OPR-J311-KR-19Chandeleur IslandsChandeleur Islands, LouisianaDavid Evans and AssociatesH13263425 NM East of Freemason IslandsLouisianaUnited States400002019Jonathan L. Dasler, PE, PLS, CHNavigable Area2019-06-192019-07-032019-11-23Multibeam Echo SounderMultibeam Echo Sounder Backscatter &Side Scan SonarmetersUTCAtlantic 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 16N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit.ContractorDavid Evans and Associates, Inc. (DEA) conducted a hydrographic survey of the assigned area in the Chandeleur Islands. Survey H13263 was conducted in accordance with the May 21, 2019 Statement of Work and Hydrographic Survey Project Instructions June 19, 2019. The Hydrographic Survey Project Instructions reference the National Ocean Service (NOS) Hydrographic Surveys Specifications and Deliverables Manual (HSSD) (March 2019) as the technical requirements for this project.29.660712611188.56533529.787688194488.4368416944Survey Limits were surveyed in accordance with the requirements in the Project Instructions and the HSSD.OPR-J311-KR-19 Assigned Survey Areasfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/OPR-J311-KR-19_Assigned_Survey_Areas.PNGThe project’s survey purpose for all surveys, which was defined in the Project Instructions, is “The Chandeleur Islands is an active oil and gas exploration area, as well as a popular fishing grounds and includes the Breton National Wildlife Refuge.*1 The Chandeleur Islands were also severely impacted by recent hurricanes like Dennis and Katrina, which resulted in major erosion of the islands. Erosion, sea level rise, and sediment influx from the Mississippi River have endangered the future of these islands.*2 This area also supports a wide variety of vessel traffic and commercial and sport fishing traffic near the Mississippi Entrance Channel and includes a major portion of the safety fairway. Due to the high traffic, this project has been planned as one of a multi-year approach to update charts in this area. Before this project, this area was last surveyed by the Office of Coast Survey in 1922 and 1940. This survey will allow vessel traffic safe passage to offshore Gulf of Mexico. The purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products, this project will address numerous approximately charted hazards, reducing the risk to navigation. Survey data from this project is intended to supersede all prior survey data in the common area.” *1 Breton National Wildlife Refuge. Wikipedia. Retrieved 27 February 2019 *2 Moore, Laura J.; Patch, Kiki; List, Jeffery H.; Williams, S. Jeffress (2014). “The potential for sea-level-rise-induced barrier island loss: Insights from the Chandeleur Islands, Louisiana, USA”. Marine Geology. 355: 244-259. doi:10.1016/j.margeo.2014.05.022. ISSN 0025-3227The entire survey is adequate to supersede previous data.All waters in survey area Complete Coverage Option B (Refer to HSSD Section 5.2.2.3)Multibeam echosounder (MBES) data with time series backscatter was collected concurrently with side scan sonar (SSS) data to obtain complete coverage in all waters in the survey area. This coverage type follows Option B of the Complete Coverage requirement specified in Section 5.2.2 of the 2019 HSSD. Surveyed contacts and features were developed at complete coverage resolution as required by the coverage classification. Complete coverage multibeam was also obtained within the search radii for all feature disapprovals. Survey coverage was obtained within the survey area depicted in the Project Reference File (PRF) OPR-J311-KR-19_PRF_FINAL.000. Figure 2 depicts the survey outline that was obtained for H13263. H13263 Survey Outlinefile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_Survey_Coverage.pngS/V Blake029.39000470.07021.620029.39000470.07021.6204.33300033.002019-07-032019-07-042019-07-052019-07-062019-07-082019-08-012019-08-022019-11-192019-11-23The OPR-J311-KR-19 Data Acquisition and Processing Report (DAPR), previously submitted with survey H13260, details equipment and vessel information as well as data acquisition and processing procedures. There were no vessel or equipment configurations used during data acquisition that deviated from those described in the DAPR.S/V Blake824.5S/V Blakefile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/OPR-J311-KR-19_Blake.pngEdgeTech4200SSSApplanixPOS MV 320 v5Positioning and Attitude SystemAML OceanographicMVP30-350Sound Speed SystemAML OceanographicMicroX SVSound Speed SystemAML OceanographicBaseXSound Speed SystemTrimbleSPS851Positioning SystemTeledyne RESONSeaBat 7101MBESMultibeam crosslines were run across the entire survey area to provide a varied spatial and temporal distribution for analysis of internal consistency within the survey data. Crossline analysis was performed using the CARIS Hydrographic Information Processing System (HIPS) Quality Control (QC) Report tool, which compares crossline data to a gridded surface and reports results by beam number. Crosslines were compared to a 2-meter CUBE surface encompassing mainscheme, fill, and investigation data for the entire survey area. The QC Report tabular output and plots are included in Separate II Crossline Comparison. DEA performed an additional crossline analysis using the NOAA Pydro Compare Grids tool to analyze the differences between gridded mainscheme depths and gridded crossline depths. Input grids were 2-meter resolution CUBE surfaces of mainscheme and crossline depths. Results from the crossline to mainscheme difference analysis are depicted in Figure 4, units are represented in meters. H13263 Crossline Differencefile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_2m_XL-H13263_2m_MS_depth_delta.pngERS via VDATUM0.050.168S/V Blaken/a1.00.5Additional discussion of these parameters is included in the DAPR. During surface finalization in HIPS, the "Greater of the two values" option was selected, where the calculated uncertainty from Total Propagated Uncertainty (TPU) is compared to the standard deviation of the soundings influencing the node, and where the greater value is assigned as the final uncertainty of the node. The uncertainty of the finalized surfaces increased for nodes, where the standard deviation of the node was greater than the TPU. To determine if the surface grid nodes met IHO Order 1 specification, a ratio of the final node uncertainty to the allowable uncertainty at that depth was determined. As a percentage, this value represents the amount of error budget utilized by the total vertical uncertainty (TVU) at each node. Values greater than 100% indicate nodes exceeding the allowable IHO uncertainty. The resulting calculated TVU values of all nodes in the submitted finalized surfaces are shown in Figures 5 and 6.Node TVU statistics - 2m finalizedfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_2m_MLLW_Final.QAv5.tvu_qc.pngNode TVU statistics - 4m finalizedfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_4m_MLLW_Final.QAv5.tvu_qc.pngSurvey H13263 junctions with current surveys H13261, H13262, H13264, and H13266. Prior survey H13135 was specified as a junction in the Project Instructions for survey H13263. Figure 7 depicts H13263 and the junctioning surveys. Survey junctions with registry number H13263file:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_Junctions_graphic.pngH13261400002019David Evans & Associates, Inc.NThe mean difference between H13263 and H13261 survey depths is 0 centimeters, shown in Figure 8. Distribution summary plot of survey H13263 2-meter vs H13261 2-meterfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_2m_MLLW-H13261_MB_2m_MLLW_depth_delta.pngH13162400002019David Evans & Associates, Inc.WAt the time of writing, data from survey H13262 was still being processed. The Descriptive Report for H13262 will include the junction analysis with H13263. H13164400002019David Evans & Associates, Inc.NAt the time of writing, data from survey H13264 was still being processed. The Descriptive Report for H13264 will include the junction analysis with H13263. H13266400002019David Evans & Associates, Inc.SEAt the time of writing, data from survey H13266 was still being processed. The Descriptive Report for H13266 will include the junction analysis with H13263. H13135400002018LeidosSThe mean difference between H13263 and H13135 survey depths is 31 centimeters (H13263 deeper than H13135), shown in Figure 9. Major differences are representative of surveys impacted by subsidence over a one year period and the use of varying tidal application methods. According to the Descriptive Report for the prior survey, H13135 used ERS with Poor Mans VDATUM for Vertical Control methods where survey H13263 used ERS methods relying on the published VDATUM model for the area. Using prior data available on the National Centers for Environmental Information (NCEI) website, the separation model used for survey H13135 was recreated and compared to the separation model used for survey H13263. The prior model was reconstructed by computing a difference surface between the combined MLLW and ellipsoid bathymetry grids available for survey H13135. The hydrographer found a 14-centimeter difference between the two models at the survey junction. Distribution summary plot of survey H13263 2-meter vs H13135 1-meterfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_2m_MLLW-H13135_MB_2m_MLLW_Combined_depth_delta.pngQuality control is discussed in detail in Section B of the DAPR. Results from weekly position checks and weekly multibeam bar checks are included in Separate I Acquisition and Processing Logs of this report. Sound speed checks can be found in Separate II Sound Speed Data Summary of this report. Multibeam data were reviewed at multiple levels of data processing including: CARIS HIPS conversion, subset editing, and analysis of anomalies revealed in CUBE surfaces.None ExistThere were no conditions or deficiencies that affected equipment operational effectiveness.None ExistThere were no other factors that affected corrections to soundings.Approximately 20 minute intervals An AML Oceanographic Moving Vessel Profiler (MVP) was the primary instrument used to acquire sound speed readings during multibeam operations. Additional discussion of sound speed methods can be found in the DAPR. For H13263 survey operations, casts were distributed both temporally and spatially based on observed changes in sound speed profiles. Sound speed readings were applied in CARIS using the nearest in distance within a one-hour interval. All sound speed measurements were made within 500 meters of the survey limits. During survey operations on July 8, 2019 (DN189), the MVP was receiving intermittent data on the up cast due to a failing cable termination. All MVP casts for this day were processed using the down cast rather than the up cast which is the standard procedure discussed in the DAPR. The sound speed readings were applied in CARIS using the nearest in distance within a two-hour interval due to the frequency between casts extending to preserve the failing cable. The deviation from one hour to two hours between casts had no discernable impact on data quality as casts were relatively consistent. In general, a sound speed measurement was made immediately preceding bathymetric operations, per HSSD. On November 23, 2019 (DN327), the first cast of the day exceeded 500 meters outside of the planned sheet boundary while conducting roll lines. The first cast of this day was rejected during data quality control. This deviation from the HSSD had no discernable impact on data quality as casts were relatively consistent in this area. Survey speeds were maintained to meet or exceed along-track sounding density requirements and side scan sonar ensonification requirements. Multibeam data and side scan mosaics were thoroughly reviewed for holidays and areas of poor-quality coverage due to biomass, vessel wakes, or other factors. Side scan sonar contacts were developed with multibeam sonar to obtain a least depth of the contact using Complete Coverage requirements. Complete coverage multibeam was acquired inside the disproval radii for assigned charted features and over all new features. Additional discussion of coverage methods can be found in the DAPR.DensityThe sounding density requirement of 95% of all nodes, populated with at least five soundings per node, was verified by analyzing the density layer of each finalized surface. Individual surface results are stated in Figures 10 and 11.Node density statistics - 2m finalizedfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_2m_MLLW_Final.QAv5.density.pngNode density statistics - 4m finalizedfile:///Q:/Survey/H13263_J311_KR_19/AHB_H13263/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13263_MB_4m_MLLW_Final.QAv5.density.pngData reduction procedures for survey H13263 are detailed in the DAPR. Summary multibeam and side scan sonar processing logs are included in Separate I of this report.All sounding systems were calibrated as detailed in the DAPR.Multibeam backscatter was logged in Hypack 7k format and included with the H13263 digital deliverables. Data were processed periodically in CARIS HIPS to evaluate backscatter quality, but the processed data is not included with the deliverables. For data management purposes, the names of multibeam crosslines have been appended with the suffix XL. This change was made to HIPS files only. The original file names of raw data files (Hypack HSX and 7k) have been retained.CARISHIPS/SIPS10.4.5Chesapeake Technology, Inc.SonarWiz7.04.01NOAA Profile Version 5.7A detailed listing of all data processing software is included in the OPR-J311-KR-19 DAPR.H13263_MB_2m_MLLWCARIS Raster Surface (CUBE)223.27236.856NOAA_2mComplete MBESH13263_MB_4m_MLLWCARIS Raster Surface (CUBE)423.29336.607NOAA_4mComplete MBESH13263_MB_2m_MLLW_FinalCARIS Raster Surface (CUBE)223.27236.856NOAA_2mFinalized Complete MBESH13263_MB_4m_MLLW_FinalCARIS Raster Surface (CUBE)436.00036.607NOAA_4mFinalized Complete MBESH13263_SSSAB_1m_600kHz_1of1SSS Mosaic1.00.0000.000N/A100% SSSBathymetric grids were created relative to Mean Lower Low Water (MLLW) in CUBE format using Complete Coverage resolution requirements as specified in the HSSD. Designated Soundings A total of two soundings in H13263. One sounding was designated in bathymetric data to faciliate feature management for inclusion in the H13263 Final Feature File (FFF). One sounding is designated to override the gridded surface model.CARIS HDCS Navigation Sources During processing of HDCS lines, navigation information was imported from SBET.out files while importing motion and associated RMS values. This navigation source, Applanix.SBET, is automatically applied at merge when it exists. However, when a CARIS project file is rebuilt, CARIS will report that the navigation source is the HDCSNav. This is a display issue only and does not change the navigation source. Additionally, when a line is renamed, such as with the suffix _XL, the HDCSNav source disappears from the metadata display. Again, this appears to be a display issue only and does not change any navigation sources. All HDCS lines were processed using the SBET.out files and the navigation source is Applanix.SBET for this survey. Additional processing information is detailed in the DAPR.A summary of the horizontal and vertical control for survey H13263 follows.Mean Lower Low WaterERS via VDATUMOPR-J311-KR-19_VDatum2_xyNAD83-MLLW_geoid12b.csarThe separation model listed in Table 13 was provided with the Project Instructions and used for sounding correction within the assigned survey area. Realtime navigation for all MBES survey lines were overwritten with post-processed navigation solutions in SBET format. Post-processed solutions were generated using Applanix POSPac MMS using the Trimble CenterPoint RTX option which relies on precise satellite orbit and timing information to create centimeter level positioning and elevation without the use of traditional local base stations. Information on survey control is detailed in the DAPR.North American Datum 1983Projected UTM 16English Turn, LA (293 kHz)Real-time positioning for side scan sonar operations was provided by differential GPS using corrections received from the US Coast Guard National Differential GPS (NDGPS) coverage network from differential beacons at English Turn, LA (293 kHz). The Federal Aviation Administration Wide Area Augmentation System (FAA WAAS) was enabled to be active if the English Turn station experienced periods of down time. The chart comparison was performed by comparing H13263 survey depths to a digital surface generated from electronic navigational charts (ENCs) covering the survey area. A 50-meter product surface was generated from a triangular irregular network (TIN) created from the ENC’s soundings, depth contours, and depth features. The 50-meter HIPS product surface of the entire survey area was generated from the 4-meter CUBE surface. The chart comparison was conducted by creating and reviewing a difference surface using the ENC surface and survey surface as inputs. The chart comparison also included a review of all assigned charted features within the survey area. The results of the comparison are detailed below. The relevant charts used during the comparison were reviewed to check that all US Coast Guard (USCG) Local Notice to Mariners (LNMs) issued during survey acquisition, and impacting the survey area, were applied and addressed by this survey.US3GC04M250000632019-08-012019-11-19 No Dangers to Navigation (DtoNs) were submitted for this survey. This survey does not contain any charted features labeled PA, ED, PD, or Rep inside the survey extents. All uncharted features are portrayed in the FFF as surveyed and attributed with the description of ‘New’.No channels exist within the survey extents. There are no precautionary areas, traffic separation schemes, or pilot boarding areas within the survey limits. The Mississippi River-Gulf Outlet Channel to Mobile Ship Channel Safety Fairway (33 CFR 166.200) is charted crossing the northwest corner of the survey area. No new obstructions or dangers were located within the safety fairway in the survey area. The hydrographer recommends encoding the name of this and other safety fairways in the ENCs. Safety fairway names are included in the Code of Federal Regulations.No Aids to Navigation (ATONs) exist for this survey. No Maritime Boundary Points were assigned for this survey.Three bottom samples were acquired on August 1, 2019 (DN213) and August 2, 2019 (DN214). The bottom sampling plan followed suggested sample locations included in the Project Reference File (PRF) provided. Minor adjustments were made to the recommended sampling locations in order to sample the varying bottom types observed in the side scan data. This modification was approved by the Contracting Officer’s Representative (COR). Correspondence is included in Appendix II Supplemental Survey Records & Correspondence of this report.No overhead features exist for this survey.There are eight assigned submerged pipelines in the survey extents for H13263. These features were carefully reviewed for any portion of pipeline that was exposed or posed a risk to navigation. These pipelines are included in the FFF with a description of 'Retain' due to the inability of the field unit to determine if pipelines are buried. A pipeline report included in Appendix II, was submitted to the BSEE on February 10, 2020, reporting the sections of exposed or unburied pipeline visible in the MBES and SSS data. The reports indicate the positions of the start and end points of sections of what appear to be exposed pipelines based on interpretation of multibeam data. Due to the inability to accurately depict the location and orientation of all exposed pipelines with a single line segment, these features have been included in the FFF with a description of 'New', should further action be required after survey submittal. It is not the hydrographer’s intention that these pipeline features be used as source information for charting without further validation of origin. No platforms exist for this survey. The U.S. Air Force Communication Tower in the center of the survey area was found approximately 12 meters southwest of its charted position. The charted tower has been included in the FFF with a description of 'Delete' and a feature depicting the surveyed position of the tower has been included with description ‘New’. There are no published or charted lights marking the tower. No working lights were observed on the tower during nighttime survey operations. There are two assigned wellheads, Well (cov 16 fms), in the survey extents for H13263. The charted obstructions were not observed inside an assigned disproval radius with 100% MBES coverage. The charted obstructions have been included in the FFF with a description of 'Delete'. 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 and Specifications 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.Jonathan L. Dasler, PE, PLS, CHNSPS/THSOA Certified Hydrographer, Chief of Party2020-02-19Jason Creech, CHNSPS/THSOA Certified Hydrographer, Charting Manager / Project Manager2020-02-19Callan McGriff, EITIHO Cat-A Hydrographer, Lead Hydrographer2020-02-19Steven LoyIHO Cat-A Hydrographer, Lead Hydrographer2020-02-19Data Acquisition and Processing Report2020-02-18