OPR-P358-FA-21 Prince William Sound, AK Prince William Sound, AK NOAA Ship Fairweather (S220) H13421 4 Cochrane Bay Alaska United States 10000 2021 CAPT John Lomnicky Navigable Area 2021-02-24 2021-03-26 2021-08-08 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 NAD83 UTM 6N, 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 Field Units) CC0-1.0 https://creativecommons.org/publicdomain/zero/1.0/ https://creativecommons.org/publicdomain/zero/1.0/legalcode These data were produced by NOAA and are in the public domain within the United States. NOAA waives any potential copyright and related rights in these data worldwide through the Creative Commons Zero 1.0 Universal Public Domain Dedication (CC0). NOAA The survey area is located in Cochrane Bay, Alaska 60.790088 148.45737 60.614271 148.206525 H13421 sheet limits (in blue) overlaid onto Chart 16705 SupportFiles\Survey limits.png Data were acquired to the survey limits in accordance with the requirements in the Project Instructions and the 2021 NOS Hydrographic Surveys Specifications and Deliverables (HSSD). Coverage acquired in H13421 is shown in Figure 4. In all areas where the 3.5 meter depth contour or the sheet limits were not met, the Navigable Area Limit Line (NALL) was defined as the inshore limit of bathymetry due to the risks of maneuvering the survey vessel in close proximity to rocks and steep, rocky shoreline. Examples of such areas are shown in Figure 2 and Figure 3. Area where NALL was defined by risks of maneuvering near steep and rocky shoreline SupportFiles\NALL defined by safety 1 of 2.jpg Area where NALL was defined by risks of maneuvering near steep and rocky shoreline SupportFiles\NALL defined by safety 2 of 2.jpg Prince William Sound has 3,800 miles of coastline, supporting the fishing, oil, and tourism industries. This project will provide modern bathymetric data to the Prince William Sound region, primarily focusing on areas left unsurveyed due to significant glacial retreat. The area has experienced increased tour boat and cruise ship traffic in recent years. In 2019, the Port of Valdez estimated almost 20,000 passengers aboard cruise ships with the numbers expected to increase. As the area is becoming more popular, there is greater vessel traffic near the unmapped glacier faces. Most of these glacier areas have not been surveyed since the 1990s with sedimentation potentially changing the submerged glacial moraines. 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. Data acquired in H13421 meet multibeam echo sounder (MBES) coverage requirements for complete coverage, as required by the HSSD. This includes crosslines (see Section B.2.1), NOAA allowable uncertainty (see Section B.2.10), and density requirements (see Section B.2.11). All waters in survey area Complete Coverage (Refer to HSSD Section 5.2.2.3) The entirety of H13421 was acquired with Complete Coverage, meeting the requirements listed above and in the HSSD. See Figure 4 for an overview of coverage. H13421 survey coverage overlaid onto Chart 16705 SupportFiles\Survey coverage.png FA 2805 0.0 5.53 0.0 0.0 0.0 0.0 0.0 0.0 0.0 FA 2807 0.0 95.63 0.0 0.0 0.0 0.0 0.0 3.34 0.0 FA 2808 0.0 81.99 0.0 0.0 0.0 0.0 0.0 6.41 0.0 S220 0.0 30.59 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 213.74 0.0 0.0 0.0 0.0 0.0 9.75 0.0 4.56 8 0 0 0 20.0 2021-03-26 2021-03-27 2021-03-28 2021-03-30 2021-08-08 Refer to the OPR-P358-FA-21 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. 2805 8.6 1.1 2807 8.6 1.1 2808 8.6 1.1 S220 70.4 4.8 MBES Kongsberg Maritime EM 2040 MBES Kongsberg Maritime EM 710 Conductivity, Temperature, and Depth Sensor Sea-Bird Scientific SBE 19plus V2 Conductivity, Temperature, and Depth Sensor AML Oceanographic MVP200 Sound Speed System Teledyne RESON SVP 70 Sound Speed System Teledyne RESON SVP 71 Positioning and Attitude System Applanix POS MV 320 v5 The equipment was installed on the survey platform as follows: S220 utilizes the Kongsberg EM 710 MBES, a POS M/V v5 system for position and attitude, SVP 70 surface sound speed sensors, and AML Oceanographic MVP 200 for conductivity, temperature, and depth (CTD) casts. All launches utilize the Kongsberg EM 2040 MBES, a POS M/V v5 system for position and attitude, SVP 71 surface sound speed sensors, and Sea-Bird SBE 19plus v2 CTDs for conductivity, temperature, and depth casts. Crosslines were collected, processed and compared in accordance with Section 5.2.4.2 of the HSSD. To evaluate crosslines, a surface generated via data strictly from mainscheme lines and a surface generated via data strictly from crosslines were created. From these two surfaces, a difference surface (mainscheme - crosslines = difference surface) was generated (Figure 5). Statistics show the mean difference between the depths derived from mainscheme data and crossline data was 0.11 meters (with mainscheme being shoaler) and 95% of nodes falling within 1.66 meters (Figure 6). For the respective depths, the difference surface was compared to the allowable NOAA uncertainty standards (Figure 6). In total, 99% of the depth differences between H13421 mainscheme and crossline data were within allowable NOAA uncertainties. Overview of H13421 crosslines SupportFiles\Crossline Comparison.png H13421 crossline and mainscheme difference statistics SupportFiles\Crossline Statistics.png ERS via ERTDM 0.13 S220 1 4 0.5 280x (all launches) 2 0.5 In addition to the usual a priori estimates of uncertainty via device models for vessel motion and ERTDM, real-time and post-processed uncertainty sources were also incorporated into the depth estimates of survey H13421. Real-time uncertainties were provided via EM 2040 and EM 710 MBES data and Applanix Delayed Heave RMS. Following post-processing of the real-time vessel motion, recomputed uncertainties of vessel roll, pitch, gyro and navigation were applied in CARIS HIPS and SIPS via a Smoothed Best Estimate of Trajectory (SBET) RMS file generated in Applanix POSPac. Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR. None Exist There were no conditions or deficiencies that affected equipment operational effectiveness. None Exist There were no other factors that affected corrections to soundings. Casts were conducted at a minimum of one every four hours during launch acquisition. Casts were conducted more frequently in areas where the influx of freshwater had an effect on the speed of sound in the water column and when there was a change in surface sound speed greater than two meters per second. MVP casts on S220 were conducted at an average interval of 164 minutes, guided by observation of the surface sound speed and targeted to deeper areas. All sound speed methods were used as detailed in the DAPR. All equipment and survey methods were used as detailed in the DAPR. Holidays H13421 data were reviewed in CARIS HIPS and SIPS for holidays in accordance with Section 5.2.2.3 of the HSSD. Ten holidays which meet the definition described in the HSSD for complete coverage were identified via HydrOffice QC Tools Holiday Finder tool. This tool automatically scans the surface for holidays as defined in the HSSD and was run in conjunction with a visual inspection of the surface by the hydrographer. All 10 holidays are displayed in Figure 7. Two holidays are due to acoustic shadowing in rocky areas. These shadows are formed due to lack of coverage on the “back” side of a feature, usually due to rapid drops in the seafloor in conjunction with poor geometry from the sonar head. In the field, these areas were determined to be too unsafe to investigate further. All areas with acoustic shadows were investigated in CARIS subset editor, and least depths were not able to be found. Eight holidays represent updated or added features included in the Final Feature File. Reasonable attempts were made to cover all gaps in coverage that resulted from lack of coverage over the tops of features when it was safe and prudent to do so. For areas where it was unsafe or impossible to do so, the features were added or updated accordingly in the Final Feature File accompanying this submission. There are eight such features for H13421. H13421 Holiday overview SupportFiles\Holiday overview.png NOAA Allowable Uncertainty The surface was analyzed using the HydrOffice QC Tools Grid QA feature to determine compliance with specifications. Overall, more than 99.5% of nodes within the surface meet NOAA Allowable Uncertainty specifications for H13421 (Figure 8). H13421 allowable uncertainty statistics SupportFiles\Allowable uncertainty statistics.png Density The surface was analyzed using the HydrOffice QC Tools Grid QA feature to determine compliance with specifications. Density requirements for H13421 were achieved with at least 99% of surface nodes containing five or more soundings as required by HSSD Section 5.2.2.3 (Figure 9). H13421 data density statistics SupportFiles\Data density requirements.png All data reduction procedures conform to those detailed in the DAPR. All sounding systems were calibrated as detailed in the DAPR. Raw backscatter data were stored in the .all files for Kongsberg systems. All backscatter were processed to GSF files and a floating point mosaic was created by the field unit via Fledermaus FMGT 7.9.0. See Figure 10 for a greyscale representation of the complete mosaic. A relative backscatter calibration was performed by the field unit via a backscatter calibration site in order to bring the survey systems on each of the launches into alignment. See Figure 11 for a table of the calibration values entered into the Processing Settings within FMGT. Approximate inter-calibration corrections for offsets between sonar systems were applied to the mosaic. Backscatter mosaic for H13421 SupportFiles\Backscatter mosaic.png Backscatter calibration values SupportFiles\Backscatter calibration values.PNG CARIS HIPS and SIPS 11.3 QPS FMGT 7.9.0 NOAA Profile Version 2021 H13421_MB_VR_MLLW.csar CARIS VR Surface (CUBE) Variable Resolution -1.6 437.8 NOAA_VR Complete MBES H13421_MB_VR_MLLW_Final.csar CARIS VR Surface (CUBE) Variable Resolution -1.6 437.8 NOAA_VR Complete MBES The NOAA CUBE parameters defined in the HSSD were used for the creation of all CUBE surfaces for H13421. The surfaces have been reviewed where noisy data, or "fliers" are incorporated into the gridded solutions causing the surface to be shoaler or deeper than the true sea floor. Where these spurious soundings cause the gridded surface to vary from the reliably measured seabed by greater than the maximum allowable Total Vertical Uncertainty at that depth, the noisy data have been rejected by the hydrographer and the surface recomputed. Flier Finder, part of the QC Tools package within HydrOffice, was used to assist the search for spurious soundings following gross cleaning. Flier Finder was run iteratively until all remaining flagged fliers were deemed to be valid aspects of the surface. Per Section 5.2.2.1.3 of the 2020 Field Procedures Manual no Horizontal and Vertical Control Report has been generated for H13421. Mean Lower Low Water ERS via ERTDM OPR-P358-FA-21_PWS_ERTDM21_NAD83-MLLW.csar ERS methods were used as the final means of reducing H13421 to MLLW for submission. In accordance with the Project Instructions for H13421, the survey team set up a base station to reoccupy the Cochrane Bay tidal benchmark. The survey team set up a base station overnight and recomputed the local tidal datum relationship with the ellipsoid. This data was sent to the National Geodetic Survey, Office of Coast Survey and was not used to position any data for sheet H13421. Email correspondence regarding this base station can be found in Appendix II, Supplemental Records. North American Datum 1983 Projected UTM 6 RTX Vessel kinematic data were post-processed using Applanix POSPac processing software and RTX positioning methods described in the DAPR. Smoothed Best Estimate of Trajectory (SBET) and associated error (RMS) data were applied to all MBES data in CARIS HIPS and SIPS. During real-time acquisition, all platforms received correctors from the Wide Area Augmentation System (WAAS) for increased accuracies similar to USCG DGPS stations. WAAS and SBETs were the sole methods of positioning for H13421 as no DGPS stations were available for real-time horizontal control. US4AK2AM 80000 12 2021-09-08 2021-09-08 No shoals or potentially hazardous features exist for this survey. All assigned charted features are attributed in the Final Feature File. Survey H13421 has 64 new features that are addressed in the H13421 Final Feature File. Of these features, there are 3 new Land Elevation, 5 new Land Area, 22 new Underwater/awash Rock, and 34 new Seabed Area features. On March 29th 2021 (DN 088), launch FA 2806 accompanied the shoreline skiff to log POS data for ERS water level positioning. However, FA 2806 experienced intermittent POS issues during shoreline acquisition. As a result, the SBET could not be created and used for ERS water level positioning for five new Underwater/awash Rock features, resulting in an "unknown" water level effect value for these features. These are noted in the S-57 file. There are only 27 new SBDARE features mentioned in this survey, not the 34 mentioned above. These 27 new SBDARE feature are actually updated extents of existing charted ledges. 5 of the 22 new rock features are actually updated positions of existing charted rocks No channels exist for this survey. There are no designated anchorages, precautionary areas, safety fairways, traffic separation schemes, pilot boarding areas, or channel and range lines within the survey limits. No Aids to navigation (ATONs) exist for this survey. No Maritime Boundary Points were assigned for this survey. Eight bottom samples were acquired in accordance with the Project Instructions for survey H13421. All bottom samples were entered in the H13421 Final Feature File. See Figure 12 for a graphical overview of sample locations. H13421 Bottom sample locations SupportFiles\Bottom samples.png No overhead features exist for this survey. No submarine features exist for this survey. No platforms exist for this survey. No ferry routes or terminals exist for this survey. No abnormal seafloor or environmental conditions exist for this survey. 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, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives. 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 noted in the Descriptive Report. CAPT John Lomnicky Chief of Party 2021-11-09 LT Shelley Devereaux Operations Officer 2021-11-09 ACHST Simon Swart Chief Survey Technician 2021-11-09 ENS Jessica Spruill Sheet Manager 2021-11-09