1-ITB 2026002 - WSP Report of Geotechnical Exploration.pdf

REPORT OF GEOTECHNICAL

EXPLORATION

CC W.A. Fountain Elementary School Geotechnical Exploration

FOREST PARK, Georgia

WSP Project No. US0041394.0400

Prepared for:

Sophia Tarkhan, AIA, NOMA, LEED AP Principal Cooper Carry 191 Peachtree Street NE, Suite 2400 Atlanta, Georgia 30303-1770

2/26/2025

1/17/2025

Revised 2/26/2025

Sophia Tarkhan, AIA, NOMA, LEED AP Principal Cooper Carry 191 Peachtree Street NE, Suite 2400 Atlanta, Georgia 30303-1770

Subject: Report of Geotechnical Investigation

CC W.A. Fountain Elementary School Geotechnical Exploration Forest Park, Georgia WSP Project No. US0041394.0400

Dear Mrs. Tarkhan:

WSP USA Environment & Infrastructure Inc. (WSP) is pleased to submit this geotechnical engineering evaluation report for the planned CC W.A. Fountain Elementary School development located in Forest Park, Georgia. This exploration was conducted in general accordance with our proposal dated October 29, 2024.

This report briefly discusses our understanding of the project, describes our exploratory procedures and results, and presents our conclusions and recommendations related to the project design and construction.

We appreciate the opportunity of working with you on this project and look forward to our continued association during the construction phases of the project. Please contact us if you have any questions about this report or if we may be of further service.

Sincerely, WSP USA Environment & Infrastructure Inc.

Roseline Hartz Geologist

Yanbo Huang, Ph.D., P.E.

Assistant Vice President, Geotechnical Engineer

REPORT OF GEOTECHNICAL EXPLORATION

Forest Park, Georgia

WSP Project No. US0041394.0400

Prepared for:

Sophia Tarkhan, AIA, NOMA, LEED AP Principal Cooper Carry 191 Peachtree Street NE, Suite 2400 Atlanta, Georgia 30303-1770

Prepared by:

WSP USA Environment & Infrastructure Inc.

2677 Buford Highway Atlanta, GA 30324

2/26/2025

Copyright and non-disclosure notice

The contents and layout of this report are subject to copyright owned by WSP (© WSP USA Environment & Infrastructure Inc.), save to the extent that copyright has been legally assigned by us to another party or is used by WSP under license. To the extent that we own the copyright in this report, it may not be copied or used without our prior written agreement for any purpose other than the purpose indicated in this report. The methodology (if any) contained in this report is provided to you in confidence and must not be disclosed or copied to third parties without the prior written agreement of WSP. Disclosure of that information may constitute an actionable breach of confidence or may otherwise prejudice our commercial interests. Any third party who obtains access to this report by any means will, in any event, be subject to the Third-Party Disclaimer set out below.

Third-party disclaimer

Any disclosure of this report to a third party is subject to this disclaimer. The report was prepared by WSP at the instruction of, and for use by, our client named on the front of the report. It does not in any way constitute advice to any third party who is able to access it by any means. WSP excludes to the fullest extent lawfully permitted all liability whatsoever for any loss or damage howsoever arising from reliance on the contents of this report. We do not however exclude our liability (if any) for personal injury or death resulting from our negligence, for fraud or any other matter in relation to which we cannot legally exclude liability.

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Table of Contents

1.0 Introduction

2.0 Project Information

3.0 Field Exploration

3.1 Standard Penetration Tests

3.2 Hand-Auger

3.3 Infiltration Testing

4.0 Site and Subsurface Conditions

4.1 Area and Site Geology

4.2 Subsurface Conditions

4.2.1 General

4.2.2 Subsurface Soils

4.2.3 Groundwater

4.2.4 MASW results

4.2.5 Infiltration Results

5.0 Conclusions and Recommendations

5.1 Site Preparation

5.2 Existing Fill

5.3 Excavation and Earthwork Construction Considerations

5.4 Fill Placement

5.5 Foundation Recommendations

5.6 Floor Slabs

5.7 Retaining walls

5.8 Seismic Design Parameters – Seismic Site Class

5.9 Other Recommendations

5.10 Qualifications of Recommendations

Appendix

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Appendix

Figure 1 - Site Location Plan Figure 2 – Boring Location Plan WSP Key to Symbols and Descriptions Hand Auger Boring Logs Soil Test Boring Records Infiltration Test Summary Laboratory Test Results

MASW

GBA Information About Geotechnical Reports

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1.0 Introduction

WSP has completed a geotechnical exploration for the proposed development project, located at 5215

West St in Forest Park, Georgia. The objective of this exploration was to explore the general subsurface conditions for use in proposed development and to analyze the conditions as they relate to site suitability.

This report discusses our understanding of the project, describes our exploratory procedures and presents our conclusions and recommendations.

2.0 Project Information

We understand that Cooper Carry intends to redevelop the existing W.A. fountain Elementary School located at 5215 West St in Forest Park, GA. The site consists of an existing elementary school with associated amenities such as parking lots, driveways, a playground, a baseball field and is surrounded by scattered wooded areas and open fields. A creek runs across the northeast area of the site, north of the existing building and a high-pressure gas easement is located on the western boundary of the site. The redevelopment would consist of an overall footprint of 143,000 square feet with the existing gym to be saved and renovated. Design loads provided by PES proposes the exterior column loads to be 150 kips and the interior column loads to be 225 kips. Wall loads of 8 klf are also provided. No grading plans were provided.

Based on the provided loading we anticipate the proposed building may be supported on shallow foundations. We anticipate site grading will be minimal and less than 2 feet of cut, or fill based on the existing site topography.

3.0 Field Exploration

In order to explore the general subsurface conditions in the areas of the planned construction, a total of twenty-one (21) boring, nine (9) infiltration and shear wave velocity tests were performed at the approximate locations for phase I development as shown on the attached boring location plan. The infiltration and most of the boring test locations encountered shallow refusal. The boring locations are shown on the Boring Location Plan (Figure 2) in the Appendix and should be considered approximate.

3.1 Standard Penetration Tests

All standard penetration tests were performed using a GeoProbe and a Diedrich D50 drill rig utilizing an automatic hammer. The borings were performed by Piedmont Environmental Drilling, LLC, subcontracted by WSP. Prior to the commencement of drilling operations, an 811 ticket was created, and a private utility locator was subcontracted by WSP to check for the presence of underground utilities at the site. The boring

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WSP Project No. US0041394.0400 | 1/17/2025 Page 2 locations were staked in the field by a geotechnical engineer by measuring distances from existing landmarks and using a handheld GPS device.

The Soil Test Boring Records, in the Appendix, graphically show the penetration resistances and present the soil descriptions for selected SPT borings. The stratification lines and depth designations on the boring records represent the approximate boundaries between soil types. In some instances, the transition between types may be gradual.

3.2 Hand-Auger

Hand auger boring techniques were used to extend the borings B-1 and B-2 to refusal depth of 4 feet below ground surface (bgs) by manually rotating a hand-held auger into the soil. The stratification lines and depth designations on the boring records represent the approximate boundaries between soil types. In some instances, the transition between types may be gradual.

3.3 Infiltration Testing

Infiltration tests I-2 through I-9 were prepared by extending hollow stem auger borings to depths of 2 to 8 feet. Auger borings were advanced mechanically using a drill rig using a hollow stem auger into the soil. I-

2, I-4, I-5 encountered shallow refusals ranging from 2 feet to 6 feet BGS. I-7 encountered groundwater at

4 feet BGS and was moved and terminated at 2 feet bgs.

Infiltration test I-1 was prepared using a hand-auger and advanced to a shallow refusal of 4 feet below grade.

After advancing the test borehole, an Aardvark Permeameter was used to conduct infiltration rate measurements at regular intervals until a constant infiltration rate was observed. Test results are discussed in section 4.2.5 and are attached in the appendix.

4.0 Site and Subsurface Conditions

4.1 Area and Site Geology

The project site is in the Piedmont Physiographic Province, an area underlain by metamorphic rocks with localized igneous intrusions. Published geologic data from USGS indicate the site is underlain by Granite

Gneiss/ Amphibolite from Precambrian-Paleozoic age.

The residual soils encountered in the Piedmont are the product of in-place chemical and physical weathering of the parent rock. Typically, weathering is most advanced at the surface and decreases with depth. This results in a residual soil profile consisting of slightly clayey soils near the surface underlain by

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WSP Project No. US0041394.0400 | 1/17/2025 Page 3 sandy silts and silty sands that generally become harder or denser and coarser with depth to the top of the unweathered bedrock. In deeper residual soil strata, known as saprolites, the banded structural appearance of the parent rock is typically evident.

The boundary between soil and rock in the Piedmont is typically not sharply defined. A transitional zone termed “partially weathered rock” is normally found overlying bedrock. Partially weathered rock (PWR) is defined for engineering purposes as residual material with a standard penetration resistance exceeding 100 blows per foot (bpf). Weathering is facilitated by fractures, joints, and by the presence of less resistant rock types. Consequently, the surface elevation of PWR and unweathered rock can vary significantly over short horizontal distances. Lenses and boulders of hard rock and zones of PWR may be present within the soil mantle, above the general bedrock level.

4.2 Subsurface Conditions

4.2.1 General

The subsurface conditions discussed in the following paragraphs and those shown on the Soil Test Boring

Records represent an interpretation of the boring and other data using normally accepted geotechnical engineering judgments considering local geology and experience.

The Boring Records represent our interpretation of the field conditions based on the driller's field logs and an engineer's examination of the split-spoon samples. The groundwater condition indicated on the Soil Test

Boring Records represent observations at the time of drilling. The lines designating the interfaces between various strata represent approximate boundaries only, as transitions between materials may be gradual. Soil conditions may vary between and away from the boring locations. Soil samples will be discarded after 30 days from the date of this report unless otherwise requested.

4.2.2 Subsurface Soils

In general, below the ground surface, the borings encountered topsoil or asphalt underlain by fill, residual soils and partially weathered rocks. Several borings encountered refusal shallower than the planned boring termination depths with the shallowest auger refusal material encountered at 4 feet below grade (proposed depth of 30 feet) at B-13. Please refer to the table below for a summary of termination depths. Subsurface materials encountered by the borings performed for this exploration are summarized with more detailed information shown on the Soil Test Boring Records located in the Appendix.

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Table 1: Termination Depths Vs. Planned Termination Depths

Boring Number

Termination depth (feet) Planned termination depth (feet)

B-01* 4 10 B-02* 4 10 B-03 15 15 B-04 15 15 B-05 15 15 B-06 15 15 B-07 10 15 B-08 6 30 B-09 30 30 B-10 30 30 B-11 29 30 B-12 11 30 B-13 4 30 B-14 28 30 B-15 11 30 B-16 11 30 B-17 6 30 B-18 16 30 B-19 8 15 B-20 8 15 B-21** 25 15

*Hand Auger ** Encountered construction and/or household debris (e.g., brick fragment, concrete, chains, plastics and wires)

At borings B-21, we encountered potentially contaminated soil as there was a chemical odor encountered.

At I-5 we also encountered construction and/or household debris (e.g., brick fragment, concrete, plastics).

Asphalt/GAB: The asphalt encountered at B-5, B-6, B-8, B-9 and B-10 had a thickness of 5 inches with no observed GAB underneath.

Fill: Most borings, with the exception of B-1, B-2, B-19 and B-20, encountered existing fill. Fill soils were approximately 3.5 to 6 feet thick. The fill typically consisted of Silty Sands ranging from loose to dense. N-values generally ranged between 2 to 33 blows. A layer of possible fill was noted in B-4 from 6 to 13.5 feet

(bgs). Possible fill is soil was encountered at borings B-4 at 6 to 13.5 feet (bgs). Fill that contains inorganic debris and landfill type material was encountered in B-21 from surface to a boring termination depth of 25 feet (bgs).

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Residual Soils: Residual soil, formed by in-place weathering of the parent rock, was encountered in each boring beneath the undocumented fill. Residual soil typically consisted of very loose to very dense silty sands with N-values generally ranging between 2 to 62 blows.

4.2.3 Groundwater

Groundwater was only observed in borings B-3 at 9 feet bgs and I-7 at 4 feet bgs at the time of drilling.

Groundwater levels can fluctuate with changes in weather, climate, local drainage, and with construction activity in the area. Since groundwater level variations are anticipated, design drawings and specifications should accommodate such possibilities and construction planning should be based on the assumption that variations will occur.

4.2.4 MASW results

A shear wave velocity investigation was conducted using a combination of passive and active MASW

(Multichannel Analysis of Surface Waves) methods to establish the IBC seismic soil site classification for the proposed construction being considered on this property. The northern-most test location exhibits lower shear wave velocities than the southern-most test location where rock outcrops were observed.

Passive and active arrays using a 24-channel Geometrics Geode seismograph with 4.5-Hz geophones were used to collect seismic data. The results are as followed:

MASW-1 Vs100 = 1090.8 ft/sec Site Class D MASW-2 Vs100 = 1865.7 ft/sec Site Class C MASW-3 Vs100 = 1967.8 ft/sec Site Class C

Please refer to the report conducted by GeoWave dated December 27, 2024 in the appendix for further information on test methods and results.

4.2.5 Infiltration Results

The infiltration tests were conducted around the perimeter of the proposed building footprint. The following table shows the infiltration rates from the three tests performed. Saturated hydraulic conductivity (Ksat) is a quantitative measure of a saturated soil’s ability to transmit water when subjected to a hydraulic gradient.

The infiltration testing utilized an Aardvark Model 2840 Permeameter. The Aardvark is a constant head permeameter, meaning the height of water in the borehole remains constant during measurements. The rate of water supplied during the test corresponds to the infiltration rate from the bottom and side surfaces of the borehole. The Aardvark Permeameter records the infiltration rate by measuring the amount of water supplied to the borehole at equal time intervals. The infiltration rate is measured until the rate of loss does

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WSP Project No. US0041394.0400 | 1/17/2025 Page 6 not change over several consecutive readings. The steady state infiltration flow rate is then used to calculate saturated hydraulic conductivity (Ksat). Additional information can be found in the appendix.

Table 2: Summary of Infiltration Results

Test Number Test Depth (in) Soil Type Ksat (in/hr)

I-1 33 Clayey SAND (SC) 0.02 I-2 33 Silty SAND (SM) >0.5* I-3 10 Silty SAND (SM) >0.5* I-4 35 Silty SAND (SM) 0.01 I-5 31 Silty SAND (SM) 0.01 I-6 91 Silty SAND (SM) 0.12 I-7 29 Silty SAND (SM) >0.5* I-8 101 Silty SAND (SM) >0.5* I-9 91 Silty SAND (SM) >0.5*

*Greater than target amount of 0.5 inch/hr provided by Eberly & Associates, Inc

5.0 Conclusions and Recommendations

The following conclusions and recommendations are based on the previously discussed project information, our observations at the site, interpretation of the field data obtained during the exploration, and our experience with similar subsurface conditions. Subsurface conditions in unexplored locations may vary from those encountered at the specific boring locations. If the construction scheme should vary significantly from that previously described, we request the opportunity to review these recommendations and amend them if necessary.

5.1 Site Preparation

All underground utilities should be removed and all vegetation, including stumps and root systems, organic topsoil and other deleterious materials should be stripped from proposed construction areas. In addition, any debris or landfill type material should be removed if encountered. After clearing and stripping, areas intended to support the structures, including new fill should be carefully assessed by a qualified geotechnical engineer or his representative. This assessment should include proofrolling to locate soft or weak subgrades that may need repair. Any areas that pump or deflect excessively should be addressed as appropriate.

Areas intended to support new fill should be proofrolled with a fully-loaded, tandem-axle, dump truck or other pneumatic-tired vehicle of similar size and weight under the observation of the geotechnical engineer.

The purpose of proofrolling is to locate soft, weak, or excessively wet surficial soils present at the time of construction. Proofrolling consists of trafficking the site with a fully loaded, tandem axle dump truck or pneumatic tired vehicle of similar size and weight (20 tons). Proofrolling should detect shallow, soft, wet, or

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WSP Project No. US0041394.0400 | 1/17/2025 Page 7 otherwise unsuitable soils. Materials judged to be unstable during proofrolling operations will require remedial action and should be treated as recommended by the engineer. The geotechnical engineer can recommend treatment based on the planned construction in the area and severity of the issues discovered.

These recommendations often include harrowing and disking the upper one foot of exposed surface to alter moisture content followed by recompaction of the harrowed materials.

Some relatively soft soils were encountered near the existing surface. In general, if soft or loose soils are encountered in structural areas, the soils may need to be reworked or undercut to a point 10 feet outside the perimeter of the structural areas. The extent of the reworking necessary will depend on the final grading plans and the climatic conditions at the time of construction. All undercut areas should be backfilled with structural fill as described in Fill Placement Section of this report.

If earthwork is conducted in hot, dry weather favorable for drying soils, issues with wet unstable soils tend to be less of a concern. However, if the required treatment effort and volumes for stabilization become widespread or grading is performed during unfavorable weather conditions, additional measures such as lime or cement stabilization might be required to dry and stabilize the soils in wet or unfavorable weather.

5.2 Existing Fill

As noted in the Subsurface Conditions section, most of the borings encountered existing fill to depths ranging from about 3.5 to 8.5 feet. The fill appears to have been placed in a controlled manner, but we have no records to indicate the degree of compaction achieved during placement. If such records (density test, etc.) exist, they should be provided to us for evaluation. Support of footings and floor slabs, on or above existing fill soils, is discussed in this report. However, even with the recommended construction procedures, there is inherent risk for the owner that compressible fill or unsuitable material, within or buried by the fill, will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by following the recommendations contained in this report.

If the owner elects to construct the footings and floor slabs on the existing fill, the following protocol should be followed. Prior to any planned fill placement in the building area, the area should be undercut two feet within the building area and 10 feet beyond the lateral limits of the building area. Once materials have been removed, the entire area should be proofrolled with heavy, rubber tire construction equipment, to aid in delineating areas of soft or otherwise unsuitable soil. Once unsuitable materials have been remediated, and the subgrade has passed a proofroll, the existing and undocumented fill that was removed can be evaluated for reuse as structural fill.

Areas of soft or otherwise unstable material should be undercut and replaced with either new structural fill or suitable, existing on-site materials.

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However, all debris or unsuitable materials (e.g., organic matters) should be removed if encountered during site preparation. Undocumented fill should be suspect of concealing zones of organic matter or poorly compacted material. To reduce risks associated with the fill, it should generally be removed or undercut if encountered below the proposed building area during the site preparation, unless the risks of future settlement associated with these masked conditions are acceptable to the owner or cost prohibitive. If these risks are not acceptable, we recommend excavating all existing fill until undisturbed, residual soils are encountered.

5.3 Excavation and Earthwork Construction Considerations

We assumed the bottom of footing for the building will be at least one foot above the depth of refusal materials. Based on the results of our borings, we anticipate that difficult to excavate materials, such as Partially Weathered Rock (PWR), rock lenses or boulders, and bedrock will be encountered during site grading and subsequent excavation of shallow foundations and during utility installation. If shallow PWR lenses are encountered, very dense soil and PWR typically require loosening by ripping with large dozers pulling single tooth rippers in mass excavation and possibly blasting in confined (trench) excavation. Reuse of excavated material as fill is anticipated. PWR fragments can be re-used and mixed into engineered fill provided that it is pulverized to less than three inches in diameter and mixed with soil to create a well graded fill material. Typically, large compaction equipment such as a Caterpillar 815 is required to properly compact and break down very dense soil and PWR, if possible.

According to our discussion with Cooper Carry on February 19, 2025, we understand the foundation may be embedded below the depth of auger refusal encountered. Excavation of auger refusal material (apparent rock) typically requires blasting. Mass excavation by blasting is generally less expensive on a cubic yard basis than blasting in trenches, therefore, it may be more cost effective to over-excavate (overshoot) the auger refusal materials below planned footings and utilities and backfill the over-excavated area with engineered soil fill. This will allow conventional installation of shallow foundations and utilities. In addition, support of the building on engineered fill will aid in limiting differential settlement between areas supported on rock and engineered fill

We recommend a rock excavation definition be included in the grading contract for clarity. Rock excavation can be defined in many ways. A method specification based on the grading equipment commonly used in the project area is typical. The following is a guideline rock excavation specification for your review.

In Mass Excavation: Any material occupying an original volume of more than 1 cubic yard which cannot be excavated with a single-tooth ripper drawn by a crawler tractor having a minimum draw bar pull rating of not less than 56,000 pounds usable pull (Caterpillar D-8K or larger) or the excavator listed below.

In Trench Excavation: Any material occupying an original volume of more than ½ cubic yard which cannot be excavated with a track excavator having a bucket curling rate of not less than 25,700 pounds, using a rock bucket and rock teeth (Caterpillar 225 or larger).

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In addition, we recommend pricing for mass and trench rock excavation be obtained prior to award of the grading contract. Excavation limits beyond those required to install utilities should also be defined.

It should be noted that boulders and/or discontinuous rock lenses will likely be encountered during grading.

Boulders will likely need to be reduced in size prior to placement, wasted on site in non-developed areas or hauled off site. This could result in a reduction of the excavated material available for use as engineered fill material.

In foundation and slab areas where grade is established by blasting, removal of all blast damaged rock will be required. Slab areas may be backfilled to grade with structural fill after verification by geotechnical evaluation that the damaged blast rock has been satisfactorily removed.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become frozen, desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction and observed by a WSP representative.

Surface water should not be allowed to pond on the site and soak into the soil during construction.

Construction staging should provide drainage of surface water and precipitation away from the building area. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils. Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage.

Groundwater was encountered at 4 to 9 feet bgs at the time of exploration. If groundwater is encountered during construction, some form of temporary or permanent dewatering may be required. Conventional dewatering methods, such as pumping from sumps or trenching, should likely be adequate for temporary removal of any groundwater encountered during excavations at the site.

A grading plan is not available yet. Depending on final grades, we anticipate that some new fill could be required in the building pad area.

All excavations should be sloped or braced as required by Occupational Health and Safety Administration

(OSHA) regulations to provide stability and safe working conditions. The grading contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope, or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state, and federal safety regulations, including the current OSHA Excavation and Trench Safety Standards.

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

5.4 Fill Placement

Fill to replace undercut areas or achieve finished grades should be low to moderate plasticity soil (PI less than 20), free of deleterious materials and rock fragments larger than about 3 inches in any dimension. All structural fill should be placed in maximum 8-inch thick loose lifts and compacted to at least 95 percent of the soil's maximum dry density as determined by the standard Proctor compaction test (ASTM D 698). Soil moisture during placement should be maintained within 3 percent of the optimum moisture content. The upper 2 feet of fill beneath foundations or slabs should be compacted to 98 percent. Fill should be placed in horizontal lifts and adequately keyed into stripped and scarified subgrade soils. In confined areas such as utility trenches or over anchor blocks, portable compaction equipment and thin lifts of 3 to 4 inches may be required to achieve specified degrees of compaction.

Fill placement should be observed by a qualified soils technician under the supervision of the geotechnical engineer and that frequent fill density and moisture tests be performed to verify that the specified degree of compaction is being achieved. Areas that do not meet the compaction specifications should be reworked to achieve compliance and retested.

5.5 Foundation Recommendations

The subsurface soil conditions of this site are variable. The residual soils were encountered as deep as 30 ft

BGS (i.e., termination depth of the boring) while auger refusal was encountered as shallow as 4 ft BGS. We performed shallow foundation settlement analysis using the provided structural loads and the soil parameters derived from the SPT borings. The total settlement was estimated in the range 0.5 to 1.5 inches.

For the borings (i.e., B-9, B10, B-11) with settlement greater than one inch, significant portion of the settlement was from the very loose to loose soils in the upper 6 to 10 ft. Therefore, conventional, shallow foundations bearing on residual soil or fill compacted in accordance with the recommendations in this report may be designed for an allowable soil bearing capacity of 2,000 psf provided undercutting and backfilling with compacted fill was performed at least 8 ft below the existing ground surface for the areas with deep very loose to loose soils. Ground improvement methods such as aggregate piers may be needed to increase the bearing pressure to accommodate greater loads. Total settlement at individual footing locations is expected to be on the order of 1 inch or less and differential settlements between widely spaced, similarly loaded columns are not expected to exceed ½ inch. The allowable foundation bearing pressures apply to dead loads plus design live load conditions. The design bearing

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WSP Project No. US0041394.0400 | 1/17/2025 Page 11 pressure may be increased by one-third when considering total loads that include wind or seismic conditions. The weight of the foundation concrete below grade may be neglected in dead load computations. Interior footings should bear a minimum of 12 inches below finished grade. Finished grade is the lowest adjacent grade for perimeter footings and floor level for interior footings.

Footings, foundations, and masonry walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in masonry walls is recommended.

Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ from those presented in this report, supplemental recommendations can be required.

The base of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Should the soils at bearing level become excessively dry, disturbed or saturated, or frozen, the affected soil should be removed prior to placing concrete. Place a lean concrete mud-mat over the bearing soils if the excavations must remain open over night or for an extended period of time. It is recommended that the geotechnical engineer be retained to observe and test the soil foundation bearing materials.

If unsuitable bearing soils are encountered in footing excavations, the excavations should be extended deeper to suitable soils and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The footings could also bear on properly compacted backfill extending down to the suitable soils. Overexcavation for compacted backfill placement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing base elevation. The overexcavation should then be backfilled up to the footing base elevation with well-graded granular material placed in lifts of 9 inches or less in loose thickness and compacted to at least 95 percent of the material's maximum standard Proctor dry density (ASTM D-698).

We recommend widths of not less than 24 inches for footings for ease of construction and to reduce the possibility of localized shear failures. In addition, exterior footing bottoms should be at least 18 inches below exterior grades for protection against frost damage. A qualified geotechnical engineer should observe all footing excavations and assess whether the foundations are placed on a competent bearing stratum.

For foundations near or adjacent to slopes, a minimum horizontal setback of five (5) feet should be maintained between the foundation base and slope face. In addition, the setback should be at a location where an imaginary line extending downward at 45 degrees from the nearest edge of the foundation does not intersect the slope face.

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5.6 Floor Slabs

A subgrade prepared and tested as recommended in this report should provide adequate support for lightly loaded floor slabs. A properly prepared subgrade should have an available modulus of subgrade reaction of 100 pci. A compacted layer of graded aggregate base (GAB) is recommended in order provide more uniform support and improved performance. This GAB will also provide a capillary break to reduce moisture intrusion. Minimum recommended thickness of the GAB is 4 inches.

Where appropriate, saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or any cracks that develop can be sealed with a waterproof, non-extruding compressible compound.

The use of a vapor retarder or barrier should be considered beneath concrete slabs on grade that will be covered with moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 and ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder/barrier.

On most project sites, the site grading is generally accomplished early in the construction phase, however as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab subgrade may not be suitable for placement of base rock and concrete and corrective action may be required.

We recommend the area underlying the floor slab be rough graded and then thoroughly proofrolled with a loaded tandem axle dump truck prior to final grading and placement of base rock. Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by removing and replacing the affected material with properly compacted fill. All floor slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the base rock and concrete.

The slab should be isolated from column and wall foundations to reduce the risk of cracking because of the differential loading.

5.7 Retaining walls

We anticipate that below grade walls may be required for this site. The following recommendations are provided for reference. The lateral earth pressure recommendations herein are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity type concrete walls. These

Forest Park, Georgia

WSP Project No. US0041394.0400 | 1/17/2025 Page 13 recommendations are not applicable to the design of modular block – geogrid reinforced backfill walls.

Recommendations covering these types of wall systems are beyond the scope of services and are typically the responsibility of specialty wall designers. However, we would be pleased to develop recommendations for the design of such wall systems upon request.

Active earth pressure conditions apply to relatively flexible earth retention structures, such as freestanding walls, where some movement and rotation may occur to mobilize the soil’s shear strength. Rigidly restrained walls, such as basement or foundation walls or walls supported on piles or other rigid foundations, should be designed for the at-rest condition.

Experience indicates that development of the full active earth pressure case requires a magnitude of horizontal wall movement that often cannot be tolerated or cannot occur due to the rigidity of the wall or other design restrictions such as the impact on adjacent structures. In such cases, walls are often designed for either the at-rest condition or a condition intermediate of the active and at-rest conditions, depending on the amount of permissible wall movement.

Passive earth pressure represents the maximum possible pressure when a structure is pushed against the soil and is used in wall foundation design to help resist active or at-rest pressures. Because significant wall movements are required to develop the passive pressure, the total calculated passive pressure is usually reduced by one-half for design purposes. Passive pressure should generally not be considered for soils in slopes or soils near the surface that may erode or be excavated. Lateral earth pressure parameters for a typical fill material (sandy silt/silty sand) compacted as outlined in the fill section of this report are summarized in the table below:

Table 3. Lateral Earth Pressure Parameters

Earth Pressure Condition Earth Pressure Coefficient Recommended Equivalent Fluid Unit

Weight (pcf) Active Ka = 0.36 43 At-Rest K0 = 0.53 64 Passive Kp = 2.8 330

Note: no factor of safety was included for the values provided in above table.

To calculate resistance to sliding, a coefficient of friction between foundation concrete and the soils encountered at this site of 0.32 may be considered. Our recommendations assume that the ground surface above and below the wall is level and that residual soils like those found in our borings will be used for structural wall backfill.

The recommended equivalent fluid pressures assume that constantly functioning drainage systems are installed between walls and soil backfill to prevent the build-up of hydrostatic pressures and lateral stresses

Forest Park, Georgia

WSP Project No. US0041394.0400 | 1/17/2025 Page 14 in excess of those stated. Soil strength parameters may be impacted by saturation, so design of walls without drainage is not recommended. Drainage should include a linear collector drain near the upslope end of the footing and filtered gravel or prefabricated drains against the wall. Wall drainage should end about 2 feet below exterior grade to prevent infiltration of surface water into the wall drainage system. The ground surface at the top of walls should generally slope away from the wall.

Construction equipment should not operate within 10 feet of retaining walls to prevent lateral pressures in excess of those cited. If footings or other surcharge loadings are located a short distance outside below grade walls, they may also exert appreciable additional lateral pressures.

Wall movements may create settlement of backfill within at least a horizontal distance equal to twice the wall height. This settlement could impact structures, pavements, and utilities in the area. Wall movements may also impact the density of retained fill, impacting the fill’s strength and permeability.

5.8 Seismic Design Parameters – Seismic Site Class

Please refer to the report of probabilistic seismic hazard analysis for the seismic design parameters.

5.9 Other Recommendations

With the chemical smell encountered at B-21, we recommend an environmental exploration to look into the potential contaminated soil at B-21 if there are not already plans by the owner to address the soil. WSP does have an environmental group that can provide the exploration if requested.

5.10 Qualifications of Recommendations

Our evaluation of foundation design and construction conditions has been based on our understanding of the site, the available project information, our assumptions and the data obtained during our field exploration as described herein. The general subsurface conditions used were based on interpolation of the subsurface data at our soundings. The design recommendations in this report have been developed on the basis of the previously described project characteristics and subsurface conditions. If project criteria or locations change, we must be permitted to determine if our recommendations are still applicable or if they must be modified. The findings of such a review will be presented in a supplemental report.

Subsurface conditions in unexplored locations may vary from those encountered at specific sounding location. The nature and extent of variations may not become evident until the course of construction. If such variations then appear evident, it will be necessary to re-evaluate the recommendations of this report after on-site observations of the conditions.

Forest Park, Georgia

WSP Project No. US0041394.0400 | 1/17/2025 Page 15

Regardless of the thoroughness of a subsurface exploration, there is the possibility that conditions will differ from those at the sounding location, that conditions are not as anticipated by the designers, or that the construction process has altered the soil conditions. Therefore, experienced geotechnical engineers must observe earthwork and foundation construction to assess if the conditions anticipated in design actually exist.

Our professional services have been performed, our findings derived, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties either express or implied. This company is not responsible for the conclusions, opinions or recommendations of others based on these data.

Appendix

Figure 1 - Site Location Plan

Figure 2 – Boring Location Plan

WSP Key to Symbols and Descriptions

Hand Auger Boring Logs

Soil Test Boring Records

Infiltration Test Summary

Laboratory Test Results

MASW

GBA Information About Geotechnical Reports

CC W.A. Fountain Elementary School

WSP

2677 Buford Highway Atlanta, Georgia 30324

(404) 873 4761

SITE LOCATION PLAN

Drawn By: RMH DATE:

January 2025

FIGURE 1

Legend:

Site Location

CC W.A. Fountain Elementary School

WSP

2677 Buford Highway Atlanta, Georgia 30324

(404) 873 4761

BORING LOCATION PLAN

Drawn By: RMH DATE:

January 2025

FIGURE 2

MAJOR DIVISIONS

GRAVELS

CLEAN

GROUP

SYMBOLS

GW

TYPICAL NAMES

Well graded gravels, gravel - sand mixtures, little or no fines.

Poorly graded gravels or grave - sand

Undisturbed Sample

Standard Penetration Test or Dynamic Cone Penetration Test

Auger Cuttings

Bulk Sample

COARSE

GRAINED

SOILS

(More than 50% of material is

LARGER than No. 200 sieve size)

(More than 50% of coarse fraction is

LARGER than the No. 4 sieve size)

SANDS

(More than 50% of

(Little or no fines)

WITH FINES

(Appreciable amount of fines)

CLEAN

SANDS

(Little or no fines)

GP mixtures, little or no fines.

GM Silty gravels, gravel - sand - silt mixtures.

Clayey gravels, gravel - sand - clay mixtures.

Well graded sands, gravelly sands, little or no fines.

SP Poorly graded sands or gravelly sands, Rock Core

Dilatometer

Packer

Water Table at time of boring

Crandall Sampler

Pressure Meter

No Recovery

Water Table after 24 hours coarse fraction is SMALLER than the No. 4 Sieve

SANDS WITH

little or no fines.

SM Silty sands, sand - silt mixtures

Correlation of Standard Penetration Resistance with Relative Density and Consistency

Size) FINES SAND & GRAVEL SILT & CLAY

FINE

GRAINED

SOILS

(More than 50% of material is

(Appreciable amount of fines)

SILTS AND CLAYS

(Liquid limit LESS than 50)

SC Clayey sands, sand - clay mixtures.

Inorganic silts and very fine sands, rock flour, ML silty of clayey fine sands or clayey silts and with slight plasticity.

Inorganic lays of low to medium plasticity, CL gravelly clays, sandy clays, silty clays, lean clays.

Organic silts and organic silty clays of low plasticity.

Inorganic silts, micaceous or

MH diatomaceous fine sandy or silty soils, No. of Blows 0 - 4

5 - 10 11 - 30 31 - 50 Over 50

Relative Density Very Loose

Loose Medium Dense

Dense Very Dense

No. of Blows 0 - 2 3 - 4 5 - 8 9 - 15 16 - 30 31 - 50 Over 50

Consistency Very Soft

Soft Firm Stiff

Very Stiff Hard

Very Hard

SMALLER than No. 200 sieve

SILTS AND CLAYS

elastic silts.

Inorganic clays of high plasticity, fat

Correlation of Dynamic Cone Penetration Resistance with Relative Density and Consistency (Piedmont Residual Soils) size) (Liquid limit GREATER than 50)

HIGHLY ORGANIC SOILS

FILL

CH clays

Organic clays of medium to high plasticity, organic silts.

PT Peat and other highly organic soils.

Fill

SAND & GRAVEL SILT & CLAY

BOUNDARY CLASSIFICATIONS: Soils possessing characteristics of two groups are designated by combinations of group symbols. KEY TO SYMBOLS AND

DESCRIPTIONS

No.200 No.40 No.10 No.4 3/4" 3" 12"

U.S. STANDARD SIEVE SIZE

Reference: The Unified Soil Classification System, Corps of Engineers, U.S. Army Technical Memorandum No.

3-357, Vol. 1, March, 1953 (Revised April, 1960)

GC

SW

OL

OH

SILT OR CLAY

SAND GRAVEL

Cobbles Boulders

Fine Medium Coarse Fine Coarse

No. of Blows Relative Density No. of Blows Consistency 0 - 4 Very Loose 0 - 2 Very Soft

5 - 15 Loose 3 - 4 Soft 16 - 30 Medium Dense 5 - 10 Firm

11 - 30 Stiff

P

D SOIL CLASSIFICATION

E AND REMARKS

T

H SEE KEY SHEET FOR EXPLANATION OF SYMBOLS AND ABBREVIATIONS USED BELOW.

L E E L G E E V N (ft)

SAMPLES

I T D Y E P N E

PL (%) NM (%)

FINES (%)

LL (%)

(ft)

D

RESIDUUM: Brown, silty fine to coarse SAND (SM), trace rock fragments, trace organics, trace mica

- Black, clayey fine to coarse SAND (SC), trace mica

Boring terminated at approximately 4 feet

AU-1

AU-2

AU-3

AU-4

10 20 30 40 50 60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100

THIS RECORD IS A REASONABLE INTERPRETATION OF

SUBSURFACE CONDITIONS AT THE EXPLORATION

LOCATION. SUBSURFACE CONDITIONS AT OTHER

LOCATIONS AND AT OTHER TIMES MAY DIFFER.

INTERFACES BEWEEN STRATA ARE APPROXIMATE.

TRANSITIONS BETWEEN STRATA MAY BE GRADUAL.

DRILLER:

EQUIPMENT:

METHOD:

HOLE DIA.:

WSP

Hand Auger Hand Auger 3 inches

REMARKS: Groundwater not encountered at time of drilling.

PREPARED BY: RMH REVIEWED BY: DW

S O

IL

T

E S

T B

O R

IN

G

T E

ST

.G

P J

A M

E C

.G D

T

/1 4/

HAND AUGER BORING RECORD

BORING NO.: B-01

PROJECT: CC W.A. Foutain Elementary School LOCATION: Forest Park, GA DRILLED: December 19, 2024

PROJECT NO.: US0041394.0400 PAGE 1 OF 1

D SOIL CLASSIFICATION

E AND REMARKS

H SEE KEY SHEET FOR EXPLANATION OF SYMBOLS AND ABBREVIATIONS USED BELOW.

L E

G E E V N (ft)

SAMPLES

I T D Y E P N E

PL (%) NM (%)

FINES (%)

LL (%)

RESIDUUM: brown, clayey fine to coarse SAND (SC), some organics, trace mica

- Red, trace rock fragments, trace organics

Brown, silty fine to medium SAND (SM), trace mica

- Trace rock fragments

Boring terminated at approximately 4 feet

AU-1

AU-2

AU-3

AU-4

LOCATION. SUBSURFACE CONDITIONS AT OTHER

LOCATIONS AND AT OTHER TIMES MAY DIFFER.

INTERFACES BEWEEN STRATA ARE APPROXIMATE.

TRANSITIONS BETWEEN STRATA MAY BE GRADUAL.

DRILLER:

EQUIPMENT:

METHOD:

HOLE DIA.:

WSP

Hand Auger Hand Auger 3 inches

REMARKS: Groundwater not encountered at time of drilling.

PREPARED BY: RMH REVIEWED BY: DW

S O

IL

T

E S

T B

O R

IN

G

T E

ST

.G

P J

A M

E C

.G D

T

/1 4/

HAND AUGER BORING RECORD

BORING NO.: B-02

PROJECT: CC W.A. Foutain Elementary School LOCATION: Forest Park, GA

G

D SOIL CLASSIFICATION L E SAMPLES PL (%) NM (%) LL (%)

E P T H

AND REMARKS E

E

SEE KEY SHEET FOR EXPLANATION OF N

SYMBOLS AND ABBREVIATIONS USED BELOW. D

TOP SOIL: 2 inches FILL: Medium dense, brown, silty fine to coarse SAND (SM), trace rock fragments, trace organics

- Loose

RESIDUUM: Very loose, brown, silty fine to coarse SAND (SM), trace rock fragments, trace mica

PARTIALLY WEATHERED ROCK: Sampled as black and white, silty fine to coarse SAND (SM), trace rock fragments

RESIDUUM: Medium dense, brown and black, silty fine to medium SAND (SM), some mica

Boring terminated at approximately 15 feet

L E V

(ft)

D T

E Y

N P

T E

SPT-1

SPT-2

SPT-3

SPT-4

SPT-5

N-COUNT

7-8-9

(N = 17)

5-4-5

(N = 9)

WOH-1-1

(N = 2)

50/5

2-4-9

(N = 13)

FINES (%)

SPT (bpf)

LOCATION. SUBSURFACE CONDITIONS AT OTHER

LOCATIONS AND AT OTHER TIMES MAY DIFFER.

INTERFACES BEWEEN STRATA ARE APPROXIMATE.

TRANSITIONS BETWEEN STRATA MAY BE GRADUAL.

I

DRILLER:

EQUIPMENT:

METHOD:

HOLE DIA.:

Piedmont Drilling Diedrich D-50 Track (Auto-Hammer)

3 1/4" HSA

6 inches

REMARKS:…