GEOTECHNICAL EXPLORATION

WAXAHACHIE CITY HALL RECONSTRUCTION

401 South Rogers Street

Waxahachie, Texas

ALPHA Report No. W240597-rev1

August 27, 2024

Prepared for:

CITY OF WAXAHACHIE

Waxahachie, TX 75165

Attention: Mr. Dale Sigler

Prepared By:

Geotechnical

Construction Materials

Environmental

TBPE Firm No. 813

5058 Brush Creek Road

Fort Worth, Texas 76119

Tel: 817-496-5600

Fax: 817-496-5608 www.alphatesting.com

Dallas • Fort Worth • Houston • San Antonio

City of Waxahachie

Waxahachie, TX 75165

Attention: Mr. Dale Sigler

Re: Geotechnical Exploration

Waxahachie City Hall Reconstruction

401 South Rogers Street

Waxahachie, Texas

Attached is the report of the geotechnical exploration performed for the project referenced above.

This study was authorized by Mr. Dale Sigler on February 26, 2024 and performed in accordance with ALPHA Proposal No. 103254 dated February 22, 2024.

The purpose of this revision is to provide retaining wall foundation recommendations and lateral earth pressures.

This report contains results of field explorations and laboratory testing and an engineering interpretation of these with respect to available project characteristics. The results and analyses were used to develop geotechnical recommendations to aid in design of foundations.

ALPHA TESTING, LLC appreciates the opportunity to be of service on this project. If we can be of further assistance, such as providing construction materials testing services, please contact our office.

Sincerely, ALPHA TESTING, LLC

Karina Cohuo Brian J. Hoyt, P.E.

Geotechnical Project Manager Area Managing Director

KC/BJH/rc

Copies: (1-PDF)

TABLE OF CONTENTS

ALPHA REPORT NO. W240597-REV1

PURPOSE AND SCOPE

PROJECT CHARACTERISTICS

FIELD EXPLORATION

LABORATORY TESTS

GENERAL SUBSURFACE CONDITIONS

DESIGN RECOMMENDATIONS

6.1 Existing Fill, Demolition and Differential Movements

6.2 Drilled, Straight-Shaft Piers

6.3 Spread Footings (Alternative for Building, Retaining Walls)

6.4 Floor Slab and Potential Seasonal Movements

6.5 Lateral Earth Pressures for Site Retaining Walls

6.6 Exterior Flatwork

6.7 Seismic Considerations

6.8 Drainage and Other Considerations

GENERAL CONSTRUCTION PROCEDURES AND GUIDELINES

7.1 Site Preparation and Grading

7.2 Foundation Excavations

7.3 Fill Compaction

7.4 Utilities

7.5 Groundwater

LIMITATIONS

APPENDIX

A-1 Methods of Field Exploration

Boring Location Plan – Figure 1

B-1 Methods of Laboratory Testing

Log of Boring

Key to Soil Symbols and Classifications

PURPOSE AND SCOPE

The purpose of this geotechnical exploration is for ALPHA TESTING, LLC (ALPHA) to evaluate for the City of Waxahachie (Client) some of the physical and engineering properties of subsurface materials at selected locations on the subject site with respect to formulation of appropriate geotechnical design parameters for the proposed construction. The field exploration was accomplished by securing subsurface samples from widely spaced test boring performed across the expanse of the site. Engineering analyses were performed from results of the field exploration and results of laboratory tests conducted on representative samples. Information from a previous study performed on the site (Alpha Report No. W231300-rev1 dated November 1, 2021) was incorporated into our analyses.

Also included are general comments pertaining to reasonably anticipated construction problems and recommendations concerning earthwork and quality control testing during construction. This information can be used to evaluate subsurface conditions and to aid in ascertaining construction meets project specifications.

Recommendations provided in this report were developed from information obtained in the test boring depicting subsurface conditions only at the specific boring location and at the particular time designated on the log. Subsurface conditions at other locations may differ from those observed at the boring location, and subsurface conditions at the boring location may vary at different times of the year. The scope of work may not fully define the variability of subsurface materials and conditions that are present on the site.

The nature and extent of variations at the boring may not become evident until construction. If significant variations then appear evident, our office should be contacted to re-evaluate our recommendations after performing on-site observations and possibly other tests.

PROJECT CHARACTERISTICS

We understand the project will consist of reconstructing the southern half of the to the existing city hall building. The project site is located at 401 South Rogers Street in Waxahachie, Texas. A site plan illustrating the general outline of the property is provided as Figure 1, the Boring Location

Plan, in the Appendix.

At the time the field exploration was performed, the site was occupied by the existing city hall building and associated concrete paved parking and drive areas. No information regarding previous development on the site was provided to us. Review of the topographical maps available at http://www.dfwmaps.com indicates the site generally slopes down to the southeast about 6 ft

(Approximate Elevation: 546 ft to 540 ft). No information regarding previous development on the site was provided to us.

Our findings indicate the addition could be supported with drilled piers or spread footings. We understand the new structure will be designed for about 1 inch of post-construction seasonal movement. Grading plans were not available at the time of this study. Based on conversations with the Client, we understand cuts and fills of up to 2 ft will be required to achieve final grade within the building pad area.

Review of grading plans prepared by RLG Consulting Engineers (Sheet No. C04.01, dated June

24, 2024) indicates retaining walls with heights of up to 10 ft are proposed in the northern and southern areas of the building. Recommendations for lateral earth pressures and allowable bearing pressures for site retaining walls are provided herewith. However, global stability analyses of retaining walls and/or slopes are outside the scope of this study. Our office should be contacted if retaining walls taller than 10 ft are planned or if global stability analyses are desired.

FIELD EXPLORATION

Subsurface conditions on the site were explored by drilling one (1) test boring to a depth of about

25 ft. The test boring was performed in general accordance with ASTM D 420 using standard rotary drilling equipment. The approximate location of each test boring is shown on the Boring

Location Plan, Figure 1, enclosed in the Appendix. Details of drilling and sampling operations are briefly summarized in Methods of Field Exploration, Section A-1 of the Appendix.

Subsurface types encountered during the field exploration are presented on the Log of Boring sheet

(boring log) included in the Appendix. The boring log contains our Field Technician's and

Engineer's interpretation of conditions believed to exist between actual samples retrieved.

Therefore, the boring log contains both factual and interpretive information. Lines delineating subsurface strata on the boring log are approximate and the actual transition between strata may be gradual.

LABORATORY TESTS

Selected samples of the subsurface materials were tested in the laboratory to evaluate their engineering properties as a basis in providing information for foundation design and earthwork construction. A brief description of testing procedures used in the laboratory can be found in

Methods of Laboratory Testing, Section B-1 of the Appendix. Individual test results are presented on the Log of Boring sheet in the Appendix.

GENERAL SUBSURFACE CONDITIONS

Based on geological atlas maps available from the Bureau of Economic Geology, published by the

University of Texas at Austin, the project site lies within the Austin Chalk formation. The Austin

Chalk formation consists predominantly of limestone and marl (limey shale). Residual soils associated with the Austin Chalk formation generally consist of clay soils with moderate to high shrink/swell potential.

Subsurface conditions encountered in the boring generally consisted of clay to a depth of about 1 ft below the ground surface underlain by tan limestone to a depth of about 3½ ft. Gray limestone was then encountered, extending to the 25 ft termination depth of the boring. About 6 inches of concrete was encountered at the surface in the boring. More detailed stratigraphic information is presented on the Log of Boring sheet.

Most of the materials encountered in the boring are relatively impermeable and are anticipated to have a relatively slow response to water movement. Therefore, several days of observation would be required to evaluate actual groundwater levels within the depths explored. Also, the groundwater level at the site is anticipated to fluctuate seasonally depending on the amount of rainfall, prevailing weather conditions and subsurface drainage characteristics.

Free groundwater was not encountered in the boring. However, it is common to encounter seasonal groundwater from natural fractures within the clayey matrix, at the soil/rock (limestone) interface or from fractures in the rock (limestone), particularly during or after periods of precipitation. If more detailed groundwater information is required, monitoring wells or piezometers can be installed.

Further details concerning subsurface materials and conditions encountered can be obtained from the Boring Log provided in the Appendix.

DESIGN RECOMMENDATIONS

The following design recommendations were developed on the basis of the previously described

Project Characteristics (Section 2.0) and General Subsurface Conditions (Section 5.0). Should the project criteria change, including the building location on the site, our office should conduct a review to determine if modifications to the recommendations are required.

The following design criteria was developed based on cuts and/or fills of up to 2 ft will be required to achieve final grade in the building pad area. Cutting or filling on the site more than 2 ft can alter the recommended design parameters. Therefore, it is recommended our office be provided with a copy of final grading plans to verify appropriate design parameters are utilized for final design.

6.1 Existing Fill, Demolition and Differential Movements

As discussed in Section 5.0, existing fill material was encountered to a depth of about 3 ft below the existing ground surface in Boring 1 of ALPHA Report No W231300-rev1 dated November 1, 2023. It is not known if this fill was placed under engineering supervision with compaction records. If compaction records for this fill cannot be obtained, the existing fill should be considered as uncontrolled fill. Uncontrolled fill is generally not considered suitable for support of foundations or floor slabs due to the risk of under-compacted zones resulting in failures of weak soil and/or indeterminate levels of settlement. Any existing uncontrolled fill should be removed from the building pad area and replaced with engineered fill as recommended in Section 7.3. The excavated materials may be suitable for reuse as engineered fill provided they are free of organics, boulders, rubble, and other debris.

The lateral extent, depth and nature of the existing fill are not known. Test pits could be performed prior to construction to verify the presence, lateral extent, depth, and nature of the existing fill materials. ALPHA would be pleased to provide this service if desired.

We understand parts of the existing city hall building will be demolished prior to new construction.

Any areas disturbed from removal of the structures should be re-compacted under moisture-density compaction control as discussed in Section 7.3. All foundation elements of the existing structures should be removed or cut off at least 1 ft below finished grade or 1 ft below the new structural elements, whichever is deeper. All abandoned utility lines should be either removed or positively sealed to prevent possible water seepage into the subsurface clay materials.

As discussed in Section 2.0, the proposed addition is anticipated to be supported on drilled piers or spread footings. The existing building foundation was not known at the time of this study.

Differential movements can occur between the existing building and the proposed additions even if the additions are constructed with a similar foundation as the existing building. Methods should be implemented to allow for possible differential movement between the foundation system of the existing building and the new additions. Further, preventative measures should be taken to avoid damaging or adversely affecting the integrity of the existing foundation system during construction activities.

6.2 Drilled, Straight-Shaft Piers

Our findings indicate the addition could be supported using a system of drilled, straight-shaft piers bearing at least 2 ft into gray limestone. Gray limestone was encountered at a depth of about 3½ ft below the ground surface in the boring. Deeper penetrations will be required to develop sufficient skin friction and/or uplift resistance. Drilled piers should have a minimum length of 6 ft.

Piers can be dimensioned using net allowable bearing pressure and skin friction values in

Table A.

TABLE A

Allowable End Bearing and Skin Friction Parameters

Bearing Stratum

Allowable End

Bearing

(ksf)

Skin Friction in

Compression

(ksf)

Skin Friction in

Uplift Resistance

(ksf)

Gray Limestone

(neglecting upper 2 ft) 40 6.0 5.0

Skin friction should be neglected in the upper 2 ft of gray limestone and above the bottom of temporary casing.

At least two (2) pier shaft diameters should remain between the bottom of the pier and the termination depth of our deepest boring (about 25 ft below existing grade) to use the allowable end bearing parameters. If the minimum clearance between the bottom of the pier and the deepest boring is not provided, piers should be designed as friction piers, neglecting end bearing. In no case should piers bear deeper than the deepest boring (about 25 ft below the existing ground surface). Deeper borings will be required to verify the bearing stratum below 25 ft if deeper piers are planned.

The minimum clear spacing between piers should be at least two (2) pier shaft diameters, based on the larger pier, to develop the full load carrying capacity from skin friction. The allowable skin friction should be reduced by 50 percent for piers with adjacent touching edges. The allowable skin friction can be interpolated between 100 percent and 50 percent for piers spaced between two

(2) pier shaft diameters and piers with adjacent touching edges.

The allowable bearing pressure in Table A has a factor of safety of at least 3 and the skin friction values have a factor of safety of at least 2. Normal elastic settlement of piers under loading is estimated at less than about ½ inch.

Each pier should be sufficiently embedded into the limestone and should be designed with full length reinforcing steel to resist the uplift pressure (soil-to-pier adhesion) due to potential soil swell along the shaft from post construction heave and other uplift forces applied by structural loadings.

The magnitude of uplift adhesion due to soil swell along the pier shaft cannot be defined accurately and can vary according to the actual in-place moisture content of the soils during construction. It is estimated the average uplift adhesion will not exceed about 2.2 kips per sq ft. This soil adhesion is approximated to act uniformly over the portion of the pier shaft in contact with clay soils extending to the top surface of limestone.

All grade beams connecting piers should be formed and not cast in earthen trenches. Grade beams should be formed with a nominal 6-inch void at the bottom. Grade beams formed on limestone do not require a void space. Commercially available cardboard box forms (cartons) are made for this purpose. The cardboard cartons should extend the full length and width of the grade beams. Prior to concrete placement, cartons should be inspected to verify they are firm, properly placed, and capable of supporting wet concrete. Some type of permanent soil retainer, such as pre-cast concrete panels, must be provided to prevent soils adjacent to grade beams from sloughing into the void space at the bottom of the grade beams. Additionally, backfill soils placed adjacent to grade beams must be compacted as outlined in Section 7.3.

Table B contains L-PILE design parameters for design of lateral resistance of drilled piers. Lateral resistance should be neglected in the overburden soils due to potential soil shrinkage and/or disturbance.

TABLE B

Lateral Parameters for Drilled Shafts

Material Tan Limestone Gray Limestone

L-Pile p-y Model Weak rock Weak rock

Effective Unit Weight (γ), pci 0.078 0.078

Rock Uniaxial Compressive Strength (qu), psi 100 333

Rock Mass Modulus (Er), psi 10,000 33,300

Rock Quality Designation (RQD)1, % 50-70 70-90

Rock Strain Factor (krm) 0.0005 0.00005 1 Rock Quality Designation (RQD) is based on our area experience and the results of the field exploration.

6.3 Spread Footings (Alternative for Building, Retaining Walls)

As an alternative to drilled piers, the building could be supported with spread footings bearing on tan limestone. The retaining walls can also be supported with spread footings bearing on tan limestone. Tan limestone was encountered at a depth of about 1 ft below the ground surface in the boring.

Footings bearing on tan limestone can be designed using a net allowable bearing pressure of 8 kips per sq ft. Continuous footings should have a least dimension of 18 inches in width and spot footings should have a least dimension of 24 inches for bearing capacity considerations.

It is estimated the resulting total foundation movements should be limited and not exceed 1 inch.

Differential movements should not exceed 75 percent of the predicted total movement. Careful field inspection of footing excavations should be performed by the construction testing laboratory which will contribute substantially to reducing foundation movements.

Careful monitoring during construction is necessary to locate any pockets or seams of unsuitable materials or clay layers which might be encountered in excavations for footings. Any clay seams encountered in footing excavations should be over-excavated to expose competent rock.

Unsuitable materials encountered at the foundation bearing level should be removed and replaced with lean concrete (at least 200 psi strength at 28 days) or structural concrete.

Resistance to sliding will be developed by friction along the base of the footings and passive earth pressure acting on the vertical face of the footing and a (possible) key installed in the base of the footings, if required. We recommend a coefficient of base friction of 0.35 be used along the bottom of the footing. The available passive earth resistance on the vertical face of the foundation and a

(possible) key bearing against vertical undisturbed cuts in native clay or against clay fill placed and compacted as discussed in Section 7.3 may be calculated using a uniform passive earth resistance of 500 psf. An increased passive resistance of 2,000 psf can be used for footings and keys bearing against vertical cuts in tan limestone. The passive resistance along the vertical face of all footings should be neglected within 2 ft of the final site grade.

6.4 Floor Slab and Potential Seasonal Movements

Our findings indicate floor slab constructed within 2 ft of existing grade could experience post construction seasonal movements of up to about 1 inch, due to shrinking and swelling of active clay soils. Estimates of potential movements are based on the assumption that any fill used to raise the grade will consist of onsite or similar soil with a plasticity index of 15 or less. Backfill of uncontrolled fill should consist of onsite ore similar soil with a plasticity index of 20 or less. The use of fill with a higher plasticity index could result in movements exceeding our estimates and therefore should be avoided. Floor slabs supported on uncontrolled fill material are subject to indeterminate levels of settlement as discussed in Section 6.1.

Potential seasonal movements were estimated in general accordance with methods outlined by

Texas Department of Transportation (TxDOT) Test Method Tex-124-E, from results of absorption swell tests and engineering judgment and experience. The estimated movements were calculated assuming the moisture content of the in-situ soil within the normal zone of seasonal moisture content change varies between a "dry" condition and a "wet" condition as defined by methods outlined in Texas Department of Transportation Test Method Tex-124-E. Also, it was assumed a

1 psi surcharge load from the floor slab acts on the subgrade soils. Movements exceeding those predicted herein could occur if the existing soils are exposed to an extended dry period, positive drainage of surface water is not maintained or if soils are subject to an outside water source, such as leakage from a utility line or subsurface migration from off-site locations.

6.5 Lateral Earth Pressures for Site Retaining Walls

Site retaining walls should be designed to resist the expected lateral earth pressures. The magnitude of lateral earth pressure against retaining walls and below grade walls is dependent on the method of backfill placement, type of backfill soil, drainage provisions, and type of wall (rigid or yielding) after placement of the backfill. Experience demonstrates when a wall is held rigidly against horizontal movement (restrained at the top); the lateral pressure (at-rest lateral earth pressure) against the wall is greater than the normally assumed active pressure. Yielding walls

(rotation at the top of at least 0.1 percent of the wall height) and walls not sensitive to some movements can be designed for active earth pressures (ka). Rigid walls should be designed using the higher at-rest lateral earth pressures (ko). Walls should be designed using the equivalent fluid pressures provided in the Table C, considering a triangular distribution and assuming a horizontal ground surface extending back from the top of the wall. The equivalent fluid pressures provided do not include a factor of safety.

TABLE C

Lateral Earth Pressures: Horizontal Ground Surface Behind the Wall

Material Condition

Equivalent Fluid Pressure, pcf

Drained

Undrained including

Hydrostatic

Pressure

Free Draining Granular

Soil

Ф=35˚, ϒт =125 pcf

At-Rest, ko=0.42 53 89

Active, ka=0.27 34 79

Site Clay Soil, Ф=15˚, ϒт =120 pcf

At-Rest, ko=0.74 --- 105

Active, ka=0.59 --- 96

Free draining granular backfill should consist of a clean, non-plastic, relatively well-graded granular soil consisting of sand, gravel or a sand and gravel mixture, with less than 5 percent finer than the No. 200 sieve size. To reduce surface water seepage into the free draining backfill, the top 1-ft of the backfill should consist of on-site clay soil with a plasticity index of at least 25.

If drained parameters are used for wall design, the free draining granular backfill should extend outward at least 2 ft from the base of the wall and then extend upward on a 1 (horizontal) to 2

(vertical) slope. The free draining granular backfill should be separated from the adjacent native soils using a filter fabric (Mirafi 140N, or equivalent) to prevent intrusion of native soils into the free draining granular backfill.

Complete drainage of the free draining granular backfill could be provided to prevent the development of hydrostatic pressures behind the wall. A typical drainage system could consist of perforated plastic PVC pipes placed in filter trenches excavated parallel to the base of the walls for their entire length. The drain pipes should be positioned at a depth lower than the bottom elevation of the wall and should also be wrapped with filter fabric (Mirafi 140N, or equivalent).

A drainage system is beneficial regardless of the type of backfill used behind the wall. As a minimum, weep holes should be provided for freestanding walls. However, weep holes alone will not prevent occasional build-up of hydrostatic pressures behind the walls.

Lightweight, hand-controlled vibrating plate compactors are recommended for compaction of backfill adjacent to walls to reduce the possibility of increases in lateral pressures due to over-compaction. Heavy compaction equipment should not be operated near the walls. Also, compaction of backfill soils behind walls should not exceed 100 percent standard Proctor maximum dry density (ASTM D 698) to further limit lateral earth pressures against walls.

The lateral earth pressures in Table C do not include the effects of surcharge loading on the wall due to sloping backfill or from other loads near the walls. Surcharge loads should be multiplied by the appropriate lateral earth pressure coefficient from Table C and applied as a uniform lateral load over the full height of the wall.

6.6 Exterior Flatwork

Flatwork planned for the project is subject to potential seasonal movements as discussed for floor slab in Section 6.4 (about 1 inch). If this level of movement is not acceptable, flatwork can be structurally suspended on drilled piers as discussed in Section 6.2.

6.7 Seismic Considerations

The Site Class for seismic design is based on several factors that include soil profile (soil or rock), shear wave velocity, and strength, averaged over a depth of 100 ft. Since our boring did not extend to 100-foot depths, we based our determinations on the assumption that the subsurface materials below the bottom of the boring were similar to those encountered at the termination depth. Based on Section 1613.3.2 of the 2012 International Building Code and Table 20.3-1 in the 2010 ASCE-

7, we recommend using Site Class C (very dense soil or soft rock) for seismic design at this site.

6.8 Drainage and Other Considerations

Adequate drainage should be provided to reduce seasonal variations in the moisture content of foundation soils. All pavement and sidewalks within 10 ft of the structure should be sloped away from the building to prevent ponding of water around the foundation. Final grades within 10 ft of the structure should be adjusted to slope away from the structure at a minimum slope of 2 percent.

Maintaining positive surface drainage throughout the life of the structure is essential.

In areas with pavement or sidewalks adjacent to the new structure, a positive seal must be maintained between the structure and the pavement or sidewalk to minimize seepage of water into the underlying supporting soils. Post-construction movement of pavement and flatwork is common. Normal maintenance should include inspection of all joints in paving and sidewalks, etc. as well as resealing where necessary.

Several factors relate to civil and architectural design and/or maintenance, which can significantly affect future movements of the foundation and floor slab system:

• Preferably, a complete system of gutters and downspouts should carry runoff water a minimum of 5 feet from the completed structure.

• Large trees and shrubs should not be allowed closer to the foundation than a horizontal distance equal to roughly one-half of their mature height due to their significant moisture demand upon maturing.

• Moisture conditions should be maintained "constant" around the edge of the slab. Ponding of water in planters, in unpaved areas, and around joints in paving and sidewalks can cause slab movements beyond those predicted in this report.

• Planter box structures placed adjacent to the building should be provided with a means to assure concentrations of water are not available to the subsoil stratigraphy.

Trench backfill for utilities should be properly placed and compacted as outlined in Section 7.4 and in accordance with requirements of local City standards. Since granular bedding backfill is used for most utility lines, the backfilled trench should not become a conduit and allow access for surface or subsurface water to travel toward the new structures. Concrete cut-off collars or clay plugs should be provided where utility lines cross building lines to prevent water from traveling in the trench backfill and entering beneath the structures.

GENERAL CONSTRUCTION PROCEDURES AND GUIDELINES

Variations in subsurface conditions could be encountered during construction. To permit correlation between test boring data and actual subsurface conditions encountered during construction, it is recommended a registered Professional Engineering firm be retained to observe construction procedures and materials.

Some construction problems, particularly degree or magnitude, cannot be reasonably anticipated until the course of construction. The guidelines offered in the following paragraphs are intended not to limit or preclude other conceivable solutions, but rather to provide our observations based on our experience and understanding of the project characteristics and subsurface conditions encountered in the boring.

7.1 Site Preparation and Grading

Existing fill was encountered to a depth of about 3 ft below the ground surface in Boring 1 of

ALPHA Report No. W231300-rev1 dated November 1, 2021. Although not encountered in the boring, existing fill materials could contain organics, boulders, rubble and other debris which could be encountered during site grading and general excavation. The earthwork and excavation contracts should contain provision for removal of unsuitable materials in the existing fill. Test pit excavations performed prior to construction can be used to evaluate the depth, lateral extent and composition of uncontrolled fill at this site. ALPHA would be pleased to provide this service if desired.

Limestone was encountered at a depth of about 1 ft of the ground surface in the boring. We expect limestone will be encountered during grading and general excavation at this site. From our experience, this limestone can be hard and difficult to excavate. Rock excavation methods

(including, but not limited to rock teeth, rippers, jack hammers, or sawcutting) may be required to remove the limestone. Crushing equipment may be required to process this limestone if it is desired to use this material as compacted fill on the site. The contractor selected should have experience with excavation in hard limestone.

All areas supporting floor slabs, flatwork, pavement or areas to receive new fill should be properly prepared.

• After completion of the necessary stripping, clearing, and excavating, and prior to placing any required fill, the exposed soil subgrade should be carefully evaluated by probing and testing. Any undesirable material (organic material, wet, soft, or loose soil) still in place should be removed.

• The exposed soil subgrade should be further evaluated by proof-rolling with a heavy pneumatic-tired roller, loaded dump truck or similar equipment weighing approximately

20 tons to check for pockets of soft or loose material hidden beneath a thin crust of possibly better soil.

• Proof-rolling procedures should be observed routinely by a Professional Engineer or his designated representative. Any undesirable material (organic material, wet, soft, or loose soil) exposed during proof-rolling should be removed and replaced with well-compacted material as outlined in Section 7.3.

• Prior to placement of any fill, the exposed soil subgrade should then be scarified to a minimum depth of 6 inches and re-compacted as outlined in Section 7.3.

If fill is to be placed on existing slopes (natural or constructed) steeper than six horizontal to one vertical (6:1), the fill materials should be benched into the existing slopes in such a manner as to provide a minimum bench width of five (5) feet. This should provide a good contact between the existing soils and new fill materials, reduce potential sliding planes, and allow relatively horizontal lift placements.

Even if fill is properly compacted as described in Section 7.3, fills in excess of about 10 ft are still subject to settlements over time of up to about 1 to 2 percent of the total fill thickness. This should be considered when planning or placing deep fills.

Slope stability analysis of embankments (natural or constructed) and global stability analysis for retaining walls was not within the scope of this study.

The contractor is responsible for designing any excavation slopes, temporary sheeting or shoring.

Design of these structures should include any imposed surface surcharges. Construction site safety is the sole responsibility of the contractor, who shall also be solely responsible for the means, methods and sequencing of construction operations. The contractor should also be aware that slope height, slope inclination or excavation depths (including utility trench excavations) should in no case exceed those specified in local, state and/or federal safety regulations, such as OSHA

Health and Safety Standard for Excavations, 29 CFR Part 1926, or successor regulations.

Stockpiles should be placed well away from the edge of the excavation and their heights should be controlled so they do not surcharge the sides of the excavation. Surface drainage should be carefully controlled to prevent flow of water over the slopes and/or into the excavations.

Construction slopes should be closely observed for signs of mass movement, including tension cracks near the crest or bulging at the toe. If potential stability problems are observed, a geotechnical engineer should be contacted immediately. Shoring, bracing or underpinning required for the project (if any) should be designed by a professional engineer registered in the

State of Texas.

Due to the nature of the clay soils found near the surface at the boring, traffic of heavy equipment

(including heavy compaction equipment) may create pumping and general deterioration of shallow soils. Therefore, some construction difficulties should be anticipated during periods when these soils are saturated.

7.2 Foundation Excavations

All foundation excavations should be properly monitored to verify loose, soft or otherwise undesirable materials are removed and foundations will bear on satisfactory material. Soil exposed in the base of all foundation (pier and footing) excavations should be protected against detrimental change in condition, such as surface sloughing or side disturbance, rain or excessive drying.

Drilled pier foundations should be completed in one day.

Prolonged exposure of the bearing surface to air or water will result in changes in strength and compressibility of the bearing stratum. Therefore, if delays occur, straight shaft pier excavations should be slightly widened and deepened, or a new design penetration made to provide a fresh bearing surface. Footing excavations should be deepened and cleaned.

All pier shafts should be at least 1.5 ft in diameter for pier stability considerations and to facilitate clean-out of the base and for proper monitoring. Concrete placed in pier holes should be directed through a tremie, hopper, or equivalent. Placement of concrete should be vertical through the center of the shaft without hitting the sides of the pier or reinforcement to reduce the possibility of segregation of aggregates. Concrete placed in piers should have a minimum slump of 5 inches

(but not greater than 7 inches) to avoid potential honey-combing.

Observations during pier drilling should include, but not necessarily be limited to, the following items:

• Verification of proper bearing strata and consistency of subsurface stratification with regard to the boring log,

• Confirmation the minimum required penetration into the bearing strata is achieved,

• Complete removal of cuttings from bottom of pier holes,

• Proper handling of any observed water seepage and sloughing of subsurface materials,

• No more than 2 inches of standing water should be permitted in the bottom of pier holes prior to placing concrete, and

• Verification of pier diameter size and steel reinforcement.

Free groundwater was not encountered in the boring. However from our experience, groundwater seepage could be encountered during pier installation. The risk of encountering groundwater during pier drilling is increased during or after periods of precipitation. Where submersible pumps or bailing cannot control groundwater, temporary casing may be required to control seepage. The casing should be properly seated into the limestone, and all groundwater and soil should be removed prior to beginning the design penetration. As casing is extracted, care should be taken to maintain a positive head of plastic concrete and minimize the potential for intrusion of water seepage. A separate bid item should be provided for casing on the contractor bid schedule.

7.3 Fill Compaction

Select fill used as non-expansive material in the building pad should have a liquid limit less than

35, a plasticity index (PI) not less than about 4 nor greater than 15 and contain no more than 0.5 percent fibrous organic materials, by weight. All select material should contain no deleterious material and should be compacted to a dry density of at least 95 percent standard Proctor maximum dry density (ASTM D 698) and within the range of 1 percentage point below to 3 percentage points above the material's optimum moisture content. The plasticity index and liquid limit of material used as select non-expansive material should be routinely verified during placement using laboratory tests. Visual observation and classification should not be relied upon to confirm the material to be used as select, non-expansive material satisfies the Atterberg-limit criteria.

Flexible base used as non-expansive material in the building pad should consist of material meeting the requirements of TxDOT Standard Specifications Item 247, Type A or D, Grade 1-2 or 3. The flexible base should be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 2 percentage points below to 2 percentage points above the material's optimum moisture content.

Clay soils with a plasticity index less than 25 should be compacted to a dry density of at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 1 percentage point below to 3 percentage points above the material's optimum moisture content.

Clay soils with a plasticity index of 25 or higher should be compacted to a dry density of at least

93 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 2 to

6 percentage points above the material's optimum moisture content.

Clayey materials used as fill should be processed such that the largest particle or clod is less than

6 inches prior to compaction.

Processed limestone used as fill should be compacted to at least 95 percent of standard Proctor maximum dry density. The compacted moisture content of the processed limestone is not considered crucial to proper performance. However, if the material's moisture content during placement is within 3 percentage points of optimum, the compactive effort required to achieve the minimum compaction criteria may be minimized. Individual rock pieces larger than 6 inches in dimension should not be used as fill. However, if rock fill is utilized within 3 ft below the bottom of floor slabs, the maximum allowable size of individual rock pieces should be reduced to 3 inches.

Processed limestone used as fill should incorporate sufficient fines to prevent the presence of voids around larger diameter rock pieces. A gradation of at least 40 percent passing a standard No. 4 sieve is recommended.

Where mass fills are deeper than 10 ft, the fill/backfill below 10 ft should be compacted to at least

100 percent of standard Proctor maximum dry density (ASTM D-698) and within 2 percentage points of the material's optimum moisture content. The portion of the fill/backfill shallower than

10 ft should be compacted as outlined herein.

Compaction should be accomplished by placing fill in about 8-inch thick loose lifts and compacting each lift to at least the specified minimum dry density. Field density and moisture content tests should be performed on each lift.

In general site grading areas where final fill slopes will be four horizontal to one vertical (4:1) or steeper and greater than 5 ft in height, field density and moisture content tests should be performed on each lift.

7.4 Utilities

Where utility lines are deeper than 10 ft, the fill/backfill below 10 ft should be compacted to at least 100 percent of standard Proctor maximum dry density (ASTM D 698) and within –2 to +2 percentage points of the material's optimum moisture content. The portion of the fill/backfill shallower than 10 ft should be compacted as previously outlined. Density tests should be performed on each lift (maximum 12-inch thick) and should be performed as the trench is being backfilled.

Even if fill is properly compacted, fills in excess of about 10 ft are still subject to settlements over time of up to about 1 to 2 percent of the total fill thickness. This should be considered when designing pavement over utility lines and/or other areas with deep fill.

If utility trenches or other excavations extend to or beyond a depth of 5 ft below construction grade, the contractor or others shall be required to develop an excavation safety plan to protect personnel entering the excavation or excavation vicinity. The collection of specific geotechnical data and the development of such a plan, which could include designs for sloping and benching or various types of temporary shoring, is beyond the scope of this study. Any such designs and safety plans shall be developed in accordance with current OSHA guidelines and other applicable industry standards.

7.5 Groundwater

Free groundwater was not encountered in the boring. However, from our experience, seasonal groundwater seepage could be encountered in excavations for foundations, below grade areas, utilities and other general excavations at this site. The risk of seepage increases with depth of excavation and during or after periods of precipitation. Standard sump pits and pumping may be adequate to control seepage on a local basis.

In any areas where cuts are made, attention should be given to possible seasonal water seepage that could occur through natural cracks and fissures in the newly exposed stratigraphy. The risk of seepage is increased where limestone is exposed in slopes and excavations or is near final grade.

In these areas subsurface drains may be required to intercept seasonal groundwater seepage. The need for these or other dewatering devices should be carefully addressed during construction. Our office could be contacted to visually observe final grades to evaluate the need for such drains.

LIMITATIONS

Professional services provided in this geotechnical exploration were performed, findings obtained, and recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. The scope of services provided herein does not include an environmental assessment of the site or investigation for the presence or absence of hazardous materials in the soil, surface water or groundwater. ALPHA, upon written request, can be retained to provide these services.

ALPHA is not responsible for conclusions, opinions or recommendations made by others based on this data. Information contained in this report is intended for the exclusive use of the Client

(and their designated design representatives), and is related solely to design of the specific structures outlined in Section 2.0. No party other than the Client (and their designated design representatives) shall use or rely upon this report in any manner whatsoever unless such party shall have obtained ALPHA’s written acceptance of such intended use. Any such third party using this report after obtaining ALPHA’s written acceptance shall be bound by the limitations and limitations of liability contained herein, including ALPHA’s liability being limited to the fee paid to it for this report. Recommendations presented in this report should not be used for design of any other structures except those specifically described in this report. In all areas of this report in which ALPHA may provide additional services if requested to do so in writing, it is presumed that such requests have not been made if not evidenced by a written document accepted by ALPHA.

Further, subsurface conditions can change with passage of time. Recommendations contained herein are not considered applicable for an extended period of time after the completion date of this report. It is recommended our office be contacted for a review of the contents of this report for construction commencing more than one (1) year after completion of this report. Non-compliance with any of these requirements by the Client or anyone else shall release ALPHA from any liability resulting from the use of, or reliance upon, this report.

Recommendations provided in this report are based on our understanding of information provided by the Client about characteristics of the project. If the Client notes any deviation from the facts about project characteristics, our office should be contacted immediately since this may materially alter the recommendations. Further, ALPHA is not responsible for damages resulting from workmanship of designers or contractors. It is recommended the Owner retain qualified personnel, such as a Geotechnical Engineering firm, to verify construction is performed in accordance with plans and specifications.

APPENDIX

A-1 METHODS OF FIELD EXPLORATION

Using standard rotary drilling equipment, one (1) test boring was performed for this geotechnical exploration at the approximate locations shown on the Boring Location Plan, Figure 1. The test boring locations were staked by using a handheld GPS unit or by pacing/taping and estimating right angles from landmarks which could be identified in the field and as shown on the site plan provided during this study. The locations of test boring shown on the Boring Location Plan are considered accurate only to the degree implied by the methods used to define it.

Relatively undisturbed soil samples were obtained by hydraulically pressing 3-inch O.D. thin-wall sampling tubes into the underlying soils at selected depths (ASTM D 1587). These samples were removed from the sampling tubes in the field and evaluated visually. One representative portion of each sample was sealed in a plastic bag for use in future visual evaluation and possible testing in the laboratory.

Texas Department of Transportation Texas Cone Penetration (TCP) tests were completed in the field to determine the apparent in-place strength characteristics of the rock type materials. A 3-inch diameter steel cone driven by a 170-pound hammer dropped 24 inches is the basis for TxDOT strength correlations. Depending on the resistance (strength) of the materials, either the number of blows of the hammer required to provide 12 inches of penetration, or the inches of penetration of the cone due to 100 blows of the hammer are recorded on the field log and are shown on the Log of Boring sheet as “TX Cone” (reference: TxDOT Test Method TEX 132-E).

The boring log is included in the Appendix. The log shows visual descriptions of subsurface strata encountered in the boring using the Unified Soil Classification System. Sampling information, pertinent field data, and field observations are also included. Samples not consumed by testing will be retained in our laboratory for at least 14 days and then discarded unless the Client requests otherwise.

BORING LOCATION PLAN

FIGURE 1

SOUTH ROGERS STREET

W

ES

T M

A D

IS

O

N S

TR

EE

T

SOUTH ROGERS STREET

W

ES

T M

A D

IS

O

N S

TR

EE

T

N

APPROXIMATE BORING LOCATION

APPROXIMATE BORING LOCATION

(W231300-rev1)

GEOTECHNICAL EXPLORATION

WAXAHACHIE CITY HALL RECONSTRUCTION

401 SOUTH ROGERS STREET

WAXAHACHIE, TEXAS

ALPHA PROJECT NO. W240597-REV1

B-1 METHODS OF LABORATORY TESTING

Representative samples were evaluated and classified by a qualified member of the Geotechnical

Division and the boring log was edited as necessary. To aid in classifying the subsurface materials and to determine the general engineering characteristics, natural moisture content tests (ASTM D

2216), Atterberg-limit tests (ASTM D 4318), percent material passing the No. 200 sieve tests

(ASTM D 1140) were performed on selected samples. In addition, pocket-penetrometer tests were conducted on selected soil samples to evaluate the soil shear strength. Results of these laboratory tests are provided on the Log of Boring sheet.

Client:

Project:

Start Date: End Date:

Drilling Method:

BORING NO.:

PROJECT NO.:

Location:

Surface Elevation:

West:

North:

Hammer Drop (lbs / in):

D ep th , f ee t

G ra ph ic

L og

MATERIAL DESCRIPTION

Sa m pl e

Ty pe

R ec ov er y

R Q

D

TX

C on e or

S td

Pe n.

(b lo w s/ ft, in

Po ck et Pe ne tro m et er (t sf

U nc on fin ed C om p.

St re ng th

(t sf

U

U S he ar

St re ng th

(t sf

P as si ng

N o.

S ie ve U ni t D ry W ei gh t (p cf

W at er C on te nt

Li qu id L im it

Pl as tic L im it

Pl as tic ity

In de x

Sw el l, GROUND WATER OBSERVATIONS

On Rods (ft):

After Drilling (ft):

After Hours (ft):

City of Waxahachie Waxahachie City Hall Renovations

5/23/2023 5/23/2023

CONTINUOUS FLIGHT AUGER

W231300

Waxahachie, Texas

170 / 24

NONE

DRY

5058 Brush Creek Rd.

Fort Worth, Texas 76119 Phone: 817-496-5600 Fax: 817-496-5608 www.alphatesting.com

6" CONCRETE 0.5

Tan CLAY with asphalt and limestone fragments

- FILL

3.0 Tan LIMESTONE

8.0 Gray LIMESTONE

25.0

TEST BORING TERMINATED AT 25 FT

4.5+ 101.3 108

3.0 18 34 17 17 0.0

100/ 2.50" 100/ 2.50"

100/ 1.50"

100/ 1"

100/ 1"

100/ 1"

Sheet 1 of 1

Client:

Project:

Start Date: End Date:

Drilling Method:

BORING NO.:

PROJECT NO.:

Location:

Surface Elevation:

West:

North:

Hammer Drop (lbs / in):

D ep th , f ee t

G ra ph ic

L og

MATERIAL DESCRIPTION

Sa m pl e

Ty pe

R ec ov er y

R Q

D

TX

C on e or

S td

Pe n.

(b lo w s/ ft, in

Po ck et Pe ne tro m et er (t sf

U nc on fin ed C om p.

St re ng th

(t sf

U

U S he ar

St re ng th

(t sf

P as si ng

N o.

S ie ve U ni t D ry W ei gh t (p cf

W at er C on te nt

Li qu id L im it

Pl as tic L im it

Pl as tic ity

In de x

Sw el l, GROUND WATER OBSERVATIONS

On Rods (ft):

After…