | Materials ii

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed building to be located at 3900 Loch

Raven Blvd in Baltimore, MD. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Foundation design and construction

■ Floor slab design and construction

■ Lateral earth pressures

The geotechnical engineering Scope of Services for this project included the advancement of test borings, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and as separate graphs in the Exploration Results section.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Item Description

Information

Provided

Email dated December 18, 2023 from Above Group, which included Loch Raven Constructed Boiler Spaces Concept

Drawings dated December 6, 2023

Concept Plan showing anticipated structural loads provided by

Above Group in an email on February 1, 2024

Site Topographic Survey CAD file provided by Above Group in an email on February 8, 2024

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Project

Description

The project includes construction of a new building to house hot water boilers for the VA Loch Raven campus, new manholes, and new piping to the existing buildings.

Proposed

Structures

Structures associated with the project include a slab-on-grade building and manholes

Finished Floor

Elevation

We understand that the proposed finished floor elevation (FFE) for the building will be at about elevation (EL) 213.

Maximum Loads

We understand that the maximum loads for the proposed building will not exceed the following:

■ Columns: 200 kips

■ Wall: 4 klf

Grading/Slopes

Based on the provided FFE of EL 213, fills of up to approximately five feet are anticipated to achieve design subgrades at the building.

Utilities We assume invert elevations of new utilities will not exceed about five feet below existing grades.

Terracon should be notified if any of the above information is inconsistent with the planned construction as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project is located at 3900 Loch Raven Blvd in Baltimore, Maryland. Latitude/Longitude (approximate) 39.336624, -

76.596747 (See Exhibit D). See Site Location

Existing

Improvements

Loch Raven VA Medical Center, Loch Raven Community Living

Center, associated buildings, and parking.

Current Ground

Cover Grass, asphalt paving, tree cover

Existing

Topography

The ground surface elevation (EL) at the new boiler building ranges from EL 208 to EL 212. The elevation at the site ranges from about EL 205 to EL 230.

Facilities | Environmental | Geotechnical | Materials 3

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 Existing Fill generally loose to medium dense, POORLY

GRADED SAND WITH GRAVEL, SILTY SAND, FILL,

black, brown, light brown

2 Residual generally medium dense to dense, SILTY SAND

(SM) with varying amounts of gravel, CLAYEY

SAND WITH GRAVEL (SC), yellow, brown, white

3 Weathered Rock very dense, SILTY SAND (SM), SILTY CLAYEY

SAND (SC-SM), light yellow, white, brown

Groundwater

Groundwater level observations were made in the field during drilling and upon completion of drilling. Groundwater was not encountered during our investigation.

The groundwater observations presented herein are considered to be an indication of the groundwater levels at the dates and times indicated. Where more impervious soils are encountered, the amount of water seepage into the borings is limited, and it is generally not possible to establish the location of the groundwater table through short-term water level observations. Accordingly, the groundwater information presented herein should be used with caution. Also, fluctuations in groundwater levels should be expected with seasons of the year, construction activity, changes to surface grades, precipitation, or other similar factors.

Facilities | Environmental | Geotechnical | Materials 4

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic

Design Category. Site Classification is required to determine the Seismic Design

Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of

ASCE 7 and the International Building Code (IBC). Based on the soil and bedrock properties observed at the site and as described in the exploration logs and results, our professional opinion is that a Seismic Site Classification of C be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 20 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

Corrosivity

The table below lists the results of laboratory soluble sulfate, soluble chloride, electrical resistivity, and pH testing. The values may be used to estimate potential corrosive characteristics of the onsite soils with respect to contact with the various underground materials which will be used for project construction.

Boring

No.

Sample

Depth

(ft)

Sulfate

(mm/Kg)

Chloride

(mg/Kg)

Sulfide

(mg/Kg)

Resistivity

(ohm-cm)

Redox

Potential

(mV) pH Moisture

B-1 0-5 18 60 <1.2 2900 +180 7.7 11

Results of soluble sulfate testing can be classified in accordance with ACI 318 – Building

Code Requirements for Structural Concrete. Numerous sources are available to characterize corrosion potential to buried metals using the parameters above.

ANSI/AWWA is commonly used for ductile iron, while threshold values for evaluating the effect on steel can be specific to the buried feature (e.g., piling, culverts, welded wire reinforcement, etc.) or agency for which the work is performed. Imported fill materials may have significantly different properties than the site materials noted above and should be evaluated if expected to be in contact with metals used for construction.

Consultation with a NACE-certified corrosion professional is recommended for buried metals on the site.

Facilities | Environmental | Geotechnical | Materials 5

Earthwork

Earthwork is anticipated to include clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Site Preparation

Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.

Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

Mature trees are located within or near the footprint of some of the proposed buildings, which will require removal at the onset of construction. Tree root systems can remove substantial moisture from surrounding soils. Where trees are removed, the full root ball and all associated dry and desiccated soils should be removed. The soil materials which contain less than five percent organics can be reused as engineered fill provided the material is moisture-conditioned and properly compacted.

Where fill is placed on existing slopes steeper than 5H:1V, benches should be cut into the existing slopes prior to fill placement. The benches should have a minimum vertical face height of one foot and a maximum vertical face height of three feet and should be cut wide enough to accommodate the compaction equipment. This benching will help provide a positive bond between the fill and natural soils and reduce the possibility of failure along the fill/natural soil interface.

Subgrade Preparation

The subgrade should be proofrolled with an adequately loaded vehicle such as a fully-loaded (minimum 20-ton) tandem-axle dump truck. The proofrolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Excessively wet or dry material should either be removed or moisture-conditioned and recompacted.

All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 10 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. Compacted structural fill soils should then be placed to the proposed design grade and the moisture

Facilities | Environmental | Geotechnical | Materials 6 content and compaction of subgrade soils should be maintained until foundation or pavement construction.

Existing Fill

As noted in Geotechnical Characterization, all borings except for B-MH1 encountered previously placed fill to depths ranging from about 2 to 6 feet below existing ground surface. We have no records to indicate the degree of control, and consequently, the fill is considered unreliable for support of foundation loads. Support of floor slabs on or above existing fill soils is discussed in this report. However, even with the recommended construction procedures, inherent risk exists for the owner that compressible fill or unsuitable material, within or buried by the fill will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by following the recommendations contained in this report.

If the owner elects to construct the floor slabs on the existing fill to reduce initial construction costs in exchange for increased potential longer-term distress, the following protocol should be followed. After the planned grading has been completed, the area should be undercut 2 feet within the building area and 10 feet beyond the lateral limits of the building area. Following this overexcavation, the entire area should be proofrolled with heavy, rubber tire construction equipment, to aid in delineating areas of soft or otherwise unsuitable soil. Once unsuitable materials have been remediated, and the subgrade has passed the proofroll test, backfill to finished subgrade elevation can begin.

The existing undocumented fill that was removed can be evaluated for reuse as structural fill.

Excavation

We anticipate that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. However, rock excavation methods such as hoe-ramming or blasting may be required for some of the site development. The elevations where rock excavation methods may be required for removal of bedrock at the test boring locations are estimated in the table below. Estimated rock elevations at the boring locations are based on materials equal to or harder than an SPT resistance of

50/3”:

Boring No.

Estimated Depth where Rock Excavation Methods May Be

Required (ft)

Estimated Elevation where Rock Excavation Methods May Be Required (MSL)

B-1 18.5 EL 190.5

B-2 18.5 EL 192.5

B-MH2 3 EL 227

Facilities | Environmental | Geotechnical | Materials 7

Boring No.

Estimated Depth where Rock Excavation Methods May Be

Required (ft)

Estimated Elevation where Rock Excavation Methods May Be Required (MSL)

B-MH4 13.5 EL 194.5

B-MH5 3 EL 202

B-MH9 6 EL 210

The depths given above are based upon the use of normal earth excavation equipment including up to a Caterpillar 330 hydraulic backhoe or equivalent, for mass excavation.

Project specifications should include the following as a definition of rock excavation for mass excavation: “Rock is defined as any material which cannot be dislodged by a

Caterpillar 330 hydraulic backhoe without the use of hoe-ramming or blasting. This classification does not include material such as loose rock, concrete or other materials that can be removed by means other than hoe-ramming or blasting, but which for reasons of economy in excavating, the contractor chooses to remove by hoe-ramming or blasting.” Variations in rock conditions should be expected from the elevations presented in the table above since the rock surface can vary over the site. Also, the extent of rock excavation will depend on Contractor’s methods, rock jointing, and rock foliation/bedding.

The depth-to-rock information included in this report is for design purposes and not to estimate excavation cost. Any use of this report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly affect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing.

The bottom of excavations should be thoroughly cleaned of loose soils and disturbed materials prior to backfill placement and/or construction.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill is material used below, or within 10 feet of structures, pavements, or constructed slopes. General fill is material used to achieve grade outside of these areas.

Reuse of Onsite Soil: Excavated onsite soil may be selectively reused as fill below pavement and landscaping areas.

Imported Fill Materials: Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of

Facilities | Environmental | Geotechnical | Materials 8 approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Material property requirements for onsite soil for use as general fill and structural fill are noted in the table below:

Soil Type 1,2

USCS

Classification Acceptable Parameters (for Structural Fill)

Low Plasticity

Cohesive

CL, CL-ML

ML, SM, SC

Liquid Limit less than 40

Plasticity index less than 15

Max Dry Density > 105 pcf

Granular

GW, GP, GM, GC,

SW, SP

Max Dry Density > 105 pcf

1. Structural and general fill should consist of approved materials free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

Additional geotechnical consultation should be provided prior to use of uniformly graded gravel on the site.

2. Existing fill free of deleterious material may be reused for fill if it meets the requirements presented above.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift

Thickness

Eight inches or less in loose thickness when heavy, self-propelled compaction equipment is used

Four to six inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used

Same as structural fill

Minimum

Compaction

Requirements 1,2

98% of max. below foundations and within one foot of finished pavement subgrade

95% of max. above foundations, below floor slabs, and more than one foot below finished pavement subgrade

85% of max.

Facilities | Environmental | Geotechnical | Materials 9

Item Structural Fill General Fill

Water Content

Range

-2% to +2% of optimum

As required to achieve min.

compaction requirements

1. Maximum density and optimum water content as determined by the modified

Proctor test (ASTM D 1557).

2. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least

70% relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility to be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1H:1V projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

Onsite materials are considered suitable for backfill of utility and pipe trenches from one foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab

Facilities | Environmental | Geotechnical | Materials 10 and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or

Facilities | Environmental | Geotechnical | Materials 11 instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency prescribed by local agencies and local codes.

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical

Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Shallow Foundations

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description

Maximum Net Allowable Bearing Pressure 1, 2, 3 3,000 psf

Minimum Foundation Dimensions Columns: 30 inches

Continuous: 18 inches

Ultimate Coefficient of Sliding Resistance 5 0.35 (granular material)

Minimum Embedment below Finished Grade 6 Exterior footings in unheated areas: 30 inches

Estimated Total Settlement from Structural Loads 3 Less than about one inch

Facilities | Environmental | Geotechnical | Materials 12

Estimated Differential Settlement 3,7 Less than about 1/500

(0.002) angular distortion

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation.

Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. The allowable bearing capacity can be increased by 33% for transient/seismic loading conditions

3. Values provided are for maximum loads noted in Project Description.

Additional geotechnical consultation will be necessary if higher loads are anticipated.

4. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Frictional resistance for granular materials is dependent on the bearing pressure which may vary due to load combinations. For fine-grained materials, lateral resistance using cohesion should not exceed ½ the dead load.

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within five horizontal feet of the structure.

7. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable bearing soils are observed at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The lean concrete replacement zone is illustrated on the sketch below.

Facilities | Environmental | Geotechnical | Materials 13

Floor Slabs

Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

As previously described, any existing fill present beneath floor slabs should be removed to a minimum depth of two feet below the slab and replaced with approved compacted fill.

Floor Slab Design Parameters

Item Description

Floor Slab Support1

Minimum six inches of free-draining (less than 5% passing the

U.S. No. 200 sieve) crushed aggregate compacted to at least

95% of ASTM D 1557

At least 18 inches of low plasticity cohesive or granular soils with no more than 15% passing the U.S. No. 200 sieve material should be present below aggregate layer where lean to fat clay or fat clay soils are present

Estimated Modulus of

Subgrade Reaction 2 100 pounds per square inch per inch (psi/in) for point loads

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the

Facilities | Environmental | Geotechnical | Materials 14 floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture-sensitive or impervious coverings, when the project includes humidity-controlled areas, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut contraction joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations, refer to the ACI Design Manual.

Joints or cracks should be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy-duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

Settlement of floor slabs supported on existing fill materials cannot be accurately predicted but could be larger than normal and result in some cracking. Mitigation measures, as noted in Existing Fill within Earthwork, are critical to the performance of floor slabs. In addition to the mitigation measures, the floor slab can be stiffened by adding steel reinforcement, grade beams, and/or post-tensioned elements.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed, and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should observe the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high-traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

Facilities | Environmental | Geotechnical | Materials 15

Lateral Earth Pressures

Design Parameters

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to values indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction, and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The “at-rest” condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

Earth

Pressure

Condition 1

Coefficient for

Backfill Type 2

Surcharge

Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

Active (Ka) Granular - 0.31 (0.31)S (38)H (82)H

At-Rest (Ko) Granular - 0.47 (0.47)S (59)H (92)H

Passive (Kp) Granular – 3.25 (0.47)S (407)H (266)H

1. For active earth pressure, wall must rotate about base, with top lateral movements 0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance. Fat clay or other expansive soils should not be used as backfill behind the wall.

2. Uniform, horizontal backfill, with a maximum unit weight of 125 pcf for granular soils.

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

Facilities | Environmental | Geotechnical | Materials 16

5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage for Below-Grade Walls below. “Submerged” conditions are recommended when drainage behind walls is not incorporated into the design.

Backfill placed against structures should consist of granular soils or low-plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 degrees from vertical for the active case.

Footings, floor slabs or other loads bearing on backfill behind walls may have a significant influence on the lateral earth pressure. Placing footings within wall backfill and in the zone of active soil influence on the wall should be avoided unless structural analyses indicate the wall can safely withstand the increased pressure.

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity-type concrete walls. These recommendations are not applicable to the design of modular block-geogrid reinforced backfill walls (also termed MSE walls). Recommendations covering these types of wall systems are beyond the scope of services for this assignment. However, we would be pleased to develop a proposal for evaluation and design of such wall systems upon request.

Subsurface Drainage for Below-Grade Walls

A perforated rigid plastic drain line installed behind the base of walls and extends below adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage to daylight or to a sump pit and pump. The drain line should be surrounded by clean, free-draining granular material having less than 5% passing the

No. 200 sieve, such as No. 57 aggregate. The free-draining aggregate should be encapsulated in a filter fabric. The granular fill should extend to within two feet of final grade, where it should be capped with compacted cohesive fill to reduce infiltration of surface water into the drain system.

Facilities | Environmental | Geotechnical | Materials 17

As an alternative to free-draining granular fill, a prefabricated drainage structure may be used. A prefabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion and is fastened to the wall prior to placing backfill.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the

Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services onsite, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not

Facilities | Environmental | Geotechnical | Materials 18 intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly effect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others.

Construction and site development have the potential to affect adjacent properties. Such impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

Attachments

Figures

Contents:

GeoModel (2 pages)

Note: All attachments are one page unless noted above.

E L E

V A

T

IO

N

M S

L

(f e e t)

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1

B-2

Legend

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

GeoModel

3901 Loch Raven Blvd | Baltimore, MD

Terracon Project No. JD235427

Loch Raven Construct Consolidated Boiler Spaces

19955 Highland Vista Drive Suite 170 Ashburn, VA

Asphalt Fill

Silty Sand Weathered Rock

Topsoil Clayey Sand

Clayey Sand with Gravel

Model Layer Layer Name General Description generally loose to medium dense, POORLY GRADED SAND WITH GRAVEL, SILTY SAND, FILL, black, brown, light brown

3 very dense, SILTY SAND (SM), SILTY CLAYEY SAND (SC-SM), light yellow, white, brown generally medium dense to dense, SILTY SAND (SM) with varying amounts of gravel, CLAYEY SAND WITH GRAVEL (SC), yellow, brown, white

Existing Fill

Weathered Rock

Residual

13.5

E L E

V A

T

IO

N

M S

L

(f e e t)

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-MH1

B-MH2

B-MH4

B-MH5

B-MH9

Legend

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

GeoModel

3901 Loch Raven Blvd | Baltimore, MD

Terracon Project No. JD235427

Loch Raven Construct Consolidated Boiler Spaces

19955 Highland Vista Drive Suite 170 Ashburn, VA

Topsoil Silty Sand

Asphalt Fill

Weathered Rock Silty Sand with Gravel

Poorly-graded Gravel

Model Layer Layer Name General Description generally loose to medium dense, POORLY GRADED SAND WITH GRAVEL, SILTY SAND, FILL, black, brown, light brown

3 very dense, SILTY SAND (SM), SILTY CLAYEY SAND (SC-SM), light yellow, white, brown generally medium dense to dense, SILTY SAND (SM) with varying amounts of gravel, CLAYEY SAND WITH GRAVEL (SC), yellow, brown, white

Existing Fill

Weathered Rock

Residual

6.6

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

2 20 New Boiler Building

5 15 Manholes

Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±3 feet) and referencing existing site features. Approximate ground surface elevations were obtained by interpolation from the Site Topographic Survey CAD file provided by Above Group in an email on February 8, 2024. If elevations and a more precise boring layout are desired, we recommend borings be surveyed.

Subsurface Exploration Procedures: We advanced the borings with a track-mounted, using hollow stem augers. Five samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. In the thin-walled tube sampling procedure, a thin-walled, seamless steel tube with a sharp cutting edge was pushed hydraulically into the soil to obtain a relatively undisturbed sample. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal

18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value.

The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. For safety purposes, all borings were backfilled with auger cuttings after their completion. Pavements were patched with cold-mix asphalt and/or pre-mixed concrete, as appropriate.

We also observed the boreholes while drilling and at the completion of drilling for the presence of groundwater. Groundwater was not encountered at these times in the boreholes.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following types of tests:

■ Moisture Content

■ Atterberg limits

■ Grain size analysis

■ Corrosion series

The laboratory testing program often included examination of soil samples by an engineer. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System.

Site Location and Exploration Plans

Site Location Plan

Exploration Plan

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Site Location Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

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When paragraph markers are turned on you may notice a line of hidden text above and outside the table – please leave that alone. Limit editing to inside the table.

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Exploration Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

Exploration and Laboratory Results

Boring Logs (7 pages)

Summary of Laboratory Results

Atterberg Limits

Grain Size Distribution (2 pages)

Corrosion Series Results (3 pages)

208.4

195.5

Asphalt = 6 in.

FILL - POORLY GRADED SAND WITH GRAVEL, fine to medium, black with light gray, medium dense

RESIDUAL - SILTY SAND (SM), fine to medium, light yellow with gray, moist, medium dense micaceous loose

WEATHERED ROCK - SILTY SAND (SM), fine to medium, black with light yellow, very dense

Boring Terminated at 20 Feet

Boring Log No. B-1

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

M o d el

L ay er

25.1 35-31-4

0.6

2.0

13.5

20.0

8-11-7-6 N=18

15-17-12-8 N=29

7-12-9-12 N=21

7-6-5-5 N=11

5-2-3-6 N=5

50/5"

50/2"

3900 Loch Raven Blvd | Baltimore, MD

Terracon Project No. JD235427 Ashburn, VA

19955 Highland Vista Drive Suite

Drill Rig D 50

Hammer Type Automatic

Driller Terracon (A.Fowler)

Logged by Terracon (S.Koneru)

Boring Started 01-31-2024

Boring Completed 01-31-2024

Abandonment Method Boring backfilled with auger cuttings upon completion.

Advancement Method

3-1/4" ID HSA

Notes

Water Level Observations

Cave-in Depth: 17 ft.

Not encountered upon completion

Not encountered during driling

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Elevation Reference: Elevations were interpolated from a topographic site plan.

VAMC Loch Raven

S am pl e

T yp e

W at er C o n te n t

Elevation: 209 (Ft.) +/-

Atterberg Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 39.336632° Longitude: -76.596978°

Depth (Ft.)

R ec o ve ry

In

N

Fi el d T es t

R es u lt s

210.8

197.5

Topsoil = 2 in.

FILL - POORLY GRADED SAND WITH GRAVEL, medium to coarse, brown with light yellow, loose

RESIDUAL - CLAYEY SAND (SC), fine to medium, brown with light yellow, moist, loose

RESIDUAL - CLAYEY SAND WITH GRAVEL (SC), medium to coarse, light yellow with white, moist, medium dense

RESIDUAL - SILTY…