S-K924-NRT4-20Entrance to Galveston Bay ResponseGalveston BayNOAA Navigation Response Team 4F008001NRT4 is assigned to develop a shoal area discovered near the G"9" buoy, Galveston Bay Entrance.Entrance to Galveston BayTexasUnited States100002020Dan JacobsNavigable Area2020-02-132020-02-142020-02-14Multibeam Echo SoundermetersUTCPacific 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 15N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit.NOAAThe USCG reported a 16.5 ft depth at the position 29° 20.481'N and 094° 42.825'W near the Galveston Bay Entrance. NRT4 was assigned to develop the shoal area at that location.29.34432194.71823929.3387194.709392The USCG has requested an OCS hydrographic survey in the Entrance to Galveston Bay near the G”9” buoy. The USCG is reporting a 16.5 ft. depth at the position of 29° 20.481’N and 094° 42.825'W, where a 26 ft. charted sounding is. The USCG is concerned that there may be shoaling in this area. NRT4 is assigned to develop the shoal area is this location. Survey data from this project is intended to supersede all prior survey data in the common area.Survey Limits, Galveston Bay Entrance. Blue polygon is survey limits.\Support_Files\SurveyLimits_1.JPGSurvey limits (red dashed line) and Complete MBES Coverage, NOAA Chart 11324.\Support_Files\SurveyLimits_2.JPGThe USCG has requested for OCS to do a hydrographic survey in the Entrance to Galveston Bay near the G”9” buoy. The USCG is reporting a 16.5 ft. depth at the position of 29° 20.481’N and 094° 42.825'W, where a 26 ft. charted sounding is. The USCG is concerned that there may be shoaling in this area. NRT4 is assigned to develop the shoal area is this location. Survey data from this project is intended to supersede all prior survey data in the common area.The entire survey is adequate to supersede previous data.The entire survey is adequate to supersede previous data. Complete coverage was attained IAW project instructions and HSSD Section 5.2.2.3.1 holiday existed at 29-20.540893N 094-43.030851W. Its approximately 18 meters square.F00800 Holiday\Support_Files\Holiday_2.JPGOverview, F00800 Survey Coverage onto ENC US5TX53M.\Support_Files\SurveyLimits_Overview_ENC_1.JPGS3008016.4000001.110016.4000001.1106.700000.142020-02-14Survey dates occurred on DN045, Friday, February 14th, 2020. The project area was sized appropriately for a quick response survey as NRT4 staffing challenges precluded a larger project. 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.S300810.50.5NOAA S3008\Support_Files\NRT4_Vessel.JPGNOAA Survey Vessel S3008 is a 30 foot, aluminum hulled fire boat modified for NOAA hydrographic survey operations. Its powered by dual 225 horsepower Honda outboard engines. A Kohler 7.5 EKD generator supplies AC power for two workstations, 5 monitors, one POS system, one multibeam echo sounder system, and one side scan sonar system.Kongsberg MaritimeEM 2040CMBESKongsberg EM2040C Multibeam Echo Sounder\Support_Files\Kongsberg_EM2040C.pngThe Kongsberg EM2040C system is a digital recording multibeam echo sounder which is capable of operating at 200kHz, 300kHz, 400kHz, or in a Frequency Modulation (FM) Chirp. The system is comprised of a receiver unit that is hull mounted, a Hydrographic Work Station (HWS), and a Processor Unit (PU). The EM2040C is operated through Seafloor Information System (SIS) software; version 4.3.2. The EM2040C is used to acquire full and partial bottom bathymetric coverage throughout a survey area to determine least depths over critical items such as wrecks, obstructions, dangers-to-navigation, and general object detection. The maximum depth range for a single head system in cold ocean water is 520 m at 200 kHz with a swath width up to 580 m. The angular coverage for 200 to 320 kHz is 130° with one sonar head, allowing coverage 4.3 times water depth. For frequencies above 320 kHz the angular coverage per head is gradually decreasing to 70° at 400 kHz.The nadir beam width is 1° x 1° at 400 kHz. The system has a maximum ping rate of 50 Hz with 400 soundings per ping.Per 2019 HSSD paragraph 5.2.4.2 lineal mileage of crosslines exceeded 4 percent of main scheme mileage. 16.4 LNM of mainscheme survey lines were collected for F00800. Four MBES crosslines totaling 1.11 LNM were acquired at the end of DN045 totaling 6.7 percent of MBES mainscheme acquisition. A 1 meter crossline surface was compared to a 1 meter mainscheme surface invoking the Pydro Compare Surfaces script. The two surfaces were in excellent agreement with each other as 99 percent of the nodes passed the allowable error fraction. The analysis was performed on MBES data reduced to MLLW using ellipsoidally referenced RTX SBET methods. Please reference the folder named Crossline_Comparisons for all analysis outputs. See graphics, below.F00800 Crossline Coverage, 1m Surface.\Support_Files\Crosslines_1.JPGF00800 Crossline Coverage, 99 percent nodes pass allowable error fraction.\Support_Files\F00800_MB_1m_MLLW_Crosslines_Only-F00800_MB_1m_MLLW_MainScheme_Only_fracAllowErr_Freq.pngERS via VDATUM0.1260S30084000.5Per HSSD paragraph 5.2.3.6 the factors associated with this uncertainty estimate include (1) the ability to accurately measure sound speed or calculate sound speed from temperature, conductivity and pressure, (2) the spatial and temporal changes of sound speed throughout the survey area and (3) how the sound speed profile is used to convert measured time to depth. Commonly reported values range between 0.3 and 4 m/s.No junctions were assigned for S-K924-NRT4-20.Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.Kongsberg swath angle reduced.Kongsberg swath angles were reduced from 65 degrees port and 65 degrees starboard to 55 degrees port and 55 degrees starboard in Kongsberg's Seafloor Information System (SIS) software. The reduction in swath angle was on account of noisy bubble sweep artifacts generated by wind waves. S3008 hull design with respect to MBES sonar location exacerbate such artifacts. Hull design modifications are being investigated by NRB/HSTB to mitigate the issue.None ExistThere were no other factors that affected corrections to soundings.Sound speed cast frequency for F00800 was not less than 1 cast per every four hours of survey.Cast frequency was 1 cast per every four hours of survey. Two casts were taken on the survey day, DN045.All equipment and survey methods were used as detailed in the DAPR.All data reduction procedures conform to those detailed in the DAPR.All sounding systems were calibrated as detailed in the DAPR.Backscatter was not acquired for this survey.During review, backscatter data was found to have been logged to the MBES .ALL files. NOAA's Navigation Response Branch field units are waived from producing backscatter mosaics for the 2020 field season. A backscatter mosaic was created during review.Version 5.7: CARIS_Support_Files_5_8Version 5.7: CARIS_Support_Files_5_8 was released on 05/17/2018. It updated the support files with the new version 5.8. Additionally, it modified environment and added the "hsdrec" attribute.F00800_MB_1m_MLLW_FinalCARIS Raster Surface (CUBE)14.7516.26NOAA_1mComplete MBESF00800_MB_1m_MLLWCARIS Raster Surface (CUBE)14.7516.26NOAA_1mComplete MBESAdditional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterERS via VDATUMS-K924-NRT4-20_VDatum_10m_NAD83-MLLW_geoid12bThe vertical datum for this project is Mean Lower Low Water. The vertical control method used was VDatum. The vertical uncertainty for this project is Mean Lower Low Water (MLLW). Soundings were reduced from NAD83 to MLLW using Vdatum file "S-K924_VDatum_10m_NAD83-MLLW_geoid12b.csar" located in the survey "Water_Levels" folder. The vertical uncertainty for this model was 12.5595cm. This value was applied in Charlene v3.1.5.North American Datum 1983Projected UTM 15Survey soundings with depths within 3 feet of charted (11324) depths were deemed to be acceptable taking into account sand waves and hydro dynamics in this constricted entrance area. All charted soundings on ENC US5TX53M and Raster 11324 are within two feet of survey soundings. However, shoaling trends are occurring in two regions, between charting soundings. Charted (11324) depths between 25-26 feet were surveyed at 19 to 21 feet. Likewise, charted (11324) depths between 22 to 26 feet were surveyed at 15 and 20. The shoaling is not deemed a danger to navigation (DtoN) as vessel traffic bearing drafts greater than 12 feet do not occur outside of the shipping channel. Graphic of the shoals, below.Shoaling occurring between ENC US5TX53M soundings.\Support_Files\ENC_Compare_1.JPGUS5TX53M10000582019-11-052020-01-30falseShoaling trends are occurring in two regions inside of the sheet limits, between charting soundings. Charted (11324) depths between 25-26 feet were surveyed at 19 to 21 feet. Likewise, charted (11324) depths between 22 to 26 feet were surveyed at 15 and 20. The shoaling is not deemed a danger to navigation (DtoN) as vessel traffic bearing drafts greater than 12 feet do not occur outside of the shipping channel. Graphic shown below. Graphics were provided to Western Gulf Navigation Manager, Chief NRB, Project Manager of NRB and crew member LTJG Collin Walker. See project correspondence folder for specific communication. A USCG Local Notice to Mariners chart correction was issued for Week 8 subsequent to the discovery of the shoaling and the discovery of a non-DtoN obstruction on 17FEB2020. See "Uncharted Features" section of this descriptive report for additional information about this obstruction. Shoaling in two places, ENC US5TX53M. Migrating shoals are reddish color on the 1 meter grid. Survey soundings in feet shown atop of survey grid.\Support_Files\ENC_Compare_2.JPGLocal Notice to Mariners, chart correction entry, Week 8, 2020.\Support_Files\LNM_Week_8.JPGNo Maritime Boundary Points were assigned for this survey.No charted PA, ED, PD, or Rep features exist for this survey.A sunken obstruction was discovered on 17FEB2020 during the cleaning phase of F00800. Conferring with USCG SFO Galveston, the object is thought to be Buoy "9" from a time not specified. The object is located at 29.-20.4878N 094-42.7612W with a height of 1.55 meters. Its least depth is 24 feet with a length of approximately 6 meters. Please reference the pdf entitled "Re_ USCG Report, Charted Depth Galveston" for additional information pertaining to this new object. A USCG Local Notice to Mariners chart correction was issued for Week 8 subsequent to the discovery of the shoaling and the discovery of a non-DtoN obstruction on 17FEB2020. See "Uncharted Features" section of this descriptive report for additional information about this obstruction.Non DtoN object seen in F00800 1 meter Bathy, 2D.\Support_Files\F00800_Object_1a.JPGNon DtoN object seen in F00800 1 meter Bathy, 3D.\Support_Files\F00800_Object_1b.JPGLocal Notice to Mariners, chart correction entry, Week 8, 2020.\Support_Files\LNM_Week_8.JPGShoals discovered were discussed at the beginning of D.1 of this report.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 bottom samples were required for this survey.Shoreline was not assigned in the Hydrographic Survey Project Instructions or Statement of Work.Galveston Entrance Buoy "9" resided on the edge of survey F00800. It was observed to be on station and serving its intended purpose. See the project's final feature file for additional information.Buoy "9" observed to be on station and serving its intended purpose.\Support_Files\Buoy9_intendedPurpose.JPGNo overhead features exist for this survey.No submarine features exist for this survey.No platforms exist for this survey.No ferry routes or terminals exist for this survey.No abnormal seafloor and/or environmental conditions exist for this survey.No present or planned construction or dredging exist within the survey limits.No new surveys or further investigations are recommended for this area.No new insets are recommended for this area.As Chief of Party, field operations for this hydrographic survey were conducted under my direct supervision, with frequent personal checks of progress and adequacy. I have reviewed the attached survey data and reports.All field sheets, this Descriptive Report, and all accompanying records and data are approved. All records are forwarded for final review and processing to the Processing Branch.The survey data meets or exceeds requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required with the exception of deficiencies noted in the Descriptive Report.Dan JacobsChief of Party2020-02-26