Submittal #2 Abutment Protection.pdf

JG(ION EN
G
REYNOLDS
COMPANY, INC.
SINCE'19M0
Date: 1-2-2024
TO: Town of Cary RE:Symphony Lake Dredging
Eric Kulz Architect Project #:GG1188
CC: Schnabel Project 22210081
Schnabel Engineering
Brendan Stepek
Submittal #: 2
Submittal Title: Abutment Protection for Existing Greenway
Spec Section #: 210000-1 Related
FOR: 0 Approval ❑Your Records ❑ Comment ❑ Other
Contractor: H.G. Reynolds Co., Inc.
❑✓ Approved/Approved As Noted
❑ Rejected
❑ Revise & Resubmit
❑ For Record
❑ Prior to Approval
Reviewed By: Bert Long
Signature:
Date: 1-2-2024

rH.(G
" 0
REYNOLDS
Z/N C
January 2, 2024
Mr. Eric Kulz
Town of Cary
316 N.Academy Street
Cary, NC 27513
RE: Symphony Lake Dredging
Abutment Protection
H.G. Reynolds Co., Inc. offers the following submittal for the protection of the existing greenway
trail bridge abutment. As noted in the engineer's report that follows,there was substantial bank erosion
that took place in two heavy rain events before the end of the year. Following submittal is our
suggestion for protecting the abutments of the greenway trial bridge that is along our access road for
the dredging operation. It is our opinion that leaving the gabions along the creek bank would be of
lasting benefit to the town. Work on the higher reaches of the bank will be removed and dressed up
Please review this submittal and advise acceptance. If there are questions, please let me know.
Sincerely,
H.G. Reynolds Co., Inc.
fie +Lo*xg
Building a better community. I P.O. Box 209 Henderson, NC 27536 1 [phone]
www.hgreynolds.net

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Existing abutment Z
Depth of Headwall Headwall _0
Existing Greenway Bridge Footing Unknown };
Existing "approach" & a a
"Bearing" pad of �, o =
abutment i
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Estimated 2 yr storm 6
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from proximate gauge data c :3 •= c~
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and observation of Dec. 2023 Q W
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Storms Fill In areas E, zM
0 AObserved regular creek between gabions and N y U
stage headwall with rip-wrap
a p pp o z
g a
28 oz/sqyd geotextile (magenta) 3 0
under gabion m
anchored in to bank with 20quantitiy s2 °
platipus anchors each side C
Approximate creek bottom •N
inspected 6 Dec 23 Conservative soil mass lost
in December storms from bank W v N_
1 (orange hatch) co J CL
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install 7 quantity 3' by 1' by 6' gabions filled CD W
with 4%8" diameter rip-wrap each bank of bridge. pp
14 total � (n U
Greenway Bridge Abutment Scour Hog ring all gabions together. 0 }' z
Protrude upstream on bank from bridge IT-- C Q
ProtectionSection Recomended Post December 1.5 gabions width or 4.5'. Q� (n
2023 Storm and Erosion Events o E
NOTE Cz C
A) This Drawing to be read with accompanying report and plan drawings. W O N D
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8) Final preparation to be inspected by Little Environments PLLC prior to loading. QD
C) Engineer to approve all products prior to purchase or procurement. \ 00
N
D) Gabions placed where bank was eroded(See orange hatching) in last storm will
not impede flow under bridge. CARo�'i�� J U
E) Apply 28 oz/sq yard geotextile as shown for permanent application or install ES s/
geotextile for temporary projectapplication.
I z
without a - W
g p pp lication. ' 0 85 X
111
Scale: 1 "=2' � J O Confirm all measurements on site with tape

Approximate Edge of Bank Prior to \ +` 1 cA,///o/�i T_
December 23 Storms ���
Existing ������ s
0
Bearing Abutment Pad SEAL
Es �oy''�: _
Existing Bridge Deck owes (n
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Existing Concrete Abutment Head Wall
12" Thick CL CD
Affix, Join, & Close Backfill and gabions a Z _
gabions with hog rings to intimately contact c I:
on 6" spacings abutment headwall!
CD
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a d 14'�}" ° Temporary Gabions, Filled with Rip-wrap a) tM CD
°' ` 3 Each Side of each abutment i6 y a
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12�.4?, d. O 3
n q °° ° a a Line void Inside Abutment with 24 oz/sq yard geotextile Q i
,a and fill with 301b sand bags. Voids in between sand bag and O a
a 1 0 and abutment wall to be filled with washed screenings y U =
and sprayed with water to compact such that U
° q ° screenings and sand bags are intimate with abutment o z
° d 8' to 10' upto the top elevation of the abutment headwall. (n
general radius Cover surface of screening with 28 oz/sq yard y L)
° geotextile and blanket over to surface of concrete bearing and m N
d °d ° approach pads. • • L
°
°
Backfill and gabions 28 oz/sq yard .� N
to intimately contact Backfill and gabions Geotextile Atop J
abutment headwall! to intimately contact M J (n
abutment headwall! Temp. Bridge N J
Existing Existing Greenway Bridge Abutment Bearing Surface NO m
Approach Pad Temporary Earth Pressure Shoring Existing asphalt greenway N z
Plan View, Typical Both Sides
301b sand bags and voids filled Q
with washed screenings M (n
Temporary Gabions, Filled with Rip-wrap C
Note 3 Each Side of each abutment 4"x4" Bridge N
A) This Drawing to be read with accompanying report and plan drawings. Bearing LLI (�
B) Final preparation to be inspected by Little Environments PLLC prior to loading. Pad
C) Engineer to approve all products prior to purchase or procurement. > 00 N
Exiting Abutment
Headwall J 00 U
Existing Terrain Surface Compact surface with W CO z
Varies mechanical tamper
Line pit and surface X
of 41 8� with Curve of existing terrain with 0
Typical Section A 28 oz/sq yard geotextile, m �
Scale: 1 =4� Continuous up and over O
See This Drawing bearing pad and to top J
Confirm all measurements on site with tape
of abion.

Little Environments PLLC
Engineers&Environmental Consultants 22 Dec 2023
Memo:
Symphony Lake Greenway Bridge Abutment Erosion and
Sanitary Sewer Pipe Deflection in this Last Rain Storm Event
13 pages
To whom it may concern,
This letter is to express preliminary concerns relating to (a) greenway bridge abutment
erosion, (b) existing concrete abutment cracking on the greenway bridge that was exacerbated
by the erosion, and (c) deflection of the sanitary sewer just downstream from the greenway
bridge along with basal erosion around the sanitary sewer concrete stanchions.
Little Environments is working with HG Reynolds in the process of consulting on the
temporary crossing across the top of the existing greenway bridge that would bear atop the
existing abutments and associated concrete pads. Little Environments had a site meeting this
morning with HG Reynolds at the location. In the last two weeks we have had two intense rain
events that are likely in and around the 2 year storm event. I, Joseph Little PE, visited the sites
on the 4tn, 6tn, 14t", and 22nd. Between the 6t" and the 4t" there was the first storm event.
Between the 14t" and the 22nd there was the second event. From retrieved stream gauge data
as well as observing wash lines on the bank of the stream one can see that the water level rose
about 2' in additional depth in each event.
During this time there has been significant bank loss under the bridge. Water reached the
greenway bridge abutments. The following was observed:
1) Erosion of the soil adjacent the abutments by 1-2 horizontally on both sides. This
creates significant concern of destabilizing the greenway abutments regardless of future
traffic.
2) Significant cracking of the bearing beam on the western side of the greenway, enough
to be a structural concern. It appears this has been attempted to be repaired in the past
with grout.
3) Further the ductile iron sanitary sewer line just downstream from this location has
deflected at the retainer ring by more than 1" creating the risk of sewage release into
the creek. The stanchions on either side of the creek, supporting the sanitary sewer
crossing all seem to be undermined or eroded around.
It is my opinion that point No 3 above needs to be addressed immediately due to the potential
consequences of sewage release.
1

Little Environments PLLC
Engineers&Environmental Consultants 22 Dec 2023
It is my opinion that the abutments of the greenway bridge need to be protected from scour
immediately as not to add insult to injury of the compromised concrete abutment. Given that
the abutments I already significantly cracked, it is likely to crack further in the state it is already
in and when used as the bearing pad for the future temporary bridge to be placed atop. This
considered, it is not unsafe to use as the bearing pad given the following: (A) the soil
surrounding the abutment is protected from scour by secured means such as gabion mattresses
(Rip-wrap alone is insufficient) and (B) plans are made ahead of time to replace or significantly
repair the concrete abutments after use as the bearing pad for the temporary bridge.
I have attached photos from each date listed above. A site inspection is recommended to better
observe the issues of concern as the photos do not completely do problems at hand justice.
Sincerely, \�����'�CAS///��
0 DES S j0 !,.r
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Little Environments PLLC
Engineers&Environmental Consultants 22 Dec 2023
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Significant Cracking
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Engineers&Environmental Consultants 22 Dec 2023
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Erosion of west bank
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Erosion of bank

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Engineers&Environmental Consultants 22 Dec 2023
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Erosion of West Bank, Note 2" Dia Root Exposed
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EnvironmentsLittle PLLC
DECEngineers&Environmental Consultants 22 Dec 2023
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Engineers&Environmental Consultants 22 Dec 2023
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Little Environments PLLC
Engineers&Environmental Consultants 22 Dec 2023
DEC 4/6 Photos
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West bank
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Engineers&Environmental Consultants 22 Dec 2023
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