OPR-R341-KR-19Kuskokwim Bay, AK & VicinityKuskokwim Bay, AKTerrasondH13246129 NM SE of KwigillingokAlaskaUnited States400002019Andrew OrthmannNavigable Area2019-05-102019-06-302019-08-19Multibeam Echo SounderMultibeam Echo Sounder BackscattermetersUTCPacific Hydrographic BranchAny 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.ContractorThe project area is located in southwest Alaska near the entrance to the Kuskokwim River in a relatively remote area of the Arctic. Vessel traffic in the region largely consists of barges and other traffic that are transiting to or from Bethel (population 6,456), the hub for SW Alaska which is located up the Kuskokwim River to the north, as well as native communities in the region. The area is heavily influenced by current and sediment transport from the Kuskokwim River. As a result it is relatively shallow with shifting shoals, sandbars, and channels. Fine sand is the predominant bottom type. The area is normally not navigable during winter due to discontinuous sea ice in the bay and river ice flows from the Kuskokwim River. The area is exposed to the west and south, with limited protection from the north and east. Bathymetric data collection was carried from June through August of 2019 under project OPR-R341-KR-19, with final processing and reporting carried out from September through December, 2019. Supporting tide data was acquired from June through October, 2019. Work was completed concurrently with other assigned areas within Kuskokwim Bay and near Nunivak Island, and done in accordance with the Hydrographic Survey Project Instructions (dated May 10th, 2019) and the NOS Hydrographic Surveys Specifications and Deliverables (HSSD), March 2019 edition.59.4737680556163.46337166759.3065313889162.239956667Image showing survey extents.SupportFiles\H13246_Extents.jpgData was successfully acquired to the survey limits or the NALL, whichever was encountered first. The NALL for this survey was the 3.5 m depth limit. 3.5 m water depth was achieved at the required line spacing (400 m). Line segments were intentionally extended or run outside the assigned survey limits on the survey's northern side to ensure good overlap with junctioning surveys there. A gap between this survey and the assigned extents at the junction with overlapping survey H13250 is covered by H13250 within the required line spacing.The overall project OPR-R341-KR-19 is intended to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products in the U.S. Arctic to support commerce in the region. Automatic Identification Systems (AIS) traffic patterns feeding the Hydrographic Health model, along with direct user feedback helped to define the survey area in Kuskokwim Bay, Southwest Alaska. This area is largely unsurveyed and contains mud flats, uncharted shoals, and poorly modeled tides, forcing vessel traffic between the Kuskokwim River and northern communities to take an extended southerly route to stay in safe water. Surveying these areas within Kuskokwim Bay will allow for shorter routes, increasing the safety and efficiency of vessel traffic. This work will also directly support the maritime services available to the native communities of Kwigillingok and Kongiganak. Furthermore, this project will provide support for other NOAA Hydrographic surveys and regional tidal products by installing temporary water level measuring stations in the vicinities of Cape Newenham and Nushagak Peninsula located in Bristol Bay. Survey data within the survey limits is intended to supersede all prior survey data within the project limits.The entire survey is adequate to supersede previous data.All waters in survey area within Sheet 1Set Line Spacing MBES at 400 m (Refer to HSSD Section 5.2.2.4 Option A)All waters in survey areaComplete 5301 LNM. 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 survey area shall be squared off and ensure the full investigation of any features within the surveyed extent.Coverage requirements were met. 5,761 linear nautical miles (LNM) was acquired project-wide, which exceeded the required minimum of 5,301 LNM. The overage of 460 LNM (about 8.7% of required LNM) was collected to compensate for any inefficiencies incidental to the execution of line collection such as excess crossline LNM, data acquired on turns in order to scout depths between lines in shallow water, or lines ran closer together than required. Splits were acquired periodically to disprove charted soundings shoaler than adjacent survey soundings. Splits were usually collected parallel to mainscheme lines, but on occasion were collected perpendicular to mainscheme, transecting the charted sounding location.Image showing survey coverage.SupportFiles\H13246_Coverage.jpgASV-CW50802.30000070.30Qualifier 1050692.10000068.1001494.400000138.409.311000294.62019-06-302019-07-012019-07-032019-07-042019-07-072019-07-082019-07-092019-07-102019-07-122019-07-142019-07-152019-07-162019-07-192019-07-202019-07-232019-07-242019-07-282019-08-022019-08-052019-08-062019-08-082019-08-092019-08-112019-08-142019-08-152019-08-162019-08-172019-08-182019-08-19As described later in this report, there are three lines in the CARIS project incorrectly time-stamped as occurring on JD187 (7/6/19), but they were actually acquired on JD188 (7/7/19). No data was acquired on JD187.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.ASV-CW55.50.5Qualifier 105321.8ASV-CW5 (foreground), and Q105 (background).SupportFiles\Vessels.jpgThe Qualifier 105 (Q105) is a 32 m aluminum-hull vessel owned and operated by Support Vessels of Alaska. The Q105 acquired multibeam data and provided housing and facilities for on-site data processing. The vessel was also used to collect bottom samples, deploy/recover BMPG tide gauges, conduct sound speed casts, and deploy/recover the ASV-CW5 vessel. The ASV-CW5 (C-Worker 5) is a 5.5 m aluminum-hull Autonomous Surface Vessel (ASV) owned and operated by L3-Harris ASV. The ASV was operated in an unmanned but monitored mode, collecting multibeam data in close proximity to the Q105.Teledyne RESONSeaBat 7125 SVMBESTeledyne RESONSeaBat 7101MBESApplanixPOS MV 320 v5Positioning and Attitude SystemTeledyne OceansciencerapidCASTSound Speed SystemValeportrapidPro SVTSound Speed SystemBoth survey vessels were outfit for MBES data collection with similar survey equipment. The ASV-CW5 was equipped with a Reson SeaBat 7125 MBES while the Q105 used a Reson SeaBat 7101 MBES. Both vessels used Applanix POSMV 320 V5 (Wavemaster II) units for attitude and position measurements. Sound speed profiles were collected using a Valeport rapidPro SVT sensor (deployed using a Teledyne Oceanscience RapidCast system) from the Q105 only.Effort was made to ensure crosslines 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 both vessels to ensure there was ample overlap for inter-vessel comparisons, with each vessel crossing the other's mainscheme lines. Since the two vessels worked in close proximity and normally ran parallel lines, crosslines were often collected in sets whenever both vessels were in simultaneous operation. Crosslines were also occasionally 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. Since the area is highly changeable, reconnaissance lines that followed the main channels were usually collected first before proceeding with collection of mainscheme lines that ran perpendicular to the channels. These reconnaissance channel lines sometimes doubled as crosslines, and utilizing them as crosslines caused the crossline percentage to exceed 8%. 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. 0318-Q105-205-A1XL00000 -- 100.0% pass 0416-Q105-218-A4-XL-01 -- 100.0% pass 0458-Q105-221-AC-Junction-02 -- 100.0% pass 0519-Q105-227-AXL-15 -- 100.0% pass 0522-Q105-228-AXL-16 -- 100.0% pass 0525-Q105-228-AXL-16 -- 100.0% pass 0544-Q105-229-AXL-18 -- 100.0% pass 0546-Q105-229-AXL-19 -- 100.0% pass 0092-ASV-CW5-188-AIS -- 100.0% pass 0379-ASV-CW5-193-A2NS08400 -- 100.0% pass 0634-ASV-CW5-205-A1EW15200 -- 100.0% pass 0828-ASV-CW5-218-A3_XL -- 100.0% pass 1138-ASV-CW5-221-AC-Junction-01 -- 100.0% pass 1401-ASV-CW5-227-A_XL -- 100.0% pass 1407-ASV-CW5-227-A_XL -- 100.0% pass 1408-ASV-CW5-227-A_XL -- 100.0% pass 1429-ASV-CW5-227-AXL-14 -- 100.0% pass 1481-ASV-CW5-228-AXL-15 -- 100.0% pass 1143-ASV-CW5-221-A5EW09200 -- 100.0% pass 0462-Q105-221-A4XL-03 -- 100.0% pass 1409-ASV-CW5-227-AXL-13 -- 100.0% pass 0517-Q105-227-AXL-11 -- 100.0% pass 0826-ASV-CW5-218-A3_XL -- 100.0% pass 0927-ASV-CW5-214-C1_01 -- 100.0% pass 0518-Q105-227-AXL-11 -- 100.0% pass 1515-ASV-CW5-229-A_XL -- 100.0% pass 1508-ASV-CW5-228-A_XL -- 100.0% pass 0223-ASV-CW5-190-A5EW10000 -- 100.0% pass 1405-ASV-CW5-227-A_XL -- 100.0% pass 0493-ASV-CW5-195-A5EW03600 -- 99.9% pass 1477-ASV-CW5-228-AXL-15 -- 99.8% pass 0516-Q105-227-AXL-11 -- 99.6% pass 0222-ASV-CW5-190-A5EW12400 -- 99.6% pass 0264-ASV-CW5-191-A5EW03600 -- 99.2% pass 0520-Q105-227-AXL-16 -- 99.0% pass 0404-Q105-214-A4_XL_01 -- 98.8% pass 0515-Q105-227-AXL-01 -- 98.7% pass 1403-ASV-CW5-227-A_XL -- 98.6% pass 1428-ASV-CW5-227-AXL-14 -- 97.9% pass 0227-ASV-CW5-190-A5NS06800 -- 95.0% pass Results: Agreement between the mainscheme surface and crossline soundings is excellent. All crosslines pass QC, with at least 95% of crossline soundings comparing to the mainscheme surface within IHO Order 1a. Refer to Separate II: Digital Data for the detailed Crossline QC reports.ERS via ERTDM0.130ASV0.8.025Q1050.8.0250.13 was provided and used as the uncertainty of the NOAA-provided ERTDM model. Refer to Appendix I for correspondence. The uncertainty layer of the final surface was examined in CARIS HIPS. Uncertainty falls in the range of 0.231 to 0.794 m. Most grid cells are on the lower end of the uncertainty range, approximately 0.270 m. The larger values were observed to be on sand wave features or other areas of highly variable seafloor such as steep seafloor as well as areas exhibiting bottom change, where many soundings of different depths contribute to the depth value of the relatively large 4 m grid cell and result in a higher standard deviation of contributing soundings. The final surface was also analyzed in QCTools (3.1.2), which reported that greater than 99.5% of grid cells in the final surface have uncertainty within allowable TVU for the depth.NOAA's "Gridded Surface Comparison V19.4" utility was used to complete the junction comparisons. The utility differences the surfaces from the junctioning surveys and generates statistics, including the percentage of grid cells that compare to within allowable TVU for the depth. 4 m-resolution CUBE surfaces were used for all Current surveys.Image showing survey junctions.SupportFiles\H13246_Junctions.jpgH13250400002019Terrasond, Ltd.NWAgreement between the two surveys is very good, with a mean difference of 0.09 m with a standard deviation of 0.13 m. 100% of overlapping grid cells compare within the allowable TVU for the depth.H13247400002019Terrasond, Ltd.WAgreement between the two surveys is excellent. The mean difference is 0.01 m with a standard deviation of 0.06 m. 100% of overlapping grid cells compare within the allowable TVU for the depth.H13248400002019Terrasond, Ltd.NEAgreement between the two surveys is excellent, with a mean difference of 0.03 m with a standard deviation of 0.11 m. At least 99.5% of overlapping grid cells compare within the allowable TVU for the depth.Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.POSMV Dropouts (ASV-CW5)Approximately every 24 hours during survey operations the POSMV on the ASV-CW5 would drop offline. This was observed as sudden output of obviously erroneous data by the POSMV such as excessive vessel speeds, incorrect headings, and erroneous motion, followed by an automatic reinitialization of the POSMV. The issue would often repeat 1-2 additional times over a 5-10 minute period before resuming normal operations for an additional 24 hours. No definite cause was determined. When this occurred the ASV-CW5 would break offline, note the issue in the acquisition log, circle back and proceed with rerunning the affected section of line. The affected section of line was subsequently rejected in processing. Since affected data was rejected and reran there is no adverse affect on final deliverables.Bottom ChangeBottom change is evident throughout this survey, especially when data was collected days to weeks apart. The survey area is a sediment deposition area at the mouth of a major river. Large tidal and riverine currents flow across the area and form transitory features such as channels, sandbars, and submerged shoal areas. Sandwaves and related signs of sediment transport are readily apparent in the MBES data. As a result, vertical busts that exceed allowable TVU occur periodically in the dataset. These vertical changes commonly approach 0.5 m, with extreme changes of up to 1.8 m in areas of large sandwaves, such as in the example shown in the following figure. No attempt was made to edit or otherwise manually choose a seafloor in areas where this occurred. Bottom change example from the project patch test location, which was completed in the SE portion of this survey area. Light green soundings were collected on JD195, while dark green soundings were collected on JD231. Movement of the sandwaves during this 36 day period results in horizontal shifts of 2-5 meters and up to 1.8 meters of vertical change.SupportFiles\Bottom_Change_Example.png2 hoursSound speed profiles or "casts" were acquired aboard the Q105 while underway with a Teledyne Oceanscience RapidCAST system, which utilized a Valeport rapidPro SVT sound speed profiler. Surface sound speed at the sonar head 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 favored to ensure that changes across the full water column were measured. The cast data was used to correct the sounding data for both vessels, using the "nearest in distance within time" (set to 4 hours) within CARIS HIPS.All equipment and survey methods were used as detailed in the DAPR.GPS Vertical BustsVertical busts attributable to GPS height positioning error between crosslines or overlapping mainscheme are apparent periodically in the data set. These are normally less than 0.15 m, with extreme cases showing up to 0.30 m of vertical separation. However, all crosslines--including those exhibiting or crossing areas exhibiting these vertical busts--agree with mainscheme within IHO Order 1a, and final surfaces are within allowable TVU for the depth.Deviations from the Corrections to Echo Soundings section of the DAPR are itemized below. Note that in all cases final data is within specifications. Delayed Heave Exceptions The following lines could not have Delayed Heave loaded. This was usually due to a software crash or other issue causing logging to the associated POS file to cease early. Real-time heave was used instead during all processing phases including SVP correction, Compute GPS Tide, and Merge on these lines. 0004-ASV-CW5-181-A5EW00000_-_0005 0475-ASV-CW5-195-A2EW14400_-_0002 0927-ASV-CW5-214-C1_01_-_0001 0011-ASV-CW5-181-A4EW02800_-_0005 0011-ASV-CW5-181-A4EW02800_-_0006 0011-ASV-CW5-181-A4EW02800_-_0007 1438-ASV-CW5-227-A_IN_23_-_0001 0252-Q105-201-A3EW03600_-_0002 0265-ASV-CW5-191-A4EW03600_-_0002 0266-ASV-CW5-191-A4EW03600_-_0001 0268-ASV-CW5-191-A4EW03600_-_0001 Applanix Smart Base (ASB) Exceptions The following lines used SBETs processed using ASB instead of PPRTX to improve vertical agreement. ASV lines: ASV lines with prefix 4 through 24, 265 to 268, and 491-492 Q105 lines: Q105 lines with prefix 165 to 178 GPS Height Smoothing The following lines were loaded with GPS heights that had been smoothed to remove spikes and/or short term drifts using a 6-minute moving average. The GPS height data was loaded using CARIS' Generic Data Parser utility from text files at a rate of 1 Hz, which are included with the survey deliverables. Since the smoothing process removed heave data from the GPS record, the Apply Dynamic Heave option was set to "None" during computation of GPS Tide for these lines. More details on this process are available in the DAPR. 0006-Q105-185-A5EW02000_-_0001 0067-Q105-188-A1EW08000_-_0002 0096-Q105-191-A4EW03200_-_0001 0097-Q105-191-A3EW03200_-_0001 0138-Q105-193-A3EW09600_-_0001 0163-Q105-195-A2EW10800_-_0001 0164-Q105-195-A2EW10000_-_0001 0164-Q105-195-A2EW10000_-_0002 1129-ASV-CW5-221-A4EW13200_-_0001 1129-ASV-CW5-221-A4EW13200_-_0002 1495-ASV-CW5-228-A2EW14000_-_0001 1509-ASV-CW5-228-A1EW12800 (all segments) 1515-ASV-CW5-229-A_XL (all segments) Time Stamp Error For unknown reasons a few lines imported into CARIS with incorrect bathymetric timestamps. The lines were acquired on JD188 (7/7/19) but the bathymetric timestamps are 24 hours behind, showing JD187 (7/6/19). The lines were salvaged by shifting attitude, navigation, and SVP data back 24 hours to match the bathymetric times. This was done by loading motion, gyro, heave, and delayed heave (from POS file) and navigation and GPS height (from SBET) with a -86400 second time correction. SVP correction was accomplished using a custom SVP file ("Q105_SheetA_Lines54-61only_minus1day.svp", included with the SVP data) that contained applicable SVP casts with their time likewise shifted back 1 day. The lines are fully repaired but incorrectly show as 1 day behind actual time of acquisition in CARIS. 0054-Q105-188-A1EW10800 (all segments) 0056-Q105-188-A1EW10000 (all segments) 0061-Q105-188-A1EW09200 (all segments)All sounding systems were calibrated as detailed in the DAPR.All equipment and survey methods were used as detailed in the DAPR.NOAA Extended Attribute Files V2019.3NOAA Extended Attributes were used for the Final Feature File (FFF) submitted with the survey deliverables.H13246_MB_4m_MLLW_FinalCARIS Raster Surface (CUBE)4080NOAA_4mMBES Set Line SpacingH13246_MBAB_1m_ASV_400kHz_1of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingH13246_MBAB_1m_ASV_400kHz_2of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingH13246_MBAB_1m_ASV_400kHz_3of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingH13246_MBAB_1m_Q105_240kHz_1of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingH13246_MBAB_1m_Q105_240kHz_2of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingH13246_MBAB_1m_Q105_240kHz_3of3MB Backscatter Mosaic1080N/AMBES Set Line SpacingThe final depth information for this survey was submitted as a CARIS BASE surface (CSAR format) which best represented the seafloor at the time of the 2019 survey. The surface was created from fully processed data with all final corrections applied. The surface was created using NOAA CUBE parameters and resolutions by depth range in conformance with the 2019 HSSD. The surface was finalized, and designated soundings were applied where applicable. Horizontal projection was selected as UTM Zone 3 North, NAD83. A non-finalized versions of the CSAR surface is also included which does not have a depth cutoff applied. This does not have the "_Final" designation in the filename. An S-57 (.000) Final Feature File (FFF) was submitted with the survey deliverables as well. The FFF contains data not readily represented by the final surface, including bottom samples and shoreline verification results (if any). Each object is encoded with mandatory S-57 attributes and NOAA Extended Attributes (V2019.3). Georeferenced multibeam backscatter mosaics (Geotif format in NAD83 UTM Zone 3N, 1 m resolution) were also produced and are provided with the survey deliverables. Separate mosaics were produced for each vessel. Note that backscatter processing and mosaic generation was not a requirement and the mosaics are provided as-is. The mosaics may have flaws or holidays which could be addressed through further processing. However, they are of sufficient quality to show the relative changes in seafloor type across the survey area.SAR: Only two mosaics are required for H13246: one for the vessel ASV at 400kHz and one for 400kHz, and one for Q105 at 240kHz. The reviewer was tasked with creating paired GSF files from the .db and .qpd files. As a result, it was easy to simply re-mosaic backscatter geotiffs in review for the final products. These new mosaics are H13246_MBAB_ASV_400kHz_1of2 and H13246_MBAB_Q105_240kHz_2of2. Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterPort Moller9463502Cape Pierce9465137Naknek9465203Kulukak Point9465265Levelock9465419Ishkowik9465993Cape MendenhallAAAAAAASW Kuskokwim BayBBBBBBBCape CorwinCCCCCCCERS via ERTDMR341KR2019_ERTDM_NAD83-MLLWAll soundings were reduced to MLLW using the ERTDM NAD83 to MLLW separation model grid file provided by NOAA using ERS methodology. Discrete tide zones were generated using project gauge data but were used for comparison purposes only. A comparison between the provided ERTDM model and a ERZT model created using the tide zones was undertaken. There is generally good agreement between the models, with project-wide agreement averaging 0.033 m with a standard deviation of 0.271 m. See the HVCR for additional information.North American Datum 1983Projected UTM 3Smart BaseRTXThe Trimble PP-RTX subscription-based correction service within POSPac was used for final positioning. Results were good overall, usually at 0.10 m or better vertically. Applanix Smart Base (ASB) was utilized on a small number of lines (itemized earlier in this report) instead of PPRTX to improve vertical agreement. Refer to the DAPR for additional details.The survey vessels were configured to receive RTK-level correctors via Hemisphere AtlasLink SBAS (L-band) receivers. This was utilized throughout the survey on the ASV-CW5 but only briefly at the start of operations on the Q105. However, all real-time correctors were superseded in processing with PPK correctors from Applanix POSPac. Refer to the DAPR for additional detail.The FAA Wide Area Augmentation System (WAAS) was used for real-time positioning on the Q105 for the majority of the survey. These positions were superseded in processing with PPK correctors from Applanix POSPac, as described in the DAPR.The chart comparison was performed by examining the best-scale Electronic Navigational Charts (ENCs) that intersect the survey area. The latest edition(s) available at the time of report compilation were used. The chart comparison was accomplished by overlaying the finalized BASE surface(s) with shoal-biased soundings and the final feature file (FFF) on the charts in CARIS HIPS. The general agreement between charted soundings and survey soundings was then examined and a more detailed comparison was undertaken for any shoals or other dangerous features. In areas where a large scale chart overlapped with a small scale chart, only the larger scale chart was examined. When comparing to survey data, chart scale was taken into account so that 1 mm at chart scale was considered to be the valid radius for charted soundings and features. Results are shown in the following sections. It is recommended that in all cases of disagreement this survey should supersede charted data. USCG Notice to Mariners (NM) and USCG Local Notice to Mariners (LNM) for District 17 from week 26/2019 through 34/2019 were checked and no items were found that affected the survey area. Note that ENC metadata and non-specific geographic area objects on the ENCs that overlap the survey area were not investigated.US3AK84M200000122018-08-072019-10-08US2AK95M153407692018-08-202019-10-16Shoals or potentially hazardous features exist for this survey, but were not investigated. Shoals, either exposed or submerged at low water, are common inshore of the 3.5 m depth limit. Areas inshore of 3.5 m should be clearly marked on the charts as unsurveyed or otherwise hazardous for navigation. All previously charted shoals have shifted position and should be updated based on the results of this survey. All charted notes regarding tidal currents, tide rips, breakers, and ripples on submerged shoals should be retained. No DTONs were submitted for this survey. The CTNARE (CAUTION AREA) objects on the ENCs noting the region as a "Changeable Area" should be retained.No charted features exist for this survey.No uncharted features exist for this survey.No maintained 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.A charted buoy on US3AK84M at 59-18-44.4 N, 162-18-32.4 W was confirmed to be serving its intended purpose at this approximate position. Note however that all buoys in this area are placed seasonally by the USCG and their position is subject to change.No Maritime Boundary Points were assigned for this survey.Twelve bottom samples were assigned in this area via the PRF. Samples were obtained at all but one location. All returned primarily fine to medium grained sand. One sample could not be obtained at the assigned location 59-23-54.289 N, 162-15-54.458 W. Three attempts were made at the location but no sample could be obtained. Refer to the FFF submitted with the survey deliverables for results.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.As described earlier in this report, the area is in the depositional zone of a major river. Migrating sandbars, shoals, and channels are common. Sandwaves are evident on the seafloor in many areas. During survey operations, currents of 2-3 knots were commonly experienced, with strongest currents on the survey's east side. Currents were oriented north-south, parallel to the orientation of the channels and shoals. Greatest current speeds were experienced on the ebb tide due to the combination of river and tidal current.No present or planned construction or dredging exist within the survey limits.Additional survey to the south and southwest of this sheet is recommended. Relatively shallow depths that extend in a linear fashion from this survey's northern limits to its southern limits will require that many vessels that are transiting in an east-west direction, for example between Etolin Strait and the Kuskokwim River, will need to navigate to the south of this sheet through an area that is still largely uncharted.No new insets are recommended for this area.Field operations and data processing contributing to the completion of this survey were conducted under my direct supervision with frequent personal checks of progress, integrity, and adequacy.This report, digital data, and all other accompanying records are approved. All records are hereby respectfully submitted for final review and acceptance.The survey data meets or exceeds the requirements set forth in the 2019 NOS Hydrographic Surveys Specifications and Deliverables document as well as the Hydrographic Survey Project Instructions and Statement of Work. This data is 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 this Descriptive Report.Andrew Orthmann, C.H.TerraSond Charting Program Manager2019-12-16Survey Outlines2019-09-10MMO Training Logsheet and Observation Logs2019-09-12NCEI Sound Speed Data Submission2019-09-12Coast Pilot Report2019-09-13Tides and Water Levels Package - 9465419 Levelock2019-11-15Tides and Water Levels Package - 9465993 Ishkowik2019-11-15Tides and Water Levels Package - 9463502 Port Moller2019-11-16Tides and Water Levels Package - 9465203 Naknek2019-11-18Tides and Water Levels Package - 9465137 Cape Pierce2019-11-19Tides and Water Levels Package - 9465265 Kulukak Point2019-11-20Tides and Water Levels Package - AAAAAAA Cape Mendenhall2019-11-23Tides and Water Levels Package - BBBBBBB SW Kuskokwim Bay2019-11-23Tides and Water Levels Package - CCCCCCC Cape Corwin2019-11-27