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 the review were used. The chart comparison was accomplished by overlaying the finalized BASE surfaces with shoal-biased soundings, and final feature file 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. USCG LNM and NMs applicable to the survey area issued subsequent to the start of operations and prior to completion of operations were also examined. This consisted of LNM/NMs 36/18 through 07/19. None were found that were applicable to this survey. 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. It is recommended that in all cases of disagreement this survey should supersede charted data. Results are shown in the following sections. false2019-03-1980000US4TX31M2019-03-1126General sounding agreement is excellent, with most soundings agreeing to 0.5 m or better. There are no apparent trends in deepening or shoaling.file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/US4TX31M_Soundings.jpgSoundings from this survey (blue) overlaid on US4TX31M (black). Soundings in meters.false2019-03-0480000US4TX28M2018-11-1618General sounding agreement is excellent, with most soundings agreeing to 0.5 m or better. There are no apparent trends in deepening or shoaling.file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/US4TX28M_Soundings.jpgSoundings from this survey (blue) overlaid on US4TX28M (black). Soundings in meters.One obstruction feature was found with SSS and developed with MBES during this survey. It is located at 28-06-53.2548 N, 96-39-31.3949 W, with a least depth of 12.763 m. Nearby charted depths range from 14.6 to 15.5 m. It is recommened for charting. Three charted wrecks were assigned for investigation in the CSF: 1. Two wrecks in close proximity (one at 28-10-20.40924 N, 96-40-05.38788 W, the other at 28-10-19.14924 N, 96-40-00.7799 W) were not found by this survey. The area received Complete MBES within the assigned search radii and no evidence of these wrecks were found. These are recommended for deletion. 2. A wreck at 28-14-10.41432 N, 96-36-24.9048 W was not fully investigated due to its position inside the NALL. The survey crew visually checked the nearby beach and could not find evidence of this wreck. However, it is possible it is between the NALL and the beach. It is recommeded this be retained and charted. Refer to the FFF for all results. No DTONs were submitted 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.No charted features exist for this survey.6 samples were assigned in the project PRF. Samples were successfully obtained at all locations. Photographs were taken but samples were discarded. Bottom sample results are provided in the accompanying FFF.No uncharted features exist for this survey.No Maritime Boundary Points were assigned for this survey.Shoreline was not assigned in the Hydrographic Survey Project Instructions or Statement of Work.No ferry routes or terminals exist for this survey.A private buoy is charted at 28-10-46.902 N, 96-41-03.549 W within the survey area. It was not observed during operations. It is unclear what purpose this may have originally served since there are no features of note nearby. This was not reported to the USCG because this ATON is not registered in the USCG Light List (V4, 2019). Recommend removal from the chart. No other ATONs, charted or observed, exist in the survey area.No abnormal seafloor and/or environmental conditions exist for this survey.No prior survey comparisons were required for this survey.Platforms exist within the survey area. Most were found near their charted location but better positions were commonly determined based on sonar data. Platforms were photographed when practical. Refer to the FFF for results.No present or planned construction or dredging exist within the survey limits.Charted pipelines exist in the area but were not readily discernible in the survey data. None were found to be elevated or of navigational concern. All are recommended for retention in the FFF.No overhead features exist for this survey.No new insets are recommended for this area.No new surveys or further investigations are recommended for this area.Port Lavaca, TXOPR-K376-KR-18Terrasond, Ltd.Port Lavaca, TXSide Scan SonarMultibeam Echo Sounder2019-02-042018-09-04Atlantic Hydrographic BranchNavigable Area2019UTC2018-07-18Universal Transverse Mercator (UTM)Andrew 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 14N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit.metersContractor6United StatesH13184Texas4000014 NM ENE of Cedar BayouAdditional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.North American Datum 1983Positions were post-processed in Applanix POSPac MMS software using Trimble PP-RTX as the correction source. RMS errors were generally at 0.10 m or better, both horizontally and vertically.Applanix Smart Base (ASB) was used as a comparison against Trimble PP-RTX results, and generally compared to 0.10 m or better.Smart BaseProjected UTM 14Except for any exceptions noted earlier in this report, WAAS was used for real-time positioning only, and was replaced in post-processing with PP-RTX solutions for final MBES data. However SSS positions were not post-processed and are therefore based on WAAS positioning.Reduction to MLLW was accomplished using ERS methodology via VDATUM, except for any exceptions noted earlier in this report. The VDATUM model was provided by NOAA prior to operations and had an uncertainty specified as 10.4 cm. The VDATUM model was validated during this survey using comparisons with NWLON gauge data and found to be acceptable for tidal reduction. See the HVCR for validation reports.VDATUM_Outline_Shape_xyNAD83-MLLW_geoid12b.csarERS via VDATUM*Survey H13184 is considered a hybrid ERS survey as the Project Instruction's ERS requirement was not met as detailed in DR section B.3.3. No waiver was obtained by the Field Unit acknowledging the vertical correction deviation of H13184 bathymetric data to MLLW through traditional correction referencing direct water levels from NOAA's NWLON reference station Matagorda Bay Entrance (8773767).Mean Lower Low WaterThis project is located in the vicinity of Port Lavaca, which includes the Matagorda Bay Shipping Channel. Port Lavaca is a major sea port that allows shipping to support the fishing, manufacturing, agriculture, tourism, as well as the fishing industries in the state of Texas. As a leader in the shrimp processing industry, Port Lavaca allows million tons of seafood to be shipping through its port yearly. Port Lavaca also supports shipping for Matagorda Bay, which houses several large manufacturing plants and a nuclear station. The U.S. Army Corps of Engineers maintains the Matagorda Bay Shipping Channel which is dredged and there are future plans to expand this dredged channel to 44 ft in depth and 400 ft wide. The survey area covers the approaches to the shipping channel in an effort to cover all shipping traffic into the Matagorda Shipping Channel. Recent hurricane activity in 2017 has made previous bathymetry in the area unreliable. This survey will allow shipping activities to continue into the Port of Lavaca.Survey total LNM was 1325.25 nmi, and the total Square NM was 54.51004.60580445.40820.1000642.848.00324.0000Bunny Bordelon00177.310.00121.4000Bella Marie060054.82018-09-042018-09-092018-09-102018-09-122018-09-182018-10-092018-10-122018-10-172018-10-202018-10-222018-10-232018-10-242018-10-252018-10-262018-10-282018-10-292018-10-302018-11-022018-11-032018-11-042018-11-052018-11-062018-11-072018-11-082018-11-152018-11-172018-11-182018-12-032018-12-042018-12-052018-12-062018-12-102018-12-112018-12-152018-12-162019-01-242019-02-04file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13184_Survey_Coverage.jpgGraphic showing survey coverage extents.Approximately 9,103 LNM were collected project-wide, which exceeds the minimum of 7,869 required in the Project Instructions. The 13.5% overage was largely due to unplanned infill/rerun work in areas of marginal data. Both "Option A: Complete Coverage Multibeam" and "Option B: 100% side scan sonar coverage with concurrent multibeam" were used to meet HSSD Section 5.2.2.3 "Complete Coverage" requirements during this survey. Option B was favored whenever possible and used for most of the area, but Option A was also frequently exercised when the SSS equipment was experiencing issues or SSS data quality had degraded to an unacceptable degree. Infills/reruns on holidays in Option B areas were also frequently MBES-only if MBES was capable of efficiently covering the holiday. Holidays without either coverage type that were found to be inshore of the NALL after initial data processing (including application of tide correctors) were normally not infilled. Additionally, in a few cases minor holidays between the coverage types opened after application of final MBES and SSS correctors -- these were examined for evidence of features and none were found. Similarly, minor holidays covered with the overlap of Junctioning surveys were generally not infilled.file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13184_CompleteMBES.jpgGraphic showing areas covered with "Option A" Complete Coverage. All others received "Option B". Crosslines as well as MBES-only developments and infills on "Option B" areas not shown.Complete Coverage (Refer to HSSD Section 5.2.2.3)H13180-H13187, except H13181LNM no less than 7869 LNM. Report significant shoaling via weekly progress report. COR may adjust survey prioritization based on observed shoaling.All waters in survey areaThe entire survey is adequate to supersede previous data.The survey area is located offshore SE Texas, centered on Port Lavaca. Water depths range from approximately 3.5 to 15 meters. Field work was carried out between September, 2018 and February, 2019. Final processing and reporting was carried out between March and May, 2019. Eight other nearby sheets were surveyed concurrently. Work was done in accordance with the Hydrographic Survey Instructions (dated July 18th, 2018) and the NOS Hydrographic Surveys Specifications and Deliverables (HSSD), April 2018 edition.96.744734888928.254328333396.516757944428.0777411111file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13184_Survey_Outline.jpgGraphic showing survey extents.Survey limits were acquired in accordance with the requirements in the Project Instructions and the HSSD.TerraSond Charting Program Manager2019-05-13Andrew Orthmann, C.H.The survey data meets or exceeds requirements as set forth in the 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 the Descriptive Report.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.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.2019-04-25Coast Pilot Report2019-04-24VDatum Validation Report for Port Lavaca2019-04-09NCEI Sound Speed Data Submission2019-03-22Marine Mammal Observers Training Logsheet and Observation Logs2018-09-18Port Lavaca Boat Float Tide AnalysisNOAA Profile V_5_7NOAA Extended Attribute File V5.7 was used as the most current feature file version at the commencement of survey acquisition.The final depth information for this survey was submitted as CARIS BASE surfaces (CSAR format) which best represented the seafloor at the time of the survey. The surfaces were created from fully processed data with all final corrections applied. Surfaces were created using NOAA CUBE parameters and resolutions by depth range in conformance with the 2018 HSSD. Surfaces were finalized, and designated soundings were applied. Horizontal projection was selected as UTM Zone 14 North, NAD83. Non-finalized versions of the CSAR surfaces are also included which do not have a depth cutoff applied. These do not have the "_Final" designation in the filename. A crossline QC surface is also included with the surface deliverables ("H13184_XLQC-MS-only_2m"). This is the 2 m resolution CUBE surface in CSAR format discussed previously in the crossline section used to create the crossline QC reports. This surface excludes crosslines. It is included for reference only and should not be used for charting. SSS mosaics were exported from Chesapeake SonarWiz 7 software at 1 m resolution using a grayscale pallet per the 2018 HSSD. Separate coverages were exported from each vessel and then combined into one image in CARIS HIPS. The grayscale coverages are not the SonarWiz default color pallet, which is a bronze color -- as a result the grayscale images appear rougher and less visually appealing than the bronze images. Therefore, bronze color versions are also included for reference and are recommended for use over the grayscale versions. An S-57 (.000) Final Feature File (FFF) was submitted with the survey deliverables as well. The FFF contains meta-data and other data not readily represented by the final surfaces, including bottom samples and feature investigation results. An S-57 SSS contact file is also included. Each object is encoded with mandatory S-57 attributes and NOAA Extended Attributes (V#5.7).CARIS Raster Surface (CUBE)1NOAA_1mComplete MBESH13184_MB_1m_MLLW_Final020SSS Mosaic1N/A100% SSSH13184_SSSAB_1m_400kHz020All sounding systems were calibrated as detailed in the DAPR.1. SVP Profile Exceptions As described earlier, in processing, lines with excessive sound speed error were analyzed to determine if better results could be obtained from manually choosing a specific sound speed profile instead of using the project default "nearest in distance within time 4 hours". To apply in CARIS, this necessitated either using different selection criteria (such as nearest in distance), or placing individual casts in their own CARIS SVP file and applying using the custom file instead of the sheet-wide file which contained all casts. These often also required utilizing a custom time allowance instead of the standard 4-hour cast selection criteria. These files are included with the CARIS SVP data (if applicable) and were applied as follows: (All Bunny Bordelon) JD299 Used NDT 4-hrs with cast: JD299 02:43 (File 0425-0427_JD299-0243.svp) 0425-Bunny-299-F2-341_-_0001 0426-Bunny-299-F2-329_-_0005 0427-Bunny-299-F2-353_-_0002 JD308 Use cast JD308 13:04 (file JD308-1304.svp) with NDT 4 hrs 0610-Bunny-308-F2-429_-_0002 0611-Bunny-308-F2-434_-_0001 JD309 Used cast JD309 11:32 (file JD309-1132.svp) with Nearest in Distance on lines: 0612-Bunny-308-F2-440_-_0001 0612-Bunny-308-F2-440_-_0002 0613-Bunny-308-F2-445_-_0001 0613-Bunny-308-F2-445_-_0002 0614-Bunny-308-F2-451_-_0001 0614-Bunny-308-F2-451_-_0002 0615-Bunny-308-F2-459_-_0001 0615-Bunny-308-F2-459_-_0001 2. SBET Exceptions The following lines needed to have SBETs loaded in CARIS using "load partial" option due to incomplete coverage over affected data: Load SBET 2018-296-0318_BB with partial coverage Effects line 0399-Bunny-296-F1-719-0001 Load SBET 2018-302-0442_BB with partial coverage Effects line 0500-Bunny-302-F2-389-0003 Load SBET 2018-302-0852_BB with partial coverage Effects line 0500-Bunny-302-F2-389-0004 Load SBET 2018-307-1638_BB with partial coverage Effects line 0594-Bunny-307-F1-619-0003 3. Delayed Heave Exceptions Delayed Heaves was not available for these lines, used real-time Heave instead: 0500-Bunny-302-F2-389_-_0003 0500-Bunny-302-F2-389_-_0004 0499-Bunny-302-F2-389_-_0002 4. No SBET / Tides Exception Lines collected at the start of survey operations on the Bella Marie did not have the correct POSMV records logged to enable POSPac PPK post-processing. In this sheet, only lines run on the first day of the survey (JD2018-247) are affected. Post-processed SBET data is not available, so these lines use WAAS DGPS for horizontal positioning and do not have precise GPS heights. Since these lines only lack PPK positioning and were otherwise of good quality, verified tide data from the nearby NWLON station Matagorda Bay Entrance (8773767) were applied for tidal corrections. These lines were compared to overlapping lines that did utilize standard SBET positioning and found to compare to 0.10 or better on average.The Field Unit submitted 23 lines that were reduced to MLLW with direct water levels. The lines affected were on DN 2018-247, lines with prefix of 0025 to 0028. There is an additional like (on DN 2018-261, line 0237-261-Bella_Marie-F1-Nearshore_-_0002) which also had no SBET applied.All equipment and survey methods were used as detailed in the DAPR.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.Refer to the DAPR for equipment dates of usage.Seabat 7125Teledyne RESONMBESSeabat T50Teledyne RESONMBESSeabat T50 IDHTeledyne RESONMBES4200EdgeTechSSSPOS MV 320 v5ApplanixPositioning and Attitude SystemMinos-XAML OceanographicSound Speed SystemMicroX SVSAML OceanographicSound Speed SystemRapidSVValeportSound Speed SystemSWIFT SVPValeportSound Speed SystemRapidCastTeledyne OceanscienceUnderway Sound Speed Deployment SystemThe RV Bunny Bordelon is owned and operated by Bordelon Marine Services, LLC of Houma, Louisiana. It was outfit with a 20' conex on the back deck for working space, an A-frame and a winch for towed SSS operations, and a retractable MBES pole mid-ship on its port-side. This vessel worked 24/7 and surveyed the deeper parts of this area, generally from 7 meter water depth and deeper. The RV Bella Marie is owned and operated by TerraSond and is based out of Corpus Christi, TX. It worked daylight-only ops (12 hours per day) based out of the nearby town of Port O'Conner, TX. It surveyed the shoaler portion of this area, generally from the NALL to 7 meter water depth. Both vessels were outfit with similar survey systems. Overlap between the two vessels was achieved.3.545.7Bunny Bordelon0.7611Bella Mariefile://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/BunnyBordelon.jpgBunny Bordelonfile:///C:/Users/Bryan.Chauveau/AppData/Roaming/Microsoft/Windows/Network%20Shortcuts/BellaMarie.jpgBella MarieSound speed profiles ("casts") were collected while underway on the Bunny Bordelon, and by hand at a slow speed on the Bella Marie. A combination of AML Minos-X, Valeport RapidSV, and Valeport SWIFT SVP profilers were used over the course of the project. Changes in sound speed at the MBES sonar head were monitored and a sound speed profile was acquired when the sound speed at the head differed from the sound speed at the depth of the sonar head in the previous profile by greater than 2 m/s. This resulted in an interval of approximately 2 hours between subsequent casts. Casts were taken as deep as possible, usually extending to the seafloor. These were normally applied nearest in distance in time within 4 hours in CARIS HIPS to exclude profiles too outdated or distant from the applicable sounding data. Refer to the DAPR for more information on SVP profiling including specific instruments used, SVP confidence checks performed, and processing methodology.2 hoursAll equipment and survey methods were used as detailed in the DAPR.Effort was made to ensure crosslines had good temporal and geographic distribution, were angled to enable nadir-to-nadir as well as nadir-to-outer beam comparisons, and that the required percent of mainscheme LNM was achieved. For good inter-vessel comparisons, crosslines were intentionally run as shallow as possible on the deep-drafted vessel (the Bunny Bordelon) to ensure significant overlap with the shallow-drafted Bella Marie mainscheme data. Likewise, Bella Marie crosslines were often extended offshore to overlap Bunny Bordelon mainscheme. The crossline analysis was conducted using CARIS HIPS “Line QC Report” process. Each crossline was selected individually and run through the process, which calculated the depth difference between each accepted crossline sounding and a "QC" BASE (CUBE-type, 2 m resolution) surface’s depth layer created from the mainscheme data. QC surfaces were created with the same parameters used for 2 m surfaces as the final surfaces, with the important distinction that the QC surfaces 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(s) could be counted as a QC failure under this process. Lines used as crosslines and their % of soundings passing IHO Order 1a, sorted from highest passing to lowest, are listed below. 1394-Bunny-340-SHeetF_XL_01 -- 100.0% pass 1408-Bunny-340-SHeetF_XL_01 -- 100.0% pass 1417-Bunny-340-SheetF_XL_13 -- 100.0% pass 1421-Bunny-340-SHeetF_XL_02 -- 100.0% pass 1430-Bunny-340-SheetF_XL_03 -- 100.0% pass 1434-Bunny-340-SHeetF_XL_04 -- 100.0% pass 1435-Bunny-340-SHeetF_XL_04 -- 100.0% pass 1438-Bunny-340-SHeetF_XL_04 -- 100.0% pass 1442-Bunny-340-SHeetF_XL_04 -- 100.0% pass 1443-Bunny-340-SheetF_XL_05 -- 100.0% pass 1445-Bunny-340-SheetF_XL_05 -- 100.0% pass 1448-Bunny-340-SheetF_XL_05 -- 100.0% pass 1481-Bunny-340-F_XL_06 -- 100.0% pass 1485-Bunny-340-F_XL_06 -- 100.0% pass 1499-Bunny-340-F_XL_14 -- 100.0% pass 1504-Bunny-340-F_XL_08 -- 100.0% pass 1509-Bunny-340-F_XL_08 -- 100.0% pass 1513-Bunny-340-F_XL_15 -- 100.0% pass 1518-Bunny-340-F_XL_10 -- 100.0% pass 1520-Bunny-340-F_XL_10 -- 100.0% pass 1929-Bunny-344-F_XL_20 -- 100.0% pass 0324-024-Bella7125-F_XL_104 -- 100.0% pass 1517-Bunny-340-F_XL_09 -- 100.0% pass 1523-Bunny-340-F_XL_10 -- 100.0% pass 0311-024-Bella7125-F_XL_100 -- 100.0% pass 0314-024-Bella7125-F_XL_101 -- 100.0% pass 0909-Bunny-322-F1-33XL -- 100.0% pass 0842-035-Bella7125-F_XL_200 -- 100.0% pass 0318-024-Bella7125-F_XL_102 -- 100.0% pass 1488-Bunny-340-F_XL_07 -- 100.0% pass 0320-024-Bella7125-F_XL_103 -- 100.0% pass 1503-Bunny-340-F_XL_07 -- 100.0% pass 0322-024-Bella7125-F_XL_105 -- 100.0% pass 1425-Bunny-340-SheetF_XL_03 -- 100.0% pass 1422-Bunny-340-SheetF_XL_03 -- 100.0% pass 1440-Bunny-340-SHeetF_XL_04 -- 100.0% pass 1510-Bunny-340-F_XL_09 -- 99.9% pass 1506-Bunny-340-F_XL_08 -- 98.4% pass Note that individual crosslines often have two or more files (or segments) in CARIS due to the automatic file splitting option in the acquisition software (QPS QINSy). For each individual crossline, all applicable segments were selected and ran together through the QC report process so that the QC report would reflect the crossline as a whole instead of its individual file segments. Results: Agreement between the mainscheme-only surface and crossline soundings is excellent. Compared to the mainscheme-only surface, all crosslines (38) have at least 95% of soundings comparing within IHO Order 1a. 36 of 38 crosslines have 100% of soundings comparing within IHO Order 1a, and the remainder (2) have at least 98.4% comparing within IHO Order 1a. Refer to Separate II: Digital Data for the Crossline QC Reports.Sound speed error or refraction is common in this data set. This is observed as a general downward or upward cupping ("frowning" or "smiling") of the seafloor MBES profiles. The issue was exacerbated by use of a dual-head MBES system on the Bunny Bordelon, which increased swath-width in order to cover more area per LNM collected but also resulted in outer beam data that was more susceptible to induced error from variations in sound speed profiles. The error is more pronounced in the offshore Bunny Bordelon dual-head data but can also be observed in near-shore Bella Marie single-head data as well. In processing, lines with excessive sound speed error were analyzed to determine if better results could be obtained from manually choosing a specific sound speed profile instead of using the project default "nearest in distance within time 4 hours". If custom/single-profiles were utilized they are itemized later in this report. Finally, swath filters as well as manual editing in CARIS subset mode was used to reject outer beam soundings that appeared to exceed allowable TVU (considered to be greater than 0.5 m from estimated true seafloor based on nadir depth). Manual editing often left isolated nodes or speckled edges in the final surfaces. Crossline analysis, which included crossings of good near-nadir crossline data over outerbeam mainscheme data exhibiting sound speed error, passes within IHO Order 1a indicating final surfaces are within specifications.Sound Speed ErrorThe SSS image quality is intermittently affected by thermocline refraction as well as water column noise due to waves at the surface as well as vessel wake or prop noise, leading to variable artifacts in SSS data. SSS image quality was monitored continually during acquisition and SSS operations were stopped when it was determined that imagery quality had degraded to a point that significant objects were unlikely to be resolved. At this time either MBES-only operations were carried out with a tighter line spacing to obtain Complete Coverage, or vessel downtime due to weather was commenced. Bunny Bordelon SSS quality is generally higher than Bella Marie SSS quality due to difficulties in optimizing towfish height in shallow areas on the Bella Marie so as to maintain sufficient towfish altitude while minimizing vessel wake and surface noise effects. SSS lines with excessive noise were reviewed in processing and rejected if necessary and rerun with either SSS or MBES.SSS Refraction and Surface NoiseThe surfaces were finalized in CARIS HIPS so that the uncertainty value for each grid cell is the greater of either standard deviation or uncertainty. The surfaces were then ran through NOAA's QC Tools "QA" utility to compare uncertainty values to allowable TVU by depth. Results: Greater than 99.5% of grid cells for all final surfaces have uncertainty within the allowable TVU. The relatively few grid cells exceeding allowable TVU were found to primarily be on the edges of swaths without overlap, overlap areas exhibiting sound speed refraction error, or over features. The surfaces in these areas were examined and determined to be within specifications. Refer to the DAPR for more information on derivation of the values used for TPU estimates.020.025Bunny Bordelon020.025Bella Marie0ERS via VDATUM0.104Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.This survey junctions with three Current surveys. All were surveyed concurrently with this survey. NOAA's "Gridded Surface Comparison V18.4" utility was used to complete the junction comparisons. The utility differences the surfaces of the junctioning surveys and generates statistics, including the percentage of grid cells that compare to within allowable TVU. 1 m-resolution CUBE surfaces were used for all comparisons.Agreement is excellent between the two Current surveys. The mean difference is 0.01 m, and greater than 99.5% of grid cells compare to within the allowable TVU.NETerrasond, Ltd.H13183201940000Agreement is excellent between the two Current surveys. The mean difference is 0.03 m, and greater than 99.5% of grid cells compare to within the allowable TVU.SETerrasond, Ltd.H13185201840000There is incidental overlap between these the two surveys on their corners. Agreement is excellent, with a mean difference of 0.04m, and 100% of grid cells compare to within the allowable TVU.ETerrasond, Ltd.H13186201840000file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13184_SurveyJunctions.jpgGraphic showing junctions with this survey.A Reson Seabat T50-IDH (integrated dual-head) MBES system was initially installed and operated on the Bella Marie. A near-nadir artifact and excessive noise was experienced with this installation that could not be tuned out. After consultation with the sonar manufacturer it was decided that the likely cause was insufficient sonar deployment depth between the catamaran-style hulls on this vessel causing acoustic reverberation off the twin hulls. Instead of modifying the mount to deploy the MBES deeper and run additional risk of damaging the system on the seafloor, the system was reconfigured to operate as a standard single-head system, which eliminated the issue. The system was configured as a dual-head from JD2018-247 to JD2018-256 and all data collected during this period exhibits the issue. Noisy data as well as the nadir artifact was manually rejected in either CARIS Swath Editor or Subset mode. Due to the upward curvature at nadir, a nadir artifact of about 5-10 cm adversely affects the data. However, this is within specifications and final surfaces meet TVU requirements. Note that the Bunny Bordelon was also outfit with a Reson Seabat T50 Dual-Head MBES and did not exhibit similar issues, likely due to the depth of the mount on that vessel. An example is shown below.Bella Marie DH Beam Pattern / Noisefile://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/Bella_T50IDH_Artifact1.jpgBella Marie T50-IDH artifact after manual editing of soundings. Near-nadir soundings are adversely impacted by 5-10 cm.file://OCS-S-AHB-FS01/Delta/Survey/H13184_K376_KR_18/AHB_H13184/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/Bella_T50IDH_Artifact2.jpgBella Marie T50-IDH artifact showing rejected soundings (gray).During the 2019 deployment of the Bella Marie to the survey site, the vessel utilized an alternate MBES and POSMV system compared to what was used in 2018. This included a POSMV IMU mounted well forward of the vessel CoG (and MBES). This resulted in remote heave, where vessel pitch was unintentionally measured by the system as additional heave. The majority of the effect was removed through a remote heave computation in the CARIS HVF as well as the POSMV system. However, some unresolved remote heave effects remains in the data, which appears as vertical busts both above and below previously run T50 data. The effect is usually less than 0.10 m but can approach 0.15m in places. Despite the residual remote heave artifact, final surfaces are within allowable TVU. This affects only data collected on with the Bella Marie in 2019, JD2019-015 to JD2019-038. Refer to the DAPR for more information and offsets.Bella Marie Remote Heave Busts