No Maritime Boundary Points were assigned for this survey.Four bottom samples were assigned via the PRF. Samples were obtained at or near all locations. Samples in this area were primarily black sand and mud. Refer to the FFF submitted with the survey deliverables for results.No new insets are recommended for this area.No new surveys or further investigations are recommended for this area.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 during the ebb and flood portions of the tidal cycle. Currents were generally oriented north-south, running parallel to the channels.No overhead features exist for this survey.No Aids to navigation (ATONs) exist for this survey.No ferry routes or terminals exist for this survey.No platforms exist for this survey.No present or planned construction or dredging exist within the survey limits.No submarine features exist for this survey.No charted features exist for this survey.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.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.2018-08-07122019-10-08200000US3AK84M2018-08-2092019-10-161534076US2AK95MAerial view of a sandbar exposed at low water in this survey area, located at 59-29-47 N, 162-51-44 W. Similar sandbars (exposed at low water) and other shoals are common in the unsurveyed areas less than 3.5 m depth.SupportFiles\Sandbar_Example.jpgShoals or potentially hazardous features exist for this survey, but were not investigated. This survey was tasked to survey to 3.5 m water depth. However shoals and sandbars of significantly less depth, often exposed at low water, were observed inside the 3.5 m contour during survey operations. The areas inside 3.5 m water depth should be clearly noted as unsurveyed on the updated charts to discourage navigation by mariners.No uncharted features exist for this survey.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 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.Projected UTM 3The 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) processing mode within POSPac was utilized for a handful of POS files to improve vertical agreement. These were itemized earlier in this report. Refer to the DAPR for additional detail.Smart BaseRTXNorth American Datum 1983Port Moller9463502Cape Pierce9465137Naknek9465203Kulukak Point9465265Levelock9465419Ishkowik9465993Cape MendenhallAAAAAAASW Kuskokwim BayBBBBBBBCape CorwinCCCCCCCMean Lower Low WaterAll 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.R341KR2019_ERTDM_NAD83-MLLWERS via ERTDMAdditional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.2019-09-10Survey Outlines2019-09-12MMO Training Logsheet and Observation Logs2019-09-12NCEI Sound Speed Data Submission2019-09-13Coast Pilot Report2019-11-15Tides and Water Levels Package - 9465419 Levelock2019-11-15Tides and Water Levels Package - 9465993 Ishkowik2019-11-16Tides and Water Levels Package - 9463502 Port Moller2019-11-18Tides and Water Levels Package - 9465203 Naknek2019-11-19Tides and Water Levels Package - 9465137 Cape Pierce2019-11-20Tides and Water Levels Package - 9465265 Kulukak Point2019-11-23Tides and Water Levels Package - AAAAAAA Cape Mendenhall2019-11-23Tides and Water Levels Package - BBBBBBB SW Kuskokwim Bay2019-11-27Tides and Water Levels Package - CCCCCCC Cape CorwinTerraSond Charting Program Manager2019-12-15Andrew Orthmann, C.H.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.All equipment and survey methods were used as detailed in the DAPR.GPS Vertical BustsVertical busts attributable to GPS 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 vertical busts--pass within IHO Order 1a, and final surfaces are well within allowable TVU for the depth.Image showing survey junctions.SupportFiles\H13250_Junctions.jpgNOAA'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.Agreement between the two surveys is excellent, with a mean difference of 0.00 m with a standard deviation of 0.09 m. At least 99.5% of overlapping grid cells compare within the allowable TVU for the depth.Terrasond, Ltd.NH13251100002019Agreement 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.Terrasond, Ltd.SH13246400002019POSMV 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.All equipment and survey methods were used as detailed in the DAPR.The NOAA-provided ERTDM model has an uncertainty of 0.13 meters. Refer to Appendix I for correspondence. The uncertainty layer of the final surface was examined in CARIS HIPS. Uncertainty falls in the range of 0.261 to 0.567 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 cut banks of shoals and sandbars where many soundings of different depths contribute to the depth value of the relatively large 4 m grid cell, resulting in a higher standard deviation for the grid cell. 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.ASV-CW50.96NA0.025NAQ1050.96NA0.025NA00.13ERS via ERTDM2 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.Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.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 was uncharted, 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. Use of these lines as crosslines as well as the collection of crosslines in two-vessel sets led to incidental collection of additional crossline LNM beyond the required 8% of mainscheme. 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. 0095-ASV-CW5-188-E3NS10000 -- 100.0% pass 0963-ASV-CW5-218-E_North_XL -- 100.0% pass 0395-ASV-CW5-194-E3EW11200 -- 100.0% pass 0380-ASV-CW5-193-E1EW00800 -- 100.0% pass 1048-ASV-CW5-219-E3_XL -- 100.0% pass 0096-ASV-CW5-188-E3NS13200 -- 100.0% pass 0406-ASV-CW5-194-E4EW02000 -- 100.0% pass 0097-ASV-CW5-188-E4NS15600 -- 99.6% pass 0462-ASV-CW5-195-E1NS06000 -- 99.2% pass 0094-ASV-CW5-188-E1NS15600 -- 97.9% pass Results: Agreement between the mainscheme surface and crossline soundings is excellent. At least 95% of 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.Example of bottom change in an area of sandwaves from CARIS Subset view (at 59-39-28 N, 162-48-54 W). Light green soundings were collected on JD192, dark green soundings on JD219. There is about 5 m of horizontal displacement of the sandwaves over this 27 day period, leading to vertical differences of up to 0.7 m.SupportFiles\BottomChangeExample.jpgBottom 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 and horizontal busts that exceed allowable TVU occur periodically in the dataset. No attempt was made to edit or otherwise manually choose a seafloor in areas where this occurred. A common example showing the migration of sandwaves is included below.NOAA Extended Attributes were used for the Final Feature File (FFF) submitted with the survey deliverables.NOAA Extended Attribute Files V2019.3The 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. Mosaics were produced separately 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.CARIS Raster Surface (CUBE)H13250_MB_4m_MLLW_FinalMBES Set Line Spacing0804NOAA_4mMB Backscatter MosaicH13250_MBAB_1m_Q105_240kHz_1of1MBES Set Line Spacing0801N/AMB Backscatter MosaicH13250_MBAB_1m_ASV_400kHz_1of3MBES Set Line Spacing0801N/AMB Backscatter MosaicH13250_MBAB_1m_ASV_400kHz_2of3MBES Set Line Spacing0801N/AMB Backscatter MosaicH13250_MBAB_1m_ASV_400kHz_3of3MBES Set Line Spacing0801N/ABoth 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.Teledyne RESONSeaBat 7125 SVMBESTeledyne RESONSeaBat 7101MBESApplanixPOS MV 320 v5Positioning and Attitude SystemTeledyne OceansciencerapidCASTSound Speed SystemValeportrapidPro SVTSound Speed SystemRefer 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-CW5 (foreground), and Q105 (background).SupportFiles\Vessels.jpgASV-CW50.55.5Qualifier 1051.832The 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.All sounding systems were calibrated as detailed in the DAPR.Deviations from the Corrections to Echo Soundings section of the DAPR are itemized below. Note that in all cases final data is within specifications. POSPac Processing Mode Exceptions In some cases, Applanix Smart Base (ASB) processing mode in Applanix POSPac MMS software was utilized instead of the project default PP-RTX to improve vertical agreement with overlapping data. SBETs and associated files included with the survey deliverables include "ASB" in their filename to denote their use of the alternative processing mode. Affected POS files and survey lines are listed below. POS files: 2019-219-0004-Q105 2019-228-0020-ASV 2019-193-0058-Q105 2019-193-0503-Q105 Survey Line Files: 0425-Q105-219-E4-XL-01_-_0001 1459-ASV-CW5-228-E1EW09600_-_0001 1460-ASV-CW5-228-E1EW09200_-_0001 1461-ASV-CW5-228-E1NS06400_-_0001 1461-ASV-CW5-228-E1NS06400_-_0002 1462-ASV-CW5-228-E1EW04400_-_0001 1463-ASV-CW5-228-E1EW04800_-_0001 0120-Q105-193-E2EW02000_-_0001 0120-Q105-193-E2EW02000_-_0002 0121-Q105-193-E2EW00800_-_0001 0121-Q105-193-E2EW00800_-_0002 0122-Q105-193-E1EW09200_-_0001 0122-Q105-193-E1EW09200_-_0002 0123-Q105-193-E1EW08800_-_0001 0124-Q105-193-E1EW08000_-_0001 0125-Q105-193-E1EW06800_-_0001 0127-Q105-193-E1EW04000_-_0001 0128-Q105-193-E1EW03200_-_0001 0129-Q105-193-E1EW02400_-_0001 0129-Q105-193-E1EW02400_-_0002 0130-Q105-193-E1EW01200_-_0001 0131-Q105-193-E1EW00400_-_0001 0131-Q105-193-E1EW00400_-_0002 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. 1055-ASV-CW5-219-E5_Explore_-_0001 1055-ASV-CW5-219-E5_Explore_-_0002 0458-ASV-CW5-194-E1NS07600_-_0001 0274-ASV-CW5-191-E4NS11600_-_0002 0133-ASV-CW5-189-E4EW00800_-_0001 0134-ASV-CW5-189-E4EW00800_-_0001 0382-ASV-CW5-193-E3EW06400_-_0001 0385-ASV-CW5-193-E3EW08800_-_0001 0386-ASV-CW5-193-E3EW08800_-_0001 0387-ASV-CW5-193-E3EW08400_-_0001 0388-ASV-CW5-193-E3NS08800_-_0001 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 smoothed 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 are available in the DAPR. 0110-Q105-192-E2EW10400_-_0001 0112-Q105-192-E2EW09200_-_0001 xxx 0146-Q105-194-E2EW00400_-_0001 0356-ASV-CW5-193-E1EW08400_-_0001 0357-ASV-CW5-193-E1EW07600_-_0001 1055-ASV-CW5-219-E5_Explore_-_0001 1055-ASV-CW5-219-E5_Explore_-_0002 1451-ASV-CW5-227-E1NS12800_-_0001 1451-ASV-CW5-227-E1NS12800_-_0002 1451-ASV-CW5-227-E1NS12800_-_0003Image showing survey coverage.SupportFiles\H13250_Coverage.jpgThe entire survey is adequate to supersede previous data.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.Image showing exploratory lines that extend outside survey area in an attempt to connect an alternate navigable route to the Kuskokwim River. Soundings from the lines are recommended for charting to provide depth information in an otherwise uncharted area.SupportFiles\ExploratoryLines.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). In consultation with OCS OPS, a small number of exploratory lines were collected outside the survey limits to the east. These were collected in an attempt to determine if there was a navigable (>3.5m depth) route between this survey's SE portion and the Kuskokwim River, which had the potential to provide an alternate route into the river for mariners. However, the lines terminated in 3.5 m water depth and a navigable route was not found. The lines were collected to the same standards as all other lines on this survey, and it is therefore recommended their sounding data be used to update overlapping charts which would otherwise remain devoid of soundings in this area. Correspondence regarding the collection of these lines is included in Appendix II.ASV-CW50000061.8554.300Qualifier 105000000129.6000000061.89.04683.9002019-07-072019-07-082019-07-102019-07-112019-07-122019-07-132019-07-142019-07-232019-07-242019-08-062019-08-072019-08-082019-08-152019-08-1640111.400Image showing survey extents.SupportFiles\H13250_Extents.jpgThe project area is located in southwest Alaska near the entrance to the Kuskokwim River in a relatively remote area of the Arctic. The area was uncharted at the time of this survey. Vessel traffic largely consists of barges that are transiting to or from Bethel (population 6,456), the hub for the SW Alaska region which is located up the Kuskokwim River, 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. Sand and mud are the predominant bottom types. 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 open and exposed in all directions except the north. Bathymetric data collection was carried out in July and 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. Work was 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.59.4426162.63300833359.8663472222163.116705556All waters in survey area within Sheets 1 through 5 and Sheet 8Set 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. Note that on the SW and SE portions of the survey area lines were not run along the survey extents, leaving an apparent gap between the southernmost lines and the southern survey extents. This was done intentionally to avoid collecting redundant LNM since the area is within 400 m of lines run in junctioning Current survey H13246 to the south, which was surveyed to identical requirements.ContractorKwigillingok to Kongiganak ApproachesUnited States40000Alaska5H13250Kuskokwim Bay, AKTerrasondOPR-R341-KR-19Kuskokwim Bay, AK & Vicinity2019Navigable Areameters2019-07-072019-08-16Andrew OrthmannAny 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 BranchUTC2019-05-10Multibeam Echo Sounder