OPR-K354-KR-16Approaches to Atchafalaya BayGulf of MexicoOcean Surveys, Inc.H12906225 NM SSW of Point Au FerLouisianaUnited States400002016George G. ReynoldsNavigable Area2016-07-262016-08-182016-09-30Multibeam Echo SounderSide Scan SonarMultibeam Echo Sounder BackscattermetersUniversal Transverse Mercator (UTM)UTCAtlantic Hydrographic BranchThe purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products. All times are recorded in UTC. Data recorded and presented relative to UTM Zone 15 North.
THE INFORMATION PRESENTED IN THIS REPORT AND THE ACCOMPANYING BASE SURFACES REPRESENTS THE RESULTS OF SURVEYS PERFORMED BY OCEAN SURVEYS, INC. DURING THE PERIOD OF 16 AUGUST 2016 TO 30 SEPTEMBER 2016 AND CAN ONLY BE CONSIDERED AS INDICATING THE CONDITIONS EXISTING AT THAT TIME. REUSE OF THIS INFORMATION BY CLIENT OR OTHERS BEYOND THE SPECIFIC SCOPE OF WORK FOR WHICH IT WAS ACQUIRED SHALL BE AT THE SOLE RISK OF THE USER AND WITHOUT LIABILITY TO OSI.
ContractorThis survey provides hydrographic data for the Gulf of Mexico waters approaching Atchafalaya Bay. The general locations of the survey limits are presented in Table 1.29.174222222291.768194444429.057638888991.5929166667Survey limits were acquired in accordance with the requirements in the Project Instructions and the HSSD.Per the hydrographic project instructions, the purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products. This project area is located within the vicinity of the Atchafalaya River Delta and the Port of Morgan City. The proposed project will cover both nearshore and offshore areas in the vicinity of the Atchafalaya River Basin and will update the nautical chart where depth contours have migrated. The project will cover approximately 130 square nautical miles of critical survey area in the Approaches to Atchafalaya Bay as designated in NOAA Hydrographic Survey Priorities, 2012 edition. Survey data from this project are intended to supersede all prior survey data in the common area.The entire survey is adequate to supersede previous data.All waters in survey areaComplete Coverage accomplished using either: A) Complete coverage MBES depth and backscatter data or B) 100% SSS coverage with concurrent set line spacing MBES depth and backscatter data.Survey Coverage is in accordance with the requirements in the Hydrographic Survey Project Instructions (July 26, 2016), the Statement of Work, [May 2016 (SOW)], and the Hydrographic Surveys Specifications and Deliverables, [March 2016 (HSSD)]. In all waters, Complete Coverage was accomplished by acquiring one hundred percent (100%) side scan sonar (SSS) coverage with concurrent multibeam echosounder (MBES) with backscatter. MBES data were acquired on a set line spacing plan.
A large number of concurrent SSS and MBES splits were acquired in the center of the survey area to develop shoals and ensure 100% SSS coverage was obtained. Additional SSS and MBES lines were run to fill gaps in coverage, to provide a least depth for all significant SSS contacts and for charted feature disprovals. Gaps in the 100% SSS coverage were addressed with SSS fill-in lines or covered with complete MBES data. Additional bathymetric splits were collected to develop a new shoal in the vicinity of 29-06-07.23 N, 91-41-14.96 W and to verify or disprove charted depths that fell between two MBES survey lines that were shallower than the adjacent survey soundings.
The final survey area covers 38.00 square nautical miles (Figure 1).Survey H12906 MBES coverage overlaid on RNC 11340.H12906_Figure_1_Coverage.jpgR/V Ocean Explorer048.8000.1001485.160140.220048.4700.1001438.110140.2209.75500038.002016-08-182016-08-192016-08-222016-08-232016-08-242016-08-252016-08-262016-08-272016-08-282016-08-292016-08-302016-08-312016-09-082016-09-122016-09-132016-09-142016-09-152016-09-162016-09-172016-09-182016-09-192016-09-202016-09-212016-09-232016-09-252016-09-272016-09-282016-09-292016-09-30The lineal nautical miles (LNM) for MBES only development and fill-in lines were included under the heading "Mainscheme MBES" and the LNM for SSS only fill-in lines were included under the heading "Mainscheme SSS" in Table 2. Hydrographic Survey Statistics.Refer to the OPR-K354-KR-16 Data Acquisition and Processing Report (DAPR) for a complete description of data acquisition and processing systems, survey vessel, 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.R/V Ocean Explorer182Survey operations were conducted from the R/V Ocean Explorer. The R/V Ocean Explorer, O.N. 905425, is an 18-meter aluminum vessel, with a 5.1-meter beam and nominally 2-meter draft, powered by two 1,000 HP Iveco diesel engines.Reson7125MBESEdgeTech4125SSSODIMMVP30 w/AML SVPTSound Speed SystemAMLMicro-XSound Speed SystemApplanixPOS MV 320 V.4Positioning and Attitude SystemTrimbleProBeaconPositioning SystemTrimbleSPS 461Positioning SystemTable 5 summarizes the primary equipment used to acquire MBES and SSS data. All equipment was installed, calibrated and operated in accordance with the DAPR.A total of 140.22 nm of cross line data were acquired August 18 and 19, 2016 (DNs 231 to 232). Cross line mileage equaled 9.75% of the mainscheme MBES lines. Cross lines were run nominally perpendicular to mainscheme lines (Figure 2).
Soundings from mainscheme lines and cross lines were compared periodically throughout survey operations reviewing preliminary MBES surfaces and using CARIS HIPS Subset Editor. Cross line comparisons provided confirmation that the system offsets and biases were entered correctly and verified the accuracy of sounding correctors (i.e. tide, sound speed, TrueHeave).
Statistical quality control information was compiled from a difference surface, generated in CARIS HIPS, between the depth layer of a 1-meter CUBE surface composed only of cross line data and the depth layer of a 1-meter CUBE surface composed only of mainscheme data. The cross line analysis results demonstrate excellent agreement between cross line soundings and mainscheme soundings, with an average depth difference of 4 centimeters. Figure 3 is a histogram showing the distribution of depth differences for all comparison grid cells considered. The total number of 1-meter comparison cells equaled 2,072,765. Of the possible comparison cells, 2,002,625 or 96.61% of the cells include cross line and mainscheme soundings that match within +/- 20 centimeters.An overview of the cross line layout on a 1-meter surface created from mainscheme MBES data and colored by depth. RNC 11351 is visible in the background.H12906_Figure_2_XLs.jpgThe graph shows a frequency distribution of the depth differences between the H12906 cross line data and the H12906 mainscheme MBES data. Statistics from the depth difference sample set are displayed above the graph.H12906_Figure_3_XL_Histogram.jpg0.030.09Discrete ZoningR/V Ocean Explorer11The methods used to minimize the uncertainty in the corrections to echo soundings are described in detail in Section B. Processing and Quality Control of the project DAPR. Survey H12906 did not deviate from the methods documented in the DAPR.
The Total Vertical Uncertainty Quality Check (TVU QC) "Ratio Method" was used to evaluate IHO uncertainty for all finalized surfaces. The TVU QC "Ratio Method" is described in the Chapter 4 Appendices of the NOAA OCS Field Procedures Manual (FPM) dated April 2014. Per the FPM TVU QC section, "The hydrographer should use the finalized surface because this surface will identify areas where either the uncertainty or the standard deviation exceeded the maximum allowable error and the greater of these two values is used in addition to having the uncertainty scaled to a 95% CI, whereas unfinalized surface uncertainties are reported at the 68% CI." The FPM TVU QC section also states that, "[ratio] values which do not require further examination are from -1 to 0 and the values which do require further examination are from -100 to -1".
Finalized surfaces were used in this analysis. Surfaces were finalized using the “greater of the two” option as the basis for calculating “Final Uncertainty” in the CARIS “Finalize Base Surface” utility.
Seventeen (17) MBES CUBE (Combined Uncertainty and Bathymetric Estimator) surfaces were delivered along with Survey H12906 including "H12906_MB_1m_MLLW_Final" and sixteen (16) 50-centimeter item investigation surfaces. The 1-meter surface is intended to satisfy coverage and sounding density requirements for Complete Coverage, Option B: 100% side scan sonar coverage with concurrent multibeam. The remaining 0.5-meter surfaces are intended to satisfy Object Detection Coverage and sounding density requirements over significant features.
Results from the TVU QC indicate that 99.99% of the nodes from all submitted surfaces meet IHO Order 1 uncertainty specifications, i.e. the ratio values of nearly all the nodes are less than -1. Of the 56,922,447 nodes considered, 5,909 had a ratio value below -1. Upon examination it was found that the nodes with ratio values below -1 were located over significant features resulting in higher standard deviation values and finalized uncertainty values, which is to be expected over discrete features. Two (2) prior surveys and two (3) contemporary surveys junction with Survey H12906. Figure 4 displays the location of the prior and contemporary junction surveys for Project OPR-K354-KR-16.Survey junctions for Project OPR-K354-KR-16. RNC 11340 is displayed in the background.H12906_Figure_4_Junctions.jpgH11288200002005NOAA Time CharterENOAA Time Charter's Survey H11288, a hydrographic survey conducted in 2005, overlapped the eastern border of H12906. Depth data for Survey H11288 were downloaded from the NGDC website in the form of four (4) 2-meter resolution BAGs: "H11288_2m_MLLW_1of8," "H11288_2m_MLLW_2of8," H11288_2m_MLLW_3of8," and "H11288_2m_MLLW_4of8". MBES data for H12906 and H11288 were acquired for 100 or 200% SSS coverage with Set Line Spacing; therefore, the overlap between the two surveys was patchy with an approximate overlap of 100 to 1000 meters.
To conduct the junction comparison a 2-meter CUBE surface was generated from the entire MBES data set for Survey H12906, "H12906_MB_2m_MLLW". In CARIS HIPS, depths from each of the H11288 2-m BAGs were subtracted from the depths in the H12906 2-meter surface using the CARIS HIPS Difference Surface function. A histogram of the differences is shown in Figure 5. The majority of depths from the H12906 survey were deeper than depths from the H11288 survey, with a maximum depth discrepancy of 86 centimeters and an average difference of 27 centimeters.
The mean and maximum depth differences between surveys were relatively large. One reason for the large depth discrepancies between the surveys was a vertical offset (most likely tide related) noted between the depth values of adjacent mainscheme lines on the western edge of Survey H11288. In Figure 6, a portion of the junction area is shown that highlights the vertical offset between adjacent H11288 survey lines and how it influenced the H12906-H11288 difference surface results. The H11288 2m BAG is colored by depth with green colored survey lines approximately 10-30 centimeters deeper than those represented as yellow or orange. The depth discrepancies between Survey H11288 and H12906 varied between each adjacent H11288 mainscheme line, matching the vertical offset apparent in the H11288 data.
Per the H11288 DR, the primary tide gauge utilized for the survey changed during data acquisition from a tertiary water level station at Eugene Island (876-4311) to the National Water Level Observation Network (NWLON) station in Galveston Pleasure Pier, TX (877-1510). Section C.1.2 Vertical Control from the H11288 DR states: "After application of approved tides to the survey, a tide bust was discovered during processing at the Atlantic Hydrographic Branch. This bust occurs on August 16th, the day the water level station was destroyed, and is thought to be related to the destruction of the station. Predicted water levels from Eugene Island (876-4311) were applied to all data acquired on August 16th, 2006 to correct this tide bust problem." While it is unknown from the H11288 BAG if the data overlapping with H12906 were acquired before or after August 16th, a change in the primary tide gauge and zoning used to apply tide correction to H11288 soundings may account for the vertical offset between adjacent survey lines in the H11288 BAG and for the line-to-line variability in depth differences between H12906 and H11288.
Another reason for the larger depth discrepancies between Surveys H11288 and H12906 was sediment transport and the natural migration of sand over large, prominent shoals that coincide with the junction area. The shoals have migrated between 2005 and 2016 resulting in areas of deepening along the shoal edges and shoaling at the peaks (Figure 7).
Furthermore, it is noted that data acquisition dates for Survey H11288 spanned from July 23 to August 30, 2005 during which time Hurricane Katrina made landfall in south Louisiana. Given the relatively shallow water depths in this area, it is possible that the massive storm and subsequent storm events could be responsible for some depth change between surveys.Surface-to-surface difference histogram comparing Survey H12906 to H11288.H12906_Figure_5_H11288_Histogram.jpgThe top image shows a portion of a 2m BAG from Survey H11288 colored by depth, with a color change noted between adjacent mainscheme survey lines due to a vertical offset in the data of 10-30 cm. The middle image shows the 2m H112906 surface colored by depth for the same subset of the junction area. The bottom image shows the difference surface overlaid on the partially transparent H12906 and H11288 2m surfaces. The difference values between survey data vary with each H11288 survey line.H12906_Figure_6_H11288_Tide_offset.jpgA large migrating shoal coincided with the junction area of H12906 and H11288 surveys, as shown in the top row of images. The bottom images highlight the difference surface along the edge with the blue coloration representing the most change: deepening due to shoal migration to the southwest.H12906_Figure_7_H11288_Shoal.jpgH11290200002005NOAA Time CharterSNOAA Time Charter's Survey H11290, a hydrographic survey conducted in 2005, overlapped the southern border of H12906. Depth data for Survey H11290 were downloaded from the NGDC website in the form of two (2) 1-meter resolution BAGs: "H11290_1m_MLLW_1of4" and "H11290_1m_MLLW_2of4". MBES data for H12906 and H11290 were acquired for 100 or 200% SSS coverage with Set Line Spacing; therefore, the horizontal overlap between the two surveys was patchy with an approximate overlap of up to 1600 meters.
To conduct the junction comparison a 1-meter CUBE surface was generated from the entire MBES data set for Survey H12906, "H12906_MB_1m_MLLW". In CARIS HIPS, depths from each of the H11290 1-m BAGs were subtracted from the depths in the H12906 1-m surface using the CARIS HIPS Difference Surface function. A histogram of the differences is shown in Figure 8. The majority of depths from the H12906 survey were deeper than depths from the H11290 survey, with a maximum depth discrepancy of 1.25 meters and an average difference of 33 centimeters.
The overall deepening trend from 2005 to 2016 could have several causes including sediment transport and the fact that the H11290 survey data were corrected with a different tide source than H12906. The primary tide gauge for the H11290 survey was a tertiary water level station installed at Eugene Island (876-4311) and Survey H12906 soundings were corrected with water levels from the LAWMA, Amerada Pass, LA NWLON station. An unrecognized datum difference between the tide stations may contribute to consistent depth bias between surveys.
Natural deepening of the seafloor accounts for the largest depth discrepancies (0.8 to 1.25 meters) with two junction locations highlighted in Figure 9. As noted above, regular storm events could account for some depth changes between surveys.Surface-to-surface difference histogram comparing Survey H12906 to H11290.H12906_Figure_8_H11290_Histogram.jpgThe top image is an overview of the junction area between Surveys H12906 to the north and H11290 to the south. The bottom images highlight areas of deepening where the largest depth differences were encountered in the junction analysis.H12906_Figure_9_H11290_Deepening.jpgH12905400002016Ocean Surveys, Inc.NThe approximate overlap between the bathymetric data from contemporary Surveys H12905 and H12906 varied approximately between 300 to 800 meters. Given that both surveys were acquired to meet 100% SSS Coverage, not complete MBES coverage, the junction area between the two surveys was patchy.
Depths from 1-meter BASE surfaces compiled from the MBES data from each survey, "H12905_MB_1m_MLLW" and "H12906_MB_1m_MLLW," were compared using the CARIS HIPS Difference Surface function. A histogram of the differences is shown in Figure 10. Depths from the H12906 survey show good agreement with the depths from the H12905 survey. Depth discrepancies generally equaled 20 centimeters or less with a mean difference of 4 centimeters.Surface-to-surface difference histogram comparing Survey H12906 to Survey H12905.H12906_Figure_10_H12905_Histogram.jpgH12907400002016Ocean Surveys, Inc.WThe overlap between the bathymetric data from contemporary Surveys H12906 and H12907 is approximately 400 meters. Given that both surveys were acquired to meet 100% SSS Coverage, not complete MBES coverage, the junction area between the two surveys occurs at track line ends that are generally overlapping.
Depths from 1-meter BASE surfaces compiled from the MBES data from each survey, "H12906_MB_1m_MLLW" and "H12907_MB_1m_MLLW," were compared using the CARIS HIPS Difference Surface function. A histogram of the differences is shown in Figure 11. Depths from the H12906 survey show good agreement with the depths from the H12907 survey. Depth discrepancies generally equaled 25 centimeters or less with a mean difference of 9 centimeters. The minor biases between surveyed depths appear to be tide related, as the agreement between survey depths from H12906 and H12907 vary with survey
day. Where a difference between survey depths is present, the offset is noted across the full swath of coincident lines from the same survey day, without any modification to system configuration, which is indicative of a tidal offset.Surface-to-surface difference histogram comparing Survey H12906 to Survey H12907.H12906_Figure_11_H12907_Histogram.jpgH12908400002016Ocean Surveys, Inc.SWA small portion of Survey H12906 intersected the northeast corner of Survey H12908 with the approximate overlap of bathymetric data being 100 to 600 meters. Given that both surveys were acquired to meet 100% SSS Coverage, not complete MBES coverage, the junction area between the two surveys was patchy.
Depths from 1-meter BASE surfaces compiled from the MBES data from each survey, "H12906_MB_1m_MLLW" and "H12908_MB_1m_MLLW," were compared using the CARIS HIPS Difference Surface function. A histogram of the differences is shown in Figure 12. Depths from the H12906 survey show good agreement with the depths from the H12908 survey. Depth discrepancies generally equaled 15 centimeters or less with a mean difference of -5 centimeters.Surface-to-surface difference histogram comparing Survey H12906 to H12908. H12906_Figure_12_H12908_Histogram.jpgSonar system quality control checks were conducted as detailed in the Quality Control section of the DAPR. Results from the weekly MBES bar checks are included in Appendix II of the DAPR.MBES Time Sync Errors and GapsOccasional time sync alarms were observed on the Reson 7125 Seabat display during data acquisition. The field personnel noted that along with the time sync alarm a brief gap would be observed in the real time display of the Seabat waterfall window. Several small along track data gaps associated with the Reson time sync error were noted in CARIS HIPS Subset Editor during data processing of the MBES data, wherein there is a short break in recorded profiles (Figure 13). Larger holidays were filled with additional MBES coverage. Remaining gaps do not exceed 3x3 surface nodes in the 1-meter Complete Coverage surface.Example of a small gap in MBES data associated with the Reson time sync error as it appears in CARIS Subset Editor (top left and bottom) and the same gap as it appears in a 1-meter CUBE surface (top right).H12906_Figure_13_Time_Sync_Error.jpgTide OffsetReview of surface data indicated that there were a number of tide-related offsets between MBES data collected on different days scattered throughout Survey H12906. There were no noteworthy tide events that affected this survey, though there was a consistent offset on the scale of 10 to 40 centimeters between the predicted and verified tides at the LAWMA, Amerada Pass LA tide station. Overall, the tide correctors were modeled well for Survey H12906, showing good agreement between survey days. Tide offsets generally equaled 25 cm or less and are likely associated with local environmental effects, i.e. wind setup.
Figure 14 highlights a portion of the survey area where a tide offset was noted between MBES data from several survey days. There was good agreement between the cross line (yellow, DN 232) and the mainscheme data from DN 260 (blue), but a tide-related vertical offset was present between the cross line and data collected on DN 243 (purple) and DN 263 (orange).The left image shows a subset window displayed over the Standard Deviation layer from the H12906 1-meter CUBE surface. The green and cyan colors indicate areas of higher standard deviation in the surface due to a minor tide offset. The right image displays MBES data loaded into CARIS Subset Editor with a tide offset noted between DN 232 (yellow) and survey lines from DN 243 (purple) and DN 263 (orange) but agreeing well with survey lines from DN 260 (blue). Depths and distances are in meters.H12906_Figure_14_Tide_Offset.jpgSSS RefractionDynamic sound speed changes affected the SSS imagery at times, causing refraction in the outer ranges of the SSS swath. As noted in the DAPR, an OSI utility was developed to plot the speed of sound recorded at the MBES transducer head, as it was found that dynamic changes in sound speed at the surface often correlated with increased refraction in the outer range of the SSS imagery. A number of mainscheme survey lines acquired on DN 236 through DN 238 exhibited pronounced refraction in the SSS imagery in the northern half of the H12906 survey area while the imagery for the southern half of the SSS lines was clear of refraction affects. Figure 15 shows an example of where the refraction observed in the SSS imagery for a survey line from DN 237 correlated with increased variability in the surface speed of sound.
A review of the sound speed profiles acquired along the lines affected by refraction showed that there were rapid changes in sound speed of approximately 3 to 4 m/s within the top 3 meters of water in the northern half of the survey area compared to the profiles collected in the southern half of the survey area which showed little to no change (< 1 m/s) within the top 3 meters of the water column (Figure 16). Dynamic change in speed of sound near the 4125 SSS transducer head which had an approximate draft of 1.5 meters most likely accounted for the conspicuous increase in refraction on the affected survey lines from DN 236 through DN 238. To ensure that 100% coverage of high quality SSS data were acquired, SSS lines with excessive refraction were rejected or the portion of the line with severe refraction was re-run.The top three images display subsets of SSS imagery from line 20160824184120 and the bottom image is a plot of the surface speed of sound recorded for that line. The left image shows SSS clear of refraction from the SW start of the line at time 18:41. The middle SSS image displays slight refraction at time 19:00 and the right SSS image shows pronounced refraction in the NE end of the line at time 19:20. The absence and presence of refraction in the SSS imagery correlates to times of low and high variability in the surface SOS. H12906_Figure_15_Refraction.jpgTwo sound speed profiles from DN 237 are plotted above with one cast taken at the SW end (blue) and the other at the NE end (orange) of line SSS 20160824184120. Higher variability in sound speed at the top of the water column was noted at the NE end of multiple lines on DNs 236 -238. High variability in surface sound speed correlated with an increase in SSS refraction.H12906_Figure_16_SoS_Profiles.jpgSea State Induced White Streaks in SSS Imagery and MBES "Blowouts"The Reson 7125 system experienced periodic bursts of motion-induced noise or “blowouts,” typically affecting between 1 and 4 sequential profiles. Efforts were made to reduce this noise during acquisition, including adjustments to system gain and power, in addition to the multibeam pole fairing that was installed to reduce cavitation effects. The noise bursts were infrequent and were encountered when sea state worsened. Accepted data effected by blowouts did not show any nadir gaps in coverage in excess of 3 x 3 surface nodes in the 1-meter MBES coverage surface.
The fixed mount SSS data were also impacted by sea state conditions, such that when the wave frequency and height increased, more cavitation effects were observed near the transducer head with a dark return noted at the top of the water column in the raw SSS record. The cavitation noise at the transducer head resulted in intermittent "white streaks" across the SSS record, which occasionally coincided with blowouts in the MBES data (Figure 17). To ensure that 100% coverage was attained where the white streaks occurred, holiday fill-in lines were acquired over the location of the streaks with either MBES or SSS coverage. This figure shows how cavitation noise at the SSS and MBES transducer heads presented in the converted data. Noise at the 4125 TX head is visible as a dark return at the top of the water column in the raw SSS imagery (top right), which presented as white streaks across the processed SSS record (top left). In this instance, the SSS white streak coincided with an MBES blowout (bottom).H12906_Figure_17_Streaks_Blowout.jpgFish in SSS Imagery and MBES dataAn abundance of fish and marine sea life were seen in the SSS and MBES data, either as lone swimmers or in schools (Figures 18 - 19). Fish and dolphins were noted in the acquisition log by the field team, and these areas were carefully reviewed during data processing. Shadows in the SSS, usually detached from a dark return, were typically associated with fish either in the water column or at a position closer to nadir. In the cases where a visible shadow was recorded in the SSS, the contact was designated as a fish, for two reasons: 1) the possibility that the assumed fish was actually a feature and 2) to assist processors in rejecting fish-related noise from the MBES data.
Dolphin pods were present within the survey area, as well as large schools of fish, which at times created large shadows in the SSS imagery and gaps in the MBES data where soundings on fish and dolphins were rejected (Figure 20). To ensure that possible significant features were not located in these fish and dolphin shadows, these fish/dolphin related coverage gaps were developed with 200% SSS coverage or complete MBES coverage.A large school of fish as it appears in the MBES data and in the slant range corrected SSS imagery. The image on the left was taken in CARIS Subset Editor 3D with rejected soundings on fish leaving small gaps in MBES coverage.H12906_Figure_18_Fish.jpgThe top image shows fish or shrimp "balls" as they appeared in the slant range corrected SSS imagery. The bottom image shows a school of fish as it appeared in the water column of the raw, un-slant range corrected SSS imagery.H12906_Figure_19_SSS_Fish.jpgExamples of fish and dolphins as they appear in the MBES data and the SSS imagery, whether in the water column of the raw, un-slant range corrected imagery (top) or the slant range corrected SSS data (bottom).H12906_Figure_20_Big_Fish.jpgSound speed profile data were acquired with the ODIM MVP30 approximately every 15 minutes as documented in the DAPR.All MBES lines were sound speed corrected using CARIS HIPS' "Nearest in Distance Within Time" method with the time set to two (2) hours. Based on prior survey experience in the northern Gulf of Mexico, OSI expected to encounter high variability in the speed of sound with abrupt gradient changes linked to dynamic salinity and temperature conditions. Fortunately for the majority of data acquisition for Project OPR-K354-KR-16, the water column was relatively well-mixed, which reduced the incidence of refraction in the SSS and MBES data sets as compared to OSI's recent Gulf of Mexico survey experience.
OSI submitted H12906 sound speed data in NetCDF format to the National Centers for Environmental Information (NCEI) on December 14, 2016 (DN 349) via the S2N tool. NCEI assigned the sound speed submission Accession Number 0157605. Correspondence regarding the NCEI data submission is included in Appendix II.This survey was conducted to develop 100% SSS coverage along with concurrent MBES with backscatter for all survey depths, i.e. Complete Coverage, Option B as defined in Section 5.2.2.3 of the HSSD 2016. All depths within Survey H12906 were shallower than 20 meters. Per the HSSD which states "Gaps in SSS coverage should be treated as gaps in MBES coverage and addressed accordingly," gaps in SSS coverage and holidays caused by fish, dolphins, or white line noise were developed with Complete Multibeam or 200% SSS coverage. All potentially significant features located with mainscheme SSS or MBES were developed with high density multibeam sonar data to meet the HSSD requirement of Object Detection coverage.
The survey methods used to meet coverage requirements did not deviate from those described in the DAPR.DensityTo confirm the HSSD Density coverage requirements, the Compute Statistics tool was utilized within CARIS HIPS and SIPS to generate statistics for the Density layer for each CUBE surface. The HSSD states that at least 80% of the surface nodes shall be populated with at least 5 soundings for the Complete Coverage (Option B) 1-meter surface, and that at least 95% of the nodes shall be populated with at least 5 soundings for the 50-cm Object Detection surfaces.
For the purpose of obtaining the most accurate surface density statistics, the unfinalized surfaces were used for the Density QC check as it was discovered that during surface finalization a density value of one (1) was assigned to all nodes containing a designated sounding, regardless of the node's sounding density value pre-finalization. The Compute Statistics tool generates an ASCII export containing two columns: 1) sounding density value and 2) the number of nodes that returned that value. This export was used to determine the percentage of nodes with a sounding density ≥ 5 for every submitted CUBE surface.
The percentage of nodes with density greater than or equal to 5 soundings for the 1-meter Complete Coverage surface was as follows: H12906_MB_1m_MLLW = 99.71%.
For thirteen (13) of the sixteen (16) object detection coverage surfaces generated over significant figures, 100% of the surface nodes had a sounding density greater than 5 soundings. The remaining three (3) object detection surfaces all had at least 95% of the nodes populated with at least 5 soundings with the percentages of nodes with density ≥ 5 as follows: H12906_MB_50cm_MLLW_6-215 = 99.58%, H12906_MB_50cm_MLLW_6-220 = 99.93%, and H12906_MB_50cm_MLLW_6-235 = 99.73%.All data reduction procedures conform to those detailed in the DAPR with the exception of one MBES line from August 28, 2016 (DN 241), line 2016OC2410024_6048, which didn't have delayed heave applied due to a gap in the TrueHeave data at the start of the line. The affected line was corrected with the real time heave values which were more than sufficient given the calm sea conditions on DN 241.All sounding systems were calibrated as detailed in the DAPR.Backscatter data were acquired concurrent with bathymetry data for Survey H12906. Backscatter data were recorded with HYSWEEP SURVEY in .7K format. These data were periodically reviewed to ensure function of the backscatter acquisition process. No specific instructions were made in the Project Instructions regarding coverage, ground truthing or processing for the Backscatter data, as such, these data are delivered in raw format in the “Backscatter” directory per the HSSD, Section 8.3.4 Backscatter Deliverables.CARISHIPS/SIPS7.1.2CARISHIPS/SIPS7.1.2NOAA Profile V_5_4.Software versions described in Section A of the DAPR were used throughout acquisition and processing of data for Project OPR-K354-KR-16.H12906_MB_1m_MLLW_FinalCUBE13.58.66NOAA_1mComplete Coverage (Option B)H12906_MB_50cm_MLLW_6-007_FinalCUBE0.54.916.85NOAA_0.5mObject DetectionH12906_MB-50cm_MLLW_6-016_FinalCUBE0.53.856.01NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-076_FinalCUBE0.55.646.26NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-215_FinalCUBE0.54.098.29NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-217_FinalCUBE0.54.946.38NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-220_FinalCUBE0.57.017.59NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-221_FinalCUBE0.55.476.85NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-223_FinalCUBE0.55.686.59NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-225_FinalCUBE0.55.337.86NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-228_FinalCUBE0.56.047.05NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-230_FinalCUBE0.54.735.81NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-233_FinalCUBE0.56.216.82NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-235_FinalCUBE0.56.156.76NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-238_FinalCUBE0.55.906.63NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-245_FinalCUBE0.54.878.40NOAA_0.5mObject DetectionH12906_MB_50cm_MLLW_6-246_FinalCUBE0.55.437.13NOAA_0.5mObject DetectionH12906_SSS_1m_100SSS Mosaic GeoTiff1N/A100% SSSH12906_SSS_1m_200SSS Mosaic GeoTiff1N/A200% SSSSeventeen (17) MBES CUBE surfaces and two (2) SSS mosaics comprise the total surfaces delivered with Survey H12906. To demonstrate MBES coverage requirements were met for Complete Coverage (Option B), a 1-meter CUBE surface was generated for the entire survey area. Sixteen (16) small field sheets were generated over significant features and populated with 50-centimeter CUBE surfaces to demonstrate Object Detection coverage.
Two 1-meter SSS mosaics were submitted as GeoTIFFs to satisfy the SSS coverage requirements of 100% coverage and 200% coverage over charted feature disprovals and SSS fill-ins. In addition, a higher resolution, 25-centimeter SSS mosaic image composed of all SSS lines was submitted in the ECW (Enhanced Compressed Wavelet) format to assist with the survey review.Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying Horizontal and Vertical Control Report (HVCR) for Project OPR-K354-KR-16.Mean Lower Low WaterLAWMA, Amerada Pass, LA876-4227Eugene Island, LA876-4314Offshore Bottom Mounted Pressure Gauge N/ADiscrete Zoning8764227.tidVerified ObservedK354KR2016 Revised Zoning 20161103.zdfFinalA final verified tide file was created from verified water level data from the primary tide station LAWMA, Amerada Pass, LA (876-4227) obtained from the CO-OPS website upon completion of survey operations. The Eugene Island gauge data were used only for tide zone refinement analysis not for reducing soundings to MLLW. Discrete zoning methods were utilized to apply tide correctors in CARIS HIPS and SIPS. The survey area is located within Zones WGM282, WGM281 and WGM280 as provided in the preliminary tidal zoning scheme included with the project SOW.
Pursuant to the "strong recommendation" in the Tides and Water Levels Statement of Work provided with the Project Instructions, two Bottom Mounted Pressure Gauges (BMPGs) were installed in the southwestern end of the project area in order to better understand the tidal propagation and zoning error for the discrete zones. The BMPG water level data were not used for tide correction of soundings; the gauges served as a zoning station to update the tidal range and phase correctors and to derive a tide zoning error estimate for the project area. Two BMPGs, one primary gauge and a back-up, were deployed for over 30 days from August 17 (DN 230) to September 24 (DN 268), logging data continuously for the entire deployment.
OSI's subcontractor, JOA Surveys, processed the downloaded pressure data to calculate water levels and to compute the tidal datum for the BMPG zoning station. Water levels from the BMPG station were used along with data from the LAWMA and Eugene Island NWLON stations to refine the phase and range correctors provided in CO-OPS preliminary zoning scheme. The final zoning scheme, K354KR2016 Revised Zoning 20161103.zdf, includes new time and range correctors for each preliminary zone, but the preliminary zone geometry was retained along with the CO-OPS provided names. Based on the results of cross line analysis, the time and range factors as provided in the final zoning scheme are adequate.
Please refer to JOA's OPR-K354-KR2016 Zoning Report.pdf included with the Tide deliverables. All tide station deliverables required in Section 4.7.5 were submitted to CO-OPS on November 9, 2016, as documented in an email included with Correspondence in Appendix II, OPR-K354-KR-16_BMPG_Transmittal.pdf. As of this time, OSI has not received and does not anticipate receiving a station name or ID number for the BMPG Gauges.
Tables 14 and 15 list the water level and tide corrector files applied to the H12906 sounding data.North American Datum of 1983 (NAD83)UTM Zone 15 NorthEnglish Turn, LA (primary), 293 kHzAngleton, TX (secondary), 301 kHzAll data products, except the S-57 Final Feature File (FFF) are referenced to Latitude/Longitude, UTM Zone 15 North. The S-57 Final Feature File, H12906.FFF.000, is referenced to the World Geodetic System Datum of 1984 (WGS 84) as specified in HTD 2016-03, which revised the HSSD 2016 Section 2.1 Horizontal Datum such that all positions will be referenced to the NAD 83 and "the only exception for the NAD 83 datum requirement is that the S-57 feature file will be in the WGS 84 datum."
All MBES and SSS line and item investigation position data were acquired using an Applanix POS-MV operating in Differential GPS (DGPS) mode. The unit was configured to receive USCG Differential beacon correctors from the English Turn, LA station and, on occasion, USCG Differential beacon correctors from the Angleton, TX station. A secondary GPS, used to facilitate real-time horizontal control confidence checks, was supplied with correctors from the Marinestar subscription service.
Prior to and during the course of the survey the accuracy of the primary positioning system was verified by means of a physical measurement to a horizontal control point established at the vessel’s base of operation, a dock at the Port of Morgan City. Position confidence checks were accomplished, when possible, during fuel or weather stops. Refer to the DAPR and HVCR for additional details. Positioning system confidence checks were performed utilizing both DGPS signal sources mentioned above.
On September 12, 2016 (DN 256), the survey vessel lost signal to the English Turn, LA DGPS station at approximately 14:00 UTC. The station was scheduled for maintenance per the USCG navigation center website (www.navcen.uscg.gov). The station's down time lasted approximately 6 hours, during which time the survey crew used correctors from the Angleton, TX DGPS station. During another period, lasting almost 48 hours on DN 257 to DN 259, the Angleton, TX signal was utilized due to generally poor reception of the English Turn, LA signal. In this case, the poor reception is believed to be attributable to foul weather between the English Turn, LA station and the survey area.Horizontal Offset in DGPS PositioningA horizontal offset of approximately 0.5 to 1.5 meters was noted between the MBES survey lines collected over significant features developed to meet object detection coverage (Figure 21). The shift in horizontal position between lines can be attributed to the use of DGPS correctors for positioning with the survey area located over 150 kilometers from the English Turn station. The horizontal positional shift was well within the limits of horizontal accuracy as defined in Section 3.1.1 Horizontal Position Uncertainty of the HSSD 2016.Example of a feature developed with object detection MBES coverage that exhibited a horizontal positioning shift between survey lines. The new obstruction is shown in CARIS Subset Editor 3D window (left) and 2D window (right) with soundings colored by line and all depths and distances in meters. H12906_Figure_21_Horiz_Offset.jpgChart comparisons were performed in CARIS HIPS/SIPS and Notebook using finalized BASE surfaces and contours and selected soundings. The latest editions of the NOAA NOS Raster Nautical Charts (RNC) and Electronic Nautical Charts (ENC) were downloaded from the NOAA Office of Coast Survey website (http://www.nauticalcharts.noaa.gov/) regularly during survey operations, and after the survey was completed for final comparisons. The RNCs and ENCs used for final comparisons were downloaded on December 19, 2016 and are submitted with the survey deliverables.
Local Notice to Mariners (LNM) and Notice to Mariners (NM) spanning the period beginning at the date of issuance of the Hydrographic Project Instructions (June 28, 2016) and ending on December 14, 2016 were consulted in conjunction with the chart comparison.
The following sections adhere to the Descriptive Report sounding rounding system as described in Section 5.1.2 of the HSSD. Specifically, features described below having “precision” depths are presented along with the sounding's TPU. Depth and TPU are rounded to the nearest centimeter by standard arithmetic rounding ("round half up").
The chart comparisons documented below will discuss general seafloor changes, shoaling and deepening trends, within the H12906 survey area. Significant new or updated charted features will be discussed in the appropriate DR sections. All new or charted features identified, updated or disproved within Survey H12906 were addressed and attributed in the S-57 Final Feature File. For more information on the methodology that was used to build the FFF see Section B.2.5 Feature Verification in the DAPR.
An overview of the areas of change between charted depths and H12906 surveyed soundings is shown in Figure 22. The figure displays a difference surface made by subtracting a 10-meter resolution depth surface generated from the H12906 MBES data from a 250-meter resolution depth surface interpolated from the charted ENC soundings within the project area. Regions of shoaling are represented by positive depth differences and regions of deepening are represented by negative depth differences. The greatest areas of change were deepening and shoaling trends associated with large migrating shoals in the eastern portion of the survey area. A detailed description of each chart comparison follows.A depth difference surface overlaid on RNC 11351 provides an overview of the areas of change between charted depths and H12906 surveyed soundings.H12906_Figure_22_Chart_Comp_Overview.jpg113496480000462014-032016-11-152016-10-29Data from Survey H12906 do not intersect RNC 11349.113516380000432012-032016-11-292016-10-29Surveyed depths overall were deeper than charted depths, particularly in the eastern portion of the survey area with surveyed depths being 0 to 9 feet (2.7 meters) deeper than charted depths. Figure 23 highlights a significant area of deepening in the northeastern portion of the survey area where surveyed depths were 5 to 9 feet (1.5 to 2.7 meters) deeper than the charted 12- to 13-foot soundings centered around 29-08-17.50 N, 91-38-14.70 W. Other locations of significant deepening in the southeastern portion of the survey area centered around 29-06-17.00 N, 91-39-31.50 W are highlighted in Figure 24 where surveyed depths were 6 to 8 feet (1.8 to 2.4 meters) deeper than the charted 13- to 15-foot depths. There was good agreement between the majority of surveyed and charted depths on the western half of the H12906 survey area with soundings differing by approximately 0 to 2 feet (0.6 meters).
The size of a charted shoal defined by an 18-foot contour has diminished significantly, with the 18-foot contour having migrated to the northwest by over 6 kilometers in some locations. That said multiple "finger like" shoals extend close to and beyond the charted 18-foot contour. Based on comparison to prior Survey H11288, the "finger like" shoals appear to have migrated southwest of their 2005 position, accounting for the deepening trend on the eastern half of the survey area. Figure 25 is an overview of the surveyed position of the 18-foot contour in comparison to the charted 18-foot contour location and the shoal as it appears in the H12906 1-meter coverage surface.
Two charted 18-foot depth areas centered on 29-04-57.90 N, 91-44-46.20 W and 29-04-24.90 N, 91-41-58.80 W were disproved with surveyed soundings measuring 2 to 4 feet (0.6 to 1.2 meters) deeper than charted.
The only significant shoaling was observed in the vicinity of 29-05-43.50 N, 91-40-54.80 W, where surveyed depths of 11 and 12 feet (3.3 to 3.6 meters) were developed over a shoal located between charted depths of 15 to 16 feet. The shoal was reported as a DtoN (see DR Section D.1.6 Dangers to Navigation) and a charted 16-foot sounding located at 29-05-57.63 N, 91-41-10.93 W on the 11351 RNC downloaded from the OCS website on August 26, 2016 was replaced with 11 and 12-foot charted depths per LNM 44/16 (Figure 26). This figure highlights areas where surveyed depths were significantly deeper than charted depths. The surveyed depths are colored by depth and shown in feet with NOAA rounding applied in comparison to RNC 11351 in the background.H12906_Figure_23_11351_Deep.jpgThis figure highlights areas where surveyed depths were significantly deeper than charted depths. The surveyed depths are colored by depth and shown in feet with NOAA rounding applied in comparison to RNC 11351 in the background.H12906_Figure_24_11351_Deep.jpgThe left image shows a representative set of soundings ≤ 18 feet from H12906 in comparison to the charted 18-foot contour and a shoal area colored in blue on RNC 11351. The image on the right displays the shoal area as it appears in the H12906 1-meter coverage surface colored by depth. H12906_Figure_25_18ft_Ctr_Shrink.jpgOn the left, a subset of RNC 11351 downloaded from OCS on August 26, 2016. The right image shows the same subset area of RNC 11351 downloaded from OCS on December 19, 2016 overlaid with surveyed soundings from H12906 colored by depth. The RNC was updated with H12906 11- to 12-foot depths developed over the new shoal.H12906_Figure_26_New_Shoal.jpg1134049458896792016-022016-11-292016-10-29Five charted depths from RNC 11340 not associated with charted features overlapped with the H12906 survey area. Overall surveyed depths were deeper than charted depths, with four of the charted depths being 0.2 to 0.5 fathoms (0.4 to 0.9 meters) shallower than surveyed depths. Surveyed soundings were significantly deeper than the charted 2-fathom depth positioned at 29-08-10.25N, 91-37-10.30 W, with surveyed soundings measuring 1.6 fathoms (2.9 meters) deeper than charted.
A charted shoal demarcated by a 3-fathom contour has shrunk in size, as discussed above regarding the 18-foot contour on RNC 11351 (Figure 27). Surveyed depths along the charted 3-fathom contour were 0.1 to 0.5 fathoms (0.2 to 0.9 meters) deeper than the charted 3-fathom contour.The image shows a representative set of soundings ≤ 3 fathoms from H12906 in comparison to the charted 3-fathom contour on RNC 11340.H12906_Figure_27_11340_3fm_ctr.jpgUS4LA15M80000232014-11-062016-10-24falseData from Survey H12906 do not intersect ENC US4LA15M.US4LA21M80000272015-03-252016-12-08falseRNC 11351 is the source for ENC US4LA21M; therefore, the positions and values of the majority of the soundings and contours included in ENC US4LA21M are identical to those charted on RNC 11351. With the exception of a few minor differences discussed below, the chart comparison notes entered under the RNC 11351 apply to US4LA21M.
There were a few discrepancies noted between RNC 11351 and ENC US4LA21M. The disproved 18-foot depth areas discussed in the RNC 11351 section above were not charted on ENC US4LA21M. In that same vicinity, there is a discrepancy between the position of the charted 18-foot contour on ENC US4LA21M in comparison to RNC 11351, with the ENC contour positioned up to 480 meters north of the charted contour in the vicinity of 29-04-45.20 N, 91-42-50.70 W (Figure 28). This image highlights the discrepancy between the charted 18-foot contour from ENC US4LA21M (in blue) and that charted on RNC 11351 shown in the background. Surveyed soundings in feet are overlaid on RNC 11351.H12906_Figure_28_ENC-RNC_ctr_diff.jpgUS3GC03M458596472015-02-202016-12-12falseRNC 11340 is the source for ENC US3GC03M; therefore, the positions and values of the soundings and contours included in ENC US3GC03M are identical to those charted on RNC 11340. All chart comparison notes entered under the RNC 11340 apply to US3GC03M.No Maritime Boundary Points were assigned for this survey.Ninety-three (93) features were assigned for investigation within the Composite Source File: thirteen (13) charted platforms (OFSPLF), six (6) charted wrecks (WRECKS), three (3) charted obstructions (OBSTRN) and seventy-one (71) BSSE well head obstructions (OBSTRN). The BSSE well head obstructions were not charted but were submitted to be verified or disproved by OSI; multiple BSSE well heads were duplicates or correlated with a second or third well head feature. Investigation requirements for the BSSE well heads were provided to OSI in an email dated April 22, 2016 which is submitted with the Correspondence in the DR Appendix II. The well head investigation requirements were as follows:
- If obstruction is found and considered a danger to navigation, develop the feature (7.3.3), designate the feature (7.4), submit it as a DtoN (1.5), and include it in the FFF (7.3).
- If obstruction is found and merits individual cartographic representation, develop the feature (7.3.3), designate it (7.4), and submit in FFF (7.3).
- If obstruction is found and does not merit cartographic representation, do not investigate it as a feature. Include it in the FFF with “descrp = delete” and “remrks=obstruction addressed as represented in the surface”.
- If the obstruction is not found, in cases where 100% SSS with concurrent multibeam is being used as the primary coverage technique, a 50m disproval search radius using a technique described in Section 7.3.4 is necessary.
All six (6) charted wrecks labeled as either position approximate (PA) or position doubtful (PD) were disproved with 200% SSS and partial MBES coverage at their charted positions within a search area centered on the CSF provided position and defined by an 80-meter radius. Two new wrecks were developed as item investigations and are the assumed true positions of the Wreck PA, the wreck of the barge PIONEER per the AWOIS database, with a CSF position of 29-06-54.00 N, 91-43-17.99 W and the Wreck PD, the wreck of the barge CARIBE per the AWOIS database, with a CSF position of 29-06-00.30 N, 91-41-59.04 W. The new wrecks were submitted as DtoNs (see Section D.1.6 Dangers to Navigation).
A Subm pile PA (OBSTRN) charted at 29-06-20.01 N, 91-45-29.41 W was disproved with 200% SSS and partial MBES coverage within a search area defined by an 80-meter radius.
An obstruction labeled as "(3 ft rep) PA" on RNC 11351 positioned at 29-05-08.54 N, 91-42-22.08 W was disproved with 200% SSS and partial MBES coverage within a search area defined by an 80-meter radius. The AWOIS database reports the obstruction as a collapsed platform with a depth of 3 feet. No evidence of a collapsed platform was found within the vicinity of the verified charted platform adjacent to the charted obstruction PA.
An obstruction charted on ENC US4LA21M at the position 29-06-47.36 N, 91-38-17.32 W was not charted on RNC 11351. The obstruction was disproved with 200% SSS and partial MBES coverage within a search area defined by a 50-meter radius. The obstruction was located on a charted pipeline approximately 150 meters east of a long segment of exposed pipeline that was reported as a DtoN.
Of the seventy-one (71) BSSE well head obstructions, sixty-nine (69) of them do not merit cartographic representation and it is recommended that they remain uncharted. For two of the BSSE well heads located at 29-08-18.74 N, 91-45-15.44 W and 29-07-09.39 N, 91-43-17.65 W, significant obstructions were developed with object detection MBES coverage within the 50 meters of the CSF provided well head positions. Within the H12906 FFF, the significant features were included as "new" obstructions and the BSSE well head obstructions located within 50-meters were attributed as "delete" such that the 16-foot and 12-foot obstructions would be charted at their true least depth positions of 29-08-18.82 N, 91-45-15.85 W and 29-07-10.42 N, 91-43-17.75 W. See DR Sections D.1.5 and D.1.6 for more information regarding the new obstructions.
Nine (9) of the BSEE well heads were coincident with verified charted platforms; however, no evidence of a well head aside from the verified platform was found within the disproval area centered on the CSF provided positions defined by a 50-meter search radius.
Two (2) of the BSEE well heads had exposed pipeline segments located within the disproval area, but no evidence of a well head obstruction.
Fifty-eight (58) of the well heads were disproved with 200% SSS coverage and partial or full MBES without any significant features located within 50 meters of the CSF provided well head positions.
For a more complete description of the well head investigations, refer to the H12906 FFF. The source date (SORDAT) and source indication (SORIND) attribute fields were blank for the BSSE well head features submitted in the CSF; therefore, the SORDAT and SORIND fields are blank for the disproved well heads attributed with a description (descrp) of "Delete" in the FFF.
See DR Section D.2.7 Platforms for information regarding the verification or disproval of the charted platforms.Three new obstruction features are included in the S-57 Final Feature File, but were not submitted as DtoNs. One significant obstruction is discussed below, but was not included in the FFF because it was located less then 80 meters (2mm at 1:40,000 scale) distant from a 16-foot wreck that was submitted as a DtoN and is included in the FFF. Per Section 7.4 Designated Soundings of the HSSD 2016: "When the distance between two features that would otherwise warrant individual designation is less than 2 mm at the scale of survey...then only the shoalest of those featues shall be designated and included in the FFF."
A bent, pipe-like feature with a least depth of 16 feet (4.91 m, ±0.23 TPU) was developed with object detection MBES coverage at 29-08-18.82 N, 91-45-15.85 W (Figure 29). The bent over pipe was positioned within 20 meters of an uncharted BSSE obstruction feature that was included in the CSF for investigation. The OSI proposed action in the FFF, is that a new obstruction be charted at the pipe's least depth position and the CSF provided BSSE well head position be deleted.
Two cylindrical, tank-like obstructions with a least depth of 17 feet (5.33 m, ±0.23 TPU) were developed with object detection MBES coverage at 29-04-54.94 N, 91-41-12.49 W (Figure 30). The tanks appear to be in a deteriorating state.
An obstruction that appears to be a collection of pipe-like debris with a least depth of 18-feet (5.47 m, ±0.23 TPU) was developed with object detection MBES coverage at 29-04-45.83 N, 91-41-40.22 W (Figure 31). It's possible that the obstruction is the remnants of the base of a ruined or removed platform.
An obstruction, a 4-foot (1.2 meter) tall post or pipe, with a least depth of 16-feet (4.94 m, ±0.23 TPU) was developed with object detection MBES coverage at 29-05-44.87 N, 91-42-46.53 W. The obstruction was located approximately 25 meters northeast of a large 16-foot wreck submitted as H12906 DtoN #1 (see below); therefore, a designated sounding was not selected on the obstruction and it was not included in the FFF as the wreck is the cartographic priority.A 16-foot obstruction is represented in CARIS HIPS Subset Editor 3D with the soundings colored by depth and depths and units in meters (left) and in the SIPS waterfall SSS imagery (right).H12906_Figure_29_16-ft_Obstn.jpgA 17-foot obstruction is represented in CARIS HIPS Subset Editor 3D with the soundings colored by depth and depths and units in meters (left) and in the SIPS waterfall SSS imagery (right).H12906_Figure_30_17-ft_Obstn.jpgAn 18-foot obstruction is represented in CARIS HIPS Subset Editor 3D with the soundings colored by depth and depths and units in meters (left) and in the SIPS waterfall SSS imagery (right).H12906_Figure_31_18-ft_Obstn.jpg6H12906_DtoN_1.0002016-09-07H12906_DtoN_2_Shoal.0002016-10-04H12906_DtoN_3_Wk.0002016-10-04H12906_DtoN_4_Pipelines.0002016-11-28H12906_DtoN_5_GasLeak.0002016-11-28H12906_DtoN_6_Obstn.0002016-11-28Six (6) Danger to Navigation (DtoN) S-57 files (.000) were submitted to the Atlantic Hydrographic Branch (AHB) for Survey H12906 to report two wrecks, a dangerous shoal, exposed pipelines, an obstruction, and a gas leak. The wrecks, the shoal and the obstruction have since been updated on all affected charts.
The DtoN #1 submission included a position for a new wreck, a barge measuring 64 meters by 10 meters, with a least depth of 16-feet (4.87 m, ±0.23 TPU) developed with object detection MBES coverage at 29-05-43.81 N, 91-42-47.73 W (Figure 32). It is believed that the new wreck is the true position of the CARIBE Wreck PD as discussed above in DR Section D.1.4 Charted Features. The wreck was submitted to the Nautical Data Branch (NDB) and Marine Chart Division (MCD) on September 7, 2016 and has since been updated on RNCs 11351 and 11340 and ENCs US4LA21M and US3GC03M. The Local Notice to Mariners (LNM) Edition 38 for District 8 (38/16) included chart updates to add the wreck at the following position: 29-05-43.80 N, 91-42-47.70 W.
A selection of representative soundings measuring 12 feet or less were submitted with DtoN #2 over a new shoal developed between the approximate coordinates of 29-05-26.17 N, 91-40-31.20 W and 29-06-24.40 N, 91-41-25.60 W. The shoal soundings were submitted to NDB and MCD on October 5, 2016 and two new depths of 11 and 12 feet have since replaced a 16-foot depth on RNC 11351 and ENC US4LA21M. The LNM Edition 44 for District 8 (44/16) included chart updates to add an 11-foot sounding at 29-05-43.60 N, 91-40-54.90 W and substitute a 12-foot sounding for a 15-foot sounding at 29-05-59.60 N, 91-41-09.60 W.
The H12906 DtoN #3 submission included two depths on a large wreck measuring 77 meters by 15 meters (Figure 33), which is believed to be the true position of the PIONEER Wreck PA that was previously charted approximately 250 meters SE of the surveyed wreck position. In the interest of safety, the survey vessel did not collect data over the top of the wreck as the SSS record indicated possible high points shallower than 12 feet that could pose a danger to the vessel; therefore, object detection MBES coverage was not obtained over the top of the entire wreck. The least depth obtained with the MBES system was 13 feet (4.09 m, ±0.23 TPU) at 29-07-01.74 N, 91-43-24.11 W and the least depth derived from the SSS imagery was 12-feet (3.67 m) at 29-07-00.48 N, 91-43-23.65 W. Both the MBES and SSS derived depths were reported in the DtoN file. The 12-foot depth on the wreck was submitted to NDB and MCD on October 5, 2016 and the Wreck PA symbol has since been replaced with the surveyed wreck position on RNC 11351 and ENCs US4LA21M and US3GC03M. The LNM Edition 44 for District 8 (44/16) included chart updates to add a 12-foot wreck at 29-07-00.50 N, 91-43-23.60 W and to delete a dangerous wreck PA at 29-06-54.07 N, 91-43-17.99 W.
Included in H12906_DtoN_4.000 were seventeen (17) possible exposed pipeline features that were submitted as DtoNs following guidance found in Section 1.5 of the 2016 HSSD which states that "Dangers to Navigation shall be recommended for," among other things, "Exposed or leaking submerged pipelines". The exposed pipeline segments were not submitted to NDB and MCD, but they were submitted to NOAA's Central Gulf Coast Navigation Manager Tim Osbourne on November 29, 2016 such that the information could be relayed to the proper authorities.
DtoN #5 reported a gas leak developed at the northern terminus of a charted pipeline attributed as a "supply pipe" with a product of "Gas" and with a status of "permanent" in ENC US4LA21M. The leak was located at 29-06-15.31 N, 91-42-26.27 W and was observed on mainscheme and investigation MBES lines and in the water column of multiple SSS lines (Figure 34). A disproved BSSE well head obstruction was located within 30 meters of the gas leak. The gas leak was not submitted to NDB or MCD, but was submitted to the Gulf Coast Manager, Tim Osbourne, on November 29, 2016 such that it could be relayed to the proper authorities. Sounding returns on the gas leak plume were rejected from the MBES data.
An obstruction that appears to be an uncharted well head was submitted as H12906_DtoN_6_Obstn.000 (Figure 35). The obstruction with a least depth of 13-feet (3.85 m, ±0.23 TPU) developed at 29-07-10.41 N, 91-43-17.75 W was located within 30 meters of an uncharted BSSE obstruction feature that was included in the CSF for investigation. The OSI proposed action in the FFF, is that a new obstruction be charted at the obstruction's least depth position and the CSF provided BSSE well head position be deleted. The obstruction was submitted to NDB and MCD on November 29, 2016 and has since been charted on RNCs 11351 and 11340 and ENCs US4LA21M and US3GC03M. The LNM Edition 50 for District 8 (50/16) included chart updates to add a 12-foot obstruction (11351) and a 2-fathom obstruction (11340) at 29-07-10.40 N, 91-43-17.70 W.
All DtoNs except the gas leak are included in the H12906 S-57 FFF, H12906.FFF.000. The value of sounding (VALSOU) depths for the obstructions, soundings, and wrecks submitted as DtoNs have been updated in the FFF following the application of final tides to the MBES data set. Danger to Navigation Reports as well as correspondence regarding the DtoN submissions are included in Appendix II of this report.The 16-foot wreck submitted as DtoN #1 is shown in CARIS Subset Editor 3D window with soundings colored by depth (left) and in SSS imagery from CARIS Side Scan Editor (right).H12906_Figure_32_DtoN_1_Wk.jpgThe 12-foot wreck submitted as DtoN #3 is shown in SSS imagery from CARIS Side Scan Editor (left) and in CARIS Subset Editor 3D window with soundings colored by depth (right).H12906_Figure_33_DtoN_3_Wk.jpgThe gas leak as it presented in the MBES data in CARIS Subset Editor 3D window with soundings colored by line (top) and as it presented in the raw, un-slant range corrected SSS imagery (bottom).H12906_Figure_34_DtoN_5_Leak.jpgThe well head obstruction shown in CARIS Subset Editor 2D window with soundings colored by depth. Depths and distances are in meters.H12906_Figure_35_DtoN_6_Obstn.jpg A caution area (CTNARE) note encompasses the entirety of the intersection of the H12906 survey area and RNC 11340 and ENC US3GC03M stating the following: "Gas and Oil Well Structures. Platforms, gas and oil well structures, some of which are submerged and capped, and submarine pipelines and cables are charted."
Similarly, a Caution Note for RNC 11351 and ENC US4LA21M states: "Additional uncharted submarine pipelines and submarine cables may exist within the area of this chart. Not all submarine pipelines and sub-marine cables are required to be buried, and those that were originally buried may have become exposed. Mariners should use extreme caution when operating vessels in depths of water comparable to their draft in areas where pipelines and cables may exist, and when anchoring, dragging, or trawling. Covered wells may be marked by lighted or unlighted buoys." The caution note was included in the text files referenced in the TXTDSC (textual description) fields of the PIPSOL (pipeline) and M_NPUB (nautical publication information) features.
The Caution Notes are warranted given the abundance of charted platforms, pipelines and possible well heads within the project area. Seventeen (17) exposed pipeline segments were located within H12906. 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.Five (5) bottom samples were acquired to determine bottom characteristics. Bottom samples were assigned in the S-57 Project Reference File (PRF) provided with the Hydrographic Survey Project Instructions. There were no deviations from the assigned bottom sampling plan. A position and description of each sample are provided as attributed SBDARE objects in the FFF. Digital images with identification reference numbers are submitted with the survey data and referenced in the NOAA extended attributes ‘images’ field.No shoreline exists within this survey.Prior survey data exist for this survey area. However, with the exception of the assigned junction surveys, prior data were not investigated.No Aids to navigation (ATONs) exist for this survey.Overhead features do not exist for this survey.Numerous charted pipelines are located within Survey H12906. Pipes colored magenta represent supply pipelines for oil, gas, chemicals, or water, according to Chart No. 1: Nautical Chart Symbols, Abbreviations and Terms downloaded from the Office of Coast Survey (OCS) website. None of the charted pipelines have a buried depth value (BURDEP). That being said the majority of the charted pipelines were not visible in the SSS or MBES data.
Linear contacts presumed to be exposed sections of charted pipelines were selected in the side scan records and were confirmed with MBES coverage. As mentioned in the DtoN section of this report, seventeen (17) exposed pipeline sections were presented with the DtoN #4 submission for this survey. Some of the exposed pipelines had pronounced arches and some were situated in trenches; seafloor scour was visible for all exposed pipes. Several of the exposed pipeline segments appear to have protective articulated concrete mats covering them, or attempting to cover them, as many of the mats were partially covering the pipes or displaced alongside the pipes as was the case in a 197-meter long segment of pipeline centered on 29-06-47.90 N, 91-39-54.95 W (Figure 36). The exposed pipeline sections' images and relevant attribution are included in the H12906 S-57 Final Feature File.
Review of information contained in a shape file (.SHP) downloaded from the Bureau of Ocean Energy Management (BOEM) on April 25, 2016 suggests that there may be as many as five uncharted pipe segments within Survey H12906. The BOEM pipeline shape file that intersects with the OPR-K354-KR-16 project area was reprojected to UTM Zone 15N, NAD83 and saved as a .DXF file and converted to a .HOB file. In CARIS Notebook, the BOEM pipeline HOB file was then visually compared to the charted pipelines within the project area to identify any potentially uncharted BOEM pipelines. While the majority of the pipelines in the BOEM file corresponded with charted pipelines, up to five BOEM reported pipeline segments are not charted. Though there was no visible evidence in the MBES or SSS data of the existence of the uncharted pipelines, an overview of the uncharted BOEM-defined pipelines that intersect Survey H112906 is provided in Figure 37. The uncharted pipelines in the southern reach of Survey H12906 appear to terminate at charted platforms. The single uncharted pipeline in the northeastern corner of the survey extends between two disproved BSSE wellheads.
The shape file, “ppl_arcs.shp” and re-projected .DXF file, “Pipelines_UTM_15N_NAD83_Meters.dxf” are included with the digital deliverables along with the RNC/ENC charts considered in the chart comparison. BOEM pipeline data were obtained at the following web address: http://www.data.boem.gov/homepg/data_center/mapping/geographic_mapping.asp.A portion of an exposed pipeline is displayed in CARIS Subset Editor 3D window with soundings colored by depth. Protective concrete mats are situated on top of the pipeline in some areas and have become displaced in others.H12906_Figure_36_Exposed_Pipe_Displaced_Mat.jpgBOEM-defined pipelines that are not charted are highlighted in blue in reference to RNCs 11351 with the H12906 survey shown in the background.H12906_Figure_37_Uncharted_BOEM_Pipes.jpgNo ferry routes or terminals are located within the surveyThirteen (13) "assigned" platforms were included for investigation in the CSF. Six (6) of the charted platforms were disproved visually at the surface and with 200% SSS coverage and partial MBES coverage within the disproval area defined by a 50-meter radius centered on the CSF provided platform position. The disproved platforms positions are as follows:
29-08-20.82 N, 91-45-15.42 W, TEXACO 197-1
29-08-13.81 N, 91-37-44.41 W, CHEVRON-EI-74-5
29-08-12.50 N, 91-43-47.09 W, WOG-EI-72-4
29-05-34.71 N, 91-45-32.56 W, Name Unknown
29-05-12.41 N, 91-41-50.33 W, Name Unknown
29-05-00.96 N, 91-42-17.81 W, Name Unknown
Seven (7) of the platforms were verified and given that the surveyed positions of all the verified platforms were located less than 80 meters distant from the charted positions, the platforms were attributed with a "Retain" value (80 m is equivalent to 2 mm at a scale of 1:40,000). Images were included in the FFF for all verified platforms. The verified platforms positions are as follows:
29-07-35.24 N, 91-43-07.96 W, Fieldwood-103-60
29-05-59.70 N, 91-42-42.69 W, MOI-EI-89-21
29-05-28.81 N, 91-42-33.60 W, MOI-EI-88-A
29-05-15.70 N, 91-41-55.89 W, MOI-EI-95-F
29-05-05.50 N, 91-42-18.98 W, MOI-EI-95-5
29-04-50.40 N, 91-42-08.80 W, SH-EI-95-18
29-04-30.00 N, 91-42-09.89 W, Name Unknown
See the FFF for additional information regarding the disproved and verified charted platforms.Many small circular depressions were visible in the MBES data throughout the survey area and were clustered in the scour areas around platforms, obstructions and the exposed pipeline features (Figure 38). The holes are randomly spaced, less than 50 centimeters deep, and do not appear to be associated with industrial activity. They are more likely related to a natural phenomenon, possibly ground fish-created habitat, as some species in the Gulf of Mexico (i.e. red grouper) are known to excavate depressions in flat, sandy bottoms (See Wall, Carrie C., et al. "Spatial and temporal variability of red grouper holes within Steamboat Lumps Marine Reserve, Gulf of Mexico." Marine Ecology Progress Series (Impact Factor: 2.62). 2011. 431:243-254.)
A unique change in sediment reflectivity was visible in the SSS mosaic over the large migrating bedforms.Possible ground fish habitat holes as they appeared in the MBES data displayed in CARIS Subset Editor 3D window with the soundings colored by depth.H12906_Figure_38_Fish_Holes.jpgNo construction or dredging existed within the survey limits at the time of data acquisition.Marine Mammal ObservationsPer direction in Section 1.4 and 1.4.1 of the HSSD all personnel aboard the survey vessel used during Project OPR-K354-KR-16 were "trained" as Marine Mammal Observers prior to commencement of the survey. Training consisted of each surveyor and vessel crew member watching the US Navy video referenced in the HSSD.
As noted multiple times in the survey acquisition log, large, mobile water column sonar targets (assumed to be dolphins) were ensonified by either the MBES or the SSS. The dolphin-assumption is based on both the size and behavior of the sonar targets. Often times these observations did not coincide with a visual (above water) sighting. Visual observations, when noted, were recorded on NOAA/NMFS,AFSC/NMML Form 11US (POP) which is included as Appendix K of the HSSD.
As compared to OSI's past years conducting survey work in the Gulf of Mexico, dolphin sightings during data collection for Project OPR-K354-KR-16 were relatively sparse. This is attributed to the area of operation for the 2016 surveys. During the course of Project OPR-K354-KR-16 only 13 individual visual dolphin sightings occurred.
Completed digital 11US (POP) forms were compiled and transmitted along with the Project's digital marine mammal training record to the OCS Environmental Compliance Coordinator, Jay Nunenkamp, with a CC to the Project's COR, Paul Turner. These records are also included in Descriptive Report Appendix II.Coast Pilot Review A "Coast Pilot Field Report" as described in Section 8.1.3 in the HSSD was not provided by HSD Operations nor was a Coast Pilot Field Report included or specifically assigned with the Hydrographic Survey Project Instructions dated July 26, 2016. Therefore, OSI was not able to “respond to each question posed in the Coast Pilot Field Report” as mentioned in Section 8.1.3 of the HSSD. In lieu of targeted responses to an assigned Coast Pilot Field Report, OSI conducted a general review of relevant Coast Pilot excerpts. Specifically, pertinent paragraphs from the following Coast Pilot section were considered:
Coast Pilot 5 - 44th Edition, 2016 updated through 13-November-2016, Mississippi River to Sabine Pass.
Within the Coast Pilot Edition mentioned above there are no specific, detailed, relevant entries concerning the assigned H12906 survey area. Rather, only entries of a general nature are mentioned and are not refutable based on the observations of the OSI field team. Regarding “areas frequently transited” (as mentioned in the HSSD Section 8.1.3), Coast Pilot entries are somewhat more relevant. However, there are only a few Coast Pilot entries that OSI's general review attempts to address as most entries were not relevant to the "areas frequently transited by the survey vessel".
OSI's Coast Pilot Review is included in Descriptive Report Appendix II. Correspondence between OSI and the Project COR confirming OSI's understanding of the Coast Pilot reporting requirement is included in the Correspondence directory of the Descriptive Report Appendix II.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 Manual, 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.George G. ReynoldsChief of Party2017-01-23Data Acquisition and Processing Report2017-01-23Horizontal and Vertical Control Report2017-01-23