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Home My WebLink About00 - Buxton - AppA-GeotechReportAPPENDIX A GEOTECHNICAL DATA ANALYSIS Beach Renourishment to Protect NC Highway 12 at Buxton, Dare County, North Carolina Prepared on Behalf of.- Dare County Board of Commissioners Bob Woodard, Chairman 954 Marshall C Collins Drive, Manteo, NC 27954 Prepared by: High Value Services Coos Sustainable Solutions PO Box 8056, Columbia, SC 29202-8056 [2403M-TASK 2-JULY 20211 — THIS PAGE INTENTIONALLY LEFT BLANK — Coastal Science & Engineering ii Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina SYNOPSIS This report contains geotechnical data on the native beach and proposed borrow area sediments for a proposed beach renourishment project along -3 miles of shoreline in Buxton, North Carolina, extending north into Cape Hatteras National Seashore. The maximum sand volume to be placed along the project area is 1.2 million cubic yards (cy). The proposed borrow source is a sandy ridge -2-3 miles offshore of the old Cape Hatteras Lighthouse site, within state waters. Another borrow area was considered -3-4 miles from the Lighthouse site but was ultimately rejected due to insufficient compatibility of material for the proposed project. The report presents detailed results of beach sampling and borrow area sampling via cores collected in 2020 and 2021. Beach samples obtained along the visible beach and inshore zone, as well as offshore borings, were all obtained in accordance with North Carolina Technical Standards for Beach Fill Projects (15A NCAC 07H .0312 - see Attachment4) and National Park Service Sediment Management Framework (NPS 2021). Beach Sampling Ten stations (transects) were established by Coastal Science & Engineering (CSE) in 2014 along the Buxton project area and adjacent shoreline at 1,000 to 4,000-foot (ft) spacing (10 stations between Sta 1760+00 to 1980+00) for sampling at 14 cross -shore positions (NPS/USACE 2015). In August 2019, sand samples were collected in anticipation of the proposed beach renourishment. The mean grain size of beach sand at the Buxton project area was 0.321 millimeters (mm) as of August 2019. Samples collected below -8 ft NAVD were markedly finer than those collected from the upper portions of the profile. The mean grain size of samples collected above mid -tide level (MTL) is 0.400 mm. Both sets of beach samples contained -7 percent shell material,1.1 percent granules (2 to 4 mm), and <1 percent gravel (4 to 76 mm) by weight. Offshore Borrow Area Compatibility Analysis The proposed offshore borrow area encompasses -200 acres and was sampled by 3-inch borings spaced -700 ft apart. Each boring was collected to a uniform depth of 10 ft beneath the seafloor. The borings were subsampled and analyzed for grain -size distribution and comparison with the existing beach sand, then pro -rated according to the length of each sample interval. This allows the calculation of boring statistics to a specified "composite" depth, which is useful forthe operational considerations of dredge vessels. After calculating the composite values to 6 ft, 8 ft, and 10 ft depths, all borings were found to have beach -quality sand to a depth up to 10 ft. The mean grain size of the proposed borrow area, composited to a 10-ft depth, is 0.517 mm with 15.6 percent shell material, 7.1 percent granules (2 to 4 mm), and <1 percent gravel (4 to 76 mm) by weight. The boring density is Coastal Science & Engineering i Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina approximately 1 core per 20 acres. Based on these descriptive statistics, the proposed borrow area meets the requirements of the North Carolina Technical Standards for Beach Fill Projects (15A NCAC 07H .0312 - see Attachment4) and National Park Service Beach Nourishment Guidance (NPS 2021). The proposed 200-acre borrow area would provide up to 3.3 million cubic yards of beach quality sand if excavation is permitted to a depth of 10 ft. The proposed -200-acre borrow area will provide sufficient volume to accomplish a -1.2 million cubic yard project; the minimum excavation area to provide the design volume would be -65 acres, assuming a dredge cut averaging -10 ft deep. Coastal Science & Engineering ii Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE OF CONTENTS SYNOPSI 1.0 INTRODUCTION......................................................................................................................... 1 2.0 METHODS.................................................................................................................................7 2.1 Beach Samples............................................................................................................................................7 2.2 Borrow Samples........................................................................................................................................11 3.0 RESULTS- BEACH SAMPLES.....................................................................................................19 3.1 Beach Statistics -August 2019................................................................................................................19 3.2 Comparative Sample Statistics...............................................................................................................29 3.3 Selection of Native Mean Grain Size........................................................................................................31 4.0 BORROW AREA INVESTIGATIONS ................................ 4.1 Selection of Borrow Area Mean Grain Size ................. 33 42 5.0 SEDIMENT COMPATIBILITY.......................................................................................................47 REFERENCES CITED Attachment 3A) Grain Size Distributions (GSDs) - Individual Beach Samples Attachment 1B) GSDs - Beach Composites Attachment 2) Core Logs and Core Photos Attachment 3A) GSDs - Individual Core Samples Attachment 3B) GSDs - Composite Samples -Upper 6 ft of Section by Core Attachment 3C) GSDs - Composite Samples -Upper 8 ft of Section by Core Attachment 3D) GSDs - Composite Samples -Upper 10 ft of Section by Core Attachment 4) North Carolina Technical Standards for Beach Fill (15A NCAC 07H.0312) 53 Coastal Science & Engineering iii Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina — THIS PAGE INTENTIONALLY LEFT BLANK — Coastal Science & Engineering iv Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 1.0 INTRODUCTION This report provides sediment data for the Buxton, North Carolina, project area based on sampling and analysis in 2019-2021. Samples were obtained along the beach and inshore zone in accordance with North Carolina Technical Standards for Beach Fill Projects (15A NCAC 07H .0312 - see Attachment 4) and National Park Service Beach Nourishment Guidance (NIPS 2021). Ten stations (transects) were established by CSE in 2014 along the Buxton project area and adjacent shoreline at 1,000 to 4,000-foot (ft) spacing (10 stations between Sta 1760+00 to 1980+00) for sampling at 14 cross -shore positions. An offshore sand search area encompassing -200 acres was sampled by 3-inch borings spaced -700 ft apart (Fig 1.1). The borings were subsampled and analyzed for grain - size distribution and comparison with the existing beach sand. Nourishment success depends on finding a source of sand that is similar in character to the native beach. The degree to which a particular borrow sediment matches the native beach sediments strongly influences project longevity and environmental impacts. Three outcomes are possible (Fig 1.2) (cf, Dean 1991, 2002): • Borrow sediment is finer than native - The majority of fill will shift offshore and yield a more gently sloping profile. The dry beach will be the narrowest. • Borrow sediment is coarserthan native - The majority of fill will tend to "perch" on the visible beach and yield a steeper profile through the surf zone. The dry beach will be the widest. • Borrow sediment matches the native sediment - The fill will tend to follow the natural contours of the profile and retain similar slopes and morphology. It is generally accepted that the environmental impacts of nourishment are most likely to be minimized if the borrow sediment "matches" the native (NRC 1995). However, the question of what constitutes "native" is still debatable. In some settings, such as many South Carolina beaches, sediments exist over a very narrow size range between the foredune and inshore zone [eg - mean = 0.18-0.22 millimeters (mm) with well -sorted sand at Isle of Palms SC]. In these cases, it is relatively easy to distinguish between "coarser" and "finer" than native. Most North Carolina beaches, by contrast, exhibit more variable sediment size distributions. Fine sand may dominate in the dunes and offshore, while coarse sand dominates the inner surf zone (USACE 2010). Coastal Science & Engineering 1 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina t 74D+Dp ► 0 2000, Cape Hatteras 12 National Seashore Scale (Feet) t76p+Op Pamlico Sound 178D+DD 180D+pp d a O t M CD d 1820+pp to Fa — C D OCD uO v;z L(j O Ct S L} v LO 1840+00 N rn a� -o 4 o i'+ Atlantic Ocean W o a� 0 a 0 1880+00 } EL I 12 0 4 ' o Proposed r� Borrow Area L 1940+06 Cape • Hatteras Light TKO+pp Cape Hatteras National Seashore FIGURE 1.1. Map showing the Buxton project area, stationing of beach profiles along the fill template, and proposed borrow area with location of borings. Coastal Science & Engineering 2 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 92.4m T=-- 8 = t .5m h . = 6m 1 interseciing Profiles, A N = 0.1MI 3AF = 0.14m1 3 45.3m }- h . 6m Non -Intersecting Profiles � AN= AF = 0.1m1/3 9m h, = 6m Hon -Intersecting Profiles - - AN = 0.1 m1/3 AF = 0.09m1 13 Z 10 — j h, 6m W 5 r r W Llmiting Case of Nourishment Advancement, Non -Intersecting Profiles, AN= 0.1mV3OAF = 0.085m113 i I I I Ir .. I 0 100 200 300 400 500 600 OFFSHORE DISTANCE (m) FIGURE 1.2. Effect of borrow material grain size (nourishment scale parameter, AF) on the width of the dry beach for a fixed volume of nourishment sand added per unit of beach length (from Dean 1991, Fig 25). In simple terms, coarser sand relative to the native sediment produces a wider visible beach than finer sand. [Note: 1 m z 3.28 ft] Coastal Science & Engineering 3 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina North Carolina beaches are typically composed of quartz sand in the medium size range [0.25-0.5 millimeter (mm) mean diameter]. Northern Outer Banks beaches tend to be coarser than southern North Carolina beaches with a wider range of sediment grain sizes (USACE 2000, 2010). Waves and nearshore currents, as well as winds, sort the sediments of the littoral zone and introduce characteristic topography across the profile. The coarsest material tends to concentrate at the inshore "plunge" point of breaking waves where energy dissipation is focused (Miller & Ziegler 1958, Greenwood & Davidson-Arnott 1972, Komar 1998). Finer sands are winnowed and shifted offshore, leaving coarser sediments near the low watermark (Fig 1.3). Sands washed up the profile across the berm at high tide dry out and become sorted by winds, leading to the accumulation of finer sand in the dunes. 8.0 -3 4.0 -2 1 PERCENT 2.0 40 W 0. 0 1.0 ry !u N N h z I I 1 0.50 Z F � I 0 y 0 2 � I I 0.25 3 1 0.125 I f/l f / MEAN I / 0.063 4 0 0 a I f I I 1 I I I 1 I a Q I ht w "' -10 0 100 200 300 400 500 600 700 800 900 1000 DISTANCE, M FIGURE 1.3. Grain size distributions along a profile at Duck, North Carolina, -70 miles north of the Buxton project area, illustrating the variation in grain sizes as a function of position (from Birkemeier et al 1985). Coastal Science & Engineering 4 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Each sand size typically finds its equilibrium position across the profile, with accumulations developing a particular slope and geometry. The longshore bar is often composed of fine sand (<0.25 mm diameter), which equilibrates at a gentler slope than the swash zone. Any suite of sediment sizes introduced to a beach by natural or artificial means will similarly sort under waves and migrate across the profile. Figure 1.4 illustrates a typical profile across the littoral zone showing primary features such as the foredune, dry beach (berm), beach face, trough, and outer bar. The visible beach (ie - above low water) along most coasts tends to exhibit well -sorted (poorly graded) sands of some dominant size class. A composite mean grain size of samples from each position for Buxton, as measured in August 2019, is shown at the bottom of Figure 1.4. In other locations along the Outer Banks near Buxton, dune sands are typically -0.3 mm in mean diameter, while swash zone samples are coarse (0.5-1.0 mm) or very coarse sand (1.0-2.0 mm). Seaward of the inner surf zone, sediments are consistently fine sand (0.12-0.25 mm). At Buxton, dune and berm sands are slightly coarser than normal (eg- -0.4 to 0.5 mm). This is because chronic erosion can remove finer grains from the berm and dune toe, particularly in locations where there is not adequate room for wind-blown sediment to accumulate along the landward margin of the dry beach. The peaks in grain size observed at the berm and trough along Buxton are reflective of breaking waves winnowing finer sediments landward and seaward. Under North Carolina rules and standards for beach fill projects, any sediments within the sand -size range (0.0625-2.0 mm) are considered acceptable for use in nourishment projects. However, borrow areas must meet three important criteria: 1) Borrow sediments must not contain more than 5 percent fine-grained sediment (<0.0625 mm) by distribution above ambient conditions. 2) Borrow sediments must not contain more than 10 percent granules (2 mm to 4.76 mm) and 5 percent gravel (4.76 mm to 76 mm) by distribution above ambient conditions. 3) Shell content (percent CaCO3 material) may not exceed 15 percent by distribution above ambient conditions (ref —15A NCAC 07H .0312). The following sections provide detailed results of sampling and analyses performed to identify potential borrow sediments meeting state standards for beach fill. The potential borrow sediments are also evaluated in terms of their likely performance in widening the beach. Coastal Science & Engineering 5 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Buxton Beach Sediment Grain Sizes - August 2019 Visible Beach — — —All Beach }Mean 0.600 0.550 - coarse sand 0.500 - 0.450 a s�+ a F0.400....................................................................................... ......................................................................................... 0 0.350 a — 0.300 0.250 medium sand 0.200 0.150 fine sand Dune Dune Berm BC MHW BF LTT Trough Bar -8 ft -12 ft -16 ft -20 ft -24 ft Toe Cross -Shore Position FIGURE 1.4. [UPPER] Littoral profile showing eight sediment sampling positions based on morphology. [LOWER] Overall trends in mean grain size by position across the profile based on 10 transects along Buxton. Note the predominance of finer sands in the underwater zone and coarsest sand in the active surf zone. Coastal Science & Engineering 6 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 2.0 METHODS 2.1 Beach Samples CSE collected beach samples along the Buxton project area in August 2019, encompassing the entire littoral profile to a water depth of —24 ft NAVD. Samples were collected along ten transects (140 samples total). Figure 2.1 shows the cross -shore sample locations, and Figure 2.2 shows the sampling tool used for surface grabs in the upper 15 centimeters (cm) (6 inches) of substrate. Station locations for the 2019 samples are illustrated in Figure 2.3. 20 a - Dune Sediment Grab Sample Positions Dune Toe (Typical Beach Profile) loft --�- Berm Crest Berm MHW 0 e MTL MLW Bar $ Trough -16 -20 -20 ft - - - - - - - - - --- --- -------------------------------------------------------------- -24 -30 ft F-- 500 ft 1000 ft 1500 ft 2000 ft 2500 ft FIGURE 2.1. Sample positions for "beach" grab samples along Buxton following North Carolina sediment sampling criteria rules. The Buxton littoral profile exhibits a narrow berm (dry -sand beach) and deep trough separating the outer bar from the beach. Elevations and depths (y-axis) are relative to approximately Mean Sea Level. t.7' ' a FIGURE 2.2. Uniform sediment samples were collected on the beach in the upper 6 inches (15 centimeters), mixed, and subsampled for laboratory testing. Coastal Science & Engineering 7 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina FIGURE 2.3. Location of sediment sample transects (14 samples per transect) along the Buxton project area. Samples were collected in August 2019. Coastal Science & Engineering g Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Samples were inspected for mud, then washed, dried, and weighed in splits for analysis of grain size, gravel, and shell content. The split for grain size (-100-gram sample) was mechanically sieved at 0.25-phi intervals (ie - -21 sieves in the sand size range), and each subsample was split, weighed, and recorded on lab sheets. The split for shell analysis (-20-gram sample) was immersed in diluted muriatic acid (ie - nearly pure hydrochloric acid-HCl). After -24 hours or once there was no evidence of bubbling, the remainderwas rinsed, dried, and reweighed to the nearest 0.01 gram. The difference represented the proportion of shell in the sample. Summary tables of results, including sediment size distribution statistics, shell percentages, and fines percentages, are given in Section 3.0 (Results). Fines are defined here as material passing the US Standard Sieve #230 (ie - <0.0625 mm) and generally consist of minute fractions of silt. No beach samples were observed to contain measurable quantities of clays or organics. Gra nule and gravel percentage was determined from the split retained on the US Standard Sieve #5 (>2 mm). In some cases, additional coarse sieves were used in the analysis for a breakdown of the small gravel sizes. Sample splits were converted to percentages and graphed as frequency and cumulative frequency distributions. Standard statistical measures were computed, including true -moment measures, graphic means, and standard deviations (ie - Inman 1952, Folk and Ward 1957). Results were reported in millimeters as well as standard phi units. Figure 2.4 shows a typical datasheet for one sample; the set of laboratory datasheets is given in Attachment 1. Statistical composites of groups of samples were determined mathematically by averaging results for each individual size class for a given group of samples, then calculating moment measures for the composite. Composites were developed for each morphological unit sampled (ie - all dune samples combined, all toe -of -dune samples combined, etc). Groups of morphological units, such as dune and toe -of -dune, were also composited mathematically. Results of composite size distributions are given after the individual sample results in Attachment 1. In general, they are identified on the datasheets as a morphological group or all samples. Multiple groups include a numerical value in the name corresponding to the applicable number of samples represented by the result (ie - All Samples -Comp 140, Subaerial Samples -Comp 60). Percent fines are given on the sample datasheets, and summary tables provide all key statistics, including mean, standard deviation, skewness, percent shell, and percent gravel. Coastal Science & Engineering 9 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Grain Size Distribution Grain Size (mm) 25 Project 2403-M Location Buxton, NC Date Aug 05 2019 Station 1870+00 Sample Bar Mean 0.373 mm STD 0.447 mm Skewness -1.367 USCS Wentworth SP Medium Sand Fine Sand Poorly Sorted Poorly Graded Strongly Coarse Skewed Leptokurtic Total weight (gram) 116.88 %finer than 0.0625 mm (dry) 0.01 %gravel (dry) 0.00 %granule (dry) 5.65 Ca CO3 11.4 Class Limits Mid Point Weight Weight% Cumm.Wt% percentiles Moment Measures (phi) (mm) (0) (0) (gram) 1 -2.915 Mean 1.423 0.373 -4 -4.5 0.00 0.00 0.00 Standard Deviation 1.161 0.447 -3 -3.5 0.00 0.00 0.00 5 -1.405 Skewness 1.367 -2 -2.5 2.00 1.71 1.71 16 0.360 -1.5 -1.75 2.13 1.82 3.53 25 0.895 Kurtosis 4.742 -1 -1.25 2.47 2.11 5.65 Dispersion -0.75 -0.875 1.72 1.47 7.12 50 1.595 Standard Deviation -0.5 -0.625 2.17 1.86 8.98 75 2.105 Deviation from Normal -0.25 -0.375 1.65 1.41 10.39 84 2.320 0 -0.125 1.90 1.63 12.01 0.25 0.125 2.15 1.84 13.85 95 2.585 0.5 0.375 2.68 2.29 16.14 99 2.935 0.75 0.625 3.16 2.70 18.85 Graphic Phi Parameters Inman Folk & Ward 1 0.875 6.51 5.57 24.42 1.25 1.125 9.30 7.96 32.38 1952 1957 1.5 1.375 11.63 9.95 42.33 1.75 1.625 10.17 8.70 51.03 Mean 1.340 1.425 2 1.875 16.54 14.15 65.18 Standard Deviation 0.980 1.095 2.25 2.125 12.46 10.66 75.84 2.5 2.375 12.31 10.53 86.37 Skewness (1) -0.260 -0.382 2.75 2.625 12.11 10.36 96.73 Skewness (2) -1.026 3 2.875 2.33 1.99 98.73 Kurtosis 1.036 1.351 3.25 3.125 1.29 1.10 99.83 3.5 3.375 0.09 0.08 99.91 3.75 3.625 0.09 0.08 99.98 4 3.875 0.01 0.01 99.99 >4.0 4.25 0.01 0.01 100.00 FIGURE 2.4. Representative datasheet for a sediment sample along Buxton beach obtained in August 2019 (summer accretional conditions). Coastal Science & Engineering 10 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Summary tables of results, including shell and gravel percentages, follow in Section 3.0. Consistent with North Carolina sediment standards, arithmetic (non -weighted) means of groups of samples were computed from tabulated results using simple statistics (ie - mean, standard deviation, and skewness). Mean is the commonly reported typical grain size; standard deviation is a measure of the degree of sorting, and skewness reflects the degree to which the sample contains higher proportions of coarse sediment or fine sediment. Most beaches tend to have well -sorted and slightly coarse (ie - negative), skewed sediments. Shell material often adds a coarse fraction, as do granules and pebbles, which are common on Dare County beaches. 2.2 Borrow Area Samples There are delineated borrow areas off Rodanthe for emergency nourishment in the area around the NC Highway 12 S-curve near Mirlo Beach (USACE 2014), but these are not close enough to provide an economical option for fill at the Buxton project area. The 2017 initial Buxton restoration project used material dredged from a -300-acre borrow area -2-3 miles off the old Cape Hatteras Lighthouse site (Fig 2.5), but the vast majority of this area was used in that effort and should not be re -dredged at this time. Prior to the 2017 initial restoration at Buxton, the most detailed core data had been collected by the North Carolina Geological Survey (NCGS) with funding by Minerals Management Service and others (eg - Boss & Hoffman 2000, Hoffman et al 2001). A reconnaissance grid of borings obtained in the 1990s between Oregon Inlet and Cape Hatteras is summarized in an excellent report by NCGS (Hanna & Nickerson 2009). For the 2017 project, CSE identified one boring (SNL-199) off Buxton from the 1990s that contained relatively clean medium -size sand. Core spacing for the Boss and Hoffman borings was relatively large (typically>4,000 ft), which means that sediment quality over broad areas is unknown. The 2017 Buxton borrow area was centered on Core SNL-199, and situated along a low ridge with the crest located at depths of -35 to 45 ft. The ridge extends northeast from the 2017 borrow area, with similar depths along the crest for -3,000 ft north. In 2017, CSE collected borings along the ridge crest to the north of the eventually -permitted borrow area. Those borings indicated that portion of the ridge contained sediments with similar properties to native beach sands along Buxton, but it was not included in the dredge plans due to a magnetic anomaly along the northern -1/3rd of the area. For the proposed renourishment, CSE initially delineated two search areas (Fig 2.5). One was located southeast of the old borrow area, along the flanks of Diamond Shoals, while another was located north of the magnetic anomaly detected as part of the 2017 project. Initial sediment Coastal Science & Engineering 11 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina samples from the sand search area near Diamond Shoals were collected via vibracore in August 2020 and did not indicate a good match for the beach at Buxton. October 2020, CSE elected to sample the search area just north of the 2017 borrow area. These borings were obtained using CSE's proprietary system, which creates a partial vacuum that allows penetration of a 3-inch aluminum core barrel into the substrate. The cores are retrieved by removingthe core device, then capping and sealingthe ends before they are brought to the coringvessel. CSE collected 11 borings distributed every -1,000 ft across a -250-acre area along the northern portions of the ridge, and nine of these indicated the search area contained beach -quality sediment. CSE used the favorable 9 borings to lay out a -200-acre final search area off Buxton. The final investigation consisted of 10 borings in a more closely -spaced grid (typically <800 ft spacing) to determine whether the location with good -quality sand extended 10 ft beneath the seafloor. All 10 of these final borings were determined to contain beach -quality sand and are used herein to determine the borrow area mean grain size. With 10 borings collected to a 10-ft depth across a -200-acre borrow area, CSE's sand search meets North Carolina Technical Standards for Beach Fill Projects (15A NCAC 07H .0312 -see Attachment 4) and National Park Service Sediment Management Framework (NPS 2021) with a boring density of one core per -20 acres of seafloor. Cores were split, logged under the supervision of a NC -registered professional geologist, and subsampled forsediment analysis. The "saved" core half was photographed and archived in plastic sleeves. Subsamples representing the section lithology were taken from the other half of the core at full -section intervals as given on the core logs. Samples were dried, weighed, disaggregated (if mud was present) and/or washed of salts, dried, weighed, and subsampled (-100 grams) for grain -size analysis via dry sieves at 0.25-phi intervals in the sand size range and several intervals as appropriate up to the "pea" gravel range (-4.0 phi, or 16 mm). Any pebbles, cobbles, or shells greater than 16-mm diameter were retained on the -4.0 phi sieve and included in the weight percentages. Visual inspections indicated that only trace amounts of mud occurred in most of the borings, so mud analysis was only performed on a few samples. A separate subsample (-20 grams) was taken for "shell" analysis (CaCO3 content) which was determined by acid -burning using dilute hydrochloric acid. Percent granule and gravel were determined by percent weight of particles 2 to 4 mm and 4 to 76 mm diameter, respectively. Coastal Science & Engineering 12 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 75°31.30"W 75°3110'W 75°30WW 75°3Q7W 751!5'301W 75°2n W 75°28'MW 75°P3'0"W 35°16WN W167N 3$IWN 35`1 T30"N I Legend • CSE pril2021 • CSE tober202O CSE A gust 2020 3s,30"N •SSE 2 17 2019 o iginaf sands arch Propos d BorrowA a 2017 B rrow Area 35`,230 N 17 n -work buffers 0 2,000 4,QQQ 6,000 8,000 Feet Bux-30 Elux31 Bux32 • • • 7 OW M2 BuA93 Bux-25 •vyu-w Bux-39 • Ux 4k ' *Bux-H • • • `.i N W E 5 FIGURE 2.5. Location of 45 CSE borings off Buxton obtained between August 2020 and April 2021, along with borings obtained in preparation for the 2017 initial restoration project. Coastal Science & Engineering 13 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Figures 2.7 and 2.8 contain example photo -mosaic and core logs for one of the final 10-ft borings (CSE core Bux-44). The location of this core is shown in the inset panels of Figure 2.7. Attachment 2 contains the set of photo -mosaic and core logs. Attachment 3 contains the set of grain -size distributions (statistics, frequency, and cumulative frequency curves) for individual samples. Sample results were composited (weighted by section length) for the upper 6 ft, 8 ft, and 10 ft of substrate (Fig 2.8). This provides a practical operational result for evaluating sediment quality under representative dredge cut depths. Sediment quality for beach nourishment can be evaluated using the analytical model of James (1975), which is a standard method adopted by the USACE (CERC 1984). The James method computes an "overfill factor" (RA), which uses two simple parameters (mean grain size and standard deviation) to compare a prospective borrow sediment with the native size distributions. The overfill factor, RA, compares these parameters (using phi units) with a prospective borrow material and yields a simple ratio between one and ten. A value of RA=1.0 means the prospective borrow material matches or exceeds the native beach in terms of its potential performance (not necessarily a duplicate size distribution). A value of RA=1.5 means that-1.5 times more borrow material would have to be placed to provide performance equaling the native beach. Borrow material that is considerably finer than the native sediment may have RA's >>1 and, consequently, require many times more volume to yield the same performance as native sand. The overfill factor, RA, is consistent with Dean's equilibrium profile predictions, as previously illustrated in Figure 1.2. The similarity between borrow sediments and native beach sedimentswas also evaluated by means of comparative size -frequency curves for composited samples, which offers a more critical comparison of the beach and borrow sediments. If the two frequency curves are similar, the nourished beach will generally maintain the same aesthetic qualities. In general, the broader the size distribution of the native beach, the less likely there will be a perfect match with prospective borrow areas (Kana & Mohan 1998). As Gravens et al (2008) report, sediment grain size is the most important borrow material characteristic. Coastal Science & Engineering 14 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina GS � Bux-44 0 4 CmswSne�:e G Eng�rnrg Buxton NC X:3051330 Y:567308 x1,jElev Of Top: 42.0 ft NAVD 0.5 4.5 5.8 5.75 5.7 5.65 5.6 5.55 1 5 1.5 5.5 2 .. 6 3.035 3.04 3.045 3.05 3.055 x106 5.7 5.69 5.68 5.67 5.66 5.65 x 3.049 3.05 3.051 3.052 3A53 3.054�;^':.'`'y x10$ 4 8 i 11 H 11.5 12 FIGURE 2.6. Example core photo log for one of the 10-ft borings (BUX-44) obtained by AVS in April 2021. Coastal Science & Engineering 15 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina CORELOG Coostal Science & Engineering sheets of COORDINATES: HOLE NUMBER.' PROJECT. 24030 - Buxton Maintenance Northing: 567308.000 Easting: BUX-44 LOCALITY.- Buxton NC 3051330.000 Grid Datum: NAd 183 ass o— on M16 raw 9 and Aw no.) DATE.' 2021- r-06 TOP ELEVATION: DEVICE DESIGNATION., Coastal Science & Engineering BORE ANGLE: 90.000 BURDEN BOTTOM BARREL 3 in. Aluminum THICKNESS: 10.0 ft. ELEVATION: SIZE/TYPE: CORE WATER GEOLOGIST TWK RECOVERY. 10 ft. (100.0�) DEPTH: .. _4200 ft FIELD TEAM: (operational note only) Classification Of Materials d Remarks $ o (Description) a r d A a co 0.0 to 4.0 ft: Medium Sand - w/ minor shell S1: 0.0 ft. to 4.0 ft. ' hash 5Y-7/2 Shell: 25.7% Mud: 0.0-t ' Mean Grain Size: 0.557mm 1 ' 2 S1 3 -- 9,0 to 14.0 ft: Medium Sand - w/ minor fs and 52: 4.0 ft. to 10.0 ft. shell hash 5Y-6/1 Shell: 12.7% Mud: 0.7% Mean Grain Size: 0.413mm 5 '•� 6 • S2 8 ' 9 , ' 10 FIGURE 2.7. Core log for BUX-44 showing the lithology, sample intervals, and mean grain sizes. Coastal Science & Engineering 16 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 100' 90 80 70 60 0 50 40 30 20 10 0 Grain Size Distribution Grain Size (mm) 1 U.5 U.25 U.1 ...................... ...................... -4 -3 -2 -1 0 1 2 3 4 Grain Size (0) Project 2403-M Location Buxton, NC Date Apr 06 2021 Station BUX-44 Sample 10 ft COMP Mean 0.557 mm STD 0.386 mm Skewness -1.374 USCS Wentworth SP Coarse Sand Medium Sand Poorly Sorted Poorly Graded Strongly Coarse Skewed Leptokurtic Total weight (gram) 108.94 %finer than 0.0625 mm (dry) 0.00 %gravel (dry) 2.34 %granule (dry) 8.54 CaCO3 17.9 FIGURE 2.8. Example grain -size distribution (GSD) for the upper 10 ft of one of the 10-ft borings (Bux-44). Results were composited from individual samples (weighted) for the upper 6 ft, 8 ft, and 10 ft of substrate. See Attachment 3 for composite GSDs for each core calculated for the upper 6 ft, 8 ft, and 10 ft. These thicknesses are representative of typical dredging depths (excavation sections) for offshore sediments along the East Coast (USACE 2010). Coastal Science & Engineering 17 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina — THIS PAGE INTENTIONALLY LEFT BLANK — Coastal Science & Engineering 18 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 3.0 RESULTS - BEACH SAMPLES 3.1 Beach Sediment Statistics - August 2019 The Buxton project area grain -size distributions (GSDs) for August 2019 samples (140) are given in Attachment 1 and summarized in Tables 3.1 to 3.4. Table 3.2 lists the means by station and cross - shore position. Primary measures based on the method of moments and graphical methods show that arithmetic mean grain size for all samples is 0.321 mm (coarse sand) with 7.2 percent shell and 1.6 percent gravel (Table 3.3 "UPPER"). However, there is a range of mean grain sizes moving in a cross -shore direction. Averaging by sample position (Table 3.3 "LOWER"), mean grain size ranges from -0.19 mm seaward of the bar to>0.49 mm along the berm crest. Figure 3.1 plots the results of all samples by station (north to south). As Table 3.3 indicates, the low tide terrace and trough contain a high shell percentage at 10.0 percent and 12.3 percent (respectively). This result is also quite different compared with samples at Duck and Nags Head (see Figs 1.3 and 1.4). The mean grain size (unweighted, arithmetic means, and standard deviations) by cross -shore sample position is shown in Figure 3.2. The relatively low standard deviation at each point indicates the results were fairly consistent from station to station. Compared with Nags Head (-60 miles north of Buxton), the Buxton results are coarser, particularly in the foredune and berm. Coarsest sediments along Nags Head were observed along the mean low water zone. Nags Head dune samples tested -0.3 to 0.35 mm (typical), whereas Buxton dune samples averaged -0.35 to 0.45 mm in August 2019. This difference may reflect the previous manipulations of the Buxton dunes whereby storm deposits of coarse berm sand were scraped off Highway NC 12 and pushed up to form a protective dune (J Jennings, NCDOT, pers comm, August 2014). The underwater samples (seaward of the bar to -24 ft NAVD-North American Vertical Datum) along Buxton generally exhibit mean grain sizes <0.25 mm (fine sand), similar to underwater samples along Nags Head (see Fig 1.4). Table 3.3 and Figure 3.3 show the sample averages. Mean grain size decreases from north to south along Buxton in the range of-0.35-0.30 mm (see trend line in Fig 3.3). The percent shell and gravel by station with and without trough stations is shown in Figure 3.4. Shell and gravel content are relatively uniform (approximately <5 percent) from north to south. Figures 3.5 and 3.6 show the mean grain sizes by station for groups of sample positions across the littoral zone. Dune samples (n=10) are fairly uniform in size from north to south, with arithmetic means ranging from 0.35 mm to 0.45 mm. The visible beach (berm to mid -tide level) exhibited the largest grain sizes between stations 1840+00 and 1920+00 within a range (trend) from -0.30 mm to -0.60 mm. Coastal Science & Engineering 19 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina The low -tide "step" (wave plunge point) and trough (Fig 3.6, upper) show thew idest range of mean sizes from 0.7 mm to 2.9 mm—material that is much coarser than typical for North Carolina beach sand. The grain sizes occur in the deep trough between the low tide line and the outer bar. It is likely this surficial sediment in the trough represents a coarse lag deposit remaining after finer sands have been winnowed from the area under strong littoral currents. Finally, the group of 60 underwater samples from the bar to a depth of -24 ft shows a predominance of 0.20-0.25 mm sand (Fig 3.6, lower). The grain -size distributions (Attachment 1A) show nearly all gravel (sizes>2 mm, -1.0 phi) falls in the 2-8 mm (-1.0 phi to -3.0 phi) size range with few large shell clasts. No significant concentration of large clasts was observed along the beach at the time of CSE samplings in April 2021. A large clast survey was conducted during April2021 per requirements under North Carolina sediment standards for beach nourishment. The main findings of the large clast survey are summarized herein, and the full conclusions are presented in a separate report (CSE 2021). The large clast survey was performed in March 2021 in preparation for the proposed renourishment. Photo processing and data analysis were performed in April - May 2021 under Grant Contract No. CW20490 between the North Carolina Department of Environmental Quality and the County of Dare. Photographs of the samples were examined, and the sediments were classified into three groups by a licensed professional geologist. These groups are `shell,' `sediment,' and `a nth ropogenic.' Basic diagnostic characteristics of shell material include a smooth shiny surface, sharp angular edges (in the case of shell fragments), scars from tube worms, radial ribs and/or growth rings (more useful for bivalves), and an apex or siphonal notch (more useful for univalves). Samples classified as `sediment' were differentiated based on the common characteristics of marl and beach rock common along many southeastern beaches. These types of sediments commonly exhibit either more shell material or a more consistent grain size than anthropogenic materials like asphalt or paving cement (Fig 2.4). Along the Outer Banks, anthropogenic material is often found on beaches where chronic erosion has resulted in structural foundations or roads being undermined and eroded by surf. These clasts are distinguished from natural beach rock because they often exhibit different density/weight, surface roughness, and chemical makeup. There were 154 samples observed along the Buxton project area in March 2021. Each transect averaged -20 shell fragments greater than 3" in diameter, -2 sediment samples greater than 1" in diameter, and <1 anthropogenic sample greater than 1" in diameter. 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Buxton project area beach sediment characteristics (descriptive) in August 2019. See Attachment 1 for detailed frequency and cumulative frequency results of each sample. IISCS Description Wentworth Description 1760+00 Dune SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1760+00 Dune Toe SP FirieSarid Poorly Graded Medium Sand WellSorted Symmetrical Leptokurtic 1760+00 Berm SP Fine5arid Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1760+00 Be SP Fine5arid Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1760+00 MHW SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1760+00 MR SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1760+00 MLW SP Medium Sand Poorly Graded Coa rse 5a rid Poorly Sorted Symmetrical Mesokurtic 1760+00 Trough SP Fi ne Sand Poorly Graded Medium Sand Moderately Sorted 51ro Coarse Skewed Leptokurtic 1760+00 Bar SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed Leptokurtic 1760+00 -8ft SP Fine Sand Poorly Graded Fine Sand Moderately Weil Sorted Coarse Skewed Leptokurtic 1760+00 -12 ft SP Fine5and Poorly Graded FirteSand Moderately Wei ISorted Strongly Coarse Skewed Very Leptokurtic 1760+00 -16 ft SP FineSarid Poorly Graded FineSarid Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1760+00 -20 ft SP Fine Sand Poorly Graded Fine Sand We II Sorted Coarse Skewed Leptokurtic 1760+00 -24ft SP Fine5arid Poorly Graded Fine Sand Moderately Wei Sorted Coarse Skewed Leptokurtic 1790+00 Dune SP Fine5and Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1790+00 DuneTce SP Fine Sand Poorly Graded Medium Sand Moderately Wei ISorted Symmetrical Leptokurtic 1790+00 Berm SP Medium Sand Poorly Graded Coarse Sand Moderately Wei ISorted Symmetrical Mesokurtic 1790+00 Berm Cresi SP Medium Sand Poorly Graded Medium Sand Moderately Weil Sorted Coarse Skewed Leptokurtic 1790+00 MHW SP Fine5and Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 17%+Oo MfL 5P Fine5and Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Mesokurtic 1790+00 MLW 5P Fine5ard Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1790+00 Trough SP Medium Sand Poorly Graded Coarse 5a rid Poorly Sorted Coarse Skewed Leptokurtic 1790+00 Bar SP Fine Sand Poorly Graded Medium Sand Moderately Sorted Coarse Skewed Leptokurtic 1790+00 -$ft SP Fi ne Sand Poorly Graded Fi ne Sand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 1790+00 .12 ft SP Fine Sand Poerly Graded Medium Sand Poorly Sorted Coarse Skewed Mesokurtic 1790+00 .16 ft SP FineSarid Poorly Graded Medium Sand Moderately Well Sorted Symmetrical Mesokurtic 1790+00 .20 ft SP Fine5arid Poorly Graded FineSarid Moderately Wei ISorted Strongly Coarse Skewed Leptokurtic 1790+00 .24ft SP Fine5arid Poorly Graded Fine Sand Moderately Wei Sorted Strongly Coarse Skewed Very Leptokurtic 1820+00 Dune SP Medium Sand Poorly Graded Medium Sand Moderately Wei Sorted Coarse Skewed Leptokurtic 1820+00 Dune Toe SP Fine5and Poorly Graded Medium Sand Moderately Wei ISorted Symmetrical Leptokurtic 1820+00 Berm SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Coarse Skewed Leptokurtic 1820+00 Be SP Medium Sand Poorly Graded Goa rseSand Moderately Sorted Coarse Skewed Mesokurtic 1820+00 MHW SP Fine5arid Poorly Graded Medium Sand We II Sorted Coarse Skewed Leptokurtic 1820+00 MTL SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1820+00 MLW SP Fi ne 5a rid Poorly Graded Medium Sand Moderately Wei l Sorted Goa rse Skewed Leptokuric 1820+00 Trough SP Medium Sand Poorly Graded Coarse 5a rid Poorly Sorted Strongly Coarse Skewed Leptokurtic 1820+00 Bar SP Fine Sand Poorly Graded Medium Sand Moderately Sorted Coarse Skewed Leptokurtic 1320+00 -8 ft SP Fine Sand Poorly Graded Fine Sand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1820+00 -12 ft SP Fine Sand Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1820+00 -16 ft SP Fine5arid Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1820+00 -20 ft SP Fine5arid Poorly Graded Fine Sand Moderately Well Sorted Strongly Coarse Skewed Leptokurtic 1820+00 .24ft SP Fine5arid Poorly Graded FirteSarid Moderately Sorted Strongly Coarse Skewed Leptokurtic 1840+00 Dune SP Fine5arid Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic 1840+00 Dune Toe SP Fine Sand Poorly Graded Medium Sand Moderately Wei ISorted Coarse Skewed Leptokurtic 1840+00 Berm SP Medium Sand Poorly Graded Medium Sand Moderately Wei Sorted Coarse Skewed Leptokurtic 1840+00 Be SP Medium Sand Poorly Graded Goa rseSand Moderately Sorted Coarse Skewed Leptokurtic 1840+00 MHW SP Fine Sand Poorly Graded Medium Sand Well Sorted Symmetrical Mesokurtic 1840+00 MR 5P Fi ne Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1840+00 MLW 5P Fi ne Sa rid Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokuric 1840+00 Trough SP Fi rre 5a rid Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Very Leptokurtic 1840+00 Bar SP FineSorid Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic 1840+00 -8ft SP Fine Sand Poorly Graded Fine Sand Moderately WelISorted Coarse Skewed Leptokurtic 1840+00 -12 ft SP Fine Sand Poorly Graded Fine Sand Moderately Well Sorted Strongly Coarse Skewed Leptokurtic 1840+00 -16 ft SP Fine5arid Poorly Graded FineSand Moderately Wei Sorted Strongly Coarse Skewed Very Leptokurtic 1840+00 -20 ft SP Fine5arid Poorly Graded FineSand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1840+00 .24ft SP Fine5arid Poorly Graded FineSand Moderately Wei Sorted Strongly Coarse Skewed Very Leptokurtic 1870+00 Dune SP Fine5arid Poorly Graded Medium Sand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1870+00 Dune SP Fine5and Poorly Graded Medium Sand Moderately Wei ISorted Symmetrical Leptokurtic 1870+00 Berm SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Coarse Skewed Leptokurtic 1870+00 Be SP Medium Sand Poorly Graded Medium Sand Moderately Wei Sorted Coarse Skewed Mesokurtic 1870+00 MHW SP Fine5arid Poorly Graded Medium Sand We II Sorted Symmetrical Leptokurtic VM+00 MR 5P Fi ne Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1870+00 MLW 5P Fine5and Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokuric 1870+00 Trough SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Coarse Skewed I-elotokurfic 1870+00 Bar SP Fine Sand Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic 1870+00 -8ft SP Fine Sand Poorly Graded Fine Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic 1870+00 .12 ft SP Fine Sand Poorly Graded Fine Sand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1870+00 .16 ft SP Fine Sand Poorly Graded FineSarid Moderately Well Sorted Strongly Coarse Skewed Leptokurtic 1870+00 -2o ft SP Fine5and Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1870+00 -24 ft SP Fine Sand Poorly Graded FineSand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic Coastal Science & Engineering 23 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 3.1b (continued). Buxton project area beach sediment characteristics (descriptive) in August 2019. See Attachment 1 for detailed frequency and cumulative frequency results of each sample. LSCS Description Wentworth Description 1990+00 Dune SF FineSand Poorly Graded Medium Sand Well Sorted Symmetrical Leptokurtic 1890+00 Dune SP Fine Sand Poorly Graded Medium Sand Moderately WeIISorted Symmetrical Leptokurtic 1890+00 Berm SP Medium Sand Poorly Graded Medium Sand Moderately Wel I Sorted Symmetrical Mesokurtic 1890+00 Bc SP Medium Sand Poorly Graded Medium Sand Moderately Sorted Coarse Skewed Mesokurtic 1890+00 MNW SP Fi ne Sand Poorly Graded Medium Sand WellSorted Symmetrical Leptokurtic 1890+00 NRL SP Medium Sand Poorly Graded Coarse Sa nd Poorly Sorted Strongly Coarse Skewed Very Leptokurtic 1890+00 MLW SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 18%+00 Trough SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Coarse Skewed Leptokurtic 1890+00 Bar SP FineSand Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic 18%-W -8ft SP FineSand Poorly Graded Medium Sand Moderately Sorted CoarseSkewed Leptokurtic 1890+00 -12ft SP FineSarid Poorly Graded FineSand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1890+00 -16ft SP Fine Sand Poorly Graded FineSand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1890+00 .20 ft SP Fine Sand Poorly Graded Fine Sand Moderately Wel I Sorted Strongly Coarse Skewed Leptokurtic 1990+00 •24ft SP Fine Sand Poorly Graded Fine Sand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 19W+00 Dune SP Fine Sand Poorly Graded Medium Sand Wellsorted Symmetrical Leptokurtic 19W+00 Dune SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Symmetrical Leptokurtic 19W+00 Berm SP Medium Sand Poorly Graded CoarseSarid Moderately Wel I Sorted Symmetrical Leptokurtic 19W+00 Bc SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Coarse Skewed Mesokurtic 19W+00 MNW SP Fine5and Poorly Graded Medium Sand Well Sorted Symmetrical Leptokurtic 19W+00 MfL SP Medium Sand Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 19W+00 MLW SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 19W+00 Trough SP FineSarid Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic 19W+W Bar SP FineSarid Poorly Graded Medium Sand Moderately Sorted CoarseSkewed Leptokurtic 19W+00 -8ft SP FineSarid Poorly Graded FineSand Moderately Well Sorted Coarse Skewed Leptokurtic 19W+00 -12ft SP Fine Sand Poorly Graded FineSand Moderately Wel I Sorted Goa rseSkewed Leptokurtic 19W+00 -16ft SP Fine Sand Poorly Graded FineSand Moderately Wel ISorted Coarse Skewed Leptokurtic 19W+00 -20 ft SP Fine Sand Poorly Graded FineSand Moderately Wel I Sorted Coarse Skewed VeryLeptokurtic 19DD+00 -24ft SP Fine Sand Poorly Graded Finesand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 1920+00 Dune SP Fine Sand Poorly Graded Medium Sand Very Well Sorted Symmetrical Leptokurtic 1920+00 Dune SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1920+00 Berm SP Fine Sand Poorly Graded Medium Sand we II Sorted Coarse Skewed VeryLeptokurtic 1920+00 Bc SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic 1920+0D MNW SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 1920+00 MfL SP Fine Sand Poorly Graded Medium Sand We I Sorted Symmetrical Leptokurtic 1920+00 MLW SP Medium Sand Poorly Graded Coarse Sa nd Moderately Sorted Strongly Coarse Skewed Leptokurtic 1920+00 Trough SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Coarse Skewed Leptokurtic 1920+W Bar SP Fine Sand Poorly Graded Medium Sand Moderately Sorted CoarseSkewed Leptokurtic 1920+DD -8ft SP Fine -Sand Poorly Graded FineSand Moderately WeIISorted Strongly Coarse Skewed Very Leptokurtic 1920+00 -12ft SP Fine Sand Poorly Graded Finesand Moderately Wel I Sorted Goa rseSkewed Leptokurtic 1920+00 -16ft SP Fine Sand Poorly Graded Finesand Moderately Wel ISorted Coarse Skewed Leptokurtic 1920+00 -20 ft SP Fine Sand Poorly Graded Finesand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 1920+00 -24ft SP Fine Sand Poorly Graded FineSand Moderately Wel ISorted Strongly Coarse Skewed Leptokurtic 1940+00 Dune SP FineSand Poorly Graded Medium Sand we II Sorted Symmetrical Leptokurtic 1940+00 Dune SP FineSand Poorly Graded Medium Sand WellSorted Symmetrical Leptokurtic 1940+00 Berm SP Medium Sand Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 1940+00 Bc SP Medium Sand Poorly Graded Medium Sand WellSorted Coarse Skewed Leptokurtic 1940+0D MNW SP Fi ne Sa nd Poorly Graded Medium Sand Well Sorted Symmetrical Leptokurtic 1940+00 MfL SP Fine Sand Poorly Graded Medium Sand Well Sorted Coarse Skewed Leptokurtic 1940+00 MLW SP Medium Sand Poorly Graded Coarse Sa nd Poorly Sorted Co rse Skewed Leptokurtic 1940+00 Trough SP Fin. -Sand Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1940+W Bar SP Fi ne Sand Poorly Graded Medium Sand Moderately Sorted Co rse Skewed Leptokurtic 1940+DD -8ft SP Fine Sand Poorly Graded Fine Sand Moderately Well Sorted Strongly Coarse Skewed Leptokurtic 1940+00 -12ft SP Fine Sand Poorly Graded FineSand Moderately Wei I Sorted Strongly Coarse Skewed VeryLeptokurtic 1940+00 -16ft SP Fine Sand Poorly Graded Fine Sand Moderate Well Sorted Strongly Coarse Skewed Very Leptokurtic 1940+00 -20 ft SP FirreSand Poorly Graded Fine Sand Moderately Sorted Strongly Coarse Skewed Leptokurtic 1940+00 -24ft SP FirreSand Poorly Graded FineSand Moderately Well Sorted Strongly Coarse Skewed Ve Leptokurtic 19W+00 Dune SP Fine Sand Poorly Graded Medium Sand we II Sorted Coarse Skewed VnLeptokurtic 19W+00 Dune SP Medium Sand Poorly Graded Medium Sand Moderately Wel I Sorted Coarse Skewed Leptokurtic 19W+00 Berm SP Medium Sand Poorly Graded Medium Sand we II Sorted Coarse Skewed Leptokurtic 1990+00 Be SP Medium Sand Poorly Graded Medium Sand Moderately Wel I Sorted Strongly Coarse Skewed Very Leptokurtic 1980+0D MNW SP Fine Sand Poorly Graded Medium Sand We I Sorted Symmetrical Leptokurtic 19W+00 MfL SP Fi rre Sa nd Poorly Graded Medium Sand Moderately Well Sorted Coarse Skewed Leptokurtic 19W+00 MLW SP Fine Sand Poorly Graded Medium Sand Moderately Well Sorted Strongly Coarse Skewed Leptokurtic 19W+00 Trough SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic 1980+W Bar SP Fi ne Sa nd Poorly Graded Medium Sand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 19W-W -8ft SP Fi ne Sand Poorly Graded Fi ne Sand Moderately Well Sorted Coarse Skewed Leptokurtic 19W+00 -12ft SP FirreSarid Poorly Graded FineSand Moderately Sorted Strongly Coarse Skewed Very Leptokurtic 19W+00 -16ft SP Fine Sand Poorly Graded FineSand Moderately Well Sorted coarse Skewed Leptokurtic 19W+00 -20 ft ISP Fine Sand Poorly Graded FineSard Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic 19W+00 •24 ft ISP Fine Sand Poorly Graded Fi ne Sand I Moderately Well Sorted I Coarse Skewed JVery Leptokurtic Coastal Science & Engineering 24 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 3.2. Mean grain size (mm) for August 2019 beach samples in the Buxton project area. Station Dune Dune Toe Berm BC MHW MTL I MLW 1760+00 0,389 0.342 0.312 0.324 0.357 0.292 0.914 1790+00 0.367 0.410 0.646 0.465 0.311 0.335 0.302 1820+00 0,430 0.374 0.563 0.511 0.317 0.361 0.305 1840+00 0.411 0.387 0.490 0.528 0.319 0.342 0.297 1870+00 0,407 0.377 0.538 0.453 0.313 0.363 0.297 1890+00 0.333 0.378 0.494 0.485 0.297 0.629 0.306 1900+00 0,379 0.419 0.662 0.549 0.318 0.459 0.300 1920+00 0.371 0.387 0.393 0.365 0.364 0.370 0.522 1940+00 0,348 0.373 0.449 0.435 0.339 0.359 0.549 1980+00 0.399 0.441 0.481 0.451 0.309 0.392 1 0.318 Average 0.383 0.388 0.492 0.451 0.324 0.382 1 0.380 Station Trough Bar -8 ft -12 ft -16 ft -20 ft -24 ft 1760+00 0.335 0.622 0.226 0.218 0.213 0.213 0.195 1790+00 0,509 0.310 0.215 0.295 0.378 0.230 0.205 1820+00 0.533 0.404 0.232 0.271 0.261 0.244 0.196 1840+00 0,391 0.311 0.227 0.223 0.212 0.200 0.158 1870+00 0.488 0.373 0.225 0.234 0.237 0.306 0.168 1890+00 0,470 0.340 0.289 0.227 0.217 0.223 0.192 1900+00 0.338 0.335 0.235 0.218 0.203 0.203 0.192 1920+00 0,466 0.314 0.206 0.223 0.215 0.194 0.225 1940+00 0.328 0.318 0.248 0.211 0.211 0.235 0.191 1980+00 0.452 0.322 0.221 0.219 0.211 0.216 0.183 Average 0.425 0.357 0.232 0.233 0.232 0.225 0.189 Coastal Science & Engineering 25 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 3.3. [UPPER] Arithmetic mean grain size and related statistics based on 14 samples per transect (n=140). [LOWER] Arithmetic mean grain size and related statistics by sample position for 10 transects along the Buxton project area in August 2019. Station Averages -August 2019 Mean Gravel Granules Station �rnrn� STD (mrn) Shell �9roj ��} �� Fines (9'o) 1760+00 0,319 0,515 6.6 0.1 2.0 0.0 1790+00 0.338 0.557 6.8 0.0 0.9 0.0 1820+00 0.334 0.550 6.8 0.0 1.2 0.0 1940+00 0,303 0,539 8.4 0.3 0.8 0.1 1870+00 0,325 0,549 8.2 0,0 13 01 1890+00 0.329 0.540 7.1 0.1 1.3 0.0 1900+00 0.320 0.546 6.7 0.0 0.8 0.0 1920+00 0,314 0,578 6.6 0.0 1.1 0.1 1940+00 0,312 0,568 7.9 0,0 12 0,0 1980+00 0.313 0.573 6.5 0.1 0.9 0.0 V[s Beach 0.400 0.635 7.1 0.0 0.7 0.0 All Beach 0.321 0.550 7.2 0.1 1.1 0.0 Cross -Shore Averages - August 2019 Mean Gravel Granules Sample �rnrn� STD iimrnj Shell �9ro� �� Fines (9ro) Dune 0,383 0,698 4,8 0.0 0.4 0,0 Dune Toe 0,388 0,682 5,5 0.0 0.2 0,0 Berm 0,492 0.596 9.9 0.0 1.5 0.0 BC 0,451 0.619 9.0 0.0 1.1 0.0 MHW 0.324 0.724 5.4 0.0 0.1 0.0 MTL 0.382 0.603 8.2 0.2 0.8 0.0 MLW 0,380 0,532 10,0 0,0 2.5 0,0 Trough 0,425 0.447 12.3 0.5 4.7 0.0 Bar 0,357 0.494 9.9 0.1 3.4 0.0 -8 ft 0.232 0.645 4.0 0.0 0.3 0.0 -12 ft 0.233 0.603 4.1 0.0 0.3 0.0 -16 ft 0,232 0,627 52 0,0 0.2 0,0 .20 ft 0,225 0.637 5.8 0.0 0.2 0.1 .24 ft 0,188 0.635 6.2 0.0 0.2 0.3 Vis Beach 0.400 0.635 7.1 0.0 0.7 0.0 All Beach 0.321 0.550 7.2 0.1 1.1 0.0 Coastal Science & Engineering 26 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 1.000 0.900 0.800 0.700 E E 0.600 m Ln 0.500 m C7 v 0.400 0.300 0.200 0.100 0.000 Buxton Beach Mean Grain Size August 2019 —Dune Dune Toe Berm BC —*—MHW --o--MTL tMLW tTrough tBar -8ft --)412ft —*--16ft t-20ft t-24ft 1760+00 1790+00 1820+00 1840+00 1870+00 1890+00 1900+00 1920+00 1940+00 1980+00 FIGURE 3.1. Mean grain size by station and sample position in August 2019. 0.600 0.550 0.500 E E 0.450 v v E 0.400 a LE 0.350 r m v 0.300 0.250 0.200 0.150 Buxton Beach Sediment Grain Sizes - August 2019 ♦Mean ......... -1a-----+1a fine sand i Dune Dune Berm BC MHW BF LTT Trough Bar -8 ft -12 ft -16 ft -20 ft -24 ft Toe Cross -Shore Position FIGURE 3.2. Mean grain size by sample position based on 14 samples per station. Coastal Science & Engineering 27 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Mean Grain Size by Station, Buxton August 2019 0.350 0.340 • 0.330 • • E in 0.320 0.310 v 0.300 0.290 - 0.280 1760+00 1790+00 1820+00 1840+00 1870+00 1890+00 1900+00 1920+00 1940+00 1980+00 Station FIGURE 3.3. Sediment mean grain sizes for 10 transects in the Buxton area in August 2019. The trend shows relative uniformity in the medium sand range (0.3-0.4 mm). Variations in the underwater zones led to the minimum at Station 1840+00, but the difference is not significant from adjacent profiles. Buxton Beach Percent Shell, Gravel (4-76 mm), and Granules (2-4 mm) by Station August 2019 --*--Shell (%) Gravel (%) Granule (%) 10.0 9.0 8.0 7.0 L a 6.0 3 a 5.0 v `a 4.0 a 3.0 2.0 1.0 0.0 1760+00 1790+00 1820+00 1840+00 1870+00 1890+00 1900+00 1920+00 1940+00 1980+00 FIGURE 3.4. Percent shell, granules (2 to 4 mm), and gravel (4 to 76 mm) by station in August 2019 along the Buxton project area. Buxton village encompasses stations 1880 to -1920. Coastal Science & Engineering 28 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 3.2 Comparative Sample Statistics (2019 vs 2014 before the Initial Restoration) CSE sampled the project beach in August 2019 in preparation for the proposed renourishment project, and in October 2014 for the initial 2017 beach restoration project. Table 3.4 shows mean grain size, percent shell, and percent gravel at ten stations. The August 2019 samples exhibited mean grain sizes in the range of -0.35 to 0.5 mm, finer than the October 2014 samples with means in the range of 0.45 mm to 0.555 mm. Shell content was similar between both sampling periods (-7 to 8 percent), while the combined gravel and granule percentage (eg>2 mm) was lower in 2019 (-1.8 percent in August 2019 compared to -6.6 percent in October 2014). This latter result confirms that shell material on the visible beach observed in August 2019 is predominantly small fragments <2 mm diameter (ie - within sand size ranges). The results in Tables 3.1 and 3.2 suggest surficial sand sizes in the Buxton project area (visible beach) fluctuate between the upper limit of medium sand (0.4-0.5 mm) and the lower limit of coarse sand (0.5-0.8 mm). Swift et al (1971) reported finer sediment in the Buxton area (Transect "11") with berm samples testing around 0.3 mm. A "typical" mean grain is likely to fall between 0.4 mm and 0.6 mm in diameter and probably vary with the season —finer during accretional periods and coarser during erosional periods. More sampling would be required to confirm this observation. Southern North Carolina beaches, as well as a majority of beaches that have been nourished, are dominated by finer sand (-0.25-0.3 mm typical) and are less likely to exhibit as large a difference in "native" sand sizes from season to season. Beaches of New England, where glacial moraines have yielded broad mixtures of gravel and sand, commonly exhibit wide grain -size variability (Colony 1932, Taney 1961). Coastal Science & Engineering 29 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 3.4. Native subaerial beach sediment sample mean grain -size, shell percentage, and gravel percentage for samples collected in [UPPER] October2014 and [LOWER] August 2019. Station Averages -October 2014 Station can STD (mm) Shell 9'a} Gravel Fines (%) 1760+00 0,442 0,453 6.6 4.8 0.1 1790+00 0,495 0.444 6.8 5.1 0.1 1820+00 0.499 0.420 6.8 7.3 0.0 1840+00 0,544 0.376 8.4 8.9 0.1 1870+00 0.476 0.386 8.2 9.1 0.2 1890+00 0.430 0.415 7.1 5.2 0.3 1900+00 0.440 0.405 6.7 7.1 0.0 1920+00 0.492 0.410 6.6 7.1 -0.1 1940+00 0.457 0.441 7.9 5.7 0.1 1980+00 0.403 0.407 6.5 5.7 0.3 Vis Beach 0.582 0.598 8.3 1.6 0.0 All Beach 1 0.465 0.413 1 7.2 6.6 0.1 Station Averages - August 2019 Mean Gravel Granules Station STD (mrn) Shell Fines (9ra) 1760+00 0.319 0.515 6.6 0.1 2.0 0.0 1790+00 0.338 0.557 6.8 0.0 0.9 0.0 1820+00 0.334 0.550 6.8 0.0 1.2 0.0 1940+00 0.303 0.539 8.4 0.3 0.8 0.1 1870+001 0.325 0.549 8.2 0.0 1 1.3 0.1 1890+00 0.329 0.540 7.1 0.1 1.3 0.0 1900+00 0.320 0.546 6.7 0.0 0.8 0.0 1920+00 0.314 0.578 6.6 0.0 1.1 0.1 1940+00 0.312 0. 5 68 7.9 0.0 1.2 0.0 1980+001 U.313 0.573 6.5 0.1 1 0.9 0.0 Vis Beach 0.400 0.635 7.1 0.0 0.7 0.0 All Beach 0.321 0.550 7.2 0.1 1.1 0.0 Coastal Science & Engineering 30 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 3.3 Selection of Native Mean Grain Size According to North Carolina sediment standards for beach nourishment, the native sand should be determined based on an arithmetic average of means for all cross -shore sand samples. This simple calculation yields a mean and standard deviation of 0.341 mm and 0.633 mm (respectively) for the August 2019 samples (see Table 3.3). However, grain -size distributions are non -linear, so an average of mean grain sizes does not equal the mean grain size of the same collection of samples mixed in a bin, then tested for grain -size distribution (and resulting mean). It can be shown that a more realistic mean for a group of samples (composite mean) can be computed using the results of each sample split. CSE combined results of all subsamples retained on each sieve to compute the total weight by each size class for a designated number of samples, the total weight of all subsamples, and the corresponding proportions of the total. Data were normalized to the weight of each sample. This yields means and standard deviations via the method of moments, analogous to combining all physical samples into one big sample for sieving by standard lab methods. All 140 samples (10 stations, 14 cross -shore samples each station) yielded a mean and standard deviation of 0.321 mm and 0.550 mm (respectively), marginally lower than the arithmetic mean. These results are skewed by relatively small grain sizes from -8 ft to -24 ft water depth, which averaged 0.222 mm. If only the visible beach samples (from the dune to MTL) are included, the resulting mean and standard deviation are 0.400 mm and 0.635 mm (respectively). Under the Wentworth size classification, the composite means are in the medium sand -size range (0.25-0.5 mm) for calculations involving all samples above -8 ft water depth. The subaerial samples have a composite mean in the medium sand range (0.25-0.5 mm). Few nourishment projects along the U.S. East Coast have involved such coarse sand and such wide admixtures across the profile. These ranges slightly exceed those observed at Nags Head (USACE 2010, CSE 2019) and significantly exceed Bogue Banks (CSE 2001, 2004), where composite mean grain size was-0.3-0.35 mm. Beach sediments in the southern part of North Carolina and the northern part of South Carolina (the Grand Strand) are typically in the range of 0.2-0.3 mm with less cross -shore variation (eg - USACE 1993). Coastal Science & Engineering 31 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina — THIS PAGE INTENTIONALLY LEFT BLANK — Coastal Science & Engineering 92 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 4.0 BORROW AREA INVESTIGATIONS Two potential borrow areas were evaluated for the proposed Buxton renourishment project: 1) Offshore area near "Diamond Shoals" as illustrated in Figure 2.5. 2) The Proposed borrow area as illustrated in Figures 1.1 and 2.5. Other potential borrow areas have been previously evaluated by CSE (2005, 2017) and others (eg - Dolan & Lins 1986), and were rejected because of transportation distances and costs (eg - upland - off -island - borrow pits), insufficient quantities available (on -island borrow pits), sediments too fine (eg - Pamlico Sound deposits), or other environmental considerations [eg- NPS or USFWS protected areas within Cape Hatteras National Seashore (CAHA) or Pea Island, such as the accreted lands of Cape Point (used for nourishment in the 1971 and 1973 projects -NIPS 1980)]. Offshore Area Near "Diamond Shoals" — This area was delineated because of its proximity to Diamond Shoals, where accumulations of sand form a series of prominent ridges extending miles out into the Atlantic Ocean. Previous studies by Boss & Hoffman (2000) and CSE (2013) indicated this area may have beach -quality material. Water depths in this area range from -30 ft to -45 ft and are therefore considered well outside the normal limits of the beach zone. Deeper water (-50 ft) exists between the shoal and longshore bar over one mile landward of the sand search area. Based on these preliminary data points, in August 2020, CSE outlined a sampling scheme wherein 20 borings would be collected at -2,000 ft spacing. Ideally, this area could have provided enough beach -quality sediment to constitute multiple renourishment projects at Buxton. However, the preliminary borings indicated the area does not contain beach -quality sediment similarto the sand quality of the Buxton beach. Proposed Borrow Area — The proposed borrow area was considered because of its proximity and similar depths to the borrow area used in 2017. None of the Boss & Hoffman (2000) borings are within the proposed area, but four borings collected by CSE for the 2017 project are in this area. These borings indicated the area contained beach -quality sediment without any apparent hard bottom habitats. Water depths in this area range from -30 to -50 ft and are well outside the normal limits of the beach zone at Buxton. The proposed borrow area is located atop a ridge oriented southwest -to -northeast, with maximum elevations towards the middle and southern portions of the proposed borrow area (Figs 4.1 and 4.2). The following sections of the report summarizes the results and evaluation of the proposed borrow source. Coastal Science & Engineering 33 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina rs 31o^w MW Boring Easting(X) Northing(Y) BUX-35 3049560 567971 BUX-36 3051250 568625 BUX-37 3052470 567817 BUX-38 3051860 566236 BUX-39 3050910 566248 BUX-40 3049250 566375 BUX-41 3050080 567469 BUX-42 3050460 568300 BUX-43 3051770 568156 BUX-44 3051330 567308 • CSE April2021 • CSE October2020 • CSE August 2020 ° CSE 2017 — Borrow Area transects Proposed Borrow Area 2017 Borrow Area 2017 no -work buffers Bathymetry (it NAVD) High : -30 Low: -50 0 2,000 4,000 Feet RM • ra ct 2 • 0 0 • • 49 • Transect3 Bux-43 _• Bux-37 0 Bux-44 Transect 1 • • ixe-39 Buz-38 N E s FIGURE 4.1. Location of proposed borrow area and relevant borings off Buxton. Three red lines labeled "Transect 1," etc. are the locations of bathymetric profiles shown in Figure 4.2. Coordinates of individual borings are given in NC State Plane Projected Coordinate System, in Easting and Northings (feet). Coastal Science & Engineering 94 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina -30 Transect 1 (intersections shown) -32 -34 WEST T ra nsect 3 EAST -36 -38 r -40 a N cl -42 -44 -46 -48 approximate borrow area limits -50 1000 ft 2000 ft 3000 ft -30 Transect 2 (intersections shown) -32 -34 WEST EAST -36 -38 r L -40 Q N -42 Transect3 -44 -46 -48 approximate borrow area limits -50 1000 ft 2000 ft 3000 ft -30 Transect 3 (intersections shown) -32 -34 -36 Tra nsect 2 ---38 s -40 a N 0-42 -44 Transectl 46 -48 approximate borrow area limits -50 NORTH SOUTH 1000 ft 2000 ft 3000 ft FIGURE 4.2. Bathymetric profiles measured along transects as shown in Figure 4.1. The borrow area is situated atop a-3,000-ft ridge with a maximum elevation of (-)-32 ft NAVD. The long axis of the ridge trends north-northeast, and drops slowly to a depth of -50 ft along the northern boundary of the proposed borrow area. Along either side of the ridge, following its short axes (Transectl 1 and 2), the ridge slopes down to a depth of -48 ft. Coastal Science & Engineering 35 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina The October 2020 samples, obtained via CSE's proprietary coring methodology, were collected to an average depth of 5.1 ft. The April 2021 borings (ie - Buxt-35 to Bux-44) were collected to a uniform depth of 10 ft via vibracore by subconsultant AVS*. The October 2020 samples are exploratory and were not collected with the intention of delineating a final cut depth and borrow area boundaries; the April 2021 samples were collected with those goals in mind. As such, CSE's selection of a borrow area mean gran size (Section 4.1) is based on the 10-ft April 2021 samples. Figure 2.7 presented one of the 10-ft cores (Bux-44) situated in the center eastern quarter of the proposed borrow area. For the most part, sediments in each core were light tan or grayish tan in color and consisted of various mixtures of medium to coarse sand with minor amounts of shell material and fine -sized grains (<0.125 mm diameter). Munsell color numbers were interpreted for each sample. Granules and "pea" gravel occurred in some cores. Core logs and photos of each core are provided in Attachment 2. The core logs in Attachment 2 document visual breaks in sediment type. In general, the CSE cores tend to have only trace amounts of mud. A couple of cores terminated in muddy layers, particularly sites close to the western side of Area C or in deeper water. Visually, the appearance of a majority of core sediments was similar to the beach. Cores contained similar mixtures of sand, granules, pea gravel, and shell fragments found on the beach along Buxton with only trace fines except for an occasional thin mud lens, as noted (see Attachment 2). Shell percentages for individual samples range from 3.3 percent to 39.5 percent, while gravel (>2 mm) percentages were in the range of 0.0 to 28.4 percent. Approximately 10 percent of the samples (3 out of 30) tested >25 percent shell, whereas 90 percent of the samples ranged between -3 and 25 percent shell. The low statistical agreement between shell and gravel percentages (R2Z0.5) confirms that shell material is predominantly small particles under 2 mm in diameter. Such material is referred to as shell has and often is composed of Donax sp. Shell fragments because these small, thin -walled shells break easily under the action of waves in the surf zone. Core photo logs (Attachment 2) further confirm nearly all samples contained negligible concentrations of coarse (>2 mm) shell material. Grain -size distributions for each core sample are given in Attachment 3. 'AVS -American Vibracore Services, a division ofAmdrill Inc. based in Brooksville FL using the vessel R/V Thunderforce Coastal Science & Engineering 36 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Table 4.1a-b lists the key descriptive statistics for each core sample along with the Unified Soil Classification System (USCS) and Wentworth description and the interpreted Munsel color. The unweighted arithmetic mean grain size for all samples is 0.45 mm (medium sand size comparable to the overall average mean grain size for the beach as discussed in Section 3.0). The unweighted arithmetic mean shell, gravel, and granule percentages for all 10-ft cores (30 samples) are 15.1 percent, 0.3 percent, and 6.2 percent (respectively). For purposes of evaluating sediment quality within the sand search area, CSE computed weighted composite statistics to 6 ft, 8 ft, and loft depths below the seafloor. Under operational conditions, dredges excavate to a particular depth, mixing sediments before discharge along the beach. The results of random length core samples were weighted proportionally over the applicable section. This yields a "composite" mean grain size, shell content, and gravel content for each designated interval. Similarities between the results for each composite are a measure of the down -core consistency of the sediments. A goal of the design is to leave sediments at the base of the excavation, which are similar in size and character to the removed sediments. This improves the chance for rapid recovery of benthic organisms (Van Dolah et at 1998, NPS 2012). Table 4.2a-b provides key statistics for each core to the composited lengths of 6 ft and 8 ft. The composite grain -size distributions for each set of data are given in Attachment 3B. Table 4.3 provides weighted mean sizes, standard deviations, shell percentages, and gravel percentages for individual samples and weighted composite samples. The number of borings included in each composite depth is a function of the recovery length for each individual core sample listed in Table 4.1a. For instance, Bux-22 was obtained to a depth of 6.3 ft below the seafloor. Therefore, that boring is included in the 6 ft composite statistics but is not included in the 8-ft composites. All the borings collected in April 2021, which constituted the final round of sample collection for the proposed borrow area, were obtained to a depth of 10 ft below the seafloor. These are described in greater detail in the following section. Coastal Science & Engineering 37 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 4.1a. Proposed borrow area sediment characteristics (statistical measures) for 21 cores (58 samples obtained in October 2020 and April 2021). See Attachment 3A for detailed frequency and cumulative frequency results of each sample. Method of Moments Falk Graphical Method Gravel Granules DryFines Shell %} Mean STD Skew Kurt C� Mean Std mm Mean STD ISTD Skew Kurt Sample Interval BIJX-21.1 0-2.5 0.89 0.55 -0.39 9.40 0.539 0.683 0.79 036 GAO -0.17 1.34 0.0 1.5 0.0 17.2 B IJx-21.2 2S-3.3 0.92 o.fi1 -0.50 9.66 0.529 0.657 0.83 036 0.42 -012 1.56 0.0 2A 0.1 15.8 BIJx-22.1 0-3.6 0.96 OA6 -1.77 6AO 0.513 0514 0.95 031 0.86 -0.49 1.75 0.2 6D 0.0 19.9 BIJx-22.2 3.6.6.3 1.69 031 -1.22 8A3 0.309 0.702 1.60 0.41 0.44 -0.14 1.14 0.0 03 O.0 8.4 BIJx-23.1 0-2.2 1.39 ass -1.37 4A8 0.392 0556 133 OA6 038 -OAO 139 0.0 35 0.0 11.4 BIJx-23.2 22-5.2 164 034 -1.S5 633 0.321 0.599 1.58 037 0.64 -035 131 0.0 L6 o.0 10.5 BIJx-23.3 52-5.9 2.29 OA8 -1.58 6A8 0.204 0.508 2.24 031 0.84 -037 1.40 0.0 25 as 8A BIJx-24.1 0-1.8 0.01 1.13 -0.94 2AS 0.991 OASS -0.14 120 1.20 -0.fi0 1.10 0.0 203 0.0 3DA BIJx-24.2 19.4.3 0.87 OA3 -0.37 739 0.547 0.645 0.77 OA4 0.51 -010 1.48 0.0 21 OA 173 BIJx-24.3 43-5.7 log 030 o.fi1 7A2 0.470 0.614 0.93 OA4 0.51 -0.16 1.37 0.0 1.1 03 103 BIJx-25.1 0-1.4 OA6 1.01 -1.71 SA8 0.549 OA98 0.85 035 0.91 -030 162 0.0 71 0.0 211 B IJx-25.2 IA-5.0 1.32 OA6 -0.fi6 7A5 0.401 1 0.727 1.21 0.41 0.41 -0.17 1.03 0.0 0.2 0.0 14.0 BIJx-25.3 5A-7.2 1.34 031 -1.04 7.02 0.394 0.704 1.25 0.46 OAS -0.12 0.99 0.0 0.4 0.0 12.8 BIJx-26.1 0-1.4 0.52 114 -0.81 2.83 0.699 OA24 0.41 132 1.3D -OA3 1.01 0.0 14.6 0.0 28.9 BIJx-26.2 1A-2.7 -0.20 1 137 -0.53 1 2.42 1.146 0336 -039 1A1 1.75 -01-3 0.94 73 21.1 0.0 37A BIJx-26.3 2.7-3.9 163 032 -0.87 6.85 0.162 0.605 2.54 OA-4 OAS OD6 1.32 0.0 0.2 23 65 BIJx-27.1 0-1.9 032 117 -1.63 7.01 0.607 OA15 0.74 OA7 1.11 -035 2.56 4.5 3.6 0.1 17.1 BIJx-27.2 1.9-3.3 OX 134 0.33 4.01 0.587 0395 0.53 OA7 1.25 -0.04 2.09 0.0 8.2 1.1 343 BIJx-27.3 33-5.0 2.11 1.44 -0.29 2.49 1 0.232 0309 2.08 134 1.48 0.03 0.95 O.O 33 13.4 12.9 BIJx-28.1 0-3.3 0.52 1.OS -1.21 4.17 0.696 OA72 0.46 OA4 1.09 -0.45 1.51 0.0 10.8 0.0 24.4 BIJx-28.2 33-6.3 0.64 1.05 -0.97 4.07 0.641 OA82 0.56 OA6 1.01 -034 1.17 0.0 8.4 OA 27.5 BUX-29.1 0-2.0 1.45 0A1 -1.30 SAO 0.367 0.572 1.18 OA2 032 -033 1.38 OD 2.6 OD 73 BLDC-29.2 2A-4.1 L23 1.01 -165 717 0.426 OA96 1.18 038 0.86 -01-3 1 1.23 0.7 1 33 OA 151 BUX-29.3 4.1-5.0 3.37 0A5 -1.26 4.89 0.097 0.553 3.29 0A1 036 -050 0.85 OD 0.1 22.1 7.0 BUX-30.1 0-1.9 0.97 032 -038 436 0.510 0.608 0.88 OA4 OAS -014 1.22 OD 2.1 0.0 16.0 BUX-30.2 1.9-2.5 2.20 L60 -0.59 310 0.218 0330 2.20 L63 1.56 0.04 0.86 OD 43 20.5 16.1 BUX-31.1 0-1.9 2.09 ass -0.32 1 6.94 1 0.235 0.682 1 1.96 0.41 OA7 a.a5 1.26 OD 0.1 OA 43 BUX-31.2 1.9-2.9 3.01 1.15 -1.01 3.97 0.124 OA49 2.93 L04 1.05 -0.12 0.91 OD 0.3 27A 13.0 BUX-35.1 0-2.3 038 OA2 OX SA8 0.582 0.528 0.58 0.fi1 0.82 -099 1.99 OD 4.1 OA 25.2 BUX-35.2 23.4.6 1.45 L07 -DAD 3A5 0.M7 OA76 133 OA2 1.02 -0.01 1.18 OD 3.2 23 18.1 BIJx-35.3 4.6-10 2.13 038 -161 737 0.229 0.669 2.06 OA8 0.51 -017 1 1.09 0.0 1 0.2 0.0 33 BIJx-36.1 0.6.2 1.90 1.26 -0.90 3.36 0.268 OA17 1,83 1.11 1.22 -OA3 1.20 0.0 4.9 2.5 9.6 BIJx-36.2 62-8.4 157 137 -0.19 1.88 0.168 0387 2.42 1.49 1.32 0.05 0.62 0.0 0.1 25.5 20.4 BIJx-36.3 8A-10 167 OA3 -OA3 5.03 0.314 0.524 1.55 033 0.81 -0.08 L31 0.0 1.7 3.4 43 BIJx-37.1 0-3.0 1.02 1A7 -0.80 1 2.72 1 0.493 0273 1 0.82 1.99 2.00 -032 1.11 2.7 15.5 1.8 112 BIJx-37.2 3A-7.0 0.66 131 0.39 1.93 0.632 0352 0.53 139 1.59 0.19 033 0.0 13A 1.0 39.5 BLM-37.3 7A-10 2.58 137 -0.21 1.90 0.168 0387 2.43 1.49 1.32 0.04 0.fi2 OD OD 25.0 11.0 BLM-38.1 0-5.6 0.80 OA2 0.82 SA6 0.574 0.530 0.60 059 0.81 -0.04 107 OD 3A 0.9 9.6 BUX-38.2 5.6-10 1.43 1.07 -0.10 3A4 0.371 OA77 L32 OA3 1 1.03 0.00 1 1.18 OD 31 21 13A BUX-39.1 0.6.0 039 0.91 OX SA6 0.579 0.531 0.59 039 0.8U -099 1.93 OD 3A OA 14A BUX-39.2 6A-8.3 039 136 O-M L90 0.579 0.339 0.65 1A2 163 0.13 033 OD 131 1A 233 BUX-39.3 83-10 038 OA2 030 5.41 0.583 0.529 0.58 OA4 OAS -0.07 1.93 OD 3A as 81 BUX-40.1 0-3.2 OAS 135 0.23 1 1.11 1 0.730 0392 0.42 SAS 161 031 OX 0.0 163 3.4 24.1 BIJx-40.2 32-9.6 0.80 OA2 0.84 5.90 0.575 0.530 0.60 039 0.82 -0.03 2.12 0.0 3A 0.8 IDA BIJx-40.3 9.6-10 2.38 136 -0.12 2.03 0.192 0391 2.27 132 1.34 0.11 OA6 0.0 OA 16.9 22.6 BIJx-41.1 0-1.7 0.66 OA8 -1.85 -2.82 0.633 0.626 0.57 039 033 -0.20 1.63 0.0 4.0 -2.0 16.0 BIJx-41.2 1.7-3.0 1.41 1D6 -0.15 3.62 0.377 OA80 131 0.92 1.01 -0.02 1.16 0.0 3.3 1.8 14.1 Bux-41.3 2.0-7.0 0.65 OA7 -2.07 -386 0.639 0.628 0.56 OW 0.74 -0.20 1.62 O.0 4.2 -2.0 133 Box-41.4 7A-10 0.62 1.47 0.37 1.88 0.650 0.360 0.49 139 1.57 o21 0.73 0.0 14.0 0.4 173 BIJx-42.1 0-3.0 0.61 199 -1.50 4A9 0.657 OA70 0.52 OA2 1.06 -O.fi1 1.96 0.0 13.2 0.0 19.7 BIJx-42.2 3.0-6.5 1.19 OA3 0.22 1 634 1 0.440 0.646 1.06 OA8 0.52 -OD6 1.25 0.0 0.5 0.2 12.4 BIJx-42.3 65A.5 2.51 OS9 -1.29 SA1 0.176 0.540 235 033 0.81 -0.41 1.92 0.0 0.7 16 5.6 BIJx-43.1 0-2.9 0.93 OS3 -035 333 0.524 0.562 0.86 037 0.82 -016 1.23 0.0 4.2 0.0 20.6 BUX,U2 2.9-5.0 OA8 137 -0.83 337 0.626 0337 0.49 1 133 1.59 1 -033 1 131 31 133 1.7 273 BI➢443.3 5.0-7.6 OA9 139 034 2A6 0.712 0332 034 1A4 1.70 1 01-3 1 0.89 0.0 203 1A 31.4 BIJx-43.4 7b-10 2.38 138 -0.98 3A8 0.192 0384 239 125 1.42 235 1.47 0.0 5.1 11.4 9.fi elA(-44.1 14.1 1.1 137 -1.37 459 0.557 0.386 tl.8fi 1.10 1.33 -UA5 1.48 23 85 0.0 253 B IJx-442 1 6A-10 1.28 OS2 -OA-3 538 0.413 0366 1.18 1 GAS 032 1 -010 1 1.22 0.0 25 0.7 1 123 Coastal Science & Engineering 38 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 4.1b. Proposed borrow area sediment characteristics (descriptive) for 21 cores (58 samples obtained in October 2020 and April 2021). See Attachment 3A for detailed frequency and cumulative frequency results of each sample. sample Interval USCS Description Wentworth Desciprtion BUX-21.1 0.23 SP Medium Sand Poorly Graded Coarse Sand Moderately Well Sorted Symmetrical Very Leptokurtic BUX-212 2.5.59 SP Medium Sand Poo rly Graded Coa rse Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic BUX-22.1 0.3.6 SP Medium Sand Poo rly Graded Goa rse Sand Moderately Sorted St ro ngly Coa rse S kewed Leptokurtic BUX-222 3.6.6.3 SP Fine Sand Poo rly Graded Medium Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic BUX-23.1 62.2 SP Fine Sand Poorly Graded Medium5and Moderately Sorted St ro ngly Coa rse 5 kewed Leptokurtic BUX-232 22-5.2 SP Fine Sa nd Poorly Graded Medium Sand Moderately Sorted St ro ngly Coa rse 5 kewed Leptokurtic BLJX-233 52-5.9 SP Fine Sa nd Poo rly Graded Fine Sa nd Moderately Sorted St ro ngly Coa rse S kewed Leptokurtic BUX-24.1 0.1.8 SP Medium Sand Poorly Graded Co. rse Sand Poorly Sorted Co. rse Skewed Mesokurtic BUX-242 1.8.4.3 SP I Medum Sa nd PoorlyGraded Coarse Sand Moderately Wel l Sorted Symmetrical Very Leptokurtic BUX-243 43-5.7 SP Medum Sand Poorly Graded MedumSand Moderately Sorted Fine Skewed Very Leptokurtic BUX-25.1 0-1.4 SP MedumSand PoorlyGraded Coarse Sand Poorly Sorted St ro ngly Coa rse S kewed Leptokurtic BUX-252 IA-5.0 SP Fine Sa nd Poorly Graded MedumSand Well Sorted Coa rse Skewed Very Leptokurtic BUX-253 5.0-7.2 SP Fine Sa nd PoorlyGraded MedumSand Moderately Wel l Sorted Coa rse Skewed Leptokurtic BUX-26.1 0-1.4 SP Medium Sand Poorly Graded Co. rse Sand Poorly Sorted Co. rse Skewed Mesokurtic BUX-262 IA-2.7 SP MedumSand PoorlyGraded Very Coa rse Sand Poorly Sorted Coa rse Skewed Platykurtic BUX-263 2.7-3.8 SP Fine Sa nd Poorly Graded Fine Sa rd Moderately5orted Coa rse Skewed Le tokurtic BUX-27.1 0-1.9 SP I Medum Sa nd PoorlyGraded Coarse Sand Poorly Sorted St ro ngly Coa rse S kewed Leptokurtic BIJX-272 1.9-3.3 SP MedumSand Poorly Graded Goa rse Sand Poorly Sorted Symmetrical Leptokurtic BIJX-273 33-5.0 SP Fine Sa nd PoorlyGraded Fine Sand Poorly Sorted Symmetrical Platykurtic BUX-28.1 0-3.3 SP MedumSand PoorlyGraded Coarse Sand Poorly Sorted Coa rse Skewed Leptokurtic BIJX-282 33-6.3 SP MedumSand PoorlyGraded Coarse Sand Poorly Sorted Coa rse Skewed Leptokurtic BUX-29.1 0-2.0 SP Fine Sa nd PoorlyGraded MedumSand Moderately Sorted St ro ngly Coa rse S kewed Leptokurtic BLJX-292 2.0.4.1 SP MedumSand PoorlyGraded MedumSand Poorly Sorted St ro ngly Coa rse S kewed Leptokurtic BLJX-293 4.1-5.0 SM Fine Sa nd PoorlyGraded Very Fine Sa nd Moderately Sorted Coa rse Skewed Leptokurtic BUX30.1 0-1.9 SP I Medum Sa nd Poorly Graded Coarse Sand Moderately Sorted Coa rse Skewed Leptokurtic BLJX302 1.9-2.5 SP Fine Sa nd Poorly Graded Fine Sa nd Poorly Sorted Coa rse Skewed Mesokurtic BUX-31.1 0.1.9 SP Fine Sa nd Poo rly Graded Fine Sa nd Moderately Wel l Sorted Symmetrical Leptokurtic BLJX312 1.9-2.9 SP-SM Fine Sa nd Poorly Graded Very Fine Sa nd Poorly Sorted Coa rse Skewed Leptokurtic BUX-35.1 0-2.3 SP MedumSand PoorlyGraded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BLJX-352 23.4.6 SP Fine Sa nd PoorlyGraded MedumSand Poorly Sorted Symmetrical Mesokurtic BUX353 4.6-10 SP Fine Sa nd Poorly Graded Fine Sa nd Moderately Wel l Sorted St ro ngly Coa rse 5 kewed Very Leptokurtic BUX36.1 0.6.2 SP Fine Sa nd PoorlyGraded MedumSand Poorly Sorted Coa rse Skewed Mesokurtic BUX362 62-8.4 SP-SM I Fine Sa nd Poorly Graded Fine Sa nd Poorly Sorted Symmetrical Platykurtic BUX363 8.4-10 SP Fine Sa nd PoorlyGraded MedumSand Moderately Sorted Symmetrical Leptokurtic BUX37.1 0-3.0 SP Medum Sand Poorly Graded MedumSand Poorly Sorted Co. rse Skewed Mesokurtic BUX372 3.04.0 SP MedumSand PoorlyGraded Goa rse Sand Poorly Sorted Symmetrical Platykurtic BUX373 7.0-10 SP-SM Fine Sa nd Poorly Graded Rne Sa nd Poorly5orted Symmetrical Platykurtic BUX38.1 0-5.6 SP MedumSand PoorlyGraded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BUX382 5.6-10 SP Fine Sa nd Poorly Graded Medi um Sa nd Poorly Sorted Symmetrical Mesokurtic BUX39.1 0.6.0 SP MedumSand PoorlyGraded Goa rse Sand Moderately Sorted Fine Skewed Leptokurtic BUX392 61F8.3 SP MedumSand Poorly Graded Co. rse Sand Poorly Sorted Symmetrical Platykurtic BUX393 8.3-10 SP Medum Sa nd PoorlyGraded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BUX40.1 0.3.2 SP MedumSand Poorly Graded Coarse Sand Poorly Sorted Symmetrical Very Platykurtic BUX-402 32.8.6 SP MedumSand PoorlyGraded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BUX403 8.6.10 SP-SM Fine Sa nd Poorly Graded Fine Sa nd Poorly Sorted Symmetrical Platykurtic BUX41.1 0-1.7 SP MedumSand Poorly Graded Coarse Sand Moderately Wel l Sorted St ro ngly Coa rse Skewed Very Platykurtic BUX412 1.7-3.0 SP Fine Sa nd Poorly Graded MedumSand Poorly Sorted Symmetrical Mesokurtic BUX41.3 3.0-7.0 SP MedumSand Poorly Graded Coarse Sand Moderately Wel l Sorted St ro ngly Coa rse Skewed Very Platykurtic BUX41A 7A-10 SP MedumSand Poorly Graded Coarse Sand Poorly Sorted Symmetrical Platykurtic BUx42.1 0-3.0 SP Medum Sa nd PoorlyGraded Coarse Sand Poorly Sorted St ro ngly Coa rse Skewed Leptokurtic BUX422 3.0.6.5 SP MedumSand PoorlyGraded MedumSand Moderately Wel l Sorted Symmetrical Leptokurtic BUX423 65-9.5 SP Fine Sa nd PoorlyGraded Fine Sa nd Moderately Sorted Coa rse Skewed Leptokurtic BUx43.1 0-2.9 SP MedumSand PoorlyGraded Coarse Sand Moderately Sorted Coa rse Skewed Mesokurtic BUX432 2.9-5.0 SP MedumSand PoorlyGraded Coarse Sand Poorly Sorted Goa rse Skewed Mesokurtic BUX43.3 5.67.6 SW Medium Sand Well Graded Goa rse Sand Poorly Sorted Fine Skewed Platykurtic BUX43.4 7.6.10 SP Fine Sand Poorly Graded Fine Sand Poorly Sorted Coarse Skewed Mesokurtic BUX44.1 0.4.0 SP Medium Sand Poo rly Graded Coarse Sand Poorly Sorted St ro ngly Coa rse S kewed Leptokurtic BUX44.2 4.610 SP I Fine Sa nd Poo rly Graded Medi um Sa no Moderately Sorted Coa rse Skewed Leptokurtic Coastal Science & Engineering 99 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 4.2a. Composited offshore core sediment statistics and descriptions to a 6 ft depth, based on weighted averages of individual samples. See Attachment 3B for size frequency curves. Method of Moments Folk Graphical Gravel Granules Dry Fines Shell IN phi Mean Sib Skew Kurt mm Mean STD phi Mean STD ISTD SKEW Kurt BUx-21 GftCOMP BUx-22 GftOOMP BUx-23 GftOOMP BUx-24 GftOOMP BUx-25 GftOOMP BUx-27 GftOOMP BUx-28 GftOOMP BUx-29 GftOOMP BUx-35 GftCOMP BUx-36 GftOOMP BUx-37 GftOOMP BUX-18 6ftCOMP BUX-39 6ftCOMP BUx-00 GftOOMP BUx-41 GftOOMP BUx-42 GftOOMP BUx43 GftOOMP BUx-44 6!!OOMP 0.91 0.58 -0.45 CIA3 0.533 GAO 0.81 036 0.42 -OA9 1.49 0.0 2A OA 163 114 O.29 -1.90 7.25 0.423 0.539 1.22 0.61 0.74 -033 1.53 DA 3.8 0.0 153 1.63 0.85 -1.15 5.37 0.324 0.554 1% 0.G6 036 -0.29 1.45 0.0 2A 0.1 10A 0.66 0.94 -1.14 6.18 0.431 0.521 0.62 0.64 0.79 -0.40 1.73 0.0 7.5 0.1 19.9 1.22 0.6G -2.27 12.34 0.430 0.631 1.16 0.46 030 -0.26 1.22 0.0 1.9 0.0 153 1.20 1.50 -0.25 4.09 0.435 0.355 1.20 130 1.47 0.19 1.64 1.7 4A 4A 20A 038 1.07 -1.11 4.16 0.670 0.476 0.50 0.94 1A6 -0.40 1.37 0.0 9.7 0.0 25.8 130 1.20 1 -0.29 4.59 1 0.307 0.436 1.62 0.94 1.11 0.03 1.64 0.3 2A 4.0 103 135 1.05 -0.08 3.20 0.392 OARS 1.25 DAB 1.01 0.07 0.97 0.0 IS 11 17A 1.90 1.26 -0.90 3.36 0.268 0.417 1.83 1.11 1.22 -OA3 1.20 0.0 4A 23 9.6 0.59 1.76 -0.48 2.45 0.S38 0.295 0.78 1.86 1.86 -035 0.91 1.7 14.9 15 253 0.84 0.94 0.76 5.48 0.557 0.521 0.65 0.62 0.84 0.00 2.05 0.0 3.6 1.0 CIA 0.79 0.91 0.77 5.96 0.S79 0.531 0.59 039 0.80 -099 1.93 0.0 3.8 0.9 14A 0.66 1.13 0.26 2.62 0.04 0.4SS 0.47 1.11 1.21 -OA6 1.34 0.0 S.S -03 173 0.52 0.83 -0.37 2.57 0.568 0.561 0.70 0.69 0.85 -OA4 1.78 0.0 3.9 -1.2 14.2 0.29 OA4 1 -1.57 6.77 1 0.SW 0.521 U7 1 034 032 -039 2.01 1 0.0 7.0 0.1 16.1 0.78 1.27 -0.72 4.31 1 0.582 1 0.415 0.65 1 1.17 1.17 -035 1.20 1.2 CIA 0.9 24.7 0,98 1.24 1,49 5.66 0.W6 0.423 0.98 0.94 1.15 -039 1.52 1.6 a6 01 213 ALL GROMP SAG 1.14 1 -0.50 1 4.71 1 0.478 1 0.4S3 1 0.97 1 0.90 1 1A7 1 A119 1 1.51 1 0.4 1 5.4 1 0.9 1 17.0 USCS Destriptwk Wentworth De4triptior5 BUx-21 6ft COMP SP Medium Sand Poorly Graded Coarse Sand Moderately Well Sorted Coarse Skewed Very Leptokurtic BUx-22 6 It COMP SP Medium Sand Poorly Graded Medium Sand Moderately Sorted St rongl y Coarse Skewed Ve ry Le ptokurtic BUX-23 6 It COMP SP Fine Sand Poorly Graded Medium Sand Moderately Sorted Coarse Skewed Leptokurtic BUx-24 6 It COMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Coarse Skewed Leptokurtic BUx-25 SftCOMP SP Mudium5and Poorly Graded MediumSand Moderately Well Sorted Strongly Coarse Skewed Very Leptokurtic BUx-27 6ftCOMP SP MediumSand Poorly Graded MediumSand Poorly Sorted Symmetrical Leptokurtic BUx-28 6ftCOMP ISP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed Leptokurtic BUx-29 6ftCOMP SP Fine Sand Poorly Graded Medium Sand Poorly Sorted Symmetrical Leptokurtic BUx-3S 6ftCOMP SP Fine Sand Poorly Graded MediLim Sand Poorly Sorted Symmetrical Mesokurtic BUx-36 6ftCOMP SP Fine Sand Poorly Graded Medium Sari Poorly Sorted Coarse Skewed Mesokurtic BUx-37 6ft COMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed Platykurtic BUx-38 6 It COMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BUx-39 .6ft COMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Fine Skewed Leptokurtic BUx-40 6ftCOMP ISP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Symmetrical Mesokurtic BUx-41 6ftCOMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Symmetrical Mesokurtic BUx-42 6ftCOMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted St rongl y Coa rse Skewed Leptokurtic BUx-43 6ft COMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed Leptokurtic BUx-44 6ft COMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic ALL 6 It COMP SP MediumSand Poorly Graded iMediumSard I Poorly Sorted Coarse Skewed ILeptokurtic Coastal Science & Engineering 40 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 4.2b. Composited offshore core sediment characteristics and descriptions to an 8 ft depth, based on weighted averages of individual samples. See Attachment 3C for size frequency curves. Method of Moments Folk Graph iraI Gravel Granules Dry Fines Shell N phi Mean STD Skew Kurt mm Mean STD phi Mean STD ISTD SKEW Kurt BUX-25 SftCOMP BUX-35 8ItCOMP BUX-36 8ItCOMP BUX-37 8ItCOMP BUX-39 9ItCOMP BUX-39 8ItCOMP BUX-40 SftCOMP BUX-41 SftCOMP BUX-42 SftCOMP BDX-43 SftCOMP 13UX-44 9 KOMP 1.24 0.64 -2.21 12.44 0.424 0.641 117 0.46 0.49 -0.23 1.18 0.a 1.6 OA 15.0 1.54 1.02 -0.42 3.24 0.343 0.494 1.48 036 036 -0.22 0.87 W) 2.2 03 119 2.05 1.32 -0.60 3.18 0.241 0.401 1.95 1.14 130 -0.23 1.29 0.0 18 73 12.1 1.13 1.79 -0.38 2.53 0.457 0.288 0.97 1.84 1.90 -0.26 0.99 1.3 116 5.0 25.3 0.99 1.01 0.53 4.37 0.503 0.499 0.88 0.22 0.96 0.14 1.76 W) 1 13 10.8 039 1.04 0.61 4.44 0.579 0.485 0.56 0.79 1.02 -0.08 1.94 0.0 5.4 1.1 163 030 1.07 0.34 3.24 0.616 0.476 0.47 0.93 1.10 -0.10 1.57 0.0 7.2 -0.4 15A 032 0.22 -0.30 1 2.55 0.S83 0.543 0.65 0.75 0.93 -0.02 1.78 0.0 4.7 -1.2 143 111 1.11 -0.62 5.01 0.434 0.464 1.21 0.85 11 0.13 2.07 0.0 5.4 0.7 13.1 0.82 1.39 -0.27 3.48 0.565 0_.3 0.62 131 137 -010 1.18 1.0 11.0 1.6 253 1.05 1.16 -1.51 619 0.481 0.448 1.04 0.25 1.02 -035 1.42 1.2 5.6 03 191 ALL 8ftcoMP 1.13 1 1.21 1 -0.28 1 3.98 0.4S7 1 0.432 1.04 1.07 1.18 -0.04 1.39 1 0.3 5.5 15 16.6 USCS Description I Wentworth Description BUX-25 SftCOMP SP Medium Sari Poorly Graded Metliuin Sand Moderately Well Sorted Strongly Coarse Sketred VeryLuptukurtir BUX-3S 9ItCOMP SP FineSand Poorly Graded MudiumSand Poorly Sorted Symmetrical Mesukurtir BUX-36 Sft COMP SP Fine Sand Poorly Graded Fi ne Sand Poorly Sorted Coarse Skewed Mesokurtic BUX-37 81tCOMP SP Medium Sand Poor lyGraded Medium Sand Poorly Sorted Symmetrical Platykurtic BUX-38 81t COMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Fine Skewed Leptokurtic BUX-39 8ft COMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Fine Skewed Leptokurtic BUX-40 8ft COMP Sr, Medium Sand Poorly Graded Coarse Sand Poorly Sorted Symmetrical Mesokurtic BUX-41 SftCOMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Symmetrical Platykurtic BUX-42 SftCOMP SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Coarse Skewed Leptokurtic BUX-43 SftCOMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Symmetrical Mesokurtic BUX-44 SftCOMP SP Medium Sand Poorly Graded Medium Sand Poorly Sorted Strongly Coarse Skewed Leptokurtic ALL 9ItCOMP SP MedlumSand PoorlyGraded Medium Sand Poorly Sorted Symmetrical Leptokurtic- TABLE 4.3. Weighted mean grain size, standard deviation, shell percentage, and gravel percentage for the 10-ft borings (30 samples) off Buxton ("All Samples"). Composites are weighted by the applicable length of individual samples forthe upper 6 ft of core (Comp 6), the upper 8 ft of core (Comp 8), and the upper 10 ft of core (Comp 10). Composite statics are based on the 10-ft cores within the box shown in Figures 2.5 and 4.1. The standard deviation for shell and gravel percentages is given in parentheses. Std Deviation Granules Core Samples Mean Size (mm) Shell (%) Gravel (%) (mm) N All Samples 0.464 0.502 16.6 0.4 5.2 Comp 6 ft 0.478 0.453 17.0 0.4 5.4 Comp 8 ft 0.457 0.432 16.6 0.3 5.5 Comp 10 ft 0.517 0.426 15.6 0.6 7.1 Coastal Science & Engineering 41 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 4.1 Mean Grain Size of the Proposed Borrow Area Borrow area sediments must reasonably match the native beach sediments in order for a beach nourishment project to be successful. If borrow sediments are finer than the native material, the beach will adopt a shallower slope and eroded more quickly (Dean 2002). If borrow sediments are coarser, the opposite will occur. The final round of borings within the proposed borrow area were collected in April 2021 to a uniform depth of 10 ft below the seafloor. There were 30 samples extracted from 10 borings across the -200-acre proposed borrow area, meaning each boring is assumed to represent -20 acres of sediment characteristics to a 10-ft depth. The composite statistics and descriptions of these 10 borings, composited to a 10-ft depth, are provided in Table 4.4. Based on the calculated composite statistics, the proposed borrow area mean grain size is 0.517 mm with a standard deviation of 0.426, granule (2-4 mm) content of 7.1 percent, gravel (4-76 mm) content of 0.6 percent, and shell content of 15.6 percent to a depth of 10 ft beneath the seafloor. These values, as well as the core spacing (-20 acres per core), meet the NC Technical Standards for Beach Fill Projects (15A NCAC 07H .0312 - see Attachment 4) and NPS Sediment Management Framework (NPS 2021). Figure 4.3 shows composite statistics for each core within the sand search area. To more easily visualize the results, Figures 4.4-4.6 provide color isopach maps of mean grain size, shell percentages, and gravel percentages for 10 ft composite results. Coarsest sediments are found over a broad area encompassing the southern 75 percent of the search area. Mean grain size is lower along the northern and northeastern edges. The size minima are at the northeastern corner of the grid (core Bux-29 -0.01 mm below 4 ft). The coarsest samples are in the central -western portion of the search area (core Bux-40 -0.7 mm 10-ft composite). Figure 4.5 (percent shell) shows similar isopachs and a correlation of shell percentage with mean grain size. Gravel percentages (Fig 4.6) are generally low, with only two composite averages exceeding 2 percent. Granule percentages are variable throughout the sand search area, ranging from -3.6 percent (core Bux-38,10 ft composite) to -15.3 percent (core Bux-37, 10 ft composite). Coastal Science & Engineering 42 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina TABLE 4.4. Composited offshore core sediment characteristics and descriptions to a 10 ft depth, based on weighted averages of individual samples. See Attachment 3D for size frequency curves. Method of Moments Falk Graphical Gravel Granules Dry Fines Shell {96} phi Mean STO Skew Kurt mm Mean STO phi Mean $TO IST0 SKEW Kurt BUx-35 10ft COMP BUX-36 10ft COMP BUX-37 30ft COMP BUX-39 SOft COMP BUx-39 loft COMP BUx-40 loft COMP BUx•41 loft COMP BUx•42 lOftCOMP BUx•43 loft COMP 10ftCOMP PALL 1.07 1.04 0.39 3.97 0.478 OA8fi 0.96 0.88 1.OD 0.13 1.47 0.0 3.7 1.5 11.8 1.OD 1.26 -0.90 33b 0.269 OA17 1.83 1.11 1.22 -0.43 1.20 0.0 4.9 2.5 11.1 0.97 IA-1 -0.67 2.60 0.512 0282 0.81 L91 1.93 -OA4 0.99 2.3 15.3 1.6 22.5 0.80 OA2 OA2 5.96 0.574 053o tl.60 O39 0.81 -0.04 2.07 0.0 3.6 0.9 11.4 0.79 OA1 0.77 5.96 0.579 O.S31 0. 59 039 O.SD -0.09 10.3 0.0 _;A 0.9 153 0.55 115 0.20 1.64 0.681 OA21 0.57 139 1.47 DAD 0.97 0.0 12.6 0.0 163 0.90 OA9 -0.13 3.17 0.536 0.539 0.83 0.81 0.92 0.44 1.66 0.0 3.a 0.0 15.a D.7s 1.03 -1.55 5.47 0.996 OA90 0.72 0.69 0.90 -a30 2.02 0.0 10.1 OA 12.6 D.86 1.10 -1.13 5.55 0.552 OA67 tl.82 0.9tl tl.99 -033 134 0.9 6.$ tl.5 22.1 D.84 1.37 -1.37 4.59 0.557 0.386 0.86 1.10 1.33 -0.42 1.48 23 8.5 tl,0 17.9 loft COMP US123 -0.49 4,11 {).517 0,426 0,85 lA8 1.19 -OAS 1.44 1 0.5 1 7.1 0.5 15r6 USCS Description Wentworth Description BU%-3S 10ftCOMP Sp Medium Sand Poorly Graded Medium Sand Poorly Sorted Symmetrical Leptokurtic BU%-36 10ftCOMP SP Fine Sand Poorly Graded Medium Sand Poorly Sorted Coarse Skewed Mesokurtic BU%-37 10ftCOMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed Mesokurtic BU%-38 10ftCOMP SP MediumSand Poorly Graded CoarseSand Moderately Sorted Fine Skewed Leptokurtic BU%-39 10ftCDMP SP MediumSand Poorly Graded Coarse Sand Moderately Soned Fine Skewed Leptokurtic BU%-40 10ftCOMP SW Medium Sand WelIGraded Coarse Sand Poorly Sorted Symmetrical Ve ry Plat kunic BU%-41 10ftCOMP SP Medium Sand Poorly Graded Coarse Sand Moderately Sorted Symmetrical Mesokurtic BU%-42 10ftCDMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted 51 rongl y Coa rse Skewed Leptokurtic U%-43 10ftCDMP SP Medium Sand Poorly Graded Coarse Sand Poorly Sorted Coarse Skewed LeptokurticU%-44 p 10ftCDMPSP MediumSand Poorly Graded Coarse Sand Poorly Sorted St rongl y Coa rse Skewed Leptokurtic ALL 10ftcoMPSP Medium5and Poorly Graded Coam Sand Poorly Sorted Coam Skewed Leptokurtic Coastal Science & Engineering 49 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina ,,� a soo Scale BUX-36 e-r-os ti0. BUX-42 4.9 4.9 0.596 BUX-35 12.16 0.478 11.8 3.7 BUX-41 0.536 15.0 � BUX-44 a Bux-04 3.8 0.557 17.9 10.9 BUX-40 0.681 BUX49 a eu�-0s 12.6 0.579 15.5 7 3.8 o Bux-35 / ~�aBuxM`--� / Bux-38 Bux-31 Bux-33 / a / Previous Borrow Area (2018) Y o Bux!34 a Bux-32 / Buz-29 / BUX-43 0.552 22.1 7.7 0.512 22.5 17.5 0.574 11.4 3.6 Boring MGS (mm) Shell % Gravel % Granule % BUX-35 0.479 11.8 0.0 3.7 BUX-36 0.268 11.1 0.0 4.9 BUX-37 0.512 22.5 2.3 15.3 BUX-38 0.574 11.4 0.0 3.6 BUX-39 0.579 15.5 0.0 3.8 BUX-40 0.681 16.5 0.0 12.6 BUX-41 0.536 15.0 0.0 3.8 BUX-42 0.596 12.6 0.0 10.1 BUX-43 0.552 22.1 0.9 6.8 BUX-44 0.557 17.9 2.3 8.5 FIGURE 4.3. Mean grain size, percent shell, and percent gravel for core composite samples to 10 ft in the proposed Buxton offshore borrow area based on borings obtained in April 2021. Composite results of the ten 10 ft vibracores are listed in table on the lower right. The ten 10-ft vibracores obtained in 2021 are highlighted in bold text with red dots. Other cores from previous sand searches are shown in small text with black boxes. The mean grain size of the ten 10-ft cores is 0.517 mm with 15.6 percent shell material and 7.7 percent gravel by weight. Coastal Science & Engineering 44 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Buxton NC X 10' 10 ft Composite 5.69 5.685 0.55 5.68 0.5 5.675 0.45 E a� 5.67 N 0.4 C7 c 5.665 0.35 0 5.66 0.3 5.655 0.25 5.65 1 0.2 3.048 3.0485 3.049 3.0495 3.05 3.0505 3.051 3.0515 3.052 3.0525 3.053 X 10, FIGURE 4.4. Isopach map of mean grain size to 10 ft based on 10+ cores within the proposed borrow area off Buxton. Buxton NC X 10, 10 ft Composite 25 5.69 5.685 5.68 20 5.675 0 c a� 5.67 c U O� U 5.665 U 15 5.66 5.655 110 5.65 3.048 3.0485 3.049 3.0495 3.05 3.0505 3.051 3.0515 3.052 3.0525 3.053 X 10, FIGURE 4.5. Isopach map of percent shell to 10 ft based on 10+ cores within the proposed borrow area off Buxton. Coastal Science & Engineering 45 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina x 105 5.69 5.685 5.68 5.675 5.67 5.665 5.66 5.655 Buxton NC 10 ft Composite 15 10 0 c CD 5 CD a 565' ' �0 3.048 3.0485 3.049 3.0495 3.05 3.0505 3.051 3.0515 3.052 3.0525 3.053 x 1d FIGURE 4.6. Isopach map of percent >2 mm to 10 ft based on 10+ cores within the proposed borrow area off Buxton. Coastal Science & Engineering 46 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 5.0 SEDIMENT COMPATIBILITY CSE evaluated sediment compatibility by comparison of grain -sized istribution (GSD) of all "native" beach and offshore borrow areas sampled. The composite GSDs of the "Visible Beach" and "All Beach" samples are weighted using the results of individual sample splits to derive numeric results for each size interval. Figure 5.1 contains the composited beach sample GSDs. Underwater samples, particularly those collected below 8 ft water depth, average 0.222 mm and skew the "All Beach" composite statistics towards a finer mean grain size. As a result, the visible beach (above MTQ has a mean grain size of 0.400 mm, but the entire profile has a mean grain size of 0.321 mm. Similar composite GSDs were computed for cores in the offshore sand search area. All cores in the proposed borrow area were evaluated. Weighted GSDs were computed for the upper 6 ft, upper 8 ft, and upper 10 ft composited length (Attachment 3). Because there are sufficient borings collected to a 10-ft depth beneath the seafloor within the -200-acre borrow area (to meet NC Technical Standards for Beach Fill Projects), and those borings indicate beach - quality sand is available to a 10-ft depth, the Sediment Compatibility analysis will focus on the 10 ft composite statistics. Figure 5.2 contains the set of 10-ft composited borrow area GSDs. The results show little variation in mean grain size distribution outside boring Bux-36 (0.268 mm); all other 10-ft composite mean grain sizes are between 0.478 mm (Bux-35) and 0.681 mm (Bux-40). Composite borrow sediments are classified as poorly sorted and coarse skewed, typical of many littoral profiles (Komar 1998). Coastal Science & Engineering 47 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Grain Size Distribution Grain Size (mm) 8 4 2 1 0.5 0.25 0.125 0.0625 Project 2403-M 10016 Location Buxton, NC 90 ........:....: ....:...:...:...:.. ....... . Date Aug 05 2019 80 ...:........; .................. . ................ Station ALL Sample Vis Beach 70 :...:....:....:...:...:.. ; .. Mea 0.400 mm 0 60 .... ... _ .. _ . _ ...... STDn 0.636 mm 50 Skewness -1.073 40........ .................;...I......:...; :.. USCS Wentworth SP Medium Sand Fine Sand Moderately Well Sorted 20 ...:....:....:....:....:....:... :... .....:....:....:...:... .....:.... Poorly Graded Coarse Skewed = = Leptokurtic 10 ........... ................. Total weight (gram) 116.75 =_ = %finer than 0.0625 mm (dry) 0.00 0 4 3 -2 1 0 1 2 3 4 %gravel (dry) 0.03 Grain Size (�) %granule (dry) 0.69 CaCO3 7.1 Grain Size Distribution Grain Size (mm) 10016 8 4 2 1 0.5 0.25 0.125 0.06 90 ...=....:....:....:...:...:... :... ...:...:...:... . 80...:....:....:....:....:....:....:... ... ...:........:........... . 70 .......:...:....:.... 60 50 40 ....... L 30 20 ... 10 ..:.....:.................; 0 Li -4 -3 -2 -1 0 1 2 3 4 Grain Size (0) Project 2403-M Location Buxton, NC Date Aug 05 2019 Station ALL Sample All Beach Mean 0.321 mm STD 0.552 mm Skewness -1.045 USCS Wentworth SP Medium Sand Fine Sand Moderately Sorted Poorly Graded Coarse Skewed Leptokurtic Total weight (gram) 116.55 %finer than 0.0625 mm (dry) 0.04 %gravel (dry) 0.05 %granule (dry) 1.15 Ca CO3 7.2 FIGURE 5.1. Grain -size distribution (frequency and cumulative frequency) for composited August 2019 beach samples showing the relatively coarse nature of visible beach sands [UPPER] compared to composited samples from across the entire profile [LOWER]. Coastal Science & Engineering 48 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina 100 90 80 70 6 0 0 CM 50 40 fill 1 Grain Size Distribution Grain Size (mm) 6 8 4 2 1 0.5 0.25 0.125 HE 0 -4 -3 -2 -1 0 1 2 3 4 Grain Size (0) 25 Project 2403-M Location Buxton, NC Date Apr 06 2021 Station ALL Sample 10 ft COMP Mean 0.517 mm STD 0.426 mm Skewness -0.489 USCS Wentworth SP Coarse Sand Medium Sand Poorly Sorted Poorly Graded Coarse Skewed Leptokurtic Total weight (gram) 100.11 %finer than 0.0 62 5 mm (dry) 0.59 %gravel (dry) 0.57 %granule (dry) 7.11 CaCO3 15.6 FIGURE 5.2. Grain -size distribution (frequency and cumulative frequency) for offshore borings to a composite depth of 10 ft beneath the seafloor. Figure 5.3 provides comparative frequency and cumulative frequency size distributions for native and borrow sediments. Beach samples are compared with the composite 10-ft borrow area statistics for all 10-ft borings within the proposed borrow area (n=10). Note the fair match in D50 for each comparison (ie - where the two cumulative curves intersect the 50% line), evident in the matching shapes of the frequency curves. As previously discussed, sampling of the subaerial beach in August 2019 yielded a mean grain size of 0.321 mm, a result that is within 0.1-0.2 mm of the various composited borrow area means in Figure 5.3. CSE also computed overfill factors, RA, for native beach GSDs and each 10-ft composited boring. The overfill factor, RA (CERC 1984), provides a measure of how a particular sediment will perform as beach nourishment. Low RA's are generally preferred, with the ideal being equal to 1.0. To apply the method, a native sediment size must be assumed. As discussed in Section 3.3, the native beach grain size is 0.321 mm along the entire profile and 0.400 mm along the visible beach. Table 5.1 provides RA's for each core composite to 10 ft. Each table lists the applicable mean and standard deviation in phi units which are required in the James (1975) formulation (CERC 1984). RA values were calculated for 10 ft composite core mean grain sizes compared to both the entire Coastal Science & Engineering 49 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina profile (`RA (all)') and the visible beach (`RA (vis)'). Inspection of Table 5.1 shows that RA's range from -1.0 to -1.3 for the entire profile, and from -1.0 to -1.8 for the visible beach. All of the samples have RA's less than 1.5 compared to the entire littoral profile, and less than 1.8 compared to the visible beach. All of the core composites have low RA's when compared with the native beach size distribution. While RA's are not considered to be definitive in matching sediment texture for nourishment (Dean 2002), the results herein suggest the majority of cores will provide good nourishment performance. The overlap of the GSDs (Fig 5.3) further supports this finding. The proposed -200-acre borrow area will provide sufficient volume to accomplish the proposed -1.2 million cubic yard project. The minimum excavation area to provide the design volume would be -65 acres, assuming a dredge cut averaging -10 ft deep. TABLE 5.1. Computed RAs (overfill factor) for each composite core sample (loft composite) compared with the composite native "All Beach" as well as "Visible Beach" results, along with other descriptive statistics for the 10-ft borings collected across the proposed borrow area. MethodM Monle nts Folk Graphleal Gravel Granules Dry Fines Shell M Ra{allj Ra{,kI phl Mean STD Skew Kurt mm Mean STD phi Mean STD ISTD SKEW Kurt 8111435 10 it COMP B 111435 10 it COMP 1.07 2.04 0.39 1. 7 0.478 0.486 0.96 0.88 1.00 0.13 1.47 0.0 3.7 1.5 11.8 1.00 1.21 1.90 2.26 -0.90 3.36 0.268 0.417 1.83 1.11 1.22 -0.43 1.20 0.0 4.9 2.5 11.1 1.34 1.92 B111437 10 it COMP B111438 10 it COMP 0.97 1.83 .0.67 2.60 0.512 0.182 0.81 1.91 1.93 .0.44 0." 2.3 15.3 1.6 22.5 1.16 1.33 0.90 0.92 0.82 5.96 0.574 0.530 0.60 0.59 0.92 -0.04 2.07 0.0 3.6 0.9 11.4 1.00 1.02 B111439 10 it COMP BUk40 10 it COMP 0.79 0.92 0.77 5.96 0.579 0.531 0.59 0.59 0.80 -0.09 1.93 0.0 3.8 0.9 15.5 1.00 1.02 0.55 1.25 0.20 1.64 0.681 0.421 0.57 1.59 1.47 0.10 0.97 0.0 12.6 0.0 16.5 1.01 1.07 Buk41 10 it COMP B111442 10 it COMP 0.90 0.89 -0.13 3.27 0.516 0.510 0.83 0.92 0.92 0.04 1.66 0.0 3.9 0.0 15.0 2.00 1.02 0.75 1.03 -1.11 1.41 0.596 0.490 0.72 0.69 0.90 -0.50 2.02 0.0 10.1 0.0 12.6 1.00 1.04 B111443 10 it COMP Bux-aa 10 it COMP 0.96 2.10 1 -2.13 5.55 0.552 O.d67 0.82 0.90 0.99 -0.33 1.34 0.9 6.8 0.5 22.1 1.00 1.09 0.94 2.37 .2.37 4.59 0.557 0.385 0.86 1.10 1.33 A.42 1.48 2.3 8.5 0.0 17.9 1.04 1.17 ALL 10 it COMP 0.95 1.23 1 -0.44 1 411 1 0.517 1 0.426 0.85 L08 1 1.19 -0.08 1 1." Q5 1 7.1 1 0.6 1 15.6 L02 1.15 Coastal Science & Engineering 50 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Grain Size Distribution Grain Size (mm) Project CSE 2403-M Location Buxton (NC) Date May 2021 BA 10 ft COMP Mean 0.517 mm BA 10 ftCOMP STD 0.426 mm BA 10 ft COMP Skew-0.489 mm BA 10 ft COMP Kurt 4.107 mm BA 10 ft COMP Shell 12.3% All Beach Mean 0.321 mm All Beach STD 0.552 mm All Beach Skew -1.045 mm All Beach Kurt 5.621 mm All Beach Shell 7.2% Grain Size Distribution Grain Size (mm) 10016 B 4 2 1 0.5 0.25 0.125 0.0625 Borrow Area 10 ft COMP 90 Vis Beach . . = : . . . Project CSE 2403-M Location Buxton (NC) 80 ......:. :.........:......... ........: Date May 2021 70 - � ........ BA 10 ft COMP Mean 0.517 mm BA 10 ft COMP STD 0.426 mm 60 ± ..........:...:. . BA 10 ft COMP Skew-0.489 mm BA 10 ft COMP Kurt 4.107 mm o� 50 BA 10 ft COMP Shell 12.3% 40 :•••]•••: :......•• Vis Beach Mean 0.400mm Vis Beach STD 0.636 mm 30 ........................... Vis Beach Skew -1.073 mm Vis Beach Kurt 6.358 mm 20 :...:...:............:....... ;. .;. Vis Beach Shell 7.2% 10 . 0 4 -3 -2 -1 0 1 2 3 4 Grain Size FIGURE 5.3. GSDs for Buxton native beach samples (n=140) compared with offshore samples to 10 ft (composite). The "Vis Beach" consists of all native samples collected on the visible beach (above MTL), while "All Beach" contains all samples. In both cases, the borrow area sediments are expected to be coarser than the native beach initially. Over time, the grain size of the post -nourishment beach is expected to move closer to the historical grain size distribution around Buxton. Coastal Science & Engineering 51 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina — THIS PAGE INTENTIONALLY LEFT BLANK — Coastal Science & Engineering 52 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina REFERENCES CITED Birkemeier, W, H Miller, S. Wilhelm, A. DeWall, and C Gorbics. 1985. A user's guide to the Coastal Engineering Research Center's (CERC's) Field Research Facility. Tech Rept CERC-85-1, USACE-WES, Vicksburg, MS. Boss, SK, and CW Hoffman. 2000. Sand resources of the North Carolina Outer Banks: assessment of Pea Island study area. 4th Interim Report for Outer Banks Task Force and the North Carolina Department of Transportation, 87 pp. CERC. 1984. Shore Protection Manual. 41h Edition, US Army Corps of Engineers, Coastal Engineering Research Center, Ft Belvoir, VA; US Government Printing Office, Washington, DC, 2 vols. CSE. 2001. Analysis of alternatives for Bogue Inlet channel realignment and beach nourishment along western Emerald Isle, NC. Summary Report for Town of Emerald Isle, NC; CSE, Columbia, SC, 79 pp + appendix. CSE. 2004. Survey report 2004, Bogue Banks, North Carolina. Monitoring Report for Carteret County Shore Protection Office, Emerald Isle, North Carolina; Coastal Science & Engineering (CSE), Columbia (SC) and Morehead City (NC), 82 pp +4 appendices. CSE. 2005 (June). Post -Isabel emergency dune restoration project at Nags Head. Final Report for Town of Nags Head, North Carolina; Coastal Science & Engineering (CSE), Columbia (SC) and Morehead City (NC), 12 pp + figures + two appendices. CSE. 2013. Shoreline erosion assessment and plan for beach restoration, Rodanthe and Buxton areas, Dare County, North Carolina. Feasibility Report for Dare County Board of Commissioners, Manteo, NC. CSE, Columbia, SC, 159 pp with synopsis plus appendices. CSE. 2019. Final Construction Report - 2019 Nags Head Beach Renourishment Project. Coastal Science & Engineering Inc (CSE), Columbia (SC), 17 pp+appendix. CSE. 2021. Large Sediment Sampling - Dare County North Carolina. Coastal Science & Engineering Inc (CSE), Columbia (SC), 74 pp + appendices (2458). Colony, RJ. 1932. Source of the sand on the south of Long Island and the coast of New Jersey. Jour Sed Petrol, Vol 3(3), pp 150-159. Dean, R.G. 1991. Equilibrium beach profiles: characteristics and applications. Jour. Coastal Research, Vol. 7(1), pp. 53- 84. Dean, RG. 2002. Beach Nourishment: Theory and Practice. World Scientific, NJ, 399 pp. Dolan, R, and H Lins. 1986. The Outer Banks of North Carolina. Professional Paper 1177-B, Prepared in cooperation with the National Park Service, US Geological Survey, Reston, VA, 49 pp. Folk, RL, and WC Ward. 1957. Brazos River bar: a study in significance of grain -size parameters. Jour. Sed. Petrology, Vol. 27, pp. 3-26. Gravens, MB, B Ebersole, T Walton, and R Wise. 2008. Beach fill design. In Coastal Engineering Manual, Part V, Coastal Project Planning and Design, Chapter IV-4, CEM 1110-2-1100, US Army Engineer Waterways Experiment Station, Vicksburg, MS. Greenwood, B, and RGD David son-Arnott. 1972. Textural variation in the subenvironments of the shallow water wave zone, Kouchibouguac Bay, New Brunswick. Canadian Journal of Earth Sciences, Vol9, pp 679-688. Hanna, HD, and JG Nickerson. 2009. Offshore sand resource investigation, North Carolina Outer Banks: Ocracoke Inlet to Oregon Inlet. NCDOT Sand Resource Study, NC Geological Survey, 45 pp plus appendices. Hoffman, CW, SK Boss, and RW Brooks. 2001. Interactive database: vibracores offshore of Hatteras and Ocracoke Islands, North Carolina. NC Geological Survey Open -File Report 2001-01, Raleigh, NC (on CD). James, W.R. 1975. Techniques in evaluating suitability of borrow material for beach nourishment. Rept. No. TM-60, CERC, U.S. Army Waterways Experiment Station, Vicksburg, MS. Komar, PD. 1998. Beach Processes and Sedimentation. Second Edition, Prentice -Hall, Inc, Simon & Schuster, Upper Saddle River, NJ, 544 pp. Coastal Science & Engineering 53 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina Inman, DL. 1952. Measures for describing the size distribution of sediments. Jour Sed Petrology, Vol 22(3), pp 125-145. Miller, RL, and JM Ziegler. 1958. A model relating sediment patterns in the region of shoaling waves, breaker zone, and foreshore. Journal of Geology, Vol 66, pp 417-441. NIPS. 1980. Cape Hatteras Lighthouse, Buxton, North Carolina. National Park Service, Authors: MTMA Design Group, JL Machemehl, NIPS, 139 pp. NIPS. 2012. National Park Service Beach Nourishment Guidance. Technical Report NOPS/NRSS/GRD/NRTR-2012/581, National Park Service, Fort Collins, CO, 59 pp. NIPS. 2021. Cape Hatteras National Seashore Sediment Management Framework - Final Environmental Impact Statement. National Park Service, Fort Collins, CO, 50 pp + appendices. NIPS. 2021. Joint Record of Decision Sediment Management Framework - Cape Hatteras National Seashore. National Park Service, Fort Collins, CO, 13 pp + appendices. NRC. 1995. Beach Nourishment and Protection. Committee on Beach Nourishment and Protection, Marine Board, Commission on Engineering and Technical Systems, National Research Council; National Academy Press, National Academy of Sciences, Washington, DC, 334 pp. Riggs, SR, WJ Cleary, and SW Snyder. 1995. Influence of inherited geologic framework upon barrier shoreface morphology and dynamics. Marine Geol, Vol 126, pp 213-234. Swift, DJP, DB Duane, and TF McKinney. 1973. Ridge and swale topography of the middle Atlantic Bight, North America: secular response to the Holocene hydraulic regime. Marine Geol, Vol 15, pp 227-247. Swift, DJP, RB Sanford, CE Dill, Jr, and N.F. Avignone. 1971. Textural differentiation on the shoreface during erosional retreat of an unconsolidated coast, Cape Henry to Cape Hatteras, Western North Atlantic Shelf. Sedimentology, Vol 16, pp 221-250. Taney, NE. 1961. Littoral materials of the south shore of Long Island, New York. Tech Memo No 129, US Army Corps of Engineers, Beach Erosion Board, Washington, DC, 59 pp. USACE. 1993. Myrtle Beach, South Carolina, shore protection project. Draft General Design Memorandum, U.S. Army Corps of Engineers, Charleston District, SC, 46 pp+ appendices. USACE. 2000 (Sep). Final feasibility report and environmental impact statement on hurricane protection and beach erosion control: Dare County beaches (Bodie Island portion), Dare County, North Carolina. Vol I and Vol 11, US Army Corps of Engineers, Wilmington District, South Atlantic Division, 99 pp + appendices. USACE. 2010. Final environmental impact statement, beach nourishment project, Town of Nags Head, North Carolina. USACE Wilmington District, Washington Regulatory Field Office, NC (Action ID SAW-2006-40282-182), 164 pp + executive summary, references, and appendices. USACE-USDOI-NPS. 2015. Environmental assessment — beach restoration to protect NC Highway 12 at Buxton, Dare County, North Carolina. US Army Corps of Engineers, US Department of Interior, National Park Service, NPS 603/129663, Volume 1 (204 pp) and Volume 11 (Appendixes A to G). Van Dolah, RF, VJ Digre, PT Gayes, P Donovan-Ealy, and MIN Dowd. 1998. An evaluation of physical recovery rates in sand borrow sites used for beach nourishment projects in South Carolina. Final Report to SC Task Force on Offshore Resources and Minerals Management Service Office of International Activities and Marine Minerals; SCDNR, Charleston, SC, 77 pp + appendices. Coastal Science & Engineering 54 Geotechnical Data Analysis [2403M-Task 2-Appendix A] Buxton, Dare County, North Carolina