Attachment 2 - Geotechnical Report.pdf

ECS Southeast, LLP

Geotechnical Engineering Report Lexington VA Healthcare System – Utility Replacement

2250 Leestown Road Lexington, Fayette County, Kentucky 40511

ECS Project Number 61-3013

August 17, 2023

August 17, 2023

Mr. Pete Cloutier Integrity Federal Services 148 S Queen Street, Suite 201 Martinsburg, WV 25401

Reference: Geotechnical Engineering Report Lexington VA Healthcare System – Utility Replacement 2250 Leestown Road

Lexington, Fayette County, Kentucky 40511 ECS Project No. 61-3013

Dear Mr. Cloutier, ECS Southeast, LLP (ECS) has completed the subsurface exploration, laboratory testing, and geotechnical engineering analyses for the above referenced project. Our services were performed in general accordance with our agreed to scope of work, described in ECS Proposal No. 61:P3211 and dated July 11, 2023.

This report presents our understanding of the geotechnical aspects of the project along with the results of the field exploration and laboratory testing conducted, and our geotechnical related design and construction recommendations.

It has been our pleasure to be of service to Integrity Federal Services during the design phase of this project. We would appreciate the opportunity to remain involved during the continuation of the design phase and would like to provide our services during construction operations as well to confirm the interpreted subsurface conditions utilized in this report. Should you have any questions concerning the information contained in this report, or if we can be of further assistance to you, please contact us.

Respectfully submitted, ECS SOUTHEAST, LLP

Bryn Kabbes, EIT Liz Newcomb, PE Project Engineer Principal Engineer bkabbes@ecslimited.com lnewcomb@ecslimited.com

Lexington VA Healthcare System – Utility Replacement August 17, 2023 ECS Project No. 61-3013 Page i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1.1 General

2.0 PROJECT INFORMATION

2.1 Site Information

2.2 Proposed Construction

3.0 SITE GEOLOGY

4.0 FIELD EXPLORATION AND LABORATORY TESTING

4.1 Subsurface Characterization

4.2 Laboratory Test Summary

5.0 GEOTECHNICAL CONCERNS

5.1 Existing Utilities

5.2 Existing Pavements

5.3 Existing Fill

5.4 Lower Strength Soils

5.5 Highly Plastic Clays

5.6 Shallow Refusal

5.7 Karst Potential

5.8 Groundwater Seepage

5.9 Degradable Soils

5.10 Reuse of On-site Soils

5.11 Subgrade Improvement

5.12 Trees

5.13 Weather Considerations

6.0 SITE CONSTRUCTION RECOMMENDATIONS

6.1 Planning

6.2 Existing Construction

6.3 Subgrade Preparation

6.4 Existing Fill

6.5 Structural Fill

6.6 Highly Plastic Clays

6.7 Karst Potential

6.8 Groundwater

7.0 DESIGN RECOMMENDATIONS

7.1 Utility Installations

7.2 Slabs on Grade/Sidewalk design

7.3 Seismic Design Considerations

7.4 Flexible Pavement Design

7.5 Rigid Pavement Design

8.0 CLOSING

ECS Project No. 61-3013 Page ii

APPENDICES

Appendix A – Drawings & Reports

• Site Location Diagram

• Boring Location Diagram

• Geologic Unit Diagram Appendix B – Field Operations

• Soil & Rock Classification

• Boring Legend

• Boring Records

• Boring Composites Appendix C – Laboratory Testing

• Field Procedures

• Laboratory Procedures Appendix D – Supplemental Report Documents and Calculations

• GBA “Important Information About Your Geotechnical Engineering Report”

ECS Project No. 61-3013 Page 1

EXECUTIVE SUMMARY

ECS Southeast, LLP (ECS) has completed the subsurface exploration for the proposed underground utility replacements for the Lexington VA Medical Center. The project information summarized below is based exclusively on the information made available to us by the client at the time of this report and the results of our subsurface exploration. Our findings, conclusions, and recommendations are summarized below.

• Surface materials generally consisted of approximately 1 to 5 inches of topsoil in grass-covered areas of the site.

• Existing fill was encountered in five (5) of the seven (7) borings beneath surface materials and extended approximately 1.5 to 4.5 feet below existing grades.

• Surface materials and/or existing fill were generally underlain by native soils which consisted of low to moderate plasticity, soft to very stiff, moist to very moist, silty LEAN CLAY (CL) and/or shades of orange, yellow, red, and brown, moderate to high plasticity, firm to hard, very moist to moist, silty, FAT CLAY (CH).

• Approximately 1 to 8 inches of highly to completely weathered rock was encountered in four (4) of the seven (7) borings prior to refusal depths.

• Evidence of groundwater seepage was observed at the soil/rock interface in four (4) of the seven (7) borings (B-01, B-02, B-03, and B-06). Groundwater seepage was not encountered in the remainder of the borings at the time of drilling.

• Equipment refusal was encountered at approximately 7.3 to 13.8 feet below existing grades in the borings.

GEOTECHNICAL CONCERNS:

− Existing Utilities

− Existing Pavements

− Existing Fill

− Lower Strength Soils

− Highly Plastic Clays

− Shallow Refusal

− Karst Potential

− Groundwater Seepage

− Degradable Soils

− Reuse of On-Site Soils

− Subgrade Improvement

− Trees

− Weather Considerations

DESIGN & CONSTRUCTION RECOMMENDATIONS:

• The soils encountered during our exploration are expected to generally be suitable for support of utility pipes. Any loose or unsuitable materials encountered should be removed and replaced with suitable compacted Structural Fill, or pipe stone bedding material.

• Existing fill was encountered beneath surface materials in five (5) of the seven (7) borings. It is likely that additional areas of existing fill will be observed during excavations.

• Lower strength soils were encountered in two (2) of the borings between approximately 4.0 and 5.5 feet below existing grades.

• Some areas may require improvement to the subgrade in order to be adequate for construction of new fill, utility trench and pavement areas.

• Slabs on grade may be designed with a subgrade modulus of 100 pci.

• A site class of “C” may be used in seismic design per the 2018 Kentucky Building Code.

• Subgrade and fill soils may require moisture conditioning to achieve required compaction and to provide adequate support conditions for floors and foundations.

This Executive Summary is intended as a very brief overview of the preliminary geotechnical conditions that are expected to affect design and construction. Information gleaned from this Executive Summary should not be utilized in lieu of reading the entire geotechnical report.

ECS Project No. 61-3013 Page 2

1.0 INTRODUCTION

1.1 GENERAL

The purpose of this study was to provide geotechnical information for the design of floors, foundations, and pavements for the proposed development. Also included are geotechnical subgrade preparation and fill placement guidelines. The recommendations developed for this report are based on project information supplied by Mr. Pete Cloutier of Integrity Federal Services.

This report contains the results of our subsurface exploration and laboratory testing programs, site characterization, engineering analyses, and recommendations for the design and construction of the planned development.

This report describes our exploratory and testing procedures, presents our findings and evaluations, and includes the following:

• Summary of project information provided.

• Description of existing site conditions, reported geology, and encountered subsurface conditions.

• Assessment of general suitability of the site for the intended use from a geotechnical standpoint.

• Recommendations for site preparation and structural fill placement, including an evaluation of on-site soils for use as compacted fills and identification of encountered potentially inadequate soils.

• Recommendations for utility trench excavations.

• Recommended slab-on-grade and sidewalk design parameters and associated construction guidelines.

• Recommended flexible and rigid pavement design parameters and associated construction guidelines for light, medium, and heavy-duty pavement sections.

• Site class for seismic design based on the soil test boring data and on available data from the site vicinity.

• Other identified geotechnical concerns and recommended additional sampling/testing/analysis.

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2.0 PROJECT INFORMATION

2.1 SITE INFORMATION

SUBJECT SUMMARY OF EXISTING SITE CONDITIONS

Site Location The site consists of the Lexington VA Medical Center, Franklin R. Sousley campus, which is located at 2250 Leestown Road, Lexington, Fayette County, Kentucky. Refer to Site Location Diagram in the Appendix for approximate location of the site.

General Description The site consists of several healthcare buildings, connected by indoor walkways or outdoor walking paths, and several ancillary maintenance/facilities buildings. Landscaped open areas, paved driveways and parking areas, and walking pathways are located throughout the site.

Topography The site slopes downward from the northeastern boundary of the site (Leestown Road) towards the southern boundary of the site.

Approximately 65 feet of feet of fall occurs across the entire site. Areas of steeper slopes generally occurred within the northwestern and southwestern portions of the site.

Surface Water Drainage Existing surface drainage appeared to be good at the time of drilling.

Ground Cover Primarily short, maintained grass, with isolated large trees throughout the site. Paved driveways, parking areas, and sidewalks are located throughout the entire site.

Utilities Existing underground electric, water, sanitary sewer, storm water, and communication utilities were reported throughout the site.

2.2 PROPOSED CONSTRUCTION

SUBJECT DESIGN INFORMATION / EXPECTATIONS

Project Description The proposed project consists of replacing the existing underground utilities (water, sanitary, and storm sewers) for the existing healthcare facilities campus.

Maximum Cut/Fill ± 6 to 7 feet overall for utility trench locations (assumed).

Project Information Conversations/Emails:

Mr. Pete Cloutier, PE of Integrity Federal Services Documents Provided:

“PC MARKUP 2023-06-27 VAMC LEXINGTON SD PLAN”, prepared by Integrity Federal Services, dated June 27, 2023.

“SOIL BORINGS EXHIBIT”, prepared by Integrity Federal Services, dated July 19, 2023.

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3.0 SITE GEOLOGY

According to the Geologic Map of the Lexington West 24K Quadrangle, Fayette County, Kentucky, published by the United States Geological Survey (USGS), and information obtained from the Kentucky Geological Survey (KGS) Geologic Information Service website, the subject site is underlain by several members of the Lexington Limestone geologic unit. Refer to Geologic Unit Diagram in the Appendix for approximate boundaries of the underlying formations.

SITE GEOLOGY – UNDERLYING FORMATIONS

FORMATION UNIT DESCRIPTION

KARST

POTENTIAL(1,2)

Lexington Limestone

(Lower Part)

Tanglewood Limestone Member (Lower Tongue)

Primary Lithology: Limestone and minor shale

a) Limestone appears medium gray to medium-brownish gray, fine to medium-grained, and slightly phosphatic.

b) Thin bioclastic shale partings are present throughout limestone and crossbedded in part.

c) The lower part of the Tanglewood member interfingers between two layers of the Brannon Limestone member and the Cane Run Bed of the Grier Limestone member.

Very High(5)

Lexington Limestone

(Upper Part)

Brannon Member

Primary Lithology: Limestone and shale

a) Limestone appears light gray to light brownish-gray, microgranular, and argillaceous. Limestone weathers to a yellowish clayey soils containing abundant porcelaneous chert and siltstone fragments.

b) Limestone is silty in part, with thin beds of medium-dark gray shale and locally present interbeds or clastic limestone.

c) Convolute bedding and flow rolls are common in thicker beds.

d) Chert occurs as thin beds and as nodules. Thin beds of swelling bentonite locally occur near the base of the member.

Low(3)

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Lexington Limestone

(Lower Part)

Grier Limestone Member (Above Cane Run Bed)

Primary Lithology: Limestone

a) Limestone appears medium to dark gray, fine to medium grained, and fossiliferous, with few very thin shale layers in the upper few feet.

b) Interfingers with and grades into lower part of the Tanglewood Limestone member.

Cane Run Bed

Primary Lithology: Limestone

a) Limestone appears light gray to light brownish-gray, microgranular, argillaceous, and silty in part.

b) Dense limestone nodules and boulders in convolute beds locally.

c) Chert appears as nodules and thin beds in upper few feet of the diagnostic lithographic feature.

d) Unit interfingers with and grades into the lower part of the Tanglewood Limestone member.

Grier Limestone Member (Below Cane Run Bed)

Primary Lithology: Limestone and shale

a) Limestone appears light to dark gray, microgranular to medium grained, bioclastic, argillaceous, and fossiliferous.

b) Shale appears medium to olive gray, in thin beds and sandy interbeds within limestone.

c) Unit interfingers with and grades into the lower part of the Tanglewood Limestone member.

High(4)

Notes:

(1) Karst is topography commonly formed over limestone and characterized by sinkholes, irregular rock conditions, underground drainage, springs, and caves.

(2) The karst potential is based on the tendency for the unit to develop or have karst features as shown on the Kentucky Geological Survey (KGS)

Geologic Information Service Karst Potential Map and is not necessarily indicative of the actual presence or absence of existing karst activity at the site.

(3) According to the KGS Karst Potential Classification definitions, formations designated with a “Low” karst potential are “Siliciclastic units with minor limestone beds or units primarily composed of dolomite. Karst features are poorly developed or absent.”

(4) According to the KGS Karst Potential Classification definitions, development of karst features in areas with karst potential listed as “High” is likely.

(5) According to the KGS Karst Potential Classification definitions, formations designated with a “Very High” karst potential are areas underlain by “thick-bedded, typically fine grained and pure limestone units with little or no insoluble content.” Formations with this designation “will exhibit mature karst, including caves, sinkholes, and springs where they crop out.”

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4.0 FIELD EXPLORATION AND LABORATORY TESTING

4.1 SUBSURFACE CHARACTERIZATION

SUBJECT SUMMARY OF SUBSURFACE EXPLORATION (1)

Boring Method Direct Push

Sampling Method Standard Penetration Testing (ASTM D-1586)

Number of Borings Seven (7) soil test borings

Boring Locations Refer to Boring Location Diagram in the Appendix for locations.

Boring Depths Refer to Boring Records in the Appendix.

Logging Method Full-time presence of an ECS engineer to observe, direct, and document the drilling, sampling and test results, and encountered conditions.

Groundwater Evidence of groundwater seepage was observed at the soil/rock interface in 4 of the 7 borings (Borings B-01, B-02, B-03, and B-06). Groundwater seepage was not encountered in the remainder of the borings at the time of drilling.

Refusal (2) Equipment refusal was encountered at approximately 7.3 to 13.8 feet below existing grades in all seven (7) of the borings.

Notes:

(1) Detailed descriptions of the exploration methods are listed in the Field Procedures section of the Appendix.

(2) Refusal is the term applied to material that cannot be penetrated with drilling tools or has a standard penetration resistance exceeding 50 blows per 6-inch increment or 10 blows with little to no penetration of the split spoon. Refusal may be encountered on continuous bedrock, discontinuous floaters, cemented soil, weathered rock, buried construction debris, buried structures, or other hard subsurface materials.

The following sections provide generalized characterizations of the soil strata. Please refer to the Boring Records and Boring Composite in the Appendix.

APPROXIMATE

DEPTH (FT)

STRATUM DESCRIPTION

N-VALUES

BLOWS

PER FOOT

(BPF)(2)

0.0 – 0.4 I TOPSOIL – Approximately 1 to 5 inches of topsoil. N/A

0.1 – 4.5 II

EXISTING FILL – Typically shades of yellow brown and medium to dark brown, low plasticity, moist, silty clay, or crushed stone with sand was encountered in five (5) of the seven (7) borings below surface materials.

Various amounts of crushed stone, sand, gravel, root fibers/organics, brick and concrete fragments, and debris were observed in the borings within existing fill.

N/A

0.4 – 6.5 III

LEAN CLAY (CL) – Typically shades of orange brown and medium to dark brown, low to moderate plasticity, soft to very stiff, moist to very moist, silty, LEAN CLAY, (CL), with varying amounts of organics/root fibers, large roots, black oxide nodules, and weathered rock

3 to 10

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APPROXIMATE

DEPTH (FT)

STRATUM DESCRIPTION

N-VALUES

BLOWS

PER FOOT

(BPF)(2)

fragments was encountered below Stratum I or II in five

(5) of the seven (7) borings. Generally extended to 4.0 to 6.5 feet below existing grades.

1.5 – 13.8 IV

FAT CLAY (CH) – Typically shades of orange brown, yellow brown, red brown, and mottled medium to dark brown, moderate to high plasticity, firm to hard, very moist to moist, silty, FAT CLAY, (CH), with varying amounts of black oxide nodules and weathered rock fragments was encountered in all seven (7) of the borings.

4 to 24

7.0 – 9.8 V WEATHERED ROCK – Typically in shades of yellow, brown and light gray, highly to completely weathered, fine grained.

N/A

Notes:

(1) This summary is generalized and does not describe the actual conditions in each boring. These zones also may not occur at each location as described above. Depths are approximate. Detailed descriptions of the encountered materials are listed on the Boring Records in the Appendix.

4.2 LABORATORY TEST SUMMARY

The laboratory testing was performed on selected samples obtained during field exploration operations.

Classification and index property tests were performed. The laboratory testing program included:

• Natural Moisture Content

• Atterberg Limits

Each sample was visually classified on the basis of texture and plasticity in accordance with ASTM D2488 Standard Practice for Description and Identification of Soils (Visual-Manual Procedures), including Unified Soil Classification System (USCS) classification symbols, and ASTM D2487 Standard Practice for Classification for Engineering Purposes. After classification, the samples were grouped in the major zones noted on the Boring Records in the Appendix. The group symbols for each soil type are indicated in parentheses along with the soil descriptions. The stratification lines between strata on the logs are approximate; in situ, the transitions may be gradual.

SUMMARY OF LABORATORY TEST RESULTS(1)

STRATUM

MOISTURE

CONTENT

LIQUID LIMIT

PLASTIC

LIMIT

PLASTICITY

INDEX

UNIFIED SOIL

CLASSIFICATION

III 23.8 – 33.0 % -- -- -- N/A

IV 27.6 – 68.3 % 50 22 28 CH

Notes:

(1) A more detailed summary of the laboratory test results is included on the Boring Records in the Appendix. Detailed descriptions of the laboratory test methods are listed in the Laboratory Procedures section of the Appendix.

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5.0 GEOTECHNICAL CONCERNS

Analysis of the provided project information, observed site conditions, encountered subsurface conditions, and our past experience with similar projects, revealed the following important geotechnical considerations. These considerations should be properly addressed in planning, budgeting, design, and construction phases to reduce impacts on construction cost, completion schedule, performance of the building and site improvements, and long-term maintenance of the proposed construction. Our recommendations for addressing these concerns are provided in subsequent sections of this report.

5.1 EXISTING UTILITIES

• Due to the number of existing structures occupying the site, a portion of the utilities for those structures are likely present and may be encountered in areas of the proposed construction footprint.

• If former underground utilities were abandoned and not removed or grouted full, soil may migrate into open voids (e.g., open pipes from utilities), causing subsidence of the overlying construction.

• In addition, existing and/or former utility lines located within proposed construction areas may cause the new construction to behave unexpectedly due to the variable and poor support conditions caused by old backfill, which can cause settlement or distress of the overlying new construction. Existing utility backfill rarely is adequate for support of new structures.

• The load support characteristics of the backfill along utility lines typically can be assessed with careful proofrolling and subgrade evaluation during construction. Some undercutting and/or bridging of poorly compacted backfill along existing and former utility lines should be anticipated in slab areas if utilities are left in-place.

5.2 EXISTING PAVEMENTS

• In some cases, subgrades below pavements are not prepared to the same level as would be the case for building slabs-on-grade and therefore may not be adequate for support of new slabs.

• Existing pavements can obscure the presence of karst features, voids, and poor subgrade conditions. It is not unusual for existing surface materials, even those in good condition, to bridge (hide) poor subgrade conditions. These conditions can be better identified and addressed with removal of the existing pavement surface. Some undercutting of poor-quality materials should be anticipated in areas overlain by existing pavement.

• Water is easily trapped under existing surface materials (i.e., pavements). Accordingly, soft, saturated soils likely are present in some areas below existing pavement.

• Moisture conditioning and recompaction of the soils underlying existing pavement may be necessary, especially if construction occurs during the wetter months of the year.

5.3 EXISTING FILL

• Existing, uncontrolled fill was encountered below surface materials in five (5) of the seven

(7) borings (B-01, B-02, B-03, B-05, and B-06) and consisted of low plasticity, silty clay or crushed stone with sand, which extended approximately 4.5 feet below existing grades.

• The fill was considered uncontrolled because no recorded data is available documenting the material quality or content of the existing fill.

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• It is likely that additional areas of existing fill will be encountered on the site in areas which were not explored during drilling activities (i.e., in closer proximity to the existing buildings, pavements, and buried utilities). These unexplored areas should be evaluated by an ECS representative during construction to confirm that encountered conditions are consistent with the findings of the explored areas.

• The fill encountered on site creates numerous subsurface challenges that increase costs, including the cost of designing foundations to mitigate or reduce the risks inherent with uncontrolled fill.

• Potential problems for the proposed construction created by the presence of the existing uncontrolled fill include larger than normal total and differential settlements, collapse of buried objects, and poor bearing support. The manifestation of these problems can cause poor slab performance.

5.4 LOWER STRENGTH SOILS

• Soft to firm soils were encountered in two (2) of the seven (7) borings (B-03 and B-04) within the native soils, between approximately 4.0 to 5.5 feet below existing grades.

• The low strength soils may not be adequate for pavement or building support, yielding and/or “pumping” when subjected to construction equipment, especially under wet conditions.

• Exposure to wet or dry weather conditions may result in the need to adjust moisture contents to achieve the desired compaction and fill texture.

• Replacement or improvement of some of the weaker soils also may be necessary, with the lateral extent and depth of improvement increasing during wetter periods of the year.

5.5 HIGHLY PLASTIC CLAYS

• Highly plastic clays (i.e., plasticity index greater than 25 – generally designated as “CH” or FAT CLAYS in the report and on boring logs) were encountered in the seven (7) borings.

• Highly plastic clays are susceptible to volume changes (shrink/swell problems) with changes in moisture. Accordingly, it is advisable to reduce the potential for moisture changes to the soil because of the shrink/swell concerns and the possible impact on the proposed construction.

• Volume changes associated with the highly plastic clays in the geologic formation underlying the site have the potential to produce building or other improvement damage (e.g., floor heave or subsidence, door/window alignment changes, hardscape movements, and drywall cracking).

• Movement may be cyclic (shrink when dry, swell when wet), continuing to produce building distortions that require increased and regular maintenance or repair.

• Typically, the volume changes are not of the magnitude to result in damage that would impair the structural integrity of buildings.

• Exposure to prolonged wet or dry weather conditions during construction can result in volume changes in bearing and subgrade materials or problems achieving the required compaction levels.

• The risks associated with highly plastic clays are common for the project vicinity and are not unique to the site. Most of the effects of highly plastic clays can be reduced by employing

ECS Project No. 61-3013 Page 10 the design and construction recommendations described in subsequent sections of this report.

5.6 SHALLOW REFUSAL

• Equipment refusal was encountered approximately 7.3 to 13.8 feet below existing grades in the borings.

• Based on our assumed utility trench excavation depth, it is not likely that refusal material will be a concern for the majority of the site excavations. However, it is possible that the depth to rock in unexplored areas may vary significantly from the depths indicated by the test borings.

• The presence of refusal above utility elevations can increase site development costs and slow construction, especially if the higher costs associated with excavations in rock are not considered in planning and design.

• Should it be necessary, the difficulty of removal will be affected by the methodology used, the experience of the operator, and the type of equipment used.

5.7 KARST POTENTIAL

• The geological formations underlying the site have a low to very high susceptibility for the formation of solution features, including an irregular rock surface, isolated rock slabs or “floaters”, sinkholes, soil-filled or open joints and bedding planes, soft soil zones or voids.

• Karst features were not observed on the site at the time of this exploration. However, it is possible that karst features were obscured by areas mantled by existing pavements, buildings, or landscaped areas. According to the Kentucky Geological Survey (KGS) Geologic Information Service website, sinkholes and karst features are scattered within the region, with the nearest recorded sinkhole approximately 2,900 feet within the project vicinity.

• Construction in karst areas presents risks that the owner must be willing to accept.

• The primary geotechnical risks include:

− Settlement, subsidence and/or collapse of the subsurface materials.

− Deposits of poor soft and/or organic soils in existing sinkholes.

− Irregular upper rock surface, discontinuous rock layers, highly weathered rock, and generally variable conditions.

− Poor correlation between refusal depths and the actual depth to rock.

• Site development costs typically are higher in karst areas due to the costs associated with reducing the karst risks during design and construction. However, the risks associated with karst geology are common for the project vicinity and are not unique to the site.

5.8 GROUNDWATER SEEPAGE

• Evidence of perched water was observed in Borings B-01, B-02, B-03, and B-06 at the soil/rock interface. Groundwater seepage was not observed in the remainder of the borings at the time of drilling.

• Perched water and/or groundwater seepage, if encountered, will require appropriate project scheduling, budgeting, and construction methodologies.

• Groundwater seepage, even minor seepage, commonly degrades subgrades and bearing surfaces when not properly treated.

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• Excavations may encounter seepage, especially during the wet seasons. Perched groundwater could impact excavations, because seeping water tends to lower stability and cause sidewall collapse, requiring even shallow excavations to be laid back or braced.

• Typically, groundwater can be removed with pumps in sumps or trenches. Care should be taken not to allow fines to wash into sumps resulting in subsidence of the surrounding ground.

5.9 DEGRADABLE SOILS

• Most of the soils on-site are susceptible to degradation. Degradable soils readily lose strength, become soft, and “pump” when subjected to construction equipment, especially under wet conditions.

• Undercutting and/or stabilization of soft clay soils could have a cost impact on the project, especially if not properly addressed in the project documents (e.g., definition of what is poor quality soils and the responsibility for maintenance of these soils once stabilized) or if not properly addressed during construction (e.g., subjected to repeated construction traffic with no protection or to construction traffic during wet weather).

5.10 REUSE OF ON-SITE SOILS

• In general, most of the on-site native soils appeared adequate for reuse as structural fill provided the soils are moisture conditioned to appropriate moisture contents for compaction.

• Topsoil and existing fill are not recommended for reuse in their current conditions.

• To manage risks associated with the highly plastic clays, careful consideration and planning will be required coordinating cut and fill operations so that the impact and potential risk associated with the highly plastic clays can be reduced.

• Due to the likely highly plastic nature of soils generated from deeper cuts or utility excavations, reuse of these soils should be limited to non-building areas or three feet or more below footing bearing elevation. The plasticity of some clays is expected to be high enough that their reuse in upper fill areas of buildings would not be recommended.

• Some wetting, drying, mixing or chemical treatment of the soils may be necessary to obtain workable moisture contents for the on-site soils, especially during wetter times of the year.

• Reuse of the on-site soils will be subject to the weather considerations described subsequently.

5.11 SUBGRADE IMPROVEMENT

• Widespread subgrade improvement is not expected to be necessary. However, recompaction of the upper soils, once the surface materials are removed, will likely be necessary.

• The required extent of improvement will depend to a large degree on when earthwork operations take place as well as on how the earthwork contractor prepares the site. The level of improvement will likely increase if:

− Construction traffic is concentrated along localized poor-quality subgrade routes.

− Earthwork occurs during cool, wet periods (typically November through May).

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• Provided construction occurs during the drier time of the year, it would be our expectation that much of the improvement could be achieved by scarifying, drying and recompacting the soils.

• If construction occurs during the wetter periods of the year, more aggressive treatment would likely be required (i.e., removal and replacement or lime drying).

• Subgrade improvement alternatives, if required, include but are not limited to:

− Scarification, drying, and recompaction of surface materials.

− Removal of inadequate materials and replacement with structural fill.

− Bridging with a thick lift of limestone aggregate.

− Placement of a geosynthetic or geo-grid in combination with granular fill.

− Chemical stabilization and/or modification (e.g., kiln dust, lime, or Portland cement).

• The type of subgrade improvement chosen should take weather limitations, or other limitations unique to each method, into consideration. Some of the subgrade improvement alternatives provided above are affected by the weather considerations described previously. For example, scarification, drying, and recompaction of surface materials would be difficult during the cool, wet months of the year.

5.12 TREES

• According to the provided construction information, several existing large trees may need to be removed to accommodate the proposed utility replacements or associated construction activities.

• Care should be taken to remove the entire rootball of trees since soils high in organic contents will not provide adequate support characteristics for the proposed construction.

• In addition, the resulting excavation should be backfilled with properly placed and compacted fill to avoid localized soft spots that can compromise the performance of the proposed construction.

• Fill material that contains significant tree roots (i.e., more than 3 percent organics as determined by loss-on-ignition testing) is not adequate for use as controlled fill.

5.13 WEATHER CONSIDERATIONS

• Conducting site work during periods of cool and/or wet weather (typically November to May) can be problematic for sites in the project region.

• Proper compaction of clay fill generally is very difficult to achieve during periods of cool and/or wet weather. Some drying, mixing, or chemical treatment of the soils would be necessary to obtain workable moisture contents for the on-site soils or proposed borrow materials if placed during the cool, wet seasons.

• If compaction of clay fill takes place under wet weather conditions, increased earthwork costs, an extended construction schedule, and soil improvement (likely chemical stabilization) likely would be required. In addition, reuse of the site soils may be severely limited.

• Surface soils tend to be softer during wet weather conditions due to the excess moisture in the near surface soils.

• Weather-softened surface soils tend to result in more undercutting and/or stabilization than would be required during dry weather conditions, which increases site development costs.

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• Project specifications should include definitions and require contractors to provide unit rates for subgrade stabilization, removal of inadequate soils, and replacement of inadequate soils with structural fill appropriate for use during the anticipated construction season.

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6.0 SITE CONSTRUCTION RECOMMENDATIONS

6.1 PLANNING

• Adjust project plans, specifications, schedules and budgets to incorporate the issues discussed in Section 5.0 and the recommendations provided herein.

• Findings and recommendations in this report are based on an assumed excavation depths for the proposed utility installations. As such, ECS should be contacted to provide appropriate values and recommendations for changes to the assumed excavation depths.

6.2 EXISTING CONSTRUCTION

General Comments:

• Recommendations to address existing construction can be affected by many factors, including factors that are not obvious until construction (e.g., removal of some features creates more potential problems and risks than leaving them in-place).

• As such, the recommendations provided below should be considered general guidelines. If modification to the recommendations provided below is needed, ECS should be contacted for guidance.

Existing Building Components:

• Evidence of buried former structures was not observed in the borings at the time of drilling.

However, due to the number of structures occupying the site and the history of site improvements on the property, it may be possible that former building components are encountered in other areas not explored during drilling activities.

• If encountered, demolish and remove existing construction from within the proposed utility replacement areas. Be sure to remove existing foundations, slabs, below grade walls, pavements, and buried utilities in their entirety.

• Existing pavements outside of the proposed construction limits should be left intact, where possible, to avoid exposing the clays on site to weather conditions and construction traffic and to work as a stabilized haul road/construction platform, where applicable.

• Backfill the resulting excavations with properly placed and compacted fill that is keyed into the native soil in one foot steps to provide a gradual transition in support conditions.

• Old floors or pavements, if encountered, should be removed completely unless the owner is willing to accept the associated risks with leaving them below floor slabs or pavements and new foundation areas.

• Existing utilities may be located within the proposed utility replacement areas. If existing utilities are retired from use, they should be removed in their entirety (including lines and associated backfill) unless the risk of damage to the proposed replacements and/or site improvements has been understood and accepted by the owner. The resulting excavation should then be backfilled in accordance with the recommendations in this report (including benching side slopes and proper compaction).

• Provided the risks associated with leaving utilities in-place are acceptable to the owner, abandoned lines should be grouted full.

• Needed improvements to poor backfill conditions should be identified during construction via proofrolling and surface probing by an ECS representative and remediated in accordance with the recommendations provided by ECS at the time of construction.

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• In addition to proofrolling, very careful earthwork evaluations should be conducted during construction to detect the presence and/or potential anomalies associated with the existing construction.

6.3 SUBGRADE PREPARATION

• The following sections describe our general recommendations for preparing the site subgrade prior to fill placement operations.

Stripping and Grubbing:

• Materials required to be stripped:

− Vegetation, topsoil, asphalt and concrete pavements, crushed stone, organic material, and excessively wet, desiccated, frozen, contaminated or otherwise inadequate materials.

• Minimum extent of stripping:

− 5 feet beyond the utility trench excavations and pavement limits.

• ECS should observe and document that inadequate surficial materials have been removed prior to the placement of structural fill or construction of structures.

• Stripped material not meeting structural fill requirements should be considered for reuse in landscaped areas only.

Subgrade Improvement:

• Based on the conditions encountered at the site and in the borings, the highly plastic clays and existing fill could require undercutting to develop an adequate construction platform and fill base in isolated areas.

• The construction budget should be adjusted to reflect the adverse subgrade conditions expected in some areas.

• Subgrade improvement options include but are not limited to:

− Scarification, drying, and recompaction of surface materials.

− Removal of inadequate materials and replacement with controlled fill.

− Bridging with a thick lift of limestone aggregate.

• The adequacy of subgrade improvements should be determined in the field by ECS personnel, in accordance with project specifications.

Subgrade Evaluation:

• Proofroll the site in the presence of an ECS representative with a pneumatic-tired vehicle (e.g., triaxial dump truck) loaded as recommended by the ECS representative.

• Proofroll subgrades prior to filling or after excavation to grade.

• Proofroll slab and pavement subgrades prior to granular base placement.

• Areas judged by the ECS representative to deflect excessively during proofrolling should be remediated in accordance with the recommendations provided at that time.

• Prepare subgrades with a slight slope to maintain surface drainage.

Other Measures:

• Roll subgrade surfaces smooth if rain is expected.

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• Slope final subgrades away from the proposed structure.

• Rough grade subgrades high to allow for removal of degraded soil.

• Remove soil frozen or softened by rain.

6.4 EXISTING FILL

General Comments:

• The recommendations contained in this report assume that the existing fill is uncontrolled fill.

• Structural fill should be placed and compacted in accordance with the recommendations provided in this report.

Concrete Slabs and Pavements:

• Existing uncontrolled fill was encountered in five (5) of the seven (7) borings and extended approximately 0.7 to 4.5 feet below existing grades.

• Due to the consistency observed and the planned construction loading, existing fill may be left in-place below floor slabs and pavements provided the owner is willing to accept the associated risks described in Section 5.3, unless the fill is associated with an existing filled/partially filled closed depression.

• If existing fill is left in-place in floor slab and pavement areas and the owner is willing to accept the associated risks, the risks associated with the existing fill in floor slab and pavement areas can be reduced by implementing the following recommendations:

o Visual observation and proofrolling evaluation of the subgrade by an ECS representative at the time of construction.

o Improvement of the subgrade where and how recommended by ECS based on the results of proofrolling and observations.

• If the risks associated with the existing fill, as described in a previous section, are not acceptable, the existing fill should be removed and replaced with structural fill.

6.5 STRUCTURAL FILL

Subgrade Requirements:

• Subgrade proofrolled and required improvements completed.

Fill Material Requirements:

• No deleterious debris.

• No rock pieces larger than 3 inches.

• Less than 3% organic material (loss on ignition).

• Maximum dry density of at least 100 pcf according to the Standard Proctor compaction method (ASTM D-698), unless approved otherwise by ECS.

• Acceptable Unified Soil Classifications (USCS): CL, CH (if approved by ECS for the intended use), ML, GW, GM, GC, GP, SW, SP, SM, SC.

• Unacceptable USCS classifications: CH (if not approved by ECS for the intended use), OL, OH, Pt, MH.

• Evaluated and approved by ECS prior to construction.

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Fill Placement Guidelines:

• Minimum compaction:

− 98 % standard Proctor maximum dry density (ASTM D-698).

• Moisture Content:

− Within 2 % of optimum (ASTM D-698) if plasticity index less than 25.

− At or up to 3 % above optimum (ASTM D-698) if plasticity index greater than or equal to 25.

• Maximum loose lift thickness: 8 inches.

• Compaction test frequency:

− One test per lift for each 5,000 square feet of fill placed.

− Minimum of 3 tests per lift.

• Bench new fill into existing slopes or sidewalls in 1-foot steps or as approved by ECS at the time of construction.

• Compact and test each lift prior to placing additional lifts.

• Scarify smoothed fill surfaces prior to placing the next lift.

• Maintain positive surface drainage on fill surfaces during placement to avoid ponding of water.

• Roll fill surfaces smooth if rain is expected.

• Rough grade high to allow for removal of degraded surface soils if fill will be exposed to adverse weather conditions.

• Do not place fill on a frozen subgrade. At a minimum, remove frozen material, or allow to thaw and then recompact.

6.6 HIGHLY PLASTIC CLAYS

• If the risk associated with highly plastic clays are not acceptable, then no highly plastic clays should be present within 36 inches of the proposed subgrade or foundations.

• The measures provided below will reduce but not eliminate the risk that the proposed construction will be impacted by the presence of highly plastic clays.

− If highly plastic clays are exposed at the subgrade and are allowed to dry out, the subgrade should be moisture conditioned prior to base placement (i.e., at or up to 3 % above the optimum moisture content as determined by ASTM D698).

− Foundations should be placed the same day they are excavated or covered with a mud mat.

− Roof drains and surface drainage should not outlet or be directed to the ground surface within 25 feet of the proposed structure, unless the surface is impervious (such as concrete or pavement), to reduce moisture changes of the foundation soils.

− The subgrade should be rough graded high to allow for removal of desiccated or saturated soil immediately prior to stone base placement.

− Proper drainage should be provided around the proposed construction (e.g., slope the surface away from the building).

− The floor slab subgrade should be sloped to drain. Where feasible, provide outlets for water that may collect in the gravel base for the floor slab.

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− Fill comprised of highly plastic clays should be placed at or up to 3 % above the optimum moisture content.

− Unlined landscape areas and trees should not be placed adjacent to the building, since the vegetation tends to absorb excess water, resulting in shrinkage, especially during droughts.

6.7 KARST POTENTIAL

General Comments:

• The members of the Lexington Limestone geological formations underlying the site have a low to very high potential for karst features. Construction in karst prone areas presents risks that the owner must be willing to accept. The following measures can reduce these risks:

− Evaluate and proofroll the subgrade prior to fill placement under the direction of a ECS representative.

− Remediate karst features encountered during construction per recommendations provided by ECS during construction.

− Provide proper drainage around the proposed construction, including sloping the surface away from the buildings.

− Floor slab and pavement subgrades should be sloped to drain similar to the surface conditions. Provide outlets for water that may collect in the floor slab or pavement gravel base. This may include providing drainage mechanisms in building areas or installing weepholes in catch basins in pavement areas.

− Roof drains should not discharge to the ground surface within 20 feet of proposed or existing structure, unless the surface is impervious (such as concrete or pavement).

• If karst features are discovered during onsite earthwork activities, ECS should be contacted to provide treatment and construction recommendations during the construction phase of the project, based on additional evaluation at that time.

• Treatment of individual sinkholes, if encountered, is heavily dependent on the conditions unique to each sinkhole, but typically would consist of stabilization of the feature and construction of an inverted filter over the feature (larger rocks progressing to smaller rocks, enclosed in non-woven filter fabric).

• In general, mitigation should be accomplished as follows:

− ECS should be retained to observe the encountered conditions at the time of construction to provide remedial recommendations for karst features observed within the construction limits at the time of construction.

− Retain ECS to observe proofrolling of the subgrades to identify sinkholes and springs not detected during the initial site reconnaissance. Extensive proofrolling does not eliminate the risk of building over an undiscovered sinkhole(s). However, it does reduce the risk.

− The ECS representative would provide remedial recommendations for these features at the time that site grading and building construction is carried out. The details of remediation would depend on the actual subsurface conditions disclosed at each feature as well as the location of the feature. For example, different recommendations would apply for remediation of sinkholes in each of the following locations: below a building foundation; below a building floor slab; below a parking lot or drive lane pavement; in a landscape area; and in a sinkhole that is to be used for stormwater drainage.

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− In general, remediation typically would consist of excavating loose and poor-quality materials from the sinkhole and filling with select materials (generally by placing larger stones at the bottom and progressing to smaller stones at the top, encased in a non-woven geotextile fabric) chosen for the actual encountered conditions and overlying structure.

6.8 GROUNDWATER

• The contractor should be prepared and experienced in handling perched water and groundwater conditions.

• Care should be taken not to allow fines to wash into sumps, since subsidence of the surrounding ground could occur. ECS should be contacted if silting of pumps or excessive groundwater seepage occurs.

• Water seepage will lower the stability of the on-site soils. Consequently, where water seepage is encountered, temporary support and flatter slopes should be anticipated.

• Groundwater, except for spring flow and flow at the soil/rock interface, likely can likely be removed with a conventional sump and pump.

• Spring boxes and/or finger drains may be necessary where more concentrated flows are encountered, such as at springs or the where heavy flow at the soil/rock interface is encountered.

• Drainage behind walls, foundations, and floors will be critical. Proper design and construction of drainage components will be crucial.

• Since recommendations to address groundwater encountered will be heavily dependent on the actual condition of the underlying karst drainage, recommendations to address groundwater cannot be provided until construction.

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7.0 DESIGN RECOMMENDATIONS

7.1 UTILITY INSTALLATIONS

Utility Subgrades:

• The soils encountered in our exploration are expected to be generally suitable for the support of utility pipes.

• The pipe subgrades should be observed and probed for stability by an ECS representative.

Any loose or unsuitable materials encountered should be removed and replaced with suitable compacted Structural Fill, or pipe stone bedding material.

Utility Backfilling:

• The granular bedding material (often AASHTO #57 stone) should be at least 4 inches thick, but not less than that specified by the civil engineer’s project drawings and specifications.

• ECS recommends that the bedding materials be placed up to the springline of the pipe. Fill placed for support of utilities, as well as backfull over the utilities, should satisfy…