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Meridian Pipeline Survey Massachusetts Bay, Boston, MA

5 August 2013

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Table of Contents

Section 1: Mission Overview ........................................................................................................................ 3

Vehicle General Information: .................................................................................................................... 3

Mission Report: ......................................................................................................................................... 3

Area of Operation: ..................................................................................................................................... 3

Mission Track: ........................................................................................................................................... 4

Mission Goal: ............................................................................................................................................ 5

Section 2: Individual Missions ...................................................................................................................... 6

Segment 1: ................................................................................................................................................. 6

Segment 2: ................................................................................................................................................. 7

Segment 3: ................................................................................................................................................. 8

Segment 4: ................................................................................................................................................. 9

Segment 5: ............................................................................................................................................... 10

Segment 6: ............................................................................................................................................... 11

Segment 7: ............................................................................................................................................... 12

Segment 8: ............................................................................................................................................... 13

Segment 9: ............................................................................................................................................... 14

Segment 10: ............................................................................................................................................. 15

Comments: .............................................................................................................................................. 15

Section 3: Areas of Interest ......................................................................................................................... 16

Image Specifications: .............................................................................................................................. 16

Buried Regions of Pipeline: .................................................................................................................... 16

Exposed Regions of Pipeline: ................................................................................................................. 19

Interesting Bottom Features: ................................................................................................................... 23

Comments: .............................................................................................................................................. 24

Section 4: Image Distortion ......................................................................................................................... 25

DVL: ........................................................................................................................................................ 25

Images: .................................................................................................................................................... 26

Section 5: Summary .................................................................................................................................... 27

Summary: ................................................................................................................................................ 29

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Section 1: Mission Overview

Vehicle General Information: Participants Meridian, OceanServer Technology, Inc. UMass CST Group Vehicle Identification no. 199 Sensor payload DVL, Klein 3500 SideScan Sonar Active sensors DVL, Klein 3500 SideScan Sonar Sensor log files available DVL, Klein 3500 SideScan Sonar Operating area Massachusetts Bay - Boston, Massachusetts, USA Date and day of run Thursday, 18 July 2013

Mission Report: Number of segments along pipeline 10 Start time of missions 7:53:05 AM (Eastern Time Zone) (UTC-4) End time of missions 3:03:36 PM (Eastern Time Zone) (UTC-4)

Area of Operation:

Figure 1: Area where mission was conducted, pin tag indicates location

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Mission Track:

Figure 2: Mission Track, indicating the 10 mission segments

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Mission Goal:

Sonar imagery was collected over a stretch of about 10 miles of the pipeline in order to find out if any areas of the pipeline were exposed. While surveying, the vehicle made a single pass on each side of the 10 pipeline segments. During the post-processing phase of the project, the CST team utilized Chesapeake Technology’s SonarWiz5 software Chesapeake Technology to render the high-resolution Klein 3500 sonar images acquired during the missions.

Figure 3: Sonar Overlay of the entire surveyed pipeline

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Section 2: Individual Missions

Segment 1:

Figure 4: Segment 1 Mission Track and overlaid Sonar

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Segment 2:

Figure 5: Segment 2 Mission Track and overlaid Sonar

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Segment 3:

Figure 6: Segment 3 Mission Track and overlaid Sonar

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Segment 4:

Figure 7: Segment 4 Mission Track and overlaid Sonar

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Segment 5:

Figure 8: Segment 5 Mission Track and overlaid Sonar

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Segment 6:

Figure 9: Segment 6 Mission Track and overlaid Sonar

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Segment 7:

Figure 10: Segment 7 Mission Track and overlaid Sonar

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Segment 8:

Figure 11: Segment 8 Mission Track and overlaid Sonar

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Segment 9:

Figure 12: Segment 9 Mission Track and overlaid Sonar

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Segment 10:

Figure 13: Segment 10 Mission Track and overlaid Sonar

Comments: These graphs indicate a high degree of variation in pitch – as much as 50 degrees over a short period of time. Since the vehicle’s height from bottom was rapidly changing, it is reasonable to conclude that this factor would contribute to some of the distortion observed in the sonar files.

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Section 3: Areas of Interest

Image Specifications: Pictures: Sidescan type Klein 3500 Frequencies enabled Low and High, 450 kHz and 900 kHz Range 100 m Speed of vehicle underwater 2.5 Kn HFB 32.81 ft

Buried Regions of Pipeline:

Figure 14: Segment 2, WP4, 900 kHz

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Figure 15: Segment 6, WP 4, 900 kHz

Figure 16: Segment 7, WP 9, 900 kHz

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Figure 17: Segment 8, WP 4, 450 kHz

Figure 18: Segment 10, WP 4, 450 kHz

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Exposed Regions of Pipeline:

Figure 19: Segment 1, WP4, 450 kHz

Description: Part of the pipeline in Figure 11 is covered (bottom half of image), while the pipeline near the mesh-like material (top half of image) looks to be partially exposed.

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Figure 20: Segment 1, WP 9, 900 kHz

Description: The pipeline appears to be resting exposed on a rectangular mesh-like material. The mesh material has a length of 81.2 m and width of 5.9 m. Towards the bottom end of the image, the pipeline curves sharply and is connected with a large machine-like apparatus.

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Figure 21: Segment 6, WP 4, 450 kHz

Description: The pipeline appears to be partially exposed near Neptune LNG Deepwater Port Lighted Buoy North A1 and A2. Near the bottom half of the image, the pipeline feeds into a machine-like apparatus similar to the one shown in Figure 12.

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Figure 22: Segment 6, WP4, 900 kHz

Description: The machine-like apparatus in Figure 14 is the same one that is observed in Figure 13. The bottom half of the image shows the end of the buried region. A thinner exposed pipe is shown across the middle of Figure 14 and the pipe is again buried in Figure 13.

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Interesting Bottom Features:

Figure 23: Segment 1, WP 4, 900 kHz

Description: Figure 15 is an image of Neptune LNG Deepwater Port Lighted Buoy North B1 and B2. Nine cables are shown radiating from the buoy. This feature is approximately 100 m from the machine-like apparatus displayed in the bottom of Figure 12.

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Figure 24: Segment 7, WP9, 900 kHz

Description: On the port side of the nadir region the pipeline is buried completely, while on the starboard side of the nadir region there is evidence of a possible shipwreck or machinery (having the dimensions of 6.0 m by 5.1 m).

Comments: It should be noted that the distortion in Figures 8-15 was likely a result of a rapidly changing pitch while the vehicle was submerged. Image clarity improves on stretches where the pitch remains more constant.

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Section 4: Image Distortion

DVL: Due to a hardware malfunction in the RDI DVL system, the DVL didn’t obtain a bottom lock during the submerged legs. Therefore, sonar image quality was reduced because of the inconsistent depths the vehicle was operating at. Three fundamental observations support this conclusion of a faulty DVL system. As can be seen in the data table (bellow) comprised of sample data, there is an erroneous beam range measurement corresponding to each time.

Time Beam1Range(cm) Beam2Range(cm) Beam3Range(cm) Beam4Range(cm) 7:55:12 AM 5202 121 5059 7111 7:55:13 AM 5059 121 4820 7063 7:55:14 AM 5154 121 4820 7301 7:55:15 AM 5106 73 4772 7254 7:55:16 AM 5059 25 4772 7015 7:55:17 AM 4916 25 4725 7015 7:55:18 AM 4820 6586 4582 6967 7:55:19 AM 4772 6395 4438 73 *Sample of data from Segment 1 Another observation was that the vehicle changed pitch rapidly as it tried to maintain its target depth. A third trend noticed throughout many of the missions was that the jump distances were often parallel to the mission track and thus comprised of large amounts of along-track error (DVL error) in the direction of the vehicle.

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Images:

Figure 25: Segment 2, WP 9, an example of image distortion due to pitch, notice how surface features appear to be stretched

Figure 26: Roll & Pitch vs. Time (Segment 2)

As can be seen in the Roll and Pitch graph above, after the vehicle dives the second time, the Pitch Angle varies drastically during the second submerged leg, and the image is distorted as expected. The other evidence of the changing pitch, is the yellow line that SonarPro shows as

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Roll & Pitch vs. Time (Seg 2) Roll Angle

Pitch Angle

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where the bottom is, and as can be seen in all of these examples, the yellow line is broken and at varying heights as the DVL loses and regains its bottom tracking.

Figure 27: Segment 4, WP 4, 900 kHz

Figure 28: Roll & Pitch vs. Time (Segment 4)

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10:26:24 AM 10:33:36 AM 10:40:48 AM 10:48:00 AM 10:55:12 AM 11:02:24 AM

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Roll & Pitch vs. Time (Seg 4) Roll Angle

Pitch Angle

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Figure 29: Segment 6, WP 4, 900 kHz

Figure 30: Roll & Pitch vs. Time (Segment 6)

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Roll & Pitch vs Time (Seg 6) Roll Angle

Pitch Angle

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Section 5: Summary

Summary: The pipeline appears to be completely buried in Segments 2-5 and Segments 7-10. Segment 1 and Segment 6 of the pipeline have exposed regions located in close proximity to the deepwater Neptune LNG buoys as specified in Figure 1. Both of these sites had machine-like apparatus’ positioned approximately 100 m away from their respective deepwater buoys. In Segment 1, the exposed pipeline sits on a mesh-like material. However, the exposed pipeline in Segment 6 appears to be resting exposed on the sea floor (with no mesh).