PK26_01 _ BRP _ GEOTECH RPT.pdf

Proposal Cover Page

Report Cover Page

Bunten Road Park Improvements Duluth, Gwinnett County, Georgia

Geotechnical Engineering Report

December 12, 2024 | Terracon Project No. 49245278

Prepared for:

Columbia Engineering 2862 Buford Highway, Suite 200 Duluth, Georgia 30096

2105 Newpoint Place, Suite 600 Lawrenceville, GA 30043

P (770) 623-0755 Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

December 12, 2024

Columbia Engineering 2862 Buford Highway, Suite 200 Duluth, Georgia 30096

Attn: Ms. Erin White, PLA P: (678) 769 8901 E: erinwhite@columbia-engineering.com

Re: Geotechnical Engineering Report Bunten Road Park Improvements 3180 Bunten Road Duluth, Gwinnett County, Georgia Terracon Project No. 49245278

Dear Ms. White:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. P49245278 dated October 11, 2024. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations for the proposed project.

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

Sincerely, Terracon

E. Kelly Watson, P.E. William J, Sheffield, P.E.

Senior Geotechnical Engineer Principal / Department Manager - Geotechnical https://na3.documents.adobe.com/verifier?tx=CBJCHBCAABAAPG0ORTE_vzfb6AeMjJM4InMz9wGsQsRs https://na3.documents.adobe.com/verifier?tx=CBJCHBCAABAAPG0ORTE_vzfb6AeMjJM4InMz9wGsQsRs

Geotechnical Engineering Report Bunten Road Park Improvements | Duluth, Gwinnett County, Georgia December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i Introduction Project Description Site Conditions Geotechnical Characterization

Site Geology Typical Subsurface Profile Groundwater

Infiltration Rate Geotechnical Overview

MSE or Gabion Wall Paved Multi-Use Trails

Earthwork Site Preparation Subgrade Preparation Existing Fill Excavation Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Groundwater Considerations Earthwork Construction Considerations Construction Observation and Testing

General Comments

Attachments

Exploration and Testing Procedures Photography Log Site Location and Exploration Plans Exploration and Laboratory Results Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com. Refer to each individual Attachment for a listing of contents.

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Report Summary

Topic 1 Overview Statement 2

Project Description

The project will include reconstruction of the existing paved multi-purpose trails and parking areas, new retaining walls, and storm drainage, landscaping, and various other ADA improvements.

Geotechnical Characterization

Some areas of existing fill up to 5 of more feet deep.

Hand auger refusal occurred in all of the borings at the proposed MSE/Gabion wall. Depths ranged from about 3 to 5½ feet.

Difficult excavation techniques may be required for excavations at the MSE/Gabion wall.

Groundwater not observed in the borings during our exploration.

Earthwork

Existing lean clays, sandy silt, and silty sands can be used for engineered fill.

Clays should not be used as wall backfill.

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

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Introduction

This report presents the results of our subsurface exploration and Geotechnical Engineering services performed for the proposed Improvements to Bunten Road Park.

The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Hand auger boring logs with dynamic cone penetrometer (DCP) data.

■ Soil stratification based on visual soil classification.

■ Groundwater levels observed during and after the completion of drilling.

■ Site Location and Exploration Plans.

■ Subsurface exploration procedures.

■ Description of subsurface conditions.

■ Earthwork recommendations including use of on-site soils as structural fill, structural placement, excavation conditions, groundwater control, and site/subgrade preparation.

■ Comments on the stability of the slope and MSE wall and a design foundation bearing pressure.

■ Measured walking trail pavement thicknesses at 6 locations.

■ Infiltration rate testing results at 4 on-site stormwater treatment facilities

Drawings showing the site and boring locations are shown on the Site Location and Exploration Plans, respectively.

Project Description

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

Item Description

Information Provided

The following plans were provided in an emailed RFP from Erin White dated 9-30-24:

ADA and Trail Improvements, Bunten Road Park, Concept

Plan, Sheet 1, dated 2-26-24.

Bunten Park – grading and concept plan for Flex/MSE Wall Bunten Road Park Improvement Project, Preliminary

Construction Plans (60% set), dated 5-23-24.

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Item Description

Project Description

The project will include reconstruction of the existing paved trails and parking areas, storm drainage and retention, retaining walls, landscaping, and various other ADA improvements.

Proposed Structure

No new building structures were shown in the project information provided.

Grading/Slopes Mass grading is expected to be minimal.

Below-Grade Structures

No underground structures, with the exception of underground storm and sanitary pipes and structures, are planned.

Free-Standing Retaining Walls

A new mechanically stabilized earth (MSE) or gabion wall is planned for a slope along the paved path between Soccer Field 1 and Softball Field 2. We estimate that the wall will be about 62 feet long and up to about 6 feet tall.

Pavements

A considerable amount of removal and replacement of old asphaltic concrete in the paved multi-use trails is planned.

The 60% drawings specify a 6-inch thick layer of asphaltic concrete (Sheet C-6.1) for the paved multi-use trails.

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

Site Conditions

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

Item Description

Parcel Information

The project is located at 3180 Bunten Road in Duluth, Gwinnett County, Georgia.

The project site covers approximately 44.76 acres.

Latitude/Longitude (approximate): 34.0007 / -84.1212 See Site Location

Existing Improvements

Two soccer fields, two baseball fields, two softball fields and several buildings. Infrastructure consists of paved parking areas, underground utilities, and paved walking trails.

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Item Description

Current Ground Cover

Ranges from grass surfaced athletic fields and landscaping to asphaltic concrete paved parking lots and trails. Portland cement paved sidewalks are present in some areas.

Existing Topography

The athletic fields have been graded relatively flat. Rolling topography exists in the wooded areas surrounding the fields.

We also collected photographs at the time of our field exploration program.

Representative photos are provided in our Photography Log.

Geotechnical Characterization

Site Geology

The project site is located in the Piedmont Physiographic Province of Georgia which is characterized by medium to high grade metamorphic rocks and scattered igneous intrusions. The term metamorphic describes rocks that have been subjected to high temperatures and/or pressures, usually deep within the earth’s crust. These high temperatures and pressures cause the textural and mineralogical characteristics of the original rock to be altered and can also cause certain rock types to fully melt, becoming what is known as magma. Magma is less dense than the surrounding solidified rock and tends to move upward through fractures and joints, displacing the surrounding rock.

This rock type is known as an igneous intrusion. Metamorphic rocks are predominant in this region but, due to erosion and uplift, both of these rocks will eventually become exposed at the land surface.

The subsurface bedrock in this region has undergone differing rates of weathering, which often produces a considerable variation in depth to competent rock over short horizontal distances. It is also not unusual for lenses and boulders of hard rock and zones of partially weathered rock to be present within the soil mantle above the general bedrock level. The typical residual soil profile consists of clayey soils near the surface, where soil weathering is more advanced, underlain by sandy silts and silty sands, which often consist of saprolites (native soils which maintain the original fabric of the parent rock).

Generally, the soil becomes harder with depth to the top of parent crystalline rock or “massive bedrock” which occurs at depth.

The boundary between soil and rock 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).

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Fill soils are those soils that have been placed or reworked by man in conjunction with past construction grading, underground utility installation, farming or other previous activity at the site. Fill can be composed of different soil types from various sources and can contain debris from building demolition, organics, topsoil, trash, etc. The engineering properties of the fill depend primarily on its composition, density, and moisture content.

Typical Subsurface Profile

Below the surface materials (topsoil or asphaltic concrete pavement), the hand auger borings encountered existing fill, residual soils, and hand auger refusal material.

Three of the borings encountered existing fill. The fill was not completely penetrated in the 5-foot boring depths. 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 records are available, they should be provided to Terracon for use in our evaluation and development of geotechnical recommendations. We note that Terracon performed materials testing services when renovations and improvements were made to the park in 2014. We have no record of Terracon being present when the park was originally built in the 1990s.

Hand auger refusal occurred in all of the borings drilled at the MSE/Gabion wall. Hand auger refusal can occur on a wide variety of materials, ranging from bedrock, rock lenses, boulders to dense to hard soils, gravel, or relatively small rocks. Hand auger refusal occurred in residual soil in all of the borings drilled at the proposed MSE/gabion wall (Borings W-1 through W-4). We expect that hand auger refusal at the MSE/gabion wall may have been caused by cobbles or small boulders in residual soils.

Based on the results of the borings, subsurface conditions at the project site can be generalized as follows:

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Typical Subsurface Profile

Description Approximate Depth to Bottom of Stratum

Material Encountered Consistency/Density

Stratum 1A1 3 inches2 Topsoil --

Stratum 1B1 4½ - 6¼ inches Asphaltic Pavement --

Stratum 2 Not completely penetrated at 5 feet Fill - Sandy Silt (ML)3 Stiff to Hard

Stratum 3 Residuum was not completely penetrated.

Residuum – Lean Silty Clay (CL), Sandy Silt (ML), Silty Sand (SM)

Very Stiff Stiff to Hard

Medium Dense

Stratum 4 3 - 5½ feet Hand Auger Refusal4 --

1. Asphaltic concrete was present in the paved walking trails at Borings P-1 though P-6.

Topsoil was present at the surface in Borings W-1 through W-4, which were drilled along the proposed MSE wall.

2. Topsoil was encountered only in Borings W-1, W-1A, and W-2.

3. Fill was encountered only in Borings P-1, P-3 and P-5.

4. Hand auger refusal occurred only in the borings drilled at the proposed

MSE/Gabion wall (W-1 through W-4).

Specific conditions encountered at each boring location are indicated on the individual hand auger boring logs. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Details for each of the borings are presented on the boring logs included in the Exploration Results.

Groundwater

The hand auger boreholes were observed while drilling and after completion for the presence of groundwater. Groundwater was not observed in the borings while drilling, or for the short duration that the borings were allowed to remain open. Long term observations in piezometers or observation wells sealed from the influence of surface water are often required to define groundwater levels in materials of this type.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were drilled. In addition, perched water can develop over low permeability soil or rock strata. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

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Infiltration Rate

Infiltration rate testing was performed by Terracon subcontractor Applied Environmental Sciences, Inc. (AES) on November 6, 2024. The test results are presented in the Exploration Results section and are summarized in the following table:

Infiltration Rate Test Summary Test

Number Test Depth

(inches) Soil Type

Ksat (inches/hour)

Location

I-1 24 Sandy Loam / Residual 0.87 Enhanced Dry Swale I-2 24 Sandy Loam / Residual 0.15 Bioretention Area I-3 24 Sandy Loam / Residual 1.67 Enhanced Dry Swale I-4 24 Sandy Loam / Residual 18.83 Bioretention Area

Each infiltration test was performed at an approximate depth of 2 feet below existing grade. After completion of the infiltration test, each boring was extended to an approximate depth of 4 feet. This was done to determine if rock or groundwater was present within 2 feet of the test depth. No rock or groundwater was present in the extended boreholes.

Geotechnical Recommendations

MSE or Gabion Wall

A new mechanically stabilized earth (MSE) or gabion wall is planned to replace a slope along the paved path between Soccer Field 1 and Softball Field 2. The wall will be about 62 feet long and up to about 6 feet high. The western approximately 20-foot long section of the existing slope has an inclination of about 1(H):1(V). The inclination of the slope approaches 2(H):1(V) across its eastern approximately 42-foot long section. We note that 1(H):1(V) slopes are typically not stable in this geology unless they are in hard rock.

Dense residual silty sand was encountered in the majority of the hand auger borings drilled at the proposed MSE/Gabion wall. Hand auger refusal occurred at depths ranging from about 3 to 5½ feet in all of the borings drilled at the MSE/Gabion wall. Hand auger refusal can occur on a wide variety of materials, ranging from bedrock, rock lenses, boulders to dense to hard soils, gravel, or relatively small rocks. We expect that hand auger refusal at the MSE/gabion wall may have been caused by cobbles or small boulders in residual soils. We expect difficult excavation techniques will be required to excavate the dense soils and boulders from the reinforced zone of the wall and from proposed utility trenches in the area.

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The subsurface data obtained in the area was limited due to shallow hand auger refusal.

However, it may be possible to flatten the existing slope to 2(H):1(V). A 2(H):1(V) slope in the materials encountered should be stable.

An allowable foundation bearing pressure of 2,500 psf can be supported at the MSE/Gabion wall location. This should be field verified by the geotechnical engineer at the time of construction.

The wall design will be performed by others. Our scope of services did not include establishing soil parameters for use in wall design. If required by the wall designer, additional soil sampling and laboratory testing can be performed. The wall designer should perform both internal and global stability analyses of the proposed wall as part of their design.

Paved Multi-Use Trails

Distress, in the form of cracked “shoving” humps in the pavement surface, was observed across a considerable amount of the existing paved, multi-use trails (see Photograph Logs). We drilled six hand auger borings (designated Borings P-1 trough P-6) at random locations around the multi-use trails to check the consistency of the subgrade soils. The hand auger borings were drilled close enough to the pavement to check the thickness of the pavement. The thickness of the multi-use trail pavement ranged from about 4½ to 6¼ inches. We note the 60% drawings recommend a 6-inch thick section of asphaltic concrete for new multi-use trails. It is our opinion that this section will be sufficient for the proposed use. Subgrade preparation should be performed as recommended in the Earthwork section of this report.

Dynamic cone penetrometer (DCP) tests were performed at regular intervals in the hand auger borings to check the consistency and relative density of the subgrade soils. The soils encountered in the hand auger borings included stiff to hard sandy silt (ML) and very stiff silty lean clay (CL) and medium dense silty sand (SM). The soil consistencies and relative densities observed should be capable of supporting the proposed or existing pavement, provided the recommendations in the report are adhered to.

The damage appears to have been caused by shallow spreading roots typical of maple (and possibly other) trees that extend below the pavement. No soil subgrade issues were observed or encountered in the borings. We suggest that you consult with an arborist regarding removal of larger roots from beneath the proposed new pavement sections.

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Earthwork

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

Site Preparation

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

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

Mature trees are located within or near the disturbance area. Some of the trees will require removal at the onset of construction. Tree root systems can remove substantial moisture from surrounding soils. Where trees are removed, the full root ball and all associated dry and desiccated soils should be removed. The soil materials which contain less than 5 percent organics can be reused as engineered fill provided the material is moisture conditioned and properly compacted.

Where fill is placed on existing slopes steeper than 5H:1V, benches should be cut into the existing slopes prior to fill placement. The benches should have a minimum vertical face height of 1 foot and a maximum vertical face height of 3 feet and should be cut wide enough to accommodate the compaction equipment. This benching will help provide a positive bond between the fill and natural soils and reduce the possibility of failure along the fill/natural soil interface.

Although no evidence of fill or underground facilities (such as septic tanks, cesspools, basements, and utilities) was observed during the exploration and site reconnaissance, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

Subgrade Preparation

The subgrades of any multiuse trails to be paved should be proofrolled with a loaded tandem-axle dump truck after the pavement or topsoil has been removed. The proofrolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

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Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Existing Fill

As noted in Geotechnical Characterization, Borings P-1, P-3, and P-5 encountered previously placed fill to a depth of 5+ feet. The fill appears to have been placed and compacted in a controlled manner, and we have records to indicate the degree of compaction achieved during placement. We consider fill placed in a controlled manner with passing compaction tests to be an engineered fill.

Excavation

Based on the results of our hand auger borings, we anticipate that difficult to excavate materials, such as very dense soils, and possible boulders will be encountered during excavation of the reinforced zone of the MSE/Gabion wall. Excavation techniques will vary based on the weathering of the materials, fracturing and jointing in the rock, and the overall stratigraphy of the feature.

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. Any ripped PWR fragments can be re-used and mixed into engineered fill provided that it is pulverized to less than four 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.

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 foundation 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.

The descriptions provided below are a guide to conditions generally encountered in the region of the project site. Required excavation techniques will vary based on weathering of the materials to be excavated, and the fracturing, jointing and overall stratigraphy of the feature. Actual field conditions usually display a gradual weathering progression with poorly defined and uneven boundaries between layers of different materials. We

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Facilities | Environmental | Geotechnical | Materials 10 recommend that the following definitions for rock in earthwork excavation be included in bid documents:

Excavation Type Definition

Mass Excavation

Any material occupying an original volume of more than 1 cubic yard which cannot be excavated with a single-toothed 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).

Trench Excavation

Any material occupying an original volume of more than 1/2 cubic yard which cannot be excavated with a backhoe having a bucket curling rate of not less than 25,600 pounds, using a rock bucket and rock teeth (Caterpillar M318 or larger).

Removal of rock by blasting is expensive. Hence, control of quantities is important.

Survey methods are the best way to measure in-place rock quantities using cross-sectioning when the top of rock is identified by ripping or large excavator, as per the rock definition. However, there may be site constraints or conditions that will hinder the use of ripping or a large excavator to identify rock. Contractors may request that the soil overburden be left in-place, and the top of rock “profile” be estimated using an air-track drill. This approach is open to interpretation, and can result in greater rock excavation quantities and costs. Before the definition of rock is changed by using air-track drilling or other approach, the owner and design team should agree to the change while being aware of potential additional costs.

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.

Actual field conditions usually display a gradual weathering progression with poorly defined and uneven boundaries between layers of different materials. Rock levels in the Piedmont physiographic province can vary considerably in short horizontal distances and may be at higher or lower elevation between our boring locations.

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Fill Material Types

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

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

Soils used for structural and general fill should mee the following material property requirements :

Soil Type 1,2,3 USCS Classification

Acceptable Parameters (for Structural Fill)

Fine Grain CL and ML Liquid Limit less than 45 Plasticity index less than 25

Granular SP, SM, SC, and

SW

Less than 50% passing No. 200 sieve

On-Site Soils 4 CL, ML, and SM Liquid Limit less than 45 Plasticity index less than 25 Less than 50% passing No. 200 sieve

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

2. All fill should have a maximum dry density of at least 95 pounds per cubic foot (pcf) as determined by the standard Proctor test (ASTM D 698).

3. Any materials proposed as fill from off-site sources should be tested for compliance with these criteria before being hauled to the site.

4. Re-use of existing fill should meet the requirements noted above.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift Thickness

8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used

Same as structural fill

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Item Structural Fill General Fill

Minimum Compaction

Requirements 1,2

98% of max. dry density within 1 foot of floor slabs or finished pavement subgrades 95% of max. dry density below foundations and more than 1 foot below finished floor slabs or pavement subgrades

92% of max.

Water Content

Range 1,2,3 Fine Grain Soils: -2% to +3% of optimum Granular: -2% to +3% of optimum

As required to achieve min.

compaction requirements

1. Maximum density and optimum water content as determined by the standard Proctor test (ASTM D 698).

2. Fill should be tested for compaction and moisture content during placement.

Should the results of the in-place density tests indicate that the specified moisture or compaction requirements have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved.

3. Moisture levels should be maintained low enough to allow for satisfactory compaction to be achieved without pumping when proofrolled.

Utility Trench Backfill

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

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

On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors.

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Grading and Drainage

Adequate positive drainage should be provided during construction and maintained throughout the life of the development to prevent an increase in moisture content of the foundation, pavement and backfill materials. Surface water drainage should be controlled to prevent undermining of fill slopes and structures during and after construction.

It is recommended that all exposed earth slopes be seeded to provide protection against erosion as soon as possible after completion. Seeded slopes should be protected until the vegetation is established. Sprinkler systems should not be installed behind or in front of walls or near slopes.

Groundwater Considerations

Groundwater was not encountered in any of the borings during our exploration. Based on our understanding of the proposed development, we do no expect groundwater to impact construction. If groundwater is encountered during construction, some form of temporary or permanent dewatering may be required. Conventional dewatering methods, such as pumping from sumps, should likely be adequate for temporary removal of any groundwater encountered during excavation at the site. Well points would likely be required for significant groundwater flow, or where excavations penetrate groundwater.

Earthwork Construction Considerations

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

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

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

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

Construction Observation and Testing

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

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Any areas that do not meet the compaction specifications should be reworked to achieve compliance.

In areas of foundation excavations, the bearing subgrade should be evaluated by the Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical Engineer should prescribe mitigation options.

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

General Comments

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

Variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials 15 absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

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

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

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

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

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

P-1 through P-6 5 Paved multi-use trails

W-1 through W-4 3 - 5½

(All encountered hand auger refusal)

Proposed MSE/Gabion Wall

Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) and referencing existing site features.

Subsurface Exploration Procedures: Our subsurface exploration consisted of advancing hand auger borings. At regular intervals, our field engineer removed the hand auger and inserted a dynamic cone penetrometer (DCP) into the boring. After seating the cone, the DCP was driven 1.75 inches using the 15-pound hammer. The number of blows required to drive the DCP 1.75 inch is called the DCP penetration resistance. The DCP penetration resistance provides an index of soil strength and consistency when properly evaluated and correlated with Standard Penetration Test (SPT) N-values.

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

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

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

Photo 1: Shoving damage in multi-use trail pavement near Boring P-3. Many of these were observed throughout the park. Trees were recently cut here.

Photo 2: Single transverse crack in multi-use trail pavement at Boring P-2.

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

Photo 3: Pavement in good condition in multi-use trail near Boring P-1.

Photo 4: Transverse crack in multi-use trail pavement at P-5.

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

Site Location and Exploration Plans

Contents:

Site Location Exploration Plan A – Conceptual Plan Exploration Plan B – Aerial Photograph Exploration Plan C – MSE/Gabion Wall

Note: All attachments are one page unless noted above.

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Site Location

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

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Exploration Plan A – Conceptual Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES

MAP PROVIDED BY MICROSOFT BING MAPS

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Exploration Plan B – Aerial Photograph

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

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

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Exploration Plan C – MSE/Gabion Wall

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

December 12, 2024 | Terracon Project No. 49245278

Facilities | Environmental | Geotechnical | Materials

Exploration and Laboratory Results

Contents:

Boring Logs (P-1 through P-6, W-1 through W-4)

Infiltration Rate Testing Report

Bunten Road Park Improvements 3180 Bunten Road, Duluth, Georgia

11/26/2024 | Terracon Project No. 492455278

HAND AUGER BORING RECORDS

Boring P-1 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 6¼” ASPHATIC CONRETE 1’ 11

6¼” 5’ FILL – Sandy SILT (ML), orange, moist, stiff to very stiff 3’ 18

No groundwater encountered at the time of boring. 5’ 22 Boring Terminated at 5 feet

Boring P-2 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 5½” ASPHATIC CONRETE 1’ 12

5½” 3’ RESIDUUM – Sandy SILT (ML), orange, moist, stiff 3’ 10 3’ 5’ Silty SAND (SM), fine to medium, orange, moist, medium dense 5’ 16

No groundwater encountered at the time of boring.

Boring Terminated at 5 feet

Boring P-3 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 6¼” ASPHATIC CONRETE 1’ 9

6¼” 5’ FILL – Sandy SILT (ML), orange, moist, stiff 3’ 11

No groundwater encountered at the time of boring. 5’ 13 Boring Terminated at 5 feet

Boring P-4 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 5½” ASPHATIC CONRETE 1’ 23

5½” 5’ RESIDUUM – Lean Silty CLAY (CL), red, brown, moist, very stiff 3’ 19

No groundwater encountered at the time of boring. 5’ 26 Boring Terminated at 5 feet

11/26/2024 | Terracon Project No. 492455278

Boring P-5 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 4½” ASPHATIC CONRETE 1’ 12

4½” 5’ FILL – Sandy SILT (ML), sandy, red, brown, moist, stiff to hard 3’ 23

No groundwater encountered at the time of boring. 4’ 30/¾” Boring Terminated at 5 feet

Boring P-6 Drilling Date: 11/26/2024

Depth Description DCP Blow Counts From To Test Depth n

0 4½” ASPHATIC CONRETE 1’ 18

4½” 5’ RESIDUUM – Silty SAND (SM), fine to medium, moist, medium 3’ 12 dense, orange, yellow 5’ 17 No groundwater encountered at the time of boring.

Boring Terminated at 5 feet

11/26/2024 | Terracon Project No. 492455278

HAND AUGER BORING RECORDS

Boring W-1 Drilling Date: 11/13/2024

Depth Description DCP Blow Counts From To Test Depth n

0 3” TOPSOIL

3” 3’ RESIDUUM – SILTY SAND (SM), trace mica, fine to medium, orange, 0 15 moist, medium dense to dense 2’ 30/1½” No groundwater encountered at the time of boring.

Hand Auger Refusal at 3 feet Boring was offset approximately 25 feet east and redrilled as Boring W-1A

Boring W-1A Drilling Date: 11/13/2024

Depth Description DCP Blow Counts From To Test Depth n

0 3” TOPSOIL

3” 3’ RESIDUUM – SILTY SAND (SM), trace mica, fine to medium, orange, moist, dense 3’ 5½’ -with mica 4’ 30/1”

No groundwater encountered at the time of boring.

Hand Auger Refusal at 5½ feet

Boring W-2 Drilling Date: 11/13/2024

Depth Description DCP Blow Counts From To Test Depth n

0 3” TOPSOIL 0’ 6

3” 2’ RESIDUUM – SILTY SAND (SM), fine to medium, orange, moist, 2’ 30/1½” loose 2’ 4½’ Silty SAND (SM), trace mica, fine to medium, orange, moist, dense 4’ 30/1”

No groundwater encountered at the time of boring.

Hand Auger Refusal at 4½ feet

11/26/2024 | Terracon Project No. 492455278

Boring W-3 Drilling Date: 11/13/2024

Depth Description DCP Blow Counts From To Test Depth n

0 3’ RESIDUUM – SILTY SAND (SM), rocky, trace mica, fine to medium, 0 27 orange, moist, medium dense to dense 2’ 30/½”

No groundwater encountered at the time of boring.

Hand Auger Refusal at 3 feet

Boring W-4 Drilling Date: 11/13/2024

Depth Description DCP Blow Counts From To Test Depth n

0 4½ RESIDUUM – Silty SAND (SM), trace mica, fine to medium, orange, 0 12 moist, loose to medium dense. 2’ 30/1”

No groundwater encountered at the time of boring. 4’ 30/½” Hand Auger Refusal at 4½ feet

90-F Glenda Trace #327, Newnan, GA 30265 678.262.4020 / www.aesciences.net

November 7, 2024

Terracon Consultants, Inc.

2105 Newpoint Place, Suite 600 Lawrenceville, Georgia 30043

ATTN: Mr. E. Kelly Watson, P.E.

Senior Geotechnical Engineer

RE: Infiltration Rate Testing Bunten Road Park Tract 3180 Bunten Road Duluth, Gwinnett County, Georgia AES Project No.: 241103

Dear Mr. Watson:

Applied Environmental Sciences, Inc. (AES) has completed Infiltration Rate Testing on the above-referenced site. This report contains information regarding testing methodology and the results of the investigation.

Background

The Bunten Road Park Tract (hereinafter referred to as the Project Site) consists of a public park located at 3180 Bunten Road in the City of Duluth, Gwinnett County, Georgia. The Project Site study area consists of four proposed stormwater infiltration areas located on the Project Site (See Figure 1).

Methodology and Boring Hole Preparation

Saturated hydraulic conductivity (Ksat) is an indicator of water flow rate in soil and is a key parameter for studying water flow through a soil profile.