OPR-S327-KR-24 Kotzebue, AK Kotzebue, AK Terrasond H13912 1 na Approaches to Deering Alaska United States 40000 2024 Andrew Orthmann Navigable Area 2024-05-01 2024-07-19 2024-10-09 Multibeam Echo Sounder Multibeam Echo Sounder Backscatter meters UTC Pacific Hydrographic Branch Any revisions to the Descriptive Report (DR) applied during office processing are shown in red italic text. The DR is maintained as a field unit product, therefore all information and recommendations within this report are considered preliminary unless otherwise noted. The final disposition of survey data is represented in the NOAA nautical chart products. All pertinent records for this survey are archived at the National Centers for Environmental Information (NCEI) and can be retrieved via https://www.ncei.noaa.gov/. Products created during office processing were generated in WGS84 UTM 3N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit. CC0-1.0 (NOAA Contractors) CC0-1.0 https://creativecommons.org/publicdomain/zero/1.0/ https://creativecommons.org/publicdomain/zero/1.0/legalcode These data were produced under contract with NOAA and any potential copyright was assigned to NOAA. NOAA waives any potential copyright and related rights in these data worldwide through the Creative Commons Zero 1.0 Universal Public Domain Dedication (CC0). Contractor The survey area is located in Kotzebue Sound, Alaska. Kotzebue Sound is located in northwestern Alaska. The Arctic region is unnavigable for most of the year due to sea ice, with open water from approximately July through October. At the time of this survey, most of the area was poorly charted, with some areas uncharted altogether. The remote area is off the road system, and the bulk of supplies (including fuel) necessary for local communities are transported here by barge during the short ice-free season. Nearby communities are relatively small, consisting primarily of Shishmaref, Kivalina, Deering, and Kotzebue. Members of these communities commonly engage in various subsistence activities throughout Kotzebue Sound, usually traveling by skiff. Kotzebue is the largest community, with a population of 2,979 (2023). Limited services, including daily jet service to Anchorage, are available here. However, only shallow-draft vessels can navigate directly to Kotzebue due to a shoal of approximately 2 meters depth about 9 NM west of town, which necessitated relatively long transits to Nome—at least a 60-hour round trip—for most rotations and resupplies on this project. The Port of Red Dog is located on the north side of Kotzebue Sound. The Port serves as the terminal for Red Dog Mine, one of the largest zinc and lead mining operations in the world. Ore is mined year-round and stored at the Port for transport out during the limited ice-free season. Shallow-draft vessels lighter the ore from the Red Dog dock to deep-draft bulk ore carriers, which typically wait at least 3 NM offshore. On-site field work for project OPR-S327-KR-24 was carried out from July through October 2024. The overall project consisted of thirteen individual surveys. Final processing and reporting occurred from October 2024 through January 2025. Work was completed in accordance with the Hydrographic Survey Project Instructions (dated May 1, 2024), the accompanying Scope of Work, and the NOAA Hydrographic Surveys Specifications and Deliverables (HSSD, 2022 edition). 66.55985277777778 163.22686966666666 66.0425981111111 162.45849830555554 Figure showing the survey extents. SupportFiles\H13912_Survey_Extents.png Survey limits were acquired in accordance with the requirements in the Project Instructions and the HSSD. The purpose of this survey is described as follows in the Project Instructions: This project will provide modern bathymetric data within Kotzebue Sound, Alaska. Kotzebue acts as the service and transportation center for all villages in the northwest region of Alaska, as well as the transfer point between ocean and inland shipping. Portions of Kotzebue Sound were last surveyed between 2011 and 2015, however a majority of the area has not been surveyed to modern standards. The area experiences significant vessel traffic, particularly near the approaches to Kotzebue and Deering. The survey will focus on collecting data in the highly trafficked corridors, as well as for vessel lightering areas identified by the Western Alaska Tanker Lightering Best Practices Committee. These areas are used for ship-to-ship transfers of oil products, including fuel, which is of key importance to local residents. Conducting a modern bathymetric survey in this area will address Seabed 2030 data gaps, identify hazards and changes to the seafloor, provide critical data for updating National Ocean Service (NOS) nautical charting products, and improve maritime safety. Survey data from this project is intended to supersede all prior survey data in the common area. The entire survey is adequate to supersede previous data. All waters in survey area Complete a minimum of 12,896 LNM. Unlogged transit mileage, system calibration mileage, and data which do not meet HSSD specifications shall not count towards the completion of the LNM requirement. Notify the COR/Project Manager upon nearing completion of LNM requirement. The final area shall be squared off and ensure the full investigation of any features within the surveyed extent. All waters in survey area Set Line Spacing MBES (Refer to HSSD Section 5.2.2.4 Option A) Sheet H13912 Sounding lines shall be acquired with spacing adequate to collect data at an interval of at least 240 meters All Shoreline Sheets SDB Checklines Within each shoreline sheet, acquire four geographically dispersed sounding lines that extend to the inshore limit of safe navigation. The field unit will choose the location for the safe and efficient acquisition of shoal depths. Coverage requirements were met. Additional clarification on specific requirements are provided below. LNM requirements: A minimum of 12,896 LNM was required project-wide. 12,932 LNM were actually acquired. The excess was collected to compensate for incidental data collection such as crossline mileage that exceeded requirements, data acquired during run-ins or run-outs (including in shallow water while scouting depths between lines), and excess overlap (if any). LNM quantities do not include transit or calibration data, or data that doesn't meet HSSD requirements. NALL: The inshore depth contour definition of the NALL was 3.5 m. This minimum depth (or shoaler) was successfully achieved fully along the coast, with the exception of a handful of lines north of Cape Deceit where a steep, rocky coast prevented closer approach and the limit of safe navigation served as the NALL. SDB Checklines: SDB (Satellite Derived Bathymetry) checklines, to be used for future SDB calibrations, were acquired at geographically dispersed locations chosen by the field crew. Personnel and vessel safety considerations took precedence in deciding their location and the minimum depth achieved. For the checklines, the ASV-LR1 vessel collected data as shallow as possible, until it was deemed unsafe to continue closer to shore. All checkline data is incorporated in the final surface submitted with the survey deliverables. Four checklines were successfully acquired. The image below shows their locations. Figure showing SDB checkline locations, and their minimum depth (in meters), relative to the nearshore portion of the survey area. SupportFiles\SDB_Sds.png Figure showing coverage achieved on this survey. SupportFiles\H13912_Survey_Coverage.png Poseidon 0.0 803.87 0.0 0.0 0.0 0.0 0.0 61.63 0.0 ASV-LR1 0.0 375.11 0.0 0.0 0.0 0.0 0.0 34.49 0.0 0.0 1178.98 0.0 0.0 0.0 0.0 0.0 96.12 0.0 8.15 14 0 0 0 143.9 2024-07-19 2024-07-20 2024-07-21 2024-08-04 2024-08-05 2024-08-06 2024-08-07 2024-08-21 2024-08-22 2024-08-23 2024-09-04 2024-09-05 2024-09-20 2024-10-09 Refer to the Data Acquisition and Processing Report (DAPR) for a complete description of data acquisition and processing systems, survey vessels, quality control procedures and data processing methods. Additional information to supplement sounding and survey data, and any deviations from the DAPR are discussed in the following sections. Poseidon 41.0 2.6 ASV-LR1 7.6 1.0 The R/V Poseidon. SupportFiles\Poseidon.png The ASV-LR1. SupportFiles\ASV-LR1_2024.png The R/V Poseidon (Poseidon) is a 41 m steel-hull vessel owned and operated by Support Vessels of Alaska. The Poseidon was operated 24/7, acquiring multibeam data and providing housing and facilities for on-site data processing. The vessel was also used to collect bottom samples, conduct sound speed casts, and deploy/recover the ASV-LR1 launch. The ASV-LR1 (LR1) is a 7.6 m aluminum-hull Autonomous Surface Vessel (ASV). The vessel was configured to be "optionally crewed", enabling it to operate with or without a crew as operations required. When uncrewed it collected multibeam data in close proximity to the Poseidon, normally running parallel lines within 2 NM. MBES Teledyne RESON SeaBat T50-R MBES Backscatter Teledyne RESON SeaBat T50-R Positioning and Attitude System Applanix POS MV WaveMaster Positioning and Attitude System Applanix POS MV OceanMaster Sound Speed System Valeport SWiFT SVP Sound Speed System AML Oceanographic MicroX SV The survey vessels were configured for MBES data collection with nearly identical survey equipment and software. The Poseidon and LR1 utilized Teledyne Reson Seabat T50-R MBES systems, with surface sound speed measurements provided by AML Oceanographic Micro-X sensors. Both vessels used Applanix POSMVs with submersible IP-68 rated IMUs for attitude and position measurements. QPS QINSy software, running on Microsoft Windows 10-based PCs, was used for multibeam data logging and vessel navigation. Sound speed profiles were collected using a Valeport SWiFT sensor, which was deployed while underway using a C-MAX Vigo winch on the Poseidon, or taken by hand from the LR1 when it was operating with a survey crew. The percentage of crossline to mainscheme miles is 8.15%. Effort was made to ensure crosslines (XLs) had good temporal and geographic distribution, were angled to enable nadir-to-nadir comparisons, and that the required minimum percent of mainscheme LNM was achieved. Crosslines were conducted with all vessels to ensure there was ample overlap for inter-vessel comparisons, with each vessel crossing the other's mainscheme lines. Crosslines were often collected while transiting across the survey area to reach a different survey priority such as bottom sample locations or infills, leading to crosslines that were diagonal to the direction of mainscheme lines. The crossline analysis was conducted using CARIS HIPS “Line QC Report” process. Each crossline (with all associated file segments) was selected and run separately through the process, which calculated the depth difference between each accepted crossline sounding and a "QC" BASE (CUBE-type) surface’s depth layer created from the mainscheme data. The QC surface was created with the same parameters and resolution used for the final surface, with the important distinction that the QC surface did not include crosslines so as to not bias the results. Differences in depth were grouped by beam number and statistics were computed, including the percentage of soundings with differences from the QC surface falling within IHO Order 1a. When at least 95% of the sounding differences exceed IHO Order 1a, the crossline was considered to “pass,” but when less than 95% of the soundings compare within IHO Order 1, the crossline was considered to “fail.” A 5% (or less) failure rate was considered acceptable since this approach compares soundings to a surface (instead of a surface to a surface), allowing for the possibility that noisy crossline soundings that don't adversely affect the final surface could be counted as a QC failure in this process. Lines selected as crosslines and their percentage (%) of soundings passing IHO Order 1a, sorted from highest passing to lowest, are listed below. Note that lines used as crosslines have their "Line Class" attribute set to "Check" within the CARIS HIPS projects provided with the survey deliverables. In addition to lines run specifically as crosslines, these can also include lines run as junction comparisons and/or as shoreline trace lines where advantageous -- for example if they improve spatial distribution. 0262-JD202-Poseidon-A1WB -- 100.0% pass 1240-JD264-Poseidon-A1XL1005 -- 100.0% pass 0729-JD249-LR1-A2XL1001 -- 100.0% pass 0668-JD248-LR1-A3XL1000 -- 100.0% pass 0911-JD248-Poseidon-A3XL1001 -- 100.0% pass 0921-JD249-Poseidon-A3XL1004 -- 100.0% pass 0922-JD249-Poseidon-A3XL1004 -- 100.0% pass 0714-JD249-LR1-A3XL1003 -- 100.0% pass 0708-JD248-LR1-A3ShoreTrace -- 100.0% pass 0669-JD248-LR1-A3EW12480 -- 100.0% pass 0912-JD248-Poseidon-A3XL1002 -- 100.0% pass 1238-JD264-Poseidon-A1XL1004 -- 100.0% pass 0262-JD219-LR1-A3-Shoreline -- 100.0% pass 1237-JD264-Poseidon-A1XL1003 -- 100.0% pass 0923-JD249-Poseidon-A2XL1000 -- 100.0% pass 0730-JD249-LR1-A2XL1002 -- 100.0% pass 0924-JD249-Poseidon-A2XL1003 -- 100.0% pass 1235-JD264-Poseidon-A1XL1002 -- 100.0% pass 0233-JD201-Poseidon-A1XL1000 -- 100.0% pass 1239-JD264-Poseidon-A1XL1005 -- 99.8% pass 1234-JD264-Poseidon-A1XL1001 -- 99.8% pass 1236-JD264-Poseidon-A1XL1003 -- 99.8% pass Results: Agreement between them mainscheme surface and crossline soundings is excellent. At least 95% of all crossline soundings compare to the mainscheme surface within IHO Order 1a for all crosslines. Refer to Separate II: Digital Data for the detailed Crossline QC reports. ERS via ERTDM 0.14 0.0 Poseidon 0 5 0 0.025 ASV-LR1 0 5 0 0.025 ASV-LR1 (crewed) 0 1 0 0.025 The uncertainty layer of the final surface was examined in CARIS HIPS software, as well as analyzed in Pydro QC Tools V3.10.20 Grid QA v6. The computed uncertainty of the final grid cells range from 0.351 to 0.878 m. Greater than 99.5% of grid cells have TVU that fall within the allowable range by depth. Areas with elevated TVU were found to be in deeper water during times of rougher weather. Despite the calculated higher uncertainty on these cells, their depth data is within allowable TVU. Note that a separate sound speed uncertainty was calculated for the LR1 for when it was crewed. This was done because SVP casts were conducted aboard the LR1 only when it was operating with a crew, and these were analyzed for uncertainty independently of the SVP casts taken from the Poseidon. During field operations, effort was made to ensure sufficient overlap was achieved between this survey and any overlapping surveys for junction analysis. This included extending survey lines into overlapping sheets, and often running lines along junction boundaries. The "Gridded Surface Comparison V24.6" utility within Pydro was used to compare survey junctions. The utility differences the surfaces from the two surveys and generates statistics that include the percentage of grid cells that compare to within allowable TVU for the depth. In some cases where variable resolution (VR) surfaces could not be read by the utility, the statistics were calculated in Excel instead. 4 m resolution surfaces were used for all sheets completed under this project. Prior surveys, where applicable, were downloaded from NOAA NCEI in BAG format. The resolution available in NCEI for each BAG surface varied by sheet and is noted below. Note that a trend exists in the comparisons, with the NOAA Ship Rainier data from 2015 consistently shoaler than this survey, by 0.06 to 0.27 m. This was also observed in the other sheets in this project that overlapped the 2015 Rainier sheets. However, despite this trend, at least 99.5% of all grid cells compared to within allowable TVU by depth. H12812 40000 2015 NOAA Ship Fairweather N A 2 m resolution surface from NOAA NCEI ("H12812_MB_2m_MLLW_2of3") and a 4 m resolution surface ("H12812_MB_4m_MLLW_3of3"), each covering different areas, overlapped this survey and were utilized for the comparison. Significant overlap was achieved along the junctions with both. For the 2 m surface, agreement is acceptable. The mean difference is 0.31 m (H13912 is deeper), with a standard deviation of 0.08 m. 100% of grid cells agree within allowable TVU by depth. For the 4 m surface, agreement is acceptable. The mean difference is 0.31 m (H13912 is deeper), with a standard deviation of 0.10 m. 100% of grid cells agree within allowable TVU by depth. H12813 40000 2015 NOAA Ship Fairweather NW Two variable resolution (VR) surfaces from NOAA NCEI ("H12813_MB_VR_MLLW_2of3" and "H12813_MB_VR_MLLW_3of3"), each covering different areas, overlapped this survey and were utilized for the comparison. Significant overlap was achieved along the junctions with both. For the "2of3" surface, agreement is good. The mean difference is 0.06 m (H13912 is deeper), with a standard deviation of 0.12 m. 99.9% of grid cells agree within allowable TVU by depth. For the "3of3" surface, agreement is acceptable. The mean difference is 0.19 m (H13912 is deeper), with a standard deviation of 0.10 m. 99.2% of grid cells agree within allowable TVU by depth. Much of the difference causing some cells to differ by more than allowable TVU appear to be due to changes in the seafloor between the 2015 and 2024 surveys due to ice scour. H12819 40000 2015 NOAA Ship Fairweather NW A 1 m resolution surface was available from NOAA NCEI and was used for the comparison. Only a small amount of overlap was achieved due the intersection area being at the corner of the two surveys. Agreement between the two surveys is acceptable. The mean difference is 0.27 m (H13912 is deeper), with a standard deviation of 0.12 m. 100% of grid cells agree within allowable TVU by depth. H13913 40000 2024 TerraSond W The two surveys were completed concurrently under the same overall project. There is a small amount of overlap due to the surveys meeting on their corners. Agreement between the two surveys is very good. The mean difference is 0.05 m (H13912 is deeper), with a standard deviation of 0.12 m. 100% of grid cells agree within allowable TVU by depth. Figure showing survey junctions. SupportFiles\H13912_Survey_Junctions.png Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR. Poseidon Roll Misalignment An across-track misalignment, or roll bias, is evident periodically in Poseidon data, adversely affecting outer beam soundings. The exact cause is unknown but is likely attributable to shifts in the POSMV lever arm from movement of the hydraulic MBES arm on the Poseidon. Affected lines were identified by difference surface methodology, wherein a surface made from all soundings was differenced from a TIN surface created using only near-nadir data. Lines that exhibited differences from the TIN approaching or exceeding allowable TVU received additional outer beam filters that rejected the erroneous data. Refer to the DAPR for additional detail on this process. Following these corrections the negative effect on final surfaces, where this occurs, is generally less than 0.20 m and is within allowable TVU. Sound Speed Error Sound speed error, which is normally characterized by a general upward or downward across-track cupping of sounding data that increases in magnitude towards the outer beams, is evident sporadically in the dataset. Profiles were taken frequently, usually not exceeding two hours, and whenever changing areas, but some residual error remains. In processing, beam filters were applied to reject outer beams greater than 65 degrees from nadir on all lines in order to reject soundings most subject to sound speed error. The dataset was also systematically examined and additional filters were applied to individual lines where outer beam error appeared to approach or exceed specifications, removing the erroneous data. The effect on the final surfaces is relatively minor, normally less than 0.20 m where it occurs. Final data is within specifications. 2 hours Sound speed profiles or "casts" were acquired aboard the Poseidon while underway with a C-MAX Vigo profiling winch, utilizing a Valeport SWiFT sound speed profiler. These profiles were used to correct all Poseidon sounding data, as well as all LR1 sounding data for periods when the LR1 was operating uncrewed. This was possible because when uncrewed the LR1 worked in close vicinity to the Poseidon, usually within 2 NM. However, when operating in crewed mode, casts were also collected abord the LR1. In this case a Valeport SWiFT sound speed profiler was manually lowered to the seafloor. Note that LR1 casts conducted for crewed operations were placed within their own SVP file for CARIS HIPS processing and used only for correcting LR1 crewed data. This was done so that LR1 crewed casts would not be used to correct Poseidon data, and vice versa, since the LR1--when crewed--often operated at significant distance away from the Poseidon. These profiles have "LR1" in the SVP filename in CARIS HIPS. Lines applicable to this SVP file are listed later in this report. Surface sound speed at the sonar head on the Poseidon (and LR1 when crewed) was monitored continuously and a new cast was collected when the surface speed varied from the previous profile's speed at the same depth by greater than 2 m/s, leading to a cast interval of approximately 2 hours. Casts were taken as deep as possible. On survey lines with significant differences in depth, the deeper portion of the line was normally favored to ensure that changes across the full water column were measured. The cast data was used to correct the sounding data using the "nearest in distance within time" (set to 2 hours) within CARIS HIPS. Exceptions, if any, are noted later in this report. All equipment and survey methods were used as detailed in the DAPR. Crewed LR1 Lines using LR1 SVP file: The following lines were completed while the LR1 vessel was crewed and conducting its own SVP casts. These utilized the "_LR1" SVP file included with the survey deliverables. JD248: Lines with prefix 0675 through 0713 JD249: Lines with prefix 0714 through 0728 JD283: Lines with prefix 1835 through 1858 SVP Exceptions: The following line was SVP corrected using nearest in distance within 3 hours instead of the standard 2 hours: 0728-JD249-LR1-A3NS09360_-_0001 0715-JD235-Poseidon-A1NS03120 segments 4, 5, and 6 All sounding systems were calibrated as detailed in the DAPR. All equipment and survey methods were used as detailed in the DAPR. NOAA Profile Version 2024 The most current version of NOAA's Extended Attribute Files available at the start of survey operations was utilized for this project. H13912_MB_4m_MLLW_Final CARIS Raster Surface (CUBE) 4 1.527 21.506 NOAA_4m MBES Set Line Spacing H13912_MBAB_2m_400kHz_1of1 MB Backscatter Mosaic 2 1.527 21.506 N/A MBES Set Line Spacing The final depth information for this survey was submitted as a 4 m resolution CARIS BASE surface (CSAR format), computed with the CUBE algorithm, which best represents the seafloor at the time of the 2024 survey. The surface was created from fully processed data with all final corrections applied. The surface was created using NOAA CUBE parameters and resolutions in conformance with the 2022 HSSD. The surface was finalized with a 0 to 80 m depth limit, "Uncertainty" selected as the final uncertainty source, and designated soundings were applied (if present). Horizontal projection was selected as WGS84 / UTM zone 3N. A non-finalized version of the CSAR surface is also included with the survey deliverables for reference. This does not have the "_Final" designation in the filename. The Multibeam Acoustic Backscatter (MBAB) surface(s), produced with QPS Fledermaus Geocoder Toolbox (FMGT), is also provided. All vessels ran their sonars at 400 kHz, therefore their MBAB data was combined in a single 400 kHz mosaic. Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR. Mean Lower Low Water ERS via ERTDM OPR-S327-KR-24_AK_ERTDM_2023_WGS84(G2139)-MLLW.csar All soundings were reduced to MLLW using the ERTDM WGS84 to MLLW separation model grid file provided by NOAA using ERS methodology. The uncertainty stated for the model in the Project Instructions was 0.14 m. Note all altitudes are relative to the WGS84 datum, therefore the WGS84 to MLLW ERTDM model was utilized to reduce soundings to MLLW. World Geodetic System (WGS) 1984 Projected UTM 3 RTX Post-processing of all navigation data for final positions was done in Applanix POSPac MMS (v9.1) software. Trimble PP-RTX was used as the primary processing methodology within POSPac. Exceptions (if any) were noted previously. Real-time positions were primarily RTK. The POSMVs on each vessel were configured to receive Trimble CenterPoint RTX corrections using NTRIP protocol over the internet via Starlink Maritime receivers. This allowed the POSMVs to operate in RTK mode, assisting with real-time positioning in the field. Real-time positioning sources in the raw MBES records are therefore normally RTX. However, all real-time positions were replaced in post-processing, as described previously. The Wide Area Augmentation System (WAAS) was used for real-time horizontal control during data acquisition only if issues with reception of CenterPoint RTX corrections were experienced. These are usually noted in the Survey Line Logs, included with the survey deliverables. HSSD Section 2.2 (NAD83) A waiver to HSSD Section 2.2 was was granted for this project. All products are submitted with horizontal positions as WGS84 instead of NAD83(2011). This was done to provide a consistent dataset from raw data, which was acquired in WGS84, through final processed data. See project correspondence for the waiver. An overview of this survey overlaid on the largest scale chart(s) covering the survey area is shown below. This survey overlaid on affected large scale ENCs. Soundings from this survey are blue. All soundings in meters. SupportFiles\Chart_Overlay.png US4AK6WT 90000 2 2024-09-17 2024-09-17 US4AK6WS 90000 1 2023-12-01 2023-12-01 US4AK6XS 90000 1 2023-12-01 2023-12-01 US4AK6XR 80000 1 2021-03-04 2021-03-04 No shoals or potentially hazardous features exist for this survey. No DTONs were submitted for this survey. No charted features exist for this survey. No uncharted features exist for this survey. No channels exist within the survey limits. Cape Deceit Light ATON was observed to be on station and serving its intended purpose. Cape Deceit Light. SupportFiles\SheetA_ATON_Light.JPG No Maritime Boundary Points were assigned for this survey. The Project Instructions required 10 bottom samples for this survey. 14 were actually acquired, at geographically dispersed locations, with specific locations chosen in regards to the acquired multibeam backscatter. The four additional samples were acquired after being reallocated here from H13917 and H13921 per the Project Instructions (refer to those surveys for additional information). An overview of their locations and results is shown below. Samples were examined, photographed, and then discarded overboard. Detailed results are provided in the project FFF. An overview of bottom sample locations and results. SupportFiles\Bottom_Samples.png No overhead features exist for this survey. A charted cable transects the southern part of this survey running to Deering, with a reported date of August 2023. Note this cable is charted on the smaller scale chart (US2AK92M) covering the area but NOT on the applicable large scale chart, US4AK6WS. It is recommended that the cable be added to applicable large scale charts as well. The cable was not assigned for investigation, but a brief examination of the dataset was conducted nonetheless. A 1 m resolution surface was created of the MBES data in this area and examined. There is very subtle indication of the cable, or a surface disturbance associated with the cable, at many of its intersections with this dataset. The cable appears to roughly charted correctly, though the charted position is consistently 18 to 20 m west of the actual position. An example is shown below. An example of MBES data that transects the charted cable. There is indication of the cable (indicated by the red arrows). The charted position appears to be 18 to 20 m west of the actual position. SupportFiles\Cable.png No platforms exist for this survey. No ferry routes or terminals exist for this survey. Ice scour is a relatively common feature of the seafloor in this area. These generally long, linear features of disturbed sediment can reach 1 m above or below the surrounding seafloor in some cases. An example is shown below. In this area they are observed in all areas deeper than 10 m. An example of ice scour on the seafloor in this survey. The depth in this area is 17 m. SupportFiles\Ice_Scour.png No present or planned construction or dredging exist within the survey limits. No new surveys or further investigations are recommended for this area. No new ENC scales are recommended for this area. As Chief of Party, field operations for this hydrographic survey were conducted under my direct supervision, with frequent personal checks of progress and adequacy. I have reviewed the attached survey data and reports. All field sheets, this Descriptive Report, and all accompanying records and data are approved. All records are forwarded for final review and processing to the Processing Branch. The survey data meets or exceeds requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables, Hydrographic Survey Project Instructions, and Statement of Work. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required with the exception of deficiencies, if any, noted in the Descriptive Report. Andrew Orthmann, CH Charting Program Manager 2025-01-25 Survey Outline Submittal 2024-11-11 Final Progress Report 2024-11-15 Trained Marine Mammal Observer Log 2024-12-02 Marine Mammal Sightings Forms 2024-12-02 NCEI Sound Speed Data Submittal 2024-12-23 Coast Pilot Report 2025-01-16