ATT 2 - G2 Geotech Report_12.17.24.pdf

Attachment 2

Geotechnical Report

Report on Geotechnical Investigation

Mott Community College – Parking Lot G Pavement

Improvements 1404 E. Court Street

City of Flint, Genessee County, Michigan

Latitude 43.02201˚ N Longitude 83.67641˚ W

Prepared for:

Walker Consultants 525 Avis Drive, Suite 1

Ann Arbor, Michigan 48108

G2 Project No. 213812 December 17, 2024

Mr. Rick G. Klein, P.E.

Vice President Walker Consultants 525 Avis Drive, Suite 1 Ann Arbor, Michigan 48108

Re: Report on Geotechnical Investigation

Mott Community College – Parking Lot G Pavement Improvements 1404 E. Court Street City of Flint, Genessee County, Michigan G2 Project Number 213812

Dear Mr. Klein:

We have completed the geotechnical investigation related to the proposed site improvements associated with the demolition of Parking Garage G at the Mott Community College in Flint, Michigan. This report presents the results of our observations, analyses, and recommendations for pavement section design, and pavement reconstruction as they relate to the subsurface soil and groundwater conditions of the site.

We appreciate the opportunity to be of service to you on this project and look forward to discussing the recommendations presented. In the meantime, if you have any questions regarding this report or any other matter pertaining to the project, please contact us.

Sincerely, G2 Consulting Group, LLC

Colin C. Gross, E.I.T.

Staff Engineer

Michael G. Dagher, P.E.

Project Manager

CCG/

Enclosures

EXECUTIVE SUMMARY

The project consists of the demolition of the existing Parking Garage G located at the Mott Community College in Flint, Michigan. Following the demolition of the garage the new pavements will be constructed in place of the garage and the surrounding pavements to the north and south will be improved. We understand that stairs will be constructed along the relatively steep slope located to the west of the existing parking garage, to allow for access to Crapo Street to the northwest from the new parking lot.

The bituminous concrete pavement is generally in poor condition throughout the parking lot areas and access drives. We observed moderate to severe alligator and block cracking, high severity potholes and depressions, and joint cracking. It appears some surface patching has been performed in the past within the southern parking lot, near boring P-06. In addition, we also observed several areas of standing water within the northern parking, generally located near the western edges and near the low-lying area to the northeast.

Approximately 4 to 6 inches of bituminous concrete are present at the ground surface of the soil borings. The pavements are underlain by aggregate base ranging in thickness from 5 to 8 inches. We performed grainsize distribution determinations of the existing aggregate base at P-02 and P-06. In general, the materials can be best represented by the aggregate gradation requirements for MDOT 21AA and MDOT 22A; however, the materials do not satisfy all of the specifications for either 21AA or 22A due to a relative lack of material finer than the No. 200 sieve.

The existing bituminous concrete pavements and underlying aggregate should be completely removed to expose the underlying soil conditions. Soils exhibiting elevated organic matter contents or instability, such as severe rutting, should be removed and replaced with engineered fill. The construction of a new pavement section should generally accommodate a pavement life of 20 years. We recommend the new pavements within the footprint of the garage consist of the full-depth reconstruction pavement section.

We recommend the proposed full-depth reconstruction pavement consist of 2 inches of MDOT 5EML wearing course, and 2 inches of MDOT 4EML leveling course, supported by 8 inches of MDOT 21AA dense-graded aggregate base. We estimate this proposed pavement cross-section can support 180,000 18-kip Equivalent Single-Axle Loads (ESALs) over a 20-year design life.

Consideration can be given to using the existing aggregate base for support of the new pavement section. Following the removal of the existing pavements, the exposed aggregate base should be thoroughly proof-compacted with a 15-ton vibratory smooth-drum roller. Areas exhibiting unstable or otherwise unsuitable conditions should be improved with further compaction or removed and replaced with engineered fill. The exposed aggregate base should be graded to promote effective subsurface drainage. The construction of new pavements over the existing aggregate base could result in a reduced lifecycle ranging from 10 to 15 years. If the surface reconstruction option is selected, we recommend a new bituminous concrete pavement section consisting of 2 inches of MDOT 5EML wearing course over 2 inches of 4EML leveling course supported by the existing aggregate, having a minimum thickness of 5 inches. We estimate the surface reconstruction option can support approximately 50,000 18-kip ESALs over a design life of 10 to 15 years.

Based on the existing soil conditions, we recommend the proposed stairwell be supported on shallow strip and spread footings bearing on native very stiff to hard cohesive soils, native compact granular soils, or engineered fill placed over the very stiff to hard native cohesive and/or compact native granular soils. Footings bearing on native soils or bearing on engineered fill placed over native soils may be designed based on a net allowable bearing pressure of 2,000 psf.

Do not consider this summary separate from the entire text of this report, with all the conclusions and qualifications mentioned herein. Details of our analysis and recommendations are discussed in the following sections and in the Appendix of this report.

PROJECT DESCRIPTION

The project consists of the demolition of the existing Parking Garage G located at the Mott Community College in Flint, Michigan. Following the demolition of the garage the new pavements will be constructed in place of the garage and the surrounding pavements to the north and south will be improved. We understand that stairs will be constructed along the relatively steep slope located to the west of the existing parking garage, to allow for access to Crapo Street to the northwest from the new parking lot.

Anticipated traffic conditions for the proposed pavements were not available to us at the time of this report; however, we understand the proposed pavements will be used as student parking which typically consists of primarily passenger vehicle traffic with intermittent truck traffic. If actual traffic conditions become available, please let us know.

The purpose of our investigation is to determine and evaluate the general pavement and subsurface conditions within the loading dock area and develop general recommendations for the proposed pavement reconstruction.

SCOPE OF SERVICES

The field operations, laboratory testing, and engineering report preparation were performed under the direction and supervision of a licensed professional engineer. Our services were performed according to generally accepted standards and procedures in the practice of geotechnical engineering in this area.

Our scope of services for this project is as follows:

1. We performed a cursory visual identification of the types and relative magnitudes of observable pavement distress.

2. We drilled a total of eight (8) soil borings throughout the proposed stairwell and existing pavement areas. Soil borings B-01 and B-02 were drilled within the general location of the proposed stairwell on the west side of the existing parking garage. Soil boring B-01 was drilled on the top of the relatively steep sloped area extending to a depth of 35 feet. Soil boring B-02 was drilled at the toe of the relatively steep sloped area extending to a depth of 15 feet. Soil borings P-01 through P-04 were drilled throughout the parking lot on the north side of the parking garage. Soil borings P-05 and P-06 were drilled in the parking lot on the south side of the parking garage.

3. We performed laboratory testing on samples obtained from the soil borings. Laboratory testing included visual engineering classification, moisture content, unconfined compressive strength, and grain-size distribution determinations.

4. We prepared this engineering report which includes our recommendations for the pavement improvements.

FIELD OPERATIONS

G2 Consulting Group, LLC (G2), in conjunction with Walker Consultants, selected the number, depth, and location of the soil borings based on the site layout provided to us. We assigned soil boring locations in the proposed pavement areas based on aerial imagery available in Google Earth Pro. We staked the locations of the proposed soil borings in the field using hand-held GPS equipment based on the latitude and longitude of the assigned positions in Google Earth. If you would like more accurate positional information at the soil boring locations, we recommend their as-drilled positions be determined in the field using conventional surveying techniques.

We subcontracted Xterra Drilling to perform the soil boring operations. The soil borings were advanced to the target depths using hollow-stem augers. For soil borings P-01 through P-06, we obtained soil samples at regular 2-1/2-foot intervals extending to the explored depths of 5 feet. For soil borings B-01 and B-02, we obtained soil samples at regular 2-1/2-foot intervals within the upper 10 feet and at intervals of 5 feet thereafter extending to the explored depths. We obtained the soil samples in accordance with the Standard Penetration Test (SPT) method (ASTM D1586). The SPT test involves driving a 2-inch outside diameter split-spoon sampler into the ground using a 140-pound hammer falling 30 inches. The sampler is generally driven in three successive 6-inch increments with the number of blows for each increment recorded. The number of blows required to advance the sampler the final 12 inches is termed the Standard Penetration Resistance (N or N-value). The blow counts for each 6-inch increment and the resulting N-values are presented on the individual soil boring logs at the depths they were determined.

The soil samples were placed in sealed containers in the field and brought to the laboratory for testing and classification. During drilling operations, the drilling crew maintained field logs of the encountered subsurface soil and groundwater conditions to be used in conjunction with our analysis of the subsurface conditions. The final soil boring logs are based on the field logs and laboratory soil classification and testing. Upon completion of the drilling operations, the boreholes were backfilled with excavated soil and capped with cold-patch asphalt, where applicable.

LABORATORY TESTING

We subjected representative samples to laboratory testing to determine soil parameters pertinent to foundation design and site preparation. An experienced geotechnical engineer classified the soils in general accordance with the G2 General Notes Terminology and applications of the Visual-Manual Unified Soil Classification System (ASTM D2488). Laboratory testing included determinations in accordance with the following test methods:

• ASTM D2216 – Moisture Content

• ASTM D2974 – Organic Matter Content

• ASTM D2488 – Visual-Manual Unified Soil Classification

• ASTM C136 – Sieve Analysis of Fine and Coarse Aggregates

We estimated the unconfined compressive strength of cohesive soils using a spring-loaded hand penetrometer. The hand penetrometer can be used to estimate the unconfined compressive strength to a maximum of 4-1/2 tons per square foot (tsf) by measuring the resistance of the soil sample to the penetration of a spring-loaded cylinder.

We present the results of the moisture content and unconfined compressive strength determinations on the individual soil boring logs, Figure Nos. 1 through 8, at the applicable depths. We present the graphical results of the Sieve Analysis of Fine and Coarse Aggregates determinations by ASTM C136 on Figure No. 9. These figures are presented in the Appendix. We will hold the soil samples for a period of 60 days following the issuance of this report after which we will discard them. If you would like to have the soil samples, please let us know.

EXISTING PAVEMENT CONDITIONS

The bituminous concrete pavement is generally in poor condition throughout the parking lot areas and access drives. We observed moderate to severe alligator and block cracking, high severity potholes and depressions, and joint cracking. It appears some surface patching has been performed in the past within the southern parking lot, near boring P-06. In addition, we also observed several areas of standing water within the northern parking, generally located near the western edges and near the low-lying area to the northeast.

Approximately 4 to 6 inches of bituminous concrete are present at the ground surface of the soil borings. The pavements are underlain by aggregate base ranging in thickness from 5 to 8 inches. We performed grainsize distribution determinations of the existing aggregate base at P-02 and P-06. In general, the materials can be best represented by the aggregate gradation requirements for MDOT 21AA and MDOT 22A; however, the materials do not satisfy all of the specifications for either 21AA or 22A due to a relative lack of material finer than the No. 200 sieve.

The pavements generally appear to be poorly drained. We did not observe catch basins within the parking lot areas nor did we see drains on the edges of the pavement surface. In general, the pavements appear to sheet drain to the edges of the existing pavements.

EXISTING SUBSURFACE CONDITIONS

A range of granular and cohesive fill soils are present below the pavement section within boings P-02, P- 04, P-05, and P-06. The pavement section is underlain generally by cohesive soil extending to a depth of 3 feet and underlain by granular fill soils extending to the explored depths of 5 feet. The fill soils in soil boring P-06 extend to an approximate depth of 3 feet and are underlain by native granular soils which extend to the explored depth of 5 feet.

Native cohesive soils, consisting of silty and sandy clay, are present below the pavement section within boring B-01, extending to depths of approximately 31-3/4 feet. The native cohesive soils in B-01 are underlain by native granular soil, consisting of silty sand, extending to the explored depth of 35 feet.

The pavement section in soil boring B-02 is underlain by alternating layers of granular and cohesive soils extending to the explored depth of 15 feet. The pavement section in soil borings P-01 and P-03 are underlain by a range of native granular and cohesive soils extending to the explored depth of 5 feet.

The cohesive fill soils are generally very stiff to hard in consistency with natural moisture contents ranging from 6 to 25 percent, and unconfined compressive strengths ranging from 3,000 to 9,000 pounds per square foot (psf). The granular fill soils are loose to compact in relative density with Standard Penetration Test (SPT) N-values ranging from 7 to 35 blows per foot (bpf). In soil borings P-02, P-04, and P-06 we observed an organic matter content ranging from 2 to 4 percent.

The native cohesive soils are generally stiff to hard in consistency with natural moisture contents ranging from 6 to 25 percent, and unconfined compressive strengths ranging from 4,500 to 9,000 psf.

The native granular soils are loose to very compact in relative density with Standard Penetration Test (SPT) N-values ranging from 5 to 88 bpf.

The stratification depths shown on the soil boring logs represent the soil conditions at the boring locations. Variations may occur between borings. Additionally, the stratigraphic lines represent the approximate boundaries between soil types. The transition may be more gradual than what is shown.

We have prepared the boring logs based on laboratory classification and testing as well as field logs of the soils encountered.

Soil Boring Location Plan, Plate No. 1, Soil Boring Logs, Figure Nos. 1 through 8, and Grain Size Distribution, Figure No. 9, are presented in the Appendix. The Photographic Documentation Log is included in Plate 2 through Plate 4. The soil profiles described above are generalized descriptions of the conditions encountered at the boring location. General Notes Terminology defining the nomenclature used on the soil boring logs and elsewhere in this report are presented in Figure No. 10.

GROUNDWATER CONDITIONS

We observed the natural groundwater level both during and upon completion of the drilling operations.

We observed the natural groundwater level at a depth of 6 feet both during and upon completion of the drilling operations in soil boring B-02 and at a depth of 3-1/2 feet within soil boring P-06 during drilling.

No measurable groundwater was observed within the other borings during or upon completion of drilling operations. At P-06, this is likely due to the collapse of the granular soil above the observed water level. Fluctuations in perched and long-term groundwater levels should be anticipated due to seasonal variations and following periods of prolonged precipitation. It should also be noted that groundwater observations made during drilling operations in predominantly cohesive soils are not necessarily indicative of the static groundwater level. This is due to the low permeability of such soils and the tendency of drilling operations to seal off the natural paths of groundwater flow.

PAVEMENT RECOMMENDATIONS

General

We understand the existing garage will be removed and replaced with asphalt pavement and the surrounding pavements will be improved. We observed fill soils having organic matter contents ranging from approximately 2 to 4 percent at a depth range starting at 10 inches in soil boring P-02, starting at 13 inches in P-06, and extending to 3 feet. We also observed organic material in soil boring P-04 starting at 3 feet and extending to a depth of 5 feet. Lastly, we observed a depression in the northeast of the pavement improvement area adjacent to a low-lying area. We anticipate this depression is associated with the settlement/consolidation of soils associated with the low-lying area. In general, we consider soils having organic matter contents of more than 4 percent to be unsuitable for the support of pavement slabs. Soils having elevated organic matter contents, but less than 4 percent may remain in place, provided they pass a proof-roll.

Due to the existing aggregate base material’s observed thickness, ranging from 5 to 8 inches, and the distressed pavements we observed associated with weak subgrade support, we recommend reconstructing the pavement by removing both the existing pavements and aggregate base and constructing a new pavement section consisting of 4 inches of bituminous concrete and 8 inches of MDOT 21AA aggregate base. The construction of a new pavement section should generally accommodate a pavement life of 20 years. We recommend the new pavements within the footprint of the garage consist of the full-depth reconstruction pavement section, listed below.

Consideration could be given to using the existing aggregate base in place; however, at the cost of a reduced pavement lifecycle. The construction of new pavements over the existing aggregate base could result in a reduced lifecycle ranging from 10 to 15 years.

New and Full-Depth Reconstruction Recommendations

The existing bituminous concrete pavements and underlying aggregate should be completely removed to expose the underlying soil conditions. Following the removal of the existing pavement we recommend the exposed cohesive subgrade be thoroughly proof-rolled with a fully-loaded tandem axle dump truck or equivalent and visually evaluated for unstable or otherwise unsuitable soil conditions. The exposed granular subgrade soils should be thoroughly proof-compacted using a 15-ton smooth drum vibratory roller. We recommend the proof compaction operations consist of at least 10 passes in two perpendicular directions. Soils exhibiting elevated organic matter contents or instability, such as severe rutting, should be removed and replaced with engineered fill.

The existing aggregate base material has a loss by wash of 1.0 percent, which is outside the gradation specifications for MDOT 21AA and 22A aggregates. However, provided the existing aggregate base is removed, segregated from the underlying soils, and stockpiled properly, the existing aggregate base may be used as engineered fill for undercuts extending below the proposed pavement cross-section. We recommend G2 be on-site during proof rolling operations to observe and document the proof rolling operations.

Surface Reconstruction Recommendations

Consideration can be given to using the existing aggregate base for support of the new pavement section. Following the removal of the existing pavements, the exposed aggregate base should be thoroughly proof-compacted with a 15-ton vibratory smooth-drum roller. We recommend the proof-compaction operations consist of a minimum of 10 passes in two perpendicular directions. Areas exhibiting unstable or otherwise unsuitable conditions should be improved with further compaction or removed and replaced with engineered fill. The exposed aggregate base should be graded to promote effective subsurface drainage.

Undercuts and Engineered Fill

We anticipate significant undercuts will be required in the area of the depression to the northeast of the existing pavement adjacent to the existing low-lying area. Please refer to the Photographic Documentation Log, Plate No. 4, Photograph No. 3, for the approximate location of the surface depression.

Subgrade undercuts, if required, should be evaluated by a qualified engineering technician to determine if subgrade stabilization is necessary. We recommend that undercut excavations, where required, be backfilled with either the existing aggregate base materials or new MDOT 21AA placed in an engineered manner. For subgrade undercuts extending into cohesive soils, a drain tile should be placed at the deepest portion of subgrade undercuts and connected to the closest catch basin to prevent trapped water from collecting in the cohesive soils. Lifts of aggregate base or undercut material backfill should not exceed 9 inches in loose thickness. All engineered fill should be compacted to a density of at least 95 percent of the maximum dry density as determined by the Modified Proctor Compaction Test (ASTM D1557). All engineered fill material should be placed and compacted at approximately the optimum moisture content. Frozen material should not be used as fill, nor should fill be placed on a frozen subgrade.

Engineered fill should be free of organic matter, frozen soil, clods, or harmful material. The fill should be placed in uniform horizontal layers not more than 9 inches in loose thickness. The engineered fill should be compacted to achieve a dry density corresponding with 95 percent of the maximum dry density as determined by the Modified Proctor Compaction test (ASTM D1557).

In order to economically conduct earthwork operations at the site, imported fill, adhering to the aforementioned requirements, should consist of low plasticity clays or well-graded aggregates. Low plasticity clays, having a plasticity index of less than 20 percent, should be placed within +3 or -1 percent of the optimum moisture content as determined by the Modified Proctor Test (ASTM D1557).

For well-graded aggregates, such as MDOT Class II Sand, we recommend the engineered fill be placed at ±2 percent of the optimum moisture content as determined by ASTM D1557. In no case should high-plasticity clays (fat clays) be used as engineered fill.

Pavement Design

We performed pavement design analyses in accordance with the “AASHTO Guide for Design of Pavement Structures”. The subgrade soils will generally consist of cohesive soils. Based on the existing subgrade soils, we have provided design pavement sections based on an effective subgrade resilient modulus of 7,500 pounds per square inch (psi). In our design, we used a serviceability loss of 2.0, a standard deviation of 0.49, and a reliability of 0.95.

We recommend the proposed full-depth reconstruction pavement consist of 2 inches of MDOT 5EML wearing course, and 2 inches of MDOT 4EML leveling course, supported by 8 inches of MDOT 21AA dense-graded aggregate base. We estimate this proposed pavement cross-section can support 180,000 18-kip Equivalent Single-Axle Loads (ESALs) over a 20-year design life.

Alternatively, if the surface reconstruction option is selected, we recommend a new bituminous concrete pavement section consisting of 2 inches of MDOT 5EML wearing course over 2 inches of 4EML leveling course supported by the existing aggregate, having a minimum thickness of 5 inches. We estimate the surface reconstruction option can support approximately 50,000 18-kip ESALs over a design life of 10 to 15 years.

All pavement materials are specified within the 2020 Standard Specifications for Construction from the Michigan Department of Transportation. The HMA pavement materials are described in Section 501. The leveling and wearing course HMA can be assigned a structural coefficient number of 0.42. Imported MDOT 21AA material can be assigned a structural coefficient number of 0.14. The existing aggregate base material may be assigned a structural coefficient of 0.12.

Pavement Drainage and Maintenance

The existing pavements do not appear to incorporate stormwater catch basins. In general, we recommend the new pavements incorporate surface drainage features for stormwater management. We recommend edge drains be provided continuously along curbs since they can become a source of water infiltration into the pavement subgrade. Such drains should extend to minimum depths of 4 inches below the bottom of the proposed aggregate base course or granular fill placed within undercut areas.

These drains could be connected to nearby catch basins.

The pavement and subgrade should be properly sloped to promote effective surface drainage and prevent water from ponding. We also recommend pavement subbase materials consist of non-frost-susceptible aggregates where possible.

Regular timely maintenance should be performed on the bituminous pavement to reduce the potential deterioration associated with moisture infiltration through surface cracks. The owner should be prepared to seal the cracks with a hot-applied elastic crack filler as soon as possible after cracking develops and as often as necessary to block the passage of water to the subgrade soils.

STAIRWELL FOUNDATION RECOMMENDATIONS

Based on the existing soil conditions, we recommend the proposed stairwell be supported on shallow strip and spread footings bearing on native very stiff to hard cohesive soils, native compact granular soils, or engineered fill placed over the very stiff to hard native cohesive and/or compact native granular soils. Footings bearing on native soils or bearing on engineered fill placed over native soils may be designed based on a net allowable bearing pressure of 3,000 psf. Exterior foundations must bear at a minimum depth of 3-1/2 feet below finished grade for protection against frost heave. We recommend G2 be on-site during construction to observe the foundation excavations and visually confirm the bearing soils.

To achieve a change in the level of a strip footing, the footing should be gradually stepped at a grade no steeper than two units horizontal to one unit vertical (2H:1V). If required to construct foundations at different levels, adjacent spread foundations should be designed and constructed so the least lateral distance between the foundations is equivalent to or more than the difference in their bearing levels.

If the recommendations outlined in this report are adhered to, total and differential settlements for the completed structure should be within 1 inch and 1/2 inch, respectively. We expect settlements of these magnitudes to be within tolerable limits for the type of structures proposed. We recommend all foundations be suitably reinforced to minimize the effects of differential settlements associated with local variations in subsoil conditions.

CONSTRUCTION CONSIDERATIONS

We anticipate undercuts extending into organic soils associated with low-lying areas will encounter groundwater. Although we did not observe the natural groundwater level in the adjacent soil borings, low-lying areas are typically associated with shallow groundwater. In general, we anticipate the natural groundwater level can be lowered by 1 to 2 feet with a system of properly constructed sumps and pumps. To lower the natural groundwater level beyond a depth of 2 feet, we recommend using a system of tightly spaced well points.

We anticipate excavations extending below the natural groundwater level be stabilized by placing non-woven geotextile separation fabric over the subgrade soils, backfilling the resulting excavation to at least 6 inches above the encountered groundwater level with open-graded stone such as 1x3, and choking the 1x3 layer off with a minimum thickness of 6 inches of MDOT 21AA placed and compacted to achieve at least 95 percent of the maximum dry density as determined using the Modified Proctor Compaction Test (ASTM D1557).

We do not anticipate trenching methods will be used to construct stair foundations. Therefore, the contractor should be prepared to over excavate and form foundations, as necessary. The side of the spread and/or strip foundations should be constructed straight and vertical to reduce the risk of frozen soil adhering to the concrete and raising the foundations.

We recommend maximum slope inclinations of 2 horizontal unit to 1 vertical unit (2H:1V) within the loose granular soils, 1-1/2H:1V within the medium compact granular soils, 1H:1V within the compact to very compact granular and stiff cohesive soils, and 3/4H:1V within the very stiff to hard silty clay soils for excavations extending below a depth of 5 feet. Where seepage from excavation cuts is observed, the slopes will need to be flattened sufficiently to achieve stability, but in no case left steeper than 3H:1V at and below the seepage level.

All excavations should be safely sheeted, shored, sloped, or braced in accordance with MI-OSHA requirements. If material is stored or equipment is operated near an excavation, lower angle slopes or stronger shoring must be used to resist the extra pressure due to the superimposed loads.

GENERAL COMMENTS

We have formulated the evaluations and recommendations presented in this report relative to pavement reconstruction and site preparation based on data provided to us relating to the general location for the proposed pavement improvements. Any significant change in this data should be brought to our attention for review and evaluation with respect to the prevailing subsurface conditions.

The scope of the present investigation was limited to evaluation of subsurface conditions for the support of the pavements and foundation recommendations for the proposed stairwell. No chemical, environmental, or hydrogeological testing or analyses were included in the scope of this investigation. If changes occur in the design, location, or concept of the project, the conclusions and recommendations contained in this report are not valid unless G2 Consulting Group, LLC reviews the changes. G2 Consulting Group, LLC will then confirm the recommendations presented herein or make changes in writing.

We have based the analyses and recommendations submitted in this report upon the data from soil borings performed at the approximate locations shown on the Soil Boring Location Plan, Plate No. 1.

This report does not reflect variations that may occur between the actual boring locations. The nature and extent of any such variations may not become clear until the time of construction. If significant variations then become evident, it may be necessary for us to re-evaluate our report recommendations.

Soil conditions at the site could vary from those generalized on the basis of soil borings made at specific locations. It is, therefore, recommended that G2 Consulting Group, LLC be retained to provide soil engineering services during the site preparation and pavement construction phases of the proposed project. This is to observe compliance with the design concepts, specifications, and recommendations.

Also, this allows design changes to be made in the event that subsurface conditions differ from those anticipated prior to the start of construction.

APPENDIX

Soil Boring Location Plan Plate No. 1

Soil Boring Logs Figure Nos. 1 through 8

Grain Size Distribution Figure No. 9

Photographic Documentation Plate 2 through Plate 4

General Notes Terminology Figure No. 10

Scale: NTS

Soil Boring Location Plan

Date: 11/26/2024

Drawn By: CCG

Project No. 213812

Plate No. 1

Mott Community College - Parking Lot G Improvements 1401 E. Court Street, Flint, Genesee County, Michigan

Legend

Soil borings drilled by Xterra Drilling, Inc. on November 8th, 2024.

B-01

B-02

P-06

P-03

P-04

P-05

P-01

P-02

S-01

S-02

S-03

S-04

S-05

S-06

S-07

S-08

S-09

24.5

21.2

15.1

12.0

9.2

6.5

7.4

20.2

9000*

9000*

4500*

5500*

9000*

9000*

9000*

9000*

0.5 0.9

5.5

8.0

31.8

35.0

Bituminous Concrete (6 inches)

Aggregate Base (5 inches)

Hard Mottled Brown and Gray Silty Clay with trace sand

Very Stiff Brown Sandy Clay with trace silt; occasional weathered rock

Very Stiff to Hard Gray Sandy Clay with trace silt and gravel; occasional silt partings

Very Compact Gray Silty Sand

End of Boring @ 35 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

IN

G

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

D T

/1

/2

Soil Boring No. B-01

SUBSURFACE PROFILE

Figure No. 1

Water Level Observation:

Dry during and upon completion

Notes:

* Calibrated Hand Penetrometer

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

35 ft November 8, 2024 Xterra Drilling J. Bowerman

Latitude: 43.02201 Longitude: 83.67641

S-03

S-04

S-05

6.2

7.1

9000*

9000*

0.5 0.9

3.0

5.5

8.0

11.8

15.0

Bituminous Concrete (6 inches)

Aggregate Base (5 inches)

Compact Brown Silty Sand with trace clay and gravel

Hard Gray Sandy Clay with trace gravel

Compact Brown Silty Sand with trace gravel

Compact Gray Clayey Sand with trace silt

Hard Gray Sandy Clay

End of Boring @ 15 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. B-02

SUBSURFACE PROFILE

Figure No. 2

Water Level Observation:

6 feet during drilling and upon completion

Notes:

Borehole collapsed at 8 ft after auger removal

* Calibrated Hand Penetrometer

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

15 ft November 8, 2024 Xterra Drilling

Latitude: 43.02177 Longitude: 83.67624

15.3

0.4 1.0

5.0

Bituminous Concrete (5 inches)

Aggregate Base (7 inches)

Loose Sand and Clay with trace gravel

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-01

SUBSURFACE PROFILE

Figure No. 3

Water Level Observation:

Dry during and upon completion

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02235 Longitude: 83.67498

BS-01

S-03

20.5 3000*

0.3 0.8

3.0

5.0

Bituminous Concrete (4 inches)

Aggregate Base: Gray Gravel and Sand with trace silt

(6 inches) Fill: Stiff Mottled Gray and Dark Gray

Sandy Clay with trace organics (Organic Matter Content = 3.7%)

Fill: Loose Grayish Brown Clayey Sand with trace gravel

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-02

SUBSURFACE PROFILE

Figure No. 4

Water Level Observation:

Dry during and upon completion

Notes:

* Calibrated Hand Penetrometer

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02209 Longitude: 83.67558

0.4 0.9

5.0

Bituminous Concrete (5 inches)

Aggregate Base (6 inches)

Loose Gray Silty Sand

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-03

SUBSURFACE PROFILE

Figure No. 5

Water Level Observation:

Dry during and upon completion

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02192 Longitude: 83.67479

13.1

16.6

9000*

0.3 0.8

3.0

5.0

Bituminous Concrete (4 inches)

Aggregate Base (5 inches)

Fill: Hard Gray Sandy Clay with trace gravel; weathered rock

Fill: Medium Compact Gray Clayey Sand with trace gravel and organics

(Organic Matter Content = 3.4%)

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-04

SUBSURFACE PROFILE

Figure No. 6

Water Level Observation:

Dry during and upon completion

Notes:

* Calibrated Hand Penetrometer

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02156 Longitude: 83.67465

17.0 3500*

0.4 1.1

3.0

5.0

Bituminous Concrete (5 inches)

Aggregate Base (8 inches)

Fill: Stiff Gray Sandy Clay with trace silt and gravel

Fill: Medium Compact Gray Sand with little gravel; occasional clay clods

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-05

SUBSURFACE PROFILE

Figure No. 7

Water Level Observation:

Dry during and upon completion

Notes:

* Calibrated Hand Penetrometer

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02167 Longitude: 83.67580

BS-01

S-03

14.1

0.4 1.1

3.0

5.0

Bituminous Concrete (5 inches)

Aggregate Base: Gray Sand and Gravel with trace silt

(8 inches) Fill: Compact Sand and Clay with trace gravel; occasional cobbles and asphalt

(Organic Matter Content = 2.5%) Medium Compact Sandy Silt

End of Boring @ 5 ft

SAMPLE

TYPE-NO.

BLOWS/

6-INCHES

STD. PEN.

RESISTANCE

(N)

MOISTURE

CONTENT

DRY

DENSITY

(PCF)

UNCONF.

COMP. STR.

(PSF)

SOIL SAMPLE DATA

SO

IL

P

A V

EM

EN

T B

O R

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

Soil Boring No. P-06

SUBSURFACE PROFILE

Figure No. 8

Water Level Observation:

3-1/2 feet during drilling; dry at cave-in depth of 3 feet upon completion

Notes:

Borehole collapsed at 3 ft after auger removal

Excavation Backfilling Procedure:

Auger cuttings and cold asphalt patch

PRO-

FILE

DEPTH

( ft)

DEPTH

( ft)

G2 Project No. 213812

Project Name:

Project Location:

Mott Community College - Parking Lot G Improvements 1401 E. Court Street Flint, Genessee County, Michigan

GROUND SURFACE ELEVATION: N/A

Total Depth:

Drilling Date:

Inspector:

Contractor:

Driller:

Drilling Method:

2-1/4 inch inside diamter hollow-stem augers

5 ft November 8, 2024 Xterra Drilling

Latitude: 43.02140 Longitude: 83.67529

0.0010.010.1110100

GRAVEL

coarse

PI Cc Cu

P-02

P-06

54.0

47.1

%Silt %Clay

1.1

1.9

3 200

Specimen ID

6 140

37.5

37.5

D60

7.71

5.781

D30 D10

0.476

0.353

Description fine

U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER

PE

R

C

EN

T F

IN

ER

B Y W

EI

G

H T

COBBLES

coarse

GRAIN SIZE IN MILLIMETERS

%Sand

10 30 fine medium

SAND

SILT OR CLAY

GRAIN SIZE DISTRIBUTION

LL PL

Gray Gravel and Sand with trace silt

Gray Sand and Gravel with trace silt

P-02

P-06

16.2

16.4

%Gravel

3 60

44.8

51.1

4 2 1 1/2 6 16 50 100

1.5 3/4 3/8 4 8 14 40

Specimen ID

D100

1.971

1.445

BS-01

BS-01

BS-01

BS-01

Figure No. 9

1.1

1.0

Project Name:

213812G2 Project No.:

Mott Community College - Parking Lot G Improvements

Project Location: 1401 E. Court Street Flint, Genessee County, Michigan

U S_

G R

A

IN

_S

IZ

E

.G

P J

G

C O

N

SU

LT

IN

G D

A T

A T

EM

PL

A T

E.

G

/1

/2

PROJECT NO.:

DATE:

DRAWN BY:

CHECKED BY:

213812

12/9/2024

IRG

MGD, PE

PLATE NUMBER

LOCATION

PROJECT NAME

1401 E. Court Street City of Flint, Michigan

Mott Community College Pavement Improvements

R

EV

IS

IO

N

D

ES

C R

IP

T

IO

N

IN

IT

IA

L D

R A

W

IN

G

1350 EISENHOWER PLACE

ANN ARBOR, MICHIGAN 48108

O: 734.390.9330 F: 734.390.9331

/0

/2

SHEET TITLE

THIS DRAWING IS COPYRIGHTED AND IS PRODUCED

SOLEY FOR USE BY THE OWNER AND ITS AFFILIATES.

REPRODUCTION OR USE OF THIS DRAWING AND/OR

THE INFORMATION CONTAINED IN IT IS FORBIDDEN

WITHOUT THE WRITTEN PERMISSION OF THE OWNER.

Photographic Documentation Log

NTS

High Severity Alligator & Block Cracking, Potholes2

NTS

High Severity Alligator Cracking

NTS

Parking Lot G - Plan View

NTS

High Severity Longitudinal & Edge Cracking3

DRAWN BY:

CHECKED BY:

213812

12/9/2024

IRG

MGD, PE

PLATE NUMBER

LOCATION

PROJECT NAME

1401 E. Court Street City of Flint, Michigan

Mott Community College Pavement Improvements

R

EV

IS

IO

N

D

ES

C R

IP

T

IO

N

IN

IT

IA

L D

R A

W

IN

G

1350 EISENHOWER PLACE

ANN ARBOR, MICHIGAN 48108

O: 734.390.9330 F: 734.390.9331

/0

/2

SHEET TITLE

THIS DRAWING IS COPYRIGHTED AND IS PRODUCED

SOLEY FOR USE BY THE OWNER AND ITS AFFILIATES.

REPRODUCTION OR USE OF THIS DRAWING AND/OR

THE INFORMATION CONTAINED IN IT IS FORBIDDEN

WITHOUT THE WRITTEN PERMISSION OF THE OWNER.

Photographic Documentation Log

NTS

High Severity Alligator & Edge Cracking; Potholes2

NTS

High Severity Alligator Cracking

NTS

Parking Lot G - Plan View

High Severity Depressions, Pooling Water3

DRAWN BY:

CHECKED BY:

213812

12/9/2024

IRG

MGD, PE

PLATE NUMBER

LOCATION

PROJECT NAME

1401 E. Court Street City of Flint, Michigan

Mott Community College Pavement Improvements

R

EV

IS

IO

N

D

ES

C R

IP

T

IO

N

IN

IT

IA

L D

R A

W

IN

G

1350 EISENHOWER PLACE

ANN ARBOR, MICHIGAN 48108

O: 734.390.9330 F: 734.390.9331

/0

/2

SHEET TITLE

THIS DRAWING IS COPYRIGHTED AND IS PRODUCED

SOLEY FOR USE BY THE OWNER AND ITS AFFILIATES.

REPRODUCTION OR USE OF THIS DRAWING AND/OR

THE INFORMATION CONTAINED IN IT IS FORBIDDEN

WITHOUT THE WRITTEN PERMISSION OF THE OWNER.

Photographic Documentation Log

NTS

High Severity Block and Alligator Cracking2

NTS

High Severity Block Cracking; Potholes

NTS

Parking Lot G - Plan View

High Severity Alligator Cracking; Depression3

Figure No. 10

GENERAL NOTES TERMINOLOGY

Unless otherwise noted, all terms herein refer to the Standard Definitions presented in ASTM 653.

PARTICLE SIZE

Boulders - greater than 12 inches Cobbles - 3 inches to 12 inches Gravel - Coarse - 3/4 inches to 3 inches

- Fine - No. 4 to 3/4 inches Sand - Coarse - No. 10 to No. 4

- Medium - No. 40 to No. 10

- Fine - No. 200 to No. 40 Silt - 0.005mm to 0.074mm Clay - Less than 0.005mm

CLASSIFICATION

The major soil constituent is the principal noun, i.e. clay, silt, sand, gravel. The second major soil constituent and other minor constituents are reported as follows:

Second Major Constituent (percent by weight)

Minor Constituent (percent by weight)

Trace - 1 to 12% Trace - 1 to 12% Adjective - 12 to 35% Little - 12 to 23% And - over 35% Some - 23 to 33%

COHESIVE SOILS

If clay content is sufficient so that clay dominates soil properties, clay becomes the principal noun with the other major soil constituent as modifier, i.e. sandy clay. Other minor soil constituents may be included in accordance with the classification breakdown for cohesionless soils, i.e. silty clay, trace sand, little gravel.

Consistency

Unconfined Compressive Strength (psf)

Approximate Range of (N)

Very Soft Below 500 0 - 2 Soft 500 - 1,000 3 - 4

Medium 1,000 - 2,000 5 - 8 Stiff 2,000 - 4,000 9 - 15

Very Stiff 4,000 - 8,000 16 - 30 Hard 8,000 - 16,000 31 - 50

Very Hard Over 16,000 Over 50

Consistency of cohesive soils is based upon an evaluation of the observed resistance to deformation under load and not upon the Standard Penetration Resistance (N).

COHESIONLESS SOILS

Density Classification Relative Density % Approximate Range of (N) Very Loose 0 - 15 0 - 4

Loose 16 - 35 5 - 10 Medium Compact 36 - 65 11 - 30

Compact 66 - 85 31 - 50 Very Compact 86 - 100 Over 50

Relative Density of cohesionless soils is based upon the evaluation of the Standard Penetration Resistance (N), modified as required for depth effects, sampling effects, etc.

SAMPLE DESIGNATIONS

AS - Auger Sample – Cuttings directly from auger flight BS - Bottle or Bag Samples S - Split Spoon Sample - ASTM D 1586 LS - Liner Sample with liner insert 3 inches in length ST - Shelby Tube sample - 3 inch diameter unless otherwise noted PS - Piston Sample - 3 inch diameter unless otherwise noted RC - Rock Core - NX core unless otherwise noted

STANDARD PENETRATION TEST (ASTM D 1586) - A 2.0 inch outside-diameter, 1-3/8 inch inside-diameter split barrel sampler is driven into undisturbed soil by means of a 140-pound weight falling freely through a vertical distance of 30 inches. The sampler is normally driven three successive 6-inch increments. The total number of blows required for the final 12 inches of penetration is the Standard Penetration Resistance (N).