20211818 Ver 2_More Information Received_20220511

Strickland, Bev
From: Kris Bass <[e-mail]>
Sent: Wednesday, May 11, 2022 9:36 AM
To: Cohn, Colleen M
Cc: Phillips, George L CIV USARMY CESAW (USA)
Subject: Re: [External] RE: [URL Verdict: Unknown][Non-DoD Source] Re: Hsu Pond Spillway
Repairs / Raleigh / Wake County / SAW-2016-01125 / Request for Additional
Information
Attachments: 9313 Macon Road 7.27.20 (S).pdf; hsu_photos.pdf
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Report Spam.
I am responding with some answers to each in blue.
On Fri, May 6, 2022 at 4:32 PM Cohn, Colleen M <[e-mail]> wrote:
Good afternoon Kris,
I'm reviewing the application for the Hsu Pond Spillway Repairs, and have some additional questions.
1. In the 4/6/22 response to the USACE, you state that the temporary wetland impact is "related to stone that will
be placed in the water". And the PCN states that the temporary impact area will "remain after project
completion". I can't quite tell from the drawings, but my understanding is that this is a permanent impact, but
not a loss of waters. Can you please provide additional details?
This particular wetland area is slightly confusing. The area is in -line with the receiving stream coming out of the pond.
This area will require some stone addition at the very end of the spillway repair. The stone will be a permanent addition,
but will submerged similar to a stream restoration cross vane or riffle structure. My interpretation of this was based on
similar stream structures. Please advise whether I should change this impact to permanent.
1. Plan sheet 3 of 5 says "Extend Pipe or Abandon Backfill Area". Once more for clarity, the project is proposing to
close off the pipe and backfill around it, and not to extend it, correct?
Correct, the pipe will be closed after all work is complete. This text was from an earlier version of plans and should have
been changed.
1.
2. Please provide a copy of the geotechnical engineering report that is referenced in the 4/6/22 response.
attached.
1

1.
2. Will the "broken concrete/debris" be removed from the spillway?
Yes. You will see this in the photos.
1.
2. Do you have some pictures of the area?
Yes. I am attaching a brief set of photos. I'm not sure they really do justice to the scale of the damage.
1.
Thanks,
Colleen Cohn
Environmental Specialist II
North Carolina Department of Environmental Quality
Division of Water Resources
Raleigh Regional Office
380o Barrett Drive
Raleigh, NC 27609
Office: 919-791-4258
E-mail correspondence to and from this address may be subject to the
North Carolina Public Records Law and may be disclosed to third parties.
From: Phillips, George L CIV USARMY CESAW (USA) <[e-mail]>
Sent: Thursday, May 5, 2022 7:53 AM
To: [e-mail]
Cc: Cohn, Colleen M <[e-mail]>

Subject: [External] RE: [URL Verdict: Unknown][Non-DoD Source] Re: Hsu Pond Spillway Repairs / Raleigh / Wake
County / SAW-2016-01125 / Request for Additional Information
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Hey Kris,
I apologize. I missed that email. I have it now and will review the information today. If I need anything else I will let you
know.
Lyle Phillips
Regulatory Specialist
US Army Corps of Engineers
CE-SAW-RG-R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Phone: [phone], Ext. 25.
Fax: [phone]
Email: [e-mail]
We would appreciate your feedback on how we are performing our duties. Our automated Customer Service Survey is
located at https://regulatory.ops.usace.army.mil/customer-service-survey/ . Thank you for taking the time to visit this
site and complete the survey.
From: Kris Bass <[e-mail]>
Sent: Wednesday, May 4, 2022 3:46 PM
To: Phillips, George L CIV USARMY CESAW (USA) <[e-mail]>
Cc: Cohn, Colleen M <[e-mail]>
Subject: Re: [URL Verdict: Unknown][Non-DoD Source] Re: Hsu Pond Spillway Repairs / Raleigh / Wake County / SAW-
2016-01125 / Request for Additional Information
3

Did you have a chance to review my response document? I was thinking I responded to each item but am happy to
provide more.
I only suggested a site visit if you agree it will be helpful or if questions remain.
Kris
On Wed, May 4, 2022, 2:56 PM Phillips, George L CIV USARMY CESAW (USA) <[e-mail]>
wrote:
Mr. Bass,
I can make a site visit if it will help but I will still need RFAI addressed. I have to be able to document that the proposed
activities are in compliance with the permit conditions.
Lyle Phillips
Regulatory Specialist
US Army Corps of Engineers
CE-SAW-RG-R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Phone: [phone], Ext. 25.
Fax: [phone]
Email: [e-mail]
We would appreciate your feedback on how we are performing our duties. Our automated Customer Service Survey is
located at https://regulatory.ops.usace.army.mil/customer-service-survey/ . Thank you for taking the time to visit
this site and complete the survey.
4

From: Kris Bass <[e-mail]>
Sent: Wednesday, April 20, 2022 1:05 PM
To: Phillips, George L CIV USARMY CESAW (USA) <[e-mail]>
Cc: Cohn, Colleen M <[e-mail]>
Subject: [URL Verdict: Unknown][Non-DoD Source] Re: Hsu Pond Spillway Repairs / Raleigh / Wake County / SAW-
2016-01125 / Request for Additional Information
Hello,
I just wanted to check back on this and see if additional information or discussion is needed.
thank you,
Kris
On Wed, Apr 6, 2022 at 10:32 AM Kris Bass <[e-mail]> wrote:
Thank you for the prompt and detailed review. I am providing the attached document as a draft with additional
information. I will be happy to edit this or include additional based on your response.
Many of the impacts associated with this project are the result of a delineation surrounding a severely damaged
pond. I think a site visit would go a long way towards understanding the conditions at the time of the delineation, the
conditions now, and the benefits of what we are proposing.
Please let me know your thoughts. I am available by phone and for meetings of all types!
Kris
On Tue, Apr 5, 2022 at 4:03 PM Phillips, George L CIV USARMY CESAW (USA) <[e-mail]>
wrote:
Mr. Bass,
5

I have reviewed the above referenced project and need the following comments/questions addressed to evaluate
the proposed activities.
1. The PCN states that "the design is the minimum required to provide needed improvements." The need for
improvements is not disputed; however, it is unclear if the project is avoiding and minimizing to the
maximum extent practicable per general condition 23 (a) and (b). Please provide additional information to
support each impact. For example, what is the justification for the expansion of the embankment slope?
How will the proposed open water impacts "improve the safety of the embankment?"
2. It appears that the proposed impacts for spillway repair will result in permanent stream impacts. Based on
of review of the plans the proposed activities consist of the permanent discharge of fill material within a
stream channel.
3. It does not appear that the proposed impacts for the spillway repair meet the intent of NWP 3. NWP is for
repair of previously authorized fill. Based on the information provided it appears the boulder step pool
activity is a fill that was not previously authorized.
4. Will the proposed activities raise the level of the ordinary pool for the pond?
Please submit the above information within 30 days of receipt of this Notification or we may consider your
application withdrawn and close the file. Please call or email ([e-mail]) me if you have any
questions.
Please let me know if you have any questions or concerns.
Lyle Phillips
Regulatory Specialist
US Army Corps of Engineers
CE-SAW-RG-R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Phone: [phone], Ext. 25.
Fax: [phone]
Email: [e-mail]
6

We would appreciate your feedback on how we are performing our duties. Our automated Customer Service Survey
is located at https://regulatory.ops.usace.army.mil/customer-service-survey/ . Thank you for taking the time to
visit this site and complete the survey.
Kris Bass Engineering
p: 919.960.1552
e: [e-mail]
w: www.kbeng.org
Kris Bass Engineering
p: 919.960.1552
e: [e-mail]
w: www.kbeng.org
Kris Bass Engineering
p: 919.960.1552
e: [e-mail]
w: www.kbeng.org

TerraTech Engineers, Inc.
NC Engineering Corp. C-1356 | NC Geology Corp. C-560
4905 Professional Court, Raleigh, NC 27609
[phone]
Geotechnical Engineering
Environmental Consulting
Construction Materials Testing
July 27, 2020

NV5 Engineers & Consultants
Attn: Mr. Michael Allen, P.E.
[e-mail]

Report of Geotechnical Engineering Evaluation
9313 Macon Road
Raleigh, North Carolina
Our Project Number 121-20-101640

Gentlemen:

As requested, representatives of TerraTech Engineers, Inc. were recently present to perform an evaluation
of the existing dam embankment at the eastern side of the pond at the above referenced site. The scope
of our engineering evaluation is presented within our proposal number 8150-N dated January 10, 2020.
In general, the purpose of our evaluation was:

1. To perform measurements of the approximate length, height, and downstream slope gradient of
the dam embankment.
2. To document the current condition of the dam including vegetative cover and any readily visible
signs of failure including tension cracks at the crest of the dam, bulging at the toe of the dam,
sloughing on the embankment slope, erosion on the dam face, over-topping of the dam, and other
signs that may indicate slope instability.
3. To document any readily visible signs of seepage on the dam face and at the toe of the downstream
slope of the dam.
4. To perform a total of three (3) soil test borings to planned depths of 10 feet to evaluate subgrade
soil and ground water conditions at selected locations along the crest of the dam and the
downstream toe of the dam.
5. To perform a preliminary slope stability analysis of the dam utilizing available topographic
information and the results of our observations and testing at the site.
6. To provide a preliminary discussion of possible repair methods if our evaluation indicates that
repairs are necessary.

This evaluation is not intended to provide an evaluation of the design of the pond, nor any components or
design criteria of the pond. Our scope of services did not include surveying of the soil test boring locations
or dam components. Locations are based on information provided by others and our visual observations.
We note that we were not present during original construction of the pond and have not been provided
construction documentation related to the pond.

OBSERVATIONS AND FIELD EVALUATIONS

Our evaluations began with our observations and testing in the field as well as our review of available
aerial photographs and topographic information on the Wake County Geographic Information System
(GIS) website. Based on our records review and observations at the site, we understand that the pond ,
which has a surface area of approximately 4.75 acres, is located on the southeastern portion of the parcel
at 9313 Macon Road in Raleigh, North Carolina. An overview of the general site location is provided as
the attached Figure 1. The subject dam embankment extends approximately 200 linear feet along the

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Geotechnical Engineering
Environmental Consulting
Construction Materials Testing
eastern side of the pond and along portions of the southern side of the pond, adjacent to Macon Road. The
dam embankment has a maximum height of approximately 15 to 18 feet along the eastern side of the pond
and a maximum height of approximately 5 feet along the southern side of the pond. The crest of the dam
embankment ranges between approximately 5 and 15 feet wide. Based on our observations at the site,
the crest of the dam embankment was generally covered with grass and other low-lying vegetation, while
the downstream slope was generally covered with a combination of trees and low-lying vegetation (see
Photograph 1). At the time of our site visit, the water level in the pond was approximately 48 to 60 inches
below the crest of the upstream slope. However, at the southern end of the eastern dam embankment, we
only observed approximately 6 inches of freeboard relative to the water level at the time of our visit.
Based on our observations and measurements at the site as well as our review of information available on
the Wake County GIS website, the gradient of the downstream slope of the dam generally ranged from
2(H):1(V) to 2.5(H):1(V).

A spillway was present at the northern end of the eastern dam embankment. At the time of our visit, water
was flowing over the spillway. Rip-rap was present within the spillway and remnants of a concrete channel
liner were present, however significant portions of the concrete liner appeared to have fractured and were
deposited downstream of the spillway. Significant erosion of the underlying soils was also observed in
the area of the existing spillway (See Photographs 2 and 3). Our review of historical aerial photographs
suggests that significant erosion of the soils in the area of the spillway has been occurring since at least
2013. There was no visible evidence of a riser structure within the pond, however, we did observe a
handle which reportedly operates a gate valve for the principal spillway pipe. At the approximate center
of the toe of the eastern downstream embankment, we observed a principal spillway pipe. At the time of
our site visit, we did not observe water flowing through the principal spillway pipe. A large scarp,
approximately 6 to 8 feet wide and approximately 5 feet deep, was present above the spillway pipe. Large
quantities of soil, below the scarp, appeared to have either been previous excavated or lost to erosion or
slope movement. Isolated tension cracks were observed along the downstream slope, above the referenced
scarp. At the time of our visit, water appeared to be seeping through the soil below the scarp, adjacent to
the principal spillway pipe (Photographs 4 and 5).

Other than the previously identified scarps and apparent seepage locations, we observed no additional
indications of slope failure such as tension cracks in the ground surface near the crest of the embankment
on either the upstream or downstream slope faces.

We performed hand auger borings at selected locations along the crest of the eastern dam to evaluate
subgrade soil and ground water conditions. The approximate locations of our hand auger borings are
shown on the attached Figure 2. The hand auger borings were performed to planned depths of
approximately 10 feet below the existing ground surface. However, Hand Auger Boring #3 encountered
refusal at approximately 7 feet below the existing ground surface. The soils encountered in our hand auger
borings generally consisted existing fill soil comprising sandy micaceous silts (USCS Classification: ML)
and sandy clays (USCS Classification: CL).

Dynamic cone penetrometer testing (ASTM STP-399) was performed at selected intervals throughout our
hand auger borings. The penetration resistances, combined with the soil classifications, provide an
indication of the shear strength characteristics of the soils used to construct the dam. The results of our
dynamic cone penetrometer testing are provided in the following Table 1.

Page 3

Geotechnical Engineering
Environmental Consulting
Construction Materials Testing
B-1 B-2 B-3
0 4 5 6
1 5 6 12
2 8 7 10
3 6 9 8
4 8 12 6
5 5 8 7
6 9 8 Refusal
7 6 6 -
8 4 6 -
9 2 4 -
10 1 3 -
Depth
(ft)
Dynamic Cone Penetrometer
Resistance (blows per
Table 1: Summary of Dynamic Cone Penetrometer Results

Dynamic cone penetrometer resistances throughout the encountered existing fill soils ranged from
1 to 12 blows per increment. The average penetration resistance was approximately 6.5 blows per
increment.

Ground water was not encountered in our hand auger borings at the time of our testing. However, soil
test borings B-1 and B-2, which were performed at the crest of the dam embankment, encountered moist
to very moist soils from depths of 7 feet to the boring termination depths. The hand auger borings wer e
backfilled with grout upon completion of our boring operations. Therefore, long term ground water
readings were not available.

A more detailed description of the soils encountered in our hand auger borings is provided in the attached
Test Boring Record.

CONCLUSIONS AND RECOMMENDATIONS

The results of our observations at the site indicate to us that shallow to moderate-depth slope failure may
have already occurred at the location of the principal spillway pipe along the downstream slope of the
dam. The presence of water discharging over the spillway, the apparent erosion of the soils in the area of
the spillway, and our observations that water was not flowing through the principal spillway pipe, all
indicate to us that the principal spillway is likely not functioning and that the spillway has been
functioning as the primary discharge point for the pond. The presence of water discharging below the
principal spillway pipe, in conjunction with the moist to very moist soils encountered in the lower portions
of HAB-1 and HAB-2, indicate to us that it is likely that water is currently seeping through portions of
the dam. Highly micaceous silt soils were encountered in the upper 3 to 5 feet of our soil test borings.
These soils are not typically considered suitable for use in dam embankment construction due to their
relatively low shear strength. Additionally, the dynamic cone penetration resistances of the soils
encountered throughout our soil test borings were lower than those which would be expected for similar
soils compacted to 95% of the standard Proctor maximum dry density. It is our opinion that the soils
placed within the dam embankment may not have been adequately compacted at the time of construction.

Page 4

Geotechnical Engineering
Environmental Consulting
Construction Materials Testing

We performed a preliminary slope stability analysis of the downstream dam embankment using soil and
topographic conditions derived from our visual observations, our soil test borings, and our review of
information available on the Wake County GIS website. The results of our slope stability analysis
indicated that, even in areas where slope movement was not readily visible, the current factor of safety
against slope instability is less than the industry standard minimum acceptable factors of safety against
slope instability of a dam embankment.

For the reasons described above, it is our opinion that repairs to the dam structure are currently necessary.
In our opinion, the principal spillway pipe and the spillway channel should be repaired or replaced and
the portions of the downstream slope where the dam is greater than or equal to 8 feet should be flattened
to exhibit a slope gradient no steeper than 3(H):1(V). In locations where the embankment is less than 8
feet in height, we recommend a slope gradient of 2.5(H):1(V) or flatter. A North Carolina licensed
Professional Engineer should be consulted for a detailed dam repair plan which complies with current
regulations of the NC Dam Safety Section of the North Carolina Department of Environmental Quality.
The detailed repair plan should provide, among others, specifications related to: the size and support
methodologies for the replacement spillway pipe; the design of the spillway repair or replacement; the
design of the replacement dam embankment; and the proper methodologies to be utilized for breaching
the dam and preventing the development of a rapid drawdown condition. The design professional in
responsible charge of the dam repair plan should also review the low freeboard conditions at the southern
end of the eastern dam embankment to ensure that flooding of the adjacent Macon Road does not occur.

While re-establishing the dam embankment and flattening the downstream slope, it is important to note
that soils suitable for dam construction should be “benched in” utilizing a series level lifts no greater than
8 inches, by loose measurement. The soils should be compacted to at least 95% of the standard Proctor
maximum dry density and within 3% of the optimum moisture content. We recommend that our
representative be present during dam repair in order to verify compliance with the approved dam repair
plan and to observe and perform periodic testing during the placement of structural fill soils.

We appreciate the opportunity to provide this geotechnical engineering evaluation related to the dam
embankment at 9313 Macon Road. If you have questions concerning this information, please do not
hesitate to contact us.

Sincerely,

TerraTech Engineers, Inc. (C-1356)

Justin R. Pescosolido, P.E. Glen A. Malpass, Ph.D, P.E.
Geotechnical Engineer Principal Geotechnical Engineer

JRP/sk
Project:9313 Macon Road Dam Evaluation
Raleigh, North Carolina
Our Project Number 121-20-101640
Figure 1: Site Location Overview
TerraTech Engineers, Inc. (C-1356)
4905 Professional Court
Raleigh, NC 27609
919-876-9799
N
Legend:
Red Line = Approximate Property Boundary
9313 Macon
Road
Project:9313 Macon Road Dam Evaluation
Raleigh, North Carolina
Our Project Number 121-20-101640
Figure 2: Site Layout and Approximate Soil Test Boring
Locations
TerraTech Engineers, Inc. (C-1356)
4905 Professional Court
Raleigh, NC 27609
919-876-9799
N
Legend:
Yellow Line = Approximate Downstream Slope Crest Location
Blue Line = Approximate Downstream Slope Toe Location
Green Arrows = Approximate Boring Locations
B-1
B-2
B-3
Symbols and Nomenclature
Sample Identification
Classification of soil samples was performed in general accordance with
ASTM D-2488 and ASTM D-2487.The soil classifications include our
evaluation of the geologic origin of the soils.
Dynamic cone penetration resistance (ASTM STP-399)
Number of blows (25) without penetrating the test increment
Weight of Hammer, Weight of Rods
Water table at least 24 hours after drilling
Water table one hour or less after drilling
Atterberg Limits test performed
Grain size test performed
Proctor compaction test performed
Natural moisture content (percent)
25+
A
GS
P
18
W-O-H, R
Drilling Procedures
Soil sampling and dynamic cone penetration testing performed in accordance
with ASTM D-1452 and ASTM STP-399.The dynamic cone penetration
resistance is the number of blows of a 15 pound hammer falling 20 inches to
drive a 1.5 inch diameter cone 1.75 inches.
TEST BORING RECORD
Water Level 24 hr.:
Water Level 1 hr.:
Boring Number:
Project Number:
Date Drilled:
TerraTech Engineers, Inc.
4905 Professional Court
Raleigh, NC 27609
Depth
2
4
6
8
10
12
14
Description Elev.Water
Level Blow Counts
Topsoil (Approximately 3 inches)
Dark red and brown fine sandy micaceous silt
(ML)
Brown and red fine sandy clay (CL)
BORING TERMINATED
3.0
10.0
4
5
8
6
8
5
9
6
4
2
1
5 10 15 20 25Blows per Increment
Dynamic Cone Penetrometer Resistance
Boring Backfilled Upon Completion
Not Encountered
HAB-1
121-20-101640
6/27/20
(FILL)
(FILL)
TEST BORING RECORD
Water Level 24 hr.:
Water Level 1 hr.:
Boring Number:
Project Number:
Date Drilled:
TerraTech Engineers, Inc.
4905 Professional Court
Raleigh, NC 27609
Depth
2
4
6
8
10
12
14
Description Elev.Water
Level Blow Counts
Topsoil (Approximately 3 inches)
Tan and orange fine to medium sandy
micaceous silt (ML)
Dark red and brown fine sandy micaceous silt
(ML) (FILL)
Brown and red fine sandy clay (CL) (FILL)
BORING TERMINATED
1.0
5.0
10.0
5
6
7
9
12
8
8
6
6
4
3
5 10 15 20 25Blows per Increment
Dynamic Cone Penetrometer Resistance
Boring Backfilled Upon Completion
Not Encountered
HAB-2
121-20-101640
6/27/20
(FILL)
TEST BORING RECORD
Water Level 24 hr.:
Water Level 1 hr.:
Boring Number:
Project Number:
Date Drilled:
TerraTech Engineers, Inc.
4905 Professional Court
Raleigh, NC 27609
Depth
2
4
6
8
10
12
14
Description Elev.Water
Level Blow Counts
Topsoil (Approximately 2 inches)
Tan and orange fine to medium sandy
micaceous silt (ML) (FILL)
Dark red and brown fine sandy micaceous silt
(ML) (FILL)
Brown and red fine sandy clay (CL) (FILL)
HAND AUGER REFUSAL
1.0
4.0
6.0
6
12
10
8
6
7
5 10 15 20 25Blows per Increment
Dynamic Cone Penetrometer Resistance
Boring Backfilled Upon Completion
Not Encountered
HAB-3
121-20-101640
6/27/20
View looking upstream towards spillway. Foreground area is “wetland” shown at the bottom of the spillway. Spillway is badly e roded as seen
on sideslopes and fallen trees
Closer view looking up the destroyed spillway. Entire area will be stabilized with natural boulder step pools and all sideslopes repaired and
vegetated.
View inside the destroyed spillway area