OPR-J317-KR-18Approaches to Tampa Bay, FLApproaches to Tampa Bay, FLOceaneering International, Inc.H13176707/17/201816 NM West of Mullet KeyFloridaUnited States200002018Scott MelanconNavigable Area2018-07-172018-11-072019-06-21Multibeam Echo SounderSide 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 17N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit.ContractorThe survey area is located 16 NM West of Mullet Key, in the general locality of the Approaches to Tampa Bay, Florida. 27.729076222283.126623527.507896944483.0087710278H13176 Survey LimitsSupportFiles\Fig01_H76-SurveyLimits.PNGSurvey limits were acquired in accordance with the requirements in the Project Instructions and the HSSD (2018).The purpose of the project is to provide contemporary surveys to update National Ocean Service nautical charting products to support an increase in vessel traffic into Tampa Bay, Florida. There is a lack of modern data in the area and the area is subject to strong storm events that have the potential to cause shoaling.The entire survey is adequate to supersede previous data.All waters in the survey area (except Sheet 4)Complete CoverageAll waters in the survey areaReport significant shoaling via weekly progress reports. PM/COR may adjust prioritization based on observed shoaling.All waters in the survey areaAcquire backscatter data during all multibeam data acquisition.Survey coverage was in accordance with the requirements listed above and in the HSSD.H13176 Survey CoverageSupportFiles\Fig02_H76-SurveyCoverage.PNG123709400000508.91028.96000000508.91028.9600.059017043.492018-11-072018-11-082018-11-222018-11-232018-11-242018-11-252018-11-292018-11-302019-04-232019-04-242019-04-252019-06-21It was observed that there were several unit options for nautical miles within the CARIS program. However, 'area' only had one option for the nautical mile units as Square Int. Nautical Miles. To be consistent, Int. Nautical Miles was used as the unit for the LNM shown in Table 3. Detached Positions (DP) include CTD casts and lead line comparisons conducted within survey bounds, but not bottom samples because there is a separate entry for those.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.123709440.841.98The R/V Sea Scout (Hull ID 1237094) was used as the survey platform for all data acquisition within H13176.Kongsberg MaritimeEM 2040CMBESKlein Marine SystemsSystem 5000 V2SSSC-Nav3050Positioning SystemSeaBirdSBE19Conductivity, Temperature, and Depth SensorSeaBirdSBE19plusConductivity, Temperature, and Depth SensorYSI600-BCR-C-TConductivity, Temperature, and Depth SensorTeledyneMeridian SurveyorGyrocompassTeledyneDMS05Attitude SystemMultibeam echosounder data were collected with a single head EM2040C system in 2018, a dual head EM2040C system in April 2019 and a single head EM2040C in a dual head configuration in June 2019. All other systems remained the same.Crosslines were run generally perpendicular to mainscheme lines in order for quality control statistics to be generated after completion of mainscheme survey lines. The total crossline mileage was 28.96 nautical miles and total mainline mileage was 508.91 nautical miles. Multibeam fill-ins were included in the total mainline mileage. Investigation lines and SSS rerun lines (if denoted with an 'rr') for which MB was also acquired were not included. Separate 1-meter mainline and crossline Combined Uncertainty and Bathymetric Estimator (CUBE) surfaces were generated and the surface difference tool within CARIS HIPS was used to evaluate crossline and mainscheme line agreement. The mainline surface was used as Surface 1 and the crossline surface as Surface 2. Statistical information about the difference surface was generated using the Compute Statistics tool (Figure 3). The analysis shows that greater than 99% of depth difference values are between ±0.25 meters. This is well within the maximum allowable Total Vertical Uncertainty (TVU) for the depths of the comparison area of the mainline surface (12.40 - 24.15 meters), which ranges from ±0.525 to ±0.590 meters. One small area displays differences greater than 50 cm (Figure 4); review of this area indicates bottom change but no obvious outliers. The crossline surface, mainline surface, difference surface and exported ASCII file of histogram results are located in Separates\II_Digital_Data\Crossline_Comparison.H13176 crossline comparison statistics and histogram output from CARIS compute statistics tool.SupportFiles\Fig03_H76-CrosslineComparison1.PNGH13176 survey area where depth differences between crosslines and mainlines are greater than 0.5 meters (black symbols).SupportFiles\Fig04_H76-CrosslineComparison2.PNGERS via VDATUM0.10.13112370942n/a0.8The Total Propagated Uncertainty (TPU) for each sounding was computed within CARIS, the multibeam processing software. The vessel file stores static values of the estimated uncertainties associated with each individual sensor. The Compute TPU dialog contains placeholders for the user to specify tidal and sound speed uncertainty, as well as whether the sources of uncertainty are static (come from the vessel file) or were collected in real-time. This particular survey contains all static uncertainty sources. The above uncertainty estimates are combined with a DeviceModels.xml that contains individual sonar model characteristics to calculate the total TPU. Currently there is no entry for static vertical uncertainty associated with a positioning system or the separation model within CARIS. The workaround is to enter these values in the Tide Measured and Zoning entry locations. Internal verification indicates the C-Nav® 3050 systems have a vertical uncertainty of ~20 cm at the 95% confidence level. The 95% confidence level is expressed as 1.96 standard deviations from the mean. CARIS entries of uncertainty are assumed to be 1-sigma (one standard deviation from the mean) and this value of 20 cm is divided by 1.96 for a value of 10 cm to enter into CARIS. The 1-sigma VDATUM Maximum Combined Uncertainty (MCU) value for the separation model (13.1 cm) is provided in the project instructions. An Uncertainty child layer is generated during the bathymetric surface creation process that shows the uncertainty at each node of the surface. HydrOffice QCTools was used to analyze the uncertainty of all un-finalized and finalized grids. It was observed that all uncertainty values are within specifications for all un-finalized surfaces (Figures 5 and 6) but the finalized surfaces contain less than 0.1% of values that do not meet specifications (Figure 7 and 8). Review indicates that this is due to the finalization parameter where the uncertainty is defined as the greater of either the standard deviation or uncertainty for a particular node. In general, areas of higher uncertainty are associated with features and seafloor change. However, it was also observed that some area of higher uncertainty were associated with potential erroneous MBES pings that, although do not contribute substantially to the surface depth values as reviewed in subset editor with the reference surface loaded, appear to still contribute to the overall standard deviation.Uncertainty QA output from HydrOffice QCTools for surface H13176_MB_1m_MLLW.SupportFiles\Fig05_H76_MB_1m_MLLW.QAv5.tvu_qc.pngUncertainty QA output from HydrOffice QCTools for surface H13176_MB_2m_MLLW.SupportFiles\Fig06_H76_MB_2m_MLLW.QAv5.tvu_qc.pngUncertainty QA output from HydrOffice QCTools for surface H13176_MB_1m_MLLW_Final.SupportFiles\Fig07_H76_MB_1m_MLLW_Final.QAv5.tvu_qc.pngUncertainty QA output from HydrOffice QCTools for surface H13176_MB_2m_MLLW_Final.SupportFiles\Fig08_H76_MB_2m_MLLW_Final.QAv5.tvu_qc.pngSurvey H13176 junctions with five contemporary surveys: H13171, H13173, H13174, H13175 and H13178 (Figure 9). Survey areas H13174, H13175, H13178, and H13173 were either not complete or partially complete at the time this report was generated and will be addressed in the respective Descriptive Reports for those surveys. A junction analysis between H13176 and H13171 was conducted to ensure general agreement of depths. A difference surface between the depth layers of H13176 and the adjoining survey was generated. Difference values greater than 2^0.5 * TVU, as outlined in the HSSD (2018), are addressed below.H13176 Survey JunctionsSupportFiles\Fig09_H76-SurveyJunctions.PNGH13171200002018OceaneeringNESurvey H13176 junctions with H13171 to the east and northeast. The overlap consists of mainlines and crosslines that extend into the adjoining sheet. A difference surface was generated between the two surveys with H13176_MB_1m_MLLW_Final as surface 1 and H13171_MB_1m_MLLW_Final as surface 2. The difference surface indicates that data from H13176 and H13171 agree well (Figure 10) with greater than 99% of difference values between -0.12 and 0.18 meters. Difference values greater than 2^0.5 * TVU were addressed with the following reasoning. The minimum depth in the H13176 survey area is 12.4 meters with a TVU of ±0.525 meters and 2^0.5 * TVU of 0.743 meters. Depth difference values greater than 2^0.5 * TVU would need to at least exceed 0.743 meters. It was observed that two depth difference values exceed this threshold that are associated with a natural seabed feature (Figure 11); the difference in depth may be due at least in part to a small positional difference between the two datasets over the feature. Further review of the area indicates the water depth according to the H13176 surface is ~15.3 meters which would have 2^0.5 * TVU of 0.761 meters. Depth difference values do not exceed this value.Histogram of depth difference values between overlapping data of H13176 and H13171.SupportFiles\Fig10_H76-JunctionHistogram.PNGArea and zoomed image of difference greater than the nominal 0.743-meter value at the H13176 and H13171 junction.SupportFiles\Fig11_H76-Junction.PNGH13173200002018OceaneeringSEThe survey junction between H13176 and H13173 will be addressed in the Descriptive Report for H13173.H13174200002018OceaneeringWThe survey junction between H13176 and H13174 will be addressed in the Descriptive Report for H13174.H13175200002018OceaneeringSWThe survey junction between H13176 and H13175 will be addressed in the Descriptive Report for H13175.H13178400002018OceaneeringSThe survey junction between H13176 and H13178 will be addressed in the Descriptive Report for H13178.Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.Sonar SettingsIf necessary, the angle of the multibeam sonars were modified in order to moderate the effects of factors such as increased sea state or to increase coverage; any changes are documented in the acquisition logs.Environmental FactorsWeather, sea state, thermoclines, and fish/marine life were all temporary factors that affected the data periodically throughout the duration of the survey. These are noted in the acquisition and processing logs and reruns were collected when necessary.Twice per day and more often as necessary.Sea-Bird Scientific SBE19 and SBE19plus Conductivity, Temperature, and Depth (CTD) sensors were used for speed of sound measurements through the water column. The water column sound speed profiles were applied in Kongsberg's Seafloor Information System (SIS) multibeam control software to correct the multibeam data in real-time. Endeco YSI sondes were used to determine the sound speed at the transducers. Sound speed data are located in Separates\II_Digital Data\Sound Speed Data Summary.Mainline coverage within the survey area consisted of Complete Coverage (100% side scan sonar with concurrent multibeam data) acquisition. Assigned investigations were surveyed with 200% side scan sonar. Potentially significant contacts were surveyed with full coverage MBES. Bathymetric data were acquired with a Kongsberg EM2040C multibeam echo sounder. Side scan sonar acoustic imagery was collected with a Klein 5000 V2 system.DensityHydrOffice QCTools was used to analyze the density of all finalized surfaces. The density of all finalized surfaces meet the density requirements for which at least 95% of all nodes on the surface shall be populated with at least 5 soundings (Figures 12 and 13).Statistical information about the density child layer of the H13176_MB_1m_MLLW_Final surface generated from HydrOffice QCTools.SupportFiles\Fig12_H76_MB_1m_MLLW_Final.QAv5.density.pngStatistical information about the density child layer of the H13176_MB_2m_MLLW_Final surface generated from HydrOffice QCTools.SupportFiles\Fig13_H76_MB_2m_MLLW_Final.QAv5.density.pngHolidaysThe complete coverage surface was reviewed visually; MBES fill-ins were conducted when possible where along track data gaps existed. MBES data were acquired over all potentially significant contacts and visually inspected for coverage; no holidays were observed.All data reduction procedures conform to those detailed in the DAPR.All sounding systems were calibrated as detailed in the DAPR.All equipment and survey methods were used as detailed in the DAPR. Backscatter data were logged within each raw Kongsberg EM file. However, potential issues were recognized with respect to the dual head data collected in April 2019. The EM2040 files were tested for mosaic generation in FMGT and although there were a substantial amount of 'pings fail to correlate' errors, a 1-meter mosaic was generated.TeledyneCARIS HIPS10.4Chesapeake TechnologySonarWizV6005.0025NOAA Extended Attribute Files V5_8CARIS HIPS version 10.4 was the primary software program used for bathymetric data processing and Sonarwiz V6005.0025 was the primary software program used for side scan sonar data processing. H13176_MB_1m_MLLWCARIS Raster Surface (CUBE)112.4024.15NOAA_1mComplete MBESH13176_MB_1m_MLLW_FinalCARIS Raster Surface (CUBE)112.4020.00NOAA_1mComplete MBESH13176_MB_2m_MLLWCARIS Raster Surface (CUBE)212.4123.82NOAA_2mComplete MBESH13176_MB_2m_MLLW_FinalCARIS Raster Surface (CUBE)218.0023.82NOAA_2mComplete MBESH13176_SSS_1m_455kHz_1of2SSS Mosaic1N/A100% SSSH13176_SSS_1m_455kHz_2of2SSS Mosaic1N/A200% SSSMBES Data Processing and ReviewIt was observed during MBES office review that the ASCII navigation files, for the 2018-collected data as compared to those processed in the field, were slightly different. The field-processed and office-checked files are identical up to the VDATUM step, where VDATUM is used to convert the coordinates from ITRF to NAD83(2011). The differences in latitude and longitude are at the 9th decimal point and the difference in ellipsoid heights were observed to be ~0.6 millimeters. The field and office VDATUM log files are identical and the data appear to have been processed in the same way. Specifications state horizontal positions should retain a precision of at least decimeters (for decimal degrees positions: 6 decimal places), and vertical positions with ERS, including values reported in survey records and deliverables, shall retain a precision of centimeters. Data were therefore not reprocessed. It was recognized that data collected in April of 2019 had incorrect motion offsets applied in the SIS software during acquisition. The data were corrected for this in the CARIS processing software using the vessel file to input the correct offsets and sound velocity correct the data. However, due to small and intermittent gaps in the motion string from the DMS05 attitude, the sound velocity correction process created minor motion artifacts within the data (Figure 14). The magnitude of these is generally up to ~10 cm. The data were filtered using a surface filter set to reject data greater than 1 meter away from the CUBE surface with a protective radius around critical soundings, which were reviewed separately. The data were also filtered to 60 degrees on either side of nadir to remove a large amount of edge fliers present in the data. The surface was then reviewed systematically for additional fliers and anomalous features. The FlierFinder utility within HydrOffice QCTools was used as an additional quality control tool to evaluate the surface for fliers. Identified fliers were manually rejected.Section of data showing small artifact after SVC.SupportFiles\Fig14_H76-Artifact.PNGMosaic GenerationWhile processing the side scan sonar data in the office, it was found to have a collection (possibly equipment-related) issue in the starboard channel that created a black stripe along the channel range edge. This was removed from the data prior to processing the mosaic by trimming the channels to display only 96% of the collected range. This did not cause any data gaps and removed the black stripes from the finalized mosaic.Fixed File PathDuring post-processing, ASCII navigation files (time, lat, lon, GPS height) were imported into CARIS with an associated .info file containing information on the contents and formatting of the ASCII navigation files. When projects processed in the above manner were copied from a network location to external or internal drives, or from internal to external drives, it was observed that the path of the *.info file remained fixed to the original path name. Upon opening the copied project, the CARIS program asked to update the navigation folder, but not the *.info file. Keeping the info file in with the ASCII navigation did not appear to change this. Certain editors such as navigation editor or swath editor could not be opened within CARIS and the lines became locked. The workaround is to recreate the exact folder structure of the original project on the internal or external drive. It is recognized, however, that this is an issue for submission because files are placed in the appropriate submission folders without regard for how the projects were originally set up. A request was logged with CARIS support and the information sent to the development team. Information from CARIS support indicates that the Check Project process was not checking for an *.info file when using an ASCII file for auxiliary navigation. CARIS correspondence indicates that this has been fixed so that the check process will look for *.info missing files, enabling users to update their location using the Reset Raw Data Location dialog box. This fix should be available in both versions 10.4.10 and 11.1.0. Due to licensing limitations this has not been tested in-house and the workaround to maintain original path names and drive letters was used. The original path for this project is: N:\2018-OPR-J317-KR-18_193519-TampaBay\Sheets\H13176-Sheet7\Geo\Software_Projects\CARIS\H13176.Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterERS via VDATUMTampaBay_EC_poly_xyNAD83-MLLW_geoid12b.txtNorth American Datum 1983Projected UTM 17The positioning systems aboard the vessel utilize Oceaneering® C-Nav® systems, which deliver Precise Point Positioning (PPP). The C-Nav® GPS system receives corrections through the C-Nav® Subscription Services.A combination of sounding selection layers and user-defined depth ranges were used to compare surveyed soundings to charted depths using tools within the CARIS multibeam processing software. The sounding selection layer was generated from a 1-meter surface containing all data (prior to applying a depth range to the finalized surface) using a shoal biased, single defined radius of 150 meters. This provided sufficient soundings across the survey area with which to compare charted depths and contours. User-defined color maps were generated to match the contour intervals present on US5FL11M, US3GC07M and US3GC06M. US5FL11M40000472019-03-112019-05-13falseNOAA Local Notice to Mariners (LNM) were reviewed subsequent to the date of the Project Instructions and before the end of the survey for RNC 11415. The last LNM reviewed for Chart: 11415, Current Edition: 13, Print Date: Nov./2018, Tampa Bay Entrance; Manatee River Extension was LNM 22/19, 7th Dist posted on 6/13/2019 to make a Change to the Egmont Channel Lighted Buoy 4. No LNM were issued within the H13176 survey bounds. Surveyed soundings range from 12.4 to 24.15 meters. Surveyed depths are shallowest in the eastern half of the survey area and increase to the west and southwest. The 18.2-meter contours of US5FL11M are present and the main contour trends north to south across the center of the H13176 survey area. In general, surveyed depths match well to the charted 18.2-meter contour (Figure 15). However, survey data indicate soundings deeper than 18.2 meters within two closed, isolated contours (red circles, Figure 15). Survey data also indicate several areas of soundings less than or equal to 18.2 meters outside the currently charted 18.2-meter contour or depth area (black circles, Figures 15, 16 and 17). Surveyed depths are generally within 0.5 meters of charted depths although there are several areas where surveyed soundings are up to 2 meters deeper than charted depths (Figures 18 and 19). US5FL11M covers all but the western most portion of the H13176 survey area.Comparison of surveyed depths (central area) to charted depths on USFL11M. Red and black circles denote locations of contour variance.SupportFiles\Fig15_H76-ChartCompUS5FL11M-1.PNGComparison of surveyed depths (southern area) to charted depths on USFL11M. Black circles denote locations of contour variance.SupportFiles\Fig16_H76-ChartCompUS5FL11M-2.PNGComparison of surveyed depths (northern area) to charted depths on USFL11M. Black circle denotes location of contour variance.SupportFiles\Fig17_H76-ChartCompUS5FL11M-3.PNGComparison of selected soundings to charted depths on USFL11M. Selected soundings in black and charted depths in red. Black circles indicate surveyed soundings are deeper than charted depths by up to 2 meters.SupportFiles\Fig18_H76-ChartCompUS5FL11M-4.PNGComparison of selected soundings to charted depths on USFL11M. Selected soundings in black and charted depths in red. Black circles indicate surveyed soundings are deeper than charted depths by up to 2 meters.SupportFiles\Fig19_H76-ChartCompUS5FL11M-5.PNGUS4FL10M80000342019-03-182019-05-13falseNOAA Local Notice to Mariners (LNM) were reviewed subsequent to the date of the Project Instructions and before the end of the survey for RNC 11412. The last LNM reviewed for Chart: 11412, Current Edition: 49, Print Date: Feb./2019, Tampa Bay and St. Joseph Sound was LNM 22/19, 7th Dist posted on 6/13/2019 to make a Change to the Egmont Channel Lighted Buoy 4. No LNM were issued within the H13176 survey bounds. Chart US4FL10M overlaps a small portion of the eastern survey area already covered by US5FL11M. The 18.2-meter contour is present in the southeastern portion of the survey area and is similar to that of US5FL11M except at the northern extents, where there is a larger deviation (the contour of US4FL10M is east of the contour on US5FL11M). Surveyed soundings, 18.2 meters and less, generally fall within the charted contour limits. Surveyed depths also generally align with charted depths on US4FL10M within 0.5 meters with the exception of deeper than charted depths also noted within the comparison for US5FL11M. US3GC07M350000342019-03-112019-05-08falseNOAA Local Notice to Mariners (LNM) were reviewed subsequent to the date of the Project Instructions and before the end of the survey for RNC 11420. The last LNM reviewed for Chart: 11420, Current Edition: 32, Print Date: Oct./2018, Havana to Tampa Bay was LNM 14/19, 7th Dist posted on 4/25/2019 to Delete the Fort Jefferson Buoy B. No LNM were issued within the H13176 survey bounds. Chart US3GC07M overlaps the southern portion of the H13176 survey area. Charted contours are broad and charted soundings sparse due to the scale of the chart. Surveyed depths are generally deeper than US3GC07M charted depths by 10 cm to 3 meters. One larger difference was observed: a charted sounding of 12.8 meters exists within surveyed depths of 21.5 meters (Figure 20, red circle). This results in a shift of the 18.2-meter contour to the east at this location and in general, surveyed soundings less than or equal to 18.2 meters are eastward of the currently charted contour. Comparison of surveyed depths to charted depths on US3GC07M. Red circle denotes location of sounding variance.SupportFiles\Fig20_H76-ChartCompUS3GC07M.PNGUS3GC06M456394242019-03-122019-03-29falseNOAA Local Notice to Mariners (LNM) were reviewed subsequent to the date of the Project Instructions and before the end of the survey for RNC 11400. The last LNM reviewed for Chart: 11400, Current Edition: 37, Print Date: Apr./2019, Tampa Bay to Cape San Blas was LNM 16/19, 7th Dist posted on 4/11/2019 to Add an Obstruction in Fathoms. Two LNM were issued within the H13176 survey bounds. No LNM were issued within the H13176 survey bounds. Chart US3GC06M overlaps the northern portion of the surveyed area. Charted contours are broad and charted soundings sparse due to the scale of the chart. Surveyed depths align with charted depths to within 0.5 meters, and surveyed soundings 18.2 meters or less generally fall within the currently charted contour with two exceptions (Figure 21). Comparison of surveyed depths to charted depths on US3GC06M. Black circles denote location of sounding variance.SupportFiles\Fig21_H76-ChartCompUS3GC06M.PNGNo Maritime Boundary Points were assigned for this survey.Prior to commencing survey operations, the Composite Source File indicated one shipwreck, three obstructions, one seaweed area, and one pipeline exist within the survey area. The survey area partially covers an anchorage area, the fairway around Egmont Channel and a small part of a spoil area in the southwest portion of the survey area. Refer to the Final Feature File for additional information regarding all assigned, charted features.An additional three obstructions were added to the Final Feature File that were not addressed as Dangers to Navigation due to factors such as surrounding charted depths and features. Refer to the Final Feature File for additional information. Contacts observed within the multibeam data that were found to be less than 1 meter in height were often marked as 'Examined' to show that they had been reviewed; these remain 'Examined' in the CARIS project.One Danger to Navigation Report was submitted for this survey which encompassed a discrete obstruction and and delineated polygon of the same area; refer to the FFF and Supplemental Survey Correspondence for additional information. A portion of the safety fairway and anchorage adjacent to Egmont Channel lies within the surveyed area. Data indicate surveyed soundings are generally in line with charted depths to within ±0.5 meters with the exceptions noted in the chart comparison section and Figure 22. The 18.2-meter contour crosses the safety fairway in the center of the survey area. Surveyed depths indicate no significant shift in this contour.Comparison of survey data to charted depths for US5FL11M within the charted fairway and anchorage (black outline). Selected soundings in blue, charted depths in black. Black circles indicate areas where surveyed soundings are deeper than charted depths and red circles indicate areas where surveyed soundings are shallower than charted depths,SupportFiles\Fig22_H76-FairwayComparison.PNGNine bottom samples were acquired within the bounds of H13176. This is one more than as shown in the PRF file. Review indicates that an early PRF file shows two bottom sample locations very close to each other (8 and 9) in the southeast corner of the survey area. It appears that these were carried over into the project set up files; instead of doing two grab samples in one location, the second location was moved during field operations. Refer to the Final Feature File for more information on bottom sample results.Shoreline was not assigned in the Hydrographic Survey Project Instructions or Statement of Work for H13176.No Aids to navigation (ATONs) exist for this survey.No overhead features exist for this survey.One pipeline, labeled as 'Gulfstream Natural Gas System' in the CSF, extends east-west through the southern half of the survey area. Three potential exposures were identified along the pipeline and submitted to BSEE as per the HSSD (2018). At some points along the pipeline, surveyed soundings indicated shallower depths than surrounding charted depths; this appears to be coverings over the pipeline. Refer to the Supplemental Survey Records and Correspondence, surfaces and Final Feature File for additional information.No platforms exist for this survey.No ferry routes or terminals exist for this survey.Two abnormal seafloor areas were observed within survey data. One has similarities to a drag scar (Figure 23). The second is a square area of potential debris (Figure 24).Potential drag scar within survey bounds.SupportFiles\Fig23_H76-Abnormal-Seafloor1.PNGSquare area of debris within survey bounds.SupportFiles\Fig24_H76-Abnormal-Seafloor2.PNGNo 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. 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 meet or exceed requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables, Statement of Work and Project Instructions. 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.Lynn SamuelGeoscientist2019-06-11Nicole GallowayGeoscientist2019-06-25Scott MelanconChief of Party2019-06-25Horizontal and Vertical Control Report2019-03-11Horizontal and Vertical Control Report2019-06-28