Soils Report
April 15, 2024
Mr. Trey Lewis
Lewis Coastal Homes and Renovations, LLC
7930 Champlain Drive
Wilmington, North Carolina 28412
Reference: Report of Seasonal High Water Table Estimation and Infiltration Testing
Manassas Site
Wilmington, New Hanover County, North Carolina
ECS Project No. 49.22856
Dear Mr. Lewis:
ECS Southeast, LLC (ECS) recently conducted a seasonal high water table (SHWT) estimation
and infiltration testing within the stormwater control measure (SCM) area(s) at 501-505 Manassas
Drive in Wilmington, New Hanover County, North Carolina. This letter, with attachments, is the
report of our testing. Field Testing
On April 15, 2024, ECS conducted an exploration of the subsurface soil conditions, in accordance
with the NCDEQ Stormwater Design Manual section A-2, at two requested locations shown on
the attached Boring Location Plan (Figure 1). ECS used GPS equipment in order to determine
the boring locations. The purpose of this exploration was to obtain subsurface information of the
in situ soils for the SCM area(s). ECS explored the subsurface soil conditions by advancing one
hand auger boring into the existing ground surface at each of the requested boring locations.
ECS visually classified the subsurface soils and obtained representative samples of each soil type
encountered. ECS also recorded the SHWT elevation observed at the time of the hand auger
borings. The attached Infiltration Testing Form provides a summary of the subsurface conditions
encountered at the hand auger boring locations.
The SHWT elevation was estimated at the boring locations below the existing grade elevation. A
summary of the findings are as follows:
Location SHWT
I-1 58 inches
I-2 66 inches
ECS has conducted two infiltration tests utilizing a compact constant head permeameter near the
hand auger borings in order to estimate the infiltration rate for the subsurface soils. Infiltration
tests are typically conducted at two feet above the SHWT or in the most restrictive soil horizon.
The tests were conducted at the approximate subgrade elevation of the proposed pervious
pavement SCM.
Report of SHWT Estimation and Infiltration Testing
Manassas Site
Wilmington, New Hanover County, North Carolina
ECS Project No. 49.22856
April 15, 2024
2
Field Test Results
Below is a summary of the infiltration test results:
Location Description Depth Inches/
hour
I-1 White fine to coarse SAND 18 inches 21.35
I-2 White fine to coarse SAND 12 inches 24.58
Infiltration rates and SHWT may vary within the proposed site due to changes in elevation, soil
classification and subsurface conditions. ECS recommends that a licensed surveyor provide the
elevations of the boring locations.
Closure
ECS’s analysis of the site has been based on our understanding of the site, the project information
provided to us, and the data obtained during our exploration. If the project information provided
to us is changed, please contact us so that our recommendations can be reviewed and
appropriate revisions provided, if necessary. The discovery of any site or subsurface conditions
during construction which deviate from the data outlined in this exploration should be reported to
us for our review, analysis and revision of our recommendations, if necessary. The assessment
of site environmental conditions for the presence of pollutants in the soil and groundwater of the
site is beyond the scope of this geotechnical exploration.
ECS appreciates the opportunity to provide our services to you on this project. If you have any
questions concerning this report or this project, please contact us.
Respectfully,
ECS SOUTHEAST, LLC
K. Brooks Wall W. Brandon Fulton, PSC, PWS, LSS
Project Manager Environmental Department Manager
bwall@ecslimited.com bfulton@ecslimited.com
910-686-9114 704-525-5152
Attachments: Figure 1 - Boring Location Plan
Infiltration Testing Form
GBA Document
APPROXIMATE BORING LOCATIONS
SCALE SHOWN ABOVE
Manassas Site
Wilmington, New Hanover County,
North Carolina
ECS Project # 49.22856
April 15, 2024
KBW
Figure 1– Boring Location Plan
Provided by: Google Earth
I-1
I-2
N
W
S
E
N
W
S
E
Infiltration Testing Form
Manassas Site
Wilmington, New Hanover County, North Carolina
ECS Project No. 49.22856
April 15, 2024
Location Depth USCS Soil Description
I-1 0-10” SM Brown fine SAND w/ silt
10”-66” SP White fine to coarse SAND
Seasonal High Water Table was estimated to be at 58 inches below the
existing grade elevation.
Test was conducted at 18 inches below existing grade elevation
Infiltration Rate: 21.35 inches per hour
Location Depth USCS Soil Description
I-2 0”-66” SP White fine to coarse SAND
Seasonal High Water Table was estimated to be at 66 inches below the
existing grade elevation.
Test was conducted at 12 inches below existing grade elevation
Infiltration Rate: 24.58 inches per hour
Geotechnical-Engineering Report
Important Information about This
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The following information is provided to help.
The Geoprofessional Business Association (GBA)
has prepared this advisory to help you – assumedly
a client representative – interpret and apply this
geotechnical-engineering report as effectively
as possible. In that way, clients can benefit from
a lowered exposure to the subsurface problems
that, for decades, have been a principal cause of
construction delays, cost overruns, claims, and
disputes. If you have questions or want more
information about any of the issues discussed below,
contact your GBA-member geotechnical engineer.
Active involvement in the Geoprofessional Business
Association exposes geotechnical engineers to a
wide array of risk-confrontation techniques that can
be of genuine benefit for everyone involved with a
construction project.
Geotechnical-Engineering Services Are Performed for
Specific Purposes, Persons, and Projects
Geotechnical engineers structure their services to meet the specific
needs of their clients. A geotechnical-engineering study conducted
for a given civil engineer will not likely meet the needs of a civil-
works constructor or even a different civil engineer. Because each
geotechnical-engineering study is unique, each geotechnical-
engineering report is unique, prepared solely for the client. Those who
rely on a geotechnical-engineering report prepared for a different client
can be seriously misled. No one except authorized client representatives
should rely on this geotechnical-engineering report without first
conferring with the geotechnical engineer who prepared it. And no one
– not even you – should apply this report for any purpose or project except
the one originally contemplated.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical-
engineering report did not read it in its entirety. Do not rely on an
executive summary. Do not read selected elements only. Read this report
in full.
You Need to Inform Your Geotechnical Engineer
about Change
Your geotechnical engineer considered unique, project-specific factors
when designing the study behind this report and developing the
confirmation-dependent recommendations the report conveys. A few
typical factors include:
• the client’s goals, objectives, budget, schedule, and
risk-management preferences;
• the general nature of the structure involved, its size,
configuration, and performance criteria;
• the structure’s location and orientation on the site; and
• other planned or existing site improvements, such as
retaining walls, access roads, parking lots, and
underground utilities.
Typical changes that could erode the reliability of this report include
those that affect:
• the site’s size or shape;
• the function of the proposed structure, as when it’s
changed from a parking garage to an office building, or
from a light-industrial plant to a refrigerated warehouse;
• the elevation, configuration, location, orientation, or
weight of the proposed structure;
• the composition of the design team; or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
changes – even minor ones – and request an assessment of their
impact. The geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical
engineer was not informed about developments the engineer otherwise
would have considered.
This Report May Not Be Reliable
Do not rely on this report if your geotechnical engineer prepared it:
• for a different client;
• for a different project;
• for a different site (that may or may not include all or a
portion of the original site); or
• before important events occurred at the site or adjacent
to it; e.g., man-made events like construction or
environmental remediation, or natural events like floods,
droughts, earthquakes, or groundwater fluctuations.
Note, too, that it could be unwise to rely on a geotechnical-engineering
report whose reliability may have been affected by the passage of time,
because of factors like changed subsurface conditions; new or modified
codes, standards, or regulations; or new techniques or tools. If your
geotechnical engineer has not indicated an “apply-by” date on the report,
ask what it should be, and, in general, if you are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying it. A minor amount of additional testing or
analysis – if any is required at all – could prevent major problems.
Most of the “Findings” Related in This Report Are
Professional Opinions
Before construction begins, geotechnical engineers explore a site’s
subsurface through various sampling and testing procedures.
Geotechnical engineers can observe actual subsurface conditions only at
those specific locations where sampling and testing were performed. The
data derived from that sampling and testing were reviewed by your
geotechnical engineer, who then applied professional judgment to
form opinions about subsurface conditions throughout the site. Actual
sitewide-subsurface conditions may differ – maybe significantly – from
those indicated in this report. Confront that risk by retaining your
geotechnical engineer to serve on the design team from project start to
project finish, so the individual can provide informed guidance quickly,
whenever needed.
This Report’s Recommendations Are
Confirmation-Dependent
The recommendations included in this report – including any options
or alternatives – are confirmation-dependent. In other words, they are
not final, because the geotechnical engineer who developed them relied
heavily on judgment and opinion to do so. Your geotechnical engineer
can finalize the recommendations only after observing actual subsurface
conditions revealed during construction. If through observation your
geotechnical engineer confirms that the conditions assumed to exist
actually do exist, the recommendations can be relied upon, assuming
no other changes have occurred. The geotechnical engineer who prepared
this report cannot assume responsibility or liability for confirmation-
dependent recommendations if you fail to retain that engineer to perform
construction observation.
This Report Could Be Misinterpreted
Other design professionals’ misinterpretation of geotechnical-
engineering reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a full-time member of the
design team, to:
• confer with other design-team members,
• help develop specifications,
• review pertinent elements of other design professionals’
plans and specifications, and
• be on hand quickly whenever geotechnical-engineering
guidance is needed.
You should also confront the risk of constructors misinterpreting this
report. Do so by retaining your geotechnical engineer to participate in
prebid and preconstruction conferences and to perform construction
observation.
Give Constructors a Complete Report and Guidance
Some owners and design professionals mistakenly believe they can shift
unanticipated-subsurface-conditions liability to constructors by limiting
the information they provide for bid preparation. To help prevent
the costly, contentious problems this practice has caused, include the
complete geotechnical-engineering report, along with any attachments
or appendices, with your contract documents, but be certain to note
conspicuously that you’ve included the material for informational
purposes only. To avoid misunderstanding, you may also want to note
that “informational purposes” means constructors have no right to rely
on the interpretations, opinions, conclusions, or recommendations in
the report, but they may rely on the factual data relative to the specific
times, locations, and depths/elevations referenced. Be certain that
constructors know they may learn about specific project requirements,
including options selected from the report, only from the design
drawings and specifications. Remind constructors that they may
perform their own studies if they want to, and be sure to allow enough
time to permit them to do so. Only then might you be in a position
to give constructors the information available to you, while requiring
them to at least share some of the financial responsibilities stemming
from unanticipated conditions. Conducting prebid and preconstruction
conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplines. That lack of understanding has nurtured
unrealistic expectations that have resulted in disappointments, delays,
cost overruns, claims, and disputes. To confront that risk, geotechnical
engineers commonly include explanatory provisions in their reports.
Sometimes labeled “limitations,” many of these provisions indicate
where geotechnical engineers’ responsibilities begin and end, to help
others recognize their own responsibilities and risks. Read these
provisions closely. Ask questions. Your geotechnical engineer should
respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study – e.g., a “phase-one” or “phase-two” environmental
site assessment – differ significantly from those used to perform
a geotechnical-engineering study. For that reason, a geotechnical-
engineering report does not usually relate any environmental findings,
conclusions, or recommendations; e.g., about the likelihood of
encountering underground storage tanks or regulated contaminants.
Unanticipated subsurface environmental problems have led to project
failures. If you have not yet obtained your own environmental
information, ask your geotechnical consultant for risk-management
guidance. As a general rule, do not rely on an environmental report
prepared for a different client, site, or project, or that is more than six
months old.
Obtain Professional Assistance to Deal with Moisture
Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, none of the engineer’s
services were designed, conducted, or intended to prevent uncontrolled
migration of moisture – including water vapor – from the soil through
building slabs and walls and into the building interior, where it can
cause mold growth and material-performance deficiencies. Accordingly,
proper implementation of the geotechnical engineer’s recommendations
will not of itself be sufficient to prevent moisture infiltration. Confront
the risk of moisture infiltration by including building-envelope or mold
specialists on the design team. Geotechnical engineers are not building-
envelope or mold specialists.
Copyright 2016 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly
prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission
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kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent
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