Amendment 0001_USACE_LakeMontaukHarbor_MOD1_LetterReport_20230612_1200 e4.pdf

www.e4sciences.com 55 Post Road, Suite 200 Westport, Connecticut 06880 Daniel A. Rosales Roche, Ph.D. Mobile: 203.764.0526 Managing Scientist Postal: P.O. Box 178

Newtown, CT 06470-0178

Prepared for:

Kurt Schollmeyer, P.E.

60 Broad Street, 24th floor, Suite 2422 New York, New York

m. (845) 242.1516

June 12, 2023

Lake Montauk Harbor – Jetty Stability Evaluation – MOD1– Dredging Obstructions

Mr. Schollmeyer, The following letter report summarizes the scope, methodology, and results of a modification to the geophysical investigation relating to jetty stability evaluation for the Lake Montauk Harbor Navigation Improvement Project.

Summary

The United States Army Corps of Engineers New York District (USACE-NAN) is planning to make the following improvements to the Lake Montauk Harbor Channel. The objectives are:

1. Deepen the existing navigation channel from an authorized depth of -12ft Mean Lower Low Water (MLLW) to -17ft MLLW, plus 2 feet of over dredge to -19ft MLLW.

2. Create a 100ft wide sediment deposition basin immediately east of the channel; and

3. Place dredge spoils on the shoreline west of the inlet.

The objectives listed above result as recommendations from a dredge deepening feasibility study performed by the USACE. Items 1 and 2 above will be referred to as the dredging template. In this report an alternate channel-only template, comprising a 150ft channel with 1v:3h slopes to the east and west, will be characterized by the material expected to be encountered when dredging.

Located in East Hampton, Suffolk County, NY, the Lake Montauk Harbor Navigation Improvement project includes Lake Montauk Harbor, the jetty-protected inlet connecting Lake Montauk Harbor to Block Island Sound, and the Montauk shoreline east and west of the Lake Montauk Harbor Inlet Channel.

Preliminary interpretation of seismic data during the jetty investigation identified a subsurface layer of cobble and boulder rich material that exists throughout the dredge template. This hard layer onlaps the stone cover layer above and adjacent to the jetty-stone of the eastern jetty. This letter report focuses on the interpretation, characteristics, and volume of this subsurface layer within the dredge template. We refer to this subsurface horizon interchangeably as the hard surface (top-of-hard-layer) and when discussing its properties as the hard layer.

The hard layer likely consists of cobbles, boulders, sands, and gravels. This layer will likely impede hydraulic dredging methods and will complicate the separation of dredge spoils into material that is suitable for beach placement.

e4sciences was not tasked to collect SPT borings or cores to sample the material within the Area of Investigation (AOI); however, we expect the material below the hard layer to be a mixture of sands, gravels, and likely boulders.

For this mod, e4 performed a detailed interpretation of the seismic data to map the extent and thickness of the hard layer. This hard layer varies in thickness between one and three feet. The thickest portions of the hard layer are in the planned deposition basin and between STA 6+00 and STA 8+00. Within the planned deposition basin, this hard layer onlaps the stone cover layer.

In the Lake Montauk Harbor inlet between STA 0+00 and STA 15+00, e4 estimates the total volume of expected dredge material within the dredge template (including 2ft over dredge) and the 100ft wide deposition basin to be 91,901 cubic yards. e4 estimates 52,186 cubic yards of material exist above the hard surface and 39,715 cubic yards of material below the hard surface. Of the nearly 40,000 cubic yards of material below the hard surface, 10,848 cubic yards are within the dredge template of the western slope and inlet channel, and 28,867 cubic yards are within the dredge template of the deposition basin and its eastern slope. It should be noted that in the areas where the top-of-jetty and stone cover encroaches into the deposition basin dredge template, the volume of material below the hard surface reported may include jetty stone and cover stone.

The dredging template recommended in the feasibility studies will encounter a hard layer in the channel and deposition basin, as well as stone cover in the deposition basin’s eastern slope. An alternate channel-only template that does not include a deposition basin will reduce the volume of hard material that needs to be removed.

The alternate channel-only template includes a 150ft wide navigation channel with a 1v:3h slopes east and west of the channel toe. Between STA 0+00 and STA 15+00, the total volume of material to be dredged for this alternate channel-only template (and 2ft over dredge) is 41,253 cubic yards. e4 estimates 29,332 cubic yards above the hard surface and 11,921 cubic yards of material below the hard surface exist within the channel-only template.

In addition to the hard surface material there are an estimated 1,910 cubic yards of boulders above the hard surface, including boulders resting on the inlet floor. This estimate is based on the interpretation and analysis of side-scan and multibeam data of the material on the inlet floor and from interpretation of reflectors in seismic data.

For the dredge template (including the deposition basin) e4 estimated that between STA 0+00 and 15+00 there are 41,625 cubic yards of hard material. In this dredge template there are 26,408 cubic yards of material above the hard surface.

For the channel-only template e4 estimates that there are 13,831 cubic yards of hard material. The hard material includes the volume below the hard surface and boulders above the hard surface and on the inlet floor.

Methodology

Project Geodesy

The locations of all data from the geophysical investigation were referenced to the North American Datum of 1983 (NAD 83) New York Long Island State Plane. The units were US Survey ft. All elevations were referenced to MLLW, which is 1.52ft below North American Vertical Datum of 1988 (NAVD88).

Multibeam Bathymetry e4sciences used an Edgetech 6205 to map the bathymetric elevations of the eastern jetty and inlet floor.

The multibeam echo sounder (MBES) was paired with an RTK GNSS receiver with dual GPS antennae and an IMU. Data was collected in Hypack. e4sciences conducted the geophysical surveys from the survey vessel Half Moon.

Four measurements are critical to establish elevation. These are: (1) velocity of sound in water, (2) travel time of acoustic wave from source to first break, (3) lever arm offsets and sensor calibration, and (4) water level (tide stage). e4sciences used a castaway CTD to measure the velocity of sound in water. Lever arm offsets were measured during the installation of the multibeam echo sounder (MBES), the inertial motion unit (IMU), and the GPS antennae. e4sciences recorded local water level measurements using Real Time Kinetic (RTK) Virtual Reference Station (VRS) GNSS aided GPS. e4sciences created water level corrections for the waterline elevations in the AOI based on the RTK water levels and compared these to the water level data recorded at the survey benchmark.

Multibeam data processing was completed using Chesapeake’s Sonar Wiz software. Data was processed in two basic steps. During the first step, the operator performed QC checks of the position, elevation, and vessel sensor attitude data from the GPS and IMU collected by Edgetech’s Discover software. Sound velocity profiles and water level correction profiles were also generated and applied to the multibeam data at this stage. Once all peripheral data were acceptable, the workflow progressed to the combination of position data with sensor data. During the second step, sonar data was integrated with the multibeam sensor data. Iterative patch testing was performed to ensure that the yaw, pitch, and roll values assigned to the sensor were as accurate as possible and that motion artifacts were minimized. Cursory analysis of the multibeam data was focused on identifying spurious data points (i.e., fish, debris, or aquatic vegetation) both manually and through statistical analysis of the dataset. Once the data were cleaned and all artifacts were removed the operator exported the data as average bathymetry XYZ files in 1ft x 1ft, 3ft x 3ft, and 10ft x 10ft bin sizes.

The resulting XYZ ASCII text files output from Sonar Wiz software were used to create 3D contours as .dxf and surface maps that are presented in this report as figures. e4sciences produced 1ft contours of the average elevation per 1ft x1ft bin referenced to North American Datum of 1983 (NAD 83) New York Long Island State Plane. The units are US Survey ft. All elevations are referenced to MLLW, which is 1.52ft below North American Vertical Datum of 1988 (NAVD88).

To create surface maps or contours of the XYZ point files, e4sciences used Golden Software’s Surfer to grid, triangulate, and contour the data. Surface maps were exported as geotiffs.

Reflectivity Mapping e4sciences used an Edgetech 6205 at 540kHz to produce side-scan orthosonographs of the Lake Montauk Harbor inlet.

The side-scan sonar transmits ultrasonic waves obliquely into the water and measures the amplitude of the backscatter from the inlet bottom as a function of range. The reflectivity is a function of the inlet bottom roughness and the sediment acoustic properties. These reflectivity images produce a high-definition image of the inlet bottom to delineate debris, structures, and sediments on the inlet bottom.

e4sciences surveyed the AOI with lines parallel to the inlet to produce orthosonographs insonified from the west and east. In addition, e4 surveyed the northern tip of the eastern jetty to produce orthosonographs insonified from the north. Line spacing was designed to allow sufficient overlap in coverage so that e4sciences could produce seamless orthosonographs that utilize the ideal ranges of the reflectivity data.

Portions of the data where the signal attenuates beyond e4sciences standards were removed.

Horizontal accuracy of the side-scan measurements is approximately +/- 6ft.

Side-scan images produced 100% coverage with nearly 200% overlap of the inlet bottom in the AOI. The two independent orthosonographs insonified from two directions suffice to constitute nearly 200% coverage. Orthosonographs are seamless aerial-photograph-like images that are insonified from one direction only. The resolution of e4sciences orthosonographs is approximately 0.3ft per pixel.

Reflection Seismology e4sciences employed an Edgetech SB-512i and implemented multiple frequencies to map the subsurface in the AOI. e4sciences selected the 1-10kHz pulse to image and interpret recent sediment thickness in the shallow subsurface and shallow obstructions. e4sciences used the 0.5-6kHz pulse to investigate the surfaces underneath any potential loose stone in the AOI.

e4sciences acquired a total of 13 nautical miles of seismic data comprising 113 seismic profiles in the AOI.

e4sciences based the survey plan on a site-specific survey pattern to fit the inlet floor geomorphology and safely navigate in shallow water. Note that e4sciences acquired data at different frequencies on different lines.

Horizontal accuracy of the reflection seismic measurements is approximately +/- 6ft. Under ideal conditions, vertical accuracy is approximately +/- 1ft per 10ft of penetration.

e4sciences processed the navigation data to produce a navigation point for every seismic trace. e4sciences filtered the seismic data using frequency bandpass. The data were processed by splitting the real and imaginary components utilizing an automatic gain control operator as well as a derivative operator. The real component seismic data were enhanced to map the diffractions caused by hard subsurface layers. e4 converted the seismic profiles to depth using a constant velocity model that used water velocities measured on site with a sound velocity probe during the seismic survey. The seismic data were interpreted in the Kingdom interpretation system. e4sciences used multibeam bathymetry data to adjust the depth of seismic profiles to the inlet floor elevation.

Interpreting processed data collected with the single channel zero offset chirp sub-bottom profiler (SB- 512i) at multiple frequencies allowed e4 to delineate the top of jetty-stone and to identify a layer of unconsolidated (loose) stone, gravel, sands, and silts that overlies the top of the east jetty, and a hard layer of material in the channel and deposition basin. e4sciences’ processing techniques were critical to achieve the results presented herein.

Data integration, interpretation, and mapping

After processing each single-tool measurement, e4sciences integrated all the data to 1) map the elevation of the hard surface, 2) map the location and estimate the size of boulders on the inlet floor, and 3) determine the volume of material expected to be encountered within two different dredge templates considered for the project.

Seismic data was interpreted for the elevation, and in some locations the thickness, of the hard surface and to identify any subsurface boulders in the material above the hard surface.

Boulders on the inlet floor inside the AOI were interpreted and outlined using bathymetry and side-scan orthosonographs. The location and elevation of the features and targets identified in the target map are based on the bathymetry data.

Results

A previous report documents the results of an investigation focused on the eastern jetty protecting the Lake Montauk Inlet for which e4sciences collected, post-processed, and analyzed multibeam bathymetry, side-scan sonar, three-dimensional sonar, and reflection seismic measurements. e4 provided an integrated point cloud of east jetty geometry from bathymetry, seismic interpretation, and drone photogrammetry (collected by Baird) and created top-of-groin cross sections across the jetty every 50ft from STA 0+00 to STA 14+50.

e4sciences' efforts for this letter report and the task order modification focused on 1) interpretating all the seismic data collected to map and quantify the presence of boulders in the sub-surface, and 2) mapping the subsurface hard. This letter report details the interpretation, characteristics, and volume of this subsurface layer within the dredge template. We refer to this subsurface horizon interchangeably as the hard surface (top-of-hard-layer) and when discussing its properties as the hard layer.

During maintenance dredging in 2018 the dredging contractor (H&L Contracting, LLC) encountered numerous large rocks and/or boulders that prevented their cutterhead dredge from achieving the specified contract depth of -14ft (undefined vertical datum) plus 2ft over depth. The contractor communicated that the previous authorized depth of -12ft was achievable but the presence of the rocks/boulders prevented them from achieving over depth throughout much of the channel.

Geological description

Geomorphology

The Lake Montauk inlet channel is a dynamic system. There are areas of net erosion and areas of net accumulation of sediment. Sandwaves of varying scales dominate the inlet floor throughout most of the navigation channel. There is net erosion northwest of the pinch-point at approximately STA 7+00 of the navigation channel that is exposing boulders on the inlet floor. South of this pinch point, active sand layers dominate the inlet floor morphology. In areas of the inlet that are shallower than -12ft MLLW, predominantly north and east of the pinch point at of STA 7+00 e4 interprets net accumulation of material.

Figure 1 plots elevations of the inlet floor derived from multibeam bathymetry with a color bar designed for the specified dredging limits.

In the area of net erosion northwest and west of the pinch point at STA 7+00 boulders are exposed on the inlet floor. The highest density of boulders on the floor of the inlet occurs in water depths ranging from - 17ft MLLW to deeper than -19ft MLLW. Distribution of boulders is interpreted to be influenced by elevation and slope. This is consistent with scour and previous dredging activity preferentially removing sand and leaving boulders in place.

In the area of net accumulation northeast of the pinch point at STA 7+00 a smooth surface of predominantly sand with trace gravel is interpreted from side-scan orthosonographs and historical vibrocore data. e4 interpreted a small relatively sparse cluster of smaller boulders just north of STA 7+00.

Sandwaves of varying amplitude and wavelength are present south and southeast of STA 7+00. Sand is actively moving through this section of the inlet. A set of smaller amplitude and smaller wavelength sandwaves are present on the north and western slope of the bathymetric high on the east side of the channel.

Current is the main force that determines the presence of scour, deposition, and the amplitude and wavelengths of the sandwaves present in the channel.

Figure 2 is a map of interpreted geomorphological features and boulders plotted on a multibeam bathymetry surface map.

Figure 3 is a map of interpreted geomorphological features boulders plotted on a side-scan orthosonograph.

Table 1 summarizes the targets associated with the geomorphological features and boulders interpreted from the multibeam bathymetry maps and side-scan sonar data. Figure 4 is the target map.

Appendix I shows the list of targets above the hard surface. Figure 5 plots these targets and compares them with the 2018 H&L Contracting obstructions.

Table 1. List of targets in and adjacent to the channel.

Ta rg et n um be r

Target Ae ria l/v is ua l

Ba th ym et ry

Si de

-s ca n

Se is m ic

Description Po in t n um be r

Corner Easting

Corner Northing a

Le ng th b Le ng th

Y=yes NYSP LI USft NYSP LI

USft ft ft

101 Western jetty Y Y Y Y western limit of investigation 101a 1,552,381.8 339,119.3 1077 108 101b 1,552,487.3 339,143.7 n.a. n.a.

101c 1,552,705.8 338,078.4 n.a. n.a.

101d 1,552,613.7 338,067.7 n.a. n.a.

102 Scour and boulders Y Y Y Area of net scour and exposed boulders 102a 1,552,428.7 339,326.2 298 136

102b 1,552,679.4 339,486.8 n.a. n.a.

102c 1,552,751.4 339,371.5 n.a. n.a.

102d 1,552,491.8 339,207.9 n.a. n.a.

103 Scour and boulders Y Y Y Area of net scour and exposed boulders 103a 1,552,449.9 339,179.1 581 147

103b 1,552,593.6 339,212.2 n.a. n.a.

103c 1,552,706.7 338,691.3 n.a. n.a.

103d 1,552,673.0 338,677.4 n.a. n.a.

103e 1,552,681.1 338,635.6 n.a. n.a.

103f 1,552,594.1 338,615.9 n.a. n.a.

104 Active sedimentation Y Y Y Area of accumulation and active sedimentation with small sand bedforms

104a 1,552,557.1 339,244.3 368 238

104b 1,552,747.5 339,377.2 n.a. n.a.

104c 1,552,831.8 339,254.9 n.a. n.a.

104d 1,552,674.7 339,164.6 n.a. n.a.

104e 1,552,737.0 338,912.3 n.a. n.a.

104f 1,552,651.5 338,889.2 n.a. n.a.

105 Slope with boulders Y Y boulders exposed on top and at base of slope 105a 1,552,580.8 338,749.3 234 87

105b 1,552,665.7 338,769.2 n.a. n.a.

105c 1,552,727.6 338,539.6 n.a. n.a.

105d 1,552,632.2 338,521.2 n.a. n.a.

106 Slope with boulders Y Y boulders exposed on top and at base of slope 106a 1,552,648.4 338,523.1 364 54

106b 1,552,701.6 338,534.6 n.a. n.a.

106c 1,552,789.0 338,182.0 n.a. n.a.

106d 1,552,736.1 338,169.5 n.a. n.a.

107 Channel constriction Y Y Y sand deposited across channel. North of this point scour is extensive. South of this point is active sedimentation and accumulation.

107a 1,552,554.9 338,709.7 298 149

107b 1,552,843.2 338,784.4 n.a. n.a.

107c 1,552,881.3 338,639.9 n.a. n.a.

107d 1,552,584.1 338,561.3 n.a. n.a.

108 Sand with bedforms Y Y Y Area of accumulation and active sedimentation with large and small sand bedforms

108a 1,552,673.0 338,677.4 884 178

108b 1,552,852.3 338,724.2 n.a. n.a.

108c 1,553,057.3 337,861.0 n.a. n.a.

108d 1,552,874.5 337,816.9 n.a. n.a.

109 Elongate object Y Y possible cable or piling approximately

0.8 feet diameter 109a 1,552,723.3 338,406.7 18 7

109b 1,552,730.2 338,407.9 n.a. n.a.

109c 1,552,734.3 338,390.3 n.a. n.a.

109d 1,552,727.3 338,389.0 n.a. n.a.

110 Elongate object Y Y possible horizontal tree trunk or piling approximately 1.5feet diameter 110a 1,552,709.0 338,395.6 31 14

110b 1,552,722.5 338,397.2 n.a. n.a.

110c 1,552,726.7 338,366.6 n.a. n.a.

110d 1,552,713.2 338,365.3 n.a. n.a.

111 Elongate object Y Y Y Partially buried elongate object, Possible piling or cable

111a 1,552,828.5 338,078.1 48 13

111b 1,552,841.1 338,082.4 n.a. n.a.

111c 1,552,855.8 338,039.0 n.a. n.a.

111d 1,552,843.7 338,032.9 n.a. n.a.

112 Elongate feature Y Y Y Partially buried elongate object, Possible piling or cable 112a 1,552,919.2 337,968.1 40 13

112b 1,552,930.6 337,975.1 n.a. n.a.

112c 1,552,950.4 337,943.8 n.a. n.a.

112d 1,552,940.4 337,934.7 n.a. n.a.

113 Elongate feature Y Y Y Elongate ridge or object. 113a 1,552,991.5 337,979.4 35 17

113b 1,553,007.2 337,973.2 n.a. n.a.

113c 1,552,996.5 337,939.5 n.a. n.a.

113d 1,552,978.7 337,946.5 n.a. n.a.

114 Sand ridge Y Y Y Apparent sand ridge extending across channel 114a 1,552,832.5 337,882.3 158 31

114b 1,552,851.5 337,906.5 n.a. n.a.

114c 1,552,983.4 337,819.5 n.a. n.a.

114d 1,552,964.5 337,795.3 n.a. n.a.

115 Vertical piling Y Y Y Vertical piling extending above water 115a 1,552,762.6 337,931.0 8 7 115b 1,552,770.5 337,931.0 n.a. n.a.

115c 1,552,770.5 337,923.7 n.a. n.a.

115d 1,552,762.6 337,923.7 n.a. n.a.

116 Pier of pilings Y Y Y Pier of pilings 116a 1,552,673.3 337,953.8 71 65 116b 1,552,734.0 337,975.6 n.a. n.a.

116c 1,552,758.3 337,908.5 n.a. n.a.

116d 1,552,697.5 337,886.7 n.a. n.a.

117 Pier on pilings Y Y Y Pier on pilings 117a 1,552,647.8 338,048.5 89 44 117b 1,552,731.9 338,077.1 n.a. n.a.

117c 1,552,748.2 338,035.9 n.a. n.a.

117d 1,552,664.1 338,007.3 n.a. n.a.

Figure 1. Bathymetry surface map.

Figure 2. Map of interpreted geomorphological features and boulders plotted on a multibeam bathymetry surface map.

Figure 3. Map of interpreted geomorphological features and boulders plotted on a side-scan map.

Figure 4. Target Map.

Figure 5. Targets above the hard surface layer as they compare with the 2018 H&L Contracting obstructions.

Hard material

Interpretation of multibeam bathymetry, side-scan sonar, and sub-bottom seismic reflection data indicates the presence of a hard layer that consists of boulders, cobbles, and gravels. This layer will likely impede hydraulic dredging methods. e4sciences was not tasked to collect SPT borings or cores to sample the material within the Area of Investigation (AOI); however, we expect the material below the hard layer to be a mixture of sand, gravels, and likely boulders.

Material above the hard surface layer is expected to consist of mainly sands and isolated gravels and boulders.

Figure 6 plots a strip map of the interpreted top-of-hard-surface. The interpretation is limited to profiles collected along seismic acquisition tracklines. Figure 7 plots an interpolated surface map that grids data between seismic profiles interpreted for the top-of-hard-surface. e4 used a triangulation with linear interpolation algorithm to create the interpolated surface.

Figure 8 plots the locations of the obstructions encountered during 2018 maintenance dredging operations on top of the interpolated top-of-hard-surface strip map.

Figure 9 plots a strip map of the thickness of the material below the hard layer within the dredge template.

Figure 10 plots a strip map of the thickness of material above the hard layer within the dredge template.

Figure 11 is an interpreted seismic cross section along the center of the Lake Montauk Inlet, profile A-A’.

The red line is the interpreted top-of-hard surface. Green lines represent the proposed dredge template.

Above the hard surface the fabric of the geophysical data is indicative of sand deposits. Thick deposits of sand are accumulating from STA 0+00 to STA 7+50. Sandwaves are visible above the hard surface between STA 7+50 to STA 12+00. There are features below the hard surface that are interpreted to be sandwaves and stratified deposits of sand and likely gravel.

Figure 12 is an interpreted seismic profile (B-B’) across the inlet at STA 3+50. The interpreted top-of-jetty is represented by a black line, and the top of stone cover is represented by a brown line. The interpreted top-of-hard surface onlaps the top of the stone cover layer. Below the top-of-hard surface e4 interpreted strata that are both sand and likely gravel (orange) and other hard surfaces (red). Green lines represent the proposed dredge template.

Figure 13 is an interpreted seismic profile (C-C’) across the inlet at STA 5+50. The interpreted top-of-hard surface is deeper at C-C’ than in B-B’, and it onlaps the stone cover layer at a deeper elevation. The top-of-hard surface, in western section of the profile below the channel is at approximately -19ft MLLW.

Figure 14 is an interpreted seismic profile (D-D’) is a higher frequency seismic profile at STA 10+00. e4 interpreted cobbles, boulders, and stratified sand deposits above the hard layer.

Figure 6. Strip map of hard surface layer.

Figure 7. Interpolated surface map of hard surface layer.

Figure 8. Locations of 2018 obstructions as per H&L Contracting, LLC. The locationsoverlie the strip map of the hard surface layer.

Figure 9. Strip map of thickness of material below hard surface layer within the designed dredge template.

Figure 10. Strip map of thickness of material above hard surface layer.

Figure 11. Interpreted sub-bottom seismic cross section parallel to the inlet.

Figure 12. Interpreted sub-bottom seismic cross section perpendicular to the inlet.

Figure 13. Interpreted sub-bottom seismic cross section across the inlet.

Figure 14. Interpreted sub-bottom seismic cross section across the inlet.

Volumes of material

This section of the report focuses on the results of the volume calculations that we performed by calculating differences between interpreted geophysical surfaces and inlet floor elevations as measured by multibeam bathymetry, and by estimates of volumes of discrete boulders as interpreted from side-scan sonar data.

The dredging template recommended in the feasibility studies will encounter a hard layer in the channel and deposition basin, as well as stone cover in the deposition basin’s eastern slope. An alternate channel-only template that does not include a deposition basin will reduce the volume of hard material that needs to be removed.

Figure 15 shows a schematic cross-sectional representation of the interpreted hard surface in relationship to the channel and the eastern jetty. This schematic representation divides the dredge template into the western slope and the inlet channel and then the deposition basin and the eastern slope.

Figure 15. Schematic cross section showing interpreted hard surface in relationship to dredge template and eastern jetty.

Table 2 shows the total volumes to be dredged from STA 0+00 to STA 15+00. e4 estimates the total volume of material to be dredged to achieve the deepening of the inlet (including 2ft over dredge) and the 100ft wide deposition basin as designed to be 91,901 cubic yards. e4 estimates 52,186 cubic yards volume of material above the hard surface and 39,715 cubic yards of material below the hard surface.

Table 2. Total volumes in dredge areas from STA 00+00 to STA 15+00 based on March 2023 bathymetry.

Volume above hard surface1

Volume below hard surface1

Total dredge area cu yd cu yd cu yd

Total volume above -17ft MLLW dredge template 41,631 20,382 62,014 Total volume between -17ft and -19ft MLLW dredge template 10,555 19,333 29,887 Total volume above -19ft MLLW dredge template 52,186 39,715 91,901

1. Top of hard layer includes top of stone cover layer in the deposition basin and eastern slope

Table 3 tabulates the volume of material above the hard surface separated by grade and over depth for each component of the dredging template.

Table 4 tabulates the volume of material below the hard surface separated by grade and over depth for each component of the dredging template.

Table 5 tabulates the total volume of material below separated by grade and over depth for each component of the dredging template.

Table 4 shows that of the nearly 40,000 cubic yards of material below the hard surface, 10,848 cubic yards are within the dredge template of the western slope (303 cubic yards) and inlet channel (10,545 cubic yards), and 28,867 cubic yards are within the dredge template of the deposition basin (23,749 cubic yards) and eastern slope (5,118 cubic yards). It should be noted that where the top-of-jetty and stone cover encroaches into the deposition basin slope dredge template the volume of hard material reported may include jetty stone and cover stone.

Table 3. Total volumes above hard layer per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry.

Volume above hard surface

Total Volume above hard surface Western

Slope Inlet

Channel Deposition

Basin1 Eastern Slope1 cu yd cu yd cu yd cu yd cu yd

Total volume above -17ft MLLW dredge template 41,631 0 16,661 19,623 5,348 Total volume between -17ft and -19ft MLLW dredge template 10,555 2,537 6,580 1,058 380 Total volume above -19ft MLLW dredge template 52,186 2,537 23,241 20,681 5,727

1. Top of hard layer includes top of stone cover layer in the deposition basin and eastern slope.

Table 4. Total volumes below hard layer per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry.

Volume below hard surface below hard surface Western

Slope Inlet

Channel Deposition

Basin1 Eastern Slope 1

Total volume above -17ft MLLW dredge template 20,382 0 2,288 15,066 3,028 Total volume between -17ft and -19ft MLLW dredge template 19,333 303 8,257 8,683 2,090 Total volume above -19ft MLLW dredge template 39,715 303 10,545 23,749 5,118

1. Top of hard layer includes top of stone cover layer in the deposition basin and eastern slope.

Table 5. Total volumes per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry.

Total Inlet dredge

Western

Slope Inlet

Channel Deposition

Basin Eastern Slope

Total volume above -17ft MLLW dredge template 62,014 0 18,949 34,689 8,376 Total volume between -17ft and -19ft MLLW dredge template 29,887 2,840 14,837 9,741 2,469 Total volume above -19ft MLLW dredge template 91,901 2,840 33,786 44,430 10,845

1. Top of hard layer includes top of stone cover layer in the deposition basin and eastern slope.

Figure 16 shows a schematic representation of the interpreted hard surface in relationship to an alternate dredge template that eliminates the emplacement of a deposition basin and the eastern jetty. This model represents a dredge template of the inlet channel with its corresponding western and eastern 1:3 slopes.

Figure 16. Schematic cross section showing interpreted hard surface in relationship to channel and eastern jetty.

Table 6 shows the total volumes to be dredged for this alternate channel from STA 0+00 to STA 15+00. e4 estimates the total volume of material above -19ft MLLW is 41,523 cubic yards. e4 estimates 29,602 cubic yards of material above the hard surface and 11,921 cubic yards of material below the hard surface.

Table 7 tabulates the volume of material above the hard surface separated by grade and over depth for each component of the dredging template.

Table 8 tabulates the volume of material below the hard surface separated by grade and over depth for each component of the dredging template.

Table 9 tabulates the total volume of material below separated by grade and over depth for each component of the dredging template.

Table 6. Total volumes in dredge areas from STA 00+00 to STA 15+00 based on March 2023 bathymetry for updated dredge template.

Volume above hard surface

Volume below hard surface

Total dredge cu yd cu yd cu yd

Total volume above -17ft MLLW new dredge template 19,140 2,770 21,910 Total volume between -17ft and -19ft MLLW dredge template 10,070 9,151 19,221 Total volume above -19ft MLLW dredge template 29,602 11,921 41,523

Table 7. Total volumes above hard layer per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry and updated dredge template.

Volume above hard surface above hard surface Western Slope Inlet Channel Eastern Channel cu yd cu yd cu yd cu yd

Total volume above -17ft MLLW dredge template 19,140 0 16,661 2,479 Total volume between -17ft and -19ft MLLW dredge template 10,070 2,537 6,580 953 Total volume above -19ft MLLW dredge template 29,602 2,537 23,241 3,824

Table 8. Total volumes below hard layer per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry and updated dredge template.

Volume below hard surface below hard surface Western Slope Inlet Channel Eastern Channel

Total volume above -17ft MLLW dredge template 2,770 0 2,288 482 Total volume between -17ft and -19ft MLLW dredge template 9,151 303 8,257 591 Total volume above -19ft MLLW dredge template 11,921 303 10,545 1,073

Table 9. Total volumes per dredge subareas areas in inlet from STA 00+00 to STA 15+00 based on March 2023 bathymetry and updated dredge template.

Total Inlet dredge area Western Slope Inlet Channel Eastern Channel

Total volume above -17ft MLLW dredge template 21,910 0 18,949 2,961 Total volume between -17ft and -19ft MLLW dredge template 19,221 2,840 14,837 1,544 Total volume above -19ft MLLW dredge template 41,523 2,840 33,786 4,897

In addition to the hard surface material there are an estimated 1,910 cubic yards of boulders above the hard surface, including at the surface of the inlet floor. This estimate is based on the interpretation and analysis of side-scan and multibeam data of the material on the inlet floor, and from interpretation of reflectors in seismic data.

Volume calculations were calculated using two independent methods; the results varied by approximately 1%. Total uncertainty is also impacted by data density and interpretation. Based on previous results using the same methodology we anticipate the total uncertainty to be +/- 8%-10%.

Appendix I: Targets above hard surface

Target id

Easting Northing Elevation Feet below channel floor

Within Channel Dredge template

Location relative to channel

Relationship to channel dredge templates

Relationship to Hard layer

2001 1552801.1 338108.8 -14.1 0.0 yes in 19ft channel above 17ft model above hard layer 2002 1552907.1 338289.8 -15.3 -0.1 yes in 19ft channel above 17ft dredge model above hard layer 2003 1552764.8 338403.6 -16.0 -0.1 yes in 19ft channel above 17ft dredge model above hard layer 2004 1552823.6 338380.5 -15.7 -0.1 yes in 19ft channel above 17ft dredge model above hard layer 2005 1552868.0 338283.2 -16.5 -0.2 yes in 19ft channel above 17ft dredge model above hard layer 2006 1552867.2 338028.9 -14.8 -0.2 yes in 19ft channel above 17ft dredge model above hard layer 2007 1552834.6 338271.5 -15.7 -0.2 yes in 19ft channel above 17ft dredge model above hard layer 2008 1552792.5 338120.7 -14.1 -0.2 yes in 19ft channel above 17ft dredge model above hard layer 2009 1552812.2 338376.2 -15.9 -0.3 yes in 19ft channel above 17ft dredge model above hard layer 2010 1552784.0 338117.4 -12.8 -0.3 yes in 19ft channel above 17ft dredge model above hard layer 2011 1552864.7 338079.9 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2012 1552864.3 338079.8 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2013 1552864.0 338079.7 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2014 1552863.6 338079.5 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2015 1552863.2 338079.4 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2016 1552931.7 338114.0 -16.0 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2017 1552862.9 338079.3 -15.6 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2018 1552947.0 338047.7 -16.8 -0.4 yes in 19ft channel above 17ft dredge model above hard layer 2019 1552825.5 338381.4 -16.0 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2020 1552862.5 338079.1 -15.6 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2021 1552862.2 338079.0 -15.6 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2022 1552861.8 338078.9 -15.6 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2023 1552861.4 338078.8 -15.6 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2024 1552861.1 338078.7 -15.6 -0.5 yes in 19ft channel above 17ft dredge model above hard layer 2025 1552860.7 338078.6 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2026 1552860.4 338078.5 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2027 1552828.1 338428.5 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2028 1552954.8 338050.3 -16.3 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2029 1552860.0 338078.4 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2030 1552859.6 338078.3 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2031 1552859.3 338078.2 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2032 1552858.9 338078.1 -15.6 -0.6 yes in 19ft channel above 17ft dredge model above hard layer 2033 1552927.0 338194.5 -15.4 -0.7 yes in 19ft channel above 17ft dredge model above hard layer 2034 1552880.9 338031.0 -15.7 -0.7 yes in 19ft channel above 17ft dredge model above hard layer 2035 1552710.3 339094.4 -11.9 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2036 1552798.1 338117.5 -15.0 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2037 1552798.2 338117.3 -15.0 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2038 1552798.2 338117.1 -15.0 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2039 1552775.1 338521.4 -16.0 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2040 1552834.7 338384.6 -16.3 -0.8 yes in 19ft channel above 17ft dredge model above hard layer 2041 1552811.5 338086.7 -14.9 -0.9 yes in 19ft channel above 17ft dredge model above hard layer 2042 1552889.6 338239.4 -16.5 -0.9 yes in 19ft channel above 17ft dredge model above hard layer 2043 1552713.2 338658.3 -14.1 -1.0 yes in 19ft channel above 17ft dredge model above hard layer 2044 1552908.0 338056.6 -16.6 -1.0 yes in 19ft channel above 17ft dredge model above hard layer 2045 1552650.9 339111.8 -15.3 -1.1 yes in 19ft channel above 17ft dredge model above hard layer 2046 1552683.7 339219.6 -12.9 -1.1 yes in 19ft channel above 17ft dredge model above hard layer 2047 1552653.0 339162.0 -14.4 -1.2 yes in 19ft channel above 17ft dredge model above hard layer 2048 1552922.5 338142.8 -17.1 -1.2 yes in 19ft channel above 17ft dredge model above hard layer 2049 1552872.1 338132.1 -16.3 -1.2 yes in 19ft channel above 17ft dredge model above hard layer 2050 1552713.6 339013.7 -12.3 -1.2 yes in 19ft channel above 17ft dredge model above hard layer 2051 1552660.0 339010.9 -15.7 -1.4 yes in 19ft channel above 17ft dredge model above hard layer 2052 1552845.7 338225.4 -16.7 -1.4 yes in 19ft channel above 17ft dredge model above hard layer 2053 1552868.3 338389.4 -16.4 -1.5 yes in 19ft channel above 17ft dredge model above hard layer 2054 1552657.9 338900.7 -16.6 -1.5 yes in 19ft channel above 17ft dredge model above hard layer 2055 1552747.3 338714.6 -11.8 -1.7 yes in 19ft channel above 17ft dredge model above hard layer 2056 1552784.3 338572.0 -16.9 -1.8 yes in 19ft channel above 17ft dredge model above hard layer 2057 1552722.6 339044.2 -12.4 -1.8 yes in 19ft channel above 17ft dredge model above hard layer 2058 1552739.7 338670.2 -13.5 -1.8 yes in 19ft channel above 17ft dredge model above hard layer 2059 1552843.1 338578.0 -11.8 -1.8 yes in 19ft channel above 17ft dredge model above hard layer 2060 1552627.9 339152.0 -16.6 -1.9 yes in 19ft channel above 17ft dredge model above hard layer

2061 1552754.9 338715.0 -11.6 -2.0 yes in 19ft channel above 17ft dredge model above hard layer 2062 1552826.2 338686.9 -10.1 -2.0 yes in 19ft channel above 17ft dredge model above hard layer 2063 1552679.3 339010.0 -15.0 -2.0 yes in 19ft channel above 17ft dredge model above hard layer 2064 1552687.9 338914.2 -14.9 -2.2 yes in 19ft channel above 17ft dredge model above hard layer 2065 1552643.5 338704.8 -14.9 -2.4 yes in 19ft channel above 17ft dredge model above hard layer 2066 1552721.3 338714.1 -15.1 -2.4 yes in 19ft channel above 17ft dredge model above hard layer 2067 1552815.3 338687.4 -10.8 -2.4 yes in 19ft channel above 17ft dredge model above hard layer 2068 1552741.3 338868.5 -12.2 -2.5 yes in 19ft channel above 17ft dredge model above hard layer 2069 1552684.7 338913.7 -15.7 -2.6 yes in 19ft channel above 17ft dredge model above hard layer 2070 1552705.5 339123.5 -14.7 -3.6 yes in 19ft channel above 17ft dredge model above hard layer 2071 1552684.3 339166.9 -15.8 -4.0 yes in 19ft channel above 17ft dredge model above hard layer 2072 1552709.1 339014.2 -15.5 -4.2 yes in 19ft channel above 17ft dredge model above hard layer 2073 1552724.7 339013.3 -14.9 -4.4 yes in 19ft channel above 17ft dredge model above hard layer 2074 1552678.5 339214.1 -17.0 -4.9 yes in 19ft channel above 17ft dredge model above hard layer

2075 1552961.4 337919.3 -16.3 -0.1 yes in 19ft channel above 17ft dredge model area of no hard layer

2076 1552602.7 339101.7 -17.9 -0.2 yes in 19ft channel between 17 and 19 model above hard layer

2077 1552626.5 338846.9 -17.3 -0.4 yes in 19ft channel between 17 and 19 model above hard layer

2078 1552600.1 339120.8 -18.0 -0.5 yes in 19ft channel between 17 and 19 model above hard layer

2079 1552636.4 339304.2 -18.7 -0.6 yes in 19ft channel between 17 and 19 model above hard layer

2080 1552623.0 339024.8 -17.6 -0.6 yes in 19ft channel between 17 and 19 model above hard layer

2081 1552612.9 338990.0 -17.8 -0.7 yes in 19ft channel between 17 and 19 model above hard layer

2082 1552622.9 338997.3 -17.7 -0.7 yes in 19ft channel between 17 and 19 model above hard layer

2083 1552608.4 338988.8 -17.9 -0.8 yes in 19ft channel between 17 and 19 model above hard layer

2084 1552626.0 338857.4 -17.6 -1.0 yes in 19ft channel between 17 and 19 model above hard layer

2085 1552632.2 338995.5 -17.5 -1.0 yes in 19ft channel between 17 and 19 model above hard layer

2086 1552659.3 339308.0 -18.2 -1.0 yes in 19ft channel between 17 and 19 model above hard layer

2087 1552631.3 338873.7 -17.6 -1.0 yes in 19ft channel between 17 and 19 model above hard layer

2088 1552611.4 339143.6 -17.4 -1.2 yes in 19ft channel between 17 and 19 model above hard layer

2089 1552964.5 338052.8 -16.7 -1.2 yes in 19ft channel between 17 and 19 model above hard layer

2090 1552882.6 338387.8 -16.5 -2.1 yes in 19ft channel between 17 and 19 model above hard layer

2091 1552624.9 339224.9 -17.2 -2.2 yes in 19ft channel between 17 and 19 model above hard layer

2092 1552706.7 339171.3 -13.2 -2.3 yes in 19ft channel between 17 and 19 model above hard layer

2093 1552608.4 339251.2 -18.9 -2.4 yes in 19ft channel between 17 and 19 model above hard layer

2094 1552846.1 338022.1 -17.1 -2.5 yes in 19ft channel between 17 and 19 model above hard layer

2095 1552849.8 338579.5 -12.7 -3.1 yes in 19ft channel between 17 and 19 model above hard layer

2096 1552936.9 338296.9 -14.7 -0.1 yes below 19ft channel between 17 and 19 model above hard layer

2097 1552922.1 338293.4 -15.2 -0.2 yes below 19ft channel between 17 and 19 model above hard layer

2098 1552851.2 338726.3 -7.0 -0.2 yes below 19ft channel between 17 and 19 model above hard layer

2099 1552951.8 338130.3 -15.7 -0.4 yes below 19ft channel between 17 and 19 model above hard layer

2100 1552677.5 339315.4 -17.5 -0.4 yes below 19ft channel between 17 and 19 model above hard layer

2101 1552999.7 338059.2 -14.8 -0.5 yes below 19ft channel between 17 and 19 model above hard layer

2102 1552674.2 339314.5 -17.6 -0.6 yes below 19ft channel between 17 and 19 model above hard layer

2103 1552843.7 338727.8 -7.7 -0.6 yes below 19ft channel between 17 and 19 model above hard layer

2104 1552693.4 339317.4 -17.3 -0.7 yes below 19ft channel between 17 and 19 model above hard layer

2105 1552940.0 338197.8 -15.6 -0.7 yes below 19ft channel between 17 and 19 model above hard layer

2106 1552682.5 339315.9 -17.7 -0.7 yes below 19ft channel between 17 and 19 model above hard layer

2107 1552942.7 338248.0 -15.3 -0.7 yes below 19ft channel between 17 and 19 model above hard layer

2108 1552677.0 339325.0 -18.7 -0.8 yes below 19ft channel between 17 and 19 model above hard layer

2109 1552928.0 338397.2 -11.2 -0.8 yes below 19ft channel between 17 and 19 model above hard layer

2110 1552981.5 338057.2 -16.0 -0.9 yes below 19ft channel between 17 and 19 model above hard layer

2111 1552691.2 339320.4 -18.0 -0.9 yes below 19ft channel between 17 and 19 model above hard layer

2112 1552707.4 339321.9 -17.5 -0.9 yes below 19ft channel between 17 and 19 model above hard layer

2113 1552909.2 338447.1 -11.1 -1.3 yes below 19ft channel between 17 and 19 model above hard layer

2114 1552938.1 338246.1 -15.7 -1.4 yes below 19ft channel between 17 and 19 model above hard layer

2115 1552898.5 338443.7 -12.3 -1.4 yes below 19ft channel between 17 and 19 model above hard layer

2116 1552949.7 338152.4 -16.4 -1.5 yes below 19ft channel between 17 and 19 model above hard layer

2117 1552962.0 338155.5 -15.9 -1.5 yes below 19ft channel between 17 and 19 model above hard layer

2118 1552758.9 339028.9 -10.9 -1.5 yes below 19ft channel between 17 and 19 model above hard layer

2119 1552873.2 338583.2 -10.3 -1.6 yes below 19ft channel between 17 and 19 model above hard layer

2120 1552771.3 339081.3 -10.9 -1.6 yes below 19ft channel between 17 and 19 model above hard layer

2121 1552855.7 338626.2 -10.7 -2.4 yes below 19ft channel between 17 and 19 model above hard layer

2122 1552855.4 338627.5 -10.7 -2.4 yes below 19ft channel between 17 and 19 model above hard layer

2123 1552856.9 338621.9 -10.7 -2.4 yes below 19ft channel between 17 and 19 model above hard layer

2124 1552861.1 338689.5 -9.8 -2.4 yes below 19ft channel between 17 and 19 model above hard layer

2125 1552857.7 338618.2 -10.8 -2.4 yes below 19ft channel between 17 and 19 model above hard layer

2126 1552863.7 338611.9 -11.4 -3.1 yes below 19ft channel between 17 and 19 model above hard layer

2127 1552767.0 339031.9 -12.5 -3.2 yes below 19ft channel between 17 and 19 model above hard layer

2128 1552766.2 339082.3 -13.6 -4.1 yes below 19ft channel between 17 and 19 model above hard layer

2129 1552941.7 337967.4 -17.7 -0.9 yes in 19ft channel between 17 and 19 model area of no hard layer

2130 1552958.6 337926.3 -18.2 -1.6 yes in 19ft channel between 17 and 19 model area of no hard layer

2131 1553017.7 338257.7 -5.7 -0.4 no in larger dredge area in larger dredge area above hard layer

2132 1552912.5 338653.2 -7.6 -0.5 no in larger dredge area in larger dredge area above hard layer

2133 1552799.8 339188.0 -9.8 -0.5 no in larger dredge area in larger dredge area above hard layer

2134 1552975.4 338305.8 -9.4 -0.7 no in larger dredge area in larger dredge area above hard layer

2135 1552746.9 339331.9 -16.8 -0.8 no in larger dredge area in larger dredge area above hard layer

2136 1552941.0 338455.1 -8.6 -0.8 no area in larger dredge area above hard layer

2137 1552752.7 339333.3 -16.8 -0.8 no in larger dredge area in larger dredge area above hard layer

2138 1552731.3 339327.3 -16.9 -0.9 no in larger dredge area in larger dredge area above hard layer

2139 1552718.9 339324.0 -17.3 -1.0 no in larger dredge area in larger dredge area above hard layer

2140 1553021.1 338059.6 -13.4 -1.3 no in larger dredge area in larger dredge area above hard layer

2141 1552845.9 338990.3 -8.9 -1.4 no in larger dredge area in larger dredge area above hard layer

2142 1552973.9 338411.1 -8.6 -1.4 no in larger dredge area in larger dredge area above hard layer

2143 1552733.3 339301.1 -15.4 -1.6 no in larger dredge area in larger dredge area above hard layer

2144 1552798.5 339187.3 -10.9 -1.7 no in larger dredge area in larger dredge area above hard layer

2145 1552916.6 338698.5 -8.1 -1.7 no in larger dredge area in larger dredge area above hard layer

2146 1552947.9 338714.0 -8.0 -1.9 no in larger dredge area in larger dredge area above hard layer

2147 1552754.9 339176.8 -11.6 -2.0 no in larger dredge area in larger dredge area above hard layer

2148 1552990.1 338256.2 -10.5 -2.1 no in larger dredge area in larger dredge area above hard layer

2149 1552793.4 339344.3 -17.1 -2.1 no in larger dredge area in larger dredge area above hard layer

2150 1552942.9 338714.4 -8.0 -2.2 no in larger dredge area in larger dredge area above hard layer

2151 1552889.4 338695.3 -9.6 -2.7 no in larger dredge area in larger dredge area above hard layer

2152 1552778.1 339079.1 -11.8 -2.8 no in larger dredge area in larger dredge area above hard layer

2153 1552841.4 338879.2 -9.4 -3.1 no in larger dredge area in larger dredge area above hard layer

2154 1552799.4 339033.0 -11.4 -3.2 no in larger dredge area in larger dredge area above hard layer

2155 1552963.8 338407.4 -10.8 -3.3 no in larger dredge area in larger dredge area above hard layer

2156 1552872.6 338721.7 -10.7 -4.2 no in larger dredge area in larger dredge area above hard layer

2157 1552978.2 339385.9 -15.5 -0.7 no in larger dredge area in larger dredge area area of no hard layer

2158 1552799.3 339345.2 -16.0 -0.8 no in larger dredge area in larger dredge area area of no hard layer

2159 1552841.3 339206.2 -9.7 -0.8 no in larger dredge area in larger dredge area area of no hard layer

2160 1552905.4 339372.9 -15.6 -1.0 no in larger dredge area in larger dredge area area of no hard layer

2161 1552837.2 339357.1 -15.7 -1.0 no in larger dredge area in larger dredge area area of no hard layer

2162 1552852.8 339363.3 -15.6 -1.0 no in larger dredge area in larger dredge area area of no hard layer

2163 1552923.6 339374.6 -15.3 -1.1 no in larger dredge area in larger dredge area area of no hard layer

2164 1552818.9 339349.4 -15.6 -1.1 no in larger dredge area in larger dredge area area of no hard layer

2165 1552831.3 339354.8 -15.8 -1.2 no in larger dredge area in larger dredge area area of no hard layer

2166 1552861.8 339365.9 -15.7 -1.2 no in larger dredge area in larger…