Table Of ContentDRAFT DETAILED PROJECT REPORT
TANGIER ISLAND JETTY
ACCOMACK COUNTY, VIRGINIA
SECTION 107
NAVIGATION STUDY
APPENDIX A
ENGINEERING, DESIGN AND COST ESTIMATES
U.S. Army Corps of Engineers
Norfolk District
803 Front Street
Norfolk, Virginia 23510
Tangier Island Jetty Section 107 Study, Accomack County, Virginia
TANGIER ISLAND JETTY, ACCOMACK COUNTY, VIRGINIA SECTION 107,
NAVIGATION STUDY, DRAFT DETAILED PROJECT REPORT
APPENDIX A
ENGINEERING, DESIGN AND COST ESTIMATES
TABLE OF CONTENTS
PURPOSE…………………………………………………………………………..………A-1
ATTACHMENTS
A1. MODELING STUDY FOR TANGIER ISLAND JETTIES
A2. GEOTECHNICAL ENGINEERING DESIGN ANALYSIS REPORT
A3. DETAILED COST ESTIMATES
June 10 2015 Page A‐i
Tangier Island Jetty Section 107 Study, Accomack County, Virginia
APPENDIX A
ENGINEERING, DESIGN AND COST
ESTIMATES
PURPOSE
The purpose of this appendix is to provide detailed information concerning the
engineering design (coastal and geotechnical engineering) related aspects of the study
area and are shown in two reports attached to this appendix. Detailed cost estimates
are also included.
The technical report entitled Modeling Study for Tangier Island Jetties,
Tangier Island, Virginia (EDRC/CHL TR-14-8) was published in March 2015. This
report includes the coastal engineering and design analysis, and detailed design of the
coastal structures for five alternative plans. The report also includes the details of the
modeling efforts performed for the project. The report was written by the Project
Delivery Team (PDT) members from the Engineering Research Development Center
(ERDC), Coastal Hydraulics Laboratory (CHL). The United States Army Corps of
Engineers (USACE), Norfolk District, performed shoreline, nearshore, and bathymetry
surveys in support of ERDC’s engineering design and modeling efforts. Bathymetric
surveys are referenced to Mean Lower Low Water (MLLW). Planimetric features,
developed by stereo-photogrammetric methods taken from aerial photographs flown in
2001 by Earth Data, also support the technical report. The horizontal coordinates are
in U.S. survey feet referred to the Virginia State Plane Coordinate System (South
Zone) and are based on North American Datum 1983. Norfolk District also provided
ERDC survey data available for Tangier Island from recent LIDAR (LIght Detection
And Ranging) survey. As mentioned in the first attachment of this appendix, at the
time of the coastal modeling, geotechnical data of the soil at the footprint of the
proposed structure(s) was not available. However, since the development of ERDC
report, the Geotechnical analysis has shown that 15 inches of settlement could occur at
the proposed project area. To account for this, the final jetty(s) design shall be raised
one foot to compensate for the settlement. Other data and images used to complete the
coastal engineering design and modeling are referred in the first attachment of this
appendix.
June 10 2015 A‐1
Tangier Island Jetty Section 107 Study, Accomack County, Virginia
The Geotechnical Engineering Design Analysis Report of this appendix
discusses the geotechnical investigation and foundation analysis results. USACE,
Norfolk District partnered with Savannah District to perform a subsurface
investigation for the Tangier Island Jetty project. Savannah District and Norfolk
District collected split spoon and vibracore samples during the week of 20 May 2013.
Due to the shallow water conditions, the drillers used a barge-mounted cone
penetration test rig to collect the samples as well as a crane mounted vibracore core
sampler. Penetrations and vibracores were performed in the vicinity of the proposed
breakwater/jetty, to support the jetty design analysis. Samples collected during the
subsurface investigation are classified according to the Unified Soils Classification
System. Selected samples were analyzed for Atterberg Limits, Gradations and
Moisture Content. Savannah District was not able to obtain an undisturbed sample due
to the type of material encountered and the method necessary for collecting samples in
such shallow waters. Refer to the attached geotechnical report for boring logs, grain
size distribution graphs and Atterberg limits results. A foundation analysis was also
performed based on the assumption that the proposed jetties are underlain by high
tensile strength woven geotechnical fabric. Based on the foundation analysis, bearing
capacity and stability will not be a problem. However, there is a potential that up to
fifteen (15) inches of settlement could occur in the clay layer. It is recommended that
the top elevation of the structure be raised to compensate for the settlement. Proper
subgrade preparation will also reduce settlement and allow for controlled settlement.
The detailed Cost Estimates of this project alternatives and used a basis for the
economic analysis, shown in the third attachment of Appendix A.
The Coastal and Geotechnical reports both mention that the preferred
engineering plan is Alternative 4. This is due to the modeling results showing that
Alternative 4 had the highest percentage of wave reduction. As it was mentioned in the
modeling report, all the alternatives provided some form of wave reduction benefits. A
comparison of the alternatives showed that the three that include a south spur jetty
(Alternatives 3, 4, and 5) outperformed the other two (Alternatives 1 and 2, with no S
spur) in reducing wave energy in the channel. However, based off of the economic
analysis (see Appendix B) the tentatively selected plan is Alternative 1. This plan
June 10 2015 A‐2
Tangier Island Jetty Section 107 Study, Accomack County, Virginia
maximized net National Economic Development benefits and was selected as the
National Economic Development plan. Choosing Alternative 1 over the Alternative 4
does not affect the coastal modeling and geotechnical calculations and results. Also,
the lengths of the jetty(s) structure mentioned in the main portion report is different
from that of the Appendix A. As mentioned in the modeling report, the land of where
the original north jetty tie-in into (which was what was modeled) had eroded severe. It
was decided to move the tie-in further north and therefore slightly increasing the length
of the north jetty.
June 10 2015 A‐3
ATTACHMENT A-1
MODELING STUDY FOR TANGIER ISLAND
JETTIES
8
-
4
1
-
R
T
L
H
C
/
C
D
R
E
Coastal Inlets Research Program
Modeling Study for Tangier Island Jetties,
Tangier Island, Virginia
Zeki Demirbilek, Lihwa Lin, Donald L. Ward, and David B. King March 2015
y
r
o
t
a
r
o
b
a
L
s
c
i
l
u
a
r
d
y
H
d
n
a
l
a
t
s
a
o
C
Approved for public release; distribution is unlimited.
The U.S. Army Engineer Research and Development Center (ERDC) solves
the nation’s toughest engineering and environmental challenges. ERDC develops
innovative solutions in civil and military engineering, geospatial sciences, water
resources, and environmental sciences for the Army, the Department of Defense,
civilian agencies, and our nation’s public good. Find out more at
www.erdc.usace.army.mil.
To search for other technical reports published by ERDC, visit the ERDC online library
at http://acwc.sdp.sirsi.net/client/default.
Coastal Inlets Research Program ERDC/CHL TR-14-8
March 2015
Modeling Study for Tangier Island Jetties,
Tangier Island, Virginia
Zeki Demirbilek, Lihwa Lin, Donald Ward, David B. King
Coastal and Hydraulics Laboratory
U.S. Army Engineer Research and Development Center
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
Final report
Approved for public release; distribution is unlimited.
Prepared for U.S. Army Engineer District, Norfolk
803 Front Street, VA 23510
Under Coastal Inlets Research Program
ERDC/CHL TR-14-8 ii
Abstract
This report documents numerical wave and flow modeling for evaluation
of the jetties on a shallow draft navigation channel on Tangier Island, VA,
located in Chesapeake Bay. Because it is heavily used by the local fishing
fleet, the U.S. Army Engineer District, Norfolk (CENAO) maintains the
Tangier Island boat canal. CENAO is considering the construction of
structures to protect the western entrance of the channel and reduce the
wave energy in the lee of the structures, and asked the U.S. Army Engineer
Research and Development Center (ERDC), Coastal and Hydraulics La-
boratory (CHL) to perform a numerical modeling study to investigate how
waves and hydrodynamics would be affected by structures, to identify the
optimal location for the structures, and to develop a preliminary structure
design. The primary goal of the study was to develop a quantitative esti-
mate of waves and wave reduction in the canal for a relative comparison of
alternatives investigated and for the preliminary structural design calcula-
tions.
CMS-Wave, a spectral wave model, was used to estimate waves in Chesa-
peake Bay and propagate waves into the entrance channel and boat canal.
The numerical modeling results indicated that maximum wave energy re-
duction inside the canal was obtained using a dogleg jetty connecting to
the north shoreline and a spur on the south shoreline.
DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes.
Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products.
All product names and trademarks cited are the property of their respective owners. The findings of this report are not to
be construed as an official Department of the Army position unless so designated by other authorized documents.
DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.
Description:surveys in support of ERDC's engineering design and modeling efforts. Bathymetric breakwater/jetty, to support the jetty design analysis. Samples
