Public Safety Pavement Repairs and Site Improvements

Report of Subsurface Exploration
and Geotechnical Engineering Evaluation
Stair Settlement and Pavement Rehabilitation
Duluth Public Safety Center
Duluth, Georgia
Geo-Hydro Project Number 253175.20
Prepared for POND
February 17, 2026

Mr. Kevin Hendrix, P.E. February 17, 2026
Pond
55 Ivan Allen Jr. Boulevard
Suite 850
Atlanta, Georgia 30308
Report of Subsurface Exploration
and Geotechnical Engineering Evaluation
Stair Settlement and Pavement Rehabilitation
Duluth Public Safety Center
Duluth, Georgia
Geo-Hydro Project Number 253175.20
Dear Mr. Hendrix:
Geo-Hydro Engineers, Inc. has completed the authorized subsurface exploration for the above referenced
project. The scope of services for this project was outlined in proposal number 253175.P0 dated
December 30, 2025.
Project Information
The Duluth Public Safety Center is located at 3276 Buford Highway in Duluth, Georgia. Figure 1 in the
Appendix shows the approximate location of the facility.
The existing building is a one-story structure with a daylighted basement level. The northwest side of the
building includes stairs, which appear to be settling relative to the first floor elevation, and some stairs have
also tilted according to the information outlined in
the Structural Site Observation Report produced by
Pond dated July 8, 2025.
Stairs
The overall project will include stabilizing or
rehabilitating the steps, and rehabilitation of the
existing access drives and parking lots. The existing
parking lots and access drives, including landscape
islands and related curbing, occupy approximately
8,200 square yards. The documents provided to us
indicate some noticeable deformations including
settlement around a drop inlet, standing water due to
localized subsidence, and a large crack between the
drive aisle and the parking stalls. The annotated
aerial photograph to the right shows the approximate
property limits and current site conditions. The
photographs on the following page show the
condition of the stairs at the time of our field
exploration as well as evidence of exterior floor slab
subsidence at the building wall.
400 Chastain Center Boulevard, Suite 430 * Kennesaw, Georgia 30144
o: 770.426.7100 * www.geohydro.com

Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
Exploratory Procedures
The subsurface exploration consisted of three hand auger borings within the stairs area and five hand auger
borings within the parking lots and access drives. The borings were performed at the approximate locations
shown on Figure 2 in the Appendix. The boring locations were selected based on visual observations of
the stairs and pavement areas, and each test location was recorded using a handheld GPS unit.
Dynamic cone penetrometer testing (ASTM STP-399) was performed at select depths in the hand auger
borings. Soil samples obtained from hand auger boring operation were examined and classified in general
accordance with ASTM D2488 (Visual-Manual Procedure for Description of Soils). Soil classifications
include the use of the Unified Soil Classification System described in ASTM D2487 (Classification of Soils
for Engineering Purposes). The soil classifications also include our evaluation of the geologic origin of the
soils. Evaluations of geologic origin are based on our experience and interpretation and may be subject to
some degree of error.
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
Descriptions of the soils encountered, groundwater conditions, penetration resistances, and other pertinent
information are provided in the hand auger log included in the Appendix.
Regional Geology
The project site is located in the Southern Piedmont Geologic Province of Georgia. Soils in this area have
been formed by the in-place weathering of the underlying crystalline rock, which accounts for their
classification as "residual" soils. Residual soils near the ground surface that have experienced advanced
weathering frequently consist of red brown clayey silt (ML) or silty clay (CL). The thickness of this
surficial clayey zone may range up to roughly 6 feet. For various reasons, such as erosion or local variation
of mineralization, the upper clayey zone is not always present.
With increased depth, the soil becomes less weathered, coarser grained, and the structural character of the
underlying parent rock becomes more evident. These residual soils are typically classified as sandy
micaceous silt (ML) or silty micaceous sand (SM). With a further increase in depth, the soil eventually
becomes quite hard and take on an increasing resemblance to the underlying parent rock. When these
materials have a standard penetration resistance of l00 blows per foot or greater, they are referred to as
partially weathered rock. The transition from soil to partially weathered rock is usually a gradual one, and
may occur at a wide range of depths. Lenses or layers of partially weathered rock are not unusual in the
soil profile.
Partially weathered rock represents the zone of transition between the soil and the indurated metamorphic
rocks from which the soils are derived. The subsurface profile is, in fact, a history of the weathering process
that the crystalline rock has undergone. The degree of weathering is most advanced at the ground surface,
where fine-grained soil may be present. Conversely, the weathering process is in its early stages
immediately above the surface of relatively sound rock, where partially weathered rock may be found.
The thickness of the zone of partially weathered rock and the depth to the rock surface have both been
found to vary considerably over relatively short distances. The depth to the rock surface may frequently
range from the ground surface to 80 feet or more. The thickness of partially weathered rock, which overlies
the rock surface, may vary from only a few inches to as much as 40 feet or more.
Soil Test Boring Summary
Starting at the floor surface, hand auger borings HA-1, HA-2, and HA-3 encountered approximately 434 to
614 inches of concrete underlain by approximately 6 to 712 inches of graded aggregate base (GAB). Hand
auger borings HA-4 through HA-8 initially encountered approximately 2 to 312 inches of asphalt underlain
by approximately 314 to 712 inches of GAB. Reinforcing steel was encountered within the layer of GAB in
borings HA-1 and HA-2, resulting in a boring offset.
Beneath the surface materials, all hand auger borings encountered fill materials extending to depths ranging
from approximately 112 to greater than 10 feet. Boring HA-3 was terminated in fill at a depth of
10 feet, while borings HA,4, HA-5, and HA-6 were terminated in fill materials at depth of 4 feet. The fill
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
materials were classified as clayey sand and silty sand. Dynamic cone penetrometer resistances recorded
in the fill ranged from 4 to 17 blows per increment.
Beneath the fill materials, hand auger borings HA-1, HA-2, HA-7, and HA-8 encountered residual soils
typical for the Piedmont region. The residual soils were classified as silty sand with dynamic cone
penetrometer resistances ranging from 9 to greater than 25 blows per increment.
At the time of the exploration, groundwater was not encountered in the hand auger borings. The borings
were backfilled with soil cuttings after the groundwater check and patched with fresh concrete or cold patch
asphalt as appropriate. It should be noted that groundwater levels will fluctuate depending on yearly and
seasonal rainfall variations.
For more detailed descriptions of subsurface conditions, please refer to the hand auger logs included in the
Appendix.
Hand Auger Boring Summary
Concrete Asphalt GAB Depth to Hand Hand Auger Depth to
Bottom of Fill
Boring Thickness Thickness Thickness Auger Refusal Termination Groundwater
(feet)
(inches) (inches) (inches) (feet) Depth (feet) (feet)
HA-1 6 NE 6 2 NE 4 NE
HA-2 614 NE 612 4 NE 6 NE
HA-3 434 NE 712 >10 NE 10 NE
HA-4 NE 312 712 >4 NE 4 NE
HA-5 NE 214 314 >4 NE 4 NE
HA-6 NE 2 412 >4 NE 4 NE
HA-7 NE 234 634 112 NE 4 NE
HA-8 NE 314 634 112 NE 4 NE
All Depths in this Summary Table are Approximate
NE: Not Encountered
GAB: Graded Aggregate Base
VISUAL PAVEMENT EVALUATION
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
This pavement evaluation revealed the pavement on site to be degraded to varying levels. The asphalt
thickness ranged from approximately 2 to 312 inches. Beneath the asphalt, all pavement borings
encountered 314 to 712 inches of crushed stone base materials. Minimal to moderate longitudinal cracking
and some alligator cracking were observed throughout the parking lot footprint. Longitudinal cracking is
typically a function of age. Alligator cracking is mostly caused by repetitive loading, and generally
indicates that the pavement has been overstressed either by heavy vehicle traffic (vehicles with a relatively
high gross vehicle weight) or high frequency of traffic, often both. Furthermore, relatively thin asphalt
pavement as sampled in the hand auger borings will have a shorter service life. An additional contributor
to pavement distress involves a deteriorated or relatively weak soil subgrade.
The pictures above, facing the southwest corner of the parking lot, show minor pavement distress (left), and
alligator cracking typical of pavement overstress and failure (right). The pavement distress patterns
throughout the facility suggest a combination of thin asphaltic concrete and localized traffic concentration
as the main causes of distress. The absence of noticeable pavement rutting or potholes are indicators of a
relatively stable subgrade.
Evaluations and Recommendations
The following evaluations and recommendations are based on the information available on the existing
construction, the data obtained from the hand auger borings, our observations on site, and our experience
with soils and subsurface conditions similar to those encountered at this site. Because the borings represent
a statistically small sampling of subsurface conditions, it is possible that conditions may be encountered
during supplemental exploration or during repairs/grouting that are substantially different from those
indicated by the test borings. In these instances, adjustments to the remedial work may be necessary.
* All hand auger borings encountered fill materials extending to depths ranging from approximately 112
feet to greater than 10 feet. Boring HA-3 was terminated in fill at a depth of 10 feet, while borings
HA,4, HA-5, and HA-6 were terminated in fill materials at depth of 4 feet. The fill underlaying the
concrete stairs varies in depth and consistency, ranging from about 2 feet to greater than 10 feet, and
from loose to moderately firm.
* The Structural Site Observation Report by Pond notes that noticeable differential settlement can be
observed between the stairway slab and the building structure located in proximity of boring HA-3.
Boring HA-3 encountered relatively deeper and looser soils in comparison with borings HA-1 and
HA-2.
* Historic, publicly available aerial photos from Google Earth show that the Public Safety Center was
constructed in 2005. It is our opinion that the slow rate of differential settlement along the stair-on-
grade slab is likely the result of ground subsidence caused by consolidation of the fill underlying the
slab. Differential settlement between the building and the entrance floor slabs and elements supported
at grade is aggravated by the fact that the building is supported at a greater depth, and its
settlement/deformation patterns are different from those experienced by the fill materials at grade
matching the first floor level, which is elevated.
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
* A formal grouting program intended to improve the fill materials underlying the stairway slab may be
considered to address the root cause and provide long-term stability. It is imperative to acknowledge
that variations will exist in the quantity of grout needed and the number of injection points required
across different areas. Geo-Hydro emphasizes the importance of entrusting these decisions to a
competent firm such as Gibson's Pressure Grouting Service, Jensen's Pressure Grouting Services, or
other experienced specialty contractor. Engaging a company well-versed in the intricacies of the
specific site conditions and the principles of effective grouting aligns with industry best practices, and
will ensure a tailored application of grouting to achieve reliable rehabilitation and longevity.
* Other options concerning removal and replacement of concrete panels and subgrade stabilization, or
crack sealing as described in Pond's report are viable for rehabilitation purposes. For this project, the
invasiveness and cost of the intervention is likely to be commensurate with the longevity of the repair.
* Our pavement evaluation revealed the pavement on site to be degraded to varying levels. The asphalt
thickness ranged from approximately 2 to 312 inches. Beneath the asphalt, all pavement borings
encountered 314 to 712 inches of crushed stone base materials. Minimal to moderate longitudinal
cracking and some alligator cracking were observed throughout the parking lot footprint.
* The more intense pavement distress patterns throughout the facility suggest a combination of thin
asphaltic concrete and localized traffic concentration as the main causes of distress. In areas where
only longitudinal cracks are present, it is likely that the pavement distress is mostly age-related. The
absence of noticeable pavement rutting or potholes are indicators of a relatively stable subgrade.
* Based on the results of the pavement coring, hand auger borings, and our observations, we recommend
implementing full-depth reclamation (FDR) to rehabilitate the pavements. FDR using Portland cement
is a favorable option for pavement rehabilitation/reconstruction. FDR involves pulverizing the existing
asphalt pavement, crushed stone base materials, and some soil subgrade, applying a predetermined
amount of Portland cement and water, and shaping and compacting the mixture into a stable base
course. A new asphalt wearing course can then be placed on the stabilized FDR section.
The following sections provide general recommendations regarding these issues and other geotechnical
aspects of the project.
Existing Fill Materials
Fill materials were encountered in all hand auger borings extending to depths ranging from approximately
112 to greater than 10 feet. There are several important facts that should be considered regarding existing
fill materials and the limitations of subsurface exploration.
* The quality of existing fill materials can be highly variable, and test borings are often not able to detect
all of the zones or layers of poor-quality fill materials.
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
* The interface between existing fill materials and the original ground surface may include a layer of
organic material that was not properly stripped off during the original grading. If such organic layers
are encountered during construction, it may be necessary to "chase out" the organic layer by excavating
the layer along with overlying soils.
* Subsurface exploration is simply not capable of disclosing all conditions that may require remediation.
Suitability of Excavated Material for Reuse as Structural Fill
Based on the results of test borings and our observations, residual soils and fill materials on site appear to
be suitable for reuse as structural fill. Soft, unstable fill soils free of deleterious materials may be reusable
after routine moisture adjustment.
It is important to establish as part of the construction contract whether soils having elevated moisture
content will be considered suitable for reuse. We often find this issue to be a point of contention and a
source of delays and change orders. From a technical standpoint, soils with moisture contents wet of
optimum as determined by the standard Proctor test (ASTM D698) can be reused provided that the moisture
is properly adjusted to within the workable range. From a practical standpoint, wet soils can be very
difficult to dry in small or congested sites, and such difficulties should be considered during planning and
budgeting. A clear understanding by the general contractor and grading subcontractor regarding the reuse
of excavated soils will be important to avoid delays and unexpected cost overruns.
Structural Fill
We offer the following recommendations for any fill or backfill that may be required for the project.
Materials selected for use as structural fill should be free of organic debris, waste construction debris, and
other deleterious materials. The material should not contain rocks having a diameter over 4 inches. It is
our opinion that the following soils represented by their USCS group symbols will typically be suitable for
use as structural fill and are usually found in abundance in the Piedmont: (SM), (ML), and (CL). The
following soil types are typically suitable but are not abundant in the Piedmont: (SW), (SP), (SC), (SP-SM),
and (SP-SC). The following soil types are considered unsuitable: (MH), (CH), (OL), (OH), and (Pt).
Laboratory Proctor compaction tests and classification tests should be performed on representative samples
obtained from the proposed borrow material to provide data necessary to determine acceptability and for
quality control. The moisture content of suitable borrow soils should generally be no more than 3
percentage points below or above optimum at the time of compaction. Tighter moisture limits may be
necessary with certain soils.
Suitable fill material should be placed in thin lifts. Lift thickness depends on the type of compaction
equipment, but a maximum loose-lift thickness of 8 inches is generally recommended. The soil should be
compacted by a self-propelled sheepsfoot roller. Within small excavations such as in utility trenches, we
recommend the use of "wacker packers" or "Rammax" compactors to achieve the specified compaction.
Loose lift thicknesses of 4 to 6 inches are recommended in small area fills.
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
We recommend that structural fill be compacted to at least 95 percent of the standard Proctor maximum
dry density (ASTM D698). The upper 12 inches of subgrade soils should be compacted to at least 98
percent of the standard Proctor maximum dry density (ASTM D698). Additionally, the maximum dry
density of structural fill should be no less than 90 pcf. Geo-Hydro should perform density tests during fill
placement.
Earth Slopes
Temporary construction slopes should be designed in strict compliance with OSHA regulations. The
exploratory borings indicate that most soils at the site are Type B and Type C as defined in 29 CFR 1926
Subpart P. This dictates that temporary construction slopes in fill materials, or any soil type below the
groundwater level, for excavation depths of 20 feet or less should be no steeper than 1.5H:1V. Excavations
in residual soils above the groundwater level should be no steeper than 1H:1V. Temporary construction
slopes should be closely observed on a daily basis by the contractor's "competent person" for signs of mass
movement: tension cracks near the crest, bulging at the toe of the slope, etc. The responsibility for
excavation safety and stability of construction slopes should lie solely with the contractor.
We recommend that extreme caution be observed in trench excavations. Several cases of loss of life due
to trench collapses in Georgia point out the lack of attention given to excavation safety on some projects.
We recommend that applicable local and federal regulations regarding temporary slopes, and shoring and
bracing of trench excavations be closely followed.
Formal analysis of slope stability was beyond the scope of work for this project. Based on our experience,
permanent cut or fill slopes should be no steeper than 2H:1V to maintain long term stability and to provide
ease of maintenance. The crest or toe of cut or fill slopes should be no closer than 10 feet to any foundation
or to the edge of any pavement that will support truck traffic. The crest or toe should be no closer than 5
feet to the edge of any pavements supporting cars or light truck traffic or parking. Erosion protection of
slopes during construction and during establishment of vegetation should be considered an essential part of
construction.
Pavement Rehabilitation - Full-Depth Reclamation
Full-depth reclamation (FDR) using Portland cement is a viable option for pavement
rehabilitation/reconstruction. FDR involves pulverizing the existing asphalt pavement, crushed stone base
materials, and some soil subgrade, applying a predetermined amount of Portland cement and water, and
shaping and compacting the mixture into a stable base course.
FDR has several advantages and benefits including recycling the existing pavement materials to reduce
waste, relatively short construction schedule, and a high-quality base material for support of the new asphalt
pavement.
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Stair Settlement and Pavement Rehabilitation * Duluth Public Safety Center - Duluth, Georgia
Project Number 253175.20
The disadvantages of FDR include the need to engage a qualified and experienced specialty contractor with
experienced personnel and the appropriate equipment capable of performing the work. Also, dust is created
during the addition of cement to the pulverized material.
We recommend obtaining pricing information to perform FDR by blending Type I Portland cement at a
rate of 60 pounds per square yard for a mix depth of 10 inches. This amendment rate is based on
incorporating the asphalt and crushed stone base into the reclaimed mix base.
We recommend that the depth of underground utilities be verified in areas where utility lines may be located
within the proposed 10-inch thick FDR treatment zone. Where the utilities are shallow enough to be
affected by the FDR process, the utilities should be exposed, and the conditions should be evaluated on a
case-by-case basis.
Non-structural shrinkage cracking of the FDR base will likely occur and some of this shrinkage cracking
may reflect through to the asphalt surface. To reduce the potential for shrinkage cracking of the FDR base
to reflect back through the finished surface, we recommend pre-cracking (microcracking) the finished
surface in accordance with the Portland Cement Association Guide to FDR with Cement by running a
vibratory compactor across the surface after initial curing and prior to asphalt placement.
We recommend that you engage us to perform verification testing of the cement application rate prior to
implementation of FDR. This is an integral part of the FDR construction process which will allow
adjustments to the cement application rate based on actual samples of treated materials from the site. It is
likely that cement application rate lower than 60 pounds per square yard will be viable, which would reduce
the overall cost of FDR construction. High rates of cement application will exacerbate shrinkage cracking.
Additionally, field testing of the FDR treated zone should be performed to verify thickness and compaction.
At your request, we can provide a detailed proposal outlining our recommended laboratory and field testing
services for FDR, and associated costs.
For planning purposes, we recommend the following FDR sections:
Parking Stalls and Automobile Traffic Only
Material Thickness (inches)
Asphaltic Concrete 9.5mm (Type II) Superpave 2
FDR mix (Asphalt, Crushed Stone, and Subgrade)
10
Approximately 6% Portland cement by weight
Main Traffic Lanes and Areas Subject to Truck/Bus Traffic
Material Thickness (inches)
Asphaltic Concrete 9.5mm (Type II) Superpave 112
Asphaltic Concrete 19mm Superpave 2
FDR mix (Asphalt, Crushed Stone, and Subgrade)
10
Approximately 6% Portland cement by weight
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