A chart comparison was conducted using the Triangle Rule script within the Chart Review Tool of Pydro QC Tools. A combined s57 file of charted soundings extracted from ENCs listed in the project instructions and an s57 file of surveyed soundings were compared with the following results. Survey H13452 surveyed soundings exhibit 0 instances where surveyed soundings are shoal to charted soundings by greater than 1m.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 charted features exist for this survey.No shoals or potentially hazardous features exist for this survey.No uncharted features exist for this survey.2019-03-20US3AK61M300000252020-09-29No Maritime Boundary Points were assigned for this survey.No ferry routes or terminals exist for this survey.No platforms exist for this survey.No Aids to Navigation (ATONs) exist for this survey.No abnormal seafloor or environmental conditions exist for this survey.No new ENC scales are recommended for this area.No present or planned construction or dredging exist within the survey limits.No submarine features exist for this survey.No overhead features exist for this survey.No bottom samples were required for this survey.No new surveys or further investigations are recommended for this area.Unimak, AKUnimak Island, AKFugro USA Marine, Inc.OPR-Q350-KR-21Contractor920NM North East of Oksenof PointH13452500 meter Multibeam Sonar Set Line Spacing without Concurrent Side Scan Sonar Coverage (HSSD 2020 5.2.2.4, Option A). Note: The requirement to verify or disprove all charted depth falling between sounding lines and shallower than adjacent surveyed soundings is waived. H13452 is an expansion sheet to accomplish LNM requirement. 40000AlaskaUnited States2021Multibeam Echo SounderMultibeam Echo Sounder BackscattermetersNavigable AreaAny 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 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.Pacific Hydrographic BranchAllison Stone2021-04-02UTC2021-07-232021-07-26All positioning and attitude data associated with OPR-Q350-KR-21 was post-processed in POSPac MMS using PP-RTX methods. For further discussion, reference the DAPR submitted with this report.ERS via VDATUMOPR_Q350_KR_21_CapeSarichef_ERTDM21-1_NAD83-MLLWMean Lower Low WaterProjected UTM 3All positioning and attitude data associated with OPR-Q350-KR-21 was post-processed in POSPac MMS using PP-RTX methods. North American Datum 1983No vertical or horizontal control reports were generated for this survey. All data were reduced to MLLW via VDatum model. This project will provide contemporary data to update NOS nautical charting products; increasing maritime safety and commerce in the region. The waters around the the North side of Unimak Island are an important fishing ground for the Bering Sea Pacific Cod and other fisheries. This area is part of the main route transited by vessels between Bristol Bay and Dutch Harbor, AK. The North shore of Unimak Island commonly serves as a refuge from weather and waves coming off of the open waters from the North Pacific. The area has been identified by the Western Alaska Tanker Lightering Best Practices Committee as a primary location for lightering operations to occur. The project area has also been identified as an area of inadequate coverage by a risk-based model with respect to the desired coverage needed to support modern navigational needs. R/V Woldstad00196.1921.440000000196.1921.44010.9200002021-07-232021-07-242021-07-252021-07-2653.260000Survey H13452 MBES coveragefile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_Coverage.pngSurvey H13452 8m finalized set line MBES density QCfile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_MB_8m_MLLW_Final.QAv6.density.pngSurvey coverage was in accordance with the requirements listed above and in the HSSD.All waters in Sheet 8500m Set Line Spacing (Reference HSSD Section 5.2.2.4 Option A). Note: the requirement to verify or disprove all charted depths falling between sounding lines and shallower than adjacent surveyed soundings is waived. Note: Change was made in set line spacing requirement by COR after it was determined original requirement of 320m created more coverage than neccesary for desired level of data acquisition. 500m set line MBES was achieved within the survey limits of H13451 (Figures 2 and 3). The entire survey is adequate to supersede previous data.Survey H13452 (Figure 1 and Table 1) is located 20 nautical miles North East of Oksenof Point, Unimak Island, AK. This area is utilized extensively by vessels involved in diverse fisheries activities in the region, including cod and crab. The R/V Woldstad acquired 500m set line spaced Multibeam Echosounder (MBES) and Multibeam Echosounder Acoustic Backscatter (MBAB) within the assigned survey limits 23-26 July 2021 (Tables 2-4).55.0800785833165.10284919455.0351839167164.835942972Survey H13452 relative to overall sheet limits of OPR-Q350-KR-21file:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_Overview.pngSurvey limits were not fully acquired. H13452 was an expansion survey utilized to achieve contract mileage. Chief of PartyAllison C Stone2021-09-30All 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.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.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.2021-09-30Data Acquisition and Processing Report2021-07-26Coast Pilot ReportNOAA Profile Version 2021CARIS Raster Surface (CUBE)H13452_MB_8m_MLLW8MBES Set Line SpacingNOAA_8m112.4294.21CARIS Raster Surface (CUBE)H13452_MB_8m_MLLW_Final8MBES Set Line SpacingNOAA_8m112.4294.21Refer 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.For a detailed listing of equipment, refer to the DAPR submitted with this report.SeaBat 7125 SV2MBESTeledyne RESONSVP 70Sound Speed SystemTeledyne RESONPOS MV 320 v5Positioning and Attitude SystemApplanixrapidCASTConductivity, Temperature, and Depth SensorTeledyne OceanscienceR/V Woldstad (Table 5 and Figure 4) acquired MBES, MBAB, surface sound velocity, sound velocity profiles, and attitude and positioning data within the survey limits of H13452 (Table 6). For a detailed listing of equipment used to acquire survey data, refer to the DAPR submitted with this report under Project Reports.R/V Woldstadfile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/woldstad.jpgR/V Woldstad12112No backscatter deliverables are submitted with survey H13451. One line of data per vessel, per day was processed to ensure quality control. All equipment and survey methods utilized in the acquisition and processing of backscatter are detailed in the DAPR.All sounding systems were calibrated as detailed in the DAPR.All data reduction procedures conform to those detailed in the DAPR.Static draft uncertainty values in the HVF differ slightly from what is reported in the DAPR, the value for the Static Draft Uncertainty for H13451 is -0.03m.Survey H13452 uncertainty values (Tables 7 and 8) were evaluated in both CARIS HIPS 10.4 and via Pydro QC Tools v3.4.7. The finalized 8m (Figure 7) bathymetric grid meets uncertainty standards with 100% of nodes passing.H13452 8m finalized grid TPU QCfile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_MB_8m_MLLW_Final.QAv6.tvu_qc.png0.1010.08ERS via VDATUMN/AR/V Woldstad0.25N/A1.458All equipment and survey methods were used as detailed in the DAPR.There were no other factors that affected corrections to soundings.None ExistSonar system quality control checks were conducted as detailed in the quality control section of the DAPR.Crosslines for survey H13452 were acquired in accordance with section 5.2.4.2 of the HSSD 2020 (Figure 5). Mainscheme to crossline mileage percentage across H13452 is 10.92%. Of the 115,234 grid nodes compared between H13452 mainscheme MBES and MBES crosslines, 100% were within 1m difference. The mean difference is 0.04m, with a standard deviation of 0.14m (Figure 6).H13452 MBES mainscheme and MBES crossline distributionfile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_XL_dist.pngH13452 MBES mainscheme differenced from MBES crosslines statistical outputfile:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_XL_diff.pngTwo contemporary surveys are available for comparison to H13452: H13451and H13449 (Table 9 and Figure 8).Junction surveys to H13452file:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/H13452_JNX.pngSurvey H13451 was acquired by Fugro USA Marine, Inc. in 2021 as a part of OPR-Q350-KR-21. Of the19,565 grid nodes compared between H13452 and H13451 the mean difference is 0.08m; 100% agree within 1m (Figure 9).Survey H13452 junction with Survey H13451file:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/52_JNX_51.png2021W40000H13451Fugro USA Marine, Inc.Survey H13449 was acquired by Fugro USA Marine, Inc. in 2021 as a part of OPR-Q350-KR-21. Of the 27,638 grid nodes compared between H13452 and H13449 the mean difference is 0.04m; 99.9% agree within 1m (Figure 10).Survey H13452 junction with Survey H13449file:///M:/OPRQ350KR21/Surveys/H13452/01_HDR/Reports/Descriptive_Report/Components/52_JNX_49.png2021S40000H13449Fugro USA Marine, Inc.Refer to the DAPR for additional information.Sound velocity profiles were acquired approximately every two hours from the R/V Woldstad using a Teledyne Ocean Science Rapid Cast.There were no conditions or deficiencies that affected equipment operational effectiveness.None Exist