W912EP23B0008 ES_PR Puma Energy Dredging to -47 ft Flattened Slope Drained Stability.pdf
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- Attached to
- San Juan Harbor Construction and Maintenance Dredging, 44-Foot and 36-Foot Project, San Juan, Puerto Rico
- Solicitation number
- W912EP23B0008
About this file
This document is a geotechnical engineering report analyzing the stability of dredging near an existing oil platform structure in Guaynabo, Puerto Rico to a depth of 47 feet below mean lower low water. The analyses found that dredging to the proposed depth of 47 feet would require setting the dredge limit at a minimum of 28 feet from the face of the structure to achieve a minimum acceptable safety factor of 1.3 for slope stability under drained soil conditions, as required by the U.S. Army Corps of Engineers. The report presents the results of additional slope stability modeling conducted using drained soil strength parameters and recommends dredging no closer than 28 feet from the structure based on achieving a calculated safety factor of 1.34.
The related federal contract opportunity is a solicitation from the U.S. Army Corps of Engineers Engineering District Jacksonville for construction and maintenance dredging of designated areas within the Federal navigation channel and ports in San Juan, Puerto Rico. The work includes deepening several channels and basins to depths ranging from 36 to 47 feet below mean lower low water and widening a portion of one channel. All dredged material will be disposed of at the San Juan Ocean Dredge Material Disposal Site approximately 2.3 nautical miles from the entrance channel. The solicitation is inclusive of environmental monitoring and is divided into a base requirement and two options.
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3925 Coconut Palm Drive, Tampa FL 33619 ● Phone: (813) 620-3389 ● FAX: (813) 628-4008 Offices in: Bartow, Cocoa, Fort Lauderdale, Fort Myers, Miami, Orlando, Port St. Lucie, Sarasota, Tallahassee, Tampa, W. Palm Beach
January 6, 2023
P100-PTR-T41904 Tt
File No. : 22-55-9403
Doc. 07
Tetra-Tech
251 Calle Recinto Sur
San Juan, PR 00901
Attention: Ms. Renee Vandermause, PE
Mr. Fernando Pages, PE
Subject: Analyses of Dredge Effects to El. -47 feet
With Drained Soil Strength and Flattened Slope
Puma Energy – Guaynabo, Puerto Rico
Gentlemen:
As requested by Ms. Renee Vandermause, PE of Tetra Tech PR, Ardaman & Associates, Inc. performed additional analyses to evaluate the effect of dredging to El. -47 feet with a flattened lower slope near the
Puma Energy Chiksan Platform.
Project Information
The project site is located in Guaynabo, Puerto Rico in San Juan Bay. Analyses of lateral load performance of the existing Chiksan Platform piles with respect to dredging from about El. -36 feet to El. -46 feet for the US ACE harbor dredging project were performed and presented in a report dated March 29, 2022, and an updated report for drained soil strengths was provided on November 18, 2022.
In an email dated December 23, 2022, Ms. Nicole Bohaczyk, PE of the US ACE noted that a minimum safety factor of 1.3 “(per Section 3-4 of EM 1110-2-19-2) for the long-term loading conditions (drained conditions)”… Ms. Bohaczyk further noted “Based on the internal EN USACE memo subject titled
Programmatic Engineering Procedure for Dredging near Existing Structures”, a 25-feet offset from the existing structure may be the necessary offset required to meet the FS of 1.3 requirement.
Additional bathymetric surveying was performed November 8, 2022 to verify existing slope conditions.
The Attached Figure 1 shows the bathymetry at the Chiksan Platform, the most heavily loaded system at the Puma Energy marine facilities.
Additional Analyses
Additional slope stability analyses were performed using the Computer Program SLIDE 6.0, Spencer
Method, and calculated drained soil strength as requested by the US ACE. The attached Figure 1 shows the slope geometry and the critical potential slip surface from analyses for a dredge slope of 1V:2H from the face of the Chiksan Platform structure plus 5 feet to the proposed dredge elevation of -47 feet.
Figure 2 shows the output from the slope stability analyses with an elevation scale and soil properties table.
This figure shows the circular-arc surfaces for the 10 surfaces with the lowest safety factor and the critical potential slip surface. The critical potential slip surface had a calculated safety factor of 1.34.
Additional Analyses for Dredging to -47 ft.
Drained Soil Strength Analyses
Puma Energy, Guaynabo, Puerto Rico January 6, 2023
Recommendations
The standard of practice for the US ACOE dredging projects is to dredge with the cutterhead no closer than
5 feet to a structure, and the dredge equipment no closer than 3½ feet to the structure. As noted above, the
US ACE requires a safety factor of 1.3 when slope stability analyses are performed using drained strength soil properties. The analyses performed by Ardaman for this project using Drained Soil Strength
Parameters set the dredge limit at 28 feet from the face of the structure as shown on Figure 1 for a safety factor against slope failure equal to 1.34.
We appreciate the opportunity to work with you on this project. If you have any questions on the analyses or recommendations presented in this letter, please contact the undersigned at your convenience.
Very Truly Yours, Ardaman & Associates, Inc.
Martin E. Millburg, P.E. (FL) Ross T. McGillivray, P.E. (FL)
Senior Geotechnical Engineer Senior Consultant
Florida License No. 36584 Florida License No. 17920
G:\Projects\2022\22-9403\07-PR Puma Energy Dock Dredging to -47 ft Flattened Slope Drained Stability.docx
Attachments: Figure 1 – Post Dredge Slope Toe at -46 w/ 1’ Overcut – Chiksan Platform
Figure 2 – Slope Stability Analyses Results – Revised Slope
Ardaman & Associates, Inc.
Consulting Engineers in Soils, Hydrogeology, Foundations, and Materials Testing
DATE:
FILE NO. APPROVED BY:
DRAWN BY: CHECKED BY:RTM 01-04-2023
22-55-9403
R T
M
A rd a m a n
-9
-F
IG
-0
D re d g e S lo p e S ta b ili ty .d c d
FIGURE NO.Puma Energy - Chiksan Platform - Guaynabo, Puerto Rico
Tetra Tech Inc - San Juan, PiertoRico
Scale: 1-inch = 20 ft.
FL Firm Registration: 5950 FL Registration: 17920 (FL)
Post Dredge Slope Toe at -47 ft. - Stability
Sta. 2+50 (2020 c = 0 = 34°
T = 114.6 pcfγ c = 0 = 24°
T = 95.8 pcfγ c = 0 = 36°
T = 121 pcfγ c = 0 = 36°
T = 121 pcfγ c = 0 = 28°
T = 114.6 pcfγ
Chiksan Platform at Stations 2+00 and 2+50 Bathymetery - DRAINED SOIL STRNGTH
0 50 100 150 200
+10
-10
-20
-30
-40
-50
-60
E le v at io n
F ee t
M L
L W
Dredge Line, 28 ft. off-Structure
-47 ft. MLLW
Dredge Depth
N-1 (62)
Silt
Clay
LR
Silt w/ LR Fragments
LR
MB-1
0.0 ft. Elev. MLLW
28- Ft.
Existing Bathymetry
34.652° φ φ φ φ φ
Existing Slope
SF = 1.344
Proposed 2023 Dredge Slope (1V:2.1H)
Safety Factor for Proposed 2023 Dredge Slope (1V:2.1H)
Sec. B 11-17-22
Sec. A 11-17-22
1.3441.344
W
1.3441.344
Material Name Color Unit Weight
(lbs/�3)
Sat. Unit
Weight
(lbs/�3)
Strength Type Cohesion
(psf) Phi (deg)
So� Silt 95.8 95.8 Mohr-Coulomb 0.02 24
Drained Clay 114.6 114.6 Mohr-Coulomb 0.02 34
Decomposed Limestone 121 121 Mohr-Coulomb 0.02 36
Porous Limestone 114.6 114.6 Mohr-Coulomb 0.02 28
Safety Factor
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4.500
5.000
5.500
6.000+
-2
-4
-6
-8
-1
-80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280
ICE Soil Profile - Fully Drained Strengths
Ardaman & Associates, Inc.Drawn By: Ross T. McGillivray, PE File Name
Drained Slope3 -47 ft Flatten Slope Toe.slim Date: 01/04/2023
11/18/2022, 11:36:55 AM
Guaynabo, Puerto Rico, Puma Energy Chiksan Platform - Dredge to El. -47 at 28 ft. Setback from Platform
SLIDEINTERPRET 6.015
El ev at io n
- F ee t M
LL
W
10 Lowest Slkp Surfaces
Figure 2
| 2023-01-06T16:39:27-0500 | |
| State of Florida, Professional Engineer, License No. 17920. This item has been digitally signed and sealed by Ross T. McGillivray, PE on the date indicated here. Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies. | |
| Ross T McGillivray |
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