SW I MBDS-G MBDS-D A MDA08 Buoy MBDS-C MBDS-E MBDS-F MBDS ... · • Develop a model of impact...
Transcript of SW I MBDS-G MBDS-D A MDA08 Buoy MBDS-C MBDS-E MBDS-F MBDS ... · • Develop a model of impact...
!(
!(
!(!(
!(
!(
!( AMBDS-G
MBDS-F
MBDS-A
MBDS-EMBDS-C
MBDS-B
MBDS-D MDA08 Buoy
2008 C
ap D
emo Area
Approximate area of high barrel
density
FADS
IWS
MBDS Boundar
y
The Industrial Waste Site (IWS)
1958 Saturday Evening Post
Nuclear Waste Site at the IWS
Container Density
Photos: The Massachusetts Bay Industrial Waste Site: A Preliminary Survey of Hazardous Waste Containers and an Assessment of Seafood Safety. NOAA 1996.
Potential Boston Harbor Deep Draft Project
Approximately 10 million cubic yards of improvement material
Potential for Use
• Large volume of material
• Close to IWS
Concerns for Use
• Highly consolidated Boston Blue Clay
• Capping cannot interfere with dredging and disposal operations
Conceptual Model
Capping Approach
Capping Demonstration Project
Objectives
• Assess the ability to precisely direct material placement at the IWS from a production–level dredging project
• Assess the impact of the disposal process on ambient seafloor sediments
• Assess any differences in impact disturbance between disposals placed on ambient seafloor and those placed on a berm of disposal material.
Sequential Disposal and Monitoring
Monitoring Operations
• Bathymetry/Backscatter/Side‐Scan Sonar
• Sub‐bottom Profiling
• Sediment‐Profile & Plan‐View Imaging
• Sediment Coring
Disposal Operations
• Directed placement of split‐hull scows
• Individual placements and sequential, overlapping placements
84
86
87
88
85.5
83.5
84.5
86.5
87.5
88.5
85
85
Line 0
Single impact ~250 ft diameter
Placement
• Single placement impacts were measureable on the seafloor
• Impact points were very close to target coordinates (often within the length of the scow)
• Targeted placement did not affect disposal operations
Crater Characteristics
Disposal Profiles
-85.40 100 200 300
-83.0
-84.0
-82.2
-85.0
Elev
atio
n (m
)
Bathymetric Profile (25X Vertical Exaggeration)
Distance (m)
Ambient Seafloor Berm Material
0 100 200 300
-83.5
-84.0
-84.5
-85.0
-85.5
Ele
vatio
n (m
)
Bathymetric Profile (25X Vertical Exaggeration)
Line 0
Line 1
Line 5
Line 9
Line 7
Line 6
Line 3Line 4
Line 8
Line 2
October 2
008 Bathy
metric S
urvey
Exte
nt
Impact Analysis
y = 43.576e-0.398x
R² = 0.6483
0
10
20
30
40
50
60
70
80
-2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00
MBDS Ambient 210Pb (dgpm/g)
Dep
th (c
m)
Conclusions
• Individual placement events were highly discernible on the seafloor—based on their location it was concluded that it was possible to accurately direct placement of material at this site.
• Horizontal spread from individual placement events were focused within 650 ft (200 m) of the impact center. Vertical displacement of the ambient seafloor ranged from 1.5 to 5 feet (0.5 to 1.5 m).
• The buildup of a berm of “flank” material over the ambient seafloor with limited impact can be observed after multiple, overlapping placement events.
Next Steps
• Develop a model of impact potential from Boston Blue Clay disposal at the IWS
• Use the model and empirical data to develop minimum thickness dimensions for the berm area to successfully mitigate impact forces from disposal
• Turn those dimensions into a useable capping plan for potential full‐scale implementation using Boston Harbor Deep Draft Project material
Thanks for your attention – questions?